List of Articles Andesite

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  1 - Introduction of Mari Copper Deposit as a Stratabound Manto-Type Copper Deposit in Tarom Zone, Northwest of Iran
  Mehadi Moradi Sajad Maghfori Mohsen Moayyed Vahid Faridasl
  Similar to other deposits of this type in the world, three major stages could be considered for mineralization in Mari copper deposit. The Mari Copper deposit is located in the northwest of Iran and Tarom metallogenic zone in the north of Zanjan. The ore-body is strata- More

  Similar to other deposits of this type in the world, three major stages could be considered for mineralization in Mari copper deposit. The Mari Copper deposit is located in the northwest of Iran and Tarom metallogenic zone in the north of Zanjan. The ore-body is strata-bound and hosted by the Eocene mega-porphyritic andesites. The major copper sulfides are bornite, chalcocite, and chalcopyrite associated mainly with pyrite that represent open-space filling, disseminated, vein-veinlet, and replacement textures. The volcanic rocks of the study area mostly represent intermediate to acidic composition with high potassium shoshonitic magmatic series related to intra-arc rift environments. Wall rock alterations include carbonatization, chloritization, epidotization, and sericitization. The abundances of Cu and Ag in fresh mega-porphyritic andesite are up to 3200 and 216 ppm respectively. Based on the main characteristics of Mari ore body such as tectonic setting, host rock, strata-bound form, mineralogy, metal content, and wall rock alterations and comparison of these features with Manto - type copper deposits, Mari Cu deposit can be introduced as a Manto -type Cu deposit in NW Iran. The first stage includes submarine volcanic activity and eruption of mega-porphyritic andesitic lava associated with regional propylitic alteration. In the second stage, the early diagenesis and the activity of sulfate-reducing micro-organisms resulted in the generation of pyrite in the form of open-space filling and disseminated in the mega-porphyritic andesite. Finally, in the third stage, increasing of the thickness of sediments, basin subsidence, and burial diagenesis accompanied with the entry of metal-rich fluids into the reduced host rock, caused the replacement of the first stage pyrites by copper sulfides and mineralization in the Mari deposit. Manuscript profile
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  2 - Petrography, geochemistry and mineralization of volcanic rock in Sistanak area (South East Qaen)
  Hojat Mahvelati  Rasa Ida Mohebbi
  Sistank copper deposit is geographically located in East and South-East city of Qain. In general, copper range in Sistanak is in East Central Zone, part of which is located in the Filishy zone and another part in the Lut Block. The stratigraphy in the study area have More

  Sistank copper deposit is geographically located in East and South-East city of Qain. In general, copper range in Sistanak is in East Central Zone, part of which is located in the Filishy zone and another part in the Lut Block. The stratigraphy in the study area have shown that old rocks than the Jurassic age in the study area. According to petrographic studies, the volcanic rocks are divided into two groups of lavas (andesite and andesite -basalt) and pyroclastics (tuff and agglomerate). These rocks are placed in a class of high potassium calc-alkaline and calc-alkaline. According to chemical composition, volcanic rocks occur in andesite and andesite-basalts range. Copper is the main mineral in andesitic lavas, including native copper, chalcocite and malachite. In addition, in some samples the iron oxide minerals such as hematite and, gotite are presant. Mineralized zone is placed at the highest level of volcanic lava and the mineral is stratabound. Such characteristics, are indicative of epigenetic in origin. According to geological characteristics and based on geological and mineralogical charactristis, copper deposits in Sistanak is probably similar to Michigan type deposits. Manuscript profile
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  3 - Geology, alteration, mineralization and geochemical study in copper mine, Golcheshmeh Area, South of Neyshbour
  Fatemeh  Najmi  Mazaheri Saeid saadat Azam Entezari
  The Golcheshmeh copper deposit is located in the NE of Iran (south of Neyshabour) at the margin of Sabzevar Structural Zone. Based on geological and labratory studies, the outcroped rocks consist of Eocene volcanic rocks such as andesite, basaltic- andesite and basalt t More

