Magnatism in the initial stage of subduction : inference from the Oman ophiolite

俯冲初期的磁力：来自阿曼蛇绿岩的推断

• 批准号: 15540458
• 负责人: ISHIKAWA Tshuyoshi
• 金额: $ 2.3万
• 依托单位: Shizuoka University (2004-2005)Kochi University (2003)
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2005
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15540458/
• 关键词: Oman ophiolite; island arc; volcanic rocks; boninites; trace elements; isopotes; geochemistry; magmas

(1)Estimation of the trace element composition of magmas using clinopyroxene phenocrystsMost of the volcanic rocks of the Oman ophiolite suffer from hydrothermal alternation, and does not preserve their original compositions. In this study, primordial trace element composition of the magma was estimated for the altered rocks by analyzing the relict clinopyroxene phenocrysts. Six distinct types of magma (A,B,C,D,E and F) were recognized in terms of the fluid-mobile trace element composition.(2)Estimation of the trace element spectrum of the fluids using metamorphic soleSlivers of the amphibolite-facies metamorphic rocks (metamorphic sole) are observed at the base of the Oman ophiolite. These rocks are considered to represent uppermost part of the ancient subducted oceanic lithosphere. Trace element spectrums of the fluids liberated from the amphibolite-facies slab were estimated based on the compositional change of the metamorphic sole as a function of the metamorphic temperature.(3)Development of the analytical methods of rare-earth elements and Sr,Nd, and Pb isotopesAn analytical method of rare-earth elements using a high-performance ion chromatography was developed. Analytical techniques of Sr,Nd and Pb isotopes were also developed using thermal ionization mass spectrometry and multi-collector inductively coupled plasma mass spectrometry.(4)DiscussionThe results of this study shows that magmatism at the spreading axis (type A) was followed by subduction-related magmatism of types B and C (tholeiitic), and then magmatism of types D,E and F (both tholeiitic and boninitic) finally took place. Trace element spectrums of the type-B, type-D and type-C magmas are consistent with the involvement of the fluids similar to those estimated from the metamorphic sole. This suggests that these magmas were derived from melting of the mantle wedge metasomatized by fluids liberated from the amphibolite-facies slab in the initial stage of subduction.

（1）利用单斜辉石斑晶估算岩浆的微量元素组成阿曼蛇绿岩中的火山岩大部分经历了热液蚀变作用，并不保持其原始成分。在这项研究中，原始微量元素组成的岩浆蚀变岩的残余单斜辉石斑晶分析估计。根据微量元素的流体活动性，可分为A、B、C、D、E和F六种岩浆类型。（2）利用变质底估算流体微量元素谱在阿曼蛇绿岩基底上观察到角闪岩相变质岩（变质底）的碎屑。这些岩石被认为代表了古代俯冲洋壳岩石圈的最上部。微量元素光谱的流体释放的角闪岩相板估计的基础上的组成变化的变质鞋底作为一个功能的变质温度。（3）稀土元素及Sr、Nd、Pb同位素分析方法的发展建立了稀土元素的高效离子色谱分析方法。锶，钕和铅同位素的分析技术也开发了使用热电离质谱和多接收电感耦合等离子体质谱。（4）讨论研究结果表明，伸展轴上的岩浆活动（A型）之后，是与俯冲有关的B型和C型（拉斑玄武岩）岩浆活动，最后是D型、E型和F型（拉斑玄武岩和玻安岩）岩浆活动。B型、D型和C型岩浆的微量元素光谱与流体的参与相一致，与从变质底估计的流体相似。这表明，这些岩浆来自地幔楔熔融交代的流体释放的角闪岩相板在俯冲的初始阶段。

项目成果

高知県仁淀村に分布する鳥巣石灰岩のストロンチウム同位体年代

高知县仁淀村分布的鸟栖石灰岩的锶同位素年龄

• 发表时间: 2005
• 期刊: 地質学雑誌 111
• 作者: 白石史人;早坂康隆;高橋嘉夫;谷水雅治;石川剛志;松岡淳;村山雅史;狩野彰宏
• 通讯作者: 狩野彰宏

Development of rapid and precise Pb isotope analytical techniques using MC-ICP-MS and new results for GSJ rock reference samples

• DOI: 10.2343/geochemj.40.121
• 发表时间: 2006-04
• 期刊: Geochemical Journal
• 影响因子: 0.8
• 作者: M. Tanimizu;T. Ishikawa

Determination of rare-earth elements in rock samples by an improved high-performance ion chromatography

改进的高效离子色谱法测定岩石样品中的稀土元素

• 发表时间: 2003
• 期刊: Geochemical Journal 37
• 作者: T.Ishikawa;K.Sugimoto;K.Nagaishi
• 通讯作者: K.Nagaishi

Trace element characteristics of the fluid liberated from amphibolite-facies slab: Inference from the metamorphic sole beneath the Oman ophiolite and implication for boninite genesis

• DOI: 10.1016/j.epsl.2005.09.049
• 发表时间: 2005-12-01
• 期刊: EARTH AND PLANETARY SCIENCE LETTERS
• 影响因子: 5.3
• 作者: Ishikawa, T;Fujisawa, S;Masuda, T
• 通讯作者: Masuda, T

Strontium isotopic age of the Torinosu Limestone in Niyodo Village, Kochi Prefecture, SW Japan.

日本西南部高知县 Niyodo 村 Torinosu 石灰岩的锶同位素年龄。

• 发表时间: 2005
• 期刊: Journal of Geological Society of Japan Vol.111
• 作者: F.Shiraishi;Y.Hayasaka;Y.Takahashi;M.Tanimizu;T.Ishikawa;J.Matsuoka;M.Murayama;A.Kano
• 通讯作者: A.Kano