Thermal structure of the Costa Rica - Nicaragua subduction zone

Publication Type  Journal Article
Year of Publication  2005
Authors  Peacock, S. M.; van Keken, P. E.; Holloway, S. D.; Hacker, B. R.; Abers, G. A.; Fergason, R. L.
Journal Title  Physics of the Earth and Planetary Interiors
Volume  149
Issue  1-2
Pages  187-200
Journal Date  Mar 15
ISBN Number  0031-9201
Accession Number  ISI:000227856000012
Key Words  subduction; thermal modelling; metamorphism; are magmatism; lithosphere; central-american arc; convergent margin; heat-flow; regional-variations; northeast japan; cocos plate; lavas; earthquakes; constraints; trench
Abstract  

We constructed four high-resolution, finite-element thermal models across the Nicaragua - Costa Rica subduction zone to predict the (i) thermal structure, (ii) metamorphic pressure (P)-temperature (T) paths followed by subducting lithosphere, and (iii) loci and types of slab dehydration reactions. These new models incorporate a temperature- and stress-dependent olivine rheology for the mantle-wedge that focuses hot asthenosphere into the tip of the mantle-wedge. At P = 3 GPa (100 km depth), predicted slab interface temperatures are similar to 800 degrees C, about 170 degrees C warmer than temperatures predicted using an isoviscous mantle-wedge rheology. At the same pressure, predicted temperatures at the base of 7 km thick subducting oceanic crust range from 500 degrees C beneath SE Costa Rica to 400-440 degrees C beneath Nicaragua and NW Costa Rica. The high thermal gradients perpendicular to the slab interface permit partial melting of subducting sediments while the underlying oceanic crust dehydrates, consistent with recent geochemical studies of arc basalts. Hydrous eclogite is predicted to persist to - 120 km depth beneath Nicaragua. This is slightly less than the - 150 km depth extent of a dipping low-seismic-velocity wave guide which may reflect deeper persistence of metastable gabbro. Along-strike variations in the calculated thermal structure are relatively minor compared to variations in the distribution of Wadati-Benioff earthquakes and arc geochemistry, suggesting that regional variations in slab stresses, crustal thickness, incoming sediment load, and the distribution of hydrous minerals in the incoming lithosphere play important roles. (c) 2004 Elsevier B.V. All rights reserved.

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909JKTimes Cited:14Cited References Count:48

URL  <Go to ISI>://000227856000012
DOI  DOI 10.1016/j.pepi.2004.08.030