| タイトル | Experimental modeling of the cooling history of Apollo 12 olivine basalts |
| 著者（英） | Donaldson, C. H.; Williams, R. J.; Lofgren, G. E.; Usselman, T. M. |
| 著者所属（英） | NASA Johnson Space Center|Lunar and Planetary Inst. |
| 発行日 | 1975-01-01 |
| 言語 | eng |
| 内容記述 | An analog of the Apollo 12 olivine vitrophyres has been crystallized in a 1-atm gas-mixing furnace at cooling rates ranging between 1250 and 0.7 C/hr and isothermally at degrees of supercooling ranging from 10 C to 325 C. Mineral chemistry, crystal shapes, grain sizes and textures are systematically related to cooling rate and degree of supercooling. At linear cooling rates not exceeding 40 C/hr the texture is porphyritic - large olivine crystals are set in a groundmass of finer-grained pyroxene, plagioclase, and ilmenite; a later generation of olivine never crystallizes. There are three shapes of olivine crystals in the Apollo 12 olivine vitrophyres: glomerocrysts of subhedral crystals, large subequant skeletons, and highly elongate skeletons. These result from three generations of nucleation and a two-stage cooling history - a slow preeruption stage and a rapid continuously increasing posteruption stage. It seems likely that the Apollo 12 olivine basalt magmas were erupted with olivine crystals in suspension. The nucleation temperature of olivine in cooling-rate experiments is dependent on the experimental technique, and hence results of cooling experiments should be applied with caution. |
| NASA分類 | LUNAR AND PLANETARY EXPLORATION |
| レポートNO | 78A46649 |
| 権利 | Copyright |
| URI | https://repository.exst.jaxa.jp/dspace/handle/a-is/431610 |
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