RENDICONTI Socldd ltaIlana dl Minual09ia e Perrolo9ia. 39 (1): pp. r93-228

THE PALEOZOIC METALLOGENIC EPOCHSOF THE SAHDINIAN MICHOPLATE

(WESTEHN MEDITEHHANEAN):AN ATTEMPT OF SYNTHESIS ON GEODINAMICEVOLUTION AND MINEHALIZING PHOCESSES

CARLO GARBARINO, $ILVANA MARIA GRILLO, CARLO MARINI,

ANTONELLO MAZZELLA, FELICITA MELlS, GIORGIO PADALINO,

SANDRO Tocco, MAUR1ZIO VIOLO

15t. di Giacimenti Minerari, Geoflsica e Sdenze Geologiche, Facolra di Ingegneria dell'Universitlt.piazza d'Armi, 09100 Cagliari

LUCIANO MACCIONI

Dipartimento Seienze della Terra dell'Universitlt, via Tremino 52, 09100 Cagliari

MADDALENA FJORI

via Zagabria 49, 09100 Cagliari

RIASSUNTO. - 11 preseme lavoro, sviluppalO anra­verso i cinque anni del progello finaliualo +: Geo­dinamka» (souoprogeuo 4), finanziato, SOstenulO C

coordinalO dal CNR, rappresema un tentativo disintesi sulle conoscenze riguardanti le correlazionitra evoluzione geodinamka e deposizioni metallifere,

11 quadro di riferimenlO fondamemale c riferilOalla microplacca sarda, sede del piu imporramedistrellO minerario d'Iralia.

I piu anrichi processi metaUogenki, almenoquelli direttamente investigabili, sono caranerizzatida deposizione di solfuti di Pb·Zn·Fe e di baritenelle dolomie e cakari della pianaforma del Cam.briano inferiore e medio. Qucsti depositi, del tipoMBS, mostrano una zonalira verticale _ e quindicronologica - e orizzontale, doe paleoombientale.Gli amhienti sedimemari evolvono da quelli marini·deltaici verso quelli di laguna 0 di «tidal·flals ».

Le mineraliuazioni di solfuri ricorrono in baciniron ristretla rirrolazione d'acqua, mentre la deposi·zione di barite i: prevaleme nd hacini con condi­zioni di mare aperto, 0 con maggiore circolazioned'acqua.

L'.. annegamento» della piattaforma carbonaticacambriana arresta la deposizione primaria dei me.talli, ma successive fenomenologie diagenetiche,retroniche ed erosive hanno contrihuito grande·mente alia rimobilizzazione dei solfuri e solfati ealia formazione di corpi mineralizzati, economica.mente coltivabili.

La seconda epoca metallogenica, quella ordoviria­no-siluriana, c caratrerizzata da deposizioni vulcano­sedimemarie di solfuri misti con paragenesi piucomplesse di queUe cambriane. L'orizzonte minera.lizzata, ubiralO al pasS<lggio tra I'Ordoviciano e iI

Siluriano i: costituito da uno skarn quarzoso dori­lico-epidotico con rari granati e pirosseni. Taleskarn I: il prodono metamorflco di un orizzontetufltico formato dall"appono vulcanico di silire (emetalli) ne! bacino sedimenrario e dalla sedimen­tazionc dctritico-carbonatica de! Siluriano.

Una potente coltre vulcanica con trends calco­alcalini (vanno infatti dalle rioliti fino aJle andesiricon relativi tufi) si c insediata essenzialmeme nel­l'Ordovdano e Iimitalamenre ne! Siluriano inferiorce pub essere collegata alle ultime tasi dell'OrogenesiCaledoniana e, almeno in parte, ai prodromi di que!­la Ercinica. L'area in cui ricorrono il vulcanismo e igiacimenti metalliferi pub essere considerala comeun paleomargine altivo tra la fine dell'Orogenesi Ca­ledoniana e l'individuazione dei primi segmentistrutturali di quella Ercinica.

L'ultima epoca metallogenira paleozoica rappre­senta iI prodolto della grande c importante oroge·nesi Ercinira. In questa lavoro non sono statesludiale le ben note mineralizzazioni idrolermalifiloniane di Pb-Zn·Ba·P; sono Slate analizzate inverealcl,lne mineralizzazioni meno conosciUle - scienti·firamente parlando - e ubicate nei «granitoidi»dell'Ogliastra. Si tralla di pieco!i corpi con strunuraa slock·work. allungali secondo le direnrici teno­niche regional!, con una paragenesi di tipo Zn·Cu-Mo.Le assodazioni, gli ambienti geodinamici, i « trends»gt'QChimici sembrano suggerire una ipotcsi geneticadi tipo .. porphyry ». Il meccanismo dell'intrusionemagmatira ercinka e I'eta degli stocks graniroidirulta"ia rappresemano un limite .. strultl,lrale .. perquanto riguarda le dimensioni economiche di ralimineraliuazioni.

In condusione I'evoluzione geodinamica di que-

194 C. GAKBARINO, S.M. GRILLO, C. MARINl, A. MAZZEllA, F. MELIS ET AL.

sto frammcnto della carena erdoica, che c la micro­placea sarda, ha condizionalO fancmcnlc le tipo­logi'! giadmcntologichc che vi rioorrono e costitui­soono un concreto esempio cli correlazionc tfa palco­ambicnti c deposizioni rnclalliferc.

AIISTUCT, _ Several papers and researches overthese lasl few years have "greally improved theknowledge on the tectonic. snaligraphic andmagmatic pattern of the Sardinian minoplalc, afragment of the Hcrcynian chain.

The synthesis of the correlation between ,hegcodynamic environments and ore-deposits has notyet been altcmplcd despite the CCQnomic importanceof this mining district.

The present paper, which is the result of fiveyears of research in the ambit of the «Geodina·mic:!» project (sponsored by CNR), attempts thissynthesis.

The oldest metallogenk processes are characterizedby deposition of Pb-Zn-Fe sulphides and Ba suI·phate in the Cambrian carbonate platform. Thesedeposits, which may be classified as MBS type,show vertical and lateral zonings closely connectedto the different pakoenvironments and carbonaticfacies; these environments evolve from marine·deltaic to lagoons and tidal·Aats.

The sulphide mineralizations occur in basinsof reduced water movements, while the badtedeposits occur mainly in the area of open seaconditions.

The drowning of the middle Cambrian carbonateplatform ends the primary metal depositions, butfurther diagenetic, tectonic and weathering pro­cesses contributed greatly to the reworking of oresand the formation of exploitable ore bodies.

The second metallogenic epoch, the Ordovician·Silurian one. is characterized hy volcano-sediment.!t)·deposition of mixed sulphides; the ote·bearinghorizon, located along the Ordovician·Silurianboundary is made up of a tuffitic rock, later meta­morphosed and transformed inlO skarn during theHercynian orogenesis.

A thick volcanic cycle (metarhyolites, metandesitcsand wffs) mainly developed during the Ordovician,shows a calc·alkaline trend and it may be linked10 the latter phases of the Gledonian orogenesis.Metal zoning is present in Central Sardinia whichrepresented, structurally and geodynamically, anactive paleomargin. This metal zoning seems 10 beassociated to the volcanic zoning marked by moreacid suites in the southern area (Sarrabus) and morebask ones toward North (Barbagia-Ogliastra).

The last PalCQzoic metallogenic epoch was causedby the Hercynian orogenesis. The Authors of thepresent paper have not studied the well knownhyd.rothermal veins of Pb-Zn-Ba.F; the object oftheir research has been the lesser known Cu·lI.lo·Znmineralizations of the Ogliastra plutonites. Smallbodies of Cu-Zn and minor amounts of Mo arescattered throughout the granodiorite and leuco­granite of Hercynian plutonic stocks. The oreparagenesis, the general structures of the minera·lizations, the geodynamic environmenrs and thegeochemical trends of' host·rocks seem to suggesta genetic hypothesis of «porphyry» system forthese metal occurrences. The mechanism of the

Hercrnian «granilOid» emplacement and the ageof these magmatic stocks represent nevertheless aStrOng limitation for the economic occurrence ofthese mineralizations.

In conclusion, the geodynamic evolution of theSardinia microplate strongly conditioned the rypeand the amount of base metal occurrences givingrise 10 a valuable example of correlation betweenpalcocnvironmems and ore·deposits.

1. Foreword

The prjmary purposes of this paper are theunderstanding of the ore-forming processesin the Paleozoic rocks of the Sardinian micro­plme (fig. 1) as well as the definition of therelationship between the metal depositionsand the geodynamic environments.

, " pi~:~,:~ :

'0Km

Fig. I. _ Sketch map of the island of Sardinia.The different areas referred 10 in the present paper,are shown. 1= Prehercynian basement; 2 = Her­cynian granilOids; 3 = Mesozoic carbonatic plat·form; 4 = Cenozoic volcanites and sediments.

TilE PAlEOZOIC METAllQCENIC EPOCHS OF TilE SARDINIAN ETC. 195

Wilh this in view the Authors have at­tempted over the last five years to idenlifythe main metallogenic epochs of the Sardinianmicropl:lle and their relationship with theevolution of the paleogeodynamic environ­menls.

The general improvemenl of geologicalknowledge was of grca! assistance to theAuthors; however in spite of this, sever-oilareas and topics had to be studied in greatdetail due 10 the Jack of sedimemological,stratigraphical, structural and volcanic dat,!.

For instance the Authors expended con·siderable efforts on the volcanic frameworkin the central Sardinia, as well as onsedimentological research on the Cambrianplatform in the Southern part of the island.

Throughout the research several colleagueslent their assistance in order that the Authorsmight avail of their specific competcnces andthey would mention in particular: Prof.N. MINZONt (Istituto di Mincralogia del.l'Universidl di Ferrara) for his most valuablecontribution towards a correct understandingof the stratigraphical sequence in centralSardinia; Prof. A. GANDtN (lstituto di Geo­logia dell'Universita di Siena) who furnish~

the basic outlines of the sedimentologicalparameters in the Cambrian carbonaticplatform; Prof. S. BARCA (Dipanimento diScienze della Terra dell'Universita di CagIia·ri) for his precious suggestions concerningthe stratigraphic sequence of the Sarrabus·Gerrei area.

2. IntrOlluctioll

A better understanding of Sardiniangeology has been acquired in recent years;several papers have been published outliningthe different characters of the stratigraphy,structural geology, etc..

The Authors referred to these papers fordetailed information concerning the generalstructunl pattern of the Sardinia (sce re­ferences).

On the other hand the Authors preferredto stress how the mineralizations of theSardinia offer, it is believed, one of the finestexamples of correlation between geodynamicenvironments and ore deposits in the Me·diterranean area.

This fact is to be allributed not so much10 the extent and the importance of themineralizations as to the variety of themin a relatively limited area. Thus the Authors,in this p3per, attempt to summ3rize theknowledge previously gained and lhe resultsof research carried OUl in the ambit of the• Geodinamica ... projec! of CNR reJ:tardingthe mineralizing phases and the influencesthat the geodynamic environments have h3don them.

With this in view the Sardinia microp!arc,just as far as the Paleozoic sequences areconcerned, will be divided into three mainstructural areas (CoCOZZA et al., 1974; CAR­MIGNANI et al., 1982).

I) South-western Sardinia; characterizedby the sediment:ltion of cllrbonate pllltform.This area, in which the Cambrian sequenccoutcrops, may represent the foreland of IheHercynian orogene (CARMtGNANI et al.,1979).

Imponant ore deposits of Pb, Zn, B3occur in the Cambrian dolomilcs andlimestones showing interesting phenomenaof diagenetic concentration and tectonic andsupergene remobilization of metals.

In this sedimentary basin the POSt­cambrian sequence is relatively thin and theOrdovician·Silurian volcani!es also seems tobe limited.

In spite of the Ordovician-Silurian strati·graphic reduction, strata·bound mineraliza­tions, hosted in a .. skarnoid ... horizon, 3reto be found in the Ordovieian-Siluriansequence bordering the Cambrian carbonaticplatform.

1I) Central Sardinia (.. internal trough»COCOZZA et HI., 1974). This area, from Sar·rabus to Barbagia and Nurm, includes thethickest Paleozoic sequence of the Sardiniamicroplate. Apart from some bHsal laminatedporphyties (. Porfiroidi ») whose role is stillobscure (Precambrian?l. sediments and vol·canites from the Upper-cambrian up to theLower-carboniferous are present which canattain a thickness 10,000 m. The volcanitt:sand tuffites are f'.lther more widespread thanin the south-western region and mixed­sulphide mineralizations are present. Researchon the volcanic trends and the model of thevolcano-sedimentary mineralizations (Funta·

196 C. GARBARINO, S.M. GRIl.LO, C. MARINI, A. MAZZELLA, F. MELlS ET AL.

..,....,...,-~..

!

!,!

!!

II•i

-

...

...

...

.. *'...."... 1<0<1

,.:.r.: .

.... '.l ' 1•••1 , 1 ....I ,,., I_t IU ., ".f '" '1000 " ,.,_..... _1." •• lOo IL ....I. I _ .

'''.,if .,,, f " I"' ,,•• I.- ,., .. ,I< 1,,_ ,.. 1_. _ ..,.

.. ,

__......1....

. -. ...f '_1:"'11 ',I" ...1. <l__...

..'.......ol.', I_I.. ,.. , ,,,_,,,1..,-".. ,l.. ''''Ill' , <l _ •••1......1"••••, .,.....U ,..ltl..• -'1.. ,...."-.-.._.

_ _.Ilt._. _ "' ~,_ ,..' _........- ,''''', .".1., '-'" _ .

L.....--.,' 1.. <140'-"",1__'V'-"" l. to ...I...._M.'......1.,_._.1_....'_.._._._........,_.

not.> _.I,I_.f .-.,__-.1"" _ .-,......" ...,.-.ld ~h",'_._1I_1_

_ , ,....."". to ... t..._ ...1_.,,, ..1111. 1••1.._. _._..............

...

...

;i

!•;

;!•

;·

!!i,

i

.;

Fig. 2. - Lilhosuaugr:lphiC s.equcncc and mincu.liunion ocrurrmces of the Cambrian platform (Iglc­$ientc - Nonhem Sulcis district).

na Raminosa type) represented the largestengagement by Authors.

III) Northern Sardinia and Corsica. Thisarea is believed by some Authors «(ARMI­GNANI ct al., 1979) to be the rOOI of theHercynian belt. Large occurrences of « gran i­[aids» outcrop in this area as well as Cu-Momineralizations (in the Ogliastra region),

This Paleozoic basement is overlain by aMesoloic and Cenozoic cover, affected bydifferent types of paleoenvironmems andmineralizations.

3. The melallogenic epoche

Five main metallogenic epochs are re­cognizable in the Sardinia island (PADALlNOet al., 1979); the first thrtt, the mostimportant, occur in the Paleozoic ba~ment

while the last twO in the Mesozoic and in theCenozoic cover (lab. I).

TABLE 1Schematic distribution 0/ the stages 0/ mine­ralhation according to ages, paleoenviron­ments, magmatic trends and orogenetic phases-_. ... "-'" 1.....1.

W ....1_•• ..........,. ,.... ~.., .... '1.. .,,,.... ........ I ....""_I..• .....

"'_'01' "",.....~. <:0,,-.,..,._ , ... <:Oh""11l.<l.. ..m ...... ~~Il_ "'t! .1........... ..oral_<:o.-If.- _..."' ............ <:0,,-.,..11..

>_..~ ca.....I .. ...,...."".. "._.... ......1-. ,-,

• "'-" "....... .......... - -........-_ ...I.....-,.•_..

w .. ~ ....~- <:0,,,,,,,,,,,__..... ,••1-0". ..,........ .............,""

THE PALEOZorc METALLOGENIC EPOCHS OF THE SARDINIAN ETC.

•••~

~.~

~.~~

t-

l/t,

N

t0 5Km, ,

19i

Fig. 3. Geological sketch map of the Cambnan terrams (lgleSlenle and Norlhern SUlclS dlstrlcts) ­1 = Lower<ambrian sandstones and phyllites; 2 = Lower-cambrian carbonates; 3 = Mldd[e<ambri~n

slales; 4 = Middle-ordovician conglomerate, sandslOnes and siltstones; 5 = Hercynian granitoids;6 = Post-paleozoic lerrains.

Thus lead, zinc, silver, barite and fluoriteand to a lesser extent copper, represent themost valuable mining activities in Sardinia,while bauxite and coal offer interestingperspectives.

Tab. 1 gives the general outline of themineralizing phases and the main paragenesisaccording to age and geodynamie environ­ment. Despite this scheme, it is useful topoint out that the mineralizing processesrepresent systems in equilibrium with the

environmental evolutions and they cannot bebelieved as restricted in time and space. Thusf.i. the Pb-Zn-Ba mineralizations in theCambrian carbonates have been subjected toseveral reworking phases, by stresses duringthe Hercynian orogenesis. by supergenefactors during the Triassic peneplanation andAlpine tectOnic rejuvenation; the Ordovidan.Silurian mixed sulphides have been subjectedto Hercynian metamorphism that gave riseto new ore associations and textures, etc..

198 C. GARBARINO, S.M. GRILLO, C. MARINI, A. MAZZELLA, F. MEL.lS ET AL.

THE PALEOZOlC METAI.LOCENtC EPOCHS OF THE SARDINIAN ETC. 199

Another element emerges from lab. I; theincrease of the number of metals in Iheore associalions from the Cambrian metal­logenic epoch [Q the Hercynian one; in factthe Hercynian ore-paragenesis reveals a widevariery of paragenelic associations, in conuast10 the relatively simple and monotonousCambrian paragenesis.

Some Authors (ZUFFARDt, 1968; PADA­LINO et aI., 1978) suggested that thcpersistcnce of lead.zinc and barium in IhePaleozoie metallogenic epochs could be as·signed [Q extensive heredity phenomenafrom the oldest ore-associatlons to theyounger ones.

In conclusion, the Authors deemcd itexpedient [Q furnish, for the Paleozoic metal­logenic epochs, thc gcneral data closely ns­sociated with orc forming processes andenvironmental characteristics, while theyrefer [Q the literature and to other sub­projects of the «Geodinamiea,. project fordetailed analyses of the geological history ofthc island of Sardinia.

