43. PALYGORSKITE, SEPIOLITE, AND OTHER CLAY MINERALS …Martin-Vivaldi and Cano-Ruiz (1956) have supported this idea. But in comparing chemical compositions of sepiolite and palygorskite

43. PALYGORSKITE, SEPIOLITE, AND OTHER CLAY MINERALSIN LEG 41 OCEANIC SEDIMENTS: MINERALOGY, FACIES, AND GENESIS

P.P. Timofeev, V.V. Eremeev, and M.A. Rateev,Geological Institute of the USSR Academy of Sciences, Moscow, USSR

INTRODUCTION

Leg 41 holes, drilled near the northwest margin ofAfrica, penetrated Mesozoic and Cenozoic sediments.The

P. P. TIMOFEEV, V. V. EREMEEV, M. A. RATEEV

370 369

cu

— αi

•α o

S ^

cu

mid

dle

L

c MLo

we

rne

Eo

cen<

man

ian-

r Pa

leoc

e

O cuC Q.ö %

c cco ro

••P l α

< <

ü

HmMlad. K,Ch

MlHmad. Ch,M, K

MlHmPI

MPISp

MMlK

MlHmK

70

170

300

cQ>

—

CU

α * - CJ

α_

cro-Q

<

MlHmKad. M,Ch

MlKHm

Z,PI,MI

PI, Mad. Ml,K

30

150

310

350

430

368

530

620

700

820

810

900

Figure 1. Occurrence of palygorskite and sepiolite in Leg 41 sediments.

en

eM

ioc

T3

ε

Lo

we

r

c33

O3

-up

per

Pa

om

an

ian

Cen

P

H

m 1

M

P

S

Claystoneswith inter-beds of sandysilty material

Alternationof nanno-marls withclaystonesand silt-stones

Mid

dle

E

oce

ne

Alb

ian

P

m 1

C

P

M

m 1

K

Limestoneswith interbedsof clay matter

Nanno-marlwith burrows

C

§LU

&

03

Eo

cer

s-lo

we

r

sIòCL

P

K

m 1

H

P

S

M

Claystoneswith inter-bedsof siltymaterial

Clay andclaystoneswith gentlewavelikelamination

367 366

ΦtzCU

8UJ

ow

er

_ i

snoa

tac

r C

re;e

ne

α> oQ- cuQ. —

c• ro

c •—

• ― ro

E εcu ot cro cu

CO O

cro

Ooocu

Z

MZHmad. PI

HmKad. PI

MHmK

HmKAd. M

315

355

590

740

350

400

460

600

650

800

850

Palygorskitic sediments

Palygorskite-sepioliticsediments

PI = PalygorskiteK = KaoliniteSp = SepioliteZ = ZeolitesHm = Hydromica (illite)M = MontmorilloniteMl = Mixed layer mineralsCh = Chloritead. = admixture

o

-i O

CJ

Z>LLJ

α> α>— c

~ O

ene

LU

>

3

-a

CJ

Ml, K

Ml, ad.K,Hm,Ch

MlMChHm

M

Ml, ad. M

955

HOLE 367

leo

cer

sP

ata

ceo

u

2u

TABLE 1Clay Minerals in Hole 366

ooo

Agerm

ost

of ;ene

Low

eip

arts

'O

ligo<


•s im

atio

n

H

oto ^

fa gO

nd

i

zone

ol

cto

|

to ^ -V.

1 ^

ε«, εis

OB

, o

o 2

O O111n o öto cβ O

>, 8 g

B >> to

3

| g

pUB I3AVOI ' UBIUBQ

'ato>,

-r-σtox

ac

morphic series talc-pyrophyllite, with progressivesubstitution of Al for Mg positions in octahedral layersof the montmorillonite type. Martin-Vivaldi and Cano-Ruiz (1956) have supported this idea. But in comparingchemical compositions of sepiolite and palygorskite inLeg 41 sedimentary rocks, we recognized no reliablefeatures of isomorphism. All Russian-platformcarboniferous sepiolites that we studied, from both thearid zone (middle and upper Carboniferous) and thehumid zone (lower Carboniferous), were completelypure. Chemical analyses of sepiolites, after exclusion ofcarbonates, yielded typical compositions (Table 2).Rare deviations from the standard compositionresulted from admixtures of other minerals. Chambers(1959) found a thick bed of sepiolite in the sedimentarydeposits of Vallecas (Spain) to be homogeneous. Thus,we are unable to find any transitional members on thebasis of the Al and Mg contents of sedimentary beddedsepiolites and palygorskites.

