The Gaojiacun Mafic-Ultramafic Complex （Sichuan, SW China）：Neoproterozoic Magmatic Activity at the Western Margin of the Yangtze Craton

1 Introduction The Gaojiacun intrusive complex is one of the numerous ultramafic-mafic intrusions in Sichuan Province of China. It was mapped during the 1970s and studied mainly by Chinese scientists (e.g. Geological Team 106, 1975; Shen et al., 1986, 1989; CGGJC, 1986; Yang et al., 1993; Li et al., 1995; Shen et al., 2003; Zhu et al., 2004a). Since the year 2000, China has become one of the largest PGE consumers. While the country can produce only less than 1 ton PGE/year, the Chin…     

Quantitative textural analysis of packings of elongate crystals

The spatial distribution of grains in a solidifying igneous rock controls the physical properties of the crystal mush, and in turn is controlled by the rate of crystal growth and accumulation. A predominant non-spherical habit for igneous minerals brings into question the use of spherical particles in reference packings used for quantification of spatial distribution. Furthermore, variations of crystal clustering/ordering with length scale require spatial statistics which take into account the distribution of particles beyond nearest neighbours. Using random close packings of spherocylinders, we demonstrate the importance of aspect ratio for the aggregation index (usually known as R) and show that packings of spherical particles have more structure than packings of rods. The spatial distribution functions demonstrate that the plagioclase grains in the colonnade from the Holyoke basalt are clustered on a length scale of 0.5 mm. Understanding the controls on grain spatial distribution in igneous rocks will depend on the application of these techniques to well-understood environments.     

Surface Geophysical Methods used to Verify the Karst Geological Structure in the Built-up Area: A Case Study of Specific Engineering-Geological Conditions

This article presents a research study of complex limestone karst engineering-geological conditions in the municipality Valaská near Banská Bystrica in Slovakia. The aim of the study is to demonstrate the impossibility of spatial identification of cave spaces using surface geophysical methods due to the specific engineering-geological conditions of a thick surface layer of anthropogenic fill containing highly heterogeneous anthropogenic material. Its maximum thickness is 3 m. Another specificific condition of the study area is its location in the built-up area, due to which the applicability of geophysical methods was limited. The article contains methodological recommendations to be used in analogous geological conditions with karst structures topped with anthropogenic fill, which complicates the identification of cave spaces. The recommended solution herein is the identification of the cave system using underground mapping of the karst and its projection onto the surface for which surface geophysical methods have been combined.     

Monitoring of heat transmission from buildings into geological environment and evaluation of soil deformation consequences in foundation engineering

In engineering geology a number of factors affecting foundation conditions are taken into consideration during engineering-geological investigations. This article deals with the factor of heat sourced from a structure (brick kiln) as a restrictive factor in foundation engineering in clay soils and introduces a documentation of soil deformation observations as an impact of the heat transmission into the geological environment. It was carried out in Southern Moravia in the Czech Republic, where the dominant foundation soils are Neogeneous clays where differential settlements of a tunnel kiln structure occurred as a result of ignoring the boundary conditions of temperature changes in the soil environment. The brick kilns caused heterogeneous spatial changes in the subsoil temperatures. This consequently resulted in differential settlements due to temperature changes originating from the kilns. The differential settlements reached as much as 150 mm. The major objective of the article is to highlight the importance of the heat transmission from buildings into the geological environment as a factor which should be considered in engineering geology and its application in planning. A new procedure for reducing or elimination of ground movements sourced from underlying clayey soils depending on the heat changes was also suggested in this context.     

Boron concentrations in carbonaceous chondrites

We have analyzed B in carbonaceous chondrites in order to clarify a factor of 100 difference between the solar system B abundance derived from the solar photosphere and that inferred from previous meteorite data. Consistent results were obtained from two instrumental methods for B analysis: (a) counting of the high energy betas from ¹²B produced by the ¹¹B(d,p) reaction, and (b) measurement of particle track densities from ¹⁰B(n,α)⁷Li in a plastic track detector affixed to a homogenized meteorite sample. Contamination is a major problem in B analyses, but extensive testing showed that our results were not seriously affected. Our B concentrations are typically 1–2 ppm and are a factor of 2–6 lower than previous carbonaceous chondrite measurements. Our data for the Cl chondrites Ivuna and Orgueil would indicate a solar system B/Si atomic abundance ratio of 58 × 10^?6, but this is still a factor of 2–10 higher than the photospheric estimates. It may be that B is depleted in the sun by thermonuclear processes; however, the similarity of photospheric and meteoritic Be abundances is a problem for this point of view. Alternatively, B may be enhanced in carbonaceous chondrites, but this would make B a cosmochemically unique element. A mm-sized (Fe,Mn,Mg)CO₃ crystal from Orgueil shows no B enrichment. We find ¹⁰B ≤ 10¹⁶ atoms/g in two Allende fine-grained inclusions suggesting that B is not a refractory element under solar nebula conditions. This ¹⁰B limit, when taken as a limit on ¹⁰Be when the inclusion formed, puts constraints on the possibility of a solar system synthesis of ²⁶Al. For a proton spectrum of E^?a, a must be ≥ 3 if a solar gas is irradiated or a ≥1.5 if dust of solar composition is irradiated.     

Evaluation of the Presence of Methane in Złoczew Lignite: Comparison with Other Lignite Deposits in Poland

Natural Resources Research - Catastrophic cases of methane explosion during exploratory drilling within the Be?chatów ortholignite deposit have led to testing for methane in other Polish...     

