Churchill craton
Encyclopedia
Canadian Shield
The Canadian Shield, also called the Laurentian Plateau, or Bouclier Canadien , is a vast geological shield covered by a thin layer of soil that forms the nucleus of the North American or Laurentia craton. It is an area mostly composed of igneous rock which relates to its long volcanic history...
and stretches from southern Saskatchewan
Saskatchewan
Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....
and Alberta
Alberta
Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
to northern Nunavut
Nunavut
Nunavut is the largest and newest federal territory of Canada; it was separated officially from the Northwest Territories on April 1, 1999, via the Nunavut Act and the Nunavut Land Claims Agreement Act, though the actual boundaries had been established in 1993...
. It has a very complex geological history punctuated by at least seven distinct regional tectonometamorphic intervals, including many discrete accretionary magmatic events. The Western Churchill province
Province
A province is a territorial unit, almost always an administrative division, within a country or state.-Etymology:The English word "province" is attested since about 1330 and derives from the 13th-century Old French "province," which itself comes from the Latin word "provincia," which referred to...
is the part of the Churchill craton that is exposed north and west of the Hudson Bay
Hudson Bay
Hudson Bay , sometimes called Hudson's Bay, is a large body of saltwater in northeastern Canada. It drains a very large area, about , that includes parts of Ontario, Quebec, Saskatchewan, Alberta, most of Manitoba, southeastern Nunavut, as well as parts of North Dakota, South Dakota, Minnesota,...
. The Archaen (ca. 1.83 Ga) Western Churchill province contributes to the complicated and protracted tectonic history of the craton, and marks a major change in the behaviour of the Churchill craton with many remnants of Archean
Archean
The Archean , also spelled Archeozoic or Archæozoic) is a geologic eon before the Paleoproterozoic Era of the Proterozoic Eon, before 2.5 Ga ago. Instead of being based on stratigraphy, this date is defined chronometrically...
supracrustal
Supracrustal rock
Supracrustal rocks are rocks that were deposited on the existing basement rocks of the crust, hence the name. They may be further metamorphosed from both sedimentary and volcanic rocks....
and granitoid
Granitoid
A granitoid or granitic rock is a variety of coarse grained plutonic rock similar to granite which mineralogically are composed predominately of feldspar and quartz. Examples of granitoid rocks include granite, quartz monzonite, quartz diorite, syenite, granodiorite and trondhjemite. Many are...
rocks.
Major tectonometamorphic intervals
- 2.69 Ga: deformation in the northern Hearne Domain.
- 2.685 Ga: greenschistGreenschistGreenschist is a general field petrologic term applied to metamorphic or altered mafic volcanic rock. The term greenstone is sometimes used to refer to greenschist but can refer to other rock types too. The green is due to abundant green chlorite, actinolite and epidote minerals that dominate the...
-grade metamorphismMetamorphismMetamorphism is the solid-state recrystallization of pre-existing rocks due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids. Mineralogical, chemical and crystallographic changes can occur during this process...
and deformation in the central Hearne Domain. - 2.60 Ga: granitoid plutonism across the northern Hearne and Rae Domains.
- 2.50-2.55 Ga: metamorphism and deformation in the northern Hearne domain.
- 1.9 Ga: metamorphism and deformation in the northern Hearne Domain.
- 1.83 Ga: magmatism and deformation in the northern Hearne and Rai Domains.
- 1.755 Ga: plutonism in the western Hearne and eastern Rae Domains. (Sandeman, 2001)
Hearne Domain, Western Churchill province
A north-northwest-trending crustal segment transects from Kaminak LakeKaminak Lake
Kaminak Lake is a lake in Kivalliq Region, Nunavut, Canada. The sub-Arctic lake is one of eleven lakes of the Ferguson River system which ultimately flows into the northwestern Hudson Bay...
(central Hearne Domain) in the south to Yathkyed Lake
Yathkyed Lake
Yathkyed Lake is a lake in Kivalliq Region, Nunavut, Canada. Located between Angikuni Lake and Forde Lake, it is one of several lakes on the Kazan River....
(northern Hearne Domain) in the northwest, consisting of Archaen supracrustal belts that preserve mostly Archaen mafic
Mafic
Mafic is an adjective describing a silicate mineral or rock that is rich in magnesium and iron; the term is a portmanteau of the words "magnesium" and "ferric". Most mafic minerals are dark in color and the relative density is greater than 3. Common rock-forming mafic minerals include olivine,...
to felsic
Felsic
The word "felsic" is a term used in geology to refer to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium....
volcanic rocks (greenschist
Greenschist
Greenschist is a general field petrologic term applied to metamorphic or altered mafic volcanic rock. The term greenstone is sometimes used to refer to greenschist but can refer to other rock types too. The green is due to abundant green chlorite, actinolite and epidote minerals that dominate the...
