Geodynamic Implications of Synchronous Norite and TTG Formation in the 3 Ga Maniitsoq Norite Belt, West Greenland

Abstract

the emplacement of the norite magmas. Contemporaneous production of both TTGs and norite, their emplacement in thin crust, and the rapid transition to high temperature, low pressure granulite-facies metamorphism is best explained by their formation in an ultra-hot orogeny. Formation of norites in this setting may be restricted to >2.7 Ga, when geothermal gradients were higher on Earth.

The Mesoarchean Amikoq Layered Complex of SW Greenland: Part 1. Constraints on theP–Tevolution from igneous, metasomatic and metamorphic amphiboles

“…Finally, it should be emphasised that the intrusive ages we report here for samples QUA and FOS2 are not actually from the ALC, which is the focus of the present study, but they are rather for intrusive noritic rocks that do not have a verified co-magmatic relationship to the ALC. Ravenelle et al (2017) and Waterton et al (2020) found similar ages of 3014 ± 2.8 Ma to 3002 ± 5.4 Ma for the Maniitsoq Norite Belt, but a robust magmatic age of the ALC remains to be established.…”

“…Corroded, partly recrystallised <250 μm zircons displaying well-preserved igneous-style oscillatory zoning from homogeneous norite samples FOS2 and QUA yield a pooled age of 3011 ± 4 Ma. It is contended that 3011 Ma is a best estimate of the age of intrusion of the Amikoq and similar northern bodies, assuming a coeval relation (Waterton et al , 2020). In contrast, zircon domains in these samples that indicate recrystallisation of oscillatory-zoned zircon yield an age of 2997 ± 8 Ma, which is interpreted as reflecting recrystallisation during high temperature (amphibolite–granulite facies) metamorphism.…”

Archaean Plate Tectonics in the North Atlantic Craton of West Greenland Revealed by Well-Exposed Horizontal Crustal Tectonics, Island Arcs and Tonalite-Trondhjemite-Granodiorite Complexes

“…About 75 noritic intrusions ∼3.0 Ga old with hybrid margins to their hosts occur in the northern Fiskefjord block, and related post-kinematic diorites farther south (Secher 1983;Garde 1991;Garde et al, 2013b;Waterton et al, 2020). The very variable geochemistry of these highly unusual rocks with high Ni and Cr contents suggests derivation from ultramafic magmas contaminated with 30% TTG material.…”

The Mesoarchean Amikoq Layered Complex of SW Greenland: Part 2. Geochemical evidence for high-Mg noritic plutonism through crustal assimilation

“…Both magmatic phases intruded as sheets resulting in an intercalation with subordinate amphibolitic successions of MORB affinity and minor ultramafic-mafic complexes of probable cumulate origin (Garde, 1997;Garde et al, 2000;Guotana et al, 2018;Szilas et al, 2015aSzilas et al, , 2018Waterton et al, 2020). The amphibolites can be subdivided into dominantly homogenous and subordinate heterogeneous types where the former might represent subvolcanic intrusives and the latter volcanic given the common association with metasedimentary rocks (Garde, 1997).…”

“…This is especially acute for Archean cratons such as the North Atlantic Craton in SW Greenland where the dominating tonalite-trondhjemite-granodiorite (TTG) orthogneisses (Garde, 1997;Nutman et al, 2015) dominate the rock record. There is important geological information hidden in the older subordinate ultramafic-mafic layered complexes, both in terms of geodynamic setting (Myers, 1985;Szilas et al, 2015b, Huang et al, 2012McIntyre et al, 2019) and economic aspects (Szilas et al, 2018;Waterton et al, 2020).…”