4:00 PM - 4:15 PM
[SCG54-13] Drilling the leading edge of the mantle wedge and the underlying metamorphic sole of the Samail Ophiolite: Hole BT1B, Oman Drilling Project
Keywords:Oman Drilling Project, Carbonatized Peridotite
Hole BT1B sampled 3 bands of carbonated peridotite (listvenite) consisting of carbonates + quartz + Fe-oxyhydroxides, plus minor relict spinel ± chromian mica (fuchsite), 2 carbonate-veined serpentinite bands at 80-100 and 180-185 m depth, and then a few cm of ultracataclasite and 70 cm of fault gouge at 197 m depth, followed by 103 m of the metamorphic sole. Onboard Chikyu, core underwent X-ray computed tomography (CT) and multi-sensor logging, imaging and spectroscopy, macroscopic and thin section observations, physical properties measurements, and XRF, XRD and ICP-MS analyses. Listvenites formed and deformed viscously at < 150°C. Brittle deformation is recorded by older veins and generally younger breccias and faults. Listvenites are as dense as gabbros, with generally higher P-wave speeds. The metamorphic sole is composed of fine-grained to microcrystalline metasediments and metabasalts. Metasediments have qtz + plag and mica + amphibole layers, with minor epidote, and become less abundant and poorer in K downhole. Metabasalts are massive, with more epidote and less qtz & mica. Pleochroic blue-green actinolite and possible needles of pumpellyite in quartz suggest low T/P. Sediment and basalt compositions are similar, resembling alkali basalt.