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1.
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Recent O-isotope and fluid inclusion studies have provided evidence on the nature of the fluids associated with the late-Alpine quartz-gold deposits of the Monte Rosa district. The most abundant inclusions in quartz from these deposits contain a low salinity aqueous fluid (about 2% to 10% wt. NaCl eq.), and a CO2 phase (usually less than 20% mol), in places with minor methane. CO2 densities and total homogenization temperatures vary widely throughout the district, reflecting diverse conditions of trapping (P = 1 to 3 kb, T = 300° to 450°C). At Miniera dei Cani, unmixing between CO2-rich and H2O-rich fluids possibly occurred. A second type of inclusion contains an aqueous brine without recognizable CO2, and is especially abundant at Val Toppa. O-isotope studies suggest that fluids were largely equilibrated in a metamorphic environment. It is concluded that the gold-related fluids in the district were mainly of a metamorphic nature; at Val Toppa, both isotopic and fluid inclusion data point to contributions of unexchanged meteoric waters. Mechanisms of gold transport and precipitation are less contrained. A possible model involves transport of gold as bisulfide complexes, and precipitation due to one or more of the following processes: decrease of sulfur activity due to precipitation of sulfides, wall-rock reaction, cooling/dilution, and/or fluid unmixing.  相似文献   

3.
The Lepontine dome represents a unique region in the arc of the Central and Western Alps, where complex fold structures of upper amphibolite facies grade of the deepest stage of the orogenic belt are exposed in a tectonic half-window. The NW-verging Mont Blanc, Aar und Gotthard basement folds and the Lower Penninic gneiss nappes of the Central Alps were formed by ductile detachment of the upper European crust during its Late Eocene–Early Oligocene SE-directed underthrust below the upper Penninic and Austroalpine thrusts and the Adriatic plate. Four underthrust zones are distinguished in the NW-verging stack of Alpine fold nappes and thrusts: the Canavese, Piemont, Valais and Adula zones. Up to three schistosities S1–S3, folds F1–F3 and a stretching lineation XI with top-to-NW shear indicators were developed in the F1–F3 fold nappes. Spectacular F4 transverse folds, the SW-verging Verzasca, Maggia, Ziccher, Alpe Bosa and Wandfluhhorn anticlines and synclines overprint the Alpine nappe stack. Their formation under amphibolite facies grade was related to late ductile folding of the southern nappe roots during dextral displacement of the Adriatic indenter. The transverse folding F4 was followed since 30 Ma by the pull-apart exhumation and erosion of the Lepontine dome. This occurred coevally with the formation of the dextral ductile Simplon shear zone, the S-verging backfolding F5 and the formation of the southern steep belt. Exhumation continued after 18 Ma with movement on the brittle Rhone-Simplon detachment, accompanied by the N-, NW- and W-directed Helvetic and Dauphiné thrusts. The dextral shear is dated by the 29–25 Ma crustal-derived aplite and pegmatite intrusions in the southern steep belt. The cooling by uplift and erosion of the Tertiary migmatites of the Bellinzona region occurred between 22 and 18 Ma followed by the exhumation of the Toce dome on the brittle Rhone–Simplon fault since 18 Ma.  相似文献   

4.
Ordovician orogeny in the Alps: a reappraisal   总被引:1,自引:0,他引:1  
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The Julian Alps are located in NW Slovenia and structurally belong to the Julian Nappe where the Southern Alps intersect with the Dinarides. In the Jurassic, the area was a part of the southern Tethyan continental margin and experienced extensional faulting and differential subsidence during rifting of the future margin. The Mesozoic succession in the Julian Alps is characterized by a thick pile of Upper Triassic to Lower Jurassic platform limestones of the Julian Carbonate Platform, unconformably overlain by Bajocian to Tithonian strongly condensed limestones of the Prehodavci Formation of the Julian High. The Prehodavci Formation is up to 15 m thick, consists of Rosso Ammonitico type limestone and is subdivided into three members. The Lower Member consists of a condensed red, well-bedded bioclastic limestone with Fe–Mn nodules, passing into light-grey, faintly nodular limestone. The Middle Member occurs discontinuously and consists of thin-bedded micritic limestone. The Upper Member unconformably overlies the Lower or Middle Members. It is represented by red nodular limestone, and by red-marly limestone with abundant Saccocoma sp. The Prehodavci Formation unconformably overlies the Upper Triassic to Lower Jurassic platform limestone of the Julian Carbonate Platform; the contact is marked by a very irregular unconformity. It is overlain by the upper Tithonian pelagic Biancone (Maiolica) limestone. The sedimentary evolution of the Julian High is similar to that of Trento Plateau in the west and records: (1) emergence and karstification of part of the Julian Carbonate Platform in the Pliensbachian, or alternatively drowning of the platform and development of the surface by sea-floor dissolution; (2) accelerated subsidence and drowning in the Bajocian, and onset of the condensed pelagic sedimentation (Prehodavci Formation) on the Julian High; (3) beginning of sedimentation of the Biancone limestone in the late Tithonian.  相似文献   

