Sample records for geodynamics

  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. 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)

  4. Journal of Geodynamics

    NSDL National Science Digital Library

    The Journal of Geodynamics, from Elsevier Science, focuses on "solid earth research in geodetic, geophysical, geological and geochemical geodynamics, with special emphasis on the large scale processes involved."

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. NASA: Geodynamics Branch

    NSDL National Science Digital Library

    The Geodynamics Branch at NASA's Goddard Space Flight Center conducts "research into the structure, dynamics, and evolution of the solid Earth and planets using space-techniques and remote sensing data." The website features the Branch's latest scientific findings, internship opportunities, and annual reports. Users can find fantastic images and text detailing many of its research projects such as the monitoring of oceanic islands with satellite remote sensing and the development of an interactive analysis tool to study the Mars Orbiter Laser Altimeter (MOLA) gridded data. Educators and students can find links to numerous, graphically enhanced tutorials and activities.

  11. Geodynamic basin classification

    SciTech Connect

    Klein, G.

    1987-05-01

    Four criteria (continental margin type, basin position within a plate, crustal type, geodynamic models and processes of basin formation) are used to classify sedimentary basins. Within plate interiors, cratonic margin basins and interior cratonic basins are distinguished by position on a tectonic plate. In passive margins, rift basins, aulacogens, and flexure basins are distinguished by orientation with respect to margins (rifts parallel and aulacogens normal to margins) and geodynamic process (rifts and aulacogens form by stretching, flexure basins by elastic or viscoelastic flexure). Basins associated with active continental margins are distinguished by position with respect to margin, crustal type, and stress regimen. Trench-slope basins involve compressional-extensional regimens, whereas trench basins, forearc basins and retroarc basins form in compressional regimes (retroarc basins on continental crust; forearc and trench basins occupy different positions on margin boundaries). Extensional intra-arc basins form on continental crust whereas backarc basins form by rifting oceanic crust and rapid thermal subsidence. Both pull-apart and transform basins form in transform margins by rifting and thermal subsidence with different translational stress regimens. In collision margins, foreland basins occur within continental plates, and superposed (or collage) basins occur along suture zones. Polyhistory basins include successor basins involving changing tectonic styles, and resurgent basins involving repeated tectonic styles. Many mapped basins show polyhistory. Thus the cratonic Illinois basin evolved through stages of a rift basin, followed by thermal subsidence akin to passive margins, followed by viscoelastic basin formation akin to a foreland basin.

  12. 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.

  13. 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.

  14. 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.

  15. Geodynamics map of northeast Asia

    USGS Publications Warehouse

    Parfenov, Leonid M., (compiler); 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Preliminary northeast Asia geodynamics map

    USGS Publications Warehouse

    Parfenov, Leonid M., (compiler); 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 metallogenic belt maps (Obolenskiy and others, 2001; in press b); (3) a lode mineral deposits and placer districts location map for Northeast Asia (Ariunbileg and others, in press b); (4) descriptions of metallogenic belts (Rodionov and others, in press); and (5) a database on significant metalliferous and selected nonmetalliferous lode deposits, and selected placer districts (Ariunbileg and others, in press a).

  1. 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.

  2. Information Technology Developments for Geodynamics

    NASA Astrophysics Data System (ADS)

    Bensen, G. D.; Meertens, C. M.; Sheehan, A. F.

    2004-12-01

    Some recent research at UNAVCO and the University of Colorado has been focused on Rocky Mountain tectonics, and Information Technology (IT) in the areas of data visualization and distributed data serving. At UNAVCO, we are participating in the geodynamics work in the Rocky Mountain Testbed of the GEON NSF funded (IT) Research project (www.geongrid.org). As part of this work, a variety of seismic tomography models, GPS velocity vector data, strain rate models and other data have been recompiled into a standard format. These data and models are being incorporated into our OPeNDAP server and the Integrated Data Viewer (IDV). OPeNDAP servers are platform independent, self-describing distributed data servers allowing easy access to a wide audience. The IDV is a freely distributed visualization and analysis tool developed by UCAR that has several exciting capabilities such as online collaboration, and a variety of 1-d, 2-d and 3-d viewing options. Necessary solid earth viewing capabilities (earthquakes, focal mechanisms, faults, etc.) are currently being added to the IDV. Both our OPeNDAP server and visualization tool are being integrated into the GEON portal, a website for data searching, analysis, and visualization. Designing and implementing such systems now allows us to be more prepared for the volumes of data anticipated from various EarthScope projects. As part of the scientific research for GEON, we have also begun investigations of Colorado seismicity. The 1992 Rocky Mountain Front IRIS/PASSCAL seismic experiment recorded many local earthquakes. We have begun to locate these events and are working to create focal mechanisms and calculations of stress drop for this region. These will aid in improving seismic hazard and risk assessments for the rapidly growing Rocky Mountain population. New IT capabilities will help augment the quality of this work through sharing the data with a larger audience, providing a means to view and analyze integrated data, and quickly providing a computationally intensive baseline by which results can be checked.

  3. Subduction zones: observations and geodynamic models

    Microsoft Academic Search

    Scott D. King

    2001-01-01

    This review of subduction and geodynamic models is organized around three central questions: (1) Why is subduction asymmetric? (2) Are subducted slabs strong or weak? (3) How do subducted slabs interact with phase transformations, changes in mantle rheology, and possibly chemical boundaries in the mantle? Based on laboratory measurements of the temperature dependence of olivine, one would conclude that the

  4. Geodynamics - Tracking satellites to monitor global change

    SciTech Connect

    Beutler, G.; Morgan, P.; Neilan, R.E. (Bern Univ., (Switzerland) Canberra Univ. (Australia) JPL, Pasadena, CA (United States))

    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.

  5. Adaptive Finite Element Methods in Geodynamics

    Microsoft Academic Search

    R. Davies; H. Davies; O. Hassan; K. Morgan; P. Nithiarasu

    2006-01-01

    Adaptive finite element methods are presented for improving the quality of solutions to two-dimensional (2D) and three-dimensional (3D) convection dominated problems in geodynamics. The methods demonstrate the application of existing technology in the engineering community to problems within the `solid' Earth sciences. Two-Dimensional `Adaptive Remeshing': The `remeshing' strategy introduced in 2D adapts the mesh automatically around regions of high solution

  6. 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.

  7. Constraints on Subduction Geodynamics from Seismic Anisotropy

    NASA Astrophysics Data System (ADS)

    Long, Maureen D.

    2013-01-01

    Much progress has been made over the past several decades in delineating the structure of subducting slabs, but several key aspects of their dynamics remain poorly constrained. Major unsolved problems in subduction geodynamics include those related to mantle wedge viscosity and rheology, slab hydration and dehydration, mechanical coupling between slabs and the ambient mantle, the geometry of mantle flow above and beneath slabs, and the interactions between slabs and deep discontinuities such as the core-mantle boundary. Observations of seismic anisotropy can provide relatively direct constraints on mantle dynamics because of the link between deformation and the resulting anisotropy: when mantle rocks are deformed, a preferred orientation of individual mineral crystals or materials such as partial melt often develops, resulting in the directional dependence of seismic wave speeds. Measurements of seismic anisotropy thus represent a powerful tool for probing mantle dynamics in subduction systems. Here I review the observational constraints on seismic anisotropy in subduction zones and discuss how seismic data can place constraints on wedge, slab, and sub-slab anisotropy. I also discuss constraints from mineral physics investigations and geodynamical modeling studies and how they inform our interpretation of observations. I evaluate different models in light of constraints from seismology, geodynamics, and mineral physics. Finally, I discuss some of the major unsolved problems related to the dynamics of subduction systems and how ongoing and future work on the characterization and interpretation of seismic anisotropy can lead to progress, particularly in frontier areas such as understanding slab dynamics in the deep mantle.

  8. Precise geodynamic measurements in South America

    NASA Astrophysics Data System (ADS)

    Groten, E.

    First high precision gravity measurements carried out in 1984 were repeated in November 1987 when in a wider frame, ranging from Santa Cruz de la Sierra (Bolivia) down to Santiago de Chile and Mendoza (Argentina), a regional densified network in Northern Chile was observed. The carefully monumented regional network extends from the earthquake-active coastal area in Chile up to Salta in Argentina. The repeated measurements are considered as a first step in a longtime study where geometric vertical control will be provided by GPS-measurements. Additional geodynamic information is provided by parallel seismic and other observations. Special interest arose from the fact that briefly after the first observations in 1984 significant earthquake deformation occurred in the area of Mendoza and Santiago de Chile. As far as gravimetry is concerned, all possible error sources are being carefully considered where also absolute measurements in view of scaling errors are planned. Reference is being made with respect to those areas which appear to be decoupled from the well known uplift of the High Andes. A detailed discussion and analysis of gravimetric data is presented. Correlation with geodynamic phenomena is studied. Future prospects of the general concept "GPS-gravimetry" as a geodynamic tool for studying vertical phenomena are interpreted.

  9. 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

  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 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.

  12. Global land hydrology and its geodynamic effects

    NASA Astrophysics Data System (ADS)

    Johnson, T. J.; Chao, B. F.; Au, A. Y.; Rodell, M.

    2003-04-01

    The global land hydrological budget has remained largely uncertain as far as its time- variable geodynamic effects are concerned. In this paper we make and compare estimates from different data sources. We first calculate the global soil moisture field, based on atmospheric data as "proxy" assuming an equation of hydrological continuity, using two global datasets--the NCEP Reanalysis (1958-present) and the ECMWF ERA15 Reanalysis (1979-1993). The soil moisture is taken as the sum of global precipitable water, vertically integrated divergence of the global water vapor flux, and the runoff. Low-degree Stokes coefficients for time-variable gravity and Earth rotation parameters are then determined based on these derived global soil moisture fields. However, unrealistic secular trends are observed in the derived geodynamic parameters (which involves time integration) according to the aforementioned Reanalysis data. To remedy this artifact and to address the water mass conservation issue, we adopted a simple runoff algorithm based on Chao and O'Connor (1988). A third data set that we examined was produced by NASA's Global Land Data Assimilation system driving the Mosaic land surface model in an offline mode (uncoupled to the atmosphere). This state of the art hydrological model was developed to better account for complex land processes. For the sake of completeness, we have also included a global data base of water-equivalent snow cover. We then compare the estimates with the geodetically observed time-variable Earth rotation and low-degree gravity field, for both seasonal and non-seasonal signals.

  13. (C.Bina, 9/2011) From thermodynamics to geodynamics

    E-print Network

    Cerveny, Vlastislav

    (C.Bina, 9/2011) From thermodynamics to geodynamics: An overview of the geophysical thermodynamics of these models were calculated using the growth rate parameters of kinetic model 1 (see Table 2), (a) Young, warm

  14. (C.Bina, 9/2011) From thermodynamics to geodynamics

    E-print Network

    Cerveny, Vlastislav

    (C.Bina, 9/2011) From thermodynamics to geodynamics: An overview of the geophysical thermodynamics for pyrolite composition of Table 1, excluding the effects of Cr2O3. Cr and Fe3+ partition into sp #12;(C

  15. On the usage of XML file format in geodynamic calculations

    NASA Astrophysics Data System (ADS)

    Choliy, V.

    2012-12-01

    We recommend the extended usage of XML data format for the representation of geodynamic observations and processing results. A short introduction to the technology and a simple example for a Consolidated Laser Ranging Data Format (CRD) data file are presented.

  16. 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.

  17. 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 simulation implemented in FEniCS that investigates the effect of using DG elements in reducing the overshoot problem.

  18. Geodynamic modeling of the South Pacific superswell

    NASA Astrophysics Data System (ADS)

    Adam, Claudia; Yoshida, Masaki; Suetsugu, Daisuke; Fukao, Yoshio; Cadio, Cecilia

    2014-04-01

    The South Pacific superswell is a broad region situated in the south central Pacific, characterized by numerous geophysical anomalies including very shallow seafloor compared to the depth predicted for its age by classical seafloor subsidence models, a negative geoid anomaly, a mantle characterized by slow seismic velocities, and a high volcanism concentration. Until recently, the image of the mantle provided by the seismic tomography models was rather blurry due to the sparse distribution of seismometers. This shortcoming has been lately overcome by regional seismic observations on islands and seafloor. The new P-wave seismic tomography model derived from these regional data in addition to global data provides a more reliable and precise image of the mantle, in particular beneath the French Polynesia region. We use it to perform numerical simulations of the instantaneous flow occurring in the mantle, using realistic laws for converting velocity anomalies into density anomalies and for describing the viscosity variations. We compute the associated dynamic topography and geoid anomaly. We show that the superswell could be caused by the large-scale slow velocity anomalies in the lower mantle, which are recognized as the South Pacific superplume. The surface geodetic observations are explained by a model including a low viscosity asthenosphere situated immediately beneath the lithosphere, and a lower mantle viscosity 100 times greater than the upper mantle one. Our study assumes a purely thermal origin of the velocities anomalies. Although the existence of compositional heterogeneities is often invoked to explain the dynamics of the South Pacific superplume in previous numerical and laboratory experiments, and are important to account for plume/superplumes phenomenology, we cannot definitively conclude the presence of such compositional heterogeneities from our geodynamic modeling.

  19. Geodynamic implications of earthquake data in the southern Tyrrhenian sea

    Microsoft Academic Search

    G. Neri; D. Caccamo; O. Cocina; A. Montalto

    1996-01-01

    Data from short-period seismic stations operating in Calabria, Sicily and the Aeolian Islands have been used to investigate earthquake properties of the southern Tyrrhenian lithosphere. The results have been analyzed, taking into account other geophysical and geological information available in the literature for the same region, with the main purpose of contributing to the definition of local geodynamic processes.Space distribution

  20. (C.Bina, 9/2011) From thermodynamics to geodynamics

    E-print Network

    Cerveny, Vlastislav

    (C.Bina, 9/2011) From thermodynamics to geodynamics: An overview of the geophysical thermodynamics through five-dimensional hyper-ellipsoid about best-fit equation of state (Table 1, line 1). Four panels of state (Table 1, line 1). Four panels give complete illustration of parameter trade-offs. Contour values

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

    Microsoft Academic Search

    A. Ismail-Zadeh

    2005-01-01

    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

  2. The Ukrainian geodynamics school of Alexander Ya. Orlov.

    NASA Astrophysics Data System (ADS)

    Yatskiv, Ya. S.

    First of all a short review of the Orlov's biography is given. Afterwards some scietific achievements of A. Orlov in the field of geodynamics are discussed. Particular attention is paid on the definition of the "mean latitude" and the "mean pole of epoch" given by A. Orlov.

  3. Metamorphic chemical geodynamics of subduction zones Gray E. Bebout

    E-print Network

    Bebout, Gray E.

    Frontiers Metamorphic chemical geodynamics of subduction zones Gray E. Bebout Lehigh University.N. Halliday Available online 12 June 2007 Abstract Study of metamorphic suites directly representing the deep-pressure (UHP) metamorphic suites incorporating knowledge of mineral chemistry and reactions, kinetics

  4. 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 summary of available open source software relevant to AFE analysis in geodynamics with the intent to provide interested practitioners of computational geodynamics with a starting point for “first hand” geodynamic experimentation using AFE analysis.

  5. 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 probably floored by exhumed mantle, while WDB seems to have normal oceanic crust. These basins thought to be developed sequentially from north to south, possibly due to back arc extension resulting from trench retreat and roll-back of the northwards subducting Indo-Australian oceanic plate below the SE Eurasian margin along the Sunda-Banda subduction zone. We suggest that a trench-perpendicular tear in the subducting slab extends from the southwestern corner of Celebes Sea to the northeastern corner of Seram Island. It defines the southern boundary of the Banggai-Sula and Bird's Head (BH) blocks and northern boundary of Banda Sea micro-plate. The dominant character of this structure is sinistral strike-slip fault zone that eastward gradually become transpressional to ultimately thrusting at the tip of the tear east of Seram Island. Here, deformation results in a large accretionary wedge, the Seram Accretionary Belt (SAB) that is partitioned by intensely sheared strike-slip faults. The deformation mechanisms within the SAB is difficult to interpret due to poor seismic imaging below a shallow (Pliocene?) unconformity and the inferred complexity of the deformation within the belt. However, geometries of faults and fault blocks are very well pronounced on bathymetric data which provide hints for the deformation style of the belt.

  6. 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.

  7. Geodynamic setting of recent volcanism in North Eurasia

    Microsoft Academic Search

    V. I. Kovalenko; V. V. Yarmolyuk; O. A. Bogatikov

    2009-01-01

    A GIS layout of the map of recent volcanism in North Eurasia is used to estimate the geodynamic setting of this volcanism.\\u000a The fields of recent volcanic activity surround the Russian and Siberian platforms—the largest ancient tectonic blocks of\\u000a Eurasia—from the arctic part of North Eurasia to the Russian Northeast and Far East and then via Central Asia to the

  8. 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.

  9. Monitoring of global geodynamic processes using satellite observations

    NASA Astrophysics Data System (ADS)

    Tatevian, S. K.; Attia, G. F.; Abou-Aly, N.; Ghoneim, R.; Hegazy, M.

    2014-06-01

    To study mechanisms of destructive geodynamic phenomena including determination of places of possible severe earthquakes, volcano eruptions and some other natural hazards, it is important to have means to evolve areas where maximum changes of the displacement velocities and the terrestrial crust vertical movements are possible. The previous experience has shown that the satellite geodesy techniques including global navigation systems and satellite laser ranging are the most effective for research activities in this field. Permanent control of secular movement of GPS-stations of the international geodynamic network, located in Russia, has allowed improving the reference coordinate frame for North Eurasia since Russian network stations provide representative covering of the largest stable areas (the Siberian and the East European) of the Eurasian plate. Along its southern border, there is a zone consisting of a great number of microplates surrounding the South-Eurasian stable plate. Interaction of these small plates and blocks influences distribution of seismic stresses in internal parts of the continent that is confirmed by the highest seismic activity of the triangle bordered by thrusts of the Himalayas and faults of the Pamirs, the Tien-Shan, the Baikal and the North-Eastern China. One of the active tectonic zones of Egypt located in Aswan, is characterized by regional basement rock uplift and regional faulting. In 1997, the African Regional Geodynamic Network was developed around the northern part of Lake Nasser, consists of 11 points, on both sides of the Lake. Its main goal is to study the geodynamical behavior around the northern part of the lake. The collected data were processed using the Bernese software version 5.0. From the velocity results, including also the African plate motion, it can be noticed that all stations of this network are moved to the northeast direction and it is typically the direction of the African plate motion.

  10. 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 heterogeneities in mantle convection models. Incorporation of a suite of geodynamic benchmarks into the automated test-bed. These recent advances, which all work in combination with the parallel mesh-optimization technology, enable Fluidity to simulate geodynamical flows accurately and efficiently. Initial results will be presented from: (i) a range of 2-D and 3-D thermal convection benchmarks; kinematic and dynamic subduction zone simulations; (iii) Comparisons between model predictions and laboratory experiments of plume dynamics. These results all clearly demonstrate the benefits of adaptive, unstructured meshes for geodynamical flows.

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

    Microsoft Academic Search

    S. Rudenko

    1997-01-01

    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

  12. Strike-slip faults on Mars: Observations and implications for global tectonics and geodynamics

    E-print Network

    Hauck II, Steven A.

    and geodynamic evolution of Mars. We model the tectonic evolution of the planet in response to the evolving evolution of Mars in which the gradual secular cooling of the planet over time was augmented by plumeStrike-slip faults on Mars: Observations and implications for global tectonics and geodynamics

  13. Geodynamics of oroclinal bending: Insights from the Mediterranean

    NASA Astrophysics Data System (ADS)

    Rosenbaum, Gideon

    2014-12-01

    The Alpine Orogen in the Mediterranean region exhibits a series of orogenic curvatures (oroclines). The evolution of these oroclines is relatively well constrained by a plethora of geophysical and geological data, and therefore, their origin can inform us on the fundamental processes controlling oroclinal bending. Here, a synthesis of the geometry of Mediterranean oroclines, followed by a discussion on their geodynamic origin is presented. The geometrical synthesis is based on a new classification of Mediterranean oroclines, which defines a first-order orocline (Adriatic Orocline) by the general northward-convex shape of the Alpine Orogen from Cyprus to Gibraltar. Superimposed on the limbs of this orocline, are second-, third- and fourth-order oroclines. The major process that led to the formation of the Adriatic Orocline is the indentation of Adria into Europe, whereas second- and third-order oroclines (e.g., Western Mediterranean and Gibraltar oroclines, respectively) were primarily controlled by a combination of trench retreat and slab tearing. It appears, therefore, that the geodynamics of Mediterranean oroclines has been entirely dependent on plate boundary migration and segmentation, as expressed in the interlinked processes of indentation, trench retreat and slab tearing. The relative contribution of specific geodynamic processes, and their maturity, could be inferred from geometrical characteristics, such as the amplitude-to-width ratio, the orientation of the curvature (convex or concave) relative to the convergence vector, and their geometrical relationship with backarc extensional basins (e.g., in the concave side of the orocline). Based on the information from the Mediterranean oroclines, it is concluded that oroclinal bending commonly involves lithospheric-scale processes, and is not restricted to thin-skinned deformation. However, contrary to previous suggestions that assume that the whole lithosphere can buckle, there is no clear evidence that such processes occur in modern tectonic environments.

  14. Constraining effective rheology through parallel joint geodynamic inversion

    NASA Astrophysics Data System (ADS)

    Baumann, Tobias S.; Kaus, Boris J. P.; Popov, Anton A.

    2014-09-01

    The dynamics of crust and lithosphere is to a large extent controlled by its effective viscosity. Unfortunately, extrapolation of laboratory experiments indicates that viscosity is likely to vary over many orders of magnitude. Additional methods are thus required to constrain the effective viscosity of the present-day lithosphere using more direct geophysical observations. Here we discuss a method, which couples 3D geodynamic models with observations (surface velocities and gravity anomalies) and with a Bayesian inversion scheme on massively parallel high performance computers. We illustrate that the basic principle of a joint geodynamic and gravity inversion works well with a simple analytical example. In a next step, we test our approach using a synthetic 3D model of salt tectonics with erosion and sedimentation, and check how much noise conditions, model resolution, and sparse data coverage affect the resolving power of the method. Results show that it is possible to constrain the effective viscosity and density of layers that contribute to the large-scale dynamics, provided that those layers are numerically well resolved. The properties of thin layers that do not contribute much to the overall dynamics cannot be constrained, but noise or sparse data sampling does not significantly affect the inversion results. This thus illustrates that a joint geodynamic and gravity inversion is a potentially powerful method to constrain the dynamics of the crust and lithosphere. Having better constraints on the structure of the present-day crust and lithosphere will help to narrow the parameter space for models that aim to unravel lithosphere dynamics on a geological time scale.

  15. Software for Geodynamical Researches Used in the LSGER IAA

    E-print Network

    Malkin, Zinovy; Skurikhina, Elena

    2014-01-01

    Laboratory of Space Geodesy and Earth Rotation (LSGER) of the Institute of Applied Astronomy (IAA) of the Russian Academy of Sciences has been carrying on, since its creation, the computation of geodynamical products: Earth Orientation Parameters (EOP) and station coordinates (TRF) based on observations of space geodesy techniques: Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), Global Positioning System (GPS). Principal software components, used for these investigations, include: package GROSS for processing of SLR observations, package Bernese for processing of GPS observations, package OCCAM for processing of VLBI observations, software for data exchange, and software for combination of space geodesy products.

  16. 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.

  17. 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. The QRV method was most recently introduced in geodynamic modelling (Ismail-Zadeh et al., 2007, 2008; Tantsyrev, 2008; Glisovic et al., 2009). The advances in computational geodynamics and in data assimilation attract an interest of the community dealing with lithosphere, mantle and core dynamics.

  18. 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 the recently recorded seismic activity in the period 1990 - 2001. We expect that the results obtained in the frame- work of this project could be a valuable contribution to assess the stress accumulation and to make a reliable evaluation of the seismic risk in the region.

  19. 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.

  20. 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.

  1. Present-day geodynamics of the northern North American Cordillera

    NASA Astrophysics Data System (ADS)

    Finzel, Emily S.; Flesch, Lucy M.; Ridgway, Kenneth D.

    2014-10-01

    Diffuse continental deformation results from interactions at plate boundaries, buoyancy forces generated by gradients in gravitational potential energy, and loads applied to the base of the lithosphere. Using finite element models, we calculate a deviatoric stress field associated with buoyancy forces, and then perform an iterative inversion to calculate deviatoric stress fields associated with boundary forces in the northern North American Cordillera. Our results reveal the presence of two distinct geodynamic domains. In the outboard domain, approximately equal magnitudes of boundary and buoyancy forces can account for the observed deformation along the Aleutian megathrust. In contrast, large boundary forces related to subduction of the Pacific and Yakutat slabs dominate the force-balance in south-central Alaska and combine with relatively small buoyancy forces to reproduce the observed kinematic indicators. In the inboard domain, encompassed by interior and northern Alaska and western Canada, boundary and buoyancy forces alone cannot reproduce the observed deformation. Therefore, we infer that deviatoric stresses due to basal tractions from a deeper mantle convection cell contribute to surface deformation in the inboard domain. Low effective lithospheric viscosity in south-central Alaska and the balancing effect of an independent geodynamic system driven by basal tractions in northern Alaska combine to confine the anomalously large Yakutat-related boundary deviatoric stresses to south-central Alaska. Deviatoric stresses associated with flat-slab subduction of the Yakutat microplate are a factor of two greater than boundary force estimates for the Andean and Indian-Eurasian convergent margins, where buoyancy and boundary forces are roughly equal in magnitude and dominate the force-balance.

  2. Solar System Processes Underlying Planetary Formation, Geodynamics, and the Georeactor

    E-print Network

    J. Marvin Herndon

    2007-01-02

    Only three processes, operant during the formation of the Solar System, are responsible for the diversity of matter in the Solar System and are directly responsible for planetary internal-structures, including planetocentric nuclear fission reactors, and for dynamical processes, including and especially, geodynamics. These processes are: (i) Low-pressure, low-temperature condensation from solar matter in the remote reaches of the Solar System or in the interstellar medium; (ii) High-pressure, high-temperature condensation from solar matter associated with planetary-formation by raining out from the interiors of giant-gaseous protoplanets, and; (iii) Stripping of the primordial volatile components from the inner portion of the Solar System by super-intense solar wind associated with T-Tauri phase mass-ejections, presumably during the thermonuclear ignition of the Sun. As described herein, these processes lead logically, in a causally related manner, to a coherent vision of planetary formation with profound implications including, but not limited to, (a) Earth formation as a giant gaseous Jupiter-like planet with vast amounts of stored energy of protoplanetary compression in its rock-plus-alloy kernel; (b) Removal of approximately 300 Earth-masses of primordial gases from the Earth, which began Earth's decompression process, making available the stored energy of protoplanetary compression for driving geodynamic processes, which I have described by the new whole-Earth decompression dynamics and which is responsible for emplacing heat at the mantle-crust-interface at the base of the crust through the process I have described, called mantle decompression thermal-tsunami; and, (c)Uranium accumulations at the planetary centers capable of self-sustained nuclear fission chain reactions.

  3. Regional geodynamic monitoring system for ensuring safety in geological and exploratory production of oil and gas

    NASA Astrophysics Data System (ADS)

    Vartanyan, G. S.

    2010-12-01

    Global geodynamic processes have a significant influence on the tempo of human society development and can cause the complete devastation of large areas of the Earth and mass mortality in a number of catastrophic cases. Technogenous factors can sometimes trigger geodynamic events. The potential consequences of natural and technogenous disasters became apparent during the catastrophe on the Deepwater Horizon platform on April 20, 2010. This paper takes a brief look at some aspects of this disaster. The possibilities of preventing the similar events in the future are discussed here. For this purpose, the development of a geodynamics information system (IS-Geodynamics) based on a network of global (subglobal) monitoring of the Earth's hydrogeodeformation (HGD) field, is suggested.

  4. The dynamics of oceanic transform faults : constraints from geophysical, geochemical, and geodynamical modeling

    E-print Network

    Gregg, Patricia Michelle Marie

    2008-01-01

    Segmentation and crustal accretion at oceanic transform fault systems are investigated through a combination of geophysical data analysis and geodynamical and geochemical modeling. Chapter 1 examines the effect of fault ...

  5. Interactions between mantle plumes and mid-ocean ridges : constraints from geophysics, geochemistry, and geodynamical modeling

    E-print Network

    Georgen, Jennifer E

    2001-01-01

    This thesis studies interactions between mid-ocean ridges and mantle plumes using geophysics, geochemistry, and geodynamical modeling. Chapter 1 investigates the effects of the Marion and Bouvet hotspots on the ultra-slow ...

  6. 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.

