Geochemistry and Provenance of Source Rock for Matoushan Formation Rocks (Late Cretaceous) in the Mouding Area, Central Yunnan

Key words: 
• geochemistry

Abstract: The Matoushan Formation, one of the most important orebearing stratum, is located in the Redbed basin of central Yunnan Province, China. Its lithology is mainly clastic rocks, including mudstone, sandstone, as well as conglomerate. The geochemical compositions of sandstones and argillaceous rocks could discriminate the tectonic setting and provenance of source rock area. Based on the geochemical signatures of major elements, trace elements, and rare earth elements of the nonmineral rocks, which picked from Matoushan Formation of Mouding, reveal that the sandstones and argillaceous rocks of Matoushan Formation, which are characterized by: ①high contents of SiO2; ②Enrichment some chalcophile elements such as Ag,Pb,Bi and Ni, loss of some lithophile elements for example Be,Ga,Rb,Y,Nb,Ta,Hf,Sr and Sn; ③LREE enrichment, HREE depletion and slightly negative Eu anomaly. The differentiate diagrams refer that the provenance of Matoushan Formation belong to passive continental margin and active continental margin tectonic setting. The primary materials of sedimentary rocks should come from the upper continental crust, and are mainly composed by felsic rocks. Combined with the data of sedimentary facies and palaeogeography, we know that the principal source rock area of Matoushan Formation are Kangdian ancient land and Ailaoshan orogenic belt.