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Sample records for bohemian massif se

  1. Recent geodynamic pattern of the eastern part of the Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Schenk, V.; Schenková, Z.; Grácová, M.

    2009-04-01

    The Bohemian Massif, a Precambrian cratonic terrane, had been affected by several orogeneses forming its tectonic pattern. To detect the recent geodynamic motions going on fundamental geological structures of the Massif four regional geodynamic networks were established for epoch GPS measurements and one countrywide GEONAS network for permanent GPS satellite signals monitoring. In the east part of the Bohemian Massif sinistral movements on the Sudetic NW-SE faults and as well on the NNE-SSW faults of the Moravo-Silesian tectonic system have been detected. The sinistral trends dominate on many faults situated close to the contact of the Moldanuabian and Lugian parts and the Moravo-Silesian part of the Bohemian Massif. Because of tectonic systems intersections an existence of dextral movements cannot be excluded. Additional analyses displayed that eastern part of the Massif could be under extending trends. The preliminary site velocities assessed from GPS data for the eastern part of the Bohemian Massif are discussed from a viewpoint of regional geological structure motions. The work was supported by the Grant Agency of the Academy of Sciences of the Czech Republic (Project IAA300460507), the Targeted Research Programme of the Academy of Sciences of the CR (1QS300460551) and by the Ministry of Education, Youth and Sport of the Czech Republic (Projects LC506 and 1P05ME781).

  2. Extending a thickened crustal bulge: toward a new geodynamic evolution model of the paleozoic NW Bohemian Massif, German Continental Deep Drilling site (SE Germany)

    NASA Astrophysics Data System (ADS)

    Krohe, Alexander

    1998-09-01

    Fault-bounded (tectonic) metamorphic complexes assembling the NW Bohemian Massif around the German Continental Deep Drilling (KTB) site are seen to be extremely heterogeneous in tectonic and metamorphic histories. In current models, the different complexes were supposed to reflect a puzzle of small pre-Devonian microplates, and the related collision events supposedly lasted until the Carboniferous. Opposed to these models, it will be shown that all the boundaries among the complexes were formed by detachment, late in a prolonged overall geodynamic history of a thickened crustal bulge, during extensional tectonics and associated thermal events that outlasted the onset of collision in the Silurian/Lower Devonian by about 70-80 Ma. (Micro-)structures, petrological and geochronological data of individual complexes predominantly preserve the late stages rather than the unbroken record of their tectonometamorphic histories. Such partial histories strongly different among individual complexes, depict diverse snapshots taken at different places in the evolving thickened crustal bulge and at different instants in its overall evolution, and do not define different precollisional microplates. Predominantly P- T and deformation episodes after terrane juxtaposition are preserved. This article presents an integrated view of the structural geology, microscopic fabrics, P- T data and geochronology of such diverse metamorphic complexes. This integrated view provides a new understanding of (1) the tectonic evolution during Upper Silurian/Devonian collision of the Gondwana-derived Central European lithosphere with Laurussia, (2) the postaccretionary events that lasted through the Upper Carboniferous and (3), the earlier (Lower Ordovician) metamorphic and magmatic history, which is only locally recorded. Metamorphic complexes occupying the structurally highest position (upper tectonic complexes) record Devonian and earlier tectonometamorphic and magmatic events. After the Mid

  3. Age and mineralogy of supergene uranium minerals — Tools to unravel geomorphological and palaeohydrological processes in granitic terrains (Bohemian Massif, SE Germany)

    NASA Astrophysics Data System (ADS)

    Dill, H. G.; Gerdes, A.; Weber, B.

    2010-04-01

    Uranyl phosphates (torbernite, autunite, uranocircite, saleeite) and hydrated uranyl silicates (normal and beta-uranophane) found in various erosion levels and structures in the Late Variscan granites at the western edge of the Bohemian Massif, Germany, were the target of mineralogical investigations and age dating, using conventional and more advanced techniques such as Laser-Ablation-Inductive-Coupled-Plasma Mass Spectrometry (LA-ICP-MS). Supergene U minerals have an edge over other rock-forming minerals for such studies, because of their inherent ‘clock’ and their swift response to chemical and physical environmental changes on different scales. Uraniferous phoscretes and silcretes, can be used to characterize the alkalinity/acidity of meteoric/per descensum fluids and to constrain the redox conditions during geomorphic processes. This study aims to decipher the geomorphological and palaeohydrological regime that granitic rocks of the Central European Variscides (Moldanubian and Saxothuringian zones) went through during the Neogene and Quaternary in the foreland of the rising Alpine mobile fold belt. The study provides an amendment to the current sub-division of the regolith by introducing the term “hydraulith”, made up of percolation and infiltration zones, for the supergene alteration zone in granitic terrains. It undercuts the regolith at the brink of the phreatic to vadose hydrological zones. Based upon the present geomorphological and mineralogical studies a four-stage model is proposed for the evolution of the landscape in a granitic terrain which might also be applicable to other regions of the European Variscides, considering the hydrological facies changes along with paleocurrent and paleoslope in the basement and the development of the fluvial drainage system in the foreland. Stage I (U mineralization in the infiltration zone) is a mirror image of the relic granitic landscape with high-altitude divides and alluvial-fluvial terraces. Its

  4. Low pressure granulites from the Bohemian Massif, Upper Austria

    NASA Astrophysics Data System (ADS)

    Sorger, Dominik; Daghighi, Donia; Simic, Katica; Pichler, Ruth; Schwaiger, Christian; Hauzenberger, Christoph; Linner, Manfred; Iglseder, Christoph

    2014-05-01

    Low pressure granulite facies rocks are commonly found in the Bohemian Massif in Upper Austria. They belong to the Moldanubian Unit and were metamorphosed during the last stage of the Variscan orogeny. The investigated granulites from the Donau valley (west of Linz), Lichtenberg (northwest of Linz), Sauwald (south of the river Danube) and Bad Leonfelden zone comprise mainly migmatic paragneisses. Most of these rocks underwent high degrees of melting forming meta- and diatexites (''Perlgneise)''. Al-rich metapelites with partly cm-sized garnet porphyroblasts, which are suitable for precise PT and PT-path determinations, can be found in some localities of this unit. In this study samples taken along the Danube valley between Linz and Wilhering, from Lichtenberg and from Bad Leonfelden (north of Linz) were sampled and investigated petrographically in detail. Since garnets are rare and usually consumed by cordierite, a sample with large garnets was investigated in detail. A chemical zoning profile across the c. 1cm large garnet displayed elevated Ca contents (Xgrs=0.06) in the central part which decreased discontinuously towards the rim to Xgrs=0.02. Almandine, pyrope and spessartine components do not show any pronounced zoning pattern. Most of the smaller garnet grains in other samples are also homogeneous in composition with a slight Xalm increase and Xprp decrease at the rims, typical for retrograde diffusional zoning. The cordierite-garnet-sillimanite-granulites as well as some mafic granulites were used for geothermobarometry. Metamorphic conditions of around 770°C to 850°C and 0.5-0.6 GPa could be obtained, which are similar to the values obtained by Tropper et al. (2006). P. Tropper I. Deibl F. Finger R. Kaindl (2006). P-T-t evolution of spinel-cordierite-garnet gneisses from the Sauwald Zone (Southern Bohemian Massif, Upper Austria): is there evidence for two independent late-Variscan low-P / high-T events in the Moldanubian Unit? Int J Earth Sci (Geol

  5. A Treasure Chest of Nanogranites: the Bohemian Massif (Central Europe)

    NASA Astrophysics Data System (ADS)

    Ferrero, S.; O'Brien, P. J.; Walczak, K.; Wunder, B.; Ziemann, M. A.; Hecht, L.

    2014-12-01

    Despite 150 years of investigation of the Bohemian Massif (Central Europe), it is only recently that the investigation of old and new samples displayed the occurrence of tiny portions of crystallized anatectic melt in regional migmatites. These vestiges of magma, called "nanogranites", are natural probes of the partial melting processes in the crust. Original melt composition and water content can be directly analyzed after piston cylinder re-homogenization. When compared to classic re-melting experiments, nanogranites are ideal "natural" experimental charges of anatectic melt. They are encapsulated in peritectic garnet immediately after production - both phases are products of the same partial melting reaction. Sheltered inside garnet, they remain unaffected by the physico-chemical changes which affected the host migmatites during their slow cooling, unlike leucosomes and anatexis-related plutons. Five different case studies of nanogranite-bearing high-grade rocks have been identified so far: three in metapelites from the Moldanubian Zone, and two in metagranitoids from the Granulitgebirge and Orlica-Śnieżnik Dome. Their characterization provides insights into how the continental crust melts at different depths, from shallow levels to mantle depths, during different moments of its metamorphic history (prograde vs. decompressional melting). For example, the investigation and experimental re-melting of nanogranites from Grt+Ky leucogranulites (Orlica-Śnieżnik Dome) recently provided evidence of prograde melting of metagranitoids under eclogite-facies conditions (T≥875°C and P~2.7 GPa), close to the stability field of coesite. The melt generated is granitic, hydrous (6 wt% H2O) and metaluminous (ASI=1.03), and is at the moment the "deepest" glass obtained through re-homogenization of primary polycrystalline inclusions in natural rocks. This work confirms that nanogranites in migmatites 1) are a powerful tool to constrain anatexis in natural rocks, and 2) can

  6. Crustal structure of the Bohemian Massif in the light of seismic refraction data

    NASA Astrophysics Data System (ADS)

    Hrubcova, Pavla

    2010-05-01

    The Bohemian Massif is one of the largest stable outcrops of pre-Permian rocks in Central and Western Europe. It forms the easternmost part of the Variscan Belt, which developed approximately between 500 and 250 Ma during a stage of large-scale crustal convergence, collision of continental plates and microplates, and possibly also subduction. It consists mainly of low- to high-grade metamorphic and plutonic Palaeozoic rocks. The area of the Bohemian Massif can be subdivided into various tectonostratigraphic units separated by faults, shear zones or thrusts trending roughly in a SW-NE direction, and reflecting varying influence of the Cadomian and Variscan orogenies: the Saxothuringian, Teplá-Barrandian, Moldanubian and Moravo-Silesian. Geographically, it comprises the area of the Czech Republic, partly Austria, Germany and Poland. While the post-collisional history of the Variscan Bohemian Massif is relatively clear, the kinematics of plate movements before and during collision is still subject of debates. To investigate such a complex structure, the Bohemian Massif has been covered by a network of seismic experiments as a result of a massive international cooperative effort in central Europe. Detailed analyses of the data from the main profiles of the CELEBRATION 2000, ALP 2002, and SUDETES 2003 refraction and wide-angle reflection seismic experiments show crustal and uppermost mantle structure of the massif and delimit the continuation of various tectonic units in depth. The differences in seismic velocities reflect, to some extent, the structural variances and give some indications for tracing of crust-forming processes during individual tectonic events. Lower crust in the Saxothuringian exhibits complicated structure, ranging from a highly reflective lower crustal layer above Moho with a strong velocity contrast at the top of this layer. Another possible explanation can be a double Moho or the Moho with some lateral topography. This complicated lower crust

  7. Significance of Geological Units of the Bohemian Massif, Czech Republic, as Seen by Ambient Noise Interferometry

    NASA Astrophysics Data System (ADS)

    Růžek, Bohuslav; Valentová, Lubica; Gallovič, František

    2016-05-01

    Broadband recordings of 88 seismic stations distributed in the Bohemian Massif, Czech Republic, and covering the time period of up to 12 years were processed by a cross-correlation technique. All correlograms were analyzed by a novel approach to get both group and phase dispersion of Rayleigh and Love waves. Individual dispersion curves were averaged in five distinct geological units which constitute the Bohemian Massif (Saxothuringian, Teplá-Barrandean, Sudetes, Moravo-Silesian, and Moldanubian). Estimated error of the averaged dispersion curves are by an order smaller than the inherent variability due to the 3D distribution of seismic velocities within the units. The averaged dispersion data were inverted for 1D layered velocity models including their uncertainty, which are characteristic for each of the geological unit. We found that, overall, the differences between the inverted velocity models are of similar order as the variability inside the geological units, suggesting that the geological specification of the units is not fully reflected into the S-wave propagation velocities on a regional scale. Nevertheless, careful treatment of the dispersion data allowed us to identify some robust characteristics of the area. The vp to vs ratio is anomalously low (~1.6) for all the units. The Moldanubian is the most rigid and most homogeneous part of the Bohemian Massif. Middle crust in the depth range of ~3-15 km is relatively homogeneous across the investigated region, while both uppermost horizon (0-3 km) and lower crust (>15 km) exhibit lower degree of homogeneity.

  8. (222)Rn activity concentration differences in groundwaters of three Variscan granitoid massifs in the Sudetes (NE Bohemian Massif, SW Poland).

    PubMed

    Przylibski, Tadeusz A; Gorecka, Joanna

    2014-08-01

    Based on research conducted in three Variscan granitoid massifs located within the crystalline Bohemian Massif, the authors confirmed that the higher the degree of their erosional dissection, the smaller the concentration of (222)Rn in groundwaters circulating in these massifs. This notion implies that radon waters and high-radon waters, from which at least some of the dissolved radon should be removed before feeding them as drinking water to the water-supply system, could be expected in granitoid massifs which have been poorly exposed by erosion. At the same time, such massifs must be taken into account as the areas of possible occurrence of radon medicinal waters, which in some countries can be used for balneotherapy in health resorts. Slightly eroded granitoid massifs should be also regarded as very probable radon prone areas or areas of high radon potential. PMID:24657989

  9. Exotic crustal components at the northern margin of the Bohemian Massif-Implications from Usbnd Thsbnd Pb and Hf isotopes of zircon from the Saxonian Granulite Massif

    NASA Astrophysics Data System (ADS)

    Sagawe, Anja; Gärtner, Andreas; Linnemann, Ulf; Hofmann, Mandy; Gerdes, Axel

    2016-06-01

    The Saxonian Granulite Massif is located at the northern margin of the Saxo-Thuringian Zone of the peri-Gondwana Bohemian Massif. Eight felsic and mafic granulites were studied with respect to their geochemistry and Usbnd Pb zircon geochronology. The felsic granulites are interpreted to be derived from continental crust of possible granitoid composition. An origin from depleted mantle sources with IAT to MORB composition can be assumed for the mafic granulites. The peak of metamorphism is thought to be timed at about 340 Ma, while several earlier metamorphic events are supposed to have occurred at about 355-360, 370-375, 405, and 450 Ma. They reveal a complex and polyphased geologic evolution of the Saxonian Granulite Massif. Protolith emplacement likely took place at c. 450 and 494 Ma. Hf isotopic data suggest Mesoproterozoic crustal ages at least for parts of the massif. As these crustal ages are exotic for the Bohemian Massif, their origin has to be searched elsewhere. Potential source areas could be Amazonia and Baltica, of which the latter is the one preferred. Furthermore, a composite architecture with at least two components-the felsic granulites with Mesoproterozoic crustal model ages, and the mafic granulites of potential island arc origin-is hypothesised. Their amalgamation to the recent appearance of the Saxonian Granulite Massif is likely bracketed between 375 and 340 Ma.

  10. Tonalite sill emplacement at an oblique plate boundary: northeastern margin of the Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Parry, Matthew; Sˇtípská, Pavla; Schulmann, Karel; Hrouda, Frantisˇek; Jezˇek, Josef; Kröner, Alfred

    1997-10-01

    A tonalitic sill has been examined at the Variscan transpressive boundary of the Lugian and Silesian plates at the NE margin of the Bohemian Massif. A structural, petrological and geochronological study reveals that it was emplaced syn-tectonically with major ductile shearing in lower crustal rocks. Magmatic and pre-rheological critical melt percentage (RCMP) fabrics are concordant with the hanging wall structures but discordant with those of the footwall. The AMS study shows the predominance of flattening strain at the margins and plane strain fabrics in the core. Numerical modelling of AMS fabrics is in good agreement with the hypothesis of magma flow and deformation in oblique transpression. A tectonic model was developed explaining emplacement and syn-tectonic deformation of progressively cooled tonalitic intrusion.

  11. Re-Os geochemistry and geochronology of the Ransko gabbro-peridotite massif, Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Ackerman, Lukáš; Pašava, Jan; Erban, Vojtěch

    2013-10-01

    The Ransko gabbro-peridotite massif in Eastern Bohemia is a strongly differentiated intrusive complex, which hosts low-grade Ni-Cu ores mainly developed close to the contact of olivine-rich rocks with gabbros, in troctolites, and to a much lesser extent in both pyroxene and olivine gabbros and plagioclase-rich peridotites. Gabbro, troctolite, peridotite and Ni-Cu ores from the Jezírka Ni-Cu (PGE) deposit, considered to be a typical example of the liquid segregation style of mineralization, were analyzed for Re-Os concentrations and isotopic ratios. Seven barren and mineralized samples from the Jezírka deposit yielded a Re-Os regression of 341.5 ± 7.9 Ma (MSWD = 69). Strongly mineralized peridotite with mantle-like initial 187Os/188Os ratio of 0.125 suggests that Os as well as other PGE present in the Ni-Cu mineralization are predominantly of mantle origin. On the other hand, barren and low-mineralized samples have radiogenic initial 187Os/188Os ratios of 0.14-0.16 suggesting some import of Re and/or radiogenic 187Os most likely through contamination by continental crust during magma emplacement. The Re-Os age of the Ransko Massif is significantly younger than the previously suggested Lower Cambrian age, but it is similar to and/or younger than the age of metamorphism of the adjacent Kutná Hora crystalline complex and the Moldanubian unit. Therefore, it is likely that the emplacement of the Ransko massif and its Ni-Cu mineralization was closely connected with the late-stage evolution of the Kutná Hora crystalline complex.

  12. Adjusting stream-sediment geochemical maps in the Austrian Bohemian Massif by analysis of variance

    USGS Publications Warehouse

    Davis, J.C.; Hausberger, G.; Schermann, O.; Bohling, G.

    1995-01-01

    The Austrian portion of the Bohemian Massif is a Precambrian terrane composed mostly of highly metamorphosed rocks intruded by a series of granitoids that are petrographically similar. Rocks are exposed poorly and the subtle variations in rock type are difficult to map in the field. A detailed geochemical survey of stream sediments in this region has been conducted and included as part of the Geochemischer Atlas der Republik O??sterreich, and the variations in stream sediment composition may help refine the geological interpretation. In an earlier study, multivariate analysis of variance (MANOVA) was applied to the stream-sediment data in order to minimize unwanted sampling variation and emphasize relationships between stream sediments and rock types in sample catchment areas. The estimated coefficients were used successfully to correct for the sampling effects throughout most of the region, but also introduced an overcorrection in some areas that seems to result from consistent but subtle differences in composition of specific rock types. By expanding the model to include an additional factor reflecting the presence of a major tectonic unit, the Rohrbach block, the overcorrection is removed. This iterative process simultaneously refines both the geochemical map by removing extraneous variation and the geological map by suggesting a more detailed classification of rock types. ?? 1995 International Association for Mathematical Geology.

  13. UHP kyanite eclogite associated with garnet peridotite and diamond-bearing granulite, northern Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Kotková, Jana; Janák, Marian

    2015-06-01

    Kyanite eclogites enclosed in garnet peridotites may provide important information on P-T evolution of orogenic peridotites in deep subduction and collision zones. Kyanite eclogite interlayered with garnet peridotite occurs in the borehole T-7, in the Saxothuringian basement of the northern part of the Bohemian Massif. This orogenic peridotite of mantle origin is associated with felsic granulites, which contain diamond as a consequence of deep subduction of the continental crust. Here, we report on the metamorphic evolution of kyanite eclogite, which shows a well-preserved peak-pressure mineral assemblage of garnet, omphacite, kyanite and phengite. Conventional geothermobarometry, average PT method and thermodynamic modelling constrain the metamorphic conditions of this assemblage up to 3.5-4.5 GPa at 900-1050 °C. Two compositional types of garnet, i.e., Mg-rich and Ca-rich, have been recognised. Thermodynamic modelling shows that the composition of Ca-rich garnet with XCa (0.35-0.37) in the core corresponds to stability of garnet at 3.5-4.5 GPa. Amphibole and zoisite are preserved as inclusions in garnet cores, and they are stable below 2.5 GPa, indicating that garnet grew at the expense of these phases at increasing P-T conditions during the prograde evolution of the rock. A post-peak metamorphism decompression and cooling are recorded by decrease of Ca-Eskola end-member in omphacite, drop in XMg and XGrs at garnet rim and a very restricted formation of pargasitic amphibole in the matrix. The absence of symplectites after omphacite in the investigated eclogite may be due to a very low content of quartz and possibly also fluid in the rock. Our study suggests that kyanite-bearing eclogite underwent UHP metamorphism as a consequence of subduction, together with interlayered garnet peridotite. Both rocks were incorporated into the subducted continental crust (diamond-bearing granulites) during the Variscan orogeny.

  14. The rare earth element potential of kaolin deposits in the Bohemian Massif (Czech Republic, Austria)

    NASA Astrophysics Data System (ADS)

    Höhn, S.; Frimmel, H. E.; Pašava, J.

    2014-12-01

    Four kaolin deposits in the Bohemian Massif were studied in order to assess the potential for the recovery of rare earth elements (REE) as by-products from the residue after extraction and refining of the raw kaolin. The behaviour of REE + Y during kaolinitization was found to be largely a function of pre-alteration mineralogy. In the examples studied, i.e. granite-derived deposits of Kriechbaum (Austria) and Božičany, and arkose-derived deposits of Kaznějov and Podbořany (all Czech Republic), the REE + Y are predominantly hosted by monazite which has remained unaffected by kaolinitization. The overall REE + Y content of the variably kaolinitized rocks is strongly dependent on their genesis. While ion adsorption plays only a minor role in the concentration of REE + Y in the studied kaolinitized rocks, the processing and refining of the raw kaolin leads to residues that are enriched in REE + Y by a factor of up to 40. The use of a magnetic separator and a hydrocyclone in the processing of the raw material can yield REE + Y contents of as much as 0.77 wt%. Although this value compares well with the REE + Y concentration in some potentially economic REE + Y projects elsewhere, the overall tonnage of the (REE + Y)-enriched residue is by far not sufficient to consider economic extraction of REE + Y as by-product. Our results are most probably applicable also to other kaolin deposits derived from the weathering of Hercynian basement granites elsewhere (e.g. in Saxonia and Bavaria, Germany). Overall, the potential for REE + Y production as by-product from kaolin mining has to be regarded as minimal.

  15. Petrological Characterization of the Triassic Paleosurface in the Northern Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Yao, Kouakou; Thiry, Medard; Szuszkiewicz, Adam; Turniak, Krzysztof

    2010-05-01

    ‘Albitization' is a widespread alteration process affecting sedimentary, igneous and metamorphic rocks. Albitized facies usually show a pinkish to red colour, depending on the degree of alteration. The main mineralogical process of this phenomenon is the pseudomorphic replacement of the primary Ca-Na plagioclases by secondary albite (Na). During this replacement biotite is often transformed to chlorite and inclusions of hematite, apatite, titanite, and calcite develop. So far, albitization has been systematically regarded as caused by magmatic derived hydrothermal brines, alkaline metasomatism reactions (Cathelineau, 1986; Petersson and Eliasson, 1997), or as a low grade metamorphic facies (Boles and Coombs, 1977). Recent studies in the Morvan Massif granites (Ricordel et al., 2007; Parcerisa et al., 2009) showed that the albitization there is related to the Triassic paleosurface. The decrease of this alteration with depth and its paleomagnetic age support the link of the albitization to the Triassic paleosurface. Furthermore, the petrographic data suggest the import of sodium by weathering solutions. The enrichement in Na+ of the fluids that triggered this alteration is probably linked to the Triassic salt deposits. Albitised pinkish facies have been recognized in the northern part of the Bohemian Massif (Polish Sudetes). Typical igneous and metamorphic rocks of the Klodzko area (southern Poland) are granites, granodiorites, schists, amphibolite, and gneisses, mostly of Paleozoic age. Three sites in the Klodzko area were sampled in detail from N to S: (1) Laski quarry, (2) Laski village, and (3) Chwalislaw. Here, the occurrence of the albitization is well developed and specific in its mineralogical paragenesis. Throughout the sample sites different albitization stages can be observed. The most albitized and therefore reddish facies can be found at the Laski village granite that consists of primary quartz and K-feldspar, biotite, and development of secondary

  16. Inherited fossil anisotropic fabric in mantle lithosphere domains of the Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Babuska, Vladislav; Plomerova, Jaroslava; Vecsey, Ludek

    2013-04-01

    Research of deep structure of the Bohemian Massif (BM) and other European regions exploits teleseismic data from dense temporary arrays of seismic stations. To study building elements of the BM we model 3D anisotropy and infer fabric of the mantle lithosphere by inverting jointly P-wave travel-time deviations and shear-wave splitting parameters from recordings of portable and permanent stations operating in the region for more than 20 years. Changes in orientation of the large-scale anisotropy, caused mainly by systematic preferred orientation of olivine, identify boundaries of domains of mantle lithosphere. Individual domains are characterized by a consistent large-scale orientation of anisotropy approximated by hexagonal symmetry with generally inclined symmetry axes (inclined foliation and/or lineation). We map five domains (microplates), each of them bearing a consistent fossil olivine fabric formed before their Variscan assembly. The domains are separated by tectonic boundaries (sutures) identified in the mantle lithosphere. The mantle domains correspond to major crustal units, but crustal and mantle boundaries are often shifted. The fabric of the northern and north-eastern BM is approximated best by peridotite aggregates with the (a,c) foliations dipping to the NNW and NE, respectively, whereas a model with the westerly dipping a lineation fits best the fabric of the south-eastern domain. The Saxothuringian fabric, NW of the Eger Rift, extends to the east across the Elbe Fault Zone (EFZ) and continues along this zone to the southeast beneath the Cretaceous Basin. The southeastward continuation of the Elbe Fault Zone seems to be related to the boundary between two different fabrics of the northern and southern parts of the Brunovistulian domain underlying the Moravo-Silesian zone. The anisotropy shows an underthrusting of the Brunovistulian micro-plate beneath the eastern rim of the BM and indicates that its northern and southern parts might represent

  17. Decorative marbles from the Krkonoše-Jizera Terrane (Bohemian Massif, Czech Republic): provenance criteria

    NASA Astrophysics Data System (ADS)

    Šťastná, Aneta; Přikryl, Richard

    2009-03-01

    Marbles from western part of the Krkonoše-Jizera Terrane (northern part of the Bohemian Massif) have been studied to obtain mineropetrographic and chemical reference data for provenance studies. Samples from six different quarries were analysed by mineralogical-petrographic and geochemical methods (optical microscopy, X-ray diffraction, stable isotope ratio analysis, cathodoluminescence, bulk magnetic susceptibility). Petrographic characteristics permit a distinction between fine-grained to medium-grained marbles from the Jizera Mts (amphibolite metamorphic facies) and fine-grained marbles from the Ještěd Mts (low-grade greenschist facies). The samples studied are mainly calcitic, with the exception of those from Raspenava in which dolomite is abundant in two types. The mineralogical composition of the insoluble residues is clinochlore ± serpentine ± tremolite ± diopside ± pyrite + magnetite in case of the locality Raspenava and clinochlore + muscovite ± quartz ± pyrite ± rutile ± haematite in case of the localities from the Ještěd Mts. δ13C and δ18O variations in primary and secondary carbonate phases allow to distinguish genetically different carbonate veins and permit quarry separation in one case (Raspenava, Jizera Mts). The δ13C and δ18O values of the groundmass range from -1 to +3‰ and from -8 to -20‰ (PDB), respectively. The δ13C and δ18O values of secondary carbonate veins decrease to -3‰ and reach more negative values up to -26‰ in case of δ18O. The fabric of cathodomicrofacies allows the distinction between calcite and dolomite, except three localities (Pilínkov, Horní Hanychov, Jitrava—rose type) with majority of quenchers (high content of iron in carbonate). The genetically different calcite is characterised by a pale and dark orange luminescence distribution. Serpentine, tremolite, forsterite, opaque minerals and quartz have no luminescence and very dull luminescence, respectively. The majority of studied marbles

  18. Morphometric analysis of a reactivated Variscan fault in the southern Bohemian Massif (Budějovice basin, Czech Republic)

    NASA Astrophysics Data System (ADS)

    Popotnig, Angelika; Tschegg, Dana; Decker, Kurt

    2013-09-01

    Quantitative geomorphic parameters are used to assess active vertical displacements at the NW-SE striking Hluboká fault and the NNE-SSW striking Rudolfov fault in the southern Bohemian Massif. The faults are part of a late Variscan fault system that was repeatedly reactivated in Mesozoic, Miocene, and Pliocene times forming the margins of the Budějovice basin. This basin is filled with up to 340-m-thick Cretaceous to Quaternary sediments and forms morphological lowland surrounded by hill country. We compared the basin-facing hillslopes along the faults with other slopes that are not fault-controlled. All creeks and drainage basins share similar geological and hydrological settings and the common base level of the Vltava River. Morphological differences in valley shapes, stream profiles, and drainage basin geometry therefore are likely to reflect different uplift of the crystalline basement with respect to the Budějovice basin. All calculated geomorphic parameters characterise the hillslope along the Hluboká fault as a very straight mountain-piedmont junction with a morphology that is influenced by uplift along the fault. Differential uplift is indicated by extremely low values of mountain front sinuosity (Smf 1.01 to 1.06), high stream length gradients (SL up to 200), and very low valley floor width to height ratios (Vf 0.05 to 0.26). The values are clearly distinct from the values observed at the other hillslopes. Streams showing convex-up thalweg sections with marked single knickpoints close to the Hluboká fault and previously published geodetic data (Vyskočil, 1973) support the interpretation of active vertical fault displacement. Values observed at the Hillslope crossing the Rudolfov fault (Smf 1.17 to 2.20, SL up to 130, Vf 0.29 to 2.5) and convex-up stream profiles of creeks crossing the fault may classify the slope along the Rudolfov fault as moderately active. The interpretation is again corroborated by published geodetic data. The analysed part of

  19. Cross-border radon index map 1:100 000 Lausitz - Jizera - Karkonosze - Region (northern part of the Bohemian Massif).

    PubMed

    Barnet, Ivan; Pacherová, Petra; Preusse, Werner; Stec, Bartosz

    2010-10-01

    The first cross-border map describing the radon (Rn) risk from bedrock was assembled in the northern part of the Bohemian Massif at a scale 1:100 000. The map covers the area of Lausitz (Germany), Karkonosze (Czech Republic and Poland) and Jizera (Czech Republic). The map is based on 818 measurements of soil gas Rn in rock types of Precambrian to Mesozoic age with variable geology. Geographic information system (GIS) processing enabled a good coincidence of soil gas Rn concentrations between data from all three countries in lithologically adjacent rock types as well as the direct correlation to georeferenced indoor Rn values, which was tested using the Czech indoor Rn data. The method of data processing can contribute to assembling the European Geogenic Radon Map. PMID:20022148

  20. Multistage evolution of UHT granulites from the southernmost part of the Gföhl Nappe, Bohemian Massif, Lower Austria

    NASA Astrophysics Data System (ADS)

    Schantl, Philip; Hauzenberger, Christoph; Linner, Manfred

    2016-04-01

    A detailed petrological investigation has been undertaken in leucocratic kyanite-garnet bearing and mesocratic orthopyroxene bearing granulites from the Dunkelsteiner Wald, Pöchlarn-Wieselburg and Zöbing granulite bodies from the Moldanubian Zone in the Bohemian Massif (Austria). A combination of textural observations, conventional geothermobarometry, phase equilibrium modelling as well as major and trace element analyses in garnet enables us to confirm a multistage Variscan metamorphic history. Chemically homogenous garnet cores with near constant grossular-rich plateaus are considered to reflect garnet growth during an early HP/UHP metamorphic evolution. Crystallographically oriented rutile exsolutions restricted to those grossular-rich garnet cores point to a subsequent isothermal decompression of the HP/UHP rocks. Overgrowing garnet rims show a pronounced zonation and are interpreted as the result of dehydration melting reactions during an isobaric heating phase which could have taken place near the base of an overthickened continental crust, where the previously deeply subducted rocks were exhumed to. For this HP granulite facies event maximum PT conditions of ~1050 °C and 1.6 GPa have been estimated from leucocratic granulites comprising the peak mineral assemblage quartz, ternary feldspar, garnet, kyanite and rutile. The pronounced zoning of garnet rims indicates that the HP granulite facies event must have been short lived since diffusion in this temperature region is usually sufficient fast to homogenize a zoning pattern in garnet. A retrogressive metamorphic stage is documented in these rocks by the replacement of kyanite to sillimanite and the growth of biotite. This retrograde event took place within the granulite facies but at significantly lower pressures and temperatures with ~0.8 GPa and ~760 °C. This final stage of re-equilibration is thought to be linked with a second exhumation phase into middle crustal levels accompanied by intensive

  1. Seismic tomography of the upper mantle beneath the Bohemian Massif (central Europe)

    NASA Astrophysics Data System (ADS)

    Karousova, H.; Plomerova, J.; Vecsey, L.; Munzarova, H.

    2012-04-01

    We present a comprehensive test for teleseismic tomography of the upper mantle beneath the southern part of the Bohemian Massif (BM) based on data of passive experiments BOHEMA III and the northern part of the ALPASS (Mitterbauer et al., Tectonophysics 2011) as well as preliminary results. A new semi-automatic picker was applied for measuring P-wave arrival times from correlated extremes of waveforms recorded at 58 temporary seismic stations and 55 permanent observatories during 2005-2006. To calculate P-velocity perturbations, we selected 173 events from epicentral distances between 25° and 90°, and with magnitude higher than 4.5. Before the travel-time inversion itself, we analysed carefully relative P-wave residuals and cleaned the dataset of the travel-times from outliers and instabilities in timing for further processing. To eliminate leakage of crustal effects into the upper mantle velocity images, we corrected the observed travel-times for crustal structure according to 3D models of the BM and Eastern Alps crust (Karousova et al., Studia Geophys. Geod. 2012; Behm et al., GJI 2007). In order to optimize model parameterization, initial velocities and damping factors we perform different synthetic tests. Checkerboard and synthetic tests with artificial heterogeneities and shifted parameterization are calculated to explore sensitivity and resolution in individual nodes. Models with indistinctive velocity perturbations in the resolved parts tend to be more sensitive to ray geometry in the upper mantle and consequently could accentuate even insignificant heterogeneities. We show series of velocity perturbation images in three parts of the BM retrieved in three successive passive seismic experiments BOHEMA I-III. No distinct 'tube-like' low velocity heterogeneity, which could be interpreted as a small plume beneath the Eger Rift is imaged in tomography in western BM from the BOHEMA I data. Relatively small velocity perturbations exist in the upper mantle beneath

  2. The systematics and paleobiogeographic significance of Sub-Boreal and Boreal ammonites (Aulacostephanidae and Cardioceratidae) from the Upper Jurassic of the Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Hrbek, Jan

    2014-10-01

    Upper Jurassic marine deposits are either rarely preserved due to erosion or buried under younger sediments in the Bohemian Massif. However, fossil assemblages from a few successions exposed in northern Bohemia and Saxony and preserved in museum collections document the regional composition of macro-invertebrate assemblages and thus provide unique insights into broad-scale distribution and migration pathways of ammonites during the Late Jurassic. In this paper, we focus on the systematic revision of ammonites from the Upper Oxfordian and Lower Kimmeridgian deposits of northern Bohemia and Saxony. The ammonites belong to two families (Aulacostephanidae and Cardioceratidae) of high paleobiogeographic and stratigraphic significance. Six genera belong to the family Aulacostephanidae (Prorasenia, Rasenia, Eurasenia, Rasenioides, Aulacostephanus, Aulacostephanoides) and one genus belongs to the family Cardioceratidae (Amoeboceras). They show that the Upper Jurassic deposits of the northern Bohemian Massif belong to the Upper Oxfordian and Lower Kimmeridgian and paleobiogeographically correspond to the German-Polish ammonite branch with the geographical extent from the Polish Jura Chain to the Swabian and Franconian Alb. Therefore, the occurrences of ammonites described here imply that migration pathway connecting the Polish Jura Chain with habitats in southern Germany was located during the Late Oxfordian and Early Kimmeridgian in the Bohemian Massif.

  3. Petrochronological and structural arguments for upper plate thickening and relamination of the lower plate buoyant material in the Variscan Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Peřestý, Vít; Holder, Robert; Lexa, Ondrej; Racek, Martin; Jeřábek, Petr

    2014-05-01

    Recent tectonic models for the Variscan evolution of the Bohemian Massif emphasize the role of Rayleigh-Taylor instability for the 355-340 Ma evolution of the Moldanubian domain. This model is based on the presence of weak, low-density felsic material tectonically underplating a high-density mafic layer and its subsequent gravity-driven overturn. However, earlier phases of the Variscan orogeny concerning the emplacement of felsic low-density material to the base of the upper plate are so far poorly documented. We contribute to this problem by deciphering of polyphase early-Variscan (~375 Ma) deformation and metamorphism close to the main Variscan suture. Detailed structural, pseudosection and microstructural analyses combined with LASS monazite dating were carried out in metapelites along the western margin of the upper plate represented by the Teplá Crystalline Complex (TCC). This region is represented by a ~25 km wide deformation zone with E-W metamorphic gradients associated with two distinct early-Variscan events (~380-375 and ~375-370 Ma). The first compressional event produced a vertical NNE-SSW trending fabric and a continuous and prograde Barrovian metamorphic sequence ranging from biotite to kyanite zones at a field geotherm of 20 to 25 °C/km. Subsequently, a gently SE dipping normal shear-zone associated with retrogression develops along the base of the TCC. This sub-horizontal fabric shows normal metamorphic zonation ranging from sillimanite, biotite to chlorite zones and indicates vertical shortening related to unroofing of high pressure metabasites of the underlying Mariánské-Lázně Complex. The first metamorphic fabric is interpreted to result from early thickening of the upper plate during continental underthrusting of Saxothuringian continent (380 to 375 Ma) while the second deformation and metamorphism (~370 Ma) reflects vertical shortening produced by buoyant uplift of accreted Saxothuringian felsic crust. This event is the unique yet

  4. Late Cretaceous and Cenozoic dynamics of the Bohemian Massif inferred from the paleostress history of the Lusatian Fault Belt

    NASA Astrophysics Data System (ADS)

    Coubal, Miroslav; Málek, Jiří; Adamovič, Jiří; Štěpančíková, Petra

    2015-07-01

    An analysis of fault-slip data from the Lusatian Fault Belt, limiting the Lusatian Block of the Bohemian Massif in the SW, yielded parameters of eight successive paleostress patterns, Late Cretaceous to Plio-Pleistocene in age. These patterns were linked with specific stages in fault kinematics and fault-belt deformation. They include (1) α1, NE- to NNE-directed compression in a reverse fault regime (σ3 vertical) associated with major thrusting and drag zone formation in the latest Cretaceous, preceded by pre-drag origin of deformation bands α0; (2) αβ1-2, WNW-directed extension associated with emplacement of polzenite-group volcanics (≈80-61 Ma) and influx of hydrothermal fluids, overlapping in time with α1; (3) α2, N-directed compression in a reverse fault regime, probably Paleocene in age, associated with thrusting and intensive shear faulting in adjacent parts of blocks; (4) αβ3, Early Oligocene W- to WNW-directed extension in a regime of strike-slip faulting (σ2 vertical), probably connected with an emplacement of phonolitic magmas and influx of hydrothermal fluids; (5) α3, NNW-directed compression associated with activation of transverse/oblique faults of the fault belt, close in age to αβ3 with unclear mutual superposition; (6) β, Late Oligocene-Early Miocene multi-stage N- to NE-directed extension in a normal fault regime, specific to the Bohemian Massif, responsible for downfaulting of the hangingwall block; (7) γ, Mid to Late Miocene NE-directed compression in a reverse fault regime associated with thrusting; (8) δ, Pliocene (to Pleistocene?) NW- to NNW-directed compression in a strike-slip regime, associated with transverse faulting in the fault belt. The identified paleostress patterns show a good correlation with the hitherto identified paleostress fields transmitted to the Alpine foreland and refine the temporal sequence of paleostress states, especially in the post-Lower Miocene period.

  5. Southeastern slope of the Bohemian Massif: Paleogene submarine fill of the Nesvacilka depression and its importance for petroleum exploration

    SciTech Connect

    Benada, S.; Berka, J.; Brzobohaty, J.; Rehanek, J. )

    1993-09-01

    The Nesvacilka depression is a trough-like paleovalley, about 2000 m deep, that was cut at the transition from the Cretaceous to the Paleocene by fluvial erosion into Jurassic and Carboniferous strata. This morphological feature, which is superimposed on an ancient tectonic zone, trends to the present southeast boundary of the Bohemian massif and is, from a hydrocarbon exploration point of view, the most important structure in the Czech Republic. During the Paleogene, marine transgressions gradually flooded this paleovalley. In the resulting relatively closed water body, more than 1500 m of thick deeper water clastics accumulated. These clastics display features similar to those described from submarine fan lobes in other hydrocarbon-producing basins. Following the discovery of two oil and gas accumulations contained in Jurassic and Paleogene clastic rocks, exploration was focused on the central parts of the Nesvacilka depression. The depositional pattern of its Paleogene fill was worked out on the basis of well data and the results of two-dimensional and three-dimensional seismic surveys. From this, it was concluded that accumulation of the Paleogene clastic series was significantly influenced by sea level changes. The depositional concepts developed may be applied to the deeper parts of the Nesvacilka Canyon, where exploration for hydrocarbons is still at an early stage. Results obtained so far indicate that the Nesvacilka depression can be ranked as the most prospective oil play in the Czech Republic. Play concepts developed may be extrapolated to similar morphological features occurring elsewhere in the Carpathian foreland.

  6. Magnetic fabric and modeled strain distribution in the head of a nested granite diapir, the Melechov pluton, Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Trubač, Jakub; Žák, Jiří; Chlupáčová, Marta; Janoušek, Vojtěch

    2014-09-01

    The Melechov pluton, Bohemian Massif, is interpreted as a mid-crustal nested granitic diapir with an apical part exposed at the present-day erosion level. The diapir head exhibits a concentric structure defined by lithologic zoning and by the anisotropy of magnetic susceptibility (AMS). In concert with theoretical models, outward-dipping margin-parallel magnetic foliations are associated with oblate shapes of the susceptibility ellipsoids and higher degree of anisotropy, passing inward into weaker triaxial to prolate fabric. By contrast, magnetic fabric in an inner granite unit is in places oriented at a high angle to internal contacts and is interpreted as recording an internal diapir circulation. We use inverse modeling to calculate strain variations across the diapir from the AMS data. The magnetic fabric parameters and calculated strains are in agreement with strain distribution in heads of model Newtonian diapirs traveling a distance of two body radii and suggest granitic magma ascent as a crystal-poor suspension followed by crystallization of fabric markers and their response to strain near the final emplacement level. The intrusive fabric thus formed late but, though generally weak, was still capable of recording incremental strain gradient in the granite diapir.

  7. P T and fluid evolution of barren and lithium pegmatites from Vlastějovice, Bohemian Massif, Czech Republic

    NASA Astrophysics Data System (ADS)

    Ackerman, Lukáš; Zachariáš, Jiří; Pudilová, Marta

    2007-08-01

    Fluid inclusions, mineral thermometry and stable isotope data from two types of mineralogically and texturally contrasting pegmatites, barren ones and lithium ones, from the Moldanubian Zone of the Bohemian Massif were studied in order to constrain P T conditions of their emplacement, subsolidus hydrothermal evolution and to estimate composition of the early exsolved fluid and that of the parental melt. Despite the fact that the lithium pegmatites are abundant throughout the crystalline units of the Bohemian Massif, data similar to this paper have not been published yet. The studied pegmatites are hosted by iron-rich calcic skarn bodies. This specific setting allowed scavenging of calcium, fluorine and some other elements from the host rocks into the pegmatitic melts and post-magmatic fluids. Such contamination process was important namely in the case of barren pegmatites, as can be deduced from the variation in anorthite contents in plagioclase and from the presence of fluorite, hornblende (with F content) or garnet in the contact zones of pegmatite dykes. Fluid inclusions were studied mostly in quartz, but also in fluorite, titanite and apatite. Early aqueous carbonic and late aqueous fluids were identified in both pegmatite types. The P T conditions of crystallization as well as the detailed composition of exsolved magmatic fluid, however, particularly differ. The magmatic fluids associated with barren pegmatites correspond to H2O CO2 low salinity fluids, composition of which evolved from 20 to 23 to <5 mol% CO2, and from 2 to 4 6 mol% NaCl eq. Sudden decrease in the CO2 content of the post-magmatic fluids (<5 mol% CO2) seems to coincide with the enrichment of the fluid in calcium (from the contamination process) and resulted in precipitation of calcites (frequently found as trapped solid phases in fluid inclusions). The fluids associated with lithium pegmatites are more complex (H2O CO2/N2 H3BO3 NaCl). The CO2 content of early exsolved fluid is 26 20 mol% CO2

  8. Monazite and zircon as major carriers of Th, U, and Y in peraluminous granites: examples from the Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Breiter, Karel

    2016-06-01

    The chemical compositions of zircon and monazite and the relationships between the contents of Th, U, Y, and REE in both minerals and in the bulk samples of their parental rocks were studied in three Variscan composite peraluminous granite plutons in the Bohemian Massif. It was established that granites of similar bulk composition contain zircon and monazite of significantly different chemistry. Monazite typically contains 5-13 wt% (rarely up to 28 wt%) ThO2, 0.4-2 wt% (up to 8.2 wt%) UO2, and 0.5-2 wt% (up to 5 wt%) Y2O3, whereas zircon typically contains less than 0.1 wt% (rarely up to 1.7 wt%) ThO2, less than 1 wt% UO2 (in the Plechý/Plockenstein granite, commonly, 1-2 wt% and scarcely up to 4.8 wt% UO2), and less than 1 wt% Y2O3 (in the Nejdek pluton often 2-5, maximally 7 wt% Y2O3). Monazite is an essential carrier of thorium, hosting more than 80 % of Th in all studied granites. Monazite also appears to be an important carrier of Y (typically 14-16 %, and in the Melechov pluton, up to 81 % of the total rock content) and U (typically 18-35 % and occasionally 6-60 % of the total rock budget). The importance of zircon for the rock budget of all the investigated elements in granites is lower: 4-26 % U, 5-17 % Y, and less than 5 % Th.

  9. Compositional evolution and substitutions in disseminated and nodular tourmaline from leucocratic granites: Examples from the Bohemian Massif, Czech Republic

    NASA Astrophysics Data System (ADS)

    Buriánek, David; Novák, Milan

    2007-04-01

    Two distinct textural types of tourmaline have been distinguished in leucocratic granites of the Bohemian Massif (Moldanubicum, Saxothuringicum): (i) commonly euhedral disseminated tourmaline (DT) crystallized during relatively early stage of the granite consolidation, and (ii) typically interstitial nodular tourmaline (NT) formed during the stage transitional from late solidus to early subsolidus crystallization. The following substitutions (exchange vectors) participated in tourmaline from the studied granites: (1) X□ YAl XNa - 1 YR 2+- 1 in the DT granites from the Moldanubicum; (2) X□ YAl 3WO 2XNa - 1 YR 2+- 3 W(OH) - 2 and (6) XNa YR 2+WF X□ - 1 YAl - 1 WOH - 1 in the DT and NT granites from the Saxothuringicum. Tourmaline in the NT granites from the Moldanubicum yielded a complicated pattern indicating participation of several substitutions such as (1), (2) and (3) X□ YAl 2WO XNa - 1 YR 2+- 2 W(OH) - 1 . Very similar chemical compositions and similar fractionation trends in both DT and NT tourmaline types indicate crystallization in a quasi-closed system from early solidus to early subsolidus stage of granite consolidation. Substitutions in tourmaline from NT granites in the Moldanubicum are more similar to substitutions in tourmaline from Li-poor granitic pegmatites in the same region relative to tourmaline from DT granites. Plotting up EMP analyses of tourmaline indicates that a combination of two ternary diagrams Al-Fe-Mg and Na-Ca- X-site vacancy, coupled with simple plots involving single cations (elements) such as Na/Al, F/Na, Fe/Mg, characterizes both their chemical composition as well as the probable substitution mechanisms. Complex diagrams such as R1 + R2 versus R3 do not enable a proper investigation of the compositional evolution in the X-site and W-site and oversimplify the real substitutions. As a consequence the use of specific diagrams for specific tourmaline compositions (e.g., Ca-rich, Li-rich) is recommended.

  10. The Blaník Gneiss in the southern Bohemian Massif (Czech Republic): a rare rock composition among the early palaeozoic granites of Variscan Central Europe

    NASA Astrophysics Data System (ADS)

    René, Miloš; Finger, Fritz

    2016-01-01

    Metamorphosed and deformed tourmaline-bearing leucogranites with a Cambro-Ordovician formation age are widespread in the Monotonous Group of the Variscan southern Bohemian Massif, Czech Republic. The rocks, known locally as Blaník gneiss, are strongly peraluminous and classify as phosphorus-rich low-T, S-type granite. The magma formed from a metapelitic source, most likely through muscovite dehydration melting. With respect to its low-T origin and the abundance of tourmaline, the Blaník gneiss is exotic within the spectrum of Early Palaeozoic granites of the Variscan fold belt of Central Europe. Coeval granitic gneisses in the neighbouring Gföhl unit of the Bohemian Massif can be classified as higher T S-type granites and were probably generated through biotite dehydration melting. The geochemical differences between the Early Palaeozoic granitic magmatism in the Gföhl unit and the Monotonous Group support models claiming that these two geological units belonged to independent peri-Gondwana terranes before the Variscan collision. It is suggested here, that the Gföhl unit and the Monotonous Group represent zones of higher and lower heat flow within the Early Palaeozoic northern Gondwana margin, respectively. The geochemical data presented in this study could be helpful for terrane correlations and palaeogeographic reconstructions.

  11. The Blaník Gneiss in the southern Bohemian Massif (Czech Republic): a rare rock composition among the early palaeozoic granites of Variscan Central Europe

    NASA Astrophysics Data System (ADS)

    René, Miloš; Finger, Fritz

    2016-08-01

    Metamorphosed and deformed tourmaline-bearing leucogranites with a Cambro-Ordovician formation age are widespread in the Monotonous Group of the Variscan southern Bohemian Massif, Czech Republic. The rocks, known locally as Blaník gneiss, are strongly peraluminous and classify as phosphorus-rich low-T, S-type granite. The magma formed from a metapelitic source, most likely through muscovite dehydration melting. With respect to its low-T origin and the abundance of tourmaline, the Blaník gneiss is exotic within the spectrum of Early Palaeozoic granites of the Variscan fold belt of Central Europe. Coeval granitic gneisses in the neighbouring Gföhl unit of the Bohemian Massif can be classified as higher T S-type granites and were probably generated through biotite dehydration melting. The geochemical differences between the Early Palaeozoic granitic magmatism in the Gföhl unit and the Monotonous Group support models claiming that these two geological units belonged to independent peri-Gondwana terranes before the Variscan collision. It is suggested here, that the Gföhl unit and the Monotonous Group represent zones of higher and lower heat flow within the Early Palaeozoic northern Gondwana margin, respectively. The geochemical data presented in this study could be helpful for terrane correlations and palaeogeographic reconstructions.

  12. Mapping seismic anisotropy of the lithospheric mantle beneath the northern and eastern Bohemian Massif (central Europe)

    NASA Astrophysics Data System (ADS)

    Plomerová, Jaroslava; Vecsey, Luděk; Babuška, Vladislav

    2012-09-01

    We evaluate 3D body-wave anisotropic parameters—shear-wave splitting (fast S polarizations and delay times of the split slow shear waves) and directional terms of relative P-wave residuals from data of passive seismic experiment BOHEMA II (2004-2005). Data from 34 temporary stations increased substantial density of observations in the Bohemain Massif (BM) and allowed us to scan in detail the upper mantle structure of its northern and eastern parts. For the first time, we delimit domains of the mantle lithosphere in this part of the BM and infer 3D self-consistent models of their fabrics by a joint inversion of the body-wave anisotropic parameters. Fabrics of the northern and north-eastern parts of the BM are approximated best by peridotite aggregates with the (a,c) foliations dipping approximately to the N and NE, respectively, whereas a model with the westerly dipping a lineation fits best the fabric of the south-eastern domain. The Saxothuringian fabric, NW of the Eger Rift, extends to the east across the Elbe Fault Zone and continues along this zone to the southeast beneath the Cretaceous Basin. The south-eastward continuation of the Elbe Fault Zone seems to be related to the boundary between two different fabrics of the northern and southern Brunovistulian domains below the Moravo-Silesian zone. This study shows an underthrusting of the Brunovistulian micro-plate beneath the eastern rim of the BM and indicates that its northern and southern fragments might have originally belonged to Baltica and to Gondwana, respectively. According to a zone of distinctly decreased anisotropic signals, the Brunovistulian micro-plate extends at least about 100 km westward beneath the Moldanubian. With these new findings we update the domain-like mantle structure of the BM and compare the results with inferences from the upper mantle velocity tomography and depth changes of the lithosphere-asthenosphere boundary retrieved in a detailed model from relative residuals and from the

  13. Evidence of unadulterated mantle-depth, granitic melt inclusions: kumdykolite and kokchetavite crystallized from melt in Bohemian Massif granulites.

    NASA Astrophysics Data System (ADS)

    O´Brien, Patrick J.; Ferrero, Silvio; Ziemann, Martin A.; Walczak, Katarzyna; Wunder, Bernd; Hecht, Lutz; Wälle, Markus

    2016-04-01

    Partial melting under near-UHP conditions of metagranitoids (now HP felsic granulites) at mantle depth in the Orlica-Śnieżnik Dome (Bohemian Massif, Poland) is recorded in small volumes of hydrous melt trapped as primary melt inclusions (MI) in peritectic garnets. When free of cracks connecting the inclusion with the leucocratic matrix, these "nanogranites" (≤ 50μm inclusion diameter) contain a unique assemblage including kumdykolite, kokchetavite and cristobalite - polymorphs of albite, K-feldspar and quartz, respectively. These usually metastable phases crystallized from the melt (glass?) during rapid exhumation (cm/a) at high T but the crack-free state strongly suggests over-pressuring of the inclusion with respect to the pressure-time path followed by the matrix. Reports of both kumdykolite and kokchetavite have been mainly from natural rocks equilibrated in the diamond stability field. The precise calculation of the PT path of the MI on cooling and the comparison with previous studies suggests, however, that pressure is not influential to their formation, ruling out the possible interpretation of kumdykolite and kokchetavite as indicators of ultra-high pressure conditions. Experimental re-homogenization of these crack-free nanogranites was achieved using a piston cylinder apparatus at 2.7 GPa and 875°C. These conditions are consistent with the results of geothermobarometric calculations on the host rock, suggesting that no H2O loss occurred during exhumation as this would have caused a shift of the inclusion melting T toward higher values. Coupled with the absence of H2O-loss microstructural evidence, e.g. decrepitation cracks and/or vesciculation in re-homogenized nanogranites, this evidence suggests that the nanogranites still preserve the original H2O content of the melt. Both experimental and microstructural evidence support the hypothesis that the presence of these polymorphs should be regarded as direct mineralogical criterion to identify former

  14. Two Lithologies in Lithospheric Mantle Beneath Nothern Margin of the Bohemian Massif (e Germany and SW Poland).

    NASA Astrophysics Data System (ADS)

    Matusiak-Małek, Magdalena; Puziewicz, Jacek; Ntaflos, Theodoros; Kukuła, Anna; Ćwiek, Mateusz

    2014-05-01

    The subcontinental lithospheric mantle (SCLM) occurring beneath Bohemian Massif in Central Europe has been sampled in Cenozoic times by numerous lavas. Recent studies (Puziewicz et al. 2011 and references therein) show that mantle in this region is mostly anhydrous, harzburgitic, and was subjected to various kinds of metasomatic events. Two major mantle lithologies characterized by different major element composition of peridotite- forming minerals occur in the SCLM Lower Silesia and Lusatia (op. cit. and unpublished results, 9 sites). Lithology "A" (minimal temperatures from 900 to 1000ºC or no equilibrium between cpx and opx) contains olivine Fo90.5 -92.0. Part of the population "A" peridotites contain clinopyroxene of mg# 94 - 95, typical for low temperatures of equilibration. The lithology "B" (equilibration temperatures close to 900 ºC) contains olivine Fo87.5-90.0. Elevated contents of LREE in clinopyroxene from both the lithologies "A" and "B" suggest their equilibration with one of the two metasomatic agents stated in this area: anhydrous silicate alkaline melt or carbonatite-silicate melt. Action of hydrous alkaline melts in the mantle in the region is recorded only locally (e.g. Wilcza Góra). In some sites (e.g. Krzeniów) the trace element patterns show that decreasing mg# of clinopyroxene in the "A" peridotites is due to gradual replacement of primary lower-temperature mineral assemblage by the later higher-temperature one. This suggests that the variation of mineral chemistry is rather due to chromatographic fractionation of metasomatic agents than due to vertical variation in lithospheric mantle temperatures (Christensen et al.,2001). The "B" peridotites originated due to "Fe-metasomatism" of more magnesian peridotites by silicate melts percolating through lithospheric mantle. The peridotites belonging to lithology "A" might have been partly the protolith of the lithology "B". The data on Central European lithospheric mantle are equivocal and thus

  15. Gallium and germanium geochemistry during magmatic fractionation and post-magmatic alteration in different types of granitoids: a case study from the Bohemian Massif (Czech Republic)

    NASA Astrophysics Data System (ADS)

    Breiter, Karel; Gardenová, Nina; Kanický, Viktor; Vaculovič, Tomáš

    2013-06-01

    Contents of Ga and Ge in granites, rhyolites, orthogneisses and greisens of different geochemical types from the Bohemian Massif were studied using inductively coupled plasma mass spectrometry analysis of typical whole-rock samples. The contents of both elements generally increase during fractionation of granitic melts: Ga from 16 to 77 ppm and Ge from 1 to 5 ppm. The differences in Ge and Ga contents between strongly peraluminous (S-type) and slightly peraluminous (A-type) granites were negligible. The elemental ratios of Si/1000Ge and Al/1000Ga significantly decreased during magmatic fraction: from ca. 320 to 62 and from 4.6 to 1.2, respectively. During greisenization, Ge is enriched and hosted in newly formed hydrothermal topaz, while Ga is dispersed into fluid. The graph Al/Ga vs. Y/Ho seems to be useful tool for geochemical interpretation of highly evolved granitoids.

  16. Underground electromagnetic activity in two regions with contrasting seismicity: a case study from the Eastern Alps and Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Baroň, Ivo; Koktavý, Pavel; Stemberk, Josef; Macků, Robert; Trčka, Tomáš; Škarvada, Pavel; Lenhardt, Wolfgang; Meurers, Bruno; Rowberry, Mattew; Marti, Xavi; Plan, Lukas; Grasemann, Berhnard; Mitrovic, Ivanka

    2016-04-01

    Electromagnetic emissions (EME) occur during the fracturing of solid materials under laboratory conditions and may represent potential earthquake precursors. We recorded EME from May 2015 to October 2015 in two caves situated in contrasting seismotectonic settings. Zbrašov Aragonite Caves are located close to the seismically quiescent contact between the Bohemian Massif and the Outer Western Carpathians while Obir Caves are located near the seismically active Periadriatic Fault on the southern margin of the Eastern Alps. The specific monitoring points are located at depths of tens of metres below the ground surface as such places are assumed to represent favourably shielded environments. The EME signals were continuously monitored by two custom-made Emission Data Loggers (EDLOG), comprising both analogue and digital parts. The crucial analogue component within the EDLOG is a wideband shielded magnetic loop antenna. To be able to observe EME related rock deformation and microfracturing we recorded signals between 10 and 200 kHz with a sampling frequency of 500 kHz. An ultralow noise preamplifier placed close to the antenna increases the signal-to-noise ratio. Further signal processing consisted of filtering, such as antialiasing and interference rejection, and additional amplification to fit the signal to the full scale range of the AD convertor. The digital part of the EDLOG comprises a range of PC components such as high-capacity replaceable data storage and unbuffered RAM, high-speed multichannel DAQ cards, and custom made control software in the programming environment LabVIEW. During our EME monitoring all the raw data were stored. This has allowed us to perform advanced data processing and detailed analysis. During the study period some artificial EME signals were observed in Zbrašov Aragonite Caves. This artificial noise may have overprinted any natural signals and is most likely to relate to the pumping of CO2. In contrast, markedly different signals were

  17. The use of caves as observatories for recent geodynamic activity and radon gas concentrations in the Western Carpathians and Bohemian Massif.

    PubMed

    Briestensky, M; Thinova, L; Stemberk, J; Rowberry, M D

    2011-05-01

    In recent years, many underground spaces such as caves and deep mines have been used to monitor geodynamic activity in the Western Carpathians and Bohemian Massif. In addition, long-term radon gas monitoring has also being undertaken in three of the caves. The observed radon concentrations have shown diurnal, seasonal and yearly variations. A significant correlation with external temperature has been registered. This pattern is considered to result from the movement of air caused by the contrast between the broadly constant internal and fluctuating external temperatures. The same seasonal effects have been observed in the record of active fault displacements at sites close to the surface. These seasonal effects lead to peak-to-peak massif dilation amplitude that affects the overall trend of fault displacement. It is also noted that a significant decrease in this amplitude occurs with increasing depth beneath the surface. However, high variability has also been observed in both the radon concentration and fault displacement activity recorded. Many events have been registered that link these two geofactors. PMID:21478172

  18. Constraining long-term denudation and faulting history in intraplate regions by multisystem thermochronology: An example of the Sudetic Marginal Fault (Bohemian Massif, central Europe)

    NASA Astrophysics Data System (ADS)

    DanišíK, Martin; Å TěPančíKová, Petra; Evans, Noreen J.

    2012-04-01

    The Rychlebské hory Mountain region in the Sudetes (NE Bohemian Massif) provides a natural laboratory for studies of postorogenic landscape evolution. This work reveals both the exhumation history of the region and the paleoactivity along the Sudetic Marginal Fault (SMF) using zircon (U-Th)/He (ZHe), apatite fission track (AFT), and apatite (U-Th)/He (AHe) dating of crystalline basement and postorogenic sedimentary samples. Most significantly, and in direct contradiction of traditional paleogeographic reconstructions, this work has found evidence of a large Cretaceous sea and regional burial (to >6.5 km) of the Carboniferous-Permian basement in the Late Cretaceous (˜95-80 Ma). During the burial by sediments of the Bohemian Cretaceous Basin System, the SMF acted as a normal fault as documented by offset ZHe ages across the fault. At 85-70 Ma, the basin was inverted, Cretaceous strata eroded, and basement blocks were exhumed to the near surface at a rate of ˜300 m/Ma as evidenced by Late Cretaceous-Paleocene AFT ages and thermal modeling results. There is no appreciable difference in AFT and AHe ages across the fault, suggesting that the SMF acted as a reverse fault during exhumation. In the late Eocene-Oligocene, the basement was locally heated to <70°C by magmatic activity related to opening of the Eger rift system. Neogene or younger thermal activity was not recorded in the thermochronological data, confirming that late Cenozoic uplift and erosion of the basement blocks was limited to less than ˜1.5 km in the study area.

  19. Two-stage exhumation of subducted Saxothuringian continental crust records underplating in the subduction channel and collisional forced folding (Krkonoše-Jizera Mts., Bohemian Massif)

    NASA Astrophysics Data System (ADS)

    Jeřábek, Petr; Konopásek, Jiří; Žáčková, Eliška

    2016-08-01

    The Krkonoše-Jizera Massif in the northern part of the Variscan Bohemian Massif provides insight into the exhumation mechanisms for subducted continental crust. The studied region exposes a relatively large portion of a flat-lying subduction-related complex that extends approximately 50 km away from the paleosuture. wide extent of HP-LT metamorphism has been confirmed by new P-T estimates indicating temperatures of 400-450 °C at 14-16 kbar and 450-520 °C at 14-18 kbar for the easternmost and westernmost parts of the studied area, respectively. A detailed study of metamorphic assemblages associated with individual deformation fabrics together with analysis of quartz deformation microstructures and textures allowed characterisation of the observed deformation structures in terms of their subduction-exhumation memory. An integration of the lithostratigraphic, metamorphic and structural data documents a subduction of distal and proximal parts of the Saxothuringian passive margin to high-pressure conditions and their subsequent exhumation during two distinct stages. The initial stage of exhumation has an adiabatic character interpreted as the buoyancy driven return of continental material from the subduction channel resulting in underplating and progressive nappe stacking at the base of the Teplá-Barrandian upper plate. With the transition from continental subduction to continental collision during later stages of the convergence, the underplated high-pressure rocks were further exhumed due to shortening in the accretionary wedge. This shortening is associated with the formation of large-scale recumbent forced folds extending across the entire studied area.

  20. Kumdykolite, kokchetavite, and cristobalite crystallized in nanogranites from felsic granulites, Orlica-Snieznik Dome (Bohemian Massif): not an evidence for ultrahigh-pressure conditions

    NASA Astrophysics Data System (ADS)

    Ferrero, Silvio; Ziemann, Martin A.; Angel, Ross J.; O'Brien, Patrick J.; Wunder, Bernd

    2016-01-01

    A unique assemblage including kumdykolite and kokchetavite, polymorphs of albite and K-feldspar, respectively, together with cristobalite, micas, and calcite has been identified in high-pressure granulites of the Orlica-Snieznik dome (Bohemian Massif) as the product of partial melt crystallization in preserved nanogranites. Previous reports of both kumdykolite and kokchetavite in natural rocks are mainly from samples that passed through the diamond stability field. However, because the maximum pressure recorded in these host rocks is <3 GPa, our observations indicate that high pressure is not required for the formation of kumdykolite and kokchetavite, and their presence is not therefore an indicator of ultrahigh-pressure conditions. Detailed microstructural and microchemical investigation of these inclusions indicates that such phases should instead be regarded as (1) a direct mineralogical criteria to identify former melt inclusions with preserved original compositions, including H2O and CO2 contents and (2) indicators of rapid cooling of the host rocks. Thus, the present study provides novel criteria for the interpretation of melt inclusions in natural rocks and allows a more rigorous characterization of partial melts during deep subduction to mantle depth as well as their behavior on exhumation.

  1. Granitic magma emplacement and deformation during early-orogenic syn-convergent transtension: The Staré Sedlo complex, Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Tomek, Filip; Žák, Jiří; Chadima, Martin

    2015-07-01

    The Late Devonian Staré Sedlo complex, Bohemian Massif, was emplaced as a subhorizontal sheeted sill pluton into a transtension zone. The transtensional setting is documented by strong constrictional fabric, corroborated by the anisotropy of magnetic susceptibility (AMS), with variably developed subhorizontal magmatic to solid-state foliation suggesting vertical shortening. Intrusive contacts of the granitoids with metapelitic screens and tapered sill tips indicate that magma wedging was the dominant process of sill propagation. The sills exhibit two intrusive styles, ranging from thin lit-par-lit injections to widely spaced meter-thick sills. These two styles are interpreted as reflecting variable viscosities of intruding magma where low-viscosity magma percolated along foliation planes whereas high-viscosity magma produced more localized thicker sills. We propose that the magma/host rock system in transtension must have evolved from initial crack tip propagation and vertical expansion due to new magma additions through conduit flow to ductile thinning after the magma input had ceased. The sill emplacement and their subsequent deformation are then interpreted as recording early-orogenic syn-convergent sinistral transtension along the rear side of an upper-crustal wedge, which was extruded both upward and laterally in response to subduction and continental underthrusting.

  2. Crustal melting during subduction at mantle depth: anatomy of near-UHP nanogranites (Orlica-Śnieżnik Dome, Bohemian Massif)

    NASA Astrophysics Data System (ADS)

    Ferrero, Silvio; Ziemann, Martin; Walczak, Katarzyna; Wunder, Bernd; O'Brien, Patrick J.; Hecht, Lutz

    2015-04-01

    Small volumes (≤ 50µm) of hydrous melt were trapped as primary inclusions in peritectic garnets during partial melting of metagranitoids from the Orlica-Śnieżnik Dome (Bohemian Massif) at mantle depth [1]. Detailed microstructural/microchemical investigation confirmed the occurrence of a granitic assemblage (biotite+feldspars+quartz) in every investigated inclusion, i.e they are nanogranites [2]. MicroRaman mapping of unexposed inclusions showed the occurrence of residual, H2O-rich glass in interstitial position. Despite the oddity of this finding within a classic regional HP/HT terrain, an incomplete crystallization of the melt inclusions (MI) is consistent with the (relatively) rapid exhumation of the Orlica-Śnieżnik Dome proposed by some authors [e.g. 3]. Moreover glassy and partially crystallized MI have been already reported in lower-P (<1 GPa) migmatites [4]. MicroRaman investigation also showed the possible presence of kumdykolite, a high-temperature polymorph of albite reported in UHP rocks from the Kokchetav Massif as well as the Bohemian massif ([5] and references therein). Experimental re-homogenization of nanogranites was achieved using a piston cylinder apparatus at 2.7 GPa and 875°C under dry conditions, in order to investigate melt composition and H2O content with in situ techniques. The trapped melt is granitic, hydrous (6 wt% H2O) and metaluminous (ASI=1.03), and it is similar to those produced experimentally from crustal lithologies at mantle conditions. Re-homogenization conditions are consistent with the results of geothermobarometric calculations on the host rock, suggesting that no H2O loss occurred during exhumation - this would have caused a shift of the inclusion melting T toward higher values. Coupled with the absence of H2O-loss microstructural evidence, e.g. decrepitation cracks and/or vesciculation [4] in re-homogenized nanogranites, this evidence suggests that the nanogranites still preserves the original H2O content of the

  3. Joint inversion of P-waveforms from teleseismic events and surface waves group velocities from ambient seismic noise in Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Ruzek, Bohuslav

    2010-05-01

    Joint inversion of P-waveforms from distant earthquakes recorded by 41 broadband seismic stations located on the territory of Bohemian Massif and Rayleigh/Love group velocities gained by using cross-correlation technique applied to seismic noise recorded by the same set of broadband stations has been performed. Together with joint inversion also individual inversions using single data sets have been carried out. All computations were arranged inside isotropic, locally 1D layered models. Remarkable result is indication of horizons just above MOHO in the lower crust below some stations where low-velocity S-wave channel is needed in order to ensure correct modeling of measured events. This indication follows both from individual and joint inversions. P-waveform inversion is based on using a set of 271 well-recorded teleseismic events from epicentral distances 3000-10000 km. The inversion was originally based on the popular 'receiver function' methodology, but due to the instability of needed deconvolution it was modified. We search for optimum layered velocity model, which correctly projects radial to vertical components (and vice versa, deconvolution is no more needed). Regarding second source of data, both Rayleigh and Love surface waves were extracted from seismic noise by using cross-correlation. Long time series covering the period 2001-2009 were processed. Such measurements provide group velocities between arbitrary pairs of stations. Local group velocity dispersion curves were computed by using 2D tomography-like approach for periods 4-20 s. The subject of inversion (both individual and joint) were just group velocity dispersion curves. Inversion required exhaustive computations. We used HPC cluster nemo.ig.cas.cz and ANNI inversion software, capable to run in parallel regime.

  4. Fluid evolution of the Hub Stock, Horní Slavkov-Krásno Sn-W ore district, Bohemian Massif, Czech Republic

    NASA Astrophysics Data System (ADS)

    Dolníček, Zdeněk; René, Miloš; Prochaska, Walter; Kovář, Michal

    2012-10-01

    The Horní Slavkov-Krásno Sn-W ore district is hosted by strongly altered Variscan topaz-albite granite (Krudum granite body) on the northwestern margin of the Bohemian Massif. We studied the fluid inclusions on greisens, ore pockets, and ore veins from the Hub Stock, an apical expression of the Krudum granite. Fluid inclusions record almost continuously the post-magmatic cooling history of the granite body from ˜500 to <50°C. Rarely observed highest-temperature (˜500°C) highest-salinity (˜30 wt.% NaCl eq.) fluid inclusions are probably the result of secondary boiling of fluids exsolved from the crystallizing magma during pressure release which followed hydraulic brecciation of the gneissic mantle above the granite cupola. The greisenization was related to near-critical low-salinity (0-7 wt.% NaCl eq.) aqueous fluids with low amount of CO2, CH4, and N2 (≤10 mol% in total) at temperatures of ˜350-400°C and pressures of 300-530 bar. Crush-leach data display highly variable and negatively correlated I/Cl and Br/Cl values which are incompatible with both orthomagmatic and/or metamorphic origin of the fluid phase, but can be explained by infiltration of surficial and/or sedimentary fluids. Low fluid salinity indicates a substantial portion of meteoric waters in the fluid mixture that is in accordance with previous stable isotope data. The post-greisenization fluid activity associated with vein formation and argillitization is characterized by decreasing temperature (<350 to <50°C), decreasing pressure (down to ˜50-100 bar), and mostly also decreasing salinity.

  5. Geochronology and geochemistry of a dyke host rock association and implications for the formation of the Bavarian Pfahl shear zone, Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Siebel, Wolfgang; Blaha, Ulrich; Chen, Fukun; Rohrmüller, Johann

    2005-02-01

    To place constraints on the formation and deformation history of the major Variscan shear zone in the Bavarian Forest, Bavarian Pfahl zone, SW Bohemian Massif, granitic dykes and their feldspar-phyric massive host rock (so-called “palite”), zircons were dated by the U Pb isotope dilution and Pb-evaporation methods. The dated samples comprise two host rocks and four dykes from a K-rich calc-alkaline complex adjoining the SW part of the Bavarian Pfahl shear zone. The palites, which appear to be the oldest magmatic rocks emplaced in the shear zone, yield ages of 334±3, 334.5±1.1 Ma (average 207Pb/206Pb-evaporation zircon ages) and 327 342 Ma (range of U/Pb zircon ages) suggesting a Lower Carboniferous age for the initiation of the Pfahl zone. Absence of inherited older cores in all investigated zircons indicates that incorporation of crustal zircon material has played virtually no role or that the melting temperature was very high. Determination of the dyke emplacement age is complicated by partial Pb-loss in most of the fractions analysed. This Pb-loss can be ascribed to higher U content of the dyke zircons compared to those from host rock. Upper discordia intercept ages of the different dykes range from 322±5 to 331±9 Ma. The dykes are pre- to synkinematic with respect to penetrative regional mylonitisation along the Pfahl zone, and the upper intercept ages provide a maximum age for this tectonic event.

  6. Variscan granitoids related to shear zones and faults: examples from the Central Sudetes (Bohemian Massif) and the Middle Odra Fault Zone

    NASA Astrophysics Data System (ADS)

    Oberc-Dziedzic, T.; Kryza, R.; Pin, C.

    2015-07-01

    The granitoid intrusions of the Central Sudetes (CS) and of the Middle Odra Fault Zone (MOFZ), NE part of the Bohemian Massif, are both spatially and temporally related to large-scale shear zones and faults (including possible terrane boundaries) that provided effective channels for melt migration. Summarizing common features of the CS and MOFZ granitoids, we have delineated a set of characteristics of the fault-related and shear zone-related granitoids: (1) they are mainly generated by partial melting of crustal sources, with variable contribution (or no contribution) of mantle materials; (2) the sheet-like, steeply inclined, narrow and rather small granitoid intrusions are emplaced within shear zones at mid-crustal level (c. 20 km depth), whereas the larger, flat-lying plutons intrude into the upper crust, outside or above these shear zones; (3) the magmatic foliation and lineation in granitoids of the deeper, sheet-like intrusions are concordant with those in the surrounding metamorphic rocks, suggesting that the solidification of granitoids was coeval with the deformation in the shear zones; instead, the magmatic foliation in the shallower and larger dome-like plutons reflects magma flow; (4) ductile, transcurrent movements along the shear zones postdate medium-pressure regional metamorphism and are accompanied by an increase in the local thermal gradient, as documented by the crystallization of cordierite, andalusite and sillimanite; (5) the increase in the thermal gradient precedes the emplacement of granitoids and their concomitant thermal influence on the country rocks. The granitoids related to the final stages of tectonothermal activity of the shear zones are good-time markers of their evolutionary path.

  7. Variscan potassic dyke magmatism of durbachitic affinity at the southern end of the Bohemian Massif (Lower Austria)

    NASA Astrophysics Data System (ADS)

    Zeitlhofer, Helga; Grasemann, Bernhard; Petrakakis, Konstantin

    2016-06-01

    Dykes in the Strudengau area (SW Moldanubian Zone, Austria) can be mineralogically divided into lamprophyres (spessartites and kersantites) and felsic dykes (granite porphyries, granitic dykes and pegmatoid dykes). Geochemical analyses of 11 lamprophyres and 7 felsic dykes show evidence of fractional crystallization. The lamprophyres are characterized by metaluminous compositions, intermediate SiO2 contents and high amounts of MgO and K2O; these rocks have high Ba (800-3000 ppm) and Sr (250-1000 ppm) contents as well as an enrichment of large-ion lithophile elements over high field strength elements, typical for enriched mantle sources with variable modifications due to fractionation and crustal contamination. This geochemical signature has been reported from durbachites (biotite- and K feldspar-rich mela-syenites particularly characteristic of the Variscan orogen in Central Europe). For most major elements, calculated fractionation trends from crystallization experiments of durbachites give an excellent match with the data from the Strudengau dykes. This suggests that the lamprophyres and felsic dykes were both products of fractional crystallization and subsequent magma mixing of durbachitic and leucogranitic melts. Rb-Sr geochronological data on biotite from five undeformed kersantites and a locally deformed granite porphyry gave cooling ages of c. 334-318 Ma, indicating synchronous intrusion of the dykes with the nearby outcropping Weinsberger granite (part of the South Bohemian Batholith, c. 330-310 Ma). Oriented matrix biotite separated from the locally deformed granite porphyry gave an Rb-Sr age of c. 318 Ma, interpreted as a deformation age during extensional tectonics. We propose a large-scale extensional regime at c. 320 Ma in the Strudengau area, accompanied by plutonism of fractionated magmas of syncollisional mantle-derived sources, mixed with crustal components. This geodynamic setting is comparable to other areas in the Variscan belt documenting an

  8. Thermochronological record of long term faulting, burial and exhumation history in the Sudetes (Bohemian Massif, Central Europe): a multi-system thermochronological approach

    NASA Astrophysics Data System (ADS)

    Štěpančíková, P..; Danišík, M.; Evans, N. J.

    2012-04-01

    Reconstructing erosional and faulting history in the old crystalline basement terrains, with lacking or sparse post-tectonic geological records, is a challenging task where even radiometric data on the basement rocks need not to provide ultimate answers. NE part of the Bohemian Massif (known as the Sudetes) represents a classic example where numerous attempts to constrain denudation, faulting and relief formation on the Variscan basement, often based on incomplete lines of evidence, led to formulation of controversial models. In this study we aim to reconstruct the post-orogenic exhumation history of the Rychlebské hory Mts. in the eastern Sudetes and constrain paleo-activity along the Sudetic Marginal Fault (SMF) - one of the morphologically most prominent, but poorly understood features of Central Europe, forming a >140 km long escarpment separating the Sudetic Mountains from the foreland in the northeast. We do so by applying zircon (U-Th)/He (ZHe), apatite fission track (AFT) and apatite (U-Th)/He (AHe) dating methods to the basement samples from different fault-bounded blocks and sparsely preserved post-orogenic sedimentary samples. New thermochronological data reveals that in the Late Cretaceous at ~95-80 Ma, the Carboniferous-Permian basement blocks SW and NE of the SMF were buried to ~4-7 km and >6.5 km depths, respectively, by sediments of the Bohemian Cretaceous Basin System. This finding contradicts the traditional paleogeographic reconstructions suggesting exposure of large portions of the Sudetes for most of the Mesozoic-Cenozoic. During the burial, the SMF acted as a normal fault as documented by offset in ZHe ages across the fault. At 85-70 Ma, the basin was inverted, Cretaceous strata eroded and basement blocks were exhumed to the near-surface at exhumation rate of ~300 m/Ma as evidenced by Late Cretaceous-Paleocene AFT ages and thermal modelling results. There is no appreciable difference in AFT and AHe ages across the fault suggesting that the

  9. Re-Os and Lu-Hf isotopic constraints on the formation and age of mantle pyroxenites from the Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Ackerman, Lukáš; Bizimis, Michael; Haluzová, Eva; Sláma, Jiří; Svojtka, Martin; Hirajima, Takao; Erban, Vojtěch

    2016-07-01

    We report on the Lu-Hf and Re-Os isotope systematics of a well-characterized suite of spinel and garnet pyroxenites from the Gföhl Unit of the Bohemian Massif (Czech Republic, Austria). Lu-Hf mineral isochrons of three pyroxenites yield undistinguishable values in the range of 336-338 Ma. Similarly, the slope of Re-Os regression for most samples yields an age of 327 ± 31 Ma. These values overlap previously reported Sm-Nd ages on pyroxenites, eclogites and associated peridotites from the Gföhl Unit, suggesting contemporaneous evolution of all these HT-HP rocks. The whole-rock Hf isotopic compositions are highly variable with initial εHf values ranging from - 6.4 to + 66. Most samples show a negative correlation between bulk rock Sm/Hf and εHf and, when taking into account other characteristics (e.g., high 87Sr/86Sr), this may be explained by the presence of recycled oceanic sediments in the source of the pyroxenite parental melts. A pyroxenite from Horní Kounice has decoupled Hf-Nd systematics with highly radiogenic initial εHf of + 66 for a given εNd of + 7.8. This decoupling is consistent with the presence of a melt derived from a depleted mantle component with high Lu/Hf. Finally, one sample from Bečváry plots close to the MORB field in Hf-Nd isotope space consistent with its previously proposed origin as metamorphosed oceanic gabbro. Some of the websterites and thin-layered pyroxenites have variable, but high Os concentrations paralleled by low initial γOs. This reflects the interaction of the parental pyroxenitic melts with a depleted peridotite wall rock. In turn, the radiogenic Os isotope compositions observed in most pyroxenite samples is best explained by mixing between unradiogenic Os derived from peridotites and a low-Os sedimentary precursor with highly radiogenic 187Os/188Os. Steep increase of 187Os/188Os at nearly uniform 187Re/188Os found in a few pyroxenites may be connected with the absence of primary sulfides, but the presence of minor

  10. Behavior of trace elements in quartz from plutons of different geochemical signature: A case study from the Bohemian Massif, Czech Republic

    NASA Astrophysics Data System (ADS)

    Breiter, Karel; Ackerman, Lukáš; Svojtka, Martin; Müller, Axel

    2013-08-01

    In this study, the trace-element content in igneous quartz from granitoids of different geochemical types was investigated using the laser ablation ICP-MS technique. The Variscan granitoids in the Bohemian Massif provide an excellent opportunity to study the chemical composition of magmatic quartz from the following granite types: (1) geochemically primitive I-type tonalites and granodiorites, (2) peraluminous S-type two-mica granites, (3) moderately fractionated A-type volcano-plutonic complexes of the Teplice caldera, and (4) highly fractionated S- and A-type rare-metal granites. This diversity of granitoids permitted the study of the chemical composition of magmatic quartz as the result of (i) different magma protoliths and (ii) variable degrees of differentiation. There were only small differences in the quartz trace-element contents, ranging from weakly to moderately differentiated plutons of all geochemical types: Al (mostly in the range between 20 and 250 ppm), Ti (mostly 20-110 ppm), B (< 13 ppm), Be (< 0.7 ppm), Ge (< 1 ppm), Li (< 30 ppm), and Rb (< 2 ppm). Only the S-type granites from western Erzgebirge contain Al-enriched quartz (mostly 200-400 ppm Al) since the beginning of its evolution. However, quartz from the highly fractionated granites (group 4) differs significantly: this quartz is generally poor in Ti (< 20 ppm Ti) and enriched in Al (up to 600 ppm in A-type, and up to 1000 ppm in S-type granites), Be (up to 3.2 ppm), Ge (up to 5.7 ppm), Li (up to 132 ppm, particularly in the S-type granites), and Rb (up to 15 ppm). The contents of the analyzed lithophile elements in the quartz from the highly fractionated granites are similar to the contents reported to be present in evolved complex pegmatites. Although the input of Ti into quartz is controlled mainly by the temperature and pressure of quartz crystallization, the entry of Al into quartz increases as a function of the water and fluorine content of the residual melt. The contents of Ge and Li

  11. Diamond and other mineralogical records of ultra-deep origin in spinel-garnet peridotite from Moldanubian Zone, Bohemian Massif (Invited)

    NASA Astrophysics Data System (ADS)

    Naemura, K.; Ikuta, D.; Kagi, H.; Odake, S.; Ueda, T.; Ohi, S.; Kobayashi, T.; Hirajima, T.; Svojtka, M.

    2010-12-01

    Several pieces of mineralogical evidence suggesting precursor ultra-deep conditions (~ 6 GPa) have been newly identified from a spinel-garnet peridotite at Plešovice, occurring as a lenticular body in the Gföhl granulite of the Bohemian Massif, Czech Republic. The first data set suggesting the precursor ultra-deep conditions are carbon phases, including a micro-diamond grain obtained by the mineral separation process and various graphitic carbons. Synchrotron X-ray fluorescence analysis indicates that this diamond contains Fe-Ni metal (taenite) and Cu-Zn-rich phases (possibly sulfide) as inclusions. In particular, the latter phase supports the natural origin of this diamond, although the aggregation state of nitrogen in the diamond is very similar to the synthetic one. Raman spectroscopy reveals that the graphites mainly occur as members of composite inclusions with carbonates in spinel, garnet, and olivine, and that they show a variety of ordered states, from poorly to highly ordered. More disordered graphitic carbons occur as inclusions in garnet, one of which shows a cubic morphology, suggesting that these graphite crystals would be transformed from diamond. Some graphite crystals sealed in garnet show up-shifts of G-band up to 1600 cm-1. Such up-shifts are most likely due to internal pressure, supporting the high-pressure origin of graphites. Another line of evidence for ultra-deep condition was recognized as pyroxene lamellae developed in coarse-grained chromian spinel grains. EBSD analysis shows that pyroxene lamellae have topotaxy relationships with the host spinel, suggesting that these lamellae could be formed by the exsolution process from high-pressure polymorph of spinel (Ca-ferrite and/or Ca-titanite structure), which could be stable at very high pressure condition (> 12.5 GPa). The diamond-bearing Plešovice peridotite was probably derived from the asthenosphere (> 200 km) to near the earth surface by a diapiric plume and then incorporated into the

  12. The Rožná uranium deposit (Bohemian Massif, Czech Republic): shear zone-hosted, late Variscan and post-Variscan hydrothermal mineralization

    NASA Astrophysics Data System (ADS)

    Kříbek, Bohdan; Žák, Karel; Dobeš, Petr; Leichmann, Jaromír; Pudilová, Marta; René, Miloš; Scharm, Bohdan; Scharmová, Marta; Hájek, Antonín; Holeczy, Daniel; Hein, Ulrich F.; Lehmann, Bernd

    2009-01-01

    Three major mineralization events are recorded at the Rožná uranium deposit (total mine production of 23,000 t U, average grade of 0.24% U): (1) pre-uranium quartz-sulfide and carbonate-sulfide mineralization, (2) uranium, and (3) post-uranium quartz-carbonate-sulfide mineralization. (1) K-Ar ages for white mica from wall rock alteration of the pre-uranium mineralization style range from 304.5 ± 5.8 to 307.6 ± 6.0 Ma coinciding with the post-orogenic exhumation of the Moldanubian orogenic root and retrograde-metamorphic equilibration of the high-grade metamorphic host rocks. The fluid inclusion record consists of low-salinity aqueous inclusions, together with H2O-CO2-CH4, CO2-CH4, and pure CH4 inclusions. The fluid inclusion, paragenetic, and isotope data suggest that the pre-uranium mineralization formed from a reduced low-salinity aqueous fluid at temperatures close to 300°C. (2) The uraniferous hydrothermal event is subdivided into the pre-ore, ore, and post-ore substages. K-Ar ages of pre-ore authigenic K-feldspar range from 296.3 ± 7.5 to 281.0 ± 5.4 Ma and coincide with the transcurrent reorganization of crustal blocks of the Bohemian Massif and with Late Stephanian to Early Permian rifting. Massive hematitization, albitization, and desilicification of the pre-ore altered rocks indicate an influx of oxidized basinal fluids to the crystalline rocks of the Moldanubian domain. The wide range of salinities of fluid inclusions is interpreted as a result of the large-scale mixing of basinal brines with meteoric water. The cationic composition of these fluids indicates extensive interaction with crystalline rocks. Chlorite thermometry yielded temperatures of 260°C to 310°C. During this substage, uranium was probably leached from the Moldanubian crystalline rocks. The hydrothermal alteration of the ore substage followed, or partly overlapped in time, the pre-ore substage alteration. K-Ar ages of illite from ore substage alteration range from 277.2 ± 5.5 to

  13. Tectonic and paleogeographic interpretation of the paleomagnetism of Variscan and pre-Variscan formations of the Bohemian Massif, with special reference to the Barrandian terrane

    NASA Astrophysics Data System (ADS)

    Krs, M.; Pruner, P.; Man, O.

