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Epithermal
Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with the assistance of. Roderick McKenzie.'' Oxford: Clarendon Press. and θέρμη, ''heat'' ). Hydrothermal circulation occurs most often in the vicinity of sources of heat within the Earth's crust. In general, this occurs near volcanic activity, but can occur in the shallow to mid crust along deeply penetrating fault irregularities or in the deep crust related to the intrusion of granite, or as the result of orogeny or metamorphism. Seafloor hydrothermal circulation Hydrothermal circulation in the oceans is the passage of the water through mid-oceanic ridge systems. The term includes both the circulation of the well-known, high-temperature vent waters near the ridge crests, and the much-lower-temperature, diffuse flow of water through sedim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ore Genesis
Various theories of ore genesis explain how the various types of mineral deposits form within Earth's crust. Ore-genesis theories vary depending on the mineral or commodity examined. Ore-genesis theories generally involve three components: source, transport or conduit, and trap. (This also applies to the petroleum industry: petroleum geologists originated this analysis.) *''Source'' is required because metal must come from somewhere, and be liberated by some process. *''Transport'' is required first to move the metal-bearing fluids or solid minerals into their current position, and refers to the act of physically moving the metal, as well as to chemical or physical phenomena which encourage movement. *''Trapping'' is required to concentrate the metal via some physical, chemical, or geological mechanism into a concentration which forms mineable ore. The biggest deposits form when the source is large, the transport mechanism is efficient, and the trap is active and ready at the r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Porphyry Copper
Porphyry copper deposits are copper ore bodies that are formed from hydrothermal fluids that originate from a voluminous magma chamber several kilometers below the deposit itself. Predating or associated with those fluids are vertical dikes of porphyritic intrusive rocks from which this deposit type derives its name. In later stages, circulating meteoric fluids may interact with the magmatic fluids. Successive envelopes of hydrothermal alteration typically enclose a core of disseminated ore minerals in often stockwork-forming hairline fractures and veins. Because of their large volume, porphyry orebodies can be economic from copper concentrations as low as 0.15% copper and can have economic amounts of by-products such as molybdenum, silver, and gold. In some mines, those metals are the main product. The first mining of low-grade copper porphyry deposits from large open pits coincided roughly with the introduction of steam shovels, the construction of railroads, and a surge in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ancient Greek
Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic period (), and the Classical period (). Ancient Greek was the language of Homer and of fifth-century Athenian historians, playwrights, and philosophers. It has contributed many words to English vocabulary and has been a standard subject of study in educational institutions of the Western world since the Renaissance. This article primarily contains information about the Epic and Classical periods of the language. From the Hellenistic period (), Ancient Greek was followed by Koine Greek, which is regarded as a separate historical stage, although its earliest form closely resembles Attic Greek and its latest form approaches Medieval Greek. There were several regional dialects of Ancient Greek, of which Attic Greek developed into Koine. Dia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geyser
A geyser (, ) is a spring characterized by an intermittent discharge of water ejected turbulently and accompanied by steam. As a fairly rare phenomenon, the formation of geysers is due to particular hydrogeological conditions that exist only in a few places on Earth. Generally all geyser field sites are located near active volcanic areas, and the geyser effect is due to the proximity of magma. Generally, surface water works its way down to an average depth of around where it contacts hot rocks. The resultant boiling of the pressurized water results in the geyser effect of hot water and steam spraying out of the geyser's surface vent (a hydrothermal explosion). A geyser's eruptive activity may change or cease due to ongoing mineral deposition within the geyser plumbing, exchange of functions with nearby hot springs, earthquake influences, and human intervention. Like many other natural phenomena, geysers are not unique to Earth. Jet-like eruptions, often referred to as cryoge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geothermal Gradient
Geothermal gradient is the rate of temperature change with respect to increasing depth in Earth's interior. As a general rule, the crust temperature rises with depth due to the heat flow from the much hotter mantle; away from tectonic plate boundaries, temperature rises in about 25–30 °C/km (72–87 °F/mi) of depth near the surface in most of the world. However, in some cases the temperature may drop with increasing depth, especially near the surface, a phenomenon known as ''inverse'' or ''negative'' geothermal gradient. The effects of weather, sun, and season only reach a depth of approximately 10-20 metres. Strictly speaking, ''geo''-thermal necessarily refers to Earth but the concept may be applied to other planets. In SI units, the geothermal gradient is expressed as °C/km, K/km, or mK/m. These are all equivalent. Earth's internal heat comes from a combination of residual heat from planetary accretion, heat produced through radioactive decay, latent heat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcanogenic Massive Sulfide Ore Deposit
Volcanogenic massive sulfide ore deposits, also known as VMS ore deposits, are a type of metal sulfide ore deposit, mainly copper-zinc which are associated with and created by volcanic-associated hydrothermal events in submarine environments. These deposits are also sometimes called volcanic-hosted massive sulfide (VHMS) deposits. The density generally is 4500 kg/m3. They are predominantly stratiform accumulations of sulfide minerals that precipitate from hydrothermal fluids on or below the seafloor in a wide range of ancient and modern geological settings. In modern oceans they are synonymous with sulfurous plumes called black smokers. They occur within environments dominated by volcanic or volcanic derived (e.g., volcano-sedimentary) rocks, and the deposits are coeval and coincident with the formation of said volcanic rocks. As a class, they represent a significant source of the world's copper, zinc, lead, gold and silver ores, with cobalt, tin, barium, sulfur, selenium, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uranium Ore Deposits
