Dr. Chris Mattinson
My research interests center on using the evidence recorded in metamorphic rocks to address regional tectonic questions and to examine the time-scales of orogenic processes at convergent margins. In particular, my work with ultrahigh-pressure (UHP) rocks examines the behavior of the lithosphere during subduction and continental collision using metamorphic petrology, geochronology, geochemistry, and thermodynamics/thermobarometry. My main laboratory techniques are mineral chemistry by electron microprobe, U/Pb geochronology and trace element analyses by ion microprobe (SHRIMP-RG) and laser ablation ICPMS, coupled with evaluation of the geological context of the samples analyzed through field geology. My current and recent research projects include:
Ultrahigh-pressure metamorphism and geochronology, western China: One of the outstanding questions of ultrahigh-pressure metamorphism metamorphism is: How did these rocks return to the surface while preserving their high P/T mineral assemblages? Critical to addressing this question is a better understanding of exhumation rates from depths >80 km to the upper crust. These rates can be determined by combining geochronology and petrology, and therefore, I have focused on zircon U-Pb geochronology using the ion microprobe (SHRIMP-RG) linked to pressure, temperature, and mineral paragenesis by REE geochemistry, mineral inclusion analysis, and thermobarometry. Field work in the North Qaidam ultrahigh-pressure terrane in western China includes five field seasons in western China in 2001, 2002, 2008, and 2009. Graduate students: Wesley Weisberg, David Hernández Uribe, Jake Meyer, Brittany Fagin, Megan Regel, Ben Christensen.
Deep-crustal processes of continental growth, North Cascades, Washington: The Chelan Migmatite Complex records deep crustal magma mixing, fractionation, and assimilation of older arc rocks, providing an opportunity to directly study the record of crustal growth processes in a continental arc setting. We hypothesize that the Chelan Migmatite Complex represents a lower-crustal melt processing zone that contributed melt to the adjacent Okanogan Range batholith, so these two units together represent a crust-building system. Few exposures of the deep roots of arcs exist, and most existing studies have focused on oceanic rather than continental arcs. Our approach will enable us to document assimilation of relatively juvenile crust; this process is expected to be significant in long-lived continental magmatic arcs, but is difficult to detect by other methods. Our results will have implications for understanding how felsic melt is generated in the lower crust, how it migrates, and how plutons are connected to deep-crustal migmatites. Graduate student: Megan Kjelland.
Granulite facies metamorphism and geochronology, eastern Mojave, California: Granulites of the eastern Mojave record Early Proterozoic tectonism during the growth of the North American continent. This project uses field and petrographic investigation, combined with U/Pb geochronology of zircon and monazite, to address the timing of these events, and REE geochemistry, thin section and mineral inclusion relationships connect the U/Pb ages to metamorphic fabrics and mineral assemblages.
Fluid release in accretionary wedge metasediments, Olympic Peninsula, Washington: Field and petrographic investigation to constrain fluid volumes and fluid overpressure potentially related to seismicity. Graduate student: Holly Rotman.
Mineral separation yield efficiency and method development: This project evaluates the time and yield efficiency of heavy mineral separation using a spiral panner. Method development with a test sample of Mt. Stuart batholith granodiorite has improved the yield efficiency, and demonstrated spiral panning to be an effective method for small- to moderate-sized samples with typical zircon concentrations. Undergraduate researchers: Brittany Fagin, Ashley Edwards.