Table T8. Minerals identified by XRD analysis, Hole 1188A.

Table T8. Minerals identified by XRD analysis, Hole 1188A.

Core, section, interval (cm)

Unit

Description

XRD identification: major (minor, "trace") minerals*

Anhydrite (%)

193-1188A-

2R-1, 9-12 1 Moderately vesicular rhyodacite Opaline silica, plagioclase (augite, "smectite")

5R-1, 38-40 2 Completely altered aphyric volcanic rock with perlitic texture Opaline silica (illite, smectite, pyrite, plagioclase)

5R-1, 42-45 2 Completely altered aphyric volcanic rock with perlitic texture Opaline silica (plagioclase, anorthite, sepiolite, k-feldspar, pyrite, "smectite")

7R-1, 62-64 4 Gray rock with anhydrite-pyrite veins Cristobalite, anhydrite (pyrite, plagioclase)

7R-1, 92-93 4 Flow-banded rock with anhydrite-pyrite veins Cristobalite (anhydrite, pyrite, plagioclase, smectite, "chl/sm mixed-layer clays, hematite")

7R-1, 119-120 5 Jigsaw breccia with textures replaced by anhydrite and chlorite Anhydrite, cristobalite (pyrite, chlorite, illite)

7R-1, 145-147 5 Rock with a pseudoclastic texture Anhydrite (cristobalite, pyrite, pyrophyllite, "quartz")

7R-2, 39-41 6 Completely altered fractured volcanic rock Cristobalite (anhydrite, pyrite, chlorite, illite, "barite")

7R-2, 51-53 6 Completely altered fractured volcanic rock Anhydrite, cristobalite (pyrite, quartz, illite, "barite")

8R-1, 66-69 6 Completely altered fractured volcanic rock Cristobalite (anhydrite, pyrite, chlorite, illite, "barite")

8R-1, 124-127 6 Completely altered fractured volcanic rock Cristobalite (anhydrite, pyrite, illite, "chlorite, barite")

8R-1, 147-148 7 Completely bleached vesicular volcanic rock with silicification Cristobalite, anhydrite (pyrite, quartz, illite, "barite")

9R-1, 13-14 7 Completely altered fractured volcanic rock Cristobalite, anhydrite, quartz (pyrophyllite, "pyrite, barite")

9R-1, 67-70 8 Completely altered fractured volcanic rock Cristobalite (pyrophyllite, pyrite, anhydrite, "barite")

9R-2, 79-81 8 Completely altered fractured volcanic rock Cristobalite (anhydrite, quartz, pyrite, illite)

10R-1, 35-37 8 Completely altered fractured volcanic rock Quartz, cristobalite (pyrophyllite, "barite, pyrite")

11R-1, 35-38 9 Completely bleached vesicular volcanic rock with silicification Cristobalite (plagioclase, quartz, anhydrite, pyrite, "chlorite")

11R-1, 56-57 9 Completely bleached vesicular volcanic rock with silicification Cristobalite, plagioclase, quartz (pyrite, anhydrite, "illite, barite")

12R-1, 51-52 10 Completely altered fractured perlitic and flow-banded rock Quartz, cristobalite, anhydrite (pyrophyllite, pyrite)

12R-1, 69-70 10 Completely altered fractured perlitic and flow-banded rock Cristobalite (anhydrite, pyrite, "illite, chlorite, chl/sm mixed-layer clays, smectite, barite")

12R-1, 117-118 10 Completely altered fractured perlitic and flow-banded rock Cristobalite, plagioclase (quartz, "pyrite, anhydrite, barite")

12R-2, 48-51 10 Completely altered fractured perlitic and flow-banded rock Cristobalite, plagioclase (quartz, pyrite, "anhydrite, barite, chlorite")

13R-1, 9-12 11 Completely altered, pervasively bleached volcanic rock Cristobalite, plagioclase (quartz, pyrite, "anhydrite, barite, chl/sm mixed-layer clays")

14R-1, 4-10 12 Completely altered volcaniclastic, granule to pebble breccia Quartz (illite, "pyrite")

14R-1, 44-45 13 Pervasively bleached fractured volcanic rock Quartz (cristobalite, anhydrite, pyrite, illite, "talc") 2-5

14R-1, 92-93 13 Pervasively bleached fractured volcanic rock Quartz, anhydrite (pyrite, illite, "talc") 5-10

14R-1, 105-108 14 Completely altered volcaniclastic breccia Quartz (anhydrite, illite) 2-5

15R-1, 14-21 15 Anhydrite vein Anhydrite 100

15R-1, 76-80 16 Completely bleached and silicified, vesicular volcanic rock Quartz (illite, pyrite, "anhydrite") <2

16R-1, 77-78 17 Completely silicified, sparsely vesicular volcanic rock Quartz (anhydrite, plagioclase, illite, "pyrite, chlorite") 2-5

16R-1, 95-98 17 Completely silicified, sparsely vesicular volcanic rock Quartz (anhydrite, plagioclase, illite, "chlorite") 2-5

