"compared to carbon‑12, relative to typical diamonds). Carbonado exhibits strong luminescence (photoluminescence and cathodoluminescence) induced by nitrogen and by vacancies existing in the crystal lattice. Luminescence halos are present around radioactive inclusions, and it is suggested that the radiation damage occurred after formation of the carbonados, an observation perhaps pertinent to the radiation hypothesis listed below. The origin of carbonado is controversial. Some proposed hypotheses are as follows: None of these hypotheses for carbonado formation had come into wide acceptance in the scientific literature by 2008. Supporters of an extraterrestrial origin of carbonados propose that their material source was a"
"Carbonatite Carbonatite () is a type of intrusive or extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. Carbonatites may be confused with marble and may require geochemical verification. Carbonatites usually occur as small plugs within zoned alkalic intrusive complexes, or as dikes, sills, breccias, and veins. They are almost exclusively associated with continental rift-related tectonic settings. It seems that there has been a steady increase in the carbonatitic igneous activity through the Earth's history, from the Archean eon to the present. Nearly all carbonatite occurrences are intrusives or subvolcanic intrusives. This is because carbonatite"
"Carbonate rock Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major types are limestone, which is composed of calcite or aragonite (different crystal forms of CaCO) and dolostone, which is composed of the mineral dolomite (CaMg(CO)). Calcite can be either dissolved by groundwater or precipitated by groundwater, depending on several factors including the water temperature, pH, and dissolved ion concentrations. Calcite exhibits an unusual characteristic called retrograde solubility in which it becomes less soluble in water as the temperature increases. When conditions are right for precipitation, calcite forms mineral coatings that cement the"
"existing rock grains together or it can fill fractures. Karst topography and caves develop in carbonate rocks because of their solubility in dilute acidic groundwater. Cooling groundwater or mixing of different groundwaters will also create conditions suitable for cave formation. Marble is the metamorphic carbonate rock. Rare igneous carbonate rocks exist as intrusive carbonatites and even rarer volcanic carbonate lava. Carbonate rock Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major types are limestone, which is composed of calcite or aragonite (different crystal forms of CaCO) and dolostone, which is composed of the"
"mineralogy, the term ""carbonate"" can refer both to carbonate minerals and carbonate rock (which is made of chiefly carbonate minerals), and both are dominated by the carbonate ion, . Carbonate minerals are extremely varied and ubiquitous in chemically precipitated sedimentary rock. The most common are calcite or calcium carbonate, CaCO, the chief constituent of limestone (as well as the main component of mollusc shells and coral skeletons); dolomite, a calcium-magnesium carbonate CaMg(CO); and siderite, or iron(II) carbonate, FeCO, an important iron ore. Sodium carbonate (""soda"" or ""natron"") and potassium carbonate (""potash"") have been used since antiquity for cleaning and preservation,"
"Geology of Barbados The geology of Barbados includes exposures of reef-related carbonate rocks spanning 85 percent of the island's surface. This Coral Rock Formation is 70 meters thick and dates to the Pleistocene. Unlike neighboring islands in the Lesser Antilles volcanic arc, Barbados is unusual because it is not a volcanic island (the only volcanic rocks are some ash beds from eruptions on neighboring islands). Instead, the island of Barbados is the exposed part of the Barbados Ridge Accretionary Prism, left as deep ocean sediments ""scraped"" to the surface as the Atlantic oceanic crust subducted beneath the Caribbean Plate. The"
