Practical and Applied Reflectance Spectroscopy: Automated Drill Core Logging and Mineral Mapping

• Author / Creator

  Tappert, Michelle C.

• This thesis investigates three ways that automated reflectance spectroscopy can be used for applied purposes: the automated logging of drill core into ore-bearing and barren zones, the analysis of minerals to provide evidence of hydrothermal alteration, and the creation of mineral maps to show crystal orientation.

  Reflectance spectra collected from 300 meters of drill core from the iron oxide-copper-gold deposit (IOCG) at Olympic Dam using HyLogger were analyzed between 870 and 960, and 2,190 and 2,230 nm to identify hematite (i.e., mineralized lithologies) and phengite (i.e., barren lithologies), respectively. The results were plotted as a function of depth to produce a log that accurately identified ore-bearing and barren zones. The most intense absorption features between 870 and 960 nm, and 2,190 and 2,230 nm were also found to correspond to iron and aluminum concentrations, respectively.

  Reflectance spectra were also collected from the same drill core using HyLogger 2 and were analyzed between 2.190 and 2.230 µm to evaluate the abundance and mineral chemistry of phengite. Microprobe results from 597 phengite grains were compared to the spectral results, and it was revealed that in the ore-bearing zones, phengite displayed a higher-Al content and lower Mg-number than phengite from the barren zones. Mid-infrared spectra collected from individual phengite crystals revealed that high-Al phengites produced a peak at 9.59 µm, and low-Al phengites produced a peak at 9.57 µm.

  To document the effect that crystal orientation has on the mid-infrared reflectance spectrum of quartz, spectra were collected at a 100 x 100 µm spot size from an oriented quartz crystal and from quartz crystals contained within a quartz-bearing granite hand sample (Inco-37). Spectra from the optic axis (i.e., c-axis) produced an intense trough at 8.63 µm, and a peak at 12.50 µm. Spectra from the a-axis produced a less intense trough at 8.63 µm, and two peaks at 12.50 and 12.79 µm. Furthermore, the band ratio Ref9.01/Ref8.63 was used to estimate the orientation of quartz crystals.

• Subjects / Keywords

  • Reflectance spectroscopy
  • Olympic Dam
  • Infrared spectroscopy
  • Automated drill core logging
  • Phengite

• Graduation date

  Fall 2012

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R37D86

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.