Late Pleistocene Volcanic Rocks From Tengchong Volcanic Field at

SE

Tibetan Plateau: Constraints on Petrogenesis and Mantle and Crustal Processes

Late Pleistocene (< 0.2 Ma) mafic and evolved volcanic rocks occur in northern Tengchong Volcanic Field, SE Tibetan Plateau and contain information on magma generation and evolution in a post‐collisional orogenic setting. We report their whole‐rock major oxides, trace elements and Sr–Nd–Hf isotopes and zircon Hf–O isotopes to constraint the origin and magmatic processes of these late Pleistocene volcanic rocks. Volcanic zircons from the primitive mafic lavas (SiO

2

 = 52–54 wt.%, MgO ≥ 5 wt.%) have relatively high δ

18

O (6.6‰–7.9‰) and enriched Hf isotopic compositions, providing strong evidence of deep recycling of supracrustal materials into the mantle beneath Tengchong. The occurrence of volcanic zircons in these mafic lavas also reveals early saturation and crystallisation of zircon in post‐collisional volcanic rocks, likely due to high initial water content and high initial Zr content in the primitive magma. Inherited (14–2506 Ma) zircons are common in most evolved lavas but are rare or absent in mafic lavas. The age distributions of inherited zircons indicate multiple sources of crustal contaminations from Carboniferous country rocks, Gaoligongshan basement and granitoids of Palaeozoic, Late Mesozoic and Cenozoic ages. Inherited zircon ages also reveal unexposed magmatic rocks aged 33–14 Ma beneath Tengchong. This study provides new insights into the nature of enriched mantle, generation of mafic lavas and the contaminant materials for evolved magmas.