FIG. 2.

High-resolution photomosaic of a cross-section through a cut face of Finn (A) and corresponding schematic diagram (B) showing key mineralogical and structural features. Fractures originating from the exterior and interior portions of the chimney indicate that there was active fluid entrainment into and out of the chimney wall. The temperature of exiting hydrothermal fluid was measured in situ and was determined to be 302°C. Measurement of the temperature of diffuse flow along the exterior surface of the chimney typically yielded values between 2 and 20°C.