The assembly of the South China and Indochina blocks: Constraints from the Triassic felsic volcanics in the Youjiang Basin

2021 ◽  
Author(s):  
Chengshi Gan ◽  
Yuejun Wang ◽  
Yuzhi Zhang ◽  
Xin Qian ◽  
Aimei Zhang
Keyword(s):  
South China ◽  
Foreland Basin ◽  
Suture Zone ◽  
Igneous Rocks ◽  
South China Block ◽  
The South ◽  
Crustal Rocks ◽  
O Isotopes ◽  
Youjiang Basin ◽  
Geochemical Analyses

The Youjiang Basin is usually regarded as an important foreland basin in the southern part of the South China Block that is related to the convergence of the South China and Indochina blocks during the Permian-Triassic. However, the nature of the basin remains controversial due to questions about the subduction polarity and suture boundary between these two blocks. Permian-Triassic felsic volcanics across the Dian-Qiong and Song Ma suture zones could offer new insights into the convergent processes of the South China and Indochina blocks. This study presents detailed petrological, zircon U-Pb dating, and Hf-O isotope and whole-rock geochemical analyses for the Triassic felsic volcanics of the Youjiang Basin (northeast of the Dian-Qiong). The dacites and rhyolites from the Beisi and Baifeng Formations were dated at ca. 240−245 Ma. All of the felsic volcanics are characterized by high SiO2 (69.40−73.15 wt%), FeOt/MgO, 10000*Ga/Al, and TZr, δ18O (9.7−11.8‰) and negative εNd(t) (from −9.6 to −12.3) and zircon εHf(t) (from −6.2 to −14.5) with A-type granitoid geochemical affinities, suggesting the reworking of crustal rocks in an extensional setting. Permian-Triassic felsic igneous rocks display similar geochemical signatures across the Dian-Qiong suture zone, whereas they show distinctive Sr-Nd and zircon Hf-O isotopes across the Song Ma suture zone. The felsic igneous rocks to the northeast of the Song Ma suture zone have much lower εNd(t) and higher δ18O with negative zircon εHf(t) than those to the southwest, which have positive zircon εHf(t). Combined with other geological and geophysical features, it is inferred that the Song Ma suture zone was probably the suture boundary between the South China and Indochina blocks, and the Youjiang Basin was likely a peripheral foreland basin in response to the southwestward convergence of the South China Block toward the Indochina Block.

The occurrence of Neoproterozoic low δ18O igneous rocks in the northwestern margin of the South China Block: Implications for the Rodinia configuration

2020 ◽  
Vol 347 ◽  
pp. 105841 ◽  
Author(s):  
Peng Wu ◽  
Shao-Bing Zhang ◽  
Yong-Fei Zheng ◽  
Qiu-Li Li ◽  
Zhen-Xin Li ◽  
...  
Keyword(s):  
South China ◽  
Igneous Rocks ◽  
South China Block ◽  
The South ◽  
Northwestern Margin

Subduction polarity of the Ailaoshan Ocean (eastern Paleotethys): Constraints from detrital zircon U-Pb and Hf-O isotopes for the Longtan Formation

2019 ◽  
Vol 132 (5-6) ◽  
pp. 987-996
Author(s):  
Xiao-Ping Xia ◽  
Jian Xu ◽  
Chao Huang ◽  
Xiaoping Long ◽  
Meiling Zhou
Keyword(s):  
South China ◽  
Detrital Zircon ◽  
South China Block ◽  
The South ◽  
Forearc Basin ◽  
Isotopic Signatures ◽  
Northeastern Japan ◽  
O Isotopes ◽  
A Minor ◽  
Back Arc

Abstract The Paleotethys Ailaoshan Ocean separated the South China and Indochina blocks during the late Paleozoic. Uncertainty remains regarding subduction of this ocean—whether it was subducted eastward beneath the South China block or westward beneath the Indochina block. In this study, we present new detrital zircon U-Pb age, and Hf and O isotope data from the Longtan Formation, which was recognized to be deposited before the ocean closed. Our results show that the formation can be divided into three units: Unit 1 is distributed west of the suture and dominates the area; it contains major age peaks at 290–250 Ma and minor multiple old age peaks. Unit 2 consists of a minor distribution west of the suture, and it shows a dominant 250 Ma age peak; old zircons are very few or not present. Their Hf and O isotopic signatures are similar to those of unit 1. Unit 3 is distributed east of the suture and is characterized by a single distinct ca. 240 Ma age peak with almost no Precambrian zircons. We interpret that units 1 and 2 were likely deposited in a back-arc and forearc basin, respectively, and a volcanic arc developed on the eastern margin of the Indochina block, similar to the present-day northeastern Japan arc. Meanwhile, unit 3 was likely deposited in a forearc basin on the western margin of the South China block. Therefore, the Ailaoshan Ocean may undergone bipolar subduction both westward and eastward beneath the Indochina and South China blocks, respectively.

