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Sample records for geodynamic model radionuklidnoe

  1. Geodynamics.

    ERIC Educational Resources Information Center

    Flinn, Edward A.

    1983-01-01

    Discusses trends, research activities, and conferences in geodynamics. These include topics on the lithosphere and lower continental crust formation discussed at a U.S. Geodynamics Committee workshop (Austin, Texas 1982) and symposia (each dealing with specific topics) sponsored by the Inter-Union Commission on Dynamics and Evolution of the…

  2. Geodynamics

    NASA Technical Reports Server (NTRS)

    Walter, L. S.

    1984-01-01

    The status of space geodynamics is examined, major scientific questions that need to be addressed are identified, and program activities are recommended for the next decade. Progress made in measuring tectonic plates, polar motion, and coupling of fluid motion of the Earth's core to the mantle is reviewed.

  3. Geodynamic models of deep subduction

    NASA Astrophysics Data System (ADS)

    Christensen, Ulrich

    2001-12-01

    Numerical and laboratory models that highlight the mechanisms leading to a complex morphology of subducted lithospheric slabs in the mantle transition zone are reviewed. An increase of intrinsic density with depth, an increase of viscosity, or phase transitions with negative Clapeyron slope have an inhibiting influence on deep subduction. The impingement of slabs on a viscosity and density interface has been studied in laboratory tanks using corn syrup. Slab interaction with equilibrium and non-equilibrium phase transitions has been modelled numerically in two dimensions. Both the laboratory and the numerical experiments can reproduce the variety of slab behaviour that is found in tomographic images of subduction zones, including cases of straight penetration into the lower mantle, flattening at the 660-km discontinuity, folding and thickening of slabs, and sinking of slabs into the lower mantle at the endpoint of a flat-lying segment. Aside from the material and phase transition properties, the tectonic conditions play an important role. In particular, the retrograde motion of the point of subduction (trench-rollback) has an influence on slab penetration into the lower mantle. A question that still needs to be clarified is the mutual interaction between plate kinematics and the subduction process through the transition zone.

  4. Experimental, Numerical and Observational Models in Geodynamics

    NASA Astrophysics Data System (ADS)

    Lithgow-Bertelloni, Carolina

    2015-04-01

    Geodynamics, the study of the forces that drives all Earth's processes is a rich field that deeply connects all aspects of geological and geophysical studies, from surface observations of the sedimentary record to knowledge of deep Earth structure from mineral physics and seismology. In the context of the solid Earth geodynamics primarily focuses on lithosphere and mantle dynamics, while core dynamics is the purview of geomagnetism. I will focus this talk on the former, its historical context and future developments. We have known the equations of motion and mechanics for ~200 years, but only relatively recently can they be solved with enough accuracy and resolution to do geology. We have made great strides since Arthur Holmes conceptual models of mantle flow, thanks to computational and experimental advances. We can know model plate boundaries globally with resolutions in the order of a few kms and image temperature and velocity simultaneously in the laboratory in 3D and non-intrusively. We have also learned a great deal about the physics of the Earth, from composition to rheology. New theories on plate boundary rheology are paving the way for self-consistent generation of plates from mantle flow. New computational methods allow for adaptive meshing, fabric development and history, so we can study deformation and compare directly to geological observations in mountain ranges and continental rifts. We can use ever more sophisticated images of mantle structure from seismic and other geophysical data to probe the relationship between melting, flow and dynamical processes. We can reconstruct landscapes and relief, plate motions and sedimentation and ask how much the mantle has contributed to drainage reversal, sedimentation and climate change. The future of the field is ever brighter.

  5. Towards Modelling slow Earthquakes with Geodynamics

    NASA Astrophysics Data System (ADS)

    Regenauer-Lieb, K.; Yuen, D. A.

    2006-12-01

    We explore a new, properly scaled, thermal-mechanical geodynamic model{^1} that can generate timescales now very close to those of earthquakes and of the same order as slow earthquakes. In our simulations we encounter two basically different bifurcation phenomena. One in which the shear zone nucleates in the ductile field, and the second which is fully associated with elasto-plastic (brittle, pressure- dependent) displacements. A quartz/feldspar composite slab has all two modes operating simultaneously in three different depth levels. The bottom of the crust is predominantly controlled by the elasto-visco-plastic mode while the top is controlled by the elasto-plastic mode. The exchange of the two modes appears to communicate on a sub-horizontal layer in a flip-flop fashion, which may yield a fractal-like signature in time and collapses into a critical temperature which for crustal rocks is around 500-580 K; in the middle of the brittle-ductile transition-zone. Near the critical temperature, stresses close to the ideal strength can be reached at local, meter-scale. Investigations of the thermal-mechanical properties under such extreme conditions are pivotal for understanding the physics of earthquakes. 1. Regenauer-Lieb, K., Weinberg, R. & Rosenbaum, G. The effect of energy feedbacks on continental strength. Nature 442, 67-70 (2006).

  6. Geodynamic evolution of the lithosphere beneath the Eastern Anatolia region: Constraints from geodynamic modeling

    NASA Astrophysics Data System (ADS)

    Memis, Caner; Hakan Gogus, Oguz; Pysklywec, Russell; Keskin, Mehmet; Celal Sengor, A. M.; Topuz, Gultekin

    2016-04-01

    The east Anatolian orogenic plateau is characterized by an average elevation of 2 km, and is delimited by the Bitlis-Zagros collision zone to the south and the Pontide arc to the north. Stratigraphic evidence suggests that the high plateau attained its current elevation since the Serravallian (about 12 million years ago), but probably did not reach its present height until at least the latest Pliocene. While the crustal shortening following the Arabia-Eurasia collision in the south enabled its relatively rapid rise and regional tectonic evolution, the presumed removal of the downgoing slab beneath east Anatolia has potentially played a significant role in this geodynamic configuration. According to the proposed scenario, the northward subducting slab of Neo-Tethys peels away from the overlying crust similar to the lithospheric delamination model. In this work, we performed a series of lithospheric removal models by varying rheological, physical and mechanical properties by using 2D numerical geodynamic experiments, (e.g. plate convergence rate, crustal thickness, mantle lithosphere yield-stress). Our model results show that the average amount of delamination hinge motion is maximum (18 km/my) when the lower crustal rheology is felsic granulite. The slab break-off only occurs at lower convergence rates (≤ 2 cm/yr), and is imposed on the margin of delaminating mantle lithosphere. The surface uplift takes place above the asthenospheric column (or plateau gap) through isostatic and thermal support of asthenospheric upwelling, and varies dependent on the width of the asthenospheric column. However; with higher plate convergence rates (≥3 cm/yr), the asthenospheric column does not widen enough and the continental collision occurs rather than delamination/peeling away. In this case, the average uplift appears in the central section of the crust, and this exceeds a surface elevation of 3 km. All model results are consistent with the observations from the Eastern

  7. Numerical Modeling in Geodynamics: Success, Failure and Perspective

    NASA Astrophysics Data System (ADS)

    Ismail-Zadeh, A.

    2005-12-01

    A real success in numerical modeling of dynamics of the Earth can be achieved only by multidisciplinary research teams of experts in geodynamics, applied and pure mathematics, and computer science. The success in numerical modeling is based on the following basic, but simple, rules. (i) People need simplicity most, but they understand intricacies best (B. Pasternak, writer). Start from a simple numerical model, which describes basic physical laws by a set of mathematical equations, and move then to a complex model. Never start from a complex model, because you cannot understand the contribution of each term of the equations to the modeled geophysical phenomenon. (ii) Study the numerical methods behind your computer code. Otherwise it becomes difficult to distinguish true and erroneous solutions to the geodynamic problem, especially when your problem is complex enough. (iii) Test your model versus analytical and asymptotic solutions, simple 2D and 3D model examples. Develop benchmark analysis of different numerical codes and compare numerical results with laboratory experiments. Remember that the numerical tool you employ is not perfect, and there are small bugs in every computer code. Therefore the testing is the most important part of your numerical modeling. (iv) Prove (if possible) or learn relevant statements concerning the existence, uniqueness and stability of the solution to the mathematical and discrete problems. Otherwise you can solve an improperly-posed problem, and the results of the modeling will be far from the true solution of your model problem. (v) Try to analyze numerical models of a geological phenomenon using as less as possible tuning model variables. Already two tuning variables give enough possibilities to constrain your model well enough with respect to observations. The data fitting sometimes is quite attractive and can take you far from a principal aim of your numerical modeling: to understand geophysical phenomena. (vi) If the number of

  8. Fluidity: A New Adaptive, Unstructured Mesh Geodynamics Model

    NASA Astrophysics Data System (ADS)

    Davies, D. R.; Wilson, C. R.; Kramer, S. C.; Piggott, M. D.; Le Voci, G.; Collins, G. S.

    2010-05-01

    Fluidity is a sophisticated fluid dynamics package, which has been developed by the Applied Modelling and Computation Group (AMCG) at Imperial College London. It has many environmental applications, from nuclear reactor safety to simulations of ocean circulation. Fluidity has state-of-the-art features that place it at the forefront of computational fluid dynamics. The code: Dynamically optimizes the mesh, providing increased resolution in areas of dynamic importance, thus allowing for accurate simulations across a range of length scales, within a single model. Uses an unstructured mesh, which enables the representation of complex geometries. It also enhances mesh optimization using anisotropic elements, which are particularly useful for resolving one-dimensional flow features and material interfaces. Uses implicit solvers thus allowing for large time-steps with minimal loss of accuracy. PETSc provides some of these, though multigrid preconditioning methods have been developed in-house. Is optimized to run on parallel processors and has the ability to perform parallel mesh adaptivity - the subdomains used in parallel computing automatically adjust themselves to balance the computational load on each processor, as the mesh evolves. Has a novel interface-preserving advection scheme for maintaining sharp interfaces between multiple materials / components. Has an automated test-bed for verification of model developments. Such attributes provide an extremely powerful base on which to build a new geodynamical model. Incorporating into Fluidity the necessary physics and numerical technology for geodynamical flows is an ongoing task, though progress, to date, includes: Development and implementation of parallel, scalable solvers for Stokes flow, which can handle sharp, orders of magnitude variations in viscosity and, significantly, an anisotropic viscosity tensor. Modification of the multi-material interface-preserving scheme to allow for tracking of chemical

  9. Precambrian geodynamics: models vs. concepts and constrains (Invited)

    NASA Astrophysics Data System (ADS)

    Gerya, T.; Sizova, E.; Brown, M.

    2013-12-01

    In contrast to modern-day plate tectonics, studying Precambrian geodynamics presents a unique challenge as currently there is no agreement upon paradigm concerning the global geodynamics and lithosphere tectonics for the early Earth. Further progress in this direction requires cross-disciplinary efforts with a special emphasis placed upon quantitative testing of existing geodynamic concepts and extrapolating back in geological time, using both global and regional scale thermomechanical numerical models, which have been validated for present day Earth conditions. Here, we focus on discussing results of recent modeling studies in the context of existing concepts and constraints for Precambrian geodynamics. The three key features of Precambrian Earth evolution are outlined based on combining available observations and thermomechanical models (cf. review by Gerya, 2013): (1) Early Archean pre-subduction geodynamics was dominated by plume tectonics and the development of hot accretionary orogens with low topography, three-dimensional deformation and pronounced gravitational tectonics. Mantle downwellings and lithospheric delamination (dripping-off) processes are likely to have played a key role in assembling and stabilizing the hot orogens on a timescale up to hundreds of millions of years. Both oceanic-like and continental-like lithospheres were rheologically weak due to the high Moho temperature (>800 °C) and melt percolation from hot partially molten sublithospheric mantle (Sizova et al., 2010). (2) Wide spread development of modern-style subduction on Earth started during Mesoarchean-Neoarchean at 3.2-2.5 Ga. This is marked by the appearance of paired metamorphic complexes and oldest eclogite ages in subcontinental lithospheric mantle. Numerical models suggest that the transition occurred at mantle temperatures 175-250 °C higher than present day values, and was triggered by stabilization of rheologically strong plates of both continental and oceanic type (Sizova

  10. Efficient stencil assembly in global geodynamic models

    NASA Astrophysics Data System (ADS)

    Bauer, Simon; Mohr, Marcus; Rüde, Ulrich; Wittmann, Markus

    2016-04-01

    In mantle circulation models the simulation domain is a thick spherical shell representing the earth's mantle. Typically, finite elements are the method of choice to account for the spherical geometry. The wide range of length scales involved in earth dynamics is a major challenge. Capturing localized features such as faulted plate boundaries requires local resolutions in the order of

  11. Recent advances in data assimilation in computational geodynamic models

    NASA Astrophysics Data System (ADS)

    Ismail-Zadeh, Alik

    2010-05-01

    To restore dynamics of mantle structures in the geological past, data assimilation can be used to constrain the initial conditions for the mantle temperature and velocity from their present observations and estimations. The initial conditions so obtained can then be used to run forward models of mantle dynamics to restore the evolution of mantle structures. If heat diffusion is neglected, the present mantle temperature and flow can be assimilated using the backward advection (BAD) into the past. Two- and three-dimensional numerical approaches to the solution of the inverse problem of the Rayleigh-Taylor instability were developed for a dynamic restoration of diapiric structures to their earlier stages (e.g., Ismail-Zadeh et al., 1998, 2001, 2004; Kaus and Podladchikov, 2001). The mantle flow was modelled backwards in time from present-day mantle density heterogeneities inferred from seismic observations (e.g., Steinberger and O'Connell, 1998; Conrad and Gurnis, 2003). The variational (VAR) (or also called adjoint) data assimilation has been pioneered by meteorologists and widely used in oceanography and in hydrological studies. The use of VAR data assimilation in models of geodynamics has been put forward by Bunge et al. (2003) and Ismail-Zadeh et al. (2003). The VAR data assimilation algorithm was employed to restore numerically models of mantle plumes (Ismail-Zadeh et al., 2004, 2006; Hier-Majumder et al., 2005; Liu and Gurnis, 2008; Liu et al., 2008). The use of the quasi-reversibility (QRV) technique (more robust computationally) implies the introduction into the backward heat equation of the additional term involving the product of a small regularization parameter and a higher order temperature derivative (the resulting regularized heat equation is based on the Riemann law of heat conduction). The data assimilation in this case is based on a search of the best fit between the forecast model state and the observations by minimizing the regularization parameter

  12. On the global geodynamic model of the earth

    NASA Astrophysics Data System (ADS)

    Nedoma, J.

    A geodynamic-evolution model based on plate tectonics, the assumed gradual density differentiation of the earth's masses, their phase transitions in response to high temperature and pressure, and the theory of thermoelastoviscoplasticity is developed and illustrated with diagrams. In the model, an unstable layer of light materials enriched with Fe, Mg, and other elements arises at the outer core-mantle boundary by density differentiation of the molten materials and migrates upward through channels of greater temperature and lower viscosity between the mantle convective cells to generate rift zones which eventually break the lithosphere into colliding megaplates. The model is shown to provide explanations of such phenomena as the primary geomagnetic field and its fluctuations; the origin of the protocontinent Pangaea; the basifications of the beds of the original oceans, the present inland and marginal seas, and marginal subduction regions of continents; recent tectonic movements; the unfolded sediments of the deep-sea trenches; and the Conrad, Mohorovicic, and other transitional zones.

  13. Coupling a geodynamic seismic cycling model to rupture dynamic simulations

    NASA Astrophysics Data System (ADS)

    Gabriel, Alice; van Dinther, Ylona

    2014-05-01

    The relevance and results of dynamic rupture scenarios are implicitly linked to the geometry and pre-existing stress and strength state on a fault. The absolute stresses stored along faults during interseismic periods, are largely unquantifiable. They are, however, pivotal in defining coseismic rupture styles, near-field ground motion, and macroscopic source properties (Gabriel et al., 2012). Obtaining these in a physically consistent manner requires seismic cycling models, which directly couple long-term deformation processes (over 1000 year periods), the self-consistent development of faults, and the resulting dynamic ruptures. One promising approach to study seismic cycling enables both the generation of spontaneous fault geometries and the development of thermo-mechanically consistent fault stresses. This seismo-thermo-mechanical model has been developed using a methodology similar to that employed to study long-term lithospheric deformation (van Dinther et al., 2013a,b, using I2ELVIS of Gerya and Yuen, 2007). We will innovatively include the absolute stress and strength values along physically consistent evolving non-finite fault zones (regions of strain accumulation) from the geodynamic model into dynamic rupture simulations as an initial condition. The dynamic rupture simulations will be performed using SeisSol, an arbitrary high-order derivative Discontinuous Galerkin (ADER-DG) scheme (Pelties et al., 2012). The dynamic rupture models are able to incorporate the large degree of fault geometry complexity arising in naturally evolving geodynamic models. We focus on subduction zone settings with and without a splay fault. Due to the novelty of the coupling, we first focus on methodological challenges, e.g. the synchronization of both methods regarding the nucleation of events, the localization of fault planes, and the incorporation of similar frictional constitutive relations. We then study the importance of physically consistent fault stress, strength, and

  14. On the Coupling of Geodynamic and Resistivity Models: A Progress Report and the Way Forward

    NASA Astrophysics Data System (ADS)

    Heise, Wiebke; Ellis, Susan

    2016-01-01

    Magnetotelluric (MT) studies represent the structure of crust and mantle in terms of conductivity anomalies, while geodynamic modelling predicts the deformation and evolution of crust and mantle subject to plate tectonic processes. Here, we review the first attempts to link MT models with geodynamic models. An integration of MT with geodynamic modelling requires the use of relationships between conductivity and rheological parameters such as viscosity and melt fraction, which are provided by laboratory measurements of rock properties. Owing to present limitations in our understanding of these relationships, and in interpreting the trade-off between scale and magnitude of conductivity anomalies from MT inversions, most studies linking MT and geodynamic models are qualitative rather than providing hard constraints. Some recent examples attempt a more quantitative comparison, such as a study from the Himalayan continental collision zone, where rheological parameters have been calculated from a resistivity model and compared to predictions from geodynamic modelling. We conclude by demonstrating the potential in combining MT results and geodynamic modelling with examples that directly use MT results as constraints within geodynamic models of ore bodies and studies of an active volcano-tectonic rift.

  15. Introduction to the special issue celebrating 200 years of geodynamic modelling

    NASA Astrophysics Data System (ADS)

    Strak, Vincent; Schellart, Wouter P.

    2016-10-01

    Since the first published laboratory models from Sir James Hall in 1815, analogue and numerical geodynamic modelling have become widely used as they provide qualitative and quantitative insights into a broad range of geological processes. To celebrate the 200th anniversary of geodynamic modelling, this special issue gathers review works and recent studies on analogue and numerical modelling of tectonic and geodynamic processes, as an opportunity to present some of the milestones and recent breakthroughs in this field, to discuss potential issues and to highlight possible future developments.

  16. Rheology and geodynamic modelling: the next step forward

    NASA Astrophysics Data System (ADS)

    Handy, M.; Braun, J.; Brown, M.; Kukowski, N.; Paterson, M.; Schmid, S.; Stöckhert, B.; Stüwe, K.; Thompson, A.; Wosnitza, E.

    2001-05-01

    The application of continuum mechanics and microstructural analysis to geological studies over the past 30 years has spurred earth scientists to reassess fundamental tectonic processes such as subduction, collision and rifting in terms of dynamics. Armed with new analytical methods, geologists have returned to the field to look at rock structures with more mechanistic eyes. The advent of sophisticated computers, programs, and laboratory deformation equipment has facilitated the simulation of geodynamic processes that range in scale from the grain to the lithosphere. The result has been specialization, with the concomitant opening of communication gaps between geodynamicists, field geologists and rock mechanicists. Partly, these gaps reflect differences of perception and approach. In order to bridge these gaps, a workshop was organized after the DRM conference to debate how field and laboratory studies of deformed rocks can improve our understanding of lithospheric rheology, and in turn, how this understanding can be used to refine dynamic models of orogenesis. The workshop hosted participants with backgrounds in structural geology, experimental rock mechanics, metamorphic petrology and both numerical and analogue modelling. This paper summarizes the main controversies and conclusions reached during the workshop. For the sake of brevity, referencing in this summary is restricted to literature referred to during the oral presentations and to comments made by speakers themselves (names italicized).

  17. Fundamentals studies in geodynamics

    NASA Technical Reports Server (NTRS)

    Anderson, D. L.

    1980-01-01

    Research in geodynamics, seismology, and planetary quakes is presented. Terradynamics and plate tectonics are described using dynamic models. The early evolution of the Earth's mantle is also discussed.

  18. Geodynamic model for the development of the Cameroon Hot Line (Equatorial Africa)

    NASA Astrophysics Data System (ADS)

    Nkono, Collin; Féménias, Olivier; Demaiffe, Daniel

    2014-12-01

    This work proposes a new geodynamic model for the development of the Cameroon Hot Line (CHL) in Equatorial Africa. It is based on the analysis of the distribution of lineaments and of magmatic bodies (Paleogene anorogenic ring-complexes and Neogene volcanic centres). Two successive geodynamic models are proposed to explain the distribution of the Cainozoic to recent magmatic activity. They are both sinistral. The first one, during the Paleogene, developed around the N ∼ 70°E direction while the second one (Neogene) is oriented around the N ∼ 130°E direction. The two periods are separated by a short transition. The emplacement follows the local reactivation of pre-existing (Pan-African) faults in relation to the collision between the Afro-Arabian and Eurasian plates, during the Alpine history.

  19. How craton margins are preserved: Insights from geodynamic models

    NASA Astrophysics Data System (ADS)

    Currie, Claire A.; van Wijk, Jolante

    2016-10-01

    Lateral variations in lithosphere thickness are observed in many continental regions, especially at the boundary between the ancient cratonic core and the adjacent more juvenile lithosphere. In some places, such as the North America craton margin in western Canada and the Sorgenfrei-Tornquist Zone in northern Europe, the transition in lithosphere thickness has a steep gradient (>45°) and it appears to be a long-lived feature (at least 50 Ma). We use thermal-mechanical numerical models to address the dynamics of lithospheric thickness changes on timescales of 100 Ma. Models start with the juxtaposition of 60 km thick lithosphere ("mobile belt") and 160 km thick lithosphere ("craton"). In the reference model, all mantle materials have a damp olivine rheology and a density comparable to primitive mantle. With this configuration, edge-driven mantle convection occurs at the craton boundary, resulting in a lateral smoothing of the thickness transition. The density and rheology of the craton mantle lithosphere are then varied to approximate changes in composition and water content. For all densities, a steep transition is maintained only if the craton strength is 5-50 times stronger than the reference damp olivine. If dry olivine is an upper limit on strength, only cratonic mantle with moderate compositional buoyancy (20-40 kg/m3 less dense than primitive mantle) remains stable. At higher densities, the thick lithosphere is eroded through downwellings, and the craton margin migrates inboard. Conversely, a compositionally buoyant craton destabilises through lateral spreading below the mobile belt.

  20. The geodynamical evolution of the Northern Apennines chain (Central Italy): an exploring numerical model

    NASA Astrophysics Data System (ADS)

    Pauselli, Cristina; Federico, Costanzo; Braun, Jean

    2004-04-01

    In this paper, 2D thermo-mechanical models with crustal deformation, driven by subduction, are performed to test the geodynamical scenario of a slab-retreat for the Northern Apennines chain (Central Italy). In the models, the lithosphere is regarded as a non-linear Maxwell visco-elastic body capable of brittle failure at low pressure and temperature and of viscous creep at elevated temperature, in Lagrangian description of deformations. We focus particularly on the time variation of the thermal field across the chain in order to evaluate the influence of temperature on the final crustal-scale deformation. Bearing in mind the difficulty to "frame" the history of an orogen in a simple, unique model and the intrinsic limitations of numerical technique, the performed models were able to give a deeper insight into the evolution of this region. On the basis of the results, we suggest that the presence of roll-back retreat together with the intrusion of an asthenospheric rise on the retreating lithosphere justify particular geological and geophysical features observed today across the chain. The models predict that this geodynamical scenario determines both the collapse of the previously formed Alpine orogen and the observed progradation of the deformation front toward east. The models also predict that the regional uplift that has interested the western sector of the chain (Tuscany), is due to the increase of temperature connected with the asthenospheric rise.

  1. Geodynamics Project

    ERIC Educational Resources Information Center

    Drake, Charles L.

    1977-01-01

    Describes activities of Geodynamics Project of the Federal Council on Science and Technology, such as the application of multichannel seismic-reflection techniques to study the nature of the deep crust and upper mantle. (MLH)

  2. Probabilistic seismic hazard study based on active fault and finite element geodynamic models

    NASA Astrophysics Data System (ADS)

    Kastelic, Vanja; Carafa, Michele M. C.; Visini, Francesco

    2016-04-01

    We present a probabilistic seismic hazard analysis (PSHA) that is exclusively based on active faults and geodynamic finite element input models whereas seismic catalogues were used only in a posterior comparison. We applied the developed model in the External Dinarides, a slow deforming thrust-and-fold belt at the contact between Adria and Eurasia.. is the Our method consists of establishing s two earthquake rupture forecast models: (i) a geological active fault input (GEO) model and, (ii) a finite element (FEM) model. The GEO model is based on active fault database that provides information on fault location and its geometric and kinematic parameters together with estimations on its slip rate. By default in this model all deformation is set to be released along the active faults. The FEM model is based on a numerical geodynamic model developed for the region of study. In this model the deformation is, besides along the active faults, released also in the volumetric continuum elements. From both models we calculated their corresponding activity rates, its earthquake rates and their final expected peak ground accelerations. We investigated both the source model and the earthquake model uncertainties by varying the main active fault and earthquake rate calculation parameters through constructing corresponding branches of the seismic hazard logic tree. Hazard maps and UHS curves have been produced for horizontal ground motion on bedrock conditions VS 30 ≥ 800 m/s), thereby not considering local site amplification effects. The hazard was computed over a 0.2° spaced grid considering 648 branches of the logic tree and the mean value of 10% probability of exceedance in 50 years hazard level, while the 5th and 95th percentiles were also computed to investigate the model limits. We conducted a sensitivity analysis to control which of the input parameters influence the final hazard results in which measure. The results of such comparison evidence the deformation model and

  3. Constraining the rheology of the lithosphere and upper mantle with geodynamic inverse modelling

    NASA Astrophysics Data System (ADS)

    Kaus, Boris; Baumann, Tobias

    2016-04-01

    The rheology of the lithosphere is of key importance for the physics of the lithosphere. Yet, it is probably the most uncertain parameter in geodynamics as experimental rock rheologies have to be extrapolated to geological conditions and as existing geophysical methods such as EET estimations make simplifying assumptions about the structure of the lithosphere. In many geologically interesting regions, such as the Alps, Andes or Himalaya, we actually have a significant amount of data already and as a result the geometry of the lithosphere is quite well constrained. Yet, knowing the geometry is only one part of the story, as we also need to have an accurate knowledge on the rheology and temperature structure of the lithosphere. Here, we discuss a relatively new method that we developed over the last few years, which is called geodynamic inversion. The basic principle of the method is simple: we compile available geophysical data into a realistic geometric model of the lithosphere and incorporate that into a thermo-mechanical numerical model of lithospheric deformation. In order to do so, we have to know the temperature structure, the density and the (nonlinear) rheological parameters for various parts of the lithosphere (upper crust, upper mantle, etc.). Rather than fixing these parameters we assume that they are all uncertain. This is used as a priori information to formulate a Bayesian inverse problem that employs topography, gravity, horizontal and vertical surface velocities to invert for the unknown material parameters and temperature structure. In order to test the general methodology, we first perform a geodynamic inversion of a synthetic forward model of intra-oceanic subduction with known parameters. This requires solving an inverse problem with 14-16 parameters, depending on whether temperature is assumed to be known or not. With the help of a massively parallel direct-search combined with a Markov Chain Monte Carlo method, solving the inverse problem

  4. Using Interactive Visualization to Analyze Solid Earth Data and Geodynamics Models

    NASA Astrophysics Data System (ADS)

    Kellogg, L. H.; Kreylos, O.; Billen, M. I.; Hamann, B.; Jadamec, M. A.; Rundle, J. B.; van Aalsburg, J.; Yikilmaz, M. B.

    2008-12-01

    The geological sciences are challenged to manage and interpret increasing volumes of data as observations and simulations increase in size and complexity. Major projects such as EarthScope and GeoEarthScope are producing the data needed to characterize the structure and kinematics of Earth's surface and interior at unprecedented resolution. At the same time, high-performance computing enables high-precision and fine- detail simulation of geodynamics processes, complementing the observational data. To facilitate interpretation and analysis of these datasets, to evaluate models, and to drive future calculations, we have developed methods of interactive visualization with a special focus on using immersive virtual reality (VR) environments to interact with models of Earth's surface and interior. VR has traditionally been used primarily as a presentation tool allowing active navigation through data. Reaping the full intellectual benefits of immersive VR as a tool for accelerated scientific analysis requires building on the method's strengths, that is, using both 3D perception and interaction with observed or simulated data. Our approach to VR takes advantage of the specialized skills of geoscientists who are trained to interpret geological and geophysical data generated from field observations. Interactive tools allow the scientist to explore and interpret geodynamic models, tomographic models, and topographic observations, while feature extraction tools support quantitative measurement of structures that emerge from numerical simulations or field observations. The use of VR technology enables us to improve our interpretation of crust and mantle structure and of geodynamical processes. Mapping tools based on computer visualization allow virtual "field studies" in inaccessible regions, and an interactive tool allows us to construct digital fault models for use in numerical models. Using the interactive tools on a high-end platform such as an immersive virtual reality

  5. Testing geodynamic models of lowermost mantle flow with a regional shear wave splitting data set

    NASA Astrophysics Data System (ADS)

    Ford, H. A.; Long, M. D.

    2015-12-01

    Global flow models rely on a number of assumptions, including composition, temperature, viscosity, and deformation mechanism. In the upper mantle, flow models and their associated assumptions can be tested and refined with observations of seismic anisotropy, which is treated as a proxy for flow direction. Beneath the transition zone, direct observations of seismic anisotropy are scarce, except for in the lowermost ~250 km of the mantle. In this study, we utilize a comprehensive, previously published (Ford et al., 2015) shear wave splitting study in order to test a three-dimensional global geodynamic flow model (Walker et al., 2011). Our study focuses on a region of the lowermost mantle along the eastern edge of the African Superplume beneath the Afar region. We find that our observations are fit by a model which invokes slip along the (010) plane of post-perovskite with flow directed down and to the southwest. Critically, we demonstrate the ability of a regional data set to interrogate models of lower mantle flow.

  6. Geodynamic models of convergent margin tectonics: transition from rifted margin to overthrust belt and consequences for foreland-basin development

    SciTech Connect

    Stockmal, G.S.; Beaumont, C.; Boutilier, R.

    1986-02-01

    A quantitative geodynamic model for overthrusting of a passive continental margin during attempted continental subduction demonstrates the mechanical and thermal coupling between overthrust loads, the lithosphere, and the associated foreland basin. The model treated the lithosphere as a two-dimensional nonuniform elastic plate whose strength is controlled thermally. The thermal and flexural evolution of a margin is followed from initial rifting and passive-margin development, through overthrusting and foreland-basin deposition, to postdeformational erosion.

  7. Tomographic-Geodynamic Model Comparisons and the Presence of Post-Perovskite and Chemical Heterogeneity in Earth's Lowermost Mantle

    NASA Astrophysics Data System (ADS)

    Koelemeijer, P.; Deuss, A. F.; Ritsema, J.; van Heijst, H. J.; Davies, R.; Schuberth, B. S. A.; Chust, T.

    2014-12-01

    Dynamic processes occurring in the mantle and core interact at the core-mantle boundary (CMB), which marks the largest thermal and compositional interface inside the Earth. This interplay has produced a myriad of complex structures in the lowermost mantle that offer valuable insights into the dynamics of this region. Large-low-shear velocity provinces (LLSVPs) dominate shear wave velocity (Vs) models of the deep mantle. In addition, global tomography studies generally find an increase in the ratio of shear wave to compressional wave velocity (Vp) variations, accompanied by a significant anti-correlation between shear wave and bulk sound velocity (Vc) variations. These seismic characteristics, also observed in the recent SP12RTS tomographic model, have primarily been interpreted in terms of chemical variations but could potentially also be explained by the presence of the deep mantle post-perovskite (pPv) phase. In this contribution, we attempt to interpret the observed seismic characteristics by linking them to dynamic processes occurring in the deep mantle. For this purpose, we compare the shear and compressional wave velocity structure of SP12RTS to mantle structure derived from geodynamic models of mantle convection. We project the geodynamic models into the SP12RTS model parametrization and use its resolution operator to account for the limited tomographic resolution. We include geodynamic models with and without the post-perovskite phase and/or chemical variations and in addition vary the CMB temperature. Although the reparametrization and tomographic filtering significantly affect the obtained mantle structure, we demonstrate that the patterns observed in the ratios and correlations of seismic velocities are robust features. Our tomographic-geodynamic model comparison suggests that the seismic characteristics can be explained by the presence of post-perovskite but it allows no discrimination between isochemical and thermochemical models of mantle convection.

  8. Geodynamic models of the deep structure of the natural disaster regions of the Earth

    NASA Astrophysics Data System (ADS)

    Rodnikov, A. G.; Sergeyeva, N. A.; Zabarinskaya, L. P.

    2012-04-01

    Investigation of the deep structure and creation of geodynamic models of natural disaster regions are important for understanding of the nature of such phenomena as earthquakes, eruptions of volcanoes, tsunami and others. Carrying out of such researches is necessary for definition of areas of potential risk, forecasting and the prevention of negative consequences of acts of nature. Research region is active continental margins of the Sea of Okhotsk, and especially the area of Neftegorsk earthquake which has occurred on May, 28th 1995 in the North Sakhalin and caused many victims and destructions. The geodynamic model of the lithosphere in the region of Neftegorsk earthquake has been constructed along the profile crossing the North Sakhalin Basin, Deryugin Basin and ophiolite complex between them. The Deryugin Basin was formed at the site of an ancient deep trench after the subduction of the Okhotsk Sea Plate under Sakhalin. The basin is located above a hot plume in the mantle at a depth of 25 km. The ophiolite belt of ultramafic magmatic rocks is an ancient (K2-Pg) paleosubduction zone separating the Deryugin basin from the North Sakhalin Basin. The thickness of the ancient seismic focal zone is 80 km. It is probably that the structures of the North Sakhalin have been formed in the following way. In the Late Cretaceous the oceanic Okhotsk Sea Plate subducted under Sakhalin, the eastern part of which was an andesite island arc. Approximately in Miocene the subduction of the plate apparently ceased. In that time the Tatar Rift Strait was formed. Ophiolite rocks of the subduction zones as a result of compression have been squeezed out on a surface. The ophiolite complex combined by the ultrabasic rocks, fixes position of ancient subduction zone. It is probable that the manifestation of the Neftegorsk earthquake was a result of activization of this ancient subduction zone. On a surface the subduction zone manifests itself as deep faults running along Sakhalin. The

  9. Reconciling laboratory and observational models of mantle rheology in geodynamic modelling

    NASA Astrophysics Data System (ADS)

    King, Scott D.

    2016-10-01

    Experimental and geophysical observations constraining mantle rheology are reviewed with an emphasis on their impact on mantle geodynamic modelling. For olivine, the most studied and best-constrained mantle mineral, the tradeoffs associated with the uncertainties in the activation energy, activation volume, grain-size and water content allow the construction of upper mantle rheology models ranging from nearly uniform with depth to linearly increasing from the base of the lithosphere to the top of the transition zone. Radial rheology models derived from geophysical observations allow for either a weak upper mantle or a weak transition zone. Experimental constraints show that wadsleyite and ringwoodite are stronger than olivine at the top of the transition zone; however the uncertainty in the concentration of water in the transition zone precludes ruling out a weak transition zone. Both observational and experimental constraints allow for strong or weak slabs and the most promising constraints on slab rheology may come from comparing inferred slab geometry from seismic tomography with systematic studies of slab morphology from dynamic models. Experimental constraints on perovskite and ferropericlase strength are consistent with general feature of rheology models derived from geophysical observations and suggest that the increase in viscosity through the top of the upper mantle could be due to the increase in the strength of ferropericlase from 20-65 GPa. The decrease in viscosity in the bottom half of the lower mantle could be the result of approaching the melting temperature of perovskite. Both lines of research are consistent with a high-viscosity lithosphere, a low viscosity either in the upper mantle or transition zone, and high viscosity in the lower mantle, increasing through the upper half of the lower mantle and decreasing in the bottom half of the lower mantle, with a low viscosity above the core. Significant regions of the mantle, including high

  10. Project MANTIS: A MANTle Induction Simulator for coupling geodynamic and electromagnetic modeling

    NASA Astrophysics Data System (ADS)

    Weiss, C. J.

    2009-12-01

    A key component to testing geodynamic hypotheses resulting from the 3D mantle convection simulations is the ability to easily translate the predicted physiochemical state to the model space relevant for an independent geophysical observation, such as earth's seismic, geodetic or electromagnetic response. In this contribution a new parallel code for simulating low-frequency, global-scale electromagnetic induction phenomena is introduced that has the same Earth discretization as the popular CitcomS mantle convection code. Hence, projection of the CitcomS model into the model space of electrical conductivity is greatly simplified, and focuses solely on the node-to-node, physics-based relationship between these Earth parameters without the need for "upscaling", "downscaling", averaging or harmonizing with some other model basis such as spherical harmonics. Preliminary performance tests of the MANTIS code on shared and distributed memory parallel compute platforms shows favorable scaling (>70% efficiency) for up to 500 processors. As with CitcomS, an OpenDX visualization widget (VISMAN) is also provided for 3D rendering and interactive interrogation of model results. Details of the MANTIS code will be briefly discussed here, focusing on compatibility with CitcomS modeling, as will be preliminary results in which the electromagnetic response of a CitcomS model is evaluated. VISMAN rendering of electrical tomography-derived electrical conductivity model overlain by an a 1x1 deg crustal conductivity map. Grey scale represents the log_10 magnitude of conductivity [S/m]. Arrows are horiztonal components of a hypothetical magnetospheric source field used to electromagnetically excite the conductivity model.

  11. Geodynamics Branch research report, 1982

    NASA Technical Reports Server (NTRS)

    Kahn, W. D. (Editor); Cohen, S. C. (Editor)

    1983-01-01

    The research program of the Geodynamics Branch is summarized. The research activities cover a broad spectrum of geoscience disciplines including space geodesy, geopotential field modeling, tectonophysics, and dynamic oceanography. The NASA programs which are supported by the work described include the Geodynamics and Ocean Programs, the Crustal Dynamics Project, the proposed Ocean Topography Experiment (TOPEX) and Geopotential Research Mission. The individual papers are grouped into chapters on Crustal Movements, Global Earth Dynamics, Gravity Field Model Development, Sea Surface Topography, and Advanced Studies.

  12. THERIAK_D: An add-on to implement equilibrium computations in geodynamic models

    NASA Astrophysics Data System (ADS)

    Duesterhoeft, Erik; Capitani, Christian

    2013-11-01

    This study presents the theory, applicability, and merits of the new THERIAK_D add-on for the open source Theriak/Domino software package. The add-on works as an interface between Theriak and user-generated scripts, providing the opportunity to process phase equilibrium computation parameters in a programming environment (e.g., C or MATLAB®). THERIAK_D supports a wide range of features such as calculating the solid rock density or testing the stability of mineral phases along any pressure-temperature (P-T) path and P-T grid. To demonstrate applicability, an example is given in which the solid rock density of a 2-D-temperature-pressure field is calculated, portraying a simplified subduction zone. Consequently, the add-on effectively combines thermodynamics and geodynamic modeling. The carefully documented examples could be easily adapted for a broad range of applications. THERIAK_D is free, and the program, user manual, and source codes may be downloaded from http://www.min.uni-kiel.de/˜ed/theriakd/.

  13. 3D Geodynamic Modelling Reveals Stress and Strain Partitioning within Continental Rifting

    NASA Astrophysics Data System (ADS)

    Rey, P. F.; Mondy, L. S.; Duclaux, G.; Moresi, L. N.

    2014-12-01

    The relative movement between two divergent rigid plates on a sphere can be described using a Euler pole and an angular velocity. On Earth, this typically results in extensional velocities increasing linearly as a function of the distance from the pole (for example in the South Atlantic, North Atlantic, Woodlark Basin, Red Sea Basin, etc.). This property has strong implications for continental rifting and the formation of passive margins, given the role that extensional velocity plays on both rift style (wide or narrow), fault pattern, subsidence histories, and magmatism. Until now, this scissor-style opening has been approached via suites of 2D numerical models of contrasting extensional velocities, complimenting field geology and geophysics. New advances in numerical modelling tools and computational hardware have enabled us to investigate the geodynamics of this problem in a 3D self-consistent high-resolution context. Using Underworld at a grid resolution of 2 km over a domain of 500 km x 500 km x 180 km, we have explored the role of the velocity gradient on the strain pattern, style of rifting, and decompression melting, along the margin. We find that the three dimensionality of this problem is important. The rise of the asthenosphere is enhanced in 2D models compared to 3D numerical solutions, due to the limited volume of material available in 2D. This leads to oceanisation occurring significantly sooner in 2D models. The 3D model shows that there is a significant time and space dependent flows parallel to the rift-axis. A similar picture emerges from the stress field, showing time and space partitioning, including regions of compression separating areas dominated by extension. The strain pattern shows strong zonation along the rift axis, with increasingly localised deformation with extension velocity and though time.

  14. Simulation of late Cenozoic South American flat-slab subduction using geodynamic models with data assimilation

    NASA Astrophysics Data System (ADS)

    Hu, Jiashun; Liu, Lijun; Hermosillo, Armando; Zhou, Quan

    2016-03-01

    The formation mechanisms of flat slabs in South America remain unclear. To quantitatively evaluate the earlier proposed mechanisms, we simulate the post-100 Ma subduction history below South America using 4-D geodynamic models by progressively incorporating plate kinematics, seafloor ages and key tectonic features including the buoyant oceanic crust, continental cratons, oceanic plateaus (i.e. the inferred Inca plateau, subducting Nazca Ridge and Juan Fernandez Ridge), as well as deformable trench profiles according to recent geological reconstructions. We find that, in the absence of an overriding plate and subducting buoyancy features, the seafloor age affects slab dip angle by controlling the slab's mechanical strength (i.e., the resistance to bending) and negative buoyancy (integrated positive density anomaly that enhances bending). Our models show that slab strength dominates its buoyancy at age >30 Ma and the opposite for younger ages. The existence of a thick overriding plate reduces the slab dip by increasing dynamic suction, and individual cratonic roots further lead to along-trench variations of dip angle reduction. While dynamic suction from the overriding plate generates a permanent reduction of the long-wavelength slab dip angle, it is the final addition of subducting oceanic plateau and aseismic ridges that produces the transient and localized flat-slabs as observed. These results suggest that all mechanisms except the buoyancy features affect the slab dip only at large spatial scales. Our best-fit model with all the above tectonic features included provides a good match to both the upper mantle Benioff zones and the temporal evolution of volcanic arcs since the mid-Miocene. The imperfect match of the Peruvian flat-slab is likely associated with the uncertain 3-D configuration of the Amazonian craton.

  15. NASA geodynamics program: Bibliography

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The Seventh Geodynamics Program report summarizes program activities and achievements during 1988 and 1989. Included is a 115 page bibliography of the publications associated with the NASA Geodynamics Program since its initiation in 1979.

  16. NASA Geodynamics Program

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Activities and achievements for the period of May 1983 to May 1984 for the NASA geodynamics program are summarized. Abstracts of papers presented at the Conference are inlcuded. Current publications associated with the NASA Geodynamics Program are listed.

  17. Basic research for the geodynamics program

    NASA Technical Reports Server (NTRS)

    Mueller, I. I.

    1982-01-01

    Work performed and data obtained in geodynamic research is reported. The purpose was to obtain utilization of: (1) laser and very long baseline interferometry (VLBI); (2) range difference observation in geodynamics; (3) development of models for ice sheet and crustal deformations. The effects of adopting new precession, nutation and equinox corrections on the terrestrial reference frame are investigated.

  18. Reconstructing palaeo-volcanic geometries using a Geodynamic Regression Model (GRM): Application to Deception Island volcano (South Shetland Islands, Antarctica)

    NASA Astrophysics Data System (ADS)

    Torrecillas, C.; Berrocoso, M.; Felpeto, A.; Torrecillas, M. D.; Garcia, A.

    2013-01-01

    This article describes a reconstruction made of the palaeo-volcanic edifice on Deception Island (South Shetland Islands, Antarctica) prior to the formation of its present caldera. Deception Island is an active Quaternary volcano located in the Bransfield Strait, between the South Shetland Islands and the Antarctic Peninsula. The morphology of the island has been influenced mainly by the volcanic activity but geodynamics and volcanic deformation have also contributed. A volcanic reconstruction method, the Geodynamic Regression Model (GRM), which includes a terrain deformation factor, is proposed. In the case of Deception Island, the directions of this deformation are NW-SE and NE-SW, and match both the observed deformation of the Bransfield Strait and the volcanic deformation monitored over the last 20 years in the island, using Global Navigation Satellite System (GNSS) techniques. Based on these data, possible volcanic deformation values of 5-15 mm/yr in these directions have been derived. A possible coastline derived from a current bathymetry is transformed, according to values for the chosen date, to obtain the palaeo-coastline of Deception Island of 100 k years ago. Topographic, geomorphologic, volcanological and geological data in a GIS system have been considered, for computation of the outside caldera slope, palaeo-coastline, palaeo-summit height and palaeo digital elevation model (DEM). The result is a 3D palaeo-geomorphological surface model of a volcano, reaching 640 m in height, with an increase of 4 km3 in volume compared to the current edifice, covering 4 km2 more surface area and the method reveals the previous existence of parasite volcanoes. Two photorealistic images of the island are obtained by superposition of textures extracted from a current Quick Bird satellite image also. This technique for reconstructing the terrain of an existing volcano could be useful for analysing the past and future geomorphology of this island and similar locations.

  19. Geodynamic Models for Various Styles of Melting in the Lithosphere Delamination Process

    NASA Astrophysics Data System (ADS)

    Gogus, Oguz; Ueda, Kosuke; Gerya, Taras; Gün, Erkan

    2016-04-01

    Lithospheric delamination in the sense of peel away of the mantle lithosphere from the overlying crust may occur during and at the terminal phase of the orogenic cycle and it has been recognized as a significant geodynamic process to identify the elevated surface topography, widespread magmatism and distinct crustal deformation patterns (i.e extension and shortening). However, the role of decompression melting of the mantle and slab melting in conjunction with the delamination of the lithosphere as well as the resulting magmatism/surface topography remains uncertain. In this work, by using thermomechanical numerical experiments we investigate the evolution and emplacement of the melt produced by slab-derived fluids and the decompression melting under an accretionary crust. Our numerical experiments with varying activation volume of the mantle lithosphere and the asthenospheric mantle as well as plate convergence velocity aims to configure the orogenic evolution from ocean lithosphere subduction to delamination in the course of melt related weakening process. Our results suggest that the entrainments of the melting induced by the subducting slab reaches under the accretionary wedge and fosters the plate decoupling/delamination between accretionary crust and the underlying mantle lithosphere. With all parameters kept the same and the convergence velocity of Vp = 4 cm/year, decrease in the activation volume in the mantle nearly 5% results in the % 70 increase for the amount of decompression melting, therefore the widening the delamination zone. Surface elevation above the zone of delamination may lower the topography at least 1 km due to the crustal stretching as a response to melt induced weakening of the crust. When there is no decompression melting under the delamination zone the surface crust may uplift as much 3 km. Our results may explain the role of melting and widesprad magmatic activity under the orogenic plateaus where they are underlain by weak accretionary

  20. A High-resolution 3D Geodynamical Model of the Present-day India-Asia Collision System

    NASA Astrophysics Data System (ADS)

    Kaus, B.; Baumann, T.

    2015-12-01

    We present a high-resolution, 3D geodynamic model of the present-day India-Asia collision system. The model is separated into multiple tectonic blocks, for which we estimate the first order rheological properties and the impact on the dynamics of the collision system. This is done by performing systematic simulations with different rheologies to minimize the misfit to observational constraints such as the GPS-velocity field. The simulations are performed with the parallel staggered grid FD code LaMEM using a numerical resolution of at least 512x512x256 cells to resolve dynamically important shear zones reasonably well. A fundamental part of this study is the reconstruction of the 3D present-day geometry of Tibet and the adjacent regions. Our interpretations of crust and mantle lithosphere geometry are jointly based on a globally available shear wave tomography (Schaeffer and Lebedev, 2013) and the Crust 1.0 model (Laske et al. http://igppweb.ucsd.edu/~gabi/crust1.html). We regionally refined and modified our interpretations based on seismicity distributions and focal mechanisms and incorporated regional receiver function studies to improve the accuracy of the Moho in particular. Results suggest that we can identify at least one "best-fit" solution in terms of rheological model properties that reproduces the observed velocity field reasonably well, including the strong rotation of the GPS velocity around the eastern syntax of the Himalaya. We also present model co-variances to illustrate the trade-offs between the rheological model parameters, their respective uncertainties, and the model fit. Schaeffer, A.J., Lebedev, S., 2013. Global shear speed structure of the upper mantle and transition zone. Geophysical Journal International 194, 417-449. doi:10.1093/gji/ggt095

  1. NASA geodynamics program

    NASA Technical Reports Server (NTRS)

    1980-01-01

    The history and development of the geodynamics program are described, in addition to accomplishments and plans for the future years activities. Extramural grant titles are listed for general research, Lageos investigations, and Magsat investigations.

  2. Earth rotation and geodynamics

    NASA Astrophysics Data System (ADS)

    Bogusz, Janusz; Brzezinski, Aleksander; Kosek, Wieslaw; Nastula, Jolanta

    2015-12-01

    This paper presents the summary of research activities carried out in Poland in 2011-2014 in the field of Earth rotation and geodynamics by several Polish research institutions. It contains a summary of works on Earth rotation, including evaluation and prediction of its parameters and analysis of the related excitation data as well as research on associated geodynamic phenomena such as geocentre motion, global sea level change and hydrological processes. The second part of the paper deals with monitoring of geodynamic phenomena. It contains analysis of geodynamic networks of local, and regional scale using space (GNSS and SLR) techniques, Earth tides monitoring with gravimeters and water-tube hydrostatic clinometer, and the determination of secular variation of the Earth' magnetic field.

  3. Fundamental studies in geodynamics

    NASA Technical Reports Server (NTRS)

    Anderson, D. L.; Hager, B. H.; Kanamori, H.

    1981-01-01

    Research in fundamental studies in geodynamics continued in a number of fields including seismic observations and analysis, synthesis of geochemical data, theoretical investigation of geoid anomalies, extensive numerical experiments in a number of geodynamical contexts, and a new field seismic volcanology. Summaries of work in progress or completed during this report period are given. Abstracts of publications submitted from work in progress during this report period are attached as an appendix.

  4. Geodynamics: Introduction and Background

    NASA Technical Reports Server (NTRS)

    1984-01-01

    An overview is given of the field of geodynamics and its major scientific questions. The NASA geodynamics program is described as well as its status and accomplishments projected by 1988. Federal coordination and international cooperation in monitoring tectonic plate motion, polar motion, and Earth rotation are mentioned. The development of a GPS receiver for civilian geodesy and results obtained using satellite laser ranging and very long baseline interferometry in measuring crustal dynamics, global dynamics, and the geopotential field are reported.

  5. Including the effects of elastic compressibility and volume changes in geodynamical modeling of crust-lithosphere-mantle deformation

    NASA Astrophysics Data System (ADS)

    de Monserrat, Albert; Morgan, Jason P.

    2016-04-01

    Materials in Earth's interior are exposed to thermomechanical (e.g. variations in stress/pressure and temperature) and chemical (e.g. phase changes, serpentinization, melting) processes that are associated with volume changes. Most geodynamical codes assume the incompressible Boussinesq approximation, where changes in density due to temperature or phase change effect buoyancy, yet volumetric changes are not allowed, and mass is not locally conserved. Elastic stresses induced by volume changes due to thermal expansion, serpentinization, and melt intrusion should cause 'cold' rocks to brittlely fail at ~1% strain. When failure/yielding is an important rheological feature, we think it plausible that volume-change-linked stresses may have a significant influence on the localization of deformation. Here we discuss a new Lagrangian formulation for "elasto-compressible -visco-plastic" flow. In this formulation, the continuity equation has been generalised from a Boussinesq incompressible formulation to include recoverable, elastic, volumetric deformations linked to the local state of mean compressive stress. This formulation differs from the 'anelastic approximation' used in compressible viscous flow in that pressure- and temperature- dependent volume changes are treated as elastic deformation for a given pressure, temperature, and composition/phase. This leads to a visco-elasto-plastic formulation that can model the effects of thermal stresses, pressure-dependent volume changes, and local phase changes. We use a modified version of the (Miliman-based) FEM code M2TRI to run a set of numerical experiments for benchmarking purposes. Three benchmarks are being used to assess the accuracy of this formulation: (1) model the effects on density of a compressible mantle under the influence of gravity; (2) model the deflection of a visco-elastic beam under the influence of gravity, and its recovery when gravitational loading is artificially removed; (3) Modelling the stresses

  6. The Multi-factor Predictive Seis &Gis Model of Ecological, Genetical, Population Health Risk and Bio-geodynamic Processes In Geopathogenic Zones

    NASA Astrophysics Data System (ADS)

    Bondarenko, Y.

    I. Goal and Scope. Human birth rate decrease, death-rate growth and increase of mu- tagenic deviations risk take place in geopathogenic and anthropogenic hazard zones. Such zones create unfavourable conditions for reproductive process of future genera- tions. These negative trends should be considered as a protective answer of the com- plex biosocial system to the appearance of natural and anthropogenic risk factors that are unfavourable for human health. The major goals of scientific evaluation and de- crease of risk of appearance of hazardous processes on the territory of Dnipropetrovsk, along with creation of the multi-factor predictive Spirit-Energy-Information Space "SEIS" & GIS Model of ecological, genetical and population health risk in connection with dangerous bio-geodynamic processes, were: multi-factor modeling and correla- tion of natural and anthropogenic environmental changes and those of human health; determination of indicators that show the risk of destruction structures appearance on different levels of organization and functioning of the city ecosystem (geophys- ical and geochemical fields, soil, hydrosphere, atmosphere, biosphere); analysis of regularities of natural, anthropogenic, and biological rhythms' interactions. II. Meth- ods. The long spatio-temporal researches (Y. Bondarenko, 1996, 2000) have proved that the ecological, genetic and epidemiological processes are in connection with de- velopment of dangerous bio-geophysical and bio-geodynamic processes. Mathemat- ical processing of space photos, lithogeochemical and geophysical maps with use of JEIS o and ERDAS o computer systems was executed at the first stage of forma- tion of multi-layer geoinformation model "Dnipropetrovsk ARC View GIS o. The multi-factor nonlinear correlation between solar activity and cosmic ray variations, geophysical, geodynamic, geochemical, atmospheric, technological, biological, socio- economical processes and oncologic case rate frequency, general and primary

  7. Geodynamic modeling of the capture and release of a plume conduit by a migrating mid-ocean ridge

    NASA Astrophysics Data System (ADS)

    Hall, P. S.

    2011-12-01

    plates over the relatively stationary, long-lived conduits of mantle plumes. However, paleomagnetic data from the Hawaii-Emperor Seamount Chain suggests that the Hawaiian hotspot moved rapidly (~40 mm/yr) between 81 - 47 Ma [Tarduno et al., 2003]. Recently, Tarduno et al. [2009] suggested that this period of rapid motion might be the surface expression of a plume conduit returning to a largely vertical orientation after having been captured and tilted as the result of being "run over" by migrating mid-ocean ridge. I report on a series of analog geodynamic experiments designed to characterize the evolution of a plume conduit as a mid-ocean ridge migrates over. Experiments were conducted in a clear acrylic tank (100 cm x 70 cm x 50 cm) filled with commercial grade high-fructose corn syrup. Plate-driven flow is modeled by dragging two sheets of Mylar film (driven by independent DC motors) in opposite directions over the surface of the fluid. Ridge migration is achieved by moving the point at which the mylar sheets diverge using a separate motor drive. Buoyant plume flow is generated using a small electrical heater placed at the bottom of the tank. Plate velocities and ridge migration rate are controlled and plume temperature monitored using LabView software. Experiments are recorded using digital video which is then analyzed using digital image analysis software to track the position and shape of the plume conduit throughout the course of the experiment. The intersection of the plume conduit with the surface of the fluid is taken as an analog for the locus of hotspot volcanism and tracked as a function of time to obtain a hotspot migration rate. Results show that the plume conduit experiences significant tilting immediately following the passage of the migrating ridge.

  8. Integrating Geochemical and Geodynamic Numerical Models of Mantle Evolution and Plate Tectonics

    NASA Astrophysics Data System (ADS)

    Tackley, P. J.; Xie, S.

    2001-12-01

    The thermal and chemical evolution of Earth's mantle and plates are inextricably coupled by the plate tectonic - mantle convective system. Convection causes chemical differentiation, recycling and mixing, while chemical variations affect the convection through physical properties such as density and viscosity which depend on composition. It is now possible to construct numerical mantle convection models that track the thermo-chemical evolution of major and minor elements, and which can be used to test prospective models and hypotheses regarding Earth's chemical and thermal evolution. Model thermal and chemical structures can be compared to results from seismic tomography, while geochemical signatures (e.g., trace element ratios) can be compared to geochemical observations. The presented, two-dimensional model combines a simplified 2-component major element model with tracking of the most important trace elements, using a tracer method. Melting is self-consistently treated using a solidus, with melt placed on the surface as crust. Partitioning of trace elements occurs between melt and residue. Decaying heat-producing elements and secular cooling of the mantle and core provide the driving heat sources. Pseudo-plastic yielding of the lithosphere gives a first-order approximation of plate tectonics, and also allows planets with a rigid lid or intermittent plate tectonics to be modeled simply by increasing the yield strength. Preliminary models with an initially homogeneous mantle show that regions with a HIMU-like signature can be generated by crustal recycling, and regions with high 3He/4He ratios can be generated by residuum recycling. Outgassing of Argon is within the observed range. Models with initially layered mantles will also be investigated. In future it will be important to include a more realistic bulk compositional model that allows continental crust as well as oceanic crust to form, and to extend the model to three dimensions since toroidal flow may alter

  9. Investigating the presence of post-perovskite and large-scale chemical variations in Earth's lower mantle using tomographic-geodynamic model comparisons.

    NASA Astrophysics Data System (ADS)

    Koelemeijer, Paula; Ritsema, Jeroen; Deuss, Arwen; Davies, Rhodri; Schuberth, Bernhard

    2016-04-01

    Tomographic models of the Earth's mantle consistently image two large provinces of low shear-wave velocities (LLSVPs) in the lowermost mantle beneath Africa and the Pacific. Seismic studies also find an increase in the ratio of shear-wave velocity (Vs) to compressional-wave velocity (Vp) variations, accompanied by a significant negative correlation between shear-wave and bulk-sound velocity (Vc) variations, both of which are also observed in the recent SP12RTS model. The LLSVPs have consequently been suggested to represent intrinsically dense piles of thermochemical material. Alternatively, they have been interpreted as poorly imaged clusters of thermal plumes, with the deep mantle post-perovskite (pPv) phase invoked as explanation for the high Vs/Vp ratios and Vs-Vc anti-correlation. Geodynamical calculations of thermal plumes and thermochemical piles predict a fundamentally different style of mantle convection, interface topographies and CMB heat flow. However, to interpret tomographic images using these high-resolution models, the limited resolving power of seismic tomography has to be accounted for. Here, we interpret the observed seismic characteristics of SP12RTS by comparing the velocity structures to synthetic tomography images derived from 3D mantle convection models. As in previous studies, geodynamic models are converted to seismic velocities using mineral physics constraints and subsequently convolved with the tomographic resolution operator. In contrast to these studies, where generally only the shear-wave velocity structure has been compared, we use both the Vs and Vp resolution operator of SP12RTS to allow direct comparisons of the resulting velocity ratios and correlations. We use geodynamic models with and without pPv and/or chemical variations to investigate the cause of the high Vs/Vp ratio and Vs-Vs anti-correlation. Although the tomographic filtering significantly affects the synthetic tomography images, we demonstrate that the patterns

  10. Joint seismic-geodynamic-mineral physical modelling of African geodynamics: A reconciliation of deep-mantle convection with surface geophysical constraints

    SciTech Connect

    Forte, A M; Quere, S; Moucha, R; Simmons, N A; Grand, S P; Mitrovica, J X; Rowley, D B

    2008-08-22

    Recent progress in seismic tomography provides the first complete 3-D images of the combined thermal and chemical anomalies that characterise the unique deep mantle structure below the African continent. With these latest tomography results we predict flow patterns under Africa that reveal a large-scale, active hot upwelling, or superplume, below the western margin of Africa under the Cape Verde Islands. The scale and dynamical intensity of this West African superplume (WASP) is comparable to that of the south African superplume (SASP) that has long been assumed to dominate the flow dynamics under Africa. On the basis of this new tomography model, we find the dynamics of the SASP is strongly controlled by chemical contributions to deep mantle buoyancy that significantly compensate its thermal buoyancy. In contrast, the WASP appears to be entirely dominated by thermal buoyancy. New calculations of mantle convection incorporating these two superplumes reveal that the plate-driving forces due to the flow generated by the WASP is as strong as that due to the SASP. We find that the chemical buoyancy of the SASP exerts a strong stabilising control on the pattern and amplitude of shallow mantle flow in the asthenosphere below the southern half of the African plate. The asthenospheric flow predictions provide the first high resolution maps of focussed upwellings that lie below the major centres of Late Cenozoic volcanism, including the Kenya domes and Hoggar massif that lies above a remnant plume head in the upper mantle. Inferences of sublithospheric deformation from seismic anisotropy data are shown to be sensitive to the contributions of chemical buoyancy in the SASP.

  11. Geodynamics from satellites

    NASA Technical Reports Server (NTRS)

    Kaula, W. M.

    1979-01-01

    The NASA Geodynamics Program is developing a variety of techniques in support of national programs in geodynamics, geomagnetics and earthquake hazard reduction. Global tectonics are to be observed by satellite laser tracking and radio interferometry, which will be used to measure the movements of extended (greater than 200 km) regions to an accuracy of 3 cm, while for shorter distances, lasers enable a more rapid measuring of regional strain accumulation patterns than ground systems. The techniques of Doppler tracking between two satellites to measure the gravity field over the ocean is also under NASA study

  12. Time-dependent convection models of mantle thermal structure constrained by seismic tomography and geodynamics: implications for mantle plume dynamics and CMB heat flux

    NASA Astrophysics Data System (ADS)

    Glišović, P.; Forte, A. M.; Moucha, R.

    2012-08-01

    One of the outstanding problems in modern geodynamics is the development of thermal convection models that are consistent with the present-day flow dynamics in the Earth's mantle, in accord with seismic tomographic images of 3-D Earth structure, and that are also capable of providing a time-dependent evolution of the mantle thermal structure that is as 'realistic' (Earth-like) as possible. A successful realization of this objective would provide a realistic model of 3-D mantle convection that has optimal consistency with a wide suite of seismic, geodynamic and mineral physical constraints on mantle structure and thermodynamic properties. To address this challenge, we have constructed a time-dependent, compressible convection model in 3-D spherical geometry that is consistent with tomography-based instantaneous flow dynamics, using an updated and revised pseudo-spectral numerical method. The novel feature of our numerical solutions is that the equations of conservation of mass and momentum are solved only once in terms of spectral Green's functions. We initially focus on the theory and numerical methods employed to solve the equation of thermal energy conservation using the Green's function solutions for the equation of motion, with special attention placed on the numerical accuracy and stability of the convection solutions. A particular concern is the verification of the global energy balance in the dissipative, compressible-mantle formulation we adopt. Such validation is essential because we then present geodynamically constrained convection solutions over billion-year timescales, starting from present-day seismically constrained thermal images of the mantle. The use of geodynamically constrained spectral Green's functions facilitates the modelling of the dynamic impact on the mantle evolution of: (1) depth-dependent thermal conductivity profiles, (2) extreme variations of viscosity over depth and (3) different surface boundary conditions, in this case mobile

  13. A review of analogue modelling of geodynamic processes: Approaches, scaling, materials and quantification, with an application to subduction experiments

    NASA Astrophysics Data System (ADS)

    Schellart, Wouter P.; Strak, Vincent

    2016-10-01

    We present a review of the analogue modelling method, which has been used for 200 years, and continues to be used, to investigate geological phenomena and geodynamic processes. We particularly focus on the following four components: (1) the different fundamental modelling approaches that exist in analogue modelling; (2) the scaling theory and scaling of topography; (3) the different materials and rheologies that are used to simulate the complex behaviour of rocks; and (4) a range of recording techniques that are used for qualitative and quantitative analyses and interpretations of analogue models. Furthermore, we apply these four components to laboratory-based subduction models and describe some of the issues at hand with modelling such systems. Over the last 200 years, a wide variety of analogue materials have been used with different rheologies, including viscous materials (e.g. syrups, silicones, water), brittle materials (e.g. granular materials such as sand, microspheres and sugar), plastic materials (e.g. plasticine), visco-plastic materials (e.g. paraffin, waxes, petrolatum) and visco-elasto-plastic materials (e.g. hydrocarbon compounds and gelatins). These materials have been used in many different set-ups to study processes from the microscale, such as porphyroclast rotation, to the mantle scale, such as subduction and mantle convection. Despite the wide variety of modelling materials and great diversity in model set-ups and processes investigated, all laboratory experiments can be classified into one of three different categories based on three fundamental modelling approaches that have been used in analogue modelling: (1) The external approach, (2) the combined (external + internal) approach, and (3) the internal approach. In the external approach and combined approach, energy is added to the experimental system through the external application of a velocity, temperature gradient or a material influx (or a combination thereof), and so the system is open

  14. The use of the Finite Element method for the earthquakes modelling in different geodynamic environments

    NASA Astrophysics Data System (ADS)

    Castaldo, Raffaele; Tizzani, Pietro

    2016-04-01

    Many numerical models have been developed to simulate the deformation and stress changes associated to the faulting process. This aspect is an important topic in fracture mechanism. In the proposed study, we investigate the impact of the deep fault geometry and tectonic setting on the co-seismic ground deformation pattern associated to different earthquake phenomena. We exploit the impact of the structural-geological data in Finite Element environment through an optimization procedure. In this framework, we model the failure processes in a physical mechanical scenario to evaluate the kinematics associated to the Mw 6.1 L'Aquila 2009 earthquake (Italy), the Mw 5.9 Ferrara and Mw 5.8 Mirandola 2012 earthquake (Italy) and the Mw 8.3 Gorkha 2015 earthquake (Nepal). These seismic events are representative of different tectonic scenario: the normal, the reverse and thrust faulting processes, respectively. In order to simulate the kinematic of the analyzed natural phenomena, we assume, under the plane stress approximation (is defined to be a state of stress in which the normal stress, sz, and the shear stress sxz and syz, directed perpendicular to x-y plane are assumed to be zero), the linear elastic behavior of the involved media. The performed finite element procedure consist of through two stages: (i) compacting under the weight of the rock successions (gravity loading), the deformation model reaches a stable equilibrium; (ii) the co-seismic stage simulates, through a distributed slip along the active fault, the released stresses. To constrain the models solution, we exploit the DInSAR deformation velocity maps retrieved by satellite data acquired by old and new generation sensors, as ENVISAT, RADARSAT-2 and SENTINEL 1A, encompassing the studied earthquakes. More specifically, we first generate 2D several forward mechanical models, then, we compare these with the recorded ground deformation fields, in order to select the best boundaries setting and parameters. Finally

  15. Deformation of the Western Caribbean: Insights from Block and Geodynamic Models of Geodetic, Seismic and Geologic Data

    NASA Astrophysics Data System (ADS)

    La Femina, P. C.; Geirsson, H.; Kobayashi, D.

    2012-12-01

    Cocos - Caribbean convergence along the Middle America Trench, including subduction of the Cocos Ridge and seamount domain, and Nazca - Caribbean oblique convergence along the South Panama Deformed Belt have resulted in complex plate boundary zone deformation since Miocene - Pliocene time. Plate boundary evolution and upper plate deformation in the western Caribbean is well studied and indicates, 1) Quaternary migration of the volcanic arc toward the back-arc northwest of the Cocos Ridge; 2) Pleistocene to present northwestward motion of the Central American Fore Arc (CAFA); 3) Quaternary to present deformation within the Central Costa Rica Deformed Belt; 4) Miocene-Pliocene cessation of volcanism and uplift of the Cordillera de Talamanca inboard the ridge; 5) Quaternary to present shortening across the fore-arc Fila Costeña fold and thrust belt and back-arc North Panama Deformed Belt (NPDB); 6) Quaternary to present outer fore-arc uplift above the seamount domain (Nicoya Peninsula), and above (Osa Peninsula) and flanking (Burica Peninsula) the ridge; and 7) Quaternary to present faulting along the Sona-Azuero and Canal Discontinuity fault systems. We investigate the dynamic effects of Cocos and Nazca convergence along the entire Central American margin, and the implications on western Caribbean plate boundary evolution with a new GPS derived three-dimensional (horizontal and vertical) velocity field and kinematic block and geodynamic models. Specifically, we test the hypotheses that the Cocos Ridge is the main driver for upper plate deformation and that there is an independent Panama block. Our model results provide new Euler vectors for the CAFA and Panama block, rates of relative plate and block motions in the region, and constraints on interseismic coupling along the Middle America Trench and other major block bounding fault systems. These results are compared to existing geophysical and geologic data for the region and add insights into the rates of

  16. A new free-surface stabilization algorithm for geodynamical modelling: Theory and numerical tests

    NASA Astrophysics Data System (ADS)

    Andrés-Martínez, Miguel; Morgan, Jason P.; Pérez-Gussinyé, Marta; Rüpke, Lars

    2015-09-01

    The surface of the solid Earth is effectively stress free in its subaerial portions, and hydrostatic beneath the oceans. Unfortunately, this type of boundary condition is difficult to treat computationally, and for computational convenience, numerical models have often used simpler approximations that do not involve a normal stress-loaded, shear-stress free top surface that is free to move. Viscous flow models with a computational free surface typically confront stability problems when the time step is bigger than the viscous relaxation time. The small time step required for stability (< 2 Kyr) makes this type of model computationally intensive, so there remains a need to develop strategies that mitigate the stability problem by making larger (at least ∼10 Kyr) time steps stable and accurate. Here we present a new free-surface stabilization algorithm for finite element codes which solves the stability problem by adding to the Stokes formulation an intrinsic penalization term equivalent to a portion of the future load at the surface nodes. Our algorithm is straightforward to implement and can be used with both Eulerian or Lagrangian grids. It includes α and β parameters to respectively control both the vertical and the horizontal slope-dependent penalization terms, and uses Uzawa-like iterations to solve the resulting system at a cost comparable to a non-stress free surface formulation. Four tests were carried out in order to study the accuracy and the stability of the algorithm: (1) a decaying first-order sinusoidal topography test, (2) a decaying high-order sinusoidal topography test, (3) a Rayleigh-Taylor instability test, and (4) a steep-slope test. For these tests, we investigate which α and β parameters give the best results in terms of both accuracy and stability. We also compare the accuracy and the stability of our algorithm with a similar implicit approach recently developed by Kaus et al. (2010). We find that our algorithm is slightly more accurate

  17. The Multi-factor Predictive Seis &Gis Model of Ecological, Genetical, Population Health Risk and Bio-geodynamic Processes In Geopathogenic Zones

    NASA Astrophysics Data System (ADS)

    Bondarenko, Y.

    I. Goal and Scope. Human birth rate decrease, death-rate growth and increase of mu- tagenic deviations risk take place in geopathogenic and anthropogenic hazard zones. Such zones create unfavourable conditions for reproductive process of future genera- tions. These negative trends should be considered as a protective answer of the com- plex biosocial system to the appearance of natural and anthropogenic risk factors that are unfavourable for human health. The major goals of scientific evaluation and de- crease of risk of appearance of hazardous processes on the territory of Dnipropetrovsk, along with creation of the multi-factor predictive Spirit-Energy-Information Space "SEIS" & GIS Model of ecological, genetical and population health risk in connection with dangerous bio-geodynamic processes, were: multi-factor modeling and correla- tion of natural and anthropogenic environmental changes and those of human health; determination of indicators that show the risk of destruction structures appearance on different levels of organization and functioning of the city ecosystem (geophys- ical and geochemical fields, soil, hydrosphere, atmosphere, biosphere); analysis of regularities of natural, anthropogenic, and biological rhythms' interactions. II. Meth- ods. The long spatio-temporal researches (Y. Bondarenko, 1996, 2000) have proved that the ecological, genetic and epidemiological processes are in connection with de- velopment of dangerous bio-geophysical and bio-geodynamic processes. Mathemat- ical processing of space photos, lithogeochemical and geophysical maps with use of JEIS o and ERDAS o computer systems was executed at the first stage of forma- tion of multi-layer geoinformation model "Dnipropetrovsk ARC View GIS o. The multi-factor nonlinear correlation between solar activity and cosmic ray variations, geophysical, geodynamic, geochemical, atmospheric, technological, biological, socio- economical processes and oncologic case rate frequency, general and primary

  18. A consistent geodynamic model for predicting the velocity and plate-internal deformation of Eurasia

    NASA Astrophysics Data System (ADS)

    Govers, Rob; Garcia-Sancho, Candela; Warners-Ruckstuhl, Karin; van der Burgt, Janneke; Wortel, Rinus

    2015-04-01

    The motion and deformation of tectonic plates is driven by gravity and resisted by frictional forces. In principle it should thus be possible to build mechanical models that reproduce plate velocities and surface deformation. Here we present a new approach that overcomes many of the previous obstacles to achieving this goal. Our approach to quantify the forces is based on mechanical equilibrium of the whole Eurasian plate, meaning that an increase in, for instance collision, forces must be matched by other plate tectonic forces. We first focus on present-day Eurasia. We include basal tractions from a global convection model, lithospheric body forces, and edge forces resulting from the interaction of the Eurasian plate with neighboring plates. The resulting force distribution is constrained by observed plate motion and by stress observations. Eurasia's stress field turns out to be most sensitive to the distribution of collision forces on the plate's southern margin and, to a lesser extent, to lithospheric density structure and normal pressure from mantle flow. Stress observations require collision forces on the India-Eurasia boundary of 7.0 - 10.5 TN/m. A similar analysis is performed for Eurasia at 20 Ma and 40 Ma. Plate geometry is taken from the global Lausanne (Stampfli) reconstruction, as are plate velocities and oceanic ages. Lithospheric body forces are accounted for in a simplified way because we lack detailed enough information on the plate scale topography. For the Miocene, we find ˜1.2 TN/m for the collision force on the India-Eurasia boundary. In the Eocene, the collision force we find is ˜0.4 TN/m. We conclude that the magnitude of the collision force on Tibet increased significantly after 20 Ma: from 40-20 Ma, the plate contact force on the India/Tibet plate boundary segment was of the same order of magnitude as resistive forces on subduction plate boundaries elsewhere. Our timing of the collision force on Eurasia, is substantially younger than the

  19. Research program of the Geodynamics Branch

    NASA Technical Reports Server (NTRS)

    Kahn, W. D. (Editor); Cohen, S. C. (Editor); Boccucci, B. S. (Editor)

    1986-01-01

    This report is the Fourth Annual Summary of the Research Program of the Geodynamics Branch. The branch is located within the Laboratory for Terrestrial Physics of the Space and Earth Sciences Directorate of the Goddard Space Flight Center. The research activities of the branch staff cover a broad spectrum of geoscience disciplines including: tectonophysics, space geodesy, geopotential field modeling, and dynamic oceanography. The NASA programs which are supported by the work described in this document include the Geodynamics and Ocean Programs, the Crustal Dynamics Project and the proposed Ocean Topography Experiment (TOPEX). The reports highlight the investigations conducted by the Geodynamics Branch staff during calendar year 1985. The individual papers are grouped into chapters on Crustal Movements and Solid Earth Dynamics, Gravity Field Modeling and Sensing Techniques, and Sea Surface Topography. Further information on the activities of the branch or the particular research efforts described herein can be obtained through the branch office or from individual staff members.

  20. Geodynamical evolution of the Southern Carpathians: inferences from computational models of lithospheric gravitational instability

    NASA Astrophysics Data System (ADS)

    Lorinczi, Piroska; Houseman, Gregory

    2010-05-01

    The Carpathians are a geologically young mountain chain which, together with the Alps and the Dinarides, surround the extensional Pannonian and Transylvanian basins of Central Europe. The tectonic evolution of the Alpine-Carpathian-Pannonian system was controlled by convergence between the Adriatic and European plates, by the extensional collapse of thickened Alpine crust and by the retreat of the Eastern Carpathians driven by either a brief episode of subduction or by gravitational instability of the continental lithospheric mantle. The Southeast corner of the Carpathians has been widely studied due to its strong seismic activity. The distribution and rate of moment release of this seismic activity provides convincing evidence of a mantle drip produced by gravitational instability of the lithospheric mantle developing beneath the Vrancea region now. The question of why gravitational instability is strongly evident beneath Vrancea and not elsewhere beneath the Southern Carpathians is unresolved. Geological and geophysical interpretations of the Southern Carpathians emphasise the transcurrent deformation that has dominated recent tectonic evolution of this mountain belt. We use computational models of gravitational instability in order to address the question of why the instability appears to have developed strongly only at the eastern end of this mountain chain. We use a parallelised 3D Lagrangean-frame finite deformation algorithm, which solves the equations of momentum and mass conservation in an incompressible viscous fluid, assuming a non-linear power-law that relates deviatoric stress and strain-rate. We consider a gravitationally unstable system, with a dense mantle lithosphere overlying a less dense asthenosphere, subject to boundary conditions which simulate the combination of shear and convergence that are thought to have governed the evolution of the South Carpathians. This program (OREGANO) allows 3D viscous flow fields to be computed for spatially

  1. Cratonic roots under North America are shifted by basal drag: new evidence from gravity and geodynamic modeling

    NASA Astrophysics Data System (ADS)

    Kaban, M. K.; Petrunin, A.; Mooney, W. D.

    2013-12-01

    The impact of basal drag on the long-lived cratonic roots has been debated since the discovering of plate tectonics. Previously, evidence for a shifted mantle structure under North America was postulated from a comparison of the surface expression of the Great Meteor hotspot track versus its location at 200 km depth as inferred from seismic tomography (Eaton and Frederiksen, 2007). We present new results that are based on the integrative modeling of gravity and seismic data. The starting point is the residual gravity anomaly and residual topography, which are computed by removing of the crustal effect and of the effect of temperature variations in the upper mantle from the observed fields (Mooney and Kaban, 2010). After the temperature correction both residual fields chiefly reflect compositional density heterogeneity of the upper mantle. The residual gravity and topography are jointly inverted to determine the 3D density structure of the upper mantle. The inversion technique accounts for the fact that although these parameters are controlled by the same factors, the effect depends on depth and wavelength. Therefore, we can resolve the vertical distribution of density more reliable than by interpreting only one parameter. We found a strong negative anomaly under the North American craton, as expected for a depleted mantle. However, starting from a depth of about 200 km the depleted root is shifted west-southwest. The maximal shift reaches about 1000 km at a depth of 300 km. The direction agrees with the North American plate movement and with the anisotropy pattern in the upper mantle (e.g. Bokelmann, 2002). The results of the gravity modeling are confirmed by geodynamic modeling. The mantle flow is estimated from the density and temperature distribution derived from seismic tomography models. A 3D viscosity model is supplemented with weak boundaries based on an integrated model of plate boundary deformations. The calculated plate velocities are in a good agreement

  2. Geodynamic modeling of eclogite-bearing mantle plumes: Ascent dynamics, plume-plate-interaction and surface manifestations

    NASA Astrophysics Data System (ADS)

    Dannberg, Juliane; Sobolev, Stephan

    2014-05-01

    According to widely accepted models, plumes ascend from the deep mantle and cause massive melting when they reach the base of the lithosphere. Classical geodynamic models consider plumes as purely thermal and thus predict a flattening of the plume head to a disk-like structure and thin plume tails. However, geochemical data indicate that plumes have a different composition than the average mantle material and it has been suggested a long time ago that subducted oceanic crust could be recycled by mantle plumes. In addition, seismic imaging reveals thicker plume tails as well as a more complex plume structure in the upper mantle, including broad low-velocity anomalies up to 400 km depth and elongated low-velocity fingers fed by plumes. While recent numerical models have considered a different chemistry to explain complex plume shapes or zoning within plumes, they either are restricted to only a part of the plume evolution or use simplified material models. However, due to the high density of recycled oceanic crust, thermo-chemical plumes are expected to have much smaller buoyancy than thermal plumes. Therefore it is especially important to incorporate realistic material properties, as they can influence the plume dynamics crucially and determine if a plume reaches the lithosphere or remains in deeper parts of the mantle. We perform numerical experiments in a 3D spherical shell geometry to study the dynamics of the plume ascent, the interaction between plume- and plate-driven flow and the dynamics of melting in a plume head. For that purpose, we use the finite-element code ASPECT, which allows for complex temperature-, pressure-, and composition-dependent material properties. Moreover, our models incorporate phase transitions (including melting) with the accompanying rheological and density changes, Clapeyron slopes and latent heat effects for the peridotite and eclogite phase, mantle compressibility and a highly temperature- and depth-dependent viscosity. We study

  3. A geodynamic model of the evolution of the Arctic basin and adjacent territories in the Mesozoic and Cenozoic and the outer limit of the Russian Continental Shelf

    NASA Astrophysics Data System (ADS)

    Laverov, N. P.; Lobkovsky, L. I.; Kononov, M. V.; Dobretsov, N. L.; Vernikovsky, V. A.; Sokolov, S. D.; Shipilov, E. V.

    2013-01-01

    The tectonic evolution of the Arctic Region in the Mesozoic and Cenozoic is considered with allowance for the Paleozoic stage of evolution of the ancient Arctida continent. A new geodynamic model of the evolution of the Arctic is based on the idea of the development of upper mantle convection beneath the continent caused by subduction of the Pacific lithosphere under the Eurasian and North American lithospheric plates. The structure of the Amerasia and Eurasia basins of the Arctic is shown to have formed progressively due to destruction of the ancient Arctida continent, a retained fragment of which comprises the structural units of the central segment of the Arctic Ocean, including the Lomonosov Ridge, the Alpha-Mendeleev Rise, and the Podvodnikov and Makarov basins. The proposed model is considered to be a scientific substantiation of the updated Russian territorial claim to the UN Commission on the determination of the Limits of the Continental Shelf in the Arctic Region.

  4. Research activities of the Geodynamics Branch

    NASA Technical Reports Server (NTRS)

    Kahn, W. D. (Editor); Cohen, S. C. (Editor)

    1984-01-01

    A broad spectrum of geoscience disciplines including space geodesy, geopotential field modeling, tectonophysics, and dynamic oceanography are discussed. The NASA programs, include the Geodynamics and Ocean Programs, the Crustal Dynamics Project, the proposed Ocean Topography Experiment (TOPEX), and the Geopotential Research Mission (GRM). The papers are grouped into chapters on Crustal Movements, Global Earth Dynamics, Gravity Field Model Development, Sea Surface Topography, and Advanced Studies.