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Paul Stangl 《GeoJournal》2008,73(3):245-253
Recent geographical literature has given extensive consideration to monumental landscapes and collective memory. Vernacular landscapes have been given limited attention, though they too bear testimony to collective memory. The vernacular and monumental are intertwined in urban space, and ambiguity and fluidity mark their border, yet their distinction remains significant. The monumental sustains collective memory, linking the past, present and future. The vernacular provides spatial forms for the routines of everyday life. Yet, professionals and critics often interpret and present the vernacular as a symbol of collective memory, or a monument, rather than recognizing that collective memory in the vernacular is critical when centered on the complex relation between space and lived experience. The case study of Berlin during post-WWII reconstruction as well as the reconstruction following reunification demonstrates consistency in problems arising from treating the vernacular as the monumental.  相似文献   

9.
Stamps are products or `windows' of the state that illustrate how it wishes to be seen by its own citizens and those beyond its boundaries. The topics of the first issues reveal what messages the state considers most important. The first issues from nineteen new East European and Central Asian states illustrate the importance of maps, flags, coats of arms and prominent religious and political symbols; overt propaganda and ideology were lacking.  相似文献   

10.
The two Alpine orogenic phases of the Eastern Alps, in the Cretaceous and in the Tertiary, were both accompanied by the formation of mineral deposits. However, subduction-related magmatic belts as well as the typical “Andean” ore deposits are missing. Therefore, the role of metamorphism in East Alpine metallogeny was tentatively explored for more than 60 y, although for a long time without tangible results. Microthermometric, geochemical and isotopic investigations of fluid inclusions from selected Alpine mineral deposits presented allow a preliminary confirmation of the involvement of metamorphic fluids in their origin. Deposits which were formed immediately after the first, Cretaceous orogeny, were produced at high pressures by fluids of very high salinity and high density, and with an isotopic composition of the water falling into the metamorphic field. These fluids are best understood as products of metamorphic de-volatilization of rocks of the subducted South Pennine domain. In contrast to this, the deposits formed after the second, Tertiary orogeny, originated at relatively low pressures from fluids with an appreciable content of CO2 and of low to moderate salinities. Isotopic compositions of this carbon indicate a deep crustal or even mantle source for CO2, while the water is isotopically more heterogeneous and may have mixed sources, both surficial and metamorphic. Tectonic control of these mineralizations is late-orogenic trans-tensional faulting, which exposed hot metamorphic rocks to fluid convection along brittle structures. These deposits conform best to the model of metamorphogenic metallogenesis by retrograde leaching, although ponded metamorphic fluids and mantle volatiles may also have been involved. Received: 4 August 1998 / Accepted: 5 January 1999  相似文献   

