Mineralogical aspects of CO₂ sequestration during hydrothermal basalt alteration 鈥?An experimental study at 75 to 250 掳C and elevated pCO₂

详细信息	查看全文 | 推荐本文 |

• 作者：Alexander P. Gysi ; ^{alexander.gysi@mail.mcgill.ca} ; Andri Stefá ; nsson
• 关键词：Basalt alteration ; Carbonates ; Hydrothermal experiments ; Reaction path ; CO2 mineralization ; Water&ndash ; rock interaction
• 刊名：Chemical Geology
• 出版年：2012
• 期刊代码：12_00092541
• 类别：ear
• 出版时间：4 May, 2012
• 卷：306-307
• 期：Complete
• 页码：146-159
• 文件大小：2723 K

摘要

The alteration of basaltic glass was studied experimentally at elevated CO₂ pressures (~ 10-25 bar) and hydrothermal conditions (75-250 掳C) to determine the effects of temperature and extent of reaction (尉) on the secondary mineral formation and compositional evolution of alteration assemblages resulting from CO₂-water-basalt interaction. At < 100 掳C, the alteration products consisted of concentric layers of ankerite and dolomite-ankerite solid solutions (Ca-Mg-Fe carbonates) and amorphous silica. At 鈮?#xA0;150 掳C, mixed Ca-Mg-Fe smectites and chlorite, calcite, amorphous silica and zeolites formed instead of Ca-Mg-Fe carbonates. Competing reactions between carbonates and clays for major divalent cations (Ca, Mg and Fe) were affected by the extent of reaction with smectites formed initially and progressively being replaced by calcite and chlorite. The basaltic glass dissolution rate and mechanism were also affected by temperature and reaction time. At lower temperatures (鈮?#xA0;150 掳C), a hydrated leached layer formed on the glass surface and the mass fluxes in the system were largely controlled by the dissolution rate and mechanism of the glass, whereas at higher temperature (250 掳C) the dissolution rate of the basaltic glass was fast with the reactions primarily driven by secondary mineral replacement and growth. We conclude that the driving force for carbonate mineralization in basaltic glass at elevated CO₂ conditions is linked to the geochemical behavior and mobility of Ca, Mg and Fe together with the availability of Si for Al-Si-mineral formation. At < 100 掳C, the divalent cations are available for Ca-Mg-Fe carbonate formation, whereas at 鈮?#xA0;150 掳C abundant clays limit the availability of Mg and Fe resulting in calcite being the only carbonate formed. This implies a quantitatively more effective fixation of CO₂ at < 100 掳C associated with the formation of Ca-Mg-Fe carbonates.