Nature of the coordination polyhedra around M 2 cations in pigeonite

An understanding of the irregular coordination polyhedra exhibited by the M2 cations in clinopyroxenes is of prime importance in connection with the behaviour of solid solutions and polymorphism in pyroxenes.As shown by unfolding the silica chains in pigeonite, cations with octahedral stereochemistry like Mg⁺⁺and Fe⁺⁺ cause kinking of the silica chains, whereas larger cations like Ca⁺⁺and Na⁺have an opposite namely straightening effect. This is a probable factor causing immiscibility in the Mg⁺⁺-Ca⁺⁺ solid solutions in pyroxenes. In pyroxene structures with kinked silica chains the arrangement of oxygen atoms approaches close packing; consequently different stacking sequences will be energetically possible leading to polymorphism in pyroxenes.When Pauling's electrostatic valence rule is applied to clinopyroxenes, the charge balance will be exceedingly improved if effective coordination number of M2 cation is assigned and if the distortions of M 2 coordination polyhedron is considered.     

The anthracite smokers of eastern pennsylvania: PS2 (g)P_{S_2 (g)} -T stability diagram by TL analysis

Coal seams and culm banks associated with mine fires in the anthracite region of eastern Pennsylvania have been burning for decades. Many of the fires may have ignited by spontaneous combustion or by the burning of trash. Minerals associated with the combustion of anthracite form by the condensation of gas exhaled through surficial gas vents or anthracite smokers. A Pressure-Temperature (P-T) stability diagram is constructed for the condensation of orthorhombic sulfur from anthracite gas using Thermodynamic Loop Analysis (TL analysis). This method of analyzing chemical systems incorporates Kirchhoff's Law into a four step procedure structured around a closed thermodynamic cycle or thermodynamic loop. The four steps, referred to us The Four S S of Thermodynamic Loop Analysis, include: (1) Set Up—graphical characterization of the problem. (2) Sum—the application of thermodynamic principles. (3) Substitute—the use of materials data available from the literature, and (4) Solve—computation of one or more variables. The example presented demonstrates that thermodynamic loops can incorporate any number of polymorphic phase transformations. In addition, thermodynamic loop analysis is applicable to any geologic process involving the condensation of minerals from a gas. The stability diagram derived by TL analysis may have applicability in monitoring the release of sulfur gas into the atmosphere.     

The US army in operations other than War: A time to revive military geography

This paper revisits and interrelates the scope of military geography and the changing role of the military, two themes previously addressed in the 1993 and 1994 special editions ofGeoJournal. I begin by tracing the evolution of military geography in the US from World War I through the end of the Gulf War to reveal the demise of the subfield within American academic geography. Within the context of the post-Cold War era, I describe the military's reorientation and emphasize the need and opportunity to broaden the scope of military geography accordingly. The military's current operating environment is best characterized by operations other than war, undertaken on an unprecedented scale. Military geographers and regional, systematic, and technical experts throughout the discipline now have an unparalleled opportunity to contribute to the success of peacekeeping, humanitarian, and disaster assistance missions with which the military is currently preoccupied. Initiatives by academic geographers would not only enhance mission accomplishment from the military and federal government's perspective, but might also help to revive military geography as a legitimate subfield by demonstrating that military geographic endeavors can be both socially responsible and politically correct, particularly within operations other than war.     

Non-recognition of continental tholeiites using the Ti-Y-Zr diagram

Continental tholeiites cannot be identified using the Ti-Y-Zr diagram. Two-hundred and thirteen analyses from 16 localities representing 7 continental tholeiitic provinces all plot outside the within-plate basalt field of this diagram.Analyses representing about 50% of the population plot in the ocean-floor basalt field, the rest plots in the calc-alkali basalt field. Therefore problems might arise when attempts are made to classify ancient tectonomagmatic environments using the Ti-Y-Zr diagram.     