3.1. THE CAM8RtAN METALLOGENtC EPOCH

The Paleozoic occurrences of the south­\llestern Sardinia are characterized, as is wellknown, by a thick Cambrian sequence anda lesser Ordovician·Silurian-Devonian cover.

This area represents the most importantlead·zine-barium region of Italy and for thisreason the existing literature is plentifulboth from a metallogenic and geological pointof view.

Fig. 4. - a) Polimodlll gf1linstone, made up ofooated oolites, bioclasu, intradam (M.te S. Giorgio. Nebida fonnation, P.ta Manna member); thinsection, polarized light. b) Mudstone with irregularpisoids and vadose peloids (M.le S. Miai ·Nebidaformation, P.ta Manna Member); lhin section, p0­larized light. cl Planar laminated mudstone, withmicropeloidal levels (M.te S. Miai - Gonnesa for·mation, or Dolomia rigata" member); Ihin section,polarized light. JI Cryptalgal boundstone wilhgeodk open space filling and recryslaUized lrappedooids (M.le S. Miai • Goonesa formadon - " Dolomiarigala,. ~mber): thin section, polarized lighl.t) Feneslral murlslOoe: fine disscminadon of sphale.rile in pcloids (5. Giovanni mine· Gonnesa fonna·rion, or alare ccroide .. member); thin 5«lion,polarized lighl. Il uminaled mudslOIle; teaonklamination evidenced by a gffICral orientarion nonnal10 lhe original beddins with calcite tttryStallization{M.le S. Miai - Gonl1t$a formation, «calcare cc·roide,. m~llJbttl; thin S«t:ion, polarized light.The bar is } mm Ions.

200 C. GARBARINQ, S.M. GRILLO, C. MARINI, A. MAZZELLA, F. MELlS ET AL.

The general features of the mineralizationsrepresent the finding of research carried outby the Autohrs (and theit colleagues) overthese last few years; the results now allowan interpretation of the depositional anddiagenetic environments of the carbonaticplatform, their evolution and their relation­ships with the mineralizing processes.

}.I.I. Stratigraphic, sediment%gica/ andpetrographic scheme

The well known Cambrian sequence maybe schematized from bottom to top as fol­lows (figg. 2-}):

I) the sequence, whose base is unknown,starts as a clastic sedimentation (sandstones,siltstones), that is followed by an ahernanceof sandstones and carbonatic intercalation ofvariable thickness (<< Nebida Formation »,more than 750 m thick).

The carbonatic intercalations, somelimeoolitic and fossiliferous, are precursory to thesetting of the carbonatic platform;

11) a thick carbonatic sequence perfectlyconformable, characterized by laminated do­lomite at the bottom and limcstone towardsthe top. The entire mineralized bodies arecomprised in this sequence (. metallifero •Auct., «Gonnesa Formation., from 500­800 m thick);

Ill) a thin horizon (max 40 m thick) ofnodular limestone, preluding a new clasticsedimentation, followed by a thick sequenceof phylIires and sandstones (c Cabitza For­mation ») more than 600 m thick, that de­lineates the end of Cambrian sedimentation(CoCOZZA, 1979).

The sedimentological studies of the dif­ferent carhonatic facies allowed to draw upa general paleogeographic scheme of theepicontinental platform, whose evolution maybe summarized as follows:

- On a Iittoral-dehaic platform (detritalsedimentation of the basal sandstone:s (AN­GELUCCI, 1970) a neritic environme:ntestablished. This neritic environment isconfirmed by the presence of orbonaticlenticular bodies with Archeocyatus andEpiphyton inte:rpreted by the: some Authorsas biohe:rmal lxxI.ies (DEBRENNE, 1964).

- The carbonatic sedimentation increasc=s

upwards and an alternation of limestoneand sandstone-silstones developed (CocOZZAand GANDIN, 1977).

This increase of carbonatic sedimentationis marked, at its base, by a continuous oolitichorizon (6g. 4a). The limestone intercalationsdecrease upwards and they are replaced bydolomites chal1lcterized by evidence of earlydiagenetic dolomitization (6g. 4b).

- This change: of sedimentation indiotesan early sign of environmental modificalion;the reduced energy, the depositional cha·racter of the dolomite denote an evolutiontoward a "lagoon type» basin. Probablythe oolitic bar limits the exchanges with theopen sea; the supplies of marine waler areensured only through tidal channels and hur­ricane floods.

A muddy carbonatic sediment, subjecrcd10 a vadose diagenesis in an intertidal­supratidal environment, may settle in theareas where the terrigenous supplies arenegligible.

- Equilibrium and slability of the sedi.mentation basin are, at this point, reachwand a tidal flat environment established.

On a gently undulating floor and probablyin an arid, hot climate: a thick orbonaticcomplex is deposited. Dolomites still pre:vailat the bottom but upwards the role oflimestones Mome:s more prominent (6g.4 c, d).

Dolomites, believed by several Authors(FANNI et al., 1981; CARMIGNANI et al.,1982) primary deposition or very earlydiagenesis, exhibit different facies, homo­geneously distributed on a regional scale.

MudstOnes, sometime finely bedded withpseudomorph nodules of evaporites, bound­stone, composed of algal mats, fenestralmudstOnes and boundstones up 10 vadoscpysolites represent the facies most com­monly encounte:red.

- The most fre:quenl limestones faciesare representw by mudstone and more rarelyby boundSlone (6gg. 4 e, /l; these fades giverise to the typiol vadose pisolites faciesduring the more: developed stages of dis­solution and redeposition. Sometime fadesof laminated mudstone and mudstone­wackestone are also present; these faciesseem to be have no connection with dry andvadose diagenesis.

o

N

t

THE PALEOZOIC METALLOGENIC EPOCHS OF TilE SARDlNIAN ETc.

5 KmL

201

fig, 5. _ Geological sketch map of the Gmbrian terrains, showing the directions of the probable sup.plies from the Pre·Cambrian continent to the Cambrian basin. _ I = Probable supply during the .. AI­ternanze ... deposition. I I = Probable supply during dolomite and limestone deposition. The geologic.!lindex of the terrains as fig. 3.

The presence of the above mentionedfacies is evidence of a platform evolution,with the formation of differentiated sub­environments that lead to suppose thepresence of paleoreliefs and basins.

Subaereal diagenesis is prevalent on thepaleoreliefs while the under-water one pre­dominates in the basins, sometimes withrestricted water circulation.

- The general trend to emersion, evi·denced by some carbonatic facies is abruptlyinverted during the limestone sedimentation.The nodular limestone deposition substan­tiates this inversion of trend; the basindeepens and detrital matter from the con­tinent supplies the sedimentation.

The carbonatic platform is drowned andthe phyllites terminate the Middle-Cumbriansequence.

202 c. GARBAll.INO, S.M. GRILLO, C. MARINt, A. MAZZELLA, F. MELIS ET AL.

different orogenetic events; theend the Hercynian. The Alpineshows mainly wrench fault

3.1.2. Geochemistry

About 500 carbon:lle samples have beencollected in the Iglesiente-Sulcis area alongtwelve complete Cambrian sequence fromtop to bottom. The samples have beenanalyzed by A.A. and XRF for Ca, Mg, Fe,AI, Mn, K, Na, Sr, Pb, Zn, Cu and Ba; thegeochemical data seem to confirm the abovementioned paleogeographic features.

The Authors investigated the distributionof some metals such as Sr, Na, Mn, characte­ristic elements from an environmental pointof view (FRlTZ &< KATZ, 1972; LAND&< Hoops, 1973; CooK, 1973; BENCtNI&< TURI, 1974: RAO &< NAQVI, 1977; RAo,1981). As far as the geochemical data (tab.2) are concerned the following considerationsshould be taken into account;

I) Mn content decreases constant..ly frombottom (<< Alrernanze ,.) of the Cambriancarbonatic sequence towards the top (<< li­mestone »). The limestone marks a sharpdecrease in Mn content.

11) Geographically the Mn content de­creases - in the «Ahernanze» - fromEast to West; contrarily in the case ofdolomhes and limestone; the Mn contentdecreases from West to East.

HI) The vertical and horizontal distri­bution of Mn should denote a less oxidizingenvironment from tOp to bottom of [hecarbonatic sequence, an early influence ofcontinental supply from E-NE and sub­sequent..ly from W-NW (6g. 5).

IV) The Sr-Na contents and its ratioshow highest salinity of diagenetic environ·ments during the «bedded dolomites»deposition.

V) The high contenl of Sr in the «Alter­nanze » may con6rm a late dolomitization ofthese facies.

Hence, the geochemical findings confirmthe sedimenlological data :md are thus ingood agreement with the above mentionedpaleoenvironmental scheme. Their influenceon the mineralizing processes will be ana­Iyzed later on.

3.1.3. Tectonic scheme

The schematic structural frame of theCambrian outcrops may be represented by asystem of folds and faults due to at least

two main,Caledonianorogenesischaracters.

I) The oldest tectonic structures arerepresented by an early «Caledonian phase »which, acting in a N-S stress direction, causedE-\VI folds and a series of faults StrikingN 300 \VI and N 30° E. The N 300 W foldsmay be considered a typically Caledoniandirection (VALERA, 1967) owing to its greatnumber and development.

11) The subsequent tectonic events, theCaledonian s.s. and Hercynian, at the begin­ning still shows a N-S stress direction (POLLand ZWART, 1969). During this phase theearly Caledonian folds shrunk and theN 30" \VI faults rejuvenated.

Ill) The persistence of a N-S trendenabled the development of a second stressphase acting in NW-SE and NE-SW di­rections. These should be responsible forthe wide dispersion of the fold axes (CAR­MIGNANI et al., 1978).

In the Cambrian terrains the folds withthe axis striking N-S may be imputed to thesephases. In the Post<ambrian terrainsN 700 E represents the typical Hercyniandirection.

The final struCture of the Cambrian se­quence, caused by the above tectonic events,is characterized by folds with axes from E-\VIto N-S and a ser of fractures striking N30"W,N·S, N 30" E and N 700 E.

Several papers are now available on thetectonic structures of the Sardinian micro­plate to which the reader is referred for moredetailed information.

3.1.4. The model 0/ the mineralizing pro­cesses

The sedimentological, structural and geo­chemical dara enabled the evolution ofcarbonatic platform and the processes leadingto sulphide and sulphate depOOirions to bedelineated.

The following considerations may beoutlined before to deal the model of oredeposition;

I) The mineralizations and importanttraces are almost always in carbona!ic litho­fades; limestone, as host-rock, prevails over

THE PALEOZOIC METALLOGENIC EPOCHS OF THE SARDlNtAN ETC. 203

dolomite. Few and only limited ore occur­rcnces [lrc hosted in basal I'l ahcrnanzc » andin the «ca1cari nooulari ».

II) On a regional scale ore bodies exhibita strata-bound features; on a ore-depositscale epigenetic features are predominant.

Ill) Ore-associations are rather simple andmonotonous; sphalerite, galena, pyrite andbarite.

IV) No genetic relationships havc beenobserved between ore bodies and igneousrocks (both plutonites and/or volcanites).

V) On a regional scale a veniC'lI zoningis present; pyrite-sphalerite or barite occurat the botlom of the carbonate sequence andnamely in the dolomitic facies, while galenaand sphalerite (and minor pyrite) occur inthe limestone.

VI) When barite occurs as beds in thebasal laminated dolomite sulphides are absentand viceversa.

VII) The carbonatic platform is cha­racterized by an increase in barhe mine­ralizations southwards, and, of course, adecrease in sulphide bodics.

VI Il) A close relationship c:m be observedbetween stress directions and ore bodies(AMMI, 1961; McMooRE, 1968); this re·lation to be explained by remobilizationphenomena and not 10 genetic faclOrs.

IX) The geochemical analises of Pb, Zn,Ba of the carbonatic lithofacies (tab. 2)revealed how the regional metal averagesare higher than world average (TUREKIANand WEDEPHOL, 1981) in the epicontinentalcarbonates.

In view of the foregoing the Authors cannow examine the mineralizing processes andanswer lour main questions:

I) the origin of the metals,2) the origin of the sulphur,3) the environment of ore deposition,4) the environment of ore reconcentration.

As regards the origin of the metals it ispossible to hypothesize a supply by leachingof an unknown paleocontinent; thc thicknessof basal Cambrian sandstones, the continen·tal and/or shallow water environmentsduring dolomite deposition may aC'COunt forthe large volume of materials, carried out to

TABLE 2Geochemical data oJ the Cambriarl

carbonatic lirbo,lacies

• .. .. • .. .. ..," " " '" '" ..

• .. .. " •• " .. ,., u..._

" " .. .. " .. "• .. " .. 111• " '" -• " • " ~ .. • ••• 4oloool'u

" " " " .. .. .., .. .. " ".. .. ...< • " " •• .. • ••• ·AU......... •

" " .. .. • .. ..i = a\'cr2ge content in ppm; (f = standard dcvu..·lion; n = number of samplt'S. The number ofsamplt'S «n,. is CliIrried 001 from x· te5l, whichshowed diffcrent distribution for each clement;only samples ioside mean ± 3 a have been utilized.

the sedimentary basin. As previouslyremarked non volcanic rocks occur in theCambrian sequence apart from same diabasedykes that seem to be connected to Hercynianmagmatic cycles (BEccALUvA et al., 1981)and to have nOt any relationship with orebodies.

As lor the origin of sulphur, isotopicresearch (BRuscA et aI., 1965) revealed itsbiogenic origin, by bacteria reduction ofsulphates. This assumption is in goodagreement with the sedimentological dataand evolution of the Cambrian platform.

The environments of ore deposition in factare strictly conditioned by the evolution.

The deposition of "Alternanze." (P.taManna member) is characterized by a lagoonenvironment, middle to high salinity,strongly oxidizing; the mineralizing pa­rameters were favourable only to sporadicsulphates deposition (bathe nodules) whilelow geochemical contents of Pb-Zn and thepH-Eh parameters were not conducive tosulphide depositions.

The deposition of "dolomia rigata." ischaracterized by a tidal environment, lowenergy, very high salinity, strongly oxidizingbut with some mieroenvironments locallyreducing or at least less oxidizing (GANDlNet al., 1974).

A general trend to cmersion is present aswell as long periods of conlinental phases.The high geochemical contents of Zn andBa (and by contrast the low content of Pb)

204 C. GARBARINO, S.M. GRILLO, C. MARINI, A. MAZZELLA, F. MELIS ET AL.

Fig. 6. - Stnl.1igraphic sequenttS of central Sardinia.namely Sarrabus and San:idano· Barbagia.1 ::: Porphyroids of unknown age. 2::: Upper·cambrian 10 Lov..c:r-ordovician; sandSlonc:s phyllit<:s(S. Viu)·Solanas formalions); 3::: Lo"'cr 10 r-.liddlc:­ordovician; rhyolilcs and IUffs (. Porfidi grigi cbianchi. Auet.); 4::: Tuffs and vokanodastic me.­l.asc:dimc:nu; ,::: Middle: to Upper-orclovician; me·t:andc:silcs and ruffitcs; 6::: Caradocian-Ashgillian:sandSIOnc:s phyllites and limestone:, sometime S1ronglysilicilic:d; 7::: Silurian--Dc:vonian; blKk shales, phyl.liles, \"Olcanites and rulEles, limeslones. Slratiformsulphides occur into lhe orc:.t)caring horizon;8::: Lowcr<arboniferous (?); phylliles and sand·stoncs.

3.2. TilE ORDOVICIAN.$ILURIAN r-IETALLo­GENIC EI'OCU (l)

The minerlllizarions of the second geo·dynamic environment (the so called «internalbasin») exhibit a sharp modification accordingto hOSHOCks, gcncral geological features andore associations (fig. 6, 7l; the Middle·ordovician and the Lowcr·silurian exhibitseveral occurrences of mixed sulphides. Thestrala·bound features, the more complex oreassocialions compared to those of the Cam­brian, the metamorphic phenomena and 1'$­

sentially Ihe relationship between mine­raHzalions and volcanires allow to outlinethe evolution and modification of geodynamicparameters acting in the area, includedbetween Cambrian outcroups (lglesiente) andthe large Hercynian plulOniles (Gallura).

3.2.1. Stratigraphic and tectonic schemeThe different geodynamic environments,

the tectonic transport toward SW and themetamorphic zoning of Hercynian orogene~ls

allow to divide the Sardinian microplate intothree NW-SE belts, namely; North·easternbelt, Central belt and South-western belt(CARMIGNANI Cl al., 1978, 1982).

As previously noted the south-westernbelt is characterized by sligthly deformedcarbonate platform (Sulds Iglesiente) withPb·Zn sulphides.

On the contrary the North-eastern beltexhibit high grade metamorphism, «grani­tization.. phenomena, and tectonic shor­tenings.

The Cenlral belt ($arcidano-Barbagia-

Cl TIle rc:scarchc:5 on the Ordovician-Silurianmetallogc:nc:sis have been catried out aho in theambil of lhe JGCP project n. 60 (Project leader:Prof. F.M. VOKES; chairman of italian ",,'orkinggroup; Prof. M. VIOW).

of Cambrian sulphides, achieving 10 somecase exploitable volumes of ores.

Furthermore, the important erosive cycle:of Trias and the: landscape rejuvenation ofAlpine orogenesis favoured a large supergenereconet:ntration of sulphides and sulphates.

