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GEOREF RECORD

Preliminary results of a study on gold dispersion in laterite around the Misseni gold indicator, Mali

Frederic Sea, Marc G. Tanguay, Pierre Trudel and Guy Perrault
Resultats preliminaires d'une etude sur la dispersion de l'or en milieu lateritique autour de l'indice aurifere de Misseni, au Mali (in Recent developments in the study of Archean gold deposits--Developpements recents dans l'etude des gisements d'or archeens, Pierre Trudel (editor))
Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre (December 1990) 27 (12): 1686-1698

Abstract

The study of gold dispersion in laterite above a gold zone is based on 58 analyses of soil samples from two shafts and one trench located in the Misseni Au anomaly area, Mali. The bedrock in this area includes Birrimian volcano-sedimentary rocks (Lower Proterozoic). At Misseni, primary gold is associated with disseminated copper and iron sulphides in a silicified shear zone within andesites. The area is dominated by a dry tropical climate, including two contrasting seasons (a short rainy season and a long dry season) and a mean annual rainfall of < 1500 mm. The Misseni area is characterized by low plateaux averaging 350 m in altitude and by a very thick weathered cover (> 35 m) of laterite topped by iron cuirasse. In general, the laterite profiles show, from bottom to top: 1) saprolite ('pistache' laterite), variegated and mottled clays; 2) iron hardpan; 3) iron cuirasse, and 4) eluvium. Mineralogical analyses reveal that the laterite is dominated by kaolinite, goethite, quartz, mica and hematite. The mean chemical composition is SiO (sub 2) 46, Al (sub 2) O (sub 3) 22, Fe (sub 2) O (sub 3) 20, TiO (sub 2) 1, K (sub 2) O 1, CaO 0.05 and Na (sub 2) O 0.03%. The laterite profile showed an iron enrichment and a silica depletion (upper part: 0-2 m) and a very weak variation in alumina. The iron enrichment is correlated with increasing goethite toward the surface, whereas silica decreases with lower mica content. The gold concentration increases in the iron hardpan immediately below the cuirasse. The upper saprolith provided low gold values, but these increase with depth. Conversely, As and Co tend to increase towards the surface (0-2 m) in the hardpan, cuirasse, or eluvium. A deep core (> 35 m) assayed for Au reveals: 1) anomalous gold in laterite (0.2-1.0 ppm), and 2) higher gold values (5.5-8.8 ppm) occurring between 11.45 and 17.75 m depth, associated with oxide minerals in certain saprolith levels, reflecting probably an ancient groundwater table.


ISSN: 0008-4077
EISSN: 1480-3313
Coden: CJESAP
Serial Title: Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre
Serial Volume: 27
Serial Issue: 12
Title: Resultats preliminaires d'une etude sur la dispersion de l'or en milieu lateritique autour de l'indice aurifere de Misseni, au Mali
Translated Title: Preliminary results of a study on gold dispersion in laterite around the Misseni gold indicator, Mali
Title: Recent developments in the study of Archean gold deposits--Developpements recents dans l'etude des gisements d'or archeens
Author(s): Sea, FredericTanguay, Marc G.Trudel, PierrePerrault, Guy
Author(s): Trudel, Pierreeditor
Affiliation: Univ. Montreal, Dep. Genie Miner., Montreal, QC, Canada
Affiliation: Inst. Rech. Explor. Miner., Montreal, QC, Canada
Pages: 1686-1698
Published: 199012
Text Language: French
Summary Language: English
Publisher: National Research Council of Canada, Ottawa, ON, Canada
Meeting name: Geological Association of Canada and Mineralogical Association of Canada, joint annual meeting special session on Archean gold deposits
Meeting location: Montreal, QC, CAN, Canada
Meeting date: 19890515May 15-17, 1989
Accession Number: 1991-000829
Categories: Economic geology, geology of ore depositsGeochemistry of rocks, soils, and sediments
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus.
N10°10'00" - N10°19'60", W06°10'00" - W06°00'00"
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 1991
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