Intermediate Chamber Research Articles

Mathematical modeling of drives with tandem pneumatic cylinders

The article considers the issue of mathematical modeling of tandem pneumatic cylinders. Despite the fact that the mathematical description of the operation of drives with single-piston cylinders is considered in sufficient detail in the literature, the peculiarity of drives with tandem cylinders, namely the commutation of their working cavities with pneumatic discharge and exhaust lines through one pneumatic distributor, requires the formation of a certain approach to their mathematical description. The paper shows two developed versions of mathematical models that describe their work. The first option involves taking into account some conventional intermediate chambers behind the pneumatic distributor, where the division and combination of compressed air flows between the pneumatic distributor and the working cavities of the tandem pneumatic cylinder takes place. The second one (the simplified) considers the working cavities of the cylinder independently. Comparison of the results of mathematical modeling for two options showed a fairly significant difference in the time of movement of the piston of the cylinder. Moreover, it can be seen from the results that this difference is primarily associated with the distribution of air pressure between the intermediate chambers and the working cavities of the cylinder. According to the obtained results, it follows that when developing pneumatic drives and pneumatic actuators with tandem pneumatic cylinders, despite the complexity of the calculation, it is preferable to take into account in the mathematical model the intermediate chambers, where the division and combination of compressed air flows takes place. The developed model can be used in the design of pneumatic drives of various machines and mechanisms that use tandem pneumatic cylinders. This modeling approach can be used in the study of other multi-piston pneumatic engines or drives with several engines controlled by a single pneumatic switchgear.

Ankaramites of Gorny Altai: Mineralogical, Petrographic, and Petrochemical Features of Diopside Porphyry Basalts of the Ust’-Sema Formation

Abstract —The mineral composition, petrography, and petrochemistry of middle Cambrian diopside porphyry basalts of the Ust’-Sema Formation in Gorny Altai are considered in comparison with ankaramites of different geodynamic settings. The basalts of the Ust’-Sema Formation are enriched in phenocrysts of high-Mg clinopyroxene (Mg# ≤ 94) (20 to 40–50 vol.%) with a high content of Cr2O3 (up to 1.11 wt.%), enclosed in the clinopyroxene–plagioclase microlitic groundmass. In addition, there are minor phenocrysts of saussuritized plagioclase (An49–71), olivine replaced by secondary minerals, amphibole with Mg# = 55.7–68.2, and Cr-spinel with Cr# = 36.2–41.7. Inclusions of Cr-spinel in high-Mg clinopyroxene are richer in Cr (Cr# ≤ 72.8). The basalts of the Ust’-Sema Formation are chemically heterogeneous and are subdivided into two main groups: high-Ca (MgO = 7.98–14.77 wt.% and CaO/Al2O3 = 1.0–1.8) and low-Ca (MgO = = 2.84–9.89 wt.% and CaO/Al2O3 = 0.2–0.9). The obtained data on the high-Ca basalts of the Ust’-Sema Formation show that the rocks are similar to the reviewed ankaramites and thus can be assigned to this type of rocks. The low-Ca basalts of the Ust’-Sema Formation might have resulted from the fractionation of ankaramitic melt in intermediate magma chambers. The Gorny Altai ankaramites formed through the melting of the wehrlitized suprasubductional lithospheric mantle during the closure of the Paleoasian Ocean.