  5. GLOBAL DISASTERS: Geodynamics and Society

    NASA Astrophysics Data System (ADS)

    Vikulina, Marina; Vikulin, Alexander; Semenets, Nikolai

    2013-04-01

    The problem of reducing the damage caused by geodynamic and social disasters is a high priority and urgent task facing the humanity. The vivid examples of the earthquake in Japan in March 2011 that generated a new kind of threat - the radiation pollution, and the events in the Arabic world that began in the same year, are dramatic evidences. By the middle of this century, the damage from such disastrous events is supposed to exceed the combined GDP of all countries of the world. The database of 287 large-scale natural and social disasters and global social phenomena that have occurred in the period of II B.C.E. - XXI A.D. was compiled by the authors for the first time. We have proposed the following phenomenological model: the scale of disasters over the time does not decrease, there is a minimum of accidents in the XV century; the numbers of accidents have cycles lasting until the first thousand years, natural and social disasters in the aggregate are uniformly distributed in time, but separately natural and social disasters are nonuniform. Thus, due to the evaluation, a 500-year cycle of catastrophes and 200-300 and 700-800-year periodicities are identified. It is shown that catastrophes are grouped into natural and social types by forming clusters. The hypothesis of the united geo-bio-social planetary process is founded. A fundamentally new feature of this research is the assumptions about the statistical significance of the biosphere and the impact of society on the geodynamic processes. The results allow to formulate a new understanding of global disaster as an event the damage from which the humanity will be unable to liquidate even by means of the total resource potential and the consequence of which may turn into the irreversible destruction of civilization. The correlation between the natural and social phenomena and the possible action mechanism is suggested.

  6. Testing geodynamic models for surface uplift of the central Andean plateau through volcanic glass paleoaltimetry and basin analysis in southern Peru

    NASA Astrophysics Data System (ADS)

    Sundell, K. E., II; Saylor, J. E.; Villarreal, D. P.; Horton, B. K.

    2014-12-01

    Differentiating between geodynamic models describing the formation mechanism(s) of the central Andean plateau (CAP) requires information concerning the timing and location of basin formation, crustal deformation, and surface uplift. All models involve the removal of lithospheric mantle, and typically fall into one of two end-members: 1) slow, continuous uplift (km over 10s of Myr) involving protracted removal of mantle lithosphere through ablative subduction or thermal weakening that is predicted to be coincident with crustal shortening, or 2) punctuated uplift (km over Myr) driven by rapid wholesale or piecemeal foundering of a dense lithospheric root, likely post-dating major crustal shortening. However, these models are not mutually exclusive, nor must any one geodynamic mechanism describe the entire history of the formation of the CAP, an area spanning ~1800 km N-S by up to 500 km E-W, comprised of multiple physiographic regions of differing compositional and geophysical characteristics resulting from protracted orogenesis. We present new stratigraphic, stable isotopic, and geochronologic data for temporally overlapping yet spatially separate Cenozoic intermontane basins in the northern CAP to evaluate the contribution of these end-member scenarios to the formation of the CAP. Data span multiple physiographic regions of the CAP, including basins near Puquio (Western Cordillera), the Huacochullo basin (western Altiplano margin), and the Macusani and Crucero basins of the Cordillera de Carabaya (Eastern Cordillera). The magnitude of paleoelevation changes is reconstructed from δD values of volcanic glass, while timing is constrained by zircon U-Pb geochronology. Initial results indicate early, rapid, high-magnitude surface uplift from initially low elevations in the Western Cordillera but a later, lower-magnitude pulse of uplift from initially moderate elevations in the Eastern Cordillera. This diachronous uplift history, together with published reports of

  7. Rheological and geodynamic controls on the mechanisms of subduction, HP/UHP exhumation and PT conditions within crustal rocks during continental collision: insights from numerical models

    NASA Astrophysics Data System (ADS)

    Burov, Evgueni

    2014-05-01

    Mechanisms of continental convergence are so versatile that it is impossible to elucidate them from conventional set of observations. Additional discriminatory data are needed such as those derived from petrology data, since burial/exhumation dynamics inferred from metamorphic P-T-t paths potentially provides independent constraints on the collision mechanism. While subduction of crustal rocks is increasingly accepted as common phenomenon inherent to convergent processes involving continental plates and micro-continents, the conditions of their formation and mechanisms of their exhumation in the form of high- and ultra-high-pressure (HP/UHP) units remain a subject of controversy. In particular, deep burial and exhumation of continental crust occur in various settings, including subduction of micro-continental terrains carried down with the subducting oceanic lithosphere and transition between the oceanic and continental subduction. Geodynamic inferences from P-T data can be made only after providing a consistent approach to decryption of both pressure and temperature in terms of depth or at least in terms of characteristic geodynamic conditions. Thermo-mechanical thermodynamically coupled numerical models of continental collision provide some elements of solution to this problem through testing various geodynamic scenarios within relatively unconstrained framework which allows for account of non-lithostatic pressure variations and for deviations of temperature from commonly inferred thermal models. We here explore several possible scenarios of subduction and exhumation of continental crust, and their relation to PT conditions and mechanisms of HP/UHP exhumation inferred from conceptual and thermo-mechanical numerical models accounting for thermo-rheological complexity and diversity of the continental lithosphere. Numerical experiments suggest that in most cases both exhumation and continental subduction are transient processes, so that long-lasting (> 10-15 Myr

  8. Palaeoproterozoic (1.83 Ga) zircons in a Bajocian (169 Ma) granite within a Middle Jurassic ophiolite (Rubiku, central Albania): a challenge for geodynamic models

    NASA Astrophysics Data System (ADS)

    Kryza, Ryszard; Beqiraj, Arjan

    2014-04-01

    Two distinct zircon populations, 1,827 ± 17 and 169 ± 2 Ma in age, have been found in the Rubiku granite dyke in the Middle Jurassic Mirdita ophiolite in central Albania. The old inherited zircons represent a homogeneous population formed during a discrete Palaeoproterozoic, likely magmatic, zircon crystallization event. These older zircons were likely incorporated, in large part, into the granite magma that crystallized broadly at the time of the ophiolite emplacement (around 169 Ma). The limited data available do not allow for the construction of an unequivocal petrogenetic model, though several palaeotectonic scenarios are discussed as possible settings for the granite formation. The models refer to recent findings of old inherited zircons in rocks at recent mid-ocean ridge settings, but also consider likely contributions of crustal materials to primary basic ophiolitic magmas within supra-subduction settings and subsequent accretion/collision circumstances. The presence of old zircons in much younger rocks within ophiolite successions runs counter to geodynamic models of interaction between the oceanic lithosphere and continental crust, but constraining their genesis would require further systematic studies on these old inherited zircons, both in mafic (if present) and in felsic rocks of the ophiolites.

  9. Preliminary northeast Asia geodynamics map

    USGS Publications Warehouse

    Parfenov, Leonid M.; Khanchuk, Alexander I.; Badarch, Gombosuren; Miller, Robert J.; Naumova, Vera V.; Nokleberg, Warren J.; Ogasawara, Masatsugu; Prokopiev, Andrei V.; Yan, Hongquan

    2003-01-01

    This map portrays the geodynamics of Northeast Asia at a scale of 1:5,000,000 using the concepts of plate tectonics and analysis of terranes and overlap assemblages. The map is the result of a detailed compilation and synthesis at 5 million scale and is part of a major international collaborative study of the Mineral Resources, Metallogenesis, and Tectonics of Northeast Asia conducted from 1997 through 2002 by geologists from earth science agencies and universities in Russia, Mongolia, Northeastern China, South Korea, Japan, and the USA. This map is the result of extensive geologic mapping and associated tectonic studies in Northeast Asia in the last few decades and is the first collaborative compilation of the geology of the region at a scale of 1:5,000,000 by geologists from Russia, Mongolia, Northeastern China, South Korea, Japan, and the USA. The map was compiled by a large group of international geologists using the below concepts and definitions during collaborative workshops over a six-year period. The map is a major new compilation and re-interpretation of pre-existing geologic maps of the region. The map is designed to be used for several purposes, including regional tectonic analyses, mineral resource and metallogenic analysis, petroleum resource analysis, neotectonic analysis, and analysis of seismic hazards and volcanic hazards. The map consists of two sheets. Sheet 1 displays the map at a scale of 1:5,000,000, explanation. Sheet 2 displays the introduction, list of map units, and source references. Detailed descriptions of map units and stratigraphic columns are being published separately. This map is one of a series of publications on the mineral resources, metallogenesis, and geodynamics,of Northeast Asia. Companion studies and other articles and maps , and various detailed reports are: (1) a compilation of major mineral deposit models (Rodionov and Nokleberg, 2000; Rodionov and others, 2000; Obolenskiy and others, in press a); (2) a series of

  10. Basic research for the geodynamics program

    NASA Technical Reports Server (NTRS)

    1986-01-01

    Further development of utility program software for analyzing final results of Earth rotation parameter determination from different space geodetic systems was completed. Main simulation experiments were performed. Results and conclusions were compiled. The utilization of range-difference observations in geodynamics is also examined. A method based on the Bayesian philosophy and entropy measure of information is given for the elucidation of time-dependent models of crustal motions as part of a proposed algorithm. The strategy of model discrimination and design of measurements is illustrated in an example for the case of crustal deformation models.

  11. The NASA Geodynamics Program: An overview

    NASA Technical Reports Server (NTRS)

    1983-01-01

    This NASA Geodynamics Program overview collectively examines the history, scientific basis, status, and results of the NASA Program and outlines plans for the next five to eight years. It is intended as an informative nontechnical discussion of geodynamics research.

  12. Basic research for the geodynamics program

    NASA Technical Reports Server (NTRS)

    Mueller, I. I.

    1985-01-01

    The current technical objectives for the geodynamics program consist of (1) optimal utilization of laser and Very Long Baseline Interferometry (VLBI) observations for reference frames for geodynamics; (2) utilization of range difference observations in geodynamics; and (3) estimation techniques in crustal deformation analysis.

  13. Kinematic analysis of recent and active faults of the southern Umbria-Marche domain, Northern Apennines, Italy: geological constraints to geodynamic models

    NASA Astrophysics Data System (ADS)

    Pasqui, Valeria; Viti, Marcello; Mantovani, Enzo

    2013-04-01

    strain field. The coexistence of extensional and strike-slip regimes, in principle difficult to achieve, may be explained in the framework of a transtensional deformation model where extensional components, normal to the main NW-directed structural trends, are associated to left-lateral strike-slip movements parallel to the main NW-directed structural trends. Critical for the evaluation of the internal consistency of a deformation model for the brittle upper crustal levels is the definition of the kinematics of active faults. In this study we illustrate the preliminary results of a kinematic analysis carried out along 20, exceptionally well exposed, recent and active fault surfaces cropping out in the southernmost portion of the Umbria-Marche belt adjacent to its termination against the the Latium-Abruzzi domain to the East. The collected data indicate that the investigated faults reflect a kinematically oblique character, and that development of these structures may be explained in the framework of a left-dominated transtensional strain field. More important, the data indicate that fault kinematic analysis is an effective tool in testing geodynamic models for actively deforming crustal domains.

  14. Geological, petrologic, isotopic, and geochemical constraints of geodynamic models simulating formation of the archean tonalite-trondhjemite-granodiorite associations in ancient cratons

    NASA Astrophysics Data System (ADS)

    Vrevsky, A. B.; Lobach-Zhuchenko, S. B.; Chekulaev, V. P.; Kovalenko, A. V.; Arestova, N. A.

    2010-07-01

    The geological setting, geochemistry, and Nd isotopic systematics of tonalite-trondhjemite-granodiortite (TTG) series in ancient cratons are considered. It is shown that the TTG series were formed from ˜4.2 to 2.6 Ga ago in the oldest continental cores; many TTG series do not reveal chronological links to greenstone belts. This follows from the evolution of the Slave Craton in the Canadian Shield, the Vodlozero Craton in the Baltic Shield, and the Pilbara and Yilgarn cratons in the Australian Shield, where greenstone associations postdated TTG series. As has been established at the Baltic Shield, the primary melts of the Mesoarchean TTG associations were formed at a shallower depth ( P < 15 kbar) compared to the Neoarchean TTG, likely, due to the increasing thickness of the continental crust beneath the Baltic Shield over time. The Nd isotopic composition of worldwide TTG associations indicates that most of them are characterized by a substantial time interval (>150 Ma) that separates the formation of the TTG melts from the age of the source involved in melting. Taking into account the calculated rate of cooling of the lithospheric plates, these data indicate that most Archean TTG series likely were not formed in the convergent subduction-related and accretionary geodynamic settings. The isotopic and geochemical data constrain compositions of the sources that produced Archean TTG series. Petrologic modeling of the formation conditions and Nd isotopic composition of the metabasalts in greenstone belts show that these rocks could not have been the source of TTG series. The most plausible isotopic and geochemical analogue of this source are the Archean amphibolites (ENd mafic rocks), which differ from the metabasalts of greenstone belts by their lower Sm/Nd ratio and enrichment in some lithophile elements. The available data suggest that the primary TTG melts were generated as products of melting of amphibolites and granulites forming the lower crust.

  15. Overriding plate deformation and variability of fore-arc deformation during subduction: Insight from geodynamic models and application to the Calabria subduction zone

    NASA Astrophysics Data System (ADS)

    Chen, Zhihao; Schellart, Wouter P.; Duarte, João. C.

    2015-10-01

    In nature, subducting slabs and overriding plate segments bordering subduction zones are generally embedded within larger plates. Such large plates can impose far-field boundary conditions that influence the style of subduction and overriding plate deformation. Here we present dynamic laboratory models of progressive subduction in three-dimensional space, in which the far-field boundary conditions at the trailing edges of the subducting plate (SP) and overriding plate (OP) are varied. Four configurations are presented: Free (both plates free), SP-Fixed, OP-Fixed, and SP-OP-Fixed. We investigate their impact on the kinematics and dynamics of subduction, particularly focusing on overriding plate deformation. The results indicate that the variation in far-field boundary conditions has an influence on the slab geometry, subduction partitioning, and trench migration partitioning. Our models also indicate that in natural (narrow) subduction zones, assuming a homogeneous overriding plate, the formation of back-arc basins (e.g., Tyrrhenian Sea, Aegean Sea, and Scotia Sea) is generally expected to occur at a comparable location (250-700 km from the trench), irrespective of the boundary condition. In addition, our models indicate that the style of fore-arc deformation (shortening or extension) is influenced by the mobility of the overriding plate through controlling the force normal to the subduction zone interface (trench suction). Our geodynamic model that uses the SP-OP-Fixed setup is comparable to the Calabria subduction zone with respect to subduction kinematics, slab geometry, trench curvature, and accretionary configuration. Furthermore, the model can explain back-arc and fore-arc extension at the Calabria subduction zone since the latest middle Miocene as a consequence of subduction of the narrow Calabrian slab and the immobility of the subducting African plate and overriding Eurasian plate. This setting induced strong trench suction, driving fore-arc extension, and

  16. The evolution of Hadean-Eoarchaean geodynamics

    NASA Astrophysics Data System (ADS)

    O'Neill, C.; Debaille, V.

    2014-11-01

    Geodynamic modelling of Hadean/Eoarchaean tectonics typically requires higher rates of internal heat production, and higher mantle temperatures, in models that possess temperature-dependent viscosity and a yield criterion. In such models under Hadean conditions, for a wide range of geodynamic configurations and modelling approaches, subduction has a propensity to fail. This has led to the suggestion that the predominant tectonic regime in the Hadean was stagnant-lid convection, with intermittent recycling events. Various lines of evidence support this suggestion, from i) the long mixing time of mantle isotopic anomalies or compositional heterogeneities, such as 142Nd, 182W, and platinum group elements, to ii) the long residence time of the Hadean protolith to the Jack Hills zircons, and iii) thermal evolution models, which typically require lower heat flux in the past to avoid the "Archaean thermal catastrophe". The framework provided by stagnant lid, or episodic overturn, convection, iv) provides an explanation for the formation of early Archaean TTGs and greenstones, and v) explains the interleaving arc-plume sequence observed in many Archaean terranes, suggesting subduction initiation events may have been common, increasing their preservation potential. Implications include a low magnetic field strength in the Hadean, which is consistent with emerging paleointensity data from these times.

  17. Geophysical and petrological modelling of the structure and composition of the crust and upper mantle in complex geodynamic settings: The Tyrrhenian Sea and surroundings

    NASA Astrophysics Data System (ADS)

    Panza, G. F.; Peccerillo, A.; Aoudia, A.; Farina, B.

    2007-01-01

    structure shows a rigid body dipping westward, a feature that continues southward, up to the eastern Aeolian arc. In contrast, at Ischia the upper mantle contains a shallow low-velocity layer ( Vs = 3.5-4.0 km/s) just beneath a thin but complex crust. The western Aeolian arc and Ustica sit over an upper mantle with Vs ˜ 4.2-4.4 km/s, although a rigid layer ( Vs = 4.55 km/s) from about 80 to 150 km occurs beneath the western Aeolian arc. In Sardinia, no significant differences in the LAS structure are detected from north to south. The petrological-geochemical signatures of Italian volcanoes show strong variations that allow us to distinguish several magmatic provinces. These often coincide with mantle sectors identified by Vs tomography. For instance, the Roman volcanoes show remarkable similar petrological and geochemical characteristics, mirroring similar structure of the LAS. The structure and geochemical-isotopic composition of the upper mantle change significantly when we move to the Stromboli-Campanian volcanoes. The geochemical signatures of Ischia and Procida volcanoes are similar to other Campanian centres, but Sr-Pb isotopic ratios are lower marking a transition to the backarc mantle of the Central Tyrrhenian Sea. The structural variations from Stromboli to the central (Vulcano and Lipari) and western Aeolian arc are accompanied by strong variations of geochemical signatures, such as a decrease of Sr-isotope ratios and an increase of Nd-, Pb-isotope and LILE/HFSE ratios. The dominance of mafic subalkaline magmatism in the Tyrrhenian Sea basin denotes large degrees of partial melting, well in agreement with the soft characteristics of the uppermost mantle in this area. In contrast, striking isotopic differences of Plio-Quaternary volcanic rocks from southern to northern Sardinia does not find a match in the LAS geophysical characteristics. The combination of petrological and geophysical constraints allows us to propose a 3D schematic geodynamic model of the

  18. The intraplate Mw 7 Machaze earthquake in Mozambique: Improved point source model, stress drop, and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Attanayake, Januka; Fonseca, João F. B. D.

    2016-05-01

    The February 22nd 2006 Mw = 7 Machaze earthquake is one of the largest, if not the largest, earthquakes reported since 1900 within Continental Africa. This large continental intraplate event has important implications to our understanding of tectonics and strong ground motion prediction locally and in the global context. Thus, accurate estimates of source parameters of this earthquake are important. In this study, we inverted the complete azimuthally distributed high frequency (0.05-2 Hz) P waveform dataset available for a best-fitting point source model and obtained stress drop estimates assuming different theoretical rupture models from spectral fitting. Our best-fitting point source model confirms steep normal faulting, has strike = 173° (309°), dip = 73° (23°), rake = -72° (-132°), and shows a 12%-4% improvement in waveform fit compared to previous models, which translates into an error minimization. We attribute this improvement to higher order reverberations near the source region that we took in to account and the excellent azimuthal coverage of the dataset. Preferred stress drop estimates assuming a rupture velocity = 0.9 x shear wave velocity (Vs) are between 11 and 15 MPa though, even higher stress drop estimates are possible for rupture velocities lower than 0.9Vs. The estimated stress drop is significantly higher than the global stress drop average of intraplate earthquakes, but is consistent with stress drop estimated for some intra-continental earthquakes elsewhere. The detection of a new active structure that appears to terminate in Machaze, its step-like geometry, and lithospheric strength all favors a hypothesis of stress concentration in the source region, which is likely the cause of this event and the higher than average stress drop.

  19. Tectonic Evolution of the Cretaceous Sava-Klepa Massif, Former Yugoslav Republic of Macedonia, based on field observations and microstructural analysis - Towards a new geodynamic Model

    NASA Astrophysics Data System (ADS)

    Altmeyer, Tobias; Peternell, Mark; Prelević, Dejan; Köpping, Jonas

    2016-04-01

    The Balkan Peninsula was formed during the Mesozoic collision of Gondwana and Eurasia, associated with the closure of the Neo-Tethyan Ocean. As a result, two ophiolitic belts were formed: Dinaride-Hellenide ophiolitic belt in the southwest and the Vardar ophiolitic belt in the northeast. The bulk of Balkan ophiolites originated in the Jurassic (Robertson & Karamata, 1994), and only recently the Late Cretaceous Sava-zone ophiolites are discovered. Ophiolit-like outcrops of Mount Klepa in the Central Macedonia represents a part of Late Cretaceous oceanic lithosphere within the Sava Zone, comprising of pillow lavas, sheet flows, columns, hyaloclastites, dikes as well as cumulates. In this study we investigate the geodynamic setting and evolution of the Late Cretaceous Klepa Massif. Our working hypotheses we want to test is that Klepa Massif represents a new ocean opened through rifting after the closure of Tethyan ocean(s) and collision of Europe and Gondwana already in the Late Jurassic to Early Cretaceous. This hypothesis contradicts the accepted model suggesting that Sava ophiolites represent a relic of the Neo-Tethyan Ocean that closed in the Late Cretaceous. During detailed structural geology field studies, the ophiolitic rock sequence of Klepa Mountain area was mapped in several profiles and about 60 rock samples were taken. These field data in addition to the north-south trending outcrops of the Klepa ophiolite and the north-south trending shear zones which bound the Klepa basalt, lead to the assumption of the existence of a pull apart basin. With the help of microstructural analyses we will determine the deformation history and temperatures which also will be confirmed by the analyses of calcite twins (Ferril et al., 2004). Quartz grain size analysis of quartz bearing rocks, were used for stress piezometry. Furthermore, quartz crystal geometry and crystallographic orientations, which were measured with the Fabric Analyser G60 (Peternell et al., 2010), reveal

  20. Fundamental studies in geodynamics

    NASA Technical Reports Server (NTRS)

    Anderson, D. L.

    1980-01-01

    Progress in modeling instantaneous plate kinematics is reviewed, with emphasis on recently developed models of present day plate motions derived by the systematic inversion of globally distributed data sets. Rivera plate motions, the Caribbean South American boundary, Indian plate deformation, Pacific-North America, seismicity and subduction processes, and the study of slow earthquakes and free oscillations are discussed.

  1. Geodynamics map of northeast Asia

    USGS Publications Warehouse

    Parfenov, Leonid M.; Khanchuk, Alexander I.; Badarch, Gombosuren; Miller, Robert J.; Naumova, Vera V.; Nokleberg, Warren J.; Ogasawara, Masatsugu; Prokopiev, Andrei V.; Yan, Hongquan

    2013-01-01

    This map portrays the geodynamics of Northeast Asia at a scale of 1:5,000,000 using the concepts of plate tectonics and analysis of terranes and overlap assemblages. The map is the result of a detailed compilation and synthesis at 5 million scale and is part of a major international collaborative study of the mineral resources, metallogenesis, and tectonics of northeast Asia conducted from 1997 through 2002 by geologists from earth science agencies and universities in Russia, Mongolia, northeastern China, South Korea, Japan, and the USA.

  2. Overview of adaptive finite element analysis in computational geodynamics

    NASA Astrophysics Data System (ADS)

    May, D. A.; Schellart, W. P.; Moresi, L.

    2013-10-01

    The use of numerical models to develop insight and intuition into the dynamics of the Earth over geological time scales is a firmly established practice in the geodynamics community. As our depth of understanding grows, and hand-in-hand with improvements in analytical techniques and higher resolution remote sensing of the physical structure and state of the Earth, there is a continual need to develop more efficient, accurate and reliable numerical techniques. This is necessary to ensure that we can meet the challenge of generating robust conclusions, interpretations and predictions from improved observations. In adaptive numerical methods, the desire is generally to maximise the quality of the numerical solution for a given amount of computational effort. Neither of these terms has a unique, universal definition, but typically there is a trade off between the number of unknowns we can calculate to obtain a more accurate representation of the Earth, and the resources (time and computational memory) required to compute them. In the engineering community, this topic has been extensively examined using the adaptive finite element (AFE) method. Recently, the applicability of this technique to geodynamic processes has started to be explored. In this review we report on the current status and usage of spatially adaptive finite element analysis in the field of geodynamics. The objective of this review is to provide a brief introduction to the area of spatially adaptive finite analysis, including a summary of different techniques to define spatial adaptation and of different approaches to guide the adaptive process in order to control the discretisation error inherent within the numerical solution. An overview of the current state of the art in adaptive modelling in geodynamics is provided, together with a discussion pertaining to the issues related to using adaptive analysis techniques and perspectives for future research in this area. Additionally, we also provide a

  3. Yellowstone Hotspot Geodynamics

    NASA Astrophysics Data System (ADS)

    Smith, R. B.; Farrell, J.; Massin, F.; Chang, W.; Puskas, C. M.; Steinberger, B. M.; Husen, S.

    2012-12-01

    The Yellowstone hotspot results from the interaction of a mantle plume with the overriding N. America plate producing a ~300-m high topographic swell centered on the Late Quaternary Yellowstone volcanic field. The Yellowstone area is dominated by earthquake swarms including a deadly M7.3 earthquake, extraordinary high heat flow up to ~40,000 mWm-2, and unprecedented episodes of crustal deformation. Seismic tomography and gravity data reveal a crustal magma reservoir, 6 to 15 km deep beneath the Yellowstone caldera but extending laterally ~20 km NE of the caldera and is ~30% larger than previously hypothesized. Kinematically, deformation of Yellowstone is dominated by regional crustal extension at up to ~0.4 cm/yr but with superimposed decadal-scale uplift and subsidence episodes, averaging ~2 cm/yr from 1923. From 2004 to 2009 Yellowstone experienced an accelerated uplift episode of up to 7 cm/yr whose source is modeled as magmatic recharge of a sill at the top of the crustal magma reservoir at 8-10-km depth. New mantle tomography suggest that Yellowstone volcanism is fed by an upper-mantle plume-shaped low velocity body that is composed of melt "blobs", extending from 80 km to 650 km in depth, tilting 60° NW, but then reversing tilt to ~60° SE to a depth of ~1500 km. Moreover, images of upper mantle conductivity from inversion of MT data reveal a high conductivity annulus around the north side of the plume in the upper mantle to resolved depths of ~300 km. On a larger scale, upper mantle flow beneath the western U.S. is characterized by eastward flow beneath Yellowstone at 5 cm/yr that deflects the plume to the west, and is underlain by a deeper zone of westerly return flow in the lower mantle reversing the deflection of the plume body to the SE. Dynamic modeling of the Yellowstone plume including a +15 m geoid anomaly reveals low excess plume temperatures, up to 150°K, consistent with a weak buoyancy flux of ~0.25 Mg/s. Integrated kinematic modeling of GPS

  4. Geodesy and geodynamics

    NASA Astrophysics Data System (ADS)

    Whitten, Charles A.

    1986-11-01

    Man's interest in the dynamics of the earth's crust goes back several centuries. Ekman recently pointed out the theory of post-glacial uplift in Fennoscandia. In the 15th century, towns along the Baltic-Sea experienced receding of the sea. In this century, Bowie had started a program for repeating surveys in seismically active regions. Wegeners' hypothesis of Continental Drift aroused the interest of scientists. In January 1985, Walter Sullivan traced the evolution from Wegener's continental drift through plate tectonics to the latest suggestion of the formation of continents from "terranes". Spatial techniques. Laser Ranging, VLBI, GPS have given geodesists the ability to monitor continental drift, intracontinental deformations and other phenomena. Along faults, such as the San Andreas Fault, the conventional geodetic approach to deformation has been to use a linear concept, except for episodic events such as earthquakes and so on. Wayne Thatcher's model on the declining strain rate is justified if sufficient geodetic data, well distributed, are available. Strain components can be computed from distortion patterns which might develop when an earlier survey is adjusted to be made consistent with a later survey. There exists a correlation of the movement of the instantaneous pole of rotation with the energy release of all earthquakes.

  5. Rotational waves in geodynamics

    NASA Astrophysics Data System (ADS)

    Gerus, Artyom; Vikulin, Alexander

    2015-04-01

    The rotation model of a geoblock with intrinsic momentum was constructed by A.V. Vikulin and A.G. Ivanchin [9, 10] to describe seismicity within the Pacific Ocean margin. It is based on the idea of a rotational motion of geoblocks as the parts of the rotating body of the Earth that generates rotary deformation waves. The law of the block motion was derived in the form of the sine-Gordon equation (SG) [5, 9]; the dimensionless form of the equation is: δ2θ δ2θ δξ2 - δη2 = sinθ, (1) where θ = β/2, ξ = k0z and η = v0k0t are dimensionless coordinates, z - length of the chain of masses (blocks), t - time, β - turn angle, ν0 - representative velocity of the process, k0 - wave number. Another case analyzed was a chain of nonuniformly rotating blocks, with deviation of force moments from equilibrium positions μ, considering friction forces α along boundaries, which better matched a real-life seismic process. As a result, the authors obtained the law of motion for a block in a chain in the form of the modified SG equation [8]: δ2θ δ2θ δθ- δξ2 - δ η2 = sin θ+ α δη + μδ(ξ)sin θ (2)

  6. A westward propagating slab tear model for Late Triassic Qinling Orogenic Belt geodynamic evolution: Insights from the petrogenesis of the Caoping and Shahewan intrusions, central China

    NASA Astrophysics Data System (ADS)

    Hu, Fangyang; Liu, Shuwen; Zhang, Wanyi; Deng, Zhengbin; Chen, Xu

    2016-10-01

    Late Triassic granitoid intrusions are widespread in the South Qinling Belt (SQB), providing excellent subjects to understand the geodynamic evolution of the Qinling Orogenic Belt and the collision between the North China Craton (NCC) and Yangtze Craton (YZC). This study shows newly obtained geological, geochemical and zircon U-Pb-Hf isotopic data of the Caoping and Shahewan intrusions, revealing that the Caoping intrusion consists of ~ 215 Ma fined-grained granites, and ~ 221-215 Ma porphyritic and coarse to medium-grained tonalites, granodiorites and monzogranites, which assemble with coeval mafic magmatic enclaves (MMEs). The Shahewan intrusion is composed of ~ 215-210 Ma porphyritic granodiorites and monzogranites, which also assemble with coeval MMEs. The fine-grained granites from the Caoping intrusion are characterized by high SiO2, Rb and (La/Yb)N ratio, but low MgO, CaO and Sc contents, with εHf(t) values of - 8.6 to + 4.3 and TDM2(Hf) ages of 883-1596 Ma, suggesting that they are mainly derived from partial melting of the Meso- to Neoproterozoic metagreywackes. The porphyritic and coarse to medium-grained granitoid rocks from both Caoping and Shahewan intrusions are characterized by higher MgO, CaO, Sc, Mg# values, but low SiO2, Rb contents and (La/Yb)N ratio, with εHf(t) values of - 0.7 to + 2.8 and TDM2(Hf) values of 961-1158 Ma, suggesting that they are mainly formed by magma mixing between melts that were derived from Meso- to Neoproterozoic basement rocks of the SQB and metasomatized lithospheric mantle. The MMEs from Caoping and Shahewan intrusions are characterized by low SiO2, Sr/Y ratio, high MgO, K2O, Rb, Sc, total REE contents, with εHf(t) values of + 0.5 to + 6.1 and TDM(Hf) values of 661-846 Ma, suggesting that they are produced by partial melting of metasomatized lithospheric mantle. The rapakivi-like textures of the rocks from Shahewan intrusion may be caused by continued underplating and injection of mafic magma resulting in higher

  7. Scientific Data Analysis and Software Support: Geodynamics

    NASA Technical Reports Server (NTRS)

    Klosko, Steven; Sanchez, B. (Technical Monitor)

    2000-01-01

    The support on this contract centers on development of data analysis strategies, geodynamic models, and software codes to study four-dimensional geodynamic and oceanographic processes, as well as studies and mission support for near-Earth and interplanetary satellite missions. SRE had a subcontract to maintain the optical laboratory for the LTP, where instruments such as MOLA and GLAS are developed. NVI performed work on a Raytheon laser altimetry task through a subcontract, providing data analysis and final data production for distribution to users. HBG had a subcontract for specialized digital topography analysis and map generation. Over the course of this contract, Raytheon ITSS staff have supported over 60 individual tasks. Some tasks have remained in place during this entire interval whereas others have been completed and were of shorter duration. Over the course of events, task numbers were changed to reflect changes in the character of the work or new funding sources. The description presented below will detail the technical accomplishments that have been achieved according to their science and technology areas. What will be shown is a brief overview of the progress that has been made in each of these investigative and software development areas. Raytheon ITSS staff members have received many awards for their work on this contract, including GSFC Group Achievement Awards for TOPEX Precision Orbit Determination and the Joint Gravity Model One Team. NASA JPL gave the TOPEX/POSEIDON team a medal commemorating the completion of the primary mission and a Certificate of Appreciation. Raytheon ITSS has also received a Certificate of Appreciation from GSFC for its extensive support of the Shuttle Laser Altimeter Experiment.

  8. International GPS Service for Geodynamics

    NASA Technical Reports Server (NTRS)

    Zumberge, J. F. (Editor); Urban, M. P. (Editor); Liu, R. (Editor); Neilan, R. E. (Editor)

    1996-01-01

    This 1995 annual report of the IGS International GPS (Global Positioning System) Service for Geodynamics - describes the second operational year of the service. It provides the many IGS contributing agencies and the rapidly growing user community with essential information on current organizational and technical matters promoting the IGS standards and products (including organizational framework, data processing strategies, and statistics showing the remarkable expansion of the GPS monitoring network, the improvement of IGS performance, and product quality). It also introduces important practical concepts for network densification by integration of regional stations and the combination of station coordinate solutions. There are groups of articles describing general aspects of the IGS, the Associate Analysis Centers (AACs), Data Centers, and IGS stations.

  9. Basic research for the geodynamics program

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Some objectives of this geodynamic program are: (1) optimal utilization of laser and VLBI observations as reference frames for geodynamics, (2) utilization of range difference observations in geodynamics, and (3) estimation techniques in crustal deformation analysis. The determination of Earth rotation parameters from different space geodetic systems is studied. Also reported on is the utilization of simultaneous laser range differences for the determination of baseline variation. An algorithm for the analysis of regional or local crustal deformation measurements is proposed along with other techniques and testing procedures. Some results of the reference from comparisons in terms of the pole coordinates from different techniques are presented.

  10. Fuzzy Logic Modelling and Hidden Geodynamic Parameters of Earth: What is the role of Fluid Pathaways and Hydrothermal Stages on the Mineralization Variations of Kozbudaklar Pluton over Southern Uludag

    NASA Astrophysics Data System (ADS)

    Kocaturk, Huseyin; Kumral, Mustafa

    2016-04-01

    Plate tectonics is one of the most illustrated theory and biggest geo-dynamic incident on earth surface and sub-surface for the earth science. Tectonic settlement, rock forming minerals, form of stratigraphy, ore genesis processes, crystal structures and even rock textures are all related with plate tectonic. One of the most known region of Turkey is Southern part of Uludaǧ and has been defined with three main lithological union. Region is formed with metamorphics, ophiolites and magmatic intrusions which are generally I-type granodiorites. Also these intrusion related rocks has formed and altered by high grade hydrothermal activity. This study approaches to understand bigger to smaller frameworks of these processes which between plate tectonics and fluid pathways. Geodynamic related fuzzy logic modelling is present us compact conclusion report about structural associations for the economic generations. Deformation structures and fluid pathways which related with plate tectonics progressed on our forearc system and each steps of dynamic movements of subducting mechanism has been seemed affect both hydrothermal stages and mineral variations together. Types of each deformation structure and mineral assemblages has characterized for flux estimations which can be useful for subsurface mapping. Geoanalytical results showed us clear characteristic stories for mutual processes. Determined compression and release directions on our map explains not only hydrothermal stages but also how succesion of intrusions changes. Our fuzzy logic models intersect sections of physical and chemical interactions of study field. Researched parameters like mafic minerals and enclave ratios on different deformation structures, cross sections of structures and relative existing sequence are all changes with different time periods like geochemical environment and each vein. With the combined informations in one scene we can transact mineralization processes about region which occurs in

  11. Study of a close-grid geodynamic measurement system

    NASA Technical Reports Server (NTRS)

    1977-01-01

    The Clogeos (Close-Grid Geodynamic Measurement System) concept, a complete range or range-rate measurement terminal installed in a satellite in a near-polar orbit with a network of relatively simple transponders or retro-reflectors on the ground at intervals of 0.1 to 10 km was reviewed. The distortion of the grid was measured in three dimensions to accuracies of + or - 1 cm with important applications to geodynamics, glaciology, and geodesy. User requirements are considered, and a typical grid, designed for earthquake prediction, was laid out along the San Andreas, Hayward, and Calaceras faults in southern California. The sensitivity of both range and range-rate measurements to small grid motions was determined by a simplified model. Variables in the model are satellite altitude and elevation angle plus grid displacements in latitude, and height.

  12. The NASA Geodynamics Program report, 1981

    NASA Technical Reports Server (NTRS)

    1982-01-01

    The activities of the NASA Geodynamics Program in 1981 both in achieving improved measurement precision and in establishing the foundation for the acquisition and analysis of scientific data are discussed.

  13. Geodynamic monitoring in real times

    NASA Astrophysics Data System (ADS)

    Outkin, V.; Yurkov, A.; Klimshin, A.; Kozlova, I.

    2011-12-01

    For the decision of problems of the short-term and intermediate term forecast of tectonic earthquakes the technique conditionally named - geodynamic monitoring which does not use the data of seismic monitoring for the operative decision of problems of the forecast is offered. Geodynamic monitoring (GDM) is to studying tensely - deformed conditions of the separate block of rock on change of activity natural radioactive gas is carried out by accommodation in the chosen file of specially designed monitors of radon - devices fixing change in time (VAR). The monitor of radon, (the detector of radon) as the basic measuring device located in the block of rocks, possesses enormous tensosensitivity to relative strain condition of a file. Depending on the enclosed pressure choose three characteristic points: 1) 30-35 % of "background" size VAR - the beginning of accumulation of inelastic energy; 2) 50 % of background VAR - the process of stabilization of an elastic condition of a file; 3) 70-75 % "background" VAR - a critical pressure in the mountain block, an opportunity as spontaneous dump of elastic energy, and under action external "triggerring" forces. If the size of the saved up energy is close to critical dump needs energy at a level of energy of variations of rotation of the Earth. Such significant energy causes "plenty" of earthquakes on all planet simultaneously. This fact confirms an opportunity of the short-term forecast of strong (destructive) earthquakes: dump of elastic pressure of the Earth in this case occurs in 25-30 hours after passage of variations of rotation of the Earth. It is for the notification of the population about coming nearer earthquake. External power functions (mechanical, electromagnetic, etc.), preparations influencing system and occurrence of tectonic earthquakes, are divided on two big classes: 1) "forecasting " functions - processes functionally connected to accumulation of elastic pressure and to dump by its rather small dozes; 2

  14. Geodynamic contributions to global climatic change

    NASA Technical Reports Server (NTRS)

    Bills, Bruce G.

    1992-01-01

    Orbital and rotational variations perturb the latitudinal and seasonal pattern of incident solar radiation, producing major climatic change on time scales of 10(exp 4)-10(exp 6) years. The orbital variations are oblivious to internal structure and processes, but the rotational variations are not. A program of investigation whose objective would be to explore and quantify three aspects of orbital, rotational, and climatic interactions is described. An important premise of this investigation is the synergism between geodynamics and paleoclimate. Better geophysical models of precessional dynamics are needed in order to accurately reconstruct the radiative input to climate models. Some of the paleoclimate proxy records contain information relevant to solid Earth processes, on time scales which are difficult to constrain otherwise. Specific mechanisms which will be addressed include: (1) climatic consequences of deglacial polar motion; and (2) precessional and climatic consequences of glacially induced perturbations in the gravitational oblateness and partial decoupling of the mantle and core. The approach entails constructing theoretical models of the rotational, deformational, radiative, and climatic response of the Earth to known orbital perturbations, and comparing these with extensive records of paleoclimate proxy data. Several of the mechanisms of interest may participate in previously unrecognized feed-back loops in the climate dynamics system. A new algorithm for estimating climatically diagnostic locations and seasons from the paleoclimate time series is proposed.

  15. Recent geodynamics of dangerous faults

    NASA Astrophysics Data System (ADS)

    Kuzmin, Yu. O.

    2016-09-01

    The analysis of the existing information concerning the present-day deformation activity of the fault zones in seismically active and aseismic regions suggests that the notions of an active fault and a dangerous fault should be distinguished. It is shown that a fault which is active for an expert in geotectonics will not be considered dangerous by an expert in geotechnical monitoring of buildings. The definition is given according to which a dangerous fault is understood as a zone of linear destruction which accommodates the contemporary short-period (a few months and years) pulsed and/or alternating motions with strain rates above 5 × 10-5 per annum and earthquakes with M ≥ 5. A technique is developed for identifying the dangerous faults based on monitoring the recent ground surface displacements in accordance with a special protocol which ensures an increased degree of detail in time and space. Based on the idea of the probable accumulation of dangerous strains during the operating cycle of the objects, the criteria for assessing their geodynamical risks are formulated.

  16. Effects of differentiation on the geodynamics of the early Earth

    NASA Astrophysics Data System (ADS)

    Piccolo, Andrea; Kaus, Boris; White, Richard; Johnson, Tim

    2016-04-01

    Archean geodynamic processes are not well understood, but there is general agreement that the mantle potential temperature was higher than present, and that as a consequence significant amounts of melt were produced both in the mantle and any overlying crust. This has likely resulted in crustal differentiation. An early attempt to model the geodynamic effects of differentiation was made by Johnson et al. (2014), who used numerical modeling to investigate the crust production and recycling in conjunction with representative phase diagrams (based on the inferred chemical composition of the primary melt in accordance with the Archean temperature field). The results of the simulations show that the base of the over-thickened primary basaltic crust becomes gravitational unstable due to the mineral assemblage changes. This instability leads to the dripping of dense material into the mantle, which causes an asthenospheric return flow, local partial melting and new primary crust generation that is rapidly recycled in to mantle. Whereas they gave important insights, the previous simulations were simplified in a number of aspects: 1) the rheology employed was viscous, and both elasticity and pressure-dependent plasticity were not considered; 2) extracted mantle melts were 100% transformed into volcanic rocks, whereas on the present day Earth only about 20-30% are volcanic and the remainder is plutonic; 3) the effect of a free surface was not studied in a systematic manner. In order to better understand how these simplifications affect the geodynamic models, we here present additional simulations to study the effects of each of these parameters. Johnson, T.E., Brown, M., Kaus, B., and VanTongeren, J.A., 2014, Delamination and recycling of Archaean crust caused by gravitational instabilities: Nature Geoscience, v. 7, no. 1, p. 47-52, doi: 10.1038/NGEO2019.

  17. Geodynamics - Tracking satellites to monitor global change

    SciTech Connect

    Beutler, G.; Morgan, P.; Neilan, R.E. Canberra Univ. JPL, Pasadena, CA )

    1993-02-01

    The major goals and organizational structure of the International GPS Geodynamics Service (IGS), a new Navstar satellite tracking service, are described. IGS activities are aimed at providing the scientific community with data on GPS orbits accurate enough for performing regional and local GPS analysis and daily earth rotation information.

  18. Geodynamics - Tracking satellites to monitor global change

    NASA Technical Reports Server (NTRS)

    Beutler, Gerhard; Morgan, Peter; Neilan, Ruth E.

    1993-01-01

    The major goals and organizational structure of the International GPS Geodynamics Service (IGS), a new Navstar satellite tracking service, are described. IGS activities are aimed at providing the scientific community with data on GPS orbits accurate enough for performing regional and local GPS analysis and daily earth rotation information.

  19. Geodynamic Research at the Department of Planetary Geodesy, SRC PAS

    NASA Astrophysics Data System (ADS)

    Brzeziński, Aleksander; Jóźwik, Mieczysław; Kaczorowski, Marek; Kalarus, Maciej; Kasza, Damian; Kosek, Wiesław; Nastula, Jolanta; Szczerbowski, Zbigniew; Wińska, Małgorzata; Wronowski, Roman; Zdunek, Ryszard; Zieliński, Janusz B.

    2016-06-01

    The Department of Planetary Geodesy of the Space Research Centre PAS has been conducting research on a broad spectrum of problems within a field of global dynamics of the Earth. In this report we describe the investigations on selected subjects concerning polar motion (modeling and geophysical interpretation of the Chandler wobble, hydrological excitation of seasonal signals, search for optimal prediction methods), tectonic activity in the region of the Książ Geodynamic Laboratory of the SRC, and finally the new joint Polish-Italian project GalAc analyzing feasibility and usefulness of equipping second-generation Galileo satellites with accelerometers.

  20. Software and Algorithms for Solving Computational Geodynamic Problems using Next Generation Hardware

    NASA Astrophysics Data System (ADS)

    Zheng, Liang; Gerya, Taras

    2014-05-01

    Numerical geodynamic modeling is typically based on solving a series of partial differential equations which describe the long-term behavior of the solid visco-elasto-brittle/plastic Earth as a highly viscous incompressible fluid with strongly variable non-Newtonian viscosity. Coding for solving geodynamic equations is catching up with the advance of modern high performance computing. In the past five years, newly developed many-core computing technology, including GPU (Graphics Processing Unit) and MIC (Many Integrated Core), has also been utilized for geodynamic modeling. However, the lack of easy-to-expand or easy-to-use geo-computing toolkits limits the high performance software catching up with the endless updating of high performance hardware. In this presentation, we will firstly show two examples of the implementation of solving geodynamic problems based on Stokes and continuity equations with strongly variable viscosity using many-core hardware, with a specific focus on the GPU. The first example is a geometric multi-grid (GMG) solver, which solves a synthetic sinking cube problem using a staggered grid finite difference discretization. The second example is a preconditioned minimal residual (MINRES) solver for incompressible Stokes flow problem with many viscous inclusions which is discretized using the finite element method. Through these two implementation examples, we will analyze the cost of coding and running advantages and disadvantages of the two kinds of coding methodologies, and in a hope to discuss a potential general coding flowchart for solving geodynamic equations using many-core devices. Finally, a software stack based many-core computing framework oriented to geodynamic modeling is proposed for the future.

  1. Appraisal of geodynamic inversion results: a data mining approach

    NASA Astrophysics Data System (ADS)

    Baumann, T. S.

    2016-11-01

    Bayesian sampling based inversions require many thousands or even millions of forward models, depending on how nonlinear or non-unique the inverse problem is, and how many unknowns are involved. The result of such a probabilistic inversion is not a single `best-fit' model, but rather a probability distribution that is represented by the entire model ensemble. Often, a geophysical inverse problem is non-unique, and the corresponding posterior distribution is multimodal, meaning that the distribution consists of clusters with similar models that represent the observations equally well. In these cases, we would like to visualize the characteristic model properties within each of these clusters of models. However, even for a moderate number of inversion parameters, a manual appraisal for a large number of models is not feasible. This poses the question whether it is possible to extract end-member models that represent each of the best-fit regions including their uncertainties. Here, I show how a machine learning tool can be used to characterize end-member models, including their uncertainties, from a complete model ensemble that represents a posterior probability distribution. The model ensemble used here results from a nonlinear geodynamic inverse problem, where rheological properties of the lithosphere are constrained from multiple geophysical observations. It is demonstrated that by taking vertical cross-sections through the effective viscosity structure of each of the models, the entire model ensemble can be classified into four end-member model categories that have a similar effective viscosity structure. These classification results are helpful to explore the non-uniqueness of the inverse problem and can be used to compute representative data fits for each of the end-member models. Conversely, these insights also reveal how new observational constraints could reduce the non-uniqueness. The method is not limited to geodynamic applications and a generalized MATLAB

  2. Appraisal of geodynamic inversion results: A data mining approach

    NASA Astrophysics Data System (ADS)

    Baumann, T. S.

    2016-07-01

    Bayesian sampling based inversions require many thousands or even millions of forward models, depending on how non-linear or non-unique the inverse problem is, and how many unknowns are involved. The result of such a probabilistic inversion is not a single `best-fit' model, but rather a probability distribution that is represented by the entire model ensemble. Often, a geophysical inverse problem is non-unique, and the corresponding posterior distribution is multimodal, meaning that the distribution consists of clusters with similar models that represent the observations equally well. In these cases, we would like to visualise the characteristic model properties within each of these clusters of models. However, even for a moderate number of inversion parameters, a manual appraisal for a large number of models is not feasible. This poses the question whether it is possible to extract end-member models that represent each of the best fit regions including their uncertainties. Here, I show how a machine learning tool can be used to characterise end-member models, including their uncertainties, from a complete model ensemble that represents a posterior probability distribution. The model ensemble used here, results from a non-linear geodynamic inverse problem, where rheological properties of the lithosphere are constrained from multiple geophysical observations. It is demonstrated that by taking vertical cross-sections through the effective viscosity structure of each of the models, the entire model ensemble can be classified into 4 end-member model categories that have a similar effective viscosity structure. These classification results are helpful to explore the non-uniqueness of the inverse problem and can be used to compute representative data fits for each of the end member models. Conversely, these insights also reveal how new observational constraints could reduce the non-uniqueness. The method is not limited to geodynamic applications and a generalised MATLAB

  3. Coupling geodynamic earthquake cycles and dynamic ruptures

    NASA Astrophysics Data System (ADS)

    van Zelst, Iris; van Dinther, Ylona; Gabriel, Alice-Agnes; Heuret, Arnauld

    2016-04-01

    Studying the seismicity in a subduction zone and its effects on tsunamis requires diverse modelling methods that span spatial and temporal scales. Hundreds of years are necessary to build the stresses and strengths on a fault, while consequent earthquake rupture propagation is determined by both these initial fault conditions and the feedback of seismic waves over periods of seconds up to minutes. This dynamic rupture displaces the sea floor, thereby causing tsunamis. The aim of the ASCETE (Advanced Simulations of Coupled Earthquake and Tsunami Events) project is to study all these aspects and their interactions. Here, we present preliminary results of the first aspects in this modelling chain: the coupling of a seismo-thermo-mechanical (STM) code to the dynamic rupture model SeisSol. STM models of earthquake cycles have the advantage of solving multiple earthquake events in a self-consistent manner concerning stress, strength and geometry. However, the drawback of these models is that they often lack in spatial or temporal resolution and do not include wave propagation. In contrast, dynamic rupture models solve for frictional failure coupled to seismic wave propagation. We use the software package SeisSol (www.seissol.org) based on an ADER-DG discretization allowing high-order accuracy in space and time as well as flexible tetrahedral meshing. However, such simulations require assumptions on the initial fault stresses and strengths and its geometry, which are hard to constrain due to the lack of near-field observations and the complexity of coseismic conditions. By adapting the geometry as well as the stress and strength properties of the self-consistently developing non-finite fault zones from the geodynamic models as initial conditions for the dynamic rupture models, the advantages of both methods are exploited and modelling results may be compared. Our results show that a dynamic rupture can be triggered spontaneously and that the propagating rupture is

  4. The compressible adjoint equations in geodynamics: equations and numerical assessment

    NASA Astrophysics Data System (ADS)

    Ghelichkhan, Siavash; Bunge, Hans-Peter

    2016-04-01

    The adjoint method is a powerful means to obtain gradient information in a mantle convection model relative to past flow structure. While the adjoint equations in geodynamics have been derived for the conservation equations of mantle flow in their incompressible form, the applicability of this approximation to Earth is limited, because density increases by almost a factor of two from the surface to the Core Mantle Boundary. Here we introduce the compressible adjoint equations for the conservation equations in the anelastic-liquid approximation. Our derivation applies an operator formulation in Hilbert spaces, to connect to recent work in seismology (Fichtner et al (2006)) and geodynamics (Horbach et al (2014)), where the approach was used to derive the adjoint equations for the wave equation and incompressible mantle flow. We present numerical tests of the newly derived equations based on twin experiments, focusing on three simulations. A first, termed Compressible, assumes the compressible forward and adjoint equations, and represents the consistent means of including compressibility effects. A second, termed Mixed, applies the compressible forward equation, but ignores compressibility effects in the adjoint equations, where the incompressible equations are used instead. A third simulation, termed Incompressible, neglects compressibility effects entirely in the forward and adjoint equations relative to the reference twin. The compressible and mixed formulations successfully restore earlier mantle flow structure, while the incompressible formulation yields noticeable artifacts. Our results suggest the use of a compressible formulation, when applying the adjoint method to seismically derived mantle heterogeneity structure.

  5. Is uplift of volcano clusters in the Tohoku Volcanic Arc, Japan, driven by magma accumulation in hot zones? A geodynamic modeling study

    NASA Astrophysics Data System (ADS)

    George, Ophelia A.; Malservisi, Rocco; Govers, Rob; Connor, Charles B.; Connor, Laura J.

    2016-06-01

    In many volcanic arcs, the rate of tectonic uplift cannot be explained by lithospheric plate motion alone but may be associated with dynamic uplift. Buoyant forces associated with underplated magma bodies lift the upper crust and leads to relatively high rates of topographic change. One such region is northern Honshu, Japan, where Quaternary volcano clusters are spatially associated with uplifted crust and isostatic gravity anomalies. Axisymmetric inversion of Bouguer gravity data for the Sengan volcano cluster shows that these gravity anomalies can be modeled by 30 km radius bodies emplaced at ˜15 km depth. Axisymmetric, finite element models, generated using GTECTON, of a layered Earth representative of the Tohoku crust indicate that the deformation of these midcrustal intrusions produces elevated topography on the surface directly above the intrusion that is bounded by a shallow peripheral trough. The wavelengths of vertical deformation produced by these bodies are sensitive to the thickness of the models' elastic layer and relatively insensitive to the models' rheology. This suggests that the amplitude of the vertical deformation represents a trade-off between the size of the intrusion and the thickness of the elastic layer and is less strongly influenced by the rheology of the lithosphere into which the bodies are emplaced. Our results are consistent with hot zone and hot finger models for the arc and indicate that Tohoku Volcanic Arc features such as gravity anomalies and uplifted basement are related to crustal magma intrusions and hot zones rather than directly related to mantle processes.

  6. Coupled Petrological and Geodynamic Models of Mantle Flow in Subduction Zones; the Importance of Chlorite in the Emergence of a Low-Viscosity Channel

    NASA Astrophysics Data System (ADS)

    Smith, P. M.; Baker, L. J.; Asimow, P. D.; Gurnis, M. C.

    2007-12-01

    Seismic velocity and attenuation studies have shown that 5-20 km thick low velocity layers exist above seismically fast slabs and are associated with broad zones of high attenuation in many subduction zones. These observations are generally interpreted as formation of hydrous phases by dehydration of the slab, although the impact of water in nominally anhydrous minerals (NAM) on seismic wave propagation is largely unknown. Recent petrological experiments on hydrous peridotite at subduction zone conditions suggest that chlorite will be stable adjacent to the subducting slab in sufficient quantities to be a significant water sink. We use a scheme that couples a petrological model (pHMELTS) with a 2-D thermal and variable viscosity flow model (ConMan) to model energy and mass transfer within a subduction zone. By varying input parameters including the convergence rate and slab dip we have developed models for cases in the Costa-Rica and Izu- Bonin-Marianas arc systems and are able to predict major and trace element compositions of primary melts, as well as geophysical observables, such as the topography and geoid. We find that the emergence of a slab- adjacent low-viscosity channel (LVC) is a natural consequence of the thermal and chemical controls on mantle dynamics and feedback between them. In our earlier models, as the LVC is dragged downwards by the subducting slab, hornblende breaks down at about 2.5 GPa and other hydrous phases such as serpentine are secondary in importance to the NAM water reservoir. The spatial limit of the LVC is the water-saturated solidus of the hydrated peridotite; the LVC thickens as the peridotite is progressively depleted by melting and the solidus migrates into the warmer wedge, despite water replenishment at depth. pHMELTS is a hybrid of the pMELTS model of Ghiorso and co-workers and includes amphiboles, serpentines and micas. Chlorite was lacking but we have recently rectified this omission. Following De Capitani and co- workers, we

  7. Geodynamics--where are we and what lies ahead?

    PubMed

    Drake, C L; Maxwell, J C

    1981-07-01

    The introduction and evolution of the plate tectonics hypothesis during the past two decades has sparked the current renaissance of research in the earth sciences. An outgrowth of active geophysical and geological exploration of the oceans, the plate tectonics model has come under intense scrutiny by geologists, geochemists, and geophysicists who have attempted to apply the model to the origin and growth of continents, the generation of oceanic and continental crust, and the nature of the lithosphere, asthenosphere, and underlying mantle with respect to their evolution through time and to the driving mechanism or mechanisms for plate tectonics. The study of other terrestrial planets and moons has been helpful in understanding the earth model. The unequal distribution of geological features, both in the continents and oceans, emphasizes the need for ongoing studies of international scope such as the recently completed International Geodynamics Project and its successor, the International Lithosphere Program, both stressing studies related to the dynamics of the lithosphere. PMID:17741165

  8. Rheological and geodynamic controls on the mechanisms of subduction and HP/UHP exhumation of crustal rocks during continental collision: Insights from numerical models

    NASA Astrophysics Data System (ADS)

    Burov, Evgene; Francois, Thomas; Agard, Philippe; Le Pourhiet, Laetitia; Meyer, Bertrand; Tirel, Celine; Lebedev, Sergei; Yamato, Philippe; Brun, Jean-Pierre

    2014-09-01

    While subduction of crustal rocks is increasingly accepted as a common scenario inherent to convergent processes involving continental plates and micro-continents, its occurrence in each particular context, as well as its specific mechanisms and conditions is still debated. The presence of ultra-high pressure(UHP) terranes is often interpreted as a strong evidence for continental subduction (subduction of continental crust) since the latter is seen as the most viable mechanism of their burial to UHP depths, yet if one admits nearly lithostatic pressure conditions in the subduction interface (or "channel"). The presumed links of continental subduction to exhumation of high- and ultra-high-pressure (HP/UHP) units also remain a subject of controversy despite the fact that recent physically consistent thermo-mechanical numerical models of convergent processes suggest that subduction can create specific mechanisms for UHP exhumation. We hence review and explore possible scenarios of subduction of continental crust, and their relation to exhumation of HP and UHP rocks as inferred from last generation of thermo-mechanical numerical models accounting for thermo-rheological complexity and structural diversity of the continental lithosphere. The inferences from these models are matched with the petrology data, in particular, with P-T-t paths, allowing for better understanding of subtleties of both subduction and burial/exhumation mechanisms. Numerical models suggest that exhumation and continental subduction are widespread but usually transient processes that last for less than 5-10 Myr, while long-lasting (> 10-15 Myr) subduction can take place only in rare cases of fast convergence of cold strong lithospheres (e.g. India). The models also show that tectonic heritage can play a special role in subduction/exhumation processes. In particular, when thicker continental terrains are embedded in subducting oceanic plate, exhumation of UHP terranes results in the formation of

  9. Magnetohydrodynamic Convection in the Outer Core and its Geodynamic Consequences

    NASA Technical Reports Server (NTRS)

    Kuang, Weijia; Chao, Benjamin F.; Fang, Ming

    2004-01-01

    The Earth's fluid outer core is in vigorous convection through much of the Earth's history. In addition to generating and maintaining Earth s time-varying magnetic field (geodynamo), the core convection also generates mass redistribution in the core and a dynamical pressure field on the core-mantle boundary (CMB). All these shall result in various core-mantle interactions, and contribute to surface geodynamic observables. For example, electromagnetic core-mantle coupling arises from finite electrically conducting lower mantle; gravitational interaction occurs between the cores and the heterogeneous mantle; mechanical coupling may also occur when the CMB topography is aspherical. Besides changing the mantle rotation via the coupling torques, the mass-redistribution in the core shall produce a spatial-temporal gravity anomaly. Numerical modeling of the core dynamical processes contributes in several geophysical disciplines. It helps explain the physical causes of surface geodynamic observables via space geodetic techniques and other means, e.g. Earth's rotation variation on decadal time scales, and secular time-variable gravity. Conversely, identification of the sources of the observables can provide additional insights on the dynamics of the fluid core, leading to better constraints on the physics in the numerical modeling. In the past few years, our core dynamics modeling efforts, with respect to our MoSST model, have made significant progress in understanding individual geophysical consequences. However, integrated studies are desirable, not only because of more mature numerical core dynamics models, but also because of inter-correlation among the geophysical phenomena, e.g. mass redistribution in the outer core produces not only time-variable gravity, but also gravitational core-mantle coupling and thus the Earth's rotation variation. They are expected to further facilitate multidisciplinary studies of core dynamics and interactions of the core with other

  10. Quaternary Hot-spot Activity within the Australian Continent Fueled by Edge-driven Convection: Combined Evidence from Seismic Tomography and 3D Geodynamic Modelling

    NASA Astrophysics Data System (ADS)

    Rawlinson, N.; Davies, R.

    2013-12-01

    Although the Australian continent is often regarded as tectonically quiescent owing to its intra-plate setting, it is not entirely free from large-scale processes, which result in lithospheric-scale changes in composition and structure. A clear example of this is the Newer Volcanics Province (NVP), located in the state of Victoria, southeast Australia, which exhibits the youngest evidence (~5ka) of basaltic intra-plate volcanism within Australia. Over the last few decades there has been much conjecture as to whether the source of volcanism originates deep in the mantle - for example, a rising plume - or is somehow localized in the uppermost mantle. In order to directly address this question, we use teleseismic arrival time residuals recorded by the WOMBAT transportable array in eastern Australia - the largest of its type in the southern hemisphere - to image 3-D variations in P-wavespeed in the upper mantle beneath the NVP. Our results unequivocally show the presence of a low velocity anomaly beneath the NVP which terminates at around 250 km depth. Assuming that this distinct anomaly is associated with increased temperatures and melting, then it appears likely that the NVP is a shallow, rather than deeply rooted feature. It is not possible to completely rule out the presence of a plume, because a narrow plume that spreads out on contact with the base of the lithosphere may yield a similar signature; however, our seismic results, combined with complementary evidence, including: (i) the lack of a hotspot chain; (ii) modest topographic response; and (iii) elongation of the eruption centers in a direction perpendicular to contemporary plate motion, all support the same conclusion. An idea that has been invoked to explain the NVP is so-called edge driven convection, where a change in lithospheric thickness drives a localized convection cell, which can transport deeper and hotter material to the surface. It has been inferred, from regional surface wave models, that the

  11. Geodynamics branch data base for main magnetic field analysis

    NASA Technical Reports Server (NTRS)

    Langel, Robert A.; Baldwin, R. T.

    1991-01-01

    The data sets used in geomagnetic field modeling at GSFC are described. Data are measured and obtained from a variety of information and sources. For clarity, data sets from different sources are categorized and processed separately. The data base is composed of magnetic observatory data, surface data, high quality aeromagnetic, high quality total intensity marine data, satellite data, and repeat data. These individual data categories are described in detail in a series of notebooks in the Geodynamics Branch, GSFC. This catalog reviews the original data sets, the processing history, and the final data sets available for each individual category of the data base and is to be used as a reference manual for the notebooks. Each data type used in geomagnetic field modeling has varying levels of complexity requiring specialized processing routines for satellite and observatory data and two general routines for processing aeromagnetic, marine, land survey, and repeat data.

  12. Application of space technology to geodynamics.

    PubMed

    Flinn, E A

    1981-07-01

    Measurements of the movement and deformation of tectonic plates are needed for many research areas in geodynamics, but observations with adequate accuracy and frequency of measurement are not feasible if classical geodetic methods are used. Long-baseline microwave interferometry and laser ranging to Earth satellites are among the new techniques that have been developed within the past decade to make the required measurements. Fixed and mobile stations using both these methods have been constructed in several countries and are now being used in an internationally coordinated research program. Baseline length accuracy better than 2 to 3 centimeters (1 standard deviation) is expected within the next 5 years. PMID:17741174

  13. Geodynamic environments of ultra-slow spreading

    NASA Astrophysics Data System (ADS)

    Kokhan, Andrey; Dubinin, Evgeny

    2015-04-01

    Ultra-slow spreading is clearly distinguished as an outstanding type of crustal accretion by recent studies. Spreading ridges with ultra-slow velocities of extension are studied rather well. But ultra-slow spreading is characteristic feature of not only spreading ridges, it can be observed also on convergent and transform plate boundaries. Ultra-slow spreading is observed now or could have been observed in the past in the following geodynamic environments on divergent plate boundaries: 1. On spreading ridges with ultra-slow spreading, both modern (f.e. Gakkel, South-West Indian, Aden spreading center) and ceased (Labrador spreading center, Aegir ridge); 2. During transition from continental rifting to early stages of oceanic spreading (all spreading ridges during incipient stages of their formation); 3. During incipient stages of formation of spreading ridges on oceanic crust as a result of ridge jumps and reorganization of plate boundaries (f.e. Mathematicians rise and East Pacific rise); 4. During propagation of spreading ridge into the continental crust under influence of hotspot (Aden spreading center and Afar triple junction), under presence of strike-slip faults preceding propagation (possibly, rift zone of California Bay). Ultra-slow spreading is observed now or could have been observed in the past in the following geodynamic environments on transform plate boundaries: 1. In transit zones between two "typical" spreading ridges (f.e. Knipovich ridge); 2. In semi strike-slip/extension zones on the oceanic crust (f.e. American-Antarctic ridge); 3. In the zones of local extension in regional strike-slip areas in pull-apart basins along transform boundaries (Cayman trough, pull-apart basins of the southern border of Scotia plate). Ultra-slow spreading is observed now or could have been observed in the past in the following geodynamic environments on convergent plate boundaries: 1. During back-arc rifting on the stage of transition into back-arc spreading (central

  14. Frontiers in mineral physics relevant to geodynamics issues

    NASA Astrophysics Data System (ADS)

    Karato, Shun-ichiro

    2014-05-01

    Mineral physics plays a critical role in understanding geodynamics for two reasons. First, properties of mineral play an important role in mass and energy transport in Earth's interior. Particularly important are the rheological properties that control the nature of mantle convection. Key issues in this area are the rheological properties of deep mantle and those of the lithosphere. Second, mineral physics knowledge is critical in interpreting various geophysical observations in terms of geodynamics. Interpretation of geophysical observations such as anomalies in seismic wave velocities, seismic anisotropy and electrical conductivity is not straightforward, and requires understanding of subtle details such as the role of minor element, hydrogen. In this talk, I will present a review of some of the recent advances in these areas focusing on the results obtained in my group. Understanding of rheological properties under the deep mantle conditions is challenging because of technical difficulties. We have developed a new deformation apparatus (RDA: rotational Drickamer apparatus) to study rheological properties under deep mantle conditions. This apparatus has been operated to P~25 GPa and T~2200 K. Even the study of rheological properties under the lithospheric conditions requires some technical development because orthopyroxene that is stable only above ~1 GPa plays a key role (commonly used gas apparatus cannot be used under these conditions). I will review some new results using these new techniques including the first quantitative results on the rheological properties of a perovskite + (Mg,Fe)O mixture and the strain weakening of a model peridotite under the lithospheric conditions. These new results provide some hints as to plausible models of dynamics and evolution of Earth's interior. However, Earth is complex and geodynamic studies must also be constrained by observations. Seismological observations including seismic discontinuities, lateral variation in

  15. Arctic region: new model of geodynamic history

    NASA Astrophysics Data System (ADS)

    Nikishin, Anatoly; Kazmin, Yuriy; Malyshev, Nikolay; Morozov, Andrey; Petrov, Eugene

    2014-05-01

    Basement of the Arctic shelf areas is characterizes with a complex structure. Age of the defined domains is early Pre-Cambrian, Neoproterozoic to Cambrian (Timanian and Baykalian), early-middle Paleozoic (Caledonian) and late Paleozoic (Uralian, Taimyrian and Ellesmerian). Mesozoic deformations affected Novaya Zemlya, Southern Taimyr and southern parts of the Laptev Sea, the East Siberian Sea, and the Chukchi Sea regions. There are several Paleozoic rift-postrift basins. The North Kara Basin and the Timan-Pechora Basin was formed during the early Ordovician time as subduction-related back-arc rift systems. The East-Barents Basin has the same origin but the age of its formation is late Devonian. Carboniferous rifting took place in the Norwegian part of the Barents Sea, the Chukchi Sea (Hanna Trough Basin) and the Sverdrup Basin. There are also rift-postrift basins of the Mesozoic age. Late Permian to Early Triassic rifting took place in the South Kara Basin; it was connected with both collapse of the Uralian Orogen and activity of the Siberian mantle plume. Aptian to Albian rifting was affected with really big area in the Laptev Sea, the East Siberian Sea and the Chukchi Sea right after the De-Long plume-related magmatic event. Paleogene (mainly Eocene) rifting was also widely spread in these areas. The Arctic Ocean consists of three main domains: the Canada Basin, Alpha-Mendeleev-Podvodnikov-Makarov domain, and the Eurasia Basin. The Canada Basin is a typical oceanic one. There are many uncertainties in the definition of spreading age, but in accordance with the prevalent point of view, it should be early Cretaceous, Neocomian. Alpha-Mendeleev-Podvodnikov-Makarov domain is an enigmatic region. We propose the following scenario for the formation of this domain: Aptian to Cenomanian plume-related large-scale intraplate basalt magmatism was followed by Albian to late Cretaceous rifting. Few axes of rifting were nearly orthogonal to the pre-existing one in the Canada Basin. The Alpha-Mendeleev Ridge is a rifted continental terrane covered by pre-rift basalts. The Eurasian Basin is a small oceanic one. Defined age of spreading is 56-0 Ma. The basin is characterized by a very slow spreading rate. Eocene to recent sediments covers the system of prominent linear ranges and valleys of former mid-oceanic ridge. The Lomonosov Ridge is a well known continental terrane dissected by Neogene-Quaternary faults. New data shows that the area of the Lomonosov and the Alpha-Mendeleev ridges was affected by strong Neogene to recent extension or transtension tectonics with the formation of numerous normal faults and related topographic highs and valleys. Recent bathymetry of these ridges is a result of this Neogene to recent tectonics. Our report is based on a new set of seismic lines in the Russian part of the Arctic region.

  16. Episodic Earth Evolution: a Mantle Geodynamic Model

    NASA Astrophysics Data System (ADS)

    Davaille, A.; Arndt, N.

    2008-12-01

    Three major regimes of crust-mantle evolution are recorded in U-Pb ages of zircons in granites and large rivers. Plate tectonics operated in the first stage, from ~4.4 to 2.7 Ga; huge peaks of crustal growth separated by long troughs dominated the second stage, from 2.7 to 1.8 Ga, and semi-continuous growth punctuated by large peaks characterized the last stage, from 1.8 to 0 Ga. Individual peaks in the second stage, at 2.7, 2.5, 2.1 and 1.8 Ga, open with massive mafic-ultramafic volcanism and climax 30 m.y. later with intrusion of voluminous granitoids: each peak was initiated by enhanced mantle plume activity, culminated with accelerated plate tectonics that produced large amounts of granitoid crust, and was followed by a long period of diminished tectonic activity. New fluid-mechanics experiments show that this second regime could have resulted from destabilization of a hot dense layer at the bottom of the lower mantle. Domes rising from this layer partially melt to form voluminous mafic magmas, and also trigger enhanced subduction. The first pulse of thermochemical instabilities was synchronous over the whole mantle, like the major 2.7 Ga crustal- growth peak, and later pulses were more disorganized, like the later peaks. During each peak, enhanced subduction removes quickly the upper cold thermal boundary layer: it is therefore followed by an inter-peak period of diminished activity, during which the cold boundary layer is growing again. This episodic evolution closely links continental growth and the extraction of heat from the core. In particular, the onset of the second regim could have been decisive for the timing of the inner core crystallization and the establishment of today's core dynamo regim.

  17. Mantle Plume Dynamics Constrained by Seismic Tomography and Geodynamics

    NASA Astrophysics Data System (ADS)

    Glisovic, P.; Forte, A. M.

    2012-12-01

    We construct a time-dependent, compressible mantle convection model in three-dimensional spherical geometry that is consistent with tomography-based instantaneous flow dynamics, using an updated and revised pseudo-spectral numerical method [Glisovic et al., Geophys. J. Int. 2012]. We explored the impact of two end-member surface boundary conditions, for a rigid and plate-like surface, along with geodynamically-inferred radial viscosity profiles. In each case we find that deep-mantle hot upwellings are durable and stable features in the mantle-wide convective circulation. These deeply-rooted mantle plumes show remarkable longevity over very long geological time spans (several hundred million years), mainly owing to the high viscosity in the lower mantle. Our very-long time convection simulations suggest that the deep-mantle plumes beneath the following hotspots: Pitcairn, Easter, Galapagos, Crozet, Kerguelen, Caroline and Cape Verde, are most reliably resolved in the present-day tomographic images.

  18. Geodynamical Evolution and Tectonic Framework of China

    NASA Astrophysics Data System (ADS)

    LIU, Guangding

    In this paper, we show that the tectonic framework of mainland China consists of "three latitudinal strips", namely, Tianshan-Yinshan-Yanshan, Qinling-Dabie, and Nanling; "two longitudinal strips" namely, Daxing'anling Taihangshan Wulingshan, Helanshan-Longmenshan; and "two triangles", Songpan-Ganzi, and Chaidamu. The geodynamic evolution of China can be considered in five-stages, which can be summarised as a kind of "teeterboard-like" process. The evolutionary process is that in the Palaeozoic era, the China mainland had lower elevation in the west and higher in the east, with OrdosSichuan as an axis. After the Mesozoic era, because the blocks of Qiangtang, Gangdese, and India collided and sutured with the Tarim block. During this time closure of the Tethys ocean occurred, and the Qinghai-Tibet Plateau formed. In the Cenozoic subduction of the Pacific plate northwestwards under the Philippine Sea began, and the Philippine Sea block converged towards the Eurasian plate. This was associated with extension and thinning of the crust in East China, which resulted in the uplift of the land in the west and subsidence in the east of China. Finally, we point out that research on the geodynamic evolution of the terranes is of practical significance in prospecting for mineral deposits and hydrocarbon resources.

  19. Iranian Permanent GPS Network for Geodynamics (IPGN)

    NASA Astrophysics Data System (ADS)

    Tavakoli, F.; Nankali, H. R.; Sedighi, M.; Djamour, Y.; Mosavi, Z.

    2009-04-01

    Iran is one of the most tectonically active zone in Alpine-Himalayan seismic belt where has been shaken by largely destroying historical and instrumental earthquakes. Iran is located in the convergence zone between Arabia and Eurasia with a velocity of 22 mm/yr nearly to the North. The shortening between Arabian and Eurasian plates in Iran is mainly distributed on Zagros and Alborz belts. Despite the historical and scientific awareness of seismic hazard in Iran, unfortunately this country lacked a Continuous GPS network to study geodynamic and tectonic movements. Such geodetic measurement can play an important role to understand the tectonic deformation then to evaluate the seismic hazard on Iran. Since early 2005 National Cartographic Center of Iran (NCC) is establishing a continuous GPS network named Iranian Permanent GPS Network for Geodynamics (IPGN). Taking into account the number of provided GPS receivers, (108) we made a priority based on two factors of seismicity and population. At the first, in order to study general tectonic behavior in Iran 41 stations, globally distributed in whole of Iran, were been considered. Three other areas in the priority list were: Centeral Alborz, North-West of Iran and North-East of Iran. The rest of receivers, i.e. ~60, were considered for these areas as local networks. These four networks are daily processed and give us a continuous monitoring of any surface deformation. In this paper we try to present the results obtained from the network

  20. A geodynamical perspective on the subduction of Cocos and Rivera plates beneath Mexico and Central America

    NASA Astrophysics Data System (ADS)

    Manea, V. C.; Manea, M.; Ferrari, L.

    2013-12-01

    The Middle America subduction zone (MASZ) is one of the world’ most complex convergent margins as it involves the subduction of the Rivera and Cocos young oceanic plates beneath the North American and Caribbean plates and is bounded by the Gulf of California rift and the Panama slab window. Characterized by contorted and unusual slab geometry, irregularly distributed seismicity and volcanism, exceptionally large slow slip events (SSE) and non-volcanic tremors (NVT), this subduction system represents a great natural laboratory for better understanding geodynamic processes at a fundamental level. Based on a solid observational foundation, and incorporating the latest experimental results into a coherent geodynamical framework, we shed light on the main processes controlling the subduction system evolution in this region. The tectonics, volcanism, slab geometry and segmentation along the margin are reviewed from a geodynamical perspective. We proposed and discussed a series of evolutionary scenarios for the Mexican and Central American subduction zones, providing a coherent starting base for future geodynamical modeling studies tailored to this active margin. We discuss comparatively the recently discovered SSEs and NVTs along the MASZ, and try to differentiate among the proposed mechanisms responsible for these observations. Finally we discuss the recent seismic anisotropy observations in a geodynamic context, offering an integrated view of mantle flow pattern along the entire active margin. Although the MASZ as a whole may be considered a fairly complicated region with many unusual features and sometimes controversial interpretations, its complexity and unusual characteristics can improve our knowledge about the linkage between deep and surface processes associated with subduction zone dynamics.

  1. Lithosphere-scale geodynamics in the Rhodope: assumptions and implications

    NASA Astrophysics Data System (ADS)

    Moulas, Evangelos; Burg, Jean-Pierre; Kostopoulos, Dimitrios; Schenker, Filippo

    2014-05-01

    The Rhodope Metamorphic Complex (RMC) is a synmetamorphic nappe stack located in the hinterland of the Hellenide orogen which is part of the Alpine-Himalayan chain. Advances in analytical instrumentation in petrology over the last 10 years made possible the documentation of high-to ultrahigh-pressure conditions in this complex. Despite the wealth of petrologic P-T-t data and the multitude of generic models on the evolution of the RMC, only few geodynamic restorations project long enough back in time to cover the entire life span of the orogen since the Jurassic. There are many reasons for the different (and often contrasting) models proposed for the RMC that deserve to be mentioned. Here, we present the different reconstructions published together with the assumptions on which they were built and their geodynamic implications. We then proceed to carefully assess those implications individually from the mineral to the lithosphere scale. Our assessment poses important constrains on the pressure, temperature and deformation history of the complex on a regional scale that cannot be satisfied by all reconstructions. Such constrains involve the length of the subducting plate, the thermal histories of the metamorphic rocks, the age response of the isotopic systems and last, but not least, the structural record of km-scale movements that can be identified in the field. In addition, the presence of ultrahigh-pressure rocks is restricted to shear zones all across the RMC and this requires an explanation. We examine the possibility of non-lithostatic pressure variations within crustal-scale ductile shear zones.

  2. A Feasibility Study of Space VLBI for Geodesy and Geodynamics

    NASA Astrophysics Data System (ADS)

    Kulkarni, Madhav Narayan

    1992-01-01

    Space Very Long Baseline Interferometry (VLBI) is an extension of the ground based VLBI to the space. With the launching of two or more Space VLBI satellites in the future, Space VLBI observations will be available for astrometric, geodetic and geodynamic applications. This new technique holds potential for various important applications including monitoring Earth rotation and interconnection of the reference frames used in geodesy and geodynamics. The aim of this feasibility study has been to investigate the possibility of precise estimation of geodetic parameters, with emphasis on the Earth rotation parameters (ERP's), from Space VLBI observations. A brief description of the Space VLBI technique, it's possible applications, and the Space VLBI missions being planned has been given. Estimability analysis to investigate the estimability of geodetic parameters from Space VLBI observations has been carried out and a simplified mathematical model is derived in terms of estimable parameters. Results of sensitivity analysis carried out to study the sensitivity of the Space VLBI observables to the geodetic parameters of interest, including the number of these parameters and random errors in their a priori values, have been presented. Some of the dominant systematic effects including atmospheric refraction, solar radiation pressure and relativistic effects have also been investigated. Simulation studies have been carried out to study the influence of these systematic effects and a priori information on the estimation of the Earth rotation parameters. The results from the simulation studies indicate that it may be possible to use the Space VLBI technique for monitoring Earth rotation and polar motion, only if the orbital systematic effects can be modeled to a high degree of accuracy (or the satellites can be tracked, with high accuracy, independently), and precise a priori information on station coordinates from other sources is used. A brief description of the Space VLBI

  3. Proceedings of the International Committee on Geodynamics

    NASA Astrophysics Data System (ADS)

    Jacob, Klaus

    This special volume, vol. 13, 1980, of the Geological Bulletin, University of Peshawar, Pakistan, on the Geodynamics of the NW Himalayas, contains 213 pages, 23 articles with 96 figures and 28 tables, authored by 36 contributors from 7 countries (Pakistan, U.S., France, India, Switzerland, Italy, U.K.). The volume truthfully reflects the diversity and intensity of the recent international scientific effort toward understanding Himalayan geodynamics.To be frank: The editorial, production, and scientific quality of this conference book is as mixed as Himalayan collision tectonics itself. Yet, beneath the poor editorial melange, there rest valuable scientific treasures. Particularly to those earth scientists' interested in oceanic subduction zones and island arcs, this book on (now) purely continental tectonics is a really surprising find. The centerpiece of attention is the now deeply eroded Kohistan belt interpreted to be an uplifted Mesozoic island arc and its associated fore-arc, back-arc, and subduction complexes. Cenozoic collision tectonics has partially exposed lower crustal or subcrustal levels of any or all of the arc-trench elements. They appear petrologically characterized by pyroxene granulites, eclogite, and garnet amphibolitic mineral assemblages. Structural and stratigraphic control is poor in most regions; and, thus, tectonic interpretations given by some authors may need revisions. But, geochemists will find a surprising number of major and minor element analyses and composition diagrams to test for possible affinities of the sampled rocks with ocean floor-, island arc-, and continent-derived igneous or metamorphic assemblages. Trace element and isotope studies are still few.

  4. An efficient and general approach for implementing thermodynamic phase equilibria information in geophysical and geodynamic studies

    NASA Astrophysics Data System (ADS)

    Afonso, Juan Carlos; Zlotnik, Sergio; Díez, Pedro

    2015-10-01

    We present a flexible, general, and efficient approach for implementing thermodynamic phase equilibria information (in the form of sets of physical parameters) into geophysical and geodynamic studies. The approach is based on Tensor Rank Decomposition methods, which transform the original multidimensional discrete information into a separated representation that contains significantly fewer terms, thus drastically reducing the amount of information to be stored in memory during a numerical simulation or geophysical inversion. Accordingly, the amount and resolution of the thermodynamic information that can be used in a simulation or inversion increases substantially. In addition, the method is independent of the actual software used to obtain the primary thermodynamic information, and therefore, it can be used in conjunction with any thermodynamic modeling program and/or database. Also, the errors associated with the decomposition procedure are readily controlled by the user, depending on her/his actual needs (e.g., preliminary runs versus full resolution runs). We illustrate the benefits, generality, and applicability of our approach with several examples of practical interest for both geodynamic modeling and geophysical inversion/modeling. Our results demonstrate that the proposed method is a competitive and attractive candidate for implementing thermodynamic constraints into a broad range of geophysical and geodynamic studies. MATLAB implementations of the method and examples are provided as supporting information and can be downloaded from the journal's website.

  5. A reduced basis approach for implementing thermodynamic phase-equilibria information in geophysical and geodynamic studies

    NASA Astrophysics Data System (ADS)

    Afonso, J. C.; Zlotnik, S.; Diez, P.

