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

Studied area is located in Kerman province, Iran. This area belongs to the Urumia-Dokhtar magmatic arc (UDMA) zone. Several porphyry copper deposits were known in this magmatic arc. UDMA is marked by voluminous Tertiary volcanic sequences of up to 3000 m thickness. It seemed that these Cu occurrences are related to structures, especially major and main faults.In this study, magnetic structures were extracted by using the aeromagnetic data. This data was extracted by Atomic Energy Organization of Iran (AEOI) during 1977 and 1978. The flight lines distance and the sensor altitude were about 500 and 120 m, respectively. Airborne magnetic method is among the most efficient geophysical techniques for the detection of buried anomalies.In the first step, total magnetic intensity map was prepared and reduction to pole transformation was done on it. Reduction to the pole (RTP) is a standard part of magnetic data processing method, especially for large-scale mapping. RTP operation can transform a magnetic anomaly caused by an arbitrary source into the anomaly that the same source would produce if it is located at the pole and magnetized by induction only. Interpretation of magnetic data can further be helped by RTP in order to remove the influence of magnetic latitude on the anomalies, which is significant for anomalies caused by crust. Most of the studied areas are covered by mafic volcanic rocks. These rocks produce moderate to high magnetic anomalies. In some parts, the effect of demagnetization can be observed in these rocks because of the spread of alteration in this area. A low magnetic anomaly is observed in the northern part of the studied area related to sedimentary rocks in this area. In the next step, body magnetic anomalies were extracted from reduction to pole map. A tilt angle filter used to extract magnetic lineaments was applied to the reduction to pole data. Upward continuation filter was implemented at 200 m, 500 m and 1000 m on the tilt angle map and magnetic lineaments were extracted from tilt angle maps. Several magnetic lineaments and magnetic bodies were extracted from magnetic maps (tilt angle maps and reduction to pole maps). There is good correspondence between magnetic structures and copper occurrences. The P-A curve confirms this result.

The Niaz Cu prospect is located 25 km west of Meshkinshahr, east of the Qaradagh metallogenic zone. The intrusion Oligo-Miocene magmatic bodies into the Paleocene-Eocene rock units has led to alteration and mineralization. The rock units of this area include batholiths Ι and ΙΙ (Khanbaz granodiorite and Khankandi granodiorite), Niaz quartz-monzonite/ quartz-monzodiorite and ore-bearing rhyodacite breccia.

In this research, the geological features, alteration, mineralization and physicochemical conditions of mineralizing fluids have been studied. In this regard, sampling from altered, mineralized zones and drilling cores were carried out and 23 samples were analyzed by XRF and 18 samples by ICP-OES methods and microthermometric measurements were performed on 8 doubly-polished thin sections.

The intrusive units have high-K calc-alkaline to shoshonitic nature, and the geochemical characteristics of their trace elements indicate similarities with subduction-related magmas. The negative anomaly of Ti and Nb in these rocks can be due to the magmatism related to the subduction processes, as well as the stability of the phases containing these elements during partial melting or their separation during the differentiation process. The enrichment of Pb, La, K, U, and Th elements and the depletion of Sr, Ti, and Nb can be attributed to crustal contamination. Hypogene alterations at Niaz include potassic, phyllic, propylitic and intermediate argillic types. Mineralization has occurred during early, middle, and late stages. Based on the mineralogy and paragenetic sequence, at least five types of veins/veinlets can be distinguished in Niaz deposit. Group A veinlets contain quartz+pyrite+chalcopyrite+magnetite, group B veins are also present in the potassic and phyllic alteration zones, veinlets of group C are mainly formed in the middle stage of mineralization, group D veins are mostly observed in the phyllic alteration zone, which are formed in the middle and later stages of hydrothermal activities and group E veins are almost devoid of sulfide minerals and mainly contain bright-color minerals (quartz and/or calcite)±tourmaline and are mostly present in the propylitic alteration zone. Studies on fluid inclusions (FIs) within the quartz veinlets showed that there are four types of FIs at room temperature, (1) mono-phase vapor, (2) liquid-rich 2-phase, (3) vapor-rich 2-phase, and (4) multi-phase solid containing daughter solid phases. The ranges of FIs are about 280-360°C in the potassic, 280-360°C and 280-300°C in phyllic and 170-330°C in propylitic alteration zones.

The petrology and petrogenesis of magmatic host rocks, mineralogy, hydrothermal alteration in the Niaz area testify to a porphyry-type Cu mineralization. The main sulfide mineralization includes vein-type pyrite, molybdenite, chalcopyrite, sphalerite and galena. Fluid inclusion microthermometry results show a Th range of 170-360 °C and salinity values of 0.2-60 wt%NaCl equiv., corresponding to the ranges of porphyry Cu deposits. Boiling and simple colling of ore-bearing fluids were the main processes for ore precipitation.

The Zamin Hossein copper deposit, as a part of the Dehaj- Sarduiyeh metallogenic belt, is located about 170 km southeast of Kerman city. This deposit is accompanied by Eocene volcanic (andesite, andesi-basalt and pyroclastic) and Eocene intrusive body (granodiorite and granite). The propylitic, sericitic, argillic-sericitic and silicic alterations are associated with this deposit. Chalcopyrite and pyrite are the most important hypogene sulfide minerals which are accompanied by supergene mineral assemblages such as goethite, hematite, limonite, malachite, and azurite. The hypogene minerals show generally vein-veinlet, stockwork and crustiform textures. The microthermometric studies in quartz crystalscogenetic with the ore minerals revealed four types of fluid inclusions on the basis of phase content: 1-( L-V), 2-(L-V-S), 3-(V-L), and 4-(V). The results of microthermometric analyses revealed that the fluid inclusions have a wide range of Th (170°C to 530°C). The L-V-S type fluid inclusions displayed Th and salinity ranges of 190-473°C and 31.4-55.6 wt% NaCl eq., respectively. The liquid-rich 2-phase inclusions (L-V) show salinities within the range of 1.74-6.45 wt% NaCl eq. Based upon microthermometric data, boiling, mixing, and simple cooling of the fluids were the essential mechanisms in deposition and evolution of this deposit. The ore-forming fluids were probably of magmatic and mixed magmatic-meteoric sources. According to the structural and textural aspects, alteration and mineralization of mineral assemblages and microthermometric data, the Zamin Hossein ore deposit can be categorized as porphyry copper-type.

