Metamorphic evolution and SIMS zircon U-Pb geochronology of mafic granulite and amphibolite enclaves of the Pingyang trondhjemitic pluton, Fuping terrane, North China

• Published in: Precambrian research 2017-12, Vol.303, p.75-90
• Main Authors: Meng, Jie, Peng, Tao, Liu, Jia-Hui, Zhang, Hui C.G., Wang, Guo-Dong, Lu, Jun-Sheng, Chen, Hong-Xu, Wang, Hao Y.C., Zhang, Qian W.L., Wu, Chun-Ming
• Format: Article
• Language: English
• Subjects: Enclave; P-T path; Pingyang trondhjemitic pluton; SIMS U-Pb dating; Trans-North China Orogen; Zircon
• ISSN: 0301-9268; 1872-7433
• DOI: 10.1016/j.precamres.2017.02.014

•The Pingyang trondhjemitic pluton formed at ∼2.52Ga.•The mafic granulite and amphibolite enclaves record clockwise P-T-t paths.•The mafic granulite enclaves metamorphosed at ∼1.89–1.86Ga. The discrete mafic granulite and amphibolite enclaves within the Pingyang trondhjemitic pluton, Fuping metamorphic terrane, middle Trans-North China Orogen, ubiquitously record three stages of metamorphic assemblages. For the mafic granulite enclaves, the prograde metamorphic assemblage (M1) is represented by mineral inclusions (clinopyroxene+hornblende+plagioclase+quartz±apatite) preserved in the garnet porphyroblast, the metamorphic peak (M2) assemblage consists of garnet and matrix minerals of clinopyroxene+orthopyroxene+hornblende+plagioclase+quartz±magnetite±ilmenite±zircon, and the retrograde (M3) stage is represented by symplectite assemblage of orthopyroxene+plagioclase±clinopyroxene±hornblende±quartz rimming the garnet porphyroblast. The metamorphic P-T paths of the mafic granulite enclaves are defined to pass from 560–750°C/6–9kbar (M1) through 740–880°C/11–14kbar (M2) to 720–800°C/6–8 (M3), indicative of a collisional orogenic process. The metamorphic P-T path of the amphibolite enclave experienced from 670–730°C/9.3–11.8kbar to 710–730°C/3.9–5.5kbar, further certify such metamorphic feature of an orogenic belt. SIMS U-Pb dating of zircons of the trondhjemitic gneiss yields the magmatic crystallization age of ∼2.52Ga, and both the trondhjemitic gneiss and the mafic granulite enclaves yield the metamorphic age of ∼1.89–1.86Ga. Therefore, it can be concluded that the Fuping terrane was involved in the late Palaeoproterozoic subduction-collision-uplifting tectonic process caused by amalgamation of the Eastern and Western Blocks of the North China Craton along the Trans-North China Orogen.