Gold-bearing ferroselite (FeSe2) from Trogtal, Harz, Germany, and significance of its Co/Ni ratio

Cabral, Alexandre Raphael; Koglin, Nikola; Brätz, Helene

doi:10.3190/jgeosci.129

Cited by 2 publications

(1 citation statement)

References 23 publications

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“…However, Fe (III) reducers can sequester selenium (Klonowska et al 2005 ; Pearce et al 2009 ), and precipitate it as selenides, consistent with their occurrence instead of sulfides. Selenium may be co-precipitated with Fe (III) oxides (e.g., Howard 1977 ; Cabral et al 2012 ), so on microbial reduction of the oxides both iron and selenium are liberated and the selenium is readily available for concentration and reprecipitation. Although selenium forms selenide anions, it behaves like a metal and is reduced by Fe (III) reducing bacteria along with other metals.…”

Section: The Origin Of Reduction Spheroidsmentioning

confidence: 99%

Metalliferous Biosignatures for Deep Subsurface Microbial Activity

Parnell

Brolly

Spinks

et al. 2015

Orig Life Evol Biosph

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The interaction of microbes and metals is widely assumed to have occurred in surface or very shallow subsurface environments. However new evidence suggests that much microbial activity occurs in the deep subsurface. Fluvial, lacustrine and aeolian ‘red beds’ contain widespread centimetre-scale reduction spheroids in which a pale reduced spheroid in otherwise red rocks contains a metalliferous core. Most of the reduction of Fe (III) in sediments is caused by Fe (III) reducing bacteria. They have the potential to reduce a range of metals and metalloids, including V, Cu, Mo, U and Se, by substituting them for Fe (III) as electron acceptors, which are all elements common in reduction spheroids. The spheroidal morphology indicates that they were formed at depth, after compaction, which is consistent with a microbial formation. Given that the consequences of Fe (III) reduction have a visual expression, they are potential biosignatures during exploration of the terrestrial and extraterrestrial geological record. There is debate about the energy available from Fe (III) reduction on Mars, but the abundance of iron in Martian soils makes it one of the most valuable prospects for life there. Entrapment of the microbes themselves as fossils is possible, but a more realistic target during the exploration of Mars would be the colour contrasts reflecting selective reduction or oxidation. This can be achieved by analysing quartz grains across a reduction spheroid using Raman spectroscopy, which demonstrates its suitability for life detection in subsurface environments. Microbial action is the most suitable explanation for the formation of reduction spheroids and may act as metalliferous biosignatures for deep subsurface microbial activity.

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Section: The Origin Of Reduction Spheroidsmentioning

confidence: 99%

Metalliferous Biosignatures for Deep Subsurface Microbial Activity

Parnell

Brolly

Spinks

et al. 2015

Orig Life Evol Biosph

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Germanium and precious metals (Ag–Au–Pt–Pd) at low temperature: the hematite–carbonate–selenide vein system of Tilkerode, Harz Mountains, Germany

Lohmeier

Cabral

Ehling³

et al. 2023

Miner Deposita

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At the historical Eskeborner Berg underground workings at Tilkerode (Eastern Harz Mountains, Germany), Fe was mined from a carbonate–hematite vein system that was locally enriched in selenide minerals. Clausthalite [PbSe] was the most abundant selenide mineral in a carbonate matrix with laths of specular hematite. To date, the selenide-bearing carbonate–hematite vein system at Tilkerode has not been geochemically investigated. Here, we present the first whole-rock chemical data for a wide suite of trace elements. The following metals are enriched relative to bulk continental crust (orders of magnitude in parentheses): Se (>105), Hg (>104), Ag and Pb (103), Au, Bi, Pt, Ge, Te, Pd and Cd (102). Samples from Tilkerode have up to 2640 ppm Ag, 338 ppm Ge, 1560 ppb Au, 970 ppb Pt and 365 ppb Pd, with Pt/Pd > 1, and a significant positive correlation of Ge vs. (Pd+Pt). The selenide mineralisation took place below 112 °C, the maximum temperature stability of umangite [Cu3Se2]. Our data indicate there is potential for prospecting Ge and precious metals in low-temperature vein systems.

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Gold-bearing ferroselite (FeSe2) from Trogtal, Harz, Germany, and significance of its Co/Ni ratio

Cited by 2 publications

References 23 publications

Metalliferous Biosignatures for Deep Subsurface Microbial Activity

Metalliferous Biosignatures for Deep Subsurface Microbial Activity

Germanium and precious metals (Ag–Au–Pt–Pd) at low temperature: the hematite–carbonate–selenide vein system of Tilkerode, Harz Mountains, Germany

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