Abstract

Thermochronology and thermobarometry of two plutons and a ductile shear zone at their contact in the central Sierra Nevada, California, as defined over the range 700 to 300 °C by 40Ar/39Ar dating of hornblende and biotite and U-Pb dating of zircon, indicate that ductile shear coincided closely with dramatically increased cooling and possible decompression of both plutons. Deformation occurred as the younger (∼90 Ma) Mount Givens pluton was emplaced against the older (∼102 Ma) Dinkey Creek pluton, which was softened by conductive heating, during extension. These events coincided with significant regional exhumation, possibly a result of crustal inflation, recorded by a major pulse of rapid sediment accumulation in contemporaneous fore-arc strata of the Great Valley sequence.

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