A multivariate statistical study of copper mineralization in the central section of Mosaboni Mine, Eastern Singhbhum, India

A multivariate statistical analysis was carried out with log-transformed values of Cu, Ni, Co, Pb, Zn, Ag, Cr, Mn, Ca, and Sr in several sets of samples collected across the mineralized base metal zone in sheared soda granite, feldspathic schist, and chlorite schist from the central section of Mosaboni Mine of the famous Singhbhum Copper Belt of eastern India. Linear correlation coefficient matrices of two sets of ore samples (>0.5% Cu)—one from levels 18 and 21 and the other from levels 25 and 28—indicate two well-defined and distinct clusters comprising Cu, Ni, Co, Pb, and Zn on one hand and Ca, Sr, and Mn on the other. Varimax-rotatedR-mode factor analysis of two above-noted sample sets, taken along with available geologic information, indicates that over 80% of the variability in data matrices for 9–10 elements can be accounted for by four distinct processes: (a) an early phase of copper mineralization which apparently replaced Mn, Ca, and Sr in the host rock; (b) a silicate-cum-oxide phase of crystallization/recrystallization of host rock; (c) remobilization of sulfide-forming ore elements (Cu, Ni, Co, Pb, and Zn); and (d) a phase of mineralization of Ag which appears to have replaced Cr, Ca and Cu. Process (c) was quantitatively most important. Factor score studies are suggestive of preferred introduction of Ni, Co, Pb, and Zn along central parts of preexisting copper-mineralized zones.     

Deposit modeling of a nickel belt in Finland

Data from 34 Ni−Cu deposits of the 315^c-striking, 420-km long, and 10–40-km wide Kotalahtinickel belt have been recorded in the previously described system of the Ore Data File of Finland. For comparison data from four Ni−Cu deposits outside the belt have been collected. The statistical treatment of the data begins with cluster analysis and four classes are distinguished on the basis of 303 data elements. These classes form eight groups within the linear belt. Two groups containing the largest deposits, Hitura and Kotalahti, are processed by characteristic analysis, and factor analysis is applied to test the interdependence of the characteristics. This paper was presented at the International Geological Correlation Program (IGCP) Project 98: “Standards for Computer Applications in Resource Studies” held at Taita Hills, Kenya, November 8–15, 1977.     

Application of a neural network model in establishing a stage–discharge relationship for a tidal river

This paper presents the applicability of neural network (NN) modelling for forecasting and filtering problems. The multilayer feedforward (MLFF) network was first constructed to forecast the tidal‐level variations at the mouth of the River Chao Phraya in Thailand. Unlike the well‐known conventional harmonic analysis, the NN model uses a set of previous data for learning and then forecasting directly the time‐series of tidal levels. It was found that lead time of 1 to 24 hourly tidal levels can be predicted successfully using only a short‐time hourly learning data. The MLFF network was further used to establish a stage–discharge relationship for the tidal river. The results show a considerably better performance of the NN model over the conventional models. In addition, the stage–discharge relationship obtained by the NN model can indicate reasonably well the important behaviour of the tidal influences. Copyright © 2003 John Wiley & Sons, Ltd.     

Long-term growth of the oil industry in the United States

A number of growth models have been developed and used in an attempt to project the historical pattern of oil activities to some estimate of their upper limit. Techniques are outlined for the estimation of parameters of the logistic and Gompertz curves. Factor analysis indicated a close relationship between production and demand, whereas annual discoveries and discoveries classified by year of discovery tended to comprise unique factors which were indifferent to changes in time. The growth models projected relatively high values for ultimate demand and production in comparison to the figures for ultimate reserves. Inasmuch as these trends seemed to be occurring independently, some reconciliation of the results was necessary. Using the highest projections of estimates for reserves suggests that over 420 billion barrels of oil in place will eventually be discovered in the United States, with perhaps 200 billion barrels of this eventually to be proved in the form of reserves. Projections for production were higher, corresponding to a trend indicating high levels in demand for crude oil. The only credible long-term estimate of demand was given by a bounded exponential growth model, in which ultimate cumulative demand for crude oil would reach about 416 billion barrels. These figures imply that over 150 billion barrels of oil would be imported into the United States from 1970 to 2070. Provided the time pattern for one of the variables has been determined, then estimates of the other variables probably would be facilitated because of the high interrelationship between variables. Models are suggested in which accurate pivotal forecasting in the short term might be possible—assuming the particular future trend in some of the independent variables has been predetermined.Research Council of Alberta Contribution No. 596.     

