Mawson Kraton

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The Mawson Craton in its assumed maximum extent.

The Mawson craton (also Mawson continent or Mawson block ) was a craton formed during the Mesoproterozoic Era , which includes today's Gawler craton in South Australia and part of the East Antarctic craton . The Kraton was named after the Australian geologist and polar explorer Douglas Mawson , the first scientific description was made by the geologist Mark Fanning in 1995 as Mawson Block . The connection between the ice-free regions of King George V Land on the coast of Antarctica and the opposite coast of South Australia has been researched best .

The existence of the Mawson craton was defined by the Nimrod orogenesis and Kimban orogenesis around 1700 million years ago ( mya ) from various older crust fragments , the age of which dates back to 2.56 billion years. Its expansion within the Antarctic continent is not very certain due to the ice cover. Since in the Miller Range of the Transantarctic Mountains and the Shackleton Range a mountain formation can be proven before 1700 million years, geologists assume that the Antarctic part of the craton covers almost all of East Antarctica . However, geophysical data have also been published that suggest a much smaller portion of the Mawson craton in East Antarctica. In particular, the existence of the Gamburzew Mountains , up to 3400 m high but completely covered with ice, is difficult to interpret in the middle of a craton that has not been affected by orogenesis since the Ordovician . In more recent publications, the part of the East Antarctic craton facing the Indian Ocean with the basement of the southern Prince Charles Mountains is referred to as the Crohn craton , which only collided with the Mawson craton during the Pinjarra orogeny 1080 million years ago. In the course of this mountain formation, a continent was created that included what is now Australia and East Antarctica.

About 540 million years ago, this continent collided with parts of what is now Africa and India and became part of the supercontinent Gondwana . The tectonic division of the Mawson Craton occurred in the Upper Jurassic around 160 mya with rift formation between Antarctica and Australia. In the Upper Cretaceous an ocean floor spreading developed up to 43 mya, which led to their separation and separation of the Terre Adélie craton from the Gawler craton.

geology

Components and location

The Mawson kraton consisted of the originally connected Australian archaic Gawler kraton and the Terre Adélie kraton as well as the East Antarctic archaic Miller Range and the paleoproterozoic Shackleton Range .

The outcrops of the Miller Range emerge along the western flank of the Marsh Glacier . The most important geological unit is the Nimrod Group, whose oldest rocks are up to 3,100 mya old. The crystalline basement of the Paleoproterozoic Shackleton Range bites out at the southeast end of the Filchner-Ronne Ice Shelf , where it is visible as a window within the Read Mountains . For their little-explored rocks and geological history, an age of 2,000 to 1,900 mya is assumed. These geological units extend to the inland areas of the Ross orogen or today's Transantarctic Mountains .

The Australian and East Antarctic Cratonic Geological Units form the nucleus of the Mawson Craton. The Gawler and Terre Adélie cratons have a comparable geodynamic history. However, they differ significantly from those of the Miller and Shackleton ranges. All were subject to common orogenic processes, from which it was concluded that they were originally tectonically adjacent. However, there was no direct tectonic connection between the Australian and East Antarctic craton constituents.

The East Antarctic Kraton Blocks are mostly hidden under the mighty Antarctic Ice Sheet , which makes geological investigations difficult. In addition to the usual near-surface sampling, remote sensing is used in particular to identify hidden geological structures. They can be done by satellites or aircraft using a variety of methods.

Essential features that led to the hypothesis of the Mawson craton were orogenesis and tectonomagmatic processes that occurred at the respective areas of the kraton.

Eastern craton area

The Nimrod and Kimbam Orogenes occurred on the eastern continental margin facing today's Pacific . These tectonic processes are collectively referred to as the Nimrod-Kimban orogenesis, which were related to the subduction of lithospheric plates and the closure of ocean basins . In terms of time, they fall within the formation range of the hypothetical supercontinent Columbia , which developed from around 2,000 mya.