    2001-03-01

    Paleomagnetic data from Variscan and pre-Variscan formations of the Bohemian Massif (BM) have been interpreted tectonically, and paleogeographically evaluated with respect to the European paleomagnetic results. The interpretation of data from the BM was preceded by the evaluation of the effect of the Trans-European Suture Zone (TESZ) on the dispersion of the European paleomagnetic pole positions during the Variscan orogeny. Stability of the European lithospheric plate is well documented by paleomagnetic results for the Early Permian to the Quaternary rocks of the regions between the Ural Mountains and Great Britain, north of the Alpine tectonic belt. For the Late Carboniferous and earlier times, the stable plate is defined in the regions NE of the TESZ in the East European Craton only. Late Carboniferous and older rocks from the regions SW of the TESZ, largely occupied by the West-European Variscides, show tectonic deformations controlled by prominent horizontal rotations. These rotations can be studied on a theoretical model simulating the distribution of pole positions controlled by rotation of rock formations about a vertical axis. In the BM, horizontal paleotectonic rotations are well documented for Variscan and pre-Variscan rocks: they reach several tens of degrees (up to 180° in extreme cases) of mostly clockwise sense. The study of the tectonics and paleogeography of Cambrian to Devonian formations of the Barrandian area, which is considered a peri-Gondwana terrane with affinities to Armorica, may serve as a case history of the study of a terrane incorporated into a stable lithospheric plate. Here, the Barrandian terrane became a part of the European Plate as a component of the emerging Pangea supercontinent in the final phase of the Variscan orogeny. High, almost peri-polar paleolatitudes for the Cambrian rocks of the Barrandian area are — within the limits of data scatter — in agreement with the presumed position of Gondwana and Armorica. Rocks of

  14. Continental crust subducted deeply into lithospheric mantle: the driving force of Early Carboniferous magmatism in the Variscan collisional orogen (Bohemian Massif)

    NASA Astrophysics Data System (ADS)

    Janoušek, Vojtěch; Schulmann, Karel; Lexa, Ondrej; Holub, František; Franěk, Jan; Vrána, Stanislav

    2014-05-01

    The vigorous Late Devonian-Early Carboniferous plutonic activity in the core of the Bohemian Massif was marked by a transition from normal-K calc-alkaline, arc-related (~375-355 Ma), through high-K calc-alkaline (~346 Ma) to (ultra-)potassic (343-335 Ma) suites, the latter associated with mainly felsic HP granulites enclosing Grt/Spl mantle peridotite bodies. The changing chemistry, especially an increase in K2O/Na2O and 87Sr/86Sri with decrease in 143Nd/144Ndi in the basic end-members, cannot be reconciled by contamination during ascent. Instead it has to reflect the character of the mantle sources, changing over time. The tectonic model invokes an oceanic subduction passing to subduction of the attenuated Saxothuringian crust under the rifted Gondwana margin (Teplá-Barrandian and Moldanubian domains). The deep burial of this mostly refractory felsic metaigneous material is evidenced by the presence of coesite/diamond (Massonne 2001; Kotková et al. 2011) in the detached UHP slices exhumed through the subduction channel and thrusted over the Saxothuringian basement, and by the abundance of felsic HP granulites (> 2.3 GPa), some bearing evidence for small-scale HP melt separation, in the orogen's core (Vrána et al. 2013). The subduction channel was most likely formed by 'dirty' serpentinites contaminated by the melts/fluids derived from the underlying continental-crust slab (Zheng 2012). Upon the passage through the orogenic mantle, the continental crust-slab derived material not only contaminated the adjacent mantle forming small bodies/veins of pyroxenites (Becker 1996), glimmerites (Becker et al. 1999) or even phlogopite- and apatite-bearing peridotites (Naemura et al. 2009) but the felsic HP-HT granulites also sampled the individual peridotite types at various levels. Eventually the subducted felsic material would form an (U)HP continental wedge under the forearc/arc region, to be later redistributed under the Moldanubian crust by channel flow and crustal

  15. Partial melting of granitoids under eclogite-facies conditions: nanogranites from felsic granulites from Orlica-Śnieżnik Dome (Bohemian Massif)

    NASA Astrophysics Data System (ADS)

    Ferrero, Silvio; O'Brien, Patrick; Walczak, Katarzyna; Wunder, Bernd; Hecht, Lutz

    2014-05-01

    Melt inclusions (MI) study in migmatites is a powerful tool to retrieve the original composition of the anatectic melt, both as major elements (Ferrero et al., 2012) and fluid contents (Bartoli et al., 2013). Crystallized MI, or "nanogranites" (Cesare et al., 2009), were identified within HP felsic granulites from Orlica-Śnieżnik Dome, NE Bohemian Massif (Walczak, 2011). The investigated samples are Grt+Ky leucogranulites originated from a granitic protolith, with assemblage Qtz+Pl+Kfs+Grt+Ky+Ttn+Rt+Ilm. Nanogranites occur in garnet as primary inclusions, and consist of Qtz+Ab+Bt+Kfs±Ep±Ap. Such assemblage results from the crystallization of a melt generated during a partial melting reaction; the same reaction is also responsible for the production of the host garnet, interpreted therefore as a peritectic phase. Besides nanogranites, former presence of melt is supported by the occurrence of tiny pseudomorphs of melt-filled pores (Holness & Sawyer, 2008) and euhedral faces in garnet. Garnet composition, with Grs =0.28-0.31, phase assemblage (kyanite, ternary feldspar) and classic thermobarometry suggest that partial melting took place at T≥875°C and P~2.2-2.6 GPa, under eclogite-facies conditions. Although other authors reported palisade quartz after coesite in this area (see e.g. Bakun-Czubarow, 1992), no clear evidence of UHP conditions have been identified during this study. Piston cylinder re-homogenization experiments were performed on MI-bearing garnet chips to obtain the composition of the pristine anatectic melt. The first data from experiments in the range 850-950°C and 2-2.2 GPa show that nanogranites can be re-melted at T≥875°. However, homogenization has not been reached yet since new Grt, with lower CaO and higher MgO, crystallizes on the walls of the inclusion. As P increases, the modal amount of new phase decreases, while its composition evolves closer to those of the host garnet. Further experiments at higher pressure are in underway, with

  16. UHP-UHT peak conditions and near-adiabatic exhumation path of diamond-bearing garnet-clinopyroxene rocks from the Eger Crystalline Complex, North Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Haifler, Jakub; Kotková, Jana

    2016-04-01

    Intermediate garnet-clinopyroxene rocks from the Eger Crystalline Complex, North Bohemian Massif, contain microdiamonds enclosed in garnet and zircon. The variable mineral assemblage of these rocks allows for an evaluation of the P-T evolution using numerous univariant equilibria and thermodynamic modelling, in addition to the ternary feldspar solvus, Ti-in-garnet, Zr-in-rutile and Ti-in-zircon thermometry. Zircon mantle domains with diamond inclusions contain 111-189 ppm Ti, reflecting temperatures of 1037-1117 °C. The peak pressure consistent with diamond stability corresponds to c. 4.5-5.0 GPa. Ti-in-garnet thermometry using the Ti content of diamond-bearing garnet core yielded temperatures of 993-1039 °C at c. 5.0 GPa. An omphacite inclusion in garnet (reflecting c. 2.3-2.4 GPa at c. 1050 °C) and metastably preserved kyanite represent relics of eclogite-facies conditions. The dominant high-pressure granulite-facies mineral assemblage of low-Ca garnet, diopsidic clinopyroxene, antiperthitic feldspar and quartz equilibrated at 1.8-2.1 GPa and c. 1050 °C, based on the XGrs isopleth of the garnet mantle, garnet-feldspar-kyanite-quartz univariant equilibria and ternary feldspar solvus. Our thermodynamic modelling shows that a steep decrease of XGrs from a maximum core value of 0.32 to 0.17 at the rim as well as a rimward XMg increase (from 0.42 to 0.50) are consistent with significant decompression without heating. The latter is related to omphacite and kyanite breakdown reactions producing garnet and plagioclase. The Ti content in the rim zone of zircon (13-42 ppm), exsolved plagioclase and K-feldspar associated with matrix diopside and garnet rim, and late biotite reflect temperatures of c. 830-900 °C at c. 1.4 GPa. A similar temperature is recorded by matrix rutile grains, containing 2028-4390 ppm Zr and representing a relatively homogeneous population in contrast to rutile enclosed in garnet with variable Zr content. Our results show that the garnet

  17. Quantitative geomorphologic data of the reactivated variscan Hluboká fault system (Budĕjovice Basin, southern Bohemian Massif)

    NASA Astrophysics Data System (ADS)

    Popotnig, Angelika; Tschegg, Dana; Decker, Kurt

    2015-04-01

    The NW-SE and NNE-SSW striking Hluboká-Rudolfov-Fault System in southern Bohemia is a potentially active late Variscan fault. It was repeatedly activated in Mesozoic, Miocene and Pliocene times and forms a "disputed seismic source" in the vicinity of the nuclear power plant of Temelin. The Fault System at the NE and SE margin of the Budĕjovice Basin with its up to 340 m thick Cretaceous to Neogene sediments overlaying the hanging wall of the Fault System is partly characterized by a prominent linear morphological scarp. Geomorpholigic analysis mainly focus on mountain fronts at the basin margin crossing the Hluboká and Rudolfov fault as well as on the NE facing slope of the Racice Mountain which is not crossing the fault. Analyses use morphological parameters of small ephemeric tributaries of the Vltava River, which are all similar with respect to their catchments, hydrological conditions and location in crystalline basement rocks. Morphological differences in valley shapes are therefore likely to result from different amounts of uplift of the catchments with respect to the Vltava River. All parameters were measured from a 10 m resolution DEM and digital topographic maps 1:10,000. Additional field measurements were made at locations where the resolution of the digital data is insufficient. Data show extremely low mountain-front-sinuosity of the hillslope forming the footwall of the Hluboká Fault characterizing a very straight mountain front at the fault and an uplift influenced morphology. Almost all values differ significantly from those observed at the other mountain slopes. The results are in line with the evidence obtained from mountain sinuosity. The mountain slope at the faults show deep and narrow V-shaped valleys with streams that are actively incising probably responding to continuous uplift. Vf (Valley-Floor-Width-to-Height) and SL (Stream Length) values are generally lower than those from drainages not crossing the fault. Convex-up thalweg sections

  18. Cancrinite from nepheline syenite (mariupolite) of the Oktiabrski massif, SE Ukraine, and its growth history

    NASA Astrophysics Data System (ADS)

    Dumańska-Słowik, Magdalena; Pieczka, Adam; Heflik, Wiesław; Sikorska, Magdalena

    2016-03-01

    Secondary cancrinite, (Na5.88K< 0.01)∑ 5.88(Ca0.62 Fe0.01Mn0.01Zn< 0.01 Mg< 0.01)∑ 0.64[Si6.44Al 5.56O24](CO3)0.67(OH)0.26(F< 0.01,Cl< 0.01)·2.04H2O), was found as accessory component of mariupolite (albite-aegirine nepheline syenite) from the Oktiabrski massif in the Donbass (SE Ukraine). It probably crystallized from a subsolidus reaction involving nepheline (and sodalite?) and calcite dissolved in the aqueous-carbonic fluid at the maximum temperature of 930 °C, decreasing to hydrothermal conditions. It is depleted in sodium, calcium and carbon, what results in the occurrence of vacant positions at both cationic and anionic sites. Ca-deficient cancrinite crystallized from the same hydrothermal Si-undersaturated fluids enriched in the ions such as Na+, Ca2 +, Cl-, F-, HCO3-, which formed calcite, sodalite, natrolite and fluorite. It has dark-red CL colours with patchy zoning, what indicates the variable/diverse fluid composition during its formation. In the CL spectrum of cancrinite only one broad emission band at 410 nm is observed, which can be attributed to O* center (the recombination of a free electron with an O- hole center). The formation of secondary CO3-rich species, i.e. cancrinite and calcite in mariupolite suggests that redox conditions in the Oktiabrski massif were oxidizing at the postmagmatic stage.

  19. Cancrinite from nepheline syenite (mariupolite) of the Oktiabrski massif, SE Ukraine, and its growth history.

    PubMed

    Dumańska-Słowik, Magdalena; Pieczka, Adam; Heflik, Wiesław; Sikorska, Magdalena

    2016-03-15

    Secondary cancrinite, (Na5.88K<0.01)∑5.88(Ca0.62 Fe0.01Mn0.01Zn<0.01 Mg<0.01)∑0.64[Si6.44Al 5.56O24](CO3)0.67(OH)0.26(F<0.01,Cl<0.01)·2.04H2O), was found as accessory component of mariupolite (albite-aegirine nepheline syenite) from the Oktiabrski massif in the Donbass (SE Ukraine). It probably crystallized from a subsolidus reaction involving nepheline (and sodalite?) and calcite dissolved in the aqueous-carbonic fluid at the maximum temperature of 930 °C, decreasing to hydrothermal conditions. It is depleted in sodium, calcium and carbon, what results in the occurrence of vacant positions at both cationic and anionic sites. Ca-deficient cancrinite crystallized from the same hydrothermal Si-undersaturated fluids enriched in the ions such as Na(+), Ca(2+), Cl(-), F(-), HCO3(-), which formed calcite, sodalite, natrolite and fluorite. It has dark-red CL colours with patchy zoning, what indicates the variable/diverse fluid composition during its formation. In the CL spectrum of cancrinite only one broad emission band at 410 nm is observed, which can be attributed to O* center (the recombination of a free electron with an O(-) hole center). The formation of secondary CO3-rich species, i.e. cancrinite and calcite in mariupolite suggests that redox conditions in the Oktiabrski massif were oxidizing at the postmagmatic stage. PMID:26773267

  20. High-pressure granulites of the Podolsko complex, Bohemian Massif: An example of crustal rocks that were subducted to mantle depths and survived a pervasive mid-crustal high-temperature overprint

    NASA Astrophysics Data System (ADS)

    Faryad, Shah Wali; Žák, Jiří

    2016-03-01

    The Podolsko complex, Bohemian Massif, is a mid-crustal migmatite-granite dome exposed along a tectonic boundary separating the upper crust from the deeply eroded interior of the Variscan orogen, referred to as the Moldanubian Zone. This study examines metamorphic history of mafic and felsic granulites that occur in this complex as minor lenses or layers hosted in pervasively anatectic rocks. The mafic granulite contains garnet with preserved high-Ca cores, which based on pseudosection modelling indicates pressure conditions near the coesite stability field at temperatures of ca. 550-600 °C. The relicts of an earlier eclogite-facies stage have been overprinted by a later granulite-facies assemblage consisting of ternary feldspar, orthopyroxene, and spinel in the mafic granulite and sillimanite and spinel in the felsic granulite. Composition of younger garnet (in rims and as smaller grains) in both granulites suggests that a near isothermal decompression of these rocks was followed by heating that reached temperature of ca. 900 °C at pressure of ca. 0.5 GPa. It is thus concluded that the granulites underwent at least two temporally separate tectonometamorphic events: they were first subducted to mantle depths and exhumed rapidly at relatively low temperatures and then near isobarically heated at mid-crustal levels. The preservation of earlier eclogite-facies garnet in the mafic granulite indicates that the latter event was short-lived and was followed by near isobaric cooling. The geologically brief granulite-facies metamorphism was previously explained as a result of slab break-off and mantle upwelling after the main phase of microplate convergence in the Bohemian Massif. To put the Podolsko complex into a broader tectonic context, we synthesize the available petrologic and structural data from the correlative (U)HP assemblages of the Moldanubian Zone to suggest that they typically do not preserve structural record of the subduction stage, only rarely preserve an

  1. Surface structure of micro-diamond from ultrahigh-pressure felsic granulite, Bohemian Massif: AFM study of growth and resorption phenomena

    NASA Astrophysics Data System (ADS)

    Kotková, J.; Klapetek, P.

    2012-04-01

    Morphology, associated phases and retrogression phenomena of in-situ microdiamonds formed at extreme pressures in ultrahigh-pressure metamorphic terranes represent excellent tools to study character of diamond-forming media at great depths. Well-preserved microdiamonds discovered recently along with coesite in ultrahigh-pressure granulites of the north Bohemian crystalline basement, European Variscan belt (Kotková et al., 2011), provide unique material for such investigations. The diamonds are enclosed in major granulite phases, i.e. garnet both in felsic and intermediate lithologies and in kyanite in the felsic sample, as well as in zircon. Transmitted and reflected light microscopy of the felsic granulite sample, with peak mineral assemblage garnet, kyanite, feldspar and quartz, revealed presence of numerous, 5-20 μm-sized, perfectly preserved diamond crystals enclosed in kyanite grains. In contrast, diamonds within garnet are rare, can reach up to 30 μm in size, and graphite rims as well as polycrystalline graphite aggregates possibly representing complete diamond retrogression are common. We applied atomic force microscopy to study in-situ crystal morphology and surface microtopographic features, representing clues to the conditions and mechanisms of crystal formation as well as diamond resorption and retrogression. Both diamond enclosed in garnet and in kyanite of the felsic granulite occur exclusively as single crystals. The crystals have octahedral crystal shapes with straight but rounded edges and rounded corners. Concentric triangular terraces delimiting a flat triangular table on crystal scale and small micron-sized negatively oriented downward-pointing trigons developed on the octahedron crystal faces. Higher magnification reveals presence of discontinuous elongate hillocks oriented parallel to the octahedron face edge with positively oriented trigons. We suggest that the large-scale triangular terraces represent growth features. In contrast, the

  2. Melt-melt immiscibility as result of synchronous melting of metapelites and impure marbles at crustal depth in the Moldanubian Zone, Bohemian Massif.

    NASA Astrophysics Data System (ADS)

    Ferrero, Silvio; O´Brien, Patrick J.; Ziemann, Martin A.; Wunder, Bernd; Hecht, Lutz; Wälle, Markus

    2016-04-01

    Investigation of melt and fluid inclusions in migmatites grants access to the unadultered products of crustal melting, shedding light on the processes driving crustal differentiation. Stromatic migmatites from the Oberpfalz (Moldanubian Zone, Bohemain Massif) present a unique occurrence of calcite-rich inclusions (CRI), crystallized inclusions of anatectic melt (nanogranites) and CO2-rich inclusions, all hosted in peritectic garnet. Their distribution as clusters in the host suggests a primary nature, i.e. that they formed during garnet growth, thus testifying for the coexistence of different melts and fluid during partial melting in the middle-lower crust. CRI are generally small (≤10 μm in diameter) and, from a microstructural point of view, strikingly resemble the coexistent nanogranites, i.e. they show a well-developed negative crystal shape and have a cryptocrystalline nature. Their phase assemblage, identified via Raman spectroscopy and EDS mapping, consists of calcite, white mica and chlorite, with quartz as accessory mineral. Moreover, calcite crystals locally develop euhedral faces, further supporting the hypothesis that this phase crystallized from an originally homogeneous calcite-rich melt. Piston-cylinder re-homogenization experiments achieved nanogranites re-melting at pressure-temperature conditions consistent with geothermobarometric estimates, 800-850°C and 0.7-0.9 GPa. After having been re-heated at these conditions, the coexistent calcite-rich inclusions appear modified, with formation of internal porosity and re-crystallization of calcite in microcrystalline aggregates, suggesting that during the experimental run calcite melting was achieved. LA-ICPMS analyses show that CRIs are generally highly enriched in LILE (particularly Sr, Ba) and LREE (up to LaN ≈500, with moderate to low fractionation among LREE, La/Sm=1-9) with respect both to the host garnet and the coexistent nanogranites. The higher abundance of LREE in CRIs is consistent with

  3. Geochemical characteristics and petrogenesis of phonolites and trachytic rocks from the České Středohoří Volcanic Complex, the Ohře Rift, Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Ackerman, Lukáš; Ulrych, Jaromír; Řanda, Zdeněk; Erban, Vojtěch; Hegner, Ernst; Magna, Tomáš; Balogh, Kadosa; Frána, Jaroslav; Lang, Miloš; Novák, Jiří K.

    2015-05-01

    distinct fluids are implicated from the Li-Cs correlations. The derivation of these melts/liquids from sedimentary and/or meta-sedimentary crustal sources is underscored by variable but overall light Li isotopic compositions. Some phonolites exhibit enrichments in high-field-strength elements coupled with increased Zr/Nb ratios. In contrast to previous studies, we show that this feature, apparent in many volcanic rocks from the Bohemian Massif, can be explained with progressive melt fractionation of parental magmas involving amphibole and plagioclase.

  4. First finding of microdiamond, coesite and other UHP phases in felsic granulites in the Moldanubian Zone: Implications for deep subduction and a revised geodynamic model for Variscan Orogeny in the Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Perraki, Maria; Faryad, Shah Wali

    2014-08-01

    Heavy mineral fractions and polished thin sections from felsic granulites from the Moldanubian Zone of the Bohemian Massif were thoroughly studied by means of Raman microspectroscopy combined with optical microscopy and scanning electron microscopy. The following phases were identified, among others, as inclusions in robust minerals such as garnet and zircon: Diamond, characterized by an intense narrow peak at 1332 cm- 1, was found in two inclusions in zircon. They have a size of ~ 5 μm. Coesite, identified by its very characteristic peak at ~ 520 cm- 1, was found in an inclusion in garnet together with quartz. Coesite has been almost completely transformed into quartz; only minor coesite nano-domains remain. Kumdykolite, the orthorhombic polymorph of NaAlSi3O8, characterized by strong peaks at 220, 456 and 492 cm- 1, occurs either as single crystals or as a part of multiphase inclusions in garnet and in zircon along with other mineral phases such as K-feldspar, phengite, rutile. Moissanite, SiC, exhibiting the characteristic Raman bands at ~ 767, 788 and 969 cm- 1, occurs as inclusions in garnet. Diamond and coesite are considered to have formed at the peak ultrahigh-pressure metamorphic (UHPM) conditions. Kumdykolite has been proposed to be a metastable phase formed during rapid cooling from high temperature. Moissanite points to extremely reduced conditions during subduction to great depths. The finding of UHP phases in felsic granulites in the Moldanubian Zone is clear evidence for subduction of crustal materials to mantle depths. The garnet hosting the UHP phase inclusions usually preserves prograde compositional zoning; this in combination with the UHPM mineral inclusions suggests that the felsic material should have passed UHP metamorphism at a low-temperature gradient. Isothermal decompression (the commonly accepted model) at temperatures of 850-950 °C would have substantially modified and homogenized the garnet composition eliminating any compositional

  5. Low-Enthalpy Geothermal Potential of the Czech Republic with Particular Focus on Waters of Metalliferous Mining Districts in Crystalline Structures of the Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Stibitz, M.; Jirakova, H.; Frydrych, V.

    2012-04-01

    Nowadays, numerous underground mines in the Czech Republic are mostly left to spontaneous natural flooding with water. These huges volumes and favourable water temperature represent promissing source of thermal energy. The primary temperature of the mine waters is given by the rock massif temeprature, i.e. by the heat flux which is in the moldanubikum region around 50 - 60 mWm-2 (Michálek et al., 2007). Higher heat flux has been observed in several mountainous regions throughout the country. The real water temperature results form the depth of mines, geothermal gradient and the water circulation in the mine. Temperature measurements suggest a distinct temperature depth stratification. Several metalliferous mining districts in Crystalline Structures with the water outflow exceeding 1 Ls-1 have been subject of investigation. The temperature was not the only determining factoras it is relatively stable in mines all year round. The data on yield, temperatures, etc. prepared for further mathematical modeling were primarily measured in uranium and oremines in Příbram mining district, Jáchymov, Zlaté Hory and Rožná. Water of about 18°C and radioactivity make favourable condition for the Jáchymov spa purposes. The average yield reaches 20 Ls-1. The entire outflow for the Jáchymov mines before its decommissioning reached 136 Ls-1.The entire heat capacity of mine waters is supposed to be around 1.150 kW. Severa l galleries in Zlaté Hory region could be used for thermal purposes. The yield around 60 Ls-1 and temeperature around 7°C was observed in the main drainage gallery. Measurements were accompanied by chemical analysis of water having both a huge pH range from 3 to 9 and huge mineralization range from 135 to 6 500 mgL-1. The Rožná and Příbram conditions are quite similar with the outflow from 20 - 45 Ls-1 and temperatures from 11 - 18°C. Possible temperature decrease originates from the fact that colder shallow groundwater will inflow into mine spaces

  6. Petrographic, geochemical and isotopic evidence of crustal assimilation processes in the Ponte Nova alkaline mafic-ultramafic massif, SE Brazil

    NASA Astrophysics Data System (ADS)

    Azzone, Rogério Guitarrari; Montecinos Munoz, Patricio; Enrich, Gaston Eduardo Rojas; Alves, Adriana; Ruberti, Excelso; Gomes, Celsode Barros

    2016-09-01

    Crustal assimilation plus crystal fractionation processes of different basanite magma batches control the evolution of the Ponte Nova cretaceous alkaline mafic-ultramafic massif in SE Brazil. This massif is composed of several intrusions, the main ones with a cumulate character. Disequilibrium features in the early-crystallized phases (e.g., corrosion and sieve textures in cores of clinopyroxene crystals, spongy-cellular-textured plagioclase crystals, gulf corrosion texture in olivine crystals) and classical hybridization textures (e.g., blade biotite and acicular apatite crystals) provide strong evidence of open-system behavior. All samples are olivine- and nepheline-normative rocks with basic-ultrabasic and potassic characters and variable incompatible element enrichments. The wide ranges of whole-rock 87Sr/86Sri and 143Nd/144Ndi ratios (0.70432-0.70641 and 0.512216-0.512555, respectively) are indicative of crustal contribution from the Precambrian basement host rocks. Plagioclase and apatite 87Sr/86Sr ratios (0.70422-0.70927) obtained for the most primitive samples of each intrusion indicate disequilibrium conditions from early- to principal-crystallization stages. Isotope mixing-model curves between the least contaminated alkaline basic magma and heterogeneous local crustal components indicate that each intrusion of the massif is differentiated from the others by varied degrees of crustal contribution. The primary mechanisms of crustal contribution to the Ponte Nova massif involve the assimilation of host rock xenoliths during the development of the chamber environment and the assimilation of partial melts from the surrounding host rocks. Thermodynamic models using the melts algorithm indicate that parental alkaline basic magmas can be strongly affected by contamination processes subsequently to their initial stages of crystallization when there is sufficient energy to assimilate partial melts of crustal host rocks. The assimilation processes are considered to

  7. New insights into the history and origin of the southern Maya block, SE Mexico: U-Pb-SHRIMP zircon geochronology from metamorphic rocks of the Chiapas massif

    USGS Publications Warehouse

    Weber, Bodo; Iriondo, Alexander; Premo, Wayne R.; Hecht, Lutz; Schaaf, Peter

    2007-01-01

    The histories of the pre-Mesozoic landmasses in southern México and their connections with Laurentia, Gondwana, and among themselves are crucial for the understanding of the Late Paleozoic assembly of Pangea. The Permian igneous and metamorphic rocks from the Chiapas massif as part of the southern Maya block, México, were dated by U–Pb zircon geochronology employing the SHRIMP (sensitive high resolution ion microprobe) facility at Stanford University. The Chiapas massif is composed of deformed granitoids and orthogneisses with inliers of metasedimentary rocks. SHRIMP data from an anatectic orthogneiss demonstrate that the Chiapas massif was part of a Permian (∼ 272 Ma) active continental margin established on the Pacific margin of Gondwana after the Ouachita orogeny. Latest Permian (252–254 Ma) medium- to high-grade metamorphism and deformation affected the entire Chiapas massif, resulting in anatexis and intrusion of syntectonic granitoids. This unique orogenic event is interpreted as the result of compression due to flat subduction and accretionary tectonics. SHRIMP data of zircon cores from a metapelite from the NE Chiapas massif yielded a single Grenvillian source for sediments. The majority of the zircon cores from a para-amphibolite from the SE part of the massif yielded either 1.0–1.2 or 1.4–1.5 Ga sources, indicating provenance from South American Sunsás and Rondonian-San Ignacio provinces.

  8. Late Devonian - Early Carboniferous polyphase metamorphic evolution of the Orlica-Śnieżnik Dome (NE Bohemian Massif, Poland): evidence from Th-U-total Pb monazite dating

    NASA Astrophysics Data System (ADS)

    Budzyń, Bartosz; Jastrzębski, Mirosław; Stawikowski, Wojciech

    2014-05-01

    The Orlica-Śnieżnik Dome, located in the NE part of the Bohemian Massif, mainly consists of Cambro-Ordovician orthogneisses and the metavolcano-sedimentary Młynowiec and Stronie Formations. This study constrains electron microprobe Th-U-total Pb ages of monazite in (1) orthogneisses, (2) paragneisses of the Młynowiec Formation (MF), (3) mica schists of the Stronie Formation (SF) and (4) light quartzites. The latter light quartzites form a continuous 'horizon' between two metavolcano-sedimentary formations, however, they are traditionally treated as the lowest member of the Stronie Formation (SF). Our field and structural studies conducted along the transects crossing the boundaries between the above-mentioned rocks indicate that there is a stratigraphic and structural continuity between the Młynowiec and Stronie Formations. Samples for the monazite dating were collected at different distances from the contact between orthogneisses and metasediments. The aim of this study was to provide a new data to verify a hypothesis of Cambro-Ordovician contact or regional metamorphism of the Młynowiec-Stronie Group and to constrain age of the Variscan metamorphic events in the Orlica-Śnieżnik Dome. Monazite from medium-grained orthogneiss yield dates ranging from 546 to 322 Ma, while three age domains of ca. 481 Ma, ca. 421 Ma and ca. 370 Ma are defined in fine-grained orthogneiss. Monazite in two porphyroblastic paragneisses (MF) yields two age domains of 369-361 Ma and 340-336 Ma. It should be noted that the older ages are recorded by inclusions of monazite in staurolite and plagioclase, as well as by matrix monazite. Monazite in leucosome of the migmatized paragneiss (MF) yields ca. 337 Ma age, while matrix monazite in melanosome yields ages of ca. 331 Ma age and a faint record of ca. 355 Ma. In two K-feldspar bearing light quartzites (SF), older spectrum of ages within 524-463 Ma, as well as younger ages of ca. 358 Ma and 347 Ma are obtained. On the other hand, only

  9. The transformation of nepheline and albite into sodalite in pegmatitic mariupolite of the Oktiabrski Massif (SE Ukraine).

    PubMed

    Dumańska-Słowik, Magdalena; Heflik, Wiesław; Pieczka, Adam; Sikorska, Magdalena; Dąbrowa, Łukasz

    2015-11-01

    Sodalite, Na8Al6Si6Cl2, from a pegmatitic variety of mariupolite in the Oktiabrski Massif (SE Ukraine) was studied using electron microprobe, electron microscopy, spectroscopic cathodoluminescence and Raman techniques to determine its growth history during the evolution of the host rock. Three generations of the mineral were distinguished: (1) the oldest forms patches with a pink-violet cathodoluminescence colour, (2) a younger one, with a dark blue colour, forms the matrix of the crystals, and (3) the youngest generation forms veins with light blue cathodoluminescence in the older sodalite generations; all are undoubtedly secondary phases formed during the post-magmatic evolution of the host rock. The close spatial association of the sodalite with coexisting albite, nepheline, natrolite and K-feldspar, forming inclusions in each other, and the embayed contacts of sodalite with nepheline and albite, and the patchy appearance of sodalite under CL, together suggest that the two older sodalite varieties formed from the conversion of nepheline and albite under the action of Na-, Cl- and Al-bearing, but Si undersaturated basic fluids released during cooling of the host. The excess of SiO2 (aq.) released as a result of albite metasomatism could be accommodated by natrolite occurring as tiny inclusions within the sodalite crystals. The youngest, veinlet, generation was probably formed via a fluid-mediated dissolution-recrystallization process, perhaps simultaneously with the coexisting veins of natrolite. PMID:26114248

  10. Paleomagnetism of Ordovician carbonate rocks from Malopolska Massif, Holy Cross Mountains, SE Poland — Magnetostratigraphic and geotectonic implications

    NASA Astrophysics Data System (ADS)

    Schätz, M.; Zwing, A.; Tait, J.; Belka, Z.; Soffel, H. C.; Bachtadse, V.

    2006-04-01

    The structural and geodynamic history of the Malopolska Massif (Holy Cross Mountains — Poland), situated within the Trans-European Suture Zone (TESZ) is still a matter of debate. Recent provenance studies and biogeographical data indicate that the Malopolska is a Gondwana-derived terrane accreted to Baltica between late Mid-Cambrian and Tremadocian times. Existing paleomagnetic data, however, are equivocal. They indicate either close proximity and coherence with Baltica since Silurian times or a significant Variscan dextral strike-slip displacement of Malopolska with respect to the latter along the Teisseyre-Tornquist Line. In order to address this problem a detailed paleomagnetic study of a condensed sequence of Middle to Upper Ordovician carbonate rocks from the Malopolska Massif (Mójcza quarry) has been undertaken. Samples were taken every 10 to 15 cm through the 4.5 m sequence which covers the Upper Llanvirnian and Caradocian. After detailed stepwise thermal demagnetization, a high unblocking temperature direction of magnetization with mixed polarities is identified. The directions pass the reversal test and yield an overall mean direction of Dec.: 323°, Inc.:- 63°, k: 16.6, α95: 5.8 after bedding correction. This corresponds to a paleo-(south)pole of 11°N, 46.8°E (d p: 7.2°, d m: 9.1°), which plots directly on the Ordovician segment of the apparent polar wander path for Baltica, thus rendering major post-Ordovician rotations of the area relative to Baltica unlikely. The paleomagnetic results reveal three zones of each reversed (R1-R3) and normal polarity (N1-N3). The section starts with a reversed polarity interval in the mid-Llanvirnian stage (R1). The transitions from R1 to N1 and from N1 to R2 in Middle Llanvirnian and from R2 to N2 during Upper Llanvirnian correspond well with previous paleomagnetic results based on graptolite biostratigraphy. After a short normal polarity interval (N2) the lower Caradocian is dominated by inverse polarity (R3

  11. The dynamics of serpentinite dehydration reactions in subduction zones: Constrains from the Cerro del Almirez ultramafic massif (Betic Cordillera, SE Spain)

    NASA Astrophysics Data System (ADS)

    Dilissen, Nicole; Garrido, Carlos J.; López Sánchez-Vizcaíno, Vicente; Padrón-Navarta, José Alberto

    2015-04-01

    Arc volcanism, earthquakes and subduction dynamics are controlled by fluids from downgoing slabs and their effect on the melting and rheology of the overlying mantle wedge. High pressure dehydration of serpentinite in the slab and the subduction channel is considered as one of the main sources of fluids in subduction zones. Even though this metamorphic reaction is essential in subduction activities, the behavior of the fluids, the kinetics and thermodynamics during the breakdown reaction are still poorly understood. The Cerro del Almirez (Nevado-Filábride Complex, Betic Cordillera, SE Spain) uniquely preserves the dehydration front from antigorite serpentinite to chlorite-harzburgite and constitutes a unique natural laboratory to investigate high-pressure dehydration of serpentinite. This reaction occurred in a subduction setting releasing up to 13 wt% of water, contributing significantly to the supply of fluids to the overlying mantle wedge. A key to the understanding of the metamorphic conditions prevailing during serpentinite dehydration is to study the two prominent textures -granofels and spinifex-like chlorite harzburgite- occurring in this reaction product. The detailed texture differences in the Chl-harzburgite can provide insights into diverse kinetic and thermodynamic conditions of this dehydration reaction due to variations in effective pressure and drainage conditions. It has been proposed that difference in overpressure (P') and deviation from growth equilibrium, i.e. overstepping, is responsible for these two types of textures [Padrón-Navarta et al., 2011]. The magnitude and duration of P' is highly dependent on dehydration kinetics [Connolly, 1997]. The fast pressure drop, with spinifex-texture as a product, can be linked to draining events expected after hydrofracturing, which are recorded in grain size reduction zones in this massif. According to this hypothesis, mapping of textural variation in Chl-harzburgite might be used as a proxy to

  12. Micas from mariupolite of the Oktiabrski massif (SE Ukraine): an insight into the host rock evolution--geochemical data supported by Raman microspectroscopy.

    PubMed

    Dumańska-Słowik, Magdalena; Wesełucha-Birczyńska, Aleksandra; Pieczka, Adam

    2015-02-25

    Muscovite and two dark mica varieties (the coarse-crystalline, pegmatitic, and fine-crystalline with signs of early weathering) representing members of the biotite series, originating from mariupolite of the Oktiabrski massif, (Ukraine), were investigated along with their solid inclusions using electron microprobe and Raman micro-spectroscopy to discuss their genesis and relationship to the parental magma. The coarse-crystalline, pegmatitic biotite, (K1.90Rb0.02Na0.01)(Fe3.56(2+)Mg1.34Ti0.36Fe0.34(3+)Mn0.03)[(Si5.73Al2.10Fe0.17(3+))O20](OH3.24 F0.76) represents the primary, magmatic annite that crystallized from an alkaline, Fe-rich and Mg-depleted host magma, whereas the fine-crystalline biotite, partly altered to vermiculite, (K1.75Rb0.03Na0.03)(Fe3.23(3+)Fe1.16(2+)Mg0.26Mn0.04Ti0.10)[(Si5.16 Al2.84)O20](OH)4.00, devoid of F, represents a re-equilibrated or secondary, post-magmatic Fe(3+)-bearing mica crystallized from alkaline to the subalkaline host magma. Muscovite, (K1.96Na0.06)(Al3.97Fe0.06(2+))[(Si5.99Al2.01)O20](OH)4, with low Na/(Na+K) ratio, low Fe and devoid of Ti and also F, forms only tiny, subhedral flakes formed in the post-magmatic, hydrothermal stage. The primary, unaltered biotite contains numerous solid inclusions of primary origin (albite, aegirine, zircon, K-feldspar, nepheline, pyrochlore, magnetite) and secondary origin (natrolite, hematite, Ti-Mn oxides/hydroxides); most of them are accompanied by a carbonaceous substance, all confirmed by scanning electron microscopy and Raman microspectroscopy. PMID:25277630

  13. Micas from mariupolite of the Oktiabrski massif (SE Ukraine): An insight into the host rock evolution - Geochemical data supported by Raman microspectroscopy

    NASA Astrophysics Data System (ADS)

    Dumańska-Słowik, Magdalena; Wesełucha-Birczyńska, Aleksandra; Pieczka, Adam

    2015-02-01

    Muscovite and two dark mica varieties (the coarse-crystalline, pegmatitic, and fine-crystalline with signs of early weathering) representing members of the biotite series, originating from mariupolite of the Oktiabrski massif, (Ukraine), were investigated along with their solid inclusions using electron microprobe and Raman micro-spectroscopy to discuss their genesis and relationship to the parental magma. The coarse-crystalline, pegmatitic biotite, (K1.90Rb0.02Na0.01)(Fe2+3.56Mg1.34Ti0.36Fe3+0.34Mn0.03)[(Si5.73Al2.10Fe3+0.17)O20](OH3.24 F0.76) represents the primary, magmatic annite that crystallized from an alkaline, Fe-rich and Mg-depleted host magma, whereas the fine-crystalline biotite, partly altered to vermiculite, (K1.75Rb0.03Na0.03)(Fe3+3.23Fe2+1.16Mg0.26Mn0.04Ti0.10)[(Si5.16 Al2.84)O20](OH)4.00, devoid of F, represents a re-equilibrated or secondary, post-magmatic Fe3+-bearing mica crystallized from alkaline to the subalkaline host magma. Muscovite, (K1.96Na0.06)(Al3.97Fe2+0.06)[(Si5.99Al2.01)O20](OH)4, with low Na/(Na + K) ratio, low Fe and devoid of Ti and also F, forms only tiny, subhedral flakes formed in the post-magmatic, hydrothermal stage. The primary, unaltered biotite contains numerous solid inclusions of primary origin (albite, aegirine, zircon, K-feldspar, nepheline, pyrochlore, magnetite) and secondary origin (natrolite, hematite, Ti-Mn oxides/hydroxides); most of them are accompanied by a carbonaceous substance, all confirmed by scanning electron microscopy and Raman microspectroscopy.

  14. Geochemistry and detrital zircon U-Pb and Hf isotopes of the paragneiss suite from the Quanji massif, SE Tarim Craton: Implications for Paleoproterozoic tectonics in NW China

    NASA Astrophysics Data System (ADS)

    Zhang, Lu; Wang, Qinyan; Chen, Nengsong; Sun, Min; Santosh, M.; Ba, Jin

    2014-12-01

    The Delingha paragneiss suite in the Quanji massif, southeastern Tarim Craton, is composed of mica schist, paragneiss, leptynite and quartzite, similar to the 'khondalite suites' described from elsewhere in the world. The mica schist is rich in Al2O3 (up to ∼26 wt%) and contains graphite and diagnostic minerals including sillimanite and garnet, with metamorphism under amphibolite-facies to locally granulite-facies conditions as manifested by association with amphibolite and granulite. The detrital zircon U-Pb ages and geochemical data indicate that the protolith materials of the Delingha paragneiss suite were mainly sourced from 2.20 to 2.45 Ga granites, felsic volcanic rocks and TTG, and were deposited at 2.17-1.92 Ga. The detrital zircon Hf and whole-rock Nd isotopes document important crustal growth at ∼2.5-2.7 Ga. The detrital zircon age spectra, the whole rock Nd and zircon Hf model ages, the low-maturity of the protolith, and short-distance transportation suggest that the detritus were derived from the underlying Delingha Complex and the lower Dakendaban sub-Group. The timing of magmatic activities in the source region, the depositional age and metamorphic histories of the Delingha paragneiss suite are all comparable to those recorded in the khondalite belt along northern margin of the Ordos Block in the North China Craton. Our study shows that the 2.2-2.45 Ga magmatic rocks were generated in arc or active continental margin settings, suggesting a prolonged subduction and accretion history prior to final amalgamation (∼2.5-1.8 Ga) to form the unified North China Craton and the assembly of the Tarim Craton in NW China.

  15. An early extensional event of the South China Block during the Late Mesozoic recorded by the emplacement of the Late Jurassic syntectonic Hengshan Composite Granitic Massif (Hunan, SE China)

    NASA Astrophysics Data System (ADS)

    Wei, Wei; Chen, Yan; Faure, Michel; Martelet, Guillaume; Lin, Wei; Wang, Qingchen; Yan, Quanren; Hou, Quanlin

    2016-03-01

    Continental scaled extension is the major Late Mesozoic (Jurassic and Cretaceous) tectonic event in East Asia, characterized by faulting, magmatic intrusions and half-grabens in an area with a length of > 5000 km and a width of > 1000 km. Numerous studies have been conducted on this topic in the South China Block (SCB), However, the space and time ranges of the compressional or extensional regimes of the SCB during the Jurassic are still unclear, partly due to the lack of structural data. The emplacement fabrics of granitic plutons can help determine the regional tectonic background. In this study, a multidisciplinary approach, including Anisotropy of Magnetic Susceptibility (AMS), macro and microstructural analyses, quartz c-axis preferred orientation, gravity modeling and monazite EPMA dating, was conducted on the Hengshan composite granitic massif in SCB that consists of the Triassic Nanyue biotite granitic pluton and the Late Jurassic Baishifeng two-mica granitic pluton. The magnetic fabrics are characterized by a consistent NW-SE oriented lineation and weakly inclined foliation. A dominant high temperature deformation with a top-to-the-NW shear sense is identified for both plutons. The deformation increasing from the center of the Baishifeng pluton to its western border is associated to the development of the West Hengshan Boundary Fault (WHBF). The gravity modeling shows a "saw tooth-shaped" NE-SW oriented structure of the Baishifeng pluton, which may be considered as NE-SW oriented tension-gashes formed due to the NW-SE extension. All results show that the Triassic Nanyue pluton was deformed under post-solidus conditions by the WHBF coeval with the emplacement of the Late Jurassic Baishifeng pluton. All these observations comply with the NW-SE extensional tectonics coeval with the emplacement of the Baishifeng pluton, which argues that the NW-SE crustal stretching started since the Late Jurassic, at least in this part of the SCB.

  16. Bohemian circular structure, Czechoslovakia: Search for the impact evidence

    NASA Technical Reports Server (NTRS)

    Rajlich, Petr

    1992-01-01

    Test of the impact hypothesis for the origin of the circular, 260-km-diameter structure of the Bohemian Massif led to the discovery of glasses and breccias in the Upper Proterozoic sequence that can be compared to autogeneous breccias of larger craters. The black recrystallized glass contains small exsolution crystals of albite-oligoclase and biotite, regularly dispersed in the matrix recrystallized to quartz. The occurrence of these rocks is limited to a 1-sq-km area. It is directly underlain by the breccia of the pelitic and silty rocks cemented by the melted matrix, found on several tens of square kilometers. The melt has the same chemistry as rock fragments in major and in trace elements. It is slightly impoverished in water. The proportion of melted rocks to fragments varies from 1:5 to 10:1. The mineralogy of melt viens is the function of later, mostly contact metamorphism. On the contact of granitic plutons it abounds on sillimanite, cordierite, and small bullets of ilmenite. Immediately on the contact with syenodiorites it contains garnets. The metamorphism of the impact rock melt seems the most probable explanation of the mineralogy and the dry total fusion of rocks accompanied by the strong fragmentation. Other aspects of this investigation are discussed.

  17. Craddock Massif and Vinson Massif remeasured

    USGS Publications Warehouse

    Gildea, Damien; Splettstoesser, John F.

    2007-01-01

    The highest peak in Antarctica, the Vinson Massif (78º35’S, 85º25’W), is at an elevation of 4892 m (16,046 ft), as determined in 2004. Measurements of the elevation have fluctuated over the years, from its earliest surveyed elevation of 5140 m (16,859 ft), to its present height. Vinson Massif and three of its near neighbors in the Sentinel Range of the Ellsworth Mountains are the highest peaks in Antarctica, making them a favorite objective of mountaineers. Well over 1,100 people have climbed Vinson since the first ascent by a team in the 1966-67 austral summer. The range is composed of Crashsite quartzite, making the Sentinel’s very resistant to erosion. Very accurate elevations have been achieved annually by GPS mapping done by a climbing team sponsored by the Omega Foundation, active in Antarctica since 1998. The Craddock Massif now includes Mt. Craddock, the ninth highest peak in Antarctica, at 4368 m (14,327 ft). Both are named for Campbell Craddock*, a U.S. geologist active in Antarctic research beginning in 1959-60.

  18. The Freyenstein Shear Zone - Implications for exhumation of the South Bohemian Batholith (Moldanubian Superunit, Strudengau, Austria)

    NASA Astrophysics Data System (ADS)

    Griesmeier, Gerit; Iglseder, Christoph; Konstantin, Petrakakis

    2016-04-01

    The Moldanubian superunit is part of the internal zone of the Variscan Orogen in Europe and borders on the Saxothuringian and Sudetes zones in the north. In the south, it is blanketed by the Alpine foreland molasse. Tectonically it is subdivided into the Moldanubian Nappes (MN), the South Bohemian Batholith (SBB) and the Bavarian Nappes. This work describes the ~ 500 m thick Freyenstein shear zone, which is located at the southern border of the Bohemian Massif north and south of the Danube near Freyenstein (Strudengau, Lower Austria). The area is built up by granites of Weinsberg-type, which are interlayered by numerous dikes and paragneisses of the Ostrong nappe system. These dikes include medium grained granites and finegrained granites (Mauthausen-type granites), which form huge intrusions. In addition, smaller intrusions of dark, finegrained diorites und aplitic dikes are observed. These rocks are affected by the Freyenstein shear zone und ductily deformed. Highly deformed pegmatoides containing white mica crystals up to one cm cut through the deformed rocks and form the last dike generation. The Freyenstein shear zone is a NE-SW striking shear zone at the eastern edge of the SBB. The mylonitic foliation is dipping to the SE with angles around 60°. Shear-sense criteria like clast geometries, SĆ structures as well as microstructures show normal faulting top to S/SW with steep (ca. 50°) angles. The Freyenstein shear zone records a polyphase history of deformation and crystallization: In a first phase, mylonitized mineral assemblages in deformed granitoides can be observed, which consist of pre- to syntectonic muscovite-porphyroclasts and biotite as well as dynamically recrystallized potassium feldspar, plagioclase and quartz. The muscovite porphyroclasts often form mica fishes and show top to S/SW directed shear-sense. The lack of syntectonic chlorite crystals points to metamorphic conditions of lower amphibolite-facies > than 450° C. In a later stage fluid

  19. Kondyor Massif, Russia

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This is neither an impact crater nor a volcano. It is a perfect circular intrusion, about 10 km in diameter with a topographic ridge up to 600 m high. The Kondyor Massif is located in Eastern Siberia, Russia, north of the city of Khabarovsk. It is a rare form of igneous intrusion called alkaline-ultrabasic massif and it is full of rare minerals. The river flowing out of it forms placer mineral deposits. Last year 4 tons of platinum were mined there. A remarkable and very unusual mineralogical feature of the deposit is the presence of coarse crystals of Pt-Fe alloy, coated with gold. This 3-D perspective view was created by draping a simulated natural color ASTER composite over an ASTER-derived digital elevation model.

    The image was acquired on June 10, 2006, and is located at 57.6 degrees north latitude, 134.6 degrees east longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  20. Precambrian reservoirs sealed by Western Carpathian nappes, southeast slope of the Bohemian Massif, Moravia, Czechoslovakia

    SciTech Connect

    Krejci, J.J. )

    1991-08-01

    The West Carpathian overthrust in Moravia, Czechoslovakia, overlies Proterozoic crystalline basement productive from buried topographic ridges and hills. The Neogene thrust belt forms the seal for oil and gas trapped in the Precambrian crystalline rocks which have been disaggregated by joint, fractures, and weathering. The reservoir rocks include granite, granodiorite, and quartz diorite. Five oil and gas fields have been discovered in this unusual setting. Zdanice-Krystalinikum field is the largest of this type of field in Czechoslovakia (its cumulative production is 66,000 tons of oil), and the ultimate potential is unknown as development is still in process. Three separate pools have been discovered in this field, with differing oil/water contacts and sometimes different oil gravities. These pools appear to be separated by fault zones that have sealed and become impermeable. Other Precambrian reservoir production in Moravia includes East and West Kostelany, West Zdanice, and Korycany fields. Zdanice-Krystalinikum field was discovered using refraction and reflection seismic lines and correlations with previously drilled dry holes which had encouraging shows.

  1. Tectonic rotations south of the Bohemian Massif from palaeomagnetic directions of Permian red beds in Hungary

    USGS Publications Warehouse

    Marton, E.; Elston, D.P.

    1987-01-01

    Palaeomagnetic studies were carried out in Permian red beds of the Balaton Highlands, the Mecsek Mountains and the Bu??kk Mountains of Hungary. Statistically well defined directions were obtained from six localities in the Balaton Highlands and two localities in the Mecsek Mountains. No meaningful results were obtained from the Bu??kk Mountains. Three magnetic components were identified from red beds of the Balaton Highlands: (1) in haematite with a very high unblocking temperature (700??C), interpreted as a Permian magnetization (Dc= 79??, Ic=-11??, k = 24, ??95 = 13.6 ??), in six samples from three beds in a single locality (2) a secondary but ancient component residing mainly inmaghemite (D = 314??, I = 49??, k = 48, ??95 = 10.0??), in 84 samples from six localities with a within-locality scatter increasing on unfolding; and (3) a direction parallel to the present field (D = 7??, I = 62??, k = 46, ??95 = 7.7 ??), in nine samples from a single locality. For the Balaton Highlands, the component 1 direction agrees with directions obtained from Permian red beds and volcanics in the eastern part of the Southern and Eastern Alps and the Inner West Carpathians. All show large, apparent rotations relative to stable Europe since the Permian. Component 2 is of post-folding (post-Aptian) age. Its direction agrees with known Late Cretaceous directions from the Transdanubian Central Mountains, which also show significant counterclockwise rotation relative to stable Europe. The characteristic magnetization for the Mecsek Mountains resides in haematite and may be primary. The directions indicate only a slight net counterclockwise rotation of the Mecsek Mountains with respect to stable Europe since the Permian. ?? 1987.

  2. Metamorphic history of LP/HT migmatites from the Bavarian Unit (Bohemian Massif)

    NASA Astrophysics Data System (ADS)

    Sorger, Dominik; Hauzenberger, Christoph; Linner, Manfred; Iglseder, Christoph

    2016-04-01

    Granulite facies migmatites are commonly observed in the Bavarian Unit which were formed during a late Variscan (post 330 Ma) LP-HT overprint. This event is related to a delamination of mantle lithosphere and subsequent asthenospheric upwelling. Most of these rocks underwent high degrees of melting forming meta- and diatexites. Former work in the Sauwald area, Upper Austria, by Tropper et al. (2006) determined metamorphic conditions of 700-800°C and 0.4-0.5 Gpa. In this study samples were taken along the (1) Danube valley (west of Linz), from the (2) Lichtenberg area (north of Linz), the (3) Bad Leonfelden area (west of the Rodl Fault) and the (4) Sauwald area (south of the river Danube). Biotite and plagioclase bearing migmatite is very common and occurs all over the investigated area. These rocks are the product of intensive melting (anatexite) and formed at conditions of ~650-700°C and 0.25-0.45 Gpa. Scarce outcrops of garnet bearing Al-rich migmatitic metapelites occur along the Danube valley. The formation of the migmatitc texture with well-developed leucosomes (K-feldspar, plagioclase, quartz) and melanosomes (garnet, cordierite, sillimanite, spinel, ilmenite, ± biotite) indicate high temperature metamorphism. Most of the garnet grains show a homogenous iron-rich composition and form generally an almandine-pyrope (Xalm=0.78-0.80, Xprp=0.16-0.18) solid solution with minor contents of grossular and spessartine (Xgrs=0.028-0.032, Xsps=0.020-0.024). Large garnet porphyroblasts (up to 1cm in size) display a distinct chemical zoning, especially in grossular component. Elevated homogeneous grossular content in the core is followed discontinously by low grossular content at the rim indicating a two stage growth. Garnet core and rim also display different mineral inclusions. Thermobarometric calculations using garnet core compositions with inclusions and garnet rim compositions with matrix phases as well as pseudosection calculations allow the reconstruction of a P-T path. A first HP-HT stage (740-825°C and 1.1-1.3 Gpa) is indicated by the garnet core which is followed by decompression and cooling to 580- 610°C and 0.44-0.54 GPa. The main LP-HT metamorphic event gives 830-910°C and 0.60-0.66 GPa using the garnet rims and matrix minerals. TROPPER, P., DEIBL, I., FINGER, F., KAINDL, R. (2006): International Journal of Earth Sciences: Geologische Rundschau 95.6, 1019-1037.

  3. The tectonics of anorthosite massifs

    NASA Technical Reports Server (NTRS)

    Seyfert, C. K.

    1981-01-01

    Anorthosite massifs developed approximately 1.4 to 1.5 billion years ago along an arch which developed parallel to a zone of continental separation as a block which included North America, Europe, and probably Asia separated from a block which included parts of South America, Africa, India, and Australia. Anorthosite massifs also developed at the same time along a belt which runs through the continents which comprise Gondwanaland (South America), Africa, India, Australia, and Antarctica. This was a zone of continental separation which subsequently became a zone of continental collision about 1.2 billion years ago. The northern anorthosite belt also parallels an orogenic belt which was active between 1.8 and 1.7 billion years ago. Heat generated during this mountain building period helped in the formation of the anorthosites.

  4. Documentation and evaluation of slope instabilities and other geological phenomena in the Geopark Bohemian Paradise (Czech Republic)

    NASA Astrophysics Data System (ADS)

    Krejčí, Oldřich; Krejčí, Vladimíra; Švábenická, Lilian; Hartvich, Filip

    2016-04-01

    Geographically, the area is part of the Bohemian Cretaceous Basin, the unit Jičín Hilly land. Since October 2005, the area belongs to the European Geopark UNESCO Bohemian Paradise. The reason of the protection is a major complex of rocks, natural forest communities and geomorphological valuable territory. The territory has been newly geologically mapped in a scale of 1 : 25,000. Sediments of the Czech Cretaceous Basin covers an area of 181 km2 and were deposited transgressively on the Permian - Carboniferous and crystalline basement of the Bohemian Massif. Except for locally developed basal sediments of fluvial origin they are mostly shallow marine sediments. Middle Turonian to Lower Coniacian rocks of the Jizera lithofacies are dominant by calcareous sandstones deposited under extremely dynamic conditions. Scattered alkaline volcanics penetrate the older formations as small intrusions and form locally preserved bodies at the surface. Area is strongly predisposed to the development of various types of landforms by structural segmentation of the Cretaceous sandstones and claystones and by Plio-Pleistocene inverse erosion. Numerous archival manuscripts are available from this area together with published geological, engineering-geological, geomorphological and historical papers. This is due to the fact that in 1926 a large landslide destroyed a substantial part of the village Dneboh, situated on the slope below a rock castle Drabske Svetnicky. Drabske Svetnicky is a ruin of a 13th century castle. It is located on the ragged edge of a sandstone cliff high above surrounding landscape. The castle covers a group of seven sandstone rocks, connected with wooden bridges. In the 50ies of the 20th century, an increased attention was paid to Drabske Svetnicky by experts on medieval architecture and a restoration of the original state of the castle rock was accomplished. Remnants of pottery and other findings suggest that the plateau region of the castle was first inhabited

  5. A key extensional metamorphic complex reviewed and restored: The Menderes Massif of western Turkey

    NASA Astrophysics Data System (ADS)

    van Hinsbergen, Douwe J. J.

    2010-09-01

    have been previously shown to thrust to the SE between 23 and 15 Ma over at least 75 km. This is contemporaneous with, and orthogonal to stretching along the Simav detachment. I here argue that the amount of SE-wards displacement of the Lycian Nappes was twice the minimum amount of 75 km, which would restore them back on top of most of the Menderes Massif, apart from the ˜ 50 km unroofed along the Simav detachment. A decollement was likely formed by a high-pressure, low-temperature metamorphosed nappe immediately underlying the Lycian Nappes in the north — the Ören unit. Latest Oligocene to early Miocene fission track ages of the Menderes Massif, as well as NE-SW trending lower Miocene grabens on the Massif are in line with this hypothesis. The main implications of this restoration are that 1) the eastern part of the Aegean back-arc accommodated not more than 50 km of NE-SW extension in the early Miocene, and 2) any pre-Miocene exhumation of the Menderes Massif cannot be attributed to the known extensional detachments. The restoration in this paper suggests that most of the Menderes Massif already resided at upper crustal levels at the inception of extensional detachment faulting, a situation reminiscent of the role of extensional detachments on the island of Crete.

  6. Crustal structure of the northern Menderes Massif, western Turkey, imaged by joint gravity and magnetic inversion

    NASA Astrophysics Data System (ADS)

    Gessner, Klaus; Gallardo, Luis A.; Wedin, Francis; Sener, Kerim

    2016-05-01

    In western Anatolia, the Anatolide domain of the Tethyan orogen is exposed in one of the Earth's largest metamorphic core complexes, the Menderes Massif. The Menderes Massif experienced a two-stage exhumation: tectonic denudation in the footwall of a north-directed Miocene extensional detachment, followed by fragmentation by E-W and NW-SE-trending graben systems. Along the northern boundary of the core complex, the tectonic units of the Vardar-Izmir-Ankara suture zone overly the stage one footwall of the core complex, the northern Menderes Massif. In this study, we explore the structure of the upper crust in the northern Menderes Massif with cross-gradient joint inversion of gravity and aeromagnetic data along a series of 10-km-deep profiles. Our inversions, which are based on gravity and aeromagnetic measurements and require no geological and petrophysical constraints, reveal the salient features of the Earth's upper crust. We image the northern Menderes Massif as a relatively homogenous domain of low magnetization and medium to high density, with local anomalies related to the effect of interspersed igneous bodies and shallow basins. In contrast, both the northern and western boundaries of the northern Menderes Massif stand out as domains where dense mafic, metasedimentary and ultramafic domains with a weak magnetic signature alternate with low-density igneous complexes with high magnetization. With our technique, we are able to delineate Miocene basins and igneous complexes, and map the boundary between intermediate to mafic-dominated subduction-accretion units of the suture zone and the underlying felsic crust of the Menderes Massif. We demonstrate that joint gravity and magnetic inversion are not only capable of imaging local and regional changes in crustal composition, but can also be used to map discontinuities of geodynamic significance such as the Vardar-Izmir-Ankara suture and the West Anatolia Transfer Zone.

  7. Geological structures and deformation sequence of the eastern Gyeonggi massif, central Korea

    NASA Astrophysics Data System (ADS)

    Kihm, You Hong; Hwang, Jae Ha

    2010-05-01

    The Gyeonggi massif, situated between the Nangrim and Yeongnam massifs of the Korean Peninsula, is a Precambrian terrane consists primarily of Archean to Proterozoic crystalline basement. Although the Gyeonggi massif has been suspected as an eastern extension of the Qinling-Dabie collision belt of China, a structural data about the Gyeonggi massif are very short, especially about the eastern part of the Gyeonggi massif. This study focused the deformation sequence of the eastern part of Gyeonggi massif and comparison with that of western part of Gyeonggi massif. At least, five phases of deformational events can be recognized. The first phase of deformation produced gneissic and schistose structures with intrafolial and recumbent folds. During the second phase of deformation, mylonite, mineral lineation, intrafolial recumbent folds and irregular folds were formed. The Bangsan Anticline (BSA) and its sub-order folds were produced by the third phase of deformation. SE-vergent thrust and south-vergent kink folds resulted from the forth and fifth phases of deformation, respectively. Axis of the BSA can be traced over 5km and the representative orientations of two limbs of the BSA are N17°W/32°SE, N29°E/25°NW, respectively. Interlimb angle of the BSA is measured as 128° and can be classified into open fold. Structural transect analysis of regional foliation shows that axis of the BSA is located about 4.6km toward East from longitude 127°53'45″E. If the BSA is correlated with very large-scale NS-trending folds occurred in the western part of the Gyeonggi massif based on characteristics of fold structure, the third phase of deformation can be interpreted in age from the Late Proterozoic to the Early Paleozoic (750~390 Ma). Mylonite of the study area cannot be correlated to the Gyeonggi Shear Zone, which was suggested as post-collisional top-to-the-north extensional structure. The SE-vergent thrust of the forth phase of deformation is probably correlated to the

  8. Variable mineral composition of metamorphic rocks from a single quarry compared to their ASR potential (Bohemian Massif, Czech Republic)

    NASA Astrophysics Data System (ADS)

    Stastna, Aneta; Sachlova, Sarka; Pertold, Zdenek; Nekvasilova, Zuzana; Prikryl, Richard

    2013-04-01

    The alkali-silica reaction (ASR) is one of the most damaging factors for concrete structures. ASR originates due to the presence of reactive silica (SiO2) that reacts with alkaline ions under wet conditions. The reaction mechanism consists of four different steps: initial attack of OH- compounds on SiO2 at aggregate-cement paste boundary; formation of silanol groups at SiO2 surface; formation of siloxane groups and their polymerization; adsorption of alkaline and Ca2+ ions and formation of alkali-silica gels. Alkali-silica gels tend to absorb water molecules and swell causing increasing internal pressures in concrete and microcracking. The most reactive aggregates are mainly composed of amorphous and/or fine-grained SiO2-rich phases. In the Czech Republic, ASR was observed in deteriorating concrete structures containing very fine-grained quartz (quartz in tuffaceous sandstones and greywackes), as well as quartz indicating variable degree of deformation (quartz in quartzite, granodiorite and various metamorphic rock types). In this study, mineralogical-petrographic methods (polarizing, electron and cathodoluminescence microscopy) were combined with the accelerated mortar bar test (following the standard ASTM C1260), with the aim to quantify the ASR potential, as well as to distinguish reactive mineral phases. Different aggregate varieties from the Těchobuz quarry (Moldanubian Zone, Czech Republic) have been compared. Mineralogical-petrographic characteristics permit a distinction between 1) medium-grained plagioclase quartzite and 2) fine-grained biotite-plagioclase-quartz paragneiss and 3) fine-grained calc-silicate rock. Mineralogical composition of the first type is quartz + Ca-plagioclase + K-feldspar + biotite + chlorite + diopside + pyrite + apatite + titanite ± calcite. The second type has mineral assemblage including quartz + Ca-plagioclase + K-feldspar + biotite + chlorite + pyrite + tourmaline + apatite + titanite ± calcite. The third type contains quartz + calcite + Ca-plagioclase + diopside + amphibole+ clinozoisite + muscovite + K-feldspar + pyrite + apatite + titanite + zircon. Alkali-silica reactivity of aggregate types was quantified based on the expansion of mortar bar specimens. Investigated samples display the expansion above 0.1 % and thus are classified as reactive. Variable reactivity is mostly caused by the presence of quartz characterized by different degree of deformation and grain size. Calcite and mafic minerals exhibit no ASR potential. The role of feldspars would be discussed due to possible leaching of alkalis into a solution.

  9. Late variscan evolution of the Pelvoux Massif in the light of 3D mapping of granites

    NASA Astrophysics Data System (ADS)

    Strzerzynski, P.; Guillot, S.; Courrioux, G.; Ledru, P.

    2003-04-01

    The Pelvoux massif is a fragment of Paleozoic crustal rock involved in the alpine belt. The inner part of the massif is composed by anatectic and amphibolitic gneisses intruded by Stephanian granites. The Turbat-Lauranoure, Etages and Berarde granites have a N160 vertical magmatic foliation cross cut by N135 vertical ductile strike slip faults. A three dimensional modeling of the shape of the Turbat-Lauranoure, Etages and Berarde granites has been realized using field and cartographic data. The method based on potential field allows the integration of structural data as foliation and contact orientation measurements. The granite shapes have been modeled with three types of surface with different geological significance: The first type of surface is constrained by granite foliation measurements. They are NNW-SSE and vertical oriented. They form the eastward and westward granite-gneiss and Etages-Berarde granites boundaries. The second surface is a well known alpine structure called the Meije-Muzele Trust. This structure is oriented N50 50^oSE. The third surface is a granite-gneiss boundary in where gneisses are located on of the top the granite. The granite-gneiss contact has a northward plunge on the north and a southward plunge on the south of the massif. The NNW-SSE elongated shape of the granite associated with a left lateral ductile strike slip fault and the dome like shape of the massif are consistent with a N-S direction of extension during Stephanian time. In order to integrate this Stephanian Pelvoux Massif magmatic event in the Variscan scheme, an anticlockwise rotation occurred during Permian time. The observed N20 dextral strike slip faults are at the origin of the Permian rotation of the Pelvoux Massif.

  10. Maldzhangarsky rare metal carbonatite massif in the NE-part of the Anabar shield.

    NASA Astrophysics Data System (ADS)

    Vladykin, Nikolai

    2015-04-01

    In the SW part of the Anabar shield Th-anomaly was he drilled by ALROSA company by 6 bore holes to a depth of 100 m, which revealed a new Maldzhangarsky rare metal carbonatite massif (Vladykin 2008). It is oval-shaped and elongated NW to SE having dimensions 4.2 x 2.5 km.. and total square ~ 10.5 km2 Carbonatites are from mean- to fine-grained light-colored. Mineral and chemical composition, tracery, dolomite are ankerite and carbonaties. Besides the carbonate it is composed by phlogopite, apatite, alkali amphibole, rarely magnetite and accessory minerals like pyrochlore, zircon, barito-celestine, rare earth carbonates and apatite, reaching 20-30%. In addition to the prevailing carbonatite the carbonatized pyroxenite xenoliths were found in the drilling cores. Geochemical study of the Maldzhangarsky massif carbonatites indicated the presence of significant quantities of typical carbonatite elements- Sr, Ba, Nb, Ta, P, Y, TRE, which is similar to the carbonatites of the Tomtor massif. Many parts of the massif are the ores for Nb, TR, Sr and P. The highest concentrations based on TRE 100 analyses of Nb-8000 ppm, Y-800 ppm; TRE-4%, Sr-10%,. The REE patterns of carbonanites are highly inclined with the r sharp prevalence of light REE on heavy with a rather steep slope., There are now Eu anomalies which is typical for the mantle carbonitetes, and which evidence for the early fractionation of alkaline carbonatite fluid orliquid from silicate melt. Pair correlation of rare earth elements in carbonatite shows their origin from a single source. The intrusive nature of the drilled carbonatites of Maldzhangarsky massif suggest them to be the top part of the unexposed massif. The belonging of this massif to any genetic type is unclear and needs more detail exploration. RBRF grant (15-05-01005). Vladykin N.v. New rare metal ore karbonatitov province EAST of the Anabarskiy shield. In: Geochemistry of magmatic rocks, St. Petersburg, 2008, pp. 24-27.

  11. The Lassell Massif - a Silicic Lunar Volcano

    NASA Astrophysics Data System (ADS)

    Ashley, J.; Robinson, M. S.; Stopar, J. D.; Glotch, T. D.; Hawke, B. R.; Lawrence, S. J.; Jolliff, B. L.; Greenhagen, B. T.; Paige, D. A.

    2013-12-01

    Lunar volcanic processes were dominated by mare-producing basaltic extrusions. However, limited occurrences of non-mare, geochemically evolved (Si-enriched) volcanic deposits have long been suspected on the basis of spectral anomalies (red spots), landform morphologies, and the occurrence of minor granitic components in Apollo sample suites [e.g., 1-5]. The LRO Diviner Lunar Radiometer Experiment (Diviner) measured thermal emission signatures considered diagnostic of highly silicic rocks in several red spot areas [6,7], within the Marius domes [8], and from the Compton-Belkovich feature on the lunar farside [9]. The present study focuses on the Lassell massif red spot (14.73°S, 350.97°E) located in northeastern Mare Nubium near the center of Alphonsus A crater. Here we use Diviner coverage co-projected with Lunar Reconnaissance Orbiter Camera (LROC) images [10] and digital elevation models to characterize the Lassell massif geomorphology and composition. Localized Diviner signatures indicating relatively high silica contents correlate with spatially distinct morphologic features across the Lassell massif. These features include sub-kilometer scale deposits with clear superposing relationships between units of different silica concentrations. The zone with the strongest signal corresponds to the southern half of the massif and the Lassell G and K depressions (formerly thought to be impact craters [11]). These steep-walled pits lack any obvious raised rims or ejecta blankets that would identify them as impact craters; they are likely explosive volcanic vents or collapse calderas. This silica-rich area is contained within the historic red spot area [4], but does not appear to fully overlap with it, implying compositionally distinct deposits originating from the same source region. Low-reflectance deposits, exposed by impact craters and mass wasting across the massif, suggest either basaltic pyroclastics or minor late-stage extrusion of basaltic lavas through vents

  12. Geochemistry of carbonatites of the Tomtor massif

    USGS Publications Warehouse

    Kravchenko, S.M.; Czamanske, G.; Fedorenko, V.A.

    2003-01-01

    Carbonatites compose sheet bodies in a 300-m sequence of volcanic lamproites, as well as separate large bodies at depths of >250-300 m. An analysis of new high-precision data on concentrations of major, rare, and rare earth elements in carbonatites shows that these rocks were formed during crystallization differentiation of a carbonatite magma, which resulted in enrichment of the later melt fractions in rare elements and was followed by autometasomatic and allometasomatic hydrothermal processes. Some independent data indicate that the main factor of ore accumulation in the weathered rock zone (also known as the "lower ore horizon" comprising metasomatized volcanics with interbedded carbonatites) was hydrothermal addition of Nb and REEs. The giant size of the Tomtor carbonatite-nepheline syenite massif caused advanced magma differentiation, extensive postmagmatic metasomatism and recrystallization of host rocks, and strong enrichment of carbonatites in incompatible rare and rare earth elements (except for Ta, Zr, Ti, K, and Rb) compared to the rocks of many other carbonatite massifs. We suggest that a wide range of iron contents in carbonatites-2 can be related to extensive magnetite fractionation at the magmatic stage in different parts of the huge massif. Copyright ?? 2003 by MAIK "Nauka/Interperiodica" (Russia).

  13. Œdème vulvaire massif pendant la grossesse: à propos d'un cas

    PubMed Central

    El Hassani, Moulay Elmehdi; Kassidi, Farid; Benabdejlil, Youssef; Kouach, Jaouad; Moussaoui, Driss Rahali; Dehayni, Mohammed

    2014-01-01

    L’œdème vulvaire massif est rare pendant la grossesse, mais requiert une attention particulière car il peut se greffer de complications maternelles et fœtales. Il peut être associé à plusieurs pathologies spécifiques ou non spécifiques à la grossesse dont le diagnostic fait appel obligatoirement à un interrogatoire et un examen clinique minutieux, puis à un bilan biologique standard. Le traitement doit être étiologique chaque fois que possible à coté du traitement symptomatique. Cette situation peut nécessiter un accouchement par césarienne. En dehors du risque potentiel de nécrose tissulaire et du risque exceptionnel de décès maternel associé à l’œdème vulvaire massif du post-partum l’évolution est favorable sous traitement bien conduit. PMID:25922627

  14. Tertiary carbonate development on the Shenhu Massif, South China Sea

    SciTech Connect

    Turner, N.L. ); Siemann-Gartmann, S. )

    1994-07-01

    The Shenhu Massif lies between the Zhu III Depression to the northwest, the Kaiping/Baiyun depressions to the northeast, and the Xisha Basin to the south. Major faulting began in the Paleocene, and initial basins formed on and around the Shenhu Massif during this time. Continental coarse clastics, derived from the massif area, filled the basins prior to the middle Oligocene though larger, deeper basins may have contained lacustrine environments. During the marine incursion from the middle Oligocene and until the early Miocene, coarse clastics were deposited adjacent to exposed basement areas, fine marine clastics were deposited on the massif, carbonate buildups formed along the massif rim, and carbonate platforms developed from the massif edge back into the shallow-water high-massif interior. In mid-lower Miocene, the carbonate areas were reduced in size and replaced by shales. Carbonate deposition as layers and mounds was reestablished over much of the Shenhu Massif in the early and middle Miocene. Prodelta shales in the east Shenhu Massif area and coarser clastics present in clinoforms in the Baiyun Depression are the distal components of a southerly prograding delta system located to the north. Carbonates continued to develop along the southeast side of the west Shenhu Massif during the latter part of the middle Miocene, but fine clastics dominated the rest of the area except in the Kaiping/Baiyun Depression where coarser clastics from the delta were deposited. Amoco and its partners, Nanhai West Oil Co. and Kerr-McGee Co., have begun evaluation of the Shenhu Massif area with the drilling of a Miocene carbonate buildup, the Amoco 23-1 Baodao prospect.

  15. Hydrochemical monitoring results in relation to the vogtland-nw bohemian earthquake swarm period 2000

    NASA Astrophysics Data System (ADS)

    Kämpf, H.; Bräuer, K.; Dulski, P.; Faber, E.; Koch, U.; Mrlina, J.; Strauch, G.; Weise, S. M.

    2003-04-01

    The Vogtland-NW Bohemian earthquake swarm area/Central Europe is characterised by carbon dioxide- rich mineral springs and mofetts. The August-December 2000 earthquake period was the strongest compared with the December 1985/86 swarms occurred in the area of Novy Kostel, Czech Republic. Here, we present first results of long-term hydrochemical monitoring studies before, during and after the 2000 swarm period. The swarm 2000 lasted from August 28 until December 26 and consisted of altogether nine sub-swarm episodes, each of them lasting for several days. At the mineral spring Wettinquelle, Bad Brambach/Germany the water chemistry and isotope (D, 18O) composition was monitored weekly and two-weekly, respectively, since May 2000. The mineral spring Wettinquelle is located in a distance of about 10 km from the epicentral area of Novy Kostel. The aim of our investigation was to look for seismic induced or seismic coupled changes of the chemical and isotope composition of the mineral water. We had to separate seismohydrological effects from seasonal and hydrological caused changes. The seasonal caused shifts were found for water temperature and alkaline elements (Li, Na, K, Rb and Cs) as well as for discharge, conductivity, hydrogenecarbonate- concentration, and the concentration of the alkaline earth's (Ca, Mg, Sr). Strain related anomalies which could influence the hydrogeochemistry of the mineral water seems to be visible in the iron- concentration of the spring water, in the methane- concentration of the free gas component and caused probably changes of the groundwater level of the well H3 located about 5 km SE of the Wettinquelle at Skalna.

  16. Understanding the Tectonic Deformation of Turkish Blocks since Mesozoic; A Paleomagnetic study on the Nigde-Kirsehir Massif and the Taurides

    NASA Astrophysics Data System (ADS)

    Mualla, Cinku; Mumtaz, Hisarli; Ulker, Beyza; Kaya, Nurcan; Oksum, Erdinc; Yilmaz, Yucel; Orbay, Naci

    2015-04-01

    It is reported that the Nigde-Kirsehir massif which constitutes the main fragment of Anatolia is rifted from the Taurides-Anatolides in Mesozoic and that the Intra-Tauride ocean exist between these blocks. Another group of researchers believed that the Intra Tauride ocean did not exist. They assumed that the Nigde-Kirsehir massif existed as a promotory of the Taurides. In this sense, both the Nigde-Kirsehir massif and the Taurides experienced several deformation phases due to the consumption of the oceanic strand (s) and the amalgamation of the Anatolian blocks after collision in the end of the paleotectonic time, whereas in the neotectonic time the traces of the westwards excursion of Anatolia was effective. Previous paleomagnetic studies showed that the Nigde-Kirsehir massif rotated 90° anticlockwise during Jurassic to Eocene time and other studies showed that the collision between the Nigde-Kirsehir massif and the Pontides resulted by deformation which was accomodated by regional faults. In the south of the Nigde-Kirsehir massif, it was proposed that all the rocks in Carboniferous to Eosen were remagnetized due to nap emplacement in Eocene. Because of several alternative interpretations about the tectonic deformation of the Nigde-Kirsehir massif in relation between the Taurides and the Pontides, we report new paleomagnetic results from Late Jurassic to Miocene rocks in the Nigde-Kirsehir massif and its surrounding. A total of 138 different sites were sampled from Jurassic to Miocene rocks in the south of the Nigde-Kirsehir massif around Ki ri kkale, Tuzgölü, Uluki şla and Kayseri, whereas in the Central Taurides Late Jurassic- Lower Cretaceous platform type carbonates and ophiolitic rocks from Mersin and Pozanti were collected. Paleomagnetic results evaluated together with previous paleomagnetic data indicate that all the studied rocks carry a magnetization before folding according to positive incremental fold tests. It has been shown that in the SE/E (SE

  17. Lower crust exhumation and ongoing continental convergence in the Variscan Maures-Tanneron Massif, France, geological synthesis and numerical models

    NASA Astrophysics Data System (ADS)

    Gerbault, Muriel; Schneider, Julie; Corsini, Michel; Reverso-Peila, Alexandre

    2015-04-01

    internal volume forces rose and exceeded far-field boundary forces, linked with the balancing of masses in all three directions. The original location of this portion of the Variscan belt remains unclear but it presents consistent transitional characteristics between the Massif Central and the Bohemian massif.

  18. Experimental and Modeling Studies of Massif Anorthosites

    NASA Technical Reports Server (NTRS)

    Longhi, John

    1999-01-01

    This termination report covers the latter part of a single research effort spanning several grant cycles. During this time there was a single title, "Experimental and Modeling Studies of Massif Anorthosites", but there were several contract numbers as the mode and location of NASA contract administration changed. Initially, the project was funded as an increment to the PI's other grant, "Early Differentiation of the Moon: Experimental and Modeling Studies", but subsequently it became an independent grant. Table 1 contains a brief summary of the dates and contract numbers.

  19. Long lasting paleolandscapes stability of the French Massif Central during the Mesozoic

    NASA Astrophysics Data System (ADS)

    Ricordel-Prognon, C.; Thiry, M.; Theveniaut, H.; Lagroix, F.

    2009-04-01

    wander path of the European plate in Upper Triassic-Lower Jurassic times and the Liassic intraplate fracturing of the Pangea : New palaeomagnetic constraints from NW France and SW Germany. Geophysical Journal International 128 (2), 331-344. Parcerisa D., Thiry M., Schmitt J.-M., 2009, Albitization related to the Triassic unconformity in igneous rocks of the Morvan Massif (France), International Journal of Earth Sciences, DOI: 10.1007/s00531-008-0405-1 Ricordel C, Parcerisa D, Thiry M, Moreau M-G, Gómez-Gras D (2007) Triassic magnetic overprints related to albitization in granites from the Morvan massif (France). Palaeogeogr Palaeoclimatol Palaeoecol 251: 268-282 Ricordel C. (2007) - Datations par paléomagnétisme des paléoaltérations du Massif central et de ses bordures : implications géodynamiques. Thèse Ecole Nat. Sup. Des Mines de Paris, Paris, 172 p. Ricordel C., Thiry M., Moreau M.-G., Théveniaut H. (2005) Paleomagnetic datings on "Siderolithic" paleoweathering profiles along French Massif Central. European Geosciences Union, Vienne, Autriche, 24-29 avril, Geophysical Research Abstracts, vol. 7, 06631, 6 p. Schmitt J.M. (1992) Triassic albitization in southern France: an unusual mineralogical record from a major continental paleosurface In: Schmitt JM, Gall Q (eds). Mineralogical and geochemical records of paleoweathering. Paris, ENSMP, Mem Sci Terre 18, pp 115-131

  20. Constraining the deformation and exhumation history of the Ronda Massif, Southern Spain

    NASA Astrophysics Data System (ADS)

    Myall, Jack; Donaldson, Colin

    2016-04-01

    The Ronda peridotite, southern Spain is comprised of four peridotite units hosted within metasedimentary units of the Betic Cordillera, Western Alps. These four areas of differing mineral facies are termed: the Garnet Mylonite , the Foliated Spinel Peridotite, the Granular Spinel Peridotite and the Foliated Plagioclase Peridotite. Whilst two of these units show a strong NE-SW foliation, the granular unit has no foliation and the Plagioclase facies shows a NW-SE foliation. The massif is separated from the metasedimentary host through a mylonite shear zone to the NW and thrust faults to the SE. The Garnets contain rims of Kelyphite which when combined with the rims of Spinel on the Plagioclase crystals illustrate the complicated exhumation of this massif. The Kelyphite shows the breakdown of garnet back to spinel and pyroxene showing the deeper high pressure high temperature mineral is under shallowing conditions whereas in contrast to this the low pressure low temperature plagioclase crystals have spinel rims showing that they have been moved into deeper conditions. The P-T-t pathway of the massif suggests slow exhumation to allow for partial recrystallisation of not only the garnets and plagioclases but of a 100m band of peridotite between the Foliated Spinel Peridotite and the Granular Spinel Peridotite facies. The tectonic model for the Ronda Peridotite that best describes the field data and subsequent lab work of this study is Mantle Core complex and slab roll back models. These models support mantle uprising during an extensional event that whereby slab roll back of the subducting lithosphere provides uplift into a void and emplacement into the crust. Further extension and final exhumation causes rotation of a mantle wedge into its present day position.

  1. Spatial thermal radiometry contribution to the Massif armoricain and the Massif central (France) litho-structural study

    NASA Technical Reports Server (NTRS)

    Scanvic, J. Y. (Principal Investigator)

    1980-01-01

    The author has identified the following significant results. Although the limited number of images received did not permit construction of a thermal inertia map, important geological details were obtained in the areas of lithology and tectonics. Interpretation of day, night, and seasonal imagery resulted in differentiating broad calcareous and dolomitic units in the Causse Plateau. In the Massif amoricain, some granite massifs were delineated which were not observed by LANDSAT. Neotectonic faults were also revealed.

  2. Garzon Massif basement tectonics: A geopyhysical study, Upper Magdalena Valley, Colombia

    NASA Astrophysics Data System (ADS)

    Bakioglu, Kadir Baris

    basement rocks throughout the Garzon Massif and asymmetric loading (sedimentary basin is much deeper on NW flank -- Upper Magdalena Valley). Crust thickens to the NW toward the Central Cordillera. Euler deconvolution of the magnetic field shows pronounced NE-SW trending features under the Massif which are interpreted as faults bounding a possible pre-Cambrian sedimentary rift graben. Retrodeformed 2D regional models indicate 13 km of shortening on the Garzon basement thrust in the last 12 Ma. Approximately 9 km of shortening occurred on the SE marginal basement thrust fault, probably also in the last 12 Ma. This was preceded by approximately 43 km of shortening by thin-skinned imbricate thrusting to the southeast (12 - 25 Ma). This study provides a well-documented example of an active basement uplift on low angle thrust faults.

  3. Origin of earthquake swarms in the western Bohemian Massif: Is the mantle CO2 degassing, followed by the Cheb Basin subsidence, an essential driving force?

    NASA Astrophysics Data System (ADS)

    Babuška, Vladislav; Růžek, Bohuslav; Dolejš, David

    2016-02-01

    We propose a new model of the origin of earthquake swarms in West Bohemia/Vogtland (central Europe) by extensive CO2 degassing of carbonates in the metasomatized junction of three mantle domains. The associated volume change of the decarbonation reaction accounts for the continuing subsidence of the Cheb Basin adjacent to the major focal zone. The local stress perturbation created by the subsidence, in combination with the regional stress field, may account for the recurring swarm seismicity. The largest earthquake energy has been continuously released along a steep contact between orthogneisses of the uplifting Krušné Hory/Erzgebirge domain and granites of the subsiding Smrčiny/Fichtelgebirge domain, forming boundary between two lithospheric segments. The physical parameters of both lithologies, Poisson's ratio and bulk modulus, derived from the P- and S-wave velocities at different depths indicate that this high-friction suture might be able to accumulate deformation energy that is being released as periodically recurring seismic swarms. The proposed model represents an alternative to prevailing considerations suggesting that the earthquake swarms were triggered by pressurized fluids of mantle origin, whose sources are however separated from the earthquake foci.

  4. The timing of eclogite facies metamorphism and migmatization in the Orlica–Śnieżnik complex, Bohemian Massif: Constraints from a multimethod geochronological study

    USGS Publications Warehouse

    Brocker, M.; Klemd, R.; Cosca, M.; Brock, W.; Larionov, A.N.; Rodionov, N.

