内蒙古太平川铜钼矿成矿斑岩时代、地球化学及地质意义

内蒙古太平川Cu-Mo矿床位于得尔布干成矿带北段额尔古纳地区,为新近发现的斑岩型矿床。矿区内发育环带状热液蚀变,由内向外主要为硅化-绢云母化和泥化。热液蚀变围绕花岗闪长斑岩分布,Cu-Mo矿化主要受控于硅化-绢云母化蚀变,主要分布在花岗闪长斑岩中。本文获得成矿斑岩岩浆锆石U-Pb谐和年龄为202±5.7Ma,指示该矿床可能形成于晚三叠世。同时在样品中也发现继承锆石(784Ma),表明该地区可能存在晚元古基底。成矿斑岩的元素地球化学数据表明,主量元素SiO2(65.86%～68.84%)56%、Al2O3(15.18%～16.28%)15%、MgO(0.84%～1.06%)3%、Na2O/K2O1;微量元素亏损重稀土,Sr(471×10-6～513×10-6)400×10-6、Y(15.0×10-6～17.9×10-6)18×10-6、Yb(1.27×10-6～1.81×10-6)1.9×10-6,表明该花岗闪长斑岩具有明显的埃达克质岩石的地球化学特征。同时成矿斑岩具有相对高的SiO2、Yb含量和Th/Nb、Ce/Nb比值,而相对低的Al2O3、TiO2、MgO、Sr、Th含量和Th/Ce比值,这些特征与源于俯冲板片的埃达克岩相似。然而成矿斑岩(87Sr/86Sr)i(0.70943～0.71019)较大,εNd(t)为-3.4～-3.9,我们推测额尔古纳地块在岩浆上升过程中贡献了部分物质。结合区域构造演化,我们认为该矿区成矿斑岩岩浆形成于俯冲洋壳的部分熔融,矿床形成背景为早中生代蒙古-鄂霍茨克洋向额尔古纳地块俯冲的陆缘弧环境。     

Particle size distributions in Saturn's rings from voyager 1 radio occultation

Observations of microwave opacity τ[λ] and near forward scatter from Saturn's rings at wavelengths λ of 3.6 and 13 cm from the Voyager 1 ring occultation experiment contain information regarding ring particle sizes in the range of about a = 0.01 to 15 m radius. The opacity measurements τ[3.6] and τ[13] are sufficient to constrain the scale factor n(a₀) and index q of a power law incremental size distribution n(a) = n(a₀)[a₀/a]^q, assuming known minimum and maximum sizes and a many-particle-thick model. The families of such distributions are highly convergent in the centimeter-size range. Forward scatter at 3.6 cm can be used to solve for a general distribution over the radius range $\text{1 ? a ? 15}\text{m}$ by integral inversion and inverse scattering methods, again assuming a many-particle-thick slab-type radiative transfer model. Distributions n(a) valid over $\text{0.01 ? a ? 15}\text{m}$ are obtained by combining the results from the two types of measurements above. Mass distributions may be computed directly from n(a). Such distributions, partly measured and partly synthesized, have been obtained for four features in the ring system centered at 1.35, 1.51, 2.01, and 2.12 Saturn radii (R_s). The size and mass distributions both cut off sharply at a ? 4–5 m; the mass distribution peaks over the narrow size range $\text{3 ? a ? 4}\text{m}$ for all four locations. No single power law distribution is consistent with the data over the entire interval $\text{0.01 ? a ? 5}\text{m}$, although a power law-type model is consistent with the data over a limited size range of $\text{0.01 ? a ? 1}\text{m}$, where the indices q = 3.4 and 3.3 are obtained from the slab model for the features located at 1.51 and 2.01 R_s. The fractional contribution of the suprameter particles to the microwave opacity in each feature appears to be about $\text{1}\text{3}\text{,}\text{1}\text{3}\text{,}\text{2}\text{3}\text{,}\text{and}\text{1}$, respectively, with the fraction at 2.12 R_s being the least certain. The cumulative surface mass per unit area obtained for the classical slab model is approximately 11, 16, 41, and 132 g/cm² for the four features, respectively, if the particles are solid H₂O ice. Both the fractional opacity and the mass density estimates represent upper bounds implied by the assumption of a uniformly mixed set of particles in a many-particle-thick vertical profile; lower estimates would result if the rings were assumed to be nearly a monolayer or if the vertical distribution of particles were size dependent.     

