Mapping Alteration In Geothermal Drill Core Using A Field Portable Spectroradiometer

This article was written by Analytik partner Malvern Panalytical, it featured in their ‘Materials Talks’ blog on the 26th February 2019.

This paper, by long time ASD customer Wendy Calvin, describes how an ASD FieldSpec spectroradiometer has been used to analyse drill cores in geothermal systems. These types of drill holes are typically used in early-stage geothermal exploration and help to locate geothermal resources for energy generation (see the paper’s introduction section for a good summary of the application). While in this case a FieldSpec was used, this would be a better fit for an ASD TerraSpec 4 plus TSG software. Here is the abstract:

Hydrothermal alteration mineralogy in geothermal systems is commonly used to infer system temperature and past fluid flow patterns. (Near) Infrared spectroscopy is particularly good at identifying a wide variety of hydrothermal alteration minerals. The technique requires little sample preparation, and is especially helpful in discrimination among a wide range of phyllosilicate minerals that may be difficult to distinguish in hand sample or require lengthy preparation for XRD analysis. There have been several pilot studies of geothermal drill core and chips to prototype rapid alteration characterisation over large depths. These preliminary studies have established reliable methods for core/chip surveys that can quickly measure samples with high depth resolution and show the efficiency of the technique to sample frequently and provide alteration logs similar to geophysical logs. Studies have successfully identified a wide variety of phyllosilicates, zeolites, opal, calcite, iron oxides, and hydroxides, and note depth-associated changes in alteration minerals, patterns, or zones. Alteration mineralogy identified using these techniques shows good correlation with traditional petrographic microscope and XRD method.

To read the full paper by Wendy M. Calvin, click the button below:

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