Mapping Advanced Argillic Alteration at Cuprite, Nevada, Using Imaging Spectroscopy

Abstract

Mineral maps based on Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data were used to study late Miocene advanced argillic alteration at Cuprite, Nevada. Distributions of Fe-bearing minerals, clays, micas, sulfates, and carbonates were mapped using the Tetracorder spectral-shape matching system. The Al-content of white micas increases toward altered areas and near intrusive rocks. Alunite composition varies from pure K to intimate mixtures of Na-K endmembers with subpixel occurrences of huangite, the Ca-analogue of alunite. Intimately mixed Na-K alunite marks areas of relatively lower alteration temperature, whereas co-occurring Na-alunite and dickite may delineate relict hydrothermal conduits. The presence of dickite, halloysite, and well-ordered kaolinite but absence of disordered kaolinite is consistent with acidic conditions during hydrothermal alteration. Partial lichen cover on opal spectrally mimics chalcedony, limiting its detection to lichen-free areas. Pods of buddingtonite are remnants of initial quartz-adularia-smectite alteration. Thus, spectral maps provide a synoptic view of the surface mineralogy, and define a previously unrecognized early steam-heated hydrothermal event. Faulting and episodes of hydrothermal alteration at Cuprite were intimately linked to upper plate movements above the Silver Peak-Lone Mountain detachment and growth, collapse, and resurgence of the nearby Stonewall Mountain volcanic complex between 8 and 5 Ma. Isotopic dating indicates that hydrothermal activity started at least by 7.61 Ma and ended by about 6.2 Ma. Spectral and stable isotope data suggests that Cuprite is a late Miocene lowsulfidation adulariasericite type hot spring deposit overprinted by late-stage steam-heated advanced argillic alteration formed along the margin of the Stonewall Mountain caldera.

Geological Mapping by Combining Spectral Unmixing and Cluster Analysis for Hyperspectral Data

“…As a result of spectral unmixing by using these four representative mineral endmembers, high abundance spots of hydrothermally altered minerals were identified, as shown in Figure 4. The mineral distributions shown on these images corresponded well with the existing clay mineral maps (Swayze et al, 2014).…”

“…The study area is located in Cuprite in western Nevada, U.S.A. Cuprite is one of the most popular sites for testing the performance of new sensors and spectral mapping methods in geologic remote sensing studies (e.g., Abrams et al, 1977;Ashley and Abrams, 1980;Swayze et al, 2014). In this area, the Tertiary volcanic rocks were hydrothermally altered in the Midto Late-Miocene epoch.…”

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

“…There is a wealth of publications describing methods and applications of different sensors and datasets (e.g., [3][4][5][6][7][8]) for remote sensing mineral exploration. Expert knowledge is often required to get reliable results if the target is rather small [9,10].…”

Hyperspectral Transformation From Eo-1 Ali Imagery Using Pseudo-Hyperspectral Image Synthesis Algorithm

“…With an extremely arid climate condition, the Cuprite site is barren and sparsely vegetated land, which is suitable for remote sensing-based mineral mapping. Cuprite served as the test site of many remote sensing instruments including airborne and orbital visible, near-infrared, thermal-infrared, and hyperspectral sensors (Swayze et al, 2014). To further evaluate PHISA, we selected the AVIRIS image as a ground truth data collected on July 12, 2002 for mineral mapping.…”