Geochronology and provenance of the Huangyangling Formation in the East Kunlun orogen, NW China: Insight from detrital zircon and calcite cement records

The Huangyangling Formation in the East Kunlun area, central China, is an important host for numerous Sb(-Hg) deposits. Locally, it can contain up to 11 ppm Sb (in comparison to the 0.2 ppm in the continental crust) and thus is ascribed as a potential source of ore-forming materials. However, the age and detrital source of the Huangyangling Formation are poorly constrained. In this study, we report new mass spectrometry U-Pb dating of both detrital zircon and calcite cement from sandstones of the Huangyangling Formation, which hosts the large Xiao’erkule Sb deposit. Detrital zircons from three samples can be classified into three subtypes: magmatic, metamorphic, and hydrothermal. The youngest zircons of the first two subtypes yielded a weighted mean age of 255.3 ± 3.6 Ma, which is consistent with the age of calcite cement within error, i.e., 253.2 ± 21.1 Ma (n = 45; mean square of weighted deviates [MSWD] = 0.41). Combined with the presence of paleontological fossils, the deposition of the Huangyangling Formation should be no earlier than 255 Ma. An additional set of 10 hydrothermal zircons produced a weighted mean 206Pb/238U age of 211.1 ± 2.8 Ma (MSWD = 0.78), which possibly records the age of the hydrothermal alteration and mineralization at the Xiao’erkule deposit. Most detrital zircons (110 out of 252) yielded ages between 524 Ma and 252 Ma, suggesting a dominant Paleozoic detritus source. When compared with surrounding terranes, the Tarim block to the northwest is the most probable source for the Huangyangling Formation material. The results thus indicate the presence of the Paleo-Tethys Ocean between the North Qiangtang block and Tarim block or East Kunlun orogen during the late Permian.