The Maher abad and Khopik porphyry Cu deposits occurred in the Upper Eocene (39-37 Ma) in Lut block. All of them associated with intermediate (mostly monzonite) rocks. Porphyry deposits are closely associated with oxidized magmas. Oxygen fugacity (fO2) is a key factor that controls the formation of porphyry Cu deposits. The composition of the major and trace elements of zircon grains related to several ore-bearing monzonite were measured in Maher abad and Khopik porphyry copper indices. Zircon grains show moderate to low Ce4+/Ce3+ with a range of 19 to 610 and an average of 155. The average of oxygen fugacity (logfO2) values of Meher abad and Khopik ore-bearing magmas, range ∆FMQ -3.2 to MFMQ -1.3 with mean ∆FMQ -2.2, indicate formation under moderate oxidation conditions (between Ni-NiO (NNO) and Faylite magnetite-quartz (FMQ) buffers, but magnetite-hematite (HM) buffer, which ), which is not ideal for the formation of porphyry deposits. This is supported by whole-rock and Sr-isotopic data, and absence of high oxidation minerals such as hematite, and the poor adakitic charactristic of rocks in both deposits, which are due to factors involved in magma origin such as rock type and partial melting rate (possibly peridotite with low participation of slab).

Bagh Khoshk deposit is located 35 km northeast of Sirjan in the southern Urmia- Dokhtar magmatic belt (Kerman metallogenic area). The magmatic activities and copper mineralization in this belt are attributed to the Eocene-Oligocene, middle-late Oligocene, and middle-late Miocene. Meanwhile, fertile porphyry copper deposits are genetically associated with middle-late Miocene granitoids (adakitic intrusive rocks). In Kerman metallogenic area, intrusive rocks are divided into productive with Miocene age (Kuh-Panj type) and semi-productive to barren groups with Eocene-Oligocene age (Jebal Barez type). Bagh Khoshk copper deposit has not been studied in terms of mineralization and genesis. In addition, it is not clear whether the Bagh Khoshk granitoid intrusion is a productive or semi-productive to barren magmatic system in the Kerman region. In this research, Bagh Khoshk deposit has been studied from the perspective of lithology, alteration, geochemistry, mineralization and fluid inclusion and by determining the geochemical nature of Bagh Khoshk granitoids, the origin of copper mineralization has been investigated.

In this research, the number of 21 samples from the outcrops and 24 samples of drilling cores have been selected for petrographic and mineralogical studies. 13 unaltered to less altered rock samples were taken from the outcrops and drilling cores for petrological studies and analyzed using XRF and ICP-OES/MS methods for major and trace elements. Ore geochemistry study has been done on 491 rock samples from drilling cores. To study the fluid inclusion, 4 mineralized samples were selected from the potassic and phyllic alteration zones and after preparation of double polished sections, micro-thermometry studies were done on quartz crystals.

The Eocene andesite to basaltic andesite lava flows and tuffs are the most widespread rock units in the Bagh Khoshk area. Late Miocene hypabyssal porphyry granodiorite and diorite stocks are intruded into the volcanic rocks. The alterations include potassic, prophylitic, phyllic, and argillic zones from the inside out. This deposit includes sulfide minerals (pyrite, chalcopyrite, bornite, molybdenite, chalcocite, and covellite), iron oxides (magnetite, olygiste, hematite, and goethite) and malachite which are mostly observed as disseminated and vein-veinlet forms in the potassic and phyllic zones. Copper is the major element, which has a positive correlation with molybdenum. Fluid inclusions in quartz crystals include LV, VL, and LVH types. The homogenization temperature of the LV, VL, and LVH fluid inclusions ranging from 180 to 289, 331 to 565, and 207 to 276 ⁰C. Their salinity varies from 0.35 to 10.24, 0.88 to 11.22, 33.55 to 42.66 wt.% NaCl eq., respectively. The Bagh Khoshk magmatic system in the Urmia-Dokhtar belt, was formed by partial melting of mantle source and thickening of lower crust, where the share of lower crust has been dominant. Finally, the Bagh Khoshk mineralization is a porphyry copper deposit, which is associated with adakitic and productive late Miocene magmas.

The late Miocene granodiorite intrusions host copper mineralization in the Bagh Khoshk area. These intrusions have the geochemical properties of adakitic magmas and are located in a normal continental arc environment. Enrichment in LREE, high Sr/Y and La/Yb ratios, enrichment in LILE and Sr, and depletion in HFSE are prominent geochemical features of Bagh Khoshk granitoids. Chalcopyrite is the most important copper-bearing mineral that is found as disseminated and vein- veinlets forms in the potassic and phyllic alteration zones. Based on fluid inclusion studies, the normal cooling of magmatic fluids and their mixing with meteoric waters has been one of the most important factors of metal deposition and the average depth of fluid inclusions entrapment and placement of the Bagh Khoshk porphyry stock is estimated at about 1200 m. The Bagh Khoshk magmatic system consists of partial melting of a mantle source with garnet amphibolite composition and a thickened lower crust, in which the share of lower crust has been dominant. The rapid rise of productive adakitic magma has led to the formation of economic copper deposit in this area.

The widespread Cenozoic magmatic assemblages in Iran host a variety of ore deposits including porphyry Cu-Mo-Au, skarn type ores, and epithermal base and precious metals deposits. Silicic zones of variable sizes are common in the Kerman belt in the southern section of the Urumieh-Dokhtar arc, and some might be representing the upper parts of porphyry copper systems known as lithocap. To investigate this potential relation, a silicic zone in Meideh, north Pariz, is studied. The silicic zone lies in an area with several known porphyry copper deposits (PCD) including Sarcheshmeh, Nochun, Seridun, Sarkooh, and Bagh-Khoshk. For comparison, silica ledges and veins in Seridun and a mineralized silica vein system to the east of the Sarcheshmeh mine are also studied.

The study is based on field studies and investigation of textures and structures, and sampling for mineralogy (microscopic and X-ray diffraction analysis), and fluid inclusions. The XRD analyses were accomplished in the Iranian Mines and Mining Industries Development and Renovation Organization (IMIDRO) and Kansaran Binaloud Co, Tehran. The fluid inclusion studies were performed in the Iranian Mineral Processing Research Center (IMPRC) using a Linkam THMS600 equipped with a Zeiss microscope.

