Kerman Copper Belt Research Articles

Evaluation of the modified AHP-VIKOR for mapping and ranking copper mineralized areas, a case study from the Kerman metallogenic belt, SE Iran

Exploration and prioritization of potentially mineralized areas by integrating different geoscientific datasets help to manage the time and costs of an exploration project. In this study, copper exploration and prioritization of explored areas were done on the Kerman copper belt, which was formed due to the subduction of the Arabian plate under the Iranian plate. After processing geoscientific layers (geology, hydrothermal alteration zones, stream sediment geochemistry, and airborne geophysics), the analytic hierarchy process (AHP) method was used to compute the weights of geoscientific layers by a decision-making group consisting of ten local experts in copper exploration. The weight of evidence (WofE) method was used to compare and assess the fairness of the AHP weights. The AHP weights were used for the multi-criteria optimization and compromise solution (VIKOR) method to integrate the geoscientific layers and create an AHP-VIKOR copper mineralization potential map. The “v” parameter of the VIKOR method was modified by replacing the concept of mathematical expectation value with the manual assignment. The real value-area (RV-A) fractal method was used to select optimum threshold values for different AHP-VIKOR copper mineralization potential classes. The accuracy of the classified AHP-VIKOR copper mineralized potential map was assessed by creating a confusion matrix and using existing mineralization locations. The average pixel values of the copper mineralization class were extracted and sorted to rank the very high potential areas. The AHP-VIKOR ranking results were compared with recorded ore grade and ore tonnage information of each copper deposition. The results demonstrated that the AHP ranks are roughly similar to the WofE ranks, except for lithology. An accuracy of 84% for classified copper mineralization potential map with the RV-A fractal method was obtained. The used expectation value for the “v” parameter of the VIKOR method showed that the decision-making group’s opinion was more important than the individual opinions (v = 0.6). The AHP-VIKOR method identified mineralization areas, especially porphyry deposits. Also, the outcome of the AHP-VIKOR ranking showed that the currently active mines, especially porphyry deposits, have the highest priority for mining. This study showed that the AHP-VIKOR approach helps explore and rank favorable areas with high copper ore grade and tonnage characteristics.

Geology, fluid inclusion, S and O stable isotope compositions and Sm-Nd systematics of Sarkuh porphyry Cu deposit, Kerman copper belt, SE Iran

Geology, fluid inclusion, S and O stable isotope compositions and Sm-Nd systematics of Sarkuh porphyry Cu deposit, Kerman copper belt, SE Iran

A new hypothesis on parameters controlling the formation and size of porphyry copper deposits: Implications on thermal gradient of subducted oceanic slab, depth of dehydration and partial melting along the Kerman copper belt in Iran

Porphyry copper deposits in the Tethyan metallogenic belt broadly occur in early Mesozoic, late Mesozoic, Paleogene, and Neogene within a wide range of tectonic setting. These deposits in Iran often occur within the Cenozoic Urumieh-Dokhtar Magmatic Arc (UDMA), mostly in the Kerman porphyry copper belt (KPCB) located in the southeast of this arc. These deposits along the UDMA are mainly associated with the granitoids of Miocene age (18.82–9.20 Ma). In this research, geochemical characteristics, Pb and Sr isotopes, tectonic environment, oxidizing conditions and source of magmas for the most important porphyry copper deposits of the UDMA have been compared and discussed. On the basis of trace element discrimination diagrams, the Kerman belt granitoids formed in a volcanic arc-type setting, whereas the Jebal Barez granitoids seem to have formed in a different tectonic setting. The Eu/Eu* of granitoids from the Kerman belt are greater than 1.2, representing the oxidizing conditions for the crystallization of the granitoid magma, whereas Jebal Barez granitoids were formed under reducing conditions. The Sr/Y ratio for Kerman granitoids is greater than 60, indicating adakitic affinities and (La/Yb)n for these granitoid rocks is between 17 and 35, suggesting that their parental magma was generated from a deep garnet-bearing source. Based on (87Sr/86Sr)i values for Kerman belt granitoids of 0.704–0.705, it is suggested that parental magmas originated from a subducted oceanic slab. In the Sarcheshmeh porphyry copper deposit, the thermal gradient of the oceanic slab at depth was less than 9 °C/Km (warm-cold slab). The oceanic slab was highly hydrated and more than 80% of the water within the oceanic slab was released in the deep zone of the sub-arc region at a depth of 110–130 Km. Under saturated conditions, the oceanic slab partially melted (20–25%). A large volume of magma and magmatic water formed Sarcheshmeh as a giant porphyry copper deposit. In the Iju deposit, a small porphyry copper deposit, the oceanic slab was slightly hydrated and minor water was released at the depth of 110–130 Km. A small volume of magma was formed due to water undersaturated melting conditions. Finally, a new hypothesis is introduced regarding the roles of down-dip thermal gradient of the oceanic slab, water content, depth of dehydration and degree of partial melting of oceanic slab which are important controls on the formation and size of the porphyry copper deposits within continental volcanic arcs.

