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81.
We have performed experiments to evaluate Au solubility in natural, water-saturated basaltic melts as a function of oxygen fugacity. Experiments were carried out at 1000 °C and 200 MPa, and oxygen fugacity was controlled at the fayalite-magnetite-quartz (FMQ) oxygen fugacity buffer and FMQ + 4. All experiments were saturated with a metal-chloride aqueous solution loaded initially as a 10 wt% NaCl eq. fluid. The stable phase assemblage at FMQ consists of basalt melt, olivine, clinopyroxene, a single-phase aqueous fluid, and metallic Au. The stable phase assemblage at FMQ + 4 consists of basalt melt, clinopyroxene, magnetite-spinel solid solution, a single-phase aqueous fluid, and metallic Au. Silicate glasses (i.e., quenched melt) and their contained crystalline material were analyzed by using both electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Measured Au concentrations in the quenched melt range from 4.8 μg g−1 to 0.64 μg g−1 at FMQ + 4, and 0.54 μg g−1 to 0.1 μg g−1 at FMQ. The measured solubility of Au in olivine and clinopyroxene was consistently below the LA-ICP-MS limit of detection (i.e., 0.1 μg g−1). These melt solubility data place important limitations on the dissolved Au content of water-saturated, Cl- and S-bearing basaltic liquids at geologically relevant fO2 values. The new data are compared to published, experimentally-determined values for Au solubility in dry and hydrous silicate liquids spanning the compositional range from basalt to rhyolite, and the effects of melt composition, oxygen fugacity, pressure and temperature are discussed. 相似文献
82.
This article examines visitors’ normative acceptance of encounters with boats at a marine protected area and the extent that the number of boats, size of boats, and size of boat on which individuals were traveling influences these encounter norms. Data were obtained from a survey of 439 people visiting Molokini Shoal Marine Life Conservation District in Hawai’i, and photographs depicting four levels of boat use and three proportions of boat size measured encounter norms. Number of boats most strongly influenced encounter norms, boat size was less influential, and the size of boats on which respondents were traveling had little influence. Visitors wanted fewer boats at this site and a majority would not accept encountering more than 15 or 16 boats at one time. When the impact of boat size was considered, they would not accept encountering more than 12 large boats to 17 small boats. Implications for future research and managing standards of quality and social carrying capacity indicators at this marine protected area are discussed. 相似文献
83.
Mark A. Shields David K. WoolfEric P.M. Grist Sandy A. KerrA.C. Jackson Robert E. HarrisMichael C. Bell Robert BeharieAndrew Want Emmanuel OsalusiStuart W. Gibb Jonathan Side 《Ocean & Coastal Management》2011,54(1):2-9
Many countries now recognise the need for mitigation of climate change induced by human activities and have incorporated renewable energy resources within their energy policy. There are extensive resources of renewable energy within the marine environment and increasing interest in extracting energy from locations with either large tidal range, rapid flow with and without wave interaction, or large wave resources. However, the ecological implications of altering the hydrodynamics of the marine environment are poorly understood. Ecological data for areas targeted for marine renewable developments are often limited, not least because of the considerable challenges to sampling in high energy environments. In order to predict the scale and nature of ecological implications there is a need for greater understanding of the distribution and extent of the renewable energy resource and in turn, of how marine renewable energy installations (MREIs) may alter energy in the environment. Regional ecological implications of a MREI need to be considered against the greater and global ecological threat of climate change. Finally, it is recommended that the identification of species and biotopes susceptible to the removal of hydrokinetic energy could be a suitable strategy for understanding how a MREI may alter flow conditions. 相似文献
84.
Contaminated and possibly hazardous ground represents a problem in all of the industrialized countries of the world. The
investigation of a site that is suspected of being contaminated differs somewhat from a routine site investigation. Sampling
of soils, groundwater and gas-producing material may be required. Various precautions may be necessary in doing this and operatives
may have to wear protective clothing. Four case histories have been chosen to illustrate different aspects of the rehabilitation
of abandoned contaminated land, namely, investigation, assessment, ground treatment and redevelopment. The first comes from
Leeds in West Yorkshire, England, and outlines how a site investigation was undertaken and the nature of the contamination
present, together with a note on the suggested redevelopment. The remaining three case histories are taken from the heavily
industrialized district of the Ruhr in Germany, where extensive mining of coal and associated industries were developed from
the mid-19th century onwards. The first considers the site of the former Graf Moltke mine near Essen. In this instance, the
somewhat novel methods of data assessment and ground treatment are dealt with. The Mont Cenis site at Herne-Sodingen is one
of the more notable old mining/industrial sites undergoing redevelopment in the state of North Rhine Westphalia. Hence, the
case history concentrates of this aspect of rehabilitation. This involves not only the construction of new and interesting
structures but an attempt to reduce energy consumption in an attempt to effect the concept of sustainable development of an
urban area. The last example deals with the abandoned site of the Minister Achenbach mine at Lünen, where the ground conditions
were further complicated by the presence of old bomb craters that had been filled with a variety of materials. In addition,
because of the suspected presence of former foundation structures in the ground an electromagnetic survey was carried out
across part of the site, the areas of high conductivity suggesting their presence.
Received: 15 September 1999 · Accepted: 14 March 2000 相似文献
85.
