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Abstract

The Chahgaz Zn–Pb–Cu volcanogenic massive sulphide (VMS) deposit occurs within
a metamorphosed bimodal volcano–sedimentary sequence in the south Sanandaj–Sirjan
Zone (SSZ) of southern Iran. This deposit is hosted by rhyodacitic volcaniclastics and
is underlain and overlain by rhyodacitic flows, volcaniclastics, and pelites. Peperitic
textures between rhyodacite flows and contact pelites indicate that emplacement of the
rhyodacite occurred prior to the lithification of the pelites. The rhyodacitic flows are
calc-alkaline, and show rare earth and trace elements features characteristic of arc
magmatism. Zircons extracted from stratigraphic footwall and hanging-wall rhyodacitic
flows of the Chahgaz deposit yield concordant U–Pb ages of 175.7 ± 1.7 and
172.9 ± 1.4 Ma, respectively, and a mean age of 174 ± 1.2 Ma. This time period is
interpreted to represent the age of mineralization of the Chahgaz deposit. This Middle
Jurassic age is suggested as a major time of VMS mineralization within pull-apart
basins formed during Neo-Tethyan oblique subduction-related arc volcano-plutonism
in the SSZ. Galena mineral separates from the layered massive sulphide have uniform
lead isotope ratios of 206Pb/204Pb = 18.604–18.617, 207Pb/204Pb = 15.654–15.667, and
208Pb/204Pb = 38.736–38.769; they show a model age of 200 Ma, consistent with the
derivation of Pb from a Late Triassic, homogeneous upper crustal source.

Item Type:	Article
Authors/Creators:	Mousivanda, F and Rastad, E and Meffre, S and Peter, J and Solomon, M and Zaw, K
Keywords:	Chahgaz; VMS; U–Pb; SSZ; Iran
Journal or Publication Title:	International Geology Review
ISSN:	0020-6814
DOI / ID Number:	10.1080/00206811003783364
Additional Information:	The definitive published version is available online at: http://www.tandf.co.uk/journals This is a iFirst article
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