## 4 Discussion and Conclusions
The samples presented characteristics favorable to industrial raw materials when they were evaluated in terms of MgO content (36.67% on average) and SiO\({}_{2}\) content (high at 35-43). In the MgO-SiO\({}_{2}\)-H\({}_{2}\)O-CO\({}_{2}\) equilibrium system, the equilibrium temperatures required for the serpentinization reaction and the presence of chrysotile minerals (record-ed by SEM, TG and XRD analyses) are approximately 350-425 \({}^{\circ}\)C, depending on the pressure (P\({}_{\rm f}\)-PH\({}_{2}\)O). Gulleman serpentinites are industrially durable serpentinites with high MgO (32-42 wt.%, except for Sp 01) and low Al\({}_{2}\)O\({}_{3}\) contents (0.4-6.9 wt.%; Table 1). As a result, in the experimental studies, serpentinization temperatures for chrysotile were found to be 350-425 \({}^{\circ}\)C, depending on the pressure, lizardite and chrysotile were stable at temperatures below <400-440 \({}^{\circ}\)C, and antigorite developed at higher temperatures. So, serpentine minerals may feature areas of gradual stability depending on their composition (Fe and Al amounts), oxygen fugacity (Fe\({}^{2+}\), Fe\({}^{3+}\)) and H\({}_{2}\)O activity [18; 55; 56; 57]. Figure 7 shows SEM images of the examined samples, showing that the serpentinites minerals are less chrysotile and predominantly lizardite. SEM images of the examined samples and MgO-SiO\({}_{2}\), MgO-Fe\({}_{2}\)O\({}_{3}\) and Ni-Ce diagrams also confirm the presence of chrysotile and lizardite minerals. The large DTA peak in sample 2 at 810-830 \({}^{\circ}\)C is a sign of dehydration, transformation reactions and thermal decomposition. Serpentine minerals, which are phyllosilicates containing water in their crystal structure, begin to lose water around 800 \({}^{\circ}\)C. This occursas an endothermic (heat sinking) peak in the DTA. Regarding the sample examined, the XRD data show that it is forsterite (Mg\({}_{2}\)SiO\({}_{4}\)). Additionally, at such high temperatures, olivine and pyroxene forsterite, enstatite and clinoenstatite may develop [40; 41; 42; 43; 56]. A sudden decrease in the mass of a sample around 800 \({}^{\circ}\)C under thermogravimetric analysis (TG or TGA) indicates the development of a significant mass loss in the TG curve as water molecules leave the structure during dehydration. Thermal decomposition at high temperatures can cause a sudden decrease in mass. The decomposition products can often be gaseous or present in different solid phases, leading to mass loss. The presence of carbonate minerals (e.g., magnesite, MgCO\({}_{3}\)) in the serpentinite sample also makes it possible that these carbonates will thermally decompose at around 800 \({}^{\circ}\)C, releasing carbon monoxide (CO) and carbon dioxide (CO\({}_{2}\)) gas (Figure 6). The sudden mass loss in the TG curve can be explained as forsterite transformation or CO\({}_{2}\) release. Similarly, the same situations apply in sample 5 and sample 6. The absence or scarcity of carbonate minerals (calcite, dolomite) in the serpentinites examined generally indicates that the XCO\({}_{2}\) values given during serpentinization are negligibly low [5; 45]. The large DTA peak in sample 2 at 810-830 \({}^{\circ}\)C is a sign of dehydration, transformation reactions and thermal decomposition. Serpentine minerals, which are phyllosilicates containing water in their crystal structure, begin to lose water around 800 \({}^{\circ}\)C. This manifests as an endothermic (heat sinking) peak under DTA. The samples' XRD data show that this was forsterite (Mg\({}_{2}\)SiO\({}_{4}\)). A peak at 810-830 \({}^{\circ}\)C on the DTA graph indicates dehydration or mineral phase transformations. At this temperature, serpentine, a hydrous phyllosilicate, is endothermic. The fact that serpentinites contain magnesite causes the release of CO\({}_{2}\) gas through thermal decomposition at approximately 800 \({}^{\circ}\)C, and the sudden mass loss in the TG curve indicates the release of forsterite and CO\({}_{2}\).