CCSD中HP-UHP岩石稀有气体同位素地球化学及其对板块折返过程的示踪意义

Nobel Gasesisotopic Compositions of HP-UHP Rocks in Chinese Continental Scientific Drilling (CCSD) Project and Their Constraints on Exhumation Process

利用高真空气相质谱系统测定了CCSD中HP-UHP变质岩中主要造岩矿物流体包裹体的稀有气体同位素组成,得出其3He/4He为(0.004~0.775)×10-6,相应R/Ra为0.003~0.553,40Ar/36Ar变化较大,为316.2~11358.8,高于大气40Ar/36Ar(295.5);20Ne/22Ne和21Ne/22Ne分别为9.47~12.4和0.026~0.051,而134Xe/132Xe和136Xe/132Xe分别为0.376~0.484和0.324~0.416,均高于其相应大气值。CCSD中HP-UHP岩石主要造岩矿物的He-Ar、Xe和Ne等同位素组成清楚显示其中流体包裹体主要由地壳变质流体和少量大气饱和水组成,而深源地幔流体组分很低,其中He主要来自地壳,Ar主要由壳源放射性成因40Ar*和少量(平均32.6%)大气Ar混合组成,少量Ne和Xe可能来自地幔。

Noble gases isotopic compositions of fluid inclusions in major rock-forming minerals in HP-UHP metamorphic rocks collected from the Chinese Continental Scientific Drilling (CCSD) were analysed by using a high vacuum gas mass spectrum. The results show that the ~ 3 He/ ~ 4 He ratios are (0.004~0.775) 10~ -6 , and the corresponding R/R_a are 0.003~0.553; The ~ 40 Ar/ ~ 36 Ar ratios are 316.2~11358.8, much higher than that of the air (295.5). ~ 20 Ne/ ~ 22 N and ~ 21 Ne/ ~ 22 Ne are 9.47~12.4 and 0.026~0.051 r...