Missed out on the Tea?

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)

For this episode, Steve delves into the practical challenges and breakthroughs in using portable XRF and LIBS technology for field-based geochemistry. He shares his journey to create a real-time assay setup, covering the intricacies of calibrating equipment, customizing standards, and the art of reliable sample preparation. If you’re interested in how portable analysis tools can enhance exploration, this episode dives into the essentials of making pXRF and LIBS work effectively in the field. 

For this episode we read:

⁠Reliable and Repeated Field Assays⁠

⁠LIBS and pXRF in Lithium Exploration⁠

⁠What does this rock carry - know in the field

Let's learn about upscaling LA-ICP-MS pyrite results to whole rock geochemistry data using principal components analysis (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.

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. 

Have you ever had the bad luck of not being able to work on your M.Sc. project for almost two years because of a broken instrument? Follow-up question... have you used this situation to turn lemons into lemonade? 

Welcome to this episode! Sam talks about a paper that he is working to publish that is a side project to his M.Sc. ... working in a carbonate replacement deposit in Peru, Sam systematically worked with the UV to create a system by which it can be applied in exploration programs to identify similar looking or completely unidentifiable minerals with the naked eye. 

The tea's good too - nothing like (kindly) telling your elders that they're identifying minerals incorrectly! 

For this episode we read Chapter 8 of Sam's thesis, entitled: Stable Isotopes as an Exploration Tool: Tracking Cryptic Alteration Surrounding the Iscaycruz Zn (Pb-Cu-Ag) Skarn-CRD Deposit, Central Peru.

A big thanks to Heidi Pass, Michelle Carery, Dave Lawie, Pim van Geffen, Putra Sadikin, Mike Whitbread, Des Pascoe, & Steve Sugden for rolling with this as we tried for our Holiday special to embody the Dickens-esq theme of Geochemistry: Past, Present & Future.

Everyone on the show this month was part of the ioGlobal team, a global applied geochemistry consultancy for the mineral exploration and mining industries, the likes of which has not been seen since the company was bought in the early 2010s.

Part charming family reunion, part educational, and many parts geochemistry. Happy holidays to everyone from GeOCHemISTea <3

We always talk about fluids in geochemistry. How the ore metals are moving and how they are depositing - we think in pressure-temperature-redox space. 

However, when we get our geology, structure and geochemistry in 3D... and then we start to rotate a model for the first time... it is the most rewarding moment because we see the fluid pathway and why our metals have deposited. 

Nothing, perhaps, in exploration geochemistry is more rewarding then spinning a 3D model. I've paraphrased myself from this interview here, but I hope everyone listening finds a friend in Julia because all geochemistry is 3D and deserves to be seen as we discuss! 

For this episode we read and watched a few blog posts:

⁠https://www.seequent.com/technical-tuesday-linking-lithology-and-geochemistry-with-iogas-and-leapfrog-geo-workflows/⁠

⁠https://www.seequent.com/connect-your-exploration-teams-with-the-power-of-a-fast-and-agile-workflow/⁠

⁠https://www.seequent.com/mapping-metal-deposits-in-canada/⁠

⁠https://www.seequent.com/data-is-a-solid-investment-for-junior-exploration-companies-2/⁠

⁠https://www.seequent.com/modelling-large-and-complex-data-in-the-integra-gold-rush-challenge/

There are geochemists and isotope geochemists... this episode we're speaking with the latter and this discussion could not be more interesting! Seriously. I found myself at different points so riveted (by that I mean thinking too hard) that I forgot I was supposed to be asking more questions.

As usual, my favorite part of the episode is Tea Time, but for a different reason. As an undergraduate, Libby asked a question to established researchers that were giving a talk to her university 8000+ of miles from their lab en route to do some fieldwork at the Platreef (Bushveld Complex, South Africa) that became a huge contribution to science and ore deposits research, as well as the focus for her MSc and PhD research. So cool.

For this episode we read: 

Sulfate recycling at subduction zones indicated by sulfur isotope systematics of Mesozoic ultramafic island arc cumulates in the North American Cordillera (Milidragovic et al., 2023)

Critical metals are merely lists built based on geopolitics and supply chain, but are nonetheless essential for advanced technology and particularly the 'green' energy transition.

Our interview spans softball critical metal questions to talking about the dredged material containing sulfate-reducing bacteria that is generating pyrite on the bottom of a canal in the Chesapeake watershed through to more typical acid mine drainage. 

All the while we retain focus on the recovery of critical metals from unconventional sources to supplement domestic supplies.

For this episode we read two papers:

Critical metal geochemistry in groundwaters influenced by dredged material (Goodman et al., 2023)

Rare earth element recovery in hard-rock acid mine drainage and mine wate: A case study in Idaho Springs, Colorado (Goodman et al., 2023)

 This episode returns to our roots... to our very first episode with Simon where we talked about the geochemistry of Carlin deposits, except this time we're talking about high sulfidation epithermal systems.

We're talking scale, exploration methodologies, geochemistry, and even a light amount of geophysics, all with a stiffly brewed cup of tea.

