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The Neogene post-collisional volcanism in eastern Iran is represented by the Sikh Kuh and Bobak high-Na rocks including trachybasalt, trachyandesite, trachydacite, and dacite. We report whole rock geochemistry and Nd–Sr isotopic data which constrain the characteristics of the mantle source. The rocks are highly enriched in incompatible trace elements, suggesting a metasomatized subcontinental lithospheric mantle (SCLM) as the magma source. Felsic rocks record abundant petrographic evidence, major and trace element data, and isotopic (87Sr/86Sr(i) = 0.70727–0.70902) signatures indicative of fractional crystallization, and potentially, crustal assimilation. Such processes however, have not significantly affected the isotopic signatures (87Sr/86Sr(i) = 0.70417–0.70428) of the mafic members, suggesting that they are derived from a mantle source. The geochemical and isotopic data for the Sikh Kuh and Bobak volcanic rocks suggest that these Neogene magmas were derived from a small degree of partial melting (~ 2–10 vol%) of a spinel-bearing subcontinental lithospheric mantle source in a post-collisional setting. The generated more unfractionated mafic magmas erupted during an episode of extensional tectonics, presumably caused by extension that followed Eocene collision between the Lut and Afghan continental blocks. These melts interacted with continental crust during ascent, experiencing crystal fractionation, and crustal assimilation, to produce more evolved felsic volcanic rocks. [ABSTRACT FROM AUTHOR]

The area discussed in this exploration methodology case study is situated along the Sistan Suture Zone where the granitoid suite is a mantle-derived multiphase intrusive complex. One of the characteristics of this region is the presence of large areas of sulfide-bearing, quartz-rich stockwork and pyritic veins. Geochemical findings show that it is limited to the calc-alkaline to shoshonitic series intrusions and is associated with a volcanic arc (I-type) formed within an active continental margin subduction setting. The associated intrusive complex has characteristics consistent with Cu productive porphyries, supported by high K-adakitic Sr/Y, La/Yb, Y and Al2O3/TiO2 geochemical signatures. The stockwork mineralization includes the hypogene (chalcopyrite and bornite), with locally superimposed supergene (covellite, malachite, goethite and hematite) zones. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images (visible-near infrared (VNIR), and shortwave infrared (SWIR) bands) and mixture tuned matched filtering (MTMF) algorithm enable identification of each hydrothermal alteration type, especially where pictures were innovatively classified using a concentration–number (C–N) fractal method. Four alteration types are evident (i.e. phyllic, argillic and propylitic), as well as secondary (supergene) jarosite, that are associated with gossans, which are an indicator of the hypogene pyritic shell. The propylitic alteration envelopes the phyllic and argillic varieties, forming a belt around the pyritic shell; alteration assemblages were confirmed by X-ray powder diffraction (XRD) analysis. Finally, all results show a mineralization alteration pattern within the case study region that is similar to those of known porphyry copper and associated molybdenum- and gold-bearing systems in this region of Iran and worldwide. [ABSTRACT FROM AUTHOR]

Sefidabe and Hyderabad antimony ore deposits are located in the southwest of Sefidabe and in the Sistan Suture Zone. In order to structural analysis of these areas, at first, using satellite images, tectonic lineaments were extracted and the areas with the highest density of length and direction were determined. Then, in the field surveys, veins, faults and mineralization occurred along them were taken. By using stress analysis software, the direction of the principal stresses in the area and the relationships between these structures, tectonic faults and mineralization were analyzed. Compressive shear zones with a northwest-southeast trend are caused by a constraining bend formed between the two of Neh and West-Asagi main faults, is the main factor of mineralization in the study area. This positive flower structure has strongly affected the Paleogene sedimentary and igneous rocks of the region. The Moore's circle indicate a compressional to wrench tectonic regime with the maximum stress direction (03/215) in the northwest-southeast. In this stress regime, in addition to thrust faults, a group of conjugate faults with an acute angle and tensile fractures aligned with the direction of maximum principal stress have formed, which have provided a suitable environment for fluid injection by creating weak zones. [ABSTRACT FROM AUTHOR]