"as dikes and discontinuous pods. Dozens of carbonatites are known including: In 2017, the discovery of a new carbonatite deposit was confirmed north-west of Prince George, British Columbia, in a region termed the ""Rocky Mountain Rare Metal Belt"". The volcano Ol Doinyo Lengai, in the East African Rift is the world's only active carbonatite volcano. Other older carbonatite volcanoes are located in the same region, including Mount Homa. Carbonatites may contain economic or anomalous concentrations of rare-earth elements, phosphorus, niobium–tantalum, uranium, thorium, copper, iron, titanium, vanadium, barium, fluorine, zirconium, and other rare or incompatible elements. Apatite, barite and vermiculite are"
"features within them such as stalactite and stalagmites, and karst landforms. Carbonates are most often formed as biogenic or chemical sediments in marine environments. The carbonate group is structurally a triangle, where a central C cation is surrounded by three O anions; different groups of minerals form from different arrangements of these triangles. The most common carbonate mineral is calcite, which is the primary constituent of sedimentary limestone and metamorphic marble. Calcite, CaCO, can have a high magnesium impurity. Under high-Mg conditions, its polymorph aragonite will form instead; the marine geochemistry in this regard can be described as an aragonite"
"The lava is natrocarbonatite dominated by nyerereite and gregoryite. The magmatic origin of carbonatite was argued in detail by Swedish geologist Harry von Eckermann in 1948 basen on his study of Alnö Complex. It was however the 1960 eruption of Ol Doinyo Lengai in Tanzania that led to geological investigations that finally confirmed the view that carbonatite is derived from magma. Carbonatites are ""rare"", ""peculiar"" igneous rocks formed by unusual processes and from unusual source rocks. Three models of their formation exist: Evidence for each process exists, but the key is that these are unusual phenomena. Historically, carbonatites were thought"
"among the industrially important minerals associated with some carbonatites. Vein deposits of thorium, fluorite, or rare-earth elements may be associated with carbonatites and may be hosted internal to or within the metasomatized aureole of a carbonatite. As an example, the Palabora complex of South Africa has produced significant copper (as chalcopyrite, bornite and chalcocite), apatite, vermiculte along with lesser magnetite, linnaeite (cobalt), baddeleyite (zirconium–hafnium), and by-product gold, silver, nickel and platinum. Carbonatite Carbonatite () is a type of intrusive or extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. Carbonatites may be confused with marble"
"a solution supersaturated with the chemical constituents of calcite. Tufa, a porous or cellular variety of travertine, is found near waterfalls. Coquina is a poorly consolidated limestone composed of pieces of coral or shells. During regional metamorphism that occurs during the mountain building process (orogeny), limestone recrystallizes into marble. Limestone is a parent material of Mollisol soil group. Two major classification schemes, the Folk and the Dunham, are used for identifying limestone and carbonate rocks. Robert L. Folk developed a classification system that places primary emphasis on the detailed composition of grains and interstitial material in carbonate rocks. Based on"
"to form by melting of limestone or marble by intrusion of magma, but geochemical and mineralogical data discount this. For example, the carbon isotopic composition of carbonatites is mantle-like and not like sedimentary limestone. Primary mineralogy is highly variable, but may include natrolite, sodalite, apatite, magnetite, barite, fluorite, ancylite group minerals, and other rare minerals not found in more common igneous rocks. Recognition of carbonatites may be difficult, especially as their mineralogy and texture may not differ much from marble except the presence of igneous minerals. They may also be sources of mica or vermiculite. Carbonatites are classed as calcitic"
"is carbonate- or sulphate-rich. Limestone is by far the most common, but others include dolomite, gypsum, marble, chalk and marlstone. Alongside physical weathering, which breaks down the structure of rocky material, chemical weathering, in particular the dissolution of carbonate, contributes to rendzina development. When water with dissolved carbon dioxide comes into contact with carbonate minerals, the carbonate is dissolved and leaches out with the water. The overall reaction is as follows: CaCO(s) + HO(l) + CO(aq) → 2 HCO(aq) + Ca(aq) Loss of soluble minerals leaves the upper part of the soil enriched in insoluble materials, particularly clay minerals. At"
