Abstract

The Golden Bear dike in the Sierra Nevada and the Coso dikes in the Coso Range crop out on opposite sides of Owens Valley, California, and strike roughly perpendicular to it. Neither dike reappears along strike across the valley. New data demonstrate that the dike sets are ca. 83 Ma in age, share nearly identical mineralogy and petrography, and intrude similar wall rocks including distinctive 102 Ma leucogranite. Dike bulk-chemical and Sr and Nd isotope compositions are nearly indistinguishable. These data suggest that the dike sets were originally continuous and were offset dextrally by ∼65 km. This displacement estimate is consistent with other recent estimates of total slip across Owens Valley. If faulting began during the Pliocene, the average slip rate was significantly faster than the current rate. Alternatively, motion could have been episodic and have begun as early as the Late Cretaceous.

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