1. Department of Earth Sciences University of Windsor
The 3075 Ma Ivisaartoq Greenstone Belt, SW Greenland: Supra-subduction Zone Mesoarchean Oceanic Crust
Ali Polat
Department of Earth Sciences University of Windsor

2. The 3075 Ma Ivisaartoq greenstone belt
Nuuk region, SW
Greenland and
The 3075 Ma Ivisaartoq greenstone belt

3. Age of the belt
Zircons from volcanoclastics yielded an age of 3075 Ma (Friend and Nutman, 2005)

4. Conclusions
The Mesoarchean Ivisaartoq greenstone belt is composed of well-preserved pillow lavas, ultramafic cumulates, peridotites, gabbros, anorthosites, and cherts.
Pillow lavas and cumulates are compositional comparable to modern island arc picrites (e.g., Solomon Islands).
Initial Nd isotopic compositions (eNd= +2 to +5) are consistent with a long term depleted mantle source.

5. Conclusions
The Ivisaartoq pillow lavas and gabbros contain epidosite metasomatic assemblage, which typically occur in Phanerozoic ophiolites, recording Mesoarchean seafloor hydrothermal alteration.
Given the lithological similarities between the Ivisaartoq belt and the crustal section of Phanerozoic ophiolites, we interpret the belt as Mesoarchean supra-subduction zone oceanic crust.

6. 3075 Ma Ivisaartoq greenstone belt

7. (c) (a) (d) (b) Rock Types Pillow basalts Gabbro Pillow basalts
Cumulate

8. (a)
Pyrite-rich cherts
(c)
Epidosites
(b)
Peridotites
(d)
Epidosites

9. (a) NW SE
(c)
(b) SE NW
Collision tectonics

10. Volcanic rocks (a) eNd= +2.1 to +3.1 (b) eNd= +4.2 to +5.0
Pillow lavas
Subduction derived
(a)
eNd= +2.1 to +3.1
Ultramafic cumulates
Subduction-derived
(b)
eNd= +4.2 to +5.0

11. Anorthositic inclusions
(b)

12. Anorthosite inclusions
(b)

13. Interpreted geodynamic setting for the 3.1 Ga Ivisaartoq

14. Ontong Java-Plateau-Solomon Islands convergent zone (From Mann and Taira, 2004)

15. Conclusions
The Mesoarchean Ivisaartoq greenstone belt is composed of well-preserved pillow lavas, ultramafic cumulates, peridotites, gabbros, anorthosites, and cherts, representing the crustal section of a supra-subduction zone ophiolite.
Geological characteristics of the Ivisaartoq belt in particular and other Archean greenstone belts in general are comparable to Phanerozoic (Cordilleran-Altaid-Japan) accretionary complexes, consistent with the operation of plate tectonics.