Geology,fluid inclusion and sulphur isotope characteristics of the El Cobre VHMS deposit,Southern Cuba |
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Authors: | Xiomara Cazañas Pura Alfonso Joan Carles Melgarejo Joaquín Antonio Proenza Anthony Edward Fallick |
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Institution: | (1) Instituto de Geología y Paleontología, Vía Blanca, Línea del Ferrocarril s/n, San Miguel del Padrón, Havana, Cuba;(2) Departament d’Enginyeria Minera i Recursos Naturals, Universitat Politècnica de Catalunya, Av. de les Bases de Manresa, 08242 Manresa, Barcelona, Spain;(3) Departament de Cristal·lografia, Mineralogia i Dipòsits Minerals, Universitat de Barcelona, c/ Martí i Franquès s/n, 08028 Barcelona, Spain;(4) Isotope Geosciences Unit, SUERC, East Kilbride, Glasgow, G75 0QF, UK |
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Abstract: | The El Cobre deposit is located in eastern Cuba within the volcanosedimentary sequence of the Sierra Maestra Paleogene arc.
The deposit is hosted by tholeiitic basalts, andesites and tuffs and comprises thick stratiform barite and anhydrite bodies,
three stratabound disseminated up to massive sulphide bodies produced by silicification and sulphidation of limestones or
sulphates, an anhydrite stockwork and a siliceous stockwork, grading downwards to quartz veins. Sulphides are mainly pyrite,
chalcopyrite and sphalerite; gold occurs in the stratabound ores. Fluid inclusions measured in sphalerite, quartz, anhydrite
and calcite show salinities between 2.3 and 5.7 wt% NaCl eq. and homogenisation temperatures between 177 and 300°C. Sulphides
from the stratabound mineralisation display δ
34S values of 0‰ to +6.0‰, whilst those from the feeder zone lie between −1.4‰ and +7.3‰. Sulphides show an intra-grain sulphur
isotope zonation of about 2‰; usually, δ
34S values increase towards the rims. Sulphate sulphur has δ
34S in the range of +17‰ to +21‰, except two samples with values of +5.9‰ and +7.7‰. Sulphur isotope data indicate that the
thermochemical reduction of sulphate from a hydrothermal fluid of seawater origin was the main source of sulphide sulphur
and that most of the sulphates precipitated by heating of seawater. The structure of the deposit, mineralogy, fluid inclusion
and isotope data suggest that the deposit formed from seawater-derived fluids with probably minor supply of magmatic fluids. |
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Keywords: | VHMS deposit Sulphides Fluid inclusions S isotopes Cuba |
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