Mapping Surface Mineralogy Research Articles

MAPPING LITHOLOGICAL AND MINERALOGICAL UNITS USING HYPERSPECTRAL IMAGERY

 Hyperspectral images such as the Earth Observer-1 (EO-1) provides an efficient method of mapping surface mineralogy because it can measures the energy in narrower bands compared with multispectral sensors. The Kirkuk anticline northern Iraq is one of the most petroleum-rich provinces. It is characterized, that is an asymmetrical, cylindrical anticline, with a fold axis trend towards North West- East, South East. The study’s primary goal is to apply satellite processing and techniques on the Eo-1 imagery for identifying lithological and mineral units at a part of Kirkuk anticline northern Iraq. The EO-1 image was corrected at the beginning of atmospheric impacts using the FLAASH module in ENVI software. Processing of (Minimum Noise Fraction- MNF) processing was applied and then it reduced the dimensionality of data, as well as, the processing of (PPI) pixel purity index was applied to spatial reduction. This study tested the potential of (spectral angle mapper supervised classification-SAM) classification for mapping the lithological and mineral units using the Hyperion imagery. three different sources of endmembers or spectra are used for SAM classifications. The one:  is done by Analytical Spectral Devices (ASD) Spectrometer. The second: reference spectra have been taken from the spectral library of USGS. Third: extracting endmembers from the purest pixels of the hyperion image, which was done by applying (MNF and PPI). The endmembers were provided, generated as the training area for SAM classification.  The present results demonstrated the great potential of data used to map the distribution of alteration of minerals and lithological units in a part of Kirkuk anticline. The classified Hyperion image shows that Jarosite and illite are the most dominant altered minerals, as well as, the main lithological units of the upper member of Fatha formation are revealed in the core of the Kirkuk anticline with scattered and small outcrops towards the flanks.

Estimation of surface temperatures on Mercury in preparation of the MERTIS experiment onboard BepiColombo

The Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) is part of the payload on the joint ESA-JAXA BepiColombo Mission, launched in October 2018. The spectrometer is designed to map surface composition, identify rock-forming minerals, map surface mineralogy, and study surface temperature variations. The surface of Mercury undergoes large temperature variations depending on solar irradiation. Mineral spectra show significant changes in spectral features with changing temperature. In preparation of the experiment, we developed a thermal model that calculates surface temperatures based on appropriate insolation conditions and thermo-physical properties. This model has been validated with lunar parameters and hence been applied to the conditions of Mercury. Here we present surface temperature maps based on MESSENGER albedo and topography data. The results have been compared to previous models and measurements of Mercury's surface temperatures.The surface of Mercury undergoes large temperature variations each diurnal period. At the equator temperatures vary between less than 100 K during the night up to 700 K at local noon at longitudes 0° W and 180° W, and up to 570 K at longitudes 90° W and 270° W. Due to the 3:2 spin orbit resonance local noon at longitudes 0° W and 180° W coincide with perihelion, while longitudes 90° W and 270° W experience local noon at aphelion, which results in “hot” and “warm” poles around the equator. At 45° N surface temperatures at local noon reach 645 K (0° W and 180° W) and 510 K (90° W and 270° W).

Exposed soil and mineral map of the Australian continent revealing the land at its barest

Multi-spectral remote sensing has already played an important role in mapping surface mineralogy. However, vegetation – even when relatively sparse – either covers the underlying substrate or modifies its spectral response, making it difficult to resolve diagnostic mineral spectral features. Here we take advantage of the petabyte-scale Landsat datasets covering the same areas for periods exceeding 30 years combined with a novel high-dimensional statistical technique to extract a noise-reduced, cloud-free, and robust estimate of the spectral response of the barest state (i.e. least vegetated) across the whole continent of Australia at 25 m2 resolution. Importantly, our method preserves the spectral relationships between different wavelengths of the spectra. This means that our freely available continental-scale product can be combined with machine learning for enhanced geological mapping, mineral exploration, digital soil mapping, and establishing environmental baselines for understanding and responding to food security, climate change, environmental degradation, water scarcity, and threatened biodiversity.

Estimation of lunar surface temperatures and thermophysical properties: test of a thermal model in preparation of the MERTIS experiment onboard BepiColombo

The Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) is part of the payload on the joint ESA-JAXA BepiColombo Mission, scheduled for launch in 2016. The spectrometer is designed to map surface compositions, to identify rock-forming minerals, to map surface mineralogy, and to study surface temperature variations. In preparation of the experiment we developed a thermal model that calculates surface temperatures based on appropriate insolation conditions and thermophysical properties. In the absence of thermal measurements on Mercury, we validate the model with lunar parameters. The results show good agreement with Apollo 17, Clementine and LRO-Diviner data. With appropriate changes of the orbital parameters and ephemeris data this model can be applied to the conditions of Mercury.

