Implications for the origins of Eoarchean ultramafic rocks of the North Atlantic Craton: a study of the Tussaap Ultramafic complex, Itsaq Gneiss complex, southern West Greenland

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Implications for the origins of Eoarchean ultramafic rocks of the North Atlantic Craton : a study of the Tussaap Ultramafic complex, Itsaq Gneiss complex, southern West Greenland. / McIntyre, T.; Pearson, D. G.; Szilas, K.; Morishita, T.

I: Contributions to Mineralogy and Petrology, Bind 174, Nr. 12, 96, 2019.

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningfagfællebedømt

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McIntyre, T, Pearson, DG, Szilas, K & Morishita, T 2019, 'Implications for the origins of Eoarchean ultramafic rocks of the North Atlantic Craton: a study of the Tussaap Ultramafic complex, Itsaq Gneiss complex, southern West Greenland', Contributions to Mineralogy and Petrology, bind 174, nr. 12, 96. https://doi.org/10.1007/s00410-019-1628-9

APA

McIntyre, T., Pearson, D. G., Szilas, K., & Morishita, T. (2019). Implications for the origins of Eoarchean ultramafic rocks of the North Atlantic Craton: a study of the Tussaap Ultramafic complex, Itsaq Gneiss complex, southern West Greenland. Contributions to Mineralogy and Petrology, 174(12), [96]. https://doi.org/10.1007/s00410-019-1628-9

Vancouver

McIntyre T, Pearson DG, Szilas K, Morishita T. Implications for the origins of Eoarchean ultramafic rocks of the North Atlantic Craton: a study of the Tussaap Ultramafic complex, Itsaq Gneiss complex, southern West Greenland. Contributions to Mineralogy and Petrology. 2019;174(12). 96. https://doi.org/10.1007/s00410-019-1628-9

Author

McIntyre, T. ; Pearson, D. G. ; Szilas, K. ; Morishita, T. / Implications for the origins of Eoarchean ultramafic rocks of the North Atlantic Craton : a study of the Tussaap Ultramafic complex, Itsaq Gneiss complex, southern West Greenland. I: Contributions to Mineralogy and Petrology. 2019 ; Bind 174, Nr. 12.

Bibtex

@article{8b77f562a2e947ce84d0372b4f9d3b10,
title = "Implications for the origins of Eoarchean ultramafic rocks of the North Atlantic Craton: a study of the Tussaap Ultramafic complex, Itsaq Gneiss complex, southern West Greenland",
abstract = "Ultramafic rocks found within the ~ 3.81 Ga Itsaq Gneiss Complex (IGC) have some mantle-like geochemical characteristics that have led to them being used to directly constrain the nature of the Eoarchean mantle. The discrimination of mantle peridotites that are the residues of partial melting, from cumulate peridotites generated by crystal accumulation from mantle-derived magmas can be difficult in ancient, altered ultramafic rocks whose field relations have been obscured by multiple tectonic episodes. Hence it is important to scrutinize significant individual occurrences of Eoarchean ultramafic rocks in some detail prior to using them to constrain the nature of Earth’s early mantle. Here we present mineral chemistry, whole rock major-, trace-, and platinum-group-element abundances, and Re–Os isotope compositions of a previously unstudied large ultramafic enclave in the IGC—the Tussaap Ultramafic Complex (TUC)—with the aim of documenting its origin. High FeO contents of up to 15.5 wt{\%} and correlations between MgO and Os provide strong evidence that the TUC evolved through fractional crystallization rather than partial melt extraction. In addition, co-variations of major elements in the TUC lithologies can be modeled via fractional crystallization of picritic basalts using MELTS. Later alteration and metasomatism of these ultramafic rocks has largely overprinted primary mineral chemistry and resulted in a redistribution of light rare earth elements, rendering these tools ineffective for ascertaining the origin of the TUC or quantifying some of the petrogenetic processes that formed the body. In addition, it is clear that many geochemical features used to identify residual mantle peridotites can also be produced by cumulate or alteration processes, such as some variations in olivine and chromite chemistry, whole rock Al/Si vs Mg/Si systematics, and trace and platinum group element patterns. Finally, combined discrimination diagrams for high field strength elements and moderately high 187Os/188Os ratios suggest the parental melt of the TUC partially assimilated basaltic crust prior to precipitating the TUC cumulates. As such, these rocks represent a variably obscured record of Eoarchean crystal fractionation from mantle-derived melts. Despite not being prima facie mantle rocks, it is possible that such early formed ultramafic cumulates in nascent continents found their way into the later-stabilized roots of Archean cratons, helping to explain the high compositional variability of cratonic peridotites.",
keywords = "Eoarchean, Itsaq gneiss complex, Platinum group elements, Re–Os isotopes, Ultramafic cumulates",
author = "T. McIntyre and Pearson, {D. G.} and K. Szilas and T. Morishita",
year = "2019",
doi = "10.1007/s00410-019-1628-9",
language = "English",
volume = "174",
journal = "Contributions to Mineralogy and Petrology",
issn = "0010-7999",
publisher = "Springer",
number = "12",

}

RIS

TY - JOUR

T1 - Implications for the origins of Eoarchean ultramafic rocks of the North Atlantic Craton

T2 - a study of the Tussaap Ultramafic complex, Itsaq Gneiss complex, southern West Greenland

AU - McIntyre, T.