The silicic zone in Meideh is developed in andesitic lava flows and pyroclastic materials, and covers an area of ~ 1 km2. Silica occurs in white to grey colors and in massive, brecciated and locally vuggy textures; the grain sizes range between 0.01mm to 1mm. The silica is locally associated by minor sulfides (pyrite and locally chalcopyrite) carbonates, and clay minerals.The silicic zone grades outward into a silicic-argillic halo and into the host volcanic rocks with propylitic alteration. Chemical analysis of samples from the zone indicated enrichments in Cu, Mo, Ag, As, Bi and Au relative to the average composition of intermediate-mafic volcanic rocks in the Kerman belt. Small outcrops of a quartz-tourmaline rock occur in the southeast of the silicic zone.In Seridun, silica ledges and veins occur in the periphery and in the upper parts of a porphyry copper deposit developed in Miocene shallow intrusive bodies and older volcanic rocks. In east of Sarcheshmeh, several N-S striking silica veins locally containing pyrite, chalcopyrite, malachite, and Fe-oxides/hydroxides occur in Cenozoic volcanic and intrusive host rocks. In both areas, the silicic zones are products of pervasive silicic alteration, and occur in massive, breccia, and vuggy textures. Vuggy texture is well developed in Seridun. XRD analysis of representative samples from Meideh indicated the occurrence of kaolinite and illite, in addition to quartz. Minerals characteristic of advanced argillic alteration (i.e. alunite, pyrophyllite, diaspore and andalusite) are missing. The minerals, however, were identified in Seridun.Fluid inclusions in quartz from all three areas are dominated by two-phase liquid-vapor. Homogenization temperature (TH) varies between 140-263 oC (average: 202 oC) for Meideh, 195-320 oC (average: 247 oC) for Seridun, and 140-264 oC (average: 177 oC) for east of Sarcheshmeh. Salinities vary between 0.18-5.71 (average: 1.62), 1.22-4.18 (average: 2.27), and 0.7-3.39 (average: 1.57) wt.% NaCl eq., respectively. The quartz-tourmaline rock from Meideh is distinguished by the occurrence of liquid-vapor-halite±hematite and liquid-vapor-opaque inclusions, in addition to liquid-vapor inclusions. The TH and salinity for the liquid-vapor inclusions, homogenizing to liquid, varies, respectively, between 202-269 oC (average: 231 oC) and 3.71-7.16 (average: 5.43) wt.% NaCl eq. The TH and salinity for the halite bearing inclusions, homogenized by halite dissolution, varies between 240-480 oC (average: 345 oC) and 33.40-56.90 (average: 42.80) wt.% NaCl eq.

The textures, structure, and spatial relations with the host volcanic rocks suggest that the Meideh silicic zone developed as a result of pervasive silicic alteration, rather than open space filling. Textures indicative of open space filling, including crustification and symmetric banding, are absent in Meideh. The silicic ledges in Seridun, and the N-S striking silicic zones in east of Sarcheshmeh, are the products of pervasive silicic alteration of the host volcanic and intrusive rocks.The XRD analysis of representative samples from Meideh indicated the occurrence of kaolinite and illite, in addition to quartz. Minerals characteristic of advanced argillic alteration (i.e. alunite, pyrophyllite, diaspore and andalusite) are missing. The minerals, however, were identified in Seridun. Fluid inclusions in quartz from the three silicic zones are dominated by two-phase liquid-dominant L-V inclusions. No distinction in salinity can be made between the three zones; Seridun, however, is distinguished by higher homogenization temperature. The local quartz-tourmaline zones in Meideh developed from distinctly higher temperature and salinity fluids (240-480 oC and 33.9-64 wt.% NaCl eq., respectively). A comparison of fluid inclusion data with several epithermal base and precious metals systems in the Urumieh-Dokhtar arc and elsewhere in Iran suggest that no meaningful distinction can be made between barren (i.e. Meideh, at current exposure level) and productive epithermal systems.Our data indicate that the silicic zone in Meideh cannot be considered as a porphyry-related lithocap at current exposure. The quartz-tourmaline rock developed from fluids of higher salinity and temperature suggests a link with magmatic-hydrothermal systems and warrants further investigation.

Oxygen fugacity (fO2) and zircon crystallization temperatures (Ti-in-zircon) of ore-bearing quartz monzonite intrusive rocks of ChahShaljami and Dehsalam Cu-Mo porphyry deposits were measured by using calculations of zircon trace element values and oxidation conditions of parental magma were investigated. The Ce4+/Ce3+ values for ChahShaljami and Dehsalam are in a range of 8 to 295 with an average of 125 and 3 to 171 with an average of 35, respectively, therefore they were not in the favorable range for porphyry mineralization. The estimated fO2 values for ChahShaljami and Dehsalam are in the range of ∆FMQ -1.8 to MFMQ +0.6 with an average of ∆FMQ -0.6 and ∆FMQ -1.3 to ∆FMQ -0.4 with an average of ∆FMQ -0.8 which is at least ∆FMQ +1 less than the values of porphyry copper mineralization in the world.. Based on the zircon log fO2 values of ore-bearing intrusive rock, the parental magma originated from partial melting of supra-subduction mantle peridotite zone within oceanic slab. Melting under unfavorable conditions (under magnetite-hematite (HM) buffer and in faylite-magnetite-quartz (FMQ) buffer condition, and lack of sufficient Cu and sulfur at the source), which is supported by evidences in deposit such as lack of magnetite-hematite intergrowths, was not ideal for porphyry Cu porphyry mineralization in the two regions. The results are supported also by previous whole-rock major and trace element geochemistry and Sr-Nd isotopic values.

The Takht-e-Gonbad copper mineralization is located about 63 km of northeast of Sirjan city. Hypogene mineralization occurred as stockwork vein-veinlets and thick quartz veins hosted by Oligo-Miocene micro-granodiorite body and Eocene pyroclastic materials (mainly tuff with intermediate composition). The stockwork vein-veinlets contain three generations of mineralization, (1) quartz + magnetite ± chalcopyrite, (2) quartz + chalcopyrite + pyrite + magnetite, and (3) quartz + pyrite + chalcopyrite. Phyllic alteration was mainly developed in the wall rocks around the stockwork quartz vein-veinlets. The supergene mineralization in this deposit is characterized by the replacement of ferrous sulfides by hematite and goethite. Also, formation of the malachite, azurite, and native copper during destruction of the hypogene iron and copper sulfides occurred under oxidizing conditions. The study of the fluids inclusion in quartz crystals of the stockwork vein-veinlets showed that they are chiefly of L+V+S, L+V and V+L types having temperature and salinity ranges of 140-450°C and 0.35-57.8 wt% NaCl eq., respectively. The solid phases are halite, sylvite, and opaque minerals. The studied fluids inclusion in the thick quartz veins are of L+V type having temperature and salinity within the range of  207-344°C and 0.35-3.39 wt% NaCl eq., respectively. Based on microthermometric data, the boiling of the magmatic fluids was the effective factor of the ore and gangue minerals deposition in the stockwork vein-veinlets. Also, cooling and mixing of the atmospheric fluids with magmatic ones account for the deposition of the minerals in the thick quartz veins.  In general, the obtained data in this research revealed that the development and evolution trend of the hydrothermal system in the Takht-e-Gonbad is mostly similar to that of the porphyry copper system.

