The Geochemical Cycles of 9-Be and 27-Al and Other Reactive Trace Elements

这个项目最初是为了建立海洋中Be和Al稳定同位素的系统，以期利用它们的宇宙成因放射性同位素作为地质年代学工具。这里与C- 14有一个明确的类比。碳参与生物地球化学循环；因此，衰变对放射性同位素分布的影响被非放射性成因过程所掩盖。然而，稳定同位素C-12只受生物成因过程的影响，因此可以用来校正它们对放射性同位素的影响。这种方法的成功很大程度上得益于这样一个事实，即碳同位素共享一个共同的、混合良好的储集层——大气。be和Al的情况并非如此。该项目的目的是确定这些元素在海水中的停留时间和化学行为是否足以在海洋储层中实现同位素平衡。如果这是真的，那么在0到1500万年的范围内，海洋沉积物的直接放射性测年将是可行的。请支助继续研究Be和Al同位素的地球化学循环，以期将其发展成为地球时计。建议参加南大西洋通风实验考察，将覆盖范围扩大到南大西洋，并研究大西洋水团从其北部源区传播时同位素分布的演变。还要求支持与Orsay的Raisebeck小组合作，利用我们的专业知识和他专用的Be-10加速器来描绘Be同位素的大陆旋回。

This project began as an attempt to establish the systematics of the stable isotopes of Be and Al in the oceans with a view to using their cosmogenic radio-isotopes as geochronologic tools. There is an explicit analogy here to C- 14. Carbon is involved in the biogeochemical cycle; hence the effect of decay on the distribution of the radio-isotope is overprinted by non-radiogenic processes. However the stable isotope C-12 is affected only by the biogenic processes and hence can be used to correct for their effects on the radio- isotope. The success of this approach is greatly facilitated by the fact that the carbon isotopes share a common, well-mixed reservior, the atmosphere. The latter is known not to be the case for Be and Al. The objective of this project is to establish whether the residence time and chemical behaviours of these elements in seawater is such that isotope equilibrium is achieved in the oceanic reserviour. If this were true then direct radiometric dating of marine sediments would be feasible in the range 0 to - 15 million years. Support is requested to continue investigations of the geochemical cycles of the isotopes of Be and Al with a view to developing them as geochronometers. It is proposed to participate in the South Atlantic Ventilation Experiment expedition to extend coverage into the South Atlantic and to examine the evolution of the isotope distributions as the Atlantic water masses propagate from their northern sources areas. Support is also requested for collaboration with Raisebeck's group in Orsay in a delineation of the continental cycles of the Be isotopes using our expertise and his dedicated Be-10 accelerator.