## 6 Discussion
### Origin of the #50 Phlogopite Zone
#### 6.1.1 Origin of #50 Low-Ti-Cr Phlogopite Cores  
Zonation is a prevalent feature in phlogopite from the kimberlite area in southern Liaoning. The cores of phlogopite generally have resorption (i.e., embayment, rounded shape) and deformation textures [14, 28]. Furthermore, the compositions of the majority of the phlogopite macrocryst cores observed in kimberlite samples from southern Liaoning exhibit a broad similarity to those found in mantle-derived xenoliths from Kimberley and other kimberlites in southern Africa (Figure 6A,C,E). This implies that there is a possibility of their shared origin, indicating that these phlogopite cores are derived from the disaggregation of metasomatized mantle rocks entrained by kimberlite magmas [23, 28, 47], as previously inferred for olivine [30, 60, 61] and spinel [62] in kimberlites. Therefore, these cores are xenocrystic and do not crystallize directly from the host-kimberlite magma [9]. Based on the limited compositional changes observed in the macrocryst cores of the low-Ti-Cr (xencorycistic) samples, it can be inferred that the mantle source rock may have undergone similar metasomatic events. The phlogopite macrocrysts exhibit a compositional variation from xenocrystic cores with low Ti-Cr contents to inner rims with high Ti-Cr contents, accompanied by a decrease in Mg\({}^{\#}\) and an increase in the contents of Al and Ba. This results in the typical zoned structure observed in the phlogopite macrocrysts from southern Liaoning. These observations, in combination with the embayments and deformation structures in the macrocryst cores of phlogopite, suggest that the low-Ti-Cr xenocrystic cores cannot have existed stably at any stage of the evolution of the kimberlite magma. \begin{table}
\begin{tabular}{l c c c c c c c c c c c c c c c c} \hline \hline
**Sample** & **F** & **Na\({}_{2}\)O** & **SiO\({}_{2}\)** & **Al\({}_{2}\)O\({}_{3}\)** & **MgO** & **Cl** & **K\({}_{2}\)O** & **CaO** & **NiO** & **FeO** & **MnO** & **Cr\({}_{2}\)O\({}_{3}\)** & **TiO\({}_{2}\)** & **BaO** & **Total** & **Mg\({}^{\#}\)** \\ \hline  
\hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._Altered minerals (as shown in Figures 3 and 4, with talc and serpentine as examples) were observed within the cores, where deformation features, cleavage development, and crystal distortion were commonly present. The formation of metasomatic minerals may occur after the entrapment of the phlogoptite macrocrytsic core (xencoryst) by the kimberlite-like magma. Based on petrographic observations, both talc and serpentine are present in the macrocryst cores, whereas no serpentine or talc is found at the edges of the cores. If the  
Figure 6: Major element variation diagrams for phlogopite from southern Liaoning kimberlites. (**A,C,E**) The light-yellow field “M” shows the composition of phlogoptite from metasomatized peridotite xenoliths; the light-green field shows the composition of phlogoptite from kimberlite groundmass; the light-pink field “HTi” shows the composition of high-Ti-Cr phlogoptic from mantle xenoliths, including polymitic breccia (modified from [PERSON] et al., 2019) [63]. (**B,D,F**) are major oxide co-variation diagrams for phlogopite grains from the southern Liaoning kimberlites. metasomatic event involving hydrothermal (H\({}_{2}\)O-rich fluid/melt) occurred before capture by the magma, why are the edges of the low-Ti-Cr xenocrystic cores not affected, and why do metasomatic minerals occur only in the cores? We hypothesize that the outer margins of the phlogopite developed a sequence of high-Ti-Cr and low-Cr/Cr-poor inner and outer rims (as described below) after the entrapment of the low-Ti-Cr xenocrystic cores by the kimberlite-like magma and that these rims protected the cores. Therefore, we propose that the metasomatic event occurred after xenocryst entrapment by the kimberlite magma, most likely during the later magmatic stage.