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Title

Re-Os and Pb-Pb geochronology of the Archean Salobo iron oxide copper-gold deposit, Carajás mineral province, northern Brazil

Authors
Requia, Karin
Stein, Holly
Published in Mineralium Deposita. 2003, vol. 38, no. 6, p. 727-738
Abstract Rhenium–osmium ages were determined for two molybdenite samples and a Pb–Pb age was derived from bornite–chalcopyrite–magnetite at the Salobo iron oxide copper–gold deposit to determine the timing of mineralization and its relation to the nearby Old Salobo Granite. Rhenium–osmium dating of molybdenite spa- tially associated with copper sulfide minerals yields ages with weighted means of 2576±8 and 2562±8 Ma. Removing the error multiplier introduced by the decay constant uncertainty, appropriate for comparing ages from the same isotopic system, these data convincingly argue for two temporally separated pulses of molybde- nite deposition at 2576.1±1.4 Ma (n=2) and 2561.7±3.1 Ma (n=3). The 2576±8 Ma age coincides with a previously published U–Pb age of 2573±2 Ma for the Old Salobo Granite, suggesting that main stage ore formation may have been contemporaneous with granite magmatism. The slightly younger 2562 Ma age most likely represents new molybdenite precipitation associated with the development or reactivation of local shear zones. Lead–lead stepwise leaching of copper sulfide minerals yields a less precise isochron age of 2579±71 Ma, and supports an Archean age for the Salobo ores. This is the first documentation of an Archean iron oxide copper–gold deposit, and the Re–Osand Pb–Pb geochronology herein support 2580– 2550 Ma estimates for basement reactivation and regional granite magmatism associated with the devel- opment of brittle–ductile shear zones.
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Structures
Research groups Isotope Geochemistry, Geochronology and Thermochronology
Mineral Resources and Geofluids
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(ISO format)
REQUIA, Karin et al. Re-Os and Pb-Pb geochronology of the Archean Salobo iron oxide copper-gold deposit, Carajás mineral province, northern Brazil. In: Mineralium Deposita, 2003, vol. 38, n° 6, p. 727-738. https://archive-ouverte.unige.ch/unige:19397

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Deposited on : 2012-04-16

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