Slab melting as a barrier to deep carbon subduction

Interactions between crustal and mantle reservoirs dominate the surface inventory of volatile elements over geological time, moderating atmospheric composition and maintaining a lifesupporting planet1. While volcanoes expel volatile components into surface reservoirs, subduction of oceanic crust is responsible for replenishment of mantle reservoirs2,3. Many natural, ‘superdeep’ diamonds originating in the deep upper mantle and transition zone host mineral inclusions, indicating an affinity to subducted oceanic crust4–7. Here we show that the majority of slab geotherms will intersect a deep depression along the melting curve of carbonated oceanic crust at depths of approximately 300 to 700 kilometres, creating a barrier to direct carbonate recycling into the deep mantle. Low-degree partial melts are alkaline carbonatites that are highly reactive with reduced ambient mantle, producing diamond. Many inclusions in superdeep diamonds are best explained by carbonate melt–peridotite reaction. A deep carbon barrier may dominate the recycling of carbon in the mantle and contribute to chemical and isotopic heterogeneity of the mantle reservoir

PARKING SPACES NEAR MASS GRAVITY CENTERS IN URBANIZED TERRITORIES: METHODOLOGY FOR ESTIMATING THE REQUIRED PLACES

Introduction. The paper discusses the problems of organizing the vehicles’ parking near large shopping centers and also describes their relevance, taking into account the transport services of retail outlets and residence places. The authors present the research of the problem by leading scientists, which is reflected in the regulatory documentation.Materials and methods. The authors used a mathematical description of the average parking duration and identified the main affecting factors, taking into account the proportion of workers in the mass gravity center. The authors proposed a mathematical dependence based on the average parking duration, taking into account reservation of parking places for workers and the required number of parking spaces for other categories. The paper considered the possibility of the intra-hour deficit of parking places based on the PHF-factor.Results. As a result, the authors made the comparison of the obtained values of the required parking spaces with the standard ones. The paper provided more than 30 types of mass gravity centers and urban areas. In addition, the authors considered the examples of assessing the required number of parking spaces near a large housing estate at the 8 km distance from the city center. Therefore, the authors proposed the technique for assessing the required number of parking spaces based on normative values per 100 m2 of the area of the mass gravity centers.Discussion and conclusions. The authors present recommendations are made for the practical application of the required number of parking spaces by the normative values.Financial transparency: the authors have no financial interest in the presented materials or methods. There is no conflict of interest

INFLUENCE OF EXTERNAL LIGHTING POLLUTION BY THE CHEMICAL DEICING MATERIALS ON TRAFFIC SAFETY OF THE MOTOR VEHICLES

Introduction. Road transport remains the most dangerous form of transportation in our time. On the roads of our country about 25 thousand people are killed per year, are injured and maimed more than 250 000 people per year. In fact, every third traffic accident happens in the night time. Therefore, the question of the motor vehicles traffic’s safety increasing on winter roads continues to be relevant nowadays. The duration of the winter slipperiness’ period in Russia is 5-6 months. One way to prevent the winter slipperiness is the deicing materials’ application. While motor vehicles’ driving on the road, which is covered with anti-icing materials, the pollution of the vehicles’ external lights by anti-icing agents is happen, and this process significantly reduces the illumination of the road and the visibility of the traffic conditions in the darkness time and it also negatively affects the road safety situation. Materials and methods. The analysis of the literary sources, the scientific works and the publications about the problem of the external lighting of the car pollution by the deicing materials, which influences on the driver’s visibility of the traffic conditions in the dark time is made in the article. In addition, the analysis of normative documents, which regulate the requirements to the condition of the operated motor vehicles in terms of the road safety is presented in this research.Results. The modern theory of the vehicle’s operational properties does not contain the results about the illumination influence of the road headlights on the traffic safety in terms of their pollution with chemical deicing materials in dark time. Therefore, the research is aimed to identify the patterns how the lighting devices’ pollution of the vehicle by anti-icing agents influences on road illumination and visibility.Discussion and conclusion. The question about the motor vehicles’ safety and about their operating conditions on the winter roads, which cover with the chemical anti-icing agents is urgent nowadays, because of the information lack about the regularities of the reagents’ influence on the traffic safety in dark time. For this reason, the systematic scientific research should be conducted to obtain new information of such influence

Distinct Groups of Low- and High-Fe Ferropericlase Inclusions in Super-Deep Diamonds: An Example from the Juina Area, Brazil

Diamonds from the Rio Sorriso placer in the Juina area, Mato Grosso State, Brazil, contain mineral inclusions of ferropericlase associated with MgSiO3, CaSiO3, magnesite, merrillite, and other minerals. The ferropericlase inclusions in Rio Sorriso diamonds are resolved into two distinct genetic and compositional groups: (1) protogenetic, high-Ni and low-Fe (Ni = 8270–10,660 ppm; mg# = 0.756–0.842) ferropericlases, and (2) syngenetic, low-Ni and high-Fe (Ni = 600–3050 ppm; mg# = 0.477–0.718) ferropericlases. Based on the crystallographic orientation relationships between natural ferropericlase inclusions and host diamonds, high-Ni and low-Fe ferropericlases originate in the upper part of the lower mantle, while low-Ni and high-Fe ferropericlases, most likely, originate in the lithosphere. Mineral inclusions form the ultramafic lower-mantle (MgSiO3, which we suggest as bridgmanite, CaSiO3, which we suggest as CaSi-perovskite, and high-Ni and low-Fe ferropericlase) and lithospheric (CaSiO3, which we suggest as breyite, Ca(Si,Ti)O3, and low-Ni and high-Fe ferropericlase) associations. The presence of magnesite and merrillite inclusions in association with ferropericlase confirmed the existence of a deep-seated carbonatitic association. Diamonds hosting high-Ni and low-Ni ferropericlase have different carbon-isotopic compositions (δ13C = −5.52 ± 0.75‰ versus −7.07 ± 1.23‰ VPDB, respectively). It implies the carbon-isotopic stratification of the mantle: in the lower mantle, the carbon-isotopic composition tends to become isotopically heavier (less depleted in 13C) than in lithospheric diamonds. These regularities may characterize deep-seated diamonds and ferropericlases not only in the Juina area of Brazil but also in other parts of the world

Growth medium and carbon source of unusual rounded diamonds from alluvial placers of the North-East of Siberian Platform

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Parental growth media of Siberian diamonds - relation to kimberlites

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