  7. The continental collision zone, South Island, New Zealand: Comparison of geodynamical models and observations

    SciTech Connect

    Beaumont, C.; Hamilton, J.; Fullsack, P. [Dalhousie Univ., Halifax, Nova Scotia (Canada)] [Dalhousie Univ., Halifax, Nova Scotia (Canada); Kamp, P.J.J. [Univ. of Waikato, Hamilton (New Zealand)] [Univ. of Waikato, Hamilton (New Zealand)

    1996-02-10

    In this report geodynamical models are used to test the applicability of the mantle subduction model to the compressional character and evaluation of the South Island continental convergence zone of New Zealand.

  8. Fluidity: A fully unstructured anisotropic adaptive mesh computational modeling framework for geodynamics

    Microsoft Academic Search

    D. Rhodri Davies; Cian R. Wilson; Stephan C. Kramer

    2011-01-01

    To introduce Fluidity, and its unique numerical capabilities, to the communityTo validate the code against known benchmark and laboratory solutionsTo demonstrate the applicability of mesh adaptivity for geodynamical flows

  9. Discussion of The Eclogite Engine: Chemical geodynamics as a Galileo thermometer

    E-print Network

    Anderson, Don L.

    Discussion of The Eclogite Engine: Chemical geodynamics as a Galileo thermometer by Don L. Anderson an adiabatic gradient nor does it yield the deep mantle geotherm. In the perisphere and Galileo thermometer

  10. Anisotropy and deformation in the Earth's mantle : seismological observations, geodynamical models, and laboratory experiments

    E-print Network

    Long, Maureen Devaney

    2006-01-01

    In this thesis I report the results of several studies of elastic anisotropy and deformation in the Earth's mantle, using shear wave splitting measurements, numerical models of geodynamical processes, and laboratory ...

  11. Applying multi-resolution numerical methods to geodynamics

    NASA Astrophysics Data System (ADS)

    Davies, David Rhodri

    Computational models yield inaccurate results if the underlying numerical grid fails to provide the necessary resolution to capture a simulation's important features. For the large-scale problems regularly encountered in geodynamics, inadequate grid resolution is a major concern. The majority of models involve multi-scale dynamics, being characterized by fine-scale upwelling and downwelling activity in a more passive, large-scale background flow. Such configurations, when coupled to the complex geometries involved, present a serious challenge for computational methods. Current techniques are unable to resolve localized features and, hence, such models cannot be solved efficiently. This thesis demonstrates, through a series of papers and closely-coupled appendices, how multi-resolution finite-element methods from the forefront of computational engineering can provide a means to address these issues. The problems examined achieve multi-resolution through one of two methods. In two-dimensions (2-D), automatic, unstructured mesh refinement procedures are utilized. Such methods improve the solution quality of convection dominated problems by adapting the grid automatically around regions of high solution gradient, yielding enhanced resolution of the associated flow features. Thermal and thermo-chemical validation tests illustrate that the technique is robust and highly successful, improving solution accuracy whilst increasing computational efficiency. These points are reinforced when the technique is applied to geophysical simulations of mid-ocean ridge and subduction zone magmatism. To date, successful goal-orientated/error-guided grid adaptation techniques have not been utilized within the field of geodynamics. The work included herein is therefore the first geodynamical application of such methods. In view of the existing three-dimensional (3-D) spherical mantle dynamics codes, which are built upon a quasi-uniform discretization of the sphere and closely coupled structured grid solution strategies, the unstructured techniques utilized in 2-D would throw away the regular grid and, with it, the major benefits of the current solution algorithms. Alternative avenues towards multi-resolution must therefore be sought. A non-uniform structured method that produces similar advantages to unstructured grids is introduced here, in the context of the pre-existing 3-D spherical mantle dynamics code, TERRA. The method, based upon the multigrid refinement techniques employed in the field of computational engineering, is used to refine and solve on a radially non-uniform grid. It maintains the key benefits of TERRA's current configuration, whilst also overcoming many of its limitations. Highly efficient solutions to non-uniform problems are obtained. The scheme is highly resourceful in terms RAM, meaning that one can attempt calculations that would otherwise be impractical. In addition, the solution algorithm reduces the CPU-time needed to solve a given problem. Validation tests illustrate that the approach is accurate and robust. Furthermore, by being conceptually simple and straightforward to implement, the method negates the need to reformulate large sections of code. The technique is applied to highly advanced 3-D spherical mantle convection models. Due to its resourcefulness in terms of RAM, the modified code allows one to efficiently resolve thermal boundary layers at the dynamical regime of Earth's mantle. The simulations presented are therefore at superior vigor to the highest attained, to date, in 3-D spherical geometry, achieving Rayleigh numbers of order 109. Upwelling structures are examined, focussing upon the nature of deep mantle plumes. Previous studies have shown long-lived, anchored, coherent upwelling plumes to be a feature of low to moderate vigor convection. Since more vigorous convection traditionally shows greater time-dependence, the fixity of upwellings would not logically be expected for non-layered convection at higher vigors. However, such configurations have recently been observed. With hot-spots widely-regard

  12. Mechanical problems in geodynamics and work done in China

    NASA Astrophysics Data System (ADS)

    Wang, Ren

    1995-09-01

    The subject of geodynamics concerns the dynamics of the global motion of the earth, of the motion in the earth's interior and its interaction with surface features, together with mechanical processes in the deformation and rupture of geological structures. A brief historical review is given from Sir I. Newton, Maclauwin, Jacobi, Poincaré, Poisson, Lamé, Darwin, Rayleigh, and Love, who dealt with the homogeneous sphere, to Leibenson, Takeuchi, and Meinesz, concentrating on layered spheres, and after the advent of plate tectonics, on the use of numerical simulation, to the analyses of tectonic features, earthquake mechanism, the application of nonlinear dynamics. By discussing the forward and inverse mechanical problems, and the questions facing the inverse problems of searching for the structural parameters, driving forces, etc. are raised in more detail. Thereafter, some works accomplished in China on the global and regional stress fields analyses; tectonic features' analyses, mantle flow studies; experimental studies of rocks and their constitutive relations are presented. Finally, the interdisciplinary nature of the subject is emphasized, and the main mechanical problems that need special attention are then proposed.

  13. 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.

  14. Application of VLBI and satellite laser ranging to geodynamics

    NASA Technical Reports Server (NTRS)

    Coates, R. J.

    1983-01-01

    The NASA Crustal Dynamics Project has developed very-long baseline interferometer (VLBI) systems and satellite laser ranging (SLR) systems for geodynamics measurements. In VLBI, a radio noise signal from a distant quasar is received by two or more radio antennas and coherently recorded. These recordings are cross-correlated to determine the relative signal delays between stations which are used to derive the vector baselines between the stations. The SLR systems accurately determine the range to a retroreflector satellite as a function of time with short laser pulses. These range measurements from several stations to the same satellite are used in orbit analysis programs to determine the position of the stations and the vector baselines between the stations. Measurements with these systems have achieved precisions of a few centimeters in length for distances of several thousand km. These systems are now operating in a global network for measuring the relative motion of the N. American, Pacific, S. American, Nazca, Eurasian and Australian tectonic plates. Highly mobile VLBI and SLR systems are being operated at many sites in the active earthquake areas in western N. America in order to determine the crustal deformation and strain accumulation.

  15. 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.

  16. 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 tectonics.

  17. Dynamical approach to study and interpret geodynamical and geophysical effects

    NASA Astrophysics Data System (ADS)

    Ferronsky, V.

    2009-04-01

    It was proved by satellite and terrestrial observation that the hydrostatics, which operates by the outer forces, is not able to ensure correct description and interpretation of geodynamical and geophysical effects. In order to find solution of the problem, we applied to dynamics. For this purpose the outer force field of the Earth was replaced by its inner (volumetric) force pressure. Doing so we introduced new physical basis for study dynamics of the planet in its own force field. The analytics for that is as follows. The body is considered as a system of n elementary particles (n ? ?) of masses mi and many degrees of freedom. The volumetric moment of a particle pi is written as pi = midri/dt. Then the moment of momentum M of the system is found to be derivative from the moment of inertia I in the form: M = ?piri = ?miridri/dt = d/dt(?½ miri2) = ½ dI/dt. Then derivative on time from M gives the energy of the system as second derivative from I: M' = ?pidri/dt + ?ridpi/dt = ½I" where ?pidri/dt = 2T is the kinetic energy and ?ridpi/dt = U is the potential energy of the oscillating moment of inertia (interacting particles). So, equation of dynamical equilibrium (equation of state) of a body, where the interacted particles are presented by nonlinear oscillators, is ½I" = 2T + U. We used this for study and interpretation of oscillation and rotation parameters of the Earth. Note that the center of mass of the Earth is presented here by a surface of asymmetric spheroid. For more information see our works: Ferronsky V.I. and S.V.Ferronsky (2007). Dynamics of the Earth, Scientific World, Moscow; Ferronsky V.I. (2008) Non-averaged virial theorem for natural systems: http://zhurnal.ape.relarn.ru/articles/2008/066e.pdf

  18. Geodynamics of the northern Andes: Subductions and intracontinental deformation (Colombia)

    NASA Astrophysics Data System (ADS)

    Taboada, Alfredo; Rivera, Luis A.; Fuenzalida, AndréS.; Cisternas, Armando; Philip, Hervé; Bijwaard, Harmen; Olaya, José; Rivera, Clara

    2000-10-01

    New regional seismological data acquired in Colombia during 1993 to 1996 and tectonic field data from the Eastern Cordillera (EC) permit a reexamination of the complex geodynamics of northwestern South America. The effect of the accretion of the Baudó-Panama oceanic arc, which began 12 Myr ago, is highlighted in connection with mountain building in the EC. The Istmina and Ibagué faults in the south and the Santa Marta-Bucaramanga fault to the northeast limit an E-SE moving continental wedge. Progressive indentation of the wedge is absorbed along reverse faults located in the foothills of the Cordilleras (northward of 5°N) and transpressive deformation in the Santander Massif. Crustal seismicity in Colombia is accurately correlated with active faults showing neotectonic morphological evidences. Intermediate seismicity allows to identify a N-NE trending subduction segment beneath the EC, which plunges toward the E-SE. This subduction is interpreted as a remnant of the paleo-Caribbean plateau (PCP) as suggested by geological and tomographic profiles. The PCP shows a low-angle subduction northward of 5.2°N and is limited southward by a major E-W transpressive shear zone. Normal oceanic subduction of the Nazca plate (NP) ends abruptly at the southern limit of the Baudó Range. Northward, the NP subducts beneath the Chocó block, overlapping the southern part of the PCP. Cenozoic shortening in the EC estimated from a balanced section is ˜120 km. Stress analysis of fault slip data in the EC (northward of 4°N), indicates an ˜E-SE orientation of ?1 in agreement with the PCP subduction direction. Northward, near Bucaramanga, two stress solutions were observed: (1) a late Andean N80°E compression and (2) an early Andean NW-SE compression.

  19. Geodynamic setting of the mineral deposits of the Urals

    NASA Astrophysics Data System (ADS)

    Koroteev, V. A.; de Boorder, H.; Necheukhin, V. M.; Sazonov, V. N.

    1997-07-01

    The first-order geodynamic domains of the Uralide orogen constitute a relatively simple pattern across the orogenic belt. Continental rifting along the western margin is expressed by a system of Vendian-early Palaeozoic structures with shale-hosted siderite and magnesite and basalt-hosted base metals. It is superimposed on a Middle Riphean rift system with layered mafic-ultramafic complexes with chromite and ilmenite-titano-magnetite and subordinate ophiolite massifs with gold and magnetite. An oceanic spreading domain, immediately east of the Main Uralian Fault is associated with chromite, titano-magnetite and massive sulphide deposits (Dombarovsky or Cyprus type). Further east, bimodal volcanic associations in island arcs with oceanic crust have formed copper-zinc massive volcanic sulphide deposits (Uralian type). Subsequently, complex volcanic sulphide deposits are associated with belts of andesite-dacite and co-magmatic diorite (Baymak or Kuroko type). The eastern, destructive, margin of the orogen is characterized by magnetite and copper-magnetite skarns and porphyry systems. Relatively small plagiogranite to granodiorite complexes, related to oceanic crust, carry scheelite and gold. Calc-alkaline granitic massifs have formed associations of tungsten, tantalum and beryllium. This pattern was dissected by major thrusts and transcurrent shear zones. Increased fluid activity in the course of deformation, inferred to have been involved in complex multi-phase gold mineralization was most probably controlled by deep-reaching faults and shears. Although the recognition of the first-order domains represents a guideline for exploration, detailed structural geological studies of the kinematics of the major faults and shear zones are required in conjunction with radiometric dating of suitable fault- and ore-associated minerals, in association with on-going deep-reaching geophysical investigations.

  20. 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.

  1. 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. Tholeiites represent perhaps the most widespread terrestrial magmatic rocks. At the same time about 40 % of them are represented by rocks in which REE relative concentration continuously decreases from Eu to La while the total REE content exceeds the chondritic one ten times. Naturally in this case the Sm/Nd ratio in tholeiites is higher than the same ratio in chondritic. As for the concentration of the main and rare-earth elements in tholeiites these rocks are undoubtedly enriched material. They compose a considerable part of an oceanic crust and, apparently, are an essential component of lower crust as a result of underplating. However during melting of the tholeiites, in which Sm/Nd ratio is higher, than in PM, and which had enough time to change Nd isotope composition according to this ratio, the melts will be marked by values of ENd>0. In common Sm-Nd isotope systematics these isotope characteristics correspond to derivatives of the depleted material. So, in terms of the Nd isotope analysis the derivatives of the enriched material of oceanic or even of lower continental crust will be referred to derivatives of the depleted mantle. The same situation is observed in Lu-Hf isotope systematics of tholeiites. Isotope-petrochemical identification of xenoliths corresponding to the material of geochemically closed primitive mantle, has shown that MORB source is not depleted mantle as it was considered to be earlier, but a primitive mantle - PM (Pushkarev, 2006, 2007). It means that deficiency of Nd relative to Sm in PM in comparison with their concentrations in chondrites is caused not by crust formation. This peculiarity is either a primary feature of protoplanetary material, whose composition was different from chondritic one, or it reflects predominant capture of LREE by a component of segregating core, or it is a consequence of both reasons simultaneously. Identity of MORB source to primitive mantle and its discrepancy with the composition of chondrits in Sm-Nd isotope systematics was discovered earlier by J.A.Kostitsyn (2004) on the basis of the represe

  2. Geodynamic Effects on the Dams in Cascade of the Sulak Hydraulic Power Systems

    Microsoft Academic Search

    A. N. Marchuk; A. R. Abakarov; M. G. Daniyalov; O. A. Asmanov; M. M. Mirzaliev; R. A. Levkovich

    2001-01-01

    In view of the passage of the Federal statute, ”On the safety of hydraulic structures,” in 1999 and 2000 the Institute of Physics of the Earth of the Russian Academy of Sciences, the Dagestan Power Authority, and the Dagestan Scientific Center (Russian Academy of Sciences) carried out field investigations of geodynamic effects on the safety of the cascade of Sulak

  3. Advances in Global Positioning System Technology for Geodynamics Investigations: 1978-1992

    E-print Network

    Tingley, Joseph V.

    Advances in Global Positioning System Technology for Geodynamics Investigations: 1978 of the Global Positioning System (GPS) have developed the technology capable of meeting the stringent class of technical development. The last decade has witnessed the rise of the Global Positioning System

  4. Geodynamic significance of the Raspas Metamorphic Complex (SW Ecuador): geochemical and isotopic constraints

    E-print Network

    Demouchy, Sylvie

    Geodynamic significance of the Raspas Metamorphic Complex (SW Ecuador): geochemical and isotopic Metamorphic Complex of southwestern Ecuador is regarded as the southernmost remnant of oceanic and continental. The present-day well defined internal structure of the Raspas Metamorphic Complex seems to be inconsistent

  5. Journal of Geodynamics 41 (2006) 128132 Advances in Southern Ocean tide modeling

    E-print Network

    Journal of Geodynamics 41 (2006) 128­132 Advances in Southern Ocean tide modeling Yuchan Yia,, Koji Kingdom Accepted 30 August 2005 Abstract Tides in the polar region play a major role in the dynamics of sea ice and floating glacial ice shelves. Existing ocean tide models are much less accurate in coastal

  6. Mantle flow pattern and geodynamic cause of the North China Craton reactivation: Evidence from seismic anisotropy

    Microsoft Academic Search

    Liang Zhao; Mei Xue

    2010-01-01

    We investigate the mantle flow pattern and geodynamic cause of North China Craton (NCC) reactivation using shear wave splitting measurements from 140 broadband stations. Using a newly developed method for simulating wave propagation in a two-dimensional anisotropic medium, we first examined the influence of sedimentary structures on SKS splitting measurements. The simulations show that a sedimentary layer, whether isotropic or

  7. 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.

  8. Geodynamics of The Polar Urals In The Early Palaeozoic Time

    NASA Astrophysics Data System (ADS)

    Didenko, A.; Lubnina, N.

    Ordovician time - one of the key events at the Urals: during this time the Urals pale- oocean was maximum opening. Thus paleomagnetic data contribute to the reconstruc- tion of the primary tectonic position of the blocks of the paleoocean crust and blocks, surrounded this ocean. Revelation of geodynamic formations, boarded the Urals pale- oocean to the east and theirs tectonic position, are still remains debatable. Based on the original and literary data the history of the Urals paleoocean is represented the following. During early Ordovician the East-European continent (EEC) from tropical northern latitudes has moved in tropical southern. The Siberia at this time was lo- cated at equator. In the Late Tremadoc - Arenig along the Uralian margin of EEC was formed active continental margin, to the west of which the Lemva deep-sea basin was generated. According to the new paleomagnetic data, the Uralian margin of EEC (the Eletsk zone) located on 10S, and the Lemva zone - in near-equatorial latitudes. Dur- ing the maximal rifting, width of this zone was more than 500 kms. Probably, at this time the Lemva zone was clockwise rotated about East-European continent. From the north this zone was boarded by Manitanyrd-Paypudine microcontinent, located at 14S. Probably, this latitudinal difference was the result of forming the first oceanic basin of the PaleoUrals to the east from the Lemva zone (Ruzhentsev, 1998). At the end of Arenig-Middle Ordovician time Manitanyrd-Paypudine microcontinent jointed the East-European continent. The maximal speed of latitudinal displacement of the EEC to the south occurred at 450-470 Ma and was about 6 sm/years (Pechersky, Didenko, 1995). In the same time for the short period the EEC has changed counter-clockwise replaced to rotation clockwise. Probably, change of a mark of rotation (~470 Ma) fixes a beginning of opening the Urals paleoocean at the Middle Ordovician time. Middle- Late Ordovician - time of the maximal opening of the Ural paleoocean, the spreading zone was to the northeast from the Lemva zone and the East-European continent mar- gin, its strike was north- northwest. Spreading complexes of the Voikar-Synia and Khadata ophiolites massifs were formed at 10-15N. The age of paleospreading com- plexes of the Voikar-Synia and Khadata ophiolites massifs is still discussed and re- quires the further investigations. Ordovician-Silurian island-arc formation of the East slope of the Polar Urals (MalouralSskaya zone) were formed much to the south East- Europe continent at the southern tropical latitudes: Kharmatolou suite was formed at 13S and Voikar suite U at 20S. Probably rocks of these zones were located at south- eastern active margin of the Kazakhstan-Siberian composite paleocontinent. Further, 1 in Silurian-Devonian time, differential rotation of the East-European and Kazakhstan- Siberian continents caused SobliqueT collision and as a result of these, Ordovician & cedil;island-arc complexes of MalouralSskaya zone were joined to the Polar Urals margin of the East-European continent. 2

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

    SciTech Connect

    Roure, F.; Montadert, L.; Mueller, C. (Institut Francais du Petrole, Rueil-Malmaison)

    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.

  10. 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.

  11. Thermal and geodynamic setting of the Buem volcanic rocks near Tiélé, Northwest Bénin, West Africa

    Microsoft Academic Search

    Pascal Affaton; Luis Aguirre; René-Pierre Ménot

    1997-01-01

    The mafic volcanic rocks of Tiélé occur as intercalations within very low-grade metasediments, mainly metapelites and meta-arenites. These Proterozoic supracrustal rocks are considered as part of the Buem Structural Unit (BSU) which is the most external tectonic unit of the Pan-African Dahomeyide fold belt. The geodynamic significance of the BSU is still debated: it could represent either a portion of

  12. Adaptive finite element methods in geodynamics : Convection dominated mid-ocean ridge and subduction zone simulations

    Microsoft Academic Search

    D. R. Davies; J. H. Davies; O. Hassan; K. Morgan; P. Nithiarasu

    2008-01-01

    Purpose – The purpose of this paper is to present an adaptive finite element procedure that improves the quality of convection dominated mid-ocean ridge (MOR) and subduction zone (SZ) simulations in geodynamics. Design\\/methodology\\/approach – The method adapts the mesh automatically around regions of high-solution gradient, yielding enhanced resolution of the associated flow features. The approach utilizes an automatic, unstructured mesh

  13. GIS-project: geodynamic globe for global monitoring of geological processes

    Microsoft Academic Search

    V. Ryakhovsky; D. Rundquist; Yu. Gatinsky; E. Chesalova

    2003-01-01

    A multilayer geodynamic globe at the scale 1:10,000,000 was created at the end of the nineties in the GIS Center of the Vernadsky Museum. A special soft-and-hardware complex was elaborated for its visualization with a set of multitarget object directed databases. The globe includes separate thematic covers represented by digital sets of spatial geological, geochemical, and geophysical information (maps, schemes,

  14. Online Geodynamics: interactive web-applications for graduate students in Earth Sciences

    Microsoft Academic Search

    M. Manea; V. C. Manea

    2009-01-01

    In teaching geosciences classes it is essential to provide students with the possibility of having hands-on experiences, even if sometimes they happen to be only in the virtual world. In the portal created for the Computational Geodynamics Laboratory (http:\\/\\/www.geociencias.unam.mx\\/geodinamica), we present web-based applications, which will help students to manipulate and visualize not only data but also to understand concepts like

  15. Origin and geodynamic significance of Tertiary postcollisional basaltic magmatism in Serbia (central Balkan Peninsula)

    Microsoft Academic Search

    V Cvetkovi?; D. Prelevic; H. Downes; M. Jovanovic; O. Vaselli; Z. Pecskay

    2004-01-01

    Tertiary basaltic magmatism in Serbia occurred through three episodes: (i) Paleocene\\/Eocene, when mostly east Serbian mafic alkaline rocks (ESPEMAR) formed, (ii) Oligocene\\/Miocene, dominated by high-K calc–alkaline basalts, shoshonites (HKCA–SHO) and ultrapotassic (UP) rocks, and (iii) Pliocene episode when rocks similar to (ii) originated. In this study, the geodynamics inferred from petrogenesis of the (i) and (ii) episodes are discussed.The ESPEMAR

  16. 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.

  17. Online Geodynamics: interactive web-applications for graduate students in Earth Sciences

    NASA Astrophysics Data System (ADS)

    Manea, M.; Manea, V. C.

    2009-04-01

    In teaching geosciences classes it is essential to provide students with the possibility of having hands-on experiences, even if sometimes they happen to be only in the virtual world. In the portal created for the Computational Geodynamics Laboratory (http://www.geociencias.unam.mx/geodinamica), we present web-based applications, which will help students to manipulate and visualize not only data but also to understand concepts like mantle convection, plate reconstruction or plate deformation. The "Toolbox" option provides a set of state of the art applications (WebMap, WebPlates, WebFlexure, WebGravity, and WebConvec), in which logged-in users can run on-line various programs, without previous knowledge of advanced programming. WebPlates is used in Plate Tectonics classes, helping students to identify and familiarize themselves with various tectonic plates, different tectonic limits, hotspots, etc. WebFlexure is used to study the mechanical behavior of oceanic plates at trenches. WebConvec comes with four cases, analyzing the thermal and thermo-chemical convection in different conditions. In this way the students can be aware of how variation of various physical parameters can affect the modeling results. The "Models" section presents a collection of dynamic numerical models created in the Computational Geodynamics Laboratory. In this section, the logged-in user can visualize convection and deformation models, tectonic plate reconstructions, or geophysical field data, like geoid, gravity, etc. All these applications are actively used in the Geodynamics classes.

  18. Convergent plate margin dynamics: New perspectives from structural geology, geophysics and geodynamic modelling

    NASA Astrophysics Data System (ADS)

    Schellart, W. P.; Rawlinson, N.

    2010-03-01

    Convergent plate margins occur when two adjoining tectonic plates come together to form either a subduction zone, where at least one of the converging plates is oceanic and plunges beneath the other into the mantle, or a collision zone, where two continents or a continent and a magmatic arc collide. Convergent plate margins are arguably the most complicated and dynamic plate boundaries on Earth and have been the subject of many investigations and discussions since the advent of plate tectonic theory. This paper provides a historical background and a review of the development of geological and geodynamic theories on convergent plate margins. Furthermore, it discusses some of the recent advances that have been made in the fields of structural geology, geophysics and geodynamics, which are fundamental to our understanding of this phenomenon. These include: (1) the finding that plates and plate boundaries move at comparable velocities across the globe; (2) the emerging consensus that subducted slabs are between two to three orders of magnitude stronger than the ambient upper mantle; (3) the importance of lateral slab edges, slab tearing and toroidal mantle flow patterns for the evolution of subduction zones; and (4) clear evidence from mantle tomography that slabs can penetrate into the lower mantle. Still, many first-order problems regarding the geodynamic processes that operate at convergent margins remain to be solved. These include subduction zone initiation and the time of inception of plate tectonics, and with it convergent plate margins, on Earth. Fundamental problems in orogenesis include the mechanism that initiated Andean mountain building at the South American subduction zone, the potential episodicity of mountain building with multiple cycles of shortening and extension, and the principal driving force behind the construction of massive mountain belts such as the Himalayas-Tibet and the Andes. Fundamental questions in subduction dynamics regard the partitioning of subduction into a trench and plate component, and the distribution of energy dissipation in the system. In seismic imaging, challenges include improving resolution at mid to lower mantle depth in order to properly understand the fate of slabs, and better constraining the 3-D flow-related anisotropic structure in the surrounding mantle. Future insights into such fundamental problems and into the regional and global dynamics of convergent plate margins will likely be obtained from integrating spatio-temporal data, structural geological data, geophysical data and plate kinematic data into plate tectonic reconstructions and three-dimensional geodynamic models of progressive deformation.

  19. 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.

  20. Great earthquakes in the 21st century and geodynamics of the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Zhang, Pei-Zhen; Engdahl, Eric Robert

    2013-01-01

    What are the geodynamic processes that caused these deadly earthquakes? Why have these earthquakes caused so much damage? What are the key lessons that we have learned from these devastating earthquakes? Answers to these questions will significantly enhance not only our understanding of earthquake occurrence but also our ability to reduce seismic hazard. Under the framework of bi-lateral cooperation on earthquake sciences between China and USA, the Second Bi-Lateral Workshop on Earthquake Sciences was held in Chengdu, Sichuan Province, China, from April 22 to 25, 2011. Among the goals of this workshop was a review of recent advances in the study of great earthquakes and the exchange of ideas on earthquake disaster reduction. The principle theme of the workshop was "Great Earthquakes in the 21st Century and Geodynamics." This Special Issue contains a total of 24 papers presented during the workshop. The contributions cover a wide-range of topics associated with the theme. This preface summarizes the main points of the papers presented in this issue.

  1. 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.

  2. Marine karstic infillings: evidence of extreme base level changes and geodynamic consequences (Paleocene of Languedoc, south of France)

    E-print Network

    Demouchy, Sylvie

    Marine karstic infillings: evidence of extreme base level changes and geodynamic consequences filled with sediments containing evidences of marine origin. Field and structural relationships as well for the sedimentary filling. The 350 m vertical extent of this karst system and its subsequent marine filling gives

  3. The Deep Electromagnetic Structure of the Wenchuan Ms8.0 Earthquake Region and Its Geodynamic Implications

    Microsoft Academic Search

    X. Chen; G. Zhao; Q. Xiao; Y. Zhan; L. Wang; J. Tang; J. Wang

    2009-01-01

    The great Wenchuan Ms8.0 Earthquake in Sichuan, China intrigues further investigation of the deep structure of the Longmenshan region and its geodynamic implications. In this study, we have obtained a magnetotelluric (MT) profile (Beichuan - Songpan profile) crossing the magistoseismic area (Beichuan). Our study shows two prominent features in the region: 1) high resistivity bodies are found in the crust

  4. A new geodynamic interpretation for the South Portuguese Zone (SW Iberia) and the Iberian Pyrite Belt genesis

    E-print Network

    Paris-Sud XI, Université de

    A new geodynamic interpretation for the South Portuguese Zone (SW Iberia) and the Iberian Pyrite the Iberian Pyrite Belt (IPB) and flysch deposits forming the southern extent of the zone. Structural analysis, tectonics, volcanism, me´lange, VMS, pyrite. Citation: One´zime, J., J. Charvet, M. Faure, J.-L. Bourdier

  5. Investigation some algorithms for solving problems of local geodynamics with using base GlonassGps stations. (Russian Title: ???????????? ????????? ?????????? ??????? ????? ????????? ??????????? ? ?????????????? ??????? ???????/Gps ???????)

