滇西墨江西部石炭、二叠纪火山岩

CARBONIFEROUS AND LATE PERMIAN VOLCANIC ROCKSOF WESTERN MOJIANG, YUNNAN

墨江西部出露有石炭纪和晚二叠世两套火山岩,它们呈平行的两条带分布。石炭纪火山岩以拉斑玄武岩为主,少量流纹岩,它们是由上地幔源区10%部分熔融形成的原始岩浆,经橄榄石、辉石和斜长石不同程度结晶分异作用形成。其喷发环境可能是一个发育在大陆边缘的张性海盆地。晚二叠世火山岩较为复杂,熔岩与火山碎屑岩交互发育,熔岩主要属于拉斑系列,还含有少量钙碱性系列岩石;形成于陆缘火山弧环境。

There are two parallel volcanic rock belts in western Mojiang.The eastern Carboniferous volcanic rocks consist mainly of tholeiitic basalts and some rhylites and they might be formed at an attenuated intra-continental basin.The primary magma was derived from upper mantle's 10% partial melting,and these volcanic rocks formed by fractional crystallization of olivine, pyroxene and plagioclase. The western late Permian volcanic rocks are complex,consisting of interbeding lavas and pyroclastic rocks.Lavas mainly contain tholeiitic series rock,and some calc-alkalic dacites. They might be formed at a volcanic arc of continental margin. It was suggested that the research area had undergone a whole Wilson cycle during C_1-W_3.