The Asagi Igneous Complex is located about 160 km northwest of Zahedan in the Sistan Suture Zone, southeast Iran. It is composed of Oligocene, Miocene, and Pliocene extrusive and intrusive igneous rocks. The host rocks of the Asagi Igneous Complex are Cretaceous ophiolite and Eocene sedimentary flysch-type rocks. The Oligo-Miocene extrusive rocks are mainly andesite, trachyandesite, dacite, lithic tuff, ignimbrite, breccia, and the Pliocene extrusive rocks are basalt and andesite basalt. They contain plagioclase, K-feldspar, amphibole, biotite, and pyroxene as the main primary minerals. The plagioclase compositions vary from Ab45 to Ab78 and K-feldspars are sanidine and anorthoclase in composition. The clinopyroxene is mainly magnesian augite in composition and plot near to diopside field. The amphiboles are two types of hornblendes and pargasite and the biotite is mainly magnesian in composition and plot in phlogopite field. The Oligo-Miocene extrusive rocks are mainly K-rich (high-K calc-alkaline and shoshonitic), while Pliocene extrusive rocks are Na-rich alkaline. These rocks are characterized by LREE and LILE enrichment on the chondrite- and primitive mantle-normalized spider diagrams. These features attribute to magmatic rocks that crystalize from magmas that originate from modified upper mantle in subduction-related settings. On the discrimination diagrams, the Oligo-Miocene K-rich extrusive rocks fall within continental arc field, while the Pliocene Na-rich extrusive rocks fall within post-collisional field. The geochemical data show that the Na-rich basalts and K-rich volcanic rocks in the SSZ originated from a deep-to-semi-deep metasomatized lithospheric mantle source with garnet, amphibole, phlogopite, and spinel assemblages. It seems that the residual mineralogy of the source mantle is affected by subducted sediments and crustal rocks. The degree of LREE and LILE enrichment and geochemistry of major elements are consistent with magmas that generated from partial melting of the heterogeneous and enriched mantle source which contains peridotites with abundant hydrated phases, such as sodic amphibole (for Pliocene Na-rich extrusive rocks) and phlogopite (for Oligo-Miocene K-rich extrusive rocks). [ABSTRACT FROM AUTHOR]

The Oligocene Lar igneous complex is located in the Sistan suture zone of Iran, being emplaced in Paleocene to Eocene flysch-type rocks. This complex includes mainly intermediate K-rich volcanic (trachyte, latite and andesite) and plutonic (syenite and monzonite) rocks that belong to shoshonitic magma. The geochemical characteristics of the Lar igneous complex, such as an enrichment of LREE and LILE relative to HREE and HFSE, respectively, a negative anomaly of Ti, Ba and Nb and a positive anomaly of Rb and Th are similar to those of arc-type igneous rocks. Tectonic discrimination diagrams also show that rocks of the Lar igneous complex fall within the arc-related and post-collisional fields and K-enrichment of these rocks confirm the post-collisional setting. Based on geochemical features, the Lar igneous complex magma was derived from partial melting of a phlogopite-bearing, enriched and metasomatised lithospheric mantle source and the magma was affected by some evolutionary processes like fractional crystallisation and crustal contamination. [ABSTRACT FROM AUTHOR]

The eastern parts of the Sistan and Baluchistan province, southeast Iran is a tectono-magmatically active zone that continues to witness numerous small and large earthquakes. The volcanism in this region is related to the subduction of the Oman plate below the Eurasian plate. The study of the spatial distribution of the epicenter and focus of the earthquakes suggests close association with the numerous faults related to collisional tectonics. Evidence of ground fractures and faulting related to Saravan earthquake of 16th April 2013 which is the largest (7.8 Mw) recorded earthquake in the region is documented. This earthquake occurred along a segment of the NW-SE trending Saravan normal fault and its reverberations were felt as far away as New Delhi and Dubai. En echelon, 2-km long, northwest-southeast trending surface fractures and faults are recorded in the field near Hampani village southwest of Gosht city. The epicenter is located in the remote hilly terrain east of Gosht. Many of the fractures are listric. The fault records a downthrow of about half a meter and some segments record brecciation of phyllite, liquefaction of sediments and emergence of saline springs are associated features. Despite the high magnitude only a few casualties and minor damage to civil structures were recorded in Iran due to the sparse population and its remoteness. [ABSTRACT FROM AUTHOR]

