Potassium - Argon Ages of the Amritpur Granite, District Nainital, Kumaun Himalaya and its Stratigraphic Position

Potassium - Argon ages of muscovite and biotite, separated from the Amritpur Granite, District Nainital, Kumaun Himalaya, determined in the 'Geochronology Laboratory' of the IGEM Institute of the USSR Academy of Sciences, Moscow, are 1880 ± 40 m.y. and 1330 ± 40 respectively. The granitic body apparently shows intrusive relationship with quartzite-metavolcanic association of the Bhimtal-Bhowali area of which the latter has given a whole rock K-Ar age of 228 ± 10. These reveal that the Amritpur Granite is composite in nature intruded in Middle Proterozoic Period (1880 ± 40 m.y.) and later remobilised at different periods with the development of tourmaline granite in the peripheral parts, as the latest phase.