Authored by Dr. Brian Curtiss. Brian Curtiss is one of the founders of ASD, a brand of Malvern Panalytical, and currently serves as ASD’s Chief Technical Officer. He has over 30 years of experience in the fields of geology, spectroscopy and optical remote sensing. In his current position, Dr. Curtiss applies his experience to the development of solutions to a diverse range of analytical problems in the areas of remote sensing and natural resources.
Mapping alteration in geothermal drill core using a field portable spectroradiometer
This paper, by long time ASD customer Wendy Calvin, describes how an ASD FieldSpec® spectroradiometer has been used to analyze 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 or an ASD TerraSpec Halo. 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. We have performed several pilot studies of geothermal drill core and chips to prototype rapid alteration characterization 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. We 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.
Read the full paper here: Mapping alteration in geothermal drill core using a field portable spectroradiometer
Assessment of Imaging Spectroscopy for rock identification in the Karkonosze Mountains, Poland
This paper describes a very typical remote sensing application for ASD’s FieldSpec spectroradiometer: they used reflectance spectra collected using an ASD instrument to build a spectral library which was then used to identify those materials in hyperspectral imagery. From the abstract:
Based on laboratory, field and airborne-acquired hyperspectral data, this paper aims to analyze the dominant minerals and rocks found in the Polish Karkonosze Mountains. Laboratory spectral characteristics were measured with an ASD FieldSpec spectrometer and images were obtained from VITO’s Airborne Prism EXperiment (APEX) scanner. …hyperspectral airborne imagery allowed for subpixel classifications of different types of granites, hornfels and mica schist within the research area. The hyperspectral data enabled geological mapping of bare ground that had been masked out using three advanced algorithms…. The result of this study was a set of maps and post classification statistical data of rock distribution in the area…
Read the full paper here: Assessment of Imaging Spectroscopy for rock identification in the Karkonosze Mountains, Poland
Differentiating among Four Arctic Tundra Plant Communities at Ivotuk, Alaska Using Field Spectroscopy
This is another paper where an ASD collected spectral library is used to classify material in an image – this time the application is vegetation mapping. From the abstract:
Warming in the Arctic has resulted in changes in the distribution and composition of vegetation communities. Many of these changes are occurring at fine spatial scales and at the level of individual species. Broad-band, coarse-scale remote sensing methods are commonly used to assess vegetation changes in the Arctic, and may not be appropriate for detecting these fine-scale changes; however, the use of hyperspectral, high resolution data for assessing vegetation dynamics remains scarce. …Overall classification accuracy at Ivotuk ranged from 84%–94% and from 55%–91% for the Dalton Highway test sites. The results of this study suggest that hyperspectral data acquired at the field level, along with the SPLS and LDA methodology, can be used to successfully discriminate among Arctic tundra vegetation communities in Alaska, and present an improvement over broad-band, coarse-scale methods for community classification.
Read the full paper here: Differentiating among Four Arctic Tundra Plant Communities at Ivotuk, Alaska Using Field Spectroscopy