【摘要】 通过区域地质调查研究,在湘东北文家市涧溪冲村原中元古代冷家溪群新发现一套基本无序的变质沉积-火山岩系。根据岩石矿物学、岩石地球化学研究表明,涧溪冲变质沉积-火山岩系为变质火山岩夹变质粘土质沉积岩,属绿片岩—高绿片岩相。变质火山岩的原岩为大洋拉张环境下形成的以低钾拉斑玄武岩为主,低钾玄武安山岩次之的火山-次火山岩系,其物源为亏损地幔。变火山岩Sm-Nd全岩等时线年龄为(2594±48)Ma,其形成时代可能是新太古代。因此,与传统的中元古代冷家溪群的岩石组合、形成环境、形成时代、变质变形都具有明显不同的特征,原冷家溪群应予以解体。更多还原

【Abstract】 Through regional geological investigation and research, the authors found a metasedimentary-volcanic series in the original Mesoproterozoic Lengjiaxi Group at Jianxichong Village, Wenjia City, northeastern Hunan. Mineralogical, petrological and geochemical studies indicate that this metasedimentary-volcanic series is a metamorphic series consisting of metavoIcanic rocks with metamorphosed clayey sedimentary rocks. The metamorphism is of greenschist-high greenschist farcies. The protolith of the metavolcanic rocks is a volcanic-subvolcanic rock series composed chiefly of low-K tholeiite with subordinate low-K basaltic andesite formed in an oceanic extensional environment. The provenance was the depleted mantle. Whole-rock Sm-Nd isochron dating of the metavolcanic rocks indicates a Neoarchean age. Therefore, they are notably different from the traditional Mesoproterozoic Lengjiaxi Group in rock association, formation environment, formation age and metamorphism-deformation. So the original Lengjiaxi Group should be disintegrated.更多还原