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Central Lapland Greenstone Belt
The Central Lapland Greenstone Belt (CLGB) is a greenstone belt located in the northern part of the Fennoscandian Shield. The region belongs to Lapland, northern Finland. The CLGB is part of a much larger belt of Paleoproterozoic greenstones, a cover of metamorphosed volcanic and sedimentary rocks that cover the Archean basement, the latter which is representative of the Archaean Karelian craton. Deposition of the cover sequence occurred between about 2.5 Ga and 1.8 Ga, thus it preserves information about Earth's history from a period that encompass about 700 Ma. Thus, the CLGB records a prolonged and episodic history of rifting, sedimentation and magmatism before the collision and rift closure at about 1.9 Ga. The collision was related to the amalgamation of the supercontinent Columbia. See also *Lapland Granulite Belt *List of greenstone belts This is a list of greenstone belts Africa Burkina Faso * Hounde greenstone belt * Boromo greenstone belt Democratic Republic of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Greenstone Belt
Greenstone belts are zones of variably metamorphosed mafic to ultramafic volcanic sequences with associated sedimentary rocks that occur within Archaean and Proterozoic cratons between granite and gneiss bodies. The name comes from the green hue imparted by the colour of the metamorphic minerals within the mafic rocks: the typical green minerals are chlorite, actinolite, and other green amphiboles. Greenstone belts also often contain ore deposits of gold, silver, copper, zinc and lead. A greenstone belt is typically several dozens to several thousand kilometres long. Typically, a greenstone belt within the greater volume of otherwise homogeneous granite-gneiss within a craton contains a significantly larger degree of heterogeneity and complications and forms a tectonic marker far more distinct than the much more voluminous and homogeneous granites. Additionally, a greenstone belt contains far more information on tectonic and metamorphic events, deformations, and paleogeologic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
History Of Earth
The history of Earth concerns the development of planet Earth from its formation to the present day. Nearly all branches of natural science have contributed to understanding of the main events of Earth's past, characterized by constant geological change and biological evolution. The geological time scale (GTS), as defined by international convention, depicts the large spans of time from the beginning of the Earth to the present, and its divisions chronicle some definitive events of Earth history. (In the graphic, Ma means "million years ago".) Earth formed around 4.54 billion years ago, approximately one-third the age of the universe, by accretion from the solar nebula. Volcanic outgassing probably created the primordial atmosphere and then the ocean, but the early atmosphere contained almost no oxygen. Much of the Earth was molten because of frequent collisions with other bodies which led to extreme volcanism. While the Earth was in its earliest stage (Early Earth), a gia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proterozoic Volcanism
The Proterozoic () is a geological eon spanning the time interval from 2500 to 538.8million years ago. It is the most recent part of the Precambrian "supereon". It is also the longest eon of the Earth's geologic time scale, and it is subdivided into three geologic eras (from oldest to youngest): the Paleoproterozoic, Mesoproterozoic, and Neoproterozoic. The Proterozoic covers the time from the appearance of oxygen in Earth's atmosphere to just before the proliferation of complex life (such as trilobites or corals) on the Earth. The name ''Proterozoic'' combines two forms of ultimately Greek origin: meaning 'former, earlier', and , 'of life'. The well-identified events of this eon were the transition to an oxygenated atmosphere during the Paleoproterozoic; the evolution of eukaryotes; several glaciations, which produced the hypothesized Snowball Earth during the Cryogenian Period in the late Neoproterozoic Era; and the Ediacaran Period (635 to 538.8 Ma) which is characterized b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archean Volcanism
The Archean Eon ( , also spelled Archaean or Archæan) is the second of four geologic eons of Earth's history, representing the time from . The Archean was preceded by the Hadean Eon and followed by the Proterozoic. The Earth during the Archean was mostly a water world: there was continental crust, but much of it was under an ocean deeper than today's ocean. Except for some trace minerals, today's oldest continental crust dates back to the Archean. Much of the geological detail of the Archean has been destroyed by subsequent activity. The earliest known life started in the Archean. Life was simple throughout the Archean, mostly represented by shallow-water microbial mats called stromatolites, and the atmosphere lacked free oxygen. Etymology and changes in classification The word ''Archean'' comes from the Greek word (), meaning 'beginning, origin'. It was first used in 1872, when it meant 'of the earliest geological age'. Before the Hadean Eon was recognized, the Archean ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Greenstone Belts
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. The name comes from the green hue imparted by the colour of the metamorphic minerals within the mafic rocks: the typical green minerals are chlorite, actinolite, and other green amphiboles. Greenstone belts also often contain ore deposits of gold, silver, copper, zinc and lead. A greenstone belt is typically several dozens to several thousand kilometres long. Typically, a greenstone belt within the greater volume of otherwise homogeneous granite-gneiss within a craton contains a significantly larger degree of heterogeneity and complications and forms a tectonic marker far more distinct than the much more voluminous and homogeneous granites. Additionally, a greenstone belt contains far more information on tectonic and metamorphic events, deformations, and paleogeologi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Greenstone Belts
