Fe isotope systematics of coexisting amphibole and pyroxene in the alkaline igneous rock suite of the Ilímaussaq Complex, South Greenland
The Ilímaussaq intrusion, South Greenland, provides an exceptional test case for investigating the changes of stable Fe isotope fractionation of solidus phases with changes in the Fe3+/ΣFe ratio of an evolving melt. The intrusion comprises a sequence of four melt batches that were fed from the same...
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ftgfzpotsdam:oai:gfzpublic.gfz-potsdam.de:item_238011 2023-05-15T16:28:39+02:00 Fe isotope systematics of coexisting amphibole and pyroxene in the alkaline igneous rock suite of the Ilímaussaq Complex, South Greenland Schönberg, R. Marks, M. Schuessler, J. von Blanckenburg, F. 0 Pre-GFZ, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum 2009 https://gfzpublic.gfz-potsdam.de/pubman/item/item_238011 unknown info:eu-repo/semantics/altIdentifier/doi/10.1016/j.chemgeo.2008.06.023 https://gfzpublic.gfz-potsdam.de/pubman/item/item_238011 Chemical Geology 550 - Earth sciences info:eu-repo/semantics/article 2009 ftgfzpotsdam https://doi.org/10.1016/j.chemgeo.2008.06.023 2022-09-14T05:56:50Z The Ilímaussaq intrusion, South Greenland, provides an exceptional test case for investigating the changes of stable Fe isotope fractionation of solidus phases with changes in the Fe3+/ΣFe ratio of an evolving melt. The intrusion comprises a sequence of four melt batches that were fed from the same parental alkali basaltic magma. Differentiation produced cumulate rocks that range from augite syenite (phase I) over peralkaline granite (phase II) to agpaitic syenites (phases IIIa and IIIb). Fe3+/ΣFe ratios in amphiboles increase substantially from phase I to phase II and III rocks and mark a major change in the parental magma composition from augite syenites to peralkaline granites and agpaitic syenites. Before this transition, olivine, clinopyroxene, and amphibole in augite syenite, the most primitive rock type in the Ilímaussaq Complex, have a uniform Fe isotope composition that is identical to that of the bulk of igneous crustal rocks and approximated by the average isotopic composition of basalts (δ56/54FeIRMM-014=0.072±0.046‰). After the transition, amphiboles in the peralkaline granites and agpaitic syenites yield significantly heavier Fe isotope compositions with δ56/54FeIRMM-014 values ranging from 0.123 to 0.237‰. Contamination of the Ilímaussaq magma by ongoing crustal assimilation as cause for this increase can be excluded on the grounds of Nd isotope data. Large-scale metasomatic overprint with an external fluid can also be dismissed based on amphibole O and Li isotope systematics. Rather, the increase towards heavy Fe isotope compositions most likely reflects the change in chemical compositions of amphiboles (calcic in augite syenite to sodic in the agpaitic syenites) and their Fe3+/ΣFe ratios that mirror changes in the chemical composition of the melt and its oxygen fugacity. A sensitive adjustment of equilibrium Fe isotope fractionation factors to amphibole ferric/ferrous ratios is also supported by beta-factors calculated from Mössbauer spetroscopy data. Comparison of the measured isotope ... Article in Journal/Newspaper Greenland GFZpublic (German Research Centre for Geosciences, Helmholtz-Zentrum Potsdam) Greenland Chemical Geology 258 1-2 65 77 |
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GFZpublic (German Research Centre for Geosciences, Helmholtz-Zentrum Potsdam) |
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550 - Earth sciences |
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550 - Earth sciences Schönberg, R. Marks, M. Schuessler, J. von Blanckenburg, F. Fe isotope systematics of coexisting amphibole and pyroxene in the alkaline igneous rock suite of the Ilímaussaq Complex, South Greenland |
topic_facet |
550 - Earth sciences |
description |
The Ilímaussaq intrusion, South Greenland, provides an exceptional test case for investigating the changes of stable Fe isotope fractionation of solidus phases with changes in the Fe3+/ΣFe ratio of an evolving melt. The intrusion comprises a sequence of four melt batches that were fed from the same parental alkali basaltic magma. Differentiation produced cumulate rocks that range from augite syenite (phase I) over peralkaline granite (phase II) to agpaitic syenites (phases IIIa and IIIb). Fe3+/ΣFe ratios in amphiboles increase substantially from phase I to phase II and III rocks and mark a major change in the parental magma composition from augite syenites to peralkaline granites and agpaitic syenites. Before this transition, olivine, clinopyroxene, and amphibole in augite syenite, the most primitive rock type in the Ilímaussaq Complex, have a uniform Fe isotope composition that is identical to that of the bulk of igneous crustal rocks and approximated by the average isotopic composition of basalts (δ56/54FeIRMM-014=0.072±0.046‰). After the transition, amphiboles in the peralkaline granites and agpaitic syenites yield significantly heavier Fe isotope compositions with δ56/54FeIRMM-014 values ranging from 0.123 to 0.237‰. Contamination of the Ilímaussaq magma by ongoing crustal assimilation as cause for this increase can be excluded on the grounds of Nd isotope data. Large-scale metasomatic overprint with an external fluid can also be dismissed based on amphibole O and Li isotope systematics. Rather, the increase towards heavy Fe isotope compositions most likely reflects the change in chemical compositions of amphiboles (calcic in augite syenite to sodic in the agpaitic syenites) and their Fe3+/ΣFe ratios that mirror changes in the chemical composition of the melt and its oxygen fugacity. A sensitive adjustment of equilibrium Fe isotope fractionation factors to amphibole ferric/ferrous ratios is also supported by beta-factors calculated from Mössbauer spetroscopy data. Comparison of the measured isotope ... |
author2 |
0 Pre-GFZ, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum |
format |
Article in Journal/Newspaper |
author |
Schönberg, R. Marks, M. Schuessler, J. von Blanckenburg, F. |
author_facet |
Schönberg, R. Marks, M. Schuessler, J. von Blanckenburg, F. |
author_sort |
Schönberg, R. |
title |
Fe isotope systematics of coexisting amphibole and pyroxene in the alkaline igneous rock suite of the Ilímaussaq Complex, South Greenland |
title_short |
Fe isotope systematics of coexisting amphibole and pyroxene in the alkaline igneous rock suite of the Ilímaussaq Complex, South Greenland |
title_full |
Fe isotope systematics of coexisting amphibole and pyroxene in the alkaline igneous rock suite of the Ilímaussaq Complex, South Greenland |
title_fullStr |
Fe isotope systematics of coexisting amphibole and pyroxene in the alkaline igneous rock suite of the Ilímaussaq Complex, South Greenland |
title_full_unstemmed |
Fe isotope systematics of coexisting amphibole and pyroxene in the alkaline igneous rock suite of the Ilímaussaq Complex, South Greenland |
title_sort |
fe isotope systematics of coexisting amphibole and pyroxene in the alkaline igneous rock suite of the ilímaussaq complex, south greenland |
publishDate |
2009 |
url |
https://gfzpublic.gfz-potsdam.de/pubman/item/item_238011 |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland |
genre_facet |
Greenland |
op_source |
Chemical Geology |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1016/j.chemgeo.2008.06.023 https://gfzpublic.gfz-potsdam.de/pubman/item/item_238011 |
op_doi |
https://doi.org/10.1016/j.chemgeo.2008.06.023 |
container_title |
Chemical Geology |
container_volume |
258 |
container_issue |
1-2 |
container_start_page |
65 |
op_container_end_page |
77 |
_version_ |
1766018321430347776 |