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Topic Review
Carbon-Isotope Signature of Diagenetic Carbonates
Diagenetic carbonates often show large variations in their carbon isotope compositions. Variations are mainly the result of isotope fractionation effects during microbial metabolic processes, and these processes themselves may induce carbonate formation. Inorganic carbon from dissimilatory microbial activity shows negative carbon isotope values (d13C), in particular if methane is used as a carbon source. In turn, inorganic carbon produced during methanogenesis shows positive d13C values. The range of isotope values preserved in the carbonate phase ultimately depends on the reservoir sizes, diffusive mixing of different carbon sources, and episodic formation of carbonate. The carbon-isotope signature of diagenetic carbonates therefore represents an archive of past biogeochemical activity in the subsurface.
  • 1.8K
  • 30 Oct 2020
Topic Review
Carbonaceous Biochemical Oxygen Demand
Carbonaceous biochemical oxygen demand or CBOD is a method defined test measured by the depletion of dissolved oxygen by biological organisms in a body of water in which the contribution from nitrogenous bacteria has been suppressed. CBOD is a method defined parameter is widely used as an indication of the pollutant removal from wastewater. It is listed as a conventional pollutant in the U.S. Clean Water Act.
  • 6.2K
  • 21 Nov 2022
Topic Review
Carbonate Reservoirs Permeability Prediction
Permeability is a crucial property that can be used to indicate whether a material can hold fluids or not. Predicting the permeability of carbonate reservoirs is always a challenging and expensive task while using traditional techniques. Traditional methods often demand a significant amount of time, resources, and manpower, which are sometimes beyond the limitations of under developing countries.
  • 277
  • 10 Oct 2023
Topic Review
Carbonatite-Related REE Deposits
The rare earth elements (REEs) have unique and diverse properties that make them function as an “industrial vitamin” and thus, many countries consider them as strategically important resources. China, responsible for more than 60% of the world’s REE production, is one of the REE‐rich countries in the world. Most REE (especially light rare earth elements (LREE)) deposits are closely related to carbonatite in China. Such a type of deposit may also contain appreciable amounts of industrially critical metals, such as Nb, Th and Sc. According to the genesis, the carbonatite‐related REE deposits can be divided into three types: primary magmatic type, hydrothermal type and carbonatite weathering‐crust type. This paper provides an overview of the carbonatite‐related endogenetic REE deposits, i.e., primary magmatic type and hydrothermal type. The carbonatite‐related endogenetic REE deposits are mainly distributed in continental margin depression or rift belts, e.g., Bayan Obo REE‐Nb‐Fe deposit, and orogenic belts on the margin of craton such as the Miaoya Nb‐REE deposit. The genesis of carbonatite‐related endogenetic REE deposits is still debated. It is generally believed that the carbonatite magma is originated from the low‐degree partial melting of the mantle. During the evolution process, the carbonatite rocks or dykes rich in REE were formed through the immiscibility of carbonate-silicate magma and fractional crystallization of carbonate minerals from carbonatite magma. The ore‐forming elements are mainly sourced from primitive mantle, with possible contribution of crustal materials that carry a large amount of REE. In the magmatic-hydrothermal system, REEs migrate in the form of complexes, and precipitate corresponding to changes of temperature, pressure, pH and composition of the fluids. A simple magmatic evolution process cannot ensure massive enrichment of REE to economic values. Fractional crystallization of carbonate minerals and immiscibility of melts and hydrothermal fluids in the hydrothermal evolution stage play an important role in upgrading the REE mineralization. Future work of experimental petrology will be fundamental to understand the partitioning behaviors of REE in magmatic-hydrothermal system through simulation of the metallogenic geological environment. Applying “comparative metallogeny” methods to investigate both REE fertile and barren carbonatites will enhance the understanding of factors controlling the fertility.
  • 3.3K
  • 17 Nov 2020
Topic Review
Carboniferous Rainforest Collapse
The Carboniferous rainforest collapse (CRC) was a minor extinction event that occurred around 305 million years ago in the Carboniferous period. It altered the vast coal forests that covered the equatorial region of Euramerica (Europe and America). This event may have fragmented the forests into isolated 'islands', which in turn caused dwarfism and, shortly after, extinction of many plant and animal species. Following the event, coal-forming tropical forests continued in large areas of the Earth, but their extent and composition were changed. The event occurred at the end of the Moscovian and continued into the early Kasimovian stages of the Pennsylvanian (Upper Carboniferous).
