Complementarite des rayons X et de la microscopie electronique pour la determination des diverses phases d'une argile zincifere

Rivière, Marc Serge; Rautureau, Michel; Besson, Gérard; Steinberg, M.; Amouri, M.

doi:10.1180/claymin.1985.020.1.05

Cited by 5 publications

(3 citation statements)

References 7 publications

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“…3b) is supportive of a desulfidation mechanism (reaction 1), although a sulfur-free reaction of the type (Segnit 1961 (4) sillimanite quartz may have also been responsible for the formation of coexisting gahnite and sillimanite in sulfide-free rocks, such as sillimanite-pod rocks, where minor amounts of gahnite occur in sillimanite crystals. Although the adsorption of zincite on kaolinite has not been recognized in natural settings, Rivière et al (1985) reported a spatial association between aluminous clays and Zn(OH) 2 . Further support for the participation of desulfidation mechanisms involving sphalerite in the formation of zincian spinel in Colorado comes from the mantling of gahnite by sphalerite and the presence of a fine dusting of sphalerite inclusions in gahnite at Cotopaxi (Fig.…”

Section: Zincian-spinel-forming Reactionsmentioning

confidence: 99%

Zincian Spinel Associated With Metamorphosed Proterozoic Base-Metal Sulfide Occurrences, Colorado: A Re-Evaluation of Gahnite Composition as a Guide in Exploration

Heimann

Spry

Teale³

2005

The Canadian Mineralogist

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Zincian spinel [(Zn,Fe,Mg)Al 2 O 4 ] is an accessory mineral in a variety of rock types, in particular, metamorphosed massivesulfide deposits, pegmatites, aluminous metasedimentary rocks, skarns, marbles, and sulfide-bearing granulites. Textural and compositional studies of zincian spinel in thirteen Proterozoic sulfide deposits metamorphosed to the amphibolite and granulite facies in Colorado, many of which are spatially associated with Mg-rich alteration zones, shed new light on the use of zincian spinel composition as a guide to sulfide ores. Zincian spinel from the Independence, Bon Ton, and Sedalia deposits and some cases from the Green Mountain, Betty, Caprock, Cinderella, and Cotopaxi deposits show compositions that correspond to zincian spinel associated with metamorphosed massive-sulfide deposits hosted by hydrothermally altered Fe-Al-rich metasedimentary and metavolcanic rock units elsewhere in the world (Gahnite 44-90 Hercynite 0-45 Spinel 0-25). However, other compositions of zincian spinel from these last five deposits and from three locations in the Wet Mountains (Marion and Amethyst prospects and an unnamed prospect) are depleted in Zn and enriched in Mg and Fe. These examples of Mg-rich zincian spinel occur in rocks in or adjacent to metamorphosed massive sulfides dominated by Mg-rich minerals such as phlogopite, anthophyllite, gedrite, tremolite, forsterite, cummingtonite, sapphirine, cordierite, enstatite, and clinohumite. The composition of zincian spinel in and surrounding metamorphosed massive-sulfide deposits is influenced by reactions involving Zn and Fe sulfides, as well as by bulk-rock composition, which in the case of many metamorphosed massive-sulfide deposits in Mg-rich alteration zones in Colorado, causes a marked enrichment in the spinel component of zincian spinel, to Gahnite 0-65 Hercynite 0-50 Spinel 25-90. Knowledge of the geological setting must be considered when using zincian spinel as a guide to metamorphosed massive-sulfide deposits.

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Section: Zincian-spinel-forming Reactionsmentioning

confidence: 99%

Zincian Spinel Associated With Metamorphosed Proterozoic Base-Metal Sulfide Occurrences, Colorado: A Re-Evaluation of Gahnite Composition as a Guide in Exploration

Heimann

Spry

Teale³

2005

The Canadian Mineralogist

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“…Since then, this economically valuable clay mineral has been studied in some detail Steinberg et al, 1985;Dupuis et al, 2003). Rivière et al (1985) and Steinberg et al (1985) also described another Zn-rich smectite in the studied material, namely sauconite. This mineral has not been recovered nor identified in this study.…”

Section: Introductionmentioning

confidence: 86%

Miocene karsts and associated Fe–Zn-rich minerals in Aïn Khamouda (Central Tunisia)