Studies by Nagi and Bradley (1955) and by Preisinger(1959) showed significant differences in the structuresof sepiolite and palygorskite. Palygorskites may beregarded as intermediate minerals—with compositionalextremes Mg3/OH2Si4θio (magnesian-montmoril-lonitic) and Ah/OhhSi

MINERALOGY, FACIES, AND GENESIS OF MINERALS IN OCEANIC SEDIMENTS

Age

Pliocene

Early Eocene

Paleocene-LateCretaceous

LateCretaceous

LateCretaceous

Early Albianlate Aptian

Early Aptian-Barremian

EarlyCretaceous

Sample(Interval in cm)

4-3, 54-56

14-3,18-20

15-3,70-72

16-3,118-120

17-3,92-94

23-2, 64-66

24-3,79-81

24, CC

28-2, 73-75

Clay

Iithologo-Genetic Type

Foraminifer-radiolarian-containing nannofossil marlwith interbeds of siltymaterial

Clay zeolite containing

Silty clay

Silty clay

Claystone withhorizontal lamination

Claystone with interbedsof fine-grained siltstones



Limestones with interbedsof clays

TABLE 2Minerals in Hole 367

Clay MineralFraction


Age

ow>,

37-4, 80-82

39-5, 69-70

40-3, 69-70

41-2, 70-72

42-2, 62-63

44-4, 68-70

45-4, 91-93

46-4, 60-61

47-5, 69-70

Claystone with gentle wavelikesmall discontinuous laminationClaystone with gentle wavelikesmall discontinuous laminationClaystone with gentle wavelikesmall discontinuous laminationClaystone with gentle wavelikesmall discontinuous laminationClaystone with gentle wavelikesmall discontinuous laminationClaystone with gentle wavelikesmall discontinuous laminationClaystone with gentle wavelikesmall discontinuous laminationClaystone with gentle wavelikesmall discontinuous laminationClaystone with gentle wavelikesmall discontinuous lamination

Sepiolite, palygorskite





Palygorskite, montmorillonite ormixed-layer (M-H)Sepiolite, palygorskite, montmorilloniteor montmorillonite-hydromicaSepiolite, palygorskite, montmorillonite,quartzSepiolite, palygorskite, montmorillonite

Deep-water clay sediments with dolomite(zone of quiet sedimentation); in thelower part (layers 39-47) zones of weakcurrents with a small admixture of siltymaterial and areas of discontinuouswavelike lamination

Palygorskite-sepiolitic

Palygorskite-sepiolite-montmorillonite-mixed-layer

w

>ZσowzW

OOm>znwαswzH

ö

50-3, 52-54

51-2, 60-62

52-5, 85-87

53-3,71-73

54-3,71-73

55-3, 90-92

57-4, 68-70

58-5, 68-70

59-3, 88-90

Alternation of thinly elutriatedclaystone with a sandy-sütyvariety, gentle wavelike smalldiscontinuous laminationAlternation of thinly elutriatedclaystone with a sandy-siltyvariety, gentle wavelike smalldiscontinuous laminationAlternation of thinly elutriatedclaystone with a sandy-siltyvariety, gentle wavelike smalldiscontinuous laminationAlternation of thinly elutriatedclaystone with a sandy-siltyvariety, gentle wavelike smalldiscontinuous laminationAlternation of thinly elutriatedclaystone with a sandy-siltyvariety, gentle wavelike smalldiscontinuous laminationAlternation of thinly elutriatedclaystone with a sandy-siltyvariety, gentle wavelike smalldiscontinuous laminationSilty clay, cryptohorizontallylaminatedClaystone, horizontally laminatedwith interbeds of coaly claystoneAlternation of claystone interbedsand sandy-silty varieties

Hydromica, mixed-layer (M-H),kaolinite

Kaolinite, hydromica, montmorillonite,quartz

Hydromica, mixed-layer (H-M),kaolinite

Montmorillonite, palygorskite


Montmorillonite, glauconite

Montmorillonite, hydromica, mixed-layer (M-H), kaolinite (traces)Hydromica, mixed-layer (M-H), chloritekaoliniteHydromica, mixed-layer (M-H),chlorite, quartz, feldspars

