Introduction
The study of granitic magmatism in any area is significant because any attempt to model the evolution of the continental crust needs a detailed knowledge of the granite-forming events. All along the Lesser Himalaya, large areas of Proterozoic and Paleozoic granitic rocks are exposed and have been investigated in detail. More recently, petrological, geochronological and isotopic data have been instrumental for the understanding of their role in the tectonic evolution of the Lesser Himalaya (Sharma, 1983: Singh and Jain, 2003; Islam et al., 2005). These granitic bodies reveal the presence of early to middle Proterozoic and Paleozoic basement rocks in the whole Lesser Himalaya. The ubiquitous character of the granites is their Peraluminous, collision-related, S-type nature and the association with amphibolite-grade metasediments.
Peraluminous leucogranites, thought to have been derived by melting of the continental crust, provide important information toward understanding the evolution of the continental crust. The obvious reason is that mantle involvement in the generation of leucogranites is almost negligible. The radiogenic and stable isotope studies of different plutons (France-Lanord et al., 1988; Nablek et al., 1992; Castelli and Lombardo, 1988; Inger and Harris, 1993; Friend et al., 2009) indicate that many are generated from heterogeneous sources. Negative εNd values and very high 87Sr/86Sr ratios for most of the leucogranites suggest that the sources had long crustal histories (Vidal et al., 1982; France-Lanord and LeFort, 1988).
Remarkable contributions on the study of basement granites from the northwest Himalaya are available but much less attention has been paid in the northeast Himalaya. Early research was concentrated only on geological and stratigraphical aspects of the region. In particular, geochemical work appears scarce. The Paleoproterozoic Bomdila granite body, associated with the extensive development of Proterozoic granitoids along a 2000 km linear belt in the Lesser Himalaya, was chosen for the present study. The granite has been examined thoroughly with a view toward understanding its petrogenesis, the regional implications of the Proterozoic granitic magmatism and its contribution in the evolution of the continental crust in the Himalaya.