Lützow-Holm complex

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The Lützow-Holm Complex (Lützow-Holm Complex LHC) is an orogenic belt in East Antarctica . It extends along the sea-side edge of the Queen Maud Land (Dronning Maud Land), starting at the eastern end of the Crown Prince Olav Coast , where it joins the Rayner Province . From there it runs to Lützow-Holm-Bucht on the Prinz-Harald-Coast . There it borders on the Sør Rondane as well as the Queen Fabiola Mountains (Yamato Mountains) and the Belgica Mountains , both of which form the Yamato-Belgica complex .

Education and structure

  • Queen Maud Land with the Lützow-Holm complex, the Sôya Coast and the Yamato Belgica complex

  • East African Orogen (marked in blue) and Kuunga Orogen (marked in red)

The Lützow-Holm complex is seen as a collection of three arched islands . The oldest originated in the Neo-Archean around 2500 mya in the southern LHC areas along the Prince Harald Coast. The paleoproterozoic, approx. 1800 mya old terran, which extends along the Sôya Coast , developed in central areas . The Sôya Coast represents the north-eastern section of the Lützow-Holm Bay. In the Neoproterozoic , the third crustal unit formed around 1000 mya in northern areas along the Kronprinz-Olav Coast . During the late Neoproterozoic, they collided between 600 and 500 mya during Kuunga orogeny, which led to the formation of the greater continent of Gondwana .

Rocks and metamorphoses

The LHC is mainly composed of felsic to intermediate orthogneiss , such as charnockite and biotite - gneisses containing hornblende and variously composed meta sediments with e.g. B. pelites , psammites , quartzites and marbles together. Meta basites with mafic to ultramafic granulites , amphibolites and trondhjemites are also represented. The metamorphic grade of the complex increases from amphibolite facies in the northeastern areas to granulite facies in southwestern areas. The middle area forms the transition zone with metamorphic degrees of embossment between the amphibolite and granulite facies.

Zircons and delivery areas

Detritic (dragged) zircons were found in all three LHC zones . Zircon cores from eight metasediment samples with associated igneous sequences can be divided into two dominant groups. The former group is defined by late Meso - to Neoproterozoic (approx. 1000 to 630 mya) zircons from the northeastern part of the LHC on the Crown Prince Olav Coast and the northern Sôya Coast areas. The second group contains predominantly neo-archaic to paleoproterozoic (approx. 2800 to 2400 mya) zircons in the southwestern area of ​​the Lützow-Holm-Bucht. This zircon distribution could have its delivery areas in the corresponding magmat suites of the LHC.

However, further zirconium investigations led to the assumption that some of them could come from more distant delivery areas. So come neighboring Meso- to Neoproterozoic, such as. B. Rayner Province or the East Indian East Ghats and Sri Lanka in question. Other hypotheses extend the delivery areas to South India , Madagascar and Southeast Africa . The detritic zircons from the Highland Complex of Sri Lanka, for example, show a similar age spectrum as those of the middle LHC area, which suggests that these two complexes may have formed during the earliest Neoproterozoic in a similar tectonic regime. It is also assumed that it formed a geosuture between the northern LHC area and the Vijayan complex of Sri Lanka, in which the remains of an approx. 1000 mya old magmatic island arch complex were built. The collision occurred in the period from 645 to 521 mya.

Web links

  • Kazuyuki Shiraishi, Yoshikuni Hiroi, Yoichi Motoyoshi and Keizo Yanai: Plate tectonic development of Late Proterozoic paired metamorphic complexes in eastern Queen Maud Land, East Antarctica. In: Gondwana Six: Structure, Tectonics, and Geophysics. (1987) Geophys. Monogr. Ser., Vol. 40. doi: 10.1029 / GM040p0309 , alternative
  • Kazuki Takahashi, Toshiaki Tsunogae, M. Santosh, Yusuke Takamur and Yukiyasu Tsutsumi: Paleoproterozoic (approx. 1.8 Ga) arc magmatism in the Lützow-Holm Complex, East Antarctica: Implications for crustal growth and terrane assembly in erstwhile Gondwana fragments. In: Journal of Asian Earth Sciences, Volume 157, p. 245-268. doi: 10.1016 / j.jseaes.2017.07.053 , alternatively

Individual evidence

  1. ↑ Yusuke Takamura, Toshiaki Tsunogae, M. Santosh and YukiyasuTsutsumi: Detrital zircon geochronology of the Lützow-Holm Complex, East Antarctica: Implications for Antarctica – Sri Lanka correlation. In: Geoscience Frontiers Volume 9, Issue 2, March 2018, Pages 355-375. doi: 10.1016 / j.gsf.2017.08.006 , alternatively
  2. ^ Joseph G. Meert: A synopsis of events related to the assembly of Eastern Gondwana. In: Tectonophysics 362 (1): 1-40 • February 2003. doi: 10.1016 / S0040-1951 (02) 00629-7 , alternative
  3. ↑ Yasuhito Osanai, Krishnan Sajeev, Nobuhiko Nakano, Ippei Kitano and others: UHT granulites of the Highland Complex, Sri Lanka I: Geological and petrological background. In: Journal of Mineralogical and Petrological Sciences, Volume 111 (2016) Issue 3. doi: 10.2465 / jmps.151227 , PDF
  4. ↑ A. Kröner, Y. Rojas-Agramonte, KVW Kehelpannala, T. Zack and others: Age, Nd – Hf isotopes, and geochemistry of the Vijayan Complex of eastern and southern Sri Lanka: A Grenville-age magmatic arc of unknown derivation. In: Precambrian Research, Volume 234, September 2013, Pages 288-321. doi: 10.1016 / j.precamres.2012.11.001 , alternatively