The importance of grain size and shape in controlling the dispersion of the Vedde cryptotephra

Volcanic ash is dispersed in the atmosphere according to meteorology and particle properties, including size and shape. However, the multiple definitions of size and shape for non-spherical particles affect our ability to use physical particle properties to understand tephra transport. Moreover, although particles are often excluded from operational ash dispersion model setups, ash in tephra deposits 1000 km from source can exceed . Here we measure the shape and size of samples of Vedde ash from Iceland, an exceptionally widespread tephra layer in Europe, collected in Iceland and Norway. Using X-ray computed tomography and optical microscopy, we show that distal ash is more anisotropic than proximate ash, suggesting that shape exerts an important control on tephra dispersion. Shape also impacts particle size measurements. Particle long axis, a parameter often reported by tephrochronologists, is on average greater than geometric size, used by dispersion modellers. By using geometric size and quantifying shape, we can explain the transport of Vedde ash particles more than 1200 km from source. We define a set of best practices for measuring the size and shape of cryptotephra shards and discuss the benefits and limitations of using physical particle properties to understand cryptotephra transport.     

Review of the Study on the Stable Isotopes of Nitrogen and Oxygen in Atmospheric Nitrate

Due to the emissions from intensive human activities and rapid development of industry and agriculture, atmospheric nitrate (NO {}_3^{-} ) contamination is becoming more serious and now is a worldwide environmental problem. The isotopic compositions of NO {}_3^{-} (δ¹⁵N, δ¹⁸O and Δ¹⁷O) can deliver more information than the concentration alone, i.e., the nitrogen and oxygen isotopes can suggest the sources of NO {}_3^{-} and oxidation capability of the atmosphere, providing a powerful tool for investigating atmospheric nitrogen cycling and atmospheric NO {}_3^{-} pollution control. The δ¹⁵N of different sourced NO {}_3^{-} in the atmosphere, as well as the seasonal variation of δ¹⁵N (NO {}_3^{-} ) and the associated mechanisms were reviewed. In addition, the oxygen isotopes of various oxidants and NO {}_3^{-} (δ¹⁸O and Δ¹⁷O) in the atmosphere were summarized, and the global distribution patterns of the oxygen isotopes of NO {}_3^{-} were discussed. Lastly, the available analysis techniques of isotopic compositions of NO {}_3^{-} were reviewed. Based on the research progress of NO {}_3^{-} isotopes in the atmosphere, it was suggested that further investigations should focus on measuring the isotopic compositions of oxidants and NOx from different sources, characterizing the production mechanisms of NO {}_3^{-} , as well as investigating chemical recycling between NOx and NO {}_3^{-} with the aid of atmospheric chemical models.     

Conditions for the formation of the chemical composition of the water of the Firuza MGU carbonated spring (Northern Pamirs)

We considered the geological conditions and chemical composition of the water of the Firuza MGU carbonated spring, which was discovered in 2015 in Northern Pamir. This paper reports on the detailed composition of the miсrocomponents of the water as determined by an Inductively Coupled Plasma Mass Spectrometry analysis (ICP-MS). A comparative review of the water composition and content of similar microcomponents in waters of carbonated springs in Kamchatka and the Russian Far East is given. On the basis of the B: Cl and K: Li: Rb: Cs ratios, which are close to the same ratios for chloride sodium hot springs in areas of active volcanism, it is concluded that the water of the spring has a deep origin. The temperature of the formation of water calculated by a Na–K geothermometer method is 147.3°C, suggesting the formation of the spring at a depth of approximately 5 km.     

