The Chelyabinsk meteorite: New insights from a comprehensive electron microscopy and Raman spectroscopy study with evidence for graphite in olivine of ordinary chondrites

We present results of petrographic, mineralogical, and chemical investigations of three Chelyabinsk meteorite fragments. Three distinct lithologies were identified: light S3 LL5, dark S4–S5 LL5 material, and opaque fine-grained former impact melt. Olivine–spinel thermometry revealed an equilibration temperature of 703 ± 23 °C for the light lithology. All plagioclase seems to be secondary, showing neither shock-induced fractures nor sulfide-metal veinlets. Feldspathic glass can be observed showing features of extensive melting and, in the dark lithology, as maskelynite, lacking melt features and retaining grain boundaries of former plagioclase. Olivine of the dark lithology shows planar deformation features. Impact melt is dominated by Mg-rich olivine and resembles whole-rock melt. Melt veins (<2 mm) are connected to narrower veinlets. Melt vein textures are similar to pegmatite textures showing chilled margins, a zone of inward-grown elongated crystals and central vugs, suggesting crystallization from supercooled melt. Sulfide-metal droplets indicate liquid immiscibility of both silicate and sulfide as well as sulfide and metal melts. Impact melting may have been an important factor for differentiation of primitive planetary bodies. Graphite associated with micrometer-sized melt inclusions in primary olivine was detected by Raman mapping. Carbon isotopic studies of graphite could be applied to test a possible presolar origin.     

Assessment of runoff,water and sediment quality in the Selenga River basin aided by a web-based geoservice

The Selenga River is the main artery feeding Lake Baikal. It has a catchment of ~450000 km² in the boundary region between Northern Mongolia and Southern Siberia. Climate, land use and dynamic socioeconomic changes go along with rising water abstractions and contaminant loads originating from mining sites and urban wastewater. In the future, these pressures might have negative impacts on the ecosystems of Lake Baikal and the Selenga River Delta, which is an important wetland region in itself and forms the last geobiochemical barrier before the Selenga drains into Lake Baikal. The following study aims to assess current trends in hydrology and water quality in the Selenga-Baikal basin, identify their drivers and to set up models (WaterGAP3 framework and ECOMAG) for the prediction of future changes. Of particular relevance for hydrological and water quality changes in the recent past were climate and land use trends as well as contaminant influx from mining areas and urban settlements. In the near future, additional hydrological modifications due to the construction of dams and abstractions/water diversions from the Selenga’s Mongolian tributaries could lead to additional alterations.     

The modified generalized moveout approximation: a new parameter selection

Non‐hyperbolic generalised moveout approximation is a powerful tool to approximate the travel‐time function by using information obtained from two rays. The standard approach for parameter selection is using three parameters defined from zero‐offset ray and two parameters obtained from a reference ray. These parameters include the travel time and travel‐time derivatives of different order. The original parameter selection implies more fit at zero offset compared with offset from a reference ray. We propose an alternative approach for parameter selection within the frame of generalised moveout approximation by transferring more fit from the zero offset to a reference ray by changing in parameter selection. The modified approximation is tested against the original one in few analytical model examples, including the multi‐layered model.     

Archaean Kuru-Vaara eclogites in the northern Belomorian Province,Fennoscandian Shield: crustal architecture,timing, and tectonic implications

This paper addresses the relationships between relic amphibole-eclogite facies (AE) eclogites and their host units, Archaean amphibolites, enveloped by Archaean tonalite–trondhjemite–granodiorite (TTG) gneisses, in the Kuru-Vaara study area in the northern Belomorian Province. According to observational constraints, the crystallization of the relic peak omphacite + Mg-garnet ± kyanite assemblage and the subsequent replacement of omphacite by clinopyroxene–plagioclase symplectite occurred before the earliest deformational, metamorphic, and migmatization events that are recorded in the amphibolites. The amphibolites and their TTG hosts have a shared deformational and metamorphic history that is composed of the Archaean and Palaeoproterozoic periods. This history favours the conclusion that the AE metamorphism recorded in the relic eclogites within the amphibolites occurred during the Mesoarchaean to Neoarchaean periods. The deformation and metamorphism of the amphibolite facies of the second period resulted from the Lapland–Kola collisional orogeny at 1.91–1.93 Ga, which led to eclogite–high-pressure granulite (E–HPG) facies conditions in the lowermost portions of the over-thickened crust in Belomorian Province (the southwestern foreland of the Lapland–Kola collisional orogen). The Palaeoproterozoic E–HPG overprint was reported from the Palaeoproterozoic Gridino mafic dikes. Although the ages of the oldest low Th/U zircons are close to the time of the Lapland–Kola collision, the low Th/U 1.9–1.8 Ga zircons reflect a zircon response to regional fluid infiltration in the eclogites during slow exhumation following the Lapland–Kola orogeny and do not record any metamorphic event. Contrary to the Palaeoproterozoic E–HPG overprint, the areal occurrence of the 2.7–2.8 Ga AE eclogites with mid-ocean ridge basalt-like chemistry and their paragenetic link with the TTG gneisses suggest a tectonic regime that involves subduction. This research favours concepts suggesting that the modern-style plate tectonics has operated in some places, at least since the late Mesoarchaean.     