Detrital zircon evidence for the linkage of the South China block with Gondwanaland in early Palaeozoic time

2012 ◽  
Vol 149 (6) ◽  
pp. 1124-1131 ◽  
Author(s):  
LIANG DUAN ◽  
QING-REN MENG ◽  
GUO-LI WU ◽  
SHOU-XIAN MA ◽  
LIN LI
Keyword(s):  
South China ◽  
Detrital Zircon ◽  
Age Distribution ◽  
South China Block ◽  
The South ◽  
Crustal Rocks ◽  
Pan African ◽  
Continental Block ◽  
Mixed Origin ◽  
Early Palaeozoic

AbstractLA-ICP-MS U–Pb dating of Lower Devonian detrital zircon samples from three representative sections in the South China block yields dominant Grenvillian and Pan-African populations, similar to the age distribution of early Palaeozoic samples from Gondwana, the Tethyan Himalaya and West Australia, in particular. Hf isotopic compositions indicate the contributions of juvenile crust at 1.6 Ga and 2.5 Ga, and bear a resemblance to their counterparts from SE Australia and West Antarctica, revealing the mixed origin of the Pan-African and Grenvillian grains from juvenile magmas and melting of pre-existing crustal rocks. These results suggest that the South China block should be considered an integral part of East Gondwana in early Palaeozoic time, rather than a discrete continental block in the Palaeo-Pacific or a fragment of Laurentia.

Multi-stage tectonics and metallogeny associated with Phanerozoic evolution of the South China Block: A holistic perspective from the Youjiang Basin

2020 ◽  
Vol 211 ◽  
pp. 103405
Author(s):  
Qingfei Wang ◽  
Lin Yang ◽  
Xiaojie Xu ◽  
M. Santosh ◽  
Yanning Wang ◽  
...  
Keyword(s):  
South China ◽  
South China Block ◽  
The South ◽  
Holistic Perspective ◽  
Multi Stage ◽  
Youjiang Basin

Tectonic evolution of the Paleo-Tethys Ocean in Southwest Guangxi: evidence from acidic magmatic rocks in the Pingxiang area, SW China

2021 ◽  
Author(s):  
Wenmin Huang ◽  
Xijun Liu ◽  
Zhenglin Li ◽  
Bing Zhao ◽  
Yiying Han
Keyword(s):  
Partial Melting ◽  
South China ◽  
South China Block ◽  
Guangxi Province ◽  
The South ◽  
Crustal Rocks ◽  
The North ◽  
Early Mesozoic ◽  
Innovation Project ◽  
Tethys Ocean

<p>Early Mesozoic development of Southeast Asia involved oceanic subduction, closure, accretion and collision of discrete terranes rifted from Gondwana. South China, as an important continental terrane, is bound to the north by the Qinling-Dabie collisional orogenic belt, to the south by the Indochina Block, and to the east by the Pacific Plate. The role of continental collision and subduction during the Early Mesozoic development of South China has sparked the interest of geologists worldwide and stimulated considerable research. The Triassic tectonic history of the southwestern South China Block is marked by the Indosinian orogeny that records amalgamation of the Indochina and South China blocks during the late Permian to Triassic as a result of closure of the eastern branch of the Paleo-Tethys Ocean. In South China, there is widespread granitic magmatism, metamorphism and deformation. The closure of eastern Paleo-Tethys Ocean and subsequent collision between the South China block and Indochina Block has caused the collision zone metamorphism and formation of granites during the Permo-Triassic, with the Song Ma fault zone as the collision boundary. The Indosinian magmatism in the Pingxiang region was the magmatic products in this period. We report the new results of bulk-rock major and trace element, Nd, Hf isotopic compositions and zircon U–Pb dating of granites and rhyolites in the Pingxiang region in Guangxi Province, Southwest China, to decipher their petrogenesis and tectonic settings. The granites and rhyolitics in the Pingxiang area have low Mg<sup>#</sup> values (11.1–36.7), low Nb/Ta ratios (9.26–13.74) exhibiting a both affinity from S-type to I-type granaite. The isotopic features of these rocks show negative ε<sub>Hf</sub>(t) with the values ranging from -9.89 to -6.09, negative ε<sub>Nd</sub>(t) values ranging from -12.89 to -12.02 and T<sub>2DM</sub> values of 1.8–3.3 Ga, suggesting that the Pingxiang granites and rhyolites was derived from partial melting of paleoproterozoic crust rocks. The granites yielded <sup>206</sup>Pb/<sup>238</sup>U ages ranging from 243 to 241 Ma, and the rhyolites yielded <sup>206</sup>Pb/<sup>238</sup>U ages ranging from 247 to 245 Ma, which are both within the age range of the subduction to collision. Combine the regional geology, we suggest these granitoids and rhyolites were formed by the partial melting of crustal rocks during a transition from subduction to post-collisional environment with closure of Paleo-Tethys Ocean between the South China block and Indochina Block.</p><p>This study was financially supported by Guangxi Natural Science Foundation for Distinguished Young Scholars (2018GXNSFFA281009) and the Fifth Bagui Scholar Innovation Project of Guangxi Province (to XU Ji-feng).</p>

Spatio-temporal evolution and dynamic origin of Jurassic-Cretaceous magmatism in the South China Block

2021 ◽  
Vol 217 ◽  
pp. 103605
Author(s):  
Xianzhi Cao ◽  
Nicolas Flament ◽  
Sanzhong Li ◽  
R. Dietmar Müller
Keyword(s):  
South China ◽  
Temporal Evolution ◽  
South China Block ◽  
The South ◽  
Spatio Temporal ◽  
Cretaceous Magmatism
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