The effect of partial pressure of carbon dioxide on anorthite dissolution

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Abstract

The dissolution experiment of anorthite was carried out under different partial pressures of CO<SUB>2</SUB> (P<SUB>CO<SUB>2</SUB></SUB>) to understand the role of weathering of Ca and Mg silicates in the removal of CO<SUB>2</SUB> from the atmosphere in the Precambrian. A newly-developed apparatus can control P<SUB>CO<SUB>2</SUB></SUB> in a mineral-water reaction vessel and vary P<SUB>CO<SUB>2</SUB></SUB> and temperatures from 10<SUP>−3.5</SUP> (the present atmospheric level, PAL) to 5.0 atm and from 40 to 150°C, respectively. The experiments were carried out at 150°C and pH 4.56, varying P<SUB>CO<SUB>2</SUB></SUB> from 10<SUP>−3.5</SUP> to 1.2 atm. The dissolution rate of anorthite under high P<SUB>CO<SUB>2</SUB></SUB> (=1.2 atm) is faster than that under PAL by about 4 times. Calcium and Si dissolve congruently from anorthite under PAL, whereas a Ca/Si ratio in solution is lower under high P<SUB>CO<SUB>2</SUB></SUB>. Our results suggest that the weathering rates and processes in the Archean are different from the present ones, and that the amount of Ca flux into the Archean ocean is less than that predicted assuming congruent dissolution of anorthite.

Journal

  • Mineralogical Journal

    Mineralogical Journal 21(1), 1-8, 1999-01-01

    Japan Association of Mineralogical Sciences

References:  20

Cited by:  1

Codes

  • NII Article ID (NAID)
    10008773365
  • NII NACSIS-CAT ID (NCID)
    AA00739590
  • Text Lang
    ENG
  • Article Type
    Journal Article
  • ISSN
    05442540
  • Data Source
    CJP  CJPref  J-STAGE 
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