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Identification of geochemical anomalies is a critical task in mineral exploration targeting. Decades of research and technology have resulted in new algorithms and techniques for recognizing anomaly detection methods at various scales and sample media. However, algorithms cannot always reveal the true nature of geological processes. The mineral system concept may contribute to a better understanding of the geological processes required to form and preserve ore deposits at all spatial and temporal scales. The mineral systems concept investigates the geochemical processes occurring within mineral subsystems in soil samples from the porphyry prospect area. The Cu/(Al + Ca) index was used to compare Cu, Mo, and (Pb* Zn)/(Cu*Mo) to highlight the region of interest for mineral potential mapping and pioneer borehole drilling based on fluid-rock interaction and secondary processes (e.g., alteration, weathering, and leaching). Exploratory boreholes validate a better performing Cu/(Al + Ca) index for detecting and refining soil geochemical anomalies. [ABSTRACT FROM AUTHOR]

The Urumieh-Dokhtar magmatic arc (UDMA), Iran, hosts giant to small porphyry Cu ± Au deposits associated with Miocene post-collisional magmatism. Previous studies suggested that the ore-bearing suites are derived from chalcophile element-rich juvenile lower crustal igneous rocks, and that metal contents in the magmas play an important role in the formation of porphyry Cu ± Au deposits in this region. This study investigates the whole-rock major, trace, and platinum group element (PGE) geochemistry, as well as zircon trace element geochemistry, of six porphyry Cu ± Au ore-bearing suites and three barren suites in the central and southeastern UDMA. The aim is to revisit their petrogenesis and understand the factors controlling the formation of post-collisional porphyry Cu ± Au deposits. The high Mg# and Cr and Ni contents of the most mafic variants of ore-bearing and barren rocks suggest that they are primarily derived from the mantle. However, the ore-bearing magmas from the small Dalli Cu–Au porphyry and barren magmas from central to southeastern UDMA experienced substantial crustal assimilation during evolution. The evolved ore-bearing magmas exhibit high La/Yb and Sr/Y ratios, along with concave upward chondrite-normalized REE patterns and high zircon Ce/Nd and Eu/Eu* values, suggesting that they have undergone amphibole dominant differentiation under hydrous and oxidized conditions. In contrast, the barren magmas are characterized by lower whole-rock La/Yb and Sr/Y and zircon Ce/Nd and Eu/Eu* values with flatter REE patterns, implying plagioclase dominant differentiation. The ore-bearing suites, except for the Dalli suite, have systematically higher Pd and Pt contents than barren suites with highly fractionated PGE patterns (high Pd/Ir). The chalcophile element fertility of the ore-bearing suites, as indicated by high Pd/MgO and Pd/Pt ratios, is comparable to that observed in porphyry Cu deposits found elsewhere. This similarity suggests that the Cu contents of the magma likely played acrucial role in the formation of the porphyry Cu deposits in the central and southeastern UDMA. Late sulfide saturation or small amounts of sulfide segregation may have led to the high Cu and moderate Pd contents of the ore-bearing magmas until the late stage of differentiation. In contrast, early sulfide saturation resulted in significant depletion in all PGE and Cu in the barren magma. The fractionated PGE patterns of the ore-bearing magmas could have arisen due to two potential processes. Firstly, they may have resulted from fractional crystallization of Cr-spinel in the early sulfide undersaturated differentiation. Secondly, the patterns might have been inherited from partial melting of metasomatized lithospheric mantle. The systematic geochemical differences between ore-bearing and barren suites suggest that the more hydrous and oxidized nature and higher Cu contents of the ore-bearing magmas substantially increase the porphyry Cu ore potential in the central and southeastern UDMA. [ABSTRACT FROM AUTHOR]

