sandstone mineralogy and petrology · cerning the petrology and diagenesis of these sandstones ......

12. PETROLOGY AND DIAGENESIS OF SANDSTONES, DEEP SEA DRILLING PROJECTSITE 445, DAITO RIDGE

George deVries Klein, Richard L. McConville, Janet M. Harris, and C. K. Steffensen,University of Illinois at Urbana-Champaign

INTRODUCTION

The sandstone succession in the lower 240 meters ofDSDP Site 445, on the Daito Ridge (Figure 1), providedan opportunity to evaluate the effect of burial diagene-sis of sandstones in a deep hole in a tectonic environ-ment (remnant arc) characterized by a history of highheat flow. This report provides preliminary data con-cerning the petrology and diagenesis of these sandstonesand records diagenetic changes which have occurredwith increasing depth of burial. Depths from which oursamples were obtained are shown in Tables 1 and 2.

Methods used for this study included grain-sizeanalysis (measured from thin sections using the methodof Friedman, 1958), polarizing microscopy, X-ray dif-fraction, and scanning electron microscopy. A JEOLscanning electron microscope fitted with an energy-dispersive-X-ray detector was used for obtaining quali-tative chemical data on certain minerals to aid in iden-tification.

GRAIN-SIZE DISTRIBUTIONTable 1 summarizes the grain-size distributions deter-

mined from thin-section analysis (after Friedman, 1958).Most samples are unimodal, except for conglomeraticsandstones and those sandstones containing a relativelylarge volume of clasts of the larger foraminifer Num-mulites boninensis. Median diameters range from 0.125to 2.0 mm in sandstones; higher median diameters occurin two samples of conglomeratic sandstone.

SANDSTONE MINERALOGY AND PETROLOGYTable 2 summarizes modal analyses of 27 samples

which were used in this study. A total of 320 points werecounted for each slide. Detrital grains include recogniz-able volcanic-rock fragments (plagioclase phyric basalt,aphyric basalt, andesite, and microdolerite), plagio-clase, limestone rock fragments ("lumps" of some clas-sifications), fragments of the larger foraminifer Num-mulites boninensis, other foraminifers, augite, olivine,clinopyroxene, and accessory chert.

Devitrified volcanic glass was encountered in the up-per part of the section. Scattered fragments of siltstonewere encountered in one sample, and oolites were ob-served in another. Fragments of pelecypod shells werefound in two samples.

These sandstones were poorly cemented in the upperpart of the sandstone section, being cemented only by arim cement consisting of smectite (Figures 2 and 3) and,

in one instance, mordenite (Figure 4). Smectite wasidentified by optical mineralogy (Figure 2), scanningelectron microscopy (Figure 5), energy-dispersive-X-rayanalysis (Figure 6), and X-ray diffraction. Table 3 sum-marizes the major-element composition of smectite andmordenite from selected samples. These relative abun-dances of elements are consistent with the morphologi-cal, X-ray, and optical identifications. Mordenite wasobserved in one specimen (Figure 4) and identified bythe same methods; the relative abundances of elementsare consistent with the known chemical composition ofthis mineral (Deer et al., 1966).

At greater depths, the sandstones were cemented alsoby clear sparry calcite (Figures 7 through 12). Authigen-ic components include calcite replacing both volcanic-rock fragments and plagioclase (Figure 13) and chert re-placing volcanic-rock fragments (Figures 14 and 15),plagioclase, and calcite.

PROVENANCE AND DIAGENESIS

ProvenanceThe grain components of the sandstones can be

grouped into two classes: carbonate shelly debris, andvolcaniclastic components including volcanic rock frag-ments and highly refractory minerals (augite, pyroxene,olivine). The position of Site 445 in a small basin on theflank of the Daito Ridge, a remnant arc, suggests thatthe arc was the source of these components. Dredgehauls in the Daito Ridge area by Mizuno et al. (1975)and Shiki et al. (1974) indicate that the ridge is compos-ed of volcanic rocks of the type represented in thevolcaniclastic components, which confirms this inter-pretation.

The carbonate fraction is dominantly of shallow-water derivation. The fragments of the giant shallow-water foraminifer Nummulites boninensis indicate trans-fer of material from shallow water, presumably a coastalstrip along the former arc. Other carbonate componentsalso clearly indicate derivation from shallow water alongthe former arc; these include fragments of pelecypods,micritic and bioclastic limestone, and oolites. These ma-terials presumably were transported by turbidity cur-rents; many of our sandstone samples were obtainedfrom graded intervals which show partial or completeBouma sequences. (See Site 445 report and other sedi-mentological studies in this volume.)

