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| Titel |
The role of crustal contamination in Neoproterozoic metaigneous rocks from
SW coast of Svalbard |
| VerfasserIn |
Karolina Goluchowska, Abigail K. Baker, Maciej Manecki, Jarosław Majka, Jerzy Czerny, Rob Ellam, Jakub Bazarnik |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250128168
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| Publikation (Nr.) |
 EGU/EGU2016-8125.pdf |
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| Zusammenfassung |
| This study focuses on the late Neoproterozoic metaigneous rocks that occur along the SW
coast of Svalbard to investigate magma evolution, especially magma-crust interaction,
and to assess the potential sources of contamination. To achieve these goals, trace
element geochemistry, as well as Sr and Nd isotope geochemistry have been applied.
Samples have been collected from four regions from South to North of SW Svalbard:
Werenskiøldbreen area, Orvindalen, Chamberlindalen and Nordenskiøld Land. The
metaigneous rocks are metamorphosed under a minimum of greenschist facies
conditions.
The LILE are much more scattered than HFSE and REE, which present visible and very
often separate trends for each region. The trace element profiles reveal that rocks that occur in
Wedel Jarlsberg Land have higher content of LREE and LILE and Th, U, Nb, in comparison
to rocks from Nordenskiøld Land, which show less enrichment in these elements and are
relatively more enriched in Sr. Incompatible element ratios, used to trace crustal
contamination, like Th/La, (Th/Nb)PM, (La/Nb)PM, Th/Yb and Nb/Yb decrease from South
to North. The samples from Werenskiøldbreen area are usually the most scattered and
have elevated trace element ratios (Th/La 0.12 to 0.59, (Th/Nb)PM 2.37 to 8.38,
(La/Nb)PM 1.61 to 5.02, Th/Yb 1.29 to 5.06, Nb/Yb 2.79 to 10.09) and have the
lowest ratio of Sm/La (0.11 to 0.31), in contrast to samples from Nordenskiøld
Land, which usually show a very narrow group and are depleted in trace element
ratios (Th/La 0.06 to 0.096, (Th/Nb)PM 0.40 to 0.71, (La/Nb)PM 0.71 to 1.04,
Th/Yb 0.2 to 0.31, Nb/Yb 2.9 to 4.4) and have an elevated ratio of Sm/La (0.41 to
0.64). Isotope geochemistry reveals that metaigneous rocks from Nordenskiøld
Land have the highest ratio of 143Nd/144Nd(i) 0.512164 – 0.512392, whereas rocks
from Orvindalen have the lowest ratio of 143Nd/144Nd(i) 0.511422 – 0.511811.
Metaigneous rocks from Chamberlindalen area and Werenskiøldbreen area have
intermediate ratios of 143Nd/144Nd(i). Orvindalen shows the highest ratios of 87Sr/86Sr(i)
0.700937 – 0.733005, whereas the rest of the samples have similar ratios of 87Sr/86Sr(i)
(Nordenskiøld Land 87Sr/86Sr(i) 0.704177 – 0.710285, Werenskiøldbreen area
87Sr/86Sr(i) 0.700864 – 0.713204, Chamberlindalen area 87Sr/86Sr(i) 0.703876 –
0.706138 ). The EC-AFC model used to explain 143Nd/144Nd(i) and 87Sr/86Sr(i)
trends for Werenskiøldbreen area and Orvindalen area, indicate contamination by
assimilation and fractional crystallization processes, where the potential contaminant
was metapelite, however this model does not explain the trend for samples from
Nordenskiøld Land, which imply that a different, Sr-rich, contaminant influenced on these
rocks.
Based on the trace elements geochemistry, as well as Sr and Nd isotope geochemistry, we
show that the rocks from the coast of SW Svalbard have been contaminated, where the
highest contamination is observed in the South of the Wedel Jarlsberg Land and decreases
towards the North. Samples from Nordenskiøld Land are the less affected by contamination,
however based on the 87Sr/86Sr(i) ratios and patterns of elevated trace elements, as
well as on the EC-AFC model, the potential contaminant was different in different
regions.
This work is partially funded by AGH research grant no 11.11.140.319 and partially by
NCN grant No. 2012/05/N/ST10/03594. |
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