The Sarcheshmeh porphyry copper deposit (PCD) is located in the southeast part of the arc‐related Urumieh‐Dokhtar volcano‐plutonic belt. This PCD was formed by intrusion of a Middle Miocene granodiorite to tonalite stock into the volcano‐sedimentary rocks that are mainly andesite exhibiting Early Tertiary thrusting and faulting. On the basis of geochemistry of intrusive rocks, they are calc‐alkalic and alkali‐calcic suites that are consistent with oxidized I‐type magmas. The Fe2O3/FeO ratio in the Sarcheshmeh PCD is 1 to 3, consistent with a high oxygen fugacity. The igneous rocks of Sarcheshmeh PCD belong to a mature arc, but related to a post‐collision arc setting. Considerable evidence supports adakitic affinities of the Sarcheshmeh rocks, including geochemical values of Sr > 300 ppm (ave., 594 ppm), high ratios of Sr/Y > 20 (ave., 75), La/Yb > 20 (ave., 30), and enrichment of LREE and LILE relative to HREE and HFSE. The adakites of Sarcheshmeh belong to high‐silica adakites (HSA) that can be formed by melting of subducting seawater‐altered oceanic plate, which interact with the mantle wedge then followed by slab break‐off with local transtension in the middle part of the Dehaj‐Sarduieh belt. In rocks of the region, the ratios of Th/Ce > 0.12 and Nb/Zr > 0.05 suggest that the subducting crust has a role in forming different groups of these rocks. Geotectonic discrimination diagrams are used to distinguish between normal arc and slab failure magmatic systems, including Nb versus Y, La/Sm versus Sm/Yb, La/Yb versus Gd/Yb, and Rb versus Nb + Y diagrams. The plutonic rocks of the Sarcheshmeh PCD have characteristics consistent with adakites derived via slab failure, which are obviously metallogenically favorable magmatic systems. Adakitic melts generated rapidly during sinking of a broken slab (into higher temperature mantle), buoyantly migrate through the subcontinental lithospheric mantle (SCLM), which is related to structural evolution of that SCLM with local extension or transpression. [ABSTRACT FROM AUTHOR]

LA‐ICP‐MS analysis of molybdenite from the Sar Cheshmeh porphyry Cu‐Mo deposit (PCD), Iran, shows moderate concentration of Re (average ∼207 ppm) and low concentration of chalcogenides (average of Pb + Te + Bi, ∼31 ppm) as well as metalloids (average of As + Sb + Ge, ∼4.5 ppm). The early‐formed quartz–molybdenites associated with potassic alteration are characterized by moderately low concentration of Re (21–215 ppm with an average of 83 ppm), whereas the transitional quartz–molybdenite veins related to the sericitic stage of mineralization contain more Re (62–465 ppm, with an average of 207 ppm). In contrast, the late‐formed quartz–molybdenite veins associated with phyllic alteration show the highest concentration of Re (up to 1273 ppm with an average of 395 ppm). Gradual increase in Re content of molybdenites deposited throughout the evolution of the porphyry system is probably related to elevated ƒO2 and acidic conditions of the ore fluids governing the transitional and late stage of mineralization, when compared to the moderately low ƒO2 and basic conditions of the ore fluids precipitating the low‐Re molybdenites associated with potassic alteration. The mixed mantle/crustal source of the ore‐related magma and its fractionated composition in Sar Cheshmeh are consistent with magmatic conditions for the formation of Mo‐rich and Re‐poor PCDs in the world. [ABSTRACT FROM AUTHOR]

