28. X-RAY MINERALOGY STUDIES, LEG 48—ROCKALL REGION … · basaltic ocean floor; (3) recycling by redissolution of silica precipitated by plankton. In their study of sediments in

28. X-RAY MINERALOGY STUDIES, LEG 48—ROCKALL REGION (SITES 403,404,405, AND 406)

C. Latouche and N. Maillet, Institut de Géologie du Bassin d'Aquitaine(Laboratoire associé au C.N.R.S. No. 197), Université de Bordeaux I, France

METHODS

X-ray diffraction was used on a total of 190 samples in themineralogical analysis of the fine-grained fraction (calciumcarbonate-free fraction <2 µm) using smear slides andthree-diagram X-ray method, and in analysis of bulk samplesusing powders and an internal standard.

Clay Fraction (<2 µm)Total sediments were dispersed in pure water by mechani-

cal agitation. Samples with a high content of carbonates werefirst treated with HC1 N/10. After two or three washings inpure water, <2 µm subfractions were separated by settling.The <2 µm portion of suspensions was centrifugalized andthe thick paste obtained then was spread across two slideswith a standard laboratory spatula. The amount of clay percm2 was conditioned by the amount transferred to the slide.The first slide was saturated with ethylene glycol beforeanalysis. The second slide was scanned untreated and thenheated at 550°C for one hour before secondary analysis.

The diffractometer used is a C.G.R. theta 60 and operatingconditions were as follows: Cu Kα radiation (very fine focus0.1 × 5 mm) equipped with a Guinier monochromator; 40kv, 10 mA, scanning speed 0.5° θ p min.

Minerals were identified on the basis of their typical reac-tions to classical treatment (Brown, 1961; Thorez, 1975).Several diagrams exhibited high background between 5.6and 3.6Å. This particularity is attributed to amorphoussilica (Trichet, 1970; Greenwood, 1973).

The different minerals were estimated semiquantitativelyfrom diagrams of the glycolated slides. The height of 001peaks was used to determine the percentage of smectite(17Å), illite (10Å), andkaolinite + chlorite (7.1Å), chloritebeing distinguished from kaolinite on the basis of the differ-ence in their reflections, i.e., 002 for kaolinite and 004 forchlorite. Several non-clay minerals (zeolite, silica, etc.) areassociated with the <2 µm fraction. The abundance of zeol-ite of the clinoptilolite type (9Å line which persists on heat-ing; Mumpton, 1960), was estimated as with that of the clayminerals, on the basis of the height of their characteristicreflections. Siliceous minerals of the opal-CT type gave adoublet of lines at 4.45 and 4.25Å. The presence of amorph-ous silica was noted consistently, from scatteringbackground.

Total Sediments

Dried and pulverized samples of total sediments wereanalyzed according to the powder diagrams method using aninternal standard (corindon). By a comparison with syntheticreference samples, this method enabled us to obtain semi-quantitative estimates of quartz (3.35 A) and feldspars (al-

kaline, 3.25 Å; Plagioclase, 3.20 Å). The diffractometer usedis a Philips 1310 and operating conditions were as follows:nickel-filtered copper Kα radiation at 40 kv, 20 mA; auto-matic sample changer; step-scanning device and monitoringsystem of the goniometer. The proportion of carbonates wascalculated by calcimetry.

GENERAL OUTLINE OF THE MINERALOGYOF DEPOSITS

Fractions with a granulometry of less than 2 µm are com-posed of both clay minerals and various non-clay con-stituents . Their possible origins and their significance wereconsidered in the light of works by several authors, in particu-lar, that of Mason et al. (1960), Millot (1964), Yeroschev-Shak (1964), Biscaye (1965), Bonatti (1967), Griffin et al.(1968), Rateev et al. (1969), Paquet (1969), Tardy (1969),Trichet (1970), Chamley( 1971), Latouche (1971), and Joneset al. (1971).

Clay Minerals

Clay minerals are mainly represented by smectites, illites,chlorites, and kaolinites, in order of importance.

Smectites are predominant from the Eocene to the upperMiocene. They are poorly crystallized in the lower Eocene atSites 403 and 404 (wide peaks with very rounded summits).These smectites are slow to swell when treated with ethyleneglycol, as previously noted by Fan and Zemmels (1972) withsamples from Leg 12. They are very well crystallized in thesame period at Sites 405 and 406.

These minerals may be detrital resulting from the erosionof neighboring continental soils subjected to a climate ofcontrasting seasons; or they may come from the alterationand evolution of basic volcanic material; or again, they maybe due to neoformations in a more or less confined basin richin silica.

Illites are particularly abundant in the Miocene and Plio-cene/Pleistocene and are generally accompanied by chlo-rites . These clay species are common at the present time inmarine deposits and more especially periglacial regions.Their presence, therefore, may indicate pelagodetritic sedi-ments of northern origin.

Kaolinites are poorly represented and occur especially inthe Pleistocene. It is generally admitted that their origin isdetrital and continental.