One-, two- and three-dimensional numerical results of the non-linear interaction between cosmic rays and a magnetic field are presented. These show that cosmic ray streaming drives large-amplitude Alfvénic waves. The cosmic ray streaming energy is very efficiently transferred to the perturbed magnetic field of the Alfvén waves, and the non-linear time-scale of the growth of the waves is found to be very rapid, of the order of the gyro-period of the cosmic ray. Thus, a magnetic field of interstellar values, assumed in models of supernova remnant blast wave acceleration, would not be appropriate in the region of the shock. The increased magnetic field reduces the cosmic ray acceleration time and so increases the maximum cosmic ray energy, which may provide a simple and elegant resolution to the highest energy Galactic cosmic ray problem, where the cosmic rays themselves provide the fields necessary for their acceleration. 相似文献
86.
Thomas H. Burbine Michael J. Gaffey Jeffrey F. Bell 《Meteoritics & planetary science》1992,27(4):424-434
Abstract— Asteroids 387 Aquitania and 980 Anacostia are anomalous members of the S-class. Their reflectance spectra exhibit a strong broad absorption feature longwards of 1.5 μm and no significant feature near 1 μm. Their spectra indicate the presence of spinel, an aluminum-magnesium oxide mineral commonly present in inclusions in CV3 and CO3 meteorites. Spinel probably makes up only a small percentage of the surface assemblages of these asteroids, but its spectral effect may be enhanced by its presence in fine-grained white inclusions in immature asteroid regoliths. It is speculated that Aquitania and Anacostia represent material formed in the same nebular zone as the CV3 and CO3 chondrites but either: A) at an earlier time in the nebula when such inclusions might have been a relatively larger fraction of the nebular grain population, or B) in local regions where nebular processes (e.g., settling to the midplane) had concentrated such inclusions. The close similarity of two orbital elements (a, i) suggests that Aquitania and Anacostia may be members of a partially dispersed asteroid family produced by the early disruption of a spinel-bearing parent body. 相似文献
87.
A new method for solving the transport equation and boundary condition describing diffusive shock acceleration for interplanetary corotating interaction regions is provided. It involves inverting a quindiagonal matrix. Application of this method to realistic parameters indicates that the parallel diffusion coefficient magnitude is critical in determining whether observed particle distribution functions are exponential or power law. 相似文献
88.
Some problems associated with past mining at a mine in the Witbank coalfield, South Africa 总被引:2,自引:0,他引:2
Mining in the Witbank Coalfield commenced at the turn of the century. Initially there was little environmental degradation
associated with mining activities; however, in the late 1930s and early 1940s a pillar-robbing programme commenced. At one
particular mine this has had marked effects on the environment. Primary effects include subsidence, the appearance of tension
cracks at the surface and crownhole development. Secondary effects include spontaneous combustion of the coal worked, as air
has been provided with ready access to the mine, accelerated subsidence due to the strength of many pillars being reduced
by burning, and a marked deterioration in groundwater quality in the area. Spoil heaps also form blemishes on the landscape.
These contain significant amounts of coal and have undergone spontaneous combustion. The deterioration in the water quality
has led to the decimation of vegetation in some areas and the eradication of aquatic flora and fauna in a nearby stream.
Received: 5 March 1997 · Accepted: 1 July 1997 相似文献
89.
A 400-meter-thick volcanic and fine-grained clastic sedimentary succession in Quebrada Doña Ines Chica (26°07′S latitude; 69°20'W longitude) provides a record of Late Triassic deposition in the Atacama region of northern Chile. The strata are conformably overlain by fossiliferous marine limestones and sandstones of Late Triassic to Early Jurassic (Sinemurian) age which contain the oldest ichthyosaur remains known from Central and South America. The clastic succession is interpreted as coastal fluvial deposits, with the overlying limestones representing shelf deposits. 相似文献
90.
Fault‐controlled fluid flow inferred from hydrothermal vents imaged in 3D seismic reflection data,offshore NW Australia 下载免费PDF全文
Craig Magee Oliver B. Duffy Kirsty Purnell Rebecca E. Bell Christopher A.‐L. Jackson Matthew T. Reeve 《Basin Research》2016,28(3):299-318
Fluid migration pathways in the subsurface are heavily influenced by pre‐existing faults. Although studies of active fluid‐escape structures can provide insights into the relationships between faults and fluid flow, they cannot fully constrain the geometry of and controls on the contemporaneous subsurface fluid flow pathways. We use 3D seismic reflection data from offshore NW Australia to map 121 ancient hydrothermal vents, likely related to magmatic activity, and a normal fault array considered to form fluid pathways. The buried vents consist of craters up to 264 m deep, which host a mound of disaggregated sedimentary material up to 518 m thick. There is a correlation between vent alignment and underlying fault traces. Seismic‐stratigraphic observations and fault kinematic analyses reveal that the vents were emplaced on an intra‐Tithonian seabed in response to the explosive release of fluids hosted within the fault array. We speculate that during the Late Jurassic the convex‐upwards morphology of the upper tip‐lines of individual faults acted to channelize ascending fluids and control where fluid expulsion and vent formation occurred. This contribution highlights the usefulness of 3D seismic reflection data to constraining normal fault‐controlled subsurface fluid flow. 相似文献