The Study of Major Element Geochemistry of Migmatites in and Around Melur Region, Madurai District, Tamil Nadu, India

The study investigating the exposed Archean lower continental crust of the Southern Granulite Terrain, India, shield important constraints on the nature and evolution of the deep crust, including the formation and exhumation of Granulites. The source for the high temperature granulite metamorphism for the southern granulite terrain may be attributed to high temperature carbonatite and alkaline intrusives in an extensional setting which followed an initial crustal thickening. The Southern Granulite Terrain (SGT) in India is one of the largest exposed Precambrian deep continental crustal sections in the world consisting of multiply deformed Archean and Neoproterozoic high grade metamorphic and magmatic rock.

The Archaean and Proterozoic terrains of South India, some of the granitic intrusions contain xenocrysts which resemble the porphyroblasts of nearby migmatites. Migmatites with evidence for low pressure metamorphism and partial melting occur in the melur region. Although migmatitic rocks of the region are located near the granitic intrusions, the degree of partial melting is not related to intrusions and is irregular. It appears that partial melting and migmatization pre-date the intrusion of major granitic bodies in the region. Leucosomes in stromatic migmatites are commonly parallel to bedding planes and are mostly formed by metamorphic segregation and/or in situ partial melting (showing mafic enclaves, pinch and swell structures). The melt fraction and migmatite type depend on the chemical composition of parent rocks and the distribution of high strain zones.