 |
| Titel |
Grenville-Sveconorwegian detrital zircon signatures in the High Arctic, from East Greenland to Severnaya Zemlya |
| VerfasserIn |
Henning Lorenz, Jarosław Majka, Alexander Larionov, David Gee  |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250058145
|
|
|
|
|
|
| Zusammenfassung |
| Research during the last two decades has documented detrital zircon age signatures in the
Eurasian high Arctic, providing unambiguous evidence that Mesoproterozoic basement,
apparently similar to that in the Grenville-Sveconorwegian Orogen, is well represented in the
vast continental shelves of the Kara, Barents and Norwegian seas. Its provenance age
signatures are present in both Neoproterozoic and Palaeozoic successions within the
Timanide, Caledonide and Uralide (including Novaya Zemlya) orogens, and the Taimyr and
Severnaya Zemlya fold belts.
On Svalbard, all Caledonian provinces provide evidence of Grenville-age source terrains.
The oldest metasediments on Nordaustlandet (Brennevinsfjorden and Helvetesflya groups)
yielded Mesoproterozoic detrital zircon ages of 1.05Â Ga and older. They are intruded by
c. 0.95 Ga granites and unconformably overlain by Murchisonfjorden Supergroup
sediments, containing 0.95Â Ga zircons. Johansson et al. (2005) reported inherited zircons of
similar age in Caledonian granites. All these relationships are remarkably similar to those
reported from East Greenland (Strachan et al. 1995). In Ny Friesland, the Planetfjella Group
had a Mesoproterozoic sediment source as young as 0.95Â Ga and, deeper in the
Caledonian thrust stack, the Smutsbreen Formation is characterised by Mesoproterozoic
(c. 1.2 Ga) to late Palaeoproterozoic (c. 1.73 Ga) detrital zircons populations (Gee and
Hellman 1996). In northwestern Svalbard, the Krossfjorden Group bears evidence of
Mesoproterozoic detrital zircons as young as 1.0Â Ga (Ohta & Larionov 1998, Pettersson et
al. 2009) and metasediments in the paleosome of migmatites yield c. 1.05 Ga
detrital zircons (Ohta et al. 2002). In southwestern Svalbard, 1.0-0.9Â Ga zircon
populations were reported from the Neoproterozoic Isbjørnhamna Group (Larionov et al.
2010), and voluminous populations of 1.2-0.9Â Ga detrital monazites from the early
Neoproterozoic Deilegga and late Neoproterozoic Sofiebogen groups (Czerny et al.
2010).
On Franz Joseph Land, turbidites in drill core samples from the basement beneath
Alexandra island yielded unambiguous Mesoproterozoic signatures (Pease et al. 2001),
indicating a sedimentation age younger than 1Â Ga.
On Novaya Zemlya, Permo-Triassic deformation is superimposed on a Timanide
basement. In southern parts, only latest Cambrian and earliest Ordovician strata were
analysed (Pease & Scott 2009), providing very little evidence of late Mesoproterozoic
sediment input. However, the Cambrian to Permian successions of northern Novaya Zemlya
reveal Grenville basement as a major sediment source. Late Mesoproterozoic and earliest
Neoproterozoic detrital zircons constitute only minor populations before the Late Ordovician.
Then the frequency of Proterozoic zircon ages, including 0.95-1.05Â Ga, 1.1Â Ga and
1.2-1.25Â Ga assemblages, increases to dominate throughout the Silurian and Devonian and
fall back to the earlier, late Neoproterozoic signature in the Carboniferous. The dominance of
detritus from early Neoproterozoic and older basement is interpreted as an effect of
Caledonian orogeny. In the Urals, 500Â km to the south, Mesoproterozoic detrital zircon
signatures are prominent in paragneisses in the core of the Lapinskaya anticlinorium, where
metamorphic rims yield Timanian (c. 630 Ma) ages, along with 580-600 Ma granites (Gee
et al 2007).
In Tajmyr, Mesoproterozoic basement (Mamont-Shrenk region) is intruded by c. 0.9 Ga
granites (Pease et al 2001). Along the northern coast, detrital zircon ages from early
Cambrian turbidites are mid to mainly late Neoproterozoic in age (Pease & Scott 2009). Also
the Palaeozoic successions of Severnaya Zemlya, just north of Tajmyr, are dominated
by this Timanian population; but 0.95-1.25Â Ga and older zircons are present, and
prominent in late Cambrian turbidites and Devonian Old Red Sandstones (Lorenz et al.
2008).
The data summarised above suggest that the Grenville-Sveconorwegian Orogen may well
have continued northwards through what are now the continental shelves of the North
Atlantic and into the high Arctic, implying that the Neoproterozoic relationships between
Laurentia and Baltica were more simple than is generally accepted today (cf. recent
reconstructions of Rodinia) and did not involve significant rotations of either continent,
or sinistral strike-slip displacements of thousands of kilometres between them. |
|
|
|
|
|
|