Geochemical and petrological relations in some deccan basalts, Western Maharashtra, India

Petrographic and geochemical data are given for some basaltic rocks from the Koynaghat, Ambaghat and Panvel sections of the western Deccan volcanic province. This study confirms geochemical features established earlier for the Deccan basalts but brings out minor additional characters. Mineralogical and major-element compositions of the basaltic flows from the Koyna and Panvel sections indicate tholeiitic affinity; the Ambaghat flows exhibit a slight affinity towards alkali basalt. Rare earth element (REE) distribution patterns and trace-element abundances suggest minor fractionation of olivine and plagioclase during the evolution of the flows. The general similarity of chemical and mineralogical features over a wide area and the lack of conspicuous inter-element relationships suggest that the flows reflect the combined effects of partial melting, minor mineral fractionation and selective crustal contamination.     

On the effective seismic input for non-linear soil-structure interaction systems

Two equivalent semi-discrete formulations are presented for the problem of the transient response of soil-structure interaction systems to seismic excitation, considering linear behaviour of the soil material and arbitrary non-linear structural properties. One formulation results in a direct method of analysis in which the motion in the structure and the entire soil medium, rendered finite by an artificial absorbing boundary, is determined simultaneously. The other represents a substructuring technique in which the structure and the soil are analysed separately. The forces induced in the discretized system by the incident seismic motion are obtained as part of the general formulation by using the free-field motion of the unaltered soil as the earthquake input. It is shown that these forces act within the soil region in the direct method, but only on the soil-structure interface in the substructure formulation. Both sets of forces, however, involve only the displacements and tractions acting on the fictitious surface in the unaltered (linear) soil which coincides with the soil-structure interface of the complete system. It is shown, further, that the free-field displacements alone define a minimal set of data for evaluating the seismic response of the structure, since the tractions and displacements on that surface are interrelated. In practice, the minimal set must be obtained by extrapolating the available information, as the free-field ground motion at a site is usually specified at a single reference point.     

Policy and implementation in rural planning

Although often critical of the results achieved by rural planners, research by geographers and others has for some time been constrained by an inability to isolate the precise impacts of planning procedures on rural areas. The notions of a technically solvable ‘implementation problem’ and a politically complex ‘policy problem’ are confronted here, and acknowledgement of the latter directs research into the realms of decision-making and policy-implementation iteration in rural areas. Key themes in the understanding of these matters are those of central-local state relations, inter-agency relations and public-private sector relations, all of which should figure prominently in any conceptualisation of policymaking and implementation in rural areas. One final factor which invites conceptual clarification is that of the specificity of rurality as a policy-moulding phenomenon. The idea is introduced of a ‘rural dimension’ which presents a spatial facade to aspatial structures and processes.     

Industrial decentralisation in South Africa: tool of Apartheid or spontaneous restructuring?

Industrial decentralisation (ID) has been a central component of South Africa's regional strategy for over twenty years. Until recently, though, the programme has evinced little interest amongst industrialists. The fact that ID policy has been premised upon political rather than economic considerations has been thought to lie at the root of this failure. Following recent developments, however, this view is being reassessed. The reorganisation of ID policy in 1982 and the dramatic acceleration in the rate of industrial relocations that this reorganisation appears to have induced, has led theorists to revise their thinking on both the economic and political imperatives underpinning the programme. The purpose of this paper is to review the debates that are now developing concerning ID in South Africa, and to suggest where further research and analysis might be most profitably directed.     

Constraints on the origin of mafic alkaline volcanics and included xenoliths from Oberon,New South Wales,Australia

Basanites and alkali basalts from Oberon, NSW, Australia contain variable abundances of small Cr-diopside lherzolite xenoliths. Despite a limited range in (metamorphic) textures and modal mineralogy, there is significant variation in mineral chemistry. Mineral thermometric data applied to the geotherm of O'Reilly and Griffin (1985) suggests equilibration over a narrow pressure interval corresponding to depths of 30–45 km. These data show that significant compositional variations exist over a small depth interval in the subcontinental mantle.Basaltic host rocks show near-primary chemical characteristics. Mildly and strongly incompatible element (i.e. D< 1 and D1 respectively) concentrations have been used to constrain the modal amounts of clinopyroxene and garnet in a presumed garnet peridotite mantle source. Estimated proportions of (ol+opx)=73%; cpx=16%; gar= 11% closely resemble source compositions for other basaltic rocks of eastern Australia. Batch partial melting of this source in the range F=9.5–15% applied to the available REE data suggests the source is enriched relative to chondrite 8–10 × La, 2.1–2.4 × Tb and 2.5–3.7 × Yb.     

Gas analyses from the Pu'u O'o eruption in 1985, Kilauea volcano,Hawaii

Volcanic gas samples were collected from July to November 1985 from a lava pond in the main eruptive conduit of Pu'u O'o from a 2-week-long fissure eruption and from a minor flank eruption of Pu'u O'o. The molecular composition of these gases is consistent with thermodynamic equilibrium at a temperature slightly less than measured lava temperatures. Comparison of these samples with previous gas samples shows that the composition of volatiles in the magma has remained constant over the 3-year course of this episodic east rift eruption of Kilauea volcano. The uniformly carbon depleted nature of these gases is consistent with previous suggestions that all east rift eruptive magmas degas during prior storage in the shallow summit reservoir of Kilauea. Minor compositional variations within these gas collections are attributed to the kinetics of the magma degassing process.     

