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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Robertson River areaDeformation & metamorphismHowever, detailed microstructural (FIA analysis <strong>of</strong> porphyroblasts) & CHIMEdating <strong>of</strong> monazite from the Robertson River area give a somewhat differentpicture (Cihan & others, JCU)Porphyroblasts containing FIA1 <strong>to</strong> FIA3, overgrew a S1/S2 matrix foliationFIA1 and FIA2 related <strong>to</strong> early N-S shortening associated with monazite dated at1625±15 MaFIA3 related <strong>to</strong> E-W shortening associated with monazite dated at 1586±6 MaThermobarometry indicates pressure increased progressively <strong>to</strong> 6-7kb duringFA1 <strong>to</strong> FA3S3 – a flat lying fabric associated with matrix monazite dated at 1564±8 MaProbably related <strong>to</strong> decompression and exhumationFIA4 related <strong>to</strong> NW-SE shortening associated with monazite dated at 1542±8 MaAssociated with lower pressure-high temperature metamorphism at 3-4kbS4 younger fabric associated with with monazite dated at 1512±5 Ma