Provenance and tectonic settings of the Early Silurian clastic rocks in the southeast Upper Yangtze region: Constraints from the whole-rock geochemistry and detrital zircon U-Pb geochronology

Xuefeng Uplift is located on the southeast Upper Yangtze region, west of the Cathaysia. Clastic rocks in the Early Silurian Xiaoheba Formation were deposited on northwest flank of the Xuefeng Uplift. Provenance of these clastic rocks may record the Early Silurian tectonic evolution of the Xuefeng Uplift. In this paper, we present whole-rock geochemical data and detrital zircon U-Pb ages for the Xiaoheba Formation. Geochemical signatures suggest that the Early Silurian clastic rocks were deposited in a passive margin and mainly derived from felsic igneous rocks and recycled sedimentary rocks. Two major age populations of 1000-900 Ma and 900-700 Ma, as well as four minor populations, were identified. Our data suggest that the Cathaysia, especially the Wuyi-Yunkai domains, experienced intensive uplift in the Early Silurian, resulting in numerous recycled detritus (1000-900 Ma) supplied to the study area crossed through the Xuefeng Uplift. Meanwhile, age population of 900-700 Ma suggests that the Xuefeng Uplift was an additional source for the Xiaoheba Formation, indicating the uplift had already formed in the Early Silurian. Based on aforementioned evidence and published data, we consider that the formation of Xuefeng Uplift is associated with the Early Paleozoic intraplate orogenesis. The Xuefeng Uplift may have partly uplifted above sea level in this period, but it did not obstruct sediments derived from the Cathaysia. The youngest age cluster of zircons is 436 +/- 5.7 Ma, indicating the maximum deposition age of the Xiaoheba Formation and implying the initial formation time of the uplift is roughly in the Early Telychian.