Rare-earth geochemistry of `old' phosphorites and probability of syngenetic precipitation and accumulation of phosphate1In memory of Richard P. Sheldon1

Ilyin, A. V.

doi:10.1016/s0009-2541(97)00134-4

Cited by 100 publications

(39 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Granular phosphorites may provide realistic estimates of the seawater REE patterns due to their specific growth environment close to the seawater‐sediment interface and greater exposure to seawater during their early diagenesis stage (Ilyin, ). In this study, the relict REE signal of primary seawater is clearly preserved in the granular phosphorite (Fig.…”

Section: Discussionmentioning

confidence: 99%

Marine redox variations during the Ediacaran–Cambrian transition on the Yangtze Platform, South China

Zhai

et al. 2016

Geological Journal

View full text Add to dashboard Cite

The widely developed black shales on the Yangtze Platform recorded palaeoceanographic environment information during the EdiacaranCambrian transition. This paper describes an integrated geochemical study of rare earth elements (REEs), redox-sensitive trace elements (RSTEs), and total organic carbon (TOC) contents in Ediacaran-Cambrian black shales at Daotuo, northeastern Guizhou Province, South China. Integrated RSTE data from the Daotuo area, in combination with previously published Fe speciation and Mo-based proxies from another six sections (Shatan, Jiulongwan, Zhongling, Yangjiaping, Longbizui and Wuhe), suggest three major periods of water euxinia during the Ediacaran-Cambrian transition. Under these conditions, organic matter and RSTEs experienced various levels of enrichment in the black shales, especially in the lower Jiumenchong Formation. Given the patterns of Mo-U covariations, metal-oxyhydroxide particulate shuttles may have operated during the black shale deposition of the Doushantuo Formation (Member II) at Daotuo. Conspicuously, the upper slope water was oxic-dysoxic during the earliest Cambrian, as determined by the REE, RSTE data and sedimentological characteristics of the Liuchapo Formation and the basal Jiumenchong Formation. The generally low RSTE concentrations in the Bianmachong Formation black shales (Cambrian Series 2, end of Stage 3) suggest a persistently oxic water column in upper slope settings. The coincidence between the marine oxygenation and the development of the ecosystem likely indicates the galvanizing effects of enhanced oxygen and biological element content on the fauna during the Ediacaran-Cambrian transition.

show abstract

Section: Discussionmentioning

confidence: 99%

Marine redox variations during the Ediacaran–Cambrian transition on the Yangtze Platform, South China

Zhai

et al. 2016

Geological Journal

View full text Add to dashboard Cite

show abstract

“…12a) usually associated with precipitation in an oxidizing, seawater environment (McArthur andWalsh, 1984/1985), although some present-day rivers do have "seawater-like" REE patterns (Goldstein and Jacobsen, 1988;Elderfield et al, 1990). The relative HREE depletion exhibited by the samples, uncharacteristic of Mesozoic or Cenozoic seawater patterns (McArthur andWalsh, 1984/1985;Ilyin, 1998), may also indicate alteration during weathering (McArthur andWalsh, 1984/1985;Shields and Stille, 2001). The MREE enrichment of calcite concretions from the upper diamictite unit DS 4c and, to a greater extent, of phosphatic samples from the Prince Albert Formation is often associated with river water (Hannigan and Sholkovitz, 2001).…”

Section: Origin and Depositional Environment Of The Concretionsmentioning

confidence: 99%

Depositional environments of the lower Permian Dwyka diamictite and Prince Albert shale inferred from the geochemistry of early diagenetic concretions, southwest Karoo Basin, South Africa

