首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Theoretical analysis, calculations, and comparison with the results of observations in Lake Baikal, Lake Tanganyika, and the World Ocean are performed for the vertical stability E and the Brunt-Väisäla frequency N in the form of N 2 with regard to all components (at the constant temperature T and the salinity S, the common adiabatic form at T, S Const). The adiabatic stability E ad and the Väisäla frequency N in the form of N ad 2 are always positive; at a change from the inverse to the direct temperature stratification, they have deep minimums reaching 10?16 m?1 and 10?15 s?2 and less; the minimums have the form of a special point, a reversal point of the first kind called a “cusp.” The reality of these reversal points is confirmed by the analysis of the investigation procedure, comparison with the results of previous theoretical (Sherstyankin, et al., 2007), and experimental (observations in Baikal, Shimaraev et al., 1994) works. The features of vertical profiles of E ad , E andN ad 2 , N 2, as well as the layers where the Brunt-Väisäla frequency is less than the inertial frequency, are studied. The analysis with regard to all components of the stability E ad and the Brunt-Väisäla frequency N makes a great contribution to understanding of mixing processes in theoretical and experimental investigations; it is valid in all reservoirs of the Earth with inverse and direct temperature stratification, including Lake Baikal, Lake Tanganyika, and the World Ocean.  相似文献   

2.
Doris Schmied 《GeoJournal》2000,50(2-3):91-96
After the fall of the Berlin Wall in November 1989, East Germany experienced a demographic shock as the ensuing insecurity and disorientation of the population was mirrored in their demographic behaviour. The situation is examined with respect to marriage, fertility and mortality. There are now signs of recovery but most people in the New Länder are still traumatised by events: nuptiality and fertility are still extremely low, while mortality is rapidly moving towards West German levels. Future demographic development will very much depend on socio-economic development and the provision of both hard and soft infrastructure conducive to stable partnerships and families since the current 'framework' has proved to be particularly unfriendly to women and children.  相似文献   

3.
4.
The late Archaean (ca. 2.7 Ga) Ilomantsi greenstone belt hosts a large number of small mesozonal gold occurrences. The Rämepuro deposit is spatially related to a feldspar porphyry dyke which has intruded the contact between metagreywackes and intermediate metavolcanic rocks. It consists of gold-bearing quartz-tourmaline-sulphide veins located mainly within an intensively altered and sheared zone about 20-30 m in width. Two types of fluid inclusions were distinguished in the quartz veins: (1) H2O-CH4 (Й equiv. wt% NaCl), and (2) H2O-CO2 (⢬ equiv. wt% NaCl). The two compositionally different fluid-inclusion types occur in separate veins. The compositions of decrepitate residues indicate that the type 1 fluid inclusions consist predominantly of Na, S, Ca, Cl, and in lesser proportions of K and Fe. The residues of the type 2 fluid inclusions are dominated by Na, Ca, Cl and minor K. For the type 1 and type 2 fluid inclusions, microthermometric experiments indicate average homogenisation temperatures of 310-350 and 220-250 °C respectively. Both types of fluid inclusions contain 1-3 anisotropic solids (Ca/Mg carbonate?, nahcolite?, tourmaline?). Sulphide daughter minerals occur only in the type 1 fluid inclusions. This fluid type is also often associated with short trails of sulphide inclusions which suggest mobilisation and redistribution of ore constituents. Some type 1 fluid inclusions display distinct morphological features ("implosion textures") related to post-trapping re-equilibration. The presence of the fluid-inclusion re-equilibration textures in some auriferous quartz veins and their absence in other gold-bearing quartz veins suggest an age difference between them. This conclusion is also supported by the compositionally different fluid regimes associated with the different quartz veins, indicating a change from reducing (CH4) to a more oxidising (CO2) fluid environment. The fluid-inclusion evidence suggests two separate gold mineralisation events, one related to late Archaean regional metamorphism, the other to Palaeoproterozoic thrusting and metamorphism.  相似文献   

