Wang, Y and Chen, H and Falloon, TJ and Han, J, The Paleozoic-Mesozoic magmatic evolution of the Eastern Tianshan, NW China: Constraints from geochronology and geochemistry of the Sanchakou intrusive complex, Gondwana Research, 103 ISSN 1342-937X (2022) [Refereed Article]
The Sanchakou intrusive complex (containing quartz diorite, porphyritic granodiorite, granodiorite, fine-grained granodiorite, diorite porphyry and hornblende gabbro) is located at the eastern part of the Dananhu-Tousuquan island arc belt, Eastern Tianshan. Zircon U-Pb ages suggest that the above six units were emplaced at 446–238 Ma. The Sanchakou intrusive complex therefore provides a unique opportunity to gain a better understanding of the Paleozoic-Mesozoic magmatism and its evolution in the Eastern Tianshan.
The granitoids form a subduction related calc-alkaline to low K (tholeiitic) magmatic series, characterized by enrichment in LILE and depletion in HFSE. They have low initial 87Sr/86Sr, high εNd(t) and εHf(t) values. As well as the above geochemical features, the quartz diorite, porphyritic granodiorite and fine-grained granodiorite have low Nb/U and Ta/U values, relatively high Mg#, Ti/Zr and Ti/Y values, indicating a potential role of the subducted slab in their petrogenesis. The granodiorite units have low Nb/U, Ta/U and Mg# values, and high (La/Yb)N values, suggesting an origin from the melting of juvenile lower crust. The Sanchakou diorite porphyry has positive εNd(t) and εHf(t), low SiO2 and (87Sr/86Sr)i, and high MgO, Mg#, Ti/Y and Ti/Zr values, indicating it was likely sourced from depleted mantle. The Mesozoic hornblende gabbro has low SiO2, relatively high TiO2, MgO, Al2O3 and (La/Yb)N, and minor depletion in Nb-Ta, implying an E-MORB-like mantle source.
Integrating available tectonic, stratigraphic and geochemical data, we propose that the Sanchakou quartz diorite, porphyritic granodiorite, granodiorite and fine-grained granodiorite were formed in a double-side subduction system. The younger Permian diorite porphyry was produced in a post-collisional extensional setting and the Triassic hornblende gabbro was likely formed in an intraplate environment.
|Item Type:||Refereed Article|
|Keywords:||multiple magmatism, zircon U-Pb dating, Sr-Nd-Hf isotopes, Sanchakou intrusive complex, Eastern Tianshan|
|Research Division:||Earth Sciences|
|Research Field:||Exploration geochemistry|
|Objective Division:||Expanding Knowledge|
|Objective Group:||Expanding knowledge|
|Objective Field:||Expanding knowledge in the earth sciences|
|UTAS Author:||Falloon, TJ (Dr Trevor Falloon)|
|Deposited By:||Earth Sciences|
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