For this episode we read two papers:

Alturas: A Unique Discovery Within a Mature District Through Integrating Sound Geological Practices, Multidisciplinary Expertise and Leading Technology (Astorga et al., 2017)

Multi-Scale integrated application of Spectral Geology and Remote Sensing for Mineral Exploration (Zhou et al., 2017)

This is a different conversation from those we’ve had before because we took two extremely different topics in hydrogeochemistry and pXRF on drillcore and looked at how these different techniques and scales come together in a junior exploration program.

If you've never been to Nevada, no worries... we're going there together, now. 

For this episode we read: Parts per trillion (ppt) gold in groundwater: can we believe it, what is anomalous and how do we use it? (Buskard et al., 2019)

A favorite thing Dave likes to say is "we do all sorts of things to the rocks... to try and understand them...." But then Dave often likes to tell geologists and especially mining engineers that "rocks don't give a shit to what we think of them. They're just rocks. They're just gonna sit there and be like, all right, whatever guys. I'm a rock."

And as for why you won't see Dave penning a book on his career... "because it with be complete utter bullshit." That's hindsight bias for you.

Join us as we discuss Nassim Nicholas Taleb's philosophical book "Fooled by Randomness" and try and apply it to the wide world of geochemistry... with drinks.

For this episode we read the Datarock blog post Fusing core imagery and chemistry to model stratigraphy. 

Perhaps more interesting that the foundation of Datarock is built on Aussie rules football is some of the advice that Brenton Crawford, one of the the company's founders has to impart: that we can get distracted by what we 'need' from a university in order to get the geoscience job we want. 

Brenton goes on to counsel that getting involved in a community of your choosing, albeit geochemistry, data science, or some other sector, can be a better investment of your time and energy. Importantly, if you have interested in transitioning to data science, remember that your knowledge of the geosciences is infinitely more important than an additional degree in data science - your ability to make an impact on your team is greater simply because you understand the nuances of the data you are working with.

As for working with image data and integrating it with geochemistry... you'll have to have a listen.

For this episode we read: Geochemical Modeling of Water-Rock Interactions in Mining Environments (Alpers and Nordstrom, 1997).

For those who've asked "how do I become an environmental geochemist?" ...Tom has some advice for you. And for those that have questions about the business of consulting... his tea has some hard numbers. Best, though, is when we examine geochemical modeling philosophy and the Alpers and Nordstrom quote that models are "not reality, nor [are they] reliable, correct or valid representation[s] of reality."

After this show, I think we need to interview some more environmental geochemists!

We think we speak for everyone that the geochemical community is forever enriched by Putra's decision not to study plankton biostratigraphy or go into construction. Everyone's favorite ioGAS product manager stops by the show this month to talk to us about his journey through an MSc, MBA and life in general, as well as some good off-the-cuff Tea, and then a stimulating discussion on interpreting geochemical data.  Never be too prideful to ask a question and the more questions you ask, the better you become at asking questions (Sadikin, pers. comm. 2023).  

For this episode we read: Lithogeochemical and Hyperspectral Halos to Ag-Zn-Au Mineralization in the Eastern Goldfields Superterrane, Western Australia (Hollis et al., 2021). 

 For this episode we read: "Laser-Induced Breakdown Spectroscopy – An Emerging Analytical Tool for Mineral Exploration (Harmon et al., 2019)"

Starting from the basics of what is LIBS through to cutting edge applications, Andrew Somers (Global Business Director: Geochemistry at SciAps Inc.) is here to guide us through the ins and outs of this tech. 

For our young geochemists - are you nervous about making the jump from working at a mining company to working for a vendor? Andrew has some words of wisdom on this too. 

What are we observing versus what are we supposed to see, in other words, how (and how much) is dogma directing our interpretations? We explore this concept this month when we delve into Duncan McLeish's PhD work on the transport and deposition of gold at the Brucejack Deposit (Canada). 

In a world where aqueous complexation has long been considered the only viable means of transporting gold to depositional sites in hydrothermal ore-forming systems, Duncan et al. found that rejecting dogma was of the utmost importance. For example, a major weakness of the Au transport in solution hypothesis is that it cannot readily explain the formation of ultrahigh-grade gold veins when transporting Au at ppb levels.

...so how do “bonanza” veins contain weight-percent levels of gold in some epithermal and orogenic deposits?

...what are colloids and flocculation?

...why is this research both exciting and important? 

All this and more in this episode! Put on your thinking caps, it's time to listen to some applied chemistry, economic geology and a little bit of philosophy. 

For this episode we read "Colloidal transport and flocculation are the cause of the hyperenrichment of gold in nature" by McLeish et al., 2021. 

Did you know that in addition to being one of our industry's geochemical powerhouses, JC is also an artist? But also as we continue along in the episode we'll see that he's perhaps a staunch businessman. 

For this month's episode we reviewed a PDAC short course organized by JC and Lynda Bloom entitled: "Geochemical Modeling for Orebody Knowledge and Exploration Targeting Workshop" - including his helpful Review on Methodologies for Geochemical Data Analysis. 