The Authors refer to the literature con·cerning this important aspect of the Cambrianmetallogenic province (BRUSCA et aI., 1967;PAOALlNO et aI., 1973, 1973; BoNI, 1978).I:;:;~5 ....... ~

Sarcidano- Barbagia

~ ~ ~ ~

~~~~ft~

A~~ft~~

~ ~ ~ ft ~

~~A~~~

~ ~ ~ ~ ~

~ ~ ~ ~ ft ft~ ~ ~ ~ A

~ ~ ~ ~ ~

Sarrabus- Gerrei

lead to sulphide and/or sulphate depositionsaccording to different sub-environments.

The deposition of the limestone (<< Cal·care ceroide») is characterized by a tidalenvironment, low energy, low salinity, lessoxidizing than the preceding environments.The high geochemical contents of Pb, Zn,Ba allowed sulphide depositions and an earlyconcentration by dissolution and redepo·sidon.

The neritic environments of nodular li·mestone (c;Calcescisti» Auct.) and «Cabitza»phyllites denote the drowning of the platoform and terminate the important mine­ralizing procnses of the Middle-ca.mbrian.

The subsequent up-lifting, folding andfaulting of early Caledonian. Caledonian andHercynian orogenesis caused Stress reworking

THE PALEOZOIC METALLOGEN1C EPOCHS OF TilE SARDIN1AN ETC. 205

N

to SlmL..' J!

-.:.:/::

:ktJ~:~

1~' ,f-I

.0 ,I"""d .1/1

Fig. 7. ~ Geological sketch map of central Sardinia.. I = Upper.cambrian 10 Lower-orclovician sand·stones ("Solanas,. formation). 2 = Ordovidan volcanic cycle (melarhyolites, mClandesiles, volcano­clastic sc:dimems). } = Silurian.Dcvonian; black shales, phyllites. volcanites. limestones and the orebearing horiwn. 4 = Lower<arboniferous (?) phyllitcs and sandstones. ~ = Hercynian «grllniloidslO.6 = Majot faults.

Nurral shows structural characteristics inter­mediate between the South-western andthe NOrth-eastern ones; this area is in factaffected by low grade metamorphism (chloritezone) and by superimposition of severaltectonic units (CARMIGNANI et al., 1982).

The acid volcanism is prevalent (e porfiroi­di _ and • porfldi grigi e bianchi _ Aucl.land the main volcanic events seem to beconcluded before the Caradocian-Asghilliansedimentation; apart from thin intercalationsof SO<alled basic volcanites comprised in theSilurian sediments, whose analytical data arenOI available at present (BARCA and MAXIA,1982).

In the Northern area of the central belt(Barbagia) the chemism trend of the vol­canism may reach intermediale compositionthat is Rhyodacite and Andesite. This inter­mediate volcanic sequence is covered, in theMeana Sardo unit (fig. 6), by black shale,phyllites, tuffites with sulphides and lime·stone of the Silurian·Devonian. The Authorsof this paper believe that the volcanic cycleis covered, in a limited area (f.i. FunlanaCungiada, near Aritzo), directly by the LowerCarboniferous phylliles (.Post-Gotlandiano_

AUCL); Ihe contact between volcanites andphyllites should be stratigraphic and in thisease the volcanic paleoreliefs (old volcaniccenters?) prevented the deposition of Silu·rian-Devonian sediments.

The most complete unit, from a strati·graphical point of wiew (Meana Sardo unit),shows the following sequences (from botlomto top) (fig. 6):

I) Ihe basement of the sequence consistsof ~ porfiroidi It: laminaled porphyries, withlarge k-feldspar crystals_ These e porfiroidi It

should represent the products of a late Ca­ledonian orogenic cycle;

Il) a thick clastic formation (e Formazionedi Solanas _) (MINZONI, 1975); probablyfrom the upper Cambrian to lower Ordo­VIClan.

These sandstones derive from erosionphenomena of preceding magmatic and vol­canic cycles;

Ill) a great acid to intermediate volcaniccycle.

Thin metavolcanic intercalations are pre­sent in the Ordovieian-Silurian sequencebordering the Cambrian platform in the

206 C. CARBARINO, S.M. CRILLO, C. MARINI, A. MAZZELLA, F. MELIS ET AL

••••••

..,

..,

·.,..,..,·.,•: .

••

•

.. .:.....

.' ..,......,~......;.... ' . .'...,;,. •• f'"......

• • •

~~:";:.~.:".. ~,.-" .

L----".•------'c..-,--::...---Nb!Y..

..

..

..

Fig. 10. _ SiOo vs. Nb/Y plot of metavolcanitesof Iglesiente, central Sardinia and oorthern Spain,WINCHESTEJ. and FWVD, 1977).. 1 = .. 0110 deSapo» formation (North-Western Splinl: 2 =.. Pomdo grigk>>> from Sarrabus; ) = .. Porphy­raids »; 4 =Melarh)"Olites; ,= Metandesires fromcentral Sardinia; 6 = Metandes.i1es from Iglesiente(BECCALUVA Cl aI., 1981); 7 = Metabasites fromcentral Sardinia; 8 = lo.letabasites from IglesienletBECCALUVA et aI., 1981).

Fig. 8. - Shcaral br«c:ia from rhe volcanic ('OfTIpkxof M.re S. Villoria. TIle bt'C'CCia consisl of sandmmeand V'Olcanile fragments, somelimes silicified, in aclayey, dark matrix.

South-western belt; but the volcanism at­tains its most important development in thecenual belt (Sarrabus·Gerrei and Barbagiaregions).

The chemism and the stl'lltigraphic locationof the volcanism reveal an evolution from

South (Sarrabus-Gerrei) to North (Barbagi,,).In the Southern part of the central belr

the acid volcanism (metarhyolites) prevailsand iI seems exhausted before the Cal'lldociansedimentation. In the northern part (Bar­bagia-Ogliasua) of the central belt, instead,

Fig. 11. - Zr-Ti-Y plot of mcrabasiles from centralSardinia and from Iglesienle. - Fields A+8 = Low·potauium Iholciite5; Field B = Ocean floor· Ba·salts; Fitld C+B = Cale-alkali basalts (PEARCE SeCAN, 1973). I = subalkaline basalts; 2 = alkalinebasalrs; ) = melabasires from Iglesiente (BECCA·LUVA er al., 1981).

fig. 9. - Devonian limestone folded and dippingsouthward. Funtana Raminosa mine (5. GabrieleSlope).

,..

\• •. ,* ,

THE PALEOZOIC METALLOGENIC EPOCHS OF THE SARDINIAN ETC.

P,~lool .,n .'opoO

20;

../

/C~ ­r=:--:=-- r---- -_./ -~/,.,_-------r __ ../r 1--''" r -- --~/,----",--/-:----- ---..... ----./--:::..--..--- ......-- ./

"

.::-- ... .._""",,'M .•.........~~. .:::::::::::.,., .. " ..'" ......•.... . .

•~~=~":::; '77:C=0'2''*':!-~-"'-'-"""".... .. .... -~~~.....•.... .•.•..•....................••... --------------'

P...... <_......

I.w

~,~

Fig 12. _ Scheme of the Devoman limestone folding during Hercynian orog~~is and of the oreremobilizatlon (see also fig 9) Fumana Rammosa mine (5. Gabriele).. I =Metandesite; 2 =Phyllilesand sandstOnes; J = Ore-bearing horizon; 4 = Limestone; ,= Phyllites and black·shales; 6 =Erci·nlan porphyry dyke; 7 = Fauhs and fraclures.

the volcanisffi is characterized by meta­rhyolites and metandesite. sometime directlycovered by Silurian or Low-carlxmiferousmetasediments. This different stratigraphiclocation of the volcanism may be due to theoverthrusts and also to paleogeographiccharacteristics of the basin.

Infact the volcanisffi caused in the ttntralSardinia a rather rough basin floor resultingin the numerous heteropic fades in the Ordo­vician-Silurian basin. Frequent transitionsbetween volcanites, ruffs, tuffites, volcanicbreccia (fig. 8) clastic sediments and lime­stones are observable in this area. This im­portant aspect of the paleoenvironments willbe discussed later;

IV) phyllites and sandstones lying directlyon the metandesites and passing to theSilurian-Devonian formation, consisting ofblack-shales, limestones and phyllites.

In these formations the ore·bearing horizonoccur. mainly located at the botrom of theDevonian limestone or near the boundarvwith the c Post-gotlandiano » cover (fig. 7).

This horizon exibhit sometime luffiticstructure and its mineralogical compositionis rather variable according to the Hercynianmetamorphism.

When the metamorphism is higher garnetsand pyroxenes are prevalent; where themetamorphism seems to be weaker onlydorite, quartz and epidotes are present.

Minor amounts of amphyboles. fluorite,magnetite and sulphides occur in Ihis ho­rizon. The inrense silicification, the complexparagenesis may be due, as will be discussedlater, to the metamorphism of tuffitic sub­marine deposit transformed into a "skarnoid»(Bun, 1977) during Hercynian orogenesis.

A phyllile thick cover (cPost-gotlandiano»formations Auct.) whose age is still uncertain(Lower carboniferous?) seems 10 concludethe volcanic and sedimentary cycles beforethe Hercynian orogenesis.

As far as the tectonic is concerned centralSardinia terrains have been mainly tectonizedby the Hercynian orogenesis; according toCARMIGNANI et al. (1978) three main stagesare recognizable during this orogenesls,namely:

I) the first stage, the most important,caused isoclinal folds and overthrusts towardWest and Southwest (fig. 9) thus, shorteningsof the Palemoic sequence have been pro­duced. A well developed flow-cleavage isassociated with this stage;

11) the second stage deformed the precedingtectonic setting, causing open folds wirhNW-SE or E-W axis trends. A less importantflow-cleavage is associated with this stage;

Ill) the third folding stage caused stillmore o~n folds with N·S or NE·SW axistrends.

208 c. CAR8ARINO, S.M. GR1LLO, c. MARINI, A. MAZZELLA, ,. MELlS ET AL

TABLE 3AJlalyus 01 .. porphyroids ,. ond porphyrin /ro,,, un/ral Sardinia lJud Spain... ,.. 'K .~ ~ 'x ~ - ~ '",,~ 13.1I"l' 76.2' >•• ,] 7).16 7••~" ".5' >'.02 '''.8] 'ZoS'i! ".~

1_, .~flOil .n ." .,. .,. .~ .~ ." .., .~

~~ n." '2.63 ,•.,> .).~ +3.'" .s.n , •.8-< 's.n " .... ,~.7'P 'So ",,~ ." '.~ •. n ." ." ... '.51 ,.~ 1••• 1. l. '.~

'" .n ... .~ ." .~ ... .~ ." .~ ." ."~ ." ." ." ." ." ." ." .,. .~ .~ .~

." ... ..~ •• .• ... ." ." ... '.~.,

'M ." ... .., ." .n ... .n ... ... ." .~

~" .~ .,. .~ "" , .17 t.e] 2.1' ,.~ ,.~ ... ...." ,." ".6~ ,... 6.10 ,.'6 1.50 '.1' 6.67 5.'S 6.0' ~.6".~ .~ ." • '5 ." ... . .. .., ." ... .~) ."A," ,,., <.16 '.11 ..., .M '.62 ••5 , •. n •• 1/ '.l' l.O'

"' • , , , , , , , .. , ..'" "' M M ~ "' ~ "' "' "' ." ."" .. , •• " " .. ., .. .. .. "'" " .. .. " " " " .. .. " .,.. " " " '" " n " " .. ". "" " " " " .. ., ~ • " ,. ••.. .. .. ., ,.

" .. .., M .. ., ~.. '" ~ ~, ,., ,. ,,, - ,.. ~ ... .".. ", '" ", - n' ~ .,':.0 .... ,.. m ".~

, , , .. , , , ., .. , "'~ .", 'M .~ ... .~ ... on m ... '" ..,," ~ .. ·. " .. ~" .. " ~... ..

u " , " " " .. ,. n • •" "' " " "

," .. ~ "

,• ., .. ~ • " " "

,. • ".V ~ ~ '" - • ." " •, ..... ~ •• 7 n .•• ><;. '0 ~.~ ".2, ... • '1.01 68.'] .... ... ·,,~ •• ... .,. ." .~. .'-'" .M ." .".~ ,e.~ .... ..,. ·'.1~ 06.07 ",.)6 '~.'" 'l.'S "." .1o.JJ '~.6 .. ',~, .., .~ '.~ .'< .~ .'.• '.~ '. '2 Z., •• '-'". '.os .M .00 .00 ." .~ .... ." .~ ... ~- ... ... ... ... .'" ... ... .n .n .M ,.- ." .~ ." .n .~ .M .n .00 ..~ ..~

,~ ." ." .n ..~ .0' .M ... ." .n .' ,"'~ .~ '.O~ ..~ , ...t .n .~ .~ J •• t '.02 '-' .. ,.~ ,.~ "J.26 1." 3.'>~ '.5~ '.n 1. iO '.1' ~.~. '>.Of' ' '.,~ .n ." ... ." ... ... ... .n .~ .".~ t.? '." •••0 '.61 7. , • .~ "'6 i.e. .~o •• 02 ,.."'

, ," .. "' ~ ~ •• • .. ••

" ~ ." ~ •• "' ." ." ~ ~ "' ."" .. .- " .. ~ ." ,

" " .. "w .. .. " ., " " ., .,"

., ,,,',." " .. .. ., n .. ~ " " "," "

,. .,~ • " " ~

~ ~ ~ •• " • ,. " .. ".. '" M " .., ". .M ~ ., ~, ., • ·.. ••s m' .- .017 .~ '~Ol - " ~. ·~ • , "' ." ., , • , .. ., .... ." M .. .• ~ n " " ." ., ..,," ~ .. ,.

" .. ~ ., .. ., ...- ,. .. .- " n ~ ,. ,. D " "" ~ » ",.

" .. .. .. .," M

" ~ n " •• ., " "' ,. " "- ~ "' "' lJJ'S'i ~" ~v ,.~ "w £ ..t ,. ,,,~ ..... 64." "'.69 M.6· ., .... 66.7' 70•• "." M." .7.1' .....",,~ .~ .» .» .~ ... ." .~ .51 ... .., .~

~~ i' .lS '7." '6.ft ".70 ' ••1. 'S.'? .,..' i6." .6.B'i ., .00 ., ."FEZ03 ,... '.S' ,.~ i. ? ,.~ ~.07 ' ..' ,.» '.M ....2 •• li

'" .~ .~ .~ '.~ .M .00 .00 .... '.91 '.~ t .•<

~ ... ... ." .M ... ." ." .~ .n ... ...- •• OS '.02 ••00 "~ .~ .n '." • •1>' •• 1>7 ... "~,~ ." .~ ." .~ •.n ' ••7 ." .., .n .~ ..."'~ 2. '3 t .•S '.6' t.07 1.•(\ 3.3' ." 2.S· '.n 1. ,t Z.5~

.~ S.01 '.M 5.S' '."6 s.n '.2t 5.5' ,... ..e. •. 3/ •• i~

.~ .,. .~ .n .,. ." ." .~ ." ." ... .H.~ 2. , • 2.22 '." 2.29 t.n '.2' 2.53 2.09 "'. 2." ,.~

"', , .. .. " .. "

., .. .. .." ~ ~ M ~ ~ M "' ~ M ~ M

" .. ., .. ., " " " ~ ~ " "'" .. " " .. " .. .. " " ",... .. .. " .. ~ " .. " .~ ., ..,,

" .. .. ,. • " ~ M .. " ~

P .. ~ n " 00 - ~ •• " ." .~.. ." .., .M m - .., .~ ... ." ... i5 i.. 'n '" .., ,,, ..., 'OH ... ~, .... •• ".~ "

, • " .. " •• • , • ,.. ." '" ... .~ '" 'M '" m " '" ,..,~ .. .. .. " ~ " " " "

,." n .. " .. " " ~ " » ~ "~ .. ~ .. ~ - .., .. " " " .... ~ " " " .. " n • • ~ •

Ma;or c:lancnlS ,~ 8i ...~ .. "'; ,h< 0',"" elements " ppm; ND= 00' dctn:tc:d.

The tectonic paltern of the cenlr::ll Sar~ exhibit cleavage of the stl'ainslip ,nd notdinia ,nd Nurra appears very different from of the now type, moreover shortening ,ndthat of the Southern Sardinia; on this area ovenhrusrs, even if present, do no' seemson fact the Cambrian ll:nd Ordovidan terrains " wide " in central Sardinia.

THE PALEOZOIC METALLOGENIC EPOCHS OF THE SARDlNIAN ETC.

TABLE 4Analyses 01 metarh)'oIites Irom central Sardinia

209

'>101f101~~,,,='"­~,..'"~,~

"'"~""<-

"","..""",""..

~

1~.8~_n

i~.'M'

-"-~_n-~

-"••525 ••~

-"._~,"","""'"'60}~

""""~,

"15.03

-"'<1.1.._~

-~

-"-"-"._"3.15

-",-"•""",.""".....,"'""".m

"

"1Z.23

-"'~.o·2.31

-"-~

-"-"-"~.16

-"1.1_,""•..""",

'""""".."

'"1Z.8~

-"15.81

-"-~_n-"-"-"1.72

-"'.b,"","•"...

'"',.,"~""

,.13 •• 1

_NtS.~5

1.0'

-"-"-"-"-"'-~-"'2 •••,"","""m'"""""""

".16.72

_n'~.03

_n-"_n-"-"-"••51

-"'.1.,"","""".'""..",""

'"1•. 53

-"' •• 68._"_N

-"-"-"•• 23,-"-";>.'0,"",,.•"'"m"'"""'""

GtMS'7~_~6

-"'4.~a._"

_00_n

••••-"-":l.31_N

,on

"W".."""~,.",".""'",

Major elements are I;i\lcn as %; lhc Olhcr c!cmcnlS as ppm; ND = not detectoo.

TABLE 5Analyses 01 metandes;tes Irom central Sardinia

510;>HO;>~=FE203

'"­~~'"M'M.=~

""<-

"","..""",""..

."..61.lIS

-"1•• '31.1l·.2~

-"5.511.245.13t.H-~

2.8.

""~.""...,.."'"""."".,"

"'~.55.53'.03

'6.11t.785.96

-"6.522. to,-"._"-"5.5',..".,."".""""'",

'"~..",

",y•58.50

-..15.612.5.4.H

-"'.Il].492.532.59

_n3.33

""'"~"m'""'""'"""..,

"',,,sa.~·

-"15.01t ••;>._"-"1.1.

•. 83._~

-"-"3.6'

"",..""."'"~.",".""""

."""1.<>0'. t(

.6.821.·25.03

-"5.H,-~

3.331.8;>

-"4."';>

""..,""'""".",'"""..•

GUJJ2"_M.:::3.,.08._"

~ ••5

-"._"t. 101. 1;>3.H

-"._"",,.~

'""."...".,'""..",.

"'~.55.1·-~

".61;>.535."'6

-"._~

1.11~

5./10·

-"-",-~

~

",",".'",..""""'"""""

GO,' 1".Il(

-"".83/10.65

-"-'"2.~/Io

2.5)._"2."-",-~

~

".."".."".""""..."","

le ,.59.0'\

-"" .S2

-"6.83.<0,-""

~.41

3.673.13

-",-~,.."•"','"",'"".,~.

""....

'"58.81

-"".BC,-""~.~s

-"'_006.6';>.622.24

-"-"""..."".

'",,."'""".,."""

