【摘要】 对西大别四道河含石榴子石花岗片麻岩进行了锆石U-Pb和石榴子石Lu-Hf年代学测试,锆石U-Pb谐和年龄为(223±1)Ma,石榴子石-全岩Lu-Hf等时线年龄为(212.2±0.7)Ma。石榴子石具有极高的母子体同位素比值(176Lu/177Hf=~300)。结合锆石和石榴子石的微量元素特征,该锆石U-Pb年龄代表的可能是超高压/高压变质时间,石榴子石Lu-Hf年龄代表的是石榴子石重结晶时间,可能指示了后期退变质作用流体活动。更多还原

【Abstract】 We dated a garnet-bearing granitic gneiss from the West Dabie Mountains using combined zircon U-Pb and garnet Lu-Hf isochron dating.A weighted-mean 206Pb/238U age of(223±1) Ma is older than the mineral-whole rock Lu-Hf isochron age of(212.2±0.7) Ma.The garnet fractions have extremely high parent/daughter ratios(176Lu/177Hf = ~300).Taking the trace element zoning patterns of both zircon and garnet into account,the zircon U-Pb age is,therefore,interpreted to reflect high-pressure eclogite-facies metamorphism while the Lu-Hf age records a later event of garnet recrystallization,likely indicating fluid activity during retrograde metamorphism.更多还原