Tectonic history and occurrence of 2.4 Ga mafic dyke swarms adjacent to Godavari Basin, Karimnagar, India

Proterozoic dyke swarms are exposed partly in granulitic terrain and partly in gneissic terrain and extend in a NE–SW direction near the Godavari Basin, Karimnagar area, Central India. The Karimnagar dyke swarm petrographically exhibits two groups such as fresh plagioclase and pyroxene phenocrystic dolerite dykes and altered non-phenocrystic gabbros. Dolerites show ophitic to sub-ophitic textures and gabbros are non-porphyritic and more altered. Geochemical data suggests that these dykes are tholeiitic in nature, range from basalt to basaltic andesite in composition. The rare earth element patterns show enrichment of light rare earth elements (25–60 times) and heavy rare earth elements show flat patterns (4–10 times) supporting the presence of two varieties within the dyke swarm. A laser probe 40Ar/39Ar study and Ar isotopic analyses suggest two magmatic emplacement ages at 2400 Ma and 2200 Ma which are present within the dyke swarm. Palaeomagnetic results reveal a characteristics remnant magnetization vector of Dm = 52.5, Im = –24.5 (K = 21.81, ?95 = 8.65°, N = 12) and supports the presence of two phases of dyke activity in the region