Table
T5. Minerals identified by X-ray diffraction analysis, Hole
1189A.
major (minor, "trace") minerals*
193-1189A-
1R-1,
0-4
1
Fresh,
moderately vesicular, aphyric dacite
Plagioclase,
opaline silica (augite, quartz, spinel)
2R-1,
34-35
2
Moderately
to completely altered, vesicular aphyric dacite
Plagioclase,
cristobalite (K-feldspar, pyrite, chl/sm mixed-layer clays)
2R-1,
77-78
2
Moderately
to completely altered, vesicular aphyric dacite
Anhydrite
(cristobalite, plagioclase, pyrite, "chlorite")
2R-1,
113-115
4
Hydrothermal
breccia with completely altered volcanic clasts
Anhydrite,
cristobalite (pyrite, chl/sm mixed-layer clays, "illite")
3R-1,
6-10
5
Highly
to completely bleached, vesicular aphyric dacite
Plagioclase,
cristobalite (pyrite, chlorite)
3R-1,
20-22
5
Highly
to completely bleached, vesicular aphyric dacite
Cristobalite,
plagioclase (K-feldspar, pyrite, chlorite, illite)
3R-1,
59-63
6
Hydrothermally
fractured volcaniclastic breccia
Quartz,
anhydrite (pyrite, "illite")
20-25
3R-1,
70-73
7
Bleached
and silicified, intensely veined dacite
Quartz
(K-feldspar, pyrite, "chlorite, illite")
4R-1,
17-20
8
Completely
altered dacite
Quartz
(plagioclase, pyrite, chlorite, illite)
4R-1,
21-24
8
Completely
altered dacite
Quartz
(plagioclase, chlorite, pyrite, "illite")
5R-1,
14-16
9
Completely
altered, hydraulic breccia with flow laminated clasts
Quartz
(anhydrite, chlorite, pyrite, illite)
2-5
7R-1,
27-28
10
Completely
altered, slightly vesicular volcanic rock
Quartz,
plagioclase (pyrite, anhydrite, chlorite, illite)
2-5
7R-1,
58-59
11
Completely
altered hydrothermal(?) breccia
Quartz
(anhydrite, pyrite, "illite, chlorite")
5-10
7R-1,
95-96
13
Completely
altered hydrothermal(?) breccia
Quartz
(plagioclase, chlorite, "pyrite, anhydrite")
<2
8R-1,
31-32
15
Poikiloblastically
silicified plagioclase-rich volcanic rock
Plagioclase
(quartz, pyrite, "anhydrite, chlorite")
<2
8R-1,
42-44
15
Poikiloblastically
silicified plagioclase-rich volcanic rock
Plagioclase
(quartz, K-feldspar, pyrite, "anhydrite, smectite, chlorite")
<2
8R-1,
90-92
15
Poikiloblastically
silicified plagioclase-rich volcanic rock
Plagioclase,
quartz (pyrite, K-feldspar, "anhydrite, chlorite, illite")
<2
8R-1,
113-114
15
Poikiloblastically
silicified plagioclase-rich volcanic rock
Quartz,
plagioclase ("chlorite, pyrite")
9R-1,
16-17
16
Completely
altered hydrothermal breccia
Quartz,
anhydrite (plagioclase, pyrite, "chlorite")
15-20
10R-1,
0-1
17
Completely
bleached moderately vesicular volcanic rock
Quartz
(plagioclase, pyrite, "chlorite")
10R-1,
50-51
19
Completely
altered hydrothermal breccia
Quartz,
anhydrite (plagioclase, pyrite, "chlorite, illite")
10-15
11R-1,
37-38
20
Completely
silicified, massive, vesicular volcanic rock
Quartz
(pyrite, illite, chlorite, "anhydrite")
<2
12R-1,
69-70
20
Completely
silicified, massive, vesicular volcanic rock
Quartz
(illite, pyrite)
13R-1,
24-33
22
Pervasively
bleached moderately vesicular volcanic rock
Quartz
(chlorite, pyrite, illite)
13R-1,
51-53
23
Polymict
volcaniclastic breccia
Quartz
(plagioclase, pyrite, chlorite, "illite")
13R-1,
62-71
24
Pervasively
bleached sparsely vesicular volcanic rock
Quartz
(pyrite, "chlorite, illite")
Notes: chl/sm mixed-layer clays = chlorite/smectite-mixed-layer clays. * = the terms major, minor, and trace are applied to X-ray diffraction (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 for cristobalite-dominated assemblages.