Abstract:

The genesis study of Erlangping Group is the key to reveal its sedimentary environments and tectonic settings. By studying the geological and geochemical  characteristics(SiO₂=61.35%~96.01%，Si/Al=2.77~51.53)of three types of cherts in Erlangping Group in east Qinling orogenic belt，it is believed that the cherts in Erlangping Group are impure silicalite. The normalized REE distribution patterns of chondrite and their characteristic values(∑REE-high，∑LREE-rich， ∑HREE-depletion，negative Eu and Ce anomaly)，the contents of the major elements (Al₂O₃，TiO₂)and the trace elements(Nb，Rb，Th)indicate that the cherts are hydrothermal sediments and have a few continental margin materials， but the cherts formed at the west of Nanyang basin contain more. Comprehensive analysis of geochemical characteristics of cherts shows that the cherts in Erlangping Group are formed in different marine environments， the cherts formed at the west of Nanyang  basin are deposited in continental margin basin environment， and those formed at the east of Nanyang basin are deposited in pelagic environment，so Erlangping Group is marked by back-arc basin setting.

Key words: Erlangping Group, chert, geochemistry, sedimentary environment, East Qinling