地幔流体中稀有气体同位素组成与幔源气藏

地幔流体中稀有气体同位素组成与其所处的大地构造背景和深部地幔岩浆活动性质有关。大洋中脊玄武岩的3He/4He值为8~10R;热点型地幔源区的3He/4He值最高在30R。以上;弧后盆地玄武岩和地幔包体的He同位素组成为5~22 R。,变化范围较宽;大陆地幔包体的He同位素比值为3~10Ra;金刚石的氦组分既有原始捕获的，也有外界注入的。我国东部裂谷盆地中存在3He/He比值为2.7~6.4 R。的幔源气藏，幔源气的运移和聚集成藏与区域深大断裂有关。地幔源区4Ar/3*Ar值为350左右,并随陆壳物质的加入而增高。地幔中有太阳型Ne存在,多数样品中Ne、Xe同位素比值与大气值一致,同时也发现了Ne、Xe同位素组成相对于大气的过剩现象,认为是由核成因造成的。

Noble Gas Isotopic Compositions in Mantle Fluids and Mantle-Derived Natural Gas Pool

Noble gas isotopic compositions in mantle fluids are associated with their tectonic settings and magmation in deep mantle. For'He/*He ratio, the mid-oceanic basalts range 8~ 10R; hot-spot mantle source is over 30R,; back-arc basinal basalts and mantle xenolithsvary widely frome 5Ra to 22R,; terrestrial mantle xenoliths are 3~ 10R; He component in diamonds is not only primitively captured, but al-so invaded from the outside. In rift basins of East China occurs mantle source gas pool with 3He/'He ratio of 2.7~6.4R,, and such mantlegases migration and accumulation are related to the regional deep faulting. In general, 40Ar/·*Ar value in mantle source is around 350,and increases with the feeding of continental crust materials. In mantle contains solar Ne, and samples reveal the same ratio of Ne and Xeisotopic compositions with atmospheric Ne/Xe ratio. Also, it is found out that Ne and Xe isotopic compositions appear excess phe-nomenon compared to the atmospheric ones. Study shows that they are characterized by nuclear origins.