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1.
Glenn B. Stracher 《Mathematical Geology》1995,27(4):499-511
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. 相似文献
2.
Poul E. Holm 《Contributions to Mineralogy and Petrology》1982,79(3):308-310
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. 相似文献
3.
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. 相似文献
4.
Dr. David Hooson 《GeoJournal》1977,1(6):5-12
Summary The discipline of geography, both ancient and new, is periodically subject to centrifugal tendencies, threatening its integrity and cohesion as a subject. From very different traditions, this question of philosophical unity has lain at the heart of many controversies and re-examinations of the value and place of geography in the Soviet Union and the United States in recent years, both as an academic subject and with respect to its practical applicability. This article attempts a comparative and personal view of what has happened to geography, mainly over the last quarter of a century, in these two countries, focussed on this unity question. 相似文献
5.
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). 相似文献
6.
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. 相似文献
7.
Dorothy Hill 《International Journal of Earth Sciences》1959,47(2):590-629
The known palaeontological and stratigraphical evidence is used as a basis for the construction of maps of the continents showing the extent of their inundation by the sea in Sakmarian time in the Upper Palaeozoic. In the northern hemisphere apart from India the evidence is sufficiently reliable to give reasonable maps, and the great extent of the inundations suggests that the climate would be considerably modified from that of today; no undoubted Sakmarian glacials occur there. In Southern continents and India, the Gondwana biogeographical province has made correlation with the northern continents controversial, but reasons are given for assuming that Gondwana glacial deposits were at least in part Sakmarian; the resultant maps show that the Gondwana land surfaces were but little reduced in area, and that the main glacials (except for India) lie within a belt between 40 S and 20 S. Present lack of knowledge of Sakmarian conditions in Antarctica makes reconstructions of climatic belts too hazardous for possible use in enunciating or checking hypotheses of continental drift and polar wandering. 相似文献
8.
Jacques Kornprobst Jean-Robert Kienast Jean-Claude Vilminot 《Contributions to Mineralogy and Petrology》1979,69(1):49-63
Metamorphic rocks at Milos are known in small outcrops beneath the volcanic formations, as xenoliths in the Traphores volcanic breccia and as pebbles in the Paleochora Quaternary deposits. These rocks seem to belong to three different metamorphic units which probably have intricate relationships in the basement: — the eclogites unit shows garnetjadeite or garnet-omphacite primary associations, with apparently late crystallization of lawsonite phenoblasts an recrystallization features at relatively low temperatures; — the glaucophane schist unit exhibits Jadeite+quartz or glaucophane+lawsonite primary mineralogy; — the greenschist facies unit shows low-pressure main assemblages, most generally developed after high-pressure events. The two former units involve tholeiitic meta-igneous rocks, having been spilitized before metamorphism; they generally suffered more or less advanced recrystallization features in the low-pressure field of the greenschist facies. The third unit shows only meta-sedimentary rocks, with the sole exception of one single meta-doleritic pebble having calk-alkaline affinities.Petrological and mineralogical studies, based upon 15 bulk-rock compositions and 178 probe-analysed data points, lead to suspect at least 2, perhaps 3, different metamorphic events rather than one single metamorphic evolution, to account for the 3 U distinguished. From the observation of the mineralogical assemblages and their evolution, the former events (stages 1 and 2) could be related to rapid subduction of ocean-floor or back-arc basalts, whereas, during the latter event (stage 3), the rocks experienced crystallization conditions involving both decreasing pressures and increasing temperatures. 相似文献
9.
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. 相似文献
10.
Iron- and vanadium-bearing kyanites have been synthesized at 900 and 1100° C/20 kb in a piston-cylinder apparatus using Mn2O3/Mn3O4- and MnO/Mn-mixtures, respectively, as oxygen buffers. Solid solubility on the pseudobinary section Al2SiO5-Fe2SiO5(-V2SiO5) of the system Al2O3-Fe2O3(V2O3)-SiO2 extends up to 6.5 mole% (14mole %) of the theoretical end member FeSiO5(V2SiO5) at 900°C/20 kb. For bulk compositions with higher Fe2SiO5 (V2SiO5) contents the corundum type phases M2O3(M = Fe3+, V3+) are found to coexist with the Fe3+(V3+)-saturated kyanite solid solution plus quartz. The extent of solid solubility on the join Al2SiO5-Fe2SiO5 at 1 100°C was not found to be significantly higher than at 900° C. Microprobe analyses of iron bearing kyanites gave no significant indication of ternary solid solubility in these mixed crystals. Lattice constants a
0, b
0, c
0, and V0 of the kyanite solid solutions increase with increasing Fe2SiO5- and V2SiO5-contents proportionally to the ionic radii of Fe3+ and V3+, respectively, the triclinic angles ,, remain constant. Iron kyanites are light yellowish-green, vanadium kyanites are light green. Iron kyanites, (Al1.87 Fe
0.13
3+
)SiO5, were obtained as crystals up to 700 m in length. 相似文献
11.
