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1.
The European Geotraverse (EGT) crosses along a 4000 km profile from the North Cape to Tunisia the following main suture zones:
  • the Tornquist-Teisseyre zone between the Baltic Shield and the Variscan realm,
  • the transition zones between Rhenohercynian and Saxothuringian as well as between Saxothuringian and Moldanubian zones in the Variscan part of central Europe, and
  • the collision zone between the European continent and the Adriatic microplate.
    • Some structural aspects of these suture zones are described.  相似文献   

    2.
    H. Kenneweg 《GeoJournal》1994,32(1):47-53
    The development of inventory activities in the field of forest damage assessment and monitoring during the last decade in Germany and the present state are recorded as far as remote sensing has been involved. Any forest inventory is influenced by external factors, and the resulting difficulties for an introduction of new technologies are described. The following tasks and/or methods are discussed:
  • -global approaches to deforestation monitoring
  • -working experience from local and regional case studies
  • -vegetation and vegetation-damage monitoring in ”urban forestry”
  • -sampling approaches for large areas
  • -the contribution of spectral signatures and satellite remote sensing to damage assessment
    •   相似文献   

    3.
    In the past lattice parameters b and c of muscovite s.1. from pelitic schists have been used to determine its phengite and paragonite component. A critical review of the literature and of some new data shows, however,
  • that a convincing statistical correlation between these physical and chemical properties does not exist
  • that an eventual trend-like correlation cannot be used for a quantitative analysis of phengite and/or paragonite components in muscovite.
    • Obviously further factors influence the lattice parameters of muscovite s.1., besides octahedral and interlayer chemistry.  相似文献   

    4.
    Hercynian absolute ages obtained from many plutonites and metamorphites of the Sierras Pampeanas compel to consider this polymetamorphic domain rather as an intermediate hinterland and axis of divergent symmetry between the two elementary geosyncline ranges (Cuyanides and Bolivianides) of the south america hercynian orogen. Attempt of Cuyanides paleogeographic organization indice to define during the geosyncline period (Cambrian to Devonian):
  • the Pampean zone which consist of:
    1. an internal sub-zone (eastern) or pampean s. st. with hinterland significance
    2. a more external sub-zone (western) or transpampean or Umango sub-zone with intermediate features between eugeanticlinal ridge and eugeosynclinal furrow;
    3. the Calingasta zone as a typical eugeosynclinal furrow with pelagic-terrigenous ordovician sedimentation and ophiolitic magmatism followed by early silurian than devonian Flyschs;
    4. the Zonda zone as an external ridge with neritic cambro-ordovician facies and devonian flyschs.
    The unwonted position of Zonda no metamorphic Facies surrounded by Calingasta and Umango metamorphic Facies, suggest its window situation and wide allochthonous structures for the internal zones. An eastward origin of the nappes is discussed in relation with pampean syntectonic metamorphism and plutonism. Essentially, structures are referred to the Acadian phase (= bretonic) but early paleo-hercynian phases are also emphasized to explain Flyschs sequences and some pampean plutonic cycles. Tardi- and Post-hercynian organization is briefly sketched with related molasses, neomolasses and magmatism. The remarquable geosyncline pattern of the Cuyanides is emphasizes in all stages of its evolution and under aspects however tectonic, magmatic and metamorphic. Finally, the fundamentally western polarity of the Cuyanides is replaced into the most general framework of Gondwanides organization.  相似文献   

    5.
    Wave number discretization method is applied to study the near-field of seismic sources embedded in a cracked elastic solid. Near-field solutions are obtained for horizontal and vertical line forces. Effects of modifications in cracks of focal region on ground motion, in the near-field, are studied numerically for different
  • ? values of crack density
  • ? saturation of cracks
  • ? width of cracks, and
  • ? regimes of connection between cracks.
    • An earthquake process is assumed to be going through five major stages. These stages represent continuous accumulation of stress, interconnections between cracks leading to eventual failure and drainage of fluid from cracks after the major shock. Variations in the velocity ratio of waves noted from accelerograms verify the process of preparation of an earthquake.P wave contribution to vertical acceleration is negligible when the source is a vertical line force andS wave contributes only a little to horizontal acceleration when the source is a horizontal line force.  相似文献   

    6.
    The wet tropical weathering of Precambrian spessartite quartzites leads to the formation of secondary oxidized ores. These ores result from different successions of superimposed elementary processes, among them:

