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1.
Summary Recent advances in mathematical optimization have resulted in the development of superior techniques for solving realistic decision making problems. The technique called PARETO OPTIMAL SERIAL DYNAMIC PROGRAMMING is presented here as a tool for rational mine planning. This approach always enables the identification of a set of decision alternatives considered superior to the remaining feasible, usually numerous, decision alternatives, when a number of conflicting, noncommensurable, objectives are simultaneously optimized. It is further noted that the decision makers' truly preferred decision is always one of the members identified as the superior set.Notation [A] Number of initial decision alternatives for production stage 1 - [A ] Accumulated pareto optimal stage objective vector at stage for the remainder of the stagesN – - [A] Accumulated non-pareto optimal stage objective vector at stage for the remainder of the stagesN – - [B] Number of initial decision alternatives for production stage 2 - [C] Number of initial decision alternatives for production stageN - [COG k,] Cutoff grade for decision,k, at production stage, - [D] Number of initial pareto solutions for production stage 1 - [D ] Decision at stage - [E] Number of initial pareto solutions for production stage 2 - [F] Number of initial pareto solutions for production stageN - [j] A random objective function - [J] Number of objective functions - [LIFE k,] Minelife for decision,k, at production stage, - [] An arbitrary production stage - [N] Final production stage - [NPV] Expected net present value - [NPV k,] Project net present value for decision,k, at production stage - [OPR k,] Ore production rate for decision,k, at production stage, - [S ] State of the system in stage - [ n] Immediate state objective vector at stage   相似文献   

2.
The two important classes of Archean Fe-Ni-Cu sulphide deposits in Western Australia are those hosted by (1) coarse-grained adcumulate dunites (e.g. Agnew, Mount Keith) and (2) komatiitic lavas (e.g. Kambalda). Close similarities in compositions of relict olivine, pyroxene, and chromite from dunitic and komatiitic host rocks and compositional and textural similarities between chilled margins of some dunites and some komatiites indicate origins from similar komatiitic liquids which contained 20%–32% MgO. As field relations suggest that the dunites are probably lateral stratigraphic equivalents of spinifextextured komatiites, they are interpreted as the slowcooled end member of a continuum from spinifex-textured komatiites (former liquids) through cumulate komatiites (40%–90% olivine) to adcumulate komatiitic dunite (>90% olivine). Previous classification of these Ni deposits as intrusive- and volcanic-related deposits now appears unwarranted, and the terms komatiitic dunite-hosted and komatiite-hosted deposits are preferred.  相似文献   

3.
In closed magma systems SiO2 approximately measures differentiation progress and oxygen isotopes can seem to obey Rayleigh fractionation only as a consequence of the behaviour of SiO2. The main role of 18O is as a sensitive indicator of contamination, either at the start of differentiation ( 18Oinit) or as a proportion of fractionation in AFC. Plots of 18O vs SiO2-allow to determine initial 18O values for different sequences for source comparison. For NBS-28=9.60, the 18O at 48% SiO2-varies between a high 6.4 for Kiglapait (Kalamarides 1984), 5.9 for Transhimalaya, 5.8 for Hachijo-Jima (Matsuhisa 1979), 5.6 for Koloula (Chivas et al. 1982) and a low 5.3 for the Darran Complex, New Zealand. The Transhimalayan batholiths (Gangdese belt) were emplaced in the Ladakh-Lhasa terrane, between the present-day Banggong-Nujiang, and Indus-Yarlung Tsangbo suture zones, after its accretion to Eurasia. The gradient of the least contaminated continuous ( 18O vs SiO2-igneous trend line is similar to that of Koloula, and AFC calculations suggest a low secondary assimilation rate of less than 0.05 times the rate of crystallisation. Outliers enriched in 18O are frequent in the Lhasa, and apparently rare in the Ladakh transsect. Low- 18O (5.0–0) granitoids and andesites on the Lhasa-Yangbajain axis are the result of present day or recent near-surface geothermal activity; their quartzes still trace the granitoids to the Transhimalaya 18O trend line, but the distribution of low total rock or feldspar 18O values could be a guide to more recent heat flow and thermally marked tectonic lineaments. Two ignimbrites from Maqiang show hardly any 18O-contamination by crustal material.  相似文献   

