The Arltunga Nappe Complex, macdonnell ranges, Northern Territory, Australia∗

Forman, David J.

doi:10.1080/00167617108728756

Cited by 60 publications

(5 citation statements)

References 2 publications

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“…The Heavitree Quartzite was sampled near Ruby Gap Gorge, within the Palaeozoic Arltunga Nappe Complex on the northeastern margin of the Amadeus Basin (Fig. 6) (Forman, 1971). The quartzite in this area is part of the essentially unmetamorphosed and weakly deformed basal thrust sheet of the Ruby Gap Nappe, an antiformal stack of thrust sheets which have been increasingly deformed and metamorphosed to upper greenschist facies towards the north (Dunlap et al , 1995).…”

Section: Resultsmentioning

confidence: 99%

Testing long‐term patterns of basin sedimentation by detrital zircon geochronology, Centralian Superbasin, Australia

2007

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Detrital zircon geochronology of Neoproterozoic to Devonian sedimentary rocks from the Georgina and Amadeus basins has been used to track changes in provenance that reflect the development and inversion of the former Australian Superbasin. Through much of the Neoproterozoic, sediments appear to have been predominantly derived from local sources in the Arunta and Musgrave inliers. Close similarities between the detrital age signatures of late Neoproterozoic sedimentary rocks in the two basins suggests that they were contiguous at this time. A dominant population of 1.2–1.0 Ga zircon in Early Cambrian sediments of the Amadeus Basin reflects the uplift of the Musgrave Inlier during the Petermann Orogeny between 560 and 520 Ma, which shed a large volume of detritus northwards into the Amadeus Basin. Early Cambrian sedimentary rocks in the Georgina Basin have a much smaller proportion of 1.2–1.0 Ga detritus, possibly due to the formation of sub‐basins along the northern margin of the Amadeus Basin which might have acted as a barrier to sediment transfer. An influx of 0.6–0.5 Ga zircon towards the end of the Cambrian coincides with the transgression of the Larapintine Sea across central Australia, possibly as a result of intracratonic rifting. Detrital zircon age spectra of sedimentary rocks deposited within this epicontinental sea are very similar to those of coeval sedimentary rocks from the Pacific Gondwana margin, implying that sediment was transported into central Australia from the eastern continental margin. The remarkably consistent ‘Pacific Gondwana’ signature of Cambro‐Ordovician sediments in central and eastern Australia reflects a distal source, possibly from east Antarctica or the East African Orogen. The peak of the marine incursion into central Australia in the early to mid Ordovician coincides with granulite‐facies metamorphism at mid‐crustal depths between the Amadeus and Georgina basins (the Larapinta Event). The presence of the epicontinental sea, the relative lack of a local basement zircon component in Cambro‐Ordovician sedimentary rocks and their maturity suggest that metamorphism was not accompanied by mountain building, consistent with an extensional or transtensional setting for this tectonism. Sediments deposited at ∼435–405 and ∼365 Ma during the Alice Springs Orogeny have detrital age signatures similar to those of Cambro‐Ordovician sedimentary rocks, reflecting uplift and reworking of the older succession into narrow foreland basins adjacent to the orogen.

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Section: Resultsmentioning

confidence: 99%

Testing long‐term patterns of basin sedimentation by detrital zircon geochronology, Centralian Superbasin, Australia

2007

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“…In addition, the basement was involved in a series of basement‐cored nappes (e.g. the White Range, Giles Creek and Ruby Gap nappes), which form a large duplex structure, located at the northern margin of the Amadeus Basin (Forman, 1971; Teyssier, 1985; Dunlap & Teyssier, 1995). Propagation of the thrusts towards the south is documented by detailed geochronological studies (Dunlap et al ., 1997).…”

Section: Implications For the Alice Springs Event In The Arunta Blockmentioning

confidence: 99%

Exhumation of the lower crust during crustal shortening: an Alice Springs (380 Ma) age for a prograde amphibolite facies shear zone in the Strangways Metamorphic Complex (central Australia)