Wilfried Philipp 《International Journal of Earth Sciences》1955,44(1):345-375
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. 相似文献
12.
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. 相似文献
13.
Hans-Georg Bohle 《GeoJournal》1994,34(3):245-251
The perspective of the paper is that of urban metabolism which views cities, metaphorically, as metabolic processes which take in people, food, resources, and energy, transform these into a distinctive quality of life, and emit people, products, and wastes. The paper focuses on urban food metabolism, by using the concept of the food system which includes the sub-systems of production, supply, distribution and consumption of food. The paper seeks to review the state of knowledge for each of these sub-systems, to provide examples that illustrate the functioning and determinants of urban food systems, to identify critical gaps in knowledge, to outline central research desiderata and to examine critically the analytic value of the concept of urban food metabolism.Revised version of a paper presented to the International Symposium on Urban Metabolism, held in Kobe, Japan, September 6–11, 1993 相似文献
14.
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. 相似文献
15.
Prof. Dr. Peter Misch 《International Journal of Earth Sciences》1965,54(2):944-956
Crossite schists and actinolitic greenschists of the basalt-derived Shuksan Greenschist of the northwestern Cascade Mountains in Washington contain small epidote glomeroblasts. Most of these are subspherical though some are elongate. The glomeroblasts occur individually in the very fine-grained schists, as well as in less fine-grained epidote-rich segregation bands and lenticles. The glomeroblasts grew under synkinematic conditions, crystallizing simultaneously with the surrounding schistose fabric.Some of the glomeroblasts display remarkable radial growth patterns. Three successive stages of crystallization are recognized. Stage 1 is characterized by fibrous radial growth. The aggregates thus formed resemble spherulites in appearance. During stage 2, the fibrous aggregates are replaced by well individualized tapering crystals in radial arrangement. During stage 3, the glomeroblasts recrystallize as granoblastic mosaics of lumpy grains lacking radial arrangement, and the number of crystals constituting a given glomeroblast is successively reduced (convergence toward simple porphyroblasts).Some radial glomeroblasts show a tiny core of foreign mineral matter at their growth center. Possibly, this feature is general but is seen only where the center happens to have been intersected.In addition to glomeroblasts consisting of a single radial group, there are complex glomeroblasts containing a number of radial groups that have coalesced into one aggregate. In some of these multiple-radial glomeroblasts, the growth centers of the individual radial groups are in the interior of the glomeroblast, but in others, the growth centers are at the outer margin (inward growth).More common than radial glomeroblasts are likeweise subspherical glomeroblasts the internal patterns of which resemble those of stage 3 (above). Some of these epidote balls can be shown to have formed from earlier radial growths. Locally, epidote balls are hollow, containing a large core composed of other minerals.The various types of glomeroblasts, including the epidote balls, have cleared themselves, as a rule, of very finely divided opaque impurities trapped in them. The impurities have been pushed out toward the margins of the glomeroblasts. Commonly, a sharply defined clearing front has developed there; directly outside of it impurities are heavily concentrated. During clearing, each glomeroblast functioned as a unit, as clearing proceeded independently of internal grain fabric, whether it is simple-radial, multiple-radial, granoblastic, or any combination thereof.
