Lithium Isotope Analytical Methods and Implications for Rare-Metal Mineralization in Granite-Pegmatite Systems: An Overview.

The origin of highly-fractionated granite-pegmatite systems and their associated rare metal mineralization has been widely studied, but there is still ongoing debate. Prevailing hypotheses suggest that pegmatite formation and the associated rare metal mineralization are closely related to aqueous fluid processes. Lithium (Li) isotope analysis has been widely applied to trace granite-pegmatite evolution. This is because lithium is widely present in various minerals (e.g., mica, tourmaline) that record the melt and fluid compositions, and lithium isotopes are sensitive to magmatic-hydrothermal processes. We briefly review the methodology of Li isotope analyses, the mechanisms of Li isotopic fractionation, and, in particular, Li isotope fractionation in granite-pegmatite system based on Li isotope data we have collected and the latest developments in Li isotope geochemistry. With the development of analytical technology, high-precision measurement of the Li content and isotopic compositions have facilitated a series of scientific breakthroughs in understanding the magmatic-hydrothermal evolution of rare-element ore deposits. Li isotope analyses on bulk mineral separates have demonstrated their ability to trace various hydrothermal processes. In situ Li isotope analysis methods has been enhanced by the development of new, homogeneous mineral reference materials. In situ SIMS and LA-MC-ICP-MS Li isotope measurements on minerals (e. g., tourmaline) will likely become more important in studying the fluid-rock interactions in magmatic, metamorphic, and hydrothermal processes, as well as on pegmatite petrogenesis and rare-metal mineralization. [ABSTRACT FROM AUTHOR]