## 6 Discussion
### Origin of the #50 Phlogopite Zone
#### 6.1.2 Origin of the #50 High-Ti-Cr Phlogopite Cores/Inner Rims  
The high-Ti-Cr cores/inner rims of phlogopite in the kimberlite samples from southern Liaoning exhibit similarity to both the polymictic breccia matrix and overgrowths in mantle xenoliths, suggesting a possible common origin (Figure 6). The entrained polymeric breccias are considered \"failed\" kimberlite emplacements; these early kimberlite-like melts rapidly intruded and were retained in the lithospheric mantle, and fragments were subsequently transported to the surface by kimberlite magma pulses [59; 64]. The phlogopite in the polymictic breccia matrix and the phlogopite overgrowths in the mantle xenoliths have previously been interpreted as having crystallized from kimberlite-related melts [59; 65]. We suggest a similar origin for the high-Ti-Cr zones of the #50 phlogopite macrocrysts in southern Liaoning.  
The high-Ti-Cr phlogopite is the product of the interaction between mantle rocks and kimberlite magmas at mantle depths or crystallized directly from stalled batches of kimberlite magmas (\"failed\" kimberlites) at mantle depths [9; 63]. High-Ti-Cr phlogopite is thought to be derived from less fractionated kimberlite melts, which have been extensively modified by interactions with refractory mantle peridotite wall rocks [23; 66]. The enrichment of Cr, Ni and Mg in the high-Ti-Cr phlogopite (cores/inner rims) is evidence of mantle peridotite assimilation by kimberlite magma at lithospheric mantle depths [23], which plays a buffering role in the evolution of the groundmass phlogopite composition (Mg depletion and Al and Ba enrichment in the low-Cr/Cr-poor phlogopite).  
The high-Ti-Cr zone manifests in two primary forms: either as inner rims exhibiting resorption phenomena and overgrowing the low-Ti-Cr xenocrystic cores or as a core containing both euhedral and embayed textures. Compared with the low-Ti-Cr (xenocrystic) cores, high-Ti-Cr phlogopite shows a slight but stable depletion in Mg, but Fe, Ti and Al are more enriched.  
The euhedral high-Ti-Cr cores and high-Ti-Cr inner rims/cores with resorption phenomena may represent distinct crystallization environments. First, the preservation of euhedral high-Ti-Cr cores implies formation in a relatively stable and balanced mantle environment prior to being entrapped by late-stage kimberlite magma and emplaced at the Earth's surface. These cores may represent crystals that directly precipitated from kimberlite melts that stagnated at great depths within the mantle. Second, the high-Ti-Cr inner rims/cores with resorption textures may have experienced interference from different batches of pulsed kimberlite melts. This compositional zone could exhibit an unbalanced phase (as evidenced by the embayed textures) associated with the pulsed eruption of kimberlite magmas, which is supported by discrete compositional changes. Petrographic observations can also be utilized to clarify this issue. In the matrix where high-Ti-Cr crystals occur, a distinct heterogeneity in the kimberlite matrix is observed (Figure 2C). This suggests that the formation of these high-Ti-Cr phlogopite zones with resorption phenomena is in an unbalanced stage with magma, and it is believed that later pulsed magma played a crucial role until it reached the surface. These phenomena are indicative of the complex and perturbed formation environment in which high-Ti-Cr phlogopite formed. It is widely acknowledged that kimberlite pipes are formed through a series of discontinuous volcanic activities, which might result in the formation of distinct units within a single diattreme [11; 12; 13]. This is in line with the complex zonal pattern observed through microscopic analysis and discrete compositional variations, indicating the occurrence of multistage kimberlite magmatic pulses.