Scientific Quarterly Journal of Geosciences

Scientific Quarterly Journal of Geosciences

Torghabeh Mesozonal Orogenic (pyrrhotite, pyrite, arsenopyrite) Gold Deposit, Formed in Shear Zones Within Ilmenite-type Granitoid Rocks

Document Type : Original Research Paper

Authors
Mohammadhasan Karimpour 1
Ehsan Torabian 1
Alireza Babakhani 2
1 Geology Department, Ferdowsi University of Mashhad, Mashhad, Iran
2 Geological Survey and Mining Exploration of Iran, Tehran, Iran
Abstract
The Torghabeh gold mineralized area is part of collision zone formed during Late Paleozoic-Early Triassic time due to collision of Iran and Turan Plates. Oldest exposed rocks are meta-ophiolite and meta-flysch (Paleo-Tethys remnants). Dehnow- Vakilabad - Torghabeh tonalite- granodiorite (Early Mesozoic age) intruded low grade regional metamorphosed
rocks of Late Paleozoic. Different types of schists were formed around the contact. Tonalite-granodiorite has low values of  magnetic susceptibility [(1.5 to 2.5) * 10-5 SI], therefore, it belongs to ilmenite series or reduced-type granite.
Mineralization is found within shear zones. The shear zones cut all of the exposed rocks, then, mineralization is younger than these rocks. Gold mineralization was associated with silica rich fluid. Parageneses from depth to the surface are: 1) arsenopyrite – pyrrhotite – gold, (2) pyrite – arsenopyrite – gold, and (3) pyrite – gold- galena. Gold is mainly associated with pyrite and arsenopyrite. The elemental content of Ag, Bi, Cu, Sb, Sn, Pb, Zn and W is low. Gold grade varies between 0.5 to 56 ppm and is less than 5 ppm on average. The width of mineralization is between 0.4 to 2.5 meters. Torghabeh deposit is mesozonal orogenic type gold deposit. The ore bearing solution was in reducing stage, low in S and
T = 420 ° C, pH= 7, Log fO2 < -40, Log fS2 < -14
Keywords
Gold
Orogeny
Mesozonal
Reduced
Torghabeh
Iran

Subjects

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Scientific Quarterly Journal of Geosciences
Volume 15, Issue 60
Summer 2006, Vol. 15, No.60
Summer 2006
Pages 130-141