Diagenetic sequestration of rare earths and actinides in phosphatic oil shale from the lacustrine Green River Formation (Eocene), Utah, USA: an SEM and LA-ICP-MS study

Keighley, Dave; McFarlane, Christopher R.M.; Berg, Mike

doi:10.1007/s10933-016-9905-3

Cited by 6 publications

(17 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The same material may be interspersed with, or enclosed by, amorphous to internally microlayered material mapped as carbon (Figure ), which Keighley et al. () consider to be organic material such as kerogen. Accordingly, a continuum exists between carbonate‐rich and organic‐rich lamination.…”

Section: Resultsmentioning

confidence: 99%

“…Previously, phosphogenesis in the upper GRF has been attributed to physiochemical factors active both in organic‐poor, evaporitic shale (Keighley, ) and in several beds of organic‐rich shale that outcrop at Buck Canyon (Keighley et al., ). If the globular structures are fossilized microbes, then biotic factors additionally have played a role in the phosphogenesis of at least the oil shales under current study (globular structures have not been recorded in other phosphatic and non‐phosphatic oil shale at Buck Canyon).…”

Section: Discussionmentioning

confidence: 99%

“…(b) Distribution of GRF strata in the eastern Uinta Basin, with location of outcrop (Buck Canyon) and borehole (U0112) samples. Modified from Keighley et al., [Colour figure can be viewed at wileyonlinelibrary.com]…”

Section: Introductionmentioning

confidence: 99%

“…(e) Slabbed and polished core from borehole U0112 (X18) and (f) associated LA‐ICP‐MS results. Tungsten values show no distinct trends and average 1.47 ppm in U0112, slightly less in the 128.2 m sample because of the higher proportion of P. Lanthanide and actinide anomalies associated with the phosphatic interval permit microstratigraphic subdivision into zones and subzones (see Keighley et al., for details of the zonation and analytical methodology) [Colour figure can be viewed at wileyonlinelibrary.com]…”

Section: Introductionmentioning

confidence: 99%

“…Inductively coupled plasma‐mass spectrometry (ICP‐MS) of the S128.2 chips' equivalent solutions (2 replicates) recorded values including P: 6.04–6.29 wt % (as P 2 O 5 ), Mo: 22–23 ppm, La: 15.3–18.1 ppm, Lu: 1.36–1.47 ppm, W: <1 ppm, Th: 125–133 ppm and U: 82.8–85.2 ppm (Keighley, ). Laser Ablation (LA) ICP‐MS has been performed on S128.2 and on two other R8 phosphatic oil‐shale beds cored from the subsurface (borehole U0118), several km to the north of the outcrop close to the basin's depositional axis (“X18” = 1,838 ft, 560.1 m, subsurface, and “X19” = 1,945 ft, 592.8 m; Keighley et al., ; Figures ). Results show the CFA‐rich intervals have distinct lower and upper margins containing complexly zoned enrichments of rare earth elements (REEs) and actinides (Th, U) suggesting pore‐water diffusion of the metals post‐CFA crystallization, but no such trends for the other ~40 elements analyzed, including tungsten.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Phosphatized tungsten‐metabolizing coccoid microbes interpreted from oil shale of an Eocene lake, Green River Formation, Utah, USA

2018

Self Cite

View full text Add to dashboard Cite

Microscopic globular structures have been observed in some beds of oil shale from eastern Utah. These beds comprise carbonate-dominated mud that is interlaminated with variably thick and continuous organic-rich layers. Collectively they are enriched in phosphorus, REEs, and actinides. The beds are considered of lacustrine origin and assigned to the Eocene Green River Formation. The globules themselves are of microcrystalline carbonate fluorapatite (μCFA), often contain concentric internal structures, and usually group together in clusters of up to 80, possibly more. Detailed SEM and microprobe analyses have revealed tungsten (W) to be almost exclusively associated with the globular clusters found within the more organic-rich laminae, often at concentrations of over 200 ppm, two orders of magnitude above shale standards. The globular structures are present in freshly cut sections where they occasionally grade into a μCFA matrix cement. This, together with the draping of the clusters by stringers of organic matter that would have accumulated in the Eocene lake, confirms that the structures are not a contaminant. The limited range of sizes and globular shapes is consistent with the morphology of coccoidal bacteria: Concentric internal structures may represent remnants of the nucleoid and cell wall. Paired concentric structures may indicate cell division (reproduction) processes were occurring until mineralization. The phosphate mineralization itself may have been promoted by release of phosphate from the stressed cells, bringing porewaters to supersaturation, or by the cells acting as nucleation sites. The recording of trace amounts of W almost exclusively in globular clusters preserved in the most organic-rich stringers (anoxia prone) further suggests facultative use of W-enzymes in a microbial metabolism. Combined, their context, morphology, and indication of biogenic process are strong evidence that the structures are fossilized (phosphatized) microbes, possibly sulfate-reducing bacteria, or methanogenic archaea.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations