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Provenance investigation for the Cambrian–Ordovician strata from the northern margin of the western Yangtze Block: implications for locating the South China Block in Gondwana

Published online by Cambridge University Press:  25 October 2019

Liang Luo*
Affiliation:
State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing102249, China College of Geosciences, China University of Petroleum (Beijing), Beijing102249, China
Lianbo Zeng
Affiliation:
State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing102249, China College of Geosciences, China University of Petroleum (Beijing), Beijing102249, China
Kai Wang
Affiliation:
Chinese Academy of Geological Sciences, Beijing100037, China
Xiaoxia Yu
Affiliation:
State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing102249, China College of Geosciences, China University of Petroleum (Beijing), Beijing102249, China
Yihang Li
Affiliation:
State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing102249, China College of Geosciences, China University of Petroleum (Beijing), Beijing102249, China
Chenxi Zhu
Affiliation:
State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing102249, China College of Geosciences, China University of Petroleum (Beijing), Beijing102249, China
Shuning Liu
Affiliation:
State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing102249, China College of Geosciences, China University of Petroleum (Beijing), Beijing102249, China
*
Author for correspondence: Liang Luo, Email: luoliang1225@163.com
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Abstract

We report new U–Pb isotopic data for detrital zircons from Cambrian–Ordovician strata on the northern margin of the western Yangtze Block, which together with published U–Pb isotopic data for coeval strata in the South China Block, provide critical constraints on the provenance of these sediments and further shed light on the early Palaeozoic position of the South China Block in the context of Gondwana. Detrital zircons in this study yield four major age peaks in the early Palaeoproterozoic, early Neoproterozoic, middle Neoproterozoic and late Neoproterozoic – early Palaeozoic. The dominant age population of 900–700 Ma matches well with magmatic ages from the nearby Panxi–Hannan Belt, which indicates that Cambrian–Ordovician sedimentary rocks in the western Yangtze Block were mainly of local derivation. However, compilations of detrital zircon ages for the Cambrian–Ordovician strata from the Cathaysia Block and the eastern Yangtze Block show that both blocks are dominated by late Mesoproterozoic- and early Neoproterozoic-aged detrital zircons, which suggests a remarkable exotic input with typical Gondwana signatures. According to the integrated detrital zircon age spectra of the Cambrian–Ordovician sedimentary rocks from the entire South China Block and palaeocurrent data, the South China Block should have been linked with North India and Western Australia within East Gondwana. Specifically, the Cathaysia Block was located adjacent to Western Australia, while the Yangtze Block was connected with North India.

Information

Type
Original Article
Copyright
© Cambridge University Press 2019
Figure 0

Fig. 1. (a) Sketch map showing the main tectonic units of eastern Asia with the location of the SCB (Chen, Q. et al. 2018). (b) Map showing the SCB consisting of the Yangtze (eastern, central and western parts) and Cathaysia blocks, with the distribution of Neoproterozoic intrusions along the western and northern margins of the Yangtze Block, termed the Panxi–Hannan Belt (Chen et al. 2016). (c) Simplified geologic map of the Micangshan–Longmenshan region along the western margin of the SCB (modified from Sichuan Geological Map at 1:200 < 2 > 000 scale). Location of samples in this study (represented by black stars).

Figure 1

Fig. 2. Schematic stratigraphy of the front of the Micangshan fold–thrust belt, northern margin of the western Yangtze Block. The blue stars indicate sampling locations.

Figure 2

Table 1. U–Pb dating results for detrital zircons from the Cambrian–Ordovician strata on the northern margin of the western Yangtze Block

Figure 3

Fig. 3. Representative CL images of the Cambrian–Ordovician zircon samples from the northern margin of the western Yangtze Block showing internal structure and morphology.

Figure 4

Fig. 4. Concordia plots for zircons from the Cambrian–Ordovician sedimentary rocks from the northern margin of the western Yangtze Block. Grains yielding ages with more than 10 % discordance are represented by blue ellipses.

Figure 5

Fig. 5. Probability density distribution curves of ages showing the results of LA-ICP-MS dating of detrital zircons from the Cambrian–Ordovician samples from the northern margin of the western Yangtze Block.

Figure 6

Fig. 6. Detrital zircon age distributions for (a) Ordovician sedimentary rocks from the western Yangtze Block (this study); (b) Cambrian sedimentary rocks from the western Yangtze Block (this study; Chen, Q. et al. 2018); (c) Ordovician sedimentary rocks from the eastern Yangtze Block (Wang et al. 2010; Xu et al. 2012; Yao et al. 2012; Li et al. 2013); (d) Cambrian sedimentary rocks from the eastern Yangtze Block (Wang et al. 2010); (e) Ordovician sedimentary rocks from the Cathaysia Block (Wang et al. 2010; Wu et al. 2010; Yao et al. 2011; Xu et al. 2014a); (f) Cambrian sedimentary rocks from the Cathaysia Block (Wang et al. 2010; Wu et al. 2010; Xu et al. 2014a; Yao, W. H. et al. 2014).

Figure 7

Fig. 7. Detrital zircon age distributions for the main blocks in East Gondwana. (a) Western Australia (Cawood & Nemchin, 2000; Veevers et al. 2006; Kettanah, 2015); (b) Himalaya and North India (Myrow et al. 2003, 2010; McQuarrie et al. 2008; Gehrels et al. 2011); (c) Qiangtang (Dong et al. 2011; Zhu et al. 2011).

Figure 8

Fig. 8. (a) Reconstruction of early Palaeozoic East Gondwana showing position of the SCB (modified after Fitzsimons, 2000; Boger et al. 2001; Metcalfe, 2006; Zhu et al. 2011; Burrett et al. 2014; Chen, Q. et al. 2018). LH – Lesser Himalaya; GH – Greater Himalaya; TH – Tethyan Himalaya; GI – Greater India. (b) The palaeogeographic pattern for the Cathaysia and Yangtze blocks during the Cambrian and Ordovician periods (modified after Wang et al. 2010; Wu et al. 2010).