Petrology of the Precambrian Mafic rocks of Katekalyan Area, Bastar District, Madhya Pradesh, India

Abstract

Two types of mafic rocks are exposed around the Katekalyan region viz. amphibolites and dolerites and/or meta-dolerites. Amphibolites are further classified as volcanic amphibolites (i.e. meta-volcanics) and plutonic amphibolites (mainly dykes). Dolerites occur as small dykes. Middle Proterozoic or older rock types of the area have been intruded by mafic rocks. Volcanic amphibolites show schistose texture whereas plutonic amphibolites exhibit either schistose or granoblastic textures. Porphyroblastic texture is also observed in some thin sections of both types. Dolerites and/or meta-dolerites show ophitic or sub-ophitic texture. Geochemically all types of mafic rocks may be classified as sub-alkaline high Fe-tholeiites and are enriched in Rb, K, Nb, Sr, Zr, Ti and Y than the primitive mantle. Incompatible elements concentration suggest genetic links between all types of mafic rocks and are indicated to be emplaced in the "within-plate" environment. On the basis of petrological and geochemical data presented, it is suggested that ferro-tholeiitic magma has been emplaced at least twice, one has been metamorphosed (i.e. older emplacements - amphibolitic types) and another is fresh (i.e. younger emplacements - doleritic types). It is also suggested that probably amphibolite dykes act as feeder dykes for volcanic amphibolites (i.e. meta-volcanics). Almost similar mafic rocks, particularly dykes, have been observed in the Antarctic shield which supports the juxtaposition of India and Antarctica and corroborates the views on reassembly of East Gondwanaland.