Transition Zone from Precambrian Low-grade to High-grade Metamorphic Rocks and the Cauvery Suture Zone in Southern India: Traditional Concepts and Recent Researches

ABSTRACT The contact zone (transition zone) between the low-grade tonalitic and granitic gneisses of the Archaean Dharwar craton and the Neoarchean high-grade granulite facies metamorphic rocks of the Southern Granulite Terrane (SGT) and the existence of Cauvery Suture Zone have been topics of discussion since long. Traditionally, it was strongly believed that there has been gradual transition from low- grade granitic gneisses to high- grade charnockitic rocks from north to south and the concept of transformation finds place even today in some of the latest publications. The existence of Cauvery Suture Zone/shear zone is also being questioned by a few workers. However, accumulation of large volumes of geological, geochemical, geochronological and geophysical data in the form of innumerable publications in the last 2–3 decades has transformed the traditional concepts and several new concepts and innovative ideas have emerged. Recent multidisciplinary studies clearly demarcated the tectonic contact in the place of gradual transition zone and established the existence of Cauvery suture zone and their linkage with the evolution of SGT in terms of fold-thrust tectonics related to convergent tectonic processes.