4.
Correlation coefficients of modal variables from several suites of granitic rocks have been calculated and tested for significance using the Chayes-Kruskal and Chayes methods. The results show that although Chayes' remaining-space transformation does, in general, weaken the original proportion correlations, the positive and low-negative original proportion correlations tend to increase in absolute value because of a tendency of positive increment of the covariance by such transformation. However, no satisfactory procedure for choosing the variable to be transformed (V2)could be determined, and testing of the significance of remaining-space correlations is found to be highly problematic. It is shown also that the Vistelius-Sarmanov procedure of calculation of correlation coefficients from closed-table data does not effectively eliminate the closure effect. It is concluded that assigning statistical significance to the correlation coefficients between modal variables is, in general, unsatisfactory, except where the number of variables 8,the sample size is large (say, 30),and there is no negative element in the variance vector of the corresponding open variables.  相似文献   

5.
Summary The mineral trigonite crystallizes in the monoclinic space groupPn–C s 2 witha 0=7.26,b 0=6.78,c 0=11.09Å; =91.5°,Z=2. The structure was determined from 1250 X-ray intensities collected on an automatic two circle Weissenberg-type diffractometer. The final residual isR=6.5% using anisotropic temperature factors for Pb, Mn and As, and isotropic temperature factors for O.The structure consists of MnO6 octahedra, sharing all six oxygens with arsenite groups to form a framework. The Pb atoms are attached to this framework with Pb–O distances2.23Å. One oxygen, bound only to an As atom, is interpreted as the donor for a hydrogen bond of 2.75Å.
Die Kristallstruktur des Trigonits, Pb3Mn(AsO3)2(AsO2OH)
Zusammenfassung Das Mineral Trigonit kristallisiert monoklin, RaumgruppePn–C s 2 ,a 0=7,26,b 0=6,78,c 0=11,09Å; =91,5°;Z=2. Die Strukturermittlung erfolgte anhand von 1250 Röntgenintensitäten, die auf einem automatischen Zweikreis-Weissenbergdiffraktometer gesammelt wurden. Mit anisotropen Temperaturfaktoren für Pb, Mn und As sowie isotropen für die O-Atome ergibt sich einR-Wert von 6,5%.Die MnO6-Oktaeder werden über die sechs Sauerstoffe mit Arsenitgruppen zu einem dreidimensionalen Gerüst verknüpft. Über Pb-O-Abstände2,23 Å sind die Pb-Atome in dieses Gerüst eingebaut. Ein Sauerstoff, nur an ein As-Atom gebunden, wird als Donator einer H-Brücke von 2,75 Å interpretiert.