11.
We present a synoptic overview of the Miocene-present development of the northern Alpine foreland basin (Molasse Basin), with special attention to the pattern of surface erosion and sediment discharge in the Alps. Erosion of the Molasse Basin started at the same time that the rivers originating in the Central Alps were deflected toward the Bresse Graben, which formed part of the European Cenozoic rift system. This change in the drainage direction decreased the distance to the marine base level by approximately 1,000 km, which in turn decreased the average topographic elevation in the Molasse Basin by at least 200 m. Isostatic adjustment to erosional unloading required ca. 1,000 m of erosion to account for this inferred topographic lowering. A further inference is that the resulting increase in the sediment discharge at the Miocene–Pliocene boundary reflects the recycling of Molasse units. We consider that erosion of the Molasse Basin occurred in response to a shift in the drainage direction rather than because of a change in paleoclimate. Climate left an imprint on the Alpine landscape, but presumably not before the beginning of glaciation at the Pliocene–Pleistocene boundary. Similar to the northern Alpine foreland, we do not see a strong climatic fingerprint on the pattern or rates of exhumation of the External Massifs. In particular, the initiation and acceleration of imbrication and antiformal stacking of the foreland crust can be considered solely as a response to the convergence of Adria and Europe, irrespective of erosion rates. However, the recycling of the Molasse deposits since 5 Ma and the associated reduction of the loads in the foreland could have activated basement thrusts beneath the Molasse Basin in order to restore a critical wedge. In conclusion, we see the need for a more careful consideration of both tectonic and climatic forcing on the development of the Alps and the adjacent Molasse Basin.  相似文献   

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The Alpine drainage system comprises two large orogen-parallel drainage basins in the core of the Alps (the Rhone and Rhine valleys), and smaller orogen-normal orientated systems. Discharge of the large rivers is ≈5–10 higher than that of the small ones. In addition, the courses of the Rhone and Rhine Rivers are trapped by faults and thrusts that display lower erosional resistance than the neighbouring lithologies. Enhanced discharge of these rivers and the low erosional resistance of their bedrocks potentially enhances surface erosion. Indeed, present-day and glacial sediment yields are ≈1.6–1.7 times higher in these valleys than in the orogen-normal systems. Interestingly, rates of crustal uplift are also enhanced in the Rhine and Rhone valleys, where current rates of ≈1.4–1.6 mm yr−1 are measured. The spatial coincidence between the location of enhanced erosion and maximum crustal uplift rates are interpreted to reflect a positive feedback between surface erosion and tectonic forcing.  相似文献   

14.
Eoalpine and mesoalpine tectonics in the Southern Alps   总被引:1,自引:0,他引:1  
According to structural and stratigraphic data, eoalpine and mesoalpine tectonics can be clearly recognized in the Southern Alps and distinguished from the better known neoalpine deformation.The eoalpine phase (Late Cretaceous) was generated by N-S compression. It deformed basically the central-western Southern Alps producing overthrusts to the west and flower structures by sinistral transpression in the Giudicarie Belt. Deposition of the coeval flysch successions was controlled by the trend of this belt. This tectonic pattern persisted until Middle Eocene.The mesoalpine phase (Eocene) was generated mainly by a ENE-WSW compression and produced thrust geometries with N-S or NW-SE direction in the eastern part of the Southern Alps. The coeval Eocene Flysch also followed this trend, filling the foredeep basin. This deformation is considered to be the front of the Dinarids, which began to be deformed since Late Cretaceous until at least Early Oligocene.The neoalpine tectonics inherited the eoalpine and mesoalpine structures and produced the major part of the deformation accounting for the present structural framework of the Southern Alps.
Zusammenfassung Die eo- und mesoalpidische Tektonik in den Südalpen ist strukturell und stratigraphisch erkennbar und von den bekannteren neoalpidischen Bewegungsbildern deutlich zu unterscheiden.Die eoalpidische Phase (Obere Kreide) entspricht einer N-S Kompression, die sich in den zentralen bis westlichen Südalpen bemerkbar macht. Im westlichen Bereich treten Überschiebungen auf, das Judikarische Gebiet wird hingegen durch die von linkslateralen Transpressionen bewirkten Verwerfungsbündel gekennzeichnet, die auch die altersgleichen Flysch-Ablagerungen kontrollieren. Diese tektonische Phase ist bis zum Eozän aktiv.Die mesoalpidische Phase (Eozän) ist auf eine ENE-WSW Kompression zurückzuführen. Sie verursachte in den östlichen Südalpen N-S bis NW-SE gerichtete Überschiebungsbilder. In gleichorientierten vorozeanischen Becken kommt der eozäne Flysch vor. Dieses Deformationsbild kennzeichnet schon in der Oberen Kreide die Dinariden-Front.Die neoalpidische Tektonik vererbte die eo-mesoalpidischen Gefüge-Elemente und verursachte im wesentlichen den gegenwärtig erkennbaren Gefügeplan der Südalpen.