  The Golcheshmeh copper deposit is located in the NE of Iran (south of Neyshabour) at the margin of Sabzevar Structural Zone. Based on geological and labratory studies, the outcroped rocks consist of Eocene volcanic rocks such as andesite, basaltic- andesite and basalt that associated with the sedimentary and volcanosedimentry rocks including limestone, tuff and breccia. The alteration hosted andesitic layers include carbonatization, propylitization and less argilic and sericitic alterations. The carbonatization zone is the most important alteration in this area. Mineralization mainly occurs in Eocene or younger volcanic rocks as vein- veinlets, amygdaloidal fillings and some replacement and disseminated styles. According to the minerallographical studies, the main ores which contain copper are divided into oxide and sulfide types. Mineralization mainly consists of oxide phases and can be seen as contamination of fracture surfaces and filling pores or voids in the host rocks. The main oxide minerals are malachite, azurite and chrysocolla, and sulfide minerals are chalcocite, covellite, with some minor pyrite, chalcopyrite, bornite, digenit and also native copper. Chalcocite is the most abundant ore sulfide in this area. There are probably two generations of sulfides, the first generation is a primary ore that was formed directly in joints, cracks, and fractures from the ore-containing solution and currently is replaced by covellites; and, the second generation is chalcocite that was probably formed from the conversion of bornite and chalcopyrite through substitution under supergene conditions. In most cases, the observed intergrowth between copper ores suggests the multi-stage mineralization in this region. Geochemical studies of minor and trace elements indicate that the igneous rocks in this region are characterized by the calc-alkaline basalt characteristics and, in terms of tectonic setting, could be attributed to subduction zone-related continental arc magmatism. Moreover, based on the performed geochemical analyses, the copper grade in the region varies from 13668 to 164000 g/ton. On the basis of the results of this study and with respect to some evidences such as tectonic setting, host rock type, structure and texture of ore body, mineral paragenesis, shape of the ore body and associated elements, this area is compared to Manto type deposit located in Chile. Though there are some differences, it is suggested that golcheshmeh copper mine is classified in Cu- Manto type deposit. Manuscript profile
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  4 - Tectonomagmatic setting of the Eocene volcanic rocks in Ahovan area (Semnan)
  Maryam Alipour Morteza Khalatbari-Jafari Mohsen Pourkermani Sedigheh Etesami Ali Sorbi
  Petrology and tectonomagmatic setting of the Eocene volcanic rocks exposed in the Ahovan area, east of Semnan are presented and discussed. The studied rocks include basic-intermediate and acidic volcanic lavas and dikes, accompanied by intercalations of nummulite-bearin More

  Petrology and tectonomagmatic setting of the Eocene volcanic rocks exposed in the Ahovan area, east of Semnan are presented and discussed. The studied rocks include basic-intermediate and acidic volcanic lavas and dikes, accompanied by intercalations of nummulite-bearing limestone, shallow water deposits, hyaloclastite and hyaloclastic breccia. The basic-intermediate lavas are exposed at the base and the rhyolitic and andesitic lavas are exposed at the top of the volcanic series, all of which may be attributed to a bimodal volcanism. It seems that Eocene volcanic activity occurred in shallow water to subaerial environments. Based on petrographical investigations, the volcanic lavas show basaltic, basaltic andesitic, andesitic, dacitic, rhyolitic and acidic tuffs compositions. The lavas have phyric to aphyric textures. The phyric lavas include plagioclase, augite and hornblend phenocrysts. They show microlitic, microcrystalline and intergranular groundmass in dikes. Disrupted zoning and sieve texture in plagioclase phenocrysts and heterogeneous groundmass might be interpreted by magma mixing. Study of the geochemical analyses, indicates high-k calc-alkaline to shoshonitic magmatic trends in the Ahovan area. Trace and REE spider diagrams, normalized with standard values, display enrichment of LILE and clear depletion of Nb and Ti. In tectonomagmatic diagrams, these samples plot in the arc field which tends toward an initial extensional back arc envirenment. It appears that partial melting of adjusted mantle wedge above a subducted slab provided the parental magma which was enriched by fluids-melt released from partial melting of the subducted slab. Manuscript profile
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  5 - Petrology of Oigocene volcanic rocks in the Deh Tah area, south of Dehuk, Lut Block
  Morteza Khalatbari نرمین بانه ای Mohammad فریدی
  20.1001.1.17357128.1399.14.56.6.9
  The study area in the south of Deh Tah, Lut Block comprise Oligocene volcanic rocks which are composed of andesite, trachyandesite, dacite and rhyolite. These lavas have porphyric to porphyritic textures with abundant amphibole phenocrysts. Most of the Oligocene lavas d More

  The study area in the south of Deh Tah, Lut Block comprise Oligocene volcanic rocks which are composed of andesite, trachyandesite, dacite and rhyolite. These lavas have porphyric to porphyritic textures with abundant amphibole phenocrysts. Most of the Oligocene lavas display calck alkaline to high-K calck alkaline magmatic affinities. In the binary diagrams, the andesitic to trachyandesitic samples cluster far away from the trachydacitic, dacitic and rhyolitic samples suggesting that they were not afftected only by magmatic differentiation. The REE patterns and spider diagrams show enrichement in light ion litophile element (LILE) and hight field strength element (HFSE) depletion. The normalized patterns of the andesite to trachyandsite have a reliable overlap with oceanic island basalt (OIB). The patterns of the acidic lavas are correlated with the patterns of continental crust. These geochemical evidence indicate that the andesitic to trachyandesitic lavas are generated from partial melting of lithospheric mantle which previously metasomatized by subduction components (melt-fluids). Partial melting of the continental crust has an important role in generation of the acidic lavas. Based on geological setting and geochemical data, it seems that the Oligocene volcanic rocks formed in a post-collision zone, due to thinning of the continental lithosphere in Lut Block. This process is probably related to lithospheric delamination which occurs in a post-collisional zone in Lut Block, as a part of the Alpine-Hymalaya orogenic belt. Manuscript profile