    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.

  6. Paleogeographic settings and geodynamics of the northeastern Pacific margin of Asia in the terminal Cretaceous-Early Paleogene

    Microsoft Academic Search

    V. D. Chekhovich

    2010-01-01

    Evolution of the ocean-continent transition zone in the northeastern Pacific margin of Asia in the con? text of general geodynamics continues to receive attention from geologists. This problem is considered in many circumstantial works (1-3). At the same time, these general interpretations largely concern its Meso? zoic history, while the Cenozoic remain insufficiently studied. In addition, these works ignored particular

  7. 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 are located on the three major plates that interact within the Wide Plate Margin Deformation Zone including existing permanent installations on IGS Galapagos and Malpelo Islands on the Nazca Plate, and San Andres Island on the Caribbean plate. The velocity vectors confirm the oblique subduction of the Nazca Plate and Carnegie aseismic ridge collision processes at the Colombia-Ecuador trench which are assumed to be the mechanism for the transpressional deformation and the "escape" of the North Andes Block (NAB). The northernmost vectors in Colombia are indicative of the ongoing collision of the Panama Arc with northwestern Colombia. Planned for the year 2013 is the installation of 10 additional GNSS continuously operating stations, and construction of 20 GPS campaign sites.

  8. 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.

  9. Geophysical Imprints of the Geodynamic Evolution of Moesia Following the Black Sea Opening

    NASA Astrophysics Data System (ADS)

    Besutiu, Lucian

    2014-05-01

    Genesis of the two types of the Moesia basement (the so called Walachian, and Dobrogean sectors) along with the complex fault system affecting its cover and basement are still debated issues. Besides, there are two other intriguing aspects raised by the seismicity map of Romania: the sub-crustal events in the bending zone of East Carpathians, and the crust seismicity of the eastern Moesian Plate (MoP). Both the intermediate-depth earthquakes within full intra-continental environment and the intense craton seismicity are unusual aspects, and their apparent association difficult to explain. The paper proposes an integrated geodynamic model of MoP able to justify its current tectonics and both the crustal events in front of Carpathians, and the intermediate-depth earthquakes in the Vrancea zone within the frame of a unique geodynamic process. It starts from the idea that tectonic and geodynamic evolution of the E MoP and the bending zone of East Carpathians has been strongly affected by the opening of the W Black Sea basin, and is currently maintained by active rifting in SW Arabian Plate. The model is supported by geophysical and geodetic evidence. Unlike some previous geology-based models assuming that Black Sea opened during a singular geodynamic event (northward subduction of the Neo-Tethys Ocean floor), the pattern of the gravity and geomagnetic field, along with off-shore seismics bring convincing evidence on the distinct timing of the W and E Black Sea basins opening. Fingerprints of the lithosphere expelled by the W Black Sea rifting in the NW inland may be seen in the distribution of compression (P) wave velocity. In-depth development of NW striking major faults (splitting MoP into numerous vertical compartments) is also well revealed by seismic tomography (e.g. Peceneaga-Camena Fault, as the limit between MoP and East European Plate (EEP), still separates two distinct P wave velocity domains at 150 km depth). A second major fault system was created by the downward bending of MoP pushed towards vertical edge of Intra-Alpine Plate. It seems that W Black Sea opening also created the necessary environment for a FFT unstable triple junction within the bending zone of East Carpathians (VTJ), to which intermediate-depth earthquakes should be associated through thermo-baric accommodation phenomena occurring within the lithosphere sunken into the upper mantle. The triangle-shape and in-depth increase of the lateral extension of the VTJ high velocity seismic body are revealed by the high accuracy P wave tomography performed within Vrancea zone. Current geodetic and geophysical monitoring in the area has suggested a close link between crust and intermediate-depth seismic events. The intensification in tectonic forces may firstly led to the intensification of crust seismicity in the Carpathians foreland (by provoking slips between the MoP vertical compartments), followed, after a time-span depending on the force intensity and upper mantle viscosity, by VTJ sinking and consequent intermediate-depth seismic events in the Vrancea zone.

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

    SciTech Connect

    Khain, V.E.; Sokolov, B.A. (Lomonosov State Univ., Moscow (Russian Federation)); Kleshchev, K.A.; Shein, V.S. (All-Union Petroleum Geological Research Inst., Moscow (Russian Federation))

    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.

  11. Strong intracontinental lithospheric deformation in South China: Implications from seismic observations and geodynamic modeling

    NASA Astrophysics Data System (ADS)

    Lu, Gang; Zhao, Liang; Zheng, Tianyu; Kaus, Boris J. P.

    2014-06-01

    Classical plate tectonics theory predicts concentrated deformation at plate boundaries and weak deformation within plates. Yet, the existence of intracontinental orogens shows that highly deformed regions can occur within continental plates, which is geodynamically incompletely understood. Shear wave splitting measurements in South China show belt-parallel (i.e. NE-SW) fast directions beneath the Wulingshan-Xuefengshan Belts, while no dominant fast direction is found in the cratonic Sichuan Basin. Tomographic studies in the mantle in the same area show that the thickness of lithosphere beneath the intracontinental orogen is larger than that beneath the cratonic Sichuan Basin. In order to better understand these seismic observations, we performed numerical experiments of intracontinental lithospheric deformation with the presence of cratonic basin.

  12. Geodynamic model and oil and gas prospects of the Pre-Caspian basin

    SciTech Connect

    Zholtaev, G.Z. (Kazakhstan Polytechnic Institute, Alma Ata (Kazakhstan))

    1993-09-01

    The Pre-Caspian basin has gone through three cycles of dynamic development. The third cycle, starting in the Devonian, included all the stages of geodynamic evolution: crustal destruction, spreading, convergence, collision, and isostatic compensation. In the Paleozoic, within the present boundaries of the Pre-Caspian basin were three sedimentary subbasins, which were fundamentally different from one another in terms of the dynamics of subsidence, rates of sedimentation, and heat flow, as reflected in the conversion of organic matter into hydrocarbons and the formation oil and gas accumulation zones. The eastern, south-eastern, and southern edges of the Pre-Caspian basin are complicated by overthrusts, and there are exploration prospects under the allochthons in the autochthonous carbonate complex.

  13. An attempt to monitor tectonic forces in the Vrancea active geodynamic zone: The Baspunar experiment

    NASA Astrophysics Data System (ADS)

    Besutiu, Lucian; Zlagnean, Luminita; Plopeanu, Marin

    2013-04-01

    An alternative model attempting to explain the unusual sub-crustal seismicity occurring in the bending zone of East Carpathians within full intra-continental environment (the so-called Vrancea zone) has assumed the presence of a FFT unstable triple junction between the three lithospheric compartments joining the area: East European Plate (EEP), Intra-Alpine Microplate (IaP) and the Moesian Microplate (MoP). Geophysical imprints (e.g. EM data, potential fields, seismic tomography), and indirect geological evidence (e.g. absence of the volcanism associated to subduction zones, the unusual high Neogene tectonic subsidence, symmetry and normal faulting within compressional environment of Focsani basin) support the hypothesis. The above-mentioned model considers the intermediate-depth seismicity as the result of the thermo-baric-accommodation phenomena generated within the colder lithosphere collapsed into the hotter upper mantle. Therefore, the amount of seismic energy thus released should be related to the volume of the lithosphere brought into thermo-baric disequilibrium by sinking into the upper mantle. Vertical dynamics of the Vrancea unstable triple junction (VTJ) seems to be controlled by the both tangential tectonic forces driving the neighbouring plates and the gravitational pull created by the eclogitization of VTJ lower crust. But, while eclogitization provides a relatively constant force, acceleration of sinking is expected to be provided by changes in the tectonic forces acting on VTJ. As changes in tectonic forces should reflect in changes of the dynamics of lithospheric compartments, geodetic means were considered for helping in their monitoring. The Peceneaga-Camena Fault (PCF) is a major lithospheric contact separating MoP and EEP, starting from the W Black Sea basin to the Vrancea zone. Geological evidence advocate for its variable geodynamic behaviour during the time, both as left-lateral or right-lateral fault. Unfortunately, GPS campaigns, so far (sparsely) run in the area, have provided inconsistent results on the PCF current dynamics. The Baspunar Geodynamic Observatory (BGO) has been designed and implemented by the Solid Earth Dynamics Department in the Institute of Geodynamics of the Romanian Academy in order to reveal and monitor eventual motions along PCF in the attempt to correlate variations in the slip rate with changes in the seismicity released within Vrancea zone. The first BGO records were strongly affected by changes in the atmospheric parameters. Consequently, technical measures and special corrections for the removal or at least mitigation of the effects created by changes in temperature, air pressure and humidity have been applied to the observations. In order to improve the signal to noise ratio, some mathematical filters have been applied too. The paper is aimed at revealing results of the geodetic observations along with preliminary geodynamic considerations. On the overall, after about two years of monitoring, PCF appears as an active tectonic contact. It mainly behaves as a left-lateral fault, but some short episodes with a reverse slip (dextral) were also pointed out. Correlations with crustal and intermediate-depth earthquakes occurring in both cases within the bending zone of East Carpathians are illustrated and discussed.

  14. Constraining the rheology of the lithosphere through joint geodynamic and gravity inversion

    NASA Astrophysics Data System (ADS)

    Baumann, T.; Kaus, B.; Popov, A.

    2013-12-01

    Understanding the physics of lithospheric deformation and continental collision requires good constraints on lithospheric rheology. Typically, rheology is determined from laboratory experiments on small rock samples, which are extrapolated to geological conditions - an extrapolation over 10 orders of magnitude in deformation rates. These laboratory experiments generally show that small changes in the composition of the rocks, such as adding a bit of water, can dramatically change its viscosity. Moreover, it is unclear which rock type gives the best mechanical description of, for example, the upper crust and whether a small sample is even appropriate to describe the large scale mechanical behavior of the crust. So the viscosity of the lithosphere is probably the least constrained parameter in geodynamics. Ideally, we thus need a new independent method that allows constraining the effective rheology of the lithosphere directly from geophysical data, which is the aim of this work. Our method uses the fact that the geodynamically controlling parameters of lithospheric deformation are its effective viscosity and density structure. By appropriately parameterising the rheological structure of the lithosphere we perform instantaneous forward simulations of present-day lithospheric deformation scenarios with a finite element method to compute the gravity field and surface velocities. The forward modelling results can be compared with observations such as Bouguer anomalies and GPS-derived surface velocities. More precisely, we automatize the forward modelling procedure with a Monte Carlo method, and in fact solve a joint geodynamic and gravity inverse problem. The resulting misfit can be illustrated as a function of rheological model parameters and a more detailed analysis allows constraining probabilistic parameter ranges. For a simplified setup with linear viscous rheologies we can demonstrate mathematically that a joint geodynamic-gravity inversion approach results in a unique solution as opposed to inverting for gravity alone. This is shown to work as well in combination with 3D forward models of salt tectonics on an upper crustal scale. Yet, the lithosphere has nonlinear rheologies that can be plastic or temperature-dependent powerlaw creep depending on stresses. As the thermal structure of the lithosphere is in general poorly constrained, and only affects the dynamics of the lithosphere in an indirect manner, we developed a parameterized rheology that does not include temperature but includes other nonlinearities (such as stress-dependent viscosity). To test the accuracy of this method we perform lithospheric-scale collision forward models that incorporate a temperature-dependent viscoelastic-plastic rheology to create synthetic gravity and surface velocities data. In a second step, we deploy these synthetic data sets to perform the joint inversion, using our simplified parameterized rheology. Results show that we can recover the rheology of the lithosphere reasonably well, provided that lithospheric layers contribute to the large-scale dynamics. In addition, we will show an application of our method to 2D cross-sections of the India-Asia collision system. Acknowledgements Funding was provided by the ERC under the European Community's Seventh Framework Program (FP7/2007-2013) / ERC Grant agreement #258830

  15. Nonlinearities and multigrid solvers for geodynamic applications using staggered grid finite differences.

    NASA Astrophysics Data System (ADS)

    Popov, Anton; Kaus, Boris

    2014-05-01

    We report on the state of the development of the massively parallel staggered-grid finite difference version of the LaMEM code, parts of which have scaled to over 260'000 cores. In particular we present i) our matrix-free nonlinear solution strategy for visco-elasto-plasticity, ii) updated linear solver that includes a coupled velocity-pressure geometric multigrid preconditioner, and iii) an optimized treatment of the makers with approximate stress-rotation algorithm generalized from 2D to 3D formulation. The capabilities of the solver are demonstrated with a set of geodynamically-relevant benchmarks and example problems on the massively parallel computers. Acknowledgements. Funding was provided by the European Research Council under the European Community's Seventh Framework Program (FP7/2007-2013) / ERC Grant agreement #258830. Numerical computations have been performed on JUQUEEN of the Jülich high-performance computing center.

  16. Unravelling the driving forces of Anatolian tectonics: geodynamic models and constraints (Invited)

    NASA Astrophysics Data System (ADS)

    Pysklywec, R. N.; Gogus, O. H.; Komut, T.; Gray, R.

    2013-12-01

    Western and Eastern Anatolia both demonstrate a complex geologic history of horizontal and vertical tectonics. Western Anatolia has been extending significantly since the early Miocene and is associated with normal faulting, rift basins and exhumed zones of Menderes Massif Metamorphic rocks. On the other hand, the East Anatolia plateau has been shortening, uplifting and accommodating plate convergence between Arabian and Eurasian plates along the Bitlis suture zone. At the same time as the tectonic deformation both regions are also experiencing large-scale anomalous vertical motions. For example, admittance functions between free-air gravity and topography for Western Anatolia indicate that the regional topography is isostatically uncompensated and consistent in magnitude with support by an underlying mantle flow component. In this work, we propose that the regional plate deformation is the result of the interplay between lithospheric and mantle (sub-lithospheric) dynamics. Using forward geodynamic models we consider idealized sections of Anatolian lithosphere based on tomographic inversions and examine the magnitude and pattern of surface topography and crustal deformation to reconcile with the observational constraints. The models--driven by the inferred local mantle structure--consistently show a plateau-type uplift and horizontal extension through Western Anatolia with an amplitude and wavelength consistent with the residual topography calculations. There is also a breadth of petrological and seismological research that suggests the absence of mantle lithosphere beneath both Eastern and Western Anatolia. We use the geodynamic experiments to test whether gravitational instability/delamination of the lithosphere in the region may be coupling the forces driving the (horizontal) surface deformation and (vertical) topography.

  17. Numerical modeling of seismicity and geodynamics of the Kachchh rift zone, Gujarat, India

    NASA Astrophysics Data System (ADS)

    Vorobieva, Inessa; Mandal, Prantik; Gorshkov, Alexander

    2014-11-01

    The numerical block-and-fault model of lithosphere dynamics and seismicity (BAFD) is used to understand crustal motion and features of the observed seismicity in the Kachchh rift zone, Gujarat, Western India. The block-model allows simulating seismicity and geodynamics simultaneously unlike other modeling approaches for studying seismicity or geodynamics. The model structure of Kachchh rift zone is composed of seven major crustal blocks separated by fault planes. Based on the orientation of boundary crustal block movements, we develop a set of numerical experiments to analyze the spatial distribution of earthquakes, frequency-to-magnitude relationships, earthquake focal mechanisms, velocity field, and fault slip rates in the model. The main results of our modeling suggest that an NNW-SSE trending compression is a principal driving force in the Kachchh rift zone that explains basic features of the regional seismicity, direction of block motions, and the presence of an extensional stress regime associated with the Cambay rift zone. Large synthetic events occur on the fault segments associated with the Allah-Bund fault, Katrol hill fault and north Wagad fault which have been causative faults for the 1819 Mw7.7 Allah-Bund, 1956 Mw6.0 Anjar and 2001 Mw7.7 Bhuj earthquakes. The frequency-magnitude distribution for both synthetic seismicity and observed seismicity shows a similar slope. The focal mechanisms of the synthetic events are found to be consistent with those of earthquakes in the region. A special attention has been paid to study long-term and post-seismic deformations. Our results are in a qualitative agreement with the GPS post-seismic observations in the Kachchh rift zone. We infer that the observed seismicity and crustal block motions are a consequence of the dynamics of the entire regional fault and block system rather than that of a single causative fault only.

  18. A geodynamical view on the steadiness of geodetically derived rigid plate motions over geological time

    NASA Astrophysics Data System (ADS)

    Iaffaldano, G.

    2014-01-01

    The ability to map ocean-floor magnetization is key to infer past plate motions. The advent of geodesy in the Earth Sciences offered an independent snapshot of contemporary plate kinematics, averaged over decades. Early studies suggested plate-motions steadiness through geological time, because contemporary rates were similar to past 3-Myr averages. Recent data, however, show that geodetic and paleo-magnetic motions exhibit differences beyond confidence ranges, which might suggest geodesy samples time scales shorter than a few centuries. These differences pose important questions on the character of plate kinematic variability through time. Here I derive inferences on the steadiness of geodetically derived plate motions by combining geodynamical arguments with kinematic data sets. I exploit data sets to build scenarios for the recent evolution of most of the major plates. I compare the minimum rate at which torque needs to vary to generate these scenarios, with the maximum rate at which geological processes can contribute torque. This allows assessing the geodynamical plausibility of each scenario. Results indicate that plate-motion changes recorded since ˜3 Ma must have taken at least 1 Myr to occur. Two exceptions are the Pacific and Australian plates, whose motions changed by less than 5%, and therefore, required torque variations that might be built over periods as short as 0.1 Myr. It remains unresolved for how long geodetically derived plate motions kept steady in the geological past. However, results indicate it is indeed plausible that they did over the past 1-2 Myr. These inferences call for a shift in the way we regard the figure of geodetic plate motions.

  19. Upper mantle and crustal structure of the East Greenland Caledonides: New geophysical evidence and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Schiffer, C.; Balling, N.; Jacobsen, B. H.; Hejrani, B.; Nielsen, S. B.

    2013-12-01

    The East Greenland and Scandinavian Caledonides once formed a major coherent mountain range, as a consequence of the collision of the continents of Laurentia and Baltica. The crustal and upper mantle structure was furthermore influenced by several geodynamic processes leading to the formation of the North Atlantic passive margins, including the gravitational collapse, extension, rifting and a possible influence by volcanism related to the Iceland hot spot. The landscape and topography were finally shaped by extensive erosion, finding its peak in the quaternary glaciations. Seismological data were acquired in the East Greenland Caledonides by the Ella-Ø-array for a period of two years (2009-2011). The array containing 11 broadband seismometers was situated at approximately 73 °N covering a distance of 270 km from the Greenland Ice Sheet to the Atlantic coast, north of the Iceland Ridge. A Receiver Function study based on an average of 36 events per station reveals a clear eastward dipping high-velocity structure underneath the study area. The geophysical character, supported by synthetic modelling, is consistent with a 10 km thick subducted slab of eclogitized oceanic crust. This might be the key for unravelling of a complex geodynamic setting and development leading to the formation of the Caledonides. The distinct preservation of structures in the upper mantle to depths of 100 km or more, limits the impact of subsequent collision and extension related deformation. In support of this interpretation, we present selected results from on-going detailed studies of the crustal and upper mantle, including a Receiver Function inversion, seismic P-wave travel time tomography and gravity modelling.

  20. Variational Data Assimilation and the Indirect Representer Method: Application to crustal geodynamics

    NASA Astrophysics Data System (ADS)

    Egbert, G. D.

    2005-12-01

    One standard approach to DA, now well developed in the atmospheric and oceanic sciences, is to prescribe error covariances which define a priori hypotheses on the magnitude and spatial structure of model and data errors, and then optimize the tradeoff between fitting the data and satisfying prior model assumptions by minimizing a quadratic penalty functional. Minimization of such a penalty functional using gradient based search methods is often referred to as variational data assimilation, 4D-Var, or the generalized inverse method (GIM). The GIM has proven to be particularly well suited to scientific (as opposed to operational) studies in oceanography, and this approach is likely also to prove very useful for a wide range of scientific studies in geodynamics. Over the past decade optimization methods that make GIM more practical for large non-linear DA problems have been developed and applied in oceanography. These so-called "indirect representer" methods involve minimization of the quadratic penalty functional through a series of conjugate gradient solutions of the linearized Euler-Lagrange equations, recast in the data space. A modular implementation of the indirect representer approach, the Inverse Ocean Modeling (IOM) system, is currently being developed through an NSF funded ITR project. This modular system simplifies implementation of the GIM for any client dynamical model, but requires coding of a tangent linear (TL) to the non-linear dynamical model along with the adjoint (ADJ) of this TL. I will summarize the GIM approach to DA, the indirect representer method, and the IOM. As a specific application in geodynamics, I will discuss development of TL and ADJ codes, and coupling with the IOM, for the Geophysical Finite Element Simulation Tool (GEOFEST), which has been extensively used for visco-elastic modeling of Earth deformation associated with the earthquake cycle. One important lesson from this experience is that with reasonably modular modeling code, development of TL and ADJ codes need not be so onerous as to preclude consideration of gradient based search methods.

  1. The Seismic Cycle at Subduction Thrusts: Implications of Geodynamic Simulations Benchmarked with Laboratory Models

    NASA Astrophysics Data System (ADS)

    van Dinther, Y.; Gerya, T.; Dalguer, L. A.; Corbi, F.; Funiciello, F.; Mai, P. M.

    2012-12-01

    The physics governing the seismic cycle at seismically active subduction zones remains poorly understood due to restricted direct observations in time and space. To investigate subduction zone dynamics and associated interplate seismicity, we benchmark a quasi-static, visco-elasto-plastic numerical model to a new laboratory approach. We demonstrate that our numerical method reproduces seismic cycle behavior and source parameter estimates of the laboratory setup that includes a visco-elastic gelatin wedge underthrusted by a plate with defined velocity-weakening and -strengthening regions. Our innovative geodynamic approach includes velocity-weakening friction to spontaneously generate a series of fast frictional instabilities that correspond to analog earthquakes. A match between numerical and laboratory source parameters is obtained when velocity-strengthening is applied in the aseismic regions to stabilize and limit the rupture, while promoting slip complexity. Spontaneous nucleation by coalescence of neighboring patches mainly occurs at evolving asperities near the seismogenic zone limits, with a preference for the downdip region. Consequently, a crack-, or occasionally even pulse-like, rupture propagates toward the opposite side of the seismogenic zone by increasing stresses ahead of its rupture front. The resulting surface displacements qualitatively agree with geodetic observations and show landward and, from near the downdip limit, upward interseismic motions. These are rebound and reversed coseismically as the fault slips (Figure 1). Slip produces stress shadows that are relaxed afterwards by postseismic accelerated creep or afterslip. The agreement with laboratory results and the wide range of observed physical phenomena, including back-propagation and repeated slip, demonstrate that visco-elasto-plastic geodynamic models with rate-dependent friction represent a new tool that can greatly contribute to our understanding of the seismic cycle at subduction zones.orizontal displacement of six particles at the surface.

  2. A Geodynamic Grand Challenge: Time-Reversed Mantle Convection Reconstructions From Tomographic Images of Present-Day Mantle Structure

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    One of the most complex challenges in current geodynamics research is the reconstruction of the past evolution of 3-D mantle temperature structure from seismic tomographic images of present-day lateral heterogeneity in the mantle. Early efforts to address this problem have been based on backward advection approximations based on the assumption that mantle convection is a very-high Rayleigh number process (e.g. Forte & Mitrovica 1997; Steinberger & O'Connell 1997). Over the past decade further progress has been achieved and new techniques have been proposed, such as the 4-D variational (Bunge et al. 2003) and quasi-reversible (Ismail-Zadeh et al. 2007) approaches. An enduring challenge is the construction of time-reversed mantle convection simulations that yield maximum consistency with a wide suite of surface geodynamic constraints on mantle rheology and 3-D structure inferred from seismic tomography. Resolving this outstanding problem is of crucial importance, because a successful reconstruction of the time-dependent, 3-D mantle convective structure in the geological past provides unique insights into the origin and evolution of a number of fundamental surface processes that include topography changes, eustatic sea level variations, state of stress in the lithosphere, and Earth rotation variations. A key concern in these reconstructions is quantifying the inherent uncertainties and the implications for surface geodynamic observables. We will explore these issues and compare the efficacy of different backward convection techniques using a new mantle convection model based on recent joint seismic-geodynamic tomography inversions (Simmons et al., GJI, 2009).

  3. Age, origin and geodynamic significance of plagiogranites in lherzolites and gabbros of the Piedmont-Ligurian ocean basin

    Microsoft Academic Search

    Laura Borsi; Urs Schärer; Laura Gaggero; Laura Crispini

    1996-01-01

    U-Pb zircon dating, Sr-Nd isotope tracing and major\\/trace\\/RE element analyses were performed to constrain the age, origin and geodynamic significance of plagiogranites that intrude lherzolites and gabbros in the Ligurian Alps and the Northern Apennines. In addition, a host Fe-diorite was investigated. Samples from the Ligurian Alps were collected from the Voltri Group and the Sestri-Voltaggio Zone, whereas the plagiogranites

  4. 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-like style. In the Tyrrhenian basin the roll back occurred since the Tortonian striking along a preferential east/southern-eastward direction causing crustal stretching and the formation of new oceanic basins. The Marsili basin oceanic crust formed by seafloor spreading that about 1 Ma shifted to a regime of prevailing vertical accretion of the volcanic ridge due to a new intense magmatic pulse related probably to slab tearing in the subduction system. The Vavilov ridge underwent a similar evolution during the Matuyama reverse chron (about 2.5 Ma). Our data suggest that the evolution of the entire Tyrrhenian sea was driven by two asynchronous geodynamic stages resulting in a common style: high-rate of eastward rollback during the initial phase, drastic decrease of the seafloor spreading rate and finally slab tearing with the formation of the volcanic ridges at the centre of the basins.

  5. 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

    The base of the mantle is the site of the most significant change in physical parameters in the Earth system: the core-mantle boundary. As the region which mediates core-mantle interactions and acts as the lower boundary for mantle convection understanding its properties is key to understanding the broader dynamics of the mantle. One issue is the participation of material in the lowermost mantle (often referred to as D?) in whole mantle convection. This is exemplified by the questions outstanding about the origin of the large, low shear-velocity provinces observed beneath Africa and the Pacific. While the consensus view is that these are long-term, stable features which are compositionally distinct (lending them higher density than their surroundings), a dominantly thermal origin (whereby they are lower density transitory upwellings, such as clustered plumes) is favoured by a number of very recent studies. Observations of seismic anisotropy (which results from the deformation of mantle minerals) are key to understanding the geodynamic nature of the lowermost mantle. There are a broad set of observations of D? anisotropy, ranging from tomographic to waveform studies which allow resolution of a more general anisotropy style. These observations show variation at a range of length scales, with some regions apparently very complex. To interpret them robustly in terms of geodynamics requires significant knowledge of lowermost mantle mineralogy. Mineralogical information comes from both laboratory experiments and theoretical calculations. In addition to single-crystal elasticities of relevant mantle phases we also need information about deformation mechanisms in order to calculate the aggregate seismic anisotropy. While candidate determinations of these latter parameters exist there is no consensus as to the dominant mechanism for the mineral likely to be most significant for the lowermost mantle region - post-perovskite. In order to test these candidates we have 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.

  6. 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 center of the Neftegorsk earthquake was directly formed by burst of activity of this ancient subduction zone. From a position of the ancient subduction zone under Sakhalin, which is a cause of strong earthquakes here, it follows that the region is one of seismic dangerous in Russia. Constructed on the basis of complex interpretation of the geologic-geophysical data the geodynamic models of natural disaster regions give the chance: to study a deep structure under seismic dangerous zones; to investigate a role of deep processes in the upper mantle in formation of structures of earth crust; to relate the geological features, tectonomagmatic, hydrothermal activity with the processes in the upper mantle; to plot maps in detail with zones of increasing risks to prevent active building or other economic activities in such dangerous regions.

  7. 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 region (the south-eastern part of the Zagros) the SH,max axis changed orientation from NE to NW. At this time in the north of the region (Central Pre-Caucasus) the SH,max axis was still directed towards NE. But in the middle Sarmatian, when the southern part of the region already had NE orientation of compression, in the northern part the SH,max axis reoriented in NNW direction. As in the south of the region, this reorientation was short and in late Sarmatian the SH,max axis regained his usual NE orientation. The identified short-term restructuring that began in the south-east of the region in the early middle Miocene and which reached the northern part of the region in the early Late Miocene can be interpreted as the process of the south to north moving of the solitary wave of geodynamic perturbation. The velocity of the wave is estimated as 0.1-1.0 m/year.

