GeOCHemISTea

In this episode of GeOCHemISTea, Sam talks with Mike Stock, Professor at Trinity College Dublin, about magma systems from eruption to emplacement. Drawing on work in the Galápagos and Ireland, Mike explores how the same geochemical and petrological processes govern both volcanic activity and ore formation.The conversation focuses on breaking down silos between volcanology and economic geology—highlighting shared tools, concepts, and models that are often studied in isolation. The episode closes with a discussion on batholiths and crustal-scale magma systems, offering a fresh perspective on how modern volcanology can inform interpretations of ancient intrusions and mineralized systems, making it relevant for volcanologists and economic geologists alike.For this episode we read:Integrated Petrological and Geophysical Constraints on Magma System Architecture in the Western Galápagos Archipelago: Insights From Wolf Volcano (Stock et al., 2018)Late-stage volatile saturation as a potential trigger for explosive volcanic eruptions (Stock et al., 2016)Cryptic evolved melts beneath monotonous basaltic shield volcanoes in the Galápagos Archipelago (Stock et al., 2020)

This month on GeOCHemISTea, Sam sits down with Scott Halley to talk about extracting meaningful mineralogy from standard four-acid assay data. Scott walks through how the classic MINSQ approach evolved into modern linear-programming methods that handle solid solutions, honor thermodynamics, and produce fast, first-pass mineralogy models.They also dig into ambiguity in geologic interpretation, “cognitive entrenchment” in porphyry systems, and how linking calculated mineralogy to rock physics is helping bridge the gap between geochemistry and geophysics.For this episode we read: MINSQ - a least squares spreadsheet method for calculating mineral proportions from whole rock major element analyses (Herrmann and Berry, 2002)

Alecos Demetriades, applied geochemist and Chair of the IUGS Commission on Global Geochemical Baselines (2024–2028), joins GeOCHemISTea to unpack the Global Geochemical Reference Network (GGRN): why a 160×160 km grid matters, how harmonized sampling/analysis underpins trustworthy baselines, and what QA/QC must look like before interpretation. We touch on FOREGS, leveling national datasets to global references, and practical ways exploration and mining teams can access, use, and contribute to these datasets. Plus: tea stories during Tea Time and why passing knowledge to the next generation keeps this global effort moving. For this episode we read: ⁠International Union of Geological Sciences Manual of Standard Methods for Establishing the Global Geochemical Reference Network⁠  

This month on GeOCHemISTea, we welcome back Simon Griffiths, Principal Consultant at Third Planet Exploration Services, to unpack the geochemical exploration strategies for low-sulfidation epithermal systems. From vein textures to vanadium-rich roscoelite halos, Simon walks us through practical strategies for geochemical targeting and alteration mapping. He shares insights into sampling, spectral workflows, and how roscoelite at Porgera became one of the most reliable vectors to high-grade gold. Plus a wild tale about how an ICP machine was used to crack down on gold theft in the mine lab. For this episode we read:Geology of the Porgera Gold Deposit, Papua New Guinea (Hay et al., 2020) 

In this episode of GeOCHemISTea, we're joined by Hugh De Souza to explore the evolution of gold analysis; from 4,000-year-old fire assay traditions to disruptive technologies like photon assay. With over 40 years at research and industry analytical labs and deep experience in mineralogy, geochemistry, and lab innovation, Hugh shares his unconventional path into analytical geochemistry, breaks down the physics behind modern methods, and reflects on what the future holds for gold assay. Whether you're a field geo or into analytical chemistry, this one's for you.