K-Ar等时线定年法及其应用

本文提供了11条不同成因、不同时代岩石和矿物的⁴⁰Ar/³⁶Ar-⁴⁰K/³⁶Ar等时线,其中3条是新近测定的,另8条是对以前常规K-Ar定年资料的重新处理。测定对象包括年轻火山岩、花岗岩、矿脉及古老岩系中的铁镁质岩墙。测定的时间跨度从第四纪到前寒武纪。研究证明,K-Ar等时线定年既具有常规定年测定对象广泛、可测时间跨度大的优点,又能避免常规法的缺陷,可获得更可信的年龄和更多的有用信息。但是负截距的形成及其所代表的地质意义尚有待深入研究。

K-Ar ISOCHRON DATING METHOD AND ITS APPLICATIONS

Eleven 40Ar/39Ar-40K/39Ar isochrons obtained on rocks and minerals of various times and geneses were reported. Among them three were measured recently and other eight were reestimated from previous conventional K-Ar dating data, These new dated materials include diabase dykes emplaced in Archaean gneissic rocks in Luliang area, some age-unknown mafic dykes in Junggar area of Xinjiang Region and granitic rocks emplaced in Precambrian strata in Da Higganling area- Their isochron ages are 1945 Ma, 587 Ma and 184.6Ma, respectively. The materials for reestimated isochrons include tungsten-bearing granites and wolframite-quartz veins in South China and younger volcanic rocks in Tengchong geothermal area. The dated time-interval is in a range from Mesozoic to Quarternary. All of these data indicate that the K-Ar isochron age dating like the conventional K-Ar dating method, has its advantages in dating materials in extensive time interval from Precambrian to Quarternary on the one hand, and like the Rb-Sr isochron method, can give the more reliable age data and the more useful information. It can give some information on genesis.