浙江庆元地区早—中侏罗世火山岩LA-ICP-MS锆石U-Pb年龄及其地质特征

    LA-ICP-MS zircons U-Pb ages and geological characteristics of EarlyMiddle Jurassic volcanic rocks in the Qingyuan area, Zhejiang Province

    • 摘要: 在浙江庆元大面积白垩纪火山岩分布区,首次发现层位可归入毛弄组的早-中侏罗世火山岩,用LA-ICP-MS技术测得其中流纹英安岩和流纹质弱熔结凝灰岩中的锆石U-Pb年龄分别为176.0±1.2Ma和169.1±3.3Ma。结合闽北地区发现的中侏罗世火山岩,推断东南沿海地区在早-中侏罗世时已开始进入古太平洋板块俯冲的构造体制。

       

      Abstract: The Early-Middle Jurassic volcanic rocks were discovered for the first time in Qingyuan area of southern Zhejiang Prov-ince, where the Cretaceous volcanism was intense. They consist of rhyodacite and rhyolitic ignimbrite and can be assigned to Ma-onong Formation. Their LA-ICP-MS zircon U-Pb ages are 176.5±0.7Ma and 169.1±3.3Ma respectively. Combined with Middle Jurassic volcanic rocks in northern Fujian Province, it is inferred that southeast coastal areas began to enter the paleo-Pacific plate sub-duction system in Early-Middle Jurassic.

       

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