Sudbury Basin

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Sudbury Basin
Sudbury Structure
Sudbury Wanapitei WorldWind.jpg
NASA World Wind satellite image of the Sudbury astrobleme
Impact crater/structure
ConfidenceConfirmed
Diameter130 km (81 mi)
Age 1849 Ma
Paleoproterozoic
ExposedYes
DrilledYes
Location
Coordinates 46°36′N81°11′W / 46.600°N 81.183°W / 46.600; -81.183 Coordinates: 46°36′N81°11′W / 46.600°N 81.183°W / 46.600; -81.183
Country Canada
Province Ontario
Canada location map.svg
Map pointer.svg
Location of the crater in Canada
Geological map of Sudbury Basin Sudbury Basin Non-Ferrous Metals - Eastern Canada map.png
Geological map of Sudbury Basin
Shatter cone from Sudbury Impact Structure, Cleveland Museum of Natural History Shattercone, Sudbury Impact Structure (1.85 Ga) Ontario.jpg
Shatter cone from Sudbury Impact Structure, Cleveland Museum of Natural History

The Sudbury Basin, also known as Sudbury Structure or the Sudbury Nickel Irruptive, is a major geological structure in Ontario, Canada. It is the third-largest known impact crater or astrobleme on Earth, as well as one of the oldest. [1] The crater formed 1.849 billion years ago in the Paleoproterozoic era. [2]

Geology The study of the composition, structure, physical properties, and history of Earths components, and the processes by which they are shaped.

Geology is an earth science concerned with the solid Earth, the rocks of which it is composed, and the processes by which they change over time. Geology can also include the study of the solid features of any terrestrial planet or natural satellite such as Mars or the Moon. Modern geology significantly overlaps all other earth sciences, including hydrology and the atmospheric sciences, and so is treated as one major aspect of integrated earth system science and planetary science.

Ontario Province of Canada

Ontario is a province of Canada. Located in Central Canada, it is Canada's most populous province, with 38.3 percent of the country's population, and is the second-largest province in total area. Ontario is fourth-largest jurisdiction in total area when the territories of the Northwest Territories and Nunavut are included. It is home to the nation's capital city, Ottawa, and the nation's most populous city, Toronto, which is also Ontario's provincial capital.

Impact crater Circular depression on a solid astronomical body formed by a hypervelocity impact of a smaller object

An impact crater is an approximately circular depression in the surface of a planet, moon, or other solid body in the Solar System or elsewhere, formed by the hypervelocity impact of a smaller body. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters typically have raised rims and floors that are lower in elevation than the surrounding terrain. Impact craters range from small, simple, bowl-shaped depressions to large, complex, multi-ringed impact basins. Meteor Crater is a well-known example of a small impact crater on Earth.

Contents

The basin is located on the Canadian Shield in the city of Greater Sudbury, Ontario. The former municipalities of Rayside-Balfour, Valley East and Capreol lie within the Sudbury Basin, which is referred to locally as "The Valley". The urban core of the former city of Sudbury lies on the southern outskirts of the basin.

Canadian Shield Geographic and geologic area of Canada

The Canadian Shield, also called the Laurentian Plateau, or Bouclier canadien (French), is a large area of exposed Precambrian igneous and high-grade metamorphic rocks that forms the ancient geological core of the North American continent. Composed of igneous rock resulting from its long volcanic history, the area is covered by a thin layer of soil. With a deep, common, joined bedrock region in eastern and central Canada, it stretches north from the Great Lakes to the Arctic Ocean, covering over half of Canada; it also extends south into the northern reaches of the United States. Human population is sparse, and industrial development is minimal, while mining is prevalent.

Greater Sudbury City in Ontario, Canada

Sudbury, officially Greater Sudbury, is a city in Ontario, Canada. It is the largest city in Northern Ontario by population, with a population of 161,531 at the 2016 Canadian Census. By land area, it is the largest in Ontario and the fifth largest in Canada. It is administratively a Unitary authority, and thus not part of any district, county, or regional municipality.