РУДНЫЕ, НЕФТЕГАЗОВЫЕ РАЙОНЫ ЮЖНО-ОХОТСКОЙ ПРОВИНЦИИ И ГЛУБИННАЯ ГЕОДИНАМИКА

In the South Okhotsk Sea province – on the islands of Sakhalin, Kunashir, Iturup, Urup and surrounding sea areas – many occurrences of rare, noble metal and other mineralizations as well as of oil-and-gas fields, gas hydrate accumulations, and isolated areas of active emission of water-hydrocarbon gases are known. Occurrences and deposits of solid, liquid and gaseous mineral resources are controlled by hidden deep fault transform zones: Nosappu (Tuscarora), Iturup, and Urup. These long-lived extended (more than 1000 km) zones are distinguished at the N-W Pacific megaplate margin near the S-E flank of the Kuril-Kamchatka trogue. Using the seismotomographic methods we have established their extension to the west from the seismic focal zone in the oceanic slab that subducted into the transition zone of the mantle. In the areas of strike-slip extension the faults accounted for the active formation of the drainage channels for the penetration of the sea water in the lithosphere with the following serpentinization of its ultramafites, and for decompressional generation of ascending mantle-derived abiogenic fluid flows. The latter penetrated from the underslab asthenosphere in the oversubduction mantle wedge and beneath the lithospheric mantle, where they accounted for the development of the processes of metasomatism. The subsequent migration of flows initiated the creation of primary magma reservoirs in the lower parts of the continental lithosphere, and intermediate and peripheral chambers in the Earth’s crust. The injection of melts from the chambers in the consolidated Earth's crust led to the formation of abyssal, hypabyssal intrusive massifs, arch-dome uplifts and magmatogenic-ore (ore-magmatic) systems predominantly among the rocks of the pre-Pliocene basement. The concentration of oil and gas accumulations mainly from the mantle-derived abiogenic hydrocarbons containing mercury, gold, rhenium, and PGE in the Cenozoic sedimentary basins amidst the reservoirs under the impermeable beds also resulted from deep under- and overslab fluid flows.

Siphon-Induced Droplet Break-Off for Enhanced Mixing on a Centrifugal Platform

We present a powerful and compact batch-mode mixing and dilution technique for centrifugal microfluidic platforms. Siphon structures are designed to discretize continuous flows into a sequence of droplets of volumes as low as 100 nL. Using a passive, self-regulating 4-step mechanism, discrete volumes of two fluids are alternatingly issued into a common intermediate chamber. At its base, a capillary valve acts as a fluidic shift register; a single droplet is held in place while two or more droplets merge and pass through the capillary stop. These merged droplets are advectively mixed as they pass through the capillary valve and into the receiving chamber. Mixing is demonstrated for various combinations of liquids such as aqueous solutions as well as saline solutions and human plasma. The mixing quality is assessed on a quantitative scale by using a colorimetric method based on the mixing of potassium thiocyanate and iron(III) chloride, and in the case of human plasma using a spectroscopic method. For instance, volumes of 5 µL have been mixed in less than 20 s. Single-step dilutions up to 1:5 of plasma in a standard phosphate buffer solution are also demonstrated. This work describes the preliminary development of the mixing method which has since been integrated into a commercially available microfluidic cartridge.

Gabbroides of Peterman island (West Antarctica). First information on geochemistry

Peterman Island is located in the archipelago of the Wilhelm Islands on the west coast of the Antarctic Peninsula (Graham Land). It is composed of gabbroids and granitoids of the Andean complex, which formed almost 100 million years later than the volcanic group of the Antarctic Peninsula. To clarify their genesis and geodynamic conditions of formation, gabbroids of the Andean complex are of particular interest, since the petrological models of their formation are well developed. Gabbroid intrusions comprise small bodies that are widespread along the Antarctic Peninsula. Among them stand out olivine gabbros, normal gabbros, norites and hornblende gabbros. Also are found small bodies of melanogabbro-pegmatites and intramagmatic dykes, that are associated with the manifestations of ore mineralization of magnetite, ilmenite and sulfides. For this reason, they are of interest for both the minerals search and for solving the question of their genesis. To this end, we performed geochemical studies of Peterman Island gabbroids. Gabbroids of Peterman Island are represented by amphibolized medium-grained gabbro with hypidiomorphic texture. Among them, xenoliths of thinly stratified gabbroids 3 × 8 m in size were found, which are characteristic of stratified intrusions, for example, Stillwater, Bushveld, etc. Gabbroids of Peterman Island have low content of silica and potassium and according to the petrochemical characteristics correspond to peridotite gabbro. They have low contents of Cr, Ni, V and high strength lithophilic Y and Nb elements. Gabbroids have been crystallized from basic magma, differentiated in the intermediate crustal magma chambers. Positive anomalies of Sr, Eu, and Ti in the multielement diagrams and positive anomalies of europium Eu/Eu* suggest the accumulation of plagioclase and apparently, ilmenite in the magmatic chamber. The primary magma source for gabbroids was probably the primitive mantle (PM). Gabbroids are contaminated with crustal matter. This contamination is probably due to their regressive metamorphism, caused by the introduction of later intrusions of Andean complex granitoid. Finely layered xenolithic gabbroids do not differ from other homogeneous gabbros of Peterman Island in terms of chemical composition.This xenolith most likely represents a part (fragment) of the wall of the magma chamber in which the differentiation of the initial main magma took place. According to the obtained geochemical data, a wide range of compositions of the Andean complex gabbroids formed as a result of crystallization differentiation of magma melted from rocks of the composition of the primitive mantle (PM) in crustal magma chambers, which also resulted in the accumulation of ore elements — V, Co, and Cu in the residual magmatic melts.

