中国东南沿海地区地幔岩包体中流体及熔体包裹体研究

FLUID AND MELT INCLUSION RESEARCHES OF PYROLITE XENOLITHS FROM THE SHORE OF SOUTHEASTERN CHINA

浙江新昌和福建明溪地区新生代玄武岩中地幔岩包体矿物中的ＣＯ２包裹体和含ＣＯ２硅酸盐岩浆包裹体的研究表明，它们捕获于温度１２０７℃～１２６７℃和压力８１５～１１４７ｍｐａ条件下，约相当于３０～５０ｋｍ深的上幔环境；ＣＯ２包裹体流体成分是以ＣＯ２为主，有ＣＨ４、ＣＯ、Ｈ２Ｓ、Ｈ２Ｏ、Ｎ２、和Ｈ２等次要组分，代表地幔流体成分。含ＣＯ２硅酸盐岩浆包裹体均一后成分不同于寄主玄武岩，它富ＳｉＯ２、Ａｌ２Ｏ３、ＭｇＯ和Ｋ２Ｏ，贫ＦｅＯ和ＣａＯ，反映了未分异原始玄武岩浆的成分，它们可能是研究地区的地幔软流圈－岩石圈界面抬升，压力降低在地幔流体作用下发生的部分熔融作用的产物．

Rescarcles of CO2 and CO2-magma inclusions in minerals of pyrolite xenoliths in Cenozoic alkaline silicate basalts from Xinchang area of Zhejiang Province show that they are trapped at temperatures of 1207℃～1267℃ and pressures of 815～1147MPa which correspond the uppermantle circumstances about 30～50km.The compositions of the inclusions are mainly CO2 and less CH4,CO2,H2S,H2O,N2,H2 and rich in alkaline(Na2O+K2O),and may represent composition of mantle fluid.The compoitions of CO2-silicate magma inclusions after homogenization differ from those of the host basalts and pyrolites,they are rich in SiO2,Al2O3,MgO and K2O but poor in FeO and CaO,and may represent the primitive basalt magma composition.This indicate that the kind of inclusions can be the product of partial melting of minerals of pyrolite under the metasomatism of mantle fluid.This thermal event could occur with the left of mantle asthenosphere-lithosphere boundary and pressure reduction,since balaned pressure of pyrolite and trapped pressure of inclusions are between 1130～3230MPa and 815～1147MPa respectively.