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Geology Club Seminar

Thursday, February 14, 2019
4:00pm to 5:00pm
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Arms 151 (Buwalda Room)
Leveraging Cretaceous Great Valley forearc deposits to target the Jurassic arc: an integrated detrital ZTE/field-based geochronologic investigation of the southern Sierra Nevada batholith
Diane Clemens-Knott, Professor Emeritus, California State University, Fullerton,

Part I: A zircon trace element survey of the Great Valley Group identifies a middle-to-heavy REE anomaly in Middle to Late Jurassic detrital zircon deposited in the forearc basin of the Sierra Nevada arc. After removing grains sourced in the Coast Range ophiolite, remaining ZTE anomalies are variably attributed to deep crustal fractional crystallization and mineral-resorption reactions occurring during upwelling of Late Jurassic magmas. The origin of the negative Nb anomaly characterizing most arcs is explored.

Part II: Geochronologic and petrogenetic studies aimed at understanding the arc-context of the Jurassic Summit Gabbro Middle unexpectedly tie into predictions made by the detrital ZTE study. A detailed U-Pb investigation of the massive Sacatar intrusion and adjacent plutons, along with newly recognized Jurassic volcanic sequences, form the basis for an emplacement model for late Jurassic-earliest Cretaceous gabbros of the Kern Plateau.