Evidence for 1808–1770 Ma bimodal magmatism, sedimentation, high-temperature deformation and metamorphism in the Aileron Province, central Australia

2015-12-14T13:14:42Z (GMT) by M. Hand D. Howlett T. Raimondo
<div><p>Field relationships and LA-ICP-MS U–Pb geochronology from the Yundurbungu Hills (Aileron Province, central Australia) reveal a record of 1808–1770 Ma bimodal magmatism, sedimentation, high-temperature deformation and metamorphism. Specifically, the data presented here provide the first unequivocal evidence for <i>ca</i> 1774 Ma high-temperature deformation and metamorphism during the 1790–1770 Ma Yambah Event in the southern part of the North Australian Craton. Granitic lithologies were synkinematically emplaced between 1808 and 1770 Ma, with early phases recording D<sub>1</sub> deformation and the youngest phase postdating D<sub>1</sub> deformation. The protolith to a D<sub>1</sub> deformed metasedimentary unit was deposited between 1792 and 1774 Ma, followed by the intrusion and deformation of a composite mafic–felsic magmatic association at <i>ca</i> 1774 Ma. An S<sub>1</sub> migmatitic fabric in the composite mafic–felsic gneiss is truncated by the youngest (<i>ca</i> 1770 Ma) phase of granitic magmatism, constraining the timing of S<sub>1</sub> deformation. A second period of sedimentation appears to post-date D<sub>1</sub> deformation, with deposition occurring sometime after <i>ca</i> 1774 Ma. Subsequent overprinting during the 1590–1550 Ma Chewings Event is recorded by the growth of metamorphic monazite and zircon. This event deformed the <i>ca</i> 1774 Ma S<sub>1</sub> gneissic fabric, producing a composite S<sub>1</sub>/S<sub>2</sub> gneissic fabric in early metasedimentary and magmatic lithologies and a simple S<sub>2</sub>-only fabric in lithologies that were intruded or deposited after <i>ca</i> 1774 Ma. Consistent with previous work, we suggest that localised high-temperature deformation and bimodal magmatism at <i>ca</i> 1774 Ma in the Yundurbungu Hills is consistent with a back-arc setting linked to prolonged north-directed subduction.</p></div>