Sulfide detection in drill core from the Stillwater Complex using visible/near‐infrared imaging spectroscopy

Geophysics ◽  
2003 ◽  
Vol 68 (5) ◽  
pp. 1561-1568 ◽  
Author(s):  
Brock J. Bolin ◽  
Thomas S. Moon
Keyword(s):  
Metal Ion ◽  
Imaging Spectroscopy ◽  
Visible Region ◽  
Sulfide Minerals ◽  
Absorption Feature ◽  
Drill Core ◽  
Mining Operations ◽  
Stillwater Complex ◽  
Imaging Spectrometer ◽  
Point Count

This feasibility study examines the potential of imaging spectroscopy to estimate sulfide percentage in drill core from the Stillwater Complex, Montana. The Stillwater Complex is a layered mafic to ultramafic intrusion hosting ore‐grade platinum group elements within the zone known as the JM Reef. Stillwater Mine geologists indirectly infer the platinum/palladium grade by the presence and abundance of sulfide minerals. In order to discriminate between waste and ore rock, geologists visually inspect the core and working faces for minerals such as chalcopyrite, pentlandite, and pyrrhotite. Iron sulfide minerals have a strong ultraviolet absorption that blends into the blue portion of the visible region and produces their yellow luster. The spectral differences between these pathfinder minerals and the accessory minerals are sufficiently distinct to allow classification of this mineralogy using imaging spectroscopy even in the absence of a particular absorption feature. Five different sections of split core from the JM Reef were chosen for their representative mineralogical character. The surface of each sample was scanned with Montana Tech's prototype Airborne and Laboratory Imaging Spectrometer (ALIS) and the images were analyzed for sulfides. For validation, the amount of sulfides was independently determined visually with counting grids. The imaging spectrometer results correlate well with the point‐count percentage, although all five samples consistently fall below the point‐count average. This underestimation is possibly due to metal ion substitution, linear mixing at mineral boundaries, or anisotropic scattering due to the high spatial resolution of the spectrometer. The success of this experiment suggests possible machine vision applications in future mining operations, such as automation of core logging and downhole instrumentation.

scholarly journals Detection and Quantification of Snow Algae with an Airborne Imaging Spectrometer

2001 ◽  
Vol 67 (11) ◽  
pp. 5267-5272 ◽  
Author(s):  
Thomas H. Painter ◽  
Brian Duval ◽  
William H. Thomas ◽  
Maria Mendez ◽  
Sara Heintzelman ◽  
...  
Keyword(s):  
Sierra Nevada ◽  
Wavelength Range ◽  
Spectral Reflectance ◽  
Infrared Imaging ◽  
Spectral Signature ◽  
Absorption Feature ◽  
Imaging Spectrometer ◽  
Algal Concentration ◽  
Airborne Imaging ◽  
Spectrometer Data

ABSTRACT We describe spectral reflectance measurements of snow containing the snow alga Chlamydomonas nivalis and a model to retrieve snow algal concentrations from airborne imaging spectrometer data. Because cells of C. nivalis absorb at specific wavelengths in regions indicative of carotenoids (astaxanthin esters, lutein, β-carotene) and chlorophylls a and b, the spectral signature of snow containing C. nivalis is distinct from that of snow without algae. The spectral reflectance of snow containing C. nivalis is separable from that of snow without algae due to carotenoid absorption in the wavelength range from 0.4 to 0.58 μm and chlorophyll a and babsorption in the wavelength range from 0.6 to 0.7 μm. The integral of the scaled chlorophyll a and b absorption feature (I 0.68) varies with algal concentration (Ca ). Using the relationshipCa = 81019.2 I 0.68+ 845.2, we inverted Airborne Visible Infrared Imaging Spectrometer reflectance data collected in the Tioga Pass region of the Sierra Nevada in California to determine algal concentration. For the 5.5-km2 region imaged, the mean algal concentration was 1,306 cells ml−1, the standard deviation was 1,740 cells ml−1, and the coefficient of variation was 1.33. The retrieved spatial distribution was consistent with observations made in the field. From the spatial estimates of algal concentration, we calculated a total imaged algal biomass of 16.55 kg for the 0.495-km2 snow-covered area, which gave an areal biomass concentration of 0.033 g/m2.

scholarly journals Biochemical Engineering Parameters for Hydrometallurgical Processes: Steps towards a Deeper Understanding

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
K. Kundu ◽  
A. Kumar
Keyword(s):  
Redox Potential ◽  
Metal Ion ◽  
Good Control ◽  
Point Of View ◽  
Rate Equations ◽  
Biochemical Engineering ◽  
Mining Operations ◽  
Feasible Option ◽  
Engineering Parameters ◽  
Kinetics Of