"Carbonate hardgrounds Carbonate hardgrounds are surfaces of synsedimentarily cemented carbonate layers that have been exposed on the seafloor (Wilson and Palmer, 1992). A hardground is essentially, then, a lithified seafloor. Ancient hardgrounds are found in limestone sequences and distinguished from later-lithified sediments by evidence of exposure to normal marine waters. This evidence can consist of encrusting marine organisms (especially bryozoans, oysters, barnacles, cornulitids, hederelloids, microconchids and crinoids), borings of organisms produced through bioerosion, early marine calcite cements, or extensive surfaces mineralized by iron oxides or calcium phosphates (Palmer, 1982; Bodenbender et al., 1989; Vinn and Wilson, 2010; Vinn and Toom,"
"of carbonatite intrusion, now appearing as carbonatite ring and subsided central part. The carbonatite ring is characterized by vertical scarps on inner side, with surface which often shows irregular knots, nodes, or veins of more resistant (silicate) material. Laterite covers are formed on both sides of carbonatite ring with accumulation of residual ferruginous-manganese minerals. Carbonatitic rocks are characterized by considerable variation, or great variety of textures, while the mineral composition is quite uniform and chiefly independent of texture. According to texture of carbonatite, can be distinguished: hypidiomorphic granular, medium-grained, pseudoporphyric and trachytic. The most abundant are carbonatites with granular texture,"
"Listwanite Listwanite (also sometimes spelled listvenite, listvanite, or listwaenite) is unusual rock type that forms when ultramafic rocks (most commonly mantle peridotites) are completely carbonated. The pyroxene and olivine minerals found in peridotite commonly alter to form carbonate and serpentine minerals. However, peridotites are usually not completely carbonated. Rather, they typically contain carbonate veins (primarily magnesite; also calcite, dolomite, and other carbonates). Complete carbonation of peridotite means that every single atom of magnesium and calcium as well as some of the iron atoms has combined with CO to form secondary carbonate minerals such a magnesite and calcite. The silica atoms"
"Granitoid A granitoid or granitic rock is a variety of coarse grained plutonic rock similar to granite which mineralogically is composed predominantly of feldspar and quartz. Examples of granitoid rocks include granite, quartz monzonite, quartz diorite, syenite, granodiorite, tonalite and trondhjemite. Many are created by continental volcanic arc subduction or the collision of sialic masses. Volcanic rocks are common with granitoids and typically have the same origins. However, they are normally worn away after years of erosion. While many granitoid rocks are located in areas that have experienced crustal thickening during orogenies, others known as ""anorogenic granitoids"" are unrelated to"
"Calcium carbonate Calcium carbonate is a chemical compound with the formula CaCO. It is a common substance found in rocks as the minerals calcite and aragonite (most notably as limestone, which is a type of sedimentary rock consisting mainly of calcite) and is the main component of pearls and the shells of marine organisms, snails, and eggs. Calcium carbonate is the active ingredient in agricultural lime and is created when calcium ions in hard water react with carbonate ions to create limescale. It is medicinally used as a calcium supplement or as an antacid, but excessive consumption can be hazardous."
"Dolomite Dolomite () is an anhydrous carbonate mineral composed of calcium magnesium carbonate, ideally The term is also used for a sedimentary carbonate rock composed mostly of the mineral dolomite. An alternative name sometimes used for the dolomitic rock type is dolostone. Most probably the mineral dolomite was first described by Carl Linnaeus in 1768. In 1791, it was described as a rock by the French naturalist and geologist Déodat Gratet de Dolomieu (1750–1801), first in buildings of the old city of Rome, and later as samples collected in the mountains now known as the Dolomite Alps of northern Italy."