  8. 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

    Nicolas Hawie a,b,c (nicolas.hawie@upmc.fr) Didier Granjeon c (didier.granjeon@ifpen.fr) Christian Gorini a,b (christian.gorini@upmc.fr) Remy Deschamps c (remy.deschamps@ifpen.fr) Fadi H. Nader c (fadi-henri.nader@ifpen.fr) Carla Müller Delphine Desmares f (delphine.desmares@upmc.fr) Lucien Montadert e (lucien.montadert@beicip.com) François Baudin a (francois.baudin@upmc.fr) a UMR 7193 Institut des Sciences de la Terre de Paris, Université Pierre et Marie Curie/ Univ. Paris 06, case 117. 4, place Jussieu 75252 Paris Cedex 05, France b iSTEP, UMR 7193, CNRS, F-75005, Paris, France c IFP Energies nouvelles, 1-4 avenue du Bois Préau 92852 Rueil Malmaison Cedex, France d UMR 7207, Centre de Recherche sur la Paleobiodiversité et les Paleoenvironnements. Université Pierre et Marie Curie, Tour 46-56 5ème. 4, place Jussieu 75252 Paris Cedex 05, France e Beicip Franlab, 232 Av. Napoléon Bonaparte, 95502 Rueil-Malmaison, France Sedimentological and biostratigraphic investigations onshore Lebanon coupled with 2D offshore reflection seismic data allowed proposing a new Mesozoic-Present tectono-stratigraphic framework for the northern Levant Margin and Basin. The seismic interpretation supported by in-depth facies analysis permitted to depict the potential depositional environments offshore Lebanon as no well has yet been drilled. The Levant region has been affected by successive geodynamic events that modified the architecture of its margin and basin from a Late Triassic to Middle Jurassic rift into a Late Cretaceous subduction followed by collision and Miocene-Present strike slip motion. The interplay between major geodynamic events as well as sea level fluctuations impacted on the sedimentary infill of the basin. During Jurassic and Cretaceous, the Levant Margin is dominated by the aggradation of a carbonate platform while deepwater mixed-systems prevailed in the basin. During the Oligo-Miocene, three major sedimentary pathways are expected to drive important 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

  9. 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 geodynamics in the complex geological setting of the southern Pacific Ocean. Inferences are made about the three-dimensional distribution of melting anomalies.

  10. Sink or swim? Geodynamic and petrological model constraints on the fate of Archaean primary crust

    NASA Astrophysics Data System (ADS)

    Kaus, B.; Johnson, T.; Brown, M.; VanTongeren, J. A.

    2013-12-01

    Ambient mantle potential temperatures in the Archaean were significantly higher than 1500 °C, leading to a high percent of melting and generating thick MgO-rich primary crust underlain by highly residual mantle. However, the preserved volume of this crust is low suggesting much of it was recycled. Here we couple calculated phase equilibria for hydrated and anhydrous low to high MgO crust compositions and their complementary mantle residues with 2-D numerical geodynamic models to investigate lithosphere dynamics in the early Earth. We show that, with increasing ambient mantle potential temperature, the density of primary crust increases more dramatically than the density of residual mantle decreases and the base of MgO-rich primary crust becomes gravitationally unstable with respect to the underlying mantle even when fully hydrated. To study this process we use geodynamic models that include the effects of melt extraction, crust formation and depletion of the mantle in combination with laboratory-constrained dislocation and diffusion creep rheologies for the mantle. The models show that the base of the gravitationally unstable lithosphere delaminates through relatively small-scale Rayleigh-Taylor instabilities, but only if the viscosity of the mantle lithosphere is sufficiently low. Thickening of the crust above upwelling mantle and heating at the base of the crust are the main mechanisms that trigger the delamination process. Scaling laws were developed that are in good agreement with the numerical simulations and show that the key parameters that control the instability are the density contrast between crust and underlying mantle lithosphere, the thickness of the unstable layer and the effective viscosity of the upper mantle. Depending on uncertainties in the melting relations and rheology (hydrous or anhydrous) of the mantle, this process is shown to efficiently recycle the crust above potential temperatures of 1550-1600 °C. However, below these temperatures this process ceases to work, mainly because the percent of melting in the upper mantle is insufficient to generate locally thickened new crust. We further show that melting at the base of overthickened hydrated primary crust is also plausible at the predicted temperatures and would have led to intracrustal differentiation. The tonalite-trondhjemite-granodiorite gneisses that comprise exposed Archaean crust cannot have been generated directly from primary MgO-rich crust, but could have been derived from hydrated basaltic crust formed by crystal fractionation or intracrustal differentiation.

  11. 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 scientists and phenomena modelers to develop their core interests and leverage off each other's work. In turn, we aim to produce adaptable code bases where core technologies can be interchanged. That is to provide modelers with the tools to venture beyond their present scope, whilst proving infrastructure builders real problems to test against. Furthermore we aim to match the language to the expectations of the people at those levels. We facilitate this environment through a fundamental framework named StGermain. We demonstrate its application to a spectrum of (long time scale) geodynamics problems encapsulated in the Underworld package. In particular we show three phenomena models from Underworld: mantle convection, roll back, and basin extension modeling. These are all at different scales, incorporate different physics, different work flows and maintained by different people. The methodology and technology is being applied to solve multi scale, multi physics modeling of materials manufacturing problems.

  12. Glacial isostatic adjustment in Fennoscandia from GRACE data and comparison with geodynamical models

    NASA Astrophysics Data System (ADS)

    Steffen, Holger; Denker, Heiner; Müller, Jürgen

    2008-10-01

    The Earth's gravity field observed by the Gravity Recovery and Climate Experiment (GRACE) satellite mission shows variations due to the integral effect of mass variations in the atmosphere, hydrosphere and geosphere. Several institutions, such as the GeoForschungsZentrum (GFZ) Potsdam, the University of Texas at Austin, Center for Space Research (CSR) and the Jet Propulsion Laboratory (JPL), Pasadena, provide GRACE monthly solutions, which differ slightly due to the application of different reduction models and centre-specific processing schemes. The GRACE data are used to investigate the mass variations in Fennoscandia, an area which is strongly influenced by glacial isostatic adjustment (GIA). Hence the focus is set on the computation of secular trends. Different filters (e.g. isotropic and non-isotropic filters) are discussed for the removal of high frequency noise to permit the extraction of the GIA signal. The resulting GRACE based mass variations are compared to global hydrology models (WGHM, LaDWorld) in order to (a) separate possible hydrological signals and (b) validate the hydrology models with regard to long period and secular components. In addition, a pattern matching algorithm is applied to localise the uplift centre, and finally the GRACE signal is compared with the results from a geodynamical modelling. The GRACE data clearly show temporal gravity variations in Fennoscandia. The secular variations are in good agreement with former studies and other independent data. The uplift centre is located over the Bothnian Bay, and the whole uplift area comprises the Scandinavian Peninsula and Finland. The secular variations derived from the GFZ, CSR and JPL monthly solutions differ up to 20%, which is not statistically significant, and the largest signal of about 1.2 ?Gal/year is obtained from the GFZ solution. Besides the GIA signal, two peaks with positive trend values of about 0.8 ?Gal/year exist in central eastern Europe, which are not GIA-induced, and also not explainable by the hydrology models. This may indicate that the recent global hydrology models have to be revised with respect to long period and secular components. Finally, the GRACE uplift signal is also in quite good agreement with the results from a simple geodynamical modelling.

  13. Constraining the rheology of the lithosphere through joint geodynamic and gravity inversion

    NASA Astrophysics Data System (ADS)

    Kaus, Boris; Baumann, Tobias; Popov, Anton

    2014-05-01

    Understanding the physics of lithospheric deformation requires good constraints on lithospheric rheology and in particular on the effective viscosity. Typically, rheology is determined from laboratory experiments on small rock samples, which are extrapolated to geological conditions - an extrapolation over 10 orders of magnitude in deformation rates. Ideally, we thus need a new independent method that allows constraining the effective rheology of the lithosphere directly from geophysical data, which is the aim of this work. Our method uses the fact that the geodynamically controlling parameters of lithospheric deformation are its effective viscosity and density structure. By appropriately parametrising the rheological structure of the lithosphere we perform instantaneous forward simulations of present-day lithospheric deformation scenarios with a finite element method to compute the gravity field as well as surface velocities. The forward modelling results can be compared with observations such as Bouguer anomalies and GPS-derived surface velocities. More precisely, we automatise the forward modelling procedure with a Markov-Chain Monte Carlo method, and in fact solve a joint geodynamic and gravity inverse problem. The resulting misfit can be illustrated as a function of rheological model parameters and a more detailed analysis allows constraining probabilistic parameter ranges. Yet, the lithosphere has non-linear rheologies that can be plastic or temperature-dependent powerlaw creep depending on stresses. As the thermal structure of the lithosphere is in general poorly constrained, and only affects the dynamics of the lithosphere in an indirect manner, we developed a parameterised rheology that excludes a direct temperature dependency. To test the accuracy of this approximation we perform lithospheric-scale collision forward models that incorporate a temperature-dependent visco-plastic rheology to create synthetic surface observations. In a second step, we deploy these synthetic data sets to perform a joint inversion, using our simplified parameterized rheology. Results show that we can recover the rheology of the lithosphere reasonably well, provided that lithospheric layers contribute to the large-scale dynamics. In addition, we have applied the models to the India-Asia collision zone, and first results are consistent with the Tibetan plateau having a weak lower crust, but the Indian mantle lithosphere having large viscosities.

  14. Geodynamic modeling of the Mid-Continental Rift System: Is a mantle plume required?

    NASA Astrophysics Data System (ADS)

    Moucha, R.; Rooney, T. O.; Stein, S. A.; Brown, E.

    2013-12-01

    The Mid-Continent Rift System (MCRS) is a 2000-km long trace of a massive igneous event that nearly split North America 1.1 billion years ago. The MCRS offers a snapshot of continental rifting and rift failure. The rift started, evolved, and terminated via a complex and not-yet-understood interplay of mantle dynamics, magmatism, and extension. In particular, details of the processes surrounding melt formation and the associated depletion of the lithospheric mantle, and re-thickening of the extended crust remain poorly constrained. To help unravel the complex history of the MCRS, we present a new geodynamic model for late Proterozoic rifting and compare a number of different extension scenarios in an effort to answer the following question: can the volume of magmas preserved in the MCRS be explained by extensional processes in the absence of a thermo-chemical mantle plume anomaly? In the late Proterozoic, inherently higher mantle potential temperatures may have permitted rifting at lower stress levels and favored more melt formation. Therefore, the inferred volume of magma in the MCRS may not have required a plume. To explore this idea, we compare models for the evolution of a rift under different ambient mantle temperatures and radiogenic heating conditions, i.e. Phanerozoic vs. Proterozoic, and in the absence or presence of a thermal-chemical plume. Our geodynamic model of the MCRS includes a temperature dependent visco-elasto-plastic rheology in the presence of partial melt that is dynamically determined according to given rock-type, pressure and temperature. The models include a 'sticky air' layer to mimic a free surface that is coupled to a surface processes model to account for erosion and sedimentation. The numerical method we use is based on the primitive variable particle-in-cell finite-difference method developed by Taras Gerya and others (e.g. Gerya, 2010). The advantage of this approach is that specific material properties are inherently traced through time negating the need for numerous high-resolution grids. Moreover, melt-extraction and the formation of a crust along with depletion and fertilization are also easily tracked.

  15. 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 community in current of last decades and even centuries have been solved. The fundamental phenomena in rotation of the Earth: secular drift of a pole of its axis of rotation and non-tidal acceleration of axial rotation of a planet have received an explanation. Observable secular variations of a gravity, variations of a geopotential coefficients, secular drift of the center of mass of the Earth, secular changes of a global level of ocean and change of average levels of ocean in northern and southern hemispheres of the Earth, secular geodetic changes of the Earth in present period have been explained, etc. It is shown, that there is a uniform mechanism for many bodies of solar system of excitation of natural processes in their polar areas. In particular it is shown, that polar regions of many celestial bodies, including their soil layers, are sated by fluids. The last position obtains the precise confirmation in researches of subsoil waters and a water ice on Mars, the Moon, Mercury, etc. bodies of solar system. A wide number of the natural phenomena has been predicted by the author and these predictions have already obtained and obtain confirmations and an explanations in the data of modern observations and space missions. An existence of the seas in polar regions of the Titan, concentration of water ice in polar regions of Mercury, the Moon, Mars and other bodies of solar system has been predicted. The conclusion about fluid consentrations at polar regions of celestial bodies is extremely important for revealing of carbon deposits on the Earth, first of all in regions of Arctic and Antarctic. Work is partially supported by RFBR grants: N 08-02-00367, N-09-02-92113-JF. References 1. Barkin Yu.V. (2002) An explanation of endogenous activity of planets and satellites and its cyclisity. Isvestia sekcii nauk o Zemle Rossiiskoi akademii ectestvennykh nauk. Vyp. 9, M., VINITI, pp. 45-97. In Russian. 2. Barkin Yu.V. (2009) Moons and planets: mechanism of their life. Proceedings of International Conference 'Astronomy and World Heritage: across Time and Continents' (Kazan, 19-

  16. Numerical approach to inverse problems in geodynamics: Application to lithosphere subduction

    NASA Astrophysics Data System (ADS)

    Ismail-Zadeh, A.; Tsepelev, I.; Honda, S.

    2012-04-01

    To restore mantle thermal structures and convective flow in the geological past, mathematical and computational techniques for inverse retrospective problems should be employed to constrain the initial (in the past) conditions for the temperature and velocity in the mantle from present seismic, heat flow, geodetic and some other observations. The basic principle of inverse retrospective problems in geodynamics is to consider the initial temperature as a control variable and to optimise the model temperature and flow in order to minimize the discrepancy between the present observations and the solution to a model of the inverse thermo-convective mantle flow. Our model is based on the set of the Stokes, heat flux and continuity equations at the extended Boussinesq approximation and at the appropriate initial and boundary conditions and incorporates mantle phase transformations. We use a quasi-reversibility technique (Ismail-Zadeh et al., GJI, 2007) for assimilation of the present data and discuss applicability of this technique to restoration of a descending lithosphere. A sensitivity analysis has been performed to clarify the influence of the model boundary conditions and the model viscosity on model results. We apply the methodology to study the evolution of the Pacific and Philippine plates subducting beneath the Japanese islands and present several scenarios for the evolution of the descending lithosphere.

  17. Detection of metastable olivine wedge in the western Pacific slab and its geodynamic implications

    NASA Astrophysics Data System (ADS)

    Jiang, Guoming; Zhao, Dapeng; Zhang, Guibin

    2015-01-01

    Seismic tomography and numerical simulations show that the western Pacific slab bends horizontally when it reaches the boundary between the upper mantle and lower mantle beneath northeast Asia. It is expected that a metastable olivine wedge (MOW) exists in the cold core of the slab because of a delayed phase transition from olivine to its high-pressure polymorphs. However, it is still debated whether the MOW actually exists or not, and even if it exists, its physical properties, such as seismic velocity and density, are still unclear. In this work we use high-quality arrival-time data of 17 deep earthquakes occurring within the Pacific slab under northeast Asia to study the detailed structure of the slab. The deep earthquakes are relocated precisely by applying a modified double-difference location method to arrival-time data recorded at both Chinese and Japanese stations. Based on the precise hypocentral locations, a forward modeling method and differential travel-time residuals data are used to estimate seismic velocity within the deep source zone, which can decrease or remove the influence of ambient velocity heterogeneities. Our results show that the MOW does exist within the Pacific slab under northeast Asia, and the MOW has a mean velocity anomaly of 7-9% lower than the iasp91 Earth model. The existence of MOW in the slab has important geodynamic implications. It can reduce the speed of slab subduction and affect the generation of deep earthquakes.

  18. Geodetic GNSS measurements as a basis for geodynamic and glaciological research in Antarctica

    NASA Astrophysics Data System (ADS)

    Scheinert, Mirko; Dietrich, Reinhard; Knöfel, Christoph; Fritsche, Mathias; Rülke, Axel; Schröder, Ludwig; Richter, Andreas; Eberlein, Lutz

    2013-04-01

    For about twenty years our institute has been carrying out geodetic GNSS measurements and has been actively working in international collaboration for Antarctic research. Episodic GPS (and later GNSS) measurements of all contributing nations enter the "Database of the SCAR Epoch Crustal Movement Campaigns" which is being maintained at the institute in the framework of SCAR-GIANT. GNSS measurements form a basis for the realization of the International Terrestrial Reference Frame (ITRF) and its densification in Antarctica. Linked to respective products of an ongoing activity to re-process GNSS data of globally distributed stations a consistent and precise TRF realization can be reached. We will give an overview on the latest developments and the subsequent applications for geodynamic and glaciological investigations in Antarctica. Complementary to continuous GNSS observations episodic GNSS measurements have the potential to provide independent data on vertical deformations, which can be used to investigate the present-day ice-mass balance and to refine models of the glacial-isostatic adjustment. Repeated and properly referenced GNSS measurements at the ice surface yield ice-flow velocities and local ice-surface height changes. We will present latest results, e.g. for the Amundsen Sea sector, the subglacial Lake Vostok region and near-coastal regions of Dronning Maud Land or Enderby Land. Thus, it will be discussed how geodetic GNSS measurements form an important and indispensable basis for geodetic Earth system research with the focus on Antarctica.

  19. Geodynamics of ophiolites and formation of hydrocarbon fields on the shelf of eastern Sakhalin

    NASA Astrophysics Data System (ADS)

    Raznitsin, Yu. N.

    2012-01-01

    A model is proposed showing the formation of hydrocarbon fields on the shelf of eastern Sakhalin as being caused by sustained (from the Late Cretaceous to the present) extension in the adjacent deepwater Deryugin Basin with exposure of the upper mantle rocks at the bottom of the sedimentary basin. The thrust faults and detachments formed through this process facilitated the penetration of seawater into ultramafic rocks, thus providing large-scale serpentinization accompanied by generation of hydrocarbons. Extension in the Deryugin Basin was compensated by horizontal shortening at its margins, and as a result, by the formation of ophiolitic allochthons as constituents of the accretionary prism of eastern Sakhalin. Hydrocarbons were injected and pumped in the root zones of the allochthons, giving rise to their westward migration and the formation of petroleum pools in fault-line and underthrust traps on the shelf of Sakhalin Island. The Deryugin Basin is a petroleum-collecting area for oil and gas fields localized in the upper part of its western margin. More broadly, the work considers interrelations between hydrocarbon generation and the geodynamics of tectonic couples of ophiolitic allochthons and adjacent deepwater basins of marginal seas, in particular, in the western Pacific.

  20. The topical problems of identifying the results of the observations in recent geodynamics

    NASA Astrophysics Data System (ADS)

    Kuzmin, Yu. O.

    2014-09-01

    The paper addresses the problems of identifying the results of deformational observations on the Earth, which arise from the new measurement technologies and lead to the ambiguity relationships such as the "spatial size of the anomaly—density of the observation sites" and the "duration of the anomalies—degree of temporal detail of the measurements." It is found that many "paradoxical" conclusions concerning the rates and scales of the recent geodynamical processes are removed if the parameters of the measurement system match the properties of the studied object and if the relative character of the observational means is taken into account. It is shown that the time variation in the uniaxial deviatoric stress leads to the variation in the volumetric strain and, consequently, to the variation in gravity. The ambiguity in determining the ground displacement vectors by SAR interferometry is demonstrated. It is concluded that the autonomous use of the interferometry data leads to the significant distortions of the results, and these data should be necessarily used in combination with the ground-based geodetic observations.

  1. High-resolution tomography of CMB and lowermost mantle coupled by geodynamics

    NASA Astrophysics Data System (ADS)

    Soldati, G.; Boschi, L.; Forte, A. M.

    2009-12-01

    Despite the fast advances of seismic tomography in the last decades provided us with very clear and reliable images of the Earth’s mantle,seismically and/or geodynamically inferred models of core-mantle boundary topography are still poorly correlated both in pattern and amplitude. A major cause for these discrepancies is the difficulty to separate, in travel-time anomalies, the contribution of CMB topography from that of lowermost-mantle and D" heterogeneities. As an attempt to reconcile the contrasting views of the Earth's CMB, we propose an innovative approach to mapping CMB topography from seismic travel-time inversions: instead of treating mantle velocity and CMB topography as independent parameters, as has been done so far (e.g., Soldati et al., 2003), we plan to account for their coupling by mantle flow, as formulated by e.g. Forte & Peltier (1991). In practice, we shall invert direct P waves, and core-sensitive phases, with coefficients of mantle (and, possibly, core) velocity structure as the only free parameters. CMB undulations will not be treated as free parameters, but accounted for via a modification of the tomographic matrix based on the estimated physical relationship between them and mantle velocities. For the first time, the resulting tomographic maps of CMB topography will be, by construction, physically sound, while explaining the inverted seismic data.

  2. Tectonics and geodynamics of granulite-gneiss complexes in the East European Craton

    NASA Astrophysics Data System (ADS)

    Mints, M. V.

    2014-11-01

    The Neoarchean and Paleoproterozoic granulite-gneiss complexes of the northern East European Craton, including their tectonic setting, accompanying igneous and sedimentary rocks, character of metamorphism and deep structure are considered in this paper. A similar approach was applied to the description and interpretation of the granulite-gneiss complexes of the Grenville-Sveconorwegian Orogen localized in the present-day structure of the European and North American continents. One of the most important results of this study is the recognition of a new type of tectonic structures called intracontinental oval orogens. These orogens were formed in the inner domain of the Neoarchean-Proterozoic supercontinent (2.8-0.85 Ga), which is called Lauroscandia. The extensional setting, which was initiated by a series of mantle plumes, locally passing to spreading but did not lead to the eventual breakup of the supercontinent and was followed by intracontinental collisional compression accompanied by closure of short-lived local oceans, subduction, and obduction. The Neoarchean and Proterozoic granulite-gneiss belts and areas of the East European Craton are components of the Karelian-Belomorian, Kola, Volgo-Uralia, Lauro-Russian, and Grenville-Sveconorwegian intracontinental oval orogens formed in the inner domain of Lauroscandia as a result of mantle-plume and plate-tectonic processes initiated by mantle superplumes. The geodynamic settings and tectonic processes in the Neoarchean-Proterozoic supercontinent differed markedly from both the Archean tectonics of miniplates and the Phanerozoic plate tectonics.

  3. Progress in understanding the geodynamic and palaeoenvironmental evolution of the Tethys in the Lesser Caucasus

    NASA Astrophysics Data System (ADS)

    Danelian, Taniel; Asatryan, Gayané; Zambetakis-Lekkas, Alexandra; Galoyan, Ghazar; Sosson, Marc; Seyler, Monique; Sahakyan, Lilit; Grigoryan, Araiyk

    2014-05-01

    The remnants of a Mesozoic oceanic realm exist in the Lesser Caucasus (mainly in Armenia and Karabagh); this realm was once part of the Tethyan oceanic branch positioned between Eurasia and the South-Armenian Block, a Gondwana-derived terrain that can be considered as part of the Tauride-Anatolide plate. The existing Tethyan rocks of Lesser Caucasus are part of an over 2,000 Km long suture zone, running through the northern part of Turkey towards Iran. Biostratigraphic studies of the aforementioned rocks contribute vastly to get a better understanding of the geodynamic, paleogeographic and paleoenvironmental evolution of this geologically complex area. When radiolarites are the sedimentary cover of submarine ophiolitic lavas their dating provides important time constraints for the evolution of the complex Mesozoic oceanic realm. In spite of extensive sampling during the last ten years across the Sevan-Hakari (Akera) suture zone and the Vedi ophiolite we found no Triassic or Lower Jurassic radiolarites. However, as testified by some previous studies, it is likely that oceanic floor spreading was initiated during the Late Triassic. Radiolarian biostratigraphic results we have obtained establish that radiolarian ooze accumulated, and it was occasionally interrupted by lava flows, during (at least) the Bajocian to Cenomanian time interval. The Bajocian is widely established (Vedi, Sevan and Hakari ophiolites), while we have recently obtained a Cenomanian radiolarian fauna from Amasia (NW Armenia). Two late Tithonian - Valanginian radiolarian assemblages, recovered from the NE of Lake Sevan (Dzknaged and Dali sections) are of particular significance, as radiolarites are intercalated with mafic rocks formed after episodes of submarine volcanic activity. The Dali basaltic sequence overlies (with a contact displaying cataclastic structures) layered dioritic cumulates with a few plagiogranites representing the crust of an intra-oceanic island arc. Both radiolarite sequences accumulated around the Jurassic/Cretaceous transition contain rounded blocks of oolitic grainstones with fragments of crinoids; they provide evidence for shallow water platform carbonates in the neighbourhood, fragments of which slid into a bathymetrically complex oceanic sea floor. New radiolarian ages obtained recently on numerous tuffites intercalated in siliceous sequences along the Amasia-Sevan zone (Amasia, Sarinar, Old Sodk pass sections) suggest that subaerial volcanic activity was underway for most of the Middle Jurassic to Lower Cretaceous (Bajocian/Bathonian to Albian). The Vedi area (SE of Yerevan) is important in many ways, especially because it allows the detailed study of the obduction of ophiolites to the South-Armenian carbonate sequence; the latter is overlain stratigraphically by a flysch that ends with an olistostome containing a large variety of ophiolite-derived blocks. Microfacies observation of the last 150 m of the carbonate sequence suggests a back-reef inner platform depositional environment, with the presence of benthic foraminifera characteristic of a Cenomanian age. Results from the Amasia ophiolite and the Vedi carbonate sequence point to a major geodynamic change that took place during the Cenomanian, involving both the late stage of submarine oceanic magmatic activity and the obduction of ophiolites onto the South-Armenian Block.

  4. GIS-project: geodynamic globe for global monitoring of geological processes

    NASA Astrophysics Data System (ADS)

    Ryakhovsky, V.; Rundquist, D.; Gatinsky, Yu.; Chesalova, E.

    2003-04-01

    A multilayer geodynamic globe at the scale 1:10,000,000 was created at the end of the nineties in the GIS Center of the Vernadsky Museum. A special soft-and-hardware complex was elaborated for its visualization with a set of multitarget object directed databases. The globe includes separate thematic covers represented by digital sets of spatial geological, geochemical, and geophysical information (maps, schemes, profiles, stratigraphic columns, arranged databases etc.). At present the largest databases included in the globe program are connected with petrochemical and isotopic data on magmatic rocks of the World Ocean and with the large and supperlarge mineral deposits. Software by the Environmental Scientific Research Institute (ESRI), USA as well as ArcScan vectrorizator were used for covers digitizing and database adaptation (ARC/INFO 7.0, 8.0). All layers of the geoinformational project were obtained by scanning of separate objects and their transfer to the real geographic co-ordinates of an equiintermediate conic projection. Then the covers were projected on plane degree-system geographic co-ordinates. Some attributive databases were formed for each thematic layer, and in the last stage all covers were combined into the single information system. Separate digital covers represent mathematical descriptions of geological objects and relations between them, such as Earth's altimetry, active fault systems, seismicity etc. Some grounds of the cartographic generalization were taken into consideration in time of covers compilation with projection and co-ordinate systems precisely answered a given scale. The globe allows us to carry out in the interactive regime the formation of coordinated with each other object-oriented databases and thematic covers directly connected with them. They can be spread for all the Earth and the near-Earth space, and for the most well known parts of divergent and convergent boundaries of the lithosphere plates. Such covers and time series reflect in diagram form a total combination and dynamics of data on the geological structure, geophysical fields, seismicity, geomagnetism, composition of rock complexes, and metalloge-ny of different areas on the Earth's surface. They give us possibility to scale, detail, and develop 3D spatial visualization. Information filling the covers could be replenished as in the existing so in newly formed databases with new data. The integrated analyses of the data allows us more precisely to define our ideas on regularities in development of lithosphere and mantle unhomogeneities using some original technologies. It also enables us to work out 3D digital models for geodynamic development of tectonic zones in convergent and divergent plate boundaries with the purpose of integrated monitoring of mineral resources and establishing correlation between seismicity, magmatic activity, and metallogeny in time-spatial co-ordinates. The created multifold geoinformation system gives a chance to execute an integral analyses of geoinformation flows in the interactive regime and, in particular, to establish some regularities in the time-spatial distribution and dynamics of main structural units in the lithosphere, as well as illuminate the connection between stages of their development and epochs of large and supperlarge mineral deposit formation. Now we try to use the system for prediction of large oil and gas concentration in the main sedimentary basins. The work was supported by RFBR, (grants 93-07-14680, 96-07-89499, 99-07-90030, 00-15-98535, 02-07-90140) and MTC.

  5. Geodynamic Model of the New Zealand-Antarctica Conjugate Margin Since the Late Cretaceous

    NASA Astrophysics Data System (ADS)

    Spasojevic, S.; Sutherland, R.; Gurnis, M.

