Departmental Bulletin Paper トラバーチンとその生成モデル : 無機的炭酸カルシウム沈殿の新しい速度則
Travertine and its precipitation model : a new rate law for inorganic carbonate precipitation

狩野, 彰宏

23 ( 1 )  , pp.67 - 76 , 2016-07-25 , 九州大学大学院地球社会統合科学府
A new index was proposed for the carbonate precipitation rate observed for quickly growing travertines in hydrothermal settings, where degassing of carbon dioxide from high-pCO_2 water is the principal process that induces CaCO_3 precipitation. The travertine precipitation rate hardly fits to previous surface-controlled equations that often inverse with pCO_2 . Mathematical model in this study relates the precipitation rate with the CO_2 degassing rate by assuming a stable degree of supersaturation(Ω). Here, the accelerating force by CO_2 degassing and the inhibiting force by carbonate precipitation are conceptually balanced to sustain a site-specific Ω value. The precipitation rate equals the product of the newly proposed index for degassing-induced carbonate precipitation(IDP) and an undefined hydrodynamic factor. The IDP, which can be calculated from the bulk water chemistry, is proportional to the pCO_2 excess of water from atmosphere, with secondary influence from pH and ionic strength.

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