| タイトル | Iridium in the Vredefort Bronzite Granophyre - Impact melting and limits on a possible extraterrestrial component |
| 著者（英） | Orth, C. J.; Quintana, L. R.; French, B. M. |
| 著者所属（英） | Los Alamos National Lab.; NASA Headquarters |
| 発行日 | 1989-01-01 |
| 言語 | eng |
| 内容記述 | The Bronzite Granophyre was analyzed for Ir and other elements to examine whether its origin was due to impact melting or conventional igneous assimilation and to search for a possible extraterrestrial component in the melt. No such component is identified. Ir values range from 50-130 pg/g, equivalent to less than 0.05 percent C1 material. Further evidence against an extraterrestrial source of siderophiles are the low Ir/Au ratios and the absence of systematic correlations between Ir and other elements. However, the Granophyre is significantly enriched in Ir over other Vredefort granitic rocks, implying a fundamental difference between them. Geochemical mixing models indicate that the Ir observed in the Granophyre can be supplied from high-Ir local shales and quartzites during an impact melting event. The results are consistent with the view that the Granophyre is an impact melt and that Vredefort is an impact structure. |
| NASA分類 | GEOPHYSICS |
| レポートNO | 89A36551 |
| 権利 | Copyright |
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