جستجوی مقالات مرتبط با کلیدواژه « overprinting » در نشریات گروه « زمین شناسی »

Shadan gold deposit is located 60 km southwest of Birjand and north of Lut block. the Eocene post-collision magmatism resulting from the subduction of the Sistan Ocean has played a role in the formation of the Shadan gold deposit. Gold mineralization in Shadan deposit is directly related to the emplacement of plutonic and sub volcanic plutons with a composition diorite to monzodiorite that intruded into andesite-pyroclastic units. The main alterations in the area are primary potassic and propylitic alterations, the first of which is located in the center of the hydrothermal-magmatic system and the second of which surrounds the potassic alteration. These two alterations are overprinted by the late Phyllic and Argillic alterations. Mineralization in Shadan deposit occurred in the form of stockwork, vein-veinlets, disseminated and hydrothermal breccias and the most important trigger of gold mineralization in this deposit was Shadan pluton. According to SEM studies, the most important host of gold in the hypogene part is pyrite and gold occurs as native, electrum and calavarite. The most characteristic veins of Shadan gold deposit are M and A type and banded veins. Shadan pluton contains abundant hornblende phenocrysts and biotite as well as high amounts of magnetite in various alterations which can indicate the presence of a highly oxidized magma with high amounts of water. Based on all the mentioned evidences as well as the Cu / Au ratio (3000), Shadan deposit can be introduced as the first gold-rich porphyry deposit in Iran.