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Hossein Kouhestani

Majid Ghaderi, Hossein Kouhestani, Khin Zaw, Sebastien Meffre
U–Pb geochronology and Pb isotope characteristics of Chah Zard Ag–Au epithermal deposit, West-central Iran
Abstract


The Chah Zard Ag–Au epithermal deposit is located within a high K, calc–alkaline andesitic to rhyolitic volcanic complex in the central part of Urumieh–Dokhtar Magmatic Arc (UDMA), west–central Iran. The deposit is formed in breccia bodies dominantly hosted by rhyolite porphyries. Geological field relationships show that epithermal mineralization occurred in close association with a phreatomagmatic fracturing event, being localized in breccia cements, and formed as disseminated sulfides in the matrix of the more permeable breccias, and in veins cutting breccia bodies. No volcanic and/or subvolcanic flow and domes have been observed to cross-cut zones of alteration, phreatomagmatic breccias or veining. Zircons extracted from intermediate and felsic volcanic rocks of the Chah Zard deposit yield concordant U–Pb ages of 6.29±0.29, 6.25±0.29 and 6.19±0.24 Ma, and a mean age of 6.24±0.16 Ma. This age is interpreted to represent the maximum age of mineralization of the Chah Zard deposit, and may indicate that there was a previously unrecognized mineralization event in UDMA. Galena mineral separates from the breccia cements and veins have uniform lead isotope ratios of 206Pb/204Pb=18.71–18.77, 207Pb/204Pb=15.61–15.73, and 208Pb/204Pb=38.95–39.01, implying derivation of Pb from a homogeneous upper crustal source.

 

 

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