Application of Mixture Tuned Matched Filtering on ASTER Data for Hydrothermal Alteration Mapping Related to Porphyry Cu Deposits in Jabal-Barez Ranges, Kerman Copper Belt, Iran

The study area is located in Jabal-Barez Ranges, southeastern part of Kerman Copper Belt (KCB), where the porphyry copper mineralization such as Kerver occurs. This article deals with the enhancement of hydrothermal alteration minerals for exploration of porphyry Cu mineralization, and differentiates intense hydrothermal alteration zones from those with low intensity. Shortwave Infrared (SWIR) bands of ASTER data were used for mineral enhancement. The spectra of representative alteration mineral assemblages consisting of sericite + illite, kaolinite + montmorillonite and epidote + chlorite were extracted from SWIR bands of ASTER. The spectra were applied for mineral discrimination using Mixture Tuned Matched Filtering (MTMF) technique. The image processing results were verified using field observation, spectral measurements, thin section and X-ray diffraction studies of the samples. Findings exhibit ASTER capability to discriminate different alteration zones. Findings also significantly show the role of MTMF algorithm as a useful technique for mineral exploration.

Comparison of hydrothermal alteration patterns associated with porphyry Cu deposits hosted by granitoids and intermediate-mafic volcanic rocks, Kerman Magmatic Arc, Iran: Application of geological, mineralogical and remote sensing data

The southern section of the Cenozoic Urumieh-Dokhtar Magmatic Arc (UDMA) of Iran, known as Kerman Magmatic Arc (KMA) or Kerman copper belt, is a major host to porphyry Cu ± Mo ± Au deposits, collectively known as PCDs. In this study, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and spectral angle mapper (SAM) method, combined with field data, mineralogical studies, and spectral analysis are used to determine hydrothermal alteration patterns related to PCDs in the KMA. Gossans developed over some of these porphyry type deposits were mapped using Landsat 8 data. In the NKMA gossans are more developed than in the SKMA due to comparatively lower rate of erosion. The hydrothermal alteration pattern mapped by ASTER data were evaluated using mineralogical and spectral data. ASTER data proved to be useful for mapping the hydrothermal alteration in this semi-arid type of climate. Also Landsat 8 was useful for mapping the iron oxide minerals in the gossans that are associated with the porphyry copper deposits. Our multidisciplinary approach indicates that unlike the PCDs in the northern KMA that are associated with distinct and widespread propylitic alteration, those in the granitoid country rocks lack propylitic alteration or the alteration is only weakly and irregularly developed. The porphyry systems in southern KMA are further distinguished by development of quartz-rich phyllic alteration zones in the outer parts of the PCDs that could be mapped using remote sensing data. Consideration of variations in alteration patterns and specific alteration assemblages are critical in regional exploration for PCDs.

