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Distribution of hydrous minerals in the subduction system beneath Mexico

Kim, YoungHee and Clayton, Robert W. and Jackson, Jennifer M. (2012) Distribution of hydrous minerals in the subduction system beneath Mexico. Earth and Planetary Science Letters, 341-344 . pp. 58-67. ISSN 0012-821X. http://resolver.caltech.edu/CaltechAUTHORS:20120928-155511390

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Abstract

Teleseismic converted phases are used to probe the composition of the downgoing oceanic crust as a function of depth along the Cocos slab in central and southern Mexico. Previously, modeling of the receiver function (RF) conversion amplitude of the flat Cocos slab beneath central Mexico at 45 km depth revealed a thin low-velocity upper oceanic crust of a thickness of 4 ± 1 km, which has much lower seismic velocities (∼20–30% reduction in shear wave velocities) than (normal) lower crust. High Vp/Vs ratio (∼2.0) also suggested a large concentration of hydrous minerals such as talc in combination of high pore-fluid pressure in the horizontal segment. We extend this previous effort to examine seismic properties of both the steeply subducting Cocos oceanic crust beneath the Trans-Mexican Volcanic Belt (TMVB) in central Mexico and the shallowly dipping crust beneath southern Mexico. Inverted seismic velocities using the converted amplitudes at the top and bottom of the dipping oceanic crust are compared with experimentally constrained seismic velocities of candidate mineral phases in a range of likely pressures and temperatures. The composition of the oceanic crust downdip in the steep part of slab beneath the TMVB includes the minerals such as lawsonite and zoisite at 60–100 km depth, and the eclogitization occurs around 100 km depth. This is related to arc volcanism in the TMVB directly above the slab as well as the slab rollback. In contrast, the dominant mineral phase in the upper oceanic crust of southern Mexico beneath the Isthmus of Tehauntepec is amphibole on top of unaltered gabbroic oceanic crust. The difference in mineral assemblages of the subducted oceanic crust may help explain the difference in slab geometries between central and southern Mexico.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.epsl.2012.06.001DOIArticle
http://www.sciencedirect.com/science/article/pii/S0012821X12002853PublisherArticle
ORCID:
AuthorORCID
Clayton, Robert W.0000-0003-3323-3508
Additional Information:© 2012 Elsevier B.V. Received 3 January 2012. Received in revised form 26 May 2012. Accepted 1 June 2012. Editor: P.Shearer. Available online 6 July 2012. This study was supported by the Gordon and Betty Moore Foundation through the Tectonics Observatory at California Institute of Technology (Contribution number 176) and NSF award EAR 0609707. We thank Xyoli Pérez-Campos, Arturo Iglesias, and others at the Universidad Nacional Autόnoma de México for deploying and maintaining the MASE and VEOX lines. We thank Joann Stock, Michael Gurnis, and Victor Tsai from California Institute of Technology for suggestions,and Ting Chen for providing slab contour lines for Mexican subduction zone. Finally, we thank Editor Peter Shearer and two anonymous reviewers for helpful comments which improved the manuscript.
Group:Caltech Tectonics Observatory, Seismological Laboratory
Funders:
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
NSFEAR-0609707
Subject Keywords:subduction; Mexico; receiver function; hydrous minerals; Bayesian inversion
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Caltech Tectonics Observatory176
Record Number:CaltechAUTHORS:20120928-155511390
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20120928-155511390
Official Citation:YoungHee Kim, Robert W. Clayton, Jennifer M. Jackson, Distribution of hydrous minerals in the subduction system beneath Mexico, Earth and Planetary Science Letters, Volumes 341–344, August 2012, Pages 58-67, ISSN 0012-821X, 10.1016/j.epsl.2012.06.001. (http://www.sciencedirect.com/science/article/pii/S0012821X12002853)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:34559
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:02 Oct 2012 16:10
Last Modified:31 Jan 2017 20:49

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