Characterization of Mineralogy in the Highland Valley Porphyry Cu District Using Hyperspectral Imaging, and Potential Applications

Philip Lypaczewski,Benoit Rivard,Robert G Lee,Kevin Byrne,Guillaume Lesage,Michael D’Angelo

doi:10.3390/min10050473

Abstract

The Highland Valley Copper (HVC) district in British Columbia, Canada, is host to at least four major porphyry Cu systems: Bethlehem (~209 Ma), and Valley, Lornex, and Highmont (~208 to 207 Ma). High spatial resolution (0.2–1.0 mm/pixel) hyperspectral imagery in the shortwave infrared (SWIR) were acquired on 755 rock samples and 400 m of continuous drill core. Spectral metrics are used to measure the relative abundance of 12 minerals and an additional metric is derived to estimate white mica grain size. In the Valley and Lornex deposits, coarse-grained white mica is associated with mineralization and is detectable up to 4 km away from the deposits. Kaolinite is present within 2 km of the mineralized centers but does not necessarily occur within strongly mineralized intervals. Prehnite is ubiquitous from 4 to 8 km from the deposits. In the Bethlehem deposit, tourmaline and epidote are associated with mineralization. We propose a spectral alteration score based on these proximal hyperspectral SWIR mineralogical patterns to assist explorers in targeting porphyry Cu systems when using drill core, surface rock samples and potentially remote sensing imagery. In a production environment, this metric could serve to facilitate ore-sorting.

Highlights

Numerous mineral deposits are formed by hydrothermal fluids that, in addition to potentially concentrating metallic elements, produce an extensive alteration halo in the surrounding host rocks [1]
Other minerals identified in a few samples include malachite, carbonates, and biotite. These minerals are difficult to detect in the shortwave infrared (SWIR) in the current sample suite, either due to low modal abundances, spectral mixing, low signal-to-noise ratios due to the dark nature of the minerals, or most likely a combination of these factors
The apparent 2200 nm absorption position may mica chemistry, but at Highland Valley Copper (HVC) would mostly reflect the amount of interfering kaolinite, as shown in reflect white mica chemistry, but at HVC would mostly reflect the amount of interfering kaolinite, as an absorption near 2207 nm, while distal samples present an average absorption

Summary

Introduction

Numerous mineral deposits are formed by hydrothermal fluids that, in addition to potentially concentrating metallic elements, produce an extensive alteration halo in the surrounding host rocks [1]. While a large portion of interfering kaolinite was masked from amounts of kaolinite significantly influence the position of the 2200 nm absorption (by 5 nm) In the this secondary feature, at larger distances, in the vein halo, it appears that trace amounts of kaolinite detailed spectra shown, a slight inflection occurs near 2160 nm in spectrum 2 (visible in significantly influence the position of the 2200 nm absorption (by 5 nm). In the detailed spectra shown the second derivative) and is essentially undetectable on single image pixels (the presented spectra, a slight inflection occurs near 2160 nm in spectrum 2 (visible in the second derivative) are always 3 × 3 averages). (d) Image presented in a), with masking of the pixels showing the presence of an absorption near 2160 nm. The apparent 2200 nm absorption position may mica chemistry, but at HVC would mostly reflect the amount of interfering kaolinite, as shown in reflect white mica chemistry, but at HVC would mostly reflect the amount of interfering kaolinite, as an absorption near 2207 nm, while distal samples (with no kaolinite) present an average absorption

Methods

Results

Discussion

Conclusion