Animikie Group

Last updated
Iron Range areas marked include: G-Gunflint Iron Range, F-Mesabi Iron Range, E-Cuyuna Iron Range Animikie Group, Marquette Range and Huronian supergroups2.PNG
Iron Range areas marked include: G-Gunflint Iron Range, F-Mesabi Iron Range, E-Cuyuna Iron Range

The Animikie Group is a geologic group composed of sedimentary and metasedimentary rock, having been originally deposited between 2,500 and 1,800 million years ago during the Paleoproterozoic era, within the Animikie Basin. This group of formations is geographically divided into the Gunflint Range, the Mesabi and Vermilion ranges, and the Cuyuna Range. On the map, the Animikie Group is the dark gray northeast-trending belt which ranges from south-central Minnesota, U.S., up to Thunder Bay, Ontario, Canada. The Gunflint Iron Range is the linear black formation labeled G, the Mesabi Iron Range is the jagged black linear formation labeled F, and Cuyuna Iron Range is the two black spots labeled E. The gabbro of the Duluth Complex, intruded during the formation of the Midcontinent Rift, separates the Mesabi and Gunflint iron ranges; it is shown by the speckled area wrapping around the western end of Lake Superior.

Contents

Banded-iron formations are iron formations which formed about 2,000 million years ago and were first described in the Lake Superior region. Sediments associated with the last stage of the Great Lakes tectonic zone contain banded-iron formations. These sediments were deposited for two hundred million years and extend intermittently along roughly the same trend as the Great Lakes tectonic zone, from Minnesota into eastern Ontario, Canada, and through upper Wisconsin and Michigan. They are characterized by bands of iron compounds and chert. Enough oxygen had accumulated in seawater so that dissolved iron was oxidized; iron reacts with oxygen to form compounds that precipitate out including hematite, limonite and siderite. These iron compounds precipitated from the seawater in varying proportions with chert, producing banded-iron formations. These iron formations are abundant in the Lake Superior region. The Sudbury Impact event occurred 1,850 million years ago; it is theorized that this caused the end of the banded-iron deposits. The results of the impact affected concentrations of dissolved oxygen in the sea; the accumulation of banded-iron formations suddenly ended 1,850 million years ago.

The Gunflint Range consists of a basal conglomerate, then the Gunflint Iron formation and the Gunflint Chert with the Rove Formation deposited on top. The Mesabi Range consists of the basal Pokegama Quartzite layer, then the Biwabik Iron Formation with the Virginia Formation deposited on top. The Vermilion Range consists of the basal Ely Greenstone, then the Soudan Iron formation with various granites on top. The Cuyuna Range consists of the basal North Range group, then the Trommald Formation with the Thomson Formation deposited on top.

Age, location and size

The Animikie Group sediments were deposited between 2,500 and 1,800 million years ago, [1] :4 in the Animikie Basin. [2] Deposition of sediments began after the Algoman orogeny and continued through the Great Lakes tectonic zone rupture from 2,200 to 1,850 million years ago.

The Animikie Group formations are in east-central and northeastern Minnesota, and the Thunder Bay District of Northern Ontario; they are geographically divided into the Gunflint Range, the Mesabi and Vermilion ranges, and the Cuyuna Range. [3] The Animikie Basin was an extensional basin which developed over a basement consisting of the 2,750- to 2,600-million-year-old Superior province to the north and the 3,600-million-year-old Minnesota River Valley subprovince to the south. [2] The extension was caused by the east-northeasttrending Great Lakes tectonic zone; it separates the Superior province from the Minnesota River Valley subprovince. [2] The sediments were deformed, metamorphosed and intruded by the plutonic rocks of the 1860 ± 50-million-year-old Penokean orogeny. [2]

The rocks of the Animikie Basin form a sequence up to 10 km (6.2 mi) thick and show a complete transition from a stable shelf environment to deep-water conditions. [2] Irregularities in the basement influenced the thickness of the sequence. [2] The 700 km (430 mi) by 400 km (250 mi) basin is an elongated oval parallel to and straddling the Great Lakes tectonic zone. [2]

Development of Animikie Basin

Twenty-seven hundred million years ago the Algoman orogeny formed mountains; these bare mountains eroded for several hundred million years to a broad level peneplain. [4] :6 A sea invaded central Minnesota and extended eastward through northern Wisconsin and the Upper Peninsula of Michigan. [4] :6 Sediments composed of quartz-rich sand were deposited along the shoreline of this sea; these were succeeded by thick iron-rich layers and eventually kilometers of mud and muddy sand. [4] :6 The deposition of sedimentary strata on top of the Archean basement formed the Animikie Group. [4] :6

The next tectonic event was the Great Lakes tectonic zone which began with compression caused by the collision of the Superior province and the Minnesota River Valley subprovince during the Algoman orogeny about 2,700 million years ago; [5] it continued as a pulling apart (extensional) rift from 2,450 to 2,100 million years ago, [6] :145 followed by a second compression which deformed the rocks in the Lake Superior region during the Penokean orogeny which lasted from 1,900 to 1,850 million years ago. [7] The first deposits occurred during the initial stages of extension of the Great Lakes tectonic zone in the continental crust. [5] :3 As the crust expanded it thinned, and magma was intruded through fissures in the thinned crust. [5] :3 Sedimentation stopped during this transitional period because the elevation was now above sea level. [5] :3 During later stages, the spreading center was adding oceanic crust which is heavier than continental crust so the area subsided, seas returned, and the second layer of sediments were deposited unconformably on the basin fill. [5] :3

During the Penokean orogeny the Minnesota River Valley subprovince overrode the Superior province. Orogenic wedge.jpg
During the Penokean orogeny the Minnesota River Valley subprovince overrode the Superior province.

