Geochronology,paleomagnetism and magnetic fabric of metamorphic rocks in the northeast Fraser Belt,Western Australia |
| |
| Authors: | B De Waele S A Pisarevsky |
| |
| Institution: | 1. Tectonics Special Research Centre, University of Western Australia , 35 Stirling Highway, Crawley, WA, 6009, Australia bdewaele@bgs.ac.uk;3. Tectonics Special Research Centre, University of Western Australia , 35 Stirling Highway, Crawley, WA, 6009, Australia |
| |
| Abstract: | The first zircon U–Pb SHRIMP dating on high-grade meta-igneous units in the northernmost parts of the Fraser Belt along the southern margin of the Western Australian Yilgarn Craton, reveal crystallisation ages between 1299 ± 10 and 1250 ± 23 Ma. A small number of older xenocrystic zircons, incorporated in some samples, indicate the presence of Late Paleoproterozoic crust in the region. Zircon that crystallised within a melt accumulated in the neck of a boudinaged mafic unit was dated at 1296 ± 4 Ma, indicating that the emplacement of the igneous protoliths took place syntectonically. The anisotropy of magnetic susceptibility of the granulites indicates minimum axes with a mean inclination of 4° towards 130°, corresponding to a nearly vertical southwest–northeast (50–230°) magnetic foliation. This is very close to the structural trend of the Fraser Belt suggesting that the magnetic fabric was acquired syntectonically, during the collision between the Yilgarn and Gawler Cratons. The paleomagnetic data on the granulites overlap with published poles for various 1.2 Ga units in the Albany Belt and the 1.2 Ga Fraser dykes, possibly suggesting that the remanence was acquired during the second stage of the Fraser tectonism. A younger magnetisation component resembles a pole of uncertain age published for Bremer Bay in the Albany Belt. |
| |
| Keywords: | Fraser Belt geochronology magnetic fabric metamorphic rocks paleomagnetism SHRIMP uranium–lead dating Western Australia zircon |
|
|
