| Project/Area Number |
17K05700
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Petrology/Mineralogy/Economic geology
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| Research Institution | Yamagata University |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
高橋 俊郎 新潟大学, 自然科学系, 准教授 (20392946)
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| Project Period (FY) |
2017-04-01 – 2020-03-31
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| Project Status |
Completed (Fiscal Year 2019)
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| Budget Amount *help |
¥4,550,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥1,050,000)
Fiscal Year 2019: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000)
Fiscal Year 2018: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
Fiscal Year 2017: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
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| Keywords | パタゴニア・バソリス / low Sr initial ratio / 花崗岩 / 部分溶融 / AFCモデル / low SrI S-type granite / adakitic rock / 低Sr同位体比 / 斑れい岩 / ジルコンU-Pb年代 / アダカイト質 / 低角沈み込み帯 / アダカイト質花崗岩 / マグマ・火成岩 / チリ・ノースパタゴニアバソリス |
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| Outline of Final Research Achievements |
The Miocene plutonic rocks of north Chilean Patagonia are divided into three parts : Puerto Cisnes Granites(PCG), Queulat Diorites and Tonalites(QDT) and Queulat Diorites and Porphyries (Parada et al., 2000). We classified samples in this study in five main rock types. These are S-type like rock (Kfs-free) or (Kfs-bearing), tonalite, mafic rock and diorite. The lithology ranges from diorite to Grt-bearing peraluminous granite. Initial Sr and Nd ratios of these rocks are 0.70351 - 0.70412 and 0.51264 - 0.51287, respectively. SrI of metasedimentary rock is 0.70525. The igneous activity of this region was considered from the geochemical characteristics. This study presumed that QDT tonalite was formed by 30% degree of partial melting of the mafic rock. Geochemical modeling shows that the petrogenesis of the S-type like rock (Kfs-bearing) can be explained by assimilation and fractional crystallization between the QDT tonalite magma and the metasedimentary rock.
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| Academic Significance and Societal Importance of the Research Achievements |
北部パタゴニア地方の花崗岩類の分布は既知データとしてあるが，そのほとんどは地球化学的特徴，年代，成因について不確かであり，現地調査と高精度な化学分析が必要であった．全岩主成分・微量成分組成，希土類元素組成，鉱物化学組成，Sr・Nd同位体組成，ジルコンのU-Pb年代など，パタゴニアバソリスの研究を発展させる上で不可欠なデータを得ることができた．また火山フロントより前弧側に深成岩が分布すること，Sタイプ質花崗岩であるにも関わらず非常に低いSr同位体比をもつことは，この地域が未成熟な活動的大陸縁辺であることを示す．未成熟であるということは，初期地球の大陸地殻形成を解明する手掛かりとなりうる．
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