The third tectonic event was the Penokean orogeny which is dated 1,850 million years ago. [4] :7 The intense, northward-directed compression folded the shale and greywacke of the southernmost unit the Thomson Formation and metamorphosed the shale into slate. [4] :7 The Animikie strata on the Gunflint and Mesabi ranges were far enough away so they escaped this deformation and metamorphism; they contain some of the oldest unmetamorphosed sedimentary deposits in the world. [4] :7

Hotspot causing rifting of tectonic plates Divergent border lmb.png
Hotspot causing rifting of tectonic plates

About 1,100 million years ago a fourth tectonic event occurred in the Lake Superior region. [4] :7 A hotspot of magma from the Earth's mantle beneath present-day Lake Superior rose, causing the crust to dome and break apart. [4] :7 This zone of crustal thinning and fracturing is the Midcontinent Rift System; it extends in a boomerang shape for over 2,200 km (1,400 mi) from northeastern Kansas northward through Iowa, under the Twin Cities of Minnesota, beneath Lake Superior, and then south through the eastern Upper Peninsula of Michigan and beneath the central Lower Peninsula of Michigan. [4] :7 As the crust was being stretched thin and more magma flowed out from below, the center of the rift was continuously subsiding. [4] :8 The vast quantities of rising magma created a vacuum under the crust, the weight of the solidified magma on the surface caused the crust to subside into that vacuum so the edges of the rift tilted toward the center. [4] :8 The rifting stopped after a few million years; one reason could be that the Grenville orogeny stopped the rift process when that collision occurred. [4] :9 Subsidence continued for several million years after the lava flows had ceased; immense volumes of sediments sand, gravel and mud were eroded off the barren landscape into the still-sinking basin along the rift axis. [4] :9 As much as 8 km (5.0 mi) of sedimentary rocks accumulated in the center before the sinking stopped and the region stabilized. [4] :9 A north-northeast trending branch of the Midcontinent Rift System separated the Animikie Basin into two distinct segments; the present-day Animikie Group and the Marquette Range Supergroup; [8] the historical name for the Marquette Range Supergroup is the Animikie Series.

Banded-iron formations

Hematitic banded-iron formation specimen from Michigan's Upper Peninsula; Scale bar is 5.0 mm MichiganBIF.jpg
Hematitic banded-iron formation specimen from Michigan's Upper Peninsula; Scale bar is 5.0 mm

Oceanic sediments associated with the last stage of the Great Lakes tectonic zone contain the banded-iron formations. [5] :4 Banded-iron formations are iron formations which formed about 2,000 million years ago and were first described in the Lake Superior region. [9] They are characterized by interlayers bands of iron minerals and chert (quartz). [9] These sediments were laid down for two hundred million years and extend intermittently along roughly the same trend as the Great Lakes tectonic zone, from Minnesota into eastern Canada, and through upper Wisconsin and Michigan. [5] :4

Change in atmospheric oxygen levels

Banded-iron sediments record the introduction of abundant free oxygen into earth's atmosphere. [5] :2 Microbial life played an important role in changing atmospheric conditions by releasing free oxygen as a waste product of photosynthesis. [5] :2 Free oxygen was taken up by elements with strong affinities for it hydrogen, carbon and iron. [5] :2 Evidence for the change in oxygen levels is that the sediments of the earlier Archean are dark brown and black caused by unoxidized carbon, iron sulfide, and other elements and compounds. [5] :2 As oxygen levels increased in the atmosphere and oceans, the sediments changed. [5] :2 In the late Archean, sediments went through a transitional stage with the banded-iron formations; after this transition they demonstrate an oxygen-rich environment shown by iron oxide-stained siltstones or mudstones called red beds. [5] :2

Enough oxygen had accumulated in seawater so that dissolved iron which had earlier eroded from the surrounding land was oxidized. [9] Oxygenated water has low levels of dissolved iron because iron reacts with oxygen to form compounds that precipitate out; [10] the compounds include hematite (Fe2O3), limonite (Fe2O3·2H2O) and siderite (FeCO3). [9] These iron compounds precipitated from the sea water in varying proportions with chert, producing banded-iron formations. [9] Banded-iron formations occur in several ranges around the margins of this basin, five of which contained sufficient concentrations of iron to be economically mined. [2] These banded-iron formations have been one of the world's greatest sources of iron ore since mining began in the area during the late 19th century. [4] :7 Major iron formations in different parts of the basin represent either nearly contemporaneous shelf sedimentation on either side of the main basin, or deposits formed simultaneously in isolated sub-basins of the main basin. [2]

Effect of the Sudbury Impact on atmospheric oxygen levels

A 25 to 70 cm (9.8 to 27.6 in) thick lateral layer between the metasedimentary Gunflint Iron Formation and overlying Rove Formation, and between the Biwabik Iron Formation and overlying Virginia Formation has evidence that the layer contains hypervelocity impact ejecta. [11] Radiometric dating reveals that this layer was deposited between 1,878 and 1,836 million years ago. [11] The Sudbury Impact event which occurred 650 to 875 km (404 to 544 mi) to the east 1,850 ± 1 million years ago is the likely ejecta source, making these the oldest ejecta linked to a specific impact. [11] Additional evidence indicates a 16 km (10 mi) diameter meteorite collided with Earth [12] in the current-day vicinity of Sudbury, Ontario, Canada. [13] The meteorite vaporized and created a 240 km (150 mi) wide crater. [12] Earthquakes shattered the ground hundreds of kilometers away and within seconds ejecta (cloud of ash, rock fragments, gases and droplets of molten rock) began to spread around the globe. [12] It is estimated that at ground zero the earthquake would have registered 10.2 on the Richter magnitude scale. [12]

To put the Sudbury meteorite impact in perspective, the Chicxulub impact on the Yucatán Peninsula occurred 66 million years ago with the impact of a 16.5 km (10.3 mi) diameter comet. [14] The kinetic energy from this impact probably generated earthquakes registering 13 on the Richter scale. [15] :334 The results of this impact caused the worldwide extinction of many species (including dinosaurs). [12] The Sudbury Impact would have also had global ramifications; [12] it is conjectured that this caused the end of the banded-iron deposits. The results of the impact fundamentally affected concentrations of dissolved oxygen in the sea; the accumulation of marine sediments (the banded-iron formations) were almost instantaneously shut down and banded-iron formation buildups suddenly ended about 1,850 million years ago. [13] In northeastern Minnesota these iron-banded formations lie immediately under the ejecta layer. [13]

One use of the impact layer is as a precise timeline that ties together well-known stratigraphic sequences of the various geographically separated iron ranges. [16] The Sudbury Impact layer lies at a horizon that records a significant change in the character of sediments across the region. [16] The layer marks the end of a major period of banded-iron formation deposition that was succeeded by deposition of fine clastic rocks commonly black shales. [16]

End of deposition

Sedimentation styles of the passive margin changed as deposition came to a close. [5] :4 The sedimentary environment recorded near the end changed from deep water shales derived from Archean rocks to coarser clastic rocks derived from a younger Proterozoic source. [5] :4 This change is interpreted to be from the Pembine-Wausau island arc as it closed in from the south just before its collision during the Penokean orogeny. [5] :4 Sediments shedding off the island arc settled on top of the previously deposited sequences.

