Petrogenesis and Geological Significance of the Mesozoic Granitoids in the Mangzhang-Jiucheng Area, Tengchong Terrane, Yunnan Province: Evidence from Petrology, Geochemistry and Zircon U-Pb Geochronology

Wei Liu^1,2Jinglong Wu¹Yuelei Ruan³Chen Gong¹Yan Shang¹Geng Chen⁴Yuan Liu⁵Jialing Wu⁵Xiaojun Li⁵Xiaofeng Wang⁶Xu Kong^1*Xiong Mo^5*

• ¹Ordos Institute of Technology, Ordos, China
• ²Inner Mongolia No.5 Geological and Mineral Exploration and Development Co.,Ltd, Baotou, China
• ³Shaoxing Jingling Reservoir Construction and Operation Center, Shaoxing, China
• ⁴Hunan Urban Geological Survey and Monitoring Institute, Changsha, China
• ⁵Yunnan Institute of Geology Survey, Kunming, China
• ⁶Yunnan Planning and Design Institute of Land Resources, Kunming, China

The Mangzhang-Jiucheng granitoids of the Tengchong Terrane offers critical insights into the Mesozoic tectono-magmatic evolution of the eastern Tethyan Tectonic Domain. LA-ICP-MS zircon U–Pb geochronology identifies two emplacement phases at 210.6–207.1 Ma and121.4 –118.7 Ma, recording Late Triassic and Early Cretaceous magmatic events with Ti-in-zircon crystallization temperatures of 531–720 ℃and 582–816 ℃, respectively. Geochemically, both the Late Triassic and the Early Cretaceous granitoids belong to acidic, peraluminous, exhibiting pronounced enrichment in LREE and large-ion lithophile elements (Rb, Th, U, La, Ce, Zr and Hf) and conspicuous depletion in high-field-strength elements (Nb and Ti) together with Sr, Ba and HREE. The Late Triassic granitoids exhibit S-type affinity, indicating that magma may source from metasedimentary materials. The Early Cretaceous granitoids exhibit predominantly S-type affinities and are derived from metasedimentary sources, and may have formed in volcanic-arc (VAG), syn-collisional (syn-COLG), or within-plate (WPG) tectonic settings. The Late Triassic granitoids may be related to the accretion of the Tengchong Terrane and the Indochina Block upon closure of the Paleo-Tethys Ocean (PTO), whereas Early Cretaceous granitoids may link to the subduction of the Meso-Tethys Ocean (MTO), accompanied by slab rollback, break-off and asthenospheric upwelling that associate with the final suturing of the MTO.