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)

Join us this month on GeOCHemISTea as we sit down with Brittany Hupp, Assistant Professor at George Mason University in the Department of Atmospheric, Oceanic, and Earth Sciences. Brittany specializes in micropaleontology, sedimentology, and low-temperature geochemistry, exploring ancient climates and ocean conditions to better understand modern environmental challenges.

In this episode, Brittany shares her unconventional path into geosciences—from a dairy farm in rural Ohio to oceanic research cruises—and offers practical advice for aspiring geochemists seeking interdisciplinary careers. She introduces listeners to the Paleocene-Eocene Thermal Maximum (PETM), a pivotal ancient global warming event used as a critical analog to current climate change. Brittany explains how geochemical proxies, such as stable isotopes and trace elements in microfossils (foraminifera), illuminate past temperature shifts, ocean acidification, and hydrological changes.

Tune in for captivating stories from life at sea, including the social dynamics aboard research vessels, and discover how paleoclimatology provides valuable insights into Earth's climate sensitivity and future scenarios.

Grab your tea... it's time to spill!

For this episode we read:The Paleocene-Eocene Thermal Maximum: A Perturbation of Carbon Cycle, Climate, and Biosphere with Implications for the Future (McInerney and Wing, 2011)Diagenetic Attenuation of Carbon Isotope Excursion Recorded by Planktic Foraminifers During the Paleocene-Eocene Thermal Maximum (Kozdon et al., 2018)Development of a novel empirical framework for interpreting geological carbon isotope excursions, with implications for the rate of carbon injections across the PETM (Turner and Ridgwell, 2016)Individual foraminiferal analyses: a review of current and emerging geochemical techniques (Fehrenbacher et al., 2024)

This month GeOCHemISTea talks with Oscar Benavente, an environmental geochemist at SRK Consulting, about using satellite imagery to monitor mine drainage and environmental change. They dive into how Google Earth Engine, Python, and machine learning are transforming geochemical monitoring—mapping water bodies, tracking sulfide oxidation, and improving mine site remediation.

Oscar shares insights from his career spanning geothermal exploration, environmental geochemistry, and consulting. They also discuss the importance of fieldwork, communicating complex science effectively, and the surprising connections between planetary and mining geochemistry.

Tune in for a lively conversation filled with geochemistry, remote sensing, and some unexpected tangents—including volcanic adventures, music, and the tight-knit world of geochemists.

For this episode we read:

Monitoring of mine drainage related processes through satellite imagery - Dynamic Mapping of Sulfide Oxidation (Benavente, 2024)

Dynamic Mapping of Water Bodies using Google Earth Engine (Benavente, 2024)

Historical geochemical datasets can be challenging with variable methods, missing metadata, and shifting detection limits, but they’re also an invaluable resource for mineral exploration and mining.

In this episode, we break down what qualifies as historical data, common pitfalls to watch for, and best practices for integrating legacy datasets into interpretation workflows. We also explore the newest geochemical data from field-portable and scanning technologies, examining how they complement and contrast with traditional datasets.

For this episode we read:

Advances in ICP-MS technology and the application of multi-element geochemistry to exploration (Sader and Ryan, 2019)

Advances in exploration geochemistry, 2007 to 2017 and beyond (Winterburn et al., 2019)

Evaluation of partial digestions for soils to detect a deeply buried VMS Cu-Zn prospect in boreal forests (van Geffen et al., 2014)

Major advances in exploration geochemistry, 1998-2007 (Cohen et al., 2010)

In this episode we talk with Mark Arundell, Principal Geologist at IMEx Consulting, to delve into the past, present, and future of geochemical sampling. With over 30 years of international experience, Mark shares insights into avoiding suboptimal sampling, the importance of understanding regolith, and how smarter techniques can lead to better outcomes in mineral exploration. Whether you're new to geochemistry or a seasoned professional, this conversation is packed with practical advice and thought-provoking discussions on improving exploration geochemistry strategies.

For this episode we read:

Why 80 mesh? (Garrett, 2019)

Metallogeny and mineral exploration - some personal reminiscences (Sillitoe, 2024)

Seeing through alluvial gold - fine fraction stream sediment sampling in the Sofala Area, Central New South Wales (Arundell and Gatehouse, 2004)

In this episode of GeOCHemISTea we dive into the origins of orogenic gold deposits with Rich Goldfarb, exploring the science behind fluids, isotopes, and formation processes. From debunking magmatic theories to highlighting the facts of metamorphic origins, Rich shares the real tea (and quite a number of shenanigans) on how to make an orogenic gold deposit . Join us for a conversation that’s equal parts science and intrigue.

For this episode we read:

In this episode of GeOCHemISTea, host Sam Scher sits down with Steve Tambanis, Managing Director at STX Consulting and Director at RealTime Priority Limited, to explore the challenges and innovations in field-based geochemical analysis using portable XRF (pXRF) and laser-induced breakdown spectroscopy (LIBS). Steve shares his journey from traditional exploration geology to pioneering real-time assays, recounting how he and his team set out to develop a portable field laboratory for immediate sample analysis in remote settings. Together, they dive into the highs and lows of calibrating and optimizing pXRF and LIBS, discussing the meticulous sample preparation and calibration required to achieve accuracy and reliability, even in challenging field conditions.

From overcoming unexpected hurdles, like creating custom calibration pellets to ensure consistent LIBS results, to exploring the practical limits and advantages of each technology, this episode sheds light on the adaptability required to make these devices work effectively in geochemical exploration. Sam and Steve also touch on the importance of engaging with vendors for technical support and the value of sharing field-tested insights with other users to advance best practices. Whether you're an experienced geochemist or new to the field, Steve's experiences offer invaluable guidance for anyone interested in applying portable assay technologies to improve exploration outcomes.

Reliable and Repeated Field Assays

LIBS and pXRF in Lithium Exploration

What does this rock carry - know in the field