Formations within Animikie Group

Gunflint Range

The Duluth Complex splits the Mesabi and Gunflint ranges. Duluthcomplexmap.png
The Duluth Complex splits the Mesabi and Gunflint ranges.

The Gunflint Range is a mountain range in northeastern Minnesota, U.S., and western Ontario, Canada. The Gunflint and Mesabi ranges form a belt extending from the upper Mississippi River to the extreme northeast part of Minnesota and into Canada to Thunder Bay. [17] :4 The two ranges are separated by the 1,099-million-year-old Duluth Complex which was formed during the Midcontinent Rift. [18]

The Gunflint Iron Formation is 1,878 ± 2 million years old. [19] It lies on top of a basal conglomerate, unlike the Biwabik Iron Formation which was deposited on top of the Pokegama Quartzite in the Mesabi Range, and the Cuyuna Iron Formation which was deposited on top of the Mille Lacs and North ranges. It is 150 km (93 mi) long, less than 8 km (5.0 mi) wide, [20] and 135 to 170 m (443 to 558 ft) thick. [21] This iron formation lies in a northeasterly-trending belt; most of it lies in Ontario. [20]

Rove formation represented by prv Ne mn geologic map.jpg
Rove formation represented by prv

The upper sedimentary layer is the 1,800- to 1,600-million-year-old Rove Formation. [1] The seas and laid down the shales, slates and mudstones of the Rove Formation. [22] :6 Because the formation is on the northern part of the Animikie Basin these rocks escaped the crustal deformation from the Penokean orogeny that characterizes the equivalent strata of the Thomson Formation; this left the Rove Formation unmetamorphosed and lying flat. [4] :59 These are some of the oldest undeformed and unmetamorphosed sedimentary rocks in North America. [4] :59 The dikes and sills within the Rove Formation were intruded during the Midcontinent Rift. [4] :61

Mesabi Range

The Mesabi Range is over 320 km (200 mi) long and less than 16 km (9.9 mi) wide  its typical width is 4 km (2.5 mi) [17] :4 and 110 to 240 m (360 to 790 ft) thick. [21] Its natural ore is hematite- or geothite-rich leached iron formation; [1] natural ores contain up to 50% iron and less than 10% silica. [5] :4 These thick sedimentary layers contain millions of tons of iron and minor ores which have been mined in the Great Lakes region since before the turn of the 20th century. [5] :4 Sedimentation ended when the Penokean orogeny began 1,850 million years ago. [5] :4

The three different formations exposed along the Mesabi Iron Range were deposited along the leading edge of a foredeep basin the Animikie Basin which transgressed north over the Archean craton during the Penokean orogeny. [1] Deposition of the basal Pokegama Quartzite, the medial Biwabik Iron Formation and the upper Virginia Formation's sediments represent near-shore, shelf and slope environments, respectively. [1] These three layers were formed 2,500 to 1,600 million years ago. [1]

Pokegama Quartzite occupies the lowest level of the Mesabi Range sequence and is younger than 2,500 million years old. [1] It contains shale, siltstone and sandstone, which were deposited in a flat environment of the sea that covered the Archean surface. [1] It is 0 to 153 m (0 to 502 ft) thick, with an average of 60 m (200 ft). [23] :167

The 1,900- to 1,850-million-year-old Biwabik Iron Formation is a narrow belt of iron-rich strata that extends east-northeast for 200 km (120 mi); [24] its thickness varies from 60 to 600 m (200 to 1,970 ft), its average may be 305 m (1,001 ft). [23] :168 It has four primary subdivisions: the Lower Cherty (which was deposited upon the Pokegama Quartzite), the Lower Slatey, the Upper Cherty and the Upper Slaty (which the Virginia Formation rests upon). [25] :928 The two ore-producing layers are the Upper and Lower Cherty subdivisions; [25] cherts make up the bulk of the formation. [23] :167 The east end of the Biwabik Iron Formation was metamorphosed by the heat of the Duluth Complex. [23] :168 [26] [27]

The 1,850-million-year-old Virginia Formation is the sedimentary layer on top of the Biwabik Iron Range and forms the footwall of the 1,100-million-year-old Duluth Complex [28] in the Ely Hoyt Lakes region. [29] :24 The Virginia formation consists of black to dark gray argillite, [29] :25 which does not crop out in natural exposures. [30] :41

Vermilion Range

Anticline Anticline (PSF)-vector.svg
Anticline

The Vermilion Range is north of the Mesabi Iron Range; it is 154 km (96 mi) long and ranges from 3 to 30 km (1.9 to 18.6 mi) wide. [23] :169 Its basal unit is the Ely Greenstone layer. Ely Greenstone consists of igneous rocks which were metamorphosed by the gabbro of the Duluth Complex. [23] :169 The Ely Greenstone is a belt consisting chiefly of metamorphosed volcanic rocks which have been deformed so that original bedding stands nearly vertical. [31] In the Soudan area the Ely Greenstone has been tightly folded and slightly overturned southward into the Tower-Soudan anticline, and bedding is inclined 70-80° to the north. [31] The volcanic rocks of the Ely Greenstone are divided into a lower and upper sequence; the upper and lower volcanic sequences are separated by the Soudan Iron Formation a 50 to 3,000 m (160 to 9,840 ft) thick unit that is transitional with the Ely Greenstone which consists chiefly of banded iron-formation. [31] The Soudan Iron Formation is in the western part of the Vermilion Range. [23] :169 It is in narrow belts, and consists of cherts, hematite, magnetite and small amounts of pyrite. [23] :170 The narrow belts trend eastnortheast with the widest part to the southwest. [32] :21 These iron-bearing rocks are of sedimentary origin which overlie an igneous series. [23] :170 The iron formation is tightly folded with greenstone. [23] :170 and is overlain by granites in the Vermilion, Trout, Burntside, Basswood and Saganaga lake areas. [23] :169