Rayside-Balfour Community in Ontario, Canada

Rayside-Balfour was a town in Ontario, Canada, which existed from 1973 to 2000.

The Sudbury Basin is located near a number of other geological structures, including the Temagami Magnetic Anomaly, the Lake Wanapitei impact crater, the western end of the Ottawa-Bonnechere Graben, the Grenville Front Tectonic Zone and the eastern end of the Great Lakes Tectonic Zone, although none of the structures are directly related to each other in the sense of resulting from the same geological processes.

Temagami Magnetic Anomaly

The Temagami Magnetic Anomaly, also called the Temagami Anomaly or the Wanapitei Anomaly, is a magnetic anomaly resulting from a large buried geologic structure in the Canadian Shield in the Temagami region of northeastern Ontario, Canada. It stretches from Lake Wanapitei in the west to Bear Island in Lake Temagami.

Lake Wanapitei lake in Ontario, Canada

Lake Wanapitei occupies a meteorite crater in Sudbury, Ontario, Canada. It is located near the much larger Sudbury meteorite crater but they are not related.

Ottawa-Bonnechere Graben A rift valley extending from near Montréal through Ottawa in Canada

The Ottawa-Bonnechere Graben is a geological structure that coincides with a 55 km (34 mi) wide topographic depression extending from near Montréal through Ottawa. It is part of the St. Lawrence rift system that also includes the seismically active Saguenay graben. This rift valley was formed when the Earth's crust moved downward about a kilometre between two major fault zones known as the Mattawa and Petawawa faults. The length of the graben is about 700 km (435 mi).

Formation

Onaping Fallback Breccia, polished slab, 15 by 23 cm (6 by 9 in) Melted Chaos from Sudbury Impact Crater .jpg
Onaping Fallback Breccia, polished slab, 15 by 23 cm (6 by 9 in)

The Sudbury basin formed as a result of an impact into the Nuna supercontinent from a bolide approximately 10–15 km (6.2–9.3 mi) in diameter that occurred 1,849 million years ago [2] in the Paleoproterozoic era.

Impact event Collision of two astronomical objects with measurable effects

An impact event is a collision between astronomical objects causing measurable effects. Impact events have physical consequences and have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or meteoroids and have minimal effect. When large objects impact terrestrial planets such as the Earth, there can be significant physical and biospheric consequences, though atmospheres mitigate many surface impacts through atmospheric entry. Impact craters and structures are dominant landforms on many of the Solar System's solid objects and present the strongest empirical evidence for their frequency and scale.

Columbia (supercontinent) Ancient supercontinent of approximately 2,500 to 1,500 million years ago

Columbia, also known as Nuna and Hudsonland, was one of Earth's ancient supercontinents. It was first proposed by Rogers & Santosh 2002 and is thought to have existed approximately 2,500 to 1,500 million years ago in the Paleoproterozoic Era. Zhao et al. 2002 proposed that the assembly of the supercontinent Columbia was completed by global-scale collisional events during 2.1–1.8 Ga.

Bolide extremely bright meteor that often explodes in the atmosphere

A bolide is an extremely bright meteor, especially one that explodes in the atmosphere. In astronomy, it refers to a fireball about as bright as the full moon, and it is generally considered a synonym for a fireball. In geology, a bolide is a very large impactor.

Debris from the impact was scattered over an area of 1,600,000 km2 (620,000 sq mi) thrown more than 800 km (500 mi); rock fragments ejected by the impact have been found as far as Minnesota. [3]

Minnesota State in the United States

Minnesota is a state in the Upper Midwest, Great Lakes, and northern regions of the United States. Minnesota was admitted as the 32nd U.S. state on May 11, 1858, created from the eastern half of the Minnesota Territory. The state has many lakes, and is known as the "Land of 10,000 Lakes". Its official motto is L'Étoile du Nord.

