A note on stilpnomelane mineralogy

Stilpnomelane analyses are classified into two separate groups of ferro- and ferristilpnomelanes on the H₂O(+)-Fe₂O₃/(Fe₂O₃+FeO) diagram. The relation is not comparable with that of oxyhornblende.     

A note on fault reactivation

Reactivation of existing faults whose normal lies in the σ₁^′σ₃^′ plane of a stress field with effective principal compressive stresses σ₁^′ >σ₂^′ >σ₃^′ is considered for the simplest frictional failure criterion, τ = μσ_n^′ = μ(σ_n − P), where τ and σ_n are respectively the shear and normal stresses to the existing fault, P is the fluid pressure and μ is the static friction. For a plane oriented at θ to σ₁^′, the stress ratio for reactivation is (σ₁^′/σ₃^′) = (1 + μ cot θ)/(1 − μ tan θ). This ratio has a minimum positive value at the optimum angle for reactivation given by (1/μ) but reaches infinity when θ = 2θ^*, beyond which σ₃^′ < 0 is a necessary condition for reactivation. An important consequence is that for typical rock friction coefficients, it is unlikely that normal faults will be reactivated as high-angle reverse faults or thrusts as low-angle normal faults, unless the effective least principal stress is tensile.     

A note on partition coefficient distributions

Much interest has been generated in assessing the possible risks of contamination for humans and marine life resulting from the dumping of nuclear waste in Arctic Seas by the former Soviet Union. Models are being used to predict the transport of radionuclides released from the dumping grounds. A key parameter in these models is the partition coefficient representing the uptake potential of marine sediments and seawater for radioactive contaminants. Partition coefficients are dependent upon the independent variables of sediment concentration and the sediment/water radionuclide distribution coefficients. Modelers must use estimated average values for the independent variables because data for these variables are lacking for the Arctic environment. In this note, we illustrate the differences between assuming that partition coefficients can be computed solely from the average values of the independent variables vs. exact probability distributions, and illustrate the technique for one of the radioactive contaminants,¹³⁷Cs. In general, errors in the sediment partition coefficient can be as high as 67% using average values; for¹³⁷Cs. the error is about 37%.     

A note on the Goodman Jack

SummaryA Note on the Goodman Jack Reconnaissance experiments, performed to evaluate the practical utility of the hard-rock variety of the Goodman Jack, reveal that the Hustrulid-T^* correction adequately reconciles the discrepancy between the measured and true deformation modulus of the rock mass in the range of 30 to 50 gigapascals.With 3 Figures     

A note on sand dyke orientations

The techniques of the statistics of directional data are applied to the orientations of sand dykes and bedding in strata unaffected by significant penetrative tectonic strain or compaction. From the records of the orientations of both bedding and sand dykes in 578 individual cases it is shown that the mean bedding-dyke dihedral angle for each group of dykes recorded in the literature ranged from 87.7 to 89.6°. The hypothesis is accepted that these dykes tended to form perpendicular to bedding. This has beneficial implications for their use as strain markers in compaction studies and in tectonic strain analysis.     

A cautionary note on humanitarian intervention

In the Post-Cold War environment, the role of the military has been extended to include intra-state peace enforcement on humanitarian grounds. This raises issues of legality. In this paper, four arguments are advanced that a right of states to intervene in humanitarian emergencies now exists. Problems contingent upon such intervention are then examined.     

Structural and locational evolution of industry in Southern Europe

S European Industry is characterized by the importance of certain branches and by plant size. Traditional branches of consumer goods are dominated by the national bourgeoisie, intermediate goods by oligopolistic (state) enterprises, modern consumer and capital goods by multinational corporations. Industrialization was retarded for various social and physical reasons. For the locational pattern some factors had specific importance (diffusion, shipping traffic for supplies, deficient infrastructure, urbanisation economies, social structure). Economic nationalism and interventionism from the thirties to the late fifties had structural and locational effects. Subsequent opening led to important foreign investment with diverse locational consequences: the large majority of the market-orientated companies concentrated on big cities and induced industrial suburbanisation. Export-orientated plants, relatively often in Portugal, also decided for rural areas and provincial towns. Regional industrial policy which began weakly with fiscal allowances in the fifties and soon adopted the growth pole idea led to results remaining only far beyond expectations. International economic crisis has heavily stroken the countries which turned out to be very dependant.     

A note on thermomechanical anisotropy of clays

Deep clays exhibit a pronounced strain anisotropy both during mechanical loading as well as during heating and cooling at constant stress in drained isotropic conditions. During mechanical loading vertical strain is larger than the horizontal one. During heating the vertical strain is larger than the horizontal one within the elastic range; the opposite is observed in the elasto-plastic range. The above described response can be interpreted adopting a consistent rotational, kinematic hardening thermo-elasto-plastic constitutive law.     

A note on photography in structural geology

When photographs of outcrops are required for detailed and/or accurate structural work the photographic image should be parallel to the outerop surface. A method has been developed which allows oblique photographs to be corrected when processed. The method imposes certain restrictions on the combinations of camera and enlarger lenses which will yield a correctly proportioned print, and graphs are presented which predict suitable combinations for a wide range of conditions. The technique has been successfully applied to several problems, one of which is presented as an illustrative example.     

A note on the history and literature of geochemical exploration

The widespread belief that 20th-century geochemical prospecting ‘originated’ in the old world and spread to the United States after 1945 is, at best, highly debatable. A largescale groundwater hydrogeochemical exploration survey was undertaken in Texas and Louisiana in the early 1920's. Boltman (1904) and Lester (1918) described early studies of spring waters associated with uranium ores in the United States. These can perhaps be regarded as forms of orientation surveys. There are now about 2000–3000 literature items dealing with groundwater hydrogeochemical exploration, and the total number of articles from all branches of geochemical prospecting is probably approaching 30,000.