Nimrod orogeny

During the Nimrod orogeny, the Beardmore microcontinent collided with the southeastern rim of the Mawson craton. The Beardmore microcontinent formed a narrow and continuous terran strip, which, however, has not been exposed and probably extended from the central Transantarctic Mountains of Antarctica to the southern Australian border. Between the two, the Nimrod Group of the Miller Range and the basement of the Shackleton Range became wedged. The Nimrod orogenesis is a significant event between 1,730 and 1,720 mya. It is the oldest recorded orogenic event in East Antarctica. Evidence can be found in zircons of igneous protoliths (parent rock ) of archaic gneiss and metamorphic overprints. An eclogite block inserted in the gneiss experienced a metamorphic recrystallization at 1,720 mya.

Kimban orogeny

Location of the Eyre and Yorke Peninsula

The Kimban orogenesis occurred from 1,730 to 1,690 mya between the still connected South Australian Gawler / Terre Adélie craton and the hypothetical Curnamona craton to the east. It is understood as a profound tectono-volcano-metamorphic process during a transpressional phase. It is particularly well documented on the South Australian Eyre Peninsula , a southern part of the Gawler Craton. This peninsula is characterized by the different lithostratigraphic zones of the Cleve and Spencer domains, which are separated by the highly stressed Kalinjala Shear Zone. This shear zone can be followed up to the Mertz shear zone in the Terre Adélie craton. Both represent a geosuture on the eastern edge of the craton that separates the western archaic from the younger eastern crustal units. Effects of the Kimban orogeny also affected central areas of the Gawler craton with sedimentation and volcanism .

Northern and western craton area

During the subsequent geodynamic development of the Mawson Craton, further magmatic and tectonic processes occurred on the northern and western edges.

Magmatic sequences

In the late Proterozoic , the magmatic sequences of the Tunkillia and Ifould (1690 to 1670 mya) suites and the St Peter Suite (1620 to 1610 mya) were formed. The St Peter Suite closes west on the Eyre Peninsula and occupies a large part of the south-central South Australia. It borders the Mulgathing Complex to the west. The two are separated by the Coorabie Fault Zone. On the northern edge of the St Peter Suite, the Tunkillia and Ifould Suites are open.

Location of the neighboring Mertz glaciers and Ninnis glaciers

This was followed by the magmatic extrusions of volcanic rocks and plutonites in the Hiltiba Suite (1600 to 1580 mya) and in the Gawler Ranges (1600 to 1580 mya). The magmatites of the Hiltiba Suite are widespread in the Australian part of the Mawson kraton ref name = "mulgathing" />. Correlating occurrences also exist on the western edge of the Terre Adélie Craton and possibly between the East Antarctic Mertz Glacier and the Ninnis Glacier .

These igneous extrusions are characterized by near-surface plutonites and thick, flat volcanic rocks. Their causes have not yet been fully discussed. In many cases, anorogenic arch-typical intrusions along active continental margins or subduction zones are mentioned. Alternatively or in combination with this, magmas could have risen from a mantle plume .

These igneous sequences are characterized by large deposits of gold , nickel , iron and other ores .

Orogenesis

Between 1,570 and 1,540 mya, the Kararan orogeny developed north and west of the Karari Fault Zone. It is the most recent Proterozoic orogenic event in the Gawler craton and defines the archaic edges of the Australian Mawson kraton part or Gawler kraton there. The tectonic units north and west of the Karari Fault Zone do not contain any archaic protoliths (parent rocks). The most important tectonic unit is the Nawa domain. It extends along the Karari Fault Zone on the north-western edge of the craton and formed from allochthonous (non-local) terrans that accreted to the edge of the craton during subduction processes. The paragneiss protoliths of the Nawa domain were deposited around 1,740 mya and were then metamorphically overprinted. The Karari Fault Zone can therefore be viewed as a geosuture. Although this orogeny cannot be followed directly in East Antarctica because of the mighty Antarctic ice sheet , detritic (dragged) zircons occur in sedimentary rock deposits of correlating geographical lengths , which have pretrological properties and age comparable to those of the western Gawler craton. These zircons come from areas of the Transantarctic Mountains. Their peak values ​​date between 1,580 and 1,520 mya, which can be assigned to the Kararan orogeny.

