Characterization of terrestrial analog sites is critical for detection and determination of clay miner-alogy in remote sensing studies of Mars aimed at geological, hydrological, and potentially biological investigations. In this study, we investigate a suite of hydrothermally altered early Archean rocks from the Barberton greenstone belt (BGB) of South Africa as potential petrological, mineralogical, and spectral analogs to hydrothermally altered metabasalts and mafic-ultramafic intrusions in the martian subsurface and impact craters. We present the first spectral imaging measurements on exceptionally well-preserved early Archean mafic-ultramafic rocks from the BGB, with the aim of studying their clay mineralogy and spectral signatures. Multiple spectral analyses were conducted on different sample textures (rock powders, crushed rocks, and rock slabs) appropriate for Mars rover and remote sensing exploration. Visible/near-infrared (VNIR) and mid-IR reflectance spectra were acquired on particulate samples, while VNIR spectral imaging data were collected on rock slabs. Mid-IR emission spectra were measured for the rock slabs and grains. Spectral features are compared from these different spectral techniques to identify the minerals present in the samples and compare macroscale vs. microscale detections. The measured spectra reveal absorption bands that correspond to clay mineral-ogy of the serpentine and chlorite mineral groups, consistent with petrographic observations, as well as magnetite, olivine, quartz, feldspar, and Al-phyllosilicate. The spectral data acquired in this study expand the reference spectra data set for remote sensing studies. The implications of this study are that rocks from early Archean greenstone belts, such as those of the BGB, serve as potential clay-bearing petrological analogs for hydrothermal environments on Mars.

中文翻译：

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巴伯顿绿岩带镁铁质-超镁铁质岩石中的早期太古宙蚀变矿物，作为火星粘土矿物学的岩石学类似物

在火星进行地质，水文和潜在生物学研究的遥感研究中，地面类似物位点的表征对于检测和确定黏土矿物学至关重要。在这项研究中，我们研究了一组来自南非巴伯顿绿岩带（BGB）的热液蚀变的太古宙早期岩石，它们是火成岩变质玄武岩和火成岩-超镁铁质侵入体的潜在岩石学，矿物学和光谱类似物，可用于火星地下和撞击坑。我们研究了来自BGB的保存完好的早期太古宙镁铁质-超镁铁质岩石的首次光谱成像测量，目的是研究它们的粘土矿物学和光谱特征。对不同的样品质地（岩粉，碎石，和岩石平板），适合进行火星探测车和遥感探测。在颗粒样品上采集了可见/近红外（VNIR）和中红外反射光谱，而在岩石平板上采集了VNIR光谱成像数据。测量了岩石板和颗粒的中红外发射光谱。比较了这些不同光谱技术的光谱特征，以识别样品中存在的矿物质，并比较宏观和微观检测结果。测得的光谱揭示了与蛇纹石和绿泥石矿物群的粘土矿物-银对应的吸收带，这与岩石学观察结果一致，以及磁铁矿，橄榄石，石英，长石和页硅酸铝。在这项研究中获得的光谱数据扩展了用于遥感研究的参考光谱数据集。