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Petrography and geochronology of the Pele Mountain quartz-pebble conglomerate uranium deposit, Elliot Lake District, Canada

Laura Bergen and Mostafa Fayek
Petrography and geochronology of the Pele Mountain quartz-pebble conglomerate uranium deposit, Elliot Lake District, Canada
American Mineralogist (August 2012) 97 (8-9): 1274-1283

Abstract

Uranium deposits older than about 2200 Ma are generally hosted within quartz-pebble conglomerates and are a source of economic uranium. The genesis of these deposits is controversial and genetic models include hydrothermal, detrital/placer, and modified placer. Petrography of the uranium mineralogy from the Pele Mountain quartz-pebble conglomerate uranium deposit of the Elliot Lake district, Canada, shows that the dominant uranium minerals are thorite [(Th,U)SiO (sub 4) ] and brannerite [(U,Ca,Ce)(Ti,Fe) (sub 2) O (sub 6) ]. Uranium-lead (U-Pb) and lead-lead (Pb-Pb) isotopic analyses of thorite, brannerite, and galena were obtained using secondary ion mass spectrometry. Thorite has U-Pb age of 2489 + or - 24 in the quartzose conglomerate and 280 + or - 67 Ma in the quartz arenite. Brannerite has a U-Pb age of 2403 + or - 120 Ma. Thorite Pb-Pb ages range from 521 + or - 19 to 248 + or - 8 Ma in the arenite and from 2453 + or - 12 to 935 + or - 27 Ma in the conglomerate, whereas brannerite Pb-Pb ages are between 1335 + or - 0.11 and 848 + or - 13 Ma. Galena has a Pb-Pb age of 2659 + or - 8 Ma, which likely represents the age of the source formation that produced detrital galena. The rounded texture and U-Pb age of the conglomerate thorite corresponds to the depositional age of the host conglomerate bed of the Matinenda Formation, suggesting a detrital origin. The young U-Pb age of the thorite in the arenite represents the age of a resetting event. The brannerite, which replaces rutile, has a U-Pb consistent with fluid events associated with the Blezardian or Penokean Orogenic events, and is likely of hydrothermal origin. Therefore, based on the textures and variable ages of the uranium and sulfide minerals, the Pele Mountain quartz-pebble conglomerate uranium deposit is interpreted to be a modified placer-type deposit.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 97
Serial Issue: 8-9
Title: Petrography and geochronology of the Pele Mountain quartz-pebble conglomerate uranium deposit, Elliot Lake District, Canada
Affiliation: University of Manitoba, Department of Geological Sciences, Winnipeg, MB, Canada
Pages: 1274-1283
Published: 201208
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 44
Accession Number: 2012-079893
Categories: Economic geology, geology of ore depositsGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables, sketch map
N46°00'00" - N47°00'00", W83°00'00" - W81°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201242
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