Geology of the Reindeer Lake area, Saskatchewan, with emphasis on granitic rocks
Date
1979-01-01
Authors
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ORCID
Type
Degree Level
Doctoral
Abstract
Reconnaissance geological mapping has been carried out on
8500 sq km centered on the northern part of Reindeer Lake in northern
Saskatchewan. Parts of four major litho-structural domains occur in the
area: from northwest to southeast they are the Whiskey Jack Domain, the
Rottenstone Domain, the La Ronge Domain, and the Kisseynew Domain. This
map area lies primarily in the Rottenstone Domain.
The Whiskey Jack Domain (a new name proposed here) includes
an Archaean granite basement overlain by the Aphebian Wollaston metasedimentary
gneisses, both of which have been partially remobilized
during the Hudsonian Orogeny.
In the northwest, the Rottenstone Domain contains granitoid
and younger gabbroic rocks, both of possible Archaean age. Large
areas in the central portion of the domain are underlain by rocks of
the Hudsonian Wathaman Batholith. In the southeastern part of the
domain, Aphebian migmatitic and metasedimentary gneisses are intercalated
with granitic rocks.
The La Ronge Domain consists principally of granodioritic
bodies, forming part of the South Reindeer Batholith (a term proposed
in this study). It also contains the La Ronge metasedimentarymetavolcanic
gneisses. Both granites and gneisses were folded during
the Hudsonian Orogeny.
The Kisseynew Domain is restricted to a small area. It
contains both the La Ronge and Burntwood River gneisses, which are
intercalated with deformed granitic bodies.
Twenty five major rock units were mapped, these include
metasedimentary and metavolcanic rocks, mylonites, basic and granitic
rocks. Major element chemistry indicates that some of the granitic
rocks have been magmatically fractionated. Field evidence indicates
that other granitic bodies possibly have been formed by metasomatism and
anatexis especially near the southern contact of the Wathaman Batholith,
a conclusion not completely supported by the major element chemistry.
The present study establishes that the Needle Falls Shear
Zone and the Wathaman Batholith together are related to a major crustal
discontinuity. Rocks northwest of the discontinuity include both
Archaean basement material and Aphebian supercrustal rocks, whereas
rocks to the southeast are entirely Aphebian. The Wathaman Batholith and
the Needle Falls Shear Zone formed during the peak of Hudsonian tectonothermal
activity in this part of the Churchill Province of the Canadian
Shield. The Wathaman Batholith, one of the largest in the world, is
1100 km long and 40 to 60 km wide. The isotopic and REE compositions of
rocks from the batholith indicate that the magma was probably derived by
the fusion of pre-existing continental crust at great depth. Garnet,
amphibole, and hypersthene were probably major residual phases in the
source region during the formation of the magma. Concomitant with
emplacement of the Wathaman Batholith, pre-existing granitic and metasedimentary
rocks southeast of the batholith were tectonically 'rolled
up' in a polyphase deformation sequence, and slightly younger migmatites
and autochthonous-allochthonous granites were formed immediately adjacent
to the batholith. The structural fabric of the schists and gneisses was
formed by complex superposition and transposition of foliations, some of
which are axial planar to folds though others are related to shear zones.
The emplacement of the Wathaman Batholith was preceded by
the emplacement of the large South Reindeer Batholith of Aphebian age.
This batholith parallels the Wathaman Batholith, intrudes the Burntwood
River gneisses, and appears to be unconformably overlain by the La Ronge
gneisses. The Wathaman and South Reindeer Batholiths are paired
batholiths and are analogous to the large paired batholiths in the
Western Cordilleras.
Note:This thesis contains maps that have been sized to fit the viewing area. Use the zoom in tool to view the maps in detail or to enlarge the text.
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Degree
Doctor of Philosophy (Ph.D.)
Department
Geological Sciences
Program
Geological Sciences