Hydromicaceous-kaolinitic, sometimeswith an admixture of mixed-layer(montmorillonite-hydromica ceous)minerals

Siltstone-clay sediments (zone of weakcurrents)

Palygorskite-montmorillonitic

Coaly-silty-clay sediments (zone ofquiet sedimentation)

Hydromica-chloritic with anadmixture of kaolinite and mixed-layer minerals

Note: Packets in mixed-layer minerals; M = montmorillonitic, H = hydromicaceous, Ch = chloritic.

o


Age

8so.2§

D ö' Og.SPo δ

l io

lbi

<


1-3, 84-86

2-3, 82-84

2-4,80-81

3-2,73-75

3-3,80-82

4-2, 92-94

4-4, 80-82

4-5, 84-86

6-2, 73-75

7-5, 84-86

22-3, 70-72

26-4, 70-72

27-5, 91-93

31-4,80-81

34-2, 78-81

35-2, 78-81

40-4, 83-85

41-4, 80-82

42-1, 79-81

49-4, 69-70

Lithologo-Genetic Type

Nannofossil oozes, homogeneous,cryptohorizontally laminatedNannofossil oozes, homogeneous,cryptohorizontally laminatedNannofossil oozes, homogeneouscryptohorizontally laminatedNannofossil oozes, homogeneous,cryptohorizontally laminatedNannofossil oozes, homogeneous,cryptohorizontally laminatedNannofossil oozes, homogeneous,cryptohorizontally laminatedNannofossil oozes, homogeneous,cryptohorizontally laminatedNannofossil marl with interbeds of clayenriched with ashNannofossil marl with interbeds of clayenriched with ash

Nannofossil marl with interbeds of clayenriched with ash

Nannofossil marl with abundance ofmud-eaters' tracksNannofossil marl with abundance ofmud-eaters' tracksNannofossil marl with abundance ofmud-eaters' tracksNannofossil marl with abundance ofmud-eaters' tracks

Limestone, homogeneous withinterbeds of clay matterLimestone, homogeneous withinterbeds of clay matter

Nannofossil marl with rare mud-eaters'tracks, cryptohorizontally laminated

Nannofossil marl with rare mud-eaters'tracks, cryptohorizontally laminatedNannofossil marl with rare mud-eaters'tracks, cryptohorizontally laminatedNannofossil marl with rare mud-eaters'tracks, cryptohorizontally laminated

Clay MineralFractions


Age

o

§Isi

io.25<

s

ix>• Ö

zoGOmσüwzH

TABLE 5 - Continued

Age

CD


silicate minerals can differ even within the lithologicsection of one hole. In continental facies of Africa,palygorskites are related chiefly to carbonate sedi-ments. Likewise, in Leg 41 sediments the most sig-nificant amounts of palygorskite occur with slightlycarbonaceous clays and claystones.

Comparatively pure monomineralic palygorskitic orsepiolitic clays, nearly devoid of terrigenous materialand associated with some dolomite, are likely to formthrough a chemogenic or chemogenic-diageneticprocess. Formation of these rocks in Holes 368 and 370occurred at depths below the critical level of carbonateaccumulation, very near the African continent.Chemogenic formation of palygorskite and sepiolitewas possible here not under arid conditions, as usuallyoccurs, but in an environment of normal marinesedimentation, owing to an intense inflow of dissolvedMg cations, possibly as Mg(OH)2, and of silica fromthe area of tropical weathering and laterite formation.1

Such weathering and laterization is known to haveoccurred on the African continent (Millot, 1964).Heating of the oceanic waters may also have beenimportant near the continent.

Palygorskitic clays with admixtures of terrigenousparticles and accompanying clay minerals could nothave resulted from mineral selection during eolian orfluvial transport. Authigenic, chemogenic-diageneticformation of palygorskitic clays therefore seems mostprobable.

The second type of palygorskitic clays and clay-stones, with interbeds of sandy-silty material (Holes368 and 370), was formed by transfer of palygorskitic,lacustrine, and marine epicontinental sediments,probably as turbidity currents from the Senegal Riverdelta (Hole 368) or from a submarine canyon (Hole370) into the deep oceanic environment. The clayfraction usually contains palygorskite, mont-morillonite, kaolinite, hydromica, mixed-layerminerals, occasional chlorite, etc. This is true in LowerCretaceous sediments of Hole 370 and in upper Eoceneto lower Miocene sediments of Holes 368 and 370.Millot (1964) recognized accompanying minerals insediments of similar age in the continental facies ofadjacent Africa. These palygorskitic-sepiolitic rocks ofthe arid belt are widely developed in northwest Africa;their thickness sometimes reaches 500 meters (Millot,1964), and they would have been susceptible to winderosion and transport to the ocean.