The metasomatic development of zoned ultrabasic bodies in Unst,Shetland

Read (1934b) described the mineralogy and regional setting of spectacularly zoned ultrabasic bodies occurring in Unst, Shetland. Chemical and phase compositional data are presented here for a selection of samples taken from each of the several monomineralic zones.The phase sequence and elemental distribution are discussed in some detail since both are complicated. It is shown that virtually all distributional features may be explained on the basis of a diffusion model: transport most probably having occurred via aqueous solutions in pore space.The present configurations represent frozen reaction intermediates. Controls upon the nature and extent of reaction are analysed. Certain features may be explained on the basis of local equilibrium thermodynamics. These arguments, however, are inadequate. Fairly simple kinetic considerations lead to a much more satisfactory analysis.Some of the problems associated with concepts of element mobility are discussed briefly.     

Space in geography

The concept of space is one of the most fundamental of geographical concepts. There is no work in geography that does not certain it. Nevertheless, geography has not as yet formulated an explicit and unambiguous definition of geographical space. This fact has had negative consequences for geographical theory, methodology and application. In the effort of contributing to its elimination we will try to outline the basic connotations of the concept.The concept of geographical space is a relational one. It acquires meaning and sense only when related to other concepts. The concept of space may be conceived as a supplement to things, i.e. substantively conceived objects. Space conceived in this way is the synonym of emptiness. The concept of space may be also conceived in relation ti individual landscape elements as their environments. Space conceived in this way has the character of a field of force. And, finally, space may be conceived also with respect to the totality of landscape elements, i.e. the system expressed by the term synergic. It is only this third variant of space which should be understood as the geographical space in the full menaing of the term. It is only this conception of geographical space as the space filled with qualities in relations and proportions that is considered as one of the basic prerequisites for the formulation of the theory of geography as science capable of prediction and thus also of practical utilization.     

Some approaches for location of centroids of quartz grain outlines to increase homology between Fourier amplitude spectra

The ability to test for similarities and differences among families of shapes by closed-form Fourier expansion is greatly enhanced by the concept of homology. Underlying this concept is the assumption that each term of a Fourier series, when compared to the same term in another series, represents the same thing. A method that ensures homology is one which minimizes the centering error, as reflected in the first harmonic term of the Fourier expansion. The problem is to chose a set of edge points derived from a much larger, but variable, number of edge points such that a valid homologous Fourier series can be calculated. Methods are reviewed and criteria given to define a proper solution. An algorithm is presented which takes advantage of the fact that minimization of the error term can be accomplished by minimizing the distance between the origin of the polar coordinate system in the calculation of the Fourier series and the shape centroid. The use of this algorithm has produced higher quality solutions for quartz grain provenance studies.     

Numerical analyses of deformability tests in jointed rock — “Joint Perturbation” and “No Tension” Finite Element solutions

SummaryNumerical Analyses of Deformability Tests in Jointed Rock — Joint Perturbation and No Tension Finite Element Solutions Sound design of structures in or upon rock requires a thorough knowledge of the rock mass deformability. Field test data interpretation has generally relied upon analytical or Finite Element linear elastic solutions. However, when testing in jointed rock, these can no longer be readily used since the medium cannot resist the tension induced upon loading. Accordingly, other solutions are required. If the discontinuities of the rock mass can all be mapped and their surface properties determined, the Finite Element model will use a Joint Perturbation solution where the joint elements have variable stiffnesses to account for movements along the fractures. If the discontinuities cannot be satisfactorily mapped, a global approach is provided by a No Tension analysis of the stress transfer type. The two techniques are compared in the case of bore hole jack deformability tests and found to agree remarkably well, indicating an appreciable difference from results of linear elasticity.

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ZusammenfassungNumerische Analyse von Verformungsversuchen in geklüfteten Fels — Lösungen mittels Kluft-Perturbation und No Tension Analysis auf Grund der Methode der Finiten Elemente Der Entwurf von Bauwerken in oder auf Fels erfordert eine genaue Kenntnis des Formänderungsverhaltens der Felsmasse. Im allgemeinen basiert die Interpretation der Ergebnisse von Feldversuchen auf den Lösungen des zugehörigen Randwertproblems der linearen Elastostatik mittels klassischer analytischer Methoden oder der Methode der Finiten Elemente. Wenn die Versuche aber in geklüftetem Fels durchgeführt werden, müssen die theoretischen Methoden modifiziert werden, da das Medium keine Zugspannungen aufnehmen kann. Zwei Fälle können unterschieden werden. Erstens: die Kluftflächen der Felsmasse können geometrisch erfaßt und ihre Oberflächeneigenschaften können bestimmt werden; in diesem Falle kann die Finite-Elemente-Lösung eine Kluft-Perturbations-Methode verwenden, in welcher spezielle Kluft-Elemente verschiedener Steifigkeiten normal und tangential zu den Kluftflächen die Bewegungen entlang derselben bestimmen. Zweitens: die Diskontinuitäten der Felsmasse können nicht hinreichend beschrieben werden; für diesen Fall ist vorgekehrt durch die Finite-Element-Analyse vom Typ der Spannungsumlagerung unter Ausschaltung der Zugspannungen (No Tension Analysis), um das globale Verhalten der geklüfteten Felsmasse zu erfassen. Die Lösungen dieser beiden Methoden wurden für den Fall der Bohrloch-Verformungs-Tests verglichen; der Vergleich zeigt ausgezeichnete Übereinstimmung, im Gegensatz zu den Lösungen als lineares Elastizitätsproblem.

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RésuméLa méthode des Eléments Finis appliquée aux résultats d'essais de vérins cylindriques dans les roches fissurées — solutions dites Joint Pertubé et Sans Traction La construction de structures sur ou dans des roches nécessite une connaissance approfendie de la déformabilité du massif rocheux. L'analyse des résultats d'essais en place se fait généralement à l'aide de solutions analytiques ou par Eléments Finis, qui supposent une élasticité linéaire du milieu. De fait, dans les roches fissurées, ces solutions sont inadéquates puisque le milieu ne peut résister aux sollicitations de traction. Il s'agit donc d'utiliser d'autres méthodes d'analyse. Lors qu'il est possible de déterminer la géométrie et les propriétés de toutes les discontinuités, l'on pourra utiliser une solution par Eléments Finis, dite Joint Perturbé dans laquelle la rigidité de surface du joint (ou fissure) peut varier lorsque des movements prennent place au niveau du joint. Si cela est impossible, il faudra utiliser une approche globale dite Sans Traction qui redistribue les contraintes de traction et les dissipe. On compare ces deux types de solutions dans le cas des essais de vérins cylindriques unidirectionnels. Leurs résultats sont identiques et ont nettement différents de ceux obtenus avec une solution élastique linéaire.

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Research supported by the National Aeronautics and Space Administration — Contract NAS 8-21432.

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With 8 Figures     

Use of the lattice parameter b 0 of dioctahedral illite/muscovite for the characterization of P/T gradients of incipient metamorphism

The P/T gradient or baric type of low-grade metamorphic terranes can be characterized on the basis of cumulative frequency curves of the lattice parameter b ₀ of dioctahedral micas (Sassi and Scolari 1974), which essentially reflects celadonite content and increases with pressure. The method is here applied to illite/muscovite of sub-greenschist (incipient metamorphism) and low-greenschist facies terranes from the marginal zones of the Swedish Caledonides, Swiss Alps and Venezuelan Andes, where the grade of metamorphism was determined on the basis of illite crystallinity.Complications in the determinations of b ₀ arising from (a) shifts in the spacing of the apparent 060 diffraction peaks of the illites due to the presence of inter-stratified expandable layers, and (b) persistence of more crystalline clastic micas are pointed out.In contrast to the earlier-reported decrease of b ₀ with progressive metamorphism at higher grades, b ₀ tends to increase with grade during incipient metamorphism: it is markedly lower in the diagenetic and low-grade anchimetamorphic grades in the Cambro-Silurian of the Caledonides of Jämtland, western Sweden (zone A), and the Lower Tertiary of the Helvetic zone of the Swiss Alps, than in the higher grade anchizone and epizone of the former terrane.Mean b ₀ values for the intermediate and highest (epizone) grades of the Swedish Caledonides are respectively 9.030 and 9.037 Å compared to the mean value of 9.035 Å for the medium-high pressure, Barrovian-type, terrane of Otago, N.Z. Mean b ₀ of 9.005 Å for the mainly epizonal slates of the Venezuelan Andes lies between those for the low-pressure terranes of Bosost ( 8.992 Å), and the low-medium pressure terrane of northern New Hampshire (9.010 Å). These baric estimates agree well with those for the metamorphic facies series at higher grade produced by the same events.Cumulative b ₀ curves are concluded to be useful for the characterization of P/T gradients of incipient metamorphism, particularly in the higher grade part of the anchizone and the epizone.     