Increasing interest in biomining process and the demand for better performance of the process has led to a new insight toward the mining technologies. From an engineering point of view, the complex network of biochemical reactions encompassed in biomining would best be performed in reactors which allow a good control of the significant variables, resulting in a better performance. The subprocesses are in equilibrium when the rate of particular metal ion; for example, iron turnover between the mineral and the bacteria, is balanced. The primary focus is directed towards improved bioprocess kinetics of the first two subprocesses of chemical reaction of the metal ion with the mineral and later bacterial oxidation. These subprocesses are linked by the redox potential and controlled by maintenance of an adequate solids suspension, dilution rate, and uniform mixing which are optimised in bioreactors during mining operations. Rate equations based on redox potential such as ferric/ferrous-iron ratio have been used to describe the kinetics of these subprocesses. This paper reviews the basis of process design for biomining process with emphasis on engineering parameters. It is concluded that the better understanding of these engineering parameters will make biomining processes more robust and further help in establishing it as a promising and economically feasible option over other hydrometallurgical processes worldwide.

Imaging Spectroscopy Using Fiber Optics

1997 ◽  
Vol 3 (S2) ◽  
pp. 845-846
Author(s):  
S. Michael Angel ◽  
H. Trey Skinner ◽  
Brian J. Marquardt
Keyword(s):  
Optical Fiber ◽  
Fiber Optics ◽  
Optical Fibers ◽  
Fiber Optic ◽  
Imaging System ◽  
Single Point ◽  
Imaging Spectroscopy ◽  
Small Diameter ◽  
Imaging Spectrometer ◽  
Remote Spectroscopy

Optical fiber probes are routinely used with optical spectrometers to allow measurements to be made on remotely located samples. In most of these systems, however, the optical fibers are used as non-imaging “light pipes” for the transmission of laser light, and luminescence or Raman signals to and from the sample. Thus, while these systems are suitable for remote spectroscopy, they are limited to single-point measurements. In a recent paper, we showed that a small-diameter (i.e., 350 μm) coherent optical fiber bundle can be combined with an AOTF-based imaging spectrometer for fluorescence and Raman spectral micro-imaging with increased flexibility in terms of sample positioning and in-situ capabilities. The previous paper described the operation of the fiber-optic microimaging probe and AOTF imaging system and showed preliminary Raman and fluorescence images for model compounds with 4 μm resolution. We have extended this work to include a discussion of the lateral and vertical spatial resolution of the fiber-optic microprobe in a non-contact proximity-focused configuration.

scholarly journals Imaging Spectroscopy on Very Large Telescopes

1984 ◽  
Vol 79 ◽  
pp. 515-517
Author(s):  
Paul Atherton
Keyword(s):  
Fourier Transform ◽  
Spatial Information ◽  
Broad Band ◽  
Imaging Spectroscopy ◽  
Wide Field ◽  
Two Dimensional ◽  
Imaging Spectrometer ◽  
Resolution Element ◽  
Fabry Perot ◽  
Large Telescopes

Imaging Spectroscopy is a technique in which a spectrum is obtained for each spatial resolution element across a wide field. The data is essentially 3-D, and may be viewed as a series of monochromatic images, or as a two dimensional array of spectra. A device generating such data may be called an imaging spectrometer. In a previous paper (Atherton, 1983 SPIE 445, 535) three different imaging spectrometers - based on grating, Fabry-Perot and Fourier Transform devices - were compared in terms of their ability to obtain spectral and spatial information over a wide field and broad band, to the same spectral resolution and S/N ratio, using the same detector array. From such a study it is clear that interferometer based devices are significantly faster than conventional grating spectrographs.

Imaging Spectroscopy and the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)

1998 ◽  
Vol 65 (3) ◽  
pp. 227-248 ◽  
Author(s):  
Robert O Green ◽  
Michael L Eastwood ◽  
Charles M Sarture ◽  
Thomas G Chrien ◽  
Mikael Aronsson ◽  
...  
Keyword(s):  
Infrared Imaging ◽  
Imaging Spectroscopy ◽  
Imaging Spectrometer

scholarly journals Imaging spectroscopy as a quantative tool for the retrieval of biogeophysical parameters

2003 ◽  
Vol 58 (2) ◽  
pp. 120-130 ◽  
Author(s):  
M. Schaepman ◽  
K. I. Itten ◽  
M. Rast
Keyword(s):  
Scientific Community ◽  
Global Climate ◽  
Imaging Spectroscopy ◽  
Climate Modelling ◽  
National Scale ◽  
Imaging Spectrometer ◽  
New Instrumentation ◽  
Global Climate Modelling ◽  
Key Variables ◽  
Airborne Imaging