Cuyuna Range

Constituent parts of Cuyuna Iron Range Cuyuna Iron Range general geology.PNG
Constituent parts of Cuyuna Iron Range
Cross section of Cuyuna North Range Cuyuna North Range cross section.PNG
Cross section of Cuyuna North Range

The Cuyuna Iron Range is southwest of the Mesabi Range in east-central Minnesota; it is 110 km (68 mi) by 32 km (20 mi) of tightly folded iron formations. [2] Its thickness ranges from 0 to 135 m (0 to 443 ft). [21] Two sequences the Mille Lacs and North ranges underlie the southern part of the Animike Group. [5] :4 The Mille Lacs Group is more than 2,197 ± 39 million years old. [2]

The North Range Group is the basal unit for the Cuyuna Range. It is divided into three structural units: South Range (The rocks of the South Range are assigned to the Mille Lacs group.), [33] North Range and the Emily District each with its own characteristic stratigraphy and structure. [33] The rocks of the South and North ranges are separated by a major north-verging thrust fault, and both are overlain unconformably by the Emily District. [33] The rocks of the North Range assigned to the North Range Group, [33] are divided into three formations, the Mahnomen, Trommald and Rabbit Lake. [33] The North Range of the Cuyuna Range was regionally metamorphosed during the Penokean orogeny, which peaked between 1,870 and 1,850 million years ago. [33] The iron ore of the Cuyuna is a Lake Superior-type iron-formation similar to other iron formations in the region. [9]

The Mahnomen Formation has a lower member, which lacks iron oxide components, and an upper member dominated by beds of iron oxide argillite and lean iron-formation interlayered with non-iron oxide argillite, siltstone and quartzose sandstone. [33] The Trommald Formation the principal iron formation of the North Range is a chemically precipitated unit. [33] This formation is 14 to 150 m (46 to 492 ft) thick and is composed of carbonate-silicate iron formations and associated manganese oxide deposits. [2] The iron oxidised to form hematite and goethite. [2] [34] The uppermost Rabbit Lake Formation has a lower member of black mudstone inserted with beds of iron formation and units of volcanogenic origin; and an upper member of slate, carbonaceous mudstone, greywacke and thin units of iron-rich strata. [33]

Syncline and anticlines Antecline (PSF).png
Syncline and anticlines

The top sedimentary layer is the Thomson Formation which was deposited 1,880 to 1,870 million years ago and deformed by the Penokean orogeny 1,850 million years ago. [1] The formation contains folded and metamorphosed greywacke, siltstone, mudstone and slate [1] which were originally deposited in the sea as horizontal beds of mud and sand; the Penokean orogeny subjected the rocks to intense compression from the south. [4] :26 This folded the layers into east–west trending anticlines and synclines, and compressed the muddy beds into slate, a metamorphic rock. [4] :26 The Thomson Formation has steeply dipping beds of greywacke, siltstone and slate. [1] Several basaltic dikes, from the lava of the Midcontinent Rift period, cut across the Thomson Formation slate and greywackes. [4] :28 Most of these dikes trend in a northeasterly direction; they represent magma that rose in fissures in the crust. [4] :28

Summary of Huronian and Marquette Range supergroups

The Huronian and Marquette Range supergroups are similar sedimentary groups to the Animikie Group; all three are in the Great Lakes region. Rifting of continental plates create sedimentary basins; the largest of these basins in the Great Lakes area are the Animikie Group in Minnesota, the Marquette Range Supergroup in northern Michigan and Wisconsin, and the Huronian Supergroup in eastern Ontario. [5] :4

Huronian Supergroup

The Huronian Supergroup on the north shore of Lake Huron in Ontario [35] overlies an Archean basement. [36] On the map it is the formation north of both Lake Huron and the Grenville Front Tectonic Zone. Huronian sedimentary rocks form a 300 km (190 mi) eastwest fold belt and reach a thickness of 12 km (7.5 mi) near Lake Huron. [37] :266 Deposition of sediments began 2,450 to 2,219 million years ago and continued until 1,850 to 1,800 million years ago when the rocks were deformed and metamorphosed during the Penokean orogeny. [37] :264–6 The supergroup's sedimentary layers are divided into lower and upper sequences. [37] :265 The lower sequence is subdivided into the Elliot Lake, Hough Lake and Quirke Lake groups; the upper sequence is the Cobalt Group. [37] :265 The lower sequences were deposited in a continental rift basin and the upper sequence was deposited in a stable passive margin. [37] :267

Marquette Range Supergroup

The Marquette Range Supergroup also overlies an Archean basement. [36] Originally termed the Animikie Series, it was proposed to be renamed in 1970 to avoid confusion with the Animikie Group in Ontario and Minnesota. [38] On the map it is the dark grey area south of Lake Superior with four iron ranges shown. This supergroup consists of the Chocolay, Menominee, Baraga and Paint River groups, [35] in descending order of age. The Chocolay Group up to 160 m (520 ft) thick [39] is a shallow-marine layer which was deposited on the Archean basement; [19] deposition in the Chocolay Group began 2,207 ± 5 million years ago and ended 2,115 ± 5 million years ago. [40] The Menominee Group is a foredeep deposit whose layers were deposited in second-order basins created by oblique subduction of the continental margin, rather than in basins formed on a rifting margin. [19] The upper Baraga Group represents deeper marine basins resulting from increased subsidence and continued collision. [19] Deposition continued until 1,850 million years ago [5] :4 when the Penokean orogeny began. [41]

See also

Related Research Articles

<span class="mw-page-title-main">Gunflint Range</span> Iron ore deposit in Minnesota, United States and Ontario, Canada

The Gunflint Range is an iron ore deposit in northern Minnesota in the United States and Northwestern Ontario, Canada. The range extends from the extreme northern portion of Cook County, Minnesota into the Thunder Bay District, Ontario.

