Figure F36. A. Photograph of hand specimen of a typical moderately altered gabbro from the lower gabbro sequence of Hole 1275B. A narrow, completely altered, composite magmatic vein is indicated by the arrow (interval 209-1275B-14R-1, 50–60 cm). B. Photomicrograph showing the moderate alteration of the gabbro dominated by replacement of pyroxene (px) by aggregates of fibrous green amphibole (ga). Brown amphibole (ba) of uncertain magmatic or hydrothermal origin is a minor component. The plagioclase (pl) is mostly fresh (Sample 209-1275B-14R-1, 50–53 cm) (plane-polarized light: blue + light gray filters; field of view = 1.4 mm; image 1275B

Figure F36. A. Photograph of hand specimen of a typical moderately altered gabbro from the lower gabbro sequence of Hole 1275B. A narrow, completely altered, composite magmatic vein is indicated by the arrow (interval 209-1275B-14R-1, 50–60 cm). B. Photomicrograph showing the moderate alteration of the gabbro dominated by replacement of pyroxene (px) by aggregates of fibrous green amphibole (ga). Brown amphibole (ba) of uncertain magmatic or hydrothermal origin is a minor component. The plagioclase (pl) is mostly fresh (Sample 209-1275B-14R-1, 50–53 cm) (plane-polarized light: blue + light gray filters; field of view = 1.4 mm; image 1275B_015).