Relationship of the Vp/Vs Parameter with the State of the Magmatic Substance and Activity of the Northern Group of Volcanoes in Kamchatka

The dynamics of the volcanic activity, magmatic feeding system, accumulation, movement, and composition of magmas, and structure of the roots of the Northern group of volcanoes (NGV) in Kamchatka are considered. The results of monitoring the field of the ratio of seismic P- and S-wave velocities, the VP/VS parameter in the region of the Klyuchevskaya volcanic group based on the data of the volcanic earthquakes registered by a network of telemetric seismic stations are presented. The parameter changes in space and time during the periods of volcanic activity development. Each segment of the volcanic structure and period of activity is characterized by the own behavior of the field of VP/VS values. In the intermediate magmatic chamber, low VP/VS values are observed beneath the Klyuchevskoi volcano at a depth of 8 to 10 km and beneath Plosky Tolbachik at a depth of 3 to 5 km, which is related to the state of the substance and temperature in these areas, and the entry of a new melt portion of magma and the fluid-gas component from the crust and the mantle. The relation of volcanic earthquakes and earthquakes in the focal zone of Kamchatka, i.e., the ratio of the subduction zone (the sinking Pacific Ocean Plate) and the feeding source of volcanoes, is considered. It is shown that the Klyuchevskoi peripheral chamber is not the only area feeding the NGV. According to the values of the VP/VS parameter, the volcanoes have different magma compositions, which is determined by the physicochemical and temperature features of the medium. In our opinion, the feeding area of volcanoes from the Northern group is a neutral layer that we have identified.

Middle Paleozoic Basites of the Nakyn Kimberlite Field

Within the Nakyn kimberlite field, kimberlites with a unique diamond tenor are spatially associated with different-aged basites of various composition and explosive breccias. The paper presents a detailed analysis of the specific material composition of the basites, the sequence of their formation, the relationship with kimberlites, and the age of formation of magmatites in the region. Intrusions of the Vilyui paleorift were formed first 368.5 - 374.4 myr ago (Tomshin et al. 2018). The most common are basites formed during prevailing extension of magma-controlling faults within the rift structures. These are typical basites of the Middle Paleozoic paleorifts of the eastern part of the Siberian platform. They are composed mainly of prismatic-ophitic gabbro-dolerites. According to the total content of potassium and sodium, compositions of dolerites vary within the limits of the tholeiitic and subalkaline series. Paleomagnetic data indicate that the extension mode of rift valleys was repeatedly replaced by compression conditions. This resulted in the closure of magma permeable zones and formation of local conditions for the origin of deep-seated intermediate chambers. Fractionation of a tholeiitic melt at depths of 35–40 km promoted protocrystallization of basic plagioclase and the formation of horizons and lenses of anorthositic gabbro-dolerites. Bytownite, chrysolite, moissanite, garnet, and chrome spinel are identified as the early magmatic minerals. Next manifestation of the deep evolution of the basite melt is represented by a complexly differentiated two-phase dike, which includes monzonite-porphyry. Such bodies are formed when the processes of crystallization differentiation of the tholeiite melt in a shallow-depth (no more than 20 km) intermediate chamber are combined with those in intra-chamber conditions. The dike is located in a kimberlite pipe and divides it into two bodies. At the turn of Devonian and Carboniferous (363-364 Ma), kimberlite bodies were formed in the Nakyn kimberlite field. The kimberlite-controlling faults (338.2-345.6 Ma) were pathways for ascending magma that produced post-kimberlite basites near the kimberlite pipes. High contents of potassium and titanium and low SiO2 values are distinctive features of post-kimberlite basites. Formation of the bodies of this group of basites was followed by eruptive activity with the formation of explosive breccias. This is a characteristic feature of the intrusions of post-kimberlite alkaline magmatites. Most of the intrusions are composed of fine-grained almond-shaped rocks with slightly crystallized glassy mesostasis. Magmatic activity completed within the Nakyn kimberlite field 331-324,9 myr ago with the formation of explosive breccias after bodies of alkaline basites and their host sedimentary rocks. The disintegration of rocks was followed by the manifestation of active Mg-K-metasomatism. Alkaline-type basites together with accompanying explosive breccias are good indicators of fluid-permeable zones, thus locating the kimberlite-controlling structure. Their temporal and spatial proximity to kimberlites makes it possible to use intrusions of alkaline basites as an indicator of primary diamond deposits.

