Valley J W, Eiler J M, Graham C M, Gibson E K, Romanek C S, Stolper E M
Department of Geology and Geophysics, University of Wisconsin, Madison, WI 53706, USA.
Science. 1997 Mar 14;275(5306):1633-8. doi: 10.1126/science.275.5306.1633.
The martian meteorite ALH84001 contains small, disk-shaped concretions of carbonate with concentric chemical and mineralogical zonation. Oxygen isotope compositions of these concretions, measured by ion microprobe, range from delta18O = +9.5 to +20.5 per thousand. Most of the core of one concretion is homogeneous (16.7 +/- 1.2 per thousand) and over 5 per thousand higher in delta18O than a second concretion. Orthopyroxene that hosts the secondary carbonates is isotopically homogeneous (delta18O = 4.6 +/- 1.2 per thousand). Secondary SiO2 has delta18O = 20.4 per thousand. Carbon isotope ratios measured from the core of one concretion average delta13C = 46 +/- 8 per thousand, consistent with formation on Mars. The isotopic variations and mineral compositions offer no evidence for high temperature (>650 degrees C) carbonate precipitation and suggest non-equilibrium processes at low temperatures (< approximately 300 degrees C).
火星陨石ALH84001含有小型盘状碳酸盐结核，具有同心的化学和矿物学分带。通过离子微探针测量，这些结核的氧同位素组成范围为δ18O = +9.5至+20.5‰。其中一个结核的大部分核心是均匀的（16.7±1.2‰），并且其δ18O比另一个结核高5‰以上。容纳次生碳酸盐的斜方辉石在同位素上是均匀的（δ18O = 4.6±1.2‰）。次生SiO2的δ18O = 20.4‰。从一个结核核心测得的碳同位素比率平均为δ13C = 46±8‰，这与在火星上形成一致。同位素变化和矿物成分没有提供高温（>650℃）碳酸盐沉淀的证据，并表明在低温（<约300℃）下存在非平衡过程。
