Barium-rich fluids and melts in the subduction environment (La Corea and Sierra del Convento mélanges, eastern Cuba)
Abstract
Whole-rock compositions of muscovite-bearing amphibolite, trondhjemite, pegmatite and quartz-muscovite rocks from Sierra del Convento and La Corea mélanges (eastern Cuba), as well as mineralogy, record complex circulation of Ba-rich fluids and melts in the subduction environment. Partial melting of fluid-fluxed, MORB-derived amphibolite produced trondhjemite magmas that crystallized at depth, in some cases evolving into pegmatites. Qtz-Ms rocks probably crystallized from primary fluids derived from subducted sediments. All these rocks have elevated concentrations of large-ion lithophile elements, especially Ba (up to 11,810 ppm), presumably released from slab sediments by fluids and/or melts. Fluid–rock interaction produced crystallization of phengite in parental amphibolites. The phengite crystallized in all types of rocks is rich in Ba, with concentric zoning, characterized by Ba-rich cores and Ba-poor rims, indicating a compatible behaviour of Ba in the studied systems. Zoning in phengite is governed primarily by the celadonite (tschermak) exchange vector ((Mg,Fe)Si-(Al)-2), with more moderate contributions of the celsian (BaAl-(KSi)-1) and paragonite (NaK-1) exchange vectors. Late remobilization of Ba at relatively low temperature formed retrograde celsian. The compatible behaviour of Ba in the studied rocks strengthens the importance of the stability of phengite for the transfer of LIL elements from the subduction to the volcanic arc environments.
Keywords: Ba-rich fluid; Trondhjemite; Phengite; Subduction channel; Eastern Cuba; Caribbean plate
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To Cite this article: Blanco-Quintero, I.F., Lázaro, C., García-Casco, A., Proenza, J., Rojas-Agramonte, Y. (2011): Barium-rich fluids and melts in the subduction environment (La Corea and Sierra del Convento mélanges, eastern Cuba). Contributions to Mineralogy and Petrology, 162, 395–413.
