RUI/Collaborative: Evaluating the influence of crustal deformation on episodic magmatism: southern coast mountains of batholith, British Columbia

This project will evaluate processes responsible for the non-steady-state growth of continental crust in Cordilleran-type magmatic arcs. These batholiths develop as a result of subduction of oceanic lithosphere at convergent margins, but the processes that control the tempo of magma production are unclear; even in arcs where subduction is continuous, magmatism is strongly episodic (e.g. Sierra Nevada batholith, Peninsular Ranges batholith, Central Andes). Short periods (10-15 million years) of intense magmatism or 'flare-ups' may generate as much as 90% of total batholithic volumes, with little magmatism occurring during intervening lulls. Geochemical and isotopic signatures indicate that magmas produced during flare-ups incorporate more upper plate material than magmas formed during lulls. This pattern raises the question of whether continental growth by magmatic addition is controlled primarily by the behavior of the subducting oceanic plate or by the tectonics of the continental lithosphere at the plate margin. We are investigating this question through an integrated geologic, geochronological and geochemical study of the southern Coast Mountains Batholith in British Columbia. This project directly addresses a basic question in earth science: how do continents grow? In addition to the research goals of this project, this endeavor is enhancing the scientific education and training of students at four academic institutions recognized for the diversity of their student populations. Engagement of students in fieldwork, laboratory analysis, data interpretation and presentation of results are providing them with insights into all aspects of the science process and career options, and increase retention in STEM fields. Samples and datasets generated as a result of this project are being used to design problem sets and interpretive exercises for classes taught by the investigators. Data generated during this the course of this project is being added to NSF-funded databases, such as NAVDAT, for access by the larger community.