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K-Ar dating of volcanic rocks younger than 0.1 m.y.

小于 0.1 m.y 的火山岩的 K-Ar 测年

基本信息

批准号：
60840021
负责人：
MATSUDA Jun-ichi
金额：
$ 7.17万
依托单位：
Kobe University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research
财政年份：
1985
资助国家：
日本
起止时间：
1985 至 1986
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-60840021/
关键词：
Age dating K-Ar age Age isotope 同位体比質量分析

项目摘要

In this research project it was very important to measure Ar isotopic ratios of rock samples precisely. To set up the mass spectrometer we at first made a computer program to simulate ion trajectory. This computer program draws ion trajectory for any magnet shape and ion source position, which is very useful to design a mass spectrometer. We gathered all parts of the mass spectrometer during the first year and set up the machine. Basic and necessary data were collected for ion source, collecter, Ta furnace, and gas purification system. We noticed that the discrimination factor of isotopic ratios were largely influenced by the high voltage of the electron multiplier. Complete automotion system, using a computer and A-D converter, was also developed to get the age data directly.Sensivity of the mass spectrometer have been stable and the discrimination factor was very large but was very much constant, which lead us to do age determination of actual rock samples.The age determinations were performed for two samples which ages were already known and younger than 0.1 m.y. If errors were assigned only from the variation of the discrimination factor, the obtained ages were 0.056 <-!+> 0.005 m.y. for Korean trachyte and 0.028 <-!+> 0.017 m.y. for andesite, respectively. The errors from the hot blank correction gave the relative error of 50% for trachyte and 100% for andesite. We also measured three rock smaples which ages were about 3 m.y. The ages were precisely determined for these samples if air contaminations were low.

在本研究项目中，精确测量岩石样品的氩同位素比值是非常重要的。为了建立质谱仪，我们首先编写了一个计算机程序来模拟离子轨迹。该程序可绘制任意形状的磁体和离子源位置的离子轨迹，对设计质谱仪非常有用。我们在第一年收集了质谱仪的所有部件，并安装了机器。收集了离子源、收集器、塔炉和气体净化系统的基本和必要数据。我们注意到同位素比值的判别因子在很大程度上受电子倍增器高压的影响。利用计算机和模数转换器，开发了完整的自动化系统，可直接获取年龄数据。质谱计的灵敏度是稳定的，判别因子很大，但非常恒定，这使得我们可以对实际岩石样品进行年龄测定。对年龄已知且小于0.1 m的两个样本进行了年龄测定。如果仅从判别因子的变化中分配误差，则获得的年龄为0.056 <-！+> 0.005 m.y.为韩文粗胞和0.028 <-！安山岩为0.017 m.。热空白校正的相对误差对粗面岩为50%，对安山岩为100%。我们还测量了三个岩石样本，它们的年龄约为3岁。如果空气污染低，这些样本的年龄可以精确地确定。