    2009-01-01

    The Orlica–Śnieżnik complex (OSC) is a key geological element of the eastern Variscides and mainly consists of amphibolite facies orthogneisses and metasedimentary rocks. Sporadic occurrences of eclogites and granulites record high-pressure (HP) to ultrahigh-pressure (UHP) metamorphic conditions. A multimethod geochronological approach (40Ar–39Ar, Rb–Sr, Sm–Nd, U–Pb) has been used to gain further insights into the polymetamorphic evolution of eclogites and associated country rocks. Special attention was given to the unresolved significance of a 370- to 360 Ma age group that was repeatedly described in previous studies. Efforts to verify the accuracy of c.370 Ma K–Ar phengite and biotite dates reported for an eclogite and associated country-rock gneiss from the location Nowa Wieś suggest that these dates are meaningless, due to contamination with extraneous Ar. Extraneous Ar is also considered to be responsible for a significantly older 40Ar–39Ar phengite date of c. 455 Ma for an eclogite from the location Wojtowka. Attempts to further substantiate the importance of 370–360 Ma zircon dates as an indicator for a melt-forming high-temperature (HT) episode did not provide evidence in support of anatectic processes at this time. Instead, SHRIMP U–Pb zircon dating of leucosomes and leucocratic veins within both orthogneisses and (U)HP granulites revealed two age populations (490–450 and 345–330 Ma respectively) that correspond to protolith ages of the magmatic precursors and late Variscan anatexis. The results of this study further underline the importance of Late Carboniferous metamorphic processes for the evolution of the OSC that comprise the waning stages of HP metamorphism and lower pressure HT overprinting with partial melting. Eclogites and their country rocks provided no chronometric evidence for an UHP and ultrahigh-temperature episode at 387–360 Ma, as recently suggested for granulites from the OSC, based on Lu–Hf garnet ages (Anczkiewicz et al., 2007).

  5. Pleistocene terraces of the Vltava River in the Budějovice basin (Southern Bohemian Massif): New insights into sedimentary history constrained by luminescence data

    NASA Astrophysics Data System (ADS)

    Homolová, Dana; Lomax, Johanna; Špaček, Petr; Decker, Kurt

    2012-08-01

    We studied Quaternary sediments from the Budějovice basin in southern Bohemia, now being able to reconstruct the landscape formation of this area during the late Pleistocene. The main objective of this study was to map fluvial terraces of the rivers Vltava and Malše in the basin and to constrain their ages by luminescence dating. Topographic data from a high-resolution DEM in combination with lithological profiles of more than 1000 boreholes allowed identifying five terrace levels (BB 1 to BB 5) with bases ranging from 7 m below to 26 m above the recent mean water level of the Vltava River. For the lowermost terrace level BB 1, a consistent stratigraphy with ages ranging between 84.5 ± 9.0 ka and 7.9 ± 0.8 ka was constrained. Additionally, we obtained luminescence ages of alluvial fan and colluvial deposits, which allow us to better constrain the late Pleistocene sedimentation history of the study area. Based on the spatial distribution of derived ages, the terrace level BB 1 represents a complex sediment body incorporating more distinct packages of river aggradation. The presence of stacked fluvial deposits of Pleistocene age underneath the recent floodplain points to an ongoing subsidence or relative tectonic stability of the Budějovice basin during the late Pleistocene.

  6. Types of soft-sediment deformation structures in a lacustrine Ploužnice member (Stephanian, Gzhelian, Pennsylvanian, Bohemian Massif), their timing, and possible trigger mechanism

    NASA Astrophysics Data System (ADS)

    Stárková, Marcela; Martínek, Karel; Mikuláš, Radek; Rosenau, Nicholas

    2015-07-01

    The succession of Stephanian C lacustrine and fluvial facies of the Ploužnice member (Semily Formation) paleolake in the Krkonoše Piedmont Basin (northern Czech Republic) preserved in borehole Sm-1 shows five types of soft-sediment deformation structures (SSDS): (1) sediment injections (clastic dikes), (2) load structures and ball-and-pillow structures, (3) water-escape structures (discontinuous laminations, deformed wavy bedding, recumbent folding, and dish or pillar structures), (4) deformations by growth of carbonate and silica minerals during diagenesis, and (5) bioturbation. Bioturbations disturbing mechanical SSDS suggest that soft-sediment deformations may occur syndepositionally or soon after deposition. The discussed mechanical SSDS are developed in a lacustrine environment, most being in lower shoreface and offshore facies. The mechanical SSDS found in the Ploužnice lake deposits occur in all lacustrine facies associations (290 SSDS horizons in a 67-m-thick succession). The cumulative thickness in cm of mechanical SSDS horizons per meter of thickness (ratio cm SSDS/m) is the highest in lower shoreface facies where it reaches from 50 up to 59.7 cm SSDS/m. Offshore facies association reaches 44 cm SSDS/m. Upper shoreface facies associations have 25.9 and 26.0 cm SSDS/m, while nearshore/mudflat facies associations preserve from 22.5 to 20.5 cm SSDS/m, and in palustrine carbonate, 13.5 cm mechanical SSDS/m was found. SSDS in fluvial facies are rare (2.9 cm SSDS/m). The distribution of SSDS in the Sm-1 borehole shows clear relationships to sedimentary facies and processes such as density flows or fluctuation of water level. The relationships of particular structures indicate a relative timing of formation which is as follows: sediment deposition was followed by the formation of mechanical SSDS, then by bioturbation, and finally by deformations due to early diagenetic growth of carbonates and silica. The distribution of SSDS in vertical sections and their direct relationship to sedimentary facies point to endogenic rather than external trigger mechanisms such as seismic activity. The main endogenic trigger mechanisms responsible for the origin of SSDS included a Stephanian semi-humid seasonal climate, basin morphology with relatively steep gradients, and elevated source areas, which created a conducive environment for rapid and repeated deposition of sheetfloods and hyperconcentrated flows and turbidites causing syndepositional loading.

  7. Durbachites from the Eastern Moldanubicum (Bohemian Massif): erosional relics of large, flat tabular intrusions of ultrapotassic melts—geophysical and petrological record

    NASA Astrophysics Data System (ADS)

    Leichmann, J.; Gnojek, I.; Novák, M.; Sedlák, J.; Houzar, S.

    2016-01-01

    The results of the airborne survey comprising gamma-ray spectrometry and proton magnetometry, ground gravity survey, and field geological observations (e.g., deep borehole profiles, contact aureole in dolomite marbles, distribution of granitic pegmatites within the Třebíč pluton) suggest that the ultrapotassic Třebíč and Jihlava plutons are flat intrusions. They intruded distinct deep levels of the crust, 2-4 kbar for Třebíč pluton, and 5-7 kbar for Jihlava-pluton. Current thickness of the intrusions is generally less than 2 km, with two exceptions: (1) central part of the Jihlava pluton and (2) a small body near Věžnice, where the estimated depth of tube-shaped stocks of shoshonitic and ultrapotassic gabbros or monzogabbros is around 2.5 km. These stocks could represent feeding pipes of basic and alkaline and dry magmas protruding to the upper crust level. The NE part of the Třebíč pluton is a bottom part of this body, whereas the NW corner and the southern promontory of the pluton could represent an upper (roof) part of the intrusion. Small isolated durbachite bodies located within the Moldanubian gneisses and migmatites of the Strážek Unit represent rootless remnants of a former large and flat durbachite body initially extending significantly more to N and NE and eroded since Lower Carboniferous. Discrepancy between the long-wave magnetic and gravity anomalies, and surface geological structure of the eastern part of the Moldanubian Zone indicates a crucial role of the thrust tectonics.

  8. Reactivity of North Bohemian coals in coprocessing of coal/oil mixtures

    SciTech Connect

    Sebor, G.; Cerny, J.; Maxa, D.; Blazek, J.; Sykorova, I.

    1995-12-01

    Autoclave experiments with North Bohemian coal were done in order to evaluate their reactivity in coprocessing with petroleum vacuum residue, Selected coals were comprehensively characterized by using a number of analytical methods. While the coals were of similar geological origin, some of their characteristics differed largely from one coal to another. Despite the differences in physical and chemical structure, the coals provided very similar yields of desired reaction products. The yields of a heavy non- distillable fraction and/or an insoluble solid residue were, under experimental conditions, largely affected by retrogressive reactions (coking). The insoluble solid fractions were examined microscopically under polarized light.

  9. The seismotectonic significance of the 2008-2010 seismic swarm in the Brabant Massif (Belgium)

    NASA Astrophysics Data System (ADS)

    Van Noten, Koen; Lecocq, Thomas; Shah, Anjana K.; Camelbeeck, Thierry

    2015-04-01

    Structural interpretations of the tectonic grain of orogenic mountain belts have often been based on the study of potential field data. The steep architecture of mountain belts can be highlighted by the inclination of the magnetic field and by the persistence of aeromagnetic lineaments with depth. With respect to seismology, matched filtering has proven to be very useful for linking seismicity with deep-seated tectonic structures by separating short-wavelength anomalies, that originate from shallow depths, from long-wavelength anomalies that generally originate at greater depths. Between 2008 and 2010 more than 300 low-magnitude earthquakes occurred 20 km SE of Brussels (Belgium). Thanks to a locally deployed temporary seismic network covering the epicentral area, very small events could be detected (magnitude variation between ML -0.7 and ML 3.2). The spatial distribution of the hypocenter locations show a dense spatial cluster displaying a narrow, 1.5-km long, NW-SE oriented fault zone at a depth range between 5 and 7 km, located in the Cambrian basement rocks of the Lower Palaeozoic Anglo-Brabant Massif. Its NW-SE orientation is in agreement with the structural grain in this part of the Brabant Massif. In order to find a relevant tectonic structure that could correspond to the 2008-2010 seismic swarm, we present a full seismotectonic analysis linking local geology to the seismic swarm. A systematic filtering approach was applied in which the magnetic field was carefully bandpass filtered to generate different aeromagnetic maps that highlight sources near the hypocenter depths. Filtering demonstrates that the structure responsible for the seismic swarm is limited in length as it is bordered at both ends by magnetic lineaments with different orientations than the seismic swarm. These observations explain the rather limited spatial distribution of the swarm, both in a vertical and horizontal direction. Although few of the largest historical seismic events in

  10. Structural Evolution in the Aar Massif (Central Alps): First attempts of linking the micron- to the kilometer-scale

    NASA Astrophysics Data System (ADS)

    Wehrens, P.; Baumberger, R.; Herwegh, M.

    2012-04-01

    The Aar massif belongs to the external massifs of the Alps and is mainly composed of granitoids and gneisses. Despite numerous detailed studies in the past decades, the overall exhumation history and the associated massif internal deformation (internal strain distribution and its evolution in time, kinematics etc.) are largely unknown at present. In this project, we aim to investigate the role of shear zones in the deformation history at a variety of scales. In this context it is important to understand their microstructural evolution, the involved deformation processes, kinematics and relative ages as well as the associated changes in rheology. A GIS-based remote-sensing structural map, verified by fieldwork, (see Baumberger et al., this volume) served as base for our investigations. Lithological differences between the units (Central Aare granite, ZAGr; Grimsel granodiorte, GrGr and gneisses) cause strain to localize along these contacts. Furthermore, the initial magmatic differentiation in the granitoids locally controls the Alpine deformational overprint because of differences in effective viscosity during solid-state deformation. This behavior is illustrated by the increase of foliation intensity and the number of shear zones per rock volume from ZAGr to GrGr. Preliminary results show that deformation at the N boundary of the Aar massif has to be distinguished from the central and the southern part. In the North steep NE-SW trending foliations and shear zones with subvertical lineations represent the major structures. The shear zones acted both as normal faults and as reverse faults, which mostly used pre-existing lithological boundaries between the different gneiss units. In a later stage, E-W trending shear zones and shear bands with moderate dipping angles cross cut the earlier structures. They always show a top to the North component and might be related to the late north directed movements of the Aar massif. Yet, no absolute age dating has been performed

  11. The tectonic history of the Niğde-Kırşehir Massif and the Taurides since the Late Mesozoic: Paleomagnetic evidence for two-phase orogenic curvature in Central Anatolia

    NASA Astrophysics Data System (ADS)

    Ćinku, Mualla Cengiz; Hisarli, Z. Mümtaz; Yılmaz, Yücel; Ülker, Beyza; Kaya, Nurcan; Öksüm, Erdinç; Orbay, Naci; Özbey, Zeynep Üçtaş

    2016-03-01

    The Niğde-Kırşehir Massif, known also as the Central Anatolian Block, is bordered by the sutures of the Neotethys Ocean. The massif suffered several deformation phases during and after the consumption of the surrounding oceans and the postcollisional events of the continental pieces of Anatolia in latest Cretaceous to Miocene. Previous paleomagnetic studies on the Niğde-Kırşehir Massif and its surroundings displayed either insufficient data or have claimed large rotations and/or remagnetization. In order to understand the tectonic history of the Niğde-Kırşehir Massif and its adjacent blocks we have sampled 147 different sites in the age range of Upper Jurassic to Miocene from the Niğde-Kırşehir Massif throughout its W/SW and E/SE boundaries and the central-southeastern Taurides. The results display that except the limestones in central Taurides, all rocks examined carry a primary magnetization. Among these an important finding is that rotations between the massif and the central-eastern Taurides indicate an oroclinal bending with counterclockwise rotation of R = 41.1° ± 7.6° in the SE and clockwise rotation of R = 45.9° ± 9.3° in the central Taurides from Upper Cretaceous rocks with respect to the African reference direction. Paleomagnetic rotations in the SE Taurides are compatible with the vergent direction of the thrusts generated from consumption of the Intra-Tauride Ocean prior to postcollisional convergence between Taurides and the massif. In the central Taurides it has been shown that the clockwise rotation of 45.9 ± 9.3 started in Middle Eocene, because of a remagnetization in Upper Cretaceous limestones. The deformation was linked to the final closure of the southern Neotethys and the collision between the African and Eurasian plates. In the Niğde-Kırşehir Massif counterclockwise rotation up to 25.5° ± 7.3° is recognized during Middle Eocene and interpreted in terms of block rotation together with the Taurides. After the Miocene a

  12. A Comparative Analysis on Models of Higher Education Massification

    ERIC Educational Resources Information Center

    Pan, Maoyuan; Luo, Dan

    2008-01-01

    Four financial models of massification of higher education are discussed in this essay. They are American model, Western European model, Southeast Asian and Latin American model and the transition countries model. The comparison of the four models comes to the conclusion that taking advantage of nongovernmental funding is fundamental to dealing…

  13. Massification and the Large Lecture Theatre: From Panic to Excitement

    ERIC Educational Resources Information Center

    Arvanitakis, James

    2014-01-01

    In this article I examine the role of the contemporary university in light of the mass increase in class sizes that has occurred on an international scale. While we may look nostalgically back to a time when lectures numbered a few hundred students and tutorials had as few as ten, massification at undergraduate level is an inescapable fact of…

  14. Entrepreneurship and Image Management in Higher Education: Pillars of Massification

    ERIC Educational Resources Information Center

    Mount, Joan; Belanger, Charles H.

    2004-01-01

    Mass higher education has taken hold in the developed nations, and a widely held belief exists that higher education is a "right." With massification have emerged two notable trends: an entrepreneurial emphasis fuelled by the revenue-cost squeeze ensuing from reduced and realigned government funding; and a quest for differentiation through "Image…

  15. Massification in Higher Education: Large Classes and Student Learning

    ERIC Educational Resources Information Center

    Hornsby, David J.; Osman, Ruksana

    2014-01-01

    In introducing the special issue on "Large Class Pedagogy: Opportunities and Challenges of Massification" the present editorial takes stock of the emerging literature on this subject. We seek to contribute to the massificaiton debate by considering one result of it: large class teaching in higher education. Here we look to large classes…

  16. Occurrence of springs in massifs of crystalline rocks, northern Portugal

    NASA Astrophysics Data System (ADS)

    Pacheco, Fernando António Leal; Alencoão, Ana Maria Pires

    2002-02-01

    An inventory of artesian springs emerging from fractures (fracture springs) was conducted in the Pinhão River Basin and Morais Massif, northern Portugal, comprising an area of approximately 650 km2. Over 1,500 springs were identified and associated with geological domains and fracture sets. Using cross-tabulation analysis, spring distributions by fracture sets were compared among geological environments, and the deviations related to differences in rock structure and, presumably, to differences in deformational histories. The relation between spring frequencies and rock structures was further investigated by spectral determination, the model introduced in this study. Input data are the spring frequencies and fracture lengths in each geological domain, in addition to the angles between fracture strikes and present-day stress-field orientation (θ). The model's output includes the so-called intrinsic densities, a parameter indexing spring occurrence to factors such as fracture type and associated deformational regime and age. The highest densities (12.2 springs/km of lineament) were associated with young shear fractures produced by brittle deformation, and the lowest (0.1) with old tensional and ductile fractures. Spectral determination also relates each orientation class to a dominant structural parameter: where spring occurrence is controlled by θ, the class is parallel to the present-day stress-field orientation; where the control is attributed to the length of fractures, the spring occurrence follows the strike of large-scale normal faults crossing the region. Résumé. Un inventaire des sources artésiennes émergeant de fractures (sources de fractures) a été réalisé dans le bassin de la rivière Pinhão et dans le massif de Morais, dans le nord du Portugal, dans une région couvrant environ 650 km2. Plus de 1,500 sources ont été identifiées et associées à des domaines géologiques et à des ensembles de fractures. Grâce à une analyse de tableaux

  17. A multidisciplinary study on the emplacement mechanism of the Qingyang-Jiuhua Massif in Southeast China and its tectonic bearings. Part I: Structural geology, AMS and paleomagnetism

    NASA Astrophysics Data System (ADS)

    Wei, W.; Chen, Y.; Faure, M.; Shi, Y. H.; Martelet, G.; Hou, Q. L.; Lin, W.; Le Breton, N.; Wang, Q. C.

    2014-06-01

    During the Cretaceous, the South China Block (SCB) experienced a widely distributed extensional event including numerous plutons emplacement and basin opening. Investigations on the tectonic regime coeval with pluton emplacement, and emplacement mechanism of the pluton remain relatively rare in the SCB. In order to address these questions, a multidisciplinary approach, including field structural and petrographic observations, anisotropy magnetic susceptibility (AMS) and paleomagnetic analyses, was carried out on the Qingyang-Jiuhua granitic massif which intrudes into the Lower Yangtze fold belt in the northeastern part of the SCB. The Qingyang-Jiuhua massif is composed of the granodioritic Qingyang and monzogranitic Jiuhua plutons dated by zircon U-Pb method at ca. 142 Ma, and ca. 131 Ma, respectively. Our structural observations show that the intrusion of the Qingyang-Jiuhua massif does not modify the fold strike. A weak ductile deformation of the country rocks and granitoid can be only observed in the boundary zone with limited contact metamorphism. In the contact aureole of the massif, the foliation follows the pluton contour, and the mineral lineation is rare. When present, it exhibits a down-dip attitude. Field and microstructural observations indicate isotropic magmatic textures in most parts of the massif. The AMS analysis of 93 sites reveals weak values for the anisotropy degree (PJ < 1.2) and oblate magnetic fabric dominance (T > 0) for most of the measured samples. Two principal foliation patterns are identified: horizontal foliations in the center of the plutons, and vertical foliations on the boundaries. Magnetic lineation strike is largely scattered, and weakly inclined at the scale of the entire massif. The paleomagnetic investigations indicate that (a) the younger Jiuhua pluton did not produce a remagnetization in the older Qingyang pluton, (b) no relative movement can be observed between these two plutons, (c) the entire massif did not experience

  18. The Apollo 17 samples: The Massifs and landslide

    NASA Technical Reports Server (NTRS)

    Ryder, Graham

    1992-01-01

    More than 50 kg of rock and regolith samples, a little less than half the total Apollo 17 sample mass, was collected from the highland stations at Taurus-Littrow. Twice as much material was collected from the North Massif as from the South Massif and its landslide (the apparent disproportionate collecting at the mare sites is mainly a reflection of the large size of a few individual basalt samples). Descriptions of the collection, documentation, and nature of the samples are given. A comprehensive catalog is currently being produced. Many of the samples have been intensely studied over the last 20 years and some of the rocks have become very familiar and depicted in popular works, particularly the dunite clast (72415), the troctolite sample (76535), and the station 6 boulder samples. Most of the boulder samples have been studied in Consortium mode, and many of the rake samples have received a basic petrological/geochemical characterization.

  19. K-alkaline rocks and lamproites of Tomtor massif

    NASA Astrophysics Data System (ADS)

    Vladykin, Nikolai

    2015-04-01

    Tomtor massif of the largest volcano-plutonic deep alkaline-carbonatite massifs world central type. Area of massif occupy 240 km2 and carbonatites stock is 40 km2. The super large deposit of Nb, TR, Y, Sc, Sr ,REE (Frolov et al. 2001)is found within the massif. The numerical publication are devoted to the ore mineralization there. But the geological struc-ture of the massif and the chemistry of its constituting rocks are not well understood. We obtained new ages based on U-Pb zircon and mica Ar-Ar method (Kotov, Vladykin et al. 2014 Vladykin et al. 2015). The massif was created in 2 stages: 700 and 400 Ma. We (Vla-dykin et al 1998) found rocks of lamproite series and proposed a new scheme of magmatism and the ore.genesis (Vladykin 2007, 2009). Biotite - pyroxenite, peridotite originated in first stage and then intruded iolites, nepheline and alkali syenite. Syenites occupy 70% of -massif and contain 12-13% K2O and 2-4% Na2O showing the K-alkaline-ultramafic nature of Tomtor volcano-plutonic massif (Vladykin 2009). The first stage was accomplished by nelsonitov calcite, dolomite and ankerite carbonatites. Second stage (400Ma) volcanics picrite - lamproite veins and eruptive breccias meli-lite, melanephelinites, tinguaites appered. These rocks are cut by carbonatites of second stage. It was finished by intensive explosive eruption of a silicate (lamproite) tuffs lavobrec-cia kimberlite formed Ebelyakhdiamondiferous placer, melilite rocks in diatremes (feeders), as well as carbonate-phosphate (kamaforite) explosive tuffs with siderite ores. This carbona-tite complex is preserved within the subsidence caldera. Tuff eruption in conjunction with gas and hydrothermal activity determined its rare metal mineralization. These rocks contain to: Nb- 21%, TR-15%, Y-1.5%, Sc-1%, Zr- 0,5% Zn-, Sr-6%, Ti-8%, Ba-4%, V - 8000 ppm, Be- 300 ppm, Ga- 80 ppm, Cr- 1200ppm, Ni- 230 ppm, Mo- 145 ppm, Pb- 4300 ppm, Th- 1500 ppm, U-193 ppm. Picrite - olivine (rare leucite) lamproite and

  20. The Lassell massif-A silicic lunar volcano

    NASA Astrophysics Data System (ADS)

    Ashley, J. W.; Robinson, M. S.; Stopar, J. D.; Glotch, T. D.; Hawke, B. Ray; van der Bogert, C. H.; Hiesinger, H.; Lawrence, S. J.; Jolliff, B. L.; Greenhagen, B. T.; Giguere, T. A.; Paige, D. A.

    2016-07-01

    Lunar surface volcanic processes are dominated by mare-producing basaltic extrusions. However, spectral anomalies, landform morphology, and granitic or rhyolitic components found in the Apollo sample suites indicate limited occurrences of non-mare, geochemically evolved (Si-enriched) volcanic deposits. Recent thermal infrared spectroscopy, high-resolution imagery, and topographic data from the Lunar Reconnaissance Orbiter (LRO) show that most of the historic "red spots" and other, less well-known locations on the Moon, are indeed silica rich (relative to basalt). Here we present a geologic investigation of the Lassell massif (14.65°S, 350.96°E) near the center of Alphonsus A basin in Mare Nubium, where high-silica thermal emission signals correspond with morphological indications of viscous (possibly also explosive) extrusion, and small-scale, low-reflectance deposits occur in a variety of stratigraphic relationships. Multiple layers with stair-step lobate forms suggest different eruption events or pulsing within a single eruption. Absolute model ages derived from crater size-frequency distributions (CSFDs) indicate that the northern parts of the massif were emplaced at ∼4 Ga, before the surrounding mare. However, CSFDs also indicate the possibility of more recent resurfacing events. The complex resurfacing history might be explained by either continuous resurfacing due to mass wasting and/or the emplacement of pyroclastics. Relatively low-reflectance deposits are visible at meter-scale resolutions (below detection limits for compositional analysis) at multiple locations across the massif, suggestive of pyroclastic activity, a quenched flow surface, or late-stage mafic materials. Compositional evidence from 7-band UV/VIS spectral data at the kilometer-scale and morphologic evidence for possible caldera collapse and/or explosive venting support the interpretation of a complex volcanic history for the Lassell massif.

  1. Miocene mass-transport sediments, Troodos Massif, Cyprus

    USGS Publications Warehouse

    Lord, A.R.; Harrison, R.W.; BouDagher-Fadel, M.; Stone, B.D.; Varol, O.

    2009-01-01

    Sediment mass-transport layers of submarine origin on the northern and southern flanks of the Troodos ophiolitic massif are dated biostratigraphically as early Miocene and late Miocene, respectively and therefore represent different seismogenic events in the uplift and erosional history of the Troodos terrane. Analysis of such events has potential for documenting Miocene seismic and uplift events regionally in the context of changing stress field directions and plate vectors through time. ?? 2009 The Geologists' Association.

  2. The French Atlantic littoral and the Massif Armoricain, part 3

    NASA Technical Reports Server (NTRS)

    Verger, F. (Principal Investigator); Scanvic, J. Y.; Monget, J. M.

    1977-01-01

    The author has identified the following significant results: (1) An original map of lineaments of the Armorican Massif and the Vendean platform was prepared. (2) Validity of spatial information through comparison with maps of various kinds, such as geological, geophysical, morphological, etc., was verified. (3) It was confirmed that LANDSAT images, in many cases, reflect data on deep phenomena which were only accessible geophysically and by means of borings. Tectonic domains were outlined, and known lineaments were extended.

  3. Complete Alpine reworking of the northern Menderes Massif, western Turkey

    NASA Astrophysics Data System (ADS)

    Cenki-Tok, B.; Expert, M.; Işık, V.; Candan, O.; Monié, P.; Bruguier, O.

    2016-07-01

    This study focuses on the petrology, geochronology and thermochronology of metamorphic rocks within the northern Menderes Massif in western Turkey. Metasediments belonging to the cover series of the Massif record pervasive amphibolite-facies metamorphism culminating at ca. 625-670 °C and 7-9 kbars. U-Th-Pb in situ ages on monazite and allanite from these metapelites record crustal thickening and nappe stacking associated with the internal imbrication of the Anatolide-Taurides platform during the Eocene. In addition, new 39Ar/40Ar single muscovite grain analyses on deformed rocks were performed in three localities within the northern Menderes Massif and ages range from 19.8 to 25.5 Ma. These mylonites may be related to both well-known detachments, Simav to the north and Alaşehir to the south, which accommodate Oligo-Miocene exhumation of the Menderes core complex. U-Th-Pb data on monazite grains (22.2 ± 0.2 Ma) from migmatites emplaced within the Simav detachment confirm these ages.

  4. The Front of the Aar Massif: A Crustal-Scale Ramp Anticline?

    NASA Astrophysics Data System (ADS)

    Herwegh, Marco; Mock, Samuel; Wehrens, Philip; Baumberger, Roland; Berger, Alfons; Wangenheim, Cornelia; Glotzbach, Christoph; Kissling, Edi

    2015-04-01

    The front of the Aar Massif (Swiss Central Alps) is characterized by Paleozoic basement rocks exposed at altitudes of more than 4600m above sea level, followed by a steeply north dipping Mesozoic sedimentary cover and overlying Helvetic nappes. The sediments turn into subhorizontal orientations just few kilometers to the N, where the top of the basement is situated at depths of about 7000m below sea level. What is the origin of this vertical jump of about 12000m of the basement rocks over such short horizontal distances? Recent structural investigations at the Basement-Cover contact indicate a complex structural evolution involving reactivation of extensional faults and inversion of half-grabens during early compressional stages. In the internal parts of the Aar Massif a general steepening of the faults resulted with progressive compression. In the northern frontal part, however, a new spaced cleavage evolved, which is dipping with 20-30° to the SE. In places, the new cleavage in the basement rocks is intense and pervasive and correlates with a steepening of the basement-cover contact and its offsets of several tens to hundreds of meters. Hence strain is strongly partitioned in a large number of high strain zones, which cover a cumulative thickness of at least 2000m, eventually even much more considering subsurface continuation. The Mesozoic sediments affected by this large-scale deformation zone are either intensely ductile folded in the case of limestones or faulted and imbricated in the case of dolomites. These differences in deformation style result from the deformation conditions of about < 250-300°C, where calcite still deforms in a ductile manner, while dolomite and crystalline basement preferentially undergo brittle deformation in combination of dissolution-precipitation processes. In a large-scale point of view, we suggest that the high strain domain in the crystalline basement in fact represents a crustal-scale several kilometers wide shear zone, which

  5. Petrostructural evolution of the Beni Bousera peridotite massif (Rif belt, Morocco)

    NASA Astrophysics Data System (ADS)

    Frets, E. C.; Tommasi, A.; Garrido, C. J.; Vauchez, A. R.; Mainprice, D.; Amri, I.; Targuisti, K.

    2012-12-01

    Extension of continental lithosphere occurs in continental rifts, such as the East African, Baikal and Rio Grande rifts, and active convergent continental margins, such as in the Himalayas and the Alps. While the mechanisms of crustal thinning are increasingly understood, the processes governing the thinning of the lithospheric subcontinental mantle still remain barely constrained. Detailed structural and petrological mapping associated with a thorough microstructural study in the Beni Bousera orogenic peridotite (Rif Belt, N Morocco) allows constraining the tectono-metamorphic evolution produced by exhumation of the subcontinental lithospheric mantle in a lithospheric-scale shear zone. The Beni Bousera massif is composed by four tectono-metamorphic domains showing consistent kinematics, marked by a pervasive shallowly-dipping foliation bearing a NW-SE stretching lineation, which progressively rotates towards a N20-N30 trend in the NE, lowermost part of the massif. From top to bottom: garnet-spinel mylonites, Ariègite subfacies fine-grained porphyroclastic spinel peridotites, Ariègite-Seiland subfacies porphyroclastic- and Seiland subfacies coarse-porphyroclastic to coarse-granular spinel peridotites. Microstructures and crystal preferred orientations (CPO) in the four domains are consistent with deformation by dominant dislocation creep, but the continuous increase in average olivine grain size and decrease in the recrystallized volume fraction indicate decreasing work rates from top to bottom. The microstructures are consistent with the variation in synkinematic pressure and temperature conditions, which range from 900°C-2.0 GPa in grt-sp mylonites and 1150°C-1.8 GPa in the Seiland domain. The diffuse compositional layering as well as the microstructures and CPO in the Seiland domain suggest deformation in presence of melt. Gravitational instabilities due to local melt accumulation may account for the small areas bearing a vertical lineation in this domain

  6. Contrasting lithospheric mantle domains beneath the Massif Central (France) revealed by geochemistry of peridotite xenoliths

    NASA Astrophysics Data System (ADS)

    Lenoir, Xavier; Garrido, Carlos J.; Bodinier, Jean-Louis; Dautria, Jean-Marie

    2000-09-01

    -Variscan) lithospheric block involved in the Variscan belt. Conversely, the fertile composition and the DMM signature of the southern domain evoke more juvenile lithospheric mantle, possibly accreted or rejuvenated during the Variscan orogeny. Geophysical data indicate that asthenospheric upwelling beneath Massif Central is focused beneath the southern domain and follows a NW-SE trend, roughly parallel to Variscan structures in the crust. Though poorly constrained in direction, the limit between the two SCLM domains recognised in this study is consistent with this trend. This may suggest a link between the inherited architecture of the SCLM and channelling of asthenospheric upwelling. Secular variations in xenolith geochemistry, as well as correlations between trace element data and geophysical anomalies, suggest that the geochemical imprint of Cenozoic plume upwelling on SCLM xenoliths is limited to selective enrichments in U, Sr and Pb relative to Th and REE.

  7. Cenozoic denudation of the Menderes Massif and its geodynamic framework: slab tear or not?

    NASA Astrophysics Data System (ADS)

    Gessner, Klaus; Gallardo, Luis; Markwitz, Vanessa; Ring, Uwe; Thomson, Stuart

    2014-05-01

    Despite having experienced similar rates of convergence during the Alpine Orogeny, the Hellenides and Anatolides display fundamental differences in crust and mantle structure across a region that broadly coincides with the Aegean coastline of the Anatolian peninsula. The Menderes Massif experienced early Miocene tectonic denudation and surface uplift in the footwall of a north-directed extensional detachment system, followed by late Miocene to recent fragmentation by E-W and NW-SE trending graben systems, resulting in one of Earth's largest metamorphic core complexes. Based on the interpretation of geological and geophysical data we propose that the tectonic denudation of the Menderes Massif was caused by late Oligocene/early Miocene lithosphere scale transtension along the boundary of the Adriatic and Anatolian lithospheric domains, when rollback of the Aegean slab affected the Aegean-Menderes section of the Tethyan Orogen. In addition to previously hypothesized crustal discontinuities, gravity data, earthquake locations and seismic velocity anomalies highlight a north-south oriented boundary in the upper mantle between a fast slab below the Aegean and a slow asthenospheric region below western Turkey. As an alternative to the common interpretation of this discontinuity representing the western edge of a slab tear, we propose that the change in lithospheric structure is the result of how different lithosphere domains responded to roll-back: relatively slow removal of lithospheric mantle below western Anatolia versus trench retreat in the rapidly extending Aegean Sea region. Our findings highlight the significance of lateral variations in subduction-collision systems for the formation of continental plateaux and metamorphic core complexes.

  8. Timing and Kinematics of Cretaceous to Paleogene inversion at the SE margin of the Central European Basin System: Part 2, Thermochronology

    NASA Astrophysics Data System (ADS)

    Hoffmann, V.-E.; Dunkl, I.; von Eynatten, H.; Jähne, F.; Voigt, T.; Kley, J.

    2009-04-01

    mixed age information two different age groups can be recognized. A major group that is similar to the one reported above points to a short but intense pulse of exhumation and inversion in Coniacian to Campanian time. A younger, less significant age cluster yields information on a second phase of cooling and exhumation in the Paleocene-Eocene. The length distribution of AFT data leads to the assumption of rapid, partially multi-phase, exhumation events. In addition, the data of this study provides indications for thick Jurassic burial that likely reflect phases of Mesozoic extensional tectonics in at least parts of the CEBS. Jacobs, J., Breitkreuz, C. (2003): Zircon and apatite fission-track thermochronology of Late Carboniferous volcanic rocks of the NE German Basin. International Journal of Earth Sciences (Geologische Rundschau), 92, 165-172. Thomson, S., Brix, M., Carter, A. (1997): Late Cretaceous denudation of the Harz Massif assessed by apatite fission track analysis. In: G. Büchel and H. Lützner (Editors), Regionale Geologie von Mitteleuropa, 149. Hauptversammlung Deutsche Geologische Gesellschaft, Jena. Schriftenreihe der Deutschen Geologischen Gesellschaft, 3, 115. Thomson, S.N., Zeh, A. (2000): Fission-track thermochronology of the Ruhla Crystalline Complex:. New constraints on the post-Variscan thermal evolution of the NW Saxo-Bohemian Massif. Tectonophysics, 324, 17-35. Ventura, B., Lisker, F., Kopp, J. (2003): Apatite fission track data from the dill-core Züllsdorf 1/63: implications for the reconstruction of the post Variscan exhumation of the Mid German Crystalline High. Zeitschrift für Geologische Wissenschaften, 31, 251-261. Voigt, T., Wiese, F., von Eynatten, H., Franzke, H.-J. & Gaupp, R. (2006): Facies evolution of syntectonic Upper Cretaceous deposits in the Subhercynian Cretaceous Basin and adjoining areas (Germany). Zeitschrift der Deutschen Gesellschaft für Geowissenschaften, 157/2, 203-244.

  9. Social Class Barriers of the Massification of Higher Education in Taiwan

    ERIC Educational Resources Information Center

    Ru-Jer, Wang

    2012-01-01

    In recent years, the rapid growth of higher education in Taiwan has led to an essential shift from education for the elite to the massification of higher education. Although this massification is making higher education more accessible, one of the main concerns is whether opportunities for higher education are the same among all social classes in…

  10. Massification without Equalisation: The Politics of Higher Education, Graduate Employment and Social Mobility in Hong Kong

    ERIC Educational Resources Information Center

    Lee, Siu-yau

    2016-01-01

    This article explains why the massification of higher education in Hong Kong has, contrary to the predictions of received wisdom, failed to enhance the upward social mobility of the youth in the city. Building upon recent literature in political science, it argues that massification can take different forms, which in turn determine the effects of…

  11. Higher Education, Changing Labour Market and Social Mobility in the Era of Massification in China

    ERIC Educational Resources Information Center

    Mok, Ka Ho; Wu, Alfred M.

    2016-01-01

    This article attempts to investigate the relationship between the massification of higher education, labour market and social mobility in contemporary China. Though only a short period of time has elapsed from elite to mass education, China's higher education has been characterised as a wide, pervasive massification process. Similar to other East…

  12. Mohorovicic discontinuity depth analysis beneath North Patagonian Massif

    NASA Astrophysics Data System (ADS)

    Gómez Dacal, M. L.; Tocho, C.; Aragón, E.

    2013-05-01

    The North Patagonian Massif is a 100000 km2, sub-rectangular plateau that stands out 500 to 700 m higher in altitude than the surrounding topography. The creation of this plateau took place during the Oligocene through a sudden uplift without noticeable internal deformation. This quite different mechanical response between the massif and the surrounding back arc, the short time in which this process took place and a regional negative Bouguer anomaly in the massif area, raise the question about the isostatic compensation state of the previously mentioned massif. In the present work, a comparison between different results about the depth of the Mohorovicic discontinuity beneath the North Patagonian Massif and a later analysis is made. It has the objective to analyze the crustal thickness in the area to contribute in the determination of the isostatic balance and the better understanding of the Cenozoic evolution of the mentioned area. The comparison is made between four models; two of these were created with seismic information (Feng et al., 2006 and Bassin et al., 2000), another model with gravity information (Barzaghi et al., 2011) and the last one with a combination of both techniques (Tassara y Etchaurren, 2011). The latter was the result of the adaptation to the work area of a three-dimensional density model made with some additional information, mainly seismic, that constrain the surfaces. The work of restriction and adaptation of this model, the later analysis and comparison with the other three models and the combination of both seismic models to cover the lack of resolution in some areas, is presented here. According the different models, the crustal thickness of the study zone would be between 36 and 45 Km. and thicker than the surrounding areas. These results talk us about a crust thicker than normal and that could behave as a rigid and independent block. Moreover, it can be observed that there are noticeable differences between gravimetric and seismic

  13. Petrogenetic characteristics of mafic-ultramafic massifs in Nizhne-Derbinsk complex (East Sayan Mountains)

    NASA Astrophysics Data System (ADS)

    Cherkasova, T.; Chernishov, A.; Goltsova, Yu; Timkin, T.; Abramova, R.

    2015-11-01

    The article describes the results of petrographic, petrochemical, petrofabric, mineralogical and geochemical studies of the major rock groups potentially Cu, Ni, Pt ore- bearing mafic-ultramafic massifs in the Nizhne- Derbinsk complex (Eastern Sayan Mountains). Based on the data interpretation the investigated massifs can be classified as peridotite- pyroxenite-gabbronorite formation of geosynclinal regime in Altai-Sayan folding area. Significant massif deformation occurred during the final post-consolidation formation stage. The petrographic features of gabbro and petrofabric patterns of the rock-forming minerals in the Burlakski and Nizhne-Derbinsk massifs indicated the fact that massifs were involved in the accretion-collisional development stage of the Central Asian folding belt during the final formation stages the Nizhne-Derbinsk complex.

  14. Zirconology of ultrabasic rocks of the Karabash massif (Southern Urals)

    NASA Astrophysics Data System (ADS)

    Krasnobaev, A. A.; Valizer, P. M.; Anfilogov, V. N.; Sergeev, S. A.; Rusin, A. I.; Busharina, S. V.; Medvedeva, E. V.

    2016-07-01

    Dating of zircon (SHRIMP) from dunite and harzburgite of the Karabash massif was carried out for the first time. Relics of ancient crystals (1940 ± 30 Ma in harzburgite, 1860 ± 16 Ma in dunite) provide evidence for the Paleoproterozoic age of the protolith. The morphological peculiarities of zircon crystals allow us to assume differentiation of the magmatic source 1720 m. y. ago. The major variety of zircons indicates stages of metamorphic evolution in the Neoproterozoic (530-560 Ma) and Early-Late Ordovician (440-480 Ma).

  15. Thermal history and extensional exhumation of a high-temperature crystalline complex (Hırkadağ Massif, Central Anatolia)

    NASA Astrophysics Data System (ADS)

    Lefebvre, Côme; Kalijn Peters, M.; Wehrens, Philip C.; Brouwer, Fraukje M.; van Roermund, Herman L. M.

    2015-12-01

    The Central Anatolian Crystalline Complex (CACC) is a large continental domain exposed in central Turkey that was affected by high temperature metamorphism during the Late Cretaceous. As a result of this event, Paleozoic sediments became metamorphosed, initially under Barrovian conditions, then overprinted locally by high temperature-low pressure metamorphism, and intruded by widespread batholiths. In this study we focus on the crystalline Hırkadağ Massif located in the central part of the CACC, where we applied an integrated approach involving metamorphic, structural and geochronological analysis in order to elucidate its tectonic history from burial to exhumation. Our metamorphic study reveals that conditions of metamorphism reached ~ 7-8 kbar/700 °C and were relatively homogeneous at the scale of the Hırkadağ Massif. Coeval with the regional metamorphism, the rocks were intensely deformed as reflected by isoclinal folding, the development of a pervasive foliation and top-to-the-SE shearing. This was followed by decompression to pressures of ~ 3-4 kbar at 800 °C, which may be linked to the emplacement of local granodioritic intrusions at ~ 77 Ma. Subsequent cooling of the Hırkadağ high-grade metamorphic and intrusive rocks is indicated by 40Ar/39Ar cooling ages of 68.8 ± 0.9 Ma (biotite) and 67.0 ± 1.2 Ma (potassium feldspar). Evidence for tectonic exhumation has been identified within the marbles at the NE margin of the Hırkadağ Massif, in the form of discrete protomylonitic and mylonitic shear bands showing a consistent N40-60 top-to-NE sense of shear. Further east, the contact between brecciated mylonitic marbles and non-metamorphic conglomerates preserves the typical structural features of an upper-crustal detachment fault. Restoration of the Hırkadağ Massif and the CACC to their late Cretaceous configuration suggests that the LP-HT metamorphism, magmatism and extensional structures evolved as a result of the development and exhumation of a ~ N

  16. Mesoscopic faults in the Bregaglia (Bergell) massif, Central Alps

    NASA Astrophysics Data System (ADS)

    Passerini, P.; Sguazzoni, G.; Marcucci, M.

    1991-11-01

    The strike, direction of dip and pitch of the striae along mesoscopic faults in the Oligocene granodiorite-tonalite of Val Masino-Val Bregaglia (Bergell) are analysed. Most fault planes are steeply dipping, and show strike-slip or oblique-slip motion. Dominant strikes are NNW or NNE. A relative chronology of fault sets is suggested based on the presence of different minerals (chlorite and epidote) on fault planes. The pattern of mesoscopic faults in the Val Masino-Val Bregaglia massif does not follow the earlier tectonic trends of the Pennidic nappe edifice, nor even the trend of the nearby section of the Insubric Line considered at both regional and mesoscopic scales. The mesoscopic analysis of the Val Masino-Val Bregaglia massif thus reveals a fault system largely oblique to the major Alpine lineaments. The observed fault pattern does not reveal traces of thrusting referable to late Alpine orogenic phases, and can be related to subsequent deformation, dominated by strike-slip movements; this pattern does not match the traditional schemes of extensional dip-slip faulting following orogenesis. It records a stage of tectonic evolution which follows nappe emplacement, yet it precedes vertical or extensional post-orogenic tectonics.

  17. On the occurrence of Ctenocheles (Decapoda, Axiidea, Ctenochelidae) in the Bohemian Cretaceous Basin

    PubMed Central

    HYŽNÝ, MATÚŠ; VESELSKÁ, MARTINA KOČOVÁ; DVOŘÁK, PAVEL

    2015-01-01

    Because of close morphological affinities, fossil cheliped fragments of the ghost shrimp Ctenocheles (Decapoda, Axiidea, Ctenochelidae) can be easily misidentified as remains of different decapod crustacean taxa. Re-examination of the Cretaceous decapods deposited in the National Museum in Prague revealed that all supposed specimens of the lobster genus Oncopareia found in the Middle Coniacian calcareous claystones of the Březno Formation, including one of the Fritsch’s original specimens of Stenocheles parvulus, actually belong to Ctenocheles. This material together with newly collected specimens from the same locality, allowed for erection of a new species, Ctenocheles fritschi. Its major chela possesses a serrated ischium and ovoid, unarmed merus; therefore, it is considered a close relative of the extant C. collini and C. maorianus. Ctenocheles fritschi sp. nov. represents the first report on the occurrence of the genus from the Bohemian Cretaceous Basin. It is one of the oldest records of Ctenocheles and simultaneously one of the best preserved fossils of the genus reported to date. Confusing taxonomy of S. parvulus is reviewed and shortly discussed. PMID:25983568

  18. The Auchenorrhyncha fauna of peat bogs in the Austrian part of the Bohemian Forest (Insecta, Hemiptera).

    PubMed

    Holzinger, Werner E; Schlosser, Lydia

    2013-01-01

    The first overview on the Auchenorrhyncha fauna of peat bogs of the Austrian Bohemian Forest is presented. Seven oligotrophic peat bog sites were studied in 2011 by suction sampler ("G-Vac") and 93 Auchenorrhyncha species (with 7465 adult specimens) were recorded. Eleven species (about 18 % of the individuals) are tyrphobiontic or tyrphophilous. The relative species abundance plot is not very steep; the six most abundant species represent 50 % of the individuals. The most common species is Conomelus anceps (17 % of the individuals). Compared to the whole Austrian Auchenorrhyncha fauna, the fauna of peat bogs comprises distinctly more univoltine species and more species hibernating in nymphal stage. Densities of adult Auchenorrhyncha in peat bogs are low in spring (about 10-60 individuals per m²) and high in July, with up to 180 (±50) individuals per m². Disturbed peat bogs have higher species numbers and higher Auchenorrhyncha densities in total, but lower numbers and densities in peat bog specialists. PMID:24039517

  19. Intrusion level of granitic massifs along the Hercynian belt: balancing the eroded crust

    NASA Astrophysics Data System (ADS)

    Vigneresse, J. L.

    1999-06-01

    Hercynian granitoid intrusions form a long (3200 km) belt comparable in size to other batholiths in the world. Six massifs have been selected which encompass Cabeza de Araya (Extremadura, Spain), Guitiriz (Galicia, Spain), Pontivy and Mortagne (Brittany, France), La Marche (Massif Central, France) and Fichtelgebirge (Bavaria, Germany). Detailed gravity surveys over these massifs and subsequent inversion provide their shape at depth. Correlation of the deeper zones with internal structures determine the place of the root zones. The shape of the massifs is examined along the strike of the chain. The emplacement of individual massifs is controlled by local tectonics. Most granites are not deeply rooted, but one massif (Cabeza de Araya, Spain) shows a root zone presently as deep as 14 km. Most have about half of their volume in the first 3 km below the present surface. Estimates of the magma volume transferred result in 1500 km 3 issued from one specific feeder, yielding a total of 70,000 km 3 of magma intruded all along the chain. The depth of emplacement of the granitic massifs does not show any significant trend along the strike of the chain. The shallower massifs in the French Massif Central correspond to more deeply eroded areas in the center of the chain. Their root zone, as well as the change in the dip of the walls, are presently observed at depths ranging between 4 and 6 km in Hercynian granites. Both variations are interpreted as being related to the brittle/ductile transition at the time of emplacement. Gross thermal considerations place the transition at its former place during magma emplacement, indicating that the upper crust has not been eroded by more than 6-8 km. This estimate severely contrasts with models involving a doubled crust.

  20. Taconic collision in SE Penna and Delaware

    SciTech Connect

    Crawford, M.L.; Crawford, W.A.; Hoersch, A.L.; Srogi, L.A.; Wagner, M.E.

    1985-01-01

    Taconic metamorphism and tectonism in SE Pennsylvania and northern Delaware were a result of the collision of a volcanic arc with North America. The Wilmington Complex, the infrastructure of the arc, is presently the highest structural unit. It consists of granulite facies volcanogenic sediments intruded by gabbro and a ca. 500 Ma gabbronorite-charnockite suite. Latest Precambrian-earliest Paleozoic sediments of the Glenarm series were metamorphosed to conditions above the second sillimanite isograd beneath the overthrust hot (700-800/sup 0/C) Wilmington Complex. As the edge of the continent was depressed and heated under the advancing thrust complex, basement-involved nappes of Grenville age rocks (Avondale anticline, Woodville dome) with the Glenarm sedimentary cover were thrust over still rigid autochthonous basement (West Chester Prong). On the NW flank of the orogen, Grenville age gneiss-cored massifs (Honey Brook Upland, Mine Ridge, Trenton Prong), unconformably overlain by lower Paleozoic continental shelf sediments, were involved in the thrusting but metamorphosed only to the greenschist facies. Steep anticlines developed later in the Paleozoic, contributing to the present pattern of northeast trending Grenville basement massifs mantled by overlying units.

  1. Induced seismicity in the Khibiny Massif (Kola Peninsula)

    NASA Astrophysics Data System (ADS)

    Kremenetskaya, Elena O.; Trjapitsin, Victor M.

    1995-10-01

    The topic of this paper is to review recent processes of increasing seismic activity in the Khibiny Massif in the Kcla Peninsula. It is a typical example of induced seismicity caused by rock deformation due to the extraction of more than 2·109 tons of rock mass since the mid-1960s. The dependence of seismic activity on the amount of extracted ore is demonstrated. Some of the induced earthquakes coincide with large mining explosions, thus indicating a trigger mechanism. The largest earthquake, which occurred on 16 April 1989 ( M L= 4.1) could be traced along the surface for 1200 m and observed to a depth of at least 220 m. The maximum measured displacement was 15 20 cm.

  2. Structural geology investigation on Massif Central and Parisian Basin (France)

    NASA Technical Reports Server (NTRS)

    Weecksteen, G. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. Band 5 gives the most information concerning the fracturing in the Massif Central and Parisian Basins. Band 6 and 7 show the fractures emphasized by forest boundaries and by the linear trace of water courses. The most remarkable information drawn from the preliminary investigation of two ERTS-1 images covering two different landscapes, a regular relief of shelving plateau bounded by cuestas having a sedimentary origin and a mountainous region built in crystalline and volcanic rocks, is that the deep structural elements under a thick sedimentary cover can be translated on the surface by indirect criteria. MSS imagery has permitted the Metz fault to be extended towards the west and shows clearly, through land use on the Rhone Valley fluvial deposit, the continuation towards the east of the carboniferous basin of St. Etienne.

  3. Structural investigations in the Massif-Central, France

    NASA Technical Reports Server (NTRS)

    Scanvic, J. Y.

    1974-01-01

    This survey covered the French Massif-Central (where crystalline and volcanic rocks outcrop) and its surrounding sedimentaries, Bassin de Paris, Bassin d'Aquitaine and Rhodanian valley. One objective was the mapping of fracturing and the surveying of its relationship with known ore deposits. During this survey it was found that ERTS imagery outlines lithology in some sedimentary basins. On the other hand, in a basement area, under temperature climate conditions, lithology is rarely expressed. These observations can be related to the fact that band 5 gives excellent results above sedimentary basins in France and generally band 7 is the most useful in a basement area. Several examples show clearly the value of ERTS imagery for mapping linear features and circular structures. All the main fractures are identified with the exception of new ones found both in sedimentaries and basement areas. Other interesting findings concern sun elevation which, stereoscopic effect not being possible, simulates relief in a better way under certain conditions.

  4. Serpentinization and Life: Motivations for Drilling the Atlantis Massif

    NASA Astrophysics Data System (ADS)

    Frueh-Green, G. L.; Lang, S. Q.; Brazelton, W. J.; Schrenk, M. O.

    2014-12-01

    The Atlantis Massif, located at the intersection of the Atlantis transform fault and the Mid-Atlantic Ridge at 30°N, is one of the best-studied oceanic core complexes (OCCs) and is the target of IODP Expedition 357 late 2015. Drilling will address two exciting discoveries in ridge research: off-axis, serpentinite-hosted hydrothermal activity and carbonate precipitation, exemplified by the Lost City hydrothermal field, and the significance of tectono-magmatic processes in forming heterogeneous and variably serpentinized lithosphere as key components of slow spreading ridges. Serpentinization reactions at moderate- to low-temperatures result in alkaline fluids, characterized by elevated concentrations of abiotic hydrogen, methane and low molecular weight hydrocarbons, and which lead to precipitation of carbonate and brucite upon mixing with seawater. These highly reactive systems have major consequences for lithospheric cooling, global geochemical cycles, carbon sequestration and microbial activity. However, little is known about the nature and distribution of microbial communities in subsurface ultramafic environments and the potential for a hydrogen-based deep biosphere in areas of active serpentinization and fluid circulation. The continuous flux of reduced compounds provides abundant thermodynamic energy to drive chemolithoautotrophy, however, carbon availability may be limited in these high pH environments and represent a challenge for microbial growth. Here we review serpentinization processes as fundamental to understanding the evolution of oceanic lithosphere and discuss open questions related to the impact of serpentinization on the subsurface biosphere. Motivations for drilling the shallow subseafloor of the Atlantis Massif include: (1) exploring the extent and activity of the subsurface biosphere in young ultramafic and mafic seafloor; (2) quantifying the role of serpentinization in driving hydrothermal systems, in sustaining microbiological communities

  5. Petrogenesis of massif anorthosites: a perspective from St. Urbain, Quebec

    SciTech Connect

    Gromet, L.P.; Dymek, R.F.

    1985-01-01

    The St. Urbain massif is a post-orogenic anorthosite pluton (approx. 500 km/sup 2/) emplaced within the central high-grade granulite terrain of the Grenville structural province. In contrast to other Grenville anorthosites, primary magmatic features are largely preserved. The massif consists predominantly of andesine anorthosite (AA) of remarkable purity containing abundant plagioclase megacrysts. AA has high K/sub 2/O (approx. 2 wgt.%), very high Sr contents (approx. 1200 ppm) and highly fractionated, low REE contents. Features of AA provide the following insights into anorthosite origins: (1) Crystallization from anorthositic magmas, as evidenced by early crystallization of abundant antiperthitic plag, and igneous emplacement of AA dikes and veins into older, unrelated labradorite anorthosite; (2) in situ crystallization of pyroxene after plag, with no direct evidence of earlier crystallization of mafic minerals from a basaltic parent magma; (3) limited differentiation during crystallization, indicated by small variation in plag and opx and limited variations in plag Sr and REE contents; (4) the involvement of water, suggested by the late igneous crystallization of biotite and the localized grain-boundary replacement of plag by calcic myrmekite (An/sub 80/ + qtz). (5) high temperature, relatively oxidizing conditions, indicated by magmatic hemoilmenite +/- rutile and rare ferropseudobrookite in AA and associated ores. AA crystallized from highly feldspathic, relatively oxidized, somewhat hydrous parent magma with little trapped melt. The development of a hyperfeldspathic parent magma with the requisite geochemical features can be ascribed to hydrous partial melting of mafic (to intermediate) rocks at deep crustal or greater depths, leaving a garnetiferous residue.

  6. The paleoproterozoic Monchetundra mafic massif (Kola Peninsula): New geological and geochronological data

    NASA Astrophysics Data System (ADS)

    Borisenko, E. S.; Bayanova, T. B.; Nerovich, L. I.; Kunakkuzin, E. L.

    2015-11-01

    In view of the absence of an unambiguous intrusive contact between the main mafic rocks varieties in the Monchetundra massif, the latter was considered for a long time as a large complex of syngenetic mafic rocks. On the basis of data derived from study of the outcrops and drill core samples, researchers defined various numbers of zones characterized by certain rock types. The results of geological-petrographic investigations and data on the U-Pb system in zircon and baddeleyite provided grounds for revision of the views on the structure of the massif: at least four groups of different ages of mafic rocks are now definable in the Monchetundra massif. In this communication, we discuss the relations between two groups of mafic rocks and the results of their U-Pb isotopic dating, which imply a long multiphase formation of the massif.

  7. Flash flood in 1714 in the Bohemian-Moravian Highlands - Reconstructing a Catastrophe.

    NASA Astrophysics Data System (ADS)

    Elleder, Libor; Krejčí, Jakub; Šírová, Jolana

    2015-04-01

    Read against the backdrop of the past twenty years with their exceptional frequency of summer floods, records of historical flood events have become highly topical. Aside from the May flood of 1872, the flash flood that occurred at the turn of July and August 1714 in the Bohemian-Moravian Highlands is probably the most important case of its kind in the Czech lands, and may likely be ranked among the most notable occurrences of extreme weather even within the larger Central European context. Within the catchment basin of the Sázava River, the headwater level rose about three meters above the highest floods on the hydrological record and 1.5m above the highest historical flood-mark. Taking into account the time period - i.e., the beginning of the 18th century - some of the concurrent accounts of the flood are uncommonly detailed, containing not only a specification of the damage caused, but also high water mark figures and, at least in broad strokes, a record of the changing water levels over time. The flood caused tremendous material damage at the time, breaching e.g. about 70 fish ponds and destroying essentially all bridges; over 230 people were killed. It was revealed that the area of Žďárské vrchy (Žďár Hills) at the divide of the rivers Loučná, Chrudimka, Sázava, and Svratka which was impacted by the causative extreme precipitation may have measured 800 to 1000 square kilometers. Rough estimates of the headwater flow rate equal about four times current Q100 values. We therefore used the hydrological model Aqualog in order to determine whether an event of this scope was at all realistic. The goal was to assess whether it was realistically possible that precipitation may have been of such scope as to trigger a hydrological response of this intensity.

  8. Cenozoic rejuvenation events of Massif Central topography (France): Insights from cosmogenic denudation rates and river profiles

    NASA Astrophysics Data System (ADS)

    Olivetti, Valerio; Godard, Vincent; Bellier, Olivier

    2016-06-01

    The French Massif Central is a part of the Hercynian orogenic belt that currently exhibits anomalously high topography. The Alpine orogenesis, which deeply marked Western European topography, involved only marginally the Massif Central, where Cenozoic faulting and short-wavelength crustal deformation is limited to the Oligocene rifting. For this reason the French Massif Central is a key site to study short- and long-term topographic response in a framework of slow tectonic activity. In particular the origin of the Massif Central topography is a topical issue still debated, where the role of mantle upwelling is invoked by different authors. Here we present a landscape analysis using denudation rates derived from basin-averaged cosmogenic nuclide concentrations coupled with longitudinal river profile analysis. This analysis allows us to recognize that the topography of the French Massif Central is not fully equilibrated with the present base level and in transient state. Our data highlight the coexistence of out-of-equilibrium river profiles, incised valleys, and low cosmogenically derived denudation rates ranging between 40 mm/kyr and 80 mm/kyr. Addressing this apparent inconsistency requires investigating the parameters that may govern erosion processes under conditions of reduced active tectonics. The spatial distribution of denudation rates coupled with topography analysis enabled us to trace the signal of the long-term uplift history and to propose a chronology for the uplift evolution of the French Massif Central.

  9. Distribution patterns, properties and ages of Pleistocene periglacial slope deposits in the eastern Rhenish Massif

    NASA Astrophysics Data System (ADS)

    Sauer, Daniela; Scholten, Thomas; Felix-Henningsen, Peter; Kadereit, Annette

    2010-05-01

    Pleistocene periglacial slope deposits (PPSD) cover almost continuously the low mountain areas of Germany. They are interpreted as the result of frost weathering, gelisolifluction, cryoturbation, meltwater outwash processes and loess incorporation. Four types of PPSD are distinguished in the German classification system: A Basal Layer consists entirely of debris of the underlying rock, which it usually directly overlies. It occurs in almost every relief position, and several Basal Layers may have formed on top of each other. An Intermediate Layer contains varying proportions of loess. It is only found in relief positions favourable for loess accumulation and preservation. Its position within a vertical sequence of PPSD is usually on top of a Basal Layer. An Upper Layer consists of a mixture of rock debris and loess, and contains generally a lower amount of loess than a possibly underlying Intermediate Layer. It has a remarkably steady thickness of around 50 cm, as confirmed in many studies. The Top Layer is mostly restricted to the surroundings of outcrops of particularly resistant rock in higher regions and mainly consists of rock debris. PPSD were investigated in the eastern Westerwald area, at the eastern edge of the Rhenish Massif, Germany. Parent rock, exposition, position and shape of slope were expected to be factors influencing the occurrence, thickness and properties of the different types of PPSD. Therefore, profiles were excavated on the main rock types in the area, which are shale, quartzite and diabase. On each rock type, profiles were studied along catenas in NW, SW, SE and NE exposition, each catena including a profile in upper, middle and footslope position. In upper slope positions on shale an Upper Layer covers directly the rock, independent of exposition. In downslope direction, still above the mid slope profiles, a Basal Layer appears between the Upper Layer and the rock. In upper slope positions on quartzite, a Basal Layer is already present

  10. Pyroxenites - Melting or Migration?: Evidence from the Balmuccia massif

    NASA Astrophysics Data System (ADS)

    Sossi, Paolo; O'Neill, Hugh

    2014-05-01

    The recognition of pyroxenites in the mantle, combined with their lower solidus temperatures than peridotite, have been proposed as contributors to melting (Pertermann and Hirschmann, 2003; Sobolev et al, 2005; 2007). Geochemical fingerprints of this process invoke an unspecified 'pyroxenite' as the putative source. In reality, mantle pyroxenites are diverse (Downes, 2007), requiring that their mode of origin and compositional variability be addressed. Due to the excellent preservation and exposure of the Balmuccia massif, it has become an archetype for orogenic peridotites, providing information on their composition, field relationships and metamorphic history (Shervais and Mukasa, 1991; Hartmann and Wedepohl, 1993; Rivalenti et al., 1995; Mazzucchelli et al., 2009). The Balmuccia massif consists of fertile lherzolite with subordinate harzburgite and dunite and is riddled with pyroxenite bands, which fall into two suites - Chrome-Diopside (Cr-Di) and Aluminous-Augite (Al-Aug), a pairing present in most massif peridotites. Two-pyroxene thermometry gives temperatures of 850±25°C at 1-1.5 GPa, 500°C lower than asthenospheric mantle at that pressure, meaning they do not preserve their original, high temperature mineralogy. Decimetre-sized Cr-Di bands (≡75% CPX, 25% OPX) occur as initially Ol-free and bound by refractory dunite, but, as the bands are rotated into the plane of foliation, they mechanically incorporate olivine. Al-Aug veins (60% CPX, 25% OPX, 15% Sp) discordantly cut the body, intruding lherzolites which show enrichments in Fe, Al and Ti adjacent to the dykes. Both the Cr-Di suite and the Al-Aug series have indistinguishable Sr-, Nd-isotopic compositions to the host peridotite (Mukasa and Shervais, 1999). The major element compositions of pyroxenes in the Cr-Di bands and those in the surrounding peridotites are identical. Together with isotopic evidence, this suggests a local source, not only chemically but spatially, where a very low degree melt (

  11. Tephrochronology of the Mont-Dore volcanic Massif (Massif Central, France): new 40Ar/39Ar constraints on the Late Pliocene and Early Pleistocene activity

    NASA Astrophysics Data System (ADS)

    Nomade, Sébastien; Pastre, Jean-François; Nehlig, Pierre; Guillou, Hervé; Scao, Vincent; Scaillet, Stéphane

    2014-03-01

    The Mont-Dore Massif (500 km2), the youngest stratovolcano of the French Massif Central, consists of two volcanic edifices: the Guéry and the Sancy. To improve our knowledge of the oldest explosive stages of the Mont-Dore Massif, we studied 40Ar/39Ar-dated (through single-grain laser and step-heating experiments) 11 pyroclastic units from the Guéry stratovolcano. We demonstrate that the explosive history of the Guéry can be divided into four cycles of explosive eruption activity between 3.09 and 1.46 Ma (G.I to G.IV). We have also ascertained that deposits associated with the 3.1-3.0-Ma rhyolitic activity, which includes the 5-km3 "Grande Nappe" ignimbrite, are not recorded in the central part of the Mont-Dore Massif. All the pyroclastites found in the left bank of the Dordogne River belong to a later explosive phase (2.86-2.58 Ma, G.II) and were channelled down into valleys or topographic lows where they are currently nested. This later activity also gave rise to most of the volcanic products in the Perrier Plateau (30 km east of the Mont-Dore Massif); three quarters of the volcano-sedimentary sequence (up to 100 m thick) was emplaced within less than 20 ky, associated with several flank collapses in the northeastern part of the Guéry. The age of the "Fournet flora" (2.69 ± 0.01 Ma) found within an ash bed belonging to G.II suggests that temperate forests already existed in the French Massif Central before the Pliocene/Pleistocene boundary. The Guéry's third explosive eruption activity cycle (G.III) lasted between 2.36 and 1.91 Ma. It encompassed the Guéry Lake and Morangie pumice and ash deposits, as well as seven other important events recorded as centimetric ash beds some 60 to 100 km southeast of the Massif in the Velay region. We propose a general tephrochronology for the Mont-Dore stratovolcano covering the last 3.1 My. This chronology is based on 44 40Ar/39Ar-dated events belonging to eight explosive eruption cycles each lasting between 100 and 200

  12. Preliminary hydrochemical study of Ronda ultramafic massif (South Spain)

    NASA Astrophysics Data System (ADS)

    Vadillo, Iñaki; Urresti, Begoña; Jiménez, Pablo; Martos, Sergio; José Durán, Juan; Benavente, José; Carrasco, Francisco; Pedrera, Antonio

    2016-04-01

    During 2015 more than 70 springs related to the peridotite outcrops of the Ronda mountainous massif, South Spain, have been identified. The field work included "in situ" measurements of physical-chemical parameters (T, EC, pH), and water sampling for major components and stable isotopes of water and DIC. The hydrogeochemical study allowed us to characterize different flow systems: (1) springs with very low to medium electrical conductivities (200-700 μS/cm) and pH below 9.0, and (2) springs with EC above 700 μS/cm and pH above 9.0. The first group of springs are supposed to be linked with surface and subsurface flows. The hydrogeochemical reactions that determine their composition are characterized by the low solubility of minerals, atmospheric CO2 (open system) and active serpentinization reactions that supplies hundreds of ppm of Mg2+. All of them are waters of HCO3-Mg or HCO3-Mg-Na type. The second group of springs drains water with EC above 700 μS/cm and pH over 9. In general, these springs are associated to deep flows connected to regional faults or major tectonic features. Deeper flow enhances water-rock interaction and time of contact, so this system evolves towards a closed system to O2 and CO2. All these waters are old or older than the first group and show reducing features and are of Na-Cl or OH-Ca type.

  13. Deforestation Along the Maya Mountain Massif Belize-Guatemala Border

    NASA Astrophysics Data System (ADS)

    Chicas, S. D.; Omine, K.; Arevalo, B.; Ford, J. B.; Sugimura, K.

    2016-06-01

    In recent years trans-boundary incursions from Petén, Guatemala into Belize's Maya Mountain Massif (MMM) have increased. The incursions are rapidly degrading cultural and natural resources in Belize's protected areas. Given the local, regional and global importance of the MMM and the scarcity of deforestation data, our research team conducted a time series analysis 81 km by 12 km along the Belize-Guatemalan border adjacent to the protected areas of the MMM. Analysis drew on Landsat imagery from 1991 to 2014 to determine historic deforestation rates. The results indicate that the highest deforestation rates in the study area were -1.04% and -6.78% loss of forested area per year in 2012-2014 and 1995-1999 respectively. From 1991 to 2014, forested area decreased from 96.9 % to 85.72 % in Belize and 83.15 % to 31.52 % in Guatemala. During the study period, it was clear that deforestation rates fluctuated in Belize's MMM from one time-period to the next. This seems linked to either a decline in deforestation rates in Guatemala, the vertical expansion of deforestation in Guatemalan forested areas and monitoring. The results of this study urge action to reduce incursions and secure protected areas and remaining forest along the Belize-Guatemalan border.

  14. Terrasar-X Insar Processing in Northern Bohemian Coal Basin Using Corner Reflectors (preliminary Results)

    NASA Astrophysics Data System (ADS)

    Hlaváčová, I.; Halounová, L.; Svobodová, K.

    2012-07-01

    The area of Northern Bohemian coal basin is rich in brown coal. Part of it is undermined, but large areas were mined using open-pit mines. There are numerous reclaimed waste dumps here, with a horse racetrack, roads and in some cases also houses. However, on most of the waste dumps, there are forests, meadows and fields. Above the coal basin, there are the Ore mountains which are suspected to be sliding down to the open mines below them. We installed 11 corner reflectors in the area and monitor them using the TerraSAR-X satellite. One of the reflectors is situated in the area of radar layover, therefore it cannot be processed. We present preliminary results of monitoring the remaining corner reflectors, with the use of 7 TerraSAR-X scenes acquired between June and December 2011. We process whole scene crops, as well as the artificial reflector information alone. Our scene set contains interferometric pairs with perpendicular baselines reaching from 0 to 150 m. Such a configuration allows us to distinguish deformations from DEM errors, which are usual when the SRTM (Shuttle Radar Topography Mission) DEM (X-band) is used for Stripmap data. Unfortunately, most of the area of interest is decorrelated due to vegetation that covers both the Ore mountains and the reclaimed waste dumps. We had to enlarge the scene crop in order to be able to distinguish deformations from the atmospheric delay. We are still not certain about the stability of some regions. For the installed artificial reflectors, the expected deformations are in the order of mm/year. Generally, deformations in the area of interest may reach up to about 5 cm/year for the Ervěnice corridor (a road and railway built on a waste dump). When processing artificial corner reflector information alone, we check triangular sums and perform the processing for all possible point combinations - and that allows us to correct for some unwrapping errors. However, the problem is highly ambiguous.

  15. Paleoproterozoic anorogenic granitoids of the Zheltav sialic massif (Southern Kazakhstan): Structural position and geochronology

    NASA Astrophysics Data System (ADS)

    Tretyakov, A. A.; Degtyarev, K. E.; Sal'nikova, E. B.; Shatagin, K. N.; Kotov, A. B.; Ryazantsev, A. V.; Pilitsyna, A. V.; Yakovleva, S. Z.; Tolmacheva, E. V.; Plotkina, Yu. V.

    2016-01-01

    The basement of the Zheltav sialic massif (Southern Kazakhstan) is composed of different metamorphic rocks united into the Anrakhai Complex. In the southeastern part of the massif, these rocks form a large antiform with the core represented by amphibole and clinopyroxene gneissic granite varieties. By their chemical composition, dominant amphibole (hastingsite) gneissic granites correspond to subalkaline granites, while their petroand geochemical properties make them close to A-type granites. The U-Pb geochronological study of accessory zircons yielded an age of 1841 ± 6 Ma, which corresponds to the crystallization age of melts parental for protoliths of amphibole gneissic granites of the Zheltav Massif. Thus, the structural-geological and geochronological data make it possible to define the Paleoproterozoic (Staterian) stage of anorogenic magmatism in the Precambrian history of the Zheltav Massif. The combined Sm-Nd isotopic—geochronological data and age estimates obtained for detrital zircons indicate the significant role of the Paleoproterozoic tectono-magmatic stage in the formation of the Precambrian continental crust of sialic massifs in Kazakhstan and northern Tien Shan.

  16. The promotion of geotourism in protected areas: a proposal of itinerary through the Matese Massif (Campania and Molise regions, Italy).

    NASA Astrophysics Data System (ADS)

    Rosskopf, Carmen Maria; Filocamo, Francesca; Amato, Vincenzo; Cesarano, Massimo

    2016-04-01

    The Matese Massif is a ca. 1000 km2 wide and NW-SE elongated carbonate relief, located in the inner sector of the Southern Apennine chain. It has a tabular setting with steep structural slopes bordering the central high mountain sector including its major peaks and is crossed from approximately west to east by the border between Campania and Molise regions. The Matese Mountains represent a key area for the comprehension of the geological and tectonic evolution of the Southern Apennines since Mesozoic times. Its long-term geomorphological evolution has been controlled by Quaternary tectonics and climate variations that have allowed the temporary or permanent establishment of various environments and morphodynamics. Deposits and landforms originated by glacial, periglacial, karst and fluvial processes, along with a rich assemblage of tectonic-structural features and landforms of complex origin have given origin to a geological heritage of exceptional value. The geosites actually censured within the Campanian sector of Matese are reported in the Geosites Map of Campania, available at the website of Campania Region and partly included in the Italian Geosites Inventory of ISPRA. The geosites of the Molise sector have been recently assessed within the geosite inventory carried out by Molise University. They are reported in the Geosites Map of Molise, available at the website of Molise Region, and partly included in the ISPRA's National Inventory of Geosites. The Matese area is largely included in protected areas: the Campania portion falls within the Matese Regional Park, established in 2002, while most of the Molise sector falls in the extensive ZPS/SIC IT72222287. To better protect and exploit the unique natural and geological heritage of the Matese Massif, numerous initiatives aimed at the establishment of the National Park of Matese have continued for several years and very recent attempts to promote the Matese Geopark have been made, but unfortunately without any

  17. Soil Collembola communities within Plešné Lake and Čertovo Lake catchments, the Bohemian Forest

    NASA Astrophysics Data System (ADS)

    Čuchta, Peter

    2016-04-01

    The soil Collembola communities were studied for three years in disturbed spruce forest stands in the catchments areas of Čertovo and Plešné Lakes in the Bohemian Forest, Czech Republic. The study was focused on the impact of the windthrow, bark beetle outbreak damage and consecutive changes in the forest stands including soil environment. Four different treatments were selected for the study on both study areas: undamaged (control) forest stands, "dead" forest stands damaged by bark beetle, slightly managed windthrown forest stands left for the natural succession, and freshly harvested windthrown stands. After two years of research a total of 7,294 Collembola specimens were recorded belonging to 93 species. We recorded the highest collembolan abundance and species richness in the reference stands within catchments of both lakes, while both given parameters were considerably lower in harmed forest stands. To summarize, the disturbance led to a general decrease of Collembola communities.

  18. A Library Response to the Massification of Higher Education: The Case of the University of Zambia Library

    ERIC Educational Resources Information Center

    Kanyengo, Christine Wamunyima

    2009-01-01

    This paper looks at the challenges that libraries in Africa face in responding to massification of higher education by discussing the University of Zambia library's response in library and information resources provision. As a result of massification of higher education, libraries have been forced not only to employ new and different strategies to…

  19. Critical Reflection on the Massification of Higher Education in Korea: Consequences for Graduate Employment and Policy Issues

    ERIC Educational Resources Information Center

    Yeom, Min-ho

    2016-01-01

    The paper critically reviews the results of Korean massification in higher education (HE) and focuses on the consequences related to graduate employment. By analysing statistical data and reviewing related articles, this study explores the process of the massification of HE, investigates major factors influencing the expansion, and analyses and…

  20. Volcanoes of the Tibesti massif (Chad, northern Africa)

    NASA Astrophysics Data System (ADS)

    Permenter, Jason L.; Oppenheimer, Clive

    2007-04-01

    The Tibesti massif, one of the most prominent features of the Sahara desert, covers an area of some 100,000 km2. Though largely absent from scientific inquiry for several decades, it is one of the world’s major volcanic provinces, and a key example of continental hot spot volcanism. The intense activity of the TVP began as early as the Oligocene, though the major products that mark its surface date from Lower Miocene to Quaternary (Furon (Geology of Africa. Oliver & Boyd, Edinburgh (trans 1963, orig French 1960), pp 1-377, 1963)); Gourgaud and Vincent (J Volcanol Geotherm Res 129:261-290, 2004). We present here a new and consistent analysis of each of the main components of the Tibesti Volcanic Province (TVP), based on examination of multispectral imagery and digital elevation data acquired from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). Our synthesis of these individual surveys shows that the TVP is made up of several shield volcanoes (up to 80 km diameter) with large-scale calderas, extensive lava plateaux and flow fields, widespread tephra deposits, and a highly varied structural relief. We compare morphometric characteristics of the major TVP structures with other hot spot volcanoes (the Hawaiian Islands, the Galápagos Islands, the Canary and Cape Verdes archipelagos, Jebel Marra (western Sudan), and Martian volcanoes), and consider the implications of differing tectonic setting (continental versus oceanic), the thickness and velocity of the lithosphere, the relative sizes of main volcanic features (e.g. summit calderas, steep slopes at summit regions), and the extent and diversity of volcanic features. These comparisons reveal morphologic similarities between volcanism in the Tibesti, the Galápagos, and Western Sudan but also some distinct features of the TVP. Additionally, we find that a relatively haphazard spatial development of the TVP has occurred, with volcanism initially appearing in the Central TVP and subsequently

  1. P- T- t evolution of eclogite/blueschist facies metamorphism in Alanya Massif: time and space relations with HP event in Bitlis Massif, Turkey

    NASA Astrophysics Data System (ADS)

    Çetinkaplan, Mete; Pourteau, Amaury; Candan, Osman; Koralay, O. Ersin; Oberhänsli, Roland; Okay, Aral I.; Chen, Fukun; Kozlu, Hüseyin; Şengün, Fırat

    2016-01-01

    The Alanya Massif, which is located to the south of central Taurides in Turkey, presents a typical nappe pile consisting of thrust sheets with contrasting metamorphic histories. In two thrust sheets, Sugözü and Gündoğmuş nappes, HP metamorphism under eclogite (550-567 °C/14-18 kbar) and blueschist facies (435-480 °C/11-13 kbar) conditions have been recognized, respectively. Whereas the rest of the Massif underwent MP metamorphism under greenschist to amphibolite facies (525-555 °C/6.5-7.5 kbar) conditions. Eclogite facies metamorphism in Sugözü nappe, which consists of homogeneous garnet-glaucophane-phengite schists with eclogite lenses is dated at 84.8 ± 0.8, 84.7 ± 1.5 and 82 ± 3 Ma (Santonian-Campanian) by 40Ar/39Ar phengite, U/Pb zircon and rutile dating methods, respectively. Similarly, phengites in Gündoğmuş nappe representing an accretionary complex yield 82-80 Ma (Campanian) ages for blueschist facies metamorphism. During the exhumation, the retrograde overprint of the HP units under greenschist-amphibolite facies conditions and tectonic juxtaposition with the Barrovian units occurred during Campanian (75-78 Ma). Petrological and geochronological data clearly indicate a similar Late Cretaceous tectonometamorphic evolution for both Alanya (84-75 Ma) and Bitlis (84-72 Ma) Massifs. They form part of a single continental sliver ( Alanya- Bitlis microcontinent), which was rifted from the southern part of the Anatolide-Tauride platform. The P- T- t coherence between two Massifs suggests that both Massifs have been derived from the closure of the same ocean ( Alanya- Bitlis Ocean) located to the south of the Anatolide-Tauride block by a northward subduction. The boundary separating the autochthonous Tauride platform to the north from both the Alanya and Bitlis Massifs to the south represents a suture zone, the Pamphylian- Alanya- Bitlis suture.

  2. Geomorphological and sedimentological evidences in the Western Massif of Picos de Europa since the Last Glaciation

    NASA Astrophysics Data System (ADS)

    Ruiz-Fernández, Jesus; Oliva, Marc; Cruces, Anabela; Lopes, Vera; Conceição Freitas, Maria; García-Hernández, Cristina; Nieuwendam, Alexandre; López-Sáez, José Antonio; Gallinar, David; Geraldes, Miguel

    2015-04-01

    The Western Massif of Picos de Europa includes some of the highest peaks of the Cantabrian Mountains. However, the environmental evolution in this massif since the Last Glaciation is still poorly understood. This research provides a new geochronological approach to the sequence of environmental events occurred here since the maximum expansion of glaciers during the last Pleistocene glaciation. The distribution of the glacial landforms suggests four main stages regarding the environmental evolution in the massif: maximum glacial advance, phase of second maximum glacial expansion, Late Glacial and Little Ice Age. A 5.4-m long sedimentological section retrieved from the kame terrace of Belbín, in a mid-height area of the massif, complements the geomorphological interpretation and provides a continuous paleoenvironmental sequence from this area since the Last Glaciation until nowadays. This section suggests that the maximum glacial expansion occurred at a minimum age of 37.2 ka cal BP, significantly prior to the global Last Glacial Maximum. Subsequently, a new glacial expansion occurred around 18.7-22.5 ka cal BP. The melting of the glaciers after this phase generated a shallow lake in the Belbín depression. Lake sediments do not reveal the occurrence of a cold stage during the Late Glacial, whilst, at higher locations, moraine complexes were formed suggesting a glacier readvance. The terrestrification of this lake started at 8 ka cal BP, when Belbín changed to a peaty environment. At 5 ka cal BP human occupation started at the high lands of the massif according to the existence of charcoal particles in the section. The presence of moraines in the highest northern cirques evidences the last phase with formation of small glaciers in the Western Massif of Picos de Europa, corresponding to the Little Ice Age cold event. Since then, the warming climate has led to the melting of these glaciers.

  3. Structural and petrographic analysis of hypabyssal rocks in the central Menderes Massif: implications for the role of transfer zones during detachment faulting

    NASA Astrophysics Data System (ADS)

    Erkül, Fuat; Gürboǧa, Şule; Tatar Erkul, Sibel; Deveci, Zehra

    2014-05-01

    Structural and petrographic analysis of hypabyssal rocks in the central Menderes Massif: implications for the role of transfer zones during detachment faulting Fuat ERKÜL(1), Şule GÜRBOǧA(2), Sibel TATAR ERKÜL(3), Zehra DEVECİ(4) The central Menderes Massif is formed by complex assemblages of transfer zones, detachment faults and associated syn-extensional granitoids in western Turkey. Syn-extensional Salihli and Turgutlu granitoids were widely recognized in the footwall rocks of the Gediz detachment fault, but their hypabyssal equivalents were not described in detail. Hypabyssal rocks discovered during this study include substantial structural data that may shed light into the development of transfer zones during detachment faulting. Hypabyssal rocks are mafic and felsic in compositions. Mafic rocks, which are located to the SW of the Turgutlu granitoid, were emplaced into the phyllites as sills and dykes that were surrounded by a narrow hornfelsic halo. Dykes are subvertical and trend N20oW, intersecting the phyllites of the Menderes Massif. They include abundant xenoliths of phyllite and gneiss and are mainly characterized by ophitic texture formed by plagioclase, tremolite/actinolite, biotite, and pyroxene crystals. Felsic dykes, which are located in the SE of the Salihli granitoid, are defined as three subparallel, N10oW-trending dykes that intrude into the mica schists. Felsic dykes consist of quartz, sanidine and plagioclase and zircon, apatite and allanite as accessory phases. They display holocrystalline hypidiomorphic porphyritic texture, suggesting their typical shallow-seated and hypabyssal emplacement. Microcrystalline matrix surrounds embayed quartz and locally corroded crystals. Alteration mineral assemblages of chlorite, epidote and sericite and carbonatization are also common. Their mineral constituents appear to be similar to those of the Salihli granitoid. Felsic dykes have well-preserved two sets of slip surfaces striking NE and NW in

  4. Geochemistry of alkali syenites from the Budun massif and their petrogenetic properties (Ol'khon Island)

    NASA Astrophysics Data System (ADS)

    Makrygina, V. A.; Suvorova, L. F.; Zarubina, O. V.; Bryanskii, N. V.

    2016-07-01

    The first data on the geochemistry of the alkali syenite massif in Cape Budun of Ol'khon Island, where it makes contact in the south with the Khuzir gabbroid massif, are presented. Syenites occur among granite gneisses of the Sharanur dome and, like its granites, are enriched with Zr and REEs, but depleted in other trace elements. They contain anorthoclase, corundum, rare nepheline, zircon, and hercynite and are accompanied by desilicified pegmatites. Their unusual geochemical properties allow the assumption that alkaline magmas resulted from the interaction between basic and granitoid melts.

  5. Evaluation of Water Use Efficiency of Short Rotation Poplar Coppice at Bohemian-Moravian Highlands

    NASA Astrophysics Data System (ADS)

    Hlaváčová, Marcela; Fischer, Milan; Mani Tripathi, Abhishek; Orság, Matěj; Trnka, Miroslav

    2015-04-01

    The water availability of the locality constitutes one of the main constraint for short rotation coppices grown on arable land. As a convenient characteristic assessing how the water use is coupled with the biomass yields, so called water use efficiency (WUE) is proposed. One method of water use efficiency determination is presented within this study. The study was carried out at short rotation poplar coppice (poplar clone J-105) at the Test Station Domanínek, Ltd. at Bohemian-Moravian Highlands during the growing season 2013. Diameters at breast height (DBH) were measured for 16 sample trees where sap flow measuring systems (Granier's Thermal Dissipation Probe, TDP) were installed. TDP outputs are expressed as temperature differences (ΔT) between the heated and non-heated probes. Estimation of sap flux density (Fd) by the Granier method relies on the measurement of temperature difference (ΔT). Determination of maximum temperature difference (ΔTmax) is fundamental for sap flux density (Fd) calculation. Although ΔTmax can be theoretically defined as ΔT at Fd = 0, many factors may prevent the occurrence of the zero flow state, such as night-time water movement for new growth (vegetative or reproductive) or water loss from the canopy due to high vapour pressure deficit (VPD). Therefore, the VPD condition was established for determination of ΔTmax. VPD condition was established as follows: VPD reaching values 0.2 at least 6 hours during night (from 21 p. m. to 3 a. m. and when the condition was fullfilled, the value at 3 a. m. was taken) because it is a supposed time after that the tree has no transpiration. The programmable part of Mini 32 software (www.emsbrno.cz) was used for application of the script establishing ΔTmax values under this VPD condition. Nevertheless, another script was applied on ΔT data set to determination of ΔTmax values for every night at 3 a. m. (as this is when ΔT should be at its daily maximum) without VPD condition restriction for

  6. Biodiversity impact of the aeolian periglacial geomorphologic evolution of the Fontainebleau Massif (France)

    NASA Astrophysics Data System (ADS)

    Thiry, M.; Liron, M. N.

    2009-04-01

    Landscape features The geomorphology of the Fontainebleau Massif is noteworthy for its spectacular narrow ridges, up to 10 km long and 0.5 km wide, armored by tightly cemented sandstone lenses and which overhang sandy depressions of about 50m. Denudation of the sandstone pans lead to a highly contrasted landscape, with sandstone ridges ("platières") towering sandy depressions ("vallées") and limestone plateaus ("monts"). This forms the geological frame of the spectacular sceneries of the Fontainebleau Massif (Thiry & Liron, 2007). Nevertheless, there is little know about the erosive processes that have built-up these landscapes. Periglacial processes, and among them aeolian ones, appear significant in the development of the Fontainebleau Massif physiography. The periglacial aeolian geomorphology Dunes and dune fields are known since long and cover about 15% to 25% of the Fontainebleau Massif. The aeolian dunes developed as well on the higher parts of the landscape, as well as in the lower parts of the landscape. The dunes are especially well developed in the whole eastern part of the massif, whereas the western part of the massif is almost devoid of dunes. Nevertheless, detailed mapping shows that dunes can locally be found in the western district, they are of limited extension, restricted to the east facing backslope of outliers. Loamy-sand covers the limestone plateaus of the "monts". The loam cover is of variable thickness: schematically thicker in the central part of the plateaus, where it my reach 3 m; elsewhere it may thin down to 0,20-0,30 m, especially at the plateau edges. Blowout hollows are "negative" morphologies from where the sand has been withdrawed. Often these blowouts are decametric sized and well-delimited structures. Others, more complex structures, are made up of several elongated hectometric hollows relaying each other from and which outline deflation corridor more than 1 km long. A characteristic feature of these blowout hollows is the

  7. Structural geology and sedimentology of the Sermat Quartzites, Strandja Massif, NW Turkey

    NASA Astrophysics Data System (ADS)

    Yazıcı, Müge; Natal'in, Boris A.

