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ISSN 1028-334X, Doklady Earth Sciences, 2008, Vol. 420, No. 4, pp. 538–541. © Pleiades Publishing, Ltd., 2008.Original Russian Text © O.A. Bogatikov, A.V. Veselovsky, V.B. Meshcheryakova, 2008, published in Doklady Akademii Nauk, 2008, Vol. 420, No. 1, pp. 76–79.

The Late Cenozoic subareal volcanic activity, whichstarted in the late Eocene and Oligocene and has con-tinued until the present, has produced diverse volcanicbelts [4]. Analysis of the tectonic setting of the volcanicbelt on continents using the “Volcanic Belts” GISdeveloped by the authors made it possible to classifythe volcanic belts into several groups, including the vol-canic belts in marginal zones of deepwater basins [3].Volcanic belts confined to margins of the deepwaterTyrrhenian, Balearic, and Alboran basins in the westernMediterranean belong to this category (figure).

It has been suggested that basins of the westernMediterranean have existed since the pre-Neogene timeand that their margins subsided later. They still emergedabove the sea level in the Early Neogene [6]. Intenseblock subsidences of the basins occurred in the Neo-gene and continued during the Pliocene–Quaternary.

The Earth’s crust in the Tyrrhenian Basin is 6–7 kmthick; i.e., the suboceanic crust underlies its central sec-tor. In the Balearic Basin, the undeformed Pliocene–Quaternary complex (up to 0.5–0.6 km thick) and theunderlying pre-Pliocene complex (up to 4–5 km thick),which is dislocated in marginal zones, rest upon a thickbasaltic layer in the center of the basin. The centralparts of the basin are characterized by the relative upliftof not only the Moho surface, but also the roof and bot-tom of the underlying zone of lower seismic wavevelocity, i.e., the asthenosphere located at a depth of50–200 km, which is 50 km higher than in the adjacentcontinental areas where the asthenosphere is traced at adepth of 100–250 km [2].

The dynamic analysis of stresses in earthquakesources shows that the tensile stresses oriented nor-mally to the strike of the foldbelt are recorded currentlyin the Earth’s crust of these territories.

The foldbelts around the basins represent Meso-zoic–Paleogene miogeosynclinal troughs subjected tointense tectonic reworking. They are complicated bynumerous recumbent folds and imbricate nappes thrustfrom the Tyrrhenian and Alboran basins toward thecontinental structures (Apulian–Adriatic and Ragusa–Malta plates, African Platform, and Iberian Massif). Insome places, the horizontal displacement of nappesreaches a few tens of kilometers. Inner zones of thenappes enclose metamorphic complexes transportedfrom the regions currently occupied by the Mediterra-nean and Tyrrhenian seas [6].

The Late Cenozoic tectonic processes promoted notonly the submergence of broken inner zones of Alpidesand their chains under waters of the Mediterranean andTyrrhenian seas, but also the rejuvenation and origina-tion of new large fault and rift zones, e.g., the Rhine–Nigerian Rift [5], the Gibraltar Transform Fault with azone of seismic sources, the Messina Fault, and others.

THE TYRRHENIAN VOLCANIC BELT

The tectonic setting of this belt is controlled by themargin of the deepwater Tyrrhenian Basin and the largesubmeridional Messina Fault (figure). The MessinaFault controls the location of various elements of thevolcanic belt on both land and islands. The southernsegment of the fault bounds the basin of the Ionian Seain the west and is probably traced in Africa, where it isknown as the Tibesti Fault that controls a large volcanicmassif of the same name.

The western segment of the volcanic belt (Tuscanand Central Tyrrhenian provinces) is traced in the Tyr-rhenian Sea, where the location of volcanic centers is

Late Cenozoic Subaerial Volcanism in Marginal Zones of Deepwater Basins

in the Western Mediterranean

Academician of the RAS

O. A. Bogatikov, A. V. Veselovsky, and V. B. Meshcheryakova

Received December 14, 2007

DOI:

10.1134/S1028334X08040028

Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Russian Academy of Sciences, Staromonetnyi per. 35, Moscow, 119017 Russia; e-mail: vessel@igem.ru

GEOLOGY

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determined by a series of submeridional faults that areparallel to the Messina Fault.

