The terrestrial alteration of saharan shergottites dar al gani 476 and 489: a case study of weathering in a hot desert environment
The terrestrial alteration of saharan shergottites dar al gani 476 and 489: a case study of weathering in a hot desert environment
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DOI：
10.1016/s0016-7037(00)00586-x
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发表时间：
2001-03
影响因子：
5
通讯作者：
G. Crozaz;M. Wadhwa
中科院分区：
文献类型：
--
作者：
G. Crozaz;M. Wadhwa
稀土元素（REE）和其他选定的微量元素和微量元素的浓度测定在各个阶段的达尔加尼476和489，最近发现在利比亚撒哈拉的两个玄武shergottites。而镁橄榄石和镁橄榄石玻璃组合物似乎没有被改变，因为这些陨石的秋天，橄榄石和辉石通常显示轻稀土富集，有时伴随着Ce异常，这是由于陆地蚀变。还观察到Sr和Ba富集。大多数裂缝中的碳酸钙基本上不含稀土元素，但填充某些矿脉和口袋的细粒无定形硅酸盐材料具有显著的轻稀土富集和P、Sr和Ba升高。有人认为，这种材料，可能是影响熔体，以及臭名昭著的轻稀土贫橄榄石和辉石，优先受地壳轻稀土丰富的污染物。当使用整个岩石，甚至矿物分离，成分和同位素数据热沙漠陨石时，应谨慎。
Rare earth element (REE) and other selected trace and minor element concentrations were determined in various phases of Dar al Gani 476 and 489, two basaltic shergottites recently found in the Libyan Sahara. Whereas merrillite and feldspathic glass compositions do not seem to have been altered since the fall of these meteorites, olivine and pyroxenes commonly show light REE enrichments, sometimes accompanied by Ce anomalies, that are attributed to terrestrial alteration. Sr and Ba enrichments are also observed. The calcium carbonate that resides in most cracks is essentially devoid of REE but a fine-grained amorphous silicate material that fills some veins and pockets has striking light REE enrichments and elevated P, Sr, and Ba. It is argued that this material, likely to be impact melt, as well as the notoriously light REE-poor olivine and pyroxenes, were preferentially affected by a crustal light REE-rich contaminant. Caution is urged when using whole rock, or even mineral separate, compositional, and isotopic data for hot desert meteorites.