Economic Geology
Maryam Kiaeshkevarian; Ali Asghar Calagari; Ali Abedini; GholamHossein Shamanian
Abstract
The Gheshlagh bauxitic deposit is located in ~110 km southeast of Gorgan city. Mineralogical studies indicated the presence of minerals such as boehmite, diaspore, kaolinite, hematite, goethite, anatase, rutile, chamosite, calcite, moscovite, clinoclar, provskite, quartz, and dolomite. Based on quantitative ...
Read More
The Gheshlagh bauxitic deposit is located in ~110 km southeast of Gorgan city. Mineralogical studies indicated the presence of minerals such as boehmite, diaspore, kaolinite, hematite, goethite, anatase, rutile, chamosite, calcite, moscovite, clinoclar, provskite, quartz, and dolomite. Based on quantitative mineralogy this deposite made up of (1) bauxitic clay, (2) clayey bauxite, (3) bauxitic clayey iron ore and (4) bauxitic iron ore. Calculations of the enrichment factors, with assumption of upper continental crust (UCC) as parent rocks, showed that elements such as Rb, Cs and Ba were depleted during bauxitization processes whereas elements like Y, Cr, Co, Ni, V and HREEs were encountered enrichment.Elements like Sr, Ga, Zr, Hf, Nb, Ta, U, Th and LREEs underwent both leaching and fixation processes during development of the weathered profile. Combination of the results obtained from mineralogical and geochemical investigations showed that factors such as adsorption, scavenging by metallic oxides and hydroxides, fluctuation of underground water level, type and stability of metal-containing complexes, stability of primary bearing minerals, presence in mineral phases resistant to weathering and changes in chemistry of the solutions responsible for weathering played prominent role in distribution and mobilization of elements in the studied bauxitic ores.
Mehdi Ramazani; Hojjat Ollah Safari; Homayon Safaei; Gholam Hosein Shamaanian
Abstract
Taft area is located in the central part of Urmia-Dokhtar Magmatic Arc (UDMA), adjacent to Western block of Dehshir Major Fault, in the south of Yazd city. The UDMA is one of the favorable regions for occurrence of porphyry and Skarn copper deposits with more than identified 100 copper occurrences. It ...
Read More
Taft area is located in the central part of Urmia-Dokhtar Magmatic Arc (UDMA), adjacent to Western block of Dehshir Major Fault, in the south of Yazd city. The UDMA is one of the favorable regions for occurrence of porphyry and Skarn copper deposits with more than identified 100 copper occurrences. It seemed that these Cu occurrences are related to structures, especially major and main faults. Therefore, the Taft area is selected for investigation on relationship between Cu mineralization and Tectonics (and structures). The Aliabad and Darre Zereshk are two important Cu indices in this area. In this research, the main structures are extracted and analyzed by using Remote sensing techniques, GIS environment and Field investigations. The results shown that a Structural Rhombohedral shape was created by two order faults with N150-170 and N110-120 strikes activation. In follow, the third-stage of faulting with N60-70 trend cut and offset the all of other formed structures and known as youngest order of faulting in this area. This stage of faulting was taken placed during initiation of collision between Arabian plate and Iranian Micro plates in Oligocene-Miocene episode. Because, this fault zone was formed perpendicular to collision zone, it has tension component and prepared a suitable environment for Granitoid body’s injection in this time. This phenomenon has main role in forming of Porphyry- Skarn Cu mineralization in length of this fault zone.
H. Abbasi; Gh. H. Shamanian Esfahani; F. Fardoost
Abstract
Lead and zinc mineralization occurs in limestones of the Upper Jurassic Lar Formation at Pichamto, which is located 38 km northwest of Shahroud city in East Alborz structural zone. Lead and zinc mineralization emplaced in host rocks as lens- and vein-shaped bodies due to replacement, and open-space and ...
Read More
Lead and zinc mineralization occurs in limestones of the Upper Jurassic Lar Formation at Pichamto, which is located 38 km northwest of Shahroud city in East Alborz structural zone. Lead and zinc mineralization emplaced in host rocks as lens- and vein-shaped bodies due to replacement, and open-space and fracture fillings. Petrographical and mineralogical studies indicate that smithsonite, calamine, galena, and cerrusite make the main ore minerals, whereas calcite, dolomite, aragonite, iron oxides, quartz and clay minerals are the gangue minerals. Wall-rock alteration includes carbonate recrystallization, dolomitization and brecciation. Fluid inclusion studies indicate two-phase (L+V) liquid- and gas-rich types. Final ice melting temperatures measured in inclusions rage from -19.8 to -8.3 °C. The salinity of fluid inclusions vary between 12 and 22.22 wt.% NaCl equivalent with an average value of 15.41 wt.% NaCl equivalent. Homogenization temperatures for fluid inclusions temperature range between 70 °C and 220 °C, with 176 °C as the average homogenization temperature. The salinity and homogenization temperature ranges for fluid inclusions in the Pichamto deposit suggest that ore-forming fluid derived from basinal brines, similar to hydrothermal solutions in MVT-type Pb-Zn deposits. The δ34S values for two galena samples from Pichamto deposit are +15.6 and +16.2 ‰. These values reveal that the seawater sulfate is the most probable source of sulfur. The reduced sulfur was most likely supplied through thermochemical sulfate reduction. The δ13C values of hydrothermal calcite samples are −4.16 ‰ and -9.17 ‰. The δ18O values in calcite samples are 2.6 ‰ and 0.8 ‰. The δ18O values in calcite overlap with the oxygen isotopic composition of Phanerozoic seawater, indicating possible important participation of Phanerozoic seawater in the ore-forming fluid. The negative δ13C values of calcite samples indicate that the organic materials within the host rocks contributed significantly to the hydrothermal fluid. The δ13C and δ18O values in smithsonite are -7.21 ‰ and -3.41 ‰, respectively. The light carbon isotopic composition of smithsonite reveal the secondary origin of the mineral, and the contribution of meteoric waters and waters containing CO2 derived from decomposition of organic materials in its formation.The Pichamto deposit is comparable to MVT-type Pb-Zn deposits from several points of view including tectonic setting, host rock, wall rock alteration and the source of ore-forming fluids and materials, and have formed during two primary (sulfides formation) and supergene (carbonates and silicates formation) stages.
Gh. H. Shamanian; L. Amini; Sh. Shataee; Sh. Shataee
Abstract
Grade control and ore quality determination has always been considered a challenging task for geologists and mining engineers. Ore quality is dependent on various factors such as size and geometry of a deposit, geological disturbances, and texture and ore mineralogical composition. Determination of factors ...
Read More
Grade control and ore quality determination has always been considered a challenging task for geologists and mining engineers. Ore quality is dependent on various factors such as size and geometry of a deposit, geological disturbances, and texture and ore mineralogical composition. Determination of factors which control ore grade and prediction of a suitable area are very important in terms of economics and productivity of mining operations. This study has tried to develop spatial and statistical analyses for evaluating ore quality and recognition of ore grade influencing factors at Jajarm Bauxite Mine. Through incorporating topographic, geologic and geochemical data, the effects of faults, elevation and depth on the ore grade and module (wt% Al2O3/Wt% SiO2 ratio) has been assessed. The results showed that the amounts of Al2O3 and module increased as we get closer to the faults. Furthermore, there was not any effect of faults type and strike on grade and module. A negative correlation between both elevation and depth with the amounts of Al2O3 and module indicates ore quality improvement in lowlands and shallow depths. Thus, the combination of geographic information system (GIS) methods and multivariate statistical analyses might be more efficient in geo-spatial assessments.
