| タイトル | Aqueous alteration of the Nakhla meteorite |
| 著者（英） | Gooding, James L.; Wentworth, Susan J.; Zolensky, Michael E. |
| 著者所属（英） | NASA Johnson Space Center|Lockheed Engineering and Sciences Co. |
| 発行日 | 1991-06-01 |
| 言語 | eng |
| 内容記述 | Interior samples of three different Nakhla specimens contain an iron-rich silicate 'rust' (which includes a tentatively identified smectite), Ca-carbonate (probably calcite), Ca-sulfate (possibly gypsum or bassanite), Mg-sulfate (possibly epsomite or kieserite), and NaCl (halite); the total abundance of these phases is estimated as less than 0.01 weight percent of the bulk meteorite. Rust veins are truncated and decrepitated by fusion crust and are preserved as faulted segments in partially healed olivine crystals, indicating that the rust is preterrestrial in origin. Because Ca-carbonate and Ca-sulfate are intergrown with the rust, they are also indicated to be of preterrestrial origin. Similar textural evidence regarding origins of the NaCl and Mg-sulfate is lacking. Impure and poorly crystallized sulfates and halides on the fusion crust of the meteorite suggest leaching of interior (preterrestrial) salts from the interior after Makhla arrived on earth, but coincidental addition of these same salts by terrestrial contamination cannot be exluded. At least the clay-like silicate 'rust', Ca-carbonate, and Ca-sulfate were formed by precipitation from water-based solutions on the Nakhla parent planet, although temperature and pressure conditions of aqueous precipitation are unconstrained by currently available data. It is possible that aqueous alteration on the parent body was responsible for the previously observed disturbance of the Rb-Sr geochronometer in Nakhla at or near 1.3 Ga. |
| NASA分類 | LUNAR AND PLANETARY EXPLORATION |
| レポートNO | 91A43267 |
| 権利 | Copyright |
| URI | https://repository.exst.jaxa.jp/dspace/handle/a-is/347243 |
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