大西洋洋中脊TAG热液区中块状硫化物的Os同位素研究

Os Isotopic Compositions of Seafloor Massive Sulfide from the TAG Hydrothermal Field in the Mid-Atlantic Ridge

新测得TAG热液区中 5件海底块状硫化物样品的锇含量及其同位素组成 ,187Os/ 186Os比值在 2 .30 5～7.879之间 ,均值为 5 .986 ,介于现代海水和上部洋壳岩石的锇同位素组成之间 ,表明该区海底块状硫化物中锇是海水和上部洋壳来源锇混合的产物。在海底热液循环过程中 。

New data on osmium isotopic compositions of four seafloor massive sulfide samples from the TAG hydrothermal field has been got, the 187 Os/ 186Os ratios of massive sulfide samples vary from 2.305 to 7.879, with a mean of 5.986, these ratios are between that of modern seawater and upper oceanic crust, and this range of Os isotopic compositions is likely the result of mixing of seawater with upper oceanic crust, maybe about 56% of osmium in the massive sulfides is from the seawater, and 44% is from the upper oceanic crust. The mixing of seawater with hydrothermal fluid have an obvious effect on the Os concentration and isotope composition of massive sulfide during the seafloor hydrothermal activity.