-grade supracrustal and granitoids), metamorphic cooling of hornblende
Hornblende
Hornblende is a complex inosilicate series of minerals .It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole....
, and Proterozoic
Proterozoic
The Proterozoic is a geological eon representing a period before the first abundant complex life on Earth. The name Proterozoic comes from the Greek "earlier life"...
biotite
Biotite
Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula . More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers...
.
This section of the Churchill province was formerly called the Ennadai-Rankin greenstone belt
Greenstone belt
Greenstone belts are zones of variably metamorphosed mafic to ultramafic volcanic sequences with associated sedimentary rocks that occur within Archaean and Proterozoic cratons between granite and gneiss bodies....
and include the Kaminak, Yathkyed, MacQuoid and Rankin supracrustal belts, containing a wide range of intrusive Neoarchean plutonic rocks ranging in composition from gabbro
Gabbro
Gabbro refers to a large group of dark, coarse-grained, intrusive mafic igneous rocks chemically equivalent to basalt. The rocks are plutonic, formed when molten magma is trapped beneath the Earth's surface and cools into a crystalline mass....
to syenogranite
Syenogranite
Syenogranite is a fine to coarse grained intrusive igneous rock of the same general composition as granite. They are characteristically felsic.The feldspar component of syenogranite is predominantly alkaline in character...
. The Kaminak supracrustal belt preserves igneous textures including interlocking quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
and plagioclase
Plagioclase
Plagioclase is an important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series...
that are intergrown with platy biotite (2.084-1.914 Ga) and stubby euhedral
Euhedral
Euhedral crystals are those that are well-formed with sharp, easily recognised faces. Normally, crystals do not form smooth faces or sharp crystal outlines. Many crystals grow from cooling liquid magma...
grains of prismatic
Prism (geometry)
In geometry, a prism is a polyhedron with an n-sided polygonal base, a translated copy , and n other faces joining corresponding sides of the two bases. All cross-sections parallel to the base faces are the same. Prisms are named for their base, so a prism with a pentagonal base is called a...
titanite
Titanite
Titanite, or sphene , is a calcium titanium nesosilicate mineral, CaTiSiO5. Trace impurities of iron and aluminium are typically present...
and hornblende. The Yathkyed belt contains a range of hornblende cooling (2.63-246 Ga) amphibolitic
Amphibolite
Amphibolite is the name given to a rock consisting mainly of hornblende amphibole, the use of the term being restricted, however, to metamorphic rocks. The modern terminology for a holocrystalline plutonic igneous rocks composed primarily of hornblende amphibole is a hornblendite, which are...
metamorphic rocks. The Kaminak and Yathkyed belts are overlain by the Proterozoic (2.45 Ga) Hurwitz Group. Deformation of the Hurwitz Group occurred after the 2.11 Ga intrusion
Intrusion
An intrusion is liquid rock that forms under Earth's surface. Magma from under the surface is slowly pushed up from deep within the earth into any cracks or spaces it can find, sometimes pushing existing country rock out of the way, a process that can take millions of years. As the rock slowly...
of gabbro
Gabbro
Gabbro refers to a large group of dark, coarse-grained, intrusive mafic igneous rocks chemically equivalent to basalt. The rocks are plutonic, formed when molten magma is trapped beneath the Earth's surface and cools into a crystalline mass....
sills
Sill (geology)
In geology, a sill is a tabular sheet intrusion that has intruded between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the direction of foliation in metamorphic rock. The term sill is synonymous with concordant intrusive sheet...
, but prior to the intrusion of the 1.83 Ga lamprophyre
Lamprophyre
Lamprophyres are uncommon, small volume ultrapotassic igneous rocks primarily occurring as dikes, lopoliths, laccoliths, stocks and small intrusions...
dykes
Dike (geology)
A dike or dyke in geology is a type of sheet intrusion referring to any geologic body that cuts discordantly across* planar wall rock structures, such as bedding or foliation...
associated with the ultrapotassic
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...
s of the nearby Baker Lake Basin. Parallel to the Paleoproterozoic
Paleoproterozoic
The Paleoproterozoic is the first of the three sub-divisions of the Proterozoic occurring between . This is when the continents first stabilized...
