Spectral reflectance of carbonatites and related alkalic igneous rocks; selected samples from four North American localities

Rowan, Lawrence C.; Kingston, Marguerite J.; Crowley, John S.

doi:10.2113/gsecongeo.81.4.857

Cited by 72 publications

(53 citation statements)

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“…Reflectance spectra of all carbonatite samples show carbonate absorption features that are typical for calcite at 2.34 µm [34,35]. Rowan et al [11] and Turner et al [33] showed that narrow absorption bands in the VNIR-and SWIR-range are related to specific REE-elements (mostly Nd, e.g., 0.741 and 0.798 µm [33]). The lower detection limit for Nd 3+ in high albedo samples is about 300 ppm [11].…”

Section: Carbonatitementioning

confidence: 94%

“…Rowan et al [11] and Turner et al [33] showed that narrow absorption bands in the VNIR-and SWIR-range are related to specific REE-elements (mostly Nd, e.g., 0.741 and 0.798 µm [33]). The lower detection limit for Nd 3+ in high albedo samples is about 300 ppm [11]. Selected samples from inside (e.g., sample NA-14-08-18-B2, -B5, -Sec B, see Figure 2) and outside (e.g., sample -B8, -B10) the high-grade zones were studied in the laboratory.…”

Section: Carbonatitementioning

confidence: 99%

“…Expert knowledge is often required to get reliable results if the target is rather small [9,10]. However, applications of remote sensing for the exploration of carbonatite were only tested in a few studies ( [9,[11][12][13][14][15][16][17]). Thus, there is a need to improve remote sensing exploration techniques for REEs, Nb and Ta due to an increasing demand during the past few decades and the acceleration of this demand due to their augmenting use in high-tech industry ( [18,19]).…”

Section: Introductionmentioning

confidence: 99%

“…On the basis of the classification results obtained, methods to map enrichment zones within carbonatite sequences were evaluated in a second step. Limitations due to sub-economic REE enrichment at Epembe (∼0.5% TREO+Y) and high detection limits (e.g., for Nd 3+ ∼ 300 ppm in laboratory data [11]) were circumvented by the use of indicator minerals (e.g., see Mackay et al [22] or Bull [23]), like apatite or a specific type of pyroxene (e.g., aegirine or augite), to estimate the Nb-Ta-REE potential of the deposit. Those low REE abundances also disable the use of deconvolution algorithms, as proposed by Neave et al [17] or Boesche et al [16].…”

Section: Introductionmentioning

confidence: 99%

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Remote Sensing Exploration of Nb-Ta-LREE-Enriched Carbonatite (Epembe/Namibia)

et al. 2016

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Abstract:On the example of the Epembe carbonatite-hosted Nb-Ta-LREE deposit, we demonstrate the use of hyperspectral reflectance data and geomorphic indicators for improving the accuracy of remote sensing exploration data of structurally-controlled critical raw material deposits. The results further show how exploration can benefit from a combination of expert knowledge and remotely-sensed relief, as well as imaging data. In the first stage, multi-source remote sensing data were used in lithological mapping based on Kohonen Self-Organizing Maps (SOM). We exemplify that morphological indices, such as Topographic Position Index (TPI), and spatial coordinates are crucial parameters to improve the accuracy of carbonate classification as much as 10%. The resulting lithological map shows the spatial distribution of the ridge forming carbonatite dyke, the fenitization zone, syenite plugs and mafic intrusions. In a second step, the internal zones of the carbonatite complex were identified using the Multi-Range Spectral Feature Fitting (MRSFF) algorithm and a specific decision tree. This approach allowed detecting potential enrichment zones characterized by an abundance of fluorapatite and pyroxene, as well as dolomite-carbonatite (beforsite). Cross-validation of the mineral map with field observations and radiometric data confirms the accuracy of the proposed method.

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Section: Carbonatitementioning

confidence: 94%

Section: Carbonatitementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Remote Sensing Exploration of Nb-Ta-LREE-Enriched Carbonatite (Epembe/Namibia)

et al. 2016

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“…Vincent and Thomson, 1972;Goetz and Rowan, 1981;Fu et al, 2007). Rowan et al (1986); Rowan and Mars (2003) demonstrated that transition metal enrichment can be detected via use of VNIR. Hydroxide, sulfate and carbonate minerals can be analyzed using SWIR (Kruse, 1988;Rowan and Mars, 2003;Ninomiya et al, 2005).…”

Section: Lithologic Remote Sensingmentioning

confidence: 99%

Geochemical characterization of supraglacial debris via in situ and optical remote sensing methods: a case study in Khumbu Himalaya, Nepal

2012

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Abstract. Surface glacier debris samples and field spectra were collected from the ablation zones of Nepal Himalaya Ngozumpa and Khumbu glaciers in November and December 2009. Geochemical and mineral compositions of supraglacial debris were determined by X-ray diffraction and X-ray fluorescence spectroscopy. This composition data was used as ground truth in evaluating field spectra and satellite supraglacial debris composition and mapping methods. Satellite remote sensing methods for characterizing glacial surface debris include visible to thermal infrared hyper-and multispectral reflectance and emission signature identification, semi-quantitative mineral abundance indicies and spectral image composites. Satellite derived supraglacial debris mineral maps displayed the predominance of layered silicates, hydroxyl-bearing and calcite minerals on Khumbu Himalayan glaciers. Supraglacial mineral maps compared with satellite thermal data revealed correlations between glacier surface composition and glacier surface temperature. Glacier velocity displacement fields and shortwave, thermal infrared false color composites indicated the magnitude of mass flux at glacier confluences. The supraglacial debris mapping methods presented in this study can be used on a broader scale to improve, supplement and potentially reduce errors associated with glacier debris radiative property, composition, areal extent and mass flux quantifications.

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