The role of environmental CO2 and Si on Martian FeMg-smectites formation
Description
We obtained four series of products in different Si concentrations during hydrothermal experiments. We studied the sequence of their mineral assemblages and crystal structures using several measuring methods, such as XRD, FTIR, TG, TEM and Mössbauer spectroscopy. Using this analysis, we proposed a conversion process from pyroaurite to nontronite, via lizardite as an intermediary phase. Our product spectra are compared with CRISM NIR spectra. Table 1 outlines the hydrothermal experimental conditions. Figure 1 displays X-ray diffraction (XRD) patterns of the products from different Si content solutions. Figure 2 illustrates the Thermogravimetric (TG) analyses of the 25d products in Figure 1. Table 2 sums up the mass losses and decomposition temperatures for our products and previous words. Figure 3 shows the XRD patterns of the products in conversion experiments, and Figure 4 displays the micromorphology investigated by transmission electron microscopy (TEM). Figure 5 shows the chemical composition of the supernatant. Figures 6, 7 and 8 show the FTIR, VNIR and Mössbauer spectra of our products, respectively. Table 3 lists the fitting parameters of the Mössbauer spectra.