Figure F84. Interval 185-801C-37R-1, 26-38 cm, is from the top of a lava flow that is >10 m thick. The flow is cut by fractures that are filled with calcite, some of which are more than 1 cm thick. Part of the thick calcite vein shown here was used to inoculate cultures. A thin section taken from this piece shows bands of pyrite and brown alteration along the fractures. This suggests an episode of alteration sulfide formation followed by and episode of iron oxide formation.