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.

This month on GeOCHemISTea, we are talking about one of exploration geochemistry’s most foundational, and rapidly evolving, methods: stream sediment sampling. Sam is joined by geochemical consultant and educator Mary Doherty, lead author of a 2023 review on stream sediment geochemistry, published in Geochemistry: Exploration, Environment, Analysis.

Mary shares a career’s worth of field, lab, and leadership experience, from carrying samples for her USGS geologist father as a child to building geochem training programs for Newmont and ALS, and recently teaching at the Colorado School of Mines. We talk about key developments in stream sediment methods, from fine fraction and BLEG to HMC and indicator mineral chemistry, as well as how to choose the right tool for the job.

The episode also covers the practicalities of QA/QC, field planning, and how geomorphology and hydrology shape interpretation. Mary emphasizes the importance of training, knowledge-sharing, and the growing integration of mineralogical data, and machine learning into modern workflows.

Whether you are designing your first drainage survey or revisiting legacy data, this episode is a reminder that good geochemistry begins with solid fundamentals and that the future of exploration is already here.

For this episode we read: Stream sediment geochemistry in mineral exploration: a review of fine-fraction, clay-fraction, bulk leach gold, heavy mineral concentrate and indicator mineral chemistry (Doherty et al., 2023)

In this episode of GeOCHemISTea, we're diving deep, literally, with Andy Campbell, oceanographer, geochemist, and former senior leader at the U.S. Nuclear Regulatory Commission.

Andy takes us back to his PhD days at Scripps Institution of Oceanography, where he conducted some of the earliest geochemical research on seafloor hydrothermal systems in the Guaymas Basin. His work on manganese cycling, water column anomalies, and hydrothermal plume modeling not only helped lay the foundation for modern vent geochemistry, it also offered early insight into how ore deposits might form in sediment-hosted marine environments.

But the real tea? Andy was part of the shakedown cruise for the Titanic dives... yes, that Titanic... on the iconic Alvin submersible. He shares first-hand stories about extreme ocean storms, lost samples, deep-sea discoveries, and how a science cruise turned into an unexpected government career path. From manganese-rich vent clouds to nuclear safety policy, this episode explores the many ways geochemists contribute far beyond the lab.

For this episode we read:

Water column anomalies associated with hydrothermal activity in the Guaymas Basin, Gulf of California (Campbell and Gieskes, 1984)

Manganese geochemistry in the Guaymas Basin, Gulf of California (Campbell et al., 1988)

In this episode of GeOCHemISTea, Sam sits down with geochemist and geothermal expert Stuart Simmons to discuss the unpredictable paths that shape a career in geoscience. From early work in epithermal gold systems to pioneering research in geothermal energy, Stuart shares how professional pivots, academic curiosity, and a chance encounter at a pub in New Zealand all influenced his decades-long contribution to both industry and research. The conversation also dives into the geochemistry of geothermal systems, the evolution of isotope studies, and the promise of enhanced geothermal systems (EGS). Whether you're early in your career or decades in, this episode is a reminder of the importance of staying open to unexpected opportunities... and the power of combining geoscience with real-world application.For this episode we read: Formation of a Large Cold Groundwater Mantle Helium Anomaly and High Temperature Geothermal Resources in Response to Bimodal Magmatism Near Roosevelt Hot Springs and Utah FORGE, Milford Valley, Southwest Utah (Simmons and Kirby, 2024)