JA Daily Science Report for Expedition 312, 23 November 2005
LOCATION: Site 1256
SCIENCE UPDATE: Cores 178R to 181R were cored from 1285.7 to 1304.9 mbsf with an average recovery of 8.7%. Penetration remains approximately 1 m/hr. Unit 73 is a uniform, featureless slightly altered fine-grained basalt interrupted by cryptocrystalline dike margins at ~1290 and 1295 mbsf (top of 179R-1 and 180R-1) that extends from the top of Core 177R-1 through to Core 181R-1. Sample 179R-1, piece 2, 5-9 cm incorporates two chilled contacts separating three intrusive events. Rare quartz + chlorite ́ pyrite ́ carbonate veins have light gray or dark green alteration halos. Common tiny white veinlets and thicker chlorite + quartz veins with well developed alteration halos, occur subparallel to the cryptocrystalline chilled margins. The alternation of similar fine-grained basalts with cryptocrystalline dike margins and limited recovery of small pieces suggest the hole is currently penetrating a near-vertical dike margin or many thin dikes. We are nearing 50 hrs of rotation on the bit after which the pipe will be tripped for a bit change.