Age and provenance of Cambrian sequences in the Nanping–Ninghua–Ganzhou Tectonic Belt: Implication for tectonic evolution of the Cathaysia Block. (25th May 2020) - Jiang, Jian
Abstract : To investigate the tectonic framework of the basement of the Cathaysia Block, we selected the representative Cambrian strata in different parts of the South Wuyi area along the southern Nanping–Ninghua–Ganzhou Tectonic Belt (NNGTB). Integrated petrographic and geochronologic studies, as well as geochemical analysis, were carried out on the low‐grade metasedimentary rocks of the Niujiaohe Formation in south Jiangxi Province and the Lintian Formation in south‐west Fujian Province. The metasedimentary rocks of the Niujiaohe and Lintian formations are dominated by metasandstones and metasiltstones. They have low chemical index of alteration (52.6–77.4) and high index of compositional variability (0.84–1.42) values, suggesting weak chemical weathering and low clastic maturity. Their relatively low Th/U (4.12–6.81) and Rb/Sr (0.68–5.97) ratios reflect a simple recycling history. Detrital zircon geochronological studies indicate prominent source differences for the clastic rocks along the NNGTB. In the Ruijin area, the Niujiaohe Formation displays a Neoproterozoic peak at ca. 741 Ma, which is consistent with the widespread intermediate‐acid igneous rocks in the NNGTB. By contrast, the Lintian Formation from the Changting and Mingxi areas contains more pre‐Nanhuan detritus, which are predominantly in Grenvillian ages. Furthermore, the peak numbers of detrital zircon ages increase gradually from the Ruijin to Changting and Mingxi areas, indicating that their sources become more diverse. The geochemical features, in combination with detrital zircon age distributions, indicate that the Niujiaohe and Lintian formations are probably deposited in a back‐arc basin. These evidences suggest that the Cathaysia Block was assembled by multiple terranes during the Neoproterozoic to the Early Palaeozoic.