Post-orogenic ( < 1500 Ma) thermal history of the proterozoic Eastern Fold Belt, Mount Isa Inlier, Australia

Abstract

The paucity of sedimentary rocks younger than 1500 Ma within the Mt. Isa Inlier renders it difficult to determine its post-orogenic exhumation and tectonic history, except by inference from the stratigraphy of the surrounding areas. We present hornblende, white mica, biotite and alkali feldspar 40Ar/39Ar data from the Eastern Fold Belt of the Inlier, which reveal a previously unrecognised complex, post-orogenic non-linear cooling history. Plateau and total fusion 40Ar/39Ar ages range between 1500 and 1130 Ma and record increases in regional cooling rates of up to 18°C/My during 1460-1410 and 1280-1050 Ma. Forward modelling of the alkali feldspar 40Ar/39Ar Arrhenius parameters reveals subsequ..