康定杂岩黑云母、角闪石^39Ar-^40Ar年龄及其意义

通过对康定杂岩黑云母、角闪石 Ar-Ar 年龄研究,得出康定杂岩黑云母、角闪石中 Ar 同位素组成明显存在地质离散,有过剩氩;Ar-Ar 年龄并不反映矿物形成后的变质冷却历史。坪的产生可能是由过剩~(40)Ar 存在于非晶粒边缘的缺陷之中,使其与放射性成因~(40)Ar 具有相似活化能,从而使不同种 Ar 组分等比例释气所致。经计算,样品中过剩氩约占氩总量的16%左右。

^39Ar-^40Ar dating of biotites and hornblendes in the Kangding complexes and their significances.

Through the study of Ar-Ar ages of biotites and hornblendes in the Kangding complexes by step-heating release technology,we found the existence of excess argon in these minerals and the irrelevance between the apparent age and the history after metamorphism of the plutonic complexes.Excess argon is trapped in defects which are not connected with the grain boundary,thus it needs the same energy as the radiogenic argon to come out of grain.This feature brings a mixing of different argon components which can explain the plateau ages.And excess argon may take about 16% of total argon.