Discrimination of Sericite Phyllic and Quartz-Rich Phyllic Alterations by Using a Combination of ASTER TIR and SWIR Data to Explore Porphyry Cu Deposits Hosted by Granitoids, Kerman Copper Belt, Iran

Various mapping methods such as Spectral Angle Mapper, band ratio, and Principal Component Analysis were applied to the Advanced Spaceborne Thermal Emission and Reflection Radiometer data to highlight various hydrothermal alteration minerals (e.g., sericite, kaolinite, epidote and quartz) related to Cu mineralization in the Southern Jabal–Barez Range (SJBR), Kerman province, Iran. The integration of sericite and quartz images with Boolean logic in a geographic information system environment discriminated quartz-rich phyllic hydrothermal alteration from sericitic or sericite phyllic alteration. The mapped hydrothermally altered areas were sampled randomly and studied in the laboratory (microscopic studies, spectral and X-ray diffraction analyses) for data validation. Accuracy assessment of the resulting hydrothermal alteration maps was conducted by using a confusion matrix. The overall accuracy was estimated to be 79.69%. The hydrothermal alteration zones enhanced through this research (i.e., sericite phyllic, argillic, and quartz-rich phyllic) are in good agreement with the known locations of porphyry Cu deposits (PCDs) in the SJBR. Propylitic alteration, as reported and documented from many PCDs, is absent or only poorly developed in the SJBR. The quartz-rich phyllic alteration occurs around the more common sericitic alteration. These findings indicate that the integration of sericite and quartz images is useful for mapping quartz rich-phyllic hydrothermal alteration around PCDs hosted by granitic rocks.

Geochemistry, U-Pb geochronology and Sr-Nd isotopes of the Neogene igneous rocks, at the Iju porphyry copper deposit, NW Shahr-e-Babak, Iran

The Iju porphyry copper deposit is located in the Kerman copper belt in the northwest of Shahr-e-Babak city within the southern extension of the Urumieh-Dokhtar magmatic arc. Based on a cut-off grade of 0.15%, the deposit contains 24 million tonnes (Mt) of ore with an average grade of 0.4 wt% Cu. The igneous rocks at the Iju deposit are primarily made up of Upper Miocene sub-volcanic and volcanic sequences that intruded Eocene volcanic rocks. Sub-volcanic rocks comprise barren quartz-monzonite porphyry and syn-mineralized granodiorite porphyry along with andesitic volcanic rocks. Geochemical evidences show that they are co-genetic, medium- to high-potassium calc-alkaline, and likely part of a subduction zone I-type granitoid magma. These rocks are characterized by enrichment in LREEs relative to HREEs with negative Nb–Ta anomalies similar to subduction zone magmatism. All samples exhibit enriched uniform chondrite-normalized REE patterns without noticeable Eu anomalies similar to magnetite-series granitoids. The igneous rocks of the Iju deposit exhibit geochemical features similar to adakites. The U-Pb zircon dating shows 9.33 ± 0.19 Ma (Tortonian stage) for quartz-monzonite (oldest unit), 9.01 ± 0.20 Ma for granodiorite and 8.83 ± 0.19 Ma for andesite (youngest unit) unit. The initial 87Sr/86Sr and 143Nd/144Nd ratios and εNd(t) values for the quartz-monzonites are 0.704234, 0.512819 and 3.75, respectively, similar to the values for the granodiorite, which are 0.704278, 0.512813 and 3.64, respectively. In most discrimination diagrams, the Iju samples show characteristics of both oceanic slab-derived and delaminated/collisional thickened lower crust-derived adakites. The geochronological, geochemical and isotopic data for the igneous rocks of the Iju deposit indicate that after long term subduction of the Neo-Tethys oceanic crust beneath the central Iranian plate, continental collision between the Arabian and Eurasian plates during the Miocene-Pliocene led to crustal thickening, breaking-off of a subducted slab and development of an asthenospheric window, thereby facilitating partial melting of the subduction-contaminated sub-continental lithospheric mantle and thickened lower crust and generating the Cu-bearing adakites in the Iju region.