With 2 Figures  相似文献   

6.
Zusammenfassung Die mediterrane oder alpine Trias wurde im 19. Jh. nahezu als Standard-Typus der marinen Entwicklung dieses Systems aufgefaßt. Sie lieferte fast ausschließlich die Faunenfolgen zur biochronologischen Gliederung; Schicht- und Fazies-Bezeichnungen wurden aus dem alpinen Raum bis nach Südostasien übertragen. Eine gewisse Sonderstellung maß man nur ihren Ammonoideen-Faunen zu. Ihre Erforschung schien bald nach der Jahrhundertwende abgeschlossen.Seit zwei Jahrzehnten wird jedoch die Gliederung der mediterranen Trias mit Hilfe der Ammonoidea völlig revidiert. Darüber hinaus konnten neue biochronologische Standards von der phylogenetischen Entwicklung anderer Organismen-Gruppen (Conodonten, Ostracoden, Foraminiferen, Holothurien, Dasycladaceen, Sporen und Pollen) abgeleitet werden. Die marinen Sequenzen des Mittelmeerraumes haben dabei eine wesentliche Rolle gespielt.Zahlreiche moderne Fazies-Analysen, auf die nur kursorisch verwiesen wird, erlauben, die paläogeographischen Konturen im Westteil der triassischen Tethys schärfer zu sehen und ihre geotektonische Entwicklung plattentektonisch zu deuten. Ausgehend von permischen Vorzeichnungen öffneten sich ozeanische Arme im Norden (Vardar-Zone, wahrscheinlich mit Fortsetzung bis in die Alpen) und Süden (Sizilien, Alboran). Dabei wurden einige Mikroplatten von Afrika bzw. Europa abgespalten, von denen die Adria-Platte und ihre geotektonische Differenzierung während der Trias diskutiert werden.
In a first period of exploration, until the beginning of our century, the Mediterranean or Alpine Triassic advanced to be a standard type of the marine development of that period. It served as well as the base for a world-wide biochronological division as for the deviation of facies types.Nevertheless the subdivision of the Triassic with the help of ammonoids was revised during the past decades, and new biochronological standards were derived from the phylogenetic evolution of other taxa: conodonts, ostracodes, foraminifera, holothuroids, dasycladacean algae, and from the palynological record. For these investigations, the Mediterranean region is again of special importance.The results of modern facies analysis which are not reviewed extensely in this paper, allow to discern the palaeogeographic contures in the western part of the Triassic Tethys with more accuracy and to sketch the outlines of a plate tectonic interpretation. Following to Permian configurations two deep branches of this oceans developed, one to the north (Vardar zone, probably to the Alps) and another in the south (Sicily-Alboran). Several microplates were split off from Africa and Europe. The geotectonic differentiation of one of them (Adria microplate) is discussed.
Résumé Au 19ième siècle le Trias méditerranéen ou «alpin» a presque partout été considé ré comme type standard du développement marin de ce système. La subdivision biochronologique est largement basée sur ses faunes, et sa nomenclature stratigraphique fut transférée aux autres régions. Concernant les ammonoïdes, le Trias méditerranéen a, en effet, pris une position spéciale. Au début de notre siècle leur exploration semblait bientôt être achevée.Depuis vingt ans on travaille cependant à la révision de la subdivision du Trias sur la base des ammonoïdes. De plus de nouveaux standards biochronologiques ont pu être établis sur la base de l'évolution d'autres taxa (conodontes, ostracodes, foraminifères, holothuroïdes, algues, spores et pollens). Au cours de ces recherches les séries marines ont joué un rôle important.De nombreuses analyses de faciès dont il n'a été fait mention qu'en passant, permettent de voir plus distinctement dans la région de la Téthys les contours paléogéographiques et d'interpréter, selon la théorie de la tectonique de plaques, leur évolution géotectonique. Tracés déjà au Permien, deux bras océaniques s'ouvraient dans la Téthys occidentale, l'un marqué par la zône du Vardar et allant probablement jusqu'aux Alpes et l'autre dans région de Sicile et de Tunisie. Au cours de ce processus, plusieurs microplaques furent séparées de l'Afrique ainsi que de l'Europe. L'exemple de la microplaque adriatique et son évolution géotectonique au cours du Trias sont brièvement discutés.
, , 19- , - . , . . 19- . . , — , , , , Dasycladaceen, . . , , . — — , . . , .
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7.
Zusammenfassung Die Schichten der Kreuznacher Gruppe im Nordosten des Saar-Nahe-Gebietes kann man in 3 Faziesgebiete aufteilen, und zwar 1. in die Kreuznacher-, 2. die Niersteiner- und 3. in die Rötelschiefer-Fazies. Ihre Sedimente zeigen Merkmale einer Ablagerung unter semiariden Bedingungen, die sich ebenfalls in einer Zunahme ihres Dolomit- wie Borgehaltes zum Hangenden widerspiegeln. Dies trifft besonders auf die Rötelschieferfazies zu, wo in der Zone stärksten Anstiegs dieser Komponenten auch eine Anreicherung der wichtigsten Spurenelemente vorhanden ist. Diese Kennzeichen einschließlich der Tatsache, daß in der nahegelegenen Bohrung Wolfskehlen 4 (Rheintalgraben) mariner Zechstein nachgewiesen werden konnte, sprechen für eine Einstufung der Schichten der Kreuznacher Gruppe in den Zechstein.
The Sediments of the Kreuznacher Gruppe in the northeastern part of the Saar-Nahe-region can be divided in the following facies: 1. The facies of Kreuznach, 2. the facies of Nierstein and 3. the facies of the Rötelschiefer. They all show features of sediments deposited under partly arid conditions, which are also demonstrated in an increase of dolomite- and boron-content of the younger sediments. This trend is quite clear in the facies of the Rötelschiefer, where in the zone of maximal increase in these components an enrichment of the most important trace elements can be observed as well. These characteristics and the fact, that in the cores of the nearby bore Wolfskehlen 4 (Upper Rhinegraben) Zechstein in a marine facies was found, admit the conclusion, that the sediments of the Kreuznacher Gruppe belong to the Zechstein, too.
Résumé Les couches du Kreuznacher Gruppe dans la partie Nord-Est du bassin de la Sarre/Nahe peut-on subdiviser de la manière suivante: 1. La facies de Kreuznach, 2. la facies de Nierstein et S. la facies des Rötelschiefer. Toutes les trois facies indiquent des documents d'une climat semiaride, lequel se montre aussi en forme d'une augmentation de bore et de dolomie vers la partie supérieure des couches. C'est particulièrement réalisé dans la facies des Rötelschiefer, où on trouve dans la zone d'une montée maximale de bore et de dolomie aussi un enrichissement des oligoéléments les plus importants. Ces indices et le fait, qu'on a constaté du Zechstein marin tout près dans les carottes d'un sondage (Wolfskehlen 4) au graben du Rhin, permettent de conclure, que les couches du Kreuznacher Gruppe appartiennent au Zechstein.
Saar-Nahe' : ) , ) , ) . .
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8.
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   