    2015-12-01

    We present a flexible, general and efficient approach for implementing thermodynamic phase equilibria information (in the form of sets of physical parameters) into geophysical and geodynamic studies. The approach is based on multi-dimensional decomposition methods, which transform the original multi-dimensional discrete information into a dimensional-separated representation. This representation has the property of increasing the number of coefficients to be stored linearly with the number of dimensions (opposite to a full multi-dimensional cube requiring exponential storage depending on the number of dimensions). Thus, the amount of information to be stored in memory during a numerical simulation or geophysical inversion is drastically reduced. Accordingly, the amount and resolution of the thermodynamic information that can be used in a simulation or inversion increases substantially. In addition, the method is independent of the actual software used to obtain the primary thermodynamic information, and therefore it can be used in conjunction with any thermodynamic modeling program and/or database. Also, the errors associated with the decomposition procedure are readily controlled by the user, depending on her/his actual needs (e.g. preliminary runs vs full resolution runs). We illustrate the benefits, generality and applicability of our approach with several examples of practical interest for both geodynamic modeling and geophysical inversion/modeling. Our results demonstrate that the proposed method is a competitive and attractive candidate for implementing thermodynamic constraints into a broad range of geophysical and geodynamic studies.

  6. Exploring problems in tectonics and geodynamics with seismology

    NASA Astrophysics Data System (ADS)

    Walker, Kristoffer T.

    I demonstrate in two different studies how seismology can be a powerful tool for exploring and testing tectonic/geodynamic problems. In the first study, I analyze, model, and interpret a deep marine seismic reflection/refraction, magnetics, gravity, and bathymetric profile collected across the Bristol Bay basin, a back-arc basin in the southeast Bering Sea. I test three leading models for basin subsidence, and show that the basin evolved due to both faulting and flexural subsidence associated with extension and volcanic loading of the arc. The second study is an investigation of mantle fabrics around hotspots (Eifel, Hawaii, and eastern Nevada) and beneath part of the East African Plateau (Tanzania and Kenya). I analyze, model, and interpret the splitting of teleseismic shear-waves that originate from earthquakes to determine the orientation and magnitude of seismic velocity anisotropy, which allows me to place constraints on the orientation, magnitude, and depth of mantle deformation fabrics. I show that the fabrics around hotspots are explained best as a result of current deformation associated with parabolic asthenospheric flow (PAF), the horizontal asthenospheric flow associated with the interaction of gravitationally spreading plume material with an asthenosphere that is being dragged in the direction of plate motion. The success of the PAF model in fitting the data suggests that strong anisotropy exists in the asthenosphere, which means that dislocation creep is an important deformation mechanism beneath some hotspots. It also suggests that plume-lithosphere interaction is dominated by laminar flow. Perhaps the most important implication is that shear-wave splitting can be used as a diagnostic to test between upwelling and non-upwelling sources for mantle hotspots, and can provide estimates of geodynamic parameters beneath regions of thin mantle lithosphere. Splitting beneath the East African Plateau appears to be due to asthenospheric anisotropy associated

  7. Geodynamically Consistent Interpretation of Seismic Tomography under the Hawaiian Hotspot

    NASA Astrophysics Data System (ADS)

    Bercovici, D.; Samuel, H.

    2006-12-01

    Recent theoretical developments as well as increased data quality and coverage have allowed seismic tomographic imaging to better resolve narrower structures at both shallow and deep mantle depths. However, despite these improvements, the interpretation of tomographic images remains problematic mainly because of: (1) the trade off between temperature and composition and their different influence on mantle flow; (2) the difficulty in determining the extent and continuity of structures revealed by seismic tomography. We present a study on mantle thermal plumes, which illustrate the need to consider both geodynamic and mineral physics for a consistent interpretation of tomographic images in terms of temperature composition and flow. We focus on the identification of thermal plume by seismic tomography beneath the Hawaiian hot spot: a set of 3D numerical experiments is performed in a spherical shell to model a rising plume beneath a moving plate. The thermal structure obtained is converted into body waves seismic velocities using mineral physics considerations. We then build synthetic travel time data by propagating front waves in the obtained seismic structure. This synthetic data will be used to construct a travel time tomographic model, which is compared with actual tomographic models based on data from the ongoing PLUME seismic experiment. This comparison will allow a more consistent and quantitative interpretation of seismic tomography and plume structure under Hawaii.

  8. High Speed Networking and Large-scale Simulation in Geodynamics

    NASA Technical Reports Server (NTRS)

    Kuang, Weijia; Gary, Patrick; Seablom, Michael; Truszkowski, Walt; Odubiyi, Jide; Jiang, Weiyuan; Liu, Dong

    2004-01-01

    Large-scale numerical simulation has been one of the most important approaches for understanding global geodynamical processes. In this approach, peta-scale floating point operations (pflops) are often required to carry out a single physically-meaningful numerical experiment. For example, to model convective flow in the Earth's core and generation of the geomagnetic field (geodynamo), simulation for one magnetic free-decay time (approximately 15000 years) with a modest resolution of 150 in three spatial dimensions would require approximately 0.2 pflops. If such a numerical model is used to predict geomagnetic secular variation over decades and longer, with e.g. an ensemble Kalman filter assimilation approach, approximately 30 (and perhaps more) independent simulations of similar scales would be needed for one data assimilation analysis. Obviously, such a simulation would require an enormous computing resource that exceeds the capacity of a single facility currently available at our disposal. One solution is to utilize a very fast network (e.g. 10Gb optical networks) and available middleware (e.g. Globus Toolkit) to allocate available but often heterogeneous resources for such large-scale computing efforts. At NASA GSFC, we are experimenting with such an approach by networking several clusters for geomagnetic data assimilation research. We shall present our initial testing results in the meeting.

  9. The Overshoot Phenomenon in Geodynamics Codes

    NASA Astrophysics Data System (ADS)

    Kommu, R. K.; Heien, E. M.; Kellogg, L. H.; Bangerth, W.; Heister, T.; Studley, E. H.

    2013-12-01

    The overshoot phenomenon is a common occurrence in numerical software when a continuous function on a finite dimensional discretized space is used to approximate a discontinuous jump, in temperature and material concentration, for example. The resulting solution overshoots, and undershoots, the discontinuous jump. Numerical simulations play an extremely important role in mantle convection research. This is both due to the strong temperature and stress dependence of viscosity and also due to the inaccessibility of deep earth. Under these circumstances, it is essential that mantle convection simulations be extremely accurate and reliable. CitcomS and ASPECT are two finite element based mantle convection simulations developed and maintained by the Computational Infrastructure for Geodynamics. CitcomS is a finite element based mantle convection code that is designed to run on multiple high-performance computing platforms. ASPECT, an adaptive mesh refinement (AMR) code built on the Deal.II library, is also a finite element based mantle convection code that scales well on various HPC platforms. CitcomS and ASPECT both exhibit the overshoot phenomenon. One attempt at controlling the overshoot uses the Entropy Viscosity method, which introduces an artificial diffusion term in the energy equation of mantle convection. This artificial diffusion term is small where the temperature field is smooth. We present results from CitcomS and ASPECT that quantify the effect of the Entropy Viscosity method in reducing the overshoot phenomenon. In the discontinuous Galerkin (DG) finite element method, the test functions used in the method are continuous within each element but are discontinuous across inter-element boundaries. The solution space in the DG method is discontinuous. FEniCS is a collection of free software tools that automate the solution of differential equations using finite element methods. In this work we also present results from a finite element mantle convection

  10. Geodynamic Effects of Ocean Tides: Progress and Problems

    NASA Technical Reports Server (NTRS)

    Richard, Ray

    1999-01-01

    Satellite altimetry, particularly Topex/Poseidon, has markedly improved our knowledge of global tides, thereby allowing significant progress on some longstanding problems in geodynamics. This paper reviews some of that progress. Emphasis is given to global-scale problems, particularly those falling within the mandate of the new IERS Special Bureau for Tides: angular momentum, gravitational field, geocenter motion. For this discussion I use primarily the new ocean tide solutions GOT99.2, CSR4.0, and TPXO.4 (for which G. Egbert has computed inverse-theoretic error estimates), and I concentrate on new results in angular momentum and gravity and their solid-earth implications. One example is a new estimate of the effective tidal Q at the M_2 frequency, based on combining these ocean models with tidal estimates from satellite laser ranging. Three especially intractable problems are also addressed: (1) determining long-period tides in the Arctic [large unknown effect on the inertia tensor, particularly for Mf]; (2) determining the global psi_l tide [large unknown effect on interpretations of gravimetry for the near-diurnal free wobble]; and (3) determining radiational tides [large unknown temporal variations at important frequencies]. Problems (2) and (3) are related.

  11. Recent movements of the earth crust: Composite geodynamic test areas

    NASA Astrophysics Data System (ADS)

    Bulanzhe, Iu. D.; Lilienberg, D. A.; Setunskaia, L. E.; Enman, S. V.

    This collection of papers summarizes studies of recent crustal movements on a number of test areas in the USSR in the framework of International Research Project No. 9, dealing with crustal movements in Central and Eastern Europe and Cuba. Particular papers are presented on the interpretation of movements in the Black Sea region in the light of plate tectonics; dynamic types of morphological structures of plains and low-mountain relief in Central Asia and Kazakhstan in vertical movements; horizontal movements and tectonic zoning of the earth surface on the southern Iakutsk geodynamic test area; the manifestation of crustal movements in mining regions; and movements on geodynamic test grounds in the Tiumen region.

  12. Generating volumetric composition maps from particle based computational geodynamic simulations.

    NASA Astrophysics Data System (ADS)

    May, D. A.

    2012-04-01

    The advent of using large scale, high resolution three-dimensional hybrid particle-grid based methods to study geodynamics processes is upon us. Visualizing and interpreting the three-dimensional geometry of the material configuration after severe deformation has occurred is a challenging task when adopting such a point based representation. In two-dimensions, the material configuration is readily visualized by creating a simple (x,y) scatter plot, using the particles position vector and coloring the points according to the lithology which each particle represents. Using only colored points (which do not need to be rendered as spheres), this approach unambiguous fills the 2D model domain with information defining the current material configuration. Along with an increased volume (i.e. MBytes) of output data generated by three-dimensional simulations, the higher dimensionality introduces additional complexities for visualization. The geometry of the deformed material in three-space will become topologically more complex than its two-dimensional counterpart. Secondly, the scatter plot approach used in 2D to represent the material configuration simply does not extend to three-dimensions as technique is unable to provide any sense of depth. To address some of the visualization challenges posed by such methods, we describe how an Approximate Voronoi Diagram (AVD) can be used to produce a volumetric representation of point based data. The AVD approach allows us to efficiently construct a volumetric partitioning of any subset of the model domain amongst a set points. From this representation, we can efficiently generate a representation of the material configuration which can be volume rendered, contoured, or from which cross sections can be extracted. The type of volumetric representations possible, and the performance characteristics of the AVD algorithm were demonstrated by applying the technique to simulation results from models of continental collision and salt

  13. ELEFANT: a user-friendly multipurpose geodynamics code

    NASA Astrophysics Data System (ADS)

    Thieulot, C.

    2014-07-01

    A new finite element code for the solution of the Stokes and heat transport equations is presented. It has purposely been designed to address geological flow problems in two and three dimensions at crustal and lithospheric scales. The code relies on the Marker-in-Cell technique and Lagrangian markers are used to track materials in the simulation domain which allows recording of the integrated history of deformation; their (number) density is variable and dynamically adapted. A variety of rheologies has been implemented including nonlinear thermally activated dislocation and diffusion creep and brittle (or plastic) frictional models. The code is built on the Arbitrary Lagrangian Eulerian kinematic description: the computational grid deforms vertically and allows for a true free surface while the computational domain remains of constant width in the horizontal direction. The solution to the large system of algebraic equations resulting from the finite element discretisation and linearisation of the set of coupled partial differential equations to be solved is obtained by means of the efficient parallel direct solver MUMPS whose performance is thoroughly tested, or by means of the WISMP and AGMG iterative solvers. The code accuracy is assessed by means of many geodynamically relevant benchmark experiments which highlight specific features or algorithms, e.g., the implementation of the free surface stabilisation algorithm, the (visco-)plastic rheology implementation, the temperature advection, the capacity of the code to handle large viscosity contrasts. A two-dimensional application to salt tectonics presented as case study illustrates the potential of the code to model large scale high resolution thermo-mechanically coupled free surface flows.

  14. Geodynamic Evolution of the Banda Sea Region

    NASA Astrophysics Data System (ADS)

    Kaymakci, N.; Decker, J.; Orange, D.; Teas, P.; Van Heiningen, P.

    2013-12-01

    We've carried out a large on- and offshore study in Eastern Indonesia to characterize the major structures and to provide constraints on the Neogene geodynamic evolution of the Banda Sea region. The onshore portion utilized remote sensing data and published geology. We tied the onshore to the offshore using recently acquired high resolution bathymetric data (16m and 25m bin size) and 2D seismic profiles that extend from Sulawesi in the west to Irian Jaya in the east across the northern part of the Banda Arc. We interpret the northern boundary of the 'Birds Head' (BH) of Papua, the Sorong Fault, to be a sinistral strike-slip fault zone with a minimum of 48 km displacement over the last few million years. The western boundary fault of Cendrawasih Basin defines the eastern boundary of BH and corresponds to the Wandamen Peninsula which comprises high pressure metamorphic rocks, including eclogite and granulite facies rocks, with exhumation ages from 4 to 1 Ma. Earthquake focal mechanism solutions indicate that the eastern boundary of BH is linked with a large scale offshore normal fault which we suggest may be related to the exhumation of the Wandamen Peninsula. The eastern boundary of Cendrawasih Basin is defined by a large transpressive belt along which BH is decoupled from the rest of Papua / Irian Jaya. This interpretation is supported by recent GPS studies. We propose that the BH and the Pacific plate are coupled, and therefore the Birds Head is therefore completely detached from Irian Jaya. Furthermore, Aru Basin, located at the NE corner of Banda Arc, is a Fault-Fault-Transform (FFT) type triple junction. According to available literature information the Banda Sea includes three distinct basins with different geologic histories; the North Banda Sea Basin (NBSB) was opened during 12-7 Ma, Wetar-Damar Basin (WDB) during 7-3.5 Ma and Weber Basin (WB) 3-0 Ma. Our bathymetric and seismic data indicated that the NBSB and Weber Basin lack normal oceanic crust and are

  15. Planetary cores: a geodynamic perspective (Invited)

    NASA Astrophysics Data System (ADS)

    Nimmo, F.

    2010-12-01

    How can measurements of planetary core materials improve our understanding of their geodynamical behaviour? Here I will focus on three aspects of this questions: 1) core formation; 2) the growth and rheology of solid cores; 3) dynamo activity. Core formation occurs either due to the heat generated by short-lived nuclides (for small bodies) or due to gravitational energy released during impacts (for large bodies) [1]. Core formation results in elemental fractionation; such fractionation depends on P,T and oxygen fugacity [2], and for Earth-mass bodies occurs as a succession of discrete events. Experimental measurements of siderophile element partition coefficients are necessary to infer conditions during accretion, though these inferences are non-unique [3]. Core formation may also lead to isotopic fractionation of elements such as Si [4] and Fe [5], although the latter in particular is currently uncertain and merits further experimental investigation. Core solidification depends on the slopes of the adiabat and melting curve, and on the concentration and nature of the light element(s) present [6,7]. Solidification may proceed from outside in (for small bodies) or from inside out (for larger bodies); the solid may be either lighter or heavier than the fluid, depending on the core composition. Thus, core solidification is complex and poorly understood; for instance, Ganymede and Mercury’s cores may be in a completely different solidification regime to that of the Earth [8,9]. Solidification can also vary spatially, giving rise to inner core seismological structure [10,11]. The viscosity of a solid inner core is an important and poorly constrained parameter [12] which controls core deformation, core-mantle coupling and tidal heating. Super-Earths probably lack solid inner cores [13], though further high-P experimental data are needed. Core dynamos are usually thought to be driven by compositional or thermal buoyancy [14] , with the former effect dominant for small

  16. Constraining Mantle Heterogeneities with Joint Inversions of Seismic, Geodynamic, and Mineral Physics Data

    NASA Astrophysics Data System (ADS)

    Lu, C.; Grand, S. P.; Forte, A. M.; Simmons, N. A.

    2014-12-01

    Two outstanding goals of solid earth geophysics are to determine the chemical structure of the Earth and to understand the dynamics of its interior. The dynamics of the mantle are controlled by density variations and combined knowledge of density structure and seismic velocities provide the strongest constraints on chemical heterogeneity. Unfortunately, most of the traditional geophysical methods such as seismic tomography and geodynamic modeling alone cannot adequately resolve the density structure within the mantle. Thus, seismic, geodynamic and mineral physics joint inversion methods have been applied to better understand the dynamics of the mantle in recent years (e.g. Simmons et al. 2010). In these joint inversions, P wave and S wave travel times, as well as four convection-related geodynamic observations (free air gravity, tectonic plate motion, dynamic topography, and the excess ellipticity of the core-mantle boundary) can be used to produce 3-D models of density and seismic velocities simultaneously. The approach initially attempts to find a model that assuming temperature controls lateral variations in mantle properties and then to consider more complicated lateral variations that account for the presence of chemical heterogeneity to further fit data. Here we present new joint inversion results include 50% more new S wave travel time data than in previous work and geodynamic data that extend to larger spherical harmonic degrees. In addition, temperature derivatives of P and S velocity and density have been determined using an updated mineral physics dataset. For the first time we include non-linear anelastic temperature effects on velocities in the joint inversion. The anelastic effects decrease the required high density component within the lower mantle superplumes. The hypothesis that temperature variations explain most observed heterogeneity within the mantle is consistent with our data. Reference: Simmons, N. A., A. M. Forte, L. Boschi, and S. P. Grand

  17. Use of high precision Satellite Laser Ranging Data in Space Geodynamics

    NASA Astrophysics Data System (ADS)

    Rudenko, S.

    Satellite laser ranging (SLR) data analysis is one of the modern techniques used to derive the Earth rotation parameters (ERP) and to establish a Terrestrial Reference Frame (TRF) realization. Information on the ERP and TRF is widely used in astrometry, geodynamics and geodesy, in particular, in the Terrestrial and Celestial Reference Frames transformation. Algorithms developed to model the geodynamic satellite Lageos-1 and Lageos-2 motion are described in the paper. The model precision is at a few centimeter level at two-week intervals. The paper presents the recent results of the joint processing of Lageos-1 and Lageos-2 SLR data acquired by the global network of 103 stations in 1983--1996. The data were mainly obtained from the Crustal Dynamics Data Information System (CDDIS), NASA. The data analysis has been performed using KIEV-GEODYNAMICS 5.2 software which basically follows the IERS Conventions [2] with some exceptions. The aim of the analysis was to derive the Earth rotation parameters at 13.3-year time interval and SLR tracking stations coordinates and velocities. We have obtained a set of the Earth rotation parameters (xp, yp pole coordinates, UT1-UTC) on three-day intervals since MJD 45583 till MJD 50445, coordinates of 101 SLR stations at epoch January 1, 1993 (MJD 48898) and velocities of 50 sites (66 collocated stations) with good observing histories and sufficient amount of high quality data. The formal rms errors of the station coordinates are at the level of 0.1--1 cm for the majority of the stations. The derived station coordinates and velocities have been compared with ITRF94 [1]. The Terrestrial Reference Frame realization given by our solution is at the centimeter level in agreement with the ITRF94. Our solution for ERP has been compared with the {EOP(IERS) C 04} series. The formal errors are 0.4 milliarc second for pole coordinates and 0.03 millisecond for the Universal Time.

  18. Geodynamic Evolution of the Northeastern South China Sea

    NASA Astrophysics Data System (ADS)

    Yeh, Y.; Sibuet, J.; Hsu, S.; Liu, C.

    2008-12-01

    We present a geodynamic evolution model of the northeastern South China Sea (SCS) updated the kinematic context based on a re-interpretation and analysis of all available magnetic data. Using the latest available multi-channel seismic data, two significant tectonic phases T1 and T2 were identified in the northeastern SCS. T1 is a slight tensional tectonic event and T2 is a major compressive event. In the absence of the drilling data in the deep basin, the identification of the magnetic anomalies, the age of major unconformities at ODP Sites 1146 and 1148 drilled on the northeastern SCS margin as well as a re- interpretation of the tectonic subsidence curve based on drilled holes in the west Taiwan basins provided age constraints for dating these two tectonic events. Tensional phase T1 is characterized by tilted blocks and fan-shaped deposits developed shortly (8-10 Ma) after the onset of SCS oceanic domain (37.8 Ma). It corresponds to the first ENE-WSW to E-W change in spreading directions, which occurred around chron C10 (~28.7 Ma). Tectonic phase T2 is characterized by the uplift of ENE-WSW rift features and NE-SW transverse features associated with the major plate reorganization in East Asia and a northeast shift of the Ryukyu subduction zone from the Luzon-Ryukyu transform plate boundary (LRTPB) to east of the present- day position of Taiwan, which occurred 17-18 Ma ago. As the T2 intra-plate compressive deformation only occurred south of the LRTPB, we suggest that the slab pull effect of the dead slab might have been transmitted to the oceanic crust south of the already inactive LRTPB.

  19. The DORIS benefits as seen from flight dynamics to geodynamics

    NASA Astrophysics Data System (ADS)

    Nouel, F.; Berthias, J. P.; Broca, P.; Comps, A.; Deleuze, M.; Guitart, A.; Jayles, C.; Laudet, Ph.; Pierret, C.; Piuzzi, A.

    DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) is a radio receiver designed to accurately measure the carrier frequencies of incoming signals generated by a worldwide beacon network. The DORIS concept is to minimize error sources so that the submeter level on the low Earth orbit satellite position can be reached almost permanently. The DORIS ground segment includes a control center and an orbit determination service, which were conceived to adequately process DORIS measurements and to maintain this high accuracy objective. Since February 1991, DORIS has been used to track the Earth observation satellite SPOT 2 and will also be a passenger for the following SPOT platforms. DORIS is the French tracking system of the oceanographic altimetry satellite TOPEX/POSEIDON which includes laser and experimental global positioning system (GPS) tracking on the US data. During 1990 and 1991, the SPOT Precise Orbit Determination (POD) was performed allowing an orbit time coverage of more than 70% (including frequent system tests during the first year). Taking the SPOT POD as a reference other tracking systems were evaluated and calibrated. Range, range rate, angular measurements have now generated adequate statistics characterizing their noises and their bias behavior, in terms of instrumental and propagation and time tag. Actual station keeping maneuver performances can also be estimated to the millimeter per second level in the three dimension space. Ionospheric daily maps are a by-product of the DORIS concept with its two coherent stable frequencies 2.03625 GHz and 401.24 MHz. As the measurements are performed on board, an autonomous orbit determination system prototype has been developed and performance estimated. As far as geodynamics are concerned, new Earth gravity fields have been developed by several groups from Europe and United States. These models will allow better orbit determination, especially for sun-synchronous orbits.

  20. Crisis of isotope geodynamics: Sm-Nd aspect

    NASA Astrophysics Data System (ADS)

    Pushkarev, Y. D.; Nikitina, L. P.

    2009-04-01

    Isotope geochemistry for many years contributes to improve our understanding of the Earth's interiors. There are a lot of models of the crust-mantle system evolution based on the isotope data. Indeed, identification of various types of the mantle material on the basis of isotope composition of its magmatic derivatives has opened perspective to fill geophysical models with the geochemical content. Study of the mantle material composition, changing in time and in space, with the same approach originated a new branch of geology, which was named chemical geodynamics or isotope geodynamics. Opportunities of the new approach have been unambiguously admitted more than 30 years ago after DePaolo & D.Wasserburg pioneer works, dedicated to development of Sm-Nd isotope systematics. This systematics became the most considerable component in the basement of isotope geodynamics as a whole. Since then nobody ever discussed the constrains of this siystematics. At the same time there are many contradictions in it. There are numerous mantle xenoliths depleted in main elements (Pearson et al., 2003), for which the whole variation curve normalized to chondrite is plotted below chondrite level. Paradox of the situation is that this mantle material has REE pattern which displays a continuous decrease of their concentration from La to Lu. Accordingly, Sm/Nd ratio in such material is lower than in chondrites. Through some time this material will be able to generate melts with ENd<0, which is considered to be the characteristic of the enriched mantle. At the same time, the material producing such melts in terms of the total REE concentration and the main elements concentration is high depleted. Another example, which demonstrates the independent variations of the main elements concentration, of the total REE contents, of Sm/Nd ratio and of Nd isotope composition in a source of the mantle magmatic derivatives, is connected with tholeiites of the middle ocean ridges and ocean islands

  1. Drilling the solid earth: global geodynamic cycles and earth evolution

    NASA Astrophysics Data System (ADS)

    Shervais, John W.; Arndt, Nicholas; Goodenough, Kathryn M.

    2015-09-01

    The physical and chemical evolution of the Earth is driven by geodynamic cycles that are global in scale, operating over 4.57 Ga of Earth's history. Some processes are truly cyclic, e.g., the Wilson Cycle, while others are irreversible (e.g., core formation). Heat and mass transfer between the lowermost mantle (e.g., core-mantle boundary) and the surface drives these global geodynamic processes. Subduction of lithospheric plates transfers cool fractionated material into the lower mantle and leads indirectly to the formation of new oceanic lithosphere, while the rise of thermochemical plumes recycles the remnants of these plates back to the surface, driven by heat transfer across the core-mantle boundary. These global geodynamic cycles are responsible for hotspot volcanism, the formation of continental crust, collisional orogenies, continental rifting, subduction zone processes (arcs, accretionary prisms), and ore deposits. Each of these presents opportunities for investigation by continental scientific drilling. In addition, these cycles affect other processes that are targets of continental scientific drilling: the origin and evolution of life and an oxygenated atmosphere, the impact of large volcanic eruptions on climate, and geological hazards such as earthquakes and volcanic eruptions. In this paper, we present the scientific rationale for continental scientific drilling to study global geodynamic processes, review past successes in this realm that were sponsored in part by ICDP, and suggest potential new targets for drilling campaigns that focus on solid earth evolution. This paper builds on discussions at the 2013 ICDP Science Meeting on the future of continental scientific drilling, held in Potsdam in November 2013.

  2. Applications of Geodesy to Geodynamics, an International Symposium

    NASA Technical Reports Server (NTRS)

    Mueller, I. I. (Editor)

    1978-01-01

    Geodetic techniques in detecting and monitoring geodynamic phenomena are reviewed. Specific areas covered include: rotation of the earth and polar motion; tectonic plate movements and crustal deformations (space techniques); horizontal crustal movements (terrestrial techniques); vertical crustal movements (terrestrial techniques); gravity field, geoid, and ocean surface by space techniques; surface gravity and new techniques for the geophysical interpretation of gravity and geoid undulation; and earth tides and geodesy.

  3. Time-dependent, irreversible entropy production and geodynamics.

    PubMed

    Regenauer-Lieb, Klaus; Karrech, Ali; Chua, Hui Tong; Horowitz, Franklin G; Yuen, Dave

    2010-01-13

    We present an application of entropy production as an abstraction tool for complex processes in geodynamics. Geodynamic theories are generally based on the principle of maximum dissipation being equivalent to the maximum entropy production. This represents a restriction of the second law of thermodynamics to its upper bound. In this paper, starting from the equation of motion, the first law of thermodynamics and decomposition of the entropy into reversible and irreversible terms,(1) we come up with an entropy balance equation in an integral form. We propose that the extrema of this equation give upper and lower bounds that can be used to constrain geodynamics solutions. This procedure represents an extension of the classical limit analysis theory of continuum mechanics, which considers only stress and strain rates. The new approach, however, extends the analysis to temperature-dependent problems where thermal feedbacks can play a significant role. We apply the proposed procedure to a simple convective/conductive heat transfer problem such as in a planetary system. The results show that it is not necessary to have a detailed knowledge of the material parameters inside the planet to derive upper and lower bounds for self-driven heat transfer processes. The analysis can be refined by considering precise dissipation processes such as plasticity and viscous creep. PMID:19948557

  4. Multi-phase multi-component reactive flow in Geodynamics

    NASA Astrophysics Data System (ADS)

    Oliveira, Beñat; Afonso, Juan Carlos; Zlotnik, Sergio

    2016-04-01

    Multi-phase multi-component reactive flow (MPMCRF) controls a number of important complex geodynamic/geochemical problems, such as melt generation and percolation, metasomatism, rheological weakening, magmatic differentiation, ore emplacement, and fractionation of chemical elements, to name a few. These interacting processes occur over very different spatial and temporal scales and under very different physico-chemical conditions. Therefore, there is a strong motivation in geodynamics for investigating the equations governing MPMCRF, their mathematical structure and properties, and the numerical techniques necessary to obtain reliable and accurate results. In this contribution we present results from a novel numerical framework to solve multiscale MPMCRF problems in geodynamic contexts. Our approach is based on the effective tracking of the most basic building blocks: internal energy and chemical composition. This is achieved through the combination of rigorous solutions to the conservation equations (mass, energy and momentum) for each dynamic phase (instead of the more common "mixture-type" approach) and the transport equation for the chemical species, within the context of classical irreversible thermodynamics. Interfacial processes such as phase changes, chemical diffusion+reaction, and surface tension effects are explicitly incorporated in the context of ensemble averaging. Phase assemblages, mineral and melt compositions, and all other physical parameters of multi-phase systems are obtained through dynamic free-energy minimization procedures.

  5. Automated Testing Infrastructure and Result Comparison for Geodynamics Codes

    NASA Astrophysics Data System (ADS)

    Heien, E. M.; Kellogg, L. H.

    2013-12-01

    The geodynamics community uses a wide variety of codes on a wide variety of both software and hardware platforms to simulate geophysical phenomenon. These codes are generally variants of finite difference or finite element calculations involving Stokes flow or wave propagation. A significant problem is that codes of even low complexity will return different results depending on the platform due to slight differences in hardware, software, compiler, and libraries. Furthermore, changes to the codes during development may affect solutions in unexpected ways such that previously validated results are altered. The Computational Infrastructure for Geodynamics (CIG) is funded by the NSF to enhance the capabilities of the geodynamics community through software development. CIG has recently done extensive work in setting up an automated testing and result validation system based on the BaTLab system developed at the University of Wisconsin, Madison. This system uses 16 variants of Linux and Mac platforms on both 32 and 64-bit processors to test several CIG codes, and has also recently been extended to support testing on the XSEDE TACC (Texas Advanced Computing Center) Stampede cluster. In this work we overview the system design and demonstrate how automated testing and validation occurs and results are reported. We also examine several results from the system from different codes and discuss how changes in compilers and libraries affect the results. Finally we detail some result comparison tools for different types of output (scalar fields, velocity fields, seismogram data), and discuss within what margins different results can be considered equivalent.

  6. Concept of Spatial Information System for Pieniny geodynamic polygon

    NASA Astrophysics Data System (ADS)

    Pasnikowski, M.; Chmiel, J.; Choromanski, M.; Pillich, A.; Szynal, P.; Galecka, M.; Jarmuz, D.

    2009-04-01

    The poster presents the conception of Spatial Information System (SIS) for geodynamic polygon of Pieniny Klippen Belt (PKB). Geodynamic research of the region, conducted by the staff of Faculty of Geodesy and Cartography of Warsaw University of Technology since the sixties of twentieth century, concern the vertical and horizontal movements and changes of Earth gravity parameters. The collected material all this time, very rich in observations and documentations, as well as further research planned in the region were an inspiration to establish the SIS. The designed system is concerned to be useful basically for collection of the results received so far and planned observation epochs as well. Its target functionality will allow to support the data presentations, analyses of the obtained results and planning process for next research in the future. The proposed conception of the database is described in the poster. The database of the considered SIS contains the following elements: information about geological structures of PKB, localizations of control points of geodynamic polygon and collected observations like: measurements of angles and distances, GNSS, precise and trigonometric levelling, gravimetric. The selected pilot layers of the SIS are based on: DTM, topographic maps, administrative and geologic maps. The data in the project are used to cover and characterize the three tectonic units distinguished in the study area. The ESRI software was used for main part of the work in the project.

  7. Geological and geophysical evidences for mud diapirism in south-eastern Sicily (Italy) and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Barreca, Giovanni

    2014-12-01

    A recent investigation on the northern margin of the Hyblean Plateau in south-eastern Sicily highlights the occurrence of a clayey diapiric intrusion into the foreland carbonate series. The piercing body, exposed along a ∼270 long and ∼30 m deep NE-SW elongated quarry, consists of serpentinite-bearing clayey material. As suggested by the internal contractional features and by its geometric relations with the adjacent rocks, the clayey body intruded in the foreland series producing on its flanks a set of domino-arranged normal faults which nucleated as a result of gravitative collapse. Taking into account previous petrological studies, which provided information about the origin of the mud, a deep geodynamic model for the northern part of the Hyblean Plateau is here presented. The mud diapirs originated from the uprising of pre-existing serpentinite bodies and others products of alteration probably developed along an ancient ridge-transform intersection where a hydrothermally altered mantle wedge occurred. This interpretation is supported by seismic, magnetic and gravimetric anomalies beneath the analyzed area and has implications on its geodynamic evolution.

  8. Chapter 4: Regional magnetic domains of the Circum-Arctic: A framework for geodynamic interpretation

    USGS Publications Warehouse

    Saltus, R.W.; Miller, E.L.; Gaina, C.; Brown, P.J.

    2011-01-01

    We identify and discuss 57 magnetic anomaly pattern domains spanning the Circum-Arctic. The domains are based on analysis of a new Circum-Arctic data compilation. The magnetic anomaly patterns can be broadly related to general geodynamic classification of the crust into stable, deformed (magnetic and nonmagnetic), deep magnetic high, oceanic and large igneous province domains. We compare the magnetic domains with topography/bathymetry, regional geology, regional free air gravity anomalies and estimates of the relative magnetic 'thickness' of the crust. Most of the domains and their geodynamic classification assignments are consistent with their topographic/bathymetric and geological expression. A few of the domains are potentially controversial. For example, the extent of the Iceland Faroe large igneous province as identified by magnetic anomalies may disagree with other definitions for this feature. Also the lack of definitive magnetic expression of oceanic crust in Baffin Bay, the Norwegian-Greenland Sea and the Amerasian Basin is at odds with some previous interpretations. The magnetic domains and their boundaries provide clues for tectonic models and boundaries within this poorly understood portion of the globe. ?? 2011 The Geological Society of London.

  9. Volume reconstruction of point cloud data sets derived from computational geodynamic simulations

    NASA Astrophysics Data System (ADS)

    May, D. A.

    2012-05-01

    One of the most widely used numerical modeling techniques in geodynamics to study the evolution of geomaterials is the "marker-and-cell" technique. In such methods the material lithology is represented by Lagrangian particles (markers), while the continuum equations are solved on a background mesh. Significant research has been devoted to improving the efficiency and scalability of these numerical methods to enable high-resolution simulations to be performed on modest computational resources. In contrast, little attention has been given to developing visualization techniques suitable for interrogation high-resolution 3D particle data sets. We describe an efficient algorithm for performing a volume reconstruction of the lithology field defined via particles (code available upon request from the author). The algorithm generates an Approximate Voronoi Diagram (AVD) which transforms particle data sets into a cell-based, volumetric data set. The volumetric representation enables cross sections of the material configuration to be constructed efficiently and unambiguously, thereby enabling the interior material structure of the simulation results to be analyzed. Examples from geodynamic simulations are used to demonstrate visual results possible using this visualization technique. Performance comparisons are made between existing implementations of exact and approximate Voronoi diagrams. Overall, the AVD developed herein is found to be extremely competitive as a visualizing tool for massive particle data sets as it is extremely efficient, has low memory requirements and can be trivially used in a distributed memory computing environment.

  10. Active Tectonics And Modern Geodynamics Of Sub-Yerevan Region

    NASA Astrophysics Data System (ADS)

    Avanesyan, M.

    2004-05-01

    The given work is dedicated to active tectonics and modern geodynamics of Sub-Yerevan region. This region is interesting as a one of regions with maximal seismic activity in Armenia. The high level of seismic risk of this region is conditioned by high level of seismic hazard, high density of the population, as well as presence of objects of special importance and industrial capacities. The modern structure of Sub-Yerevan region and the adjacent area, as well as the Caucasus entirely, has mosaic-block appearance, typical for collision zone of Arabian and Eurasian plates. Distinctively oriented active faults of various ranges and morphological types are distinguished. These faults, in their turn, form various-scale active blocks of the Earth's crust and their movement defines seismic activity of the region. The researches show, that all strong earthquakes in the region were caused by movements by newest and activated ancient faults. In order to reveal the character of Earth's crust active blocks movement, separation of high gradients of horizontal and vertical movements and definition of stress fields highest concentration regions by GPS observations, high-accuracy leveling and study of earthquake focal mechanisms a new seismotectonic model is developed, which represents a combination of tectonic structure, seismic data, newest and modern movements. On the basis of comparison and analysis of these data zones with potential maximal seismic hazard are separated. The zone of joint of Azat-Sevan active and Yerevan abysmal faults is the most active on the territory of Sub-Yerevan region. The directions relatively the Earth's crust movement in the zones of horizontal and vertical movement gradients lead to conclusion, that Aragats-Tsakhkunian and Gegam active blocks undergo clockwise rotation. This means, that additional concentration of stress must be observed in block corners, that is confirmed by location of strong earthquakes sources. Thus, on the North 1988 Spitak (M

  11. Fluidity: a fully-unstructured adaptive mesh computational framework for geodynamics

    NASA Astrophysics Data System (ADS)

    Kramer, S. C.; Davies, D.; Wilson, C. R.

    2010-12-01

    Fluidity is a finite element, finite volume fluid dynamics model developed by the Applied Modelling and Computation Group at Imperial College London. Several features of the model make it attractive for use in geodynamics. A core finite element library enables the rapid implementation and investigation of new numerical schemes. For example, the function spaces used for each variable can be changed allowing properties of the discretisation, such as stability, conservation and balance, to be easily varied and investigated. Furthermore, unstructured, simplex meshes allow the underlying resolution to vary rapidly across the computational domain. Combined with dynamic mesh adaptivity, where the mesh is periodically optimised to the current conditions, this allows significant savings in computational cost over traditional chessboard-like structured mesh simulations [1]. In this study we extend Fluidity (using the Portable, Extensible Toolkit for Scientific Computation [PETSc, 2]) to Stokes flow problems relevant to geodynamics. However, due to the assumptions inherent in all models, it is necessary to properly verify and validate the code before applying it to any large-scale problems. In recent years this has been made easier by the publication of a series of ‘community benchmarks’ for geodynamic modelling. We discuss the use of several of these to help validate Fluidity [e.g. 3, 4]. The experimental results of Vatteville et al. [5] are then used to validate Fluidity against laboratory measurements. This test case is also used to highlight the computational advantages of using adaptive, unstructured meshes - significantly reducing the number of nodes and total CPU time required to match a fixed mesh simulation. References: 1. C. C. Pain et al. Comput. Meth. Appl. M, 190:3771-3796, 2001. doi:10.1016/S0045-7825(00)00294-2. 2. B. Satish et al. http://www.mcs.anl.gov/petsc/petsc-2/, 2001. 3. Blankenbach et al. Geophys. J. Int., 98:23-28, 1989. 4. Busse et al. Geophys

  12. Mantle geodynamics and implications for Earth's mantle

    NASA Astrophysics Data System (ADS)

    Lassak, Teresa Mae

    Seismic evidence suggests the presence of two large, low shear wave velocity provinces in Earth's lowermost mantle beneath Africa and the central Pacific. The origin and evolution of these provinces is not constrained but is thought to be linked to Earth's large-scale mantle dynamics. The focus of this work is to determine if seismic models of core-mantle boundary (CMB) topography can be useful in characterizing Earth's mantle dynamics. The dynamic motions in Earth's mantle exert stress on the boundaries of Earth's mantle, which results in topography at the Earth's CMB. Better understanding topography on Earth's CMB could provide important constraints on mantle dynamics and on lower mantle heterogeneity. The work in this dissertation investigates two proposed dynamical hypotheses for Earth's mantle: thermal upwellings (plume clusters) and large intrinsically dense yet thermally buoyant piles of primitive mantle material (thermochemical piles). CMB topography is calculated for each model in order to identify topography patterns that are unique to each model. CMB topographic relief beneath thermochemical piles is relatively flat and upwarped compared to downwarping CMB topography beneath downwelling regions. In plume cluster models, there is a direct correlation between upwarping relief on the CMB and upwellings while downwarping relief occurs exclusively beneath downwelling regions. The results show that both thermochemical pile and plume cluster models produce unique CMB topography signatures; thus as seismic studies better resolve the global topography of Earth's CMB, there is potential to constrain the chemical and dynamic nature of Earth's lower mantle.

  13. Monitoring deep geodynamic processes within Vrancea intermediate-depth seismic zone by geodetic means

    NASA Astrophysics Data System (ADS)

    Besutiu, Lucian; Zlagnean, Luminita

    2015-04-01

    mechanism exclusively in the Vrancea seismic zone support the assumption. Recent studies on the Vrancea echoes of 2013 Galati-Izvoarele quake swarm have also confirmed our hypotheses. Based on numerical modelling of the geodynamic process, an estimate of the stretching rate has been obtained, fully consistent with results inferred from studies on the seismic energy released by the Vrancea intermediate earthquakes. Concluding remarks Looking further, the sinking of the Vrancea lithosphere into the upper mantle (and consequent crust stretching, appropriately reflected in the non-tidal gravity change) appears as an ongoing geodynamic process, tightly connected to the intermediate-depth seismicity generated within the lithosphere penetrating the upper mantle by thermo-baric accommodation phenomena. Time series provided by repeated gravity observations conducted on the above-mentioned infrastructure for about ten years have clearly revealed: (i) the persistence of the gravity lowering, and (ii) some apparent connection between the rate of the gravity change, and the amount of seismic energy released by intermediate-depth earthquakes. Acknowledgements. The research has been partly performed through CYBERDYNE project, funded through the EU structural programme (contract #184/2010).

  14. Watching structural and geodynamic features of a plate boundary: Peceneaga-Camena Fault

    NASA Astrophysics Data System (ADS)

    Besutiu, L.; Zlagnean, L.

    2009-04-01

    northern PCF flank (within the neighbouring EEP). Each instrument measures the distance to the reflector every 6 seconds and records minute averages of the observations. This way time series related to movements of the PCF compartments were acquired and stored in a computer database. To diminish the record noise, mainly due to the temperature variation and terrestrial tides, some filtering techniques were applied to data in order to better reveal the existent trends. The analysis made lead to some interesting conclusions: (i) PCF is a geodynamical active contact, which explains earthquakes presence along it; (ii) flanks displacements are irregular in both speed and strike; (iii) according to the records, PCF has behaved both as a right-lateral and / or left-lateral contact. The results are fully consistent with the geodynamic model connected to W Black Sea evolution. When the PCF northern compartment escapes toward Carpathians, PCF appears as a left-lateral fault. On the opposite, if the southern compartment is moving under the action of tectonic forces, then PCF appears as right-lateral fault. These conclusions may provide important constraints for interpreting GPS data obtained during epoch campaigns.

  15. Putting the Dynamics in Chemical Geodynamics

    NASA Astrophysics Data System (ADS)

    Spiegelman, M.; Katz, R. F.; Kelemen, P. B.; Fang, Y.; Collier, M.; Holtzman, B.

    2007-12-01

    An outstanding goal for both geochemists and geophysicists is to understand how to use the wide range of proxy geochemical (and geophysical) data to make useful inferences about the current and past dynamics of the planet. To relate data to dynamics, however, requires models that include the fundamental processes that affect chemical variability: i.e. source heterogeneity, chemical fractionation (melting/reactions), chemical transport and mixing. In particular, most models of chemical evolution do not include explicit fluid or magma transport and questions remain as to how much observed chemical variability can be attributed to magma dynamics. We discuss recent developments and models that suggest that at least some of the observed variability arises from transport processes. Driven by field observations, experiments and computational models, there is an emerging picture of partially molten regions as highly localized, channelized plumbing systems. Computations suggest that melt localization can arise from both chemical/physical and purely mechanical instabilities and can provide non-trivial mixing pathways through the mantle. Questions remain as to how the different instabilities interact and which may be dominant in the mantle. Regardless, a highly localized melt transport system can lead to significant trace element (and U-series) variability and fractionation even for a homogeneous source. Recent work extends these results to consider the interaction of a channelized melt system with a heterogeneous source and suggests that small scale spatial variations in partitioning can lead to significant scatter in the ratios of highly incompatible elements (Fang, Spiegelman & Kelemen). Current work is extending these approaches to try to understand the variability of major elements and reaction in open systems (Collier, Kelemen & Spiegelman) Looking forward, the integration of magma dynamics and small-scale localization into global mantle dynamics presents a major

  16. On the solvability of incompressible Stokes with viscoplastic rheologies in geodynamics

    NASA Astrophysics Data System (ADS)

    Spiegelman, Marc; May, Dave A.; Wilson, Cian R.

    2016-06-01

    Plasticity/failure is an essential ingredient in geodynamics models as earth materials cannot sustain unbounded stresses. However, many questions remain as to appropriate models of plasticity as well as effective solvers for these strongly nonlinear systems. Here we present some simplified model problems designed to elucidate many of the issues involved for the description and solution of viscoplastic problems as currently used in geodynamic modeling. We consider compression and extension of a viscoplastic layer overlying an isoviscous layer and introduce a single plastic yield criterion which includes the most commonly used viscoplasticity models: von Mises, depth-dependent von Mises, and Drucker-Prager. We show that for all rheologies considered, successive substitution schemes (aka Picard iteration) often stall at large values of the nonlinear residual, producing spurious solutions. However, combined Picard-Newton schemes can be effective for rheologies that are independent of the dynamic pressure. Difficulties arise when solving incompressible Stokes problems for rheologies that depend on the dynamic pressure such as Drucker-Prager viscoplasticity. Analysis suggests that incompressible Stokes can become ill-posed when the dependence of the deviatoric stress tensor on dynamic pressure (i.e., |∂τ/∂p'|) becomes large. We demonstrate empirically that, in these cases, Newton solvers can fail by introducing spurious shear bands and discuss the consequence of interpreting the results of nonconverged computations. Even for problems where solvers converge, Drucker-Prager viscoplasticity can produce dynamic pressures that deviate significantly from lithostatic and both the velocity and pressure fields should be evaluated to determine whether solutions are geologically reasonable.

  17. Basic research for the geodynamics program

    NASA Technical Reports Server (NTRS)

    1983-01-01

    Laser systems deployed in satellite tracking were upgraded to accuracy levels where biases from systematic unmodelled effects constitute the basic factor that prohibits extraction of the full amount of information contained in the observations. Taking into consideration that the quality of the instrument advances at a faster pace compared to the understanding and modeling of the physical processes involved, one can foresee that in the near future when all lasers are replaced with third generation ones the limiting factor for the estimated accuracies will be the aforementioned biases. Therefore, for the reduction of the observations, methods should be deployed in such a way that the effect of the biases will be kept well below the noise level. Such a method was proposed and studied. This method consists of using the observed part of the satellite pass and converting the laser ranges into range differences in hopes that they will be less affected by biases in the orbital models, the reference system, and the observations themselves.

  18. International GPS (Global Positioning System) Service for Geodynamics

    NASA Technical Reports Server (NTRS)

    Zumberge, J. F. (Editor); Liu, R. (Editor); Neilan, R. E. (Editor)

    1995-01-01

    The International GPS (Global Positioning System) Service for Geodynamics (IGS) began formal operation on January 1, 1994. This first annual report is divided into sections, which mirror different aspects of the service. Section (1) contains general information, including the history of the IGS, its organization, and the global network of GPS tracking sites; (2) contains information on the Central Bureau Information System; (3) describes the International Earth Rotation Service (IERS); (4) details collecting and distributing IGS data in Data Center reports; (6) describes how the IGS Analysis Centers generate their products; (7) contains miscellaneous contributions from other organizations that share common interests with the IGS.

  19. Geodynamics of Cenozoic deformation in central Asia

    NASA Technical Reports Server (NTRS)

    Liu, H.-S.

    1981-01-01

    This paper presents a study of the tectonic stresses in central Asia based on an interpretation of satellite gravity data for mantle convection and supplemented with published fault plane solutions of earthquakes. Northwest-southeast to north-south compressional stresses exist in the Tien Shan region where reverse faulting dominates. The maximum compressive stress is oriented approximately northeast-southwest in the regions of Altai and southern Mongolia. Farther north, compressive stress gives way to tensional stress which causes normal faulting in the Baikal rift system. It is also shown that all of the tectonic stresses in the Tibetan plateau and Himalayan frontal thrust are related to the convection-generated stress patterns inferred from satellite gravity data. These results suggest that the complex crustal deformation in central Asia can be convincingly described by the deformation of the lithosphere on top of the up- and down-welling asthenospheric material beneath it. This observational fact may not only upset the simple view of the fluid crustal model of the Tibetan plateau, but also provide some useful constraints for the future development of deformation theory of continental crust.

  20. Arctic geodynamics: Continental shelf and deep ocean geophysics. ERS-1 satellite altimetry: A first look

    NASA Technical Reports Server (NTRS)

    Anderson, Allen Joel; Sandwell, David T.; Marquart, Gabriele; Scherneck, Hans-Georg

    1993-01-01

    An overall review of the Arctic Geodynamics project is presented. A composite gravity field model of the region based upon altimetry data from ERS-1, Geosat, and Seasat is made. ERS-1 altimetry covers unique Arctic and Antarctic latitudes above 72 deg. Both areas contain large continental shelf areas, passive margins, as well as recently formed deep ocean areas. Until ERS-1 it was not possible to study these areas with satellite altimetry. Gravity field solutions for the Barents sea, portions of the Arctic ocean, and the Norwegian sea north of Iceland are shown. The gravity anomalies around Svalbard (Spitsbergen) and Bear island are particularly large, indicating large isostatic anomalies which remain from the recent breakup of Greenland from Scandinavian. Recently released gravity data from the Armed Forces Topographic Service of Russia cover a portion of the Barents and Kara seas. A comparison of this data with the ERS-1 produced gravity field is shown.

  1. Autonomous geodynamics of the Pamir-Tien Shan junction zone from seismology data

    NASA Astrophysics Data System (ADS)

    Lukk, A. A.; Shevchenko, V. I.; Leonova, V. G.

    2015-11-01

    The geodynamics of the Tajik Depression, the junction zone of the Pamirs and Tien Shan, is typically considered in the context of plate tectonic concept, which implies intense subhorizontal compression of the zone resulting from the subduction of the Indian and Eurasian lithospheric plates. This convergence has been reliably confirmed by the GPS measurements. However, the joint analysis of the geological structure, seismicity, and geodimeter measurements conducted during a few years at the Garm geodynamical testing site of the Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, demonstrates a widening of the Tajik Depression instead of its shortening, as should be expected from the subhorizontal compression predominant in the present-day stress-state of this region. This conclusion, together with the data from the other regions, suggests that, along with the plate tectonic mechanisms, there are also other, local, autonomous drivers that contribute to the tectogenesis of this region. Besides, the probable existence of these autonomous sources within the Tajik Depression directly follows from the seismology data. Among them is the crustal spreading within the depression suggested by the seismotectonic displacements in the focal mechanisms of the earthquakes. These displacements are directed in different azimuths off the axial's most subsided part of the depression at a depth of 20-30 km. Above this region the distribution of seismotectonic deformations (STD) is chaotic. This pattern of deformation is barely accounted for by a simple model of subhorizontal compression of the Earth's crust in the region. In our opinion, these features of the seismotectonic deformation in the crust within the studied part of the Tajik Depression is probably associated with the gain in the volume of the rocks due to the inflow of the additional material, which is supplied from the bottom crust or upper mantle by the deep fluids. This increase in the rock volume

  2. Dynamic topography of the southern Central Anatolian Plateau, Turkey, and geodynamic driving mechanisms

    NASA Astrophysics Data System (ADS)

    Schildgen, T. F.; Cosentino, D.; Dudas, F. O.; Niedermann, S.; Strecker, M. R.; Echler, H.; Yildirim, C.

    2010-12-01

    Collision between Eurasia and Arabia and subsequent westward extrusion of the Anatolian microplate explains the development of major intracontinental fault systems in Anatolia that have remained active to the present-day. Concurrent, and probable episodic uplift of the Central and Eastern Anatolian plateaus (CAP and EAP), however, suggests that additional geodynamic mechanisms have contributed to the late Cenozoic morphologic development of the region. Sedimentary basins spanning the southern margin of the CAP provide insights on the timing and rates of different phases of surface uplift, giving constraints to test which geodynamic processes have contributed to surface uplift, orogenic plateau growth, and coupled landscape/climate evolution. Stratigraphic and geomorphic records of uplift and subsidence in the Mut Basin at the southern CAP margin and along the Göksu River record dynamic topographic development. Biostratigraphy and Sr isotope stratigraphy on the highest (ca. 2 km) uplifted marine sediments of the Mut basin furnish a maximum age of ca. 8 Ma for the onset of late Cenozoic uplift of the region. A Pliocene to early Pleistocene marine section, inset within the older stratigraphy at ca. 0.2 to 1.2 km elevation, reveals a history of subsidence and renewed uplift, following the initial uplift that occurred between ca. 8 Ma and Pliocene time. The most recent phase of uplift continued with possibly minor interruptions during the Quaternary, and is recorded by a series of fluvial terraces preserved between 30 and 143 m above the modern Göksu River. One terrace (143 m) reveals a 21Ne model exposure age of ca. 160 ka; ongoing exposure age determination will further constrain the uplift history. Different geodynamic mechanisms have likely contributed to surface uplift along the southern CAP margin. Initial uplift may have been associated with the predominantly sinistral Ecemis fault system that spans the southern and southeastern CAP margin. Neogene counter

  3. Multiscale, multiphysics geomechanics for geodynamics applied to buckling instabilities in the middle of the Australian craton

    NASA Astrophysics Data System (ADS)

    Regenauer-Lieb, Klaus; Veveakis, Manolis; Poulet, Thomas; Paesold, Martin; Rosenbaum, Gideon; Weinberg, Roberto F.; Karrech, Ali

    2015-10-01

    We propose a new multi-physics, multi-scale Integrated Computational Materials Engineering framework for 'predictive' geodynamic simulations. A first multiscale application is presented that allows linking our existing advanced material characterization methods from nanoscale through laboratory-, field and geodynamic scales into a new rock simulation framework. The outcome of our example simulation is that the diachronous Australian intraplate orogenic events are found to be caused by one and the same process. This is the non-linear progression of a fundamental buckling instability of the Australian intraplate lithosphere subject to long-term compressive forces. We identify four major stages of the instability: (1) a long wavelength elasto-visco-plastic flexure of the lithosphere without localized failure (first 50 Myrs of loading); (2) an incipient thrust on the central hinge of the model (50-90 Myrs); (3) followed by a secondary and tertiary thrust (90-100 Myrs) 200 km away to either side of the central thrust; (4) a progression of subsidiary thrusts advancing towards the central thrust (? Myrs). The model is corroborated by multiscale observations which are: nano-micro CT analysis of deformed samples in the central thrust giving evidence of cavitation and creep fractures in the thrust; mm-cm size veins of melts (pseudotachylite) that are evidence of intermittent shear heating events in the thrust; and 1-10 km width of the thrust - known as the mylonitic Redbank shear zone - corresponding to the width of the steady state solution, where shear heating on the thrust exactly balances heat diffusion.

  4. Program of Geodynamic Investigation for the Site of a New Nuclear Power Plant in Hungary

    NASA Astrophysics Data System (ADS)

    Trosits, D.; Horvath, F.; Katona, T.; Gerstenkorn, A.

    2014-12-01

    Preparation of a new nuclear power plant project is going on in Hungary at Paks site. Although there is an operating plant at the site, comprehensive geological, geophysical investigation has to be implemented in accordance with Hungarian nuclear safety regulation and international norms for confirming the site acceptability and providing a neotectonic basis for site seismic hazard assessment. The scope, techniques and methods of investigations have to be adapted to the geotectonic environment of the site and Pannonian Basin as a whole. The poster presents a brief summary of the program and provides a detailed description of the seismic survey focusing on the 3D subsurface imaging that is the most important task of planned geophysical investigations. The 3D geophysical imaging provides essential geodynamic information to assess the capability of near site faults and for the seismic hazard analysis, as well as for the hydrogeological modeling. The planned seismic survey gives a unique dataset for understanding the spatial relationship between individual fault segments. The 3D survey allows predicting and characterization of deformations induced by recent lithospheric stresses that is crucial for assessing the tectonic stability of the area. 3D seismic survey has to be combined with appropriate 2D and 3D shallow seismic profiling. The obtained 3D seismic data are also used for numerical geodynamic modeling. Rheology of rocks fundamentally influences the frequency of seismic activity, i.e. the accumulation and release of seismic energy. Regarding this the Pannonian Basin has specific features: the crust is thin and thermal gradients are high. This implies the whole lithosphere can be considered rheologically weak and its behavior is mostly plastic. It is suspected that most of the fault zones in the Pannonian basin are restricted to the sedimentary fill and the uppermost crust, and rest of the lithosphere experiences aseismic deformation.

  5. Neogene stratigraphy and Andean geodynamics of southern Ecuador

    NASA Astrophysics Data System (ADS)

    Hungerbühler, Dominik; Steinmann, Michael; Winkler, Wilfried; Seward, Diane; Egüez, Arturo; Peterson, Dawn E.; Helg, Urs; Hammer, Cliff

    2002-01-01

    The present paper reviews Tertiary volcanic and sedimentary formations in the Inter-Andean region of southern Ecuador (between 2°S and 4°20'S) in order to develop a geodynamic model of the region. The formations occur in the southern shallow prolongation of the Inter-Andean Valley between the Cordillera Real to the east, and the Cordillera Occidental and Amotape-Tahuı´n Provinces to the west. One hundred fifty zircon fission-track analyses has established a detailed chronostratigraphy for the sedimentary and volcanic formations and several small intrusions. The Paleogene to early Miocene formations are dominated by intermediate and acidic volcanic and pyroclastic rocks. In addition, relics of Eocene continental sedimentary series have been identified. The Neogene sedimentary series lie unconformably on deformed and eroded metamorphic, sedimentary and volcanic formations. They were deposited in two stages, which are separated by a major unconformity dated at ≈10-9 Ma. (1) During the middle and early late Miocene (≈15-10 Ma) marginal marine deltaic, lagoonal, lacustrine and fluvial environments prevailed, which we group under the heading "Pacific Coastal sequences". They presumably covered a greater surface area in southern Ecuador than their present occurrence in small topographic depressions. We suggest that they were deposited in the shallow marine Cuenca and Loja Embayments. Deposition in a marginal marine environment is also supported by the occurrence of brackish water ostracods and other fauna. (2) Above the regional (angular) unconformity, the coastal facies are overlain by late Miocene (≈9-5 Ma) continental alluvial fan and fluvial facies which are in turn covered by mainly airborne volcanic material. They represent the "Intermontane sequences" of the basins of Cuenca, Girón-Santa Isabel, Nabón, Loja and Malacatos-Vilcabamba. Sedimentologic and stratigraphic results are used to discuss the tectonic setting of Neogene sedimentation in the forearc

  6. Role of the Earth's rotation in global geodynamics

    NASA Astrophysics Data System (ADS)

    Pavlenkova, N.

    2009-04-01

    Role of the Earth's rotation in the global geodynamics. Pavlenkova N.I., Institute of Physics of the Earth of Russian Academy of Science, B.Grusinskaja 10, 123995, Moscow, ninapav@ifz.ru Geophysical studies show several regularities in Earth's structures which are not explained by the traditional global tectonics conceptions. (1) The surface of the Earth, as well as a surface of other planets, precisely shares on two hemispheres with a different relief and structure of an earth's crust: on the Pacific (oceanic) hemisphere with the lowered relief and a thin oceanic crust, and a continental hemisphere with prevalence of the raised relief and a thick continental crust. (2) There is a regular system of global lineaments and ring structures which are stretched on thousand kilometers, covering continents and oceans. As one of examples it is possible to result system of rift zones (mid-oceanic ridges), forming a ring around of the Antarctica with rift branches from it through everyone of 90 degrees. (3) Asymmetry with a relief of a day time surface when to each raised structure there corresponds the lowered surface on the opposite side of globe is observed. (4) The continental and oceanic mantles have different compositions and deep roots (>300 km) beneath the continents are prominent as regions with relatively high seismic velocities. There are regular connections between geological structures and deep mantle roots. (5) The classical lithosphere-asthenosphere model is not confirmed by seismic data. The asthenosphere can not be traced as a continuous layer, there are disconnected lenses (asthenolenses) even beneath mid-oceanic ridges. Significant horizontal movements of the lithosphere, as proposed by the global plate tectonics, would destroy all these regularities and crust-mantle interaction. To make an agreement between all observed data, the fluids-rotation hypothesis is proposed. The hypothesis supposes two main energy sources of the global tectonics: the

  7. Software Attribution for Geoscience Applications in the Computational Infrastructure for Geodynamics

    NASA Astrophysics Data System (ADS)

    Hwang, L.; Dumit, J.; Fish, A.; Soito, L.; Kellogg, L. H.; Smith, M.

    2015-12-01

    Scientific software is largely developed by individual scientists and represents a significant intellectual contribution to the field. As the scientific culture and funding agencies move towards an expectation that software be open-source, there is a corresponding need for mechanisms to cite software, both to provide credit and recognition to developers, and to aid in discoverability of software and scientific reproducibility. We assess the geodynamic modeling community's current citation practices by examining more than 300 predominantly self-reported publications utilizing scientific software in the past 5 years that is available through the Computational Infrastructure for Geodynamics (CIG). Preliminary results indicate that authors cite and attribute software either through citing (in rank order) peer-reviewed scientific publications, a user's manual, and/or a paper describing the software code. Attributions maybe found directly in the text, in acknowledgements, in figure captions, or in footnotes. What is considered citable varies widely. Citations predominantly lack software version numbers or persistent identifiers to find the software package. Versioning may be implied through reference to a versioned user manual. Authors sometimes report code features used and whether they have modified the code. As an open-source community, CIG requests that researchers contribute their modifications to the repository. However, such modifications may not be contributed back to a repository code branch, decreasing the chances of discoverability and reproducibility. Survey results through CIG's Software Attribution for Geoscience Applications (SAGA) project suggest that lack of knowledge, tools, and workflows to cite codes are barriers to effectively implement the emerging citation norms. Generated on-demand attributions on software landing pages and a prototype extensible plug-in to automatically generate attributions in codes are the first steps towards reproducibility.

  8. Geodynamics of the Dead Sea Fault: Do active faulting and past earthquakes determine the seismic gaps?

    NASA Astrophysics Data System (ADS)

    Meghraoui, Mustapha

    2014-05-01

    The ~1000-km-long North-South trending Dead Sea transform fault (DSF) presents structural discontinuities and includes segments that experienced large earthquakes (Mw>7) in historical times. The Wadi Araba and Jordan Valley, the Lebanese restraining bend, the Missyaf and Ghab fault segments in Syria and the Ziyaret Fault segment in Turkey display geometrical complexities made of step overs, restraining and releasing bends that may constitute major obstacles to earthquake rupture propagation. Using active tectonics, GPS measurements and paleoseismology we investigate the kinematics and long-term/short term slip rates along the DSF. Tectonic geomorphology with paleoseismic trenching and archeoseismic investigations indicate repeated faulting events and left-lateral slip rate ranging from 4 mm/yr in the southern fault section to 6 mm/yr in the northern fault section. Except for the northernmost DSF section, these estimates of fault slip rate are consistent with GPS measurements that show 4 to 5 mm/yr deformation rate across the plate boundary. However, recent GPS results showing ~2.5 mm/yr velocity rate of the northern DSF appears to be quite different than the ~6 mm/yr paleoseismic slip rate. The kinematic modeling that combines GPS and seismotectonic results implies a complex geodynamic pattern where the DSF transforms the Cyprus arc subduction zone into transpressive tectonics on the East Anatolian fault. The timing of past earthquake ruptures shows the occurrence of seismic sequences and a southward migration of large earthquakes, with the existence of major seismic gaps along strike. In this paper, we discuss the role of the DSF in the regional geodynamics and its implication on the identification of seismic gaps.

  9. Geodynamic Study In The Region of Southwest Bulgaria

    NASA Astrophysics Data System (ADS)

    Georgiev, I.; Pashova, L.; Nikolov, G.; Dimitrov, D.; Botev, E.

    Southwestern (SW) Bulgaria is a region of the most expressed tectonic and seismic activity in the whole territory of Bulgaria. The area belongs to the zone of recent ex- tension of the earth crust with the complex interference the horizontal and vertical movements of geological structures. The tectonic activity is confirmed with the re- cent high seismicity in the region. The largest earthquake in Europe in the last two centuries had happened near the Krupnik-Kresna area in 04.04.1904 with magnitude M = 7.8 (Karnik, 1969). A complex geodynamic study of recent deformations in the SW Bulgaria is of particular importance because of the possibility the seismogenic faults to provoke strong earthquakes. Since 1970 the Central Laboratory of Geodesy has carried out a geodetic monitoring of the vertical movements in the local seismic active zone of Krupnik-Kresna. We present the results of this monitoring along with the analysis of the precise spirit levelling from tree epochs - 1978, 1986 and 2000 of the 1st class state levelling line crossing the Krupnik fault. They show significant ver- tical crustal movements in the neighbourhood of the main Krupnik normal fault and confirm its recent tectonic activity. In 2001 the Central Laboratory of Geodesy, the Ge- ological Institute and the Geophysical Institute at the Bulgarian Academy of Sciences in cooperation with the Geodetic Department of the University of Architecture, Civil Engineering and Geodesy initiated a research project: "Multidisciplinary study on the active geodynamic setting of the Southwest Bulgaria". A regional GPS geodynamic network for long term monitoring of the recent crustal movements in this region was established. The GPS site locations were chosen after a detail study of the available seismotectonic and geologic data. The first GPS campaign was performed in the late summer of the last year. Some main seismotectonic features of the SW Bulgaria re- gion are discussed based on the new geological data and

  10. Seismotectonics and Neotectonics of the Gulfs of Gökova-Kuşadasi-Siǧacik and Surrounding Regions (SW Turkey): Earthquake Mechanisms, Source Rupture Modeling, Tsunami Hazard and Geodynamic Implications

    NASA Astrophysics Data System (ADS)

    Yolsal-Cevikbilen, Seda; Karaoglu, Özgür; Taymaz, Tuncay; Helvaci, Cahit

    2013-04-01

    The mechanical behavior of the continental lithosphere for the Aegean region is one of the foremost interesting geological disputes in earth sciences. The Aegean region provides complex tectonic events which produced a strong heterogeneity in the crust (i.e. large thrusts and exhumation shear zones or extensional detachments) as such in among most continental regions. In order to investigate mechanical reasons of the ongoing lithospheric-scale extension within the region, we must tackle all of the existing kinematic and dynamic agents: (1) roll back of the subduction slab and back arc extension; (2) westward extrusion of the Anatolian micro-plate; (3) block rotations of the Aegean region and western Anatolia; and (4) transtensional transform faults. Furthermore, seismological studies, particularly earthquake source mechanisms and rupture modeling, play important roles on deciphering the ongoing deformation and seismotectonic characteristics of the region. Recently, many moderate earthquakes occurred in the Gulfs of Gökova, Kuşadası, Sıǧacık and surroundings. In the present study, we examined source mechanisms and rupture histories of those earthquakes with Mw > 5.0 in order to retrieve the geometry of active faulting, source characteristics, kinematic and dynamic source parameters and current deformations of the region by using teleseismic body-waveform inversion of long-period P- and SH-waves, and broad-band P-waveforms recorded by GDSN and FDSN stations. We also checked first motion polarities of P- waveforms recorded at regional and teleseismic stations and applied several uncertainty tests to find the error limits of minimum misfit solutions. Inversion results revealed E-W directed normal faulting mechanisms with small amount of left lateral strike slip components in the Gulf of Gökova and NE-SW oriented right lateral strike slip faulting mechanisms in the Gulf of Sıǧacık. Earthquakes mostly have N-S and NW-SE directed T- axes directions which are

  11. 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

  12. Brittle Solvers: Lessons and insights into effective solvers for visco-plasticity in geodynamics

    NASA Astrophysics Data System (ADS)

    Spiegelman, M. W.; May, D.; Wilson, C. R.

    2014-12-01

    Plasticity/Fracture and rock failure are essential ingredients in geodynamic models as terrestrial rocks do not possess an infinite yield strength. Numerous physical mechanisms have been proposed to limit the strength of rocks, including low temperature plasticity and brittle fracture. While ductile and creep behavior of rocks at depth is largely accepted, the constitutive relations associated with brittle failure, or shear localisation, are more controversial. Nevertheless, there are really only a few macroscopic constitutive laws for visco-plasticity that are regularly used in geodynamics models. Independent of derivation, all of these can be cast as simple effective viscosities which act as stress limiters with different choices for yield surfaces; the most common being a von Mises (constant yield stress) or Drucker-Prager (pressure dependent yield-stress) criterion. The choice of plasticity model, however, can have significant consequences for the degree of non-linearity in a problem and the choice and efficiency of non-linear solvers. Here we describe a series of simplified 2 and 3-D model problems to elucidate several issues associated with obtaining accurate description and solution of visco-plastic problems. We demonstrate that1) Picard/Successive substitution schemes for solution of the non-linear problems can often stall at large values of the non-linear residual, thus producing spurious solutions2) Combined Picard/Newton schemes can be effective for a range of plasticity models, however, they can produce serious convergence problems for strongly pressure dependent plasticity models such as Drucker-Prager.3) Nevertheless, full Drucker-Prager may not be the plasticity model of choice for strong materials as the dynamic pressures produced in these layers can develop pathological behavior with Drucker-Prager, leading to stress strengthening rather than stress weakening behavior.4) In general, for any incompressible Stoke's problem, it is highly advisable to

  13. Estimation of Geodetic and Geodynamical Parameters with VieVS

    NASA Technical Reports Server (NTRS)

    Spicakova, Hana; Bohm, Johannes; Bohm, Sigrid; Nilsson, tobias; Pany, Andrea; Plank, Lucia; Teke, Kamil; Schuh, Harald

    2010-01-01

    Since 2008 the VLBI group at the Institute of Geodesy and Geophysics at TU Vienna has focused on the development of a new VLBI data analysis software called VieVS (Vienna VLBI Software). One part of the program, currently under development, is a unit for parameter estimation in so-called global solutions, where the connection of the single sessions is done by stacking at the normal equation level. We can determine time independent geodynamical parameters such as Love and Shida numbers of the solid Earth tides. Apart from the estimation of the constant nominal values of Love and Shida numbers for the second degree of the tidal potential, it is possible to determine frequency dependent values in the diurnal band together with the resonance frequency of Free Core Nutation. In this paper we show first results obtained from the 24-hour IVS R1 and R4 sessions.

  14. Effects of turbulence on the geodynamic laser ranging system

    NASA Technical Reports Server (NTRS)

    Churnside, James H.

    1993-01-01

    The Geodynamic Laser Ranging System (GLRS) is one of several instruments being developed by the National Aeronautics and Space Administration (NASA) for implementation as part of the Earth Observing System in the mid-1990s (Cohen et al., 1987; Bruno et al., 1988). It consists of a laser transmitter and receiver in space and an array of retroreflectors on the ground. The transmitter produces short (100 ps) pulses of light at two harmonics (0.532 and 0.355 microns) of the Nd:YAG laser. These propagate to a retroreflector on the ground and return. The receiver collects the reflected light and measures the round-trip transit time. Ranging from several angles accurately determines the position of the retroreflector, and changes in position caused by geophysical processes can be monitored.

  15. Geomorphology and Geodynamics at Crustal Boundaries within Asia and Africa

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The release of SRTM images by NASA over the past two years year has been greeted by foreign Earth scientist's as "NASA's gift to the World". The goodwill that this has engendered in parts of Africa. India, Pakistan and Bangladesh, as scientists in those countries contemplated what many of them considered an unprovoked and unjustifiable US invasion of Iraq, cannot be underestimated. We have used SRTM images from Africa and India and elsewhere to examine aspects of tectonism, geodynamics and tsunami and earthquake hazards. Highlights of this research are itemized in this final report. One difficulty that has arisen is , of course, that the funding for the science lead the availability of the data by more than a year. and as a result many of the findings are as yet unpublished.

  16. Towards Grid-Enabling the Global Geodynamics Project

    NASA Astrophysics Data System (ADS)

    Lumb, I.; Aldridge, K. D.

    2004-05-01

    The Global Geodynamics Project (GGP) allows Earth scientists to access a network of globally distributed superconducting gravimeters (SGs). By establishing standards around SG instrumentation and data, in concert with various bilateral agreements, the GGP ensures scientific and organizational integrity. Now in its second phase, the GGP is proactively engaging non-traditional disciplines - i.e., those outside the tidal gravimetry community. Although GGP has generated interest with geodynamicists, seismologists, and others, there are practicalities which inhibit engangement by these `non-specialists'. For example, to geodynamicists and seismologists, tidal, atmospheric, hydrologic and oceanic signals are all unwanted. This means that the processed GGP Data must undergo further, non-trivial reductions before it is useful for geodynamic and seismic purposes. The requirement to correlate data in time and space presents another example. Currently this is a manually intensive process that requires geodynamicists and seismologists to specify temporal (e.g., a period of time, an event in time) and/or spatial (e.g., global, regional, specific instruments) specifics to allow for further analysis. These and other examples suggest infrastructural opportunities for further enabling GGP scientists. With decided emphasis on Virtual Organizations, open standards and qualities of experience, Grid Computing has the potential to facilitate deeper degrees of collaboration within the context of the GGP. Through use cases which seek to identify core resonance effects at semi-diurnal periods (e.g., Lumb et al., AGU Monograph 72, 51-68, 1993) and earthquake activity, various opportunities for Grid-enabling the GGP are identified and prioritized. Because the High Energy Physics community has figured so significantly in the development of the World Wide Web and The Grid, a Grid-enabled GGP also has the potential to play a role in shaping the ongoing evolution of Grid Computing.

  17. From StGermain to Underworld: Enabling Community-based code Development in Geodynamics

    NASA Astrophysics Data System (ADS)

    Quenette, S. M.; Moresi, L.; Sunter, P. D.; Hodkinson, L.; Lo, A.; Hassan, R.; Appelbe, B.; Turnbull, R.

    2005-12-01

    Each discipline of geophysics has traditionally focused on limited sets of closely related phenomena using methodologies and data sets optimized for its specific area of interest. Why is that? Single discipline, single scale, foundation physics problems are relatively easy to code in Fortran, and hence they eventually become optimized for best performance whilst simultaneously becoming difficult to adapt to new interests. Yet geodynamicists want to break these ``out-of-scope'' barriers, and incorporate signals of interests beyond their immediate phenomena of interest. In turn this often entails a multi physics, multi scale and multi discipline development model. Multi physics is potentially easy to code, but application limited by the choice of numerical technique of the code. Multi scale is a numerical and discretisation issue that is closely related to the fundamental data structures of the code. This is difficult to change, and the ideal is hybrids of optimized solutions at desired scales. Multi discipline is much more focused on people and how they form problem constraints, the language / ontology they use, and their expectation in usability. In summary: facilitating a multi scale, multi physics , multi disciplinary development environment is difficult, complicated and generally not of core interest to a geodynamicist. However, today, with more powerful CPU architectures, we can move away from Fortran style coding with little wall-time cost. We have more powerful numerical techniques and models for constitutive laws, where disciplines beyond those specific to geodynamics such as numerical science, material science and computational science have progressed. Furthermore, more well proven and established libraries are available, when chosen and applied appropriately, lead to less work and for better results. How can we capitalize on this? We propose a multi-level community development model that allows computational scientists, numerical scientists, material

  18. On principles, methods and recent advances in studies towards a GPS-based control system for geodesy and geodynamics

    NASA Technical Reports Server (NTRS)

    Delikaraoglou, Demitris

    1989-01-01

    Although Very Long Baseline Interferometry (VLBI) and Satellite Laser Ranging (SLR) are becoming increasingly important tools for geodynamic studies, their future role may well be fulfilled by using alternative techniques such as those utilizing the signals from the Global Positioning System (GPS). GPS, without the full implementation of the system, already offers a favorable combination of cost and accuracy and has consistently demonstrated the capability to provide high precision densification control in the regional and local areas of the VLBI and SLR networks. This report reviews VLBI and SLR vis-a-vis GPS and outlines the capabilities and limitations of each technique and how their complementary application can be of benefit to geodetic and geodynamic operations. It demonstrates, albeit with a limited data set, that dual-frequency GPS observations and interferometric type analysis techniques make possible the modelling of the GPS orbits for several days with an accuracy of a few meters. The use of VLBI or SLR sites as fiducial stations together with refinements in the orbit determination procedures can greatly reduce the systematic errors in the GPS satellite orbits used to compute the positions of non-fiducial locations. In general, repeatability and comparison with VLBI of the GPS determined locations are of the order of between 2 parts in 10 to the 7th power and 5 parts in 10 to the 8th power for baseline lengths less than 2000 km. This report is mainly a synthesis of problems, assumptions, methods and recent advances in the studies towards the establishment of a GPS-based system for geodesy and geodynamics and is one phase in the continuing effort for the development of such a system. To some, including the author, it seems reasonable to expect within the next few years that more evidence will show GPS to be as a powerful and reliable a tool as mobile VLBI and SLR are today, but largely more economical.

  19. Bends in Hotspot Tracks: Kinematic observations and geodynamic models

    NASA Astrophysics Data System (ADS)

    Tarduno, J. A.; Bunge, H.-P.; Sleep, N.; Hansen, U.

    2009-04-01

    Bends in volcanic hotspot lineaments, best represented by the large 60 degree turn in the Hawaiian-Emperor chain, were once thought to record solely changes in plate motion. Several lines of geophysical inquiry, including paleomagnetism and plate-circuit analyses, now suggest that a change in the locus of upwelling in the mantle induced by mantle dynamics causes bends in hotspot tracks. Deep flow near the core-mantle boundary may have played a role in the Hawaiian-Emperor bend. However, we suggest that capture of a plume by a ridge, followed by changes in sub-Pacific mantle flow can better explain the observations. Ridge capture of plumes may be enhanced in the Pacific Ocean basin because of its history of rapidly spreading ridges, distant from the complicating effects of continents. We explore how ridge capture may resolve apparent discrepancies between the Hawaiian-Emperor chain and other hotspots of the Pacific Ocean basin.

  20. Using mineral elasticities to link geodynamics and seismic observations in the lowermost mantle.

    NASA Astrophysics Data System (ADS)

    Wookey, J.; Walker, A. M.; Nowacki, A.; Walpole, J.; Kendall, J.

    2012-12-01

    created integrated models based on static flow fields estimated from seismic tomography. These are used to generate strain histories for a grid of points in the lowermost mantle, which in turn are used in conjunction with predicted elasticities and proposed deformation mechanisms to perform viscoplastic self-consistent modelling to generate models of general anisotropy for the lowermost mantle. We have compared these with both tomographic and local determinations of D″ anisotropy in a variety of regions using raytracing, however more robust comparison requires full waveform modelling. To this end we have modified a spectral finite-element code to allow a fully general anisotropic model, and produced waveforms which can be compared directly to observation. These show the complexity of the effect of anisotropy, and underline the importance of understanding the contributing elasticities to make robust dynamic inferences. Ultimately, properties derived from the complex mineralogy (such as the rheology) also needs to feed back into the geodynamic calculations, as developing texture changes parameters such as viscosity. Our current generation of models (which integrate texture development modelling into 3D mantle convection simulation) are a step toward this.

  1. Geodynamics of the Eastern Pacific Region, Caribbean and Scotia Arcs. Volume 9

    SciTech Connect

    Cabre, R.

    1983-01-01

    This book analyze the geodynamic phenomena related to the interaction of the eastern Pacific with the Americas between Canada and the Antarctic peninsula. Studies include the Cordilleran arcs and Juan de Fuca plate.

  2. The present-day geodynamics of the India-Asia collision system

    NASA Astrophysics Data System (ADS)

    Baumann, Tobias; Kaus, Boris

    2016-04-01

    We present a full 3D geodynamic model of the present-day India-Asia collision system, that includes the lithosphere and upper mantle. The model is separated into multiple tectonic blocks, for which we estimate the first order rheological properties and their impact on the dynamics of the collision system. This is done by performing systematic simulations with different rheologies to minimize the misfit to observational constraints such as the GPS-velocity field. The simulations are performed with the parallel staggered grid FD code LaMEM using a numerical resolution of at least 512x512x256 cells to resolve dynamically important shear zones reasonably well. A fundamental part of this study is the reconstruction of the 3D present-day geometry of Tibet and the adjacent regions. Our interpretations of crust and mantle lithosphere geometry are jointly based on a globally available shear wave tomography and a global crustal model. We regionally refined and modified our interpretations based on seismicity distributions and focal mechanisms and incorporated regional receiver function studies to improve the accuracy of the Moho in particular. Results suggest that we can identify at least one 'best-fit' solution in terms of rheological model properties that reproduces the observed velocity field reasonably well, including the strong rotation of the GPS velocity around the eastern syntaxis of the Himalaya. We also present model co-variances.

  3. Geodynamically Consistent Interpretation of Seismic Tomography for Thermal and Thermochemical Mantle Plumes

    NASA Astrophysics Data System (ADS)

    Samuel, H.; Bercovici, D.

    2006-05-01

    Recent theoretical developments as well as increased data quality and coverage have allowed seismic tomographic imaging to better resolve narrower structures at both shallow and deep mantle depths. However, despite these improvements, the interpretation of tomographic images remains problematic mainly because of: (1) the trade off between temperature and composition and their different influence on mantle flow; (2) the difficulty in determining the extent and continuity of structures revealed by seismic tomography. We present two geodynamic studies on mantle plumes which illustrate the need to consider both geodynamic and mineral physics for a consistent interpretation of tomographic images in terms of temperature composition and flow. The first study aims to investigate the coupled effect of pressure and composition on thermochemical plumes. Using both high resolution 2D numerical modeling and simple analytical theory we show that the coupled effect of composition and pressure have a first order impact on the dynamics of mantle thermochemical plumes in the lower mantle: (1) For low Si enrichment of the plume relative to a reference pyrolitic mantle, an oscillatory behavior of the plume head is observed; (2) For Si-enriched plume compositions, the chemical density excess of the plume increases with height, leading to stagnation of large plume heads at various depths in the lower mantle. As a consequence, these thermochemical plumes may display broad (~ 1200 km wide and more) negative seismic velocity anomalies at various lower mantle depths, which may not necessarily be associated with upwelling currents. The second study focuses on the identification of thermal mantle plumes by seismic tomography beneath the Hawaiian hot spot: we performed a set of 3D numerical experiments in a spherical shell to model a rising plume beneath a moving plate. The thermal structure obtained is converted into P and S wave seismic velocities using mineral physics considerations. We

  4. Geodynamic inversion to constrain the rheology of the lithosphere: What is the effect of elasticity?

    NASA Astrophysics Data System (ADS)

    Baumann, Tobias; Kaus, Boris; Thielmann, Marcel

    2016-04-01

    The concept of elastic thickness (T_e) is one of the main methods to describe the integrated strength of oceanic lithosphere (e.g. Watts, 2001). Observations of the Te are in general agreement with yield strength envelopes estimated from laboratory experiments (Burov, 2007, Goetze & Evans 1979). Yet, applying the same concept to the continental lithosphere has proven to be more difficult (Burov & Diament, 1995), which resulted in an ongoing discussion on the rheological structure of the lithosphere (e.g. Burov & Watts, 2006, Jackson, 2002; Maggi et al., 2000). Recently, we proposed a new approach, which constrains rheological properties of the lithosphere directly from geophysical observations such as GPS-velocity, topography and gravity (Baumann & Kaus, 2015). This approach has the advantage that available data sets (such as Moho depth) can be directly taken into account without making the a-priori assumption that the lithosphere is thin elastic plate floating on the mantle. Our results show that a Bayesian inversion method combined with numerical thermo-mechanical models can be used as independent tool to constrain non-linear viscous and plastic parameters of the lithosphere. As the rheology of the lithosphere is strongly temperature dependent, it is even possible to add a temperature parameterisation to the inversion method and constrain the thermal structure of the lithosphere in this manner. Results for the India-Asia collision zone show that existing geophysical data require India to have a quite high effective viscosity. Yet, the rheological structure of Tibet less well constrained and a number of scenarios give a nearly equally good fit to the data. Yet, one of the assumptions that we make while doing this geodynamic inversion is that the rheology is viscoplastic, and that elastic effects do not significantly alter the large-scale dynamics of the lithosphere. Here, we test the validity of this assumption by performing synthetic forward models and retrieving

  5. Global Biomass Variation and its Geodynamic Effects, 1982-1998

    NASA Technical Reports Server (NTRS)

    Rodell, M.; Chao, B. F.; Au, A. Y.; Kimball, J. S.; McDonald, K. C.

