(2020) Volcanic-Hosted Be-(Li-F-Ree-U) Deposits: Insights into Source Rocks, Geochemical Signatures, and Macro-To-Microscale Concentration Processes
Foley N, Ayuso R & Vazquez J
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08i: Plenary Hall, Friday 26th June 22:00 - 22:03
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Hi Nora, great presentation, I really enjoyed watching. I'm interested in your thoughts on where the Be was sourced from in the first place. Do you think it came from the sub-continental lithospheric mantle or is it sourced from the continental crust as the magmas travelled towards the surface? Is the fluorine enrichment of the fluid important for mobilisation and if so, why/how? Thanks, Clare Warren
Hi Clare, Establishing the source of beryllium at Spor Mountain (and other metals such as F, U, and Li) and in the western United States (Utah, Nevada, etc.) is a fundamental theme discussed in detail in our on-going geologic framework studies. At the moment we have several papers in USGS review: 1) one addresses the metallogeny of these beryllium-related deposits on the basis of major and trace element geochemistry and Nd-Sr-Pb radiogenic isotope studies of the volcanic sequences; 2) we also have a SHRIMP U-Pb zircon dating paper on the regional volcanics that focuses on rocks related to beryllium occurrences throughout Utah and tectonic interpretations; 3) a paper on our detailed studies of opal-bearing ores particularly results of SHRIMP U-Pb age determinations. Hopefully moving past Covid-19, those studies will be available to be released soon. We have stated that the source of the magmas and beryllium is the continental lithosphere; our metallogeny paper will be a detailed explanation of beryllium genesis. In an extended abstract (Foley and Ayuso, 2018; Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, 2018 International Conference on Magmatism of the Earth and Related Strategic Metal Deposits; Ayuso et al., 2018, Resources for Future Generations, Vancouver, Canada) we stated that “trace elements…and isotopic values such as 206Pb/204Pb ~19.00-19.64, 207Pb/204Pb ~15.62-15.79, 208Pb/204Pb ~ 39.20-39.85, 143Nd/144Nd values of ~0.51202-0.51226, and 87Sr/86Sr ~0.7120“ indicated magmatic sources originating from the continental lithosphere. Also, there is no trace element or zircon evidence that the Spor Mountain magmas assimilated continental crust (e.g., no inherited cores in the zircons, no older/inherited ages, only of euhedral magmatic zircons in all samples, etc.). F behavior is a critical part of the genesis of the Spor Mountain beryllium deposits. It is likely to affect the origin of the source of the magmas and the genesis of the ores. We have analyzed local and regional rocks for F in our studies and discuss this in detail in our papers in progress. Fluorine complexes of Be in the fluid are certainly important at hydrothermal stages as they have been shown to be the dominant Be-complexes at low temperatures; however, at higher temperatures and pressures other complexes come into play (e.g., fluorine-carbonate, possibly chlorine, etc.) These are important in deposits of the western Transbaikalia, e.g., Ermakovka (Damdinova et al., 2018, RGG and various papers by FG Reyf). I’d really like to see more experimental studies of the more complex Be-complexes over wide P-T ranges. We are delighted that you found this presentation of interest. We hope that you will contact us …
Thanks for the very interesting presentation Nora. I am interested in the opal dating technique: how do you deal with common lead and standardisation ?
Thanks so much Nora, this is a brilliant presentation, and the detailed work on the opal is fantastic. I am interested in the deportment of Li and REE in the deposit - do the nodules also contain enrichment of both elements? Like Clare, I am intrigued by the source of these metals in the circulating fluids - particularly if there is enrichment in both Li and REE, which typically have quite different sources.
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