TO: Tom Davies
FM: Jay Miller
JA Daily Science Report for Expedition 305, 17 February 2005.
SCIENCE UPDATE: Cores 305-U1309D-255R to -261R (1225.5 to 1259.1 mbsf, 43% recovery) start in medium- to coarse-grained olivine gabbro, then pass through at least 6 m of olivine-rich troctolite with interstitial plagioclase and a distinct serpentine foliation. No upper or lower contact with the troctolite was recovered. Below the troctolite, we went through ~20 m where recovery decreased significantly in coarse-grained gabbro and oxide gabbro. The rocks recovered in this interval give little indication as to why recovery dropped from continuous pieces of drilled core (commonly only one long cylinder of core per 1.5 m section) to 3-5 cm thick rounded biscuits. The rocks show little deformation (outside of drilling-induced open but unmineralized fractures) and are only slightly to moderately altered.