Application of central composite rotatable design to modelling the effect of some operating variables on the performance of the three-product cyclone

The central composite rotatable design (CCRD) was used to design an experimental program to model the effects of inlet pressure, feed density, and length and diameter of the inner vortex finder on the operational performance of a 150-mm three-product cyclone. The ranges of values of the variables used in the design were: inlet pressure: 80–130 kPa, feed density: 30–60%; length of IVF below the OVF: 50–585 mm; diameter of IVF: 35–50 mm. A total of 30 tests were conducted, which is 51 less than that required for a three-level full factorial design.Because the model allows confident performance prediction by interpolation over the range of data in the database, it was used to construct response surface graphs to describe the effects of the variables on the performance of the three-product cyclone. To obtain a simple and yet a realistic model, it was refitted using only the variable terms that are significant at greater than or equal to 90% confidence level. Considering the selected operating variables, the resultant model is significant and predicts the experimental data well.     

古物源体系多方法表征

古物源体系是深时“源—汇”系统研究的重要环节。随着沉积学理论和技术的发展,物源示踪的表征方法已从单一迈向综合、由定性走向定量,这将有助于更全面地揭示母岩发育特征、物源区构造背景、沉积物路径系统等,进而建立更可靠的古物源体系发育模式。碎屑锆石U-Pb定年等多方法物源体系表征研究表明,沾化凹陷渤南洼陷沙四下亚段（Es4x）砂岩样品主要发育岩浆成因的锆石,这些锆石颗粒自形程度较好,具有清晰的岩浆环带,其Th/U>0.4,稀土元素普遍具有“Ce正异常、Eu负异常”特征。微量/稀土元素地球化学指标和砂岩岩石学特征揭示了研究区沙四下亚段陆源碎屑具有岩浆岛弧/活动大陆边缘酸性花岗质源岩的属性。母岩的发育与华北克拉通在新太古代—古元古代及晚古生代—中生代的地球动力学背景密切相关。综合优势年龄贡献、母岩属性、岩石学特征、地球动力学背景,最终建立了渤南洼陷沙四下亚段古物源体系发育模式,即渤南洼陷沙四下亚段同时发育“近源堆积”和“远源供给”两类路径系统,发育东侧中生界岩浆岩主导型物源系、南侧新太古界/古元古界/上古生界/中生界母岩联合控制型物源系、中部混合物源系。其中,东侧物源系和中部物源系的关联性较大,应属于同一沉积物路径系统,南侧物源系相对独立。     

Dinantian sedimentation and the basement structure of the Derbyshire Dome

The depositional history of the Dinantian on the Derbyshire Dome can be divided into three phases: (1) pre-Holkerian: onlap of an irregular basement surface by evaporite and carbonate sediments, (2) Holkerian to Asbian: sedimentation on a carbonate shelf formed by the merging of early Dinantian depocentres following burial of the basement topography, and (3) Brigantian: formation of intrashelf basins and the development of a carbonate ramp on part of the pre-existing shelf. A model of the basement structure underlying the Derbyshire Dome is presented to explain the location of the Brigantian intrashelf basins and carbonate ramp. The basement consists of two main tilted fault blocks separated by a smaller tilt block. Movement on faults bounding the tilt blocks caused the development of intrashelf basins. The basin margins were controlled by structures which developed in the cover sediments. The carbonate ramp present during the late Brigantian developed in response to an eastward tilting of the basement.     

Numerical determination of the tensile response and the dissipated fracture energy of concrete: role of the mesostructure and influence of the loading rate

At the mesoscopic scale, concrete can be considered as a mix of coarse aggregates with a mortar paste matrix. In this paper, we investigate numerically the influence of aggregates arrangements and loading rate on the tensile response of concrete. Each coarse aggregate is assumed to be circular with six different radiuses following the aggregates size distribution of real gravel. Rate‐independent cohesive elements are used to model failure within the mesostructure. Our results show that the spatial distribution of heterogeneities does not influence the peak strength, while it changes the post‐peak macroscopic response. This implies that our specimen size is large enough for strength computation but that larger mesostructures should be considered to obtain fully reliable toughness predictions. Although the cohesive approach is able to capture the transition from one macro‐crack in quasi‐static to multiple micro‐cracks in fast dynamics, which increases the dissipated fracture energy, our results suggest that the full extent of the high‐rate strengthening of concrete observed experimentally for loading rates greater than 1/s cannot be captured with rate independent constitutive laws.Copyright © 2013 John Wiley & Sons, Ltd.     

