Nain province
Encyclopedia
In Labrador
, Canada, the North Atlantic craton
is known as the Nain province. The Nain geologic province
was intruded by the Nain Plutonic Suite which divides the province into the northern Saglek block and the southern Hopedale
block.
, the Scourian Complex of northwestern Scotland
and is unexposed in northern Norway
. The North Atlantic craton fragmented 2450 to 2000 million years ago. When North America and Europe rejoined, the North Atlantic craton was triangular shaped with each side 600 km (372.8 mi); this unit was separated when the Labrador Sea
formed 61 to 40 million years ago. The North Atlantic craton's crust varies between 28 to 38 km (17.4 to 23.6 mi) thick and its rocks are 85% granitoid
gneisses. The Nain province was intruded by the 1350- to 1290-million-year-old Nain Plutonic Suite; composite anorthosite
-granitic intrusion
s which divide the Nain province into the northern Saglek block and the southern Hopedale block.
es of the Nain province were last deformed and metamorphose
d when two blocks docked together 2500 million years ago with a collisional boundary extending 200 km (124.3 mi) to the north and 150 km (93.2 mi) to the south of Nain, Labrador, Canada
. These two blocks appear to represent two distinct Archean
cratonic nuclei, each with its own mineral depositional history.
Major granitic intrusions – the Wheeler Mountain, Halbach, Alliger, Sheet Hill, Loon Island, Red Island
, and Satok Island intrusions – form a north-trending 150 km (93.2 mi) linear chain which have a southerly decrease in age – 2135-million-year-old Wheeler Mountain granite in the north to the 2025-million-year-old Satok Island monzonite in the south. The Nain province was then intruded by the 1350- to 1290-million-year-old Nain Plutonic Suite; composite anorthosite-granitic intrusions which divide the Nain province into the northern Saglek block and the southern Hopedale block. The Torngat orogen
developed during the oblique convergence
of the Superior
and Nain provinces 900 million years ago.
The crystal
line crust
in the Nain province is 38 km (23.6 mi) thick; it thins to 9 km (5.6 mi) thick in the shelf area of the Labrador margin, where it is covered with up to 8 km (5 mi) of sediments.
s. Within the gneiss are variably-sized enclaves ranging from anorthosite
to ultramafic. There are also three small anorthositic, ultramafic meta-igneous complexes in the gneiss near Okak Bay.
The northward–trending Handy fault separates the Saglek block into two metamorphic parts. The gneiss complex on the western side of the Handy fault has rocks that crystallized under granulite facies
conditions; this western block is more deeply exposed than the eastern one. On the eastern side amphibolite facies rocks are exposed in the northern part; they transition to granulite facies to the south. The total crustal thickness is 33 km (20.5 mi) north of the fault and 38 km (23.6 mi) south of the fault.
and 3000-million-year-old Florence Lake greenstone belts, and the Weekes amphibolite which represents remnants of the older Hunt River greenstone belt.
Labrador
Labrador is the distinct, northerly region of the Canadian province of Newfoundland and Labrador. It comprises the mainland portion of the province, separated from the island of Newfoundland by the Strait of Belle Isle...
, Canada, the North Atlantic craton
Craton
A craton is an old and stable part of the continental lithosphere. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates. They are characteristically composed of ancient crystalline basement rock, which may be covered by...
is known as the Nain province. The Nain geologic province
Geologic province
A geologic or geomorphic province is a spatial entity with common geologic or geomorphic attributes. A province may include a single dominant structural element such as a basin or a fold belt, or a number of contiguous related elements...
was intruded by the Nain Plutonic Suite which divides the province into the northern Saglek block and the southern Hopedale
Hopedale, Newfoundland and Labrador
Hopedale is a town located in the North of Labrador, the mainland portion of the Canadian province of Newfoundland and Labrador. Hopedale is the legislative capital of the Inuit Land Claims Area Nunatsiavut, and where the Nunatsiavut Assembly meets...
block.
North Atlantic craton
The North Atlantic craton is exposed in parts of the coast of Labrador, parts of central GreenlandGreenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...
, the Scourian Complex of northwestern Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
and is unexposed in northern Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
. The North Atlantic craton fragmented 2450 to 2000 million years ago. When North America and Europe rejoined, the North Atlantic craton was triangular shaped with each side 600 km (372.8 mi); this unit was separated when the Labrador Sea
Labrador Sea
The Labrador Sea is an arm of the North Atlantic Ocean between the Labrador Peninsula and Greenland. The sea is flanked by continental shelves to the southwest, northwest, and northeast. It connects to the north with Baffin Bay through the Davis Strait...
formed 61 to 40 million years ago. The North Atlantic craton's crust varies between 28 to 38 km (17.4 to 23.6 mi) thick and its rocks are 85% granitoid
Granite
Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...
gneisses. The Nain province was intruded by the 1350- to 1290-million-year-old Nain Plutonic Suite; composite anorthosite
Anorthosite
Anorthosite is a phaneritic, intrusive igneous rock characterized by a predominance of plagioclase feldspar , and a minimal mafic component...
