Abstract:

The Tianshan CarboniferousEarly Permian riftrelated volcanism in northwestern China represents a newly recognized large igneous province. It has been deemed that an assemblage of Nbenriched arc basalt, adakite and highMg andesite occurred in the Tianshan Carboniferous volcanic successions. Divergent chemical and isotopic characteristics between this rock assemblage and the typical Nbenriched arc basalts, adakites and highMg andesites reveal that the former is not arc related. This postulated arcrelated assemblage is indeed an intracontinental volcanic assemblage that consists of crustally uncontaminated, lesscontaminated and strongly contaminated continental volcanic rocks.

Key words: Tianshan Carboniferous riftrelated volcanics; crustal contamination; Nbenriched arc basalts; highMg andesites; adakites; large igneous province; Northwest China