Stable isotope geochemistry of the Carboniferous Zn-Pb-Cu sediment-hosted sulfide deposits, Northeastern Spain

Canet, C., Alfonso, P., Melgarejo, J.C. and Fallick, A.E. (2005) Stable isotope geochemistry of the Carboniferous Zn-Pb-Cu sediment-hosted sulfide deposits, Northeastern Spain. International Geology Review, 47(12), pp. 1298-1315. (doi:10.2747/0020-6814.47.12.1298)

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Abstract

Carboniferous sedimentary rocks in the southwestern Catalonian Coastal Ranges contain stratiform (Zn, Pb, Cu) sulfide deposits. Stable isotope compositions of sulfur, oxygen, and hydrogen were studied in five localities in order to establish the source of hydrothermal fluids and the influence of metamorphism on these deposits. Sulfur isotopes were analyzed in pyrrhotite, pyrite, sphalerite, chalcopyrite, and galena. The δ34S(CDT) values lie mostly between -1.0 and +7.0‰ (average +4.4‰). Except for pyrrhotite-pyrite pairs, all the sulfide minerals show isotopic disequilibrium. δ34S values suggest that sulfur was derived by thermochemical reduction of seawater sulfate in a deep-circulating convective system. Fluid inclusions were studied in quartz crystals from the sediment-hosted stratiform occurrences. They are two-phase (L-V), with salinity between 1.1 and 18.0 wt% NaCl eq., and homogenization temperatures mainly in the range of 220-260°C. Oxygen and hydrogen isotopes were analyzed in chlorite crystals from four ore-bearing beds. δD(V-SMOW) values in chlorite range from -63 to -33‰, whereas δ18O values lie between +2.7 and +6.8‰. δ18O(V-SMOW) values in quartz range between +8.4 and +10.7‰. Most of the calculated oxygen and hydrogen isotope compositions of ore-forming fluids plot close to the isotopic composition of seawater. Therefore, the ore-forming fluid must have been mainly seawater that interacted with sedimentary rocks during convective circulation within a basin. This process took place in a subsiding Carboniferous basin divided into sedimentary highs and depressions by synsedimentary normal faults, which acted as permeable areas that favored fluid circulation.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Fallick, Professor Anthony
Authors: Canet, C., Alfonso, P., Melgarejo, J.C., and Fallick, A.E.
Subjects:G Geography. Anthropology. Recreation > GE Environmental Sciences
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:International Geology Review
ISSN:0020-6814

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