  • garnet hydrolysis: Mn, Ca, and Fe are leached, and only an amorphous, silicoaluminous phase remains.
  • lithiophorite neoformation: Added manganese combines with alumina of the amorphous, Si-Al products.
  • leaching: Voids appear in the central part of the weathered garnets. They may widen, leaving only the quartz matrix with polyhedric voids.
  • epigenic replacement: The quartz is replaced by cryptomelane, while the garnets may remain unweathered.
    • The various ore types are characterized by the sequence of transformations and by the volumes that each transformation affects. These transformations are old because they are observed not only in situ ores but also in removed detrital ores. In the same way the major part of the accumulated stocks of oxidized ores must be old.  相似文献   

    7.
    About 1,500 samples of Pb and Zn concentrates and ores from 89 ore deposits of the polymetallic province of the Andes of central Peru have been analyzed. The distributions of Cd, In, Ge, Ga, Ag, Bi, Se, Hg, and Sn in these ore deposits can be reported on the basis of
  • the typology of ore deposits, i.e., some types of ore deposits (syndiagenetic without associated volcanism and volcano-sedimentary of Triassic-Lias, exhalative sedimentary of Upper Jurassic) show very characteristic minor and trace element patterns;
  • the temperature of ore formation that controls the abundance of Bi and Hg, in general, and of Ag, Se, and Sn in the Tertiary hydrothermal deposits;
  • the age and nature of the country rock, e.g., an In, Ga, and Sn positive anomaly and Cd negative anomaly appears in the deposits with Paleozoic country rock;
  • the geographic position of ore deposits, e.g., in the northern part of the province an In, Ga, Ge, and Cd positive anomaly appears.
    •   相似文献   

    8.
    Computer Cartography has gone through many changes during its short life. This article tries to document some of the results of the development. The major conclusions are:

  • - whereas the application of computer mappins is fluurishing, conceptual development is slow;
  • - as a result the applications are simpler than they could be, given the development of computer science, and brute force reigns over elegance.
    • To exemplify these points, the main types of Geographic Information Systems are discussed with respect to their recent achievements: Catastral mapping, Thematic mapping, Topographic mapping, Resource Information Systems, and Digital Terrain Models.  相似文献   

    9.
    Massive sulfide deposits located on Hercynian islets of northwestern Morocco exhibit four main characteristics:
  • They are strata-bound massive pyrrhotite deposits mined for sulfur and/or base metals occasionally occurring as sulfides of workable grade.
  • Volcanic rocks with which these massive sulfide orebodies are associated are scarce, although always present as acid flows of submarine emissions of either rhyolitic or more often quartz-keratophyric nature. Later on, basic plutonics intruded the pelitic country rocks.
  • Stockworks underlying the massive sulfide orebodies are common, but not systematic. When present, they occur in siltite ± phyllite ± carbonate rocks at the wall of massive sulfide lenses. They consist of fissural disseminations transformed by epimetamorphic recrystallization and by one schistosity generally concordant with s0.
  • Associated alterites and exhalites belong to three types, i.e., sericitite (or biotite-rich rock), chloritite, and/or chert (jasper).
    • Generally well located in a back-arc basin environment characterized by a two-phase geological history, i.e., “extension and volcanism, compression and metamorphism”, these volcano-sedimentary deposits exhibit distal features with regard to the volcanism coeval with their sedimentation. They are mostly linked with strongly reducing environmental properties entailing pyrrhotite and/or magnetite syngenetic deposition, whatever the iron activity.  相似文献   

    10.
    Chemical and mineralogical compositions of granitic rocks of the French Massif Central enable us to classify them into two distinct groups: (i) leucogranites, (ii) granodiorites or quartz-monzonites, separated by a natural gap. The differences between these two groups are not only chemical and mineralogical, but are also reflected by:
  • conditions of crystallization as deduced from compositions and from thermal metamorphism of xenoliths.
  • nature of inclusions and, especially, the occurrence of basic fine-grained igneous xenoliths restricted to the granodiorite — quartz-monzonite group
  • relations between intrusive and autochtonous migmatitic masses;
  • levels of formation and of intrusion; the granodioritic and quartz-monzonitic magmas have originated at deeper horizons of the earth's crust than the leucogranitic one, but have risen higher.
    • In our opinion these differences are linked, and the specific characteristics of the granodiorites and quartz-monzonites are related to the presence of basic igneous inclusions. These inclusions are relics of deep basic intrusions in the earth's crust, which have overheated the surrounding acid rocks beyond the minimum temperature of melting. Thus granodioritic or quartz-monzonitic melts were produced and were able to rise to superficial levels. These inclusions are missing in leucogranites. The compositions of the latter and their poor mobility suggest a wet anatectic origin in minimal PT conditions.  相似文献   

