Compositional Zoning Research Articles

Estimating the Effective Lifetime of the z ∼ 6 Quasar Population from the Composite Proximity Zone Profile

Abstract The lifetime of quasars can be estimated by means of their proximity zone sizes, which are regions of enhanced flux blueward of the Lyα emission line observed in the rest-frame UV spectra of high-redshift quasars because the intergalactic gas has a finite response time to the quasars’ radiation. We estimate the effective lifetime of the high-redshift quasar population from the composite transmitted flux profile within the proximity zone region of a sample of 15 quasars at 5.8 ≤ z ≤ 6.6 with precise systemic redshifts, and similar luminosities, i.e., −27.6 ≤ M 1450 ≤ −26.4, and thus a similar instantaneous ionizing power. We develop a Bayesian method to infer the effective lifetime from the composite spectrum, including robust estimates of various sources of uncertainty on the spectrum. We estimate an effective lifetime of the quasar population as a whole of log 10 ( t Q / yr ) = 5.7 − 0.3 ( − 0.5 ) + 0.5 ( + 0.8 ) given by the median and 68th (95th) percentile of the posterior probability distribution. While our result is consistent with previous quasar lifetime studies, it poses significant challenges on the current model for the growth of supermassive black holes located in the center of the quasars’ host galaxies, which requires that quasar lifetimes are more than an order of magnitude longer.

Petrogenesis of coeval lamproites and kimberlites from the Wajrakarur field, Southern India: New insights from olivine compositions

Olivine is one of the most abundant phases in kimberlites and cratonic lamproites, where it occurs as mantle-derived xenocrysts and magmatic phenocrysts or rims overgrowing xenocrystic cores, indicating its prevalence throughout most of the crystallisation sequence of these magmas. Thus, olivine can provide valuable insights into kimberlite and lamproite petrogenesis. Here, we present a detailed study of olivine compositional zoning in two lamproites (P2 and P12) of the Mesoproterozoic Wajrakarur kimberlite-lamproite field in southern India and use these data to propose a genetic link between lamproites and kimberlites in the region.Olivine macrocrysts (i.e., anhedral grains >1 mm) from the P2 and P12 intrusions are strongly zoned. Comparisons with olivine from mantle xenoliths worldwide demonstrate that the cores of olivine macrocrysts are xenocrysts derived from disaggregated mantle wall-rocks. The internal zones and overgrowth rims of olivine macrocrysts and the cores of olivine phenocrysts from P2 and P12 contain magmatic Mg-chromite and Ti-magnetite inclusions and hence crystallized from the host lamproite melt. These magmatic olivine zones show increasing Mg# (molar Mg/(Mg + Fe2+)), CaO and MnO contents with decreasing NiO. This reverse differentiation trend appears to be a characteristic feature of olivine in lamproites from the Wajrakarur field.To evaluate potential petrogenetic links between coeval lamproites and kimberlites from Wajrakarur, the composition of olivine xenocrysts (i.e., macrocryst cores) was compared with that of early crystallized olivine in P2, P12 and previously studied kimberlites and lamproites. The average Mg# of olivine macrocryst cores is directly correlated with the average Mg# of magmatic olivine in lamproites and kimberlites from Wajrakarur. Coupled with their indistinguishable Sr-Nd-Hf isotope compositions, these data suggest derivation of the Wajrakarur lamproites and kimberlites from a common source, The more Fe-rich composition of liquidus olivine in the Wajrakarur lamproites compared to coeval kimberlites suggests a higher degree of assimilation of metasomatised Fe-richer lithospheric mantle by the lamproites and provides a plausible explanation for the different petrological features of the Wajrakarur lamproites and kimberlites Our results suggest that cratonic lamproites can have a remarkably similar petrogenetic history to kimberlites.

Evolution of Nb–Ta Oxide Minerals and Their Relationship to the Magmatic-Hydrothermal Processes of the Nb–Ta Mineralized Syenitic Dikes in the Panxi Region, SW China

