Polymetamorphltes of Balaram-Abu Road Area North Gujarat and Southwest Rajasthan

The crystalline rocks of Balaram-Abu Road area comprise a varied assemblage of metamorphic and igneous rocks of Precambrian age. Earlier workers have considered the rocks of the area to belong to the Alwar & Ajabgarh Series of Delhi System intruded by mafic rocks and granites. These rocks are petrologically more complex and ate much older-Aravallis or even earlier. The mineralogical assemblages of these rocks suggest metamorphism under pyroxene granulite facies, pointing to anhydrous or dry conditions.

These granulitic rocks are seen involved in Delhi deformation and later invaded by the Erinpura granite. A superimposition of contact metamorphism (due to Erinpura granite) on the granulites, has caused the development of hornfelsic rocks containing andalusite. The rocks of Balaram-Abu Road area thus comprise a polymetamorphic terrain.

The abundance of cordierite and its association with garnet and hypersthene in pelitic granulites, the occurrence of scapolite and diopside in calc-granulites, the coexistence of olivine and plagioclase in basic rocks, absence of garnet in charnockitic rocks and the development of horn felsic rocks with andalusite indicate that the rocks of the area belong to a low pressure granulite province of metamorphism.