The third and fourth facies types of palygorskite-bearing rocks are represented by organogenic lime-stones with interbeds of clay matter and nannofossilmarls. These are typical pelagic sediments of an opensea or of an oceanic basin which bordered theundrained coast of Africa during the arid climate ofEarly Cretaceous and Eocene times. To explain theirpresence, the magnesian silicates of the regions of Holes366 and 369 would seem to require epicontinental seasin the Late Cretaceous and the Eocene, with extremelyshallow, strongly heated water, and chemogenic sedi-mentation of palygòrskite-sepiolite, followed by

subsidence to a great depth. Or they could have beencarried into these basins from the arid zone of Africa bywind.

The palygorskites in the clay fraction of pelagicsediments from Holes 366 and 369 are terrigenous, asconfirmed by the presence of such minerals asmontmorillonite, mixed-layer minerals, kaolinite, andquartz. Also, Pow-foong Fan and Rex (1972) say thatin lower Pliocene to lower Miocene limey nannofossiloozes of Hole 136, palygorskite occurs with mica,montmorillonite, kaolinite, quartz, hematite, andchlorite in the


368 10.6

31-2 (78-80)

\J

368

37-4 (80-82)

\J

368

34-2 (61-62)

36839-5 (69-70)

3-34 m n3.25 4.67

3.12 | 4.08 5.074.26

36836-2 (38-40)

36846-4 (60-61)

36836-3 (37-39)

368 12.17

54-3 (71-73)

Figure 3. X-ray diffraction scans of Leg 41 magnesian silicates.

1098


369A49-4 (69-70)

Figure 3. (Continued).

Evidence Against Volcanic Origin of Palygorskite andSepiolites in Leg 41 Sediments

The following evidence argues against the assumedeffect of hydrothermal flow of magnesian solutions: theoccurrence of palygorskites and sepiolites in differentfacies; their occurrence in carbonate rocks peculiar todeep-sea red clays; monomineral palygorskite clayswith no traces of hydrothermal metasomatic replace-ment, decoloration, or disturbance of textural features(lamination), and frequently without pyroclastics.

The isotopic compositions of sulfur and carbon inpalygorskite-bearing rocks of Holes 366, 368, and 370provide an important additional argument. Table 8shows that the isotopic composition of sulfide sulfur ismostly negative, about -2O°/oo. Such values are peculiarto sedimentary-diagenetic sulfides that result fromsulfate reduction. They may mean that sulfidesappeared in the uppermost layer of sediments underconditions of free exchange of the oozy and bottomwater; i.e., sediments may have inherited sulfide sulfurfrom the moment of their accumulation, at the earlieststages of diagenesis.

Despite low concentrations of carbonates inpalygorskite-bearing clays, we attempted to determinethe isotopic composition of the carbonate (Table 9).Some carbonate has carbon with an isotopic composi-tion that is lighter than normal sea carbonate. Thelatter is characterized by the value


TABLE 8Isotopic Composition of Sulfide Sulfur in the Core of Deep-Sea Holes, Hole 368


29-1,68-70

30-2,51-53

30-2,58-60

31-2, 78-80

31-2,71-73

34-2,51-53

34-2,61-62

36-3, 37-39

36-3, 68-70

37-4, 80-82

39-5, 69-70

40-3, 68-70

41-2,61-63

41-2, 70-70

42-2,62-63

44-4, 68-70

45-4, 84-96

45-4, 91-92

46-4, 60-61

47-5,69-70

FaciesType of Sediments

Red deep-sea clays(quiet sedimentation)Red deep-sea clays(quiet sedimentation)Red deep-sea clays(quiet sedimentation)Red deep-sea clays(quiet sedimentation)Red deep-sea clays(quiet sedimentation)Red deep-sea clays(quiet sedimentation)Red deep-sea clays(quiet sedimentation)Red deep-sea clays(quiet sedimentation)Red deep-sea clays(quiet sedimentation)Red deep-sea clays(quiet sedimentation)Red deep-sea clays(quiet sedimentation)Red deep-sea clays(quiet sedimentation)Red deep-sea clays(quiet sedimentation)Red deep-sea clays(quiet sedimentation)Red deep-sea clays(quiet sedimentation)Red deep-sea clays(quiet sedimentation)Red deep-sea clays(quiet sedimentation)Red deep-sea clays(quiet sedimentation)Red deep-sea clays(quiet sedimentation)Red deep-sea clays(quiet sedimentation)