Previous geochemical and petrological studies have concluded that initially magmatic Nb–Ta mineralization is often modified by post-magmatic hydrothermal fluids; however, there is still a lack of mineralogical evidence for the syenite-related Nb–Ta deposit. From the perspective of Nb–Ta minerals, the pyrochlore supergroup minerals have significance for indicating the fluid evolution of alkaline rock or related carbonatite type Nb–Ta deposits. The Panzhihua–Xichang (Panxi) region is a famous polymetallic metallogenic belt in southwestern China, abound with a huge amount of Nb–Ta mineralized syenitic dikes. This study focuses on the mineral textures and chemical compositions of the main Nb–Ta oxide minerals (including columbite-(Fe), fersmite, fergusonite-(Y), and especially pyrochlore group minerals) in samples from the Baicao and Xiaoheiqing deposits, in the Huili area, Panxi region, to reveal the magma evolution process of syenitic-dike-related Nb–Ta deposits. The Nb–Ta oxides in the Huili syenites are commonly characterized by a specific two-stage texture on the crystal scale, exhibiting a complex metasomatic structure and compositional zoning. Four types of pyrochlore group minerals (pyrochlores I, II, III, and IV) formed in different stages were identified. The euhedral columbite-(Fe), fersmite, and pyrochlores I and II minerals formed in the magmatic fractional crystallization stage. Anhedral pyrochlore III minerals are linked to the activity of magma-derived hydrothermal fluids at the late stages of magma evolution. The pyrochlore IV minerals and fergusonite-(Y) tend to be more concentrated in areas that have undergone strong albitization, which is a typical phenomenon of hydrothermal alteration. These mineralogical phenomena provide strong evidences that the magmatic-hydrothermal transitional stage is the favored model for explaining the Nb–Ta mineralization process. It is also concluded that the changes in chemical composition and texture characteristics for pyrochlore group minerals could serve as a proxy for syenite-related Nb–Ta mineralization processes.

URBAN DEVELOPMENT OF RESIDENTIAL AREAS IN THE CITY OF CHERNIVTSI

The territorial development of the city is studied on the basis of town-planning documentation and full-scale researches of residential and former industrial territories, the factors which have formed the basis of the concept of the general plan of development of the city are resulted. Options for the transformation of territories occupied by industrial enterprises are considered. The integrated concept of city development is analyzed, in particular, conversion proposals of development and improvement and modernization of abandoned territories of non-functioning and partially functioning industrial enterprises, the concept of residential development is analysed. The city of Chernivtsi in its economic and geographical location is an industrial, administrative and cultural center of the region, with a large historical and architectural heritage. Due to the growing demand for living space and the diversification of forms of housing, the intensive development of the city is becoming more expressed. Aspects of land consolidation are not yet a priority, however, thanks to a quality planning policy, sustainable development of the city can still be achieved. Newly built areas are characterized by a high level of compaction.
 The study of the territorial development of the city can lead to a better balance in the use of land resources, options for the transformation of the territories of former industrial zones and enterprises that are partially functioning in these areas or abandoned and liquidated. The application of the principles of sustainable urban development according to the European model has been further developed, the integration of the housing function into industrial areas has been improved on the example of the town-planning proposal for the development of former industrial zones. The city is constantly expanding. There is a tendency to build large-scale buildings outside the old town and traditional suburbs, which are not typical for this area, especially multi-storey residential and retail facilities. Their inclusion in the general structure of the city by type (function) and size (form) in accordance with the context of urban development is not observed. At the same time, the territory of the city on the outskirts is constantly increasing, which leads to further use of natural spaces and maximizing the distance to public and commercial institutions, as well as workplaces, due to which the ammount of traffic increases.
 Territorial development of the city is a consequence of the general concept of the general plan of development of the city on the basis of the factors which have formed its basis. These include:
 
 The concept of economic development of the city, which is based on a market economy and private initiative, the priority development of the service sector, the development of the tourism and leisure industry.
 Population dynamics. Hence the output of the quantitative indicator of the required areas.
 Planning constraints, environmental protection and rational use of natural resources.
 Available territorial resources and efficient use of territories.
 The concept of three-dimensional composition, planning structure and functional zoning of the city.
 Rational system of resettlement in relation to places of employment.
 
 A number of territories, which have a very favorable position in relation to the places of employment, to transport connections due to one reason or another have not been developed - complex engineering training, lack of networks, the presence of other restrictions.
 All areas are partially occupied by individual manor buildings.
 The master plan envisages the development of these areas by 2032 without access to agricultural land.
 The article also discusses the options for the transformation of the territories occupied by industrial enterprises. These options can be as follows:
 
 Change in the functional purpose of the territory due to the removal or closure of industrial enterprises that adversely affect the environment.
 Technical re-equipment of the enterprise on new technologies (with preservation of a profile) for the purpose of reduction of harmful influence on environment.
 Replacement of the profile or functional use of real estate due to the bankruptcy of the enterprise.
 
