| タイトル | Na, K-Rich Rim Around a Chondrule in Unequilibrated Ordinary Chondrite Lew 86018 (L3.1) |
| 本文（外部サイト） | http://hdl.handle.net/2060/20150002979 |
| 著者（英） | Mishra, R. K.; Simon, J. I.; Needham, A. W.; Ross, D. K.; Han, J.; Messenger, S.; Marhas, K. K.; Keller, L. P. |
| 著者所属（英） | NASA Johnson Space Center |
| 発行日 | 2015-03-16 |
| 言語 | eng |
| 内容記述 | Ordinary chondrites represent the most abundant early Solar system extra-terrestrial (approximately 85% abundance) material available for laboratory studies and expectedly record the most extensive range of alterations effects from unmetamorphosed chondritic material to the highest temperatures of thermal metamorphism. The least metamorphosed chondrites belonging to petrologic type 3, the so called unequili-brated ordinary chondrites (UOCs), provide insights into alteration that happened during the primeval, ear-liest stage of Solar system formation. The higher grade petrologic types 4-6 ordinary chondrites on the other hand document up to near textural equilibrium (in type 6) extensive thermal metamorphism consisting of minerals and phases providing evidence of equilibration of heterogeneous mineral composition, solid-state recrystallization. Despite being the most abundant, the effect of alteration is less explicitly understood in ordinary chondrites (even less in UOCs) compared to other groups (e.g. CV, CO, CR). Additionally, the relationship between metasomatism (also referred as aqueous alteration or fluid-assisted metamorphism) and metamorphism (primarily thermal driven) has not been studied and alterations in the ordinary chondrites have been considered to have occurred in absence of fluids in general. Despite this conventional view, UOCs of lowest grades (3.0-3.2) show some evidence of low temperature (approximately 200 C), fluid assisted metamorphism in the form of the presence of phyllosilicates, ferroan olivine, and magnetites in their matrices and occasionally in chondrules. Here, we present petrographic and mineralogical studies of UOC, Lewis Hills (LEW) 86018 to further our understanding of the extent and relative importance of metasomatism and/or metamorphism in UOCs. |
| NASA分類 | Geosciences (General); Lunar and Planetary Science and Exploration |
| レポートNO | JSC-CN-32810 |
| 権利 | Copyright, Distribution as joint owner in the copyright |
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