Evolution of the Mineralizing Fluids and Possible Genetic Links between Miduk Porphyry Copper and Latala Vein Type Deposits, Kerman Copper Belt, South Iran

ABSTRACT The Cenozoic Urumieh-Dokhtar Magmatic Belt (UDMB) of Iran is a major host to porphyry Cu-Mo-Au deposits (PCDs), represented by the world-class Sarcheshmeh deposit and Miduk deposit in the south and the Sungun deposit in the north. Vein type, base and/or precious metal deposits are also common and some are spatially associated with PCDs. Latala and Chahmessi are vein type, base and precious metal deposits in the north and southwest Miduk deposit. The area is covered mainly by Paleocene-Eocene volcanic and pyroclastic rocks of basaltic, basaltic-andesitic and trachy-andesitic compositions, and minor marls and limestones. The volcanic and pyroclastic rocks are intruded by Miocene shallow intrusions of quartz diorite, quartz monzonite and granodiorite compositions.The rocks are host to a set of ore-bearing quartz veins. Mineralization in both the Chahmessi and Latala deposits are controlled by faults and fractures. The role of the ring structures and faults in the distribution of hydrothermal alteration zones and mineralization is important in the Latala deposit. In these veins, euhedral quartz with sulfide mineralization occurs as open space fillings, minor replacement bodies and hydrothermal breccia. The veins consist of quartz, calcite, pyrite, chalcopyrite, galena, sphalerite, bornite and minor sulfosalts, particularly enargite. According to studies based on fluid inclusions in the Miduk porphyry, three types of fluids are responsible for mineralization. Homogenization temperatures and salinity in porphyry-type fluids vary from 566 to 162 °C and 61.3 to 1.2 wt% NaCl equiv. For the Latala vein type base and precious metals deposit, homogenization temperature and salinity vary from 380 to 131 °C and 10.6 to 0.17 wt% NaCl equiv. The gas phase in fluid inclusions of Latala is dominated by CO2 but also shows the presence of CO and H2, characterizing reducing conditions associated with ore deposition. The change from lithostatic to hydrostatic regime, boiling and fluid dilution associated with the introduction of meteoric fluids provides an explanation for the widespread Th and salinity data. Calculated pressure for examples of Miduk fluid inclusions varies from 700 to 200 bars. These pressures correspond to depths of 2500 to 1500 metres for porphyry mineralization. The three-phase fluid inclusions, corresponding to magmatic fluid, show the highest pressure. The Latala base and precious metals deposit has formed at pressures between 200 and 100 bars, corresponding to a depth of less than 1 km. Sphalerite mineralization occurs in shallow parts of the sedimentary-volcanic sequence from magmatic fluids diluted by meteoric fluids and also occurs in more distal parts of the porphyry. The sulphur isotopic composition for sulfide minerals varies between -9.8 and -1.0‰, which correspond to values of magmatic sulfur. This suggests that magmatic water was responsible for transportation of metals in Latala. Epithermal mineral precipitation occurred upon dilution of the low-salinity magmatic fluid with meteoric water, which entered the hydrothermal system as it cooled and successively diluted during continued magmatic fluid ascent.

The Parkam exploration district, Kerman, Iran: Geology, alterations, and delineation of Cu- and Mo-mineralized zones using U-spatial statistic with associated software development

The Parkam exploration district represents an area of approximately 4 km2 located 50 km north of Shahr-E-Babak (Kerman Province, Iran) , and has several traces of old copper mining and smelting activities. This area lies in the Kerman Copper Belt which is part of the larger Sahand-Bazman igneous and metallogenic zone hosting numerous known porphyry copper deposits and systems. The geology of the Parkam exploration district demonstrates that the area contains a diorite-type porphyry copper system hosted by volcanic and pyroclastic rocks of predominantly andesitic composition. Based on field and microscopic investigation, it was determined that the dominant types of alteration were propylitic, phyllic, argillic, and potassic, and the alteration map of the study area was produced. Expect for the propylitic alteration which was observed mainly in the host rocks, the other types of alteration are associated mainly with the dioritic subvolcanic body. Accompanied by subordinate amounts of primary sulfides, fracture-filling malachite is widespread in the potassic and phyllic zones and comprises the dominant style of mineralization at the surface of the porphyry system. Lithogeoc hemical data resulting from 377 samples were analyzed, and the results of background and anomaly separation by means of conventional and the U-spatial statistic method were compared. The Cu and Mo mineralizations were subsequently delineated using the U-spatial statistic. The delineated Cu mineralization is closely associated with the defined zone of potassic alteration, which is also consistent with the field and microscopic observation of the Cu mineralization in this alteration zone. The Mo mineralization delineated by the U-statistic method is mostly associated with the phyllic alteration and is spatially conformable with the zone defined for it. The source code for a software program, which was developed in the MATLAB programming language in order to perform the calculations of the U-spatial statistic method, is additionally provided. This software is compatible with geochemical variates other than Cu and Mo and can be used in similar exploration projects.

