Abundant evidence exists for microbial life within the oceanic volcanic crust (Deming and Baross, 1993; Furnes et al., 1996; Giovannoni et al., 1996; Thorseth et al., 1995; Fisk et al., 1998). Two objectives of Leg 168 were to understand the alteration of the ocean crust and the formation of fluids in the relatively young ocean crust. The microbial communities that may exist in this environment could have significant effects on both the alteration of rocks and the chemistry of circulating fluids and so are relevant to the primary objectives of Leg 168. Fluids and rocks collected from Hole 1026B were examined to determine the presence and identity of the subsurface microbial community.
Hole 1026B was drilled in the northeast Pacific Ocean (47°45.739´N, 127°45.552´W) on the east flank of the Juan de Fuca Ridge (Fig. 1). At this location there is a smooth abyssal plain at 2658 m and 250 m of sediment above volcanic basement. The hole was designed to be reentered, so it was cased through sediment to basement (256 mbsf) with 10.75-in. pipe. Drilling below the casing fractured the basalts, which fell into the hole and jammed the drill string. The hole was deepened to 295 mbsf, but rubble in the hole limited water sampling and temperature measurements to a maximum depth of 286 mbsf. The hole was left on July 22, 1996 to continue work on other holes, and when Hole 1026B was revisited on August 2, it had filled with 64°C water from a subsurface aquifer (formation water).