DEVELOPING LASER-INDUCED BREAKDOWN SPECTROSCOPY (LIBS) TO IDENTIFY DETRITAL HEAVY MINERALS FOR CORRELATING TRENDS IN BASIN PROVENANCE

Early provenance analysis studies typically analyzed detrital heavy mineral assemblages to determine sources of sediment to depositional systems and correlate trends in provenance across sedimentary basins. This project updates the detrital heavy mineral technique using Laser-Induced Breakdown Spectroscopy (LIBS) combined with multivariate analysis to rapidly identify heavy mineral grains from synorogenic stratigraphic successions. A sample set of 10+ specimens each of 23 minerals is being built to construct a multivariate matching algorithm that identifies heavy mineral grains. Currently, the algorithm contains spectra from 109 specimens of 10 minerals (apatite, barite, beryl, epidote, kyanite, olivine, pyrite, titanite, topaz, zircon). Calibration of a series of binary Partial Least Squares Regression (PLSR) models were constructed using 75% of the spectra. The remaining 25% of the spectra were used in test-set validation to estimate model success, calculated as the percent of correct predictions. This preliminary matching algorithm correctly predicted 100% of the validation spectra. These mineral data will be further analyzed with cluster analysis to identify compositional subgroups of each mineral.

The full 23-mineral matching algorithm will be used to identify the proportions of detrital heavy mineral assemblages in two locations of Early Permian (Wolfcampian) non-marine strata in New Mexico. Results from this study will compliment and be compared with results from a recent U-Pb detrital zircon geochronologic provenance study which focused on source and sediment dispersal during the final stage of Ancestral Rocky Mountain orogenesis in New Mexico. A successful test of the LIBS approach in this study should result in a distinct set of spectrographic signals that correspond with and support previous findings by Bonar (2018) on (1) the source of detritus to Early Permian basins in New Mexico and (2) sediment dispersal pathways during the Ancestral Rocky Mountains.