Collaborative Research: A New Approach to Detrital Provenance Determination: Application of Laser-Induced Breakdown Spectroscopy (LIBS) to the Tourmaline Supergroup Minerals

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Understanding Earth's geological history provides insight into processes that shape our planet and the distribution of economic resources. However, ancient geological events can be difficult to decipher because their physical presence may be lost to erosion. Fortunately, information on the types and ages of rocks (i.e., their provenance) that were present prior to weathering and erosion are encoded in some minerals that are preserved in sediments and sedimentary rocks. Tourmaline is one such mineral. It is a key repository of geologic information because it incorporates a wide range of chemical elements that reflect the rock environment in which it forms - that is, it encodes the chemical signature of that rock, similar to a fingerprint. Tourmaline is also a chemically and mechanically resistant mineral that, when weathered out of the rock in which it formed, it can become a sand grain that is incorporated into sediments (and rocks). Once it incorporates its original chemical signature, the tourmaline grain stores that signature for millions or billions of years.This work uses a synergistic approach to decipher former geological events, their record in sediments and rocks, by integrating chemical analyses of the mineral tourmaline using the new technology Laser-Induced Breakdown Spectroscopy (LIBS) with the established technology Electron Microprobe analyses (EMP). Both yield in-situ chemical fingerprints: LIBS is advantageous because it collects signals of all elements and their complexes, including the light elements, and provides relative compositions of elements, while EMP is a mature analytical technique and is used for highly precise and accurate micrometer-scale chemical data for most elements (except light elements H, Li). One goal of this work is to use these complementary techniques to develop robust approaches to provenance determination based on an extensive collection of tourmaline samples of known provenance. The provenance techniques will be applied, in a case study, to the geologic development of the East Antarctic Mountains (650-480 million years ago). The goal of this case study is to test the efficacy of tourmaline analysis by LIBS and EMP in deciphering complex geologic history of East Antarctic. This study has two major implications. First, it will develop new avenues of provenance studies to refine our understanding of Earth history using the widespread mineral tourmaline. An additional societal benefit is the potential to differentiate tourmalines from different gem deposits that command radically different prices. Samples, data and techniques from this study will be used in both undergraduate and graduate classes at two minority-serving Universities to educate the next generation of geoscientists. A student exchange between the two universities will broaden their educational and analytical experience, necessary for today?s global workforce. This research team includes two female co-PIs and all PIs serve as mentors to a significant number of women in STEM disciplines. Collaboration with industry brings together academics and industrial partners including a woman-owned for-profit small business, in addition to collaborations with faculty at another undergraduate-focused university.