Abstract:
Abstract:In this paper the authors conducted zircon U-Pb SHRIMP isotopic dating of the granitic garnet-biotite gneiss of the Aojiao Group at Aojiao Village of Dongshan County in Fujian Province. The Th/U ratios in the range of 0.31-1.01 (0.48 on average) show that the zircon is a typical magmatic mineral. The weighted mean 206Pb/238U age is 152.8±1.6 Ma(n=17,MSWD=1.12), which is considered to be the formation age of the gneiss. Some conclusions have been reached:(1)The granitic garnet-biotite gneiss of the Aojiao Group was formed in late Jurassic rather than in pre-Devonian;(2)the Qinyingshan Formation of the Aojiao Group should be divided into metamorphic intrusions and metamorphic sedimentary strata.