    2008-12-01

    Present-day plate boundaries in the Southwest Pacific were created through continental rifting since Late Cretaceous. Spreading on the Pacific-Antarctic Ridge and the southeast Indian Ridge started around 95-90 Ma and continues to the present. The New Zealand and Antarctica conjugate margins are characterized by a number of anomalous observations. The Antarctica margin and adjacent sea floor is approximately 1 km shallower than the conjugate Campbell plateau. Backstripping of the sediments from the boreholes in Campbell plateau indicates anomalously high tectonic subsidence, with a rapid subsidence phase in the period 70-40 Ma, coincident with northward drift of the Campbell plateau. Finally, the Antarctic margin is associated with a large negative geoid anomaly and low S-wave seismic velocities. We developed a three-dimensional geodynamic model of the New Zealand-Antarctica conjugate margins for last 100 million years. We used global finite-element models of mantle flow (with CitcomS) while imposing surface velocities based on the plate reconstructions from GPlates. Models are iteratively updated based on the discrepancy between predicted dynamic topography and observed borehole subsidence on the Campbell plateau and the Antarctic margin topography. Additional constraints on the model are imposed based on the discrepancies between predicted and observed present-day geoid. Long-wavelength features of anomalous observations on the New Zealand-Antarctica conjugate margin can be attributed to time-dependent evolution of a large-scale mantle upwelling. The mantle upwelling at the present day is located on the Antarctic margin, causing a relatively long-lived topography high. Campbell plateau experiences tectonic subsidence as it drifts away from this mantle upwelling. Geoid low observed on the Antarctic margin is associated with both mantle upwelling and lower mantle "slab graveyards".

  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. 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.

  8. 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.

  9. New data on the Vrancea Nappe (Moldavidian Basin, Outer Carpathian Domain, Romania): paleogeographic and geodynamic reconstructions

    NASA Astrophysics Data System (ADS)

    Amadori, Maria Letizia; Belayouni, Habib; Guerrera, Francesco; Martín-Martín, Manuel; Martin-Rojas, Iván; Micl?u?, Crina; Raffaelli, Giuliana

    2012-09-01

    A study has been performed on the Cretaceous to Early Miocene succession of the Vrancea Nappe (Outer Carpathians, Romania), based on field reconstruction of the stratigraphic record, mineralogical-petrographic and geochemical analyses. Extra-basinal clastic supply and intra-basinal autochthonous deposits have been differentiated, appearing laterally inter-fingered and/or interbedded. The main clastic petrofacies consist of calcarenites, sub-litharenites, quartzarenites, sub-arkoses, and polygenic conglomerates derived from extra-basinal margins. An alternate internal and external provenance of the different supplies is the result of the paleogeographic re-organization of the basin/margins system due to tectonic activation and exhumation of rising areas. The intra-basinal deposits consist of black shales and siliceous sediments (silexites and cherty beds), evidencing major environmental changes in the Moldavidian Basin. Organic-matter-rich black shales were deposited during anoxic episodes related to sediment starvation and high nutrient influx due to paleogeographic isolation of the basin caused by plate drifting. The black shales display relatively high contents in sub-mature to mature, Type II lipidic organic matter (good oil and gas-prone source rocks) constituting a potentially active petroleum system. The intra-basinal siliceous sediments are related to oxic pelagic or hemipelagic environments under tectonic quiescence conditions although its increase in the Oligocene part of the succession can be correlated with volcanic supplies. The integration of all the data in the "progressive reorientation of convergence direction" Carpathian model, and their consideration in the framework of a foreland basin, led to propose some constrains on the paleogeographic-geodynamic evolutionary model of the Moldavidian Basin from the Late Cretaceous to the Burdigalian.

  10. GGP - An International Project Dedicated to Studies of Geodynamics Based on Superconducting Gravimeter Observations

    NASA Astrophysics Data System (ADS)

    Kroner, C.; Crossley, D.; Hinderer, J.

    2008-12-01

    The Global Geodynamics Project (GGP) first established in 1997 and further extended in 2003 comprises a worldwide network of superconducting gravimeters (SG). Recent new observation sites include Pecný (Czech Republic), Ghuttu (India), and Austin (Texas). Several new stations are about to be established resp. panned extending the network to about 30 stations in 2009. During the last IUGG assembly in 2007 it was decided to move to a permanent network hosted by IAG and being part of GGOS. Specific GGP recommendations have been given for observation conditions, data processing, and reductions. Raw SG data are made available to the scientific community via the GGP database. A standard processing of the data sets is carried out by the International Center for Earth Tides (ICET). Of ongoing interest within GGP is the issue of consistently combining observations from absolute gravimeters and permanent GPS at the SG stations for studies related to long-term phenomena such as tectonic uplift, subduction zone slip, post-glacial rebound, and present-day ice melting, but also for research related to changes in continental hydrology. One of the most attractive innovative ideas within GGOS is the determination of the geocenter using a combination of satellite and terrestrial gravimetry. GGP can contribute in a unique way in this respect through continuous high-resolution gravity data sets (better than 1 nm/s2) in addition to measurements of absolute gravity. The continuous monitoring of temporal variations of the Earth's gravity field provides a tool to investigate many aspects of dynamics in the Earth's system and to contribute to other disciplines like seismology, volcanology, tectonics, earth rotation, oceanography, and hydrology. Another promising application is the deployment of SG sub-networks to assess temporal gravity field variations derived from satellite observations i.e. from the GRACE mission and large-scale hydrological modeling.

  11. 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.

  12. Retrieving past geodynamic events by unlocking rock archives with ?-XRF and ?-spectroscopy

    NASA Astrophysics Data System (ADS)

    De Andrade, V.; Ganne, J.; Dubacq, B.; Ryan, C. G.; Bourdelle, F.; Plunder, A.; Falkenberg, G.; Thieme, J.

    2014-04-01

    Rocks are commonly polycrystalline systems presenting multi-scale chemical and structural heterogeneities inherited from crystallization processes or successive metamorphic events. This work illustrates how spatially resolved analytical techniques coupled with thermodynamic approaches allow rock compositional variations to be related to large-scale geodynamic processes. Emphasis is placed on the contribution of quantitative chemical imaging to the study of 2.2-2.0 Gy old metamorphic rocks from the West African Craton. A thorough analysis of elemental chemical maps acquired on rock thin sections enabled high pressure relic minerals to be located and re-analyzed later with precise point analyses. The pressure-temperature conditions of crystallization calculated from these analyses are typical of modern subduction zones. These results push back the onset of modern-style plate tectonics to 2.15 Gy, i.e. more than one billion years earlier than was consensually accepted. The second part of the paper describes the imaging capabilities offered by the new ultra-bright diffraction limited synchrotron sources. Experimental data acquired with the Maia detector at beamline P06 at Petra III as well as simulations of ?-XRF spectra that will be generated at the SRX beamline at NSLS-II are presented. These results demonstrate that cm2 large chemical maps can be acquired with submicron spatial resolution and a precision suitable for thermobarometric estimates, with dwell time smaller than 1 millisecond. The last part of the paper discusses the relevance of utilizing recent X-ray fluorescence nanoprobes for diagenetic to low grade metamorphism applications.

  13. 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.

  14. Comparison, cross-validation and consolidation of the results from two different geodynamic projects working in the eastern Carpathians

    NASA Astrophysics Data System (ADS)

    Ambrosious, B.; Dinter, G.; van der Hoeven, A.; Mocanu, V.; Nutto, M.; Schmitt, G.; Spakman, W.

    2003-04-01

    Since 1995 several projects/programmes are working in the Vrancea-region in Romania with partly different intensions. First of all, the CERGOP project installed the CEGRN-network and performed GPS-measurements ('95,'96,'97,'99,'01), mainly to realise a geodetic reference frame for local geodynamic projects. In the framework of the Collaborative Research Center CRC461 "Strong Earthquakes" the Geodetic Institute of the University Karlsruhe (GIK) Densified the network up to 35 stations and carried out three GPS-campaigns ('97, '98 and '00). First results of this project were presented at the EGS-meeting 2001 in Nice. In 2002 a new geodynamic research project was initiated at the Delft Institute of Earth-Oriented Space Research (DEOS). In the context of this project, 4 permanent stations and 10 new campaign stations were installed, which leads to a common network of about 50 stations. In tight cooperation with the GIK and the University of Bucarest (Departement of Geophysics) the currently last GPS-campaign was successfully carried out in 2002. Now the great challenge and at the same time the great difficulty is a correct combination of all available GPS datasets particularly in consideration of station excentricities and variations of antenna- and receiver-types. Different evalutation strategies and software packages (Bernese-GPS-Software, GIPSY) were used to analyse the GPS data and to estimate the station velocities. Main focus of this joint-presentation is the comparison of the results from the German and Dutch geodynamic projects. The results of the two working groups are cross-validated and finally joined together in a most reasonable solution. Even if three-dimensional analysis is in work, the presentation is limited to the horizontal component.

  15. Tectono-sedimentary evolution of the Tertiary Piedmont Basin (NW Italy) within the Oligo-Miocene central Mediterranean geodynamics

    NASA Astrophysics Data System (ADS)

    Maino, Matteo; Decarlis, Alessandro; Felletti, Fabrizio; Seno, Silvio

    2013-06-01

    analyze the tectono-sedimentary and thermochronometric constraints of the Tertiary Piedmont Basin (TPB) and its adjoining orogen, the Ligurian Alps, providing new insights on the basin evolution in response to a changing geodynamic setting. The geometry of the post-metamorphic faults of the Ligurian belt as well as the fault network that controlled the Oligo-Miocene TPB deposition has been characterized through a detailed structural analysis. Three main faulting stages have been distinguished and dated thanks to the relationships among faults and basin stratigraphy and thermochronometric data. The first stage (F1, Rupelian-Early Chattian) is related to the development of extensional NNW-directed faults, which controlled the exhumation of the orogen and the deposition of nearshore clastics. During the Late Chattian, the basin drowning is marked by mudstones and turbidites, which deposition was influenced by the second faulting stage (F2). This phase was mainly characterized by NE- to ENE-striking faults developed within a transtensional zone. Since the Miocene, the whole area was dominated by transpressive tectonics. The sedimentation was represented by a condensed succession followed by a very thick, turbiditic complex. At the regional scale, this succession of events reflects the major geodynamic reorganization in the central Mediterranean region during the Oligo-Miocene times, induced by the late-collisional processes of the Alps, by the eastward migration of the Apennines subduction and by the opening of extensional basins (i. e., the Liguro-Provençal Ocean).

  16. The geodynamic evolution of the Alps: what can we learn further from the metasediments

    NASA Astrophysics Data System (ADS)

    Bousquet, R.; Oberhänsli, R.; Wiederkehr(1), M.; Schuster, R.; Schmid(2), S. M.; Koller, F.; Goffé, B.

    2009-04-01

    Based on mineralogical works, Ernst (1971) was able to use the plate tectonic concept for proposing a first modern model for the evolution of the Alps. In the meantime, Frey (1969), as well as Trommsdorff (1966), started to investigate metamorphism in isochemical systems provided by shales and siliceous carbonates, respectively. This allowed for quantitatively constraining the Cenozoic temperature evolution in the Central Alps. Frey et al. (1999) compiled all available information on the peak temperature distribution, and used the occurrence of eclogites to display the dynamics of the Alpine evolution. The regional distribution of late Cretaceous-Tertiary metamorphic conditions, documented in post-Hercynian metasediments across the entire Alpine belt from Corsica-Tuscany in the West to Vienna in the East, will be presented. Based on metamorphic studies in metasediments, we evidence substantial differences in the metamorphic, and hence the geodynamical evolution along strike the Alpine orogen. The Western Alps did not reach the mature stage of a head-on colliding belt as is indicated by a continuous metamorphic evolution, representing all the subduction related processes ranging from lower greenschist to UHP conditions. All the metamorphic rocks behind the Pennine frontal thrust were already exhumed to upper crustal level during ongoing oceanic and continental subduction and before collision with the Dauphinois domain from around 32 Ma onwards. Hence, the Western Alps represent a frozen-in subduction zone. Since then only exhumation by erosional processes affected the inner parts of the orogen. The rest of the Alpine orogen later underwent a more important collision process due to the ongoing head-on geometry of subduction and collision. It therefore often but not always shows a bimodal metamorphic evolution with two distinct P and T peaks. The intensity of the thermal overprint relates to the amount of crustal material incorporated to the orogenic wedge. Thermal overprint is primarily related to the amount of crust involved in the subduction and collision processes rather than to processes of shear or viscous heating. The latter mechanism, which suppose high deformation rate will not allow for the preservation of HP-LT assemblages within high-grade rocks. The relation between the volume of continental crust imbricated and intensity of high-temperature orogenic metamorphism can be generalized over the entire alpine edifice, except for Tuscany where the late (< 8 Ma) thermal overprint is clearly related to lithospheric thinning.

  17. 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 monitoring. The volcano source location at Westdahl is determined to be approx. 7 km below sea level and approx. 3.5 km north of the Westdahl peak. This study demonstrates that Fisher caldera has had continuous subsidence over more than 10 years and there is no evident deformation signal around Shishaldin peak.

  18. 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 initiation and evolution of hinterland basins along convergent margins has been variably attributed to partitioning of pre-existing flexural foreland basins, drainage closure by uplift of flanking topographic barriers, and/or isolated strike-slip or extensional processes. In the central Andean plateau, the upper Oligocene to middle Miocene basin fill of the northernmost Altiplano in southern Peru preserves a record of orogenesis between the Western Cordillera magmatic arc and the Eastern Cordillera fold-thrust belt. New stratigraphic, provenance, geochronologic and structural datasets from the ~3.7-km-high Ayaviri hinterland basin suggest that upper-crustal shortening was the dominant factor controlling basin evolution. The basin preserves a ~2300 m thick succession (Puno Group and Lower Tinajani Formation) of fluvial sandstone and overbank siltstone capped abruptly by ~400 m of alluvial fan pebble-boulder conglomerate (Upper Tinajani Formation). New U-Pb zircon geochronologic constraints from 8 tuff horizons and the youngest age populations from 10 sandstone horizons constrain the depositional age between 29.6 ± 1.2 Ma and 15.71 ± 0.97 Ma. The resulting ~15 Myr basin record yields sediment accumulation rates between 110 and 660 m/Myr, comparable to those of major lowland foreland basins. A prominent shift in basin provenance is recorded by detrital zircon U-Pb spectra, conglomerate clast compositions, modal sandstone compositions and paleocurrent data. Newly dated growth strata along the two basin-bounding thrust faults highlight the role of Andean shortening on basin evolution. Footwall growth strata along the southwest-directed Ayaviri fault defining the Eastern Cordillera margin suggests deformation at ~28 Ma. Younger footwall growth strata along the northeast-directed Pasani fault defining the Western Cordillera margin demonstrate an episode of out-of-sequence thrusting at ~16.4 Ma. This event is associated with the provenance and depositional shift of 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.

  19. 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

    Numerous oceanographic surveys have been conducted in Santorini Volcanic Group (South Aegean Sea) since 2001, revealing the spectacular morphology of the seafloor (multibeam data) and the sub-seafloor stratigraphic horizons (seismic profiles). Technological advancements in seafloor exploration such as ROVs and a submersible, enabled us to observe products of submarine volcanism that were previously inaccessible. In addition, gravity and box coring, geological and biological samples have been collected from selected areas for further analysis. The offshore geophysical survey in Santorini shows that recent volcanism occurred along a NE-SW tectonic zone named as Christianna-Santorini-Kolumbo (CSK) line. Christiana islets and three newly discovered submarine volcanic domes, with small colonies of yellow, presumably sulfur-reducing hydrothermal bacteria, occur in the southwestern part of the line. The presently active intra caldera volcanic domes of Palea and Nea Kameni islands and the low temperature (17-24°C) vent mounds covered by yellowish bacterial mat occupy the middle part of the line. The Santorini vent field is linked with the Kolumbo normal fault onshore which is likely controlling the pathways of hydrothermal circulation within the caldera. The most prominent feature at the NE part of this zone, is Kolumbo submarine volcanic chain which is extended 20Km with several volcanic domes aligned along this direction. The Kolumbo volcano had an explosive eruption in 1650 that killed 70 people on Santorini. The hydrothermal vent field in the crater floor of Kolumbo consists dominantly of active and inactive sulfide-sulfate structures in the form of vertical spires and pinnacles, mounds and flanges along a NE-SW trend, with temperatures up to 220°C and vigorous CO2 gas emission. For several years, the highest frequency of earthquakes was concentrated mainly in the vicinity of Kolumbo volcano. However, during 2011-2012 both seismic and geodetic unrest began abruptly 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.

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

    NASA Astrophysics Data System (ADS)

    Hetényi, György; AlpArray Working Group

    2013-04-01

    AlpArray is an initiative to study the greater Alpine area with a large-scale broadband seismological network. The interested parties (currently 57 institutes in 16 countries) plan to combine their existing infrastructures into an all-out transnational effort that includes data acquisition, processing, imaging and interpretation. The experiment will encompass the greater Alpine area from the Black Forest and the Bohemian Massif in the north to the Northern Apennines in the south and from the Pannonian Basin in the east to the French Massif Central in the west. We aim to cover this region with a high-quality broadband seismometer backbone by combining the ca. 220 existing permanent stations with additional 300-340 instruments from mobile pools, all of them to be deployed from 2014-2015 until 2017. In this way, we plan to achieve homogeneous and high resolution coverage (ca. 40 km average station spacing). Furthermore, we also plan to deploy a few densely spaced targeted networks along swaths across - and in regions of - key parts of the Alpine chain on shorter time scales. These efforts on land will be combined with deployments of ca. 40-45 ocean bottom seismometers in the Mediterranean Sea. We also aim to implement the best practice for synchronizing mobile pool operation procedures and data handling: common data centre and data management procedure, free access to data to participants as soon as possible through EIDA. Data will be open to the public 3 years after the experiment ends. The main scientific goal of AlpArray is to investigate the structure and evolution of the lithosphere beneath the Alps. A primary target is the geometry and configuration of subducting slabs and their polarity switch beneath the arc. Numerous regional questions such as seismic hazard will be tackled. Targets will be imaged at several depths (e.g., from near-surface structure down to upper mantle anisotropy), scales (e.g., from local seismicity to mantle transition zone thickness 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.

  1. 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 ca. 750 Ma, ages which were previously unknown from the EAAO. The Forster anomaly therefore separates distinctly different parts of the EAAO: a) a reworked, mainly Grenville-age crust to the W (the overprinted margin of the Kalahari Craton) and b) a part of the orogen dominated by Neoproterozoic accretionary tectonics to the E. This difference is also reflected in the geochemistry of voluminous late-tectonics granitoids across the belt.

  2. 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 practically did not cease to affect crustal growth and transformations in CAOB in relation to the migration of the Siberian continent throughout the whole time span when the belt was formed above a cluster of hotspots, which is compared with the African superplume.

  3. `rI D E NSIF IC A T I O N O F T H E IERS International GPS Service for Geodynamics

    E-print Network

    Tingley, Joseph V.

    [ J R E G I O N A L G P S N E T W O R K S IGS Central Bureau Jet Propulsion loborotory Colifornio by the IGS Central Bureau at the Jet Propulsion Laboratory, California Institute of Technology and sponsored GPS Service for Geodynamics (IGS) began discussing a new initiative, the densification of the global

  4. The seismic cycle on subduction thrusts: a laboratory validation and implications from large-scale geodynamic simulations

    NASA Astrophysics Data System (ADS)

    van Dinther, Ylona; Gerya, Taras; Dalguer, Luis; Mai, Martin; Corbi, Fabio; Funiciello, Francesca; Morra, Gabriele

    2013-04-01

    The physics governing the seismic cycle at seismically active subduction zones remains poorly understood due to restricted direct observations in time and space. In this study, we present visco-elasto-plastic continuum numerical simulations as a new tool that may help to shed light onto the interaction of subduction mechanics and associated seismicity. First, we validate that these models, typically used in long-term geodynamic simulations, are able to reproduce seismological observables. Its ability to model cycles of large analogue earthquakes is demonstrated through a validation with innovative laboratory models (van Dinther et al., 2013). This benchmark shows cycles of fast frictional instabilities can be simulated (and matched), if velocity-weakening (and velocity-strengthening) friction are incorporated in the analogue seismogenic zone (and up- and downdip of it). The resulting model captures a wide range of physical phenomena observed in nature, including a) ruptures propagating as cracks or self-healing pulses; b) repeated slip on a single patch; and c) afterslip leading to postseismic surface displacements that complement a qualitative agreement with geodetic observations. In subsequent large-scale simulations, we include slip rate dependent friction into a thermo-mechanical model of a petrologically realistic continental margin to simulate earthquake-like events with recurrence intervals of a thousand years. These events exhibit surface displacements and earthquake source parameters comparable to nature, including the amount of slip, stress drop, and rupture width. However, rupture propagation is much slower than observed. These models reveal interesting geodynamic and seismological implications, including a) a reconciliation of low effective friction expected from geodynamic models (? < 0.1) with high strengths attained in laboratory experiments (static friction of ~0.7); b) a spontaneous downdip seismogenic limit near the Moho due to plastic strength increase and stress decrease as ductile flow becomes dominant; and c) a spontaneous deceleration of the rupture speed in the up-dip direction, though velocity-strengthening friction is needed to prevent the rupture from regularly breaking the trench.

  5. 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 gases emitted since 4 billion years ago, which corresponds to an age of 1.9 to 2.3 Gyr. The variations of CO2 pressure over this period seem relatively low (50 mbar at most). This seems in line with the assumption that the heavy loss of volatiles occurred before 500 Myr. Surface temperature variations are likely to be small (several Kelvin) and would not be responsible for periods of flowing liquid surface water by themselves. Water is abundant on Mars during the whole 4 billion years evolution (between 30% and 150% of the present day water) but is unlikely to reside in the atmosphere or in liquid form. In the case of Venus, we are able to reproduce a mantle convection behaviour showing what could be interpreted as resurfacing events with times of high activity separated by quieter periods. Atmospheric escape is also different; it is much lower than on Mars. During the last 4 Gyr, CO2 pressure doesn't seem to vary significantly, while water pressure decreased by several millibars, which induced a surface temperature variation of several tens of kelvins and illustrates the dry state of present-day Venus.This is in agreement with calculated isotopic ratios for noble gases such as Neon and Argon.

  6. Eclogite in West Papua (Wandamen Peninsula), petrological and geochemical characterization : geodynamical implications

    NASA Astrophysics Data System (ADS)

    de Sigoyer, Julia; Pubellier, Manuel; Bailly, Vivien; Ringenbach, Jean-Claude

    2010-05-01

    The Lengguru accretionary wedge (West Papua) is located in a very active geodynamical context. It results from the oblique convergence between the Pacific plate and the Australian plate. All the wedge has been build between 11 and 2 Ma (Bailly et al., 09). Exceptional boulders of fresh eclogites were discovered in the internal part of the Lengguru wedge, in the so called Wandamen peninsula. The Wandamen peninsula displays an increasing metamorphic gradient from West to East. This metamorphic peninsula may also be regarded as the continuation of the inner part of the Central range of Papua New Guinea farther east. The eclogites area embedded in metasediments that present similarities with Mesozoic and Cenozoic sediments of the Australian margin in the continuation of Lengguru wedge. According to geochemical analysis of major and traces elements on the two freshest eclogites, their protolith has a Fe-Ti gabbroic composition. The CIPW norm of these rocks suggest a protolith, with 32% of pyroxenes, 47% of anorthite, less than 3% of olivine, with 7% of ilmenite and 7% of magnetite. Major elements show a tholeiitic characters. Traces elements suggest a T MORB signature with a high content of TiO2. The eclogites are medium to coarse grained. The metamorphic paragenesis consists of clinopyroxenes, garnets, amphiboles, rutiles, quartz and accessory minerals like apatites. Clinopyroxenes with omphacitic composition (XJd: 0.3-0.4) are poecilitic, rare textures of retrogression (symplectites) are observed. Symplectites are composed by diopside or Na-Ca-Fe pyroxene XJd (0.18) and albite, locally calcic amphiboles can replace the clinopyroxene. Garnet of several millimeters (3-4 mm) result from the aggregation of smaller euhedral crystals (500-700 µm). Some of them display atoll microstructure and exhibit a core filled by omphacite, slightly green amphibole, or by quartz. They contain minute inclusions of omphacite, amphibole, apatite, quartz. Many rutiles exsolutions are observed within the garnets, suggesting high metamorphic conditions. Garnets have a mixed composition between almandine and grossular. Inclusions of quartz in both garnet and omphacite are surrounded by fractures suggesting the previous occurrence of coesite. The sodic calcic and calcic greenish amphiboles are also important minerals of these eclogites. The PT conditions deduced from the eclogitic paragenesis are 14±3 kbar, 650±50°C. The Lengguru accretionary wedge has been active during 8 millions years, (between 11 and 2 Ma). So far we do not know the age of eclogitisation. However it is probably related to the accretionary wedge. Miocene pebbles were found engulfed within unmetamorphozed conglomerate (no metamorphic or magmatic pebbles were in the conglomerate) that overlies the eastern flank of the Wandamen massif suggesting that exhumation of eclogite was active after Miocene. Most of blueschist and eclogitic rocks in the world require at least 15 Ma for their formation and exhumation. These eclogites require the exceptional rapid process. Agard, P.,Yamato, P., Jolivet, L., Burov, E., (2009) Exhumation of oceanic blueschists and eclogites in subduction zones:Timing and mechanisms, EPSL, , 53-79 Bailly V., Pubellier M., Ringenbach J-C., de Sigoyer J., Sapin F. Jumps of deformation zones in a young convergent setting; the Lengguru fold-and-thrust belt, New Guinea Island, Lithos, doi:10.1016/j.lithos.2009.08.013

  7. Tracing lithosphere amalgamation through time: chemical geodynamics of sub-continental lithospheric mantle

    NASA Astrophysics Data System (ADS)

    Wittig, Nadine

    2014-05-01

    The theory of plate tectonics is a relatively young concept in the Earth Sciences and describes the surface expression of planetary cooling via magmatism and reconciles mantle convection and plate movement with orogenesis, earthquakes and volcanism. Detailed observation of current tectonic plate movement has purported a relatively clear picture of the planet's geodynamics. Modern oceanic basins are the predominant sites of thermal equilibration of Earth interior resulting from decompressional, convective melting of peridotites. This magmatism generates mid-ocean ridge mafic crust and depleted upper mantle and in this model, oceanic crust becomes associated with buoyant mantle to form oceanic lithosphere. Subduction zones return this material together with sediments into the deeper mantle and presumably aid the formation of continental crust via arc magmatism. The mechanisms of continental crust amalgamation with buoyant mantle are less clear, and distinctly more difficult to trace back in time because metamorphism and metasomatism render the processes associating convecting mantle with continental crust elusive. Paramount in assessing these mechanisms is understanding the timing of crust and mantle formation so that the onset of plate tectonics and potential changes in modi operandi with respect to convection, mantle composition and melting pressure and temperature may be traced from the early Hadean to the present day. Typically the formation age of continental crust is more easily determined from felsic samples that contain accessory and relatively robust phases such as zircon and monazite that render a geochronological approach feasible. The lack of equally robust minerals and pervasive and ubiquitous metasomatism afflicting obducted orogenic peridotites and mantle xenoliths obliterates primary mineralogical and geochemical information. Hence it has proven difficult to acquire mantle depletion ages from continental lithospheric mantle, perhaps with the exception of Re-Os isotope dating of cratonic peridotites. Empiric mineralogical and geochemical data of continental and oceanic lithospheric mantle has been examined extensively and metasomatism has been studied in great detail. I will present a numerical modelling approach generating a comprehensive catalogue of variously depleted plagioclase-, spinel- and garnet-peridotite major and trace element compositions. In addition primary Pb, Sr, Nd, Hf and Os isotope data will approximate refractory mantle generated during Earth's major episodes of depletion and continental crust formation (1.2, 1.8, 2.9, 3.8 Ga). These hypothetical compositions will be compared to natural peridotites from on- and off-cratonic xenoliths, abyssal and orogenic peridotites to identify those rare samples least altered by interaction with silicate, hydrous and carbonatitic melts. Extremely depleted mantle has the potential to harbour Pb, Sr, Nd, Hf and Os isotope compositions that would be easily recognized if silicate melts were generated from this type of pristine mantle and the record of volcanic rocks will be examined to identify potential lithospheric melts.

  8. Geodynamical and Geochemical Features of Oil Generation in Sedimentary Basin of Volga-Ural Region

    NASA Astrophysics Data System (ADS)

    Plotnikova, I.