胡杨(Populus euphratica)径向生长日变化特征分析

利用树木径向生长测定仪、自动气象站和土壤水分自动监测仪,在黑河下游胡杨河岸林内,同步监测了胡杨径向生长日变化和太阳辐射、气温、空气相对湿度及主要根系层土壤水分动态等环境因子.结果表明:胡杨径向生长日变化呈抛物线形,每日16:00～20:00时达到最低值点,随后逐步上升至翌日06:00～09:00时达到最高值点,完成一个由收缩期、膨胀恢复期和生长期3阶段构成的日变化周期;不同季节,胡杨径向生长变动幅度存在较大差异.就监测样树而言,不同胡杨个体,胸径越大,日净生长量越大.对各环境因子统计表明,胡杨径向生长日变化与总辐射、气温和土壤体积含水率呈负相关关系,与空气相对湿度呈正相关关系.各环境因子对胡杨径向生长影响存在延时滞后作用,特别是土壤水分条件.     

Simulation of the development of karst aquifers: role of the epikarst

 The evolution of a karst aquifer is modelled taking into account the karst groundwater flow as well as the dissolution kinetics of calcite. In particular, infiltration of water from the epikarst is simulated which controls the temporal and spatial distribution of recharge to the phreatic zone. The results show that the evolution of karst conduits is initiated in the spring. The existence of preferential flow paths leads to the evolution of highly conductive so-called dendritic cave systems, i.e., single passages which concentrate the flow and drain the catchment. With time, the amount of undersaturated water flowing directly into the conduit system is increased leading to an acceleration of the conduits enlargement. Three phases are identified for the evolution of karst aquifers: (a) an initiation stage; (b) an enlargement stage; and (c) a stagnation phase. Received: 4 August 1997 / Accepted: 19 January 1998     

A quantitative study of the degradation of whale bone lipids: Implications for the preservation of fatty acids in marine sediments

The degradation and preservation affecting the biomarker record of ancient metazoa are not fully understood. We report on a five month experiment on the fate of fatty acids (FAs) during the degradation of recent whale vertebrae (Phocoena phocoena). Whale bones were analysed for extractable FAs and macromolecularly bound n-acyl compounds. Fresh bone showed extractable FAs dominated by 16:1ω7c, 16:0, 18:1ω9c and 18:0. Calculated degradation rate constant (k) values showed a rapid decrease in FA concentration, with k values higher for unsaturated than for saturated compounds (0.08/day for 18:1ω9c, 0.05/day for 16:0). The appearance or increased abundance of distinctive methyl branched (e.g. i/ai-15:0 and -17:0, 10Me-16:0) and hydroxy FAs (e.g. 10OH-16:0 and 10OH-18:0) were observed, providing clear evidence for the microbial degradation of bone organic matter and an input of lipids from specialised bacteria. Catalytic hydropyrolysis (HyPy) of demineralised extraction residues released up to 0.13% of the total n-C₁₆ and n-C₁₈ moieties in the degraded bones. This revealed that only a small, yet sizeable, portion of bone-derived fatty acyl units was sequestered into (proto)kerogen during the earliest stages of degradation.     

