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:
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 exploration geochemistry, 2007 to 2017 and beyond (Winterburn et al., 2019)
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:
Metallogeny and mineral exploration - some personal reminiscences (Sillitoe, 2024)
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: Orogenic gold: is a genetic association with magmatism realistic? (Goldfarb and Pitcairn, 2022)
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.
For this episode we read:
Reliable and Repeated Field Assays
Let's learn about upscaling LA-ICP-MS pyrite results to whole rock geochemistry data using PCA. On the way we'll hear about the life and times of an early career geochemist and some of the ins and outs of being a geochemical consultant.
For this episode we read: Using whole rock and in situ pyrite chemistry to evaluate authigenic and hydrothermal controls on trace element variability in a Zn mineralized Proterozoic subbasin (Magnall et al., 2022)
For this episode we read: Archean Lode Gold Deposits in Ontario (Colvine et al., 1984) aka the Greenstone Bible.
We talk about Simon's transition from working from large mining companies to opening his own consultancy for all those considering this as part of their future.
Our tea... have you ever been late to your flight, anxious on the shores of Lake Victoria, Tanzania?
As for the heart of the show? We talk about the applications of geochemistry to greenstone gold exploration. This one is dedicated to the fans of the show in Dubreuilville (Canada) who wanted some extra insight on geochemistry in greenstones. I hope you enjoy this one!
This is our second episode on GeOCHemISTea where we have branched out from geochemistry into a sister geoscience - spectral geology. For this episode take a look at another of the spectral ecosystem's end-members: hyperspectral core imaging.
Join us as we talk about hyperspectral imaging, the data load, and some interesting applications to porphyry geoscience.
For this episode we read: Hyperspectral Core Imaging Applications in Porphyry Deposits (Corescan)
Herein we present a general microanalytical technique rant, at least three soap boxes (my favorite being "I want to also rant about bulk chemistry techniques and why if these techniques are “so routine” that we still have some labs that suck at understanding (or respecting) how to do basic chemistry well"), and the story of how a geologist with a graduate degree in geochemistry found themself crushing rocks at the USGS and living in both Omaha, Nebraska and ::shudder:: Newark, New Jersey.
If you are an aspiring analytical geochemist or generally have questions / concerns about analytical techniques... this episode is for you!
In lieu of a paper we looked at some notes from a short course that Alan presented in 2016 on LA-ICP-MS.
This is our first episode on GeOCHemISTea where we have branched out from geochemistry into a sister geoscience - spectral geology. For this episode we start from one of the spectral ecosystem's end-members: remote sensing, or satellites and airborne.
Join us as we talk about the newest developments in sensor tech and data processing, while still paying proper attention to the role of remote sensing in the mining value chain.
For this episode we read: Improvements in Mineralogical Classification with Increased Spectral Resolution: A Case Study over Cuprite, Nevada comparing Fused Bare Earth Composite and EnMAP Data (Wickert and Casement, 2024)
Hyperspectral Imaging for Mining: EnMAP Satellite Data versus SpecTIR Airborne Data (Wickert and Casement, 2024) And we'd like to give a shout out to @LucaCongedoGIS on YouTube who we referenced numerous times in the podcast as the "Italian guy." You are a legend!
For this episode we read Rob's paper: Natural attenuation in the vadose zone: Nature's gift to mine closure (Bowell, 2023) From rethinking the green economy to recovering metals and ores in naturally occurring ways, this episode encompasses a lot of topics currently in the news but a uniquely Rob perspective.
Along the way, we may even learn about the vadose zone and the potential to remediate sites naturally.
Want to hear some more of Rob's thoughts? But also just general silliness from before we started to record? Enjoy!
At GeOCHemISTea we love it when someone is so passionate about their geochemistry topic that they reach out and request(!!) to be on the show. An honor, Ben!
So what ground did we cover... manifest your own destiny (or was that the US in the 1800s?). Ben has been a geochemist, a geophysicist, and a data scientist; there's lots of nuggets in there for young geos who are looking for the how-to... so how did Ben become a geochemist?
Our topic of interest this month was to talk about methodology selection to solve geochemical, geometallurgical, and dare I say geophysical situations that arise during the course of exploration and mining programs... and dare I say... Ben has a lot of opinions, advice and ideas on the matter!
For this episode we read: Characterization of Ore Properties for Geometallurgy (Butcher et al., 2023)
For this episode we read: Using machine learning to estimate a key missing geochemical variable in mining exploration: application of the Random Forest algorithm to multi-sensor core logging data (Schnitzler et al., 2019) A big difference between applied geochemistry and machine is the terminology, but once you start to chip away at this, like Britt, you will realize that the two disciplines are not so different.
Join us as we talk about dimensionality reductions, transformations, and workflows pre- and post- her introduction to the realm of data science. And talk about a really neat paper that used random forest to predict sodium for an alteration study.
For this episode we read a chapter from Sam Cantor's thesis entitled: Exploration Tool: Tracking Cryptic Alteration Surrounding the Iscaycruz Zn (Pb-Cu-Ag) Skarn-CRD Deposit, Central Peru (Cantor, 2020)
Have you implemented UV lamps into your exploration programs to help try and sort out complex mineralogy and vein paragenesis? Sam Cantor explains his side hustle at the Mineral Deposits Research Unit at the University of British Columbia, where he was able to start to build out workflows to tackle this in a complex skarn and carbonate replacement deposit in Peru.
If this has not yet peaked your interest, perhaps come for the tea where he talks about his role as a green junior geologist in Nicaragua using hyperspectral to overturn high sulfidation epithermal mineral identifications using the field geologist's tried and true method of tasting minerals :)
