Occurrence and Formation of Water-Laid Placers

Slingerland, Rudy; Smith, Norman D.

doi:10.1146/annurev.ea.14.050186.000553

Cited by 95 publications

(35 citation statements)

References 49 publications

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“…Running water is probably the major agent involved in placer formation ( Slingerland and Smith, 1986). At this stage, titanium must reside as oxide, either rutile or ilmenite, to be liable to concentration processes, hence the importance of the source rock (Force, 1991a;Stanaway, 1996).…”

Section: Mechanical Enrichmentmentioning

confidence: 99%

“…At this stage, titanium must reside as oxide, either rutile or ilmenite, to be liable to concentration processes, hence the importance of the source rock (Force, 1991a;Stanaway, 1996). Settling, entrainment, differential transport and shearing are the principal mechanisms involved during the formation of a water-laid placer, where particle size and density intervene (Stapor, 1973;Kornar and Wang, 1984;Slingerland and Smith, 1986;Stanaway, 1992). Concentration of heavy minerals usually result in a simultaneous combination of these mechanisms.…”

Section: Mechanical Enrichmentmentioning

confidence: 99%

“…Based on this principle, coarse light grains are in equilibrium with finer heavy grains during deposition (Slingerland and Smith, 1986;Force, 1991b). At this point, no enrichment occurs, apart the removal of small light grains and floating particle such as micas and clay.…”

Section: Mechanical Enrichmentmentioning

confidence: 99%

“…According to this principle, on a layer, coarse grains are preferentially removed by transport agents rather than finer ones, due to greater contact area (Slingerland and Smith, 1986;Force, 1991b). Waves, for example, are probably the best natural concentrator of heavy minerals by entrainment, created by wash and back-wash movements on a beach (Force, 1991a).…”

Section: Mechanical Enrichmentmentioning

confidence: 99%

“…The large particles move faster than finer ones with increasing velocity of the flowing water. Thus heavy particles can be concentrated by a combination of the above-mentioned hydraulic equivalences (settling and entrainment; Slingerland and Smith, 1986;Force, 1991b).…”

Section: Mechanical Enrichmentmentioning

confidence: 99%

See 4 more Smart Citations

Processus dynamo-métamorphiques de bonification des gîtes de Fe-Ti /

Hebert¹

2007

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Section: Mechanical Enrichmentmentioning

confidence: 99%

Section: Mechanical Enrichmentmentioning

confidence: 99%

Section: Mechanical Enrichmentmentioning

confidence: 99%

Section: Mechanical Enrichmentmentioning

confidence: 99%

Section: Mechanical Enrichmentmentioning

confidence: 99%

See 3 more Smart Citations

Processus dynamo-métamorphiques de bonification des gîtes de Fe-Ti /

Hebert¹

2007

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Rock magnetic and geochemical evidence for authigenic magnetite formation via iron reduction in coal‐bearing sediments offshore Shimokita Peninsula, Japan (IODP Site C0020)

Phillips

Johnson

Clyde

et al. 2017

Geochem Geophys Geosyst

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Sediments recovered at Integrated Ocean Drilling Program (IODP) Site C0020, in a fore‐arc basin offshore Shimokita Peninsula, Japan, include numerous coal beds (0.3–7 m thick) that are associated with a transition from a terrestrial to marine depositional environment. Within the primary coal‐bearing unit (∼2 km depth below seafloor) there are sharp increases in magnetic susceptibility in close proximity to the coal beds, superimposed on a background of consistently low magnetic susceptibility throughout the remainder of the recovered stratigraphic sequence. We investigate the source of the magnetic susceptibility variability and characterize the dominant magnetic assemblage throughout the entire cored record, using isothermal remanent magnetization (IRM), thermal demagnetization, anhysteretic remanent magnetization (ARM), iron speciation, and iron isotopes. Magnetic mineral assemblages in all samples are dominated by very low‐coercivity minerals with unblocking temperatures between 350 and 580°C that are interpreted to be magnetite. Samples with lower unblocking temperatures (300–400°C), higher ARM, higher‐frequency dependence, and isotopically heavy δ56Fe across a range of lithologies in the coal‐bearing unit (between 1925 and 1995 mbsf) indicate the presence of fine‐grained authigenic magnetite. We suggest that iron‐reducing bacteria facilitated the production of fine‐grained magnetite within the coal‐bearing unit during burial and interaction with pore waters. The coal/peat acted as a source of electron donors during burial, mediated by humic acids, to supply iron‐reducing bacteria in the surrounding siliciclastic sediments. These results indicate that coal‐bearing sediments may play an important role in iron cycling in subsiding peat environments and if buried deeply through time, within the subsequent deep biosphere.

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The Channel Bed – Contaminant Transport and Storage

Miller

Miller²

Contaminated Rivers

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Occurrence and Formation of Water-Laid Placers

Cited by 95 publications

References 49 publications

Processus dynamo-métamorphiques de bonification des gîtes de Fe-Ti /

Processus dynamo-métamorphiques de bonification des gîtes de Fe-Ti /

Rock magnetic and geochemical evidence for authigenic magnetite formation via iron reduction in coal‐bearing sediments offshore Shimokita Peninsula, Japan (IODP Site C0020)

The Channel Bed – Contaminant Transport and Storage

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