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On the origin of El Chichón volcano and subduction of Tehuantepec Ridge : a geodynamical perspective

Manea, Marina and Manea, Vlad C. (2008) On the origin of El Chichón volcano and subduction of Tehuantepec Ridge : a geodynamical perspective. Journal of Volcanology and Geothermal Research, 175 (4). pp. 459-471. ISSN 0377-0273.

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The origin of El Chichón volcano is poorly understood, and we attempt in this study to demonstrate that the Tehuantepec Ridge (TR), a major tectonic discontinuity on the Cocos plate, plays a key role in determining the location of the volcano by enhancing the slab dehydration budget beneath it. Using marine magnetic anomalies we show that the upper mantle beneath TR undergoes strong serpentinization, carrying significant amounts of water into subduction. Another key aspect of the magnetic anomaly over southern Mexico is a long-wavelength (~150 km) high amplitude (~500 nT) magnetic anomaly located between the trench and the coast. Using a 2D joint magnetic-gravity forward model, constrained by the subduction P–T structure, slab geometry and seismicity, we find a highly magnetic and low-density source located at 40–80 km depth that we interpret as a partially serpentinized mantle wedge formed by fluids expelled from the subducting Cocos plate. Using phase diagrams for sediments, basalt and peridotite, and the thermal structure of the subduction zone beneath El Chichón we find that ~40% of sediments and basalt dehydrate at depths corresponding with the location of the serpentinized mantle wedge, whereas the serpentinized root beneath TR strongly dehydrates (~90%) at depths of 180-200 km comparable with the slab depths beneath El Chichón (200- 220 km). We conclude that this strong deserpentinization pulse of mantle lithosphere beneath TR at great depths is responsible for the unusual location, singularity and, probably, the geochemically distinct signature (adakitic-like) of El Chichón volcano.

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Additional Information:© 2008 Elsevier B.V. Accepted 12 February 2008; available online 6 May 2008. We thank Yuri Taran, Luca Ferrari, William Bandy and an anonymous reviewer for constructive reviews. Ivan Savov, Colin Macpherson and Daniel Selles are also acknowledged for discussion on the adakitic magmatism and slab dehydration. This project is financed by PAPIT no IN105607. Numerical simulations were performed at DGSCA-UNAM Supercomputer Center (KanBalam), Mexico.
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Subject Keywords:Mexican subduction zone; Tehuantepec Ridge; mantle wedge; serpentinization; El Chichón
Issue or Number:4
Record Number:CaltechAUTHORS:MANjvgr08
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13647
Deposited By: Jason Perez
Deposited On:17 Jun 2009 21:37
Last Modified:03 Oct 2019 00:42

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