Brian McNulty completed his PhD research on the lithological setting and geochronology of the West Block area at the Myra Falls VHMS district on Vancouver Island, Canada, during 2019. Brian’s research has advanced the overall understanding of the H-W member stratigraphy, the nature of hydrothermal alteration, and the temporal relationship of felsic host rocks at Myra Falls. These advancements have implications for the geology and genesis of the Myra Falls district VHMS deposits, as well as for mineral exploration within the Myra Falls district and throughout Vancouver Island.

In 2019 Brian submitted a paper to Economic Geology, co-authored with Dr Nathan Fox and Professor Bruce Gemmell, entitled ‘Assessing hydrothermal alteration intensity in VHMS systems using pXRF analysis of drill core: An example from Myra Falls, Canada’. Current portable X-ray fluorescence (pXRF) technology can rapidly and inexpensively yield concentrations of geologically significant elements, typically with instrument detection limits below several 10’s of ppm. Based on conventional XRF whole-rock geochemical data, both the Ishikawa Alteration Index and the Chlorite-Carbonate-Pyrite Index increase with proximity to sulfide mineralisation at Myra Falls. However, available pXRF technology is typically unable to detect all of the elements required to calculate these alteration indices. As a result, there is a need to utilise the elements that are readily detectable using pXRF and apply these to hydrothermal alteration assessment. Brian proposed 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 range from <0.1 for least altered rocks, 0.1 to 0.5 for weakly altered rocks, 0.5 to 1.0 for moderately altered rocks, 1.0 to 2.0 for strongly altered rocks and >2.0 for intensely altered rocks. Down-hole 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. This paper has been accepted and will be published in 2020.

Brian McNulty neared the completion of his PhD research on the lithological setting and geochronology of the West Block area at the Myra Falls VHMS district on Vancouver Island, Canada, during 2018. Brian’s research has advanced the overall understanding of the H-W member stratigraphy, the nature of hydrothermal alteration, and the temporal relationship of felsic host rocks at Myra Falls. These advancements have implications for the geology and genesis of the Myra Falls district VHMS deposits, as well as for mineral exploration within the Myra Falls district and throughout Vancouver Island.

In 2018 Brian published a paper, co-authored with Nathan Fox, Ron Berry and Bruce Gemmell, entitled ‘Lithological discrimination of altered volcanic rocks based on systematic portable X-ray fluorescence analysis of drill core at the Myra Falls VHMS deposit, Canada’ in the Journal of Geochemical Exploration. His results indicate that both pXRF sampling methods reproduce the laboratorybased XRF results for Ti and Zr, and that there is no significant improvement in accuracy or precision between drill core powders and unprepared drill core samples. He proposed a calibration, estimation of total measurement uncertainty, and data reduction procedure for systematic three-spot pXRF analysis of drill core samples to improve lithological logging of altered volcanic rock types. Brian suggested that pXRF analysis become a routine part of lithology logging providing, for some key elements, robust and time-efficient chemical analyses with results that can be used to define important, often cryptic, lithological boundaries, and that portable XRF has the ability to improve geological and stratigraphic interpretations, which are vital for developing mineral exploration models, for VHMS deposits and other economic mineral systems.

Brian McNulty continued his PhD research on the lithological setting and geochronology of the West Block area at the Myra Falls VHMS district on Vancouver Island, Canada. His research aims to propose a model for the genesis of the VHMS deposits in the West Block, which can be compared to the other deposits in the area, with the aim of developing useful criteria for exploration in the Myra Falls District.

In May, Brian gave a presentation on the application of systematic portable X-ray fluorescence analysis of drill core to identify the lithology of altered volcanic rocks at the annual CODES Science Planning Meeting in Hobart. He submitted a research grant annual report for his findings using a combination of LA-ICP-MS and CA-ID-TIMS zircon U-Pb geochronology to constrain the timing of volcanic host rock stratigraphy at Myra Falls to the SEG Canada Foundation in mid-2017. Additionally, he presented these results at the 14th SGA Biennial International Meeting in Québec City, Canada, in August.

Research in 2017 focussed on three themes: geochronology, hydrothermal alteration characterisation, and ore mineralogy. A combination of whole rock lithogeochemistry, electron microprobe analysis and shortwave infrared spectroscopy are being utilised to assess possible mineral exploration vectors in the variably altered footwall volcanic stratigraphy in the West Block. Detailed ore microscopy using Mineral Liberation Analysis and electron microprobe analyses are being used to characterise the mineralisation styles in the West Block area, which will be compared to other mineralised zones at Myra Falls. Thesis compilation has been ongoing, and the candidate is expected to complete in mid-2018.