Details
| Original language | English |
|---|---|
| Pages (from-to) | 857-876 |
| Number of pages | 20 |
| Journal | Mineralogical magazine |
| Volume | 79 |
| Issue number | 4 |
| Publication status | Published - 1 Aug 2015 |
| Externally published | Yes |
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 ε 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 εNd2970Ma values of the least-altered amphibolites range from 0.0 to +5.7 and initial εHf2970Ma 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
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Geochemistry and Petrology
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In: Mineralogical magazine, Vol. 79, No. 4, 01.08.2015, p. 857-876.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Sm-Nd and Lu-Hf isotope and trace-element systematics of Mesoarchaean amphibolites, inner Ameralik fjord, southern West Greenland
AU - Szilas, Kristoffer
AU - Hoffmann, J. Elis
AU - Hansmeier, Christina
AU - Hollis, Julie A.
AU - MüNker, Carsten
AU - Viehmann, Sebastian
AU - Kasper, Haino U.
N1 - Publisher Copyright: © 2015 Mineralogical Society.
PY - 2015/8/1
Y1 - 2015/8/1
N2 - 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 ε 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 εNd2970Ma values of the least-altered amphibolites range from 0.0 to +5.7 and initial εHf2970Ma 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.
AB - 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 ε 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 εNd2970Ma values of the least-altered amphibolites range from 0.0 to +5.7 and initial εHf2970Ma 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.
KW - Archaean
KW - greenstone belt
KW - Hf isotope data
KW - Nuuk region
KW - supracrustal rocks
UR - http://www.scopus.com/inward/record.url?scp=84946135918&partnerID=8YFLogxK
U2 - 10.1180/minmag.2015.079.4.02
DO - 10.1180/minmag.2015.079.4.02
M3 - Article
AN - SCOPUS:84946135918
VL - 79
SP - 857
EP - 876
JO - Mineralogical magazine
JF - Mineralogical magazine
SN - 0026-461X
IS - 4
ER -