Petrology and tectonic settings of the Sarcheshmeh porphyry copper deposit with emphasis on granodiorite and quartz eye porphyry

Introduction The Sarcheshmeh porphyry copper deposit (PCD) and other porphyry deposits occur in the the most important metallogenic belt in Iran, i.e. the Urumieh-Dokhtar magmatic belt (UDMB). The main phase of intrusion generation in various episodes of mineralization in the Sarcheshmeh area is a stock of granodiorite to tonalite (Shahabpour and Kramers, 1987) that is called the Sarcheshmeh porphyry. This stock intruded volcano-sedimentary rocks and alteration has centered on it. The oldest rock units of the area are Eocene volcanic rocks (Waterman and Hamilton, 1975), which are mainly andesites accompanying marine sedimentary rocks that is consistent with a submarine volcano-sedimentary basin environment. Granodiorite and quartz eye porphyry crop out in the northern part of the Sarcheshmeh PCD. The main objective of this study is to investigate their petrology and geotectonic environment. Materials and Methods Forty samples from drill cores and surface samples from granodiorite and quartz eye porphyry were collected. Twelve samples were chosen with the lowest degree of alteration (less than 5% of representative samples and low LOI) from amongst them for lithogeochemical analyses by ICP-OES and ICP-MS. Lithogeochemical analysis of the main elements was carried out using ICP-OES (Inductively Coupled Plasma-Atomic Emission Spectroscopy) by lithiumborate fusion, and elemental analysis of trace and rare earth elements was performed by ICP-MS (Inductively Coupled Plasma-Mass Spectrometry) using sodium peroxide fusion in the SGS Company, Toronto, Canada. Results and Discussion Based on the Na2O+K2O versus SiO2 values on Cox et al. (1979) and Middlemost (1985) diagram, also R1-R2 diagram of De la Roche et al. (1980), the samples were plotted in the field of granodiorite and quartz diorite. On Harker diagrams, the contents of FeOt, CaO, P2O5, Al2O3, MgO, and TiO2 versus SiO2 show a decreasing pattern. Decreasing amounts of MgO and TiO2 can be related to early crystallization of ferromagnesian minerals and of CaO, ...