Geochemistry and Tectonic Setting of the Amritpur Granite Series, Kumaun Lesser Himalaya, India

Pre-Himalayan granites are important in the study of evolution of Himalaya. Amritpur Granite Series (AGS) in the Kumaun Lesser Himalaya is one such Pre-Himalayan, Precambrian granite and is of three types, viz. Porphyritic Amritpur Granite (PAG), Equigranular Amritpur Granite (EAG) and Amritpur Porphyry (AP). The field, mineralogical and geochemical characteristics of AGS are consistent with those of S-type granites. The AGS is peraluminous with A/CNK (>1.1) and high normative corundum. besides high (⁸⁷Sr/⁸⁶Sr) ratio of 0.7117+0.0044. Major and trace element geochemistry of AGS indicates a syn-collisional regime and anatexis associated with pre-Himalayan collision during Precambrian times. The melt produced by anatexis has intruded into the Precambrian Bhimtal-Bhowalj Formation.