Non-Clay Minerals

Zeolites of clinoptilolite type are abundant in the Eocene atSites 403 and 404 (where the clay phases are exclusivelysmectitic). Suggestions vary as to their origin and mode offormation. According to Nayudu (1964), in continuation of

665

C. LATOUCHE, N. MAILLET

the work of Goldberg (1959), their association with smectitescould indicate a derivation from the alteration of basic vol-canic rocks; this appears to be the case at these two sites.

Silica (crystalline, in the form of opal-CT, or else amorph-ous) appears in the Eocene at Site 405 and from the Eocene tothe lower Miocene at Site 406. The formation of opal-CTimplies an environment rich in silica. Leclaire (1974)suggests three sources of silica in sea-water: (1) derived fromalteration of the continents; (2) derived from alteration of thebasaltic ocean floor; (3) recycling by redissolution of silicaprecipitated by plankton. In their study of sediments in theLaw-Basin, Griffin et al. (1972) associate the presence ofcristobalite-tridymite with eruptions of lava rich in silica. Inthis case, however, it should be noted that the cristobalite-tridymite is attended by numerous fragments of volcanicrocks. The amorphous silica appears to be largely biogenic,as suggested by the frequency of siliceous organisms in theepisodes where amorphous silica has been observed.

Bulk Samples

The principal mineral components are carbonates andquartz-feldspars. Carbonates, here represented by calcite,are very abundant in the Miocene and the Oligocene. Theyhave been regarded as mainly biogenic, without excludingthe possibility of disturbance of older carbonates. Quartz andfeldspars occur in limited quantities but in well-definedepisodes in the lower Eocene at Sites 403 and 404 and fromthe Pliocene on at all four sites. They have been considered asdetritus of continental origin.

RESULTS

On the basis of mineralogical characteristics, two groupswere isolated: Sites 403 and 404 and Sites 405 and 406;several successive mineralogical assemblages were distin-guished along the line of bore holes. These assemblages aredefined in terms of the stratigraphic units proposed in theshipboard report and of the lithological units.

Sites 403 and 404 (Figures 1 and 2, Tables 1 and 2)

Three types of mineralogical associations appear at thesesites. Assemblage 1 at Site 403 corresponds to Units 3A and3B (Paleocene, lower Eocene), Sections 403-43-1, to 403-28-1 inclusive; and at Site 404, to Units 3A, 3B, and 2(Paleocene, lower and middle Eocene, and middle Miocene),Sections 404-26-1 to 404-7-2, inclusive.

The dominant characteristics of this mineralogical as-semblage are: smectites, very abundant and poorly crystal-lized (e.g., peak wide and rounded at Site 403) to very poorlycrystallized (Site 404); zeolites (clinoptilolite), frequentlypresent and often plentiful; quartz and feldspars (plagioclasespredominate); carbonates, relatively scarce; and amorphoussilica, frequently present (especially at Site 403).

The sedimentation is probably detrital. The smectites ap-pear to come from soils characteristic of climates with con-trasting seasons and in all likelihood from the products ofweathering of basic volcanic rocks. This type of climate hasoften been described as being Eocene. Nevertheless, associa-tions of poorly crystallized smectites with Plagioclasefeldspars, zeolites, and amorphous silica have already beenrecorded (Latouche, 1975) in present-day marine deposits inthe neighborhood of the basaltic Faeroes archipelago in a

cool, temperate climate. This seems to show that the parentrock is the most important factor.

Assemblage 2 at Site 403 corresponds to Units 2 and IB(middle Eocene, lower middle Oligocene, upper Miocene,and base of upper Pliocene), Sections 403-26-2 to 403-7-1,inclusive; and at Site 404, to Unit IB (upper Miocene andlower Pliocene), Sections 404-5-2 to 404-3-1, inclusive.

The dominant mineralogical characteristics are: smectites,abundant or relatively abundant and highly crystalline; il-lites, always present; appearance of chlorite and kaolinite;and high proportion of carbonates (about 80%). Quartz andfeldspars are absent.

The sedimentation is of pelagic type (rich in biogeniccarbonates but without detritus of quartz and feldspars) andincludes fine-grained elements with abundant smectites,characteristic of pedogenesis under a hot climate. Nonethe-less, the abrupt appearance of illite and chlorite suggestsalimentation from sources in northern latitudes. This mightbe a sign of the establishment of deep-ocean circulation inthis region.

Assemblage 3 at Site 403 corresponds to Unit 1A (end ofupper Pliocene and Pleistocene), Sections 403-5-2 to 403-1-4, inclusive; and at Site 404, to Unit 1A (upper Pliocene andPleistocene), Sections 404-2-6 to 404-1-1.

The dominant characteristics are: illites, very abundant(dominant in Site 403); smectites, present; chlorites andkaolinites, better represented than in Assemblage 2; carbo-nates, in varying quantities but less abundant than in As-semblage 2; and the reappearance of quartz and feldspars.

