Identification of quartz and carbonate minerals across northern Nevada using ASTER thermal infrared emissivity data—Implications for geologic mapping and mineral resource investigations in well-studied and frontier areas

Abstract

ASTER (Advanced Spaceborne ThermalEmission and Refl ection Radiometer) thermal infrared imagery over a 389 km × 387 km area in northern Nevada (38.5°-42°N, 114°-118.5°W) was analyzed to evaluate its capability for accurate and cost-effective identifi cation and mapping of quartz and carbonate minerals at regional to local scales. The geology of this area has been mapped at a wide range of scales and includes a diversity of rock types and unconsolidated surficial materials, many of which are composed primarily of quartz and carbonate minerals. This area is also endowed with a wide variety of economically and scientifi cally important ore deposit types that contain an array of commodities (Au, Ag, Pb, Zn, Cu, Mo, W, Sn, Be, F, Mn, Fe, Sb, Hg, and barite). The hydrothermal systems that generated these deposits frequently deposited large amounts of quartz where fl uids cool, and generally smaller amounts of calcite or dolomite by other mechanisms.To identify and map quartz and carbonate minerals, band ratioing techniques were developed based on the shapes of laboratory reference spectra and applied to ASTER Level 2 surface emissivity products of 108 overlapping scenes. These mineral maps were mosaicked into a single coverage that was overlain with published, vector-format geologic maps of various scales to determine which geologic terranes, formations, and geomorphic features correspond to identifi ed quartz or carbonate. Where quartz or carbonate minerals were mapped in rocks composed primarily of other minerals, they were inferred to be hydrothermal in origin and compared to known occurrences of hydrothermal alteration and mineralization.The ASTER-based quartz mapping identifi ed thick sequences of quartzite, bedded radiolarian chert, quartz sandstone, conglomerates with clasts of quartzite and chert, silicic and/or altered rhyolites, and silicic welded tuffs. Alluvial fan surfaces, sand dunes, and beach deposits composed of quartz and/or carbonate are prominent, well-mapped features. Quartz was also identifi ed in smaller bodies of jasperoid, quartzalunite, and quartz-sericite-pyrite alteration, hot spring silica sinter terraces, and several diatomite and perlite mines and prospects. The ASTER-based carbonate mapping identifi ed thick sequences of dolomite, limestone, and marble, as well as small hot spring travertine deposits. Eolian carbonate was identifi ed in several playas. Dolomite exhibited a stronger carbonate response than calcite, as predicted based on their thermal spectral characteristics. Quartz was detected at lower concentrations than carbonates because of the greater strength of the quartz reststrahlen features in the thermal infrared compared to the bending-related spectral features of carbonates. The 90 m ground pixel size of the ASTER thermal imagery prevents the identifi cation of small-scale features. Despite this limitation, numerous bodies of hydrothermal quartz were detected in or near known Carlin-type gold deposits, distal disseminated Au-Ag deposits, high-and low-sulfi dation epithermal ...

Effect of Grain Size and Mineral Mixing on Carbonate Absorption Features in the SWIR and TIR Wavelength Regions

“…Besides the interest in oil and gas reservoir characterization, there is an interest in looking into calcite-dolomite mineralogy from an 'ore geology' perspective, as carbonates are important pathfinder and alteration minerals associated with calcic skarn deposits, low sulphidation epithermal deposits and porphyry Cu deposits [11,12]. In addition, coral reefs are under worldwide decline as a result of climate change [13].…”

Integration of Palsar and Aster Satellite Data for Geological Mapping in Tropics

“…Quartz shows absorption features in bands 10 and 12 of ASTER, and has high emissivity in band 14. The common carbonate minerals such as calcite and dolomite have an absorption feature at band 14 and high emissivity at band 13 of ASTER (Rockwell and Hofstra, 2008). The QI, CI and MI indices have been employed to the ASTER level 1B and 2B04 aim at the detection of quartz-rich and carbonate-rich rocks.…”

A Hyperspectral Thermal Infrared Imaging Instrument for Natural Resources Applications

“…The similarity between the emissivity spectra obtained by the Hyper-Cam and reference spectra (Bruker Vertex 70 and JHU spectral library) appears close enough for mapping such minerals from airborne hyperspectral (or spaceborne multispectral) TIR measurements (such as ASTER Level 2 surface emissivity products) based on the shapes of the laboratory reference spectra, for instance using respective band ratio techniques [28].…”