In summary, the sandstones at Site 445 were derivedfrom an active island arc (now a remnant arc, DaitoRidge).

609

G. deV. KLEIN, R. L. McCONVILLE, J. M. HARRIS, C. K. STEFFENSEN

60°N

2000-T7135°W 150°

Figure 1. Location of DSDP Site 445.

165° 180°W

Diagenesis

Examination of the authigenic mineral componentsand cements (Table 2) indicates that diagenetic changesare related to depth of burial. Thin section and SEMstudy.revealed that the earliest authigenic mineral phaseis smectite, found as rim cement (Figures 2, 7-12) andmordenite (Figure 4). Smectite rim cementation is firstobserved in sandstone from a sub-bottom depth ofabout 645 meters. At a sub-bottom depth of 700 meters,two additional changes are observed: recrystallizationof carbonate grains, and the development of pressure-welded, embayed grain contacts in limestone fragments.At a depth of 735 meters, sparry-calcite pore-filling ce-ment, completely filling original pore space, is first ob-

served; this change persists downhole (Figures 7-12). At745 meters, calcite has replaced both plagioclase (Figure13) and volcanic rock fragments; this replacement is ob-served also in one or two grains from higher samples. At750 meters, chertification of volcanic-rock fragmentsbecomes dominant (Figures 14, 15). Below 810 meters,recrystallization of calcite cement is common.

These depth-dependent diagenetic changes are sum-marized in Figure 16.

PRELIMINARY CONCLUSIONS

The sandstones in the basal portion of the sequenceat Site 445 consist of dominant grain components of an-desitic volcaniclastic fragments and of fragments of lar-

610

PETROLOGY AND DIAGENESIS OF SANDSTONES

TABLE 1Grain-Size Distribution (%) by Phi-Unit Classes, Determined from Thin Sections of Sandstones, Site 445 (100 Points Counted)

Sample(interval in cm)

Sub-bottomDepth

(m) -1.75 -1.25 -0.75 -0.25 +0.25 0.75

Φ Units

1.25 1.75 2.25 2.75 3.25 3.75 4.25 4.75 >4.75

ΦSO(median

diameter)

445-69-2, 70-72

2, 143-149

71-1,90-91

2, 37-40

75-6,97-100

76-1,23-28

1, 122-125

3, 23-25

77-4,99-104

78-3,58-63

5,0-4

79-2,143-148

84-2, 124-126

85-1, 18-20

86-1,92-94

4, 73-75

88-2, 24-26

89-1, 131-142

90-2, 11-14

2,17-21

2, 22-26

91-2, 64-70

4, 84-88

92-3, 40-48

93-4,127-132

94-2,78-82

4, 132-134

647.20

647.93

664.90

665.87

710.47

711.73

712.72

714.73

726.49

734.08

736.50

743.93

790.24

797.18

797.92

811.73

827.24

836.31

846.11

846.17

846.22

856.14

859.34

866.90

878.77

884.78

888.32

20_

_

_

-

_

-

-

—

5

11

-

-

-

-

-

-

6

-

4

-

—

64

_

_

_

58

22_

1

_

_

_

_

_

3

1

15

-

_

_

-

_

_

1

5

16

3

—

2

_

_

2

19

25

2

5

_

_

_

_

1

1

—

26

4

3

—

—

-

19

3

9

19

1

8

8

_

_

6

—

18

2

19_

_

1

3

_

4

5

18

2

4

8

-

-

20

79

7

7

13

5

2

1

4

7

5

3

13_

3

1

8

3

18

9

11

7

6

20

11

_

26

8

15

8

12

18

4

9

3

10

6

4

11

25_

6

10

11

2

13

20

10

13

8

18

18

2

10

14

16

14

17

15

4

18

13

15

5

4

16

17_

20

27

19

2

20

21

5

21

17

25

24

11

10

26

30

22

14

15

418

20

25

3

_

21

12_

17

22

25

10

21

16

2

10

15

12

9

16

5

11

8

5

11

11

3

24

31

7

2

1

26

6

4

24

21

25

15

15

14

1

19

23

13

22

33

5

21

5

5

13

10

4

23

19

16_

1

12

2

5

16

5

6

19

5

8

1

11

14

3

9

24

3

2

3

—

6

4

2

5

10

10

_

—

5

_

11

10

8

3

23

-

-

-

9

8

—

5

7

2

1

-

_

11

3

-

1

3

4

—

_

1

_

9

4

4

_

16

-

1

—

4

2

—

1

5

—

—

—

—

2

2

—

—

—

1

—

—

1

_

15

_

—

_

6

-

—

-

—

—

1

1

2

-

-

—

—

-

1

—

—

—

—

-

19 37

-1.00+1.64+0.40+2.95+1.95+1.50+1.45+2.80+1.33+1.35-0.79+1.65+2.05+1.15+1.25+2.15-0.20+0.85+0.63-0.10+1.10+0.60-2.00+1.33+1.55+1.10-1.50

ger foraminifers. These sandstones were derived from anisland-arc source, and a shallow-water setting. Trans-port of this sediment was by gravity processes, mostlyturbidity currents, debris flow, and slumping.

