Porphyry and Hydrothermal Cu-Au Deposits

Iran, as a bridge between Gondwana and Eurasia, is composed of composite subduction-collisional belts. Each of these resulted from the resorption and closure of Tethys components and related successive episodes of volcano-plutonism. Although many authors have explained the genesis of copper deposits in Iran by a simplified geodynamic model and consumption of Zagrosside Tethys, recent geological and metallogenic research studies suggest a new model of structural and tectono-magmatic evolution for the genesis of different types of copper deposits in various segments of the country. The successive stages of opening, closing and subduction of oceanic basins resulted in the formation of different types of copper deposits during Alpine structural evolution.

The major copper deposits of Iran can be classified into: a) porphyry, b) manto, c) pluton-related vein, d) pluton-related stockwork/breccia, e) Cyprus-style massive sulphide, f) skarn, and g) volcanogenic hydrothermal ore types. The widespread copper mineralisation in Iran is represented by Cu-Mo, Cu, Cu-Ni-Co, Cu-Ni-Co-polymetallic and Cu-Pb-Zn associations. It has been found in recent years that many copper deposits and occurrences show a considerable admixture of silver and gold

There are twelve major copper bearing districts within Iran (Fig. 2). In order of economic significance, the most important of these are the:

Anarak-Sarcheshmeh-Kharestan Cu belt with many porphyry deposits. Of these, only Sarcheshmeh is currently mined, although there are several that could be exploited in the future such as Miduk, Kali Kafi, Dozardalu and Kharestan.
Qarahdagh-Sabalan volcano-plutonic zone in NNW Iran, the second most important copper bearing district in Iran, which except for the Songun porphyry deposit, has not been explored in detail.
Torud-Abbasabad region in north and north-eastern Iran where Cu mineralisation occurs as veins in andesitic volcanic rocks although Cu has also been found in the metamorphic bedrock.
Ferdows-Qalehzari belt in NE Iran, within continental margin-type volcanics which were developed after consumption of Neo-Tethys oceanic crust beneath the Central Median Mass. Qaleh Zari is the only deposit being mined in this region, but there are other prospective zones yet to be explored.
Mokran Ophiolite complex in south-eastern Iran, which hosts massive sulphide-type copper mineralisation, similar to those explored in the Sultanate of Oman.

Among the known deposits, a brief description of a representative selection will be presented in this paper. These are the Sarcheshmeh porphyry Cu(Mo), the Kale Kafi porphyry Cu-Mo (Au), the Songun porphyry Cu and the Qaleh Zari manto-type Cu-Au deposit.

The principal deposit to be discussed is Sar Cheshmeh. This major deposit lies within a late Tertiary granodiorite porphyry stock and surrounding Tertiary volcanics. Proven and probable reserves to a depth of 150 m only, comprise 350 mt @ 0.9% Cu, 0.03% Mo, 0.3 g/t Au as hypogene ore, with a 37 m thick chalcocite blanket containing an additional 95 mt @ 2% Cu. The global resource is 1100 mt @ 0.9% Cu.

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