Petrogenesis of granitoid rocks in the Kangding Complex, western margin of the Yangtze Craton and its tectonic significance.

Gneissic granitoid rock suite in the Kangding Complex, located in western margin of the Yangtze Craton, comprises mainly tonalite, granodiorite, hoar fine-grained monzogranite with a little of pink coarse-grained monzogranite. SHRIMP zircon U-Pb isotopic dating revealed that the tonalite and granodiorite emplaced at 797 similar to 795Ma, and a new SHRIMP zircon U-Pb chronological data yield a weighted average age of Pb-206/U-238 age of 767 +/- 24Ma for a hoar fine-grained monzogranite (sample Kd-18), interpreted as emplacement age of the hoar fine-grained monzogranite. Tonalites, granodiorites, hoar fine-grained monzogranites, comprising dioritic enclaves in the gneissic granitoids, are characterized by right-inclined chondrite-normalized REE patterns with high (La/Yb)(N) values and without Eu anomalies, and significantly negative Nb, Ta, P and Ti in primitive mantle normalized multi-element spider diagrams. Whereas, pink coarse-grained monzogranites show flat chondrite-normalized REE patterns, strongly negative Eu and Nb, Ta, Sr, P and Ti anomalies but LILEs enrichment. Sm-Nd isotopes analyses reveal that the granitoids have epsilon(Nd) (t) = -0.57 similar to +5.67, and most of the samples epsilon(Nd) (t) > 0. Integrated features of geology, petrology to petrochemistry and Sm-Nd isotopes, the magma of the tonalite, granodiorite and hoar fine-grained monzogranite may be derived from partial melting of juvenile basaltic rocks and greywacks with depleted mantle affinity under high pressure condition, and the magma of the pink coarse-grained monzogranite could come from supracrust materials at the relative lower pressure condition. Petrogenesis of these granitoids, combining with tectonic discrimination, suggests that the Neoproterozoic Kanding Complex in the western margin of the Yangtze Craton could be produced in a tectonic setting of the subduction-related active continental margin.