Palaeomagnetic and Geochemical Study of Precambrian Kawar Volcanic Formation (Bijawar Traps), Central India

The Bijawar Group of rocks unconformably overlie the 2555 Ma Bundelkhand Granite massif and contain in its lower sub-group the Kawar Volcanic Formation exposed near the Bhusor village (24° 39'N; 79° 51' 3O"E) SW of Panna.

The Kawar volcanics are fine grained, magnesium rich tholeiites, basalt to basaltic andesite in composition, with spinifex texture. The immobile trace elements suggest that these volcanics were emplaced in a continental environmental setting in rapid succesion with a low residence time. The REE pattern reveals that these rocks were derived from a depleted mantle source. A comparison of average chemical compositions of Mahakoshal and Gwalior basalts with a Kawar volcanics suggest that these were originated in different environmental conditions although they had previously believed to be the same.

Detailed AF and thermal demagnetization of 20 oriented block samples from 4 sites revealed a characteristic stable remanence in the Kawar volcanics with a declination of 254.9 and inclination of -64.0 (K = 70.75, α₉₅, = 8.32, N = 4). The corresponding VGP, located at p = 27.6° N, Lp = 129.3° E (δp = 6.29, δm = 13-26), appears to be approximately 2000 Ma when compared with other Indian Precambrian data. This age is in agreement with the stratigraphic position above the Bundelkhand granite massif.