New experimental data and semi-empirical parameterization of H2O-CO2 solubility in mafic melts
New experimental data and semi-empirical parameterization of H2O-CO2 solubility in mafic melts
复制标题
DOI：
10.1016/j.gca.2012.08.035
复制
发表时间：
2012-11-15
影响因子：
5
通讯作者：
Gaillard, Fabrice
中科院分区：
文献类型：
--
作者：
Iacono-Marziano, Giada;Morizet, Yann;Gaillard, Fabrice
我们在此提出了关于 H2O-CO2 在化学成分可变的镁铁质熔体（碱性玄武岩、钾镁铁矿和卡玛镁铁矿）中的溶解度的新实验数据，这些数据扩展了现有数据库。我们发现，在 3500 bar (350 MPa) 和 1200 摄氏度下，富含钾和钙的熔体可以溶解类似于 1 wt% CO2 的溶解度，而传统模型预测在类似的 P-T 条件下溶解度为 0.2-0.5 wt%。这些新数据与文献中的数据一起强调了熔体化学成分对二氧化碳溶解度的根本控制。我们提出了镁铁质熔体的半经验 H2O-CO2 溶解度模型，该模型采用气体熔体热力学的简化概念以及硅酸盐熔体的化学成分和结构的参数化。该模型在选定的数据库上进行校准，该数据库由 44 种不同镁铁质成分的 289 项实验组成。实验数据的统计分析表明，在镁铁质熔体中，熔体的化学成分和结构对二氧化碳的溶解度起着重要作用。 CO2 溶解度很大程度上取决于熔体中每氧非桥接氧 (NBO/O) 的量，但与 NBO 结合的阳离子的性质也很关键。与 NBO 结合的碱金属 (Na + K) 会强烈增强 CO2 的溶解度，而 Ca 的效果则较为温和。与 NBO 键合的 Mg 和 Fe 对 CO2 溶解度的影响最弱。最后，我们模拟了水的影响，得出结论：H2O 在熔体中的溶解很可能通过触发 NBO 的形成来增强 CO2 的溶解度。与 CO2 相反，但与早期发现一致，H2O 在镁铁质熔体中的溶解度受熔体成分和结构的影响可以忽略不计：它仅与 NBO/O 表现出弱相关性。 (C) 2012 Elsevier Ltd. 保留所有权利。
We present here new experimental data on H2O-CO2 solubility in mafic melts with variable chemical compositions (alkali basalt, lamproite and kamafugite) that extend the existing database. We show that potassium and calcium-rich melts can dissolve similar to 1 wt% CO2 at 3500 bar (350 MPa) and 1200 degrees C, whereas conventional models predict solubilities of 0.2-0.5 wt%, under similar P-T conditions. These new data, together with those in the literature, stress the fundamental control of melt chemical composition on CO2 solubility. We present a semi-empirical H2O-CO2 solubility model for mafic melts, which employs simplified concepts of gas-melt thermodynamics coupled with a parameterization of both chemical composition and structure of the silicate melt. The model is calibrated on a selected database consisting of 289 experiments with 44 different mafic compositions. Statistical analyses of the experimental data indicate that, in mafic melts, the chemical composition and therefore the structure of the melt plays a fundamental role in CO2 solubility. CO2 solubility strongly depends on the amount of non-bridging oxygen per oxygen (NBO/O) in the melt, but the nature of the cation bonded to NBO is also critical. Alkalis (Na + K) bonded to NBO result in a strong enhancement of CO2 solubility, whereas Ca has a more moderate effect. Mg and Fe bonded to NBO have the weakest effect on CO2 solubility. Finally, we modelled the effect of water and concluded that H2O dissolution in the melt enhances CO2 solubility most likely by triggering NBO formation. In contrast with CO2 but in agreement with earlier findings, H2O solubility in mafic melts is negligibly affected by melt composition and structure: it only shows a weak correlation with NBO/O. (C) 2012 Elsevier Ltd. All rights reserved.