The Muskox intrusion is a layered intrusion in 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...

, Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

. It is located 144 km (89.5 mi) northeast of Great Bear Lake

Great Bear Lake

Great Bear Lake is the largest lake entirely within Canada , the third or fourth largest in North America, and the seventh or eighth largest in the world...

 and 90 km (55.9 mi) south of Kugluktuk

Kugluktuk, Nunavut

Kugluktuk is a hamlet located at the mouth of the Coppermine River in the Kitikmeot Region of Nunavut, Canada, on Coronation Gulf, southwest of Victoria Island...

 on Coronation Gulf

Coronation Gulf

Coronation Gulf lies between Victoria Island and mainland Nunavut in Canada. To the northwest it connects with Dolphin and Union Strait and thence the Beaufort Sea and Arctic Ocean; to the northeast it connects with Dease Strait and thence Queen Maud Gulf. To the southeast lies Bathurst...

. It was formed during a large magmatic event during the 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"...

 by hotspot

Hotspot (geology)

The places known as hotspots or hot spots in geology are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the mantle elsewhere. They may be on, near to, or far from tectonic plate boundaries. There are two hypotheses to explain them...

 or mantle plume

Mantle plume

A mantle plume is a hypothetical thermal diapir of abnormally hot rock that nucleates at the core-mantle boundary and rises through the Earth's mantle. Such plumes were invoked in 1971 to explain volcanic regions that were not thought to be explicable by the then-new theory of plate tectonics. Some...

 volcanism that emplaced the widespread Coppermine River Group flood basalt

Flood basalt

A flood basalt or trap basalt is the result of a giant volcanic eruption or series of eruptions that coats large stretches of land or the ocean floor with basalt lava. Flood basalts have occurred on continental scales in prehistory, creating great plateaus and mountain ranges...

s.

The intrusion is a tilted trough shaped body with an exposed length of 120 km (74.6 mi) and a thickness or origiinal vertical dimension of over 6 km (3.7 mi). Rock types include picrite, peridotite

Peridotite

A peridotite is a dense, coarse-grained igneous rock, consisting mostly of the minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium, reflecting the high proportions of magnesium-rich olivine, with appreciable iron...

, dunite

Dunite

Dunite is an igneous, plutonic rock, of ultramafic composition, with coarse-grained or phaneritic texture. The mineral assemblage is greater than 90% olivine, with minor amounts of other minerals such as pyroxene, chromite and pyrope. Dunite is the olivine-rich end-member of the peridotite group...

, pyroxenite

Pyroxenite

Pyroxenite is an ultramafic igneous rock consisting essentially of minerals of the pyroxene group, such as augite and diopside, hypersthene, bronzite or enstatite. They are classified into clinopyroxenites, orthopyroxenites, and the websterites which contain both pyroxenes...

, 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....

 and granophyre

Granophyre

Granophyre is a subvolcanic rock that contains quartz and alkali feldspar in characteristic angular intergrowths such as those in the accompanying image....

. A feeder dike

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...

 of olivine

Olivine

The mineral olivine is a magnesium iron silicate with the formula 2SiO4. It is a common mineral in the Earth's subsurface but weathers quickly on the surface....

 gabbro is exposed "below" the now tilted sequence.

Potassium argon dating in the region provides an age of 1095 - 1155 Ma for the Muskox intrusion, 1100 - 1200 Ma for the Mackenzie dike swarm

Mackenzie dike swarm

The Mackenzie dike swarm, also called the Mackenzie dikes, form a large igneous province in the western Canadian Shield of Canada. It is part of the larger Mackenzie Large Igneous Province and is one of more than three dozen dike swarms in various parts of the Canadian Shield...

 and 740 - 1200 Ma for the Coppermine basalt flows (younger dates are interpreted as having been reset by later intrusion of gabbro sills at 604 - 718 Ma). Further stratigraphic and structural evidence provides further support that the Muskox, the MacKenzie dikes and the Coppermine flows are of the same magmatic event that formed the Mackenzie Large Igneous Province

Mackenzie Large Igneous Province

The Mackenzie Large Igneous Province is a major Mesoproterozoic large igneous province of the southwestern, western and northwestern Canadian Shield in Canada. It consists of a group of related igneous rocks that were formed during a massive igneous event starting about 1,270 million years ago...

 and the Muskox is interpreted as occupying the magma chamber which fed the volcanism.

See also

• Volcanism of Canada
• Volcanism of Northern Canada
  Volcanism of Northern Canada
  Volcanism of Northern Canada has led to the formation of hundreds of volcanic areas and extensive lava formations across Northern Canada, indicating volcanism played a major role in shaping its surface...
  
  
• Mackenzie hotspot
  Mackenzie hotspot
  The Mackenzie hotspot was a volcanic hotspot that existed about 1,267 million years ago across Canada from the Northwest Territories and Nunavut. It is responsible for the creation of the Mackenzie Large Igneous Province, which contains the largest dike swarm on Earth...