Screening barrier plants to reduce crop attack by sweet potato weevil (Cylas formicarius).

Sweet potato weevil, Cylas formicarius (Fabricius) attacks stems and storage roots of sweet potato, Ipomoea batatas, and is a major pest of this globally significant crop. To minimize the immigration of weevils into sweet potato fields from nearby donor habitat, we assessed scope for a barrier plant approach. Here, we report a novel, two-stage, multiple choice olfactometer method to screen candidate barrier plant species and a field study of the effects of shortlisted barrier plants of weevil movement and plant damage. Initial work established that a combination of sweet potato foliage and storage root was significantly more attractive to adult C. formicarius than either tissue alone in the distal chamber of choice arms. Among 15 candidate barrier plant species in intermediate chambers in arms, spring onion, oregano, chilli, basil, sweetcorn, fennel, lime mint and lemongrass significantly reduced passage of C. formicarius. Of these, sweetcorn and lime mint significantly reduced the numbers of oviposition holes in sweet potato storage roots. A field study showed that basil and chives were effective barrier plants for reducing weevil damage to sweet potato storage roots. Our method has utility for screening additional candidate plants, and suggests that weevil dispersal and subsequent oviposition are affected by passage through some plants, suggesting scope for barrier plants to contribute to the management of this major pest. © 2019 Society of Chemical Industry.

Pressure Observer Based Adaptive Dynamic Surface Control of Pneumatic Actuator with Long Transmission Lines

In this paper, the needle insertion motion control of a magnetic resonance imaging (MRI) compatible robot, which is actuated by a pneumatic cylinder with long transmission lines, is considered and a pressure observer based adaptive dynamic surface controller is proposed. The long transmission line is assumed to be an intermediate chamber connected between the control valve and the actuator in series, and a nonlinear first order system model is constructed to characterize the pressure losses and time delay brought by it. Due to the fact that MRI-compatible pressure sensors are not commercially available, a globally stable pressure observer is employed to estimate the chamber pressure. Based on the model of the long transmission line and the pressure observer, an adaptive dynamic surface controller is further designed by using the dynamic surface control technique. Compared to the traditional backstepping design method, the proposed controller can avoid the problem of “explosion of complexity” since the repeated differentiation of virtual controls is no longer required. The stability of the closed-loop system is analytically proven by employing the Lyapunov theory. Extensive experimental results are presented to demonstrate the effectiveness and the performance robustness of the proposed controller.

Research on the Vapor Injection of Two-stage Rotary Compressor

In order to understand the vapor injection flow characteristics of two-stage rotary compressor in the course of compression, a mathematical model based on mass conservation equation, energy equation and thermodynamic identity was established and proved by P-V diagram testing results. Some useful conclusions about pressure in the intermediate chamber and mass flow of vapor injection in the course of compression were also given out. The results show that, gas backflow between the intermediate chamber and the vapor injection channel is an important defection of two-stage rotary compressor which can be solved by the application of injection valve in vapor injection channel. The injection valve can obviously reduce the gas backflow and the power loss in the course of compression while increasing the pressure fluctuation in the intermediate chamber. Experiments show that the COP of two-stage rotary compressor with the injection valve increased by over 2% in ASHRAE/T working condition.