Associations of Clay Minerals


Admixture of sepiolite

Palygorskite, admixture ofmixed-layer mineralPalygorskite, admixture ofmixed-layer mineralPalygorskite

Palygorskite

Palygorskite

Palygorskite-sepiolite

Palyg or skite-sep iolite



Sepiolite-palygorskite







Sepiolite, palygorskite,montmorillonite, quartzSepiolite, palygorskite,montmorillonite

Age

IuoW>,

3

Cβ

ö

3

Concentration(mg/g)

6.5

7.3

2.3

2.3

0.9

5.5

7.4

42.9

15.4

15.6

1.3

3.6

13.6

4.6

14.5

3.6

12.5

14.4

0.5

13.6

6 34(7oo)

-23.3

+15.6

-

-20.2

-23.4

-22.2

-22.2

-24.9

-28.4

-27.9

-19.5

Note: Analyses by V. I. Vinogradov.

TABLE 9Isotopic Composition of Carbonates in

Deep-Sea Holes of Leg 41


368-27-3, 41-43368-30-2,51-53368-34-2,51-53368-36-2, 79-81368-37-4,71-73368-45-4, 84-86366-2-3, 82-84366-3-3, 70-72366-7-3, 72-74366-11-1,50-52366-19-1, 105-107366-21-2,61-63366-24-2, 106-108366-40-3, 74-76

Concentrationof CO2 (mg/g)

3.41.5

15.33.41.04.4

70.4169.2190.7166.5132.0198.0

52.8165.0

δ 1 3 C

(7oo)

-13.8-18.9-12.4-14.9-18.0

—+4.2+3.5+3.3+3.2+4.2+2.8+2.7+3.1

1) Three genetic types of magnesian silicate rockshave been distinguished.

a. The first type is pelagic palygorskitic-sepioliticclay with dolomite, but without terrigenous orvolcanogenic material. Formation occurs bychemogenic-diagenetic processes in the pelagic zoneof the ocean adjacent to a continent with tropical orarid climate. The zone is characterized by anabnormally intense inflow of magnesium [apparentlyin the form of Mg(OH)2] and silica from the areas oflaterite formation, and by irregularly high heating ofoceanic waters. ;

b) The second type is palygorskite-bearing clayand claystone with interbeds of silty material,frequently contains mica, montmorillonite, chlorite,or kaolinite. This type formed under the influence ofsuspension currents transporting deltaic sedimentsfrom the Senegal River and an underwater delta orcanyon in the vicinity of Hole 370.

c) The third type is pelagic limestone andnannofossil marl with interbeds of palygorskite-bearing clay material. The clay fraction


quartz. Formation of this type of palygorskite-bearing deposit took place in carbonate pelagicsediments near drainless parts of the arid continent;particles of palygorskite were supplied by eoliantransport.

d) On the basis of Leg 14 cores, a fourth genetictype of palygorskitic-zeolitic clays, not observed byus in Leg 41 sediments, may result from diagenetictransformation of volcanic ash (von Rad and Rösch,1972).2) On the basis of new data, fluvial and eolian

transport of palygorskite-sepiolite particles seemspossible, as does redeposition of the particles. Ourconclusions are in good agreement with Wirth's (1968)data on eolian transport of palygorskite from the aridSenegal River area. The source for palygorskite in theRed Sea was also shown by Müller (1961) to becontinental, as was that for palygorskite in the PersianGulf (Hartmann et al., 1971). The occurrence ofpalygorskite and sepiolite in Upper Cretaceous andPaleogene sediments only, and their paragenesis withauthigenic clinoptilolite and with slowly deposited claysabout 20-25 m.y. old confirms the diagenetic origin ofthese magnesian silicates (von Rad and Rösch, 1972).Palygorskite and sepiolite probably are not forming atpresent. The occurrence of palygorskite in the surfacelayer of Atlantic Ocean sediments would seem tosuggest their formation in oceanic sediments near thecontinents, but it is more likely a result of fluvial oreolian transport.