Herbert

Compton

2007

Sedimentary Geology

View full text Add to dashboard Cite

The upper Dwyka and lower Ecca Groups in the Karoo Basin of South Africa document the climatic and palaeoenvironmental changes associated with the final Permo-Carboniferous deglaciation of the Gondwana supercontinent. The depositional environments of these groups have, until recently, been interpreted on the basis of sedimentological and palaeontological evidence. Here we use the geochemistry of early diagenetic concretions -septarian calcite concretions from the upper Dwyka Group and phosphatic chert concretions and beds from the lower Ecca Group -to infer the depositional environment of these rocks in the southwestern Karoo Basin. δ 18 O values (7.8 to 8.9‰ SMOW) suggest that the calcite concretions precipitated from a mixture of meteoric and glacial melt waters rather than Permian seawater. δ 13 C values (−15 to − 3‰ PDB) indicate that the carbon was derived from a mixture of craton-derived calcareous material and organic matter, bacterially degraded in the lower sulphatereduction to upper methanogenesis zones during early burial diagenesis. The rare-earth element (REE) patterns, Sr concentrations and 87 Sr/ 86 Sr ratios (0.716-0.737) significantly greater than Permian seawater (0.708), together also support the interpretation that calcite and phosphatic concretions formed in glacial, fresh water sediments.

show abstract

“…Phosphorites from this time interval are well‐known in many palaeogeographic areas, such as the Siberian Platform (Ilyin, ,b), the West African craton (Blot et al ., ; Bertrand‐Sarfati et al ., ; Flicoteaux & Trompette, ), China (Chen et al ., ; Jiang et al ., ; Ling et al ., ), Australia (Creveling et al ., ) and India (Banerjee et al ., ; Mazumdar et al ., ). Other areas of economic and subeconomic interest have been less studied, such as those located along the western margins of Gondwana and Baltica (Andersson, ; Notholt & Brasier, ; Wallin, ).…”

Section: Introductionmentioning

confidence: 99%

Ediacaran–Cambrian phosphorites from the western margins of Gondwana and Baltica

et al. 2015

View full text Add to dashboard Cite

The late Ediacaran–mid Cambrian occurrences of phosphorites in the western Mediterranean region (West Gondwana) and southern Sweden (north‐west Baltica) are related to the poleward drift of West Gondwana and the northern drift of Baltica. As a result, these regions crossed subtropical and temperate palaeolatitudes of the Southern Hemisphere, in which oceanic upwelling and high organic productivity were the probable sources of phosphorus along their western margins. A parallel south‐west/north‐east migration trend of evaporites and delayed, time transgressive phosphorites point to distal upwelling environments associated with shallower arid conditions. Concentration of hardground‐derived phosphate accumulations took place by repeated alternations of low sedimentation rates and condensation, in situ early diagenetic and microbially mediated precipitation of amorphous and cryptocrystalline, carbonate‐bearing francolite, winnowing and polyphase reworking of previously phosphatized skeletons and hardground‐derived clasts. Thicker phosphorites of economic importance display a spiculate sponge‐thromboid consortium that points to a distinct benthic community developed on suboxic, slope to basinal substrates. For most phosphorite samples an up to ten‐fold enrichment in rare earth element concentration relative to post‐Archaean average Australian shale reflects significant incorporation of rare earth elements and yttrium after deposition. Considerable scavenging took place from anoxic pore waters, following reductive dissolution of iron oxides as evidenced from the medium rare earth element enrichment in most samples. This contrasts with the rare preservation of primary sea water features, such as cerium depletion and yttrium enrichment, in phosphatized thrombolites from the shallower realms (for example, Montagne Noire). The data are consistent with phosphogenesis after upwelling and transgression of nutrient‐rich, suboxic–anoxic, ferruginous waters over more oxygenated, rifting settings and inland portions of an evolving passive margin.

show abstract

Rare-earth geochemistry of `old' phosphorites and probability of syngenetic precipitation and accumulation of phosphate1In memory of Richard P. Sheldon1

Cited by 100 publications

References 9 publications

Marine redox variations during the Ediacaran–Cambrian transition on the Yangtze Platform, South China

Marine redox variations during the Ediacaran–Cambrian transition on the Yangtze Platform, South China

Depositional environments of the lower Permian Dwyka diamictite and Prince Albert shale inferred from the geochemistry of early diagenetic concretions, southwest Karoo Basin, South Africa

Ediacaran–Cambrian phosphorites from the western margins of Gondwana and Baltica

Contact Info

Product

Resources

About