'"58.~5

_n16.'.;>_~s

'.;>4

-"._""5.8'2.S~

2.H-.,i.n

",.'""~'"~."".•...""""

Major elcmems ar~ given as fib· lhe Olhcr clemems as ppm; ND = nOI deux:ted.

The detailed studies on the tectonic pat­tern of paramount importance from a miningand ore·prospecting point of view; in factthe Hercynian tectOnic stages caused the« splitting .. of the ore·bearing horizon andits overthrust towards South or South.West.

Funhermore the isoclinal folds of the firststage might be the cause of the ore·bearinghorizon redoubling, thus forming ore bodiesof valuable volume (figg. 9 and 12).

.3.2.2. Volcanic trends 01 central Sardinia

The Pre-hercynian volcanites of the centralSardinia are represented by acid terms (<<pot.firaidi», mctsrhyolites. «porfidi grigi e bian­chi» Aut.), intermediate (metandesite) andbasic ones (metaba5aIt5) (01 $IMPLlCIO et

al.. 1974; GARBAIUNO et al., 1980; MEMMIet al., 1982).

210 C. GARBARINO, S.M. GRILLO, C. MARINI, A. MAZZELLA, F. MELlS ET AL.

,ElFig. IJ. - Block-diagram showmg the hypothesIzed model of ore forming processes during the Ordo­vician-Silurian metallogenesis.. 1 = SandslOnes and phyllltes (<< Solonas" formation}, 2 = Volcanic cycle(metarhyolites, rnetandesites, tufts and tuffites); J = black·shales, phyllncs and limestones; 4 = ore·bearing horizon.

- The «podiroidi» consists of shearedporphyries and rhyolites and seem to be at­tributable to the Precambrian and, at leastpartly, to the Ordovician (MEMMI et al.,1982).

They are similar la the well-known « 0110de Sapo» porphyries from Spain and forIhis reason they have been analyzed (tab. 3)and compared with the other volcanites fromSardinia (fig. 10).

- The metarhyolites and their tuffs arecomposed of a thick cover with evidentcharacters of ignimbrite facies. They couldbe of Tremadoc-Arenig age as well as the«porfidi grigi e bianchi» (BARCA et aI.,1981); these latter vokanites outcrop mainlyin the Sarrabus area.

- The metandesite consists of dome­shaped bodies and horizons interstratifiedwith phyIIites; these volcanic rocks showsecondary silicification phenomena.

Their occurrences are localized mainly inthe Northern area (Barbagia·Ogliastra) andfor this reason their age is still uncertain; infact even if the whole volcanic cycle seemsla be of Pre-caradocian (BARCA et aI., 1981)

it is possible to ipothesize that some volcanicpaleoreliefs may range up to the Lower­silurian thus preventing the Upper-ordo­vician sedimentation (GARBARINO et al.,1980).

Lastly the metabasites made up ofsmall dykes and lenses interbedded withSilurian volcanodastic sediments.

All these volcanic rocks have beensubjected la the Hercynian orogenesis thatcaused neverthless weak metamorphic phe­nomena.

The petrographic investigations carriedout revealed that the original texture of themetavolcanics is badly preserved.

The quartz and K·feldspar phenocrysts inthe acid metavolcanites are fractured andcemented by a quartz-feldspar-se;ricite micro­crystalline matrix, while the plagioclase andmica (biotite) arc generally transformed intoalbite-sericite-epidote and chlorite-epidoterespectively.

Evident phenomena of transformations ofplagioclases, sometimes with neoformationof calcite, and of malic minerals into chlorite­epidote are recognizable in the metandesite.

THE PALEOZOIC METALLOGENIC EPOCHS OF THE SARDINIAN ETC.

TABLE 6Analyses 01 calc-alkaline basalIs Irom cenlral Sardinia

211

$[02Tl02~w,

fE203

'",~'00,~

~"

'"•=­"00D00

'"o".."~'",CO

"..

00'"5' .1>9

.M~6.()O

3.065.89

."., .362.29,."•.n."4.61.""'",'"."~.....•m

"n,.,

00'"5·.3~

."'6.022.266.6'

. "'o.• ~

4.622.97'.43

."3.S"I'00

"'"•'"...'""'"~'".,,...,

GU3~1

_6.1>8•.•4~6.58

7.'>41>.15...'>.1>­•• 5.2.57.~

."..".­~"..,.",n'""'"­,~.,""~

"",­_9.~.."'0.683.331. la

• I~0.59•• 17_.9'

•5.

."4.1>3.."."""."."..,

'""'"",.",

.=.53.16'.0'

15.203.'>67 ••n

."0 ••71••7

'.00....n,.~

'""'",..,."~

".-."'"...."~

"""53. '6

."'5 ••e2.5b6.68."

9 ...3._'l4.n.".w

3.33

""...••mm."..'",".,.n

""

GU3.05'.49

."17. ,72.205.53

."8.0'3.69,......­."'.M'""..."~".'""•066

•"."".."

W.3.72

••09'6. '5$.010.76.n

10.4e_.652,'3•.2'."S.'l6

'"n...•

~.

m.""..."..,""'"~

l'Ptl!53.22

.00,2.2113.553.83

."9.515.51>'.1 I

."...9.03..,"­"'"'",..~

",."""""

Major demem5 are given as 9&; the OIher ekments as ppm; 'ND = nOl detected.

TABLE 7AnalySt's 01 alkali basalIs 01 central Sardinia

$1021102

~'"~E203

~f.O

'00~

'"~w'".='w""D00

'"o".."~",CO

"..

".43.82, .85

'S. '05.279.3_...6.9S9.S23.40

.00

."'.M",.","'"­,,~~'"D..,""~,

'"•••IIS'.00u .• I

'2.S'5.89

."6.3...-~2.9....

."5.75

".."n~,

~,."~...""."""•

PEP)'3.1 ,

1.93.9.7.3.5'Q. "."5.2'5.'>0,.~._3•."6.04..~

~

"'"~.~..,'"""....."•

PE"._3.71

2. ".9.91;2.62o.ge."

•• 3''.00'.00,."."1>.92

""~"".,..,..~

'00'"".".."..

UILl3_3.26'.48

17 .1>7'. ,t6.55

.258.636.303.21>...."4.97

"~"...~

'"....."""...""",

Major demenlS are given as 9ll; the other elements as ppm; ND = nOl detected.

The plagiodases of the metabasites arealso altered into albite-sericire-('pidote, andthe mafic minerals consist now of an anhedralassociation of chlorite-epidote-actinoIite andiron ore.

The average chemical composition of 66samples of Paleozoic volcanites coming fromcentral Sardinia is given in tabb. 3, 4, 5,6 and 7.

The acid metavolcaniC5 (the «porfiroidi )t

and metarhyolites) (tabb.: 3 and 4), areincluded 10 the classification diagram ac­cording to FLOYD and WINCHESTER (l97.5)in the area of rhyolites and rhyodacites whilethe intermediate and basic ones (tabb.: 5,6 and 7) are included in the areas of andesitesand basalts respectively (fig. 10). For com­parative purpose, the «0110 de Sapo­porphyroids » (four samples collected by rheAuthors in the North-Western Spain - tab. 3,

212 C. GARBARINO, S.M. GRllLO, C. MARINI, A. MAZZEllA, F. MELtS ET Al.

TABLE 8Lead, zinc and copper contents in thePaleozoic sequence 0/ Central Sardinia

~ • ~

y • ~ ~ -0- • ~ n

n " • ..• " '" n ·w....~·

11I>clud-\noJ ~lli_,0- , ". .. black ohal_,-.._1-....)n n " ..;r .. '" n

\0:>],.,.,1_ (-.1_.

0- • ~ ~ -'-""" U.!r \llff_ln " n ..

i = a\'e:rage: oonte:nt in ppm; a = standard devia­tion; n = number of samples. The: numbc:r ofsamples .. n. is a.rric:d out from x' test, whichshowed diffe:renl distribution for each e1e:ment;only samples inside: mean ± ) a have bec:n ulilized.

samples E 139, E 140, E 142, E 143) andone sample of gray porphyry (c Pomdo gri­gio It) (tab. 3, sample GU 454) from Sar­rabus are also reported in the diagram offig. 9. These rocks show a more pronounceddacitic trend.

Moreover, using the elements believed im­mobile also during low grade metamorphism(CANN, 1970; PEARCE and CANN, 1973;FLOYD and WINCHESTER, 1977), it has beenpossible to specify the presence of eale­alkaline basahs and within.plate alkali basalts(tabb. 6 and 7) (fig. 11).

These characteristics are further confirm~d

by the Y /Nb ratio; this ratio is less thanone for the former metabasic rocks and it isequal to four for the latter.

The chemical data moreover indicate howthe acid metavolcanites underwent rema­bilization phenomena of Na, K and Ca whilethe intermediate and basic ones have beensubjC<"ted to importance modification in theircontents of Ni, Cr and partly Mg, withevident enrichment of LREE.~ presence, in the Lower Paleozoic of

Sardinia, of two volcanic families, and

namely sub-alkaline and alkaline (DI 51 M­PLICIO et aI., 1975; RICCI and 5ABATlNI,1978; GARBARtNO et al., 1980; BECCALUVAet al., 1981) should denote twO differentphases of Pre-hercynian volcanic activities.The first, the sub alkaline trend, should beconnected to the late stages of Caledonianorogenesis, as well as the similar, mainlyacid, occurrences of the Alps and EuropeanContinent (BELLtENI and SASSI, 1981;BElOV, 1981; HEINISH, 1981).

The second, the alkaline [fend, may beconnected to Prc·hercynian rifting phenomenaof the paleo-European continental margin(RICCI and 5ABATlNI, 1972; BECCALUVA etal., 1981; BARCA et al., 1981).

3.2.3. Geochemis/ry

About 250 samples have been collected inthe Barbagia region (mainly around Fun­tana Raminosa area), along stratigraphicsequences, from c Post-gotlandiano.. for­mation (phyllites and sandstones), «5i1urian..formation (phyllites, black-shales, limestonesand cskarnoid .. horizon), volcanic formation(metandesiles). All the samples have beenanalyzed for Pb-Zn-Cu by A.A. and XRF.

The geochemical data, reported in tab. 8lead to the following observations:

I) lead content is ralher constant amongthe three groups of formations, but it showshigh variability whithin the same group offotmations;

II) copper content is also rather constanland low, apart from small increases in theSilurian formations;

III) zinc content shows the highest vahlesand variability among the three groups offormations.

These remarks are in good agreement withthe mineralizing processes model (see later).Taking into account that the highest geo­chemical anomalies are localized in thec skamoid .. horizon, it is possible to obser­ve, whithin this horizon, great and gentlevariations of the metal contents. In fact thecontents of the mineralized areas decreaselaterally till the regional average, forming

THE PALEOZOIC MEl'ALLOGENIC EPOCHS OF THE SARDTNIAN ETe. 2IJ

along the <' skarnoid» horizon a sort of« spots» having high metal content.

Another interesting datum is the fol·lowing; ar a geochemical level the differentparagenetie associations ate confirmed; aswill be described later, two main ore as­sociations prevail; the Fe-Zn-Cu and Pb-Zn.These geochemieal analyses revealed as apositive anomaly of Zn and/or Zn-Cu alwayswith very low Ph contents; on the countrarywhen positive anomaly of Pb and/or Pb-Znare present the Cu contents are rather low.

3.2.4. The model of the mineralizing pro­cesses

On the basis of the geodynamic environ·ments described in the foregoing the Authorsdeemed it expedient to outline the followingdata in order to depict a general model ofthe mineralizations in central Sardinia;

I) the presence of an ore-bearing horizonlocated at the transietion Upper-ordovician.Lower-siIurian, or at the bottom of the De­vonian;

II) the relationship between the volcanismand the ore bearing horizon;

Ill) the relationship between the ore as·sociations and the chemism of the volcanism.In fact in the Southern area (Sarrabus.Gerrei) fluorite, galena, sphalerite, arseno­pyrite and Ag are prevalent; further North(Barbagia} Fe and Cu assume a more im­portant role.

This is in good agreement with the increaseof the intermediate and basic volcanism ina South-North direction;

IV) the primary metal traps seem to be(he thick volcanic paleoreliefs; in these paleo·reliefs the mineralizations (generally smallveins in the volcanic rocks) are very lean.On the contrary the most important mine­ralizations occur around the paleoreliefsalways at the base of th~ Silurian limestoneor in a synchronous stratigraphie level;

V) the role played by Sb is somewhatobscure; recent investigations (CARMiGNANtet al., 1978) ascribe the deDOsition of Sbmineralizations to Hercynian magmatism.The Authors believe the Sb is connected tothe Ordovician-Silurian volcanic cycle, evenif strongly remobilized during the Hercyni::morogenesis. For this reason Sb has been

classified, even if dubitatively, as a productof Ordovician-Silurian metallogenic epoch(tab. 1);

VI) only epigenetic mineralized veins anddykes are present in the « Post-gorlandiano »cover. These mineralizations are clearly as­sociated with the Hercynian metallogenieepoch;

VII) important phenomena of ore remo­bilization occur in the Ordovician-Silurianore-beating horizon. These phenomena arecaused by the Hercynian folding and meta­morphism; the ore-bearing horizon, foldedand faulted by the former events, lost itsspatial continuity and has been split andreworked in the nuclei of the folds, givingrise to the typical «sausage» feature (fig. 12).

The latter event transformed the meta­volcanites and tuffites of the ore-bearinghorizon into a « skarnoid ».

The block-diagram of fig. 13 attemptsto synthesize the model of the ore formingprocesses during the Ordovician-Silurian me­tallogenic epoch.

It is obvious that this picture representsthe scheme of the metallogenesis during thedeposition of Devonian carbonatic platformand before the deposition of the «Post­gorlandiano» formation.

Apart from the role of the « porphyroid »basement (Caledonian magmatism?) theUpper-cambrian and the Lower~ordovician

are characterized by the deposition of a thickdetritical sequence (<< arenarie di S. Vito»and «Solanas» l.

A great acid-intermediate volcanic cyclefollows (meta-rhyolites, meta-rhyodacites andmeta-andesitel throughout the whole ofcentral Sardinia.

The sedimentological and geodynamicenvironments in the Southern (Serrabus) andin the central area (Barbagia) differ.

In the Southern area the rhyolites werecovered by the sedimentation of phyllites,sandstones and limestone of Caradocian­Ashgillian, while in the Northern area thesesediments seem sometime to be absent.

Even if the most important volcanic cycle\Vas exhausted before the Caradocian­Ashgiallian sedimentation, minor volcanicproducts were deposited in the Siluri::tnbasin.

214 C. GARBARINQ, S.M. GRILLO, C. MAR 1Nl, A. MAZZELLA, F. MELIS ET AL.

This, may be proved also by the thinvolcanic intercalations in the Silurian andby several dikes (supply channels), nowstrongly alterated, cutting the terrains belowthe Lower.ordovician formations.

In the central area (Barbagial; the vol­canic paleoreliefs were perhaps preventedthe deposition of Caradocian-AshgiaIJian andthe volcanites are covered directly by theSilurian-Devonian sediments.

The area of Funtana Raminosa mine israther significant in the understanding ofvolcanism emplacement and ore deposition.From Meana-Gadoni to Tertenia, alongNW-SE direction, the Ordovician volcanitesare characterized by variable thickness anddifferent relationship with the Post-ordo­vician cover; at Meana rhe metandesite arecovered by Silurian limestone and phyllites,at Funtana Cungiada (near Aritzo), the vol­canites are very thick and covered directlyby the sandstones and phyllites of «Post­gotlandiano» formation.

