T75 Refining Predictive Models of Modern and Ancient Source-to-Sink Systems

Tuesday, 27 October 2020
1:30 PM - 5:30 PM
Meeting Rooms

IDENTIFICATION OF DETRITAL HEAVY MINERALS USING LASER-INDUCED BREAKDOWN SPECTROSCOPY (LIBS) AND MULTIVARIATE ANALYSIS

Paper number: T75-15
Program: Technical Sessions
Time: 4:15 PM – 4:25 PM

Authors

Abstract

Prior to the development of detrital zircon geochronology techniques, the primary method for understanding provenance trends was to visually identify the constituent detrital heavy minerals in a sediment or sedimentary rock. The development of Laser-Induced Breakdown Spectroscopy (LIBS), a rapid laser ablation optical emission analytical technique, makes possible rapid and accurate identification of the heavy minerals in a clastic sediment and measurement of their proportions, providing valuable information to enhance detrital zircon U-Pb studies. Multivariate analysis of LIBS spectra taken from heavy grains can both identify and separate minerals into clusters of compositional subgroups within a specific mineral. To accomplish this, LIBS spectra from 10+ samples of 17 mineral groups were collected. A multivariate decision tree was calibrated with 75% of these spectra. The remaining 25% were used as a validation set testing the accuracy of the algorithm. This mineral identification decision tree consists of a series of binary Partial Least Squares Regression (PLSR) models, with each model targeting a detrital heavy mineral. A previous iteration of this PLSR decision tree was able to separate and identify with 100% accuracy seven of the targeted mineral groups. LIBS spectra acquired from ca. 500 heavy mineral grains from each of three outcrops of the of the Early Permian (Wolfcampian) non-marine Abo Formation in New Mexico were classified by mineral species using the mineral identification decision tree. In addition to the counts of the 17 targeted mineral groups, each mineral group will be analyzed using PCA cluster analysis to test for compositional subgroups. The mineral counts and subgroups will supplement the findings of a previous detrital zircon analysis of the Abo Formation done by Bonar (2018) showing sediment dispersal pathways from active Ancestral Rocky Mountain uplifts.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-356883

© Copyright 2020 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.