Provenance analysis of the Palaeogene clastic rocks in the western part of northern Qaidam Basin

The provenance analysis of the sediments is considered to be of vital importance to the study of tectonic evolution, basin deposition and the division of petroleum areas in the orogenic zones. In the light of clastic and lithic composition, heavy mineral assemblage and ZTR index, in integration of the previous results of research, five provenances have been distinguished for the Palaeogene clastic rocks in the western part of northern Qaidam Basin. (1) The Niudong provenance is located in the eastern part of the Altun Mountains. The heavy mineral assemblages contain stable and higher contents of tourmaline, which are different from those in the adjacent areas. The clastics dominantly consist of quartz and feldspar with high contents, with minor amount of carbonate rock debris in the lithic fragments. (2) The Lengbei provenance is located in the Lesser Serteng Mountains. The contents of titanite and hematite are remarkably higher in the heavy mineral assemblages, and the clastic components are characterized by higher contents of lithic fragments. (3) The Saixi provenance appears in the western part of the Serteng Mountains, where there exist higher contents of tourmaline and hornblende and uniform clastic compositions. The parent rocks are made up of dominated metamorphic and igneous rocks, with minor amount of carbonate rock debris. (4) The Saidong provenance lies in the eastern part of the Serteng Mountains, where the contents of leucoxene are noticeably higher than those in the adjacent areas. The clastics mainly consist of quartz and feldspar, and the lithic fragments are dominantly composed of metamorphic, igneous and sedimentary rock debris. (5) The Jiulongshan provenance occurs in the Jiulong Mountains and Luliang Mountains. Different from those in the other above-mentioned provenances, the ultra-high contents of garnet and lower contents of magnetite represent the characteristics of the heavy mineral assemblages in the provenance. The clastics are uniform in composition, and the parent rocks are dominantly made up of metamorphic and igneous rocks, with minor amount of noncarbonate rock debris.