TRACE ELEMENT MINERAL CHEMISTRY OF LI-RICH PEGMATITES IN THE CAROLINA TIN-SPODUMENE BELT, NORTH CAROLINA

Lithium is a critical mineral for the transition to a low-carbon energy economy. Granitic pegmatites are an important source of Li, and the Li-rich pegmatites in the Carolina Tin-Spodumene Belt (CTSB), North Carolina, are on par with the largest pegmatite Li ore deposits in the world in terms of resource size and grade. Exploration efforts are currently underway in the CTSB to open Li mines, and this provides a unique opportunity to study a world-class Li pegmatite deposit. Understanding the petrogenesis and geochemistry of these pegmatites is important for understanding Li-rich pegmatite resources worldwide. The CTSB pegmatites have been historically mined and studied for over a century, yet no detailed study exists of trace element mineral chemistry. Here we present trace element LA-ICP-MS mineral analyses of CTSB pegmatites to decipher the geochemical evolution of these pegmatites and put them in the context of similar rare element-enriched pegmatites worldwide. Muscovite K/Rb-Li systematics show that CTSB pegmatites are moderately to highly fractionated compared to other Li-rich pegmatites in the world. Muscovite, quartz, and K-feldspar K/Rb-Li systematics can be used to determine if a CTSB pegmatite contains spodumene (LiAlSi₂O₆) or not, an essential question for Li ore exploration efforts in the area. Garnet Ga-Li systematics distinguishes the CTSB pegmatites from Li-rich pegmatites of Maine, and apatite REE patterns of the CTSB show a distinct tetrad effect possibly caused by either fractionation or fluid-rich magma environments. Taken together, detailed trace element mineral chemistry studies like this one are powerful tools that aid in understanding pegmatite petrogenesis and geochemical evolution, Li ore exploration campaigns, and placing pegmatites in the context of rare-element pegmatites worldwide.