摘要
本文叙述了电子自旋共振(ESR)地质年龄测定法的发展,并结合贝壳、珊瑚、石笋和黄土的年龄测定,讨论了直线和曲线拟合求TD值,以及有限和无限元体系求D值的计算法.最后引用一些实例,表明ESR年代法有广阔的发展前景.
ESR dating in Quaternary geology is a relatively new technique. lts deve-lopment, principles and applications have been described in this paper.
Early in 1960's, the age of coal was once dated by ESR technique. Then about 20 minerals, moon rocks and ancient pottery and porcelain were studied by this method. But, most of the results did not have definite geological signi-ficance because the beginning points in their geological clocks were not sure rhen to be set.
Since 1975, great more samples, stich as speleothom, corals, shells, forami-nifera, fossil bones etc. have been determined by ESR dating. The reliability of their ages is confirmed by crosschecking with other dating methods such as 14C, U/Th and paleomagnetism.
ESR dating has been studied in China for the latest four years. There are about 10 units including universities and institutes, where the scholars have been engaged in stutying the new method.
The principles of ESR dating are briefly explained as follows. Natural radi-ation1 (ray) from decay of the radioactive elements (U, Th, K) creates unpaired electrons/holes, which fill the vacant electron/hole traps. The concen-tration of stable and unpaired electrons. can be determined from the ESR sig-nal intensity. The total dose (TD), received by the sample during the geologin-cal time sinde formed, is directly proportional to the concentration of unpaired electrons, and can be measured by the additive dose method. On the other hand, the annual dose (D), received by the sample for one year, can be determined by different model designs such as close-equilibrium model and 222Rn logs model etc., based on different geologica] setting. It is obvious that the age (T) of the sample is calculated by the formula:T =TD/D. In respect of the applications, there are five fields should be concerned: 1. age determinations of the secondary carboaates, 2. age determinatioas of tha biological fossils, 3. age determinations of loess and fault goup, 4. study of the geothermal histories, 5. age determinatioas of other miaerals such as gypsutn, dolomite, fluoride.halite, mica, zircon and feldspar.
As mentioned above, ES.R dating has just devsloped in the recent decade. Therefore, some technique and model designs need more refinement so as to coincide witli geological and archaeological studies.
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
1989年第2期89-100,共12页
Marine Geology & Quaternary Geology
