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 spectrometer with EZ-ID can help identify the dominant minerals to creat a more accurate mineral map and better decisions on where to drill and what they can expect to find.

With an oreXpress geological spectrometer and EZ-ID, a geologist can match the target minerals from outcrops, pits, trenches and benches against two mineral spectral libraries from USGS and SPECMin. 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 scan using an oreXpress or oreXpress platinum and see results in real-time
  • Simple, consistent user interface
  • USGS and SpecMIN libraries available
  • Weighted score for best matches
  • Include or exclude spectral regions of interest for optimal results
  • Compare and contrast match regions
  • Select the match regions and results to save and process to an Excel file using batch mode

Using an oreXpress 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 the oreXpress is 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, minerasl mapping and 3D imagery.

oreXpress field portable spectrometer for mineral identification and analysis with EZ-ID

SPECTRAL EVOLUTION’S EZ-ID software has identified our target sample as kaolinite 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.

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