Flounders follow the tides to feed: Evidence from ultrasonic tracking in an estuary

Ultrasonically tagged flounders were tracked in the estuary of the River Bann, Northern Ireland, for periods of between 2 and 12 h (11 fish for a total of 92 h and 2·5 km), during their summer residence. Positions were determined by triangulation with two receivers.All fish remained within 400 m of the release point; on average flounders moved about 270 m during one tidal cycle, equivalent to 830 body lengths, or just over 1 body length per minute. Movements were most likely at dusk, but other parameters were not contingent upon time of day, although no data were gathered at dawn. Frequency, direction, distance, speed and duration of movement and turn rate were all significantly contingent upon state of the tide. The movement data are interpreted in terms of feeding behaviour, supported by results from other parts of the study. At high tide flounders made active but meandering searches for food on the inundated mudflats. Similar but faster searches heading downstream on falling tides reflected (a) completion of feeding while littoral invertebrates were still available and (b) avoidance of stranding. Flounders made infrequent but long and linear passages downstream at low tide, when they tended to bury themselves at the edge of the main channel where there was little food. Subsequently, the fish followed the rising tide upstream so that the cycle of movements kept most fish in the same area of the estuary in the short term. It is suggested that tolerance of changing salinities enables flounders, more than other flatfish species, to exploit dense populations of estuarine intertidal invertebrates as food.     

Transport of suspended matter in a bar-built Danish estuary

The river Varde Å discharges into the bay of Ho Bugt on the western coast of Jutland forming a small, bar-built estuary. This paper deals with tidal fluxes of water and sediment in the Varde Å estuary.The inflowing water at flood tide is part of a turbidity maximum in the northern part of the bay. At high tide slack water the suspended material deposits inside the estuary. During ebb-tide it is resuspended, and the estuary bottom is washed clean coinciding with the influx of relatively pure freshwater from the drainage area.From one station in the estuary mouth, current velocities and concentrations of suspended material have been measured during 10 tidal periods covering all four seasons. It is shown how these data can be used in a quantitative calculation of the transport of water and suspended material through the cross-section of study.A model has been formulated which—based on half-tidal periods—quantifies the transport of water and suspended material through the estuary mouth.The model is calibrated on the basis of measurements made during the above-mentioned 10 tidal periods. The rather small number of measurements is to some extent compensated for by a carefully pre-arranged selection of tidal periods.The model is discussed in relation to the prediction of net suspended transport through the estuary mouth in different weather and tidal situations.     

Deposition and preservation of fluvio-tidal shallow-marine sandstones: A re-evaluation of the Neoproterozoic Jura Quartzite (western Scotland)

The 2 to 5 km thick, sandstone-dominated (>90%) Jura Quartzite is an extreme example of a mature Neoproterozoic sandstone, previously interpreted as a tide-influenced shelf deposit and herein re-interpreted within a fluvio-tidal deltaic depositional model. Three issues are addressed: (i) evidence for the re-interpretation from tidal shelf to tidal delta; (ii) reasons for vertical facies uniformity; and (iii) sand supply mechanisms to form thick tidal-shelf sandstones. The predominant facies (compound cross-bedded, coarse-grained sandstones) represents the lower parts of metres to tens of metres high, transverse fluvio-tidal bedforms with superimposed smaller bedforms. Ubiquitous erosional surfaces, some with granule–pebble lags, record erosion of the upper parts of those bedforms. There was selective preservation of the higher energy, topographically-lower, parts of channel-bar systems. Strongly asymmetrical, bimodal, palaeocurrents are interpreted as due to associated selective preservation of fluvially-enhanced ebb tidal currents. Finer-grained facies are scarce, due largely to suspended sediment bypass. They record deposition in lower-energy environments, including channel mouth bars, between and down depositional-dip of higher energy fluvio-ebb tidal bars. The lack of wave-formed sedimentary structures and low continuity of mudstone and sandstone interbeds, support deposition in a non-shelf setting. Hence, a sand-rich, fluvial–tidal, current-dominated, largely sub-tidal, delta setting is proposed. This new interpretation avoids the problem of transporting large amounts of coarse sand to a shelf. Facies uniformity and vertical stacking are likely due to sediment oversupply and bypass rather than balanced sediment supply and subsidence rates. However, facies evidence of relative sea level changes is difficult to recognise, which is attributed to: (i) the areally extensive and polygenetic nature of the preserved facies, and (ii) a large stored sediment buffer that dampened response to relative sea-level and/or sediment supply changes. Consideration of preservation bias towards high-energy deposits may be more generally relevant, especially to thick Neoproterozoic and Lower Palaeozoic marine sandstones.     