Imaging spectroscopy of jarosite cement in the Jurassic Navajo Sandstone

Imaging spectroscopy is a powerful tool for mapping surface mineralogy. Interactions of energy and surface materials on atomic and molecular levels result in specific absorption features that are diagnostic of mineralogy. Hyperspectral airborne sensors such as HyMap have sufficient spectral resolution to identify subtle features over narrow wavelength ranges. An anomalous zone of jarosite cement within the Jurassic Navajo Sandstone in southern Utah was identified with airborne hyperspectral data. To date no other locations of sulfate-rich cements such as this have been documented in the Navajo Sandstone. Here, we use multiple spectral analysis techniques over a micro to macro spatial continuum in order to focus our evaluation on the distribution and relative abundance of jarosite in this area. In this study, imaging spectroscopy is used to help determine the extent of the distribution of jarosite [KFe3(SO4)2(OH)6], at “Mollie's Nipple” (MN), a significant geomorphic landmark located within the Grand Staircase-Escalante National Monument, in the Jurassic Navajo Sandstone of south central Utah. The extent of the jarosite across the butte is identified in this study by mapping two diagnostic absorption features, referred to as the ∼2.26μm and near-infrared ferric iron absorption features (∼0.70–1.15μm), independently. This analysis shows that there is a single circular zone of abundant jarosite ∼1km in diameter that includes both in-situ and weathered out accumulations. Jarosite formation requires acidic and sulfate-rich fluids, which are unusual for the Navajo Sandstone. Imaging and field spectroscopy provides the spectral resolution needed to map and analyze the mineralogic characteristics of this area; characteristics that may help constrain the conditions under which this atypical butte formed.

Acid sulphate soil mapping with hyperspectral imagery at South Yunderup, Western Australia

One of Australia?s National Research Priorities for achieving an ?Environmentally Sustainable Australia? is tackling the problem of acid sulfate soils (ASS) which affect many of our most desirable lands for urban and agricultural development. Fitzpatrick et al. (1998) stated that currently ?There is no consistent standard for mapping their [sic ASS] extent or severity.? To help address this problem a national atlas on ASS has been established which has been incorporated into the ?Australian Soil Resource Information System? website. However, these current GIS map products are based on interpolation of isolated ground sample points and the interpretation of remote sensing data that is not optimum for detection of ASS related mineralogy. In addition, these map products, especially for the large area assessments such as the Murray-Darling Basin, are not suitable for monitoring purposes except for those (few) sites where ground data is being routinely collected. Hyperspectral sensing technologies from both aircraft and satellites have the potential to provide accurate mapping and monitoring of ASS through its ability to measure often subtle but diagnostic compositional information of surface materials (Clark & Roush, 1984; Clark et al., 1990a; 1990b). This includes the measurement of the abundances, compositions and crystallinity of the specific minerals, including those associated with ASS such as jarosite, goethite, hematite, kaolinite and gypsum. Typical ASS minerals include iron oxyhydroxides (goethite), oxyhydroxyl-sulphates (jarosite) and sulphates minerals (barite and gypsum) (Fanning et al., 2002). Fitzpatrick & Self (1997) found that minerals found in acid sulphate soil environments are similar to those analogous to acid mine drainage. These environments consisted of ferrihydrite, schwertmannite, goethite, lepidocrocite and jarosite. Although there have been a number of studies of the application of hyperspectral for mapping and monitoring acid conditions associated with mined environments (e.g. Swayze et al., 2000; Crowley et al., 2003 and Ong et al., 2003) there has been little work on its use for mapping acid sulphate soils (e.g. Lau et al., 2006) despite its potential value for large area (catchment-scale) mapping and monitoring of ASS. The main aim of this study is to assess whether airborne hyperspectral imagery can be a useful tool for mapping surface mineralogy potentially associated with ASS in coastal areas undergoing urban development. A collaborative project was established in 2007 between the Department of Environment and Conservation (DEC) and CSIRO to investigate the ability of the airborne hyperspectral imagery to help identify potential ?hot-spot? sites of ASS contamination in the South Yunderup area of the Peel region of WA.