 As a result of field surveys of residential and industrial areas of the city and research of urban planning documentation of the city of Chernivtsi and the Integrated Concept of Urban Development, the former industrial areas of the city were also analyzed.
 During the survey of all districts of the city, old industrial areas were identified, which today, due to significant use and a favorable location within the city, need to be improved and modernized.
 According to the Integrated Concept of City Development, conversion proposals for the development and improvement and modernization of abandoned areas of non-functioning and partially operating industrial enterprises were provided.

Ecological Footprint of Residential Buildings in Composite Climate of India—A Case Study

Buildings are accountable for waste generation, utilization of natural resources, and ecological contamination. The construction sector is one of the biggest consumers of resources available naturally and is responsible for significant CO2 emissions on the planet. The effects of the buildings on the environment are commonly determined using Life Cycle Assessments (LCA). The investigation and comparison of the Life Cycle Ecological Footprint (LCEF) and Life Cycle Energy (LCE) of five residential buildings situated in the composite climatic zone of India is presented in this study. The utilization of resources (building materials) along with developing a mobile application and a generic model to choose low emission material is the uniqueness of this study. The utilization of eco-friendly building materials and how these are more efficient than conventional building materials are also discussed. In this investigation, the two approaches, (a) Life Cycle Energy Assessment (LCEA) and (b) Life Cycle Ecological Footprint (LCEF), are discussed to evaluate the impacts of building materials on the environment. The energy embedded due to the materials used in a building is calculated to demonstrate the prevalence of innovative construction techniques over traditional materials. The generic model developed to assess the LCEA of residential buildings in the composite climate of India and the other results show that the utilization of low-energy building materials brings about a significant decrease in the LCEF and the LCE of the buildings. The results are suitable for a similar typology of buildings elsewhere in different climatic zone as well. The MATLAB model presented will help researchers globally to follow-up or replicate the study in their country. The developed user-friendly mobile application will enhance the awareness related to energy, environment, ecology, and sustainable development in the general public. This study can help in understanding and thus reducing the ecological burden of building materials, eventually leading towards sustainable development.

Drivers of biomagnification of Hg, As and Se in aquatic food webs: A review

Biomagnification of trace elements is increasingly evident in aquatic ecosystems. In this review we investigate the drivers of biomagnification of mercury (Hg), arsenic (As) and selenium (Se) in aquatic food webs. Despite Hg, As and Se biomagnify in food webs, the biomagnification potential of Hg is much higher than that of As and Se. The slope of trophic increase of Hg is consistent between temperate (0.20), tropical (0.22) and Arctic (0.22) ecosystems. Se exerts a mitigating role against Hg toxicity but desired maximum and minimum concentrations are unknown. Environmental (e.g. latitude, temperature and physicochemical characteristics) and ecological factors (e.g. trophic structure composition and food zone) can substantially influence the biomagnification process these metal (oids). Besides the level of bioaccumulated concentration, biomagnification depends on the biology, ecology and physiology of the organisms that play a key role in this process. However, it may be necessary to determine strictly biological, physiological and environmental factors that could modulate the concentrations of As and Se in particular. The information presented here should provide clues for research that include under-researched variables. Finally, we suggest that biomagnification be incorporated into environmental management policies, mainly in risk assessment, monitoring and environmental protection methods.

Decoding multiple zoning patterns in clinopyroxene phenocrysts at Vulcano Island: A record of dynamic crystallization through interconnected reservoirs

Here we document how the different growth features and intracrystalline distributions of both major and trace cations in clinopyroxene phenocrysts are important recorders of the intricate magma dynamics at Vulcano Island (Aeolian Arc, Italy). The compositions of clinopyroxene phenocrysts from products erupted over the last ~54 ka cluster at different degrees of evolution, paralleling the polybaric-polythermal differentiation of mantle-derived mafic magmas into more evolved silicic melts. The hotter lower crust is the most favorable location for the storage of mafic magmas and the early crystallization of diopsidic (Mg#91) clinopyroxene (Pmax ≈ 750 MPa and Tmax ≈ 1220 °C). Diopsidic phenocrysts are depleted in both rare earth elements (REE) and high field strength elements (HFSE) but are enriched in transition elements (TE). The transfer and accumulation of primitive magmas in the colder upper crustal regions lead to the formation of an interconnected series of more differentiated magmatic reservoirs (P ≈ 100–450 MPa and T ≈ 1100–1180 °C) hosting discrete populations of clinopyroxene (Mg#84–85) with a broad spectrum of zonations and dissolution features. Recharge bands in clinopyroxene are markers of multiple inputs of primitive REE-HFSE-poor, TE-rich magmas from depth. Augitic phenocrysts (Mg#82) with strong negative Eu anomaly and REE + HFSE enrichments crystallizes from highly differentiated trachytic and rhyolitic melts stored at very shallow crustal conditions (P ≤ 50 MPa and T ≤ 1100 °C). These silicic reservoirs represent residual melts trapped-extracted from crystal-dominated mush regions in the uppermost part of the plumbing system. The residence time of clinopyroxene increases from ∼0.1 to ∼44 years from basalt to rhyolite, together with an increasing number of recharge bands. The mineral assemblage in more silicic and viscous mush melts is sufficiently resilient to record numerous mafic injections and high degrees of magma mixing, hybridization, and crystallization before eruption. Overall, the compositional zoning pattern of clinopyroxene presents a picture of plumbing system that extends through the crust and is characterized by distributions of melts and crystals which are progressively more evolved and heterogeneous in both space and time.