In this research, we have used different integration methods for creating the geochemical evidential map that is one of the most important layers in mineral potential mapping. The Study area (Varzaghan 1:100,000 sheet) is located in East Azarbaijan province and Ahar-Arasbaran metallogenic zone. This region, because of its geological situation and presence of several porphyry copper deposits like Sungun porphyry-skarn deposit, is considered as an important metallogenic province in the northwest of Iran. In this study, we have used 1067 stream sediment samples as primary data that picked up by Geological Survey & Mineral Explorations organization of Iran. By selecting indicator elements of porphyry copper deposit, like Cu, Mo, Au, Ag, Pb, Zn, Au and As, the evidential map of each element have generated by the continuous fuzzy method. In the next step, by using Union Score (US) method, fuzzy OR operation, and geometric average, the individual geochemical maps have integrated. Finally, Prediction-Area plots have drawn to validate the evidential maps. This plot showing that geochemical evidential map that produced by US method, can predict 76 percent of known mineral occurrences and it can consider as a proper method for creating the geochemical evidential map for porphyry copper deposits.

The Bolboli2 copper ore deposit is located about 110 km southwest of Kerman and lies in the Dehaj-Sarduieh metallogenic belt (Kerman Cenozoic Mamatic Arc, KCMA). This ore deposit is hosted by the Eocene extrusive igneous rocks (tuff, agglomerate, andesite, and dacite) and the Oligo-Miocene intrusive igneous body (granodiorite). These rocks are host the propylitic, phyllic, and silicic alteration zones (product of the mineralization fluids). Hypogene mineralization was dominant and occurs mainly as stockwork vein-veinlets and disseminate (chalcopyrite, pyrite, and magnetite). This mineralization is overprinted by supergene assemblages such as hematite, goethite, malachite, and azurite at superficial part of ore deposit. The hypogene minerals show generally vein-veinlet, stockwork, brecciated, granular, and crustiform textures. Microthermometric studies in quartz crystals cogenetic with the ore minerals reveal 4 types (1) L-V, (2) L-V-S, (3) V-L, and (4) V fluid inclusion. Study of fluid inclusions display a Th range of 190-427ºC. The L-V-S fluid inclusions were homogenized with halite disappearance with the Ts(NaCl) ranging from  213ºC to 425ºC which corresponds with salinities within the range of 32-50 wt% NaCl equivalent. The liquid-rich 2-phase inclusions (L-V) show salinities within the range of 0.6-10 wt% NaCl equivalent. Based on microthermometric data, boiling, mixing, and simple cooling of the ore-bearing fluids were the essential mechanisms in deposition and evolution of this ore deposit. The ore-forming fluids were probably of magmatic and mixed magmatic-meteoric sources. The geological setting, structural and textural aspects, alteration and mineralization of mineral assemblages, as well as microthermometric data show that the Bolboli2 ores can be categorized as porphyry copper-type ore deposit.

In porphyry copper deposits, turquoise is considered to be a supergene oxidation product (John et al., 2010; Chavez, 2000). Based on Rezaian et al., 2003; Zarasvandi et al., 2005 and Eslamizadeh, 2004, the Aliabad index is introduced as a porphyry copper system. The first published report on turquoise events around Ali-Abad was presented by Momenzadeh et al., 1988. This area is located 57 km southwest of Yazd. Alterations often include siricitization, advanced argillization. Kaolinization and silicification have occurred frequently in the arkose and microcan glomerate of the Sangestan formation. The aim of this research study is to try to reconstruct and investigate the formation and origin of turquoise by using the latest mineralogical and geochemical data. Field evidence shows occurrence of turquoise in the form of a veinlet and nodules, with blue-green and blue-white colors. Jarosite, alunite, quartz and iron oxides are found together with turquoise.

A geological map of the area with a scale of 1/15000 was prepared. 35 samples of intrusive bodies, sandstones and altered rocks were selected to produce thin and polished sections. XRD and the EDS analyses were carried out at the central laboratory of Isfahan University and the University of Oklahoma, USA, respectively in order to identify the chemical composition of phases.

Based on the studies, several chain processes have been involved in the form of turquoise: the initiator of the reactions is the formation of an oxidant environment (gossan), in which metal sulfides (Cu, Fe) in the phyllic zone of porphyry copper deposit have played a fundamental role. Turquoise has two species in this area. One is in the form of direct deposition in the veinlets, away from the alteration of the host rock and the mineralization center, and the other one is in the form of substitution. It is undeniable that the host rock with Kaolinite-sericite alteration is required for substitution. The close association of alunite-turquoise may imply that turquoise is a product of the phosphatization process of alunite. The Alunite Supergene event in the alteration zone and its accompaniment with turquoise indicates the mineral complex of advanced argillic alteration. The mineral chemistry highlighted the high percentages of aluminum concentration which is a property of minerals in advanced argillic zone.

The phyllic zone has the largest part of the region's alteration (Taghipour and Mackizadeh, 2011; Moore et al., 2011). An advanced argillic zone with the presence of alunite-jarosite with turquoise is scattered inside the phyllic zone. To confirm microscopic observations, XRD and EDS analyses were used. These analyses prove the presence of the turquoise phase. In some analyses performed on the turquoise mineral phase, the presence of potassium and silicon probably indicates the transitional phase of conversion of sericite or alunite to turquoise. Pyrite in the oxidant condition has been disrupted by the effects of atmospheric water and created goethite and sulfuric acid. The produced ferric sulfate can induce dissolution of chalcopyrite. The occurrence of iron oxides and oxy-hydroxides will lead to the development of the gossan zone. Gossan's transformation, in addition to supplying copper, causes acidic fluids to continue the reaction. Under acidic conditions, the phosphate leaching from the arkose has been subjected to the following reaction: Ca5 (PO4)3OH + 5H2SO4 + 9/2O2 → 5CaSO4 2H2O + 3H3PO4 In addition to phosphate and copper, aluminum is the most important element in the structure of turquoise. Under an acidic environment, arkose feldspars and hydrolysis reactions during alteration will be used for the formation of sericite, kaolinite and gypsite. With the presence of sulfate and potassium released from the alteration of feldspars, alunite and turquoise can be formed. The alunite-turquoise paragenesis confirms formation of turquoise by alunite (Espahbod, 1976). Turquoise will be formed by the reaction of potassium, copper sulfate and anion phosphate with alunite: 8K+ + CuSO4 + 4H2PO4- + 2KAl3 (SO4)2(OH) 6 → CuAl6 (PO4)4(OH)8 4H2O + 5K2SO4 + 4H+ The hydrogen ions released in this reaction will lower the pH of the environment and cause progression of hydrolysis reactions. Finally, jarosite will be formed by the interaction of K+, sulfate and Fe3+. Based on these reactions, an aluminum-rich phase is needed for stabilizing phosphate and soluble copper.

