Document Type : Original Research Paper
Author
Assistant Professor, Department of Geology, Payame Noor University, Iran
Abstract
The Sar Cheshmeh mine, a world-class porphyry copper deposit, is located in the Kerman metallogenic zone. The rock outcrops in the deposit are Eocene basalt, basaltic andesite and andesite, Oligocene granular and porphyry granodioritic intrusions and Miocene Sar Cheshmeh granodioritic porphyry stock, granitic late fine-grained porphyry and andesitic to dacitic hornblende, plagioclase, and biotite porphyry dykes. In the spider diagrams, studied rocks show LILE enrichment and HFSE depletion pattern similar to volcanic arc rocks. Eocene volcanic rocks and Oligocene granular and porphyry granodioritic intrusions represent typical magmas characteristics of volcanic arcs whereas Miocene intrusions and dykes have adakitic nature. The (La/Yb)N ratio in the volcanic rocks and Oligocene intrusions varies between 1-5 and 7-11 respectively, while Miocene intrusions and dykes show highest amount of this ratio(20-40). Low aboundancy of HREE in the Miocene intrusions and dykes implies that garnet have been in the source, which has been formed due to increasing crustal thickness during Oligocene and Miocene. According to U-Pb dating, the Sar Cheshmeh porphyry stock and granitic late fine grained have been emplaced in 12.97 ± 0.23 Ma and 12.37 ± 0.1 Ma respectively, while hornblende porphyry dykes has been intruded in 12.16 ± 0.8 Ma. According to trace element characteristics in zircon crystals, Miocene intrusions and dykes originated from same source. Middle Miocene intrusions and dykes have been generated in a post collisional tectonic setting from various degree partial melting of amphibolitic mafic lower crust with variable garnet.
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