Fig. 2.

(A) Thin section back-scattered electron (BSE) image showing the brecciated serpentinite host, mainly composed of serpentine (Srp) cemented by calcite (Cal) and brucite (Brc). (B) Thin section photomicrograph of brucite−carbonate altered serpentinite host in crossed polarized light. (C) Core photograph showing the brecciated and veined host. The pink mineral is stichtite (Stt), a hydrous Mg−Cr carbonate that formed at the expense of Cr spinel and brucite. The large vein is composed of brucite and calcite in approximately equal amounts, whereas brucite/calcite ratios in smaller veins vary. (D and E) BSE images of calcite in a feathery texture together with large subhedral brucite crystals similar to chimney material from the Lost City hydrothermal field (7).