Models suggest that for such a large impact, debris was most likely scattered globally, [4] but has since been eroded away. Its present size is believed to be a smaller portion of a 130 km (81 mi) round crater that the bolide originally created. Subsequent geological processes have deformed the crater into the current smaller oval shape. Sudbury Basin is the third-largest crater on Earth, after the 300 km (190 mi) Vredefort crater in South Africa, and the 150 km (93 mi) Chicxulub crater under Yucatán, Mexico.

Vredefort crater The largest verified impact crater on earth, dating from the Paleoproterozoic Era

The Vredefort crater is the largest verified impact crater on Earth. More than 300 kilometres (190 mi) across when it was formed, what remains of it is in the present-day Free State province of South Africa. It is named after the town of Vredefort, which is near its centre. Although the crater itself has long since been worn away, the remaining geological structures at its centre are known as the Vredefort Dome or Vredefort impact structure. The crater is estimated to be 2.023 billion years old, with impact being in the Paleoproterozoic Era. It is the second-oldest known crater on Earth.

South Africa Republic in the southernmost part of Africa

South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by 2,798 kilometres (1,739 mi) of coastline of Southern Africa stretching along the South Atlantic and Indian Oceans; to the north by the neighbouring countries of Namibia, Botswana, and Zimbabwe; and to the east and northeast by Mozambique and Eswatini (Swaziland); and it surrounds the enclaved country of Lesotho. South Africa is the largest country in Southern Africa and the 24th-largest country in the world by land area and, with over 58 million people, is also the world's 24th-most populous nation. It is the southernmost country on the mainland of the Old World or the Eastern Hemisphere. About 80 percent of South Africans are of Bantu ancestry, divided among a variety of ethnic groups speaking different African languages, nine of which have official status. The remaining population consists of Africa's largest communities of European, Asian (Indian), and multiracial (Coloured) ancestry.

Chicxulub crater prehistoric impact crater buried underneath the Yucatán Peninsula in Mexico

The Chicxulub crater is an impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is located near the town of Chicxulub, after which the crater is named. It was formed by a large asteroid or comet about 11 to 81 kilometres in diameter, the Chicxulub impactor, striking the Earth. The date of the impact coincides precisely with the Cretaceous–Paleogene boundary, slightly less than 66 million years ago, and a widely accepted theory is that worldwide climate disruption from the event was the cause of the Cretaceous–Paleogene extinction event, a mass extinction in which 75% of plant and animal species on Earth became extinct, including all non-avian dinosaurs.

Structure

The full extent of the Sudbury Basin is 62 km (39 mi) long, 30 km (19 mi) wide and 15 km (9.3 mi) deep, although the modern ground surface is much shallower.

The main units characterizing the Sudbury Structure can be subdivided into three groups: the Sudbury Igneous Complex (SIC), the Whitewater Group, and footwall brecciated country rocks that include offset dikes and the Sub layer. The SIC is believed to be a stratified impact melt sheet composed from the base up of sub layer norite, mafic norite, felsic norite, quartz gabbro, and granophyre.

The Whitewater Group consists of a suevite and sedimentary package composed of the Onaping (fallback breccias), Onwatin, and Chelmsford Formations in stratigraphic succession. Footwall rocks, associated with the impact event, consist of Sudbury Breccia (pseudotachylite), footwall breccia, radial and concentric quartz dioritic breccia dikes (polymict impact melt breccias), and the discontinuous sub layer.

Because considerable erosion has occurred since the Sudbury event, an estimated 6 km (3.7 mi) in the North Range, it is difficult to directly constrain the actual size of the diameter of the original transient cavity, or the final rim diameter. [5]

The deformation of the Sudbury structure occurred in five main deformation events (by age in Mega years):

  1. formation of the Sudbury Igneous Complex (1849 Ma) [2]
  2. Penokean orogeny (1890–1830 Ma)
  3. Mazatzal orogeny (1700–1600 Ma) [6]
  4. Grenville orogeny (1400–1000 Ma)
  5. Lake Wanapitei impact (37 Ma)

Disputes over origin

Geological map of the Copper Cliff area, produced in the 1950s. Geological map of the vicinity of Copper Cliff Sudbury mining district.pdf
Geological map of the Copper Cliff area, produced in the 1950s.