The Jebal Barez area is situated in the Urmia-Dokhtar magmatic belt, and the porphyry copper mineralization in this region has close relationship with faults and granitoid masses. Determination of the structural lineaments is a good guide to identify the location of copper mineralization in the region. In this paper, an automatic algorithm was used to extract the lineaments from ASTER images. This algorithm can highly reduce user errors and runtime. In this paper, the CANNY algorithm was used as an edge-detector filter while Hough transform was used to extract linear features from satellite imagery. Finally, after investigating and detecting their operation, the faults associated with copper mineralization were recognized in the region. According the rose-diagram, two fault systems were highlighted that the main fault system is located along the NW-SE, and the fault system along the N-S boundary forms a small fraction of the total fractures in the region. the fault density map of the area shows a high potential for porphyry copper mineralization. In order to investigate the success of the ASTER images in extracting faults in the region these faults were compared with the faults of geology map, that 63.05% of them had overlapping with geology faults.

The Baft district in Kerman province is located in the southeastern segment of the Urumieh-Dokhtar magmatic arc. This arc is characterized by thick accumulations of Cenozoic plutonic and volcanic rocks and provide favorable conditions to the development of hydrothermal systems and mineral deposition, in particular porphyry copper mineralization. For mineral prospectivity mapping (MPM) to delineate prospective areas some individual maps of evidence including distance to intrusive contacts, fault density, distance to hydrothermal alterations and multi-element geochemical signature were generated. Spatial evidence values in each map were transformed using a logistic function of unbounded values into the [0,1] range. Thus continuous maps of fuzzy evidence layers were integrated using geometric average function. To evaluate results of final potential map a data-driven prediction-area was used. The results showed that for the geometric average prospectivity model, 87% of the known mineral occurrences are predicted in 13% of the study area. Hence, this method can be utilized for mineral prospectivity mapping to delineate target areas for further exploration of a certain deposit-type.

This work intends to apply ASTER images to discriminate hydrothermal alteration zones in Kerman Cenozoiic Magmatic Belt (KCMB). Band ratio, principal component analysis, Crosta and color composite images are important methods to analyze satellite images. Previous researches showed that these techniques are not able to discriminate hydrothermal alteration zones and they usually detect vegetation covering as alteration zones. The reason is found in the spectral signature of vegetation and alteration minerals. It means that they present the same interaction when face with electromagnetic energy in different wavelengths. Hydroxyl-bearing minerals are the important products of hydrothermal alteration. Clays, which contain Al-OH- and Mg-OH-bearing minerals and hydroxides in alteration zones, are distinguished by absorption bands in the 2.1–2.4 µm range of ASTER data. Solving these problems is difficult when using standard image-processing techniques such as band rationing, principal component analysis, or spectral angle mapper. In recent years, several attempts were made to extract altered regions in the areas covered with vegetation. To overcome this problem, this research uses ASTER data by applying support vector machine (SVM) algorithmn. SVM is a new technique for data classification in remote sensing application. This paper aims to investigate the potential of SVM algorithm in mapping of hydrothermally altered areas. In many applications, SVM has been shown to provide higher performance than traditional learning machines and has been introduced as powerful tools for solving classification problems. The adopted dataset contains three ASTER scenes using SWIR and VNIR bands, covering the Meiduk porphyry copper deposit, Kader, Abdar and Iju occurrences located in Kerman Province, southeast Iran.

This work has been prepared on three ASTER level 1B scenes. Two scenes were acquired on 18th April 2000 and another scenes on 15th June 2007. These scenes were georeferenced by using an orthorectified ETM +  image,  in  UTM projection and WGS-84 ellipsoid as a datum.  The first two data sets were corrected for Crosstalk. Atmospheric corrections were also performed by using Fast Line of Sight Atmospheric Analysis of Spectral Hypercubes (FLAASH). The data sets were then mosaicked. Internal Average Relative Reflectance (IARR) correction was also applied. In this part, the training and test samples of the ASTER data are presented. The adopted image is a multispectral satellite image that contains 2204 training pixels which 516 pixels are related to arjillic zone, 1278 pixels are related to phyllic zone and 500 pixels are pertinent to propylitic zone (Fig. 1).

Fig. 1. Training pixels for learning SVM algorithm; Red pixels: arjillic; Green pixels: phyllic; Blue pixels: propylitic

ASTER bands 4, 6, 7 and 8 were applied for determination of phyllic and arjilic zones and 9 bands of ASTER for propylitic alteration. In order to evaluate the developed algorirhm, confusion matrix was used and validation showed that discrimination of phylic and arjilic is not possible but propylitic zone could be identified by SVM. Also, the present research introduced a new error function, so called blind error, which is calculated using confusion matrix. Based on blind error, SVM did not classify 73.6 percent of the alteration pixels. But the remained pixels were classified with accuracy of 66.06%. Honarmand et al. (2011) and Mojedifar et al. (2013) studied the field samples of the present study area. Their studies showed that sericitization is the most widespread form of hydrothermal alteration at the Iju, Serenu, Chahfiroozeh, Meiduk, Parkam, Kader and Abdar porphyry copper deposits. Two types of phyllic alteration could be found in the study area including ferric-iron-rich and iron-oxide poor phyllic alteration. ASTER images were also analyzed by band rationing and principal component analysis (PCA) in order to compare their results with the SVM classified image. A comparison of the field data with altered areas mapped by PCA reveals errors in the classified map. Vegetation cover and sedimentary rocks are enhanced, which are erroneously identified as areas of alteration. The band ratio approach yields similar errors to those produced by the PCA method. These problems are less evident in the classified image obtained by SVM. The qualitative assessment of the accuracy of these methods indicates that SVM algorithm could be a reliable technique for alteration mapping, provided that the nature of the training areas is well known.

A comparison of the results obtained from traditional classification methods and support vector machine algorithm was performed in order to map hydrothermal alteration. Since the known occurrence of mineralization in the study area is consistent with the mapped distribution of hydrothermal alteration using SVM, this method is suggested to apply in exploring for hydrothermal alteration in other parts of the Iranian Cenozoic magmatic belt.