The increase in illite and chlorite indicates increasedalimentation from northern sources and/or a local cooling ofthe climate. The reappearance of quartz and feldsparssuggests a coarser-grained sedimentation. This would meanthat ocean currents had a greater competence and implies areinforcement of circulation in the ocean. The colder climatemay also entail sedimentation of elements brought by ice-rafting.

Sites 405 and 406 (Figures 3 and 4, Tables 3 and 4)

Again, there are three mineralogical assemblages. Thefirst in this series is distinctly different from the first as-semblage described for Sites 403 and 404; for this reason it isdesignated IB. Conversely, the two other assemblages areidentical to those at Sites 403 and 404.

Assemblage IB at Site 405 corresponds to Units 2D, 2C,2B, and 2A (lower and lower-middle Eocene), Sections405-43-6 to 405-8-2, inclusive; and at Site 406, to Units 5,4C, 4B, 4A, and 3 (upper Eocene, upper-middle and upperOligocene, and lower Miocene), Sections 406-49-1 to 406-26-2, inclusive.

The dominant characteristics are the exclusive presence ofvery highly crystalline smectites where clay minerals arerepresented, alternate presence of opal CT (sometimes theonly component in the fraction of <2 µJTI) and amorphoussilica, carbonates in varying quantities (low in Site 405, highin Site 406), and very exceptionally quartz and feldspars.

The high content of crystalline or amorphous silica,coupled with the scarcity of quartz, suggests a "chemical"type sedimentation. The origin of silica remains to beexplained as the result of intensive leaching under a hot,damp climate, or possibly a hydrothermal origin. The alter-

666

X-RAY MINERALOGY STUDIES

Lithologic Units < 2 µm fraction Bulk Sediment

UnitSub•botDepth<m)

Series CoreSmectite

50%I

Illite50%

Kaolinite30%

I

Chlorite30%I

Zeolite20%

I

Silicaphase

20%

Carbonate50%I

Quartz

20%1

Feldsparsalkali plagioc

20% 20%I I

PLEISTOCENE

1-4. 82-842-3, 65-673-1, 33-343-3, 22-24

1A 4-1. '-69

UPPERPLIOCENE

100

1B

UPPERMIOCENE

8-2.87-898-6, 86-889-2, 132-134

12-7, 32-3413-3,41-43

16-4, 143-14717-1, 135-137

18-2, 65-67

19-1. 64-67

20-1,47-49

21-2.87-89

200

UPPER/MIDDLEOLIGOCENE

26-2, 108-110

MIDDLEEOCENE

29-1,87-9029-*. 71-7330-1,33-35

300

3ALOWEREOCENE

34-2. 59-6334-6.28-32^35-1, 27-2935-2.74-76^35-4, 71-73-'36-1, 64-67 J37-1, 114-11637-4,35-3738-1,66-6838-4, 66-68

39-2, 137-13940-1, 38-40-\•0-2, 46-480-3, 100-1031-2, 76-78 ->1-3. 59-62 v

2-1. 116-1182-3. 14-163-1. 103-105

3B 400

PALEOCENE (Low

crystallinity)amorphous Silica

Figure 1. Mineralogical log of Site 403.

nation of crystalline and amorphous forms might beexplained by the concentration of silica in the waters: highconcentration due to precipitation of opal by saturation, andlesser concentration caused by the development of siliceousorganisms whose tests enrich the deposit in amorphous silica.

Assemblage 2 corresponds to part of Unit IB at Site 405(upper Miocene), Sample 405-7-1, 11-13 cm; and to Units

2B and a part of 2A at Site 406 (middle and upper Mioceneand base of lower Pliocene), Samples 406-24-2 to 406-4-2,96-98 cm inclusive.

The dominant characteristics are a sudden appearance ofillites, chlorites, and kaolinites, and an abundance of smec-tites. Carbonates are very abundant, while quartz andfeldspars are absent.

667



UnitSub-boDepth(m

Series CoreSmectite

50%Illite50%

Kaolinite30%

I

Chlorite30%1

Zeolite20%

Silicaphase

20%L_

Carbonate50%

Quartz20%


20% 20%

PLEISTOCENE1A

100

1B LOWERPLIOCENE

UPPERMIOCENE

4-2, 67-695-1,84-865-2, 141-143

200

MIDDLEMIOCENE

MIDDLEEOCENE

3A

LOWEREOCENE

300

16-1, 127-129

17-3. 52-5417-6, 127-12918-2, 15-18

3B

PALEOCENE

21-1,7-922-1, 8-1022-3, 131-13322-4, 131-13323-1, 115-11723-5, 147-150

25-1, 5-7

26-1, 14-16

(Lowcrystallinity)

amorphous Silica


This episode is extremely condensed in Site 405 and marksa sharp transformation in relation to the underlying units.This assemblage is identical with Assemblage 2 at Sites 403and 404 and holds the same significance, i.e., carbonatedpelagic deposits associated with very fine, clayish, detritalmaterial in which the abundance of smectites is evidence ofpedogenesis under a hot climate. Besides this, the abruptappearance of illites and chlorites suggests a second type ofalimentation from colder zones and, therefore, the estab-

lishment of deep-water circulation originating in northernlatitudes.

