摘要
据横断山地区花岗岩类获得的Rb、Sr同位素结果,讨论和提出了全岩Rb-Sr等时线种类及其地质意义,以及影响同位素均一化的因素。对经常得不到线性较好的等时线的闪长岩类和富碱侵入岩(包括碱性岩和碱性花岗岩),用单矿物外部等时线,可能获得线性关系较好的等时线,以及可信度大的Sr初始比值和年龄。要获得好的Rb-Sr等时线必须根据样品Rb/Sr值与可能的年龄计算判别值,符合要求的才可作Rb-Sr等时线。衡量等时线的质量,应根据相关系数、MSWD值和均一度3个指标。
Based on the Rb-Sr isotopic study of the granitoids in the Hengduan Mountains, the classification and geologic significance of whole-rock Rb-Sr isochrons as well as the factors influencing homogenization of the isotopic system are discussed. Usually, there is no good linear correlation of isochrons for diorites and alkaline intrusions. But by means of the outside isochron of minerals from those rocks, isochrons with good linear relation as well as ages and initial ratios with a high confidence can be obtained. In order to obtain a satisfied isochron, the discriminant value should be calculated from the Rb/Sr ratios and estimated ages of the samples. Only those that meet the requirements can be used as the Rr-Sr isochrons. The quality of an isochron should be judged from three factors, i.e. correlation- coefficient, MSWD and homogeneous degree.
出处
《地质学报》
EI
CAS
CSCD
北大核心
1989年第4期373-382,共10页
Acta Geologica Sinica
