Dizhi lixue xuebao (Jul 2024)

Zircon U-Pb dating of the Dizhuanggou Formation, Changjiaoba Group in the South Qinling Belt and its tectonic significance

  • LIU Zhihui,
  • LIU Xiaochun,
  • CHEN Longyao,
  • ZHENG Guanggao,
  • HU Juan

DOI
https://doi.org/10.12090/j.issn.1006-6616.2024027
Journal volume & issue
Vol. 30, no. 6
pp. 1012 – 1027

Abstract

Read online

Objective The Changjiaoba Group, located in the Foping area of the South Qinling Belt, is one of the few poorly-studied strata in the belt. The lack of an accurate composition and formation age of these strata has restricted research on the tectonic affinity and evolution of the South Qinling Belt. Method This paper investigates the petrological characteristics and zircon U-Pb chronology of two metasedimentary rocks from the Dizhuanggou Formation of the Changjiaoba Group. Results The results show that the dominant peak detrital zircon dates of the two samples were approximately 810–835 Ma, with the youngest date range being approximately 600–700 Ma, indicating that the maximum depositional age was Neoproterozoic. This age spectrum differs significantly from that of the most exposed Devonian Heilongtan Formation of the Changjiaoba Group, but is highly similar to that of another sample from the Foping Group, which has a minimum age peak of 718 Ma and a major peak at 810 Ma. In addition, metamorphic zircons from the Dizhuanggou Formation and the Foping Group yielded ages of 207 Ma and 193 Ma, respectively. Conclusion The distinct depositional age of the Changjiaoba Group indicate the complexity of its composition. Combined with the petrological and field geological features, the Dizhuanggou Formation and a Neoproterozoic strata of the Foping Group are considered to form the transitional basement of the western South Qinling Belt. This is comparable to the transitional basement of the Wudang and Yaolinghe Groups east of the Ningshan Fault in the South Qinling Belt. Significance The identification of Neoproterozoic and Mesozoic materials in the Changjiaoba Group provides a new basis for the division of metamorphic units in the Foping area, identifying three units with different degrees of layering and metamorphism, which, in turn, facilitates understanding of the Mesozoic orogenic process in the South Qinling Belt.

Keywords