ARGON DIFFUSION CHARACTERISTICS OF PYROXENES

辉石的氩扩散特性

• 批准号: 12640480
• 负责人: HYODO Hironobu
• 金额: $ 2.24万
• 依托单位: Okayama University of science
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12640480/
• 关键词: PROTEROZOIC MAFIC ROCKS; PYROXENES; AUTOMATIC LASER STEP HEATING; <40>^Ar; <39>^Ar DATING; LASER MICROPROBE; DIFFUSION PARAMETERS; CLOSURE TEMPERATURE; 原生代玄武岩質岩脈; 完全自動レーザー段階加熱

In the summer of 2000, Proterozoic mafic intrusives were collected from 28 sites in themiddle part of Ontario, Canada. Fresh orthopyroxene and clinopyroxene grains were separated, and irradated in a nuclear reactor to carry out 40Ar/39Ar dating.Combining fast and accurate ion current measurement with an automatic laser temperaturecontrol, we built an automatic laser step heating 40Ar/39Ar dating system, which improved the statistics of data. An automatic XYZ stage control was purchased in November, and a program to carry out continuous pin point measurements were also developed. During the measurements, a momentum from a vaporized sample released during the irradiation of a laser pulse causes a move of the thin section. This destroys the alignment of sampling points. A thin section were sandwitched with metal (titanium) washers by its weight. This new method allows to perform thin section dating with transmitted light.In 2001, several laser step heating experiments were carried out. Different age spectrawere often obtained from pyroxene grains in the same rock. A method to distinguish pyroxene samples which give plateaux in 40Ar/39Ar dating has not been established. Diffusion parameters of pyroxenes were calculated from the experiments, and estimated closure temperature was approximately 450ーC, which is higher than that of biotites and muscovites, and lower than hornblendes. This implies a significant role of pyroxene as a thermochronometer. These results will be presented in the ninth internatinal symposium on experimental mineralogy, petrology and geochemistry (Zurich, Switzerland).

2000年夏天，在加拿大安大略省中部的28个地点采集了元古代镁铁质侵入岩。将新鲜的斜方辉石和单斜辉石颗粒分离出来，并在核反应堆中进行辐照进行40Ar/39Ar测年。将快速准确的离子电流测量与自动激光温控相结合，建立了自动激光步进加热40Ar/39Ar测年系统，提高了数据的统计性。 11 月购买了自动 XYZ 载物台控制装置，并开发了执行连续精确点测量的程序。在测量过程中，激光脉冲照射期间蒸发的样品释放的动量导致薄片移动。这破坏了采样点的对齐。将薄的部分按其重量与金属（钛）垫圈夹在一起。这种新方法可以利用透射光进行薄片测年。2001年，进行了几次激光步进加热实验。同一岩石中的辉石颗粒经常获得不同年龄的光谱。尚未建立区分 40Ar/39Ar 测年中出现平台的辉石样品的方法。通过实验计算辉石的扩散参数，估计闭合温度约为450℃，高于黑云母和白云母，低于角闪石。这意味着辉石作为测温计的重要作用。这些结果将在第九届国际实验矿物学、岩石学和地球化学研讨会（瑞士苏黎世）上公布。

项目成果

Hyodo, H., Itaya, T.and Matsuda, T.,: "Laser microprobe 40Ar/39Ar age dating"Journal of Gteography. 109. 827-835 (2000)

Hyodo, H.、Itaya, T. 和 Matsuda, T.，“激光微探针 40Ar/39Ar 测年”Gteography 杂志。

Nam, T.N., Hyodo, H., Itaya, T., Matsuda, T.: "Early Proterozoic tectonothermal event south of the red river shear zone in Vietnam : First evidence from ^<40>Ar/^<39>Ar dating of single grain hornblende"Viet. Nat. Univ. J. Sci. Nat. Sci.. 16. 26-34 (2000)

Nam, T.N.、Hyodo, H.、Itaya, T.、Matsuda, T.：“越南红河剪切带以南的早元古代构造热事件：来自 ^<40>Ar/^<39>Ar 测年的第一个证据

Imaoka, T., Nakashima, K., Itaya, T., Okada, T.: "Timing of hydrothermal activity in the Oligocene Hamada cauldron, SW Japan : evidence from K-Ar ages of sericites"Mineral Resources. 51. 55-62 (2001)

Imaoka, T.、Nakashima, K.、Itaya, T.、Okada, T.：“日本西南部渐新世滨田大锅中热液活动的时间：来自绢云母 K-Ar 年龄的证据”矿物资源。

兵藤博信: "レーザー段階加熱^<40>Ar/^<39>Ar年代測定自動化システム"岡山理科大学自然科学研究所研究報告. 26. 41-59 (2000)

Hironobu Hyodo：“激光台加热^<40>Ar/^<39>Ar测年自动化系统”冈山理科大学自然科学研究所的研究报告 26. 41-59 (2000)。

Tatsumi, Y., Ishikawa, N., Anno, K.and Itaya, T: "Tectonic setting of high-Mg andesite magmatism in the SW Japan arc : K-Ar chronology of the Setouchi volcanic belt."Geophysical Journal International. 144. 625-631 (2001)

Tatsumi, Y.、Ishikawa, N.、Anno, K. 和 Itaya, T：“日本西南弧高镁安山岩岩浆作用的构造背景：濑户内火山带的 K-Ar 年代学。”《国际地球物理杂志》。