  • 9.4K
  • 08 Oct 2022
Topic Review
Carcharodontosaurus
Carcharodontosaurus (/ˌkɑːrkəroʊˌdɒntoʊˈsɔːrəs/; lit. sharp-toothed lizard) is a genus of large carcharodontosaurid theropod dinosaur that existed during the Cenomanian age of the Late Cretaceous in Northern Africa. The genus Carcharodontosaurus is named after the shark genus Carcharodon, itself composed of the Greek karchar[os] (κάρχαρος, meaning "jagged" or "sharp") and odōn (ὀδών, "teeth"), and the suffix -saurus ("lizard"). It is currently known to have two species: C. saharicus and C. iguidensis.
  • 3.1K
  • 09 Nov 2022
Topic Review
Carfree City
A car-free city or carfree city is a population center that relies primarily on public transport, walking, or cycling for transport within the urban area. Carfree cities greatly reduce petroleum dependency, air pollution, greenhouse gas emissions, automobile crashes, noise pollution, urban heat island effect and traffic congestion. Some cities have one or more districts where motorized vehicles are prohibited, referred to as car-free zones.
  • 271
  • 28 Nov 2022
Topic Review
Carterton, New Zealand
Carterton (Māori: Taratahi) is a small town in the Wellington Region of New Zealand and the seat of the Carterton District (a territorial authority or local government district). It lies in a farming area of the Wairarapa in New Zealand's North Island. It is located 14 km (8.7 mi) southwest of Masterton and 80 km (50 mi) northeast of Wellington. The town has a population of 5,850 (June 2021), out of a total district population of 10,050. Carterton was founded in 1857. Originally known as Three Mile Bush, it served as housing for workers building the road between Wellington and Masterton. It was later renamed after Charles Carter, who was in charge of the building of the Black Bridge over the Waiohine River south of the town. The town describes itself as New Zealand's daffodil capital, holding a Daffodil Festival each year on the second Sunday in September, with the main event taking place at Middle Run along Gladstone Road.
  • 678
  • 27 Oct 2022
Topic Review
Cartographic Labeling
{{Multiple issues| Cartographic labeling is a form of typography and strongly deals with form, style, weight and size of type on a map. Essentially, labeling denotes the correct way to label features (points, arcs, or polygons).
  • 663
  • 11 Nov 2022
Topic Review
Cartography of Jerusalem
The cartography of Jerusalem is the creation, editing, processing and printing of maps of Jerusalem from ancient times until the rise of modern surveying techniques. Almost all extant maps known to scholars from the pre-modern era were prepared by Christian mapmakers for a Christian European audience. Maps of Jerusalem can be categorized between original factual maps, copied maps and imaginary maps, the latter being based on religious books. The maps were produced in a variety of materials, including parchment, vellum, mosaic, wall paintings and paper. All maps marking milestones in the cartography of Jerusalem are listed here following the cartographic histories of the city, from Titus Tobler and Reinhold Röhricht's studies in the 19th century to those of Hebrew University of Jerusalem academics Rehav Rubin and Milka Levy-Rubin in recent decades. The article lists maps that progressed the cartography of Jerusalem before the rise of modern surveying techniques, showing how mapmaking and surveying improved and helped outsiders to better understand the geography of the city. Imaginary maps of the ancient city and copies of existing maps are excluded. The Madaba Map is the oldest known map of Jerusalem, in the form of a mosaic in a Greek Orthodox Church. At least 12 maps survive from the Catholic mapmakers of the Crusades; they were drawn on vellum and mostly show the city as a circle. The first printed map of the city was drawn by Erhard Reuwich and published in 1486 by Bernhard von Breydenbach in his Peregrinatio in Terram Sanctam, based on his pilgrimage of 1483. Approximately 500 maps are known between the late-1400s and the mid-1800s; the significant increase in number is due to the advent of the printing press. Few of the mapmakers had travelled to Jerusalem – most of the maps were either copies of others' maps or were imaginary (i.e. based on reading of religious texts) in nature. The first map based on actual field measurements was published in 1818 by the Czech mapmaker Franz Wilhelm Sieber. The first map based on modern surveying techniques was published by Charles Wilson of the Palestine Exploration Fund in 1864–65, who produced two maps for the British Ordnance Survey.
  • 584
  • 07 Oct 2022
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