Constraining magmatic processes with ID-TIMS U-Pb geochronology: towards better P-T-X-t paths in magmatic systems

Wednesday, 10 January 2018: 09:00
Salon Quinamavida (Hotel Quinamavida)
Blair Schoene1, Kyle M Samperton1,2, C. Brenhin Keller1,3, Ayla S Pamukcu1 and Melanie Barboni1,4, (1)Princeton University, Department of Geosciences, Princeton, NJ, United States, (2)Lawrence Livermore National Laboratory, Livermore, CA, United States, (3)Berkeley Geochronology Center, Berkeley, CA, United States, (4)University of California Los Angeles, Earth, Planetary, and Space Sciences, Los Angeles, CA, United States
Abstract:
A combination of field, laboratory, and theoretical investigations have led to models for construction of upper crustal batholiths through pulsed emplacement of smaller batches of magma. Whether melt accumulates or freezes at the level of emplacement depends in part on the magma flux and the size of individual injections. Calibrating these variables in real systems has benefited greatly from the application of U-Pb geochronology of zircon, but doing this accurately requires better understanding of zircon crystallization histories and potential for its transport through magmatic systems from the lower to upper crust.

This contribution will evaluate recent progress and challenges in using U-Pb ID-TIMS geochronology to build models for magma transport and residence in magmatic systems, driven by the goal of answering the following questions: What are the timescales and locations of magmatic differentiation? What are the supersolidus temperature-time paths of magmas? What are the controls on the accumulation and eruptibility of magma? To answer these questions, recent work has focused on integration of high-precision zircon geochronology, geochemistry, and thermometry with petrologic techniques, numerical modeling, and field mapping. Using these techniques on volcanic and plutonic systems on a variety of scales, we can now better characterize the pulsed nature of upper crustal magmatism and track the presence and crystallization history of melts, but still require a much better understanding of, e.g., zircon trace element partition coefficients, controls on magma zircon saturation, and understanding how sampling bias both at the handsample and regional scale effects our models of crustal magmatism.

Ultimately, time is a critical component of any numerical or schematic model for a magmatic system, so continuing to develop new methods for calibrating P-T-t-x paths of liquids and crystals is key. Such studies will continue to constrain the underlying physics and chemistry that lead to such a diverse range of processes observed in the geologic record.

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