The Structural State of K-Feldspars and Regional Metamorphism in the Precambrian of S-E Mysore

The Precambrian of S-E Mysore belongs to the non-charnockitic province of Fermor and the amphibolite facies of Pichamuthu, and include the rock formations between the longitudes 77°E and 79°E. Along the southern and the eastern margins of the formations in the State are the transitional amphibolite-charnockite facies rocks.

Field features of the metamorphic rocks across the prevailing N-S regional trend of the formations suggest a correspondence between the K-feldspar structural state and metamorphism.

The structural state of K-feldspars determined both by X-ray and infrared absorption techniques reveals (i) partially disordered feldspars occur in the transitional facies zone and completely disordered feldspars in the charnockites of Halagur, (ii) a decrease in the intensity of metamorphism as the Closepet belt is approached from the south-west margin and (iii) ordered feldspars of high obliquity are characteristic of amphibolite facies of granitic complex between the Closepet belt in the west and the Kolar schist belt in the east.