3) Palygorskite is detrital, and its quantitativeincrease toward the continent cannot always beobserved, depending on the submarine topography andthe nature of suspension currents.

4) We agree with von Rad and Rösch (1972) that asurplus of cations in interstitial waters is necessary foroptimal chemogenic or chemogenic-diagenetic forma-tion of sepiolite and palygorskite. Origins can varyextensively (Hathaway and Sachs, 1965). We recognizethe inflow of silica by rivers draining the regions oflaterization as a contributing factor for formation ofmagnesian minerals in sediments of Leg 41.

5) Most other minerals of the clay fraction of Leg 41oceanic sediments are detrital. Kaolinite is known toabound in the crusts of laterization. Dioctahedral micaand trioctahedral chlorite are unstable in the profile oflaterization, but they can remain preserved to a certainextent; this might explain their limited quantitativedistribution in sediments of Leg 41. They can becomemore abundant during increasing aridity. In addition,chlorite can be related to washout of old magmatic

rocks of northwest Africa. Montmorillonite and mixed-layer minerals could have been brought from thelateritic areas of arid zones, or could have resulted fromdiagenetic alteration of volcanogenic material.

REFERENCES

Bonatti, E. and Ioensuu, O., 1968. Palygorskite from Atlanticdeep-sea sediments: Am. Mineralogist., v. 53, p. 975.

Chambers, G.P., 1959. Some industrial applications of theclay minerals sepiolite: Silicates Industr., v. 24, no. 4.

Elouard, P., 1959. Etude géologique et hydrogéologique desformations sédimentaires du Guebla Mauritanien et de laValée du Senegal: These Sci.

Goldberg, E.D. and Griffin, J.J., 1970. The sediments of thenorthern Indian Ocean: Deep-Sea Res., v. 17, p. 513-537.

Hartmann, M., Lange, H., Seibold, E., and Walger, E., 1971.Oberflachensedimente im persischen Golf und Golf vonOman Geologisch-hydrologischer Rahmen und erste, sedi-mentologische Ergebnisse: "Meteor" Forchungs-ergebnisse, v. 4, p. 1.

Hathaway, J.C. and Sachs, P.L., 1965. Sepiolite andclinoptilolite from the Mid-Atlantic Ridge: Am. Min-eralogist., v. 50, p. 852.

Martin-Vivaldi, J. and Cano-Ruiz, J., 1956. Contribution tothe study of sepiolite. pt. Ill: Nat. Res. Council Publ., 456.

Millot, G., 1964. Géologie des argiles: Paris (Masson et Cie).Müller, G., 1961. Palygorskit und sepiolith in tertiaren und

quartaren sedimenten von Hadramaut (S-Arabien): NeuesJahrb. Mineralogic Abhandl., v. 97, p. 275.

Mumpton, T.A. and Roy, R., 1958. New data sepiolite andattapulgite: Fifth Natl. Conf. Clays and Clay Minerals,Proc, Washington.

Nagy, B. and Bradley, W., 1955. The structural scheme ofsepiolite: Am. Mineralogist., v. 40, p. 885-892.

Pow-foong Fan and Rex, R.W., 1972. X-ray mineralogystudies. In Hayes, D,E., Pimm, A.C., et al., Initial Reportsof the Deep Sea Drilling Project, Volume 14: Washington(U.S. Government Printing Office), p. 677-726.

Preisinger, A., 1959. X-ray study of the structure of sepiolite.Sixth Natl. Conf. Clays and Clay Minerals, Proc,London.

Seibold, E. and Hinz, K., 1974. Continental slope construc-tion and destruction West Africa: In Burk, C.A. andDrake, C.L. (Eds.), The geology of continental margins:New York (Springer-Verlag), p. 179-196.

von Rad, W. and Rösch, H., 1972. Mineralogy and origin ofclay minerals, silica and authigenic silicates in Leg 14sediments. In Hayes, D.E., Pimm, A.C., et al., InitialReports of the Deep Sea Drilling Project, Volume 14:Washington (U.S. Government Printing Office), p. 727-752.

Wirth, L., 1968. Attapulgites du Senegal Occidental:Laboratoire Géol. Univ. Dakar, Rapport no. 26.

1101

Documents

43. PALYGORSKITE, SEPIOLITE, AND OTHER CLAY MINERALS …Martin-Vivaldi and Cano-Ruiz (1956) have supported this idea. But in comparing chemical compositions of sepiolite and palygorskite