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TitleAge, tectonic setting, lithogeochemistry and hydrothermal alteration of volcanogenic massive sulfide mineralization in the Chahgaz region, South Sanandaj-Sirjan zone of Iran
AuthorMousivand, F; Rastad, E; Peter, J; Solomon, M
SourceExplore vol. 150, 2011 p. 2-10
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20100375
Mediapaper; on-line; digital
File formatpdf
AreaChahgaz; South Sanandaj-Sirjan; Iran (Islamic Republic of)
Lat/Long WENS 53.0000 56.0000 31.0000 29.0000
Subjectseconomic geology; geochronology; tectonics; mineral occurrences; mineral deposits; mineralization; sulphides; volcanogenic deposits; alteration; hydrothermal alteration; hydrothermal deposits; lithogeochemistry; tectonic setting; uranium lead dates; uranium lead dating; radiometric dating
Illustrationslocation maps; photographs; stratigraphic columns; plots
ProgramTargeted Geoscience Initiative (TGI-3), 2005-2010, Deep Search TGI-3
AbstractIran hosts several volcanogenic massive sulfide (VMS) deposit types that occur within different tectonic assemblages formed during discrete time periods (Mousivand et al. 2008a). The most prospective area for VMS exploration in Iran is the Sanandaj-Sirjan zone (SSZ) (Fig. 1), particularly the southern part of this zone. The Chahgaz region of the SSZ (Fig. 2) is of the most important regions in the south SSZ for VMS exploration and hosts several deposits and occurrences, including the economically important Chahgaz Zn-Pb-Cu deposit (Fig. 2) which was first recognized as a VMS-type deposit by Mousivand et al. (2008b).
Iran has an arid to semi-arid climate, with much rock outcrop exposure; for this reason, surficial and lithogeochemical techniques are effective and commonly used in mineral exploration there. Host rocks to the Chahgaz deposits are dominantly fresh to weakly weathered, and close to the deposits the rocks have been intensely hydrothermally altered.
Mining in Iran dates back to at least 5000 years B.C., and most mineral deposits in the country show indications of ancient mining activities (e.g. Momenzadeh 2004). The Chahgaz deposit was (re)discovered by tracing evidence of ancient mining activities. Modern mining at this deposit commenced in 2007, and it is one of the largest VMS deposit in the country (see below). Mousivand (2010) recently completed detailed geological and geochemical studies on the Chahgaz deposit. Host rock and mineralization samples were analyzed for their bulk composition by inductively coupled-plasma mass spectrometry and inductively coupled-plasma atomic emission spectrometry (ICP-MS/AES) methods for major, trace and rare earth element contents at Acme laboratories (Vancouver, Canada) to determine rock type, petrotectonic setting, chemostratigraphy, hydrothermal alteration style and intensity, and deposit metal zonation. Herein, we provide a brief synopsis of our research on VMS mineralization in the Chahgaz region, including its age, tectonic setting, metal zonation and wallrock alteration.
The Chahgaz region of the Sanandaj-Sirjan zone in southern Iran is highly prospective for VMS deposits. This region hosts the Chahgaz Zn-Pb-Cu VMS deposit which occurs within a metamorphosed sequence of bimodal volcanic and sedimentary rocks. This deposit is hosted by rhyodacitic volcaniclastic rocks and is underlain and overlain by rhyodacitic flows, volcaniclastics and pelites. Peperitic textures between rhyodacite flows and adjacent pelites indicate that emplacement of the rhyodacite occurred prior to the lithification of the pelites. The rhyodacitic flows are calc-alkaline, and show REE and trace element 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, 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 time period in the Middle Jurassic is suggested to be a time of significant VMS deposit formation within pull-apart basins formed during Neo-Tethyan oblique subduction-related arc volcano-plutonism in the SSZ. The VMS mineralization exhibits pronounced metal and hydrothermal alteration mineral zonations.