    2005-01-01

    Redistribution of mass near Earth's surface alters its rotation, gravity field, and geocenter location. Advanced techniques for measuring these geodetic variations now exist, but the ability to attribute the observed modes to individual Earth system processes has been hampered by a shortage of reliable global data on such processes, especially hydrospheric processes. To address one aspect of this deficiency, 17 yrs of monthly, global maps of vegetation biomass were produced by applying field-based relationships to satellite-derived vegetation type and leaf area index. The seasonal variability of biomass was estimated to be as large as 5 kg m(exp -2). Of this amount, approximately 4 kg m(exp -2) is due to vegetation water storage variations. The time series of maps was used to compute geodetic anomalies, which were then compared with existing geodetic observations as well as the estimated measurement sensitivity of the Gravity Recovery and Climate Experiment (GRACE). For gravity, the seasonal amplitude of biomass variations may be just within GRACE'S limits of detectability, but it is still an order of magnitude smaller than current observation uncertainty using the satellite-laser-ranging technique. The contribution of total biomass variations to seasonal polar motion amplitude is detectable in today's measurement, but it is obscured by contributions from various other sources, some of which are two orders of magnitude larger. The influence on the length of day is below current limits of detectability. Although the nonseasonal geodynamic signals show clear interannual variability, they are too small to be detected.

  6. Deep geodynamics and uranium giants of southeastern Russia

    NASA Astrophysics Data System (ADS)

    Khomich, V. G.; Boriskina, N. G.

    2014-10-01

    The southeast of Russia with hydrothermal and hydrogenic U deposits is one of the largest provinces in the world with the unique U-bearing El'kon (South Yakutia) and Urulyungui (Transbaikalia) regions with similar geological, magmatic, petrological-geochemical characteristics and resources and commonly accepted formation from mantle derivatives. The seismotomographic data of the region indicate the presence of an oceanic slab that stagnated in its transit zone (410-670 km). The Pt-bearing alkaline-ultramafic massifs of the Inagli-Konder-Feklistovskii belt and the superlarge U-bearing regions are located along the east-northeastern flank and western frontal zone of the slab, respectively. The formation of the U-bearing regions, as well as the Pt-bearing massifs with dunitic core, is caused by involvement of derivatives of the lower mantle into the upper mantle plumes that was accompanied by the melting of the lithosphere. The acceptance of the influence of the deep geodynamics of the southeast of Russia on formation of the U-bearing regions allows us to outline the areas of further detailed studies along the frontal zone of the slab.

  7. Chronological constraints on the Permian geodynamic evolution of eastern Australia

    NASA Astrophysics Data System (ADS)

    Li, Pengfei; Rosenbaum, Gideon; Vasconcelos, Paulo

    2014-03-01

    The New England Orogen in eastern Australia developed as a subduction-related orogen in the Late Devonian to Carboniferous, and was modified in the Permian by deformation, magmatism and oroclinal bending. The geodynamics associated with the development of the New England oroclines and the exact timing of major tectonic events is still enigmatic. Here we present new 40Ar/39Ar results from metasedimentary and volcanic rocks from the southern New England Orogen. Eight grains from four metasedimentary samples (Texas beds) that originated in the Late Devonian to Carboniferous accretionary wedge yielded reproducible plateau ages of ~ 293, ~ 280, ~ 270 and ~ 260 Ma. These results suggest a complex thermal history associated with multiple thermal events, possibly due to the proximity to Permian intrusions. Two samples from mafic volcanic rocks in the southernmost New England Orogen (Alum Mountain Volcanics and Werrie Basalt) yielded eruption ages of 271.8 ± 1.8 and 266.4 ± 3.0 Ma. The origin of these rocks was previously attributed to slab breakoff, following a period of widespread extension in the early Permian. We suggest that this phase of volcanism marked the transition from backarc extension assisted by trench retreat to overriding-plate contraction. The main phase of oroclinal bending has likely occurred during backarc extension in the early Permian, and terminated at 271-266 Ma with the processes of slab segmentation and breakoff.

  8. Geodynamics of passive margins: insights from the DFG Schwerpunktprogramm SAMPLE for the South Atlantic and beyond

    NASA Astrophysics Data System (ADS)

    Bunge, Hans-Peter

    2016-04-01

    The DFG Priority Program SAMPLE (South Atlantic Margin Processes and Links with onshore Evolution: http://www.sample-spp.de/), which is to be completed 2016, has studied the evolution of the South Atlantic from its Cretaceous inception to the present day. The program has an explicit interdisciplinary focus, drawing on constraints from deep Earth geophysics, lithosphere and basin dynamics, petrology, landscape evolution and geodesy, thus linking processes that are commonly studied in isolation. Starting from the premise that passive margins are first-order geo-archives, the program has placed the South Atlantic opening history into an observational and theoretical context that considers seismic imaging, plate motion histories, uplift and subsidence events, magmatic and surface evolution, together with models of mantle convection and lithosphere dynamics. A primary lesson is that passive margins are active, displaying a range of vertical motion (i.e. dynamic topography) events, apparently correlated with plate motion changes, that do not conform to traditional rifting models of passive margins. I will summarize some observational results of the program, and place them into a geodynamic context.

  9. Ambiguity resolution strategies using the results of the International GPS Geodynamics Service (IGS)

    NASA Astrophysics Data System (ADS)

    Mervart, Leoš; Beutler, Gerhard; Rothacher, Markus; Wild, Urs

    1994-03-01

    Resolving the initial phase ambiguities of GPS carrier phase observations was always considered an important aspect of GPS processing techniques. Resolution of the so-called wide-lane ambiguities using a special linear combination of the L 1 and L 2 carrier and code observations has become standard. New aspects have to be considered today: (1) Soon AS, the so-called Anti-Spoofing, will be turned on for all Block II spacecrafts. This means that precise code observations will be no longer available, which in turn means that the mentioned approach to resolve the wide-lane ambiguities will fail. (2) Most encouraging is the establishment of the new International GPS Geodynamics Service (IGS), from where high quality orbits, earth rotation parameters, and eventually also ionospheric models will be available. We are reviewing the ambiguity resolution problem under these new aspects: We look for methods to resolve the initial phase ambiguities without using code observations but using high quality orbits and ionospheric models from IGS, and we study the resolution of the ”narrow-lane ambiguities” (after wide-lane ambiguity resolution) using IGS orbits.

  10. The wave-like geodynamic reorganizations revealed by the change in orientation of the paleostress axes

    NASA Astrophysics Data System (ADS)

    Mukhamediev, Shamil; Belousov, Tomas

    2014-05-01

    Sedimentary rock fracturing is a reliable stress indicator when properly measured, processed and interpreted. Our long-term field observations and theoretical considerations show that the primary joint sets are formed at the stage of diagenesis of sediments at horizontal bedding. Most likely, it happens due to internal instability of sediments manifested in localised form, which leads to formation of two conjugate systems of shear discontinuities. This model allows us to reconstruct the orientation of the axis of the maximum horizontal paleo-compression SH,max and to determine the period of its existence up to the scale of geological time. During more than 30 years of our field observations, we collected about 400,000 individual joint measurements in many regions of Eurasia. These data were applied to paleostress reconstruction by using interpretation of primary jointing formation mentioned above. Both spatial distributions of paleostress axes and the evolution of these distributions in time determined by our techniques are in reasonably good agreement with paleogeodynamic reconstructions obtained by other approaches. A distinctive feature of the paleostress evolution is that at certain times orientation of the SH,max axes changes abruptly, turning at an angle up to 90° . Sometimes these changes are gradually spreading to neighboring regions. We attribute this phenomenon to the geodynamic reorganization which spreads over the space at a certain speed. Such wave-like spreading was observed in the East-European platform, the Tien-Shan, along the arc Pamirs-Tibet-Vietnam and in other regions. From the perspective of this phenomenon, the Caucasus-Zagros region is of particular interest. Here from the end of the Early Cretaceous to the present time the SH,max axis with small spatial variations was NE oriented. However, we identified a relatively short period in the Miocene characterized by geodynamic reorganization. In the early middle Miocene in the south-east of the

  11. Geodynamic evolution and sedimentary infill of the northern Levant Basin: A source to sink-perspective

    NASA Astrophysics Data System (ADS)

    Hawie, N.

    2013-12-01

    quantities of clastic material into the Levant Basin: (1) the marginal canyons along the Levant Margin, (2) the Latakia region and the Palmyrides Basin (Syria) and (3) the Red Sea area and Nile Delta. Regional drainage system analysis was performed to estimate the contribution to the infill of the basin of the different sediment sources, and in particular, to estimate erosion of Nubian siliciclastic material, granitic Red Sea rift shoulders and Arabian Shield. A numerical stratigraphic forward model, Dionisos, was used to test these source-to-sink assumptions; a sensitivity analysis was then performed to understand better the impact of the different geodynamic and stratigraphic scenarios on the architecture and sedimentary infill of the Levant Basin, and thus on the expected petroleum systems of this frontier basin

  12. Crustal Accretion and Mantle Geodynamics at Microplates: Constraints from Gravity Analysis

    NASA Astrophysics Data System (ADS)

    Ames, K.; Georgen, J. E.; Dordevic, M. M.

    2013-12-01

    Oceanic crustal accretion occurs in a variety of locations, including mid-ocean ridges and back-arc spreading centers, and in unique settings within these systems, such as plate boundary triple junctions, intra-transform spreading centers, and microplates. This study focuses on crustal accretion and mantle geodynamics at microplates. The Easter and Juan Fernandez microplates are located in the South Pacific along the Pacific, Nazca and Antarctic plate boundaries. Both microplates formed 3-5 Ma and they are currently rotating clockwise at 15 deg/Ma and 9 deg/Ma respectively (e.g., Searle et al. J. Geol. Soc. Lond. 1993). The study area also encompasses the Easter/Sala y Gomez mantle plume and the Foundation seamount chain, both of which are located close to spreading centers. We calculate mantle Bouguer anomaly (MBA) from satellite gravity measurements and shipboard soundings in order to gain a better understanding of the thermal structure of these two oceanic microplates and to quantify the effect that melting anomalies may have on their boundaries. We assume a crustal thickness of 6.0 km, a 1.7 g/cm^3 density difference at the water/crust interface, and a 0.6 g/cm^3 density difference at the crust/mantle interface. The west rift of the Easter microplate has an MBA low ranging from approximately -50 to -100 mGal, while the east rift has slightly higher MBA values ranging from roughly 10 to -50 mGal. The west rift of the Juan Fernandez microplate has a maximum MBA low of about -100 mGal with a sharp increase to -20 mGal at -35 deg S. The east rift of the Juan Fernandez microplate is characterized by more variable MBA, ranging from 0 to -140 mGal. The MBA low associated with the Easter/Sala y Gomez mantle plume has a maximum amplitude about 150 mGal. Likewise, the Foundation seamounts show a gravity low of -140 to -150 mGal. These spatial variations in gravity, as well as published isotopic data and exploratory numerical models, are used to constrain upper mantle

  13. The relationship between global palaeointensity variations and geodynamics: documenting the evolutionary cycle of Pangaea

    NASA Astrophysics Data System (ADS)

    Biggin, A.; Thomas, N.

    2003-04-01

    Long-term variations in the geomagnetic field palaeointensity (PI) are fundamentally linked to global geodynamics through a chain of events commencing with intense plate tectonic activity at the surface and culminating in changes in the pattern of outer core convection which essentially control the field intensity. Therefore, establishing a reliable palaeointensity record over geological timescales can provide a valuable source of information in documenting broad geodynamic changes such as the evolutionary cycle of supercontinents. In this paper, we present an interpretation of palaeointensity variation for the 400--100 Ma period, based on a detailed statistical analysis of the PINT global palaeointensity database. We link palaeointensity changes to four major stages in the evolutionary cycle of Pangaea. (1) From 400 to 350 Ma, during supercontinent amalgamation, the PI is low reflecting low heat flux, a hot lowermost mantle (LMM) and layered mantle convection. (2) Between 350 and 250 Ma, the PI initially rose rapidly reflecting increased heat flux resulting from cooling of the LMM achieved by catastrophic avalanching of ancient subducted ocean crust following a period of ponding at the 660 km boundary layer. Subsequently, from 325--250 Ma, PI decreased reflecting decreased heat flux across the CMB, which we interpret as a response to mantle restabilisation and warming. (3) From 250--175 Ma the PI was generally low in response to mantle insulation during a period of supercontinent assembly when the mantle became very hot. (4) The final period in the evolutionary cycle, from 180--10 Ma, is initially characterised by a gradual rise in PI (175--120 Ma) which is interpreted as being a response to the introduction of cold material into the lower mantle following widespread subduction during the dispersal of Pangaea. Subsequently, from 120--10 Ma, PI appears to have risen to a peak at around 50 Ma, then decreased, possibly documenting another catastrophic mantle

  14. Estimation of Non-Seasonal Oceanic Mass Redistribution and its Geodynamic Effects from the Topex/Poseidon Observation

    NASA Technical Reports Server (NTRS)

    Chao, Benjamin F.; Ray, Richard D.; Au, A. Y.

    1999-01-01

    Mass redistribution in terms of angular momentum will change the Earth's rotation under the conservation of angular momentum. It also changes the external gravitational field according to Newton's gravitational law. These small geodynamic variations can be measured very accurately by modem space geodetic techniques. We report on new estimates of the oceanic tidal angular momentum and hence the tidal variations in the Earth's rotation rate and polar motion. These are deduced from the new tidal solutions GOT99 and TPXO.3, plus M2 and Mf estimates (with error bars) from TPXO.4a. Comparisons with observed diurnal/semidiurnal tidal variations are generally similar to previous model estimates. Comparisons of models and observations of Mf polar motion are confused, with neither models nor observations agreeing among themselves or with each other. Part of this is caused by differences in Mf currents; model TPXO.4 shows current-intensive Rossby modes along western boundaries of major basins, which are indeed expected on theoretical grounds. Unfortunately, there are no reliable in situ observations of Mf currents useful for comparing models. On non-tidal oceanic mass redistribution we compute the principal components of the multi-year T/P sea surface height (SSH) field using EOF (empirical orthogonal functions) taking into consideration of the latitude-dependent area weighting. Emphasis is placed upon non-seasonal and interannual oscillations on regional scales, including ENSO and the North Atlantic Oscillation. Steric corrections to the observed SSH due to sea surface temperature changes (which has no geodynamic effects) is now under study using POCM ocean model output.

  15. Geodynamic investigation of the processes that control Lu-Hf isotopic differences between different mantle domains and the crust

    NASA Astrophysics Data System (ADS)

    Jones, Rosie; van Keken, Peter; Hauri, Erik; Vervoort, Jeff; Ballentine, Chris J.

    2016-04-01

    The chemical and isotopic composition of both the Earth's mantle and the continental crust are greatly influenced by subduction zone processes, such as the formation of continental crust through arc volcanism and the recycling of surface material into the deep mantle. Here we use a combined geodynamical-geochemical approach to investigate the long term role of subduction on the Lu-Hf isotopic evolution of the mantle and the continental crust. We apply the geodynamic model developed by Brandenburg et al., 2008. This model satisfies the geophysical constraints of oceanic heat flow and average plate velocities, as well as geochemical observations such as 40Ar in the atmosphere, and reproduces the geochemical distributions observed in multiple isotope systems which define the HIMU, MORB and EM1 mantle endmembers. We extend this application to investigate the detail of terrestrial Lu-Hf isotope distribution and evolution, and specifically to investigate the role of sediment recycling in the generation of EM2 mantle compositions. The model has been updated to produce higher resolution results and to include a self-consistent reorganisation of the plates with regions of up-/down-wellings. The model assumes that subduction is initiated at 4.5 Ga and that a transition from 'dry' to 'wet' subduction occurred at 2.5 Ga. The modelling suggests that the epsilon Hf evolution of the upper mantle can be generated through the extraction and recycling of the oceanic crust, and that the formation of continental crust plays a lesser role. Our future intention is to utilise the model presented here to investigate the differences observed in the noble gas compositions (e.g., 40Ar/36Ar, 3He/4He) of MORB and OIB. Brandenburg, J.P., Hauri, E.H., van Keken, P.E., Ballentine, C.J., 2008. Earth and Planetary Science Letters 276, 1-13.

  16. Geodynamics of Venice tidal marshes observed by radar interferometry

    NASA Astrophysics Data System (ADS)

    Tosi, L.; Teatini, P.; Strozzi, T.

    2010-12-01

    Inter-tidal environments, such as lagoons and deltas, are naturally dynamic coastal systems that are unique in their close links to both land-based fluvial and coastal sea processes. These landscapes are generally experiencing a destructing phase over the last decades primarily caused by river sediment trapping in the upland drainage basins, sea level rise due to climate changes, and land subsidence. Accurate monitoring of the geodynamics of tidal environments is very difficult because of various concurrent causes: i) the logistical difficulties (or inaccessibility) to reach the areas precluding the use of traditional leveling and differential GPS surveys; b) the limited effectiveness of permanents GPS stations due to the significant small-scale variability of the litho-stratigraphy and the soil hydro-geomechanical properties because of the recent development of these environments, usually occurred over the late Holocene; and c) the lack of permanent natural/anthropogenic structures that reduces the capability of SAR interferometry. Because land subsidence is expected to give an important contribution to the cumulative sediment budget of the Venice Lagoon, Italy, the Venice Water Authority has supported a research aimed at improving the quantification of the present land subsidence by exploring the use of radar interferometry on a number of artificial corner reflectors. A network of 58 trihedral corner reflectors (TCR) was installed in the salt marshes of the Venice Lagoon before the summer 2007. The TCR are characterized by 60 cm long edge, made of aluminium to reduce their weight, placed in areas without any other strong scatterer, and oriented to be visible with ENVISAT ASAR and TerraSAR-X acquisitions of descending orbits. Salt marshes are constantly visible, except when the tide rises. The TCR, usually installed at a height of 1 m above the mean sea level, are therefore constantly outside the water. In order to mitigate atmospheric artifacts and to properly

  17. Application of the pseudorelief method for the territory of the Bishkek geodynamic polygon

    NASA Astrophysics Data System (ADS)

    Batalev, V. Yu.

    2013-02-01

    Based on 143 magnetotelluric soundings, the Berdichevskii impedance, the Wiese—Parkinson matrix, and the phase tensor component are calculated for the Bishkek geodynamic polygon 50 × 150 km in size. The pseudoreliefs of the apparent resistance Ro brd , phase Fi brd , Wiese-Parkinson matrix norm, and apparent phase Fi k calculated from the phase tensor are constructed. An area of the crustal conductor with elevated conductivity located below the northern part of the Chui depression is distinguished during analysis of pseudoreliefs. Its characteristics will be used for solution of the 3D direct task and creation of the starting model of 2D inversion. The reliability of anomalous objects and estimation of their size during the use of real data is caused by the fact that the anomalies are displayed by different parts of the observation system for the various parameters of the MT-field: the phases vary directly over the anomalous object, and magnetovariational parameters form the rim around it. This allows us more completely and effectively to use the network of real data.

  18. Compositional Stratification in the Upper Mantle: Seismic Evidence and Geodynamic Implications

    NASA Astrophysics Data System (ADS)

    Cammarano, F.; Romanowicz, B.; Tackley, P. J.

    2008-12-01

    The study of interior dynamics requires knowing the current physical properties (e.g., rheology, elasticity) and understanding the relations between the driving forces and their effects, which lead to the current conditions. Mineral physics provides a description of these physical properties as a function of composition (C), temperature (T) and pressure (P). The knowledge of T-C conditions in the Earth relies on the interpretation of geophysical data based on mineral physics. Recently, we inverted long-period seismic waveforms directly for temperature or composition. We found that lateral variations of temperature can explain a large part of the data in the upper mantle. However, the radial average VS profile we obtain cannot be explained with a homogenous composition. A relative enrichment with depth in garnet and pyroxenes is consistent with seismic data. A similar compositional structure characterizes recent geodynamic models that include the phase transitions of the non-olivine system. Here, we use the same physical properties for the seismic inversion and to model the thermochemical evolution of the mantle with the code STAGYY. The flow field is computed with a finite-volume multigrid solver and tracers are used for composition. Multi-component phase changes and melting-induced compositional differentiation are included. The principal features of the modeled T-C structure are compared with the one inferred from observations and the presence of compositional stratification in the upper mantle is examined in details. In addition, the thermo-chemical models give insights on small-scale heterogeneities that are not resolved from the geophysical observations. In order to account for the large uncertainties of some key mineral physics parameters at mantle conditions (e.g., viscosity and seismic attenuation, density relation between depleted and enriched compositions), the seismic inversion and the modeling are repeated using different possible parameters.

  19. The solution of fundamental problems of geodynamics, geophysics, geology and planetology

    NASA Astrophysics Data System (ADS)

    Barkin, Yury

    2010-05-01

    On the base of geodynamic model of the forced gravitational swing and displacement of shells of a planet under action of a gravitational attraction of surrounding (external) celestial bodies [1], [2] the fundamental problems of geodynamics, geology, planetology, geophysics, etc. have been studied and solved. 1). The mechanism of cyclic variations of activity of natural processes in various time scales. 2). The nature of eccentric positions of the core and the mantle of the Earth. A role of the Moon, the Sun, Neptune and other celestial bodies in activization of the swing of core-mantle system of the Earth. 3). Power of endogenous activity of planetary natural processes on planets and satellites. 4). The nature of correlations of natural processes with features of motion of baricenter of the solar system. 5). An explanation of influence of bodies of solar system on excitation of variations of planetary processes with Milankovitch's periods (in tens and hundred thousand years). 6). A possible explanation of geological cycles as result of excitation of solar system at its motion in a gravitational field of the Galaxy. 7). The phenomenon of polar inversion of natural processes on the Earth, both other planets and satellites. 8). Spasmodic (step-by-step) and catastrophic changes of activity of natural processes. 9). Sawtooth (gear curve) variations of natural processes. 10). The phenomenon of twisting of hemispheres (latitude zones) of celestial bodies. 11). Formation of the pear-shaped form of celestial bodies and the mechanism of its change. 10). Ordered planetary structures in spatial distribution of geological formations. 12). The phenomena of bipolarity of celestial bodies and antipodality of formations. Many fundamental problems of natural sciences have been obtained an explanation on the basis of developed geodynamic model (Barkin, 2002, 2009). The fundamental problems of celestial mechanics and geodynamics, geophysics and the geology, excited of scintific

  20. Geodynamic constraints on stress and strength of the continental lithosphere during India-Asia collision.

    NASA Astrophysics Data System (ADS)

    Kaus, B. J. P.; Schmalholz, S. M.; Lebedev, S.; Deschamps, F.

    2009-04-01

    There has been quite some debate in recent years on what the long-term strength of the continental lithosphere is and how it is related to the occurrence of earthquakes. One of the best studied areas in this respect is the India-Asia collision zone, where -in some profiles- the Moho depth is known to within a few km's. A relocation of earthquake source locations revealed that in India earthquakes occur throughout the whole lithosphere whereas in Tibet, earthquakes are restricted to the upper 10-15 km of the crust with few exceptions slightly above or below the Moho. The lack of substantial earthquake activity in the sub-Moho mantle lithosphere seems puzzling since (1D) strength envelop models for the continental lithosphere predict large differential stresses (and brittle failure) in these locations. A way out of this paradox is to assume that the rheology of the mantle lithosphere (i.e. the effective viscosity) is significantly smaller than usually assumed, either because of the effects of hydration, or because of increased Moho temperatures. As a consequence, the strength of the lithosphere resides in the crust and not in the upper mantle as previously assumed. This conclusion gets some support from spectral-based inverse models of the effective elastic thickness (using topography and gravity as input data), which is typically smaller than the seismogenic thickness. Even though this explanation might appear appealing at first, there are at least two major problems with it: (1) Estimations of the effective elastic thickness (EET) of the lithosphere are non-unique and model-dependent. Others, using a direct (non-spectral) modelling approach, find significantly larger values of the EET in the same locations (again using gravity & topography as constraints). (2) Long term geodynamic models indicate that if the mantle lithosphere would indeed be as weak as suggested, it would be very difficult to generate plate-tectonics like behavior: Subducting slabs behave more

  1. Error analysis for the proposed close grid geodynamic satellite measurement system (CLOGEOS)

    NASA Technical Reports Server (NTRS)

    Mueller, I. I.; Vangelder, B. H. W.; Kumar, M.

    1975-01-01

    The close grid geodynamic measurement system experiment which envisages an active ranging satellite and a grid of retro-reflectors or transponders in the San Andreas fault area is a detailed simulated study for recovering the relative positions in the grid. The close grid geodynamic measurement system for determining the relative motion of two plates in the California region (if feasible) could be used in other areas of the world to delineate and complete the picture of crustal motions over the entire globe and serve as a geodetic survey system. In addition, with less stringent accuracy standards, the system would also find usage in allied geological and marine geodesy fields.

  2. Second phase of the European Project CERGOP-2/Environment (Central Europe Regional Geodynamics Project)

    NASA Astrophysics Data System (ADS)

    Sledzinski, Janusz

    The paper includes concise information on the status of the international geodynamic project CERGOP (Central Europe Regional Geodynamics Project). The achievements of the realisation of the first phase of the Project are summarised. The enlarged objectives, the programme and scope of work of the second phase of the Project are shortly described. List of workpackages covering particular fields of activities within the Project is given. Project is supported financially by the European Commission. Project CERGOP was an impulse for the establishment of the CEGRN Consortium of institutes involved in realisation of the Project. The Consortium will also be a seedbed of new European projects and initiatives.

  3. Grain size evolution in the mantle and its effect on geodynamics and seismic observables

    NASA Astrophysics Data System (ADS)

    Myhill, R.; Dannberg, J.; Eilon, Z.; Gassmoeller, R.; Moulik, P.; Faul, U.; Asimow, P. D.

    2014-12-01

    Dynamic models of Earth's convecting mantle usually implement flow laws with constant grain size, stress-independent viscosity and a limited treatment of variations associated with changes in mineral assemblage. These simplifications greatly reduce computational requirements but preclude effects such as shear localisation and transient changes in rheology associated with phase transitions, which have the potential to fundamentally change flow patterns in the mantle. Here we use the finite-element code ASPECT (Bangerth et al., 2013) to model grain size evolution and the interplay between grain size, stress and strain rate in the convecting mantle. We include the simultaneous and competing effects of dynamic recrystallisation resulting from work done by dislocation creep, grain growth and recrystallisation at phase transitions. Further expressions account for slow growth in multiphase assemblages resulting from pinning. Grain size variations also affect seismic properties of mantle materials. We use several formulations from the literature to relate intrinsic variables (P, T, and grain size) from our numerical models to seismic velocity (Vs) and attenuation (Q). Our calculations use thermodynamically self-consistent anharmonic elastic moduli determined for the mineral assemblages in the mantle using HeFESTo (Stixrude and Lithgow-Bertelloni, 2013). We investigate the effect of realistically heterogeneous grain sizes by computing seismic observables such as body wave travel times, ray paths, and attenuation (t*) as well as mode eigenfrequencies and quality factors at different frequencies. We highlight the frequency-dependent sensitivity of seismic waves to grain size, which is important when interpreting Vs and Q observations in terms of mineral assemblage and temperature. This work is based on a project started at the CIDER 2014 summer program. References: Bangerth, W. et al., 2014, ASPECT: Advanced Solver for Problems in Earth's ConvecTion. Computational

  4. U/Pb dating of subduction-collision in the Brooks Range: implications for Mesozoic geodynamics of Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Lemonnier, Nicolas; Labrousse, Loic; Agard, Philippe; McClelland, Bill; Cobble, Mattew; Till, Alison; Roeske, Sarah

    2016-04-01

    The paleogeographic and geodynamic evolution of Northern Alaska is crucial to understand the connection between the Arctic and Pacific realms. The opening of the Canada Basin (CB) is debated both in terms of inception time (between 190 and 140 Ma) and driving mechanisms. The prevalent model assumes that CB opened in a back-arc position within the Arctic-Alaska-Chukotka (AAC) terrane following a change in subduction polarity from S- to N-dipping subduction The adjacent Brooks Range orogen (BRO) is thought to have formed when the Koyukuk volcanic arc collided with the southern extension of AAC. This collision therefore potentially provides key information for Arctic geodynamics, and for the mechanisms of CB opening, but neither the detailed timing of this collisional history nor its duration are well known. In order to constrain the timing of the collision, we performed in-situ zircon U-Pb SIMS analyses on eclogites from the BRO s.l. (BR and Seward Peninsula), which indicate that peak burial (at 510 ± 60°C, 1.6 ± 0.2 GPa) during continental subduction and subsequent collision occurred at 141 ± 6 Ma (n=10, MSWD = 1.6). Eclogite metamorphism therefore postdates the initial rifting stage of the CB but predates effective sea-floor spreading. Younger zircon domains (114 ± 13 Ma) associated with retrograde assemblages could indicate a late thermal pulse or recrystallisation during exhumation in the collisional wedge. Combined with all available information on timing, these new age constraints are used to build a tectonic model for coeval evolution of the Brooks Range and the Canada Basin. The intra-Kingak "Jurassic Unconformity" at the Jurassic Cretaceous Boundary (Houseknecht, pers. communication) could actually be considered as the signature of the AAC-Koyukuk arc collision stage in the CB.

  5. A new view for the geodynamics of Ecuador: Implication in seismogenic source definition and seismic hazard assessment

    NASA Astrophysics Data System (ADS)

    Yepes, Hugo; Audin, Laurence; Alvarado, Alexandra; Beauval, Céline; Aguilar, Jorge; Font, Yvonne; Cotton, Fabrice

    2016-05-01

    A new view of Ecuador's complex geodynamics has been developed in the course of modeling seismic source zones for probabilistic seismic hazard analysis. This study focuses on two aspects of the plates' interaction at a continental scale: (a) age-related differences in rheology between Farallon and Nazca plates—marked by the Grijalva rifted margin and its inland projection—as they subduct underneath central Ecuador, and (b) the rapidly changing convergence obliquity resulting from the convex shape of the South American northwestern continental margin. Both conditions satisfactorily explain several characteristics of the observed seismicity and of the interseismic coupling. Intermediate-depth seismicity reveals a severe flexure in the Farallon slab as it dips and contorts at depth, originating the El Puyo seismic cluster. The two slabs position and geometry below continental Ecuador also correlate with surface expressions observable in the local and regional geology and tectonics. The interseismic coupling is weak and shallow south of the Grijalva rifted margin and increases northward, with a heterogeneous pattern locally associated to the Carnegie ridge subduction. High convergence obliquity is responsible for the North Andean Block northeastward movement along localized fault systems. The Cosanga and Pallatanga fault segments of the North Andean Block-South American boundary concentrate most of the seismic moment release in continental Ecuador. Other inner block faults located along the western border of the inter-Andean Depression also show a high rate of moderate-size earthquake production. Finally, a total of 19 seismic source zones were modeled in accordance with the proposed geodynamic and neotectonic scheme.

  6. A simulation to study the feasibility of improving the temporal resolution of LAGEOS geodynamic solutions by using a sequential process noise filter

    NASA Technical Reports Server (NTRS)

    Hartman, Brian Davis

    1995-01-01

    A key drawback to estimating geodetic and geodynamic parameters over time based on satellite laser ranging (SLR) observations is the inability to accurately model all the forces acting on the satellite. Errors associated with the observations and the measurement model can detract from the estimates as well. These 'model errors' corrupt the solutions obtained from the satellite orbit determination process. Dynamical models for satellite motion utilize known geophysical parameters to mathematically detail the forces acting on the satellite. However, these parameters, while estimated as constants, vary over time. These temporal variations must be accounted for in some fashion to maintain meaningful solutions. The primary goal of this study is to analyze the feasibility of using a sequential process noise filter for estimating geodynamic parameters over time from the Laser Geodynamics Satellite (LAGEOS) SLR data. This evaluation is achieved by first simulating a sequence of realistic LAGEOS laser ranging observations. These observations are generated using models with known temporal variations in several geodynamic parameters (along track drag and the J(sub 2), J(sub 3), J(sub 4), and J(sub 5) geopotential coefficients). A standard (non-stochastic) filter and a stochastic process noise filter are then utilized to estimate the model parameters from the simulated observations. The standard non-stochastic filter estimates these parameters as constants over consecutive fixed time intervals. Thus, the resulting solutions contain constant estimates of parameters that vary in time which limits the temporal resolution and accuracy of the solution. The stochastic process noise filter estimates these parameters as correlated process noise variables. As a result, the stochastic process noise filter has the potential to estimate the temporal variations more accurately since the constraint of estimating the parameters as constants is eliminated. A comparison of the temporal

  7. Bayesian geodynamic inversion to constrain the rheology of the flat subduction system in southwestern Mexico

    NASA Astrophysics Data System (ADS)

    Gérault, Mélanie; Bodin, Thomas

    2016-04-01

    The flat slab in southwestern Mexico differs from others at the present-day because (1) it is associated with abundant arc volcanism, (2) it is associated with extension in the arc and a neutral state of stress in the fore-arc, (3) it generates relatively low seismic activity, (4) the continental mantle lithosphere is very thin or nonexistent, (5) it is not directly caused by the subduction of thickened oceanic crust, and (6) there is no nearby cratonic keel. In a recent study, we showed that the topography in the area is controlled by both isostatic and dynamic contributions. The Trans-Mexican Volcanic Belt is either isostatically supported or slightly buoyed up by a low-density mantle wedge. To the contrary, the forearc is pulled downward by the flat slab, resulting in about 1 km of subsidence. Using a two-dimensional instantaneous Stokes flow finite-elements model, we found a combination of slab, mantle, and subduction interface properties that can predict the observed topography, plate velocities, and stress state in the continent. However, this solution is not unique, and there are trade-offs between these properties such that several combinations can provide a similarly good fit to the data. In this work, we present a geodynamic inversion to further investigate what viscosities and densities are required in different zones of the subduction system to explain the observations collected at the surface. The inverse problem is cast in a Bayesian framework, where model parameters (e.g. the viscosity in the mantle wedge and along the subduction interface) can be reconstructed in a probabilistic sense, and where trade-offs and uncertainties can be quantitatively constrained. We use a direct parameter search approach based on a Markov chain Monte Carlo (McMC) scheme to test a large number of potential scenarios.

  8. The Tertiary dike magmatism in the Southern Alps: geochronological data and geodynamic significance

    NASA Astrophysics Data System (ADS)

    Bergomi, Maria Aldina; Zanchetta, Stefano; Tunesi, Annalisa

    2015-03-01

    The relationships between tectonics and magmatic activity in the Alps are still debated. Despite an active subduction since the Late Cretaceous, no arc-related magmatism is recorded prior of the Middle Eocene. The emplacement of plutons along the Insubric Fault in a short time span (~34-28 Ma) has been generally interpreted in terms of the slab break-off model. The Tertiary magmatism, however, is also characterized by the occurrence of widespread calcalkaline dikes not necessarily intruded along the Insubric Fault. The geochemical features of dikes vary along the Alps belt and are interpreted in terms of mantle source heterogeneity and degree of crustal contamination. U-Pb zircon dating of studied dikes indicates intrusion ages in the 42- to 34-Ma time interval. These data provide evidence for a pre-Oligocene magmatic activity that was not solely limited to the Adamello batholith. Moreover, it appears that dikes rejuvenate from SE to NW, in an opposite direction with respect to the Alpine subduction polarity. Thus, a more complex geodynamic scenario than the slab break-off model must be envisaged. The absence of arc magmatism prior to the Middle Eocene can be explained by the low-angle subduction of the Tethyan slab that confined the mantle partial melting zone away from the orogenic wedge. The onset of the Apennines subduction at 55-50 Ma caused the Alpine slab to retreat. The partial melting zone progressively migrated beneath the orogenic wedge and finally reached the axial belt in the Late Eocene, when the Alpine collision was completed. Only at this stage, slab break-off occurred and promoted the intrusion of the Periadriatic plutons.

  9. Slab dragging and the recent geodynamic evolution of the western Mediterranean plate boundary region

    NASA Astrophysics Data System (ADS)

    Spakman, Wim; Chertova, Maria V.; van den Berg, Arie P.; Thieulot, Cedric; van Hinsbergen, Douwe J. J.

    2016-04-01

    The Tortonian-Present geodynamic evolution of the plate boundary between North Africa and Iberia is characterized by first-order enigmas. This concerns, e.g., the diffuse tectonic activity of the plate boundary; the crustal thickening below the Rif; the closing of the northern Moroccan marine gateways prior to the Messinian Salinity Crisis; crustal extension of the central to eastern Betics; the origin and sense of motion of the large left-lateral Trans Alboran Shear Zone (TASZ) and Eastern Betic Shear Zone (EBSZ); and lithosphere delamination of the North African continental edge. Many explanations have been given for each of these seemingly disparate tectonic features, which invariably have been addressed in the plate tectonic context of the NW-SE relative plate convergence between the major plates since the Tortonian, mostly independently from each other. Usually there is no clear role for the subducted slab underlying the region, except for presumed rollback, either to SW or to the W, depending on the type of observations that require explanation. Here we integrate the dynamic role of the slab with the NW-SE relative plate convergence by 3-D numerical modelling of the slab evolution constrained by absolute plate motions (Chertova et al., JGR,2014 & Gcubed 2014). By combining observations and predictions from seismology, geology, and geodesy, with our numerical 3-D slab-mantle dynamics modelling, we developed a new and promising geodynamic framework that provides explanations of all noted tectonic enigmas in a coherent and connected way. From the Tortonian until today, we propose that mantle-resisted slab dragging combines with the NW-SE plate convergence across the (largely) unbroken plate boundary to drive the crustal deformation of the region. Slab dragging is the lateral transport, pushing or pulling, of slab through the mantle by the absolute motion of the subducting plate (Chertova et al., Gcubed, 2014). Because the slab is connected to both the Iberian

  10. A scalable, parallel matrix-free Stokes solver for geodynamic applications

    NASA Astrophysics Data System (ADS)

    May, D.

    2013-12-01

    Here I describe a numerical method suitable for studying non-linear, large deformation processes in crustal and lithopspheric dynamics. The method utilizes a hybrid spatial discretisation which consists of mixed finite elements for the Stokes flow problem, coupled to a Lagrangian marker based discretisation to represent the material properties (viscosity and density). This approach is akin to the classical Marker-And-Cell (MAC) scheme of Harlow and the subsequently developed Material Point Method (MPM) of Sulsky and co-workers. The geometric flexibility and ease of modelling large deformation processes afforded by such mesh-particle methods has been exploited by the lithospheric dynamics community over the last 20 years. The strength of the Stokes preconditioner fundamentally controls the scientific throughput achievable and represents the largest bottleneck in the development of our understanding of geodynamic processes. The possibility to develop a 'cheap' and efficient preconditioning methodology which is suitable for the mixed Q2-P1 element is explored here. I describe a flexible strategy, which aims to address the Stokes preconditioning issue using an upper block triangular preconditioner, together with a geometric multi-grid preconditioner for the viscous block. The key to the approach is to utilize algorithms and data-structures that exploit current multi-core hardware and avoid the need for excessive global reductions. In order to develop a scalable method, special consideration is given to; the definition of the coarse grid operator, the smoother and the coarse grid solver. The performance characteristics of this hybrid matrix-free / partially assembled multi-level preconditioning strategy is examined. The robustness of the preconditioner with respect to the viscosity contrast and the topology of the viscosity field, together with the parallel scalability is demonstrated.

  11. Emplacement of the Arzachena Pluton (Corsica-Sardinia Batholith) and the geodynamics of incoming Pangaea

    NASA Astrophysics Data System (ADS)

    Casini, Leonardo; Cuccuru, Stefano; Maino, Matteo; Oggiano, Giacomo; Tiepolo, Massimo

    2012-05-01

    The assembly of the Corsica-Sardinia Batholith (C-SB) coincides with final shaping of the Variscan belt and represents a key structure to unravel the feedbacks between partial melting, rheology and the evolution of collisional orogens. This paper presents a model for the genesis of the Arzachena pluton (AZN), one of the major calc-alkaline massifs of the C-SB, based on U-Pb zircon dating, thermobarometry and structural analysis. Major and trace element compositions indicate that AZN has hybrid characteristics between that of typical S- and I-type granites, that could be explained in terms of incremental melting of a heterogeneous crustal source made of metatexites and Ordovician calc-alkaline granitoids. Growth of the pluton started around 320-315 Ma with the emplacement at middle crustal level (0.37-0.4 GPa) of granodioritic melts within narrow, conjugate, NW-SE sinistral and E-W dextral shear zones. The main growth stage (311 + 6/- 4 Ma) is marked by emplacement of large volumes of monzogranitic melts that induced a local decrease of the crustal strength expressed by horizontal channel flow driven by the gravity. Finally (307.6 ± 3.5 Ma), leucogranites emplaced within radial and peripheral dilatant fractures developed during the cooling of the main body. The transition from magmatic to sub-magmatic and HT-solid state fabric observed throughout AZN indicates that deformation plays a non-trivial role during the growth of the magmatic system. Restoring the position of the Corsica-Sardinia block to early Permian coordinates allow to recast the birth of the C-SB in a consistent geodynamic framework that conciliates the development of conjugates strike-slip structures, the oroclinal bending of the chain and the thermal relaxation. This study indicates that the C-SB had an active role during post-orogenic extension rather than being just a consequence of it.

  12. Transformation of Tidal Deformations into Geodynamic Processes and Fractal Rheology of the Earth's Substance

    NASA Astrophysics Data System (ADS)

    Maslov, L. A.; Avsyuk, Y. N.

    2008-12-01

    The kinematics and dynamics of a binary "Earth-Moon" planet system have been studied with respect to the rotational motion of the Earth and Moon about the barycenter of the system, situated at a distance of 4641 km from the center of the Earth. The Earth's orbital motion, rotation and tidal deformations have a significant influence on the geodynamic processes, generation and support of the magnetic field, and climate changes of the planet. It has been shown that the tidal force causes displacements of the inner core; the corresponding gravitational effect on the Earth's surface has been evaluated (Avsyuk, 2001; Avsyuk, Suvorova, 2006). To explain these correlations, a number of mechanisms of transformations of radial tidal deformations into lateral displacements of the Earth's substance have been considered. In addition, three rheological models were taken to model tidal deformations: viscous, granular, and a fractal model based on Zener's standard rheological element. Mathematical modeling of tidal deformations for different rheologies of the substances of Earth demonstrated that the radial planetary tides are being transformed into lateral motion of planetary layers. Evaluation of the rate of lateral motion shows that this mechanism can be responsible for the westward drift of the lithosphere. The rate of lateral motion of planetary layers depends on the magnitude of the rate of radial tidal deformations, k(r). Mathematical modeling of tidal deformations for different distributions k(r) showed that the radial variation of this coefficient produces differential motion of deep planetary layers resulting in internal frictional heating of deep layers which can raise temperatures at given depths to the melting point of this material (Maslov, Anokhin, 2007; Maslov, 2007). This melting can be one of the factors influencing and amplifying the Earth's magnetic field. It is shown that the rate and energy of differential lateral motion of material in the core are enough to

  13. Cenozoic geodynamic evolution of the western Mediterranean domain: A view from the Neogene peri-Tyrrhenian basins

    SciTech Connect

    Roure, F.; Montadert, L.; Mueller, C.

    1988-08-01

    Biostratigraphic and structural studies of synorogenic Neogene deposits in the southern Apennines, Calabria, and Cicily are compared to similar data from Sardinia and the Tyrrhenian Sea to trace the geodynamic evolution of the western Mediterranean domain.

  14. Seismic-geodynamic constraints on three-dimensional structure, vertical flow, and heat transfer in the mantle

    USGS Publications Warehouse

    Forte, A.M.; Woodward, R.L.

    1997-01-01

    Joint inversions of seismic and geodynamic data are carried out in which we simultaneously constrain global-scale seismic heterogeneity in the mantle as well as the amplitude of vertical mantle flow across the 670 km seismic discontinuity. These inversions reveal the existence of a family of three-dimensional (3-D) mantle models that satisfy the data while at the same time yielding predictions of layered mantle flow. The new 3-D mantle models we obtain demonstrate that the buoyancy forces due to the undulations of the 670 km phase-change boundary strongly inhibit the vertical flow between the upper and lower mantle. The strong stabilizing effect of the 670 km topography also has an important impact on the predicted dynamic topography of the Earth's solid surface and on the surface gravity anomalies. The new 3-D models that predict strongly or partially layered mantle flow provide essentially identical fits to the global seismic data as previous models that have, until now, predicted only whole-mantle flow. The convective vertical transport of heat across the mantle predicted on the basis of the new 3-D models shows that the heat flow is a minimum at 1000 km depth. This suggests the presence at this depth of a globally defined horizon across which the pattern of lateral heterogeneity changes rapidly. Copyright 1997 by the American Geophysical Union.

  15. Seismic Structure and Geodynamic Evolution of the Lithosphere and Upper Mantle in the Pannonian - Carpathian Region

    NASA Astrophysics Data System (ADS)

    Houseman, G.; Brückl, E.; Hegedüs, E.; Radovanovic, S.; Brisbourne, A.; Lorinczi, P.; Dando, B.; Hausmann, H.; Kovács, A.; Török, I.

    2008-12-01

    The Pannonian Basin is the largest of a group of Miocene-age extensional basins within the arc of the Alpine-Carpathian Mountain Ranges. These basins are extensional in origin, but the surrounding Carpathians result from sustained convergence during and since the period of active extension. A significant part of the mantle lithosphere here has been replaced, as gravitational instability caused an overturn of the upper mantle. The Carpathian Basins Project (CBP) is a major international broadband seismology experiment, supported by geodynamical modelling and designed to improve our understanding of the structure and evolution of the lithosphere and upper mantle beneath the Pannonian and Vienna Basins. Between 2005 and 2007 we deployed 56 portable broadband seismic stations in Austria, Hungary and Serbia, spanning the Vienna Basin and the western part of the Pannonian Basin. Arrival time residuals from teleseismic earthquakes are delayed by about 0.8 sec in the Vienna Basin and early by a similar amount in southwest Hungary. Tomographic inversion of the travel time residuals shows relatively fast P-wave velocities in the upper mantle beneath the western Pannonian Basin and slow P-wave velocities beneath the West Carpathians. Seismic anisotropy (SKS) measurements reveal an intriguing pattern of lithospheric anisotropy: in the north-west the fast direction is generally elongated EW, perpendicular to the shortening direction across the Alps. Across the Vienna Basin the fast direction is NW-SE, perpendicular to the major bounding fault systems. Across the Pannonian Basin the dominant fast direction is EW, but in several locations the vectors are rotated toward NW-SE. The Mid-Hungarian Line, a major strike-slip structure already clearly identified in the gravity field, also is associated with abrupt changes in the azimuth of lithospheric anisotropy, and crustal receiver function signature. The object of these investigations is to use the seismic data to discriminate

  16. Seismic Structure and Geodynamic Evolution of the Lithosphere and Upper Mantle in the Pannonian - Carpathian Region

    NASA Astrophysics Data System (ADS)

    Houseman, G.; Stuart, G.; Dando, B.; Hetenyi, G.; Lorinczi, P.; Brueckl, E.; Hegedus, E.; Radovanovic, S.; Brisbourne, A.

    2009-04-01

    The Pannonian Basin is the largest of a group of Miocene-age extensional basins within the arc of the Alpine-Carpathian Mountain Ranges. These basins are extensional in origin, but the surrounding Carpathians result from sustained convergence during and since the period of active extension. A significant part of the mantle lithosphere here has been replaced, as gravitational instability caused an overturn of the upper mantle. The Carpathian Basins Project (CBP) is a major international broadband seismology experiment, supported by geodynamical modelling and designed to improve our understanding of the structure and evolution of the lithosphere and upper mantle beneath the Pannonian and Vienna Basins. Between 2005 and 2007 we deployed 56 portable broadband seismic stations in Austria, Hungary and Serbia, spanning the Vienna Basin and the western part of the Pannonian Basin. Arrival time residuals from teleseismic earthquakes are delayed by about 0.8 sec in the Vienna Basin and early by a similar amount in southwest Hungary. Tomographic inversion of the travel time residuals shows relatively fast P-wave velocities in the upper mantle beneath the western Pannonian Basin and slow P-wave velocities beneath the West Carpathians. Seismic anisotropy (SKS) measurements reveal an intriguing pattern of lithospheric anisotropy: in the north-west the fast direction is generally elongated EW, perpendicular to the shortening direction across the Alps. Across the Vienna Basin the fast direction is NW-SE, perpendicular to the major bounding fault systems. Across the Pannonian Basin the dominant fast direction is EW, but in several locations the vectors are rotated toward NW-SE. The Mid-Hungarian Line, a major strike-slip structure already clearly identified in the gravity field, also is associated with abrupt changes in the azimuth of lithospheric anisotropy. Receiver function analysis of the seismic discontinuity at 670 km shows significant structure on scales of order 100 km, and

  17. Correlating basaltic composition with stages of geodynamic settings associated with breakup of supercontinent Rodinia

    NASA Astrophysics Data System (ADS)

    Sinha, A.; Hanan, B. B.

    2010-12-01

    The breakup of supercontinents is often accompanied by magmatism associated with many possible geodynamic scenarios and interactions between the mantle and the overlying continental lithosphere. We examine the geochemical and isotopic signature of late Proterozoic basalts of the Catoctin Volcanic Province (CVP) along eastern North America to identify the temporal tectono-magmatic stages associated with dispersal. We model Stage I basalt generation to be associated with incipient supercontinent extension with its chemical/isotopic signature dominated by sub-continental lithosphere mantle (SCLM). Stage II basalts mark transition to an incipient oceanic rift where Ocean island basalt (plume) or mid-ocean ridge basalt sources are diluted by SCLM. Stage III basalts are related to a mature mid-ocean ridge system where the source is dominated by the depleted asthenosphere MORB source. New isotopic and geochemical data from the Catoctin Formation (type area of CVP) in the region of the central Appalachian orogen show incompatible element ratios of Zr/Y = 4.91, La/Yb = 5.73, Th/Ta = 1.37 and Hf/Th = 2.82, as well as primitive mantle normalized trace element abundances with OIB affinity like Hawaii. These lavas have similar low Nb/La (0.63-1.04) as Hawaii but slightly higher Th/Ta (1.1-2.12). In Pb-Pb isotope space define a pseudo- binary trend between continental lithosphere-like sources and an OIB-like source similar to a C-like plume component suggestive of Stage II. Basalts of the Unicoi, Bassett and Sams Creek Formations are similar to the Catoctin Formation and are modeled as Stage II magmatism. Other basalts hosted within the Lynchburg and Ashe-Alligator Back formations are of both high (>2 wt %) and low (<2%) TiO2 types, where the low Titanium group is best modeled as stage I, while higher TiO2 samples reflect stage II OIB dominated source similar to the basalts of the Catoctin Formation. We emphasize that in order to confirm these stages additional precise

  18. On the Utility of High-Resolution InSAR Data for Geodynamic Applications

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Amelung, F.

    2014-12-01

    High-spatial and high-temporal resolution InSAR data acquired by the TerraSAR-X and Cosmo-Skymed satellites is becoming increasingly available for geodynamic applications, including volcanic crises, the arctic ice sheets and land subsidence problems. The advantage of these second-generation SAR systems is that processes can be resolved that were not visible by the low-resolution first-generation systems, such as pre-eruptive deformation of a volcanic dome and uplift or subsidence of the bedrock in response to a glacial surge. The drawback is the limited temporal coherence because these satellites operate at X-Band, which makes them suitable only for particular environments. In this poster we present a variety of applications. Our purpose is to better define the potential of these systems for geodynamic applications.

  19. Is the geodynamic process in preparation of strong earthquakes reflected in the geomagnetic field?

    NASA Astrophysics Data System (ADS)

    Finkelstein, M.; Price, C.; Eppelbaum, L.

    2012-10-01

    A methodology of detecting geomagnetic variations caused by dangerous geodynamic processes at depth has been developed. This methodology was tested using data from three Japanese observatories within the network of the International project ‘Intermagnet’ (www.intermagnet.org 2011). Anomalous behaviour of the geomagnetic field was detected during the period of the great Tohoku-oki earthquake on 11 March 2011. Theoretical evaluation of the possible mechanisms of these anomalous geomagnetic variations (AGV) has been examined. The possibility of the emergence of an AGV in the vicinity of earthquake epicentres in Japan and their rapid monitoring (online or with a delay of one day) is demonstrated. The main tool of the developed methodology is delineation of the geodynamic magnetic effect by the use of a differential function.

  20. Joint seismic and geodynamic evidence for a long-lived, stable mantle upwelling under the East Pacific Rise

    NASA Astrophysics Data System (ADS)

    Forte, A. M.; Glisovic, P.; Rowley, D. B.; Simmons, N. A.; Grand, S. P.

    2013-12-01

    Global seismic tomography has consistently imaged large-scale structures in the lower mantle under the Pacific Ocean and under Africa that are characterised by strongly reduced seismic shear velocities. These so-called "low shear-velocity provinces" (LVSP) have been variously interpreted as hot, stagnant thermochemical "piles" that are compositionally dense, or as deeply rooted expressions of positively buoyant, active upwellings. To distinguish which of these two end-member models is relevant to the actual dynamics in the deep mantle requires robust constraints on the density structure of these LVSP. Recent global tomography models reveal what appear to be three distinct 'lobes' of the Pacific LVSP: one located in the Western-Pacific mantle under the Caroline Islands, another in the South-Central-Pacific mantle under French Polynesia, and another below the East Pacific Rise (EPR), centred under Easter Island. To understand the dynamics and time-dependent evolution of these structures we employ recent tomography models derived from the joint inversion of global seismic and geodynamic data sets, which also include constraints from mineral physics (Simmons et al., GJI 2009, JGR 2010). A critically important feature of these joint tomography models is the inclusion of a laterally variable scaling between density and seismic shear velocity, thereby accounting for the spatially localized effect of compositional heterogeneity in the lower mantle. These lower-mantle compositional contributions to density are directly constrained by long-wavelength gravity anomaly data and the excess ellipticity of the CMB. We show that it is not possible to properly account for this compositional heterogeneity using a constant, or simple depth-dependent density-velocity scaling. We have carried out very-long-time mantle convection simulations employing as a starting condition the joint seismic-geodynamic inferences of mantle density structure (Glisovic et al., GJI 2012). We demonstrate

  1. Seismological and Geodynamic Monitoring Network in the "javakheti" Test Zone in the Southern Caucasus

    NASA Astrophysics Data System (ADS)

    Arakelyan, A.; Babayan, H.; Karakhanyan, A.; Durgaryan, R.; Basilaia, G.; Sokhadze, G.; Bidzinashvili, G.

    2012-12-01

    The Javakheti Highland located in the border region between Armenia and Georgia (sharing a border with Turkey) is an area in the Southern Caucasus of young Holocene-Quaternary volcanism and a region with convergence of a number of active faults. Issues related to the geometry, kinematics and slip-rate of these faults and assessment of their seismic hazard remain unclear in part due to the fragmentary nature of the studies carried out soley within the borders of each of the countries as opposed to region wide. In the frame of the ISTC A-1418 Project "Open network of scientific Centers for mitigation risk of natural hazards in the Southern Caucasus and Central Asia" the Javakheti Highland was selected as a trans-border test-zone. This designation allowed for the expansion and upgrading of the seismological and geodynamic monitoring networks under the auspices of several international projects (ISTC CSP-053 Project "Development of Communication System for seismic hazard situations in the Southern Caucasus and Central Asia", NATO SfP- 983284 Project "Caucasus Seismic Emergency Response") as well as through joint research programs with the National Taiwan University and Institute of Earth Sciences (IES, Taiwan), Universite Montpellier II (France) and Ecole et Observatoire des Sciences de la Terre-Université de Strasbourg (France). Studies of geodynamic processes, and seismicity of the region and their interaction have been carried out utilizing the newly established seismological and geodynamic monitoring networks and have served as a basis for the study of the geologic and tectonic structure . Upgrading and expansion of seismological and geodynamic networks required urgent solutions to the following tasks: Introduction of efficient online systems for information acquisition, accumulation and transmission (including sattelite systems) from permanent and temporary installed stations, Adoption of international standards for organization and management of databases in GIS

  2. Thermal and geodynamic contributions to the elevation of the Altiplano-Puna plateau

    NASA Astrophysics Data System (ADS)

    Prezzi, Claudia; Iglesia Llanos, María Paula; Götze, Hans-Jürgen; Schmidt, Sabine

    2014-12-01

    The most remarkable feature of the Central Andes is the Altiplano-Puna plateau. This plateau is characterized by 3.5 km average elevation, approximately 70 km crustal thickness and very high heat flow. The upper mantle structure changes along strike below the plateau. The upper mantle below the Puna becomes hotter, and the lithosphere becomes thinner and weaker. These features suggest that thermal isostasy could play a role in the compensation of the Altiplano-Puna. Thermal isostasy is the geodynamic process whereby regional variations in the lithospheric thermal regime cause changes in elevation. Elevation changes result from variations in rock density in response to thermal expansion. The aim of this study is to estimate the thermal and geodynamic contributions to the elevation. While the thermal component of the Altiplano elevation would be of 1 km, the thermal contribution to the southern Puna elevation would be of 1.5 km. However, in the case of the southern Puna a portion of the actual topography (∼20%) cannot be explained considering only compositional and thermal effects, suggesting additional geodynamical support. The obtained results suggest that the thermal state of the lithosphere would play a significant role in the elevation of the Central Andes, and may be responsible of some of the geological differences displayed by the Altiplano and the Puna.

  3. Long-term monitoring of geodynamic surface deformation using SAR interferometry

    NASA Astrophysics Data System (ADS)

    Gong, Wenyu

    Synthetic Aperture Radar Interferometry (InSAR) is a powerful tool to measure surface deformation and is well suited for surveying active volcanoes using historical and existing satellites. However, the value and applicability of InSAR for geodynamic monitoring problems is limited by the influence of temporal decorrelation and electromagnetic path delay variations in the atmosphere, both of which reduce the sensitivity and accuracy of the technique. The aim of this PhD thesis research is: how to optimize the quantity and quality of deformation signals extracted from InSAR stacks that contain only a low number of images in order to facilitate volcano monitoring and the study of their geophysical signatures. In particular, the focus is on methods of mitigating atmospheric artifacts in interferograms by combining time-series InSAR techniques and external atmospheric delay maps derived by Numerical Weather Prediction (NWP) models. In the first chapter of the thesis, the potential of the NWP Weather Research & Forecasting (WRF) model for InSAR data correction has been studied extensively. Forecasted atmospheric delays derived from operational High Resolution Rapid Refresh for the Alaska region (HRRR-AK) products have been compared to radiosonding measurements in the first chapter. The result suggests that the HRRR-AK operational products are a good data source for correcting atmospheric delays in spaceborne geodetic radar observations, if the geophysical signal to be observed is larger than 20 mm. In the second chapter, an advanced method for integrating NWP products into the time series InSAR workflow is developed. The efficiency of the algorithm is tested via simulated data experiments, which demonstrate the method outperforms other more conventional methods. In Chapter 3, a geophysical case study is performed by applying the developed algorithm to the active volcanoes of Unimak Island Alaska (Westdahl, Fisher and Shishaldin) for long term volcano deformation

  4. What can zircon ages from the Jack Hills detrital zircon suite really tell us about Hadean geodynamics?

    NASA Astrophysics Data System (ADS)

    Whitehouse, Martin; Nemchin, Alexander

    2015-04-01

    As the only direct sample of the Hadean Earth, detrital zircon grains from the Jack Hills, Western Australia, have been the subject of intense investigation over the almost three decades since their discovery. A wide variety of geochemical and isotopic analyses of these grains, as well as their mineral inclusions, have been used variously to support two fundamentally different models for Hadean geodynamics: (i) Some form of (not necessarily modern-style) plate recycling generating felsic (continental-type?) crust at the boundaries [1, 2], or conversely (ii) the persistence of a long-lived, stagnant basaltic lid within which magmatism occurred as a result of internal temperature perturbations and/or impacts [3, 4], a model also generally consistent with a wide range of observations from post-Hadean geochemical reservoirs. Despite the considerable time and resources expended, the majority of these studies uncritically accept the individual U-Pb zircon ages, even though their veracity is key to many of the interpretations [5, 6]. We report here the results of an in-depth evaluation of all published (and new) U-Pb ages from the Jack Hills zircon suite in order to define age populations that can be used with a high degree of confidence in geodynamic interpretations. A notable problem in the interpretation of U-Pb data from ancient zircon grains (including those as young as the Neoarchean) is that disturbance of the systematics even several 100 Ma after crystallization causes data to spread along the concordia curve without becoming discernably discordant within the relatively large error bounds associated with U/Pb ages from in situ dating methods (e.g. SIMS). While 207Pb/206Pb ages are typically more precise, individually they provide no means to detect Pb-loss-induced younging. However, if two or preferably more analyses have been made in the same zircon growth zone, a reasonable evaluation of the possibility of Pb-loss can be made. In the available Jack Hills zircon

  5. Paleoproterozoic andesitic volcanism in the southern Amazonian craton (northern Brazil); lithofacies analysis and geodynamic setting

    NASA Astrophysics Data System (ADS)

    Roverato, Matteo; Juliani, Caetano; Capra, Lucia; Dias Fernandes, Carlos Marcelo

    2016-04-01

    Precambrian volcanism played an important role in geological evolution and formation of new crust. Most of the literature on Precambrian volcanic rocks describes settings belonging to subaqueous volcanic systems. This is likely because subaerial volcanic rocks in Proterozoic and Archean volcano-sedimentary succession are poorly preserved due to erosive/weathering processes. The late Paleoproterozoic Sobreiro Formation (SF) here described, seems to be one of the rare exceptions to the rule and deserves particular attention. SF represents the subaerial expression of an andesitic magmatism that, linked with the upper felsic Santa Rosa F., composes the Uatumã Group. Uatumã Group is an extensive magmatic event located in the Xingú region, southwestern of Pará state, Amazonian Craton (northern Brazil). The Sobreiro volcanism is thought to be related to an ocean-continent convergent margin. It is characterized by ~1880 Ma well-preserved calc-alkaline basaltic/andesitic to andesitic lava flows, pyroclastic rocks and associated reworked successions. The superb preservation of its rock-textures allowed us to describe in detail a large variety of volcaniclastic deposits. We divided them into primary and secondary, depending if they result from a direct volcanic activity (pyroclastic) or reworked processes. Our study reinforces the importance of ancient volcanic arcs and rocks contribution to the terrestrial volcaniclastic sedimentation and evolution of plate tectonics. The volcanic activity that produced pyroclastic rocks influenced the amount of detritus shed into sedimentary basins and played a major role in the control of sedimentary dispersal patterns. This study aims to provide, for the first time, an analysis of the physical volcanic processes for the subaerial SF, based in field observation, lithofacies analysis, thin section petrography and less geochemical data. The modern volcanological approach here used can serve as a model about the evolution of Precambrian

  6. AlpArray - an initiative to advance understanding of Alpine geodynamics

    NASA Astrophysics Data System (ADS)

    Hetényi, György; AlpArray Working Group

    2013-04-01

    variations), using different methodologies in the sub-regions of interest. An overview of these targets and the methodologies intended to be applied in connection with the seismological measurements will be presented. The geodynamic interpretation of the acquired data will be complemented by other Earth Science disciplines such as state-of-the-art numerical and analogue modelling, gravity and magneto-telluric measurements, as well as structural geology. In conclusion, we hope to turn the strong community interest into a truly interdisciplinary and collaborative project in the key region for seismotectonic activity and dynamics of Europe.

  7. Geodynamic evolution and the history of the atmospheres of Mars and Venus

    NASA Astrophysics Data System (ADS)

    Gillmann, C.; Tackley, P. J.; Lognonne, P.

    2011-12-01

    To investigate in what measure the interactions between the mantle and the atmosphere would have caused the divergent evolutions of the terrestrial planets in our solar system, we propose to model the effects of mantle dynamics on the evolution of CO2, H2O and other species like Argon or Nitrogen in the atmosphere, but also of the surface temperature. We consider several processes that are considered to have a strong influence on the atmosphere of terrestrial planets. First, the main source of volatiles in our model is the degassing from the mantle. We use and adapt the StagYY code developed by Tackley (Tackley, 2008) for the geodynamic part of the study. This modeling gives a realistic and advanced account of the mantle convection processes. When possible, we compare those results to published modeling (Breuer and Spohn, 2006; Grott et al., 2011) and observation. Atmospheric escape is considered as the main volatile loss flux. Early escape is thermal, caused by hydrodynamic escape. Its effects can be modeled, as we did for Venus. After the first few hundred of million years, the main atmospheric escape flux becomes non-thermal. We model the evolution of the present escape flux by comparing recent study on these processes and ASPERA (Analyzer of Space Plasma and EneRgetic Atoms) measurements. Differences in present-day escape depending on solar activity are used to extrapolate early escape. We combine these models to calculate the state of the atmosphere of Venus and Mars. This lets us estimate the surface temperature of those planets either from a Mars Global Circulation Model (e.g. Forget at al., 1999), or with a gray radiative-convective atmosphere model, for Venus. In the case of Mars, Ar appears to be a tracer of volcanic degassing. We also show that the present-day atmosphere of Mars is likely to be constituted by a large part of volcanic gases. Even with a low CO2 concentration in the magma (150 ppm), present-day atmosphere is constructed of 50% of volcanic

  8. Geodynamic significance of the TRM segment in the East African Rift: active tectonics and paleostress in western Tanzania

    NASA Astrophysics Data System (ADS)

    Delvaux, D.; Kervyn, F.; Macheyeki, A. S.; Temu, E. B.

    2012-04-01

    The Tanganyika-Rukwa-Malawi (TRM) rift segment in western Tanzania is a key sector for understanding the opening dynamics of the East African rift system (EARS). In an oblique opening model, it is considered as a dextral transfer fault zone that accommodates the general opening of the EARS in a NW-SE direction. In an orthogonal opening model, it accommodates pure dip-slip normal faulting with extension orthogonal to the rift segments and a general E-W extension for the entire EARS. We investigated the active tectonic architecture and paleostress evolution of the Ufipa plateau and adjacent Rukwa basin and in order to define their geodynamic role in the development of the EARS and highlight their pre-rift brittle tectonic history. The active fault architecture, fault-kinematic analysis and paleostress reconstruction show that the recent to active fault systems that control the rift structure develop in a pure extensional setting with extension direction orthogonal to the trend of the TRM segment. Two pre-rift brittle events are evidenced. An older brittle thrusting is related to the interaction between the Bangweulu block and the Tanzanian craton during the late Pan-African (early Paleozoic). It was followed by a transpressional inversion during the early Mesozoic. This inversion stage caused dextral strike-slip faulting along the fault systems that now control the major rift structures. It has been erroneously interpreted as related to the late Cenozoic EARS which instead is characterized by pure normal faulting.

  9. Geodynamical Interpretation of Crustal and Mantle Shear-Wave Velocity Structures Beneath the Carpathian-Pannonian Region

    NASA Astrophysics Data System (ADS)

    Ren, Yong; Stuart, Graham; Houseman, Gregory; Grecu, Bogdan; Ionescu, Constantin; Hegedüs, Endre; Radovanović, Slavica; Shen, Yang; South Carpathian Project working Group

    2013-04-01

    the Carpathian-Pannonian region. In the finite-frequency teleseismic tomography of S waves, we have selected earthquakes with magnitude greater than 5.5 in the distance range 30°-95°, which occurred between 2006 and 2011. Using multi-channel cross-correlation technique, over 29661 and 41875 relative S arrival times were measured in high and intermediate frequency bands (0.1-0.5 Hz and 0.05-0.1 Hz) respectively. The relative arrival times are inverted for S-wave velocity distribution in the upper mantle according to the 3-D finite frequency kernel formulation. Our shear-wave velocity models provide a uniquely complete and relatively high-resolution view of the crustal and upper mantle structures in the region. We will discuss the interpretations of these velocity variations for the formation and geodynamical evolution of the lithosphere and upper mantle of the Carpathian-Pannonian region.

  10. Origin and geodynamic significance of the early Mesozoic Weiya LP and HT granulites from the Chinese Eastern Tianshan

    NASA Astrophysics Data System (ADS)

    Mao, Ling-Juan; He, Zhen-Yu; Zhang, Ze-Ming; Klemd, Reiner; Xiang, Hua; Tian, Zuo-Lin; Zong, Ke-Qing

    2015-12-01

    Late Devonian regional metamorphism and were overprinted by the Early Triassic contact metamorphism. Therefore, Early Triassic geodynamic models for the southwestern part of the CAOB, which are based on a previously suggested regional metamorphic orogenic event of the Weiya granulites, need to be viewed with caution.

  11. Geodynamic investigation of a Cretaceous superplume in the Pacific ocean

    NASA Astrophysics Data System (ADS)

    Xue, Jing; King, Scott D.

    2016-08-01

    The similarity in both age and geochemistry of the Ontong-Java, Hikurangi, and Manihiki plateaus suggests that they formed as a single superplateau from a unique mantle source. We investigate the necessity of a thermal superplume to form the Great Ontong-Java plateau at about 120 Ma using 3D spherical models of convection with imposed plate reconstruction models. The numerical simulations show that the giant plateau which formed as a result of melting due to the interaction of a plume head and the lithosphere would have been divided into smaller plateaus by spreading ridges, and end up at the present locations of Ontong-Java, Manihiki, and Hikurangi plateaus as well as a fragment in the western Caribbean. By comparing temperature and melt fraction between models with and without an initial thermal superplume, we propose that a Cretaceous superplume in Pacific at 120 Ma is required to form large igneous plateaus.

  12. Integration of permanent and periodic GPS/GNSS measurements for local and regional geodynamic research in the area of the Polish-Czech Network SUDETEN

    NASA Astrophysics Data System (ADS)

    Kontny, Bernard; Kaplon, Jan; Schenk, Vladimir; Schenkova, Zdenka; Badura, Janusz

    2014-05-01

    Since 1997 all current local geodynamic studies in the area of the Polish and Czech parts of the Sudeten and the Sudetic Foreland have been associated with annual periodic GPS campaigns, epoch measurements. The most epochs consisted of more than twelve observation hours and some of them kept on two or three 24-hour observations. Experience collected by international research teams carrying out geodynamic researches with the GPS technique in seismically active areas (USA, Japan) proved that more information can give permanent measurements. However, the Sudeten area, regarded as an area of the weak tectonic activity, can be hardly covered with the dense network of GNSS stations from economic reasons. Hence rational using of existing permanent GPS stations located in studied area and in its vicinity detects the coordinate changes that cannot be appointed from periodic campaign data and that, on the other hand, have rather regional than local character. Creating the spatial models of irregularities of the continuous signals should improve results of the epoch measurements. From this viewpoint, in this project authors used measurement data of chosen permanent GPS stations located in the area: the EPN stations, ASG-EUPOS stations, GEONAS stations and all epoch observations. These data were gained as part of research projects carried out within 1997-2009 period, as well as during new supplementing campaigns realized in the frame of the project N526278940 in the 2011 and 2012 years. Reprocessing of all the permanent and epoch data performed by the latest version of Bernese GNSS Software (V5.2) was performed using EPN guidelines for the processing, reference frame realization and the usage of physical models (atmosphere, Earth rotation, etc.). Standardized results of processing the aggregated GPS network, including permanent stations and all local networks on the area of research, serve for conducting new geodynamic interpretation. Further parameters that estimate the

  13. Reconstructing Pliocene coastlines, topography and bathymetry: A geodynamic perspective

    NASA Astrophysics Data System (ADS)

    Chandan, D.; Peltier, W. R.

    2014-12-01

    The middle Pliocene period (~3.3-3.0 Mya) was characterized by warm temperatures (2-3℃ higher) and high carbon-dioxide (~400 ppmv) concentrations which has led to its recognition as a possible analogue for the future climate. Under the auspices of the Pliocene Modeling and Intercomparison Project (PlioMIP), general circulation models (GCM's) are being employed to simulate mid-Pliocene climate to better understand the biases in these models, which are presently used to make future climate predictions. Necessary boundary conditions for these simulations — land mask, topography, surface albedo and vegetation cover are being provided by the Pliocene Research, Interpretation and Synoptic Mapping (PRISM) project. Bathymetry, which is not part of the PRISM supplied dataset has been adjusted by raising the sea-level by an assumed constant eustatic amount. At present the PRISM land mask, topography and bathymetry reconstructions do not incorporate the gravitationally self consistent changes that would be required to account for the mass loss from the Greenland and Antarctic ice-sheets that produced the assumed rise in eustatic sea level. The effects of dynamic topography induced corrections, due to the action of the mantle convection process, have also been neglected.The influence of these corrections on the predictions of Pliocene climate using modern GCM's remains unexplored. The continuing failure of these models to simulate proxy inferred levels of warming in high-latitude [Dowsett et al., 2013, Sci. Rep.] regions where the magnitude of the required corrections are expected to be largest make it especially important that their impact be assessed. Here, we present the results from a preliminary of the required modifications to the boundary condition data sets.We compute the gravitationally self consistent corrections using the viscoelastic theory of global, glacial isostatic adjustment and relative sea level history for a spherically symmetric Earth model. Dynamic

  14. Geodynamic inversion to constrain the non-linear rheology of the lithosphere

    NASA Astrophysics Data System (ADS)

    Baumann, T. S.; Kaus, Boris J. P.

    2015-08-01

    , we first perform a geodynamic inversion of a synthetic forward model of intraoceanic subduction with known parameters. This requires solving an inverse problem with 14-16 parameters, depending on whether temperature is assumed to be known or not. With the help of a massively parallel direct-search combined with a Markov Chain Monte Carlo method, solving the inverse problem becomes feasible. Results show that the rheological parameters and particularly the effective viscosity structure of the lithosphere can be reconstructed in a probabilistic sense. This also holds, with somewhat larger uncertainties, for the case where the temperature distribution is parametrized. Finally, we apply the method to a cross-section of the India-Asia collision system. In this case, the number of parameters is larger, which requires solving around 1.9 × 106 forward models. The resulting models fit the data within their respective uncertainty bounds, and show that the Indian mantle lithosphere must have a high viscosity. Results for the Tibetan plateau are less clear, and both models with a weak Asian mantle lithosphere and with a weak Asian lower crust fit the data nearly equally well.

  15. Thermal rocketing and the Laser Geodynamic Satellite (LAGEOS-1)

    SciTech Connect

    Miller, W.A.

    1997-08-01

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory. LAGEOS is the most accurately tracked satellite in orbit. It is a totally passive, dense spherical satellite covered with 426 cube corner reflectors. Besides its great utility in measuring the Earth`s length of day and polar wobble, this satellite can be used to measure, for the first time, the general relativistic frame-dragging effect. Of the five dominant error sources in such an experiment, the largest one involves surface interaction of thermal forces (thermal rocketing) and its influence on the orbital nodal precession. The project objective was to enhance an already available theoretical model (computer code) developed at Los Alamos based on new optical-spin data obtained at the University of Maryland. The project objective was met and the enhanced code will serve as the new spin-dynamics model for future LAGEOS satellite missions.

  16. Upper crust response to geodynamic processes beneath Isparta Angle, SW Turkey: Revealed by CMT solutions of earthquakes

    NASA Astrophysics Data System (ADS)

    Över, Semir; Özden, Süha; Kamacı, Züheyr; Yılmaz, Hüseyin; Ünlügenç, Ulvi Can; Pınar, Ali

    2016-09-01

    The Isparta Angle is an important area of SW Anatolia where extensions in all directions (N-S, NE-SW, NW-SE and E-W) meet. These extensions were determined by normal faulting structures as well as by shallow earthquakes. All extensions, except the E-W one, were attributed to the deviatoric stresses in relation to slab forces and/or extrusion of Anatolia. The moment tensor inversion of 40 shallow earthquakes which occurred in the inner part of the Isparta Angle give focal mechanisms mostly indicating normal faulting. Inversion of all focal mechanisms of the earthquakes obtained from the moment tensor inversion yields normal faulting characterized by an approximately E-W (N268°E) σ3 axis. The calculated stress ratio R is 0.6944 indicating a triaxial stress state. Commonly accepted geodynamic models for the eastern Mediterranean region do not include plate boundary forces acting in the east or west direction. Our hypothesis is that the cause of the E-W extension is the combined forces of Gravitational Potential Energy and the hot asthenosphere upwelling through a tear fault in the subducted African plate between the Hellenic and Cyprus arcs beneath the Isparta Angle.

  17. Crustal structure and geodynamic of the Middle and Lower reaches of Yangtze metallogenic belt and neighboring areas: insights from deep seismic reflection profiling

    NASA Astrophysics Data System (ADS)

    Lu, Q.; Shi, D.; Liu, Z.; Zhang, Y.; Zhao, J.

    2014-12-01

    A 300 km deep seismic reflection profile across the middle and lower Yangtze River metallogenic belt (YRMB) and its adjacent areas established the architecture and geodynamic framework of the region. Results based on the interpretation of the deep seismic data include the deep complicated geometry of the Tan-Lu fault and Zhangbaling uplift, appears as a subvertical thrust fault with its deep portion dip toward the southeast, and along which the Zhangbaling uplift is squeezed out; complex upper crust deformation structure beneath Chuquan depression, within which there are both kink bands, thrusts, imbrication and fold structures reflecting contraction deformation, and detachment fault and normal-fault structures reflecting extensional deformation; the "crocodile" reflection structure emerging beneath the Tan-Lu fault and Ningwu-Lishui volcanic basin, i.e., the upper crust reflection thrust upward, and the lower crust reflection thrust downward and offsetting the Moho discontinuity, which reflects the decoupled deformation process of the upper and lower crust, and is interpreted as an intracontinental subduction. Further to the southeast, the upper crust deformation shows a large-scale "wave-form" pattern, making crustal scale syncline and anticline. The entire section of the reflection Moho is clearly discernible at depth of 30.0-34.5 km, and the Moho beneath the YRMB is shallowest, while the Moho beneath the North China block is deeper than that beneath the Yangtze block. Moho offsets could be seen beneath the Ningwu volcanic basin. Overall, the seismic data show evidence for an intracontinental orogeny and imposes constraints on the deep geodynamic model applied to study region. Our interpretation of seismic profile supports the view that the Yanshanian orogeny, due to the northwest subduction of the paleo-Pacific plate during the Middle-Late Jurassic, is the major event that shaped the tectonic framework of the region. A geodynamic model is proposed for the

  18. Geodynamic and Magmatic Evolution of the Eastern Anatolian-Arabian Collision Zone, Turkey

    NASA Astrophysics Data System (ADS)

    Keskin, Mehmet

    2014-05-01

    The Eastern Anatolian-Arabian Collision Zone represents a crucial site within the Tethyan domain where a subduction system involving a volcanic arc (i.e. Cretaceous to Oligocene Pontide volcanic arc in the north) associated with a large subduction-accretion complex (i.e. Cretaceous to Oligocene Eastern Anatolian Accretionary Complex i.e. "EAAC" in the south) turned later into a major continental collision zone that experienced a series of geodynamic events including lithospheric delamination, slab-steepening & breakoff, regional domal uplift, widespread volcanism and tectonic escape via strike slip fault systems. The region includes some of the largest volcanic centers (e.g. Karacadaǧ, Aǧırkaya caldera, Ararat, Nemrut, Tendürek and Süphan volcanoes) and plateaus (e.g. The Erzurum-Kars Plateau) as well as the largest transform fault zones in the Mediterranean region. A recent geodynamic modeling study (Faccenna et al., 2013) has suggested that both the closure of the Tethys Ocean and the resultant collision were driven by a large scale and northerly directed asthenospheric mantle flow named the "Tethyan convection cell". This convection cell initiated around 25 Ma by combined effects of mantle upwelling of the Afar super plume located in the south, around 3,000 km away from the collision zone and the slab-pull of the Tethyan oceanic lithosphere beneath Anatolia in the north. The aforementioned mantle flow dragged Arabia to the north towards Eastern Anatolia with an average velocity of 2 cm/y for the last 20 My, twice as fast as the convergence of the African continent (i.e. 1 cm/y) with western and Central Turkey. This 1 cm/y difference resulted in the formation of the left lateral Dead Sea Strike Slip Fault between the African and Arabian plates. Not only did this mantle flow result in the formation of a positive dynamic topography in the west of Arabian block, but also created a dynamic tilting toward the Persian Gulf (Faccenna et al., 2013). Another

  19. The Geodynamic Origins of Western U.S. Topography: Correlations and Speculations.

    NASA Astrophysics Data System (ADS)

    Coblentz, D.; van Wijk, J.; Phillips, S.; Karlstrom, K.; Chase, C.

    2008-12-01

    The topography of the Earth's surface provides important information for regional and global geomorphic studies because it reflects the interplay between tectonic-associated processes of uplift and climate- associated processes of erosion. The topography of the actively deforming western U.S. Cordillera is characterized by high relief and regionally high elevation, typically exceeding 1.5 km. Intriguingly, much of the high elevation coincides with thin or attenuated continental crust, necessitating topographic support by anomalous buoyancy of the mantle - suggesting that geodynamics responsible for the topography in the Western U.S. has a significant component associated with deep sources in the upper mantle. In an attempt to sharpen our understanding of the underlying geodynamics, we present a quantitative comparison of three databases (topography, geoid and Lg Q) that provide information about the geodynamics of the western U.S. at different depth scales. The unprecedented breadth and density of the USArray allows us to resolve lateral variations of 1-Hz Lg (a prominent seismic phase on most short period, regional distance seismograms along continental paths, resulting from the superposition of trapped, crustal shear waves) attenuation to 0.5 degrees over much of the western United States. In the Western U.S., Lg Q ranges from 60 to 550 and shows striking correlation with regional geology and topography, with lowest Q associated with recent volcanic and geothermal activity, and active shear zones, and highest Q associated with older, stable crust, intrusives, and competent, topographically bounded blocks in the Basin and Range. Several areas - most notably Yellowstone, the margins of the Colorado Plateau, and the Aspen Anomaly - exhibit a strong correlation between the surface topography, long-wavelength geoid anomalies and Lg Q and provide compelling support for the notion that many of the topographic features that characterize the Western U.S. are associated

  20. Diffuse Crustal Deformation in Asia: From Kinematics to Geodynamics

    NASA Astrophysics Data System (ADS)

    Liu, M.; Zhang, H.; Yang, Y.; Wang, S.

