Spectral properties of halite-rich mineral mixtures: Implications for middle infrared remote sensing of highly saline environments

Eastes, John W.

doi:10.1016/0034-4257(89)90089-8

Cited by 24 publications

(23 citation statements)

References 25 publications

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“…Pure halite (NaCl) is transparent (as quartz) and its chemical composition and crystal cubic structure cannot induce absorption bands in visible, and near to thermal infrared (Hunt et al, 1972;Eastes, 1989). Only water bands (1.4, 1.9 and 2.25 /im) are observed due to moisture and fluid inclusions in fresh samples and in fluid inclusions after drying (Hunt et al, 1972;Mulders, 1987;Mougenot, 1991).…”

Section: Chloridesmentioning

confidence: 99%

“…Combinations with visible and infrared bands (0.4 to 2.5 /¿m) are necessary to identify salts and substrate and to improve resolution. Eastes (1989) measured in laboratory thermal infrared spectra (between 2.5 and 14 fim) of halite mixtures with calcite, gypsum, quartz and montmorillonite (2 to 100%). The new spectra are a non-linear function of both particle-size distribution and weight fraction.…”

Section: Thermal Infraredmentioning

confidence: 99%

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Remote sensing of salt affected soils

Mougenot¹,

Pouget²,

Epema

1993

Remote Sensing Reviews

181

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Remote sensing is an important aid in mapping and surveying salt affected soils. Both spatial and temporal variation can be followed. We emphasize this overview on reflectance properties by sunlight. Thermal infrared information, which can be used to detect hygroscopic characteristics of salts, and microwaves, which give indirectly information on salt are only described briefly.Spectral properties of different salts consisting of chlorides and sulphates are presented. Also calcite spectra are evaluated. This evaluation gives the background to examine possibilities of present day operational satellites and new technologies like imaging spectroscopy. Possibilities of operational systems, working in broad bands are treated separately with direct observations on bare soils and indirect observations on vegetation covered surfaces. In the visible part of the spectrum the high reflectance of salt covered areas is prominent. Bands in the middle infrared give information on moisture content, which is often associated with salt content differences, and some information on type of salts. The overview ends with a discussion on possibilities of future remote sensing system.

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Section: Chloridesmentioning

confidence: 99%

Section: Thermal Infraredmentioning

confidence: 99%

Remote sensing of salt affected soils

Mougenot¹,

Pouget²,

Epema

1993

Remote Sensing Reviews

181

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“…This scattering is caused by the geometric optics of the particles with respect to wavelength together with the absorption coefficient of the minerals [Hapke, 1981;Johnson et al, 1983;Moersch and Christensen, 1995]. With many minerals having a much smaller absorption coefficient, and hence a larger photon path length than the TIR region, photons undergo significantly greater volume scattering at these shorter wavelengths [Eastes, 1989;Wald and Salisbury, 1995]. Volume scattering occurs where a photon passes through one or more grains of a mixture and is incoherently scattered at every particle interface and grain asperity.…”

Section: Visible/near-infrared Photon Scatteringmentioning

confidence: 99%

Mineral abundance determination: Quantitative deconvolution of thermal emission spectra