Application of ASTER data for exploration of porphyry copper deposits: A case study of Daraloo–Sarmeshk area, southern part of the Kerman copper belt, Iran

The Cenozoic Urumieh–Dokhtar Magmatic Belt (UDMB) of Iran is a major host to porphyry Cu±Mo±Au deposits (PCDs). Most known PCDs in the UDMB occur in the southern section of the belt, also known as the Kerman Copper Belt (KCB). Three major clusters of PCDs are distinguished in the KCB and include the Miduk, Sarcheshmeh and Daraloo clusters. The Daraloo and Sarmeshk deposits occur in a northwest–southeast-trending fault zone that is characterized by the presence of a narrow zone of alteration–mineralization that contains a series of Oligocene granitoids and Miocene porphyritic tonalite–granodiorite plutons that cut Eocene andesitic lava flows and pyroclastic rocks. Here we use various techniques, including different ratio images, minimum noise fraction, pixel purity index, and matched filter processing to process ASTER data (14 bands) and generate maps that portray the distribution of hydrothermal minerals (e.g., sericite, kaolinite, chlorite, epidote and carbonate) related to PCD alteration zones. In order to validate the ASTER data, follow-up ground proofing and related mineralogical work was done which, in all cases, proved to be positive. The results of this work have identified the regional distribution of hypogene alteration zones (i.e., phyllic, argillic, propylitic and silicic), in addition to areas of secondary Fe-oxide formation, which are coincident with known sites of PCDs. The regional distribution and extent of the alteration zones identified also highlighted the role of regional structures in focusing the mineralizing/altering fluids. These results demonstrate very convincingly that ASTER imagery that uses the appropriate techniques is reliable and robust in mapping out the extent of hydrothermal alteration and lithological units, and can be used for targeting hydrothermal ore deposits, particularly porphyry copper deposits where the alteration footprint is sizeable.

SHRIMP zircon U–Pb and biotite and hornblende Ar–Ar geochronology of Sungun, Haftcheshmeh, Kighal, and Niaz porphyry Cu–Mo systems: evidence for an early Miocene porphyry-style mineralization in northwest Iran

The Cenozoic Urumieh–Dokhtar magmatic belt (UDMB) extends for over 2,000 km from northwest to southeast Iran and is characterized by dominantly calc-alkaline volcanic, pyroclastic, and intrusive rocks. The UDMB hosts numerous porphyry-type Cu ± Mo deposits, mostly distributed in two separate areas, one known as the Kerman copper belt (KCB) in the south, and the other, here referred to as the Arasbaran Metallogenic Zone (AMZ), in the north, of the UDMB. The two areas are represented by two world-class Cu–Mo deposits, Sarcheshmeh (1,200 Mt of ore at 0.69 % Cu and 300 ppm Mo) and Sungun (>500 Mt of ore at 0.69 % Cu and ~250 ppm Mo), respectively. Chronology data were obtained for the Sungun, Haftcheshmeh, Kighal, and Niaz deposits in the AMZ. The Sungun deposit is associated with a suite of porphyritic granodiorite to monzodiorite stocks and late dykes intruding older andesitic lavas and limestones. SHRIMP zircon U–Pb data indicate that the host andesites were emplaced at 27.65 ± 0.51 Ma (±0.2σ). The main Sungun porphyritic intrusion crystallized at 20.69 ± 0.37 (±0.2σ) Ma. The Haftcheshmeh deposit is associated with a porphyritic granodiorite body intruding an older gabbro-diorite intrusion. Primary magmatic hornblende from the gabbro-diorite host rock yielded a 40Ar/39Ar plateau age of 27.47 ± 0.17 Ma. The main porphyritic intrusion crystallized at 19.46 ± 0.39 Ma. The Kighal porphyry system is associated with a porphyritic monzonite body intruding into older andesitic and dacitic lavas, and the Niaz porphyry system is associated with a porphyritic granodiorite stock cutting through an older monzodiorite intrusion. For the Kighal and Niaz, secondary biotite concentrates collected from potassic alteration zones in the parent porphyritic bodies yielded plateau ages of 20.1 ± 1.8 and 22.14 ± 0.13 Ma, respectively. The timing of the porphyritic intrusions and the associated mineralizations in the AMZ is considerably older than that in KCB in southern UDMB (14–7 Ma). There is evidence that the AMZ formed on a separate arc related to the southern lesser Caucasus subduction zone. The arc extends from northwest Iran to Armenia and Azerbaijan to the north. Similar deposits of the same age have been discovered in Armenia, exemplified by Kajaran and Dastakert.