The Miocene Kuh-Panj porphyry copper deposit, with reserve estimated at about 100 Mt. at 0.21 % Cu, is located 120 km SW of Kerman in the southern part of the Urumieh-Dokhtar magmatic arc. The Eocene host rocks consist of tuff, lithic tuff, breccia tuff, and lava flows, ranging in composition from rhyodacite to andesite. A late Miocene granodiorite porphyry stock (8.57 ± 0.49 Ma, U/Pb zircon) intruded into the Eocene sequence. Subvolcanic dykes cut the Eocene rocks and porphyry stock. The Kuh-Panj porphyry system has an extensive and typical hydrothermal alteration zoning pattern, which is comprised of potassic, phyllic, argillic, and propylitic alteration types from inner proximal to outer distal zones. Copper mineralization occurs in potassic and to some extent in phyllic zones. Mineralization is mostly observed as disseminated, stockwork, and vein-veinlets forms in the porphyry stock. Vein paragenesis includes barren quartz, M-type (magnetite+biotite), A 1 -type (quartz+magnetite+chalcopyrite±chlorite±biotite), A 2 -type (quartz+chalcopyrite±pyrite), D-type (quartz+pyrite±chalcopyrite), and L-type (galena+sphalerite±chalcopyrite±pyrite) veins. The I-type granitoids with calc-alkaline affinity have enrichments of LILE (Pb, K, U, Sr, and Cs), depletion of HFSE (P, Nb, Ta, Zr, and Ti), and enrichment in LREE displaying geochemical similarity to arc-related magmatic rocks. The high SiO 2 (ave. 68.9 wt%), high Al 2 O 3 (ave. 14.5 wt%), low MgO (ave. 1.3 wt%), low P 2 O 5 (< 0.2 wt%), high Sr (ave. 365 ppm), high Sr/Y (ave. 45), relatively high La N /Yb N (ave. 28), relatively high Th (ave. 8 ppm), low Y (ave. 8 ppm), and low Yb (0.5 ppm) contents are similar to those of fertile porphyries and lower crust-derived adakites. The most dominant type of fluid inclusions in quartz from mineralized veins are liquid-vapor-halite-solid (LVHS), liquid-vapor-halite (LVH), liquid-vapor (LV), and vapor-liquid (VL) fluids. Homogenization temperatures of LVHS, LVH, LV, and VL fluids range from 306 to 574 °C, 141–566 °C, 215–422°, and 349–571 °C, respectively. Salinities of LVHS, LVH, LV, and VL fluid inclusions range from 30 to 69, 29.0–65.5, 0.35–22.0, and 0.7–13.0 wt% NaCl eq., respectively. The extreme variations in salinities of fluid inclusions represent the combined effects of varying salinity of the magmatic fluid, aqueous fluid-phase immiscibility (boiling), and mixing with lower salinity meteoric water later in the cooling history of the porphyry system. Normal cooling, water-rock interaction, surface fluid dilution, and boiling are dominant factors that control both the distribution and abundance of mineralization. Zircon from the Kuh-Panj system has high Th/U (0.53 to 0.83), low Dy/Yb (<0.3) ratios, positive Eu/Eu* (1.28–1.85), strong positive Ce/Ce* (1.36 to 197) reflecting high Ce4+/Ce3+ ratios, and enrichment in HREEs relative to LREEs, which indicate the magmatic origin of zircon, oxidized, and hydrous conditions of the primary magma. This magma with adakitic affinities is favorable for producing fertile porphyry systems. Based on these multidisciplinary studies, the Kuh-Panj deposit is classified as a continental arc-related porphyry copper system hosted predominantly at the transition zone between potassic and phyllic alteration zones due to decreasing temperature, boiling, and fluid-rock reaction that all enhance Cu Fe sulfide saturation. [Display omitted] • Mineralization in Kuh-Panj occurred in a Miocene granodiorite stock that intruded Eocene volcanic host rocks. • Alteration zoning pattern and vein paragenesis are similar to porphyry Cu deposits elsewhere. • Geochemical features of the Kuh-Panj system are similar to those of fertile porphyries. • The zircon 206Pb/238U ages of the porphyry stock ranging from 7.7 to 9.7 Ma (ave. 8.57 ± 0.49 Ma). • The Kuh-Panj deposit is classified as continental arc-related porphyry copper deposit. [ABSTRACT FROM AUTHOR]

The Bondar Hanza porphyry Cu deposit, hosted by a granitoid stock, is located 120 km south of Kerman city in the elongated NW–SE trending Urumieh‐Dokhtar magmatic arc (UDMA), Iran. The granitoid stock is a multiphase intrusive body, 2 km2 in surface area, which comprises microdiorite–microquartz diorite and granite–granodiorite. Petrological and geochemical analyses show that granitoids are peraluminous, magnesian, calcic to alkali‐calcic, and non‐adakitic intrusions characterized by negative Eu* anomalies. Thermobarometric and oxygen fugacity calculations indicate that magma emplacement occurred at 719–784°C, <100 MPa, and at a log fO2 of NNO +1.6 to +3.2. Sulphur isotopic composition of sulphide minerals (δ34S = 5.0–6.8 ‰) are similar to other porphyry Cu deposits worldwide. Molybdenite separates yield Re–Os ages of 28.22–28.03 Ma, indicating that the Cu mineralization and associated magmatism occurred during the Oligocene. The Bondar Hanza is one of the several granitoids from small porphyry Cu deposits in the UDMA that is related to island arc sub‐productive granitoids. It seems that the largest ore‐hosting porphyry systems within the UDMA are generally restricted to Miocene intrusions with adakitic affinity (e.g., Sarcheshmeh granitoids) and that the temporally discrete non‐adakitic magmatic systems are sub‐productive to barren. These data are interpreted to show that magmatism in the Bondar Hanza region was likely associated with partial melting of juvenile lower crust induced by north‐eastward subduction of the Neo‐Tethys oceanic lithosphere. [ABSTRACT FROM AUTHOR]

