古老地体形成后经历的复杂历史:共存副矿物U-Pb定年约束木子店地体的后期改造OA

[Objective]The Muzidian gneiss complex,located on the northern margin of the Yangtze Craton,represents the oldest Eoarchean terrane reported in China to date.Ancient terranes typically undergo a protracted and complex history of post-formational reworking,yet whether and how such processes affected the Muzidian terrane remains poorly constrained.Further study is warranted to investigate the extent of this late-stage modification and how these processes were recorded by accessory minerals.[Methods]This study conducted in-situ U-Pb dating on coexisting geochronometers,including zircon,titanite,and apatite,within Muzidian gneiss samples.[Results]The geochronological results reveal that zircon preserves two groups of Archean initial crystallization ages at approximately～2.5 Ga and～3.7 Ga.In contrast,the U-Pb age of titanite is 125.3±1.5 Ma and apatite is 120.7±3.4 Ma,they are significantly younger than the magmatic crystallization ages.This discrepancy indicates that the Muzidian gneissic body underwent a subsequent reworking event,likely a tectono-thermal pulse,between 125-120 Ma.Combined with recently reported monazite data,the REE-rich accessory minerals in the Muzidian gneiss generally record Early Cretaceous ages(between 130 and 120 Ma).Notably,these minerals exhibit a chronological succession—monazite(～130 Ma),titanite(～125 Ma),and apatite(～121 Ma)—that correlates with their respective closure temperatures,likely representing a cooling sequence following a thermal event.[Conclusions]In summary,the multi-mineral dating results demonstrate that the Eoarchean Muzidian gneiss has been profoundly influenced by complex geological processes since its formation.The preserved whole-rock geological records likely represent a composite of multiple magmatic episodes rather than a simple product of a single primary magma's crystallization.Therefore,the interpretation of geochemical and isotopic data from ancient rocks must fully account for such inherent geological complexity.