Use of HyMap imaging spectrometer data to map mineralogy in the Rodalquilar caldera, southeast Spain

The Rodalquilar epithermal gold alunite deposit occurs within the Rodalquilar caldera complex, in the Cabo de Gata volcanic field, a semi‐arid region in southeast Spain. The epithermal mineralization is associated with an extensive east–west trending zone of hydrothermally altered rocks. The presence of several short‐wave infrared (SWIR) active minerals in the hydrothermal alteration assemblage makes an investigation of the spatial distribution of the hydrothermal alteration mineralogy using remote sensing imagery possible. Multiple Endmember Spectral Mixture Analysis (MESMA) was applied to analyse SWIR imaging spectrometer data recorded by the HyMap imaging system, in order to map surface mineralogy in the Rodalquilar caldera. A nine endmember set derived from the imagery was used. The MESMA was based on models of two up to five endmembers assessed in terms of fraction and root‐mean‐square‐error criteria. MESMA allowed identification of short‐wave infrared active surface mineralogy and resolved the mixed spectral response from the surface mineralogy and vegetation cover. Field spectral measurements were also used to verify the mineral maps. The results of this study have potential to refine the map of the hydrothermal alteration zones in the Rodalquilar caldera complex. The study demonstrates that MESMA is an effective unmixing technique in geological applications of imaging spectrometry in semi‐arid regions. Present address: Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, 1350 Copenhagen K, Denmark.

MESSENGER Mission Overview

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, launched on August 3, 2004, is nearing the halfway point on its voyage to become the first probe to orbit the planet Mercury. The mission, spacecraft, and payload are designed to answer six fundamental questions regarding the innermost planet: (1) What planetary formational processes led to Mercury’s high ratio of metal to silicate? (2) What is the geological history of Mercury? (3) What are the nature and origin of Mercury’s magnetic field? (4) What are the structure and state of Mercury’s core? (5) What are the radar-reflective materials at Mercury’s poles? (6) What are the important volatile species and their sources and sinks near Mercury? The mission has focused to date on commissioning the spacecraft and science payload as well as planning for flyby and orbital operations. The second Venus flyby (June 2007) will complete final rehearsals for the Mercury flyby operations in January and October 2008 and September 2009. Those flybys will provide opportunities to image the hemisphere of the planet not seen by Mariner 10, obtain high-resolution spectral observations with which to map surface mineralogy and assay the exosphere, and carry out an exploration of the magnetic field and energetic particle distribution in the near-Mercury environment. The orbital phase, beginning on March 18, 2011, is a one-year-long, near-polar-orbital observational campaign that will address all mission goals. The orbital phase will complete global imaging, yield detailed surface compositional and topographic data over the northern hemisphere, determine the geometry of Mercury’s internal magnetic field and magnetosphere, ascertain the radius and physical state of Mercury’s outer core, assess the nature of Mercury’s polar deposits, and inventory exospheric neutrals and magnetospheric charged particle species over a range of dynamic conditions. Answering the questions that have guided the MESSENGER mission will expand our understanding of the formation and evolution of the terrestrial planets as a family.

OARS - A New System for Mapping Surface Mineralogy Simultaneously with Airborne Geophysics

The Operational Airborne Research Spectrometer (OARS) is a novel hyperspectral profiling reflectance spectrometer developed by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and Fugro Airborne Surveys (FAS) to examine alternative means to collect and deliver exploration data, based on the principles of reflectance spectroscopy. OARS is a component of CSIRO's "Airborne Mineralogy" concept.OARS can be integrated with other airborne geophysical instruments that principally collect magnetic, gamma-ray spectrometry and digital elevation data, and can be flown simultaneously on exactly the same flight lines. OARS will measure ground reflectance spectra from contiguous 8-m pixels from an altitude of 80 m.After data processing, interpolated images of relative mineral abundance can be reconstructed using differential GPS (DGPS) positioning data to produce a variety of mineralogical maps.The OARS system consists of a downward and an upwardlooking spectrometer. Each spectrometer covers 190 spectral channels in the visible to short-wave infrared range, with an average spectral resolution of 12 nm. This wavelength range allows OARS to map most species of phyllosilicates, clays, sulphates, carbonates and iron oxides, that occur in alteration zones, regolith and host rocks. Green and dry vegetation can also be identified. A CCD camera (Charge Coupled Device – Silicon Array) allows monitoring of the flight path while flight attitude sensors and DGPS are used for geo-location.The instrument was first tested in late 1998. Subsequent test surveys in early 1999, over a more challenging geological area in NW Australia, verified its ability to deliver new mineralogical data and its capability as part of an integrated system incorporating magnetic and gamma-ray spectrometry surveying. The resulting case study shows that this line profiling spectrometer can deliver useful interpolated mineral maps with potential synergistic benefits from co-registered magnetic and gamma ray images.

