Copper-nickel-enriched ferromanganese nodules and associated crusts from the Bauer Basin,northwest Nazca plate

Analysis of a suite of ferromanganese nodules and crusts from the dredge Y73-3-22D in the Bauer Deep (13°40′S, 102°08′W) shows distinct differences between the nodules and crusts. Ultra-slow-scan X-ray diffraction shows that the nodules are more enriched in todorokite while the crusts are more enriched in δ MnO₂. Both have phillipsite and smectite as accessory minerals as well as minor amounts of apatite, barite, and quartz. Chemical analyses show that the nodules also have higher abundances of Mn, Ni, Cu, Zn, and Ba, while crusts are more enriched in Fe, Co, and Ca. We suggest that normal authigenic precipitation of ferromanganese oxyhydroxides from seawater controls the mineralogy and chemistry of the crusts, while nodule mineralogy and chemistry are governed by small-scale diagenetic reactions in the sediment. Todorokite may form because iron in the Fe-Mn oxyhydroxide material dispersed in the sediment reacts with amorphous silica to form iron-rich smectites. The remaining oxyhydroxide material recrystallizes as todorokite.     

Experimental ‘syntectonic’ hydration of basalt

This paper outlines in general terms the role of metamorphic transformations during rock deformation. Long duration, triaxial stress relaxation tests at 600°C. 160 MPa confining pressure on wet crushed basalt, sheared in sawcuts made in intact basalt cylinders are reported. Mechanical data are interpreted in terms of a material which shows a small strain-rate sensitivity to large variations in applied stress, but which work hardens dramatically as a result of marked microstructural changes which occur during straining. Permanent distortions of c. 20% were produced in the samples.Tests at 100 MPa pore-water pressure resulted in the formation of oriented overgrowths of amphibole, preferentially developed on less stressed interfaces between original grains and in pore spaces. Substantial redistribution of feldspar also occurred. At low pore pressures no amphibole formed and only feldspar was recrystallized. Much of the original porosity of the rock was eliminated in all cases.The mechanical and microstructural data are interpreted in terms of flow by some combination of grain sliding and diffusional accommodation, with the reprecipitated, diffused material being the product of a chemical reaction involving all original solid phases plus water. From a consideration of the effects of the reaction on the chemical potential gradients driving diffusion, it is concluded that although the syntectonic hydration exerts a profound effect on the microstructural and mineralogical development of the rock during deformation, there is no substantial enhancement of the rate of strain.Similar microstructural developments also occur in natural rocks deformed during retrogressive metamorphic events, and examples are described for comparison.     

A magnetic method for determining the geometry of hydraulic fractures

Summary We propose a method that may be used to determine the spatial orientation of the fracture plane developed during hydraulic fracture. In the method, magnetic particles are injected into the crack with the fracturing fluid so as to generate a sheet of magnetized material. Since the magnetization of a body with extreme dimension ratios, such as a crack, exceeds that of an equidimensional body and since this magnetization is sensitive both to orientation and geometry, this could be used to obtain information about the crack. By measuring the vertical and horizontal components of the magnetic field and field gradients at the earth's surface surrounding the injection well with superconducting magnetometers having 10^–4 gamma sensitivity and also by measuring field direction within the well itself, it should be possible to calculate the orientation and perhaps infer the approximate geometry of the fracture surface. Experiments on electric field potential operated in conjunction with this experiment could further constrain estimates of shape and orientation.     

Stress dependence of recrystallized-grain and subgrain size in olivine

New experiments on Mt. Burnet dunite have been carried out to evaluate the effects of important physical parameters on recrystallized-grain size and subgrain size in olivine deforming under steady-state conditions. The experiments, done under both wet and dry conditions in a Griggs solid-pressure-medium apparatus, were conducted in constant strain rate, constant stress and stress relaxation modes at 10 kbar confining pressure, temperatures from 1000°C to 1300°C, strain rates from 10⁻⁴ to 10⁻⁸/sec and stress differences of from 0.5 to 10 kbar. For dunite deformed under wet conditions, recrystallized-grain size is slightly temperature-dependent but under dry conditions it is only stress-dependent with D = 137 σ^−1.27 for D in μm and σ in kbar. Subgrain sizes also depend only on stress; for the dry experiments d = 28 σ^−0.62 and for the wet ones d = 15 σ^−0.69. Subgrain sizes decrease with increasing stress but do not increase with decreasing stress and hence record only maximum stress levels. Recrystallized-grain sizes adjust to both increasing and decreasing stress levels, at minimal strains and times, and thus record the stress history. Because of this and of the inherent stability of recrystallized grains, this technique is regarded as more reliable than the subgrain size and free dislocation density and curvature methods for estimating stress magnitudes in tectonites having deformed in the steadystate.     

A study of the infiltration characteristics of undisturbed soil under simulated rainfall

Infiltration is the single most important parameter in deriving the net quick response rainfall which contributes to stream flood discharges. Rainfall simulation is used to study the infiltration characteristics in a typical catchment, the Six Mile Water in N. Ireland. The design of the simulator was such that it could be easily moved from one test area to another within the catchment to examine the effect of soil and slope variation. The simulator was first calibrated in controlled laboratory conditions and later the calibration was checked in the field. The simulator was mounted over an undisturbed plot of 37 m² and the surface runoff from the area measured by means of a collecting channel located along a lower edge of the plot. Soil moisture variations were monitored using a soil moisture neutron probe. Soil classification tests and gravimetric moisture contents were carried out on each plot. The field tests were carried out with variations in rainfall intensity, initial conditions, changing seasons, and for different plots within the catchment area. The results obtained are unique in that they present data obtained under field conditions for undisturbed soil within a natural catchment. The infiltration behaviour was found to depend upon rainfall intensity, initial conditions of the plot under consideration, seasonal temperature, and a slope of the plot. The data showed that while a classical Horton type equation for infiltration was suitable for the later stages of each test result when significant surface runoff was taking place, the model failed to represent early response adequately due to storage effects being omitted in the equation. A modified form of Horton equation is proposed, which models more accurately the infiltration characteristics of the full period of each test run.     

Socio-hydrology with hydrosocial theory: two sides of the same coin?

ABSTRACT

This paper reviews socio-hydrology and hydrosocial research, finding a sophisticated relationship with emergent syntheses. We examined 419 papers by topic, region of study, theories implemented, journal, and year published to ascertain trends in both subfields. We found important overlap and considerable difference between subfields. Whereas hydrosocial research took years to develop, socio-hydrology commenced with an inaugural paper in 2012. While the former focuses on power and scale in studying water demand, the latter concentrates on practical responses to climate extremes. Hydrosocial research usually relies on qualitative methods, and socio-hydrology research the quantitative. In the geographic regions where the former does not focus, the latter does. The former often relies on post-structuralist theory, whereas the latter uses positivist approaches. Our review concludes that socio-hydrology and hydrosocial research exist in a complex epistemological relationship, offering fertile grounds for lively discussions from which both will continue to benefit.     

Entropy-Maximizing and the Iterative Proportional Fitting Procedure

In a recent paper, Wong outlined the benefits of the IPF procedure, which he claimed had received little attention from geographers. This follow-up paper introduces a large literature, ignored by Wong, which uses that procedure, but within the context of another mathematical model. Its application is illustrated with new analyses of recent voting patterns in Great Britain.