The solution of the double-sphere model and experimental research of the longterm shear strength of frozen sand based on spherical template indenter test北大核心CSCD

The distribution of frozen soil in our country is very broad, and the area of permafrost alone accounts for 22. 4% of the total land area. As a special kind of soil, frozen soil has many properties that thawing soil does not have due to the influence of ice cement in the soil. Among the many properties of frozen soil, the deformation and strength of frozen soil are the basic problems affecting engineering construction in frozen soil areas. The spherical template indenter test is widely used in the test of the mechanical properties of frozen soil because of its simple test process and relatively accurate test results. Compared with the conventional triaxial test or direct shear test, the test process of the spherical template indenter test is simple and easy to implement, the test period is short, and the sample preparation requirements are low. The advantage of effective cohesion is more significant. Therefore, based on the spherical template indenter test of the frozen soil, this paper estimates the strength and mechanical index of the soil through the indentation depth of the spherical template indenter test, and establishes the relationship between the force of the sample and the indentation depth of the indenter test. The specific test method is as follows:take the water-saturated frozen sandy soil made of different particle size groups(the moisture content of the sample is affected by the particle size in the saturated state)as the research object, study the variation law of the depth of the frozen soil sample pressed into the soil by the spherical indenter with time under the conditions of different fixed loads. By comparing and referring to the frozen sands of each particle size group, the long-term equivalent cohesion of the frozen sands of different particle size groups is summarized. The change law of force(long-term shear strength)with time, and the research method of elastic mechanics to solve space problems, summed up the mutual conversion between the depth St of spherical template indenters pressed into frozen sand samples under different fixed load test conditions relation. The research results show that the long-term shear strength of frozen sand based on the spherical mold test is positively correlated with its particle size. At the same time, since the ice content of frozen soil samples is proportional to its particle size, the long-term shear strength of frozen sand is also proportional to the test. The ice content of the sample increases year-on-year;the long-term shear strength of the frozen sand is related to the maximum contact pressure on the contact surface between the frozen soil and the indenter during the test, which can be expressed as Ct = γq0. The size of the relationship coefficient γ is inversely proportional to the diameter of the spherical indenter. In this paper, the spherical indenter is selected as 22 mm, and γ=3. 82×10-3. By establishing the relationship between the maximum contact pressure q0 and the long-term shear strength Ct When the maximum contact pressure q0 is the same under different fixed loads, the long-term shear strength Ct is also the same. According to this, the depth curve and the freezing depth of the frozen sand pressed into the soil by the spherical indenter over time under different fixed loads can be converted. Long-term shear strength curve of frozen sandy soil with time. It has been verified by experiments that the conversion curve of the depth of the indenter pressed into the soil with time under a fixed load of 7. 0 kg is highly consistent with the measured curve of the depth of the indenter pressed into the soil with time under a fixed load of 5. 1 kg and 7. 0 kg. © 2022 Nanjing Forestry University. All rights reserved.     

THE CENOZOIC GEORECORDS IN THE NORTHWEST OF YUNNAN AND THE EVOLUTION OF QING—ZANG PLATEAU

THE CENOZOIC GEORECORDS IN THE NORTHWEST OF YUNNAN AND THE EVOLUTION OF QING—ZANG PLATEAU     

甘肃北山地区小西弓金矿床成矿流体性质及矿床成因

小西弓金矿床位于甘肃北山造山带南部,矿体受NWW向次级断裂控制,赋矿围岩主要为中元古界西尖山群变质岩。成矿过程可分为3个阶段:石英-黄铁矿阶段(早阶段)、石英-多金属硫化物阶段(主成矿阶段)和石英-碳酸盐阶段(晚阶段)。对主成矿阶段石英中的流体包裹体、微量元素和氢、氧同位素开展研究,以期查明成矿流体性质,探讨矿床成因。主成矿阶段石英中主要发育气液两相水溶液包裹体、CO₂-H₂O三相包裹体和纯液相CO₂包裹体,均一温度介于194~397 ℃,盐度为2.2%~8.9% NaCl_eqv,密度为0.63~0.98 g/cm³。利用CO₂-H₂O三相包裹体计算出主成矿阶段流体包裹体捕获压力为257~395 MPa,成矿深度为9.5~14.6 km。流体包裹体测温、激光拉曼光谱分析与石英微量元素特征表明,成矿流体为中高温、低盐度、中低密度的CO₂-H₂O-NaCl±CH₄体系,且具有相对还原性的特点。主成矿阶段石英的δD_V-SMOW值为-100.2‰~-75.6‰,δ¹⁸ {\mathrm{O}}_{{\mathrm{H}}_2\mathrm{O}} 值为+4.15‰~+8.31‰,主成矿阶段流体以变质水为主,流体不混溶作用是金富集成矿的重要机制。综合分析认为,小西弓金矿床为中深成造山型金矿床。     

