Dissolution of nontronite in chloride brines and implications for the aqueous history of Mars
Dissolution of nontronite in chloride brines and implications for the aqueous history of Mars
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绿脱石在氯化物盐水中的溶解及其对火星水历史的影响
DOI：
10.1016/j.gca.2016.08.035
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发表时间：
2016
影响因子：
5
通讯作者：
Smith, J.S.
中科院分区：
文献类型：
--
作者：
Steiner, M.H.;Hausrath, E.M.;Elwood Madden, M.E.;Tschauner, O.;Ehlmann, B.L.;Olsen, A.A.;Gainey, S.R.;Smith, J.S.
越来越多的证据表明，火星上最近存在液态水，包括盐水。因此，盐水可能会影响粘土矿物，如富含铁的矿物绿脱石在火星古代地形发现。为了解释这些相互作用，我们进行了批次实验，以测量绿脱石在25.0 °C下的表观溶解速率常数，水活度（aH 2 O）为1.00（0.01 M CaCl 2或NaCl），0.75（饱和NaCl或3.00 mol kg− 1CaCl 2）和0.50（5.00 mol kg− 1CaCl 2）。aH 2 O = 1.00时的实验（0.01 M CaCl 2）的溶解速率常数，以测量绿脱石溶解的表观活化能。1.18 × 10−12± 9 × 10− 14 mol矿物m−2s−1（aH 2 O = 1.00）> 2.36 × 10−13± 3.1 × 10− 14 mol矿物m−2s−1（aH 2 O = 0.75）> 2.05 × 10−14± 2.9 × 10− 15 mol矿物m−2s−1（aH 2 O = 0.50）。在25.0 °C下，在含NaCl的溶液中观察到类似的结果：1.89 × 10−12± 1 × 10− 13 mol矿物m−2s−1（aH 2 O = 1.00）> 1.98 × 10−13± 2.3 × 10− 14 mol矿物m−2s−1（aH 2 O = 0.75）。表观溶解速率常数随水活度的降低而降低，其关系式为：logkdiss= 3.70 ± 0.20 × aH 2 O − 15.49，其中kdiss为表观溶解速率常数，aH 2 O为水活度。该关系的斜率（3.70 ± 0.20）在其他矿物的不确定性范围内，其中已测试了溶解速率与水活度之间的关系，包括镁橄榄石（logR= 3.27 ± 0.91 × aH 2 O − 11.00）（Olsen等人，2015）和黄钾铁矾（logR= 3.85 ± 0.43 × aH 2 O − 12.84）（狄克逊等人，2015），其中R是矿物溶解速率。该结果允许预测作为水活性的函数的矿物溶解，并且表明随着水活性的降低，由于水在反应中的配位作用，矿物的溶解速度会降低。在稀NaCl溶液中的表观溶解速率常数（1.89 × 10−12± 1 × 10− 13 mol矿物m−2s−1）略大于稀CaCl 2溶液中的（1.18 × 10−12± 9 × 10− 14 mol矿物m−2s−1）。我们把这种效应归因于钠与钙在绿脱石夹层中的交换。在4.0 °C、25.0 °C和45.0 °C的温度下，根据含CaCl 2稀溶液中的表观溶解速率常数计算表观活化能为54.6 ± 1.0 kJ/mol：2.33 × 10−13± 1.3 × 10− 14 mol矿物m−2s−1（4.0 °C），1.18 × 10−12± 9 × 10− 14 mol矿物m−2s−1（25.0 °C），4.98 × 10−12± 3.8 × 10− 13 mol矿物m−2s−1（45.0 °C）。绿脱石在盐水和低温下的溶解大大减少，表明发现的任何火星绿脱石在火星上普遍存在的低温条件下，风化的岩石可能经历了很长时间的水-岩石相互作用，与盐水相互作用，这对火星的古气候和长期潜在的可居住性具有重要意义。
Increasing evidence suggests the presence of recent liquid water, including brines, on Mars. Brines have therefore likely impacted clay minerals such as the Fe-rich mineral nontronite found in martian ancient terrains. To interpret these interactions, we conducted batch experiments to measure the apparent dissolution rate constant of nontronite at 25.0 °C at activities of water (aH2O) of 1.00 (0.01 M CaCl2or NaCl), 0.75 (saturated NaCl or 3.00 mol kg−1CaCl2), and 0.50 (5.00 mol kg−1CaCl2). Experiments ataH2O = 1.00 (0.01 M CaCl2) were also conducted at 4.0 °C, 25.0 °C, and 45.0 °C to measure an apparent activation energy for the dissolution of nontronite.Apparent dissolution rate constants at 25.0 °C in CaCl2-containing solutions decrease with decreasing activity of water as follows: 1.18 × 10−12± 9 × 