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A non-plate tectonic model for the yilgarn craton, western Australia - exploration implications and comparisons with the superior craton, Canada.

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Harris, Lyal B.; Bédard, Jean H. (2015). A non-plate tectonic model for the yilgarn craton, western Australia - exploration implications and comparisons with the superior craton, Canada. In: Québec mines 2015, 23-26 novembre 2015, Québec, Canada.

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Résumé

The Yilgarn Craton, Western Australia, comprises terranes traditionally interpreted as forming and being assembled through subduction-accretion processes, viz. the 3.2-2.6 Ga Narryer & Southwestern, 3.0-2.6 Ga Youanmi, 2.76-2.63 Kalgoorlie and 2.95-2.63 Ga E Yilgarn. The boundaries of Nd model age domains correlate with contacts between the Youanmi and Kalgoorlie terranes portrayed by P-wave seismic tomography. These two terranes host the majority of Au deposits. Komatiite sequences intruded the edges of these distinct continental blocks within mantle plume-related rifts (Mole et al. 2014, PNAS) depicted by enhanced long wavelength gravity images. Major Au deposits overlie rift-related transfer faults. Comparison between seismic profi les and centrifuge models suggests regional folds in the mid-upper crust formed during displacement on extensional shear zones. Rift margins localize subsequent regional sinistral transpressional shear zones which are reactivated and displaced by dextral transcurrent shears; orogenic Au mineralization occurred during both dextral and sinistral shearing. Similarly, Neoarchean granitegreenstone sequences of the Superior Province formed during rifting and fragmentation of terranes that previously constituted a composite Superior I craton. In the Abitibi, broad ductile shear zones however dextrally offset and rotate early N-S structures that may represent rifts or rift-related transfer faults. Conjugate brittle-ductile transcurrent shears formed during bulk N-S shortening displace earlier structures. Recognition of transfer faults is thus far more diffi cult than in the Yilgarn. Undoing shear displacements portrays a N-S to NNE-SSW elongate, denser/mafi c dominated crustal block, interpreted as a > 300 km long oceanic plateau, in which all gold deposits in the Abitibi are situated. The contact between the Abitibi-Opatica ‘terranes’ of the Superior Province is not marked by a high strain shear zone nor by an abrupt change in metamorphic grade, and the Opatica simply represents basement to the Abitibi (Daoudene et al. 2014, MB 2014-04, MERN). Similarly, re-interpretation of seismic and MT data for the Yilgarn Craton shows that the Narryer Terrane is basement to the Youanmi Terrane, instead of being accreted to its NW margin. Field, geochronological, isotopic and geophysical studies in both the Yilgarn and Superior cratons do not support plate tectonic models for subduction and arc accretion for their formation and deformation.

Type de document: Document issu d'une conférence ou d'un atelier
Informations complémentaires: Affiche
Mots-clés libres: plaque tectonique; craton; Australie
Centre: Centre Eau Terre Environnement
Date de dépôt: 11 nov. 2020 17:10
Dernière modification: 11 nov. 2020 17:10
URI: http://espace.inrs.ca/id/eprint/4106

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