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اطلاعات کتابشناختی
عنوان اصلی: برسي دگرساني و كانه زايي طلا در توده گرانيتوئيدي آستانه (جنوب غرب اراك)
پدیدآورندگان : زهرا (پديدآور)
افشوني (پديدآور)
داريوش (پديدآور)
اسماعيلي (پديدآور)
محمدولي (مشاور)
ولي زاده (مشاور)
نعمت الله (مشاور)
رشيدنژاد عمران (مشاور)
گروه زمين شناسي-دانشكده علوم (پديدآور)
نوع : متن
جنس : پايان نامه
صاحب محتوا :

کتابخانه دیجیتالی دانشگاه تهران

وضعیت نشر :
خلاصه : The Astaneh granitoid massif located in 40 km to Arak city, west of Iran, is a part of structural Sanandaj-Sirjan Zone. These intrusion rocks which are mainly consist of grnodioritic rocks, which have cut Jurassic metamorphic rocks and have been cut by microgranitic and aplitic dykes and also mineralized quartz-tourmaline veins.According to field and petrographic studies, eight alteration zones including phyllic (sericitic), chloritic, propylitic, argillic, silicic, albitic, hematitisation and tourmalinisation alteration zones could be identified. In Astaneh, sericitic alteration is the most significant alteration zone and observed pervasively. Calculates of mass changes and study of REE and trace elements behavior show: (1) The oxides including K2O, SiO2 and LOI have increased in the sericitic alteration zones, whereas, Fe2O3, MgO, CaO, Na2O, TiO2 oxides have been decreased. LREE enriched, but HREE, unchanged in this zone. Y, Sc and Ga, in HFSE group, are decreased and U increased in this zone; (2) The oxides including SiO2, Fe2O3, MgO, CaO, Na2O, TiO2 have been decreased in the chloritic alteration zones, whereas, MnO, K2O oxides and LOI have increased. Ga in HFSE group, increased and Y, Sc and U decreased in this zone. LREEs depleted, but HREEs represent different behaviors; (3) In the propylitic alteration zones K2O and LOI were added to the alteration system. Other major oxides are decreased in this zone. HFSE, was leached out of the system. In this zone, compared with HREE, the LREE represent more depletion; (4) In the argillic alteration zone SiO2, Na2O, K2O, P2O5 increased and LOI and other major oxides decreased. In this zone, all REE and HFSE depleted; (5) In the silicic alteration zone, LREE represent enrichment compare with HREE; (6) In the albitic alteration zone K2O, TiO2 SiO2, Fe2O3, MnO, MgO, CaO decreased and Na2O, P2O5 and LOI increased. In HFSE group, were leached out of the system and all REE are depleted; (7) In the hematitisation alteration zone, compared with HREE, the LREE are enriched and (8) In the tourmalinisation alteration zones SiO2, Na2O, P2O5 were increased and Fe2O3, MnO, MgO, CaO, K2O, TiO2 were decreased. HFSE and REE are depleted in this alteration zone. In such zones the amount of Eu/Eu* are low and represent the Eu will segregate from plagioclases structure trough alteration and represent depletion. Mineralization, in Astaneh, is observed in five shapes: (1) tourmaline and scheelite bearing aplitic veins; (2) copper- gold bearing quartz veins; (3) gold (+ tin ± tungsten) bearing quartz veins; (4) tungsten bearing carbonate xenoliths and (5) pyrite bearing silicic amphibolite xenoliths.High concentrations of gold in Astaneh observed in goethitic quartz-sulphide and arsenopyritic veins in granodiorites and altered granodioritic dykes in Shirmazd Mt. These veins are about 1-3 meters and the maximum concentration of gold in them, reaches to 4.2 ppm. They have composed of quartz as the most important gangue minerals as well as chalcopyrite, pyrite, scheelite, azurite, malachite, goethite, lepidocrocite, hematite, arsenopyrite, pyrrhotite, bornite, sphalerite, galen, ilmenite, rutile, molibdenite, marcasite, digenite- covelite- chalcocite, tenorite and scorodite accompanied by gold. In Astaneh, gold was not observed purely, so probably exist as involved in sulphide lattices. The results of the undertaken researches represent that post magmatic fluids enriched by quartz dependent to Shirmazd granodiorite, have a role in gold mineralization of Astaneh. Such fluids are mixed by meteoric water and then mineralizing fluids have caused to produce quartz- sulphide and alteration of Shirmazd granodiorite and micrigranodioritic dykes. So consequently by placing the samples in a diagram in which the homogenization temperatures of the involved fluids places versus their salinity grades, results ore deposit of Astaneh places in granite related Sn- W deposit. However, Astaneh intrusion rocks, based on field observations microscopic research, chemical analysis and study of fluid inclusions, have been introduced of those rocks with potential of Au- Sn- W, but also, the effective magmatic- hydrothermal processes in Astaneh, were not so heavy to appear in Sn- W economic reservations. Whereas regarding the gold, there are placer reservations in Astaneh it can be said that gold mineralization, which exist in the roof of the rock shape of vein- veinlet and in the mostly along with copper, pyrite, iron oxide-hydroxides, while passing the time has been moved towards the bottom of the river and have produced the Astaneh placer reservation that have been discovered and even used in past up to now.
یادداشت :
كتابنامه: به فارسي و انگليسي
عنوان به انگليسي: The study of atterration and gold mineralization in the granitoid rocks of astaneh (sw of arak)
چكيده: به فارسي و انگليسي
رشته زمين شناسي - پترولوژي
كارشناسي ارشد
شناسه : oai:ut.ac.ir:thesis/1-42650
تاریخ ایجاد رکورد : 1387/1/17
تاریخ تغییر رکورد : 1393/10/17
قیمت شيء دیجیتال : دارای قیمت

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* محتوای این صفحه توسط کارشناسان این درگاه ویرایش نشده است. لطفا در صورت مشاهده ایراد در محتوا از این طریق اطلاع رسانی کنید.

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