Ramsey¹,

Christensen²

1998

J. Geophys. Res.

376

413

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Abstract. A linear retrieval (spectral deconvolution) algorithm is developed and appliedto high-resolution laboratory infrared spectra of particulate mixtures and their endmembers. The purpose is to place constraints on, and test the viability of, linear spectral deconvolution of high-resolution emission spectra. The effects of addition of noise, data reproducibility, particle size variation, an increasing number of minerals in the mixtures, and blind end-member input are also examined. Thermal emission spectra of 70 mineral mixtures ranging from 2 to 15 end-members and having particle diameters of 250-500 p,m were obtained. Deconvolution results show that the assumption of linear mixing is valid and enables mineral percentage prediction to within 5% on average with residual errors of less than 0.1% total emissivity. One suite (21 distinct mixtures), varying from <10 •m to 500/xm, was also prepared to test the limits of the model at decreasing particle sizes. Incoherent volume scattering at grain diameters less than several times the wavelength (---60/xm) produces significant changes in spectral band morphology and hence, an increase in the root-mean-squared (RMS) error of the model. Because of this, it appears that spectral mixing remains essentially linear to ---60 •m (using the 250-500/xm size fraction as end-members). Below this threshold, the linear retrieval algorithm fails. However, with the appropriate particle diameter end-member spectra for the corresponding mixtures, the errors are reduced significantly and linearity continues through to the 10-20/xm size fraction. Additions of increasing amounts of noise cause a deviation of an additional 2.4%, whereas variability due to spectrometer reproducibility produces an average error of 4.0%. The model is also able to detect accurately minerals in mixtures containing 15 end-members, well beyond the number of geological significance. Extensive error analysis and model testing confirm the appropriateness of linear deconvolution as a useful and powerful too! to examine complexly mixed emission spectra in the laboratory and the field. The results of this study provide a foundation for remote sensing analyses of thermal infrared data from current airborne and future satellite instruments planned for Earth and Mars.

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“…Improved methods for characterizing salts at the surface would enhance mapping and monitoring of salinity gradients and improve understanding of salt‐forming pathways including aqueous processes, volcanism, aerosol deposition, freezing, and hydrothermal activity. However, there are relatively few studies of salts on Earth using thermal infrared (TIR) spectroscopy [e.g., Eastes , ; Crowley , ; review in Metternicht and Zinck , ]. Two hurdles have obstructed the quantification of halide salts with TIR techniques.…”

Section: Introductionmentioning

confidence: 99%

“…Two hurdles have obstructed the quantification of halide salts with TIR techniques. First, halides are transmissive and spectrally featureless over TIR wavelengths (~2500–700 cm −1 ; ~4–14 µm) [ Eastes , ]. Second, salts may form in a variety of textural settings with a wide range of particle sizes, roughness, mixing, packing, cementation, and disaggregation.…”

Section: Introductionmentioning

confidence: 99%

Effect of halite coatings on thermal infrared spectra

Berger

King

Green³

et al. 2015

JGR Solid Earth

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Characterizing the occurrence and distribution of soluble salts on planetary surfaces allows us to model or monitor aqueous and geochemical conditions. Thermal infrared (TIR) remote sensing is useful for identifying some types of salt deposits; however, mineral abundance determinations are based on the interaction of infrared with only the top few hundred micrometers of the surface. Thus, distinguishing massive deposits from coatings presents a challenge to TIR remote sensing. To better understand the TIR properties of spectrally transmissive halite coatings, we investigated the effects of coating thickness and texture on the TIR reflectance spectra of halite-coated glasses. We analyzed two coating textures with variable thickness: (1) continuous and (2) discontinuous particulate coatings. As halite coating thickness increases, the intensity of substrate absorption bands decreases nonlinearly. The substrate is not detected with halite coatings >150 μm thick. Therefore, when coatings are present, it is not possible to apply TIR models of mineral abundances using linear deconvolution algorithms. We show that continuous and coarse particulate halite coatings increase the reflectance minimum (emissivity maximum), making them potentially detectable on planetary surfaces by the methods of Osterloo et al. (2008). However, the reflectance minimum does not change if coatings have low areal coverage (<50%) or are composed of fine particles (<5 μm). Thus, halite that forms as efflorescent coatings or has been redistributed as fine dust is not detected using TIR spectroscopy. Our results explain why Cl salts are not detected with TIR spectroscopy at many locations on Mars despite high Cl contents.

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Spectral properties of halite-rich mineral mixtures: Implications for middle infrared remote sensing of highly saline environments

Cited by 24 publications

References 25 publications

Remote sensing of salt affected soils

Remote sensing of salt affected soils

Mineral abundance determination: Quantitative deconvolution of thermal emission spectra

Effect of halite coatings on thermal infrared spectra

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