Hyperspectral REE (Rare Earth Element) Mapping of Outcrops - Applications for Neodymium Detection

In this study, an in situ application for identifying neodymium (Nd) enriched surface materials that uses multitemporal hyperspectral images is presented (HySpex sensor). Because of the narrow shape and shallow absorption depth of the neodymium absorption feature, a method was developed for enhancing and extracting the necessary information for neodymium from image spectra, even under illumination conditions that are not optimal. For this purpose, the two following approaches were developed: (1) reducing noise and analyzing changing illumination conditions by averaging multitemporal image scenes and (2) enhancing the depth of the desired absorption band by deconvolving every image spectrum with a Gaussian curve while the rest of the spectrum remains unchanged (Richardson-Lucy deconvolution). To evaluate these findings, nine field samples from the Fen complex in Norway were analyzed using handheld X-ray fluorescence devices and by conducting detailed laboratory-based geochemical rare earth element determinations. The result is a qualitative outcrop map that highlights zones that are enriched in neodymium. To reduce the influences of non-optimal illumination, particularly at the studied site, a minimum of seven single acquisitions is required. Sharpening the neodymium absorption band allows for robust mapping, even at the outer zones of enrichment. From the geochemical investigations, we found that iron oxides decrease the applicability of the method. However, iron-related absorption bands can be used as secondary indicators for sulfidic ore zones that are mainly enriched with rare earth elements. In summary, we found that hyperspectral spectroscopy is a noninvasive, fast and cost-saving method for determining neodymium at outcrop surfaces.

[1]  J. Hill,et al.  Using Imaging Spectroscopy to study soil properties , 2009 .

[2]  Carle M. Pieters,et al.  Deconvolution of mineral absorption bands: An improved approach , 1990 .

[3]  Lawrence C. Rowan,et al.  Spectral reflectance of carbonatites and related alkalic igneous rocks; selected samples from four North American localities , 1986 .

[4]  D. Harlov,et al.  Resetting monazite ages during fluid-related alteration , 2011 .

[5]  Runsheng Wang,et al.  Quantitative estimation of concentrations of dissolved rare earth elements using reflectance spectroscopy , 2013 .

[6]  T. Andersen.  Magmatic fluids in the Fen carbonatite complex, S.E. Norway , 1986 .

[7]  L. Rowan,et al.  Lithologic mapping in the Mountain Pass, California area using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data , 2003 .

[8]  I. Ramberg.  Gravity studies of the Fen complex, Norway, and their petrological significance , 1973 .

[9]  W. McDonough,et al.  Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes , 1989, Geological Society, London, Special Publications.

[10]  Timothy E. Townsend,et al.  Discrimination of iron alteration minerals in visible and near‐infrared reflectance data , 1987 .

[11]  Enton Bedini,et al.  Review of Survey activities 2008: Using spectral mixture analysis of hyperspectral remote sensing data to map lithology of the Sarfartoq carbona tite complex, southern West Greenland , 2009 .

[12]  Roger H. Mitchell,et al.  Rare earth element geochemistry of the Fen alkaline complex, Norway , 1975 .

[13]  E. Cloutis,et al.  Review Article Hyperspectral geological remote sensing: evaluation of analytical techniques , 1996 .

[14]  I. Kjarsgaard.  Rare Earth Elements in Sovitic Carbonatites and their Mineral Phases , 1998 .

[15]  Tom Andersen,et al.  Evolution of peralkaline calcite carbonatite magma in the Fen complex, southeast Norway , 1988 .

[16]  S. J. Sutley,et al.  Imaging spectroscopy: Earth and planetary remote sensing with the USGS Tetracorder and expert systems , 2003 .

[17]  E. Bedini,et al.  Using spectral mixture analysis of hyperspectral remote sensing data to map lithology of the Sarfartoq carbona tite complex, southern West Greenland , 1969 .

[18]  Carle M. Pieters,et al.  Estimating modal abundances from the spectra of natural and laboratory pyroxene mixtures using the modified Gaussian model , 1993 .

[19]  William B. White,et al.  Diffuse-Reflectance Spectra of Rare-Earth Oxides , 1967 .

[20]  Hornig-Kjarsgaard Ingrid.  Rare Earth Elements in Sövitic Carbonatites and their Mineral Phases , 1998 .

[21]  Atsushi Momose,et al.  Mapping pegmatite using HyMap data in southern Namibia , 2011, 2011 IEEE International Geoscience and Remote Sensing Symposium.

[22]  E. Bedini.  Mapping lithology of the Sarfartoq carbonatite complex, southern West Greenland, using HyMap imaging spectrometer data , 2009 .

[23]  P. Laznicka,et al.  Giant Metallic Deposits , 2010 .

[24]  T. Emge,et al.  Near-Infrared Optical Characteristics of Chalcogenide-Bound Nd3+ Molecules and Clusters , 2007 .

[25]  E. Zuleger,et al.  Determination of the REE and Y in silicate materials with ICP-AES , 1988 .

[26]  G. Dieke,et al.  The Spectra of the Doubly and Triply Ionized Rare Earths , 1963 .

[27]  Hermann Kaufmann,et al.  Spaceborne Mine Waste Mineralogy Monitoring in South Africa, Applications for Modern Push-Broom Missions: Hyperion/OLI and EnMAP/Sentinel-2 , 2014, Remote. Sens..

[28]  Cheng Xu,et al.  Carbonatites in China: A review for genesis and mineralization , 2010 .

[29]  Rainer Reuter,et al.  STABLE DECONVOLUTION OF NOISY LIDAR SIGNALS , 2000 .

[30]  Hermann Kaufmann,et al.  Hyperspectral digital image analysis and geochemical analysis of a rare earth elements mineralized intrusive complex (fen carbonatite complex in Telemark region, Norway) , 2015 .

[31]  Benoit Rivard,et al.  Visible and short-wave infrared reflectance spectroscopy of REE fluorocarbonates , 2014 .

[32]  L. Guanter,et al.  Spectral calibration of hyperspectral imagery using atmospheric absorption features. , 2006, Applied optics.

[33]  Thorfinnur Gunnlaugsson,et al.  Photochemistry and Photophysics of Coordination Compounds: Lanthanides , 2007 .

[34]  Tsehaie Woldai,et al.  Multi- and hyperspectral geologic remote sensing: A review , 2012, Int. J. Appl. Earth Obs. Geoinformation.

[35]  S. Misra,et al.  Absorption Difference and Comparative Absorption Spectrophotometry of Neodymium(III) Haloacetates in Non-Aqueous Media and in Crystalline State , 1992 .

[36]  Angela Lausch,et al.  Reduction of Radiometric Miscalibration—Applications to Pushbroom Sensors , 2011, Sensors.