Two-side cathode microbial electrolysis cell for nutrients recovery and biogas upgrading

Here a three-chamber microbial electrolysis cell (MEC) has been developed to couple the CO2 removal from a gas mixture to the ammonium nitrogen recovery. The here proposed MEC adopted an innovative two-side cathode configuration, where two identic cathodic chambers are connected in parallel by a titanium wire and separated from an intermediate anodic compartment by an anion and a cation exchange membrane (AEM and CEM). The two-side configuration has been proposed as a post treatment unit capable to perform the biogas upgrading through the CO2 reduction and removal into the cathodic chambers as well as the ammonium recovery from a liquid waste stream due to its migration for the electroneutrality maintenance of the cell. The experiments have been conducted at two different anodic potential (i.e. +0.2 and −0.1 V vs Standard Hydrogen Electrode SHE), using a synthetic feeding solution and a gas mixture simulating a domestic wastewater and a biogas, respectively. The results obtained using the new configuration have been also compared to the performances reported in a previous work where a three – chamber MEC, characterized by the presence of an intermediate accumulation chamber, was aimed to the CO2 removal and to nitrogen recovery; this comparison highlighted higher performances of the two-side configuration in terms of methane production, CO2 removal and energy consumption, keeping the same anodic performances.

Quality and treatment of waste water from concrete plants: a case study

The objective of this study was to evaluate the quality of waste water from a concrete plant that was treated with chemical coagulants combined with Moringa oleifera. In the treatment system employed at the plant, waste-water samples were collected at three different points at the beginning and end of each production week throughout the 1 month production life cycle. The monitored parameters included turbidity, pH, alkalinity and hardness. Samples were collected from an intermediate chamber of the treatment system and treated with coagulants in the laboratory. The results indicated that the quality of the waste water exceeded the established limits for the supply of non-potable water, especially for turbidity. The introduction of the coagulation process significantly improved the quality of the waste water or recycled water (significance of 5%) and 99·94% of the turbidity was removed, which enabled the reuse of water for washing vehicles, producing concrete and flushing toilets.

2.6 Ga high-Si rhyolites and granites in the Kursk Domain, Eastern Sarmatia: Petrology and application for the Archaean palaeocontinental correlations

A 2.61 Ga intraplate magmatism took place locally within the Kursk Domain of the Eastern Sarmatia forming a volcanic-plutonic association of rhyolites and granites. The zircon Lu-Hf and Sm-Nd whole rocks isotope data indicate the crustal source heterogeneity of these Neoarchaean intraplate granitoids. Their protoliths were dominated by Palaeoarchaean metapelites and Mesoarchaean TTG associations.The Neoarchaean rhyolites of the Kursk Domain are characterized by the high crystallization temperatures of c. 900 °C according to the data of mineral geothermobarometry and geochemistry of zircons (TiQ and TiZr). The magmatic chambers were located at a depth of no more than 7 km. The silicic melt, parental for these 2.61 Ga old rhyolites and granites could be formed as a result of 20% dehydration melting of the metapelite-TTG mixture in equilibrium with the Ilm-Bt-Opx-Pl restite at a pressure of no more than 4 kbar. The Atamansky Complex granites crystallized at deeper levels and contain an admixture of Opx-Pl restite or cumulus component. This caused their geochemical differences from rhyolites when these phases were removed during the melts migration to higher levels of the crust. The Atamansky granites are considered as intermediate chambers where differentiation of the initial silicic magmas took place with the formation of the residual rhyolitic melts.The heat source could be a mafic plume magmatism, known in the Eastern Sarmatia. There, in intraplate settings, hot deep plume generated mafic magmas intruded into the crust forming shallow interim chambers; the latter initiated melting of the felsic host-rocks (predominantly metapelites and TTG) in the upper parts of the crust producing the silicic volcanic-plutonic association.The simultaneous 2.61 Ga old granitoid intraplate magmatism in the Eastern Sarmatia and Dharwar Craton, caused by the mafic heat source, adds one more argument in favor of an assumption that the Sarmatia, Pilbara, Kaapvaal and, possibly, Dharwar Cratons composed a single supercontinent Vaalbara in the Neoarchaean. The Dharwar Craton, perhaps, was at the periphery of the Vaalbara supercontinent next to the Eastern Sarmatia.