Résumé Dans les Alpes Méridionales, des données stratigraphiques et structurales permettent de reconnaître les tectoniques éoalpine et mésoalpine et de les distinguer des déformations néoalpines, mieux connues.La phase éoalpine (Crétacé supérieur) a été engendrée par une compression N-S. Celle-ci a affecté surtout la partie centre-occidentale des Alpes Méridionales en produisant des charriages à l'ouest et des structures de décrochement sénestres dans la chaîne des Giudicarie, dont l'orientation a déterminé la sédimentation du flysch concommittant. Cette tectonique s'est poursuivie jusqu' à l'Eocène.La phase mésoalpine a été engendrée surtout par une compression ENE-WSW; elle a produit, dans la partie est des Alpes Méridionales, des charriages de direction N-S à NW-SE. Le flysch éocène a suivi cet alignement structural, en remplissant le bassin de l'avant-fosse. Cette déformation est considérée comme le front des Dinarides, dont la formation a commencé dés le Crétacé supérieur.La tectonique néoalpine a hérité des structures éoalpines et mésoalpines et est responsable de la plus grande part de la structure actuelle des Alpes Méridionales.

- , , . ( ) . , , — , . . () ENE WSW; , N — S NW — SE . - . . , , - .
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15.
In the considered wide sector of the West-Mediterranean southern Europe, the collisional phase of the Variscan orogeny during Late Carboniferous and Permian times was followed by magmatic intrusive and effusive activity and sedimentation into intracontinental, alluvial to lacustrine basins originated by wrench- to normal-fault systems. The first volcanic cycle (generally Late Carboniferous-Early Permian in age) is represented by early calc-alkaline andesites and rhyolites, in variable amounts, and by following large volume of rhyolites, and by dacites. Both andesites and rhyolites show K-normal and high-K calc-alkaline character. The origin of the liquids of the first cycle is ascribed to partial melting processes at the mantle–crust interface telescoped within a thickened crust. The melting is considered as the consequence of thermal re-equilibration following isostatic disequilibrium and the subsequent collapse of the orogenic belt; the ascent of liquids occurred in a (trans-)tensional regime. The second magmatic cycle is represented by alkaline magmatism, and exhibits typical anorogenic features consistent with a rifting regime. This event was no more related with the collapse of the Variscan belt, but rather to the post-Variscan global re-organization of plates that evolved during Late Triassic times to the neo-Tethyan rifting. In both cycles, important differences in timing, areal distribution and outpoured volumes arise.  相似文献   

16.
This paper explores the ideology and materiality of ‘bio-socialism’, through which the Ecuadorian government is attempting to catalyse a ‘post-neoliberal’ transition from the ‘finite resources’ of Amazonian oil reserves to the ‘infinite resources’ of biodiversity and scientific knowledge. This experiment is embodied in Ikiam, a public university under construction in the Ecuadorian Amazon. Drawing on extensive field research, we argue that, despite its radical intentions, bio-socialism is functioning as a strategy for the real subsumption of nature to capital, which is being operationalized in Ikiam in ways that reproduce the neoliberal knowledge economy. However, the contradictions of this process imply that, in practice, Ikiam is only intensifying established patterns of the formal subsumption of nature, by commodifying the genetic wealth and indigenous knowledge of the Amazon, and legitimating the expansion of the oil and mineral frontiers. The case of bio-socialism demonstrates the paradoxical nature of actually-existing post-neoliberalism, and illustrates the tendency for utopian ideologies to reproduce the material conditions they are seeking to escape.  相似文献   

17.
Extracted from large surveys of France, Italy and Switzerland, airborne magnetic data covering the western Alpine Arc have been compiled into a single homogeneous map of magnetic anomalies at the constant altitude of 3000 m. For this purpose, each data set has been revised thoroughly and accurately to give a single coherent large-scale pattern.