The Lar Cu-Mo prospect is located 20 km north of Zahedan in Sistan and Baluchestan Province. This area is geologically situated in the Sistan Suture Zone. The Cu-Mo mineralization occurs as silicic veins in the Lar igneous rocks and includes hypogene chalcopyrite, bornite, and molybdenite mineralization. The syenite to monzonite host rocks occur as stock and dyke and display granular to porphyritic texture. In this study, mineral chemistry and petrographic examination of igneous rocks are used to constrain the crystallization conditions of the magma. The compositional range of plagioclase is relatively narrow (0.11%-26.05% An), whereas that of potassium feldspar is wide (11.80%-96.02% Or). Analyses of representative Lar biotite samples with electron microprobe analysis suggest that crystallization took place at average temperature of 731 °C. Amphiboles are calcic and compositionally range from pargasite to ferro-pargasite, edenite, actinolite, and magnesio-hornblende. Estimation of temperature and pressure using calcic amphibole geothermobarometry equations indicates that crystallization is estimated to have taken place at 831 °C and 7.65 kbar. Clinopyroxenes are mainly diopside and were crystallized in a magma chamber at an average temperature and pressure of 926 °C and 7.54 kbar, respectively. According to the mineral composition, the studied igneous rocks are calc-alkaline in magmatic series and were crystallized from a calc-alkaline oxidized magma. The whole-rock chemical data show that the study rocks are shoshonitic and high-K calc-alkaline. [ABSTRACT FROM AUTHOR]

The Mesozoic Bazman granitoids are located in Sistan and Baluchestan province, southeastern Iran. Geology of the study area consists of Carboniferous shale, sandstone, and limestone and Permian siltstone, shale, sandstone, limestone, and dolomite that were intruded by the Bazman granitoids. These granitoids include various phases of granite, granodiorite, quartz-monzodiorite, monzodiorite, diorite, and gabbro. They are metaluminous to slightly peraluminous, reduced, calc-alkaline and I-type, and display geochemical characteristics of continental margin (ensialic) granitoids. In this paper, field, petrography, and geochemical data were used to discriminate the Bazman granitoids either as productive or barren granitoids. Although there are a few skarn-related mineral occurrences adjacent to the Bazman granitoids, most exposed intrusions are not hydrothermally altered and mineralized. Rb/Sr, Zr/Hf, and K/Rb ratios indicate that the granitic magmas that formed most of the Bazman granitoids indicate that they are moderately evolved and have generally not undergone post-magmatic hydrothermal activity. The Sm/Eu and Rb/Ba ratios and the concentrations of Rb, Ba, and Sr within the aforementioned granitoids show that the rocks are similar to the averages of granitoids devoid of Li, Be, U, Sn, W, and Ta deposits. The I-type arc characteristics and other geochemical features of the Bazman granitoids show that they are not typical of parental magmas to Sn, W, Mo, and Zn mineralization, but are mainly fertile for Cu and Fe (Au) skarn-related granitoids. [ABSTRACT FROM AUTHOR]

