Timing of Metamorphism and Provenance of the Metamorphic Basement of the Xiangshan Uranium Orefield, Jiangxi Province, China

Abstract

The origin, age and evolution of the Precambrian metamorphic basement of southern China provide useful insights into early crustal development. Here, we present new laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) U–Pb age data for detrital zircons from five samples of the Precambrian metamorphic basement of the Xiangshan uranium orefield. Two of these samples, from the northern Xiangshan volcanic basin, yielded a total of 140 U–Pb ages that cluster within the Neoproterozoic (773–963 Ma; 79.3% of data points), with the rest being scattered through the Paleoproterozoic and Mesoproterozoic, along with a single Archean age. These ages indicate that this basement material is associated with the Cathaysia Block. In comparison, the 172 concordant ages from the other three samples from the southern part of the Xiangshan volcanic basin cluster within the Neoproterozoic (767–944 Ma; 59.8%) as well as the Proterozoic (37.8%) and the Archean (2502–2712 Ma; 14.5%). These samples are also free of zircons with Grenvillian ages, indicating that these units are associated with the southeastern Yangtze Block. Combining these data with the geochemistry of these units, which suggests that the metamorphosed sedimentary rocks within the northern and southern parts of the Xiangshan basin have a common component from a magmatic island arc that formed during the early Neoproterozoic, we infer that the basin was located along the boundary between the Cathaysian and Yangtze blocks. In addition, the zircons within the samples from the southern and northern parts of the Xiangshan basin show different pre‐Neoproterozoic (963 Ma) age populations but similar post‐Neoproterozoic zircon populations, indicating that the amalgamation of the Cathaysian and Yangtze blocks occurred after the Neoproterozoic (960 Ma), with magmatism peaking at 830 Ma and rifting starting at ∼770 Ma, leading to the subsequent deposition (from bottom to top) of the Shenshan, Kuli, and Shangshi formations.

An Early Paleozoic Tectonic Mélange at the Western Margin of West Cathaysia: Constraints from Organic‐walled Microfossils

“…Although their phylogenetic affinities and classifications are still to be solved, they have a great potential for dating late Neoprozerozoic to Early Paleozoic sedimentary rocks (Moldowan and Talyzina, 1998;Talyzina and Moczydlowska, 2000;Servais et al, 2004;Nowak et al, 2015;Yin, 1995), including low-grade clastic meta-sedimentary sequences (Montenari et al, 2000;Bian et al, 2001;Beccaletto et al, 2005). Organicwalled microfossils have previously been noted in the "Shenshan and Kuli formations" in the study area (DJMRJP, 1997;Ling et al, 2004;Guo et al, 2018), but no description has been provided.…”

“…770 Ma, based on the youngest peak ages. Guo et al (2018) reported U-Pb zircon ages of 773 ± 13 Ma and 767 ± 12 Ma from a turbidite in the Xiangshan area, about 10 km east of the study area (see also Yu et al, 2018). It should be noted that the youngest zircon ages obtained by Wang et al (2020) are ca.…”

“…1). Thick volcanic and sedimentary rocks (including turbidite) with ages of 850-700 Ma were broadly distributed in the Wuyi domain (Guo et al, 2018;Yu et al, 2018;Jiang et al, 2019;Qi et al, 2019). The late Neoproterozoic to early Paleozoic sedimentary sequences in the West Cathaysia terrane are dominated by thick sequences of clastic rocks, with detritus derived from Gondwana sources (Yao et al, 2014).…”

“…The Neoproterozoic strata in central and southern Jiangxi belong to the West Cathaysia terrane, including the lower Shenshan Formation and the upper Kuli Formation. These rocks are characterized by a series of bathyal facies turbidite sequences and have experienced greenschist-facies metamorphism (DGMRJP, 1997;Yang et al, 2012;Guo et al, 2018).…”

Neoproterozoic–Early Paleozoic Tectonic Evolution of the South China Craton: New Insights from the Polyphase Deformation in the Southwestern Jiangnan Orogen

“…4) (Li, 1999;Yao et al, 2014c), which were subsequently exposed at the surface. In the central JO, the initial collision and final assemblage of the Yangtze with the Cathaysia Block was constrained to between 830 and 810 Ma, respectively Guo et al, 2018).…”