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Assessing hydrothermal alteration intensity in volcanic-hosted massive sulfide systems using portable x-ray fluorescence analysis of drill core: An example from myra falls, Canada

McNulty, B, Fox, N and Gemmell, JB ORCID: 0000-0002-1636-6723 2020 , 'Assessing hydrothermal alteration intensity in volcanic-hosted massive sulfide systems using portable x-ray fluorescence analysis of drill core: An example from myra falls, Canada' , Economic Geology, vol. 115, no. 2 , pp. 443-453 , doi: 10.5382/ECONGEO.4714.

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Abstract

Current portable X-ray fluorescence (pXRF) technology can rapidly and inexpensively yield concentrations of geologically significant elements, typically with instrument detection limits below several tens of parts per million. Based on conventional XRF whole-rock geochemical data, both the Ishikawa alteration index and the chlorite-carbonate-pyrite index increase with proximity to sulfide mineralization at Myra Falls. However, available pXRF technology is typically unable to detect all the elements required to calculate these alteration indices. As a result, there is a need to utilize the elements that are readily detectable using pXRF and apply these to hydrothermal alteration assessment.We propose that Rb/Sr ratios provide a robust proxy for the Ishikawa alteration index and demonstrate that conventional whole-rock XRF analytical results for Rb and Sr can be reproduced using pXRF analysis from drill core surfaces. At Myra Falls, the Rb/Sr ratios vary from 2.0 for intensely altered rocks. Downhole profiles of alteration intensity generated from systematic pXRF analysis of drill core surfaces can be used to inform drilling and targeting decisions. The application of the Rb/Sr ratio as a proxy for alteration intensity extends beyond this case study and can be applied to other hydrothermal systems that produce phyllosilicate minerals as alteration products of feldspar.

Item Type: Article
Authors/Creators:McNulty, B and Fox, N and Gemmell, JB
Keywords: British Columbia, exploration, lithogeochemistry, deposits, rocks, spectrometer
Journal or Publication Title: Economic Geology
Publisher: Economic Geology Publ Co
ISSN: 0361-0128
DOI / ID Number: 10.5382/ECONGEO.4714
Copyright Information:

©2020 Society of Economic Geologists, Inc

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