    11.
    The exploration for hydrocarbons in the deepest tectonic »floor« underneath the Vienna basin with depths of 6.5–8.5 km, was undertaken between 1977 and 1985 and based on several important conditions:
  • -The assumption that an autochthonous sedimentary cover lies upon the Crystalline Basement (Bohemian massif) below the Neogene basin infill and the Alpine-Carpathian nappes.
  • -Expressed high zones exist within the Vienna basin with exploration targets at depths reachable by drilling.
  • -The significant accumulation of oil- and gasfields m shallower position over the area of interest.
    • As a result of the 4 deep wells drilled for the abovementioned targets more information has been acquired concerning the stratigraphy, facies distribution and depth positions of the autochthonous Jurassic, Upper Cretaceous and Tertiary Molasse along the Eastern flank of the Crystalline basement spur of the Bohemian Massif. The allochthonous, Waschberg- und Flyschzone, both Alpine-Carpathian units underneath the Vienna basin, have been penetrated by these wells for the first time and the overthrust of the Calcareous Alps over the Flysch nappes has been proven (well Aderklaa UT1). Additional information about Neogene sedimentation and faulting was obtained. Drilling results made it possible to get a more comprehensive picture of the 3 tectonic »floors« of the Vienna basin, m detail represented by the Zistersdorf and Aderklaa profiles. Thick basin marls of the Upper Jurassic represent a large source potential for hydrocarbons. The favourable reservoir layers, detected in the Mesozoic sections of the foreland area have not been encountered here till now. A high supply of free hydrocarbons within the deepest floor must be assumed on the basis of many oil and gas shows, a major gas kick in Zistersdorf ÜTla and a limited oil production from a fractured zone along a thrustline in the Maustrenk ÜTla well, both occurring in an overpressured environment.  相似文献   

    12.
    Detailed petrographic and geochemical investigations on the rocks underlying the Devonian stratiforme pyrite and barite deposits of Eisen (Saar district), Meggen (Westphalia), and Rammeisberg (Harz Mountains) in the Rhenish Schiefergebirge have led to the following conclusions:
    1. These deposits are tied to dark shales of the pelagic basin facies. In all cases a local depression of the sea floor coincides largely with the spatial extension of the overlying pyrite and barite bodies. These depressions are marked by a large number of sand and silt intercalations, accumulations of reef debris and a significant lower carbonate content.
    2. The dark shales underneath the deposits have conspicuously high, but strongly varying contents of Mn, Zn and Pb. This, corresponding with the low carbonate content, is characteristic for the presence of hydrothermal, metalliferous emissions.
    3. Predepositional phases of sulfide and barite emplacement are indicated by small layers and lenses.
      相似文献   

    13.
    Various stratigraphic and paleoenvironmental results arise from mineralogical, geochemical and micromorpho logical investigations on Late Cretaceous and Cenozoic sediments recovered by the Deep Sea Drilling Project in the West Pacific:
  • Stratigraphic correlations. The deep pelagic red clays deposited on either side of the Shatsky Rise contain a variety of clay minerals, which point to the importance of eolian detrital supply and allow rough stratigraphic correlations.
  • Climate and paleocirculation. Neogene sediments of the Lord Howe Rise area reflect closely the relationship between the evolution of the Antarctic ice sheet and related aridification stages, and the atmospheric and oceanic circulation pattern since 14 my.
  • Regional and global tectonics. The post-Eocene deposits around New Zealand express a sequence of tectonic events and of relaxation stages, associated with changes in the circulation regime. Along the inner wall of the Japan Trench, clay mineral successions document the existence of an outer continental landmass until the late Oligocene, its collapse associated with volcanism close to the Paleogene-Neogene boundary, and an increased detrital influence from Japan since the early-middle Miocene.
  • Volcanism, diagenesis and detrital supply. The Aptian to Maastrichtian sediments in the Mariana Basin document a complex sequence of geochemical and geodynamical events: proximal volcanism and local supply from subaerial archipelagoes; early marine diagenesis during lithospheric subsidence and plate migration; and finally the occurrence and evolution of terrigenous input from distant sources distributed by marine currents.
    •   相似文献   