Assemblage 3 at Site 405 corresponds to Units IB (in part)and 1A (lower Pliocene to Pleistocene), Sections 405-6-1 to405-1 -1 , inclusive; and at Site 406, to Units 2A (in part) and 1(lower Pliocene to Pleistocene), Sections 406-4-1, 116-118cm, to 406-1-1, inclusive.

The dominant characteristics are predominance of illites;chlorites and kaolinites, well represented; smectites, present;


TABLE 1X-Ray Diffraction Analyses of the Fine-Grained (<2 µm) and Bulk Samples From Site 403

Sample(Interval in cm)

1-4, 82-842-3, 65-673-1, 33-343-3, 22-244-1,67-695-2, 22-247-1,56-588-2, 87-898-6, 86-889-2, 132-134

11-2,80-8212-7, 32-3413-3,41-4314-2, 52-5416-4, 143-14717-1, 135-13718-2, 65-6719-1, 64-6720-1,47-4921-2, 87-8922-3, 106-10822-6, 38-4024-1,30-3225-1, 11-1326-2, 108-11028-1,94-9629-1, 87-9029 Φ, 71-7330-1,33-3534-2, 59-6334-6, 28-3235-1, 27-2935-2, 74-7635-4, 71-7336-1,64-6737-1, 114-11637-4, 35-3738-1,66-6838-4, 66-6839-2,137-13940-1,38-4040-2, 46-4840-3, 100-10341-2, 76-7841-3,59-6242-1, 116-11842-3, 14-1643-1, 103-105

Depth(m)

5.326.65

14.3317.2224.1734.7752.5663.8769.8673.8292.30

108.82112.41120.52143.43148.35158.65166.64175.97187.37198.56202.38213.80223.11235.08252.44261.87266.21270.83310.59316.28318.27320.24323.21328.14338.14341.85347.16351.66358.87365.88367.46369.50377.26378.59385.66387.64395.03

<2 µm Fraction

O Co"

s w

433235313236495446

10060807750543743576464706271747994

10073

100100

71100100100

8152

1007752

100100

76100100100100100

70

"*-* t-p'r «^

323930394242273033_282014353140332723222023161414—_27-—15——_1019_1115_____—__30

o

1311151212

811

511_5

trace549

1412

7766

10334

—__——_—_______________

-

u

121820181414131110_7

trace4

1169

1296845

1093

__——————_____

________

-

</} PL,

_

_

_

_

_

_

_

_

_

_

_

_

_

_

_

_

_

_

_

_

_

_

—

_

_

_

—

—

_

_

_

_

_

_

_

_

_

_

_

_

_

_

_

_

_

-

"o ^N ^

_

tracetracetracetrace

____

trace___

presence________

presencepresence

6_

trace_

trace14

presence_

trace9

29_

1233__24_____

-

Comment

not much clay

N

σ635167

trace__

trace————————

trace__

trace

_

trace—_33

11_4

143

2211

1542

_5

_4

_

trace15

Bull<

US133 U

u w

6361537635388692907688888684849090869186848890929510_

10——_—____

3_

7____

3trace

5_

-

: Sediment

| g"o w

Q

_

-

—

_

—

—

—

—

—

—

—

—

_

—

—

_

_

—

—

—

_

—

—

—

—

—

_

_

-

-

—

—

—

_

_

_

_

_

_

_

_

_

_

_

_

_

_

-

S S<—--—11

———————--————————--——325

_55

trace1019

276

__4

trace_———6

| g'So

ε_

8--

31

----———-—————-———-—

7352

12—

>5018112012

831

86

1367

_——

39

carbonates, variable (10 to 70%); and quartz and feldspars,present.

This assemblage is identical with Assemblage 3 at Sites403 and 404. The detrital nature of the sedimentation re-sumes (quartz, feldspars). The predominance of illite and theabundance of chlorite attest to the arrival of sediment of anorthern type, to a cooling in the climate, and to the de-velopment of deep-ocean circulation in a north-south direc-tion.

SYNTHESIS AND CONCLUSIONSThree entirely contrasting mineralogical assemblages are

found in succession along the line of holes sunk in the four

sites. The oldest of these shows conflicting characteristics atSites 403 and 404 (Assemblage 1) on the one hand, and atSites 405 and 406 (Assemblage IB) on the other (Figures 5and 6).

The two more recent assemblages (2 and 3) are, however,virtually identical in all four sites.