The course spans fundamentals (including QA/QC), a review of methodologies, interpretation of 4 acid ICP data, geometallurgy, ore body knowledge, regional soil geochemistry, and applications of till and indicator minerals in glaciated geochemistry. The idea is that as geochemists we need to move past just exploration and into the realms of mine, mill and reclamation. If we have geochemistry collected at any point, by any group it must be standardized as a true multi-client dataset. Sample the overburden! Have a geochemist overseeing your database and controlling how the rocks are sampled from a multiclient perspective. "Until we do this, geochemistry will never be looked at in a company as a valuable asset, but as an expense." 

As a sidenote, JC's section of the course contains topics, such as compositional data, geochemistry templates, and unsupervised and supervised learning. Buckle up geochemists and geochemistry enthusiasts... see you on the other side of this fascinating interview!  

For this episode we looked at Mac's first publication and a truly great resource with easy to understand terminology for those interested in both pXRF and machine learning: Random forest rock type classification with integration of geochemical and photographic data (Trott et al., 2022)

Do you want to integrate machine learning into your exploration workflow, but feel precluded from doing so because of complicated terminology in the majority of the literature? Have a crack at Mac's first paper and then join us for this discussion on how he implemented a relatively simple, but well-constrained, study to provide explorationists with confidence on joining the ML push towards making core logging more quantitative. 

For our young listeners, Mac has some twists and turns on his way towards his current position as a PhD student at Queen's as well as being an embedded researcher and the senior geodatascientist at Goldspot. 

Also... the tea is good. 

Have you perused a geochemistry lab schedule and not known where to start? Don't worry - the answers are not obvious and GeocHemiSTea is here to help! 

We broke this episode into six sections to get to your answers quicker, but considering the complexity of the topic and the importance of having the best data possible we recommend listening to this episode in its entirety! 

1. Orientation survey (9:24)
2. Sample prep (14:56)
3. Digests (21:16)
4. Finishes (47:50)
5. Inseparable digest/finish questions (57:35)
6. Databases and impacts on making changes to your geochemical program during a project (1:07:10)

For this episode we had a squiz at: "Mineral Geochemistry Vectoring: Uncovering Northwest Queensland’s Hidden Potential" (Steadman et al., 2021), "Improving geological logging of drill holes using geochemical data and data analytics for mineral exploration in the Gawler Ranges, South Australia" (Hill et al., 2021), and the tutorials on the Mineral Mapping website. 

There's a role for classical geochemistry (bivariate plots, probability plots, etc.) to play, but the future is moving towards a data science approach to geochemical data. Come listen to Mike's take on where geochemistry in industry is heading and where it still needs to shift. 

For this episode we read: "A User's Guide to Basalt Discrimination Diagrams" by Pearce (1996).

Surely you have seen a geochemical diagram before... Winchester and Floyd (1977) for the classification of volcanic rocks or even Pearce's 1996 diagram to classify basalts. Have you combed the literature to find the most fit-for-purpose diagram for your own rock samples? Look no further! In this discussion with Pim van Geffen we talk about how to use the principles outlined in this book chapter to create your own diagrams. 

For this episode we read: "Rapid crystallization of precious-metal-mineralized layers in mafic magmatic systems" (Hepworth et al., 2020).

What does a computational geochemist and igneous petrologist do? Apparently, they think a lot on crystal mushes and bifurcation. Seeing mafic magmatic PGE and Cr systems from an igneous petrology perspective has its benefits and there's something in this episode for everyone interested in these systems. Separately, we also asked about his views on predatory scientific journals and their implications for geoscientists and researchers.

"...and the moment you run into this will tell you a lot about how you feel as a person, to learn something you might have been wrong about." -Tom Carmichael 

Tom is the Chief Data Scientist at Datarock and we spent a long time at the beginning of this episode talking about the fields of mathematical and computational geology, particularly from the perspective of someone at the university level that is interested in getting into these fields. The rest of the show is about Tom losing his membership to the AGU and a lot of Q&A on the concept of spatial autocorrelation - and importantly how it applies to geochemical data. 

For this episode we read: Importance of spatial predictor variable selection in machine learning applications - Moving from data reproduction to spatial prediction by Meyer et al., 2019.

For this episode we read: "Geochemical mapping: technique or art" (Reinmann, 2005).

When preparing this episode, German immediately gravitated to the concept that all geoscientists can be geochemists AND that all geochemists should be good geoscientists. In this episode we explore how the basic principles of survey design lead to the generation of meaningful geochemical summary outputs, e.g., maps, that can help exploration teams make decisions.

 For this episode we read: "The Oil-Bearing, Carlin-Type Gold Deposits of Yankee Basin, Alligator Ridge District, Nevada" (Hulen & Collister, 1999). 

Our chat ranges from lithogeochemistry to isotopes to pathfinder elements in the Carlin (Nevada) with Simon Griffiths. More interesting, let's see his path from a young Welsh structural geologist to the proprietor and principal consultant of 3PXS, a UK-based economic geology and geochemistry consulting firm.