Bruyère

Putter

Decrée

et al. 2010

Journal of African Earth Sciences

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“…Segnit proposed that• the ZnO originally was adsorbed on kaolinite but this relationship has not been recognized in natural settings. Riviere et al (1985) reported a spatial association between aluminous clays and Zn-hydroxide. Alternatively, Zn derived from exhalative processes may have subsequently been linked to organic or phosphatic material.…”

Section: Quartz-gahnite Horizonsmentioning

confidence: 99%

Metamorphic and Metamorphogenic Ore Deposits

Vokes¹,

Marshall²,

Spry³

1998

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Meta-exhalites consist of a variety of rock types including iron formation, coticule (garnet-quartz rock), tourmalinite, quartz-gahnite rock, apatite-rich rock, zincian staurolite-bearing rock, and barite-rich rock. Such lithologies may be spatially associated with a diversity of ore deposits, but they are particularly linked to sea floor base metal sulfides that formed in rift settings. Meta-exhalites generally form layers less than 2 m thick, above, below, in, and along strike from stratiform or exhalative ore deposits. Geochemical diagrams for iron formations, coticules, and tourmalinites (chondrite-normalized rare earth element (REE), ternary Al-Fe-Mn, Al/ (Al+ Fe+ Mn) vs. Fe/Ti, Ti0 2 vs. Al 2 0 3 ) suggest ~riable contributions of detrital material and hydrothermal components, The detrital component, terrigeilous or elastic, is generally less than 30 wt percent for iron formations, whereas for coticules and tourmalinites it is generally 30 to 70 wt percent and greater than 70 wt percent, respectively. Of the major constituents of meta-exhalites, Fe, Mn, B, P, and Zn generally have a hydrothermal source, whereas Al and Ti are from detrital elastic material. Silica can have hydrothermal and/ or detrital sources. Hydrogenous contributions are generally small.The variable setting, mineralogy, primary sedimentary structures, geochemistry, and lithological variants of exhalites show that precursor constituents formed under a variety of physicochemical conditions (e.g., T, fo 2 , pH, ionic strength, Js 2 , fco 2 ) and were derived from different sources (elastic and volcanic).Iron formations, coticules, and tourmalinites form by the replaceme9t of permeable aluminous sediment~ and by exhalation into submarine brine pools. Hydrothermal fluids responsible for the formation of precursors to meta-exhalites range in temperature from approximately 100° to 400°C. Layering in meta-exhalites reflects rapid fluctuations in Eh-pH conditions, metal contents, f 82 , Jc 02 , and detrital input. Fractionation of Fe and Mn in the hydrothermal fluids is due to gradual increases in pH_ or Eh during mixing of ambient seawater with the fluids and may account for differences in proximity br"iron formations and coticules to sulfide deposits. The amount of hydrothermal input via venting, fluid/ rock ratio, bottom current drift, and the degree of basin isolation from elastic sedimentation also dictate the chemical composition and mineralogy of meta-exhalites.The presence of a meta-exhalite is indicative qf a fossil zone of sea floor hydrothermal activity and, as such, can be utilized as a field guide in the exploration for ore deposits, particularly base metal sulfides. Relative abundance of certain minerals (e.g., iron carbonates, apatite, gahnite, zincian staurolite), bulk compositional variations that record increased ratios of hydrothermal components to detrital material, characteristic elements and elemental ratios, variations in the compositions of mineral phases (e.g., Zn to Fe ratio of staurolite, gahnite, and hogbomite as well a...

show abstract

Complementarite des rayons X et de la microscopie electronique pour la determination des diverses phases d'une argile zincifere

Cited by 5 publications

References 7 publications

Zincian Spinel Associated With Metamorphosed Proterozoic Base-Metal Sulfide Occurrences, Colorado: A Re-Evaluation of Gahnite Composition as a Guide in Exploration

Zincian Spinel Associated With Metamorphosed Proterozoic Base-Metal Sulfide Occurrences, Colorado: A Re-Evaluation of Gahnite Composition as a Guide in Exploration

Miocene karsts and associated Fe–Zn-rich minerals in Aïn Khamouda (Central Tunisia)

Metamorphic and Metamorphogenic Ore Deposits

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