运用碳稳定同位素进行底栖生物组合环境古盐度的比较研究

从葡萄牙卢西塔尼亚盆地侏罗纪生物底栖组合的化石中选取了５４件样品用作碳稳定同位素成分测试，分析其古盐度。按这种方法所恢复的古盐度数据和按底栖组合分析所得到的古盐度能够较好地吻合，由此可作下列结论：（１）尽管化石壳体的原始稳定同位素值可能会受到成岩作用、生物效应、温度差异等因素的影响，但碳稳定同位素值与氧同位素值相比，其重结晶作用产生的成岩影响很小，生物效应却是非常明显地表现于双壳类壳顶区和壳缘的碳同位素值的差异。（２）碳同位素的古盐度表明，葡萄牙卢酉塔尼亚盆地在侏罗纪时曾是一半咸水海湾，其水体含盐度低于２４‰。，所以生物组合中以机会种和半咸水地方性种占优势。（３）机会种分布于中盐至高半咸水的盐区域，而大部分地方性半咸水种局限于中盐度域．（４）卢西塔尼亚盆地晚侏罗世的牡蛎类生存于真盐和高半成水域，定量的盐度研究可能提供牡蛎类自中生代以来对盐度的适应演化。（５）卢西塔尼亚盆地晚侏罗世双壳类虽然属于半咸水属种，但仍然具有厚壳体大的特征。     

The role of precursor emissions on ground level ozone concentration during summer season in Poland

Three online coupled chemical transport model simulations were analyzed for three summer months of 2015 in Poland. One of them was run with default emission inventory, the other two with NO_x and VOC emissions reduced by 30%, respectively. Obtained ozone concentrations were evaluated with data from air quality measurement stations and ozone sensitivity to precursor emissions was estimated by ozone concentration differences between simulations and with the use of indicator ratios. They were calculated based on modeled mixing ratios of ozone, total reactive nitrogen and its components, nitric acid and hydrogen peroxide. The results show that the model overestimates ozone concentrations with the largest errors in the morning and evening, which is primarily related to the way vertical mixing is resolved by the model. Better model performance for ozone is achieved in rural than urban environment, as PBL and mixing mechanisms play more significant role in urban areas. Modeled ozone shows mixed sensitivity to precursor concentrations, similarly to other European regions, but indicator ratios have different values than are found in literature, particularly H₂O₂/HNO₃ is larger than in southern Europe. However, indicator ratios often differ between locations and transition values need to be established individually for a given region.     

LA-ICP-MS study of apatite- and K feldspar-hosted primary carbonatite melt inclusions in clinopyroxenite xenoliths from lamprophyres, Hungary: Implications for significance of carbonatite melts in the Earth’s mantle

We report the results of LA-ICP-MS analyses of rock forming minerals in clinopyroxene-apatite-K feldspar-phlogopite (CAKP) metasomatic xenoliths and primary carbonatite melt inclusions (CMI) hosted in apatite (Ap) and K feldspar (Kfs). The xenoliths are from the Cretaceous lamprophyre dikes of the Transdanubian Central Range, Hungary. The CMI in Ap have phosphorus dolomitic composition as opposed to CMI in Kfs, which display dolomitic alkali-aluminosiliceous character. The melts found in CMI in Ap and in Kfs likely formed by liquid-liquid separation from an originally carbonate- and phosphorous-rich melt. Primitive mantle (PM) normalized trace element distributions of both Ap- and Kfs-hosted CMI (n = 60 and 20, respectively) reveal a strong negative Ti-anomaly, and an extreme enrichment in incompatible elements (U, Th, LILE and LREE) relative to HREE, Sc, V, Ni and Cr. Rarely, apatites contain unique CMI, which show major- and trace-element signature transitional to K feldspar-hosted CMI. This is due to heterogeneous entrapment of an immiscible phosphorous-bearing carbonatite melt and a carbonate-bearing alkali aluminosiliceous melt, which is a further evidence for their co-existence. CMI reveal that U, Th, Pb, Nb, Ta, P, Sr, Y and REE partitioned into the phosphorous-bearing carbonatite melt, whereas Cs, Rb, Na, K, B, Al, Zr and Hf preferred the silicate-bearing liquid.PM normalized REE pattern (high LREE/HREE), elevated Zr and Hf contents and negative Ti anomaly of clinopyroxene (Cpx) indicate that its formation is genetically linked to carbonatite metasomatism attested by CMI. Trace element partitioning between the studied Cpx and CMI is in accordance with experimentally determined trace element distributions between Cpx and carbonatite melt. Cpx, which occur in samples with high modal proportion of apatite represent mantle section, which interacted with a higher amount of “initial” carbonatite melt than Cpx from apatite-poor xenoliths. This is confirmed by higher Cr, Ni, V, Sc, Ti and lower Zr, as well as Hf concentration in Cpx from xenoliths with low modal abundance of Ap. CMI reveal that Ti, V, Ni and Cr were in lower concentration in the “initial” carbonatite melt than in PM. Contrarily, Zr and Hf were more abundant in this melt than in PM. Consequently, a continuously migrating “initial” carbonatite melt, increased Zr and Hf concentration, and decreased Ti, Sc, V, Ni and especially Cr in the clinopyroxenes. Our findings suggest that the studied CAKP rocks were formed by carbonatite melt metasomatism, which occurred in an open system in the upper mantle.     

