JA Daily Science Report for Expedition 309, 22 July 2005


LOCATION: Site 1256


SCIENCE UPDATE: Core 85R was on deck at 0125 after coring from 811.40 to 821.00 mbsf with 7.11 m of recovery (74.1%). Core 85R marks a transition from predominantly thin basaltic sheet flows above to a basaltic massive flow greater than 3 m in thickness. The degree of alteration in Core 85R increases overall as indicated by abundant brown and mixed brown and black halos in Sections 1 to 5. The brown color comes from an abundance of iron-oxyhydroxides. Section 85R-6  contains no brown halos but vesicles filled with saponite are common, possibly indicating more reducing conditions. Below Section 85R-1 the distribution of fracturing also changes. Fracturing is more heterogeneously distributed and partitioned into 20-40 mm thick fault zones characterized by nearly parallel and anastomosing veins and shear veins with local  protocataclasite. Slickenfibers in the faults are consistent with a normal sense of shear. Veins (0.2 to 10 mm) in the fault zones are filled with iron-oxyhydroxides, saponite, minor silica and sulfides.