Herrn Prof. Dr. Dr. h. c.Erich Bederke zum 70. Geburtstag gewidmet. 相似文献
Zusammenfassung Crossitschiefer und aktinolithische Grünschiefer des metabasaltischen Shuksan Greenschist der nordwestlichen Cascade Mountains in Washington enthalten kleine Epidotglomeroblasten. Die meisten sind annähernd kugelig, manche auch länglich. Die Glomeroblasten finden sich in den sehr feinkörnigen Schiefern und auch in weniger feinkörnigen epidotreichen Bändern und Linsen. Die Glomeroblasten wuchsen unter synkinematischen Bedingungen, und zwar zugleich mit der Kristallisation des umgebenden schiefrigen Gefüges.Manche Glomeroblasten besitzen bemerkenswerte radiale Gefüge. Drei Stadien der Kristallisation sind zu erkennen. Das Stadium 1 ist durch faseriges radiales Wachstum gekennzeichnet. Die so entstandenen Aggregate sehen wie Sphärolithe aus. Während des Stadiums 2 werden die faserigen Aggregate durch wohlgeformte separate keilförmige Kristalle in radialer Anordnung ersetzt. Während des Stadiums 3 rekristallisieren die Glomeroblasten als granoblastisches Mosaik frei von Radialgefüge, und die Anzahl der Kristalle in einem gegebenen Granoblasten vermindert sich stetig (Konvergenz zu einfachen Porphyroblasten).Manche radialen Glomeroblasten haben einen winzigen Kern fremder Mineralsubstanz in ihrem Wachstumszentrum. Möglicherweise gilt das allgemein, jedoch sind die Kerne nur dann sichtbar, wenn das Zentrum angeschnitten ist.Außer den Glomeroblasten, die aus einer einzigen radialen Gruppe bestehen, gibt es auch komplexe Glomeroblasten, die eine Anzahl radialer Gruppen enthalten, welche in ein Aggregat zusammengewachsen sind. In manchen dieser vielfach-radialen Glomeroblasten liegen die Wachstumszentren der einzelnen radialen Gruppen im Innern des Glomeroblasten und in anderen am Rande (Wachstum nach innen).Häufiger als radialgebaute Glomeroblasten sind ebenfalls mehr oder weniger kugelige Glomeroblasten, deren Innenbau dem des Stadiums 3 (s. o.) gleicht. Manche dieser Epidotkugeln lassen sich auf ein frühes Stadium radialen Wachstums zurückführen. Gelegentlich sind Epidotkugeln hohl, indem sie einen Kern von anderen Mineralen umschließen.Die verschiedenen Arten von Glomeroblasten, einschließlich der Epidotkugeln, haben sich meist von eingeschlossenen staubförmigen opaken Verunreinigungen geklärt, indem diese Verunreinigungen in den randlichen Teil der Glomeroblasten hinausgeschoben worden sind. Hier findet sich häufig eine wohldefinierte Klärungsfront. Unmittelbar außerhalb dieser Front sind die Verunreinigungen konzentriert. Während des Klärens hat jeder Glomeroblast als eine Einheit funktioniert, denn die Klärung vollzog sich unabhängig vom Innenbau, ob er radial, vielfach-radial, granoblastisch oder irgendeine Kombination davon ist.
Résumé Des schistes à crossite et des schistes verts actinolitiques appartenant à la série des greenschist métabasaltiques de Shuksan, dans la partie nord-ouest des Cascade Mountains (Washington), contiennent de petits gloméroblastes d'épidote. La plupart de ces derniers ont une forme plus ou moins sphérique, tandis que d'autres ont une forme allongée. Les gloméroblastes se trouvent dans des schistes à grain très fin, ainsi que dans des rubans et lentilles riches en épidote à granularité moins fine. Les gloméroblastes se sont développés dans des conditions syncinématiques au cours même de la cristallisation de la texture schisteuse associée.Quelques gloméroblastes possèdent une structure radiaire remarquable. On peut distinguer trois stades de cristallisation. Le premier stade est caractérisé par la croissance radiaire et fibreuse. Les agrégats ainsi formés ressemblent à des sphérolithes. Pendant le deuxième stade les agrégats fibreux sont remplacés par des cristaux cunéiformes, bien séparés et bien formés, ayant une disposition radiaire. Pendant le troisième stade les gloméroblastes recristallisent suivant une mosaïque granoblastique exempte de toute structure radiaire, en même temps que le nombre des cristaux dans un granoblaste donné diminue constamment (convergence vers des porphyroblastes simples).Quelques gloméroblastes à structure radiaire