M.A Rajabzadeh; S Esmaeili
Abstract
The Jian copper deposit is hosted by the Permo-Triassic SurianVolcano-Sedimentary Complex on the eastern edge of the Sanandaj-SirjanMetamorphic Zone at a distance of 195 Km NE of Shiraz, southwestern Iran. The complex consists mainly of metabasalt, chlorite-quartz schist, chlorite-muscovite schist, ...
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The Jian copper deposit is hosted by the Permo-Triassic SurianVolcano-Sedimentary Complex on the eastern edge of the Sanandaj-SirjanMetamorphic Zone at a distance of 195 Km NE of Shiraz, southwestern Iran. The complex consists mainly of metabasalt, chlorite-quartz schist, chlorite-muscovite schist, mica schist and graphite schist. Pyrite is the most important sulfide and chalcopyrite is the major Cu-bearing mineral occurred as massive ores in lens to nearly tabular shapes and also as disseminations in veins and veinlets hosted by chlorite-quartz schist. On the basis of geochemical data the mobile elements (Na, k, Ba, Sr) and rare earth elements (REE) show an intense influence of mineralizing fluid on the host rocks. Co/Ni=8.02, Y/Ho (29.09-32.5) and Se/S*106
M Boveiri Konari; E Rastad; N Rashidnejad-Omran
Abstract
Lower Cretaceous volcano-sedimentary sequence in the northwest and southeast of Safashahr (Dehbid) in marginal subzone of southern Sanandaj-Sirjan Zone comprises the Keshtmahaki deposit and few other occurrences of copper (-silver). The oldest rock units in the region are Jurassic shale and sandstone, ...
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Lower Cretaceous volcano-sedimentary sequence in the northwest and southeast of Safashahr (Dehbid) in marginal subzone of southern Sanandaj-Sirjan Zone comprises the Keshtmahaki deposit and few other occurrences of copper (-silver). The oldest rock units in the region are Jurassic shale and sandstone, which are unconformably overlain by the Lower Cretaceous progressive sequence with basal conglomerate, sandstone and silty shale. Copper (-Ag) mineralization occurred in the Lower Cretaceous pyroclastics and volcanic lava. The host rock is a crystal lithic tuff with trachyandesite-andesite affinity in which the stratabound and lenticular ore body is extended discontinuously over 35 km that laterally and vertically changed into orbitolina limestone. Ore minerals include chalcocite, bornite, native copper, digenite, chalcopyrite, pyrite, Ag-bearing clausthalite, covellite, anilite, malachite and azurite. Ore textures and structures are open space filling, vein-veinlet, replacement, disseminated and laminated-like. The lithogeochemical studies in 6 lithostratigraphic profiles from NW to SE of Safashahr indicated Cu (-Ag) mineralization occurrence in a specific stratigraphic unit and a positive relationship with Zn. The lithological, mineralogical, lithogeochemical and microscopic investigations revealed that mineralization initially occurred contemporaneously with volcanism in volcano-sedimentary sequences (absorption of Cu by ferric hydroxide, clay minerals and replacement in feldspar lattice) and then in burial diagenesis during dehydration of pyroclastic and detrital units and alteration resulting from this hydrothermal fluid, Cu released and transported by hydrothermal diagenesis fluids. When this ore-bearing hydrothermal fluid received by the rock unit with high permeability (pyrite-bearing crystal lithic tuff) and reduced conditions resulted from abundance of pyite, replaced them as copper sulphide minerals. S isotopic data of sulphidic minerals indicated that the bacterially sulfate reduction of sea water as an important role provided the nessecary sulfur for sulfide mineralization. Geochemical features of volcanic and pyroclastic units indicated that they formed in an intra-arc rift. On the basis of this study and with respect to some evidences such as tectonic setting, host rock, lenticular shape of the ore body, structure and texture as well as mineral paragenesis we suggest that Keshtmahaki Cu (-Ag) mineralization and surrounding occurrences are Volcanic Red Bed (VRB) type deposit that formed and concentrated contemporaneously with submarine volcanism to deep burial diagenesis processes.
Kh. Khosrotehrani; M. Afghah; V. Ahmadi
Abstract
In this research, two stratigraphic sections were chosen from the late Paleocene to early Miocene (Jahrum and Asmari Formations). These sections includes Sadra and Dodaj plus 645 meters of late Paleocene to early Miocene scdiments. For this investigation 360 thin sections were prepared and 12 samples ...
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In this research, two stratigraphic sections were chosen from the late Paleocene to early Miocene (Jahrum and Asmari Formations). These sections includes Sadra and Dodaj plus 645 meters of late Paleocene to early Miocene scdiments. For this investigation 360 thin sections were prepared and 12 samples analysed by XRF. We studied Biotope that includes biozone. These index biozones and percentage of elements that appears in biotope are identified. Principally index foraminifers, identified in the studied sections, are listed bellow: Miscellanea sp. Kathina sp., Fallotella alavensis Mangin, Opertorbitionlites sp. Alveolina sp. Lituonella ruberti Stache, Rhapydionina urensis Sirel, Orbitolites complanatus Lamark, somalina Stefaninii Silvestri, Dictyoconus sp. Coskinolina liburnica Atache., Nummulites fabianii Prever, Silvestriella tetraedra Gumbel., Nummulites fichteli Michelotti, Austrotrillina howchini Schlumberger, Meandropsina anahensis Henson.
Regarding the frequency, type of wall and biotope percentage ratio of each foraminiferal biozone, there are different biotopes that indicate change in the trend of paleoecologic conditions of the late Paleocene to Oligocene sediments.