The main aim of this study is to investigate the applicability of a Fuzzy Inference System (FIS) approach to produce a copper mineral potential map (MPM) at the Saveh area in the Markazi province of Iran. Seven indicator layers extracted from the geological, geochemical, and geophysical data sets are casted in a geospatial database for data integration. Indicator layers are rock types, alterations, Cu concentration anomaly, main geochemical principal component anomaly, reduced-to-pole magnetic data, electrical chargeability, and electrical resistivity. A fuzzy gamma operator is used at the first phase of exploratory data integration to produce three criterium layers that are geology, geochemistry, and geophysics. Then, at the second phase, the FIS is implemented in three main stages consisting of: 1) fuzzification of input/output data, 2) designing an inference engine, and 3) defuzzification of integrated data. The mineral favourability map is prepared and reclassified into five zones through a multifractal approach at the third phase. In order to evaluate the accuracy of the FIS method, the productivity index of 18 boreholes are utilised to examine the correlation between the mineralised zones and the MPM output. Whereby the synthesised indicator layers demonstrated a Pearson's linear correlation coefficient of 0.44 in recognising copper mineralisation at depth. In addition, the eastern and central portions of the Saveh prospect were proposed as favourable potential zones for further mining operation. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a novel gradient model for exploration of blind mineralization. The concentration gradient coefficient techniques have been proved to be very well-suited for typical mining geochemistry applications. Gradient concentration corresponds to concentration variations. Large concentration changes due to geochemical data distribution correspond to surfacing anomaly, and less concentration variations are more likely to be related to the deeper geochemical anomalies. The introduced technique is capable to distinguish the difference between the blind mineralization and zone dispersed mineralization, computationally and without exploration drilling. In this research, deep geochemical anomalies are investigated using the gradient concentration values for the porphyry–Cu deposits of the Jebal-Barez region in Iran. Based on the results obtained from the proposed gradient model, values >1.0 in G(Vz) reveal the existence of blind mineralization in the study zone. The findings based on this method suggest that SW of Jebal-Barez is a highly favourable zone for exploration of blind mineralization. The value for G(Vz) in this zone is equal to 5.04. The results obtained in this research were consistent well with the findings of the previous research in the area and the detected Kerver as the main blind mineralization in Jebal-Barez. A local exploration was carried out in this zone in four areas of Kerver using the gradient model. Highlights • New method of concentration gradient has been introduced in geochemical exploration. • This new method solves the defect of zonality method. • The cut off value was presented for detection of BM from ZDM. [ABSTRACT FROM AUTHOR]

Abstract This investigation of leached caps in Meiduk and Parkam porphyry copper deposits (PCD) in Kerman Cenozoic magmatic arc (KCMA) of SW Iran indicated that the fertility of supergene enrichment zones may be inferred from the mineralogical and geochemical characteristics of their associated leached caps. That is, the indigenous mature leached caps characterized by strong leaching of Cu, large ion lithophile elements (LILEs), and high field strength elements (HFSEs), commonly form above intrusions where supergene enrichment is strongly developed. Mineralogically, these leached caps (e.g., SE Meiduk) are characterized by abundant hematite and minor goethite (Hem:Gt ≈ 5.48), whereas immature leached caps (e.g., NW Meiduk and Parkam) are associated with poorly developed supergene enrichment zones characterized by abundant goethite (Hem:Gt ≈ 0.56 for NW Meiduk and 0.38 for Parkam), boxwork textures, secondary copper minerals and remnant pyrite. Calculated rock quality designation (RQD) from drilling cores in Meiduk deposit also revealed the relation between joint density and the extent of supergene enrichment. Moreover, increasing the rare earth elements (REEs) content in the immature and fewer REEs concentration in the mature leached caps also reflects the fertility of supergene enrichment zone in PCDs. Highlights • The fertility of supergene zone is reflected in the mineralogical and geochemical characteristics of their associated leached caps. • Calculated rock quality designation (RQD) revealed the extent of supergene enrichment. • REEs are the best geochemical indicators for supergene enrichment development. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Calculated log f O 2 values and FMQ buffer conditions (ΔFMQ < 2) of parental magmas of Eocene and Oligocene porphyry copper deposits in Lut block indicate never reached to ideal conditions of worldwide giant to large porphyries (Hematite-Magnetite buffer; ΔFMQ < 4). • Zircon trace element data, log f O 2 values along with the whole-rock geochemistry show slab metazomatized supra-subduction partial melted peridotite source for all primary magmas. • High parthial melting of a low water warm/hot deep steep slab subduction in a W-diredcted subduction system suggest to Eocene Cu-Au (Maher abad and Khupic) and Oligocene Cu-Mo (ChahShaljami and Dehsalm) porphyry deposits in Lut block related to the Indo-Asia and Arabian-Eurasian collision events. The small (<50 Mt) Eocene porphyry Cu-Au deposits of Maher abad and Khupic and the Oligocene Cu-Mo deposits of ChahShaljmi and DehSalam are attributed to the subduction of the Sistan ocean crust beneath the Lut block of eastern Iran. The calculated Ce4+/Ce3+ ratios of Dehsalm and ChahShaljami zircons are clustered around 10–50 and 75–155, and the values for Maher abad and Khupic are clustered around 120–300 and 50–150, respectively. The calculated log f O 2 values indicate FMQ buffer conditions for Eocene and Oligocene magmas (ΔFMQ < 2; ΔFMQ −1.8 to + 0.6 ± ∼1.5 for ChahShaljami; ΔFMQ −1.3 to −0.4 ± ∼1.5 for Dehsalm, and ΔFMQ −3.2 to −2.1 ± ∼1.5 for Maher abad; ΔFMQ −2.6 to −1.3 ± ∼1.5 for Khupic), which never reached the ideal values of the worldwide giant to large porphyries (ΔFMQ < 4; HM buffer). The 30–60% partial melting of a slab (∼10–25% garnet) can explain ChahShaljami and Dehsalm, while it is > 60% partial melting of a slab (garnet > 50%) + ∼10% of metasomatized garnet-lherzolite (∼10% garnet) for Maher abad and Khupic. High partial melting of a slab has produced magma poor in copper in the magmatic subarc of the Lut block. Our zircon data and whole-rock geochemical characteristics of the Eocene and Oligocene ore-bearing intrusions along with the kinematics studies of the subduction zones are well consistent with a west-directed subduction system in eastern Iran. In such a system, a higher subduction rate > convergence rate causes deep steep subduction and in the continuation roll-back of the slab occurs in response to the opening and closing of the back-arc basin. This event caused the thinning of the Lut continental crust, mantle delamination and hot asthenospheric upwelling. The ascent of magmas resulting from the partial melting of a hydrous slab through a hot mantle and thinned continent caused widespread volcanism, and large amounts of water, sulfur and, volatiles were released to the atmosphere in an island arc regime during the middle-upper Eocene. The poor in metal low-volume magmas resulting from the high partial melting of a low water warm/hot deepest slab slightly metasomatized the mantle that subsequently amphibole-FC process with low contamination in the MASH zones and their emplacement during the transition from the island- to normal continental arc in the upper Eocene-Oligocene formed upper Eocene high-K calc-alkaline I/A-type (ferroan) arc magmatism and lower Oligocene adakite-like high-K calc-alkaline-Shoshonitic I-type (magnesian) arc magmatism, led to the formation of small Cu-Au and Cu-Mo porphyry deposits in Lut block, respectively. These events occur in a particular tectonic condition where subduction and collision were accompanied by rotation of the block affected by both Indo-Asian and Arabian-Eurasian collisions. Our study implies that W-directed subduction systems do not have favorable conditions for the formation of large porphyry deposits such as the ideal down-dip thermal gradient of the oceanic slab, water content, depth of dehydration, degree of partial melting of oceanic slab, and thickened continental crust. [ABSTRACT FROM AUTHOR]

