Table T5. Minerals identified by X-ray diffraction analysis, Hole 1189A.
 
Core, section, interval (cm)
Unit
Description
XRD identification:
major (minor, "trace") minerals*
Anhydrite (wt%)
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.