A. Imamalipour
Abstract
The Khoy ophiolite complex in northwest Iran hosts several podiform chromitite bodies. The chromitite deposits of Aland area in this ophiolite have lenticular, tabular and irregular vein shapes and emplaced in depleted mantle hurzburgite. Chromitites have different textures including disseminated, massive, ...
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The Khoy ophiolite complex in northwest Iran hosts several podiform chromitite bodies. The chromitite deposits of Aland area in this ophiolite have lenticular, tabular and irregular vein shapes and emplaced in depleted mantle hurzburgite. Chromitites have different textures including disseminated, massive, nodular, banded and cataclastic textures. The ore bodies are surrounded by dunitic envelopes of variable thickness. Mineral chemistry of chromite grains indicate that they are recognized by #Cr [Cr/(Cr+Al)] values range between 0.66 and 0.88, #Mg [Mg/( Mg +Fe+2)] values range between 0.42 and 0.66. Cr2O3, Al2O3 and MgO values range between 45.89 and 54.95 %, 8.53-17.18 % and 8.38-14.29% respectively. There is a negative correlation among #Cr and #Mg of chromites, typical of podiform chromitites. The composition of chromites including #Cr, #Mg, their contents of Cr2O3, Al2O3, Fe2O3, MgO and TiO2 and also correlation coefficients between different components of them have conformity with total composition of podiform chromitites. Compositions of chromites in Aland area correspond to Cr-rich chromites with #Cr>0.6 and Al2O3<25%. Their lower content of TiO2 accompanied with their compositional location in TiO2 vs. Cr/(Cr+Al) and TiO2 vs. Al2O3 diagrams may reflect the crystallization of chromites from boninitic magmas in supra-subduction geotectonic setting. The bulk rock analyses of chromitites indicate that their Cr2O3 values have widespread range, 19-51.6 wt %. Compositional variations in their Cr2O3, Al2O3, Fe2O3, SiO2 and MgO components are reflections of their textural characteristics.
N. KhajehMohammadlo; E. Rasa; A. Emamalipur
Abstract
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 ...
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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.
