| 变质岩中白云母的钾-氩法适应性研究 |
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| 引用本文：刁乃昌,张华丽,唐淑兰,王艳英.1986.变质岩中白云母的钾-氩法适应性研究[J].地球学报,8(2):73-79. |
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| 中文摘要:变质岩中白云母在承受热力作用的时候,其物理性质随温度升高而变化,在700℃之前N_m一直是增大的,2V角等没有可察觉的变化。当温度高于700℃时,物理性质、光学特征变化显著,N_m和2V角急剧降低,在曲线变化的拐点上,氩的逸失也是强烈的,白云母逸失曲线表明,它有三个临界阻隔温度,300℃、700℃和900℃,相应可分为三个氩逸失阶段:300—700℃,氩析出5％;700—900℃,氩析出70％±;1000℃以上,氩析出25％±。用白云母测得的K-Ar年龄具有较高的可信度,当其物理性质没有明显变化时,年龄偏 |
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| STUDY OF ADAPTABILITY OF THE K-Ar METHOD FOR MUSCOVITE IN METAMORPHIC ROCKS |
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| Abstract:When muscovite in rocks undergoes a thermodynamic metamorphic process, its physical properties will change with the temperature increment. Below 700℃, its refractive index Nm is in the incremental stage, and the angle 2V, the luster and the elasticity do not change distinctly. Above 7001, the values of Nm and 2V decreas suddenly, and the physicaJ properties and optical features change greatly. It has been found that at the points of inflexion on the variation curves for Nm and 2V the escape of argon gas is strong.The curve of escape of argon gas for muscovite indicates that there are three critical temperature values, i. e. 300℃, 700℃ and 900℃. Accordingly three sections or phases for the argon escape could be divided, within the ranges of 300-700℃, 700-900℃ and above 1000℃-The amounts of gas-escaping are about 5%, 70% and 25% respectively.The K-Ar data given by muscovite which does not show abnormal physical properties, are quite reliable. The isotopic age value thus obtained may have an error of up to 5% due to the escape of argon caused by the increase of temperature. And this indicates that the mineral has never been subjected to a temperature over 700℃. |
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