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Δ34S
The δ34S (pronounced ''delta 34 S'') value is a standardized method for reporting measurements of the ratio of two stable isotopes of sulfur, 34S:32S, in a sample against the equivalent ratio in a known reference standard. The most commonly used standard is Vienna-Canyon Diablo Troilite (VCDT). Results are reported as variations from the standard ratio in parts per thousand, per mil or ''per mille'', using the ‰ symbol. Heavy and light sulfur isotopes fractionate at different rates and the resulting δ34S values, recorded in marine sulfate or sedimentary sulfides, have been studied and interpreted as records of the changing sulfur cycle throughout the earth's history. Calculation Of the 25 known isotopes of sulfur, four are stable. In order of their abundance, those isotopes are 32S (94.93%), 34S (4.29%), 33S (0.76%), and 36S (0.02%). The δ34S value refers to a measure of the ratio of the two most common stable sulfur isotopes, 34S:32S, as measured in a sample against that s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfur Cycle
The sulfur cycle is a biogeochemical cycle in which the sulfur moves between rocks, waterways and living systems. It is important in geology as it affects many minerals and in life because sulfur is an essential element (CHNOPS), being a constituent of many proteins and cofactor (biochemistry), cofactors, and sulfur compounds can be used as oxidants or reductants in microbial respiration. The global sulfur cycle involves the transformations of sulfur species through different oxidation states, which play an important role in both geological and biological processes. Steps of the sulfur cycle are: * Mineralization of Organosulfur compounds, organic sulfur into inorganic forms, such as hydrogen sulfide (H2S), elemental sulfur, as well as sulfide minerals. * Oxidation of hydrogen sulfide, sulfide, and elemental sulfur (S) to sulfate (). * Reduction of sulfate to sulfide. * Incorporation of sulfide into organic compounds (including metal-containing derivatives). * Disproportionation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Canyon Diablo (meteorite)
The Canyon Diablo meteorite refers to the many fragments of the asteroid that created Meteor Crater (also called Barringer Crater), Arizona, United States. Meteorites have been found around the crater rim, and are named for nearby Canyon Diablo (canyon), Canyon Diablo, which lies about three to four miles west of the crater. History The impactor fell about 50,000 years ago. Initially known and used by pre-historic Native Americans in the United States, Native Americans, Canyon Diablo meteorites have been collected and studied by the scientific community since the 19th century. Meteor Crater, from the late 19th to the early 20th century, was the center of a long dispute over the origin of craters that showed little evidence of volcanism. That debate was largely settled by the early 1930s, thanks to work by Daniel Barringer (geologist), Daniel M. Barringer, F.R. Moulton, and Harvey H. Nininger, Harvey Harlow Nininger. In 1953, Clair Patterson, Clair Cameron Patterson measured rat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isotopes Of Sulfur
Sulfur (16S) has 23 known isotopes with mass numbers ranging from 27 to 49, four of which are stable: 32S (95.02%), 33S (0.75%), 34S (4.21%), and 36S (0.02%). The preponderance of sulfur-32 is explained by its production from carbon-12 plus successive fusion capture of five helium-4 nuclei, in the so-called alpha process of exploding type II supernovas (see silicon burning). Other than 35S, the radioactive isotopes of sulfur are all comparatively short-lived. 35S is formed from cosmic ray spallation of 40 Ar in the atmosphere. It has a half-life of 87 days. The next longest-lived radioisotope is sulfur-38, with a half-life of 170 minutes. Isotopes lighter than 32S mostly decay to isotopes of phosphorus or silicon, while 35S and heavier radioisotopes decay to isotopes of chlorine. The beams of several radioactive isotopes (such as those of 44S) have been studied theoretically within the framework of the synthesis of superheavy elements, especially those ones in the vicinity o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terrestrial δ34S Values
Terrestrial refers to things related to land or the planet Earth, as opposed to extraterrestrial. Terrestrial may also refer to: * Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on or near the ground, as opposed to arboreal life (in trees) ** A fishing fly that simulates the appearance of a land insect is referred to as a terrestrial fly. * Terrestrial ecoregion, land ecoregions, as distinct from freshwater ecoregions and marine ecoregions * Terrestrial ecosystem, an ecosystem found only on landforms * Terrestrial gamma-ray flash, a burst of gamma rays produced in Earth's atmosphere * Terrestrial locomotion, evolutionary adaptation from aquatic types of locomotion * Terrestrial plant, a plant that grows on land rather than in water or on rocks or trees * Terrestrial planet, a planet that is primarily composed of silicate rocks, and thus "Earth-like" * Terrestrial radio, radio signals received through a conventional a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anoxic Waters
Anoxic waters are areas of sea water, fresh water, or groundwater that are depleted of dissolved oxygen. The US Geological Survey defines anoxic groundwater as those with dissolved oxygen concentration of less than 0.5 milligrams per litre. Anoxic waters can be contrasted with hypoxic waters, which are low (but not lacking) in dissolved oxygen. Often, hypoxia is defined as waters that have less than 2 milligrams per litre of dissolved oxygen. This condition is generally found in areas that have restricted water exchange. In most cases, oxygen is prevented from reaching the deeper levels by a physical barrier, as well as by a pronounced density stratification, in which, for instance, denser, colder or hypersaline waters rest at the bottom of a basin. Anoxic conditions will occur if the rate of oxidation of organic matter by bacteria is greater than the supply of dissolved oxygen. Anoxic waters are a natural phenomenon, and have occurred throughout geological history. The Permia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Water Column