Analysis of fossil pigments from algae and bacteria in meromictic Lake Fidler, Tasmania, and its application to lake management

Lake Fidler is an ectogenic meromictic lake with a monimolimnion maintained by periodic incursions of brackish water from the lower Gordon River estuary. A dam across the middle reaches of the Gordon River has restricted these incursions of brackish water and meromictic stability has rapidly declined. A palaeolimnological study was carried in order to assess the historical development of meromixis and the impact of the dam on the microbiological communities in the lake. Fossil pigments in a 17 m sediment core were analysed using reverse phase high performance liquid chromatography (rp-HPLC) and mass spectrometry (MS). In addition, taphonomic studies of pigment production, deposition and degradation in the water column and surface sediments were used to identify planktonic and benthic pigment degradation processes and constrain the stratigraphic interpretation. Results comparing the pigment composition of pelagic sediment traps and littoral surface sediments indicated that the core from the centre of the lake would permit a historical reconstruction of planktonic bacterial and algal communities. Marked increases in prokaryotic pigments ca 3500 yr B.P. suggested the possible colonisation of a chemocline by phototrophic bacteria. Further changes in chlorophyll: carotenoid ratios and changes in relative abundances of both chlorophyll a and bacteriochlorophyll c derivatives also indicated that a change in the depositional environment had occurred; possibly due to altered stratification or anoxia. From this we infer the onset of either intermittent or permanent meromixis. Further increases in prokaryotic pigment abundance suggested that the present state of permanent meromixis was firmly established by 2070 ±50 ¹⁴C yr B.P., and diatom analysis confirmed the development of a stable mixolimnion. High resolution studies of the top 10 cm of sediments measured pigments in mean concentrations of 15.1 ng g^-1 with a mean S.D. of only 2.78 indicating little change in pigment abundance since the construction of the dam. Thus, Lake Fidler still retains most of the features of meromixis. However, evidence from nearby Lake Morrison and Sulphide Pool has shown that any further declines in meromictic stability will cause a rapid reversion to holomixis. Palaeolimnological evidence from the early stages of meromictic development of Lake Fidler suggests that such reversion to holomixis may not permanently eliminate all the microbiological communities, and that, given time, they may return and prosper with re-establishment of a suitable chemocline. These studies will guide recommendations for a management strategy to prevent the further decay of meromixis in the Gordon River lakes.     

Comparison of Quasi-specular radar scatter from the moon with surface parameters obtained from images

Quasi-specular radar data used to determine apparent surface roughness σ_χ of geologic surfaces displays a variable wavelength λ dependence ranging between $\text{σ}{}_{\mathrm{\chi }}\text{～ λ}{}^0\text{and}\text{σ}{}_{\mathrm{\chi }}\text{～ λ}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>3</mtext>}}$ for $\text{0.01 ? λ ? 1}\text{m}$. The strongest changes in σ_χ with wavelength are observed in lunar mare, while scatter from lunar highlands is nearly wavelength independent. Commonly used, gently undulating surface models for electromagnetic scatter predict no wavelength dependence. Wavelength dependence occurs whenever a significant fraction of the surface has local radii of curvature comparable to the observing wavelength. This condition can be determined by comparison of the value of the integrated surface curvature spectrum with the radar wavenumber, multiplied by a constant that depends on the geometry. Variations in curvature statistics calculated from photogrammetric reduction of lunar images are consistent with the observed variations in quasi-specular scatter between λ = 13 and 116 cm at the same locations. Variations in the strength of the wavelength dependence are correlated with the sizes of lunar craters that lie near the upper size limit for the local steady-state distribution. This correlation is also consistent with variations in the curvature spectrum calculated from crater size-frequency distributions.     

Specification of a Coupled Geological and Wellbore Fluid Dynamics Model for Uncertainty Analysis and Risk-Based Design on a Subsea Oil Project

This paper describes the method and results of a probabilistic risk analysis that was used to provide a quantitative basis for a complex and high-stakes design decision for a subsea oil project. Geologic properties were specified as probability density functions based on information from a small number of exploration and appraisal wells. The geological information was coupled to a wellbore fluid dynamics model to simulate operational outcomes for potential well kill operations. Conventional probabilistic sampling and a more efficient experimental design approach were both employed. The key results are cumulative density functions for critical bases of design that are used for risk analysis and final equipment selection. The analysis reinforces the importance of interdisciplinary collaboration, in this case the subsurface disciplines and well engineering, to achieve efficient risk-based designs.     

