Evolution of regoliths and landscapes in deeply weathered terrain — implications for geochemical exploration

Butt, C.R.M.; Lintern, M.J.; Anand, Ravi

doi:10.1016/s0169-1368(99)00029-3

Cited by 132 publications

(53 citation statements)

References 9 publications

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“…4p). The leaching process observed in this study is consistent with that experienced beneath organic horizons in humid areas with high rainfall (i.e., Alexander and Cady 1962;Butt and Zeegers 1992;Aleva 1994;Butt et al 1997). The climate of the Freetown peninsula has produced a cover of tropical rainforest that consists of broad-leafed trees with undergrowth.…”

Section: The Primary Pgm and Their Alteration In Weathered Rockssupporting

confidence: 83%

Weathering of PGE sulfides and Pt–Fe alloys in the Freetown Layered Complex, Sierra Leone

et al. 2017

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Fresh and weathered rocks and saprolite from Horizon B of the Freetown Layered Complex contain platinum-group minerals (PGM). The PGM in the fresh rocks are 1-7 μm across, including cooperite (PtS), isoferroplatinum (Pt 3 Fe), minor tetraferroplatinum (PtFe), tulameenite (Pt 2 FeCu), Os-bearing laurite (RuS 2 ), and other base metalsulfide (BMS)-bearing PGM. The weathered rocks contain fewer of those PGM but a high proportion of disordered Cu-(±Pd)-bearing Pt-Fe alloys. The saprolite hosts scarce, smaller (1-3 μm) ordered PtFe and disordered PtFe 3 . The PtFe alloys became increasingly Fe rich as weathering proceeded. Pt-Fe oxides appeared during weathering. Copper sulfides associated with the primary PGM and cooperite (with <3% Pd) were destroyed to provide the minor Cu and Pd found in some of the disordered Pt-Fe alloys. Platinum-and Pd-bearing saprolites have retained the original rock fabric and, to a depth of about 2 m, surround residual rocks that show progressive weathering (corestones). Ground water passing through the saprolite has transported Pt and Pd (and probably Au) in solution down slope into saprolite over unmineralized rocks. Transport is marked by changes in the Pt/Pd ratio indicating that the metals have moved independently. Palladium is present in marginally higher concentrations in the deeper saprolite than in the corestones suggesting some retention of Pd in the deeper saprolite. Platinum and Pd are less concentrated in the upper saprolite than the deeper saprolite indicating surface leaching. Alteration occurred over a long period in an organic and microbial rich environment that may have contributed to the leaching and transport of PGE.

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Section: The Primary Pgm and Their Alteration In Weathered Rockssupporting

confidence: 83%

Weathering of PGE sulfides and Pt–Fe alloys in the Freetown Layered Complex, Sierra Leone

et al. 2017

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“…One aim of geochemical exploration in such terrains is to find easily accessible sampling materials and appropriate analytical procedures, which provide indicators for the presence of buried deposits. Sampling and analysis of regolith materials, such as gossans, calcrete or laterite and soil, or vegetation are used to locate buried ore deposits (Lintern and Butt, 1993;Lintern et al, 1997;Butt and Lintern, 2000). Samples are commonly analysed for bpathfinder elementsQ associated with Au such as Sb, As, Bi, Cu, Pb, Se, Ag, Te and Zn besides the Au itself (Boyle and Jonasson, 1973;Boyle, 1979).…”

Section: Introductionmentioning

confidence: 99%

Bacillus cereus, gold and associated elements in soil and other regolith samples from Tomakin Park Gold Mine in southeastern New South Wales, Australia

Reith

McPhail

Christy

2005

Journal of Geochemical Exploration

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“…ASRIS), help inform decisions, for example, about geochemical exploration (e.g. dispersion of metals in the regolith) (Butt et al 2000), soil nutrient status (e.g. likely abundance of base cations), soil amendment requirements (e.g.…”

Section: Discussionmentioning

confidence: 99%

The pH of Australian soils: field results from a national survey

2011

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Abstract. The pH is one of the fundamental soil properties governing nutrient availability, metal mobility, elemental toxicity, microbial activity, and plant growth. The field pH of topsoil (0-0.10 m depth) and subsoil (~0.60-0.80 m depth) was measured on floodplain soils collected near the outlet of 1186 catchments covering >6 Mkm 2 (6 Â10 12 m 2 ) or~80% of Australia. Field pH duplicate data, obtained at 124 randomly selected sites, indicate a precision of 0.5 pH unit (or 7%), and mapped pH patterns are consistent and meaningful. The median topsoil pH is 6.5, while the subsoil pH has a median of 7 but is strongly bimodal (6-6.5 and 8-8.5). In most cases (64%) the topsoil and subsoil pH values are similar; among the sites exhibiting a pH contrast, those with more acidic topsoils are more common (28%) than those with more alkaline topsoils (7%). The distribution of soil pH at the national scale indicates the strong controls exerted by precipitation and ensuing leaching (e.g. low pH along the coastal fringe, high pH in the dry centre), aridity (e.g. high pH where calcrete is common in the regolith), vegetation (e.g. low pH reflecting abundant soil organic matter), and subsurface lithology (e.g. high pH over limestone bedrock). The new data, together with existing soil pH datasets, can support regional-scale decision-making relating to agricultural, environmental, infrastructural, and mineral exploration decisions.

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Evolution of regoliths and landscapes in deeply weathered terrain — implications for geochemical exploration

Cited by 132 publications

References 9 publications

Weathering of PGE sulfides and Pt–Fe alloys in the Freetown Layered Complex, Sierra Leone

Weathering of PGE sulfides and Pt–Fe alloys in the Freetown Layered Complex, Sierra Leone

Bacillus cereus, gold and associated elements in soil and other regolith samples from Tomakin Park Gold Mine in southeastern New South Wales, Australia

The pH of Australian soils: field results from a national survey

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