Detrital zircon U-Pb and 40Ar/39Ar hornblende ages from the Aileu Complex, Timor-Leste: provenance and metamorphic cooling history

Geochronological data from the Aileu Complex provide new constraints on the development of the Banda Arc-continent collision. Detrital zircons of the Aileu Complex have major U-Pb age modes at 270-440 Ma, 860-1240 Ma and 1460-1870 Ma, most compatible with a sediment source located in SE Asia as part of the now fragmented Sula Spur. 40Ar/39Ar cooling ages of hornblende demonstrate an extended cooling history across the complex, with the eastern parts cooling through hornblende closure temperature by 10 Ma and central parts by 6 Ma, consistent with a variable exhumation history. The onset of cooling by 10 Ma implies that metamorphism was probably coeval with initiation of the Banda Arc. We propose that the Aileu Complex cooling ages record deformation related to fragmentation of the Sula Spur and early development of the Banda Arc, rather than collision between the Australian continent and the Banda Arc.