    2005-12-01

    Asian continent is a classical example of broadly diffuse crustal deformation that defies the prediction of the plate tectonics theory. The kinematics of Asian crust delineated by extensive neotectonics studies and GPS measurements are now sufficient to constrain the cause of the diffuse deformation. Using these constraints, we have developed a 3D viscous shell model to explore the dynamic interplay of major driving forces and lithospheric structure in controlling Asian tectonics. Calculated on parallel computers, the finite element model has nearly one million nodes, allowing inclusion of most major faults and lithospheric structures. Our preliminary results indicate that the effects of the plate boundary force from the Indian indenter are largely limited to the Tibetan Plateau and surrounding regions; active crustal deformation in much of the east and southeast Asia is mainly driven by the gravitational potential energy from the Tibetan Plateau and other uplifted landmasses in central Asia. Subduction along the eastern margin of the Eurasian plate has only secondary impact on active tectonics in east Asia, but may be important during the early Cenozoic. The large lateral heterogeneity of lithospheric structure causes strain to localize within narrow deforming zones marked by active fault systems. The predicted deviatoric stress is relatively high in the North China block but low in the South China block, consistent with the contrasting seismicity between these regions. The total seismic energy released in the past two thousand years is comparable to the predicted long-term spatial pattern of strain energy in China.

  1. Gravimetry and Space Techniques Applied to Geodynamics and Ocean Dynamics

    NASA Astrophysics Data System (ADS)

    Schutz, Bob E.; Anderson, Allen; Froidevaux, Claude; Parke, Michael

    The variety of disciplines represented in this volume (including space geodesy, oceanography, geophysics, and celestial mechanics) attest to the interdisciplinary applications of gravimetry and space techniques. The relation to sea level is addressed within some of the papers and the contributions of the techniques to development of global gravity models are discussed. The space technique of satellite altimetry has become a prominent contributor to sea surface topography as well as ocean tide models and determination of gravity, especially in ocean areas. Ocean tides influence the motion of near-Earth satellites and the rotation of the Earth. Modern space geodesy is increasingly relying on the Global Positioning System for measuring geophysical phenomena manifested at the surface through crustal deformations. Furthermore, the geophysical interpretation of gravity anomalies has been facilitated by the introduction of modern techniques. This volume represents only a small "snapshot" of the interdisciplinary research being conducted. Modem space geodesy is one of the common links between the disciplines reflected in this volume. New developments in gravimetry and space techniques will further enhance and foster interdisciplinary work in coming years.

  2. Plume capture by a migrating ridge: Analog geodynamic experiments

    NASA Astrophysics Data System (ADS)

    Mendez, J. S.; Hall, P.

    2010-12-01

    Paleomagnetic data from the Hawaii-Emperor Seamount Chain (HESC) suggests that the Hawaiian hotspot moved rapidly (~40 mm/yr) between 81 - 47 Ma but has remained relatively stationary since that time. This implies that the iconic bend in the HESC may in fact reflect the transition from a period of rapid hotspot motion to a stationary state, rather than a change in motion of the Pacific plate. Tarduno et al. (2009) have suggested that this period of rapid hotspot motion might be the surface expression of a plume conduit returning to a largely vertical orientation after having been “captured” and tilted by a migrating mid-ocean ridge. We report on a series of analog fluid dynamic experiments designed to characterize the interaction between a migrating spreading center and a thermally buoyant mantle plume. Experiments were conducted in a clear acrylic tank (100 cm x 70 cm x 50 cm) filled with commercial grade high-fructose corn syrup. Plate-driven flow is modeled by dragging two sheets of Mylar film (driven by independent DC motors) in opposite directions over the surface of the fluid. Ridge migration is achieved by moving the point at which the mylar sheets diverge using a separate motor drive. Buoyant plume flow is modeled using corn syrup introduced into the bottom of the tank from an external, heated, pressurized reservoir. Small (~2 mm diameter), neutrally buoyant Delrin spheres are mixed into reservoir of plume material to aid in visualization. Plate velocities and ridge migration rate are controlled and plume temperature monitored using LabView software. Experiments are recorded using digital video which is then analyzed using digital image analysis software to track the position and shape of the plume conduit throughout the course of the experiment. The intersection of the plume conduit with the surface of the fluid is taken as an analog for the locus of hotspot volcanism and tracked as a function of time to obtain a hotspot migration rate. Experiments are

  3. The Role of Carbon in Extrasolar Planetary Geodynamics and Habitability

    NASA Astrophysics Data System (ADS)

    Unterborn, Cayman T.; Kabbes, Jason E.; Pigott, Jeffrey S.; Reaman, Daniel M.; Panero, Wendy R.

    2014-10-01

    The proportions of oxygen, carbon, and major rock-forming elements (e.g., Mg, Fe, Si) determine a planet's dominant mineralogy. Variation in a planet's mineralogy subsequently affects planetary mantle dynamics as well as any deep water or carbon cycle. Through thermodynamic models and high pressure diamond anvil cell experiments, we demonstrate that the oxidation potential of C is above that of Fe at all pressures and temperatures, indicative of 0.1-2 Earth-mass planets. This means that for a planet with (Mg+2Si+Fe+2C)/O > 1, excess C in the mantle will be in the form of diamond. We find that an increase in C, and thus diamond, concentration slows convection relative to a silicate-dominated planet, due to diamond's ~3 order of magnitude increase in both viscosity and thermal conductivity. We assert then that in the C-(Mg+2Si+Fe)-O system, there is a compositional range in which a planet can be habitable. Planets outside of this range will be dynamically sluggish or stagnant, thus having limited carbon or water cycles leading to surface conditions inhospitable to life as we know it.

  4. The role of carbon in extrasolar planetary geodynamics and habitability

    SciTech Connect

    Unterborn, Cayman T.; Kabbes, Jason E.; Pigott, Jeffrey S.; Panero, Wendy R.; Reaman, Daniel M.

    2014-10-01

    The proportions of oxygen, carbon, and major rock-forming elements (e.g., Mg, Fe, Si) determine a planet's dominant mineralogy. Variation in a planet's mineralogy subsequently affects planetary mantle dynamics as well as any deep water or carbon cycle. Through thermodynamic models and high pressure diamond anvil cell experiments, we demonstrate that the oxidation potential of C is above that of Fe at all pressures and temperatures, indicative of 0.1-2 Earth-mass planets. This means that for a planet with (Mg+2Si+Fe+2C)/O > 1, excess C in the mantle will be in the form of diamond. We find that an increase in C, and thus diamond, concentration slows convection relative to a silicate-dominated planet, due to diamond's ∼3 order of magnitude increase in both viscosity and thermal conductivity. We assert then that in the C-(Mg+2Si+Fe)-O system, there is a compositional range in which a planet can be habitable. Planets outside of this range will be dynamically sluggish or stagnant, thus having limited carbon or water cycles leading to surface conditions inhospitable to life as we know it.

  5. International Tectonic Map of the Circumpolar Arctic and its Significance for Geodynamic Interpretations

    NASA Astrophysics Data System (ADS)

    Petrov, O. V.; Morozov, A.; Shokalsky, S.; Leonov, Y.; Grikurov, G.; Poselov, V.; Pospelov, I.; Kashubin, S.

    2011-12-01

    In 2003 geological surveys of circum-arctic states initiated the international project "Atlas of Geological Maps of Circumpolar Arctic at 1:5 000000 scale". The project received active support of the UNESCO Commission for the Geological Map of the World (CGMW) and engaged a number of scientists from national academies of sciences and universities. Magnetic and gravity maps were prepared and printed by the Norwegian Geological Survey, and geological map was produced by the Geological Survey of Canada. Completion of these maps made possible compilation of a new Tectonic Map of the Arctic (TeMAr), and this work is now in progress with Russian Geological Research Institute (VSEGEI) in the lead of joint international activities. The map area (north of 60o N) includes three distinct roughly concentric zones. The outer onshore rim is composed of predominantly mature continental crust whose structure and history are illustrated on the map by the age of consolidation of craton basements and orogenic belts. The zone of offshore shelf basins is unique in dimensions with respect to other continental margins of the world. Its deep structure can in most cases be positively related to thinning and rifting of consolidated crust, sometimes to the extent of disruption of its upper layer, whereas the pre-rift evolution can be inferred from geophysical data and extrapolation of geological evidence from the mainland and island archipelagoes. The central Arctic core is occupied by abyssal deeps and intervening bathymetric highs. The Eurasia basin is commonly recognized as a typical oceanic opening separating the Barents-Kara and Lomonosov Ridge passive margins, but geodynamic evolution of Amerasia basin are subject to much controversy, despite significant intensification of earth science researchin the recent years. A growing support to the concept of predominance in the Amerasia basin of continental crust, particularly in the area concealed under High Arctic Large Igneous Province, is

  6. Neotethyan closure history of western Anatolia: a geodynamic discussion

    NASA Astrophysics Data System (ADS)

    Pourteau, Amaury; Oberhänsli, Roland; Candan, Osman; Barrier, Eric; Vrielynck, Bruno

    2016-01-01

    This paper addresses the lithosphere-scale subduction-collision history of the eastern termination of the Aegean retreating subduction system, i.e. western Anatolia. Although there is some general consensus on the protracted subduction evolution of the Aegean since the early Cenozoic at least, correlation with western Anatolia has been widely debated for more than several decades. In western Anatolia, three main tectonic configurations have been envisaged in the past years to reconstruct slab dynamics during the closure of the Neotethyan oceanic realm since the Late Cretaceous. Some authors have suggested an Aegean-type scenario, with the continuous subduction of a single lithospheric slab, punctuated by episodic slab roll-back and trench retreat, whereas others assumed a discontinuous subduction history marked by intermittent slab break-off during either the Campanian (ca. 75 Ma) or the Early Eocene (ca. 55-50 Ma). The third view implies three partly contemporaneous subduction zones. Our review of these models points to key debated aspects that can be re-evaluated in the light of multidisciplinary constraints from the literature. Our discussion leads us to address the timing of subduction initiation, the existence of hypothetical ocean basins, the number of intervening subduction zones between the Taurides and the Pontides, the palaeogeographic origin of tectonic units and the possibility for slab break-off during either the Campanian or the Early Eocene. Thence, we put forward a favoured tectonic scenario featuring two successive phases of subduction of a single lithospheric slab and episodic accretion of two continental domains separated by a continental trough, representing the eastern end of the Cycladic Ocean of the Aegean. The lack of univocal evidence for slab break-off in western Anatolia and southward-younging HP/LT metamorphism in continental tectonic units (from ~85, 70 to 50 Ma) in the Late Cretaceous-Palaeogene period suggests continuous subduction

  7. Geodynamic and Magmatic Evolution of the Eastern Anatolian-Arabian Collision Zone, Turkey

    NASA Astrophysics Data System (ADS)

    Keskin, Mehmet

    2014-05-01

    The Eastern Anatolian-Arabian Collision Zone represents a crucial site within the Tethyan domain where a subduction system involving a volcanic arc (i.e. Cretaceous to Oligocene Pontide volcanic arc in the north) associated with a large subduction-accretion complex (i.e. Cretaceous to Oligocene Eastern Anatolian Accretionary Complex i.e. "EAAC" in the south) turned later into a major continental collision zone that experienced a series of geodynamic events including lithospheric delamination, slab-steepening & breakoff, regional domal uplift, widespread volcanism and tectonic escape via strike slip fault systems. The region includes some of the largest volcanic centers (e.g. Karacadaǧ, Aǧırkaya caldera, Ararat, Nemrut, Tendürek and Süphan volcanoes) and plateaus (e.g. The Erzurum-Kars Plateau) as well as the largest transform fault zones in the Mediterranean region. A recent geodynamic modeling study (Faccenna et al., 2013) has suggested that both the closure of the Tethys Ocean and the resultant collision were driven by a large scale and northerly directed asthenospheric mantle flow named the "Tethyan convection cell". This convection cell initiated around 25 Ma by combined effects of mantle upwelling of the Afar super plume located in the south, around 3,000 km away from the collision zone and the slab-pull of the Tethyan oceanic lithosphere beneath Anatolia in the north. The aforementioned mantle flow dragged Arabia to the north towards Eastern Anatolia with an average velocity of 2 cm/y for the last 20 My, twice as fast as the convergence of the African continent (i.e. 1 cm/y) with western and Central Turkey. This 1 cm/y difference resulted in the formation of the left lateral Dead Sea Strike Slip Fault between the African and Arabian plates. Not only did this mantle flow result in the formation of a positive dynamic topography in the west of Arabian block, but also created a dynamic tilting toward the Persian Gulf (Faccenna et al., 2013). Another

  8. On information-provided monitoring of geodynamic processes in the Kuznetsk Coal Basin in the conditions of highly intensive sub-soil usage

    SciTech Connect

    Oparin, V.N.; Potapov, V.P.; Tanaino, A.S.

    2006-09-15

    It is shown that formation of underground hollows of the Kuznetsk Coal Basin (Kuzbass), induced by opencut and underground mining has reached an intensity of 1.3-1.5 million m{sup 3}/day. In the conditions of high concentration of mines and open-cuts in small areas, a regional monitoring network is required in view of a generated geomechanical space, hazardous in geodynamic manifestations. A developed information support of this network is presented, including information models of a geological environment and database obtained from instrumental observations on geomechanical processes. The equations of connection between structural and strength characteristics of rocks, their metamorphization grade and occurrence depth are given for five geological-tectonic zones of the Kuzbass as a way of prediction of their properties.

  9. Detrital provenance of Early Mesozoic basins in the Jiangnan domain, South China: Paleogeographic and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Xu, Xianbing; Tang, Shuai; Lin, Shoufa

    2016-04-01

    Detrital provenance analysis is an effective way to understand paleogeographic change and geodynamics. In this paper, we present petrological, whole-rock geochemical and detrital zircon U-Pb geochronological analysis of Early and Middle Jurassic terrestrial clastic rocks in the Jingdezhen Basin and the Huangshan Basin in the Jiangnan domain, South China. Petrology and whole-rock geochemistry show that the source rocks are dominated by intermediate to acid component. The Chemical Index of Alteration ranges from 69 to 86, suggesting a moderate weathering history for the source rocks. The Early-Middle Jurassic sediments in the Jingdezhen and Huangshan basins were mostly sourced from magmatogenic greywackes and felsic magmatic rocks, respectively. Detrital zircons have seven age peaks at ~ 240 Ma, ~ 430 Ma, ~ 1390 Ma, ~ 1880 Ma, ~ 2500 Ma, -3200 Ma and 788-999 Ma (a wide peak). Provenance analysis indicates that the source rocks are in the Jiangnan domain, the Northwest Zhejiang Basin and the Wuyishan domain. Combining these with previous results and paleocurrent directions, we infer that the NE-trending Wuyishan and Xuefengshan domains and the nearly E-W-Jiangnan domain and Nanling tectonic belt were orogenic uplifts and watersheds during the Late Triassic to Middle Jurassic. The Early Mesozoic geodynamics in the South China Block was related to the westward subduction of the Paleo-Pacific Plate and the northward continent-continent collision following the closure of the Paleo-Tethys Ocean.

  10. Geodetic implications on block formation and geodynamic domains in the South Shetland Islands, Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Berrocoso, M.; Fernández-Ros, A.; Prates, G.; García, A.; Kraus, S.

    2016-01-01

    The South Shetland Islands archipelago is dynamically complex due to its tectonic surroundings. Most islands are part of a formerly active volcanic arc, although Deception, Penguin and Bridgeman Islands, as well as several submarine volcanoes, are characterized by active back-arc volcanism. Geodetic benchmarks were deployed and the movement of the lithosphere to which they were fixed measured to provide geodynamic insight for the South Shetland Islands, Bransfield Basin and Antarctic Peninsula area based on surface deformation. These benchmarks' data add spatial and temporal coverage to previous results. The results reveal two different geodynamic patterns, each confined to a distinct part of the South Shetland Islands archipelago. The inferred absolute horizontal velocity vectors for the benchmarks in the northeastern part of the archipelago are consistent with the opening of the Bransfield Basin, while benchmark vectors in the southwestern part of the archipelago are similar to those of the benchmarks on the Antarctic Peninsula. In between, Snow, Deception and Livingston Islands represent a transition zone. In this area, the horizontal velocity vectors relative to the Antarctic plate shift northeastwards from N to NW. Furthermore, the South Shetland Islands benchmarks, except for that at Gibbs (Elephant) Islands, indicate subsidence, which might be a consequence of the slab roll-back at the South Shetland Trench. In contrast, the uplift revealed by the Antarctic Peninsula benchmarks suggests glacial isostatic adjustment after the Larson B ice-shelf breakup.

  11. Finite-frequency tomography of P and S waves in the Carpathian-Pannonian region: Implications for geodynamics of the continental collision

    NASA Astrophysics Data System (ADS)

    Ren, Y.; Stuart, G. W.; Houseman, G. A.; Dando, B. D.; Ionescu, C.; Hegedus, E.; Radovanovic, S.

    2011-12-01

    The Carpathian-Pannonian system which is the most tectonically active region in Eastern and Central Europe, represents an unique geodynamical case in continental collision zone for studying the interaction between the surface tectonic processes and the deep lithospheric and mantle processes. Particularly, the geodynamical processes involved in the formation of both Pannonian basin and Vrancea seismogenic zone are still debated today. Here, we present high-resolution upper mantle structures beneath the region from finite-frequency tomography using P and S waves in order to bring constraints on geodynamical models. We have selected teleseismic earthquakes with magnitude greater than 5.5, which occurred between 2005 and 2010. The data were recorded on 57 temporary stations deployed in the South Carpathian Project, 56 temporary stations deployed in the earlier Carpathian Basins Project (CBP), and 50 permanent broadband stations. The differential travel times are measured in high, intermediate and low frequencies (0.5-2.0 Hz, 0.1-0.5 Hz and 0.03-0.1 Hz for both P-wave, 0.1-0.5 Hz, 0.05-0.1 Hz and 0.02-0.05 Hz for S-wave), and are inverted according to the 3-D finite-frequency formulation to produce P and S-wave velocity maps at different depths in the mantle. Our images show the presence of a sub-vertical fast material beneath the eastern Alps which extends across the centre of the Pannonian region below ~ 300 km depth. It extends downward into the mantle transition zone and appears to spread outward beneath the entire basin. The upper mantle below the Pannonian basin is dominated by a slow anomaly extending down to ~ 300 km depth. We suggest that a late stage of gravitational instability with detachment of cold mantle lithospheric downwellings is occurring beneath the eastern Alps in the present-day. The same mechanism could also have occurred below the Pannonian basin in the past and though explain the mantle lithospheric extension. In the Vrancea Zone, the seismicity

  12. Geodynamic constraints on deep-mantle buoyancy: Implications for thermochemical structure of LLSVP and large-scale upwellings under the Pacific Ocean.

    NASA Astrophysics Data System (ADS)

    Forte, A. M.; Glisovic, P.; Grand, S. P.; Lu, C.; Simmons, N. A.; Rowley, D. B.

    2015-12-01

    Convection-related data constrain lower-mantle density anomalies that contribute to mantle convective flow. These include global gravity and topography anomalies, plate motions and excess ellipticity of the core-mantle boundary (CMB). Each datum possesses differing wavelength and depth dependent resolution of heterogeneity and thus the strongest constraints on density anomalies are obtained by jointly inverting all data in combination. The joint-inversions employ viscous response functions (i.e. geodynamic kernels) for a flowing mantle. Non-uniqueness is greatly reduced by including seismic and mineral physics data into the joint inversions. We present the results of inversions where seismic and geodynamic data are singly and jointly inverted to map density anomalies. Employing mineral physical data we estimate thermal and compositional contributions to density anomalies. We evaluate the extent to which "Large Low Shear Velocity Provinces" (LLSVP) are anomalous and we determine their impact on the global pattern of convective flow. The inversions yield consistent maps of lower-mantle flow (see figure) that are dominated by two large upwellings, under the Western Pacific (next to the Caroline microplate) and Eastern Pacific (under the East Pacific Rise). These hot upwellings effectively delimit the margins of the Pacific LLSVP, suggesting intrinsic negative buoyancy within this structure impedes large-scale upwellings in the mantle above. These two upwellings do not resemble classical mantle "plumes" found in simple isoviscous and isochemical convection models but their contribution to mass and heat transport across the lower mantle is significant and thus behave similarly to plumes. The large scale of these upwellings may be understood in terms of the high viscosity in the lower mantle, inferred from geodynamic constraints on mantle rheology. Very-long time convection simulations initiated with present-day structure inferred from these inversions show the two

  13. Daly Lecture: Geochemical Insights into Mantle Geodynamics and Plume Structure (Invited)

    NASA Astrophysics Data System (ADS)

    Weis, D. A.

    2010-12-01

    It is almost 50 years since the first documentation of mantle heterogeneity through the study of ocean island basalts (OIB) [1]. The origin, scale and source of these heterogeneities have been the subject of debate since then. One of the most common approaches in the study of mantle heterogeneities is to analyze the geochemistry of oceanic basalts brought to the surface by mantle plumes. The composition of these ocean island basalts is usually different from those extruded at mid-ocean ridges (MORB), even if some of the post-shield/rejuvenated volcanism of some islands present depleted isotopic signatures. Improved analytical precision for radiogenic isotopes, combined with statistical data treatment, allow for more detailed investigations into the geochemical variations of basalts related to hotspots and mantle plumes and for modeling of the shallow and deep plume structure. Identification of two clear geochemical trends (Loa and Kea) among Hawaiian volcanoes [2, 3] in all isotope systems [4], together with the recurrence of similar isotopic signatures at >350 kyr intervals, have implications for the dynamics and internal structure of the Hawaiian mantle plume conduit [5]. In this lecture, I will present a compilation of recent isotopic data for samples from the shield, post-shield/late shield and rejuvenated stages on Hawaiian volcanoes, focusing specifically on high-precision Pb isotopic data (MC-ICP-MS or DS, TS TIMS) and integrated with Sr, Nd and Hf isotopes. The Hawaiian mantle plume represents >80 Myr of volcanic activity in a pure oceanic setting and corresponds to a high plume flux. All isotopic systems indicate source differences for Loa- and Kea-trend volcanoes that are maintained throughout the ~1 Myr activity of each volcano and that extend back in time on all the Hawaiian Islands (to ~5 Ma). The Loa-trend source is more heterogeneous in all isotopic systems by a factor of ~1.5 than the Kea-trend source. There are also different geochemical trends

  14. Neoproterozoic geodynamic evolution of SW-Gondwana: a southern African perspective

    NASA Astrophysics Data System (ADS)

    Frimmel, H. E.; Basei, M. S.; Gaucher, C.

    2011-04-01

    Our current understanding of the tectonic history of the principal Pan-African orogenic belts in southwestern Africa, reaching from the West Congo Belt in the north to the Lufilian/Zambezi, Kaoko, Damara, Gariep and finally the Saldania Belt in the south, is briefly summarized. On that basis, possible links with tectono-stratigraphic units and major structures on the eastern side of the Río de la Plata Craton are suggested, and a revised geodynamic model for the amalgamation of SW-Gondwana is proposed. The Río de la Plata and Kalahari Cratons are considered to have become juxtaposed already by the end of the Mesoproterozoic. Early Neoproterozoic rifting led to the fragmentation of the northwestern (in today's coordinates) Kalahari Craton and the splitting off of several small cratonic blocks. The largest of these ex-Kalahari cratonic fragments is probably the Angola Block. Smaller fragments include the Luis Alves and Curitiba microplates in eastern Brazil, several basement inliers within the Damara Belt, and an elongate fragment off the western margin, named Arachania. The main suture between the Kalahari and the Congo-São Francisco Cratons is suspected to be hidden beneath younger cover between the West Congo Belt and the Lufilian/Zambezi Belts and probably continues westwards via the Cabo Frío Terrane into the Goiás magmatic arc along the Brasilia Belt. Many of the rift grabens that separated the various former Kalahari cratonic fragments did not evolve into oceanic basins, such as the Northern Nosib Rift in the Damara Belt and the Gariep rift basin. Following latest Cryogenian/early Ediacaran closure of the Brazilides Ocean between the Río de la Plata Craton and the westernmost fragment of the Kalahari Craton, the latter, Arachania, became the locus of a more than 1,000-km-long continental magmatic arc, the Cuchilla Dionisio-Pelotas Arc. A correspondingly long back-arc basin (Marmora Basin) on the eastern flank of that arc is recognized, remnants of which

  15. Geodynamic problems

    NASA Technical Reports Server (NTRS)

    Kaula, W. M.

    1978-01-01

    The understanding of the solid earth and suggestions of what measurements should be undertaken based on estimates of instrumental feasibilities were reviewed. The observations include: (1) earth evolution and mantle convection; (2) lithosphere-asthenosphere-surface load interaction; (3) glacier-ocean-solid earth interaction; (4) solid earth interactions with the sun, moon, core, oceans, and atmosphere; (5) zones of strain accumulation; and (6) earthquakes.

  16. Application of a long-range terrestrial laser scanner in research on lowland geodynamic processes

    NASA Astrophysics Data System (ADS)

    Wiśniewska, Daria; Kramkowski, Mateusz; Tyszkowski, Sebastian

    2015-04-01

    Progress in the LIDAR technology allows collection of data over a longer range and with a higher precision than most of geodetic measurement methods. It is particularly useful in areas that are inaccessible, dangerous, or with a highly variable morphology. These include mountains, steep slopes of river valleys, and edges of water bodies. Because of a high variation in altitude, they are particularly prone to geodynamic processes. In recent years, such areas have been surveyed more and more often with the use of Airborne Laser Scanning, but the high costs and low frequency of surveys make it difficult to trace the dynamics of phenomena and recorded processes. A few years ago, a new method for imaging of land surfaces started to be used: Terrestrial Laser Scanning. The latest scanners make long-distance scanning possible, up to several kilometres), which until recently had been reserved exclusively for Airborne Laser Scanning. The ease and mobility of scanning allows recording of geodynamic processes immediately after their initiation and their constant monitoring, with a high frequency of data collection. The usefulness of long-distance Terrestrial Laser Scanning is presented here on the basis of mass movements on slopes of a large river valley (the lower Vistula valley) and edges of artificial water bodies. These areas were selected because of a high dynamics of geodynamic processes. The scanning was performed at a distance of 2-4 km from the objects, with a resolution of 0.002°. Such parameters of the equipment and the broad scope and long range enable researchers simultaneous scanning of wide belts of the marginal zone. They also allow precise imaging of slopes, including the microforms that cannot be recorded with any other method. Thanks to the characteristics of laser beam reflection, it is also possible to perform analyses that allow identification of landslide initiation, as well as initial stages of erosion of river banks and edges of water bodies. In this

  17. Gnss Geodetic Monitoring as Support of Geodynamics Research in Colombia, South America

    NASA Astrophysics Data System (ADS)

    Mora-Paez, H.; Acero-Patino, N.; Rodriguez-Zuluaga, J. S.; Diederix, H.; Bohorquez-Orozco, O. P.; Martinez-Diaz, G. P.; Diaz-Mila, F.; Giraldo-Londono, L. S.; Cardozo-Giraldo, S.; Vasquez-Ospina, A. F.; Lizarazo, S. C.

    2013-05-01

    To support the geodynamics research at the northwestern corner of South America, GEORED, the acronym for "Geodesia: Red de Estudios de Deformación" has been adopted for the Project "Implementation of the National GNSS Network for Geodynamics" carried out by the Colombian Geological Survey, (SGC), formerly INGEOMINAS. Beginning in 2007, discussions within the GEORED group led to a master plan for the distribution of the base permanent GPS/GNSS station array and specific areas of interest for campaign site construction. The use of previously identified active faults as preferred structures along which stresses are transferred through the deformational area led to the idea of segmentation of the North Andes within Colombia into 20 tectonic sub-blocks. Each of the 20 sub-blocks is expected to have, at least, three-four permanent GPS/GNSS stations within the block along with construction of campaign sites along the boundaries. Currently, the GEORED Network is managing 46 continuously including: 40 GEORED GPS/GNSS continuously operating stations; 4 GNSS continuously operating stations provided by the COCONet (Continuously Operating Caribbean GPS Observational Network) Project; the Bogotá IGS GPS station (BOGT), installed in 1994 under the agreement between JPL-NASA and the SGC; and the San Andres Island station, installed in 2007 under the MOU between UCAR and the SGC. In addition to the permanent installations, more than 230 GPS campaign sites have been constructed and are being occupied one time per year. The Authority of the Panama Canal and the Escuela Politecnica de Quito have also provided data of 4 and 5 GPS/GNSS stations respectively. The GPS data are processed using the GIPSY-OASIS II software, and the GPS time series of daily station positions give fundamental information for both regional and local geodynamics studies. Until now, we have obtained 100 quality vector velocities for Colombia, 23 of them as part of the permanent network. The GPS/GNSS stations

  18. Understanding the geodynamic setting of São Miguel, Azores: A peculiar bit of mantle in the Central Atlantic

    NASA Astrophysics Data System (ADS)

    Wilson, M.; Houlie, N.; Khan, A.; Lithgow-Bertelloni, C. R.

    2012-12-01

    The Azores Plateau and Archipelago in the Central Atlantic Ocean has traditionally been considered as the surface expression of a deep mantle plume or hotspot that has interacted with a mid-ocean ridge. It is geodynamically associated with the triple junction between the North American, African and Eurasian plates. (Yang et al., 2006) used finite frequency seismic tomography to demonstrate the presence of a zone of low P-wave velocities (peak magnitude -1.5%) in the uppermost 200km of the mantle beneath the plateau. The tomographic model is consistent with SW deflection of a mantle plume by regional upper mantle shear flow driven by absolute plate motions. The volcanic island of Sao Miguel is located within the Terceira Rift, believed to represent the boundary between the African and Eurasian plates; magmatic activity has been characterised by abundant basaltic eruptions in the past 30,000 years. The basalts are distinctive within the spectrum of global ocean island basalts for their wide range in isotopic composition, particularly in 87Sr/86Sr. Their Sr-Nd-Pb isotopic compositions show systematic variations from west to east across the island which can be interpreted in terms of melting of a two-component mantle source. The low melting point (enriched) component in the source has been attributed to recycled ancient (~3 Ga) oceanic crust(Elliott et al., 2007). Using the thermo-barometry approach of (Lee et al., 2009) we demonstrate that the pressure and temperature of magma generation below Sao Miguel increase from west (2 GPa, 1425 °C) to east (3.8 GPa, 1575 °C), consistent with partial melting along a mantle geotherm with a potential temperature of ~ 1500 °C. This is consistent with the magnitude of the thermal anomaly beneath the Azores Plateau (ΔT ~ 150-200 °C) inferred on the basis of the seismic tomography study. The site of primary magma generation extends from the base of the local lithosphere (~ 50 km) to ~ 125 km depth. To understand the geodynamic

  19. The Calama-Olacapato-El Toro fault system in the Puna Plateau, Central Andes: Geodynamic implications and stratovolcanoes emplacement

    NASA Astrophysics Data System (ADS)

    Norini, Gianluca; Baez, Walter; Becchio, Raul; Viramonte, Jose; Giordano, Guido; Arnosio, Marcelo; Pinton, Annamaria; Groppelli, Gianluca

    2013-11-01

    The structural evolution of the Puna Plateau is characterized by the activity of both orogen-parallel and orogen-oblique faults. Understanding the possible relationship between these two structural styles, their geodynamic implications and the influence on the migration of magmas is important to get insights into the tectonic and magmatic evolution of the Central Andes. In this study, we present a structural analysis of the orogen-oblique Calama-Olacapato-El Toro fault system and the surrounding orogen-parallel thrust faults in the central-eastern Puna Plateau. Morphostructural analysis and field mapping reveal the geometry, kinematics and dynamics of the tectonic features in the studied area. We propose a three-dimensional geometrical reconstruction of the main fault planes showing their attitude and intersections at depth. The study indicates that the crust underwent simultaneous deformation along both the vertical transcurrent Calama-Olacapato-El Toro fault system and the low-angle thrust faults, and that the back-arc portion of the Calama-Olacapato-El Toro fault system developed as a transfer zone among the main N-striking thrusts. Our model considers that both orogen-parallel and orogen-oblique fault systems should be regarded as parts of the same tectonic system, accommodating crustal shortening of a thickened crust. The study suggests that the tectonic control on the magma and fluid circulation in the crust is mainly related to the geometry of the fault planes and the orientation of the stress field, with a previously unrecognized important role played by the orogen-parallel thrust faults on the emplacement of the stratovolcanoes.

  20. Tectonic and geodynamic setting of oil and gas basins of the Soviet Union

    SciTech Connect

    Khain, V.E.; Sokolov, B.A. ); Kleshchev, K.A.; Shein, V.S. )

    1991-02-01

    Within the territory of the Soviet Union and its off-shore economic zone are about 70 sedimentary basins containing oil and gas. The basins include almost all basin types described in present-day plate-tectonic classifications, namely (1) intracontinental and pericontinental rifts, suprarift syneclises, and zones of pericratonic downwarps; (2) ancient passive margins of continents with adjacent overthrust fold system; (3) modern passive margins of continents; (4) zones of convergence of lithospheric plates (i.e., zones of subduction of oceanic plates below continental plates); and (5) zones of collision of continental lithospheric plates. So, far, the only type of basin not identified within the territory of the Soviet Union is the pull-apart basin. The location and distribution of oil and gas deposits in the section of a basin, prevailing types of traps, and scale of potential resources are all features influenced by the geodynamic type of the basin.

  1. Geodynamic settings of microcontinents, non-volcanic islands and submerged continental marginal plateau formation

    NASA Astrophysics Data System (ADS)

    Dubinin, Evgeny; Grokholsky, Andrey; Makushkina, Anna

    2016-04-01

    Complex process of continental lithosphere breakup is often accompanied by full or semi isolation of small continental blocks from the parent continent such as microcontinents or submerged marginal plateaus. We present different types of continental blocks formed in various geodynamic settings. The process depends on thermo-mechanical properties of rifting. 1) The continental blocks fully isolated from the parent continent. This kind of blocks exist in submerged form (Elan Bank, the Jan-Mayen Ridge, Zenith Plateau, Gulden Draak Knoll, Batavia Knoll) and in non-submerged form in case of large block size. Most of listed submerged blocks are formed in proximity of hot-spot or plume. 2) The continental blocks semi-isolated from the parent continent. Exmouth Plateau, Vøring, Agulhas, Naturaliste are submerged continental plateaus of the indicated category; Sri Lanka, Tasmania, Socotra are islands adjacent to continent here. Nowadays illustration of this setting is the Sinai block located between the two continental rifts. 3) The submerged linear continental blocks formed by the continental rifting along margin (the Lomonosov Ridge). Suggested evolution of this paragraph is the rift propagation along existing transtensional (or another type) transform fault. Future example of this type might be the California Peninsula block, detached from the North American plate by the rifting within San-Andreas fault. 4) The submerged continental blocks formed by extensional processes as the result of asthenosphere flow and shear deformations. Examples are submerged blocks in the central and southern Scotia Sea (Terror Bank, Protector Basin, Discovery Bank, Bruce Bank etc.). 5) The continental blocks formed in the transform fault systems originated in setting of contradict rifts propagation in presence of structure barriers, rifts are shifted by several hundreds kilometers from each other. Examples of this geodynamic setting are Equatorial Atlantic at the initial development stage

  2. Upper Mantle Anisotropy Beneath the Ordos Basin in China and its geodynamic significance

    NASA Astrophysics Data System (ADS)

    Wang, Liangshu; Mi, Ning; Huang, Zhouchuan; Xu, Mingjie

    2016-04-01

    The Ordos basin is a stable block between the Eastern and Western China, and surrounded by active thrust belts and extensional graben systems. Investigations on the upper-mantle deformation and flowing pattern beneath the Ordos basin will help to illuminate how the different geodynamical processes affect the intra-continental deformation in China. From five portable seismic arrays in the southern Ordos block, SKS and SKKS phases are used to estimate the S-wave splitting parameters. The results show distinct anisotropy in the upper mantle beneath the Ordos area. To the southwest of the Ordos, the orientations of anisotropy are NNW-SSE, which are subparallel to the thrust belt and boundary faults between the Ordos and the Northeast Tibetan Plateau, mapping a clockwise mantle flow induced by the eastward extrusion of the Northeast Tibetan Plateau and deflected by the Ordos block. To the south of the Ordos, mantle flow direction is nearly E-W, parallel to the strike-slip direction of the Weihe graben, indicating an eastward mantle flow from the NE Tibetan plateau to the eastern part of China. To the east of the Ordos, the direction of fast S-wave is changing slowly from NWW-SSE to E-W, perpendicular to the main tectonic direction in Shanxi graben system, showing an extension feature similar to that of the North China. Above results illuminate much information on the mass deformation and migration in the upper mantle resulting from the interactions between the Ordos block and its surrounding dynamic systems. It can be seen that the thrust faults and extensional grabens around the Ordos block are the positions where the anisotropy shows obvious change. As the boundary area of different blocks, they are the key areas to adjust the transformation between different geodynamic systems.

  3. The demise of the Oligo-Miocene fluvial system of the Levant and its geodynamic significance

    NASA Astrophysics Data System (ADS)

    Vachtman, Dina; Mart, Yossi

    2015-04-01

    The Levant rift system is a linear assemblage of axial rifts and their mountainous flanks that comprises two structurally distinct sections. The southern segment is built of series of secondary axial grabens, which trend northwards and are separated from each other by poorly rifted threshold zones, which is the northern extension of the Red Sea continental break-up. The northern section comprises the SW-trending Karasu - Hatay rifts, from which the Ghab graben branches southwards, which is tectonically attributed to the westward migration of Anatolia. A system of large rivers transected the southern section of the Levant from central Arabia in the east to the Mediterranean Sea in the west during the Oligo-Miocene, leaving behind 5 km thick series of clastic deposits at sea, and sandstones and conglomerates of variable thickness on land. The demise of that fluvial system was gradual, stretching from the late Miocene to the early Pleistocene, where coastal rivers were truncated from their sources due to the growth of segmented rift. The geodynamic process that constrains the development of the rifts of the southern Levant and their elevated flanks is oblique rifting, where several small rifts start the evolution along a weakness zone concurrently, separated by wide and inactive threshold zones. Gradually the rifts grow along their long axes to interconnect, shrinking the threshold zone to their disappearence. Such geodynamic history best accounts for the observations of relicts of late Miocene fluvial deposits on mountaintops, large river beds dated to the late Miocene-early Pliocene, and large marine fan deposits of early Pliocene age, where rivers continued to flow in the threshold zones, but truncated by the emerging rifts.

  4. Large-scale Geodynamics Controls Secular Trend of the Total Ozone

    NASA Astrophysics Data System (ADS)

    Steblova, R. S.

    2014-12-01

    A steady tendency towards decrease in the observed total ozone cannot be attributed to space sources of energy such as the sun and cosmic galactic rays because the energy of these sources is stable for several decades. The north-south asymmetry of ozone in the global structure of ozonosphere rules out man-made sources as a significant factor of the ozone decrease. Most of the pollutants come to the northern hemisphere; however, there is about 30% more ozone in it than in the southern hemisphere. We jointly analyzed the global distribution of ozone from TOMS satellite data, the surface of the earth's core from seismic tomography, and lithospheric plate movements from GPS and concluded the following: (1) There are sources of energy in the solid earth which contribute to the atmospheric ozone; (2) The large-scale geodynamics should be considered among the mechanisms responsible for the global structure of ozonosphere and its evolution with time. We also note similarities in the pattern of ozone caused by sources in the solid earth ("terrestrial ozone") and the patterns of geomagnetic and gravity fields. The global morphology of terrestrial ozone suggests a "breakup" in the initial ozone distribution at about the same time as a breakup of Pangea and subsequent spreading of the area of higher ozone content. A restored initial breakup is located in the oceanic region and runs northwest to southeast across Africa. We propose a large-scale geodynamic process: a convective flow in the mantle from the earth's core surface provokes the breakup of Pangea and the breakup of ozone distribution

  5. Basin geodynamics and sequence stratigraphy of Upper Triassic to Lower Jurassic deposits of Southern Tunisia

    NASA Astrophysics Data System (ADS)

    Carpentier, Cédric; Hadouth, Suhail; Bouaziz, Samir; Lathuilière, Bernard; Rubino, Jean-Loup

    2016-05-01

    Aims of this paper are to propose a geodynamic and sequential framework for the late Triassic and early Jurassic of and south Tunisia and to evidence the impact of local tectonics on the stratigraphic architecture. Facies of the Upper Triassic to Lower Jurassic of Southern Tunisia have been interpreted in terms of depositional environments. A sequential framework and correlation schemes are proposed for outcrops and subsurface transects. Nineteen middle frequency sequences inserted in three and a half low frequency transgression/regression cycles were evidenced. Despite some datation uncertainties and the unknown durations of Lower Jurassic cycles, middle frequency sequences appear to be controlled by eustasy. In contrast the tectonics acted as an important control on low frequency cycles. The Carnian flooding was certainly favored by the last stages of a rifting episode which started during the Permian. The regression accompanied by the formation of stacked angular unconformities and the deposition of lowstand deposits during the late Carnian and Norian occured during the uplift and tilting of the northern basin margins. The transpressional activity of the Jeffara fault system generated the uplift of the Tebaga of Medenine high from the late Carnian and led to the Rhaetian regional angular Sidi Stout Unconformity. Facies analysis and well-log correlations permitted to evidence that Rhaetian to Lower Jurassic Messaoudi dolomites correspond to brecciated dolomites present on the Sidi Stout unconformity in the North Dahar area. The Early-cimmerian compressional event is a possible origin for the global uplift of the northern African margin and Western Europe during the late Carnian and the Norian. During the Rhaetian and the early Jurassic a new episode of normal faulting occured during the third low frequency flooding. This tectonosedimentary evolution ranges within the general geodynamic framework of the north Gondwana margin controlled by the opening of both

  6. New insights on the deep geodynamic processes within Vrancea active seismic zone as inferred from non-tidal gravity changes

    NASA Astrophysics Data System (ADS)

    Besutiu, L.

    2012-04-01

    gravity values separated by a 20 years time-span have been obtained and compared on each pillar of the gravity network. Overall, a gravity decrease has been revealed in the area. The lowest gravity low has been recorded just within the epicentre area, along with a slight subsidence of topography. This unusual coupling of altitude decrease and gravity lowering looks clearly connected to deep geodynamic processes. 2D and 3D computer models simulating the gravity change have revealed a mass deficit (starting at approx 10 km depth) located in the epicentre area of the intermediate-depth earthquakes. It has been interpreted in terms of volume increase caused by an assumed lithosphere stretching created by the eclogitization of the lower crust penetrating the upper mantle. Sets of gravity values obtained along the geo-traverse from successive yearly campaigns have confirmed the previous assumption revealing the crust stretching as an on-going process. Based on the gravity results and their interpretation along with other kind of observations (e.g. high resolution tomography provided by joint inversion of the seismic and gravity data), some concluding remarks and speculations on the genesis of the intermediate-depth seismicity are finally presented. Acknowledgement. The research has been supported through the grant POS CCE O 2.1.2. ID 593 (contract 182/2010).

  7. Miocene Onset of Extension in the Turkana Depression, Kenya: Implications for the Geodynamic Evolution of the East African Rift System

    NASA Astrophysics Data System (ADS)

    Boone, S.; Gleadow, A. J. W.; Kohn, B. P.; Seiler, C.

    2015-12-01

    The Paleogene-Recent East African Rift System (EARS) is the foremost modern example of continental rifting, providing much of our understanding of the early stages of continental breakup. The EARS traverses two regions of crustal uplift, the Ethiopian and East African Domes, separated by the Turkana Depression. This wide region of subdued topography coincides with the NW-SE trend of the Jurassic-Paleogene Anza Rift. Opinions on the fundamental geodynamic driver for EARS rifting are divided, however, principally between models involving migrating plume(s) and a single elongated 'superplume'. While competing models have similar topographic outcomes, they predict different morphotectonic evolutions for the Turkana Depression. Models inferring southward plume-migration imply that the plume must have passed below the Turkana Depression during the Paleogene, in order to have migrated to the East African Dome by the Miocene. The possible temporal denudational response to such plume activity is testable using low temperature thermochronology. We present apatite fission track (AFT) and (U-Th)/He (AHe), and zircon (U-Th)/He (ZHe) data from the Lapurr Range, an uplifted Precambrian basement block in northern Turkana. Low radiation damage ZHe results displaying an age range of ~70-210 Ma, and combined with stratigraphic evidence, suggest ~4-6 km of Jurassic-Early Cretaceous denudation, probably associated with early Anza Rift tectonism. AFT ages of ~9-15 Ma imply subsequent burial beneath no more than ~4 km of overburden, thus preserving the Jurassic-Cretaceous ZHe ages. Together with AFT results, AHe data (~3-19 Ma) support ~2-4 km of Miocene-Pliocene uplift of the Lapurr Range in the footwall of the E-dipping Lapurr normal fault. Miocene AFT and AHe ages are interpreted to reflect the initiation of the EARS in the Turkana Depression. If extension is associated with plume activity, then upwelling in the Turkana region is unlikely to have started prior to the Miocene, much

  8. A late Tortonian paleotectonic restoration of the Gibraltar Arc System (GAS) based on the restoration of block rotations. Consequences on the GAS geodynamic evolution

    NASA Astrophysics Data System (ADS)

    Crespo-Blanc, Ana; Comas, Menchu; Balanyá, Juan Carlos

    2014-05-01

    The Gibraltar Arc System (GAS) closes the Alpine-Mediterranean orogenic system to the west and includes the Betic-Rif orogenic belt, the Alboran and Argelian-Balearic basins and the accretionary prism present in the Cadiz Gulf. Previous investigations on this orogenic system, both onshore and offshore have permit to establish the first order milestones of its Miocene to Recent geodynamic evolution. In most of the models of the geodynamic evolution of the GAS, the external boundary of the Betic-Rif orogenic wedge, initially N-S directed, sweeps from east to west the Gibraltar Arc area, acquiring his arcuate geometry during this westward movement. Nevertheless, most of these models are generally at scale equivalent to 1:10.000.000 or even smaller, and frequently based on 2D schematic cross-sections from which a model for the whole arc is deduced. This fact under evaluates not only the mass movements oblique to the selected cross-section plane, but also the diachronism of the deformation, in turn expected in a so closed arc. In this communication, we want to zoom on the Gibraltar Arc area, to draw a detailed Late Tortonian paleotectonic restoration and to highlight the consequence of this reconstruction on the final evolution of the westernmost Mediterranean. Our approach is based on: 1) the identification and characterization of structural domains of the Gibraltar Arc orogenic system and the transfer fault zones that separate them, 2) an accurate dating of the superposed events of deformations for each one of these domains, 3) the restoration of vertical axis-rotations of some of these structural domains (evidenced by paleomagnetic data previously published), and 4) the quantification of Miocene shortening in the External zones. This exercise makes us to put all together the results of twenty years of research of our teams on this natural case-study, mainly with field and marine geology techniques, and to test it through the revision of an extensive bibliography. It

  9. Gravity, Magnetics and Geodynamic evolution of the Vavilov and Marsili Backarc Basins in the Tyrrhenian Sea

    NASA Astrophysics Data System (ADS)

    Cocchi, L.; Muccini, F.; Carmisciano, C.; Caratori Tontini, F.; Bortoluzzi, G.; Ligi, M.; D'Oriano, F.; Bonatti, E.

    2012-12-01

    The Southern Tyrrhenian Sea, the youngest basin of the West Mediterranean, is made of two sub-basins partly carpeted by oceanic crust. One is the Vavilov Basin, with crust as old as 5-6 Ma; the other is the Marsili Basin where the seafloor spreading process occurred about 2.0 Ma. Each of the two basins displays a prominent volcanic ridge oriented NNE/SSW that mask the former oceanic spreading axes. In this paper, we present new potential field data obtained from Vavilov and Marsili volcanic systems during the recent cruises R/V Universitatis PROMETHEOUS 2006 and R/V Urania MAVA2011. We performed a detailed description and interpretation of the peculiar patterns of magnetic and gravity anomalies considering the morphostructural features of the oceanic seafloor basin and the particular setting of the two seamounts. Both the Vavilov and Marsili volcanic systems have a similar gravity signature with low average density (2.2 g/cm3) due probably to the eruptive mechanisms that prevailed in the two volcanoes. Both systems show NNE-SSW magnetic stripes, particularly well developed at Marsili. The two seamounts present shallow manifestation of hydrothermal alteration that in the case of Vavilov is completely extinct while in the case of the Marsili, it is still active as confirmed by the presence, on the volcano's summit of hydrothermal chimneys rich in Fe-Mn-oxyhydroxides. The similarity between the two basins may be due to similar geodynamic processes affecting the southern Tyrrhenian at different times. Since the Oligocene, the geodynamic evolution of western Mediterranean Sea was mainly driven by passive sinking of the Ionian-African plate within the European mantle modifying, step by step, the crustal setting of the Valencia region, of the Provençal basin and of the Tyrrhenian Sea. The roll back movement triggered stretching of upper-middle crust of the European plate with a different stress rate inducing variable depleting effects that can recall a typical boudinage

  10. New age constraints for the geodynamic evolution of the Neotethyan Sistan ocean, eastern Iran

    NASA Astrophysics Data System (ADS)

    Broecker, M.; Fotoohi Rad, R.; Burgess, R.; Salimi, Z.

    2012-12-01

    The paleotectonic history of Iran is characterized by the existence of numerous microcontinental blocks which record the fragmentation of a Gondwana-derived crustal segment [1]. Due to the complex interaction between individual blocks and a severe lack of robust geochronologic evidence it has yet not been possible to fully resolve the regional geodynamic framework. Detailed knowledge about the existence and life span of oceanic basins surrounding individual continental segments plays a key role in unravelling the subsequent geotectonic record that has been strongly controlled by various stages of the Arabia-Eurasia collision and the closing of different Tethyan ocean basins. The focus of this study is on the Sistan Suture Zone (SSZ) in eastern Iran which extends as a N-S trending belt over more than 700 km along the border area between Iran and Aghanistan. The SSZ formed as a result of eastward-directed subduction of a Neotethyan ocean basin beneath the Afghan block and includes a tectonic mélange consisting of disrupted meta-ophiolitic rocks within a low-grade matrix of ultramafic, mafic and pelitic schists. Large slabs of ultramafic and mafic rocks record no or only low-grade metamorphism, but some smaller (<200 m) and volumetrically subordinate blocks were affected by eclogite-, blueschist- and/or epidote amphibolite facies P-T conditions. Understanding of the petrological and geochronological record of the HP and amphibolite-facies rocks plays a key role in unravelling the geodynamic evolution of the SSZ. Published Ar-Ar data for such samples indicate a considerable range of apparent ages (ca. 116-139 Ma) for white mica and amphibole [2]. These dates were interpreted to indicate cooling below ca. 350 °C, which led to the conclusion that both HP metamorphism and the epidote-amphibolite-facies stage are older than 125 Ma. The main aim of the present study was to assess the geological significance of this data set in the light of a potential contamination with

  11. On the use of the stabilised Q1P0 element for geodynamical simulations and why this is a bad choice for buyoancy-driven flows.

    NASA Astrophysics Data System (ADS)

    Thieulot, Cedric

    2016-04-01

    Many Finite Element geodynamical codes (Fullsack,1995; Zhong et al., 2000; Thieulot, 2011) are based on bi/tri­-linear velocity constant pressure element (commonly called Q1P0), because of its ease of programming and rather low memory footprint, despite the presence of (pressure) checker­board modes. However, it is long known that the Q1P0 is not inf­-sup stable and does not lend itself to the use of iterative solvers, which makes it a less­ than­ ideal candidate for high resolution 3D models. Other attempts were made more recently (Burstedde et al., 2013; Le Pourhiet et al., 2012) with the use of the stabilised Q1Q1 element (bi/tri­-linear velocity and pressure). This element, while also attractive from an implementation and memory standpoint, suffers a major drawback due to the artificial compressibility introduced by the polynomial projection stabilization. These observations have shifted part of the community towards the Finite Difference Method while the remaining part is now embracing inf­sup stable second­ order elements [May et al., 2015; Kronbichler,2012). Rather surprinsingly, a third option exists when it comes to first ­order elements in the form of the stabilised Q1P0 element, but virtually no literature exists concerning its use for geodynamical applications. I will then recall the specificity of the stabilisation and will carry out a series of benchmark experiments and geodynamical tests to assess its performance. While being shown to work as expected in benchmark experiments, the stabilised Q1P0 element turns out to introduce first-order numerical artefacts in the velocity and pressure solutions in the case of buoyancy-driven flows. Burstedde, C., Stadler, G., Alisic, L., Wilcox, L. C., Tan, E., Gurnis, M., & Ghattas, O. (2013). Large­scale adaptive mantle convection simulation. Geophysical Journal International, 192(3), 889­906. Fullsack, P. (1995). An arbitrary Lagrangian­Eulerian formulation for creeping flows and its application in

  12. AlpArray Austria - Illuminating the subsurface of Austria and understanding of Alpine geodynamics

    NASA Astrophysics Data System (ADS)

    Fuchs, Florian; Bokelmann, Götz; Bianchi, Irene; Apoloner, Maria-Theresia; AlpArray Working Group

    2015-04-01

    AlpArray Austria is a research project to study the geodynamics of the Eastern Alps and the subsurface of Austria with a large-scale mobile broadband seismological network. AlpArray Austria is part of the AlpArray project - a unique European transnational research initiative in which 64 research institutes from 17 countries join their expertise to advance our knowledge about the structure and evolution of the lithosphere beneath the entire Alpine area. AlpArray Austria is coordinated by the Department of Meteorology and Geophysics (IMGW) at the University of Vienna and funded by the Austrian Science Fund (FWF). During spring 2015 the deployment of 42 mobile broadband seismometers (and two permanent stations) will commence and by autumn 2015 Austria will be completely covered by a dense seismological network with an average station spacing of about 40 kilometers. The mobile network consisting of 27 Reftek 151 60s sensors (provided by IMGW) and 15 Trillium 120s instruments (provided by the Dublin Institute for Advanced Studies, DIAS, Ireland) will complement the permanent Austrian seismic network operated by the Austrian Zentralanstalt für Meteorologie und Geodynamik (ZAMG) that will also install the two permanent stations. AlpArray Austria will be continuously recording high-quality ground motion data for three years. Seismic data will be distributed through the European Integrated Data Archive (EIDA) and shared with the collaborating AlpArray institutes. AlpArray Austria will shed light on the detailed geological structure and geodynamical evolution of the Eastern Alps and the subsurface of Austria. Utilizing seismic analysis methods such as shear wave splitting, receiver functions and body wave dispersion the AlpArray Austria working group at IMGW will, together with the international partners, focus on seismic anisotropy in the upper mantle, the location of interfaces and tomography, to answer outstanding questions on slab geometry and subduction polarity under

  13. Geophysical Monitoring of Geodynamic Processes of Earth Crust of Central Armenia

    NASA Astrophysics Data System (ADS)

    Pashayan, R.

    2012-12-01

    applied which allows with the help of hydrogeodynamic observations, observations of geochemistry of underground water, module of full vector of magnetic field and seismic regime of the region to carry out the monitoring of modern geodynamic processes of Armenia. The character of distribution of hydrogeodeformational processes in time and space was studied. The character of time-spatial distribution of geodynamic stress was defined. Key Words: Deformation , Geophysical Monitoring, Earthqukae Source

  14. Parallel implementation of the particle simulation method with dynamic load balancing: Toward realistic geodynamical simulation

    NASA Astrophysics Data System (ADS)

    Furuichi, M.; Nishiura, D.

    2015-12-01

    Fully Lagrangian methods such as Smoothed Particle Hydrodynamics (SPH) and Discrete Element Method (DEM) have been widely used to solve the continuum and particles motions in the computational geodynamics field. These mesh-free methods are suitable for the problems with the complex geometry and boundary. In addition, their Lagrangian nature allows non-diffusive advection useful for tracking history dependent properties (e.g. rheology) of the material. These potential advantages over the mesh-based methods offer effective numerical applications to the geophysical flow and tectonic processes, which are for example, tsunami with free surface and floating body, magma intrusion with fracture of rock, and shear zone pattern generation of granular deformation. In order to investigate such geodynamical problems with the particle based methods, over millions to billion particles are required for the realistic simulation. Parallel computing is therefore important for handling such huge computational cost. An efficient parallel implementation of SPH and DEM methods is however known to be difficult especially for the distributed-memory architecture. Lagrangian methods inherently show workload imbalance problem for parallelization with the fixed domain in space, because particles move around and workloads change during the simulation. Therefore dynamic load balance is key technique to perform the large scale SPH and DEM simulation. In this work, we present the parallel implementation technique of SPH and DEM method utilizing dynamic load balancing algorithms toward the high resolution simulation over large domain using the massively parallel super computer system. Our method utilizes the imbalances of the executed time of each MPI process as the nonlinear term of parallel domain decomposition and minimizes them with the Newton like iteration method. In order to perform flexible domain decomposition in space, the slice-grid algorithm is used. Numerical tests show that our

  15. Tectonics, recent geodynamics and seismicity of Azerbaijan part of the Greater Caucasus

    NASA Astrophysics Data System (ADS)

    Aliyev, Fuad; Kangarli, Talat; Rahimov, Fuad; Murtuzov, Zaur; Aliyev, Ziya

    2016-04-01

    Transition area of the Eastern Caucasus - Caspian Megadepression corresponds to a periclinal submergence zone of the mountain folded structure of the Greater Caucasus under Pliocene-Holocenic sedimentary complex of Caspian megabasin. Being a part of Alpine-Himalayan folded belt, Greater Caucasus has formed during alpine stage of tectogenesis under geodynamic conditions of convergent interactions between Northern and Southern Caucasus continental microplates. This process has been accompanied by pseudosubduction of the first plate under the second with formation of allochtonous accretion prism above underthrust zone. Modern folding and napping structure of the orogeny has formed as a result of the horizontal movements of different phases and subphases of alpine tectogenesis, that are presented represented by Late Cimmerian - Wallachian tectonic phases within Azerbaijan territory. Limited by meridional fault-slip zones, Caspian megadepression present itself as a young structure that layered on sublatitudinal convergent zone and developed during Late Miocene (10 million years ago) as a flexure zone between two indenters which actively move northward provoking their separation from the African continent and Arabian plate in the west and secession from Central Iranian plate of the Lut block in the east. The acting movement of Arabian plate to the north results in accumulation of the horizontal stress at the current stage of tectogenesis. Current process reveals itself both in the fragmentation of Southern and Northern Caucasus continental microplates into various-size blocks along the general and anti-Caucasus trended faults, and in consideration horizontal and vertical movements within the convergence zone. All these factors define the complexity of geodynamic condition revealed here, in which seismic activity of a transition zone become apparent. There exist the seismic zones here that are confined both to a convergence line and to the fault zones that confine Caspian

  16. Preliminary results of systematic sampling of gas manifestations in geodynamically active areas of Greece

    NASA Astrophysics Data System (ADS)

    Daskalopoulou, Kyriaki; D'Alessandro, Walter; Calabrese, Sergio; Kyriakopoulos, Konstantinos

    2016-04-01

    Greece is located on a convergent plate boundary comprising the subduction of the African Plate beneath the Eurasian, while the Arabian plate approaches the Eurasian in a northwestward motion. It is considered to be one of the most tectonically active regions of Earth with a complex geodynamic setting, deriving from a long and complicated geological history. Due to this specific geological background, conditions for the formation of many thermal springs are favoured. In the past years, almost all the already known sites of degassing (fumaroles, soil gases, mofettes, gas bubbling in cold and thermal waters) located in the Hellenic area were sampled at least one time. Collected samples were analysed for their chemical (He, Ne, Ar, O2, N2, H2, H2S, CO, CH4 and CO2) and isotopic composition (He, C and N). Some of these sites have been selected for systematic sampling. Four of them have records longer than 10 years with tens of samplings also considering some literature data. Two of the sites are located in active volcanic areas (Santorini and Nisyros) while the other two are close to actively spreading graben structures with intense seismic activity (Gulf of Korinth and Sperchios basin). Results allowed to define long term background values and also some interesting variation related to seismic or volcanic activity.

  17. Geodynamic Inferences from Integrated Ocean Drilling Program Expedition 330 to the Louisville Seamount Trail

    NASA Astrophysics Data System (ADS)

    Koppers, A. A.; Yamazaki, T.; Geldmacher, J.; Scientific Party, E. 3; IODP Expedition 330 Scientific Party

    2011-12-01

    Integrated Ocean Drilling Program (IODP) Expedition 330 drilled five different guyots in the Louisville Seamount Trail ranging in age between 80 and 50 Ma. The primary goals of this expedition were to drill a sufficiently large number of in situ lava flows at each seamount for high-quality estimates of their paleolatitudes using paleomagnetic measurements, for improving the overall age progression using high-precision 40Ar/39Ar geochronology, and for detailed geochemical studies of the volcanic evolution of these seamounts. With these data we can provide the unique record of the paleolatitude shift (or lack thereof) of the Louisville mantle plume and compare it with the ~15° paleolatitude shift observed for seamounts in the Hawaiian-Emperor Seamount Trail over the same time period. These comparisons are of fundamental importance to determine whether these two primary hotspots have moved coherently or not, to understand the nature of hotspots and convection in the Earth's mantle, and to evaluate the possibility of true polar wander. We will present new 40Ar/39Ar age data for Sites U1372, U1373, U1374 and U1376 in conjunction with Expedition 330 shipboard paleomagnetic inclination data to discuss the geodynamic inferences from the resulting paleolatitude history of the Louisville hotspot between 80 and 65 Ma.

  18. Tracing the origin of Geodynamics: The Alfred Wegener Memorial Expedition 2014

    NASA Astrophysics Data System (ADS)

    Stüwe, Kurt

    2015-04-01

    2012 marked the 100st anniversary of the seminal publications on Continental Drift Theory by Alfred Wegener. These publications (and Wegener's book "On the origin of the continents", published three years later) are widely accepted to be the fundamental breakthrough that opened the path to the Theory of Plate Tectoncis and ultimately the path to modern Geodynamics some 50 years later. In the same historic year of the 1912 publications, Alfred Wegener set off for what was to become the most dramatic of his three Greenland expeditions. On this expedition Wegener and Koch crossed the entire northern icecap of Greenland. In honour of the hundreds anniversary of Wegener's publications, the Austrian Academy of Sciences funded an expedition to trace the footsteps of the 1912 expedition in the spirit of Alfred Wegener, while also conducting modern Earth Science. This expedition that was conducted in summer 2014. For the expedition, a 1952 Cessna180 was acquired in Alaska, adapted with bush wheels, wing extensions and extra tanks and was flown by the author and one of the worlds most renown bush pilots from Alaska in a 10 day effort to Greenland. There, the entire NE Greenland Caledonides were covered and photographed. Field work for a masters projects was conducted and samples were collected from a series of some of the most remote locations in the Caledonides ever visited. Most spectacularly, the original sled of Wegeners 1912 expedition was found some 30 kilometers from its expected location in the Dove Bugt Region of northeastern Greenland.

  19. Geodynamic Implications of Himu Mantle In The Source of Tertiary Volcanics From The Veneto Region (south Eastern Alps)

    NASA Astrophysics Data System (ADS)

    Macera, P.; Gasperini, D.; Blichert-Toft; Bosch, D.; del Moro, A.; Dini, G.; Martin, S.; Piromallo, C.

    DuringTertiary times extensive mafic volcanism took place in the South-Eastern Alps, along a half-graben structure bounded by the Schio-Vicenza main fault. This mag- matism gave rise to four main volcanic centers: Lessini, Berici, Euganei, and Maros- tica. The dominating rock types are alkali basalts, basanites and transitional basalts, with hawaiites, trachybasalts, tephrites, basaltic andesites, and differentiated rocks be- ing less common. Major and trace element and Sr-Nd-Hf-Pb isotopic data for the most primitive lavas from each volcanic center show the typical features of HIMU hotspot volcanism, variably diluted by a depleted asthenospheric mantle component (87Sr/86Sr48Ma = 0.70314-0.70321; eNd48Ma = +6.4 to +6.5; eHf48Ma = +6.4 to +8.1, 206Pb/204Pb48Ma = 18.786-19.574). Since the HIMU component is consid- ered to be of deep mantle origin, its presence in a tectonic environment dominated by subduction (the Alpine subduction of the European plate below the Adria plate) has significant geodynamic implications. Slab detachment and ensuing rise of deep man- tle material into the lithospheric gap is proposed to be a viable mechanism of hotspot magmatism in a subduction zone setting. Interaction between deep-seated plume ma- terial and shallow depleted asthenospheric mantle may account for the geochemical features of the Veneto volcanics, as well as those of the so-called enriched astheno- spheric reservoir (EAR) component. Ascending counterflow of deep mantle material through the lithospheric gap to the top of the subducting slab further may induce heat- ing of the overriding plate and trigger it to partially melt. Upwelling of the resulting mafic magmas and their subsequent underplating at the mantle-lower crust bound- ary would favor partial melting of the lower crust, thereby giving rise to the bimodal mafic-felsic magmatism that characterizes the whole Periadriatic province. According to this model, the HIMU-like magmatism of the Alpine foreland is therefore

  20. Performance of Basic Geodynamic Solvers on BG/p and on Modern Mid-sized CPU Clusters

    NASA Astrophysics Data System (ADS)

    Omlin, S.; Keller, V.; Podladchikov, Y.

    2012-04-01

    Nowadays, most researchers have access to computer clusters. For the community developing numerical applications in geodynamics, this constitutes a very important potential: besides that current applications can be speeded up, much bigger problems can be solved. This is particularly relevant in 3D applications. However, current practical experiments in geodynamic high-performance applications normally end with the successful demonstration of the potential by exploring the performance of the simplest example (typically the Poisson solver); more advanced practical examples are rare. For this reason, we optimize algorithms for 3D scalar problems and 3D mechanics and design concise, educational Fortran 90 templates that allow other researchers to easily plug in their own geodynamic computations: in these templates, the geodynamic computations are entirely separated from the technical programming needed for the parallelized running on a computer cluster; additionally, we develop our code with minimal syntactical differences from the MATLAB language, such that prototypes of the desired geodynamic computations can be programmed in MATLAB and then copied into the template with only minimal syntactical changes. High-performance programming requires to a big extent taking into account the specificities of the available hardware. The hardware of the world's largest CPU clusters is very different from the one of a modern mid-sized CPU cluster. In this context, we investigate the performance of basic memory-bounded geodynamic solvers on the large-sized BlueGene/P cluster, having 13 Gb/s peak memory bandwidth, and compare it with the performance of a typical modern mid-sized CPU cluster, having 100 Gb/s peak memory bandwidth. A memory-bounded solver's performance depends only on the amount of data required for its computations and on the speed this data can be read from memory (or from the CPUs' cache). In consequence, we speed up the solvers by optimizing memory access and CPU

  1. Geodynamic models of the Wilson Cycle: From rifts to mountains to rifts

    NASA Astrophysics Data System (ADS)

    Buiter, Susanne; Tetreault, Joya; Torsvik, Trond

    2015-04-01

    The Wilson Cycle theory that oceans close and reopen along the former suture is a fundamental concept in plate tectonics. The theory suggests that subduction initiates at a passive margin, closing the ocean, and that future continental extension localises at the ensuing collision zone. Each stage of the Wilson Cycle will therefore be characterised by inherited structural and thermal heterogeneities. Here we investigate the role of Wilson Cycle inheritance by considering the influence of (1) passive margin structure on continental collision and (2) collision zones on passive margin formation. Passive margins may be preferred locations for subduction initiation because inherited faults and areas of exhumed serpentinized mantle may weaken a margin enough to localise shortening. If subduction initiates at a passive margin, the shape and structure of the passive margins will affect future continental collision. Our review of present-day passive margins along the Atlantic and Indian Oceans reveals that most passive margins are located on former collision zones. Continental break-up occurs on relatively young sutures, such as Morocco-Nova Scotia, and on very old sutures, such as the Greenland-Labrador and East Antarctica-Australia systems. This implies that it is not always post-collisional collapse that initiates the extensional phase of a Wilson Cycle. We highlight the impact of collision zone inheritance on continental extension and rifted margin architecture. We show numerical experiments of one Wilson Cycle of subduction, collision, and extension. Subduction initiates at a tapered passive margin. Closure of a 60 Ma ocean leads to continental collision and slab break-off, followed by some tens of kilometres of slab eduction. Mantle flow above the sinking detached slab enhances deformation in the rift area. The resulting rift exposes not only continental crust, but also subduction-related sediments and oceanic crust remnants. Renewed subduction in the post-collision phase is enabled by lithosphere delamination and slab rollback, leading to back-arc extension in a style similar to the Tyrrhenian Sea.

  2. Plate Tectonics: Geodynamic models of evolution of oil and gas bearing basins of Kazakhstan

    SciTech Connect

    Zholtayev, G. )

    1994-07-01

    Five types of sedimentary basins in Kazakhstan have been recognized by using plate tectonics to reinterpret geological and geophysical data: (1) intracontinental, central pre-Caspian, above rift, south pre-Caspian; (2) passive margin, east pre-Caspian; (3) back-arc, Turgan and Sir-Daria; (4) intra-arc, north Kisil-Koum, interior, Tengis and Chu-Sarisiu; and (5) marginal, north Usturt. Paleozoic history of these basins was connected with the spreading and collision of two lithospheric plates: east European and Kazakhstanian, which were separated by the paleo-Ural Ocean. Different tectonic positions of sedimentary basins were the reason for their different oil and gas potential.

  3. Paleomagnetic and geochronologic constraints on the geodynamic evolution of the Central Dinarides

    PubMed Central

    de Leeuw, Arjan; Mandic, Oleg; Krijgsman, Wout; Kuiper, Klaudia; Hrvatović, Hazim

    2012-01-01

    The geodynamic evolution of the Dinaride Mountains of southeastern Europe is relatively poorly understood, especially in comparison with the neighboring Alps and Carpathians. Here, we construct a new chronostratigraphy for the post-orogenic intra-montane basins of the Central Dinarides based on paleomagnetic and 40Ar/39Ar age data. A first phase of basin formation occurred in the late Oligocene. A second phase of basin formation took place between 18 and 13 Ma, concurrent with profound extension in the neighboring Pannonian Basin. Our paleomagnetic results further indicate that the Dinarides have not experienced any significant tectonic rotation since the late Oligocene. This implies that the Dinarides were decoupled from the adjacent Adria and the Tisza–Dacia Mega-Units that both underwent major rotation during the Miocene. The Dinaride orogen must consequently have accommodated significant shortening. This is corroborated by our AMS data that indicate post-Middle Miocene shortening in the frontal zone, wrenching in the central part of the orogen, and compression in the hinterland. A review of paleomagnetic data from the Adria plate, which plays a major role in the evolution of the Dinarides as well as the Alps, constrains rotation since the Early Cretaceous to 48 ± 10° counterclockwise and indicates 20° of this rotation took place since the Miocene. It also shows that Adria behaved as an independent plate from the Late Jurassic to the Eocene. From the Eocene onwards, coupling between Adria and Africa was stronger than between Adria and Europe. Adria continued to behave as an independent plate. The amount of rotation within the Adria-Dinarides collision zone increases with age and proximity of the sampled sediments to undeformed Adria. These results significantly improve our insight in the post-orogenic evolution of the Dinarides and resolve an apparent controversy between structural geological and paleomagnetic rotation estimates for the Dinarides as well

  4. GNSS strain rate patterns and their application to investigate geodynamical credibility of the GNSS velocities

    NASA Astrophysics Data System (ADS)

    Araszkiewicz, Andrzej; Figurski, Mariusz

    2015-04-01

    The potential that lies in the use of GNSS measurements for crustal deformation studies have already noticed in the beginning of the first of such a system (GPS). Today thanks to the development of satellite positioning techniques it is possible to detect displacement on the Earth surface with an accuracy less than 1 cm. With long-term observations we can determine the velocities even more accurately. Growing demand in the last years for GNSS applications, both for scientific and civil use, meant that new networks of the reference stations were created. Such a dense GNSS networks allow to conduct research in the field of crust deformation at a higher spatial resolution than before. In Europe most of the research focuses on Mediterranean regions, where we can monitor events resulting from the tectonic plates collision. But even in Central Europe we can see effect of Africa push. In our research we focused on Polish territory, where in the past 5 years a nearly 300 reference stations were established. With minimal movements that have been observed in Poland, a key issue in this type of research is to determine the geodynamic reliability of the estimated stations velocities. While the long-term observations enable us to determine the very accurate velocities, it hard to indicate how reliably they reflect actual tectonic movements is. In this paper we proposed a method for testing the reliability of stations velocities based on the strain rate field analysis. The method is based on the analysis of the distribution of the rate of deformation tensor components obtained for triangular elements built on the basis of assessed station. The paper presents the results of numerical simulations and initial use of the method for the Polish network of reference stations: ASG-EUPOS

  5. Continental Flood Basalts of Bennett Island, East Siberian Sea: High Arctic Geodynamics

    NASA Astrophysics Data System (ADS)

    Tegner, Christian; Pease, Victoria

    2014-05-01

    Volcanism provides a means of tracing mantle melting events and crustal evolution. The High Arctic includes a rich portfolio of volcanic rocks outcropping in the Circum-Arctic borderlands and imaged geophysically beneath the Alpha-Mendeleev Ridge that have been lumped together as a High-Arctic Large Igneous Province (HALIP). However, the ages (c. 440-60 Ma) and compositions (tholeiitic-alkaline-calc-alkaline) reported varies considerably and geological correlations remain elusive. One of the possible correlative events is the formation of continental flood basalts and sills in the Canadian Arctic Islands, Svalbard, Franz Josef Land and Bennett Island. These flood basalts have previously been linked to mantle plume melting and may represent a short-lived LIP event at c. 124-122 Ma. We present new data for a 350 m thick continental flood basalt succession at Bennett Island examined during fieldwork in Septemer 2013 on a joint Russian (VSEGEI) - Swedish (SWEDARCTIC) expedition to the De Long Archipelago. This volcanic succession is composed of 20 near-horisontal, undeformed flow units overlying a thin sedimentary succession of Cretaceous age (?) including coal seams and possibly volcaniclastic material that, in turn, unconformably overlies a more steeply dipping succession of Cambrian and Ordovician sediments. The flows are thinnest (c. 2-10 m) and aphyric to very-sparsely olivine-phyric in the lower portion. In contrast, the flows in the upper portion are thicker (>20 m) and aphyric to sparsely plagioclase-phyric. We will discuss new petrographic and compositional data for the Bennett Island flood basalts, possibly including new U-Pb age data. The aim is to evaluate their petrogenesis, to discuss their possible correlation to the flood basalt and sill successions of the Canadian Arctic Islands, Svalbard and Franz Josef Land and evaluate the geodynamic evolution of the High Arctic.

  6. Study of the recent geodynamic processes in the Kopet-Dag region

    NASA Astrophysics Data System (ADS)

    Izyumov, S. F.; Kuzmin, Yu. O.

    2014-11-01

    The time series of the uniquely long geodetic observations of recent geodynamic processes in the Kopet-Dag region are analyzed. The regional observations of contemporary vertical movements cover a 75-year period; the zonal and local systems of leveling measurements, which provide an increased degree of spatiotemporal detail (the distance between the benchmarks is less than 1 km and the measurements are repeated with a frequency of once per month to two times per annum), have been functioning for 50 years. It is shown that during the last 40-50 years, the regional stress field in the forefront of the Main Kopet-Dag thrust and collision zone of the Turanian and Iranian plates is quasi static. The annual average trend rate of strains estimated from a set of the time series of uniquely long geodetic observations is (3-5) × 10-8 yr-1, which is only one to two amplitudes of tidal deformations of the solid Earth. The local deformations in the fault zone reach the rates that are by 1.5-2 orders of magnitude higher than in the block part of the region. It is found that the segments of the Earth's surface within the axial part of the depression experience persistent uplifting, which indicates that they do not follow the scheme of inherited evolution characteristic of the fault-block structures of the region. It is demonstrated that these anomalous uplifts can be caused by the variations in the weak seismicity in the zone of the North Ashgabat Fault.

  7. Active geodynamics of the Marmara Sea region: How to combine all geophysical observations?

    NASA Astrophysics Data System (ADS)

    Karabulut, Hayrullah; Schmittbuhl, Jean; Lengliné, Olivier; Bouchon, Michel

    2016-04-01

    The Marmara Sea region is presently hosting a major seismic gap along the North Anatolian Fault (NAF). The region is located at the western termination of a unique sequence of large earthquakes initiated by the 1939 Mw 7.9 Erzincan earthquake and propagated westwards over 1000 km. Understanding the active geodynamics of the Marmara region is essential to assess the seismic behaviour of the Main Marmara Fault (MMF) and its related structures. We therefore have taken an initiative to give a comprehensive view of the regional lithosphere and the geomechanical response of the fault trying to combine all important geophysical observations. Using the broadband seismic data acquired between 2007-2015, we computed crustal seismic velocity distribution (from ambient noise tomography), crustal thickness map (from receiver function analysis) and uppermost mantle velocity distribution (from Pn tomography). The vast amount of data provides a good spatial coverage of the region and high resolution of images. Along the Main Marmara Fault (MMF), we present the seismicity below the Marmara Sea for the period the 2006-2015 to provide insights on the seismic response of the fault. The analysis shows that the seismic behaviour is varying along the fault. In addition, long term repeating earthquakes are searched along the MMF and found in the western part of the MMF. In the light of accurate and extensive observations, several open questions emerge from this compilation: Is the cumulated seismic moment released by the repeaters comparable to tectonic rate of the fault in the region? Are there any correlations between the rheology of the crust and the seismic response of the fault? Is there an influence of the fault asymmetry on the fault rupture?

  8. Cross-sectional anatomy and geodynamic evolution of the Central Pontide orogenic belt (northern Turkey)

    NASA Astrophysics Data System (ADS)

    Hippolyte, J.-C.; Espurt, N.; Kaymakci, N.; Sangu, E.; Müller, C.

    2016-01-01

    Geophysical data allowed the construction of a ~250-km-long lithospheric-scale balanced cross section of the southern Black Sea margin (Espurt et al. in Lithosphere 6:26-34, 2014). In this paper, we combine structural field data, stratigraphic data, and fault kinematics analyses with the 70-km-long onshore part of the section to reconstruct the geodynamic evolution of the Central Pontide orogen. These data reveal new aspects of the structural evolution of the Pontides since the Early Cretaceous. The Central Pontides is a doubly vergent orogenic wedge that results from the inversion of normal faults. Extensional subsidence occurred with an ENE-trend from Aptian to Paleocene. We infer that the Black Sea back-arc basin also opened during this period, which was also the period of subduction of the Tethys Ocean below the Pontides. As in the Western Pontides, the Cretaceous-Paleocene subsidence was interrupted from Latest Albian to Coniacian time by uplift and erosion that was probably related to a block collision and accretion in the subduction zone. The restoration of the section to its pre-shortening state (Paleocene) shows that fault-related subsidence locally reached 3600 m within the forearc basin. Structural inversion occurred from Early Eocene to Mid-Miocene as a result of collision and indentation of the Pontides by the Kırşehir continental block to the south, with 27.5 km (~28 %) shortening along the section studied. The inversion was characterized by NNE-trending shortening that predated the Late Neogene dextral escape of Anatolia along the North Anatolian Fault and the modern stress field characterized by NW-trending compression within the Eocene Boyabat basin.

  9. Carbon-dioxide flow measurement in geodynamically active area of West Bohemia

    NASA Astrophysics Data System (ADS)

    Vlcek, Josef; Fischer, Tomas; Heinicke, Jens

    2016-04-01

    Geodynamically active area of West Bohemia is interesting not only due to its earthquake swarms occurrence but also due to degassing flux of magmatic origin occurring in natural moffettes and mineral springs. While monitoring of earthquakes is done by a standard local seismic network, monitoring of amount of CO2 is at its initial stage. Despite lack of data, the 2014 earthquake swarm showed also very interesting increase in CO2 flow. This correlation with seismicity motivated us to develop robust and reliable methods of CO2 flow measurement, which would be sufficient to create denser monitoring network. Standard usage of gas-flowmeter for the purpose of gas flow measurement is dependent on the weather and device conditions, which makes the measurement instable in time and unreliable. Although gas-flowmeter is also accompanied with measurement of the gas pressure in the well to check flow rate value, reliability of this method is still low. This problematic behavior of the flow measurement was the reason to test new methods to measure CO2 amount - the first is based on measuring the density water with bubbles in the well by differential pressure gauge. The second one utilizes electric conductivity measurement to determine the density of bubbles in the water-gas mixture. Advantage of these methods is that their probes are directly in the well or moffette, where the concentration is measured. This approach is free of the influence of moving parts and assures the independence of measurements of environmental conditions. In this paper we show examples of obtained data series from selected sites and compare the trend of the curves, the mutual relations of the measured quantities and the influence of environmental conditions.

  10. Tectonosedimentary evolution of the Crotone basin, Italy: Implications for Calabrian Arc geodynamics

    SciTech Connect

    Smale, J.L. ); Rio, D. ); Thunell, R.C. )

    1990-05-01

    Analysis of outcrop, well, and offshore seismic data has allowed the Neogene tectonosedimentary evolution of an Ionian Sea satellite basin to be outlined. The Crotone basin contains a series of postorogenic sediments deposited since Serravallian time atop a complex nappe system emplaced in the early Miocene. The basin's evolution can be considered predominantly one of distension in a fore-arc setting punctuated by compressional events. The earliest sediments (middle-late Miocene) consist of conglomerates, marls, and evaporites infilling a rapidly subsiding basin. A basin-wide Messinian unconformity and associated intraformational folding mark the close of this sedimentary cycle. Reestablishment of marine conditions in the early Pliocene is documented by sediments which show a distinct color banding and apparent rhythmicity, which may represent the basin margin to lowermost Pliocene marl/limestone rhythmic couplets present in southern Calabria. A bounding unconformity surface of middle Pliocene age (3.0 Ma), which corresponds to a major northwest-southeast compressional event, closes this depositional sequence. The basin depocenter shifted markedly toward the southeast, and both chaotic and strong subparallel reflector seismic facies of wide-ranging thicknesses fill the depositional topography created during this tectonic episode. Basin subsidence decreases dramatically in the late Pliocene and cessates in response to basin margin uplift in the early Pleistocene. The chronostratigraphic hierarchy of these depositional sequences allows them to constrain the deformational history of the basin. In addition, similar depositional hierarchies in adjacent basins (i.e., Paola, Cefalu, and Tyrrhenian Sea) allow them to tie the stratigraphy and evolution of the Crotone basin to the geodynamic evolution of the Calabrian arc system.

