TY - JOUR

T1 - Mesoarchaean peridotite-norite cumulates of SW Greenland – The Miaggoq ultramafic complex

AU - Zemeny, Aliz

AU - Kinney, Carson

AU - Yakymchuk, Chris

AU - Olierook, Hugo K.H.

AU - Kirkland, Christopher L.

AU - Gardiner, Nicholas

AU - Szilas, Kristoffer

N1 - Funding Information: This study was funded by VILLUM FONDEN through Grant VKR18978 awarded to Kristoffer Szilas. Some of the samples were collected as part of fieldwork organized by Julie Hollis and supported by The Ministry of Mineral Resources and Labour, Greenland Government. A. Zemeny would like to thank to M.K. Traun for providing the R code of cumulate calculation for processing the MELTs output data and P. Waterton for the introductory workshop on the easyMELTS software. Publisher Copyright: © 2023 The Authors

PY - 2023

Y1 - 2023

N2 - Several studies focused on the ultramafic bodies of the Archaean continental crust in southern Greenland in order to gain information on early Earth petrogenetic, metamorphic and metasomatic processes. This research provides the first petrological dataset of the Miaggoq Ultramafic Complex (∼1 km2) in the Akia terrane, with a minimum age of 2997 ± 15 Ma. It comprises ultramafic (dunite, peridotite) and mafic (orthopyroxenite, norite) rocks along with chromitites and provides a window into Mesoarchaean mantle compositions. Field observations, such as chromitite bands, mineral layering, and orthopyroxenite oikocrysts in peridotites coupled with chemical analysis displaying high abundance of chromites in the dunitic rocks and high forsterite contents (Mg# 91 to 92.5) of the olivines, all point to a layered cumulate origin for the Miaggoq body. Pseudosection calculations along with geothermometry estimations reveal peak metamorphic conditions of 850–1100 °C at pressures of 0.7–1.25 GPa under anhydrous conditions followed by a possible metamorphic overprint at 650–800 °C and 0.7 GPa with relatively dry melting (0.025–0.125 wt% H2O). MELTS fractional crystallization coupled with cumulate modelling approximated the compositional trends with conditions on ∼3 kbar with 1 wt% H2O. This research concludes that the Miaggoq body represents a layered cumulate complex that was derived by large degrees of partial melting of the mantle with possible assimilation (synonymous with contamination) of basalts in the crust. Overall, this study provides complementary data for the Mesoarchaean cumulate bodies of the Akia Terrane and their petrological processes.

AB - Several studies focused on the ultramafic bodies of the Archaean continental crust in southern Greenland in order to gain information on early Earth petrogenetic, metamorphic and metasomatic processes. This research provides the first petrological dataset of the Miaggoq Ultramafic Complex (∼1 km2) in the Akia terrane, with a minimum age of 2997 ± 15 Ma. It comprises ultramafic (dunite, peridotite) and mafic (orthopyroxenite, norite) rocks along with chromitites and provides a window into Mesoarchaean mantle compositions. Field observations, such as chromitite bands, mineral layering, and orthopyroxenite oikocrysts in peridotites coupled with chemical analysis displaying high abundance of chromites in the dunitic rocks and high forsterite contents (Mg# 91 to 92.5) of the olivines, all point to a layered cumulate origin for the Miaggoq body. Pseudosection calculations along with geothermometry estimations reveal peak metamorphic conditions of 850–1100 °C at pressures of 0.7–1.25 GPa under anhydrous conditions followed by a possible metamorphic overprint at 650–800 °C and 0.7 GPa with relatively dry melting (0.025–0.125 wt% H2O). MELTS fractional crystallization coupled with cumulate modelling approximated the compositional trends with conditions on ∼3 kbar with 1 wt% H2O. This research concludes that the Miaggoq body represents a layered cumulate complex that was derived by large degrees of partial melting of the mantle with possible assimilation (synonymous with contamination) of basalts in the crust. Overall, this study provides complementary data for the Mesoarchaean cumulate bodies of the Akia Terrane and their petrological processes.

KW - Archean

KW - Layered intrusion

KW - Norite

KW - Nuuk region

KW - Ultramafic cumulates

U2 - 10.1016/j.lithos.2023.107352

DO - 10.1016/j.lithos.2023.107352

M3 - Journal article

AN - SCOPUS:85170253079

VL - 458-459

JO - Lithos

JF - Lithos

SN - 0024-4937

M1 - 107352

ER -