Mineralogical Assemblage 1 is characteristic of detritalsedimentation, apparently inherited in the main from basicvolcanic rocks. Conditions of weathering under a hot, dampclimate with contrasting seasons may in addition have beeninstrumental in producing this type of assemblage. Sedimen-tation of this nature involves in particular the lower Eocene

669


TABLE 2X-Ray Diffraction Analysis of the Fine-Grained (<2 µm) and Bulk Samples From Site 404


1-1,70-7214, 133-1352-1,47-492-2, 88-902-4, 76-782-5, 134-1362-6, 96-972-6, 127-1293-1, 73-754-2, 67-695-1, 84-865-2, 141-1437-2, 25-288-1,98-102

11-1,57-6611-1,404216-1, 127-12917-3, 52-5417-6, 12-1418-2, 15-1821-1,7-922-1, 8-1022-3, 131-133224,131-13323-1,115-11723-5, 147-15025-1,5-726-1, 14-16

Depth(m)

0.705.83

21.9723.8826.7628.8429.9630.27

104.73172.67180.84182.91200.75209.48237.57265.90285.77297.52301.62305.15332.07341.58345.81347.31352.15358.47370.05379.64

<2 µm Fraction

<o

is1721234441_

4439286558

100100100

32100

84075

10010044602847

100100100

o ••-s

.ts *&

49464929336230364621

9_______

trace___20_18

tracetracetrace

<D

'3 ^

CS

i4

1725

911

91812161399

_--_____

_______-

u

o s£

178

19161720149

135

trace________________-

£ « S1

____________________

______-

<o

"o ^<D w

N__________9___

68_

926025

trace-

56207235

trace--

Comment

not much clay

not much claynot much claynot much clay

not much claynot much claynot much clay

not much claynot much clay

Bulk Sediment

N

a145

1084424-

trace------66

trace42

17trace

4652

trace

I ISü

32333537505368489090867812

75

-10-53

30-3

-33-17-

<o'3 ~.J w§

----------------------------

Feldspar

'é

li%

i44

-2

21-

trace----

trace6

-trace

--2

trace181

1725

16trace

u

!§εbK

288

121

trace-2

----

trace6

-587

1712

33413171422-

trace

(Site 403) but continues up to and including the middleMiocene at Site 404.

Mineralogical Assemblage IB (Sites 405 and 406) revealssedimentation of chemical or biochemical nature, rich insilica and whose origin could be either climatic or hyd-rothermal. This type of sedimentation develops in the Eoceneand continues to the end of the lower Miocene (Site 406).

Mineralogical Assemblage 2 (Sites 403,404,405 and 406)reflects a pelagic sedimentation, with deposits rich in carbo-nated biogenic elements. Detrital components, exclusivelyclay, are scarce. Among them, smectites in large proportionsreflect continued alimentation in fine-grained matter,originating in soils formed under a hot climate with contrast-ing seasons. But the sudden appearance of illites and chlo-rites indicates an additional influx of other types of supply,formed under colder climates and probably transported bydeep-water currents. This acts as a marker for the differentstages in the establishment of deep-water circulation in thevarious areas of drilling. The effects of this circulation arebrusquely apparent at the middle Eocene at Site 403, betweenthe lower and middle Miocene at Site 406, and between themiddle and upper Miocene at Site 404. As for Site 405, thistype of sedimentation occurs only very briefly during theupper Miocene. The upper limit of this assemblage is, how-ever, practically contemporaneous in all four sites and can beplaced in the Pliocene; the break is seen very clearly at Site406 during the lower Pliocene.

Mineralogical Assemblage 3 (Sites 403,404,405 and 406)reflects a resumption of erosion (quartz and feldspars) and a

cooling of the climate (illites predominant, chlorites abun-dant) in the late Pliocene and the Pleistocene.

The similarity in sedimentation in Assemblages 2 and 3,following the sharply contrasted Assemblages 1 and IB,shows that an appreciable change in ocean circulation occur-red after the middle Eocene (Site 403) or the lower, middle,or upper Miocene (Sites 406, 404, and 405, respectively).The divergence in the timing of this transformation resultspartly from gaps in sedimentation. It may also be connectedwith local differences in tectonic phenomena and subsequentreadjustments. As a result of the change, the pattern ofsedimentation (previously dependent on local peculiarities,including basins of detrital sedimentation and chemicalsedimentation) assumes a uniform, pelagic character over theentire zone under study. Subsequently, sedimentation is ofthe modern North Atlantic type, and denotes both a markedcooling in the climate and the development of deep-seacurrents from the north.

ACKNOWLEDGMENTS

We wish to thank R. W. Thompson, L. Montadert, D. G.Roberts who made it possible for us to participate in this study.

We acknowledge the contribution of the scientific officers in-volved. We are also very grateful to Pr. G. Millot for criticallyreviewing the manuscript and for making valuable suggestions forimprovement.

This investigation was supported in part by ATP No. 2685 fromthe Centre National de la Recherche Scientifique.

