Petrogenetic modeling of rock variety in the Khalkhab–Neshveh pluton,NW of Saveh,Iran |
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Authors: | MEHDI REZAEI‐KAHKHAEI DARIUSH ESMAEILY FERNANDO CORFU |
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Institution: | 1. School of Geology, College of Science, University of Tehran, PB 14155‐6455 Tehran, Iran (email: mehdi.rezaei@khayam.ut.ac.ir);2. Department of Geosciences, University of Oslo, PB 1047 Blindern, N‐0316 Oslo, Norway |
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Abstract: | The Khalkhab–Neshveh (KN) pluton is a part of Urumieh–Dokhtar Magmatic Arc and was intruded into a covering of basalt and andesite of Eocene to early Miocene age. It is a medium to high‐K, metaluminous and I‐type pluton ranging in composition from quartz monzogabbro, through quartz monzodiorite, granodiorite, and granite. The KN rocks show subtle differentiation trends strongly controlled by clinopyroxene, plagioclase, hornblende, apatite, and titanite, where most major elements (except K2O) are negatively correlated with SiO2; and Al2O3, Na2O, Sr, Eu, and Y define curvilinear trends. Considering three processes of magmatic differentiation including mixing and/or mingling between basaltic and dacitic magmas, gravitational fractional crystallization and in situ crystallization revealed that the latter is the most likely process for the evolution of KN magma. This is supported by the occurrence of all rock types at the same level, the lack of mafic enclaves in the granitoid rocks, the curvilinear trends of Na2O, Sr, and Eu, and the constant ratios of (87Sr/86Sr)i from quartz monzodiorite to granite (0.70475 and 0.70471, respectively). In situ crystallization took place via accumulation of plagioclase and clinopyroxene phenocrysts and concentration of these phases in the quartz monzogabbro and quartz monzodiorite at the margins of the intrusion at T ≥ 1050°C, and by filter pressing and fractionation of hornblende, plagioclase, and later biotite in the granitoids at T = ~880°C. |
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Keywords: | in situ crystallization Iran magma mixing petrogenetic modeling Urumieh– Dokhtar Magmatic Arc |
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