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Geochemical variations in the Cocos Plate subducting beneath Central America : implications for the composition of arc volcanism and the extent of the Galaṕagos Hotspot influence on the Cocos oceanic crust / Seth Sadofsky...

Sadofsky, Seth ; Hoernle, Kaj ; Duggen, Svend *1969-* ; Hauff, Folkmar *1965-* ; Werner, Reinhard *1959-2022* ; Garbe-Schönberg, Dieter

graph. Darst

New geochemical data from the Cocos Plate constrain the composition of the input into the Central American subduction zone and demonstrate the extent of influence of the Galaṕagos Hotspot on the Cocos Plate. Samples include sediments and basalts from Ocean Drilling Program (ODP) Site 1256 outboard of Nicaragua, gabbroic sills from ODP Sites 1039 and 1040, tholeiitic glasses from the Fisher Ridge off northwest Costa Rica, and basalts from the Galaṕagos Hotspot Track outboard of Central Costa Rica. Site 1256 basalts range from normal to enriched MORB in incompatible elements and have Pb and Nd isotopic compositions within the East Pacific Rise MORB field. The sediments have similar 206 Pb/204 Pb and only slightly more radiogenic 207 Pb/204 Pb and 208 Pb/204 Pb isotope ratios than the basalts. Altered samples from the subducting Galaṕagos Hotspot Track have similar Nd and Pb isotopic compositions to fresh Galaṕagos samples but have significantly higher Sr isotopic composition, indicating that the subduction input will have a distinct geochemical signature from Galaṕagos-type mantle material that may be present in the wedge beneath Costa Rica. Gabbroic sills from Sites 1039 and 1040 in East Pacific Rise (EPR) crust show evidence for influence of the Galaṕagos Hotspot ~100 km beyond the morphological hotspot track.

In: International journal of earth sciences. - Berlin : Springer, 1999- , ISSN: 1437-3262 , ZDB-ID: 1477600-5

. - 2008, insges. 13 S.

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