Down-hole, progressive changes occur in the ap-pearance of authigenic components. These include ini-tial rim cementation of grains by smectite and morden-ite, subsequent pressure welding and pore-space reduc-tion, and later pore-filling by sparry-calcite cement.Down-hole, carbonate materials were observed to re-crystallize with depth. Carbonate minerals replace pla-gioclase and volcaniclastic rock fragments with increas-ing depth. The last replacement event to occur that isalso depth-dependent is the chertification of recogniz-able rock fragments; this replacement increases in fre-quency down-hole.

These vertical changes are clearly a function of depthof burial. The effect of high regional heat-flow valuescould not be evaluated, because of lack of temperaturedata from the drill site.

ACKNOWLEDGMENTS

Financial support for the laboratory phase of this studycame from a grant awarded by the University of Illinois

Research Board. Division of labor on this project is as follows:Grain-size study was completed by Harris and Steffensen;scanning electron microscopy and energy-dispersive-X-rayanalysis was completed by McConville; and petrology anddiagenesis were completed by Klein. D. D. Ebert kindly madethe X-ray identification of the rim-cementing minerals. E. D.Pittman and F. G. Ethridge reviewed an earlier manuscriptversion of this paper.

REFERENCES

Deer, W. A., Howie, R. A., and Zussman, J., 1966. An Intro-duction to the Rock-Forming Minerals: London (Long-man).

Friedman, G. M., 1958. Determination of sieve-size distribu-tion from thin-section data for sedimentary petrologicalstudies. J. Geol., 66, 394-416.

Mizuno, A., Okuda, Y., Tamaki, K., Kinoshita, Y., Nohara,M., Yuasa, M., Nakajima, M., Murakami, S., and Ishi-baski, K., 1975. Marine geology and geological history ofthe Daito Ridge area, northwestern Philippine Sea. Mar.ScL, 7,484-491, 543-548.

Shiki, T., Aoki, H., Suzuki, H., Masashino, M., and Okuda,Y., 1974. Geological and petrographical results of theGDP-8 cruise in the Philippine Sea. Mar. ScL, 6, 51-55.

611

O\ o

TABLE 2Modal Analyses of Sandstones, Hole 445 (%, based on 320 points)

Sample(interval in cm)

445-69-2, 70-722, 143-149

71-1, 90-912, 37-40

75-3, 23-256,97-100

76-1,23-281, 122-125

77-4,99-10478-3, 58-63

5,0-479-2,143-14884-2, 124-12685-1,18-20

1,92-9486-4,73-7588-2, 24-2689-1,131-14290-2,11-14

2,17-212, 22-26

91-2,64-704, 84-88

92-3, 40-4893-4, 127-13294-2, 78-82

4,132-134

Sub-bottomDepth

(m)

647.20647.93664.90665.87705.23710.47711.73712.72726.49734.08736.50743.93790.24797.18797.92811.73827.24836.31846.11846.17846.22856.14859.34866.90878.77884.78888.32

Plagio-clase

2.36.61.6

6.915.724.018.410.1

1.31.9

0.32.9

2.53.34.8

3.61.22.32.92.23.83.00.38.06.9

3.60.3

VolcanicRockFrag-ments

63.773.430.877.639.937.844.047.943.855.074.144.776.571.284.985.076.877.478.579.786.975.582.682.880.787.713.0

