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在大陆环境中,相对于大气的~(129)Xe过剩在美国的Harding County和澳大利亚Caroline的二氧化碳气井,以及美国Navajo和印度Gujarat的烃类气中发现.这些~(129)Xe过剩,是地球早期形成现已灭绝的放射性核素~(129)I的衰变产物,它代表着地壳中地球原始组成的加入.中国东部由于拉张,沿北东～南西向断裂构造带分布着一系列中.新生代沉积盆地,其中普遍存在着幔源氦和氖.本文继续以前的工作,试图探讨天然气中氙的来源及其地质意义.1 样品及实验本项研究采集了中国东部的松辽、渤海湾、苏北和三水等4个沉积盆地共30个天然气样品.气体类型包括有二氧化碳、烃类和二氧化碳-甲烷-氮气混合气.天然气藏储层,松辽盆地为白垩系,其余3个盆地以第三系为主.利用全金属稀有气体净化系统和VG5400静态真空质谱计,测定氙同位素组成.制备系统和质谱计的氙本底变化为(5～8)×10~(-15)Cm~3(STP),对样品测量的影响可忽略不计.以大气作为标准,测定结果以既非放射性衰变成因核素也非裂变产物的~(130)Xe归一化绘于图1,同位素比值误差为1б.
In continental environments, ~ 129 Xe excess relative to the atmosphere is found in carbon dioxide gas wells in Harding County, the United States and Caroline, Australia, and hydrocarbon gases in Navajo, USA and Gujarat, India, which are excess The decay product of the now-extinct radionuclide ~ (129) I is formed in the early stage and represents the original composition of the Earth in the crust. The eastern part of China is distributed along a series of faults along the north-east-southwest fault zone. Cenozoic sedimentary basins, in which mantle-derived helium and neon are ubiquitous.This paper continues the previous work to explore the source of xenon in natural gas and its geological significance.1 Samples and experiments This study collected Songliao and Bohai Bay in eastern China , 30 samples of natural gas in 4 sedimentary basins of Northern Jiangsu and Sanshui, including gas mixtures of carbon dioxide, hydrocarbons and carbon dioxide-methane-nitrogen gas, reservoirs of natural gas, Cretaceous in Songliao Basin, and the remaining 3 basins (Tertiary), and the isotope composition of xenon was measured by using all-metal noble gas purification system and VG5400 static vacuum mass spectrometer.The change of xenon background in preparation system and mass spectrometer was (5 ~ 8) × 10 ~ (-15) Cm ~ 3 (STP) with negligible effect on sample measurements.Using the atmosphere as a standard, the results are normalized to ~ (130) Xe, which are both non-radioactive decay and non-fission products, with an isotopic ratio error of 1б.