9.
Triangle based interpolation is introduced by an outline of two classical planar interpolation methods, viz. linear triangular facets and proximal polygons. These are shown to have opposite local bias. By applying cross products of triangles to obtain local gradients, a method designated slant-top proximal polygon interpolation is introduced that is intermediate between linear facets and polygonal interpolation in its local bias. This surface is not continuous, but, by extending and weighting the gradient planes, a C1 surface can be obtained. The gradients also allow a roughness index to be calculated for each data point in the set. This index is used to control the shape of a blending function that provides a weighted combination of the gradient planes and linear interpolation. This results in a curvilinear, C1,interpolation of the data set that is bounded by the linear interpolation and the weighted gradient planes and is tangent to the slant-top interpolation at the data points. These procedures may be applied to data with two, three, or four independent variables.  相似文献   

10.
Only recently have sedimentological studies been integrated with orogenic research. The analysis of the Lechtaler Kreideschiefer (Lechtal Shale; Lower Cretaceous) demonstrates that these sediments reflect orogeny. Subduction and compressive tectonics resulted in the formation of a nappe pile. Folding of the epicontinental shelf formed long syn- and anticlines. In contrast to the uplifting anticlines the synclines represent subsiding depocenters with continuous sedimentation. Sheet-like olistostromes migrated in a broad front towards the axes of the Inner-Calcalpine synclines. The line-source character of unchannelized clastic influx from anticlines is different from fault-scarp breccias, slope aprons and the point-source of fan models. Some olistostromes document the initial tectonic elimination of various depocenters and can be recognized below following tectonic units: The Lechtal and the Inntal Nappe, the Braunarlspitz Wedge, the Hasenfluh Klippe, the Krabachjoch Thrust Outlier. These tectonic bodies arose from apparent overturning (UeberfaltungBlumer, 1905; UntermuldungLeiss, 1988, 1989 1990) and lie on synclines filled with synorogenic sediments. The thrust distance is 5–10 km.After the transport of the Inntal Nappe into the depocenter of the Lechtal Syncline, the Upper-Cretaceous Muttekopf Gosau was deposited in a depression on the back of the Inntal Nappe. The basal Gosau marks a molasse. The axial plane of the Muttekopf Syncline coincides with that of the Lechtal Syncline. The framework of the dominant Lechtal Syncline does not just contain a Lower but also an Upper Cretaceous profile separated by the Inntal Nappe.The so-called Klesenza Window represents not a true tectonic window of uncovered Arosa Zone, but a deposit of Lechtal Shale with spilite olistoliths.
Zusammenfassung Erst in jüngster Zeit wird die Sedimentologie in die Orogenese einbezogen. Die Lechtaler Kreideschiefer (Unter-/Mittelkreide) der Lechtaler Alpen wurden mittels der Beckenanalyse auf synorogene Ablagerungen untersucht. Die beginnende Faltung zerteilt den epikontinentalen Schelf in weithin aushaltende Synklinal- und Antiklinalzüge. Während die Antiklinalen als Hebungsareale in Erscheinung treten, akkumulieren die Synklinalen als Depozentren Sedimente mit durchgehenden Profilen. Eingeschaltete Olistostrome in Hemipelagiten entlang den Beckenachsen sind typisch für diese Intraplate-Tröge. Rezente Fächermodelle vom Kontinentalhang sind nicht vergleichbar. Olistostrome als finale orogene Serien wurden in den Depozentren unterhalb folgenden tektonischen Einheiten erkannt: Lechtal Decke, Braunarlspitz Schuppe, Hasenfluh Klippe, Inntal Decke, Krabach Masse, Laagers (Larsenn) Deckscholle.Nach der tektonischen Platznahme der westlichen Inntal Decke im ehemaligen Sedimentationsraum der Lechtal Synklinale wird dort nach einem Hiatus die Gosau der Oberkreide als Molasse abgelagert. Die Sedimentationsräume der Lechtal Synclinale/Synclinorium und der Muttekopf Gosau liegen in senkrechter Projektion, nur durch die Gesteinsplatte der Inntal Decke getrennt. Hiermit vergleichbar ist der NW-Rand der Lechtal Decke.Schuppen und Decken der Lechtaler Alpen entwickeln sich aus abgescherten Falten (Blumer, 1905), wobei die dislozierten Antiklinalfirste die Synklinalen mit ihrer Sedimentfüllung überfahren. Der Tektonismus beruht auf Subduktion.Das sogenannte Klesenza-Fenster stellt als Vorkommen der Lechtaler Kreideschiefer mit einem Schwarm von Spilit-Olistholithen kein echtes tektonisches Fenster dar.
Résumé Ce n'est qu'à une époque récente que la sédimentologie a été intégrée aux recherches orogéniques. L'analyse des bassins, appliquée aux «Lechtaler Kreideschiefer» (Crétacé inférieur à moyen, Alpes de Lechtal) montre le caractère synorogénique de cette formation. Le début du plissement a engendré dans le shelf épicontinental une série d'anticlinaux et de synclinaux allongés. Tandis que les anticlinaux formaient des zones soulevées, les synclinaux ont constitué des aires subsidentes de sédimentation continue. Des olistostromes intercalaires mis en place tout le long de ces structures caractérisent ces bassins intraplaques. Ce dispositif n'est pas comparable aux modèles récents de dépôts en éventail effectués à partir du talus continental ou d'escarpements de failles. Certains de ces olistostromes peuvent être identifiés sous les unités tectoniques suivantes, dont la mise en place sur les aires de sédimentation synorogénique a marqué la fin de celles-ci: la nappe du Lechtal, l'écaille du Braunarlspitz, la clippe de Hasenfluh, la nappe de l'Inntal, la masse charriée de Krabach. La flèche de ces charriages est de 5 à 10 km. Le transport de la nappe de l'Inntal occidentale sur le bassin du synclinal du Lechtal a été suivi, après un hiatus, du dépôt, au Crétacé supérieur, de la formation molassique du Gosau du Muttekopf, dans une dépression située sur le dos de la nappe. Il en résulte que l'ensemble du Lechtal comporte une série crétacée inférieure et une série crétacée supérieure, séparées par la nappe de l'Inntal. La bordure nord-ouest de la nappe du Lechtal présente une disposition analogue.La prétendue «fenêtre de Klesenza» n'est pas une vraie fenêtre tectonique découvrant la zone d'Arosa, mais une zone d'affleurement des schistes des schistes de Lechtal accompagnés d'ophiolites spillitiques.
. ( ) . . , , , . . . , , , : , Braunarlspitz, Hasenfluh, , (Larsenn), — . , . »«. . - . (BLUMER, 1905), , . , , ..., » « , , » «.
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11.
Sulfur isotope ratios have been determined in 27 selected volcanic rocks from Iceland together with their whole rock chemistry. The 34S of analyzed basalts ranges from –2.0 to +0.4 with an average value of –0.8 Tholeiitic and alkaline rocks exhibit little difference in 34S values but the intermediate and acid rocks analyzed have higher 34S values up to +4.2 It is suggested that the overall variation in sulfur isotope composition of the basalts is caused by degassing. The small range of the 34S values and its similarity to other oceanic and continental basalts, suggest that the depleted mantle is homogeneous in its sulfur isotope composition. The 34S of the depleted mantle is estimated to be within the range for undegassed oceanic basalts, –0.5 to +1.0  相似文献   