This is a list of greenstone belts Africa Burkina Faso * Hounde greenstone belt * Boromo greenstone belt Democratic Republic of the Congo *Kilo-Moto Angola * Lufico - Cabinda *Cassinga South Africa *Barberton greenstone belt * Pietersberg greenstone belt Tanzania * Kilimafedha greenstone belt * Lake Victoria Greenstone Belt * Nzega Greenstone Belt Zimbabwe * Belingwe Greenstone Belt * Gweru-Shurugwi Greenstone Belt * Harare greenstone belt * Bindura-Shamva greenstone belt * Wedza Greenstone belt * Bulawayo-Bubi Greenstone belt * Makaha Greenstone Belt * Beatrice Greenstone Belt * Dindi Greenstone Belt * Mt Darwin Greenstone Belt Eurasia Russia *Kostomuksha greenstone belt Finland *Central Lapland Greenstone Belt (Lapland) * Tipasjärvi-Kuhmo-Suomussalmi greenstone belt Norway * Mauken greenstone belt Oceania *Harris greenstone belt (Australia) *Jack Hills greenstone belt (Australia) * Norseman-Wiluna greenstone belt (Australia) *Saddleback greenstone belt (Australia) * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lapland Granulite Belt
The Lapland Granulite Belt is an elongate and arcuate zone of granulite rock in the Cap of the North spanning areas within Norway, Finland and Murmansk Oblast in Russia. At most the belt is 80 km broad. The main rocks of the belt are migmatized greywacke and argillites. Studies of detrital zircon show that the sedimentary protolith of the metamorphic rocks of the belt could not be older than 2900–1940 million years. The belt has norite and enderbite intrusions of calc-alkaline chemistry. It is believed that the belt formed by the closure of an ancient Lapland-Kola Ocean and the continental collision of two continents of Archean age. The granulite belt with its arcuate shape is part of the larger Inari orocline An orocline — from the Greek words for "mountain" and "to bend" — is a bend or curvature of an orogenic (mountain building) belt imposed after it was formed. The term was introduced by S. Warren Carey in 1955 in a paper setting forth how comp .... This or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Columbia (supercontinent)
Columbia, also known as Nuna or Hudsonland, was one of Earth's ancient supercontinents. It was first proposed by John J.W. Rogers and M. Santosh in 2002 and is thought to have existed approximately , in the Paleoproterozoic Era. The assembly of the supercontinent was likely completed during global-scale collisional events from 2100 to 1800 million years ago. Columbia consisted of proto-cratons that made up the cores of the continents of Laurentia, Baltica, Ukrainian Shield, Amazonian Shield, Australia, and possibly Siberia, North China, and Kalaharia as well. The evidence of Columbia's existence is provided by geological and paleomagnetic data.; Size and location Columbia is estimated to have been approximately from north to south at its broadest part. The eastern coast of India was attached to western North America, with southern Australia against western Canada. In this era most of South America was rotated such that the western edge of modern-day Brazil lined up wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supercontinent
In geology, a supercontinent is the assembly of most or all of Earth's continent, continental blocks or cratons to form a single large landmass. However, some geologists use a different definition, "a grouping of formerly dispersed continents", which leaves room for interpretation and is easier to apply to Precambrian times. To separate supercontinents from other groupings, a limit has been proposed in which a continent must include at least about 75% of the continental crust then in existence in order to qualify as a supercontinent. Supercontinents have assembled and dispersed multiple times in the geologic past (see table). According to modern definitions, a supercontinent does not exist today; the closest in existence to a supercontinent is the current Afro-Eurasian landmass, which covers approx. 57% of Earth's total land area. The last time the continental landmasses were near to one another was 336 to 175 million years ago as the supercontinent, Pangaea. The positions of con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rifting
In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-graben with normal faulting and rift-flank uplifts mainly on one side. Where rifts remain above sea level they form a rift valley, which may be filled by water forming a rift lake. The axis of the rift area may contain volcanic rocks, and active volcanism is a part of many, but not all, active rift systems. Major rifts occur along the central axis of most mid-ocean ridges, where new oceanic crust and lithosphere is created along a divergent boundary between two tectonic plates. ''Failed rifts'' are the result of continental rifting that failed to continue to the point of break-up. Typically the transition from rifting to spreading develops at a triple junction where three converging rifts meet over a hotspot. Two of these evolve to the poin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Annum
A year or annus is the orbital period of a planetary body, for example, the Earth, moving in its orbit around the Sun. Due to the Earth's axial tilt, the course of a year sees the passing of the seasons, marked by change in weather, the hours of daylight, and, consequently, vegetation and soil fertility. In temperate and subpolar regions around the planet, four seasons are generally recognized: spring, summer, autumn and winter. In tropical and subtropical regions, several geographical sectors do not present defined seasons; but in the seasonal tropics, the annual wet and dry seasons are recognized and tracked. A calendar year is an approximation of the number of days of the Earth's orbital period, as counted in a given calendar. The Gregorian calendar, or modern calendar, presents its calendar year to be either a common year of 365 days or a leap year of 366 days, as do the Julian calendars. For the Gregorian calendar, the average length of the calendar year (the mea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fennoscandian Shield
The Baltic Shield (or Fennoscandian Shield) is a segment of the Earth's crust belonging to the East European Craton, representing a large part of Fennoscandia, northwestern Russia and the northern Baltic Sea. It is composed mostly of Archean and Proterozoic gneisses and greenstone which have undergone numerous deformations through tectonic activity. It contains the oldest rocks of the European continent with a thickness of 250–300 km. The Baltic Shield is divided into five ''provinces'': the Svecofennian and Sveconorwegian (or Southwestern gneiss) provinces in Fennoscandia, and the Karelian, Belomorian and Kola provinces in Russia. The latter three are divided further into several ''blocks'' and ''complexes'' and contain the oldest of the rocks, at 2500-3100 Ma (million years) old. The youngest rocks belong to the Sveconorwegian province, at 900-1700 Ma old. Thought to be formerly part of an ancient continent, the Baltic Shield grew in size through collisions with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