<span class="mw-page-title-main">Cuyuna Range</span> Iron mining range in northern Minnesota

The Cuyuna Range is an inactive iron range to the southwest of the Mesabi Range, largely within Crow Wing County, Minnesota. It lies along a 68-mile-long (109 km) line between Brainerd, Minnesota, and Aitkin, Minnesota. The width ranges from 1 to 10 miles.

The Penokean orogeny was a mountain-building episode that occurred in the early Proterozoic about 1.86 to 1.83 billion years ago, in the area of Lake Superior, North America. The core of this orogeny, the Churchill Craton, is composed of terranes derived from the 1.86–1.81 Ga collision between the Superior and North Atlantic cratons. The orogeny resulted in the formation of the Nena and Arctica continents, which later merged with other continents to form the Columbia supercontinent. The name was first proposed by Blackwelder 1914 in reference to what is known as the Penokee Range, sometimes incorrectly called the Gogebic Range, in northern Michigan and Wisconsin.

<span class="mw-page-title-main">Geology of Minnesota</span> Overview of the geology of the U.S. state of Minnesota

The geology of Minnesota comprises the rock, minerals, and soils of the U.S. state of Minnesota, including their formation, development, distribution, and condition.

<span class="mw-page-title-main">Duluth Complex</span>

The Duluth Complex, the related Beaver Bay Complex, and the associated North Shore Volcanic Group are rock formations which comprise much of the basement bedrock of the northeastern part of the U.S. state of Minnesota in central North America. The Duluth and Beaver Bay complexes are intrusive rocks formed about 1.1 billion years ago during the Midcontinent Rift; these adjoin and are interspersed with the extrusive rocks of the North Shore Volcanic Group produced during that same geologic event. These formations are part of the Superior Upland physiographic region of the United States, which is associated with the Laurentian Upland of the Canadian Shield, the core of the North American Craton.

<span class="mw-page-title-main">Circum-Superior Belt</span>

The Circum-Superior Belt is a widespread Paleoproterozoic large igneous province in the Canadian Shield of Northern, Western and Eastern Canada. It extends more than 3,400 km (2,100 mi) from northeastern Manitoba through northwestern Ontario, southern Nunavut to northern Quebec and into western Labrador. Igneous rocks of the Circum-Superior Belt are mafic-ultramafic in composition, deposited in the Labrador Trough near Ungava Bay, the Cape Smith Belt near the southern shore of Hudson Strait and along the eastern shore of Hudson Bay in its northern portion; the Thompson and Fox River belts in the northwest and the Marquette Range Supergroup in its southern portion. The Circum Superior Belt also hosts a rare example of Proterozoic Komatiite, in the Winnipegosis komatiite belt.

The Rove Formation, is a sedimentary rock formation of Middle Precambrian age underlying the upper northeastern part of Cook County, Minnesota, United States, and extending into Ontario, Canada. It is the youngest of the many layers of sedimentary rocks which constitute the Animikie Group.

The Great Lakes tectonic zone (GLTZ) is bounded by South Dakota at its tip and heads northeast to south of Duluth, Minnesota, then heads east through northern Wisconsin, Marquette, Michigan, and then trends more northeasterly to skim the northernmost shores of lakes.

<span class="mw-page-title-main">Tectonic evolution of the Aravalli Mountains</span> Overview article

The Aravalli Mountain Range is a northeast-southwest trending orogenic belt in the northwest part of India and is part of the Indian Shield that was formed from a series of cratonic collisions. The Aravalli Mountains consist of the Aravalli and Delhi fold belts, and are collectively known as the Aravalli-Delhi orogenic belt. The whole mountain range is about 700 km long. Unlike the much younger Himalayan section nearby, the Aravalli Mountains are believed much older and can be traced back to the Proterozoic Eon. They are arguably the oldest geological feature on Earth. The collision between the Bundelkhand craton and the Marwar craton is believed to be the primary mechanism for the development of the mountain range.

<span class="mw-page-title-main">Geology of the Democratic Republic of the Congo</span>

The geology of the Democratic Republic of the Congo is extremely old, on the order of several billion years for many rocks. The country spans the Congo Craton: a stable section of ancient continental crust, deformed and influenced by several different mountain building orogeny events, sedimentation, volcanism and the geologically recent effects of the East Africa Rift System in the east. The country's complicated tectonic past have yielded large deposits of gold, diamonds, coltan and other valuable minerals.

<span class="mw-page-title-main">Geology of Ivory Coast</span>

The geology of Ivory Coast is almost entirely extremely ancient metamorphic and igneous crystalline basement rock between 2.1 and more than 3.5 billion years old, comprising part of the stable continental crust of the West African Craton. Near the surface, these ancient rocks have weathered into sediments and soils 20 to 45 meters thick on average, which holds much of Ivory Coast's groundwater. More recent sedimentary rocks are found along the coast. The country has extensive mineral resources such as gold, diamonds, nickel and bauxite as well as offshore oil and gas.

The geology of Mozambique is primarily extremely old Precambrian metamorphic and igneous crystalline basement rock, formed in the Archean and Proterozoic, in some cases more than two billion years ago. Mozambique contains greenstone belts and spans the Zimbabwe Craton, a section of ancient stable crust. The region was impacted by major tectonic events, such as the mountain building Irumide orogeny, Pan-African orogeny and the Snowball Earth glaciation. Large basins that formed in the last half-billion years have filled with extensive continental and marine sedimentary rocks, including rocks of the extensive Karoo Supergroup which exist across Southern Africa. In some cases these units are capped by volcanic rocks. As a result of its complex and ancient geology, Mozambique has deposits of iron, coal, gold, mineral sands, bauxite, copper and other natural resources.

