JA Daily Science Report for Expedition 309, 09 August 2005


LOCATION: Site 1256


SCIENCE UPDATE:  Shortly after midnight the VIT was launched and Hole 1256D was re-entered for the eighth time on Expedition 309 at 0148 with the seventh CC-9 rotary coring bit. Discussions the previous evening between the science and operations teams considered changing to CC-7 drill bits with more conical cutting teeth that might improve penetration rates. However, because of the flush nature of the gauge-cutters on the CC-7 bit as opposed to their more durable bulbous profile on a CC-9, it was decided to continue with the CC-9 coring bits, as these had performed admirably to date.  Approximately 3 m of fill was encountered at the bottom of the hole and this was reamed and washed before coring recommenced at 0800.


Drilling progressed in Hole 1256D from 1108.9 to 1118.5 mbsf and returned 2.78 m of core (29 % recovery).  Core 139R comprises cryptocrystalline to microcrystalline basalt with some saponite + anhydrite + pyrite vein networks that strongly disrupt the igneous fabric. Core 140R includes more than 50 cm of spectacular, sulfide impregnated dike margin breccia with complex intrusive relationships and intricate multiple, margin-parallel sulfide veins and cross-cutting anhydrite veins.  In addition to split core photographs, the outside surfaces of these breccias were also photographed. The photogenic appearance of these cores was greatly improved by the use of the nylon-bristled core grooming tool.