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玄武岩内刚玉巨晶中的稀有气体同位素组成,国内外文献均未有报道.对山东昌乐新生代玄武岩内刚玉巨晶研究显示,其3He/4He为1.13～7.37Ra,介于大气比值和MORB比值之间;20Ne/22Ne为9.67～10.75,21Ne/22Ne为0.0280～0.0372,在20Ne/22Ne-21Ne/22Ne图解中投影点沿MFL线和大气比值至MORB比值线分布;38Ar/36Ar为0.177～0.194,总体高于大气比值,40Ar/36Ar为280.9～404.2,近大气比值但略高;128～136Xe/132Xe普遍高于大气比值,其中129Xe明显较大气过剩.总体看,刚玉与该区地幔包体、辉石及歪长石巨晶矿物内的稀有气体同位素组成基本一致,与中国东部许多地区发育的幔源包体和巨晶矿物的He和Ar同位素组成也很相似.个别刚玉较其他样品具有异常稀有气体同位素比值,认为它曾长期暴露地表受宇宙射线作用所致.刚玉中的稀有气体继承自其形成环境中的流体,这种流体代表着俯冲板块脱出的流体与地幔发生混染/交代作用后的一种“地幔流体”.刚玉中稀有气体同位素组成不具壳源比值特征,刚玉矿物氧同位素组成也未反映出有壳源物质加入,因此,研究区刚玉巨晶可能是从幔源岩浆演化出的碱性熔体中直接结晶形成,壳源物质的贡献不明显.
The rare gas isotopic composition of corundum in basalts has not been reported in domestic and foreign literatures.Studies on the giant corundum in the Changle Cenozoic basalts from Shandong show that the 3He / 4He ranged from 1.13 to 7.37Ra, 20Ne / 22Ne is 9.67-10.75, and 21Ne / 22Ne is 0.0280-0.0372. In the 20Ne / 22Ne-21Ne / 22Ne diagram, the projection points are linearly distributed along the MFL line and the atmospheric ratio to the MORB ratio line. The distributions of 38Ar / 36Ar are 0.177 ~ 0.194, generally higher than the atmospheric ratio, 40Ar / 36Ar is 280.9 ~ 404.2, near the atmospheric ratio but slightly higher; 128 ~ 136Xe / 132Xe generally higher than the atmospheric ratio, 129Xe significantly more than the excess air.Overall, corundum and the area mantle The isotopic compositions of noble gases in the body, pyroxene and illuvial macrite minerals are basically the same, which are similar to the He and Ar isotopic compositions of mantle-derived inclusions and megacrysts developed in many areas of eastern China. Some corundums have abnormalities compared with other samples Rare gas isotope ratio, that it has long been exposed to the surface by cosmic rays caused by the corundum of rare gases inherited from its formation of fluids in the environment, this fluid represents the subduction of fluids and mantle occurred Dyeing / dating of a kind of “mantle fluid.” Rare gas isotopic composition of corundum is not characterized by the ratio of shell and source, corundum mineral oxygen isotope composition does not reflect the addition of the shell-like material, therefore, the study area corundum giant crystal may be from The alkaline melt evolved from the mantle magma directly crystallizes, and the contribution of the crust source material is not obvious.