Helium, neon and argon isotope compositions of fluid inclusionshave been measured in hydrothermal sulfide samples from the TAG hydrothermal field at the Mid-Atlantic Ridge. Fluid-inclusion 3He/4He ratios are 2.2-13.3 ...Helium, neon and argon isotope compositions of fluid inclusionshave been measured in hydrothermal sulfide samples from the TAG hydrothermal field at the Mid-Atlantic Ridge. Fluid-inclusion 3He/4He ratios are 2.2-13.3 times the air value (Ra), and with a mean of 7.2 Ra. Com-parison with the local vent fluids (3He/4He=7.5-8.2 Ra) and mid-ocean ridge basalt values (3He/4He=6-11 Ra) shows that the variation range of 3He/4He ratios from sulfide-hosted fluid inclu-sions is significantly large. Values for 20Ne/22Ne are from 10.2 to 11.4, which are significantly higher than the atmospheric ratio (9.8). And fluid-inclusion 40Ar/36Ar ratios range from 287 to 359, which are close to the atmospheric values (295.5). These results indicate that the noble gases of fluid inclu-sions in hydrothermal sulfides are a mixture of mantle- and seawater-derived noble gases; the partial mantle-derived components of trapped hydrothermal fluids may be from the lower mantle; the helium of fluid inclusions is mainly from upper mantle; and the Ne and Ar components are mainly from seawater.展开更多
基金The authors would like to thank Prof. Zhao Yiyang, Prof. Li Jincheng, Dr. Li Yanhe, Dr. Chu Feng-you for their critical review and constructive comments for improving the manuscript This work was financially supported in part by the Natural Science Fou
文摘Helium, neon and argon isotope compositions of fluid inclusionshave been measured in hydrothermal sulfide samples from the TAG hydrothermal field at the Mid-Atlantic Ridge. Fluid-inclusion 3He/4He ratios are 2.2-13.3 times the air value (Ra), and with a mean of 7.2 Ra. Com-parison with the local vent fluids (3He/4He=7.5-8.2 Ra) and mid-ocean ridge basalt values (3He/4He=6-11 Ra) shows that the variation range of 3He/4He ratios from sulfide-hosted fluid inclu-sions is significantly large. Values for 20Ne/22Ne are from 10.2 to 11.4, which are significantly higher than the atmospheric ratio (9.8). And fluid-inclusion 40Ar/36Ar ratios range from 287 to 359, which are close to the atmospheric values (295.5). These results indicate that the noble gases of fluid inclu-sions in hydrothermal sulfides are a mixture of mantle- and seawater-derived noble gases; the partial mantle-derived components of trapped hydrothermal fluids may be from the lower mantle; the helium of fluid inclusions is mainly from upper mantle; and the Ne and Ar components are mainly from seawater.
