PETROLOGY OF S-TYPE BIOTITE GRANITOIDS AND THEIRS MAFIC ENCLAVES, SOUTH OF ELMALI, NİĞDE

Abstract

Biotite granitoid contain mainly quartz, biotite, plagioclase, K-feldspar, muscovite as main phases with minor amphiboles, and apatite, zircon, allanite and chlorite and serisite as accessory components. In contrast, enclaves are composed mainly of plagioclase, amphibole, augite, biotite, with accessory sphene, zircon and calcite and epidote. The granitoids including enclaves with metaluminous composition, display chemical and mineralogical characteristics of S-type granitoids, such as peraluminous composition (A/CNK ratio mostly >1.15) and existence of muscovites. Granitoids are enriched in LILEs and LREEs, and depleted in HFSEs; suggesting that they were developed by crustal melting. Granitoid also have negative Eu anomalies and large ion lithophile element enrichment suggest crystal fractionation of plagioclase. Enclaves are enriched in LILEs and depleted in HFSEs and show flat REE pattern with large negative Eu anomaly, suggesting they were derived from enriched lithospheric mantle, with possible crystal fractionation involving plagioclase and amphibole. Based on field, petrographic and geochemical data, it has been suggested that volcanic-arc granitoids could be formed by intrusion of mantle-derived mafic magmas into the lower crust and with possible crustal thickening, and mingled with mafic magma producing enclaves.

Keywords

• S-tipi Granitoid, Mafik anklav, Jeokimya, Fraksiyonel kristalleşme, Orta Anadolu