Abstract. Representing the dynamic character of Vegetation in global climate modelling is a challenging task. We present a new Instrumentation approach in the form of APEX, an airborne imaging spectrometer to address the key variables and processes relevant for monitoring the biogeophysical and biochemical parameters at the local, regional and national scale. We are able to demonstrate that a large number of relevant processes and variables have been monitored successfully using imaging spectrometers. In particular, the accuracy of the variable retrieval using this observational approach has much improved and the quantification of the interaction of the radiation field with Vegetation has been made possible. The airborne instrument APEX will be made available to the scientific Community in early 2005, whereas it's space successor SPECTRA is scheduled for launch in 2008. The inclusion of the spectro-directional and thermal components will contribute toward minimizing retrieval uncertainties. Until these instruments are introduced into the market, there is enough time to develop the necessary products and to inform the scientific Community about the new possibilities.

scholarly journals A Comparison of Feature-Based MLR and PLS Regression Techniques for the Prediction of Three Soil Constituents in a Degraded South African Ecosystem

2012 ◽  
Vol 2012 ◽  
pp. 1-20 ◽  
Author(s):  
Anita Bayer ◽  
Martin Bachmann ◽  
Andreas Müller ◽  
Hermann Kaufmann
Keyword(s):  
Reference Data ◽  
Imaging Spectroscopy ◽  
Clay Content ◽  
Absorption Feature ◽  
Least Squares Regression ◽  
Soil Constituent ◽  
Feature Based ◽  
Regression Techniques ◽  
Soil Constituents ◽  
Land Changes

The accurate assessment of selected soil constituents can provide valuable indicators to identify and monitor land changes coupled with degradation which are frequent phenomena in semiarid regions. Two approaches for the quantification of soil organic carbon, iron oxides, and clay content based on field and laboratory spectroscopy of natural surfaces are tested. (1) A physical approach which is based on spectral absorption feature analysis is applied. For every soil constituent, a set of diagnostic spectral features is selected and linked with chemical reference data by multiple linear regression (MLR) techniques. (2) Partial least squares regression (PLS) as an exclusively statistical multivariate method is applied for comparison. Regression models are developed based on extensive ground reference data of 163 sampled sites collected in the Thicket Biome, South Africa, where land changes are observed due to intensive overgrazing. The approaches are assessed upon their prediction performance and significance in regard to a future quantification of soil constituents over large areas using imaging spectroscopy.

Synthesis and Characterization of Mixed-Halide Inorganic-Organic Hybrid CH3NH3PbBr2.5Cl0.5 Perovskite for Photodetector Application

2021 ◽  
Vol 16 (5) ◽  
pp. 707-714
Author(s):  
Yan Chen ◽  
Siwen Tao ◽  
Yaqi Liu ◽  
Xuewei Fu ◽  
Mengyi Pei ◽  
...  
Keyword(s):  
Light Intensity ◽  
Visible Light ◽  
Single Crystal ◽  
Bias Voltage ◽  
Metal Ion ◽  
Low Cost ◽  
Visible Region ◽  
High Sensitivity ◽  
Photocurrent Density ◽  
Organic Hybrid

Inorganic-organic hybrid perovskite (ABX3, A = organic cation, B = metal ion, X = halogen anion) combines the advantages of inorganic and organic materials. However, the properties and performance of mixed-halide CH3NH3PbBr2.5Cl0.5 (MAPbBr2.5Cl0.5) are still poorly understood. In this study, we synthetized MAPbBr2.5Cl0.5 single crystal and studied its structure, optical, thermal stability properties and optoelectronics applications for photodetector device. Compared with those of MAPbCl3, the interplanar distance of (100) crystal plane for MAPbBr2.5Cl0.5 becomes larger and the absorption spectrum of MAPbBr2.5Cl0.5 is extended to the visible region. The band gap of the MAPbBr2.5Cl0.5 single crystal is 2.28 eV. We find the device based on MAPbBr2.5Cl0.5 has high selectivity from 369 to 564 nm. The maximum ▴J (Jon– Joff) under 3.0 V bias voltage is about 1.2 µAcmr-2 at 454 nm visible light with 1 W mr-2 light intensity (1/1000 of the standard sunlight intensity), which proves the device has a high sensitivity. The linear relationship is established between the value of ▴J and light intensity and bias voltage. The fast current intensity transients (Fit) shows that the disappearance period of photocurrent density is 0.3 ms, which indicates the device is rapidly responsive photodetector. The highest value (1.7%) of external quantum efficiency (EQE) and the highest value of detectivities (D) both appear at 480 nm visible light at 4.0 V bias voltage when the irradiation power is 30 W m-2. Therefore, this simple and low-cost photoresponsive device is promising for industrial production of photodetector and photocatalysts device in the future.

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