U–Pb geochronology of Upper Triassic – Lower Jurassic detrital sequences from SE margin of the South China Block: implications for Palaeo-Pacific subduction and tectonic evolution

Abstract

We performed U–Pb dating of detrital zircons and conducted petrological and whole-rock geochemical analyses to assess the provenance of the Upper Triassic – Lower Jurassic clastic rocks in the southeastern margin of the South China Block. Detrital zircon U–Pb ages are mainly classified into age groups of 2000–1700, 900–700, 490–390 and 280–210 Ma, consistent with derivation from the Jiangnan orogenic belt, Nanling Belt, as well as Wuyi and Yunkai domains. Lower Jurassic samples yield a special main age population of 200–190 Ma, and these detrital zircon grains have low Th/U and Nb/Hf ratios and high Th/Nb and Hf/Th ratios, showing they are derived from a continental magmatic arc. However, the cross-correlation and likeness coefficients of kernel density estimates of Upper Triassic and Lower Jurassic sandstones are 0.8608 and 0.8403, indicating that their populations are highly similar. Since the tectonic setting is the key factor in controlling the relationship between source and sink, the stable supply of identical provenance suggests that the tectonic setting did not significantly change during Late Triassic – Early Jurassic time. Sandstone petrography, regional facies distribution and the detrital zircon age patterns all reflect a consistent tectonic setting for the South China Block during Late Triassic – Early Jurassic time. The Palaeo-Pacific subduction therefore did not control the tectonic evolution of the South China Block until after the Early Jurassic Epoch.

Closing of the east Palaeo‐Tethys Ocean: Source–sink records from Middle Triassic sediments, Hainan Island, China

“…Consistent with the discovery that the Middle-Late Triassic volcanic rock sequence in the Jinshajiang-Ailaoshan area is covered by a conglomerate unconformity of the Upper Triassic Yongwanshui Formation, the Middle Triassic Lizhigou acidic magmatic F I G U R E 1 4 Geotectonic unit division model of Hainan Island (a) according to Long et al, 2022; according to Tang, 2010; according to Liu et al, 2006; according to Liu, Hu, Chen, et al, 2021;Liu, Hu, et al, 2022. rock in the southern part of Hainan Island is covered by an overlying conglomerate angular unconformity of the Upper Triassic (Gou et al, 2019;He et al, 2020). The detrital zircons obtained by Liu, Hu, Chen, et al (2021) in the southeastern sea area of Hainan Island recorded a metamorphic age of approximately 250 Ma in the Indosinian period, comparable with the high-grade metamorphism of 247-253 Ma in northern Vietnam (Owada et al, 2007) Halpin et al, 2016;Liu, Peng, et al, 2022;Xu, Xia, Lai, Long, & Huang, 2019); (d) southwest margin of the SCB (data from Chai et al, 2022;Duan et al, 2018;Hu et al, 2017;Liu, Peng, et al, 2022;Xu, Xia, Lai, Long, & Huang, 2019;Yang et al, 2012a); (e) southeast margin of the SCB (Hu et al, 2015;Kong, Xu, Tao, et al, 2022;Xu et al, 2018). MDS diagram based on Cross-correlation, Likeness, Kuiper test V value and K-S test D value (e-h), the solid line represents the closest neighbour.…”

“…Considering the above question, in this study, the detrital zircon ages of the Middle Triassic strata in central Vietnam (Kham Duc Complex in Kontum Massif, Kenta et al, 2021), west of the Ailaoshan fault (Halpin et al, 2016; Liu, Peng, et al, 2022; Xu, Xia, Lai, Long, & Huang, 2019) and on the southwestern (Chai et al, 2022; Duan et al, 2018; Hu et al, 2017; Liu, Peng, et al, 2022; Xu, Xia, Lai, Long, & Huang, 2019; Yang et al, 2012a) and southeastern margins of the SCB (Hu et al, 2015; Kong, Xu, Tao, et al, 2022; Xu et al, 2018), were collected and compared with those of the Lingwen Formation (Figure 15a–e). In the figures, it can be observed that the detrital zircon age groups in the Triassic strata of Hainan Island, central Vietnam, west of the Ailaoshan fault and the southwestern margin of the SCB all have a strong main peak at approximately 250 Ma, as well as secondary peaks in the range of 500–320 Ma.…”

“…(a–d) Synthesis and comparison of Kernel Density Estimate (KDE) diagrams of detrital zircon U–Pb ages. (a) Lingwen Formation (this study); (b) central Vietnam (data from Kenta et al, 2021); (c) west of the Ailaoshan fault (data from Halpin et al, 2016; Liu, Peng, et al, 2022; Xu, Xia, Lai, Long, & Huang, 2019); (d) southwest margin of the SCB (data from Chai et al, 2022; Duan et al, 2018; Hu et al, 2017; Liu, Peng, et al, 2022; Xu, Xia, Lai, Long, & Huang, 2019; Yang et al, 2012a); (e) southeast margin of the SCB (Hu et al, 2015; Kong, Xu, Tao, et al, 2022; Xu et al, 2018). MDS diagram based on Cross‐correlation, Likeness, Kuiper test V value and K–S test D value (e–h), the solid line represents the closest neighbour.…”

Early Jurassic initiation of the modern drainage pattern of the Dabie orogen (East China) revealed by a multi‐proxy provenance approach

“…If not carefully identified as such in the field, these paleocurrent data may lead to erroneous conclusions. Lastly, regional geological data do not support the emergence of an Eastern Plateau as early as Early Jurassic times, as shown by the littoral‐shallow sea deposits in the Upper Triassic‐Lower Jurassic of eastern China (Kong et al., 2022), and paleoaltimetry evidence for the emergence of Eastern Plateau after the Late Cretaceous with paleoelevations >2 km by 100 Ma (Zhang et al., 2016).…”