Collaborative Research: Ion Probe Analysis of O and C Isotope Ratios in ALH84001

9713978 Valley 9714028 Eiler，Stolper 摘要该奖项支持使用离子探针对“火星”陨石（SNC类陨石）ALH 84001中碳酸盐、硅酸盐、氧化物和可能减少的含碳相中氧同位素（18 O/16 O）和碳同位素（13 C/12 C）的微米级分布进行合作研究。 它由极地计划办公室，化学部和MPS多学科活动办公室支持。 这项工作将提供该岩石经历的热和流体渗透历史的限制，以及ALH 84001碳酸盐岩可能的生物成因。 这项工作将建立在以前完成的试点研究，包括超过500个分析12个良好的特征碳酸盐标准，11个氧同位素分析ALH 84001硅酸盐，9个氧同位素分析加上4个碳同位素分析ALH 84001碳酸盐结核。 这项初步研究表明，在ALH 84001碳酸盐中，10微米以上的氧同位素组成中存在10，000分之10以上的梯度，表明这些矿物的精细尺度稳定同位素变化中有足够的“信号”，使我们能够从我们提出的分析中提取有意义的信息。 氧同位素分带的进一步表征和寻找低碳-13阶段将是至关重要的解释这些碳酸盐结核的形成环境。 在这个样本中已经记录的异质性表明，这项工作的大部分将只可能使用离子微探针技术。 在该奖项下完成的研究工作包括对各种碳酸盐、硅酸盐和含铁矿物中10-30微米点（约5-10微米深）的大量分析，以建立氧和碳同位素的成分分布。 这些新的分析方法可用于：（1）测试结核的核-缘氧分带;（2）测试和改进以前对各种碳酸盐矿物相形成温度的估计;（3）研究非碳酸盐相记录的流体入渗历史，和（4）验证碳酸盐结核外部可能含有低碳-13成分的初步观察结果，这可能与陨石ALH 84001中推断的结核边缘的所谓“生物膜”有关。 这些分析将评估已发表的报告，即碳酸盐和相关还原碳之间的碳同位素分馏与生物过程一致。 这些限制是解释ALH 84001中碳酸盐起源的核心，无论是关于其生物起源的可能性，还是它们提供的早期火星挥发物性质的证据。

9713978 Valley 9714028 Eiler, Stolper Abstract This award supports a collaborative study of the micron-scale distribution of oxygen isotopes (18O/16O) and carbon isotopes (13C/12C) in carbonates, silicates, oxides and possibly reduced carbon-bearing phases in the "Martian" meteorite (SNC class of meteorites), ALH84001, using the ion microprobe. It is supported by the Office of Polar Programs, the Chemistry Division, and the MPS Office of Multidisciplinary Activities. This work will provide constraints on the thermal and fluid-infiltration history experienced by this rock and the possible biogenic origin of ALH84001 carbonate. This work will build on a previously completed pilot study comprised of over 500 analyses of 12 well characterized carbonate standards, 11 oxygen isotope analyses in ALH84001 silicates, and 9 oxygen isotope analyses coupled with 4 carbon isotope analyses in ALH84001 carbonate concretions. This pilot study demonstrated the presence of gradients in the oxygen isotope composition of more than 10 parts in 10,000 in ALH84001 carbonates over 10's of microns, showing that there is sufficient `signal' in the fine- scale stable isotope variations of these minerals for us to extract meaningful information from our proposed analyses. Further characterization of the oxygen isotope zonation and search for low carbon-13 phases will be critical to interpreting the environment of formation of these carbonate concretions. The heterogeneity already documented in this sample indicates that much of this work will only be possible using ion microprobe techniques. The research work to be completed under this award includes a large number of analyses of 10-30 micron spots (about 5-10 microns deep) in a variety of carbonate, silicate and iron bearing minerals to establish compositional profiles for oxygen and carbon isotopes. These new analyses will allow the following: (1) test concretions for core-to-rim oxygen zonation; (2) test and refine previo us estimates of the temperatures of formation of the various carbonate mineral phases; (3) investigate the fluid-infiltration history recorded by non-carbonate phases, and (4) verify initial observations that the outer portions of carbonate concretions may contain low carbon-13 compositions, which may be related to purported `biofilms' at concretion margins that have been inferred in meteorite ALH84001. These analyses will evaluate published reports that the fractionation of carbon isotopes between carbonate and associated reduced carbon is consistent with biological processes. These constraints are central to the interpretation of the origin of carbonates in ALH84001, both with regard to the possibility of their biogenic origin and the evidence they provide of the nature of volatiles on early Mars.