Heavy Mineral Surveys in Exploration of Lateritic Terrain

Friedrich, G.; Marker, A.; Kanig, M.

doi:10.1016/b978-0-444-89095-5.50024-9

Cited by 13 publications

(9 citation statements)

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“…They are of reddish-brown colour (2.5 YR 4/6-5YR 4/6, 5/6), having a loose homogeneous consistency without visible sedimentary structures and are characterized by abundant goethite, kaolinite, quartz and gibbsite with subordinate serpentine and chlorite. Within this horizon, the proportions of HM species like zircon, ilmenite, Ti magnetite and rutile, primarily absent in the underlying ultramafics, increase upward while the proportions of "ultramafic" chrome-spinels decrease, being indicative for the partly transported origin of this profile portion (Friedrich et al, 1990;Fig. 2a).…”

Section: The Laterite Covers --Results and Discussionmentioning

confidence: 98%

“…This zone is considered to coincide with the erosion level of a former landscape on which the semi-autochthonous laterite has evolved (Oliveira and Trescases, 1985 ). Relic structures of the parent rock and HM assemblages indicate that the profile zone underneath the semi-autochthonous laterite represents the in-situ weathering product of the ultramafic bedrock, thus being referred to as autochthonous laterite (Friedrich et al, 1990). There is a gradational change to saprolite with depth, which in Jacupiranga consists predominantly of chlorite/vermiculite mixed layer minerals and in Las Buenas and Olympic of serpentine.…”

Section: The Laterite Covers --Results and Discussionmentioning

confidence: 99%

“…Consequently, the contents of "ultramafic" elements like Mn, Co, Zn and Cr are low. A gradual increase of the AI, Si, Ti and Zr contents towards the top is characteristic for the semi-autochthonous horizon (Friedrich et al, 1990). The compositional distinction between autochthonous and semi-autochthonous laterite is demonstrated by the Ti-AI correlation (Fig.…”

Section: Semi-autochthonous Lateritementioning

confidence: 86%

“…The processes leading to the formation of partly transported (semiautochthonous) laterites are not thoroughly investigated yet. Friedrich et al ( 1990 ) pointed out the significance of heavy minerals for the recognition of semi-autochthonous laterites. In this study, some aspects regarding the characterization and evolution of laterites overlying ultramafic complexes with emphasis on semi-autochthonous laterites are presented.…”

Section: Introductionmentioning

confidence: 99%

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Control of the distribution of Mn, Co, Zn, Zr, Ti and REEs during the evolution of lateritic covers above ultramafic complexes

Marker¹,

Friedrich

Carvalho³

et al. 1991

Journal of Geochemical Exploration

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Laterites above ultramafic complexes in Brazil and the Philippines consist of in-situ (autochthonous) and partly transported (semi-autochthonous) horizons. Enrichment and distribution of minor and trace elements in the laterites are controlled by weathering processes and the morphology of the peridotite massifs. Mn and Co migrate towards the base of doline-like depressions of the peridotite karst where they precipitate in the ferruginous horizon above the saprolite, due to rising pH and concentration of the solution. Mass balance calculations reveal absolute enrichment of Mn and Co and depletion of Zn and Cr. Semi-autochthonous laterites represent a mixture of Fe-Cr-rich limonitic material derived from ultramafic rocks and Al-Si-Ti-Zr-rich kaolinitic material derived from sialic rocks. They may reveal unusually high contents of A1203, SiO2, TiO2 and Zr, thus camouflaging the underlying ultramafic bedrock. During and after deposition of semi-autochthonous laterites, acidic leaching under humid (sub-) tropical climate leads to the mobilization of REES from the weathering products of sialic rocks. Subsequent migration and precipitation of REES together with Mn at the base of depressions result in concentrations of predominantly Ce which under favourable conditions exceed 0.5 wt.%. High proportions of sialic weathering material in laterites can be expected in geological settings where ultramafic and sialic rocks occur in close spatial association. Enrichment of REES in weathering profiles above ultramafics is favoured by the abundance of weathering material from REErich alkaline rocks like those of the Alkaline Complex of Jacupiranga, Brazil.

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Section: The Laterite Covers --Results and Discussionmentioning

confidence: 98%

Section: The Laterite Covers --Results and Discussionmentioning

confidence: 99%

Section: Semi-autochthonous Lateritementioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Control of the distribution of Mn, Co, Zn, Zr, Ti and REEs during the evolution of lateritic covers above ultramafic complexes

Marker¹,

Friedrich

Carvalho³

et al. 1991

Journal of Geochemical Exploration

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“…Magnetite and titanomagnetite are prevalent in basic magnetic rocks, and concentrations of these minerals may be higher in soils than in the associated parent rock material due to residual enrichment during soil formation processes (Singer and Fine, 1989). This enrichment occurs because these minerals have a higher resistance to weathering compared to a variety of other soil minerals (Friedrich et al, 1992). Maghemite is formed during weathering and soil genesis and is the product of magnetite oxidation (Schwertmann, 1988) or can be formed as a new mineral by dissolved iron crystallisation (Mullins, 1977).…”

Section: Magnetic Susceptibilitymentioning

confidence: 98%