    2015-04-01

    The Strandja Massif, NW Turkey, is the eastern continuation of the Rhodope Massif in Bulgaria. The massif is generally correlated with the Hercynian orogenic belt that was later modified by the Cimmerian orogeny. The basement of the massif is composed by various kinds of gneisses and schists, which are intruded by the metagranites. In the studied area, the Cambrian K-feldspar metagranites are unconformably overlain by metaclastics, where both units have fault contacts with volcano-sedimentary rocks. The metagranite intrusions yield Carboniferous U-Pb zircon ages (Natal'in et al., 2012a). All of them constitute the basement of the Strandja Massif. Cambrian age of metagranites and their subduction related nature as well as the subduction related nature of the Carboniferous igneous rocks suggest a prolong evolution of the Strandja Massif (Natal'in et al., 2012a). The Cambrian metagranites are unconformably overlain by a metasedimetary cover unit, which is known in the literature as the Şermat Quartzite of presumably Permo-Triassic age (Çağlayan and Yurtsever, 1998). In the studied region, detrital zircons extracted from quartzites show that their depositional age is not younger than the Ordovician (Natal'in et al., 2012a). The basement of the Strandja Massif is subjected to the epidote-amphibolite-greenschist facies of metamorphism and high strain deformation in the late Jurassic - early Cretaceous times. The Şermat Quartzite forms a transgressive sequence, which starts with metaconglomerates, metasandstones and grades up to quartz-sericite schists. The thickness of bedding changes from thin to medium with parallel bedding planes, containing lens-shaped bodies of massive quartzites. The late Jurassic - early Cretaceous foliation (S1) is generally parallel to the primary bedding plane. Foliations and lineations consistently dip to the northeast and kinematic indicators suggest a tectonic transport in the same direction. High strain in the Şermat Quartzite

  8. Relict permafrost features in Mediterranean environments: the Majella Massif

    NASA Astrophysics Data System (ADS)

    Cocco, S.; Basili, M.; Cioci, C.; di Peco, D.; Brecciaroli, G.; Agnelli, A.; Corti, G.

    2009-04-01

    The Earth's climate has warmed by about 0.74 °C over the past century and a further warming is predicted for the next decades. Climatic changes propagate downward into the ground and modify soil thermal regime inducing many transformations. It is expected that climate warming will cause increased permafrost melting in high latitude environments and even to total permafrost degradation in regions of lower latitude. In fact, direct observations in the tundra region have shown recent increases in surface and soil temperatures and permafrost melting while in many European mountains recent micro-climatologic studies have identified only small alpine enclaves of screes with permafrost. However, in the literature no reports exist on relict permafrost in the Apennines, except for few observations about the presence of periglacial features such as rock glaciers. Some authors indicated in the past the presence of favourable conditions for preserving sporadic mountain permafrost in the Majella Massif (Central Apennines, Italy), especially in the upper Cannella Valley, where sun irradiation is particularly reduced and winds blow very energetically during the cold period. In the same valley, we monitored soil temperatures at different depths since 2006, in order to study the effects of climate change on pedogenesis and to evaluate the resilience of soils to change. The temperature data referred to the 2006-2007 and those of 2007-2008 showed different trends. The temperatures of the first year were relatively mild and soil freezing was progressively induced from top to down soil. In contrast, during the winter of the second year the temperatures assumed the lowest values (minus 2-3°C) atop the soil, increased down soil (plus 0.5-1.5°C) till he depth of 30-40 cm and decrease to minus 1-2°C more in depth (60 cm); in addition, in depth, the temperature below 0°C were reached before than at surface. This behaviour was evidently due to a deep cold source and interpreted as a

  9. Structure, age, and ore potential of the Burpala rare-metal alkaline massif, northern Baikal region

    NASA Astrophysics Data System (ADS)

    Vladykin, N. V.; Sotnikova, I. A.; Kotov, A. B.; Yarmolyuk, V. V.; Sal'nikova, E. B.; Yakovleva, S. Z.

    2014-07-01

    The Burpala alkaline massif is a unique geological object. More than 50 Zr, Nb, Ti, Th, Be, and REE minerals have been identified in rare-metal syenite of this massif. Their contents often reach tens of percent, and concentrations of rare elements in rocks are as high as 3.6% REE, 4% Zr, 0.5% Y, 0.5% Nb, 0.5% Th, and 0.1% U. Geological and geochemical data show that all rocks in the Burpala massif are derivatives of alkaline magma initially enriched in rare elements. These rocks vary in composition from shonkinite, melanocratic syenite, nepheline and alkali syenites to alaskite and alkali granite. The extreme products of magma fractionation are rare-metal pegmatites, apatite-fluorite rocks, and carbonatites. The primary melts were related to the enriched EM-2 mantle source. The U-Pb zircon ages of pulaskite (main intrusive phase) and rare-metal syenite (vein phase) are estimated at 294 ± 1 and 283 ± 8 Ma, respectively. The massif was formed as a result of impact of the mantle plume on the active continental margin of the Siberian paleocontinent.

  10. Time of formation and genesis of yttrium-zirconium mineralization in the Sakharjok massif, Kola Peninsula

    NASA Astrophysics Data System (ADS)

    Vetrin, V. R.; Skublov, S. G.; Balashov, Yu. A.; Lyalina, L. M.; Rodionov, N. V.

    2014-12-01

    The Kola geotectonic province in the northeastern Fennoscandian Shield accommodates a significant number of alkaline rock massifs differing in age. They are of mantle and mantle-crustal origin (alkali and nepheline syenites, carbonatites) and related to crustal sources (Neoarchean alkali granites). Among them, the Neoarchean Sakharjok nepheline syenite massif is related to the oldest intrusions of this kind bearing yttrium-zirconium mineralization. The crystallization of alkali syenite pertaining to the first intrusive phase of the intrusive Sakharjok massif is dated to 2645 ± 7 Ma, and this implies that this syenite postdated alkali granites (2.66-2.67 Ga). To date the yttrium-zirconium ore, we applied the local U-Pb method to zircon crystals occurring in the mineralized block hosted in nepheline syenite. The earliest fragments of zircon crystallized 1832 ± 7 Ma ago; the age of metamorphism is estimated at 1784 ± 13 Ma. These dates indicate the Paleoproterozoic age of the yttrium-zirconium mineralization, which was formed as a product of fluid reworking of the Neoarchean nepheline syenite of the Sakharjok massif.

  11. Teaching Quality after the Massification of Higher Education in Taiwan: A Student Perspective

    ERIC Educational Resources Information Center

    Dian-Fu, Chang; Yeh, Chao-Chi

    2012-01-01

    To explore whether teaching quality was improved by the Taiwan Ministry of Education's implementation of the Teaching Excellence Program after the massification of higher education, the authors used data from a 2007 student survey to build a Teaching Quality Assessment Model to analyze university students' views of the Teaching Excellence…

  12. Massification of University Education in Nigeria: Private Participation and Cost Challenges

    ERIC Educational Resources Information Center

    Ahunanya, S.; Chineze, U.; Nnennaya, I.

    2013-01-01

    This study investigated the massification of university education in Nigeria as a result of the reforms in the education subsector that led to private participation in the provision of university education from 1999. The question of the study hinges on the percentage of access and if the increased number of universities has led to increased…

  13. Reforming Higher Education in Hong Kong towards Post-Massification: The First Decade and Challenges Ahead

    ERIC Educational Resources Information Center

    Wan, Calvin

    2011-01-01

    The process of reforming Hong Kong's higher education sector commenced in 2001, and the system moved into the post-massification era. Within five years, the post-secondary participation rate for the 17-20 age cohort had increased to 66 per cent. This target was achieved much earlier than the Government had planned. More educational opportunities…

  14. Unique paragenesis of cerium and yttrium allanites in tourmalinite of the Severny massif (Chukotka)

    NASA Astrophysics Data System (ADS)

    Alekseev, V. I.; Marin, Yu. B.

    2016-07-01

    A description of hydrothermal allanite-(Y) and its unique association with allanite-(Ce) from tourmaline metasomatic rock of the Severny granite massif in Chukotka is presented in the article. Examination of the composition of metasomatic rims in allanite-(Y) allowed us to estimate the limit of isomorphic replacement in allanite of Y and heavy lanthanides by LREE, reaching 25%.

  15. Niklas - a Hitherto Unknown Deep Magmatic Massif in the Eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Rybakov, M.; Voznesensky, V.; Ben-Avraham, Z.

    2004-12-01

    A Niklas massif was discovered recompiling the gravity and magnetic maps and interpreting in 3-D mode all the available data in the area around Eratosthenes Seamount (ESM). The updated datasets clearly show two partially superimposed magnetic dipoles, which also correspond well to disturbances in the gravity field. The pronounced Eratosthenes magnetic anomaly (EMA) is only the positive part of the southeastern dipole. There is no large gravity anomaly here, however the specific gravity pattern corresponds to the magnetic body. The northwestern `magnetic dipole coincides with a prominent (about of 100mGal) gravity high that was recently delineated by Russian geophysicists. Such grav/mag combination allowed us to interpret the anomalies as being caused by a hitherto unknown dense and magnetic body which we have named the Niklas massif. The parameters and depth of causative bodies were calculated by inverse programs and forward modeling using the seismic refraction and reflection constraints. The reliability of the final model was verified using forward modeling. The magnetic data were interpreted by assuming an induced magnetization as the main magnetizing factor. The final model consists of two large compact features oriented NE-SW and located south of the Cyprian arc,as the Eratosthenes and Niklas bodies. The gravity and magnetic pattern of the Niklas is typical for the ophiolite massifs of the Eastern Mediterranean and Southern Turkey (Troodos, Hatay, Antalya). Based on this likeness we assume the Niklas composed by dense and magnetic ophyolites. This large (~100*75km) deep-seated (~7km) thick (~7km) massif is located ~95km southwest of Cyprus. We consider the Niklas as the south-most fragment of the large allochthonous ophiolite thrust slab including the Troodos massif. The tectonic situations of the Niklas area and the central segment of the Cyprian Arc are similar to that of the Eastern Taurus, Bayer-Bassit and Hatay areas. Interaction of the large Late

  16. PGE mineralization of dunite-wehrlite massifs at the Gutara-Uda interfluve, Eastern Sayan

    NASA Astrophysics Data System (ADS)

    Mekhonoshin, A. S.; Tolstykh, N. D.; Podlipsky, M. Yu.; Kolotilina, T. B.; Vishnevsky, A. V.; Benedyuk, Yu. P.

    2013-05-01

    The Pt-Pd and Au-Ag mineralization hosted in both wehrlite without visible links to sulfide mineralization (dispersed assemblage of the Tartai massif) and disseminated Cu-Ni sulfide ore (ore assemblage of the Ognit massif) was found in dunite-wehrlite massifs localized in the fold framework of the Siberian Craton. The Pt minerals in both assemblages comprise sperrylite (PtAs2) and secondary Pt-Fe-Ni alloys in the Ognit massif and Pt-Fe-Cu and Pt-Cu alloys in the Tartai massif. The Pd minerals are widespread in the ore assemblages as compounds with Te, Sb, and Bi, whereas in the dispersed assemblage Pd is concentrated primarily in Pd-Cu-Sb compounds. Both assemblages are characterized by similar substitution of sperrylite with orcelite (Ni5 - xAs2) and then with secondary Pt-Fe-Ni or Pt-Fe-Cu and Pt-Cu alloys; the occurrence of Au-Ag alloys with prevalence of Ag over Au; and replacement of them with auricupride (Cu3Au) at the late stage. Sperrylite in both assemblages contains Ir impurities, while the Pd minerals contain Cu and Ni admixtures, which are typical of mineral assemblages related to the ultramafic intrusions with nickel specialization. PGM were formed under a low sulfur fugacity and high As, Bi, and Sb activities. The postmagmatic fluids affected the primary mineral assemblages under reductive conditions, and this effect resulted in replacement of sperrylite with Ni arsenide (orcelite) and Pt-Fe-Ni and Pt-Fe-Cu alloys; Ni and Cu sulfides were replaced with awaruite and native copper.

  17. Evolution of stocks and massifs from burial of salt sheets, continental slope, northern Gulf of Mexico

    SciTech Connect

    Seni, S.J. )

    1991-03-01

    Salt structures in a 4000-km{sup 2} region of the continental slope, the northeast Green Canyon area, include stocks, massifs, remnant structures, and an allochthonous sheet. Salt-withdrawal basins include typical semicircular basins and an extensive linear trough that is largely salt-free. Counterregional growth faults truncate the landward margin of salt sheets that extend 30-50 km to the Sigsbee Escarpment. The withdrawal basins, stocks, and massifs occur within a large graben between an east-northeast-trending landward zone of shelf-margin growth faults and a parallel trend of counterregional growth faults located 48-64 km basinward. The graben formed by extension and subsidence as burial of the updip portion of a thick salt sheet produced massifs and stocks by downbuilding. Differential loading segmented the updip margin of the salt sheet into stocks and massifs separated by salt-withdrawal basins. Initially, low-relief structures evolved by trap-door growth as half-graben basins buried the salt sheet. Remnant-salt structures and a turtle-structure anticline overlay a salt-weld disconformity in sediments formerly separated by a salt sheet. Age of sediments below the weld is inferred to be be late Miocene to early Pliocene (4.6-5.3 Ma); age of sediments above the weld is late Pliocene (2.8-3.5 Ma). The missing interval of time (1-2.5 Ma) is the duration between emplacement of the salt sheet and burial of the sheet. Sheet extrusion began in the late Miocene to early Pliocene, and sheet burial began in the late Pliocene in the area of the submarine trough to early Pleistocene in the area of the massifs.

  18. August, 2002 - floods events, affected areas revitalisation and prevention for the future in the central Bohemian region, Czech Republic

    NASA Astrophysics Data System (ADS)

    Bina, L.; Vacha, F.; Vodova, J.

    2003-04-01

    Central Bohemian Region is located in a shape of a ring surrounding the capitol of Prague. Its total territorial area is 11.014 sq.km and population of 1 130.000 inhabitants. According to EU nomenclature of regional statistical units, the Central Bohemian Region is classified as an independent NUTS II. Bohemia's biggest rivers, Vltava and Labe form the region's backbone dividing it along a north-south line, besides that there are Sazava and Berounka, the two big headwaters of Vltava, which flow through the region and there also are some cascade man made lakes and 2 important big dams - Orlik and Slapy on the Vltava River in the area of the region. Overflowing of these rivers and their feeders including cracking of high-water dams during the floods in August 2002 caused total or partial destruction or damage of more than 200 towns and villages and total losses to the extend of 450 mil. EUR. The worst impact was on damaged or destroyed human dwellings, social infrastructure (schools, kindergartens, humanitarian facilities) and technical infrastructure (roads, waterworks, power distribution). Also businesses were considerably damaged including transport terminals in the area of river ports. Flowage of Spolana Neratovice chemical works caused critical environmental havoc. Regional crisis staff with regional Governor in the lead worked continuously during the floods and a regional integrated rescue system was subordinated to it. Due to the huge extent of the floods the crisis staff coordinated its work with central bodies of state including the Government and single "power" resorts (army, interior, transport). Immediately after floods a regional - controlled management was set up including an executive body for regional revitalisation which is connected to state coordinating resort - Ministry for Local Development, EU sources and humanitarian aid. In addition to a program of regional revitalisation additional preventive flood control programs are being developed

  19. Devonian-Ordovician Magmatism in Chiapas Massif, Southern Maya Block, Mexico

    NASA Astrophysics Data System (ADS)

    Pompa-Mera, V.; Schaaf, P.; Weber, B.; Solis-Pichardo, G.; Hernandez-Trevino, T.; Ortega-Gutierrez, F.

    2008-12-01

    The Chiapas Massif (CM) is located in SE Mexico and extends over an area of more than 20,000 Km2 parallel to the Pacific coast between the Isthmus of Tehuantepec and the Guatemalan border. It constitutes the largest batholitic complex in Mexico and belongs to the Maya Block. The CM is predominantly formed by igneous, metaigneous and metasedimentary rocks. In the central CM several magmatic and metamorphic events have been identified in igneous rocks between Late Permian and Triassic times (220-240 Ma), together with a Jurassic tectonothermal event. Recent geochronological studies have been focused on granitic rocks from the central-southeastern CM and from this area, single grain zircon ages were also obtained from metasedimentary rocks. The results suggest that the basement rocks of the eastern CM and the Maya Block underwent several tectonothermal events since Ordovician and Devonian times. In this work, we present new data of magmatic and metamorphic rocks from the easternmost part of CM which confirms this hypothesis. Additionally, we present a semi-detailed geological map of this area showing some field relationship between the different units. We identified a new basal sequence significantly older than the Santa Rosa Formation, which has been considered up to now as forming the major underlying sequence of the CM, as well as the occurrence of several magmatic events in the Maya Block and in rocks from surrounding areas. The petrological, geochemical and geochronological features of these rocks show continuous crust recycling, the occurrence of within-plate magmatism in some parts with inherited Greenvillian and Archaean zircon grains as well as the occurrence of arc magmatism previous to accretion, deformation and terrane separation of the crustal blocks. Our new geochronological results obtained from the south easternmost part of the CM include a Rb-Sr biotite-muscovite age of 392+/-9 Ma and an Ar-Ar muscovite age of 406+/- 4 Ma from a tectonized granitic

  20. A new interpretation of Stephanian deformation in the Decazeville basin (Massif Central, France): consequences on late Variscan tectonism

    NASA Astrophysics Data System (ADS)

    Basile, Christophe

    2006-09-01

    Five stages of faulting were observed in and around the Stephanian Decazeville basin, in the SW French Massif Central, at the southern edge of the Sillon houiller fault. The older stage ends during middle Stephanian time, and corresponds to a strike-slip regime with N-S shortening and E-W extension. Before the end of the middle Stephanian, three other stages were recorded: two strike-slip regimes with NW-SE, then E-W compression and NE-SW, then N-S extension; and finally a NNE-SSW extensional regime during the main subsidence of the basin from the end of the middle Stephanian to late Stephanian. Based on mining documents, a new interpretation of the N-S striking folds of the Decazeville basin is proposed. Folding may not be associated with E-W compression but with diapirism of coal seams along syn-sedimentary normal faults during the extensional phase. A last strike-slip regime with N-S compression and E-W extension may be related to Cainozoic Pyrenean orogeny. At a regional scale, it is suggested that from the end of the middle Stephanian to the late Stephanian, the main faults in the Decazeville basin may represent a horsetail splay structure at the southern termination of the Sillon houiller fault.

  1. Research of dynamical Characteristics of slow deformation Waves as Massif Responses on Explosions

    NASA Astrophysics Data System (ADS)

    Hachay, Olga; Khachay, Oleg; Shipeev, Oleg

    2013-04-01

    The research of massif state with use of approaches of open system theory [1-3] was developed for investigation the criterions of dissipation regimes for real rock massifs, which are under heavy man-caused influence. For realization of that research we used the data of seismic catalogue of Tashtagol mine. As a result of the analyze of that data we defined character morphology of phase trajectories of massif response, which was locally in time in a stable state: on the phase plane with coordinates released by the massif during the dynamic event energy E and lg(dE/dt) there is a local area as a ball of twisted trajectories and some not great bursts from that ball, which are not greater than 105 joules. In some time intervals that burst can be larger, than 105 joules, achieving 106 joules and yet 109 joules. [3]. Evidently there are two reciprocal depend processes: the energy accumulation in the attracted phase trajectories area and resonance fault of the accumulated energy. But after the fault the system returns again to the same attracted phase trajectories area. For analyzing of the thin structure of the chaotic area we decided to add the method of processing of the seismic monitoring data by new parameters. We shall consider each point of explosion as a source of seismic or deformation waves. Using the kinematic approach of seismic information processing we shall each point of the massif response use as a time point of the first arrival of the deformation wave for calculation of the wave velocity, because additionally we know the coordinates of the fixed response and the coordinates of explosion. The use of additional parameter-velocity of slow deformation wave propagation allowed us with use method of phase diagrams identify their hierarchic structure, which allow us to use that information for modeling and interpretation the propagation seismic and deformation waves in hierarchic structures. It is researched with use of that suggested processing method the thin

  2. Long lasting paleolandscapes stability of the French Massif Central during the Mesozoic

    NASA Astrophysics Data System (ADS)

    Ricordel-Prognon, C.; Thiry, M.; Theveniaut, H.; Lagroix, F.

    2009-04-01

    Regional geodynamical evolution is mainly constrained by the sedimentary record in the basins. Usually, little is known about geodynamics of the peripheral areas and even less on the evolution of the basement areas. Continental unconformities are essential to estimate erosion rates of basement and to model the crustal dynamics that control subsidence of surrounding sedimentary basins but also uplift and erosion on their edges. Dating such unconformities has always been the stumbling block while it is a prerequisite to constrain geodynamical models. Paleomagnetism has been proven as a suitable tool to date ferrugineous paleoweathering features. The method has been applied to paleoweathering occurrences resting on the Massif Central crystalline basement as well as to paleoweathering features affecting the crystalline basement itself. The remanence measurements were obtained at the Paleomagnetic Laboratory of the Institut Physique du Globe de Paris and data analyses were carried out using PaleoMac 5 software (Cogné, 2003). Relative dating of the paleoweathering profiles have been acquired by comparing the recorded paleomagnetic poles from the analysed samples to the apparent polar wandering path of the Eurasian plate (Edel et Duringer, 1997 ; Besse and Courtillot, 2003). Thick red kaolinitic formations rest locally on the Massif Central basement. They are generally bounded by the Tertiary grabens and buried by the Oligocene formations. Thus these azoic red formations have classically been ascribed to the "Siderolithic" formations of Eocene-Oligocene age. They show many pedogenic features (termites burrows, illuviation and hydromorphic features and nodules) and strong relationships with paleolandscape organisation (leaned against fault scarps, infilling paleovalleys, etc.). Macro and micromorphological arrangements show that these formations are in situ paleosols. Paleomagnetic ages range from 160 Ma (Late Jurassic) in the centre of the Massif Central to 140 Ma (Early

  3. Cross-borehole flow analysis to characterize fracture connections in the Melechov Granite, Bohemian-Moravian Highland, Czech Republic

    USGS Publications Warehouse

    Paillet, Frederick L.; Williams, John H.; Urik, Joseph; Lukes, Joseph; Kobr, Miroslav; Mares, Stanislav

    2012-01-01

    Application of the cross-borehole flow method, in which short pumping cycles in one borehole are used to induce time-transient flow in another borehole, demonstrated that a simple hydraulic model can characterize the fracture connections in the bedrock mass between the two boreholes. The analysis determines the properties of fracture connections rather than those of individual fractures intersecting a single borehole; the model contains a limited number of adjustable parameters so that any correlation between measured and simulated flow test data is significant. The test was conducted in two 200-m deep boreholes spaced 21 m apart in the Melechov Granite in the Bohemian-Moravian Highland, Czech Republic. Transient flow was measured at depth stations between the identified transmissive fractures in one of the boreholes during short-term pumping and recovery periods in the other borehole. Simulated flows, based on simple model geometries, closely matched the measured flows. The relative transmissivity and storage of the inferred fracture connections were corroborated by tracer testing. The results demonstrate that it is possible to assess the properties of a fracture flow network despite being restricted to making measurements in boreholes in which a local population of discrete fractures regulates the hydraulic communication with the larger-scale aquifer system.

  4. Petrological and geochemical evolution of the Tolbachik volcanic massif, Kamchatka, Russia

    NASA Astrophysics Data System (ADS)

    Churikova, Tatiana G.; Gordeychik, Boris N.; Iwamori, Hikaru; Nakamura, Hitomi; Ishizuka, Osamu; Nishizawa, Tatsuji; Haraguchi, Satoru; Miyazaki, Takashi; Vaglarov, Bogdan S.

    2015-12-01

    Data on the geology, petrography, and geochemistry of Middle-Late-Pleistocene rocks from the Tolbachik volcanic massif (Kamchatka, Klyuchevskaya group of volcanoes) are presented and compared with rocks from the neighboring Mount Povorotnaya, Klyuchevskaya group basement, and Holocene-historical Tolbachik monogenetic cones. Two volcanic series of lavas, middle-K and high-K, are found in the Tolbachik massif. The results of our data analysis and computer modeling of crystallization at different P-T-H2O-fO2 conditions allow us to reconstruct the geochemical history of the massif. The Tolbachik volcanic massif started to form earlier than 86 ka based on K-Ar dating. During the formation of the pedestal and the lower parts of the stratovolcanoes, the middle-K melts, depleted relative to NMORB, fractionated in water-rich conditions (about 3% of H2O). At the Late Pleistocene-Holocene boundary, a large fissure zone was initiated and the geodynamical regime changed. Upwelling associated with intra-arc rifting generated melting from the same mantle source that produced magmas more enriched in incompatible trace elements and subduction components; these magmas are high-K, not depleted relative to N-MORB melts with island arc signatures and rift-like characteristics. The fissure opening caused degassing during magma ascent, and the high-K melts fractionated at anhydrous conditions. These high-K rocks contributed to the formation of the upper parts of stratovolcanoes. At the beginning of Holocene, the high-K rocks became prevalent and formed cinder cones and associated lava fields along the fissure zone. However, some features, including 1975-1976 Northern Breakthrough, are represented by middle-K high-Mg rocks, suggesting that both middle-K and high-K melts still exist in the Tolbachik system. Our results show that fractional crystallization at different water conditions and a variably depleted upper mantle source are responsible for all observed variations in rocks within

  5. Scorpions from the Mitaraka Massif in French Guiana. II. Description of a new species of Ananteris Thorell, 1891 (Scorpiones: Buthidae).

    PubMed

    Lourenço, Wilson R

    2016-01-01

    A new remarkable species belonging to the genus Ananteris Thorell, 1891 (Buthidae) is described from the Mitaraka Massif in French Guiana, a site located near the borders of French Guiana, Brazil, and Suriname. The description of this new species brings further evidence about the biogeographic patterns of distribution presented by most species of the genus Ananteris, which are highly endemic in most biogeographic realms of South America, including the Tepuys and Inselberg Massifs. PMID:27156170

  6. Seismic characterization of an active metamorphic massif, Nanga Parbat, Pakistan Himalaya

    NASA Astrophysics Data System (ADS)

    Meltzer, Anne; Sarker, Golam; Beaudoin, Bruce; Seeber, Leonardo; Armbruster, John

    2001-07-01

    Earthquakes recorded by a dense seismic array at Nanga Parbat, Pakistan, provide new insight into synorogenic metamorphism and mass flow during mountain building. Microseismicity beneath the massif drops off sharply with depth and defines a shallow transition between brittle failure and ductile flow. The base of seismicity bows upward, mapping a thermal boundary with 3 km of structural relief over a lateral distance of 12 km. Anomalously low seismic velocities are observed at the core of the massif and extend to depth through the crust. The main locus of seismicity and low velocities correlates with a region of high topography, rapid exhumation, high geothermal gradients, young metamorphic and igneous ages, and crustal fluid flow. We suggest a genetic link between these phenomena in which hot rocks, rapidly advected from depth, are pervasively modified at relatively shallow levels in the crust.

  7. Two types of noble metal mineralization in the Kaalamo massif (Karelia)

    NASA Astrophysics Data System (ADS)

    Ivashchenko, V. I.; Ruchyev, A. M.; Golubev, A. I.

    2016-05-01

    Noble metal mineralization of the syngenetic (Southern Kaalamo) and epigenetic (Surisuo) types are defined in the Kaalamo massif. The ƩPt, Pd, Au content is as high as 0.9-1.1 g/t. Syngenetic mineralization started at the late magmatic stage (at around 800°C) gradually evolving to cease during the hydrothermal-metasomatic stage (<271°C). Epigenetic mineralization was formed at temperatures ranging from 500 to <230°C in zones of intense shear deformations and low-temperature metasomatosis during the collisional stage of the Svecofennian tectono-magmatic cycle (approximately 1.85 Ga ago). Taking into consideration the geological position of the Kaalamo massif in the Raakhe-Ladoga metallogenic zone with widely developed intense shear dislocations, the epigenetic mineralization type seems to be more promising with respect to noble metals.

  8. Mineralogy and geochemistry of the Tartai massif, East Siberian metallogenic province

    NASA Astrophysics Data System (ADS)

    Podlipsky, M. Yu.; Mekhonoshin, A. S.; Tolstykh, N. D.; Vishnevskiy, A. V.; Polyakov, G. V.

    2015-05-01

    The Tartai ultramafic-mafic massif is located in the central part of the East Siberian metallogenic (PGE-Cu-Ni) province (728-712 Ma), which constitutes part of the southern margin of the Siberian craton. This dunite-peridotite-pyroxenite-gabbro massif is the host to low-sulfide PGE-Cu-Ni mineralization. The massif was formed by fractional crystallization of picritic magmas and is composed of wehrlite, dunite, plagiowehrlite, and olivine melanogabbro. The composition of olivine varies from Fo89.9 in dunite to Fo83 in melanocratic olivine gabbro; clinopyroxene is esentially augite. Chrome-spinels crystallized at a low degree of oxidation and have a high iron content. Disseminated sulfide mineralization (pentlandite and heazlewoodite) with high PGE concentrations was identified in wehrlites. Pentlandite is enriched in Fe and Co and depleted in S. These features and the association pentlandite with heazlewoodite suggest that the sulfide mineralization was formed over a wide temperature range (600-400°C) at low sulfur activity (log fS2 from -16 to -9). PGM are represented by Ir-bearing sperrylite, Pd-Cu-Sb panning compounds of variable compositions, Pt-Fe-Cu and Pt-Cu alloys. The evolutionary trend of the ore system was from essentially Ni compositions at the early magmatic stage during formation of disseminated mineralization toward Cu-rich composition at the post-magmatic stage. The PGM assemblage from heavy concentrate haloes differs from bedrock-hosted mineralization in its wider variety of mineral species and the presence of refractory platinoids. Sperrylite from heavy concentrate haloes of the Tartai massif serves as a reliable prospecting guide for bedrock-hosted sulfide Cu-Ni deposits.

  9. Origin and significance of tourmalinites and tourmaline-bearing rocks of Menderes Massif, western Anatolia, Turkey

    NASA Astrophysics Data System (ADS)

    Yücel-Öztürk, Yeşim; Helvacı, Cahit; Palmer, Martin R.; Ersoy, E. Yalçın; Freslon, Nicolas

    2015-03-01

    In the western central portion of Anatolia lies the Menderes Massif - a large metamorphic crystalline complex made of Neoproterozoic to Precambrian basement rocks overlain by Palaeozoic to early Tertiary metasedimentary rocks, and with a multistage metamorphic evolution developed from the late Neo-Proterozoic to Eocene. We have undertaken a study of the petrology, geochemistry and boron isotope composition of these tourmaline occurrences aiming to constrain the processes responsible for the enrichment of boron and other fluid mobile elements in the Menderes Massif. The dispersed tourmaline has chemical and boron isotope compositions typical of a continental crust setting, but while some of the tourmalinites display similar signatures, others have heavier boron isotope compositions (up to + 7.5‰). We suggest that the tourmalinites with continental characteristics formed part of the original Pan African basement rocks, whereas those with heavier δ11B signatures formed by later metamorphism during the Alpine orogeny, possibly through interaction with subduction-like fluids. This proposed process may also have been coincident with metasomatism of the lithospheric mantle beneath the massif, which is known to have experienced multistage metasomatism and enrichment history up to Neogene time.

  10. Age and sources of Precambrian zircon-rutile deposits in the Kokchetav sialic massif (northern Kazakhstan)

    NASA Astrophysics Data System (ADS)

    Degtyarev, K. E.; Kovach, V. P.; Tret'yakov, A. A.; Kotov, A. B.; Wang, Kuo-Lun

    2015-10-01

    The U-Pb geochronological data on detrital zircons from placers confined to Neoproterozoic quartzite-schist sequences, which are widespread in the Kokchetav massif of northern Kazakhstan, are discussed. Detrital zircons (332 grains in total) originate from the ore occurrences in the central, northern, and western parts of the massif. The concordant ages of detrital zircons from all the examined occurrences largely correspond to intervals of 1017-1528, 1628-1946, and 2653-2739 Ma. The obtained data imply that material of quartzite-schist sequences of the Kokchetav massif was provided by Mesoproterozoic, Paleoproterozoic, and Neoarchean rock complexes. The lower age limit determined for these sequences is approximately 1.06 Ga. The dates obtained for detrital zircons are most consistent with events that took place in Laurentia. They correspond to the formation and breakup of the Columbia/Nuna supercontinent (approximately 1650-1580 and 1450-1380 Ma ago, respectively) and formation of the Rodinia supercontinent in the period of 1300-900 Ma ago.

  11. Chain Lakes massif, west central Maine: northern Appalachian basement or suspect terrane

    SciTech Connect

    Cheatham, M.M.; Olszewski, W.J. Jr.; Gaudette, H.E.

    1985-01-01

    The Chain Lakes massif of west-central Main is a 3 km thick sequence of diamictite and aquagene metavolcanics and metasediments, which contrasts strikingly with its surrounding Paleozoic rocks in lithology, structural style and metamorphic grade. The rocks of the massif are characterized by mineral assemblages developed during two separate metamorphic events. The first, of second sillimanite grade, is reflected by qtz-oligoclase-Kspar-sillimanite-biotite and muscovite. The second metamorphism is a retrograde event of greenschist facies, and chlorite grade. Isotopic Rb-Sr and Sm-Nd whole rock, and Rb-Sr mineral analyses of samples of the diamictite members, now gneiss and granofels, indicate that the first prograde metamorphism occurred at 770 Ma. with the retrograde event at approximately 405 Ma. Due to the restricted range of /sup 147/Sm//sup 144/Nd, no Sm-Nd isochron age could be determined. However, model ages for both Sr and Nd are approximately 1500 Ma for derivation of the Chain Lakes protolith material from depleted mantle. Lithology, bounding formations, complexes and plutons, and the isotopic data support previous contentions that the Chain Lakes massif is a suspect terrane. However, similarities with Proterozoic rocks along the Eastern Margin, as well as recent suggestions of similar rocks underlying the Kearsarge-Central Main synclinorium may suggest the possible widespread occurrence of dismembered masses of a perhaps once coherent, Precambrian terrane underlying the Northern Appalachians.

  12. Re-Os isotopic evidence for a lower crustal origin of massif-type anorthosites

    PubMed

    Schiellerup; Lambert; Prestvik; Robins; McBride; Larsen

    2000-06-15

    Massif-type anorthosites are large igneous complexes of Proterozoic age. They are almost monomineralic, representing vast accumulations of plagioclase with subordinate pyroxene or olivine and Fe-Ti oxides--the 930-Myr-old Rogaland anorthosite province in southwest Norway represents one of the youngest known expressions of such magmatism. The source of the magma and geodynamic setting of massif-type anorthosites remain long-standing controversies in Precambrian geology, with no consensus existing as to the nature of the parental magmas or whether these magmas primarily originate in the Earth's mantle or crust. At present, massif-type anorthosites are believed to have crystallized from either crustally contaminated mantle-derived melts that have fractionated olivine and pyroxenes at depth or primary aluminous gabbroic to jotunitic melts derived from the lower continental crust. Here we report rhenium and osmium isotopic data from the Rogaland anorthosite province that strongly support a lower crustal source for the parental magmas. There is no evidence of significantly older crust in southwest Scandinavia and models invoking crustal contamination of mantle-derived magmas fail to account for the isotopic data from the Rogaland province. Initial osmium and neodymium isotopic values testify to the melting of mafic source rocks in the lower crust with an age of 1,400-1,550 Myr. PMID:10866196

  13. First SHRIMP U Pb zircon dating of granulites from the Kontum massif (Vietnam) and tectonothermal implications

    NASA Astrophysics Data System (ADS)

    Nam, Tran Ngoc; Sano, Yuji; Terada, Kentaro; Toriumi, Mitsuhiro; Van Quynh, Phan; Dung, Le Tien

    2001-02-01

    The Kontum massif in Central Vietnam represents the largest continuous exposure of crystalline basement of the Indochina craton. The central Kontum massif is chiefly made of orthopyroxene granulites (enderbite, charnockite) and associated rocks of the Kannack complex. Mineral assemblages and geothermobarometric studies have shown that the Kannack complex has severely metamorphosed under granulite facies corresponding to P-T conditions of 800-850°C and 8±1 kbars. Twenty-three SHRIMP II U-Pb analyses of eighteen zircon grains separated from a granulite sample of the Kannack complex yield ca 254 Ma, and one analysis gives ca 1400 Ma concordant age for a zoned zircon core. This result shows that granulites of the Kannack complex in the Kontum massif have formed from a high-grade granulite facies tectonothermal event of Indosinian age (Triassic). The cooling history and subsequent exhumation of the Kannack complex during Indosinian times ranged from ˜850°C at ca 254 Ma to ˜300°C at 242 Ma, with an average cooling rate of ˜45°C/Ma.

  14. Jurassic hot spring deposits of the Deseado Massif (Patagonia, Argentina): Characteristics and controls on regional distribution

    NASA Astrophysics Data System (ADS)

    Guido, Diego M.; Campbell, Kathleen A.

    2011-06-01

    The Deseado Massif, Santa Cruz Province, Argentinean Patagonia, hosts numerous Middle to Late Jurassic age geothermal and epithermal features represented by siliceous and calcareous chemical precipitates from hot springs (sinters and travertines, respectively), hydrothermal breccias, quartz veins, and widespread hydrothermal silicification. They indicate pauses in explosive volcanic activity, marking the final stages in the evolution of an extensive Jurassic (ca. 178-151 Ma) volcanic complex set in a diffuse extensional back-arc setting heralding the opening of the Atlantic Ocean. Published paleo-hot spring sites for the Deseado Massif, plus additional sites identified during our recent field studies, reveal a total of 23 locations, five of which were studied in detail to determine their geologic and facies associations. They show structural, lithologic, textural and biotic similarities with Miocene to Recent hot spring systems from the Taupo and Coromandel volcanic zones, New Zealand, as well as with modern examples from Yellowstone National Park, U.S.A. These comparisons aid in the definition of facies assemblages for Deseado Massif deposits - proximal, middle apron and distal siliceous sinter and travertine terraces and mounds, with preservation of many types of stromatolitic fabrics - that likely were controlled by formation temperature, pH, hydrodynamics and fluid compositions. Locally the mapped hot spring deposits largely occur in association with reworked volcaniclastic lacustrine and/or fluvial sediments, silicic to intermediate lava domes, and hydrothermal mineralization, all of which are related to local and regional structural lineaments. Moreover, the numerous geothermal and significant epithermal (those with published minable resources) deposits of the Deseado Massif geological province mostly occur in four regional NNW and WNW hydrothermal-structural belts (Northwestern, Northern, Central, and Southern), defined here by alignment of five or more hot

  15. Geological mapping of the Rainbow Massif, Mid-Atlantic Ridge, 36°14'N

    NASA Astrophysics Data System (ADS)

    Ildefonse, B.; Fouquet, Y.; Hoisé, E.; Dyment, J.; Gente, P.; Thibaud, R.; Bissessur, D.; Yatheesh, V.; Momardream 2008 Scientific Party*, T.

    2008-12-01

    The Rainbow hydrothermal field at 36°14'N on the Mid-Atlantic Ridge is one of the few known sites hosted in ultramafic basement. The Rainbow Massif is located along the non-transform offset between the AMAR and South AMAR second-order ridge segments, and presents the characteristic dome morphology of oceanic core complexes, although no corrugated surface has been observed so far. One of the objectives of Cruises MOMAR DREAM (July 2007, R/V Pourquoi Pas ?; Aug-Sept 2008, R/V Atalante) was to study the petrological and structural context of the hydrothermal system at the scale of the Rainbow Massif. Our geological sampling complements previous ones achieved during Cruises FLORES (1997) and IRIS (2001), and consisted in dredge hauls, and submersible dives by manned submersible Nautile and ROV Victor. The tectonics of the Rainbow Massif is dominated by a N-S trending fault pattern on the western flank of the massif, and a series of SW-NW ridges on its northeastern side. The active hydrothermal site is located in the area were these two systems crosscut. The most abundant recovered rock type is peridotite (harzburgite and dunite) that presents a variety of serpentinization styles and intensity, and a variety of deformation styles (commonly undeformed, sometimes displaying ductile or brittle foliations). Serpentinites are frequently oxidized. Some peridotite samples have melt impregnation textures. Massive chromitite was recovered in one dredge haul. Variously evolved gabbroic rocks were collected as discrete samples or as centimeter to decimeter-thick dikes in peridotites. Basalts and fresh basaltic glass were also sampled in talus and sediments on the southwestern and northeastern flanks of the massif. Our sampling is consistent with the lithological variability encountered in oceanic core complexes along the Mid-Atlantic Ridge and Southwest Indian Ridge. The stockwork of the hydrothermal system has been sampled on the western side of the present-day hydrothermal

  16. Mapping of the Ronda peridotite massif (Spain) from AVIRIS spectro-imaging survey: A first attempt

    NASA Technical Reports Server (NTRS)

    Pinet, P. C.; Chabrillat, S.; Ceuleneer, G.

    1993-01-01

    In both AVIRIS and ISM data, through the use of mixing models, geological boundaries of the Ronda massif are identified with respect to the surrounding rocks. We can also yield first-order vegetation maps. ISM and AVIRIS instruments give consistent results. On the basis of endmember fraction images, it is then possible to discard areas highly vegetated or not belonging to the peridotite massif. Within the remaining part of the mosaic, spectro-mixing analysis reveals spectral variations in the peridotite massif between the well-exposed areas. Spatially organized units are depicted, related to differences in the relative depth of the absorption band at 1 micron, and it may be due to a different pyroxene content. At this stage, it is worth noting that, although mineralogical variations observed in the rocks are at a sub-pixel scale for the airborne analysis, we see an emerging spatial pattern in the distribution of spectral variations across the massif which might be prevailingly related to mineralogy. Although it is known from fieldwork that the Ronda peridotite massif exhibits mineralogical variations at local scale in the content of pyroxene, and at regional scale in different mineral facies, ranging from garnet-, to spinel- to plagioclase-lherzolites, no attempt has been done yet to produce a synoptic map relating the two scales of analysis. The present work is a first attempt to reach this objective, though a lot more work is still required. In particular, for the purpose of mineralogical interpretation, it is critical to relate the airborne observation to field work and laboratory spectra of Ronda rocks already obtained, with the use of image endmembers and associated reference endmembers. Also, the pretty rough linear mixing model used here is taken as a 'black-box' process which does not necessarily apply correctly to the physical situation at the sub-pixel level. One may think of using the ground-truth observations bearing on the sub-pixel statistical

  17. Country, Cover or Protection: What Shapes the Distribution of Red Deer and Roe Deer in the Bohemian Forest Ecosystem?

    PubMed Central

    Heurich, Marco; Brand, Tom T. G.; Kaandorp, Manon Y.; Šustr, Pavel; Müller, Jörg; Reineking, Björn

    2015-01-01

    The Bohemian Forest Ecosystem encompasses various wildlife management systems. Two large, contiguous national parks (one in Germany and one in the Czech Republic) form the centre of the area, are surrounded by private hunting grounds, and hunting regulations in each country differ. Here we aimed at unravelling the influence of management-related and environmental factors on the distribution of red deer (Cervus elaphus) and roe deer (Capreolus capreolus) in this ecosystem. We used the standing crop method based on counts of pellet groups, with point counts every 100 m along 218 randomly distributed transects. Our analysis, which accounted for overdispersion as well as zero inflation and spatial autocorrelation, corroborated the view that both human management and the physical and biological environment drive ungulate distribution in mountainous areas in Central Europe. In contrast to our expectations, protection by national parks was the least important variable for red deer and the third important out of four variables for roe deer; protection negatively influenced roe deer distribution in both parks and positively influenced red deer distribution in Germany. Country was the most influential variable for both red and roe deer, with higher counts of pellet groups in the Czech Republic than in Germany. Elevation, which indicates increasing environmental harshness, was the second most important variable for both species. Forest cover was the least important variable for roe deer and the third important variable for red deer; the relationship for roe deer was positive and linear, and optimal forest cover for red deer was about 70% within a 500 m radius. Our results have direct implications for the future conservation management of deer in protected areas in Central Europe and show in particular that large non-intervention zones may not cause agglomerations of deer that could lead to conflicts along the border of protected, mountainous areas. PMID:25781942

  18. Silvibacterium bohemicum gen. nov. sp. nov., an acidobacterium isolated from coniferous soil in the Bohemian Forest National Park.

    PubMed

    Lladó, Salvador; Benada, Oldrich; Cajthaml, Tomáš; Baldrian, Petr; García-Fraile, Paula

    2016-02-01

    During the course of a study assessing the bacterial diversity of a coniferous forest soil (pH 3.8) in the Bohemian Forest National Park (Czech Republic), we isolated strain S15(T) which corresponded to one of the most abundant soil OTUs. Strain S15(T) is represented by Gram-negative, motile, rod-like cells that are 0.3-0.5μm in diameter and 0.9-1.1μm in length. Its pH range for growth was 3-6, with optimal conditions found at approximately 4-5. It can grow at temperatures between 20°C and 28°C, with optimum growth at 22-24°C. Its respiratory quinone is MK-8, and its main fatty acid is iso-C15:0 (73.7%). The G+C DNA content was 58.2mol%. According to the 16S rRNA gene sequence analysis, strain S15(T) belongs to subdivision 1 of the phylum Acidobacteria, being affiliated to the cluster of Acidipila rosea AP8(T) and Acidobacterium capsulatum ATCC 51196(T). Analysis of the S15(T) genome revealed the presence of 404 genes that are involved in carbohydrate metabolism, which indicates the metabolic potential to degrade polysaccharides of plant and fungal origin. Based on genotypic and phenotypic characteristics, the strain S15(T) represents a new genus and species within the family Acidobacteriaceae, for which the name Silvibacterium bohemicum gen. nov., sp. nov. is proposed (type strain S15(T)=LMG 28607(T)=CECT 8790(T)). PMID:26774420

  19. Country, cover or protection: what shapes the distribution of red deer and roe deer in the Bohemian Forest Ecosystem?

    PubMed

    Heurich, Marco; Brand, Tom T G; Kaandorp, Manon Y; Šustr, Pavel; Müller, Jörg; Reineking, Björn

    2015-01-01

    The Bohemian Forest Ecosystem encompasses various wildlife management systems. Two large, contiguous national parks (one in Germany and one in the Czech Republic) form the centre of the area, are surrounded by private hunting grounds, and hunting regulations in each country differ. Here we aimed at unravelling the influence of management-related and environmental factors on the distribution of red deer (Cervus elaphus) and roe deer (Capreolus capreolus) in this ecosystem. We used the standing crop method based on counts of pellet groups, with point counts every 100 m along 218 randomly distributed transects. Our analysis, which accounted for overdispersion as well as zero inflation and spatial autocorrelation, corroborated the view that both human management and the physical and biological environment drive ungulate distribution in mountainous areas in Central Europe. In contrast to our expectations, protection by national parks was the least important variable for red deer and the third important out of four variables for roe deer; protection negatively influenced roe deer distribution in both parks and positively influenced red deer distribution in Germany. Country was the most influential variable for both red and roe deer, with higher counts of pellet groups in the Czech Republic than in Germany. Elevation, which indicates increasing environmental harshness, was the second most important variable for both species. Forest cover was the least important variable for roe deer and the third important variable for red deer; the relationship for roe deer was positive and linear, and optimal forest cover for red deer was about 70% within a 500 m radius. Our results have direct implications for the future conservation management of deer in protected areas in Central Europe and show in particular that large non-intervention zones may not cause agglomerations of deer that could lead to conflicts along the border of protected, mountainous areas. PMID:25781942

  20. Conditions of crystallization of the Ural platinum-bearing ultrabasic massifs: evidence from melt inclusions

    NASA Astrophysics Data System (ADS)

    Simonov, Vladimir; Puchkov, Victor; Prikhod'ko, Vladimir; Stupakov, Sergey; Kotlyarov, Alexey

    2013-04-01

    Conditions of the Ural platinum-bearing ultramafic massifs formation attract attention of numerous researchers. A most important peculiarity of such plutons is their dunite cores, to which commercial Pt deposits are related. There are a different opinions about genesis of these massifs and usual methods not always can solve this question. As a result of melt inclusions study in the Cr-spinel the new data on physical and chemical parameters of dunite crystallization of the Nizhnii Tagil platinum-bearing ulrabasic massif (Ural) was obtained. The comparative analysis of Cr-spinels, containing melt inclusions, has shown essential differences of these minerals from chromites of the ultrabasic ophiolite complexes and of modern oceanic crust. Contents of major chemical components in the heated and quenched melt inclusions are close to those in the picrite and this testifies dunite crystallization from ultrabasic (to 24 wt.% MgO) magma. On the variation diagrams for inclusions in Cr-spinel the following changes of chemical compositions are established: during SiO2 growth there is falling of FeO, MgO, and increase of CaO, Na2O contents. Values of TiO2, Al2O3, K2O and P2O5 remain as a whole constant. Comparing to the data on the melt inclusions in Cr-spinel from the Konder massif, we see that values of the most part of chemical components (SiO2, TiO2, K2O, P2O5) are actually overlapped. At the same time, for the Nizhnii Tagil platinum-bearing massif the big maintenances of FeO and CaO in inclusions are marked. Distinct dependence of the majority of components from the MgO content in inclusions is observed: values TiO2, Al2O3 FeO, CaO and Na2O fall at transition to more magnesia melts. On the peculiarities of distribution of petrochemical characteristics melt inclusions in considered Cr-spinels are co-ordinated with the data on evolution of compositions of melts and rocks of model stratified ultramafic plutons during their crystallization in the magmatic chambers. On the

  1. Structural Pattern, P-t Conditions and Timing of Alpine Deformation In The Argentera Massif (western Alps)

    NASA Astrophysics Data System (ADS)

    Corsini, M.; Caby, R.; Ruffet, G.

    The Argentera massif is located in the southern part of the Western Alps and belongs to the paleo-European basement. It forms the southernmost crystalline massif of the external domain. Hercynian high-grade metamorphic rocks and Carboniferous sedi- mentary basins were intruded at the end of the Hercynian orogen by the calc-alkaline Argentera granite. This massif experienced a polyphase deformation history, Hercy- nian and Alpine. The Alpine history is characterized by the development of a network of NNW-SSE trending transcurrent dextral ductile shear zones branching into E-W ductile thrust faults with a top to the south displacement. We interpret the uplift of the massif as the result of movements along these shear zones, relative to a sub-meridian compressional event. Our P-T condition estimates indicate a regional temperature at ca 350 rC for pressure at 0.35-0.4 GPa for Alpine metamorphism implying a mini- mum burial of 14 km for the Argentera massif. 39Ar-40Ar analyses of neo-crystallized phengites collected within a major E-W alpine crosscutting the late Hercynian Argen- tera granite shear zone (Frema Morte) yielded an age at ca 22.5 Ma. This is the first absolute age constraint of a late Alpine metamorphism in the external crystalline mas- sifs of the Western Alps. This metamorphism could result from overload imposed by thrusting of the internal nappes between 28 Ma and 22.5 Ma.

  2. New Isotopic age data for understanding the resetting radioactive clock of the Kazdaǧı Massif (Western Anatolia, Turkey)

    NASA Astrophysics Data System (ADS)

    Hasözbek, Altug; Akay, Erhan; Sherlock, Sarah Christine

    2016-04-01

    The Kazdaǧı Massif comprises one of the well-known high-grade metamorphic complexes in the western Anatolia (Turkey). This high-grade succession is subdivided into two units, which is separated by regionally defined unconformity. The lower unit defines a typical oceanic crust package including ultramafic rocks and cumulate gabbros (Tozlu metaophiolite unit). The upper unit comprises of a thick platform succession of detritals and carbonates with mafic volcanic intercalations. Carbonates of this succession are now found as white coarse-crystalline marbles, detritals are schists, metagranites and migmatites and mafic volcanic intercalations are as amphibolites (Sarikiz unit). The whole sequence is cut by shallow-seated Late Oligocene-Early Miocene non-metamorphic granites (Evciler, Eybek granites). New 40Ar-39Ar amphibole ages of 22-19.7 Ma state that both associations of the Tozlu metaophiolite and Sarıkız units experienced almost the same age era as the youngest granites (Evciler, Eybek granites) in the study area. In addition to that, previous U-Pb zircon age results indicate a peak metamorphism age of the Kazdaǧı Massif is around 30-35 Ma. Such young Ar-Ar ages from the Kazdaǧı Massif, which gather close to the granite intrusion crystallization ages, are likely indicators of the resetting radioactive clock of the Kazdaǧı Massif. This data is also in agreement of a single stage migmatization of the massif during the Alpine Orogeny.

  3. PGE distribution in sulfide ores from ultramafic massifs of the central East Sayan Mountains, Southern Siberia, Russia

    NASA Astrophysics Data System (ADS)

    Kolotilina, T. B.; Mekhonoshin, A. S.; Orsoev, D. A.

    2016-01-01

    Data on the composition of sulfide ores from ultramafic massifs in the central East Sayan Mountains and on the regularities of platinum group elements (PGE) in these ores are presented. It is found that the highest PGE contents are characteristic for net-textured and massive ores from the Zhelos massif: total PGE content there is up to 15 ppm, with Pd/Pt = 3-8, for Ni and Cu contents of 1.5-2.8 and 0.5-2.7 wt%, respectively. In the disseminated ores of the Zhelos massif, PGE contents vary from 1 to 7 ppm, at Ni and Cu contents varying in the ranges of 0.5-1.0 and 0.2-0.4 wt %, respectively. In the Tokty-Oi massif, disseminated ores are characterized by higher absolute PGE contents (1.6 to 3.3 ppm) at similar Ni content. PGE tenor of disseminated ores is higher compared to that of massive and net-textured ones. In the cross-sections of both massifs, net-textured and massive ores of an essentially pyrrhotine composition are found at the contact between ultramafic and host rocks. Total PGE in these ores is up to 12 ppm. The obtained data on sulfur isotopes indicate the common, well-homogenized sources, and close physical-chemical depositional conditions of all ore types.

  4. Biodiversity impact of the aeolian periglacial geomorphologic evolution of the Fontainebleau Massif (France)

    NASA Astrophysics Data System (ADS)

    Thiry, M.; Liron, M. N.

    2009-04-01

    Landscape features The geomorphology of the Fontainebleau Massif is noteworthy for its spectacular narrow ridges, up to 10 km long and 0.5 km wide, armored by tightly cemented sandstone lenses and which overhang sandy depressions of about 50m. Denudation of the sandstone pans lead to a highly contrasted landscape, with sandstone ridges ("platières") towering sandy depressions ("vallées") and limestone plateaus ("monts"). This forms the geological frame of the spectacular sceneries of the Fontainebleau Massif (Thiry & Liron, 2007). Nevertheless, there is little know about the erosive processes that have built-up these landscapes. Periglacial processes, and among them aeolian ones, appear significant in the development of the Fontainebleau Massif physiography. The periglacial aeolian geomorphology Dunes and dune fields are known since long and cover about 15% to 25% of the Fontainebleau Massif. The aeolian dunes developed as well on the higher parts of the landscape, as well as in the lower parts of the landscape. The dunes are especially well developed in the whole eastern part of the massif, whereas the western part of the massif is almost devoid of dunes. Nevertheless, detailed mapping shows that dunes can locally be found in the western district, they are of limited extension, restricted to the east facing backslope of outliers. Loamy-sand covers the limestone plateaus of the "monts". The loam cover is of variable thickness: schematically thicker in the central part of the plateaus, where it my reach 3 m; elsewhere it may thin down to 0,20-0,30 m, especially at the plateau edges. Blowout hollows are "negative" morphologies from where the sand has been withdrawed. Often these blowouts are decametric sized and well-delimited structures. Others, more complex structures, are made up of several elongated hectometric hollows relaying each other from and which outline deflation corridor more than 1 km long. A characteristic feature of these blowout hollows is the

  5. Diverse subaerial and sublacustrine hot spring settings of the Cerro Negro epithermal system (Jurassic, Deseado Massif), Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Guido, Diego M.; Campbell, Kathleen A.

    2012-06-01

    The Late Jurassic (~ 150 Ma) Cerro Negro volcanic-epithermal-geothermal system (~ 15 km2 area), Deseado Massif, Patagonia, Argentina, includes two inferred volcanic emission centers characterized by rhyolitic domes linked along NW-SE regional faults that are associated with deeper level Au/Ag mineralization to the NW, and with shallow epithermal quartz veins and mainly travertine surface hot spring manifestations to the SE. Some travertines are silica-replaced, and siliceous and mixed silica-carbonate geothermal deposits also are found. Five hot spring-related facies associations were mapped in detail, which show morphological and textural similarities to Pleistocene-Recent geothermal deposits at Yellowstone National Park (U.S.A.), the Kenya Rift Valley, and elsewhere. They are interpreted to represent subaerial travertine fissure ridge/mound deposits (low-flow spring discharge) and apron terraces (high-flow spring discharge), as well as mixed silica-carbonate lake margin and shallow lake terrace vent-conduit tubes, stromatolitic mounds, and volcano-shaped cones. The nearly 200 mapped fossil vent-associated deposits at Cerro Negro are on a geographical and numerical scale comparable with subaerial and sublacustrine hydrothermal vents at Mammoth Hot Springs, and affiliated with Yellowstone Lake, respectively. Overall, the Cerro Negro geothermal system yields paleoenvironmentally significant textural details of variable quality, owing to both the differential preservation potential of particular subaerial versus subaqueous facies, as well as to the timing and extent of carbonate diagenesis and silica replacement of some deposits. For example, the western fault associated with the Eureka epithermal quartz vein facilitated early silicification of the travertine deposits in the SE volcanic emission center, thereby preserving high-quality, microbial macro- and micro-textures of this silica-replaced "pseudosinter." Cerro Negro provides an opportunity to reconstruct

  6. Dating low-temperature deformation by 40Ar/39Ar on white mica, insights from the Argentera-Mercantour Massif (SW Alps)

    NASA Astrophysics Data System (ADS)

    Sanchez, Guillaume; Rolland, Yann; Schneider, Julie; Corsini, Michel; Oliot, Emilien; Goncalves, Philippe; Verati, Chrystèle; Lardeaux, Jean-Marc; Marquer, Didier

    2011-07-01

    neocrystallized synkinematic white mica allows the determination of precise ages of deformation and fluid activity. Together with precise thermobarometry undertaken on the basis of mineral chemistry and whole-rock composition, 40Ar/39Ar dating of white mica leads to the reconstitution of precise depth-deformation history of low-grade (< 400 °C) metamorphic units. At the Argentera-Mercantour massif scale, several stages of shear zone development at 15-21 km depth are dated between 33 and 20 Ma. In the SE part of the massif shear zone ages are well constrained to be either (1) 33.6 ± 0.6 Ma or in the range (2) 26.8 ± 0.7 Ma-26.3 ± 0.7 Ma. In the West of the massif, younger shear zone ages range between (3) 22.2 ± 0.3 Ma and (4) 20.5 ± 0.3 Ma.

  7. Thermal and structural evolution of the external Western Alps: Insights from (U-Th-Sm)/He thermochronology and RSCM thermometry in the Aiguilles Rouges/Mont Blanc massifs

    NASA Astrophysics Data System (ADS)

    Boutoux, A.; Bellahsen, N.; Nanni, U.; Pik, R.; Verlaguet, A.; Rolland, Y.; Lacombe, O.

    2016-06-01

    In the Western Alps, the External Crystalline Massifs (ECM) are key places to investigate the kinematics and thermal structure of a collisional crustal wedge, as their paleo-brittle/ductile transition is now exhumed at the surface. New (U-Th-Sm)/He data on zircon and new Raman Spectroscopy on Carbonaceous Material (RSCM) data from the Aiguilles Rouges and the Mont Blanc massifs, coupled to HeFTy thermal modeling, constrain the thermal evolution and exhumation of the massifs. In the cover of the Aiguilles Rouges massif, we found that the maximal temperature was about 320 °C (+/- 25 °C), close to the maximal temperature reached in the cover of the Mont Blanc massif (~ 350 °C +/- 25 °C). We show that, after a fast heating period, the thermal peak lasted 10-15 Myrs in the Mont Blanc massif, and probably 5-10 Myrs in the Aiguilles Rouges massif. This thermal peak is synchronous with crustal shortening documented in the basement. (U-Th-Sm)/He data and thermal modeling point toward a coeval cooling of both massifs, like other ECM, at around 18 Ma +/- 1 Ma. This cooling was related to an exhumation due to the initiation of frontal crustal ramps below the ECM, quite synchronously along the Western Alps arc.

  8. Geological structures and geochronology of the Gonam Complex in the Gyeonggi Massif, South Korea

    NASA Astrophysics Data System (ADS)

    Kihm, You Hong; Kim, Sung Won

    2013-04-01

    Geological structures and geochronology of the Gonam Complex in the Gyeonggi Massif, South Korea You Hong Kihm and Sung Won Kim The Gonam complex is exposed in the westernmost part of the Gyeonggi Massif, which is recently thought be related with Triassic collision of China. This complex consists of various lithologies such as quartz schist, mica schist, quartzite, marble, leucocratic granite, mafic dyke and alkali granite. The Gonam complex can be divided into three units from south to north. The first is dominated by alternation of quartz schist and mica schist, which are intruded by leucocratic granites and mafic dykes. The second unit is highly sheared and folded quartzite. The last unit is composed of schists and marble intruded by acidic dykes, mafic dykes and foliated syenite. The deformation of the Gonam complex is characterized by one ductile shearing, two generations of folding, and four generations of faulting. The most prominent geological structures developed in the Gonam Complex are ductile structures, such as mylonitic foliations, mineral stretching lineations, sheath folds and oblique folds. At most outcrops the Gonam Complex was strongly sheared and intruded by amphibolitic dykes and leucocratic granites, which are also sheared. Widely developed mylonite indicates the ductile shearing occurred in high temperature metamorphic condition. SHRIMP zircon ages of detrital zircons obtained from schist and quartzite range from 3313 to 1819 Ma indicating the Gonam Complex deposited after Paleoproterozoic. Intrusion ages of foliated leucocratic granite, mafic dyke and foliated syenite are 821 Ma, 812 Ma and 751 Ma, respectively. And massive mafic dyke, syenite and two-mica granite (232~228 Ma) are interpreted as post-collisional igneous activity. These events are similar to those of Qinling-Dabie Belt and suggest that the Gyeonggi Massif is probably correlated to the Qinling-Dabie Belt.

  9. Catalog of Apollo 17 rocks. Volume 1: Stations 2 and 3 (South Massif)

    NASA Technical Reports Server (NTRS)

    Ryder, Graham

    1993-01-01

    The Catalog of Apollo 17 Rocks is a set of volumes that characterize each of 334 individually numbered rock samples (79 larger than 100 g) in the Apollo 17 collection, showing what each sample is and what is known about it. Unconsolidated regolith samples are not included. The catalog is intended to be used by both researchers requiring sample allocations and a broad audience interested in Apollo 17 rocks. The volumes are arranged geographically, with separate volumes for the South Massif and Light Mantle, the North Massif, and two volumes for the mare plains. Within each volume, the samples are arranged in numerical order, closely corresponding with the sample collection stations. The present volume, for the South Massif and Light Mantle, describes the 55 individual rock fragments collected at Stations two, two-A, three, and LRV-five. Some were chipped from boulders, others collected as individual rocks, some by raking, and a few by picking from the soil in the processing laboratory. Information on sample collection, petrography, chemistry, stable and radiogenic isotopes, rock surface characteristics, physical properties, and curatorial processing is summarized and referenced as far as it is known up to early 1992. The intention has been to be comprehensive: to include all published studies of any kind that provide information on the sample, as well as some unpublished information. References which are primarily bulk interpretations of existing data or mere lists of samples are not generally included. Foreign language journals were not scrutinized, but little data appears to have been published only in such journals. We have attempted to be consistent in format across all of the volumes, and have used a common reference list that appears in all volumes. Where possible, ages based on Sr and Ar isotopes have been recalculated using the 'new' decay constants recommended by Steiger and Jager; however, in many of the reproduced diagrams the ages correspond with the

  10. The pre-oceanic evolution of the Erro-Tobbio peridotite (Voltri Massif, Ligurian Alps, Italy)

    NASA Astrophysics Data System (ADS)

    Piccardo, G. B.; Vissers, R. L. M.

    2007-05-01

    This paper presents the results of field, structural, petrologic and geochemical investigations on the Erro-Tobbio (E-T) ophiolitic peridotite (Voltri Massif, Ligurian Alps, Italy). This massif represents a mantle section equilibrated at spinel-facies conditions in the subcontinental lithosphere of the Europe-Adria system prior to the Early Jurassic that has been exhumed and emplaced at the sea-floor during rifting and opening of an ocean basin. The E-T massif comprises km-scale volumes of peridotites with structural and compositional characteristics pointing to melt-peridotite interaction. Their formation is thought to result from the interaction of pristine lithospheric peridotites with MORB-type melts ascending by porous flow, leading to the development of reactive spinel harzburgites, impregnated plagioclase peridotites and replacive spinel dunites. The melt-related events were followed by MORB melt intrusion. Field relationships between sheared lithospheric peridotites, including coarse tectonites as well as fine-grained mylonites developed during lithosphere extension, and melt-modified peridotites suggest that melt-related processes occurred during exhumation of the E-T mantle. These melt-related processes likely included both diffuse percolation and focused intrusion and are considered to be a consequence of MORB-forming partial melting of the asthenosphere induced by near-adiabatic decompressional upwelling related to lithosphere extension and thinning. Field, structural and petrological data allow us to conclude that the entire pre-oceanic evolution of deformation, metamorphism and magmatism recorded by the E-T mantle started during the Early-Middle Jurassic and was related to lithospheric extension leading to the Late Jurassic opening of the Ligurian Tethys ocean.

  11. Metamorphic evolution of pelitic-semipelitic granulites in the Kon Tum massif (south-central Vietnam)

    NASA Astrophysics Data System (ADS)

    Tích, Vu Van; Leyreloup, Andrey; Maluski, Henry; Lepvrier, Claude; Lo, Chinh-hua; Vượng, Nguyễn V.

    2013-09-01

    Pelitic and semipelitic anatectic granulites form one of the major lithological units in Kan Nack complex of the Kon Tum massif (in south-central Vietnam), which comprises HT metamorphic and magmatic rocks including granulites and charnockites is classically regarded as the older part of the Gondwana-derived Indosinia terrain. Metamorphic evolution study of pelitic granulite, the most abundant among granulites exposed in this massif, facilitates to understand that tectonic setting take place during the Indosinian time. The paragenetic assemblages, mineral chemistry, thermobarometry and P-T evolution path of pelitic-semipelitic granulites from Kon Tum massif has been studied in detail. Petrographic feature demonstrates that the pelitic granulite experienced prograde history, from pregranulitic conditions in the amphibolite facies up to the peak granulitic assemblages. Successive prograde reactions led to the temperature-climax giving rise to assemblages with cordierite-hercynite and cordierite-hercynite-K-feldspar. Then, as attested by the mineralogic association occurring in cordieritic coronas, these rocks have been affected by retrograde conditions coeval with a decrease of the pressure. Thermobarometic results show that the highest temperature obtained by ksp/pl thermometry is 850 °C and the highest pressure obtained by GASP (Garnet Alumino-Silicate Plagioclase) is 7.8 kbar. The obtained clockwise P-T evolution path involving heating decompression, then nearly isothermal decompression and nearly isobar cooling conditions shows that high temperature-low pressure metamorphism of the studied pelitic anatectic granulites of Kan Nack complex occurred possibly in extensional setting during the Indosinian orogeny of 260-240 Ma in age.

  12. Microstructure and texture in lherzolites of the Balmuccia massif and their significance regarding the thermomechanical history

    NASA Astrophysics Data System (ADS)

    Skrotzki, W.; Wedel, A.; Weber, K.; Müller, W. F.

    1990-07-01

    The microstructure and crystallographic preferred orientation (here referred to as texture) in lherzolites of the Balmuccia massif have been investigated in order to unravel the thermomechanical history of this massif. Two deformation events may be recognized in the microstructure. In olivine the first deformation led to a coarse-grained dynamic recrystallization. The second deformation produced the subgrain and dislocation structure and a fine-grained dynamically recrystallized rim around the matrix grains. The subgrain boundaries are (100) and occasionally (001) tilt boundaries with variable tilt axis. The free dislocations are mainly screw dislocations with an [001] Burgers vector. An analysis of the dislocations bound in subgrain boundaries and the free dislocations yields {0 kl}[100] and { hk0}[001] as main activated slip systems. The orthopyroxenes are not recrystaUized and show deformation-induced clinoenstatite lamellae. The texture of olivine is characterized by [010] perpendicular to the foliation and [100] parallel to the lineation. In the orthopyroxene [100] is normal to the foliation and [001] normal to the lineation. The results are comparable with those found in similar massifs except the texture in the orthopyroxene. Stress and temperature estimates based on the dislocation density, subgrain size, dynamically recrystaUized grain sizes and the ortho-clinoenstatite transformation yield ≈ 20 MPa and ≈ 1000°C for deformation event I and 300 MPa and 650°C for deformation event II. The first and second deformation events are interpreted as intrusion of mantle material into the lower crust and the tilting of the Ivrea zone, respectively. From the correlation of the texture and microstructure it is concluded that the texture in the olivine reflects the first deformation event. The texture of the relatively hard and therefore only weakly deformed orthopyroxene may be explained by external rotation in the ductile olivine matrix.

  13. Formation of the Red Hills Ultramafic Massif during Subduction Initiation along an Oceanic Transform Fault

    NASA Astrophysics Data System (ADS)

    Tikoff, B.; Stewart, E. D.; Newman, J.; Lamb, W. M.

    2015-12-01

    The Red Hills ultramafic massif in the South Island, New Zealand, is part of the Dun Mountain Ophiolite Belt (DMOB). The DMOB was created at the onset of subduction in a forearc setting in the Middle Permian, and it likely formed immediately prior to the establishment of a magmatic arc along the New Zealand and Australian portions of the Gondwanan margin. The Red Hills ultramafic massif records a two-stage history of high temperature mantle flow during subduction initiation along the Gondwanan margin. Initial deformation was homogeneous and fabrics are constrictional. Kilometer-scale deformation zones, part of the second stage of deformation, overprinted the early homogeneous fabric throughout the western portion of the massif. Timing of all high-temperature mantle deformation in the Red Hills was between 285 and 274 Ma during subduction initiation based on the earliest ages of igneous activity in adjacent volcanic rocks, and a new U-Pb zircon age of 274.55±0.43 Ma from a cross-cutting dike. We present a kinematic model to explain the occurrence of the constructional fabrics during subduction initiation, and find that the three-dimensional boundary conditions for deformation in the incipient mantle wedge must have been transtensional, with a dominant trench-parallel component of motion. Such a scenario indicates subduction likely initiated along an active oceanic transform fault. We test this model by kinematically restoring the Red Hills ultramafics to their Permian orientation, and find the consistent elongation direction of the constructional fabrics was oriented nearly parallel to the trench. Stage 2 deformation zones were variably oriented, but all accommodated normal motion. These results support a model where the incipient mantle wedge was undergoing highly oblique transtension, and the lack of evidence for contraction suggests the onset of subduction along the Permian margin of New Zealand occurred along a transform fault due to spontaneous, density driven

  14. Subsurface Implications of Spatially Variable Seafloor Character on the Atlantis Massif

    NASA Astrophysics Data System (ADS)

    Greene, J. A.; Tominaga, M.; Blackman, D. K.

    2014-12-01

    We documented and mapped the characteristics of the seafloor on the Atlantis Massif, an ocean core complex located at 30°N on the Mid-Atlantic Ridge. Our goal is to investigate the implications of these surficial features, particularly whether their spatial variations might reflect subsurface lithology and geological processes. We utilized data collected during the MARVEL 2000 cruise AT3-60, specifically Alvin videos and rock samples, Argo II digital still photos, and TOBI/DSL-120 side-scan sonar mosaic. The Alvin dives studied occurred over the Central Dome and Eastern Block, which is interpreted as the hanging wall to the detachment that unroofed the dome. We also studied two Argo II dives located over the Central Dome, one over the Eastern Block, and one over the Western Shoulder of the southern dome. The TOBI/DSL-120 side-scan sonar followed a widespread, looped track providing near total coverage of the massif. We classified the character of the seafloor based on imagery, the acoustic reflectivity, and the basic composition of rock samples. To aid in our classification, we merged Argo II still images to produce photo-mosaics displaying tens of meters long transects. We then classified the seafloor as unconsolidated sediment, lithified sediment (a carbonate crust or cap), exposed bedrock, or rubble. To obtain a broader understanding of the Atlantis Massif, we analyzed the distribution of these classes of seafloor. Over the Central Dome and Western Shoulder, we found most seafloor classes present in notable amounts, with many individual areas dominated by a particular type.

  15. Types Of The Focal Mechanisms Of Seismic Events In The Khibiny Massif

    NASA Astrophysics Data System (ADS)

    Fedotova, I. V.; Yunga, S. L.

    The stress-strain state of Khibiny massif and the focal mechanisms of microseismic events (magnitudes as many M=1) were investigated. This analysis was based on seis- mical data registered by automized monitoring system of in the ore mines "Apatite" as well as on the catalogue of earthquakes registered by Kola regional seismological centre. The main goal of this study is the estimation of applicability of methods of quantitative seismology for a solution of local tasks of prognosis of the dynamic phe- nomena in the ore mines of Khibiny massif during widescale mining operations. On the basis of the existing methods original computer programs were developed. Taking into account features of local monitoring systems of seismicity and collection of the obtained data on focal mechanisms, calculations of matrix of mean "composite" focal mechanisms of the registered seismic events were carried out. The process of grouping of events was based on revealing of similar focal mechanisms. Eigen value analysis of average matrix was performed and the directions of main stresses and tendency of principal deformation directions in the massif are revealed. Thus schema of relative blocks movements is created. As a result of this study 5 basic groups with different types of focal mechanisms of seismic events are selected: normal fault; strike-slip fault (with contraction along the strike of ore bodies), thrust fault, and two interme- diate types - strike-slip with normal movement and strike-slip with upthrust move- ment. Specific structural blocks are revealed on the basis of schema of fault zones and zones of tectonic weakness and analysis of seismic events with the particular focal mechanisms. The directions of main stresses based on the composite focal mecha- nisms well correlates with the directions obtained by other methods. Composite focal mechanisms determined for low magnitude seismic events may be effectively used to control stress-strain state in rock massif, to select

  16. Accelerated glacier shrinkage in the Ak-Shyirak massif, Inner Tien Shan, during 2003-2013.

    PubMed

    Petrakov, Dmitry; Shpuntova, Alyona; Aleinikov, Alexandr; Kääb, Andreas; Kutuzov, Stanislav; Lavrentiev, Ivan; Stoffel, Markus; Tutubalina, Olga; Usubaliev, Ryskul

    2016-08-15

    The observed increase in summer temperatures and the related glacier downwasting has led to a noticeable decrease of frozen water resources in Central Asia, with possible future impacts on the economy of all downstream countries in the region. Glaciers in the Ak-Shyirak massif, located in the Inner Tien Shan, are not only affected by climate change, but also impacted by the open pit gold mining of the Kumtor Gold Company. In this study, glacier inventories referring to the years 2003 and 2013 were created for the Ak-Shyirak massif based on satellite imagery. The 193 glaciers had a total area of 351.2±5.6km(2) in 2013. Compared to 2003, the total glacier area decreased by 5.9±3.4%. During 2003-2013, the shrinkage rate of Ak-Shyirak glaciers was twice than that in 1977-2003 and similar to shrinkage rates in Tien Shan frontier ranges. We assessed glacier volume in 2013 using volume-area (VA) scaling and GlabTop modelling approaches. Resulting values for the whole massif differ strongly, the VA scaling derived volume is 30.0-26.4km(3) whereas the GlabTop derived volume accounts for 18.8-13.2km(3). Ice losses obtained from both approaches were compared to geodetically-derived volume change. VA scaling underestimates ice losses between 1943 and 2003 whereas GlabTop reveals a good match for eight glaciers for the period 2003-2012. In comparison to radio-echo soundings from three glaciers, the GlabTop model reveals a systematic underestimation of glacier thickness with a mean deviation of 16%. GlabTop tends to significantly underestimate ice thickness in accumulation areas, but tends to overestimate ice thickness in the lowermost parts of glacier snouts. Direct technogenic impact is responsible for about 7% of area and 5% of mass loss for glaciers in the Ak-Shyirak massif during 2003-2013. Therefore the increase of summer temperature seems to be the main driver of accelerated glacier shrinkage in the area. PMID:27100016

  17. Recycled gabbro signature in Upper Cretaceous Magma within Strandja Massif: NW Turkey

    NASA Astrophysics Data System (ADS)

    Ulusoy, Ezgi; Kagan Kadioglu, Yusuf

    2016-04-01

    Basic magma intrusions within plate interiors upwelling mantle plumes have chemical signatures that are distinct from mid-ocean ridge magmas. When a basic magma interact with continental crust or with the felsic magma, the compositions of both magma changes, but there is no consensus as to how this interaction occurs. Here we analyse the mineral behavior and trace element signature of gabbroic rocks of the samples collected from the Strandja Massif. Srednogorie magmatic arc is a part of Apuseni- Banat-Timok-Srednogorie magmatic belt and formed by subduction and closure of the Tethys Ocean during Upper Cretaceous times. Upper Cretaceous magmatic rocks cutting Strandja Massif in NW Turkey belong to eastern edge of Srednogorie Magmatic arc. Upper Cretacous magmatic rocks divided into four subgroup in Turkey part of Strandja massif: (I) granitic rocks, (II) monzonitic rock, (III) syenitic rocks and (IV) gabbroic rocks. Gabbroic rocks outcropped around study area in phaneritic - equigranular texture. According to mineralogic - petrographic studies gabbros have mainly holocrystalline texture and ophitic to subophitic texture composed of plagioclase, amphibole, pyroxene, and rarely olivine and opaque minerals. Also because of special conditions there have been pegmatitic texture on mafic minerals with euhedral form up to 3 cm in size and orbicular texture which reach 15cm in size and rounded - elliptical form. Confocal Raman Spectroscopy studies reveals that plagioclase are ranging in composition from labradorite to bytownite, the pyroxene are ranging in composition from diopside to augite acting with uralitization processes and the olivine are generally in the composition of forsterite. Petrographic and mineralogical determination reveals some metasomatic magmatic epidote presence. Confocal Raman Spectroscopy studies on anhydrous minerals within gabbroic rocks shows affect of hydrous process because of magma mixing. The gabbroic rocks have tholeiitic and changed towards

  18. Isotopic age and heterogeneous sources of gabbro‒anorthosites from the Patchemvarek massif, Kola Peninsula

    NASA Astrophysics Data System (ADS)

    Vrevsky, A. B.; Lvov, A. P.

    2016-07-01

    New U‒Pb (SHRIMP II) data on the age (2661.8 ± 7.1 Ma) and isotopic (Sm‒Nd) composition of the Patchemvarek gabbro‒anorthosite massif located in the junction zone between the Neoarchean Kolmozero-Voron'ya greenstone belt and Keivy paragneiss structure are discussed. The established age and geological‒tectonic position of gabbro‒anorthosites allow the prognostic metallogenic estimate of Ti‒V‒Fe mineralization to be extended to the entire Kolmozero-Voron'ya‒Keivy infrastructural zone of the Kola‒Norwegian province of the Fennoscandian shield.

  19. Deglaciation and post-glacial environmental evolution in the Western Massif of Picos de Europa

    NASA Astrophysics Data System (ADS)

    Ruiz-Fernández, Jesús; Oliva, Marc; García, Cristina; López-Sáez, José Antonio; Gallinar, David; Geraldes, Miguel

    2014-05-01

    This study examines the process of deglaciation of the Western Massif of Picos de Europa through field work, geomorphological mapping, sedimentary records and absolute datings of 14C. This massif has several peaks over 2,400 m a.s.l. (Peña Santa de Castilla, 2,596 m; Torre Santa María, 2,486 m; Torre del Mediu, 2,467 m). It is composed mainly by Carboniferous limestones. This area has been intensively affected by karstic dissolution, Quaternary glaciers and fluvio-torrential processes (Miotke, 1968; Moreno et al, 2010; Ruiz-Fernández et al, 2009; Ruiz-Fernández, 2013). At present day, periglacial processes are active at the highest elevations (Ruiz-Fernández, 2013). We have identified four main glacial stages regarding the deglaciation of the massif: (i) maximum advance corresponding to the Last Glaciation, (ii) retreat and stabilization after the maximum advance, (iii) Late Glacial, and (iv) Little Ice Age. Sedimentological studies also contribute data to the understanding of the chronological framework of these environmental changes. The datings of the bottom sediments in two long sequences (8 and 5.4 m) provided a minimum age of 18,075 ± 425 cal BP for the maximum advance stage and 11,150 ± 900 cal BP for retreat and stabilization in the phase following the maximum advance. The ongoing analyses of these sequences at very high resolution will provide new knowledge about the environmental conditions prevailing since the deglaciation of the massif. References Miotke, F.D. (1968). Karstmorphologische studien in der glazial-überformten Höhenstufe der Picos de Europa, Nordspanien. Hannover, Selbtverlag der Geografischen Gessellschaft, 161 pp. Moreno, A., Valero, B.L., Jiménez, M., Domínguez, M.J., Mata, M.P., Navas, A., González, P., Stoll, H., Farias, P., Morellón, M., Corella, J.P. & Rico, M. (2010). The last deglaciation in the Picos de Europa National Park (Cantabrian Mountains, Northern Spain). Journal of Quaternary Science, 25 (7), 1076-1091. Ruiz

  20. MASSIF-1: a beamline dedicated to the fully automatic characterization and data collection from crystals of biological macromolecules.

    PubMed

    Bowler, Matthew W; Nurizzo, Didier; Barrett, Ray; Beteva, Antonia; Bodin, Marjolaine; Caserotto, Hugo; Delagenière, Solange; Dobias, Fabian; Flot, David; Giraud, Thierry; Guichard, Nicolas; Guijarro, Mattias; Lentini, Mario; Leonard, Gordon A; McSweeney, Sean; Oskarsson, Marcus; Schmidt, Werner; Snigirev, Anatoli; von Stetten, David; Surr, John; Svensson, Olof; Theveneau, Pascal; Mueller-Dieckmann, Christoph

    2015-11-01

    MASSIF-1 (ID30A-1) is an ESRF undulator beamline operating at a fixed wavelength of 0.969 Å (12.8 keV) that is dedicated to the completely automatic characterization of and data collection from crystals of biological macromolecules. The first of the ESRF Upgrade MASSIF beamlines to be commissioned, it has been open since September 2014, providing a unique automated data collection service to academic and industrial users. Here, the beamline characteristics and details of the new service are outlined. PMID:26524320

  1. Utilization of digital LANDSAT imagery for the study of granitoid bodies in Rondonia: Case example of the Pedra Branca massif

    NASA Technical Reports Server (NTRS)

    Parada, N. D. J. (Principal Investigator); Almeidafilho, R.; Payolla, B. L.; Depinho, O. G.; Bettencourt, J. S.

    1984-01-01

    Analysis of digital multispectral MSS-LANDSAT images enhanced through computer techniques and enlarged to a video scale of 1:100.000, show the main geological and structura features of the Pedra Branca granitic massif in Rondonia. These are not observed in aerial photographs or adar images. Field work shows that LANDSAT photogeological units correspond to different facies of granitic rocks in the Pedra Branca massif. Even under the particular characteristics of Amazonia (Tropical Forest, deep weathering, and Quaternary sedimentary covers), an adequate utilization of orbital remote sensing images can be important tools for the orientation of field works.

  2. MASSIF-1: a beamline dedicated to the fully automatic characterization and data collection from crystals of biological macromolecules

    PubMed Central

    Bowler, Matthew W.; Nurizzo, Didier; Barrett, Ray; Beteva, Antonia; Bodin, Marjolaine; Caserotto, Hugo; Delagenière, Solange; Dobias, Fabian; Flot, David; Giraud, Thierry; Guichard, Nicolas; Guijarro, Mattias; Lentini, Mario; Leonard, Gordon A.; McSweeney, Sean; Oskarsson, Marcus; Schmidt, Werner; Snigirev, Anatoli; von Stetten, David; Surr, John; Svensson, Olof; Theveneau, Pascal; Mueller-Dieckmann, Christoph

    2015-01-01

    MASSIF-1 (ID30A-1) is an ESRF undulator beamline operating at a fixed wavelength of 0.969 Å (12.8 keV) that is dedicated to the completely automatic characterization of and data collection from crystals of biological macromolecules. The first of the ESRF Upgrade MASSIF beamlines to be commissioned, it has been open since September 2014, providing a unique automated data collection service to academic and industrial users. Here, the beamline characteristics and details of the new service are outlined. PMID:26524320

  3. Système hydrogéologique d'un massif minier ultrabasique de Nouvelle-Calédonie

    NASA Astrophysics Data System (ADS)

    Join, Jean-Lambert; Robineau, Bernard; Ambrosi, Jean-Paul; Costis, Claire; Colin, Fabrice

    2005-12-01

    Ultramafic rocks outcrop over more than one third of New Caledonia's main island. Under tropical conditions, thick lateritic mantles with nickel concentrations developed on these rocks by geochemical weathering. Groundwater in ultramafic mined massifs represents a valuable resource, but also a severe constrain for mining engineering. Previous works describe several water tables in the various layers of the weathering mantle. From a hydrologic study of the Tiebaghi massif, the hydraulic continuity across the weathering layers down to the bedrock is proposed. To cite this article: J.-L. Join et al., C. R. Geoscience 337 (2005).

  4. Oriented feldspar-feldspathoid intergrowths in rocks of the Khibiny massif: genetic implications

    NASA Astrophysics Data System (ADS)

    Ageeva, Olga A.; Abart, Rainer; Habler, Gerlinde; Ye. Borutzky, Boris; Trubkin, Nikolay V.

    2012-09-01

    Poikilitic megacrysts of alkali feldspar with abundant inclusions of feldspar-nepheline and feldspar-kalsilite micrographic or lamellar intergrowths are characteristic for the rischorrites of the Khibiny massif. Strict crystallographic orientation relations were identified among the intergrowth phases based on optical investigation using a 4-axes universal stage and crystal orientation imaging using electron back scatter diffraction. The most frequently observed orientation relation is the parallel orientation of the kalsilite and nepheline [001] directions with the [010] direction of the alkali feldspar host and concomitant coincidence of the feldspathoid [100] directions with the [100]-, [101]- and [001] directions of the alkali feldspar. The presence of relic nepheline within intergrowth domains and the successive replacement of precursor nepheline by alkali feldspar and associated formation of feldspar-feldspathoid intergrowth suggest development of the rischorrites from feldspar urtites, in which nepheline is the dominant felsic phase. The metasomatic nature of the transformation of urtites to rischorrites is identified from massive introduction of potassium and silica and removal of sodium. Metasomatism occurred at high temperature; the gigantic apatite deposits of the Khibiny massif seem to be related to this metasomatic event.

  5. The topographic signature of Quaternary tectonic uplift in the Ardennes massif (Western Europe)

    NASA Astrophysics Data System (ADS)

    Sougnez, N.; Vanacker, V.

    2011-04-01

    Geomorphic processes that produce and transport sediment, and incise river valleys are complex; and often difficult to quantify over longer timescales of 103 to 105 y. Morphometric indices that describe the topography of hill slopes, valleys and river channels have commonly been used to compare morphological characteristics between catchments and to relate them to hydrological and erosion processes. This study aims to analyze the link between tectonic uplift rates and landscape morphology based on slope and channel morphometric indexes. To achieve this objective, we selected 10 catchments of about 150 to 250 km2 across the Ardennes Massif (a Palaeozoic massif of NW Europe, principally located in Belgium) that cover various tectonic domains with uplift rates ranging from about 0.06 to 0.20 mm yr-1 since mid-Pleistocene times. The morphometric analysis indicates that the slope and channel morphology of third-order catchments is not yet in topographic steady-state, and exhibits clear convexities in slope and river profiles. Our analysis indicates that the fluvial system is the main driver of topographic evolution and that the spatial pattern of uplift rates is reflected in the distribution of channel steepness and convexity. The spatial variation that we observe in slope and channel morphology between the 10 third-order catchments suggests that the response of the fluvial system was strongly diachronic, and that a transient signal of adjustment is migrating from the Meuse valley towards the Ardennian headwaters.

