Chemistry of K-feldspar and micas from Ebrahim Attar pegmatite, in Southwest of Qorveh, Kurdistan

K-feldsapr, muscovite, and biotite exist in barren granites, fertile granites and rare-element pegmatites. These minerals can be host of Rb, Sr, Ba, Li, Cs, F, Sn, Zn, Sc, Nb, and Ta. Abnormalcy in the content of these elements is a good exploration tool for discriminating barren and fertile granites. Also, K/Rb ratio and Rb, Li, Cs, F, Sn, and Zn values in mentioned minerals are useful indicators for determining the degree of granitic magma fractionation. These minerals are used in classifying pegmatites and studying their genesis. In this paper, the behavior of major elements and some indicator trace elements in three minerals including K-feldsapr, muscovite, and biotite belonging to the wall zones of Ebrahim Attar pegmatite have been studied.
Ebrahim Attar pegmatite was sampled. After polished thin sections preparation and minerals study, the contents of major elements and some trace elements such as Ta, Cs, Rb, Sr, Ba, F, and Cl in three minerals including K-feldsapr, muscovite, and biotite were measured using electron microprobe analysis (EMPA) in Russian Academy of Sciences. Finally, the analyzed data was interpreted.
In this section, the chemical composition of major oxides and some rare elements such as Rb, Sr, Ba, Ta, Cs, F, and Cl, has been investigated in order to considering the affecting processes on minerals concentration and determining the fractionation degree of the parental magma. The wall zones of the Ebrahim Attar pegmatite have low fractionation degree. During crystallization, the parental magma has interacted with mafic crustal materials and host carbonates. Increasing in Cl, Iron oxides, Mg, Ca, Mn, and Ti contents, resulted from crustal materials, have facilitated the circumstances for crystallizing the micas (especially biotite) and have prevented Ebrahim Attar transformation from peraluminous nature to highly peraluminous. So, the common economical minerals of a LCT pegmatite and tourmaline and garnet minerals haven't formed in the wall zones of Ebrahim Attar pegmatite. The poverty of Sr in parent magma has also contributed in this matter.
The parental magma of Ebrahim Attar pegmatite has interacted with mafic crustal materials and host carbonates and its fractionation degree had been low in wall zones. So, Al-bearing minerals such as tourmaline and garnet haven't engendered and LCT-type mineralizations haven't formed. Beryl concentration in intermediate and core zones confirms that the results which have been understood about a zone in a pegmatite aren't necessarily accurate for other zones or pegmatites of the studied region, because of heterogeneous distribution of crystals in the pegmatites.