LIBS as a tool for Li-pegmatite exploration and prospect evaluation: Soil mica and soil analysis from the Carolina Tin-Spodumene Belt

Lithium is an essential element along the pathway to a high-technology future. Being able to efficiently explore for Li deposits and fully assess prospects is necessary to reduce exploration costs, shorten time between discovery and production, and minimize environmental impacts of exploration and production. Laser-induced breakdown spectroscopy (LIBS) is an analytical technology for real-time geochemical analysis in both the laboratory and the field that has potential to enhance current capabilities for Li pegmatite exploration and prospect evaluation. This study was conducted in a portion of the Carolina Tin-Spodumene Belt in Gaston County, NC at one of the largest Li-pegmatite prospects in the USA. Analysis by handheld LIBS first observed the same Li–K/Rb systematics for individual mica grains in soil as for mica in both barren quartz-feldspar and spodumene-bearing pegmatites, suggesting that soil mica analysis might be used for geochemical vectoring towards mineralized pegmatite. The contents of Li, K, and Rb in Bt horizons of residual Kanhapludult soil were determined in the field from matrix-matched LIBS calibrations along five transects across an area where a subsurface spodumene pegmatite dike was known from drilling to be present at ∼15-m depth. Unlike the situation for mica, no systematic variation was observed for soil K and Rb abundances, with K/Rb ratios not reflective of the presence of subsurface mineralization. By contrast, soil Li content spiked sharply where a sampling transect passed directly over the spodumene mineralized dike. It was also noted that soil Li abundances are significantly elevated across the domain of the Carolina Tin-Spodumene Belt of pegmatite mineralization on a regional scale compared to other Piedmont and Coastal Plain soils. Thus, there is potential for rapid soil geochemical analysis by LIBS in Li-pegmatite exploration at both local and regional spatial scales.

Duke Scholars

Author Daniel D. Richter Earth and Climate Sciences