    2009-04-01

    Oil and gas prospects of Paleozoic sedimentary rocks of Volga-Ural Anticline (VUA) various researchers evaluate in different ways. More than 150 oil fields in Paleozoic formations were discovered in the eastern half of Republic of Tatarstan of the East European Platform. There were not found any significant fields in the western areas of investigation region. According to many investigators, the western part of the Tatarstan has unfavourable geological structure from oil and gas potential view. Solution of problem concerning revealing HC source for the fields of Volga-Ural oil and gas province certainly would alow to discuss about further prospects of this territory. Data available evidence that during Paleozoic time, an area of the present-day South-Tatarian Arch (STA) and North-Tatarian Arch was a passive continental margin along which a sediments rocks up to 2 km thick was accumulated. Generation potential of organic matter containing in increased concentrations in domanikoid deposits was obtained. It has been discovered that the cumulative production in some oil areas of the Romashkino oil field substantially exceeds formerly proven, recoverable, reserves. Moreover, the volume of oil produced has already significantly exceeded the amount of oil that the Domanik strata could have generated as supposed source rocks of the South Tatarstan arch and the adjacent areas. Cumulative oil production in Tatarstan has already reached 3.0B tons, thus substantially exceeding 709M tons, calculated geochemically on the basis of the Paleozoic source rock potentials of all sedimentary strata. This discrepancy obviously shows the impossibility for the commercial amounts of hydrocarbons of being generated from the available material of the sedimentary cover. Some experts explain this phenomenon by the errors made in the reserve estimates. But another consider this as the inflow or replenishment by the hydrocarbon flow from the crystalline basement along the faults. Who is right? It is very difficult and debatable scientific problem. Based on numerous facts of many years studies of Archean-Proterozoic basement and it role in oil field formation of sedimentary cover it is being developed a working hypothesis about sources of oil. Oil from the Paleozoic of the STA is genetically identical to bitumoids of the basement, which is in itself indicative of the vertical migration of oil, for the sedimentary cover above STA has no adequate petroleum source. It is possible, source of oil don't connected with only sedimentary rocks of STA and the adjacent areas. This fact is forced us to search for another reasons of formation such gigantic oil field as Romashkino. As result of this there is appear the hypothesis of vertical migration of oil and oil saturated fluid from source located below the surface of crystalline basement. Existence of process of the modern fluid migration is confirmed by results of different examinations, which have carry out independently in different field of science. Analysis of a variety of elements by several methods of rocks, oil, bitumen samples from sedimentary cover and crystalline basement was performed. New geodynamical features of generation of Kamsko-Kinelskaia intraformational flexure were investigated.

  9. 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's density were built by the interpolation from the values of the ratio of oil flow rates before and after the inversion in the wells. These data was selected as a characterizing of the inversion strength. Thereby we created the convenient and informative geodata base through using GIS technology. The comprehensive interpretation of a series of maps, created by ArcGIS software package, is in progress. Firstly an analysis of the location of arrangement of the production wells, in which was occurred inversion of oil production in the process of production activity was made. After this, we compared their location with the block structure scheme. We noticed that the wells are grouped in linear- elongated zone along the fault, there is an affinity of this well to the certain parts of the small-sized blocks. The development of scientific and practical research in this direction is of a high significant because it can lead to a change in the strategy and methodology of the geological prospecting on the one hand and of the exploration of hydrocarbon deposits on the other hand.

  10. Absolute gravity measurements in Switzerland: Definition of a base network for geodynamic investigations and for the Swiss fundamental gravity net

    NASA Astrophysics Data System (ADS)

    Marson, I.; Kahle, H.-G.; Chaperon, F.; Mueller, St.; Alasia, F.

    1981-09-01

    Results of two absolute gravity surveys performed in Switzerland between 1978 and 1979 are presented and discussed in the framework of the uplift history of the Swiss Alps. Five absolute stations have been established as a contribution to the Swiss fundamental gravity net as well as to geodynamic investigations on the Alpine uplift. Two sites (Interlaken-Jungfraujoch) form the end points of a calibration line for field gravimeters. The gravity range of this line amounts to 605 × 10-5 ms-2 (=605 mgal). It can be traversed in a relatively short time interval of less than 3 hours. Two other sites (Brig and Chur) are located in the area of the most negative gravity anomalies and highest uplift rates encountered in Switzerland. They serve as reference stations for a more extended gravity net for studying non-periodic secular gravity variations associated with the Alpine uplift.

  11. Six years analysis of HemusNET permanent GPS network data - impact on geodynamics of the Balkans

    NASA Astrophysics Data System (ADS)

    Georgiev, Ivan; Ganas, Athanassios

    2013-04-01

    The presentation outlines results for horizontal motion of the crust in the Balkans, mainly Bulgaria and Northern Greece, obtained by processing and analyzing of data from permanent GPS sites during the period 2007 - 2012. Estimates of horizontal velocities of stations in Bulgaria and Northern Greece obtained by GAMIT/GLOBK along with geological and seismotectonic information give the opportunity to draw inferences about the recent tectonic activity in this area and its position within the East Mediterranean geodynamic processes. The GPS velocities in Bulgaria and Northern Greece exhibit a clear tendency to increase from north to south. The obtained results suggest that the transition zone between "stable" Eurasia and the Aegean extensional province is located south from the Balkan (Hemus) Mountain and to the western parts of the North Anatolian Fault - the so-called South Balkan extensional region.

  12. Subduction geodynamics in Archean and formation of diamond-bearing lithospheric keels and early continental crust of cratons

    NASA Astrophysics Data System (ADS)

    Shchipansky, A. A.

    2012-03-01

    The diamond-bearing mantle keels underlying Archean cratons are a unique phenomenon of Early Precambrian geology. The common stable assemblage of the Archean TTG early continental crust and underlying subcontinental lithospheric mantle clearly shows their coupled tectogenesis, which was not repeated in younger geological epochs. One of the least studied aspects of this phenomenon is concerned with the eclogitic xenoliths carried up by kimberlite pipes together with mantle-derived nodules. The eclogitic xenoliths reveal evidence for their subduction-related origin, but the Archean crustal counterparts of such xenoliths remained unknown for a long time, and the question of their crustal source and relationships to the formation of early continental crust remained open. The Archean crustal eclogites recently found in the Belomorian Belt of the Baltic Shield are compared in this paper with eclogitic xenoliths from kimberlites in the context of the formation of both Archean subcontinental lithospheric mantle (SCLM) and early continental crust. The crustal eclogites from the Belomorian Belt are identical in mineral and chemical compositions to the eclogite nodules (group B), including their diamond-bearing varieties. The eclogite protoliths are comparable in composition with the primary melts of the Meso- and Neoarchean oceanic crust, which was formed at a potential temperature of the upper mantle which exceeded its present-day temperature by 150-250 K. The reconstructed pathways of the Archean oceanic crust plunging in the upper mantle suggest that the Archean mantle was hotter than in the modern convergence settings. The proposed geodynamic model assumes coupled formation of the Archean diamond-bearing SCLM and growth of early continental crust as a phenomenon related to the specific geodynamics of that time controlled by a higher terrestrial heat flow.

  13. 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.

  14. 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.

  15. 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 like vertical drips; and topography cannot be sustained for geologically relevant timescales. Yet, despite those problems, the relative lack of earthquakes underneath the Moho remains an intriguing fact, which is also found in other mountain belts such as the Swiss Alps. The two modelling approaches that are used to interpret the data, however, are based on highly simplified assumptions. The 1D Christmas-tree approach assumes that strain rates are homogeneous throughout a vertical section of the lithosphere. EET-based estimations assume that the lithosphere is an elastic layer over an infinite half space. In reality, however, the lithosphere is expected to have depth- and temperature-dependent material properties, and it is unclear whether strain rates in such a lithosphere are indeed constant with depth. For this reason, we here use a 2D modelling approach that takes geometrical complexities as well as mantle-lithosphere interaction into account. Rather than modelling the evolution of the India-Asia collision over a million-year timescale, as would typically be done with such an approach, we here restrict ourselves to the present-day rheological stratification of the lithosphere. The advantage of such quasi-instantaneous lithospheric models is that they require only a few time steps per simulations and can therefore cover a wide parameter space. As input we use relatively well-constrained datasets such as surface topography, Moho depth (where available), and far field convergence velocity. From this, the state-of-stress of the lithosphere, its surface velocity, gravity anomalies and mantle flow fields are computed as a function of lithospheric geometry and rheological stratification. Model results show that the response of the lithosphere and flow in the underlying mantle are significantly influenced by the rheology of the lithosphere, in particular by the effective viscosity of the mantle lithosphere. Models, in which the mantle lithosphere and lower crust are ‘weak' become unstable and result in a Tibetan plateau that disappears in geologically small time

  16. 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 oil and organic matter in sedimentary cover rocks that were carried out within the last decade gave us new and unexpected conclusions. First, on the basis of pyrolysis it was found that the top agent of domanikits of the upper Devonian (which were traditionally considered to be a source rock for most crudes of the Volga-Ural region) is characterized by a low degree of catagenetic maturity. These rocks were not submerged to the depth of more than 2.5 km and were not included in the main area of oil and gas formation in most parts of its distribution within the Republic of Tatarstan, which corresponds to the main territory of North- and South-Tatar arch with surrounding areas of deflections and depressions. Comprehensive study of oil from the anomalous wells showed that these oils have certain characteristics different from normal oil wells, therefore, the hypothesis of a modern inflow of hydrocarbons is consistent and specific studies of this process should be continued. The estimated (by biomarker parameters) lack of genetic relationship between oil from producing under-domanik horizons (Pashi, Timansky, Ardatovsky and Vorobyevsky) and the top agent in domanikits indicates the need for searching of the sources of oil generation and confirms the viability of the hypothesis of deep origin of HC and their inflow into the sedimentary cover through the crystalline base. The oil from the anomalous wells should be subject to special investigations in the monitoring mode designed to examine the isotopic systematics of Sr and Nd, isotope characteristics of helium, carbon, hydrogen, nitrogen in the dissolved gases. The design of these studies needs to be linked, in the first place, with the seismic events continuing on the territory of Tatarstan, as the relationship between the change of the carbon isotopic composition and the seismic events has previously been established. Also in the condition of a recurrent inflow of new portions of the deep HC, it would be logical to assume the changes in the isotopic composition of elements of the dissolved gas.

  17. 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.

  18. Comparative analysis of geodynamic activity of the Caucasian and Eastern Mediterranean segments of the Alpine-Himalayan convergence zone

    NASA Astrophysics Data System (ADS)

    Chelidze, Tamaz; Eppelbaum, Lev

    2013-04-01

    The Alpine-Himalayan convergence zone (AHCZ) underwent recent transverse shortening under the effect of collisional compression. The process was accompanied by rotation of separate microplates. The Caucasian and Eastern Mediterranean regions are segments of the of the AHCZ and are characterized by intensive endogenous and exogenous geodynamic processes, which manifest themselves in occurrence of powerful (with magnitude of 8-9) earthquakes accompanied by development of secondary catastrophic processes. Large landslides, rock falls, avalanches, mud flows, etc. cause human deaths and great material losses. The development of the aforesaid endogenous processes is set forth by peculiarities of the deep structure of the region and an impact of deep geological processes. The Caucasus is divided into several main tectonic terranes: platform (sub-platform, quasi-platform) and fold-thrust units. Existing data enable to perform a division of the Caucasian region into two large-scale geological provinces: southern Tethyan and northern Tethyan located to the south of and to the north of the Lesser Caucasian ophiolite suture, respectively. The recent investigations show that the assessments of the seismic hazard in these regions are not quite correct - for example in the West Caucasus the seismic hazard can be significantly underestimated, which affects the corresponding risk assessments. Integrated analysis of gravity, magnetic, seismic and thermal data enables to refine the assessment of the seismic hazard of the region, taking into account real rates of the geodynamic movements. Important role play the last rheological constructions. According to Reilinger et al. (2006) tectonic scheme, the West flanking of the Arabian Plate manifests strike-slip motion, when the East Caucasian block is converging and shortening. The Eastern Mediterranean is a tectonically complex region located in the midst of the progressive Afro-Eurasian collision. The recent increasing geotectonic activity in this region highlights the need for combined analysis of seismo-neotectonic signatures. For this purpose, this article presents the key features of the tectonic zonation of the Eastern Mediterranean. Map of derivatives of the gravity field retracked from the Geosat satellite and novel map of the Moho discontinuity illustrate the most important tectonic features of the region. The Post-Jurassic map of the deformation of surface leveling reflects the modern tectonic stage of Eastern Mediterranean evolution. The developed tectono-geophysical zonation map integrates the potential geophysical field analysis and seismic section utilization, as well as tectonic-structural, paleogeographical and facial analyses. Tectonically the map agrees with the earlier model of continental accretion (Ben-Avraham and Ginzburg, 1990). Overlaying the seismicity map of the Eastern Mediterranean tectonic region (for the period between 1900 and 2012) on the tectonic zonation chart reveals the key features of the seismo-neotectonic pattern of the Eastern Mediterranean. The results have important implications for tectonic-seismological analysis in this region (Eppelbaum and Katz, 2012). A difference in the geotectonic patterns makes interesting comparison of geodynamic activity and seismic hazard of the Caucasian and Eastern Mediterranean segments of the AHCZ.

  19. About Geodynamic Situation of the Formation and Development of the Inside Formation Throughs of the Volga-Ural Region

    NASA Astrophysics Data System (ADS)

    Plotnikova, Irina

    2010-05-01

    The study area is the South Tatarstan Arch located in the Volgo-Ural Region, which is an enigmatic crustal segment occupying one third of the East European Platform. Tatarstan remains the oil-richest region of the Volga-Urals petroleum province. Sedimentary geological section consists of terrigenous-carbonate rocks of Devonian, Carboniferous and Permian systems. Its thickness is as much as 1,6 - 1,7 km in the most elevated parts of South Tatarsky Arch. It is supposed that deposits of Semilukian horizon (D3fm) represented by carbonate and argillo-carbonate silicified rocks characterized by the 3-5% abundance of organic carbon are major oil-generating complexes within the limits of this area. Oil accumulations are confined mostly to terrigenous reservoirs of the Lower Frasnian stage and to a lesser extent to sandy-aleurolite rocks of the Lower and Middle Carboniferous. Submeridional, latitudinal and diagonal faults related to processes taking place in the crystalline basement at the Early Paleozoic stage are predominating among faults identified within the limits of the studied area. The traces of discontinuities are identified from the gabbro - diabase dykes, products of the volcanic activity encountered in the Middle Devonian deposits, and from increased fracturing of rocks. Faults of various ranks are distinctly exhibited in the up-to-date relief. In the sedimentary cover faults are exhibited as flexure - discontinuity zones or structural terraces, they serve as boundaries between sharply replaced facies and sharp changes in the thickness of deposits. Problem of the origin and development of the Kama-Kinel inside formation through (KKIFT) as before is topical and significant for understanding of geodynamic situation of paleoshelf of East-European platform in Middle-Upper Devonian. Absence in KKIFT of thick, massive carbonaceous rocks and occurrence of decreased thickness of clay- silicon-carbonaceous organic-rich sediments - result of the different conditions of the sedimentation processes, different conditions of the gas-water composition characteristics of the marine basin, different conditions of the lithosphere. Paleogeografical, paleotectonical, lithofacies conditions - result of the specific geodynamic and fluid regime of the sedimentftion. Similar forms are widespread on the territory of the Volga-Ural antecline (from Samara area in the south to Perm in the north) and are of significant interest for regional petroleum geology as a whole. Section correlation of recognized components demonstrates their tectonic regime was deal with lithosphere decompression, active gas-fluid regime of the reduced system. Problem of studying carbonate deposits and their reservoir potential is related to the most important for board parts of the KKIFT.

  20. New evidence of delamination in the Western Alboran Sea. Geodynamic evolution of the Alboran domain and its margins

    NASA Astrophysics Data System (ADS)

    Timoulali, Youssef; Djellit, Hamou; Hahou, Youssef; Jabour, Nacer; Merrouch, Redouane

    2014-07-01

    The presence of continuous upper crustal blocks between the Iberian Betics and Moroccan Rif in the western and middle Alboran Sea, detected with tomography, can add new information about the lithosphere structure and geodynamic evolution in this region. A large volume of seismic data (P and S wave arrival times) has been collected for the period between 1 December 1988 and 31 December 2008 by 57 stations located in northern Morocco (National Institute of Geophysics, CNRST, Rabat), southern Portugal (Instituto de Meteorologia, Lisbon) and Spain (Instituto Geografico National, Madrid) and used to investigate the lithosphere in the western Alboran Sea region. We use a linearized inversion procedure comprising two steps: (1) finding the minimal 1-D model and simultaneous relocation of hypocenters and (2) determination of local velocity structure using linearized inversion. The model parameterization in this method assumes a continuous velocity field. The resolution tests indicate that the calculated images give near true structure imaged at 5 km depth for the Tanger peninsula, the Alhoceima region and southern Spain. At 15, 30 and 45 km depth we observe a near true structure imaged in northern Morocco, and southern Spain. At 60 and 100 km, southern Spain and the SW region of the Alboran Sea give a near true structure. The resulting tomographic image shows the presence of two upper crustal bodies (velocity 6.5 km/s) at 5-10 km depth between the Betics, Rif, western and central Alboran Sea. Low velocities at the base of these two bodies favor the presence of melt. This new evidence proves that the Tethysian ocean upper crust was not totally collapsed or broken down during the late Oligocene-early Miocene. These two blocks of upper crust were initially one block. The geodynamic process in the eastern of the Mediterranean is driven by slab rollback. The delamination process of the lithospheric mantle terminates with the proposed slab rollback in the western part of the Mediterranean. This can be explained by the removal of the major part of the lithosphere beneath the area, except in the SW part of the Alboran Sea where a small part of the lithospheric mantle is still attached and is extends and dips to SE beneath the Rif, slowly peeled back to the west. A second detached lithospheric mantle is located and extends to eastern part of the Rif and dips to the SE. The removal of lithosphere mantle from the base of the crust was replaced and heated by extrusion of asthenospheric material coming from depth to replace the part of crust detached. A combination of isostatic surface/topographic uplift and erosion induced a rapid exhumation and cooling of deep crustal rocks.

  1. 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 popula- tion sickness cases in Dnipropetrovsk City (1.2 million persons) are described by the multi-factor predictive SEIS & GIS model of geopathogenic zones that determines the human health risk and hazards. Results and Conclusions. We have created the SEIS system and multi-factor predictive SEIS model for the analysis of phase-metric spatio- 1 temporal nonlinear correlation and variations of rhythms of human health, ecological, genetic, epidemiological risks, demographic, socio-economic, bio-geophysical, bio- geodynamic processes in geopathogenic hazard zones. Cosmophotomaps "CPM" of vegetation index, anthropogenic-landscape and landscape-geophysical human health risk of Dnipropetrovsk City present synthesis-based elements of multi-layer GIS, which include multispectral images SPOT o, maps of different geophysical, geochem- ical, anthropogenic and citogenic risk factors, maps of integral oncologic case rate frequency, general and primary population sickness cases for administrative districts. Results of multi-layer spatio-temporal correlation of geophysical field parameters and variations of population sickness rate rhythms have enabled us to state grounds and to develop medico-biological and bio-geodynamic classification of geopathogenic zones. Bio-geodynamic model has served to define contours of anthropogenic-landscape and landscape-geophysical human health risk in Dnipropetrovsk City. Biorhythmic vari- ations give foundation for understanding physiological mechanisms of organism`s adaptation to extreme helio-geophysical and bio-geodynamic environmental condi- tions, which are dictated by changes in Multi-factor Correlation Stress Field "MCSF" with deformation of 5D SEIS. Interaction between organism and environment results in continuous superpositioning of external (exogenic) Nuclear-Molecular-Cristallic "NMC" MCSF rhythms on internal (endogenic) Nuclear-Molecular-Cellular "NMCl" MCSF rhythms. Their resonance wave (energy-information) integration and disinte- gration are responsible for struc

  2. Methodical questions and accuracy problems of GPS observations by the example of the geodynamic proving ground in Bishkek

    NASA Astrophysics Data System (ADS)

    Kuzikov, S. I.

    2014-11-01

    The key questions concerning the modern methodical tasks and accuracy of GPS measurements of crustal motion spanning are discussed for a full cycle of the survey from the organization of the field operations to the interpretation of the final results. The presented data rely on the 20-year experience of the geophysicists of the Research Station of the Russian Academy of Sciences in Bishkek (RS RAS) in GPS monitoring at the Geodynamic Proving Ground in Bishkek (GPGB) and in a large part of Central Asia. The comparative characteristics of the constellations of visible GPS and GLONASS satellites are analyzed from the standpoint of their practical application for precise scientific observations of crustal motions. The studies of the contemporary movements of the Earth's crust by the methods of satellite geodesy generally comprise three stages: (1) organization of the measurement networks and acquisition of the data; (2) data processing; and (3) interpretation of the results. Each stage is associated with its own block of the tasks and problems, and neither is guaranteed against uncertainties and errors which may affect the results, conclusions, and reconstructions.

  3. 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.

  4. 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.

  5. 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.

  6. Geodynamic control on carbonate diagenesis: Petrographic and isotopic investigation of the Upper Jurassic formations of the Paris Basin (France)

    NASA Astrophysics Data System (ADS)

    Vincent, Benoit; Emmanuel, Laurent; Houel, Pascal; Loreau, Jean-Paul

    2007-04-01

    The Oxfordian and Kimmeridgian carbonates of the eastern edge of the Paris Basin display poor reservoir properties ( ? < 15% and K < 0.1 md). The petrographic investigation and the resultant paragenetic sequence show that this is due to extensive precipitation of 2 types of almost synchronous blocky LMC (Low Magnesian Calcite) cements during mesogenesis (burial). Stable isotope investigation of these non-recrystallized cements, through both microdrilling sampling and in-situ SIMS (Secondary Ion Mass Spectrometry) analysis, shows that they originated from slightly buffered meteoric fluids (- 3‰ SMOW to - 8‰ SMOW) flowing through the Malm carbonate aquifers of the eastern edge of the Paris Basin. After a review of the post-Upper Jurassic history of the Paris Basin, it appears that meteoric water supplies leading to such cementations were associated with the evolution of the basin's geodynamic setting, and notably with the LCU (Late Cimmerian Unconformity) major event which corresponds to the uplift of the London-Brabant massif. Denudation of the Oxfordian and Kimmeridgian carbonates on the southern flank of the London-Brabant massif, to the north of the study area, then lead to lateral recharging of the associated aquifers with meteoric fluids. This scenario is similar to the one proposed to explain cementations of the Jurassic carbonates in the Wessex-Weald Basins which emphasizes the main role played by the Cretaceous unconformities over carbonate diagenesis at the scale of the northwestern Tethys margin.

  7. Robust coupled fluid-particle simulation scheme in Stokes-flow regime: Toward the geodynamic simulation including granular media

    NASA Astrophysics Data System (ADS)

    Furuichi, Mikito; Nishiura, Daisuke

    2014-07-01

    present a simulation scheme for solving high-viscosity fluid and particle dynamics in a coupled computational fluid dynamics and discrete element method (CFD-DEM) framework. This simulation scheme is intended to be used for geodynamical magmatic studies such as crystal settling at the melting roof of a magma chamber. The high-viscosity fluid is treated by the Stokes-flow approximation, where the fluid interacts with particles via the drag force in a cell-averaged manner. The particles are tracked with contact forces by DEM. To efficiently solve such Stokes-DEM coupled equations, we propose two key techniques. One is formulation of particle motion without the inertial term, allowing a larger time step at higher viscosities. The other is a semi-implicit treatment of the cell-averaged particle velocity in the fluid equation to stabilize the calculation. We simulate the settling particles in strongly viscous fluids in three dimensions and compare the results with the experimental and theoretical results. Our solution strategy is found to be robust and successfully captures the collective behavior of the particles. The simulation method presented here will be useful in various fields interested in long-term dynamics of high-viscosity granular media.

  8. Geodynamic significance of Late Triassic to Early Cretaceous volcanic sequences of Vizcaino Peninsula and Cedros Island, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Rangin, C.; Girard, D.; Maury, R.

    1983-09-01

    The Mesozoic prebatholitic terranes of central Baja California include distinct volcanic sequences associated with sediments, ranging in age from Late Triassic to Early Cretaceous. These volcanic-sedimentary sequences are parts of a large “nappe” lying on top of blueschist-bearing melanges. The magmatic parentages of basic lavas from the allochthonous units have been determined from major- and trace-element analyses of total rocks and microprobe data from their calcic clinopyroxene phenocrysts. The results show two major types of basic volcanism, linked to extensional processes (nonorogenic tholeiites) and to compressional processes (orogenic tholeiites), respectively. This study documents a complex Mesozoic geodynamic evolution for this area before nappe emplacement during the Albian. On the basis of these data, the Late Triassic to Albian geologic history of this area is interpreted in terms of two successive episodes of marginal oceanic basin development, followed, respectively, by subduction and collision processes. Note: A sample locality map and cross sections and tables of geochemical data on Mesozoic rocks of Puerto Escondido, San Andrés-Cedros, and Morro Hermoso, and of microprobe analyses of calcic clinopyroxene phenocrysts, Puerto Escondido and San Andrés-Cedros are available by requesting Supplementary Data 83-16 from Documents Secretary, Geological Society of America, P.O. Box 9140, Boulder, CO 80301.

  9. Present-day geodynamics of the Mediterranean-Lesser Caucasus part of the Alpine-Indonesian Mobile Belt

    NASA Astrophysics Data System (ADS)

    Shevchenko, V. I.; Lukk, A. A.; Prilepin, M. T.; Reilinger, R. E.

    2014-01-01

    At present, the concept of plate tectonics is predominant in the Earth sciences. However, there are also other, less popular ideas concerning the geodynamics of the Earth's crust/lithosphere. The highly accurate modern geodetic measurements such as GPS, SLR, and VLBI provide a new framework for assessing different standpoints. The results of global-scale geodetic measurements are in close agreement with the global plate tectonic reconstructions. However, the same measurements of regional networks in the Mediterranean part of the Alpine-Indonesian Mobile Belt yield results that disagree with the plate's tectonic reconstructions for this region. These measurements show that the belt's width in many areas of Eurasian and African lithospheric plates' convergence is not decreasing at present, as follows from the plate reconstructions, but increasing. At the same time, the segments of the belt under consideration are in a state of stress characterized by near-horizontal compression oriented across the strike of the belt. This contradiction can only be explained if it is assumed that the formation of the tectonic structure of the mobile belt is related to the active growth of the volume of the bedded rocks of the belt, i.e., of the plate's convergence zone. This growth is apparently due to the additional mineral material gained by the ascending mantle fluid flows. This implies that local, autonomous dynamic processes are required in addition to the lithospheric plate's interactions to account for the tectonic deformations observed in the mobile belt.

  10. Palaeostress analysis, a contribution to the understanding of basin tectonics and geodynamic evolution. Example of the Permian/Cenozoic tectonics of Great Britain and geodynamic implications in western Europe

    NASA Astrophysics Data System (ADS)

    Hibsch, Christian; Jarrige, Jean-Jacques; Cushing, Edward Marc; Mercier, Jacques

    1995-12-01

    Microtectonic analysis in association with tectonic-sedimentological observations enables us not only to define palaeostress tensors but also to date each of them. Such a study, carried out in central and northeastern England and in southernmost Wales has permitted us to point out several tectonic stages during the Permian-Cenozoic period. (1) Inferred from syn-sedimentary faulting in the Late Permian series, the Permian/Early Triassic tectonic regime is characterised by a NNW-SSE-oriented extension. (2) During the Late Triassic to the early Late Jurassic, an E-W- to ENE-WSW-oriented extension was acting as suggested by syn-sedimentary normal faulting in Keuper, Lias and Middle Dogger sediments and post-sedimentary normal faulting in Oxfordian sediments. (3) The following tectonic event probably started during the Malm and was particularly active during the Early Cretaceous. It was characterised by a N-S- to NNE-SSW-oriented extension and was associated with an E-W- to WNW-ESE-oriented strike-slip tectonic regime (transtension). (4) A locally observed NW-SE-oriented transpressional strike-slip tectonic regime is thought to correspond to the 'Laramide' inversion phase of the Middle Paleocene. (5) The later tectonic event is characterised by a N-S-oriented transpressional strike-slip regime and affects a Paleocene tholeiitic dyke ('Cleveland dyke'). It is supposed to be synchronous with the so-called Eocene 'Pyrenean' to the Early Miocene 'Helvetic' compressional stages. These paleostress tensors are compared with others defined in France, the Benelux countries and Germany and are also collated to the tectonic evolution of oil basins assessed from geophysical analyses. These comparisons raise discussions about the paleostress distribution within the geodynamic evolution of the West European shelf.

  11. 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 (?T ~ 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 setting of the Sao Miguel magmatism we combine GPS data and mantle convection models with our interpretation of the geochemistry of the basalts. We demonstrate strong south-westerly and downward flow in the asthenospheric mantle above the Transition Zone (410 km seismic discontinuity), consistent with a zone of upper mantle shearing below the base of the lithosphere. The maximum flow velocity is broadly consistent with the depth of magma generation. The advection of the mantle with respect to the oceanic plate "moves" an isotopically distinct mantle source component beneath the active volcanoes of Sao Miguel and carries its previous melting residues to the south-west. We discuss the nature of this mantle source and its contribution to the mantle velocity anomalies determined by seismic tomography. This study opens-up new perspectives for seismic tomography and potentially new connections between the fields of geophysics and geochemistry in oceanic domains.

