Establishment of the stable isotopic stratigraphy of Banded Iron Formations

带状铁地层稳定同位素地层学的建立

基本信息

批准号：
08640598
负责人：
HAYASHI Ken-ichiro
金额：
$ 1.41万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08640598/
关键词：
Banded Iron Formation Stable isotope Oxygen isotope Carbon isotope Hydrothermal solution BIF ハマスレ-地域熱水活動

项目摘要

Banded iron formations (BIFs), bedded manganese deposits, and silica sinters are the typical examples of chemical sediments that possess clear banding texture. These sedimentary rocks have precipitated on seafloor or subaerial surface, from seawater or hydrothermal solutions with the decrease of solubilities of silica, iron, and manganese in solutions. Variation of stable isotopic compositions of oxygen, carbon, and sulfur in these banded chemical sedimentary rocks have been measured to clarify their genesis.1.Newly developed CO_2-laser microprobe fluorination technique was applied to the Brockman Iron Formation, Hamersley basin, Western Australia, to investigate submillimeter scale oxygen isotopic compositions of quartz both hosted in chert and iron-oxide mesobands. Our data show that delta^<18>O values of BIFs vary between 16.0 and 23.0*, on the contrary to the previous studies that BIFs are isotopically homogeneous. The wide variation of delta^<18>O probably suggests that hydrothermal activities have been responsible for the formation of Hamersley BIFs.2.Isotopic values of organic and carbonate carbon in shale macrobands of the Marra Mamba Iron Formation, Western Australia were measured. The very low delta^<13>C values of organic C,-41.0--37.1*, suggest the activity of the metanogens and metanotrophs in the ocean. The delta^<13>C of dissolved bicarbonate in seawater estimated from carbon isotopic compositions of carbonate was delta^<13>C=--12*. This low value, compared to that of the modern marine HCO_3^- (--1.0*), was also explained as the results of a carbon-cycle system affected by the activities of metanogens and methanotrophs.3.The delta^<18>O values of quartz in silica sinter from the Kitano-oh gold deposits, and those of manganese silicate minerals from the metamorphosed bedded manganese deposits of the Noda-Tamagawa mine were measured. The origin of hydrothermal solutions is discussed.

带状铁层（BIF），卧床锰矿和二氧化硅烧结物是具有清晰带纹理的化学沉积物的典型例子。这些沉积岩在海水或水热溶液中在海底或海底表面沉淀，在溶液中二氧化硅，铁和锰的溶解度减少。 Variation of stable isotopic compositions of oxygen, carbon, and sulfur in these banded chemical sedimentary rocks have been measured to clarify their genesis.1.Newly developed CO_2-laser microprobe fluorination technique was applied to the Brockman Iron Formation, Hamersley basin, Western Australia, to investigate submillimeter scale oxygen isotopic compositions of quartz both hosted in chert and铁氧化物甲添。我们的数据表明，与先前的研究相反，BIF在同位素上是同质性的，BIF的Delta^<18> O值在16.0至23.0*之间变化。 Delta^<18> o的广泛变化可能表明，水热活动是造成了Hamersley Bif的形成。2。西澳大利亚州Marra Mamba Iron形成的页岩大型岩体中有机和碳酸盐碳的异位值测量。有机c，-41.0--37.1*的非常低的delta^<13> C值表明元素和巨基在海洋中的活性。根据碳酸盐碳同位素组成估计的碳酸盐溶解的碳酸氢盐的溶解的二氧化碳^<13> C为delta^<13> c = -12*。与现代海洋HCO_3^ - （ - 1.0*）相比，这种低价值也被解释为受碳循环系统影响的结果，该系统受元素和甲烷营养的活性影响。3。delta^<18> o在硅胶enter中的硅质粉状物中石英的值的值。测量了野川矿山。讨论了水热溶液的起源。