Investigation of the Evolution of the Earth Based on ^<40>Ar-^<39>Ar Ages and Noble Gas Isotopes for Very Small Samples

基于 ^<40>Ar-^<39>Ar 年龄和稀有气体同位素的极小样本地球演化研究

• 批准号: 05403001
• 负责人: KANEOKA Ichiro
• 金额: $ 22.34万
• 依托单位: University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (A)
• 财政年份: 1993
• 资助国家: 日本
• 起止时间: 1993 至 1995
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-05403001/
• 关键词: Evolution of the Earth; Very Small Sample; Argon-Argon Age; Argon-Laser; Plateau Age; Noble Gas; Isotopic Composition; Rock; 希ガス同位体比; ^<40>Ar-^<39>Ar年代; レーザー加熱; 海嶺玄武岩; ガラス部分

In this study, we have aimed to establish the methods by which we can measure ages and noble gas isotopes for very small samples and apply them to reveal the evolution of the Earth. To accomplish them, we have developed the system by combining an Ar-laser and a mass spectrometer with a high sensitivity so that we can measure noble gases degassed from very small samples of less than a few mg. Since the amounts of noble gases degasssed from concerned samples are very low, we tried to construct a system with low volume as much as possible and selected materials with least degassing in order to gain the minimum blank. In order to establish the Ar-Ar dating mathod with stepwise heating by using the laser system, a lot of fundamental experiments were performed and succeeded in getting plateau ages for samples with ages of a few hundred million years. Hence, it is concluded that samples with older ages of a few hudred million years can be safely measured by this method. However, precision is not sufficient enough for younger samples of less than 10 million years. Further, noble gases were degassed from a komatiite from Canada with an age of more than 2 b.y.and a present basalt of Izu-Oshima volcano by laser heating and their isotopes were measured. Except for radiogenic ^4He and ^<40>Ar, Kr and Xe contents seem to be a little enriched in the komatiite than the basalt. Since only limited samples were treated in the present study, it is difficult to relate the difference to the evolution of the Earth at present. In order to identify the characteristics of noble gas signatures with the evolution of the Earth, it is required to get data further for various kinds of samples with wider ranges of ages.

在这项研究中，我们的目标是建立我们可以测量非常小的样品的年龄和惰性气体同位素的方法，并应用它们来揭示地球的演化。为了实现这些目标，我们开发了一个系统，结合Ar激光器和质谱仪具有高灵敏度，使我们可以测量惰性气体从小于几毫克的非常小的样品脱气。由于相关样品脱气的稀有气体量很低，我们试图构建一个尽可能小体积的系统，并选择脱气最少的材料，以获得最小的空白。为了建立激光分步加热Ar-Ar定年方法，进行了大量的基础实验，成功地获得了数亿年样品的坪年龄。因此，可以得出结论，用这种方法可以安全地测量几个几百万年的老样品。然而，对于不到1000万年的年轻样本来说，精度还不够。此外，惰性气体脱气的年龄超过2亿年的加拿大科马提岩和伊豆大岛火山的现代玄武岩的激光加热和它们的同位素测量。除放射成因的^4He和^<40>Ar外，科马提岩的Kr和K2 O含量略高于玄武岩。由于本研究中仅处理了有限的样品，因此很难将这种差异与目前地球的演化联系起来。为了确定地球演化过程中惰性气体特征的特征，需要进一步获得各种样品的数据，年龄范围更广。

项目成果

Kaneoka, I.: "Noble gas constraints on the plume sources in the Earth's deep interior" The Earth's Central Part : Its Structure and Dynamics, ed.by T.Yukutake. 343-355 (1995)

Kaneoka, I.：“稀有气体对地球内部深处羽流源的限制”，《地球的中心部分：其结构和动力学》，T.Yukutake 编辑。

I.Kaneoka: "Noble gas constraints on the plume sources in the Earth's deep interior" The Earth's Central Part:Its Structure and Dynamics. (印刷中). (1995)

I.Kaneoka：“惰性气体对地球内部深处羽流源的限制”地球的中心部分：其结构和动力学（1995 年出版）。

Kaneoka,I.: "Noble gas constraints on the plume sources in the Earth's deep interior" The Earth's Central Part:Its Structure and Dynamics,ed. by T. Yukutake. 343-355 (1995)

Kaneoka，I.：“稀有气体对地球内部深处羽流源的限制”地球的中心部分：其结构和动力学，编辑。

Kaneoka,I.: "^<40>Ar-^<39>Ar analyses of Juvinas fragments from a large block" Proc. NIPR Symp.Antarctic Meteorites. 8. 287-296 (1995)

Kaneoka,I.：“来自大块的 Juvinas 片段的 ^<40>Ar-^<39>Ar 分析”Proc。

Kaneoka, I.: "^<40>Ar-^<39>Ar analyzes of Juvinas fragments from a large block" Proc.NIPR Symp.Antarctic Meteorites. 8. 287-296 (1995)

Kaneoka, I.：“来自大块的 Juvinas 碎片的^ 40 Ar-^ 39 Ar 分析”Proc.NIPR Symp.Antarctic Meteorites。