12.
The shear strength of rock joints in theory and practice   总被引：62，自引：10，他引：62  
SummaryThe Shear Strength of Rock Joints in Theory and Practice The paper describes an empirical law of friction for rock joints which can be used both for extrapolating and predicting shear strength data. The equation is based on three index parameters; the joint roughness coefficientJRC, the joint wall compressive strengthJCS, and the residual friction angle r . All these index values can be measured in the laboratory. They can also be measured in the field. Index tests and subsequent shear box tests on more than 100 joint samples have demonstrated that r can be estimated to within ± 1° for any one of the eight rock types investigated. The mean value of the peak shear strength angle (arctan/ n ) for the same 100 joints was estimated to within 1/2°. The exceptionally close prediction of peak strength is made possible by performing self-weight (low stress) sliding tests on blocks with throughgoing joints. The total friction angle (arctan/ n ) at which sliding occurs provides an estimate of the joint roughness coefficientJRC. The latter is constant over a range of effective normal stress of at least four orders of magnitude. However, it is found that bothJRC andJCS reduce with increasing joint length. Increasing the length of joint therefore reduces not only the peak shear strength, but also the peak dilation angle and the peak shear stiffness. These important scale effects can be predicted at a fraction of the cost of performing large scale in situ direct shear tests.With 20 Figures  相似文献   

