کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5783579 | 1637957 | 2017 | 51 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Solubility of water in lunar basalt at low pH2O
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موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
ژئوشیمی و پترولوژی
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چکیده انگلیسی
We report the solubility of water in Apollo 15 basaltic “Yellow Glass” and an iron-free basaltic analog composition at 1 atm and 1350 °C. We equilibrated melts in a 1-atm furnace with flowing H2/CO2 gas mixtures that spanned â¼8 orders of magnitude in fO2 (from three orders of magnitude more reducing than the iron-wüstite buffer, IWâ3.0, to IW+4.8) and â¼4 orders of magnitude in pH2/pH2O (from 0.003 to 24). Based on Fourier transform infrared spectroscopy (FTIR), our quenched experimental glasses contain 69-425 ppm total water (by weight). Our results demonstrate that under the conditions of our experiments: (1) hydroxyl is the only H-bearing species detected by FTIR; (2) the solubility of water is proportional to the square root of pH2O in the furnace atmosphere and is independent of fO2 and pH2/pH2O; (3) the solubility of water is very similar in both melt compositions; (4) the concentration of H2 in our iron-free experiments is <â¼4 ppm, even at oxygen fugacities as low as IWâ2.3 and pH2/pH2O as high as 11; (5) Secondary ion mass spectrometry (SIMS) analyses of water in iron-rich glasses equilibrated under variable fO2 conditions may be strongly influenced by matrix effects, even when the concentration of water in the glasses is low; and (6) Our results can be used to constrain the entrapment pressure of lunar melt inclusions and the partial pressures of water and molecular hydrogen in the carrier gas of the lunar pyroclastic glass beads. We find that the most water-rich melt inclusion of Hauri et al. (2011) would be in equilibrium with a vapor with pH2O â¼Â 3 bar and pH2 â¼Â 8 bar. We constrain the partial pressures of water and molecular hydrogen in the carrier gas of the lunar pyroclastic glass beads to be 0.0005 bar and 0.0011 bar respectively. We calculate that batch degassing of lunar magmas containing initial volatile contents of 1200 ppm H2O (dissolved primarily as hydroxyl) and 4-64 ppm C would produce enough vapor to reach the critical vapor volume fraction thought to be required for magma fragmentation (â¼65-75 vol.%) at a total pressure of â¼5 bar (corresponding to a depth beneath the lunar surface of â¼120 m). At a fragmentation pressure of â¼5 bar, the calculated vapor composition is dominated by H2, supporting the hypothesis that H2, rather than CO, was the primary propellant of the lunar fire fountain eruptions. The results of our batch degassing model suggest that initial melt compositions with >â¼200 ppm C would be required for the vapor composition to be dominated by CO rather than H2 at 65-75% vesicularity.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Geochimica et Cosmochimica Acta - Volume 200, 1 March 2017, Pages 330-352
Journal: Geochimica et Cosmochimica Acta - Volume 200, 1 March 2017, Pages 330-352
نویسندگان
M.E. Newcombe, A. Brett, J.R. Beckett, M.B. Baker, S. Newman, Y. Guan, J.M. Eiler, E.M. Stolper,