Some 1.8 billion years of weathering and deformation made it difficult to prove that a meteorite was the cause of the Sudbury geological structures. A further difficulty in proving that the Sudbury complex was formed by meteorite impact rather than by ordinary igneous processes was that the region was volcanically active at around the same time as the impact, and some weathered volcanic structures can look like meteorite collision structures. Since its discovery, a layer of breccia has been found associated with the impact event [7] and stressed rock formations have been fully mapped.

Geologists reached consensus by about 1970 that the Sudbury basin was formed by a meteorite impact[ citation needed ]. Reports published in the late 1960s described geological features that were said to be distinctive of meteorite impact, including shatter cones [8] and shock-deformed quartz crystals in the underlying rock. [9] In 2014, analysis of the concentration and distribution of siderophile elements as well as the size of the area where the impact melted the rock indicated that a comet rather than an asteroid most likely caused the crater. [10] [11]

Modern uses

Rich ore sample from Sudbury, collected in 1932: Pentlandite - Chalcopyrite - Pyrrhotite Pentlandite-Chalcopyrite-Pyrrhotite-199634.jpg
Rich ore sample from Sudbury, collected in 1932: PentlanditeChalcopyritePyrrhotite

The large impact crater filled with magma containing nickel, copper, platinum, palladium, gold, and other metals. In 1856 while surveying a baseline westward from Lake Nipissing, provincial land surveyor Albert Salter located magnetic abnormalities in the area that were strongly suggestive of mineral deposits. The area was then examined by Alexander Murray of the Geological Survey of Canada, who confirmed "the presence of an immense mass of magnetic trap".

Due to the then-remoteness of the Sudbury area, Salter's discovery did not have much immediate effect. The later construction of the Canadian Pacific Railway through the area, however, made mineral exploration more feasible. The development of a mining settlement occurred in 1883 after earth moving at the railway construction site revealed a large concentration of nickel and copper ore at what is now the Murray Mine site.

As a result of these metal deposits, the Sudbury area is one of the world's major mining communities. The region is one of the world's largest suppliers of nickel and copper ores. Most of these mineral deposits are found on the outer rim of the basin.

Due to the high mineral content of its soil, the floor of the basin is among the best agricultural land in Northern Ontario, with numerous vegetable, berry, and dairy farms located in the valley. However, because of its northern latitude, it is not as productive as agricultural lands in the southern portion of the province. Accordingly, the region primarily supplies products for consumption within Northern Ontario, and is not a major food exporter.

An Ontario Historical Plaque was erected by the province to commemorate the discovery of the Sudbury Basin. [12]

Astronaut training

NASA used the site to geologically train the Apollo astronauts in recognizing rocks formed as the result of a very large impact, such as breccias. Astronauts who would use this training on the Moon included Apollo 15's David Scott and James Irwin, Apollo 16's John Young and Charlie Duke, and Apollo 17's Gene Cernan and Jack Schmitt. Notable geologist instructors included William R. Muehlberger. [13]

See also

Related Research Articles

Breccia Rock composed of broken fragments cemented by a matrix

Breccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix that can be similar to or different from the composition of the fragments.

Pentlandite sulfide mineral

Pentlandite is an iron–nickel sulfide, (Fe,Ni)9S8. Pentlandite has a narrow variation range in Ni:Fe but it is usually described as having a Ni:Fe of 1:1. It also contains minor cobalt, usually at low levels as a fraction of weight.