NummulitesFrag-ments

18.70.3

41.6_1.35.36.57.1

36.819.4

2.615.4

1.93.90.3

0.3___0.3_3.90.30.30.3

0.376.5

Detrital Grains

Lime-stoneFrag-ments

2.02.3

14.4

5.931.124.021.025.012.210.4

2.622.8

3.75.60.6

1.00.60.6_0.3_3.9_1.2-

0.36.3

OtherFora-

minifers

_2.6-

1.01.63.91.94.23.62.6

0.3-

0.90.7-

0.3--

__

0.6__-_

0.9

Augite

__1.0

2.30.6_

1.90.6--_-__-_

_-—

0.6—

_-_

-

Olivine

_0.30.3_

1.31.0_—_-_-__-_________

_

-

Clino-pyroxene

0.30.31.0_

2.92.33.61.50.60.6_

0.3

0.30.3-____-—----_

-

Chert

_

1.60.3_

0.31.30.3---_-

0.6_-_

1.2-_

0.6-----_

-

Cement

Smectite

7.312.56.2

6.36.20.3_1.80.3-

13.01.6

2.28.82.9

3.96.77.74.20.30.61.8_1.81.6

1.31.8

Calcite

__-______1.0

6.57.7

11.75.20.3

0.61.87.47.86.33.57.64.80.90.7

1.31.2

Authigenic Minerals

CalciteReplacement ofPlagioclase andVolcanic Rock

Fragments

__-_

0.3__

0.9_-_

0.6__-__1.61.61.00.6_1.61.22.0

1.6-

ChertReplacement ofVolcanic Rock

Fragments

__-_

0.6_

2.30.60.60.9_

0.3__

6.1

5.29.42.94.99.23.83.3

10.23.47.5

3.9-

DevitrifiedVolcanic

Glass

5.7_-___

__-_-__-_________-_

-

Remarks

Plus 2.6 siltstonefragments

Oolite (0.3)Pelecypod shells(6.7)Pelecypod shells(1.6)

Chert replacescalcite (0.03)

Calcite replaceschert (0.03)


Figure 2. Photomicrograph (crossed nicols) showingfragment o/Nummulites boninensis (A) with rim ce-ment of smectite around pore edges. (B) volcaniclas-tic grains (C) also are rim cemented with smectite.Bar scale is 0.5 mm long. Sample 445-69-2, 70-72 cm.

Figure 4. Scanning electron photomicrograph of mor-denite rim cement (A) on volcaniclastic grain (B). Barscale is 5 µm. Sample 445-69-2, 143-149 cm.

Figure 3. Scanning electron photomicrograph showingvolcaniclastic grain (A), with rim cement of smectite(B), and calcite pore fill (C). Bar scale is 25 µm. Sam-ple 445-84-2, 124-126 cm. Figure 5. Scanning electron photomicrograph of smec-

tite. Bar scale is 10 µm. Sample 445-69-2, 70-72 cm.

613


Figure 6. X-ray spectrum of smectite shown in Figure 5.Major peaks are silicon, potassium, and calcium.

TABLE 3Chemical Elements (in order of decreasing abundance)

Determined from Energy-Dispersive-X-rayAnalysis of Specific Minerals

Sample(interval in cm) Mineral Elements

445-69-2, 70-72445-69-2, 143-149445-84-2,124-126445-93-4,127-132

SmectiteMordeniteSmectiteSmectite

Si,Fe, Ca,K, ALTiSi,K,Ca,AlAl,Ca,Si,Fe,KSi,Al,Fe,Ca,K

Figure 7. Photomicrograph of volcaniclastic sandstone(A) with rim cement of smectite (B) and pore-fillingcement of calcite (C). Bar scale is 0.1 mm. Crossednicols. Sample 445-78-5, 0-4 cm.

Figure 8. Same as Figure 7, plane light.

Figure 9. Photomicrograph of volcaniclastic sandstone(A), containing Nummulites fragments (B), with rimcement of smectite (C), and pore-fill cement of cal-cite (D). Crossed nicols. Bar scale is 0.1 mm. Sample445-78-5, 0-4 cm.


614


Figure 11. Photomicrograph of volcaniclastic sandstone,showing volcanic-rock fragments (A), plagioclase(B), rim cement of smectite (C) and pore filling ce-ment of calcite (D). Crossed nicols. Bar scale is 0.1mm. Sample 445-78-5, 0-4 cm.


Figure 13. Volcaniclastic sandstone containing volcanic-rock fragments (A), plagioclase (B), and calcite re-placement of plagioclase (C). Crossed nicols. Barscale is 0.1 mm. Sample 445-84-2, 124-126 cm.

Figure 14. Photomicrograph of volcaniclastic sandstoneshowing volcaniclastic rock fragment replaced bychalcedony (A). Crossed nicols. Bar scale is 0.5 mm.Sample 445-91-4, 84-88 cm.

Figure 15. Photomicrograph of volcaniclastic sandstoneshowing volcaniclastic grains totally replaced bychalcedony and chert (A). Crossed nicols. Bar scale is0.1 mm. Sample 445-93-4, 127-132 cm.

615

"2 ε

— >- u <5

ra ~n £

850

900 J

Figure 16. Depth distribution of lithologies and diagen-etic changes in sandstones at Site 445.


616

sandstone mineralogy and petrology · cerning the petrology and diagenesis of these sandstones ......

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