AU - Pearson, D. G.

AU - Szilas, K.

AU - Morishita, T.

PY - 2019

Y1 - 2019

N2 - Ultramafic rocks found within the ~ 3.81 Ga Itsaq Gneiss Complex (IGC) have some mantle-like geochemical characteristics that have led to them being used to directly constrain the nature of the Eoarchean mantle. The discrimination of mantle peridotites that are the residues of partial melting, from cumulate peridotites generated by crystal accumulation from mantle-derived magmas can be difficult in ancient, altered ultramafic rocks whose field relations have been obscured by multiple tectonic episodes. Hence it is important to scrutinize significant individual occurrences of Eoarchean ultramafic rocks in some detail prior to using them to constrain the nature of Earth’s early mantle. Here we present mineral chemistry, whole rock major-, trace-, and platinum-group-element abundances, and Re–Os isotope compositions of a previously unstudied large ultramafic enclave in the IGC—the Tussaap Ultramafic Complex (TUC)—with the aim of documenting its origin. High FeO contents of up to 15.5 wt% and correlations between MgO and Os provide strong evidence that the TUC evolved through fractional crystallization rather than partial melt extraction. In addition, co-variations of major elements in the TUC lithologies can be modeled via fractional crystallization of picritic basalts using MELTS. Later alteration and metasomatism of these ultramafic rocks has largely overprinted primary mineral chemistry and resulted in a redistribution of light rare earth elements, rendering these tools ineffective for ascertaining the origin of the TUC or quantifying some of the petrogenetic processes that formed the body. In addition, it is clear that many geochemical features used to identify residual mantle peridotites can also be produced by cumulate or alteration processes, such as some variations in olivine and chromite chemistry, whole rock Al/Si vs Mg/Si systematics, and trace and platinum group element patterns. Finally, combined discrimination diagrams for high field strength elements and moderately high 187Os/188Os ratios suggest the parental melt of the TUC partially assimilated basaltic crust prior to precipitating the TUC cumulates. As such, these rocks represent a variably obscured record of Eoarchean crystal fractionation from mantle-derived melts. Despite not being prima facie mantle rocks, it is possible that such early formed ultramafic cumulates in nascent continents found their way into the later-stabilized roots of Archean cratons, helping to explain the high compositional variability of cratonic peridotites.

AB - Ultramafic rocks found within the ~ 3.81 Ga Itsaq Gneiss Complex (IGC) have some mantle-like geochemical characteristics that have led to them being used to directly constrain the nature of the Eoarchean mantle. The discrimination of mantle peridotites that are the residues of partial melting, from cumulate peridotites generated by crystal accumulation from mantle-derived magmas can be difficult in ancient, altered ultramafic rocks whose field relations have been obscured by multiple tectonic episodes. Hence it is important to scrutinize significant individual occurrences of Eoarchean ultramafic rocks in some detail prior to using them to constrain the nature of Earth’s early mantle. Here we present mineral chemistry, whole rock major-, trace-, and platinum-group-element abundances, and Re–Os isotope compositions of a previously unstudied large ultramafic enclave in the IGC—the Tussaap Ultramafic Complex (TUC)—with the aim of documenting its origin. High FeO contents of up to 15.5 wt% and correlations between MgO and Os provide strong evidence that the TUC evolved through fractional crystallization rather than partial melt extraction. In addition, co-variations of major elements in the TUC lithologies can be modeled via fractional crystallization of picritic basalts using MELTS. Later alteration and metasomatism of these ultramafic rocks has largely overprinted primary mineral chemistry and resulted in a redistribution of light rare earth elements, rendering these tools ineffective for ascertaining the origin of the TUC or quantifying some of the petrogenetic processes that formed the body. In addition, it is clear that many geochemical features used to identify residual mantle peridotites can also be produced by cumulate or alteration processes, such as some variations in olivine and chromite chemistry, whole rock Al/Si vs Mg/Si systematics, and trace and platinum group element patterns. Finally, combined discrimination diagrams for high field strength elements and moderately high 187Os/188Os ratios suggest the parental melt of the TUC partially assimilated basaltic crust prior to precipitating the TUC cumulates. As such, these rocks represent a variably obscured record of Eoarchean crystal fractionation from mantle-derived melts. Despite not being prima facie mantle rocks, it is possible that such early formed ultramafic cumulates in nascent continents found their way into the later-stabilized roots of Archean cratons, helping to explain the high compositional variability of cratonic peridotites.

KW - Eoarchean

KW - Itsaq gneiss complex

KW - Platinum group elements

KW - Re–Os isotopes

KW - Ultramafic cumulates

U2 - 10.1007/s00410-019-1628-9

DO - 10.1007/s00410-019-1628-9

M3 - Journal article

AN - SCOPUS:85074349230

VL - 174

JO - Contributions to Mineralogy and Petrology

JF - Contributions to Mineralogy and Petrology

SN - 0010-7999

IS - 12

M1 - 96

ER -

ID: 230200586