The Miocene Dalli porphyry Cu–Au deposit in the central part of Urumieh–Dokhtar magmatic arc is the first reported Au-rich porphyry Cu deposit in the Zagros orogenic belt. The Cu–Au mineralization is mainly hosted in diorite and quartz diorite intrusions, presenting as numerous veinlets in the altered wall rocks, with potassic, phyllic, and propylitic alteration developed. Based on the mineral assemblages and crosscutting relations of veinlets, hydrothermal mineralization–alteration occurred in at least three stages, characterized by veinlets of (1) Qtz + Kfs + Mag ± Ccp, (2) Qtz + Py + Ccp ± Bn ± Cv ± Cc and, (3) Qtz + Chl + Bt. The ore-bearing intrusions exhibit typical geochemical characteristics of subduction zone magmas, including LREE fractionated pattern, strong enrichment in LILE (Cs, Rb, Ba, Pb, and U), and depletion of HFSE, with marked negative Ti and Nb anomalies. The adakite-like ore-hosting porphyry intrusions are characterized by a systematic gradual decreasing and increasing of Y and Eu/Eu ∗ with increasing SiO 2 content, respectively. Moreover, they exhibit a significant increasing trend of Sr/Y with decreasing of Y, which indicates progressive hornblende fractionation and suppression of plagioclase fractionation during the evolution toward high water content of parental magma. A relatively flat HREE pattern with low Dy n /Yb n and Nb/Ta values may represent that amphibole played a more important role than garnet in the generation of the adakitic melts in the thickened lower crust. Based on the phase assemblages confirmed by detailed laser Raman spectroscopy analyses and proportion of solid, liquid, and gaseous components, five types of fluid inclusions were recognized, which are categorized as; (1) liquid-rich two phase (liquid H2O + vapor H2O ) (IIA), (2) vapor-rich two phase (vapor H2O/CO2 + liquid H2O ) (IIB), (3) high saline simple fluids (IIIA; liquid H2O + vapor H2O + Hl), (4) high saline opaque mineral-bearing fluids (IIIB; liquid H2O + vapor H2O + Hl + Hem + Ccp + Py) and (5) multi-phase type (IIIAB; liquid H2O + vapor H2O + Hl + Anh + Hem + Mag + Ccp). In early stage veins, the homogenization temperature of multiphase inclusions as high as 620 °C, with corresponding salinities of up to 75 wt.% NaCl equivalent represent the initial ore-forming fluids. From early to late stage veins, the gradual decrease of homogenization temperature of saline inclusions (IIIAB, IIIA, and IIIB) from 620 to 340 °C (corresponding salinities of 75–35 wt.% NaCl equivalent) may reflect fluid boiling and mixing of the early magmatic fluids with circulating groundwater. The common association of hematite and anhydrite daughter phases with the most primitive inclusions (IIIAB) in early-stage veins and the lack of CO 2 -bearing inclusions in the middle to late stage veins reveal CO 2 content and oxygen fugacity of the fluids was significantly decreased from early to main stage of sulfide mineralization (second generation of veins). It seems that magnetite crystallization and CO 2 -escape have a decisive role in oversaturation of S 2− and subsequent rapid and large-scale precipitation of sulfides in second generation of veins at the Dalli deposit. [ABSTRACT FROM AUTHOR]

