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The syncollisional granitoid magmatism and crust growth during the West Qinling Orogeny, China : insights from the Jiaochangba pluton.

Kong, J.J. and Niu, Y.L. and Duan, M. and Xiao, Y.Y. and Zhang, Y. and Guo, P.Y. and Sun, P. and Gong, H.M (2019) 'The syncollisional granitoid magmatism and crust growth during the West Qinling Orogeny, China : insights from the Jiaochangba pluton.', Geological journal., 54 (6). pp. 4014-4033.

Abstract

The West Qinling Orogenic Belt (WQOB) is a major portion of the Qinling‐Dabie‐Sulu Orogen and holds essential information for understanding the protracted evolution of the north‐eastern branch of the Paleo‐Tethys in East Asia. In this study, we report our petrological, geochemical, and geochronological study on the five Triassic granitoid plutons of West Qinling with emphasis on the poorly studied Jiaochangba pluton with zircon U–Pb ages of 217.5 ± 1.6 Ma and 215.2 ± 1.2 Ma. The new data and the existing data on the other four plutons support the view that the West Qinling granitoids represent a magmatic response to the continental collision of the Yangtze Block (YB) with the North China Craton (NCC) in the Triassic. Like the other four plutons, the Jiaochangba pluton shows strong light rare earth element (REE) enrichment and weak heavy REE depletion ([La/Sm]N ≈ 7.14 ± 1.89; [Sm/Yb]N ≈ 4.63 ± 1.85) with varying negative Eu anomalies (Eu/Eu* ≈ 0.65 ± 0.20). In the N‐MORB normalized diagram, all the samples show relative enrichment in Rb, Pb, U, and K with negative Nb, Ta, P, and Ti anomalies, resembling those of the model continental crust. The Jiaochangba pluton has relatively lower (87Sr/86Sr)i (0.7062 to 0.7081), higher εNd(t) (−6.91 to −2.09), and εHf(t) (−5.57 to −0.14) than mature continental crust, which are consistent with their source being dominated by lower crust with significant mantle contributions. Mantle‐derived melt, which formed from partial melting of mantle wedge peridotite facilitated by dehydration of the subducted/subducting Mianlue ocean crust, provide the required heat for the crustal melting while also contributing to the compositions of these granitoids. Evolution of such parental magmas in open system crustal magma chambers with continued evolution/replenishment and crustal contamination and assimilation give rise to the observed petrological and geochemical characteristics of these granitoids.

Item Type:Article
Full text:(AM) Accepted Manuscript
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1002/gj.3368
Publisher statement:This is the accepted version of the following article: Kong, J.J., Niu, Yaoling, Duan, M., Xiao, Y.Y., Zhang, Y., Guo, P.Y., Sun, P. & Gong, H.M (2019). The syncollisional granitoid magmatism and crust growth during the West Qinling Orogeny, China: Insights from the Jiaochangba pluton. Geological Journal 54(6): 4014-4033 which has been published in final form at https://doi.org/10.1002/gj.3368. This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving.
Date accepted:10 October 2018
Date deposited:11 October 2018
Date of first online publication:16 December 2018
Date first made open access:16 December 2019

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