Legacy product - no abstract available

Legacy product - no abstract available

This digital data represents an interpretation of the metamorphic geology of Geoscience Australia's Northern Australian Craton project (NAC) in the Northern Territory and Western Australia. It consists of linework, polygons and attributes for both metamorphosed and non-metamorphosed geological features.

No abstract available

Metamorphic map of Australia

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

The Harts Range Metamorphic Complex (HRMC) in the eastern Arunta Province is part of the exhumed core of the intracratonic Alice Springs Orogen. SHRIMP U-Pb dating of intrusive rocks and metamorphism in the HRMC has constrained the timing and character of tectonism, showing that mutliphase deformation under high grade metamorphic conditions spanned at least 50 m.y. The age of a syn-tectonic pegmatite dyke in the northern HRMC records ductile shearing on E-W trending shear zones during or just after the ~380 Ma Pertnjara Movement, possibly related to extension after the main contractional phase. The age of a second syn- to late-deformational pegmatite dyke in the eastern Harts Range suggests that a SW-vergent fold and thrust system in the eastern HRMC formed during the ~360 Ma Brewer Movement. This deformation coincided with the intrusion of small granitic bodies in the northern HRMC, and the formation of rare metamorphic zircon in metasedimentary rocks during a period of crustal thickening. Metamorphic monazite and zircon reflect high-grade metamorphism during the ~330 Ma Mount Eclipse Movement, which coincided with the formation of a flat-lying, kyanite grade foliation in basement rocks of the HRMC. This foliation and later large-scale doming might reflect extensional collapse of the Alice Springs Orogen towards the end of the orogenic cycle. 40Ar-39Ar cooling ages indicate that much of the HRMC was exhumed at that time. Localisation of ASO tectonism in the eastern Arunta Province appears to be a result of thermal weakening associated with the ~480-460 Ma Larapinta Event, which partitioned plate boundary stresses into central Australia.

This study arose out of the regional geological mapping of the Cairns Hinterland which was begun in 1956 as a joint undertaking by the Bureau of Mineral Resources and the Geological Survey of Queensland. It is another unit in the series of dating surveys stemming from the co-operation between the Australian National University and the Bureau of Mineral Resources. One of us (D.A.W.), assisted by F. de Keyser, was responsible for the supervision of the field operations connected with this study; another (C.D.B.) was concerned with the general investigation of these acid igneous rocks; the others (J.R.R. and A.W.W.) were assisted by J. A. Cooper in the production of the K-Ar results. We are indebted to W. Compston and M. J. Vernon for permission to publish the Rb-Sr results on the Palaeozoic rocks, and for assistance with measurements on the Croydon Volcanics. Samples were chosen with the aim of defining more closely the time limits of the two periods of activity that were thought to have produced the granites and acid volcanic rocks now covering about half the area. Regional mapping evidence had already suggested that a Precambrian age for the older granites was a reasonable possibility, and that the second event took place in the late Palaeozoic. Fossils collected by the mapping parties suggested that these periods were pre-Upper Ordovician and late Devonian/Carboniferous to Permian/Triassic (White, 1961). The present set of age data offers a most gratifying confirmation of some of these conclusions and provides a basis for the selection of samples for further study.