Spectral characteristics of minerals in alteration zones associated with porphyry copper deposits in the middle part of Kerman copper belt, SE Iran

Visible near infrared and shortwave infrared (VNIR-SWIR, 350 to 2500nm) reflectance spectra obtained from an analytical spectral device (ASD) have been used to define alteration zones adjacent to porphyry copper deposits (PCDs), in the central part of Kerman magmatic arc, SE Iran. The spectral analysis identified sericite, illite, halloysite, montmorillonite, dickite, kaolinite, pyrophyllite, biotite, chlorite, epidote, calcite, jarosite, and iron oxyhydroxides (e.g. hematite, goethite) of hydrothermal and supergene origin. Identified alteration zones are classified into six principal types namely phyllic, phyllic/propylitic, propylitic, potassic, argillic and advanced argillic. The iron oxide minerals in the oxidized zone were also identified using spectral analysis. Results of spectral analyses of samples are consistent with mineralogical data obtained from X-ray diffraction (XRD) and petrographic studies. Spectroscopic studies by ASD demonstrate that this tool is very useful for semi-quantitative and cost effective identification of different types of alteration mineral assemblages. Furthermore, it can provide a valuable tool for evaluating aerial distribution of alteration minerals while coupled with remote sensing data analysis.

LINKING Cu MINERALIZATION TO HOST PORPHYRY EMPLACEMENT: Re-Os AGES OF MOLYBDENITES VERSUS U-Pb AGES OF ZIRCONS AND SULFUR ISOTOPE COMPOSITIONS OF PYRITE AND CHALCOPYRITE FROM THE IJU AND SARKUH PORPHYRY DEPOSITS IN SOUTHEAST IRAN

The Kerman copper belt in Iran contains a number of important porphyry copper deposits, including Sarkuh and Iju. Molybdenite Re-Os isotope dating of the Sarkuh and Iju porphyry copper deposits shows that mineralization occurred at 15.14 ± 0.08 and 9.8 ± 0.06 Ma, respectively. Compared with the previous Re-Os dating of molybdenite in the region, it is revealed that Cu mineralization was an ongoing process in an arc setting during the Miocene. The available zircon dates of the granitic rocks from the Sarkuh (15.18 ± 0.43 Ma) and Iju (9.27 ± 0.50 Ma) porphyry copper deposits indicate that the mineralization occurred contemporaneously with the emplacement of collision-related ore-hosting porphyries. The Re content (1,715.40 ppm) of molybdenite and the δ^(34)S_(CDT) values (0.05‰) of pyrite-chalcopyrite from Iju are consistent with its origin of sulfur and metals from a dominantly mantle source. However, the lower Re content (302.21 ppm) of molybdenite and higher δ^(34)S_(CDT) values (3.20‰) of pyrite-chalcopyrite from Sarkuh suggest additional contributions from crustal materials. It is likely that the younger porphyry copper deposits in the Kerman copper belt, such as Iju, are related to the greater contribution of postcollisional mantle-derived magmas, while the older deposits (e.g., Sarkuh) were formed during the collisional event at the Oligocene-Miocene interval where the magma had some additions from the lower crustal melts generated during crustal thickening.