Resumen de Post-Palaeoproterozoic thermochronology of the Precambrian northern Western Australian shield
U.D. Weber, Barry P. Kohn, David A. Foster, D.R. Nelson, A.J. Gleadow
Reconnaissance 40Ar/39Ar dating of K-feldspars and muscovites, and fission track and (U-Th)/He thermochronometry on apatites has been applied to ~1 x l(Y' km3 of the northern Western Australian Shield.
The study area includes the Archaean northern Yilgarn Craton and Pilbara Craton, and the inteiwening Proterozoic basins. K-feldspar 40ArA9Ar data reveal cooling from ~ 1800-1600 Ma or 1200-1000 Ma depending on the sample and the 4"Ar//39Ar muscovite ages lie between -900-1000 Ma. Apatite fission track data yield ages between 290-180 Ma with confined horizontal mean track length ranging between 11.5- 14.3 pm and standard deviations of track length distributions falling between 1.1-2.2 pm. Preliminary (UTh)/He apatite data yield ages ~250 Ma or older. Numerical modelling o f40A r/39A r and fission track data reveals phases o f accelerated cooling, which can be related to major tectonic Proterozoic and Phanerozoic events hitherto unrecorded in this vast area.
