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Multi-generation mineral growth and phase equilibrium modelling: Tracing the long history of granitoids in continental collisional orogen
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DOI：10.1093/petrology/egag043.png)
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Abstract
En 中文
An integrated petrographic, mineralogic, geochronologic and phase equilibrium modelling study of Jingshan granites reveals four distinct metamorphic-anatectic-magmatic-hydrothermal events recorded in zircon and garnet. Zircon geochronology identifies Paleoproterozoic, Neoproterozoic and Triassic (240–200 Ma) ages in inherited domains, alongside Late Jurassic (~160 Ma) ages in anatectic/magmatic domains. These data indicate that the Jingshan granites originated from remelting of crustal materials that experienced Triassic metamorphism. Four generations of garnet are distinguished. Metamorphic garnet (Grt I), formed during Triassic metamorphism, exhibits flat to steep middle to heavy rare earth element (M-HREE) patterns. Peritectic garnet (Grt II), produced during Late Jurassic crustal anatexis, displays Y-HREE-enrichment and high (Yb/Dy)N ratios. Magmatic garnet (Grt III), crystallized during magma cooling, exhibits negative Eu anomalies and flat to steep M-HREE distributions. Hydrothermal garnet (Grt IV), formed during the late magmatic-hydrothermal stage, shows low TiO2 contents and positive Eu anomalies. Phase equilibrium modelling constrains partial melting conditions to 720–755°C and 1.2–1.3 GPa (corresponding to depths of ~ 38–44 km in the lower crust), occurring via the fluid-present melting reaction: Ms + Pl + Qz + Ilm + H2O = Kfs + Mag + Melt, followed by the fluid-absent melting reactions: Ms + Bt + Pl + Qz = Grt + Kfs + Melt. The protoliths underwent deep subduction and metamorphism during the Triassic, followed by exhumation to lower crust levels and subsequent remelting in the Late Jurassic. The fluid-present melting was likely triggered by aqueous fluid released from the underlying metamorphic rocks during the westward low-angle subduction of the Paleo-Pacific plate in the Jurassic. The resulting magmatism formed the Jingshan granites along the southeast margin of North China Block. These granites provide a compelling example of crustal recycling and rejuvenation during accretionary orogenesis, offering key insights into the evolution of continental crust during craton destruction.
Keywords:
zircon geochronology
garnet generations
phase equilibrium modelling
crustal anatexis
continental collisional orogen
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