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چکیده
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The Haji-Abad intrusion is located in Central Iran zone of 30 km southwest of Buin Zahra city. The pluton has generally granodiorite, diorite and tonalite composition, and shows granular medium-grained and poikilitic textures. It contains plagioclase, K-feldspar, quartz, hornblende, pyroxene and, accessory minerals are zircon, titanite and apatite. Zircon U-Pb age determination of this intrusion yieldes a concordant age of 40.0±0.7 Ma. Geochemically these granites are metaluminous (A/CNK =0.69-1.03), calc-alkaline and I-type in composition, exhibiting SiO2 conents ranging from 59.7 to 66.77 wt.%, and Mg# ranging from 38.6 to 52.2. The Chondrite normalized REE plot are characterized by LREE enrichment and show slight negative Eu anomalies (Eu/Eu*= 0.60-0.93). Whereas the primitive mantle normalized multi-elemental spiderdiagram indicates interaction between both mantle and crustal components in their genesis. Whole rock Sr-Nd isotopic compositions show 87Sr/86Sri ratios ranging from 0.70498 to 0.70591, positive εNd(t) values from +0.21 to +2.3, and TDM2 from 760 to 909 Ma, that together with petrographic and gechemical composition indicate this rocks originated by interaction between lower crust-derived felsic magma and mantle-derived mafic magma. Enrichment in LILEs and depletion in HFSEs, and tectonomagmatic discrimination diagrams indicate a subduction-related magmatic origin formed in an active continental margin arc environment, that is consistent with subduction of the Neotethys oceanic crust beneath the Central Iranian microcontinent.
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