The Tyrrhenian Belt is characterized by intense neo-volcanic activity. This belt includes a number of activevolcanoes and many extinct Quaternary volcanoes.Pliocene volcanics are developed over a limited area.Miocene volcanic rocks are negligible.

The Tuscan province located in the western part ofthe belt (islands within the Tyrrhenian Sea) is character-ized by the earliest manifestation of subaerial volcan-ism (Pliocene) and deep magmatism (granites and gra-nodiorites with an age of 3.5–7.0 Ma) [7]. Felsic volca-nic rocks (rhyolites and rhyodacites), ignimbrites, andtuffs are widespread. Numerous rhyolite dikes are con-sidered volcanic conduits. Cooling of volcanic flowswas followed by the emplacement of small laccolithsand extrusive domes. The final phases of volcanic activ-ity were marked by effusions of short basic flows.

The Roman–Neapolitan province in the eastern(coastal) sector of the volcanic belt adjoins the Tuscanprovince, but the former zone is sharply different interms of volcanism. In the Messina Fault zone, a chainof young (merging in some places) volcanoes of differ-ent sizes is traced along the western coast of Italy. Theirprimary morphology is often retained. Craters andcalderas are occupied now by lakes. The extinct volca-noes are supplemented with huge active volcanic edi-fices, such as Vulsini (2300 km

2

), Cimini (~900 km

2

),

and Sabatini. The southeastern area includes ColliAlbani (Lazio region) and a group of small Gerincanvolcanic cones [6].

The volcanic activity started here in the early Pleis-tocene. The pyroclastic rocks alternate with high-alka-line potassic lavas that contain a peculiar mineral assem-blage (sanidine, andesine, spinel, garnet, and melilite).Dacitic ignimbrites are products of younger eruptions,which, in turn, are overlapped by leucite lavas.

The south area (Neapolitan district) includes the activeVesuvius Volcano (the last eruption occurred in 1944) andthe Campi Flegrei field (km

2

in area) that comprises morethan 50 volcanoes situated at the stage of fumarolic activ-ity (the last eruption is dated at 1538 A.D.) [1].

The products of Vesuvius eruptions are composed ofleucite tephrite (vesuvite) and distinguished by pro-gressive K concentration. All volcanic rocks in CampiFlegrei are close to alkali trachyte in composition.Explosive eruptions produced a thick pile of pyroclasticmaterial (the so-called Neapolitan yellow tuff) that con-sists of chaotically distributed fragments (without anyindications of bedding) of yellow color related to thesubsequent hydrothermal alteration. The late trachytic,latitic, and phonolitic squeeze-out domes and extru-sions were formed afterward along numerous fractures.

The Tyrrhenian, Balearic, and Sardinian–Pantellerian volcanic belts of the western Mediterranean. (

1

) Lava fields, (

2

) large faults,(

3

) rift zones, (

4

) volcanoes: (

a

) active, (

b

) dormant.

TyrrhenianBasin

Sardinia Is.

Gibraltar Fault

Pantelleria Is.

Sicily Is. Etna

Vesuvius

Balearic Basin

‡ b

4321

Stromboli

540

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et al.

The volcanic activity in the Roman–Neapolitanprovince lasted from the Miocene in the west to theRecent time in the east.

The southern continuation of the Tyrrhenian volca-nic belt is represented by a group of young volcanoes ofthe Liparian (Eolian) Islands in the southeastern Tyr-rhenian Sea and isolated islands located in the northernarea. Taken together, they make up a large ring structurecontrolled by sublatitudinal faults that are regarded asan extension of the Gibraltar and Messina faults.

According to the available data on the orientation ofstresses in seismic sources, this territory is situated atthe stage of the NW-oriented extension. The ring struc-ture encloses a number of earthquakes with the focuslocated at a depth of 200–300 km (450 km in one case[2]). Mount Stromboli, a large active volcano, has atotal height (including the submarine section) of morethan 2000 m. Eruption products of this volcano are rep-resented by basalts, trachybasalts, and trachyandesitesthat always contain olivine. The volcanoes of the EolianIslands erupted latites, andesites, alkali rhyolites,obsidian, and pumice.