At Tertenia the «Post-gotlandiano» alsolies on rhe Ordovician metandesite but, inthis case, the contact is clearly tectonic ratherrhan stratigraphic.

Important ore deposits OCcur, along thesame NW-SE belt, around the thickestvolcanic occurrences; Meana, Giaccuru, Fun·tana Raminosa, S. Gabriele, Talentino re­present the most valuable ore bodies ofcentral Sardinia; the paragenesis is cha­racterized by the presence of Fe, Cu, Zn, Agand minot amounts of Pb, F.

The mineral composition, as well as thethickness, of the ore-bearing horizon showssignificant modification. At Meana the« skarnoid » horizon is composed of quartz,chlorite, epidote, garnets and rare pyroxene;the thickness is reduced to 1·2 meters.

At Funtana Raminosa - S. Gabriele themineral composition of the «skarnoid»horizon in quite similar but in this areathe ore-beating horizon teaches its maximumthickness, about 10-15 metres.

The structure of the mineralization is tobe attributed essentially to concentrations ofores; in fact a fine interpenetration betweensulphide and Ca-silicate minerals is presentwhen the ore-content is not very high (fig.14). In this case the sulphides are of anhedralshape or they are included in the Ca-silicatecrystals.

With increasing ore concentration thestructure may become massif and minera­lization assumes the «massif sulphide»structure as in some stapes of the FuntanaRaminosa mine or some lenses of the Sar­rabus area.

In this case the ore bed consists almostexclusively of sulphides (and/or magnetiteas in Giaccuru); nevertheless a bedding (ora ghost-bedding) can be frequently recogni­zed in the mineralized layers.

On a microscopic scale the mineralizationsof the Barbagia area consist of a mixture ofsulphides, sulphosalts and oxides; the morecommon ores are:

I) sphalerire. galena, pyrite, chalcopyrite,magnetite and £luorite;

11) pyrrhotite may be present in the oreswhere iron mineralization is ptevalent;

Ill) reduced quantities of bournotite,hematite, pentlandite, chromite and arseno­pyrite are also present;

IV) Ag is present in the Funtana Rami­nosa ore ptoduction; about 1000 g/ton ofchalcopyrite and 1200 g/t of galena;

V) the oxidation zone is not very de­veloped, thus scanty amounts of azurite,malachite, limonite, hydrozindte are visiblein the area of ore outcrops.

Exsolutions of chalcopyrite are almostalways present in the sphalerite gtains.

In the area of Tertenia, the ore depositsof Bau Atenas and Talentinu exhibit differentcharacteristics; they occur as veins andveinlets in the basal metandesites while theyexhibit stratiform features in the phyllites.Limestones are absent; the mineral compo­sition of the ore bearing horizon is madeup of quartz and chlorite. In these ateasdikes of volcanic rocks, strongly altered, arepresent. These dikes stop at the level of theore-bearing horizon and they might repre­sent the old channels of volcanic and perhapsmineralization supplies.

Thus the ore-bearing horizon, above thevolcanic system and below the Silurian.Devonian sequence, may represent the resultof replacement phenomena beneath the seafloor, near the volcanic centres where sub­marme fumarolic activity was present(OFTEDAHL, 1958; RIDGE, 1973).

THE PALEQZOIC METALLOGENIC EPOCHS OF THE SARDlNIAN ETC. 215

This submarine activity should occur moreor less at the beginning of the carbonaticSilurian sedimentation, giving rise to theCa-silicate paragenesis of the c skarnoid •horizon.

The Hercynian orogenesis modified thisscheme; in fact according [0 the results ofresearch on the structural framework ofcentral Sardinia (CARMIGNANI et al., 1982)the difference in thickness of the ore-bearinghorizon and Ordovkian metavokanites couldbe caused by the Hercynian tectonic phases.The stratabound ore-deposits have been re.worked and now they exhibit epigeneticfeatures; this is partkularly visible inthe Southern area (Sarrabus-Gerrei) thalrepresents the front of the folds and over.thrusts. The «Filone Argentifero. of [heSarrabus, the ore-deposit of Bacu Locci andSa LilIa (ZUCCHETTI, 1958; VIOLO, 1966)may represent the result of these remobi­Lization phenomena. These deposits in factshow on a regional scale a close connectionto the above mentioned stratigraphic levels.while in detail veins and epigenetic featuresare prevalent.

Fig. 14. - Orc-bearing horizon made up of gameu,e:pidoles, quartz. The: sulphides lite: finely disse­minllted in the: rock. Crystallization broadly syn­chron0U5 with the: microfolds ate: visible:. S. Gabrie:le:SlOpe: (Funtana Raminosa).

3.3. THE HERCYNIAN METALLDGENIC EPOCH

The well known Hercynian mineralizationshave been the subject of several papers andstudies by numerous economic geologists.For this reason the Authors d~med itexpedient to refer to these previous paperfor a detailed analysis of the pneumatoLitie.hydrothermal Hercynian mineralizations(ZUFFARDI, 1948, 195J, 1958; URAS, 1951;SALVADOR I, 1959; CAVINATO, 1962; Zuc­CHETTI, 1965; DERIU and ZERBI, 1965;BACCOS, 1968; NATALE, 1969; SALVADORIand VALERA, 1972; MASSOLl NOVELLI,1973 l.

The vein systems of the Arburese (Mon­tevecchio. Ingurtosu, Gennamari), Nuorese(Sos Enaues, Gozzurra) (SALVADORI andZUFFARDI, 1960; IvlELls and SANNA, 1978);Nurra (Argentiera) (BRIGO et aI., 1982) havebeen extensively mined in the past for theirZn-Pb (Ag) ores and they represented :1nimportant non-ferrous metal supply for theItalian economy. Currently these mines havebeen closed, with the exception of Monte­vecchio whose closure represents a traumaticissue for the regional mining industry.

The Silius mine (NATALE, 1969), a largequartz vein with about 40 % CaF:t and 1,5PbS, is still operating in the Sarrabus areaand it is believed to be one of the mo.>rvaluable Auorite mines of Europe.

The Authors aim, in this paper, ro furnishdata and metaUogenic scheme on some lesserknown hydrothermal mineralizations in thecalc·alkaLine plutonites of the Ogliastra(central Sardinia), in otder to acquire someknowledge on the correlation between Her­cynian magmatic evolution and metal de­positions.

In fact even if the mineralizing processesduring the Hercynian (or late Hercynian)magmalism s~m to have been correctlyanalyzed, the origin of metals is still obscureand not easily comprensible. Previous authorshypotesized that some ores, present in thehydrothermal veins, may derive from theleaching of Pre-he.rcynian sediments, byremobilization events closely connected tothe lasl stages of magmatic phenomena (ZUF­FARDI, 1968; SALVADORI and VALERA, 1972).

Thus Pb, Zn, Fe, Cu, Ba, F, Wandperhaps Sb metals, already present in thepreceding metallogenic epochs may have been

216 C. G...RB"'RINO, S.M. GRILLO, C. M... RINI, .... M...ZZELL"', F. MELlS ET ... L.

"-'-'-'Cl'

•

'0,.'0/1'

o.

••••••••-- N

•

~•-,•

$

'Km,

Fig. IS. _ Geological sketch map of lhe OglillSlnJ ara, showing the «gnJnilOids., lhe rhyolile dykesand the OCCUrmK'eS of Cu·Zn·Mo miocfl1iutions.

reworked around the «granitic. cupolasand deposited along with quarlz, calcite andankerite as dykes and veins. Neverthelessthis scheme cannot explain the Tin (Ar­burese-F1uminese) the Uranium (Sulds andGallura) Ni-Co (Linas) and Molibdenum (inseveral parts of the island) mineralizations;in fact thcse metals are practically unknowin the previous Cambrian and Ordovician­Siluri3n metallogenic epochs.

3.3.1. The Cu-Mo-Zn mineralilations in the«granitoids» 0/ Ogliastra (CentralSardinia)

The Authors, in the ambit of the Geo­dynamic project, undertook a study of themineralizations in the Sardinia plutonites.Several occurrences of Cu, Fe, Zn and Mo,outcrop in Ihe «gnmitOids. of the Untt-d.lSardinia and namely in the Ogliaura region.The ore-association, the structures and thehost rocks seem to suggest the presence of

Hercynian «porphyry. type deposits (MAC­CIONI et al., 1979; FIORI et al., 1982;GHEZZO et al., 1982; GUASP...RRI et al.,1982). Owing to this suggestion the Authorscarried out research on plutOnire alterations,geochemical distribution of eu and Mo, andgeophisic anomalies.

About 350 samples were collected fromthe Ogliastra region at regular intervals of500 m; the Authors refcr to another paperfor the complete study of these minera­lizations (FIORI et al., 1983). These sampleswere investigated by microscopic and gea­chemical analyses carried out by XRF.

The field work revealed the presence ofseveral rhyolite (6g. 1.5) dykes with NW-SEtrend; these dykes are sometimes of con­siderable size and CUt the cgranitoid. stocks.These latter consist of a calc-alkaline suit~;

the more common rocks are represented bytonalite, granooiorite and granite (GHEZzOet al., 1972; 01 SIMPLICIO et al., 1974;CoNTt et aI., 1981).

THE PALEOZOlC METALLOGENIC EPOCHS OF THE SARDINIAN ETC. 217

TABLE 9Analyses 0/ mineralized « granitoid » rocks from Ogliastra

pr) PC30 PC28 pc:;>. pC'1> PC~3 PC23 pe'l$102 67. ?'1 63.26 60.77 6Q.6" ~~.23 V.7S " •••2 3$.43T102 0.$. 0.2' ~.69 0.26 0.03 0.1' 0.32 0.12AL203 e. \I, 20.60 10.49 '''.46 S.3B '5.2' 16.1 , '<I.MFE201 1O.:H •. 08 5.7' 5." 10.52 .3.52 26.3$ 23.06~N(1 O. :). C.O~ O. '0 0 .... 0 0.35 0.50 O.lO 0.69

"" 3.5'1 0.96 2.2' •• 35 \.02 7.68 2.00 6.9'1'OO 2.6' 0.'10 •• 27 6.'12 '1,6 • '3. '3 6.lS H.Br~~20 2.018 5.29 $.90 6.Se ,. 9~ 0.2'1 0.53 0.2?<>' O. '3 7.22 3.5" O. ''I 0.08 0.62 1.23 0.21>P2cr.', 0.06 ,L06 O••3 ".OS 0.02 0.03 0.03 0.0'1

'" •• SO 0.87 , • 3:2 , ."S 3.70 1.0. LS' •• 'i0

" 0.51 0.62 O.ot , .•e 6.<1'1 O. ,3 0.511 0.(0)

W 0." , O. ,. 0.6' 0.0' 0.3' 0.05 1.7_ 0.13

",

",

"' " " " "'" " " " "0 " ., • "" " '" '" " " .0< '" "" " " " " • ",

"" ". ". m " • " " ""'" '" " '" '".., H' ,.. ,.... .. '" ." " .. " " ""' •• " " " " " ~ "'.. ". ,.

" 2.S0~,.,

'" ... '" ." ",Major elements '" given " %. ,he other elements " ppm; ND == not detected; -= no data.

The tonalites are composed of plagioclasc(35·38 % An) sometimes altered, of hiotitcand green hornblende; quartz is rare. Epidoteis also present, pseudomorph after biotit~

and plagioc1ase.The granodiorites arc made up of plagio­

clase (30·35 % An), perthitic microcline,quartz and biotite sometimes transformed rochlorite; zircon. rutile, apatite, garnet areaccessory.

The dykes, barren of copper and mo­lybdenum mineralizations, are characterizedby a porphyric texture with quartz andfeldspar phenocrysts. Two main trends ofsub-volcanic suites are evident from thegeochemical analyses (FIORI et al., 1982): acalc-alkaline and an alkaline trends. Thealkaline trend is probably connected toPermo-Ttiassic rift magmatism (BRUNETTONet al., 1976).

The analyses of 23 plutonic rocks and 10mineralized «gtanitOids» are reported III

tabb. 9 and 10. The diagram of fig. 16shows the main trends of mineralized andunmineralized granitoid rocks from Ogliastra.

The calc-alkaline plutonites are reptesentedby tonalite and mainly by granodiorite andgranite.

The chemical analyses reveal the lowcontent of Cu, Mo and Zn; however, it isinteresting to note that in the Ogliastra« granitoid~) tocks, as far as Cu and Znare concerned the average Cu content ofgranite is higher (roughly twice that of all

the other «granitOid» rocks) while averageZn content is maximum in the granodiorites.Unlike these original characteristics of thefresh tocks, the hydrothermally altered rocks,independent of the rock-type, have a higherCu and Zn content.

The altered granitoid rocks, occurring inthe mineralized bodies, show an impoverish­ment in K~O, Rb, Ba due to the alterationof K-minerals, mainly biotite and subor­dinately K-feldspar, to chlorite and epidote.PlagiocIase appears to have been moreresistant to alteration and, therefore, Nacontent remains more or less constant, whileCa and Sr increases are connected to theformation of epidote. In conclusion, it isapparent that hydrothermal solutions carriedZn, Cu, Fe, Mo, Mn, Ca and Sr removingK, Rb, Ba and, subordinately, AI.

This kind of alteration is not typical of«porphyry copper» deposits, whereas thehydrothermally altered rocks show a K-richalteration (LOWELL and GUILBERT, 1970).

The preponderance of Zn over Cu inalmost all the samples, is also worthy ofnOte that Zn was more abundant than Cu inthe hydrothermal solutions.

Finally the typical zoning of «porphyrycopper» deposits, composed of a core ofprevalent molybdenite and belts of pyrite­chalcopyrite, sphalerite and galena etc. seemto be absent in the rocks of the Ogliastra.

Nevenhless this datum should be analyzedmore carefully; in fact the Post·hercynian

218 C. GARBARINO, S.M. GRILLO, C. MARIN1, A. MAZZELLA, F. MELlS ET AL.

TABLE 10Analyses 0/ «grani/oid» rocks from Ogliastra

Major elements are

ppm; ND = not de·

tected; - = no data.

SI02TlOlAlZ03~E203

"~~,~

~"".,,~'"''"'""'"..""..""'"M•

'"67 •• ~.."15.1>6'.10..~•• 733.59,.~

3 •• ]O. '20.58

'"","..,V

'"".'",."~,

PC3'72.ee0.2,,.. ", .920.0'0.56..",."s. "0.060.'\7,..~

~

"..,V

'"''"..."

PC,095•. 1.0.79

'2.25".6S'.M7~'O9.140.300.73O. i7C2S

'"'",'"'V"'"V,

"

PC,OOn.9S0.25

'3.76.. ss0.020.630."2.876.0.0.090.67,."""....­".

'","

pcva63.980.78

.5.505.68O. '22.9.2.a'2.783.670.1'•. 'S..,"•.,

775'..HS

'"'"

pcso62.00..'"'3.3211.6'0.462.34n.4?:LOB0.310.090.53

'"",""..n,"."

PC"63 .•9

O.M'6.574.82O.OC2.074.n3.5e,.~

O. 'b0.62,,~

","..,...'",..,..

PCS261.30..~.2.189.37O. '72,'99 ..0 .,. '"0 ••50.'"

'",.,~

",.......'""

PC377<.650.30

'2.583.950.39, .573.56'.32••02'.00o.•a

'"..""""..,'",.,""

PC3S7{1.320.'0

... 903.020.060.97

I."3 ••9'.75

O. '.0.711.""•,.."".50

'"..,"

given

Olher

as %; the

elements as

5102f10l"I.20lH203"~

"",~~~20"."2115

'"''"'""'"..""..""'"""•

PCJZO60.140.55

<6.925.800.232.35,."J."'.000."O.~6

".",~

'",.'"".'"",'"'

PC10'66.280.0'

'5.065.0~

0.122.222.6'3.5'3.21

o. "<.0'"0

",..'""'V,..'""

_C219, •• l1S0.28

13.9]2. '90.0'.."1.233.285.00O. "1.24.,"""..,'",~",,"

PCS'63.57

0.119,~."5.11'0.00'.7113.H3.253.300.2''.32

'""•"'""'",..'"""..,

PC1M70.!;S0,'7

.3.9 •3."0.0'0.7?1.0.3. '6'.?3O•• ,•. 32

'",.,•......­'",,.

'"",~.

PC'4.71."0.27

'4.232.' •0.03..~..9?3.0''.560.010.0',.",".","'",,,.."

PC".b'."0.08

.".026.'3O. '22.92'.'22.893.200.200.93

"'",...""'~6,.."""

PC2S'60'"0.59'3."'.'00.09'.572.383.593 ....0. "0.02

"",""'""".".'5?

PC'1I117'.25O.V

\•• ~3'.n0.06o.n:O.b'3.0~

5.550.0''."'"""""..."".,,.,,.

P~911

bJ.O_0.70

".0311.%0.2Cl.W••C72."2.960."0.61,n,,..'6n"'"m