Hurwitz Group are massive veins
Vein (geology)
In geology, a vein is a distinct sheetlike body of crystallized minerals within a rock. Veins form when mineral constituents carried by an aqueous solution within the rock mass are deposited through precipitation...
of green biotite that are interpreted to have been emplaced there by a hydrothermal event accompanying a deformation along this contact area. (Sandeman, 2001)
Murmac Bay Group, Western Churchill province
The Murmac Bay Group exposed in the southwestern half of the Western Churchill Craton, near Uranium City, SaskatchewanUranium City, Saskatchewan
Uranium City is a settlement in northwestern Saskatchewan, Canada. It is on the northern shores of Lake Athabasca near the border of the Northwest Territories. It is above sea level. The settlement is northwest of Prince Albert, 760 km northeast of Edmonton and south of the Northwest...
consists of a mixed package of Precambrian
Precambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
volcanic and sedimentary rocks These rocks sit on ca. 3 Ga granitoid
Granitoid
A granitoid or granitic rock is a variety of coarse grained plutonic rock similar to granite which mineralogically are composed predominately of feldspar and quartz. Examples of granitoid rocks include granite, quartz monzonite, quartz diorite, syenite, granodiorite and trondhjemite. Many are...
s and have been affected by several deformational and metamorphic
Metamorphism
Metamorphism is the solid-state recrystallization of pre-existing rocks due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids. Mineralogical, chemical and crystallographic changes can occur during this process...
events.
Taltson Magmatic Zone and Taltson basement
The Taltson Magmatic ZoneTaltson Magmatic Zone
The Taltson Magmatic Zone is a zone of Paleoproterozoic magmatic rocks in the Canadian Shield, extending from Northern Alberta to the Northwest Territories...
(south of 60°N) is a composite continental magmatic arc and collisional orogen
Orogeny
Orogeny refers to forces and events leading to a severe structural deformation of the Earth's crust due to the engagement of tectonic plates. Response to such engagement results in the formation of long tracts of highly deformed rock called orogens or orogenic belts...
resulting from the convergence of the Buffalo Head terrane with the Archean Churchill craton. The Taltson basement
Basement Rock
Basement or Basement Rock music was a sub-genre coined in 2006 in an article by music magazine TGR. This was first in relation to the existence of underground record label Criminal Records but more for the independent bands they represent. The roots of the sub-genre are noted to be as far back as...
(ca. 3.2–3.0 Ga and 2.4–2.14 Ga) and Rutledge River supracrustal gneiss
Gneiss
Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks.-Etymology:...
es (2.13–2.09 Ga) were intruded by voluminous I- and S-type magmatic rocks between 1.99 and 1.92 Ga.
Economic geology
There is aggressive diamond exploration drilling in the south Slave Province, NWT, Churchill craton (at the northwest corner of the Hudson BayHudson Bay
Hudson Bay , sometimes called Hudson's Bay, is a large body of saltwater in northeastern Canada. It drains a very large area, about , that includes parts of Ontario, Quebec, Saskatchewan, Alberta, most of Manitoba, southeastern Nunavut, as well as parts of North Dakota, South Dakota, Minnesota,...
) and in Ontario
Ontario
Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....
. The Northwest Territories
Northwest Territories
The Northwest Territories is a federal territory of Canada.Located in northern Canada, the territory borders Canada's two other territories, Yukon to the west and Nunavut to the east, and three provinces: British Columbia to the southwest, and Alberta and Saskatchewan to the south...
(NWT), North Slave craton
Slave craton
The Slave craton is a Canadian geological formation located in the Northwest Territories and Nunavut. This craton is approximately in size and forms part of the Canadian Shield. It is dominated by ca. 2.73-2.63 Ga greenstones and turbidite sequences and ca. 2.72-2.58 Ga plutonic rock, with large...
and Keewatin regions of Nunavut and the north-central region of Alberta are regions that are all underlain by diamond
Diamond
In mineralogy, diamond is an allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at ambient conditions...
-friendly cratonic rocks of the Slave craton, Churchill craton and the Buffalo Head craton. The diamonds being found in the NWT were created 50 to 600 mya during catacylismic explosions of kimberlite
Kimberlite
Kimberlite is a type of potassic volcanic rock best known for sometimes containing diamonds. It is named after the town of Kimberley in South Africa, where the discovery of an diamond in 1871 spawned a diamond rush, eventually creating the Big Hole....
, a molten magma originating up to 400 kilometers beneath the Earth's surface.
Unlike the Slave craton, which is covered with shallow lakes and swamp, the eastern part of the Churchill craton is drier. Kimberlites may be obscured by foliage rather than water, therefore many targets may be drillable during the summer, not just during the short winter window when lakes are frozen and daylight is available. In comparison drilling in the Eastern Arctic is too remote compared to the Slave craton, which is serviced by the fully developed infrastructure of Yellowknife. The Eastern Arctic is serviced by the smaller town of Rankin Inlet, which in turn is serviced by barge during summer.