فصلنامه زمین شناسی اقتصادی
سال شانزدهم شماره 4 (پیاپی 43، زمستان 1403)

The Joftrud prospect area is located in the central Lut Block and 60 Km of Birjand city. The area comprises outcrops of pyroclastic (andesitic tuff), volcanic (hornblende andesite, pyroxene andesite, basaltic andesite), intrusive (diorite porphyry, monzodiorite, gabbro) rocks. Mineralization as vein-type with mostly northeast-southwest trend has formed in andesitic units. Main alterations are consist of silicified, argillic, carbonate and propylitic. Primary minerals include chalcopyrite, pyrite, and secondary minerals are consist of chrysocolla, chalcocite, covellite, azurite, malachite, goethite, and hematite. Maximum of geochemical anomalies in veins are for copper 6000 ppm, lead 2934 ppm, zinc 6904 ppm, and Au 144 ppb. Quartz-sulfide veins are formed of fluids with temperature of 265 to 408ºC and salinity of 11.1 to 19 NaCl wt. % equivalent. Decreasing temperature and fluid mixing by high-salinity fluid can cause metal deposition. According to the available evidence of structural control of mineralization, alterations and their narrow expansions, mineralogy, texture, fluid inclusion data and depth of formation, prospect area is similar to intermediate sulfidation deposit.

Lalehzar igneous rocks are located in the southeast of Iran, the SE of Saveh-Naein-Jiroft magmatic belt. In this study, zircon U-Pb dating, and whole-rock geochemistry and Sr-Nd isotopic analyzes were performed on granitoid rocks (granite and granodiorite) and associated volcanics. The granodiorites and granite include quartz, plagioclase, alkali feldspar, biotite and amphibole with different percentages. New zircon U–Pb ages show granitic magmatism at ~28 Ma, followed by emplacement of granodiorite at ~24 Ma. Both granitoid and volcanic rocks are characterized with depletion in Nb and Ti and enrichement in large ion lithophile (LILE) and light rare earth elements (LREE). Their calc-alkaline arc geochemical signature (low Sr/Y ratio of almost <55), negative to positive Eu anomalies (Eu/Eu∗⁠ =0.6–1.3) and the negative to positive εNd (t) values of -1.4 to +0.27 offer formations in an orogenic belt.  The geochemistry and isotopic results show that they are formed during partial melting of the lower crust (amphibolite) which is impelemented by inherited mantle source components in a subduction zone.

The Oligocene Nordoz intrusive complex is located in the eastern region of Siehroud, within the East Azerbaijan province, and within the Alborz-Azerbaijan structural zone. The results of field studies have identified the presence of gabbro diorite, monzodiorite, monzonite, tonalite, granodiorite, and granite within the region. The geochemical characteristics of these rocks indicate that they belong to the metaluminous type I granitoid classification. The rocks display calc-alkaline to high-potassium calc-alkaline and Shoshonite series characteristics, exhibiting an enrichment of LREE elements relative to HREE, a positive Pb anomaly, and a depletion of Nb and Ti elements. The presence of disequilibrium textures, such as sieve texture and zoning in plagioclase, suggests the existence of multiple magma chambers and mixing between them. The isotopic geochemistry indicates that a closed system process and crystal differentiation are the primary processes of formation, with a combination of DMM and EMII identified as the principal sources for magmas in the region. This behavior can be explained by contamination of magma derived from a depleted asthenospheric mantle with lithospheric sediments during oceanic crust subduction and upper mantle wedge metasomatism. In summary, the magmatic plateau of Azerbaijan has been affected by tectonic processes and lithospheric thinning during the Eocene-Oligocene period.