Oldest Atlantic seafloor

Basalt recovered beneath Jurassic sediments in the western Atlantic at Deep Sea Drilling Project sites 100 and 105 of leg 11 has petrographic features characteristic of water-quenched basalt extruded along modern ocean ridges. Site 100 basalt appears to represent two or three massive cooling units, and an extrusive emplacement is probable. Site 105 basalt is less altered and appears to be a compositionally homogeneous pillow lava sequence related to a single eruptive episode.Although the leg 11 basalts are much more closely related in time to the Triassic lavas and intrusives of eastern continental North America, their geochemical features are closely comparable to those of modern Mid-Atlantic Ridge basalts unrelated to postulated mantle plume activity. Projection of leg 11 sites back along accepted spreading flow lines to their presumed points of origin shows that these origins are also outside the influence of modern plume activity. Thus, these oldest Atlantic seafloor basalts provide no information on the time of initiation of these plumes. The Triassic continental diabases show north to south compositional variations in Rb, Ba, La, and Sr which lie within the range of plume-related basalt on the Mid-Atlantic Ridge (20 °–40 °N). This suggests that these diabases had mantle sources similar in composition to those beneath the present Mid-Atlantic Ridge. Plumes related to deep mantle sources may have contributed to the LIL-element enrichment in the Triassic diabase and may alos have been instrumental in initiating the rifting of the North Atlantic. Systematically high values for K and Sr⁸⁷/Sr⁸⁶ in the Triassic diabases may reflect superimposed effects of crustal contamination in the Triassic magmas.Contribution Number 3953 from the Woods Hole Oceanographic Institution     

Petrogenesis of the Bosworgey granitic cusp in the SW England tin province and its implications for ore mineral genesis

The Bosworgey granite cusp forms an apical portion of the concealed northern extension of the Tregonning-Godolphin granite ridge. It is characterised by unusually high values of B, P, Mn, Fe, As, Cu, Nb, Ta, Bi, Sn, W, U and S which are present largely as tourmaline, apatite, pyrite, arsenopyrite, chalcopyrite, bismuth, columbite, cassiterite, wolframite and uraninite; and low levels of Zr, Hf, Ti and REE present in zircon, ilmenite and monazite. The granite is classified as Sn and W specialised (Tischendorf, 1974) and it belongs to the ilmenite series of Japanese workers. The classification of Chappell and White (1974) (S and I type granites) is shown to be inapplicable to Cornubian rocks although the Bosworgey samples show characteristics of S type granites. The accessory mineral assemblages are typical of high temperature lodes (cassiterite, wolframite, arsenopyrite, chalcopyrite) and the assamblage is concluded to be the cusp analogue of hypothermal lodes produced by extreme differentiation and concentration of volatiles. It is speculated that such granites could provide the parent material for the mesothermal crosscourse mineralisation (pitchblende, bismuth, pyrite, galena, sphalerite).     

Gangbildung und Tektonik im Gebiet der Spateisensteingrube “Neue Haardt” bei Weidenau/Sieg

Zusammenfassung Die Bildung des Spateisensteinganges von Grube Neue Haardt schließt an die Hauptfaltung an. Der Gang ist aus einer Abschiebung entstanden und wird von der Geisweider Überschiebung abgeschnitten.Es wird nachgewiesen, daß auf dieser Überschiebung nach Zeit und Richtung unterschiedliche Bewegungen stattgefunden haben.     

Two methods of orthogonally stepwise discrimination and their applications

In this paper, we describe two methods of discrimination based on MSE ratio and regression, respectively, and an algorithm of orthogonally stepwise discrimination. The method is not limited by the assumption that the sample covariance matrix is not ill-conditioned or singular, and by any assumption about the distribution of each population as well. So, it has wide range of application to various problems, particularly, to the problem of discrimination with both quantitative and qualitative variables. After variables are selected in the procedure of stepwise discrimination, they need not be rejected. Several examples have been calculated by using the method, and the results are quite satisfying.     

