TO: Tom Davies
FM: Jay Miller
JA Daily Science Report for Expedition 305, 3 February 2005.
SCIENCE UPDATE: Cores 305-U1309D-172R to -178R (837.4 to 871.0 mbsf, 90% recovery) resumed recovery of medium- to coarse-grained, grading to medium-grained gabbro. Medium-grained olivine gabbro occurs in sharp contact below the lowest of two 20 cm to 80 cm thick coarse-grained gabbro intervals in Core U1309D-174R (~847 mbsf). The olivine gabbro has distinct modal and grain size layering and overlies an oxide gabbro exhibiting high-temperature deformation. The rest of the cored interval is generally undeformed. Medium- to coarse-grained gabbro with rare thin (tens of cm) intervals of medium- to coarse-grained oxide gabbro characterize the lower part of the cored interval. Alteration is low throughout, primarily manifested in thin cataclastic intervals, as halos around veins, and as alteration of olivine.