13.
Strong compositional zonation of the 34 Ma Grizzly Peak Tuff in west-central Colorado is attended by non-monotonic trends in O, Sr, Nd, and Pb isotope ratios. Fiamme from the tuff cluster in chemical compositions and petrographic characteristics, indicating the magma chamber was not continuously zoned but consisted of at least seven compositional layers. The most mafic magma erupted (57 wt% SiO2, fiamme group 7) had 18O= +8.5, initial 87Sr/86Sr=0.7099, Nd, and 206Pb/204Pb=17.80, suggesting that the magma was produced by 50% fractional crystallization of basaltic magma that assimilated 20 to 40 wt% Proterozoic crust. Isotopic compositions of more evolved parts of the chamber (up to 77 wt% SiO2, fiamme group 1) depart from the mafic base-level composition of fiamme group 7, and reflect late-stage assimilation that occurred largely after compositional layering was established. 18O values decrease by as much as 1.5 from fiamme groups 7 through 4, indicating assimilation of hydrothermally altered roof rocks. 18O values abruptly inerease by up to 1.5 between fiamme groups 4 and 3. This discontinuity is interpreted to reflect evolution in an asymmetric chamber that had a split-level roof, allowing assimilation of wall rocks that varied vertically in degree of hydrothermal alteration. This chamber geometry is also supported by collapse structures in the caldera. Late-stage assimilation of heterogeneous wall rocks is also indicated by variations in Sr, Nd, and Pb isotope ratios. Large Sr isotope disequilibrium exists between some phenocrysts and whole-rock fiamme, and initial 87Sr/86Sr ratios in phenocrysts are as high as 0.7170. values regularly increase from-13.0 in fiamme group 7 to-11.3 in fiamme group 3, and then decrease to-12.2 in fiamme group 1. 206Pb/204Pb ratios generally increase from 17.80 to 17.94 for fiamme groups 7 through 1. The rhyolitic parts of the Grizzly Peak Tuff have isotopic compositions that could be attributed to a purely crustal melt. It is unlikely, however, that the mafic parts of the tuff were generated by crustal melting, and the compositional and isotopic variations across the entire zonation of the tuff are best explained by fractional crystallization of mantle-derived magmas, accompanied by extensive assimilation of Proterozoic crust.  相似文献   

14.
Stochastic models are derived for two source formulations for explosions. Using this kind of model, a comparison is made between source time functions due to Blake, Haskell, Mueller and Murphy, and Von Seggern and Blandford, for explosions, and between -square (Aki, Brune)and -cube (Aki, Haskell)models for earthquakes. When seeking a stochastic model for records of Rayleigh waves from atmospheric explosions, the k-model corresponding to Haskell's time function was found to be an appropriate choice.  相似文献   

15.
Petrology and oxide mineral chemistry are presented on 5 kimberlite dikes that are classified into three groups: (1) one dike is highly carbonated and highly oxidized (> MH) and is characterised by chlorite+Mn-titanomagnetite+rutile+hematite (after chlorite)+maghemite (after titanomagnetite), with ilmenite and perovskite being absent; (2) three dikes are typified by atoll-textured spinels +phlogopite+euhedral Mn-picroilmenite, of intermediate oxidation state (WM-FMQ) with coexisting deuterically serpentinized olivine+Ni-Fe alloys and magnetite; (3) the remaining dike records an early crystallization event under very low ( WM) redox conditions that precipitated anionic-deficient spinels and a Mg-Ti-Cr-wüstite-type phase, followed by late stage more oxidizing (=FMQ) Mnpicroilmenite.Spinels are complexly zoned and crystallization trends among the dikes are diverse, underscoring the fact that no single compositional trend, or evolutionary sequence is typical of kimberlites. Ilmenites are euhedral, and criteria for groundmass crystallization are established. Extraordinarily high MnO (max 17 wt%) contents and high geikielite (62 mole%) concentrations expand the ilmenite field typically assigned to that of kimberlites. Zirconium, Nb and Cr are present in concentrations of 0.5–3 wt% (as oxides) in ilmenite. These highly incompatible elements, along with Mn, are concentrated in late stage melt fractions. The high pyrophanite contents, which are more typical of silicic alkali suites, are accompanied by phlogopite in the Koidu dikes.Objective evaluations of kimberlite-carbonatite relations, as outlined in the literature, cannot be made based on the oxide mineral group. Much of the compositional data for oxides in kimberlites are on mantle-derived xenolith suites and are not from oxides derived from the crystallization of kimberlitic melts.Assessments of the fO2's of kimberlites have considerable potential in evaluating diamond survival through redox reactions. Manganese-rich (+Nb, Zr, Cr) ilmenites are typical of many kimberlites and should be considered in the suite of index minerals employed in prospecting.  相似文献   