Chesapeake Bay impact crater impact crater

The Chesapeake Bay impact crater was formed by a bolide that impacted the eastern shore of North America about 35.5 ± 0.3 million years ago, in the late Eocene epoch. It is one of the best-preserved "wet-target" impact craters in the world.

Rochechouart crater large astrobleme in France, remain of Mesozoic Era impact

The Rochechouart crater is an impact crater. The initial crater morphology has been lost by erosion and there is no crater visible on site. The proper term to designate what remains of the Rochechouart impact crater is Rochechouart impact structure. The term “astrobleme” introduced by R. Dietz since 1947 together with shatter cones as a symptomatic finger print for identifying an eroded impact crater on Earth, is also used to designate the Rochechouart impact structure. In 2008 the French State acknowledged the heritage value of the Rochechouart impact creating the “Réserve Naturelle Nationale de l’astroblème de Rochechouart-Chassenon” on 12 sites representative of characteristics geological features of the impact structure.

Woodleigh crater impact crater

Woodleigh is a large meteorite impact crater (astrobleme) in Western Australia, centred on Woodleigh Station east of Shark Bay, Gascoyne region. A team of four scientists at the Geological Survey of Western Australia and the Australian National University, led by Arthur J. Mory, announced the discovery in the 15 April 2000 issue of Earth and Planetary Science Letters.

Norite igneous rock

Norite is a mafic intrusive igneous rock composed largely of the calcium-rich plagioclase labradorite, orthopyroxene, and olivine. The name norite is derived from Norge, the Norwegian name for Norway.

Geology of the Moon Structure and composition of the Moon

The geology of the Moon is quite different from that of Earth. The Moon lacks a significant atmosphere, which eliminates erosion due to weather; it does not have any known form of plate tectonics, it has a lower gravity, and because of its small size, it cooled more rapidly. The complex geomorphology of the lunar surface has been formed by a combination of processes, especially impact cratering and volcanism. The Moon is a differentiated body, with a crust, mantle, and core.

Moon rock Rock from the Moon

Moon rock or lunar rock is rock that is found on the Earth's Moon including lunar material collected during the course of human exploration of the Moon, or rock that has been ejected naturally from the Moon's surface.

Pseudotachylyte

Pseudotachylyte or Pseudotachylite is a cohesive glassy or very fine-grained rock that occurs as veins and often contains inclusions of wall-rock fragments. Pseudotachylyte is typically dark in color; and is glassy in appearance. It was named after its appearance resembling the basaltic glass, tachylyte. Typically, the glass is completely devitrified into very fine-grained material with radial and concentric clusters of crystals. The glass may also contain crystals with quench textures that formed via crystallization from the melt. Chemical composition of pseudotachylyte generally reflects the local bulk chemistry. Pseudotachylyte may form via frictional melting of faults, in large-scale landslides, and by impact processes. Many researchers often define the rock as one formed via the melting. However, the original description/definition by Shand did not include interpretation about its generation, and it is suggested that there are pseudotachylytes formed via comminution without melting. Quartz in pseudotachylyte from the Vredefort impact site displays high residual stress as documented by synchrotron X-ray Laue microdiffraction.

Azuara impact structure

The Azuara impact structure is a structural feature of about 30 kilometres (19 mi) diameter, located in northeastern Spain, roughly 50 kilometres (31 mi) south of Zaragoza. The name is attributed to the small town of Azuara located near the center of the structure. The first hint to a possible impact origin was given by Wolfgang Hammann as early as 1980, and the first field evidence was provided by Johannes Fiebag in the early eighties. In 1985, Ernstson et al. published the occurrence of shock metamorphism, and Azuara was established (Grieve & Shoemaker 1994, Hodge 1994, Norton 2002 as an authentic impact structure. From stratigraphic considerations and paleontological dating, its age is estimated to be Upper Eocene or Oligocene.