Faulting in the Mikawa earthquake of 1945

This paper discusses the fault parameters of the Mikawa earthquake of January 12, 1945 on the basis of a simple dislocation model. Basically, the model assumes a rectangular shape of the fault plane striking N-S, so that it may fit the observed surface fault trace. Several sets of the fault parameters are tested to interpret the vertical and horizontal ground movements as observed geodetically. The fault model which is finally accepted is as follows: total length: 12 km; width: 11 km; dip angle: 30°; reverse dip-slip: 2 m; right-lateral strike-slip: 1 m. Geometry and slip in the present model seem to harmonize with the other sorts of evidence such as the seismological, tsunami genetic and reconnaissance data. From the tectonic point of view, this earthquake may be attributed to the secondary fault activity associated with the right lateral movement of the Median Tectonic Line.     

Unravelling the evidence of climatic change

Book reviewed in this article:
Mörner, N-A. & Karlén, W. (eds.) 1984: Climatic Changes on a Yearly to Millennial Basis .     

四川巴塘县茶洛地区温泉及间歇喷泉水化学特征和成因分析

温泉的水化学和成因研究对地热资源的开发利用有重要意义。四川巴塘县茶洛温泉的分布受茶洛—松多断层带的控制,沿北东—南西向的河流两岸出露,附近出露三叠系灰岩、砾岩和燕山期花岗岩。在温泉区出露有近20个泉眼,对其中10个泉眼进行采样测试。受出露点冷水混入的影响,东北部的两个泉眼温度为45~51 ℃,中西部地区的泉眼温度为77~89 ℃,部分为沸泉泉眼;各泉眼流量为0.01~1.8 L/s;pH值为6.1~8.1,矿化度为0.39~1.06 g/L,F^-含量为15~22 mg/L,偏硅酸含量为69~356 mg/L。泉水主要阳离子为Na⁺、K⁺和Ca²⁺,主要阴离子为 {\mathrm{CO}}_3^{2-}、 {\mathrm{HCO}}_3^{-}、Cl^-和 {\mathrm{SO}}_4^{2-},水化学类型为HCO₃-Na型。氢氧同位素数据表明,研究区地下热水来源于大气降水,补给高程约为4 400~4 800 m,补给区年均气温在-10 ℃左右。利用SiO₂温标估算茶洛温泉热储层温度约为150~200 ℃,热水循环深度约为2 810~3 480 m。茶洛温泉为大气降水入渗后在地下深循环过程中被大地热流加热,再沿断层带在河谷涌出地表而形成的温泉。在河流西北岸分布有灰岩,地下水溶蚀形成空洞,来自浅处的冷水和来自深部的热水在空洞中混合并被加热至沸点,导致热水间歇性上升喷出地面,形成间歇喷泉。     

Reinforcement with Geosynthetics of Walls of the Saltpans of the Aveiro Lagoon

The aim of this article is to investigate the solution for the reinforcement of the walls of the saltpans of the Aveiro lagoon by using geosynthetics. For that purpose literature research has been done to collect both the properties and the geometry of the walls and of the soils. Simultaneously, methods for the design of reinforced soils using geosynthetics were collected, particularly to allow the consideration of two types of backfill soil: granular and fine. So, two solutions for such walls were studied using granular and fine soils, respectively. The design methods used were the ones proposed by: Jewell (1996) and Rogbeck et al. (2002) for granular soils and Naughton et al. (2001) for fine soils. Finally, the verification of the external stability of the profiles of a selected wall has been made using the methodology described in Eurocode 7: EN1997-1: 2004.     