Mapping surface mineralogy and scattering behavior using backscattered reflectance from a hyperspectral midinfrared airborne CO/sub 2/ laser system (MIRACO/sub 2/LAS)

Airborne, high-spectral resolution, thermal-infrared (TIR) MIRACO/sub 2/LAS reflectance data were evaluated for mapping surface mineralogy and scattering behavior for a variety of semi-arid, geological test sites in Australia. MIRACO/sub 2/LAS is a rapidly tuned, airborne CO/sub 2/ laser system that measures backscattered (bidirectional) reflectance at 100 wavelengths between 9.1 and 11.2 /spl mu/m for 2-m footprints in line profile mode. An operational methodology is described that permits reduction of the raw airborne signal-to-ground reflectance. This ground reflectance has two major properties, namely, wavelength-dependent mineralogical variations and reflection albedo variations related to surface roughness. Comparisons between the airborne MIRACO/sub 2/LAS spectra and laboratory directional hemispherical reflectance (DHR) spectra show the same spectral shapes, though differences in average reflectance (albedo) occur for some types of rocks. The minerals identified using MIRACO/sub 2/LAS include silicates (for example, quartz, microcline, plagiodase, almandine, spessartine, talc, tremolite, and kaolinite) and carbonates (dolomite and magnesite) as well as vegetation (dry and green). Many of the diagnostic spectral features that allow identification of these materials are narrow (<0.2 /spl mu/m), making them difficult to detect with broadband TIR systems, like the airborne TIMS and satelliteborne ASTER. Based on an empirical relationship between the minimum and maximum reflectance established using laboratory DHR spectra, a method is proposed that allows the use of MIRACO/sub 2/LAS data to identify surfaces that are characterized by Lambertian or specular scattering. The MIRACO/sub 2/LAS results show that Lambertian-type scatterers include soils and many types of isotropic rocks.

Imaging spectrometry for geological remote sensing

Without use of imaging spectrometry, imaging of the Earth's surface from aircraft and from spacecraft is hampered by the low spectral resolution and limited number of spectral bands, typically less than 10 bands of 100 to 200 nm width. Imaging spectrometry in remote sensing concerns the acquisition of image data in many narrow (< 40 nm wide) contiguous spectral bands with the ultimate goal of producing detailed spectral reflectance curves for each pixel in the image. Many minerals and rocks have unique spectral signatures with characteristic absorption features that are 20 to 40 nm wide. Imaging spectrometers allow to depict these narrow features and thus map surface mineralogy based on spectral image characterization. This paper gives a review of imaging spectrometry and addresses the following topics: airborne and spaceborne systems available, spectral and geometric data pre-processing, atmospheric correction, techniques for thematic data analysis, and applications in the field of geological remote sensing. In the final section a case study is described where imaging spectrometer data is used for mapping surface mineralogy in a hydrothermal alteration system, thus guiding gold exploration.

Moon: Near‐infrared spectral reflectance, A first good look

A positive identification of the minerals olivine, plagioclase, and several types of pyroxenes were made at several locations on the lunar surface by using remote measurements. For example, the crater Aristarchus is found to have an average pyroxene composition of augite, and plagioclase is obviously present. A dark mantle deposit in the crater J. Herschel is at least partly composed of a mixture of 70% olivine and 30% pyroxene. These determinations were possible because the reflectance spectra for 10–20 km diameter lunar areas have been measured for the first time in the IR spectral region (0.65–2.5 μm) with sufficient spectral resolution and photometric precision to define mineral electronic absorption bands. The reflectance for all lunar regions observed (over 100 to present) continues to increase toward longer wavelengths to at least 2.5 μm, and several mineral absorption bands appear. The telescopic spectra are of similar quality and contain features similar to laboratory spectra of lunar samples. The absorption features in several spectra have been quantitatively analyzed using newly developed computer processing techniques, including thermal flux removal and absorption band fitting, to produce these mineral identifications. Detection and quantitative analysis of these absorptions provide a much improved basis for remotely determining and mapping surface mineralogy quantitatively from the ground or using airborne or spacecraft platforms.