  12. 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.

  13. Mechanism and timing of tectonic inversion in Cyrenaica (Libya): Integration in the geodynamics of the East Mediterranean

    NASA Astrophysics Data System (ADS)

    Arsenikos, Stavros; Frizon de Lamotte, Dominique; Chamot-Rooke, Nicolas; Mohn, Geoffroy; Bonneau, Marie-Claude; Blanpied, Christian

    2013-11-01

    In the eastern Mediterranean, the South-Tethys paleo-margin experienced poly-phased rifting episodes during Paleozoic and Mesozoic times. This domain has been subsequently inverted by discontinuous events occurring since the Late Cretaceous as a consequence of the Africa-Eurasia convergence. The Cyrenaica promontory (northeast Libya), including the Jabal Al Akhdar antiformal ridge, is not yet involved in the Africa-Eurasia collision zone. It thus gives an opportunity to analyze tectonic inversions occurring early in the development of the system and their possible causal links with events occurring along the plate boundary (i.e., within the Hellenic subduction). For this purpose, we present new geological cross-sections supported by offshore industrial 2D seismic profiles imaging the northeast prolongation of the antiformal ridge indenting the Mediterranean Ridge accretionary prism. The onshore part of this ENE-WSW trending structure exposes Upper Cretaceous to recent sedimentary rocks. Well calibrations allow us to be precise about the geometry of the structure, inherited from a Lower Cretaceous rift basin, and the timing of the main tectonic events. Oligocene sediments seal unconformably the main episodes of contractional deformation. Just below, growth strata of Late Ypresian to Priabonian age indicate a protracted folding episode during the Middle-Late Eocene, post-dating an older Late Cretaceous inversion. This evolution contrasts with what is observed in the adjacent Sirt Basin, characterized at the same time by extensional deformation and subsidence. Finally, we appraise how far these tectonic scenarios match the geodynamic evolution of the Hellenic domain.

  14. Discovery of Lower Cretaceous synmetamorphic thrust tectonics in French Lesser Antilles (La Désirade Island, Guadeloupe): Implications for Caribbean geodynamics

    NASA Astrophysics Data System (ADS)

    Corsini, M.; Lardeaux, J. M.; Verati, C.; Voitus, E.; Balagne, M.

    2011-08-01

    Located east of Guadeloupe, the island of La Désirade exhibits the oldest rocks of the Lesser Antilles arc and the eastern Caribbean plate. An old magmatic basement is composed of (1) late Jurassic ophiolitic complex with meta-basaltic pillow lavas and interbedded radiolarites, (2) acid igneous complex comprising meta-quartz-diorite and meta-rhyolitic lavas flows, and (3) meta-diabasic/microdioritic dyke swarm complex. We present and discuss the discovery of synmetamorphic thrust tectonics in this island. Based on detailed structural analysis we evidenced two main compressive events. The first event (D1) is characterized by pervasive folding associated with thrust development. In the northeastern part of the island, a major thrust fault, the Grand Abaque Thrust, has been discovered which displaces for several kilometers the acid igneous complex onto the ophiolitic unit. The second deformation event (D2) is featured by a main pervasive cleavage S2 observed at the regional scale associated with upright folding (F2) and by the development of two sets of conjugated steeply dipping strike-slip shear zones, dextral 130°N and sinistral 20°N striking, respectively. Microstructural observations indicate that Greenschist facies metamorphism is clearly contemporaneous with the development of D1 and D2 superimposed tectonic structures. Ar/Ar geochronology was performed on two bulk of adularia minerals sampled in the northeast volcanic complex within a deformed zone related to a D2 event. These analyses yield well-defined and concordant plateau ages at 106.2 ± 1.7 Ma and 107.2 ± 1.8 Ma. Thus, shortening and thickening tectonics occurred during Lower Cretaceous (Albian). In the available framework of Caribbean geodynamics, the synmetamorphic thrust tectonics we discovered in the French Lesser Antilles is related to the collision between an Aptian-Albian oceanic plateau and the Andean-Cordilleran east-dipping subduction zone. Our results support subduction polarity reversal during Lower Cretaceous.

  15. 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.

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

    SciTech Connect

    Mentes, Gy. [Geodetic and Geophysical Research Institute of the Hungarian Academy of Sciences, Csatkai Endre u. 6-8, H-9400 Sopron (Hungary)

    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.

  17. Role of preexisting faults in the geodynamic evolution of Northern Tunisia, insights from gravity data from the Medjerda valley

    NASA Astrophysics Data System (ADS)

    Amiri, A.; Chaqui, A.; Hamdi Nasr, I.; Inoubli, M. H.; Ben Ayed, N.; Tlig, S.

    2011-06-01

    The middle Medjerda valley belongs to the Tellian zone of Tunisia; it behaves as a post-orogenic basin where surface structural indices are almost completely absent. It is noteworthy to recall that Alpine and Atlasic tectonic prints are well expressed on both sides of this basin. This paper presents an integrated study comprising geology and gravity data. Subsurface geological modeling was based on gravity data interpretation including the complete Bouguer anomaly, upward continuation, residual and derivatives. 2.5D gravity modeling was essential for subsurface geometric features characterization. In spite of its sub-horizontal and smooth topography and the low density of the homogenous Quaternary series covering the area, well contrasted and variable gravity responses are observed reflecting the heterogeneities of the geological substratum. The enhanced horizontal gravity gradient confirms structural systems that are already evidenced by surface geology. It supports, also, the presence of new masked fault systems. The main structural features inferred are (i) NW directed Grabens located at Mellegue and S. ez Zaouam depressions, (ii) Triassic diapirs associated to NE thrust faults of El Merdja, Bousalem, Ben Bechir and Mjez el Assa. These structures are generally covered by the Quaternary series. The presence of both distensive and compressive structures within a compressive regime is explained by the solicitation of preexisting fault systems in the area. During the NW directed shortening occurred at the Upper Miocene age, the geodynamic evolution of Northern Tunisia was dominated by strike-slip thrust movements through the reactivation of deep major inherited faults: e.g. (i) the dextral EW oriented fault system of Ghardimaou-Thibar, and (ii) the sinister NS accident of Dehmani-Bousalem-Ras Rajel. These accidents shaped the Medjerda basin and contribute to its complex geological architecture.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

    Ayd?nçak?r, 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 ?Nd (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.

  20. 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 resolution of solutions obtained from standard sequential filtering methods and process noise sequential filtering methods shows that the accuracy is significantly improved using process noise. The results show that the positional accuracy of the orbit is improved as well. The temporal resolution of the resulting solutions are detailed, and conclusions drawn about the results. Benefits and drawbacks of using process noise filtering in this type of scenario are also identified.

  1. 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., (compiler); 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.

  2. Granites in the Sawuer region of the west Junggar, Xinjiang Province, China: Geochronological and geochemical characteristics and their geodynamic significance

    NASA Astrophysics Data System (ADS)

    Zhou, Taofa; Yuan, Feng; Fan, Yu; Zhang, Dayu; Cooke, David; Zhao, Guochun

    2008-12-01

    The Sawuer region is located in the west Junggar, Jimunai County of Altay district and Hefeng County of Tacheng district, Xinjiang Autonomous Region, in northwest China. In the study area granitic intrusions are widespread and can be subdivided into I-type granites (Tasite pluton, Sentasi pluton, Wokensala pluton and Kaerjia pluton) and A-type (A 2) granites (Kuoyitasi pluton and Qiaqihai pluton). The I-type granites consist of granite, adamelite, granodiorite, and the A-type granites are mainly represented by alkali granite. SHRIMP U-Pb dating results indicate that the granites in Sawuer region were formed between 337 Ma and 290.7 Ma (late Carboniferous and early Permian), with the I-type granites being formed between 337 Ma and 302.6 Ma, and the A-type between 297.9 and 290.7 Ma. From the older to the youngest granites, their composition changes from calc-alkalic to high-K calc-alkalic, to alkali series, and from I-type to A-type, based on the characteristics of whole rock trace element and rare earth elements geochemistry. This compositional range is the result of a change in the geodynamic regime from compressional to tensional during the late Paleozoic. Strontium, Nd, Pb, O isotope systematics suggest that both the I-type and A-type granites in Sawuer were sourced from the mantle (DM), but with some crustal contamination for the Kuoyitasi pluton. The I-type granites were formed by equilibrium partial melting, while the A-type granites were formed mainly by fractional crystallization. Based on the Rb-Y + Nb and Nb-Y-Ce discrimination criteria by Eby [Eby G.N., 1992. Chemical subdivision of the A-type granitoids: Petrogenetic and tectonic implications. Geology 20, 641-644] and Pearce [Pearce J.A., 1996. Sources and settings of granitic rocks. Episodes 19, 120-125] and comparisons with granites in other regions of northern Xinjiang, the I-type granites were emplaced during a transition from compressional to extensional settings in a post-collision regime, whereas the A-type granites were emplaced in an extensional setting. We concluded that the Sawuer as well as the whole Junggar region in northern Xinjiang were involved in tectonism that gradually changed from compressional to extensional between the late Carboniferous and early Permian. This late Paleozoic granitic magmatism contributed to vertical crustal growth in the region.

  3. Contributions of Fe-K subalkaline granites for the geodynamic evolution of the Iberian Massif (Northern Portugal)

    NASA Astrophysics Data System (ADS)

    Simões, P. P.; Martins, H. C. B.; Dias, G.

    2012-04-01

    In the Iberian Massif large volumes of granitic rocks were emplaced during the Variscan orogeny, mainly during the last ductile deformation phase D3. After that, an extensional tectonic regime controls the emplacement of several Fe-K subalkaline post-D3 plutons. Geochemical and isotopic results of post-D3 biotite granites in northern Portugal (Peneda-Gerês, Vila Pouca de Aguiar, Monção-Porriño and Águas Frias plutons) are presented and their contributions to the geodynamic evolution of the Iberian Variscides. They are porphyritic to coarse-medium grained biotite granites with potassium feldspar megacrysts, with rare mafic microgranular enclaves and some are associated to minor bodies of intermediate rocks and/or two mica granites. Accessory minerals include zircon, apatite, allanite, xenotime, ilmenite and sphene. Amphibole is present only in the Peneda-Gerês and Monção-Porriño plutons. Emplacement ages based on U-Pb zircon analyses indicate a value of 290-299 Ma. They are meta- to peraluminous granitoids, having evolved chemical compositions, with high SiO2. Isotopic studies reveals initial 87Sr/86Sr ratios of 0.7033 to 0.7079 and ?Nd of -1.5 to -2.6 while rare hectometric intermediate rock bodies outcrop in the Monção-Porriño shows initial 87Sr/86Sr ratios of 0.7054 to 0.7061 and ?Ndi of 0.4 to -0.7. The isotopic composition of these post-D3 biotite granites is clearly less evolved than that of the synorogenic granites in the region, indicating that the mantle sources were distinct, and shows an important change in magma composition associated to the extensional regime. An origin by mantle input followed by mantle-crust interaction is proposed, implying the contribution of a less enriched mantle component than that involved in the genesis of synorogenic granites in northern Portugal (hybrid Mg-K subalkaline granites and calc-alkaline to aluminopotassic granites) This study permits to envisage that the extensional tectonics triggered the ascension of liquids from a more depleted mantle source implying an input of juvenile magma with mixing of crustal magmas, probably derivate from metaigneous sources, in lower crust, to produce hybrid granites. This also indicates an accretion process with a crustal growth episode.

  4. Unraveling the tectonic history of northwest Africa: Insights from shear-wave splitting, receiver functions, and geodynamic modeling

    NASA Astrophysics Data System (ADS)

    Miller, M. S.; Becker, T. W.; Allam, A. A.; Alpert, L. A.; Di Leo, J. F.; Wookey, J. M.

    2013-12-01

    The complex tectonic history and orogenesis in the westernmost Mediterranean are primarily due to Cenozoic convergence of Africa with Eurasia. The Gibraltar system, which includes the Rif Mountains of Morocco and the Betics in Spain, forms a tight arc around the Alboran Basin. Further to the south the Atlas Mountains of Morocco, an example of an intracontinental fold and thrust belt, display only modest tectonic shortening, yet have unusually high topography. To the south of the Atlas, the anti-Atlas is the oldest mountain range in the region, has the lowest relief, and extends toward the northern extent of the West African Craton. To help unravel the regional tectonics, we use new broadband seismic data from 105 stations across the Gibraltar arc into southern Morocco. We use shear wave splitting analysis for a deep (617 km) local S event and over 230 SKS events to infer azimuthal seismic anisotropy and we image the lithospheric structure with receiver functions. One of the most striking discoveries from these methods is evidence for localized, near vertical-offset deformation of both crust-mantle and lithosphere-asthenosphere interfaces at the flanks of the High Atlas. These offsets coincide with the locations of Jurassic-aged normal faults that were reactivated during the Cenozoic. This suggests that these lithospheric-scale discontinuities were involved in the formation of the Atlas and are still active. Shear wave splitting results show that the inferred stretching axes are aligned with the highest topography in the Atlas, suggesting asthenospheric shearing in mantle flow guided by lithospheric topography. Geodynamic modeling shows that the inferred seismic anisotropy may be produced by the interaction of mantle flow with the subducted slab beneath the Alboran, the West African Craton, and the thinned lithosphere beneath the Atlas. Isostatic modeling based on these lithospheric structure estimates indicates that lithospheric thinning alone does not explain the anomalous Atlas topography. Instead, an upwelling component induced by a mantle anomaly is also required to support the Atlas, suggesting that the timing of uplift is contemporaneous with recent volcanism in the Middle Atlas.

  5. Paleozoic and Lower Mesozoic magmas from the eastern Klamath Mountains (North California) and the geodynamic evolution of northwestern America

    NASA Astrophysics Data System (ADS)

    Lapierre, H.; Brouxel, M.; Albarede, F.; Coulin, C.; Lecuyer, C.; Martin, P.; Mascle, G.; Rouer, O.

    1987-09-01

    The Paleozoic to Early Mesozoic geology of the eastern Klamath Mountains (N California) is characterized by three major magmatic events of Ordovician, Late Ordovician to Early Devonian, and Permo-Triassic ages. The Ordovician event is represented by a calc-alkalic island-arc sequence (Lovers Leap Butte sequence) developed in the vicinity of a continental margin. The Late Ordovician to Early Devonian event consists of the 430-480 Ma old Trinity ophiolite formed during the early development of a marginal basin, and a series of low-K tholeiitic volcanic suites (Lovers Leap Basalt—Keratophyre unit, Copley and Balaklala Formations) belonging to intraoceanic island-arcs. Finally, the Permo-Triassic event gave rise to three successives phases of volcanic activity (Nosoni, Dekkas and Bully Hill) represented by the highly differentiated basalt-to-rhyolite low-K tholeiitic series of mature island-arcs. The Permo-Triassic sediments are indicative of shallow to moderate depth in an open, warm sea. The geodynamic evolution of the eastern Klamath Mountains during Paleozoic to Early Mesozoic times is therefore constrained by the geological, petrological and geochemical features of its island-arcs and related marginal basin. A consistent plate-tectonic model is proposed for the area, consisting of six main stages: (1) development during Ordovician times of a calc-alkalic island-arc in the vicinity of a continental margin; (2) extrusion during Late Ordovician to Silurian times of a primitive basalt-andesite intraoceanic island-arc suite, which terminated with boninites, the latter suggest rifting in the fore-arc, followed by the breakup of the arc; (3) opening and development of the Trinity back-arc basin around 430-480 Ma ago; (4) eruption of the Balaklala Rhyolite either in the arc or in the fore-arc, ending in Early Devonian time with intrusion of the 400 Ma Mule Mountain stock; (5) break in volcanic activity from the Early Devonian to the Early Permian; and (6) development of a mature island-arc from the Early Permian to the Late Triassic. The eastern Klamath Mountains island-arc formations and ophiolitic suite are part of the "Cordilleran suspect terranes", considered to be Gondwana margin fragments, that have undergone large northward translations before final collision with the North American craton during Late Mesozoic or Cenozoic times. These eastern Klamath Mountains island-arcs could be associated with the paleo-Pacific oceanic plate that led to accretion of these allochthonous terranes to the American margin.

  6. The Early-Cambrian Boho volcano of the El Graara massif, Morocco: Petrology, geodynamic setting and coeval sedimentation

    NASA Astrophysics Data System (ADS)

    Álvaro, J. J.; Ezzouhairi, H.; Vennin, E.; Ribeiro, M. L.; Clausen, S.; Charif, A.; Ayad, N. Ait; Moreira, M. E.

    2006-03-01

    A major volcanic episode is recorded across the Neoproterozoic-Cambrian transition in the Moroccan Anti-Atlas. Several volcanic cones are still preserved in the El Graara massif, laterally correlatable with volcanic flows dated as Early Cambrian (U/Pb date of 534 ± 10 Ma). Volcanic ashes and flows are interbedded with the uppermost part of the Adoudou dolostones, whereas the best-preserved volcano (the Boho Jbel) is onlapped by the overlying Lie-de-vin strata. Available petro-geochemical data from the Boho volcano suggest an alkaline magmatism probably derived from low-grade melting of a garnet-lherzolite mantle source, followed by fractional crystallization. The silica-undersaturated basaltic liquid evolved to form oversaturated rocks: the fractionation of a ferromagnesian phase with high-Ca and low-Al contents is suggested as the main process to cut across the critical plane of silica undersaturation in this geochemical series. Although the Boho geochemical patterns are similar to those of some rift emplacements, more data from other coeval magmatic eruptions are necessary to constrain their geodynamic setting. Erosion of the Boho volcano favoured formation of a slope-apron composed of four sedimentary facies belts: chaotic megabreccia (related to downslope mass movements of rigid blocks), amalgamated breccia sheets (emplaced by viscous debris flows), a heterogeneous terrigenous belt (representing offshore substrates interrupted by channels intersected by cross-bedded shoals), and variegated shales and stromatolitic dolostones (typical of the Lie-de-vin Formation). Sharp changes in sedimentation rate were associated with modifications in paleorelief sloping and transport mechanisms from subaerial (?) rock fall at the foot of the cone escarpment to sheet-like debris flow on the slopes, and the replacement by sedimentation under wave and storm influence. The presence of an active carbonate productivity, recorded in the primary porosities of the Boho slope-apron, is suggested by widespread development of a robust, coelobiontic, microbial carbonate factory resilient to poisoning by terrigenous influx. Diagenesis in these deposits includes marine, meteoric and deep-burial cementation of calcite, dolomite, iron oxides, quartz, feldspar, and celestine, the latter indicating precipitation from hypersaline pore fluids.

  7. The fluids' geochemistry along the "Sperchios Basin - Northern Evoikos Gulf" Graben, a geodynamically complex area of Central Greece

    NASA Astrophysics Data System (ADS)

    D'Alessandro, Walter; Bellomo, Sergio; Brusca, Lorenzo; Calabrese, Sergio; Kyriakopoulos, Konstantinos

    2013-04-01

    The study area is a 130 km long fast spreading graben in Central Greece. Its complex geodynamical setting includes both the presence at depth of a subduction slab responsible for the recent (Quaternary) volcanic activity in the area and the western termination of a tectonic lineament of regional importance (the North-Anatolian fault). Its high geothermal gradient is evidenced by the presence of many thermal springs with temperatures from 19 to 82 °C, issuing along the normal faults bordering the graben. In the period 2004-2012 about 50 gas and water samples have been collected and their chemical and isotopic analysis revealed a wide range of compositions. Going from west to east the gas composition changes from CH4- to CO2-dominated passing through mixed N2-CH4 and N2-CO2 compositions, while at the same time the He isotopic composition goes from typical crustal values (0.05 R/Ra) up to 0.87 R/Ra (corrected for air contamination), showing in the easternmost sites a small but significant mantle input. Isotopic composition of CH4-C indicates a thermogenic origin for the CH4-rich samples and hydrothermal origin for the remaining samples. Positive ?15N values indicate a contribution of crustal derived nitrogen for the N2-rich samples. The ?13C values of most the CO2-enriched samples show a mixed origin (mantle and marine carbonates). Also the chemical composition of the waters shows differences along the graben and two main groups can be separated. The first, represented by dilute waters (E.C. < 600 ?S/cm), is found in the westernmost sites characterised by the presence of CH4-rich and mixed N2-CH4 gases. The remaining waters display higher salinities (E.C. from 12 to 56 mS/cm) due to the mixing with a modified marine component. Only the water composition of easternmost sites in the Giggenbach's cation triangular graph plots in the field of the partially equilibrated waters giving estimated temperatures at depth of 150-160°C.

  8. Crustal source of the Late Cretaceous Satansar? monzonite stock (central Anatolia - Turkey) and its significance for the Alpine geodynamic evolution

    NASA Astrophysics Data System (ADS)

    Köksal, Serhat; Toksoy-Köksal, Fatma; Göncüo?lu, 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 Satansar? 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 ?Nd(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 (2?) 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 ?Hf(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 involvement of crustal sources for other monzonitic rocks in central Anatolia and granitic magmatism in other similar tectonic environments.

  9. spe425-11 page 149 Li, Q., Liu, M., Zhang, Q., and Sandvol, E., 2007, Stress evolution and seismicity in the central-eastern United States: Insights from geodynamic modeling, in

    E-print Network

    Liu, Mian

    United States is in the middle of the North America plate where Cenozoic crustal deformation is minimal and seismicity in the central-eastern United States: Insights from geodynamic modeling, in Stein, S in the presumably rigid plate inte- riors. One such region is the central-eastern United States, defined broadly

  10. Irregular effects of tilting of foundation and probable connection with plate tectonic motions Results of many years standing measurements of long water-tubes and horizontal pendulums tiltmeters in Geodynamic Laboratory of SRC in Ksiaz

    Microsoft Academic Search

    Marek Kaczorowski

    2010-01-01

    Since 1975 until 2003 in the Geodynamic Laboratory in Ksiaz there were continuously performed clinometric observations with help of quartz horizontal pendulums only. In 2003 new tiltmeters were installed in galleries of the laboratory in Ksiaz. Tiltmeters consist of two several dozen meters length tubes partially filled with water. Principle of work of instruments bases on the law of hydrostatic

  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 fractures; the degree of albitization-hematisation progressively increases towards the top affecting the whole rock, which acquires a characteristic pink color. Finally, the top of the profile is formed by strongly altered to hematite and kaolinite rich reddish facies. These uppermost parts of the alteration profile are formed by a relatively soft rock and are therefore usually not preserved, but the intermediate albitized parts are more resistant to surface alteration than unaltered facies and protect the peneplain from weathering and erosion. The albitization-hematisation alterations observed in the Montseny-Guilleries peneplain are very similar to the Permian-Triassic paleoalteration profiles observed in other parts of Europe, affecting the Variscan basement [Ricordel et al., 2007; Parcerisa et al., 2009]. Dating these profiles using paleomagnetic methods will help us to identify the location of the Permian-Triassic surface in the area and deduce its geodynamic history during the Mesozoic and Tertiary periods. Anadón, P., Colombo, F., Esteban, M., Marzo, M., Robles, S., Santanach, P., Solé-Sugrañes, L., 1979, Evolución tectonostratigráfica de los Catalánides, Acta Geol. Hisp., 14: 242-270. Gómez-Gras, D., 1993, El Permotrias de la Cordillera Costero Catalana: facies y petrologia sedimentaria (Parte I), Bol. Geol. Min., 104 (2): 115-161. Gómez-Gras, D., Ferrer, C., 1999, Caracterización petrológica de perfiles de meteorización antiguos desarrollados en granitos tardihercínicos de la Cordillera Costero Catalana, Rev. Soc. Geol. Esp., 12(2): 281-299. Juez-Larre, J., Andriessen, P.A.M., 2006, Tectonothermal evolution of the northeastern margin of Iberia since the break-up of Pangea to present, revealed by low-temperature fission-track and (U-Th)/He thermochronology: A case history of the Catalan Coastal Ranges, Earth Planet. Sci. Let., 243 (1-2): 159-180. Juez-Larré, J., Ter Voorde, M., 2009, Thermal impact of the break-up of Pangea on the Iberian Peninsula, assessed by thermochronological dating and numerical modeling, Tectonophysics, v.

  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 linear model of position changes of test point coordinates based on results of the permanent and epoch observations had been performed. Then, applying linear site velocities, the surface deformation model for the Sudeten area was compiled. Results of this research constitute the base both for recognizing tectonic impacts to the area and for potential hazard assessments. This research had been granted by the Polish National Science Centre, project No. N526 278940, and accomplished in cooperation of specialists from the Institute of Geodesy and Geoinformatics, Wroclaw University of Environmental and Life Sciences, the Institute of Rock Structure and Mechanics of the Czech Academy of Sciences in Prague and the Polish State Geological Institute, Lower Silesia Branch in Wroclaw.

  13. Tightly Coupled Geodynamic Systems

    E-print Network

    Brown, Jed

    evolution Ridge 2D Porosity Driven Stokes Solitary Waves Isoviscous McKenzie Eqns. Specific Physical · Effective solution methods for studying dynamical systems described by very viscous, creeping flow, i.e. 5 linear and nonlinear problems to be obtained. · If the coupled problem is nonlinear, we need: · A method

  14. 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

  15. Sulphur geodynamic cycle

    NASA Astrophysics Data System (ADS)

    Kagoshima, Takanori; Sano, Yuji; Takahata, Naoto; Maruoka, Teruyuki; Fischer, Tobias P.; Hattori, Keiko

    2015-02-01

    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.

  16. Geodynamic Information in Peridotite

    E-print Network

    Claude Herzberg

    2003-01-01

    Systematic differences are observed in the petrology and major element geochemistry of natural peridotite samples from the sea floor near oceanic ridges and subduction zones, the mantle section of ophiolites, massif peridotites, and xenoliths of cratonic mantle in kimberlite. Some of these

  17. 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, Quaternary fault slip, and seismic data suggest that the gravitational potential of the Yellowstone swell creates a regional extension affecting much of the western U.S. Overall, the Yellowstone hotspot swell is the vertex of tensional stress axes rotation from E-W in the Basin-Range to NE-SW at the Yellowstone Plateau as well as the cause of edge faulting, nucleating the nearby Teton and Centennial faults. We extrapolate the original location of the Yellowstone mantle-source southwestward 800 km to an initial position at 17 million years ago beneath eastern Oregon and Washington suggesting a common origin for the YSRP and Columbia Plateau volcanism. We propose that the original plume head ascended vertically behind the subducting Juan de Fuca plate, but was entrained ~12 Ma ago in a faster mantle flow beneath the continental lithosphere and tilted into its present configuration.

  18. 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

  19. 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

    An assembly of igneous (TTG-granitoids and S-type leucogranites and calc-alkaline-, tholeiite-, kometiite-, boninite- and adakite-series metavolcanics) and metamorphic (eclogite-, moderate-pressure (MP) granulite- and MP amphibolite-facies rocks) complexes, strikingly complete for Archaean structures, is preserved in the Belomorian province of the Fennoscandian Shield. At least four Meso-Neoarchaean different-aged (2.88-2.82; 2.81-2.78; ca. 2.75 and 2.735-2.72 Ga) calc-alkaline and adakitic subduction-type volcanics were identified as part of greenstone belts in the Belomorian province (Slabunov, 2008). 2.88-2.82 and ca. 2.78 Ga fore-arc type graywacke units were identified in this province too (Bibikova et al., 2001; Mil'kevich et al., 2007). Ca.2.7 Ga volcanics were generated in extension structures which arose upon the collapse of an orogen. The occurrence of basalt-komatiite complexes, formed in most greenstone belts in oceanic plateau settings under the influence of mantle plumes, shows the abundance of these rocks in subducting oceanic slabs. Multiple (2.82-2.79; 2.78-2.76; 2.73-2.72; 2.69-2.64 Ga) granulite-facies moderate-pressure metamorphic events were identified in the Belomorian province (Volodichev, 1990; Slabunov et al., 2006). The earliest (2.82-2.79 Ga) event is presumably associated with accretionary processes upon the formation of an old continental crust block. Two other events (2.78-2.76; 2.73-2.72 Ga) are understood as metamorphic processes in suprasubduction setting. Late locally active metamorphism is attributed to the emplacement of mafic intrusions upon orogen collapse. Three groups of crustal eclogites with different age were identified in the Belomorian province: Mesoarchaean (2.88-2.86 and 2.82-2.80 Ga) eclogites formed from MORB and oceanic plateau type basalts and oceanic high-Mg rocks (Mints et al., 2011; Shchipansky at al., 2012); Neoarchaean (2.72 Ga) eclogites formed from MORB and oceanic plateau type basalts. The formation of 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

  20. 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 with silicate magma, For basalt-gabbro-associated Cu-Ni-PGE-rich sulfide ore systems that have Re-Os geochemical characteristics more similar to those associated with komatiites, R factors must have been high (??? 10,000 for Noril'sk-Talnakh and the J-M reef, Stillwater Complex). In these very dynamic magmatic ore systems, crustal contamination processes are more difficult to assess using Re-Os isotopes as the effects of contamination are masked by the R factor process in which sulfide magma equilibrates with extensive amounts of asthenospheric mantle-derived magma. Sulfide protore for these systems may, then, have been very radiogenic and of crustal origin prior to R factor processes that occurred during transport in feeder conduits and in upper crustal magma chambers. This study, therefore, highlights the need for caution when interpreting the Re-Os isotope geochemistry of sulfide ores from dynamic magmatic systems. The results of our reinvestigation of these giant ore deposits suggest that geodynamic processes associated with large magmatic systems, including major lithospheric pathways to the surface, changes in flow regime, coupled magma flow-through and magma mixing (providing enhanced R factors), may be critical to our understanding of the emplacement, localization, and quality of magmatic sulfide deposits. Thus, the timing and exact mechanism of sulfide saturation may be subordinate to dynamic magmatic processes in the localization of economic concentrations of magmatic sulfides.