A fast algorithm for 3D azimuthally anisotropic velocity scan

The conventional velocity scan can be computationally expensive for large‐scale seismic data sets, particularly when the presence of anisotropy requires multiparameter scanning. We introduce a fast algorithm for 3D azimuthally anisotropic velocity scan by generalizing the previously proposed 2D butterfly algorithm for hyperbolic Radon transforms. To compute semblance in a two‐parameter residual moveout domain, the numerical complexity of our algorithm is roughly as opposed to of the straightforward velocity scan, with N being the representative of the number of points in a particular dimension of either data space or parameter space. Synthetic and field data examples demonstrate the superior efficiency of the proposed algorithm.     

Precursors of Copepod Abundance in the Gulf of Maine in Atmospheric Centers of Action and Sea Surface Temperature

Interannual variations of total copepod abundance in the Gulf of Maine (1961-1991) are analyzed and related to the semi-permanent atmospheric pressure systems: Icelandic Low (IL) and the Azores High (AH). These centers of action dominate atmospheric and oceanic circulation in the North Atlantic. Cross-correlation analysis of zooplankton, sea surface temperature (SST) and the atmospheric characteristics have revealed different (from one to three years) time lags between the above characteristics. A multiple stepwise regression analysis gave a correlation value of 0.7 between observed and predicted interannual changes of total copepod abundance. A discussion is included of possible mechanisms that may contribute to the dynamic links that transfer atmospheric variation into observed changes in zooplankton abundance.     

An Investigation of the Reliability of HF Acid Mixtures in the Bomb Digestion of Silicate Rocks for the Determination of Trace Elements by ICP‐MS

The influence of the mixtures HF‐HNO₃ and HF‐NH₄F‐HNO₃ in bomb digestion for trace element determination from different rock types was studied using ICP‐MS. It is shown that the HF concentration, not the ratio of reagents in the decomposing mixture, controls the digestion process of a rock. Data for Zr in the granite G‐2 as a function of HF concentration gave the same results as reaction mixtures of various compositions. A complete digestion in 50‐mg sample bombs was achieved by 1.0 ml of HF alone, or with a mixture of other acids at a HF concentration of at least 35% m/m at 196 °C over 18 h. The results of the analysis of basalts BCR‐1, BIR‐1, mica schist SDC‐1, shale SBC‐1, granites G‐2, SG‐1A, garnet‐biotite plagiogneiss GBPg‐1, rhyolite RGM‐1, granodiorite GSP‐1, trachyandesite MTA‐1 and rhyolite MRh‐1 are given and compared against available data. The reproducibility of the element determinations by ICP‐MS and XRF as an independent non‐destructive analysis for a quality check in the range of concentrations typical for routine rock samples is given.     

综合数字区域模型和大范围有机废弃产品处理的测试系统的开发

综合数字区域模型在区域可持续发展的任何模型实现中都是不可或缺的,而空间数据基础设施为综合数字区域模型提供了一个可靠的基础。其可以很方便地在地图信息或者直接在地理信息系统(GIS)内形成。这种GIS系统具有开发良好的模型函数,能够集成专家系统,也能被设计全尺度多媒体产品。GIS允许集成不同的信息资源、模型、可视化和分析、各种假设的详尽细节和为诸如自然-社会-经济等的复杂系统提供可选开发方案。一个综合辅助信息系统的结构包括紧密相关的社会-政治、经济(或生产)、自然资源和环境模块。它提供了对于不同区域范围社会生态系统的全面描述,显示了自然和人类资源的重要性。人们在这个研究领域将会谈及自然和社会管理。根据它们的变化层次体系(从全局范围到局部范围)可以描述所有专题,并且考虑在不同尺度上描述的现象的专业特征。超媒体系统原理可以通过链接集成主题来实现。这种系统的日益复杂性使得系统的智能化成为必要,专家系统和神经元网络可以从很复杂并且非常模糊的问题中得出可行的解决方案。现代GIS配有很多设备,对用户来说,这使得用基础地图和互联网获取必要的数据来编制专题图成为可能。数学建模的专业方法具有特殊的重要性,特别是那些旨在追求在区域变换到可持续发展模型时设想的详尽细节的方法。最高级的AIS能作为全尺度的决策支持系统使用。莫斯科国立大学试图实现上述思想,开发了俄罗斯可持续发展信息系统框架,特以俄罗斯南部地区为一案例。该示例一方面作为更大区域即国家的一部分进行描述,另一方面作为一个或多或少、基于资源发展的单元进行描述。也能对区域发展战略和改革措施提出建议。我们已经对所有俄罗斯地区进行了分类,并且指出了不同组(工业、农业等)的最典型代表。将精心设计几个系统的区域分支来描述整个国家的不同地域类型。计算机辅助信息系统提供用户以各种各样传统地图集的计算机的模拟,为决策者对未来的设计和区域发展变量评估等创造了条件。我们正在开发一个大范围有机废弃产品处理的测试GIS系统。其主要目标是为在废弃物储存和掩埋场所的生物降解进行方法研究。其应用包括:存放生活和工业废品的场所的使用和改进(包括工业和农业的场所和废品产生的地方);污水处理设备的建设和重建等。