The Mesozoic ophiolitic mélange of Naein is located to the west of the Central-East Iranian Microcontinent (CEIM). In this ophiolite, the mantle peridotites cross cut by greenish, coarse-grained hornblendite dykes with up to 50 cm width. These dykes cross cut by carbonate veins with a few millimeters to a few centimeter width. Hornblendite dykes composed of Cr-spinel, magnesio-hornblende, chlorite, ilmenite, tremolite, calcite and dolomite. Hydrothermal spadaites (MgSiO2(OH)2·H2O) are formed in the late-stage phase. The chemical compositions of hornblendites indicate that hornblendes are magnesio-hornblende in composition (with a mean Mg# = 0.93) and chlorites are penninite and clinochlore, with a mean Mg# of 0.94. The Mg# and Cr# of Cr-spinels are 0.45 and 0.66, respectively. The presence of abundant hydrous minerals (hornblende and chlorite) and carbonate veins, as well as the chemical characteristics of hornblendes and Cr-spinels, indicates the non-magmatic origin of these dikes and veins, which were formed by the interactions of seawater-derived fluids with the uppermost mantle peridotites. The mineralogical and chemical characteristics of hornblendites demonstrate the mobility of elements such as Mg, Ca, Si, Al, Na, Cr, Fe, Ti and REE during the circulation of fluids derived from seawater within the uppermost mantle peridotites. This study suggests that the percolation of seawater ingression fluids in the uppermost mantle peridotites, resulted in the formation of hornblende dikes and, in the late-stage phase, the development of carbonate veins that contain calcite, dolomite and spadaite.

In the present study, we aimed to gain a comprehensive understanding of the Eileh 1 iron ore deposit located in Taybad City, Razavi Khorasan Province. A three-dimensional (3D) model was developed using specialized software, which incorporated lithological logs from boreholes, cross-sectional lithological profiles, and assay estimations covering the entire ore deposit area. The dominant lithology of the region consists of altered limestone and dolomite, as well as altered sediments, including sandstone, siltstone, and shale. To estimate the reserves, we employed both the classical inverse distance weighting (IDW) method and the geostatistical kriging method, tailored to the specific conditions of the ore deposit. Variogram analysis indicated that data values varied with distance and direction, revealing geometric anisotropy within the deposit. The maximum search radius in the direction of 0° azimuth was 42.6 meters, the average search radius at 90° azimuth was 10.6 meters, and the minimum search radius in the vertical direction (0° azimuth) was 32 meters. The dataset included topographic information and data from 177 boreholes, totaling 6,936 meters deep. Following geometric modeling and constructing a block model for the deposit, we estimated reserves for various iron-grade thresholds and compared the results of both methods. The findings indicate that the reserve estimates from the two methods were quite similar. While the inverse distance weighting method is recognized as one of the most accurate classical techniques for reserve estimation, the kriging method demonstrated greater precision and reliability. This is attributed to Kriging’s ability to account for the spatial structure of the deposit, its unbiased nature, and its lower estimation variance. The findings indicate that the reserve estimates from the two methods were quite similar. While the inverse distance weighting method is recognized as one of the most accurate classical techniques for reserve estimation, the kriging method demonstrated greater precision and reliability. This is attributed to Kriging’s ability to account for the spatial structure of the deposit, its unbiased nature, and its lower estimation variance.

The Kalateh Dasht deposit is situated in the northern part of the Central Iran structural zone, northeast of the Toroud-Chah Shirin magmatic arc. The Cu-Au mineralization is hosted by diorite porphyry subvolcanic rocks with a post-Eocene age. The mineralization occurs in the form of hydrothermal breccia and vein-veinlet along a fault zone with an approximately N30E extension and vertical dip. Several mineralized veins consisting of pyrite, chalcopyrite, sphalerite, bornite, galena, barite, hematite, chalcocite, covellite, malachite, and chrysocolla are observed parallel to each other in this fault zone. The gangue minerals include comb quartz, crustiform, and a small amount of amethyst as veins and blades. SEM data indicate the presence of gold within sphalerite. The porphyritic diorite host rocks have been significantly altered due to the action of hydrothermal fluids, resulting in sericitic, siliceous, and propylitic alteration (chlorite, epidote, and calcite), particularly at the margins of mineralized veins. The fluid inclusions in calcite and barite host minerals reveal that homogenization temperatures range between 143.2 and 213.1ºC and salinity varies between 3.06 and 7.73 wt.% NaCl eq. In close proximity to this ore deposit, an argillic alteration zone and other mineralization systems in this region increase the likelihood of a porphyry system at greater depth.