Viete, D.R. and Hacker, B.R. and Allen, M.B. and Seward, G.G.E. and Tobin, M.J. and Kelley, C.S. and Cinque, G. and Duckworth, A.R. (2018) 'Metamorphic records of multiple seismic cycles during subduction.', Science advances., 4 (3). eaaq0234.
Large earthquakes occur in rocks undergoing high-pressure/low-temperature metamorphism during subduction. Rhythmic major-element zoning in garnet is a common product of such metamorphism, and one that must record a fundamental subduction process. We argue that rhythmic major-element zoning in subduction zone garnets from the Franciscan Complex, California, developed in response to growth-dissolution cycles driven by pressure pulses. Using electron probe microanalysis and novel techniques in Raman and synchrotron Fourier transform infrared microspectroscopy, we demonstrate that at least four such pressure pulses, of magnitude 100–350 MPa, occurred over less than 300,000 years. These pressure magnitude and time scale constraints are most consistent with the garnet zoning having resulted from periodic overpressure development-dissipation cycles, related to pore-fluid pressure fluctuations linked to earthquake cycles. This study demonstrates that some metamorphic reactions can track individual earthquake cycles and thereby opens new avenues to the study of seismicity.
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|Publisher Web site:||https://doi.org/10.1126/sciadv.aaq0234|
|Publisher statement:||Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).|
|Date accepted:||07 February 2018|
|Date deposited:||12 March 2018|
|Date of first online publication:||21 March 2018|
|Date first made open access:||No date available|
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