10−14mol mineral m−2s−1(aH2O = 1.00) > 2.36 × 10−13± 3.1 × 10−14mol mineral m−2s−1(aH2O = 0.75) > 2.05 × 10−14± 2.9 × 10−15mol mineral m−2s−1(aH2O = 0.50). Similar results were observed at 25.0 °C in NaCl-containing solutions: 1.89 × 10−12± 1 × 10−13mol mineral m−2s−1(aH2O = 1.00) > 1.98 × 10−13± 2.3 × 10−14mol mineral m−2s−1(aH2O = 0.75). This decrease in apparent dissolution rate constants with decreasing activity of water follows a relationship of the form: logkdiss= 3.70 ± 0.20 ×aH2O − 15.49, wherekdissis the apparent dissolution rate constant, andaH2O is the activity of water. The slope of this relationship (3.70 ± 0.20) is within uncertainty of that of other minerals where the relationship between dissolution rates and activity of water has been tested, including forsteritic olivine (logR= 3.27 ± 0.91 ×aH2O − 11.00) (Olsen et al., 2015) and jarosite (logR= 3.85 ± 0.43 ×aH2O − 12.84) (Dixon et al., 2015), whereRis the mineral dissolution rate. This result allows prediction of mineral dissolution as a function of activity of water and suggests that with decreasing activity of water, mineral dissolution will decrease due to the role of water as a ligand in the reaction.Apparent dissolution rate constants in the dilute NaCl solution (1.89 × 10−12± 1 × 10−13mol mineral m−2s−1) are slightly greater than those in the dilute CaCl2solutions (1.18 × 10−12± 9 × 10−14mol mineral m−2s−1). We attribute this effect to the exchange of Na with Ca in the nontronite interlayer. An apparent activation energy of 54.6 ± 1.0 kJ/mol was calculated from apparent dissolution rate constants in dilute CaCl2-containing solutions at temperatures of 4.0 °C, 25.0 °C, and 45.0 °C: 2.33 × 10−13± 1.3 × 10−14mol mineral m−2s−1(4.0 °C), 1.18 × 10−12± 9 × 10−14mol mineral m−2s−1(25.0 °C), and 4.98 × 10−12± 3.8 × 10−13mol mineral m−2s−1(45.0 °C).The greatly decreased dissolution of nontronite in brines and at low temperatures suggests that any martian nontronite found to be perceptibly weathered may have experienced very long periods of water–rock interaction with brines at the low temperatures prevalent on Mars, with important implications for the paleoclimate and long-term potential habitability of 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：
--
发表时间：
2015
期刊：
影响因子：
--
作者：
E. M. Dixon;A. E. Elwood Madden;E. Hausrath;M. E. Elwood Madden
通讯作者：
M. E. Elwood Madden
根据nakhlites 和 MER 样品中的盐中的卤素来寻找火星盐水的线索
影响因子：
--
作者：
M. Rao;S. Sutton;D. Mckay;G. Dreibus
通讯作者：
G. Dreibus
影响因子：
4.8
作者：
Ming, D. W.;Gellert, R.;Zipfel, J.
通讯作者：
Zipfel, J.
影响因子：
5.2
作者：
Cull, Selby C.;Arvidson, Raymond E.;Lemmon, Mark
通讯作者：
Lemmon, Mark
影响因子：
1.5
作者：
Komadel, P
通讯作者：
Komadel, P