Optical transfer function of inverse-phase composite zone plate devised for deep-focusing X-ray microscopes

The optical transfer function (OTF) of an inverse-phase composite zone plate under incoherent illumination was numerically evaluated by convoluting the point spread function (PSF) and transmission distribution of a model sample with gradually changing spatial frequency. The PSF used in the simulation was obtained from our previous study on deep-focusing X-ray microscopes. As expected, the contrast in the sample image was lesser than that produced by a conventional zone plate. Phase-reversed contrast—spurious resolution—appeared at a high spatial frequency. Although the calculated OTF is slightly aberrated, its deep-focusing capability is advantageous for X-ray microimaging of thick samples.

Evaluation of the significance of the contact model particle parameters in the modelling of wet soils by the discrete element method

Modelling of the tillage process by working tools based on the method of discrete elements is currently the most promising. The results of modelling the processing process obtained by the method of discrete elements adequately describe the behaviour of the soil. Due to the large number of physical and mechanical parameters included in the description of contact models of discrete elements, the calibration process takes a lot of time. Thus, we set a research goal - to evaluate the significance of the parameters of the contact model particles in soil modelling by the discrete element method and to obtain nomograms for selecting the parameters of the Hertz-Mindlin contact model particles depending on the humidity of various types of soils. The article presents the results of calibration of the physical and mechanical parameters of the particles of the soil medium model described by the discrete element method. An improved Hertz-Mindlin JKR model was used as a contact model, the model was implemented in the Rocky DEM programme. The following properties of the modelled particles are taken as the studied factors – Poisson's ratio, static and dynamic friction coefficients, Jung's modulus, surface energy, and particle diameter. The detection of the natural slope angle of the soil was carried out for black soils of clay, light loam and sandy loam mechanical composition. The calibration was performed according to the angle of the natural slope. Comparison of the simulation results with field experiments of typical soils made it possible to establish that the nature of the change in the angle of the natural slope of the simulated soil environment is significantly affected by the surface energy and the diameter of the particles. The obtained dependences of the angle of natural slope on soil moisture and surface energy allow determining the parameters for the Hertz-Mindlin contact model as a function of humidity for Black soil zones of clay, light loam and sandy loam mechanical composition. Based on the results of field and model experiments, a nomogram was obtained that makes it possible to select parameters for the contact model - the diameter of soil particles and the value of surface energy depending on humidity and soil type. The obtained values of the parameters of the particles of the soil medium make it possible to simulate the process of tillage, optimize the design and technical parameters of the newly created working parts of tillage machines.

Fluid Fluxing and Accumulation Drive Decadal and Short-Lived Explosive Basaltic Andesite Eruptions Preceded by Limited Volcanic Unrest