<span class="mw-page-title-main">Geology of Tanzania</span>

The geology of Tanzania began to form in the Precambrian, in the Archean and Proterozoic eons, in some cases more than 2.5 billion years ago. Igneous and metamorphic crystalline basement rock forms the Archean Tanzania Craton, which is surrounded by the Proterozoic Ubendian belt, Mozambique Belt and Karagwe-Ankole Belt. The region experienced downwarping of the crust during the Paleozoic and Mesozoic, as the massive Karoo Supergroup deposited. Within the past 100 million years, Tanzania has experienced marine sedimentary rock deposition along the coast and rift formation inland, which has produced large rift lakes. Tanzania has extensive, but poorly explored and exploited natural resources, including coal, gold, diamonds, graphite and clays.

The geology of Uganda extends back to the Archean and Proterozoic eons of the Precambrian, and much of the country is underlain by gneiss, argillite and other metamorphic rocks that are sometimes over 2.5 billion years old. Sedimentary rocks and new igneous and metamorphic units formed throughout the Proterozoic and the region was partially affected by the Pan-African orogeny and Snowball Earth events. Through the Mesozoic and Cenozoic, ancient basement rock has weathered into water-bearing saprolite and the region has experienced periods of volcanism and rift valley formation. The East Africa Rift gives rise to thick, more geologically recent sediment sequences and the country's numerous lakes. Uganda has extensive natural resources, particularly gold.

The geology of Ukraine is the regional study of rocks, minerals, tectonics, natural resources and groundwater in Ukraine. The oldest rocks in the region are part of the Ukrainian Shield and formed more than 2.5 billion years ago in the Archean eon of the Precambrian. Extensive tectonic evolution and numerous orogeny mountain-building events fractured the crust into numerous block, horsts, grabens and depressions. Ukraine was intermittently flooded as the crust downwarped during much of the Paleozoic, Mesozoic and early Cenozoic, before the formation of the Alps and Carpathian Mountains defined much of its current topography and tectonics. Ukraine was impacted by the Pleistocene glaciations within the last several hundred thousand years. The country has numerous metal deposits as well as minerals, building stone and high-quality industrial sands.

The geology of Nunavut began to form nearly three billion years ago in the Archean and the territory preserves some of the world's oldest rock units.

<span class="mw-page-title-main">Geology of Colorado</span> Geology of the U.S. State of Colorado

The bedrock under the U.S. State of Colorado was assembled from island arcs accreted onto the edge of the ancient Wyoming Craton. The Sonoma orogeny uplifted the ancestral Rocky Mountains in parallel with the diversification of multicellular life. Shallow seas covered the regions, followed by the uplift current Rocky Mountains and intense volcanic activity. Colorado has thick sedimentary sequences with oil, gas and coal deposits, as well as base metals and other minerals.

<span class="mw-page-title-main">Geology of New York (state)</span> Overview of the geology of the U.S. state of New York

The geology of the State of New York is made up of ancient Precambrian crystalline basement rock, forming the Adirondack Mountains and the bedrock of much of the state. These rocks experienced numerous deformations during mountain building events and much of the region was flooded by shallow seas depositing thick sequences of sedimentary rock during the Paleozoic. Fewer rocks have deposited since the Mesozoic as several kilometers of rock have eroded into the continental shelf and Atlantic coastal plain, although volcanic and sedimentary rocks in the Newark Basin are a prominent fossil-bearing feature near New York City from the Mesozoic rifting of the supercontinent Pangea.

The geology of the Northwest Territories has been mapped in different quadrangles by the Canadian government. The region has some of the oldest rocks in the world and among the oldest in North America, formed from several sections of stable craton continental crust, including the Slave Craton, Rae Craton and Hearne Craton. These rocks form the Archean and Proterozoic Precambrian basement rock of the region and are the subject of extensive research to understand continental crust and tectonic conditions on the early Earth.

