Remote mineralogic and lithologic mapping of the Ice River alkaline complex, British Columbia, Canada, using AVIRIS data

Abstract

These complexes are interesting because of their rare petro~h~ ~i~~~ ~lk~li~~ complex is a late paleozoic intrusion logic associations and their economic value as hosts to rareof mafic alkaline rocks, syenite, and carbonatite exposed in earth (REEs) and Other sou theastern British Columbia, Canada. The complex in- associated with carbonatites. trudes Cambrian and Ordovician shales, slates, and limeThis report focuses on the northwesterly extension of the stones of the Chancellor and Ottertail Formations and the and the adjacent west the Ice River McKay Group. We examined the alkaline complex and adja- Eagle Ridge Figures and 2). We describe an a~~licacent country rocks using Airborne Visible-Infrared Imaging tion of imaging spectrometry to mineralogic and lithologic Spectrometer (AVIRIS) data. The data were first calibrated to using Airborne Imaging I relative reflectance and then used to spectrally map mineral- (AVTRIS) data acquired On 22 August lggO1 from a NASA ER-2 ogies in the study area by using a linear spectral unmixing aircraft flying about 18,200 above mean ground elevation. program. This technique models each pixel spectrum in an The A-s instrument collects radiance data in 224 AVIRIS image as a linear combination of unique endmember in the portion the spectrum spectra. We selected endmember spectra from well-exposed 0.4 to 2.5 pm (Vane et ~l.9 lgg3). Each Awus image segment and spectrally distinct mineralogic units, vegetation, and depicts an area of about 10 krn by 8 km and has a ground snow. Four of the endmembers reflect mineralogic variations (pixel) resolution 16 to 20 m. within the McKay group in the study area, and may repre- Laboratory visible-inhared (0.4 to 2.5 pm) reflectance sent lateral and vertical variations of sedimentary or meta- spectra of both weathered and surfaces Of field samples morphic facies. Otherwise, the resultant spatial distribution Were recorded On a Instruments of endmembers shows generally close agreement with the UV5240 spectrophotometer equipped with an integrating published geologic map, although, in several places, our imThe were corrected for measurement