Abstract Some volcanoes are known for repeatedly producing explosive but short-lived eruptions (< half a day) every decade or so. These eruptions are often preceded by limited unrest signals and short run-up times to eruption (a few hours to months), and thus they are difficult to anticipate. Some well-documented examples are the 1990 and 2014 eruptions of Kelud volcano in Indonesia, or the 2015 Calbuco eruption in Chile. Here we interrogate the rock record and obtain insights into the processes and pre-eruptive conditions that led to the 1990 Kelud eruption, which we integrate with monitoring data (seismicity, lake temperature and hydro-acoustics, sulfur emissions) towards a conceptual model for this type of events. Mineral-melt geothermobarometers indicate that the basaltic andesite magma carried a crystal cargo from as deep as 15–19 km, and reached volatile saturation at 4–9 km with 2–4 wt.% water in the melt. The textures and compositional zoning of orthopyroxene and plagioclase do not support intrusion of more primitive magma as the driver for the eruption, and we instead propose that pre-eruptive fluid accumulation and high-temperature fluid fluxing from depth (likely dominated by CO2) played a major role in priming the eruption to occur. Such pre-eruptive gas accumulation is also supported by mass balance calculation of the emitted excess SO2 gas. Mg-Fe diffusion profiles in reversely zoned pyroxenes constrain timescales of weeks to months before eruption for fluid addition to the reservoir, and such events may be recorded in the monitoring signals, especially in the change of hydroacoustics and water lake temperature, and probably in the seismic swarms. We propose that fluid exsolution and accumulation in the shallow reservoir plays a crucial role in modulating and triggering short-lived explosive eruptions with brief unrest at Kelud and probably other volcanoes worldwide.

Room-temperature wear resistance of tungsten carbide composite layers produced on grey cast iron by diffusion-controlled in situ reactions

To improve the tribological properties of substrate surfaces, tungsten carbide composite layers were deposited on an iron-based alloy by diffusion-controlled in situ reaction (DIR) at different temperatures. The microstructure, phase composition and worn morphology of the composite layer were characterized by utilizing scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD) and confocal laser scanning microscopy (CLSM). A thin tungsten carbide layer with an interface crack was obtained at 1000 °C. At 1100 °C, the structure of the optimized composite layer contains a thin tungsten plate, a thicker tungsten carbide layer (300 μm) and a broad composite zone (2.5 mm) from top to bottom. The indexed phase composition for the carbide layer includes WC and α-Fe, and the composite zone consists of α-Fe, Fe6W6C, FeC and graphite. The tribological properties and mechanical properties of the composite layers were evaluated by using a ball-on-disk tribometer and a nanoindentation hardness tester. The average nanohardness of the tungsten plate, carbide layer, composite region and substrate is approximately 6.4 ± 1.0 GPa, 24.1 ± 3.4 GPa, 13.5 ± 2.4 GPa and 9.6 ± 1.2 GPa, respectively. Friction wear tests of all samples against GCr15 balls were performed at room temperature under 5, 10, 15 and 20 N normal loads. The carbide layer exhibits an average coefficient of friction of 0.39–0.63, which is higher than that of the substrate under an identical load due to the lubricating effect of the flake graphite phase in the substrate during the wear process. The specific wear rate of the carbide layer with a value of 2.69–4.33 is 18.5–34.3% of that of the substrate. The results of the worn morphology presence of particle deformation, extraction and crushing reveal that abrasive wear is a dominant abrasion mechanism for the carbide layer. For the substrate, adhesive wear plays an important role and is accompanied by abrasive wear.

Petrology and geochemistry of retrograde eclogites in the Changning-Menglian suture zone, southwest China: Insights into the Palaeo-Tethyan subduction and rutile mineralization

The consumption of the Palaeo-Tethyan ocean from Permian to Triassic formed the Changning-Menglian suture zone (CMSZ) in southwest China, where abundant eclogites with diverse geochemical signatures have been discovered in recent years. Eclogites are known as specific products during the orogenic evolution from subduction to collision, which play an important role in reconstruction of the orogenic process and bear implications for rutile mineralization. Here we use the phengites Ar-Ar isotopes, rock-forming mineral and whole-rock compositions, and Nd isotopes of Mengku eclogites, together with previous data of eclogites and relevant basalts from the CMSZ to address these issues. The phengites Ar-Ar dating of the Mengku eclogites yields a metamorphic age of 244 ± 2.0 Ma. Garnets in the eclogites show evident compositional zonation, corresponding to a prograde process from core to rim as evidenced by the variation of minerals enclosed in garnets. Four types of rutile are recognized in eclogites: mineral inclusion (ru1), granular (ru2), beaded (ru3) and wispy (ru4). Granular and beaded rutile that formed in the peak metamorphic stage contributes the most to the rutile mineralization. The Mengku eclogites show enriched LREEs with high (La/Yb)N ratios of 8.89–10.88, positive Nb-Ta anomalies and negative εNd(t) values from −0.63 to −0.07, similar to the average compositions of the OIB-type volcanic rocks exposed in the CMSZ. Modeling results indicate that the protoliths of OIB-type eclogites were derived from an enriched garnet lherzolite source while those of MORB-type were either from a primitive or from a depleted spinel lherzolite source. The OIB-type eclogites have much higher TiO2 contents (2.49–4.25 wt%) than the MORB-type eclogites (1.05–2.75 wt%), which reflects different modes of rutile in the two types of eclogites. This observation is highly consistent with the higher TiO2 contents in OIB-type than in MORB-type volcanic rocks from the CMSZ, indicating that the Ti enrichment in protoliths are first-order control on the formation of high-Ti rutile ores. Our results and the integrated previous studies of paleomagnetism, biogeography, magmatism and metamorphism suggested that the Palaeo-Tethyan subduction lasted from Late Carboniferous to Late Triassic (ca. 313–230 Ma) and the eclogite-type rutile exhumed back to the surface after ca. 230 Ma. Identification of OIB-type eclogites and the high-Ti eclogites with weakly retrograde metamorphism can be key evaluative factors for Ti exploration in the CMSZ.

