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intrusions, now gneissose, (the Nuuk
gneisses ) and subjected to widespread
deformation and high-grade metamor-
phism at ~2800 Ma ago. However, more
recent, detailed mapping and precise
dating have caused this sequence to
be revised and a number of separate
terranes identified, each of which is
considered to have had a different
history to its neighbour, prior to their
amalgamation in the late Archaean.
Figure 12.9 shows a map and cross-
section of part of the gneiss complex
north of the town of Nuuk (formerly
Godthaab), which gives an impression
of the complexity of the area. The Neo-
archaean deformation has resulted in
the formation of a layered complex,
aligned roughly N-S, where terranes
of varying age have become tectoni-
cally amalgamated by a series of gently
inclined shear zones and subsequently
refolded by upright folds. Six separate
terranes have been recognised in this
area. The terrane boundaries are cut by
a late-Archaean granite. Several of these
terranes contain folded and disrupted
supracrustal layers, one of which, the
famous Isua greenstone belt, is high-
lighted in the north of the map. Two
generations of (high-grade) greenstone
belts have been recognised, each con-
taining accreted units of oceanic and
volcanic arc material similar to those
described in the Superior Province.
It is difficult to compare such an
area with more modern orogenic belts,
particularly as the scale is so small,
compared even with the Superior
Province. The area of Figure 12.12 is
only about 50 km across and the indi-
vidual terranes recorded there are of
the order of 10-20 km wide. Despite
the fact that oceanic and continen-
tal crustal units have been accreted
together, the individual terranes are
more like thrust slices than separate
micro-continents, and some have been
amalgamated before the late Archaean
orogenic event. In terms of structural
and metamorphic state, perhaps
the best analogy would be with the
mid- to lower-crustal sections of the
Himalayan or Caledonian orogenic
belts described earlier, where strong
ductile deformation at elevated tem-
perature has produced similar results.
12
112
113
Isua greenstone belt
25km
greenstone belt
Neo-archaean
granite
Neo-archaean terranes
ice cap
Isokasia
terrane
Tre Brodre
Akia terrane
Tasiusarsuak
Meso-archaean terranes
Ft
A
B
Akia
Tbt
Kapisilik
Archaean orogeny
The recognition in both the Superior
Province and the North Atlantic craton
of igneous assemblages compara-
ble to present-day oceanic plateaux
and volcanic island arcs, which have
Eo-archaean terranes
Kapisilik
terrane
Isokasia
Faeringehavn
post-
tectonic
granite
fault
Figure 12.12 Archaean terranes of the Nuuk area.
Map and E-W section across the area north of Nuuk
(formerly Godthaab) in southern west Greenland,
showing the various terranes that have been
recognised in the area. Ft, Faeringehavn terrane; TBt,
Tre Brodre terrane; Tt, Tasiusarsuak terrane; Based on
Friend & Nutman (2005).
Tre
Brodre
terrane
B
A
Tt
Nuuk
Faeringe-
havn
terrane
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