The magnetic contour map reflects the anomaly pattern over the entire length of the Western Alpine collision suture. The distribution of polarities exhibits a large anomalous low located by reduction to the pole over the whole external part of the belt. The observed anomaly suggests a large gap of magnetization between the Adriatic microplate and the European crust. The analysis of the waveband shows that the broadest wavelengths are produced in the lower crust close to the transition zone, in the granulite facies. This highly magnetic layer is used as a marker to describe the geometry of the European and Adriatic deep seated crust. The main results are presented on a composite synthetic profile showing the sloping side of the European slab and an important crustal thinning to the southeast of the Adriatic slab. This feature is emphasized on the magnetic contour map by a linear magnetic low attributed to major transcurrent fault. This trend is called the Sestri-Voghera trend and extends from the Ligurian basin by the Sestri-Voltaggio Zone to the Judicarian system. Sinistral movements can be recognized along the whole axis as well as possible uplift of rift shoulders. The magnetic anomaly pattern over the complete length of the anomalous body of Ivrea as well as the Insubric-Canavese Line limit the extension of the Adriatic microplate by a well defined linear trend. The symmetrical shears deduced from consecutive anomalies are used to propose a structural scheme.  相似文献   


18.
Bedrock fission‐track analysis, high‐resolution petrography and heavy mineral analyses of sediments are used to investigate the relationships between erosion and tectonics in the Western Alps. Along the Aosta Valley cross‐section, exhumation rates based on fission‐track data are higher in the fault‐bounded western block than in the eastern block (0.4–1.5 vs. 0.1–0.3 mm yr−1). Erosion rates based on the analysis of bed‐load in the Dora Baltea drainage display the same pattern and have similar magnitudes in the relative sub‐basins (0.4–0.7 vs. 0.04–0.08 mm yr−1). Results highlight that climate, relief and lithology are not the controlling factors of erosion in the Western Alps. The main driving force behind erosion is instead tectonics that causes the differential upward motion of crustal blocks.  相似文献   

19.
Alpine deformation of Austroalpine units south of the Tauern window is dominated by two kinematic regimes. Prior to intrusion of the main Periadriatic plutons at ~30 Ma, the shear sense was sinistral in the current orientation, with a minor north-side-up component. Sinistral shearing locally overprints contact metamorphic porphyroblasts and early Periadriatic dykes. Direct Rb-Sr dating of microsampled synkinematic muscovite gave ages in the range 33-30 Ma, whereas pseudotachylyte locally crosscutting the mylonitic foliation gave an interpreted 40Ar-39Ar age of ~46 Ma. The transition from sinistral to dextral (transpressive) kinematics related to the Periadriatic fault occurred rapidly, between solidification of the earlier dykes and of the main plutons. Subsequent brittle-ductile to brittle faults are compatible with N-S to NNW-SSE shortening and orogen-parallel extension. Antithetic Riedel shears are distinguished from the previous sinistral fabric by their fine-grained quartz microstructures, with local pseudotachylyte formation. One such pseudotachylyte from Speikboden gave a 40Ar-39Ar age of 20 Ma, consistent with pseudotachylyte ages related to the Periadriatic fault. The magnitude of dextral offset on the Periadriatic fault cannot be directly estimated. However, the jump in zircon and apatite fission-track ages establishes that the relative vertical displacement was ~4-5 km since 24 Ma, and that movement continued until at least 13 Ma.  相似文献   

20.
The eastern Central Alps consist of several Pennine nappes with different tectonometamorphic histories. The tectonically uppermost units (oceanic Avers Bündnerschiefer, continental Suretta and Tambo nappes, oceanic Vals Bündnerschiefer) show Cretaceous/early Tertiary W-directed thrusting with associated blueschist facies metamorphism related to subduction of the Pennine units beneath the Austroalpine continental crust. This event caused eclogite facies metamorphism in the underlying continental Adula nappe. The gross effect was crustal thickening. The tectonically lower, continental Simano nappe is devoid of any imprint from this event. In the course of continent-continent collision, high- T metamorphism and N-directed movements occurred. Both affected the whole nappe pile more or less continuously from amphibolite to greenschist facies conditions. Crustal thinning commenced during the regional temperature peak. A final phase is related to differential uplift under retrograde P–T conditions. Further thinning of the crust was accommodated by E- to NE-directed extensional deformation.  相似文献   

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