"the Kaiserstuhl (Henkenberg near Burkheim, Kirchberg near Oberrotweil). The subvolcanic and intrusive rocks of the central Kaiserstuhl are plutonic equivalents of the erupted material (essexite, carbonatite and coarse-granular phonolite). Several local terms which do not carry official status with the International Union of Geological Sciences have been used for different varieties of the intrusive rocks. Of major scientific interest is the consolidated carbonatite near Altvogtsburg und Schelingen. It is a quite rare volcanic rock, which crystallized from a carbonate magamatic melt rather than a silicate one. Given its unusual composition for an igneous rock, the magmatic nature of the carbonatite"
"the only significant occurrence at Ivittuut, Greenland, in a granitic pegmatite, was depleted, synthetic cryolite can be made from fluorite. The carbonate minerals are those in which the main anionic group is carbonate, [CO]. Carbonates tend to be brittle, many have rhombohedral cleavage, and all react with acid. Due to the last characteristic, field geologists often carry dilute hydrochloric acid to distinguish carbonates from non-carbonates. The reaction of acid with carbonates, most commonly found as the polymorph calcite and aragonite (CaCO), relates to the dissolution and precipitation of the mineral, which is a key in the formation of limestone caves,"
"Geology of Argentina The geology of Argentina includes ancient Precambrian basement rock affected by the Grenville orogeny, sediment filled basins from the Mesozoic and Cenozoic as well as newly uplifted areas in the Andes. The oldest rocks in Argentina date to the Precambrian. Strontium, oxygen and carbon isotope data from carbonate rocks in the Sierra de Pie de Palo are part of an ophiolite unit related to the Grenville orogeny, formed as cover rock in the Appalachian margin of the continent Laurentia around 720 million years ago. These Neoproterozoic age rocks are believed to have formed above much older Archean"
"part of Portugal and the south west corner of Spain. The oldest rocks are Precambrian forming bands in two elongated anticlines between Córdoba and Abrantes. The Cambrian rocks start with conglomerate, and then have shallow water deposits and limestone. The Ordovician Period is represented by pelitic facies. In the Late Ordovician syenite and alkaline granite intrusions rose along the Córdoba Abrantes belt The Silurian Period has volcanic rocks both acid and basic, and also pelitic deposits. The Lower Devonian was formed in shallow water. The Upper Devonian follows a break and is of flysch. In the Carboniferous it starts with"
"form the rock types: limestone, chalk, marble, travertine, tufa, and others. In warm, clear tropical waters corals are more abundant than towards the poles where the waters are cold. Calcium carbonate contributors, including plankton (such as coccoliths and planktic foraminifera), coralline algae, sponges, brachiopods, echinoderms, bryozoa and mollusks, are typically found in shallow water environments where sunlight and filterable food are more abundant. Cold-water carbonates do exist at higher latitudes but have a very slow growth rate. The calcification processes are changed by ocean acidification. Where the oceanic crust is subducted under a continental plate sediments will be carried down"
"of the platform, connecting the reef with the basin. This area acts as sink for excess carbonate sediment: most of the sediment produced in the lagoon and reef is transported by various processes and accumulates in the slope. Therefore, the slope contains coarser sediments than the reef and lagoon; these rocks are generally rudstones or grainstones. Sediments have a characteristic geometry: they are organized in clinoforms. Clinoforms are beds that have a sigmoidal or tabular shape, but are always deposited with a primary inclination. Sedimentary sequences show carbonate platforms as old as the Precambrian, when they were formed by stromatolitic"
"known in the region. The genesis of this Archaean carbonatite remains contentious as it is the sole example of an Archaean carbonatite in Australia. Carbonatite is known to form in association with concentrically zoned complexes of alkaline-igneous rocks, the typical example of this being Phalaborwa, South Africa. Carbonatites take the form of sills, lopoliths and rare dikes are reported in the Guyana Shield. The Mud Tank and Mount Weld carbonatites take the form of multi-stage cylindrical intrusive bodies with several distinct phases of carbonatite intrusion. Smaller carbonatite sills and dikes are present in other Proterozoic mobile belts in Australia, typically"
