088

A. Deposition of the Coonterunah Group in deep water

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basatt

B. Intrusion of Carlindi granitoids causes doming and metamorphism of Coonterunah Group

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Norma! subduction

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Backarc

Arc/continental margin crust

Magmatic arc    Accretionsry

(high temperaturę    complex

mełamorphism)    (high pressure

Forearc metamorphism)

Mantle lithosphere

Asthenosphere Slab

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Shallow subduction

Mantle lithosphere

Plume tectonics

Collision at sites of asthenospheric downweiling

Dispersed magmatism & intraarc sedimentation (high temperaturę metamorphism)

Arc/continental crust

Mantle metasomatism & slab melting

(adakite, high*Mg andesite)

Asthenosphere

Subduction of young, warm _    oceanie

Slab melting ^hospłwre (TTG)

Figurę 4.4: Schematic diagram showing the early evolution of Pilgangoora Belt. Tire entire terrain was then tilted and faulted that the present map view largely reflects the ancient cross-sectior

Continental crust

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Extension and lithosphere aeneration at sites of asthenospheric upwelling

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Mantle lithosphere    .    'Plurn^    dikes

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Asthenosphere

Figurę 1. Precambrian tectonic regimes may have ranged from normal subduction similar to Phanerozoic Earth (top panel), to a modified form involving shallow subduction of thickened, morę buoyant, oceanie lithosphere (middle panel), to a setting dominated by mantle plumes (bottom panel). On modern Earth, both piąte- and plume-related mechanisms operate, and it is likely that a similar relationship existed on early Earth. In three dimensions, piąte tectonic boundaries for linear belts are tied to, and influence, asthenospheric convection, whereas in plume settings, the lithosphere moves over generally fixed zones of asthenospheric upwelling.

Stratigraphic columns 2    3    4

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A A A A A A A ^b7\'

SPC

C. Uplift and erosion of Coonterunah- Carlindi terrain fomns an erosional unconformity

D. Deposition in shallow water of Warrawoona SPC and basalts onto the unconformity

Fig. 7. (a) Simpłificd gcological map of the EP, showing dis-tribution of main groups around the granitoid complcxcs, and the location of stratigraphic columns (l 5). Bold letters denote granitoid complcx names: C = Carlindi, CD = Corunna Downs, M = Mount Edgar, S = Shaw, Y = Yule. (b) Stratigraphic columns from section profiles in (a), showing age dates. I: East Strelley greenstone bclt; 2: Panorama greenstone belt in the North Pole Domc; 3: Coongan greenstone belt; 4: northwestern Kelley greenstone belt; 5: Marblc Bar greenstone belt. Time linę on right pinned at base of Euro Basalt, but linearly scaled independent of stratigraphic columns, showing three stage model of partial convectivc ovcrtum: crosses denote periods of granitoid intrusion. Combined legend for (a) and (b): 1: undivided granitoid rocks; 2: Coonterunah Group; 3: lower Warrawoona Group (undivided in (a), mainly basalt); 4: felsic volcanic Duffer Formation; 5: Panorama Formation; 6: upper Warrawoona Group (undividcd in (a), mainly Euro Basalt); 7: ca. 3325-3315 Ma Wyman Formation; 8: ca. 3308 Ma Budjan Crcck Formation; 9: Gorgc Crcck Group; 10: Dc Grcy Group; 11: ductilc shear zonc; 12: fault. Agc data from Barley and Pickard (1999), Buick et al. (1995, 2002), Nelson (2002), Thorpe et al. (I992a,b), van Koolwijk et al. (2001), and Zcgcrs et al. (2001).

(b)

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Unconformity

Age (Ma)

°° |r3308 oB

-3325

3346-

(3363)

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♦ ♦ ♦ ♦

-3515

06.12.02