Mica bearing pegmatites of Holenarasipura and Karighatta Schist belts of Western Dharwar Craton, Karnataka, India.

Abstract

Several pegmatite bodies of Precambrian age are located in and around the Holenarasipura and Karighatta schist belts of Hassan and Mandya districts respectively in the Dharwar Craton in Karnataka, These are ranging in size from few centimeters to more than 10 meters in width, with a maximum extension of about one kilometer. The pegmatites in the study area are of tabular, lensoidal and lenticular bodies, within the country rocks. Most of the pegmatites are found to be as concordant and few are discordant type of intrusions. Based on the mineralogical assemblage, the pegmatites of the study area are classified into simple and complex pegmatites. The characterization has been made for pegmatites on the basis of their petrographic, modal analysis, X-ray diffraction studies and also by field observation. The modal analysis has shown that the pegmatites fall mainly in the field of alkali feldspar granite, granite and granodiorite in QAP diagram with an indication of feldspar-rich composition followed by quartz, muscovite, biotite, garnet, zircon and apatite in decreasing abundance throughout the area. KeywordsPegmatites, Petrography, X-ray diffraction, Modal analysis, Holenarasipura and Karighatta