The Bazman granitoid complex (BGC), including a large zoned pluton, intrudes into the upper Paleozoic sedimentary cover of the Lut block. It crops out on the southern slope of the Bazman volcano in Baluchestan Province of Iran. The intrusive rocks range from gabbro to various metaluminous to weakly peraluminous granites, and they are classified as I-type magmatic series. They display geochemical characteristics of typical volcanic arc magmatism at continental margins. Major- and trace-element variation diagrams show that fractional crystallization was the major process and crustal contamination, a subordinate process during the evolution of the BGC. The decrease in CaO, MgO, Al2O3, Fe2O3, TiO2, P2O5, and Sr, as well as the increase of K2O and Rb with increasing silica, are possibly related to the fractionation of plagioclase, hornblende, apatite, and titanite, whereas the increasing K, Rb, Cs, Pb, and light rare earth elements (LREEs) can be explained by crustal contamination. The BGC rocks are enriched by large ion lithophile elements (e.g., Rb, K, Cs) and the LREEs with respect to the high field strength elements (e.g., Zr, Hf, Nb, Ta, Y) and heavy rare earth elements. New ID-TIMS U-Pb dating performed on zircon and titanite extracted from the granitic samples indicates that the BGC was emplaced during the late Cretaceous period at 83-72 Ma by subduction of the Neo-Tethyan oceanic crust beneath the Eurasian continent. Subsequently, the complex became part of the Lut block when it probably rotated counter-clockwise with respect to the Sanandaj-Sirjan zone and the Urumieh-Dokhtar volcano-plutonic belt. [ABSTRACT FROM AUTHOR]

Identifying the geochemical anomalies from background is a fundamental task in exploration geochemistry. This research is based on the application of concentration-area (C-A) method at the Siah-Jangal Au porphyry system in southeastern Iran. Lithogeochemical datasets ( n = 399) were used in this geochemical survey which was conducted for the exploration for Au mineralization. Moreover, similar surveys were also carried out for As, Cu, and Mo exploration in this region. Anomalous threshold values for the mineralized zone were computed and compared with the statistical methods based on the data obtained from chemical analysis of samples for the lithological units. Several anomalies at a local scale were identified for Au (281 ppb), As (649 ppm), and Cu (20 ppm). The obtained results suggest existence of local Au anomalies that its magnitude generally is above 400 ppb. The C-A log-log plots show existence of three stages of Au and Cu enrichment. The second and most important enrichment event is responsible for the presence of Au at grades above 400 ppb. The obtained results have been interpreted using rather extensive set of information available for the study area, consisting of structural interpretation and alteration data. Various structural features and corresponding alteration show that the geologic structures play an important role in the discrimination of geochemical anomalies and element distribution in the Siah-Jangal area. [ABSTRACT FROM AUTHOR]

Hydrothermal alteration zones have significant role in prospecting of porphyry mineral deposits. In this research, Image processing techniques were applied on the digital subset ETM + data covered the Siah-Jangal area. These techniques generated several products of enhanced satellite imagery, such as colour composite images, ratio images and principal component analysis images. These techniques have been successfully used in mapping of hydrothermal alteration and mineralization zones in the study area. The colour composite and band ratio methods show very clearly the hydrothermal altered zones of clay minerals and iron oxides in and around the Siah-Jangal area. The principal component analysis using the Crosta technique also enabled us to represent undoubtedly the altered hydroxyl and iron-oxide mineral zones as well. The Crosta method has been used on selected 6 (standard method of PCA), 4 and 3 bands. There is no significant difference of the hydroxyl images in the Band ratio and PC methods. But the best results, in terms of mapping the distribution of iron oxide alteration, were obtained using the band ratio and Crosta methods on 3 bands. The results indicate that methods is promising for identifying alteration zones and can assist exploration geologists to find new prospects of porphyry copper and gold deposits in the other virgin regions before costly detailed ground investigations. [ABSTRACT FROM AUTHOR]

