STRUCTURAL DEVELOPMENT OF THE KING LEOPOLD OROGEN, KIMBERLEY REGION, WESTERN AUSTRALIA

The King Leopold Orogen consists of two tectonic units: the Hooper Terrane, a complex of Early Proterozoic metasedimentary rocks, migmatites, felsic volcanics, basic sills and granitoid intrusions; and folded rocks of the overlying Early Proterozoic Kimberley Basin succession and a Late Proterozoic glacigene sequence. The oldest deformation (D1) affects metasedimentary rocks of the Hooper Terrane and is characterized by layer-parallel structures confined to zones of high strain. D1 was accompanied by a metamorphic event (M1), which was locally high grade. D2 post-dates the felsic volcanics but pre-dates granitoid intrusion and consists of upright NW-trending folds. D3 post-dates deposition of the Kimberley Basin succession and, in the Hooper Terrane, takes the form of WNW- to NW-trending shear zones which combine dextral, sinistral and south-sideup movements. In the northwest the Kimberley Basin succession is folded and faulted by D3 to form the Yampi Fold Belt. Two fold phases are recognized. D3a, which comprises flat-lying folds and N-directed thrusts, is refolded by D3b, comprising folds and thrusts linked to shear zones in the Hooper Terrane. D3 was accompanied by amphibolite-facies metamorphism (M2). D4 post-dates deposition of Late Proterozoic glacigene rocks, and produced SW-directed folds and thrusts to form the Precipice Fold Belt. Throughout the area discussed the contact between the Hooper Terrane and the Kimberley Basin succession is sheared or thrust. D1, D2 and M1 are Early Proterozoic in age with D1 and M1 possibly forming in an extensional environment, while D2 may represent a (?) sinistral strike-slip environment. D3 and M2 are the result of Middle to Late Proterozoic intracratonic compression and may be related to a collision located to the southwest. D4 accompanied Late Proterozoic to Early Phanerozoic sinistral faulting in the Halls Creek Orogen. A major crustal structure of probable D2 age separates the Hooper Terrane from (?) Archaean basement under the Kimberley Basin. It controls the northeast limit of the Yampi Fold belt (D3) and ramping of thrusts in the Precipice Fold Belt (D4, and could represent the site of an early Proterozoic terrane boundary. © 1990.