16R-2, 12-15 18 Gray-green finely laminated, strongly silicified volcanic rock Quartz, plagioclase (pyrite, "chlorite, anhydrite") <2

16R-2, 40-43 18 Gray-green finely laminated, strongly silicified volcanic rock Quartz, plagioclase (pyrite, "chlorite, anhydrite") <2

16R-2, 51-52 18 Gray-green finely laminated, strongly silicified volcanic rock Quartz, plagioclase (chlorite, "anhydrite, pyrite") <2

16R-2, 68-69 18 Gray-green finely laminated, strongly silicified volcanic rock Quartz, plagioclase ("chlorite, pyrite, anhydrite") <2

17R-1, 90-93 19 Silicified, bleached volcanic rock Quartz (illite, "pyrite, anhydrite, chlorite") <2

17R-1, 123-124 19 Silicified, bleached volcanic rock Quartz (anhydrite, "illite") 5-10

18R-1, 28-29 19 Silicified, bleached volcanic rock Quartz, anhydrite (magnetite, "illite") 15-20

18R-1, 87-97 20 Silicified and bleached, moderately vesicular volcanic rock Quartz (anhydrite) 2-5

19R-1, 51-57 21 Silicified volcanic rock Cristobalite, plagioclase (quartz, chlorite)

19R-1, 73-76 22 Moderately altered, vesicular volcanic rock Cristobalite, plagioclase (chlorite)

20R-1, 46-47 23 Silicified, moderately chloritic magnetite-bearing volcanic rock Quartz (plagioclase, anhydrite, corrensite, magnetite, illite, "pyrite") 2-5

20R-1, 75-76 23 Silicified, moderately chloritic magnetite-bearing volcanic rock Quartz, plagioclase (magnetite, pyrite, chlorite) 0

20R-1, 92-95 24 Distinctive dark green silicified rock Quartz, plagioclase (magnetite, pyrite, smectite, "anhydrite, chl/sm mixed-layer clays") <2

20R-1, 102-103 24 Distinctive dark green silicified rock Quartz, plagioclase (magnetite, pyrite, corrensite, "anhydrite") <2

21R-1, 20-21 25 Green-black rock with green clay in a silica-pyrite stockwork Quartz (plagioclase, magnetite, corrensite, "pyrite") 0

