摘要
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。CCSD中HP-UHP岩石具有F40ArNoble 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 respectively, and the respective ~ 134 Xe/ ~ 132 Xe and ~ 136 Xe/ ~ 132 Xe are 0.376~0.484 and 0.324~0.416, all higher than their corresponding values of the air. He-Ar, Ne and Xe isotopic compositions suggest that the ore-forming fluid of the fluid inclusions in the CCSD HP-UHP rocks were composed mainly of crustal fluid and a little air-saturated water, while the mantle-derived fluid was nearly absent. In the fluid inclusions, the He derived predominantly from the crust, the Ar are composed mainly of crustal radiogenic ~ 40 Ar and about one third air Ar. A little amount of Ne and Xe might derive from the mantle. The characteristics of F~ 40 Ar