670



UnitSub-bot

Depth Series CoreSmectite

50%

Illite

50%

Kaolinite

30%_J

Chlorite

30%

Zeolite

20%I

Silicaphase

20%i

Carbonate

50%

Quartz

20%


20% 20%L

PLEISTOCENE1A

1-2, 94-961-6. 67-69-v,2-2. 64-66 - I2 2, 142-1442-5. 76-78 S3-3, 71-734-1, 56-58

J1B

LOWERPLIOCENE/

UPPER MIOCENE

UPPER MIOCENE

2AMIDDLE/LOWER

EOCENE

100

2B

200

LOWEREOCENE

2C

300

2D

400

8-2, 90-928-5, 10-129-1, 94-96

10-1. 85-8710-5. 87-89

12-1, 97-9912-5, 97-9913-1, 60-62

15-3, 77-7916-1. 54-56

16-6, 119 12117-1, 105-10817-5, 90-92

25-1, 64-66

26-1. 18-20

27-1, 50-52

31-1, 73-7531-2, 22-24

32-1, 19-2132-3. 7-9

34-2, 144-145

35-1, 18-20

36-1, 94-9636-3, 14-15

37-2, 56-58

38-2, 120-122

39-1, 6-8

40-2, 138-140

41-5, 34-3842-1, 2-442-3, 5-843-1, 18-2043-3, 112-11643-6, 14-16

amorphous Silica

Opal C. T.


REFERENCES

Biscaye, P. E., 1965. Mineralogy and sedimentation of Recentdeep sea clay in the Atlantic Ocean and adjacent seas and oceans,Geol. Soc. Am. Bull., v. 76, p. 803-832.

Bonatti, E., 1967. Mechanisms of deep sea volcanism in the SouthPacific, Researches in Geochemistry, v. 2, p. 453-491.

Brown, G., 1961. The X-ray identification and crystal structures ofclay minerals: London (Mineralogical society), p. 544.

Chamley, H., 1971. Recherches sur la sedimentation argileuse enMediteranée, Se/ Géol. Mem., Strasbourg, no. 35, p. 209.

Fan Pow-Foong, F. and Zemmels, I., 1972. X-ray mineralogystudies—Leg 12. In Berggren, W. A., Laughton, A. S., et al.,

671


Lithologic Units

Unit

1

2A

2B

3

4A

4B

4C

5

Sub-botDepth(m)

1260

140

210

220

320

350

410

450

500

600

700

800

Series

PLEISTOCENE

PLIOCENE

LOWERPLIOCENE

UPPERMIOCENE

MIDDLEMIOCENE

LOWERMIOCENE

UPPEROLIGOCENE

UPPER/MIDDLEOLIGOCENE

UPPEREOCENE

LOWEREOCENE

Core

1-3, 58-601-3, 139-141

2-2, 92-942-4, 88-91

4-2, 96-98

6-2, 83-85

7-2, 59-618-1, 24-26

8-7, 22-24

9-1,4-6

13-4, 2-5

14-2, 17-20 '15-2,26-28

17-1, 17-20

19-1, 0-3

20 3, 3-4

21-3, 53-55

23-1,22-2423-4, 24-2624-2 28-30

26-2, 126-129

28-1, 58-61

29-2' 1 1 8 - 1 2 0 - ^ \ ^29-4, 58-60 - ^ ^ i:

30-3,125-127 ~ ^ ^ > -30-4, 113-115 —'?-^Ss-

31-1. 109-111—</ /^

33-1 ,'35-37 ^ ^ ~33-4, 23-2534-4,4-635-2, 55-57

36-3,89-9137-1, 10-12 —

37-5, 69-70 ~38-4, 16-1838-4, 98-10039-3, 35-37

40-1, 34-36 •40-2, 109-11241-3, 113-11541-5, 145-14742-1, 19-2042-4. 20-21

45-1, 40-4245-3, 119-122

46-3. 59-63 •47-3.42-45

49-1.6-8 •~~~~~^

< 2 jim fraction

Smectite50%

Mite50%i

-

Kaolinite30%

1

-

-

-

Chlorite30%

1

• = : =

-

—

-

-

Zeolite20%

1

= .

amorphous Silica

Opal C. T.

Silicaphase

20%1

- - - -

nil;

III I 1

mil

III II

Bulk Sediment

Carbonate50%

1

Quartz20%

: = : =

Feldalkali

20%

-

_

sparsplagioc.

20%1


672




1-2, 94-961-6, 67-692-2, 64-662-2, 142-1442-5, 76-783-3,71-734-1,56-585-1,76-785-3, 20-f26-1,61-637-1,11-138-2, 90-928-5,10-129-1,94-96

10-1, 85-8710-5, 85-8910-7,51-5312-1, 97-9912-5, 97-9913-1, 60-6213-7, 61-6314-2, 26-2815-3, 77-7916-1, 54-5616-6, 119-12112-1,105-10817-5,90-9219-3, 93-9525-1,64-6626-1, 18-2027-1,50-5229-1,12-1430-1, 7-931-1, 73-7531-2, 22-2432-1, 19-2132-3, 7-934-2, 144-14535-1, 18-2036-1,94-9636-3,14-1537-2,56-5838-2,120-12239-1, 6-840-2,138-14041-5, 34-3642-1,2-442-3, 5-843-1, 18-2043-3, 112-11443-6,14-16

Depth(m)

2.448.17

10.1410.9214.7621.2127.5637.2639.7046.6155.6167.4071.1075.4484.8590.8793.51

103.93109.93113.10122.11123.76135.27141.54149.69151.55157.40173.43227.14236.18246.00264.62274.07284.23285.22293.19296.07314.94321.64331.94334.14342.56352.70359.56371.88384.84388.02391.05397.68401.62405.14

<2 µm Fraction

ε w

CΛ

trace444242292335462736434438

10086

10090

100100100100100100100100100100

-100100

7376-2455-

trace2068--20164940107127585058

^

5429323442474031431537------_-_----------__-_---_----_----___-

1911131415119

12111710___---___---------______-------_----___-

1 $ S § ~r+ ,—i ,_ gfv.

