Petrogenesis of Neogene subvolcanic rocks in Kamu, North of Isfahan

Document Type : Original Article

Authors

1 استادیار گروه زمین‌شناسی، دانشگاه پیام‌نور، تهران

2 اصفهان-خیابان آپادانا دوم-کوی بهمن-بن بست کاوه-پلاک 54

10.22108/ijp.2024.140871.1325

Abstract

The studied area is situated in the middle part of the Urumieh Dokhtar magmatic arc, which is 120 km north of Isfahan. The region comprises numerous outcrops of Neogene igneous rocks with dacite-andesite composition, which have been exposed in domes and subvolcanic bodies. The rocks display a porphyroid to porphyritic texture, with a microcrystalline groundmass. The main minerals of these rocks are plagioclase, amphibole, biotite, quartz, and opaques. The whole rock chemistry of the rocks indicates that they have a metaluminous nature with calc-alkaline affinity. They are enriched in LREE, Rb, Ba, and K, and depleted in HREE, Nb, Ti, and Ta. The spider diagram, which has been normalized to chondrite, displays a pattern of negative slope from light to heavy rare earth elements, without any evidence of Eu anomaly. The ratios of major elements and REE suggest that these rocks have properties that are intermediate between calc-alkaline and adakitic magmas, which were formed due to the partial melting of garnet amphibolite at a depth of garnet stability. Based on geochemical evidence, it is suggested that these rocks were formed in a magmatic arc located on the active continental margin. The parental magma of these rocks is likely the result of partial melting of metasomatized garnet amphibolite, which occurred under the influence of fluids and melts generated by the subducted slab.

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