Palaeoproterozoic to Mesoproterozoic Geology of North Queensland
Palaeoproterozoic to Mesoproterozoic Geology of North Queensland
Palaeoproterozoic to Mesoproterozoic Geology of North Queensland
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Correlating George<strong>to</strong>wn and Mt Isa SuccessionsMaximum depositional ages for the Etheridge Group are similar <strong>to</strong> those <strong>of</strong>the Soldiers Cap and Mt Isa Groups and deformation events appear <strong>to</strong>correlate BUT ……•The provenance <strong>of</strong> the lower Etheridge Group is very different <strong>to</strong> any Mt IsaInlier Proterozoic sediments.•The provenance <strong>of</strong> the upper Etheridge Group is similar <strong>to</strong> Mount Isa Inlier,but requires an E-W event between ~1660 and 1640 Ma <strong>to</strong> bring these terranes<strong>to</strong>gether.Other differences between George<strong>to</strong>wn and Mt Isa:•Normal geothermal gradient (clockwise P-T-t with superimposed high templowpressure event) vs dominantly high geothermal gradient (anti-clockwiseP-T-t) (e.g. Boger & Hansen, 2004; Cihan et al., 2006; Rubenach 1992)•Intensity <strong>of</strong> N-S folding decreases westwards <strong>to</strong>wards Mt Isa•E-W vs N-S directed structural grain (e.g. O’Dea et al., 1997)•S-type vs I- and A-type magmatism at ~1555 Ma (e.g. Black & McCulloch, 1990;Wyborn et al., 1992)•Any rigorous geodynamic model needs <strong>to</strong> take these differences in<strong>to</strong>account