  6. New radiocarbon chronology of a late Holocene landslide event in the Mont Blanc massif, Italy

    NASA Astrophysics Data System (ADS)

    Hajdas, Irka; Sojc, Ursula; Ivy-Ochs, Susan; Akçar, Naki; Deline, Philip

    2016-04-01

    The Ferret valley Arp Nouva peat bog located in the Mont Blanc massif was critically evaluated since previously published radiocarbon dates have led to controversial conclusions on the formation of the swamp. Radiocarbon dating of roots from three pits of up to 1 m depth was applied to discuss the question whether the historical documented rock avalanche occurring in AD 1717 overran the peat bog or formed it at a later stage. Our results indicate that the rock avalanche formed the Arp Nouva peat bog by downstream blockage of the Bellecombe torrent. Furthermore, careful sample preparation with consequent separation of roots from the bulk peat sample provides possible explanation for the too old 14C ages of bulk peat samples dated previously (Deline and Kirkbride, 2009 and references therein). This work demonstrates that a combined geomorphological and geochronological approach is the most reliable way to reconstruct landscape evolution, especially in light of apparent chronological problems. The key to successful 14C dating is a careful sample selection and the identification of material that might be not ideal for chronological reconstructions. References Deline, Philip, and Martin P. Kirkbride. "Rock avalanches on a glacier and morainic complex in Haut Val Ferret (Mont Blanc Massif, Italy)".Geomorphology 103 (2009): 80-92.

  7. Thermochronology and tectonics of the Mérida Andes and the Santander Massif, NW South America

    NASA Astrophysics Data System (ADS)

    van der Lelij, Roelant; Spikings, Richard; Mora, Andrés

    2016-04-01

    New apatite U-Pb and multiphase 40Ar/39Ar data constrain the high to medium temperature (~ 500 °C-~ 300 °C) thermal histories of igneous and metamorphic rocks exposed in the Mérida Andes of Venezuela, and new apatite and zircon fission track data constrain the ~ 500 °C-~ 60 °C thermal histories of pre-Jurassic igneous and metamorphic rocks of the adjacent Santander Massif of Colombia. Computed thermal history envelopes using apatite U-Pb dates and grain size information from an Early Palaeozoic granodiorite in the Mérida Andes suggest that it cooled from > 500 °C to < 350 °C between ~ 266 Ma and ~ 225 Ma. Late Permian to Triassic cooling is also recorded in Early Palaeozoic granitoids and metasedimentary rocks in the Mérida Andes by numerous new muscovite and biotite 40Ar/39Ar plateau dates spanning 257.1 ± 1.0 Ma to 205.1 ± 0.8 Ma. This episode of cooling is not recognised in the Santander Massif, where 40Ar/39Ar data suggest that some Early Palaeozoic rocks cooled below ~ 320 °C in the Early Palaeozoic. However, most data from pre-Jurassic rocks reveal a regional heat pulse at ~ 200 Ma during the intrusion of numerous shallow granitoids, resulting in temperatures in excess of ~ 520 °C, obscuring late Palaeozoic histories. The generally accepted timing of amalgamation of Pangaea along the Ouachita-Marathon suture pre-dates Late Permian to Triassic cooling recorded in basement rocks of the Mérida Andes by > 30 Ma, and its effect on rocks preserved in north-western South America is unknown. We interpret late Permian to Triassic cooling in the Mérida Andes to be driven by exhumation. Previous studies have suggested that a short phase of shortening and anatexis is recorded at ~ 253 Ma in the Maya Block, which may have been adjacent to the basement rocks of the Mérida Andes in the Late Permian. The coeval onset of exhumation in the Mérida Andes may be a result of increased coupling in the magmatic arc, which was located along the western margin of

  8. A Paleozoic anorthosite massif related to rutile-bearing ilmenite ore deposits, south of the Polochic fault, Chiapas Massif Complex, Mexico

    NASA Astrophysics Data System (ADS)

    Cisneros, A.; Ortega-Gutiérrez, F.; Weber, B.; Solari, L.; Schaaf, P. E.; Maldonado, R.

    2013-12-01

    The Chiapas Massif Complex in the southern Maya terrane is mostly composed of late Permian igneous and meta-igneous rocks. Within this complex in southern Mexico and in the adjacent San Marcos Department of Guatemala, south of the Polochic fault, several small outcrops (~10 km2) of a Phanerozoic andesine anorthosite massif were found following an E-W trend similar to the Polochic-Motagua Fault System. Such anorthosites are related to rutile-bearing ilmenite ore deposits and hornblendite-amphibolite bands (0.1-3 meters thick). The anorthosites show recrystallization and metamorphic retrogression (rutile with titanite rims), but no relicts of high-grade metamorphic minerals such as pyroxene or garnet have been found. In Acacoyagua, Chiapas, anorthosites are spatially related to oxide-apatite rich mafic rocks; in contrast, further to the west in Motozintla, they are related to monzonites. Zircons from these monzonites yield a Permian U-Pb age (271.2×1.4 Ma) by LA-MC-ICPMS. Primary mineral assemblage of the anorthosites include mostly medium to fine-grained plagioclase (>90%) with rutile and apatite as accessory minerals, occasionally with very low amounts of quartz. Massive Fe-Ti oxide lenses up to tens of meters in length and few meters thick are an ubiquitous constituent of these anorthosites and their mineralogy include ilmenite (with exsolution lamellae of Ti-magnetite), rutile, magnetite, clinochlore, ×spinel, ×apatite, ×zircon and srilankite (Ti2ZrO6, first finding of this phase in Mexico). Rutile occurs within the massive ilmenite in two morphological types: (1) fine-grained (5-40 μm) rutile along ilmenite grain boundaries or fractures, and (2) coarse-grained rutile (<5 mm) as discrete grains, whereas magnetite and srilankite only appear as small grains along ilmenite boundaries. Zircon is present as discontinuously aligned small grains (10-40 μm) forming rims around many rutile and ilmenite grains. Attempts to date zircon rims by U-Pb using LA

  9. Possible petrogenetic associations among igneous components in North Massif soils: Evidence in 2-4 mm soil particles from 76503

    NASA Technical Reports Server (NTRS)

    Jolliff, Bradley L.; Bishop, Kaylynn M.; Haskin, Larry A.

    1992-01-01

    Studies of Apollo 17 highland igneous rocks and clasts in breccias from the North and South Massifs have described magnesian troctolite, norite, anorthositic gabbro, dunite, spinel cataclasites, and granulitic lithologies that may have noritic anothosite or anorthositic norite/gabbro as igneous precursors, and have speculated on possible petrogenetic relationships among these rock types. Mineral compositions and relative proportions of plagioclase and plagioclase-olivine particles in samples 76503 indicate that the precursor lithology of those particles were troctolitic anorthosite, not troctolite. Mineral and chemical compositions of more pyroxene-rich, magnesian breccias and granulites in 76503 indicate that their precursor lithology was anorthositic norite/gabbro. The combination of mineral compositions and whole-rock trace-element compositional trends supports a genetic relationship among these two groups as would result from differentiation of a single pluton. Although highland igneous lithologies in Apollo 17 materials have been described previously, the proportions of different igneous lithologies present in the massifs, their frequency of association, and how they are related are not well known. We consider the proportions of, and associations among, the igneous lithologies found in a North Massif soil, which may represent those of the North Massif or a major part of it.

  10. Comprenhensive Program of Engineering and Geologic Surveys for Designing and Constructing Radioactive Waste Storage Facilities in Hard Rock Massifs

    SciTech Connect

    Gupalo, T; Milovidov, V; Prokopoca, O; Jardine, L

    2002-12-27

    Geological, geophysical, and engineering-geological research conducted at the 'Yeniseisky' site obtained data on climatic, geomorphologic, geological conditions, structure and properties of composing rock, and conditions of underground water recharge and discharge. These results provide sufficient information to make an estimate of the suitability of locating a radioactive waste (R W) underground isolation facility at the Nizhnekansky granitoid massif

  11. Geochemistry and petrogenesis of post-collisional ultrapotassic syenites and granites from southernmost Brazil: the Piquiri Syenite Massif.

    PubMed

    Nardi, Lauro V S; Plá-Cid, Jorge; Bitencourt, Maria de Fátima; Stabel, Larissa Z

    2008-06-01

    The Piquiri Syenite Massif, southernmost Brazil, is part of the post-collisional magmatism related to the Neoproterozoic Brasiliano-Pan-African Orogenic Cycle. The massif is about 12 km in diameter and is composed of syenites, granites, monzonitic rocks and lamprophyres. Diopside-phlogopite, diopside-biotite-augite-calcic-amphibole, are the main ferro-magnesian paragenesis in the syenitic rocks. Syenitic and granitic rocks are co-magmatic and related to an ultrapotassic, silica-saturated magmatism. Their trace element patterns indicate a probable mantle source modified by previous, subduction-related metasomatism. The ultrapotassic granites of this massif were produced by fractional crystallization of syenitic magmas, and may be considered as a particular group of hypersolvus and subsolvus A-type granites. Based upon textural, structural and geochemical data most of the syenitic rocks, particularly the fine-grained types, are considered as crystallized liquids, in spite of the abundance of cumulatic layers, schlieren, and compositional banding. Most of the studied samples are metaluminous, with K2O/Na2O ratios higher than 2. The ultrapotassic syenitic and lamprophyric rocks in the Piquiri massif are interpreted to have been produced from enriched mantle sources, OIB-type, like most of the post-collisional shoshonitic, sodic alkaline and high-K tholeiitic magmatism in southernmost Brazil. The source of the ultrapotassic and lamprophyric magmas is probably the same veined mantle, with abundant phlogopite + apatite + amphibole that reflects a previous subduction-related metasomatism. PMID:18506262

  12. Massification, Bureaucratization and Questing for "World-Class" Status: Higher Education in China since the Mid-1990s

    ERIC Educational Resources Information Center

    Ngok, Kinglun

    2008-01-01

    Purpose: This article aims to review the latest developments of the higher education sector in China since the mid-1990s by focusing on the expansion of university education. Design/methodology/approach: It is argued that while massification of higher education is an important indication of the progress in China's higher education system, the…

  13. Has Massification of Higher Education Led to More Equity? Clues to a Reflection on Portuguese Education Arena

    ERIC Educational Resources Information Center

    Dias, Diana

    2015-01-01

    Massification is an undeniable phenomenon in the higher education arena. However, there have been questions raised regarding the extent to which a mass system really corresponds to an effective democratisation not only of access, but also of success. With regards to access, this article intends, through a brief analysis of the expansion of higher…

  14. Cenozoic remagnetization of the Paleozoic rocks in the Kitakami massif of northeast Japan, and its tectonic implications

    NASA Astrophysics Data System (ADS)

    Otofuji, Yo-ichiro; Takemoto, Kazuhiro; Zaman, Haider; Nishimitsu, Yoshitomo; Wada, Yutaka

    2003-05-01

    Secondary remanent magnetization is identified in the Paleozoic igneous and sedimentary rocks of the Kitakami massif. The secondary nature is shown by a negative fold test for the Permo-Carboniferous sedimentary rocks. The northwesterly paleomagnetic declination with moderate inclination ( D=321.2°, I=56.5°, α95=5.2°, N=18) of this secondary remanent magnetization is almost parallel to the primary magnetization reported for the Cenozoic welded tuffs of northeast Japan, indicating that the Paleozoic rocks were subjected to remagnetization at any period between 62 and 16 Ma. The secondary magnetization of the serpentinized ultramafic rocks is carried by magnetite, which grew in veins and mesh rims of serpentine, whereas the carrier of the magnetization in limestones is fine-grained pyrrhotite. Combining this with the previously reported remagnetization of the Kitakami granitic rocks, it is suggested that rocks in the Kitakami massif were subjected to crystallization remanent magnetization at low-temperature conditions. Since serpentinization requires fluid migration, one of the most likely events is the eastward lateral migration of water into the Kitakami massif. We postulate a Cenozoic suturing of the Kitakami massif with the Asian continent as a plausible tectonic event for this fluid migration.

  15. Seismic imaging of the western Iberian crust using ambient noise: Boundaries and internal structure of the Iberian Massif

    NASA Astrophysics Data System (ADS)

    Silveira, Graça; Dias, Nuno; Villaseñor, Antonio

    2013-04-01

    The Iberian Massif one of the major structural units of the Iberian Peninsula is composed by rocks with ages ranging from the Upper Precambrian to Upper Carboniferous. The massif outcrops in Central and Western Iberia and the location of its limits, as well as the relationship between its shallow and deeper structures are still a matter of debate. Several problems like source-receiver geometry, irregular seismicity distribution or, for some methods, low seismicity occurrence did not allow obtaining high-resolution models of Iberian structure using traditional imaging methods. Seismic interferometry/ambient noise surface-waves tomography allows imaging regions with a resolution that mainly depends on the seismic network coverage. This study aims to map the boundaries of the Iberian Massif particularly those that are covered or in contact with recent (Cenozoic) and older (Mesozoic) basins. Whenever possible, we intend to characterize second-order structures inside the Massif. We present new Rayleigh-wave dispersion maps of the western Iberian Peninsula for periods between 8 and 30 seconds, obtained from correlations of seismic ambient noise, following the recent increase in seismic broadband network density in Portugal and Spain. Group velocities have been computed for each station pair using the empirical Green's functions generated by cross-correlating one-day-length seismic ambient-noise records. The resulting high-path density allows us to obtain lateral variations of the group velocities as a function of period in cells of 0.5° x 0.5° with an unprecedented resolution. As a result we were able to address some of the unknowns regarding the lithospheric structure beneath SW Iberia. The dispersion maps allow the imaging of the major structural units, namely the Iberian Massif, and the Lusitanian and Algarve Meso-Cenozoic basins. The Cadiz Gulf/Gibraltar Strait area corresponds to a strong low-velocity anomaly, which can be followed to the largest period inverted

  16. SE-FIT

    NASA Technical Reports Server (NTRS)

    Chen, Yongkang; Weislogel, Mark; Schaeffer, Ben; Semerjian, Ben; Yang, Lihong; Zimmerli, Gregory

    2012-01-01

    The mathematical theory of capillary surfaces has developed steadily over the centuries, but it was not until the last few decades that new technologies have put a more urgent demand on a substantially more qualitative and quantitative understanding of phenomena relating to capillarity in general. So far, the new theory development successfully predicts the behavior of capillary surfaces for special cases. However, an efficient quantitative mathematical prediction of capillary phenomena related to the shape and stability of geometrically complex equilibrium capillary surfaces remains a significant challenge. As one of many numerical tools, the open-source Surface Evolver (SE) algorithm has played an important role over the last two decades. The current effort was undertaken to provide a front-end to enhance the accessibility of SE for the purposes of design and analysis. Like SE, the new code is open-source and will remain under development for the foreseeable future. The ultimate goal of the current Surface Evolver Fluid Interface Tool (SEFIT) development is to build a fully integrated front-end with a set of graphical user interface (GUI) elements. Such a front-end enables the access to functionalities that are developed along with the GUIs to deal with pre-processing, convergence computation operation, and post-processing. In other words, SE-FIT is not just a GUI front-end, but an integrated environment that can perform sophisticated computational tasks, e.g. importing industry standard file formats and employing parameter sweep functions, which are both lacking in SE, and require minimal interaction by the user. These functions are created using a mixture of Visual Basic and the SE script language. These form the foundation for a high-performance front-end that substantially simplifies use without sacrificing the proven capabilities of SE. The real power of SE-FIT lies in its automated pre-processing, pre-defined geometries, convergence computation operation

  17. Cambrian to Lower Ordovician complexes of the Kokchetav Massif and its fringing (Northern Kazakhstan): Structure, age, and tectonic settings

    NASA Astrophysics Data System (ADS)

    Degtyarev, K. E.; Tolmacheva, T. Yu.; Tretyakov, A. A.; Kotov, A. B.; Shatagin, K. N.

    2016-01-01

    A comprehensive study of the Lower Palaeozoic complexes of the Kokchetav Massif and its fringing has been carried out. It has allowed for the first time to discover and investigate in detail the stratified and intrusive complexes of the Cambrian-Early Ordovician. Fossil findings and isotope geochronology permitted the determination of their ages. The tectonic position and internal structures of those complexes have also been defined and their chemical features have been analyzed as well. The obtained data allowed us to put forward a model of the geodynamic evolution of Northern Kazakhstan in the Late Ediacaran-Earliest Ordovician. The accumulation of the oldest Ediacaran to Earliest Cambrian siliciclastics and carbonates confined to the Kokchetav Massif and its fringing occurred in a shallow shelf environment prior to its collision with the Neoproterozoic Daut island arc: complexes of the latter have been found in the northeast of the studied area. The Early Cambrian subduction of the Kokchetav Massif under the Daut island arc, their following collision and exhumation of HP complexes led to the formation of rugged ground topography, promoting deposition of siliceous-clastic and coarse clastic units during the Middle to early Late Cambrian. Those sediments were mainly sourced from eroded metamorphic complexes of the Kokchetav Massif basement. At the end of the Late Cambrian to the Early Ordovician within the boundaries of the massif with the Precambrian crust, volcanogenic and volcano-sedimentary units along with gabbros and granites with intraplate affinities were formed. Simultaneously in the surrounding zones, which represent relics of basins with oceanic crust, N-MORB- and E-MORB-type ophiolites were developed. These complexes originated under extensional settings occurred in the majority of the Caledonides of Kazakhstan and Northern Tian Shan. In the Early Floian Stage (Early Ordovician) older heterogeneous complexes were overlain by relatively monotonous

  18. Detachment shear zone of the Atlantis Massif core complex, Mid-Atlantic Ridge, 30°N

    NASA Astrophysics Data System (ADS)

    Karson, J. A.; Früh-Green, G. L.; Kelley, D. S.; Williams, E. A.; Yoerger, D. R.; Jakuba, M.

    2006-06-01

    Near-bottom investigations of the cross section of the Atlantis Massif exposed in a major tectonic escarpment provide an unprecedented view of the internal structure of the footwall domain of this oceanic core complex. Integrated direct observations, sampling, photogeology, and imaging define a mylonitic, low-angle detachment shear zone (DSZ) along the crest of the massif. The shear zone may project beneath the nearby, corrugated upper surface of the massif. The DSZ and related structures are inferred to be responsible for the unroofing of upper mantle peridotites and lower crustal gabbroic rocks by extreme, localized tectonic extension during seafloor spreading over the past 2 m.y. The DSZ is characterized by strongly foliated to mylonitic serpentinites and talc-amphibole schists. It is about 100 m thick and can be traced continuously for at least 3 km in the tectonic transport direction. The DSZ foliation arches over the top of the massif in a convex-upward trajectory mimicking the morphology of the top of the massif. Kinematic indicators show consistent top-to-east (toward the MAR axis) tectonic transport directions. Foliated DSZ rocks grade structurally downward into more massive basement rocks that lack a pervasive outcrop-scale foliation. The DSZ and underlying basement rocks are cut by discrete, anastomosing, normal-slip, shear zones. Widely spaced, steeply dipping, normal faults cut all the older structures and localize serpentinization-driven hydrothermal outflow at the Lost City Hydrothermal Field. A thin (few meters) sequence of sedimentary breccias grading upward into pelagic limestones directly overlies the DSZ and may record a history of progressive rotation of the shear zone from a moderately dipping attitude into its present, gently dipping orientation during lateral spreading and uplift.

  19. Thematic mapping of likely target areas for the occurence of cassiterite in the Serra do Mocambo (GO) granitic massifs using LANDSAT 2 digital imaging

    NASA Technical Reports Server (NTRS)

    Almeidofilho, R. (Principal Investigator)

    1984-01-01

    The applicability of LANDSAT/MSS images, enhanced by computer derived techniques, as essential tools in mineral research was investigated and the Serra do Mocambo granitic massif was used as illustration. Given the peculiar factors founded in this area, orbital imagery permitted the delineation of potential target areas of mineralization occurrences, associated to albitized/greisenized types. Follow up prospection for primary tin deposits in this granitic massif should be restricted to the delineated areas which are less than 5% of the total superficial area of the massif.

  20. Geothermobarometry of basaltic glasses from the Tamu Massif, Shatsky Rise oceanic plateau

    NASA Astrophysics Data System (ADS)

    Husen, Anika; Almeev, Renat R.; Holtz, François; Koepke, Jürgen; Sano, Takashi; Mengel, Kurt

    2013-10-01

    We present the results of a petrological study of core samples from Tamu Massif (Site U1347), recovered during the Shatsky Rise Integrated Ocean Drilling Program (IODP) Expedition 324. The basaltic glasses from Site U1347 are evolved tholeiitic basalts containing 5.2-6.8 wt% MgO, and are principally located within the compositional field of mid-ocean ridge basalts (MORBs) but they have systematically higher FeO, lower Al2O3, SiO2, and Na2O concentrations, and the CaO/Al2O3 ratios are among the highest known for MORBs. In this sense, glasses from Site U1347 more closely resemble basaltic magmas from the Ontong Java Plateau (OJP), although they still have lower SiO2 concentrations. In contrast to MORB and similar to OJP, our fractionation corrected values of Na2O and CaO/Al2O3 indicate more than 20% of partial melting of the mantle during the generation of the parental magmas of Tamu Massif. The water contents in the glasses, determined by midinfrared Fourier transform infrared (FTIR) spectroscopy, are MORB-like, and vary between 0.18 and 0.6 wt% H2O. The calculated pressure (P)-temperature (T) conditions at which the natural glasses represent cotectic olivine-plagioclase-clinopyroxene compositions range from 0.1 to 240 MPa and 1100 to 1150°C reflecting magma storage at shallow depth. The variation of the glass compositions and the modeled P-T conditions in correlation with the relative ages indicate that there were at least two different magmatic cycles characterized by variations in eruptive styles (massive flows or pillow lavas), chemical compositions, volatile contents, and preeruptive P-T conditions. Each magmatic cycle represents the progressive differentiation in course of polybaric crystallization after the injection of a more primitive magma batch. Magma crystallization and eruption episodes are followed by magmatic inactivity reflected in the core sequence by a sedimentary layer. Our data for Tamu Massif demonstrate that, similar to Ontong Java ocean

  1. Exploring the Notion That Subduction Erosion Has Removed or Submerged Costa Rica's Early Tertiary Arc Massifs

    NASA Astrophysics Data System (ADS)

    Scholl, D. W.

    2007-05-01

    Arc igneous rocks of Paleocene, Eocene, and Oligocene age are widely exposed in the southern, coastal region of Panama (Lissinna et al., EGU abstract, 2006). These rocks intrude or overlie mafic basement rock of the Caribbean Large Igneous Province (CLIP) of Late Cretaceous age that extends to the east to underlie the Caribbean Basin and form the Caribbean plate. Immediately west of Panama, in coastal Costa Rica, exposures of CLIP basement are not intruded or overlain by arc magmatic rocks of early Tertiary age. EXPLANATIONS: Potentially, the early Tertiary subduction zone that dipped beneath the Pacific margin of Panama did not extend to the west, thus no arc magmatism occurred where Costa Rica presently exists. Alternatively, the subduction zone bordering the Pacific edge of the CLIP extended below Costa Rica but former exposures of early Tertiary arc magmatic rocks piled there have been erosionally removed or buried beneath Miocene and younger arc massifs of interior mountain belts. EXPLORING A SUBDUCTION EROSION EXPLANATION Onshore and offshore evidence documents that subduction erosion thins and truncates the submerged rock framework of the Middle and South America forearc. The eroded (removed) material is transported toward and into the mantle within the subduction channel separating the upper plate of the forearc and lower plate of the subducting oceanic crust. The long-term (greater than 10 Myr) rate of truncation (i. e., migration of the trench toward a fixed, onshore reference) averages 2 to 3 km/Myr. Because of the subduction of the aseismic Cocos Ridge beneath Costa Rica, during at least the past 4 to 5 Myr the rate of truncation at this margin has been much higher. It is proposed that during the past 50 Myr subduction erosion has truncated the Costa Rica forearc by at least 100 km and either obliterated or deeply submerged arc massifs of early Tertiary age. Their exposed presence to the east in neighboring Panama reflects the circumstance that since

  2. New evidence of effusive and explosive volcanism in the Lower Carboniferous formations of the Moroccan Central Hercynian Massif: Geochemical data and geodynamic significance

    NASA Astrophysics Data System (ADS)

    Ntarmouchant, A.; Smaili, H.; Bento dos Santos, T.; Dahire, M.; Sabri, K.; Ribeiro, M. L.; Driouch, Y.; Santos, R.; Calvo, R.

    2016-03-01

    The Azrou-Khénifra basin, located in the SE sector of the Moroccan Central Hercynian Massif of the Western Meseta of Morocco comprises volcanic and volcanoclastic rocks where two magmatic sequences can be distinguished: i) the Dhar Lahmar Sequence, composed of Upper Visean basaltic lava flows and pyroclastic deposits; and ii) the Kef Al Asri Sequence, composed of Visean - Serpukhovian intermediate to acid rocks. A continuous spatial and temporal evolution between the two volcano-sedimentary sequences was observed during the detailed geological work performed in the studied area. Petrography and geochemical studies additionally suggest a continuous compositional evolution from the more basic magmatic rocks to the intermediate/acid rocks, which implies a cogenetic magmatic differentiation controlled by crystal fractionation (with minor crustal assimilation) of a calc-alkaline trend magmatic suite. The inferred magmatic evolution is consistent with a geodynamic environment of an orogenic zone within an active continental margin setting. This partly explosive Visean - Serpukhovian volcanism, identified for the first time in the Western Meseta of Morocco, displays very similar petrographic and geochemical characteristics to its Eastern Meseta analogues, which implies that the emplacement of these magmatic rocks must have occurred in similar collisional geodynamic settings for both major geological domains, further constraining the evolution of this major crustal segment within the Carboniferous events that shaped the Hercynian Orogeny.

  3. Macroseismic investigation of the 2008-2010 low magnitude seismic swarm in the Brabant Massif, Belgium. The link between macroseismic intensity and geomorphology

    NASA Astrophysics Data System (ADS)

    Van Noten, Koen; Lecocq, Thomas; Vleminckx, Bart; Camelbeeck, Thierry

    2013-04-01

    Between July 2008 and January 2010 a seismic swarm took place in a region 20 km south of Brussels, Belgium. The sequence started on the 12th of July 2008 with a ML = 2.2 event and was followed the day after by the largest event in the sequence (ML = 3.2). Thanks to a locally installed temporary seismic monitoring system more than 300 low magnitude events, with events as low as ML = -0.7, have been detected. Results of the relocations of the different hypocenters and analysis of the focal mechanisms show that the majority of these earthquakes took place at several km's depth (3 to 6 km) along a (possibly blind) 1.5 km long NW-SE fault (zone) situated in the Cambrian basement rocks of the Brabant Massif. Remarkably, 60 events (0.6 ˜ ML ˜ 3.2) were felt, or heard only sometimes, by the local population. This was detected by the "Did you feel it?" macroseismic inquiries on the ROB seismology website (www.seismology.be). For each event a classical macroseismic intensity map has been constructed based on the average macroseismic intensity of each community. Within a single community, however, the reported macroseismic intensities locally often vary ranging between non-damaging intensities of I and IV (on the EMS-98 scale). Using the average macroseismic intensity of a community therefore often oversimplificates the local intensity, especially in hilly areas in which local site effects could have influenced the impact of the earthquakes at the surface. In this presentation we investigate if the perception of the people of how they experienced the small events (sound, vibrations) was influenced by local geomorphological site effects. First, based on available borehole and outcrop data a sediment thickness map of the Cenozoic and Quaternary cover above the basement rocks of the Brabant Massif is constructed in a 200 km2 area around the different epicenters. Second, several electrical resistivity tomography (ERT) profiles are conducted in order to locally improve the

  4. Structural analysis and evolution of the Hadong-Sancheong-Hwagae area in the Yeongnam massif, Korea: a NS-trend tectonic frame in the Korean Peninsula

    NASA Astrophysics Data System (ADS)

    Deok-Seon, Lee; Ji-Hoon, Kang

    2016-04-01

    The Hadong-Sancheong-Hwagae area in the Jirisan province of the Yeongnam massif, Korea, is mainly composed of Precambrian Hadong anorthosite complex (HAC), Precambrian Jirisan metamorphic rock complex (JMRC), Jurassic˜Triassic granitoids which intrude them, and Cretaceous sedimentary rocks which unconformably cover them. Lithofacies distribution and tectonic frame of the Precambrian constituent rocks mainly show a NS trend, unlike a general NE trend of those in the Korean Peninsula. To unravel the geological structures associated with the NS-trend tectonic frame which was built in the HAC and JMRC, we researched the structural characteristics of each deformation phase based on the geometric and kinematic features and the forming sequence of rock structures of the multi-deformed HAC and JMRC. The results indicate that the pre-Late Paleozoic geological structures of this area were formed at least through the following three times of ductile deformation phases. The D1 deformation happened due to the large-scale top-to-the SE shearing, and formed sheath or A-type folds and a regional NE trend of tectonic frame in the HAC and JMRC. The D2 deformation occurred under the EW-directed tectonic compression, and formed a regional NS trend of active and passive folds and Hadong ductile shear zone over 2.3˜1.4 km width, and transposed most of D1 tectonic frame into D1-2 composite tectonic frame. The extensive Hadong shear zone, which was formed in the mylonitization process accompanying the passive folding, was persistently developed along the eastern boundary of HAC and JMRC which corresponds to a limb of passive fold on a geological map scale. It produced a very strong mylonitic structure and stretching lineation. The NE-trend D1 structural elements were mainly reoriented into NS trend by the powerful active and passive folding. The D3 deformation occurred under the NS-trend tectonic compression environment, and formed EW-trend kink or open folds, and partially rearranged

  5. Depleted subcontinental lithospheric mantle and its tholeiitic melt metasomatism beneath NE termination of the Eger Rift (Europe): the case study of the Steinberg (Upper Lusatia, SE Germany) xenoliths

    NASA Astrophysics Data System (ADS)

    Kukuła, Anna; Puziewicz, Jacek; Matusiak-Małek, Magdalena; Ntaflos, Theodoros; Büchner, Jörg; Tietz, Olaf

    2015-12-01

    The ca. 30 Ma Steinberg basanite occurs at the NE termination of the Eger (Ohře) Rift in the NW Bohemian Massif, Central Europe, and belongs to the Cenozoic alkaline Central European Volcanic Province. The basanite hosts a suite of mantle xenoliths, most of which are harzburgites containing relatively magnesian olivine (Fo 90.5-91.6) and Al-poor (0.04-0.13 a pfu) orthopyroxene (mg# 0.90-0.92). Some of these harzburgites also contain volumetrically minor clinopyroxene (mg# 0.92-0.95, Al 0.03-0.13 a pfu) and have U-shaped LREE-enriched REE patterns. The Steinberg harzburgites are typical for the Lower Silesian - Upper Lusatian domain of the European subcontinental lithospheric mantle. They represent residual mantle that has undergone extensive partial melting and was subsequently affected by mantle metasomatism by mixed carbonatite-silicate melts. The Steinberg xenolith suite comprises also dunitic xenoliths affected by metasomatism by melt similar to the host basanite, which lowered the Fo content in olivine to 87.6 %. This metasomatism happened shortly before xenolith entrainment in the erupting lava. One of the xenoliths is a wehrlite (olivine Fo 73 %, clinopyroxene mg# 0.83-0.85, subordinate orthopyroxene mg# 0.76-0.77). Its clinopyroxene REE pattern is flat and slightly LREE-depleted. This wehrlite is considered to be a tholeiitic cumulate. One of the studied harzburgites contains clinopyroxene with similar trace element contents to those in wehrlite. This type of clinopyroxene records percolation of tholeiitic melt through harzburgite. The tholeiitic melt might be similar to Cenozoic continental tholeiites occurring in the Central European Volcanic Province (e.g., Vogelsberg, Germany).

  6. Crystal structure of hydrogen-bearing vuonnemite from the Lovozero alkaline massif

    SciTech Connect

    Rastsvetaeva, R. K. Aksenov, S. M.; Verin, I. A.; Lykova, I. S.

    2011-05-15

    Hydrogen-bearing vuonnemite from the Shkatulka hyperagpaitic pegmatite (the Lovozero alkaline massif, Kola Peninsula) was studied by single-crystal X-ray diffraction. The triclinic unit-cell parameters are as follows: a = 5.4712(1) Angstrom-Sign , b = 7.1626(1) Angstrom-Sign , c = 14.3702(3) Angstrom-Sign , {alpha} = 92.623(2) Degree-Sign , {beta} = 95.135(1) Degree-Sign , {gamma} = 90.440(1) Degree-Sign , sp. gr. P1, R = 3.4%. The Na{sup +} cations and H{sub 2}O molecules are ordered in sites between the packets. The water molecules are hydrogen bonded to the PO{sub 4} tetrahedra.

  7. Sm-Nd dating of fluorite from the worldclass Montroc fluorite deposit, southern Massif Central, France

    USGS Publications Warehouse

    Munoz, M.; Premo, W.R.; Courjault-Rade, P.

    2005-01-01

    A three-point Sm-Nd isotope isochron on fluorite from the very large Montroc fluorite vein deposit (southern Massif Central, France) defines an age of 111??13 Ma. Initial ??Nd of -8.6 and initial 87Sr/86Sr of ???0.71245 suggest an upper crustal source of the hydrothermal system, in agreement with earlier work on fluid inclusions which indicated a basinal brine origin. The mid-Cretaceous age of ???111 Ma suggests the Albian/Aptian transition as the most likely period for large-scale fluid circulation during a regional extensional tectonic event, related to the opening of the North Atlantic ocean. ?? Springer-Verlag 2004.

  8. Geochemical characteristics of rare earth elements in soil of the Ditru Massif, Eastern Carpathians, Romania

    NASA Astrophysics Data System (ADS)

    Ion, Adriana

    2013-04-01

    The present paper describes the level of rare earth elements in soils developed from Ditrău massif area for evaluating of the background of these elements and accurate assessment of environmental impact. Also this paper contributed to understanding the important role of parent rocks in pedogenic processes. The Ditrău Alkaline Massif represent an intrusion body with a internal zonal structure, which was emplaced into pre-Alpine metamorphic rocks of the Bucovinian nappe complex close the Neogene - Quaternary volcanic arc of the Calimani-Guurghiu- Harghita Mountain chain. The center of massif was formed by nepheline syenite, which is surrounded by syenite and monazonite. North-western and north-eastern marginal sectors are composed of hornblende gabbro/hornblendite, alkali diorite, monzodiorite, monzosyenites and alkali granite. Small discrete ultramafic bodies (kaersutite-bearing peridotite, olivine, pyroxenite and hornblendite) and alkali gabbros occur in the Jolotca area. All this rocks are cut by late-stage dykes with a large variety of composition including tinguaite, phonolite, nepheline syenite, microsyenite, and aplite. The types of soils predominant in this zone are lithosoils. These soils are shallow developed, have low content in organic matter and reflects mineralogical and geochemical composition of the bedrock. The soil samples were collected from 70 location for all type of representative rocks (approximately 10 soil sampling points for each type of rock). The samples were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The pH values of these samples varied from 3.6 to 7.3, in general, the soils from massif area are acid or weakly acidic. The pH controls the abundance of REE in soil, the concentration of REE increases with decreasing pH values. In soil samples analyzed the contents of REE follow the order: Ce > La > Nd > Pr > Sm > Eu > Gd > Dy > Yb > Er > Tb > Ho >Tm. ∑ REE varied from 52.59 μg g-1 to 579.2 μg g-1 , the average

  9. Oxidation state of the lithospheric mantle beneath the Massif Central,France

    NASA Astrophysics Data System (ADS)

    Uenver-Thiele, L.; Woodland, A. B.; Downes, H.; Altherr, R.

    2012-04-01

    The Tertiary and Quaternary volcanism of the French Massif Central sampled the underlying subcontinental lithospheric mantle (SCLM) in the form of xenoliths over a wide geographic area of ~20.000km2. Such an extensive distribution of xenoliths provides an unique opportunity to investigate regional variations in mantle structure and composition. On the basis of textural and geochemical differences, Lenoir et al. (2000) and later Downes et al. (2003) identified two distinct domains in the SCLM lying north and south of latitude 45° 30' N, respectively. The northern domain is relatively refractory, but has experienced pervasive enrichment of LREE. The southern domain is generally more fertile, exhibiting depletion in LREE. A metasomatic overprint has developed to variable extents in many xenolith suites. The different histories of these two juxtaposed blocks of SCLM should also be reflected in their oxidation state, with local variations also to be expected due to metasomatic interactions. For example, if carbonate-melt metasomatism played a role in the LREE enrichment of the northern domain (Lenoir et al. 2000; Downes et al. 2003), then such mantle should be relatively oxidised. Since surprisingly little redox data are currently available, we are undertaking a study to determine the oxidation state of the SCLM beneath the Massif Central over the largest geographical area possible. All xenoliths investigated are spinel peridotites, mostly with protogranular textures (although some samples are porphyroclastic or equigranular). Most samples are nominally anhydrous although minor amphibole is present in some xenolith suites. Major element compositions of the individual minerals were determined by microprobe. Two-pyroxene temperatures (BKN) range from 750° to ~1200° C. Ferric iron contents of spinel were determined by Mössbauer spectroscopy and gave a range of Fe3+/ Fetot from 0.191 to 0.418, with a conservative uncertainty of ±0.02. These data were used to calculate

  10. Permafrost detection in the headwalls of receding glaciers at the Dachstein Massif, Northern Calcareous Alps, Austria

    NASA Astrophysics Data System (ADS)

    Rode, Matthias; Gitschthaler, Christoph; Schnepfleitner, Harald; Kellerer-Pirklbauer, Andreas; Sass, Oliver

    2014-05-01

    The Northern Calcareous Alps cover a large area of the Austrian Alps forming a boundary zone between the Alpine Foreland to the north and the crystalline Central Alps to the south. Generally, climate in this area is more maritime compared to the mountain ranges further south. Few small glaciers are to be found mostly on north-facing slopes. The Northern Calcareous Alps reach maximum elevations of about 3000 m asl. Some of highest summits are to be found are located in the Dachstein Massif reaching 2995 m asl (47° 28' 32″ N, 13° 36' 23″ E). Occurrence, thickness and thermal regime of permafrost at this mountain massif are widely unknown and knowledge is based on simulations only. In contrast, the glaciation changes at this mountain massif (e.g. Schladminger and Hallstätter glaciers) have been well documented for decades. Within the framework of the research project ROCKING ALPS - dealing with frost weathering and rockfall in alpine regions - knowledge of permafrost distribution in the headwalls surrounding the receding glaciers is substantial to understand rock decay. For this reason, several techniques have been applied in order to detect bedrock permafrost. During the winter of 2012 22 i-buttons (temperature sensors) were attached to rock walls with different orientations but at similar elevations (2600-2700 m asl). Most of these sites were later covered by an insulating winter snow cover therefore allowing the calculation of the base temperature of the winter snow cover (BTS). These BTS data have been used as a first indicator of permafrost presence. In selected rock walls of several mountains in the massif - Koppenkarstein (2863 m asl), Dirndln (2829 m asl) and Gjaidstein (2794 m asl) - additional 2D-geoelectric surveys (five ERT profiles with a length of 100 m and 2 m electrode spacing) were measured in summer 2013. The high resistivities (> 50.000 ohm.m) at about 1.5 m depth and deeper strongly suggest permafrost existence inside the bedrock at all

  11. Application of GIS technologies to monitor secondary radioactive contamination in the Delegen mountain massif

    NASA Astrophysics Data System (ADS)

    Alipbeki, O.; Kabzhanova, G.; Kurmanova, G.; Alipbekova, Ch.

    2016-06-01

    The territory of the Degelen mountain massif is located within territory of the former Semipalatinsk nuclear test site and it is an area of ecological disaster. Currently there is a process of secondary radioactive contamination that is caused by geodynamic processes activated at the Degelen array, violation of underground hydrological cycles and as a consequence, water seepage into the tunnels. One of the methods of monitoring of geodynamic processes is the modern technology of geographic information systems (GIS), methods of satellite radar interferometry and high accuracy satellite navigation system in conjunction with radioecological methods. This paper discusses on the creation of a GIS-project for the Degelen array, facilitated by quality geospatial analysis of the situation and simulation of the phenomena, in order to maximize an objective assessment of the radiation situation in this protected area.

  12. Mineral compositions of plutonic rocks from the Lewis Hills massif, Bay of Islands ophiolite

    NASA Technical Reports Server (NTRS)

    Smith, Susan E.; Elthon, Don

    1988-01-01

    Mineral compositions of residual and cumulate rocks from the Lewis Hills massif of the Bay of Islands ophiolite complex are reported and interpreted in the context of magnetic processes involved in the geochemical evolution of spatially associated diabase dikes. The mineral compositions reflect greater degrees of partial melting than most abyssal peridotites do and appear to represent the most depleted end of abyssal peridotite compositions. Subsolidus equilibration between Cr-Al spinal and olivine generally has occurred at temperatures of 700 to 900 C. The spinel variations agree with the overall fractionation of basaltic magmas producing spinels with progressively lower Cr numbers. The compositions of clinopyroxenes suggest that the fractionation of two different magma series produced the various cumulate rocks.

  13. Physical-Chemical Factors Affecting the Low Quality of Natural Water in the Khibiny Massif

    NASA Astrophysics Data System (ADS)

    Mazukhina, Svetlana; Masloboev, Vladimir; Chudnenko, Konstantin; Maksimova, Viktoriia; Belkina, Natalia

    2014-05-01

    One peculiarity of the Khibiny Massif is its spatial location. Rising over 1000 m above the surrounding hilly land and thus obstructing the passage of air masses, it promotes condensation and accumulation of surface and underground water. Annual precipitation here amounts to 600-700 mm in the valleys and up to 1600 mm on mountainous plateaus. Using this water for drinking and household purposes is problematic due to excess Al and F concentrations and high pH values. Now it is known that in its profile, the Massif is represented by three hydrogeological subzones: the upper (aerated), medium and lower ones. The upper subzone spreads throughout the Massif and is affected by the local drainage network and climatic conditions. The medium subzone is permanently saturated with underground water flowing horizontally to sites of discharge at the level of local river valleys and lakes. The fissure-vein water in the lower subzone is confined to tectonic fractures and faults in the so far underexplored, deeper parts of the Massif. Being abundant, this water ascends under high pressure. At places, water has been observed spurting from as deep as 700 m, and even 960 m. In the latter case, the temperature of ascending water was higher than 18 centigrade (Hydrogeology of the USSR, V. 27, 1971). This work was undertaken to reveal the nature of the low quality of water in the Khibiny by using physical-chemical modeling (software package Selector, Chudnenko, 2010). Processes of surface and underground water formation in the Khibiny were examined within a physical-chemical model (PCM) of the "water-rock-atmosphere-hydrogen" system. In a multi-vessel model used, each vessel represented a geochemical level of the process interpreted as spatiotemporal data - ξ (Karpov, 1981). The flow reactor consisted of 4 tanks. In the first tank, water of the Kuniok River (1000 L) interacted with atmosphere and an organic substance. The resulting solution proceeded to tanks 2-4 containing with

  14. Fluid flow and polymetallic sulfide mineralization in the Kettara shear zone (Jebilet Massif, Variscan Belt, Morocco)

    NASA Astrophysics Data System (ADS)

    N'diaye, I.; Essaifi, A.; Dubois, M.; Lacroix, B.; Goodenough, K. M.; Maacha, L.

    2016-07-01

    The Kettara shear zone is a regional wrench shear zone within the Jebilet massif of Western Morocco, part of the Variscan orogenic belt. This massif is characterized by bimodal magmatism, largely intrusive, and by a number of polymetallic massive sulfide deposits. A syntectonic mafic-ultramafic intrusion and an adjacent, deformed pyrrhotite-rich massive sulfide deposit are located within a 'compressional jog' of the shear zone. Hydrothermal alteration in both the intrusion and the wall rocks adjacent to the deposit is characterized by syntectonic replacement processes leading to formation of chlorite-schists and quartz ± calcite veins. Fluid inclusions in mineralized (pyrrhotite-bearing) quartz veins from the wall rocks adjacent to the deposit and in veins associated with chlorite-schists within the intrusion indicate a prevalence of H2O-CO2-CH4-N2 and H2O-salt fluid systems. In the mineralized veins the fluid shows reducing conditions, with gas dominated by CH4 and N2 and salinities around 7.5 wt% NaCl, whereas in the chlorite shear zones fluid is CO2 dominated and salinities are higher than 23 wt% NaCl. Hydrogen and oxygen isotopic compositions of chlorite and quartz are similar and demonstrate involvement of metamorphic water in both the deposit and the intrusion. The data are consistent with a regional metamorphic fluid flow through the Kettara shear zone. The migrating metamorphic fluids were reduced in the organic matter-rich host rocks leading to deposition of sulfides in the mineralized veins. There are two possible hypotheses for the origin of these mineralized veins: either they were formed during deformation and remobilization of a syn-sedimentary massive sulfide deposit, or they were formed synchronously with the sulfide deposit during development of the Kettara shear zone.

  15. The age of Kondyor massif dunites (Aldan Province, Russia): First U-Pb isotopic data

    NASA Astrophysics Data System (ADS)

    Malitch, K. N.; Efimov, A. A.; Badanina, I. Yu.

    2012-09-01

    The material and isotope-geochemical peculiarities of zircons from dunites of the Kondyor massif (Aldan Province, Southeast Siberian Craton) have been described for the first time. This massif is associated with an economic platinum placer deposit. On the basis of detailed study of the morphology, internal structure, and geochemical characteristics, zircons have been subdivided into two types. The first type is represented by crystals of oval and rounded shapes, characterized by a bimodal distribution of "ancient" (2477 ± 18 and 1885 ± 52 Ma) U-Pb (SHRIMP-II) ages. The second type of zircons forms idiomorphic crystals and aggregates of prismatic habitus, forming two "young" age clusters (176 ± 1.2 and 143 ± 2.0 Ma). The obtained results allow us to make a conclusion about the long evolution of platinum-bearing dunites. The first type of zircons formed by metamictic cores and homogeneous peripheral rims indicates the time of metamorphism at the Archean-Proterozoic boundary (˜2.5 Ga), implying an older age of porous zircon cores. Such zircons characterize the minimal age of the initial mantle substance or a close time when the platinum-bearing dunite was generated. Based on their formation time, the second type of zircons can be referred to the epoch of tectonic-magmatic activation of the Aldan Shield. The new geochronological data, along with the material identity of dunites from the Urals and the Aldan Province, argue for a common genetic origin of platinum-bearing dunites of the fold belts and ancient cratons.

  16. Proterozoic massif anorthosites and related rocks in Labrador: the anorthosite-charnockite connection

    SciTech Connect

    Emslie, R.F.

    1985-01-01

    Massif anorthosites of Labrador are closely associated in space and time with voluminous, felsic, fayalite- and ferrous pyroxene-bearing igneous rocks. These include charnockites, monzonites, biotite-hornblende granites, and locally syenites. Igneous charnockites form major parts of some of the granitic complexes. In Mistastin batholith for example, charnockitic assemblages comprise about 35% of a total area of 6500 sq. km. Feldspar pairs and coexisting fayalite-opx-qtz in these rocks indicate P and T near 3.5 kb, 750/sup 0/C, assumed to represent near solidus equilibration. Diorites and monzonites intruded by charnockite have mesoperthites implying crystallization T>900/sup 0/C presumably recording earlier stages of crystallization. Oxide and silicate assemblages indicate redox conditions between FMQ and WM oxygen buffers and water pressures well below Ptotal. Younger biotite-hornblende granites and quartz syenites lack Ti-mt. but retain fayalite suggesting that magmatic crystallization was largely closed to water and oxygen. Initial Sr isotope ratios in charnockite-granite suites of central labrador support derivation of the magmas largely or entirely from crustal source rocks. Compositions of mafic silicates and plagioclase, associated Fe-Ti oxide concentrations, trace elements and Sr isotopes in massif anorthosites are in accord with the rocks being crystallization products of substantially fractionated, originally more mafic, mantle magmas. Close association of high temperature, water-poor, reduced crustal melts is consistent with a fusion process in which heat supply and oxygen buffering were controlled by fractional crystallization of a substantial body of mafic magma subjacent to continental crust.

  17. Homogeneous /sup 18/O enrichment of the Marcy Anorthosite Massif, Adirondack Mountains, New York

    SciTech Connect

    Morrison, J.; Valley, J.W.

    1985-01-01

    The Marcy Anorthosite Massif in the Adirondack Mountains, New York, is a composite intrusion that was metamorphosed to granulite facies at approx. 1.1 Ga. The massif is dominantly anorthosite but ranges from anorthosite (1-10% mafics) to oxide-rich pyroxenite layers (up to 98% mafics). In the St Regis Quad (SRQ) systematic variations in the percentage of mafics (POM) roughly parallel the foliation and increase toward the contacts (Davis, 1971). In 47 SRQ samples studied the POM varies from 2-25%; garnet ranges from 0-11%, pyroxene from <1-16% and oxides from <1-8%. Percent phenocrysts varies between 1-80. The Port Kent-Westport Unit (PKW) and an associated hybrid unit show significantly greater textural variability. The POM Varies from 1-50%; garnet ranges from 0-18%, pyroxene from 0-15%, oxides from 0-3% and phenocrysts vary from 0-80%. A total of 28 unaltered plagioclase phenocrysts have been analyzed for delta/sup 18/O: in 13 SRQ samples delta/sup 18/O = 9.0-9.8 (x=9.4. sigma=0.2) and in 15 samples from the PKW and hybrid units values of delta/sup 18/O=8.5-10.5 (x=9.5.sigma0.5). No correlations exist between the modal parameters and delta/sup 18/O. The results from SRQ demonstrate an extreme homogeneity suggesting for the first time a pristine magmatic character which is supported by the virtual absence of metasedimentary inclusions. This contrasts with PKW where inclusions are common and delta/sup 18/O values are more heterogeneous. Further analyses will evaluate the possibility of an anomalous source region as a cause of the /sup 18/O enrichment in the anorthosite.

  18. Origin of mafic and ultramafic cumulates from the Ditrău Alkaline Massif, Romania

    NASA Astrophysics Data System (ADS)

    Pál-Molnár, Elemér; Batki, Anikó; Almási, Enikő; Kiss, Balázs; Upton, Brian G. J.; Markl, Gregor; Odling, Nicholas; Harangi, Szabolcs

    2015-12-01

    Mafic-ultramafic cumulates enclosed in gabbroic-dioritic rocks form part of the Mesozoic Ditrău Alkaline Massif in the Eastern Carpathians, Romania. The poikilitic olivine- and pyroxene-rich and nearly mono mineralic hornblendite rocks display typical cumulate textures with early crystallised olivine (Fo75-73), diopside and augite. In the early stages of their genesis the amphibole was intercumulus whilst in later stages it acquired cumulus status as the fractionating magma evolved. Using major and trace element compositions of minerals and whole-rock samples the origin of these cumulates is determined and the parental magma composition and depth of emplacement are calculated. Cumulus clinopyroxene has more primitive composition than intercumulus amphibole suggesting closed system fractionation for the evolution of poikilitic olivine- and pyroxene-rich cumulates. The evolution of the amphibole-rich mesocumulates is more clearly the result of closed system crystallisation dominated by the precipitation of clinopyroxene and amphibole cumulus crystals. Lamprophyre dykes of the Ditrău Alkaline Massif are proposed to reflect multiple basanitic parental magma batches from which the cumulus olivine and clinopyroxene crystallised. Relative to these dykes the calculated equilibrium melts for intercumulus amphibole in the cumulates was more primitive whilst that for the cumulus amphibole was more evolved. The calculated crystallisation temperature and pressure of ~ 1000-1050 °C and ~ 0.7 GPa, based on the composition of the amphiboles, indicate crystallisation at lower crustal depths. Rare earth element compositions are consistent with an intra-plate tectonic setting.

  19. Diamonds Discovered in Five Peridotite Massifs Along the Yarlung-Zangbo Suture in South Tibet: Tectonic Implications

    NASA Astrophysics Data System (ADS)

    Xu, X.; Yang, J.; Ba, D.; Li, Y.; Zhao, L.; Robinson, P. T.

    2011-12-01

    Many ophiolitic peridotite massifs occur along the more than 1500-km-long Yarlung-Zangbo suture in south Tibet, which marks the boundary between the Indian and Eurasian plates after closure of Neo-Tethys at about 55 Ma. Some of the massifs are very large, e.g., the Xigaze massif (ca. 700 km2) in the middle segment, and the Purang (ca. 600 km2) and Dongbo (ca. 400 km2) massifs in the western segment of the suture. In-situ diamonds and moissanite, along with many unusual, highly reduced minerals, such as native Fe, Cr, Ni and metal alloys have been previously reported from chromitites and peridotites of the Luobusa ophiolitic massif in the eastern segment of the suture. Coesite pseudomorphing stishovite from the Luobusa chromitite suggests depths of formation >300 km. Here we present the first report of diamonds and other unusual minerals in four other peridotite bodies along the Yarlung-Zangbo suture, namely from east to west, the Xigaze, Dangqiong, Purang and Dongbo massifs. These massifs consist mainly of harzburgite, lherzolite and dunite, probably of MOR type, that were modified in a SSZ environment. Several tens of diamonds and some unusual minerals such as moissanite were recovered by standard mineral separation techniques from individual samples ranging from 300 to 600 kg in weight. The diamonds are yellowish-green in color, about 0.1-0.3 mm in size, and have octahedral and cone-like forms. These diamonds are similar to those found in the Luobusa massif, and commonly contain inclusions of Ni-Mn-Co alloys, a feature that distinguishes them from kimberlitic and metamorphic diamonds. Textural evidence and Ca-K-Cl fluid inclusions indicate that they grew from C-rich fluids. Fifty analyses of diamonds from the Yarlung-Zangbo suture yielded δ13CPDB values ranging from -18.3 % to -28.7%, with an average of -24.6%. There are no statistical differences in the isotopic composition among diamonds from the different localities or among those occurring in chromitite or

  20. Carboniferous magmatism in the Evora Massif (southwest Portugal, Ossa-Morena Zone): from typical arc calc-alkaline to adakitic-like magmatism

    NASA Astrophysics Data System (ADS)

    Lima, Selma M.; Neiva, Ana M. R.; Ramos, Joao M. F.

    2014-05-01

    The Evora Massif is one of the subdivisions of western Ossa-Morena Zone. It is a dome-like structure mainly composed of Ediacaran, Cambrian and Ordovician country rocks, affected by medium- and high-grade metamorphism coeval with the emplacement of several mafic to felsic intrusive bodies. The last magmatic event recorded in this area (Carboniferous) consists of calc-alkaline volcanism and voluminous plutonism (mainly composed by tonalites, gabbros, diorites and late-orogenic granodiorites and granites) [1]. Detailed chemical and isotopic studies from Evora Massif plutons were performed in the last few years. Whole-rock chemical and isotopic data suggest that the Hospitais tonalite (HT), Alto de Sao Bento area (ASB) and Reguengos de Monsaraz pluton (RM) resulted from fractional crystallization of mantle-derived magmas followed by mixing with variable proportions of crustal melts [2-4]. U-Pb ID-TIMS data indicate an age of 337-335 for the RM [4]. The Pavia pluton is a multiphase granitic body constructed incrementally by the episodic emplacement of several batches of magma (at 328 Ma, ca. 324 Ma and 319-317 Ma) [5]. The main granitic phases range from tonalite to two-mica granite that contain rare surmicaceous and fine-grained enclaves, and granitic and amphibolitic xenoliths. On the other hand, they are cut by abundant rhyodacite porphyries, microgranites (s.l.) and pegmatite dikes, predominantly oriented NE-SW and NW-SE. Although each phase seems to represent a distinct batch of magma, whole-rock Sr-Nd isotopic data suggest a similar and fairly homogenous source for all the constituent phases. Initial 87Sr/86Sr varies between 0.70428 and 0.7058 and ɛ Ndt ranges from -3.4 to +0.4, pointing towards a mantle or juvenile crust origin. A higher variation is observed in whole-rock δ18O (5.6-9.6 o), consistent with assimilation of crust. The PP was interpreted as the result of assimilation-fractional crystallization of a basaltic magma. Substantial differences between

  1. Instability of a highly vulnerable high alpine rock ridge: the lower Arête des Cosmiques (Mont Blanc massif, France)

    NASA Astrophysics Data System (ADS)

    Ravanel, L.; Deline, P.; Lambiel, C.; Vincent, C.

    2012-04-01

    Glacier retreat and permafrost degradation are actually more and more thought to explain the increasing instability of rock slopes and rock ridges in high mountain environments. Hot summers with numerous rockfalls we experienced over the last two decades in the Alps have indeed contributed to test/strengthen the hypothesis of a strong correlation between rockfalls and global warming through these two cryospheric factors. Rockfalls from recently deglaciated and/or thawing areas may have very important economic and social implications for high mountain infrastructures and be a fatal hazard for mountaineers. At high mountain sites characterized by infrastructures that can be affected by rockfalls, the monitoring of rock slopes, permafrost and glaciers is thus an essential element for the sustainability of the infrastructure and for the knowledge/management of risks. Our study focuses on a particularly active area of the Mont Blanc massif (France), the lower Arête des Cosmiques, on which is located the very popular Refuge des Cosmiques (3613 m a.s.l.). Since 1998, when a rockfall threatened a part of the refuge and forced to major stabilizing works, observations allowed to identify 10 detachments (20 m3 to > 1000 m3), especially on the SE face of the ridge. Since 2009, this face is yearly surveyed by terrestrial laser scanning to obtain high-resolution 3D models. Their diachronic comparison gives precise measurements of the evolution of the rock slope. Eight rock detachments have thus been documented (0.7 m3 to 256.2 m3). Rock temperature measurements at the ridge and the close Aiguille du Midi (3842 m a.s.l.), and observations of the evolution of the underlying Glacier du Géant have enable to better understand the origin of the strong dynamics of this highly vulnerable area: (i) rock temperature data suggest the presence of warm permafrost (i.e. close to 0°C) from the first meters to depth in the SE face, and cold permafrost in the NW face; (ii) as suggested by the

  2. AMS significance of dykes and granite from a same pluton - An example from the French Massif Central

    NASA Astrophysics Data System (ADS)

    Talbot, J.-Y.; Chen, Y.; Faure, M.

    2003-04-01

    The relationships between plutons and dykes of granite have been the topic of many studies since the hypothesis of "dyke propagation" was proposed as the main mode of ascent and emplacement of granitic plutons. However, most of observed pluton-related dykes can not be interpreted as "feeder dykes" but are fed by the magma chamber. Nevertheless, few AMS studies were carried out in both a pluton and its associated dykes to evaluate their internal fabrics. In the Cévennes area (SE of the French Massif Central), the Aigoual -- Saint-Guiral -- Liron granitic pluton consists of two cogenetic granitic facies. The main body is a porphyritic granodiorite facies which is common in the plutons of the Cévennes area. In the northern part of the pluton, a dyke swarm develops in the continuation of the porphyritic facies. Those NE-SW-trending dykes are composed of microgranite with locally porphyritic texture. This pluton intrudes metamorphic units dated at ca. 340--330 Ma and related to a N-S-trending shortening event. The emplacement of the pluton dated at ca. 310 Ma occured during the late-orogenic extension of the Hercynian belt. This extension is characterized by an E-W to NW-SE-trending stretching. An AMS study was carried out on the two granitic facies of this pluton. As shown by surveys of magnetic mineralogy, such as thermomagnetism, hysteresis loops, bulk magnetic susceptibility measurements, microscopic observations, the paramagnetic minerals, that is biotite with amphibole in traces, are the main carriers of the AMS for the two facies. Microstructures indicate the lack of significant solid-state deformation in both facies suggesting that AMS fabric is of magmatic origin and that no deformation is recorded after the complete crystallisation of the magma. In the porphyritic facies, the AMS fabric pattern is characterized by an E-W to NW-SE-trending lineation with shallow or moderate plunges mainly eastward. In general, magnetic foliations dip moderately eastward. This

  3. Subcontinental rift initiation and ocean-continent transitional setting of the Dinarides and Vardar zone: Evidence from the Krivaja-Konjuh Massif, Bosnia and Herzegovina

    NASA Astrophysics Data System (ADS)

    Faul, Ulrich H.; Garapić, Gordana; Lugović, Boško

    2014-08-01

    The Dinaride and Vardar zone ophiolite belts extend from the south-eastern margins of the Alps to the Albanian and Greek ophiolites. Detailed sampling of the Krivaja-Konjuh massif, one of the largest massifs in the Dinaride belt, reveals fertile compositions and an extensive record of deformation at spinel peridotite facies conditions. High Na2O clinopyroxene and spinel-orthopyroxene symplectites after garnet indicate a relatively high pressure, subcontinental origin of the southern and western part of Krivaja, similar to orogenic massifs such as Lherz, Ronda and the Eastern Central Alpine peridotites. Clinopyroxene and spinel compositions from Konjuh show similarities with fertile abyssal peridotite. In the central parts of the massif the spinel lherzolites contain locally abundant patches of plagioclase, indicating impregnation by melt. The migrating melt was orthopyroxene undersaturated, locally converting the peridotites to massive olivine-rich troctolites. Massive gabbros and more evolved gabbro veins cross-cutting peridotites indicate continued melt production at depth. Overall we infer that the massif represents the onset of rifting and early stages of formation of a new ocean basin. In the south of Krivaja very localized chromitite occurrences indicate that much more depleted melts with supra-subduction affinity traversed the massif that have no genetic relationship with the peridotites. This indicates that volcanics with supra-subduction affinity at the margins of the Krivaja-Konjuh massif record separate processes during closure of the ocean basin. Comparison with published compositional data from other Balkan massifs shows that the range of compositions within the Krivaja-Konjuh massif is similar to the compositional range of the western massifs of the Dinarides. The compositions of the Balkan massifs show a west to east gradient, ranging from subcontinental on the western side of the Dinarides to depleted mid-ocean ridge/arc compositions in the Vardar

  4. Algorithm of Rock Burst Preparation Scenario Construction in Rock Massif under Explosion Influence using seismic Catalogue Data

    NASA Astrophysics Data System (ADS)

    Hachay, Olga; Khachay, Oleg; Klimko, Valeriy; Shipeev, Oleg

    2014-05-01

    A new algorithm of seismological information processing of detailed mines catalogue with use kinematic and dynamical characteristics of deformation waves, which propagate with different velocities in the rock massif, which is under heavy influence of single blasts and technological explosions is developed. It is estimated that the waves, which propagate with the velocities from 10 to 1 m/hour are primary carrier of the energy in the massif and promote its releasing. Events, which occur in the massive with these waves with releasing energy less than 104 joules promote to the creep rebuilding of the massif. Events, which occur in the massive with these waves with releasing energy more, than 105 joules, can be used as rock burst precursory and it is recommend taking into account by changing of explosions in the indicated part of the massif. The whole absence of such events indicates the growing of the stress massif state in the mine as a whole. The received joined information from the seismic catalogue is very significant for forecasting of dangerous events in the rock mines. That algorithm can be used also for analyzing seismic natural events preparation. Key words: massif response, slow deformation waves, seismic mine catalogue, analyze of observed data, algorithm of seismological information processing. 1.Hachay O. A. The reflection of synergetic Features in the Response of geological Medium on outer Force Actions. / O. A. Hachay, O. Yu. Khachay, V. K. Klimko, O. Yu. Shipeev // Advances in heterogeneous Material Mechanics - Shanghai, China, 2011. -P. 361-366. 2.Hachay O. A. Construction of a State Evolution dynamical Model of a Rock Massive, which is in a regime of energetic Pumping. / O. A. Hachay, A. Yu. Khachay, O. Yu. Khachay // Geophysical Research abstracts. -2011, -Vol. 13, - EGU2011 - 1528. 3.Khachay O.A. Dynamical model for evolution of Rock Massive State as a Response on a Changing of Stress-Deformed State. / O. A. Hachay, A. Yu. Khachay, O. Yu. Khachay

  5. Solid Inclusions in Au-nuggets, genesis and derivation from alkaline rocks of the Guli Massif, Northern Siberia

    NASA Astrophysics Data System (ADS)

    Dvorani, Sami N.

    2016-04-01

    A total of 112 Au-nuggets, collected from alluvial placer deposits of the Ingarinda River from the Guli massif, located in northem Siberia, Russia, were investigated. The Guli massif consists of a huge dunite-clinopyroxenite complex (the largest complex in the world), an alkaline to highly alkaline rock suite (melilite, nephelinite, ijolite) enveloping the dunite and carbonatite intrusions, associated with disseminated schlieren type chromitite and Au-Ag, Pt placer deposits. The nuggets are characterized by various sizes and shapes and show chemical compositions Au, Au-Ag and AuCu, typical for a derivate of carbon-atites and/or ultramafic complexes. A great variety of oxide, silicate, REE-minerals, carbonate and sulphide inclusions have been detected in the nuggets, which are identical in mineralogy and chemical composition to mineral constituents of the alkaline to highly alkaline rock suite surrounding the Guli dunite core complex thus, considered as the source for Au-nuggets.

  6. Scorpions from the Mitaraka Massif in French Guiana: Description of one new genus and species (Scorpiones: Chactidae).

    PubMed

    Lourenço, Wilson R

    2016-01-01

    A new genus and species, Spinochactas mitaraka gen. n., sp. n. (Chactidae) are described from the Mitaraka Massif in French Guiana, a site located near the borders of French Guiana, Brazil, and Suriname. The description of the new genus and species brings further evidence of the biogeographic pattern of distribution presented by some elements of the family Chactidae endemic to the Tepuys or to the Inselberg formations of South America. PMID:26995397

  7. The western limits of the Seattle and Tacoma faults and their interaction with faults of the Olympic Massif, Washington (Invited)

    NASA Astrophysics Data System (ADS)

    Lamb, A.; Blakely, R. J.; Liberty, L. M.; Pratt, T. L.; Sherrod, B. L.

    2013-12-01

    Recently acquired high-resolution seismic-reflection and magnetic data show that the Seattle fault of Washington State extends 24-km west of its previously mapped extent and thus comprises a >100-km-long active fault zone. These same data reveal largely concealed faults and folds that kinematically link the Seattle fault with active faults in the Olympic Massif. Linkage between the Seattle fault and the north-northeast-striking Saddle Mountain fault in the Olympic Massif may explain the synchroneity of M7 earthquakes occurring on both these faults approximately 1,100 years ago. The western limits of the 20-km-long east-striking Tacoma fault, a backthrust in the hanging wall of the Seattle fault zone, forms the southern margin of the Seattle uplift in contact with the Tacoma basin to the south. A ~20-km-long potential-field lineament extends from the western limits of the Tacoma fault northward to the Seattle fault and may reflect a structure linking these active faults. A geologic model based on magnetic, gravity, and seismic data shows that this potential-field lineament is likely caused by a low-angle, west-verging thrust fault, that we refer to as the Dewatto fault. We suggest that the Dewatto fault was initiated during exhumation of the Olympic Massif but, because of changes in principal strain direction, today largely accommodates north-directed, strike-slip motion along the west margin of the Seattle uplift. Thus, the Dewatto and Saddle Mountain faults and the western parts of the Seattle and Tacoma faults kinematically interact to accommodate north-directed horizontal displacement of the Seattle uplift relative to the Olympic Massif.

  8. The Galicia-Ossa-Morena Zone: Proposal for a new zone of the Iberian Massif. Variscan implications

    NASA Astrophysics Data System (ADS)

    Arenas, Ricardo; Díez Fernández, Rubén; Rubio Pascual, Francisco J.; Sánchez Martínez, Sonia; Martín Parra, Luis Miguel; Matas, Jerónimo; González del Tánago, José; Jiménez-Díaz, Alberto; Fuenlabrada, Jose M.; Andonaegui, Pilar; Garcia-Casco, Antonio

    2016-06-01

    Correlation of a group of allochthonous terranes (referred to as basal, ophiolitic and upper units) exposed in the NW and SW of the Iberian Massif, is used to propose a new geotectonic zone in the southern branch of the Variscan Orogen: the Galicia-Ossa-Morena Zone. Recent advances in SW Iberia identify most of the former Ossa-Morena Zone as another allochthonous complex of the Iberian Massif, the Ossa-Morena Complex, equivalent to the Cabo Ortegal, Órdenes, Malpica-Tui, Bragança and Morais complexes described in NW Iberia. The new geotectonic zone and its counterparts along the rest of the Variscan Orogen constitute an Internal Variscan Zone with ophiolites and units affected by high-P metamorphism. The Galicia-Ossa-Morena Zone includes a Variscan suture and pieces of continental crust bearing the imprint of Ediacaran-Cambrian events related to the activity of peri-Gondwanan magmatic arcs (Cadomian orogenesis). In the Iberian Massif, the general structure of this geotectonic zone represents a duplication of the Gondwanan platform, the outboard sections being juxtaposed on top of domains located closer to the mainland before amalgamation. This interpretation offers an explanation that overcomes some issues regarding the differences between the stratigraphic and paleontological record of the central and southern sections of the Iberian Massif. Also, equivalent structural relationships between other major geotectonic domains of the rest of the Variscan Orogen are consistent with our interpretation and allow suspecting similar configurations along strike of the orogen. A number of issues may be put forward in this respect that potentially open new lines of thinking about the architecture of the Variscan Orogen.

  9. Phanerozoic polyorogenic deformation in southern Jiuling Massif, northern South China block: Constraints from structural analysis and geochronology

    NASA Astrophysics Data System (ADS)

    Chu, Yang; Lin, Wei

    2014-06-01

    The structure of the Jiuling Massif has been investigated in order to delineate the polyorogenic deformation and discuss its geodynamic evolution and orogenic mechanisms. Detailed structural analysis indicates that the D1 event is characterized by top-to-the NNW ductile shearing with pervasive foliation, and mineral and stretching lineation developed in the entire region. Compared with the D1 deformation, D2 structures are localized in ductile shear zones with subvertical foliation and subhorizontal E-W trending lineation, indicating a dextral ductile shearing. The D3 event, marked by folds and thrusts mainly in a brittle domain, modified the D1 structures by asymmetrical folds. The dominant D4 structures are gravitational folds and normal faults, corresponding to a later extension. Our new geochronological data suggest that the D1 event occurred between 465 and 380 Ma with D2 dextral shearing at the end of this Early Paleozoic orogen, and the D3 event has been constrained at 245-215 Ma. The final uplift of the Jiuling Massif by the D4 event can be correlated with the Late Mesozoic extension across the eastern South China block. Along with previous studies in the South China block, the structural pattern of the Jiuling Massif elucidates the influence of the Early Paleozoic and Early Mesozoic intracontinental belts triggered by repeated reactivation of the Jiangshan-Shaoxing Fault. Combined with deformation to the south, the Early Paleozoic belt shows a positive flower pattern, with opposing kinematics, rooted in the Jiangshan-Shaoxing Fault. During the Early Mesozoic, a general intracontinental belt was developed with uniform kinematics in both the Jiuling Massif and the Xuefengshan Belt, possibly resulted from the far-field effect of the Triassic NW-directed Paleo-Pacific subduction.

  10. The Tolbachik volcanic massif: A review of the petrology, volcanology and eruption history prior to the 2012-2013 eruption

    NASA Astrophysics Data System (ADS)

    Churikova, T. G.; Gordeychik, B. N.; Edwards, B. R.; Ponomareva, V. V.; Zelenin, E. A.

    2015-12-01

    The primary goal of this paper is to summarize all of the published data on the Tolbachik volcanic massif in order to provide a clear framework for the geochronologic, petrologic, geochemical and to a lesser extent the geophysical and tectonic characteristics of the Tolbachik system established prior to the 2012-2013 eruption. The Tolbachik massif forms the southwestern part of the voluminous Klyuchevskoy volcanic group in Kamchatka. The massif includes two large stratovolcanoes, Ostry ("Sharp") Tolbachik and Plosky ("Flat") Tolbachik, and a 70 km long zone of the basaltic monogenetic cones that form an arcuate rift-like structure running across the Plosky Tolbachik summit. The Tolbachik massif gained international attention after the 1975-1976 Great Tolbachik Fissure Eruption (GTFE), which was one of the largest eruptions of the 20th century and one of the six largest basaltic fissure eruptions in historical time. By the end of the GTFE, 2.2 km3 of volcanic products of variable basaltic compositions with MORB-like isotopic characteristics covered an area of > 1000 km2. During the following three decades more than 700 papers on various aspects of this eruption have been published both in national and international journals. Although the recent 2012-2013 eruption, which is the main topic of this volume, was not as long as the GTFE in duration or as large in area and volume of the erupted deposits, it brought to the surface a unique volcanic material never found before. In order to understand the data from new eruptions and make significant progress towards a better understanding of the Tolbachik magmatic system it is important to be able to put the new results into the historic context of previous research.

  11. The thermal, metamorphic and magmatic evolution of a rapidly exhuming terrane: the Nanga Parbat Massif, northern Pakistan

    NASA Astrophysics Data System (ADS)

    Whittington, A. G.

    The Nanga Parbat-Haramosh Massif (NPHM) is the most northerly outcrop of Indian Plate rocks in the Himalayan orogen, exposed by rapid recent exhumation through the structurally overlying Kohistan Island Arc in northern Pakistan. Exhumation has been achieved by erosion in the apparent absence of extensional tectonics. Metabasaltic dykes intruded into polymetamorphic basement rocks provide time markers that distinguish early from late fabrics that probably correlated with Precambrian and Himalayan deformation respectively. Nanga Parbat is anomalous within the Himalayan orogen for both the timing and nature of metamorphism and anatexis. A multidisciplinary approach allows the thermal history to be tightly constrained. Metamorphism is characterised by cordierite growth during near-isothermal decompression. Garnet inclusion assemblages record P-T conditions of 720 +/- 50 deg C and 7.5 +/- 1.5 kbar, while spinel-cordierite intergrowths unique to the massif interior formed at 710 +/- 60 deg C and 5.0 +/- 1.1 kbar. Lower grade assemblages are exposed towards the massif margins. Tourmaline leucogranite plutons and sheets are characterised by similar trace element geochemistry to Miocene High Himalayan granites, indicative of vapour-absent crustal melting as would result from rapid decompression, but were emplaced more than 10 million years later. More recently, fluid infiltration into conjugate shear zones accommodating vertical stretching in the core of the massif resulted in anatexis and the formation of restitic cordierite-bearing pods. 40Ar-39Ar studies indicate regional cooling below 400 deg C as recently as 1 Ma, and the distribution of excess 40Ar in basement samples is indicative of magmatic/metamorphic fluids at depths > 10 km. One-dimensional thermal modelling indicates that increasing cooling rates through time do not require increasing exhumation rates because advection of heat results in a steepened near-surface geotherm. These models predict both the style and

  12. Granite emplacement during contemporary shortening and normal faulting: structural and magnetic study of the Veiga Massif (NW Spain)

    NASA Astrophysics Data System (ADS)

    Roman-Berdiel, T.; Pueyo-Morer, E. L.; Casas-Sainz, A. M.

    1995-12-01

    The Veiga Massif belongs to the calc-alkaline series of Hercynian granitic rocks of the Ibero-Armorican arc The Veiga granodiorite intruded during the Upper Carboniferous into the core of the WNW-ESE N-verging 'Ollo de Sapo' antiform, formed by Precambrian and Palaeozoic metasediments. Internal fabrics show that magma intrusion was contemporary with shortening. Measurements of feldspars orientations and anisotropy of magnetic susceptibility (AMS) throughout the granite are consistent and indicate a foliation striking WNW-ESE (parallel-to-folding), with a constant dip of 75-85 °N. The zonation of bulk low-field susceptibility is related to mineral content and indicates a more basic composition at the southern and western borders. The difference in elevation between outcrops (more than 600 m) allows us to infer the three-dimensional attitude of granite fabrics throughout the Massif. Syn-magmatic fabric folds are preserved in the inner part of the igneous body. The highest degree of magnetic anisotropy is observed in areas located near the bottom and top of the intrusion. At the scale of the Massif, foliation is convergent toward the bottom of the intrusion, along a line located at its northern border, where the magma source is interpreted to be located. In the western border of the Massif, the presence of C and S structures indicates that magma cooling was coeval with movement of the Chandoiro fault, a N-S striking normal fault with a N290E hanging wall displacement direction. These results indicate that emplacement of the Veiga granite is coeval with NNE-SSW shortening and with an WNW-ESE extension direction, parallel to the trend of the late folds.

  13. ZnSe/ZnSeTe Superlattice Nanotips

    PubMed Central

    2010-01-01

    The authors report the growth of ZnSe/ZnSeTe superlattice nanotips on oxidized Si(100) substrate. It was found the nanotips exhibit mixture of cubic zinc-blende and hexagonal wurtzite structures. It was also found that photoluminescence intensities observed from the ZnSe/ZnSeTe superlattice nanotips were much larger than that observed from the homogeneous ZnSeTe nanotips. Furthermore, it was found that activation energies for the ZnSe/ZnSeTe superlattice nanotips with well widths of 16, 20, and 24 nm were 76, 46, and 19 meV, respectively. PMID:20672085

  14. Lower Pliensbachian caldera volcanism in high-obliquity rift systems in the western North Patagonian Massif, Argentina

    NASA Astrophysics Data System (ADS)

    Benedini, Leonardo; Gregori, Daniel; Strazzere, Leonardo; Falco, Juan I.; Dristas, Jorge A.

    2014-12-01

    In the Cerro Carro Quebrado and Cerro Catri Cura area, located at the border between the Neuquén Basin and the North Patagonian Massif, the Garamilla Formation is composed of four volcanic stages: 1) andesitic lava-flows related to the beginning of the volcanic system; 2) basal massive lithic breccias that represent the caldera collapse; 3) voluminous, coarse-crystal rich massive lava-like ignimbrites related to multiple, steady eruptions that represent the principal infill of the system; and, finally 4) domes, dykes, lava flows, and lava domes of rhyolitic composition indicative of a post-collapse stage. The analysis of the regional and local structures, as well as, the architectures of the volcanic facies, indicates the existence of a highly oblique rift, with its principal extensional strain in an NNE-SSW direction (˜N10°). The analyzed rocks are mainly high-potassium dacites and rhyolites with trace and RE elements contents of an intraplate signature. The age of these rocks (189 ± 0.76 Ma) agree well with other volcanic sequences of the western North Patagonian Massif, as well as, the Neuquén Basin, indicating that Pliensbachian magmatism was widespread in both regions. The age is also coincident with phase 1 of volcanism of the eastern North Patagonia Massif (188-178 Ma) represented by ignimbrites, domes, and pyroclastic rocks of the Marifil Complex, related to intraplate magmatism.

  15. Seismic imaging of the western Iberian crust using ambient noise: Boundaries and internal structure of the Iberian Massif

    NASA Astrophysics Data System (ADS)

    Silveira, Graça; Afonso Dias, Nuno; Villaseñor, Antonio

    2013-03-01

    We present new Rayleigh-wave dispersion maps of the western Iberian Peninsula for periods between 8 and 30 s, obtained from correlations of seismic ambient noise, following the recent increase in seismic broadband network density in Portugal and Spain. Group velocities have been computed for each station pair using the empirical Green's functions generated by cross-correlating one-day-length seismic ambient-noise records. The resulting high-path density allows us to obtain lateral variations of the group velocities as a function of period in cells of 0.5° × 0.5° with an unprecedented resolution. As a result we were able to address some of the unknowns regarding the lithospheric structure beneath SW Iberia. The dispersion maps allow the imaging of the major structural units, namely the Iberian Massif, and the Lusitanian and Algarve Meso-Cenozoic basins. The Cadiz Gulf/Gibraltar Strait area corresponds to a strong low-velocity anomaly, which can be followed to the largest period inverted, although slightly shifted to the east at longer periods. Within the Iberian Massif, second-order perturbations in the group velocities are consistent with the transitions between tectonic units composing the massif.

  16. Geology and Tectonic Evolution of the Kazdaǧ Massif (NW Anatolia)

    NASA Astrophysics Data System (ADS)

    Erdoğan, B.; Akay, E.; Hasözbek, A.; Satır, M.; Siebel, W.

    2009-04-01

    In the northwestern part of Anatolia along the Izmir-Ankara Suture Zone, the Kazdağ and Uludağ metamorphic massifs form an E-W trending belt between the Sakarya Continent in the north and the Menderes Massif in the south. Internal succession of these two massifs have been described as metamorphic complexes consisting of various kinds of micaschists, quartz mica schist, gneisses, amphibolites and marbles. In the Kazdağ metamorphics, metaophiolites have been described additionally (Okay et al., 1991; Yaltırak and Okay, 1994; Okay et al., 1996; Duru et al., 2004). These metamorphic complexes were considered to form the basement of the Sakarya Continent tectonically overlain by the Early Permian (Topuz et al., 2004) to Late Triassic (Okay and Monie, 1997; Okay et al., 2002) Karakaya Complex. This old basement and the Karakaya Complex were suggested to be unconformably overlain by Liassic and younger platform limestones and detritals (Altıner et al., 1991). In the literature, it has also been suggested that the Kazdağ Massif had experienced polyphase metamorphism, first during Carboniferous time, second during Early Triassic and third during Tertiary (Bingöl, 1971; Okay et al., 1996; Okay and Satır, 2000). In this study we mapped the Kazdağ Massif on 1/25000 scale, studied its internal stratigraphy and structures and performed some petrologic analyses and radiogenic age determinations. Stratigraphically in the lower part of the Kazdağ metamorphic sequence, there is a part of an oceanic crust represented by metaultramafic rocks and gabbroic metacumulates. Geochemistry of these banded metagabbros show a mid-oceanic affinity. This oceanic crust is overlain, along an unconformity, by a platform type marble succession. At the base of the marbles, there is a basal conglomerate, clasts of which derived from the underlying ultramafic sequence. Thick white marble sequence is overlain along a gradational boundary with a metadetrital succession consisting of quartz mica

  17. Cl-rich hydrous mafic mineral assemblages in the Highiș massif, Apuseni Mountains, Romania

    NASA Astrophysics Data System (ADS)

    Bonin, Bernard; Tatu, Mihai

    2016-01-01

    The Guadalupian (Mid-Permian) Highiș massif (Apuseni Mountains, Romania) displays a bimodal igneous suite of mafic (gabbro, diorite) and A-type felsic (alkali feldspar granite, albite granite, and hybrid granodiorite) rocks. Amphibole is widespread throughout the suite, and yields markedly high chlorine contents. Three groups are identified: Cl-rich potassic hastingsite (2.60-3.40 wt% Cl) within A-type felsic rocks and diorite, mildly Cl-rich pargasite to hornblende (0.80-1.90 wt% Cl) within gabbro, and low F-Cl hornblende within gabbro and hybrid granodiorite. Coexisting biotite is either Cl-rich within diorite, or F-Cl-poor to F-rich within A-type felsic rocks. Chlorine and fluorine are distributed in both mafic phases, according to the F-Fe and Cl-Mg avoidance rules. The low-Ti contents suggest subsolidus compositions. Cl-rich amphibole within diorite and A-type felsic rocks yields a restricted temperature range - from 575 °C down to 400 °C, whereas mildly Cl-rich amphibole within gabbro displays the highest range - from 675 to 360 °C. Temperatures recorded by Cl-rich biotite within diorite range from 590 to 410 °C. Biotite within A-type felsic rocks yields higher temperatures than amphibole: the highest values- from 640 to 540 °C - are recorded in low-F-Cl varieties, whereas the lowest values- from 535 to 500 °C - are displayed by F-rich varieties. All data point to halogen-rich hydrothermal fluids at upper greenschist facies conditions percolating through fractures and shear zones and pervasively permeating the whole Highiș massif, with F precipitating as interstitial fluorite and Cl incorporating into amphibole, during one, or possibly several, hydrothermal episodes that would have occurred during a ~ 150 My-long period of time extending from the Guadalupian (Mid-Permian) to the Albian (Mid-Cretaceous).

  18. CRE dating on the scarps of large landslides affecting the Belledonne massif ( French Alps)

    NASA Astrophysics Data System (ADS)

    Lebrouc, V.; Baillet, L.; Schwartz, S.; Jongmans, D.; Gamond, J. F.; Bourles, D.; Le Roux, O.; Carcaillet, J.; Braucher, R.

    2012-04-01

    The southwestern edge of the Belledonne Massif (French Alps) consists of micaschists unconformably covered with Mesozoic sediments and Quaternary deposits. The morphology corresponds to a glacial plateau (Mont Sec plateau) bordered by steep slopes (around 40°), where moraines and peat bog subsist. The massif is incised by the East-West trending Romanche valley that was shaped by several cycles of quaternary glaciations and deglaciations. Slopes are affected by several active or past large scale rock mass instabilities. Cosmic Ray Exposure (CRE) dating was applied on the head scarps of three large landslides, one of which being the active Séchilienne landslide whose headscarp was already dated by Leroux et al. [2009]. Dating results suggest a concomitant initiation of these instabilities at about 7 ± 2 10Be ka, thousands years after the total downwastage of the valley. A different kinematic behaviour was however observed on two contiguous landslides for which continuous exposure profiles were obtained. On the Séchilienne landslide, 23 samples were collected from internal and lateral scarps, as well as on polished bedrock surfaces, with the aim of dating the internal kinematics of the landslide. Preliminary dating results obtained on polished surfaces and near the top of the scarps show unexpected low 10Be concentrations, suggesting the existence of thin moraine or peat bog deposits masking the bedrock, which have been subsequently eroded. The minimum thickness of these deposits was estimated assuming a constant denudation rate over time. Exposure date profiles show that the studied lateral and internal scarps were initiated at the same period as the Sechilienne headscarp. An increase in the exposure rate was also observed between 2 and 1 ka, in agreement with that evidenced along the headscarp. Forty other samples have been collected in the landslide to corroborate these results. Reference Le Roux, O., S. Schwartz , J.-F. Gamond, D. Jongmans, D. Bourles, R

  19. Cl-rich hydrous mafic mineral assemblages in the Highiș massif, Apuseni Mountains, Romania

    NASA Astrophysics Data System (ADS)

    Bonin, Bernard; Tatu, Mihai

    2016-08-01

    The Guadalupian (Mid-Permian) Highiș massif (Apuseni Mountains, Romania) displays a bimodal igneous suite of mafic (gabbro, diorite) and A-type felsic (alkali feldspar granite, albite granite, and hybrid granodiorite) rocks. Amphibole is widespread throughout the suite, and yields markedly high chlorine contents. Three groups are identified: Cl-rich potassic hastingsite (2.60-3.40 wt% Cl) within A-type felsic rocks and diorite, mildly Cl-rich pargasite to hornblende (0.80-1.90 wt% Cl) within gabbro, and low F-Cl hornblende within gabbro and hybrid granodiorite. Coexisting biotite is either Cl-rich within diorite, or F-Cl-poor to F-rich within A-type felsic rocks. Chlorine and fluorine are distributed in both mafic phases, according to the F-Fe and Cl-Mg avoidance rules. The low-Ti contents suggest subsolidus compositions. Cl-rich amphibole within diorite and A-type felsic rocks yields a restricted temperature range - from 575 °C down to 400 °C, whereas mildly Cl-rich amphibole within gabbro displays the highest range - from 675 to 360 °C. Temperatures recorded by Cl-rich biotite within diorite range from 590 to 410 °C. Biotite within A-type felsic rocks yields higher temperatures than amphibole: the highest values- from 640 to 540 °C - are recorded in low-F-Cl varieties, whereas the lowest values- from 535 to 500 °C - are displayed by F-rich varieties. All data point to halogen-rich hydrothermal fluids at upper greenschist facies conditions percolating through fractures and shear zones and pervasively permeating the whole Highiș massif, with F precipitating as interstitial fluorite and Cl incorporating into amphibole, during one, or possibly several, hydrothermal episodes that would have occurred during a ~ 150 My-long period of time extending from the Guadalupian (Mid-Permian) to the Albian (Mid-Cretaceous).

  20. Methane Seepage at Hyperalkaline Springs in the Ronda Peridotite Massif (Spain)

    NASA Astrophysics Data System (ADS)

    Etiope, G.; Vadillo, I.; Whiticar, M. J.; Marques, J. M.; Carreira, P. M.; Tiago, I.; Benavente, J.; Jimenez, P.; Urresti, B.

