نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه زمین شناسی، دانشکده علوم، دانشگاه اصفهان، اصفهان، ایران
2 دانشیار، گروه زمین شناسی، دانشکده علوم پایه، دانشگاه پیام نور، تهران، ایران
3 گروه زمین شناسی، دانشکده علوم،دانشگاه اصفهان، اصفهان، ایران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
،The granitoid body in the northern part of the Nayin ophiolitic complex includes rock units of granodiorite, tonalite, diorite, and monzodiorite with an Oligo-Miocene age, located in the central part of the structural zone of Urmia-Dokhtar. It has intruded into the Eocene volcanic and volcaniclastic rocks of the region. These volcanic rocks have undergone hydrothermal alteration due to the late-stage activities of the intrusive body and have transformed into a silicic and argillitic shear assemblage. The studied granitoid bodies have a calc-alkaline, meta-aluminous nature and belong to type I granitoids. Quartz, alkali feldspar, plagioclase, and amphibole are the main minerals, while tourmaline, sphene, zircon, and epidote occur as accessory minerals in the granitoid body. The tourmalines from the studied granitoid body are hydrothermal in origin, with a schorl-dravite chemical composition and belong to the alkali group. The chemical composition of the tourmalines indicates Fe and Mg cation exchanges at constant Ca and Al contents. In the Ca-Fe-Mg ternary diagrams, the formation sites of these tourmalines lie within the range of low-calcium metapelites, metapsammites, and quartz-tourmaline rocks poor in calcium. The substitution process in the structure of the granitoid tourmalines is mainly consistent with replacement vectors such as Ca(Fe, Mg)(Na, Al)^-1 and Ca_0.5□_0.5 Na^-1. Considering the FeO/(FeO+MgO) ratio, these tourmalines formed during the mixing of magmatic and hydrothermal fluids (influence of magmatic and hydrothermal processes and involvement of meteoric waters in the late stages of their formation). They are indicating a transitional genesis from a magmatic system to a hydrothermal environment.
کلیدواژهها [English]
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