Calcite cementation along the Refugio/Carneros fault, Coastal California:a link between deformation, fluid movement and fluid-rock interaction at a basin margin

摘要

Calcite cement occurs at two localities 24 km apart at the ends of the steep-dipping, east-west trending Refugio/Carneros fault, Santa Barbara area, California coast. These occurrences offer clear evidence for interrelated faulting and fluid movement. The Refugio fault juxtaposes Oligocene Vaqueros sandstone, with about 100 m of apparent normal offset, aginst overlying Miocene Rincon shale. At the western end of the fault, calcite, up to 1.5m thick with individual crystals 20 cm across, fills the fault zone and extends via small fratures into the adjacent sandstone. Physical and geochemical evidence from the calcite demonstrates repeated episodes of deformation and fluid movemetn. The carbon iostopic values of this fault-related calcite (#delta#~(13)C_(PDB)-40to-45per thousand)indicate the carbon was generated from oxidation of methane. Estimated crystallization temperatures are around 100deg C, although the outcrop is calculated to have been sumerged at least a few 100m subsea depth.