5.
《Gondwana Research》2014,25(3):983-990
The bivalved bradoriid arthropod Kunmingella douvillei (Mansuy, 1912) is the most common species in the Lower Cambrian Chengjiang Lagerstätte. Its soft anatomy has been reported based on well-preserved specimens. However, as with other Cambrian arthropods, its reproductive behavior is poorly documented. Rare specimens of K. douvillei preserved with eggs have been reported. Our new collections confirm that the eggs were directly attached to the last three pairs of biramous appendages and verify the head–trunk boundary suggested by previous work. The brooding behavior of K. douvillei was most probably related to its small body size, as in living crustaceans. The K. douvillei female could carry 50–80 eggs ranging from 150–180 μm in diameter, possibly indicating a K-reproductive strategy; its ontogenetic and reproductive mode might have been an adaptation in response to increasing predatory pressure across the Ediacaran–Cambrian boundary. All of the three main directions of development in the life history of living marine invertebrates, namely planktotrophic larvae, lecithotrophic larvae, and brood care, most likely evolved by Stage 3 of the Cambrian.  相似文献   

6.
Summary The Kylmäkoski deposit consists of a disseminated primary Ni-Cu mineralization hosted by a differentiated ultramafic body. It also shows sulfide veins (tens of meters long and up to 20 cm thick) that evolve laterally to massive Ni-arsenide ores. In these sulfide/arsenide veins, three different ore assemblages can be distinguished: 1) sulfide ores (S ores) composed of pyrrhotite, pentlandite and chalcopyrite with minor amounts of cubanite, sphalerite and argentopentlandite which locally occurs intergrown with Ag-free pentlandite; 2) sulfide/arsenide ores (S/As ores) made up of the former S ores corroded and replaced by nickeline (locally with graphite), with gersdorffite filling discordant veins, abundant minute grains of sudburyite and accessory molybdenite, ullmanite, stibnite, galena and breithauptite; 3) arsenide ores (As ores) composed of nickeline, maucherite and disseminated, zoned cobaltite, with minor chalcopyrite, cubanite, sperrylite, sudburyite, electrum, galena, altaite and pilsenite. These veined ore assemblages were generated by the remobilization of primary, late magmatic arsenide-rich ores (well represented in the Vammala mine) by the intrusion of pegmatitic fluids derived from the partial melting of the metasedimentary country rocks.The early fractional crystallization of the monosulfide solid solution produced a residual As-rich melt that collected most noble metals (specially Pt, Pd and Au) leaving the primary Ni-Cu sulfide ores impoverished in these elements. In fact, late magmatic arsenide ores from Vammala contain up to 42.5 ppm Pd (in the form of extremely fine inclusions of sudburyite in nickeline and maucherite, and dissolved in trace amounts in the lattice of the latter Ni arsenides) and 9.6 ppm Au (concentrated in abundant minute inclusions of electrum in Ni arsenides). Later, during the remobilization of the primary arsenide ores of Kylmäkoski, Pd concentrated both in S/As and As ores in the form of sudburyite and in a rare PdBi compound. It also occurs in trace amounts in nickeline from S/As ores and in maucherite from As ores. Pt mainly concentrated in As ores as sperrylite and, in minor amounts in pilsenite and in cobaltite coronas around sperrylite. It occurs in trace amounts in the cores of zoned cobaltite. Gold is always present in the form of irregular grains of electrum in As ores.
Pt- Pd- und Au-reiche Arseniderze von der Ni-Cu Lagerstätte Kilmäkoski (Vammala Nickel-Gürtel, SW Finnland)
Zusammenfassung Die Lagerstätte Kilmäkoski ist eine disseminierte primäre Ni-Cu-Vererzung, die in einem differenzierten ultramafischen Körper aufsitzt. Hier treten auch Sulfid-Gänge, die bis zu Zehnern von Metern lang und bis zu 20 cm mächtig sein können, auf; aus diesen entwickeln sich lateral massive Nickel-Arsenid Erze. Drei Erzparagenesen können in diesen Sulfid-Arsenid-Gängen unterschieden werden: 1. Sulfidische Erze mit Pyrrhotin, Pentlandit, Kupferkies und geringen Mengen von Cubanit, Zinkblende und Argentopentlandit der örtlich mit Ag-freiem Pentlandit verwachsen ist 2. Sulfid-Arsenid Erze, die aus korrodierten und durch Rotnickelkies verdrängten Sulfid-Erzen bestehen. Diese führen örtlich Graphit, Gersdorffit kommt als Füllung diskordanter Gänge vor. Außerdem gibt es verbreitet kleine Körner von Sudburyit und akzessorischem Molybdänit, Ullmanit, Antimonglanz, Bleiglanz und Breithaup tit. 3. Arsenid-Erze, die aus Rotnickelkies, Maucherit und disseminiertem, zonarem Kobaltit, mit Kupferkies, Cubanit, Sperrylit, Sudburyit, Elektrum, Bleiglanz, Altait und Pilsenit als Nebengemengteile bestehen. Diese gangförmigen Erzparagenesen entstanden durch die Remobilisation von primären, spätmagmatischen Arsenidreichen Erzen, die in der Vammala-Mine sehr gut aufgeschlossen sind, und auf die Intrusion pegmatitischer Fluide zurückgehen, die durch teilweises Aufschmelzen der metasedimentären Nebengesteine entstanden sind.Die frühe fraktionierte Kristallisation der Monosulfid Solid Solution führte zu einer residualen As-reichen Schmelze, die den Großteil der Edelmetalle (besonders Pt, Pd und Au) aufgenommen und die primären Ni-Cu Sulfiderze an diesen Elementen verarmt zurückgelassen hat. Spätmagmatische Arseniderze aus Vammala enthalten bis zu 42,5 ppm Pd (in Form von extrem feinkörnigen Einschlüssen von Sudburyit in Rotnickelkies und Maucherit, und als Spurengehalte im Gitter der späten Nickel-Arsenide), sowie 9,6 ppm Au, das hauptsächlich in den verbreiteten winzigen Einschlüssen von Electrum in Nickelarseniden vorkommt. Während der späteren Remobilisierung der primären Arseniderze von Kylmäkoski wurde Pd sowohl in S/As und As-Erzen in der Form von Sudburyit und in einer seltenen Pd-Bi Verbindung konzentriert. Es kommt auch als Spurenelement im Rotnickelkies aus S/As-Erzen und im Maucherit aus As-Erzen vor. Pt is vorwiegend in As-Erzen konzentriert, und zwar als Sperrylit, sowie in geringen Mengen in Pilsenit und in Colbaltit-Rändern um Sperrylit. Es kommt in Spurenelementen in den Kernen von zonaren Kobaltiten vor. Gold liegt stets in Form unregelmäßiger Elektrum-Körner in As-Erzen vor.
  相似文献   

