Iranian Journal of Geology
Year:2012 | Volume:5 | Issue:20|Papers Count:9

In this study, geology, source of ore fluids, and the mode of emplacement of mineralized quartz veins at Chah-Mesi polymetallic deposit, NE Shahr-e-Babak, have been investigated by field and laboratories studies including EMPA and stable oxygen isotopic. The results of these investigations showed that Chah-Mesi vein deposit evolved as an epithermal system within the Eocene host volcano-sedimentary rocks with the shear fractures being the major structural control of mineralization. The mineralization at Chah-Mesi comprises pyrite, chalcopyrite, sphalerite, galena, and, in much smaller amounts, sulfosalt minerals. These ore minerals contain the base metals, Cu, Pb, Zn, and to lesser amounts, precious metals, like Au and Ag, at Chah-Mesi, the EMPA investigations showed the sulfosalt minerals are the main carriers of Au and Ag at Chah-Mesi deposit. The stable O isotopic composition of quartz associated with the mineralization indicates that both magmatic and meteoric fluids contributed to the ore fluids, and thus were responsible for the formation of ore-bearing quartz veins, at Chah-Mesi.The general trend of veins at Chah-Mesi is N-S, NE-SW, and NW-SE which correlate well with the trends of fractures in the area. The structural analysis of mineralized veins at Chah-Mesi indicate the significant role of a shear system, i.e. shear fractures (types R, R', T), in the emplacement of mineralized veins. The N-S trending veins occurred in the tension fractures. These veins emplaced as tension-gash veins in mode-I shear fractures. In contrast, the NE-SW- and NW-SE-trending veins include the pennant veins in the region which have been emplaced in Riedel and anti-Riedel mode-II shear fractures.

The Sara (Parkam) porphyry copper deposit is located in Kerman province, 87 km northwest of the Sarcheshmeh deposit and 2 km from Miduk deposit. This deposit is hosted by Razak volcanic complex with Eocene age. Mineralization of copper and molybdenum is associated with emplacement of diorite and quartz diorite intrusive of Miocene age. Six alteration zones are distinguished at the Sara deposit, including potassic, potassic–phyllic, biotitic, phyllic, propylitic and argilic. Mineralization in Sara deposit is low-grade with an average grade of 0.16% Cu (range of 0.01-2.01%) and 12 ppm Mo (range of 0.5-489 ppm). Leached–oxidized zone contain minimum grade of Cu (0.12 %) with range of 0.01-1.4%. Maximum grade of Cu (0.4%) with range of 0.09-1.91% and Mo (15.93 ppm) with regard to number and amplitude of variation (0.5-489 ppm) belong to hypogene zone. Maximum grade of Pb, Zn and Fe is associated with hypogene zone. In leached–oxidized zone, correlation coefficient between Cu with Mo, Pb and Fe is negative and with Zn is slightly positive that is compatible with geochemical behavior of these elements. Cu shows good correlation coefficient with Pb in supergene sulfidation enrichment zone and that correlation coefficient with other elements is medium positive. In hypogene zone, Cu shows weak positive correlation coefficient with Mo, very weak positive correlation coefficient with Pb, Zn and negative correlation coefficient with Fe. Except in leached–oxidized zone, Pb and Zn show good positive correlation coefficient in supergene sulfidation enrichment and hypogene zones. Cu/Mo ratio decreases from dipper part of Sara deposit (hypogene zone) toward the surface (leached–oxidized zone). Variation and distribution of Cu, Mo, Pb, Zn and Fe in Sara deposit somewhat are effected by mineralization zones. Comparison of Sara deposit with porphyry copper deposits of Sarcheshmeh, Miduk and Sungun displays that Sara deposit is similar to Miduk deposit in regard to composition of intrusive stock and wall rocks and alteration pattern of Sara deposit relatively similar to Miduk, Sarcheshmeh and Sungun deposits.

Sorkh-Kuh garnitoid body is located in the Lut depression (NE Iran), representing the oldest tectono-magmatic event recorded in the East Iran Zone as a volcano-plutonic activity. It consists mainly of granodiorite, diorite and tonalite with granular hypidomorphic texture which is composed of albite, quartz, biotite, hornblende, K-feldspar and apatite. Sorkh-Kuh is a meta- to peralominous calc-alkaline intrusion and its main geochemical features is similar to those of reduced S-type intrusion of ilmenite series. The associated sulfide-oxide polymetallic mineralization comprises of hypogene (chalcopyrite, bornite, pyrite, sphalerite, magnetite hematite) and supergene (digenite, covellite, chalcocite, malachite and neotocite) mineral assemblages. The anhydrous (wollastonite, ankerite, Fe-garnet and pyroxene) and hydrous (tremolite-actinolite, chlorite and epidote) calc-silicates and silicates formed in the skarn zone. The epigenetic mineralizations occurs as disseminated, vein-veinlets, replacement and skarn-type mainly as discrete and irregular lenses, bands and sheet-like bodies, which follow the regional trends. In the skarn zone and next to the intrusion, argillic, sericitic and limonitic alterations are widespread and propylitic alteration (epidote, chlorite and pyrite assemblage) formed far-off the main intrusive body. Geochemical characteristics of the Sorkh-Kuh intrusion are similar to productive Cu-Fe-Ag intrusions.

