Provenance of the Qingshuijian Formation (Late Carboniferous), NE China: Implications for tectonic processes in the northern margin of the North China block

The Upper Carboniferous Qingshuijian Formation in the Western Hill, NE China, was deposited disconformably on a Lower Paleozoic platformal carbonate sequence. The provenance and the tectonic setting of the source area of the Qingshuijian Formation were studied using sandstone petrography and mudstone geochemistry. Sandstones consist mainly of quartz and (meta) sedimentary lithic fragments and are classified as litharenite. Feldspar is lacking in sandstones, and negative Eu anomalies similar to those displayed by Post-Archean Australian Shale (PAAS), along with depleted Ca, Na, Cs, and Rb, and low K2O/Al2O3 ratios in mudstones all suggest that feldspar was scarce in the source terrane. Abundant sedimentary lithic fragments in sandstones, low values of the index of compositional variability (< 1), values of chemical index of alteration higher than PAAS, depleted transition metals, higher total REE abundances and more fractionated REE patterns than PAAS all indicate that the source area was dominated by sedimentary rocks. Geochemical and sandstone tectonic discrimination diagrams suggest that the provenance of the Qingshuijian Formation was a recycled orogen composed of quartzose to lithic sedimentary rocks that were deposited originally in a passive margin setting. The Yinshan Uplift, located in the northern margin of the North China block, that formed as a result of the collision between the North China block and the Mongolian continent, is interpreted to be the provenance for the Qingshuijian Formation. During collision the intervening sea floor was subducted northward, and an accretionary prism was elevated, forming a barrier to arc-derived sediments.