The Crystal Chemistry of Fe3+ in Nontronite: Implications for Paleoenvironmental Evolution on Mars

We synthesized a series of samples with varying Si/Al/Fe molar ratios under controlled hydrothermal conditions. The resulting solid products were characterized using powder X-ray diffraction, infrared spectroscopy, electron microscopy, and Mössbauer spectroscopy, to elucidate structural characteristics of nontronite. X-ray diffraction (XRD) data shows changed crystallinity of these synthesized samples. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) data illustrated the different morphology and microstructure of samples. Mid infrared spectroscopy (MIR) and Visible-shortwave infrared reflectance (VSWIR) showed change of characteristic vibrations of samples, including band shift and band depth. Mössbauer spectra data identified and quantified the coordination of Fe3+ cations in these samples, including tetrahedral Fe3+ and octahedral Fe3+.

我们在可控水热条件下，合成了一系列硅（Si）、铝（Al）、铁（Fe）摩尔比各异的样品。对所得固态产物采用粉末X射线衍射（powder X-ray diffraction）、红外光谱、电子显微技术以及穆斯堡尔光谱（Mössbauer spectroscopy）进行表征，以阐明绿脱石（nontronite）的结构特征。X射线衍射（X-ray diffraction, XRD）数据表明，所合成样品的结晶度发生了变化。扫描电子显微镜（Scanning electron microscopy, SEM）与透射电子显微镜（Transmission electron microscopy, TEM）数据展示了各样品的形貌与微观结构差异。中红外光谱（Mid infrared spectroscopy, MIR）与可见-短波红外反射光谱（Visible-shortwave infrared reflectance, VSWIR）结果显示，各样品的特征振动发生了改变，具体包括谱带位移与谱带深度。穆斯堡尔光谱数据对这些样品中Fe³+阳离子的配位环境完成了鉴定与定量分析，涵盖四面体配位Fe³+与八面体配位Fe³+。