Character and kinematics of faults within the turbidite-dominated Lachlan Orogen: implications for tectonic evolution of eastern Australia

Fault zones within turbidite-dominated orogenic systems, typified by the Lachlan Orogen of eastern Australia, are characterised by higher than average strain and intense mica fabrics, transposition foliation and isoclinal folds, poly-deformation with overprinting crenulation cleavages, and steeply to moderately plunging meso- and micro-folds. They have a different character compared to the brittle–ductile fault zones of classic foreland fold-and-thrust belts such as the Appalachians and the Canadian Rocky Mountains. Multiple cleavages and transposition layering record a progressive shear-related deformation history. An intense mica fabric evolves initially during shortening of the overlying sedimentary wedge, but is progressively modified during rotation and emplacement to higher structural levels along the steep parts of inferred listric faults. The deformed wedge outside the fault zones generally undergoes one phase of deformation, shown by a weak to moderately developed slaty cleavage which is parallel to the axial surface of upright, subhorizontally plunging chevron-folds. Other faults within the turbidites of the Lachlan Orogen include the steep zones of ‘ductile’ strike-slip deformation that bound a centrally located, high T/low P metamorphic complex. Characterised by S–C mylonites, these ductile shear zones indicate a southward passage of the metamorphic complex as a crustal wedge, with emplacement to higher structural levels along a leading-edge, ductile thrust-fault. Ar–Ar dating constrains the timing of regional deformation to be mostly Late Ordovician through Silurian across the Lachlan Orogen. Faults in the low grade turbidite sequences record the kinematic evolution of the developing Lachlan Orogen and indicate progressive deformation associated with simultaneous, eastward propagating and migrating deformation fronts in both the western and eastern parts of the fold belt. These deformation fronts are related to ‘accretionary style’ deformation at the leading edges of overriding plates, in an inferred southwest Pacific-type subduction setting from the Late Ordovician to the mid-Devonian, along the former Gondwana margin. The fault zones effectively accommodate and preserve movements within the structurally thickening, migrating and prograding accretionary wedge.     

Hydrothermal environments during the genesis of silver deposits in the Northwest Territories of Canada: Evidence from fluid inclusions

The Ag-Ni-Co-Bi-As-U veins in the Northwest Territories of Canada are hosted by volcano-sedimentary and intrusive rocks of the Great Bear Batholithic Complex. Fluid inclusion data from the gangue minerals of the veins suggest a wide range in salinity and temperature for the hydrothermal fluids. The salinities of the fluids range from about 15 to 35 wt.% NaCl equivalent. The homogenization temperatures range from 150° to 250°C for stage I fluids; 220° to 480°C for stage II fluids; 250° to 350°C for stage III fluids; 150° to 250°C for stage IV fluids and 90° to 250°C for stage V fluids. The coexistence of liquid-rich and vapour-rich inclusions in stages II and III minerals suggest that the hydrothermal fluids were boiling or effervescing. The coexistence of saturated and unsaturated inclusions in stages II and III minerals may be due to effervescence of a less saline fluid, whilst for stages IV and V it may be due to mixing of a highly saline fluid with a less saline fluid, or due to alternation of hydrostatic and lithostatic pressures at the time of trapping of the inclusions.     

A study of the compaction properties of potential clay—sand buffer mixtures for use in nuclear fuel waste disposal

In-situ emplacement of clay-based buffers in a nuclear fuel waste disposal vault limits the maximum attainable buffer density. This will vary with the composition of the buffer. A study of the maximum attainable densities of candidate Na bentonite/sand and illite/sand buffers is described. The addition of sand significantly increases the achievable compacted density. This increase may be obtained without any decrease in the swelling pressures developed by Na bentonite buffers. Sand decreases the shrinkage potential of the buffer and may also decrease the mass diffusion coefficient. A mixture of 50% sand and 50% clay by mass appears to optimise the physical properties of the buffer.     

Geochemistry of phonolites and trachytes from the summit region of Mt. Kenya

Two suites of felsic eruptives and intrusives are represented in a set of samples from the summit region of the Plio-Pleistocene volcano, Mt. Kenya. Most of the samples are moderately or strongly undersaturated and have ⁸⁷Sr/⁸⁶Sr initial ratios in the range 0.70360–0.70368 (mean=0.70362). Members of this phonolitic suite are phonolites, nepheline syenites or kenytes and as a group they show a wide variation in TiO₂, FeO, P₂O₅, Sr, Ba, Zr and Nb. The minor and trace element geochemistry reflect variation in the nature of the parental basaltic magmas from which the phonolitic rocks evolved and variation in the crystal fractionation process in individual cases. Crystal fractionation involving plagioclase, alkali feldspar, clinopyroxene, olivine and magnetite is the process by which most of the phonolitic rocks evolved and variation in the relative proportions of these phases in individual cases has led to a broad spectrum of trace and minor element behaviour. The second suite of felsic samples is critically saturated and consists of trachytes showing either slight oversaturation or slight undersaturation with respect to SiO₂. This trachyte suite has lower initial ⁸⁷Sr/⁸⁶Sr ratios (mean=0.70355) and is derived from transitional alkalic basalts by low pressure (crustal) crystal fractionation involving feldspar, clinopyroxene, magnetite and olivine. The range in minor and trace element chemistry observed among the felsic rocks is a consequence of variation in the parental basalts which is related to mantle source variation and to the specific nature of the crystal fractionation process.     