Newly found Tonian metamorphism in Akebono Rock, eastern Dronning Maud Land, East Antarctica

In this paper, we report a new metamorphic age for kyanite-bearing garnet-biotite gneiss collected from Akebono Rock, which is located on Prince Olav Coast, in the Lützow-Holm Complex (LHC), East Antarctica. The metamorphic P–T path estimated from pseudosection modeling, together with garnet compositional zoning and experimentally calibrated geothermobarometry, suggests that the gneiss underwent a clockwise amphibolite-facies P–T history. Two populations of U–Pb zircon ages of 1121–1014 Ma and 972–904 Ma (n = 65) were identified, with the latter population having a weighted mean age of 937 ± 6 Ma. The younger population was dated from overgrowth rims and single zircon grains interpreted as metamorphic in origin. Ti-in-zircon thermometry supports crystallization of these zircon domains and grains at a temperature close to the metamorphic peak of 642 °C at 937 Ma. Monazite EMP dating from the other four samples show an age between 977 and 917 Ma. These lines of evidence indicate that prograde metamorphism of the Akebono Rock gneiss occurred during the Tonian, that is, substantially earlier than the LHC regional metamorphic age of late Neoproterozoic to Cambrian. Our results indicate that a fundamental revision of the sequence of metamorphic events in the Prince Olav Coast area of the LHC is required. We also identified three possible relationships between Akebono Rock and other geological units that record Tonian metamorphism, although we cannot determine which relationship is most likely. In particular, linear magnetic anomalies were identified near the boundary between the LHC and the Western Rayner Complex/inland nunataks of western Enderby Land, suggesting the presence of geological discontinuities.

Energy, exergy and economic assessments of the dual-mode evaporative cooler for various international climate zones

The conventional desert cooler is effective for dry seasons and the regenerative evaporative cooler (REC) is an effective device for humid seasons in composite climate zones. Hence, the dual-mode evaporative cooler (a two-in-one device) is an intelligent choice for air conditioning, which can operate in both direct and regenerative modes depending on the seasonal climatic condition. The exergy and economic analyses of this novel device for global climatic conditions are performed to check the suitability in different regions of the world. An experimental prototype of a dual-mode evaporative cooler is developed and tested to validate the simulation model. The effectiveness, coefficient of performance, exergy destruction, exergy efficiency, operating cost, and specific total cost (STC) are evaluated for both (direct and regenerative) modes of operation. The annual and month-wise performances of dual-mode evaporative cooler have been assessed for five cities of international climate zones. The operating cost of both modes is compared by considering electricity charges in different countries. The dual-mode device is compared with the single-mode device as well. The specific cost is similar for both modes in most of the ASHRAE climatic zones. The present study reveals that significant energy and cost savings are possible by using the dual-mode evaporative cooler. Practical application: This article considers the application of a dual-mode evaporative cooler (direct as well as regenerative mode) in different climate zones and, through investigating the exergy and economic performances, allows designers and operators to understand the potential benefits of employing various operating modes in particular climates.