Location of Western Australia

The little explored Coompana Block was formed further west of the Nawa domain. It is largely hidden under massive sediment packages. Some outcrops are exposed in southern Western Australia and are known as the Nornalup Complex. Its paragneiss protoliths are younger than those of the Nawa Domain. Their age is still unknown. They formed during the Kararan orogeny and accreted to the western edge of the Mawson craton. They were intruded by plutonites between 1,505 and 1,450 mya . Their occurrence is related to the reprocessing of shear zones in the Mawson Kraton during the accretion phase.

Separation of the Mawson Craton

The splitting of the Mawson Craton is related to the decay of Gondwana during a global stretching system . In East Antarctica, several basins with extensive sedimentation formed from the Devonian , such as B. the Beacon Supergroup and the Amery Group. Their powerful deposition sequences form a widespread overburden on basement units in West and East Antarctica .

The tectonic division of the Mawson Craton occurred in the Upper Jurassic around 160 mya with rift formation between Australia and Antarctica. In the Upper Cretaceous an ocean floor spread developed around 83 mya , which led to the complete separation of the two continental masses around 43 mya.

The Terre Adélie craton was separated from the Gawler craton and formed the Antarctic part of the Mawson craton with the Miller Range and the Shackleton Range. The Gawler craton remained in the Australian continent.

Web links

  • Georg Kleinschmidt: Geological development and tectonic structure of the Antarctic. In: Warning signal climate: The polar regions. Scientific evaluations, Hamburg. 376 pages. PDF
  • EV Mikhalsky: The Tectogenesis Stages of the Antarctic Shield: Review of Geochronological Data. In: Moscow University Geology Bulletin, 2007, Vol. 62, No. 3, pp. 143-154. doi: 10.3103 / S0145875207030027 , PDF
  • Anthony Reid: Geological overview Western Gawler Craton. In: Department for Energy and Mining, online article. PDF
  • Ian Fitzsimons: Proterozoic basement provinces of southern and southwestern Australia, and their correlation with Antarctica. In: Department of Applied Geology, Division of Resources and Environment, Journal Article. doi: 10.1144 / GSL.SP.2003.206.01.07 , alternatively

literature

  • Ian CW Fitzsimons: Proterozoic basement provinces of southern and southwestern Australia, and their correlation with Antarctica . In: Geological Society London Special Publication . tape 206 , 2003, p. 93-130 .
  • Justin L. Payne, Martin Hand, Karin M. Barovich, Anthony Reid & David AD Evans: Correlations and reconstruction models for the 2500-1500 Ma evolution of the Mawson Continent . In: Geological Society London Special Publication . tape 323 , 2009, pp. 319-355 .

