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    福建东山县澳角村澳角群花岗质石榴黑云片麻岩锆石SHRIMP U-Pb定年及其地质意义

    Zircon U-Pb SHRIMP isotopic dating of granitic garnet-biotite gneiss of the Aojiao Group at Aojiao Village of Dongshan County, Fujian Province, and its geological significance

    • 摘要: 提要:本文对福建东山县澳角村澳角群花岗质石榴黑云片麻岩中17颗锆石进行了 SHRIMP U-Pb 同位素年龄测定。结果显示锆石Th/U比值变化于0.31~1.01,平均值为0.48,为典型的岩浆锆石;其中16个分析点在谐和图上分布较为集中,206Pb/238U年龄加权平均值为(152.8±1.6) Ma(n=17,MSWD=1.12);结合锆石自形、发育岩浆环带等特点,该年龄被解释为澳角群亲营山组花岗质石榴黑云片麻岩的形成年龄。其所指示的地质意义:(1)福建东山县澳角村澳角群亲营山组花岗质石榴黑云片麻岩形成于晚侏罗纪,而非前泥盆纪;(2)福建东山县澳角村澳角群亲营山组应解体为表壳岩与变质侵入体。

       

      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.

       

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