PETROLOGY AND GEOCHEMISTRY OF THE GRANITOIDS OF CENTRAL GNEISSIC COMPLEX IN THE KAMENG DISTRICT, ARUNACHAL-PRADESH

Petrology and geochemistry (major, minor and trace elements including REE) of the different granitoids from Central Gnessic Complex indicate that, (a) the dominant Palaeoproterozoic migmatite, hornblende granit e gneiss, two-mica granite and augen gneiss are syn-kinematic, autocht honous, peraluminous, low-Ca granodiorite, with the first three being of S-type formed by high-degree (> 50%) anatexis of sediments of psamm opelitic composition, whereas the augen gneiss is I-type formed by par tial melting of a basic rock of mantle affinity coupled with notable c rustal contamination and affected by soda metasomatism; (b) the minor Mesoproterozoic Salari granite is late-kinematic, allochthonous, metaa luminous, epidote-bearing, high-Ca monzogranite of I-type formed by pa rtial melting of basic rock from crustal depth; (c) the youngest (ca. 30 Ma) tourmaline granite is post-kinematic, allochthonous, strongly p eraluminous, high-level syenogranite of S-type, with its parental melt derived from a peraluminous granitoid by anatexis induced by large vo lume of volatiles and fluids, and (d) tectonically, these granitoids a re of 'syn-collision' type.