  11. Markers for geodynamic stability of the Variscan basement: case study for the Montseny-Guilleries High (NE Iberia)

    NASA Astrophysics Data System (ADS)

    Parcerisa, David; Franke, Christine; Gómez-Gras, David; Thiry, Médard

    2010-05-01

    The Montseny-Guilleries High is a Miocene horst composed of Variscan basement rocks, situated in the northeastern part of the Catalan Coastal Ranges (NE Iberia). The Montseny-Guilleries High has an asymmetric profile with an abrupt faulted scarp at the southeastern margin and a smooth surface dipping to the Northwest; here Paleocene sediments of the Ebro basin margin are to some extend in onlap. The stratigraphic arrangement of the Mesozoic units in the Catalan Coastal Ranges indicate that the Montseny-Guilleries area was a relief during the Mesozoic, remaining exposed probably from the Permian to the Cretaceous [Anadón et al., 1979; Gómez-Gras, 1993]. The high subsequently has been faulted due to a rifting phase that took place during the Miocene [Anadón et al., 1979]. The geodynamic history (burial-exhumation processes and denudation rate) of the Montseny-Guilleries High can be deciphered from cooling markers, such as for example apatite fission tracks [Juez-Larré & Andriessen, 2006]. However, the cooling history of an area depends on many factors (i.e. denudation rate, variations of the geothermal gradient) that complicate interpretations [Juez-Larré & Ter Voorde, 2009]. Another solution is to search for datable paleoweathering records in order to obtain benchmarks for ancient surfaces of continental exposure. This is the case for the Permian-Triassic paleosurface, at which an extensive albitization-hematisation alteration occurred at shallow depth [Thiry et al., 2009]. Several paleoalterations have been identified in the Montsent-Guilleries High [Gómez-Gras & Ferrer, 1999]. These alterations are coupled to the smooth surface or peneplain of the northwestern margin of the high and form a paleoprofile with less altered rocks on the lower parts of the relief and more altered rocks located at the higher parts of the relief (i.e. on the peneplain). From base to top, the profile starts with week albitization-hematisation of the facies developed mainly in the

  12. Late Permian to Late Triassic basin evolution of North Vietnam: geodynamic implications for the South China and Indochina blocks

    NASA Astrophysics Data System (ADS)

    Rossignol, Camille; Bourquin, Sylvie; Hallot, Erwan; Poujol, Marc; Roger, Françoise

    2015-04-01

    The core of South East Asia is composed of a mosaic of continental blocks, among which the Indochina and the South China blocks (present day northern Vietnam), amalgamated during the Permian and/or the Triassic. Late Permian to Late Triassic geodynamic evolution of these two blocks remains controversial. The main discussion points concern the existence and the closure of an oceanic domain separating the Indochina and the South China blocks during this period. Especially, the polarity and the timing of the subduction zone that led to the collision between the blocks as well as the present location of the suture delimiting them are a matter of debate. Despite the valuable information they can provide, the sedimentary basins from northern Vietnam have been neglected in the previous studies dealing with the geodynamic evolution of South East Asia. To determine the geodynamic evolution of the area, the basins of Sam Nua and Song Da, presently located in North Vietnam, have been investigated using a combined approach involving sedimentology, geochronology (U-Pb/zircon) and geochemistry (whole-rock major and trace elements composition of both volcanic and volcaniclastic rocks). The palaeoenvironment evolution, the main unconformities, their age and the tectonic affinities of the interbedded volcanic and volcaniclastics series have been characterized for these two basins. Our results demonstrate (i) that the Song Da Basin exhibits a palaeogeographic affinity with the South China block, (ii) the occurrence of extensive calk-alkaline volcanism and associated volcaniclastic deposits in the Sam Nua Basin, related to the existence of an active magmatic arc during the Early and the lower Middle Triassic, (iii) a South dipping (present day coordinate) oceanic lithosphere beneath the Indochina block, deduced from the location of the magmatic arc south of the potential suture zones, (iv) that an angular unconformity postdates the lower Middle Triassic volcaniclastic deposits in the

  13. Archaean associations of volcanics, granulites and eclogites of the Belomorian province, Fennoscandian Shield and its geodynamic interpretation

    NASA Astrophysics Data System (ADS)

    Slabunov, Alexander

    2013-04-01

    eclogites is attributed to processes in a subducting slab. Correlation of the above complexes has revealed four alternating subduction systems: 2.88-2.82 Ga which comprises both suprasubduction (island-arc volcanics, graywackes) complexes and those from a subduction slab (eclogites), 2.81-2.78 Ga - island-arc volcanics, graywackes, granulites and eclogites; 2.75 Ga - island-arc volcanics only; 2.73-2.72 Ga - island-arc volcanics, granulites and eclogites. The duration of functioning of Meso-Neoarchaean subduction systems varies from 60 (or probably 30) to 15 Ma, which is consistent with the results of the numerical modelling (van Hunen, 2001) of subduction at mantle temperatures 125-150 degrees higher than the present temperature. This is a contribution to RFBR Project 11-05-00168 a References: Bibikova, E.V., Glebovitskii, V.A., Claesson, S. et al., 2001. Geochemistry International, 39(1) Mil'kevich, R.I., Myskova, T.A., Glebovitsky, V.A. et al. 2007. Geochemistry International, 45 Mints, M.V., Belousova, E.A., Konilov, A.N. et al., 2011. Geology, 38 Shchipansky, A.A., Khodorevskaya, L.I., Konilov, A.N., Slabunov, A.I., 2012. Russian Geology and Geophysics 53 Slabunov, A.I., Lobach-Zhuchenko, S.B., Bibikova, E.V. et al., 2006. European Lithosphere Dynamics, Memoir 32 Slabunov, A.I., 2008. Geology and geodynamics of Archean mobile belts (example from the Belomorian province of the Fennoscandian Shield van Hunen, J., 2001. Shallow and buoyant lithospheric subduction: couses and implications from thrmo-chemical numerical modelling. Theses PhD Volodichev, O.I., 1990. The Belomorian complex of Karelia: geology and petrology

  14. Geodynamics of magmatic Cu-Ni-PGE sulfide deposits: new insights from the Re-Os isotope system

    USGS Publications Warehouse

    Lambert, D.D.; Foster, J.G.; Frick, L.R.; Ripley, E.M.; Zientek, M.L.

    1998-01-01

    In this study, we reassess crustal contamination and sulfide ore-forming processes in some of the largest magmatic ore deposits, using published Re-Os isotope data and a modeling methodology that incorporates the R factor, defined as the effective mass of silicate magma with which a given mass of sulfide magma has equilibrated, in an Re-Os isotope mixing equation. We show that there is less disparity between conclusions based on Re-Os isotope data compared to other isotopic systems if the R factor is considered, Komatiite-associated Ni sulfide ore systems typically have high Os concentrations, low Re/Os ratios, and near-chondritic initial Os isotope compositions. For magmatic sulfide ores that are interpreted to have experienced relatively low R factors (2,000). Sulfide saturation in these ore systems may, therefore, have been achieved via changes in intensive parameters of the komatiite lavas (cooling or decompression) or changes in compositional parameters transparent to the Re-Os isotope system (e.g., fo2/fs2/fH2O)- Basalt-gabbro-associated Cu-Ni sulfide ore systems at Duluth, Sudbury, and Stillwater are quite distinct from those at Kambalda by having comparatively low Os concentrations, high Re/Os ratios, and high initial Os isotope compositions, These chemical and isotopic characteristics are indicative of significant interactions between their parental basaltic magmas and old crust because there are no known mantle reservoirs with such extreme geocheinical characteristics. Our modeling suggests that for Cu-Ni sulfide ores at Duluth, Sudbury, and Stillwater to maintain the observed high initial Os isotope compositions inherited from a crustal contaminant, R factors for these systems must have been low (< 10,000), consistent with their low metal concentrations. Thus, we interpret this style of base metal sulfide mineralization to be derived from crustally contaminated but less dynamic magmatic systems that did not permit extensive equilibration of sulfide magma

  15. Melt-induced weakening of the lithosphere: theory and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Gerya, T.

    2015-12-01

    long-term effective strength of the lithosphere. Thus, the low long-term strength of the melt-weakened lithosphere is associated with high volume-averaged deviatoric stress for this lithosphere. Possible geodynamic implications of melt-induced weakening for modern and early Earth tectonic processes are discussed.

  16. Geodynamic features along the Christianna-Santorini-Kolumbo tectonic line (South Aegean Sea, Greece)

    NASA Astrophysics Data System (ADS)

    Nomikou, Paraskevi; Papanikolaou, Dimitrios; Carey, Steve; Bejelou, Konstantina; Sakellariou, Dimitris; Kilias, Stefanos; Camilli, Rich; Escartin, Javier; Bell, Kathrine; Parks, Michelle

    2013-04-01

    inside Santorini caldera related to a shallow magmatic intrusion indicated by inflation. Recently, several earthquakes occurred in the region south of Christianna at the SW edge of the CSK line. This CSK line has possibly fed the post-caldera eruptions and is the main path for fluid circulation. In conclusion, the CSK tectonic line displays a special character in terms of morphology, volcanism, hydrothermal activity, seismicity and tectonic structure. It may cause important geohazards to the highly touristic Santorini island. Further seafloor investigations along this active line can provide insights into the overall geodynamic activity and aid the archipelago's hazard preparedness.

  17. Stratigraphic signatures of crustal shortening and central Andean geodynamics in the Altiplano plateau, southern Peru

    NASA Astrophysics Data System (ADS)

    Perez, Nicholas D.; Horton, Brian K.

    2014-05-01

    the coarse-grained Upper Tinajani Formation. Oligocene to early Miocene basin evolution was controlled by flexural subsidence driven by shortening along the Ayaviri fault and broader Eastern Cordillera. Subsequent basin reorganization was initiated by punctuated out-of-sequence motion along the southwest basin margin (Pasani fault). The record of variable, punctuated shortening and subsidence emphasizes the role of upper-crustal thrusting in driving hinterland tectonics. However, it remains unclear if out-of-sequence thrusting in the northern Altiplano was a localized deformation event indicative of critical wedge dynamics, changing magmatic-arc processes, or a geodynamic response to complex patterns of lithospheric removal and pulses of surface uplift.

  18. Upper mantle structures beneath the Carpathian-Pannonian region: Implications for the geodynamics of continental collision

    NASA Astrophysics Data System (ADS)

    Ren, Y.; Stuart, G. W.; Houseman, G. A.; Dando, B.; Ionescu, C.; Hegedüs, E.; Radovanović, S.; Shen, Y.; South Carpathian Project Working Group

    2012-10-01

    The Carpathian-Pannonian system of Eastern and Central Europe represents a unique opportunity to study the interaction between surface tectonic processes involving convergence, extension and convective overturn in the upper mantle. Here, we present high-resolution images of upper mantle structure beneath the region from P-wave finite-frequency teleseismic tomography to help constrain such geodynamical interactions. We have selected earthquakes with magnitude greater than 5.5 in the distance range 30°-95°, which occurred between 2006 and 2011. The data were recorded on 54 temporary stations deployed by the South Carpathian Project (2009-2011), 56 temporary stations deployed by the Carpathian Basins Project (2005-2007), and 131 national network broadband stations. The P-wave relative arrival times are measured in two frequency bands (0.5-2.0 Hz and 0.1-0.5 Hz), and are inverted for Vp perturbation maps in the upper mantle. Our images show a sub-vertical slab of fast material beneath the eastern Alps which extends eastward across the Pannonian basin at depths below ˜300km. The fast material extends down into the mantle transition zone (MTZ), where it spreads out beneath the entire basin. Above ˜300km, the upper mantle below the Pannonian basin is dominated by relatively slow velocities, the largest of which extends down to ˜200km. We suggest that cold mantle lithospheric downwelling occurred below the Pannonian Basin before detaching in the mid-Miocene. In the Vrancea Zone of SE Romania, intermediate-depth (75-180 km) seismicity occurs at the NE end of an upper mantle high velocity structure that extends SW under the Moesian Platform, oblique to the southern edge of the South Carpathians. At greater depths (180-400 km), a sub-circular high velocity anomaly is found directly beneath the seismicity. This sub-vertical high-velocity body is bounded by slow anomalies to the NW and SE, which extend down to the top of the MTZ. No clear evidence of a residual slab is

  19. Geodynamic evolution of eastern Dronning Maud Land: research highlights from an international geological-geophysical approach

    NASA Astrophysics Data System (ADS)

    Jacobs, Joachim; Ehlburg, Marlina; Laeufer, Andreas; Clark, Chris; Kleinhanns, Ilka; Andersen, Tom; Mieth, Matthias; Ruppel, Antonia; Damaske, Detlef; Lucka, Nicole; Estrada, Solveig; Jokat, Wilfried

    2014-05-01

    East Antarctica formed by amalgamation of a number of cratons along distinct Ediacaran mobile belts, including the ca. 600-500 Ma East African-Antarctic Orogen (EAAO) and the Kuunga Orogen that apparently converge in Dronning Maud Land (DML). In central DML, the major Forster Magnetic Anomaly separates rocks with Grenville-age protolith ages of ca. 1130-1000 Ma to the W, from rocks with Early Neoproterozic protolith ages, c. 1000-930 Ma, to the East. The Forster Magnetic Anomaly is therefore interpreted as a suture. New field-work during two recent international expeditions, Geodynamic Evolution of East Antarctica (GEA) I + II, and first geoscientic results reveal a complex tectonic architecture between Sør Rondane and central DML. East of the Forster anomaly, the magnetic anomaly pattern changes significantly and typical Maud type crust is not present any longer. GEA II targeted a range of nunataks between Sør Rondane and central DML that had never been visited previously (from Blåklettane and Bergekongen in the E to Urna and Sørsteinen in the W). These nunataks are dominated by medium- to high-grade metasedimentary and metavolcanic rocks of possibly Neoproterozoic age, including abundant marble and graphite schists. Sør Rondane in eastern DML, is dominated by two distinct blocks separated by the dextral Main Shear Zone. The northwestern block appears as part of the EAAO or the Kuunga Orogen, where new SHRIMP zircon data from metamorphic rims provide ages of ca. 560 Ma. The southeastern block is made up of a TTG terrane, which provides 12 new zircon crystallistation ages ranging from 1000-930 Ma. The TTG terrane has predominantly oceanic affinities and the wide range of ages might indicate long-lasting accretionary tectonics. The TTG terrane shows in part limited tectonic overprint and could be the southeastern foreland of the EAAO or the Kuunga Orogen. Close to the contact of the two blocks, grey geisses and augen-gneisses gave zircon crystallization ages of

  20. Neoproterozoic/Lower Palaeozoic geodynamic evolution of Dronning Maud Land: integrating geology and geophysics

    NASA Astrophysics Data System (ADS)

    Jacobs, Joachim; Andreas, Läufer; Clark, Chris; Kleinhanns, Ilka; Elburg, Marlina; Ruppel, Antonia; Estrada, Solveig; Damaske, Detlef; Jokat, Wilfried; Riedel, Sven; Lucka, Nicole

    2013-04-01

    East Antarctica probably formed by amalgamation of a number of cratons along distinct Ediacaran mobile belts, including the ca. 600-500 Ma East African-Antarctic Orogen (EAAO) that dissects Dronning Maud Land (DML). New field-work during the international expeditions Geodynamic Evolution of East Antarctica (GEA) I + II in the austral summers 2010/11 and 2011/12, and first geochronological results from eastern DML reveal a complex tectonic architecture across the belt. In western DML, the EAAO reworks older Mesoproterozoic crust of the Maud Belt; the westernmost boundary of the mobile belt is characterized by a major dextral transpressional shear zone. In central DML, a major magnetic anomaly, the Forster anomaly, was interpreted as a cryptic suture of the EAAO (Riedel et al. 2012). The area where the Forster anomaly crosses the DML mountains is poorly investigated so far, but appears to coincide with a major strike slip shear zone in the southern Kurze Mts. and the occurrence of major Ediacaran granulite bodies. East of the Forster anomaly, the magnetic anomaly pattern changes significantly and typical Maud type crust is not present any longer. GEA II targeted a range of nunataks between Sør Rondane and central DML that had never been visited previously (from Blåklettane and Bergekongen in the E to Urna and Sørsteinen in the W). These nunataks are dominated by medium- to high-grade metasedimentary and metavolcanic rocks of possibly Neoproterozoic age, including abundant marble and graphite schists. Sør Rondane in eastern DML, is dominated by two distinct blocks separated by the dextral Main Shear Zone. The northwestern block is still part of the eastern EAAO, where new SHRIMP zircon data from metamorphic rims provide ages of ca. 560 Ma. The southeastern block is made up of a TTG terrane, which provides four new SHRIMP zircon dates between 990-980 Ma, interpreted as igneous crystallization ages (oceanic arc). The TTG terrane shows limited tectonic overprint and

  1. Intraplate geodynamics and magmatism in the evolution of the Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Yarmolyuk, V. V.; Kuzmin, M. I.; Ernst, R. E.

    2014-10-01

    The Central Asian Orogenic Belt (CAOB) was produced as a consequence of the successive closure of the Paleoasian Ocean and the accretion of structures formed within it (island arcs, oceanic islands, and backarc basins) to the Siberian continent. The belt started developing in the latest Late Neoproterozoic, and this process terminated in the latest Permian in response to the collision of the Siberian and North China continents that resulted in closure of the Paleoasian ocean (Metcalfe, 2006; Li et al., 2014; Liu et al., 2009; Xiao et al., 2010; Didenko et al., 2010). Throughout the whole evolutionary history of this Orogenic Belt, a leading role in its evolution was played by convergent processes. Along with these processes, an important contribution to the evolution of the composition and structure of the crust in the belt was made by deep geodynamic processes related to the activity of mantle plumes. Indicator complexes of the activity of mantle plumes are identified, and their major distribution patterns in CAOB structures are determined. A number of epochs and areas of intraplate magmatism are distinguished, including the Neoproterozoic one (Rodinia breakup and the origin of alkaline rock belt in the marginal part of the Siberian craton); Neoproterozoic-Early Cambrian (origin of oceanic islands in the Paleoasian Ocean); Late Cambrian-Early Ordovician (origin of LIP within the region of Early Caledonian structures in CAOB); Middle Paleozoic (origin of LIP in the Altai-Sayan rift system); Late Paleozoic-Early Mesozoic (origin of the Tarim flood-basalt province, Central Asian rift system, and a number of related zonal magmatic areas); Late Mesozoic-Cenozoic (origin of continental volcanic areas in Central Asia). Geochemical and isotopic characteristics are determined for magmatic complexes that are indicator complexes for areas of intraplate magmatism of various age, and their major evolutionary trends are discussed. Available data indicate that mantle plumes

  2. ENVIMINE - developing environmental and geodynamical safety related to mine closure in the Barents region

    NASA Astrophysics Data System (ADS)

    Väisänen, Ulpu; Kupila, Juho; Kozyrev, Anatoly; Konukhin, Vladimir; Alakangas, Lena

    2015-04-01

    assessment of environmental impacts. Database will be used for developing recommendations for providing environmental and geodynamical safety of Umbozero. The project was partly funded by the European Union.

  3. Investigation some algorithms for solving problems of local geodynamics with using base GlonassGps stations. (Russian Title: Исследование некоторых алгоритмов решения задач локальной геодинамики с использованием базовых Глонасс/Gps станций)

    NASA Astrophysics Data System (ADS)

    Kuznetsova, E. V.; Bordovitsyna, T. V.; Chernitsov, A. M.

    2011-07-01

    In this paper mathematical modeling results of some algorithms for solving problems of local geodynamics by using base GLONASSGPS stations are presented. The statistical algorithm for trend discovering in coordinates of the point and ways of reduction of influencing random errors on results of coordinate determination with using third differences of measured distances are discussed.

  4. Unraveling the geodynamic evolution and tectonic history of the Guatemala Suture Zone: a world-class natural laboratory

    NASA Astrophysics Data System (ADS)

    Flores, K. E.; Brocard, G. Y.; Harlow, G. E.

    2013-12-01

    The Guatemala Suture Zone (GSZ) is the fault-bound region in central Guatemala that contains the present North American-Caribbean plate boundary. It is bounded by the Maya Block to the north and by the Chortís Block to the south. This major composite geotectonic unit contains a variety of ophiolites, serpentinite mélanges, and metavolcano-sedimentary sequences along with high-grade schist, gneisses, low-grade metasediments and metagranites thrusted north and south of the active Motagua fault system (MFS). This modern plate boundary has accommodated at least ~1100 km of left-lateral strike-slip motion over the Cenozoic and brings into contact the geological provinces described above. Classically, the GSZ has been interpreted as the result of a single progressive collision of a Chortís Block-related island arc with the passive margin of the Maya Block. This model was based on geochemical signatures of basaltic rocks in oceanic crust sequences both north and south of the MFS. However, results from our research challenge this single collision hypothesis. Oceanic and continental high-pressure-low-temperature (HP-LT) rocks astride the MFS have recorded multiple tectonic events revealed by their multiple metamorphic ages (Sm-Nd, U-Pb and Ar-Ar) and distinct PT paths. These tectonic events differ in age north and south of the MFS. Moreover, the continental and oceanic sequences across the MFS are geochemically and stratigraphically distinct, suggesting different tectonic origins. The southern margin of the Maya Block and the northern section of the GSZ can be clearly interpreted as a Cretaceous-Paleocene flexural passive margin tectonically overridden by ultramafic rocks and a Cretaceous island arc sequence. In contrast, the southern section of the GSZ is composed of a Carboniferous-Jurassic active margin tectonically imbricated with ultramafic rocks and a circum-Pacific Jurassic MORB and IAT metavolcano-sedimentary sequence. Thus, based on these results, we identify at

  5. Pre-collisional geodynamic context of the southern margin of the Pan-African fold belt in Cameroon

    NASA Astrophysics Data System (ADS)

    Nkoumbou, C.; Barbey, P.; Yonta-Ngouné, C.; Paquette, J. L.; Villiéras, F.

    2014-11-01

    We reassess the geodynamic context close to the Congo craton during the pre-collisional period of the Pan-African orogeny from whole-rock major and trace element compositions and isotopic data obtained in the westward extension of the Yaounde series (Boumnyebel area, Cameroon). The series consists of metasediments (micaschists, minor calc-silicate rocks and marbles) and meta-igneous rocks (hornblende gneisses, amphibolites, metagabbros, pyroxenites and talcschists) recrystallized under high-pressure conditions. Chemically, the micaschists correspond to shales and greywackes similar to the Yaounde high-grade gneisses. 87Sr/86Sr initial ratios (0.7084-0.7134), moderately negative εNd(620 Ma) values (-5.75 to -7.81), Nd model ages (1.66 < TDM < 1.74 Ga) and radiometric ages point to the conclusion that the Yaounde basin was filled with siliciclastic sediments derived from both reworked older continental crust (Palaeoproterozoic to Archaean in age) and Neoproterozoic juvenile volcanogenic material. This occurred in the same time span (625-1100 Ma) as the deposition of the Lower Dja, Yokadouma, Nola and Mintom series (Tonian-Cryogenian). Dolomitic marble associated with mafic/ultramafic rocks and characterized by high Cr (854-1371 ppm) and Ni (517-875 ppm) contents, are considered to result from chemical precipitation in relation with submarine magmatic activity. Talcschists (orthopyroxenitic to harzburgitic in composition) show primitive-mantle-normalized multi-element patterns with significant negative Nb-Ta anomalies, and slopes similar to that of average metasomatically altered lithospheric mantle. These rocks could be mantle slices involved in the collision tectonics. Amphibolites show the compositions of island-arc basalts with systematic negative Nb-Ta anomalies, 87Sr/86Sr initial ratios mostly <0.7047 and positive εNd(620 Ma) values (+1.41 to +6.58). They are considered to be the expression of incipient oceanisation to the north of the Congo craton during the

  6. Age and Geochemistry of Central American Forearc Basement Rocks (DSDP Leg 67 and 84) Reveal a Complex Geodynamic History

    NASA Astrophysics Data System (ADS)

    Geldmacher, J.; Hoernle, K. A.; Hauff, F.; Kluegel, A.; Bogaard, P. V.

    2006-12-01

    The wide shelf between Costa Rica and southern Mexico hosts an unusually broad forearc basin. Geophysical investigations imply that the entire forearc basement is composed of ophiolitic rocks similar to exposed terranes of the widespread Caribbean Large Igneous Province (CLIP). Various geodynamic models have been suggested for the origin of the CLIP including its formation above the Galápagos plume head. Besides it's origin, the spatial extent and duration of CLIP volcanism are controversial. During DSDP Leg 67 and 84 the forearc basement was drilled and various igneous rocks including basalts, dolerites, gabbros and serpentinized peridotites were recovered. We present 40Ar/39Ar laser age and geochemical data (including major- and trace elements and Sr, Nd, Pb and Hf isotope ratios) of the drilled samples in order to determine if the igneous forearc basement represents old Pacific ocean crust, ancient arc volcanism, and/or accreted intraplate volcanic rocks possibly related to the CLIP? The igneous forearc basement can be subdivided into two groups: a geochemically strongly depleted group and an underlying geochemically enriched group. Mafic rocks of the depleted group have tholeiitic to basaltic andesitic compositions and display a strong depletion in incompatible elements but distinct enrichments of fluid-mobile elements such as Rb, Ba, U, K, Pb and Sr characteristic of arc volcanism. In contrast, alkali basaltic to hawaiitic rocks of the enriched group exhibit enriched incompatible element signatures with marked depletions in K, Pb and heavy rare earth elements similar to Ocean Island Basalt (OIB). Consistent with the trace element division, both groups form two separate fields in Sr, Nd, Pb, and Hf isotopic space with the depleted group showing isotopically depleted initial compositions (low 206Pb/204Pb=17.93-18.48 and 207Pb/204Pb=15.49-15.53 but elevated ^{143}Nd/^{144}Nd= 0.51294-0.51318 and ^{176}Hf/^{177}Hf= 0.28304-0.28316) and the enriched group having

  7. Geodynamic significance of the TRM segment in the East African Rift (W-Tanzania): Active tectonics and paleostress in the Ufipa plateau and Rukwa basin

    NASA Astrophysics Data System (ADS)

    Delvaux, D.; Kervyn, F.; Macheyeki, A. S.; Temu, E. B.

    2012-04-01

    The Tanganyika-Rukwa-Malawi (TRM) rift segment in western Tanzania is a key sector for understanding the opening dynamics of the East African rift system (EARS). In an oblique opening model, it is considered as a dextral transfer fault zone that accommodates the general opening of the EARS in an NW-SE direction. In an orthogonal opening model, it accommodates pure dip-slip normal faulting with extension orthogonal to the rift segments and a general E-W extension for the entire EARS. The central part of the TRM rift segment is well exposed in the Ufipa plateau and Rukwa basin, within the Paleoproterozoic Ubende belt. It is also one of the most seismically active regions of the EARS. We investigated the active tectonic architecture and paleostress evolution of the Ufipa plateau and adjacent Rukwa basin and in order to define their geodynamic role in the development of the EARS and highlight their pre-rift brittle tectonic history. The active fault architecture, fault-kinematic analysis and paleostress reconstruction show that the recent to active fault systems that control the rift structure develop in a pure extensional setting with extension direction orthogonal to the trend of the TRM segment. Two pre-rift brittle events are evidenced. An older brittle thrusting is related to the interaction between the Bangweulu block and the Tanzanian craton during the late Pan-African (early Paleozoic). It was followed by a transpressional inversion during the early Mesozoic. This inversion stage is the best expressed in the field and caused dextral strike-slip faulting along the fault systems that now control the major rift structures. It has been erroneously interpreted as related to the late Cenozoic EARS which instead is characterized by pure normal faulting (our third and last stress stage).

  8. Geophysical constraints on geodynamic processes at convergent margins: A global perspective

    NASA Astrophysics Data System (ADS)

    Artemieva, Irina; Thybo, Hans; Shulgin, Alexey

    2016-04-01

    convergence rate. (4) Local isostasy is not satisfied at the convergent margins as evidenced by strong free air gravity anomalies of positive and negative signs. However, near-isostatic equilibrium may exist in broad zones of distributed deformation such as Tibet. (5) No systematic patterns are recognized in heat flow data due to strong heterogeneity of measured values which are strongly affected by hydrothermal circulation, magmatic activity, crustal faulting, horizontal heat transfer, and also due to low number of heat flow measurements across many margins. (6) Low upper mantle Vs seismic velocities beneath the convergent margins are restricted to the upper 150 km and may be related to mantle wedge melting which is confined to shallow mantle levels. Artemieva, I.M., Thybo, H., and Shulgin, A., 2015. Geophysical constraints on geodynamic processes at convergent margins: A global perspective. Gondwana Research, http://dx.doi.org/10.1016/j.gr.2015.06.010

  9. Neotectonics and Geodynamics In The Region of The Town of Bankya, Sofia Kettle (bulgaria)

    NASA Astrophysics Data System (ADS)

    Angelova, D.

    . The gravi- tation process including almost entirely the valley slopes is tectonically and erosion- tectonically predetermined. Most of the landslides are of the circus type but there are landslides of the linear type too. The erosion incision of the riverbeds resulting from the contemporary tectonic movements is in the range of 10-12 to 20 m. There was a local earthquake (intensity of VI degree, epicentre depth between 8 and 10 km) in the region of Bankya in 1910. This earthquake disturbed the Plio-Pleistocene 1 erosion-accumulation level. Considerable relief deformations took place due to a pa- leoearthquake of the seismic-gravitational type and three landslide terraces with a slope height of more than 10 m were formed. The analysis shows that the relief of the Bankya tectonic node is a result of long-term endogenic processes. The fault structures are characterized by high activity, which is classified as potentially seismic hazardous in combination with their complex morphology. The relief is under the conditions of unstable dynamic equilibrium that provides the grounds to presume that there is a change in the local stress field. It is necessary to build a geodynamic monitoring polygon. 2

  10. Geo-information approach to the study of Romashkino oil field geodynamics

    NASA Astrophysics Data System (ADS)

    Usmanov, S.; Sharipov, B.; Akhmetov, A.; Delev, A.

    2012-04-01

    Geodynamic processes have an immediate influence on a fluid dynamics, for that version they are of significant importance in the formation and reformation processes of oil and gas deposits. The object of our analysis was Romashkino oil field, which is confined to the anticlinal structure of the arch part of the South Tatar Arch. The initial data in our project include the series of a paper maps, which contain the location of the intersection of production and injection wells with the Kyn horizont at the Romashkino oil field and geologic engineering information, which contains the flow rates's inversions data of the well's production activity. Inversion occurs as a periodic increasing of the flow rates which is not caused by the external special influence on the well, against the long-term production activity's decreasing by the decreasing of oil's flow rates. During the analysis of the data we identified the anomalous wells in which the hydrocarbon feed process was observed with the highest probability based on several criteria. By the using of modern GIS technology we have compared the plots, in which an anomal wells are located, with a block structure of the basement and the sedimentary cover, and with the deconsolidated and fluid's penetrability zones of the crystalline basement. For analysis of tabular data array we used ArcGis software package. Romashkino's map was vectorized by using the EasyTrase and when we assigned a number to each object. When the project was exported to ArcGIS and data obtained the geographic coordinates. We obtained the following attributes for the testing wells: the year of exploitation's beginning, the period of the inversion, the ratio of flow rates before and after inversion, and others. We created a series of maps with location of wells, with a flow rate's inversion by the year (1957-1998) for Minnibayevo area and by the five-year intervals for Minnibayevo area separately and for the Romashkino oil field. The maps of the inversion

  11. Granitoids of different geodynamic settings of Baikal region (Russia) their geochemical evolution and origin

    NASA Astrophysics Data System (ADS)

    Antipin, Viktor; Sheptyakova, Natalia

    2016-04-01

    In the southern folded framing of the Siberian craton the granitoid magmatism of different ages involves batholiths, small low-depth intrusions and intrusion-dyke belts with diverse mineral and geochemical characteristics of rocks. Granitoid formation could be related to the Early Paleozoic collision stage and intra-plate magmatism of the Late Paleozoic age of the geologic development of Baikal area. The Early Paleozoic granitoids of Khamar-Daban Ridge and Olkhon region revealed their closeness in age and composition. They were referred to syncollision S-type formations derived from gneiss-schistose substratum of metamorphic sequences. The magmatic rocks were classified into various geochemical types comprising formations of normal Na-alkalinity (migmatites and plagiogranites), calc-alkaline and subalkaline (K-Na granitoids, granosyenites and quartz syenites) series. It is significant, that plagiomigmatites and plagiogranites in all elements repeat the shape of the chart of normalized contents marked for trend of K-Na granitoids, but at considerably lower level of concentrations of all elements. This general pattern of element distribution might indicate similar anatectic origin of both granitoid types, but from crustal substrata distinguished by composition and geochemical features. Comparative geochemical analysis pointed out that the source of melts of the Early Paleozoic granitoids of the Olkhon (505-477 Ma) and Khamar-Daban (516-490 Ma) complexes of the Baikal region could be the crustal substratum, which is obviously the criterion for their formation in the collisional geodynamic setting. Using the Late Paleozoic subalkaline magmatism proceeding at the Khamar-Daban Range (Khonzurtay pluton, 331 Ma) as an example, it was found that the formation of monzodiorite-syenite-leucogranite series was considerably contributed by the processes of hybridism and assimilation through mixing of the upper mantle basaltoid magma derived melts of granitic composition. The

  12. Upper mantle structures beneath the Carpathian-Pannonian region: Implications for the geodynamics of continental collision

    NASA Astrophysics Data System (ADS)

    Ren, Y.; Stuart, G. W.; Houseman, G. A.; Dando, B.; Ionescu, C.; Hegedus, E.; Radovanovic, S.; South Carpathian Project Working Group

    2012-04-01

    The Carpathian-Pannonian system of Eastern and Central Europe represents a unique opportunity to study the interaction between surface tectonic processes involving convergence and extension and convective processes in the upper mantle. Here, we present high-resolution images of upper mantle structure beneath the region obtained using P- and S-wave finite-frequency teleseismic tomography to help constrain the geodynamical interpretation of the region. We have selected earthquakes with magnitude greater than 5.5 in the distance range 30°-95°, which occurred between 2006 and 2011. The data were recorded on 54 temporary stations deployed in the South Carpathian Project (2009-2011), 56 temporary stations deployed in the Carpathian Basins Project (2005-2007), and 131 permanent broadband stations of national networks. The relative arrival times are measured in high, intermediate and low frequency bands (0.5-2.0 Hz, 0.1-0.5 Hz and 0.03-0.1 Hz for both P-waves, 0.1-0.5 Hz, 0.05-0.1 Hz and 0.02-0.05 Hz for S-waves), and are inverted using a 3-D finite-frequency formulation to produce P- and S-wave velocity maps at depths between 75 and 600 km in the mantle. Our images show a sub-vertical slab of fast material beneath the eastern Alps which extends eastward across the Pannonian basin at depths below ~300 km. The fast material extends down into the mantle transition zone (MTZ), where it spreads out beneath the entire basin. Above ~300 km, the upper mantle below the Pannonian basin is dominated by relatively slow velocities, the most dominant of which extends down to nearly 200 km and underlies the >7km thick sediments of the Mako-Békés rift basins. We suggest that cold mantle lithospheric downwelling occurred below the Pannonian Basin before detaching in the mid-Miocene. In the Vrancea Zone, intermediate depth seismicity occurs at the NE end of a tabular upper mantle high velocity structure that trends SW along the southern edge of the South Carpathians and extends to

  13. The Surface of Venus and Implications for its Geological and Geodynamical Evolution: The View Before Venus Express and Outstanding Questions for the Future

    NASA Astrophysics Data System (ADS)

    Head, J. W.; Ivanov, M. A.; Basilevsky, A. T.

    2008-12-01

    Prior to the Venera 15/16 and the Magellan missions to Venus, a wide range of ideas existed concerning the nature of the surface of Venus, the geological processes currently operating there, their link to interior processes, the implied geological and geodynamical history of the planet, and how all this compared with the nature and history of other terrestrial planetary bodies. The history of exploration of the surface of Venus represents the acquisition of data with increasing spatial and areal coverage, culminating in the near-global high-resolution image, altimetry, physical property and gravity data obtained by the Magellan mission. Among the most fundamental findings of the global Magellan image data are: 1) that volcanism and tectonism represent the most abundant geological processes operating on the observed surface, 2) that the styles and abundance of volcanism and tectonism combine attributes of both the Earth (e.g., very heavily tectonically deformed regions such as tessera) and the smaller terrestrial planetary bodies (e.g., vast volcanic plains deformed by wrinkle ridges), 3) that the distribution and nature of impact craters precludes active plate tectonics despite many Earth-like tectonic features (e.g., folded mountain belts), 4) that some features (e.g., coronae) are somewhat unique to Venus and may provide important information on mantle convection and lithospheric evolution processes, 5) that the number of impact craters is very small, indicating that the surface geological record is very young, less than 20% of the history of the planet itself, 6) that 80% of the geological record of Venus is no longer obviously preserved in the surface morphology, but may be preserved in the surface rocks, 7) that the distribution and state of preservation of existing impact craters may be consistent with a range of catastrophic resurfacing models, and 8) that the geological record and sequence of events can be correlated with geophysical data to assess crustal

  14. GOCE observations and geophysical constraints to better understand the lithosphere and geodynamical processes under the Paraná-Etendeka region: preliminary results of PERLA project

    NASA Astrophysics Data System (ADS)

    Mariani, Patrizia; Braitenberg, Carla

    2014-05-01

    In the light of the considerable progress made by the modern geodetic satellite mission GOCE, one of the challenges of the European Space Agency (ESA) is to improve knowledge of physical properties and geodynamic processes of the lithosphere and the Earth deep interior, and their relationship to Earth-surface changes. In this context we propose a study that aims to understand the two pieces of lithosphere underlying the Paraná-Etendeka conjugate margins (Brazil, and Angola-Namibia). It is essential to collect the geological and geophysical information about the thickness and the density of sedimentary layers, crustal thickness and mantle inhomogeneities. Our methodology integrates the geophysical database with the GOCE data, product of the innovative gravity satellite mission, that was concluded November 2013. Crustal thickness was obtained from all available seismological datasets. The density-depth relation of the shallow layers is modeled by geophysical data collected from literature and from the on-shore and off-shore drilling programs. Several compaction laws are used to estimate the density of each layer. This information is necessary to reduce the observations considering the gravity effect of all intracrustal known layers, to resolve the deep crustal structures (e.g. Moho and intracrustal bodies). A positive gravity anomaly is expected due to the magmatic activity of the Paraná-Etendeka province. The smaller-scale and shallow gravity anomaly should be due to the occurrence of the volcanic activity close to the alkaline-carbonatite complexes, while the large-scale anomaly is expected from the underplating of a wide denser body at the depth of the crustal mantle boundary. In the present work some preliminary results of the inversion of the residual gravity anomaly in terms of densities in the middle and shallow lithosphere under the Paraná-Etendeka region will be presented and interpreted.

  15. Geochemistry and zircon U-Pb-Hf isotopes of the granitoids of Baolidao and Halatu plutons in Sonidzuoqi area, Inner Mongolia: Implications for petrogenesis and geodynamic setting

    NASA Astrophysics Data System (ADS)

    Hu, Chuansheng; Li, Wenbo; Xu, Cheng; Zhong, Richen; Zhu, Feng

    2015-01-01

    The Baolidao and Halatu plutons are located in the Northern Orogenic Belt (NOB) in Sonidzuoqi area of Inner Mongolia, which has an important significance for the tectonic evolution of Xing-Meng Orogenic Belt (XMOB). The two plutons have been intensively studied but the conclusions are still controversial. Combined with the previous study, this paper gives new geological data about the two correlative plutons for gaining a better understanding of their petrogenesis and the geodynamic setting. The Baolidao granitoids contain two different series, calc-alkaline series mainly formed in the Ordovician and high K calc-alkaline series mainly formed in the Carboniferous. The Halatu granites are formed in the Triassic and belong to high-K calc-alkaline series. This study got the zircon U-Pb ages of 316-322 Ma for the Baolidao granitoids and 233 ± 2 Ma for the Halatu syenogranites, respectively. In the tectonic discrimination diagrams, they mainly fall into the area of post-orogenic granites (POG). Hf isotopic analyses for the Baolidao granitoids (Sample BLD-1 and 3) shows εHf (t) = 3.0-14.0, with two-stage Hf model age (TDM2) of 436-1138 Ma. The Halatu syenogranite (Sample HLT-1) also shows a depleted εHf (t) = 3.8-8.2, with TDM2 of 741-1024 Ma, suggesting the major involvement of juvenile crustal components. The various εHf values of the Carboniferous Baolidao and Triassic Halatu granitoids indicates a hybrid magma source of juvenile material with old crustal component, and the εHf (t) values decrease from the Carboniferous to Triassic, suggesting the increasing proportion of old continental material during this period. Combined with the regional geology, the Carboniferous Baolidao granitoids are possibly not arc rocks, but originated from the post-collisional setting. The Triassic Halatu granites were formed in the subsequently extensional environment.

  16. New data on the age and geodynamic interpretation of the Kalba-Narym granitic batholith, eastern Kazakhstan

    NASA Astrophysics Data System (ADS)

    Kotler, P. D.; Khromykh, S. V.; Vladimirov, A. G.; Navozov, O. V.; Travin, A. V.; Karavaeva, G. S.; Kruk, N. N.; Murzintsev, N. G.

    2015-06-01

    Geological and new geochronological data are summarized for the Kalba-Narym granitic batholith in eastern Kazakhstan, and their geodynamic interpretation is suggested. In the structure of the batholith, we consider (from late to early) the Kunush plagiogranitic complex, the Kalguta granodiorite-granitic association, and the Kalba granitic, Monastery leucogranitic, and Kainda granitic complexes. The granitic complexes of the Kalba-Narym batholith were formed between the Carboniferous-Permian and the Early-Middle Permian (˜30 Ma). New data indicate that formation of the Kalba-Narym batholith was related to the activity of the Tarim mantle plume. Heating of the lithosphere by the plume coincided with postcollision collapse of the orogenic structure and led to the crust melting and formation of the studied granitic complexes in a relatively short period.

  17. Paleogeographic evolution of the central segment of the South Atlantic during Early Cretaceous times: Paleotopographic and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Chaboureau, Anne-Claire; Guillocheau, François; Robin, Cécile; Rohais, Sébastien; Moulin, Maryline; Aslanian, Daniel

    2013-09-01

    The geodynamic processes that control the opening of the central segment of the South Atlantic Ocean (between the Walvis Ridge and the Ascension FZ) are debated. In this paper, we discuss the timing of the sedimentary and tectonic evolution of the Early Cretaceous rift by drawing eight paleogeographic and geodynamic maps from the Berriasian to the Middle-Late Aptian, based on a biostratigraphic (ostracodes and pollen) chart recalibrated on absolute ages (chemostratigraphy, interstratified volcanics, Re-Os dating of the organic matter). The central segment of the South Atlantic is composed of two domains, with a two phases evolution of the pre-drift ("rifting") times: a rift phase characterized by tilted blocks and growth strata, followed by a sag basin. The southern domain includes the Namibe, Santos and Campos Basins. The northern domain extends from the Espirito Santo and North Kwanza Basins, in the south, to the Sergipe-Alagoas and North Gabon Basins to the north. Extension started in the northern domain during the Late Berriasian (Congo-Camamu Basin to the Sergipe-Alagoas-North Gabon Basins) and migrated southward. At that time, the southern domain was not a subsiding domain (emplacement of the Parana-Etendeka Trapp). Extension started in this southern domain during the Early Barremian. The rift phase is shorter in the south (5-6 Ma, Barremian to base Aptian) than in the north (19 to 20 Myr, Upper Berriasian to base Aptian). The sag phase is of Middle to Late Aptian age. In the northern domain, this transition corresponds to a hiatus of Early to Middle Aptian age. From the Late Berriasian to base Aptian, the northern domain evolves from a deep lake with lateral highs to a shallower organic-rich one with no more highs. The lake migrates southward in two steps, until the Valanginian at the border between the northern and southern domains, until the Early Barremian, north of Walvis Ridge.

  18. Geodynamic Drivers of Vertical Crustal Motion: Integrating Paleoaltimetry with Basin Development in the Central Andean Plateau of Southern Peru

    NASA Astrophysics Data System (ADS)

    Sundell, K. E., II; Saylor, J. E.; Lapen, T. J.; Villarreal, D. P.; Styron, R. H.; Horton, B. K.; Cardenas, J.

    2015-12-01

    Determining the spatial and temporal relationships between surface uplift, tectonic subsidence, and exhumation during periods of oblique crustal shortening is essential to discriminating geodynamic processes controlling formation of high topography in the central Andes. Although subsidence analysis is now a standard tool, paleoelevation estimation remains a challenging task, as estimates based on proxy data can be complicated by uncertainties in the relative controls of tectonics and climate. We therefore adopt an approach of combining established tools of subsidence analysis and detrital geochronology with emerging methods of volcanic glass paleoaltimetry, which enables us to explore a broad range of viable interpretations to understand the development of intermontane basins and their relationship to the development of the central Andean plateau. We investigated a suite of temporally overlapping and spatially separate Cenozoic basins spanning the east-west extent of the central Andean plateau in southern Peru. These basins contain an exceptional record of the vertical movements of this region. We calculate sediment accumulation and subsidence rates through decompaction of measured stratigraphic sections, and reconstruct past environmental conditions based on the stable isotopic composition of ancient waters preserved in hydrated volcanic glass. These data and published records of crustal shortening and exhumation show that although paleoaltimetry data in the study areas may be interpreted in various ways, they are best explained by multiple geodynamic processes driving (i) Eocene-early Miocene development of high topography in the Western Cordillera, then (ii) a pulsed middle Miocene-present building of the central Andean plateau from west to east, consistent with global climate changes as well as regional climate shifts driven by topographic development of the Andean orogen.

  19. Installation of two high-sensitivity laser strainmeters in a new underground geodynamical observatory (GEODYN) at Canfranc (Spain)

    NASA Astrophysics Data System (ADS)

    Crescentini, L.; Botta, V.; Amoruso, A.; Bettini, A.

    2012-04-01

    High-sensitivity wide-band strain measurements allow an advanced study of different geodynamic phenomena, both local and global, in a spectrum ranging from short period seismic waves to tectonic deformation. Among the latest results produced by the few high-sensitivity wide-band laser interferometers operating allover the world, the analysis of the strain recorded by the Gran Sasso (Italy) laser interferometers before and after the 2009 L'Aquila earthquake allowed putting tight constraints on earthquake nucleation processes and other pre-seismic phenomena, and detecting the slow diffusive propagation of an aseismic rupture during the first hours following the main event.The Gran Sasso interferometers are operating since several years, proving their high reliability. An improved version of the Gran Sasso interferometers have been recently installed in the Canfranc (Spain) underground Laboratory (LSC). The LSC is located at depth in one of the most seismically active areas in Western Europe, at the Pyrenean chain that marks the boundary between the European plate and the Iberian microplate. These features make it particularly suitable and interesting for hosting an advanced integrated geodynamic observatory (GEODYN), of which the interferometers are part. The first tests on strain data evidence a much lower noise level with respect that the Gran Sasso installations, expecially in the frequency band 0.0001 to 0.1 Hz, suggesting the capability of producing clear records of low-frequency seismic waves, Earth free oscillations, and possible local aseismic stress release. We will give a technical description of the installation, show some examples of recordings, and discuss the local distortion of the deformation field, as obtained by comparing Earth tide predictions and observations.

  20. The Permian volcanism of Sardinia revisited: new geochronological and geochemical data as a key for geodynamic evolution of the western Peri-Tethian sector

    NASA Astrophysics Data System (ADS)

    Gaggero, Laura; Gretter, Nicola; Lago, Marceliano; Langone, Antonio; Oggiano, Giacomo; Ronchi, Ausonio

    2014-05-01

    mass spectrometry (LA ICP-MS) at the Institute of Geosciences and Earth Resources IGG-CNR of Pavia. The time lag of Permian ages recorded along the Sardinia cross section is significant in the modeling of the post- Variscan tectonic, sedimentary evolution and in the perspective of the geodynamic evolution of Southern Variscides. REFERENCES Casini L., Cuccuru S., Maino M., Oggiano G., Tiepolo M 2012. Emplacement of the Arzachena Pluton (Corsica-Sardinia Batholith) and the geodynamics of incoming Pangaea. Tectonophysics 544-545 (2012) 31-49. Buzzi L., Gaggero L., Oggiano G. 2008. The Santa Giusta ignimbrite (NW Sardinia): a clue for the magmatic, structural and sedimentary evolution of a Variscan segment between Early Permian and Triassic. Italian Journal of Geoscience 127(3), 683-695. Cortesogno L., Cassinis G., Dallagiovanna G., Gaggero L., Oggiano G., Ronchi A., Seno S., Vanossi M. 1998. The Variscan post-collisional volcanism in Late Carboniferous-Permian sequences of Ligurian Alps, Southern Alps and Sardinia (Italy): a synthesis. Lithos 45, 305-328.

  1. About the Relation Between Geodynamics of the Sedimentary Basin and the Properties of Crude Oil

    NASA Astrophysics Data System (ADS)

    Muslimov, R.; Plotnikova, I.

    2012-04-01

    Earlier, we wrote and reported about the modern geodynamic activity of the territory of South-Tatar arch, where the Romashkino oil field. We identified a periodic change in flow rates of oil and oil density at Romashkino and other oil fields of the South Tatar arch. Now we have studied the composition of oils and bitumoids from uneven (in terms of age) deposites of the sedimentary cover and basement rocks in the zones of possible hydrocarbon seepage in the central squares of Romashkinskoye field. The results of the comparative studies allowed us to come to the conclusion that the formation of oil-bearing deposits of Romashkinskoye field owes to the income and mixing of hydrocarbons (HC) fluids from different sources. The analysis of geological and production data (GPD) that was held during the many years of exploitation of the development wells of Romashkinskoye field by TatNIPIneft under the direction of I.F. Glumov suggests contemporary inflow of hydrocarbons in the industrial oil reservoir of the Pashi horizon of Romashkinskoye field and the existence of localized areas of inflow of new portions of HC. A number of criteria was worked out in the analysis of the GPD; that allowed us to identify among the total number of wells those, in which the process of hydrocarbon seepage was recorded with the greatest probability. Such wells were called anomalous. One of the directions of this research was to study the geochemical characteristics of oil from anomalous wells and to determine the degree of similarity and difference between this oil and the oil from both normal wells (in which the signs of deep seepage is not recorded), and bituminoid from the crystalline basement and sedimentary cover. If the hypothesis of a recurrent (also in modern times) influx of deep hydrocarbon is correct, then the oil from the anomalous wells should have specific features in comparison with the wells located outside the areas of the expected inflow. The results of geochemical studies of

  2. Geochemistry and petrogenesis of high-K "sanukitoids" from the Bulai pluton, Central Limpopo Belt, South Africa: Implications for geodynamic changes at the Archaean-Proterozoic boundary

    NASA Astrophysics Data System (ADS)

    Laurent, Oscar; Martin, Hervé; Doucelance, Régis; Moyen, Jean-François; Paquette, Jean-Louis

    2011-04-01

    The Neoarchaean Bulai pluton is a magmatic complex intrusive in the Central Zone of the Limpopo Belt (Limpopo Province, South Africa). It is made up of large volumes of porphyritic granodiorites with subordinate enclaves and dykes of monzodioritic, enderbitic and granitic compositions. New U-Pb LA-ICP-MS dating on zircon yield pluton-emplacement ages ranging between 2.58 and 2.61 Ga. The whole pluton underwent a high-grade thermal overprint at ~ 2.0 Ga, which did not affect the whole-rock compositions for most of the major and trace-elements, as suggested by a Sm-Nd isochron built up with 16 samples and yielding an age consistent with U-Pb dating. The whole-rock major- and trace-element compositions evidence that the Bulai pluton belongs to a high-K, calc-alkaline to shoshonitic suite, as well as unequivocal affinities with "high-Ti" sanukitoids. Monzodioritic enclaves and enderbites have both "juvenile" affinities and a strongly enriched signature in terms of incompatible trace elements (LREE, HFSE and LILE), pointing to an enriched mantle source. Based on trace-element compositions, we propose the metasomatic agent at their origin to be a melt deriving from terrigenous sediments. We therefore suggest a two-step petrogenetic model for the Bulai pluton: (1) a liquid produced by melting of subducted terrigenous sediments is consumed by reactions with mantle peridotite, producing a metasomatic assemblage; (2) low-degree melting of this metasomatized mantle gives rise to Bulai mafic magmas. Such a model is supported by geochemical modelling and is consistent with previous studies concluding that sanukitoids result from interactions between slab melts and the overlying mantle wedge. Before 2.5 Ga, melting of hydrous subducted metabasalts produced large volumes of TTG (Tonalite-Trondhjemite-Granodiorite) forming most of the volume of Archaean continental crust. By constrast, our geochemical study failed in demonstrating any significant role played by melting of

  3. Integrated studies of the recent evolution of Deception Island in the geodynamic setting of the Bransfield Basin opening (Antarctica): GEOMAGDEC Project

    NASA Astrophysics Data System (ADS)

    Maestro, Adolfo; Gil-Imaz, Andrés.; Gil-Peña, Inmaculada; Galindo-Zaldívar, Jesús; Rey, Jorge; Soto, Ruth; López-Martínez, Jerónimo; Llave, Estefanía.; Bohoyo, Fernando; Rull, Fernando; Martínez-Frías, Jesús; Galán, Luis; Casas, David; Lunar, Rosario; Ercilla, Gemma; Somoza, Luis

    2010-05-01

    Deception Island shows the most recent active volcanism, evidence of several eruptions since the late 18th century, and well-known eruptions in 1967, 1969, and 1970 at the western end of the volcanic ridge of the Bransfield Trough, between the South Shetland Islands and the Antarctic Peninsula. The recent tectonic activity of the Bransfield Trough is not well defined, and it presents a controversial origin. It is currently explained by two different models: (1) Opening of the basin may be related to passive subduction of the former Phoenix Plate and subsequent rollback of the South Shetland Trench; or (2) an oblique extension along the Antarctic Peninsula continental margin generated by the sinistral movement between the Antarctic and Scotia plates. This extension develops the Bransfield Trough and spread away the South Shetland tectonic block. The GEOMAGDEC project involves a multidisciplinary and integrated research of the Deception Island based on geophysical and geological methods. The purpose of this project, funded by the Spanish research agency, is the understanding of the main processes that govern the evolution of the Deception Island into the development of Bransfield Basin during recent times. Main aims are: (1) Study of the anisotropy of the magnetic susceptibility of volcanic deposits of emerged area of Deception Island to determine the relationship between magmatism (intrusive and extrusive) with the recent tectonic activity. This task allows the reconstruction of igneous flow directions of the different volcanic units established in the island, dikes emplacement modelling in active tectonic regime, and the integration of the results obtained in a kinematic and dynamic emplacement model of the different volcanic units of the Deception Island into recent geodynamic setting of Bransfield Basin opening. (2) Lito- and crono-stratigraphy analysis of the quaternary sedimentary units that filled Port Foster (inner bay of Deception Island) on the basis of the

  4. Neogene tectonics and modern geodynamics and seismicity of Pannonia north-eastern remote area (Ukrainian Transcarpathian yield)

    NASA Astrophysics Data System (ADS)

    Lozynak, Petro; Nazarevych, Andriy; Nazarevych, Lesya

    2010-05-01

    Pannonia north-eastern remote area (Ukrainian Transcarpathian yield) joins to East (Ukrainian) Carpathians and their geodynamic mode is interdependent from the alpine stage until now. Due to the detailed study in the last few years of structures of surface of basement and sedimentary layers of the Transcarpathian yield of postalpine ages (neogene - from early Miocene to Sarmatian and farther) (see Lozynak at al., 2002-2007) we have the possibility to trace the Neogene's tectonics of the region and its connection with modern geodynamics and seismicity of Ukrainian Transcarpathians and adjoining territories of Slovakia, Hungary and Romania. These data indicate that active orogenic processes (dominance of compression caused by a plate-tectonic processes) in this region to beginning of early miocene made off and began the process of formation of the Transcarpathian yield in his modern view (due to an output on the first plan of the plum-tectonic processes caused by Pannonian asthenolite?) (see Nazarevych A. and Nazarevych L., 2000-2007). The process of formation (origin) of yield (and the proper accumulation of sedimentary layers) began in his east part (in the area of border with Romania (Siget - Solotvyno)) at the beginning of early Miocene (about 23 million years ago), continue in north-western direction (in the rear of modern Carpathians) to the border with Slovakia at first as a narrow (10-15 km) bar (roughly during 2-4 million years) and then broadened (during next 2-3 million years) in north-eastern - south-west direction on all modern territory of the Transcarpathian yield. In future (in Sarmatian epoch, approximately from 12-14 to 10-11 million years ago) east part of yield (so-called Solotvyno depression) transgress to the mode of compression and raising with ending of intensive sedimentation, and in western part (so-called Tchop-Mukatcheve depression) the process of sagging was farther displaced westward and at present he is concentrated (by geodesic and

  5. George V Land paragneisses xenoliths dating. New insights for the Antarctica-Australia connection and geodynamic reconstructions.

    NASA Astrophysics Data System (ADS)

    Lamarque, Gaëlle; Bascou, Jérôme; Ménot, René-Pierre; Paquette, Jean-Louis; Rolland, Yann; Cottin, Jean-Yves

    2015-04-01

    George V Land is constituted of terrains that are considered as the southern extension of Australia in Antarctica. This region plays a key role to better understand the assembly, evolution and separation of the Gondwana and Rodinia supercontinents. In the studied area two distinct continental domains in ages, nature, structures and crustal thicknesses are juxtaposed: the 1.7-2.4 Ga Terre Adélie Craton to the west and a younger domain, comprised of 500 Ma old intrusive complex to the east. The latter is mainly composed of granitoids and is associated with the Ross Orogeny. From field evidences, these two domains are likely separated by a major dextral strike-slip structure: the Mertz shear zone (MSZ, 145°E). The MSZ was activated at 1.7 and 1.5 Ga respectively in amphibolite and greenschists facies conditions. The tectonic evolution of the eastern region between 1.5 Ga (last activation of the MSZ) and 500 Ma (age of the domain bordering the craton) is a key question to geodynamic reconstructions. For this purpose we studied samples of paragneisses xenoliths hosted by the Palaeozoic granitoids, as they represent relics from the underlying basement of this domain. Xenoliths are few-centimeters to several decimeters in size and include different types of paragneisses that may coexist. U-Pb analyses were carried out on 130 zircons from three different xenoliths. Extracted detritic zircons have similar ages from a sample to another showing a common origin of the sedimentary protolith. A large variety of ages were found from 580 Ma to 3.4 Ga and the best-represented age is about 580 Ga that may correspond to a metamorphic stage predating the intrusive event. Another interesting result is that almost no 1.6 to 2.4 Ga zircons were found, suggesting that sedimentary protolithes cannot be derived from erosion of the neighbouring Terre Adélie Craton. This result argues for a tectonic collage between the two domains. By comparing our results with previous similar studies in

  6. Digital files for northeast Asia geodynamics, mineral deposit location, and metallogenic belt maps, stratigraphic columns, descriptions of map units, and descriptions of metallogenic belts

    USGS Publications Warehouse

    Nokleberg, Warren J.; Badarch, Gombosuren; Berzin, Nikolai A.; Diggles, Michael F.; Hwang, Duk-Hwan; Khanchuk, Alexander I.; Miller, Robert J.; Naumova, Vera V.; Obolensky, Alexander A.; Ogasawara, Masatsugu; Parfenov, Leonid M.; Prokopiev, Andrei V.; Rodionov, Sergey M.; Yan, Hongquan

    2004-01-01

    This is the online version of a CD-ROM publication. It contains all of the data that are on the disc but extra files have been removed: index files, software installers, and Windows autolaunch files. This publication contains a a series of files for Northeast Asia geodynamics, mineral deposit location, and metallogenic belt maps descriptions of map units and metallogenic belts, and stratigraphic columns. This region includes Eastern Siberia, Russian Far East, Mongolia, Northeast China, South Korea, and Japan. The files include: (1) a geodynamics map at a scale of 1:5,000,000; (2) page-size stratigraphic columns for major terranes; (3) a generalized geodynamics map at a scale of 1:15,000,000; (4) a mineral deposit location map at a scale of 1:7,500,000; (5) metallogenic belt maps at a scale of 1:15,000,000; (6) detailed descriptions of geologic units with references; (7) detailed descriptions of metallogenic belts with references; and (8) summary mineral deposit and metallogenic belt tables. The purpose of this publication is to provide high-quality, digital graphic files for maps and figures, and Word files for explanations, descriptions, and references to customers and users.

  7. Geodynamical evolution of Central Andes at 24°S as inferred by magma composition along the Calama-Olacapato-El Toro transversal volcanic belt

    NASA Astrophysics Data System (ADS)

    Matteini, M.; Mazzuoli, R.; Omarini, R.; Cas, R.; Maas, R.

    2002-11-01

    Miocene to Recent volcanism on the Puna plateau (Central Andes) developed in three geological settings: (a) volcanic arc in the Western Cordillera (Miocene-Recent); (b) trans-arc along the main NW-SE transverse fault systems (Miocene); and (c) back-arc, mainly monogenic volcanic centres (Pliocene-Quaternary). We have studied the evolution of the arc-trans-arc volcanism along one of the most extensive transverse structures of Central Andes, the Calama-Olacapato-El Toro, at 24°S. Compositional variations from arc to trans-arc volcanism provide insights into petrogenesis and magma source regions. Puntas Negras and Rincon volcanic centres are arc-type and have typical calc-alkaline geochemical and Sr-Nd-Pb isotopic characteristics. East of the arc, lavas of the Tul-Tul, Del Medio and Pocitos complexes (TUMEPO) are heavy rare earth element-depleted and could be derived from 20-30% of partial melting of a lower crustal garnet-bearing metabasite. These liquids could be variably mixed with arc magmas at the base of the crust (MASH). This suggests important contributions from lower crustal sources to TUMEPO centres. Products at the Quevar and Aguas Calientes volcanic complexes to the east of TUMEPO show a prominent upper crustal signature (high 86Sr/ 87Sr, low 143Nd/ 144Nd) and could represent mixtures of 20-30% TUMEPO-type liquids with up to 70-80% of upper crustal melts. We propose a geodynamic model to explain geochemical variations for the arc-trans-arc transverse volcanism from the Upper Miocene to Recent. In our model, arc volcanism is linked to dehydration of the subducting Nazca plate, which produces typical calc-alkaline compositions. During the Upper Miocene (10-5 Ma), lithospheric evolution in the Puna plateau was dominated by thickening of ductile lower crust and thinning of the lithosphere. Lower crustal melting was promoted by concomitant asthenospheric upwelling and water release from the amphibolite-eclogite transformation, yielding TUMEPO magmas with lower

  8. The Sinemurian carbonate mud-mounds from central High Atlas (Morocco): stratigraphy, geometry, sedimentology and geodynamic patterns

    NASA Astrophysics Data System (ADS)

    Chafiki, Driss; Canérot, Joseph; Souhel, Abdellatif; el Hariri, Khadija; Eddine, Kamal Taj

    2004-06-01

    The Moroccan Central High Atlasic mud-mounds correspond to carbonate sponge-algal buildups developed in open marine conditions towards the Lower-Upper Sinemurian boundary. The structures gradually increase in size through time, from the small-sized lenses included in the Idikel coarse-bedded Lower Sinemurian grainstones to the high domes observed in the succeeding Aberdouz and Ouchbis Upper Sinemurian thin-bedded mudstones. The biological communities (mainly algae, sponges, thrombolites, stromatolites, annelids, bryozoans, brachiopods, pelecypods, gastropods, echinoderms, corals and scarce foraminifera) comprise common, well conserved remains in the rising core frameworks and small reworked bioclasts in the surrounding sedimentary depressions. These buildups are closely linked to tectonic processes as they grew on the normal synsedimentary faults which affected the central Atlasic area during the Lower Liassic period, leading to the breakup of the Early Sinemurian carbonate platform and the resultant initiation of the Upper Sinemurian subsiding basin. Silting conditions under hernipelagic sedimentation led to their death. Similar palaeogeographic changes and geodynamic evolution have been described recently from different structures in North Africa, Western Europe and North America.

  9. Development of the Côte Ivoire Basin: reading provenance, sediment dispersal, and geodynamic implications from heavy minerals

    NASA Astrophysics Data System (ADS)

    Wozazek, Stefan; Krawinkel, Hannelore

    2002-05-01

    The combined approach of conventional and varietal heavy mineral analysis was applied to constrain changes in source rock area, dispersal routes of detritus, and geodynamic setting of the Upper Cretaceous to Neogene Côte d'Ivoire basin. The heavy mineral assemblage of Albian to Turonian sediments reflect a narrow source rock area and short transport distances. A prominent change in the heavy mineral association of Late Cenomanian to Neogene sediments indicates enlargement of source area and longer fluvial transport distances, or longer storage of sediment within the littoral energy fence. The sudden change within the heavy mineral associations marks the transition from the late syn-rift stage to the early passive margin stage of the Southern Atlantic. During Albian to Late Cenomanian time, the basin geometry was mainly controlled by steep slopes and sediments were transported directly to the depocenter. The situation changed in Late Cenomanian time. A small shelf area developed where sediments from different sources were mixed and reworked before deposition. We believe that the W-E direction of the long-shore drift, which transports today huge quantities of near-shore sand, was established at the end of the Paleogene. This resulted from the drifting of southern West Africa across the paleoequator and subsequent change in surface wind directions.

  10. Seismoacoustic responses to high-power electric pulses from well logging data at the Bishkek geodynamical test area

    NASA Astrophysics Data System (ADS)

    Zakupin, A. S.; Bogomolov, L. M.; Mubassarova, V. A.; Il'ichev, P. V.

    2014-09-01

    The results of recording seismoacoustic emission (SAE) in the boreholes of the Bishkek geodynamical test area in Tien Shan, Kyrgyzstan, are presented. The spectral structure of SAE signals and the pattern of variations in SAE intensity during electromagnetic (EM) sounding of the Earth's crust by the highpower ERGU-600-2 generator unit are studied. The statistical methods for SAE data processing are adjusted for the problem of revealing the correlations between SAE responses and pulsed electrical impacts (i.e., energy input into the medium). The response of the medium to EM soundings, which are conducted for monitoring the apparent resistivity of the rocks, is revealed. The response of the medium manifests itself as the increase in SAE intensity (the responses to the electric current pulses generated during the soundings). The SAE responses belong to the same group of the effects (the signs of external forcing of rock destruction) as the variations in seismicity during the runs of the geophysical magneto-hydrodynamic (MHD) generators in 1983-1989 or experimental soundings in 2000-2005. The sources of SAE signals are located at shallow depths, near the geophone installation place. This accounts for the difference between the variations in SAE intensity and microseismicity in response to the same impact.

  11. Pressure-temperature history of the Brooks Range and Seward Peninsula, Alaska HP-LT units and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Lemonnier, N.; Labrousse, L.; Agard, P.; Till, A. B.

    2013-12-01

    Metamorphic rocks in the inner zones of mountain belts constitute a marker of vertical movements within orogenic wedges, themselves controled by balance between boundary conditions and volume forces. They provide key evidence for paleogeographic and tectonic reconstruction of convergence zones. In the Arctic, the Amerasian basin opened in cretaceous time and evolved in the upper plate of the Pacific subduction system. The tectonic evolution of the Brooks Range, northern Alaska, is a key issue for understanding possible coupling between these two dynamics. HP-LT metamorphic rocks, now exposed in the Schist belt, Brooks Range, and the Nome Complex, Seward Peninsula, were brought to the surface during Early Cretaceous to Paleocene time. The processes responsible for their exhumation (syn-collisional nappe-stacking or post-collisional extensional detachment) are still a matter of debate, and have direct implications in terms of orogenic boundary conditions and coupling between subduction processes (to the south) and basin response (to the north; the North Slope). Systematic thermometry via Raman Spectrometry (RSCM) on carbonaceous material from regional transects in the Schist Belt and the Seward Peninsula as well as pseudosections calculations allow the determination of units with contrasting pressure-temperature histories and a comparison of thermal evolution of the two areas. Geodynamic implications of their exhumation is then discussed.

  12. Dating intrusion and cooling of Cenozoic granitoids in the Dinarides of Southern Serbia and discussion of the geodynamic setting of Paleocene-Miocene magmatism in the Balkan Peninsula

    NASA Astrophysics Data System (ADS)

    Senecio, Schefer; Cvetković, Vladica; Fügenschuh, Bernhard; Kounov, Alexandre; Ovtcharova, Maria; Schaltegger, Urs; Schmid, Stefan

    2010-05-01

    This paper presents the results of high precision single grain U-Pb dating and Hf isotope analyses of thermally annealed and chemically abraded zircons from the Kopaonik, Drenje, Željin, Golija and Polumir intrusions in the inner Dinarides of southern Serbia. In addition, new zircon and apatite fission-track data together with local structural observations, allow for constraining the subsequent exhumation history of these intrusions. Two age groups were determined for the granitoid intrusions: (i) Oligocene intrusive bodies (Kopaonik, Drenje, Željin) ranging in age from 31.7 to 30.6 Ma and (ii) Miocene Golija and Polumir intrusions which emplaced at 20.58-20.17 and 18.06-17.74 Ma, respectively. The apatite fission-track modelling combined with zircon central ages show rapid cooling from above 300 to ca. 80 °C between 16 and 10 Ma for granitoids of both age groups, followed by rather slow cooling to surface temperatures for the last 10 Ma. Fast Middle Miocene cooling between 16 and 10 Ma is caused by extensional exhumation of the plutons that are located in the footwall of core-complexes. This documents that Miocene magmatism and core-complex formation leading to formation of the Pannonian basin also affected a part of the mountainous areas of the internal Dinarides. The discussion of an extensive set of age data from the literature and the geodynamic setting of the Balkan Peninsula reveals that there is no direct connection of the Dinaridic Late Eocene to earliest Miocene magmatic belt with contemporaneous Periadriatic intrusions in the Alps and along the Mid-Hungarian fault zone as proposed in the literature. We insist on the fact that the subduction polarity in the Alps, including that within the Western Carpathians north of the Mid-Hungarian fault zone, is opposite to that of the Dinarides during the given time span. Instead, we propose that Late Eocene to Oligocene magmatism, which affects the Adria-derived lower plate units of the internal Dinarides, may be

  13. Constraints on the Geodynamical History of Venus from Argon Degassing and the Cratering Record

    NASA Astrophysics Data System (ADS)

    O'Rourke, J. G.; Korenaga, J.

    2015-05-01

    Thermal evolution models of Venus featuring continuous evolution in the stagnant-lid regime possibly satisfy all available constraints, including the present-day atmospheric mass of radiogenic argon and the statistical properties of impact craters.

  14. Investigation of dynamic noise affecting geodynamics information in a tethered subsatellite

    NASA Technical Reports Server (NTRS)

    Gullahorn, G. E.

    1985-01-01

    Measurement of the gradient of the gravitational acceleration from a satellite platform is likely to provide the next improvement in knowledge of the Earth's gravity field after the upcoming Geopotential Research Mission. Observations from the subsatellite of a tethered satellite system (TSS) would increase sensitivity and resolution due to the low altitude possible. However, the TSS is a dynamically noisy system and would be perturbed by atmospheric drag fluctuations. The dynamic noise is being modeled in order to evaluate the feasibility of TSS gradiometry and to design methods of abating the error caused by this noise. The demonstration flights of the TSS are to provide an opportunity to directly observe the dynamical environment and refine modeling techniques. Random vibration analysis as a technique for modeling the TSS under atmospheric perturbation was studied.

  15. Hydrocarbon degassing of the earth and origin of oil-gas fields (isotope-geochemical and geodynamic aspects)

    NASA Astrophysics Data System (ADS)

    Valyaev, Boris; Dremin, Ivan

    2016-04-01

    formation of traditional and nontraditional hydrocarbon accumulations. The genesis of hydrocarbon fluids turn up to be associated with a hydrocarbon branch of deep degassing and recycling of crustal materials and processes of crust-mantle interaction [1,2,3]. The study was supported by the Russian Foundation for Basic Research (RFBR), grant № 14-05-00869. 1. Valyaev B.M., Dremin I.S. Deep Roots of the Fluid Systems and Oil-Gas Fields (Isotope Geochemical and Geodynamic Aspects) // International Conference Goldschmidt2015, Prague, Czech Republic, August 16-21, 2015. Abstracts. P. 3221. 2. Valyaev B., Dremin I. Recycling of crustal matter and the processes of mantle-crust interaction in the genesis of hydrocarbon fluids // International Conference on Gas Geochemistry 2013, Patras, Greece, 1-7 September 2013, Book of abstracts. P. 32. 3. Degassing of the Earth: Geotectonics, Geodynamics, Geofluids; Oil and Gas; Hydrocarbon and Life. Proceedings of the all-Russian with International Participation Conference, devoted the centenary of Academician P.N. Kropotkin, October 18-22, 2010, Moscow. Responsible editors: Academician A.N. Dmitrievsky, senior doctorate B.M. Valyaev. -Moscow: GEOS, 2010. 712 p.

  16. I. Climate change on ancient Mars. II. Exoplanet geodynamics and climate

    NASA Astrophysics Data System (ADS)

    Kite, Edwin Stephen

    This thesis describes work related to long-term climate stability, on Mars and exoplanets. Mars is the only planet known to record a major transition in planetary habitability. The evidence for surface temperatures near the melting point of water on Early Mars is difficult to explain, because theory predicts a faint young Sun. Seasonal snowmelt need not require high annual mean temperatures, but surface water ice tends to migrate away from the warmer regions of the planet where melting is energetically possible. In the first part of this thesis I use geological analysis, mesoscale models, and idealized surface energy balance models to examine two possible solutions to this problem. Impacts into icy targets, groundwater outbursts, and phreatic explosions are all expected to inject water vapor into the Mars atmosphere. I use mesoscale models to track the atmospheric response to these transient, localized vapor sources. Using idealized boundary conditions, I show that storms with updraft speeds >50 m/s and localized precipitation are expected near transient lakes >103 km2 in size. Snow deposited in this way is out of equilibrium with orbital forcing, and correspondingly more likely to melt. Canyon paleolakes in the Valles Marineris are frequently associated with streams preserved on the plateaux just downwind of the canyons. Using geologically realistic boundary conditions, I study the atmospheric response to two short-lived paleolakes. In each case, the plateau streams are in the locations expected for localized precipitation. Liquid water availability favors lithification, so the Martian sedimentary rock record is a wet-pass filter. Orbital variability strongly affects liquid water availability, so considering only averaged orbital conditions is neither sufficient not appropriate. To find the likelihood of snow melting, I consider all possible orbital forcings using an idealized but self-consistent model of snowpack energy balance and the CO2 greenhouse effect

  17. Anomalous crustal and lithospheric mantle structure of southern part of the Vindhyan Basin and its geodynamic implications

    NASA Astrophysics Data System (ADS)

    Pandey, O. P.; Srivastava, R. P.; Vedanti, N.; Dutta, S.; Dimri, V. P.

    2014-09-01

    Tectonically active Vindhyan intracratonic basin situated in central India, forms one of the largest Proterozoic sedimentary basins of the world. Possibility of hydrocarbon occurrences in thick sediments of the southern part of this basin, has led to surge in geological and geophysical investigations by various agencies. An attempt to synthesize such multiparametric data in an integrated manner, has provided a new understanding to the prevailing crustal configuration, thermal regime and nature of its geodynamic evolution. Apparently, this region has been subjected to sustained uplift, erosion and magmatism followed by crustal extension, rifting and subsidence due to episodic thermal interaction of the crust with the hot underlying mantle. Almost 5-6 km thick sedimentation took place in the deep faulted Jabera Basin, either directly over the Bijawar/Mahakoshal group of mafic rocks or high velocity-high density exhumed middle part of the crust. Detailed gravity observations indicate further extension of the basin probably beyond NSL rift in the south. A high heat flow of about 78 mW/m2 has also been estimated for this basin, which is characterized by extremely high Moho temperatures (exceeding 1000 °C) and mantle heat flow (56 mW/m2) besides a very thin lithospheric lid of only about 50 km. Many areas of this terrain are thickly underplated by infused magmas and from some segments, granitic-gneissic upper crust has either been completely eroded or now only a thin veneer of such rocks exists due to sustained exhumation of deep seated rocks. A 5-8 km thick retrogressed metasomatized zone, with significantly reduced velocities, has also been identified around mid to lower crustal transition.

  18. Quartz tube extensometer for observation of Earth tides and local tectonic deformations at the Sopronbanfalva Geodynamic Observatory, Hungary

    SciTech Connect

    Mentes, Gy.

    2010-07-15

    In May 1990, a quartz tube extensometer was installed in the Sopronbanfalva Geodynamic Observatory of the Geodetic and Geophysical Research Institute (GGRI) of the Hungarian Academy of Sciences for recording Earth tides and recent tectonic movements. The paper describes the construction of the extensometer and a portable calibrator used for the in situ calibration of the instrument. The extensometer is very sensitive. Its scale factor is 2.093{+-}0.032 nm/mV according to the highly precise calibration method developed at the GGRI. Since the stability of extensometers is strongly influenced by the geological structure and properties of the rocks in the vicinity of the recording site, the observatory instrument system was tested by coherence analysis between theoretical (as the input signal) and measured tidal data series (as the output signal). In the semidiurnal tidal frequency band the coherence is better than 0.95, while in the diurnal band it is about 0.8. Probably this is due to the fact that the noise is higher in the diurnal band (0.4-0.5 nstr) than in the semidiurnal band (0.19-0.22 nstr). Coherence analysis between theoretical and measured data corrected for barometric changes yielded a small improvement of coherence in both frequency bands, while using temperature data correction, no observable improvement was obtained. Results of the tidal analysis also show that the observatory instrument system is suitable for recording very small tectonic movements. The 18 years of continuous data series measured by the extensometer prove the high quality of the extensometer. On the basis of investigations, it was pointed out that further efforts should be done to improve the barometric correction method and that correction for ocean load, as well as considering topographic and cavity effects are necessary to increase the accuracy of determining tidal parameters.

  19. Arc-magmatism and subduction history beneath the Zagros Mountains, Iran: A new report of adakites and geodynamic consequences

    NASA Astrophysics Data System (ADS)

    Omrani, Jafar; Agard, Philippe; Whitechurch, Hubert; Benoit, Mathieu; Prouteau, Gaëlle; Jolivet, Laurent

    2008-12-01

    The Zagros Mountains were formed by convergence between Eurasia and Africa/Arabia. Compared to the wealth of recent studies on the external Zagros fold and thrust belt, the internal Sanandaj-Sirjan and Urumieh-Dokhtar magmatic arcs (SSMA, UDMA) remain poorly studied, despite being some of the best-preserved active margins within the greater Alpine-Himalayan convergent system. We focus on the key geodynamic constraints provided by the subduction-related magmatism of the upper plate, which shifted ~ 300 km inward from the SSMA to the UDMA at the end of the Mesozoic. Major and trace element data show that all studied magmatic rocks display the characteristics of subduction-related calc-alkaline magmas. Rare-earth element (REE) systematics for Mesozoic (SSMA) and Eocene (UDMA) volcanic and plutonic rocks suggest a similar mantle wedge source. In contrast, major and trace element data for volcanic rocks postdating the Late Miocene reveal a typical adakitic signature along part of the UDMA. The amphibole and SiO 2-rich (59-72 wt.%) Zagros adakites have very low Y and HREE contents. Adakitic magmas are likely to result from the melting of mafic material at depth (i.e., subducted oceanic crust from the slab and/or earlier obducted ophiolites) under unusually high temperature thermal conditions, in response to the regional-scale thermal re-equilibration accompanying collision or, to slab break-off. The fact that the distribution of these adakites is spatially restricted to the central parts of the UDMA (i.e. 200-300 km along strike) supports the slab break-off hypothesis, as do preliminary tomographic images. The timing of this event is coeval with slab-break-off below southern Turkey, which supports the view that slab detachment propagated laterally in the Neotethyan slab, both to the west (Turkey) and to the south (Iran), during the last 10-5 Ma.

  20. Moving-mass gravimeter calibration in the Mátyáshegy Gravity and Geodynamical Observatory (Budapest)

    NASA Astrophysics Data System (ADS)

    Kis, Márta; Koppán, Andras; Kovács, Péter; Merényi, László

    2014-05-01

    A gravimeter calibration facility exists in the Mátyáshegy Gravity and Geodynamical Observatory of Geological and Geophysical Institute in Hungary. During the calibration a cylindrical ring of 3200 kg mass is vertically moving around the equipment, generating gravity variations. The effect of the moving mass can be precisely calculated from the known mass and geometrical parameters. The main target of the calibration device was to reach a relative accuracy of 0.1-0.2% for the calibration of Earth-tide registering gravimeters. The maximum theoretical gravity variation produced by the vertical movement of the mass is ab. 110 microGal, so it provides excellent possibility for the fine calibration of gravimeters in the tidal range. The instrument was out of order for many years and in 2012 and 2013 it was renovated and automatized. The calibration process is aided by intelligent controller electronics. A new PLC-based system has been developed to allow easy control of the movement of the calibrating mass and to measure the mass position. It enables also programmed steps of movements (waiting positions and waiting times) for refined gravity changes. All parameters (position of the mass, CPI data, X/Y leveling positions) are recorded with 1/sec. sampling rate. The system can be controlled remotely through the internet. As it is well known that variations of the magnetic field can influence the measurements of metal-spring gravimeters, authors carried out magnetic experiments on the pillar of the calibration device as well, in order to analyze the magnetic effect of the moving stainless steel-mass. During the movements of the mass, the observed magnetic field has been changed significantly. According to the magnetic measurements, a correction for the magnetic effect was applied on the measured gravimetric data series. In this presentation authors show the facility in details and the numerical results of tests carried out by applying LCR G gravimeters.

  1. Alpine geodynamic evolution of passive and active continental margin sequences in the Tauern Window (eastern Alps, Austria, Italy): a review

    NASA Astrophysics Data System (ADS)

    Kurz, W.; Neubauer, F.; Genser, J.; Dachs, E.

    The Penninic oceanic sequence of the Glockner nappe and the foot-wall Penninic continental margin sequences exposed within the Tauern Window (eastern Alps) have been investigated in detail. Field data as well as structural and petrological data have been combined with data from the literature in order to constrain the geodynamic evolution of these units. Volcanic and sedimentary sequences document the evolution from a stable continent that was formed subsequent to the Variscan orogeny, to its disintegration associated with subsidence and rifting in the Triassic and Jurassic, the formation of the Glockner oceanic basin and its consumption during the Upper Cretaceous and the Paleogene. These units are incorporated into a nappe stack that was formed during the collision between a Penninic Zentralgneis block in the north and a southern Austroalpine block. The Venediger nappe and the Storz nappe are characterized by metamorphic Jurassic shelf deposits (Hochstegen group) and Cretaceous flysch sediments (Kaserer and Murtörl groups), the Eclogite Zone and the Rote Wand-Modereck nappe comprise Permian to Triassic clastic sequences (Wustkogel quartzite) and remnants of platform carbonates (Seidlwinkl group) as well as Jurassic volcanoclastic material and rift sediments (Brennkogel facies), covered by Cretaceous flyschoid sequences. Nappe stacking was contemporaneous to and postdated subduction-related (high-pressure) eclogite and blueschist facies metamorphism. Emplacement of the eclogite-bearing units of the Eclogite zone and the Glockner nappe onto Penninic continental units (Zentralgneis block) occurred subsequent to eclogite facies metamorphism. The Eclogite zone, a former extended continental margin, was subsequently overridden by a pile of basement-cover nappes (Rote Wand-Modereck nappe) along a ductile out-of-sequence thrust. Low-angle normal faults that have developed during the Jurassic extensional phase might have been inverted during nappe emplacement.

