Architecture of a Palaeoproterozoic Rift System: evidence from the Fiery Creek Dome Region, Mt Isa terrane

The Mt Isa Rift Event is a Palaeoproterozoic intracontinental extension eve nt that defines the beginning of sedimentation into the Isa Superbasin in t he Western Fold Belt, Mt Isa terrane. In the mildly deformed Fiery Creek Do me region, on the northwest flanks of the Mt Isa Rift, elements of the Mt I sa Rift Event rift architecture are preserved without being intensely overp rinted by later deformation. In this region two discrete generations of nor thwest-dipping normal faults have been identified. Early generation normal faults were active during the deposition of fluvial and immature conglomera te and sandstone of the Bigie Formation. Renewed rifting and the developmen t of late-generation normal faults occurred during deposition of shallow-ma rine sandstone and siltstone of the lower Gunpowder Creek Formation. Differ ential uplift between tilt blocks formed an array of spatially and temporal ly discontinuous synrift unconformities on the crests of uplifted tilt bloc ks. Applying the domino model yields similar to 28% crustal extension for t he entire Mt Isa Rift Event. Northwest-striking transverse faults facilitat ed differential displacement along normal faults and formed boundaries to n ormal fault segments, creating smaller depositional compartments along half -graben axes. Three large domes were formed during laccolith emplacement. T hese domes produced palaeogeographical highs that divided the region into s ub-basins and were a source for the coarse fluvial synrift sequences deposi ted during the early Mt Isa Rift Event. The basin architecture in the Fiery Creek Dome region is consistent with northwest-south east-directed extensi on.