Evaluating the Role of MASH Processes and the Growth of Continental Crust

The origin and evolution of continental crust along continental margins are fundamental problems in geology. Our current understanding of continental arc magmatism is largely derived from observations of upper- and middle-crustal rocks exposed at the Earth?s surface. These observations include geologic mapping, radiometric age determinations, and whole rock and mineral geochemistry which are used to construct petrologic models for the evolution of continental crust. These data are complimented by experimental studies of deep-crustal melting using likely protolith sources, and various assimilation-fractional crystallization and mixing models which attempt to reconstruct processes that occurred in the mostly inaccessible roots of arcs. However, there have been few studies directly addressing the generation and modification of arc magmas in the deep roots of continental arc systems. We propose to test the origin and evolution of deep crustal melts through targeted field mapping, whole rock and mineral (zircon, hornblende and clinopyroxene) geochemistry, and high-precision U-Pb zircon TIMS dating. We focus on the Malaspina Pluton (Fiordland, New Zealand), which has been extensively mapped and sampled in our previous NSF-funded projects (Klepeis et al., 2016). The Malaspina Pluton was emplaced at ~40 km depth and is one of the deepest and best-preserved paleo-MASH zones preserved in the geologic record. This project focuses on samples currently housed at California State University Northridge (CSUN).