The geochemistry and geochronology of Permian granitoids from central Inner Mongolia, NE China: Petrogenesis and tectonic implications

Permian granitoids have been identified in the Zhalageamu district, Inner Mongolia, NE China, which provide an excellent opportunity to constrain tectonic evolution of Central Asian Orogenic Belt (CAOB). In this study, we determined zircon U Pb ages quartz diorite, granodiorite porphyry, diorite porphyry and granite at Zhalageamu. These are 269.5 ± 1.8, 261.4 1.9, 256.4 2.0 255.2 Ma, respectively. The high contents SiO 2 (61.95–75.41 wt%) Al O 3 (11.87–15.88 wt%), their A/CNK ratios range from 0.91 1.44. Their Na + K 6.04 9.28 wt% help classify them as having calc-alkaline high-K affinity. low P 5 decrease with increasing , combination 10,000*Ga/Al (1.51–2.58) Zr Nb Ce Y (128–264 ppm) identify I-type granitoids, whereas strongly peraluminous character classifies it S-type granite. characterized by enrichment large ion lithophile elements (LILE; e.g., Rb, Ba Th) a depletion field strength (HFSE; Nb, Ta Ti). This, weakly negative Eu anomalies on chondrite-normalized REE diagrams, features typical arc magmatic rocks. ɛ Nd (t) values initial 87 Sr/ 86 Sr 2.9 4.2 0.7010 0.7039, respectively, both sets point mantle source. Hafnium isotopic analysis yielded positive ε Hf 8.5–12.3 young two-stage model (T DM2 ) 0.51–0.72 Ga, suggesting juvenile crustal similar those locally occurring coeval volcanic rocks, indicating that mostly formed partial melting mantle-derived crust. Our geochemical Sr-Nd-Hf data show were generated subduction setting related northward Paleo-Asian Ocean. • district occurred between 269 255 Ma. Ocean closed after late Permian.