M Boveiri Konari; E Rastad; M Rastad; A Nakini; M Haghdoost
Abstract
Tappehsorkh Zn-Pb-(Ag) deposit, hosted by Lower Cretaceous siltstone, tuff and dolomite, is located in the northern part of the Irankuh mountain range, south of Esfahan. Sulphides in this ore have a relatively simple mineralogy including sphalerite, galena, tetrahedrite, pyrite and to a lesser extent, ...
Read More
Tappehsorkh Zn-Pb-(Ag) deposit, hosted by Lower Cretaceous siltstone, tuff and dolomite, is located in the northern part of the Irankuh mountain range, south of Esfahan. Sulphides in this ore have a relatively simple mineralogy including sphalerite, galena, tetrahedrite, pyrite and to a lesser extent, chalcopyrite, marcasite and bornite. Gangue minerals are predominantly dolomite, quartz and barite. Based on zoning in the sulphide mineralization, texture and structure and location of ore facies relative to syn-sedimentary normal faults, theses ore facies are classified as vein-veinlet, laminated and massive. Dolomitic-silicic alteration is among the major processes concomitant with sulphide mineralization. The greatest degrees of alteration and related ore mineralization occur at the vicinity of the normal faults and decrease away from it. Geochemical studies indicate that the ore-bearing fluids were of oxidized composition, which were reduced once reaching favorable host rocks and consequently deposited sulphide minerals. Minor and trace element studies in the various sulfide ore facies demonstrate that the ore-bearing fluid in all the ore facies has a similar composition. Textures such as framboidal pyrite, contemporaneous folding of organic matter along with sulphide lamination in the laminated ore facies, and diagenetic structures such as load casts in the host siltstone indicate that sulphide mineralization has occurred in the sedimentary-diagenetic stage. However, sulphide mineralization in the regional dolomite is considered to have occurred in a shallow diagenetic environment because of replacement of regional dolomite by hydrothermal dolomite. Based on features of ore mineralization such as the extensional tectonic setting, siltstone and carbonate host rocks, and occurrence of various sulphide facies such as vein-veinlet, laminated and massive, the Tappehsorkh deposit is very similar to Sedex-type deposits.
M Abolipour; E Rastad; N Rashidnejad Omran
Abstract
The Koshkoiye district is located in Dehaj-Sardoiye subzone of Uromieh-Dokhtar Magmatic Arc in Kerman region. There are five active mines including Palangi, Cheshmeh Khezr, Tale Dozi, Abedini, and Eghbali. The geometry of mineralization is strata-bound and hosted in the Eocene Pyrobitumen-bearing porphyritic ...
Read More
The Koshkoiye district is located in Dehaj-Sardoiye subzone of Uromieh-Dokhtar Magmatic Arc in Kerman region. There are five active mines including Palangi, Cheshmeh Khezr, Tale Dozi, Abedini, and Eghbali. The geometry of mineralization is strata-bound and hosted in the Eocene Pyrobitumen-bearing porphyritic andesite. Bornite, chalcocite and chalcopyrite are important Cu-sulfides together with hematite. The textures and structures of mineralization are open space filling, disseminated, vein-veinlet and replacement. According to geochemical study, tectonic setting of Koshkoiye copper district is extensional back-arc, which generated together with subduction of the Dehaj-Sardoiye subzone. Abundant of Cu, Pb and Ag elements is up to 600, 5 and 2 ppm in fresh porphyritic andesite. Fluid inclusion microtermometry indicates probably basinal brine source for ore-forming fluids. The copper mines in the Koshkoiye district have a lot of similarity in mineralogy, minor element, host rock, textures and structures, geometry and genesis with each other and the Manto-type copper mineralization of the world. This type of copper mineralization in the Koshkoiye district of Rafsanjan indicates the importance of volcanic processes in copper mineralization plus plutonic processes that produces porphyry systems in the Dehaj-Sardoiye subzone. The presence of pyrobitumen in porphyritic andesite host rock causes these deposits exposure in a few pyrobitumen-bearing andesitic hosted copper deposits of the world. There are only a few of these deposits in the world and dominantly located in Chile. Two important stages could be separated for mineralization in these deposits like the other Manto-type copper mineralization. The first stage includes processes, which caused to generate pyrite and pyrobitumen in matrix of porphyritic andesite and produced a reduction state in it. The Second stage was related to importance of generation of the Cu-rich oxidation fluids, which replaced the first stage pyrite and pyrobitumen by Cu-sulfides and hematite and caused copper mineralization.
S Ghaderi; E Rastad; N Rashidnezhad-Omran
Abstract
Tungsten (Cu-Au) mineralization of Southern Chah Palang (SCP) deposit, located in middle part of the Yazd block, occurred as vein-veinlet in normal fault zones, which cut the sandstones and shales of Early-Middle Jurassic Shemshak formation. Based on the mineral paragenesis and quartz type, color and ...
Read More
Tungsten (Cu-Au) mineralization of Southern Chah Palang (SCP) deposit, located in middle part of the Yazd block, occurred as vein-veinlet in normal fault zones, which cut the sandstones and shales of Early-Middle Jurassic Shemshak formation. Based on the mineral paragenesis and quartz type, color and texture, ore-bearing veins can be divided into 1) k-feldspar, apatite (I) bearing milky-white quartz veins, 2) white quartz veins contain apatite (II), 3) hematite- white quartz veins and 4) late carbonate veins. Wolframite is the main tungsten ore mineral in the SCP deposit, which occurred in type 1 vein. Wolframite crystals are riched in Fe and have ferberite composition. Scheelite, as next tungsten ore mineral in SCP deposit, formed in 2nd generation and show significant enrichment in As. Scheelite (I) coexist with Wolframite in type 1 veins, and Scheelite (II) replace wolframite in its fractures and rims, also with arsenic-bearing phases occurred in type 2 veins. Gold in SCP deposit occurred as coexist with and/or fine inclusions in Scheelite (II). Other ore minerals that formed in type 2 veins include base metals and Fe sulfides, cobaltite, niccolite, Cu-Ni-Fe sulfides and native bismuth. Type 3 and 4 veins are white quartz-hematite and barren carbonate veins.
δ18 O of ore-forming fluids, which milky-white and white quartz and wolframite formed from them are 7.91-8.61‰, 5.86-6.76‰ and 3.44-6.94‰ respectively. Based on the oxygen isotope studies, progressive mixing of original magmatic fluids with meteoric waters cause precipitation of metals in veins.
S Maghfouri; E Rastad; F Mousivand