6 a á -271413101419161119_10____-_

__

-__

-______

2724

1007645

100100

8032

100100

80845160902973425042

18

trace____-_____

5662-

14presence

10___------_________--__---_-__-___-

Bulk Sediment

N

3 '—'

a13

trace7

trace12779

1215_____-

trace______--_

trace________-_

trace_-_-___

tracetrace

__11

<o

o "3 Q

u w

40821383203561313637966968483629402520172236172515221822231728183

_2010201522151216171217171717202117

u

JSa

_--_--

---------______________________

___________-

Feldspar

C

18<

trace-11_24

___12____

trace____

trace____

trace_

trace_____

____2

_____

2__

trace2

ea

S3 ^

is

1-5

_11486

14

________

trace____

trace___8

_______3

______2

__

trace15

Initial Reports of the Deep Sea Drilling Project, v. 12:Washington (U.S. Government Printing Office), p. 1127-1154.

Goldberg, E. C , 1959. Physics and chemistry of the earth, p. 294.Greenwood, R., 1973. Cristobalite: its relationship to chert forma-

tion in selected samples from the Deep Sea Drilling Project, J.Sed. Petrol., v. 43, p. 700-708.

Griffin, J. J., Window, H., and Goldberg, E. D., 1968. The dis-tribution of clay minerals in the world ocean, Deep-sea Re-search, v. 15, p. 433-459.

Griffin, J. J., Koide, M., Hohndorf, A., Hawkins, J. W., andGoldberg, E. D., 1972. Sediments of the Law Basin—rapidlyaccumulating volcanic deposits, Deep-sea Research, v. 19,p. 139-148.

Jones, J. B. and Segnit, E.R., 1971. The nature of opal. 1 nomenc-lature andcostituentphases,/. Geol.Soc. Aust., v. 18,p. 57-68.

Latouche, C., 1971. Les argues des bassins alluvionnaires aquitainset des dépendances océaniques. Contribution à 1'étude d'unenvironnement. These Sci. Nat., Bordeaux, p. 415.

673




1-3,58-601-3, 139-1412-2, 92-942-4,88-913-1,92-944-1, 116-1184-2, 96-986-2, 83-857-2,59-618-1, 24-268-7, 22-249-1,4-6

13-1,3-513-4, 2-514-1,7-914-2, 17-2015-2, 26-2817-1, 17-2019-1,0-320-3, 3-421-3,53-5523-1, 22-2423-4, 24-2624-2, 28-3026-2, 126-12928-1,58-6129-1,41-4329-2, 118-12029-4,58-6029-5,42-4430-1, 11-1230-2, 105-10730-3, 125-12730-4, 113-11530-4, 131-13331-1, 109-11131-2,84-8631-5,85-8732-4, 27-2933-1,35-3733-4, 23-2534-4, 4-635-2,55-5736-3,89-9137-1, 10-1237-3, 106-10837-5,69-7038-4, 16-1838-4,98-10039-3, 35-3739-5, 64-6640-1,34-3640-3, 109-11241-3, 113-11541-5, 145-14742-1, 19-2042-4,20-2145-1,40-4245-3, 119-12246-1,59-6146-3, 59-6347-3,42-4547-5,4-548-3, 131-13348-4, 62-6449-1,6-8

Depth(m)

3.584.39

64.4267.38

138.92215.16216.46330.33339.59347.24356.22413.54451.53456.02461.07462.67472.26489.67508.50521.03531.03546.72551.24557.78577.76594.58603.91606.18608.58609.92613.11615.55617.25618.63618.81623.59624.84629.35636.77641.85646.23655.54662.55673.89679.60683.56686.19693.66694.48701.85705.14708.34712.09721.63724.95727.19731.70755.90759.69765.59768.59777.92780.54788.31789.12793.56

O>

0 0

2821392882_64626866657280685068696981

10078778181_

100100

-10010010010083

100100100100100100100828184

100918682

10010010010010081867482956771

100100828597

10090

S w

38453541_482124182420161021332018_19_11141312_

trace-

tracetrace

-_17

tracetracetracetracetrace

_trace

106

10trace

467

_

_

_trace

_

-_

_

-

<2 µm Fraction

fiu16151315_189777

11655869

_

_4435

__

trace-

tracetrace

-____

______-__________—___—-____—-

u

— Sö

18191316_34

67734656964

_

_7532

__

trace

tracetrace

-___—_

_____

_

_____

_—-—___

____--

1

_—-—18

____

--

_31

_

—-——-----

trace

—__

-_

trace_8

13_-5

_11__

__191426185

3329

tracetrace

18153

trace10

3"o s0) w

N

trace

—_—-—————-

tracepresence

_trace

__

________-

-

__

_

__

_—

6presence

_8

-———-—————_—

presence_____

Bulk Sediment

N>-i / — *

CS ^

71

115

_9

_tracetracetrace

1-

tracetracetrace

_tracetrace

-_

tracetracetrace

2_

1-

trace-

tracetracetracetrace

_

tracetrace

tracetracetrace

-1

trace-

trace_

tracetracetrace

__1

trace_

trace

——_

tracetracetrace

cα y

25663345912 2 •

898282848682848266858587 .798277777644445150207474797774747174797669687978668471868168596854688176207171747933463526282343

