Colorado vermiculite deposits: mines, prospects, and occurrences

VanGosen, B.S.; Bush, Alfred Lerner

doi:10.3133/ofr01475

Cited by 2 publications

(2 citation statements)

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“…The largest terrestrial vermiculite deposits are associated with altered Mg-rich phlogopite-bearing igneous or metamorphic rocks. These include worldwide deposits such as the following: Libby in Montana, USA (Basset, 1961;Vam Gosen and Bush, 2001), Loolekoop, Phalaborwa, South Africa (Schoeman, 1989), or Kovdor massif, Kola Peninsula in Russia (Krasnova et al, 2004). Vermiculites in these locations are trioctahedral but have low Fe/Mg ratios, and, as such, are not expected to be good mineralogical matches for Oxia Planum.…”

Section: Terrestrial Vermiculite Depositsmentioning

confidence: 99%

Mineralogical and Spectral (Near-Infrared) Characterization of Fe-Rich Vermiculite-Bearing Terrestrial Deposits and Constraints for Mineralogy of Oxia Planum, ExoMars 2022 Landing Site

et al. 2021

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Oxia Planum is a Noachian plain on Mars. It was chosen as the final landing site for in situ studies by ExoMars 2022 rover. The main scientific objectives of the mission are to understand the mineralogy and aqueous evolution of ancient Mars with relevance to habitability. Oxia is covered by vast deposits of Fe,Mgphyllosilicates, but the exact nature of these deposits is not yet fully understood. We performed a survey of potential terrestrial analog rocks, and here we show combined mineralogical characterization of these rocks with their near-infrared spectral analysis. Samples from two terrestrial sites were studied: (1) vermiculitized chlorite-schists from Otago, New Zealand, which underwent an alteration process without significant oxidation; and (2) basaltic tuffs from Granby, Massachusetts, USA, with Fe-rich clays filling amygdales of supposedly hydrothermal origin. Both analogues are incorporated into the newly built Planetary Terrestrial Analogue Library (PTAL) collection. Oxia bedrock clay-rich deposits are spectrally matched best by a well-crystallized trioctahedral vermiculite/saponite mixture from the basaltic tuff, although the contribution of saponite must be minor. Otago vermiculite is a good analogue to Oxia vermiculite in terms of overall mineralogy and Fe content. However, spectral inconsistencies related to the Al content in the Otago clays indicate that illitization of vermiculite, which results from postalteration oxidation, did not occur at Oxia. This implies limited water/rock interactions and reducing conditions during deposition of sediments now constituting the bedrock at Oxia. Whereas the spectral match does not conclusively imply the mineralogy, trioctahedral vermiculite should be considered a likely mineral component of the bedrock unit at Oxia Planum. Vermiculite has great potential to store organic matter, and the postdeposition geological context of Oxia Planum derived from understanding of environmental conditions in analog sites is promising for organic matter preservation.

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Section: Terrestrial Vermiculite Depositsmentioning

confidence: 99%

Mineralogical and Spectral (Near-Infrared) Characterization of Fe-Rich Vermiculite-Bearing Terrestrial Deposits and Constraints for Mineralogy of Oxia Planum, ExoMars 2022 Landing Site

et al. 2021

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“…Commercial vermiculite deposits form in a range of igneous and metamorphic rocks. In central Colorado, vermiculite is associated with Proterozoic gneisses, granodiorite, and granite; Cambrian diabase and alkalic plutonic rocks; and Tertiary volcanic rocks (Van Gosen and Bush, 2001). However, safe development proceeds cautiously because a preliminary reconnaissance study by the U.S. Geological Survey found amphibole asbestos minerals in at least two Colorado vermiculite districts (Van Gosen and others, 2002).…”

Section: Geology Of Colorado Lightweight Aggregate Depositsmentioning

confidence: 99%