    2014-12-01

    Methane-rich, hyperalkaline spring waters and bubbling pools have been sampled in the Ronda peridotite massif in southern Spain. Water chemistry (T: 17.1-21.5 ºC; pH: 10.7-11.7; DO: <2 mg/L; Ca-OH facies) is characteristic of present-day serpentinization. Dissolved CH4 concentrations range from 0.1 to 3.2 mg/L. CH4 stable C and H isotope ratios suggest a dominant abiotic origin in two natural spring sites (delta13C: -13 to -29 ‰ VPDB; delta2H: -309 to -333 ‰ VSMOW) and a mixed biotic-abiotic origin in springs with artificial water delivery systems (i.e., pipes or fountains; delta13C: -44 to -69 ‰; delta2H: -180 to -319 ‰). At the natural springs, gas is mainly released through bubbles close to the water outlet (CH4 flux ~1 kg/day by individual bubble trains), and subordinately by microseepage from the ground, even at distances of ~100 m from the bubble-spring site (flux of 10's, up to 97, mg CH4 m-2day-1). Gas seepage is strictly controlled by faults. Under-saturation of CH4 in water, bubbling and seepage location suggest that CH4 is not exclusively transported to the surface by hyperalkaline water, but it follows autonomous migration pathways along faults. Similar 'dry' seepage of abiotic gas was observed in the Philippines, New Zealand, Turkey and Italy. Like other land-based serpentinization systems, the Ronda peridotite massif is characterized by low heat flow (<40 mW/m2), with temperatures <60°C at depths of 1.5 km. At these low T and high pH conditions, CO32- is the only available carbon source dissolved in the water, and unlikely contributes to catalysed Fischer-Tropsch Type reactions. Methane production from CO2 hydrogenation in a gas phase system (unsaturated fractured rocks) cannot be excluded. The presence of ruthenium-enriched chromitites in the Ronda peridotites may support the hypothesis that CH4 is produced by CO2 hydrogenation catalyzed by Ru minerals, even at temperatures below 100°C, as demonstrated in recent laboratory experiments

  1. Lithospheric Structure Along the Wide-Angle Seismic Reflection Transect of the Central Iberian Massif

    NASA Astrophysics Data System (ADS)

    Ehsan, Siddique Akhtar; Carbonell, Ramon; Cembrowski, Marcel; Marti, David; Gil, Alba; Marzan, Ignacio; Ayarza, Puy; Martinez-Poyatos, David; Simancas, Jose Fernando; Azor, Antonio

    2014-05-01

    The Iberian Massif is the largest outcrop of the Late Paleozoic Variscan Orogen in western Europe. In May 2012, a spatially dense high resolution wide-angle seismic reflection profile ALCUDIA was acquired across the Central Iberian Massif. The ALCUDIA wide-angle profile investigates lithospheric structure of the Central Iberian Zone and a suture zone (the Central Unit). The experiment consisted in a main SW-NE line of receivers, c. 300 km long, and a supplementary transect, c. 35 km long, that sampled the crust beneath the Central Iberian System. The acoustic energy generated by 5 shots, c. 70 km apart, was recorded by over 900 TEXANS (single component, digital recording stations) from the IRIS-PASSCAL Instrument Center. Each shot consisted in 1 TM of explosives fired in a single 55-65 m deep borehole. Approximately, 100 stations were deployed across the Central Iberian System in an effort to map the topography of the crust mantle boundary beneath this mountain range. This design generated enough energy to be able to identify Pn and even mantle reflections. The preliminary analysis of the shot gathers reveals that the recorded events features relatively low frequencies (4-30 Hz). The processing of the shot gathers resulted into high amplitude reflective events within the upper crust and strong PmP phases. From the southwest to northeast, the interpreted PmP arrivals are located at c. 11 s and c. 12 s (normal incidence traveltime) respectively. The ALCUDIA wide-angle profile provided a detailed P-wave velocity structural model and complemented the previously acquired normal incidence deep seismic profile ALCUDIA. The velocity model obtained by forward modelling constraints the composition of the crust and upper mantle. The upper crust is located at c. 13 km and the Moho is in the 32-36 km range, equates to normal incidence reflection profile ALCUDIA. Existing knowledge indicates that the mid-lower crust along the southern part of the CIZ is characterized by

  2. Scattering of teleseismic waves in the lower crust Observations in the Massif Central, France

    NASA Astrophysics Data System (ADS)

    Ritter, Joachim R. R.; Martin Mai, P.; Stoll, Gerald; Fuchs, Karl

    1997-02-01

    High-frequency coda signals consistently recorded by a temporary seismic network of 29 short-period stations during a 6-month survey in the French Massif Central are concordant with independent evidence for a heterogeneous lower crust obtained from wide-angle and near-vertical reflection experiments in the same region. The teleseismic recordings of 22 events have been analysed in record sections rather than as single station seismograms. Following the low-frequency (LF; 0.5-1.5 Hz) first P-arrival a high-frequency (HF) coda (2-4 Hz dominant frequency) extends over several seconds duration. The HF signals become clearly visible after bandpass filtering, but can also be identified in the original seismograms. In event sections the HF coda forms a consistent pattern of reverberations which is characterized by the following properties: (1) the duration is typically longer on the radial (4-15 s) than on the vertical (3-11 s) component; (2) the beginning of the HF coda, referred to the picked LF first P-arrivals varies between 0-2.5 s, with a dominance around 1.5-2 s; (3) the amplitude of the HF coda is about 3%-10% of the primary LF P-phase amplitude; (4) the signals are incoherent between neighbouring stations and over the network; (5) the HF coda arrives dominantly around the plane of incidence of the teleseismic wave in the first 2 s to maximum 4 s; afterwards a widening of the particle motion to an elliptical shape is observed, indicating arrivals off the sagittal plane. The data parameters (1) to (5) point to the conclusion that the HF signals are generated by a scattering process. Wide-angle and CDP-reflection experiments in the same region measured a similar reverberating coda pattern and located the origin also in the lower crust. These observations and the data parameters of the HF coda suggest that the HF teleseismic waves are scattered at heterogeneities in the lower crust in the Massif Central. In this contribution we mainly concentrate on the presentation

  3. Soil mesofauna in disturbed spruce forest stands near Čertovo and Plešné Lakes, the Bohemian Forest: preliminary results

    NASA Astrophysics Data System (ADS)

    Čuchta, Peter; Starý, Jozef

    2016-04-01

    The soil microarthropod communities were studied in disturbed spruce forest stands in the catchments areas of Čertovo (CT) and Plešné (PL) Lakes in the Bohemian Forest, Czech Republic. The study is focused on the impact of the windthrow, bark beetle outbreak damage and consecutive changes in the forest stands including soil environment. Within the soil microarthropods, two main groups, Collembola (Hexapoda) and Oribatida (Acari) are analysed. Four different treatments were selected for the study on both study areas: CT1 and PL1 stands - undamaged control forest stands, CT2 and PL2 stands - "dead" forest stands damaged by bark beetle, CT3 and PL3 stands - slightly managed windthrown forest stands left for the natural succession, and CT4 and PL4 stands - harvested windthrown stands. Soil samples were taken in June (CT1/PL1 - CT3/PL3), July and October (CT1/PL1 - CT4/PL4) 2012 from each treatment. Microarthropods were subsequently extracted in a modified high-gradient apparatus in the laboratory for seven days. Finally, the comparison of the microarthropod assemblages found at different treatment stands was performed. The most abundant groups in both study areas (Čertovo and Plešné Lakes) were Collembola and Oribatida with considerable diferences within particular treatments and in time as well.

  4. Isotope Sm-Nd age of the paleoproterozoic PGE-bearing Monchetundra massif trachytoid gabbronorites (Fennoscandian shield)

    NASA Astrophysics Data System (ADS)

    Kunakkuzin, Evgeniy; Bayanova, Tamara; Serov, Pavel; Borisenko, Elena

    2015-04-01

    Monchetundra massif is located in the central part of the Kola Peninsula (Russia) and it is the south-eastern part of the Main Ridge Intrusion. Monchetundra massif together with well-known layered mafic-ultramafic PGE-bearing intrusions in the Fennoscandian shield such as the Fedorovo-Pansky complex, the mt. Generalskaya, the Monchepluton is of interest as a target for the PGE prospecting (Mitrofanov et al. 2006; Nerovich et al., 2009; Grokhovskaya et al., 2003). According to some previously researchers (Nazimova, Rayan, 2008, Nerovich et al., 2009, Layered intrusions…p.1, 2004) rocks of the Monchetundra massif is subdivided into two to five syngenetic zones. Hence the last isotope-geochronological and isotope-geochemical data revealed that the massif includes at least four groups of mafic rocks distinguished by formation ages (Bayanova et al., 2010). The aim of this work is to present Sm-Nd dating results of trachytoid gabbronorites, which are the second mafic rocks group in the Monchetundra massif. The Sm-Nd investigations for these rocks were carried out for the first time. The second group of mafic rocks comprises of medium-grained and coarse-grained mesocratic gabbronorites of trachytoid texture, with they characterized by well-preserved primary magmatic minerals and gabbro-ophitic texture. The U-Pb ages on single zircon-baddeleyite for these rocks recently obtained (2505 ± 6 Ma, 2501 ± 8 Ma, 2504.4±2.7 Ma and 2507.5±7.7 Ma (Layered intrusions…p.1., 2004, Borisenko et al., 2013)). Two samples of trachytoid gabbronorites were selected to study these rocks by Sm-Nd isotopic method. Mineral isochrons plotted from plagioclase, ortho- and clinopyroxene and whole-rock minerals gave ages of 2496±27 (MSWD = 0.9; ɛNd = -1.6±0.5) and 2492±55 Ma (MSWD = 0.5; ɛNd = -1.7±0.5). The new Sm-Nd ages obtained are close to the U-Pb data on zircons and baddeleyites for this rocks group and consider as oridin of second mafic rocks group. All investigations are

  5. Internal structure of the Aar Massif: What can we learn in terms of exploration for deep geothermal energy?

    NASA Astrophysics Data System (ADS)

    Herwegh, Marco; Baumberger, Roland; Wehrens, Philip; Schubert, Raphael; Berger, Alfons; Maeder, Urs; Spillmann, Thomas

    2014-05-01

    The successful use of deep geothermal energy requires 3D flow paths, which allow an efficient heat exchange between the surrounding host rocks and the circulating fluids. Recent attempts to exploit this energy resource clearly demonstrate that the new technology is facing sever problems. Some major problems are related to the prediction of permeability, the 3D structure of the flow paths and the mechanical responses during elevated fluid pressures at depths of several kilometers. Although seemingly new in a technical perspective, nature is facing and solving similar problems since the beginning of the Alpine orogeny. Based on detailed studies in the Hasli Valley (Aar Massif) we can demonstrate that deformation and fluid flow are strongly localized along mechanical anisotropies (e.g. lithological variations, brittle and ductile faults). Some of them already evolved during Variscan and post-Variscan times. Interestingly, these inherited structures are reactivated over and over again during the Alpine orogeny. Their reactivation occurred at depths of ~13-15 km with elevated temperatures (400-475°C) and involved both ductile and brittle deformation processes. Brittle deformation in form of hydrofracking was always present due to the circulating fluids. It is this process, which was and still is responsible for seismic activity. With progressive uplift and exhumation of the Aar Massif, ductile deformation structures became replaced by brittle cataclasites and fault gouges during fault activity at shallower crustal levels. Existing hydrotest data from the Grimsel Test Site (Nagra's underground research laboratory) indicate that these brittle successors of the ductile shear zones are domains of enhanced recent fluid percolation. Note that although being exposed today, the continuation of these fault structures are still active at depth in both brittle and ductile deformation modes, a fact that can be inferred from recent uplift rates and the active seismicity. On the

  6. The Chineysky layered massif (Siberia, Russia) and Upper Zone of the Bushveld Complex: resemblance and difference features

    NASA Astrophysics Data System (ADS)

    Gongalskiy, B.; Krivolutskaya, N.

    2009-04-01

    Layered intrusions represent a small part of a large group of continental basic-ultrabasic complexes. They attract geologists' attention due to their unusual magmatic structures and associated PGE, Cr and V deposits. The outstanding example of this phenomenon is the Bushveld Complex in South Africa. The largest layered intrusion in Russia is the Chineysky massif (Transbaikalia, Siberia). It is characterized by excellent layering and accompanying titanomagnetite and sulfide mineralization. It hosts Russia's largest deposits of Fe-Ti-V ores which are also among the world's largest [1]. Origin of such huge metal concentrations in the crust is unsettled problem. Therefore the ore conditions' determination from different intrusions is very actually. We compared the structure, rock and parental magmas compositions for two plutons mentioned above. The Chineysky massif consists of gabbronorites and anorthozites and the petrography of the rocks resembles that of the Upper Zone of the Bushveld [3]. Vanadium ores from these two intrusions are very similar: they are represented by massive and disseminated varieties. However, the small size of Chineysky massiv gives an opportunity to observe the number of petrological processes in a frame of one area, as opposed to Bushveld, where this is impossible. The separateness of the bodies and the scarcity of geochemical data on their rocks precluded the development of a comprehensive model for the evolution of magmatism in this part of the Kodar- Udokan trough. So one of the tasks of our research was to study the spatial and genetic relations between the ultrabasite-basite intrusive bodies and their possible grouping within a single magmatic system, with the Chineysky massif being its part. The second tasks was to determine the phase characteristics of the parental magma of the massif . An important aspect of this study was the examination of the inner structure of the Chineysky massiv. The main features of the structure are following

  7. Fe distribution in GaSe and InSe

    SciTech Connect

    Kovalyuk, Z.D.; Feichuk, P.I.; Shcherbak, L.P.; Zbykovskaya, N.I.

    1985-06-01

    In this paper, the authors use tagged atoms to determine the effective coefficients of Fe distribution in GaSe and InSe during crystallization of a doped melt by the Bridgman method. The distribution of Fe in GaSe and InSe was studied with the aid of Fe tagged with the radiosotopes VVFe + VZFe. Doping of the material was combined with the processes of synthesis and crystallization. Equations are presented for the calculation of the real impurity distribution in GaSe and InSe crystals.

  8. Deeply Eroded Massif Anorthosite and Nepheline Syenite of the Chimakurti-Uppalapadu Plutons, Peninsular India: Cospatial but not Comagmatic

    NASA Astrophysics Data System (ADS)

    Kumar, K.; Frost, C. D.; Frost, B. R.

    2001-12-01

    Massif anorthosites are generally thought to be ultimately of mantle origin. However, the lack of samples representing primitive liquid compositions and paucity of early cumulates limits the understanding of the processes that produced them. Some of the most deeply eroded massif anorthosite complexes are exposed within the southern Eastern Ghat Belt of Peninsular India, and provide an excellent opportunity to study the processes that operated in the deep magma chambers beneath the massifs. In this area Si-undersaturated nepheline syenites are associated with anorthosite complexes, a case that is not reported elsewhere in the world. The objectives of the present study are two fold: 1) to identify the processes that acted at the lowest level of the anorthosite complexes and 2) to determine the relationship between cospatial anorthosites and nepheline syenites. Cospatial alkaline-tholeiitic magmatism is strikingly displayed in the Chimakurti-Uppalapadu plutons within Prakasam Province. The Chimakurti pluton is concentrically zoned, and from core to margin consists of 1) olivine clinopyroxenite, 2) anorthosite, 3) olivine gabbronorite and 4) gabbronorite. It emplaced at mid-crustal depths (~6 kb; 16-18 km) and is undeformed and unmetamorphosed. Comparably deep-seated massifs are strongly metamorphosed (Adirondacks) and unmetamorphosed ones typically have shallow emplacement histories (Laramie). Unlike many massif anorthosite complexes, the Chimakurti pluton is associated with a gravity high of the order of 20 to 30 mGal; consistent with the presence of ultramafic cumulates. The Uppalapadu pluton is composed of nepheline syenite (NS). An arcuate band of hornblende syenite with pockets of quartz syenite and ferro-syenite (HQF series) is present between the two plutons. Field, petrographic, mineralogical and geochemical evidence suggests that the Clinopyroxenite-Anorthosite-Gabbro (CAG) suite of Chimakurti is formed by crystal-liquid fractionation (compounded by

  9. Time scales of regional circulation of saline fluids in continental aquifers (Armorican massif, Western France)

    NASA Astrophysics Data System (ADS)

    Armandine Les Landes, A.; Aquilina, L.; Davy, P.; Vergnaud, V.; le Carlier, C.

    2014-06-01

    In recent decades, saline fluids have been sampled worldwide at great depths in continental basements. Although some of them have been attributed to marine transgressions the mechanisms allowing their circulation is not understood. In this paper, we describe the horizontal and vertical distribution of moderately saline fluids (60 to 1400 mg L-1) sampled at depths ranging from 41 to 200 m in aquifers at the regional scale of the Armorican Massif (northwestern France). The horizontal and vertical distributions of high chloride concentrations are in good agreement with both the altitudinal and vertical limits and succession of the three major transgressions between the Mio-Pliocene and Pleistocene ages. The mean chloride concentration for each transgression area is exponentially related to the time spanned until present. It defines the potential laws of leaching of marine waters by fresh meteoric waters. The results of the Armorican aquifers provide the first observed constraints for the time scales of seawater circulation in the continental basement and the subsequent leaching by fresh meteoric waters. The general trend of increasing chloride concentration with depth and the time frame for the flushing process provide useful information to develop conceptual models of the paleo-functionning of Armorican aquifers.

  10. Timescales of regional circulation of saline fluids in continental crystalline rock aquifers (Armorican Massif, western France)

    NASA Astrophysics Data System (ADS)

    Armandine Les Landes, A.; Aquilina, L.; Davy, P.; Vergnaud-Ayraud, V.; Le Carlier, C.

    2015-03-01

    In recent decades, saline fluids have been sampled worldwide at great depths in continental basements. Although some of them have been attributed to marine transgressions, the mechanisms allowing their circulation are not understood. In this paper, we describe the horizontal and vertical distributions of moderately saline fluids (60 to 1400 mg L-1) sampled at depths ranging from 41 to 200 m in crystalline rock aquifers on the regional scale of the Armorican Massif (northwestern France). The horizontal and vertical distributions of high chloride concentrations are in good agreement with both the altitudinal and vertical limits and the succession of the three major transgressions between the Mio-Pliocene and Pleistocene ages. The mean chloride concentration for each transgression area is exponentially related to the time spanned until the present. It defines the potential laws of leaching (displacement) of marine waters by fresh meteoric waters. The results of the Armorican aquifers provide the first observed constraints for the timescales of seawater circulation in the continental crystalline basement and the subsequent leaching by fresh meteoric waters. The general trend of increasing chloride concentration with depth and the time frame for the flushing process provide useful information to develop conceptual models of the paleo-functioning of Armorican aquifers.

  11. Vorticity analysis in calcite tectonites: An example from the Attico-Cycladic massif (Attica, Greece)

    NASA Astrophysics Data System (ADS)

    Spanos, D.; Xypolias, P.; Koukouvelas, I.

    2015-11-01

    Although calcite tectonites are widespread in nature their use to quantify flow vorticity is limited. We use new (micro-)structural, petrofabric and vorticity data to analyse the kinematics of flow in outcrop-scale calcite mylonite zones. These zones are genetically related to a crustal-scale NE-directed ductile thrust (Basal Thrust) that emplaced the Blueschist over the Basal unit during the exhumation of the Attico-Cycladic Massif. Calcite microstructures reveal that the last stage of deformation occurred at temperatures 200-300 °C achieved by mild heating, which is possibly related with the reburial of the Basal Thrust's footwall. Vorticity analyses were based on the degree of asymmetry of calcite c-axis fabrics as well as on the assumption that the orientation of the long axes of calcite neoblasts within an oblique foliation delineates the direction of instantaneous stretching axis. Both methodological approaches provide consistent estimates with a simple shear component between 55% and 82% (Wn = 0.76-0.96). The use of the stress axis (σ1) orientation recorded by twin-c-axis-pairs to quantify vorticity generally gives significantly lower simple shear component. Comparison of our vorticity estimates with previous estimates inferred from quartz fabrics and rigid porphyroclasts reveals that exhumation-related deformation in the nappe pile was steady state.

  12. Raman mapping of coesite inclusions in garnet from the Kokchetav Massif (Northern Kazakhstan).

    PubMed

    Korsakov, Andrey V; Hutsebaut, Didier; Theunissen, Karel; Vandenabeele, Peter; Stepanov, Alexander S

    2007-12-15

    Coesite inclusions occur in a wide range of lithologies and coesite is therefore a powerful ultrahigh-pressure (UHP) indicator. The transformation of coesite to quartz is evidenced by three optically well identifiable characteristics (e.g. palisade textures, radial crack patterns, polycrystalline quartz pseudomorphs). Under overpressure monomineralic coesite (on an optical basis), lacking the above transformation characteristics may survive. Raman micro-spectroscopy was applied on monomineralic coesite inclusions in garnet porphyroblasts from diamond-bearing garnet-clinozoisite-biotite gneisses of the Barchi-Kol area (Kokchetav Massif, Northern Kazakhstan). These coesite inclusions are euhedral and display a characteristic anisotropic hallo. However, Raman maps and separate spectra of these inclusions display shifted bands for coesite and quartz. Microscopically undetectable, quartz shows on the Raman map as a thin shell around coesite inclusion. Shift of the main coesite band allows to estimate their overpressure: coesite inclusions record 0-2.4 GPa in garnet and zircon. The quartz shell remains under lower pressure 0-1.6 GPa. The possible application of coesite and quartz Raman geobarometers for UHP metamorphic rocks is discussed. PMID:17553735

  13. Raman imaging of fluid inclusions in garnet from UHPM rocks (Kokchetav massif, Northern Kazakhstan).

    PubMed

    Korsakov, Andrey V; Dieing, Thomas; Golovin, Aleksandr V; Toporski, Jan

    2011-10-01

    Confocal Raman imaging of fluid inclusions in garnet porphyroblasts from diamond-grade metamorphic calc-silicate rocks from the Kumdy-Kol microdiamond deposit (Kokchetav Massif, Northern Kazakhstan) reveals that these fluid inclusions consist of almost pure water with different step-daughter phases (e.g., calcite, mica and rare quartz). These fluid inclusions are characterized by negative crystal shape of the host-garnet and they exclusively occur within the core of garnet porphyroblasts. These observations are consistent with their primary origin, most likely at ultrahigh-pressure (UHP) metamorphic conditions. The euhedral newly formed garnet, different in color and composition, was found to be associated with these fluid inclusions. It is proposed that newly formed garnet and water fluid inclusions appear by reaction between the hydrous fluid and the garnet-host. These fluid inclusions provide an unequivocal record of almost pure H(2)O fluids, indicating water-saturated conditions within subducted continental crust during prograde stage and/or ultrahigh-P metamorphism. PMID:21377920

  14. AMS 14C Dates for Extinct Lemurs from Caves in the Ankarana Massif, Northern Madagascar

    NASA Astrophysics Data System (ADS)

    Simons, Elwyn L.; Burney, David A.; Chatrath, Prithijit S.; Godfrey, Laurie R.; Jungers, William L.; Rakotosamimanana, Berthe

    1995-03-01

    An extensive late Quaternary fauna, including many extinct giant lemurs, has been collected recently in a 110+-km system of caves in the Ankarana Massif of northern Madagascar. AMS 14C dates for the acid-insoluble (collagen/gelatin) fraction of bones of the giant lemur Megaladapis (26,150 ± 400 and 12,760 ± 70 yr B.P.) confirm its presence in the area during the late Pleistocene and provide the first Pleistocene 14 C ages from bones of the extinct megafauna of the island. The first date from bones of the recently described extinct Babakotia radofilai (4400 ± 60 yr B.P.) shows that it was present in northern Madagascar in mid-Holocene times. A comparatively recent age of 1020 ± 50 yr B.P. for the extinct Archaeolemur indicates survival of this genus for at least a millennium after the first direct evidence for humans in Madagascar. This suggests that the island's "extinction window" may have represented a longer time span than would have been expected under the Blitzkrieg model of late Quaternary extinctions. A mid-Holocene age (4560 ± 70 yr B.P.) for a bone sample of the small extant lemur Hapalemur simus indicates that the disappearance of this now-restricted species from the Ankarana occurred after this date. New data from the Ankarana and other sites on the island add to the consensus that major biotic changes occurred on Madagascar in the late Holocene.

  15. Using several monitoring techniques to measure the rock mass deformation in the Montserrat Massif

    NASA Astrophysics Data System (ADS)

    Janeras, M.; Jara, J. A.; López, F.; Marturià, J.; Royán, M. J.; Vilaplana, J. M.; Aguasca, A.; Fàbregas, X.; Cabranes, F.; Gili, J. A.

    2015-09-01

    Montserrat Mountain is located near Barcelona in Catalonia, at the north-east corner of Spain, and its massif is formed by conglomerate interleaved by siltstone/sandstone with steep slopes very prone to rock falls. The increasing visitor's number in the monastery area, reaching 2.4 million per year, has pointed out the risk derived from rock falls for this building area and also for the terrestrial accesses, both roads and rack railway. A risk mitigation plan is currently been applied for 2014-2016 that contains monitoring testing and implementation as a key point. The preliminary results of the pilot tests carried out during 2014 are presented, also profiting from previous sparse experiences and data, and combining 4 monitoring techniques under different conditions of continuity in space and time domains, which are: displacement monitoring with Ground-based Synthetic Aperture Radar and characterization at slope scale, with an extremely non uniform atmospheric phase screen because of the stepped topography and atmosphere stratification; Terrestrial Laser Scanner surveys quantifying frequency for unnoticed activity of small rock falls, and monitoring rock block displacements over 1cm; monitoring of rock joints with a wireless net of sensors; and tentative surveying for singular rocky needles with Total Station.

  16. Analysis of the upper massif of the craniofacial with the radial method – practical use

    PubMed Central

    Lepich, Tomasz; Dąbek, Józefa; Stompel, Daniel; Gielecki, Jerzy S.

    2011-01-01

    Introduction The analysis of the upper massif of the craniofacial (UMC) is widely used in many fields of science. The aim of the study was to create a high resolution computer system based on a digital information record and on vector graphics, that could enable dimension measuring and evaluation of craniofacial shape using the radial method. Material and methods The study was carried out on 184 skulls, in a good state of preservation, from the early middle ages. The examined skulls were fixed into Molisson's craniostat in the author's own modification. They were directed in space towards the Frankfurt plane and photographed in frontal norm with a digital camera. The parameters describing the plane and dimensional structure of the UMC and orbits were obtained thanks to the computer analysis of the function recordings picturing the craniofacial structures and using software combining raster graphics with vector graphics. Results It was compared mean values of both orbits separately for male and female groups. In female skulls the comparison of the left and right side did not show statistically significant differences. In male group, higher values were observed for the right side. Only the circularity index presented higher values for the left side. Conclusions Computer graphics with the software used for analysing digital pictures of UMC and orbits increase the precision of measurements as well as the calculation possibilities. Recognition of the face in the post mortem examination is crucial for those working on identification in anthropology and criminology laboratories. PMID:22291834

  17. Geologic implications of seafloor character and carbonate lithification imaged on the domal core of Atlantis Massif

    NASA Astrophysics Data System (ADS)

    Greene, John A.; Tominaga, Masako; Blackman, Donna K.

    2015-11-01

    We document the seafloor character on Atlantis Massif, an ocean core complex located at 30°N on the Mid-Atlantic Ridge, with an emphasis on the distribution of carbonate features. Seafloor imagery, near-bottom backscatter, and bathymetry were analyzed on the Central Dome and the Western Shoulder of the exposed footwall to the detachment, and on the Eastern Block, a hanging wall to the fault. We merged Argo II still images to produce photo-mosaics and evaluated these together with video imagery, acoustic reflectivity, and basic rock composition. The seafloor was classified as unconsolidated sediment, lithified carbonate crust, consolidated carbonate cap, exposed basement, or rubble, and the spatial distribution of each type was assessed. Unconsolidated sediment, exposed basement, and rubble were documented in all three regions studied. Lithified carbonate crust was also present on the Western Shoulder and eastern Central Dome. Consolidated carbonate cap was found on the Eastern Block. The formation of the carbonate rock is interpreted to reflect precipitation and/or sediment cementation via fluids derived from serpentinization. Both processes occur at the nearby Lost City Hydrothermal Field. The newly documented locations of seafloor carbonate lithification therefore mark pathways of past, possibly recent, fluid flux from subsurface water-rock reaction zones and represent an additional constituent of the carbon cycling hosted by oceanic lithosphere.

  18. Spatial variability in channel and slope morphology within the Ardennes Massif, and its link with tectonics

    NASA Astrophysics Data System (ADS)

    Sougnez, N.; Vanacker, V.

    2010-09-01

    Geomorphic processes that produce and transport sediment, and incise river valleys are complex; and often difficult to quantify over longer timescales of 103 to 105 years. Morphometric indices that describe the topography of hill slopes, valleys and river channels have commonly been used to compare morphological characteristics between catchments and to relate them to hydrological and erosion processes. This work focuses on a wide range of slope and river channel morphometric indices to study their behavior and strength in regions affected by low to moderate tectonic activity. We selected 10 catchments of about 150 to 250 km2 across the Ardennes Massif that cover various tectonic domains with uplift rates ranging from about 0.06 to 0.20 mm year-1 since mid-Pleistocene times. The morphometric analysis indicates that the slope and channel morphology of third-order catchments is not yet in topographic steady-state, and exhibits clear convexities in slope and river profiles. Our data indicate that the fluvial system is the main driver of topographic evolution and that the spatial pattern of uplift rates is reflected in the distribution of channel steepness and convexity. The spatial variation that we observe in slope and channel morphology between the 10 third-order catchments suggests that the response of the fluvial system was strongly diachronous, and that a transient signal of adjustment is migrating from the Meuse valley towards the Ardennian headwaters.

  19. Nature of radioactive contamination of components of ecosystems of streamflows from tunnels of Degelen massif.

    PubMed

    Panitskiy, A V; Lukashenko, S N

    2015-06-01

    The paper provides data on environmental contamination due to radionuclides' migration with water. As a result of investigations there was obtained data on character of contamination of soil cover, surface water and underflow from tunnels of Degelen massif. Character of radionuclides' spatial distribution in environment was also shown. Mobility ranges of radionuclides' vertical and horizontal movements have been established in soils both across and along the stream flow. There was also shown a possibility to forecast radionuclides' concentration in soil by specific activity of these radionuclides in water. Different concentrations of radionuclides in associated components of the ecosystem (surface waters - ground waters - soils) have shown disequilibrium of their condition in this system. Generalization of investigation results for tunnel water streams' with water inflows, chosen as investigation objects in this work, allows to forecast radionuclides' behavior in meadow soils and other ecosystems of water streams from tunnels of Degelen test site. Based on analysis of curves, describing radionuclides' behavior in horizontal direction, we can forecast, that at this stage (137)Cs and (239+240)Pu would not be distributed more than 1.5 km from the access to the daylight surface, (90)Sr - not more than 2 km. PMID:25791901

  20. Boiling fluids in a region of rapid uplift, Nanga Parbat Massif, Pakistan

    NASA Astrophysics Data System (ADS)

    Craw, D.; Koons, P. O.; Winslow, D.; Chamberlain, C. P.; Zeitler, P.

    1994-12-01

    The Nanga Parbat massif of northern Pakistan is currently undergoing rapid uplift (approx. 5-10 mm/a), resulting in near-surface elevated temperatures. Numerous quartz veins cut geologically young structures (less than 2 Ma), attesting to widespread young fluid flow. Fluid inclusions in quartz veins are predominantly low density water vapor (down to 0.05 mg/cu m), with some low density carbon dioxide vapor, and the fluid is predominantly meteoric in origin. Fluid inclusions provide evidence for boiling near to the critical points for water and for 5 wt% NaCl solution (up to 410 C). Head-driven meteoric water was convecting in fracture permeability under hydrostatic pressures which followed the boiling point-depth curve and near-boiling springs emanate from the surface. Hydrostatic pressures persisted to depths of about 6 km below the topographic surface, or near to sea level, where the brittle-ductile transition is inferred to lie. Numerical modeling of conductive heat flow in an area of high relief during rapid uplift indicates that the shape of the near-surface conductive geotherm is significantly influenced by topographic relief. Reasonable approximations for topgraphy at Nanga Parbat produce a conductive geotherm which implies high, near-surface geothermal gradients (greater than 100 C/km, and the isotherms describe a giant pillar of heat. Above about 4 km, fluid temperature is greater than conductive rock temperature in permeable zones which carry convecting boiling meteoric fluid.

  1. Three-dimensional shape and emplacement of the Cardenchosa deformed pluton (Variscan Orogen, southwestern Iberian Massif)

    NASA Astrophysics Data System (ADS)

    Simancas, J. Fernando; Galindo-Zaldívar, Jesús; Azor, Antonio

    2000-04-01

    The Cardenchosa pluton is a Lower Carboniferous Variscan granite located in the southwestern Iberian Massif. It intruded along the contact between the Sierra Albarrana and Azuaga tectonic units. To the northwest the pluton connects with the left-lateral Azuaga fault. The pluton appears in the footwall of the low-angle normal Casa del Café fault, which crops out to the west of the granite. Gravimetric modelling shows the pluton to have a flat bottom at a depth of 2 km. Strain analysis of post-emplacement deformation of the pluton indicates that: (a) the deformation of the pluton accommodates the displacement of the Azuaga fault; and (b) the pluton prior to the solid state deformation was a lens-shaped laccolith of approximately 10 km diameter and 2 km thickness. The Cardenchosa pluton was a single pulse of magma trapped in a rheological discontinuity of the upper crust (the contact between the Sierra Albarrana and Azuaga units). The magma would ascend through dikes since no root has been detected. The tectonic scenario during the intrusion was one of regional extension.

  2. Lithologic Distribution and Geologic History of the Apollo 17 Site: The Record in Soils and Small Rock Particles from the Highland Massifs

    NASA Technical Reports Server (NTRS)

    Jolliff, Bradley L.; Rockow, Kaylynn M.; Korotev, Randy L.; Haskin, Larry A.

    1996-01-01

    Through analysis by instrumental neutron activation (INAA) of 789 individual lithic fragments from the 2 mm-4 mm grain-size fractions of five Apollo 17 soil samples (72443, 72503, 73243, 76283, and 76503) and petrographic examination of a subset, we have determined the diversity and proportions of rock types recorded within soils from the highland massifs. The distribution of rock types at the site, as recorded by lithic fragments in the soils, is an alternative to the distribution inferred from the limited number of large rock samples. The compositions and proportions of 2 mm-4 mm fragments provide a bridge between compositions of less than 1 mm fines and types and proportions of rocks observed in large collected breccias and their clasts. The 2 mm-4 mm fraction of soil from South Massif, represented by an unbiased set of lithic fragments from station-2 samples 72443 and 72503, consists of 71% noritic impact-melt breccia, 7% Incompatible-Trace-Element-(ITE)-poor highland rock types (mainly granulitic breccias), 19% agglutinates and regolith breccias, 1% high-Ti mare basalt, and 2% others (very-low-Ti (VLT) basalt, monzogabbro breccia, and metal). In contrast, the 2 mm - 4 mm fraction of a soil from the North Massif, represented by an unbiased set of lithic fragments from station-6 sample 76503, has a greater proportion of ITE-poor highland rock types and mare-basalt fragments: it consists of 29% ITE-poor highland rock types (mainly granulitic breccias and troctolitic anorthosite), 25% impact-melt breccia, 13% high-Ti mare basalt, 31 % agglutinates and regolith breccias, 1% orange glass and related breccia, and 1% others. Based on a comparison of mass- weighted mean compositions of the lithic fragments with compositions of soil fines from all Apollo 17 highland stations, differences between the station-2 and station-6 samples are representative of differences between available samples from the two massifs. From the distribution of different rock types and their

  3. Properties of Se/InSe Thin-Film Interface

    NASA Astrophysics Data System (ADS)

    Qasrawi, A. F.; Kayed, T. S.; Elsayed, Khaled A.

    2016-06-01

    Se, InSe, and Se/InSe thin films have been prepared by the physical vapor deposition technique at pressure of ˜10-5 torr. The structural, optical, and electrical properties of the films and Se/InSe interface were investigated by means of x-ray diffraction (XRD) analysis, ultraviolet-visible spectroscopy, and current-voltage ( I- V) characteristics. XRD analysis indicated that the prepared InSe films were amorphous while the Se films were polycrystalline having hexagonal structure with unit cell parameters of a = 4.3544 Å and c = 4.9494 Å. Spectral reflectance and transmittance analysis showed that both Se and InSe films exhibited indirect allowed transitions with energy bandgaps of 1.92 eV and 1.34 eV, respectively. The Se/InSe interface exhibited two energy bandgaps of 0.98 eV and 1.73 eV above and below 2.2 eV, respectively. Dielectric constant values were also calculated from reflectance spectra for the three layers in the frequency range of 500 THz to 272 THz. The dielectric constant exhibited a promising feature suggesting use of the Se/InSe interface as an optical resonator. Moreover, the Au/Se/InSe/Ag heterojunction showed some rectifying properties that could be used in standard optoelectronic devices. The ideality factor and height of the energy barrier to charge carrier motion in this device were found to be 1.72 and 0.66 eV, respectively.

  4. Sr, Nd, Hf and Pb isotope systematics of basaltic samples from IODP Site U1349A, Ori Massif of the Shatsky Rise Oceanic Plateau, Northwest Pacific

    NASA Astrophysics Data System (ADS)

    Romanova, I.; Murphy, D. T.; Geldmacher, J.; Heydolph, K.

    2011-12-01

    Shatsky Rise is located on the northwest Pacific plate, and has an elongated structure from southeast to northwest. It represents a large oceanic plateau (up to 500 km wide) that was formed between 140-150 Ma in an active spreading ridge at relatively high emplacement rates (1.2-4.6 km3/y), similar to those of some flood basalt provinces [1]. Whether the Shatsky Rise formed by the impact of a mantle plume head or by shallow mantle processes at a rapidly extending triple junction is a matter of ongoing debate. Geochemical research will provide vital information on mantle sources and melting conditions contributing to LIP magmatism [1]. The Ori Massif is one of the three elevated massifs within the Shatsky Rise, comprising a volume of 0.7 × 106 km3. It is situated in the middle of the plateau with the largest edifice Tamu Massif to the southeast and the smaller Shirshov Massif to the northwest. Within plume theory Ori Massif formed at an intermediate to early stage of a plume volcanism. In shallow mantle theory it formed from a shallow lithospheric source during oceanic spreading at a triple junction [1]. During IODP Expedition 324 two sites were drilled on Ori Massif, one of which, U1349A, targeted the summit. The Hole U1349A penetrated 250.4m beneath the seafloor, and includes 165.1m of sediments and 85.3m of igneous basement. The uppermost volcanic flows (~55m) are highly vesicular, stongly altered to reddish brown clays and contain abundant pseudomorphs after olivine. These flows are underlain by highly altered volcaniclastic breccia (>40m) [1]. Here we present Sr, Nd, Hf and Pb isotope characterisation of the U1349A basaltic basement samples. Our results on the Ori Massif will be combined with isotope data from the Tamu Massif and Shirshov Massif. Thus, some preliminary conclusions about the source of mantle material that formed the Shatsky Rise oceanic plateau and its variation in space and time can be made. [1] Expedition 324 Scientists (2010) Expedition

  5. Constraints on strain rate and fabric partitioning in ductilely deformed black quartzites (Badajoz-Córdoba Shear Zone, Iberian Massif)

    NASA Astrophysics Data System (ADS)

    Puelles, Pablo; Ábalos, Benito; Fernández-Armas, Sergio

    2013-04-01

    The Badajoz-Córdoba Shear Zone is a is 30-40 km wide and 400 km long, NW-SE trending structure located at the boundary between the Ossa-Morena and Central-Iberian Zones of the Iberian Massif. Two elongated domains can be differentiated inside: the Obejo-Valsequillo domain to the NE and the Ductile Shear Belt (DSB) to the SW. The former exhibits Precambrian to Cambrian volcano-sedimentary rocks unconformably overlaying a Neoproterozoic basement formed by the "Serie Negra". The latter, 5-15 km wide, is composed mainly of metamorphic tectonites including the "Serie Negra" and other units located structurally under it. The petrofabric of "Serie Negra" black quartzites from the DSB is analyzed in this study with the Electron Back-Scattered Diffraction technique (EBSD). Black quartzites represent originally siliceous, chemical-biochemical shallow-water marine deposits, currently composed almost exclusively of quartz and graphite. Macroscopically they exhibit an outstanding planolinear tectonic fabric. Petrographically, coarse- and fine-grained dynamically recrystallized quartz bands alternate. The former contain quartz grains with irregular shapes, mica inclusions and "pinning" grain boundaries. Oriented mica grains and graphite particles constrain irregular quartz grain shapes. Quartz ribbons with chessboard microstructures also occur, indicating recrystallization under elevated temperatures coeval with extreme stretching. Fine-grained recrystallized quartz bands are dominated by quartz grains with straight boundaries, triple junctions, a scarcer evidence of bulging, and a higher concentration of dispersed, minute graphite grains. Quartz lattice-preferred orientation (LPO) patterns permit to identify two well-developed maxima for [c] axes: one close to the Y structural direction and the other one around Z, and -axes girdles normal to Y and Z. Although both [c] axis maxima appear in the coarse- and fine-grained bands, subsets can be isolated with grain cluster

  6. Prise en charge d’un afflux massif de brûles lors d’une situation de catastrophe par incendie au Maroc

    PubMed Central

    Siah, S.; Hatimi, E.M.; Ihrai, H.; Drissi Kamili, N.

    2012-01-01

    Summary La brûlure est l’une des lésions les plus fréquemment rencontrées lors de catastrophes naturelles ou lors de catastrophes d’origine humaine (incendies de lieux publics d’origine accidentelle, ou en temps de guerre ou encore lors d’attentats terroristes). La prise en charge et le triage de brûlés en nombre reste un problème difficile; ceci souligne la nécessité d’une réflexion et de prévisions de ces crises en insistant sur la formation des médecins et des soignants. Les défis à relever sont multiples: les soins aux brûlés requièrent un nombre important de personnel qualifié; les évacuations doivent être planifiées en fonction de la gravité de la brûlure et des lésions associées; les stocks et lots de dotation (en particulier en topiques anti-infectieux et en cristalloïdes) doivent être suffisants et adéquats. Les services hospitaliers de l’Hôpital Militaire d’Instruction Mohammed V de Rabat doivent pouvoir être rapidement adaptés pour accueillir et surtout isoler ces patients. L’hypothèse d’une catastrophe par incendie avec afflux massif de brûlés à l’hôpital militaire d’instruction Mohammed V de Rabat ne doit laisser place à aucune improvisation. PMID:23467075

  7. Stress-time context of fault permeability at the Krasnokamensk Area SE Transbaikalia

    NASA Astrophysics Data System (ADS)

    Petrov, V. A.; Lespinasse, M.; Poluektov, V. V.; Cuney, M.; Nasimov, R. M.; Hammer, J.; Schukin, S. I.

    2013-03-01

    The main aim of the contribution is to combine data on the consecutive stages of deformation, inflow and migration of palaeofluids and accumulation of mineral filling with uranium traces within the faulted-fractured environment at the Krasnokamensk Area, SE Transbaikalia, Russia. Object of examination is a framework of fault zones transecting the Proterozoic-Paleozoic granitic unit to the extent of northwestern part of uranium-bearing Streltsovskaya caldera of Mesozoic age. Considerations of stress- and permeability-time relationships in faulted-fractured zones were taken with account of stress and strain dependencies within fluid saturated rock massifs at crustal seismogenic level. Stress-time consecution of fault zone permeability was developed using set of fieldwork and lab tests including structural-geological survey, fault slip data analysis, mineral-chemical diagnostics, microstructural observations, and radiographic studies. Practical applications of obtained data for solving uranium mining and environmental issues are indicated in conclusion.

  8. Electron-impact ionization of Se2+ and Se3+

    NASA Astrophysics Data System (ADS)

    Pindzola, M. S.; Loch, S. D.

    2016-06-01

    Electron-impact ionization cross sections for Se2+ and Se3+ are calculated using a semi-relativistic configuration-average distorted-wave (CADW) method. Good agreement between the CADW calculations and recent experimental measurements are found for the single ionization of Se2+ from threshold to 500 eV and for the double ionization of Se2+ from threshold to 225 eV. Good agreement between the CADW calculations and recent experimental measurements are also found for the single ionization of Se3+ from threshold to 200 eV and for the double ionization of Se3+ near the peak of the cross section at 350 eV. Disagreements at other incident electron energies may be due to the complexity of the ionization pathways for low charged Se atomic ions, the various theoretical approximations, and the difficulty in measuring relatively small double ionization events.

  9. Les dykes basiques du massif ancien de l'Ourika (Atlas de Marrakech, Maroc): géochimie et significationThe basic dykes of the Ourika old massif (High Atlas of Marrakech): Geochemistry and significance

    NASA Astrophysics Data System (ADS)

    Barakat, Ahmed; Marignac, Christian; Bouabdelli, Mohamed

    The Precambrian massif of Ourika is crosscut by two systems of basic dykes, striking N40°E and N90-120°E. Using incompatible trace elements, the two systems form two distinct chemical groups, displaying a continental tholeiitic affinity. The composition variations between the two defined groups can be due to heterogeneities of mantle sources and to contamination, during the magma ascent, by the continental crust. The emplacement of these basic dykes, before the late-PIII formations, can be related to the Neoproterozoic distension generalised to the Anti-Atlas chain. To cite this article: A. Barakat et al., C. R. Geoscience 334 (2002) 827-833.

  10. Partial re-equilibration of highly siderophile elements and the chalcogens in the mantle: A case study on the Baldissero and Balmuccia peridotite massifs (Ivrea Zone, Italian Alps)

    NASA Astrophysics Data System (ADS)

    Wang, Zaicong; Becker, Harry; Gawronski, Timo

    2013-05-01

    primitive mantle values, whereas Au, Re and S are somewhat depleted. The good linear correlation of S with Al2O3 in both suites reflects sulfide removal controlled by sulfur solubility in silicate melt, or co-precipitation with pyroxenes and spinel, and indicates very similar bulk partition coefficients for S and Al. S/Se and Se/Te in the lherzolites change little with decreasing Al2O3. Results for BM lherzolites are consistent with sulfide-silicate melt partitioning as the dominant control on abundances of the HSE, S, Se and Te during low to moderate degrees of melt extraction (DPt > DPd > DTe ⩾ DSe ⩾ DS ≈ DRe). Replacive dunites at Balmuccia have low abundances of Re, Au, Pd and chalcogens, but variable and higher abundances of Os, Ir and Ru, high S/Se and Se/Te, yet 187Os/188Os similar to BM lherzolites. The residual HSE and chalcogen compositions differ from those in dunites of subduction-related ophiolites. The composition and contact relations of the BM dunites with the host rocks likely reflect focused flow of sulfur-undersaturated melt after open system melting and re-equilibration of the lherzolites. The compositional record of the Balmuccia massif thus reflects the composition of different types of melts and their interaction with the peridotites at different P-T conditions.

  11. Rockfall hazard assessment by means of the magnitude-frequency curves in the Montserrat Massif (central Catalonia, Spain): first insights

    NASA Astrophysics Data System (ADS)

    Janeras, Marc; Domènech, Guillem; Pons, Judit; Prat, Elisabet; Buxó, Pere

    2016-04-01

    Montserrat Massif is located about 50 km North-West of Barcelona (Catalonia, North-Eastern Spain). The rock massif is constituted by an intercalation of conglomerate and fine layers of siltstones due to the Montserrat fan-delta sedimentation within the Eocene age. The current relief is consequence of the several depositional episodes and the later tectonic uplift, leading to stepped slopes up to 250 m high, and a total height difference close to 1000 m. Montserrat Mountain has been a pilgrimage place since the settlement of the monastery, around the year 1025, and a spot of touristic interest, mostly within the last 150 years, when the first rack railway was inaugurated to reach the sanctuary. The amount of 2.4 M visitors in 2014 reveals the potential risk derived from rockfalls. To assess and mitigate this risk, a plan funded by the Catalan government is currently under development. Three rockfall mechanisms and magnitude ranges have been identified (Janeras et al. 2011): 1) physicochemical weathering causing the detachment of pebbles and aggregates (0.0001 - 0.1 m3); 2) thermic-induced tensions responsible for the generation of slabs and plates (0.1 - 10 m3); and 3) intersection of structural joints within the rock mass resulting in blocks of 10 - 10,000 m3. In order to quantify the rockfall hazard, a magnitude-frequency analysis has been performed starting from an event-based inventory gathered from field surveillance and historical research. A methodology has been applied to take the maximum profit of only 30 registers with information on volume and date. The massif has been split into several domains with sampling homogeneity. For each one, there have been defined several periods of time during which, all the rockfall events of a given volume have been recorded. Thus, the magnitude-frequency relationship, for each domain, has been calculated. Results show that the curves are well fitted by a power law with exponents ranging from -0.59 to -0.68 for magnitudes

  12. Geometry and thermal structure of the Menderes Massif Core Complex (Western Turkey), implications for thermal evolution of Hellenic subduction zone

    NASA Astrophysics Data System (ADS)

    Roche, Vincent; Jolivet, Laurent; Guillou-Frottier, Laurent; Tuduri, Johann; Bouchot, Vincent; Beccaletto, Laurent; Lahfid, Abdeltif

    2016-04-01

    The eastern Mediterranean region is one of the most promising geothermal areas, with more than 250 geothermal fields discovered in Turkey (Parlaktuna, 2013), in a region of active tectonics and volcanism. Although the potential of these deep geothermal resources has not been systematically investigated yet, the geothermal activity of the western Turkey area is the most recent signature of the high heat flow (120-140 mW/m²; Aydin, 2005, from Teczan, 1995). Based on Turkish data, 2084 MWt are being utilized for direct applications and most of the energy originates from the Menderes Massif (Baba et al., 2015). This large-scale thermal anomaly at the surface is correlated to a long wavelength east-west increase of surface heat flow that could reflect the thermal state of Aegean subduction zone at depth. In order to better understand and characterize the possible connections between large-scale mantle dynamics and surface processes in space and time, we study the structure and thermal evolution of the Menderes Massif. Both the acceleration of the Aegean extension in the Middle Miocene and the recent escape of Anatolia have been proposed to result from several slab tearing events, the first one being located below western Turkey and the Eastern Aegean Sea. These events have triggered the formation of metamorphic complexes with contrasted exhumation P-T paths. While the extension in the Aegean domain is well-characterized with high-temperature domes in the center and east, the succession of several metamorphic events in the Menderes Massif and their significance in terms of geodynamics is still debated. Hence, the exhumation history is key to understanding the temporal and spatial distribution of the thermal signature of the Hellenic slab and its tearing/detachment. The Menderes Massif displays a large variety of metamorphic facies, from the Barrovian type metamorphism in the Eocene (the Main Menderes Metamorphism) to the coeval (?) HP-LT metamorphism on the southernmost

  13. The Kokchetav Massif, Kazakhstan: "Type locality" of diamond-bearing UHP metamorphic rocks

    NASA Astrophysics Data System (ADS)

    Schertl, H.-P.; Sobolev, N. V.

    2013-02-01

    After the discovery of metamorphic coesite in crustal rocks from the Western Alps (Italy) and the Western gneiss region (Norway) in the mid 1980s of the last century, metamorphic diamond was observed only a few years later "in situ" in the Kokchetav Massif (Kazakhstan). Findings of such coesite- and diamond-bearing ultrahigh pressure metamorphic (UHP) rocks with protoliths formed or embedded in crustal levels and subsequently experienced PT-conditions within or even higher than the coesite stability field have dramatically changed our geodynamic view of orogenetic processes. These occurrences provide evidence that crustal rocks were subducted into mantle depths and exhumed to the surface. Recent studies even suggest continental subduction to depths exceeding 300 km. These rocks have been extensively studied and many new and important observations have been made. Thus far, more than 350 papers have been published on various aspects of Kokchetav UHP rocks. The Kokchetav Massif of northern Kazakhstan is part of one of the largest suture zones in Central Asia and contains slices of HP and UHP metamorphic rocks. Classical UHP rocks mainly occur in the Kumdy Kol, Barchi Kol and Kulet areas, and include a large variety of lithologies such as calcsilicate rocks, eclogite, gneisses, schists, marbles of various compositions, garnet-pyroxene-quartz rocks, and garnet peridotite. Most of them contain microdiamonds; some of which reach a grain size of 200 μm. Most diamond grains show cuboid shapes but in rare cases, diamonds within clinozoisite gneiss from Barchi Kol occur as octahhedral form. Microdiamonds contain highly potassic fluid inclusions, as well as solid inclusions like carbonates, silicates and metal sulfides, which favour the idea of diamond formation from a C-O-H bearing fluid. Nitrogen isotope data and negative δ13C values of Kokchetav diamonds indicate a metasedimentary origin. PT-estimates of Kokchetav UHP rocks yield peak metamorphic conditions of at least 43

  14. Serpentinite Carbonation in the Pollino Massif (southern Italy) for CO2 Sequestration

    NASA Astrophysics Data System (ADS)

    Carmela Dichicco, Maria; Mongelli, Giovanni; Paternoster, Michele; Rizzo, Giovanna

    2015-04-01

    Anthropogenic gas emissions are projected to change future climates with potentially nontrivial impacts (Keller et al., 2008 and references therein) and the impacts of the increased CO2 concentration are, among others, the greenhouse effect, the acidification of the surface of the ocean and the fertilization of ecosystems (e.g. Huijgen and Comans, 2003). Geologic Sequestration into subsurface rock formations for long-term storage is part of a process frequently referred to as "carbon capture and storage" or CCS. A major strategy for the in situ geological sequestration of CO2 involves the reaction of CO2 with Mg-silicates, especially in the form of serpentinites, which are rocks: i) relatively abundant and widely distributed in the Earth's crust, and ii) thermodynamically convenient for the formation of Mg-carbonates (e.g., Brown et al., 2011). In nature, carbonate minerals can form during serpentinization or during hydrothermal carbonation and weathering of serpentinites whereas industrial mineral carbonation processes are commonly represented by the reaction of olivine or serpentine with CO2 to form magnesite + quartz ± H2O (Power et al., 2013). Mineral carbonation occurs naturally in the subsurface as a result of fluid-rock interactions within serpentinite, which occur during serpentinization and carbonate alteration. In situ carbonation aims to promote these reactions by injecting CO2 into porous, subsurface geological formations, such as serpentinite-hosted aquifers. In the northern sector of the Pollino Massif (southern Italy) extensively occur serpentinites (Sansone et. al., 2012) and serpentinite-hosted aquifers (Margiotta et al., 2012); both serpentinites and serpentinite-hosted aquifers are the subject of a comprehensive project devoted to their possible use for in situ geological sequestration of CO2. The serpentinites derived from a lherzolitic and subordinately harzburgitic mantle, and are within tectonic slices in association with metadolerite dykes

  15. Growth of subcontinental lithosphere: evidence from repeated dike injections in the Balmuccia lherzolite massif, Italian Alps

    NASA Astrophysics Data System (ADS)

    Mukasa, Samuel B.; Shervais, John W.

    1999-09-01

    The Balmuccia alpine lherzolite massif is a fragment of subcontinental lithospheric mantle emplaced into the lower crust 251 Ma ago during the final, extensional phase of the Hercynian orogeny. The Balmuccia massif consists largely of lherzolite, with subordinate harzburgite and dunite, and an array of dike rocks formed in the mantle before crustal emplacement. Dike rocks include websterite and bronzitite of the Cr-diopside suite, spinel clinopyroxenite and spinel-poor websterite of the Al-augite suite, gabbro and gabbronorite of the late gabbro suite, and hornblendite of the hydrous vein suite. The dike rocks display consistent intrusive relationships with one another, such that Cr-diopside suite dikes are always older than dikes and veins of the Al-augite suite, followed by dikes of the late gabbro suite and veins of the hydrous vein suite. Phlogopite (phl) veinlets that formed during interaction with the adjacent crust are the youngest event. There are at least three generations of Cr-diopside suite dikes, as shown by crosscutting relations. Dikes of the Al-augite suite form a polybaric fractionation series from spinel clinopyroxenite to websterite and feldspathic websterite, which crystallized from aluminous alkaline magmas at relatively high pressures. The late gabbro suite of dikes intruded at lower pressures, where plagioclase saturation occurred before significant mafic phase fractionation. Hornblendite veins have distinct compositional and isotopic characteristics, which show that they are not related to either the Al-augite suite or to the late gabbro dike suite. Cr-diopside suite dikes have Nd and Sr isotopic compositions similar to those of the host lherzolite and within the range of compositions defined by ocean-island basalts. The Al-augite dikes and the hornblendite veins have Sr and Nd isotopic compositions similar to those of Cr-diopside suite lherzolite and websterite. The late gabbro dikes have Nd and Sr isotopic compositions similar to mid

  16. Dirty or Tidy ? Contrasting peraluminous granites in a collapsing Orogen: Examples from the French Massif Central

    NASA Astrophysics Data System (ADS)

    Villaros, Arnaud; Pichavant, Michel; Moyen, Jean-François; Cuney, Michel; Deveaud, Sarah; Gloaguen, Eric; Melleton, Jérémie

    2013-04-01

    Post collisional collapse commonly enhances crustal melting. Such melting typically produces peraluminous granitic magmas. In the French Massif Central, a mid-crustal segment of the western Variscan belt, two large granitic bodies were produced during the collapse of the Variscan Belt. The St Sylvestre Leucogranitic Complex (SSyL) in the western part of the Massif Central and the Velay Migmatitic Complex (VMC) in the Eastern part. Although these two complexes are formed in similar geodynamic context they present meaningful petrological and geochemical differences. The VMC (~305 Ma) is clearly intrusive in migmatitic terranes. The migmatitic host recorded two successive melting events M3 (720 °C and 5kb) dated between 335 and 315 Ma and M4 (850°C and 4 kb) dated at 305 Ma. The compositions of the VMC are strictly H2O-undersaturated and ranges from leucogranitic to granodioritic. Three main successive granite types have been distinguished (1) A heterogeneous banded biotite granite, (2) A main biotite-cordierite granite, where cordierite can be prismatic, as cockade or pseudomorphic (3) a late magmatic with large K-feldspar phenocryst and prismatic cordierite. The compositions of the VMC granites are quite similar to typical Australian S-type granites in the sense that they also show a positive correlation between ferromagnesian abundance and aluminosity. The SSyL (~320 Ma) is intrusive in upper greenschist facies to upper amphibolite migmatitic metasediment and orthogneiss (~3kb). The compositional variety observed in the SSyL suggests a continuous trend from a moderately mafic, peraluminous magma (cd- and sill- granite) to a H2O saturated granite ("two-mica" granite) facies and finally to an extremely felsic, H2O-saturated magma. Three granitic units have been recognized in the SSyL: (1) the western "Brame Unit" composed of the less evolved cd- and sill- granite facies (2) the central "St Sylvestre Unit", composed mainly by U-rich two-mica granite, intruded by two

  17. Spatiotemporal waves caused by gravitational instability of an arbitrary stratified elasto-viscous rock massif

    NASA Astrophysics Data System (ADS)

    Ryzhak, Eugeny; Mukhamediev, Shamil; Sinyukhina, Svetlana

    2015-04-01

    The cause of the spatially-temporal wave-like out-of-plane distortions of originally horizontal layers of the earth's crust is still one of the most important and debated problems in solid earth physics. Are these distortions originated due to action of the high horizontal compressions applied to a massif or, contrary, they are the result of spontaneous deformation of the massif under gravity without action of another pronounced external agents? The second possibility is called the gravity instability. Understanding of the geodynamic evolution of the region is crucially dependent on what the answer will be chosen from the above alternative. Lord Rayleigh (1883) was the first who solved the problem of gravity instability for the system of 2 infinite layers of ideal incompressible fluids and showed that the system is gravitationally unstable when the upper fluid is denser than the lower one (i.e. the density inversion exists). Since then numerous attempts have been made to generalise the properties of constituents. 1961 till now were the years of unsuccessful attempts to take into account the elastic properties of fluids. We used the principally new approach to the stability analysis of a system which is a bounded 3D multi-layered fluid domain possessing cross-sections of arbitrary shape and prescribed boundary conditions at all parts of the boundary. It is assumed that the fluid is arbitrary stratified according to both density ρ and nonlinear elastic properties. By using a static energy criterion for stability/instability alongside with the reference ("Lagrangian") description of a continuum we succeeded in solving the problem completely, namely, we obtained the necessary and sufficient condition for stability (violation of which is the necessary and sufficient condition for instability). It was found that the system under study is unstable if and only if 1) density inversion exists at least at one interface between the fluids and/or 2) there exists a depth range

  18. U-Pb dating and composition of inclusions in zircon from ophiolitic gabbro of the Klyuchevsk massif (Middle Urals): Results and geological interpretation

    NASA Astrophysics Data System (ADS)

    Smirnov, V. N.; Ivanov, K. S.; Koroteev, V. A.; Erokhin, Yu. V.; Khiller, V. V.

    2016-06-01

    The U-Pb (SHRIMP) dating of zircon from the layered complex of ophiolitic gabbro in the Klyuchevsk massif yielded an age of 456 ± 6 Ma corresponding within the limits of error to zircon dates obtained for other petrographic varieties from this massif. The investigation of the composition of silicate inclusions in dated zircon grains revealed that they are represented by typical metamorphic minerals: albite, zoisite, and secondary amphiboles. The data indicate that zircon was crystallized during metamorphic transformations of gabbroids and its U-Pb age (Late Ordovician-Silurian) is characteristic of all rocks in the ophiolite association of the Klyuchevsk massif indicating the age of metamorphism, not their formation time.

  19. Relationships between gas geochemistry and release rates and the geomechanical state of igneous rock massifs

    NASA Astrophysics Data System (ADS)

    Nivin, Valentin A.; Belov, Nikolai I.; Treloar, Peter J.; Timofeyev, Vladimir V.

    2001-07-01

    In contrast to sedimentary sequences, the relationships between the stressed state of igneous rocks and the chemistry and physical properties of gases contained within them are not well known. Here, we attempt to fill this gap by using, as an example, the apatite-nepheline and rare-metal ore deposits hosted within the Khibiny and Lovozero alkaline nepheline-syenite complexes of the Kola Peninsula, NW Russia. These massifs are characterized by unusually high, for igneous rocks, contents of multi-component, essentially hydrogen-hydrocarbon, gases and also by high hardness, elasticity and unevenly distributed, subhorizontal tectonic stresses. Relationships between the chemical and dynamic characteristics of the gases and the geomechanical properties of the host rocks have been examined using field observations and laboratory experiments. Patterns of gas release variations in time and space, gas emissions from rock pillars during artificial loading, variations of gas pressure in sealed shot-holes and changes in liberation rates of gaseous components during experimental rock loading are suggested to result from changes in rock stress and deformation state. Gas compositions in sealed shot-holes in stressed rocks change with time. Partly, this is due to belated release of gases held in fluid inclusions and isolated voids and their subsequent mixing with gases held in interconnected fracture systems as the included gases are preferentially released as fluid inclusion arrays are opened during later stages of stress build-up. Partly, it may also be because released gases may react with new fracture surfaces to generate enhanced levels of reduced H 2 gases.

  20. Alpine thermal events in the central Serbo-Macedonian Massif (southeastern Serbia)

    NASA Astrophysics Data System (ADS)

    Antić, Milorad D.; Kounov, Alexandre; Trivić, Branislav; Wetzel, Andreas; Peytcheva, Irena; von Quadt, Albrecht

    2016-07-01

    The Serbo-Macedonian Massif (SMM) represents a crystalline belt situated between the two diverging branches of the Eastern Mediterranean Alpine orogenic system, the northeast-vergent Carpatho-Balkanides and the southwest-vergent Dinarides and the Hellenides. We have applied fission-track analysis on apatites and zircons, coupled with structural field observations in order to reveal the low-temperature evolution of the SMM. Additionally, the age and geochemistry of the Palaeogene igneous rocks (i.e. Surdulica granodiorite and dacitic volcanic rocks) were determined by the LA-ICPMS U-Pb geochronology of zircons and geochemical analysis of main and trace elements in whole-rock samples. Three major cooling stages have been distinguished from the late Early Cretaceous to the Oligocene. The first stage represents rapid cooling through the partial annealing zones of zircon and apatite (300-60 °C) during the late Early to early Late Cretaceous (ca. 110-ca. 90 Ma). It is related to a post-orogenic extension following the regional nappe-stacking event in the Early Cretaceous. Middle to late Eocene (ca. 48-ca. 39 Ma) cooling is related to the formation of the Crnook-Osogovo-Lisets extensional dome and its exhumation along low-angle normal faults. The third event is related to regional cooling following the late Eocene magmatic pulse. During this pulse, the areas surrounding the Surdulica granodiorite (36 ± 1 Ma) and the slightly younger volcanic bodies (ca. 35 Ma) have reached temperatures higher than the apatite closure temperature (120 °C) but lower than ca. 250 °C. The geochemistry of the igneous samples reveals late- to post-orogenic tectonic setting during magma generation.

  1. Rates of high altitude rock wall erosion: four years of laserscanning in the Mont Blanc massif

    NASA Astrophysics Data System (ADS)

    Ravanel, L.; Deline, P.; Jaillet, S.

    2009-04-01

    Many rockfalls detach from steep high-Alpine rock walls, and were especially frequent during the hot summer of 2003 in the Alps. It is hypothesized that an observed increase of high mountain rock wall instability is related to permafrost changes. Nevertheless, because of a lack of systematic observations, magnitude and frequency of high mountain rock-slope instabilities remain poorly known up to now. As a part of the French-Italian PERMAdataROC project (2005-2008) and the EU-funded transalpine PermaNET project (2008-2011), we use the Terrestrial Laserscanning method for remote monitoring of geomorphological activity from the ground, focusing on seven steep high-Alpine rock walls (elevation: 3000-4500 m a.s.l.) affected by permafrost in the Mont-Blanc massif. Here we present the methodology to get high-resolution digital elevation models (DEM) of rock walls surveyed annually by laserscanning and to make diachronic comparisons of those DEM. This work has been carried out using a ground-based LiDAR Optech ILRIS-3D, working up to 800 m in the best conditions of surface reflectivity. We present the key results of this first quantification of high altitude rock wall instability, based on the first four years of measurement at Les Drus, Aiguille du Midi, Grand Flambeau, Aiguille d'Entrèves, Tour Ronde, Aiguille Blanche de Peuterey and Piliers de Freiney - Grand Pilier d'Angle. The main instabilities affected the West Face of Les Drus (546 m3 of rock detached between October 2005 and October 2006), the Tour Ronde East Face (536 m3 between 2005 and 2006, and 266 m3 between 2007 and 2008) and the close Freshfield ridge (448 m3 between 2006 and 2007). The high resolution of the DEM also allows performing remote geomechanical characterization of the rock faces. First results about survey of fractures will be also present.

  2. Table-mountain geology and surficial geochemistry: Chimantá Massif, Venezuelan Guayana shield

    NASA Astrophysics Data System (ADS)

    Briceño, H.; Schubert, C.; Paolini, J.

    The Chimantá Massif consists of eleven table-mountains (up to more than 2600 m in elevation), which are remnants of the Auyán-tepui planation surface (with a possible Cretaceous initial age) cut into siliceous sandstones of the Matauí Formation, the highest unit of the Precambrian Roraima Group. The sandstones are gently folded and several fracture systems control weathering and erosion. The Matauí Formation was intruded by Precambrian diabase dikes and sills. This relationship invalidates previous suggestions that the Roraima Group contained an unconformity separating Lower Precambrian from upper Mesozoic units. Ombrotrophic peat-bogs are conspicuous features on the summits of the table-mountains. Peat formation probably began in the early Holocene, initiated by algae and lichens, accumulation of humidity and detritus, plant colonization of weathered rock surfaces, a low rate of organic decomposition, and high rainfall. The geochemistry of Ca, K, Fe, Si, Cl, I, and Br is discussed. The nutrient cycle consists of sunlight, which contributes to photosynthetic processes, and rainwater, which partly provides the nutrients, dissolves the bedrock, and transports the nutrients from the bedrock and eventually out of the system as river or stream water. The natural waters (rain-, river and stream, peat, and plant waters) are acid (pH range 3.5-4.7) and act on the sandstone, dissolving the siliceous cement and liberating the sand grains. This is the primary weathering mechanism and produces the karst-like topography of the table-mountain summits. Through geologic time (probably up to about 70 million years), this weathering has produced the spectacular table-mountain and savanna landscape of the Gran Sabana.

  3. Alpine thermal events in the central Serbo-Macedonian Massif (southeastern Serbia)

    NASA Astrophysics Data System (ADS)

    Antić, Milorad D.; Kounov, Alexandre; Trivić, Branislav; Wetzel, Andreas; Peytcheva, Irena; von Quadt, Albrecht

    2015-11-01

    The Serbo-Macedonian Massif (SMM) represents a crystalline belt situated between the two diverging branches of the Eastern Mediterranean Alpine orogenic system, the northeast-vergent Carpatho-Balkanides and the southwest-vergent Dinarides and the Hellenides. We have applied fission-track analysis on apatites and zircons, coupled with structural field observations in order to reveal the low-temperature evolution of the SMM. Additionally, the age and geochemistry of the Palaeogene igneous rocks (i.e. Surdulica granodiorite and dacitic volcanic rocks) were determined by the LA-ICPMS U-Pb geochronology of zircons and geochemical analysis of main and trace elements in whole-rock samples. Three major cooling stages have been distinguished from the late Early Cretaceous to the Oligocene. The first stage represents rapid cooling through the partial annealing zones of zircon and apatite (300-60 °C) during the late Early to early Late Cretaceous (ca. 110-ca. 90 Ma). It is related to a post-orogenic extension following the regional nappe-stacking event in the Early Cretaceous. Middle to late Eocene (ca. 48-ca. 39 Ma) cooling is related to the formation of the Crnook-Osogovo-Lisets extensional dome and its exhumation along low-angle normal faults. The third event is related to regional cooling following the late Eocene magmatic pulse. During this pulse, the areas surrounding the Surdulica granodiorite (36 ± 1 Ma) and the slightly younger volcanic bodies (ca. 35 Ma) have reached temperatures higher than the apatite closure temperature (120 °C) but lower than ca. 250 °C. The geochemistry of the igneous samples reveals late- to post-orogenic tectonic setting during magma generation.

  4. Conventional U-Pb dating versus SHRIMP of the Santa Barbara Granite Massif, Rondonia, Brazil

    USGS Publications Warehouse

    Sparrenberger, I.; Bettencourt, Jorge S.; Tosdal, R.M.; Wooden, J.L.

    2002-01-01

    The Santa Ba??rbara Granite Massif is part of the Younger Granites of Rondo??nia (998 - 974 Ma) and is included in the Rondo??nia Tin Province (SW Amazonian Craton). It comprises three highly fractionated metaluminous to peraluminous within-plate A-type granite units emplaced in older medium-grade metamorphic rocks. Sn-mineralization is closely associated with the late-stage unit. U-Pb monazite conventional dating of the early-stage Serra do Cicero facies and late-stage Serra Azul facies yielded ages of 993 ?? 5 Ma and 989 ?? 13 Ma, respectively. Conventional multigrain U-Pb isotope analyses of zircon demonstrate isotopic disturbance (discordance) and the preservation of inherited older zircons of several different ages and thus yield little about the ages of Sn-granite magmatism. SHRIMP U-Pb ages for the Santa Ba??rbara facies association yielded a 207Pb/206Pb weighted-mean age of 978 ?? 13 Ma. The textural complexity of the zircon crystals of the Santa Ba??rbara facies association, the variable concentrations of U, Th and Pb, as well as the mixed inheritance of zircon populations are major obstacles to using conventional multigrain U-Pb isotopic analyses. Sm-Nd model ages and ??Nd (T) values reveal anomalous isotopic data, attesting to the complex isotopic behaviour within these highly fractionated granites. Thus, SHRIMP U-Pb zircon and conventional U-Pb monazite dating methods are the most appropriate to constrain the crystallization age of the Sn-bearing granite systems in the Rondo??nia Tin Province.

  5. The structural evolution of dunite and chromite ore from the Kharcheruz Massif, the Polar Urals

    NASA Astrophysics Data System (ADS)

    Chernyshov, A. I.; Yurichev, A. N.

    2016-03-01

    The Kharcheruz block of the Syumkeu ultramafic massif is a southern fragment of the Khadata ophiolitic belt, which closes the ophiolites of the Polar Urals in the north. The block, striking in the latitudinal direction, is sheetlike in shape and primarily composed of dunite with nearly latitudinal zones of chromite mineralization. The dunites are subject to ductile deformation various in intensity, and this variability is displayed in their heterogeneous structure and texture. The following microstructural types are distinguished by the variety and intensity of their deformation: protogranular → mesogranular → porphyroclastic → porphyrolath → mosaic. The petrostructural patterns of olivines pertaining to the above types reflect conditions of ductile deformation. Protogranular dunite is formed as a product of pyroxene decomposition in mantle harzburgite accompanied by annealing recrystallization at a temperature above 1000°C. Mesogranular dunite is formed as a product of high-temperature plastic flow by means of translation sliding in olivine and diffuse creep at a temperature dropping from 1000 to 650°C and at a low rate (<10-6 s-1). Cr-spinel segregates into linear zones of disseminated chromite mineralization within zones of bedding-plane plastic flow. Porphyroclastic and mosaic dunites are formed under conditions of intense deformation at a temperature of 500-750°C and at a significant rate (>10-6 s-1). Dunite is deformed by means of syntectonic recrystallization and subordinate translation gliding. Linear zones of disseminated mineralization undergo destruction thereby, with the formation of lenticular chromitite bodies from which ductile olivine is squeezed out with the formation of densely impregnated and massive ores.

  6. Microstructural evolution of the Yugu peridotites in the Gyeonggi Massif, Korea

    NASA Astrophysics Data System (ADS)

    Park, M.; Jung, H.

    2015-12-01

    The Yugu peridotite is the largest and freshest ultramafic body in the Gyeonggi Massif, Korean Peninsula, which potentially has a tectonic affinity to the eastward extension of the Qinling-Dabie-Sulu collision belt in China. In spite of its tectonic and rheological importance, only few mineralogical and petrological studies have been reported from Yugu peridotite. In order to understand the microstructural evolution of the Yugu peridotites, we conducted a detailed analysis of the microstructures and petro-fabrics. The majority of Yugu peridotite body is significantly serpentinized, and it consists predominantly of spinel harzburgite together with minor lherzolite, dunite, and clinopyroxenite. We collected peridotites from mainly two areas (northwestern and southwestern parts) of the Yugu ultramafic body, and all samples are spinel harzburgites consisting of olivine, orthopyroxene, clinopyroxene, spinel, and amphibole. These samples have similar mineralogy except for the varied amount of clinopyroxene and amphibole. These mineral contents are generally increasing from proto-mylonite peridotites to mylonite peridotites. Based on microstructural characteristics of highly deformed peridotites (especially grain-size of olivine), we classified the samples into four textural types, which are proto-mylonite, proto-mylonite to mylonite transition, mylonite, and ultra-mylonite. Depending on the texture of specimen, it is found that the lattice-preferred orientation (LPO) of olivine varies from A-type (proto-mylonite) via D-type like (mylonite) to E-type (ultra-mylonite). The fabric strength of olivine (M-index and J-index) systematically decreases with decreasing grain-size of olivine from proto-mylonite via mylonite to ultra-mylonite. The cause of fabric evolution in the Yugu peridotites will be discussed.

  7. Geochemical study of the granitic rocks from the Ryongnam massif, Geochang, South Korea

    NASA Astrophysics Data System (ADS)

    Han, M.; Kim, J.; Yang, K.

    2009-12-01

    The geochemical studies on the granitic rocks of the central part of the Ryongnam massif were carried out in order to constrain the petrogenesis and the paleotectonic environment. The area is composed of Precambrian gneissic rocks and metamorphosed sedimentary rocks, age-unknown granite and dioritic rocks, and Jurassic granitic rocks. The modal compositions indicate that the studied granitic rocks are granodiorite, monzogranite, syeno-granite, and alkali-feldspar granite. Except for Na2O and K2O, the contents of most oxides such as P2O5, TiO2, Al2O3, CaO, MgO and Fe2O3 decrease when SiO2 increases. These granitic rocks belong to the calc-alkaline series in the TAS and AFM diagram. They also show high-K nature, indicating the rocks experienced considerable differentiations. The studied granitic rocks correspond to Peraluminous and I-type(less than 1.1) in the A/CNK diagram. Chondrite-normalized REE patterns show generally enrichment in LREE and depleted in HREE. This suggests that the magma has been largely differentiated at an early stage. REE patterns of different granitic rocks in composition are subparallel each other, suggesting cogenetic in origin. The (-) anomaly of Eu shows that the granitic rocks were generated from residual magma which had fractionated plagioclase. Furthermore, the amount of total REE of the studied granitic rocks ranges 46.93~108.84 ppm, which corresponds to the range of granitic rocks from the continental margin granite. On the N-type MORB normalized spiderdiagram, the studied rocks generally show Nb-Ta and Hf-Zr trough, indicating the subduction-related products. According to the tectonomagmatic discrimination diagram, they correspond to volcanic arc granite(VAG). The major and trace element characteristics of the granitic rocks support their emplacement at the active continental margin.

  8. The magmatic history of the Vetas-California mining district, Santander Massif, Eastern Cordillera, Colombia

    NASA Astrophysics Data System (ADS)

    Mantilla Figueroa, Luis C.; Bissig, Thomas; Valencia, Víctor; Hart, Craig J. R.

    2013-08-01

    The Vetas-California Mining District (VCMD), located in the central part of the Santander Massif (Colombian Eastern Cordillera), based on U-Pb dating of zircons, records the following principal tectono-magmatic events: (1) the Grenville Orogenic event and high grade metamorphism and migmatitization between ˜1240 and 957 Ma; (2) early Ordovician calc-alkalic magmatism, which was synchronous with the Caparonensis-Famatinian Orogeny (˜477 Ma); (3) middle to late Ordovician post-collisional calc-alkalic magmatism (˜466-436 Ma); (4) late Triassic to early Jurassic magmatism between ˜204 and 196 Ma, characterized by both S- and I-type calc-alkalic intrusions and; (5) a late Miocene shallowly emplaced intermediate calc-alkaline intrusions (10.9 ± 0.2 and 8.4 ± 0.2 Ma). The presence of even younger igneous rocks is possible, given the widespread magmatic-hydrothermal alteration affecting all rock units in the area. The igneous rocks from the late Triassic-early Jurassic magmatic episodes are the volumetrically most important igneous rocks in the study area and in the Colombian Eastern Cordillera. They can be divided into three groups based on their field relationships, whole rock geochemistry and geochronology. These are early leucogranites herein termed Alaskites-I (204-199 Ma), Intermediate rocks (199-198 Ma), and late leucogranites, herein referred to as Alaskites-II (198-196 Ma). This Mesozoic magmatism is reflecting subtle changes in the crustal stress in a setting above an oblique subduction of the Panthalassa plate beneath Pangea. The lower Cretaceous siliciclastic Tambor Formation has detrital zircons of the same age populations as the metamorphic and igneous rocks present in the study area, suggesting that the provenance is related to the erosion of these local rocks during the late Jurassic or early Cretaceous, implying a local supply of sediments to the local depositional basins.

  9. Episodic exhumation and relief growth in the Mont Blanc massif, Western Alps from numerical modelling of thermochronology data

    NASA Astrophysics Data System (ADS)

    Glotzbach, C.; van der Beek, P. A.; Spiegel, C.

    2011-04-01

    The Pliocene-Quaternary exhumational and topographic evolution of the European Alps and its potential climatic and tectonic controls remain a subject of controversy. Here, we apply inverse numerical thermal-kinematic modelling to a spatially dense thermochronological dataset (apatite fission-track and (U-Th)/He) of both tunnel and surface samples across the Mont Blanc massif in the Western Alps, complemented by new zircon fission-track data, in order to better quantify its Neogene exhumation and relief history. Age-elevation relationships and modelling results show that an episodic exhumation scenario best fits the data. Initiation of exhumation in the Mont Blanc massif at 22 ± 2 Ma with a rate of 0.8 ± 0.15 km/Myr is probably related to NW-directed thrusting during nappe emplacement. Exhumation rates decrease at 6 ± 2 Ma to values of 0.15 ± 0.65 km/Myr, which we interpret to be the result of a general decrease in convergence rates and/or extensive exposure of less erodible crystalline basement rocks from below more easily erodible Mesozoic sediments. Finally, local exhumation rates increase up to 2.0 ± 0.6 km/Myr at 1.7 ± 0.8 Ma. Modelling shows that this recent increase in local exhumation can be explained by valley incision and the associated increase in relief at 0.9 ± 0.8 Ma, leading to erosional unloading, isostatic rebound and additional rock uplift and exhumation. Given the lack of tectonic activity as evidenced by constant thermochronological ages along the tunnel transect, we suggest that the final increase in exhumation and relief in the Mont Blanc massif is the result of climate change, with the initiation of mid-Pleistocene glaciations leading to rapid valley incision and related local exhumation.

  10. 10Be exposure dating of onset and timing of Neoglacial glacier advances in the Ecrins massif, French Alps

    NASA Astrophysics Data System (ADS)

    Le Roy, Melaine; Deline, Philip; Carcaillet, Julien

    2013-04-01

    Alpine glaciers are known to be highly sensitive to change in temperature and precipitation on decadal to centennial time scales. For two decades, numerous studies on Holocene climate revealed a period marked by abrupt cold reversals (e.g. 8.2 ka event) with increasing frequency and magnitude after the Holocene Climatic Optimum, during the so-called Neoglacial period (roughly the last 4 ka). State-of-the-art studies indicate that largest alpine glaciers failed to exceed their Little Ice Age (LIA) extent during these LIA Type-Events, unlike certain smaller glaciers. In the French Alps, very few investigations were conducted to date on Holocene glacier variability. Almost all studies focused on the most glacierized area: the Mont Blanc massif, where suitable organic remains to apply radiocarbon dating and dendrochronology are available. Other glacierized massifs are poorly studied, without any Holocene/Neoglacial glacier chronology up to now. Here, we present the results of a study focusing on six glacier forefields distributed in the Ecrins massif. Detailed geomorphological mapping and in-situ produced 10Be dating were carried on multi-crested so-called "LIA composite moraines". The targeted ridges are located in distal position with respect to late LIA drift in order to identify Holocene cold pulses that have led to (or slightly exceeded) LIA-like glacier extent. The 35 10Be ages obtained revealed that the onset of Neoglacial occurred at ~4.2 ka, and that at least two other advances were recorded at ~3.3 ka and ~0.85 ka. One site has yielded a nearly complete Neoglacial record as four discrete events have been dated. These results highlight the potential of lateral moraine ridge stratigraphy which could yield accurate record when sufficiently preserved, but also the different preservation of landforms along the glacier margin which could censor the record.

  11. Perceptions of social and environmental changes in a Mediterranean forest during the last 100 years: the Gavarres Massif.

    PubMed

    Rodríguez-Carreras, Roser; Ubeda, Xavier; Outeiro, Luís; Asperó, Francesc

    2014-06-01

    During the last century the landscape of the mid-Mediterranean mountains has undergone major transformations. The precipitous decline in the economic viability of forest products has engendered ever-thickening forests and agricultural lands have reverted to forest land cover. The related exodus of existing inhabitants since 1960 has led to new styles of occupancy: residential and touristic land uses have emerged while the primary and secondary sectors have largely disappeared. The object of the present study is to review how these transformations have developed in a specific area of north-eastern of Catalonia, known as the Gavarres Massif. The study applies a qualitative approach, based on interviews with stakeholders including active members of the local community and others who utilize or visit the area, all of whom are representatives of different social groups with a wide range of interests and points of view with regard to the massif. The information collected from the perspectives and opinions of the participants is coupled with objective data about the area. The result of this investigation is a rich variety of perceptions on landscape and social transformation and its current functional dynamics. Analyzing the information obtained allows us to understand the fact that the disappearance of the rural world is directly related to the collapse of an entire economic system that relied on the environment. In this study, two divergent points of view arise, one which supports recovering past landscapes and another which favours managing changes, conserving the existing landscape. Proposals for the current and future territorial management of Les Gavarres are presented. The diversity of opinions which emerges with regard to managing necessary changes in the massif emphasizes the importance of increased social dialogue. PMID:24060242

  12. Geological and geochemical reconnaissance in the central Santander Massif, Departments of Santander and Norte de Santander, Colombia

    USGS Publications Warehouse

    Evans, James George

    1976-01-01

    The central Santander Massif is composed of Precambrian Bucaramanga Gneiss and pre-Devonian Silgara Formation intruded by Mesozoic quartz diorite, quartz monzonite, and alaskite and Cretaceous or younger porphyry. Triassic (Bocas Formation), Jurassic (Jordan and Giron Formations).and Cretaceous (Tambor, Rosa Blanca, Paja, Tablazo, Simiti, La Luna, and Umir Formations) sedimentary rocks overlie the metamorphic rocks and are younger than most of the intrusions. A geological and geochemical reconnaissance of part of the central Santander Massif included the Vetas and California gold districts. At Vetas the gold is generally in brecciated aphanitic quartz and phyllonite. Dark-gray material in the ore may be graphite. The ore veins follow steep west-northwest- and north-northeast-striking fracture zones. No new gold deposits were found. Additional geochemical studies should concentrate on western Loma Pozo del Rey and on improvement of the gold extraction process. At California the gold is in pyritiferous quartz veins and quartz breccia. Ore containing black sooty material (graphite?) is highly radioactive. Some of the mineralization is post-Lower Cretaceous. Soil samples indicate that gold deposits lie under the thick blanket of soil on the ridges above the zone of mining. Three principal gold targets are outlined by gold and associated minerals in pan concentrates. The close relation of gold and copper anomalies suggests that copper may be useful as a pathfinder for gold elsewhere in the region. Based on occurrences of gold or high concentrations of pyrite or chalcopyrite in pan concentrates and on analytical data, eight potential gold targets are outlined in the central massif. Reconnaissance of the surrounding region is warranted.

  13. Pan-African magmatism in the Menderes Massif: geochronological data from leucocratic tourmaline orthogneisses in western Turkey

    NASA Astrophysics Data System (ADS)

    Koralay, O. E.; Candan, O.; Chen, F.; Akal, C.; Oberhänsli, R.; Satır, M.; Dora, O. Ö.

    2012-11-01

    The Menderes Massif, exposed in western Anatolia, is a metamorphic complex cropping out in the Alpine orogenic belt. The metamorphic rock succession of the Massif is made up of a Precambrian basement and overlying Paleozoic-early Tertiary cover series. The Pan-African basement is composed of late Proterozoic metasedimentary rocks consisting of partially migmatized paragneisses and conformably overlying medium- to high-grade mica schists, intruded by orthogneisses and metagabbros. Along the southern flank of the southern submassif, we recognized well-preserved primary contact relationship between biotite and leucocratic tourmaline orthogneisses and country rocks as the orthogneisses represent numerous large plutons, stocks and vein rocks intruded into a basement of garnet mica schists. Based on the radiometric data, the primary deposition age of the precursors of the country rocks, garnet mica schist, can be constrained between 600 and 550 Ma (latest Neoproterozoic). The North Africa-Arabian-Nubian Shield in the Mozambique Belt can be suggested as the possible provenance of these metaclastics. The intrusion ages of the leucocratic tourmaline orthogneisses and biotite orthogneisses were dated at 550-540 Ma (latest Neoproterozoic-earliest Cambrian) by zircon U/Pb and Pb/Pb geochronology. These granitoids represent the products of the widespread Pan-African acidic magmatic activity, which can be attributed to the closure of the Mozambique Ocean during the final collision of East and West Gondwana. Detrital zircon ages at about 550 Ma in the Paleozoic muscovite-quartz schists show that these Pan-African granitoids in the basement form the source rocks of the cover series of the Menderes Massif.

