THE WHOLE NINE MICROMETERS: CLASSIFICATION OF MINERAI,IZED ZONES IN AURORA AND BODIE MINING DISTRICTS, NEVADA AND CALIFORNIA WITH SWIR AND THERMAL IR AIRBORNE HYPERSPECTRAL DATA

摘要

The Aurora and Bodie mining districts are located in Bodie Hills, north of Mono Lake, onrnopposite sides of the Nevada-California state line. From the standpoint of economic geology,rnboth deposits are structurally controlled, low-sulfidation, adularia-sericite precious metal veinrndeposits with an extensive alteration halo. The area has been exploited since late 1870's byrnboth underground and minor open pit operations (Aurora), exposing portions of alteredrnandesites, devitrified rhyolites and quartz-adularia-sericite veins. Much of the geologicrnmapping and explanation was ad-hoc and primarily in support of the mining operations,rnwithout particular interest paid to the system as a whole. The University of Nevada Reno hasrnacquired both High and Low Altitude AVIRIS data of the region, as well as MASTER andrnSEBASS (Spatially Enhanced Broadband Area-array Spectrograph System) thermal infraredrndata. The coverage was targeted on the main vein system in Aurora (Prospectus andrnHumboldt Vein), East Brawley Peak prospect (midpoint between Aurora and Bodie) andrn"Bonanza Zone" (Bodie Bluff and Standard Hill) in Bodie, where the hydrothermai alterationrnzones appear to be the most pervasive. The ground-observations and mining/prospectingrnreports suggest propylitic alteration throughout the Bodie Hills, argillic and potassic alterationrnin Aurora and Bodie, (Iow-sulfidation system) and alunitic alteration (high-sulfidation system)rnon East Brawley Peak. The airborne data allows identification of exposed quartz veins andrnassociated alteration zones containing dominant kaolinite, sericite (Aurora), alunitern(E.Brawley Peak) and Na and Ca-montmorillonite (Bodie) which have been verified withrnSWIR and FTIR spectrometers as well as XRD analysis on field collected samples.