O

oQ

_

-

-

—

—

-

—

—

-

-

-

-

-

-

-

—

-

—

—

—

-

_

_

-

-

-

-

-

-

—

—

—

-

-

-

-

_

—

—

-

-

_

-

-

-

—

—

—

—

—

—

-

—

_

—

_

-

-

Feldspar

ig><_-6_

-

--_

_

_——

__

-_--

___

-

—

_--5

-

-_

_

_

__--____

tracetrace

fiεbεn263

_12_

_-----

-—2

-

-

__

----

-

-----

-

-----

_

-

-

-_

__

trace-

674


SITE403

SITE404

281

ASSEMBLAGES

3

SITE405

1B

Smectitelow cryst.

Smectitehigh cryst.

[j :':'j Kaolinite + Chlorite

|vlv!;| Quartz + Feldspar

Lffj~j Zeolite

ε

Figure 5. Mean vß/wes öft<i relative thickness of the minerajogical assemblages.

\\

, \1 \I \I \I x

1I\\III1I\I\t\\\

SITE406

— ; :

••

— ::..;;

- !_ ;- :

Z'-:s

—-:

-:—_:-'

Ii

13

4 i42

242

| 262

s

0m

L800m

, 1975. Les minéraux argileux des sediments actuels derAtlantique Nord-oriental et du Sud de la Mer de Norvège,Proceedings Intern. Clay Conf., Mexico, 16-23 July, p. 45-54.

Leclaire, L., 1974. Hypothèse sur 1'origine des silicifications dansles grands bassins océaniques. Le role des climats hydrolsants,Bull. Soc. Géol. France, v. 7, p. 214-224.

Mason, B. and Sand, L.B., 1960. Clinoptilolite from Patagonia.The relationship between clinoptilolite and heulondite, Am.Mineral., v. 45, p. 341'350.

Millot, G., 1964. Geologie des argues: Paris (Masson et Cie),p. 499.

Mumpton, F. A., 1960. Clinoptilolite redefined, Am. Mineral,v. 45, p. 351-369.

Nayudu, Y. R., 1964. Palagonite tuffs (hyaloclastites) and theproducts of post-eruptive processes, Bull. Volcanol., v. 27,p. 391-410.

Paquet, H., 1969. Evolution géochimique des minéraux argileuxdans les alterations et les sols des climats méditerranéens ettropicaux à saisons contrastées, Mem. Serv. Carte Géol.,Alsace-Lorraine no. 30, p. 212.

Rateev, M. A., Gorbunova, Z. N., Lisitzyn, A. P., and Nosov,G. L., 1969. The distribution of clay minerals in the oceans,Sedimentology, v. 13, p. 21-43.

Tardy, Y., 1969. Géochimie des alterations. Etude des arènes et deseaux de quelques massifs cristallins d'Europe et d'Afrique,Mem. Serv. Carte Géol. Alsace-Lorraine, no. 31, p. 199.

Thorez, J., 1975. Phyllosilicates and clay minerals: Dison, (LelotteEd.), p. 582.

Trichet, J., 1970. Contribution à 1'etude de 1'alteration expérimen-tale des verres volcaniques. Travaux de Laboratoire de Geologiede 1'Ecole Normale Supérieure, Paris, p. 152.

Yeroschev-Shak, V. A., 1954. Clay minerals of the AtlanticOcean. Soviet, Oceanography, 30-2, p. 90-106.

675


SITE403 ASSEMBLAGES

SITE405

SITE406

-Unit--1A

Units1B2

Units3A3B

-Unit- 1A Illite - smectite - chlorite - kaolinite

calcite - quartz - feldspar

Smectite - illite - chlorite - kaolinitecalcite

1B

Smectite

(low crystallinity)

Zeolite

CalciteQuartz

FeldsparAmorphous silica

Smectite

(high crystallinity)

Silica

/opalC. T.\or

\amorphous/Calcite

Units" 1A1B

-(6) .

Unit1B(7)

Units2A2B2C2D

-Units" 1"2A: :

Units34A4B4C5

Figure 6. Schematic diagram of the mineralogical assemblages of the lithological units.

676

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28. X-RAY MINERALOGY STUDIES, LEG 48—ROCKALL REGION … · basaltic ocean floor; (3) recycling by redissolution of silica precipitated by plankton. In their study of sediments in