The alteration of olivine in basaltic and associated lavas

Olivines which cool under oxidizing conditions exsolve iron oxides at high temperature, and at low temperatures break down to essentially chloritic materials. Olivines which cool under non-oxidizing conditions alter at intermediate temperatures to complex assemblages of chlorite and interstratified phyllosilicates containing a smectite. Alteration under oxidizing conditions at low temperature, probably below 140° C, produces iddingsite, an orientated assemblage of goethite and interstratified phyllosilicates also containing a smectite.Post-deuteric alteration extends or initiates the breakdown of olivine to phyllosilicate mixtures often resulting in widespread movement of materials through the flow. Post-deuteric alteration of iddingsite produces strongly pleochroic, highly ordered varieties which eventually break down to green phyllosilicate assemblages.Weathering of olivine may produce orientated assemblages similar to deuteric forms of iddingsite. Weathering of green alteration products results in oxidation and the liberation of discrete iron hydroxides.Alteration in all cases requires exchange of material between interstitial components and olivine. During deuteric alteration, plagioclase and pyroxene are usually unaffected.     

Exclusive rights to fish: Towards a rational fisheries policy

Discusses the tragedy of the commons with regard to fish resources in the North Atlantic, and points to the fact that the Atlantic cod has now been so heavily exploited that a strong regulation of fisheries is needed to preserve an exploitable stock. The author argues for exclusive economic zones dividing up the remaining loopholes among coastal nations and individually transferable quotas.     

Central place preference by social geographic groups with reference to the tributary area of Shibuya,Southwest Tokyo

Conclusions Central place preference by social geographic groups is in the Tokyo area less determined by social status than by age and life cycles differentiated by sex.In case of the tributary area of Shibuya a simple classification into young people (male and female bachelors) and married people (husbands and housewives) indicates essential differences in central place preferences between these groups.The bachelors, particularly the young men, are most important for central place orientations in that they show distinctive spatial behavioural patterns in terms of complexity, mobility and intensity of distance-movements. The young people being employed — today joculously called dokushin kizoku (bachelors' aristocracy) because of their salary raised remarkably as well as of their extensive concumer demands and high buying power — are representative for the present-day economically independent young generation. The bachelors judge urban center attractiveness on the basis of shopping facilities and also in terms of atmosphere — meeting friends, strolling through town and amusing themselves. The young people are very much courted by commercial enterprises and are regarded as special trend setters having great influence on the image and vitality of Tokyo's inner urban centers.Most attractive for the young people are the ring centers. In the southwestern suburban areas Shibuya predominates; however generally speaking it is Shinjuku, the western and leading (ring)-center, which draws the young people most strongly. Special centers such as Harajuku, Aoyama and Roppongi are also preferred by this group, often in combination with a ring-center visit. Towards the inner city core (Ginza-Nihonbashi) central place preferences chiefly of the young male bachelors are declining gradually.Compared with young people the married people prefer the ring centers only slightly before the Ginza area, which for shopping is primarily visited by housewives, for going out mainly by husbands. Particularly in the inner city core near the main office districts a typical feature for Tokyo of central place preference is evident. For the salaryman — the most representative business type in the Tokyo area — going out is identical with not going home. This phenomenon depends on the place of work in two aspects. First, spatially in terms of a close connection between office and inner city amusement/shopping centers and additionally distance-movements towards a ring center nearest of the place of work or residence. Second, socially — social activities after working hours mainly carried out with colleagues result in a behavioural pattern, in which a clear differentiation between company and private life appears to be difficult. For not going home there are many reasons — among others the constricted living conditions of Japanese homes as Westerners believe — however, other factors play a much more important role: (i) Mainly the extremely long commuting distances, which allow the salaryman a real leaving home to go out only on Sundays or holidays. Other reasons for this typically Japanese feature closely related to inner city tavern and bar visits, may be seen in (ii) the traditionally very limited participation of Japanese housewives to their husbands' out-door social activities; (iii) a system of charging and crediting expenses to one's personal bank account or the company account; (iv) the personal atmosphere of taverns and bars providing the best chances for communication/relaxation and for overcoming stress and frustrations experienced in the office.Shopping is particularly for housewives the most important motivation for visiting urban centers, in this respect two Japanese characteristics should be mentioned: First, fashion and being well-groomed are, as far as the mass of people particularly the young women is concerned, more highly esteemed than in other urban societies. As a consequence good clothes are much in demand. Purchases of these kinds of articles are most often made in department stores and cause the longest distance-movements. Second, in rank of central goods next to fashion and quality clothes follow standard gifts such as seibo and chugen. The purchase of these articles is apart from the unique custom of giving gifts twice a year typically Japanese also in so far as it contradicts the least-effort criterion in central place theory. Though these patterns mostly bought by housewives or middle-aged and older people are substantially more of daily or periodical than episodical demand, they are related to surprisingly long distance-movements because of usually being bought for image reasons in leading department stores located in higher-ranking more distant urban centers.Typical behaviour for all groups visiting higher-order urban centers is an often used combination of shopping and taking part in out-door activities such as meeting friends/acquaintances, strolling around, going to the cinema or other show performances, eating, drinking and chatting together. This is due to the outstanding facilities available not only in retail-trade but also in the gastronomic, entertainment and amusement sectors.Taken all together, complexity and intensity of central place preferences in Tokyo reflect the higher and different attractiveness of Japanese urban centers compared with that of other urban societies. The urban centers are highly esteemed because of their excellent facilities as well as of their vitality, crowds and activity. These latter characteristics are summarized by the word nigiyaka meaning vivacity, which is most typical for Japanese urban centers. The inner city centers of Tokyo can be regarded in the true sense of this term as urban foci compensating for diverse problems such as environmental pollution or lack of inner urban green areas, making life in the most densely populated area of the world worthwhile.     

