Assessing hydrodynamic effects on jarosite dissolution rates, reaction products, and preservation on Mars
Assessing hydrodynamic effects on jarosite dissolution rates, reaction products, and preservation on Mars
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评估水动力对黄钾铁矾溶解速率、反应产物和火星保存的影响
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
M. E. Elwood Madden
中科院分区：
文献类型：
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作者：
E. M. Dixon;A. E. Elwood Madden;E. Hausrath;M. E. Elwood Madden
在295-298 K的超纯水（UPW）、pH 2硫酸和饱和NaCl和CaCl 2盐水中进行了黄钾铁矾流动溶解实验，以研究水文变量如何影响火星上的黄钾铁矾保存和反应产物。流动UPW中的K+-基溶解速率不随流速显著变化，表明矿物表面反应在所研究的流速范围内控制溶解速率。在所有测试的解决方案中，水文变量不会显着影响黄钾铁矾蚀变的程度，因此，黄钾铁矾同样有可能被保存在流动或停滞的沃茨在火星上。然而，增加流速确实会影响矿物学和二次反应产物的积累。稀溶液中的铁释放速率随着流速的增加而增加，这可能是由于纳米级铁（氢）氧化物在流动水中的运输。尽管温度较低，但在CaCl 2盐水流通实验中形成硬石膏，而在分批实验中观察到亚稳石膏和钙钛矿。因此，对火星上硫酸钙矿物水合状态的观测可能会为解开过去的盐度和水文条件以及温度和蒸汽压提供线索。
Jarosite flow‐through dissolution experiments were conducted in ultrapure water (UPW), pH 2 sulfuric acid, and saturated NaCl and CaCl2 brines at 295–298 K to investigate how hydrologic variables may affect jarosite preservation and reaction products on Mars. K+‐based dissolution rates in flowing UPW did not vary significantly with flow rate, indicating that mineral surface reactions control dissolution rates over the range of flow rates investigated. In all of the solutions tested, hydrologic variables do not significantly affect extent of jarosite alteration; therefore, jarosite is equally likely to be preserved in flowing or stagnant waters on Mars. However, increasing flow rate did affect the mineralogy and accumulation of secondary reaction products. Iron release rates in dilute solutions increased as the flow rate increased, likely due to nanoscale iron (hydr)oxide transport in flowing water. Anhydrite formed in CaCl2 brine flow‐through experiments despite low temperatures, while metastable gypsum and bassanite were observed in batch experiments. Therefore, observations of the hydration state of calcium sulfate minerals on Mars may provide clues to unravel past salinity and hydrologic conditions as well as temperatures and vapor pressures.