TY - JOUR

T1 - Extent and age of Mesoarchean components in the Nagssugtoqidian orogen, West Greenland

T2 - Implications for tectonic environments and crust building in cratonic orogenic belts

AU - McIntyre, T.

AU - Waterton, P.

AU - Vezinet, A.

AU - Szilas, K.

AU - Pearson, D.G.

PY - 2021/5/8

Y1 - 2021/5/8

N2 - The Nagssugtoqidian orogen (NO), which forms the northern margin of the North Atlantic craton in West Greenland, is largely comprised of ~2870 to 2720 Ma juvenile continental crust reworked during Paleoproterozoic orogenic events. Sparse evidence of components older than 3100 Ma in the area (UPb zircon ages and bulk-rock SmNd isotopes) have hinted at a unit called the Qorlortoq gneiss but were not substantiated by regional studies. Here we report the “rediscovery” of the Qorlortoq gneiss, documented through a new geochemical and geochronological dataset of this orthogneiss and related components, which include ultramafic cumulate enclaves and late basaltic dykes. Laser Ablation Split Stream (LASS) U-Pb/Lu-Hf isotopic analyses of zircon from the gneiss give a UPb concordia upper-intercept age of 3177 ± 12 Ma and weighted mean εHf(t) of 1.7 ± 0.5, indicating a juvenile protolith extracted from a depleted mantle source. Ultramafic enclaves of cumulate origin make up a key component of the Qorlortoq gneiss. Their trace element systematics indicate a parental melt with tholeiitic affinities, sourced from depleted mantle beneath relatively thin lithosphere (

AB - The Nagssugtoqidian orogen (NO), which forms the northern margin of the North Atlantic craton in West Greenland, is largely comprised of ~2870 to 2720 Ma juvenile continental crust reworked during Paleoproterozoic orogenic events. Sparse evidence of components older than 3100 Ma in the area (UPb zircon ages and bulk-rock SmNd isotopes) have hinted at a unit called the Qorlortoq gneiss but were not substantiated by regional studies. Here we report the “rediscovery” of the Qorlortoq gneiss, documented through a new geochemical and geochronological dataset of this orthogneiss and related components, which include ultramafic cumulate enclaves and late basaltic dykes. Laser Ablation Split Stream (LASS) U-Pb/Lu-Hf isotopic analyses of zircon from the gneiss give a UPb concordia upper-intercept age of 3177 ± 12 Ma and weighted mean εHf(t) of 1.7 ± 0.5, indicating a juvenile protolith extracted from a depleted mantle source. Ultramafic enclaves of cumulate origin make up a key component of the Qorlortoq gneiss. Their trace element systematics indicate a parental melt with tholeiitic affinities, sourced from depleted mantle beneath relatively thin lithosphere (

KW - Archean tectonics

KW - Mesoarchean tonalites

KW - Suprachondritic εHf

KW - LASS UPb Lu-Hf

KW - -Os isotopes

KW - Archean ultramafic enclaves

U2 - 10.1016/j.lithos.2021.106182

DO - 10.1016/j.lithos.2021.106182

M3 - Journal article

VL - 396-397

SP - 1

EP - 15

JO - Lithos

JF - Lithos

SN - 0024-4937

M1 - 106182

ER -