  2. The petrogenesis of Early Eocene non-adakitic volcanism in NE Turkey: Constraints on the geodynamic implications

    NASA Astrophysics Data System (ADS)

    Aydınçakır, Emre

    2014-11-01

    Whole-rock geochemistry, mineral chemistry, the 40Ar-39Ar age, and Sr-Nd isotopic data are presented for the Early Eocene non-adakitic volcanic rocks on the eastern corner of the Eastern Pontides orogenic belt (NE Turkey). The tectonic setting of the Eastern Pontides during the Late Mesozoic to Early Cenozoic remains a topic of debate. Here, for the first time, we describe the Early Eocene non-adakitic volcanic rocks from the Eastern Pontides. These rocks contain plagioclase, hornblende phenocrysts, and magnetite/titanomagnetite and apatite microphenocrysts. Geochronology studies based on the 40Ar-39Ar ratio of the amphibole separates reveal that the non-adakitic porphyritic volcanic rocks have a crystallization age of 50.04 ± 0.10 to 50.47 ± 0.22 Ma (Ypresian). The volcanic rocks show tholeiitic to calc-alkaline affinities and have low-to-medium K contents. They are also enriched in large-ion lithophile elements (LILE), light rare-earth elements (LREE), and depleted in high field strength elements (HFSE), with a no negative Eu anomaly (Eun/Eu* = 1.03-1.08) in mantle-normalized trace element spidergrams. The samples (Lacn/Lucn = 2.60-4.28) show low-to-medium enrichment in LREEs relative to HREEs, in chondrite-normalized REE patterns indicating similar sources for the rock suite. These rocks display a range of ISr (50 Ma) values from 0.70451 to 0.70485, and ƐNd (50 Ma) 2.9 and 3.7. The main solidification processes involved in the evolution of these volcanics consist of fractional crystallization, with minor amounts of crustal contamination. All of our evidence supports the conclusion that the parental magma of the rocks probably derived from an enriched mantle, previously metasomatized by fluids derived from the subducted slab, in a post-collisional, geodynamic setting.

  3. Grain size evolution in the mantle and its effect on geodynamics, seismic velocities and attenuation

    NASA Astrophysics Data System (ADS)

    Dannberg, Juliane; Eilon, Zach; Gassmoeller, Rene; Moulik, Pritwiraj; Myhill, Robert; Faul, Ulrich; Asimow, Paul

    2015-04-01

    Dynamic models of Earth's convecting mantle usually implement flow laws with constant grain size, stress-independent viscosity and a limited treatment of variations associated with changes in mineral assemblage. These simplifications greatly reduce computational requirements but preclude effects such as shear localisation and transient changes in rheology associated with phase transitions, which have the potential to fundamentally change flow patterns in the mantle. Here we use the finite-element code ASPECT (Bangerth et al., 2013) to model grain size evolution and the interplay between grain size, stress and strain rate in the convecting mantle. We include the simultaneous and competing effects of dynamic recrystallisation resulting from work done by dislocation creep, grain growth in multiphase assemblages and recrystallisation at phase transitions. Grain size variations also affect seismic properties of mantle materials. We use several published formulations to relate intrinsic variables (P, T, and grain size) from our numerical models to seismic velocity (Vs) and attenuation (Q). Our calculations use thermodynamically self-consistent anharmonic elastic moduli determined for the mineral assemblages in the mantle using HeFESTo (Stixrude and Lithgow-Bertelloni, 2013). We investigate the effect of realistically heterogeneous grain sizes by computing body wave travel times, ray paths, and attenuation (t*) at different frequencies. We highlight the frequency-dependent sensitivity of seismic waves to grain size, which is important when interpreting Vs and Q observations in terms of mineral assemblage and temperature. Our models show that rapid metamorphic reactions in mantle upwellings and downwellings lead to high lateral viscosity contrasts, as a result of gradual grain size evolution. Positive feedback between grain size reduction and viscosity reduction results in shear localisation. As a result, the edges of thermal plumes have smaller grain sizes and lower

  4. Deformation driven by subduction and microplate collision: Geodynamics of Cook Inlet basin, Alaska

    USGS Publications Warehouse

    Bruhn, R.L.; Haeussler, P.J.

    2006-01-01

    Late Neogene and younger deformation in Cook Inlet basin is caused by dextral transpression in the plate margin of south-central Alaska. Collision and subduction of the Yakutat microplate at the northeastern end of the Aleutian subduction zone is driving the accretionary complex of the Chugach and Kenai Mountains toward the Alaska Range on the opposite side of the basin. This deformation creates belts of fault-cored anticlines that are prolific traps of hydrocarbons and are also potential sources for damaging earthquakes. The faults dip steeply, extend into the Mesozoic basement beneath the Tertiary basin fill, and form conjugate flower structures at some localities. Comparing the geometry of the natural faults and folds with analog models created in a sandbox deformation apparatus suggests that some of the faults accommodate significant dextral as well as reverse-slip motion. We develop a tectonic model in which dextral shearing and horizontal shortening of the basin is driven by microplate collision with an additional component of thrust-type strain caused by plate subduction. This model predicts temporally fluctuating stress fields that are coupled to the recurrence intervals of large-magnitude subduction zone earthquakes. The maximum principal compressive stress is oriented east-southeast to east-northeast with nearly vertical least compressive stress when the basin's lithosphere is mostly decoupled from the underlying subduction megathrust. This stress tensor is compatible with principal stresses inferred from focal mechanisms of earthquakes that occur within the crust beneath Cook Inlet basin. Locking of the megathrust between great magnitude earthquakes may cause the maximum principal compressive stress to rotate toward the northwest. Moderate dipping faults that strike north to northeast may be optimally oriented for rupture in the ambient stress field, but steeply dipping faults within the cores of some anticlines are unfavorably oriented with respect to

  5. Fully coupled chemical thermodynamics and geodynamics simulations of melting beneath spreading plates

    NASA Astrophysics Data System (ADS)

    Tirone, M.

    2006-12-01

    To model deep earth processes a general purpose simulation program has being developed. The program solves the multiphase flow equations (transport equations for: phase abundances, phase velocities, total mass, total energy, chemical components) and thermodynamic Gibbs free energy minimization of a chemical system in space and time. Coupling of these two methods allows determination of the thermophysical properties entering at any time in the dynamic model (this part is almost 'parameter free') as well as predicting mineral compositions and abundances and other physico-chemical properties that can be compared to observations. The most critical factor to obtain realistic results is the accuracy and completeness of the thermodynamic database used in the Gibbs free energy procedure. The second most important factor is proper knowledge of the mantle rheology. This simulation approach is applied here to study the evolution of a ridge system starting from the spreading of continental lithosphere. The scenario is a polybaric dynamic melting where the composition of the residual solid is continuously changing with depth. Melt forms and travels within the same region. The thermodynamic procedure allows to reproduce the correct position of the solidus as a function of composition and to determine the amount of melt and its composition at any pressure and temperature. Some preliminary conclusions from this modeling work are outlined here. (1) When the thermal anomaly reaches the surface in the initial stage of the spreading process the large amount of melt below the surface is rapidly extracted (possible explanation for flood basalts). (2) Melt not formed on the ridge axis accumulates at the base of the lithosphere. (3) Extraction to the surface is not continuous in time and occurs only within approximately 30 Km apart from the ridge axis. Beyond this point, melt follows mantle flow and freezes at the lithosphere/asthenosphere boundary. This conclusion is not very sensitive

  6. Contribution to defining a geodetic reference frame for Africa (AFREF): Geodynamics implications

    NASA Astrophysics Data System (ADS)

    Saria, Elifuraha E.

    African Reference Frame (AFREF) is the proposed regional three-dimensional standard frame, which will be used to reference positions and velocities for geodetic sites in Africa and surrounding. This frame will play a crucial role in scientific application for example plate motion and crustal deformation studies, and also in mapping when it involves for example national boundary surveying, remote sensing, GIS, engineering projects and other development programs in Africa. To contribute to the definition of geodetic reference frame for Africa and provide the first continent-wide position/velocity solution for Africa, we processed and analyzed 16 years of GPS and 17 years of DORIS data at 133 GPS sites and 9 DORIS sites continuously operating geodetic sites in Africa and surroundings to describe the present-day kinematics of the Nubian and Somalian plates and constrain relative motions across the East African Rift. We use the resulting horizontal velocities to determine the level of rigidity of Nubia and updated a plate motion model for the East African Rift and revise the counter clockwise rotation of the Victoria plate and clockwise rotation of the Rovuma plate with respect to Nubia. The vertical velocity ranges from -2 to +2 mm/yr, close to their uncertainties with no clear geographical pattern. This study provides the first continent-wide position/velocity solution for Africa, expressed in International Terrestrial Reference Frame (ITRF2008), a contribution to the upcoming African Reference Frame (AFREF). In the next step we used the substantial increase in the geologic, geophysical and geodetic data in Africa to improve our understanding of the rift geometry and the block kinematics of the EAR. We determined the best-fit fault structure of the rift in terms of the locking depth and dip angle and use a block modeling approach where observed velocities are described as the contribution of rigid block rotation and strain accumulation on locked faults. Our results

  7. Tectono-sedimentary events and geodynamic evolution of the Mesozoic and Cenozoic basins of the Alpine Margin, Gulf of Tunis, north-eastern Tunisia offshore

    NASA Astrophysics Data System (ADS)

    Melki, Fetheddine; Zouaghi, Taher; Chelbi, Mohamed Ben; Bédir, Mourad; Zargouni, Fouad

    2010-09-01

    The structural pattern, tectono-sedimentary framework and geodynamic evolution for Mesozoic and Cenozoic deep structures of the Gulf of Tunis (north-eastern Tunisia) are proposed using petroleum well data and a 2-D seismic interpretation. The structural system of the study area is marked by two sets of faults that control the Mesozoic subsidence and inversions during the Paleogene and Neogene times: (i) a NE-SW striking set associated with folds and faults, which have a reverse component; and (ii) a NW-SE striking set active during the Tertiary extension episodes and delineating grabens and subsiding synclines. In order to better characterize the tectono-sedimentary evolution of the Gulf of Tunis structures, seismic data interpretations are compared to stratigraphic and structural data from wells and neighbouring outcrops. The Atlas and external Tell belonged to the southernmost Tethyan margin record a geodynamic evolution including: (i) rifting periods of subsidence and Tethyan oceanic accretions from Triassic until Early Cretaceous: we recognized high subsiding zones (Raja and Carthage domains), less subsiding zones (Gamart domain) and a completely emerged area (Raouad domain); (ii) compressive events during the Cenozoic with relaxation periods of the Oligocene-Aquitanian and Messinian-Early Pliocene. The NW-SE Late Eocene and Tortonian compressive events caused local inversions with sealed and eroded folded structures. During Middle to Late Miocene and Early Pliocene, we have identified depocentre structures corresponding to half-grabens and synclines in the Carthage and Karkouane domains. The north-south contractional events at the end of Early Pliocene and Late Pliocene periods are associated with significant inversion of subsidence and synsedimentary folded structures. Structuring and major tectonic events, recognized in the Gulf of Tunis, are linked to the common geodynamic evolution of the north African and western Mediterranean basins.

  8. Geodynamic stability of the primary in the binary asteroid system 65803 Didymos

    NASA Astrophysics Data System (ADS)

    Barnouin, Olivier S.; Maurel, Clara; Richardson, Derek C.; Ballouz, Ronald-Louis; Schwartz, Stephen; Michel, Patrick

    2015-11-01

    The moon of the near-Earth binary asteroid 65803 Didymos is the target of the Asteroid Impact and Deflection Assessment (AIDA) mission. This mission is a joint concept between NASA and ESA to investigate the effectiveness of a kinetic impactor in deflecting an asteroid. The mission is composed of two components: the NASA-led Double Asteroid Redirect Test (DART) that will impact the Didymos moon, and the ESA-led Asteroid Impact Monitoring (AIM) mission that will characterize the Didymos system. In order to provide AIDA constraints on the physical character of the both objects in this binary system, we undertook preliminary numerical investigations to evaluate the stability of the shape of the primary using its rapid 2.26 h rotation. We modeled the primary as a rubble pile. Each model consisted of thousands of uniform rigid spheres collapsed together under their own gravity to form a spherical pile that was then carved to match the current radar-derived shape model of the primary, as well as other comparable shapes (e.g. asteroid 1999 KW4, spheres) that were scaled to match best estimates of the size of Didymos. Each model was given a starting rotation period of 6 h with the spin axis aligned to the pole. At each timestep the spin rate was increased by a small amount so that after about 1 million timesteps the spin would match the observed rotation of 2.26 h. We tested a range of bulk densities spanning the current observational uncertainty (mean 2.4 g/cc) using "gravel"-like material parameters that provide significant resistance to sliding and rolling. We find that at the upper range of the density uncertainty it is possible for Didymos to hold its shape and not lose mass at its nominal rotation period, without the need for cohesive forces. At lower densities or with smoother particles, significant shape change occurs and mass loss is possible. We conclude that based on the radar shape available at the time of this writing, Didymos is marginally stable as a rubble

  9. Investigation of dynamic noise affecting geodynamics information in a tethered subsatellite

    NASA Technical Reports Server (NTRS)

    Gullahorn, G. E.

    1985-01-01

    Work performed as part of an investigation of noise affecting instrumentation in a tethered subsatellite, was studied. The following specific topics were addressed during the reporting period: a method for stabilizing the subsatellite against the rotational effects of atmospheric perturbation was developed; a variety of analytic studies of tether dynamics aimed at elucidating dynamic noise processes were performed; a novel mechanism for coupling longitudinal and latitudinal oscillations of the tether was discovered, and random vibration analysis for modeling the tethered subsatellite under atmospheric perturbation were studied.

  10. Low frequency electromagnetic signals in the atmosphere caused by geodynamics and solar activity

    NASA Astrophysics Data System (ADS)

    Novik, Oleg; Ruzhin, Yuri; Ershov, Sergey; Volgin, Max; Smirnov, Fedor

    Due to the composed structure of the medium and large portions of energy transferred, a seismic excitation in the oceanic or continental lithosphere disturbs all types of geophysical fields. To investigate the problem of electromagnetic (EM) forcing on the atmosphere from the seismically activated lithosphere, we have formulated two mathematical models of interaction of fields of different physical nature resulting in arising of the low-frequency (from 0.1 to 10 Hz by amplitude of a few hundreds of pT) EM signals in the atmosphere. First we have considered the EM field generation in the moving oceanic lithosphere and then in the moving continental one. For both cases, the main physical principles and geological data were applied for formulation of the model and characteristics of the computed signals of different nature agree with measurements of other authors. On the basis of the 2D model of the seismo-hydro-EM-temperature interaction in a lithosphere-Ocean-atmosphere domain, a block-scheme of a multisensory vertically distributed (from a seafloor up to the ionosphere) tsunami precursors’ detection system is described. On the basis of the 3D model of the seismo-EM interaction in a lithosphere-atmosphere domain, we explain effect of location of the future seismic epicenter area (obtained by Prof. Kopytenko, Yu. A. from Inst. IZMIRAN of Russian Acad. Sci. and co-authors) as the result of the magnetic field measurements in the atmosphere near the earth’s surface. We believe that the biosphere effects of forcing on the atmosphere may not be ignored. We formulate the result of our measurements with the system of micro-voltmeters: low-frequency EM disturbances of the atmosphere caused by solar activity (namely, geomagnetic storms with the geomagnetic index values K = 5 and K = 6), are decreasing temporarily the coherence of oscillations of the electric potentials of different points on the surface of a head, i.e. the coherence of the human brain EM processes. We are

  11. Mesozoic and Cenozoic plate tectonics in the High Arctic: new 2D seismic data and geodynamic models

    NASA Astrophysics Data System (ADS)

    Nikishin, Anatoly; Kazmin, Yuriy; Glumov, Ivan; Petrov, Eugene; Poselov, Viktor; Burov, Evgueni; Gaina, Carmen

    2014-05-01

    Our paper is mainly based on the interpretation of 2D seismic lines, obtained from Arctic-2001 and Arctic-2012 projects. We also analyzed all available open-source data concerning Arctic geology. Three domains are distinguished in the abyssal part of Arctic Ocean: (1) Canada Basin, (2) Lomonosov-Podvodnikov-Alpha-Mendeleev-Nautilus-Chukchi Plateau (LPAMNCP) area, (3) Eurasia Basin. Canada Basin has oceanic and transitional crust of different structure. The formation time of this oceanic basin is probably 134-117 Ma. New seismic data for LPAMNCP area shows numerous rift structures parallel to the Lomonosov Ridge and Mendeleev Ridge. These rift structures are also nearly orthogonal to the Canada Basin spreading axis, and this may indicate either a different mechanism for the formation of the LPAMNCP region and Canada Basin, or a very complicated basin architecture formed by processes we do not yet understand. We also observe at the base of the LPAMNCP area sedimentary cover packages of bright reflectors, they were interpreted as basalt flows probably related to the Cretaceous plume volcanism. Approximate time of the volcanism is about 125 Ma. After this event, the area experienced stretching and transtension as documented by large scale rifting structures. The younger Eurasian Basin has oceanic crust of Eocene to Recent age, and our new seismic data confirms that Gakkel Ridge has typical ultraslow-spreading zone topography. Perhaps, Eurasia Basin crust was partly formed by exhumed and serpentinized mantle. Lomonosov and Alpha-Mendeleev Ridges has typical present-day basin and range topography with Oligocene to Recent faults. It means, that all LPAMNCP area was subjected to regional intra-plate stretching during Neogene to Recent time. We assume, that this intra-plate stretching was related to the Gakkel Ridge extension. We suppose, that the deep-water part of Arctic Ocean was formed during three main stages: (1) Valanginian - Early Aptian: formation of Canada Basin; (2) 125 Ma - Large-scale magmatism at Alpha-Mendeleev Ridge area, followed by large-scale rifting at LPAMNCP area; (3) Eocene to present: Eurasian Basin formation, ultraslow spreading. This process is accompanied by LPAMNCP area stretching. These three stages are connected with main phases of the plate tectonic reorganization.

  12. New tectonic data from sw iberian variscan fold belt (ossa morena zone-southern portugal): implications for geodynamic models

    NASA Astrophysics Data System (ADS)

    Rosas, F.; Marques, F.; Ribeiro, A.

    2003-04-01

    New detailed structural mapping of the Alvito-Viana key sector, in SW Ossa Morena Zone (Southern Iberian Variscan Fold Belt), revealed the following tectonic imbrication of units of unknown age (from bottom to top): Gneiss unit (composed mostly of quartz-feldspar orthogneisses); Marbles unit; Água de Peixe metapelites unit (micaschists and disperse interbedded bodies - boudins? - of marbles and amphibolites); and Monte das Pereiras metapelites unit (mainly comprising micaschists and metabasalts).These units were intruded, to the North and to the West, by two main igneous complexes: the granitoid Évora massif (EM, ca. 318Ma), and the dioritic/gabbroic Beja igneous complex (BIC, ca. 340Ma), respectively. The study of metamorphic and geometric overprint relationships, between several types of structures, at different scales, revealed a chronological succession of tectonometamorphic events, comprising: a) An early high pressure metamorphic event (D_n) producing eclogites (Fonseca, et al., 1993), and blueschists (Rosas et al., in prep.). b) A retrogressive event (Dn+1 and Dn+2), affecting the HP rocks in lower grade metamorphic conditions and refolding the previous tectonic fabrics. c) A thermal event (T_n), related with an early stage of the BIC intrusions, represented by the strong static recrystallisation of the previous tectonic fabrics. d) An episode (Dn+3) represented by the tectonic reactivation of the prevoius metamorphic layering inducing a top to the NNW sense of shear. e) A N-S folding of all previous structures and fabrics as a response to the space problems imposed by the late intrusion of the BIC igneous rocks. f) A thermal episode (n+1) responsible for a late strong static recrystallisation of all previously formed tectonic fabrics, as a consequence of the granitic EM intrusions. Interpretation of this sequence of events includes the recognition, during the Variscan evolution of the SW Ossa-Morena zone, of northwards oblique subduction and HP metamorphism during D_n, exhumation during Dn+1 and Dn+2, orogenic magmatism associated to the BIC early intrusions during T_n, northwards (left-lateral) tectonic imbrication during Dn+3, accommodation to space problems imposed by the late BIC intrusions during Dn+4, and late orogenic magmatism associated to the EM intrusion during Tn+2. Following the contributions of Mancktelow (1995) and Petrini &Podladchikov (2000), the occurrence of tectonic ovepressure associated with the development of a tectonic wedge (flake geometry) is proposed.

  13. A massively parallel adaptive scheme for melt migration in geodynamics computations

    NASA Astrophysics Data System (ADS)

    Dannberg, Juliane; Heister, Timo; Grove, Ryan

    2016-04-01

    Melt generation and migration are important processes for the evolution of the Earth's interior and impact the global convection of the mantle. While they have been the subject of numerous investigations, the typical time and length-scales of melt transport are vastly different from global mantle convection, which determines where melt is generated. This makes it difficult to study mantle convection and melt migration in a unified framework. In addition, modelling magma dynamics poses the challenge of highly non-linear and spatially variable material properties, in particular the viscosity. We describe our extension of the community mantle convection code ASPECT that adds equations describing the behaviour of silicate melt percolating through and interacting with a viscously deforming host rock. We use the original compressible formulation of the McKenzie equations, augmented by an equation for the conservation of energy. This approach includes both melt migration and melt generation with the accompanying latent heat effects, and it incorporates the individual compressibilities of the solid and the fluid phase. For this, we derive an accurate and stable Finite Element scheme that can be combined with adaptive mesh refinement. This is particularly advantageous for this type of problem, as the resolution can be increased in mesh cells where melt is present and viscosity gradients are high, whereas a lower resolution is sufficient in regions without melt. Together with a high-performance, massively parallel implementation, this allows for high resolution, 3d, compressible, global mantle convection simulations coupled with melt migration. Furthermore, scalable iterative linear solvers are required to solve the large linear systems arising from the discretized system. Finally, we present benchmarks and scaling tests of our solver up to tens of thousands of cores, show the effectiveness of adaptive mesh refinement when applied to melt migration and compare the

  14. A change in the geodynamics of continental growth 3 billion years ago.

    PubMed

    Dhuime, Bruno; Hawkesworth, Chris J; Cawood, Peter A; Storey, Craig D

    2012-03-16

    Models for the growth of continental crust rely on knowing the balance between the generation of new crust and the reworking of old crust throughout Earth's history. The oxygen isotopic composition of zircons, for which uranium-lead and hafnium isotopic data provide age constraints, is a key archive of crustal reworking. We identified systematic variations in hafnium and oxygen isotopes in zircons of different ages that reveal the relative proportions of reworked crust and of new crust through time. Growth of continental crust appears to have been a continuous process, albeit at variable rates. A marked decrease in the rate of crustal growth at ~3 billion years ago may be linked to the onset of subduction-driven plate tectonics. PMID:22422979

  15. Investigations on the hierarchy of reference frames in geodesy and geodynamics

    NASA Technical Reports Server (NTRS)

    Grafarend, E. W.; Mueller, I. I.; Papo, H. B.; Richter, B.

    1979-01-01

    Problems related to reference directions were investigated. Space and time variant angular parameters are illustrated in hierarchic structures or towers. Using least squares techniques, model towers of triads are presented which allow the formation of linear observation equations. Translational and rotational degrees of freedom (origin and orientation) are discussed along with and the notion of length and scale degrees of freedom. According to the notion of scale parallelism, scale factors with respect to a unit length are given. Three-dimensional geodesy was constructed from the set of three base vectors (gravity, earth-rotation and the ecliptic normal vector). Space and time variations are given with respect to a polar and singular value decomposition or in terms of changes in translation, rotation, deformation (shear, dilatation or angular and scale distortions).

  16. Geodynamics of crustal deformation and seismotectonic block movements in central Europe

    NASA Technical Reports Server (NTRS)

    Liu, H. S.

    1984-01-01

    Geological observations reveal the style of neotectonic near-surface stresses and deformations in central Europe. Seismic activity, focal depths and fault plane solutions of earthquakes indicate kinematic reactions within the crust. A crustal deformation model which may account for the Rhine graben systems and the associated seismotectonic block movements in Europe is presented. A computer aided tomography to gravity anomalies is used in determining the crustal stresses in central Europe. Tomographical interpretations of gravity data with respect to seismic stresses are discussed. Kinematics and dynamics are integrated to show that the measured regional stresses in central Europe are derivable from the convection generated traction on the boundary of the elastic spherical shell of the crust as inferred from satellite derived gravity data.

  17. An early Pliocene uplift of the central Apenninic foredeep and its geodynamic significance

    NASA Astrophysics Data System (ADS)

    van der Meulen, M. J.; Buiter, S. J. H.; Meulenkamp, J. E.; Wortel, M. J. R.

    2000-04-01

    van der Meulen et al. [1998] identified a pattern of lateral shifts of Apenninic foredeep depocenters, which was interpreted as the regional expression of lateral migration of slab detachment in the sense of Wortel and Spakman [1992]. In addition to being expressed in such a pattern of lateral reorganisations, slab detachment is expected to result in rebound. This study focuses on Plio-Pleistocene vertical motions of the central Apenninic inner forearc. Here, a major late early Pliocene phase of uplift is identified, by means of (1) micropaleontology-based paleobathymetry, (2) analysis of the compaction history, and (3) numerical modeling of the flexural response of the underlying lithosphere to sediment loading. The timing of the uplift event is consistent with that of the regional reorganizations. On the basis of this consistency and the fact that it can be demonstrated that the uplift is not related to accretionary processes, we interpret this event as rebound after slab detachment.

  18. Lithospheric thermal-rheological structure of the Ordos Basin and its geodynamics

    NASA Astrophysics Data System (ADS)

    Pan, J.; Huang, F.; He, L.; Wu, Q.

    2015-12-01

    The study on the destruction of the North China Craton has always been one of the hottest issues in earth sciences.Both mechanism and spatial variation are debated fiercely, still unclear.However, geothermal research on the subject is relatively few. Ordos Basin, located in the west of the North China Craton, is a typical intraplate. Based on two-dimensional thermal modeling along a profile across Ordos Basin from east to west, obtained the lithospheric thermal structure and rheology. Mantle heat flow in different regions of Ordos Basin is from 21.2 to 24.5 mW/m2. In the east mantle heat flow is higher while heat flow in western region is relatively low. But mantle heat flow is smooth and low overall, showing a stable thermal background. Ratio of crustal and mantle heat flow is between 1.51 and 1.84, indicating that thermal contribution from shallow crust is lower than that from the mantle. Rheological characteristics along the profile are almost showed as "jelly sandwich" model and stable continental lithosphere structure,which is represent by a weak crust portion but a strong lithospheric mantle portion in vertical strength profile. Based on above , both thermal structure and lithospheric rheology of Ordos Basin illustrate that tectonic dynamics environment in the west of North China Craton is relatively stable. By the study on lithospheric thermal structure, we focus on the disparity in thickness between the thermal lithosphere and seismic lithosphere.The difference in western Ordos Basin is about 140km, which decreases gradually from Fenwei graben in the eastern Ordos Basin to the Bohai Bay Basin.That is to say the difference decreases gradually from the west to the east of North China Craton.The simulation results imply that viscosity of the asthenosphere under North China Craton also decreases gradually from west to east, confirming that dehydration of the Pacific subduction is likely to have great effect on the North China Craton.

  19. Velocity structure around the Baikal rift zone from teleseismic and local earthquake traveltimes and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Petit, Carole; Koulakov, Ivan; Deverchère, Jacques

    1998-10-01

    We present new results on the velocity structure of the Baikal rift zone, Asia, deduced from a comparative teleseismic and local tomography analysis. The aim of this paper is to better identify the role of deep mantle processes versus that of far-field tectonic effects on the occurrence of extensional tectonics within a continental plate. We use 36000 traveltimes of P-refracted waves from the ISC catalogues and Pg and Pn traveltimes of 578 earthquakes recorded by the Russian regional network to determine a velocity model by the use of local and teleseismic inversion procedures. The models show that some velocity patterns are continuous from the surface down to at least 400 km. Among them, a narrow negative anomaly goes through Mongolia and follows the southern and eastern margins of the Siberian craton: this structure is interpreted as a thin mantle plume rising beneath the rift axis. However, our results do not evidence any wide asthenospheric upwarp at this place. Other velocity anomalies observed near the surface are not deeply rooted. In particular, a negative anomaly is observed at shallow levels (48 km) beneath the northern third of Lake Baikal, which is disconnected from deeper structures. It may be explained by the existence of underplated magmatic material at the bottom of the crust. By comparing the geometry of deep-rooted anomalies to the present-day stress field patterns, we conclude that the sub-lithospheric mantle dynamics is not the main factor controlling extensional processes in the Baikal rift. However, it does contribute to a thermal weakening of the lithosphere along a mechanical discontinuity bounding the Siberian shield. We finally conclude that three favourable conditions are gathered in the Baikal area to generate extension: far-field extensional stress field, mechanical inherited lithospheric weakness and heat supply. Further studies should help to precise the genetic link between these three factors.

  20. Geodynamics and Rate of Volcanism on Massive Earth-like Planets

    NASA Astrophysics Data System (ADS)

    Kite, E. S.; Manga, M.; Gaidos, E.

    2009-08-01

    We provide estimates of volcanism versus time for planets with Earth-like composition and masses 0.25-25 M ⊕, as a step toward predicting atmospheric mass on extrasolar rocky planets. Volcanism requires melting of the silicate mantle. We use a thermal evolution model, calibrated against Earth, in combination with standard melting models, to explore the dependence of convection-driven decompression mantle melting on planet mass. We show that (1) volcanism is likely to proceed on massive planets with plate tectonics over the main-sequence lifetime of the parent star; (2) crustal thickness (and melting rate normalized to planet mass) is weakly dependent on planet mass; (3) stagnant lid planets live fast (they have higher rates of melting than their plate tectonic counterparts early in their thermal evolution), but die young (melting shuts down after a few Gyr); (4) plate tectonics may not operate on high-mass planets because of the production of buoyant crust which is difficult to subduct; and (5) melting is necessary but insufficient for efficient volcanic degassing—volatiles partition into the earliest, deepest melts, which may be denser than the residue and sink to the base of the mantle on young, massive planets. Magma must also crystallize at or near the surface, and the pressure of overlying volatiles must be fairly low, if volatiles are to reach the surface. If volcanism is detected in the 10 Gyr-old τ Ceti system, and tidal forcing can be shown to be weak, this would be evidence for plate tectonics.

  1. Shear wave splitting analyses in Tian Shan: Geodynamic implications of complex seismic anisotropy

    NASA Astrophysics Data System (ADS)

    Cherie, Solomon G.; Gao, Stephen S.; Liu, Kelly H.; Elsheikh, Ahmed A.; Kong, Fansheng; Reed, Cory A.; Yang, Bin B.

    2016-06-01

    The Tian Shan is a tectonically complex intracontinental orogenic belt situated between the Tarim Basin and the Kazakh Shield. The vast majority of the previous shear wave splitting (SWS) measurements were presented as station averages, which are only valid when the anisotropy structure can be approximated by a single layer of anisotropy with a horizontal axis of symmetry, i.e., a model of simple anisotropy. A variety of anisotropy-forming hypotheses have been proposed based on the station-averaged measurements. In this study, we measure the splitting parameters at 25 stations that recorded high-quality data from a wide back azimuthal range for the purpose of identifying and characterizing complex anisotropy. Among the 25 stations, 15 of them show systematic azimuthal variations in the observed splitting parameters with a 90° periodicity that is consistent with a model of two-layered anisotropy. The fast orientations of the upper layer range from 50° to 90° measured clockwise from the north, which are subparallel to the strike of the orogenic belt, and the splitting times are between 0.9 and 1.9 s. The corresponding values for the lower layer are -45° to -85° and 1.2-2.2 s, respectively. The remaining 10 stations demonstrate azimuthally invariant splitting parameters with strike-parallel fast orientations, and can be represented by a single layer of anisotropy with a horizontal axis of symmetry. We propose that the strike-parallel anisotropy is caused by lithospheric shortening, and anisotropy in the lower layer is associated with WNW-ward flow of asthenospheric material sandwiched between the subducting Tarim lithosphere and the thick Kazakh lithospheric root.

  2. GEODYNAMICS AND RATE OF VOLCANISM ON MASSIVE EARTH-LIKE PLANETS

    SciTech Connect

    Kite, E. S.; Manga, M.; Gaidos, E.

    2009-08-01

    We provide estimates of volcanism versus time for planets with Earth-like composition and masses 0.25-25 M {sub +}, as a step toward predicting atmospheric mass on extrasolar rocky planets. Volcanism requires melting of the silicate mantle. We use a thermal evolution model, calibrated against Earth, in combination with standard melting models, to explore the dependence of convection-driven decompression mantle melting on planet mass. We show that (1) volcanism is likely to proceed on massive planets with plate tectonics over the main-sequence lifetime of the parent star; (2) crustal thickness (and melting rate normalized to planet mass) is weakly dependent on planet mass; (3) stagnant lid planets live fast (they have higher rates of melting than their plate tectonic counterparts early in their thermal evolution), but die young (melting shuts down after a few Gyr); (4) plate tectonics may not operate on high-mass planets because of the production of buoyant crust which is difficult to subduct; and (5) melting is necessary but insufficient for efficient volcanic degassing-volatiles partition into the earliest, deepest melts, which may be denser than the residue and sink to the base of the mantle on young, massive planets. Magma must also crystallize at or near the surface, and the pressure of overlying volatiles must be fairly low, if volatiles are to reach the surface. If volcanism is detected in the 10 Gyr-old {tau} Ceti system, and tidal forcing can be shown to be weak, this would be evidence for plate tectonics.

  3. On Lateral Viscosity Contrast in the Mantle and the Rheology of Low-Frequency Geodynamics

    NASA Technical Reports Server (NTRS)

    Ivins, Erik R.; Sammis, Charles G.

    1995-01-01

    Mantle-wide heterogeneity is largely controlled by deeply penetrating thermal convective currents. These thermal currents are likely to produce significant lateral variation in rheology, and this can profoundly influence overall material behaviour. How thermally related lateral viscosity variations impact models of glacio-isostatic and tidal deformation is largely unknown. An important step towards model improvement is to quantify, or bound, the actual viscosity variations that characterize the mantle. Simple scaling of viscosity to shear-wave velocity fluctuations yields map-views of long- wavelength viscosity variation. These give a general quantitative description and aid in estimating the depth dependence of rheological heterogeneity throughout the mantle. The upper mantle is probably characterized by two to four orders of magnitude variation (peak-to-peak). Discrepant time-scales for rebounding Holocene shorelines of Hudson Bay and southern Iceland are consistent with this characterization. Results are given in terms of a local average viscosity ratio, (Delta)eta(bar)(sub i), of volumetric concentration, phi(sub i). For the upper mantle deeper than 340 km the following reasonable limits are estimated for (delta)eta(bar) approx. equal 10(exp -2): 0.01 less than or equal to phi less than or equal to 0.15. A spectrum of ratios (Delta)eta(bar)(sub i) less than 0.1 at concentration level eta(sub i) approx. equal 10(exp -6) - 10(exp -1) in the lower mantle implies a spectrum of shorter time-scale deformational response modes for second-degree spherical harmonic deformations of the Earth. Although highly uncertain, this spectrum of spatial variation allows a purely Maxwellian viscoelastic rheology simultaneously to explain all solid tidal dispersion phenomena and long-term rebound-related mantle viscosity. Composite theory of multiphase viscoelastic media is used to demonstrate this effect.

  4. A Coupled Geochemical and Geodynamical Approach for Mantle Melting Beneath Hawaii.

    NASA Astrophysics Data System (ADS)

    Lambart, S.; Kelemen, P. B.

    2014-12-01

    The presence of the Hawaiian plume is manifested by the Hawaiian swell [1] and voluminous eruption of Ni-rich lavas [2] with enriched isotopic compositions [3]. Here we estimate the conditions of melt generation needed to reproduce both features. We used thermodynamic treatment for fractional melting [4] and melting parameterizations for pyroxenites [5] and peridotite [6] to determine pyroxenite contribution in magmas Xpx as functions of potential temperature TP, pyroxenite abundance in the source P, radius of the melting zone R and distance to the plume axis. The final pressure of melting is set to correspond with the base of the lithosphere (3 GPa) at the plume axis and increases with the distance from the axis [7]. The Hawaiian plume axis is thought to be currently between Loihi (L), Kilauea (K) and Mauna Loa (ML), which are 25 km, 32 km and 44 km radially away from the plume axis, respectively [3]. To determine Xpx, we assumed that magmas are accumulated melts produced on a circular sampling zone of 50 km diameter centered beneath each volcano [8]. Preliminary calculations show that for TP = 1525°C, P = 0.07 and R = 55 km, XpxML = 0.59, XpxK = 0.49 and XpxL = 0.45. XpxML and XpxK are similar to values suggested by [2]. Computed liquidus temperatures at 3 GPa are consistent with those of Hawaiian parental melts (1500-1520°C; [9]). XpxL is higher than suggested by [2] (XpxL = 0.09) but their estimate is based on only one glass analysis. Our model is also consistent with isotopic compositions: K and L have similar ɛNd, while ML is more enriched [3]. Finally, we can compute the density deficit using parameterization of [1] and relate it to the volume flux volume flux [10]: we obtain 3.2 km3/Yr, a value similar to the estimations based on the Hawaiian swell model [1]. 1-Ribe & Christensen EPSL 1999; 2-Sobolev et al. Nature 2005; 3-DePaulo et al. GGG 2001; 4-Phipps Morgan GGG 2001; 5-Lambart et al. in prep; 6-Katz et al. GGG 2003; 7-Ito & Mahoney EPSL 2005; 8-De

  5. Petrogenesis and geodynamic significance of silicic volcanism in the western Trans-Mexican Volcanic Belt

    NASA Astrophysics Data System (ADS)

    Petrone, C. M.; Ferrari, L.; Orozco, M. A.; Lopez Martinez, M.

    2012-04-01

    Silicic volcanism in the western Trans-Mexican Volcanic Belt (WTMVB) was defined a Pliocene ignimbrite flare-up associated with the rifting of the Jalisco block from mainland Mexico (Frey et al., 2007; GSAB). With the integration of new and published geochronologic, geochemical, and isotope data we revise this interpretation and propose a new petrogenetic model. The oldest silicic volcanism consists of large silicic domes and minor pyroclastic flows (~370 km3) emplaced to the north of Guadalajara above a thick succession of ~11 to 8.7 Ma basaltic lavas, which yielded Ar-Ar and obsidian FT ages of ~7.5 to 5 Ma. Shortly after (4.9 to 2.9 Ma) large amount of rhyolitic lavas and ash flow tuffs (~500 km3) were emplaced in a WNW-ESE trending belt from Guadalajara to Compostela. Rhyolitic domes and flows (~430 km3) were emplaced also in the Pleistocene mostly between Tequila and Guadalajara with the late Pleistocene La Primavera caldera (~35 km3) as the sole explosive volcanic episodes. As a whole, silicic volcanism occurred from Late Miocene to the Pleistocene, and was dominated by dome and lava flows. Most rhyolites have high LILE/HFSE values and negative spikes at Nb, P and Ti. They also show the same Ba/Nb and K/Rb values and slightly higher Rb/Sr ratios as the 11-8 Ma basalts. Rhyolite Sr isotope data (87Sr/86Sr init = 0.70371 - 070598) are only slightly more radiogenic than the 11-8 basalts (87Sr/86Sr init = 0.70349-0.70410), whereas Nd isotope ratios are indistinguishable from them. Sr and Nd isotope ratios of the rhyolites are also similar to the crust nearby, indicating that they can be compatible either with fractional crystallization (FC) of basalts or with crust assimilation/melting. However REE contents are too low to be the result of basalt FC. Isotope and REE data can be successfully modelled with an initial crustal melt which subsequently undergone fractional crystallization of feldspar and quartz. Late Miocene slab detachment and subsequent slab rollback

  6. AlpArray - Probing Alpine geodynamics with the next generation of geophysical experiments and techniques

    NASA Astrophysics Data System (ADS)

    Kissling, Edi; Hetenyi, György; AlpArray Working Group

    2014-05-01

    AlpArray is a European initiative to advance our understanding of orogenesis and its relationship to mantle and plate dynamics, surface processes, seismotectonics and seismic hazard in the Alps and the surrounding Apennines-Carpathians-Dinarides orogenic system. The initiative will integrate present-day Earth observables with high-resolution geophysical imaging of 3D structure and physical properties of the lithosphere and of the upper mantle, with focus on a high-end seismological array. With nearly three years of scientific and technical preparation, the start of AlpArray experiments is now on the horizon. In this presentation we overview the general idea and purpose of AlpArray, reason why the initiative focuses on the greater Alpine area and discuss some of the outstanding scientific questions. We provide an overview of the planned field efforts, mainly the overall AlpArray seismic network with 40 km average station spacing and a large aerial coverage. Further plans of targeted seismological experiments with regional interests as well as of other field measurement techniques (magnetotellurics, gravity) are also presented. The outline of collaborative projects between the numerous participating institutions and researchers are described in the frame of seven main AlpArray themes. These include state-of-the-art modelling techniques that will ultimately describe the dynamic evolution of the orogenic system in great detail. Finally, the most recent news regarding the organization of the AlpArray project will be summarized.

  7. Origin of the DUPAL anomaly in mantle xenoliths of Patagonia (Argentina) and geodynamic consequences

    NASA Astrophysics Data System (ADS)

    Mazzucchelli, Maurizio; Cipriani, Anna; Hémond, Christophe; Zanetti, Alberto; Bertotto, Gustavo Walter; Cingolani, Carlos Alberto

    2016-04-01

    The sub-continental lithospheric mantle of South America has been known for some time to carry the DUPAL isotope anomaly as seen in volcanics from the Paraná volcanic province. However, this has not allowed discriminating whether the DUPAL anomaly is a primary feature of the mantle source or acquired during the upwelling and emplacement of the primary magmas. We discovered mantle xenoliths from the Tres Lagos location in Patagonia that carry evidence of percolation by metasomatic melts that imparted the DUPAL isotope anomaly signature. We discuss a model that requires four isotope components (LCC, EM2, HIMU and DM) to account for the Sr, Nd and Pb isotope variability of our samples. We propose that upwelling of hot astenosphere during the Miocene could have triggered the melting of the LCC and EM2 components carrying the DUPAL anomaly, previously entrained in the subcontinental mantle by subduction. These ascending melts would have then metasomatised the local SCLM characterised by DMM and HIMU geochemical affinity generating the hybrid DUPAL-bearing mantle sampled by the Tres Lagos xenoliths.

  8. The geodynamic province of transitional crust adjacent to magma-poor continental margins

    NASA Astrophysics Data System (ADS)

    Sibuet, J.; Tucholke, B. E.

    2011-12-01

    Two types of 'transitional crust' have been documented along magma-poor rifted margins. One consists of apparently sub-continental mantle that has been exhumed and serpentinized in a regime of brittle deformation during late stages of rifting. A second is highly thinned continental crust, which in some cases is known to have been supported near sea level until very late in the rift history and thus is interpreted to reflect depth-dependent extension. In both cases it is typically assumed that formation of oceanic crust occurs shortly after the breakup of brittle continental crust and thus that the transitional crust has relatively limited width. We here examine two representative cases of transitional crust, one in the Newfoundland-Iberia rift (exhumed mantle) and one off the Angola-Gabon margin (highly thinned continental crust). Considering the geological and geophysical evidence, we propose that depth-dependent extension (riftward flow of weak lower/middle continental crust and/or upper mantle) may be a common phenomenon on magma-poor margins and that this can result in a much broader zone of transitional crust than has hitherto been assumed. Transitional crust in this extended zone may consist of sub-continental mantle, lower to middle continental crust, or some combination thereof, depending on the strength profile of the pre-rift continental lithosphere. Transitional crust ceases to be emplaced (i.e., final 'breakup' occurs) only when emplacement of heat and melt from the rising asthenosphere becomes dominant over lateral flow of the weak lower lithosphere. This model implies a two-stage breakup: first the rupture of the brittle upper crust and second, the eventual emplacement of oceanic crust. Well-defined magnetic anomalies can form in transitional crust consisting of highly serpentinized, exhumed mantle, and they therefore are not diagnostic of oceanic crust. Where present in transitional crust, these anomalies can be helpful in interpreting the rifting

  9. Hf isotope systematics of seamounts near the East Pacific Rise (EPR) and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Meng, Fanxue; Niu, Yaoling

    2016-10-01

    We report new Hf isotopic data for basaltic glasses from seamounts flanking the East Pacific Rise (EPR) between 5° and 15°N that have been previously analyzed for Sr-Nd-Pb isotopes as well as major and trace elements. The Hf isotopic data offer new perspectives on the petrogenesis of these samples in a broader context on mantle dynamics. The Hf isotope compositions show significant correlations with Sr-Nd-Pb isotopes and with both abundances and ratios of incompatible elements. The seamount lavas are thus best interpreted as products of melting-induced mixing in a two-component mantle. The range in composition of EPR seamount lavas cannot be generated by simple mixing of melt and melting of variably heterogeneous mantle in which enriched and depleted materials contribute equally to melting (source mixing). Instead, the trace element and isotope compositions of seamount lavas can be reproduced by melting models in which more enriched, fertile mantle component are preferentially melted during mantle upwelling. At progressively lower degrees of melting, erupted lavas are thus more enriched in incompatible trace elements, have higher 87Sr/86Sr, 208Pb/204Pb ratios and lower 143Nd/144Nd, 176Hf/177Hf ratios. The "EM1" and "pyroxenite" endmember might be the suitable enriched component. The Hf-Nd isotopic variations on global scale might result from the variations in amounts of residual continental lithospheric mantle that detached into upper mantle during continental rifting. The significant correlations of Rb/Sr vs 87Sr/86Sr, Sm/Nd vs 143Nd/144Nd and Lu/Hf vs 176Hf/177Hf give pseudochron ages of 182 ± 33 Ma, 276 ± 50 Ma and 387 ± 93 Ma, respectively. These different "ages" have no significance, but result from melting-induced mixing with the pseudochron slopes controlled by the compositions of enriched component and depleted end-member.

  10. MERMAID seismometry in the oceans: resolving the detail of geodynamic processes

    NASA Astrophysics Data System (ADS)

    Nolet, Guust

    2016-04-01

    Two years of test runs in the Mediterranean and the Indian Ocean as well as two tomographic experiments in the Ligurian Sea and near the Galapagos Islands, allow us to evaluate the potential for an array of floating seismographs to fill the data gap for seismic tomography posed by the oceans. P-wave onsets obtained by three MERMAIDs in the Ligurian Sea have been validated by inverting them together with onsets measured in the same area from an OBS experiment as well as with nearby land stations. Judging from the posteriori misfits, an average accuracy of 0.4 seconds was obtained despite the presence of some outliers. Using this accuracy estimate, current detection rates as a function of distance and magnitude, and observed trajectories of floats in the oceanographic ARGO program, we have modelled the data yield expected from a global array of MERMAIDs operating for five years (a new, second generation, MERMAID has a longevity in excess of five years). With 300 MERMAIDs, we expect to obtain 102,080 onset times, which allows an almost perfect geographical coverage. This rises to 341,607 in a simulation with 1000 MERMAIDs, which is much less than the 1,567,829 delays selected over the same period from the ISC catalogue. However, inverting these together in a checkerboard test shows that we can resolve anomalies of size as small as 300 km almost perfectly in most of the lower mantle, with the exception of the mantle under polar regions, Africa and the South Atlantic. Inverting the ISC data alone leaves the oceanic domain unresolved at this length scale. The cost of such a MARISCOPE array (about 30M) compares favourably with the cost of the US-Array deployment.

  11. The Variscan belt of Northern France Southern Belgium: geodynamic implications of new palaeomagnetic data

    NASA Astrophysics Data System (ADS)

    Márton, Emő; Mansy, Jean-Louis; Averbuch, Olivier; Csontos, László

    2000-09-01

    , simply docking to the Brabant obstacle of similar shape. Variable offsets along a main thrust make possible a third model, which slightly unfolds the former passive arc.

  12. The Neoproterozoic-Paleozoic Arctic Margins: early stages of geodynamic evolution and plate reconstructions

    NASA Astrophysics Data System (ADS)

    Vernikovsky, V. A.; Metelkin, D. V.; Vernikovskaya, A. E.; Matushkin, N. Yu.; Lobkovsky, L. I.; Shipilov, E. V.

    2012-04-01

    paleomagnetic poles) according to the general model and the available global reconstructions that include the structures of the Arctic (Scotese, 1997; Lawyer et al., 2002; Golonka et al., 2003, 2006; Cocks, Torsvik, 2002, 2007). The position of those Arctida blocks that lack paleomagnetic data is reconstructed based on geological data.

  13. Tectonic Morphology of the Hustai Fault (Northern Mongolia) : Implications for Regional Geodynamics

    NASA Astrophysics Data System (ADS)

    Schlupp, A.; Ferry, M. A.; Munkhuu, U.; Munschy, M.; Fleury, S.

    2010-12-01

    Beside the famous series of M 8 earthquakes that struck western Mongolia in the first half of the 20th c., the Hustai fault presents a more directly concerning picture. With its northeastern tip located ~10 km from the city of Ulaanbaatar (1 M inhabitants), the 92-km-long fault may produce consequential M 7+ earthquakes. It displays continuous microseismicity with five M 4+ since 1974 and a M 5.4 event in that same year. Most events occur in the shallow crust. We present preliminary results of a multi-disciplinary study of the Hustai Fault, northern Mongolia. By combining high-resolution satellite images, digital elevation models, magnetic mapping, geomorphology and trenching, we provide a detailed morphotectonic map of the fault as well as insight on its recent episodes of surface faulting. The Hustai Fault is more than 100 km long and divided into four segments. The northernmost segment is 18 km long and oriented N 70; the northern central segment is 26 km long and oriented N 65; and the southern central segment is 34 km long and oriented N 55 and the southernmost segment is at least 34 km long and oriented N26. The active trace runs at the foot of the Hustai Range and is outlined by a clear composite scarp, tilted chert slabs, contrasts in water content, left-laterally offset alluvial fans and releasing step-overs (pull-apart basins and negative flower structures). Stream bed profiles show a systematic uplift of the NW block by ~10 m and high-resolution satellite images document lateral offsets in the range of 10-50 m, thus suggesting a transtentional regime. Exploratory trenches located along the central section of the active trace reflect the transtentional nature of the fault with mixed normal and strike-slip faulting geometries. Surface ruptures affect the modern soil and suggest an undocumented M 7+ earthquake occurred recently along the Hustai fault. Overall, our first results suggest that the Hustai fault is presently active under a transtentional regime

  14. Mica-dominated seismic properties of mid-crust beneath west Yunnan (China) and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Shao, Tongbin; Ji, Shaocheng; Oya, Shoma; Michibayashi, Katsuyoshi; Wang, Qian

    2016-05-01

    Measurements of crystallographic preferred orientations (CPO) and calculations of P- and S-wave velocities (Vp and Vs) and anisotropy were conducted on three quartz-mica schists and one felsic mylonite, which are representative of typical metamorphic rocks deformed in the middle crust beneath the southeastern Tibetan plateau. Results show that the schists have Vp anisotropy (AVp) ranging from 16.4% to 25.5% and maximum Vs anisotropy [AVs(max)] between 21.6% and 37.8%. The mylonite has lower AVp and AVs(max) but slightly higher foliation anisotropy, which are 13.2%, 18.5%, and 3.07%, respectively, due to the lower content and CPO strength of mica. With increasing mica content, the deformed rocks tend to form transverse isotropy (TI) with fast velocities in the foliation plane and slow velocities normal to the foliation. However, the presence of prismatic minerals (e.g., amphibole and sillimanite) forces the overall symmetry to deviate from TI. An increase in feldspar content reduces the bulk anisotropy caused by mica or quartz because the fast-axis of feldspar aligns parallel to the slow-axis of mica and/or quartz. The effect of quartz on seismic properties of mica-bearing rocks is complex, depending on its content and prevailing slip system. The greatest shear-wave splitting and fastest Vp both occur for propagation directions within the foliation plane, consistent with the fast Pms (S-wave converted from P-wave at the Moho) polarization directions in the west Yunnan where mica/amphibole-bearing rocks have developed pervasive subvertical foliation and subhorizontal lineation. The fast Pms directions are perpendicular to the approximately E-W orienting fast SKS (S-wave traversing the core as P-wave) directions, indicating a decoupling at the Moho interface between the crust and mantle beneath the region. The seismic data are inconsistent with the model of crustal channel flow as the latter should produce a subhorizontal foliation where vertically incident shear

  15. Palaeogeographic evolution of the central segment of the South Atlantic during Early Cretaceous times: palaeotopographic and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Chaboureau, A. C.; Guillocheau, F.; Robin, C.; Rohais, S.; Moulin, M.; Aslanian, D.

    2012-04-01

    influences were clearly occurring since the Early Aptian in the Northern domain and the Campos Basin. They seem sharp, brief flooding coming from the North, i.e. from the Tethys-Central Atlantic, trough a seaway crossing South America from Sao Luis, Parnaiba, Araripe and Almada basins (Arai, 1989). In the absence of data, the importance of those marine flooding during the Middle Aptian in the Santos Basin is still discussed. Keywords: South Atlantic Ocean, Early Cretaceous, Rift, Palaeogeography, Geodynamic

  16. Investigation of temperature and barometric pressure variation effects on radon concentration in the Sopronbánfalva Geodynamic Observatory, Hungary.

    PubMed

    Mentes, Gyula; Eper-Pápai, Ildikó

    2015-11-01

    Radon concentration variation has been monitored since 2009 in the artificial gallery of the Sopronbánfalva Geodynamic Observatory, Hungary. In the observatory, the radon concentration is extremely high, 100-600 kBq m(-3) in summer and some kBq m(-3) in winter. The relationships between radon concentration, temperature and barometric pressure were separately investigated in the summer and winter months by Fast Fourier Transform, Principal Component Analysis, Multivariable Regression and Partial Least Square analyses in different frequency bands. It was revealed that the long-period radon concentration variation is mainly governed by the temperature (20 kBq m(-1) °C(-1)) both in summer and winter. The regression coefficients between long-period radon concentration and barometric pressure are -1.5 kBq m(-3) hPa(-1) in the summer and 5 kBq m(-3) hPa(-1) in the winter months. In the 0.072-0.48 cpd (cycles per day) frequency band the effect of the temperature is about -1 kBq m(-3) °C(-1) and that of the barometric pressure is -5 kBq m(-3) hPa(-1) in summer and -0.5 kBq m(-3) hPa(-1) in winter. In the high frequency range (>0.48 cpd) all regression coefficients are one order of magnitude smaller than in the range of 0.072-0.48 cpd. Fast Fourier Transform of the radon concentration, temperature and barometric pressure time series revealed S1, K1, P1, S2, K2, M2 tidal constituents in the data and weak O1 components in the radon concentration and barometric pressure series. A detailed tidal analysis, however, showed that the radon tidal components are not directly driven by the gravitational force but rather by solar radiation and barometric tide. Principal Component Analysis of the raw data was performed to investigate the yearly, summer and winter variability of the radon concentration, temperature and barometric pressure. In the summer and winter periods the variability does not change. The higher variability of the radon concentration compared to the variability of

  17. The utilization of Malaysian Active GPS System data for geodynamic applications: a case study in East and West Malaysia

    NASA Astrophysics Data System (ADS)

    Abu Bakar, Rabieahtul; Azahari Razak, Khamarrul

    2010-05-01

    Geodynamic studies of Malaysia have been ventured upon in the South-East Asia region since the first GeodySEA project in 1996. Both East and West Malaysia lies on the Eurasian Plate, and assumed to have no linear distortion between any two joined points relative to one another. However, Malaysia lies at the southern tip of the plate encroached by two frequently ruptured boundaries, the Indian-Australian plate and the Philippines plate, and it is also within the buffer of the Ring of fire. Hence, this paper is essential to determine the relative movement of Malaysia, and with the possibilities to identify the presences of slip-fault formation which might be of threat to the stable platform that we have taken for granted. Availability of uninterrupted GPS observations over the Malaysian Active GPS System known as MASS stations situated across the country established by the Department of Survey and Mapping (DSMM) evidently help provides the data for this study. There are currently eighteen MASS stations mounted with Trimble 4000 dual frequency antenna and data recorded at fine second interval made accessible in hourly files. Satellite data collected continuously over a long period of time are processed by Bernese GPS processing software. Fifteen International GNSS Service (IGS) stations were selected within similar period of observations were gathered, processed, later act as tie points to the MASS stations. Apparently with this Malaysia will form a network to the globe. In this research the author will output the relative MASS stations coordinates and velocity estimates in International terrestrial reference frame (ITRF) 2000 since GPS data used are before the derivation of ITRF2005. At present the measures of quality for GPS derived coordinates given by commercial software packages tend to be unrealistic because unmodelled errors remain unaccounted for. The commercial software packages are either over-optimistic or conversely, therefore, have low fidelity. Thus

  18. Active intraplate deformation as geodynamic responses to oblique shallow subduction of a flat slab: example from central and southwest Japan

    NASA Astrophysics Data System (ADS)

    Ishiyama, Tatsuya; Sato, Hiroshi

    2015-04-01

    Subduction of a flat slab has been recognized as one of the primary driving mechanism of wide intracontinental subsidence farther away from the subduction leading edge in many subduction margins. In most cases, however, quantitative and qualitative limitations on chronological constraints prevent comprehensive understanding of these geodynamic linkages. In this study, we show distinct, geologic and seismic evidence for spatial and temporal correlation between plate subduction and intercontinental deformation, mainly driven by dynamic interaction between subducting Philippine Sea (PHS) plate and overriding continental crusts of central and southwest Japan (Eurasian plate) along the Nankai-Tonankai subduction zone since Pliocene. Based on analyses of Pliocene to Pleistocene tectonic histories by use of rich dataset of Neogene stratigraphy, drainage network evolution, and shallow to deep seismic reflection profiles, depocenters of wide sedimentary basins and active thrusting have migrated northward since ca. 5 Ma to present from forearc to backarc of the southwest Japan arc. Median tectonic line, active dextral strike-slip fault as a forearc sliver along the Nankai, is located north of the upward extension of the downdip limit of the interseismic locked zone. Southwest Japan north of the MTL, underlain by the subducting slab with steady state slip (Nakanishi et al., 2002; Kodaira et al., 2004), appears tectonically less inactive than central Japan and has behaved as a less deformed rigid block. Contrastingly, Quaternary active intraplate deformation has been prominent north of the inactive MTL above a shallow flat segment of the PHS plate along the Tonankai. Deep seismic reflection profile images upward corrugated very shallow PHS slab being contact with continental lower crust beneath actively deforming area. We interpreted temporal and spatial correlation of oblique subduction of the shallow and flat, corrugated PHS slab as an essential mechanical role to enhance

  19. Investigation of temperature and barometric pressure variation effects on radon concentration in the Sopronbánfalva Geodynamic Observatory, Hungary.

    PubMed

    Mentes, Gyula; Eper-Pápai, Ildikó

    2015-11-01

    Radon concentration variation has been monitored since 2009 in the artificial gallery of the Sopronbánfalva Geodynamic Observatory, Hungary. In the observatory, the radon concentration is extremely high, 100-600 kBq m(-3) in summer and some kBq m(-3) in winter. The relationships between radon concentration, temperature and barometric pressure were separately investigated in the summer and winter months by Fast Fourier Transform, Principal Component Analysis, Multivariable Regression and Partial Least Square analyses in different frequency bands. It was revealed that the long-period radon concentration variation is mainly governed by the temperature (20 kBq m(-1) °C(-1)) both in summer and winter. The regression coefficients between long-period radon concentration and barometric pressure are -1.5 kBq m(-3) hPa(-1) in the summer and 5 kBq m(-3) hPa(-1) in the winter months. In the 0.072-0.48 cpd (cycles per day) frequency band the effect of the temperature is about -1 kBq m(-3) °C(-1) and that of the barometric pressure is -5 kBq m(-3) hPa(-1) in summer and -0.5 kBq m(-3) hPa(-1) in winter. In the high frequency range (>0.48 cpd) all regression coefficients are one order of magnitude smaller than in the range of 0.072-0.48 cpd. Fast Fourier Transform of the radon concentration, temperature and barometric pressure time series revealed S1, K1, P1, S2, K2, M2 tidal constituents in the data and weak O1 components in the radon concentration and barometric pressure series. A detailed tidal analysis, however, showed that the radon tidal components are not directly driven by the gravitational force but rather by solar radiation and barometric tide. Principal Component Analysis of the raw data was performed to investigate the yearly, summer and winter variability of the radon concentration, temperature and barometric pressure. In the summer and winter periods the variability does not change. The higher variability of the radon concentration compared to the variability of

  20. Geodynamic evolution of the Salinas de Añana diapir in the Basque-Cantabrian Basin, Western Pyrenees

    NASA Astrophysics Data System (ADS)

    Frankovic, Allen; Eguiluz, Luis; Martínez-Torres, Luis M.

    2016-02-01

    The Salinas de Añana diapir is located in the Basque-Cantabrian basin part of the great evaporite basin, along with the Gulf of Mexico and the Central European basin, when the fragmentation of Pangea started. The evolution of these basins can only be achieved by understanding the control of salt in the sedimentary and tectonic evolution of these basins. Sedimentation began with clastic Buntsandstein sediments and minor Muschelkalk limestones. Subsequent Keuper evaporites are the bottom of sedimentary cover constituted by Jurassic limestones and marls, a clastic Lower Cretaceous and an alternant limestone and marl Upper Cretaceous, whose deposition has been conditioned by salt tectonics. The emplacement of salt extends from the Aptian until now, favored by the duplication of the salt thickness associated with the thrust of Sierra Cantabria, so it is an excellent example to study changes in the regime of intrusion along the time. The geodynamic evolution of the Salinas de Añana diapir was determined through the interpretation of 45 reprocessed seismic lines, along with information from three wells. Migration of the salt in this diapir, conditioned by N120E and N30E pre-Alpine basement lineations, was determined using time isopach maps of the various rock layers. Vertical evolution of the diapir was determined through the reconstruction of a north-south section at various geologic times by flattening the respective seismic horizons. A minimum of salt flow into the diapir coincides with a minimum rate of sedimentation during the Turonian. Similarly, maximum flows of salt into the diapir occurred during the Coniacian and Lower Santonian and again from the end of the Lower Miocene to the present, coinciding with maximum rates of sedimentation during these times. In the Tertiary, probably during the Oligocene, the diapir was displaced to the south by the Sierra Cantabria thrust, maintaining the contact between the evaporites of diapir and the same evaporites of the

  1. Geodynamic evolution of crust accretion at the axis of the Reykjanes Ridge, Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Merkur'ev, S. A.; Demets, C.; Gurevich, N. I.

    2009-05-01

    The results of analysis of the anomalous magnetic field of the Reykjanes Ridge and the adjacent basins are presented, including a new series of detailed reconstructions for magnetic anomalies 1-6 in combination with a summary of the previous geological and geophysical investigations. We furnish evidence for three stages of evolution of the Reykjanes Ridge, each characterized by a special regime of crustal accretion related to the effect of the Iceland hotspot. The time interval of each stage and the causes of the variation in the accretion regime are considered. During the first, Eocene stage (54-40 Ma) and the third, Miocene-Holocene stage (24 Ma-present time at the northern Reykjanes Ridge north of 59° N and 17-11 Ma-present time at the southern Reykjanes Ridge south of 59° N), the spreading axis of the Reykjanes Ridge resembled the present-day configuration, without segmentation, with oblique orientation relative to the direction of ocean floor opening (at the third stage), and directed toward the hotspot. These attributes are consistent with a model that assumes asthenospheric flow from the hotspot toward the ridge axis. Decompression beneath the spreading axis facilitates this flow. Thus, the crustal accretion during the first and the third stages was markedly affected by interaction of the spreading axis with the hotspot. During the second, late Eocene-Oligocene to early Miocene stage (40-24 Ma at the northern Reykjanes Ridge and 40 to 17-11 Ma at the southern Reykjanes Ridge), the ridge axis was broken by numerous transform fracture zones and nontransform offsets into segments 30-80 km long, which were oriented orthogonal to the direction of ocean floor opening, as is typical of many slow-spreading ridges. The plate-tectonic reconstructions of the oceanic floor accommodating magnetic anomalies of the second stage testify to recurrent rearrangements of the ridge axis geometry related to changing kinematics of the adjacent plates. The obvious contrast in the

  2. The Contribution of the Topo-Iberia Project to the Knowledge of the Western Mediterranean Geodynamics.

    NASA Astrophysics Data System (ADS)

    Diaz Cusi, J.

    2012-12-01

    noise allows describing the main characteristics of crustal structure. Local body-wave tomography, currently focused on Northern Morocco, has improved the location of the small magnitude events affecting the area and the details of the crustal structure. Teleseismic tomography has confirmed, using an independent data set, the presence of a high-velocity slab beneath the Gibraltar Arc. -. A number of 2-D Magnetotelluric (MT) profiles have been acquired in Iberia and Morocco. These MT profiles provide a 1500 km long N-S lithospheric transect extending from the Cantabrian Mountains to the Atlas. -. The Topoiberia GPS deployments acquired long-term time series of data allowing well resolved determinations of the relatively small velocity displacements affecting the region. Additional high-resolution active-source seismic experiments recently carried out in the Atlas, the Rif and the Central and Iberian Massifs piggy back with this large scale project are complementing this multidisciplinary data base. This new data provide a large number of physical observables to better constrain numerical models at lithospheric scale, which would result in high-quality lithospheric transects.

  3. Geographic information systems (GIS) spatial data compilation of geodynamic, tectonic, metallogenic, mineral deposit, and geophysical maps and associated descriptive data for northeast Asia

    USGS Publications Warehouse

    Naumova, Vera V.; Patuk, Mikhail I.; Kapitanchuk, Marina Yu.; Nokleberg, Warren J.; Khanchuk, Alexander I.; Parfenov, Leonid M.; Rodionov, Sergey M.; Miller, Robert J.; Diggles, Michael F.

    2006-01-01

    This is the online version of a CD-ROM publication. It contains all of the data that are on the disc but extra files have been removed: index files, software installers, and Windows autolaunch files. The purpose of this publication is to provide a high-quality spatial data compilation (Geographical Information System or GIS) of geodynamic, mineral deposit, and metallogenic belt maps, and descriptive data for Northeast Asia for customers and users. This area consists of Eastern Siberia, Russian Far East, Mongolia, northern China, South Korea, and Japan. The GIS compilation contains integrated spatial data for: (1) a geodynamics map at a scale of 1:5,000,000; (2) a mineral deposit location map; (3) metallogenic belt maps; (4) detailed descriptions of geologic units, including tectonostratigraphic terranes, cratons, major melange zones, and overlap assemblages, with references; (5) detailed descriptions of metallogenic belts with references; (6) detailed mineral deposit descriptions with references; and (7) page-size stratigraphic columns for major terranes.

  4. Uzon-Geysernaya volcano-tectonic depression: geodynamics phenomena last years

    NASA Astrophysics Data System (ADS)

    Kugaenko, Yulia

    2010-05-01

    greater than 4 km from beneath the eastern side of the caldera complex. Geological observations of extruded lavas and other deposits over the course of Uzon's history show that there have been episodic basalt intrusions into a granitic magma chamber, with the system becoming progressively more crystallized and lower in temperature with time [Belousov et al., 1984; Leonov et al., 1991]. By study of RADARSAT-1 synthetic aperture radar (SAR) data the interferometric SAR (InSAR) images of surface deformation at Uzon caldera was computed [Lundgren and Lu, 2006]. From 2000 to 2003 approximately 0.15 m of inflation occurred at Uzon caldera, extending beneath adjacent Kikhpinych volcano. This contrasts with InSAR data showing no significant deformation during either the 1999 to 2000, or 2003 to 2004, time periods. The preferred source model is an irregularly shaped, pressurized crack, dipping near 20° to the NW, 4 km below the surface. The geometry of this solution is similar to the upper boundary of the geologically inferred magma chamber. In the judgment of the authors, extension of the surface deformation and source to adjacent Kikhpinych volcano, without an eruption, suggests that the deformation is more likely of hydrothermal origin, possibly driven by recharge of the magma chamber. A natural disaster - big landslide with volume estimated 20x106 m3 - occurred on June 3, 2007 in the Valley of the Geysers (Leonov, 2007, Kugaenko, 2008). The results of landslide investigation show that heated rocks were involved in failure. One of the main reasons of landslide is weakening of semi-rock pumice soils due to their steaming during hidden unloading of hydrothermal system. Local field observations were organized in the eastern part of the Uzon-Geysernaya depression in 2008 and 2009. Main results of seismic investigation: - Shallow weak seismicity connected with Kikhpinych volcanic center and eastern part of the Uzon-Geysernaya depression was discovered; - Seismicity has spasmodic

  5. Geodynamical Processes between Antarctica and India as revealed by very long baselines between the continents estimated from continuous and long-term GPS measurements

    NASA Astrophysics Data System (ADS)

    N, R.; Ec, M.; Akilan, A.

    2006-12-01

    To holistically understand the geodynamical and crustal deformation processes in the south of Indian peninsula between India and Antarctica, two global networks have been chosen that geodetically connect the two continents, the IGS Station at Diego Garcia (DGAR) being the common station between the two networks. 8 years of data from 1997 to 2005 were used. Very long baselines have been estimated from HYDE to other chosen IGS stations in and around India including DGAR. Similarly in the other network, very long baselines have been estimated from Kerguelen to other stations in and around Antarctica again including DGAR. Since the baseline length between HYDE, India and MAITRI, Antarctica is more than 10,000 km, it is mandatory to form these two different networks to improve the accuracy of the baseline measurements by GPS. This is to circumvent the limitation in the estimation of maximum base line length by GPS is of 6,900 km only due to the availability of less number of double difference observables in the GPS data analysis. Our analysis and results show increase of baseline lengths between Kerguelen in Antarctic plate and other stations and shortening of baseline lengths between HYDE in Indian plate and other common stations. By this global network analyses, the stations HYDE and MAITRI are geodetically tied through DGAR. With this geodetic tie up, having got the first geodetic signatures of the geodynamical processes between India and Antarctica, continuous monitoring and estimation would help enhancing the understanding the crustal deformation processes between these two continents despite many plates, micro plates and ridges in this study region.These estimations reveal clearly that the stations in the Australian plate are moving away from the Indian plate conforming to the recent Plate tectonic theory that India and Australia lie in two different plates with a diffuse boundary separating them. GPS derived velocity vectors for the Australian Plate also

  6. Sulphur geodynamic cycle

    PubMed Central

    Kagoshima, Takanori; Sano, Yuji; Takahata, Naoto; Maruoka, Teruyuki; Fischer, Tobias P.; Hattori, Keiko

    2015-01-01

    Evaluation of volcanic and hydrothermal fluxes to the surface environments is important to elucidate the geochemical cycle of sulphur and the evolution of ocean chemistry. This paper presents S/3He ratios of vesicles in mid-ocean ridge (MOR) basalt glass together with the ratios of high-temperature hydrothermal fluids to calculate the sulphur flux of 100 Gmol/y at MOR. The S/3He ratios of high-temperature volcanic gases show sulphur flux of 720 Gmol/y at arc volcanoes (ARC) with a contribution from the mantle of 2.9%, which is calculated as 21 Gmol/y. The C/S flux ratio of 12 from the mantle at MOR and ARC is comparable to the C/S ratio in the surface inventory, which suggests that these elements in the surface environments originated from the upper mantle. PMID:25660256

  7. Sulphur geodynamic cycle.

    PubMed

    Kagoshima, Takanori; Sano, Yuji; Takahata, Naoto; Maruoka, Teruyuki; Fischer, Tobias P; Hattori, Keiko

    2015-01-01

    Evaluation of volcanic and hydrothermal fluxes to the surface environments is important to elucidate the geochemical cycle of sulphur and the evolution of ocean chemistry. This paper presents S/(3)He ratios of vesicles in mid-ocean ridge (MOR) basalt glass together with the ratios of high-temperature hydrothermal fluids to calculate the sulphur flux of 100 Gmol/y at MOR. The S/(3)He ratios of high-temperature volcanic gases show sulphur flux of 720 Gmol/y at arc volcanoes (ARC) with a contribution from the mantle of 2.9%, which is calculated as 21 Gmol/y. The C/S flux ratio of 12 from the mantle at MOR and ARC is comparable to the C/S ratio in the surface inventory, which suggests that these elements in the surface environments originated from the upper mantle. PMID:25660256

  8. The origin of islands in the Kandalaksha Gulf of the White Sea: joint work of internal and external geodynamic processes

    NASA Astrophysics Data System (ADS)

    Kosevich, Natalia; Romanovskaya, Maria

    2016-04-01

    deposits and bedrock outcrops; structural denudation landforms dominate over the marine and biogenic landforms in this case, rocky surfaces of these islands predominate over others. The relief of islands is a combination of smoothed rounded top bedrock surfaces (massifs) with subhorizontal sites that are covered with loose marine deposits. Analysis of the spatial distribution of the genetic types of islands in the Kandalaksha Gulf has revealed that in the apical part of the gulf all genetic types of islands occur, while upon approaching the mouth, one type (tectonic-glacial-accumulative-denudation with marine reworking) becomes predominant. Thus, geological, structural, geomorphic features of Kandalahksha Gulf islands are the results of the complex interaction of the internal and external geodynamic processes. Kosevich N. Geological-geomorphological types of islands in the Kandalaksha Gulf, White Sea. Moscow Univ. Geol.Bull., 2015, vol. 70, N 4. P. 318-326.

  9. Magmatic dyke swarms of the south shetland islands volcanic arc, west-antarctica - tracers of geodynamic history

    NASA Astrophysics Data System (ADS)

    Kraus, St.; Miller, H.

    2003-04-01

    /Pb, Zr/Hf and also some Ba/HFSE ratios have been used as a powerful means to distinguish the different intrusive events. Thus, combining the relative ages observed in the field with the geochemical information, on Hurd Peninsula (Livingston Island) 6 different intrusive events are traceable. In contrast to the subduction-related, mostly calcalcalic dykes outcropping on the rest of the South Shetland Islands, the quaternary dykes of Penguin Island are composed of Ol-bearing basalt of slightly more alcalic chemism. They are not related to the island arc part of subduction in that area but to the recent opening of the Bransfield Strait as a backarc-basin. The results prove the good suitability of magmatic dyke systems for tracing the change of the tectonic regime over time and space. Present work includes extensive isotope geochemical analysis (Sr, Nd, Pb) to get a hint on the magma sources and their possible changes as a result of changing geodynamic parameters.

  10. Long term (since the late palaeogene) tectono-sedimentary evolution of the Lesser Antilles fore-arc at Marie-Galante Basin: a clue for geodynamical behavior at the subduction interfac

    NASA Astrophysics Data System (ADS)

    Jean-Frederic, L.; DeMin, L.; Garrigou, J.; Münch, P.; Léticée, J. L.; Cornée, J. J.

    2015-12-01

    Oblique subduction of late cretaceous lithosphere of the Atlantic ocean beneath the thick (25km) crust of the Caribbean plate results in widespread deformation and vertical motions in the Lesser Antilles fore-arc. The present-day deformation includes a major transtensive left lateral fault system along the arc and several forearc transverse basins accommodating lengthening of the fore-arc northward. These deformations result from plate motion partitioning under increasing subduction obliquity from the Marie-Galante Basin (MGB) latitude (central Lesser Antilles) northward. Vertical motions in the fore-arc at a regional scale were interpreted as resulting from the effect of subducting ridges and reliefs. The present day uplift of the fore-arc islands acting since the late(?) Pleistocene is believed to attest for long wavelength bending of the plate under strongly coupled plate interface. Recent GPS data suggests a mostly uncoupled plate interface. To decipher between the models and to understand the long-term evolution of the Lesser Antilles forearc since the Late Palaeogene, we interpret high-resolution bathymetric and seismic data from the MGB, together with the onland geology of shallow water carbonate platforms. The tectonic pattern reveals both inherited and late Neogene structures (re)activated under multidirectional extensive tectonic. The sismo-stratigraphic interpretation of sedimentary deposit displays long-term drowning and flexing of the upper plate similar to that occurring under intensive tectonic erosion at the subduction interface. Several short term period of second order uplift can correlate with sweeping of subducting ridges or transient events at the plate interface. The evolution of the Lesser Antilles fore-arc since the Late Palaeogene is interpreted within the regional geodynamical evolution of the plate boundary following its last major reorganization: collision of the Bahamas Bank and inception of the Greater Antilles strike-slip fault zone.

  11. The geochemical variations of the upper cenozoic volcanism along the Calama Olacapato El Toro transversal fault system in central Andes (˜24°S): petrogenetic and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Matteini, M.; Mazzuoli, R.; Omarini, R.; Cas, R.; Maas, R.

    2002-02-01

    In this paper, we present new geochemical and Sr-Nd isotopic data for several Upper Miocene volcanic centres aligned along one of the most extensive transcurrent lineament in the Central Andes, the Calama-Olacapato-El Toro (COT). The transversal volcanic belt along COT is constituted by large composite volcanoes and a caldera structure; they are, from NW to SE, Puntas Negras, Rincon, Tul Tul, Del Medio and Pocitos (TUMEPO), Quevar Aguas Calientes and Tastil. In order to compare chemical data from the different centres along the COT transect, differentiation effects were minimised by using data extrapolated at 60% SiO2 with least-square regression method. In the western sector of the COT, the volcanic products of Puntas Negras and Rincon show relatively high K2O and 87Sr/86Sr and low Rb/Cs, Ta/Th, La/Yb, 143Nd/144Nd. To the east, the TUMEPO products have high Sr and 143Nd/144Nd, La/Yb and Ba/Rb and low Y, 87Sr/86Sr. In the easternmost COT sector, Quevar, Aguas Calientes and Tastil volcanic complexes exhibit low La/Yb, high87Sr/Sr86 and low 143Nd/144Nd. On the basis of these data, we propose a petrogenetic and geodynamical model for Central Andes at 24°S. In correspondence of Miocene-Quaternary volcanic arc (Puntas Negras and Rincon), the magmas inherited a calcalkaline signature partly modified by upper crustal and/or sediment assimilation. In the central eastern sector, melting, assimilation, storage and homogenisation (MASH) processes occurred at the base of a thickened crust. In this COT sector, TUMEPO products show an evident lower crust signature and could be considered representative for MASH derived magmas. In the easternmost sector, Quevar, Aguas Calientes and Tastil products could represent magmas generated by partial melting of underthrusted Brasilian shield and mixed with magmas derived by MASH processes.

  12. Geomorphology and geodynamics of the Cook-Austral island-seamount chain in the South Pacific Ocean: Implications for hotspots and plumes

    SciTech Connect

    Dickinson, W.R.

    1998-12-01

    Among Pacific hotspot tracks, the Cook-Austral island-seamount chain is distinctly anomalous in geodynamic behavior, exhibiting repetitive episodes of volcanism at multiple sites, uplift of selected islands long after initial immersion by subsidence, and multiple alignments of volcanic edifices. Cook-Austral islands include a variety of disparate geomorphic types: volcanic islands without reefs, with fringing reefs, and with barrier reefs enclosing shallow lagoons, low-lying atolls; and makatea islands composted of volcanic cores surrounded by annular limestone tablelands. The distribution of subsided and uplifted islands along the Cook-Austral chain reflects multiple hotspot activity, probably related to multiple mantle diapirs of local character rather than to deep-seated plumes. Rapid Pacific plate motion can generate elongate hotspot tracks from transient hotspot activity unrelated to columnar advective plumes.

  13. GyPSuM: A Detailed Tomographic Model of Mantle Density and Seismic Wave Speeds

    SciTech Connect

    Simmons, N A; Forte, A M; Boschi, L; Grand, S P

    2010-03-30

    GyPSuM is a tomographic model fo mantle seismic shear wave (S) speeds, compressional wave (P) speeds and detailed density anomalies that drive mantle flow. the model is developed through simultaneous inversion of seismic body wave travel times (P and S) and geodynamic observations while considering realistic mineral physics parameters linking the relative behavior of mantle properties (wave speeds and density). Geodynamic observations include the (up to degree 16) global free-air gravity field, divergence of the tectonic plates, dynamic topography of the free surface, and the flow-induced excess ellipticity of the core-mantle boundary. GyPSuM is built with the philosophy that heterogeneity that most closely resembles thermal variations is the simplest possible solution. Models of the density field from Earth's free oscillations have provided great insight into the density configuration of the mantle; but are limited to very long-wavelength solutions. Alternatively, simply scaling higher resolution seismic images to density anomalies generates density fields that do not satisfy geodynamic observations. The current study provides detailed density structures in the mantle while directly satisfying geodynamic observations through a joint seismic-geodynamic inversion process. Notable density field observations include high-density piles at the base of the superplume structures, supporting the fundamental results of past normal mode studies. However, these features are more localized and lower amplitude than past studies would suggest. When we consider all seismic anomalies in GyPSuM, we find that P and S-wave speeds are strongly correlated throughout the mantle. However, correlations between the high-velocity S zones in the deep mantle ({approx} 2000 km depth) and corresponding P-wave anomalies are very low suggesting a systematic divergence from simplified thermal effects in ancient subducted slab anomalies. Nevertheless, they argue that temperature variations are the

  14. Relating geodynamic setting to periods of crustal growth and reworking as illustrated by the Phanerozoic granitoids of the Eastern Cordillera of South Peru

    NASA Astrophysics Data System (ADS)

    Reitsma, M.; Schaltegger, U.; Spikings, R.; Ulianov, A.; Gerdes, A.; Chiaradia, M.

