Geochemical and Geochronological Constraints of Permian-Triassic Magmatism on Oceanic Subduction and Continental Collision during the Eastern Paleo-Tethyan Evolution

The Jinshajiang–Ailaoshan–Song Ma orogenic belt (JASB), as a vital segment of the eastern Paleo-Tethyan tectonic zone, is one most important zones in which to study evolution. We have undertaken an integrated geochronological, petrological, and geochemical mafic rocks from JASB reveal subduction closure processes Ocean during Permian Triassic. In conjunction with previous magmatic metamorphic records JASB, three stages are identified: (1) Early Triassic (ca. 288–248 Ma). Most normal mid-ocean ridge basalt (N-MORB)- or enriched MORB (E-MORB)-like rare earth elements (REE) trace element-normalized patterns positive εNd(t) εHf(t) values negative Nb Ta anomalies. Their La/Nb ratios show that approximately 3%–15% slab-derived fluid accounts for generation these rocks. These characteristics suggest formed arc/back-arc basin setting at this stage. Additionally, mainly exposed Jomda–Weixi–Yaxuanqiao–Truong Son rock (JYTB) on western side indicating westward Paleo-Tethys (JASO) began Permian. Middle Ailaoshan-Day Nui Con Voi complex JYTB both sides JASB. propose bipolar JASO occurred ended (2) 248–237 stage LREE- LILE-enriched patterns, anomalies values. variable εHf(t), were highly affected by crustal material 16%). Considering high-pressure (HP) metamorphism massive Al-enriched felsic magmatism may collisional between South China Block (SCB) North Qiangtang–Simao–Indochina (QSIB) (3) Late 235–202 terrestrial array characteristics. 30% components account Combined contemporaneous bimodal magma Triassic, we postcollisional extensional associated diapir.