"'

PC26055.11'

••02.6.67.."0.277.673.883.2'1.116O••••. 52

'"•,....."'""".."

PC10II65.53O.H

.5.505 .•3'.002.053.9'2.9'3.311O•••0.72,.

•,,....,'"'00

'""

PC'OO67.0.

0.511'5.59'.760.09'.712."3. '11a.llb0.13

'.2''"","'""'"'"'""

erosion may have modified the primarydistribution of metals.

The mineralizations consist of small ore­bodies scattered over the area, according tothe main tectonic trends and the alterationIS mainly of propylitic type.

In conclusion, on a regional scale thesemineraIizations may be considered as «por­phyry rype» deposit according ro the fol.lowing parameters: ,

• •"'_1 .-2Fig. 16. - AFM plot of the .. granitoids,. rocksfrom Ogliastr:a. The dashed line contours the calc­alkaline field (RINGWOOD, 1973). 1 = Mineralizedrocks. 2 = .. Granitoids,. rocks.

I) the geochemical trends of « granitoid »rocks;

11) the geodynamic environment; the areawhere these mineralizations occur may beincluded in the North-eastern belt (or alongthe border) that represents the axis zone ofthe Hercynian chain. In other words thisarea might play (he role of continentalpaleomargin subjected to the influence ofhigh-grade meramorphism (<< granulitic »faciesl (Northern beltl and of mineraIiz~d

horizon of the Ordovician-Silurian (Centralbelt). The influence of these two belts mightbe the cause of a sort of Cu-Mo mixing (andZn·Pb) giving rise to a new ore association;

Ill) the ore association (Cu..M:o and Zn,Fe, Pb),

IV) the presence of mineralized skarnsin the'« graniroid » stocks.

On a local scale and in detail the absenceof rhe rypical zoning of the alteration, andmineralization and the very low contents ofCu and Mo, are data in disagreement with

THE PALEOZOIC METALLOGENIC EPOCHS OF THE SARDlNIAN ETC. 219

the « porphyry» scheme (BURNHAM, 1962;HEMLEY and lONES, 1964; SUTHERLANDBROWN, 1969; CLARK, 1972).

Thus these contrasting parameters seemto give rise to a SOrt of «aborted» por­phyry deposits consisting small bodies ofFe-Cu-Mo-Zn scattered throughout the Her­cynian plutonites.

On the olher hand the absence of zoningmay be caused by the characteristics of thesedeposits which may be classified as «plu­tonic porphyry deposits» (NIELSEN, 1976).

It must be remarked moreover that thedetailed geochemical researches (FIORI er al.,1983) revealed the presence of a primarygeochemical halo of Cu and Zn around themineralized bodies.

The mineralizing processes should beinterpreted as deposition from hydrothermalfluids along a network of fractures with N-Sdirection.

Recent researches outlined how the«hercynian type» magmatism is characterisedby acid chemism and slow, diapiric upliftof magma toward less shallow - in com­parison with the «andean type» - level3of intrusion (ZWART, 1974; D'AMlco, 1974).

These differences of the mechanism ufHercynian magmatic emplacement mayfurnish an explanation of the low Cucontents and the reduced sizes of ore bodies

3.3.2. General remarks on Hercynian hydro­thermal deposits

The remobilization and leaching of metJlsfrom a more or less deep basement to youngerterrains is one of the oldest, most importantand most difficult metallogenic problems 10explain.

The problem is harder to solve for theold terrains (Paleozoic and Prepaleozoic)where it is almost impossible to find out andanalyze the hydrological systems, the com­position and the temperatures of geothermalwaters.

A comprehensive programme, of isotopicanalyses of the main sulphide associationsmay furnish definite solution to the metalremobilizations from the older metallogenicepochs to tbe younger ones.

With current knowledge, the Authors canpoint out some data resulting from the zonaldistribution of the mesothermal vein system

(Ph, Zn, Cu, F, Ba) (see the schematic mapof fig. 17).

The island of Sardinia may be roughlydivided into four main areas: the mostimportant from an economic point of view,namely the Arburese-Su1cis and the Sarrabusare characterized bv different ore associations;Pb-Zn (and Sn, Ni, Co etc.) are prevalentin the vein systems around the granitoids ofthe Linas, Oridda and Su1cis (area A), whilePb (Ag), Ba and F assume a great role inSarrabus region (area B); in the latter areathe Silius vein system occurs.

Mo is scattered in several parts of theIsland (CABOI et al., 1970, 1978; GHEZZOet al., 1982) while Cu-Mo seem to be con­centrated in the plutOnites of Central andNorthern Sardinia (DESSAU, 1956; SALVA­DORI, 1959; DERIU & ZERBI, 1965; BAKOS,1968; CABal et al., 1970, 1978; GHEZZOet al., 1982), even if in' this zone (area C)Pb-Zn veins are also present (Sos Enanos,Gozzura ore deposits).

In the Nurra (area D) a vein NE-SW,mineralized with Pb-Zn-Ag (l'Argemiera)seems to be unconnected with any magmaticstock, even if this may be hypothesized tobe at a not great depth (COCOZZA et aI.,1974).

The pneumatOlirie and hydrothermal ml­neralizations, related tc> Hercynian magma­tism, are represented by interesting ote­associations even if they seem to be ratherpoor from an economic point of view.

Tin veins of S.ta Vittoria and Canale Serci(ZUFFARDt, 1958), the narrow quanz veinswith molybdenite, arsenopyrite and Ni-Cosulphides (M,te Linas in Atburese area), theU oxides testify the evolution of ore-asso­ciations metallogenic epochs to the youngerones; this evolution is represented by theappearance of new metals, as well as Mo,Ni, Co, Sn, U, unknown in the Cambrianand Ordovician-Silurian deposits; thus thepresence of these metals seem to be relatedto the Hercynian magmatism without anyleaching and reworking phenomena fromthe older basement.

4. Conclusions on the Paleozoic metlll.logcnic epochs and discussion orresuhs

The schematic subdivision of the Paleozoic

220 C. GARBARINO, S.M. GRILLO, C. MARINI, A. MAZZEJ.LA, F. MELlS ET AL.

",Km

• ••

000 0

c

,,

oA

--//

//

/I

IIIIII\\\ .\ 0\ 0

\ *\ **',------~--

//- ......./0 0_ / 0

• -.., B

• " 0. ,,\\I/V "

•

N

~

,• 0

Fig. 17. _ Schematic distribution of the: most im·portant Hercynian vdn systems. Mineralization oflow temperature. - A = Sulcis·Arburc:sc: district:B = Sarrabus·Gerrc:i district; C = ORlillstra.GaJlu­ra district: D = Nurrll district. 1 = Pb·Zn: 2 =Ba·F (Ph-Ag): J = Zn·Cu-Fe: (Mo-Pb). >I- = 1:o = 2; * = J.

platform), the ~ internal basin» or centralbelt (clastic sedimentation and margin vol­conism) and North-Eastern belt (axis zoneof Hercynian chain).

The cross-sections of fig. t 8 may furnishan attempt of paleogeographic reconstructionof the environments up to the Hercynianorogenesis, but the data on the Precnmbrianbasement arc still meagre. Research carriedour on the South-\'Uestern and Central Sar­dinia pointed to some remarkable differences

mineralizing processes infO three main metal·logenic epochs, even if useful for an initia.lapproach fO the economic geology of theSardinia, may introduce some misunder­standings; in fact the mineralizing processe~

cannot be limited in time, but they arc inequilibrium with the geodynamic evolutionof the Paleozoic terrains (ZUfFARDI, 1968).

The sulphides, hosted in Cambrian lime­stone and dolomite, f.i., exhibit several re·mobilization phenomena; apart from thegeochemical concentration during the earlydiagenesis of limesfOne (AMSTUTZ et al.,1963) lead, barium and silver are foundin the silica horizon thtH marks the uncon­formity between Cambrian limestone andOrdovician sandstoncs and phyllites. Theearly Caledonian tectonics caused the emer­sion of the folded Cambrian tert"ains; thelimestone was covered by a thick, probablycontinental, silica crust along with galena,rich in silver, and barite; these ores weresupplied but the crosion of the upper partof the Cambrian limestone and by the freeingof lead and barium metals.

Furthermore remobilizations of Cambriansulphide occurrence by Stresses of Hercynianorogenesis occurred, giving rise 10 the wellknown sulphide bodies according to the mainHercynian tectonic trends.

The Hercynian orogenesis was followedby a long period of emersion and erosionacdvities; the weathering of Cambrian li­mestone and dolomitc Icad to the formationof an important karst system, fillcd by argen­tiferous galena, barite and more seldompyrite and sphalerite.

The Trillssic peneplanation of the Cam­brian terrains and related ore formation bysupergene deposition has been investigatedin the past and valuable results have beenpublished recently by another Author (BONI,1979).

Thus, the primary geochemical anomaliesof lead, zinc, iron, and barium in the Cam­brian sedimentation gave rise, by severalphases of tectonic and weathering reme­bilizations, to ore bodies of different age,structure and ore-association according to thegeological evolution of the host rocks.

Another important aspect of the Paleozoicgeology of Sardinia is the relationshipbetween the South-Western belt (Cambrian

THE PAlEOZOIC M£TAllOGENIC EPOCHS OF THE SARDlNIAN ETC. 221

'QLESIl!NTE ....RC'DANO-S...Rll ....US 8"'R8"'O'''' QEN"",RaENTU

-"

~ •§ •M ,~~ ,!§El ,lm •gj ,

>' ~ ,~

Fig. 18. - Pre-hercynian palcogcographic and melallogenic scheme of central and southern Sardinia. ­1= Pre-cambrian basement (?); 2 = Porphyroids; 3 = Cambrian sequence; 4 = Uppcr-cambrian roLower-ordovician sandstones and phyllilcs (<< Solann,. and .. S. Vito,. formations); .'5 = «Porfidi grigie bianchi »; 6 = Middle-ordovician conglomerales, sandstones. phyllites and limestones; 7 = Melan~e­

sites and tuffs; 8 = Silurian-Devonian black-shales, phylliles and limestones; 9 = Lower-carboniferous (?)phyllilcs (<< Poslgodandiano» formal ion); 10 = Strati form deposits of Zn-Fe and/or barite; 11 = Pb-Znsulphides bodies; 12 = Pb (Ag) and harite mineralization of silica horizon along the Cambrian-Ordo­vician unconformity; 13 = Ordovician-Silurian ore bearing horizon.

from a geological and ore-deposits point otview_

Around the Cambrian platform the Or­dovician and Silurian sediments and vokanicsare rather reduced; the strata-bound ore­deposits in Ordovician-Silurian terrains andvokanics, even if present, seem less signi­ficant for volume and spatial continuity.

The mineralizalions such as Perda S'Oliu(SOLA, 1967; MAR 1Nl and MElIS, 1981),S. Leone (VERKAEREN & BURKHARDT, 1970;VERKAEREN & BARTHOLOME, 1979), somestopes of Rosas, all located in the South­Western belt, show ore paragenesis rathersimilar to those of central Sardinia; theyconsist of galena, sphalerite, pyrite and/or

magnetite and minor amounts of chalco­pyrite, fluorite_ The presence of metals suchas Cu and F is witness 10 the influence ofmineralizing processes in which the volcanic~ctivity begin 10 play a certain role; thesemetals in fact are almost absent in the orebodies hosted by the Cambrian carbonaticplatform (PADAlINO et al., 1978)_

The geological sequence of the centralSardinia shows terrains from upper Cambrian(<< Arenarie di S. Vito» and «Solanas»)formations (BARCA and MAXIA, 1982) toLower-carboniferous (<< Post-godandiano »)formation with a prevalence of clasticsedimentation and volcanic activity; thecarbonatic facies are reduced 10 thin Ordo-

222 C. GARBARfNO, S.M. GRILLO, C. MARINI, A. MAZZELLA, F. MELlS ET AL.

vlClan and Silurian lenses and Devoni:.mplatform, strongly folded, faulted and eroded.

The stratiform ate-deposits, in theSouthern (Sarrabus) as well in as the centralarea {Barbagia}, ate located above the thickvolcanic cycle of Ordovician-Silurian age;this cycle is characterized by an increaseof basic rocks from South towatds Northand namely from Sarrabus (Rhyolites) toBarbagia-Ogliastra (Andesites). This modi­

'lication of volcanic chemism affected thecomposition of ore-associations; in fact Cu isfound mainly in the narrow belt NW-SE ofthe Barbagia (Funtana Raminosa), accordingto the volcanic occurrence of andesite, whilemainly Pb-Zn-Ag (and Sb, As) seem to berelated to more acid volcanism, even if thegeochemical trend of this volcanism mustbe analyzed yet.

Thus the spatial zoning of mineralizationmay be in agreement with the different paleo­margin volcanism; this relationship of theore associations with the geodynamic envi­ronment is well known in many ore districtsof the world (PELLISSONIER, 1972; SILL!­TOE, 1972; Bats et aI., 1976; PALOMERO,1977; ]ANKOVICH, 1980) but it must beanalyzed in detail and by further researchin the Sardinian mining district.

The Hercynian metalIogenesis confirms thespatial zoning of the preceeding mineraIi­zations, substantisting some heredity pheno­mena from the Pre-hercynian basement tothe Carboniferous-Permian magmatism.

The most important Pb-Zn hydrothermaldistrict occurs in the Arburese, not far fromthe Cambrian platform; the F mineralization(with minor amount of Ag, Pb, Zn, Ba) occurinstead in Sarrabus where the Ordoviciansequences is very thick. In fact previousstudies threw some light on the role of Fin the Paleozoic sequence; the fluoridecontent increases strongly in the transitionfrom Cambrian to Ordovician slate and~andstones (MAZZELLA et al., 1979); thisIOcrease may be due to the beginning ofPost-cambrian volcanic activity in the «in­ternal basin» and the Hercynian magmatismmight utilize the F content in the Ordovician·Silurian rocks giving rise to the importantveins of Silius, M.te Genis, etc.

The Cu-Mo mineralizations of the Oglia­stra finally, seem to be located along the

border of the old margin, near the Ordovicianandesitic belt. In this belt the most im­portant Cu mineralizations of the Sardinianmicroplate occur, some skarns with Pb-Zn­Cu-Fe mineralizations are included in theOgliastra granitoid rocks; these skarns mayderive from fragments of mineralized Ordo­vician-Silurian limestones, as can be inferredfor the Cuccuroni bodies (DEMURO et aI.,1963) near the Arzana village.

Thus from the first merallogenic epoch,the Cambrian one, subsequent mineralizingprocesses modified rhe preceeding metal­logenic scheme, but each mineralizing stageseems to be, more or less, connected to thepreceding ones.

These researches have been ClIrried out with thefinancial support of the CNR (Consiglio NazionaJedelle Ricerche) in the ambit of the «GeodinamiCll »projecl, paper n. 528 (U.o. 422 directed by VIOLa);a special gram has been provided by the EuropeanEconomic Comunity in the ambit of the CRESTprogramme.

SELECTED LITERATURE

