【摘要】 <正> 一、前言为了便于对锶同位素初始比值均一化问题以及母源继承锶影响问题的讨论,最初的沉积岩年龄测定,通常选用自生的海绿石,但是其测定结果,除了个别成功的例子外,铷锶年龄普遍偏低,通常比沉积年龄低10—20%,有的甚至偏低更多。Compston,W和Pidgeon,R.T.(1962)测定了澳大利亚三个层位的页岩样品,其中两个层位全岩铷锶等时年龄和地层年代表十分符合。。另一层位样品,因样品点分散,无法计算年龄。Whitney,P.R.和Hurley,P.M.(1964)得到的页岩全岩铷锶等时年龄结果偏高。因此他们认为,只要存在母源继承更多还原

【Abstract】 The explanation of dates on the detrital recks is very complicated. That is caused by two facts: firstly, special underwater environment might result in the opening of the Rb-Sr radiogenic system, so that the radioactive clock would be interrupted; secondly, the presence of radiogenic strontium from the mother sources makes the explanation of dating confused. Therefore, the problem of the homogenization of initial strontium of the dettital rocks, and the problem of inheritance of strontium from the mother sources, as well as the problem of the consideration of geological environment are the very important ones to be solved.This paper explaned the concept and the mechanism of homogenization of the initial strontium of fine-grained detrital rocks. A nomenclature of "analo-hom-ogenization" or "statistical homogenization" was suggested for detrital rock in order to distinguish from the "real homogenization" or "chemical homogenization" which we are very familiar with. This paper explaned the aspects of the inheritance of strontiume from the mother sources. Firstly, the heterogeneous initial strontium would make an individual sample scatter isochron or even no isochron could be obtained, and, therefore, no age could be yielded. Secondly, the difference between the initial ratio of strontium yielded by the isochron defined by detrital rocks and that of paragenatic carbonates or other authigenic minerals could only indicate the presence of inheritance from mather sources, but would not influence the results of dating. This paper also reported the result of the age determination of the shales and carbono-sbales from Suijingtuo formation, Yichang, Hubei province by the method of Rb-Sr isochron. Also reporte are the results of ex periment of mineral seperation of carbonate and the detrital components from each other and their Rb-Sr measurement in order to observe the exchange of strontium between the detrital component and the carbonate paragenetic. The result reveals that there was isotopic exchange between the detritus and the carbonate paragenetic, but without reaching equilibrium. Ultimately, the age of the shales of Suijingtuo Formation as fine-grained detrital rocks must be 577.3m.y.which was yielded by the isochron defined by the shales and the detrital components seperated from the samples of arbono-shales, while an age of 592.9m.y. was obtained by the isochron defined by the shales and the carbonates seperated from the carbono-shales, and it was 3% older than the former age.更多还原