The (oceanic) water column is a concept used in oceanography to describe the physical (temperature, salinity, light penetration) and chemical ( pH, dissolved oxygen, nutrient salts) characteristics of seawater at different depths for a defined geographical point. Generally, vertical profiles are made of temperature, salinity, chemical parameters at a defined point along the water column. The water column is the largest, yet one of the most under-explored, habitats on the planet; it is explored to better understand the ocean as a whole, including the huge biomass that lives there and its importance to the global carbon and other biogeochemical cycles. Studying the water column also provides understanding on the links between living organisms and environmental parameters, large-scale water circulation and the transfer of matter between water masses. Water columns are used chiefly for environmental studies evaluating the stratification or mixing of thermal or chemically stratif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Great Oxygenation Event
The Great Oxidation Event (GOE) or Great Oxygenation Event, also called the Oxygen Catastrophe, Oxygen Revolution, Oxygen Crisis or Oxygen Holocaust, was a time interval during the Earth's Paleoproterozoic era when the Earth's atmosphere and shallow seas first experienced a rise in the concentration of free oxygen. This began approximately 2.460–2.426 billion years ago (Ga) during the Siderian period and ended approximately 2.060 Ga ago during the Rhyacian. Geological, isotopic and chemical evidence suggests that biologically produced molecular oxygen (dioxygen or O2) started to accumulate in the Archean prebiotic atmosphere due to microbial photosynthesis, and eventually changed it from a weakly reducing atmosphere practically devoid of oxygen into an oxidizing one containing abundant free oxygen, with oxygen levels being as high as 10% of modern atmospheric level by the end of the GOE. The appearance of highly reactive free oxygen, which can oxidize or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evaporite
An evaporite () is a water- soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as ocean deposits, and non-marine, which are found in standing bodies of water such as lakes. Evaporites are considered sedimentary rocks and are formed by chemical sediments. Formation Although all water bodies on the surface and in aquifers contain dissolved salts, the water must evaporate into the atmosphere for the minerals to precipitate. For this to happen, the water body must enter a restricted environment where water input into this environment remains below the net rate of evaporation. This is usually an arid environment with a small drainage basin fed by a limited input of water. When evaporation occurs, the remaining water is enriched in salts, and they precipitate after the water becomes saturated. Depositional environments ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Warrawoona Group
The Warrawoona Group is a geological unit in Western Australia containing putative fossils of cyanobacteria cells. Dated 3.465 Ga, these microstructures, found in Archean chert, are considered to be the oldest known geological record of life on Earth. Description The fossils in this group were discovered by Arthur Hugh Hickman in 1983 in Warrawoona, , a region on the Pilbara craton in the northern part of Pilbara province. Whether or not the fossils were authentic was disputed in the past, as abiotic processes could not be ruled out. Currently the fossils are thought to be of biological origin, however there is no conclusive evidence of fossilized organisms in the formation, and whether the lines in the rock are fossilized stromatolites. The rocks also include felsic volcanic rocks. See also * North Pole, WA for similar issues * Origin of life Abiogenesis is the natural process by which life arises from abiotic component, non-living matter, such as simple o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Barite
Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate (Ba S O4). Baryte is generally white or colorless, and is the main source of the element barium. The ''baryte group'' consists of baryte, celestine (strontium sulfate), anglesite (lead sulfate), and anhydrite (calcium sulfate). Baryte and celestine form a solid solution . Names and history The radiating form, sometimes referred to as ''Bologna Stone'', attained some notoriety among alchemists for specimens found in the 17th century near Bologna by Vincenzo Casciarolo. These became phosphorescent upon being calcined. Carl Scheele determined that baryte contained a new element in 1774, but could not isolate barium, only barium oxide. Johan Gottlieb Gahn also isolated barium oxide two years later in similar studies. Barium was first isolated by electrolysis of molten barium salts in 1808 by Sir Humphry Davy in England. The American Petroleum Institute specification API 13/ISO 13500, which governs '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyrite
The mineral pyrite ( ), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic luster and pale brass-yellow hue give it a superficial resemblance to gold, hence the well-known nickname of ''fool's gold''. The color has also led to the nicknames ''brass'', ''brazzle'', and ''brazil'', primarily used to refer to pyrite found in coal. The name ''pyrite'' is derived from the Greek (), 'stone or mineral which strikes fire', in turn from (), 'fire'. In ancient Roman times, this name was applied to several types of stone that would create sparks when struck against steel; Pliny the Elder described one of them as being brassy, almost certainly a reference to what is now called pyrite. By Georgius Agricola's time, , the term had become a generic term for all of the sulfide minerals. Pyrite is usually found associated with other sulfides or oxides in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archean
The Archean ( , also spelled Archaean or Archæan), in older sources sometimes called the Archaeozoic, is the second of the four geologic eons of Earth's history of Earth, history, preceded by the Hadean Eon and followed by the Proterozoic and the Phanerozoic. The Archean represents the time period from (million years ago). The Late Heavy Bombardment is hypothesized to overlap with the beginning of the Archean. The Huronian glaciation occurred at the end of the eon. The Earth during the Archean was mostly a ocean world, water world: there was continental crust, but much of it was under an ocean deeper than today's oceans. Except for some rare Relict (geology), relict crystals, 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 Earth's atmosphere was also vastly different in atmospheric chemistry, composition from today's: the prebiotic atmosphere was a reducing atmosphere rich in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
