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Sm-Nd and Lu-Hf isotope and trace-element systematics of Mesoarchaean amphibolites, inner Ameralik Fjord, southern West Greenland

Kristoffer Szilas, J. Elis Hoffmann, Christina Hansmeier, Julie A. Hollis, Carsten Muenker, Sebastian Viehmann and Haino U. Kasper
Sm-Nd and Lu-Hf isotope and trace-element systematics of Mesoarchaean amphibolites, inner Ameralik Fjord, southern West Greenland (in North Atlantic Craton conference, Iain McDonald (prefacer), Hannah S. R. Hughes (prefacer) and K. M. Goddenough (prefacer))
Mineralogical Magazine (August 2015) 79 (4): 857-876

Abstract

Fragmented supracrustal rocks are typical components of Archaean high-grade gneiss terranes, such as those in the North Atlantic Craton. Here we present the first major, trace element and Nd-Hf isotope data for amphibolites collected in the yet poorly studied southern inner Ameralik fjord region of southern West Greenland. In addition, new U-Pb zircon ages were obtained from the surrounding TTG gneisses.Based on their trace-element patterns, two different groups of amphibolites can be distinguished. Following screening for post-magmatic alteration and outlying epsilon values, a reduced sample set defines a (super 147) Sm/ (super 143) Nd regression age of 3038 Ma + or -310 Ma (MSWD = 9.2) and a (super 176) Lu/ (super 176) Hf regression age of 2867 + or -160 Ma (MSWD = 5.5). Initial epsilon Nd (sub 2970Ma) values of the least-altered amphibolites range from 0.0 to +5.7 and initial epsilon Hf (sub 2970Ma) range from +0.7 to +10.4, indicating significant isotopic heterogeneity of their mantle sources with involvement of depleted domains as well as crustal sources.Surprisingly, the amphibolites which are apparently most evolved and incompatible element-rich have the most depleted Hf-isotope compositions. This apparent paradox may be explained by the sampling of a local mantle source region with ancient previous melt depletion, which was re-enriched by a fluid component during subduction zone volcanism or alternatively by preferential melting of an ancient pyroxenite component in the mantle source of the enriched rocks.


ISSN: 0026-461X
EISSN: 1471-8022
Serial Title: Mineralogical Magazine
Serial Volume: 79
Serial Issue: 4
Title: Sm-Nd and Lu-Hf isotope and trace-element systematics of Mesoarchaean amphibolites, inner Ameralik Fjord, southern West Greenland
Title: North Atlantic Craton conference
Author(s): Szilas, KristofferHoffmann, J. ElisHansmeier, ChristinaHollis, Julie A.Muenker, CarstenViehmann, SebastianKasper, Haino U.
Author(s): McDonald, Iainprefacer
Author(s): Hughes, Hannah S. R.prefacer
Author(s): Goddenough, K. M.prefacer
Affiliation: Stanford University, Department of Geological and Environmental Sciences, Stanford, CA, United States
Affiliation: Cardiff University, School of Earth and Ocean Sciences, Cardiff, United Kingdom
Pages: 857-876
Published: 201508
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
Meeting name: North Atlantic Craton conference (NAC 2014)
Meeting location: St. Andrews, GBR, United Kingdom
Meeting date: 20141020Oct. 20-21, 2014
References: 68
Accession Number: 2016-016661
Categories: Isotope geochemistryIgneous and metamorphic petrology
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch map
N63°00'00" - N65°30'00", W52°15'00" - E49°30'00"
Secondary Affiliation: University of the Witwatersrand, ZAF, South AfricaBritish Geological Survey, GBR, United KingdomRheinische Wilhelms-Universitaet Bonn, DEU, GermanyGeological Survey of Denmark and Greenland, DNK, DenmarkUniversitaet zu Koeln, DEU, GermanyJacobs University Bremen, DEU, Germany
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201609
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