| Project/Area Number |
17540461
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Geochemistry/Astrochemistry
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| Research Institution | University of Tsukuba |
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Principal Investigator |
ARAKAWA Yoji University of Tsukuba, Graduate School of Life and Environmental Sciences, Professor (00192469)
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| Project Period (FY) |
2005 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥3,650,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥150,000)
Fiscal Year 2007: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000)
Fiscal Year 2006: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2005: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Keywords | North China Craton / Mesozoic ieneous rocks / Chemical composition / Nd-Sr-Pb isotope / Alkaline igneous rocks / Crust-mantle structure / Geochemistry / Nd-Sr-Pb同位体 / 中生代花崗岩 / アルカリ火成岩 / 年代測定 / Sr-Nd-Pb同位体組成 |
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| Research Abstract |
We have carried out geochemical study of Mesozoic igneous rocks in North China Craton. Main results and conclusions are below.
1. Geochoronological works and geological investigation clarified that the Wu'an and Xishu and Hongshan plutons in southern pact of Noth China Craton were formed in late Cretaceous (about 130 Ma).
2. Three main plutons (Wu'an, Xishu and Hongshan) are grouped into alkaline rocks, and are classified into gabbro-monzonite (Wu'an, Xishu), and syenite-granite (Hongshan) based on petrography and chemical compositions. Volcanic rocks in that area have nearly same eruption age and same alkaline affinity.
3. Chemical compositions indicate that three plutons are characterized by high Mg# and light rare earth (LIL) enriched pattern without no Eu negative anomaly. Sr isotope ratios of three plutons are similar, but Nd and Pb isotope ratios are slightly different, each other However in tow isotope plot diagrams, the data are scattered along a linear array combining EM1 mantle and LCC (lower continental crust). These results indicate two component mixing, including mixing of EM1 derived magma and lower crust derived magma, and contamination of LCC by EM1 derived magma. Chemical compositions and modeling also show fractionation of ferromagnesian phase, such as pyroxene and hornblende in the mixed magma. For Hongshan pluton, later fractionation seems to be mainly operated.
4. These Mesozoic igneous rocks (plutonic rocks and volcanic rocks) in the area are strongly related to crustal thinning with upwelling of asthenospheric mantle beneath the North China Craton.
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