7.
The Sompujärvi PGE reef in the Penikat layered intrusion,northern Finland   总被引:1,自引:1,他引:0  
Summary The Sompujärvi (SJ) PGE Reef is located at the border between the third and fourth megacyclic units, 400–1000 metres above the base of the Penikat layered intrusion. It usually occurs in the basal bronzititic portion of megacyclic unit IV, but can occur in the overlying peridotitic cumulates or the gabbroic cumulates at the top of megacyclic unit III in places. PGE concentrations have been found to occur mainly in association with either base metal sulphide (mainly pyrite-chalcopyrite-pentlandite) or chromite disseminations, the latter type usually representing a distinctly higher grade of mineralisation.When the magma which formed megacyclic unit IV penetrated into the Penikat layered intrusion, its lower part intermixed with the older residual magma. It may be assumed that this mixing of magmas was responsible for the precipitation and PGE enrichment of sulphides in the lower part of the olivine cumulates, accounting for the sulphide-disseminated mineralization type. The entry of the new magma pulse was probably quite powerful, and when this magma spread out over the uppermost, partly consolidated gabbroic cumulate of megacyclic unit III it caused pronounced local erosion in the uppermost crystal layer and excavated elongated channels and/or depressions, as associated with faulting. These channels and depressions then trapped older residual liquid enriched in platinum-group elements and the chromite-disseminated type within the SJ Reef was formed.
Das Sompujdrvi PGE Reef in der Penikat-Intrusion, Nord-Finnland
Zusammenfassung Das Sompujärvi (SJ) PGE Reef liegt im Grenzbereich von Megazyklus III und IV, 400 1000 m oberhalb der Basis der Penikat Intrusion.Normalerweise tritt es in den liegenden Bronzititen des Megazyklus IV auf; es kann aber sehr wohl auch in den peridotitischen und gabbroiden Kumulaten in den obersten Teilen von Megazyklus 111 entwickelt sein. PGE Anreicherungen sind entweder an Sulfide (hauptsächlich Pyrit-Kupferkies-Pentlandit) oder an disseminierten Chromit geknüpft. Der letztere Vererzungstyp ist durch höhere Gehalte gekennzeichnet.Während der Intrusion der Magmen des Megazyklus IV kam es zu einer Magmenmischung zwischen diesen und älteren Magmen. Es kann angenommen werden, daß dieses magma-mixing für die Ausfällung und Anreicherung der PGE's in den Sulfiden, die in den tieferen Anteilen der Olivin-Kumulate auftreten, verantwortlich zu machen ist und der Grund für diese disseminierte an Sulfide gebundene Vererzung ist. Das Eindirngen mächtiger neuer Magmenschübe und die Ausbreitung dieses Magmas über die obersten, bereits konsolidierten Gabbro-Kumulate des Megazyklus III, verursachten eine lokal intensive Erosion in diesen obersten bereits kristallisierten Lagen. Längliche Spaltensysteme und/oder Einsenkungen, ähnlich wie bei Störungen, wurden angelegt. In diesen Spaltensystemen und Einsenkungen sammelte sich ältere Schmelze, die an Elementen der Platingruppe angereichert war. Sie bildete die an disseminierten Chromit gebundene Vererzung im SJ Reef.


