New Mexico Geological Society Annual Spring Meeting — Abstracts

            Laser-Induced Breakdown Spectroscopy (LIBS) and chemometric analyses can be used to determine tourmaline provenance and is preferable to electron microprobe analyses for three main reasons:  (1) LIBS analysis is sensitive to light elements such as Li and H; (2) LIBS spectra include a large amount of information including useful matrix effects; and (3) LIBS analysis is rapid, inexpensive and field capable. Tourmaline provenance can be used to refine models of detrital mineral provenance because tourmaline crystallizes in a wide range of rock types over broad temperature and pressure ranges and acquires the trace element signature of its host rock during crystallization. In this study, tourmaline provenance will be assigned to six categories; (1) Li-rich pegmatites, (2) Li-poor pegmatites, (3) non-pegmatitic silicic igneous rocks, (4) pelitic mica schists, (5) calc-silicate rocks, and (6) hydrothermally altered rocks.

           Tourmaline from a variety of localities around the world and within New Mexico were analyzed in an atmosphere of Ar using an Ocean Optics © 2500+ LIBS instrument with an Nd-YAG laser that emits light at 1064 nm. Principal Component Analysis (PCA) and Partial Least Squares Regression (PLSR) were used to determine the provenance of tourmaline by calibrating and validating the provenance model with tourmalines of known provenance. As expected, tourmalines from hydrothermal assemblages exhibit a wide range in composition. However, tourmalines from the other five lithologies form relatively tight groups in Principal Component space, and can be distinguished from each other using PLSR models.