The formation of the Zagros orogenic belt is attributed to northeastward oblique subduction of the Neotethys beneath the western border of central Iran. This was followed by continental collision between the Afro-Arabian plate and the central Iran microcontinet (Zarasvandi et al., 2015). The Zagros orogen is characterized by three main parallel structural zones consisting of Zagros fold and thrust belt, the Sanandaj–Sirjan metamorphic zone, and the Urumieh–Dokhtar magmatic arc (Mohajjel et al., 2003). The Urumieh–Dokhtar magmatic arc is dominated by the widespread occurrence of Eocene to Quaternary intrusive and extrusive rocks. It is considered as being one of the main Cu bearing regions in the world, where world class giant porphyry deposits, as well as large and small sub-economic porphyry Cu ± Mo ± Au systems have been reported and investigated by many authors (Shafiei et al., 2009; Zarasvandi et al., 2005). In addition to UDMA, the Sanandaj-Sirjan zone (SSZ) hosts several Jurassic-Cretaceous intrusive complexes extending from the northwest to southeast SSZ. It should be noted that these granitoids are barren and porphyry mineralization has not been accompanied with these intrusions. This paper tried to compare the available geochemical data of productive granitoids in the Urumieh-Dokhtar (i.e., Dalli, Ali-Abad and Darreh-Zerreshk, Parkam, Sarcheshmeh, Meiduk and Sungun), and those of barren intrusions in the Sanandaj-Sirjan zone (i.e., Aligodarz, Bourujerd, Alvand, Astaneh, Hasan Robat, and Siah Koh). This investigation is based on the available geochemical data on the six barren intrusions in the SSZ (i.e., Aligodarz, Bourujerd, Alvand, Astaneh, Hasan Robat and Siah Kohe), and productive intrusive rocks (porphyry associated intrusions) in the UDMA (i.e., Dalli, Ali-Abad and Darreh-Zerreshk, Parkam, Sarcheshmeh, Meiduk and Sungun). Data for the UDMA porphyry intrusions (41 samples) were adopted from studies of Daneshjou (2014), Zarasvandi et al. (2005), Taghipour and Mohammadi Laghab (2014), Barzegar (2007), Taghipour (2007), and Hezarkhani (2006). Furthermore, the data of the SSZ barren intrusions (42 samples) comes from Esna Ashari et al. (2012), Khalaji et al. (2007), Aliani et al. (2012), Tahmasbi et al. (2010), Alirezaei and Hassanzadeh (2001), and Arvin et al. (2007). Two criteria were used for selection of 83 representative samples: (1) samples with a relatively similar mineralogical and compositional range (quartz diorite, quartz monzonite, granodiorite and granite), and (2) samples with the least amount of alteration (minimal amounts of Loss On Ignition; LOI wt.% = H2O + CO2). Productive intrusions in UDMA have positive Eu anomalies, LREE enrichment relative to HREE, and high Lan/Ybn ،Sr/Y، Dyn/Ybn، Lan/Smn ratios. In comparison, barren granitoids in the SSZ are characterized by steep downward LREE to HREE, negative Eu anomalies and low Lan/Ybn ، Sr/Y، Dyn/Ybn، Lan/Smn ratios. Based on the presented results, it is proved that due to the lack of considerable crustal thickness in SSZ (during the subduction of the Neotethyan oceanic lithosphere under the SSZ zone), and the presence of dry magma (low H2O contents), the SSZ granitoids exhibit barren characteristics. In contrast, during the ongoing processes of closure of Neo-Tethys and during compression and crustal shortening, magma mixing and evolution toward high magmatic water content lead to the increasing of metal endowment in the porphyry associated granitoids of (UDMA) It seems that magma generation from the melting of thickened lower crust (garnet amphibolite source) could be considered as one important key factors for the generation of metal-rich magmas with high oxidation state and high H2O contents has led to the development of porphyry Cu systems in the UDMA compared to those of SSZ granitoids.

Nowadays, more than half of the word’s copper production is obtained from porphyry copper deposits, large (greater than 100 Mt), low- to moderate-grade, disseminated, stockwork-veinlet, carrying at least trace elements, such as molybdenum, gold, and silver (Sillitoe, 1972). Porphyry Cu systems are related to granitoid porphyry intrusions and adjacent wall rocks and most of them form at convergent plate margins (John et al., 2010). The deposits are often localized within calc-alkaline porphyry magmatic systems in subduction zone settings. Some PCDs have been formed in post-subduction settings. Ahar-Arasbaran metallogenic zone is one of the most productive metallogenic zones in Iran. Mineralization in the area is mainly associated with Tertiary magmatic events. In order to perform a comparative study of mineralization, Sungun and Kighal porphyry copper deposits (PCDs) were selected. The Sungun copper deposit is located in the north Varzaqan and the Kighal copper deposit lies 10 km to the south of the Sungun PCD (Calagari, 2003; Calagari, 2004). As recent studies show there are some similarities between the Sungun and Kighal deposits in terms of the parent intrusions, the host rocks, age and geological setting. However, the grade of copper in the Sungun PCD is 0.62 % Cu and in the Kighal PCD is 0.2 % Cu. Therefore, what are the key factors that have made the Kighal PCD subeconomic? Material and methods: Geochemical, fluid inclusion, and mineralogical studies were done on collected samples of the two porphyry copper deposits. In order to mineralogically study the Sungun and Kighal PCDs, 100 thin and polished thin sections were prepared. Eleven doubly polished sections of different quartz veins of the two PCD borehole samples were prepared for fluid inclusion studies. The measurements of 205 fluid inclusions were conducted at the Iranian Mineral Processing Research Center (IMPRC) by ZEISS microscope and Linkam TMH600, at temperature limits of - 196 to +600 °C. The precision was ±0.6 °C at 414 °C (melting point of Cesium nitrate), and ±2°C at -94.3 (melting point of n-Hexane). SPSS 17 and Flincor computer programs (Brown, 1989) were used for data analysis. Discussion and Results: In addition to some similarities of parent intrusions and host rocks (Hassanpour, 2010), there are similar fluid inclusion types and even nearly identical salinity and homogenization temperatures in these deposits (Simmonds, 2013). However, some differences in geochemical and mineralogical features, such as different low zonality index, less sulfide minerals and CO2 contents of the Kighal PCD, are notable. Some researchers have pointed out erosion (Hassanpour, 2010) and uplifting (Simmonds, 2013) as the main reasons for the sub-economic nature of the Kighal (non-productivity), comparison of Moho depth in the two deposits shows a greater crustal thickness in the Sungun PCD area (Fig. 10). The thickness of the lower crust is thought to be critical for governing arc mineralization potential, because it leads to an increase of the amount of water, metal, sulfur in adakitic magma forming arc-related bodies that is known to affect the origin of more productive (economic) porphyry copper deposits. Also low-CO2 fluid inclusions of the Kighal can have originated from a CO2-rich fluid immiscibility at depth (Simmonds, 2013). Lack of CO2 can inhibit (delays) bulk volatile saturation and in turn boiling, which influences the efficiency of metal removal from melt as well (Candela, 1997). CO2 contents of mineralizing fluids is important in increasing of pH during boiling event and ore deposition. The nonproductivity of the Kighal PCD may have resulted from all these factors. Acknowledgement: This work was supported by Bu-Ali Sina University and Iranian Mines and Mining Industries Development and Renovation Organization (IMIDRO). The authors would like to thank of the Sungun and Ahar copper companies. Special thanks to all the staff for their kind help. Thanks to the reviewers for their suggestions.