Formation of late-stage hydrothermal mineralization in the Mesoarchean Boula-Nuasahi ultramafic complex, Odisha, India: Constraints from arsenopyrite geothermometry and trace element data

The Mesoarchean Boula-Nuasahi ultramafic complex is situated in the south eastern flank of the Singhbhum Craton, India and consists mainly of gabbro-anorthosite, peridotite and pyroxenite litho-units that host a series of chromitite bodies. A contemporaneous but slightly younger magmatic event has structurally disturbed the area with intrusion of a coarse-grained gabbro unit known as the Bangur gabbro (∼3.1 Ga). This has caused extensive hydrothermal alteration of the original host rocks and is associated with hydrothermal sulphide- and Pt-Pd mineralizations. Petrographic study shows that well-crystallized and euhedral arsenopyrite crystals are associated with quartz and carbonates in veins aligned along the foliation planes/fractures in the host rocks. This vein assemblage (arsenopyrite + quartz + calcite) has formed during the late stage of hydrothermal mineralization. Electron probe micro-analysis and LA-ICP-MS analysis of arsenopyrite demonstrates that its chemical composition varies within narrow limits and that the concentrations of trace elements are below 900 ppm. The only trace element present in significant concentrations is Sb with an average value of 490 ppm. The As/S atomic ratio varies between 0.93 and 1.01 and As and S show a clear negative correlation according to the substitution FeAs1-xS1+x. The average composition is very close to the stoichiometric value. Because the arsenopyrite crystals are vein minerals, have very low concentrations of any impurities and do not show any compositional zoning, they were used for geothermometric calculations. Matching the measured As atom% with one of the experimentally calibrated isopleths in the established Fe-As-S phase diagram, calculated temperatures are in the range of 335–425 °C. This temperature range is in very good agreement with temperature estimates of 300–500 °C (based on cobaltite–gersdorffite compositions) for late-stage hydrothermal mineralization in the Boula-Nuasahi ultramafic complex available in the literature.

Sulfosalts record evolution of Cu-Bi-Co-Ni-As mineralization at Baycheh-Bagh deposit, NW Iran

Minerals of the tetrahedrite group and Bi-bearing sulfosalts and sulfides have been identified in different mineral associations in the polymetallic (Cu-Bi-Co-Ni-As) vein deposit at Baycheh-Bagh, Zanjan Province, NW Iran. The tetrahedrite group members span the complete compositional range from tetrahedrite to tennantite with Fe and less common Zn being the dominant divalent cation. Two generations of tetrahedrite group minerals can be distinguished recording changes in chemical as well as redox conditions of the mineralizing fluid. The first generation (Ia, Ib) includes tennantite-(Fe) succeeded by tetrahedrite-(Zn) to tennantite-(Fe) of variable intermediate composition. Bismuthian tennantite-(Fe) containing up to 1.17 apfu Bi represents the second generation (II) formed during the final hydrothermal stage. Bismuthian tennantite is characterized by primary growth zoning and slight Cu excess; the latter indicating an increase in the oxidation state of the fluid. The compositional variation and zoning of tetrahedrite group minerals reflect multiple pulses of hydrothermal solutions with varying As/Sb content. The significant substitution of Bi for (As + Sb) in the X site in generation II tennantite indicates higher activity of Bi in the late ore fluids. The late-stage Bi-rich assemblages also comprise emplectite, wittichenite, bismuthinite, aikinite and native bismuth. Luzonite is also found with these assemblages. These minerals mainly belong to the final stage of mineralization and formed between ∼200 and 300 °C.

Origin of alkali olivine basalts and hawaiites in the western Mexican arc: Evidence of rapid phenocryst growth and magma mixing during ascent along fractures

Abstract A detailed petrological study is presented to constrain the origin of a suite of alkali olivine basalt and hawaiite (>5 wt% MgO) lavas that were erupted in a rift zone within the western Mexican arc (Trans-Mexican Volcanic Belt), adjacent to the Sangangüey andesitic stratovolcano, together with more evolved lavas (mugearites and benmoreites; <5 wt% MgO). As previously documented in the literature, the Sangangüey mafic lavas are devoid of any arc geochemical signature, despite their location within an arc. In this study, a new olivine-melt thermometer/hygrometer, based on the partitioning behavior of Ni2+ and Mg2+, was applied to the Sangangüey basalts (SB). The results show that the high-MgO (>9 wt%) SB crystallized at higher temperatures and lower melt-water contents (0–1.3 wt%) compared to high-MgO arc basalts (≤5.7 wt% H2O) erupted in the west-central Mexican arc. The Sangangüey lavas with 5–8 wt% MgO display evidence of mixing between high-MgO alkali olivine basalts and low-MgO mugearites. It is proposed that the unique composition of the mugearites (i.e., low SiO2 contents and elevated FeO and TiO2 contents) is the result of partial melting of mafic lower crust driven by the influx of high-MgO intraplate basalts under relatively hot, dry, and reduced conditions. On the basis of crystal textures and compositional zoning patterns, it is shown that both phenocryst growth and magma mixing occurred rapidly, most likely during ascent along fractures, and not slowly during prolonged storage in a crustal magma chamber.

