火成岩中石英的Al芯和Ti芯的光衰退和ESR测年研究  

The fading of light and ESR dating of quartz Al and Ti centers for igneous rock

作　　者：金嗣炤[1] 杨刚[2] 陈江峰[2] 

机构地区：[1]中国科学技术大学结构分析开放实验室,合肥230026 [2]中国科学技术大学地球和空间科学系,合肥230026

出　　处：《核技术》2001年第12期964-968,共5页Nuclear Techniques

摘　　要：在 10 0K低温、5× 10 - 4T调制磁场的条件下 ,测得Al芯和Ti芯的电子自旋共振 (ESR)波谱并计算其年龄。由于改进了实验条件 ,得到的ESR图谱稳定 ,重复性好 ,为峰的选择和峰高的测定提供了方便。所得到的总剂量拟合直线的线性度高 ,大大减小了实验误差。本文对火成岩中的石英样品进行了光衰退实验 ,结果表明 ,在紫外光的作用下 ,Al芯和Ti芯的信号强度呈指数衰减 ,不能被光衰退的Al芯和Ti芯大约占 5 0 %。而在自然光的照射下 ,Ti芯可以衰退到原来的 2 7% ,Al芯仍为 5 0 %。The ESR dating of Al and Ti centers for the quartz in igneuse rock can give the time when the rock reached the closure temperature. But the use of this method is hindered by two factors: 1) the ESR signals of Al and Ti centers can only be obtained at low temperature(100K); 2) The ESR full-peak spectra are complex . It is difficult to choose the peak for dating. For the reasons given above, little work has been done with Al and Ti centers to date the igneous rocks. In this work, the experiments were done at 100K and in a modulation magnetic field of 5×10 -4 T, and got good results because of the suitable conditions. The spectra were stable and well reproduced. It was easy to choose a peak for dating and to determine the height of the peak. In our sample, the age of Al center and Ti center were 774.7ka and 256.0ka, respectively. The difference between the ages was induced by the fading of sun-light. Experiment had been done by sunlight and ultravoilet exposure. The result was that 50% Al-centers and 27% Ti-centers were left by sunlight, 50% Al-centers and 50% Ti-centers were left by ultraviolet exposure.

关 键 词：电子自旋共振 火成岩 Al芯 Ti芯 调制磁场 光衰退 ESR 地质样品 年代测定 

分 类 号：P588.1[天文地球—岩石学] P597[天文地球—地质学]