Mine ventilation planning in the 1980s   总被引：1，自引：0，他引：1  

Malcolm J. Mcpherson 《Geotechnical and Geological Engineering》1984,2(3):185-227

Conclusions In this paper, the author has attempted to trace the development of mine ventilation planning from the traditional, manual and largely empirical methods of the past to the numerate computer-based techniques of the 1980s.The computer revolution has changed the face of many engineering disciplines, not least mine environmental engineering. Nevertheless, the mining industries of the world have not all been equally progressive in adapting to the flexibility, power and practical utilization of the new methodologies. It is, for example, incongruous that current textbooks on mine ventilation separate completely the topics of network analysis and ventilation planning with very little cross-referencing. Many of the current generation of mine ventilation engineers recognize the need to know about computers but find difficulty in translating this into their daily work. The growing availability of self-teaching, friendly software for personal microcomputers, coupled with interactive graphics, will assist greatly in promoting uncomplicated but powerful usage of computers.Young engineers now graduating from universities and colleges have been brought up in a computer-oriented environment and are competent in interacting with these machines. Indeed, they wonder how the job was ever done without magnetic data bases and high-speed computation aid.  相似文献   

The revival of rural areas in advanced economies: a review of some causes and consequences     

Malcolm J. Moseley 《Geoforum》1984,15(3):447-456

Recent years have seen a substantial growth of population in the rural areas of the United States and Western Europe. This is explored with particular reference to census evidence relating to Great Britain. Two sets of explanations are examined. The first relates to the exercise of residential preferences unconstrained by job location, and it is notable that the retired and the otherwise non-employed have increased substantially in numbers over the past 15–20 years. The second explanation focuses on employment relocation. Much resource-based, tertiary and, especially, manufacturing employment has grown in non-metropolitan areas. British and European evidence shows the manufacturing shift to have been substantial and it is suggested that this, coupled with (pre-)retirement migration and associated multiplier developments, may explain much of the counter-urbanisation that we are witnessing. The paper briefly explores some consequence of these trends, relating to the duplication of infrastructure, pressure on rural land and housing, and social change.  相似文献   

Book reviews     

Malcolm H. Taylor  Gary R. Gaston 《Estuaries and Coasts》1986,9(2):153-154

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Ocean crust vein mineral deposition: Rb/Sr ages, U-Th-Pb geochemistry, and duration of circulation at DSDP sites 261, 462 and 516     

S. R. Hart 《Geochimica et cosmochimica acta》1986,50(12):2751-2761

Cation exchange experiments (ammonium acetate and cation resin) on celadonite-smectite vein minerals from three DSDP holes demonstrate selective removal of common Sr relative to Rb and radiogenic Sr. This technique increases the Rb/Sr ratio by factors of 2.3 to 22 without significantly altering the age of the minerals, allowing easier and more precise dating of such vein minerals. The ages determined by this technique (site 261—121.4 ±1.6 m.y.; site 462A—105.1 ±2.8 m.y.; site 516F—69.9 ±2.4 m.y.) are 34, 54 and 18 m.y. younger, respectively, than the age of crust formation at the site; in the case of site 462A, the young age is clearly related to off-ridge emplacement of a massive sill/flow complex. At the other sites, either the hydrothermal circulation systems persisted longer than for normal crust (10–15 m.y.), or were reactivated by off-ridge igneous activity.

Celadonites show U and Pb contents and Pb isotopic compositions little changed from their basalt precursors, while Th contents are significantly lower. Celadonites thus have unusually high alkali/U,Th ratios and low Th/U ratios. If this celadonite alteration signature is significantly imprinted on oceanic crust as a whole, it will lead to very distinctive Pb isotope signatures for any hot spot magmas which contain a component of aged subducted recycled oceanic crust.

Initial Sr isotope ratios of ocean crust vein minerals (smectite, celadonite, zeolite, calcite) are intermediate between primary basalt values and contemporary sea water values and indicate formation under seawaterdominated systems with effective water/rock ratios of 20–200.  相似文献   

Nd isotopic characteristics of S- and I-type granites   总被引：1，自引：0，他引：1  

Malcolm T. McCulloch  Bruce W. Chappell 《Earth and Planetary Science Letters》1982,58(1):51-64

The initial Nd and Sr isotopic composition has been determined in S- and I-type granites from the Paleozoic Berridale and Kosciusko Batholiths of southeast Australia. The Nd and Sr isotopic variations form a strongly covariant array with S-types granites having a relatively restricted range inε_Nd values from ?6.1 to ?9.8 but a large range in initial⁸⁷Sr⁸⁶Sr of from 0.7094 to 0.7184. These characteristics are indicative of an～1400-m.y. sedimentary or metasedimentary source for S-types. I-types have variable initial Nd ranging from +0.4 to ?8.9, and a more limited range in initial⁸⁷Sr⁸⁶Sr of from 0.70453 to 0.7119. These isotopic characteristics are consistent with a two-component mixing model whereby a depleted mantle-like component (DMC) withε_Nd = +6 and⁸⁷Sr⁸⁶Sr= 0.703, is mixed with a crustal component (CC) havingε_Nd = ?9 and⁸⁷Sr⁸⁶Sr= 0.720. Although this two-component mixing model satisfies the isotopic constraints the source rock chemistry of the I-types is not compatible with the large proportion (up to 50%) of sedimentary material implied by the isotopic data. This indicates that more than two components are required to account for both the isotopic and chemical data. Both the chemical and isotopic data are consistent with I-type granites having been formed from source rocks of predominantly mantle derivation and obtained progressively from the mantle over a period of 1000 m.y. prior to granite formation.  相似文献   