    2012-04-01

    The granitoids that form the backbone of the Eastern Cordillera of Peru between 12 and 14°S, are the ideal material for a case study to relate geodynamic setting to crustal growth over the period of a Wilson cycle. Extension related plutons were emplaced in the back-arc region of the Western Gondwana margin during the Ordovician, Permo-Carboniferous, Triassic and Early Jurassic. With the onset of the Andean cycle in the Middle Jurassic the South American margin was under compression, the plutonic record of this period is in the study area restricted to the Eocene and Miocene. The Ordovician to Triassic back-arc related plutons share many geochemical characteristics that point to dominant crustal reworking as the main process during their formation. These are 1) their mainly felsic and peraluminous nature; 2) the similarity of whole rock REE and trace element compositions compared to those of average continental crust; 3) the presence of negative Nb-Ta anomalies only in the more evolved samples which indicates that these excursions have been obtained by crustal melting rather than from a slab fluid and 4) the presence of significant amounts of xenocrystic cores in zircon. According to the literature the last major episode of juvenile crust formation was during the Grenvillian age Sunsas event (1.2 - 0.9 Ga) related to the collision of Laurentia and south-western Amazonia during the assembly of Rodinia. Hf-isotopes on zircons from the Ordovician, Permo-Carboniferous and Triassic plutons confirm their origin as mainly crustal melts generated by reworking of Sunsas-age crust. Under these geodynamic conditions it is mainly the crust that melts due to an elevated geothermal gradient as the result of crustal thinning. However, data from Jurassic nepheline bearing syenite and Eocene hornblende diorite and monzonite have epsilon Hfi values well above those of Sunsas crust, indicating an important mantle component in the melts. The Jurassic geodynamic setting is interpreted

  15. Cobalt and precious metals in sulphides of peridotite xenoliths and inferences concerning their distribution according to geodynamic environment: A case study from the Scottish lithospheric mantle

    NASA Astrophysics Data System (ADS)

    Hughes, Hannah S. R.; McDonald, Iain; Faithfull, John W.; Upton, Brian G. J.; Loocke, Matthew

    2016-01-01

    Abundances of precious metals and cobalt in the lithospheric mantle are typically obtained by bulk geochemical analyses of mantle xenoliths. These elements are strongly chalcophile and the mineralogy, texture and trace element composition of sulphide phases in such samples must be considered. In this study we assess the mineralogy, textures and trace element compositions of sulphides in spinel lherzolites from four Scottish lithospheric terranes, which provide an ideal testing ground to examine the variability of sulphides and their precious metal endowments according to terrane age and geodynamic environment. Specifically we test differences in sulphide composition from Archaean-Palaeoproterozoic cratonic sub-continental lithospheric mantle (SCLM) in northern terranes vs. Palaeozoic lithospheric mantle in southern terranes, as divided by the Great Glen Fault (GGF). Cobalt is consistently elevated in sulphides from Palaeozoic terranes (south of the GGF) with Co concentrations > 2.9 wt.% and Co/Ni ratios > 0.048 (chondrite). In contrast, sulphides from Archaean cratonic terranes (north of the GGF) have low abundances of Co (< 3600 ppm) and low Co/Ni ratios (< 0.030). The causes for Co enrichment remain unclear, but we highlight that globally significant Co mineralisation is associated with ophiolites (e.g., Bou Azzer, Morocco and Outokumpu, Finland) or in oceanic peridotite-floored settings at slow-spreading ridges. Thus we suggest an oceanic affinity for the Co enrichment in the southern terranes of Scotland, likely directly related to the subduction of Co-enriched oceanic crust during the Caledonian Orogeny. Further, we identify a distinction between Pt/Pd ratio across the GGF, such that sulphides in the cratonic SCLM have Pt/Pd ≥ chondrite whilst Palaeozoic sulphides have Pt/Pd < chondrite. We observe that Pt-rich sulphides with discrete Pt-minerals (e.g., PtS) are associated with carbonate and phosphates in two xenolith suites north of the GGF. This three

  16. U-Pb SHRIMP zircon dating of high-grade rocks from the Upper Allochthonous Terrane of Bragança and Morais Massifs (NE Portugal); geodynamic consequences

    NASA Astrophysics Data System (ADS)

    Mateus, A.; Munhá, J.; Ribeiro, A.; Tassinari, C. C. G.; Sato, K.; Pereira, E.; Santos, J. F.

    2016-04-01

    Bragança and Morais Massifs are part of the mega-klippen ensemble of NW Iberia, comprising a tectonic pile of four allochthonous units stacked above the Central-Iberian Zone autochthon. On top of this pile, the Upper Allochthonous Terrane (UAT) includes different high-grade metamorphic series whose age and geodynamic meaning are controversial. Mafic granulites provided U-Pb zircon ages at 399 ± 7 Ma, dating the Variscan emplacement of UAT. In contrast, U-Pb zircon ages of ky- and hb-eclogites, felsic/intermediate HP/HT-granulites and orthogneisses (ca. 500-480 Ma) are identical to those of gabbros (488 ± 10 Ma) and Grt-pyroxenites (495 ± 8 Ma) belonging to a mafic/ultramafic igneous suite that records upper mantle melting and mafic magma crustal underplating at these times. Gabbros intrude the high-grade units of UAT and did not underwent the HP metamorphic event experienced by eclogites and granulites. These features and the zircon dates resemblance among different lithologies, suggest that extensive age resetting of older events may have been correlative with the igneous suite emplacement/crystallisation. Accordingly, reconciliation of structural, petrological and geochronological evidence implies that the development and early deformation of UAT high-grade rocks should be ascribed to an orogenic cycle prior to ≈ 500 Ma. Undisputable dating of this cycle is impossible, but the sporadic vestiges of Cadomian ages cannot be disregarded. The ca. 500-480 Ma time-window harmonises well with the Lower Palaeozoic continental rifting that trace the Variscan Wilson Cycle onset and the Rheic Ocean opening. Subsequent preservation of the high heat-flow regime, possibly related to the Palaeotethys back-arc basin development (ca. 450-420 Ma), would explain the 461 ± 10 Ma age yielded by some zircon domains in felsic granulites, conceivably reflecting zircon dissolution/recrystallisation till Ordovician times, long before the Variscan paroxysm (ca. 400-390 Ma). This

  17. Geodynamic interpretation of the 40Ar/39Ar dating of ophiolitic and arc-related mafics and metamafics of the northern part of the Anadyr-Koryak region

    USGS Publications Warehouse

    Palandzhyan, S.A.; Layer, P.W.; Patton, W.W.; Khanchuk, A.I.

    2011-01-01

    Isotope datings of amphibole-bearing mafics and metamafics in the northern part of the Anadyr-Koryak region allow clarification of the time of magmatic and metamorphic processes, which are synchronous with certain stages of the geodynamic development of the northwest segment of the Pacific mobile belt in the Phanerozoic. To define the 40Ar/39Ar age of amphiboles, eight samples of amphibole gabbroids and metamafics were selected during field work from five massifs representing ophiolites and mafic plutons of the island arc. Rocks from terranes of three foldbelts: 1) Pekulnei (Chukotka region), 2) Ust-Belaya (West Koryak region), and 3) the Tamvatnei and El'gevayam subterranes of the Mainits terrane (Koryak-Kamchatka region), were studied. The isotope investigations enabled us to divide the studied amphiboles into two groups varying in rock petrographic features. The first was represented by gabbroids of the Svetlorechensk massif of the Pekulnei Range and by ophiolites of the Tamvatnei Mts.; their magmatic amphiboles show the distribution of argon isotopes in the form of clearly distinguished plateau with an age ranging within 120-129 Ma. The second group includes metamorphic amphiboles of metagabbroids and apogabbro amphibolites of the Ust-Belaya Mts., Pekulnei and Kenkeren ranges (El'gevayam subterranes). Their age spectra show loss of argon and do not provide well defined plateaus the datings obtained for them are interpreted as minimum ages. Dates of amphiboles from the metagabbro of the upper tectonic plate of the Ust-Belaya allochthon points to metamorphism in the suprasubduction environment in the fragment of Late Neoproterozoic oceanic lithosphere in Middle-Late Devonian time, long before the Uda-Murgal island arc system was formed. The amphibolite metamorphism in the dunite-clinopyroxenite-metagabbro Pekulnei sequence was dated to occur at the Permian-Triassic boundary. The age of amphiboles from gabbrodiorites of the Kenkeren Range was dated to be Early

  18. Geological setting and geochemical signatures of the mafic rocks from the Intra-Pontide Suture Zone: implications for the geodynamic reconstruction of the Mesozoic Neotethys

    NASA Astrophysics Data System (ADS)

    Sayit, Kaan; Marroni, Michele; Göncüoglu, M. Cemal; Pandolfi, Luca; Ellero, Alessandro; Ottria, Giuseppe; Frassi, Chiara

    2016-01-01

    A number of suture zones exist in Turkey, which is believed to represent the closure of Paleo and NeoTethyan oceanic basins. Regarding the development of the latter oceanic entity, namely Neotethys, the geodynamic evolution of the Intra-Pontide branch, the northernmost one of a number of oceanic basins remains enigmatic. The Intra-Pontide Suture Zone in Northwest Turkey includes several tectonic units most of which are characterized by the occurrence of mafic rocks with distinct geochemical signatures. In this paper, the mafic rocks collected from four of these units (the Domuz Dağ Unit, the Saka Unit, the Daday Unit and the Arkot Dağ Mèlange) have been studied in detail along two selected transects. The Domuz Dağ Unit is characterized by amphibolites, micaschists and marbles, which have been overprinted by low-grade metamorphism.The Saka Unit is in turn represented by an assemblage of slices of amphibolites, marbles and micaschists metamorphosed under upper amphibolite facies metamorphic conditions in the Late Jurassic time. In these units, the amphibolites and their retrograded counterparts display E-MORB-, OIB- BABB- and IAT-type signatures. The Daday Unit is characterized by metasedimentary and metamafic rocks metamorphosed under blueschist to sub-greenschist facies conditions. The metamafic rocks comprise actinolite-bearing schists and Na-amphibole-bearing varieties possibly derived from basaltic and gabbroic protoliths. They have a wide range of chemical compositions, displaying N-MORB-, E-MORB-, OIB- BABB- and IAT-type signatures. The Arkot Dağ Mèlange consists of a Late Santonian assemblage of slide-blocks mainly represented by basaltic lithologies showing affinities ranging from N-MORB- and IAT- to BABB-type magmas. The geochemical signature of the studied mafic rocks indicates that the tectonic units documented along the two studied transects of the Intra-Pontide Suture Zone have been derived from a supra-subduction zone. This hypothesis

  19. Geodynamic evolution of the SW Variscides: Orogenic collapse shown by new tectonometamorphic and isotopic data from western Ossa-Morena Zone, SW Iberia

    NASA Astrophysics Data System (ADS)

    Rosas, F. M.; Marques, F. O.; BallèVre, M.; Tassinari, C.

    2008-12-01

    The pre-Mesozoic geodynamic evolution of SW Iberia has been investigated on the basis of detailed structural analysis, isotope dating, and petrologic study of high-pressure (HP) rocks, revealing the superposition of several tectonometamorphic events: (1) An HP event older than circa 358 Ma is recorded in basic rocks preserved inside marbles, which suggests subduction of a continental margin. The deformation associated with this stage is recorded by a refractory graphite fabric and noncoaxial mesoscopic structures found within the host metasediments. The sense of shear is top to south, revealing thrusting synthetic with subduction (underthrusting) to the north. (2) Recrystallization before circa 358 Ma is due to a regional-scale thermal episode and magmatism. (3) Noncoaxial deformation with top to north sense of shear in northward dipping large-scale shear zones is associated with pervasive hydration and metamorphic retrogression under mostly greenschist facies. This indicates exhumation by normal faulting in a detachment zone confined to the top to north and north dipping shear zones during postorogenic collapse soon after 358 Ma ago (inversion of earlier top to south thrusts). (4) Static recrystallization at circa 318 Ma is due to regional-scale granitic intrusions.

  20. Petrology, 40Ar/39Ar age, Sr-Nd isotope systematics, and geodynamic significance of an ultrapotassic (lamproitic) dyke with affinities to kamafugite from the easternmost margin of the Bastar Craton, India

    NASA Astrophysics Data System (ADS)

    Rao, N. V. Chalapathi; Atiullah; Burgess, R.; Nanda, Purnendu; Choudhary, A. K.; Sahoo, Samarendra; Lehmann, B.; Chahong, Ngazipmi

    2016-04-01

    We report the mineralogy, bulk-rock geochemistry, 40Ar/39Ar (whole-rock) age and radiogenic (Sr and Nd) isotope composition of an ultrapotassic dyke from Sakri (Nuapada lamproite field) located at the tectonic contact between the easternmost margin of the Bastar craton and Eastern Ghats Mobile Belt, India. The Sakri dyke has a mineralogy which strongly resembles a lamproite sensu stricto (viz.,Ti-rich phlogopite, Na-poor diopside, Fe-rich sanidine, ulvospinel trend and Sr-rich apatite). However, its bulk-rock major element geochemical characteristics (viz., extreme silica-undersaturated nature) resemble sensu lato kamafugite from Toro Ankole, Uganda, East African Rift, and Alto Paranaiba Province, Brazil. The Sakri dyke also displays certain compositional peculiarities (viz., high degree of evolution of mica composition from phlogopite to biotite, elevated titanium and aluminum in clinopyroxene and significantly lower bulk Mg#) when compared to the ultrapotassic rocks from various Indian cratons. 40Ar/39Ar dating gave a plateau age of 1045 ± 9 Ma which is broadly similar to that of other Mesoproterozoic (i) lamproites from the Bastar and Bundelkhand cratons, and (ii) kimberlites from the Eastern Dharwar craton. Initial bulk-rock Sr (0.705865-0.709024) and Nd (0.511063-0.511154) isotopic ratios reveal involvement of an `enriched' source region with long-term incompatible element enrichment and a depleted mantle (TDM) Nd model age of 2.56 Ga straddling the Archaean-Proterozoic chronostratigraphic boundary. The bulk-rock incompatible trace element ratios (Ta/Yb, Th/Yb, Rb/Ba and Ce/Y) of the Sakri ultrapotassic dyke negate any significant influence of crustal contamination. Small-degree melting (1 to 1.5 %) of a mixed garnet-facies and spinel-facies phlogopite lherzolite can account for its observed REE concentrations. Whereas the emplacement of the Sakri ultrapotassic dyke is related to the amalgamation of the supercontinent of Rodinia, its overlapping geochemical

  1. The role of changing geodynamics in the progressive contamination of Late Cretaceous to Late Miocene arc magmas in the southern Central Andes

    NASA Astrophysics Data System (ADS)

    Jones, Rosemary E.; Kirstein, Linda A.; Kasemann, Simone A.; Litvak, Vanesa D.; Poma, Stella; Alonso, Ricardo N.; Hinton, Richard

    2016-10-01

    The tectonic and geodynamic setting of the southern Central Andean convergent margin changed significantly between the Late Cretaceous and the Late Miocene, influencing magmatic activity and its geochemical composition. Here we investigate how these changes, which include changing slab-dip angle and convergence angles and rates, have influenced the contamination of the arc magmas with crustal material. Whole rock geochemical data for a suite of Late Cretaceous to Late Miocene arc rocks from the Pampean flat-slab segment (29-31 °S) of the southern Central Andes is presented alongside petrographic observations and high resolution age dating. In-situ U-Pb dating of magmatic zircon, combined with Ar-Ar dating of plagioclase, has led to an improved regional stratigraphy and provides an accurate temporal constraint for the geochemical data. A generally higher content of incompatible trace elements (e.g. Nb/Zr ratios from 0.019 to 0.083 and Nb/Yb from 1.5 to 16.4) is observed between the Late Cretaceous (~ 72 Ma), when the southern Central Andean margin is suggested to have been in extension, and the Miocene when the thickness of the continental crust increased and the angle of the subducting Nazca plate shallowed. Trace and rare earth element compositions obtained for the Late Cretaceous to Late Eocene arc magmatic rocks from the Principal Cordillera of Chile, combined with a lack of zircon inheritance, suggest limited assimilation of the overlying continental crust by arc magmas derived from the mantle wedge. A general increase in incompatible, fluid-mobile/immobile (e.g., Ba/Nb) and fluid-immobile/immobile (e.g., Nb/Zr) trace element ratios is attributed to the influence of the subducting slab on the melt source region and/or the influx of asthenospheric mantle. The Late Oligocene (~ 26 Ma) to Early Miocene (~ 17 Ma), and Late Miocene (~ 6 Ma) arc magmatic rocks present in the Frontal Cordillera show evidence for the bulk assimilation of the Permian-Triassic (P

  2. Gravity sliding in basinal setting, a surficial record of tectonic and geodynamic evolution; examples from the southern W. Alps and their foreland

    NASA Astrophysics Data System (ADS)

    Dumont, T.; Franzi, V.; Matthews, S. J.

    2012-04-01

    The occurrence of large-scale submarine landslides, although commonly observed in the present basins, is only exceptionally mentioned in the Alpine orogen and foreland. The southern part of the Western Alpine arc and the SE basin of France provide examples of such features which could be related with particular geodynamic events, in relation with the motion of the Iberian and Adriatic microplates : - A >50km2 slump scar formed in Aptian times at the northwestern edge of the SE France (so-called Vocontian) basin, giving a low-angle detachment surface which was onlapped by Albian hemipelagic marls (Ferry & Flandrin, 1979). The latter mark the maximum deepening stage of the basin, and the head of the scar is located over a deep-seated fault bounding the platform, which strongly suggest that sliding was caused by differential subsidence due to Middle Cretaceous extension, as a consequence of Iberia-Europe divergence. - Later on, a deep-marine erosion surface developed further down the basin over a >100km2 area (Dévoluy massif; Michard et al., 2010), which had been previously affected by Mid-Cretaceous extension. Typical inversion structures are found beneath the surface, which indicate that NS shortening overprinted the extensional pattern. The removal of up to 400m of Mesozoic sediments was controlled by gravity processes, probably triggered by the deformation of the basin floor following tectonic inversion. The overlying pelagic carbonates indicate that shortening occurred before the Campanian, which is closely comparable with the earliest stages of tectonic inversion in the Pyrenees. - The transition slope between the Paleogene Alpine flexural basin and the NW-ward propagating accretionary prism provides examples of basin floor degradation and of gravity-driven emplacement of large-scale blocks, generally regarded as thrust-sheets in the Alps. These features allow to reconstruct the early stages of the Adria-Europe collision, which strongly differ from the Oligo

  3. Isotope geochemistry of recent magmatism in the Aegean arc: Sr, Nd, Hf, and O isotopic ratios in the lavas of Milos and Santorini-geodynamic implications

    USGS Publications Warehouse

    Briqueu, L.; Javoy, M.; Lancelot, J.R.; Tatsumoto, M.

    1986-01-01

    In this comparative study of variations in the isotopic compositions (Sr, Nd, O and Hf) of the calc-alkaline magmas of the largest two volcanoes, Milos and Santorini, of the Aegean arc (eastern Mediterranean) we demonstrate the complexity of the processes governing the evolution of the magmas on the scale both of the arc and of each volcano. On Santorini, the crustal contamination processes have been limited, effecting the magma gradually during its differentiation. The most differentiated lavas (rhyodacite and pumice) are also the most contaminated. On Milos, by contrast, these processes are very extensive. They are expressed in the 143Nd/144Nd vs. 87Sr/86Sr diagram as a continuous mixing curve between a mantle and a crustal end member pole defined by schists and metavolcanic rocks outcropping on these volcanoes. In contrast with Santorini, the least differentiated lavas on Milos are the most contaminated. These isotopic singularities can be correlated with the geodynamic evolution of the Aegean subduction zone, consisting of alternating tectonic phases of distension and compression. The genesis of rhyolitic magmas can be linked to the two phases of distension, and the contamination of the calc-alkaline mantle-derived magmas with the intermediate compressive phase. The isotopic characteristics of uncontaminated calc-alkaline primitive magmas of Milos and Santorini are directly comparable to those of magmas generated in subduction zones for which a contribution of subducted sediments to partial melts from the mantle is suggested, such as in the Aleutian, Sunda, and lesser Antilles island arcs. However, in spite of the importance of the sediment pile in the eastern Mediterranen oceanic crust (6-10 km), the contribution of the subducted terrigenous materials remains of limited amplitude. ?? 1986.

  4. Crustal structure and geodynamics of the Middle and Lower reaches of Yangtze metallogenic belt and neighboring areas: Insights from deep seismic reflection profiling

    NASA Astrophysics Data System (ADS)

    Lü, Qingtian; Shi, Danian; Liu, Zhendong; Zhang, Yongqian; Dong, Shuwen; Zhao, Jinhua

    2015-12-01

    A 300 km long seismic reflection profile was acquired across the Middle and Lower Reaches of the Yangtze River (MLY) metallogenic belt and its adjacent areas. The objective of the survey was to establish the deep architecture and geodynamic framework of the region. Results based on the interpretation of the deep seismic data include (1) Tan-Lu fault appears as a subvertical thrust fault or transpression fault with its deep portion dipping toward the southeast; (2) the Zhangbaling uplift is squeezed out along this fault; (3) complex upper crustal deformation structures beneath the Chuquan depression include both kink bands, thrusts, imbrication and fold structures reflecting contraction deformation, and detachment fault and normal-fault structures reflecting extensional deformation; (4) the "crocodile" reflection structure emerging beneath the Tan-Lu fault and Ningwu-Lishui volcanic basin, which represents the decoupled deformation process of the upper and lower crust associated with intra-continental subduction; (5) further to the southeast, the upper crust deformation shows a large-scale "wave-form" pattern, making crustal scale syncline and anticline; (6) the entire section of the reflection Moho is clearly discernible at depth of 30.0-34.5 km, and the Moho beneath the Middle and Lower Reaches of Yangtze River metallogenic belt is shallowest, while the Moho beneath the North China block is deeper than that beneath the Yangtze block. The Moho offsets could be seen beneath the Ningwu volcanic basin. The seismic reflection data suggest that lithosphere delamination and asthenosphere upwelling that may result from the Mesozoic intra-continental orogenesis is responsible for the formation of large scale magmatism and mineralization in the MLY metallogenic belt.

  5. A regional-scale discontinuity in western Sicily revealed by a multidisciplinary approach: A new piece for understanding the geodynamic puzzle of the southern Mediterranean

    NASA Astrophysics Data System (ADS)

    Di Stefano, Pietro; Favara, Rocco; Luzio, Dario; Renda, Pietro; Cacciatore, Maria Simona; Calò, Marco; Napoli, Giuseppe; Parisi, Laura; Todaro, Simona; Zarcone, Giuseppe

    2015-10-01

    The results of an integrated stratigraphic, structural, geophysical, and geochemical study reveal the presence of a crustal discontinuity in western Sicily that, at present, runs roughly N-S along a band from San Vito Lo Capo to Sciacca. The boundary between the two zones of this discontinuity is nearly orthogonal to the main thrust propagation of the Sicilian thrust-and-fold belt. The different Permian to Tertiary sedimentary evolution recorded by the two zones appears related to this discontinuity, with thick carbonate platforms in the western sector facing deepwater successions in the eastern one. The presence of Upper Triassic reefs, huge megabreccia bodies, and widespread submarine volcanisms along the transition zone suggests the presence of a long-lasting weakness zone. This zone has been reactivated episodically as transpressional and/or transtensional faults in relation to the different geodynamic stress acting in central Mediterranean area in different epochs. We speculate that this transition zone has represented a segment of the passive margin of the Ionian Tethys. During the Maghrebian convergence a different style of deformation has affected the two sectors floored by different sedimentary multilayers. The orthogonal-to-oblique differential convergence between the two sectors has resulted in right-lateral transpressional motions, leading to oblique thrusting of deepwater-derived thrusts onto platform-derived thrusts associated with clockwise rotations. The oblique convergence is still ongoing as demonstrated by the seismicity of the area, by the geothermal field with high mantle-derived helium fluxes and by the GPS measurements collected by different authors.

  6. Quartz tube extensometer for observation of Earth tides and local tectonic deformations at the Sopronbánfalva Geodynamic Observatory, Hungary.

    PubMed

    Mentes, Gy

    2010-07-01

    In May 1990, a quartz tube extensometer was installed in the Sopronbánfalva Geodynamic Observatory of the Geodetic and Geophysical Research Institute (GGRI) of the Hungarian Academy of Sciences for recording Earth tides and recent tectonic movements. The paper describes the construction of the extensometer and a portable calibrator used for the in situ calibration of the instrument. The extensometer is very sensitive. Its scale factor is 2.093+/-0.032 nm/mV according to the highly precise calibration method developed at the GGRI. Since the stability of extensometers is strongly influenced by the geological structure and properties of the rocks in the vicinity of the recording site, the observatory instrument system was tested by coherence analysis between theoretical (as the input signal) and measured tidal data series (as the output signal). In the semidiurnal tidal frequency band the coherence is better than 0.95, while in the diurnal band it is about 0.8. Probably this is due to the fact that the noise is higher in the diurnal band (0.4-0.5 nstr) than in the semidiurnal band (0.19-0.22 nstr). Coherence analysis between theoretical and measured data corrected for barometric changes yielded a small improvement of coherence in both frequency bands, while using temperature data correction, no observable improvement was obtained. Results of the tidal analysis also show that the observatory instrument system is suitable for recording very small tectonic movements. The 18 years of continuous data series measured by the extensometer prove the high quality of the extensometer. On the basis of investigations, it was pointed out that further efforts should be done to improve the barometric correction method and that correction for ocean load, as well as considering topographic and cavity effects are necessary to increase the accuracy of determining tidal parameters.

  7. Quartz tube extensometer for observation of Earth tides and local tectonic deformations at the Sopronbánfalva Geodynamic Observatory, Hungary.

    PubMed

    Mentes, Gy

    2010-07-01

    In May 1990, a quartz tube extensometer was installed in the Sopronbánfalva Geodynamic Observatory of the Geodetic and Geophysical Research Institute (GGRI) of the Hungarian Academy of Sciences for recording Earth tides and recent tectonic movements. The paper describes the construction of the extensometer and a portable calibrator used for the in situ calibration of the instrument. The extensometer is very sensitive. Its scale factor is 2.093+/-0.032 nm/mV according to the highly precise calibration method developed at the GGRI. Since the stability of extensometers is strongly influenced by the geological structure and properties of the rocks in the vicinity of the recording site, the observatory instrument system was tested by coherence analysis between theoretical (as the input signal) and measured tidal data series (as the output signal). In the semidiurnal tidal frequency band the coherence is better than 0.95, while in the diurnal band it is about 0.8. Probably this is due to the fact that the noise is higher in the diurnal band (0.4-0.5 nstr) than in the semidiurnal band (0.19-0.22 nstr). Coherence analysis between theoretical and measured data corrected for barometric changes yielded a small improvement of coherence in both frequency bands, while using temperature data correction, no observable improvement was obtained. Results of the tidal analysis also show that the observatory instrument system is suitable for recording very small tectonic movements. The 18 years of continuous data series measured by the extensometer prove the high quality of the extensometer. On the basis of investigations, it was pointed out that further efforts should be done to improve the barometric correction method and that correction for ocean load, as well as considering topographic and cavity effects are necessary to increase the accuracy of determining tidal parameters. PMID:20687746

  8. New geochronological ages (U-Pb/Lu-Hf) from high-pressure rocks of the Escambray terrane and Santa Clara serpentinite mélange, central Cuba. Regional correlations and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Rojas-Agramonte, Y.; García-Casco, A.; Kröner, A.; Herwartz, D.; Ibis Despaigne, A.; Wilde, S.

    2012-04-01

    of the Escambray complex show, however, enrichment in alkali and LIL elements, suggesting a) a passive continental margin origin of the protoliths or b) contamination of (altered) MOR-derived rocks by fluids in the subduction environment. A single zircon U-Pb age of 131.1±1.3 Ma for a block of garnet amphibolite from a sliver of oceanic serpentinite mélange from the Gavilanes unit (Trinidad Dome, Escambray terrane) is interpreted as reflecting the time of basaltic protolith crystallization or the time of HP metamorphism. The last interpretation, though still uncertain, is supported by a new garnet Lu-Hf age of 126,04 ± 0.54 Ma for a block of eclogite from the central Cuba serpentinite mélange. SHRIMP analyses of single-grain zircons from two eclogite samples from the Gavilanes unit on the Cipiabo River (Sancti Spiritus dome, Escambray terrane) show a broad spectrum of ages between 172 Ma and 2.4 Ga. We interpret the occurrence of Middle Jurassic to Paleoproterozoic zircons in these eclogites as inherited, suggesting crustal contamination of the basaltic protoliths. A new garnet Lu-Hf age of 70,3 ± 1.1 Ma for an eclogite on the Higuanojo River (Sancti Spiritus dome) agrees with most geochronological data from the Escambray terrane obtained so far. These data, combined with previously published age data of HP and low pressure (MOR- and arc-related) rocks, indicate continuous subduction in the Cuban branch of the northern leading edge of the Caribbean plate since ca. 130 Ma until, at least, 70 Ma and corroborate the interpretation that the onset of terrane(Caribeana)-trench collision took place during the latest Cretaceous, in agreement with geodynamic models for the region. The data also allow correlating paleosubduction zones of the Antilles and Guatemala in the same period, for ages of high pressure rocks from the Motagua valley serpentinite mélanges, the Chuacús complex, and the basement of the Maya block range 150-70 Ma.

  9. Irregularities in the secular variation and geodynamic implications; Proceedings of the Session, Cincinnati, OH, May 17, 1984

    NASA Technical Reports Server (NTRS)

    Taylor, P. (Editor); Runcorn, S. K. (Editor)

    1985-01-01

    Consideration is given to: variations in the Gauss coefficients of the geomagnetic potential over the last several hundred years; eccentric geomagnetic dipole drift; and evidence for geomagnetic jerks from 1931 to 1971. Among other topics discussed are: models of the geomagnetic field in western Europe from 1960 to 1980; the external and internal parts of the geomagnetic jerk of 1970; secular variation of the magnetic mean energy density at the source layer depth; and motions at the core surface in the geostrophic approximation. Consideration is also given to: the unpredictability of geomagnetic secular variation; the use of short-term core-mantle coupling and geomagnetic variation impulses as Lagrangian tracers of core motions; and a comparison of two sequential geomagnetic polarity transitions in the upper Olduvai and the lower Jarmillio in the Southern Hemisphere.

  10. Sediment and Crustal Structure along 85oE and Ninetyeast Ridges in the Bay of Bengal: Geodynamic Implications

    NASA Astrophysics Data System (ADS)

    Munukutla, R.; Gangumalla, S. R.; Sreejith, K. M.; Krishna, K. S.; Bull, J. M.

    2015-12-01

    The Bay of Bengal (BOB) region is characterized by the presence of two linear N-S trending aseismic ridges, the 85°E and Ninetyeast ridges which have progressively buried below thick sediments towards north. We present here the results of an integrated interpretation of geophysical data using multichannel seismic reflection, gravity and magnetic datasets over these two ridges to study the crustal structure and mode of their emplacement. The ridges divide the deep sedimentary BOB region into three major sub-basins. Considering the sediment deposition pattern within the sub-basins and over the ridges, it is found that both ridge structures have played a role in sediment dispersal pattern during the pre- and post Bengal Fan sedimentation. The Geoid-Topography Ratio (GTR) analysis indicates that both the ridges are compensated at shallow depths. Seismically constrained gravity and magnetic models and flexural gravity modeling over these ridges support their volcanic origin, and suggest the following: i) 85°E Ridge was emplaced in off-ridge environment (Te=10-15 km); ii) the higher Te values of ~ 25 km over the Afanasy Nikitin Seamount (ANS) reflect the secondary emplacement of the seamount peaks in off-ridge environment, iii) that the emplacement of the Ninetyeast Ridge north of 2°N occurred in an off-ridge environment as indicated by higher Te values (25-30 km). These results attain significance in terms of understanding of the interactions between plume- volcanism and lithosphere in the Bay of Bengal.

  11. Geodynamic controls on a salt giant formation. The Messinian salinity crisis and the tectonic evolution of the westernmost Mediterranean

    NASA Astrophysics Data System (ADS)

    Garcia-Castellanos, Daniel

    2016-04-01

    The landlocked location of the Mediterranean is presumed to be the result of the southward retreat of subducted Tethyan lithospheric slabs after the collision between Europe and Africa. The western end of the Alpine orogeny (the Gibraltar Arc) shaped the last marine connection to the ocean during the upper Miocene, but in this complex tectonic region, the dominant polarity of subduction (Tethys underneath Iberia/Europe/Anatolia) might not be accomplished, based on plate reconstructions, mantle tomography, and the present position of the Kabylies and the Alboran nappes. This tectonic evolution determined the vertical motions purportedly responsible for the restriction of the Mediterranean and the widespread salt accumulation during the Messinian Salinity Crisis. Following the concept of isostasy, the enormous and rapid mass redistribution implied by the crisis should have induced in turn remarkable vertical motions of the Mediterranean margins. While the predicted isostatic motions during the crisis range in the order of hundreds of meters, little evidence has been documented so far. The mechanical response of the Iberian margins can be inferred by using crustal and lithospheric cross sections derived from potential fields (gravity and geoid anomalies), heatflow, and topography modeling. The preliminary results are consistent with a low rigidity of the lithosphere, in agreement with their young thermomechanical age. These rigidity values are then used for a first-order estimation of the vertical motions associated to the accumulation of salt and the possible partial evaporation of the water column during the crisis. Recent seismic stratigraphic data show that the Balearic promontory hosts a unique set of intermediate-depth basins where halite deposited in smaller amounts than in the deeper basins. If future drillings provide more precise constraints on the paleobathymetry of the sedimentary units before and after the crisis, the various proposed models for its

  12. Paleomagnetism and geodynamics of the onshore High Arctic Large Igneous Province and its connection to the offshore Alpha Ridge

    NASA Astrophysics Data System (ADS)

    Tarduno, J. A.

    2009-05-01

    Here I summarize findings from the University of Rochester paleomagnetic expeditions to the High Canadian Arctic dedicated to understanding the tectonic and magmatic evolution of the region, together with recovering data useful for defining the history of the geomagnetic field. Our work has focused on what we now recognize as two distinct episodes of volcanism: i. massive flood basalt volcanism at ca. 92 Ma and ii. smaller volume, spatially restricted volcanism at ca 77 Ma. Lava flows from the older event have provided key paleomagnetic data that exclude significant latitudinal motion of the Canadian Arctic Islands relative to North America. When combined with other North American sites, these data define a time-averaged dipolar magnetic field. The younger volcanics, preserved in small basins on remote northern Ellesmere Island, may define a failed rifting event; their extent in the Arctic Ocean is uncertain, but they may correlate with dikes reported from northern Greenland. The older flood basalts thicken to the north in the Canadian Arctic (Axel Heiberg Island), near the region where Alpha Ridge of the Arctic Ocean abuts the coastline. Following results of seismic analyses, I interpret this, together with Mendeleev Ridge as a volcanic oceanic plateau, potentially with continental blocks similar in structure to Kerguelen Plateau of the Indian Ocean. Simple hotspot track models fail to predict a tie of this feature to an extant hotspot (although a tie to the Iceland hotspot has been suggested). A new model of plume tilt at mid-mantle depths toward an upper mantle upwelling may better explain the observations.

  13. Consequences of Chixculub Impact for the Tectonic and Geodynamic Evolution of the Gulf of Mexico North Carribean Region

    NASA Astrophysics Data System (ADS)

    Rangin, C.; Crespy, A.; Martinez-Reyes, J.

    2013-05-01

    The debate for Pacific exotic origin versus in situ inter American plate Atlantic origin of the Caribbean plate is active in the scientific community since decades. Independently of the origin of this plate, its fast motion towards the east at a present rate of 2cm/yr is accepted to have been initiated during the early-most Cenozoic. The Paleocene is a key period in the global evolution of Central America mainly marked also by the Chicxulub multiring meteor impact in Yucatan. We question here the genetic relationship between this impact event and the incipient tectonic escape of the Caribbean plate. The mostly recent published models suggest this impact has affected the whole crust down to the Moho, the upper mantle being rapidly and considerably uplifted. The crust was then fragmented 600km at least from the point of impact, and large circular depressions were rapidly filled by clastic sediments from Cantarell to Western Cuba via Chiapas and Belize. North of the impact, the whole Gulf of Mexico was affected by mass gravity sliding, initiated also during the Paleocene in Texas, remaining active in this basin up to present time. South of the impact, in the Caribbean plate, the Yucatan basin was rapidly opened, indicating a fast escape of the crustal material towards the unique free boundary, the paleo-Antilles subduction zone. Shear waves velocity data below the Caribbean plate suggest this crustal tectonic escape was enhanced by the fast eastward flowing mantle supporting a fragmented and stretched crust. The proposed model suggests Chicxulub impact (but also the hypothetic Beata impact) have fragmented brittle crust, then easily drifted towards the east. This could explain the Paleogene evolution of the Caribbean plate largely stretched during its early evolution. Geologically, this evolution could explain the absence of evident Paleogene oblique subduction along the Caribbean plate northern and southern margins, marked only by Mid Cretaceous dragged volcanic

  14. Geodynamics of paleo-Pacific plate subduction constrained by the source lithologies of Late Mesozoic basalts in southeastern China

    NASA Astrophysics Data System (ADS)

    Zeng, Gang; He, Zhen-Yu; Li, Zhen; Xu, Xi-Sheng; Chen, Li-Hui

    2016-10-01

    Widespread Late Mesozoic volcanic magmatism in southeastern China is generally thought to represent products in response to the subduction of paleo-Pacific plate; however, it remains unclear when this process began to affect the mantle and the related magmatism. Here we present a systematic study on the source lithology of Late Mesozoic basalts in this area to highlight a link between lithological variations of mantle and subduction process of paleo-Pacific plate. Late Mesozoic basalts can be subdivided into four groups based on their erupted ages: 178 172 Ma, approximately 150 Ma, 137 123 Ma, and 109 64 Ma. The primary source lithology of these rocks is pyroxenite rather than peridotite, and this mafic lithology can be formed by either ancient or young recycled crustal components. Notably, the source lithology of the approximately 150 Ma and 137 123 Ma basalts is primarily SiO2-rich pyroxenite, and the former is carbonated. The discovery of carbonated, SiO2-rich pyroxenite reflects the influence of a recently recycling event in the mantle. The subduction of paleo-Pacific plate is the most appropriate candidate and can be responsible for the mantle-derived magmatism after approximately 150 Ma in southeastern China. Therefore, we suggest a paleo-Pacific slab rollback with increased dip angle as a possible model to control the lithological variations of Late Mesozoic mantle beneath southeastern China.

  15. Geodynamic setting and geochemical signatures of Cambrian?Ordovician rift-related igneous rocks (Ossa-Morena Zone, SW Iberia)

    NASA Astrophysics Data System (ADS)

    Sánchez-García, T.; Bellido, F.; Quesada, C.

    2003-04-01

    An important rifting event, accompanied by massive igneous activity, is recorded in the Ossa-Morena Zone of the SW Iberian Massif (European Variscan Orogen). It likely culminated in the formation of a new oceanic basin (Rheic ocean?), remnants of which appear presently accreted at the southern margin of the Ossa-Morena Zone. Rifting propagated diachronously across the zone from the Early Cambrian to the Late Ordovician, but by Early Ordovician time, the existence of a significant tract of new ocean is evidenced by a breakup unconformity. Although early stages of rifting were not accompanied by mantle-derived igneous activity, a pronounced increase of the geothermal gradient is indicated by partial melting of metasedimentary protoliths in the upper and middle crust, and by coeval core-complex formation. Geochemistry of the main volume of igneous rocks, emplaced some million years later during more mature stages of rifting, suggests an origin in a variably enriched asthenospheric source, similar to that of many OIB, from which subsequent petrogenetic processes produced a wide range of compositions, from basalt to rhyolite. A tectonic model involving collision with, and subsequent overriding of, a MOR is proposed to account for the overall evolution, a present-day analogue for which lies in the overriding of the East Pacific Rise by North America and the rifting of Baja California.

  16. Stress Coupling Relationship between Mantle Convection and Seismogenic Layer in Southeastern Tibetan Plateau and its Geodynamic Implications

    NASA Astrophysics Data System (ADS)

    Qiang, H.

    2015-12-01

    The lithospheric stress states and interlayer coupling interaction is of great significant in studying plate driven mechanism and seismogenic environment. The coupling relationship between mantle convection generated drag stress in the lithospheric base and seismogenic layer stress in the crust represents the lithospheric mechanical coupling intensity level. We calculate the lithospheric bottom mantle convection stress field of the southeastern Tibetan Plateau using 11~36 spherical harmonic coefficients of gravity model EGM2008. Meanwhile we collect and organize the focal mechanism of 1131 earthquakes that occurred from 2000 to now in Sichuan-Yunnan region. The current seismogenic layer stress and stress field before Lushan earthquake are calculated by the damping regional stress tensor inversion. We further analyze the correlation between the two kinds of stress fields, then discuss the relation between mechanics coupling situation and strong earthquakes in different regions. The results show that: (1) Most of Sichuan-Yunnan region is located in the coupling and decoupling intermediate zone. Coupling zones distribute on the basis of block, the eastern South China block has strong coupling, and the coupling phenomenon also exists in parts of the northern Tibet block, Balyanlkalla block in the northwest and southwest Yunnan block. The decoupling mainly occurs in Songpan-Ganzi block, connecting with the strong coupling South China block and Longmenshan fault zone is their boundary. (2) We have analyzed seismogenic mechanism, then proposed the border zone of strong and weak coupling relation between mantle convection stress and seismogenic layer stress exists high seismic risk. The current coupling situation shows that Longmenshan fault zone is still in the large varying gradient area of coupling intensity level, it has conditions to accumulate energy and develop earthquakes. Other dangerous areas are: Mingjiang, Xianshuihe, Anninghe, Zemuhe, the Red River, Nantinghe

  17. Cenozoic geodynamics of the Ross Sea region, Antarctica: Crustal extension, intraplate strike-slip faulting, and tectonic inheritance

    NASA Astrophysics Data System (ADS)

    Salvini, Francesco; Brancolini, Giuliano; Busetti, Martina; Storti, Fabrizio; Mazzarini, Francesco; Coren, Franco

    1997-11-01

    An integrated study of onshore and offshore geology of the Ross Sea region (namely, Victoria Land, north of Ross Island, and the Ross Sea, Antarctica) has revealed a complex, post-Eocene tectonic framework. Regional NW-SE right-lateral, strike-slip faults are the outstanding feature of this framework and overprint an older Mesozoic extensional event, responsible for formation of N-S basins in the Ross Sea. The Cenozoic framework includes kinematic deformation and reactivation along the NW-SE faults, including formation of pull-apart basins, both positive and negative flower structures, and push-up ridges. N-S extensional faults are well developed between NW-SE faults and indicate E-W extension during the Cenozoic, produced by the NW-SE right-lateral strike-slip motion together with regional crustal extension. NNW-SSE compression, induced by the right-lateral, strike-slip kinematics, is indicated by locally inverted NE-SW faults and basins. The evolution, geometry, and location of the Rennick Graben and the Lanterman Range fit well into this model. Variations in the deformational style across the region can be linked to corresponding variations in the bulk crustal rheology, from brittle behavior in the west, to ductile deformation (at subseismic-scale resolution) near the Eastern Basin. A semibrittle region that favors N-S clustering of Cenozoic magmatic activity lies in between. In this region, Cenozoic volcanoes develop at the intersections of the NW-SE and the major N-S faults. The NW-SE faults cut almost continually from the Ross Sea to East Antarctica through lithospheric sectors with different rheology and thickness. At least two of the NW-SE faults correspond to older Paleozoic terrane boundaries in northern Victoria Land. The NW-SE faults link in the Southern Ocean with major transform faults related to the plate motions of Australia, New Zealand, and Antarctica.

  18. The Antei uranium deposit: A natural analogue of an SNF repository and an underground geodynamic laboratory in granite

    NASA Astrophysics Data System (ADS)

    Laverov, N. P.; Petrov, V. A.; Poluektov, V. V.; Nasimov, R. M.; Hammer, J.; Burmistrov, A. A.; Shchukin, S. I.

    2008-10-01

    the intensity of their metasomatic alteration and the distance from master fault planes, have been established. A 3D geological model of the deposit in combination with estimated parameters of the present-day stress field and physicomechanical properties of particular rock blocks serves as the basis for prediction of the geomechanical behavior of the massif. The practical implications of the results obtained for assessment of the long-term safety of SNF repositories in granites are discussed.

  19. Hydration of the lithospheric mantle by the descending plate in a continent-continent collisional setting and its geodynamic consequences

    NASA Astrophysics Data System (ADS)

    Massonne, Hans-Joachim

    2016-05-01

    At the beginning of continent-continent collision the descending plate dehydrates. The influence of this dehydration on the adjacent lithospheric mantle was studied. For this reason, pressure (P), temperature (T) and T-H2O pseudosections were calculated for an average mantle composition using the computer software PERPLE_X. These pseudosections were contoured by isopleths, for instance, for volumes of amphibole, chlorite, and serpentine. In addition, P-T pseudosections were considered for four psammopelitic rocks, common in the upper portion of the continental crust, in order to quantify the release of H2O in these rocks during prograde metamorphism. At pressures around 1 GPa, a maximum of slightly more than 10 vol.% chlorite, almost 20 vol.% amphibole, and some talc but no serpentine forms when only 1.8 wt.% H2O is added to the dry ultrabasite at temperatures of 600 °C. For example, hydrous phases amount to about 35 vol.% serpentine and 10 vol.% each of chlorite and amphibole at 1 GPa, 550 °C, and 5 wt.% H2O. The modelled psammopelitic rocks can release 0.8-2.5 wt.% H2O between 450 and 650 °C at 0.8-1.4 GPa. On the basis of the above calculations, different collisional scenarios are discussed highlighting the role of hydrated lithospheric mantle. In this context a minimum hydration potential of the front region of the descending continental plate is considered, which amounts to 4.6 × 1016 kg releasable H2O for a 1000 km wide collisional zone, due to a thick sedimentary pile at the continental margin. Further suggestions are that (1) the lower crustal plate in a continent-continent collisional setting penetrates the lithospheric mantle, which is hydrated during the advancement of this plate, (2) the maximum depths of the subduction of upper continental crust is below 70 km and (3) hydrated mantle above the descending crustal plate is thrust onto this continental crust.

  20. Crustal source of the Late Cretaceous Satansarı monzonite stock (central Anatolia - Turkey) and its significance for the Alpine geodynamic evolution

    NASA Astrophysics Data System (ADS)

    Köksal, Serhat; Toksoy-Köksal, Fatma; Göncüoğlu, M. Cemal; Möller, Andreas; Gerdes, Axel; Frei, Dirk

    2013-04-01

    The Late Cretaceous granitic rocks within central Anatolia (Turkey) not only date and show the magmatic aspects of the Alpine realm, but also give clues about its geodynamic character. Among them, the Satansarı monzonite stock (SMS), part of the Terlemez pluton (Aksaray), characterizing the inception of an extensional tectonic regime in central Anatolia, has a subalkaline, metaluminous and magnesian geochemical nature with depletion in Ba, Nb, P and Ti, and with enrichment of Th, U, K and Pb relative to primitive mantle. The SMS has LREE enriched patterns ([La/Yb]N = 18.45-21.21) with moderately negative Eu-anomalies ([Eu/Eu*]N = 0.65-0.73). The geochemical data infer a crustal source with an inherited subduction-related component, and fractionation of plagioclase and amphibole. A crustal signature for the SMS is also inferred from high 87Sr/86Sr(t) ratios (0.70826-0.70917), and low ɛNd(t) values (-6.9 to -7.6). Zircon crystals from the SMS typically have magmatic rims overgrowing inherited cores that are reworked, resorbed and overgrown. Completely new zircon crystals grown in a single magmatic episode have also been identified. Laser ablation ICP-MS U-Pb zircon analyses yield a mean 206Pb/238U age of 74.4 ± 0.6 Ma (2σ) for the intrusion of the SMS. Rare discordant analyses range from the Devonian to the Proterozoic (i.e., 207Pb/206Pb ages between 364 Ma and 1263 Ma). In situ zircon Hf isotope analyses reveal low 176Lu/177Hf ratios and negative ɛHf(t) values, which is consistent with a predominantly crustal source of the SMS. We suggest that the water-rich magmas were generated in a hot zone within the crust produced by residual melts from basalt crystallization and partial melts of pre-existing metamorphic and igneous rocks within the lower crust of central Anatolia. The SMS likely formed by episodic injections of these hybrid monzonite melts by adiabatic ascent to shallow crust where they crystallized. This interpretation may be useful in interpreting the

  1. Crystallization conditions of porphyritic high-K calc-alkaline granitoids in the extreme northeastern Borborema Province, NE Brazil, and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Campos, Benedita Cleide Souza; Vilalva, Frederico Castro Jobim; Nascimento, Marcos Antônio Leite do; Galindo, Antônio Carlos

    2016-10-01

    An integrated textural and chemical study on amphibole, biotite, plagioclase, titanite, epidote, and magnetite was conducted in order to estimate crystallization conditions, along with possible geodynamic implications, for six Ediacaran porphyritic high-K calc-alkaline granite plutons (Monte das Gameleiras, Barcelona, Acari, Caraúbas, Tourão, and Catolé do Rocha) intrusive into Archean to Paleoproterozoic rocks of the São José do Campestre (SJCD) and Rio Piranhas-Seridó (RPSD) domains, northern Borborema Province. The studied rocks include mainly porphyritic leucocratic monzogranites, as well as quartz-monzonites and granodiorites. Textures are marked by K-feldspar megacrysts (5-15 cm long) in a fine-to medium-grained matrix composed of quartz, plagioclase, amphibole, biotite, as well as titanite, epidote, Fesbnd Ti oxides, allanite, apatite, and zircon as accessory minerals. Amphibole, biotite and titanite share similar compositional variations defined by increasing Al and Fe, and decreasing Mg contents from the plutons emplaced into the SJCP (Monte das Gameleiras and Barcelona) towards those in the RPSD (Acari, Caraúbas, Tourão, and Catolé do Rocha). Estimated intensive crystallization parameters reveal a weak westward range of increasing depth of emplacement, pressure and temperature in the study area. The SJCD plutons (to the east) crystallized at shallower crustal depths (14-21 km), under slightly lower pressure (3.8-5.5 kbar) and temperature (701-718 °C) intervals, and high to moderate oxygen fugacity conditions (+0.8 < ΔFQM < +2.0). On the other hand, the RPSD plutons (to the west) were emplaced at slightly deeper depths (18-23 km), under higher, yet variable pressures (4.8-6.2 kbar), temperatures (723-776 °C), and moderate to low oxygen fugacity conditions (-1.0 < ΔFQM < +1.8). These results reinforce the contrasts between the tectono-strutuctural domains of São José do Campestre and Rio Piranhas-Seridó in the northern Borborema Province.

  2. Geochemistry and geodynamics of a Late Cretaceous bimodal volcanic association from the southern part of the Pannonian Basin in Slavonija (Northern Croatia)

    USGS Publications Warehouse

    Pamic, J.; Belak, M.; Bullen, T.D.; Lanphere, M.A.; McKee, E.H.

    2000-01-01

    In this paper we present petrological and geochemical information on a bimodal basaltrhyolite suite associated with A-type granites of Late Cretaceous age from the South Pannonian Basin in Slavonija (Croatia). Basalts and alkali-feldspar rhyolites, associated in some places with ignimbrites, occur in volcanic bodies that are interlayered with pyroclastic and fossiliferous Upper Cretaceus sedimentary rocks. The petrology and geochemistry of the basalts and alkali-feldspar rhyolites are constrained by microprobe analyses, major and trace element analyses including REE, and radiogenic and stable isotope data. Basalts that are mostly transformed into metabasalts (mainly spilites), are alkalic to subalkalic and their geochemical signatures, particularly trace element and REE patterns, are similar to recent back-arc basalts. Alkali-feldspar rhyolites have similar geochemical features to the associated cogenetic A-type granites, as shown by their large variation of Na2O and K2O (total 8-9%), very low MgO and CaO, and very high Zr contents ranging between 710 and 149ppm. Geochemical data indicate an amphibole lherzolite source within a metasomatized upper mantle wedge, with the influence of upper mantle diapir with MORB signatures and continental crust contamination. Sr incorporated in the primary basalt melt had an initial 87Sr/86Sr ratio of 0.7039 indicating an upper mantle origin, whereas the 87Sr/86Sr ratio for the alkalifeldspar rhyolites and associated A-type granites is 0.7073 indicating an apparent continental crust origin. However, some other geochemical data favour the idea that they might have mainly originated by fractionation of primary mafic melt coupled with contamination of continental crust. Only one rhyolite sample appears to be the product of melting of continental crust. Geological and geodynamic data indicate that the basalt-rhyolite association was probably related to Alpine subduction processes in the Dinaridic Tethys which can be correlated with

  3. Geodetic Tying of Antarctica and India With 10 Years of Continuous GPS Measurements for Geodynamical and Strain Accumulation Studies in the South of Indian Peninsula

    NASA Astrophysics Data System (ADS)

    Ec, M.; N, R.

    2008-12-01

    To holistically understand the geodynamical and crustal deformation processes between India and Antarctica, two global networks (IND and ANT) have been chosen. The objective is to geodetically connect the two continents. The IGS Station at Diego Garcia (DGAR) is the common station between the two networks. 10 years of data from 1997 to 2007 were used. By these global networks' analyses, the stations HYDE in India and MAIT at Antarctica are geodetically tied through the station DGAR. Very long baselines have been estimated from HYDE and also from Kerguelen (KERG) to other chosen IGS stations in and around India and Antarctica. Our analysis and results using ANT network show an increase in the baseline lengths between Kerguelen in Antarctic plate and other stations such as SEY1, DGAR and COCO and shortening of baseline lengths between HYDE in Indian plate and all these above stations using IND network. The analysis using ANT network also shows lengthening of baselines from Kerguelen to the sites Yaragadee (YAR1) and Tidbinbilla (TID2) in Australian plate; and Seychelles (SEY1) in Male plate, COCO in the diffuse plate boundary between India and Australia and DGAR in Capricorn plate at the rates of 5.3cm/yr, 3.8cm/yr, 5.6mm/yr, 3.03 cm/yr and 5.5 cm/yr respectively. The high rate of movement of COCO Island in comparison to Seychelles could be the result of excessive strain accumulation due to the Indo-Australia diffuse plate boundary forces acting upon this region. The estimated elastic strain accumulation shows an increasing trend of 1.27x 10-8 yr-1 in the south of Indian peninsula. Our results show the precision of approximately 3-4mm (North), 5-6 mm (East), and 10-12mm (vertical) for the estimation of site coordinates. These results provide new information on the direction and rate of Indian plate motion, the driving mechanisms of Indian plate and intraplate seismicity of the Indian Ocean on the whole.

  4. Divergence between Antarctic and South American marine invertebrates: What molecular biology tells us about Scotia Arc geodynamics and the intensification of the Antarctic Circumpolar Current

    NASA Astrophysics Data System (ADS)

    Poulin, Elie; González-Wevar, Claudio; Díaz, Angie; Gérard, Karin; Hüne, Mathias

    2014-12-01

    Continental drift processes such as major gateway openings have been historically advocated to explain the distribution of marine benthic taxa in the Southern Ocean (SO). The separation between Antarctic Peninsula and the southern tip of South America together with the onset of the Antarctic Circumpolar Current (ACC) represent the final step for the complete isolation of the Antarctic region. However, there is still controversy concerning the timing and mode of this process, and especially about the role of the Scotia Arc geodynamics in the development of a fully deep and intensified ACC circulation. Based on mitochondrial Cytochrome c Oxidase Subunit I (COI) sequences obtained from different taxa, we performed molecular comparisons between Antarctic and South American relatives to provide independent time estimations of Antarctica's isolation. We include in the analyses congeneric Antarctic and Patagonian near-shore marine benthic invertebrates including indirect developers (Nacella, Yoldia, Sterechinus, and Parbolasia) and brooders (Xymenopsis and Trophonella). Considering the levels of genetic differentiation between relatives from both regions and assuming the molecular clock hypothesis, we estimated the onset of their respective divergence. On one hand, similar levels of genetic distance in broadcast-spawners (7%-8.3%) support the hypothesis that the development of an effective barrier between Antarctica and South America occurred almost simultaneously for these groups. Divergence time estimations based on specific substitution rates indicate that the separation occurred near the Mio-Pliocene transition, long after the physical separation of both continents. Genetic distance and divergence time estimation in direct developers indicate an older separation time, close to the mid-Miocene. Even when the analyzed groups included both broadcast-spawners and brooder organisms, the divergence between Antarctic and South America lineages rather than being related to

  5. Anatomy of an ancient subduction interface at 40 km depth: Insights from P-T-t-d data, and geodynamic implications (Dent Blanche, Western Alps)

    NASA Astrophysics Data System (ADS)

    Angiboust, Samuel; Glodny, Johannes; Oncken, Onno; Chopin, Christian

    2014-05-01

    An exhumed metamorphic suture zone over 40 km long is exposed in the Dent Blanche Region of the Western Alps belt, along the Swiss-Italian border. In this region, the metasediment-bearing ophiolitic remnants of the Liguro-Piemontese ocean (Tsaté complex) are overthrusted by a continental, km-sized complex (Dent Blanche Tectonic System: DBTS) of Austro-Alpine affinity. The DBTS represents a strongly deformed composite terrane with independent tectonic slices of continental and oceanic origin. In order to better understand the nature and the geodynamic meaning of the shear zone at the base of the DBTS (Dent Blanche Thrust, DBT) we re-evaluated the pressure-temperature-time-deformation (P-T-t-d) history of these two units using modern thermobarometric tools, Rb/Sr deformation ages and field relationships. Our results show that the Tsaté complex is formed by a stack of km-thick calcschists-bearing tectonic slices, having experienced variable maximum burial temperatures of between 360°C and 490°C at depths of ca. 25-40 km, between 41 Ma and 37 Ma. The Arolla gneissic mylonites constituting the base of the DBTS experienced a continuous record of protracted high-pressure (12-14 kbar), top-to-NW D1 deformation at 450-500°C between 43 and 55 Ma. Some of these primary, peak metamorphic fabrics have been sheared (top-to-SE D2) and backfolded during exhumation and collisional overprint (20 km depth, 35-40 Ma) leading to the regional greenschist facies retrogression particularly prominent within Tsaté metasediments. The final juxtaposition of the DBTS with the Tsaté complex occurred between 350 and 500°C during this later, exhumation-related D2 event. Although some exhumation-related deformation partially reworked D1 primary features, we emphasize that the DBT can be viewed as a remnant of the Alpine early Eocene blueschist-facies subduction interface region. The DBT therefore constitutes the deeper equivalent of some shallower portions of the Alpine subduction

  6. Evolution of the Cretaceous magmatism in the Apuseni-Timok-Srednogorie metallogenic belt and implications for the geodynamic reconstructions: new insight from geochronology, geochemistry and isotope studies

    NASA Astrophysics Data System (ADS)

    von Quadt, A.; Peytcheva, I.; Heinrich, C. A.; Frank, M.; Cvetkovic, V.

    2003-04-01

    Most major Cu-Au (-PGE) deposits in the Carpathian Balkan orogen are related to a 1500 km long belt of Upper Cretaceous magmatism extending from southern Romania through Yugoslavia to Bulgaria, with a likely continuation southeast of the Black Sea into Turkey, known as the Apuseni Banat Timok Srednogorie (ABTS) belt (Popov et al., 2000). In the frame of ABTS belt a new investigation was started to reveal the relation between Cretaceous magmatism and the Cu-Au-PGE deposits across the belt in East Serbia (Yugoslavia) and the Panagyurishte district (Bulgaria). The Late Cretaceous (Palaeogene?) magmatism of East Serbia developed along the Timok Magmatic Complex (TMC) in the east and the Ridanj Krepoljin Zone (RKZ) in the west. High precision U-Pb single zircon dating and a combination of isotope tracing, geochronological data as well as petrological data were used to provide additional data for the geodynamic evolution. A maximum life span of 2.5 Ma could be calculated for the first phase of volcanic activity in TMC, starting with the Amf-andesites of Veliki Kravelj (86.29 ± 0.32 Ma) and finishing with the Timozites (84.66 ± 0.5 Ma). Ore bearing magmatism in a single deposit (Veliki Kravelj) extended a maximum of 0.6 Ma ("pre-ore": 86.29 ± 0.32 Ma, "post-ore": 86.17 ± 0.15 Ma). Preliminary data for the dacites (70.3 ± 3.5 Ma) outcropping near Krepoljin give evidence for a shifting of the volcanic activity from TMC to RKZ together with changing the ore-deposit type from Cu-Au-PGE (TMC) to Pb-Zn-Cu (RKZ). Isotope tracing give evidence for mantle dominated source with increasing of crustal contamination in the same direction: (87Sr/86Sr ratios: 0.70388 to 0.706050, e-Hf-zircon data: +12 in TMC to +4.5 in RKZ). The Panagyurishte district (Bulgaria) show a duration time of the magmatic activity of 14 Ma, starting in the north at 92 Ma and finishing in the south at 78 Ma. Ore-related magmatism becomes younger in the same direction but finishes with 86 Ma. Multiple short

  7. Petrology, geochemistry and geochronology of the magmatic suite from the Jianzha Complex, central China: Petrogenesis and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Li, Xiaowei; Mo, Xuanxue; Bader, Thomas; Scheltens, Mark; Yu, Xuehui; Dong, Guochen; Huang, Xiongfei

    2014-12-01

    sub-continental lithospheric mantle that was metasomatized previously by slab-derived fluids. The lithologies in the JZC are related in space and time and originated from a common parental magma. Geochemical modeling suggests that their primitive parental magma had a basaltic composition. The ultramafic rocks were generated through olivine accumulation, and variable degrees of fractional crystallization with minor crustal contamination produced the diorites. The data presented here suggest that the subduction in West Qinling did not cease before the early stage of the Middle Triassic (∼242 Ma), a back-arc developed in the northern part of West Qinling during this period, and the JZC formed within the incipient back-arc.

  8. 138-121 Ma asthenospheric magmatism prior to continental break-up in the North Atlantic and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Schärer, Urs; Girardeau, Jacques; Cornen, Guy; Boillot, Gilbert

    2000-09-01

    MORB-type mantle reservoirs, and the age-difference for magmatism between the Gorringe and Galicia banks suggests a rate of 4.4±0.3 cm/yr for northward progression of continental rifting. Based on the new results, a structural model for Iberia-America rifting is discussed putting forward the idea that magma emplacement produces a level of weakness and decollement between the rifting crust and its underlying lithospheric mantle.

  9. U-Pb dating of granodiorite and granite units of the Los Pedroches batholith. Implications for geodynamic models of the southern Central Iberian Zone (Iberian Massif)

    NASA Astrophysics Data System (ADS)

    Carracedo, M.; Paquette, J. L.; Alonso Olazabal, A.; Santos Zalduegui, J. F.; García de Madinabeitia, S.; Tiepolo, M.; Gil Ibarguchi, J. I.

    2009-10-01

    The first U-Pb geochronological results on the magmatic alignment of the Los Pedroches batholith are presented. The batholith is composed of a main granodioritic unit, several granite plutons and an important acid to basic dyke complex, all of them intrusive after the main Variscan regional deformation phase, D1, along the boundary between the Ossa-Morena and Central Iberian zones (SW Iberian Massif). Zircons from samples on both extremes of the granodiorite massif record nearly simultaneous magmatic crystallization at ca. 308 Ma, while the emplacement of granite plutons was diachronic between 314 and 304 Ma. The U-Pb results combined with new field and textural observations allow to better constrain the age of Variscan deformations D2 and D3 across the region, while the age of D1 remains imprecise. Transcurrent D2 shearing-tightening of D1 folds occurred around 314 Ma (lower Westphalian) in relation to the emplacement of the first granitic magmas. D3 faults and shear bands bearing a strong extensional component developed at ca. 308 Ma (upper Westphalian), associated to the intrusion of the main granodiorite pluton (granodiorite) of the batholith. Together with available geochemical and geophysical information, these results point to the Variscan reactivation of lithospheric fractures at the origin and subsequent emplacement of hybrid magmas within this sector of the Massif.

  10. Sr-Nd constraints and trace-elements geochemistry of selected Paleo and Mesoproterozoic mafic dikes and related intrusions from the South American Platform: Insights into their mantle sources and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Girardi, V. A. V.; Teixeira, W.; Mazzucchelli, M.; Corrêa da Costa, P. C.

    2013-01-01

    The study of selected mafic intrusions from cratonic areas of the South American Platform shows considerable differences among their mantle sources and geodynamic features, particularly regarding the dikes from the SW Amazonian and São Francisco Cratons. The tholeiites from the SW Amazonian Craton, which belong to the Serra da Providência Intrusive Suite (1.55 Ga), the Nova Lacerda swarm (1.44 Ga), the Colorado Complex (1.35 Ga), and the Nova Brasilândia Group (1.10 Ga), originated from a mantle source composed mainly of a N-MORB end-member, with a variable addition of slab fluids (up to 30%, according to the adopted model) from oceanic lithosphere due to episodic subductions during the Mesoproterozoic. Mafic intrusions from Nova Lacerda swarm and Colorado Complex are related to arc settings formed during the 1.47-1.35 Ga closure of the oceanic domain separating the Amazonian Craton and the Paraguá Terrane, whereas the tholeiites from the Serra da Providência Intrusive Suite and the Nova Brasilândia Group are considered intracratonic. The dike swarms of the São Francisco Craton are associated with intra-plate events. The inferred composition of the mantle source of the Lavras swarm (1.9 Ga) has a predominant E-MORB signature, and a modest contribution of up to 10% of an OIB component. The mantle composition underwent considerable changes during the Proterozoic, as indicated by the sources of the younger dikes, represented by the Diamantina (0.93 Ga) and the Salvador-Olivença swarms (0.92 Ga), to which considerable amount of slab derived fluids, probably from recycled crustal material, and OIB component were added. Changes in mantle composition and dikes intrusions could be related to the initial disruption of the Rodinia Supercontinent. The Florida (1.79 Ga) and Tandil (2.0 Ga) dikes are associated with extensional events of the Rio de La Plata Craton. In spite of the similarities between the tectonic framework of these swarms and that of Lavras (1.9 Ga

  11. Three-Dimensional Numerical Models of Subduction and Subduction-Induced Mantle Flow

    NASA Astrophysics Data System (ADS)

    Freeman, J.; Stegman, D. R.; Schellart, W. P.; Moresi, L.; May, D. A.; Turnbull, R.

    2004-12-01

    The kinematics of subduction and its influence on mantle convection and plate-scale deformation have been the focus of numerous geodynamic studies [e.g. Garfunkel et al., 1986; Gurnis and Hager, 1988; Zhong and Gurnis, 1995; Christensen, 1996; Olbertz et al., 1997; Conrad and Hager, 1999; Eberle et al., 2002]. Most geodynamic models have considered only two-dimensional aspects of subduction dynamics by incorporating the assumption that subduction zones are infinite in trench-parallel extent. However, natural subduction zones are intrinsically three-dimensional, due in part to their limited lateral extent. Lateral length scales of natural subduction zones vary from only a few hundred kilometres (e.g. the Calabrian, Hellenic and Scotia slabs) to several thousand kilometres (e.g. the Aleutian, Indonesian, Northwest Pacific and South American slabs). Here, we present results from three-dimensional numerical experiments that simulate lithospheric subduction and subduction induced mantle flow for slabs with a varying lateral extent.

  12. Magnetic Probing of Core Geodynamics

    NASA Technical Reports Server (NTRS)

    Voorhies, Coerte V.

    2004-01-01

    To better understand geomagnetic theory and observation, we can use spatial magnetic spectra for the main field and secular variation to test core dynamical hypotheses against seismology. The hypotheses lead to theoretical spectra which are fitted to observational spectra. Each fit yields an estimate of the radius of Earth's core and uncertainty. If this agrees with the seismologic value, then the hypothesis passes the test. A new way to obtain theoretical spectra extends the hydromagnetic scale analysis of Benton to scale-variant field and flow. For narrow scale flow and a dynamically weak field by the top of Earth's core, this yields a generalized Stevenson-McLeod spectrum for the core-source field, and a secular variation spectrum modulated by a cubic polynomial in spherical harmonic degree n. The former passes the tests. The latter passes many tests, but does not describe rapid dipole decline and quadrupole rebound; some tests suggest it is a bit hard, or rich in narrow scale range. In a core geodynamo, motion of the fluid conductor does work against the Lorentz force. This converts kinetic into magnetic energy which, in turn, is lost to heat via Ohmic dissipation. In the analysis at length-scale 1/k, if one presumes kinetic energy is converted in either eddy-overturning or magnetic free-decay time-scales, then Kolmogorov or other spectra in conflict with observational spectra can result. Instead, the rate work is done roughly balances the dissipation rate, which is consistent with small-scale flow. The conversion time-scale depends on dynamical constraints. These are summarized by the magnetogeostrophic vertical vorticity balance by the top of the core, which includes anisotropic effects of rotation, the magnetic field, and the core-mantle boundary. The resulting theoretical spectra for the core-source field and its SV are far more compatible with observation. The conversion time-scale of order 120 years is pseudo-scale-invariant. Magnetic spectra of other planets may differ; however, if a transition to non-conducting fluid hydrogen in Jupiter acts as a barrier to vertical flow, as well as current, then the shape of the jovi-magnetic spectrum could be remarkably Earth-like.

  13. Magnetic Probing of Core Geodynamics

    NASA Technical Reports Server (NTRS)

    Voorhies, Coerte V.

    2004-01-01

    To better understand geomagnetic theory and observation, we can use spatial magnetic spectra for the main field and secular variation to test core dynmcal hypotheses against seismology. The hypotheses lead to theoretical spectra which are fitted to observational spectra. Each fit yields an estimate of the radius of Earth's core and uncertainty. If this agrees with the seismologic value, then the hypothes pass the test. A new way to obtain theoretical spectra extends the hydromagnetic scale analysis of Benton to scale-variant field and flow. For narrow scale flow and a dynamically weak field by the top of Earth's core, this yields a generalized Stevenson-McLeod spectrum for the core-source field, and a secular variation spectrum modulated by a cubic polynomial in spherical harmonic degree n. The former passes the tests. The latter passes many tests, but does not describe rapid dipole decline and quadrupole rebound; some tests suggest it is a bit hard, or rich in narrow scale change. In a core geodynamo, motion of the fluid conductor does work against the Lorentz force. This converts kinetic into magnetic energy which, in turn, is lost to heat via Ohmic dissipation. In the analysis at lentgh-scale l/k, if one presumes kinetic energy is converted in either eddy- overturning or magnetic free-decay time-scales, then Kolmogorov or other spectra in conflict with observational spectra can result. Instead, the rate work is done roughly balances the dissipation rate, which is consistent with small scale flow. The conversion time-scale depends on dynamical constraints. These are summarized by the magneto-geostrophic vertical vorticity balance by the top of the core, which includes anisotropic effects of rotation, the magnetic field, and the core- mantle boundary. The resulting theoretical spectra for the core-source field and its SV are far more compatible with observation. The conversion time-scale of order l20 years is pseudo-scale-invarient. Magnetic spectra of other planets may differ; however, if a transition to non-conductmg fluid hydrogen in Jupiter acts as barrier to vertical flow, as well as current, then the shape of the jovi-magnetic spectrum could be remarkably Earth-like.

  14. Magnectic Probing of Core Geodynamics

    NASA Technical Reports Server (NTRS)

    Voorhies, Coerte

    2004-01-01

    To better understand geomagnetic theory and observation, we can use spatial magnetic spectra for the main field and secular variation to test core dynamical hypotheses against seismology. The hypotheses lead to theoretical spectra which are fitted to observational spectra. Each fit yields an estimate of the radius of Earth s core and uncertainty. If this agrees with the seismologic value, then the hypotheses pass the test. A new way to obtain theoretical spectra extends the hydromagnetic scale analysis of Benton to scale-variant field and flow. For narrow scale flow and a dynamically weak field by the top of Earth s core, this yields a JGR-PI, and a secular variation spectrum modulated by a cubic polynomial in spherical harmonic degree n. The former passes the tests. The latter passes many tests, but does not describe rapid dipole decline and quadrupole rebound; some tests suggest it is a bit hard, or rich in narrow scale change.In a core geodynamo, motion of the fluid conductor does work against the Lorentz force. This converts kinetic into magnetic energy which, in turn, is lost to heat via Ohmic dissipation. In the analysis at length- scale l/k, if one presumes kinetic energy is converted in either eddy- overturning or magnetic free-decay time-scales, then Kolmogorov or other spectra in conflict with observational spectra can result. Instead, the rate work is done roughly balances the dissipation rate, which is consistent with small scale flow. The conversion time-scale depends on dynamical constraints. These are summarized by the magneto- geostrophic vertical vorticity balance by the top of the core, which includes anisotropic effects of rotation, the magnetic field, and the core-mantle boundary. The resulting theoretical spectra for the core- source field and its SV are far more compatible with observation. The conversion time-scale of order 120 years is pseudo-scale-invariant. Magnetic spectra of other planets may differ; however, if a transition to non-conducting fluid hydrogen in Jupiter acts as barrier to vertical flow, as well as current, then the shape of the jovi-magnetic spectrum could be remarkably Earth-like.

  15. Magnetic Probing of Core Geodynamics

    NASA Astrophysics Data System (ADS)

    Voorhies, C. V.

    2004-05-01

    To better understand geomagnetic theory and observation, we can use spatial magnetic spectra for the main field and secular variation to test core dynamical hypotheses against seismology. The hypotheses lead to theoretical spectra which are fitted to observational spectra. Each fit yields an estimate of the radius of Earth's core and uncertainty. If this agrees with the seismologic value, then the hypotheses pass the test. A new way to obtain theoretical spectra extends the hydromagnetic scale analysis of Benton [1992; GAFD] to scale-variant field and flow [Voorhies, 2004; JGR-SE, in press]. For narrow scale flow and a dynamically weak field by the top of Earth's core, this yields a generalized Stevenson-McLeod spectrum for the core-source field [Voorhies, Sabaka and Purucker, 2002; JGR-P], and a secular variation spectrum modulated by a cubic polynomial in spherical harmonic degree n. The former passes the tests. The latter passes many tests, but does not describe rapid dipole decline and quadrupole rebound; some tests suggest it is a bit hard, or rich in narrow scale change. In a core geodynamo, motion of the fluid conductor does work against the Lorentz force. This converts kinetic into magnetic energy which, in turn, is lost to heat via Ohmic dissipation. In the analysis at length-scale 1/k, if one presumes kinetic energy is converted in either eddy-overturning or magnetic free-decay time-scales, then Kolmogorov or other spectra in conflict with observational spectra can result. Instead, the rate work is done roughly balances the dissipation rate, which is consistent with small scale flow. The conversion time-scale depends on dynamical constraints. These are summarized by the magneto-geostrophic vertical vorticity balance by the top of the core, which includes anisotropic effects of rotation, the magnetic field, and the core-mantle boundary. The resulting theoretical spectra for the core-source field and its SV are far more compatible with observation. The conversion time-scale of order 120 years is pseudo-scale-invariant. Magnetic spectra of other planets may differ; however, if a transition to non-conducting fluid hydrogen in Jupiter acts as barrier to vertical flow, as well as current, then the shape of the jovi-magnetic spectrum could be remarkably Earth-like.

  16. Geochemistry and petrogenesis of Mashhad granitoids: An insight into the geodynamic history of the Paleo-Tethys in northeast of Iran

    NASA Astrophysics Data System (ADS)

    Mirnejad, H.; Lalonde, A. E.; Obeid, M.; Hassanzadeh, J.

    2013-06-01

    Mashhad granitoids in northeast Iran are part of the so-called Silk Road arc that extended for 8300 km along the entire southern margin of Eurasia from North China to Europe and formed as the result of a north-dipping subduction of the Paleo-Tethys. The exact timing of the final coalescence of the Iran and Turan plates in the Silk Road arc is poorly constrained and thus the study of the Mashhad granitoids provides valuable information on the geodynamic history of the Paleo-Tethys. Three distinct granitoid suites are developed in space and time (ca. 217-200 Ma) during evolution of the Paleo-Tethys in the Mashhad area. They are: 1) the quartz diorite-tonalite-granodiorite, 2) the granodiorite, and 3) the monzogranite. Quartz diorite-tonalite-granodiorite stock from Dehnow-Vakilabad (217 ± 4-215 ± 4 Ma) intruded the pre-Late Triassic metamorphosed rocks. Large granodiorite and monzogranite intrusions, comprising the Mashhad batholith, were emplaced at 212 ± 5.2 Ma and 199.8 ± 3.7 Ma, respectively. The high initial 87Sr/86Sr ratios (0.708042-0.708368), low initial 143Nd/144Nd ratios (0.512044-0.51078) and low ɛNd(t) values (- 5.5 to - 6.1) of quartz diorite-tonalite-granodiorite stock along with its metaluminous to mildly peraluminous character (Al2O3/(CaO + Na2O + K2O) Mol. = 0.94-1.15) is consistent with geochemical features of I-type granitoid magma. This magma was derived from a mafic mantle source that was enriched by subducted slab materials. The granodiorite suite has low contents of Y (≤ 18 ppm) and heavy REE (HREE) (Yb < 1.53 ppm) and high contents of Sr (> 594 ppm) and high ratio of Sr/Y (> 35) that resemble geochemical characteristics of adakite intrusions. The metaluminous to mildly peraluminous nature of granodiorite from Mashhad batholiths as well as its initial 87Sr/86Sr ratios (0.705469-0.706356), initial 143Nd/144Nd ratios (0.512204-0.512225) and ɛNd(t) values (- 2.7 to - 3.2) are typical of adakitic magmas generated by partial melting of a

  17. Stress field modeling of the Carpathian Basin based on compiled tectonic maps

    NASA Astrophysics Data System (ADS)

    Albert, Gáspár; Ungvári, Zsuzsanna; Szentpéteri, Krisztián

    2014-05-01

    The estimation of the stress field in the Carpathian Basin is tackled by several authors. Their modeling methods usually based on measurements (borehole-, focal mechanism- and geodesic data) and the result is a possible structural pattern of the region. Our method works indirectly: the analysis is aimed to project a possible 2D stress field over the already mapped/known/compiled lineament pattern. This includes a component-wise interpolation of the tensor-field, which is based on the generated irregular point cloud in the puffer zone of the mapped lineaments. The interpolated values appear on contour and tensor maps, and show the relative stress field of the area. In 2006 Horváth et al. compiled the 'Atlas of the present-day geodynamics of the Pannonian basin'. To test our method we processed the lineaments of the 1:1 500 000 scale 'Map of neotectonic (active) structures' published in this atlas. The geodynamic parameters (i.e. normal, reverse, right- and left lateral strike-slip faults, etc.) of the lines on this map were mostly explained in the legend. We classified the linear elements according to these parameters and created a geo-referenced mapping database. This database contains the polyline sections of the map lineaments as vectors (i.e. line sections), and the directions of the stress field as attributes of these vectors. The directions of the dip-parallel-, strike-parallel- and vertical stress-vectors are calculated from the geodynamical parameters of the line section. Since we created relative stress field properties, the eigenvalues of the vectors were maximized to one. Each point in the point cloud inherits the stress property of the line section, from which it was derived. During the modeling we tried several point-cloud generating- and interpolation methods. The analysis of the interpolated tensor fields revealed that the model was able to reproduce a geodynamic synthesis of the Carpathian Basin, which can be correlated with the synthesis of the

  18. Linking numerical models of lithospheric deformation and magnetotelluric images

    NASA Astrophysics Data System (ADS)

    Sobolev, S. V.

    2012-12-01

    Efficient modeling of geodynamic processes requires constraints from different fields of geosciences. Frequently used are data on crustal structure and composition and their evolution constrained by seismic, gravity and petrological/geochemical studies. However, links between geodynamic modeling and rapidly developing field of magnetotelluric (MT) studies are still insufficient. I'll consider two recent examples of MT observations and geodynamic modeling demonstrating that joint analyses of thermomechanical models of lithospheric deformation and MT images may be useful to understand geodynamic processes. One set of observations is MT data for San Andreas Fault (SAF) in the region close to the SAFOD Site (Becken et al., 2011) that shows high conductivity anomalies in the mantle, that are interpreted as fluid flow feeding creeping part of SAF south of the SAFOD Site. Interestingly, zones of high conductivity do not coincide with the expected zones of the recent active deformation (SAF), but are located to the west of it. Based on thermomechanical model of the evolution of the SAFS in Central and Northern California during the last 20 Mln. years (Popov et al., 2012), I'll demonstrate that high conductivity anomalies precisely coincide with the expected zones of the highest accumulated shear strain. Possible interpretation of this coincidence is that strong preferred orientation of olivine crystals in the highly deformed mantle shear zone causes high permeability of fluids. Another set of observations is MT data showing high conductivity anomalies in the crust of Tibet (Unsworh et al., 2005, Bai et al., 2010) and Pamirs (Sass et al., 2011) that are often interpreted as an evidence for the widely spread partially molten crust. Using 2D thermomechanical models of the collision between India and Eurasia, I'll demonstrate that such structures in the crust cannot appear without delamination of the mantle lithosphere during tectonic shortening. Internal heating of the

  19. Ridge-spotting: A new test for Pacific absolute plate motion models

    NASA Astrophysics Data System (ADS)

    Wessel, Paul; Müller, R. Dietmar

    2016-06-01

    Relative plate motions provide high-resolution descriptions of motions of plates relative to other plates. Yet geodynamically, motions of plates relative to the mantle are required since such motions can be attributed to forces (e.g., slab pull and ridge push) acting upon the plates. Various reference frames have been proposed, such as the hot spot reference frame, to link plate motions to a mantle framework. Unfortunately, both accuracy and precision of absolute plate motion models lag behind those of relative plate motion models. Consequently, it is paramount to use relative plate motions in improving our understanding of absolute plate motions. A new technique called "ridge-spotting" combines absolute and relative plate motions and examines the viability of proposed absolute plate motion models. We test the method on six published Pacific absolute plate motions models, including fixed and moving hot spot models as well as a geodynamically derived model. Ridge-spotting reconstructs the Pacific-Farallon and Pacific-Antarctica ridge systems over the last 80 Myr. All six absolute plate motion models predict large amounts of northward migration and monotonic clockwise rotation for the Pacific-Farallon ridge. A geodynamic implication of our ridge migration predictions is that the suggestion that the Pacific-Farallon ridge may have been pinned by a large mantle upwelling is not supported. Unexpected or erratic ridge behaviors may be tied to limitations in the models themselves or (for Indo-Atlantic models) discrepancies in the plate circuits used to project models into the Pacific realm. Ridge-spotting is promising and will be extended to include more plates and other ocean basins.

  20. 3SMAC: an a priori tomographic model of the upper mantle based on geophysical modeling

    NASA Astrophysics Data System (ADS)

    Nataf, Henri-Claude; Ricard, Yanick

    1996-05-01

    We present an a priori three-dimensional 'tomographic' model of the upper mantle. We construct this model (called 3SMAC — three-dimensional seismological model a priori constrained) in four steps: we compile information on the thickness of 'chemical' layers in the Earth (water, sediments, upper and lower crust, etc); we get a 3D temperature distribution from thermal plate models applied to the oceans and continents; we deduce the mineralogy in the mantle from pressure and temperature and we finally get a three-dimensional model of density, seismic velocities, and attenuation by introducing laboratory measurements of these quantities as a function of pressure and temperature. The model is thus consistent with various geophysical data, such as ocean bathymetry, and surface heat flux. We use this model to compute synthetic travel-times of body waves, and we compare them with observations. A similar exercise is performed for surface waves and normal modes in a companion paper (Ricard et al., 1996, J. Geophys. Res., in press). We find that our model predicts the bulk of the observed travel-time variations. Both the amplitude and general pattern are well recovered. The discrepancies suggest that tomography can provide useful regional information on the thermal state of the continents. In the oceans, the flattening of the sea-floor beond 70 Ma seems difficult to reconcile with the seismic observations. Overall, our 3SMAC model is both a realistic model, which can be used to test various tomographic methods, and a model of the minimum heterogeneities to be expected from geodynamical modeling. Therefore, it should be a useful a priori model to be used in tomographic inversions, in order to retrieve reliable images of heterogeneities in the transition zone, which should, in turn, greatly improve our understanding of geodynamical processes in the deep Earth. 3SMAC and accompanying software can be retrieved by anonymous ftp at geoscope.ipgp.jussieu.fr.

  1. Reply to Comment on "The Jurassic-Cretaceous basaltic magmatism of the Oued El-Abid syncline (High Atlas, Morocco): Physical volcanology, geochemistry and geodynamic implications" by André Michard et al. (2013) [J. Afr. Earth Sci. 88 (December) (2013) 101-105

    NASA Astrophysics Data System (ADS)

    Bensalah, Mohamed Khalil; Youbi, Nasrrddine; Mata, João; Madeira, José; Martins, Línia; Font, Eric; Medina, Fida; Marzoli, Andrea; Hachimi, Hind El; Bertrand, Hervé; Bellieni, Giuliano; Doblas, Miguel; Mahmoudi, Abdelkader; Beraâouz, El Hassane; Miranda, Rui; Verati, Chrystèle; Min, Angelo De; Abbou, Mohamed Ben; Zayane, Rachid

    2016-06-