The literature on Ihe Paleo7.oic terrains and ore­deposits of the Sardinia is rather wide.

The Authors named only Ihe more recem papersor those directly connecled with the IOpic of thepresent JXIper.

This literature is here divided in four pans:the firsl three are grouping respectively the refe­rences about the metallogenesis of the Cambrian,Ordovician-SiJurian and Hercynian epochs. The lastpart is devoted to the general papers regardingregional, national and international references.

Rererence~ or Ihe Camhr;an mClallogenie epochin Sardinia

ANGELUCCI A. (1970) - Su a/cune stru//ure sedimen­larie nella formazione delle arenarie del Cambricoinferiore dell'lglesiente (Sardegna Sud·Occiden·lale). Rend. $em. Fac. Scienze Univ. Cagliari,40, 3-4, 1-27.

AR,THAUD F. (1963) - Un example de lecloniqu~s

superposees dans le paJeozoique de l'lg1esiente(Sardaiglle). CR. somm. Soc. Gee!. de France,Fasc. 3, 303 pp., Paris.

BI::NZ ).1'. (1964) - Le gisemenl plombo-zincifered'Arenas (Sardaigne). Travaux du Lab. Sciencesde la Terre £cole des Mines, Nancy, 126 pp.

BaNI M. (1978) - Considerazioni paleogeograjichesu alcune minerali:r;:r;azioni a solfuri della Forma·zione di Gonnesa (Cambrico inferiore edlla Sar­degna). Mem. Soc. Geol. It., 19,713·720.

BaNI M. (1979) - Zur Piilaogeographie, },fineralogieund Lagersliiuenkunde der Paleokorteru in Sad­West Sardinien (lglesiente _ Sulcirl. Diss. Univ.Heidelberg, 260 pp.

nlE PAl.EOZOIC METALLOGENIC EPOCHS OF THE SARDINIAN ETC. 223

BoNI M., MARlNELLI P. (19801 . Analisi slrati·,rajico-struuuralt dt/la tona d/ BuUt"u (/glt·sitllu) toll parlko/art riguardo alia posiuolltdt/lt mmtraliuavolli ntlla lormauont di GOII'ntsa. Boll. Sot. Gcol. It., 99, 3,...5'.

BoNI M., CANDIN A., MAllNACCl P., STA.:'<lZ10NE D.(1981) - A p4ltolll'lronmtntal stdimt"tological 4"dgtot:htmicll1 4pproacb 10 tht Go"ntSll Formatioll(l.£Il«I'" Cambri4") (BuUtrTU arta, SW Sardillla).JAS. 2nd EUR Mtg. Bologna, AbSU''lI("I, 14-16.

BIUSCA C., OESSAU C., jENZEN N.L. (196.5) ­L'oriynt dri ,iaC/menli di vneo t p/ombo nel·l'lglnitnle aUII luct della tompositione isoJopielldtl/o to/lo nti sul/uri. Symp. Probl. CeominC:r.l.riSardi, Ass. Min. Sarda, Cagliari, Iglc:sias, 1·}O.

BMUSe... c., PIETTI S .. TAMBUlI.l ..... 1 D. (1967) .u mineralhuuoni barilOSt ddla eoptrtura JiMOllle Sa Bagattu (lg/tsias . Sardegna). Rt5. Ass.Min. Sarda, LXXII, 7, 89·106.

DRuseA C., DESSAU G. (19681 . I giacimenlipiombo·tincile'; di Sail GiOIJ"1I/1i (/glesias) 1Ie1qlladro della geologia del Call/brieo Sardo. L'ln·dumia Minc:rarill, 19, 1·.53.

BRuseA C., PRETTI S., TAMIIURRINI D., Toceo S.(1971) . Su a/cune mintralitt/.ltioni a barilt tgalena insedialt nei karst del penep1lmo ercinico(iglesittlfe meridionalt . Sardegna). Rc:s. Ass,Min. Sarda, LXXVI, 5, 1·2.5. .

CAIANNA.'lTE c., CocOZZA T., D'AIGEN10 B., SAL·VADOII I. (1974) - Gmllferi deposhionaJi e dia­genttici ddla • dolomia rigala. del Cambrieodell" S"rdegna. Rc:nd. Sot. hal. Mineral. Pt1wl.,30, 2, 11.59·1173.

CAIMIG.'<IANI L., CocozZA T., GANDIS A., PElTU·SATI P.e. (19821 . lineamtnti dtfta gtoiogia dtl·l'lg)esienu • Sulcis. Cuida aUa gcoklsia de:1 Pa­Ic:ozoico "rdo. Guide: Geologiche Rcgionali, Sot.Geol. h., ,,..n.

CocoZZA T. (1969) - Slumpings e brectt inlra/or­mllt/onali ntl C"mbritlno mtdio dtl/a S#rdtgn#(nolll prdimillart). Boil. Soc. Gcol. It., 88, 71-8Q.

DI CoLaEITAUlO D. (196') . OsstrlJt/voni geolo­gicht-mintrark t gtntlieht sui gi4timtnlo dipiombo e tineo di Pira·Roma (Bullerru . 5ar­dtgnlll. Symp. Probl. Geominer. Sardi, Ass. Min.Sarda, CaRliari.Jglt5ias, 41·'4.

FAN.....I S., GANDIN A., GJILLO S.M., LIPPI F.,MAltRAS G., SALVADOR I A., Tocco S. (1981\ .Piaua/orma earbonatica eambrica della Sardef.llIJSud-(Jctidtnlale; sedimenlatione e depositioni me·talli/ere. Mem. Soc. Geol. h., 22, 123·iJ7.

GANDIN A., PADALINO G., TaceD 5., VIOLO M.(1973) . Un tstmpio di depositione strali/orllledi bariu nt/la • dolomia rigala. dtl Cambritodefla S"rdtgna lud-(Jttidtntale. TtntatilJ() di cor·rtlazione Ira I'ambiente di stdimentazione t laprecipit"tione del sol/ato di bario. (Nola primal.Boil. Soc. Ccol. h., 92, 329·354.

GANDIN A., PADALlNO C., VIOLO M. (1974) . Corrt·lalion MlliMtn stdimenl"tiOIJ environmtnl andore-prospecting. Sedimentologic,,1 "nd ort·gentsisIllIdies 0/ Cambrian .. tlrtlJllrit. and • dolomiarigalll. /ormlllions (SlIrdinu . Ital,); dtpolilionand tOnttnlration 0/ b"rite in IIn tllllporitieenvironmenl. Rend. Sot. Ital. Mineral. Pelrol.,30, 2'1·330.

JUNKEI B., ScHNEIDEl H.H. (1979) . L'in/rKlIlff.

briano del/a Sardegna sud·octidenlalt. Mem. Soc.Geol. It .. 20, p. 461.

MAJCELLO A., SALVADOII I., ZUFF.....OI P. (196'1 .Con/1ibulo aUa ronosttn;:a dtl Glmbrico Sardo.Nota 111. If f,/at1mtnto di Sedd"s AfoddiuiJ.Symp. Probl. Ceominer. Sardi, Ass. Min. Sanb,Cagliari-lglc:sias, 83·9.5.

MAJCELLO A., VALEJA R. (196') . ContribulO aUIlconosttnta dt/ umbrico sardo: nota IV. LJ tOil"

dtl Marganlli. Symp. ?rob!. Gcominer. Sardi,Ass. Min. Sarda, Cagliari.lglc:sias, IJ}.. I.54.

Me ~l00IE H.j. (1969) . Inftuence 01 strl«tureson IM bilst mttal deposits 01 soulbliMst Sardi"ill,Italy. TOllns. Insl. Min. Metall., Sot. B, 78,135-147.

PADALlNO G., PJF.TTI S., TAMBUlJlNI D., Tocco S.,Uus I., VIOLO M., ZUFFAROI P. (1973) . Ort·deposition in karsl lormation wilh examples IromSardinia. Ore in sediments. Ed. by AmstUIZ andA.]. Bemard, I.U.C.S., scrie A, 3, 209-220.

POLL j.j.K. (1966) . The geology 01 Ihe Row·Tt"aseo area (Sulds SOlllh-Sardinia). Lcidsc Geol.Med., 35, 117·208.

PRETTI S.. , SALVADOR! I. (1965) . Conlributa ai/<IeOl1ostenta del CambrieO-Iardo: nota IV. La tonadi Candiauus. Syrnp. Probl. Geominer. Sardi,Ass. Min. Sarda, Cagliari.lglc:sias, 97·132.

PJETTI S., TAMBURRlNI D. (1967) . u mineraljz·totioni di Monte Arru Sa Gru)(i (Sulcis sellen·trionalt - SlIrdtgna). Res. Ass. Min. Sarda, 72,6, 97·140.

PRETTI S., TAMBUIIISI D. (1968) . u mintralizu·riDni a barite deUa zona tU Corol'l4 Sa Craba,5trT" LMrdaf,u (Sukis-$lIrdtgna). Res. Ass. Min.Sarda, 73, 7, 13·.50.

PlETTI S., SALVADOII I., VIOLO M. (1978)· A newIIPP10lJeb to tM in~sligalions 011 lurj/ "nd ore­bodies in umbrian ellrbonale rocks 0/ SlIrdini:J(It"l,). Res. Ass. Min. Sarda, 1,67-85.

SALVADOII I., ZUFFAlDl P. (1961) . 11 f,iacimenlOdi Monle Y"mllra (Sardegna). Res. Ass. Min.Sarda, 6.5, 7, '3-87.

TAMBUlJlNI D., VIAS I. (196.51 . Conlributo aliaconosttnto dellt minmuiwnioni dd CllmbricoSardo; la .onll di M,te Flatta. Symp. Probl.Gcominer. Sardi, Ass. Min. Sarda, Cagliari.Jglc:­sillS, 293·314.

TAMBURRINI D.. VIOLO M. (196.5) . Un esempiodi deposito suptr!.enieo di galena. Rc:s. Soc. Min.SlIrdll, 70, .5, 3·1.5.

TAMBURR1Nl D .. VIOLO M. (1965) . II giadmenlOa barilina di Monu &reg,a . Monte Areau (lglt.JienU-Sardegna). Ric. ScL, 35, lI·A. 814·848.

Uus I. (1951)· Studi suI/a mineralina.ione di SaDuebessa. Periodiro di Mineralogia, XX, 1·2,117·134.

VALERA R. (1967) - Conlribulo affa conosttntadtll'tuolutione ultonic" deffa Sardegna. Res. Ass.Min. Sarda, 72, 6, 3·9'.

VIOLO M. (196.5) . ConlribulO al/a eonOSUlJlJI dtlCombrieo s"rdo; III tonll di AUe Onixtddu .M.1t Uda. Symp. Probl. Gcomi'ller. Sardi, Ass.Min. Sarda, Cagliari.lglc:sias, 191·227.

VIOLO M., ZUFUJDI P. (l97l) . Gtoehtmi~1I1 mttaldillribution in tM Cambri"n s,sltm 0/ S"rdinia(llal,) and Ihtir P"/togtogr"pbic control. Prx.IMA·IAGOD Mtttina, J, 160-162.

224 C. GARBARINO, S.M. GRILLO, C. MARINI, A. MAZZELLA, F. MELlS ET AL.

VIOLO M. (19n) - lA ~ona/ila nti glacinunli mtt"l·li/tri, una cO'UtgUtnXll dtUt variationi fJII/~

ttotrafuht durantt la stdimtntationt t I" dia;;t­ntsi. Rend. Soc. hal. Mi~1. Petrol., 30, 1109·IlJ2.

ZUFFAIDI P. (l9'l) . llvacimtnto pio",bo-tinci/~o

di "Ut Agruxiau. Conlribulo tdlo studio dti V<l'cimtnti r ouidati drll'lgltsitnu. Industri. Mine­raria, I, 1·12.

ZUFFAlDI P. (1%') • Slrutlurt stdimtnt"rit in Ill­lunt minu"liUllrioni ptdtozoitht sardt /I soi/uri.Rend. An. Min. Sarda, " )·21.

ZUFFAJ.DI P. (196') - Contributo /lUll conOSctnXlldt/lll min~"liua:tiont dt/ ymbriCO urdo. NOlllVI. RillHunto td int~prtt"zioni provvisork dt/ltconOSctnu anullli. Symp. Probl. Geominer. Sardi,Ass. Min. Sarda, Cagliari.Iglesias, 1-9.

Referenee. of lhe Ordovie:ian-Silurian metal­IOIJenie epoeh in Sardinia

BAItCA S. (1981) - Conlributo alia slraligrajia delSiluriano-Dtvoniano del Sllrrabus (Sardtgna sud·oritntalt). Boil. Soc. Gool. h., lOO, 8'-92.

BAltcA S., MASCIA M. (1982) _ AHtllo stratigrajicot ttttonico dtl Paltozoico dd Sarrabus acciden­talt. Guida alIa geologia del Paleozoiro Sardo.Guide Geologiche Rcgionali, Soc. Geol. Jr., 87·93.

BECCALUVA L, LEOSE F., MACCIONI C, MACCIOT­TA G. (1981) - Pttr%gy and t«toni, sttting0/ tht Palto~oic basic rocks from 1,{tsitntNulds(Sardini", Italy). N. Jb. Miner. Abh., 140 (2),184-201.

C.UMICNANI L.o CoI.T£CCI G., DESSAU G., Du­011 G., 0Gc1AN<! G., PEI.TUSATI P., SAlTTA M.(1978) - TIN IInlimonJ "nd Tungsttn dtposits0/ Vil/4stdto in soutkasttT1l Sardinill IInd itsrtlationsbip witb Htreyn;an t«tonICS. Sehllo·eiz.Mineral. Pctrogr. Min., ~, 1/2, 161·188.

UI.MIG.'lANI L., MINZONI N., PEI.TUSATI P.C. (1982). Lintllmtnti gtoiogid principali dtl Sarcidano­&rba,ia di Brlvi. Guida alia gcologia dd Pa­leozoiro Sardo. Guide geologiche regionali, Soc.Gee!. h., 119-125.

DEl-IURO P., UIAS I., VIOLD M., ZUFFAl.DI P.(196') - Considtrazioni gtnnicht sui ,iadmtnlisardi a sol/uri; nota 2". Alcuni giaci",tnti dtl/a~ona di Anana (Ogliastra). Symposium Ass. Min.Sarda, Cagliari.Iglesias, 343·368.

DESSAU G. (1937) - Studi sulia minitra di FuntallaRaminosa. Per. Miner., 8, 2, In·21'.

FRANCESCIIELLI M., MEMMI 1., RtCCI C.A. (1982) _Zontograjia mtlamorjica dt/la Sardtgna stUtH­trionalt. Guida alla goologia del Paloo~oico sardo.Guide geologiche regionali, Soc. Gool. h., lJ7-149.

GAl.BAItINO c., MACCIO~1 L., MI/lo'ZONI N., PADA­LINO G., Tocco S., VIOLD M. (1980) - TIN stra/a­bound copptr-ftad-tinc mintralization 0/ tM Sar­dinian microplatt ([taly). Inlern. Symposium«The European Copper Deposiu., S.G.A., Bor(Yugoslavia), 2'1-260.

HALL A. (1975) - Rtgional variation in lht crustalabund/lnct of minor dtm~nts: ~vidtnct from tINgranitts of Sardinia. Miner. Maprine, 40,29}'3OL

M,U.INI C., MELlS M.F. (1981) - U mil'l~aliWl­rioni strati/ormi a solfuri misti d~lIa strit fJIIlto.zoic" dd Flumintst (SardtgntJ sud-«ddtnttdt).

Nota J-. Rend. Soc. h. f.,lin. e Penal., 37,'41·"'.

MAZZELLA A., MELlS M.F., POI.CU R., RIVOLDI·NI A., VIOLD M. (1979) . lA distributiont g~cbimica dt/ /luoro ntlia StqurnXll ordovidllno­si/uriana dtlfll Sardtgna. Ass. Min. $arda, 1,39-62.

MEMMI J., BAIlCA S., U.I.MIGNA.'l1 L., eooo-LZA T.,F......NCESCHEI.LI M., GATTlGUO M., GHEZZO C,MINZONI N., NAUD G., PEIlTUSATI P.c., Rlc·Cl CA. (I982) • lImagmat;smo prt-.nCI1lICO ddlaS/lrdtgna_ Guida alia grologia del Paleozoicnsardo. Guide geologiche regionali, Soc. Geol. h.,157·164.

MINZONI N. (197') - lA s~it dtllt /ormationi pa­Itozoicht a Sud dtl Gtnnargtntu. Boil. Soc. Geol.It., 94, 347·36'.

PADALINO G., Tocco S., VIOLO M. (1978) - Prt's~nt

hypothtsis on tht corrda/ion bt/wttn paltogt,,"graphic environmtnu and ort deposiu. Exampltsfrom Sardinia Minin, dimict (1tal)l). Mem. Soc.Gool. It., 19, 721·72'.

SOLA C (1967) • Studio gtogiadmentologico dd/alona di Prrda S'Oliu. Rend. Assoc. Min. Sartla,31, 11-18.

VAI G.B. (1982) • fasi di «riJting ..; nl/ovi dalistratigrajid t constgutnu paefogtograjicbt ntIPaltozoico in/triort. Guida alla geologia del PJ­leozoico sardo. Guide geologiche regionali, Soc.GeoI. It., 19)·19'.

VEIlKAEI..EN J., BUI.CKIIAlDT G.E. (1970) - us sltarnsa magnttitt dt S. !Lone (Sal'daig1lt SW). C.R.Ac. Se. Paris, 270, 3-6.

VEJ.KAEJ..EN J., BAl.rnocoME P. (1979) - Pttrol01.Y0/ the S. !Lone m/lgnnic sltarn dtposit (SW Sar­dini/l). Econ. (;eol., 74, 'H,(,€,.

VIOLD M. (1966) - Conlributo tdu conosctntfl dtigiadmtnti slratoidi polimtta/lici in arta mtta·morfica. If giacimrn/o di Sa !illa (S. Vito, Ga·gl;ari - Sardtgna). Res. Ass. Min. Sarda, 8, 1-110.

ZUCQ-IETTI S. (19'8) - 11 C/lrllUtristico dtposito <I

sol/urati di Piombo t kstnico di Bacu Locd(S4rdtgna). Boil. Serv. Geol. h., LXXX, 2·3,275·301.

Referenee, or the Hcreyni:m mclallOlenie cllocltin Sardinia

BAKCOS F. (1968) . OsstTva:ioni gtologico-mintraritJul giacimento a molibdtnilt t wol/ramitt diPerda Maiori (Sardt£na Sud-Oritntale). Res. Ass.Min. Sarda, v. 72 (VI), 5-66.

BRIGO L., FERRAIlIO A., MARCCELLO A., NATALE (1.,OMENETTO P., PAOAlINO G., SALVADOR! 1., Toe­CO S., UIlAS I., VALEI.A R., ZUCCIIETTI S., ZUl'­FAROI P. (1982) - Gius jilonitns Pb, Zn, F, Bade blUSt umplralurt du domaint varisqut d'Ita­lit. BuU. du BRGM (2), II, 2, pp. 19'-206.Symposium Orle.n$.

BIlUNETTON P., BIlINET F., CocIlEME J.j., OaSINI J.,VELLUTTINI P., VINcv".,. P.M. (I976) - Prtstnud'unt str"cturt .nu{airt tn Gallura (Sarda;gntstpuntriontdd. CR. Aoo. Se. Paris, I. 282,2127-2130.

U.1I01 R, CoSOI.O A., MASSOLl·NoVELU R. (1970)­lA mintr<l/iwtiont a molibdtnitt di MonuS'Abbaf.l/na. Rend. Sem. Fac. Se. Univ. Ca&liari,v. 40 (Ill_IV), )73-424.

THE PALEOZOIC METALLOGENIC EPOCHS OF THE SARDINIAN ETC. 225

CABOI R., MASSOLl-NoVELLl R., SANNA G. (1978) .La mineraliwnione a molibdenile di P.la SII Sei­nargiu. Rend. Soc. It. Min. Peu., 34 0), 167-186,

CAVINATO A. (1972)· lA fluorite in Sardegna. Mem.Isl. Geo!. Univ. Padova, 34 pp.

CaNTI L., MACCIONI L., PiLl P. (1981) _ Pelrologiadel nue/eo cristallino di Villanova Slrisaili (Sar­degna centro orientale). Per. di Min., .5, 283·304.

DERIU M., ZERBI M. (196.5) - Notizie preliminarisul rilevamenlO geopelrografico e sulle ambienta­zioni pelrogeneliche relalive al giacimento JiMolibdenite di M.te Mannu (Oschiri). Symp.ProbJ. Geomin. Sardegna, Cagliari, 381-393.

DESSAU G. (19.56) - Cenlli sui giacimenlO dilungslmo e molibdeno di Perda Maiori, Boil.Soc. Geo!. It., 75, 239-2.50.

f'IORI M., GARBARINO C, MACCIONI L., PADALlNO G.,VIOLO M. (1983) - Evoluzione delle mineraliua·zioni metallifere della Sardegna (Ilalia) in lun·zione dei paramelri geodinamici. Industria Mine·raria, 3, 3342.

GHEZZO C, GUASPARRI G., SABATlNI G. (1972)Lineamenti geopelrologici del cristallino sardo.Lt! plulonili e la loro successione negli eventiinlmsivi. Miner. Petr. Acta, 18, 20.5-234.

