Paleoproterozoic–earliest Mesoproterozoic sequences in the Mount Isa region of northern Australia preserve a 200 Myr record(1800–1600 Ma)of intracontinental rifting,culminating in crustal thinning,elevated heat flow...Paleoproterozoic–earliest Mesoproterozoic sequences in the Mount Isa region of northern Australia preserve a 200 Myr record(1800–1600 Ma)of intracontinental rifting,culminating in crustal thinning,elevated heat flow and establishment of a North American Basin and Range-style crustal architecture in which basin evolution was linked at depth to bimodal magmatism,high temperature-low pressure metamorphism and the formation of extensional shear zones.Rifting initiated in crystalline basement≥1840 Ma old and produced three stacked sedimentary basins(1800–1750 Ma Leichhardt,1730–1670 Ma Calvert and 1670–1575 Ma Isa superbasins)separated by major unconformities and in which depositional conditions progressively changed from fluviatilelacustrine to fully marine.By 1685 Ma,a deep marine,turbidite-dominated basin existed in the E and basaltic magmas had evolved in composition from continental to oceanic tholeiites as the crust became increasingly thinned and attenuated.Except for an episode of minor deformation and basin inversion at c.1640 Ma,sedimentation continued across the region until onset of the Isan Orogeny at 1600 Ma.A near-identical record of crustal thinning and basaltic magmatism accompanied basin formation(lower Willyama Supergroup)in the formerly contiguous Broken Hill region from 1730–1670 Ma.展开更多
文摘Paleoproterozoic–earliest Mesoproterozoic sequences in the Mount Isa region of northern Australia preserve a 200 Myr record(1800–1600 Ma)of intracontinental rifting,culminating in crustal thinning,elevated heat flow and establishment of a North American Basin and Range-style crustal architecture in which basin evolution was linked at depth to bimodal magmatism,high temperature-low pressure metamorphism and the formation of extensional shear zones.Rifting initiated in crystalline basement≥1840 Ma old and produced three stacked sedimentary basins(1800–1750 Ma Leichhardt,1730–1670 Ma Calvert and 1670–1575 Ma Isa superbasins)separated by major unconformities and in which depositional conditions progressively changed from fluviatilelacustrine to fully marine.By 1685 Ma,a deep marine,turbidite-dominated basin existed in the E and basaltic magmas had evolved in composition from continental to oceanic tholeiites as the crust became increasingly thinned and attenuated.Except for an episode of minor deformation and basin inversion at c.1640 Ma,sedimentation continued across the region until onset of the Isan Orogeny at 1600 Ma.A near-identical record of crustal thinning and basaltic magmatism accompanied basin formation(lower Willyama Supergroup)in the formerly contiguous Broken Hill region from 1730–1670 Ma.
