Evidence for 1808–1770 Ma bimodal magmatism, sedimentation, high-temperature deformation and metamorphism in the Aileron Province, central Australia
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 ca 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 D1 deformation and the youngest phase postdating D1 deformation. The protolith to a D1 deformed metasedimentary unit was deposited between 1792 and 1774 Ma, followed by the intrusion and deformation of a composite mafic–felsic magmatic association at ca 1774 Ma. An S1 migmatitic fabric in the composite mafic–felsic gneiss is truncated by the youngest (ca 1770 Ma) phase of granitic magmatism, constraining the timing of S1 deformation. A second period of sedimentation appears to post-date D1 deformation, with deposition occurring sometime after ca 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 ca 1774 Ma S1 gneissic fabric, producing a composite S1/S2 gneissic fabric in early metasedimentary and magmatic lithologies and a simple S2-only fabric in lithologies that were intruded or deposited after ca 1774 Ma. Consistent with previous work, we suggest that localised high-temperature deformation and bimodal magmatism at ca 1774 Ma in the Yundurbungu Hills is consistent with a back-arc setting linked to prolonged north-directed subduction.
