جستجوی مقالات مرتبط با کلیدواژه « آذربایجان غربی » در نشریات گروه « زمین شناسی »

The Aghbolagh area is located about 21 km north of Oshnavieh city, West-Azarbaidjan Province, NW Iran. This study showed that the Fe-Cu skarn deposit in this area can be separated into two zones, (1) Garnet skarn and (2) Garnet-pyroxene skarn. Based upon the results of electron probe micro-analysis, the garnets are chemically of andradite-grossularite type with dominant andraditic component. The pyroxenes are also chemically of diopside-hedenbergite type. The skarnification processes took place in two distinct stages, (1) prograde and (2) retrograde. The lack of wollastonite, intergrowth of garnet and clinopyroxene crystals, and the lack of replacement texture indicate that garnets and pyroxenes were formed  concurrently during prograde stage within the temperature range of 450-500ºC and ƒO2 = 10-23- 10-26. During retrograde stage at temperatures < 430ºC, the anhydrous calc-silicate minerals were altered to hydrous calc-silicates, sulfides (pyrite and chalcopyrite), oxides, chlorite, quartz, and carbonates. During this stage, at temperatures <430ºC, andradite at ƒS2 > 10-6 was altered to assemblages of quartz calcite + pyrite but at ƒS2 < 10-6 to quartz + calcite + magnetite.

Gharali lateritic iron-rich deposit is located in 20 km of Boukan city, West Azarbayedjan province. Eight surveyed stratiform outcrops stretched into thedolomite and limestone of Ruteh Formationin this region. Based on mineralogy, the analysed samples indicate scattered, veinlet, acicular, replacement, spong, flow and cataclasic textures. The observed textures represents intense tectonic effects and non-residual origin.According to the chemical data, outcrops varies from iron-rich laterite to bearing ferritic bauxite, but in general the different diagrams put this ore deposit in a bauxite- laterite ore type. The results of geochemical data indicate enriched Fe, Al, and Ti and depletion Si, Ca, Na and K in ore deposits. REEs distribution pattern normalized to chondrite reveals weak differentiation of HREEs and LREEs with slightly enrichment of LREEs. The primary rock type has been considered to be a rich- iron mafic rocks (e.g. basaltic type). Following the removal of mobile elements, which have also resulted in increasing of Al2O3 andFe2O3, during alteration processes. The results show that clay minerals, Muscovite are not a suitable host for rare earth elements in the ore body. The results of chemical analyses and correlation coefficients show that neither rutile - anatase and nor clay minerals, muscovite, illite, and also Mn minerals play an important role in in hosting the REEs.The negatively correlated with Ti and Th (0.99) indicating lack of anatase titanium and thorium, and positive correlation of consentration between the Ti with Gd (0.91) shows that the consentration of rutile and anatase. Strong positive correlation of P-REEs indicate the role of secondary phosphate minerals consentration on rare earth elements except three elements such as Gd, Tb and Er in outcrops. The strong positive correlation of P with HREEs unravel phosphatic minerals role in enrichment of REEs except for three rare elements (Gd, Tb and Er) in outcrops.The Strong correlation between Gd, Tb and Er indicates their concentration with neomorphic minerals and their resistance nature against alteration and weathering are two main reasons for their difference distribution compared to other REEs inthese deposits.

East of Shahindezh (south of West Azarbaidjan province), as a part of Irano Himalayan karst bauxite belt, comprises discontinuous layers and lenses of bauxite, laterite, and kaolin within the Ruteh carbonate formation (Middle- Upper Permian). The XRD analyses show that the lateritic ores have rather simple mineralogy, and consist of hematite, boehmite, and kaolinite as major phases accompanied by minor phases such as goethite, montmorillonite, diaspore, illite, chlorite, and rutile. According to petrographical considerations, it can be deduced that the ores have polycyclic nature and their evolution being largely affected by the function of diagenetic and epigenetic processes. Petrographical features along with mineral assemblages reveal that the lateritic ores were deposited almost in a vadose environment. Based on chemistry of major elements, the ores are categorized into three types; (1) bauxitic ferrite, (2) laterite, and (3) ferritic laterite. Distribution pattern of REEs normalized to chondrite displays a low degree of differentiation between LREEs and HREEs and also a weak negative anomaly for Eu during the lateritization processes. These features along with field relations and concentration values of Al, Ti, and Zr indicate a diabasic protolith for the ores. Consideration of Ce and Eu anomalies unveil that the intensity of lateritization is directly related to the pH increase of drained water, Eh variations, and fluctuation of water table. Results from geochemical data have furnished compelling evidence that buffering of underground descending acidic weathering solutions, dissimilaritis in degree of resistance against weathering among primary minerals, discrepancies in degree of stability of complexing legands, and chemical characteristics of elements are four key controlling factors for the distribution and behavior of major, minor, trace, and rare earth elements during lateritization in east of Shahindezh.

At the farthest end of NW Iran, the Quaternary basalts crop out in Azerbaijan province, located in Alpine – Himalaya belt and highly pleatue of Iran-Turkish, eastern Anatolian. The Quaternary volcanic units of NW Azerbaijan cover a broad compositional range from basalts, basaltic andesite, trachy andesite to trachyte.These rocks are erupted from deep tension, strike-slip faults in a pull a part basin and volcanic centers. Source of primary magmas and crustal contamination processes have certainly contributed to the understanding of the origin of basaltic rocks. Based on field area, petrography and petrology studies, 10 samples were selected for 143Nd/144Nd and 87Sr/86Sr measurements. The obtained results were correlated with other isotopic data of similar Quaternary basaltic rocks from Turkey. Isotopic study indicates that all of these rocks are derived from mantle and plot in Bulk Earth field and mantle array. The basaltic rocks in the northern area are derived from a depleted mantle and those from the southern area shows contamination by crust.

Alibaltalo bauxite deposit is situated in east Shahindezh, south west of west- Azarbaijan. This ore horizon lies along the boundary between Jurassic sandstone and Triassic dolomtite. In this study for understanding the chemical process involved in the formation of the bauxite deposite and in order to determine the role and behavior of elements on weathering process, the gain and loss and mass transfer methods, enrichment -depletion diagrams were used. the result of this study diabase sills of Doroud Formation in the area is proposed as the principal source of this bauxitic horizon.. Mass change calculations for different elements compared to an immobile element (Titanium)- with. chemical stability in weathering processes. Results showed Si, Na, K, Mg, Ca depletion while Fe, Al, Ti showed secondary enrichment.The ore body shows decreasing in total mass of -21.02 for brown horizon,-21.02 for gray kaolinite layer,-22.91 for green to gray part and -23.55 for green to gray color horizon.