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Crystallization of radiolaria amorphous silica in diagenesis

Research Project

Project/Area Number 08454159
Research Category

Grant-in-Aid for Scientific Research (B)

Allocation TypeSingle-year Grants
Section一般
Research Field Petrology/Mineralogy/Science of ore deposit
Research InstitutionThe University of Tokushima

Principal Investigator

KOTO Kichiro  Tokushima Univ., Fac.Integrated Arts & Sci., Prof., 総合科学部, 教授 (40029872)

Co-Investigator(Kenkyū-buntansha) NUMAKO Chiya  Tokushima Univ., Fac.Integrated Arts & Sci., Res.Assoc., 総合科学部, 助手 (80284280)
ISHIDA Keisuke  Tokushima Univ., Fac.Integrated Arts & Sci., Prof., 総合科学部, 教授 (20116776)
Project Period (FY) 1996 – 1998
Project Status Completed (Fiscal Year 1998)
Budget Amount *help
¥6,100,000 (Direct Cost: ¥6,100,000)
Fiscal Year 1998: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1997: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1996: ¥4,200,000 (Direct Cost: ¥4,200,000)
Keywordsradiolaria / earth crust / alpha quartz / amorphous silica / microfossil / X-ray powder pattern / Sanbagawa / Jurassic period / X線回折プロファイル
Research Abstract

This work has been done to elucidate diagenesis based on mineralogy and crystallography. Shell of microfossil radiolaria consists of amorphous silica and is known to crystallize in alpha quartz in diagenesis. A degree of crystallization is considered to have a close relation with diagenesis and can be estimated by crystallinity of alpha quartz of the shell. Crystallinity of the shell of radiolaria can
be determined by measuring the line width of X-ray powder pattern.
Specimens of radiolaria were obtained from mudstone, slate and chert of Jurassic period in Shikoku Sanbagawa belt. Amorphous silica of radiolaria in deep sea was used as standard. Every X-ray diffraction pattern of radiolaria shows unoriented powder pattern of alpha quartz. No diffraction pattern was observed from radiolaria in deep sea indicating amorphous silica. The line width becomes sharper in order of madstone, chert and slate. The results agree with the degree of diagenesis.
The degree of diagenesis was also estimated from particle size of alpha quartz of radiolaria shell. Specimens of radiolaria were obtained from sedimentary rocks in Eastern part of Shikoku. Particle size was observed under Scanning Electron Microscope. The particle sizes are distributed in the range between 2 and 15 micron depending on diagenesis.
Heat treatment of amorphous silica of radiolaria shell was carried out. Amorphous silica crystallized in alpha quartz at 600 and 700 ゚C for 1 day.
In conclusion crystallinity and particle size of alpha quartz of radiolaria shell have close relations with the degree of diagenesis.

Report

(4 results)
  • 1998 Annual Research Report   Final Research Report Summary
  • 1997 Annual Research Report
  • 1996 Annual Research Report

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Published: 1996-04-01   Modified: 2016-04-21  

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