Crystalline records of crustal contamination of mafic arc magmas across the Sierra Nevada batholith, California

Earth is unique among the rocky planets of the solar system in having compositionally evolved continental crust - the reason for life as we know it. Many differentiation processes have been proposed to explain its existence. Starting with mafic, mantle-derived basalt, differentiation produces a diverse range of more evolved compositions that erupt at subduction zones and form the continental crust. However, quantifying and evaluating the role of pre-existing crust in these processes remains challenging. Focusing on the well-studied Sierra Nevada batholith which provides a framework, I document mafic compositions that reflect an early stage of differentiation in a Mesozoic arc. Transecting the central Sierra Nevada in a regional study of mafic intrusions across the batholith, I show that their ages, geochemistry, and field relationships with the rest of the batholith vary systematically, as the mafic magmas interacted with heterogeneous crustal belts.

Speaker: Juliet Ryan-Davis, Massachusetts Institute of Technology

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