Individual evidence

  1. ↑ Fanning, CM et al. (1995). The 'Mawson Block': once contiguous Archaean to Proterozoic crust in the East Antarctic Shield and Gawler Craton, Australia . Proceedings of the VII. International Symposium on Antarctic Earth Sciences, Siena 1995, p. 124
  2. ^ Geodynamic evolution of the northern Shackleton Range, East Antarctica: constraints from combined U-Pb and Lu-Hf zircon isotope analyzes. (PDF; 22 kB)
  3. ↑ Finn et al. Scouting craton's edgde in Paleo-Pacific Gondwana . In: Antarctica. Contributions to Global Earth Sciences, pp. 165-174, Springer-Verlag; Berlin, Heidelberg, New York, 2006, ISBN 3-540-30673-0
  4. ↑ Steven D. Boger (2011): Antarctica - Before and after Gondwana. Gondwana Research , Volume 19, pp. 335-371.
  5. ^ MH Monroe: Antarctica - Before and After Gondwana. In: Gondwana Research, Volume 19, Issue 2, March 2011, Pages 335-371. doi: 10.1016 / j.gr.2010.09.003 , alternatively
  6. ↑ Justin L. Payne, Martin Hand, Karin M. Barovich, Anthony Reid, and David AD Evans: Correlations and reconstruction models for the 2500-1500 Ma evolution of the Mawson Continent. In: Palaeoproterozoic Supercontinents and Global Evolution. Geological Society, London, Special Publications, 323, 319-355. doi: 10.1144 / SP323.16 , PDF
  7. ^ Hans-Martin Braun: Structural Investigations in Proterozoic to Lower Palaeozoic Rocks in the Read Mountains and Haskard Highlands of the Shackleton Range, Antarctica. In: Polarforschung 63 (2/3): 63-99, 1993 (published 1995). PDF
  8. ^ John W. Goodge and Carol A. Finn: Glimpses of East Antarctica: Aeromagnetic and satellite magnetic view from the central Transantarctic Mountains of East Antarctica. In: Journal of Geophysical Research, Vol. 155, B09103, 2010. doi: 10.1029 / 2009JB00689 , alternative
  9. ^ Nick MW Roberts: The boring billion? - Lid tectonics, continental growth and environmental change associated with the Columbia supercontinent. In: Geoscience Frontiers, Volume 4, Issue 6, November 2013, Pages 681-691. doi : 10.1016 / j.gsf.2013.05.004 , alternatively
  10. ↑ Tunkillia Suite, Stratigraphic Unit details. In: Australian Stratigraphic Units Database. Online article
  11. ↑ Ifould Suite, Stratigraphic Unit details. In: Australian Stratigraphic Units Database. Online article
  12. ^ St Peter Suite, Stratigraphic Unit Details. In: Australian Stratigraphic Units Database. Online article
  13. ↑ Anthony J. Reid and Sue J. Daly: The Mulgathing and Sleaford complexes of the Gawler Craton: a historical perspective of the geology and mineral potential. In: MESA Journal 52 March 2009. PDF
  14. ↑ Nicholas G. Direen, Allan G. Cadd, Patrick Lyons and Jonathan P. Teasdale: Architecture of Proterozoic shear zones in the Christie Domain, western Gawler Craton, Australia: Geophysical appraisal of a poorly exposed orogenic terrane. In: Precambrian Research, Volume 142, Issues 1-2, November 30, 2005, Pages 28-44. doi: 10.1016 / j.precamres.2005.09.007 , alternatively
  15. ↑ James W. Hall, Stijn Glorie, Anthony J. Reid, Samuel C. Boone, Alan S. Collins, Andrew Gleadow: An apatite U-Pb thermal history map for the northern Gawler Craton, South Australia. In: Geoscience Frontiers, Volume 9, Issue 5, September 2018, Pages 1293-1308. doi: 10.1016 / j.gsf.2017.12.010 , alternatively
  16. ^ Tom Wise, Rian Dutch, Mark Pawley, Clive Foss and Stephan Thiel: Building the Coompana Province. In: MESA Journal 88, pages 25–37, Published December 2018. Online article
  17. ^ Nornalup Complex, Stratigraphic Unit Details. In: Australian Stratigraphic Units Database. Online article
  18. ↑ Stephen McLoughlin, Sofie Lindström and Andrew N. Drinnan: Gondwanan floristic and sedimentological trends during the Permian – Triassic transition: new evidence from the Amery Group, northern Prince Charles Mountains, East Antarctica. In: Antarctic Science, Volume 9, Issue 3, September 1997, pp. 281-298. doi: 10.1017 / S0954102097000370 , alternatively
  19. ^ Joanne M. Whittaker, Simon E. Williams and R. Dietmar Müller: Revised tectonic evolution of the Eastern Indian Ocean. In: Geochemistry, Geophysics, Geosystems, Volume 14, Issue 6, Pages: 1685-2062, June 2013. doi: 10.1002 / ggge.20120 , alternative