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چکیده
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Haji Aabad granitoid (HAG) is emplaced within Eocene volcanic rocks in the central part of the Urumieh-Dokhtar magmatic assemblage (UDMA) of Iran, and comprises of granodiorite and diorite. HAG mainly consist of K-feldspar, quartz, plagioclase, pyroxene and hornblende with accessory minerals of titanite, apatite, zircon, and Fe–Ti oxide. Plagioclase grains in the rocks show a compositional range from An9.8 to An60.2, and The compositions of K-feldspar crystals vary from Or77 to Or95. Thus all of plagioclases can be classified as labradorite, andesine, and oligoclase. Amphiboles range in composition from magnesio-hornblende to tremolite-hornblende of the calcic-amphibole group. Most pyroxenes principally plot in the field of diopside. They are classified as the “Quad” or Ca-Mg-Fe clinopyroxenes. Clinopyroxenes are rich in Ca (Wo46.67) but poor in Na (Na2O<0.44). Their compositions range from En38Fs9Wo43 to En44Fs15Wo49. Opaque minerals in the HAG are represented by magnetite. The HAG yields crystallization pressures of emplacement with average 1.9 kbar (equivalent to depth of 6.7 km). The estimated temperatures using twofeldspar thermometry range from 531 to 890 °C, with average 724 °C. The calculated temperatures for clinopyroxene crystallization range from 1009 to 1144 °C (with average of 1090 °C). These temperatures are higher than estimated temperature by feldspar thermometry, indicating that the pyroxene and feldspar temperatures represent first and late stages of magmatic crystallization of Haji Abad granitoid, respectively. When the samples of the HAG are plotted on the AlVI+2Ti+Cr versus AlIV+Na diagram, most of them plot above the line of Fe3+ = 0, indicating they crystallized under relatively high oxygen fugacity or oxidized conditions. According to the plagioclase-melt hydrometer, the average of water contents in the HAG is about 3.2 wt.%. The calculated water content is consistent with generation environment of Haji Abad plutonic rocks in an active contin
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