Lipid Partitioning in the Hydrothermal Vent Shrimp Rimicaris exoculata

Abstract. This study examines the composition and partitioning of lipids in the alvinocarid shrimp Rimicaris exoculata from Mid-Atlantic hydrothermal vents. Juveniles and adults at different stages of reproductive development were dissected into abdomen, branchial and ovary/hepatopancreas tissues. Each of these tissues was analysed for total lipid and lipid class composition, and fatty acids and fatty alcohols were identified using GC and GC-MS. Adult and juvenile shrimp differ in the partitioning of lipids between tissues. Juveniles store lipids in the abdomen as wax ester droplets and may use phosphatidyl choline as an additional reserve. Adult shrimp use triglycerides as an energy store, and triglycerides and polar lipids accumulate in ovary and hepatopancreas tissue during reproductive development. The wax ester storage droplets of juvenile shrimp contain high concentrations of n-3 fatty acids, which are photosynthetically-derived and thought to be important for reproductive development in crustaceans. These n-3 fatty acids are concentrated in the ovary and hepatopancreas of adults compared to other tissues. The n-3 fatty acid content of these adult tissues is well within that estimated for whole juvenile shrimp, supporting the hypothesis that the n-3 fatty acids putatively required for adult reproduction are stored from the juvenile stage.     

Spatial,seasonal, and source variability in the stable oxygen and hydrogen isotopic composition of tap waters throughout the USA

To assess spatial, seasonal, and source variability in stable isotopic composition of human drinking waters throughout the entire USA, we have constructed a database of δ¹⁸O and δ²H of US tap waters. An additional purpose was to create a publicly available dataset useful for evaluating the forensic applicability of these isotopes for human tissue source geolocation. Samples were obtained at 349 sites, from diverse population centres, grouped by surface hydrologic units for regional comparisons. Samples were taken concurrently during two contrasting seasons, summer and winter. Source supply (surface, groundwater, mixed, and cistern) and system (public and private) types were noted. The isotopic composition of tap waters exhibits large spatial and regional variation within each season as well as significant at‐site differences between seasons at many locations, consistent with patterns found in environmental (river and precipitation) waters deriving from hydrologic processes influenced by geographic factors. However, anthropogenic factors, such as the population of a tap's surrounding community and local availability from diverse sources, also influence the isotopic composition of tap waters. Even within a locale as small as a single metropolitan area, tap waters with greatly differing isotopic compositions can be found, so that tap water within a region may not exhibit the spatial or temporal coherence predicted for environmental water. Such heterogeneities can be confounding factors when attempting forensic inference of source water location, and they underscore the necessity of measurements, not just predictions, with which to characterize the isotopic composition of regional tap waters. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.     

Lessons from co-impacts assessment under the Mitigation Action Plans and Scenarios (MAPS) Programme

The MAPS Programme has been active in Brazil, Chile, Colombia and Peru in supporting the development of an evidence base to inform the processes involved in climate mitigation policy-making. The programme combines detailed quantitative analysis with an extensive stakeholder engagement process to provide policy and decision makers with the information required for long-term climate mitigation planning.

In recognition of the critical need to consider the developmental context and agenda in climate policy-making, the projects undertaken in these countries have experimented with various types of assessments of developmental impacts at both the macro and micro levels. These impacts have been collectively termed co-impacts to reflect the fact that these may be either positive or negative. In this article the value and challenges associated with co-impacts work for climate mitigation policy are considered. The value of including co-impacts analysis in the MAPS processes included increased stakeholder buy-in, making the case for mitigation action, informing INDCs and the prioritization of particular mitigation actions. Challenges include those associated with obtaining locally relevant data, the selection and operation of appropriate macro-economic models and analytical approaches and working with multidisciplinary teams.

The article concludes by making some suggestions to optimize co-impacts work, through reference to other bodies of literature. The authors highlight that this article is situated within a dominant approach to climate mitigation policy work in developing countries, which implicitly places the non-climate benefits of any action as secondary to the primary benefit of climate change mitigation and constructs an artificial separation of policy formulation and implementation. Practitioners are encouraged to reflect on the implications of these considerations in future efforts.

Policy relevance

One of the primary challenges to advancing climate mitigation policy in developing countries is that of perceived relevance: near-term development priorities are overwhelming. Identifying, understanding and engaging with the co-impacts of mitigation actions has emerged as one way of addressing this challenge. Although still at an experimental phase, experience with co-impacts analysis in the MAPS countries provides some useful lessons in how to develop this area of work.