فصلنامه زمین شناسی اقتصادی
سال پانزدهم شماره 3 (پیاپی 38، پاییز 1402)

Balazard prospecting area is located in eastern Iran, about 120 km south-west of Nehbandan in the Central part of Lut Block. This area consists of exposed Eocene volcanic rocks, intruded by several diorite and monzodiorite dykes and stocks. These intrusive rocks display porphyritic textures with mm-sized phenocrysts, most commonly of plagioclase, clinopyroxene and hornblende, embedded in a fine-grained groundmass with variable amounts of plagioclase, quartz, and opaque minerals. The assessment of geochemical properties of the major elements showed that these granitoids are metaluminous and of high-K calc-alkaline variety. The patterns of trace elements are identical, denoting enrichments in the light REE (LREE) to heavy REE (HREE). Moreover, LILE enrichment relative to HFSE and Nb, Ti, and P show negative anomalies. The Eu/Eu* ratios range from 0.96 to 0.76, which means that the plagioclase is a slag remnant in the origin of magma. The (87Sr/86Sr)i values of the assessed intrusive rocks range from 0.706 to 0.707, assuming an Oligocene age, while the εNdi values are between -1.9 to -3.2. These results manifest that the magmas were contaminated by continental crust. The contamination has probably occurred over the ascent of magma to crustal levels, and geochemical data verifies the preposition that the investigated intrusions were intruded in a volcanic belt resting on a subduction zone. Early magmas were created through the melting of mantle wedge peridotite, occasioning magma differentiation through crystal fractionation and crust contamination as they ascended to crustal levels.

There are important deposits such as Sari Gunay epithermal gold, Dalli porphyry copper-gold, and Zarshuran Carlin deposits with a few common exploration features in the Zagros metallogenic province of Iran. This study used geological maps, remote sensing, geochemical, geophysical, mineralogical, petrographic, fluid inclusion and age dating information to characterize and identify exploration criteria of these deposits. Mineralization at Sari Gunay gold deposit is epithermal, which was formed in association with an alkaline magma and brecciated, altered dacite porphyry about 11 Ma. Mineralization at Zatshuran is Cralin with black shale and carbonate sedimentary hosts, formed indirectly in association with a deep alkaline magma about 14 Ma. Mineralization at Dalli deposit is copper-gold porphyry with diorite host, formed in association with a chalk alkaline magma about 21 Ma. Despite different host rocks, mineralization at Zarhuran and Sari Gunay gold deposits reveals some similarities. Among the common exploration criteria in the two deposits are Oligo-Miocene alkaline magma, mineralization depth of more than 300 meters, northeast trending structures, gold, arsenic and antimony geochemical association, presence of iron oxides such as jarosite and hematite, vuggy breccia textures, and silica and phyllic alteration hosting gold minerlization. The most important exploration criteria at the Dalli deposit, however, are Miocene chalk alkaline magmatism, depth of mineralization of more than 500 meters, strong potassic and phyllic alterations, presence of specularite mineral, northeast trending structures and strong high magnetic anomalies, associated with potassic alteration.

Kalateh Pialeh prospect area is located in the Kopeh Dagh zone, approximately 15 km northeastern of Esfarayen city. The area is composed of sedimentary rocks deposited during the Jurassic, Cretaceous, and Tertiary periods, which include microconglomerate, dolomitic limestone, sandy limestone, limestone, conglomerate, and marl. Mineralization occurs as epigenetic deposits hosted by dolomitic limestone and limestone. Two mineralization stages were identified. The first stage consists of a pyrite-galena-sphalerite assemblage with replacement and breccia textures, and the second stage comprising a galena-sphalerite assemblage with vein-veinlet, open space filling, and replacement textures. Dolomite and calcite are the most abundant gangue minerals associated with lesser amount of quartz and barite. Main alterations consist of calcitization and dolomitization. Galena mineral exhibits maximum geochemical anomalies of 1843 ppm for zinc, 7 ppm for arsenic, and 11 ppm for copper. Microthermometric studies on primary fluid inclusions (LV) reveal homogenization temperatures ranging from 180°C to 265°C for stage 1, and from 167°C to 214°C for stage 2. Salinities for these stages were found to be between 7.8 wt.% to 14.5 wt.% NaCl equiv., and 11.7 wt.% to 12.2 wt.% NaCl equiv., respectively. Based on evidence such as structurally controlled mineralization, the type of alterations and their linear expansion, simple mineralogy of ore, geochemistry, and fluid inclusion data, Kalateh Pialeh prospect area is similar to lead-zinc epithermal deposits.

