The synchronism of crustal thickening and high T/low P metamorphism in the Mount Isa Inlier, Australia 1. An example, the central Soldiers Cap belt

Evolution of the Isan Orogeny at the southeastern margin of the Mt Isa Inlier

“…Metamorphic grade increases from greenschist facies in the northwest to upper amphibolite facies in the southeast and reaches a maximum of 400 -600 MPa and 650 -7008C (Jaques et al 1982;Foster & Rubenach 2006). In previous microstructural and metamorphic studies, it has been argued that pressures and temperatures reached a peak during the early stages of the Isan Orogeny (Loosveld 1989;Rubenach & Barker 1998). This interpretation is consistent with U -Pb zircon, monazite and 40 Ar/ 39 Ar ages of ca 1600 -1580 Ma that have been interpreted to represent the age of peak metamorphism (Page & Sun 1998; Perkins & Wyborn 1998; Giles & Nutman 2002).…”

“…Whilst early tectonic fabrics related to crustal shortening have been recognised elsewhere in the eastern Mt Isa Inlier (Loosveld 1989;Hill et al 1992;Betts et al 2000Betts et al , 2006O'Dea et al 2006), this explanation seems inconsistent with the lack of recognisable f1 folds in the present study area. It may be that f1 fold hinges have been obliterated by transposition, that they are simply not exposed, or that we are dealing with f1 structures that are larger than the study area.…”

Isograd pattern and regional low-pressure, high-temperature metamorphism of pelitic, mafic and calc-silicate rocks along an east – west section through the Mt Isa Inlier

“…Contrasting models have been proposed for the structural and metamorphic evolution of the area particularly with respect to which deformation event formed the anticline and the sequence of metamorphic events (Ryburn et al 1988;Loosveld 1989;Rubenach & Barker 1998;Rubenach & Lewthwaite 2002;Rubenach 2005). Detailed mapping and microstructural work undertaken by Rubenach and Barker (1998) and Rubenach and Lewthwaite (2002) indicated a more complicated structural and metamorphic history for the Snake Creek Anticline than proposed by earlier workers.…”

Tectono‐metamorphic evolution of the Mary Kathleen fold belt, northwest Queensland: A reflection of mantle plume processes?

“…1982;Loosveld 1988;Reinhardt & Rubenach 1988). This range is similar to that established in many of the other northern Australian Proterozoic terranes, suggesting elevated heat flow during metamorphism, in association with shortening (Etheridge et al , 1987Loosveld 1988;Reinhardt & Rubenach 1988;Loosveld & Etheridge 1990;Sandiford & Powell 1991).…”