2010: Ba-sequestering Phases in the Subduction Environment (Eastern Cuba Mélanges): Implications for Arc Magmas

Ba-sequestering Phases in the Subduction Environment (Eastern Cuba Mélanges): Implications for Arc Magmas

Abstract

In eastern Cuba two serpentinite mélanges (La Corea and Sierra del Convento) bearing high-pressure blocks have been interpreted as fossil subduction channels formed after onset of subduction of the Proto-Caribbean (i.e. Atlantic) lithosphere in Aptian times below the Caribbean plate (García-Casco et al. 2006, 2008a; Blanco-Quintero et al., 2010). High-pressure blocks found in these subduction mélanges are mainly composed of amphibolite with N-MORB affinity (Lázaro and Garcia-Casco 2008). An exceptional characteristic is the presence of tonalitic-trondhjemitic bodies, dikes and veins formed after fluid-induced partial melting of MORB derived amphibolites at peak conditions of 700-750 ºC and 15 kbar under a hot geothermal scenario. Elemental and isotopic geochemical characteristics of amphibolites and tonalitic-trondhjemitic rocks led Lázaro and Garcia-Casco (2008) to infer a depleted fluid likely evolved from dehydrating serpentinites. However some varieties of MORBderived amphibolite, associated tonalitetrondhjemite, and vein rocks from these mélanges are rich in Ba and other LILE, suggesting the presence of additional fluids derived from sediment of oceanic lithosphere. In this contribution we study the mineral and bulk-rock geochemistry of these rocks, and give clues to understand the behaviour of fluids and melts evolved in the subduction environment, with emphasis in the mobility of barium and other LILE.

Keywords: Subduction Channel; Phengite; Celsian; Cymrite

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To Cite this article: Blanco-Quintero, I.F., Lázaro, C., García-Casco, A., Proenza, J.A. (2010): Ba-sequestering Phases in the Subduction Environment (Eastern Cuba Mélanges): Implications for Arc Magmas. Macla, 13, 49-50. http://www.ehu.es/sem/macla_pdf/macla13/Macla13_049.pdf

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