Economic Geology
Hossein Ali Tajeddin; Ebrahim Rastad; Abdolmajid Yaghoubpour; Mohammad Mohajjel
Abstract
The Mirgenaghshineh gold deposit is located 43 km northwest of Saqqez in the northwestern part of the Sanandaj–Sirjan zone. The rocks in the deposit area predominantly consist of Precambrian volcanosedimentary sequences of schist, metasandstone, slate and metaandesite which are intruded by granitoid ...
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The Mirgenaghshineh gold deposit is located 43 km northwest of Saqqez in the northwestern part of the Sanandaj–Sirjan zone. The rocks in the deposit area predominantly consist of Precambrian volcanosedimentary sequences of schist, metasandstone, slate and metaandesite which are intruded by granitoid bodies. The Gold mineralization in the Mirgenaghshineh deposit is hosted mostly in Northwest-Southeast shear zone. The high grade gold ores occure in highly deformed mylonitic and ultramylonitic rocks that are associated with quartz, sericite-muscovite and sulfide alteration minerals. Ore mineral assemblages of the deposit are simple and consist of pyrite, arsenopyrite, sphalerite, chalcopyrite, galena and electrum. The electrum grains range in size from less than 5 µm to 140 µm and occur in quartz and also in the form of inclusion and veinlet in pyrites. According of geochemical data, gold-bearing ores carry up to 64.3 ppm Au, 9.9 ppm Ag, 2096 ppm As, 506 ppm Pb, 354 ppm Zn, and 244 ppm Cu. Fluid inclusion studies on gold-bearing quartz indicate homogenization temperatures between 158 and 215°C and salinity between 3.3 to 14.5 wt% NaCl eq. for the ore fluid. The study indicates that main characteristics of the geology and mineralization of the Mirgenaghshineh are similar to those of the epizonal orogenic gold deposits.
Economic Geology
H Tajeddin; Ebrahim Rastad; Abdolmajid Yaghoubpour; Mohammad Mohajjel; Richard Goldfarb
Abstract
Barika gold (and silver)-rich volcanogenic massive sulfide deposit is located 18 km east of Sardasht city in the northwestern of Sanandaj–Sirjan metamorphic Zone. The rocks in the vicinity of the Barika deposit predominantly consist of Cretaceous volcanosedimentary sequences of phyllite, slate, ...
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Barika gold (and silver)-rich volcanogenic massive sulfide deposit is located 18 km east of Sardasht city in the northwestern of Sanandaj–Sirjan metamorphic Zone. The rocks in the vicinity of the Barika deposit predominantly consist of Cretaceous volcanosedimentary sequences of phyllite, slate, andesite and tuffite, metamorphosed under greenschist facies grade. Barika deposit is composed of stratiform ore and stringer zone that both are hosted in an altered and sheared metaandesite unit. Fluid inclusion studies indicated that quartz (stringer zone) and barite (stratiform ore) samples homogenized between 132° and 283°C. Salinities of the fluids inclusions show a range from 1.4 to 9.6% wt NaCl equivalent that are close to that of normal seawater. The study indicates the colling occurred in the initial ore fluids, as a result of mixing with sea water, is an important process in the formation of Barika deposit. The δ34S values of sulfide minerals (pyrite, sphalerite and galena) from stockwork mineralization in the Barika deposit range from -0.8 to +5.6 per mil and fall within the range of values observed for volcanogenic massive sulfide deposits. The narrow range of measured δ34S values from the sulfide minerals suggests that similar to almost of Kuroko VMS deposits, the ore-forming sulfur derived from the leaching of igneous sulfur from the underlying andesitic rocks. Calculated sulfur isotope temperatures for twelve coexisting galena-sphalerite and galena-pyrite pairs range from 146-293 ْ C that is consistent with temperatures estimated from fluid inclusion studies.
