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

verfasst von: Kristoffer Szilas, J. Elis Hoffmann, Christina Hansmeier, Julie A. Hollis, Carsten MüNker, Sebastian Viehmann, Haino U. Kasper
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 &epsi; values, a reduced sample set defines a ¹⁴⁷Sm/¹⁴³Nd regression age of 3038 Ma ±310 Ma (MSWD = 9.2) and a ¹⁷⁶Lu/¹⁷⁶Hf regression age of 2867 ±160 Ma (MSWD = 5.5). Initial &epsi;Nd_2970Ma values of the least-altered amphibolites range from 0.0 to +5.7 and initial &epsi;Hf_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.
Externe Organisation(en): Stanford University
Rheinische Friedrich-Wilhelms-Universität Bonn
Universität zu Köln
Freie Universität Berlin (FU Berlin)
Geological Survey of Denmark and Greenland
Geological Survey of Western Australia (GSWA)
Constructor University Bremen
Typ: Artikel
Journal: Mineralogical magazine
Band: 79
Seiten: 857-876
Anzahl der Seiten: 20
ISSN: 0026-461X
Publikationsdatum: 01.08.2015
Publikationsstatus: Veröffentlicht
Peer-reviewed: Ja
ASJC Scopus Sachgebiete: Geochemie und Petrologie
Elektronische Version(en): https://doi.org/10.1180/minmag.2015.079.4.02 (Zugang: Unbekannt)

BibTeX

@article{36d516a81c3041aaa8fd80a129652bd8,
title = "Sm-Nd and Lu-Hf isotope and trace-element systematics of Mesoarchaean amphibolites, inner Ameralik fjord, southern West Greenland",
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 &epsi; values, a reduced sample set defines a 147Sm/143Nd regression age of 3038 Ma ±310 Ma (MSWD = 9.2) and a 176Lu/176Hf regression age of 2867 ±160 Ma (MSWD = 5.5). Initial &epsi;Nd2970Ma values of the least-altered amphibolites range from 0.0 to +5.7 and initial &epsi;Hf2970Ma 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.",
keywords = "Archaean, greenstone belt, Hf isotope data, Nuuk region, supracrustal rocks",
author = "Kristoffer Szilas and Hoffmann, {J. Elis} and Christina Hansmeier and Hollis, {Julie A.} and Carsten M{\"u}Nker and Sebastian Viehmann and Kasper, {Haino U.}",
note = "Publisher Copyright: {\textcopyright} 2015 Mineralogical Society.",
year = "2015",
month = aug,
day = "1",
doi = "10.1180/minmag.2015.079.4.02",
language = "English",
volume = "79",
pages = "857--876",
journal = "Mineralogical magazine",
issn = "0026-461X",
publisher = "Mineralogical Society",
number = "4",
}