Sulfur isotope data on pyrite, chalcopyrite and molybdenite in the A, B and D type veinlets in porphyry systems of the Meiduk cluster, located in northwestern part of the Kerman copper belt, show that these systems have near zero δ34S values. Sulfur isotope composition for the Chah-Firouzeh and Iju deposits and Serenu, God-e-Kolvari and Kader prospects is from -1.4 to .5 (average .31), -1.3 to .1 (average .07), .1 to .4 (average .87), -1.5 to .2 (average -0.1) and -4.1 to (average -1.04), respectively. These results suggest a magmatic source for sulfur. Also, limited range of isotopic variations and analogous isotopic composition for the three types of veinlets reveals that with evolution of the hydrothermal system, no significant changes occurred in the primary and relatively homogenous source of sulfur. Comparison between the data for the Meiduk cluster with available data from other deposits in middle and southern parts of the Kerman belt suggested that in porphyry systems of the northwestern, and to some extent southern parts, of the Kerman Cenozoic magmatic arc, sulfur was provided by a mafic magma originated from metasomatized subcontinental lithospheric mantle (SCLM) which was affected by assimilation with continental crust; while in the southern parts, processes related to subduction and fluids from seawater and associated sediments had a major role in their sulfur isotope composition.

Kuh Zar Au-Cu deposit is located in the central part of the Torud-Chah Shirin Volcanic-Plutonic Belt, 100 km southeast of the city of Damghan. Mineralization including quartz-base metal veins are common throughout this Cenozoic volcano-plutonic belt (Liaghat et al., 2008; Mehrabi and Ghasemi Siani, 2010). The major part of the study area is covered with Cenozoic pyroclastic and volcanic rocks that are intruded by subvolcanic rocks. This paper aims to study the geological, geochemical and petrogenesis of the area using exploration keys for new mineral deposits in the Torud-Chah Shirin zone.

To better understand the geological units and identify the alteration zones of the area, 200 rock samples were collected from the field and 132 thin sections with 15 polished thin sections were prepared for petrography and mineralization studies. Ten samples of intrusions with the least alteration were analyzed using the XRF at the East Amethyst Laboratory in Mashhad, Iran. These samples were also analyzed for trace and rare earth elements using ICP-MS, following a lithium metaborate/tetraborate fusion in the Acme Analytical Laboratories Ltd, Vancouver, Canada. 137 geochemistry samples were prepared by the chip composite method of alteration and mineralization zones and were analyzed in the Acme laboratory by Aqua Regia AQ250.

The geology of the area consists of pyroclastic (crystal tuff) and volcanic rocks with andesite and latite composition, which were intruded by subvolcanic intrusive rocks with porphyritic texture and monzonitic composition. Monzonite rocks were intruded by younger subvolcanic units with dioritic composition. The intrusion of monzonitic pluton and stocks led to the formation of QSP, propylitic, carbonate and silicification-tourmaline broad alteration zones in the area. Monzonite rocks accompanied with disseminated mineralization of about 1 to 10% of pyrite and these sulfides have been converted to secondary iron oxides such as goethite, hematite and limonite. Lithogeochemical exploration revealed Au (up to 598 ppb), Ag (up to 3747 ppb), Cu (up to 679 ppm), Pb (up to 1427 ppm) and Zn (up to 1013 ppm) anomalies. Based on geochemical studies, intrusive rocks have characteristics of high-K Calc-alkaline to slightly shoshonitic and they are within metaluminous to the slightly peraluminous range. Enrichment of LREE versus HREE, enrichment of LILE and depletion in HFSE indicate that the magma was formed in the subduction zones. The negative Eu anomaly is due to the presence of plagioclase as a residual mineral in the magma source. The parent magma is probably formed by the partial melting of amphibolites. The presence of monzonite porphyry source rock, QSP and propylitic alterations, pyrite disseminated mineralization and geochemical anomalies of Au and Cu in the Kuh Zar deposit represents Au-Cu porphyry mineralization in the area.

Tectonic setting discrimination diagrams (Pearce et al., 1984) show that subvolcanic rocks plot almost on the fields of the volcanic arc granites (VAG). In the Rb/Zr vs. Nb diagram from (Brown et al., 1984), the samples are plotted in the field of primitive island arc/continental margin arc. The Torud-Chah Shirin Belt is a part of the Alborz magmatic assemblage (AMA). The AMA has been interpreted to represent the subduction of the Neo Tethyan oceanic lithosphere beneath the Central Iranian continental microplate and the subsequent continental collision of the Arabian and Iranian microplates in the late Cretaceous-early Cenozoic (Berberian and Berberian, 1981; Berberian et al., 1982; Alavi, 1994; Golonka, 2004).
Acknowledgement: This study has been supported by the Research Foundation of the Ferdowsi University of Mashhad, Iran (Project No. 27126.3). The authors would like to acknowledge the East Amethyst Laboratory for XRF analysis. We also thank the Gold Company of Iran for providing conditions for camping and accommodation.

