海相年轻沉积物^(36)Cl定年研究  

^(36)Cl Dating of the Young Marine Sediments

作　　者：张楠[1] 刘卉[1] 安树清[1] 林源贤[1] 

机构地区：[1]天津地质矿产研究所,天津300170

出　　处：《岩矿测试》2010年第6期655-658,共4页Rock and Mineral Analysis

基　　金：国土资源地质大调查项目资助(199920190114;20020190118)

摘　　要：提取、纯化海相沉积颗粒表面"诱导吸附"的36Cl(和Cl),制成加速器质谱(AMS)测定放射性比度I(36Cl/Cl)所需的标准样品,即高纯度AgCl;定量计算出沉积颗粒沉积封闭时的放射性比度I0(36Cl/Cl),依据放射性衰败定律I=I0e-λt计算得到沉积年龄t。研究结果表明:年轻的海相沉积物沉积封闭时的36Cl放射性比度I0与地理纬度之间存在一定比例关系,采取具有代表性、无污染的太平洋表面海水(4°18′N,161°09′E),经AMS测出的36Cl放射性比度IL为99.34±10.30,再利用36Cl产率与纬度的关系图,得出"放射性比度-产率"的比例常数μ为23.65238。测定了两个海底沉积物和一个海底锰结核的放射性比度I,计算得到的沉积年龄分别为83.2×104a、74.0×104a、17.6×104a。文章提出的I0定值计算方法具有科学依据,可操作性强,为揭示海洋沉积地层相关关系和沉积年龄精确测定提供技术支撑。Accelerate mass spectrometry（AMS） has been used to the measurement of specific activity I（^36Cl/Cl） of high purity AgCl made of ＂inducing-adsorbed＂ ^36Cl（and Cl） collected and purified from the surface of young marine sediments.Sediment age（t） was calculated from closed specific activity I0（^36Cl/Cl） of sediment grain based on the radioactive decay law I=I0e-λt.The study shows that the specific activity I0 of closed ^36Cl in earlier marine sediment has linear relationship with latitude.^36Cl specific activity IL from typical and uncontaminated seawater of the Pacific Ocean（4°18′N,161°09′E） surface was measured by AMS and the result was 99.34±10.30.And taking account of latitude factor,the proportionality constant of specific activity-yield（μ） was obtained as 23.65238.36Cl specific activity of two sediments grains and a manganese nodule from seabed has measured and the ages of sedimentation for the samples are 83.2×10^4 a,74.0×10^4 a and 17.6×10^4 a,respectively.The calculation method of I0 is of scientific foundation and accessibility and it can provide the exact sedimentation ages and explain the correlation of marine sediment layers.

关 键 词：海相年轻沉积物 36Cl 沉积物定年 放射性比度 

分 类 号：P736.211[天文地球—海洋地质] O613.42[天文地球—海洋科学]