  14. New structural field data on the timing and kinematics of deformation and exhumation of the Mont Blanc massif

    NASA Astrophysics Data System (ADS)

    Egli, Daniel; Mancktelow, Neil

    2010-05-01

    The Mont Blanc massif is one of the external crystalline massifs, which represent the basement of the former European continental margin and therefore belong to the Helvetic domain. It mainly consists of polymetamorphic Late Proterozoic to Early Paleozoic gneisses intruded by the Variscan Mont Blanc granite (Von Raumer et al. 1993). The timing and kinematics of deformation and exhumation of the Mont Blanc massif is a controversial topic and various models have been proposed. Low-temperature thermochronology studies provide an extensive data set for estimating exhumation rates in Neogene times (e.g. Seward & Mancktelow 1994; Leloup et al. 2005; Glotzbach et al. 2008), but detailed structural studies to critically asses and constrain the proposed kinematic models are largely lacking. Glotzbach et al. (2008) show that the exhumation is episodic, with rates changing from relatively fast (~2.5 km/Ma before 6 Ma) to a slow phase (<0.5 km/Ma between 6 and 3.5 Ma), in turn followed by acceleration to ~1 km/Ma after 3 Ma. Our study presents new structural data from the south-eastern side of the Mont Blanc massif and the adjacent sediments and addresses the tectonic evolution and late stage exhumation history of the massif. The goal is to assess the importance of tectonics versus climate for controlling exhumation, as well as to establish the overall geometry of uplift (2D pop-up, 3D dextral transpressive model, large scale backfolding). A major back-thrust was proposed by previous authors ("Mont Blanc back-thrust", e.g. Leloup et al. 2005, Rolland et al. 2007), characterized as a relatively steeply north-west dipping thrust bringing the Mont Blanc basement back over the tectonostratigraphically higher Helvetic and Ultrahelvetic metasediments. 40Ar¬-39Ar dating of white micas interpreted to have grown during movement on the Mont Blanc back-thrust indicates an initiation of movement around 16 Ma (Rolland et al. 2007). Leloup et al. (2005) suggest a reactivation of this

  15. Acoustic method for defining the stress state of a rock massif based on solution of the seismic inverse problem

    NASA Astrophysics Data System (ADS)

    Nazarov, L. A.; Nazarova, L. A.; Romenskii, E. I.; Tcheverda, V. A.; Epov, M. I.

    2016-02-01

    A method for estimating the stress-strain state of a rock massif in the vicinity of underground facilities is substantiated. This method is based on solution of the boundary inverse problem of defining the components of an external stress field from the acoustic sounding data. The acoustic sounding data used are the arrival times of diving head longitudinal waves, recorded in a long mine shaft. Numerical experiments have revealed the optimal arrangement of the recording network and the limited relative error in the input data, which, taken together, provide for solvability of the inverse problem.

  16. The migmatite-gneiss complex of the Chuya-Kendyktas sialic massif (Southern Kazakhstan): Structure and age

    NASA Astrophysics Data System (ADS)

    Tretyakov, A. A.; Degtyarev, K. E.; Kovach, V. P.; Kotov, A. B.; Salnikova, E. B.; Pilitsyna, A. V.; Yakovleva, S. Z.

    2016-03-01

    A migmatite-gneiss complex made up of paraand orthogneisses and crystalline schists with bodies of ultrametagenic tonalites is distinguished in the basement of the northwestern part of the Chuya-Kendyktas Massif. ID-TIMS dating of accessory zircon from orthogneisses and ultrametagenic tonalites in combination with LA-ICP-MS analyses of detrital zircons from garnet-biotite paragneisses showed that the migmatite-gneiss complex was formed after protoliths with an age within 800-770 Ma and completed its evolution in the first half of the Neoproterozoic.

  17. Quantification of low elevation relief vertical movements from global sea level curves and scattered marine deposits (Armorican Massif, France)

    NASA Astrophysics Data System (ADS)

    Bessin, Paul; Guillocheau, François; Robin, Cécile; Bauer, Hugues; Schroëtter, Jean-Michel

    2016-04-01

    Amplitudes of vertical movements, amount of burial or of denudation are often too low or too old to be quantified from thermochronological or cosmogenic isotopes methods. This is the case for the vertical movements experienced by European Variscan basements of low relief during Cenozoic times. Some of these basements bear scattered thin Cenozoic marine sediments. Thus, we proposed to quantify Cenozoic vertical movements from i) current elevation of well dated marine sediments scattered on these basements, corrected from their bathymetry of deposition provided by their sedimentary facies and ii) elevation of global sea level at time of sediment deposition from a new compilation of available curves. This compilation highlights that i) curve which takes into account ocean basin volume change are consistent for the ca. 100 to 40 Ma "greenhouse" period whereas ii) curves based on coreholes backstripping methods better reflect global sea level changes since ca. 40 Ma. For their respective time intervals, both are in accordance with curves which together take into account ocean water volume and ocean basin volume changes. We quantify Cenozoic vertical movements of the Armorican Massif showcase. This massif is French Variscan basement of low relief (elevation < 420 m), two times buried then exhumed during Jurassic to Paleocene times, which bears numerous Cenozoic remnants of marine sediments of four periods: Bartonian, Rupelian, Langhian-Serravalian and Piacezian-Gelasian. We evidence a tree-step history of Cenozoic vertical movements and deformation: i) 38-34 Ma: a phase of near stability of the massif related to no to low deformation period for the Western Europe; ii) 30-16 Ma: a phase of low subsidence which coeval to a long wavelength subsidence of Western Europe which is proposed to be mantle-driven (dynamic topography); iii) 3.5-0 Ma: an overall bulging phase of the massif related to Apulia-Eurasia convergences due to Africa-Apulia and Iberia plates convergence which

  18. Research the dynamical characteristics of slow deformation waves as a rock massif response to explosions during its outworking

    NASA Astrophysics Data System (ADS)

    Hachay, Olga; Khachay, Oleg; Shipeev, Oleg

    2015-04-01

    As a result of long-term natural geomechanics and geophysical observation data on mines of complex ore rocks, generalization of the non-linear reaction of rock massif to heavy dynamic influences have been established. In addition, pendulum type waves have been observed and the sources of them have been located inside geoblocks of different hierarchic levels (Oparin et al., 2010). At the same time, these waves propagate with wide low (compared with seismic waves) velocity values (Kurlenja et al., 1993; Oparin et al., 2006). Research into the massif state with the use of the dynamic systems theory approach (Naimark et al., 2009; Chulichkov, 2003; Hachay et al., 2010) has been developed to ascertain the criteria of dissipative regimes changing for real rock massifs, which are under heavy man-caused influence. To realize such research we used the data from the seismic record of the Tashtagol mine for the two-year period from June 2006 up to June 2008. We used the space-time coordinates for all dynamic massif event responses, which occurred during that period inside the mine space and for the explosions - values fixed by seismic station energy (Hachay et al., 2010). The phase diagrams of the massif state for the northern and southern parts of the mine space were plotted in coordinates Ev(t) and d(Ev(t))/dt, t - time - in parts of 24 hours, Ev - the dissipated massive seismic energy - in joules. Hachay et al., (2010) analysed the morphology of seismic response phase trajectories on the explosion influences during different serial intervals in the southern part of the mine. In that period, according to data for different explosions in the mine, the majority of the total energy had been injected into the southern part of the mine. Moreover, at the end of 2007, just in the southern part, the strongest rock burst during the whole history of the working mine happened. We developed a new processing method of seismological information in real, which we can use directly in the

  19. Recharge areas and hydrochemistry of carbonate springs issuing from Semmering Massif, Austria, based on long-term oxygen-18 and hydrochemical data evidence

    NASA Astrophysics Data System (ADS)

    Yehdegho, Beyene; Reichl, Peter

    2002-10-01

    Résumé. Les teneurs en oxygène-18 et l'hydrochimie des sources émergeant du massif de Semmering ont été suivies de manière intensive dans le but de caractériser les zones de recharge et l'évolution hydrochimique. L'effet d'altitude sur le δ18O a été déterminé grâce aux données isotopiques et hydrogéologiques de petites sources de référence, principalement en terrains cristallins; cet effet est d'environ -0,27 et -0,21‰ par 100 m pour les versants respectivement nord et sud du massif. En appliquant ces valeurs, l'altitude moyenne de recharge des sources a été calculée. Pour les sources à fort débit issues des carbonates, elle est comprise entre 1,100 et 1,400 m, compatible avec le cadre topographique et hydrogéologique des calcaires et des dolomies de l'Austro-alpin inférieur alimentant ces sources. La composition chimique des sources des carbonates est dominée par les ions Ca2+, Mg2+, HCO3- et SO42-. Les sources sont presque toutes proches de la saturation par rapport à la calcite, mais sont sous-saturées en dolomite (sauf quelques sources proches de la saturation). Comme cela est habituel en ce qui concerne le dioxyde de carbone fourni par les sols en régions montagneuses, la pCO2 équilibrante moyenne est faible, comprise entre 10-3.0 et 10-2.5 atm (0,1 à 0,3% en volume). En ce qui concerne les variations à long terme, le pH, SIc, Sid et la pCO2 équilibrante sont soumis à des variations saisonnières, alors que les concentrations en Ca2+, Mg2+ et HCO3- ne varient pratiquement pas. En intégrant les résultats de δ18O et les données hydrochimiques, la variabilité altitudinale du chimisme des eaux souterraines des carbonates est démontrée. Reflétant les variations d'activité biologique et des conditions de recharge dans les zones d'alimentation, une covariation négative résulte de l'altitude de recharge et de la pCO2 et la concentration en HCO3- n'est pas modifiée par aucun des termes source ou puits, ce qui fait varier

  20. Provenance Ages of Protoliths From the Chiapas Massif Complex and Adjacent Strata of the Southern Maya Block - Implications on the Paleozoic Reconstruction of Middle America.

    NASA Astrophysics Data System (ADS)

    Weber, B.; Schaaf, P.; Valencia, V. A.; Lopez-Martinez, M.; Ortega-Gutierrez, F.

    2007-05-01

    The basement of the Maya block is exposed in the Maya Mountains of Belize, the Chuacús Complex of Guatemala, and in the Chiapas Massif Complex (CMC) of SE Mexico. In the CMC medium- to high-grade metasedimentary rocks occur as isolated domains in mostly metaigneous crystalline rocks. The most important tectonothermal event in the entire CMC is of late Permian age, culminating in partial anatexis and the intrusion of the Chiapas batholith. In this work we present U-Pb data obtained by LA-MC-ICPMS from detrital zircon cores of metasediments from the CMC and from detrital zircons of Paleozoic strata exposed in SE Chiapas. The Pennsylvanian-Permian Santa Rosa Formation (SRF) contains mostly Pan-African (500-650 Ma) zircons, minor populations of Silurian-Early Devonian (400-420 Ma) and Grenville (1.0-1.25 Ga) zircons, and few Paleoproterozoic and Archean grains. The maximum sedimentation age is documented by ~320 Ma old zircons. Metagreywacke and metasandstones of the central CMC have inherited detrital zircon cores with age distributions indistinguishable from those of the SRF. High-grade metapelites and para-amphibolites from the CMC, instead, have inherited zircon cores with one single population of 1.0 Ga or with populations at 1.0, 1.2, and 1.5 Ga. In the southern part of the CMC leucocratic granites intrude sedimentary rocks whose detrital zircons yielded mostly 1.53 Ga ages with some grains in the range of 1.6-1.7 Ga, but no younger zircons. White mica grown in contact with the leucogranite has a 40Ar- 39Ar age of 406 ± 4 Ma, defining a minimum age for both deposition of the sediments and intrusion of the leucogranite. Our data indicate that the CMC has a composite pre-metamorphic basement, containing sedimentary protoliths from the Pennsylvanian-Permian SRF and from early Paleozoic strata intruded by Silurian-Early Devonian granites. This favors a similar pre-Permian geologic history for the CMC as for the Maya Mountains of Belize. The early Paleozoic

  1. Velocity structure near IODP Hole U1309D, Atlantis Massif, from waveform inversion of streamer data and borehole measurements

    NASA Astrophysics Data System (ADS)

    Harding, Alistair J.; Arnulf, Adrien F.; Blackman, Donna K.

    2016-06-01

    Seismic full waveform inversion (FWI) is a promising method for determining the detailed velocity structure of the igneous oceanic crust, especially for locations such as the Mid-Atlantic Ridge with significant lateral heterogeneity and seafloor topography. We examine the accuracy of FWI by inverting, after downward continuation to datum just above the seafloor, a multichannel seismic (MCS) profile from Atlantis Massif oceanic core complex at 30°N that passes close to Integrated Ocean Drilling Program (IODP) Hole U1309D and comparing the results against borehole measurements and existing on-bottom refraction data. The comparisons include the results of IODP Expedition 340T, which extended the sonic logging and vertical seismic profiling to the bottom of the borehole at 1400 m below seafloor. Compared to travel time tomography, the refinement in velocity and velocity gradient produced by FWI significantly improves the overall match to the borehole measurements, and allows the multilevel pattern of deformation and alteration of the detachment footwall seen in Hole U1309D to be extrapolated across the Central Dome. Prestack depth migration of the profile using the FWI velocities reveals the top and edges of the high-velocity, gabbroic core of the massif. It also indicates that the comparatively uniform gabbroic rocks drilled at Hole U1309D extend to ˜2.5 km below seafloor but overlie an extended, ˜2 km thick, mantle transition zone.

  2. Late Ordovician (post-Sardic) rifting branches in the North Gondwanan Montagne Noire and Mouthoumet massifs of southern France

    NASA Astrophysics Data System (ADS)

    Javier Álvaro, J.; Colmenar, Jorge; Monceret, Eric; Pouclet, André; Vizcaïno, Daniel

    2016-06-01

    Upper Ordovician-Lower Devonian rocks of the Cabrières klippes (southern Montagne Noire) and the Mouthoumet massif in southern France rest paraconformably or with angular discordance on Cambrian-Lower Ordovician strata. Neither Middle-Ordovician volcanism nor associated metamorphism is recorded, and the subsequent Middle-Ordovician stratigraphic gap is related to the Sardic phase. Upper Ordovician sedimentation started in the rifting branches of Cabrières and Mouthoumet with deposition of basaltic lava flows and lahar deposits (Roque de Bandies and Villerouge formations) of continental tholeiite signature (CT), indicative of continental fracturing. The infill of both rifting branches followed with the onset of (1) Katian (Ka1-Ka2) conglomerates and sandstones (Glauzy and Gascagne formations), which have yielded a new brachiopod assemblage representative of the Svobodaina havliceki Community; (2) Katian (Ka2-Ka4) limestones, marlstones, and shales with carbonate nodules, reflecting development of bryozoan-echinoderm meadows with elements of the Nicolella Community (Gabian and Montjoi formations); and (3) the Hirnantian Marmairane Formation in the Mouthoumet massif that has yielded a rich and diverse fossil association representative of the pandemic Hirnantia Fauna. The sealing of the subaerial palaeorelief generated during the Sardic phase is related to Silurian and Early Devonian transgressions leading to onlapping patterns and the record of high-angle discordances.

  3. Occurrence of an unknown Atlantic eruption in the Chaîne des Puys volcanic field (Massif Central, France)

    NASA Astrophysics Data System (ADS)

    Jouannic, G.; Walter-Simonnet, A. V.; Bossuet, G.; Cubizolle, H.; Boivin, P.; Devidal, J. L.; Oberlin, C.

    2014-08-01

    A volcanic ash layer, called MF1, was recently identified in Holocene sediments from the Gourgon and Molhiac peat bogs (Monts du Forez, French Massif Central). This ash layer consists of colorless shards with a heterogeneous trachytic to rhyolitic composition. The trace elements analyzed by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) attest to a local origin. Radiocarbon dating of peat samples taken within and below the ash layer indicates the best age at 6339 ± 61 cal yr BP, i.e. an age contemporaneous with the volcanic activity of Montchal, Montcineyre and Pavin volcanoes from the Chaîne des Puys volcanic field. These volcanoes are characterized by basaltic and trachytic products, thus the rhyolitic composition of MF1 tephra suggests that it is likely originated from an unknown eruption. These results again confirm the interest of studying the distal volcanic ash fallouts in order to establish or specify records of past eruptions of volcanic fields. Identification of this new tephra layer also provides an additional tephrochronological marker for Eastern French Massif Central.

  4. Recharge areas and hydrochemistry of carbonate springs issuing from Semmering Massif, Austria, based on long-term oxygen-18 and hydrochemical data evidence

    NASA Astrophysics Data System (ADS)

    Yehdegho, Beyene; Reichl, Peter

    2002-10-01

    Résumé. Les teneurs en oxygène-18 et l'hydrochimie des sources émergeant du massif de Semmering ont été suivies de manière intensive dans le but de caractériser les zones de recharge et l'évolution hydrochimique. L'effet d'altitude sur le δ18O a été déterminé grâce aux données isotopiques et hydrogéologiques de petites sources de référence, principalement en terrains cristallins; cet effet est d'environ -0,27 et -0,21‰ par 100 m pour les versants respectivement nord et sud du massif. En appliquant ces valeurs, l'altitude moyenne de recharge des sources a été calculée. Pour les sources à fort débit issues des carbonates, elle est comprise entre 1,100 et 1,400 m, compatible avec le cadre topographique et hydrogéologique des calcaires et des dolomies de l'Austro-alpin inférieur alimentant ces sources. La composition chimique des sources des carbonates est dominée par les ions Ca2+, Mg2+, HCO3- et SO42-. Les sources sont presque toutes proches de la saturation par rapport à la calcite, mais sont sous-saturées en dolomite (sauf quelques sources proches de la saturation). Comme cela est habituel en ce qui concerne le dioxyde de carbone fourni par les sols en régions montagneuses, la pCO2 équilibrante moyenne est faible, comprise entre 10-3.0 et 10-2.5 atm (0,1 à 0,3% en volume). En ce qui concerne les variations à long terme, le pH, SIc, Sid et la pCO2 équilibrante sont soumis à des variations saisonnières, alors que les concentrations en Ca2+, Mg2+ et HCO3- ne varient pratiquement pas. En intégrant les résultats de δ18O et les données hydrochimiques, la variabilité altitudinale du chimisme des eaux souterraines des carbonates est démontrée. Reflétant les variations d'activité biologique et des conditions de recharge dans les zones d'alimentation, une covariation négative résulte de l'altitude de recharge et de la pCO2 et la concentration en HCO3- n'est pas modifiée par aucun des termes source ou puits, ce qui fait varier

  5. Ssismic Methodologies Applied To The Characterization Of Fractured Rock Massifs: Case Studies

    NASA Astrophysics Data System (ADS)

    Marti, D.; Carbonell, R.; Flecha, I.; Palomeras, I.; Font-Capo, J.; Vazquez-Sune, E.; Perez-Estaun, A.

    2007-05-01

    The detailed characterization of fractured media in the shallow subsurface is becoming important. The detailed knowledge of the fracture network is mandatory in any hydrogeological model to constrain the potential pathways for water circulation. The geophysical methodolgies can provide a detailed image of the fractured rock and also the 3D distribution of physical properties. Two case studies are discussed in this work. The characterization of fractures in a waste disposal site and, the design and construction of a subway tunnel. In the first case, a multiseismic experiment was carried out in an old abandoned uranium mine. 2D and 3D seismic experiments including VSP, surface seismic reflection and travel time seismic tomography provided a 3D image of the internal structure of a granitic massif for hydrogeological studies of the preferred paths for the migration of contaminants. The tectonic stability of the site was also addressed by means of seismic measurements. The joint interpretation of all the available data enabled the interpretation of the low velocity anomalies in the 3D seismic tomography image as the fragile fractures and the alteration associated to them. A 3D image of the geometry of the heterogeneous weathered surface layer was also obtained. This surface is controlled by the complex network of faults and dykes observed in the area. The second case study involves 2D and 3D seismic experiments to aid the horizontal drilling of tunnels for a new subway line in Barcelona (Spain). Seismic data acquisition in a densely populated city is very difficult. The street layout determines the geometry of the acquisition experiments. The instrumentation can not always be located on the surface projection of the tunnel trace, therefore, pseudo 3D acquisition is required, deploying the instrumentation were it is possible. Furthermore, the shallow subsurface features extremely heterogeneous "weathered" layer of variable thickness (building fundations, sewage system

  6. Anatomy of an extensional shear zone in the mantle, Lanzo massif, Italy

    NASA Astrophysics Data System (ADS)

    Kaczmarek, Mary-Alix; Tommasi, AndréA.

    2011-08-01

    Analysis of the microstructures in the km-scale mantle shear zone that separates the northern and the central parts of the Lanzo peridotite massif provides evidence of an evolution in time and space of deformation processes accommodating shearing in the shallow mantle within an extensional setting. This shear zone displays an asymmetric distribution of deformation facies. From south to north, gradual reorientation of the foliation of coarse porphyroclastic plagioclase-bearing peridotites is followed by development of protomylonites, mylonites, and mm-scale ultramylonite bands. A sharp grain size gradient marks the northern boundary. Early deformation under near-solidus conditions in the south is recorded by preservation of weakly deformed interstitial plagioclase and almost random clinopyroxene and plagioclase crystal orientations. Feedback between deformation and melt transport probably led to melt focusing and strain weakening in the shear zone. Overprint of melt-rock reaction microstructures by solid-state deformation and decrease in recrystallized grain size in the protomylonites and mylonites indicate continued deformation under decreasing temperature. Less enriched peridotite compositions and absence of ultramafic dykes or widespread melt-impregnation microstructures north of the shear zone and clinopyroxene and amphibole enrichment in the mylonites and ultramylonites suggest that the shear zone acted as both a thermal barrier and a high-permeability channel for late crystallizing fluids. These observations, together with chemical data indicating faster cooling of central Lanzo relative to the northern body, corroborate that this shear zone is a mantle detachment fault. All deformation facies have crystal preferred orientations consistent with deformation by dislocation creep with dominant activation of the (010)[100] and (100)[001] systems in olivine and orthopyroxene, respectively. Dynamic recrystallization produces dispersion of olivine CPO but not a

  7. Microfracturing and fluid mixing in granites: W (Sn) ore deposition at Vaulry (NW French Massif Central)

    NASA Astrophysics Data System (ADS)

    Vallance, Jean; Cathelineau, Michel; Marignac, Christian; Boiron, Marie-Christine; Fourcade, Serge; Martineau, François; Fabre, Cécile

    2001-07-01

    The Vaulry W-(Sn) mineralisation, located at the eastern boundary of the Blond rare metal leucogranite, is contained in a set of subvertical quartz veins, locally with muscovite and minor quartz selvages. The sequence of deposition was: (1) milky quartz, predominantly as fracture filling, generally affected by subsequent ductile deformation; (2) hyaline quartz-wolframite-cassiterite; (3) minor sulphides. Other sets of quartz veinlets, although generally barren are observed in the Blond massif. Fluid migration at the microscopic scale within the granite and in the vicinity of quartz fractures was constrained by studying the geometry of fluid-inclusion planes and fluid-inclusion chemistry in and outside the mineralised area. Three major sets of subvertical fluid-inclusion planes are recognised: a N050°-060°E set, mostly developed in the veins and in the immediate vicinity, a N110°-130°E set, regionally developed in the granite and a N140-160°E set of local extent. As a whole, the density of FIP decreases from the mineralised zones toward the barren part of the pluton, except for the N140°-160°E set. These are locally abundant around quartz veinlets with similar orientations that form a broad "N-S" band near the Blond locality. Mineralising fluids observed as primary inclusions in cassiterite and in undeformed hyaline quartz are mostly aqueous, with moderate salinity and a minor volatile component, at variance with many other W-(Sn) deposits in the Variscan belt. Ore deposition occurred around 315°C, at an estimated depth of 5.5 km, under hydrostatic to slightly suprahydrostatic pressures. It resulted from fluid mixing, in the central part of a large hydrothermal system, between two end-members: (i) a hot (425-430°C) moderately saline fluid, that contained a diluted volatile component and, although Na-dominated, minor amounts of Li and Ca. The estimated δ18O indicates that this fluid was completely equilibrated with the tectono-magmatic pile (pseudo

  8. Seismicity without a fault ? Structural evidence from pseudotachylites in the UHP Dora Maira Massif

    NASA Astrophysics Data System (ADS)

    Zechmeister, M.; Ferre, E. C.; Geissman, J. W.; Cosca, M.; Caby, R.; Frima, C.; Ward, C.

    2004-12-01

    The Dora Maira massif, in the Italian Alps, is a world famous example of ultra-high pressure (UHP) metamorphism of crustal rocks with peak pressure of ca 3 GPa (depth ≈ 100 km) at about 35 My. Exhumation began shortly after the peak of metamorphism. The UHP rocks had equilibrated at a temperature of 250° C around 30 My. Pseudotachylite veins (1 to 20 mm thick) formed parallel to the syn-exhumation mylonitic foliation and were dated at 20.1 ± 0.5 Ma by Ar/Ar method. The geochronologic data suggests that the pseudotachylite veins formed at depths shallower than ≈ 10 km. These veins are found mainly in gently dipping medium grained phengite/coesite bearing orthogneiss. The generation veins are parallel to the foliation, constant in thickness and up to several tens of meters in length. Injection veins are less common and generally only a few cm in length. Structural mapping of UHP mylonitic gneisses and surrounding rocks reveals the dominance of high ductile strain, a puzzling lack of localized cataclastic deformation and the absence of fault associated with the pseudotachylite veins. The pseudotachylite veins are concentrated along a 50 m wide, foliation-parallel corridor. Conversely, the two major faults along which the UHP rocks were exhumed are > 500 m away from the pseudotachylite-bearing rocks and do not contain pseudotachylite veins. The formation of these pseudotachylite veins is clearly related to exhumation history of UHP rocks. The formation of pseudotachylite results from frictional melting as shown by microstructural criteria including corroded quartz grains and spherulitic microstructures. The localized heat source required for melting the UHP orthogneisses along narrow bands is attributed to frictional heat produced along the foliation plane. Fault-related pseudotachylite studies and friction experiments have shown that seismic strain rates (in the order of s-1) are required to maintain heat along the fault plane. At slower strain rates, heat would

  9. Apatite-hosted melt inclusions in Damiao massif anorthosite complex, North China

    NASA Astrophysics Data System (ADS)

    Wang, M.; Veksler, I. V.; Zhang, Z.

    2014-12-01

    Models for the nelsonite formation are currently highly contentious, with liquid immiscibility and fractional crystallization as frequently proposed formation mechanisms. The nelsonites in the Damiao massif anorthosite complex in the North China Craton and experimental evidence are revisited for the existence of silica-free CaO-FeO-Fe2O3-TiO2-P2O5 immiscible nelsonitic liquids. Our results of differential scanning calorimetry (DSC) demonstrate that nelsonite with the composition of one-third apatite and two-thirds Fe-Ti oxides by weight completely melts well above 1450 ºC, which is in good agreement with numerous experimental studies of the CaO-P2O5-FexO system in connection to metallurgy. Thus, the composition cannot be molten at temperatures relevant for crystallization of the Damiao magma. A review of experimental studies of liquid immiscibility and analyses of natural immiscible glasses show that all the liquids on the Fe- and P-rich side of the miscibility gap have at least 20 wt. % of aluminosilicate components. Main results of this study come from the analyses of apatite-hosted melt inclusions in Damiao nelsonite. The inclusions range from ~3 to 200 μm in diameter. They are ubiquitous and meet all the morphological criteria of primary melt inclusions crystallised into assemblages of daughter minerals. Almost all of them contain vermiculite and chlorite, and some contain biotite, amphibole, phlogopite and Fe-Ti oxides. Out of dozens analysed inclusions, only three have high contents of SiO2 (62.1-73.8 wt. %) and low contents of FeO (0.25-2.35 wt. %). Bulk compositions of other inclusions show large variations in SiO2 (20.79-50.16 wt. %) and FeOt (13.44-32.78 wt. %). With a few exceptions, the inclusions are very low in CaO (0.04-1.51 wt. %, and high in Al2O3 (10-21.17 wt. %). Despite the high Fe content, the compositions differ from those of the typical immiscible Fe-rich melts. It appears that the cumulus apatite crystallised from Fe-rich, hydrated

  10. Generation and evolution processes of Paleoproterozoic massive-type Sancheong anorthosite complex, Yeongnam massif, Korea

    NASA Astrophysics Data System (ADS)

    Kang, Ji-Hoon; Lee, Deok-Seon

    2016-04-01

    The Paleoproterozoic (˜1.87-1.79 Ga) Sancheong anorthosite complex in the Jirisan province of the Yeongnam massif, Korea, consists of massive-type and foliation-type Sancheong anorthosite (SA), Fe-Ti ore body (FTO), and mafic granulite (MG). We report their characteristics and interrelation on foliations, occurrences, lithofacies, composition minerals, suggesting the generation and evolution processes of the Sancheong anorthosite complex with the origin of their foliations. The main characteristics and interrelation are as follows: multilayer structures of FTO, straight-, anastomosing-, uneven-types FTO and MG veins derived from blocking associate with size reduction of SA, gradual or irregular boundaries of SA blocks, FTO and MG showing bulbous lobate margins and comb structures between SA blocks, flow foliations and linear arrangements of FTO and MG, discontinuous shear zone of SA, orientation of FTO and MG foliations parallel to the boundaries of SA blocks, predominance of FTO and MG foliations toward the boundaries of SA blocks, flow folding structures of FTO and MG foliation, lithfacies change of MG into FTO by the injection of MG into SA, and very similar assemblage of mafic minerals and chemical composition of ilmenite and almost equal occurrence and foliation features between FTO and MG. Such evidences indicate that the SA, FTO, MG foliations are magmatic foliations which were formed in a not fully congealed state of SA from the results of the fracturing of partly congealed SA, the injection and flow of FTO and MG melts into the fractured SA, the dynamic intercompaction between them. It also implies that the SA, FTO, MG were not formed from the intrusion and differentiation of magmas which were different from each other in genesis and age but from the multiple fractionation and polybaric crystallization of the coeval and cogenetic magma. Our new model suggests that the Sancheong anorthosite complex was generated and evolved as following sequence: the

  11. Fractionation of highly siderophile and chalcogen elements during magma transport in the mantle: Constraints from pyroxenites of the Balmuccia peridotite massif

    NASA Astrophysics Data System (ADS)

    Wang, Zaicong; Becker, Harry

    2015-06-01

    Sulfide segregation from sulfur saturated basic magmas affects the compositions of chalcophile elements such as the highly siderophile elements (HSE) and the chalcogens S, Se, Te to variable extent. Whether this process predominantly occurs in the lower crust or in the mantle and how segregation of liquid sulfide and accumulation affects concentrations and ratios of these elements at different mantle depths and in presumed primitive basic magmas remains uncertain. Abundances of the HSE, S, Se and Te and Os isotopes in websterites and spinel clinopyroxenites of the Balmuccia peridotite massif (Ivrea-Verbano Zone, Italian Alps) provide new insight on sulfide segregation and the compositional change of melt and peridotite during magma transport in the mantle. Balmuccia websterites and clinopyroxenites formed from late Paleozoic and Mesozoic melt influx into stretched continental lithospheric mantle of the Ivrea-Verbano Zone, respectively. The HSE and chalcogen element compositions of websterites and clinopyroxenites reflect the segregation and accumulation of sulfide melt from S saturated silicate melts with different abundances and ratios of chalcogens and the HSE. The pyroxenites display large variations in abundances of the platinum group elements (PGE) and Te whereas abundances of less chalcophile elements S, Se and Re are much less variable. The fractionation between the PGE and fractionation of Re/Os, S/Se and Se/Te in the mantle pyroxenites are consistent with sulfide melt-silicate melt partitioning with a sequence of apparent coefficients of DPGE > DAu ⩾ DTe > DSe ⩾ DS ≈ DRe. Concentrations in ocean ridge basalts and in gabbros of the lower oceanic crust are also consistent with such fractionation. Websterites which have formed during refertilization of depleted peridotites display ratios of the HSE and moderately suprachondritic initial 187Os/188Os similar to interstitial sulfides of refertilized peridotites. These compositions are different from

  12. Determination of Granite Rock Massif Weathering and Cracking of Surface Layers in the Oldest Parts of Medieval Mine Depending on Used Mining Method

    NASA Astrophysics Data System (ADS)

    Lednická, Markéta; Kaláb, Zdeněk

    2016-06-01

    The paper presents the use of selected non-destructive testing methods for the purpose of specifying information on weathering and cracking of surface layers of granite rock massif in the medieval Jeroným Mine (the Czech Republic). This mine has been declared the National Heritage Site of the Czech Republic and its opening as a mining museum to the public is gradually prepared. Geological and geomechanical evaluation documents the possibility to find all kinds of weathering grades of rock massif in this mine. Two non-destructive methods have been tested, namely the measurement of ultrasonic pulse velocity and the measurement of Schmidt hammer rebound value. Field measurements were performed in two selected galleries to verify the application of such methods in specific conditions of underground spaces. Used mining method is one of the parameters later influencing cracking of rock massif. In selected galleries, two different mining methods were used which means that a part of a gallery profile was mined out by hand tools in the Middle Ages and another part of the profile was later mined out by blasting. Measurements in these galleries have enabled to analyse the influence of used mining methods on cracking of rock massif in the impaired zone, and, consequently, on ongoing weathering processes in those zones.

  13. Earthquake location, active faulting, and P-wave velocity structure near a metamorphic massif in the eastern syntaxis of the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Brown, L. E.; Meltzer, A.

    2011-12-01

    Within the core of the eastern syntaxis of the Himalaya, the Namche Barwa - Gyala Peri massif is a site of rapid exhumation where high grade metamorphic rocks from the mid to lower crust are exposed at the surface. Some of the world's highest relief is observed in this massif. The two peaks, standing over 7000m tall, are only 20km apart and are separated by a major river, the Tsangpo, at an elevation of 2500m. This impressive relief is maintained because these mountains constitute an actively forming, localized, antiformal structure, which is rapidly uplifting, while the Tsangpo downcuts through the structure. This tectonic situation is interesting because there appear to be feedbacks between topography and tectonics. As part of an effort to understand the dynamics associated with this localized structure, a temporary seismic network was used to record earthquakes near the massif. In this study approximately 2000 local earthquakes are used to define a 3-D velocity model and the locations of active faulting. The majority of events are part of an impressive spatial cluster which occurred during a series of earthquake swarms. This NW trending cluster has a vertical dip, extending to 15km in depth, and closely correlates to a topographic ridge immediately to the north of Namche Barwa. The Tsangpo takes a sharp turn when it reaches this ridge, flowing parallel to the base of the ridge, and the river then makes a dramatic 180° turn around the ridge. Given that the river's erosional power is thought to be responsible for localizing deformation into this area, it is significant that the Tsangpo's course through this area might be fault controlled. A second cluster of events is located to the west of Gyala Peri and trends to the north. Comparing this cluster to a geologic map shows that the events fall on a mapped thrust fault. This fault extends to the south of the massif, where there were no recorded events. This portion of the fault is interpreted to be locked. The

  14. New data for paleoprotherozoic PGE-bearing anorthosite of Kandalaksha massif (Baltic shield): U-Pb and Sm-Nd ages

    NASA Astrophysics Data System (ADS)

    Steshenko, Ekaterina; Bayanova, Tamara; Serov, Pavel

    2015-04-01

    The aims of this researches were to study the isotope U-Pb age of zircon and rutile and Sm-Nd (rock forming and sulphide minerals) on Kandalaksha anorthosite massif due to study of polimetamorphic history. In marginal zone firstly have been obtained the presence of sulphide mineralization with PGE (Chashchin, Petrov , 2013). Kandalaksha massif is located in the N-E part of Baltic shield and consists of three parts. Marginal zone (mesocratic metanorite) lies at the base of the massif. Main zone is composed of leucocratic metagabbro. The upper zone is alteration of mataanorthosite and leucocratic metagabbro. All rocks were subjected to granulate polymetamorphism. Two fractions of single grains from anorthosite of the massif gave precise U-Pb age, which is equal to 2450± 3 Ma. Leucocratic gabbro-norite were dated by U-Pb method, with age up to 2230 ± 10 Ma. This age reflects the time of granulite metamorphism according to data of (Mitrofanov, Nirovich, 2003). Two fractions of rutile have been analyzed by U-Pb method and reflect age of 1700 ± 10 Ma. It is known that the closure temperature of U-Pb system rutile is 400-450 ° C (Mezger et.al., 1989), thus cooling processes of massif rocks to these temperatures was about 1.7 Ga. These data reflect one of the stages of metamorphic alteration of the massif. Three stages of metamorphism are distinguished by Sm-Nd method. Isotope Sm-Nd dating on Cpx-WR line gives the age of 2311 Ma which suggested of high pressure granulite metamorphism. Moreover Cpx-Pl line reflect the age 1908 Ma of low pressure granulite metamorphism. Also two-points (Grt-Rt) Sm-Nd isochrone yield the age 1687 Ma of the last metamorphic alterations in Kandalaksha anorthosite massif. Model Sm-Nd age of the leucocratic gabbro-norite is 2796 Ma with positive ɛNd (+0.32). It means that the source of gabbro-norite was mantle reservoir. All investigations are devoted to memory of academician PAS F. MItrofanov which was a leader of scientific school for

  15. Human impacts of hydrometeorological extremes in the Bohemian-Moravian Highlands derived from documentary sources in the 18th-19th centuries

    NASA Astrophysics Data System (ADS)

    Dolák, Lukáš; Brázdil, Rudolf; Valášek, Hubert

    2014-05-01

    The extent of damage caused by hydrometeorological events or extremes (HME) has risen up in the entire world in the last few years. Especially the floods, flash floods, torrential rains and hailstorms are the most typical and one of the most frequent kind of natural disasters in the central Europe. Catastrophes are a part of human history and people were forced to cope with their consequences (e. g. material damage, economical losses, impacts on agriculture and society or losses of human lives). This paper analyses the human impacts of HME in the Bohemian-Moravian Highlands (central part of the Czech Republic) on the basis of documentary sources from the 18th-19th centuries. The paper presents various negative impacts of natural disasters on lives and property and subsequent inconveniences of Czech peasants. The preserved archival documents of estates or domains became the primary sources of data (e. g. taxation reliefs, damaged records, reports of afflicted farmers, administrative correspondence etc.). Particularly taxation reliefs relate to taxation system in the Czech lands during the 17th-19th centuries allowing to farmers to ask for tax alleviation when their crops were significantly damaged by any HME. These archival documents are a highly valuable source for the study of human impacts of natural disasters. Devastating consequences of these extremes affected individual farmers much more than the aristocracy. Floods caused inundations of farmer's fields, meadows, houses and farm buildings, washed away the arable land with crops, caused losses of cattle, clogged the land with gravel and mud and destroyed roads, bridges or agricultural equipment. Afflicted fields became worthless and it took them many years to become became fertile again. Crop was also damaged by hailstorms, droughts or late/early frosts. All these events led to lack of food and seeds in the following year and it meant the decrease of living standard, misery and poverty of farmers. Acquired

  16. Use of Digital Elevation Models to understand map landforms and history of the magmatism Khibiny Massif (Kola Peninsula, Russia)

    NASA Astrophysics Data System (ADS)

    Chesalova, Elena; Asavin, Alex

    2016-04-01

    This work presents an improved geomorphological methodology that uses 3D model of relief, remotely-sensed data, geological, geophysical maps and tools of Geographical Information Systems. On the basis of maps of 1: 50,000 and 1: 200,000 the Digital Elevation model (DEM) of Khibiny massif was developed. We used software ARC / INFO v10.2 ESRI. A DEM was used for analyzing landform by extracting the slope gradient, curvature, valley pro?les, slope, aspect and so on. The results were gradually re?ned from the interpretation of satellite imagery and geological map Geomorphological analysis will allow us to determine spatial regularities in inner massive construction. We try to found areas where gas emissions (CH4/H2) enrich, according to morphometry, geology, tectonic and other environments. The main regional blocks were de?ned by different morphological evidences: impression zone, similar to subsidence caldera; uplift zone, domed area (located in the highest part of massif and zone of intersection of main faults) and others. It says that there are the few stages in the development of the Khibiny massif. There is no common concept of the consequence of intrudes magmatic phases now. And we hope that our geomorphical analysis take a new evidences about this problems. Locations of the blocks' borders (tectonic zones) were recognized by lineament analysis of valleys and tectonic faults presented in relief. Erosion system is represented by valleys of 4 ranks. It inherits the zone of tectonic disturbances 3 groups of faults were recognized: 1) Global lineament system cross whole peninsula - existing before Khibiny massif intrusion; 2) Faults associated with the formation of the intrusive phases sequence and magma differentiation and with later collision history during magma cooling; 3) Crack system related to neotectonic process. We believed that if different magmatic phases intrude in similar tectonic environment, the common spatial system of faults will be formed. Really we

  17. Optical investigation of CdSe/ZnSe quantum nanostructures

    NASA Astrophysics Data System (ADS)

    Valakh, M. Ya; Ivanov, S. V.; Mestres, N.; Pascual, J.; Shubina, T. V.; Sorokin, S. V.; Streltchuk, V. V.; Pozina, G.; Monemar, B.

    2002-02-01

    We have used resonant and non-resonant Raman scattering as well as photoluminescence and cathodoluminescence experiments to study the structure and composition properties of CdxZn1-xSe formed by migration enhanced epitaxy of CdSe layers on ZnSe buffers. The spectral change of the photoluminescence maximum correlates with the increase of the Cd content, depending on the nominal CdSe thickness in the 1.5-3.0 ML range. The inhomogeneous broadening of the photoluminescence band is caused by the composition difference between the two-dimensional mixed CdxZn1-xSe layer and the inserted islands with larger Cd concentration. This is confirmed by phonon frequency changes in resonant Raman scattering for samples with different nominal CdSe thicknesses as well as in Stokes and anti-Stokes frequency changes observed in the 1.5 ML sample. Attention is paid to the role of defects on Raman scattering and photoluminescence for the 3.15 ML sample.

  18. Record of metal workshops in peat deposits: history and environmental impact on the Mont Lozère Massif, France.

    PubMed

    Baron, S; Lavoie, M; Ploquin, A; Carignan, J; Pulido, M; De Beaulieu, J L

    2005-07-15

    This study aims to document the history of the metallurgical activities on the Mont Lozère massif in the Cévennes Mountains in Southern France. Many medieval sites of metallurgical wastes (slags) have been reported on the massif. These sites are thought to represent ancient lead workshops. The impact of past metallurgical activity on the environment was studied using geochemical and palynological techniques on a core collected in the Narses Mortes peatland near medieval smelting area. Two main periods of smelting activities during the last 2200 years were revealed bythe lead concentration and isotopic composition along the core profile: the first period corresponds to the Gallic period (approximately ca. 300 B.C. to ca. 20 A.D.) and the second one to the Medieval period (approximately ca. 1000-1300 A.D.). Forest disturbances are associated with lead anomalies for the two metallurgical activities described. The impact of the first metallurgy was moderate during the Gallic period, during which beech and birch were the tree species most affected. The second period corresponds to the observed slag present in the field. Along with agropastoral activities, the medieval smelting activities led to the definitive disappearance of all tree species on the summit zones of Mont Lozère. The abundance of ore resources and the earlier presence of wood on the massif justify the presence of workshops at this place. The relationship between mines and ores has been documented for the Medieval period. There is no archaeological proof concerning the Gallic activity. Nevertheless, 2500-2100 years ago, the borders of the Gallic Tribe territory, named the Gabales, were the same as the present-day borders of the Lozère department. Julius Caesar reported the existence of this tribe in 58 B.C. in "De Bello Gallico", and in Strabon (Book IV, 2.2) the "Gabales silver" and a "treasure of Gabales" are mentioned, but to this day, they have not been found. PMID:16082940

  19. Extinction vulnerability of tropical montane endemism from warming and upslope displacement: a preliminary appraisal for the highest massif in Madagascar

    PubMed Central

    RAXWORTHY, CHRISTOPHER J; PEARSON, RICHARD G; RABIBISOA, NIRHY; RAKOTONDRAZAFY, ANDRY M; RAMANAMANJATO, JEAN-BAPTISTE; RASELIMANANA, ACHILLE P; WU, SHENGHAI; NUSSBAUM, RONALD A; STONE, DÁITHÍ A

    2008-01-01

    One of the predicted biological responses to climate warming is the upslope displacement of species distributions. In the tropics, because montane assemblages frequently include local endemics that are distributed close to summits, these species may be especially vulnerable to experiencing complete habitat loss from warming. However, there is currently a dearth of information available for tropical regions. Here, we present a preliminary appraisal of this extinction threat using the herpetological assemblage of the Tsaratanana Massif in northern Madagascar (the island's highest massif), which is rich with montane endemism. We present meteorological evidence (individual and combined regional weather station data and reanalysis forecast data) for recent warming in Madagascar, and show that this trend is consistent with recent climate model simulations. Using standard moist adiabatic lapse rates, these observed meteorological warming trends in northern Madagascar predict upslope species displacement of 17–74 m per decade between 1993 and 2003. Over this same period, we also report preliminary data supporting a trend for upslope distribution movements, based on two surveys we completed at Tsaratanana. For 30 species, representing five families of reptiles and amphibians, we found overall mean shifts in elevational midpoint of 19–51 m upslope (mean lower elevation limit 29–114 m; mean upper elevation limit −8 to 53 m). We also found upslope trends in mean and median elevational observations in seven and six of nine species analysed. Phenological differences between these surveys do not appear to be substantial, but these upslope shifts are consistent with the predictions based on meteorological warming. An elevational range displacement analysis projects complete habitat loss for three species below the 2 °C ‘dangerous’ warming threshold. One of these species is not contracting its distribution, but the other two were not resampled in 2003. A preliminary

  20. Apatite fission track thermochronology of Khibina Massif (Kola Peninsula, Russia): Implications for post-Devonian Tectonics of the NE Fennoscandia

    NASA Astrophysics Data System (ADS)

    Veselovskiy, Roman V.; Thomson, Stuart N.; Arzamastsev, Andrey A.; Zakharov, Vladimir S.

    2015-12-01

    The thermal history of the Kola Peninsula area of NE Fennoscandia remains almost fully unknown because of the absence of any thermochronological data such as apatite and/or zircon fission track or (Usbnd Th)/He ages. In order to fill this gap and to constrain the post-Devonian erosion and exhumation history of this region, we present the results of apatite fission track (AFT) dating of eleven samples selected from the cores taken from different depths of the northern part of the Khibina intrusive massif. The Rbsbnd Sr isochron age of this alkaline magmatic complex which is located at the center of Kola Peninsula is 368 + 6 Ma (Kramm and Kogarko, 1994). Samples were analyzed from depths between + 520 and - 950 m and yielded AFT ages between 290 and 268 Ma with an age uncertainty (1σ) of between ± 19 Ma (7%) and ± 42 Ma (15%). Mean track lengths (MTL) lie between 12.5 and 14.4 μm. Inverse time-temperature modeling was conducted on the age and track length data from seven samples of the Khibina massif. Thermal histories that best predict the measured data from three samples with the most reliable data show three stages: (1) 290-250 Ma-rapid cooling from > 110 °C to 70 °C/50 °C for lower/upper sample correspondingly; (2) 250-50 Ma-a stable temperature stage; (3) 50-0 Ma-slightly increased cooling rates down to modern temperatures. We propose that the first cooling stage is related to late-Hercynian orogenesis; the second cooling stage may be associated with tectonics accompanying with opening of Arctic oceanic basin. The obtained data show that geothermal gradient at the center of Kola Peninsula has remained close to the modern value of 20 °C/km for at least the last 250 Myr. AFT data show that the Khibina massif has been exhumed not more then 5-6 km in the last 290 Myr.

  1. Mantle refertilization by melts of crustal-derived garnet pyroxenite: Evidence from the Ronda peridotite massif, southern Spain

    NASA Astrophysics Data System (ADS)

    Marchesi, Claudio; Garrido, Carlos J.; Bosch, Delphine; Bodinier, Jean-Louis; Gervilla, Fernando; Hidas, Károly

    2013-01-01

    Geochemical studies of primitive basalts have documented the presence of crustal-derived garnet pyroxenite in their mantle sources. The processes whereby melts with the signature of garnet pyroxenite are produced in the mantle are, however, poorly understood and somewhat controversial. Here we investigate a natural example of the interaction between melts of garnet pyroxenite derived from recycled plagioclase-rich crust and surrounding mantle in the Ronda peridotite massif. Melting of garnet pyroxenite at ˜1.5 GPa generated spinel websterite residues with MREE/HREE fractionation and preserved the positive Eu anomaly of their garnet pyroxenite precursor in whole-rock and clinopyroxene. Reaction of melts from garnet pyroxenite with depleted surrounding peridotite generated secondary fertile spinel lherzolite. These secondary lherzolites differ from common spinel lherzolite from Ronda and elsewhere by their lower-Mg# in clinopyroxene, orthopyroxene and olivine, lower-Cr# in spinel and higher whole-rock Al2O3, CaO, Sm/Yb and FeO* at a given SiO2. Remarkably, secondary spinel lherzolite shows the geochemical signature of ghost plagioclase in the form of positive Eu and Sr anomalies in whole-rock and clinopyroxene, reflecting the transfer of a low-pressure crustal imprint from recycled pyroxenite to hybridized peridotite. Garnet pyroxenite melting and melt-peridotite interaction, as shown in the Ronda massif, may explain how the signature of subducted or delaminated crust is transferred to the mantle and how a garnet pyroxenite component is introduced into the source region of basalts. The efficiency of these processes in conveying the geochemical imprint of crustal-derived garnet pyroxenite to extruded lavas depends on the reactivity of pyroxenite melt with peridotite and the mantle permeability, which may be controlled by prior refertilization reactions similar to those documented in the Ronda massif. Highly fertile heterogeneities produced by pyroxenite

  2. The internal deformation of the Peridotite Nappe of New Caledonia: A structural study of serpentine-bearing faults and shear zones in the Koniambo Massif

    NASA Astrophysics Data System (ADS)

    Quesnel, Benoît; Gautier, Pierre; Cathelineau, Michel; Boulvais, Philippe; Couteau, Clément; Drouillet, Maxime

    2016-04-01

    We present a structural analysis of serpentine-bearing faults and shear zones in the Koniambo Massif, one of the klippes of the Peridotite Nappe of New Caledonia. Three structural levels are recognized. The upper level is characterized by a dense network of fractures. Antigorite and polygonal serpentine form slickenfibers along fault planes with distinct kinematics. As a result, the upper level keeps the record of at least two deformation events, the first associated with the growth of antigorite (WNW-ESE extension), the second with the growth of polygonal serpentine (NW-SE compression). The lower level coincides with the 'serpentine sole' of the nappe, which consists of massive tectonic breccias overlying a layer of mylonitic serpentinites. The sole records pervasive tangential shear with top-to-SW kinematics and represents a décollement at the base of the nappe. The intermediate level is characterized by the presence of several meters-thick conjugate shear zones accommodating NE-SW shortening. Like the sole, these shear zones involve polygonal serpentine and magnesite as the main syn-kinematic mineral phases. The shear zones likely root into the basal décollement, either along its roof or, occasionally, around its base. Compared to top-to-SW shearing along the sole, the two deformation events recorded in the upper level are older. The three structural levels correlate well with previously recognized spatial variations in the degree of serpentinization. It is therefore tempting to consider that the intensity of serpentinization played a major role in the way deformation has been distributed across the Peridotite Nappe. However, even the least altered peridotites, in the upper level, contain so much serpentine that, according to theoretical and experimental work, they should be nearly as weak as pure serpentinite. Hence, no strong vertical gradient in strength due to variations in the degree of serpentinization is expected within the exposed part of the nappe

  3. The Mirdita Eastern Ophiolite, Albania: petrological evidence for MORB Mantle in the Tropoje peridotite massif?

    NASA Astrophysics Data System (ADS)

    Ntaflos, Theodoros; Onuzi, Kujtim; Hauzenberger, Christoph; Rice, A. Hugh N.; Proßegger, Peter; Mekshiqi, Nazir; Kaza, Gjon

    2016-04-01

    The Mirdita ophiolites in northern Albania are divided into the Western Mirdita Ophiolite (WMO), with MORB geochemical affinities, and the Eastern Mirdita Ophiolite (EMO), for which suprasubduction geochemical affinities have been reported. Ultramafic massifs in the WMO are often plagioclase bearing lherzolites/harzburgites whereas those in the EMO are strongly depleted spinel harzburgites. The Tropoje ultramafic-mafic complex, which forms the northernmost part of the EMO, consists of spinel harzburgites, wherlites, orthopyroxenites and gabbros. The spinel harzburgites, which experienced variable degrees of serpentinization, are coarse- to medium-grained. One of the most striking features of the Tropoje ultramafic rocks is an outcrop of exceptionally fresh coarse- to medium-grained spinel harzburgites. While occasionally the peridotites exhibit a weak foliation, the prevalent texture is protogranular. Olivine is mainly coarse-grained (up to 6 mm size), typically showing kink-bands that frequently contain submicron-sized spinel exsolution lamellae. Both orthopyroxene and clinopyroxene, with grain size up to 3 mm and 1.5 mm, respectively, carry very thin exsolution lamellae of the other pyroxene. Spinel, up to 1 mm in size, is interstitial between boundaries of the associated silicates. The mineral compositions of the spinel harzburgites indicate that they are strongly depleted in basaltic components. The rock-forming minerals (olivine, orthopyroxene and clinopyroxene) are all highly magnesian and chemically homogenous. The magnesium numbers (Mg#=100xMg/[Mg+Fe]) for olivine and orthopyroxene are fairly homogeneous and vary within the narrow range of 90.9-91.6 and 91.5-91.7, respectively. The clinopyroxene is exceptionally highly magnesian, with Mg# ranging between 93.6 and 95.4. In both orthopyroxene and clinopyroxene, the Al2O3 contents range from 0.95 to 1.75 and from 0.62 to 2.27 wt%, respectively. Spinel shows a considerable variation in Al2O3 and Cr2O3. The

  4. Syntectonic Variscan magmatism in the Aguiar da Beira region (Iberian Massif, Portugal)

    NASA Astrophysics Data System (ADS)

    Mafalda Costa, Maria; Margarida Neiva, Ana; do Rosario Azevedo, Maria; Corfu, Fernando

    2014-05-01

    The Aguiar da Beira region (Portugal) is located in the core of the Iberian Massif, more precisely in the Central-Iberian Zone, which is dominantly composed by abundant volumes of plutonic rocks, emplaced into Late Proterozoic - Early Cambrian and Palaeozoic metasediments, mainly during or slightly after the third deformation phase of the Variscan Orogeny (D3). A considerable amount of these granites are syntectonic, intruded during the peak of this deformation event (D3). In particular, at the Aguiar da Beira region, two suites of syntectonic granitoids represent distinct magmatic series: a medium- to coarse-grained porphyritic biotite granodiorite-granite (322 Ma), which belongs to the early granodiorite series, and a medium-grained muscovite-biotite granite (317 Ma) that is part of the two-mica peraluminous leucogranites suite. The petrographic, geochemical (whole-rock and mineral compositions) and isotopic (Sr-Nd, δ18O-wr and δ18O-zr) study of the two intrusions reveals their remarkably different character. It is concluded that they correspond to two independent magma pulses, derived from distinct sources and/or petrogenetic processes. The biotite granodiorite-granite is a weakly peraluminous intrusion, characterized by intermediate to felsic SiO2 contents (66 - 68 %), high Ba, Sr and REE, and biotite with high Al and Mg contents, typical of the calc-alkaline associations. The Sr-Nd initial ratios are homogeneous (87Sr-86Sr322: 0.7070 - 0.7074; ɛNd322: -3.9 to -4.6) and overlap the isotopic signatures of lower crustal felsic metaigneous granulites (Villaseca et al. 1999). This similarity, which is further supported by δ18O-wr and δ18O-zr data, may indicate an origin by anatexis of lower felsic metaigneous rocks. Alternatively, the same data, allied to the presence of microgranular enclaves seen in this intrusion, can also be explained by the mixing of lower crustal derived magmas and mantle melts. By contrast, the muscovite-biotite granite has an entirely

  5. Soil thermal regime and geomorphogenesis at Fuentes Carrionas massif (Cantabrian Range, NW Iberian Peninsula).

    NASA Astrophysics Data System (ADS)

    Pellitero, Ramon; Serrano Cañadas, Enrique

    2015-04-01

    Fuentes Carrionas is a massif within the Cantabrian Range, in NW Iberian Peninsula. Its altitude ranges between 1400 and 2500 meters and its climate is an oceanic/Mediterranean transition one, with cold temperatures and heavy snowfall in the winter/early spring season, and a warm and dry summer season. Due to its outstanding altitude and lithological variety in the Cantabrian Range context, Fuentes Carrionas holds some periglacial activity (gelifluction, frost shattering) which is absent elsewhere in NW Iberian Peninsula. This work is relates the soil thermal regime across the mountain gradient to landforms formation. 14 thermometers (11 i-button, protected in a plastic can, and three UTL data loggers) were buried at a shallow depth (10 cm.) between autumn 2009 and summer 2012. 12 thermometers were placed between 1900 and 2400 m.a.s.l. at 250 meters altitude interval at the four main aspects. Two additional thermometers were place in the Curavacas N face for permafrost identification. Thermometers were calibrated to yield a measurement every 6 hours starting from 8 AM during one year's time. Data was collected annually in the summer season. Some additional soil temperature data was obtained from an external project in the same area for the 2007-2009 interval. In this case thermometers were "Hobbo" model, and they were also buried to a shallow depth. Results show a permafrost free mountain range. Annual average soil temperatures range between 1 and 8 degrees Celsius. Snow pack appears as a decisive factor in winter temperatures, as the zero curtain effect can be tracked in many cases. Snow cover patterns show a distinctive behavior between S and N aspects, with a 3 months snow cover on the southern faces and between 6 and 9 at the northern analogues. This cover has a relevant impact on geomorphological processes. There is a clear relation between spring snow melt and solifluction or channelized erosion. Also, snow cover prevents the occurrence of freeze/thaw cycles

  6. Carbonates in mantle xenoliths from French Massif Central: inference for carbonatite-related metasomatism.

    NASA Astrophysics Data System (ADS)

    Wagner, Christiane; Deloule, Etienne

    2016-04-01

    Mantle xenoliths from the sub-continental lithospheric mantle (SCLM) frequently display evidence of metasomatism by melts or fluids of variable composition, e.g. alkali-basaltic, alkali-carbonate or carbonate melts. Carbonate-bearing mantle xenoliths are particularly interesting as highly mobile carbonate melts are likely prominent metasomatic agents of the mantle. This study presents detailed petrographic descriptions and major and trace element compositions of minerals in protogranular spinel lherzolites from the Mont Coupet occurrence (Devès province, French Massif Central), with focus on the carbonate phases to discuss their possible link to carbonatite melt. Two representative samples are described here. MC9 shows no evidence for infiltration of the host basanitic magma. Carbonates occur (1) as large (100 μm - 200 μm) anhedral crystals in interstitial pockets at triple point of primary olivine grains, (2) in a few cross-cutting veins (up to 200 μm width), (3) along grain boundaries and (4) in composite carbonate-silicate pockets from well-developed reaction zones, in which carbonates fill globular vesicles. The reaction zone contains secondary subhedral to euhedral phases: Al- and Ti-rich clinopyroxene, Ca-rich olivine, Cr-rich spinel and quenched plagioclase and relict sieved-textured primary spinel. MC2 shows carbonate-bearing thin (< 50 μm width) interconnected veinlets and only a few poorly-developed reaction zones around primary spinel. Large carbonate crystals (1), as in sample MC9, occur associated with (2) fibrous carbonate with a well-formed meniscus at the boundary between the two carbonate types. In some reaction zones the carbonate patches (3) show well-developed concentric carbonate structures, similar to those observed in the globular vesicles from the host basanite. In sample MC9, the carbonate is an alkali-free Mg-poor calcite (XCa = 0.95 - 0.98; with 0.5 - 1.8 wt. % MgO) whatever the occurrence. In sample MC2, carbonates are Mg

  7. Significance of Diamond-free Heterogeneous UHP Dolomitic Marble From the Kokchetav Massif

    NASA Astrophysics Data System (ADS)

    Aoki, K.; Ogasawara, Y.

    2003-12-01

    Local heterogeneity of fluid conditions during UHP metamorphism has been well demonstrated in a cm-scaled continuous sample of UHP marble (sample no. Y665) from the Kumdy-kol in the Kokchetav Massif. This banded carbonate rock sample consists of three zones; zone-A: dolomitic marble with abundant Ti-clinohumite, zone-B: dolomite marble, zone-C: dolomitic marble without forsterite and Ti-clinohumite. All three zones lack diamond. Zone-A consists of Ti-clinohumite, forsterite, diopside, Mg-calcite, dolomite, symplectite, and is characterized by the presence of Ti-clinohumite and by Ti-clinohumite-aragonite tie-line at the peak metamorphic condition. Diopside lacks lamella. Garnet is completely retrograded to symplectite (Di + Spl + Mg-Cal). Large-grained Ti-clinohumite shows clear compositional zoning of TiO2 between core (1.5-1.8 wt.%) and rim (2.2-3.4 wt.%). Some Ti-clinohumite grains contain very thin needles with preferred orientations. Zone-B consists mainly of dolomite, diopside, phlogopite, symplectite (Di + Spl + Mg-Cal) with minor amount of Mg-calcite, and is characterized by the stability of dolomite-diopside tie-line and by lack of Ti-clinohumite and forsterite. No lamella was observed in diopside. Garnet is rarely preserved. Zone-C consists mainly of Mg-calcite, dolomite, diopside, garnet and phlogopite and is characterized by phlogopite lamellae in diopside that indicate high pressure conditions. Phlogopite lamellae in diopside were confirmed by the laser Raman spectroscopy (Raman bands: 681.3 cm-1 and 357.9 cm-1 ) and by microprobe analysis. Lack of Ti-clinohumite and forsterite also characterizes this zone. Garnet has been well preserved from the retrograde reaction. High MgCO3 calcite (originally aragonite + dolomite) with large-grained exsolved dolomite lamellae occurs. All three zones have different bulk compositions each other; however, the tie-line relations cannot be explained by their bulk compositions. In zones C and B, diopside-dolomite tie

  8. Stability relations of Ti-bearing assemblages in UHP marbles from the Kokchetav Massif

    NASA Astrophysics Data System (ADS)

    Kikuchi, M.; Ogasawara, Y.

    2003-12-01

    Stability relations of Ti-bearing phases (rutile, titanite, Ti-clinohumite) in UHP marbles from the Kokchetav Massif, northern Kazakhstan were well analyzed by the phase relations in the model system CaO-MgO-SiO2-TiO2-CO2-H2O. Three types of UHP marbles have been described in the Kumdy-kol area: diamond-bearing dolomite marble (type-A), diamond-free Ti-clinohumite-bearing dolomitic marble (type-B), and diamond-free calcite marble (type-C) (Ogasawara et al., 2000; 2002), and they contain a distinct Ti-bearing phase, rutile, Ti-clinohumite, and titanite, respectively. The characteristics of these three marbles are as in the followings. Type-A: Dominant carbonate is dolomite. Abundant microdiamonds are included in garnet and diopside. Diopside-dolomite tie-line was stable. Diopside contains K-bearing silicate lamellar. The peak assemblage was dolomite + diopside + aragonite + garnet + rutile + diamond. Type-B: High MgCO3-calcite (originally aragonite + dolomite) is distinct. No diamond occurs. Diopside lacks lamellar texture. The peak assemblage was aragonite + dolomite + garnet + Ti-clinohumite or forsterite. Type-C: Only carbonate phase is calcite (originally aragonite). No diamond occurs. Titanite contains coesite exsolution lamellae and indicated supersilicic compositions stable at UHP conditions (P > 6GPa). Diopside contains phengite and K-feldspar lamellae. The peak assemblage was aragonite + diopside + K-feldspar + garnet + titanite. The solid-solid reaction, CaTiSiO5 (titanite) + CaMg(CO3)2 (dolomite) = CaCO3 (aragonite) + CaMgSi2O6 (diopside) + TiO2 (rutile), controlled the stability of Ti-bearing phases in calcite marble and dolomite marble. At UHP conditions, aragonite + diopside + rutile assemblage is stable compared with titanite + dolomite, and divides the compositional space into dolomite-free and dolomite-bearing tetrahedrons in the model system CaO-MgO-SiO2-TiO2. The presence of titanite in calcite marble indicates that the P-T condition was located

  9. L-tectonites and deep mantle wedge deformations in the Limo ultramafic massif (Cabo Ortegal Complex, NW Spain)

    NASA Astrophysics Data System (ADS)

    Puelles, Pablo; Ábalos, Benito; Gil Ibarguchi, José Ignacio; Mendia, Miren; José Santos Zalguegui, Francisco

    2010-05-01

    The Cabo Ortegal Complex is one of the Allochthonous Complexes of northwest Iberia. The complexes are variable subducted continental and oceanic lithosphere fragments obducted onto the Gondwana edge during the Variscan orogeny. They comprise a Lower Allochthon, a sandwiched ophiolitic complex, and an Upper Allochthon made of rock units metamorphosed under high-pressure conditions and amalgamated in an oblique subduction/collision orogenic channel. The structurally uppermost high-pressure sheet consists of arc-root lithospheric mantle peridotites that rest on high-pressure granulite facies rocks, eclogites and gneisses with eclogite boudins. The ultramafic rocks outcrop in three major massifs (Limo, Herbeira and Uzal from N to S) and in a number of much smaller klippen structures. They are serpentinized amphibole-bearing harzburgite, chromian spinel- and PGE-bearing dunite, and garnet-bearing massive pyroxenite. The Limo ultramafic massif has been considered so far as a fairly massive harzburgitic massif without a clear internal arrangement or fabric. However, new field data and microstructural observations show that harzburgites are L-tectonites and that this fabric is recognizable at various scales (from aerial photos to the outcrop and microscopic scales). The structures described form a hm-thick ultramafic tectonite stack which resembles the structural relationships already known in the easternmost sector of the neighbour Herbeira massif. Subhorizontal mineral and stretching lineations are defined by spinel and orthopyroxene and trend N010°-030°E. Extremely elongated sheath-like folds bear axes parallel to the lineation and show axial ratios >15, tubular and isoclinal structures in XZ sections and eye- and anvil-structures in structural sections perpendicular to the lineation. Sigmoidal shapes of peridotite foliation trajectories in XZ sections indicate a top-to-the-NNE tectonic displacement of hanging wall blocks (according to present-day geographic

  10. First findings of monocrystalline aragonite inclusions in garnet from diamond-grade UHPM rocks (Kokchetav Massif, Northern Kazakhstan).

    PubMed

    Korsakov, Andrey V; Vandenabeele, Peter; Perraki, Maria; Moens, Luc

    2011-10-01

    The presence of aragonite inclusions in garnet from diamond-grade metamorphic rocks from the Kokchetav Massif, Northern Kazakhstan was identified for the first time by means of Raman analyses and mapping. Aragonite appears within the inclusions up to 50 μm in size as a single crystal. These inclusions have rounded shape. The grain boundary between the host-garnet is smooth. No cracks occur around the aragonite inclusions. No significant shift in the main aragonite Raman band was measured. These observations indicate that residual pressure within the inclusion is minor. These findings imply either non-UHPM origin of the host garnet or significant plastic deformation of host minerals during retrograde stage. These features should be taken into account for recovery peak metamorphic conditions and modeling of exhumation processes of UHPM complexes. PMID:21247793

  11. The Cenozoic history of the Armorican Massif: New insights from the deep CDB1 borehole (Rennes Basin, France)

    NASA Astrophysics Data System (ADS)

    Bauer, Hugues; Bessin, Paul; Saint-Marc, Pierre; Châteauneuf, Jean-Jacques; Bourdillon, Chantal; Wyns, Robert; Guillocheau, François

    2016-05-01

    Borehole CDB1 (675.05 m) crosses the deepest Cenozoic sedimentary basin of the Armorican Massif, the Rennes Basin, to reach the underlying basement at a depth of 404.92 m, made up of the Late Neoproterozoic to Early Cambrian Brioverian Group, weathered down to 520 m depth. The basin's Cenozoic deposits are divided into seven formations, ranging from Early-Middle Bartonian to Late Pliocene in age. Coastal sediments at the very base, along with a thick Priabonian lacustrine episode, imply a major revision of the regional palaeogeography, whilst a very steady and low-energy lacustrine-palustrine environment throughout the Priabonian and Early Rupelian argue for an aggradational system associated with uniform subsidence. Palynological assemblages attest to environmental and climatic changes through the Eocene and Early Oligocene, in accordance with regional and global trends (Eocene-Oligocene Transition).

  12. Strain partitioning in the Belledonne and Pelvoux massifs. Some clues to understand the Variscan tectono-thermal evolution.

    NASA Astrophysics Data System (ADS)

    Fréville, Kévin; Trap, Pierre; Faure, Michel; Melleton, Jeremie; Blein, Olivier

    2016-04-01

    This contribution presents new structural, petrological, geochemical and geochronological data obtained in the Variscan basement of the Alpine Belledonne and Pelvoux External Crystalline massifs. The Belledonne-Pelvoux area is a stack of four litho-tectonic units. The uppermost unit is the early Ordovician Chamrousse ophiolite. It overthrusts a volcanic-sedimentary unit (VSU) made of an alternation of volcanoclastic rocks, plagiogranites and metapelites. The VSU crops out in the eastern Belledonne and western Pelvoux massifs. It is unconformably overlain by a Visean sandstone-conglomerate series with felsic lava (keratophyres). The lowermost litho-tectonic unit is made of felsic and mafic migmatites and granitoids that form the major part of the Pelvoux massif. The western boundary of this tectonic pile is the "synclinal median" strike-slip fault, on the western side of which crops out the Belledonne micaschist unit made of Cambro-ordovician turbiditic series. The structural analysis revealed four main tectono-thermal events: Dx, D1, D2, and D3. Dx is only recorded in relictual metamorphic assemblage in Ky-Grt-Ab bearing micaschist from the VSU holding an obduction metamorphic gradient (3kbar, 370°C up to 7kbar, 430°C). The age of the Dx event remains unknown. The D1 event, characterized by westward low-angle dipping foliation (S1) and a NE-SW striking stretching lineation (L1), is responsible for the crustal thickening resulting of the Eastward emplacement of the Chamrousse ophiolite upon the VSU. D1 is coeval with a barrovian metamorphism with P-T conditions of 6kbar, 600°C recorded in metapelites, and partial melting developed at the base of the VSU. Monazite LA-ICP-MS U-Pb dating revealed that D1 crustal thickening occurred at 337±7 Ma. D2 is a sinistral transpressional deformation responsible for the folding of S1 and L1, and the development of a NE-SW trending pervasive sub-vertical foliation S2. In the lower structural domain, i.e. the partially molten

  13. High grade metamorphism in the Bundelkhand massif and its implications on Mesoarchean crustal evolution in central India

    NASA Astrophysics Data System (ADS)

    Singh, S. P.; Dwivedi, S. B.

    2015-02-01

    The Bundelkhand Gneissic Complex (BnGC) in the central part of the Bundelkhand massif preserves a supracrustal unit which includes pelitic (garnet-cordierite-sillimanite gneiss, garnet-sillimanite gneiss, biotite gneiss and garnet-biotite gneiss) and mafic (hornblende-biotite gneiss and garnetiferous amphibolite) rocks. Granulite facies metamorphism of the complex initiated with breaking down of biotite to produce garnet and cordierite in the pelitic gneisses. Geothermobarometric calculations indicate metamorphic conditions of 720°C/6.2 kbar, followed by a retrograde (687°C/4.9 kbar) to very late retrograde stages of metamorphism (579°C/4.4 kbar) which is supported by the formation of late cordierite around garnet. The P-T conditions and textural relations of the garnet-cordierite-bearing gneiss suggest a retrograde cooling path of metamorphism.

  14. Platinum potential of mafic-ultramafic massifs in the western part of the Dambuka ore district (Upper Amur Region, Russia)

    NASA Astrophysics Data System (ADS)

    Melnikov, A. V.; Stepanov, V. A.; Moiseenko, V. G.

    2016-02-01

    New data on the Pt potential of mafic-ultramafic massifs of the Khani-Maya, Uldegit, and Dzhalta complexes in the western part of the Dambuka ore district are discussed. The Khani-Maya Complex is represented by metamorphosed gabbro, gabbronorites, gabbro anorthosites, subordinate pyroxenites, hornblendites, and peridotites. The Uldegit Complex is composed of pyroxenites, hornblendites, gabbro, gabbronorites, norites, troctolites, peridotites, dunites, actinolite-tremolites, serpentinites, anthophyllites, and tremolite-plagioclase rocks. The Dzhalta Complex is formed of peridotites, gabbro, eclogitized gabbro, hornblendites, cortlandites, and pyroxenites. All these complexes differ from each other by the concentrations of Ni, Cu, Co, Au, and platinoids depending on the composition of the constituting rocks and the presence of sulfide minerals.

  15. A preliminary spatial-temporal study of some soil characteristics in the calcareous massif of Sicó, Portugal.

    PubMed

    Torres, Maria Odete; Neves, Maria Manuela

    2016-01-01

    The mountainous massif of Sicó, in the centre of Portugal, is an extensive area composed of calcareous Jurassic formations. Hillside calcareous soils, with high pH, present chemical restrictions to support plant growth and are subjected to important erosion processes leading to their degradation if not protected by vegetation. In a first year of study some soil physicochemical characteristics have been measured in some geo-referenced locations of a larger design experiment and an exploratory spatial analysis has been performed. The objective of this study was to present some suggestions in order to give sustainable phosphorus fertiliser recommendations aiming to establish pastures in these soils and thus support traditional livestock activity. Ten years apart, those soil characteristics have been measured again in the same locations and comparisions have been made. The objective was to understand the variability of the soil properties under study in order to better adequate the fertiliser soil management regarding the area restoration. PMID:27087036

  16. Subduction and exhumation structures preserved in Cerro del Almirez HP metaserpentinites (Betic Cordillera, SE Spain)

    NASA Astrophysics Data System (ADS)

    Jabaloy-Sánchez, Antonio; López Sánchez-Vizcaíno, Vicente; Gómez-Pugnaire, María Teresa; Padrón-Navarta, José Alberto; Garrido, Carlos J.

    2014-05-01

    The Cerro del Almirez massif (Nevado-Filábride Complex, Betic Cordillera, SE Spain) is composed of antigorite serpentinite and chlorite harzburgite separated by a thin reaction front in a paleo-subduction setting. Structural analysis of ultramafic lithologies and metasedimentary host rocks provides information on the tectonic evolution of this massif during prograde metamorphism in a subduction zone and during subsequent exhumation. Here we report for the first time HP structures related to a subduction event underwent by ultramafic rocks of the Nevado-Filábride Complex. The oldest subduction-related structures are preserved in Atg-serpentinites: a penetrative S1 foliation and associated L1 stretching lineation were formed in a non-coaxial regime with a top-to-the-W sense of shearing. This planar linear fabric is crosscut by olivine ± Ti-clinohumite veins formed during the prograde breakdown of brucite and pre-metamorphic clinopyroxene at temperatures ranging from 465 to 500 ºC [1]. Veins occur as a system of decimetric long joints, some of them hybrid open and sheared veins with associated drag folds. They recorded embrittlement processes due to the release of 6% vol. H2O of the rock. S1 foliation can, however, be simultaneous with or be overgrown by olivine and/or tremolite porphyroblasts, product of the prograde reaction Di + Atg → Fo + Tr + H2O, which occurred at T > 600 ºC and P = 1.7-1.9 GPa [1]. Generation of S1/L1 fabric was followed by static annealing at ca. 680 ºC and 1.6-1.9 GPa [2]. The S1/L1 fabric in Atg-serpentinite is crosscut by the Atg-out isograd and overgrown by the Atg-serpentinite dehydration products that gave place to Chl-harzburgite. Peak metamorphic conditions of the Chl-harzburgite assemblage reached 680-710 ºC and 1.6-1.9 GPa [3]. Prograde Chl-harzburgite is crosscut by sets of conjugate zones associated to grain-size reduction of olivine grains [3]. These grain size reduction zones are interpreted as brittle structures

  17. Unravelling the effects of melt depletion and secondary infiltration on mantle Re-Os isotopes beneath the French Massif Central

    NASA Astrophysics Data System (ADS)

    Harvey, J.; Gannoun, A.; Burton, K. W.; Schiano, P.; Rogers, N. W.; Alard, O.

    2010-01-01

    Spinel lherzolite xenoliths from Mont Briançon, French Massif Central, retain evidence for multiple episodes of melt depletion and melt/fluid infiltration (metasomatism). Evidence for primary melt depletion is still preserved in the co-variation of bulk-rock major elements (MgO 38.7-46.1 wt.%; CaO 0.9-3.6 wt.%), and many samples yield unradiogenic bulk-rock Os isotope ratios ( 187Os/ 188Os = 0.11541-0.12626). However, many individual xenoliths contain interstitial glasses and melt inclusions that are not in equilibrium with the major primary minerals. Incompatible trace element mass balance calculations demonstrate that metasomatic components comprise a significant proportion of the bulk-rock budget for these elements in some rocks, ranging to as much as 25% of Nd and 40% of Sr Critically, for Re-Os geochronology, melt/fluid infiltration is accompanied by the mobilisation of sulfide. Consequently, bulk-rock isotope measurements, whether using lithophile (e.g. Rb-Sr, Sm-Nd) or siderophile (Re-Os) based isotope systems, may only yield a perturbed and/or homogenised average of these multiple events. Osmium mass balance calculations demonstrate that bulk-rock Os in peridotite is dominated by contributions from two populations of sulfide grain: (i) interstitial, metasomatic sulfide with low [Os] and radiogenic 187Os/ 188Os, and (ii) primary sulfides with high [Os] and unradiogenic 187Os/ 188Os, which have been preserved within host silicate grains and shielded from interaction with transient melts and fluid. The latter can account for >97% of bulk-rock Os and preserve geochronological information of the melt from which they originally precipitated as an immiscible liquid. The Re-depletion model ages of individual primary sulfide grains preserve evidence for melt depletion beneath the Massif Central from at least 1.8 Gyr ago despite the more recent metasomatic event(s).

  18. Endolithic microbial communities in carbonate precipitates from serpentinite-hosted hyperalkaline springs of the Voltri Massif (Ligurian Alps, Northern Italy).

    PubMed

    Quéméneur, Marianne; Palvadeau, Alexandra; Postec, Anne; Monnin, Christophe; Chavagnac, Valérie; Ollivier, Bernard; Erauso, Gaël

    2015-09-01

    The Voltri Massif is an ophiolitic complex located in the Ligurian Alps close to the city of Genova (Northern Italy) where several springs discharge high pH (up to 11.7), low salinity waters produced by the active serpentinization of the ultramafic basement. Mixing of these hyperalkaline waters with the river waters along with the uptake of atmospheric carbon dioxide forms brownish carbonate precipitates covering the bedrock at the springs. Diverse archaeal and bacterial communities were detected in these carbonate precipitates using 454 pyrosequencing analyses of 16S ribosomal RNA (rRNA) genes. Archaeal communities were dominated by members of potential methane-producing and/or methane-oxidizing Methanobacteriales and Methanosarcinales (Euryarchaeota) together with ammonia-oxidizing Nitrososphaerales (Thaumarchaeota) similar to those found in other serpentinization-driven submarine and terrestrial ecosystems. Bacterial communities consisted of members of the Proteobacteria, Actinobacteria, Planctomycetes, Bacteroidetes, Chloroflexi, and Verrucomicrobia phyla, altogether accounting for 92.2% of total retrieved bacterial 16S rRNA gene sequences. Amongst Bacteria, potential chemolithotrophy was mainly associated with Alpha- and Betaproteobacteria classes, including nitrogen-fixing, methane-oxidizing or hydrogen-oxidizing representatives of the genera Azospirillum, Methylosinus, and Hydrogenophaga/'Serpentinomonas', respectively. Besides, potential chemoorganotrophy was attributed mainly to representatives of Actinobacteria and Planctomycetales phyla. The reported 16S rRNA gene data strongly suggested that hydrogen, methane, and nitrogen-based chemolithotrophy can sustain growth of the microbial communities inhabiting the carbonate precipitates in the hyperalkaline springs of the Voltri Massif, similarly to what was previously observed in other serpentinite-hosted ecosystems. PMID:25874424

  19. Structure and modeling of disorder in miserite from the Murun (Russia) and Dara-i-Pioz (Tajikistan) massifs

    NASA Astrophysics Data System (ADS)

    Kaneva, Ekaterina; Lacalamita, Maria; Mesto, Ernesto; Schingaro, Emanuela; Scordari, Fernando; Vladykin, Nikolay

    2014-01-01

    The structure, structural disorder and chemistry of miserite from the charoite-bearing rocks of the Murun massif (Russia) and from alkaline-syenite pegmatitic rocks of the Dara-i-Pioz massif (Tajikistan) were investigated employing a combination of electron microprobe, single crystal diffraction and micro-Fourier transform infrared spectroscopy analysis. Chemical analysis of the sample investigated by X-ray diffraction evidenced that Dara-i-Pioz miserite has a greater REE concentration than Murun miserite (~0.22 vs. 0.05 apfu, respectively) and also contains Y (0.14 apfu), which is absent in Murun miserite. The occurrence of a band at about 1,600 cm-1 testified to the presence of H2O in miserite at hand. Structural analyses yielded average cell parameters of a = 10.092, b = 16.016, c = 7.356 Å, α = 96.60°, β = 111.27° and γ = 76.34°. Anisotropic structural refinement in space group P converged at similar values for the analyzed samples ( R ~3.4, R w ~3.8 %). An interesting feature shown by both the miserite specimen is the presence, revealed by difference Fourier analysis, of a disordered part of the structure. This turned out to be due to the flipping of the tetrahedra belonging to the isolated [Si2O7]6- diorthogroups, one of the two radicals (the other is [Si12O30]12-) characterizing the miserite structure. The sixfold and seven-vertex Ca polyhedra linked to the inverted diorthogroups show variation in coordination number with respect to those of the ordered structure.

  20. Magmatic/metasomatic amphibole in the mantle: evidence from the Balmuccia lherzolite massif, Ivrea zone, western Italian Alps

    SciTech Connect

    Shervais, J.W.

    1985-01-01

    Amphibole and mica are the most important alkali-rich phases stable under mantle P-T conditions, and constitute the primary source of the alkalis needed to form basaltic magmas. Yet, the origin and distribution of these phases in the upper mantle is poorly understood. The Balmuccia lherzolite massif is a small slice of subcontinental mantle in the western Alps that intruded granulite facies lower crust 250 m.y. ago, and was exposed during the Alpine orogeny. Amphibole (HB) ranging in composition from Ti-pargasite to kaersutite in a minor but widespread accessory phase in the lherzolite, in websterite and bronzite dikes of the Cr-Di suite, and in pyroxenite and gabbro dikes of the Al-Aug suite. Textural and compositional relations show that HB in the Cr-Di and Al-Aug suite dikes formed by crystallization of residual magma, or by reaction between this magma and earlier formed phases (primarily spinel). Hb also occurs in thin (1-2 cm) veins of hornblendite and pyroxene hornblendite, and in the HB-enriched wallrock adjacent to these veins. Similar Hb veins in the Lherz massif have been shown to form from an alkali and water-enriched residual magma derived by filter pressing of Al-Aug pyroxenites. This origin is not possible at Balmuccia because the Hb veins have higher Ti, Cr, K/Na and Mgnumbers than any accessory Hb in Al-Aug suite dikes. Fractionation trends in the veins are controlled by HB. This requires that the HB veins formed from a separate and distinct parent magma that metasomatically enriched the lherzolite on a local scale. However, remelting of the widespread pyroxenite dikes may constitute a more important source of alkalis than the rare HB-rich veins.

  1. Statistical adaptation of ALADIN RCM outputs over the French alpine massifs - application to future climate and snow cover

    NASA Astrophysics Data System (ADS)

    Rousselot, M.; Durand, Y.; Giraud, G.; Mérindol, L.; Dombrowski-Etchevers, I.; Déqué, M.

    2012-01-01

    In this study, snowpack scenarios are modelled across the French Alps using dynamically downscaled variables from the ALADIN Regional Climate Model (RCM) for the control period (1961-1990) and three emission scenarios (SRES B1, A1B and A2) by the mid- and late of the 21st century (2021-2050 and 2071-2100). These variables are statistically adapted to the different elevations, aspects and slopes of the alpine massifs. For this purpose, we use a simple analogue criterion with ERA40 series as well as an existing detailed climatology of the French Alps (Durand et al., 2009a) that provides complete meteorological fields from the SAFRAN analysis model. The resulting scenarios of precipitation, temperature, wind, cloudiness, longwave and shortwave radiation, and humidity are used to run the physical snow model CROCUS and simulate snowpack evolution over the massifs studied. The seasonal and regional characteristics of the simulated climate and snow cover changes are explored, as is the influence of the scenarios on these changes. Preliminary results suggest that the Snow Water Equivalent (SWE) of the snowpack will decrease dramatically in the next century, especially in the Southern and Extreme Southern part of the Alps. This decrease seems to result primarily from a general warming throughout the year, and possibly a deficit of precipitation in the autumn. The magnitude of the snow cover decline follows a marked altitudinal gradient, with the highest altitudes being less exposed to climate change. Scenario A2, with its high concentrations of greenhouse gases, results in a SWE reduction roughly twice as large as in the low-emission scenario B1 by the end of the century. This study needs to be completed using simulations from other RCMs, since a multi-model approach is essential for uncertainty analysis.

  2. Middle Proterozoic emplacement and deformation of metanorthosite and related rocks in the northeastern Marcy massif, Adirondack Mountains, New York

    SciTech Connect

    Fakundiny, R.H. ); Muller, P.D. . Dept. of Earth Sciences)

    1993-03-01

    Geologic mapping in the Elizabethtown and Mount Marcy 15 foot quadrangles in the northeastern Adirondack Mountains has shown that Middle Proterozoic anorthosite suite rocks of the Marcy massif were intruded in at least two temporally distinguishable episodes separated by a period of localized ductile shearing. Strain was concentrated in a 100 m to > 1 km thick zone consisting mainly of metamorphosed gabbroic anorthosite, ferrodiorite, and ferrosyenite gneiss with subordinate granite gneiss, calc-silicate gneiss, amphibolite, and marble. This zone of flat to steeply-dipping layered gneisses, designated the Elizabethtown ductile deformation zone (EDDZ) for exposures along Rt 9 south of Elizabethtown, appears to extend from Lake Champlain on the east to at least Lake Placid on the west. Its upper boundary is most clearly evident where it occurs in olivine metagabbro bodies of Jay and Iron Mountain. Massive metagabbro is sheared and recrystallized into amphibolite gneiss. The lower boundary of the zone is more difficult to map, but commonly lies within contaminated metamorphosed gabbroic anorthosite and ferrodiorite gneiss that characterize the margins of the massif in the area. Rocks of the EDDZ display pervasive mesoscopic S and LS fabrics, but exhibit totally recrystallized microtextures. Kinematic indicators such as winged porphyroclasts and S-C fabrics are sporadically developed and provide a regionally ambiguous sense of shear. The authors favor a regional extension origin for the fabrics. Mineral assemblages defining the EDDZ fabrics are consistent with granulite facies conditions during shear-zone development and suggest a lower crustal position. Mapping suggests that the younger anorthosite intrusions were mainly domical and generated a chaotic contact zone typified by block structure and dikes of ferrodiorite, ferromonzonite, and ferrosyenite.

  3. The rare-metal ore potential of the Proterozoic alkaline ultramafic massifs from eastern part of the Baltic Shield in the Kola alkaline province.

