Objective This study selected two types of biotite granitic bodies (Yanggonghai and Ermaoshan) with different degrees of pegmatite development on the periphery of the Ke’eryin lithium ore field in the Songpan−Ganzi orogenic Belt, and compared them with the Ke’eryin pluton, the parent rock of lithium−bearing pegmatite in the region, to explore their potential for rare metal mineralization.
Methods Through comprehensive studies of chronology, geochemistry and isotopes, the rock genesis and tectonic background are constrained.
Results Zircon U−Pb dating shows that the crystallization age of the Ermaoshan rock pluton is 208.19±0.99 Ma, and that of the Yanggonghai rock pluton is approximately 211 Ma, indicating that both and the parent rock of the lithium pegmatite in the area, the Ke’eryin rock pluton, were formed in the same tectonic background. The elemental geochemical characteristics of both indicate that they are both type I granites, originating from the garnet − plagioclase equilibrium domain in the lower crust of the granitic facies. The SR−Nd isotope system reveals the age of their source regions: Both the Yanggonghai rock pluton and the Ermaoshan rock pluton originated from the Mesoproterozoic crust, and their initial Sr isotope ratios ISr and εNd(t) tend to approach the western margin of the Yangtze Craton.
Conclusions Although the two types of biotite granites studied are located in the same tectonic background as the Ke'eryin rock pluton, the parent rock of the Ke'eryin lithium ore field, the maturity of their source areas is insufficient and the degree of magmatic differentiation is weak, which is significantly different from the Ke'eryin rock pluton. Therefore, the potential for the formation of pegmatite is weak and large−scale rare metal mineralization is difficult to occur. However, both still have a certain potential for magmatic hydrothermal mineral mineralization.
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