16.
One objective of the aerial radiometric surveys flown as part of the U.S. Department of Energy's National Uranium Resource Evaluation (NURE) program was to ascertain the spatial distribution of near-surface radioelement abundances on a regional scale. Some method for identifying groups of observations with similar -ray spectral signatures and radioelement concentration values was therefore required. It is shown in this paper that cluster analysis can identify such groups with or without a priori knowledge of the geology of an area. An approach that combines principal components analysis with convergentk-means cluster analysis is used to classify 6991 observations (each observation comprising three radiometric variables) from the Precambrian rocks of the Copper Mountain, Wyoming area. This method is compared with a convergentk-means analysis that utilizes available geologic knowledge. Both methods identify four clusters. Three of the clusters represent background values for the Precambrian rocks of the area, and the fourth represents outliers (anomalously high214Bi). A segmentation of the data corresponding to geologic reality as interpreted by other methods has been achieved by perceptive quantitative analysis of aerial radiometric data. The techniques employed are composites of classical clustering methods designed to handle the special problems presented by large data sets.  相似文献   

17.
The 19 November 1923 earthquake in the Aran Valley (Central Pyrenees), with observed maximum intensityI max = VIII (MSK), has been studied through the compiling and reviewing of macroseismic information and collecting and processing early seismograms. Analysis of macroseismic data gives a focal depth ofh = 5 km and an anelastic attenuation coefficient 10–3 km–1. Analysis of early instrumental records allows the computation of estimate of magnitude (M L = 5.6) and seismic moment (M o = 1.1 × 1017 N × m) which are consistent with the values ofI o andh obtained from macroseismic data.  相似文献   

18.
Mathematical methods were employed in an investigation of syntexis in the Gabbro di Sondalo, a mafic igneous formation in the Central Alps (Italy). A set of 100 specimens was selected according to sampling criteria and analyzed by X-ray fluorescence for eight elements; Q-mode and R-mode factor analysis then was applied to these data. Results of the computations indicate that the general trend of differentiation is related to the syntexis of gneissic wall rocks (Gneiss del Monte Tonale) in the mafic melt. Ca and Mg are abundant in the gabbro, and Si and K in the gneiss; the independent variation trend of Fe and Ti may be related to a differentiation episode due to a magmatic phase. Spatial representation of multivariate data on differentiation also was performed on the main elements and a picture of the trend of syntexis was mapped.  相似文献   

19.
The achievements of the mineral industry of Israel and an overall reconnaissance of the natural resources endowment of the country have been evaluated by the areal value estimation method, using the COMOD software package. In broad terms, the evaluation relies on geological variables obtained from quantifying the geological map of a region and on cumulative past production records, which, when prorated per unit area, yield a series of unit regional values (u.r.v.)measurements for individual commodities, resource sectors, and total resources. The two groups of variables facilitate conducting comparisons with other well-developed and/or geologically similar regions from which the future potential of the region, with respect to both overall endowment and individual commodities, can be assessed. The model underlying this appraisal method assumes that all regions above a size of about 5,000 sq kms are equally valuable with respect to total endowment in natural resources, regardless of inherent geological characteristics. To date, several areal value estimation studies have been carried out for 11 different countries, encompassing a total of 111 politically-administratively defined regions. These studies provide an adequate information base for between-region comparisons. The individual states of the United States, constituting what can be regarded as well-developed regions, may serve as an expectation for all such comparisons. The distribution of the u.r.v. of total resources of the individual states is lognormal with a geometric mean of 54,954 1967 U.S. dollars per square kilometer. Based on the above assumption, this value can serve as a conservative estimate for the total output any region can be expected to produce. Thirty different mineral commodities are known to exist in Israel. Of these, 19 are economically exploited and the remaining 11 are at present uneconomical mineral occurrences. Past production records have been obtained and assembled for 14 of the exploited commodities. From these records, a number of statistics were computed to evaluate the development of the mineral industry of the country and its future potential. In absolute figures, the overall cumulative production has been rather small, amounting to only 1,679.8 million deflated 1967 U.S. dollars (equivalent to 2,082 million current U.S. dollars or 10,260 million current Israeli pounds). Only bromine, potash, and phosphate are of worldwide significance, amounting respectively to 10, 2.9, and 1 percent of the world production in 1977. Construction materials, with the longest production history, have been the most valuable, accounting for 53.6 percent of the total cumulative output. They are followed by nonmetals (34.7 percent),metals (8 percent)and fuels (3.7 percent).The value-ranking of individual commodities and their respective contribution to the total cumulative output is: cement, 35 percent; potash, 19 percent; stone, 15 percent; phosphate, 11 percent; copper, 8 percent; sand and gravel, 4 percent; bromine, 3 percent; petroleum, 2.5 percent; natural gas, 1 percent; periclase, 0.7 percent; salt, 0.4 percent; and glass sand, 0.2 percent. Total annual output for the period 1948–1977 exhibited a constant growth with no indication of approaching a plateau of diminishing returns. As new commodities became exploited, the share of constructional materials in the total output gradually declined from 100 percent in 1948 to 45 percent in 1977. The contribution of the mineral industry to the annual gross national product rose steadily from 0.55 percent in 1951 to 2.2 percent in 1964. Thereafter, it fluctuated around an average of about 1.8 percent. Total output and production of constructional materials correlate very highly with both gross national product (GNP)and population size. However, when only the annual changes in these variables are considered, the correlation coefficients are found to be insignificant. The u.r.v. of Israel (with an area of 20,700 sq kms and a population of 3,653,000)is 81,154 deflated 1967 U.S. dollars per sq km. It exceeds the expected value for well-developed regions. It can therefore be concluded that Israel is not exceptionally poor in natural resources, as is commonly felt. On the other hand, its high u.r.v. also implies (unfortunately)that the development potential of its mineral industry is rather limited. The u.r.v. estimates, which are based on area alone, can be refined to some degree by considering the geological characteristics of the investigated area. The geological composition of the country was quantified by point counting the geological map, using a grid network of 40.3 sq km cells. Each map unit was assigned to one of 65 standard time-petrographic units. This sampling density results in the recognition of 11 time-petrographic units (instead of 15, which are actually present).Based on linear statistical association between mineral resource diversity and geological diversity established for the states of the United States, Israel can be expected to possess 31 different commodities. Since only 19 have thus far been exploited, Israel can be expected to produce 12 additional commodities. The identity of these missing resources can be inferred by examining the inventory of commodities produced in other regions with a similar geological framework and by evaluating the potential of the 11 noneconomical mineral occurrences, which have already been discovered in the country. The geology of Israel was compared to 12 other regions; of these Egypt, Libya, Sudan, and Sinai were found to be most similar to Israel, each having 8 or 9 time-petrographic rock types in common with Israel, 7 of which are identical. Based on these comparisons and on additional information from other sources, it appears that the commodities that are more likely to be produced in the foreseeable future include manganese, feldspar, uranium (from phosphates),lignite, oil shale, and iron. The mineral industry of Israel accomplished quite significant achievements in the course of its modern history of only 35 years. These resulted from concerted national exploration and development efforts, which were supported by massive governmental capital investments. The areal value method of mineral resources appraisal is based on a cybernetic black box system model in which the degree of commitment derived from the socioeconomic infrastructure is viewed as the driving agent in converting the inherited geological characteristics of the region into economic marketable mineral commodities. The case history of Israel provides a strong substantiation for this generalized system model.  相似文献   