With 8 Figures  相似文献   

8.
The Scandinavian Caledonides comprise nappe stacks of far-travelled allochthons that record closure of the Iapetus Ocean and subsequent continental collision of Baltica and Laurentia. The Seve Nappe Complex (SNC) of the Scandinavian Caledonides includes relics of the outermost Baltoscandian passive margin that were subducted to mantle depths. The earliest of the deep subduction events has been dated to ca. 500–480 Ma. Evidence of this event has been reported from the northern exposures of the SNC. Farther south in the central and southern segments of the SNC, (ultra)high-pressure rocks have yielded younger ages in the range of ca. 470–440 Ma.This study provides the first record of the early Caledonian event in the southern SNC. The evidence has been obtained by depth profiling of zircon grains that were extracted from the Tväråklumparna microdiamond-bearing gneiss. These zircon grains preserve eclogite facies overgrowths that crystallized at 482.6 ± 3.8 Ma. A second, chemically-distinct zircon overgrowth records granulite facies metamorphism at 439.3 ± 3.6 Ma, which corroborates previous geochronological evidence for granulite facies metamorphism at this time. Based on these results, we propose that the entire outer margin of Baltica was subducted in the late Cambrian to early Ordovician, but the record of this event may be almost entirely eradicated in the vast majority of lithologies by pervasive late Ordovician to early Silurian metamorphism.  相似文献   

9.
10.
11.
Ohne ZusammenfassungMit 6 Textabbildungen.  相似文献   

12.
13.
14.
15.
16.
《Applied Geochemistry》2001,16(3):375-386
The concentrations of the lanthanide rare earth elements (REE) and Pt group elements (PGE) were measured in the Kupferschiefer from the Polish Zechstein Basin at, and in proximity to, the Rote Fäule near the Lubin Mining District. The Rote Fäule is a zone of post-depositional oxidation characterized by the presence of extensive amounts of Fe(III) oxides replacing syn-sedimentary framboidal pyrite. Outward from the Rote Fäule, the remainder of the Kupferschiefer is composed of Cu- and Pb/Zn-mineralized shale surrounding the Rote Fäule and a non-mineralized pyritic black shale in the central basin.The leading hypothesis explaining the high concentrations of PGE, and REE in the Kupferschiefer states that PGE, REE and the associated base metals were mobilized by oxidizing Cl brines which migrated outward from the Rote Fäule into the reduced Kupferschiefer. According to available thermodynamic data, PGE were in all likelihood present as chloro-complexes in these oxidizing brines, as geologically realistic concentrations of Pt, Pd and Au could be transported as chloro-complexes. The Eh of these brines decreased as they migrated further from the Rote Fäule and into the Kupferschiefer. Base metals and PGE were precipitated in the order of their decreased solubility in these brines. As a result, the concentrations of least soluble PGE (Pt) are highest in the Rote Fäule and in the transition zone adjacent to the Rote Fäule (e.g. [Pt]=202–537 ppb) while the concentrations of the more soluble metals in these brines (Ag, Cu, Pb, and Re) are highest in the reduced-mineralized Kupferschiefer. The sources of the PGE and REE are enigmatic. It is likely that the metals were derived either from the underlying Rotliegendes sandstones and volcanics, the Variscan basement rocks, or the Kupferschiefer shale whose metals were mobilized by saline, oxidizing fluids released during intra-continental rifting in the Triassic period.  相似文献   