The Permian-Triassic boundary mass extinction affected the carbonate platforms and its critical condition resulted in deposition of only non-skeletal sediments as microbial deposits and fan-shaped aragonitic bodies that directly precipitated on seafloor. These sediments usually precipitated in shallow equatorial platform in which physiochemical condition was suitable. The Shahreza section in south of Isfahan is one of the exclusive section that recorded sedimentation continuously in Permian to Triassic intervals. Moreover the Early Triassic sediments in this section have shown abnormal sedimentation and sea water composition. Growth of aragonite fibers in the form of fans and associated in domes shows the evidence that changed by Permian-Triassic mass extinction mechanisms. These fibers have grown synsedimentary in seafloor and formed large domes. These evidences have shown that aragonite has been the original carbonate mineralogy when the ambient water was supersaturated in respect to calcium carbonate.

The chemical component of surface waters is usually very different due to contact to different geological formations, relation with other surface and groundwater resources. Solution rate of minerals and ions in river water depends on discharge. The aim of this investigation is to identify chemical components of Karoon River and its main branches in Chaharmahal and Bakhtiari Province of Iran and to determine the main factors affecting water quality. For this purpose, the location of Karoon River and main branches was determined using the ARC GIS software. We used results of chemical analysis of physiochemical parameters measured in 9 hydrometric stations in river course up to 2010 and classified using SPSS software. Hydro geochemistry and hydrochemistry analysis applied for the Chemistry, AquaChem and Aq.QA softwares. In each station, water quality was determined for drinking and irrigation by considering the water quality standards such as Wilcox and Schoeller diagrams which are generally locating in suitable water class. The water type in most stations is Ca-HCO3 and in some of them is Na-Cl. According to the results of correlation coefficients between different chemical parameters and geological analysis, the lithology of formations in the river course is the main factor in water quality change, which causes the extreme decrease of water quality in some area such as Mavarz station. Finally, by analysis of drainage network limited to Karoon River and branches, suitable quality sanctum 1500 meter was considered an area of each different formation was calculated.

The present study is concerned with granitoid body crops out in a metamorphic complex occurring around Zul village of South Khorasan Province, eastern Iran. The complex is composed of migmatite, gneiss, mica schist, garnet schist, some marble and quartzite. Based on mineralogy, modal and geochemical data, Zul granitoid includes granite and granodiorite. These rocks are granular, graphic and porphyroid in texture. Major minerals are alkali feldspar, quartz, biotite and muscovite. Tourmaline, sphene, apatite, zircon and garnet are the minor mineral components. The granitoid is calc-alkaline and peraluminous in composition. Trace element data were normalized to average crust, showing enrichment in K, U and Th. These characteristics and negative anomaly for Eu can indicate melting of crustal sediments (S-type granitoid) in a collision-related tectonic environment. Isotope age dating on zircon uranium–lead indicates that, there are two generations of heritage and magmatic zircon in granitoid phase. Heritage zircon show 168.4±2 Ma and magmatic zircon has 110.1±1.5 Ma (late Early Cretaceous) age.

The intrusion of Manshad diorite in Cretaceous carbonates of Shirkuh Mountain caused occurrences of Kuh-e-Dor skarn. Following mineral assemblage has been identified: Spinel+clintonite+phlogopite+pyroxene+garnet+vesuvianite.Paragenetic relationships show that there are a close association between spinel, clintonite and phlogopite. Transition stage from magnesian to calcic skarn is characterized by appearance of clintonite. Clintonite restricted to low XCO2, SiO2 and high XH2O values of the coexisting fluids. Textural relationships of spinel with clintonite-phlogopite show that spinel acted as precursor for genesis of these micas or they have been formed at the expense of spinel.spinel+SiO2+K2O+dolomite+H2O clintonite+phlogopite Manshad skarn is a polygenic skarn in which pyroxene is formed at the first stage of mineralization followed by garnet and vesuvianite formation. Mineral assemblage of skarn indicate temperature starting from maximum 800oC to 400oC which is followed by vesuvianite stability in XCO2<XH2O condition.