Economic Geology
Hossein Ali Tajeddin; S Hassankhanlou; Mohammad Mohajjel
Abstract
Abdossamadi barite deposit is located 80 km northeast of the city of Marivan in the northwestern part of the Sanandaj–Sirjan metamorphic zone. The rocks in the deposit area predominantly consist of Cretaceous volcanosedimentary sequences of metamorphosed andesite, calcareous shale and limestone, ...
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Abdossamadi barite deposit is located 80 km northeast of the city of Marivan in the northwestern part of the Sanandaj–Sirjan metamorphic zone. The rocks in the deposit area predominantly consist of Cretaceous volcanosedimentary sequences of metamorphosed andesite, calcareous shale and limestone, metamorphosed under greenschist facies grade. The deposit is composed of stratiform ore and stringer zone. The stratiform ore consists of a lens-like barite body associated with sulfide minerals which are underlain by metamorphosed (and altered) andesite (stringer zone) and was under the calcareous shale. Sulfide mineral assemblages of the deposit are simple and consist of pyrite, sphalerite, galena, chalcopyrite, and tetrahedrite-tennantite. Massive, bedded, colloform, framboidal and disseminated structures and textures are common in the stratiform ore and indicate deposition of the deposit on the sea floor. The stringer zone that forming footwall of the stratiform ore is altered andesite that cut by sulfide-bearing quartz-barite veins and veinlets. Fluid inclusion studies indicated that barite samples in the stratiform ore homogenized between 115° and 215°C. Salinities of the fluid inclusions show a range from 0.21 to 5.86 wt.% NaCl equivalent. Cooling of the ore-bearing hydrothermal fluid is an important process in the stratiform ore deposition. This study shows that the barite deposit is an immature Kuroko type massive sulfide deposit, which contains only black ore. The deposit underwent metamorphism and deformation after the ore deposition and therefore, shows significant changes in ore structures and textures.
Economic Geology
Behzad Hamamipour; H. A. Tajeddin; Leila Barahmand
Abstract
The Sebandoon gold deposit is located 40 km north of the Bardaskan in the northern part of the Central Iran. The rock units exposed in the area consist of upper Cretaceous volcano-sedimentary sequences of trachyte-trachyandesite, andesibasalt,tuff and carbonaceous shale which intruded by post Eocene ...
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The Sebandoon gold deposit is located 40 km north of the Bardaskan in the northern part of the Central Iran. The rock units exposed in the area consist of upper Cretaceous volcano-sedimentary sequences of trachyte-trachyandesite, andesibasalt,tuff and carbonaceous shale which intruded by post Eocene syenite-quartz monzonite subvolcanic intrusions and diabasic dikes. The main gold reservoir in the Sebandoon deposit has occurred in cone-shaped and mostly in the trachyte-trachyandesite lava with dimensions of 90×150 m in the surface which continue up to the depth of 70 m. The hydrothermal alterations occurred in the deposit area include silicic, sulphidic, partly argillic (supergen) and propylitic which two former contains most of the high grade gold ores. The main ore structures and textures in the deposit are vein-veinlets (stockwork) and breccia which consists of quartz, sulphide minerals and rare adularia. Primary ore mineral assemblages of the deposit are simple and consist of pyrite, sphalerite, chalcopyrite, bornite, galena, arsenopyrite and gold. Covellite, chalcocite and iron hydroxides are secondary minerals in the deposit. Gold grains with less of than 60 microns in size has been found as inclusion in pyrite and chalcopyrite, in sulfides rims and intergrowth with quartz. Fluid inclusion studies on ore-bearing quartz reveal that majority of primary inclusions are liquid-rich two-phase (LV). The studies indicate homogenization temperatures between 165 and 254°C and salinity between 0.9 to 7.8 wt% NaCl eq. Comparison of the main characteristics of the Sebandoon deposit with epithermal gold deposits reveals that the geology, alteration, ore mineralogy, geochemical characteristics and fluid inclusions of the Sebandoon gold deposit is similar to low to intermediate-sulphidation type epithermal deposits.