Chemical structure and evolution of the mantle and continents determined by inversion of Nd and Sr isotopic data,I. Theoretical methods     

C.J. Allègre  S.R. Hart  J.-F. Minster 《Earth and Planetary Science Letters》1983

While the chemical structure of the earth's mantle is probably rather complex, multi-box models have been used as a first approximation to evaluate this structure. Most commonly, a three-box model is used, involving the continental crust, the upper mantle and the lower mantle. The depleted upper mantle and the continental crust are assumed to represe1nt complementary reservoirs, related by crust formation processes occurring during geologic history.Here we investigate the Rb/Sr and Sm/Nd isotopic systematics of several three-box models, using mass balance equations and the definition of the mean age of the reservoirs. The geochemical uniqueness of the models, chosen from a large family of possible models, is evaluated from elementary graph theory, and these models are then solved using a total inversion approach. This paper (Part I) describes the methodology of the procedure; the companion paper (Part II) discusses the application of this approach to multi-box mantle models.  相似文献   

Optimal processing of satellite-derived magnetic anomaly data     

Malcolm G. McLeod 《Physics of the Earth and Planetary Interiors》1983,31(1):10-26

The statistical concept of the power spectrum has proven to be of great value in the analysis of time series and linear systems for which the inputs and outputs are functions of time. This paper shows how the concept can be extended to two-dimensional spatial power spectra and illustrates, by example, how the concept can be applied to the determination of optimal data processing methods for satellite-derived magnetic anomaly data and to the planning of missions to obtain such data.The analysis techniques indicated are applied to a data set and data processing procedure described by Mayhew et al. (1980). These authors describe magnetic anomaly data for Australia and surrounding ocean obtained by the polar orbit POGO series satellites. This paper shows that the data processing method used by these authors is approximately equivalent to an invariant two-dimensional linear filter and that it is reasonably close to optimal with respect to accuracy, though some possible improvements are suggested. Nevertheless, as is usual when filtering data, some real “signal” is unavoidably removed along with the “noise”, resulting in errors that can be quite large.A method for reducing these errors by using additional data from a medium inclination orbit satellite (for example, 60° inclination) is suggested.  相似文献   

Possible contribution of leakage currents from the Atlantic Ocean to the magnetic-field variations observed in Devon     

A.M. Hart  P.J. Krause  W.G.V. Rosser 《Physics of the Earth and Planetary Interiors》1983,32(2):107-113

It is suggested that leakage currents flow across Devon, north of Exeter, from large-scale electric-current systems induced in the Atlantic Ocean by the geomagnetic variations incident on the Atlantic Ocean from the ionosphere. This model can account for the variation with period of the contribution of induced current flow to the differences in the magnetic H variations of period > 30 s observed at Exeter and Sidmouth.  相似文献   

Water movement within lac du bonnet batholith as revealed by detailed thermal studies of three closely-spaced boreholes     

Malcolm J. Drury  Trevor J. Lewis   《Tectonophysics》1983,95(3-4)

Successive temperature logs have been obtained over a period of two years in three closely-spaced boreholes in the Lac du Bonnet batholith of the Superior Province of the Canadian Shield. Two of the boreholes, of depth 450 m and 830 m, intersect a dipping fracture zone at 435–450 m. In both holes water is flowing from near the surface to the fracture zone at approximately 1.5–1.9·10⁻⁵ m³ s⁻¹, the flow being inferred from analysis of the temperature logs. Below 25 m, temperatures in these two holes are 0.22–0.28 K lower than those in the third, 145 m, hole.The temperature data have been combined with over 200 thermal conductivity measurements on core samples to produce heat flow values. In the deepest hole heat flow above the fracture zone is 16% higher than that below the zone. This indicates that water is flowing up the fracture zone. The flow rate is approximately 0.3 g s⁻¹ m⁻¹, and the flow has existed for thousands of years.Observation of thermal effects of water flow in massive, relatively unfractured plutons in a region having little topographic relief causes one to be concerned about the reliability of heat flow values measured in similar environments.The regional heat flow is taken to be 50 mW m⁻² after correction for glaciation effects. The average value of 24 determinations of radioactive heat generation in granitic core samples is 5.23 ± 1.11 μW m⁻³, which is more than three times higher than expected for such a heat flow in the Superior Province. This implies that the layer of high radioactive heat generation is thin, being not more than 4 km and probably about 1.3 km thick.  相似文献   

The contribution of humic substances to the acidity of colored natural waters   总被引：1，自引：0，他引：1  

Barry G. Oliver  Earl M. Thurman  Ronald L. Malcolm 《Geochimica et cosmochimica acta》1983,47(11):2031-2035

An operationally defined carboxyl content of humic substances extracted from rivers, streams, lakes, wetlands, and groundwaters throughout the United States and Canada is reported. Despite the diversity of the samples, only small variations were observed in this humic carboxyl content. The dissociation behavior of two combined fulvic/humic acid extracts was studied and it was found that the dissociation of the humics varied in a predictable manner with pH. Using a carboxyl content of 10 μeq/ mg humic organic carbon, and mass action quotient calculated from sample pH, the ionic balances of three highly colored Nova Scotia rivers were estimated.  相似文献