摘要
本文讨论了锆石由于铅丢失造成的自晶体表层到晶体内部放射成因(^(207)Pb/^(206)Pb)_R的变化趋势;用热离子质谱计直接进行单颗粒锆石蒸发-沉积测年时,锆石在热离子质谱计灯丝上加热蒸发和在冷灯丝上沉积时物质的分布状况;锆石中的U-Pb体系是否为封闭体系的差别标志;与单颗粒锆石测年有关问题的讨论。
When a crystal of zircon is being evaporated on a thermal ionic mass spectrometer, the ratio of 207Pb/206Pb becomes greater and greater, and then gets gradually close to a definite value, which implies that the 207Pb/206Pb ratio in the outer layer of zircon is lower than that in the inner layer, and the definite value is just or close to the true ratio (without or with scarce lead loss, i. e. (207Pb/206Pb)R of the closed system). The key of dating single-grain zircon using the technique of stepwise evaporation-deposition is to judge the closed system. The material deposited on the ionic filaments is heterogeneous: the lower bed is the outer part of a zircon crystal, and the upper the inner. When the material was ionized, the top bed was measured first, and the lowest the last. Only when the area, which has been the closed system to U-Pb since the crystallization, is dated, can the crystallization age be obtained.
出处
《地质论评》
CAS
CSCD
北大核心
1995年第3期245-251,共7页
Geological Review
关键词
锆石
单颗粒锆石
年代学
质谱计
zircon, geochronology of single-grain zircon, experiment
