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Geology of the orogenic Cheminis gold deposit along the Larder Lake-Cadillac deformation zone, Ontario

Bruno Lafrance
Geology of the orogenic Cheminis gold deposit along the Larder Lake-Cadillac deformation zone, Ontario
Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre (2015) 52 (12): 1093-1108

Abstract

The Larder Lake-Cadillac deformation zone (LLCDZ) is one of two major, auriferous, deformation zones in the southern Abitibi subprovince of the Archean Superior Province. It hosts the Cheminis and the giant Kerr Addison-Chesterville deposits within a strongly deformed band of Fe-rich tholeiitic basalt and komatiite of the Larder Lake Group (ca. 2705 Ma). The latter is bounded on both sides by younger, less deformed, Timiskaming turbidites (2674-2670 Ma). The earliest deformation features are F1 folds affecting the Timiskaming rocks, which formed either during D1 extensional faulting or during early D2 north-south shortening related to the opening and closure, respectively, of the Timiskaming basin. Continued shortening during D2 imbricated the older volcanic rocks and turbidites and produced regional F2 folds with an axial planar S2 cleavage. D2 deformation was partitioned into the weaker band of volcanic rocks, producing the strong S2 foliation, L2 stretching lineation, and south-side-up shear sense indicators, which characterize the LLCDZ. Gold is present in quartz-carbonate veins in deformed fuchsitic komatiites (carbonate ore) and turbiditic sandstone (sandstone-hosted ore), and in association with disseminated pyrite in altered Fe-rich tholeiitic basalts (flow ore). All host rocks underwent strong mass gains in CO (sub 2) , S, K (sub 2) O, Ba, As, and W, during sericitization, carbonatization, and sulphidation of the host rocks, suggesting that they interacted with the same hydrothermal fluids. Textural relationships between alteration minerals and S (sub 2) cleavage indicate that mineralization is syn-cleavage. Thus, gold was deposited as hydrothermal fluids migrated upward along the LLCDZ during contractional, D2 south-side-up shearing. The gold zones were subsequently modified during D (sub 3) reactivation of the LLCDZ as a dextral transcurrent fault zone.


ISSN: 0008-4077
EISSN: 1480-3313
Coden: CJESAP
Serial Title: Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre
Serial Volume: 52
Serial Issue: 12
Title: Geology of the orogenic Cheminis gold deposit along the Larder Lake-Cadillac deformation zone, Ontario
Author(s): Lafrance, Bruno
Affiliation: Laurentian University, Mineral Exploration Research Centre, Sudbury, ON, Canada
Pages: 1093-1108
Published: 2015
Text Language: English
Summary Language: French
Publisher: National Research Council of Canada, Ottawa, ON, Canada
References: 40
Accession Number: 2016-014740
Categories: Economic geology, geology of ore deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, geol. sketch maps
N48°04'00" - N48°04'00", W79°42'00" - W79°42'00"
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 201608
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