-granitic 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...
s which divide the Nain province into the northern Saglek block and the southern Hopedale block.
Nain province
In Labrador the North Atlantic craton is known as the Nain province or Nain craton. The Nain province is more than 600 kilometres (372.8 mi) long and 100 km (62.1 mi) wide. The gneissGneiss
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 of the Nain province were last deformed and metamorphose
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...
d when two blocks docked together 2500 million years ago with a collisional boundary extending 200 km (124.3 mi) to the north and 150 km (93.2 mi) to the south of Nain, Labrador, Canada
Nain, Newfoundland and Labrador
Nain or Naina is the northernmost town of any size in the Canadian province of Newfoundland and Labrador, located about 370 kilometres by air from Happy Valley-Goose Bay. The town was established as a Moravian mission in 1771 by Jens Haven and other missionaries...
. These two blocks appear to represent two distinct 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...
cratonic nuclei, each with its own mineral depositional history.
Major granitic intrusions – the Wheeler Mountain, Halbach, Alliger, Sheet Hill, Loon Island, Red Island
Red Island, Newfoundland and Labrador
Red Island is located about 12 miles northwest of Placentia, Newfoundland and Labrador in Placentia Bay. It had five families in 1864, and had a population of approximately 350 in the 1945 census. The village of 283 was depopulated in October 1968, during the Provincial Government's Resettlement...
, and Satok Island intrusions – form a north-trending 150 km (93.2 mi) linear chain which have a southerly decrease in age – 2135-million-year-old Wheeler Mountain granite in the north to the 2025-million-year-old Satok Island monzonite in the south. The Nain province was then intruded by the 1350- to 1290-million-year-old Nain Plutonic Suite; composite anorthosite-granitic intrusions which divide the Nain province into the northern Saglek block and the southern Hopedale block. The Torngat 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...
developed during the oblique convergence
Convergent boundary
In plate tectonics, a convergent boundary, also known as a destructive plate boundary , is an actively deforming region where two tectonic plates or fragments of lithosphere move toward one another and collide...
of the Superior
Superior craton
The Superior craton forms the core of the Canadian Shield at the heart of the North American continent. It extends from Quebec in the east to eastern Manitoba in the west...
and Nain provinces 900 million years ago.
The crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
line crust
Crust (geology)
In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...
in the Nain province is 38 km (23.6 mi) thick; it thins to 9 km (5.6 mi) thick in the shelf area of the Labrador margin, where it is covered with up to 8 km (5 mi) of sediments.
Saglek block
The 3800- to 3300-million-year-old Saglek block is 375 km (233 mi) long and 50 km (31.1 mi) wide; it has a north-northwesterly trend from Nain, Labrador, extending nearly to the northern tip of Labrador. This block is a high-grade gneiss terrane; it has no greenstone beltGreenstone 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....
s. Within the gneiss are variably-sized enclaves ranging from anorthosite
Anorthosite
Anorthosite is a phaneritic, intrusive igneous rock characterized by a predominance of plagioclase feldspar , and a minimal mafic component...
to ultramafic. There are also three small anorthositic, ultramafic meta-igneous complexes in the gneiss near Okak Bay.
The northward–trending Handy fault separates the Saglek block into two metamorphic parts. The gneiss complex on the western side of the Handy fault has rocks that crystallized under granulite facies
Granulite
Granulites are medium to coarse–grained metamorphic rocks that have experienced high temperature metamorphism, composed mainly of feldspars sometimes associated with quartz and anhydrous ferromagnesian minerals, with granoblastic texture and gneissose to massive structure...
conditions; this western block is more deeply exposed than the eastern one. On the eastern side amphibolite facies rocks are exposed in the northern part; they transition to granulite facies to the south. The total crustal thickness is 33 km (20.5 mi) north of the fault and 38 km (23.6 mi) south of the fault.
Hopedale block
The 3100- to 2800-million-year-old Hopedale block is 150 km (93.2 mi) long and 90 km (55.9 mi) wide. Hopedale, Labrador, is at the eastern midpoint. This block contains the 3100-million-year-old Hunt RiverHunt River greenstone belt
The Hunt River greenstone belt, also called the Hunt River volcanic belt, is a northeast trending Mesoarchean greenstone belt in Newfoundland and Labrador, Canada, located along the coast of Labrador about west of the town of Hopedale. It is long and consists of metavolcanic and metasedimentary...
and 3000-million-year-old Florence Lake greenstone belts, and the Weekes amphibolite which represents remnants of the older Hunt River greenstone belt.