Mars may contain ores that would be very useful to potential colonists. The abundance of volcanic features together with widespread cratering are strong evidence for a variety of ores. While nothing may be found on Mars that would justify the high cost of transport to Earth, the more ores that future colonists can obtain from Mars, the easier it would be to build colonies there.

Rubielos de la Cérida impact structure

The c. 80 km x 40 km sized Rubielos de la Cérida impact structure is located in Aragon, northeast Spain, north of Teruel and is considered a companion of the Azuara impact structure and part of a large multiple impact event, the Azuara impact event, that from stratigraphic considerations and paleontological dating happened in the Upper Eocene or Oligocene. The name is attributed to the village of Rubielos de la Cérida located in the central uplift of the most northerly part of the structure.

<i>Traces of Catastrophe</i>

Traces of Catastrophe: A Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures is a book written by Bevan M. French of the Smithsonian Institution. It is a comprehensive technical reference on the science of impact craters. It was published in 1998 by the Lunar and Planetary Institute (LPI), which is part of the Universities Space Research Association (USRA). It was originally available in hard copy from LPI, but is now only available as a portable document format (PDF) e-book free download.

Geology of Ontario

The geology of Ontario consists of the study of the rock formations in the most populated province of Canada. Ontario has some of the oldest rocks on Earth. It is made up of ancient Precambrian igneous and metamorphic rock and overlain by younger sedimentary rocks and soils.

References

  1. "Sudbury". Earth Impact Database . Planetary and Space Science Centre University of New Brunswick Fredericton . Retrieved 2017-10-09.
  2. 1 2 3 Davis, Donald W. (January 23, 2008). "Sub-million-year age resolution of Precambrian igneous events by thermal extraction-thermal ionization mass spectrometer Pb dating of zircon: Application to crystallization of the Sudbury impact melt sheet". Geology. 36 (5): 383–386. Bibcode:2008Geo....36..383D. doi:10.1130/G24502A.1.
  3. Associated Press: "Ontario crater debris found in Minn.", Star Tribune, July 15, 2007
  4. Melosh, J. (1989)Impact Cratering: A Geologic Process. Oxford University Press.
  5. Pye, E.G., Naldrett, A.J. & Giblin, P.E. (1984) The Geology and Ore Deposits of the Sudbury Structure. Ontario Geological Survey, Special Volume 1, Ontario Ministry of Natural Resources.
  6. Riller, U (2005). "Structural characteristics of the Sudbury impact structure, Canada: Impact-induced versus orogenic deformation-A review". Meteoritics & Planetary Science. 40 (11): 1723–1740. doi:10.1111/j.1945-5100.2005.tb00140.x.
  7. Beales, FW; Lozej, GP (1975). "Sudbury Basin Sediments and the Meteoritic Impact Theory of Origin for the Sudbury Structure". Canadian Journal of Earth Sciences. 12 (4): 629–635. doi:10.1139/e75-056.
  8. Bray, JG (1966). "Shatter Cones at Sudbury". The Journal of Geology. 74 (2): 243–245. doi:10.1086/627158.
  9. French, BM (1967). "Sudbury Structure, Ontario: Some Petrographic Evidence for Origin by Meteorite Impact". Science. 156 (3778): 1094–1098. doi:10.1126/science.156.3778.1094. hdl:2027/pst.000020681982.
  10. Petrus, JA; Ames, DE; Kamber, BS (2015). "On the track of the elusive Sudbury impact: geochemical evidence for a chondrite or comet bolide". Terra Nova. 27 (1): 9–20. doi:10.1111/ter.12125.
  11. Ghose, Tia (November 18, 2014). "A Comet Did It! Mystery of Giant Crater Solved". LiveScience. Retrieved November 18, 2014.
  12. Brown, Alan L. "Discovery of the Sudbury Nickel Deposits". Ontario's Historical Plaques. Retrieved 2018-05-12.
  13. Phinney, William (2015). Science Training History of the Apollo Astronauts. NASA SP -2015-626. pp. 247, 252.