Core, section, interval (cm)	Unit	Description	XRD identification: major (minor, "trace") minerals*	Anhydrite (%)
193-1188A-
2R-1, 9-12	1	Moderately vesicular rhyodacite	Opaline silica, plagioclase (augite, "smectite")
5R-1, 38-40	2	Completely altered aphyric volcanic rock with perlitic texture	Opaline silica (illite, smectite, pyrite, plagioclase)
5R-1, 42-45	2	Completely altered aphyric volcanic rock with perlitic texture	Opaline silica (plagioclase, anorthite, sepiolite, k-feldspar, pyrite, "smectite")
7R-1, 62-64	4	Gray rock with anhydrite-pyrite veins	Cristobalite, anhydrite (pyrite, plagioclase)
7R-1, 92-93	4	Flow-banded rock with anhydrite-pyrite veins	Cristobalite (anhydrite, pyrite, plagioclase, smectite, "chl/sm mixed-layer clays, hematite")
7R-1, 119-120	5	Jigsaw breccia with textures replaced by anhydrite and chlorite	Anhydrite, cristobalite (pyrite, chlorite, illite)
7R-1, 145-147	5	Rock with a pseudoclastic texture	Anhydrite (cristobalite, pyrite, pyrophyllite, "quartz")
7R-2, 39-41	6	Completely altered fractured volcanic rock	Cristobalite (anhydrite, pyrite, chlorite, illite, "barite")
7R-2, 51-53	6	Completely altered fractured volcanic rock	Anhydrite, cristobalite (pyrite, quartz, illite, "barite")
8R-1, 66-69	6	Completely altered fractured volcanic rock	Cristobalite (anhydrite, pyrite, chlorite, illite, "barite")
8R-1, 124-127	6	Completely altered fractured volcanic rock	Cristobalite (anhydrite, pyrite, illite, "chlorite, barite")
8R-1, 147-148	7	Completely bleached vesicular volcanic rock with silicification	Cristobalite, anhydrite (pyrite, quartz, illite, "barite")
9R-1, 13-14	7	Completely altered fractured volcanic rock	Cristobalite, anhydrite, quartz (pyrophyllite, "pyrite, barite")
9R-1, 67-70	8	Completely altered fractured volcanic rock	Cristobalite (pyrophyllite, pyrite, anhydrite, "barite")
9R-2, 79-81	8	Completely altered fractured volcanic rock	Cristobalite (anhydrite, quartz, pyrite, illite)
10R-1, 35-37	8	Completely altered fractured volcanic rock	Quartz, cristobalite (pyrophyllite, "barite, pyrite")
11R-1, 35-38	9	Completely bleached vesicular volcanic rock with silicification	Cristobalite (plagioclase, quartz, anhydrite, pyrite, "chlorite")
11R-1, 56-57	9	Completely bleached vesicular volcanic rock with silicification	Cristobalite, plagioclase, quartz (pyrite, anhydrite, "illite, barite")
12R-1, 51-52	10	Completely altered fractured perlitic and flow-banded rock	Quartz, cristobalite, anhydrite (pyrophyllite, pyrite)
12R-1, 69-70	10	Completely altered fractured perlitic and flow-banded rock	Cristobalite (anhydrite, pyrite, "illite, chlorite, chl/sm mixed-layer clays, smectite, barite")
12R-1, 117-118	10	Completely altered fractured perlitic and flow-banded rock	Cristobalite, plagioclase (quartz, "pyrite, anhydrite, barite")
12R-2, 48-51	10	Completely altered fractured perlitic and flow-banded rock	Cristobalite, plagioclase (quartz, pyrite, "anhydrite, barite, chlorite")
13R-1, 9-12	11	Completely altered, pervasively bleached volcanic rock	Cristobalite, plagioclase (quartz, pyrite, "anhydrite, barite, chl/sm mixed-layer clays")
14R-1, 4-10	12	Completely altered volcaniclastic, granule to pebble breccia	Quartz (illite, "pyrite")
14R-1, 44-45	13	Pervasively bleached fractured volcanic rock	Quartz (cristobalite, anhydrite, pyrite, illite, "talc")	2-5
14R-1, 92-93	13	Pervasively bleached fractured volcanic rock	Quartz, anhydrite (pyrite, illite, "talc")	5-10
14R-1, 105-108	14	Completely altered volcaniclastic breccia	Quartz (anhydrite, illite)	2-5
15R-1, 14-21	15	Anhydrite vein	Anhydrite	100
15R-1, 76-80	16	Completely bleached and silicified, vesicular volcanic rock	Quartz (illite, pyrite, "anhydrite")	<2
16R-1, 77-78	17	Completely silicified, sparsely vesicular volcanic rock	Quartz (anhydrite, plagioclase, illite, "pyrite, chlorite")	2-5
16R-1, 95-98	17	Completely silicified, sparsely vesicular volcanic rock	Quartz (anhydrite, plagioclase, illite, "chlorite")	2-5
16R-2, 12-15	18	Gray-green finely laminated, strongly silicified volcanic rock	Quartz, plagioclase (pyrite, "chlorite, anhydrite")	<2
16R-2, 40-43	18	Gray-green finely laminated, strongly silicified volcanic rock	Quartz, plagioclase (pyrite, "chlorite, anhydrite")	<2
16R-2, 51-52	18	Gray-green finely laminated, strongly silicified volcanic rock	Quartz, plagioclase (chlorite, "anhydrite, pyrite")	<2
16R-2, 68-69	18	Gray-green finely laminated, strongly silicified volcanic rock	Quartz, plagioclase ("chlorite, pyrite, anhydrite")	<2
17R-1, 90-93	19	Silicified, bleached volcanic rock	Quartz (illite, "pyrite, anhydrite, chlorite")	<2
17R-1, 123-124	19	Silicified, bleached volcanic rock	Quartz (anhydrite, "illite")	5-10
18R-1, 28-29	19	Silicified, bleached volcanic rock	Quartz, anhydrite (magnetite, "illite")	15-20
18R-1, 87-97	20	Silicified and bleached, moderately vesicular volcanic rock	Quartz (anhydrite)	2-5
19R-1, 51-57	21	Silicified volcanic rock	Cristobalite, plagioclase (quartz, chlorite)
19R-1, 73-76	22	Moderately altered, vesicular volcanic rock	Cristobalite, plagioclase (chlorite)
20R-1, 46-47	23	Silicified, moderately chloritic magnetite-bearing volcanic rock	Quartz (plagioclase, anhydrite, corrensite, magnetite, illite, "pyrite")	2-5
20R-1, 75-76	23	Silicified, moderately chloritic magnetite-bearing volcanic rock	Quartz, plagioclase (magnetite, pyrite, chlorite)	0
20R-1, 92-95	24	Distinctive dark green silicified rock	Quartz, plagioclase (magnetite, pyrite, smectite, "anhydrite, chl/sm mixed-layer clays")	<2
20R-1, 102-103	24	Distinctive dark green silicified rock	Quartz, plagioclase (magnetite, pyrite, corrensite, "anhydrite")	<2
21R-1, 20-21	25	Green-black rock with green clay in a silica-pyrite stockwork	Quartz (plagioclase, magnetite, corrensite, "pyrite")	0

Notes: XRD = X-ray diffraction. * = the terms major, minor, and trace are applied to XRD analyses as explained in "Hydrothermal Alteration" in the "Explanatory Notes" chapter and do not imply quantitative abundances. Anhydrite abundances are estimated for quartz-bearing assemblages as described in "Hydrothermal Alteration" in the "Explanatory Notes" chapter. This procedure probably results in an overestimation of the anhydrite abundance because the effect of clays is ignored. In the absence of a suitable calibration, it is not possible to estimate anhydrite abundance from XRD spectra. Chl/sm mixed-layer clays = chlorite/smectite-mixed layer clays.