Deep sourced fluids for peridotite carbonation in the shallow mantle wedge of a fossil subduction zone: Sr and C isotope profiles of OmanDP Hole BT1B

International audienceCompletely carbonated peridotites represent a window to study reactions of carbon-rich fluids with mantle rocks. Here we present details on the carbonation history of listvenites close to the basal thrust in the Samail ophiolite. We use samples from Oman Drilling Project Hole BT1B, which provides a continuous record of lithologic transitions, as well as outcrop samples from listvenites, metasediments and metamafics below the basal thrust of the ophiolite. 87Sr/86 115 Sr of listvenites and serpentinites, ranging from 0.7090 to 0.7145, are significantly more radiogenic than mantle values, Cretaceous seawater, and other peridotite hosted carbonates in Oman. The Hawasina sediments that underlie the ophiolite, on the other hand, show higher 87Sr/86 118 Sr values of up to 0.7241. d13 119 C values of total carbon in the listvenites and serpentinites range from - 10.6‰ to 1.92‰. We also identified a small organic carbon component with d13 120 C as low as - 27‰. Based on these results, we propose that during subduction at temperatures above >400°C, carbon-rich fluids derived from decarbonation of the underlying sediments migrated updip and generated the radiogenic 87Sr/86Sr signature and the fractionated d13 123 C values of the serpentinites and listvenites in core BT1