1998 Fiscal Year Final Research Report Summary
RETROLOGICAL STUDY OF THE BILIBILI ALKALI LAYERED INTRUSION
| Project/Area Number |
09640574
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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 |
Petrology/Mineralogy/Science of ore deposit
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| Research Institution | KUMAMOTO UNIVERSITY (1998)
Kyushu University (1997) |
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Principal Investigator |
NISHIYAMA Tadao KUMAMOTO UNIVERSITY DEPT.SCIENCE,PROFESSOR, 理学部, 教授 (10156127)
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| Co-Investigator(Kenkyū-buntansha) |
IKEDA Takeshi KYUSHU UNIVERSITY DEPT.EARTH & PLANET.SCI., ASSOC.PROFESSOR, 理学部, 助教授 (40243852)
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| Project Period (FY) |
1997 – 1998
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| Keywords | IGNEOUS LAYERING / THE SPACING LAW / MAGMA / CHEMICAL DIFFERENTIATION / SOLIDIFICATION / HEAT FLOW |
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| Research Abstract |
This project carried out the investigation of the occurrence of the BiliBili alkali layered intrusion in the south of Sulawesi island, Indonesia, and examines the origin of the layered structures, leading to the following conclusions.
(1) There are 197 layers within 120 meters from the contact between the intrusion and the surrounding Chamba Formation of the Miocene. The thickness of the layer increases systematically towards the interior of the intrusion. The systematics obeys the Spacing Law similar to that of the Liesegang Rings.
(2) A layer consists of a hard part rich in Na2O and a soft part rich in K20.
(3) Overall chemical variation of the intrusion based on the bulk rock chemistries of randomlly collected 24 samples is almost similar to that within a single layer. Thus chemical differentiation occurred during the layer formation by solidification of a homogeneous magma.
(4) A physical model is proposed for the layer formation such that the layer represent a eutectic mushy layer where the interplay of the layer front (high temperature side of the layer) and the solidification front (low temperature side) casuses a periodical growth and solidification of the layer. Chemical differentiation within a layer was caused by mass transfer associated with heat transfer. The Spacing Law can be explained by the growth of solidified part which prevents an efficient heat loss from the intrusion that influences the thickness of the layer.
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Research Products
(10 results)