20.
Origin and differentiation of picritic arc magmas,Ambae (Aoba), Vanuatu   总被引：3，自引：2，他引：1  
Key aspects of magma generation and magma evolution in subduction zones are addressed in a study of Ambae (Aoba) volcano, Vanuatu. Two major lava suites (a low-Ti suite and high-Ti suite) are recognised on the basis of phenocryst mineralogy, geochemistry, and stratigraphy. Phenocryst assemblages in the more primitive low-Ti suite are dominated by magnesian olivine (mg 80 to 93.4) and clinopyroxene (mg 80 to 92), and include accessory Cr-rich spinel (cr 50 to 84). Calcic plagioclase and titanomagnetite are important additional phenocryst phases in the high-Ti suite lavas and the most evolved low-Ti suite lavas. The low-Ti suite lavas span a continuous compositional range, from picritic (up to 20 wt% MgO) to high-alumina basalts (<5 wt% MgO), and are consistent with differentiation involving observed phenocrysts. Melt compositions (aphyric lavas and groundmasses) in the low-Ti suite form a liquid-line of descent which corresponds with the petrographically-determined order of crystallisation: olivine + Cr-spinel, followed by clinopyroxene + olivine + titanomagnetite, and then plagioclase + clinopyroxene + olivine + titanomagnetite. A primary melt for the low-Ti suite has been estimated by correcting the most magnesian melt composition (an aphyric lava with 10.5 wt% MgO) for crystal fractionation, at the oxidising conditions determined from olivine-spinel pairs (fo2 FMQ + 2.5 log units), until in equilibrium with the most magnesian olivine phenocrysts. The resultant composition has 15 wt% MgO and an mg Fe2 value of 81. It requires deep (3 GPa) melting of the peridotitic mantle wedge at a potential temperature consistent with current estimates for the convecting upper mantle (T p 1300°C). At least three geochemically-distinct source components are necessary to account for geochemical differences between, and geochemical heterogeneity within, the major lava suites. Two components, one LILE-rich and the other LILE- and LREE-rich, may both derive from the subducting ocean crust, possibly as an aqueous fluid and a silicate melt respeetively. A third component is attributed to either differnt degrees of melting, or extents of incompatible-element depletion, of the peridotitic mantle wedge.  相似文献   

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