Gold Mineralization in Shear Zones of Zartorosht Mine, inSanandaj-Sirjan Zone (Southwest Sabzevaran
|Category||Economic geology & mineral exploration|
|Location||21th symposium on geosciences|
|Holding Date||21 May 2008|
Zartorosht gold mining district is located in southeastern most part of Sanandaj-Sirjan metamorphic zone, 70 km, SW Sabzevaran. Middle Paleozoic rocks which outcrop in the area include Sargaz & upper part of Abshur complex which are metamorphosed up to greenschist facies. Deformation within the complexes led to foliation trending N80W dipping 20S following recumbent fold. Shear zones appear as concordant with foliation & at the same trend of normal faults. Gold mineralization occurred in the upper part of Sargaz complex including alternations of metamorphosed & deformed intermediate to basic volcanic-pyroclastic rocks. Two types of mineralization distinguished in the mining district are as follows: 1) alteration zones parallel to dominating foliation which appear in distinct yellow-brown color and lenticular geometry which looks banded. Mineralization zones occur repeatedly, few centimeters to 6 meters in width, 1m to more than 100m long. 2) The main gold mineralization, along which old mining operation are observed, occur in brittle shear zones along normal (tensile) faults, trending N70-80W.High grade portions consisting of auriferous silicified veins & crushed zones which can be per suited discontinuously along more than 1Km, 1-3m thick. High-grade parts are 2-3m thick; -sometimes reach to 15m in association with surrounding alteration zone. The principal alterations in the first type of mineralization are silicified, sulfide, carbonatic and argillic whereas it is silicified and sulfidized in brittle shear zones. The paragenesis included quartz, albite, pyrite, rarely chalcopyrite, calcite, dolomite, siderite, malachite Fe-oxide and clay minerals. In the first type of mineralization, pyrite and malachite occur as banded parallel to dominating foliation. Iron oxides & carbonates are observed as vein-veinlets in association with calcite & quartz. The analysis result of samples collected from old mining excavations and outcrops as well has the highest grade in intensely silicified and brecciated within the brittle shear zones ranging from 2.7 - 17.2 ppm. Ore-bearing zones parallel to foliation, ranging from 0.05 to 6.42 ppm, gold, corresponds to silicified sulfide & carbonate alteration. Regarding Sargaz complex development in Sabzevaran and southeastern Sanandaj-Sirjan, it looks that studying gold mineralization in Zartororsht, its mechanism of formation & concentration can serve as a model for prospecting & exploration of gold deposits of the same type in Sanandaj-Sirjan and similar zones.