9805050 Bebout This research will examine the extents of devolatilization or retention of volatile components in deeply accreted rocks as functions of P-T history deep in forearcs. This integrated field, petrologic and geochemical work will concentrate on suites for which previous detailed petrologic and thermochronological studies have provided constraints on prograde and retrograde metamoprhic evolution, and will focus on selected voaltile components for which subduction cycling is expected to be important. The evidence for varying degrees of volatile loss will be linked with present mineraology and inferred prograde metamorphic reaction histories. The reserach will also provide information regarding the degree to which low-T, high-P/T metamorphic suites preserve a record of the isotopic compositions and sources of high-P/T fluids, the extents of deep pore water subduction, and the scales of fluid mobility at depth in forearcs. The field areas will include the Western Baja Terrane and parts of the Fransciscan Complex. The second task will be studied in selected exposures in the Coast Ranges.