The nickel-bearing laterites of Noorabad area are seen in the high Zagros zone along with Kermanshah ophiolitic complex. The ophiolitic complex in the studied area includes serpentinized peridotites, isotropic gabbros, plagiogranite, sheeted dykes, basaltic lavas, andesite, and radiolarite. The peridotites of this ophiolitic complex include dunite, harzburgite, and lherzolite. The tectonic activities have caused tectonization in these rocks in such a way that it has facilitated their alteration process and created laterite zones. The alterations of peridotite rocks include serpentine, dolomite, hematite, and silicification. The laterite zone is layered and lens-shaped red horizon on peridotite rocks and is covered by Miocene limestones. Based on XRD analysis, mineralogy of the lateritic zone includes dolomite, quartz, smectite, and serpentine. The ratio of La/Y changes indicates that the studied laterites were formed in alkaline pH. According to the discrimination diagrams of the source rock, the studied laterites are karst bauxites with ultrabasic origin.

In recent decades, various methods have been developed for mineral exploration. Geophysical methods are one example, which have seen significant development in recent years and have become a common approach in the field of mining exploration, particularly in Iran. The objective of this study is to investigate the exploration area of Chahshen in terms of the potential for copper mineralization using geophysical methods and to identify promising areas for drilling. During field visits, it was observed that the main mineralization on the surface is of the oxide type, specifically malachite and azurite. Therefore, to explore the potential expansion of sulphide mineralization at greater depths, induced polarization and resistivity methods were employed. For this purpose, a rectangular array with a data collection distance of 20 meters and a line distance of 40 meters was used to determine the general trends in the region. Subsequently, six profiles were designed and measured using dipole-dipole and pole-dipole arrangements at 20-meter intervals. Through modeling of the studied sections, two-dimensional models depicting chargeability and resistivity were generated. The two-dimensional models indicated that the eastern regions exhibited more anomalies. However, due to the relatively weak nature of these anomalies, the possibility of developing a sulphide zone at shallow depths was detected. To validate the obtained results, drilling points were proposed. Profile 1 suggested a drilling point at station -10 with a depth of 45 meters, while profile 2 proposed a drilling point at station -10 with the same depth.

The Khoud copper skarn ore deposit, located about 50 km northwest of the Taft City in Yazd province, is situated within the middle part of the Urumieh-Dokhtar magmatic belt. The geology of this ore deposit is dominated by upper triassic carbonate units that were intruded by an Oligo-Miocene granodiorite porphyry. Garnet and garnet-pyroxene skarn zones had replaced marble and limestone in the contact zone with the granodiorite porphyry. In this paper, δ18O and δ13C values of calcites from limestone (sedimentary calcite), marble (metamorphic calcite), and skarn calcite have been reported and interpreted. The data shows that systematic depletion of 18O and 13C has occurred in the metamorphic and skarn calcites. The skarn calcites show the highest depletion compared to calcite in marble and limestone. Calculated models showed that this systematic isotopic depletion in the study calcites can be attributed to a magmatic fluid infiltration and fluid-induced decarbonation. Depletion in 18O and 13C of various calcite types of Khoud deposit can be explained by magmatic fluid (δ18Ofluid = +9.0‰) that reacted/interacted with unaltered carbonate rocks at temperatures of less than 400oC with X(CO2) lower than 0.05 and W/R ratio of 25 to 50%.