    14.
    P, T, \(X_{{\text{CO}}_{\text{2}} }\) relations of gehlenite, anorthite, grossularite, wollastonite, corundum and calcite have been determined experimentally at P f =1 and 4 kb. Using synthetic starting minerals the following reactions have been demonstrated reversibly
    1. 2 anorthite+3 calcite=gehlenite+grossularite+3 CO2.
    2. anorthite+corundum+3 calcite=2 gehlenite+3 CO2.
    3. 3anorthite+3 calcite=2 grossularite+corundum+3CO2.
    4. grossularite+2 corundum+3 calcite=3 gehlenite+3 CO2.
    5. anorthite+2 calcite=gehlenite+wollastonite+2CO2.
    6. anorthite+wollastonite+calcite=grossularite+CO2.
    7. grossularite+calcite=gehlenite+2 wollastonite+CO2.
    In the T, \(X_{{\text{CO}}_{\text{2}} }\) diagram at P f =1 kb two isobaric invariant points have been located at 770±10°C, \(X_{{\text{CO}}_{\text{2}} }\) =0.27 and at 840±10°C, \(X_{{\text{CO}}_{\text{2}} }\) =0.55. Formation of gehlenite from low temperature assemblages according to (4) and (2) takes place at 1 kb and 715–855° C, \(X_{{\text{CO}}_{\text{2}} }\) =0.1–1.0. In agreement with experimental results the formation of gehlenite in natural metamorphic rocks is restricted to shallow, high temperature contact aureoles.  相似文献   

    15.
    The Mambéré Formation constitutes a horizontal unit located in the western and southwestern part of the Central African Republic. Stratigraphical and sedimentological study provides strong argument to attribute these deposits a glacial origin. A palaeogeographical reconstruction has been outlined in order to precise the age of the formation. Two main categories of glacial deposits have been recognized:
  • glaciogenic deposits made of basal tills (with facetted pebbles) and flow tills (with flattened blunt pebbles);
  • reworked glacial deposits formed of sandstones and conglomeratic sandstones, in continuous beds, lenses or isolated blocks, together with siltstones and bedded sandstones.
    • The southerly provenance of the detrital material is demonstrated by quartz grain surface analysis and heavy-mineral study. This material results essentially from the dismantling of the Precambrian Schistoquartzitic Complex and secondarily from the Granitogneissic Complex. According to the palaeomagnetic polar paths and the migration of the glacial centers over the African continent during the Palaeozoic, the Mambéré Formation may be attributed a Lower Silurian age by reference to similar formations observed in Cameroon or a Lower Carboniferous age by comparison with the glacial formations reported from Niger and Egypt.  相似文献   

    16.
    The formation of isolated silicateous copper deposits is controlled by two main conditions:
    1. oversaturation of groundwaters in silica
    2. lateral inflow of copper bearing and slightly acid solutions originating from the oxidation of primary sulfide deposits.
    The basic copper silicate chrysocolla is formed by chemisorption of copper ions by disilicic acid with a net-like structure. Under favourable conditions copper silicate deposits are formed which contain up to several million tons of copper as for example the La Exotica deposit in Northern Chile. The copper values of these deposits sometimes exceed those of the primary sulfide deposits. Thus, the oxidation of sulfide deposits, the migration of copper bearing solutions and the chemisorption of copper ions by the disilicic acid can result in workable new copper concentrations originating from sulfide protores. High concentrations of silica in groundwaters and thus the chemisorption of copper ions by the disilicic acid as an ore forming process is restricted to arid or semiarid regions. Therefore it is proposed to call such deposits arid silicateous infiltration deposits. Infiltration deposits are related to weathering processes. “They comprise products of weathering by which valuable substances were leached from the host rocks, migrated in groundwaters and were redeposited in other neighbouring rocks” (Smirnov, 1970, p. 324).  相似文献   