Copper isotope fractionation during surface adsorption and intracellular incorporation by bacteria

Copper isotopes may prove to be a useful tool for investigating bacteria-metal interactions recorded in natural waters, soils, and rocks. However, experimental data which attempt to constrain Cu isotope fractionation in biologic systems are limited and unclear. In this study, we utilized Cu isotopes (δ⁶⁵Cu) to investigate Cu-bacteria interactions, including surface adsorption and intracellular incorporation. Experiments were conducted with individual representative species of Gram-positive (Bacillus subtilis) and Gram-negative (Escherichia coli) bacteria, as well as with wild-type consortia of microorganisms from several natural environments. Ph-dependent adsorption experiments were conducted with live and dead cells over the pH range 2.5-6. Surface adsorption experiments of Cu onto live bacterial cells resulted in apparent separation factors (Δ⁶⁵Cu_{solution-solid} = δ⁶⁵Cu_solution − δ⁶⁵Cu_solid) ranging from +0.3‰ to +1.4‰ for B. subtilis and +0.2‰ to +2.6‰ for E. coli. However, because heat-killed bacterial cells did not exhibit this behavior, the preference of the lighter Cu isotope by the cells is probably not related to reversible surface adsorption, but instead is a metabolically-driven phenomenon. Adsorption experiments with heat-killed cells yielded apparent separation factors ranging from +0.3‰ to −0.69‰ which likely reflects fractionation from complexation with organic acid surface functional group sites. For intracellular incorporation experiments the lab strains and natural consortia preferentially incorporated the lighter Cu isotope with an apparent Δ⁶⁵Cu_{solution-solid} ranging from ∼+1.0‰ to +4.4‰. Our results indicate that live bacterial cells preferentially sequester the lighter Cu isotope regardless of the experimental conditions. The fractionation mechanisms involved are likely related to active cellular transport and regulation, including the reduction of Cu(II) to Cu(I). Because similar intracellular Cu machinery is shared by fungi, plants, and higher organisms, the influence of biological processes on the δ⁶⁵Cu of natural waters and soils is probably considerable.     

Holes in the Hα Eruptive Prominence Structure

The eruptive prominence observed on 27 May 1999 in H at Ondejov Observatory is analyzed using image-processing techniques. To understand the physical processes behind the prominence eruption, heated structures inside the cold H prominence material are sought. Two local minima of intensity (holes), the first above and the second below the erupting H prominence, have been found in the processed H images. A comparison of H images with the SOHO/EIT and Yohkoh/SXT images showed: (a) the cold H prominence is visible as a dark feature in the EIT images, (b) the upper local minimum of intensity in the H image corresponds to a hot structure seen in EIT, (c) the lower minimum corresponds to a hot loop observed by SXT. The physical significance of the H intensity minima and their relation to the hot structures observed by EIT and SXT is discussed. The time sequence of observed processes is in favor of the prominence eruption model with the destabilization of the loop spanning the prominence. For comparison with other events the velocities of selected parts of the eruptive prominence are determined.     

On the kinetics of textural equilibration in forsterite marbles

In the aureole of the Beinn an Dubhaich granite, Skye, the minimum observed median forsterite-calcite-calcite dihedral angle varies from 110° at the olivinein isograd to about 165° (the equilibrium value) at the granite-limestone contact. Laboratory experiments were performed to investigate the kinetics of this textural change. It was found that the rate of change of the forsterite-calcite-calcite dihedral angle followed approximately first-order kinetics with an activation energy of 48±4 kJ mol^-1 for fluid-present conditions, and 90 ±4 kJ mol^-1 for fluid-absent conditions. Scanning ion imaging demonstrated that, at least in the early stages of textural change, solution-reprecipitation of the calcite was the rate determining step in the fluid-present runs. The latter result and the value of the activation energy are both consistent with the activation energy found by previous authors for (albeit zeroth order) silicate-aqueous solution solution-reprecipitation reactions. The value of activation energy for the dry data does not correspond to those for either grain boundary or volume diffusion of oxygen or magnesium in forsterite. The mechanism for textural equilibration in the fluid-absent runs is uncertain. Application of the experimentally-derived rate equation to the Beinn an Dubhaich marbles gave activation energies higher than those obtained experimentally. It is concluded from consideration of grain growth effects that activation energies derived from the Beinn an Dubhaich marbles probably reflect textural equilibration under predominantly fluid-absent conditions.     

Impact of the sampling duration on the uncertainty of averaged velocity measurements with acoustic instruments

Average velocity in streams is a key variable for the analysis and modelling of hydrological and hydraulic processes underpinning water resources science and practice. The present study evaluates the impact of the sampling duration on the quality of average velocity measurements acquired with contemporary instruments such as Acoustic Doppler Velocimeters (ADV) an Acoustic Doppler Current Profilers (ADCP). The evaluation combines considerations on turbulent flows and principles and configurations of acoustic instruments with practical experience in conducting customized analysis for uncertainty analysis purposes. The study sheds new insights on the spatial and temporal variability of the uncertainty in the measurement of average velocities due to variable sampling durations acting in isolation from other sources of uncertainties. Sampling durations of 90 and 150 s are found sufficient for ADV and ADCP, respectively, to obtain reliable average velocities in a flow affected only by natural turbulence and instrument noise. Larger sampling durations are needed for measurements in most of the natural streams exposed to additional sources of data variability.