Variations of divalent cation concentrations in pore water and the precipitation of Mg-rich authigenic mineral during early diagenesis of Toyoma Formation

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概要

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• The variations of Fe, Mn and Mg concentrations in pore water were deduced from the chemistry of calcite. With depth, the Fe/Ca, Mn/Ca, Mg/Ca ratios of pore water decrease. The decrease in the Fe/Ca ratio is due to the precipitation of pyrite, whereas the decrease in the Mn/Ca ratio is due to the precipitation of Mn-rich calcite. The depletion of Mg in pore water is ascribed to the precipitation of either Mg-rich smectite or Mg-rich chlorite. A-type rock is further divided into A1 and A2 subtypes, on the basis of δ13C. Excesses of MgO and deficiencies of K舀 O above the calculated whole-rock compositions are observed mainly in the phosphatic nodules and A1 subtype. This suggests that the formation of Mg-rich smectite or Mg-rich chlorite took place at very early stage of diagenesis of the Toyoma Formation.

• 信州大学の論文

著者

• Morikiyo T

  Department Of Geology Faculty Of Science Shinshu University

• Iwamasa Kazuo

  Department Of Geology Faculty Of Science Shinshu University

• Matsunaga Kinuko

  Department Of Geology Faculty Of Science Shinshu University

関連論文

• The sources of phosphorus for the phosphatic rocks in the Toyoma Formation, Northeastern Japan
• Variations of divalent cation concentrations in pore water and the precipitation of Mg-rich authigenic mineral during early diagenesis of Toyoma Formation
• The genesis of phosphatic and carbonate rocks in the Toyoma Formation, Northeastern Japan

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