Hanza Mountain in Urmia–Dokhtar Magmatic Arc, southeast of Iran, consists of monocline of Eocene volcanic rocks into which the Oligocene granitoid rocks have been intruded. This area has excellent potential for economic porphyry copper deposits with Bondar Hanza, Daralu, and Sarmesk deposits among them. Hanza Mountain is located between NW–SE horsetail thrust faults derived from the Gowk and Sabzevaran strike-slip faults. The analysis of the kinematics of these strike-slip faults shows that they were not the cause of the formation of the pull-apart basin; thus they have not directly played any effective role in localizing the final emplacement of porphyries responsible for the formation of these copper deposits, but the Cu mineralization occurred mainly within a set of normal and thrust faults in the region. The alteration types and faults in Bondar Hanza were distinguished using detailed local geology, including distribution of known mineralization, supported by remote sensing (ASTER), airborne geophysics, and topography; the relationship between mineralization and faults was examined using Rose diagrams and Fry Analysis. This investigation of Bondar Hanza deposit has revealed that the trend of faults and dykes, as well as the distribution of copper analyses within drill cores, is aligned with the main trend of mineralization. The NW–SE trending faults in the Urmia–Dokhtar Magmatic Arc are effective in localizing the emplacement of porphyry copper ore deposits and those that trend between N125°–N145° are key to further exploration. [ABSTRACT FROM AUTHOR]

Early Miocene igneous rocks associated with the Dalli porphyry ore body are exposed within the Urumieh-Dokhtar Magmatic Arc (UDMA). The Dalli porphyry Cu–Au deposit is hosted by subduction-related subvolcanic plutons with chemical composition from diorite to granodiorite, which intruded andesitic and dacitic volcanic rocks and a variety of sedimentary sequences. 40Ar/39Ar age data indicate a minimum emplacement age of ∼21 million years for a potasically altered porphyritic diorite that hosts the porphyry system. The deposit has a proven reserve of 8 million tonnes of rock containing 0.75 g/t Au and 0.5% Cu. Chondrite-normalized rare earth element (REE) patterns for the subvolcanic rocks are characterized by light REE enrichments [(La/Sm) n  = 2.57–6.40] and flat to gently upward-sloping profiles from middle to heavy REEs [(Dy/Yb) n  = 0.99–2.78; (Gd/Yb) n  = 1.37–3.54], with no significant Eu anomalies. These characteristics are generated by the fractionation of amphibole and the suppression of plagioclase crystallization from hydrous calc-alkaline magmas. In normalized multi-element diagrams, all analysed rocks are characterized by enrichments in large ion lithophile elements and depletions in high field strength elements, and display typical features of subduction-related calc-alkaline magmas. We used igneous mineral compositions to constrain the conditions of crystallization and emplacement. Biotite compositions plot above the nickel–nickel oxide (NNO) buffer and close to oxygen fugacity values defined by the hematite–magnetite (HM) buffer, indicating oxidizing conditions during crystallization. Assuming a minimum crystallization temperature of 775°C, the oxygen (fO2) and water (fH2O) fugacities are estimated to be 10−10.3 bars (∼ΔNNO+4) and ≤748 bars, respectively, during the crystallization of biotite phenocrysts. The temperature and pressure conditions, estimated from temperature–corrected Al-in-hornblende barometry and amphibole-plagioclase thermometry, suggest that the hornblende phenocrysts in Dalli rocks crystallized at around 780 ± 20°C and 3.8 ± 0.4 kbar. An alternative method using the calcic amphibole thermobarometer indicates that the Dalli magmas were, on average, characterized by an H2O content of 4.3 wt.%, a relatively high oxygen fugacity of 10−11.0 bars (ΔNNO+1.3), and a hornblende phenocryst crystallization temperature of 880 ± 68°C and pressure of 2.6 ± 1.7 kbar. [ABSTRACT FROM AUTHOR]