The East Sicilian province of the Tyrrhenian volcanicbelt is a meridional zone controlled by the Messina Fault,which is traced here along the western margin of thedeepwater Ionian Basin. This zone is characterized bythe greatest gravity maximum (in Bouguer and isostaticreductions) and numerous earthquake hypocenters [2].

The giant volcano of Mount Etna (3263 m) restsupon the stepwise horstlike uplift composed of theupper Pliocene rocks. Basalts and less abundant teph-rites are the oldest volcanic rocks at Etna. The volcanois composed largely of andesites, basaltic andesites, tra-chyandesites, and nepheline tephrites, i.e., rocks transi-tional from calc-alkaline to alkaline series [1].

The Central Tyrrhenian province of the Tyrrhenianvolcanic belt is located in the central and southeasternparts of the Tyrrhenian Sea, where the depth is maxi-mum (3.0–3.5 km deep) and the crust belongs to thesuboceanic type. This area includes large volcanic sea-mounts up to 3000 m high (Vavilov, Alicudi, and oth-ers). They are composed of olivine basalt similar to therocks of Stromboli Volcano. The seamounts are markedby positive gravity anomalies.

THE SARDINIAN–PANTELLERIAN VOLCANIC BELT

This belt is situated at the western margin of the Sar-dinian–Corsican Massif that separates the Tyrrhenianand Balearic deepwater basins and extends in the Tuni-sian Strait. This volcanic belt is controlled by the mar-gin of the deepwater Balearic Basin and the typicallysubmeridional Rhine–Nigerian Rift (figure). In thisarea, the rift is represented by a graben up to 50 kmwide (Campidano Graben).

The Pantellerian segment of the volcanic belt islocated in the Tunisian Strait (between Sicily and

Africa), where a system of grabens is confined to theNW-striking tensile faults. The axial part of this tec-tonic zone includes a stepwise graben (>1 km deep)with positive gravity anomalies (Bouguer reduction upto +75 mGal [2]). This area is probably characterizedby the absence or drastic thinning of the granitic–meta-morphic bed. This structure includes Pantelleria,Linosa, and Malta Archipelago composed of Late Cen-ozoic volcanic rocks.

The Sardinian–Pantellerian volcanic belt is charac-terized by a combination of silicic and subordinatebasic volcanics.

In the Sardinian segment, the volcanic activity,which started in the Eocene–Oligocene, resulted ineruption of large volumes of silicic magma distin-guished by elevated alkalinity, including comenditicand trachytic ignimbrites 3.

The products of the Oligocene–early Miocene phaseconsist of rhyolites, trachytes, and vitreous andesites.Large shield volcanoes mainly composed of basic rocksfunctioned in the Miocene–Pliocene. The late(Miocene–Holocene) complex consists of variousbasalts, trachytes, and phonolites.

In general, the volcanic rocks are close to the calc-alkaline series with sporadic manifestation of the Med-iterranean potassic tendency.

The data discussed above allow us to draw the fol-lowing conclusions.

(1) The spatiotemporal contiguity of the formationand evolution of the Tyrrhenian, Balearic, and othermarine deepwater basins and subaerial volcanism attheir margins testify to the synchronous development ofthese processes during extension of the Earth’s crust.The destruction of foldbelts surrounding the basinsindicates that these processes postdated the orogenicstage of Alpine folding.

(2) The transformation of the Earth’s crust intodeepwater basins up to the point of its transition into thesuboceanic crust is consistent with the idea of mantleplumes.

(3) The marginal zones of the basins destroyed bylarge faults and rifts are characterized by long-term vol-canic activity, which has not ceased up to the present.

(4) Alkalinity and basicity of igneous rocksincreases in younger rocks. These parameters areretained in the areas situated close to the central parts ofmarine deep water irrespective of their age.

(5) We suppose to use the results obtained for thecompilation of target-oriented data set on the Cenozoicsubaerial volcanism together with information pertain-ing to metamorphism and cartographic materials.

ACKNOWLEDGMENTS

This work was supported by the VINITI program ofthe Russian Academy of Sciences (project no. 15 “The

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Electronic Earth”) and the Russian Foundation forBasic Research (project no. 05-07-90097).

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Volcanoes

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3. O. A. Bogatikov, A. V. Veselovsky, V. B. Meshcheryak-ova, and A. B. Leksin, in

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