Research and Understanding of the Evolution of the Yellow River Valley in Lanzhou

As the turning point of the Yellow River flowing from the Tibetan Plateau to the Loess Plateau, the valley evolution of Lanzhou Basin is of great significance to the study of the evolution of the Yellow River system in different geomorphic units. The evolution of the Yellow River Valley in Lanzhou has been studied for nearly 100 years. In the process of research, important research results and understandings have been obtained as follows: \mathrm{①} The denudation surface develops above the Yellow River Valley in Lanzhou Basin, and the broad and continuous 9-level terrace develops in the valley. The age of the denudation surface and 9-level Yellow River terrace was systematically determined by using a variety of dating techniques. \mathrm{②} The development pattern of the strath terraces of the Yellow River in Lanzhou was put forward. Under the background of long-term ground uplift, climate change controls the age of terrace formation, and the rate of uplift affects the number of terrace. \mathrm{③} The age of the highest terrace of the Yellow River in the basins from Lanzhou to the upper reaches of the Yellow River is gradually younger. It is revealed that the formation of the present pattern in the upper reach of the Yellow River is the result of the headward erosion from Lanzhou Basin and the drainage intergration of the internal flow basin. At the same time, the chronology of terrace sequence still needs to be deepened, the characteristics of regional tectonic uplift and deformation are lack of direct evidence, the development pattern of terrace needs to be verified by model simulation, the geomorphic response of drainage change is not clear, and the river process recorded by the deposition of terrace flood plain is lack of attention. All those issues will be the focus of future research.     

Mineral equilibrium constraints on the feasibility of diffusive H2O-fluxed melting in the continental crust

Generation of granitic melt is believed to occur predominantly by melting through the breakdown of hydrous minerals. However, melting due to the influx of H₂O has been recognized in anatectic amphibolite facies tonalitic grey gneisses, metagreywackes and low-P metapelites, and has consequently been proposed as an alternative mechanism for the generation of granitic melt. Melting induced by H₂O addition is recognized from voluminous melt production at relatively low temperature, where hydrous minerals are stable and anhydrous minerals are preferentially consumed during melting. Mineral equilibrium modelling to determine the P–T conditions, melt volumes, melting reactions and viable H₂O sources reveals that the process is not restricted to specific compositions or P–T conditions, although lower pressure and lithologies with a low hydrous mineral content are more favourable. Melting reactions in all lithologies primarily consume quartz and feldspars to yield 5–6 mol.% melt for each mol.% of H₂O added. remains constant at ~0.70 to 0.77 during progressive melting as long as alkali feldspar is present. Once alkali feldspar is exhausted, plagioclase becomes the main reactant, producing more tonalitic melt compositions with gradually higher . Our results demonstrate that, at the site of melting, melting is driven by diffusion of H₂O into the target rock along chemical potential gradients, rather than the advective flow of a mechanically distinct water-rich fluid phase. Melting will initiate and proceed as long as a gradient exists between the H₂O source and target lithology. Our calculations show that an ordinary magma, such as an I-type magma with typical H₂O content, has a high enough to be a viable H₂O source, allowing diffusive H₂O-fluxed melting to produce melt proportions and fertility comparable to that of dehydration melting. However, high degrees of partial melting require a considerable amount of H₂O, which necessitates a continuously advecting H₂O source such as a magma conduit or melt-bearing shear zone. A magmatic H₂O source at emplacement level will undergo a similar amount of crystallization as the melt fraction produced in the target rock such that there will be no net melt production. Considering that shear-zone hosted magma conduits are localized features, diffusive H₂O-fluxed melting is likely to only be viable in a small fraction of the anatectic orogenic crust. Although it may play an important role in locally raising melt volumes and modifying magma chemistry through mingling and hybridization, it does not appear to, of itself, be able to generate significant volumes of granitic melt.