Uranium ore deposits are economically recoverable concentrations of uranium within the Earth's crust. Uranium is one of the more common elements in the Earth's crust, being 40 times more common than silver and 500 times more common than gold. It can be found almost everywhere in rock, soil, rivers, and oceans. The challenge for commercial uranium extraction is to find those areas where the concentrations are adequate to form an economically viable deposit. The primary use for uranium obtained from mining is in fuel for nuclear reactors. Globally, the distribution of uranium ore deposits is widespread on all continents, with the largest deposits found in Australia, Kazakhstan, and Canada. To date, high-grade deposits are only found in the Athabasca Basin region of Canada. Uranium deposits are generally classified based on host rocks, structural setting, and mineralogy of the deposit. The most widely used classification scheme was developed by the International Atomic Energy Agen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbonate Hosted Lead Zinc Ore Deposits
Carbonate-hosted lead-zinc ore deposits are important and highly valuable concentrations of lead and zinc sulfide ores hosted within carbonate (limestone, marl, dolomite) formations and which share a common genetic origin. These ore bodies range from 0.5 million tonnes of contained ore, to 20 million tonnes or more, and have a grade of between 4% combined lead and zinc to over 14% combined lead and zinc. These ore bodies tend to be compact, fairly uniform plug-like or pipe-like replacements of their host carbonate sequences and as such can be extremely profitable mines. This classification of ore deposits is also known as Mississippi Valley Type or ''MVT'' ore deposits, after a number of such deposits along the Mississippi River in the United States, where such ores were first recognised; these include the famed Southeast Missouri Lead District of southeastern Missouri, and deposits in northeast Iowa, southwest Wisconsin, and northwest Illinois. Similarly Irish-type carbonate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meteoric Water
Meteoric water is the water derived from precipitation (snow and rain). This includes water from lakes, rivers, and icemelts, which all originate from precipitation indirectly. While the bulk of rainwater or meltwater from snow and ice reaches the sea through surface flow, a considerable portion of meteoric water gradually infiltrates into the ground. This infiltrating water continues its downward journey to the zone of saturation to become a part of the groundwater in aquifers. Overview Most groundwater is meteoric water. Other forms normally do not play a significant role in the hydrologic cycle. Non-meteoric forms of groundwater are connate water and magmatic water, also termed juvenile water. Connate water is trapped in rock strata at the time of formation. Because rock containing connate water is typically formed from ocean sediments, connate water is normally saline. Magmatic water rises from great depth accompanying magma intrusion and affects mineralogy. In other word ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magmatic Water
Magmatic water, also known as juvenile water, is an aqueous phase in equilibrium with minerals that have been dissolved by magma deep within the Earth's crust and is released to the atmosphere during a volcanic eruption. It plays a key role in assessing the crystallization of igneous rocks, particularly silicates, as well as the rheology and evolution of magma chambers. Magma is composed of minerals, crystals and volatiles in varying relative abundance. Magmatic differentiation varies significantly based on various factors, most notably the presence of water. An abundance of volatiles within magma chambers decreases viscosity and leads to the formation of minerals bearing halogens, including chloride and hydroxide groups. In addition, the relative abundance of volatiles varies within basaltic, andesitic, and rhyolitic magma chambers, leading to some volcanoes being exceedingly more explosive than others. Magmatic water is practically insoluble in silicate melts but has demonstrat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Waldemar Lindgren
Waldemar Lindgren (February 14, 1860 – November 3, 1939) was a Swedish-American geologist. Lindgren was one of the founders of modern economic geology. Biography Waldemar Lindgren was born in Vassmolösa, Kalmar Municipality, in the historical province of Småland in southern Sweden, the son of Johan and Emma Lindgren. Lindgren's father was a judge and member of parliament, his mother the daughter of a clergyman. Lindgren attended the Freiberg Mining Academy, Germany, graduating as a mining engineer in 1882. In 1884, he began a 31-year career with the U.S. Geological Survey, working on ore deposits in the Rocky Mountains. In 1905, he helped found the journal Economic Geology. In 1912, he was appointed head of the Department of Geology at the Massachusetts Institute of Technology. Lindgren was elected a foreign member of the Royal Swedish Academy of Sciences in 1931. Lindgren was a fellow of the Mineralogical Society of America. He has served as President of the Geological ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Minerals'; p. 1. In the series ''Geology: Landforms, Minerals, and Rocks''. Rosen Publishing Group. The geological definition of mineral normally excludes compounds that occur only in living organisms. However, some minerals are often biogenic (such as calcite) or are organic compounds in the sense of chemistry (such as mellite). Moreover, living organisms often synthesize inorganic minerals (such as hydroxylapatite) that also occur in rocks. The concept of mineral is distinct from rock, which is any bulk solid geologic material that is relatively homogeneous at a large enough scale. A rock may consist of one type of mineral, or may be an aggregate of two or more different types of minerals, spacially segregated into distinct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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