Arc-parallel flow in the mantle wedge beneath Costa Rica and Nicaragua

Publication Type  Journal Article
Year of Publication  2008
Authors  Hoernle, K.; Abt, D. L.; Fischer, K. M.; Nichols, H.; Hauff, F.; Abers, G. A.; van den Bogaard, P.; Heydolph, K.; Alvarado, G.; Protti, M.; Strauch, W.
Journal Title  Nature
Volume  451
Issue  7182
Pages  1094-U4
Journal Date  Feb 28
ISBN Number  0028-0836
Accession Number  ISI:000253453600039
Key Words  central-american arc; seismic anisotropy; shear-wave; elastic-constants; back-arc; olivine; history; asthenosphere; volcano; ma

Resolving flow geometry in the mantle wedge is central to understanding the thermal and chemical structure of subduction zones, subducting plate dehydration, and melting that leads to arc volcanism, which can threaten large populations and alter climate through gas and particle emission. Here we show that isotope geochemistry and seismic velocity anisotropy provide strong evidence for trench- parallel flow in the mantle wedge beneath Costa Rica and Nicaragua. This finding contradicts classical models, which predict trench- normal flow owing to the overlying wedge mantle being dragged downwards by the subducting plate. The isotopic signature of central Costa Rican volcanic rocks is not consistent with its derivation from the mantle wedge(1-3) or eroded fore- arc complexes(4) but instead from seamounts of the Galapagos hotspot track on the subducting Cocos plate. This isotopic signature decreases continuously from central Costa Rica to northwestern Nicaragua. As the age of the isotopic signature beneath Costa Rica can be constrained and its transport distance is known, minimum northwestward flow rates can be estimated ( 63 - 190 mm yr(-1)) and are comparable to the magnitude of subducting Cocos plate motion (similar to 85 mm yr(-1)). Trench- parallel flow needs to be taken into account in models evaluating thermal and chemical structure and melt generation in subduction zones.


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URL  <Go to ISI>://000253453600039
DOI  Doi 10.1038/Nature06550