Abstract: The Jiajika pegmatite-type rare-metal ore field in Sichuan Province is the largest granitic pegmatite-type lithium-enriched area in China, forming a complete Li–Be–Nb–Ta metallogenic series. To investigate the evolution of pegmatites and the lithium mineralization processes, genesis, and ore-bearing characteristics of the Jiajika rare-metal ore field, this study takes quartz from various types of pegmatite veins in the Jiajika mining area as the research object and applies LA-ICP-MS analytical techniques to determine the trace-element contents of Al, Li, B, Ge, Ti, and P in quartz from five types of pegmatites in the Jiajika rare-metal ore field. The results indicate that variations in the contents of Al, Li, B, Ge, and Ti in pegmatitic quartz, as well as changes in the Al/Ti and Ge/Ti ratios, can effectively reflect the degree of magmatic differentiation. The degree of differentiation and evolutionary development of the pegmatites gradually increases from Type I to Type V, and the evolutionary process can be divided into two stages: the evolution of Type I–III pegmatites is controlled by magmatic crystallization differentiation, whereas Type IV–V pegmatites represent a magmatic–hydrothermal transitional stage, during which rare-metal elements such as Li are enriched. The Li and Al contents in quartz indicate that the deeper parts of the Jiajika ore field still have favorable exploration potential for concealed lithium ore bodies. On the Al/10–Ti–Ge×10 ternary diagram, which reflects the genetic type of pegmatites, all data points of the Jiajika pegmatites fall entirely within the field representing RMG-type pegmatites (formed by crystallization of residual melt after granitic magma evolution), indicating that the Jiajika pegmatites are RMG-type pegmatites.