2001 Fiscal Year Final Research Report Summary
Thermal history evaluation of low-grade altered or metamorphic rocks using thermometer based on geological kinetic indicator -estimation of duration of thermal event-
| Project/Area Number |
11554019
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
Geology
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| Research Institution | Shimane University |
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Principal Investigator |
OHIRA Hiroto Shimane Univ., Life & Environ Sci., Research associate, 総合理工学部, 助手 (60273918)
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| Co-Investigator(Kenkyū-buntansha) |
SAMPEI Yoshikazu Shimane Univ., Life & Environ Sci., Associate professor, 総合理工学部, 助教授 (00226086)
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| Project Period (FY) |
1999 – 2001
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| Keywords | fission track / basin / apatite / thermal history / zircon / Songliao Basin / annealing / oil |
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| Research Abstract |
Thermal history evaluation using fission tack annealing kinetics was applied for the Songliao Basin. Firstly, to constrain the maximum deposition age of the Cretaceous Strata, zircon and apatite fission track dating and fission track length measurement have been carried out for the sedimentary rocks collected from the drilling well in the central depression area, western flank area and surrounding areas. Zircon and apatite FT ages and FT lengths for Cretaceous Strata suggest that the source region has a fairly homogeneous cooling history at 120-100 Ma. This means that the volcanic rocks in the Dahinganling Mountains near the basin were eroded soon after their deposition and were reworked toward the Songliao Basin. While, apatites from deep core sample at depression part of the basin show severely annealed ages. Secondary, to estimate post-Cretaceous paleo-geotherm, the younging trend of apatites from each depth were analyzed according to the following step. (1) Making burial history fo
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r each core sample using Sclater and Cristie's compaction model, (2) supposing the hypothetical constant paleo-geothermal gradients, (3) estimate younging trends for each sample's thermal histories using forward modeling technique, (4) statistical check between the predicted FT younging trend and observed younging trend. As a result, the good fitted paleo-geotherm was estimated for 40-45 ℃/km and several tens of Myrs was estimated for the duration of the geotherm. On the other hand, the methylphenanthrene index (MPI), wide-range maturation indicator, was analyzed especially from oil basin at green-tuff region in Japan to know the variation of MPI and its relation to Ro %. For all rock samples, the MPI showed increase from 0.7 to 4.2 in the mature zone (%Ro=0.5-1.9 and decrease from 4.2 to 1.3 in the over-mature zone %Ro=1.9-4.5. The upper slope in these trends was discussed by means of geochemical kinetics, suggesting that the MPI change depend on production of intermediate MPI and the methyl-shift from alpha-isomer to beta isomer. Less
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