31. Porphyry Systems - from Bottom to Top

01/23/23 • 57 min

Can we track the evolution of a fertile porphyry system from the mantle to the deposit? The FAMOS (From Arc Magmas to Ores) Project in the UK was conceived to tackle the fundamental processes involved in porphyry ore systems and brought a diverse set of researchers and industry collaborators together. The interdisciplinary teams combined experimental petrology, volcanology, numerical modelling and mineral analysis. They worked together to constrain the conditions for porphyry ore deposit formation and to further develop indicators of fertile systems.

The aim was to use mineral chemistry to interpret processes in the magmatic-hydrothermal systems and ultimately use the recorded signatures in minerals as a discrimination tool in exploration. As the project wraps-up we talked to three contributors about what they have learned and what this type of ‘big’ science collaboration can accomplish.
Our first guest, Jamie Wilkinson is a senior scientist at the Natural History Museum in London, UK. A self-described 'want to be petrologist', Jamie has a diverse background in ore deposits with expertise in metal transport, applications of mineral chemistry and isotopes. Jamie is a leader of the FAMOS research project and takes us through the big ideas from the mantle to the signatures in the minerals.
Growing up in Siberia, Elena Melekhova was surrounded by geology and mines, but it was the discovery of experimental petrology that united her drive to understand the natural world with her passion for laboratory experiments. Elena is the experimental petrology laboratory lead at the University of Oxford and her FAMOS research provides fundamental data that challenges some of our assumption about the Sr/Y indicator ratio.
So why would industry be interested in participating in this fundamental research into magmatic-hydrothermal processes? We talked to Christian Ihlenfeld, Anglo American to find out what was surprising to them about the outcomes and why they provided a significant, large data set on the Los Bronces District, Chile for use by the FAMOS consortium.
Theme music is Confluence by Eastwinds
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Previous Episode

30. What are carbonatites anyway?

Carbonatites are controversial rocks that are associated with a diverse range of commodities, such as niobium, phosphate, copper, and light rare earth elements (LREE). This week we dive into some of the latest thinking about carbonatite genesis and ore forming processes, and consider the challenges involved in characterizing and producing these complex ore bodies.

First off, Emma Humphreys-Williams from the Natural History Museum, UK, explains how, when and where carbonatites form in the context of global tectonics and geodynamics, and questions what the carbonatite record tells us about the evolution of the mantle throughout earth history. https://alkcarb.myrocks.info/
Next, we talk about ore forming processes in carbonatites with Wei Chen, a professor at China University of Geosciences. She provides a deep dive into the processes that generate LREE deposits on a journey that spans the magmatic and metasomatic regimes.
Finally, Tony Mariano, a long-time exploration geologist shares some real-world perspectives on the complex nature of carbonatite ore deposits, and on some of the challenges involved in converting carbonatite-hosted deposits into producing assets.

Theme music is Confluence by Eastwinds.
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Next Episode

32. Gold - On its Way to the Surface

As gold makes it way to surface, what are the key observations for exploration geologists to make? How did we come to understand epithermal deposits and their relationships to intrusions and the paleosurface? And how important are our structural observations?

Gold can occur within Cu-Au porphyries and intrusion-related lodes, but also makes its way to the surface where a range of epithermal deposit-types host mineralization. Following on from Episode 31 and the discussion of porphyry processes from bottom to top, today we are starting in the deeper parts of the system to explore K92's Kainantu Project in the eastern highlands of Papua New Guinea. Chris Muller, VP Exploration K92 took time out to talk us through this big and varied project that includes an operating mine and new exploration discoveries.

Richard Sillitoe and John Thompson are back to share their insights and extensive experience in a host of epithermal environments. Dick and John recap the history of our understanding of epithermal deposits and focus on the key relationships vital for exploration. What is most important and what do we still not really understand? This is a great conversation.

The structural controls on epithermal deposits are critical for exploration and development. We are joined by David Rhys, Panterra Geoservices, to discuss commonalities and differences among the deposit types. Dave was a co-editor with Julie Rowland of the SEG Reviews in Economic Geology Volume 21 Applied Structural Geology of Ore-Forming Systems (2020). He was also lead author on a paper in that volume entitled Structural Controls on Ore Localization in Epithermal Gold-Silver Deposits: A Mineral Systems Approach.

Theme music is Confluence by Eastwinds
eastwindsmusic.com