Grady M M, Gibson E K, Wright I P, Pillinger C T
Department of Earth Sciences, The Open University, Milton Keynes, UK.
Meteoritics. 1989;24:1-7. doi: 10.1111/j.1945-5100.1989.tb00934.x.
Isotopic analysis of nesquehonite recovered from the surface of the LEW 85320 H5 ordinary chondrite shows that the delta 13C and delta 18O values of the two generations of bicarbonate (Antarctic and Texas) are different: delta 13C = +7.9% and +4.2%; delta 18O = +17.9% and 12.1% respectively. Carbon isotopic compositions are consistent with equilibrium formation from atmospheric carbon dioxide at -2 +/- 4 degrees C (Antarctic) and +16 +/- 4 degrees C (Texas). Oxygen isotopic data imply that the water required for nesquehonite precipitation was derived from atmospheric water vapour or glacial meltwater which had locally exchanged with silicates, either in the meteorite or in underlying bedrock. Although carbonates with similar delta 13C values have been identified in the SNC meteorites EETA 79001 and Nakhla, petrographic and temperature constraints argue against their simply being terrestrial weathering products.
从LEW 85320 H5普通球粒陨石表面回收的镍菱铁矿的同位素分析表明，两代碳酸氢盐（南极和德克萨斯）的δ13C和δ18O值不同：δ13C分别为+7.9%和+4.2%；δ18O分别为+17.9%和12.1%。碳同位素组成与在-2±4℃（南极）和+16±4℃（德克萨斯）下由大气二氧化碳平衡形成一致。氧同位素数据表明，镍菱铁矿沉淀所需的水来自大气水汽或与陨石或下伏基岩中的硅酸盐发生局部交换的冰川融水。尽管在SNC陨石EETA 79001和纳赫拉中已鉴定出具有相似δ13C值的碳酸盐，但岩石学和温度限制表明它们并非简单的地球风化产物。