The geology of Newfoundland and Labrador includes basement rocks formed as part of the Grenville Province in the west and Labrador and the Avalonian microcontinent in the east. Extensive tectonic changes, metamorphism and volcanic activity have formed the region throughout Earth history.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 Jirsa, Mark A.; Boerboom, Terrence J.; Green, John C.; Miller, James D.; Morey, G.B.; Ojakangas, Richard W.; Peterson, Dean M.; Severson, Mark J. (May 4–9, 2004). "Field Trip 5 Classic Outcrops of Northeastern Minnesota" (PDF). Proceedings of the 50th Annual Meeting Part 2. Field Trip Guidebook. Institute on Lake Superior Geology. pp. 129–169. Retrieved December 8, 2019.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 Cuyuna Iron Range District (Report). Porter GeoConsultancy Pty Ltd. 1993. Retrieved April 10, 2010.
  3. Lundquist, Rebekah (March 10, 2006). "Provenance Analysis of the Marquette Range Supergroup Sedimentary Rocks From Northwestern Wisconsin and Western Michigan Using U-Pb Isotope Geochemistry on Detrital Zircons by LA-ICP-MS" (PDF). Carleton College Geology Department: Senior Integrative Exercise. Retrieved May 22, 2010.{{cite journal}}: Cite journal requires |journal= (help)
  4. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Green, John C. (1996). Geology on Display, Geology and Scenery of Minnesota's North Shore State Parks. Minnesota Department of Natural Resources. ISBN   0-9657127-0-2.
  5. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Davis, Peter (1998). The Big Picture (Thesis). University of Minnesota. pp. Assembly of the Superior Province (1), Continental Collision 2.6 Billion Years Ago (2), A Riftine Sequence in the Previously Accreted Terrane (3), Two Crustal Collisions Complete the Penokean Orogeny (4). Archived from the original on May 16, 2008. Retrieved April 18, 2010.
  6. Tohver, E.; Holm, D.K.; van der Pluijm, B.A.; Essene, E.J.; Cambray, F.W. (August 1, 2007). "Late Paleoproterozoic (geon 18 and 17) reactivation of the Great Lakes tectonic zone, northern Michigan, USA: Evidence from kinematic analysis, thermobarometry and 40Ar/39Ar geochronology" (PDF). Precambrian Research. Elsevier Science. 157 (1–4): 144–68. Bibcode:2007PreR..157..144T. doi:10.1016/j.precamres.2007.02.014. ISSN   0301-9268 . Retrieved March 31, 2010.
  7. Sims, P.K.; Card, K.D.; Morey, G.B.; Peterman, Z.E. (December 1980). "The Great Lakes tectonic zone — A major crustal structure in central North America". GSA Bulletin. 91 (12): 690. Bibcode:1980GSAB...91..690S. doi:10.1130/0016-7606(1980)91<690:TGLTZA>2.0.CO;2.
  8. Trendall, Alec Francis; Morris, R.C. (1983). Iron-formation, facts and problems. Elsevier. p. 20. ISBN   9780444421449.
  9. 1 2 3 4 5 6 McSwiggen, Peter; Cleland, Jane. Lake Superior-Type Iron Formation (Report). Minnesota Geological Survey. Archived from the original on October 14, 2008. Retrieved May 19, 2010.
  10. Seelig, Bruce; Derickson, Russell; Bergsrud, Fred (February 1992). Treatment Systems for Household Water Supplies, Iron and Manganese Removal (Report). North Dakota State University. AE-1030.
  11. 1 2 3 Addison, William D.; Brumpton, Gregory R.; Vallini, Daniela A.; McNaughton, Neal J.; Davis, Don W.; Kissin, Stephen A.; Fralick, Philip W.; Hammond, Anne L. (2005). "Discovery of Distal Ejecta from the 1850 Ma Sudbury Impact Event". Geology. 33 (3): 193. Bibcode:2005Geo....33..193A. doi:10.1130/G21048.1.
  12. 1 2 3 4 5 6 Jirsa, Mark; Weiblen, Paul. "Minnesota's Evidence of an Ancient Meteorite Impact" (PDF). Minnesota Geological Survey: 2, 4, 5. Retrieved March 9, 2010.{{cite journal}}: Cite journal requires |journal= (help)[ permanent dead link ]
  13. 1 2 3 Perkins, Sid (November 10, 2009). "Giant Asteroid Impact Could Have Stirred Entire Ocean". Wired Science: 2. Retrieved March 29, 2010.
  14. Hildebrand, A.R.; Pilkington, M.; Ortiz-Aleman, C.; Chavez, R.E.; Urrutia-Fucugauchi, J.; Connors, M.; Graniel-Castro, E.; Camara-Zi, A.; et al. (1998). "Mapping Chicxulub Crater Structure with Gravity and Seismic Reflection Data". Geological Society, London, Special Publications. 140 (1): 155. Bibcode:1998GSLSP.140..155H. doi:10.1144/GSL.SP.1998.140.01.12. S2CID   130177601 . Retrieved May 22, 2010.
  15. Bralower, Timothy J.; Paull, Charles K.; Leckie, R. Mark (April 1988). The Cretaceous-Tertiary Boundary Cocktail: Chicxulub Impact Triggers Margin Collapse and Extensive Sediment Gravity Flows (PDF). Geology (Report). Vol. 26. pp. 331–334. Archived from the original (PDF) on November 28, 2007. Retrieved May 22, 2010.
  16. 1 2 3 Cannon, W.F.; Schulz, K.J.; Horton, J. Wright Jr.; Kring, David A. Kring (January 7, 2009). "The Sudbury Impact Layer in the Paleoproterozoic Iron Ranges of Northern Michigan, USA". Geological Society of America Bulletin. 122 (1–2): 50. Bibcode:2010GSAB..122...50C. doi:10.1130/B26517.1.
  17. 1 2 Spurr, J Edward (1894). The Iron-Bearing Rock of the Mesabi Range in Minnesota, Bulletin No. X. NH Winchell, State Geologist.
  18. Paces, James B.; Miller, James D. Jr. (1993). "Precise U-Pb Ages of Duluth Complex and Related Mafic Intrusions, Northeastern Minnesota: Geochronological Insights to Physical, Petrogenetic, Paleomagnetic, and Tectonomagmatic Processes Associated With the 1.1 Ga Midcontinent Rift System". Journal of Geophysical Research. 98 (B8): 13,997. Bibcode:1993JGR....9813997P. doi:10.1029/93JB01159 . Retrieved May 24, 2010.
  19. 1 2 3 4 Schneider, D.A.; Bickford, M.E.; Cannon, W.F.; Schulz, K.J.; Hamilton, M.A. (2002). "Age of Volcanic Rocks and Syndepositional Iron Formations, Marquette Range Supergroup: Implications for the Tectonic Setting of Paleoproterozoic Iron Formations of the Lake Superior Region". Canadian Journal of Earth Sciences. 39 (6): 999. Bibcode:2002CaJES..39..999S. doi:10.1139/e02-016 . Retrieved May 17, 2010.[ permanent dead link ]