To discriminate the mineral potentiality of the trachybasalt around the Miocene Sarcheshmeh porphyry copper deposit, petrogeochemical characteristics of more than 45 samples of the volcanic rocks were studied. Sarcheshmeh is one of the world's largest Miocene porphyry copper deposits in a continental arc setting and contains about 1200 million tonnes of ores with an average grade of 1.2 percent copper, 0.03 percent molybdenum, 3.9 g/t Ag and 0.11 g/t Au. The biotized and sericitized trachybasalts around the Sarcheshmeh deposit are associated with chalcopyrite, pyrite and molybdenite and and are enriched in Cu (>3108 ppm), KO (>4.2%), Rb (>155 ppm) and MgO (>2.9%), but depleted in yttrium (<11 ppm), MnO (<0.06%), CaO (<0.6%), NaO (<0.33%), Sr (<107 ppm), and Ba (<181 ppm). The propylitized trachybasalts are enriched in CaO (>9.1%), NaO (>3.2%), MnO (>0.24%), Y (>18.2 ppm), and Ba (>323 ppm). The results demonstrate that the diagrams of loss on ignition − Cu, Cu − Y, KO/KO + NaO + CaO − Cu and Y − MnO may be used as an exploration guide for undiscovered porphyry copper mineralization in the Central Iranian volcano-plutonic copper belt. [ABSTRACT FROM AUTHOR]

Abstract: Geochemical anomaly separation using the concentration–area (C–A) method at Kahang (Gor Gor) porphyry system in Central Iran is studied in this work. Lithogeochemical data sets were used in this geochemical survey which was conducted for the exploration for Cu mineralization in dioritic and andesitic units at Kahang Cu–Mo porphyry system. Similar surveys were also carried out for Mo and Au exploration in these rock units. The obtained results have been interpreted using rather extensive set of information available for each mineralized area, consists of detailed geological mapping, structural interpretation and alteration data. 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 Cu (224ppm), Mo (63ppm), and Au (31ppb), and the obtained results suggests existence of local Cu anomalies whose magnitude generally is above 1000ppm. The correlation between these threshold values and ore grades is clearly interpreted in this investigation. Also, the log–log plots show existence of three stages of Cu enrichment, and two enrichment stages for Mo and Au. The third and most important mineralization event is responsible for the presence of Cu at grades above 1995ppm. The identified anomalies in Kahang porphyry system, and distribution of the rock types, are mainly monzodiorite and andesitic units, do have special correlation with Cu and monzonitic and dioritic rocks, especially monzodioritic type, which is of considerable emphasis. The threshold values obtained for each element are always lower than their mean content in the rocks. The study shows threshold values for Cu is clearly above the mean rock content, being a consequence of the occurrence of anomalous accumulations of phyllic, argillic and propyllitic alterations within the monzonitic and dioritic rocks especially in monzodioritic type. The obtained results were compared with fault distribution patterns which reveal a positive direct correlation between mineralization in anomalous areas and the faults present in the mineralized system. [Copyright &y& Elsevier]

