Monazite behaviour and age significance in poly-metamorphic high-grade terrains: A case study from the western Musgrave Block, central Australia

摘要: Abstract Integrated, in situ textural, chemical and electron microprobe age analysis of monazite grains a migmatitic metapelitic gneiss from the western Musgrave Block, central Australia has identified evidence for multiple events growth recrystallisation during poly-metamorphism Mesoproterozoic. Garnet + sillimanite-bearing metapelite underwent partial melting segregation to palaeosome leucosome metamorphism between 1330 1296 Ma, with recording crystallisation at ∼1300 Ma. Monazite breakdown is inferred have occurred palaeosome. During subsequent granulite facies event ∼1200 deformation resulted disturbance ages potential minor on Ma leucosome. Growth new, high-Y (+HREE) domains garnet presence sillimanite cordierite spinel, as result post-peak isothermal decompression. Diffusive enrichment resorbed rims Y + HREE suggests slower than volume diffusion REE. both were subsequently partially penetratively recrystallised retrogression that suggested ∼1150–1130 The intensity appears linked proximity retrogressed porphyroblasts their occurrence relatively reactive or ‘fertile’ local environments provided by palaeosome/mesosome volumes, which caused localised changes retrogressive fluids towards compositions more aggressive monazite. Like reaction textures, it apparent domainal equilibrium may control least strongly influence REE U–Th–Pb chemistry hence ages.