ont au centre un petit noyau de substance minérale étrangère. Il se peut que ce soit le cas général; cependant ces noyaux ne sont visibles que lorsque le centre est recoupé.En plus des gloméroblastes qui consistent en un seul groupement radiaire, il existe aussi des gloméroblastes complexes contenant un ensemble de groupes radiaires qui ont crû sous la forme d'un agrégat. Dans certains de ces gloméroblastes pluriradiaires les centres d'accroissement des différents groupes radiaires se trouvent à l'intérieur du gloméroblaste; dans d'autres ils se trouvent à sa périphérie (sens de croissance vers l'intérieur).Les gloméroblastes à forme plus ou moins sphérique, dont la structure interne ressemble à celle du troisième stade (voir plus haut), sont plus fréquents que ceux à structure radiaire. Certaines de ces «baules épidotiques» se laissent ramener à un des premiers stades de la croissance radiaire. Occasionnellement les «boules épidotiques» sont creuses, entourant un noyau d'autres minéraux.Les différents types de gloméroblastes, y compris «les boules épidotiques», se sont le plus souvent purifiés des fines impuretés opaques qui y sont incluses en les repoussant vers l'extérieur à la périphérie des gloméroblastes. Dans ce cas on trouve souvent un front de purification bien marqué. Les impuretés sont concentrées immédiatement à l'extérieur de ce front. Au cours de cette purification, chaque gloméroblaste a fonctionné comme une unité, puisqu'elle s'est effectuée indépendamment de la structure interne, que celle-ci soit à structure radiaire, pluriradiaire, granoblastique ou une combinaison de ces formes.
. — . : 1. - . - 2. . - 3. . , .
Herrn Prof. Dr. Dr. h. c.Erich Bederke zum 70. Geburtstag gewidmet. 相似文献
16.
Prediction of hydrocarbons in sedimentary basins 总被引：1，自引：0，他引：1
To estimate the undiscovered hydrocarbon potential of sedimentary basins, quantitative play assessments specific for each location in a region may be obtained using geostatistical methods combined with the theory of classification of geological objects, a methodology referred to as regionalization. The technique relies on process modeling and measured borehole data as well as probabilistic methods to exploit the relationship between geology (the predictor) and known hydrocarbon productivity (the target) to define prospective stratigraphic intervals within a basin. It is demonstrated in case studies from the oil-producing region of the western Kansas Pennsylvanian Shelf and the gas-bearing Rotliegend sediments of the Northeast German Basin. 相似文献
17.
Necip Güven 《Contributions to Mineralogy and Petrology》1969,24(3):268-274
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. 相似文献
18.
Summary A study of 304 selected biotite analyses, with 17 chemical variables (Al
IV
, Fe
IV
, Al
VI
Fe
VI
, Mg, Mn, Ti, Li, Na, K, Rb, Ca, Ba, OH, F, Cl,), was carried out using variation diagrams and statistical methods. It was our aim to verify the existence of characteristic variation patterns in the crystal chemistry of igneous biotites related to the geological setting and chemistry of the parent rocks. In the absence of a range of analyses covering the whole spectrum of igneous rocks, the biotites were grouped a priori either as volcanic (rhyolites, rhyodacites and trachyrhyolites, dacites and trachytes, andesites, trachybasalts and nephelinites) or as plutonic (granites, granodiorites, tonalites, diorites, gabbros). Variation diagrams failed to distinguish clearly between the different groups of biotites; the data overlapped considerably and were accordingly difficult to interpret. Statistical analysis, on the other hand, revealed clear chemical differences; moreover, simple statistical equations and careful coefficients were established which make it possible to evaluate the degree of discrimination between the different groups and to classify unknown biotites. The most important petrological factors affecting biotite chemistry are temperature of crystallization, rock acidity and, probably, rock alkalinity and the presence of other Fe-Mg minerals. Factors, such as/tf
and
, can cause more limited variations.
