Genesis of the Neoproterozoic-Early Cambrian banded iron ore-bearing sedimentary rocks in the Jiertieke-Zankan iron ore belt, West Kunlun Orogenic Belt, Xinjiang (NW China)

The Jiertieke-Zankan area lies in the Taxkorgan region (West Kunlun Mountains) of Xinjiang province, northwestern China. The area contains the largest commercial iron ore belt in the region. Furthermore, this iron ore belt hosts the youngest banded iron formation identified to date (the Jiertieke iron deposit), which was deposited during the Early Cambrian. Previous studies have mainly provided evidence regarding the depositional environment and formational age of this area, but the tectonic setting and geochronology of the ore deposits remains poorly studied. Here, we provide an integrated examination of high-precision SIMS zircon U-Pb dating, along with the major and trace element geochemistry of the metasedimentary rock (a biotite-quartz schist) that host the iron ores. The Jiertieke area is characterized by bedded metapelites that contain detrital zircons as young as 546 Ma, whereas the Zankan area contains metapsammites, in addition to the metapelites, as young as 541 Ma. Multiple detrital zircons age groups ranging from 700–1100 Ma, 1600–1850 Ma, and 2250–2500 Ma, indicate the input of ancient clastic material to the basin. Based on provenance indicators and Nd isotopic data, they suggest that the metasedimentary rocks are the product of an undifferentiated felsic terrain, likely ancient upper continental crust, being eroded. Given the geochronological and geochemical features of the metasedimentary rocks, and previously identified bimodal volcanics within the region, we suggest that the tectonic setting of the Zankan-Jiertieke area was a back-arc rift basin during the Late Neoproterozoic to Early Cambrian.