Acoustic performance in a lightweight ventilated façade for building refurbishment: analysing the impact of variations in airborne sound insulation according to the ventilation characteristics

The use of double-sheet enclosures with an intermediate air chamber in facades guarantees a higher quality of acoustic insulation against external airborne noise. The effective advantages of the intermediate air chamber depend mainly on its airtightness and the absorbent material contained inside. A ventilated facade with lightweight cladding (LVF) is a specific construction system for double-sheet envelope facades, characterised by an intermediate air chamber that enables a certain amount of internal air circulation, with resulting cooling effects to alleviate excess solar radiation whilst reducing the risk of dampness caused by rainwater. However, owing to this ventilation of the intermediate air chamber, the acoustic insulation of the entire facade could prove less effective than cases in which the intermediate air chamber is completely sealed. Through various methods of measurement and analysis, several authors consider that the opening of the intermediate air chamber for hygrothermal control purposes does not necessarily represent a significant reduction in the level of sound insulation in general. What does appear to have a significant influence on the acoustic behaviour is the surface and location of the intermediate air chamber openings to enable ventilation. The results of this research are presented as further evidence that the positive contribution of LVF should be acknowledged at a regulatory level regarding sound insulating, double-sheet envelope architectural facades.

Physicochemical Parameters of Magmatism of the Uksichan and Ichinsky Volcanoes (Sredinnyi Ridge, Kamchatka): Data on Melt Inclusions

Abstract —Thermobarogeochemical study of melt inclusions and investigation of clinopyroxenes and amphiboles from effusive rocks of the Uksichan and Ichinsky Volcanoes gave an insight into the parameters of deep-seated melts and the evolution of magmatic systems during the formation of minerals in intermediate chambers. Study of melt inclusions from the Uksichan volcanic rocks made it possible to estimate the pressure during the liquidus crystallization of clinopyroxenes and plagioclases from basaltic magmas and to establish four depth intervals of the formation of these minerals: ~60, 45–30, 27–18, and from 12 km to the subsurface. Comparison of the results of calculation based on melt inclusion data and of the clinopyroxene and amphibole data helped to establish the evolution paths of the P–T parameters of ascending melts of the Uksichan Volcano. The most high-temperature magmas, generated at a depth of ~60 km, are characterized by a successive temperature decrease during their ascent (1320–1240–1200 °С). Based on the representative data on the compositions of amphiboles from the Uksichan and Ichinsky Volcanoes, we have elucidated the general regularities of the evolution of intermediate and acid magmatic systems, with three depths of crystallization in intermediate chambers. Amphiboles of the Ichinsky Volcano andesites and the Uksichan Volcano latites crystallized at depths of 22.0–18.5 and 18–16 km and at temperatures of 980–930 and 1010–985 °С, respectively. As melt ascended to a depth of 15.5–11.0 km and a temperature decreased from 945 to 880 °С, amphiboles of andesites and dacites of both volcanoes were produced. At the final stage (a temperature decrease to 900–810 °С and ascent of melts to a depth of 3 km), only amphiboles of dacites of both volcanoes crystallized.

Вулканический массив Зиминых сопок: геология и минералогия пород (Ключевская группа вулканов, Камчатка)

The Ziminy Sopki Volcanic Massif is remarkable for its co-formation from magmas of different potassium alkalinity manifested by three rocks associations (series) with individual evolutional trends: I — andesite-basalts — andesites — dacites; II — andesite-basalts — the intermediate composition andesites; III — high potassium andesite-basalts. Variations of rocks from the revealed series manifest themselves in the above mentioned mineral associations, and the discreteness of rocks regression lines evidence on quite autonomous parental magmas. Orthogonal trends of minerals composition alterations in andesite-basalts with the vector correlating with the potassium alkalinity increase in rocks of associations evidence on existence of the process leading to the enrichment of these magmas with potassium. Thus, we can conclude that, within the single penetrated magmatic system, there are deep intermediate chambers with different conditions for formation of the initial andesite-basalt magmas, which during volcanic activity directly associated with the deeper parental basaltic magma.

