Tectono-magmatic evolution of the Neoarchean Yalgoo dome (Yilgarn Craton): Diapirism in a pre-orogenic setting

• Gneiss domes occur in any orogenic and anorogenic domain of the continental crust, from Precambrian cratons to present-day active orogens. They commonly contain a core of granitic rocks and/or high-grade metamorphic rocks, overlain by a mantle of lower-grade rocks. Evolutionary models of many gneiss domes are controversial. We use new structural and geochronological data to constrain the tectono-magmatic evolution of the Yalgoo dome in the Yilgarn Craton of Western Australia. The granite–migmatite core of the dome shows an overall domal foliation pattern, associated with radial and outwardsplunging lineations. A high-strain zone with top-outwards sense of shear (the Badja decollément) occurs along the granite–greenstone boundary. The greenstone sequence contains an angular unconformity that likely developed during doming. We show that doming, associated with outward flow of supracrustal material, was accompanied by the emplacement of large volumes of granitic magma at 2760–2750 Ma. The dome-scale finite strain pattern resulted from diapiric granite emplacement into the greenstone cover, with negligible background regional stress. Granitic plutons flanking the Yalgoo dome show a similar, first-order structural architecture. The dome-forming fabric is locally overprinted by a discordant, north-trending foliation caused by folding that likely developed at c. 2700 Ma, during the Neoarchean Yilgarn orogeny.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Geologi (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Geology (hsv//eng)

Nyckelord

geochronology

microstructures

preferred orientation

structural geology

tectonics

quartz crystallographic

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vet (ämneskategori)

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