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稀有气体是地球流体源区信息的有效示踪剂。利用热熔融法对山东地区幔源巨晶、包体全岩及其单矿物以及寄主玄武岩等幔源样品中稀有气体的测试表明,不同类型样品具有明显不同的稀有气体同位素组成,特别是He同位素比值差异明显。巨晶和包体单矿物中的n(3He)/n(4He)值分别为0.87～11.31Ra、0.911～10.11Ra,均值分别为6.1Ra和3.73Ra,主体介于地幔—大气—地壳源区之间;包体全岩中n(3He)/n(4He)值0.19～2.30Ra(均值为1.05Ra),且均低于相应单矿物中该比值;而玄武岩中n(3He)/n(4He)值全为10-8数量级,与地壳均值无异。各类幔源样品中n(40Ar)/n(36Ar)值无明显差异,介于296.4～864.3,高于大气但远低于典型地幔值。所获有限数据中,不同类型样品中n(20Ne)/n(22Ne)值均高于大气,具幔源特征,其中包体全岩及其单矿物n(20Ne)/n(22Ne)值分别为10.19～12.42和10.55～11.80,无明显差异;玄武岩中该值介于11.07～13.10,总体高于包体全岩及其单矿物。上述比值特征的差异反映了不同类型幔源样品各自不同的成因和演化特征:巨晶和包体单矿物中的轻稀有气体同位素组成主要反映了由于古板块俯冲所导致的岩浆源区地幔—大气/地壳的混合特征,个别样品中可能存在宇宙成因3He;除单矿物中所体现的源区混合特征外,包体全岩还存在放射成因4He;而玄武岩在喷出地表后丢失大量地幔稀有气体信息,其同位素组成主要体现了放射成因4He的影响。
Rare gas is an effective tracer of information about the source of the Earth’s fluid. The tests of rare gas in mantle-derived megacrysts, whole-body inclusions and single minerals in the Shandong area and mantle source samples such as host basalt by hot-melt method show that the different types of samples have obviously different rare gas isotope compositions, especially He isotopes The difference is obvious. The n (3He) / n (4He) values of monomorphic minerals and inclusion minerals range from 0.87 to 11.31Ra and 0.911 to 10.11Ra, with mean values of 6.1Ra and 3.73Ra, respectively. The main body lies in the mantle-atmosphere-crust source (3He) / n (4He) values range from 0.19 to 2.30Ra (average 1.05Ra) in the whole rock mass, which are lower than those in the corresponding single minerals. However, the value of n (3He) / n 4He) values are all in the order of 10-8, which is the same as the crustal mean. The values of n (40Ar) / n (36Ar) in all types of mantle source samples show no significant difference, ranging from 296.4 to 864.3, which is higher than the atmospheric level but much lower than the typical mantle values. In the limited data obtained, the values of n (20Ne) / n (22Ne) in all samples were higher than those in the atmosphere and mantle, and the values of n (20Ne) / n (22Ne) Ranging from 10.19 to 12.42 and from 10.55 to 11.80. The value of basalt is between 11.07 and 13.10, which is generally higher than that of the whole ore body and its single mineral. The differences in these ratios reflect the different genesis and evolution characteristics of different types of mantle source samples. The light rare gas isotopic composition of megacrysts and inclusions of single minerals mainly reflects that the mantle-atmosphere / Crustal assemblage. Cosmogenesis 3He may exist in some samples. Radiation genesis 4He also exists in the whole rock of the enclave, except that the source rocks are mixed in a single mineral. However, a large amount of mantle gas is lost after the basalt is discharged Information, its isotope composition mainly reflects the impact of radiation-induced 4He.