The intra-cratonic evolution of the central eastern Mount Isa Inlier, northwest Queensland, Australia

Synthesis of the proterozoic evolution of the Mt Isa Inlier

“…In the Eastern Fold Belt, the earliest stages of sedimentation of Calvert Superbasin age were domi- Betts et al (1998Betts et al ( , 2003a and Lister (2001, 2002) Loosveld 1989a;Page et al 1997;Page 1998) (Figure 6). Remnants of the Isa Superbasin are also preserved in the Tommy Creek Block (Figures 3, 4) where ca 1630 -1620 Ma felsic and mafic igneous rocks are intercalated with siltstone, marble, sandstone, graphitic, micaceous schist, and mafic and porphyritic felsic lavas of the Tommy Creek beds (Hill et al 1992) (Figure 6).…”

“…Initial attempts to correlate deformation and metamorphic events between the Eastern and Western Fold Belts assumed an early episode of north -south shortening, followed by a major period of east -west shortening that resulted in the dominant north -south structural grain of the inlier (Bell 1983;Winsor 1986;Loosveld & Schreurs 1987;Reinhardt 1987Reinhardt , 1992Loosveld 1989aLoosveld , 1992Reinhardt & Rubenach 1989;Hill et al 1992;Adshead-Bell 1998). In some areas (Connors & Lister 1995;Bell & Hickey 1998), detailed overprinting studies of structural fabrics have led to proposals of more complex deformation schemes, and recent structural and seismic studies show significant differences in the styles of crustal shortening, regional tectonic transport directions, and the overall crustal architecture between the Western and Eastern Fold Belts .…”

Structural cross-section based on the Mt Isa deep seismic transect

“…Schists in the belt commonly contain two foliations, an early micaceous schistosity (S 1 ) parallel to bedding, and a later crenulation (S 2 ) of that schistosity. Regions of overturned stratigraphy and several mylonitic shear zones have been interpreted as D 1 features and give the Marimo region a dismembered thrust nappe character (Donchak et al 1983;Loosveld 1989). S 2 is related to the upright, north -south folds that dominate the map pattern.…”

Sequential development of a mid-crustal fold-thrust complex: evidence from the Mitakoodi Culminationin the eastern Mt Isa Inlier, Australia

“…The Marimo -Staveley Block lies to the east across the steeply east-dipping Overhang Shear Zone (Huang 1994a) (Figures 1, 3). This block is approximately north -south-trending and contains upright tight to isoclinal coaxial F 1 and F 2 folds in a mid-greenschist facies sequence of downward-facing slate, pelite, and psammite (Loosveld 1989) …”

“…For example, F 1 folds are eastwest-trending in the Tommy Creek Block (Hill et al 1992) and the northern part of the Mitakoodi Culmination, and north -south-trending along the eastern limb of the Duck Creek Anticline and the Marimo -Staveley Block (Loosveld 1989). The 908 variation of orientations of D 1 structures is attributed to refolding during later deformation (Figures 3, 13).…”