"Calcirudite Calcirudite is a type of limestone that is composed predominantly, more than 50 percent, of carbonate grains that are larger in size than sand (2 mm in diameter). The grains can consist of either fragments of fossils, fragments of older limestones and dolomites, other carbonate grains, or some combination of these. The term calcirudite was originally proposed in 1903 by Grabau as a part of his calcilutite, calcarenite and calcirudite classification system based upon the size of the detrital grains composing a limestone. Depending on roundness of the grains, calcirudite is the carbonate equivalent of either a breccia, in"
"the folded and eroded remains of an ancient mountain range, created in the same orogeny that formed the Ouachita and Appalachian Mountains. The Precambrian metamorphic and igneous rocks of the Llano Uplift probably formed during the Mesoproterozoic Grenville orogeny, which was part of the assembly of the supercontinent Rodinia. Over time, the mountains of the Grenville orogeny were eroded flat, and later covered by Paleozoic and Mesozoic sediments that were not uplifted and eroded in their present manner until the late Cenozoic. Early to middle Paleozoic rocks in Texas are typically carbonate deposited in epeiric seas. Exceptions include a significant"
"layered limestone, crystalline limestone and leopard skin limestone; the Carboniferous rocks are mainly gray-white siltstone, clay rock, shale and thin layer limestone. Several layers of coal; the two rocks are mainly grayish white, dark gray sandstone and variegated mudstone and brown shale, rich in plant fossils. The Mesozoic Jurassic rocks are mainly brown sandstone, conglomerate, variegated mudstone and glutenite. The Cenozoic is made up of Tertiary and Quaternary strata. The Tertiary is sandstone, sticky sandstone, and mudstone; the Quaternary strata are loose rock formations composed of Wenyu alluvial deposits. The west is the Wenhe alluvial fan, the east is the"
"Carbonatation Carbonatation is a chemical reaction in which calcium hydroxide reacts with carbon dioxide and forms insoluble calcium carbonate: The process of forming a carbonate is sometimes referred to as ""carbonation"", although this term usually refers to the process of dissolving carbon dioxide in water. Carbonatation is a slow process that occurs in concrete where lime (CaO, or Ca(OH)) in the cement reacts with carbon dioxide (CO) from the air and forms calcium carbonate. The water in the pores of Portland cement concrete is normally alkaline with a pH in the range of 12.5 to 13.5. This highly alkaline environment"
"rocks relatively rich in carbon dioxide. Nephelinite is found on ocean islands such as Oahu, although the rock type is very rare in the Hawaiian islands. It is found in a variety of continental settings. An example is the Hamada nephelinite lava flow in southwest Japan which occurred in the late Miocene age. Nephelinite is also associated with the highly alkalic volcanism of the Ol Doinyo Lengai volcanic field in Tanzania. Nyiragongo, another African volcano known for its semipermanent lava lake activity, erupts lava made of melilite nephelinite. The unusual chemical makeup of this igneous rock may be a factor"
"diagenetic history can be studied by optical mineralogy, using a petrographic microscope. Carbonate rocks dominantly consist of carbonate minerals such as calcite, aragonite or dolomite. Both the cement and the clasts (including fossils and ooids) of a carbonate sedimentary rock can consist of carbonate minerals. The mineralogy of a clastic rock is determined by the material supplied by the source area, the manner of its transport to the place of deposition and the stability of that particular mineral. The resistance of rock-forming minerals to weathering is expressed by Bowen's reaction series. In this series, quartz is the most stable, followed"
"forms stairstep-shaped banks. Mosaic Canyon's polished marble walls are carved from the Noonday Dolomite and other Precambrian carbonate rocks. These rock formation began as limestone deposited during Late Precambrian (about 850-700 million years ago) when the area was covered by a warm sea. Later addition of magnesium changed the limestone, a rock made of calcium carbonate, to dolomite, a calcium-magnesium carbonate. The dolomite was later deeply buried by younger sediment. Far below the surface, high pressure and temperature altered the dolomite into the metamorphic rock, marble. The Noonday Dolomite has since been tilted from uplift. Mosaic Canyon was named for"