New insights into Phanerozoic tectonics of south China: Part 1, polyphase deformation in the Jiuling and Lianyunshan domains of the central Jiangnan Orogen

Abstract

The central Jiangnan Orogen, genetically formed by the Proterozoic Yangtze‐Cathaysia collision, presents as a composite structural feature in the Phanerozoic with multiple ductile and brittle fabrics whose geometries, kinematics, and ages are crucial to decipher the tectonic evolution of south China. New structural observations coupled with thermochronological and geochronological studies of these fabrics document four main stages of deformation. The earliest stage in early Paleozoic time (460–420 Ma) corresponds to combined E‐trending dextral and northwest directed thrust shearing that was variably partitioned in anastomosing high‐strain zones under greenschist‐facies conditions (~400–500°C), related to the continued Yangtze‐Cathaysia convergence externally driven by the suturing of south China with Australia. This event was heterogeneously overprinted by the second stage characterized by ~E‐oriented folding in middle Triassic time, geodynamically resulting from the continental collision of south China with Indochina and North China. The third stage was locally developed by northwest and southeast vergent thrusts that truncated ~E‐oriented folds in the Late Jurassic, due to northwestward subduction of the Paleo‐Pacific plate. The latest stage involved normal faulting and tectonic unroofing in Cretaceous time, which resulted in basin opening and reset footwall 40Ar/39Ar ages in proximity to the Hengshan detachment fault, associated with roll‐back of the subducting Paleo‐Pacific plate.

Geochronological, geochemical, and Nd–Hf isotopic constraints on the origin of magmatism in the Dabaoshan ore district of South China

“…440 Ma, during the Caledonian period. An increasing number of studies have demonstrated that the Caledonian Orogen in the SCB (>460–415 Ma), also known as the Wuyi–Yunkai Orogen, was an intraplate orogenic event (e.g., Charvet et al, ; Faure et al, ; Z. X. Li et al, ; J. H. Li et al, ; Shu et al, ; Y. J. Wang, Zhang, et al, ; Yao et al, ) rather than a continental or arc collisional event involving the closure of the proposed Huanan Ocean within the SCB (Guo et al, ; Hsü, ; Hsü et al, ). Models of crustal anatexis (L. Wang et al, ) and lithospheric delamination or orogenic collapse (Z. X. Li et al, ; Shu et al, ; Y. J. Wang, Zhang, et al, ; Yao et al, ; Yu et al, ) have been put forward to explain the Caledonian structural elements, metamorphism, and magmatism.…”

“…210 Ma) in the Dabaoshan ore district, together with coeval mafic–ultramafic magmatic rocks (e.g., Dai, Jiang, Jiang, Zhao, & Liu, ; Liang, Fan, Wang, & Li, ), indicate that lithospheric extension took place in the SCB during the late Indosinian. A number of competing models have been invoked to explain the extension, such as the flat subduction of the Palaeo‐Pacific Plate (Z. X. Li & Li, ), but the current consensus is that the Indosinian Orogeny (248–200 Ma) in the SCB was an intraplate orogenic event (e.g., J. H. Li et al, ; Shu et al, ; Y. J. Wang et al, ; Y. J. Wang, Fan, et al, , and reference therein) similar to the Caledonian Orogeny. The late Indosinian granites, mafic–ultramafic rocks, and volcanics in the SCB were generated by the partial melting of the lower crust and subcontinental lithospheric mantle due to lithospheric delamination or orogenic collapse, and the upwelling of asthenosphere and underplating of basalts (220–200 Ma).…”

“…The oblique north‐westward subduction of the Palaeo‐Pacific Plate beneath the Eurasia Plate remains the most popular model of Yanshanian tectonics in the SCB (Y. J. Wang, Fan, et al, ), although a number of distinct subduction patterns have been invoked (e.g., Charvet, Lapierre, & Yu, ; Z. Y. He, Xu, & Niu, ; J. H. Li et al, ; X. H. Li et al, ; Z. X. Li & Li, ; Jahn, Zhou, & Li, ; Jiang et al, ; Y. J. Wang, Fan, et al, ; Zhou et al, , ).…”

“…was an intraplate orogenic event (e.g., Charvet et al, 2010;Faure et al, 2009;Z. X. Li et al, 2010;J. H. Li et al, 2016;Shu et al, 2015;Yao et al, 2012) rather than a continental or arc collisional event involving the closure of the proposed Huanan Ocean within the SCB (Guo et al, 1989;Hsü, 1994;Hsü et al, 1990).…”

Mixing of Felsic Magmas in Granite Petrogenesis: Geochemical Records of Zircon and Garnet in Peraluminous Granitoids From South China

“…Biotite Ar/Ar dating gave Neoproterozoic ages (Hu et al, ), and zircon U‐Pb dating yield concordant ages of circa 800–830 Ma for the Jiuling batholith (Li et al, ; Wang et al, ; Zhong et al, ; Zhao et al, ). Although most of the batholith show no evidence of metamorphic overprint, multiple faults with deformation ages ranging from the Paleozoic to Mesozoic were developed in the Jiuling batholith and its adjacent area (Chu & Lin, ; Li et al, ). The Jiuling batholith is intruded by a small Mesozoic granitic pluton with ages of about 150 Ma (Zhong et al, ).…”