Time constraints on the closure of the Paleo–South China Ocean and the Neoproterozoic assembly of the Yangtze and Cathaysia blocks: Insight from new detrital zircon analyses

Abstract

The South China Block was built up by the assembly of the Yangtze and Cathaysia blocks along the Neoproterozoic Jiangnan Orogenic Belt. The timing of the Jiangnan Orogeny remains controversial. The widespread orogeny-related Neoproterozoic angular unconformity that separates the underlying folded Sibao (ca.1000-820 Ma) and overlying Danzhou (ca.800-720 Ma) Groups was investigated. Six sedimentary samples, below and above the unconformity in three distal localities (Fanjingshan, Madiyi, and Sibao) yield detrital zircon with U-Pb ages ranging from 779±16 Ma to 3006±36 Ma, with a prominent peak at ca. 852 Ma. The youngest ages of 832±11 Ma and 779±16 Ma are revealed for the underlying Sibao and overlying Danzhou Groups, respectively. The detrital zircon U-Pb age relative probability plot of the Jiangnan Orogen matches well with those of the Yangtze and Cathaysia blocks since ca. 865 Ma. Integrating geological, geochemical and geochronological results, we suggest that the Paleo-South China Ocean began to subduct under the Yangtze block at ca. 1000 Ma, and was partly closed at ca. 865 Ma. Afterwards, the Yangtze and Cathaysia blocks initially collide at 865 Ma, forming the Jiangnan Orogen. This collision resulted in not only the folding of the Sibao Group, but also sediment deposition in a syn-collisional setting, which makes the upper part of the Sibao

A Consistently High‐Latitude South China From 820 to 780 Ma: Implications for Exclusion From Rodinia and the Feasibility of Large‐Scale True Polar Wander

“…Note that the Luoman section consists of seven individually measured sections that were correlated to each other based on local bedding and elevation measurements. the southeast, sedimentary rocks interpreted to correlate with the Banxi and Xiajiang Groups are referred to as the "Danzhou Group" (Yan et al, 2019). There are similar regional nomenclature differences for the older Fanjingshan Group, which is referred to as the "Fanjingshan Group" in our study area and is correlated with units known as the "Lengjiaxi Group" and the "Sibao Group" elsewhere, and the younger Tiesi'ao Formation, which is referred to as the "Tiesi'ao Formation" in our study area and is correlated with units known as the "Chang'an Formation" elsewhere.…”

Early Neoproterozoic (870–820 Ma) amalgamation of the Tarim craton (northwestern China) and the final assembly of Rodinia

“…Based on the early Neoproterozoic Jiangnan orogeny between the Yangtze and Cathaysia blocks, Li et al (1995) proposed a "missing link" model for Rodinia that placed South China in the center in between Laurentia and Australia. However, U-Pb ages for the Jiangnan orogeny of 860-820 Ma (Zhao et al, 2011;Cawood et al, 2018;Lin et al, 2018;Yan et al, 2019;Yao et al, 2019) are much younger than that of Grenvillian orogenesis. Furthermore, evidence for Neoproterozoic arc magmatism along the northern margin of the Yangtze block, indicating an active plate margin, requires that South China was located along the periphery of Rodinia during the period between 990 and 820 Ma (Cawood et al, 2013(Cawood et al, , 2018Wang et al, 2013).…”

“…The polarity of this subduction zone or whether twosided subduction was involved is unresolved (Fig. 4B) due to limited data for the Central Tarim suture and competing models for the collision between Yangtze and Cathaysia that range from northwestward subduction beneath Yangtze (Zhao et al, 2011;Yan et al, 2019) to southeastward subduction beneath Cathaysia (Cawood et al, 2013;Yao et al, 2019) to two-sided subduction beneath both Yangtze and Cathaysia (Zhao, 2015). In any case, there is evidence that after peripheral accretion of Yangtze and North Tarim, a circum-Rodinia subduction girdle with arc magmatism developed along the external margins of South China, Tarim, and Australia (Fig.…”

The construction mechanism of the Neoproterozoic S-type Sanfang-Yuanbaoshan granitic plutons in the Jiangnan Orogenic Belt, South China: Insights from geological observation, geochronology, AMS and Bouguer gravity modeling

“…Some kilometer to meter-scale mafic and ultramafic blocks enclosed in the mudstone-sandstone of the Sibao group crop out around the plutons. The well folded but low greenschist-facies metamorphosed Sibao group is commonly recognized by the accretionary complex coeval with the subduction of the Paleo-South China oceanic crust (Wang et al, 2014a;Zhou et al, 2009), and recently work reveals that the upper Sibao group was deposited during the Yangtze-Cathaysia continental collision (Yan et al, 2019).…”

“…850-830 Ma (Ding et al, 2008;Zhou et al, 2004). Nevertheless, some others hold the view that the granitic plutons were formed at the post-orogenic stage (Wang et al, 2013;Yan et al, 2019;Zhang et al, 2013Zhang et al, , 2016. These suggestions are, however, proposed only on the basis of the geochronological logic, without direct geological and physical evidence.…”