Precambrian mafic-ultramafic magmatism in central Indian suture zone

The Precambrian crust of Central India comprising Bundelkhand craton in the north and Bastar craton in the south were accreted along the ENE-WSW trending Proterozoic Central Indian tectonic zone (CITZ). According to this plate tectonic model. a northward dipping subduction system leading to continent-continent collision during Mesoproterozoic, explains the growth and assembly of the different lithotectonic units within the CITZ. They are identified as (1) the suture zone represented by the Ramakona-Katangi granulite belt, (2) the active continental margin (magmatic arc) represented by the Betul belt and (3) the back arc region represented by the Mahakoshal belt, each of which is characterized by conspicuous mafic and ultramafic magmatism. They have been strongly deformed and variously metamorphosed depending upon their tectonic locations with respect to convergent type plate tectonic setting. The grade of metamorphism varies from granulite facies in the suture zone to greenschist and amphibolite facies in thee magmatic arc and back arc regions. Emplacement of significant proportion of mafic and uhramafic rocks in the form of volcanics and intrusives in different tectonic domains, within an overall convergent type plate tectonic setting is indicative of pronounced mantle activity and related magmatism. The paper deals with the petrological and geochemical characteristics of the mafic-ultramafic rocks that are emplaced during the Mesoproterozoic collisional orogeny. In general, they show a distinct tholeiitic trend irrespective of their tectonic locations. But for diorite that occurs in association with the mafic-ultramafic rocks in the Betul belt, the typical calc-alkaline andesitic volcanism, so characteristics of arc type magmatism is altogether absent in the area. Ubiquitous presence of phlogopite and conspicuous LREE enrichment in the mafic-ultramafic complex of the magmatic arc region is suggestive of a possible metasomatised mantle source rock. Mantle metasomatism through plate subduction is quite likely in convergent type tectonic setting.