Recycling of continental crust materials: Geochemical constraints from post-collisional alkaline intrusive rocks in the Dabie orogen

Frontiers in Earth Science

Earth Science

Gang Wen¹  Guo-Chao Sun¹  Qing-Yang Xu¹  Lei Qin¹  You-Shan Xia¹  Zi-Fu Zhao²  Li-Qun Dai² 

[1] CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, China;CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, China;Center of Excellence for Comparative Planetology, Chinese Academy of Sciences (CAS), Hefei, China;

关键词: alkaline intrusive rocks;    subducted continental crust;    crust-mantle interaction;    Dabie orogen;    post-collisional;   

DOI  :  10.3389/feart.2023.1194555

 received in 2023-03-27, accepted in 2023-04-17,  发布年份 2023

来源: Frontiers

【 摘 要 】

Post-collisional alkaline intrusive rocks from the Dabie orogen were studied for their whole-rock major-trace elements and Sr-Nd-Hf-Pb isotopes, as well as zircon U-Pb ages and Hf-O isotopes. The results provide geochemical constraints on the nature of their mantle sources and thus insight into crust-mantle interaction in the continental collision zone. The alkaline intrusive rocks are composed of syenite and nepheline syenite. Syn-magmatic zircon U-Pb dating by LA-ICP-MS for them yielded Early Cretaceous ages of 131.3 ± 1.4 Ma to 122.6 ± 0.6 Ma, coeval with the post-collisional magmatism in the Dabie orogen. One relict zircon with U-Pb age of 211 Ma is consistent with the timing of metamorphism for the ultrahigh-pressure (UHP) metamorphic rocks in this orogen. They have arc-like trace element distribution patterns, such as enrichment in LILE (large ion lithophile element) and LREE (light rare earth element) but depletion in HFSE (high field strength element), and enriched whole-rock Sr-Nd-Hf isotope compositions with high (87Sr/86Sr)i ratios of 0.7077–0.7131 but negative εNd(t) values of −16.0 to −9.4 and εHf(t) values of −17.5 to −12.7. Their syn-magmatic zircons have three groups of Hf-O isotope compositions comparable to those of UHP metamorphic rocks in Central-South Dabie and North Dabie, which represent the upper and middle continental crust of the subducted South China Block, respectively. In this regard, slab–mantle interaction is evident during the Triassic continental collision. We suggest that the melts derived from the subducted South China Block reacted with the lithospheric mantle wedge of the North China Block, resulting in phlogopite-bearing metasomatites, whose partial melting would generate the post-collisional alkaline intrusive rocks during the Early Cretaceous.

【 授权许可】

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Copyright © 2023 Sun, Xia, Wen, Qin, Xu, Dai and Zhao.