The Musgrave Province: Stitching north, west and south Australia

Abstract

The Musgrave Province in central Australia is an east-west trending ∼120,000 km2 region composed of lithologic units that range in age from earliest Mesoproterozoic to Neoproterozoic. It is one of the few terrains in Australia that records significant Grenvillian-aged tectonism, and has a distinctly younger geological history than the surrounding fragments of Proterozoic Australia. Compared to other Proterozoic terranes of Australia the evolution of the Musgrave Province is poorly understood. The region contains evidence for the development of earliest Mesoproterozoic arc-related magmatism, with major juvenile crustal additions comprising intercalated felsic and mafic gneisses with protolith ages ranging from ca. 1.60 to 1.54 Ga. This period of arc magmatism was followed by closure of the ocean separating the North Australian Craton (NAC) from the South Australian Craton (SAC) at ca. 1.54 Ga. Arc magmatism and collision was followed by a period of extension during which protoliths to the metasedimentary rocks of the eastern Musgrave Province were deposited at ca. 1.4 Ga. The combined juvenile Nd isotopic signature and detrital zircon ages from these metasediments suggests provenance from non-Australian sources, with possible sources originating from Laurentia. Granitic magmatic events occurred at ca. 1.3 and 1.20-1.14 Ga, the latter comprising the voluminous A-type granites of the Pitjantjatjara Supersuite. The intrusion of these magmatic units provide key temporal constraints on deformational events, and are coeval with the voluminous A-type suites of Laurentia which would invite correlation of Australia with Laurentia at ca. 1.30-1.14 Ga. These magmatic episodes are accompanied by deformation at granulite facies at ca. 1.30 Ga (unnamed event), and 1.23-1.15 Ga (Musgrave Orogeny). These deformation/metamorphic events have completely recrystallised any primary layering within the pre 1.30 Ga rocks, forcing interpretations on their genesis to be inferred from geochemical and isotopic data. The tectonic significance of these events is not clear, however they may form part of a larger Grenville-aged deformational belt extending into the western Australian Albany-Fraser Province and Antarctica. Emplacement of the voluminous mafic-ultramafic Giles Complex and associated granulite facies metamorphism of the Giles Event occurred at ca. 1.078 Ga. The layered intrusions of the Giles Complex are generally fault bound, and are considered to represent discrete bodies emplaced in an extensional regime associated with generation of the Warakurna Large Igneous Province. The ca. 1.08 Ga Alcurra Dolerite, unnamed ca. 1.0 Ga olivine dolerites, and ca. 0.8 Ga Amata Dolerite dissect much of the Musgrave Province. The Alcurra Dolerite and unnamed olivine dolerite dykes have been proposed as originating from a modified sub-continental lithospheric mantle, whereas the Amata Dolerite is proposed to be plume related, coinciding with the initiation of rifting creating the Centralian Superbasin. An earliest Cambrian intraplate transpressional event is recorded in the ca. 550 Ma Petermann Orogeny. This resulted in deep crustal exhumation of much of the northern Musgrave Province from beneath the Centralian Superbasin, with mylonitic deformation recorded at pressures of ∼12 kbar and temperatures of 700-750 °C. © 2008 Elsevier B.V. All rights reserved.