Ballèvre

Möller

Hensen

2000

Journal Metamorphic Geology

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Foliated garnet‐bearing amphibolites occur within the West Bore Shear Zone, cutting through granulite facies gneisses of the Strangways Metamorphic Complex. In the amphibolites, large euhedral garnet (up to 3 cm) occurs within fine‐grained recrystallized leucocratic diffusion haloes of plagioclase–quartz. The garnet and their haloes include a well‐developed vertical foliation, also present in the matrix. This foliation is the same as that cutting through the unconformably overlying Neoproterozoic Heavitree Quartzite. The textures indicate syn‐ to late kinematic growth of the amphibolite facies mineral assemblages. All mineral assemblages record an arrested prograde reaction history. Noteworthy is the growth of garnet at the expense of hornblende and plagioclase, and the breakdown of staurolite–hornblende to give plagioclase–gedrite. These dehydration reactions indicate increasing P–T conditions during metamorphism, and suggest heating towards the end of a period of intense deformation. Temperature estimates for the garnet–amphibolite and related staurolite–hornblende assemblages from the shear zone are about 600 °C. Pressure is estimated at about 5 kbar. An Sm–Nd isochron gives an age of 381±7 Ma for the peak metamorphism and associated deformation. This age determination confirms that amphibolite facies conditions prevailed during shear zone development within the Strangways Metamorphic Complex during the Alice Springs Orogeny. These temperature conditions are significantly higher than those expected at this depth assuming a normal geothermal gradient. The Alice Springs Orogeny was associated with significant crustal thickening, allowing exhumation of the granulite facies, Palaeoproterozoic, lower crust. Along‐strike variations of the tectonic style suggest a larger amount of crustal shortening in the eastern part of the Alice Springs Orogeny.

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“…However, these terranes are now believed to record the same structural and metamorphic evolution at different crustal levels ( Camacho & Fanning, 1995). The location of the Woodroffe Thrust west of the Musgrave Ranges has been a matter of conjecture for many years, due to the previous lack of geological data on the remote outcrops between the Mann and Petermann Ranges ( Forman, 1972; Stewart, 1995). However, a revised location of the Woodroffe Thrust beneath Quaternary cover has been inferred on the basis of field observations and geophysical data (Fig.…”

Section: Geological Setting and Previous Workmentioning

confidence: 99%

“…Outcrops comprising the southern Pottoyu Hills form part of the extensive Pottoyu Granite Complex, which has Rb–Sr whole‐rock ages of c . 1190 and 1150 Ma ( Forman, 1972), and is intruded by mafic dykes which have geochemical affinities to the c . 800 Ma Amata Dyke Swarm.…”

Section: Structural Setting and Field Relationshipsmentioning

confidence: 99%

Regional high‐pressure metamorphism during intracratonic deformation: the Petermann Orogeny, central Australia

Scrimgeour¹,

Close²

1999

Journal Metamorphic Geology

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The Petermann Orogeny is a late Neoproterozoic to Cambrian (c. 560–520 Ma) intracratonic event that affected the Musgrave Block and south‐western Amadeus Basin in central Australia. In the Mann Ranges, within the central Musgrave Block, Mesoproterozoic granulite facies gneisses, granites and mafic dykes have been substantially reworked by deep crustal non‐coaxial strain of late Neoproterozoic to early Cambrian age. Dolerite dykes have recrystallized to garnet granulite facies assemblages, associated with the development of a mylonitic fabric at P=12–13 kbar and T =700–750 °C. Migmatization is restricted to discrete shear zones, which represent conduits for hydrous fluids during metamorphism. Peak metamorphism was followed by decompression to c. 7 kbar, reflecting exhumation of the terrane along the south‐dipping Woodroffe Thrust. In scattered outcrops north of the Mann Ranges, peak metamorphism occurred at P=9–10 kbar and T =c. 700 °C. The Woodroffe Thrust separates these deep crustal mylonites from granites that were metamorphosed during the Petermann Orogeny at P=c. 6–7 kbar and T =c. 650 °C. The similarity in peak temperatures at different crustal levels implies an unusual thermal regime during this event. The existence of a relatively elevated geotherm corresponding with Th‐ and K‐enriched granites that were in the mid‐crust during the Petermann Orogeny suggests that radiogenic heat production may have substantially contributed to the thermal regime during metamorphism. This potentially has implications for the mechanisms by which intra‐plate strain was localized during this event.

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The Arltunga Nappe Complex, macdonnell ranges, Northern Territory, Australia∗

Cited by 60 publications

References 2 publications

Testing long‐term patterns of basin sedimentation by detrital zircon geochronology, Centralian Superbasin, Australia

Testing long‐term patterns of basin sedimentation by detrital zircon geochronology, Centralian Superbasin, Australia

Exhumation of the lower crust during crustal shortening: an Alice Springs (380 Ma) age for a prograde amphibolite facies shear zone in the Strangways Metamorphic Complex (central Australia)

Regional high‐pressure metamorphism during intracratonic deformation: the Petermann Orogeny, central Australia

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