مطالعه انكلاوهاي ماگمايي مجموعه پلوتونيك ملاير

The Study of Magmatic Enclaves in Malayer Plutonic Complex

Granitic rocks of the Malayer Plutonic Complex located at the periphery of Sanandaj-Sirjan zone, with NW-SE trend have a 35 x 10km extent and contains enclaves of different types. Magmatic enclaves of this area according to their shape, texture, mineralogical and chemical composition are categorized into two groups: Mafic and Felsic. Mafic magmatic enclaves have been observed in a variety of shapes (i.e. spherical, ellipsoidal, elongated and non-elongated lenses) of size <10cm->75cm. The aforementioned enclaves, while relatively similar with the host from the point of view of mineralogical composition but finer grain size and darker color, from the perspective of whole rock chemistry exhibit distinguish similarities and dissimilarities with the host. Higher contents of some oxides such as Ti02, CaO, MgO, FeO(t), MnO and lower content of other oxides (i.e. Si02, K20, Na20) is in agreement with observed mineralogical form and superiority of the ratio of modal values of Plagioclase, Biotite and Amphibole crystal in comparison to the host. Investigating the variation of fundamental elements against the scale of magmatic fractionation index (Si02) reveals a higher level of fractionation in the hosts and the role of magma mixing event in linear trend of some of oxide variations. Some of oxides (e.g. K20, Na20) have a distributed pattern in both of enclaves and hosts that related to disagreement in transformation trend of theirs between the enclave and the host (role of magma mixing and metasomatism), and coherence of the variation pattern of trace elements between them is related to the high mobility of the reduced elements and the role of compositional homogenization. Which both of them confirm the effective role of volatile substances and fluidic magma in prompting the aforementioned chemical reaction at the enclave/host interface in the molten, semi-molten and even solid phase? Considerable redistribution of K+ from the host rock (high K calc-alkaline affinity) to the magmatic enclaves to form Biotite in the enclave and especially at its interface with the host rock is among the most determinative signs of the establishment of chemical equilibrium through intermediary chemical reactions during magma mixing event.