CO2-rich fluid inclusions in mantle xenoliths from Barombi-Mbo and Nyos maars (Cameroon volcanic line, central Africa): Upper mantle equilibria and history of magma ascension

A detailed study of fluid inclusions hosted within minerals of mantle xenoliths from the Barombi-Mbo (BM) and Nyos maars provides information on the trapping conditions of fluids and subsequent upper mantle equilibria and the history of the host en route to the surface. These porphyroclastic to protogranular spinel lherzolites and their fluid inclusions were investigated using petrography, microprobe, microthermometry and Raman Microspectroscopy. They are mostly composed of olivine (Fo93-88), orthopyroxene (En91-88Fs11-8Wo2.2-0.8), Cr-diopside, aluminous spinel (Cr#: 0.32–0.08) and occasional accessory pargasite and labradorite. Thermobarometric calculations based on the mineral chemistry of the BM xenoliths indicate temperatures of 1205 to 800 °C at pressures of 23 to 14 kbar while the results on Nyos xenoliths give temperatures of 1134 to 1044 °C at pressures of 12 to 9 kbar consistent with mantle depths of 75–42 km to BM and 36-27 km to Nyos. Olivine and pyroxene crystals contain abundant CO2-rich inclusions (48-1 μm). In Nyos, Raman spectra allow the detection of CO2 and unknown species containing NH2 while CO2 and traces of nahcolite (NaHCO3) were detected in fluid inclusions in the Barombi-Mbo mantle xenoliths. The melting point (Tm) of CO2 varies from −56.6 to −58.0 °C and from −56.8 to −63.0 °C respectively in BM and Nyos xenoliths. 95% of inclusions homogenized in the liquid phase (ThL; L + V →L) and 5% in the vapor phase (ThV; L + V →V) at temperatures ranging from +31.1 to −48.1 °C in BM xenoliths, and from +31.1 to −38.1 °C in Nyos xenoliths. Densities of CO2 inclusions in minerals range from 1.1 to 0.35 g/cm3 at Nyos, and from 1.15 to 0.2 g/cm3 at BM. The high fluid pressures deduced and the corresponding depths are 11 to 8 kbar (33-24 km) at Nyos and 12 to 10 kbar (36-30 km) at BM. Taking into account the post-trapping stretch, the corrected inclusions densities and corresponding pressures and depths set the minimum xenoliths entrainment depths to 50 km beneath BM and 36 km under Nyos maars. Fluid inclusion pressures also reveal that the Moho and Conrad discontinuities lie at depths of 24 and 15 km and of 30 and 13.5 km, respectively at Nyos and BM. The estimated Moho depths are consistent with the geophysical observations along the CVL. Low densities and relative depths probably indicate short magma stops in intermediate magmatic chambers. Before eruption, the last short magma storage and fluid mixing occurred at a depth of less than 1.8 km at BM and 3 km at Nyos.

Finds of “Ancient” Zircons in Magmatic Rocks of the Shatak Complex (Southern Urals) and Their Petrogenic Implications

New data on the presence of “old” zircons in magmatic rocks of the Shatak Complex have been obtained. This suggests that the evolution of melts in intermediate magma chambers was controlled by the AFC process, in which the liquidus phases (olivine ± clinopyroxene) fractionated, the fluid phases accumulated in the apical part of the chamber, and the host rocks were partly assimilated. Hence, the “old” zircons were entrained from the Archaean–Paleoproterozoic granite–gneiss substrate and trapped by the melt during crustal contamination.