17.
18.
Zusammenfassung Es werden die tiergeographischen Unterschiede zwischen dem mediterranen und dem nordischen Mittelkambrium besprochen. Die Faunen der wichtigsten Fundgebiete werden kurz auf ihre tiergeographischen Beziehungen untersucht. Überwiegend nordisch ist die Zusammensetzung der nordeuropäischen Faunen (Skandinavien, England), sowie der älteren Faunen des Frankenwaldes und von Doberlug. Überwiegend mediterran sind die Faunen des Mittelmeer-Gebietes (S-Frankreich, Spanien, Sardinien, Marokko), Böhmens, sowie die jüngeren Faunen des Frankenwaldes und von Doberlug. - Als Ursachen für die tiergeographischen Unterschiede werden Verschiedenheiten der Lebensbedingungen (Klima?) innerhalb eines zusammenhängenden Meeres wahrscheinlich gemacht.  相似文献   

19.
Zusammenfassung Dieser Aufsatz enthält Angaben über das Vorkommen von neugebildeten (sekundären) Mineralien inmitten von normalen Sedimentgesteinen, die keinem Einfluß von magmatischen Prozessen oder von offensichtlichem Metamorphismus unterworfen waren. Die erwähnten Angaben beziehen sich hauptsächlich auf Sedimentgesteine der Sowjetunion. Insbesondere werden im Aufsatz Funde von neugebildetem (sekundären) Magnetit, Spinell, Rutil, Brukit, Anatas, Feldspäten, Zeolithen, Turmalin, Granaten, Staurolith, Zoisit, Klinozoit, Epidot, Chlorit, Glimmer, Sepiolith, Sphen und anderen Mineralien inmitten von unmetamorphisierten Sedimentgesteinen beschrieben.Der Verfasser kommt zur Schlußfolgerung, daß sich in normalen Sedimentgesteinen ohne irgendwelche Beteiligung von magmatischen Prozessen und ohne offensichtlichen Einfluß von Metamorphismus solche Mineralien bilden können, welche gewöhnlich mit ausschließlich hochtemperierten Prozessen in Verbindung gebracht werden. Der Verfasser weist auf die Notwendigkeit und Wichtigkeit eines weiteren Studiums von sekundären Mineralien hin, welche inmitten von normalen Sedimentgesteinen vorkommen.  相似文献   

20.
Zusammenfassung Die Ursache der natürlichen remanenten Magnetisierung von Gesteinen und die Schwierigkeiten, die sich bei der Deutung paläomagnetischer Messungen ergeben, werden erörtert. Es wird die Methode beschrieben, mit Hilfe derer von verschiedenen Autoren versucht wird, aus paläomagnetischen Messungen Aussagen über die Lage der Pole in der geologischen Vergangenheit zu gewinnen. Es wird darauf hingewiesen, da\ dieser Methode Annahmen zugrunde liegen, deren Richtigkeit direkt schwer zu erweisen ist. In einer Tabelle (vonIrving) sind die Lagen der Pole in der geologischen Vergangenheit angegeben, wie sie aus paläomagnetischen Messungen folgen. Die Werte dieser Tabelle entsprechen lediglich dem gegenwärtigen Stand und werden sicherlich in Zukunft eine änderung erfahren.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号