Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Geochronology, Petrogenesis and Tectonic Setting of the Late Triassic syenite porphyry from the Western Part of the North Qinling Orogenic Belt

Version 1 : Received: 10 November 2023 / Approved: 10 November 2023 / Online: 10 November 2023 (11:33:26 CET)

How to cite: Li, S.; Li, Z.; Pei, X.; Lin, H.; Qin, L.; Ji, S.; Yang, Y.; Ren, J. Geochronology, Petrogenesis and Tectonic Setting of the Late Triassic syenite porphyry from the Western Part of the North Qinling Orogenic Belt. Preprints 2023, 2023110705. https://doi.org/10.20944/preprints202311.0705.v1 Li, S.; Li, Z.; Pei, X.; Lin, H.; Qin, L.; Ji, S.; Yang, Y.; Ren, J. Geochronology, Petrogenesis and Tectonic Setting of the Late Triassic syenite porphyry from the Western Part of the North Qinling Orogenic Belt. Preprints 2023, 2023110705. https://doi.org/10.20944/preprints202311.0705.v1

Abstract

Precise determination of the tectonothermal events at the Qinling-Qilian junction is extremely significant for understanding the tectonic evolution of the eastern branch of the Paleo-Tethys. The Banpo porphyry outcrops in the northern margin of the North Qinling were chosen as the research subject, and its formation and tectonic environment were analyzed using Zircon U-Pb age estimation and geochemical studies. The results indicated the final stage of the Triassic orogeny and the closure phase of the Paleo-Tethys. The weighted average values of 206Pb/238U ages of samples from 3 sites of the Banpo porphyry corresponded to 213.4 ±2.1 Ma (MSWD = 0.56), 213.0 ±1.6 Ma (MSWD = 0.92), and 213.2 ±4.4 Ma (MSWD = 1.6). This study revealed that the Banpo porphyry was formed during the Late Triassic (Norian). The porphyry with high SiO2 and high alkali is typical A-type granite, which belongs to the weak peraluminous shoshonite series. All the samples are rich in low rare earth elements. However, the heavy rare earth elements are low, especially Eu, which exhibits a seagull-type right-leaning partitioning curve. In addition, based on the regional geological data, it can be concluded that the Banpo porphyry was formed during the transition period from a post-orogenic environment to a non-orogenic environment. This study indicated the closure of the Paleo-Tethys-Mianxian-Lveyang Ocean by the Late Triassic as well as the completion of the collision between the North China and Yangtze Blocks along the Qinling orogenic belt.

Keywords

North Qinling orogen belt; Late Triassic; tectonic setting; petrogenesis; geochronology; syenitic porphyries

Subject

Environmental and Earth Sciences, Geochemistry and Petrology

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