Abstract: The Chah-Firuzeh porphyry copper deposit is located in 35 km north of Shahre Babak (Kerman province). It is associated with granodioriteic intrusive of Miocene age which intruded Eocene volcanosedimentary rocks. Copper mineralization was accompanied by both potassic and phyllic alteration. Field observations and petrographic studies demonstrate that the emplacement of Chah-Firuzeh pluton took place in several intrusive pulses, each with associated hydrothermal ore fluid formation that was also associated with hydrostatic pressure increasing respect to that of lithostatic pressure (and fracturing development-relative boiling) by circulated fluid. Copper is concentrated as a very early hydrothermal mineralized phase in the evolution of the hydrothermal system. Early hydrothermal alteration produced a potassic assemblage (orthoclase–biotite) in the central deep part of the stock. Alteration ore fluids could be classify into two groups of liquid-reach, containing solid phases, high temperature (390 to 500 °C) high salinity (more than 60 wt.% NaCl equiv.) and gas-rich, high temperature (311 to 570 °C), no solid phase and with low salinities. These magmatic source fluids illustrate sever boiling process and also are the responsible for the both potassic alteration, quartz group I and II veins and chalcopyrite deposition. Propylitic alteration occurred by the liquid-rich, low temperature (241 to 390 °C) and Ca-rich fluid with meteoric origin. Continuous decreasing temperature let the meteoric water diffusion into the system, mixed with magmatic fluids and descending the salinities down to the 1 wt.% NaCl equiv. and leaching the Cu from vein groups II and III by sever thermodynamic anarchies from potassic to the phyllic alteration zones. Phyllic alteration and copper leaching resulted from the inflow of oxidized and acidic meteoric waters with decreasing temperature of the system followed by the incursion of this fluid into and its convection in upper part of the system. A late episode of boiling occurred in the apical the phyllic zone, and was associated with significant copper deposition. Based on the field observation on sharp alteration and related mineralization, it is possible to conclude that all these procedures have been controlled by local faults that could be active even before the pluton injection. These faults and the new form ones (which have been formed after injection), could crash the hosted rocks, and act as physical dams to restrict and limit the mineralization in special strikes and zones within the Cah-Firuzeh ore deposit. [Copyright &y& Elsevier]

• Lubin-Zardeh epithermal gold deposit is hosted in volcaniclastic (crystal tuffs) and quartz monzonite igneous host rocks. • The intrusive host rocks of the Lubin-Zardeh deposit are sub-alkaline, meta-aluminous, Cordilleran I-type. • Geochemistry of host rocks is consistent with subduction-related arc magmatism in Lubin-Zardeh gold deposit. • Geochemical and isotopic data suggest enriched mantle source for the magma in the study area. The Lubin-Zardeh Au-Cu ± Pb ± Zn deposit is located in the Azerbaijan-Western Alborz zone, 45 km NE of Zanjan, Iran. It is situated within the Eocene-Oligocene volcanic-plutonic belt of the Tarom subzone of the Alborz mountains range. Quartz monzonite and tuffs are the main host rock of the Lubin-Zardeh Au-Cu ± Pb ± Zn deposit. Granitoid rocks are predominantly high- K, calc-alkaline with shoshonitic affinities. They are I-type, metaluminous, magnesian and are characterized by LILE, LREE and Th enrichment relative to HFSE, depletion in Nb, Ta, Ti and weak depletion in HREE and Y. These granitoids show some affinities with adakites, e.g., high Sr/Y and La/Yb ratios coupled with low Yb and Y, and enrichment in LREE and LILE with weak Eu anomalies. Their relatively low to moderate initial 87Sr/86Sr values (0.7047–0.7051), positive Nd (t = 36 Ma) values (0.39–2.1) and TDM ages of 0.69 to 1.06 Ga, with Pb isotopic ratios of initial 206Pb/204Pb = 18.49–18.68, initial 207Pb/204Pb = 15.58–15.61 and initial 208Pb/204Pb = 38.33–38.77, are consistent with a phlogopite-bearing, amphibole-rich, and enriched lithospheric mantle source metasomatized by earlier subducted sediments. The geochemical and isotopic compositions of the granitoids are similar to the host rocks of porphyry and epithermal deposits in the Urumieh–Dokhtar zone. [ABSTRACT FROM AUTHOR]

Abstract: Based on the imprecise geochemical data for 62 samples from Qom, Anar and Baft regions in central Iranian magmatic arc Omrani et al. (Omrani, J., Agard, P., Witechurch, H., Benoit, M., Prouteau, G., Jolivet, L., 2008. Arc magmatism and subduction history beneath the Zagsros Mountains, Iran: A new report of adakites and geodynamic consequences. Lithos 106, 380–398.), suggested that all studied magmatic rocks display the geochemical affinity of subduction-related calc–alkalic rock suites. Here, we demonstrate that the incorrect altered and variable geochemical data (e.g., Al2O3, Sr, Y, Ni, Cr, SiO2, Na2O, La/Yb and Th/Ce), show that most of the samples actually display calc–alkaline, shoshonitic and calc–alkalic–adakitic affinities. Furthermore, as a result of alteration, rock samples of similar age (e.g., Qom) indicate both adakitic and non-adakitic compositional signatures, which is misleading. On the basis of more than 400 previously published geochemical analyses, we suggest that, after eliminating the false geochemical signatures, the calc–alkaline and adakitic affinities of the central Iranian magmatic arc are due to flat subduction and might be related to a second phase of Miocene- Pliocene porphyry copper mineralization, which is a considerable exploration target and thus merits further investigation. [Copyright &y& Elsevier]