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| Titel |
Mesozoic to Cenozoic U-Pb zircon ages from Graham Land, West Antarctica: the magmatic evolution of the Antarctic Peninsula batholith |
| VerfasserIn |
Joaquin Bastias, Richard Spikings, Alex Ulianov, Urs Schaltegger, Anne Grunow, Francisco Hervé |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250152426
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| Publikation (Nr.) |
 EGU/EGU2017-17260.pdf |
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| Zusammenfassung |
| The plutonic rocks of the Antarctic Peninsula form one of the major intrusive bodies located
along the circum-Pacific rim. Spanning ages of ∼240 to 9 Ma and emplaced over 1300 km
long and 200 km wide along Graham and Palmer Land, these rocks represents a key unit to
understand the magmatic and tectonic evolution of the Antarctic Peninsula. In the north, the
plutons intrude Paleozoic- Mesozoic low-grade meta-sedimentary rocks, and intrudes schists
and ortho- and paragneisses with Triassic to Carboniferous metamorphic ages, further
south.
The origin of the arc of Antarctic Peninsula has been in dispute since the interpretation of
Vaughan and Storey (2000) who suggested that these plutonic rocks are part of an
allochthonous arc, contradicting the traditional interpretation that these rocks are
autochthonous and are part of the continental arc which formed along the southern margin of
Gondwana (Suarez, 1976). We will address the magmatic and tectonic evolution of the
Antarctic Peninsula by providing crystallization ages (zircon U-Pb and hornblende
40Ar/39Ar) of the main plutonic units, together with the characterization of the tectonic
environment within which magmatism was occurring (geochemical studies and isotopic
tracing).
We present 45 LA-ICP-MS U-Pb (zircon) and 4 40Ar/39Ar (hornblende) dates of plutons
and dikes from the west coast of the northern Antarctic Peninsula and the South
Shetland Islands. Their geochemical composition shows affinities with calc-alkaline,
supra-subduction zone rocks (Pearce et al., 1984). The U-Pb zircon ages range between ∼160
Ma (Stonington Island) to ∼9 Ma (Cornwallis Island), with a peak in the Early
Cretaceous (Albian and Aptian). Upper Jurassic to Eocene intrusions were emplaced
in a constant, approximately stationary position. Magmatism displaced ∼50km
westwards during the Miocene, which is currently exposed on Watkin Island (∼22 Ma),
Snodgrass Island (∼19 Ma), Litchfield Island (∼19 Ma) and Cornwallis Island (∼26
Ma).
The identification of a westward displacement of the Miocene rocks may be related to the
formation of oceanic lithosphere of the Scotia Plate at the north, by changing the
configuration of the regional plate dynamics, provoking a westward migration of the arc.
Future analyses of isotopic tracing in Nd, Sr and Pb will allow to have a better
characterization of these rocks.
Suarez. 1976. Geology 4, 211-214.
Pearce et al. 1984. Journal of Petrology 25(4), 986-983.
Vaughan and Storey. 2000. Journal of the Geological Society, London 157, 1243-1256. |
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