Application of two heavy mineral analysis methods in the provenance study of Irrawaddy River sediments on the southeastern margin of Tibetan Plateau

The Irrawaddy River is one of the large rivers in Asia, and its sediments record the denudation and weathering information of the orogenic belt around the Tibetan Plateau. Tracing the sediments in this basin is an important topic to explore the impact of plateau uplift on the evolution of river system. The types of heavy minerals in sediments are closely related to source rocks, which is one of the important means for provenance analysis. There are a variety of methods to identify and analyze heavy minerals, but there is a lack of comparative analysis among different methods. This paper adopted TESCAN Integrated Mineral Analyzer (TIMA) and Optical Microscope (OM) to identify and analyze heavy minerals of Irrawaddy River sediments. The main heavy minerals in the upper reaches of the Irrawaddy are amphibole-garnet- hematite/magnetite, ilmenite. The main heavy minerals in the lower reaches of the Irrawaddy are hematite/magnetite, ilmenite-garnet-zoisite-hornblende. The main heavy mineral combination of the tributary Chindwin River is zoisite-hornblende-garnet. The results of both methods indicate that the Irrawaddy sediments are mainly derived from metamorphic and intermediate or mafic rocks of tectonic units in northern Myanmar, with the Tagaung-Myitkyina Belt contributing the most to the Irrawaddy sediments and the Chindwin River basin contributing a limited amount to the lower reaches of the Irrawaddy sediments. However, there are significant differences in the identification results of heavy mineral species and individual heavy mineral contents between the two methods. The identification species of TIMA method are more abundant, and its analysis results are more coupled with the geological lithological distribution of Irrawaddy River basin. It’s also found that TIMA cannot distinguish the minerals with the same chemical properties, and OM method is not accurate in identifying the minerals with similar optical properties. Therefore, it is promoted in this paper that TIMA should be used for accurate analysis in studies requiring more precise and accurate classification of heavy minerals, while the OM method should be supplemented to distinguish minerals with the same chemical properties.