The Hamech prospect area is located in the eastern Iran, 85 kilometers southwest of Birjand. The study area coordinates between 58¬¬˚¬53΄¬00 ˝ to 59˚¬00΄¬00˝ latitude and 32˚¬22΄¬30 ˝ to 32˚¬26΄¬00˝ longitude. Due to the high volume of magmatism and the presence of geo-structure special condition in the Lut Block at a different time, a variety of metal (copper, lead, zinc, gold, etc.) and non-metallic mineralization has been formed (Karimpour et al., 2012). The studied area (Hamech) includes Paleocene-Eocene igneous outcrops which contain a wide range of subvolcanic bodies (diorite to monzonite porphyry) associated with mafic intrusives, volcanic units (andesite), volcaniclastic and sedimentary rocks.
Material and This study was done in two parts including field and laboratory works. Sampling and structural studies were done during field work. Geological and alteration maps for the study area were also prepared. 200 thin and 60 polished sections for petrographic purpose were studied. The number of 200 thin sections and 60 polished sections were prepared and studied in order to investigate petrography and mineralogy. Major oxides (XRF method- East Amethyst Laboratory in Mashhad), rare earth elements and trace (ICP-MS method-ACME Laboratory in Vancouver, Canada) elements were analyzed for 13 samples that included subvolcanic units and intrusive bodies. Data processing and geological and alteration mapping is done by the GCD.kit and Arcgis software.
Discussion and Based on lab work and XRF analysis, the rocks in the area are composed of intrusive-subvolcanic bodies and volcanic rocks (andesite, trachyandesite and dacite) together with volcano-classic and sedimentary rocks. Also, alteration zones consist of a variety of argillic, silicified, quartz-sericite-pyrite (QSP), propylitic and carbonate. Igneous rock textures are mainly porphyritic for sub-volcanic and granular for intrusive bodies. Phenocrysts mainly consist of plagioclase and hornblende dominated with minor of biotite and pyroxene. XRF studies and output charts show that rocks include monzonite, diorite, gabbro and gabbroic diorite. Intermediate subvolcanic units (monzonite, diorite) and mafic intrusives (gabbro and gabbroic-diorite) are related to high-potassium calc-alkaline (K2O between 2.42 to 4%) and tholeiitic (K2O between 0.15 to 0.27%) series, respectively. Subvolcanic units belong to the I-type granitoid (Chappell and White, 2001).
Mantle normalized , trace-element spider diagrams display enrichment in LREE, such as Rb, Sr, K, and Cs, and depletion in HREE, e.g., Nb, Ti, Zr that indicate magma formed in the subduction zone. Nb depletion (less than 6 ppm, between 0.5 to 5.2 ppm) in subvolcanic bodies represents a volcanic arc granitoids (VAG) tectonic setting that is related to the subduction zone (Pearce et al., 1984). Also, this reduction shows that these rocks are derived of oceanic crust (Wilson, 1989). Enrichment in LREE and depletion of HREE with a low (La/Yb)N ratio in the Hamech subvolcanic rocks (6/85 to 8/13) could represent a low degree of mantle partial melting (Wass and Rogers, 1980). Zr/Nb ratio of more than 10 for Hamech rocks (between 21 and 35 for intermediate subvolcanic and 67 to 72 for mafic bodies) indicates that parental magma has minimal crustal contamination (Karimpour et al., 2012). Sr enrichment (between 646 to 1124) and low negative Eu anomaly (Eu/Eu* ratio between 0.81 to 1/02) show that plagioclase is rare (or is not present) as residue mineral in the source and melt conditions have been in oxidation state (Tepper et al., 1993). Based on Sm/Yb vs. La/Sm (Shaw, 1970) and Ce/Yb vs. Sm/Yb (Wang et al., 2002) diagrams, parent magma is composed of 1 to 5% spinel-garnet lherzolite partial melting (with small amounts of garnet) at a depth between 65 to 67 km (upper mantle) for subvolcanic units and 5 to 20% spinel lherzolite partial melting (depletion mantle-NMORB) with a depth of less than 55 km for mafic bodies.
Suitable tectonic setting, existence of subvolcanic units with intermediate composition, magnetic activity with the nature of calc-alkaline and oxidants, data from major and REE studies, mineralization as disseminated and veinlets with high secondary iron oxides in surface show suitable conditions of porphyry and epithermal mineralization in the Hamech prospect area.

IntroductionThe Iju porphyry copper deposit is located in the southern part of the Urumieh-Dokhtar magmatic arc (Dehaj-Sarduieh belt) within the Kerman copper belt (Dimitrijevic, 1973). The Porphyry Copper mineralization in the Iranian plate occurs dominantly along the Urumieh-Dokhtar arc, which has resulted from the subduction of the Arabian plate beneath the central Iran and the closure of the Neo-Tethys Ocean during the Alpine orogeny (Hassanzadeh, 1993). The Iju porphyry copper deposit with 25 million tons of ore reserves is one of the main copper deposits within the Kerman copper belt. The mining area is composed of upper Miocene volcanic and subvolcanic rocks (mineralized and barren subvolcanic rocks) and quaternary deposits. Two hydrothermal alteration zones of quartz-sericite-pyrite and propylitic zones can be identified in the Iju area. The copper mineralization in the Iju deposit occurs as disseminated, stockwork and hydrothermal breccia. In the hypogene zone, the mineral paragenesis include chalcopyrite, pyrite, with minor occurrences of bornite and magnetite. This paper reports geological, mineralogical, fluid inclusion and S isotope data from the Iju deposit in order to investigate ore-bearing fluids’ characteristics and the mechanisms of ore deposition.
Materials and methodsFifteen samples of syngenetic quartzꜪ bearing veinlets within the quartz-sericite-pyrite zone were selected from different depths across the seven boreholes. Quartz was used for double-polished thin sections and pyrite was used for sulfur isotope analysis. Fluid inclusion studies were performed using the Linkam cooling and heating stage, the THMSG 600 model. The syngenetic pyrite with thermometry quartz sample was used for the sulfur isotope experiments. Stable isotope analysis was performed at the Hatch Stable Isotope Laboratory in the University of Ottawa, Canada.
ResultsThe fluid inclusions of the Iju deposit represent a wide range in the homogenization temperatures between 140 to 480°C and salinity between 0.18 to >52.99 wt.% NaCl equiv., which are most similar to the results of the other Iranian porphyry copper deposits. Being located in the quartz-sericite-pyrite alteration zone, the results of thermometry indicates that ore deposition in the Iju deposit has occurred via mixing of magmatic and surface fluids. Variations in salinity and paragenesis of the saline multiphase fluid inclusions and two-phase gas-rich fluid inclusions indicate the occurrence of boiling phenomenon in some samples of the Iju deposit. The amount of δ34S for pyrite has a limited range close to zero (average, 0.229‰) that shows a magmatic origin for sulfur. Considering the presence of subvolcanic rocks, the type and extension of alteration zones, the structure and texture of ore bodies, thermometry results of fluid inclusions and sulfur isotope values, the Iju deposit is similar to porphyry copper deposits.
DiscussionIn the quartz-sericite-pyrite zone, three main groups of veinlets have been identified. The quartzꜪ veinlets are more abundant than the other types and they were selected for fluid inclusions and stable isotope studies. Petrographic studies of fluid inclusions identifies two groups of fluids including: 1- fluid inclusions without the halite phase, including the types L, L埤 and (L埤뗹, that is secondary), 2- fluid inclusions with halite phase, including the types L埡, L埡﹋, L埡﹋徒 and L埡﹋往. Homogenization temperature and salinity for the fluid inclusions without halite phase are as follows: 140 to 380°C and 0.18 to 24 wt.% NaCl (Fig. 8A and C) and for the fluid inclusions with halite phase they range from 230 to 480°C and 30 to 52 wt.% NaCl (Fig. 9A, B and D), In addition, the pressure and depth for the fluid inclusions containing halite phase are 750 bar and 3500 m on the average. Fluid inclusions available at the quartz veinlets of porphyry copper deposits can be formed in a wide range of chemical composition and under different temperature and pressure conditions (Rusk and Reed, 2008). The wide range in fluid inclusions data of the Iju deposit can be justified by physicochemical changes in the fluid as it is boiling and mixing with the surface fluids. Cooling, fluids mixing, boiling and fluid-rock reaction play important roles in the settling of chalcopyrite from the hydrothermal fluid and the dilution of saline ore-bearing fluids can cause the formation of copper ores from the ore-bearing fluid (Ulrich et al., 2002). Pyrite δ34S value ranges from -0.86 to .27‰ (average, .22‰) and the δ34SH2S value of the syngenetic fluid with pyrite ranges from -0.23 to -2.36‰ (average, -1.17‰). The limited and near zero range that is observed about δ34S value of the sulfur minerals indicates the controlling role of magmatic processes in the mineralization events (Chen et al., 2009).