摘要
利用分阶段热解释放气体质谱分析法研究了冲绳海槽浮岩热解释放气中CO2和H2O的碳、氢同位素组成,结果显示:浮岩中原生CO2和H2O主要释放于400～1000℃,CO2的碳同位素组成介于-6 7×10-3～-22 7×10-3,H2O的氢同位素组成从-45×10-3变到-71×10-3,均落入幔源火山岩的变化范围,而且浮岩的氢同位素组成与海槽区玄武岩的氢同位素组成非常接近,这表明冲绳海槽浮岩与玄武岩之间具有密切的成因联系,浮岩岩浆和玄武岩岩浆是同源岩浆不同程度结晶分异的产物.另外,这些浮岩较洋中脊玄武岩要贫13C,并富集D,同时具有从洋中脊玄武岩向岛弧玄武岩变化的趋势,这表明浮岩岩浆在形成或上升过程中可能受到俯冲板块释放流体的影响.
The carbon and hydrogen isotopic compositions of CO_2 and H_2O in the gas releasing from the pumice samples in the Okinawa Trough by stepped heating are determined by the mass spectrometer.The primary CO_2 and H_2O are mainly released between 400 and 1 000 ℃.The carbon isotopic compositions of CO_2 vary between-6.7×10^(-3) and -22.7×10^(-3),and hydrogen isotopic compositions of H_2O vary from -45×10^(-3) to -71×10^(-3),which indicate the mantle source of the primary magma of pumices.Also,the hydrogen isotopic compositions of pumices are almost as same as those of basalts.This infers the close petrogenic relationship between them and pumices might have common magma sources with the basalts in the trough,but only they experienced different evolving processes.However,the carbon isotopic compositions are systematically lighter than those of mid-ocean ridge basalts,and tend to gather those of island arc rocks.Hydrogen isotopic compositions are heavier than those of mid-ocean ridge basalts,and also run to those of island arc rocks.These features suggest the influence of the fluid derived from the subducting slab on the magma during its forming and ascending process.
出处
《海洋学报》
CAS
CSCD
北大核心
2004年第6期58-64,共7页
基金
国家"973"重大资助项目(G2000078503)
山东省自然科学基金资助项目(Y2000E16).
关键词
碳、氢同位素组成
俯冲板块
浮岩
冲绳海槽
carbon and hydrogen isotopic compositions
subducting slab
pumice
Okinawa Trough