Autoassociation, a new geological tool

Autoassociation is a computer method of comparing a sequence of nonnumeric elements, e.g., of rock types. The sequence is slid past a replicate of itself. At each position of overlap the number of matching elements is noted and statistics of goodness-of-match are computed. The method allows several properties to be coded at each position in the sequence. It also allows unknown, missing, or not applicable elements. Reverse matches also are performed, i.e., with the duplicate sequences reversed in direction. Autoassociation is used to detect partial repetitions in stratigraphic sequences and to compare regressive and transgressive phases of cyclothems.     

China's small town urbanization program: Criticism and adaptation

China's 12,000 designated towns and more than 40,000 rural market towns have experienced a major transformation since the institution of rural reforms in the late 1970s. Rural industrialization based on the concept of leaving the soil but not the village, entering the factory but not the town has contributed to the revitalization of many small towns. But this rural urbanization has also brought about a number of problems in the countryside, leading many to propose the adoption of the concept ofleaving the soil and the village as another basis of China's small town urbanization. This essay attempts to examine this transformation, particularly the recent criticism and adjustment made to the small town urbanization program.     

Mineralized hydrothermal solution cavities in the Co-As Aït Ahmane mine (Bou Azzer,Morocco)

In the F53 Aït Ahmane Cobalt-deposit (Bou Azzer, Anti-Atlas, Morocco) a new type of contact mineralization is described. It is carbonate hosted but displays similar depositional sequence and fluid inclusion patterns to the well-known vein mineralization from the same mine. Field studies suggest that such a contact mineralization formed early by infilling solution cavities in formerly calcified serpentinite.     

Local war and its impact on ethnic and religious identification in Southern Ethiopia

After the fall of the Mengistu regime in 1991 the extreme south of Ethiopia first went through a period of relative peace in spite, or because of, the total absence of state institutions. The structures of local societies, among them thegada or generation set system, and the local forms of food production appeared to be sufficient for the needs of the local population. Then a variety of parties and liberation fronts started to compete for the control of state institutions which were expected to reappear. This led to a local war in which group identities were re-drawn to fit the patterns of ethnic movements or micro nationalisms. The paper examines primarily the examples of Oromo and Somali identity in this context.