Pressure-temperature microscopy of coal liquefaction

A pressure-temperature microscopy system (PTM) has been developed for obtaining observations on coals and heavy hydrocarbons at elevated temperatures and hudrogen pressures commonly used in the hydroprocessing of coal, coal liquids, and petroleum residua. A Pittsburgh #8 seam coal, from near New Eagle in Washington County located south of Pittsburgh, Penna., was extensively characterized by petrographic analysis, proximate and ultimate analysis, Gieseler plastometer, and Ruhr dilatometry as well as data on grindability, ash characteristics, and oxidation properties. Novel direct microscopic observations at elevated temperatures and pressures with catalysts give observable changes in phase transition behavior of coal. Direct microscopic observations of fresh vitrain particles at elevated temperature and high nitrogen pressure in the presence of a tin chloride catalyst show plastic deformation. Upon replacement of nitrogen by pressurized hydrogen, individual vitrain particles are observed to liquefy in the presence of molten tin. After liquefaction, further temperature increase at 1950 psig hydrogen results in the formation of mesophase and the segregation of the molten tin.Pressure-temperature microscopy is also presented on the liquefaction behavior of a solvent-refined coal (SRC) from Wilsonville, Ala. Additional pressure-temperature microscopy is presented on the tin-catalyzed co-liquefaction behavior of the solvent-refined coal with the Pittsburgh #8 seam vitrain. The pressure-temperature microscopy of the liquefaction experiments and mesophase development have been video recorded and are available for viewing.     

On the definition and derivatives of macroscale energy for the description of multiphase systems

Modeling of flow and transport in environmental systems often involves formulation of conservation equations at spatial scales involving tens to hundreds of pore diameters in porous media or the depth of flow in a channel. Quantities such as density, temperature, internal energy, and velocity may not be uniform over these macroscopic length scales. The external gravitational potential causes gradients in density, pressure, and chemical potential even at equilibrium. Despite these complications, it is important to formulate the thermodynamic analysis of environmental systems at the macroscopic scale. Heretofore, this has been accomplished primarily using the approach of rational thermodynamics whereby the thermodynamic dependence of macroscale internal energy on macroscale variables is hypothesized directly without development of any systematic method for transforming microscale energy dependence from the microscale to the macroscale. However when thermodynamic variables are inhomogeneous at the microscale, the functional dependence of macroscale internal energy on macroscale variables is not a simple extension of the microscale case. In the present work, the relation between the definitions of microscale and macroscale intensive thermodynamic variables is established. Expressions for the material derivatives of macroscale internal energy of phases, interfaces, and common lines are derived from and consistent with their microscopic counterparts by integrating to the macroscale. The forms obtained and the consistency required will be important for use in analyses of systems at scales where microscopic heterogeneities cannot be neglected.     

Correcting bias in rainfall inputs to a semi-distributed hydrological model using downstream flow simulation errors

The focus of this study is on bias correcting semi-distributed rainfall inputs into a hydrological model applied in the Okavango River basin in southern Africa, where there are very few local observations and heavy reliance is placed on global rainfall datasets. While the hydrological model, before rainfall bias correction, is able to represent the broad characteristics of the sub-basin streamflow responses, as demonstrated by good agreement between observed and simulated flow duration curves, there are many years where the annual volumes are over- or underestimated. The long records of observed flow at downstream stations are successfully used to bias correct the rainfall inputs to the upstream sub-basins using an analysis of their individual contributions to downstream flow and their annual rainfall–runoff response ratios. The results show improved simulations for the relatively shorter observation periods at the upstream gauging stations.     

Liberal Intergovernmentalism,Historical Institutionalism,and British and German perceptions of the EU's Common Fisheries Policy

The aim of this paper is to determine whether British and German sea fisheries policies have been shaped by domestic factors or by European Union (EU) institutions. To achieve this aim, British and German perceptions of the EU's Common Fisheries Policy (CFP) were compared using two alternative theories of EU integration: Moravscik's Liberal Intergovernmentalism and Pierson's Historical Institutionalism. The perceptions of three sets of respondents—fisheries scientists, fishers, and politicians—were investigated in each country to determine whether they saw the CFP as a means of attaining their own nation's domestic fisheries agenda (as Liberal Intergovernmentalism would argue), or as an institutional champion of European fisheries as a whole (as might be predicted by Historical Institutionalism). The article concludes that although there were elements of both theories evident in each country's perceptions, British perceptions were more strongly indicative of Historical Institutionalism than Liberal Intergovernmentalism, and German perceptions were more strongly indicative of Liberal Intergovernmentalism than Historical Institutionalism. This difference is exemplified in Britain's euroscepticism (which sees EU institutions as obstacles to British fisheries’ interests), and Germany's environmentalism (which sees EU institutions as synchronising with Germany's national priorities).