The solid angle hidden in polyhedron gravitation formulations

Formulas of a homogeneous polyhedron’s gravitational potential typically include two arctangent terms for every edge of every face and a special term to eliminate a possible facial singularity. However, the arctangent and singularity terms are equivalent to the face’s solid angle viewed from the field point. A face’s solid angle can be evaluated with a single arctangent, saving computation.     

Time evolution of chemical exchanges during mixing of rhyolitic and basaltic melts

We present the first set of chaotic mixing experiments performed using natural basaltic and rhyolitic melts. The mixing process is triggered by a recently developed apparatus that generates chaotic streamlines in the melts, mimicking the development of magma mixing in nature. The study of the interplay of physical dynamics and chemical exchanges between melts is carried out performing time series mixing experiments under controlled chaotic dynamic conditions. The variation of major and trace elements is studied in detail by electron microprobe and Laser Ablation ICP-MS. The mobility of each element during mixing is estimated by calculating the decrease in the concentration variance in time. Both major and trace element variances decay exponentially, with the value of exponent of the exponential function quantifying the element mobility. Our results confirm and quantify how different chemical elements homogenize in the melt at differing rates. The differential mobility of elements in the mixing system is considered to be responsible for the highly variable degree of correlation (linear, nonlinear, or scattered) of chemical elements in many published inter-elemental plots. Elements with similar mobility tend to be linearly correlated, whereas, as the difference in mobility increases, the plots become progressively more nonlinear and/or scattered. The results from this study indicate that the decay of concentration variance is in fact a robust tool for obtaining new insights into chemical exchanges during mixing of silicate melts. Concentration variance is (in a single measure) an expression of the influence of all possible factors (e.g., viscosity, composition, and fluid dynamic regime) controlling the mobility of chemical elements and thus can be an additional petrologic tool to address the great complexity characterizing magma mixing processes.     

Influences of physical structures on urban energy budgets

Four typical urban surroundings were modelled, ranging from high-rise structures to low buildings and combinations thereof. These building systems were exposed to typical summer and winter climatic scenarios for latitudes 10, 34, and 50 N. Systematic variations of interior building temperatures were also introduced. The resultant changes in the components of the systems' energy budgets were examined with respect to cause and effect. The simulations produced a variety of unexpected features which intuitively had not been anticipated. It is believed that energy budget features of real cities cannot vary drastically from those simulated, and described in this report.     

Morphology and geological structure of the western part of the Olympus Mons volcano on Mars from the analysis of the Mars Express HRSC imagery

The images of the western part of Olympus Mons and adjacent plains acquired by the HRSC camera onboard the Mars Express spacecraft were studied. The morphology, topography, and color of the surface were investigated. The surface age was determined by the frequencies of impact craters. The examination of the HRSC images combined with an analysis of the MOC imagery and MOLA altitude profiles have shown that the Olympus Mons edifice, at least in its western part, is composed of not only lavas but also of sedimentary and volcanic-sedimentary rocks consisting of dust, volcanic ash, and, probably, H₂O ice that precipitated from the atmosphere. These data also indicate that glaciations, traces of which are known on the western foot of Olympus Mons (Lucchitta, 1981; Milkovich and Head, 2003), probably also covered the gentle upper slopes of the mountain. It is probable that the ice is still there, protected from sublimation by a dust blanket. Confirming (or rejecting) its presence is a challenge for the scheduled radar sounding with the MARSIS instrument mounted on the Mars Express spacecraft as well.__________Translated from Astronomicheskii Vestnik, Vol. 39, No. 2, 2005, pp. 99–116.Original Russian Text Copyright © 2005 by Basilevsky, Neukum, Ivanov, Werner, S. van Gesselt, Head, Denk, Jaumann, Hoffmann, Hauber, McCord, the HRSC Co-Investigator Team.     

Intra-event characteristics of extreme erosive rainfall on Mauritius

Mauritius is a volcanic island with a raised interior where extreme rainfall events dominate rainfall erosivity. Intra-event characteristics of the 120 highest erosive events at six selected locations between 2004 and 2008 were analyzed to provide the first detailed intra-storm data for a tropical island environment. On Mauritius, spatial variation is evident in the characteristics of extreme erosive rainfall recorded at the stations, with a noticeable increase in rainfall depth, duration, kinetic energy, and erosivity of extreme events with altitude. Extreme events in the raised interior (central plateau) show high variability of peak intensity over time as well as a higher percentage of events in which the greatest intensity occurs in the latter part of the event. Intra-event distribution of rainfall in the interior of the island shows that rainfall there has a higher potential to exceed infiltration rates as well as the ability to generate high peak runoff rates and cause substantial soil loss. The study suggests that even though within-event rainfall characteristics are complex, they have implications for soil erosion risk, and that, in tropical island environments, the within-storm distribution of rainfall should be incorporated in soil-loss modeling.