High Sulfidation Epithermal Deposits

Identifying minerals in high sulfidation epithermal deposits
High sulfidation epithermal deposits are created by fluids from hot magma. Rocks that come in contact with the fluids are altered and a definable zone formed. These alteration zones as they move away from the core are characterized by the following mineral assemblages: alunite, pyrophyllite, kaolinite, illite, and chlorite rich clays. An oreXpress, oreXplorer or oreXpert spectrometer with EZ-ID can help identify the dominant minerals to create a more accurate mineral map and better decisions on where to drill and what they can expect to find.

With an oreXpress, oreXplorer or oreXpert geological spectrometer and EZ-ID, a geologist can match the target minerals from outcrops, pits, trenches and benches against three mineral spectral libraries from USGS, SPECMin and GeoSPEC. EZ-ID allows the geologist to add spectral match regions to further identify dominant minerals from mixtures by focusing on and matching against the most important features in the spectra. For example, in high sulfidation epithermal deposits that might mean focusing on:

  • Alunite with key absorption features at 1440, 1475, 1760, 2165/2206 and 2320nm
  • Pyrophyllite at 1396, 2066/2078, 2168 and 2320nm
  • Kaolinite at 960, 1400/1412, 2160/2206, 2310, 2350 and 2380nm

EZ-ID features:

  • Fast and accurate identification of an unknown mineral to a known spectral library sample
  • Ease-of-use: take your scans and see results in real-time
  • Simple, consistent user interface
  • USGS, SpecMIN and GeoSPEC libraries available
  • Weighted score for best matches
  • Include or exclude spectral regions of interest for optimal results
  • Compare and contrast match regions and save as pre-sets
  • Select the match regions and results to save and process to an Excel file using batch mode
  • Scalars to provide additional information on crystallinity changes, alteration pattern shifts and geochemical conditions

Using an oreXpress, oreXplorer or oreXpert with EZ-ID delivers the following benefits for exploration geologists:

  • Quickly take a lot of samples
  • Cover more ground in less time
  • More accurate data provides a more complete picture of what you are looking at
  • Less time and expense than waiting for samples to come back from the lab
  • Less drilling – better results – quickly delivers a return-on- investment

In the field these spectrometers are rugged, reliable, and designed for single user operation. Field collection of spectra is fast and accurate. In the core shack, a single geologist with a contact probe could log as much as 400 meters a day. And, since DARWin saves it all in an ASCII format, it’s easy to use the data with 3rd party software for mine mapping, mineral mapping and 3D imagery.

SPECTRAL EVOLUTION’S EZ-ID software has identified our target sample as alunite using the USGS spectral library for reference. The shaded areas shown in the scan allow a geologist to concentrate on regions in the spectra of particular interest.

Kaolinite identified using multiple match regions to focus on key absorption features.