浙江东部火山岩地区的地层时代和划分

通过对浙东地区地层特征与划分、同位素年龄等综合分析,结合近年来的新资料,认为该区前寒武纪地层由太古宙地壳物质再循环重熔结晶形成;芝溪头变质杂岩原岩可能由古元古界八都(岩)群与石炭系—二叠系沉积地层组成,二者共同于晚二叠世—中三叠世发生变质作用;中生代大规模火山岩浆活动主要发生在早白垩世晚期:磨石山群形成于早白垩世晚期,以大规模喷发酸性火山岩为特征;永康群、天台群中的众多地层也主要形成于早白垩世晚期,是不同火山构造盆地(洼地)喷发—沉积的同期异相堆积物或同期同物异名地层,以双峰式火山岩、"红层"为特征。

STRATIGRAPHIC AGE AND SUBDIVISION OF VOLCANIC ROCKS IN EASTERN ZHEJIANG

A series of comprehensive studies,including stratigraphic investigation and isotopic dating,have been completed to constrain the age and origin of volcanic rocks in eastern Zhejiang.Our data indicate that Precambrian strata in this region were derived from Archean crust which had experienced recycling and remelting.The protolith of the Zhixitou metamorphic complex is probably composed of the Paleoproterozoic Badu Group and Carboniferous-Permian sedimentary strata,both of which had suffered metamorphism during the P3-T2.Large-scale Mesozoic volcanic-magmatic activities mostly took place in K31 because there are few J1 or K11-K21 strata and J2-J3 strata are absent.Most of the Moshishan Group was formed in K31,during the large-scale eruption of acidic magmas.Most strata of the Yongkang and Tiantai Groups were formed in K31,too.They represent different facies of volcanic eruption and sedimentation,and they are characterized by bimodal volcanism and red sediments.