Ancient orogenic belts - Introducing Tectonics, Rock Structures and Mountain Belts - page 109

consists of two separate collisional
zones between the North Atlantic
and Superior Archaean cratons - the
Torngat belt on the north-east side and
the New Quebec zone on the south-
west side, separated by a 200 km-wide
central zone of reworked Archaean
basement known as the Core zone . Both
the Torngat and New Quebec zones
contain deposits ranging from shelf to
oceanic assemblages strongly deformed
and thrust towards the south-west. The
western extension of the Core zone
in Baffin Island, the Meta Incognita
craton , is separated from the Sugluq
craton by the western extension of the
New Quebec subduction zone. Much
of the upper plate here is obscured by
the large Cumberland batholith . The
continuation of the New Quebec zone
around the northern margin of the
Superior craton consists of a fold-thrust
belt known as the Cape Smith belt ,
which contains a 5 km-thick ophiolite
complex (the Purtuniq ophiolite ) -
one of the earliest to be recognised.
A series of continental volcanic
arcs, now represented mainly by gran-
itic plutons such as the Wathaman and
Cumberland batholiths, line the outer
margins of the Hearne, Sugluq, North
Atlantic, and Core zone cratons, indi-
cating that subduction zones formerly
bordered these continental terranes,
which therefore represent the upper
plate of the THO collisional belt.

PPB

Slave

Rae

12

2

NAC

MI

3

3

2

108 109

1

PS

4

X X X

2

3

LL

3

1

2 4

3

Superior

SK

Wyoming

A

x x x

convergence
direction

volcanic
arc

subduction
zone

B

Hearne oceanic volcanic arcs

Rae Superior

1

2

3

4

Figure 12.10 A. Sketch map showing the tectonic evolution of the Trans-Hudson orogen in terms of
four stages: 1 , 1920-1890 Ma: the Hearne-Wyoming craton converges with the combined Slave-Rae
craton; volcanic arcs develop in the ocean between the Hearne and Superior cratons. 2 , 1880-
1865 Ma: the La Ronge-Lynn Lake volcanic arc accretes with the Hearne craton; the NAC collides
with the Core Zone terrane, and the Meta Incognita craton with the Rae craton, with consequential
closure and deformation of the Penrhyn-Piling basin; subduction beneath the Superior craton
forming the Snow Lake volcanic arc. 3 , 1865-1840 Ma: the Flin-Flon-Glennie and Parent-Spartan
volcanic arcs converge respectively with the Hearne and Sugluq cratons; the Meta Incognita terrane
converges with the Sugluq terrane and the Sask terrane with the Flin-Flon-Glennie arc; granitic
plutons emplaced along the SW margins of the Hearne, Sugluq and Meta Incognita cratons. 4 , 1830-
1800Ma: the main, end-Hudsonian event: the Superior craton collides with the combined upper-plate
cratons already amalgamated. NAC, North Atlantic craton; MI, Meta Incognita; CZ, Core Zone; LL,
La Ronge-Lynn Lake arc; FFG, Flin-Flon-Glennie arc; PS, Parent-Spartan arc; PPB, Penrhyn-Piling
basin; SL, Snow Lake belt. Based on reconstruction by Corrigan

Tectonic evolution of the THO
Four main phases of the orogeny have
been recognised, each represent-
ing a series of events culminating
in collisions, moving progressively
from west to east across the THO
(Figure 12.10). These are as follows.

. (2009). B. Cartoon sections
illustrating the possible tectonic evolution of the Trans-Hudson orogen along the line of section
shown on Figure B. Stage 1: 1920-1890 Ma; 2: 1880-1865 Ma; 3: 1865-1840 Ma; 4: 1830-1800 Ma.

et al