Nanoinclusions in zoned magnetite from the Sossego IOCG deposit, Carajás, Brazil: Implication for mineral zoning and magnetite origin discrimination

Compositional zoning is common in magnetite from different geological environments, but its formation mechanism remains controversial. Here, we characterize micron- to nano-scale textural and chemical variations in zoned magnetite from the Sossego iron oxide-copper–gold deposit (Carajás, Brazil) using electron probe microanalyzer (EPMA) and transmission electron microscopy (TEM). Lack of porosity and of a reaction front at both the micron and nanometer scales indicates that compositional zoning in magnetite is a pristine texture formed during crystal growth, rather than a secondary texture due to dissolution and reprecipitation reaction. TEM energy dispersive X-ray spectrometry analyses and mapping identify four types of nanoinclusions in zoned magnetite: 1) Mg-Fe-Al silicates, most likely amphibole, 2) Fe-Ti oxides, mainly ilmenite, 3) pyroxene, 4) Si-rich magnetite. The formation of ilmenite nanoinclusions in Sossego magnetite is possibly due to oxy-exsolution of ulvöspinel from Ti-rich magnetite, whereas nanoinclusions of other minerals likely formed by local supersaturation in the fluid boundary layer, followed by magnetite crystal entrapment. Compositional zoning in magnetite likely formed by a self-organization process where fluid composition fluctuations are feedback responses for an evolving fluid system far from equilibrium, rather than cyclic variations in external factors such as temperature and oxygen fugacity. Saturation of silicate minerals results in relative depletion of Si, Ca, and Al in boundary layer fluids, and formation of inclusion-poor zone depleted in these elements. Nanoinclusions in magnetite highlight the importance of textural characterization when using in situ chemical composition to discriminate the origin of magnetite. In addition, the assemblages of nanoinclusions in magnetite can be used to complement the discrimination of magnetite origins.

Plagioclase population dynamics and zoning in response to changes in temperature and pressure

AbstractZoned plagioclase crystals are often interpreted as proxies for magmatic history because the mineral is present in most silicic magmas and has compositional sensitivity to magmatic conditions (pressure, temperature, and composition) with slow internal diffusion that preserves compositional zones. Changes in growth rates and crystal dissolution present challenges to quantitatively relating time to particular zoning patterns. The numerical model SNGPlag uses Rhyolite MELTS to determine the equilibrium phase assemblage and compositions for a user-defined magma composition experimentally determined instantaneous nucleation and growth rates, and reasonable dissolution rates to examine plagioclase crystallization and population dynamics through time. The model tracks the numbers, sizes, morphologies, and compositional zoning of plagioclase crystals through time in response to changes in pressure, temperature, and volume or mass inputs. Model results show that significant fractions of time are functionally missing from the crystal record because of effectively zero growth rates or erased from the record through dissolution; in some instances, those processes can together remove ≫50% of time from the crystal record. The results show that temperature- (or pressure-) cycling alone will not produce substantial compositional zoning but that the addition of new magma is required to grow complexly zoned phenocrysts. Comparison of the input pressure-temperature-time series with compositional transects shows that the crystal record is biased toward more recent intervals and periods of decreasing temperature (i.e., neither the peak temperatures nor intervals of prolonged, cool storage are favored). Crystallization (or dissolution during heating) acts to return magmas to near-equilibrium crystal fractions within hundreds of days.

Constraints on the petrologic history of gabbroic shergottite Northwest Africa 6963 from pyroxene zoning profiles and electron backscattered diffraction

AbstractNorthwest Africa 6963 (NWA 6963) is a coarse‐grained, gabbroic Martian meteorite that further extends our Martian sample collection, both compositionally and texturally. Gabbroic shergottite NWA 6963 provides direct petrologic evidence of intrusive igneous conditions within the Martian crust. Here, we analyzed geochemical zoning profiles and microstructural‐crystallographic information from electron backscattered diffraction of augite and pigeonite to constrain the crystallization history of NWA 6963. Compositional zoning profiles reveal pyroxenes with augite or pigeonite cores mantled by Fe‐rich pigeonite rims. Our results suggest complex pyroxene textures and zoning profiles observed in pyroxenes in NWA 6963 are due to pyroxene accumulation from a crystallizing magma in a large intrusive environment (sill or magma chamber); however, without geologic context or companion samples, it is currently impossible to rule out accumulation at the base of a very large (>>100 m) differentiated flow.