    NASA Astrophysics Data System (ADS)

    Sorokhtina, Natalia; Kogarko, Lia

    2014-05-01

    The Kola Alkaline Province consists of intrusions of two main stages of the intraplate alkaline magmatism. The early stage of igneous activity occurred in Proterozoic 1.9 billion years ago, the next in Paleozoic at 380 million years. The Proterozoic alkaline magmatism produced Gremyakha-Vyrmes and Elet'ozero large alkaline-ultrabasic massifs, Tiksheozero carbonatite massif and numerous small syenite complexes. Paleozoic magmatism on Baltic Shield exhibited more widely, than Proterozoic. The world largest Khibiny and Lovozero alkaline intrusions, numerous alkaline-ultrabasic massifs with carbonanites, alkaline dike swarms and diatremes were formed. It is well known that carbonatites of Paleozoic alkaline-ultrabasic massifs contain large-scale deposits of rare-metal ores (Afanasiev et al., 1998). The metasomatic rocks on foidolites and carbonatites of Gremyakha-Vyrmes are final products of differentiation of Proterozoic alkaline-ultrabasic magma enriched in incompatible elements, including Nb and Zr similar to Paleozoic carbonatites. The massif Gremyakha-Vyrmes is one of the largest titanomagnetite-ilmenite deposits in Russia associated with ultrabasites. Our investigation showed that albite-microcline and aegirine-albite metasomatites formed rich rare-metal ores consisting of 3.2 wt. % Nb2O5 and 0.7 ZrO2. Zircon and pyrochlore-group minerals represent the main minerals of rare-metal ores. The following evolutionary sequences of pyrochlore group minerals has been observed: betafite or U pyrochlore - Na-Ca pyrochlore - Ba-Sr pyrochlore - "silicified" pyrochlore - Fe-Nb, Al-Nb silicates. Such evolution from primary Nb oxides to secondary silicates under low temperature hydrothermal conditions is similar to the evolution of rare metal phases in Paleozoic alkaline massifs analogous to Lovozero syenites and in carbonatites. The rare metal minerals of Gremyakha-Vyrmes crystallized in high alkaline hydrothermal environment at increased activity of Nb, Ta, Zr, U, Th and at

  4. Physico-chemical conditions of crystallization of the Guli ulrabasic massif (North Part of the Siberian Platform): evidence from melt inclusions

    NASA Astrophysics Data System (ADS)

    Simonov, Vladimir; Vasiliev, Yuri; Kotlyarov, Alexey; Stupakov, Sergey

    2014-05-01

    Conditions of formation of the Guli ultrabasic massif (Maimecha Kotui Province in the North Part of the Siberian Platform) attract attention of numerous researchers. For the solution of genetic problems of various rocks from this ultramafic complex the data on melt inclusions in minerals has been earlier used (Sokolov et al., 1999; Rass, Plechov, 2000; Sokolov, 2003; Panina, 2006). At the same time, formation of dunites, occupying the main volume of the Guli massif, remain almost not considered by means of thermobarogeochemical methods and the role of magmatic processes in this case is not ascertained. As a result of melt inclusions study in the Cr-spinel the new data on physical and chemical parameters of dunite crystallization in the Guli ulrabasic massif was obtained. On the ratio (Na2O + K2O) - SiO2 the majority of analyses of glasses and calculated compositions of inclusions settle down in the field of subalkaline series. On the diagram MgO - SiO2 bulk chemical compositions of inclusions (with the magnesium content of 19-28 wt. %) correspond to picrites and picrite-basalts. They are in close association with the data on inclusions in the Cr-spinel from dunites of Konder (Siberian Platform) and Nizhnii Tagil (Ural Mountains) platinum-bearing ultrabasic massifs and also are situated near to the field of inclusions in the olivine phenocrysts from meimechites (Maimecha Kotui Province in the North Part of the Siberian Platform). Similarity of melt inclusions in the Cr-spinel from the dunite of the Guli massif and in the olivine from meimechites is established on the variety of petrochemical components - Al2O3, CaO, Na2O, K2O. The calculated compositions of inclusions from dunites coincide mostly with the data on inclusions from meimechites, while glasses of inclusions from Cr-spinel contain less titan and magnesium. As a whole for the melts of the Maimecha Kotui Province (that form both dunites of the Guli massif and meimechites) much higher contents of TiO2 (from

  5. Electrodeposition of In-Se, Cu-Se, and Cu-In-Se thin films

    SciTech Connect

    Bhattacharya, R.N.; Fernandez, A.M.; Contreras, M.A.; Keane, J.; Tennant, A.L.; Ramanathan, K.; Tuttle, J.R.; Noufi, R.N.; Hermann, A.M.

    1996-03-01

    Indium-selenium, copper-selenium, and copper-indium-selenium thin films have been prepared by electrodeposition techniques on molybdenum substrates. Electrodeposited precursors are prepared at varying potentials, pH, and deposition times. The adhesion and uniformity of indium selenide on molybdenum substrates are improved by electrodepositing an initial copper layer (500 {angstrom}) on molybdenum. The films (In-Se, Cu-Se, and Cu-In-Se) are annealed at 250 and 450 C in Ar for 15 min and are slow-cooled (3 C/min). The films are characterized by electron microprobe analysis, inductive-coupled plasma spectrometry, X-ray diffraction analysis, Auger electron spectroscopy, and scanning electron microscopy. The as-deposited precursor films are loaded in a physical evaporation chamber and addition In or Cu and Se are added to the film to adjust the final composition to CuInSe{sub 2}. The device fabricated using electrodeposited Cu-In-Se precursor layers resulted in a solar cell efficiency of 9.4%.

  6. The fluid phase evolution during the formation of carbonatite of the Guli massif: Evidence from the isotope (C, N, Ar) data

    NASA Astrophysics Data System (ADS)

    Buikin, A. I.; Verchovsky, A. B.; Kogarko, L. N.; Grinenko, V. A.; Kuznetsova, O. V.

    2016-02-01

    The first data on variations of the isotope composition and element ratios of carbon, nitrogen, and argon in carbonatites of different generations and ultrabasic rocks of the Guli massif obtained by the method of step crushing are reported. It is shown that early carbonatite differs significantly from the later ones by the concentration of highly volatile components, as well as by the isotope compositions of carbon (CO2), argon, and hydrogen (H2O). The data obtained allow us to conclude that the mantle component predominated in the fluid at the early stages of formation of rocks of the Guli massif, whereas the late stages of carbonatite formation were characterized by an additional fluid source, which introduced atmospheric argon, and most likely a high portion of carbon dioxide with isotopically heavy carbon.

  7. Reply to Comment on "The Late Devonian Variscan suture of the Iberian Massif: A correlation of high-pressure belts in NW and SW Iberia"

    NASA Astrophysics Data System (ADS)

    Fernández, Rubén Díez; Arenas, Ricardo

    2016-02-01

    The existence of a large allochthonous nappe pile emplaced onto the hinterland of the Iberian Massif and covering most of the basement of NW and SW Iberia proposed by Díez Fernández and Arenas has been called into question on the basis of structural, geophysical, and regional data from SW Iberia. The discussion provided here is based on a revision of the fundamentals of the Variscan geology of NW Iberia and on a more detailed presentation of the geology of SW Iberia. Our counterarguments reveal the reasoning of Simancas et al. against the verisimilitude of the large allochthonous pile as inconclusive, incomplete, or erroneous in some cases. Therefore, we maintain that our structural correlation and its implications remain fully valid for the case of the Iberian Massif.

  8. Use of Digital Elevation Models to understand map landforms and history of the magmatism Khibiny Massif (Kola Peninsula, Russia)

    NASA Astrophysics Data System (ADS)

    Chesalova, Elena; Asavin, Alex

    2016-04-01

    This work presents an improved geomorphological methodology that uses 3D model of relief, remotely-sensed data, geological, geophysical maps and tools of Geographical Information Systems. On the basis of maps of 1: 50,000 and 1: 200,000 the Digital Elevation model (DEM) of Khibiny massif was developed. We used software ARC / INFO v10.2 ESRI. A DEM was used for analyzing landform by extracting the slope gradient, curvature, valley pro?les, slope, aspect and so on. The results were gradually re?ned from the interpretation of satellite imagery and geological map Geomorphological analysis will allow us to determine spatial regularities in inner massive construction. We try to found areas where gas emissions (CH4/H2) enrich, according to morphometry, geology, tectonic and other environments. The main regional blocks were de?ned by different morphological evidences: impression zone, similar to subsidence caldera; uplift zone, domed area (located in the highest part of massif and zone of intersection of main faults) and others. It says that there are the few stages in the development of the Khibiny massif. There is no common concept of the consequence of intrudes magmatic phases now. And we hope that our geomorphical analysis take a new evidences about this problems. Locations of the blocks' borders (tectonic zones) were recognized by lineament analysis of valleys and tectonic faults presented in relief. Erosion system is represented by valleys of 4 ranks. It inherits the zone of tectonic disturbances 3 groups of faults were recognized: 1) Global lineament system cross whole peninsula - existing before Khibiny massif intrusion; 2) Faults associated with the formation of the intrusive phases sequence and magma differentiation and with later collision history during magma cooling; 3) Crack system related to neotectonic process. We believed that if different magmatic phases intrude in similar tectonic environment, the common spatial system of faults will be formed. Really we

  9. The Armorican Massif (Western France) - A buried relief two times exhumed in response to Iberia-Eurasia movements (Early Cretaceous, base of Cenozoic)

    NASA Astrophysics Data System (ADS)

    Bessin, Paul; Guillocheau, François; Robin, Cécile; Bauer, Hugues; Schroëtter, Jean-Michel

    2014-05-01

    The Armorican Massif is an outcropping Variscan basement located in Western France. The age of its exhumation is debated, as most of the outcropping European basements: Is this relief a remnant of the planation of the Variscan Belt or a buried and then exhumed relief at time of the North-Atlantic (Biscay Bay) opening during Early Cretaceous or/and during the Africa-Eurasia convergence? We performed a geomorphological study (based on DEM analysis and field controls) of the different landforms of the Armorican Massif. The dating of those relief forms is based on their geometrical relationships with the weatherings and dated preserved sediments. Our results allow to propose a model of evolution of the Armorican Massif and of its relief for the Mesozoic to Cenozoic period and underscore four main points: (1) The Armorican relief preserved old landforms - planation surfaces (mainly pediments and pediplains) - of Triassic (?) to Early Cretaceous age buried by Jurassic and Upper Cretaceous (chalk) carbonate platforms. (2) Those paleo-landforms were exhumed at two periods (i) Early Cretaceous in response to the opening of the Biscay Bay and (ii) Upermost Cretaceous-Paleocene at time of the Iberia-Eurasia increasing of convergence. (3) A major planation surface - called the Armorican Surface - result from the Early Cretaceous physical and chemical (laterite) erosion when the Armorican Massif was the North rift shoulder of the Biscay Bay. This planation surface is later deformed (buckling?) and eroded during Uppermost Cretaceous and Paleocene. (4) During Paleogene times, a last generation of pediments is shaped and then flooded by the Mid-Miocene eustatic sea-level rise. (5) The Armorican relief and landforms is later incised by rivers, (i) during Upper Miocene to Pliocene and (ii) at the Early to Middle Pleistocene transition with the incision of the present-day valleys in both response to uplift (Apulia-Eurasia convergence) and climate (precipitation) change.

  10. Stable isotope and Ar/Ar evidence of prolonged multiscale fluid flow during exhumation of orogenic crust: Example from the Mont Blanc and Aar Massifs (NW Alps)

    NASA Astrophysics Data System (ADS)

    Rossi, M.; Rolland, Y.

    2014-09-01

    The spatial and temporal scales and the geometry of fluid pathways in a collisional orogen are investigated using stable isotope analysis (O, C, and H) and 40Ar/39Ar dating of vein minerals formed at circa 11-16 Ma in the Mont Blanc and the Aar External Crystalline Massifs. In both massifs 40Ar/39Ar dating of veins adularia provides evidence for progressive crystallization from 16 to 9 Ma, and mainly at 11-12 Ma following veins opening during shear zone activity. The fluid flow duration thus ranges from 4 to 5 Ma in the two massifs. The δ18O values of vein quartz and calcite are similar to those of undeformed crystalline and sedimentary host rocks, suggesting rock buffering, while carbon isotope ratios of vein calcites fall into three compositional groups. A-type veins have δ13C values that are buffered by the Helvetic metasediments, which suggests that these veins formed in a closed system from a locally derived CO2-rich fluid. The fluid in equilibrium with C-type veins has depleted δ13C values similar to mantle-CO2, while the intermediate δ13C values of B-type veins suggest mixing between the A-type and C-type fluids. These results are in agreement with crustal- to lithosphere-scale upward vertical fluid flow along vertical shear zones related to the strike-slip system bounding the Adriatic block since 16-20 Ma, connecting a deep-seated fluid to some downward flow in the sedimentary cover of External Crystalline Massifs.

  11. Genesis and significance of the silico-aluminous nodules in the Ordovician of the Montagne Noire and the Massif Armoricain (France)

    NASA Astrophysics Data System (ADS)

    Becq-Giraudon, Jean-François; Bouillé, Suzanne; Chauvel, Jean-Jacques

    1992-04-01

    Siliceous nodules of the Arenigian of the Montagne Noire (southern France) and the Massif Armoricain (western France) are made up of quartz, illite and chlorite with secondary apatite and, less frequently, dolomite. Diffractometrical and geochemical data indicate that the chlorite is a chamosite (trioctahedral 2:1 chlorite), whose development may be accompanied by that of apatite and diminution of illite. Three types of nodules are defined: Type 1, siliceous nodules, with more than 85% of SiO 2, very frequent in the Montagne Noire; Type II, nodules made of a micaceous siltstone with chlorite matrix, abundant in the Massif Armoricain but present also in the Montagne Noire; Type III, chloritic nodules with a finely globular structure, especially developed in the Massif armoricain but observed in the Montagne Noire as well. The nodules are always poorer in illite than their host sediments and often show traces of the initial sediments. Their formation occurs after the deposition and prior to the development of foliation. The frequent presence of undistorted fossil remains suggests an early formation linked to the physico-chemical modifications occurring in an unconsolidated sediment around a decaying organism. The post-depositional mineralogical evolution should have started with an illite/dolomite assemblage and end up with a chamosite-dominant one, under cold climatic conditions. The simultaneous presence of the three types of nodules in the same formation, or even in the same beds, shows that this mineralogical differentiation is not strictly related to the diagenetic and metamorphic transformation of this material.

  12. The last stages of the Avalonian-Cadomian arc in NW Iberian Massif: isotopic and igneous record for a long-lived peri-Gondwanan magmatic arc

    NASA Astrophysics Data System (ADS)

    Andonaegui, Pilar; Arenas, Ricardo; Albert, Richard; Sánchez Martínez, Sonia; Díez Fernández, Rubén; Gerdes, Axel

    2016-06-01

    The upper allochthonous units of NW Iberian Massif contain an extensive Cambrian magmatism (c. 500 Ma), covering felsic to mafic compositions. The magmatic activity generated large massifs of granitoids and gabbros, with calc-alkaline and tholeiitic compositions respectively. Petrological and geochemical features of these massifs are characteristic of volcanic arc. The plutons intruded siliciclastic sedimentary series deposited in the periphery of the West Africa Craton. U-Pb/Hf isotopic compositions of detrital zircon in the siliciclastic host series, indicate continental arc activity between c. 750 Ma and c. 500 Ma. It was characterized by a large variety of isotopic sources, including from very old continental input, even Archean, to the addition of a significant amount of juvenile mafic material. These isotopic sources experienced an extensive mixing that explains the composition and isotopic features (εHft from - 50 until + 15) of the represented Cambrian plutons. The Cambrian igneous rocks of the upper units of NW Iberia are related to the latest activity of the Avalonian-Cadomian arc. From the Middle Cambrian arc activity in the periphery of Gondwana was replaced by pronounced extension associated with the development of continental rifting, which finally led to separation of the microcontinent Avalonia. Subsequent drifting of Avalonia to the North caused progressive opening one of the main Paleozoic ocean, the Rheic Ocean.

  13. Incidence of mass movement processes after an historical episode of heavy snowfall in the Asturian Massif (Northern Spain)

    NASA Astrophysics Data System (ADS)

    Garcia-Hernandez, Cristina; Ruiz-Fernández, Jesús; Gallinar, David

    2015-04-01

    This research examines a mass movement event caused in the context of the Great Blizzard of 1888, one of the most severe recorded blizzards in the history of Europe, whose implications go far beyond. In the Asturian Massif the episode consisted in four linked and consecutive snowstorms that took place between the 14th of February 1888 and the 8th of April 1888, creating snow covers with a depth ranging between 5 and 7 m, snow avalanches and flooding, causing dozens of deaths and large material damage. The Asturian Massif belongs to the Atlantic-climate area and is composed mainly by sedimentary and metamorphic paleozoic rocks. Many sectors of the Massif are between 1.000 and 2.000 m a.s.l., and its topography is characterized by a great height difference and steep slopes. Because of the lack of deep soils suitable for farming, the main traditional activity has been livestock keeping, and goods traffic. We have devised a method that enables the reconstruction of this event on the basis of nivo-meteorogical conditions, geographical location and socio-economic impact. The mass movement episode has been studied through the issues of 6 newspapers published in Asturias between the 20th of January and 30th of May 1888, the ancient meteorological station data of the University of Oviedo, and field work. A logical database structure has been designed with the aim to store and cross the information for statistical analysis. Thirty six mass movement worthy of consideration were documented, 28 of them causing material damage (six homes destroyed and at least 22 interruptions with the traffic flow on roads, highways and railways). Ten high- and mid-elevation mountain municipalities were affected by mass movement. We must consider that only the most important events, or those that happened in crowded places, have been considered by the newspapers, so the total number of mass movements should be considered as a minimum figure. We have got to identify and classify 27 of them; 16

  14. Chronology and evolution of glacio-nival systems of Mongun-Taiga mountain massif in Late Pleistocene and Holocene

    NASA Astrophysics Data System (ADS)

    Ganushkin, Dmitry; Chistyakov, Kirill

    2013-04-01

    The main glacial complex of western Tuva - Mongun-Taiga mountain massif (3970.5 m) is situated in the center of Altai-Sayan mountain system. Modern glaciation of the massif has area about 20 km2, average firn line altitude is about 3400 m. Average summer temperatures at the firn line is 0.5°C, precipitation about 270 mm. We studied glacial fluctuations of the past on base of geomorphologic methods and radiocarbon dating of peat, soils and wood samples. Moraines of the Early Stage of the Last Glaciation (MIS 4) extend from cirques and troughs to the flat piedmonts forming lobes reaching the level of 1830 m in the south of the massif and 2200 ° in the north. There are traces of 4 glacial advances, during the maximal the area of glaciation reached 513 km2 with 800 m of depression of firn line. We reconstructed that average summer temperatures were 2.5°C below present with precipitation 2.3 times more than now. During MIS 3 the area of glaciation reduced to less than 0.5 km2 with 450-490 m of elevation of firn line. Samples of moraine-buried wood with with radiocarbon age about 58-39 and 27-25 kBP found 600 m higher than present upper limit of growth of trees give evidence of climatic conditions at least 1.5°C warmer than present (with a correction for tectonics). In the Late Stage of the Last Glaciation glaciers mostly remained inside troughs reaching during the maximum the level of 2200 m in the south and 2400 m in the north, the area of glaciation about 320 km2, firn line depression about 690 m. We estimate cooling in the maximum -3.6 °C with precipitation 65% of present. There are moraine complexes of 4 postglacial advances, in the latest of them, presumably Younger Drias, firn line depression reached 500 m. In the Early Holocene glaciers reduced rapidly, evidence of this reduction are samples of wood with age 9120±110 cal. B.P. that were found about 350 m over the present forest line. According to our reconstruction in the Boreal Holocene optimum (about 9000

  15. Review of metamorphic and kinematic data from Internal Crystalline Massifs (Western Alps): PTt paths and exhumation history

    NASA Astrophysics Data System (ADS)

    Gasco, Ivano; Gattiglio, Marco; Borghi, Alessandro

    2013-01-01

    Detailed geological mapping combined with micro-structural and petrological investigation allowed to clarify the tectono-metamorphic relationships between continental and oceanic units transition in the Penninic domain of the Western Alps. The three study areas (Gressoney, Orco and Susa sections) take into consideration the same structural level across the axial metamorphic belt of the Western Italian Alps, i.e., a geological section across the Internal Crystalline Massifs vs Piedmont Zone boundary. The units outcropping in these areas can be grouped into two Tectonic Elements according to their tectono-metamorphic evolution. The Lower Tectonic Element (LTE) consists of the Internal Crystalline Massifs and the Lower Piedmont Zone (Zermatt-Saas like units), both showing well preserved eclogite facies relics. Instead, the Upper Tectonic Element (UTE) consists of the Upper Piedmont Zone (Combin like units) lacking evidence of eclogite facies relics. In the Lower Tectonic Element two main Alpine tectono-metamorphic stages were identified: M1/D1 developed under eclogite facies conditions and M2/D2 is related to the development of the regional foliation under greenschist to epidote-albite amphibolite facies conditions. In the Upper Tectonic Element the metamorphic stage M1/D1 developed under bluschist to greenschist facies conditions and M2/D2 stage under greenschist facies conditions. These two Tectonic Elements are separated by a tectonic contact of regional importance generally developed along the boundary between the Lower and the Upper Piedmont zone under greenschist facies conditions. PT data compared to geochronology indicate that the first exhumation of ICM can be explained by buoyancy forces acting along the subduction channel that occurred during the tectonic coupling between the continental and oceanic eclogite units. These buoyancy forces vanished at the base of the crust where the density difference between the subducted crustal units and the surroundings

  16. The Alleret Maar lacustrine sequence (French Massif Central): a 150 ka long early-middle Pleistocene continental paleoenvironmental record.

    NASA Astrophysics Data System (ADS)

    Nomade, S.; Pastre, J.; Guillou, H.; Gauthier, A.; Scaillet, S.

    2008-12-01

    Lacustrine maar sequences of the French Massif Central are of great interest for paleoclimatic and paleoenvironmental reconstructions of mid-latitudes Quaternary continental environments. In particular, the western Velay region yields exceptional sequences spanning the last 450 ka (Reille et al., J. Quat. Sci. 2000). However, older sequences remain largely unknown despite the presence of interbedded alkaline tephras allowing precise absolute radiochronological control of many lacustrine squences. The Alleret maar is a 1500 m wide phreatomagmatic crater that provides a long lacustrine sequence (41 m). The upper part of this sequence (AL2 core, 14.6 m) was studied between 2005 and 2006 (Pastre et al., C. R. Acad Sci, 2007). A 39Ar/40Ar date (557 ± 5ka) obtained from an interbedded tephra layer located at 7m as well as the associated pollen data attribute the beginning of this sequence to the MIS 15. Thanks to the AL3 core recovered in 2005 (40.6 m, CNRS Meudon) several new tephra layers were discovered in the bottom part of this lacustrine sequence. Three new 39Ar/40Ar ages (single crystal analyses) from trachytic tephra layers were obtained at the LSCE Argon Laboratory (France). These layers are located at -30.2, -36.2 and -39.2m. Ages obtained relative to the ACR-2 flux standard (1,201Ma, Kuiper et al., Science, 2008) range from 692 ± 6 ka (MSWD: 2.3, n=18) for the youngest (-30.2m) to 726 ± 9Ka Ka (MSWD: 2.2, n=12) for the lowest tephra located at -39.2m. These new dates indicate a relatively homogeneous deposition rate of 3.5cm/ka and that the last 10 meters cover the MIS 17-MIS18 period. According to these current radiochronological data the complete lacustrine sequence last more than 150ka. Ongoing sedimentary and pollen studies will allow to extend the paleoenvironmental and paleoclimatic records of the French Massif Central towards the beginning of the early middle Pleistocene.

  17. Rockfalls on steep rock walls in the Mont Blanc massif: a statistical approach for the 2007 and 2008 events

    NASA Astrophysics Data System (ADS)

    Ravanel, L.; Allignol, F.; Deline, P.; Ravello, M.

    2009-04-01

    It is hypothesized that climatic warming since 1980 increases rock wall instability in high mountains due to permafrost degradation. This is supported by the observation of ice in several rockfall scars. Due to a lack of systematic observations, magnitude and frequency of high mountain rock failures remain poorly known. As a part of the French-Italian PERMAdataROC project (2005-2008) and the EU-funded transalpine PermaNET project (2008-2011), we developed a present-day rockfall database. It contains information collected during systematic surveys carried out by local people (mountain guides, hut keepers, researchers). Although difficult to implement, this approach seems an efficient way to systematically record slope instability events of all sizes related to climate variations. The database compiles the characteristics (topography, volume, scar geometry, deposit) of the 44 and the 20 rockfalls observed in 2007 and 2008, respectively, in the Mont-Blanc massif (Swiss and Saint-Gervais sides excepted). For each event, scar elevation, slope angle and aspect of the affected slopes are issues from ArcGIS, using a 50 m digital elevation model (DEM) - enhanced to 10 m for affected areas - for the French side of the massif, and a 10 m DEM for the Italian side. Among the 64 documented rockfalls, 53 occurred at an altitude above 3000 m a.s.l (but none above 3900 m), on slopes with an angle mainly in the range 50-60°. Massive ice has been directly observed in 12 scars. The four largest rockfalls occurred on the steepest, Italian side at: Dent de Jetoula (at 2810 m a.s.l.; 15,000 m3) on August 2007, one of the lowest in altitude; Tour des Grandes Jorasses (at 3830 m; 10,000 m3) on September 2007; Aiguilles de Thoules (at 3450 m; 8,000 m3) on July 2008; and Tré-la-Tête (at 3470 m; 50,000 m3) on September 2008. Detailed results are presented, statistically analysed and normalized.

  18. High frequency measurement of P- and S-wave velocities on crystalline rock massif surface - methodology of measurement

    NASA Astrophysics Data System (ADS)

    Vilhelm, Jan; Slavík, Lubomír

    2014-05-01

    For the purpose of non-destructive monitoring of rock properties in the underground excavation it is possible to perform repeated high-accuracy P- and S-wave velocity measurements. This contribution deals with preliminary results gained during the preparation of micro-seismic long-term monitoring system. The field velocity measurements were made by pulse-transmission technique directly on the rock outcrop (granite) in Bedrichov gallery (northern Bohemia). The gallery at the experimental site was excavated using TBM (Tunnel Boring Machine) and it is used for drinking water supply, which is conveyed in a pipe. The stable measuring system and its automatic operation lead to the use of piezoceramic transducers both as a seismic source and as a receiver. The length of measuring base at gallery wall was from 0.5 to 3 meters. Different transducer coupling possibilities were tested namely with regard of repeatability of velocity determination. The arrangement of measuring system on the surface of the rock massif causes better sensitivity of S-transducers for P-wave measurement compared with the P-transducers. Similarly P-transducers were found more suitable for S-wave velocity determination then P-transducers. The frequency dependent attenuation of fresh rock massif results in limited frequency content of registered seismic signals. It was found that at the distance between the seismic source and receiver from 0.5 m the frequency components above 40 kHz are significantly attenuated. Therefore for the excitation of seismic wave 100 kHz transducers are most suitable. The limited frequency range should be also taken into account for the shape of electric impulse used for exciting of piezoceramic transducer. The spike pulse generates broad-band seismic signal, short in the time domain. However its energy after low-pass filtration in the rock is significantly lower than the energy of seismic signal generated by square wave pulse. Acknowledgments: This work was partially

  19. The sequence and origin of mineralization in the tectonic zones in the Suwalki Anorthosite Massif, NE Poland

    NASA Astrophysics Data System (ADS)

    Wiszniewska, J.; Cymerman, Z.; Gaweda, A.

    2003-04-01

    The Suwalki Anorthosite Massif (SAM) is emplaced within the Mesoproterozoic rapakivi-type Mazury Complex (ca. 1.56 Ga) of the AMCG affinity. This massif has been subjected by several tectono-hydrothermal events resulted in extensive mineralization. A comprehensive structural study of the SAM requires investigation of numerous (99) boreholes because each well displays several structural components and the combination of these data can be used to summarize SAM evolution. The style of deformation in the SAM area ranges from localised ductile flow, producing shear zones (from a few cm to tens of metre wide) with a mylonitic foliation and a stretching lineation, to brittle fracturing and accompanying brecciation. The SAM features alternating zones of high- and low-strain, both in ductile and brittle conditions. Dip-parallel stretching lineations are inferred to be remnants of the Gothian shortening and ductile thrusting. Almost all shear sense indicators indicate reverse sense of movements. Younger planar fabrics in the fault zones include a well-developed pressure-solution cleavage and or fracture cleavage. Locally, the cleavage become parallel to the fault direction, suggesting rotation of a passive marker during shearing and shortening. The fault zones commonly exhibit newly formed subhorizontal stretching lineations that overprint the former dip-parallel stretching lineations. The kaolinization was the first brittle process, restricted to the close vicinity of the mylonitic structures. The syntectonic C_1 carbonate (calcite or Fe-dolomite) precipitated on the C planes of the S-C composite fabric. C_1 (calcite) carbonate is accompanied by the Fe-Mg chlorite. The further faulting process was accompanied by the crushing, brecciation and pseudotachylite formation. The cracks and fissures are filed by fine grained quartz and C_2 calcite, forming the cement of the tectonic breccias. The following relaxation event caused the opening of the earlier formed cracks and the

  20. Today's sediment budget of the Rhine River channel, focusing on the Upper Rhine Graben and Rhenish Massif

    NASA Astrophysics Data System (ADS)

    Frings, Roy M.; Gehres, Nicole; Promny, Markus; Middelkoop, Hans; Schüttrumpf, Holger; Vollmer, Stefan

    2014-01-01

    The river bed of the Rhine River is subject to severe erosion and sedimentation. Such high geomorphological process rates are unwanted for economical, ecological, and safety reasons. The objectives of this study were (1) to quantify the geomorphological development of the Rhine River between 1985 and 2006; (2) to investigate the bed erosion process; and (3) to distinguish between tectonic, hydrological, and human controls. We used a unique data set with thousands of bedload and suspended-load measurements and quantified the fluxes of gravel, sand, silt, and clay through the northern Upper Rhine Graben and the Rhenish Massif. Furthermore, we calculated bed level changes and evaluated the sediment budget of the channel. Sediment transport rates were found to change in the downstream direction: silt and clay loads increase because of tributary supply; sand loads increase because of erosion of sand from the bed; and gravel loads decrease because of reduced sediment mobility caused by the base-level control exerted by the uplifting Rhenish Massif. This base-level control shows tectonic setting, in addition to hydrology and human interventions, to represent a major control on morphodynamics in the Rhine. The Rhine bed appears to be in a state of disequilibrium, with an average net bed degradation of 3 mm/a. Sand being eroded from the bed is primarily washed away in suspension, indicating a rapid supply of sand to the Rhine delta. The degradation is the result of an increased sediment transport capacity caused by nineteenth and twentieth century's river training works. In order to reduce degradation, huge amounts of sediment are fed into the river by river managers. Bed degradation and artificial sediment feeding represent the major sources of sand and gravel to the study area; only small amounts of sediment are supplied naturally from upstream or by tributaries. Sediment sinks include dredging, abrasion, and the sediment output to the downstream area. Large uncertainties

  1. Collapse in a rock massif induced by lateral confinement loss: the case of Montegolf (Málaga, Spain)

    NASA Astrophysics Data System (ADS)

    Azañón, J. M.; Puertas, E.; Ureña, C.; Gallego, R.; Romero-Gómez, F.

    2012-04-01

    The use of computing codes allowing finite elements analysis is a very useful tool in detecting variations of the tensional state of rock massifs. Most of the codes used for ground modelling only allow 2D analysis. However, in the case of complex slope instabilities, it is necessary to consider the variation of resistant properties in a 3D model. This work presents an example in which 3D analysis carried out by finite elements methods becomes essential to understand the surface processes occurred in a urbanized rock massif (Montegolf, Malaga). The studied area is a small hill of elliptical shaped plan (300x200m plan). As a main peculiarity of this hill, it was intensively undergone to human activity in recent years. On September 11th, 2000, the collapse of an inner cavity (100m3 in volume) took place. The cavity proceeded from a mining abandoned 30 years before. The application of a 3D finite elements model showed that the highway slope digged in the Eastern face of the mount produced a change in the tensional state inside the mount. Vertical stresses shifted from compression to tension eliminating the vault effect. To define the geometry of the model, a survey of the existing contour map was carried out and conveniently transformed into ACIS format to be processed by ABAQUS (finite elements program). In the two-dimensional case an E-W section involving houses, highway and cavity was chosen. Mining hole was considered in the model, using a 10m-diameter sphere to represent the cavity. The performance of the natural materials was supposed to be elastic so Young modulus and Poisson's ratio were required. The ground strains due to collapse of the cavity and obtained by the finite elements model were accurately related to the mapping of cracks on the surface, the sinking of topographical landmarks (located on the top of the mountain) and the photographic analysis (captures before and after the collapse). Thus it is confirmed that the surface sliding which affected the

  2. Petrology and geochemistry of the Saga and Sangsang ophiolitic massifs, Yarlung Zangbo Suture Zone, Southern Tibet: Evidence for an arc-back-arc origin

    NASA Astrophysics Data System (ADS)

    Bédard, É.; Hébert, R.; Guilmette, C.; Lesage, G.; Wang, C. S.; Dostal, J.

    2009-12-01

    The Saga and Sangsang ophiolites are located about 600 and 450 km west of Lhasa and represent a western extention of the central portion of the Yarlung Zangbo Suture Zone (YZSZ) ophiolite belt. The Saga massif comprises fresh mantle lherzolite and cpx-harzburgite, an ophiolite mélange (± amphibolite), metamorphosed mafic crustal rocks (meta-gabbro, meta-basalts and amphibolites) and a sequence of uppermost crustal rocks (chert, basaltic lavas, diabase sills and dikes). The Sangsang ophiolite consists of an ophiolite mélange (harzburgite) and upper mantle harzburgite with minor lavas and gabbro. Peridotites from both massifs show variable degrees of serpentinization. Their Mg# varies between 0.89 and 0.91. All peridotites show distinct flat REE (rare earth elements) patterns with La/Yb N ratios close to 1, probably indicative of a refertilized mantle. The Olivine-Spinel equilibrium and the spinel chemistry for the Saga (Cr# ~ 0.10-0.22) and Sangsang (Cr# ~ 0.30-0.55) peridotites suggest that the Saga peridotites have a deeper mantle provenance (> 20 kbar) and have undergone lower degrees of partial melting (5-12%) than the Sangsang peridotites (< 15 kbar; 17-30%). The composition of the Saga peridotites is similar to the composition of pre-oceanic peridotites while peridotites from the Sangsang massif resemble abyssal and subduction-related peridotites. Mafic rocks from both ophiolites have basalt and basaltic andesite compositions. They are slightly depleted in light REE with respect to the heavy REE, with La/Yb N between 0.5 and 0.8 and with a small negative Ta-Nb anomaly suggesting the presence of a subduction component. The abundances of incompatible elements in these mafic rocks are similar to N-MORB (mid-ocean ridge basalt) or back-arc-basin basalts (BABB). Our data suggest that the Saga and Sangsang ophiolites belong to an intraoceanic suprasubduction zone segment as postulated for other ophiolitic massifs in the eastern portion of the YZSZ. However, the

  3. Development of a Comprehensive Plan for Scientific Research, Exploration, and Design: Creation of an Undergroung Radioactive Waste Isloation Facility at the Nizhnekansky Rock Massif

    SciTech Connect

    Jardine, L J

    2005-06-15

    ISTC Partner Project No.2377, ''Development of a General Research and Survey Plan to Create an Underground RW Isolation Facility in Nizhnekansky Massif'', funded a group of key Russian experts in geologic disposal, primarily at Federal State Unitary Enterprise All-Russian Design and Research Institute of Engineering Production (VNIPIPT) and Mining Chemical Combine Krasnoyarsk-26 (MCC K-26) (Reference 1). The activities under the ISTC Partner Project were targeted to the creation of an underground research laboratory which was to justify the acceptability of the geologic conditions for ultimate isolation of high-level waste in Russia. In parallel to this project work was also under way with Minatom's financial support to characterize alternative sections of the Nizhnekansky granitoid rock massif near the MCC K-26 site to justify the possibility of creating an underground facility for long-term or ultimate isolation of radioactive waste (RW) and spent nuclear fuel (SNF). (Reference 2) The result was a synergistic, integrated set of activities several years that advanced the geologic repository site characterization and development of a proposed underground research laboratory better than could have been expected with only the limited funds from ISTC Partner Project No.2377 funded by the U.S. DOE-RW. There were four objectives of this ISTC Partner Project 2377 geologic disposal work: (1) Generalize and analyze all research work done previously at the Nizhnekansky granitoid massif by various organizations; (2) Prepare and issue a declaration of intent (DOI) for proceeding with an underground research laboratory in a granite massif near the MCC K-26 site. (The DOI is similar to a Record of Decision in U.S. terminology). (3) Proceeding from the data obtained as a result of scientific research and exploration and design activities, prepare a justification of investment (JOI) for an underground research laboratory in as much detail as the available site characterization

  4. Negatively charged excitons in semimagnetic CdSe/ZnSe/ZnMnSe quantum dots

    SciTech Connect

    Brichkin, A. S. Chernenko, A. V.; Chekhovich, E. A.; Dorozhkin, P. S.; Kulakovskii, V. D.; Ivanov, S. V.; Toropov, A. A.

    2007-08-15

    Low-temperature (T = 1.6 K) photoluminescence (PL) of individual CdSe/ZnSe/ZnMnSe quantum dots (QDs) with different magnitudes of the sp-d exchange interaction between the magnetic impurity ions and charge carriers has been studied in a magnetic field up to 12 T applied in the Faraday and Voigt geometry. The magnitude of the interaction was controlled by changing the fraction ({eta}{sub e,h}) of the squared wave function of charge carriers in the semimagnetic barrier by means of variation of the nonmagnetic (ZnSe) layer thickness. It is established that the sp-d exchange interaction leads to a change in the sign of the effective hole g factor even for {eta}{sub e,h} {approx} 5%, while further increase in the interaction magnitude is accompanied by a rapid growth in the magnitude of spin splitting for both electrons and holes. The quantum yield of PL exhibits a significant decrease due to nonradiative Auger recombination with the excitation of Mn ions only for {eta}{sub e,h} {approx} 12%, while the rate of the holes spin relaxation starts growing only for still higher {eta}{sub e,h} values. In a strong magnetic field perpendicular to the sample plane, the alignment of Mn spins leads to suppression of the Auger recombination only in the excited spin state. For a small rate of the hole spin relaxation, this leads to a rather unusual result: the emission from an excited trion state predominates in strong magnetic fields.

  5. Inclusions in topaz from miarolitic pegmatites of the Volodarsk-Volynski Massif (Ukraine)--a Raman spectroscopic study.

    PubMed

    Dumańska-Słowik, Magdalena; Wesełucha-Birczyńska, Aleksandra; Natkaniec-Nowak, Lucyna

    2013-05-15

    The differently coloured (colourless, brown-pinkish and blue-pinkish) crystals of topaz from granitic pegmatites of Volodarsk-Volynsky Massif (VVM) have been investigated by scanning electron microscopy (SEM) and Raman microspectroscopy (RS) methods. Topaz (287, 522, 855, 929 cm(-1)), goethite (390 cm(-1)), pyrite (377-379 cm(-1)), marcasite (397 and 331 cm(-1)) and monazite (460 and 970-1070 cm(-1)) were identified as mineral inclusions in analysed crystals. On the basis of RS spectra some of this inclusions contain also organic matter, represented by carbonaceous matter (D-band at ca. 1320-1340 cm(-1) and G-band at ca. 1590-1600 cm(-1)) and liquid simple hydrocarbons consisting of aliphatic and aromatic groups (1240, 1325 and 1420 cm(-1)). Other solid phases found the host topaz, i.e. quartz, orthoclase, very rare minerals (micas) as lepidolite, zinnwaldite and also beryl and rutile, were identified with SEM-EDS analyses. All these mineral inclusions have been formed by post-magmatic, fluid-induced processes, extended from pegmatite to hydrothermal stages of magma crystallization. PMID:23501722

  6. The cyclic carbonates of the Latemar Massif: Evidence for the orbital forcing of a carbonate platform during the Middle Triassic

    NASA Technical Reports Server (NTRS)

    Hinnov, Linda

    1992-01-01

    The Latemar Massif is an exhumed carbonate platform in the Dolomites of Northern Italy that was deposited during the Ladinian stage of the Middle Triassic. The platform interior is comprised of hundreds of vertically stacked, meter scale, subtidal limestone/vadose cap carbonate cycles ('Latemar couplets') arranged into upward thinning bundles of 5. The individual couplets are interpreted as the products of sea level oscillations occurring with an approximately 20,000 year periodicity; the 5:1 bundling is indicative of a lower order approximately 100,000 year modulating component. This combination of cycling is interpreted as a platform response to precession forcing with the 5:1 bundling an expression of modulation by the eccentricity. Spectral analysis confirms the significance of the 5:1 bundling, and identifies other significant bundling components related to other components of the eccentricity. The results show that the Latemar bundling spectrum is complex, with a splitting of components around the 1 percent bundling frequency, suggestive of the multiple component eccentricity in the 100,000 year range. On the other hand, there is no direct evidence for the major 400,000 year eccentricity component, although there is a dominant approximately 700,000 year cycling in the buildup (a 35:1 bundling period). Other higher frequency bundling components may be related to obliquity forcing. Simple models are presented to argue for and against an astronomical origin of these cyclic platform carbonates.

  7. Evolution of hut access facing glacier shrinkage in the Mer de Glace basin (Mont Blanc massif, France)

    NASA Astrophysics Data System (ADS)

    Mourey, Jacques; Ravanel, Ludovic

    2016-04-01

    Given the evolution of high mountain environment due to global warming, mountaineering routes and huts accesses are more and more strongly affected by glacial shrinkage and concomitant gravity processes, but almost no studies have been conducted on this relationship. The aim of this research is to describe and explain the evolution over the last century of the access to the five alpine huts around the Mer de Glace glacier (Mont Blanc massif), the larger French glacier (length = 11.5 km, area = 30 km²), a major place for Alpine tourism since 1741 and the birthplace of mountaineering, by using several methods (comparing photographs, surveying, collecting historical documents). While most of the 20th century shows no marked changes, loss of ice thickness and associated erosion of lateral moraines generate numerous and significant changes since the 1990s. Boulder falls, rockfalls and landslides are the main geomorphological processes that affect the access, while the glacier surface lowering makes access much longer and more unstable. The danger is then greatly increased and the access must be relocated and/or equipped more and more frequently (e.g. a total of 520 m of ladders has been added). This questions the future accessibility to the huts, jeopardizing an important part of mountaineering and its linked economy in the Mer de Glace area.

  8. The carbon-isotopic composition of Proterozoic carbonates: Riphean successions from northwestern Siberia (Anabar Massif, Turukhansk Uplift)

    NASA Technical Reports Server (NTRS)

    Knoll, A. H.; Kaufman, A. J.; Semikhatov, M. A.

    1995-01-01

    Thick carbonate-dominated successions in northwestern Siberia document secular variations in the C-isotopic composition of seawater through Mesoproterozoic and early Neoproterozoic (Early to early Late Riphean) time. Mesoproterozoic dolomites of the Billyakh Group, Anabar Massif, have delta 13C values that fall between 0 and -1.9 permil versus PDB, with values in the upper part of the succession (Yusmastakh Formation) consistently higher than those of the lower (Ust'-Il'ya and Kotuikan formations). Consistent with available biostratigraphic and radiometric data, delta 13C values for Billyakh carbonates compare closely with those characterizing early Mesoproterozoic carbonates (about 1600-1200 Ma) worldwide. In contrast, late Mesoproterozoic to early Neoproterozoic limestones and dolomites in the Turukhansk Uplift exhibit moderate levels of secular variation. Only the lowermost carbonates in the Turukhansk succession (Linok Formation) have delta 13C values that approximate Billyakh values. Higher in the Turukhansk succession, delta 13C values vary from -2.7 to +4.6 permil (with outliers as low as -5.0 permil interpreted as diagentically altered). Again, consistent with paleontological and radiometric data, these values compare well with isotopic values from 1200 to 850 Ma successions elsewhere. Five sections measured in different parts of the Turukhansk basin show nearly identical patterns of variation, confirming that carbonate delta 13C correlates primarily with time and not facies. The Siberian sections illustrate the potential of integrated biostratigraphic and chemostratigraphic data in the intra- and interbasinal correlation of Mesoproterozoic and early Neoproterozoic rocks.

  9. Origin and U-Pb dating of zircon-bearing nepheline syenite xenoliths preserved in basaltic tephra (Massif Central, France)

    NASA Astrophysics Data System (ADS)

    Paquette, Jean-Louis; Mergoil-Daniel, Juliette

    2009-08-01

    Zircon-bearing xenoliths in continental basalts are often interpreted as witnesses of the continental basement uplifted during volcanic eruptions. Nevertheless, their origin is still debated. The Devès basaltic plateau belongs to the alkaline volcanic province of the French Massif Central. In few outcrops, zircon-bearing nepheline syenite xenoliths were preserved. U-Pb dating of the zircon crystals define an age of 956 ± 11 kyr constraining the crystallisation time of the zircons and consequently of the host xenoliths. This age, together with mineral chemistry arguments lead us to conclude that these minerals do not derive from a continental protolith. Rather, they likely result from the crystallisation of a liquid characterised by a nepheline-felspar composition and produced by the differentiation of a basaltic magma or, alternatively, by the low degree partial melting of a metasomatised lithospheric mantle. Such alkaline sialic rock and xenoliths may occur in large volumes at depth and generate the large amounts of zircon megacrysts discovered worldwide in secondary deposits within continental basaltic provinces.

  10. Multidisciplinary characterisation of sedimentary processes in a recent maar lake (Lake Pavin, French Massif Central) and implication for natural hazards

    NASA Astrophysics Data System (ADS)

    Chapron, E.; Albéric, P.; Jézéquel, D.; Versteeg, W.; Bourdier, J.-L.; Sitbon, J.

    2010-09-01

    Sedimentation processes occurring in the most recent maar lake of the French Massif Central (Lake Pavin) are documented for the first time based on high resolution seismic reflection and multibeam bathymetric surveys and by piston coring and radiocarbon dating on a sediment depocentre developed on a narrow sub aquatic plateau. This new data set confirms the mid Holocene age of maar lake Pavin formation at 6970±60 yrs cal BP and highlights a wide range of gravity reworking phenomena affecting the basin. In particular, a slump deposit dated between AD 580-640 remoulded both mid-Holocene lacustrine sediments, terrestrial plant debris and some volcanic material from the northern crater inner walls. Between AD 1200 and AD 1300, a large slide scar mapped at 50 m depth also affected the southern edge of the sub aquatic plateau, suggesting that these gas-rich biogenic sediments (laminated diatomite) are poorly stable. Although several triggering mechanisms can be proposed for these prehistoric sub-aquatic mass wasting deposits in Lake Pavin, we argue that such large remobilisation of gas-rich sediments may affect the gas stability in deep waters of meromictic maar lakes. This study highlights the need to further document mass wasting processes in maar lakes and their impacts on the generation of waves, favouring the development of dangerous (and potentially deadly) limnic eruptions.

  11. A new species of the genus Calotes (Squamata: Agamidae) from high elevations of the Knuckles massif of Sri Lanka.

    PubMed

    Amarasinghe, A A Thasun; Karunarathna, D M S Suranjan; Hallermann, Jakob; Fujinuma, Junichi; Grillitsch, Heinz; Campbell, Patrick D

    2014-01-01

    A new species of agamid lizard, of the genus Calotes, is described based on morphological evidence. This species is restricted to the Knuckles massif (>900 m elevation) of Sri Lanka. The genus Calotes consists of seven species in Sri Lanka, five of which appear to form an endemic radiation. The new species most closely resembles C. liocephalus Günther, 1872 which has an isolated population in the central highlands and is only known from Pundaluoya (~1000m), Dickoya (~1200m), Upcot (~1400m), Agrapatanas (1665m) and Peak Wilderness (Sri Pada) (>1400m). The populations from Pundaluoya and Dickoya appear to be locally extinct from the wild and are known only from museum specimens collected over 120 years ago. Males of the new species are different from males of C. liocephalus because of the absence of a gular pouch; by having mid gular scales smaller in size than those of its counterpart; scales on the snout which are larger in size than those on the occipital and forehead; pectoral scales which are not enlarged; elongated subcaudal scales; slightly carinate and acuminate abdominal scales; and scales on venter which are somewhat larger in size than those on dorsum at the same level. Finally, we also redescribe Calotes liocephalus, and provide a key to the Sri Lankan species of genus Calotes. PMID:24872171

  12. Co-eruption of carbonate and silicate magmas during volcanism in the Limagne graben (French Massif Central)

    NASA Astrophysics Data System (ADS)

    Chazot, Gilles; Mergoil-Daniel, Juliette

    2012-12-01

    Peperites in the Limagne graben (French Massif Central) have been interpreted up to now as phreatomagmatic eruptions involving fragmentation of sedimentary rocks during magma-water interaction. We report about the possible magmatic origin of the carbonates involved in the peperites from Gergovie and Pileyre localities. In these two volcanic deposits, carbonates are manly dolomitic in composition, while the Limagne sediments are almost exclusively detrital formations or limestones. In the studied rocks, the carbonates can be found in different habits, but are sometimes closely associated with Cr-diopsides and Cr-spinels, minerals never found in the Limagne Miocene volcanic rocks and related to deep mantle processes. Dykes crosscutting the layered deposits are mainly composed of euhedral dolomite grains. Trace elements and Sr isotopes confirm that the carbonates are chemically different compared to the sedimentary rocks from the Limagne and therefore that the studied volcanic rocks are not a mixing between silicate magma and the local sediments. Based on our new petrological and geochemical data, we interpret these carbonates as evidence for the eruption of carbonatitic magmas associated with the silicate magmas found in the deposits. The high Sr isotopic ratios of these rocks imply the melting of an enriched metasomatised mantle for the source of the carbonates, as already advocated for many ultrapotassic or carbonatitic volcanic rocks in Europe. These results call for a reappraisal of the origin of the volcanism in the Limagne volcanic province and more generally of the carbonatitic volcanic provinces in Western Europe.

  13. Inclusions in topaz from miarolitic pegmatites of the Volodarsk-Volynski Massif (Ukraine) - A Raman spectroscopic study

    NASA Astrophysics Data System (ADS)

    Dumańska-Słowik, Magdalena; Wesełucha-Birczyńska, Aleksandra; Natkaniec-Nowak, Lucyna

    2013-05-01

    The differently coloured (colourless, brown-pinkish and blue-pinkish) crystals of topaz from granitic pegmatites of Volodarsk-Volynsky Massif (VVM) have been investigated by scanning electron microscopy (SEM) and Raman microspectroscopy (RS) methods. Topaz (287, 522, 855, 929 cm-1), goethite (390 cm-1), pyrite (377-379 cm-1), marcasite (397 and 331 cm-1) and monazite (460 and 970-1070 cm-1) were identified as mineral inclusions in analysed crystals. On the basis of RS spectra some of this inclusions contain also organic matter, represented by carbonaceous matter (D-band at ca. 1320-1340 cm-1 and G-band at ca. 1590-1600 cm-1) and liquid simple hydrocarbons consisting of aliphatic and aromatic groups (1240, 1325 and 1420 cm-1). Other solid phases found the host topaz, i.e. quartz, orthoclase, very rare minerals (micas) as lepidolite, zinnwaldite and also beryl and rutile, were identified with SEM-EDS analyses. All these mineral inclusions have been formed by post-magmatic, fluid-induced processes, extended from pegmatite to hydrothermal stages of magma crystallization.

  14. Unravelling carbonatite-silicate magma interaction dynamics: A case study from the Velay province (Massif Central, France)

    NASA Astrophysics Data System (ADS)

    Valentini, Luca; Moore, Kathryn Ruth; Chazot, Gilles

    2010-04-01

    Mechanisms of interaction between a carbonatite magma and a silicate magma are inferred on the basis of the textural and geochemical features of a carbonate-bearing tuff from the Massif Central, characterized by the presence of carbonatite globules within a silicate glass matrix. A two-fluid dynamical model is proposed in order to constrain the formation of the carbonatite globules that underwent no geochemical re-equilibration with the trachyte magma due to rapid thermal re-equilibration and crystallization of dolomite. It is suggested that a viscous fingering instability occurred simultaneously with the injection of a carbonatite magma into a chamber filled with a more viscous trachytic magma. Instantaneous fragmentation of the fingers, induced by the action of gradient stresses, resulted in the formation of a magmatic emulsion. The replenishment event triggered immediate evacuation of the magma chamber such that interaction between the two magmas occurred over a short time scale and large-scale mixing was prevented. The exsolution of volatiles, perhaps as a consequence of the recharge event shortly before the eruption, drove a metasomatic event that produced the subtle chemical variations observed at the interface between carbonatite globules and silicate matrix.

  15. Shape Coexistence in ^72Se

    NASA Astrophysics Data System (ADS)

    Lister, C. J.; Fischer, S. M.; McCutchan, E. A.; Ahn, T.; Casperson, R. J.; Heinz, A.; Ilie, G.; Qian, J.; Williams, E.; Winkler, R.

    2009-10-01

    One of the original candidates for shape co-existence in nuclei was ^72Se [1,2]. We have collected extensive new data, both ``in-beam'' following the ^40Ca(^36Ar,4p)^72Se reaction using Gammasphere at Argonne's ATLAS accelerator, and from the decay of ^72Br populated in the ^58Ni(^16O,pn) reaction studied at WNSL Yale. A new J^π=0^+ state was found at 1876 keV, the published [2] decay scheme was corrected, and twenty-six new levels were established. This detailed spectroscopy of low-lying states helps to delineate the two shape minima. The mixing of prolate-deformed and near-spherical states can be now quantified, and the gamma decay path from high-spin can be followed. The inferred groundstate shape is consistent with trends in experiment and calculation of the selenium isotopes [3,4]. [4pt] [1] J.H. Hamilton, et al., Phys. Rev. Letts. 32 239 (1974)[0pt] [2] W.E. Collins, et al., Phys.Rev. C9, 1457 (1974)[0pt] [3] S.M. Fischer, et al., Phys.Rev.Lett. 84, 4064 (2000)[0pt] [4] J. Ljungvall, et al., Phys.Rev.Lett. 100, 102502 (2008)

  16. Sinfonevada: Dataset of Floristic diversity in Sierra Nevada forests (SE Spain).

    PubMed

    Pérez-Luque, Antonio Jesús; Bonet, Francisco Javier; Pérez-Pérez, Ramón; Rut Aspizua; Lorite, Juan; Zamora, Regino

    2014-01-01

    The Sinfonevada database is a forest inventory that contains information on the forest ecosystem in the Sierra Nevada mountains (SE Spain). The Sinfonevada dataset contains more than 7,500 occurrence records belonging to 270 taxa (24 of these threatened) from floristic inventories of the Sinfonevada Forest inventory. Expert field workers collected the information. The whole dataset underwent a quality control by botanists with broad expertise in Sierra Nevada flora. This floristic inventory was created to gather useful information for the proper management of Pinus plantations in Sierra Nevada. This is the only dataset that shows a comprehensive view of the forest flora in Sierra Nevada. This is the reason why it is being used to assess the biodiversity in the very dense pine plantations on this massif. With this dataset, managers have improved their ability to decide where to apply forest treatments in order to avoid biodiversity loss. The dataset forms part of the Sierra Nevada Global Change Observatory (OBSNEV), a long-term research project designed to compile socio-ecological information on the major ecosystem types in order to identify the impacts of global change in this area. PMID:24843285

  17. Sinfonevada: Dataset of Floristic diversity in Sierra Nevada forests (SE Spain)

    PubMed Central

    Pérez-Luque, Antonio Jesús; Bonet, Francisco Javier; Pérez-Pérez, Ramón; Rut Aspizua; Lorite, Juan; Zamora, Regino

    2014-01-01

    Abstract The Sinfonevada database is a forest inventory that contains information on the forest ecosystem in the Sierra Nevada mountains (SE Spain). The Sinfonevada dataset contains more than 7,500 occurrence records belonging to 270 taxa (24 of these threatened) from floristic inventories of the Sinfonevada Forest inventory. Expert field workers collected the information. The whole dataset underwent a quality control by botanists with broad expertise in Sierra Nevada flora. This floristic inventory was created to gather useful information for the proper management of Pinus plantations in Sierra Nevada. This is the only dataset that shows a comprehensive view of the forest flora in Sierra Nevada. This is the reason why it is being used to assess the biodiversity in the very dense pine plantations on this massif. With this dataset, managers have improved their ability to decide where to apply forest treatments in order to avoid biodiversity loss. The dataset forms part of the Sierra Nevada Global Change Observatory (OBSNEV), a long-term research project designed to compile socio-ecological information on the major ecosystem types in order to identify the impacts of global change in this area. PMID:24843285

  18. Geological setting and petrogenesis of symmetrically zoned, miarolitic granitic pegmatites at Stak Nala, Nanga Parbat - Haramosh Massif, northern Pakistan

    USGS Publications Warehouse

    Laurs, B.M.; Dilles, J.H.; Wairrach, Y.; Kausar, A.B.; Snee, L.W.

    1998-01-01

    Miarolitic granitic pegmatites in the Stak valley in the northeast part of the Nanga Parbat - Haramosh Massif, in northern Pakistan, locally contain economic quantities of bi- and tricolored tourmaline. The pegmatites form flat-lying sills that range from less than 1 m to more than 3 m thick and show symmetrical internal zonation. A narrow outer or border zone of medium-to coarse-grained oligoclase - K-feldspar - quartz grades inward to a very coarse-grained wall zone characterized by K-feldspar - oligoclase - quartz - schorl tourmaline. Radiating sprays of schorl and flaring megacrysts of K-feldspar (intermediate microcline) point inward, indicating progressive crystallization toward the core. The core zone consists of variable mixtures of blocky K-feldspar (intermediate microcline), oligoclase, quartz, and sparse schorl or elbaite, with local bodies of sodic aplite and miarolitic cavities or "pockets". Minor spessartine-almandine garnet and lo??llingite are disseminated throughout the pegmatite, but were not observed in the pockets. The pockets contain well-formed crystals of albite, quartz, K-feldspar (maximum microcline ?? orthoclase overgrowths), schorl-elbaite tourmaline, muscovite or lepidolite, topaz, and small amounts of other minerals. Elbaite is color-zoned from core to rim: green (Fe2+- and Mn2+-bearing), colorless (Mn2+-bearing), and light pink (trace Mn3+). Within ???10 cm of the pegmatites, the granitic gneiss wallrock is bleached owing to conversion of biotite to muscovite, with local quartz and albite added. Schorl is disseminated through the altered gneiss, and veins of schorl with bleached selvages locally traverse the wallrock up to 1 m from the pegmatite contact. The schorl veins can be traced into the outer part of the wall zone, which suggests that they formed from aqueous fluids derived during early saturation of the pegmatite-forming leucogranitic magma rich in H2O, F, B, and Li. Progressive crystallization resulted in a late-stage sodic

  19. Relationship between oxidation state and texture and the influence of metasomatism in the lithospheric mantle beneath the Massif Central, France

    NASA Astrophysics Data System (ADS)

    Uenver-Thiele, Laura; Woodland, Alan; Downes, Hilary; Altherr, Rainer

    2013-04-01

    Investigating regional variations in structure and composition of the subcontinental lithospheric mantle (SCLM) is usually hampered by the lack of samples. However, the numerous volcanic centers of the French Massif Central have brought samples of the SCLM to the surface over a geographic area of ~20.000km2. Lenoir et al. (2000) and Downes et al. (2003) identified textural and geochemical differences between two domains lying north and south of 45° 30' latitude, respectively. The northern domain is relatively refractory, but has experienced pervasive enrichment of LREE. The southern domain is generally more fertile, although the peridotites are LREE depleted. Many xenolith suites have undergone variable degrees of metasomatism. Variations in oxidation state might be expected from the differing histories of these two domains. We have undertaken an extensive study to determine the oxidation state of the SCLM beneath the Massif Central over the largest geographical area possible, including 140 peridotite xenoliths from 45 localities. All xenoliths are spinel peridotites and vary in composition from lherzolites to harzburgites. Using the nomenclature of Mercier and Nicolas (1975) the xenoliths are mostly protogranular or protogranular-porphyroclastic, although some are porphyroclastic or equigranular. Small amounts of amphibole or biotite occur in some xenoliths, particularly in the southern domain, reflecting modal metasomatism. These metasomatic phases are found predominantly in peridotites with protogranular textures. Oxidation state was determined using the equilibrium between the Fe-bearing components of olivine and pyroxene and the magnetite component in spinel (i.e. Wood et al. 1990). Major element compositions of the individual minerals were determined by microprobe. Ferric iron contents of spinel were determined by Mössbauer spectroscopy and gave values of Fe3+/ Fetot from 0.159 to 0.459, with a conservative uncertainty of ±0.02. Oxygen fugacity (fO2) of

  20. Structural, mineralogical, and paleoflow velocity constraints on Hercynian tin mineralization: the Achmmach prospect of the Moroccan Central Massif

    NASA Astrophysics Data System (ADS)

    Mahjoubi, El Mahjoub; Chauvet, Alain; Badra, Lakhlifi; Sizaret, Stanislas; Barbanson, Luc; El Maz, Abdelkader; Chen, Yan; Amann, Méderic

    2016-03-01

    The Achmmach tin mineralization (NE of the Moroccan Central Massif) is associated with tourmaline-rich alteration halos, veins, and faults hosted in sandstones and metapelites of the Upper Visean-Namurian. These deposits are reported to be late Hercynian in age and related to the emplacement of late-orogenic granite not outcropping in the studied area. Structural and paragenetic studies of the Achmmach tin deposit were conducted in order to establish a general model of the mineralization. From field constraints, the late Hercynian phase is marked by a transition from transpression to extension with deformation conditions evolving from ductile to brittle environments. The transpression (horizontal shortening direction roughly trending E-W) is coeval with the emplacement of the first tourmaline halos along several conjugated trends (N070, N020, and N120). Thereafter, a tourmaline-rich breccia formed in response to the fracturing of early tourmaline-altered rocks. Subsequently, during the extensional phase, these structures were reactivated as normal faults and breccias, allowing the formation of the main tin mineralization (cassiterite) associated with a wide variety of sulfides (arsenopyrite, chalcopyrite, sphalerite, galena, pyrrhotite, bismuthinite, pyrite, and stannite). This evolution ends with fluorite and carbonate deposition. The hydrothermal fluid flow velocity, calculated by applying statistical measures on the tourmaline growth bands, varies with the lithology. Values are lower in metapelites and higher in breccia. In the general evolution model proposed here, tourmaline alteration makes the rock more competent, allowing for brittle fracturing and generation of open space where the main Sn mineralization was precipitated.

  1. Glacial history of a mid-altitude mountain massif: cartography and dating in the Chablais area (France, Switzerland)

    NASA Astrophysics Data System (ADS)

    Perret, A.; Reynard, E.; Delannoy, J.-J.

    2012-04-01

    The Chablais area, considered as one of the cradles of glaciology (de Charpentier, 1841; Morlot, 1859), has been studied for a long time but several questions still remain unresolved. This study aims to reconstruct the glacial history of the massif, in order to explain the glacial landforms, which constitute an important part of the local geomorphology. The study focuses on the last glacial cycle (OIS 5 - OIS 2). The area is primarily associated with the the Valais glacier, by several local glacial flows and, to a lesser extent, by the Giffre glacier. Its position at the interface of the important Valais glacial flow and less powerful local flows is a specificity of the study area, which implies several bifurcations, penetration of the main glacier into laterals valleys, damming situations, and different responses of the various ice bodies to climatic changes. The study is divided in four steps. (1) The first step was to carry out a wide bibliographic survey to identify the state of knowledge, especially in relation to areas previously poorly studied and areas that needed to be reconsidered given developments in dating methods. (2) Field surveys allowed us to complete observations and prepare local geomorphological maps (of glacial landforms and associated phenomena). (3) The third step was to assemble heterogeneous data (old and new maps, Digital Terrain Models, aerial photographies) in a GIS to establish maps of glacial stages. (4) Finally, the absolute and relative chronology of deglaciation (Guitter, 2003) was completed by cosmogenic nuclide dating. Results have allowed us to address the conditions of glacial landform deposition and evolution in a mid-altitude mountain range, and show the need to be prudent in comparing results of different dating methods. Our results suggest that the ages obtained are overall too young in regard to 10Be ages on the northern alpine foreland (Ivy-Ochs et al., 2004) and are in conflict with 14C dates obtained in the area

  2. A Search for Amino Acids and Nucleobases in the Martian Meteorite Roberts Massif 04262 Using Liquid Chromatography-Mass Spectrometry

    NASA Technical Reports Server (NTRS)

    Callahan, Michael P.; Burton, Aaron S.; Elsila, Jamie E.; Baker, Eleni M.; Smith, Karen E.; Glavin, Daniel P.; Dworkin, Jason P.

    2013-01-01

    The investigation into whether Mars contains signatures of past or present life is of great interest to science and society. Amino acids and nucleobases are compounds that are essential for all known life on Earth and are excellent target molecules in the search for potential Martian biomarkers or prebiotic chemistry. Martian meteorites represent the only samples from Mars that can be studied directly in the laboratory on Earth. Here, we analyzed the amino acid and nucleobase content of the shergottite Roberts Massif (RBT) 04262 using liquid chromatography-mass spectrometry. We did not detect any nucleobases above our detection limit in formic acid extracts; however, we did measure a suite of protein and nonprotein amino acids in hot-water extracts with high relative abundances of beta-alanine and gamma-amino-eta-butyric acid. The presence of only low (to absent) levels of several proteinogenic amino acids and a lack of nucleobases suggest that this meteorite fragment is fairly uncontaminated with respect to these common biological compounds. The distribution of straight-chained amine-terminal eta-omega-amino acids in RBT 04262 resembled those previously measured in thermally altered carbonaceous meteorites. A carbon isotope ratio of -24(0/00) +/- 6(0/00) for beta-alanine in RBT 04262 is in the range of reduced organic carbon previously measured in Martian meteorites (Steele et al. 2012). The presence of eta-omega-amino acids may be due to a high temperature Fischer-Tropschtype synthesis during igneous processing on Mars or impact ejection of the meteorites from Mars, but more experimental data are needed to support these hypotheses.

  3. Different emplacement mechanisms of the granitoids from the Sanabria-Viana do Bolo lineament (Iberian Massif, Spain)

    NASA Astrophysics Data System (ADS)

    Vegas, N.; Aranguren, A.; Cuevas, J.; Tubía, J. M.

    2003-04-01

    The Ollo de Sapo Domain (OSD), a large antiform that delineates the Ibero-Armorican Arc within the northern part of the Iberian Massif in NW Spain, is pierced by several granitic plutons. The pre-, syn- or post-kinematic emplacement of such plutons is a current issue of debate. Here, we report the structural study, based on field and anisotropy of magnetic susceptibility data, of three granitic plutons located by the southern termination of the OSD. The structure of the OSD reflects the superposition of vertical folds with crenulation cleavage over older recumbent folds with slate cleavage or schistosity. The process of crustal shortening responsible for these structures ended in the development of dextral and sinistral strike-slip shear zones parallel to the vertical folds. The granites studied, the Veiga, Pradorramisquedo and Sanabria plutons, define a N130°E-trending lineament parallel to the structural grain of the Ollo de Sapo Domain. The granite lineament is located on a negative gravity anomaly (- 60 mgal), suggesting the existence of buried granites. The Sanabria granites are conformable with the schistosity of the country rocks, and are deformed by N130°E-trending dextral shear zones. In contrast, the Pradorramisquedo and the Veiga granites cut the structures of the metamorphic rocks. These observations suggest that the Sanabria granite is syn-kinematic and the remaining two plutons are post-kinematic. However, structural data show that the emplacement of the three plutons was related to a dextral transpressional strike-slip shear zone which is buried below the Pradorramisquedo and the Veiga plutons. The structural differences shown by these granites are to be related to the control of local conditions on migration and emplacement of melts.

  4. A search for amino acids and nucleobases in the Martian meteorite Roberts Massif 04262 using liquid chromatography-mass spectrometry

    NASA Astrophysics Data System (ADS)

    Callahan, Michael P.; Burton, Aaron S.; Elsila, Jamie E.; Baker, Eleni M.; Smith, Karen E.; Glavin, Daniel P.; Dworkin, Jason P.

    2013-05-01

    The investigation into whether Mars contains signatures of past or present life is of great interest to science and society. Amino acids and nucleobases are compounds that are essential for all known life on Earth and are excellent target molecules in the search for potential Martian biomarkers or prebiotic chemistry. Martian meteorites represent the only samples from Mars that can be studied directly in the laboratory on Earth. Here, we analyzed the amino acid and nucleobase content of the shergottite Roberts Massif (RBT) 04262 using liquid chromatography-mass spectrometry. We did not detect any nucleobases above our detection limit in formic acid extracts; however, we did measure a suite of protein and nonprotein amino acids in hot-water extracts with high relative abundances of β-alanine and γ-amino-n-butyric acid. The presence of only low (to absent) levels of several proteinogenic amino acids and a lack of nucleobases suggest that this meteorite fragment is fairly uncontaminated with respect to these common biological compounds. The distribution of straight-chained amine-terminal n-ω-amino acids in RBT 04262 resembled those previously measured in thermally altered carbonaceous meteorites (Burton et al. 2012; Chan et al. 2012). A carbon isotope ratio of -24‰ ± 6‰ for β-alanine in RBT 04262 is in the range of reduced organic carbon previously measured in Martian meteorites (Steele et al. 2012). The presence of n-ω-amino acids may be due to a high temperature Fischer-Tropsch-type synthesis during igneous processing on Mars or impact ejection of the meteorites from Mars, but more experimental data are needed to support these hypotheses.

  5. Contributions of natural arsenic sources to surface waters on a high grade arsenic-geochemical anomaly (French Massif Central).

    PubMed

    Bossy, A; Grosbois, C; Hendershot, W; Beauchemin, S; Crouzet, C; Bril, H

    2012-08-15

    The subwatershed studied drains a non-exploited area of the St-Yrieix-la-Perche gold mining district (French Massif Central) and it is located on an arsenic (As) geochemical anomaly. In this context, it is important to know the geochemical processes involved in the transfer of As from solid environmental compartments to the aquatic system. The stream showed a temporal variation of dissolved As (As(d)) content from 69.4 μg.L(-1) in the low flow period to 7.5 μg.L(-1) in the high flow period. Upstream, ground- and wetland waters had As(d) concentrations up to 215 and 169 μg.L(-1), respectively. The main representative As sources were determined at the subwatershed scale with in-situ monitoring of major and trace element contents in different waters and single extraction experiments. The As sources to stream water could be regrouped into two components: (i) one As-rich group (mainly in the low flow period) with groundwater, gallery exploration outlet waters and wetland waters, and (ii) one As-poor group (mainly in the high flow period) with rainwaters and soil solutions. In the soil profile, As(d) showed a significant decrease from 52.4 μg.L(-1) in the 0-5 cm superficial soil horizon to 14.4 μg.L(-1) in the 135-165 cm deep soil horizon. This decrease may be related to pedogenic processes and suggests an evolution of As-bearing phase stability through the soil profile. Quantification of As(d) fluxes at the subwatershed scale showed that groundwater was the major input (>80%) of As(d) to surface water. Moreover, natural weathering of the As-rich solid phases showed an impact on the As release, mainly from superficial soil horizons with runoff contributing about 5% to As input in surface water. PMID:22750171

  6. Geological structure and ore mineralization of the South Sopchinsky and Gabbro-10 massifs and the Moroshkovoe Lake target, Monchegorsk area, Kola Peninsula, Russia

    NASA Astrophysics Data System (ADS)

    Pripachkin, Pavel V.; Rundkvist, Tatyana V.; Miroshnikova, Yana A.; Chernyavsky, Alexey V.; Borisenko, Elena S.

    2015-08-01

    The South Sopchinsky massif (SSM), Gabbro-10 (G-10) massif, and Moroshkovoe Lake (ML) target Monchegorsk area, Kola Peninsula, are located at the junction of the Monchepluton and Monchetundra layered intrusions. The intrusions were studied in detail as they are targets for platinum-group element (PGE) mineralization. The rocks in these targets comprise medium- to coarse-grained mesocratic to leucocratic gabbronorites, medium-grained mesocratic to melanocratic norites and pyroxenites, and various veins mainly comprising norite, plagioclase-amphibole-magnetite rocks, and quartz-magnetite rocks. The veins contain Ni-Cu-PGE mineralization associated with magnetite and chromite. In all targets, the contacts between gabbronorite and norite-pyroxenite are undulating, and the presence of magmatic (intrusive) breccias suggests that these rocks formed through mingling of two distinct magmatic pulses. In places, the gabbronorites clearly crosscut the modal layering of the norites and pyroxenites. Trace element data indicate that the gabbronorites have similar compositions to rocks of the upper part of the Monchetundra intrusion, whereas the norites and pyroxenites resemble rocks from the lower to intermediate stratigraphic levels of the Monchepluton, such as in the Nude-Poaz and Sopcha massifs. Sulfide mineralization in the studied targets principally consists of secondary bornite, millerite, and chalcopyrite. In contrast, the primary sulfide assemblage within the layered sequence of the adjacent Monchepluton is characterized by pentlandite, chalcopyrite, and pyrrhotite. Therefore, the mineralization in the studied targets is interpreted to be of a contact style. We argue that the studied area represents the contact zone between gabbronorites of the Monchetundra intrusion and norites and pyroxenites of the Monchepluton. In addition, the rocks were overprinted by postmagmatic veining and remobilization of contact style sulfide and PGE mineralization.

  7. Paleomagnetic and rock magnetic results from lower crustal rocks of IODP Site U1309: Implication for thermal and accretion history of the Atlantis Massif

    NASA Astrophysics Data System (ADS)

    Zhao, Xixi; Tominaga, Masako

    2009-09-01

    Integrated Ocean Drilling Program (IODP) Expeditions 304/305 recovered a total of 1.4 km sequence of lower crustal gabbroic and minor ultramafic rocks from the Atlantis Massif oceanic core complex on the western flank of the Mid Atlantic Ridge (MAR) at 30°N. We conducted an integrated paleomagnetic and rock magnetic study on this sequence to help address the interplay between magmatism and detachment faulting. Detailed thermal and alternating-field demagnetization results demonstrate that stable components of magnetization of mainly reversed polarity with unblocking temperatures below the Curie temperature of magnetite are retained in gabbroic rocks at IODP Site U1309. Several samples also contain multicomponent remanences of both normal and reversed polarities that were acquired over sharply defined blocking temperature intervals, providing evidence for localized reheating of some intervals during both normal and reversed polarity periods. Results from a series of rock magnetic measurements corroborate the demagnetization behavior and show that titanomagnetites are the main magnetic carrier rocks recovered at Site U1309D. The overall magnetic inclination of Hole U1309D is -35°, implying significant (up to ~ 50° counterclockwise, viewed to the north) rotation of the footwall around a horizontal axis parallel to the rift axis (010°) may have occurred. The tectonic rotations inferred by the paleomagnetic data suggest that the original fault orientation dipped relative steeply toward the spreading axis and subsequently rotated to a shallower angle. Coupled with the newly published U-Pb zircon ages for Hole U1309D rocks [Grimes, C.B., John, B.E., Wooden, J.L., 2008. Protracted construction of gabbroic crust at a slow-spreading ridge: Constraints from 206Pb/ 238U zircon ages from Atlantis Massif and IODP Hole 1309D, (30°N, MAR). Geochem. Geophys. Geosyst. 9, Q08012. doi:1029/2008GC002063], the new paleomagnetic data provide temporal and thermal constraints on the

  8. Progression from South-Directed to Orogen-Parallel Mid-Crustal Flow on the Southern Margin of the Tibetan Plateau, Ama Drime Massif, Tibet

    NASA Astrophysics Data System (ADS)

    Jessup, M. J.; Cottle, J. M.; Newell, D. L.; Berger, A. L.; Spotila, J. A.

    2008-12-01

    In the South Tibetan Himalaya, two major detachment systems are exposed in the Ama Drime and Mount Everest Massifs. These structures represent a fundamental shift in the dynamics of the Himalayan orogen, recording a progression from south-directed to orogen-parallel mid-crustal flow and exhumation. The South Tibetan detachment system (STDS) accommodated exhumation of the Greater Himalayan series (GHS) until the Middle Miocene. A relatively narrow mylonite zone that progressed into a brittle detachment accommodated exhumation of the GHS. Northward, in the down-dip direction (Dzakaa Chu and Doya La), a 1-km-wide distributed zone of deformation that lacks a foliation-parallel brittle detachment characterizes the STDS. Leucogranites in the footwall of the STDS range between 17-18 Ma. Previously published 40Ar/39Ar ages suggest that movement on the STDS ended by ~ 16 Ma in Rongbuk Valley and ~ 13 Ma near Dinggye. This once continuous section of the STDS is displaced by the trans- Himalayan Ama Drime Massif and Xainza-Dinggye graben. Two oppositely dipping normal faults and shear zones that bound the Ama Drime Massif record orogen-parallel extension. During exhumation, deformation was partitioned into relatively narrow (100-300-m-thick) mylonite zones that progressed into brittle faults/detachments, which offset Quaternary deposits. U(-Th-)Pb geochronology of mafic lenses suggests that the core of the ADM reached granulite facies at ~ 15 Ma. Leucogranites in the footwall of the detachment faults range between 12-11 Ma: significantly younger than those related to movement on the STDS. Previously published 40Ar/39Ar ages from the eastern limb of the Ama Drime Massif suggest that exhumation progressed into the footwall of the Nyüonno detachment between ~ 13-10 Ma. (U-Th)/He apatite ages record a minimum exhumation rate of ~ 1mm/yr between 1.5-3.0 Ma that was enhanced by focused denudation in the trans-Himalayan Arun River gorge. Together these bracket the timing (~ 12 Ma

  9. Applicability of the RSCM geothermometry approach in a complex tectono-metamorphic context: The Jebilet massif case study (Variscan Belt, Morocco)

    NASA Astrophysics Data System (ADS)

    Delchini, Sylvain; Lahfid, Abdeltif; Plunder, Alexis; Michard, André

    2016-07-01

    The Raman Spectroscopy of Carbonaceous Materials (RSCM) geothermometry approach allows determining the peak temperature recorded by metasediments through their metamorphic history. This technique, however, has been calibrated using Meso-Cenozoic metapelitic rocks that underwent a single metamorphic cycle. Until now, the reliability of the RSCM method has never been demonstrated for contexts with superposition of regional and contact metamorphism, such as many Variscan contexts. The present study aims at testing the applicability of the RSCM method to these polyphased metamorphism terrains and at investigating the cumulative molecular transformations of carbonaceous materials related to metamorphic superposition. To address the above issues, samples were collected in the Variscan Jebilet massif of the Moroccan Meseta. This massif was first affected by a regional, greenschist facies metamorphic event (D1 phase), and then by a higher-T, regional and contact metamorphism that reached the hornfels/amphibolite facies conditions (D2 and D2/D3 phases). Mineralogical, thermobarometric and RSCM methods have been used in this study to determine the peak T recorded by the studied rocks. The results obtained for greenschist facies metapelitic rocks show a good agreement between the mineralogical assemblage Chlorite-Phengite-Felspar-Quartz and the Raman temperatures ranging from 330 to 394 ± 50 °C. In the metapelitic rocks that underwent higher metamorphism grades (hornfels/amphibolite facies), four dominant mineral assemblages were observed: (1) Chlorite-Biotite, (2) Cordierite-Biotite, (3) Andalusite-Garnet-Bt, and (4) Andalusite-Cordierite-Biotite. The corresponding Raman temperatures vary respectively between 474 ± 50 °C and 628 ± 50 °C. The pseudo-sections generated for samples from the hornfels/amphibolite facies confirmed the peak temperatures measured by the RSCM method. Our results do not support clear evidence of potential molecular cumulative effect on CM

  10. Alpine re-activation of pre-Alpine structures: details from a large-scale shear zone in the Aar massif (Central Alps)

    NASA Astrophysics Data System (ADS)

    Wehrens, Philip; Baumberger, Roland; Herwegh, Marco

    2013-04-01

    The Aar massif belongs to the external massifs of the Alps and is mainly composed of granitoids and gneisses. Post-Variscan granitoid rocks have intruded old gneisses belonging to the pre-Variscan basement. Despite numerous detailed studies in the past decades, the overall exhumation history and the associated massif internal deformation (internal strain distribution and its evolution in time, kinematics etc.) are largely unknown at present. In this project, we aim to investigate the role of shear zones in the deformation history at a variety of scales. In this context it is important to understand their microstructural evolution, the involved deformation processes, kinematics and relative ages as well as the associated changes in rheology. A detailed study was conducted along a major shear zone located at the southern margin of the Aar massif (running from Furka to Grimsel Pass and Oberaar Glacier), where the Grimsel Granodiorite (GrGr) is juxtapositioned to strongly foliated gneisses. Preliminary results show that a crenulation of these gneisses predates the age of the granitoid intrusion, meaning they must be older than 298 Ma. The crenulation and a related axial plane foliation (145/80°) define mechanical anisotropies within these Pre-Variscan rocks. The intruding granite has exploited these anisotropies a first time during its emplacement in post-Variscan times. The lithological boundary between the intruded GrGr and Pre-Variscan rocks causes strain again to localize during Alpine deformation and results in a 40 m wide large-scale shear zone. The older part of the shear zone shows cm-scale shear zones with vertical lineations shearing off the aforementioned pre-Alpine axial plane foliation. Hence the contact is reactivated, now as Alpine normal/ reverse fault, a second time. Towards the youngest parts of the shear zone the stretching lineation on the shear surfaces turns from vertical towards a subhorizontal position, indicating a change from initial vertical

  11. Effects of interaction between ultramafic tectonite and mafic magma on Nd-Pb-Sr isotopic systems in the Neoproterozoic Chaya Massif, Baikal-Muya ophiolite belt

    USGS Publications Warehouse

    Amelin, Y.V.; Ritsk, E. Yu; Neymark, L.A.

    1997-01-01

    Sm-Nd, Rb-Sr and U-Pb isotopic systems have been studied in minerals and whole rocks of harzburgites and mafic cumulates from the Chaya Massif, Baikal-Muya ophiolite belt, eastern Siberia, in order to determine the relationship between mantle ultramafic and crustal mafic sections. Geological relations in the Chaya Massif indicate that the mafic magmas were emplaced into, and interacted with older solid peridotite. Hand picked, acid-leached, primary rock-forming and accessory minerals (olivine, orthopyroxene, clinopyroxene and plagioclase) from the two harzburgite samples show coherent behavior and yield 147Sm/144Nd- 143Nd/144Nd and 238U/204Pb-206Pb/204Pb mineral isochrons, corresponding to ages of 640 ?? 58 Ma (95% confidence level) and 620 ?? 71 Ma, respectively. These values are indistinguishable from the crystallization age of the Chaya mafic units of 627 ?? 25 Ma (a weighted average of internal isochron Sm-Nd ages of four mafic cumulates). The Rb-Sr and Sm-Nd isotopic systems in the harzburgite whole-rock samples were disturbed by hydrothermal alteration. These alteration-related isotopic shifts mimic the trend of variations in primary isotopic compositions in the mafic sequence, thus emphasizing that isotopic data for ultramafic rocks should be interpreted with great caution. On the basis of initial Sr and Nd values, ultramafic and mafic rocks of the Chaya Massif can be divided into two groups: (1) harzburgites and the lower mafic unit gabbronorites with ??Nd = +6.6 to +7.1 and ??Sr = -11 to -16; and (2) websterite of the lower unit and gabbronorites of the upper mafic unit: ??Nd = + 4.6 to + 6.1 and ??Sr = - 8 to -9. Initial Pb isotopic ratios are identical in all rocks studied, with mean values of 206Pb/204Pb = 16.994 ?? 0.023 and 207Pb/204Pb = 15.363 ?? 0.015. The similarity of ages and initial isotopic ratios within the first group indicates that the isotopic systems in the pre-existing depleted peridotite were reset by extensive interaction with basaltic

  12. A re-analysis of 533 rockfalls occurred since 2003 in the Mont Blanc massif for the study of their relationship with permafrost

    NASA Astrophysics Data System (ADS)

    Ravanel, Ludovic; Magnin, Florence; Deline, Philip

    2015-04-01

    Rockfall is one of the main natural hazards in high mountain regions and its frequency is growing, especially since two decades. Collapses at high elevation are with an increasing certainty assumed to be a consequence of the climate change through the warming permafrost. In the Mont Blanc massif, data on present rockfalls (occurrence time when possible, accurate location, topographical and geological settings, volume, weather and snow conditions) were acquired for 2003 and for the period 2007-2014 thanks to a satellite image of the massif and a network of observers in the central part of the massif, respectively. The study of the 533 so-documented rockfalls shows a strong correlation at the year scale between air temperature and rockfall. Along with this data acquisition, a statistical model of the Mean Annual Rock Surface Temperature (MARST) for the 1961-1990 period has been implemented on a 4-m-resolution DEM of the Mont Blanc massif. The model runs with Potential Incoming Solar radiation (PISR) calculated with GIS tools and air temperature parameters computed from Chamonix Météo France records. We cross here the data on rockfalls with the permafrost distribution model to show that: (i) rockfall occurs mainly over modeled negative MARST (context of permafrost); (ii) simulated warm permafrost areas (> -2°C) are the most affected by instabilities; (iii) as the 1961-1990 period is supposed to be representative of the conditions at depth that are not affected by the climate warming during the two last decades, the latest results are mainly valuable for rockfalls related to pluri-decadal signal; and (iv) the higher (close to 0°C) the MARST, the deeper the detachment (possibly related to the deepening of the permafrost active layer). These results and field observations confirm that warming permafrost corresponds to the main required configuration for rockfall triggering at high elevation. In addition, we show that rockfalls for which ice observed in their scar

  13. Métamorphisme miocène de granites panafricains dans le massif de l'Edough (Nord-Est de l'Algérie)

    NASA Astrophysics Data System (ADS)

    Hammor, Dalila; Lancelot, Joël

    1998-09-01

    The Edough Massif is the easternmost crystalline core of the Maghrebides that represents the African segment of the west Mediterranean Alpine belt. U-Pb zircon dating provides upper intercept ages of 595 ± 51 My and 606 ± 55 My for an orthogneiss of the lower unit and a deformed leucogranite of the upper pelitic unit, respectively. These ages suggest emplacement of the two granitoids during the Pan-African orogeny. Monazites from a paragneiss sample gave a 18 ± 5 My U-Pb age that points to a Miocene age of the high-temperature metamorphism.

  14. Liquidus Projections of Bi-Se-Ga and Bi-Se-Te Ternary Systems

    NASA Astrophysics Data System (ADS)

    Lin, Po-han; Chen, Sinn-wen; Hwang, Jenn-dong; Chu, Hsu-shen

    2016-06-01

    This study determines the liquidus projections of both Bi-Se-Ga and Bi-Se-Te ternary systems which are constituent ternary systems of promising Bi-Se-Te-Ga thermoelectric materials. Ternary Bi-Se-Ga and Bi-Se-Te alloys are prepared. Their primary solidification phases are experimentally determined, and thermal analysis experiments are carried out. The liquidus projections are determined based on the ternary experimental results and phase diagrams of constituent binary systems. The Bi-Se-Ga system includes seven primary solidification phases, Bi, Ga, GaSe, Ga2Se3, Se, Bi2Se3, and (Bi2)n(Bi2Se3)m. In the Bi-Se-Te system, there are five primary solidification phases, Bi, (Bi2)n(Bi2Te3)m, Bi2(Se,Te)3, (Se,Te), and (Bi2)n(Bi2Se3)m. Both the (Bi2)n(Bi2Te3)m and (Bi2)n(Bi2Se3)m phases are not a single phase, but a collection of series undetermined phases. Large miscibility gaps are observed in the Bi-Se-Ga system. The temperatures of the invariant reactions, Liquid + Bi + GaSe = Ga and Liquid + Ga2Se3 = Bi + GaSe, are at 495 K (222 °C) and 533 K (260 °C), respectively.

  15. Runoff generation in SE Spain

    NASA Astrophysics Data System (ADS)

    Dalen, E. N.; Kirkb