TO: Tom Davies
FM: Jay Miller
JA Daily Science Report for Expedition 305, 19 January 2005.
SCIENCE UPDATE: Cores 305-U1309D-95R to -103R (472.6 to 515.8 mbsf, 80% recovery) are predominantly coarse-grained gabbro and olivine-bearing gabbro, with several intervals of medium- to coarse-grained olivine gabbro. The top of Core U1309D-100R (497 mbsf) contains a 40-50 cm thick interval with abundant clinopyroxene and serpentinized olivine, with very little plagioclase, and grades down section into olivine gabbro (abundance of plagioclase increases to >40% over 20-30 cm). Magmatic fabric in the coarse-grained gabbro is for the most part subtle, with thin intervals ( a few tens of cm) with more pronounced crystal orientation. The coarser grained gabbro intervals generally appear to be more intensely altered than the medium- to coarse-grained olivine-bearing gabbro.