Abstract

Short-wave infrared (SWIR) field and laboratory spectra were used to identify and characterize hydrothermal alteration mineral chemical variability in host rocks proximal to the Izok Lake Zn-Cu-Pb-Ag volcanogenic massive sulfide (VMS) deposit in Nunavut, Canada. The deposit is hosted within a sequence of predominantly felsic pyroclastic rocks of Archean age that are regionally metamorphosed to amphibolite facies. These rocks are characterized by the muscovite-biotite-sillimanite and chlorite-biotite-cordierite mineral suite. Proximal to the deposit, white micas are Al rich to potassic muscovite, and the biotite and chlorite are Mg rich. In areas that are immediately outboard of the proximal alteration zones, rocks are altered to Al-poor muscovite and intermediate to Fe-rich biotite and chlorite. Outboard of this, distal areas are characterized by potassic muscovite and Mg-rich biotite and chlorite. The white micas and biotite/chlorite group minerals display considerable variation in their Al-OH and Fe-OH absorption feature wavelength positions. The variations in muscovite and biotite/chlorite compositions (as determined by the Al-OH and Fe-OH absorption feature wavelength positions) broadly correlate with changes in hydrothermal alteration intensity, as measured by the Ishikawa and chlorite-carbonate-pyrite alteration indices. Our findings suggest that the large-scale alteration intensity trends of the Izok Lake study area can be elucidated using the spectral properties of the hydrothermal alteration minerals.

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