D, O and C isotopes in podiform chromitites as fluid tracers for hidrotermal alteration processes of the Mayarí-Baracoa Ophiolitic Belt
Abstract
The Mayarí — Baracoa Ophiolitic Belt (MBOB, eastern Cuba) is composed of two large, chromite-rich massifs: Mayarí —Cristaland Moa-Baracoa. The chromitites and hosting dunites were firstly affected by a regional serpentinization event, a subsequent episode of hydrothennal alteration (chloritization mainly) and, finally, these already altered bodies were crosscut by thin calcite-dominated veins. Analysed serpentines from serpentinized chromitites and dunites present very similar isotopic compositions (δ18O=+4.7 to +6.3 and δD= −67 to −60 , suggesting that the serpentinization process took place at moderate temperatures, in an oceanic environment. Serpentine formation by interaction with ocean water is also supported by the isotopic composition of chlorite and calcite. These results suggest that the serpentinization, chloritization and fracture filling processes of the Mayarí — Baracoa Ophiolite Belt took place in a subocean floor scenario and, thus, that the Mayarí — Baracoa serpentines represent a good example of serpentine formed during interaction with seawater. The oceanic origin of the serpentines from serpentinized chromitites and dunites from the MBOB indicate that the serpentinization of the mantle sequence occurred pre-thrusting (pre-emplacement in age).
Keywords: Fluids; Serpentinization; Stable isotopes; Ophiolites; Cuba
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To Cite this article: Proenza, J.A. Alfonso, P., Melgarejo, J.C., Gervilla, F., Tritlla, J., Fallick, A.E. (2003): D, O and C isotopes in podiform chromitites as fluid tracers for hidrotermal alteration processes of the Mayarí-Baracoa Ophiolitic Belt, eastern Cuba. Journal of Geochemical Exploration, 78-79, 117-122.