    17.
    Caliches: Large areas of the northern Sahara and the Algerian High Planes are covered by mostly 1–5 m thick caliches. Their age (Pliocene in the Sahara) decreases to the north and their precipitation is generally independent of groundwater. Their profile is composed (from top to base) as follows:
  • Upper soil, loose and mostly of eolian origin.
  • Upper part of caliche, with very characteristic, dense, partly layered-knobby texture, formed slowly by solutional and reprecipitational processes of ± freely outcropping caliches under addition of eolian material.
  • Under part of caliche, highly porous, somewhat chalky and greyish-white; precipitated mainly by capillar rise of solutions in permeable and calcareous rocks.
  • Substratum, preferentially calcareous sandstones, alluvial deposits and marls.
    • The mineralogy of the caliches (whose main components are represented in fig. 4 A-C) is rather monotonous: in addition to relicts of the substratum (partly dissolved or pushed aside by precipitation of calcite), there are only newly formed low-Mg-calcite and some quarzine (length-slow quartz). Sr-contents of calcite rise clearly from substratum to upper part of caliche. Gypsiferous Crusts (or Cementations): They are found mainly in the surroundings of Chotts (flat, ± saline lakes) and in oases of the NE-Algerian Sahara. Their formation began — mostly caused climatically — after the period of caliche formation and is still continuing in some places. Most of these gypsum-crusts are formed by evaporation of near-surface groundwaters in sandy soils. Water saturated in gypsum precipitates large crystals of gypsum (relatively low in Sr), partly filled by sand, at groundwater-surface. Fine crystalline crusts (relatively high in Sr) are formed by ascendent waters with lower gypsum content ± directly under the landsurface.  相似文献   

    18.
    According to Sakai-Ohmoto's theory regarding the evolution of sulfur isotopes in hydrothermal systems, in conjunction of new data on chemical resaction equilibrium constants and equilibrium isotopic fractionation factors as well as on individual ion activity coefficients of aqueous sulfur species, the following lgfo2.-pH diagrams are constructed:
    1. mole fractions of aqueous sulfur species (X i ),
    2. stability fields of some minerals in the Fe-S-O system,
    3. diagram depicting the oxidation-reduction-state ratio for aqueous sulfur species (R′)
    4. isotopic compositions of sulfur compounds ( \(\delta S_1 ^{34} \) ).
      相似文献   

    19.
    Laihuite reported in the present paper is a new iron silicate mineral found in China with the following characteristics:
    1. This mineral occurs in a metamorphic iron deposit, associated with fayalite, hypersthene, quartz, magnetitc, etc.
    2. The mineral is opaque, black in colour, thickly tabular in shape with luster metallic to sub-metallic, two perfect cleavages and specific gravity of 3.92.
    3. Its main chemical components are Fe and Si with Fe3+>Fe2+. The analysis gave the formula of Fe Fe 1.00 3+ ·Fe 0.58 2+ ·Mg 0.03 2+ ·Si0.96O4.
    4. Its DTA curve shows an exothermic peak at 713°C.
    5. The mineral has its own infrared spectrum distinctive from that of other minerals.
    6. This mineral is of orthorhombic system; space group:C 2h /5 ?P21/c; unit cell:α=5.813ű0.005,b=4.812ű0.005,c=10.211ű0.005,β=90.87°.
    7. The Mössbauer spectrum of this mineral is given, too.
      相似文献   

    20.
    Agglomeration areas in the GDR are those regions, which are characterized by an above average level of regional concentration of productive forces and their conditions of reproduction. The economic potential concentrated in these regions represents a large part of the national economy. It is possible to describe the territorial structure of these agglomeration areas by general indices (agglomeration core — agglomeration field — agglometation fringe; polycentric node-band-structure), but also the individual features of each one of these regions are to be attended. They are expressed for the first time by several forms of localization of plants and by the structure of settlements and settlement networks. The present main tendencies in the development of the agglomeration regions are:
  • They succeeded in minimizing the regional disparities of productivity between different agglomeration regions and within them, and in stabilizing the economic position of these regions by systematic measures for investment and rationalization and the hereby influenced structural changes.
  • At present and up to 1990 the completion of housing programme is of foremost importance by which the main activities will shift from the urban fringe to the centres of the cities; provincial towns and smaller settlements will also participate in this programme.
    • The main target of these activities is to remove imperfect structures and other burning problems of the agglomeration regions step by step. Geographical Institutes are dealing with the management of these tasks too.  相似文献   

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