Petrology
Seyevahid Shahrokhi
Abstract
The Dalayon granitoid is located in the south of Borujerd and, is part of the Sanandaj-Sirjan zone. The lithological composition includes granodiorite, granite, pegmatite-granite, tonalite, quartz diorite, tourmaline-bearing pegmatite, and quartz-tourmaline veins intruded into volcanic and metamorphic ...
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The Dalayon granitoid is located in the south of Borujerd and, is part of the Sanandaj-Sirjan zone. The lithological composition includes granodiorite, granite, pegmatite-granite, tonalite, quartz diorite, tourmaline-bearing pegmatite, and quartz-tourmaline veins intruded into volcanic and metamorphic rocks. The minerals set of granodiorite mass with color leucocratic to mesocratic index mainly minerals quartz, plagioclase, orthose and microcline and secondary minerals biotite, muscovite, zircon, garnet, apatite, rutile, leucoxene, and sphene. The indicator mineral of ferromagnesian in these rocks is biotite, which has a primary nature rich in magnesium and poor in chlorine in composition. The value of Fe/Fe+Mg ratio shows an average 0.44(apfu), that indicates that the studied micas are placed in the range of biotite and between siderophiles and anite poles. The average crystallization temperature of biotites is 681ºC and the average formation pressure is 2.95kb based on the total aluminum of biotites, which indicates formation at a shallow depth. Based on the proportions of MgO- FeO-Al2O3 in biotites, the magma that produced this mineral is of the calc-alkaline type. The existence of relatively high fugacity of oxygen and oxidant environment indicates magma of mantle-crust origin and host rock of magnetite granitoid series and I-type granitic rock for biotites.
Economic Geology
Seyevahid Shahrokhi
Abstract
The chemical composition of chlorite group minerals show that physicochemical condition of crystallization and their formation. The chemical analysis of chlorite from biotite alteration has done based on 30 points of 8 rock samples by electron microprobe. The composition of chlorite samples is located ...
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The chemical composition of chlorite group minerals show that physicochemical condition of crystallization and their formation. The chemical analysis of chlorite from biotite alteration has done based on 30 points of 8 rock samples by electron microprobe. The composition of chlorite samples is located in repidolite- pychnochlorite domain. The mole fraction in the interlayer phase, range from 0.97 to 0.99, indicating a complete lack of smectite layers and purity of chlorite. Calculation of the structural formula of chlorites in Malvak area show that the number of silicon atoms are in the range of 2.64 to 2.91 (apfu) and the sum of the octahedral cations are 6 (apfu). Chlorites of the Malvak area are trioctahedral type. The low titanium content of chlorites, the presence of titanium minerals coexite with chlorite cleavage, and the presence of early biotite crystals are evidence of biotite to chlorite alteration. The mean temperature of chlorites in the Malvak area is 340 ºC, which corresponds to the temperature obtained with the geothermometry of biotite-altered to chlorites. Mesothermal type fluids from the granitoid mass in the study area have been effective in chlorite occurrence. Also, regional metamorphism has played an important role in the chlorite formation.
S. A. Hosseini; S. V. Shahrokhi; P. Afzal; T. Farhadinejad; H. Imanzadeh
Abstract
Collected geochemical data from stream sediments, can be used in regional exploration and identifying anomalies in reconnaissance stages. In this research in order to regional exploration studies, multifractal modeling approaches include concentration-area and concentration-number has been used and geochemical ...
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Collected geochemical data from stream sediments, can be used in regional exploration and identifying anomalies in reconnaissance stages. In this research in order to regional exploration studies, multifractal modeling approaches include concentration-area and concentration-number has been used and geochemical anomalies for index elements (As,Sb,Au and Cu) has examined. 855 of stream sediment samples were collected The Alut 1:100,000 sheet and analyzed by ICP-MS method in the laboratory of Geological Survey of Iran (GSI). Then, statistical parameters and histograms were performed on the elements. Then, using fractal methods concentration-area and concentration-number, related anomalies in this sheet has prepared and anomaly maps were drawn. Respect to the Geological setting, existing structures and predominant lithology the results of two methods (concentration - area and concentration – number) has compared in the area. The results of the two methods showed that concentration of these elements has increased in central and southeast regions and formed promising areas. Although concentration-number method due to more extensive geochemical halo included well-known deposits (Barika mine) and also accommodate expected mineralization in Sanandaj - Sirjan zone.