The Khut copper skarn deposit is located at about 50 km northwest of Taft City in Yazd province in the middle part of the Urumieh- Dokhtar magmatic arc. Intrusion of granitoid of Oligocene- Miocene age into carbonate rocks of the Triassic Nayband Formation led to the formation of marble and a calcic skarn. The marble contains high grade Cu mineralization that occurs mainly as open space filling and replacement. Cu-rich sulfide samples from the mineralized marble are also anomalous in Au, Zn, and Pb. In contrast, the calcic skarn is only weakly anomalous in Cu and W. The calcic skarn is divided into garnet skarn and garnet-pyroxene skarn zones. Paragenetic relationships and microthermometric data from fluid inclusions in garnet and calcite indicate that the compositional evolution of skarn minerals occurred in three main stages as follows. (i) The early prograde stage, which is characterized by Mg-rich hedenbergite ( Hd53.7 Di42.3- Hd86.1 Di9.5) with Al-bearing andradite (69.8-99.5 mol% andradite). The temperature in the early prograde skarn varies from 400 to 500°C at 500 bar. (ii) The late prograde stage is manifested by almost pure andradite (96.2-98.4 mol% andradite). Based on the fluid inclusion data from garnet, fluid temperature and salinity in this stage is estimated to vary from 267 to 361°C and from 10.1 to 21.1 wt% NaCl equivalent, respectively. Pyrrhotite precipitation started during this stage. (iii) The retrograde stage occurs in an exoskarn, which consists of an assemblage of ferro-actinolite, quartz, calcite, epidote, chlorite, sphalerite, pyrite, and chalcopyrite that partially replaces earlier mineral assemblages under hydrostatic conditions during fracturing of the early skarn. Fluids in calcite yielded lower temperatures ( T < 260°C) and fluid salinity declined to ∼8 wt% NaCl equivalent. The last stage mineralization in the deposit is supergene weathering/alteration represented by the formation of iron hydroxide, Cu-carbonate, clay minerals, and calcite. Sulfur isotope data of chalcopyrite (δ34 S of +1.4 to +5.2‰) show an igneous sulfur source. Mineralogy and mineral compositions of the prograde assemblage of the Khut skarn are consistent with deposition under intermediately oxidized and slightly lower f S2 conditions at shallow crustal levels compared with those of other typical Fe-bearing Cu- Au skarn systems. [ABSTRACT FROM AUTHOR]

The Shurchah antimony-bearing area is located in the Eastern Iranian flysch zone. The Cretaceous to Eocene schists and phyllites are the oldest geological units in the area. These rocks have been intruded by granitic bodies, felsic dikes, and quartz and stibnite veins. The granitic rocks in this area are composed of granite, granodiorite and aplite dikes. The granitoid rocks are generally massive, gray and coarse-grained with granular, porphyritic and cataclastic textures and contain mainly plagioclase, K-feldspar, quartz, biotite, muscovite and opaques. These rocks are commonly peraluminous to metaluminous, calcalkaline and related to a magmatic arc. The SiO2 content of the intrusions varies from 61 to 75 wt.%. Variation diagrams show linear trends, with increasing SiO2 content Al2O3, CaO, FeOt, MgO, and TiO2 amounts decrease whereas, K2O and Na2O contents increase. On the base of MORB and ORG-normalized diagrams, the negative anomalies of Nb, Ti and positive anomalies of K, Rb, Th, U and especially Pb revealed an igneous mantle origin, especially the role of Sistan subduction oceanic crust and overlaying mantle wedge in the genesis of these rocks and also, the role of continental crust in magmatic contamination. [ABSTRACT FROM AUTHOR]

Mahour polymetal ore deposit is located in the eastern margin of Lut block, 130 Km west of Nehbandan. The supergene mineralization mainly occurs as a north-south trend in the Tertiary altered volcanic rocks. The supergene minerals mainly occur as iron hydroxide, Cu-carbonates, Cu and Pb sulfates and Cu sulfides. Goethite, malachite, azurite, chalcosite, covellite, linarite and atacamite are common supergene minerals in the Mahour ore deposit that were formed by oxidation of the hypogene sulfides. Some of these minerals were analyzed by electron probe microanalyses (EPMA). Ag content is considerable in most of these minerals. Covellite from the Mahour has high Pb, Zn and Ag contents. The chemistry of the supergene minerals and the way of their formation will be discussed in this paper. [ABSTRACT FROM AUTHOR]