Practical Application of Theoretical Models to Magnetometer Surveys on Hazardous Waste Disposal Sites — A Case History

Wastes were to be exhumed and removed from a hazardous and chemical waste disposal site. The major disposal practice was shallow burial of wastes in metal drums in parallel trenches. The actual boundaries of the trenches beneath the landscaped cover were not accurately known.
Theoretical two-dimensional models were used to evaluate the application of magnetic methods to define trench boundaries on the disposal site. The models predicted that both the total field and the vertical component anomalies were diagnostic; however, the vertical component anomaly was more focused on the trench boundaries.
A survey with a vertical component fluxgate magnetometer was successful in defining trench boundaries. Observations made along traverses that trended perpendicular to the long axis of the parallel trenches indicated vertical magnetic intensity values with a cyclical pattern of large positive values over trenches and large negative values over intertrench corridors. Vertical magnetic intensity values determined with theoretical two-dimensional models compared favorably to the observed vertical magnetic values. The models were used to constrain the interpretation of the field observations to define trench boundaries; the magnetic survey defined trench boundaries with an accuracy within ± 2 feet.     

Impact of agriculture on surface water in Ireland Part I. General

The inland freshwaters of Ireland are generally of good quality, a condition at least partly attributable to the relatively small population and industrial base, which are mainly located in coastal areas. The wastes generated by agricultural activities greatly exceed those resulting from domestic and industrial activities. However, the bulk of these agricultural wastes are attributable to grazing livestock and are not likely to lead to pollution of waters. The disposal of manure slurries from intensive rearing operations and silage making are the main agricultural operations which have been implicated in pollution incidents, e.g., fish kills and lake eutrophication. Contamination of surface waters with nitrate and pesticides is not a significant problem at this stage, which reflects the relatively low usage of artificial fertilizers and biocides in Ireland. It is suggested that, in the long term, the main effect of agriculture on Irish surface waters will be eutrophication.     

Emission of aliphatic amines from animal husbandry and their reactions: Potential source of N2O and HCN

We measured the emissions of volatile aliphatic amines and ammonia produced by the manure of beef cattle, dairy cows, swine, laying hens and horses in livestock buildings. The amine emissions consisted almost exclusively of the three methylamines and correlated with those of ammonia. The molar emission ratios of the methylamines to ammonia, and data on NH₃ emissions from animal husbandry in Europe, together with global statistics on domestic animals, were used to estimate the global emissions of amines. Annual global methylamine-N input to the atmosphere from animal husbandry in 1988 was 0.15±0.06 TgN (Tg=10¹² g). Almost 3/4 of these emissions consisted of trimethylamine-N. This represents about half of all methylamine emissions to the atmosphere. Other sources are marine coastal waters and biomass burning.Possible reaction pathways for atmospheric methylamines are shown. Among various speculative but possible products N₂O and HCN are of interest because the emission of methylamines could contribute to the global budgets of these compounds. Maximum atmospheric N₂O production from methylamines are below 0.4 Tg N/year, which is less than 10% of the annual N₂O growth rate. Although we do not expect the methylamine emissions to contribute in a major way to the atmospheric N₂O budget, more studies are needed to establish this conclusion beyond doubt. Similar conclusions hold for HCN.     

Evidence for Enhanced Mineral Dissolution in Organic Acid-Rich Shallow Ground Water

Total concentrations of formate, acetate, and isobutyrate varied from less than 5 to greater than 9,000 μmol/l over distances of < 3 m in ground water from a shallow hydrocarbon contaminated aquifer. Laboratory incubations of aquifer material indicate that organic acid concentrations were dependent on the amount of hydrocarbon loading in the sediment and the relative rates of microbial organic acid production and consumption. In heavily contaminated sediments, production greatly exceeded consumption and organic acid concentrations increased. In lightly contaminated sediments rates were essentially equal and organic acid concentrations remained low. Concentrations of dissolved calcium, magnesium, and iron generally were one to two orders of magnitude higher in organic acid-rich ground water than in ground water having low organic acid concentrations. Carbonate and Fe(III)-oxyhydroxide minerals were the likely sources of these elements. Similarly, concentrations of dissolved silica, derived from quartz and k-feldspar, were higher in organic acid-rich ground water than in other waters. The positive relation (r = 0.60, p < .05, n = 16) between concentrations of silica and organic acids suggests that the microbially mediated buildup of organic acids in ground water enhanced quartz/k-feldspar dissolution in the aquifer, although it was not the only factor influencing their dissolution. A model that included organic acid microequivalents normalized by cation microequivalents significantly strengthened the correlation (r = 0.79, p < .001, n = 16) between dissolved silica and organic acid concentrations, indicating that competition between silica and cations for complexation sites on organic acids also influenced quartz/k-feldspar dissolution. Physical evidence for enhanced mineral dissolution in organic acid-rich waters included scanning electron microscopy images of highly corroded quartz and k-feldspar grains from portions of the aquifer containing organic acid-rich ground water. Microporosity generated in hydrocarbon contaminated sediments may adversely affect remediation efforts that depend on the efficient injection of electron acceptors into an aquifer or on the recovery of solutes from an aquifer.