Plate P5. Photomicrographs of vein minerals in Hole 735B. 1. A felsic patch in gabbro in which amphibole is replacing plagioclase (irregular, light gray patch on right side). The amphibole is strongly zoned from dark brown to light brown and from dark green to light green. The brown amphibole is edenite to magnesio-hornblende, and the green amphibole is actinolite and ferro-actinolite (Sample 176-735B-202R-7, 96-101 cm). 2. Vein filled with natrolite and calcite. The natrolite forms radiating clusters of prismatic crystals growing around the calcite grain (Sample 176-735B-181R-1, 131-136 cm). 3. A different part of the same vein as in 2. Here the natrolite forms small white crystals with square cross-sections in a matrix of light brown aphanitic material. Carbonate fills the irregular parallel crack just above the zeolite vein (Sample 176-735B-181R-1, 131-136 cm). 4. Black to dark brown smectite vein cutting gabbro. Vein has sharp margins but tends to follow grain boundaries. At one point it has bifurcated and enclosed a piece of plagioclase. The small, white veinlet cutting the smectite is a late-stage crack filled with carbonate (Sample 176-735B-133R-7, 92-98 cm). All scale bars = 1 mm. Click on image or highlighted number to see enlargement.