GHEZZO C., GUASPARRI G., RICCOBONO F., SABA·TINI G., PRETTI S., URAS S. (1982) _ Le mine­raliuazioni a molibdeno associate al magmatismointrusivo ercinico della Sardegna: i rapporti conle plutonili e i lenomeni di alterazione-minera_lizZilzione. Rend. Soc. It. Min. e Pelr., 38, 1,133-145.

GHEZZO C, M£MMI I., RICCI CA {I982) _ Legranuliti e le ee/ogili della Sardegna nord-orien­laic. Guida alia geologia del Paleozoico sardo.Guide geologiche regionali, Soc. Geo!. It.,151-156.

CUUPARRI G., RICCOBONO P., SABATINI G. (1982)- Considerazioni sul magmalismo inlrusivo erd·nico e /e connene mineralinazioni in Sardegna.Rend. SIMP, 38, 1, 488-490.

MACCIONI L., PADALlNO G., Tocco S., VIOLO M.(1979) - 1 giacimenli dellipo «porphyry copper»:una grande prospelliva per i melal!i di base.Ipolesi e pr.mibilila in Sardegna. Eme Min. Sar­do, 1/2, 45-54.

MASSOLl-NoVELLl R. (1973) - CantribUIO allo stu·dio generico delta/co di Orani (Nuoro). Nota I":il giacimento di Sa Malta. Ass. Min. Sarda, 74,9-39.

MELlS M.F., SANNA M. (1978) - Le mineralizza­zioni piombo-zincilere del campo fi/oniano diArghenlaria. Guuurra -Su Ergiolu (Lu/a, Sarde­gna nord-orientale). Ipotesi sui meccanismo dilormazione e di rimohiliuazione dei melalli delcic/o magmatica ercinico. Atti Fat. di Ingegneriadi Cagliari, 2, 11.5-135.

NATALE P. (l%9) - Il ?,iacimento di /fuorite JiSi/ius nel Gerrei. Boil. Ass. Min. Subalpina,6, 1-3.5.

SALVADOR( I. (19.59) Segnalazione di una mani·leslazione a molibdenite nel/a zona di Villacidro.Res. Ass. Min. Sarda, 63, V-VI, 5·27.

SALVADORI I., ZUI'FARDI P. (1960) . ii campo filo­niano di Sos Enallos. Res. Ass. Min. Sarda,65, .547,

SALVATORI 1., VALERA R. (1972) - Principi erne­lodi di ricerca delle mineraiiuazioni /fuorilic()o

barilicbe ne! Sarrabus (5ardegna sud-occidental<).Ass. Min. Subalpina, 4, 533-548.

URAS I. (1956) - l/ giacimento /luorilico di Mon­reale. Per. di Mineralogia, 20, 1·42.

VENERANDI I. (1968) - Il giacimento a molibdenitee wollramile di Perda Maiori. 1st. Lombardo(Rend. Se.), A 102, 678·716.

ZUCCHETTI S. (1965) . Segnalazione di un sislemadi ji/oni di lormalinite nei dintorni di Busachi(Cagliari). Res. Ass. Min. Sarda, 6, 3-11.

ZUFFARDI P. (1948) - 11 giacimenlo piombo-zincilerodi Monlevecchio (Sardegna). Ani .. CongressoMinerario haliano, 17 pp.

ZUI'I'ARDI P. (1953) - Primi risullati delle ricerchesuI/a prolandilii delle mineralizzazioni e suWim.basamenlo granilico di Monlevecchio. Res. Ass.Min. Sarda, .58, 5-39.

ZUFFARDI P. (1958) - 5u una nuova segna/azionedi cassilerile in Sardegna e mlle presenze ditracce di slagno in alcuni adunamenli idroter­mali sardi. Res. Ass. Min. Sarda, 63, 27-38.

General literature

AMSTUTz G.C. (1958 b) - Syngenetic zoning inore deposits. Proc. Geo!. Ass. Con., It, 95-113.

AMsTuTZ G.C (1962) - L'origine des giles mi­neraux concordanls dans les roches sedimenlaires.Chron. Min. Qune Mer Rech. Miniere, 308,115·126.

AMSTUTZ G.C. (1963) - Space, time and symmelryin zoning. Symp.: «Problem of post·magmaticore-deposition *, Prague, vol. I, 33·37.

AMsTuTZ G.C., RHAMooliR P., EL BAZ F.,PARK W.C (1963) - Diagenelic behaviour 01sulphides. Develop. in sedimentology, 2, 6:;-90.

AMSTUTZ G.C (1971) - Observational crileria lorthe classificalion of Mississippi Valley - Bleiberg- Silesia Iype of deposits. Proced. of the 2nd Int.Symp. on the Mineral deposits of the Alps,Bled, 207-21.5.

BARCA S., CARMIGNANI c., COCOZZA T., GHEZZO L.,MINZONI N., PERTUSATI P.c., RICCI CA. (1981). Geolraverse B in Sardinia: straligraphie cor­relation forms. IGCP Project n . .5, Newslett~r,

3, 7-2l.BATHURST R.G,C. (l98l) . Carbonale sedimen:s

alld their diagenesis. Dev. Sedimem., 12, 620 pp.,3.59 figs., Amsterdam, Elsevier.

BELLlENI G., SASSI F.P. (198l) - New chemicaldata and a review on the SOlllh A/pine «Pre­Hercynian rhyo/ilic plateau * in the eaSlern Alps.ICCP Project n. .5, Newsletter, 3, 22-28.

BEWV A.A. (1981) - The main development slag;:sand epochs 01 tectonic activity in Ihe Mediter­ranean - Alpine lolded area in Pa/eozoic. IGCPProject n. 5, Newsletter, 28-35.

BENCINI A.• TURI A. (1974) - Mn distribulion illthe Mesozoic carbonale rocks Irom Lima Vall<'yNorthern Appennines. Jour. Sed. Petrology, 44,774-782.

BERNARD A.}., LELEU M.s. (1967) . A propos dela concentration residuelle de la blende el de lagalble. CR. Accad. Se. Paris, I. 26,., 729·732,Paris.

BERNARD A.]. (1971) . Melallogenic processes 01intra-karstic sedimentation. Ore in sediments,VIII 1nl. Sed. Congr. Heidelberg, 43-.57.

226 C. GARBARINO, S.M. GRILLO, C. MAR1NI, A. MAZZELLA, F. MELtS ET AL.

Bols j.P., PoUIT G. (1976) - us miniraliutionsd~ Zn (Pb) d~ l'ilntidinorium d~ PI",~!iIt~:

Iln ~x~mpl~ d~ vstl1unts hydrotwmllux tt sldi·mrntair~ assodis au volCtllfism~ dans It PaU~

zoiqur dts Pyrinis c~ntral~s. Bull. BRGM, 6,'43-S68.

BUIINHAM CW. (l962)· FlJCits and ty~s 01 hydro­IMrm1l1 II1trration. Econ. GeoL, v. '7, 768-784.

BUIT D.M. (1977) . Mineralogy and ~trology 01skarn drposits. Rend. Soc. It. Min. PelT., H,8'9·873.

C~NN J.R. (1970) . Rh, Sr, Y, Zr and Nb in someocean-fluor basaltic rocks. Earth Plan. Se. Letters,10,7-111. .

C,4.Il,4.NN,4./I.'TE G., CocOZZ,4. T., D'ARGENIO B, (1981). Ttetono-s~dlm~ntary tr~nds and pal~og~ography

01 SlIrJiniil. DurinR lau Pre<ambrian and Cam­brian. IAS. 2nd Eur f\!lg. Bologna. 227-2}Cl.

CAIII<oUC,'l,4.NI L., CocozzA T.. l\h:,w:-':I N., PUTU­SUI P.c., RICCI C.A. (1979) . E fa Corsica ilutrop.usr della CIIUM "dnica in SIITdegnll? Mem.Soc. Geol. h., 20, 47-".

UIIMIC,'lANI L., Cocozz,4. T., GHEZZO C., PElTU·SATI P.C., Rlccl CA. (1982) - Lineammli dtlbilummlo sardo. Guida alia geologia del Pal~

zoico sardo. Guide Geol. Regionali, Soc. G«al.h., 11-23.

CUlLlNGAR G.V., BISSEL H.}., F,4.l1l81l1DGE R.W.(1967 a) . Carbonate rocks: origin, occurmu andc1auification. Dev. Sediment., 9A, 471 pp., HIfigs., Amslcrdam, Elsevier.

CHll.ING"'R G.V., BISSEL H.J., F,4.1R8RIDGE R.W.(1967 b) . Carbonau rocks: physical and chtmicalasprcls. Dev. Sediment., 9tl, 41} pp., 80 figs,Amslerdam, E1sevier.

Cocozv. T., JAC08ACCI A., N....ol R., S...LVADO.I 1.(1974) - Scht'ma slraligra!iro Slrutluralt del Mas·siuio SilTdo-Corso t mtnerogmui i" Sardtgna.Mem. Soc. Ge-ol. 11., 12, 85-186.

Cocozv. T., MINZOSl N. (1978) . OmrllaUo"i suillulcanismo JHl!roWlCO Silrdo. G.L.P. 2, G.B. Vaicd., 2'·29.

Cocozv. T. (1979) . TM umbri4n 01 Sudinta.Soc. Geol. h., 20, )63·187.

CooK P.}. (1973) - Supratida/ tnllironment a"dgrochtmistry 0/ somt reunU dolomitt conC1~

lions, Broad Sound, Quunsland, Austrafit. Jour.Sed. Petrology, 43, 998·IOI\.

D'AMICO C. (1974) - Hereynyan plutonism in IhtAlps. A report 1973-1974. Mem. Soc. Geol. 11.,l} (1), 49·118.

DE8RENNE F. (1964) . Arthtocyata conlribution ,jl'ttud~ dts launes eambritnne du Maroc, dtSaTdaignt tt d~ Franu. NOles el Mem. Serv.leol. du Manx, 179, 2M pp.

DE LA ROCHE H., LETEUIEII J., GRAND CLAUDE P.,MAIOIAL M.(I980) - A climificiltion 0/ volCilnicand plutonic rocks usi"g R.,-R, diagrllm IInd majord~mtnt lI1Ia/yJts. III rtliltionships Wilh nom~n·ellltuT~. Olem. (;eo!., 29, 183-210.

DI£TIlo-I RV., HOBBS C.R.B., LoWM WD. (1%3J- Doiomiliu/ion inu"upt~d by silid!ication.Joor. Sed. Pelro!ogy, }) (3), 646-663.

DJ SIMPUCIO P., FEU... IIA G., GHEZZO C, GU...·SPAUI G., PELLlZZER R., Rlcel CA., RIT... F.,S,4.8ATINI G. (1974) - Il mttamorfifmo t if mllg-

millismo ptJltO~oieo ntflil S4rdtgna. Rend. SIMP,}Cl, 979·1068.

DuSH"'M J.B., QLSON E.R. (1978) . Diagentt;cdolomiu lormlltion rtfl/Ud 10 PillttJZ:oie pIIfw­grtlph, 01 tht' CordiU"an mlogw-sindint in Nt·1JIId1l. G«alogy, 6, 'S6-SS9.

ESTEBAN f\hTF.o C. (1976) . VadoJt pisoliu ilndcalicbr. Geologic Notes, 2048-20'7.

FLOYO P.A., WINCHESTER JA. (197') - Mag'llat),pt ilnd !tetonic stt/ing discriminlltion usingimmobilt! elements. Earlh Planet. Se. Ullers, 27,211-218.

FRIEDM"'N G.M., S,4.NDERS J.E. (1967) . Origin andoccurtnu 01 dolostone. Dcv. Sediment.,Amsterdam, Elsevitr.

Furz P., K,4.TZ A. (972) - Tht sodium distribulion01 dolomilt crystals. Chem. Geol., 10, 237·241,AmSlerdam.

G ... LKIEWICZ L (1967) - Gtnnis 01 Siltsilln era·couiiln Une./tild dtposill. MoOO£raphy 3, &un.Ga:J1., 1S6-168.

G ....'lOIN A., P,4.o,4.ur;o G., Tocco 5., VIOW :\1.(1974) • Corrtfillion ~tux~n stdimtntiltion en·llironmt!nt I/nd or~ PTospteting. Fourth IAGOl>Symp. V.rna, 11, 377-383.

GAIIIELS R.M.(19'4)· Mi,,"1l1 sptei~s liS Illnetions01 pH IInd oxidation·rtduction pountials, withs~ciAI rt/~rtnc~ 10 th~ zont 01 oxidation andJtcondary ~nrichment 01 sulphidt ort deposi!s.Gcoch. Cosmochim. Am, " IH·I68.

GOLDIE R., KOTILA B., SEW,4.RO D. (1979l . ThtDon ROII)'n Mint: archeon porphyry copper de­posits ntar Noronda, Qutbec. Econ. Geol., 74,1680-1684.

GRUSZCZYK H. (1967)· Tht gtnttis 01 tht Siltsiiln·Crocow d~posils 01 lead·tinc orts. Econ. G«al,Monography 3, 169·177.

HAIlASCZYK CZ. (1980) . PlI1totoic porphyry cop~r

d~posill i" Polllnd. Eumpeiln Copper Deposits,Symp. BelgraOO-Bor, 89-9'.

HEINlsH H. (I98I) - Pr~liminll" rtport on torlJPlI1tozoic acid l10kanism i" t~ tllst"n IIndsoutht'rn Alps. JGCP Project, n. " Newsletter,......

HEMLEY J.J., lOSES W.R. (1964)· Cht'mica/ IIS~ctS

01 b)'drolht'rmal afl"ation witb tmphasis onhydrog~n m~tasomatism. Econ. Gool., '9, pp.'38-'69.

IIlVINE T.N., B,4.R,4.C...R \'U.R.A. (1971) A guide10 tht chemical cloHi!icotion 01 tht Commonvolcanic rocks. Can. Jour. of Earth Se., 8, 'l3-'48.

J,4.NKOVIC S. (1980) - Ort dtposil typtS and ma;orcopper metallogrnic units in Europa. EuropeanCopper DeposilS, 9·2', Belgrade, Bor.

UG.'ff PH., ROUVl£R H. (1976) _ us giumt"tsPb-Zn tn rOCMS carbonati~s sous inconlor",it~:

giJtmmts {JIJltokllrJtiqu~s ou gis~m~nts dans JtSJHl!iokarsO Mem. h. SCt. Ga:J1. Frana::, 7, 5-69.

wo L.5., Hoops G.K. (l97}) . Sodium in (/Ir­bo1Ult~ stdimtnlJ ilnd rodu: a poJSibl~ indtx toIht' sll1initJ 0/ diagrn~tic solulion. loom. -Sed.Pelro!ogy, v. 43, 6140617.

URSEN G., UULING,4.11 G.V. (1%7) - Diogtnnisin std;mmls. Dev. Sedimenl, 8, "I pp., Amster­dam-london-New York, Elsevier.

LELEU M. (196') . us gilts plombo-zincilhts du

THE PALEOZOIC METALLOGENIC EPOCHS OF TI-IE SARDlNfAN ETC. 22i

lAuriu#t (Crt-ct'). These Doet. Ing. Fac. $c.,Nancy.

ULEU M. (1966) u {(ant ~I s~s incidtnusmtra/lo"lniqu~s. Se. Terre, Nancy, 11 (4), }85-4I}.

I...owELL ).0., GUll_BUT ).M. (1970) - lAltral and~rlictd alltralion-min~aIi:zalion zoning In por.phyry Ort dtposits. Econ. Geology, 6', 37}-408.

~iAucmt A., ScH.-:EID£I. H.). (I967) - TIN AJpint1~IId-zinc orts. Geol. Monography, 3, 71-86.

NICOUNI P. (1970) - Lilolof.i~ dts conctnlrationsminba/~s slrali/onnrs. Paris, Gauthier·Villau,769 pp.

NIELSEN R.L. (1976) - &unt dtvdopmtnts in tINsludy 01 porphyry coPMr gtology. A r~l1itw.Porphyry Deposits of the Canadian Cordillera,Soulhcrland Brown A. (Ed.), Sp«. Vo!. ",487·~.

OFTEDAH G. (19'8) - A Ih~ory 01 txdalil1t stdi·mentary orts. G~J. Foien. Stockholm Forb, SO,1·119.

PAl.OMEItO G.F. (I977} . Caracterts geologicos yrefacionts morlologicas y genelicas de la mine·raliuaciones del "Anticlinal de Rio Tinlo".Acta )almllntiensill, Salamanca, 24 pp.

PEARCE )A., CANN ).R. (1973) - TeClonic mt;'tg01 bllsic IJ(J/canic rocks de/ermined using IM;~

tl~menl analysts. Earth Planel. Se. Leners, 19,29CJ.JOO.

PELLlSSo.'l"NIEl H. (1972) - us di",tnsions des

listmenls d~ cuivre du mondt. fuJiJi d~ metal­ogeni~ qlUmtitativ~. Mem. du B.R.G.M., ",

40' pp.PuRSEI BR. (I97J) . TIN Ptrsian Cull HoIoctna

carbonat~ s~dimtntalion and diaf,tntsis in Jshallow ~piaJntin~"laI S~Il. Springer-Verlag, BerlinHeidelberg - New York, 471 pp.

RAo C.P., NAovl (1977) - PttrOf,rapby, f.roc~mislryand laclor (lnaIysis 01 a lo~ Ordovici(ln sub­surlac~ stquenu T(lsm(l"it, ~slr(lli(l. )ouma1 ofSedimentlry Petrology, 47, 10)6.10".

RAo c.P. (1981) . Geocb~mical di8utncts bttwunlropicll! (Ordovicia"j and subpolar (P~rmi(ln)

carbonalts, Tasmani(l, Auslralia. Geology, 9,20'-209.

Rice, C.A., SABATINI G. (1978) - Pttrogtntlic ai­finily and gtodynamic significanct 01 mttabasicr()(k! Irom Sardinia, Corsicll and Provence. N. )b.Miner. Mh., H. 1, 2.3-38.

RIDGE }.o. (197J) - Volcanic exhalalionr and oredtposi/ion in Ihe vicinity 01 tht sta·floor. Miner.Deposita, 8, 322-348.

RINGWOOD A.E. (197') - Composilion and pt/r%gy

01 Ihe e(lr/h's ",anllt. Mc Graw Hill Inc.,New York, 618 pp.

SILLlTO£ R.H. (1972) - A plale leelo"ic mOllel lortiN orif,i" 01 porpb).'Y copMr d~posi/J. Econ.Geo!., 67, 184-197.

STUIOIOV VJ,I. (I96S) . Principlu 01 filbof.~neJlJ.

Edinburgh, Olivier Ind Boyd, 245 pp.S1JT1-fUL.AND BlOWN A. (1969) - Min~(I/iZJltion In

Britisb Columbia (lnd I~ coppv (lnd molybd~n~m

dtposits. Canadian Mining MelaU. Bull., 62.26-40.

SUTHERL\ND BROWN A. (1976) ~ Mttallic mintr.urfsourcts 01 canadian CordiJl~ra. Grcum. Pacific.Energy and Mineral Resources, 2', ~J-Xl8.

TUOIPE R.5. (1972) - Oc~an /loor bas(l/t aDinit., 01PrtcQmbrian GI(lucophane schist lrom Afgleuy.NalUr Phys. Se., 240, 164-166.

TUREKIAN K.Y. & WEDEPUOL K.H. in MAC·QUAIt }.CL. '" LAGNY PH. (1981)- Mintrali~a/ions

Pb·Zn sous inconlormilt! des fl!rits de plaitslormes carbona/ees. Exemple du gisemenl dtTrrves (Gord, Franet). Re/a/ions eu/re dolom;!i­zalions, dissoluf;OIIJ el mineralhalions. l\lineral.Deposita, 16, 2, 283·307.

VEltItAES G. (1979) • Contribution a !'elude de !~

provinct mital!ogeniqm' sous Cevenal~: Its gUrrPb·Zn de Monldardier, la Sanguinade tl 102,dislrict dts Malints (Gord, F"mu). Memoiredu Centre d'Etudes el de Recherches Geologiqu<:$et Hydrologiques. C.E.R.G.A., t-.Ionlpcllier, 17,1-269.

ZAMAnNO 1. (19721 - us filol(lcies C(lrbon(lt(ld.ndel cambrico d~ la ~OlllJ cantabrica (N.W. ESp4iia)y su distribucion palrogrograjic(l. Trat.jos deGeologil, '. J.IlS, Oviedo.

ZUFFAl.DI P. (1968) - Tr(lslormism in tIN ge"~JJs

01 ore deposi/J: eJUlmplts Irom Sardinia le(ld·Vncdeposits. XXIII Im. Geol. Congress, 7, 137-149.

ZUFFAl.DI P. (1969) - lA meta/logent-se du plomb,du vnc ~ du bary'um tn Sardaitnt: un t'"''''pl~dt 1J"ma,,~"u, dt polyf,inhis",t tt d~ tr(lnslor.mis",e. Annales de la Soc. Grologique Belgique,92, J.

ZWAlT M.}. (1974) - L'Orogtne n-cinico in EurofJ4.Mem. Soc. Geel. It., DJI, 3-'.

WILSON ).L. (197') • Carbonalt lacits in f,toIof.i~

history. Springer.Verlag, Berlin Heidelberg. NewYork, 411 pp.

WINCHESTER Y., FLQYD P.A. (1977) . Geochemipldiscriminalion 01 di8trent magma reries and theirdifferentia/ion producls using immobilt rltmtnts.Chem. Gool., 20, 32'·343.