Serpentinization and infiltration metasomatism in the Trinity peridotite, Klamath province, northern California: implications for subduction zones

摘要: The Trinity peridotite was emplaced over metabasalts and metasedimentary rocks of the central metamorphic belt along Devonian thrust zone. Three events can be recognized in peridotite: (1) antigorite (δD= −63 to −65%.) formation related regional underthrusting belt; (2) contact metamorphism associated with Mesozoic dioritic plutons; (3) late-stage lizardite ± brucite chrysotile −127 −175%.) due infiltration meteoric waters. Abundant relict phases indicate incomplete reactions strongly suggest that availability H2O a controlling factor during serpentinization. Antigorite (event 1) formed as result into mixed H2O-CO2 fluids derived from underlying belt. Foliation defined by magnetite veins shear zones within serpentinites are subparallel thrust. assemblage Fo + Atg Chl Mag Tr Carb reflects partial hydration at 425–570° C. Talc-rich serpentinite silica-bearing fluids. Metasomatic mass-balance calculations based on silica solubilities extent serpentinization 80–175 volumes fluid have passed through given volume original probably represents subduction Thermodynamic account for ∼30–35% total heat released cooling peridotite. By analogy, similar expected overlying mantle wedge zone which act retard hanging wall, just dehydration delay heating downgoing slab. may reflect metasomatic processes those proposed occur above subducting