Heavy mineral assemblages and provenance analysis of the Upper Triassic in Renbu area, southern Tibet, China

Provenance of the Upper Triassic Langjiexue Group and Nieru Formation in Renbu area, southern Tibet was analyzed by heavy mineral association and index methods. Results indicate that common heavy minerals found in the Upper Triassic are mainly zircon, apatite, rutile, anatase, and tourmalin, both of the ZTR and ATi indexes from the mineral association are high, the MZi index is low but can be observed frequently, and the GZi index is low and sometimes zero; for Langjiexue Group, ZTR is inversely proportional to ATi indexes, but it is independent from the Nieru Formatin sandstones. It is herein proposed that most of the heavy minerals came from volcanic rocks, secondary intermediate to acidy magmatic rocks, very few from metamorphic and ultra-basic magmatic sources; by provenance analysis of heavy mineral ZRT index, clastic composition of the Langjiexue Group could be derived form the north where the Lhasa block could be the alternative, and those of the Nieru Formation could be from the south (perhaps Indian Shield). However, there are some contradictions among the indexes of heavy mineral associations to be distinguished in future although the feature of heavy minerals of the Upper Triassic can provide us a good clue to explore the source and tectonic setting of the flysch strata in northern Tethyan Himalays.