An unexploited population of oysters,Ostrea lutaria Hutton,from foveaux strait

Settlement of Ostrea lutaria on sand‐cement‐plastered asbestos plates held in steel frames on the bottom of Foveaux Strait was studied from March 1965 to April 1967. Spat mortality over the period of plate exposure (about one month) was very low (maximum of 3 percent) and was greatest shortly after settlement. There was no evidence that mortality was due to predation. Essentially the same seasonal pattern of settlement was observed each year. Eighty to 90 percent of spat settled between mid December and mid February in both summers; settlement occurred as early as October; some was observed as late as July.

Results of field experiments suggest some very tentative conclusions on the settlement behaviour of O. lutaria: (1) The larvae are benthopelagic and remain on the bottom in strong current conditions. (2) Light stimulates swimming of larvae in still water. (3) In still water and low light intensities of the area larvae tend to swim upward toward the light. (4) In still water and dim light of the area larvae settle predominantly on under surfaces. (5) In still water in the absence of light larvae settle predominantly on upper surfaces. (6) Under the conditions of current and light in the multiplate frames used to sample spatfall here, larvae settle mainly on upper surfaces. (7) Larvae tend to crawl up inclined surfaces before settling.

The results indicate that larval behaviour may be changed by small alterations of light intensity and current. The contradictory nature of surface angle preferences found by other workers for various species of Ostrea and Crassostrea may have been due to such small variations caused by the experimental techniques. It is possible that the settlement behaviour of all species of these genera is similar.     

The need for judgement in geotechnical reliability studies

ABSTRACT

A core principle of geotechnical engineering practice is the need to exercise judgement in evaluating soil and site conditions and in performing analyses. The requirement for considering judgement applies equally to performing deterministic or probabilistic analyses. In addition, for probabilistic analyses, choices must be made among the possible methods of analysis and the method of characterising variables. Consequently, geotechnical reliability studies inevitably involve significant uncertainties, and judgement is needed to perform reliability analyses and to evaluate the results. Two case histories, briefly described here, show that judgement and experience are essential prerequisites for meaningful assessment of geotechnical reliability.     

井筒与油藏耦合的压裂水平井非稳态产能计算模型

为了准确预测压裂水平井的产量,综合考虑流体在储层、井壁、压裂裂缝、射孔孔眼以及水平井筒中的流动过程,根据势叠加原理,建立了考虑射孔孔眼、压裂裂缝生产干扰作用下的井筒、油藏耦合压裂水平井非稳态产能计算模型。结果表明:只考虑裂缝生产与裂缝、孔眼同时生产时的水平井产量在生产初期差别较大,生产后期差别变小;由于裂缝、孔眼的干扰,水平井筒两端裂缝的产量高于中间裂缝的产量;由于井筒摩阻作用,关于水平井筒中心对称的裂缝流量不相等;随着裂缝长度增加,裂缝、射孔孔眼、水平井产量增大;随着裂缝导流能力增加,裂缝产量增大,射孔孔眼产量降低,水平井产量增大;射孔段越长,孔眼与裂缝的干扰愈强,单个孔眼的产量降低,但由于射孔数增加,水平井产量增大;射孔深度增加,压裂水平井产量增加。