# Characterization of Talcose Rocks Derived from
## 4 Results
### Geochemistry  
From the results of major elements (Figure 4 and Table 3), the sample from Ferraria resembles the composition of a serpentinite and the sample from Somozas resembles the composition of a talcocite. However, the Ferraria sample diverges somewhat from the serpentinite standard composition. In fact, the composition of the major element is very similar to the composition of the talcocite from Somozas, except for some elements. SiO\({}_{2}\), TiO\({}_{2}\), and Al\({}_{2}\)O\({}_{3}\) are higher in the Somozas sample compared to the Ferraria sample. In this comparison, Somozas is lower in CaO and LOI (Loss on Ignition), all being characteristic of highly carbonatized serpentinites (See Table 3 and Figure 10). Ultramafic rocks have poor trace element chemistry, except for some heavy metals such as Cr and Ni. This geochemistry may be inherited from its precursors (e.g., harzburgite), which is an important issue when discussing the potential uses of talcoc rocks as pharmaceutical or cosmetic products. In our samples, Somozas is slightly enriched in Li, Zn, Y, Zr, Nb, Th, and U, and lower in Cu, Sr, and Pb. The other elements are very similar in both samples (See Table 3 and Figure 11). \begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Sample**} & **Mesoscopic Description** & **Locality** & **Quarry** & **Phases Detected** \\ \hline Somozas & Massive & Somozas & Balbina & Tcl \(>\) Chl \(>\) Tr \(>\) Ctl \\ Ferraria & Massive & Ferraria & Ferraria de Abaixo & Tcl \(>\) Ctl \(>\) Mag \(>\) Chl \(>\) Ant \(>\) Liz \(>\) Dol \\ \hline \end{tabular}
\end{table} 
Table 1: Semi-quantitative mineralogical composition of the samples in order of declining relative quantities, detected by XRPD, DSC/DTG, and PM. Tcl = talc, Ctl = chrysotile, Liz = lizardite, Ant = antigorite, Tr = tremolite, Mag = Magnetite, Dol = dolomite, Chl = Chlorite. It is only possible to distinguish a brechoid texture in this sample under the microscope. \begin{table}
\begin{tabular}{c c c} \hline \multicolumn{3}{c}{**DSC (T \({}^{\circ}\)C)**} \\ \hline
**Phases** & **Somozas** & **Ferraria** \\ \hline Chl & 564 endo w & 591 endo \\ Ctl & 612 endo w & 653 endo \\ Liz & & 720 endo w \\ Ant & & 771 endo w \\ Fo & 820 exo & 823 exo \\ Tcl/Dol/Mag & 901 endo s & 890 endo \\ Tr & 1122 endo & \\ \hline \end{tabular}
\begin{tabular}{c c c} \hline Chl & 582 endo w & 587 endo \\ Ctl & 635 endo w & 653 endo \\ Liz & & 730 endo \\ Atg & & 770 endo \\ Tel/Dol/Mag & 905 endo s & 895 endo \\ Tr & 1130 endo w & \\ \hline \end{tabular}
\end{table} 
Table 2: Peak temperatures in DSC and DTG curves. w = weak, s = strong, endo = endothermic, exo = exothermic, Tcl = talc, Ctl = chrysotile, Liz = lizardite, Ant = antigorite, Tr = tremolite, Mag = Magnetite, Dol = dolomite, Chl = chlorite. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Somozas** & **Ferraria** \\ \hline Major elements (in \%) SiO\({}_{2}\) & 61.31 & 42.53 \\ TiO\({}_{2}\) & 0.06 & 0.01 \\ Al\({}_{2}\)O\({}_{3}\) & 1.85 & 0.08 \\ Fe\({}_{2}\)O\({}_{3}\) & 5.53 & 6.56 \\ MgO & 28.52 & 35.22 \\ MnO & 0.05 & 0.05 \\ CaO & 0.13 & 0.27 \\ Na\({}_{2}\)O & 0.01 & 0.01 \\ K\({}_{2}\)O & 0.01 & 0.01 \\ P\({}_{2}\)O\({}_{5}\) & 0.01 & 0.01 \\ LOI & 5.95 & 16.05 \\ Trace elements (in ppm) & & \\ Li & 7.8 & 2.43 \\ V & 22 & 27 \\ Cr & 2162 & 2320 \\ Co & 74 & 90 \\ Ni & 1946 & 1905 \\ Cu & 0.96 & 2.63 \\ Zn & 41 & 31 \\ Sr & 0.91 & 4.01 \\ Y & 2.15 & 0.37 \\ Ba & 1.07 & 1.38 \\ Pb & 0.38 & 0.81 \\ Be & 0.26 & 0.34 \\ Rb & 0.36 & 0.37 \\ Zr & 14 & 6 \\ Nb & 20 & 1.75 \\ Th & 0.78 & 0.16 \\ U & 0.17 & 0.08 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Content of major (%, expressed as oxide) and minor elements (ppm of elements) of Ferraria and Somozas samples. LOI = Loss on Ignition. Figure 10: Major elements in the study samples. Concentrations are in wt.%. Also, the geochemistry of serpentinites may vary depending on the geodynamic setting in which they are formed, owing to differences in the composition and temperature of the hydration fluids.