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Metamorphic records of multiple seismic cycles during subduction

DOI: 10.1126/sciadv.aaq0234 DOI Help

Authors: Daniel R. Viete (Johns Hopkins University) , Bradley R. Hacker (University of California) , Mark B. Allen (Durham University) , Gareth G. E. Seward (University of California) , Mark J. Tobin (Australian Synchrotron) , Chris S. Kelley (Diamond Light Source) , Gianfelice Cinque (Diamond Light Source) , Andrew R. Duckworth (Durham University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Science Advances , VOL 4

State: Published (Approved)
Published: March 2018
Diamond Proposal Number(s): 14590

Open Access Open Access

Abstract: 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.

Journal Keywords: Subduction seismicity; Earthquakes; Franciscan; Garnet zoning; Blueschist eclogite

Subject Areas: Earth Science

Instruments: B22-Multimode InfraRed imaging And Microspectroscopy

Other Facilities: Australian Synchrotron