With 8 Figures 相似文献
Kristallchemie von Biotiten -aus magmatischen Gesteinen
Zusammenfassung Unter Berücksichtigung von 17 chemischen Variabeln wurde eine statistische und geochemische Auswertung von 304 ausgewählten chemischen Analysen von Biotiten ausgeführt, um die Existenz von charakteristischen Variationsschemata der Kristallchemie der magmatischen Biotite, im Bezug auf geologische Lage und Zusammensetzung des Gastgesteines, zu verifizieren. Da kein vollständiger Analysensatz für die gesamte magmatische Abfolge zur Verfügung war, wurden die Biotite a priori entweder als vulkanisch (Rhyolite, Rhyodacite und Trachyrhyolite, Dacite und Trachyte, Andesite, Trachybasalte und Nephelinite) oder als plutonisch (Granite, Granodiorite, Tonalite, Diorite, Gabbros) gruppiert. Variationsdiagramme allein reichen für eine scharfe Unterscheidung der verschiedenen Biotitgruppen nicht aus. Die Daten überlagerten sich teilweise, so daß jede Interpretation zweifelhaft war. Auf der anderen Seite ergaben sich scharfe chemische Unterschiede aus der statistischen Analyse, außerdem wurden einfache statistische Gleichungen und Koeffizienten, die die Ermittlung des Diskriminationsgrades zwischen verschiedenen Gruppen und die Klassifizierung der Biotite unbekannter Herkunft ermöglichten, festgesetzt. Die wichtigsten petrologischen Faktoren, die den Biotitchemismus beeinflussen, sind die Kristallisationstemperatur, die Azidität der Gesteine, und wahrscheinlich auch deren Alkalinität, und die Anwesenheit von anderen Mg-Fe-Mineralien. Faktoren wie und haben nur einen beschränkten Einfluß.
With 8 Figures 相似文献
19.
Dr. Volker Wrede 《International Journal of Earth Sciences》1988,77(1):101-114
Zusammenfassung Der nördliche Harzrand stellt eine tektonische Grenze dar zwischen dem varistischen Grundgebirge und dem triassischmesozoischen Deckgebirge des süd-niedersächsischen Berglandes. Der Charakter dieser Störungslinie wurde in der Vergangenheit vielfach diskutiert. Es läßt sich zeigen, daß der nördliche Harzrand keine mehr oder weniger flach nach Süden einfallende Schaufelfläche darstellt. Durch den Vergleich mit ähnlichen tektonischen Elementen, die in den Steinkohlenlagerstätten Nordrhein-Westfalens aufgeschlossen sind, ergibt sich vielmehr das Bild eines bereits varistisch angelegten und saxonisch reaktivierten wrench-fault-Systems.
The northern margin of the Harz-Mountains is the tectonic border between the Variscan basement and the Triassic-Mesozoic sequence of southern Lower Saxony. The nature of this fault-zone has been controversial. It can be demonstrated by comparison with similar tectonic features exposed in the coal-mining areas of Northrhine-Westphaha that it is part of a wrench-fault-system rather than a shallow dipping décollement-structure. This fault system has been generated during the Variscan orogeny and has been reactivated by Saxonian movements.
Résumé Le bord du nord du Harz se présente comme une limite tectonique entre le soubassement varisque et les couches de couverture mésozoïques-triasiques du pays vallonné de la Basse-Saxe du Sud. Le caractère de cette ligne de dislocation a fait l'objet de discussions multiples dans le passé. On peut montrer que la limite nord du Harz n'est pas un décollement à pendage sud plus ou moins faible. Au contraire, par comparaison avec des structures tectoniques analogues, exposées dans le district houiller de la Rhénanie du Nord-Westphalie, le modèle s'impose d'un système de failles de décrochement (wrench-faults), engendrées pendant l'orogenèse varisque et réactivées par les mouvements saxoniens.
- . . , . , -- , , .相似文献
20.
59 fluorite samples have been analysed by neutron activation for La, Ce, Sm, Eu, Tb, Dy, Yb and Lu. Two properties of the partition coefficient of the R. E. E. between fluorite and poorly complexing solutions (L. Marchand, 1976) have been used for interpretations: (R. E. E.) CaF2/(R. E. E.)solution are always very high so that CaF2 records with an important magnification and without major distortion in the R. E. E. pattern from the mother solution; the partition coefficients are higher for the heavy earths than for the lighter ones. Consequently, in finite reservoirs where CaF2 precipitates, the trend for solutions will be a gradual enrichment in ceric earths. Interpretations at different scales of the Maine hydrothermal deposit (D. Joseph, 1974) permit to emphasize: — a constant geochemical signal at the scale of a growth band of homogenous colour; — a possible characterization of the ore-forming solutions dynamic (infinite vs finite reservoirs) by comparison of successive growth bands in a same sample; — distinct source rocks for the formation blanche and formation verte. 相似文献