## 3 Findings
### Geochemistry  
The bulk chemical composition of the investigated serpentinites featured low contents of SiO\({}_{2}\) (39.52% on average) and TiO\({}_{2}\) (0.1-0.2% by weight), high MgO (36.67% average) and Na\({}_{2}\)O (0.1% on average) contents, and Al\({}_{2}\)O\({}_{3}\) contents that were moderate to high (0.3 to 16.9 wt.%) (Table 1). The CaO content was high, at 1.70% on average. The substitution of Mg with Fe in antigorite, in contrast with the exclusive presence of Mg in pure lizardite, underscores the findings that lizardite is more conducive to carbonation compared to antigorite [10; 28]. The total Fe\({}_{2}\)O\({}_{3}\) content was also high (5-10.6 wt.%) (Table 1). The Mg/Si ratio of serpentinite samples was between 1.18 and 1.38 (-1.33) and Mg# [Mg/(Mg + Fe)] 0.78 and 0.92, indicating that mantle peridotites in MOR (Mg# 0.89-0.92) feature a different formation environment, or that the environment has changed in subsequent processes. The total Ni content of the samples was 1001-2033 ppm. The analysis results are listed in Tables 1 and 2. The \(\Sigma\)REE values of serpentinites varied between 2.51 and 3.42 ppm. While the \(\Sigma\)LREE contents ranged from 1.58 to 2.67 ppm, the \(\Sigma\)HREE contents ranged from 0.87 to 0.96 (Figure 4a,b) (Table 2). The \(\Sigma\)LREE/\(\Sigma\)HREE ratios were between 1 and 3, with Ce showing a strong negative anomaly (0.1-12) and Eu shooing a weak positive anomaly (0.1-0.3) (Figure 4b). The presence of these elements indicates rock-water interaction during serpentinization, and the evidence of the gradual release of highly incompatible elements (HIEs) indicates functions resulting from fluid integration into the system and following a subduction process [23]. Furthermore, the positive Eu anomaly can also be attributed to the formation of lizardite during ocean serpentinization or the dissolution of plagioclase in hydrothermal fluid circulation [25; 26]. This suggests that oceanic serpentinization fluid leaches Eu during fluid-rock interaction, rather than reacting with the plagioclase of the serpentinites [29; 30; 31]. The enrichment in LREE and HREE ratios occurs after melting or during melting due to the interactions with liquid [29]. The moderate siderophiles Ni and Co [30], highly siderophile elements Pd, Pt, Cs and Zr [31], and elements such as F, As, Cl and Sb are found in serpentinites, which shows fluid interaction between the subducted crust and sediments during the hydration of peridotites [32; 33; 34; 40]. Figure 3: Optical microscope (OM) view of thin sections taken from serpentinites. Olivine (OI) and orthopyroxene (opx) minerals surrounded by lizardite (**A**) and chrysotile (**B**). \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c c c c} \hline
**Trace Elements** & \multicolumn{1}{c}{**La**} & \multicolumn{1}{c}{**Ce**} & \multicolumn{1}{c}{**Pr**} & \multicolumn{1}{c}{**Nd**} & \multicolumn{1}{c}{**Sm**} & \multicolumn{1}{c}{**Eu**} & \multicolumn{1}{c}{**Gd**} & \multicolumn{1}{c}{**Tb**} & \multicolumn{1}{c}{**Dy**} & \multicolumn{1}{c}{**Ho**} & \multicolumn{1}{c}{**Er**} & \multicolumn{1}{c}{**Tm**} & \multicolumn{1}{c}{**Yb**} & \multicolumn{1}{c}{**Lu**} & \multicolumn{1}{c}{**Er**} & \multicolumn{1}{c}{**LREE**} & \multicolumn{1}{c}{**LREE**} & \multicolumn{1}{c}{**LREE**} \\ \hline Sp-O1 & 0.90 & 0.48 & 0.16 & 0.34 & 0.22 & 0.11 & 0.18 & 0.18 & 0.08 & 0.19 & 0.05 & 0.18 & 0.04 & 3.2  
The analyzed samples were serpentines derived from harzburgite (olivin and orthopyroxene in thin sections). The REE compositions of these samples show a compatible distribution (Figure 4a). The REE values of the samples were above \(\sim\)0.1. While Nd, Ce and Tb showed negative anomalies, the Pr, Eu, Tm and La contents showed positive anomalies in the chondrite diagram. Finally, the serpentinites were depleted or enriched in LREE (from \(\sim\)0.1 to 100 CI-Chondrite) and had HREE contents varying from 0.1 to \(\sim\)10 CI-Chondrite.