Evolution of Ore-Forming Metasomatic Processes at Large Skarn Iron Deposits Related to the Traps of the Siberian Platform

The paper presents systematized and synthesized data on the parameters and evolutionary sequence of metasomatic processes that accompanied interaction between Permian–Triassic trap complex and rocks of the sedimentary cover of the Siberian Platform at the large skarn iron deposits. Relations of the textural–compositional, morphological, and genetic diversity of the skarns and ores with the phases and stages of the origin of ore-bearing volcano-tectonic edifices are demonstrated with reference to the Korshunovskoe and Rudnogorskoe deposits. The genetic reconstructions are based on survey materials and data on the mineralogy of the rocks and ores (obtained by optical and scanning electron microscopy, microprobe analysis, EPR, Raman and IR spectroscopy, and by studying inclusions in minerals). A principally important feature of the volcano-tectonic edifices of the large mineral deposits is their multistage evolution and combinations of fluid-conducting zones, which are related to (1) volcanic apparatuses, (2) shallow-depth magmatic chambers (laccoliths) hosted in carbonate–salt rocks, and (3) multistage fracture structures produced by the collapse of the leached space. The major ore-bearing structures were formed simultaneously with the development of an intermediate magmatic chamber hosted in Cambrian carbonate–salt rocks beneath a seal of terrigenous sedimentary rocks. Magmatic-stage magnesian skarns with disseminated ores in them and in the calciphyres were produced during the prograde stage in the apical parts of the laccoliths, at contacts between the dolerites and dolomites. During the early prograde stage, skarn–ore bodies developed around injection bodies of globulated dolerites, laccoliths, and sills; stockworks and steep bodies of fragmentary magnesian and calcic skarns and ores were formed within the diatremes; and conformable bodies and veins were produced in the splay fracture zones. The later reactivation of faults and fractures and the involvement of connate brines and solutions from the evaporite complex triggered the redeposition of the ore masses, crystallization of the mineral assemblages of hydrated skarns, development of large domains of serpentine–chlorite–epidote–amphibole rocks, calcic skarns, and ores. Data on multiphase fluid inclusions in the forsterite, apatite, and halite indicate that the mineral-forming fluid initially was a highly concentrated solution–melt (total salinity of 60%) with high-density reduced gases. The magnesian skarns were formed during the following stages: (1) forsterite + fassaite + spinel + first-population magnetite (820–740°C); (2) phlogopite + titanite + pargasite + second-population magnetite (600–500°C), and (3) clinochlore + serpentine + tremolite + pyrrhotite + chalcopyrite (≥450°C).

BONINITES AS A CRITERION FOR THE GEODYNAMIC DEVELOPMENT OF MAGMATIC SYSTEMS IN PALEOSUBDUCTION ZONES IN GORNY ALTAI

Ancient primary boninitic melts of the Gorny Altai (65–105 km, 1410–1590 °C) were studied from the composition of melt inclusions in clinopyroxenes. We estimated their parameters and the conditions for the onset of magma crystallization in an intermediate chamber at a depth of about 30–35 km, which appear similar to the reference boninitic magmatism of the modern Izu-Bonin island arc. A combined analysis of the composition of inclusions and clinopyroxenes from Gorny Altai boninites shows that within a range of minimum temperature values (1140–1120 °C), the crystallizing material continuously ascends from a depth of 12 to 0.6 km. The pattern is different in case of higher-temperature magmas, and three zones of pyroxene crystallization are distinguished: 18.0–13.8 km (1245–1205 °С), 12.0–3.5 km (1240–1185 °С), and 3.3–0.6 km (1185–1145 °С). Actually, these zones correspond to the intermediate deep-seated magmatic chambers typical of modern island-arc subduction zones [ Dobretsov et al., 2016 ]. Based on the detailed study of zonal phenocrysts of clinopyroxene in boninites from the Kuray ophiolites, we established the parameters of the evolution of the ascending boninite melts. Three temperature intervals (1220–1200 °С, 1235–1210 °С, and 1120–1220 °С) and three pressure ranges (1.5–11.5 kbar, 2.0–6.0 kbar, and 2.0–0.3 kbar) are distinguished. One case shows a significant pressure drop (from 11.5 to 1.5 kbar) with a small drop in temperature (from 1220 °C to 1200 °C). In the second case, the pressure rises from 2.0 to 6.0 kbar, and the crystallization temperature decreases from 1235 to 1210°C. In the third case, crystallization begins at a stable temperature (1120–1140 °C) and a stable pressure (1.4–2.0 kbar); then, in the near-surface conditions, the temperature increases to 1220 °C, and the pressure decreases sharply to 0.3 kbar.