Universität zu Köln

Szilas, Kristoffer ORCID: 0000-0002-5541-306X, Hoffmann, J. Elis ORCID: 0000-0001-6670-1393, Schulz, Toni ORCID: 0000-0003-1248-7832, Hansmeier, Christina, Polat, Ali, Viehmann, Sebastian ORCID: 0000-0001-6138-5862, Kasper, Haino Uwe and Muenker, Carsten (2016). Combined bulk-rock Hf- and Nd-isotope compositions of Mesoarchaean metavolcanic rocks from the Ivisaartoq Supracrustal Belt, SW Greenland: Deviations from the mantle array caused by crustal recycling. Chem Erde-Geochem., 76 (4). S. 543 - 555. MUNICH: ELSEVIER GMBH. ISSN 1611-5864

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Abstract

Bulk-rock Lu-Hf and Sm-Nd isotope compositions, as well as major and trace element data are presented for metavolcanic rocks from the Mesoarchaean (ca. 3075 Ma) Ivisaartoq Supracrustal Belt in the Nuuk region of southern West Greenland. The epsilon Hf-t calculated at 3075 Ma range from +0.8 to +3.1 and the corresponding epsilon Nd-t values range from +0.7 to +3.6, which forms an array that is displaced off the mantle array for these two isotopic systems. Primitive mantle normalized trace element plots of the metabasalts display negative Nb- and Ti-anomalies in combination with the elevated Th abundances, which is consistent with a subduction zone affinity as proposed by previous studies of this metavolcanic belt. No significant correlations are observed between the isotope compositions and proxies of shallow crustal contamination in the Ivisaartoq rocks, despite clear evidence for inherited Eoarchaean zircon [Polat et al. (2009a) Chemical Geology 268, 248-271], which would have dominated the bulk-rock Hf-isotope budget. Furthermore, the measured samples are less radiogenic than the estimate for the depleted mantle composition at 3075 Ma. The lack of isotope and trace element correlation suggests incomplete equilibration between the crustal contaminant and the parental Ivisaartoq melts. We prefer a petrogenetic model with some combination of slab-derived metasomatism of the mantle source region for the Ivisaartoq magmas, which homogenized their trace element contents, in combination with the incorporation of granitoid residue with unradiogenic Hf-isotope composition at higher degrees of partial melting and finally the eruption of mechanically entrained Eoarchaean crust without significant chemical equilibration. The geochemical arc-affinity and lower than depleted mantle (DM) isotope compositions of these metavolcanic rocks support the notion that crustal recycling and plate tectonics has been operating on Earth since at least the Mesoarchaean Eon. (C) 2016 Elsevier GmbH. All rights reserved.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Szilas, Kristoffer UNSPECIFIED orcid.org/0000-0002-5541-306X UNSPECIFIED Hoffmann, J. Elis UNSPECIFIED orcid.org/0000-0001-6670-1393 UNSPECIFIED Schulz, Toni UNSPECIFIED orcid.org/0000-0003-1248-7832 UNSPECIFIED Hansmeier, Christina UNSPECIFIED UNSPECIFIED UNSPECIFIED Polat, Ali UNSPECIFIED UNSPECIFIED UNSPECIFIED Viehmann, Sebastian UNSPECIFIED orcid.org/0000-0001-6138-5862 UNSPECIFIED Kasper, Haino Uwe UNSPECIFIED UNSPECIFIED UNSPECIFIED Muenker, Carsten UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-288388
DOI:	10.1016/j.chemer.2016.09.004
Journal or Publication Title:	Chem Erde-Geochem.
Volume:	76
Number:	4
Page Range:	S. 543 - 555
Date:	2016
Publisher:	ELSEVIER GMBH
Place of Publication:	MUNICH
ISSN:	1611-5864
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language SOUTHERN WEST GREENLAND; ISUA GREENSTONE-BELT; ITSAQ GNEISS COMPLEX; OCEANIC-CRUST; LU-HF; SUPERIOR PROVINCE; TRACE-ELEMENT; TARTOQ GROUP; NUUK REGION; SM-ND Multiple languages Geochemistry & Geophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/28838