  20. 1 2 "Iron Mining: Where and Why?". Michigan State University.{{cite journal}}: Cite journal requires |journal= (help)
  21. 1 2 3 Trendall, A. F (1968). "Three Great Basins of Precambrian Banded Iron Formation Deposition: A Systematic Comparison". Geological Society of America Bulletin. 79 (11): 1527. Bibcode:1968GSAB...79.1527T. doi:10.1130/0016-7606(1968)79[1527:TGBOPB]2.0.CO;2.
  22. Bray, Edmund C (1977). Billions of Years in Minnesota, The Geological Story of the State. Library of Congress Card Number: 77:80265.
  23. 1 2 3 4 5 6 7 8 9 10 11 Chamberlin, Thomas Chrowder, ed. (1904). "The Journal of Geology". 12. University of Chicago, Department of Geology.{{cite journal}}: Cite journal requires |journal= (help)
  24. Perry, E.C.; Tan, F.C.; Morey, G.B. (November 1973). "Geology and Stable Isotope Geochemistry of the Biwabik Iron Formation, Northern Minnesota". Economic Geology. 68 (7): 1110. doi:10.2113/gsecongeo.68.7.1110 . Retrieved May 22, 2010.
  25. 1 2 Hustrulid, Willam; Kuchta, Mark (2006). Open Pit Mine Planning & Design, Balkema Proceedings and Monographs in Engineering, Water and Earth Sciences. Taylor & Francis. ISBN   9780415407373.
  26. Marsden, R.W.; Emanuelson, J.W.; Owens, J.S.; Walker, N.E.; Werner, R.F. (1968). John D. Ridge (ed.). The Mesabi Iron Range, Minnesota, in Volume 1 of Ore Deposits of the United States, 1933-1967. The American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. pp. 524–526.
  27. Gruner, John (1946). The Mineralogy and Geology of the Taconites and Iron Ores of the Mesabi Range, Minnesota. Office of the Commissioner of the Iron Range Resources and Rehabilitation. p. 40.
  28. Williams, Curtis; Ripley, Edward M.; Li, Chusi (October 28–31, 2007). "Anomalous Osmium Isotopic Ratios in Sedimentary Sulfides from the Virginia Formation Produced as a Result of Interaction with Magmatic Fluids Derived from the Duluth Complex, Midcontinent Rift System". Geological Society of America Abstracts with Programs. 2007 GSA Denver Annual Meeting. 39 (172–39): 468. Retrieved May 22, 2010.
  29. 1 2 Tyson, R. Michael; Chang, Luke L.Y. (1984). "The Petrology and Sulfide Mineralization of the Partridge River Troctolite, Duluth Complex, Minnesota" (PDF). Conadian Mineralogist. 22: 23–38. Retrieved May 23, 2010.
  30. Ojakangas, Richard W.; Matsch, Charles L. (1982). Minnesota's Geology. University of Minnesota Press. ISBN   978-0-8166-0953-6.
  31. 1 2 3 Chandler, Val W. (August 3, 2005). A Geophysical Investigation of the Ely Greenstone Belt in the Soudan Area, Northeastern Minnesota: A Preliminary Investigation for the Proposed Deep Underground Science and Engineering Laboratory (DUSEL), University of Minnesota (PDF) (Report). Minnesota Geological Survey, University of Minnesota. Minnesota Geological Survey Open File Report 05-1. Archived from the original (PDF) on July 13, 2010. Retrieved May 22, 2010.
  32. Karberg, Susan Marie (January 2009). Structural and Kinematic Analysis of the Mud Creek Shear Zone, Northeastern Minnesota; Implications for Archean (2.7 Ga) Tectonics (PDF) (Thesis). University of Minnesota. Archived from the original (PDF) on October 6, 2012. Retrieved May 23, 2010.
  33. 1 2 3 4 5 6 7 8 9 McSwiggen, Peter L.; Morey, Glenn B.; Cleland, Jane M. (1994). "The Origin of Aegirine in Iron Formation of the Cuyuna Range, East-central Minnesota" (PDF). The Canalian Mineralogist. Minnesota Geological Survey. 32: 591–592. Archived (PDF) from the original on April 21, 2014. Retrieved April 24, 2010.
  34. Schmidt, Robert (1963). Geology and Ore Deposits of the Cuyuna North Range Minnesota, Geological Survey Professional Paper 407. United States Government Printing Office. p. 11,18–24.
  35. 1 2 Cannon, W. F.; Gair, J. E. (September 1970). "A Revision of Stratigraphic Nomenclature for Middle Precambrian Rocks in Northern Michigan". GSA Bulletin. 81 (9): 2843. Bibcode:1970GSAB...81.2843C. doi:10.1130/0016-7606(1970)81[2843:AROSNF]2.0.CO;2.
  36. 1 2 Schmus, W. R. Van Schmus (January 22, 1976). "Early and Middle Proterozoic History of the Great Lakes Area, North America". Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences. The Royal Society. 280 (1298, A Discussion on Global Tectonics in Proterozoic Times): 605–628. Bibcode:1976RSPTA.280..605S. doi:10.1098/rsta.1976.0015. JSTOR   74580. S2CID   202574995.
  37. 1 2 3 4 5 McLennan, S.M.; Simonetti, A.; Goldstein, S.L. (2000). "Nd and Pb Isotopic Evidence for Provenance and Post-Depositional Alteration of the Paleoproterozoic Huronian Supergroup, Canada" (PDF). Precambrian Research. 102 (3–4): 263–278. Bibcode:2000PreR..102..263M. doi:10.1016/S0301-9268(00)00070-X. Archived from the original (PDF) on October 14, 2012. Retrieved May 17, 2010.
  38. Cannon, W. F.; Gair, J. E. (September 1970). "A Revision of Stratigraphic Nomenclature for Middle Precambrian Rocks in Northern Michigan". Bulletin of the Geological Society of America. 81 (9): 2843–46. Bibcode:1970GSAB...81.2843C. doi:10.1130/0016-7606(1970)81[2843:AROSNF]2.0.CO;2.
  39. Larue, D.K. (1981). "The Chocolay Group, Lake Superior Region, U.S.A.: Sedimentologic Evidence for Deposition in Basinal and Platform Settings on an Early Proterozoic Craton". Geological Society of America Bulletin. 92 (7): 417. Bibcode:1981GSAB...92..417L. doi:10.1130/0016-7606(1981)92<417:TCGLSR>2.0.CO;2.
  40. Vallini, Daniela A.; Cannon, William F.; Schulz, Klaus (2006). "Age Constraints for Paleoproterozoic Glaciation in the Lake Superior Region: Detrital Zircon and Hydrothermal Xenotime Ages for the Chocolay Group, Marquette Range Supergroup". Canadian Journal of Earth Sciences. 43 (5): 571. Bibcode:2006CaJES..43..571V. doi:10.1139/E06-010 . Retrieved May 18, 2010.[ permanent dead link ]
  41. Anderson, G. (1968). "The Marquette District, Michigan". In Ridge, J.D. (ed.). Ore Deposits of the United States, 1933–1967. Vol. 1. New York: American Institute of Mining, Metallurgical, and Petroleum Engineers. p. 511. OCLC   333389.