Crustal Evolution and Recycling in a Long-Lived Transcrustal Magma System

Volcanoes formed at boundaries between colliding tectonic plates are important recorders of large-scale heat and magma transfer from Earth’s interior to it’s surface. Long-term changes in these tectonic plate processes are recorded by the evolution in composition and behavior of magmas through time. A better understanding of these processes can be achieved in areas where magma systems beneath the volcanoes have been uplifted and exposed to study on the Earth’s surface.

This study will focus on long-term magma evolutionary relationships and links to tectonic processes by comparing rock products of magmatic episodes exposed in the Transverse Ranges of California. This area is remarkable because subsequent tectonic tilting and erosion have exposed on Earth’s surface magmatic rocks that formed over a range of depths within a very long-lived magma system.

Comparison of rock and mineral chemistry in a variety of samples will allow researchers to create a detailed timeline of magma evolution over a range of depths within this plate boundary magma system. As an important part of the project, undergraduate geoscience students will engage in qualitative and quantitative analysis of field and laboratory data that will supplement their course work and provide authentic research experiences.

The impact of this project will be broadened by engaging cohorts of geoscience students in a tiered sequence of quantitative research experiences. The goal of this work with student cohorts is to use a set of high impact practices to improve the year over year retention rate of geoscience students. The tiered set of authentic research experiences will help to build a supportive environment that will encourage persistence and will contribute to broadening of underrepresented groups in STEM.

Understanding the evolution of long-lived transcrustal magma systems and the role of crust recycling is a fundamental component of understanding the dynamic evolution of continental arcs. In this project researchers and students will document diverse styles of magma emplacement and pluton assembly as a function of age and paleodepth in the tilted and exhumed Transverse Ranges segment of the California continental arc.

The goal of the study is to expand upon the existing model for the architecture of the prototypical continental arc, to reflect observed processes of crustal evolution and recycling in a long-lived and pulsed arc built within much older, stratified continental crust. Whole rocks and zircon grains will yield evidence of long-term arc evolution that will complement the existing continental arc model based on single pulse, high flux arc growth.

Whole rock and zircon trace element data collected as a function of paleodepth, age and pluton assembly rate will be used to describe the diversity of crustal magma sources and the dynamics of crust recycling in this continental arc magma system. Premagmatic zircons in particular will supplement whole rock data because Pb/U and trace element analyses of diverse populations provide coupled age and mineralogic records of crustal magma provenance and evolution over the life cycle of this continental arc.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.