TO: Tom Davies

FM: Jay Miller


JA Daily Science Report for Expedition 305, 29 January 2005.


SCIENCE UPDATE: Cores 305-U1309D-161R to -167R (784.6 to 818.2 mbsf, 84% recovery) are gabbro and olivine-bearing gabbro. Grain size varies from medium to coarse, and rarely to pegmatitic, with clinopyroxene crystals as large as 15 cm. Modal and grain size transitions are, for the most part, fairly abrupt, but the scale ranges from layered intervals only a few centimeters to a few tens of centimeters thick, to sections of coarse-grained gabbro a few meters thick. Only a couple of thin seams of oxide-bearing gabbro were recovered, as well as a 5 cm thick, moderately steeply dipping diabase dike. Alteration is generally low, and some magmatic fabric is present, expressed primarily in the finer grained gabbroic rocks.