  1. From microscope to mountain belt: 150 years of petrology and its contribution to understanding geodynamics, particularly the tectonics of orogens

    NASA Astrophysics Data System (ADS)

    Brown, M.

    2001-09-01

    Thirty-five years ago the introduction of the plate tectonics paradigm led to a new understanding of orogeny. Subsequently, the development of advanced instruments for remote collection of information and for analysis of elemental and isotopic composition of materials, and the increases in computing power have enabled an unprecedented number of high-precision data about the Earth to be collected, analyzed, modelled and displayed. Within this revolution in global tectonics, the metamorphic petrologist has developed methods to unravel the depth, thermal, temporal and deformational history of orogens using detailed observations at map, hand sample and thin-section scales in combination with elemental and isotope data, and using inverse and forward modelling. Two exciting new directions in metamorphic petrology in relation to geodynamics concern the kinship between earthquakes and metamorphic reactions in subduction zones, and the petrology of the Earth's mantle. Evidence of the changes in pressure ( P) and temperature ( T) in the Earth's crust and upper mantle during the break up, movement, and collision of pieces of the continental lithosphere is sporadically recorded by the mineralogy and microstructures preserved in rocks exhumed to the surface. Better calibration of phase equilibria, the use of internally-consistent thermodynamic data sets and the development of techniques to retrieve close-to-peak P-T conditions from metamorphic rocks have yielded more precise P-T data that enhance our ability to characterize the path followed by individual rocks in P-T space. An improved ability to date segments of the P-T path, and to separate the length of time associated with the prograde (increasing T) evolution from the age of close-to-peak P-T conditions has enabled better understanding of the rates and processes involved in lithosphere thickening. At the same time, better constraints on the retrograde thermal history have contributed to our knowledge of the several tectonic processes that may operate during exhumation, although these are less well understood. The expanding database of key information, combined with predictions from modelling, has allowed the identification of characteristic P-T-t evolutions expected for rocks that have undergone distinct tectono-metamorphic histories. However, relating structural events recorded by rocks to specific points along the P-T evolution remains problematic, particularly regarding complex overprinting patterns of inclusion trails in porphyroblasts. These advances have improved our understanding of the tectonic evolution of orogens. At the extreme of conditions for crustal metamorphism are the recently discovered ultra-high pressure (UHP) and ultra-high temperature (UHT) facies of metamorphism. Both are problematic given our limited knowledge of processes at these conditions, particularly the return of UHP rocks from peak- P conditions and the mechanism for extreme heat in the crust in UHT metamorphism. The extreme depth inferred for metamorphism in some UHP terranes raises the issue of whether theoretically plausible tectonic overpressures can be dynamically maintained to affect metamorphic reactions. If the pressure gradient recorded by UHP rocks is greater than lithostatic, the UHP metamorphism may have occurred at depths shallower than currently believed. These studies have provided a reliable first-order framework for the comparison of rocks of ancient suture zones where the plate tectonics situation is less certain. However, orogens are spatially and temporally extended nonlinear systems with feedback relations. Such complex systems generate apparently simple behavior by self-organization, and the influence of unique histories must be respected.

  2. 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 ?Nd(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 ?Nd(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 early Neoproterozoic. Hornblende gneisses show andesitic compositions, with high 87Sr/86Sr initial ratios (0.7105 and 0.7125) and low ?Nd(620) values (-14.0 and -20.7) suggesting that their genesis involved juvenile and recycled older crustal materials. Syn-metamorphic metagabbro (Mamb) and metadiorite (Yaounde) intrusions show negative Nb-Ta negative anomalies but enrichment in light rare-earth and large-ion lithophile elements, suggesting a metasomatized mantle source. Overall, meta-igneous rocks seem to be representative of distinct magmatic events that accompanied the evolution of the Yaounde sedimentary basin, from opening and oceanisation to convergence and closure in relation with the collisional process. These data suggest that the Yaounde basin should not be considered as a back-arc basin, but more likely represents the expression of extensional processes to the north of the Congo craton, which led to rifting, fragmentation and limited oceanisation. In this view, the Adamawa-Yade block may represent a micro-continent detached from the Congo craton during the early Neoproterozoic.

  3. Geodynamic settings of the formation of amphibolites of the Kichera zone of the Baikal-Muya foldbelt: Results of geochemical studies

    NASA Astrophysics Data System (ADS)

    Andreev, A. A.; Rytsk, E. Yu.; Velikoslavinskii, S. D.; Kotov, A. B.; Yarmolyuk, V. V.; Kovach, V. P.; Tolmacheva, E. V.

    2015-02-01

    It was established that amphibolites of the Kichera zone of the Baikal-Muya belt (BMB) belong, at least, to two age groups: (I) Early Neoproterozoic large metamafic xenoliths entrapped by granitic rocks of 750 Ma and (II) Late Neoproterozoic (650-620 Ma) amphibolites, which compose individual tectonic sheets and lenses. The rocks of these groups are distinct in chemical composition: the low-Ti amphibolites of the first group with increased Al2O3 contents are similar to modern IABs, whereas the highly-Ti amphibolites of the second group correspond to MORBs and OIBs. The geochemical data showed that the igneous protoliths of amphibolites of the Kichera zone were formed during different stages of the BMB evolution distinct in geodynamic settings.

  4. Characteristics of mantle sources in Jurassic to Quaternary magmatic history of the territory of Armenia, as a guide to diverse geodynamic settings

    NASA Astrophysics Data System (ADS)

    Nikoghosyan, Igor; Meliksetian, Khachatur; van Bergen, Manfred; Mason, Paul; Jrbashyan, Ruben; Navasardyan, Gevorg; Ghukasyan, Yura; Melkonyan, Rafael; Karapetyan, Sergey

    2014-05-01

    Complex geological mosaic of the territory of Armenia is presented by units consisting by fragments of continental blocks of Gondwanaland origin, Mesozoic Tethian island arc and Mesozoic ophiolitic complexes. Extensive magmatic activity traced from Early Jurassic to Holocene developed in diverse geological settings, such as Jurassic Tethyian MORB lavas, Upper Cretaceous and Eocene rift-related magmas and post-collisional Pliocene-Quaternary volcanic series. Despite the remarkable existence of subduction, obduction and collisional orogenic processes, accompanied by extensional and compressional tectonics, little is known about the relation between geodynamics and magma generation conditions, as mantles sources types and primary melts characteristics during the evolution of the region. Current study is intended to get new information that help to fill the gaps between the geodynamical puzzle and conditions of the mantle sources melting within the selected key areas of the territory of Armenia and Lesser Caucasus in general. In this contribution we focus on discussion of results of detailed geochemical and petrological studies of representative, highest-MgO samples of Jurassic picrites within Vedi ophiolites, picrite dyke of Alaverdi cutting Mesozoic Tethian island arc complexes, Upper Cretaceous rift-related sub-alkaline/alkaline basaltic series of Idjevan and Gochas, Late Eocene alkaline basaltic dyke of Jajur cutting Eocene volcanic and sedimentary complexes and Pliocene - Quaternary post-collisional volcanism, presented by 1) rifting-related flood basalts (dolerites); 2) HKCA basaltic series of Aragats stratovolcano and Gegham monogenetic volcanic upland and 3) high-alkaline, silica-undersaturated basaltic series of Syunik and Kapan. Geochemical signatures of most studied samples are characterised by enrichments in LILE and LREE, but depleted in HFSE, reflecting to OIB/MORB-type mantle source that may have been modified by subduction-related processes. Exceptions are the Jurasic Vedi and Alaverdi picrites reflecting the typical Tethyan MORB-type mantle, as well the Late Cretaceous Gochas, Martuni and Idjevan and Late Eocene Djajur showing absence of pronounced subduction-related modification of OIB-type mantle sources. Detail mineralogical study of early liquidus assemblages demonstrates that most studied samples consist high-Fo (>88) olivine that are considered to have crystallized from primary mantle-derived melts. Exceptions are low-Fo olivines characterized for Quaternary Aragats, Gegham and partially volcanoes of Syunik upland, those probably crystallized from crust contaminated AFC melts and/or melt resulting from the mixture of primary and crust-melted (adakite-type) melts. Spinel inclusions trapped in high-Fo olivine contain variable amounts of Ti, Al, and Cr, pointing to involvement of heterogeneous (MORB-type, OIB-type and subduction-type) mantle sources, that well agree with differ mantle-lithosphere domains and geodynamic controls during magma generations within the region from Jurassic to Quaternary time. Geochemical signature of melts, those could be maximally close to the primary or parental magmas, we obtained from LA-ICP-MS analyses of melt inclusions trapped in high-Fo olivines from all studied samples. Wide heterogeneity of melts within the individual and between differ magmatic systems, as well the link with geodynamical control and mantle sources melting scenarios will be discussed.

  5. 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. [Univ. of Arizona, Tucson, AZ (United States). Dept. of Geosciences

    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.

  6. The Early Miocene "Bisciaro volcaniclastic event" (northern Apennines, Italy): a key study for the geodynamic evolution of the central-western Mediterranean

    NASA Astrophysics Data System (ADS)

    Guerrera, Francesco; Martín-Martín, Manuel; Raffaelli, Giuliana; Tramontana, Mario

    2015-01-01

    The Early Miocene Bisciaro Fm., a marly limestone succession cropping out widely in the Umbria-Romagna-Marche Apennines, is characterized by a high amount of volcaniclastic content, characterizing this unit as a peculiar event of the Adria Plate margin. Because of this volcaniclastic event, also recognizable in different sectors of the central-western Mediterranean chains, this formation is proposed as a "marker" for the geodynamic evolution of the area. In the Bisciaro Fm., the volcaniclastic supply starts with the "Raffaello" bed (Earliest Aquitanian) that marks the base of the formation and ends in the lower portion of the Schlier Fm. (Late Burdigalian-Langhian p.p.). Forty-one studied successions allowed the recognition of three main petrofacies: (1) Pyroclastic Deposits (volcanic materials more than 90 %) including the sub-petrofacies 1A, Vitroclastic/crystallo-vitroclastic tuffs; 1B, Bentonitic deposits; and 1C, Ocraceous and blackish layers; (2) Resedimented Syn-Eruptive Volcanogenic Deposits (volcanic material 30-90 %) including the sub-petrofacies 2A, High-density volcanogenic turbidites; 2B, Low-density volcanogenic turbidites; 2C, Crystal-rich volcanogenic deposits; and 2D, Glauconitic-rich volcaniclastites; (3) Mixing of Volcaniclastic Sediments with Marine Deposits (volcanic material 5-30 %, mixed with marine sediments: marls, calcareous marls, and marly limestones). Coeval volcaniclastic deposits recognizable in different tectonic units of the Apennines, Maghrebian, and Betic Chains show petrofacies and chemical-geochemical features related to a similar calc-alkaline magmatism. The characterization of this event led to the hypothesis of a co-genetic relationship between volcanic activity centres (primary volcanic systems) and depositional basins (depositional processes) in the Early Miocene palaeogeographic and palaeotectonic evolution of the central-western Mediterranean region. The results support the proposal of a geodynamic model of this area that considers previously proposed interpretations.

  7. Tectonic setting of the Late Triassic volcaniclastic series of the Luang Prabang Basin, Laos, and geodynamic implications from the Triassic to Jurassic in SE Asia

    NASA Astrophysics Data System (ADS)

    Rossignol, Camille; Bourquin, Sylvie; Dabard, Marie-Pierre; Hallot, Erwan; Poujol, Marc; Nalpas, Thierry

    2014-05-01

    The Luang Prabang Basin, located on the eastern margin of the Indochina block, is mainly composed of volcaniclastic continental deposits. The interpretation of U-Pb zircon geochronological dates shows that volcanism is contemporaneous with the sedimentation during the Late Triassic (c.a. 225 to 215 Ma; Blanchard et al., 2013, J. Asian Earth Sci., 70-71; 8-26). At the same time, volcanism is also known along the Eastern margin of the Indochina block (present day Thailand). There are currently two main contrasting interpretations concerning the tectonic setting related to these volcanic events: are they arc-related (e.g. Barr et al., 2006, J. Geol. Soc. London, 163; 1037-1046) or post collisional (e.g. Srichan et al., 2009, Island Arc, 18; 32-51)? We have performed geochemical analysis on both sedimentary and volcanic rocks of the Luang Prabang Basin in order to evaluate the relationships between the volcanic events and to propose a geodynamic interpretation. The geochemical characteristics of the Luang Prabang Late Triassic volcaniclastic and volcanic rocks are compatible with a volcanic arc setting. The confrontation of these results with the stratigraphic evolution of the eastern margin of the Indochina block leads to reconsider the Late Triassic to Jurassic geodynamic evolution of this area. Arc-related volcanism seems to occur during nearly the whole Triassic, implying a subduction of the Paleotethys beneath the Indochina block. As the stratigraphic record of north-eastern Thailand and western Myanmar shows an important stratigraphic gap spanning from the Early to the Middle Jurassic, the collision between the Indochina and the Sibumasu blocks likely occurred at that period.

  8. 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) continental subduction occurs in very specific cases of cold strong lithospheres while in general this process takes less than 5 Myr. During the active subduction phase (simple shear accommodation of convergence) we do not detect significant deviations (+-20%) of total pressure in the subduction channel from lithostatic values , that can be rather lower than the lithostatic pressure, while intra-channel temperatures vary in quite large limits. Hence, large volumes of HP/UHP metamorphic rocks generated and brought to the surface during subduction phase would not record significant deviations from the lithostatic pressure conditions. At the same time, strong non-lithostatic pressures (extensional and compressional) are predicted for some internal parts of the colliding plates that, however, are not prone to yield "extractable" metamorphic material. The experiments also show that high non-lithostatic pressures develop in the former subduction channel at its lock-up , during and after the transition from subduction to pure shear collision or folding, while the metamorphic material generated at this stage appears to be blocked at depth and does not return to the surface (at least if the channel is not unlocked due some external conditions). We suggest that most continental orogenic belts could have started their formation from continental subduction. This process has been generally limited in time while pressures recorded in the HP and UHP material generated at this stage can be largely treated in terms of the lithostatic approximation. In case of subduction of continental terrains embedded in the oceanic lithosphere, it can be shown that their exhumation, resulting in formation of metaphoric belts and domes, may initiate series of slab roll-back and exhumation events associated with remarkably complex and spatially variable P-T-t paths.

  9. 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., Jr.; 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 Jurassic that confirmed their assignment to the El'gevayam volcanic-plutonic assemblage. These data are consistent with geological concepts and make more precise the available age dates. Neocomian-Aptian 40Ar/39Ar age of amphibolites from the Pekulnei and Tamvatnei gabbroids make evident that mafics of these terranes (varying in geodynamic formation settings and in petrogenesis) were generated in later stages of the development of the West Pekulnei and Mainits-Algan Middle-Late Jurassic-Early Cretaceous island arc systems, presumably due to breakup of island arcs in the Neocomian. ?? 2011 Pleiades Publishing, Ltd.

  10. 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 will be shown that the proposed reconstruction permit to simplify most the kinematics models proposed at the moment. Although some key points are still problematic, this paleotectonic restoration may solve more problems than arise them. Acknowledgements: This study was supported by grants RNM-3713, RNM-215, CGL2008-03474 E/BTE, CTM2009-07715/MAR and CGL2009-11384.

  11. The Arkot Da? Mélange in Araç area, central Turkey: Evidence of its origin within the geodynamic evolution of the Intra-Pontide suture zone

    NASA Astrophysics Data System (ADS)

    Göncüoglu, M. Cemal; Marroni, Michele; Pandolfi, Luca; Ellero, Alessandro; Ottria, Giuseppe; Catanzariti, Rita; Tekin, U. Kagan; Sayit, Kaan

    2014-05-01

    In northern Turkey, the Intra-Pontide suture zone is represented by an east-west trending belt of deformed and/or metamorphic units located at the boundary between the Istanbul-Zonguldak terrane to the north and the Sakarya terrane to the south. These units can be regarded as issued from the Intra-Pontide domain, whose geodynamic history is still a matter of debate. Along the Akpinar-Araç-Bayramoren geotraverse, located in central Turkey, an ophiolite-bearing mélange known as the Arkot Da? Mélange, is well-exposed along the Intra-Pontide suture zone. The Arkot Da? Mélange plays a key role in the interpretation of the geodynamic history of the Intra-Pontide domain and can be described as a Late Santonian chaotic sedimentary deposit consisting of an up to 1000-m-thick succession of slide-blocks of different sizes and lithologies enclosed in a sedimentary matrix consisting of shales, coarse-grained arenites, pebbly mudstones and pebbly sandstones. The slide-blocks, from a few meters to hectometers in size, are represented by metamorphic rocks (mainly micaschists and gneisses), by ophiolites (peridotites, gabbros, IAT and BABB basalts and cherts) and by sedimentary rocks (cherts, neritic and pelagic limestone, marly limestone and ophiolite-bearing turbidites). The youngest age among the slide-blocks has been provided by the ophiolite-bearing turbidites where a late Coniacian nannofossil assemblage has been found. The cherts have provided a wide range of ages from the Middle Triassic to Late Cretaceous, whereas the fossils found in the limestone indicate Late Jurassic to Early Cretaceous ages. The matrix of the Arkot Da? Mélange, even if unaffected by metamorphism, shows deformations represented by multiple meters-thick cataclastic shear zones at the boundaries of the mélange slices or inside of them. According to its features, the source area of the Arkot Da? Mélange was most likely a continental and oceanic thrust sheet emplaced in the Late Cretaceous onto a continental margin. The data collected from the different slide-blocks suggest that the Intra-Pontide domain was characterised by an oceanic basin opened at the latest in the Early Jurassic. The opening of the Intra-Pontide oceanic basin was followed by the development of a subduction zone with a subsequent opening of suprasubduction oceanic basin in the Middle Jurassic-Early Cretaceous. The convergence in this suprasubduction oceanic basin started at the Early/Late Cretaceous boundary by an obduction process, whereas its final closure can be regarded as Late Paleocene in age.

  12. 3-D geodynamic models of the India-Eurasia collision zone: investigating the role of lithospheric strength variation Sarah Bischoff and Lucy Flesch EAPS, Purdue University

    NASA Astrophysics Data System (ADS)

    Bischoff, S. H.; Flesch, L. M.

    2013-12-01

    The India-Eurasia collision zone is the largest zone of continental deformation on the Earth's surface. A proliferation of geodetic, seismic, and geologic data across the zone provides a unique opportunity for constraining geodynamic models and increasing our understanding of mountain building and plateau growth. We present a 3-D, spherical, Stokes flow, finite volume, geodynamic model of the India-Eurasia collision. Lithospheric volume is constrained by seismic data. Continuous surface velocities, inferred from GPS and Quaternary fault slip data, are used to approximate velocity boundary conditions. We assume a stress-free surface, and free-slip along the model base. Model viscosity varies with depth and is calculated assuming the laterally-varying, depth-averaged viscosities of Flesch et al. (2001) and a cratonic Indian plate. Laterally the model extends from the southern tip of India northward to the Tian Shan, and from the Pamir Mountains eastward to the South China block. Vertically the model volume extends to a depth of 100 km, and is divided into three layers: upper crust, lower crust, and upper-lithospheric mantle. We use COMSOL Multiphysics (www.comsol.com) to investigate the role of vertical viscosity variation on surface deformation by holding the dynamics constant, adjusting the viscosity substructure, and determining the resultant stress and velocity fields. Solved model surface velocities are compared to the observed surface velocities inferred from GPS and Quaternary fault slip rates. A two-layer model employing laterally-variant viscosity estimates throughout the crust and mantle is ineffective at replicating the observed force balance. The weak crustal viscosities necessary for attaining the observed clockwise rotation around the eastern Himalayan syntaxis also result in erroneous southward velocities in southern Tibet, driven by excessive gravitational collapse. Strengthening crustal viscosities balances the boundary/body forces and allows for accommodation of Indian plate motion across Tibet, but no longer produces clockwise rotation around the eastern syntaxis. The best-fit velocity magnitude and rotation solution is achieved by a full three-layer model incorporating an upper crust of intermediate strength, a weaker lower crust, and a stronger upper mantle. Our three-layer model achieves rotation around the indenter without excessive gravitational collapse. Model and observed velocities diverge slightly in the Tarim Basin, the southern Gobi, and the northern South China block. Model velocities in the Tarim Basin are shifted in an easterly direction; possibly indicating a weaker than previously assumed Altyn Tagh fault, while Gobi and South China model velocities are shifted to the north; suggesting the presence of an additional level of complexity.

  13. A new numerical method to calculate inhomogeneous and time-dependent large deformation of two-dimensional geodynamic flows with application to diapirism

    NASA Astrophysics Data System (ADS)

    Fuchs, L.; Schmeling, H.

    2013-08-01

    A key to understand many geodynamic processes is studying the associated large deformation fields. Finite deformation can be measured in the field by using geological strain markers giving the logarithmic strain f = log 10(R), where R is the ellipticity of the strain ellipse. It has been challenging to accurately quantify finite deformation of geodynamic models for inhomogeneous and time-dependent large deformation cases. We present a new formulation invoking a 2-D marker-in-cell approach. Mathematically, one can describe finite deformation by a coordinate transformation to a Lagrangian reference frame. For a known velocity field the deformation gradient tensor, F, can be calculated by integrating the differential equation DtFij = LikFkj, where L is the velocity gradient tensor and Dt the Lagrangian derivative. The tensor F contains all information about the minor and major semi-half axes and orientation of the strain ellipse and the rotation. To integrate the equation centrally in time and space along a particle's path, we use the numerical 2-D finite difference code FDCON in combination with a marker-in-cell approach. For a sufficiently high marker density we can accurately calculate F for any 2-D inhomogeneous and time-dependent creeping flow at any point for a deformation f up to 4. Comparison between the analytical and numerical solution for the finite deformation within a Poiseuille-Couette flow shows an error of less than 2 per cent for a deformation up to f = 1.7. Moreover, we determine the finite deformation and strain partitioning within Rayleigh-Taylor instabilities (RTIs) of different viscosity and layer thickness ratios. These models provide a finite strain complement to the RTI benchmark of van Keken et al. Large finite deformation of up to f = 4 accumulates in RTIs within the stem and near the compositional boundaries. Distinction between different stages of diapirism shows a strong correlation between a maximum occurring deformation of f = 1, 3 and 4, and the early, intermediate and late stages of diapirism, respectively. Furthermore, we find that the overall strain of a RTI is concentrated in the less viscous regions. Thus, spatial distributions and magnitudes of finite deformation may be used to identify stages and viscosity ratios of natural cases.

  14. Tectonic framework and extensional pattern of the Malaguide Complex from Sierra Espuña (Internal Betic Zone) during Jurassic-Cretaceous: implications for the Westernmost Tethys geodynamic evolution

    NASA Astrophysics Data System (ADS)

    Martín-Martín, Manuel; Martín-Rojas, Iván; Caracuel, Jesús E.; Estévez-Rubio, Antonio; Algarra, Agustín Martín; Sandoval, José

    2006-09-01

    Mapping, lithostratigraphic, biostratigraphic and structural detailed analyses in Sierra Espuña area (Internal Betic Zone, SE Spain) have allowed us to reconstruct the Jurassic-Cretaceous evolution of the Westernmost Mesomediterranean Microplate palaeomargin and, by correlation with other sectors (Northern Rift, central and western Internal Betic Zone), to propose a geodynamic evolution for the Westernmost Tethys. Extension began from Late Toarcian, when listric normal faults activated; these faults are arranged in three categories: large-scale faults, separating hectometric cortical blocks; main faults, dividing the former blocks into some kilometre-length blocks; and secondary faults, affecting the kilometric blocks. This fault ensemble, actually outcropping, in the Sierra Espuña area, broke the palaeomargin allowing the westerly Tethyan Oceanic aperture with an extension at about 17.2%. Extension was not homogeneous in time, being the Late Toarcian to the Dogger-Malm boundary the period when blocks underwent the greatest movement (rifting phase), leading to the drowning of the area (8.2% extension). During the Malm (drifting phase) extension followed (5.7%), while during the Cretaceous a change to pelagic facies is recorded with an extension of about 3.3% ( post-drift stage). This evolution in the Westernmost Tethys seems to be related to areas out of the limit of significant crustal extension in the hanging wall block of the main cortical low-angle fault of the rifting.

  15. Time space distribution of magmatic activity in the western Mediterranean and peripheral orogens during the past 30 Ma (a stimulus to geodynamic considerations)

    NASA Astrophysics Data System (ADS)

    Savelli, Carlo

    2002-08-01

    Age and rock type, regional distribution and structural setting of volcanic and plutonic manifestations from the western Mediterranean basin and peripheral orogens during the past 30 Ma are examined. Distinct magmatic phases (which range tentatively between 30 and 15, 15 and 9, 8 and 6, 5 and 2, 2 and 1.5, and finally between 1.5 and 0 Ma) exhibit a large variety of rock types which reflect complex processes of backarc and arc extension related with convergence between the European and the African-Ionian-Adriatic plates. The overall length of a complex plate boundary zone increased with time from ca. 1400 to 2500 km along-strike. Widespread, extension-related orogenic products were emplaced subsequent to distinct convergent processes which led to formation of the Hercynian, Alpine and Apenninic orogens. Attenuation of the 'Alpine' area was initiated with eruption of plutonic and volcanic rocks of acidic calcalkaline composition and of volcanics of tholeiitic (subalkaline) affinity. Tholeiites were probably linked to faster rates of intra-orogenic extension reaching the stage of oceanic opening in the south Tyrrhenian sea. In addition, localized small-volume eruptions of ultrapotassic rocks (lamproites) accompanied thinning and stretching of the Alpine orogenic wedge. Intraplate Na-alkaline manifestations are widespread in the passive margins and in foreland areas. Overall, the episodic progression of magmatic activity in the western Mediterranean reflects complex geodynamic processes of retreating subduction, spreading and crustal attenuation which were preceded in time by continent-continent collision in the entire area.

  16. Geodynamic numerical modeling of the South Island of New Zealand: The effects of varied deposition location on surface expressions and lithospheric evolution

    NASA Astrophysics Data System (ADS)

    Anthony, T.; Pysklywec, R. N.

    2013-12-01

    The nature of continental plate collision remains as a poorly understood aspect of plate tectonics. While recent advances in geodynamics research has led to a greater understanding of coupling effects between atmospheric and solid Earth processes, one of the intriguing elements related to continental collision models is the apparent significant influence surficial processes, such as deposition, have on orogenesis and the evolution of the crust and sub-crustal lithosphere. In this study, we conduct a series of forward numerical models to investigate the thermomechanical evolution of the lithosphere-mantle system and to consider the influence of varying styles and rates of surface deposition during idealized continent-continent collisions. In particular, the numerical experiments are modeled on the collision of the Pacific-Australian plate boundary found at the South Island of New Zealand. The experiments use arbitrary Lagrangian-Eulerian finite element techniques and suggest that the evolving lithosphere during continent-continent collision is significantly altered by the location of deposited sediment. For example, our experiments show that in collisions that would otherwise be subjected to lithospheric slab retreat, a balancing sediment deposition within basins on both the pro- and retro-sides of the orogen results in the maintenance of stable, subduction-like plate consumption. The results presented represent the information obtained from thoroughly investigated models, and are interpreted in the context of available constraints for the South Island.

  17. Geology, Geochemistry and Geochronology of the Upper Cretaceous high-K volcanics in the southern Part of the Eastern Pontides: Implications for Mesozoic Geodynamic Evolution of NE Turkey

    NASA Astrophysics Data System (ADS)

    Eyuboglu, Y.

    2009-04-01

    The Eastern Pontide Orogenic Belt is one of the most complex geodynamic settings in the Alpine-Mediterranean region. Its geodynamic evolution is very controversial due to lack of systematic, quantitative structural, geochemical and geochronological data. This belt is divided into three subgroups: northern, southern and axial zones, distinguished from north to south by different lithological units, facies changes and tectonic characteristics. Especially, the southern zone is very attractive with its numerous rock associations such as alaskan-type mafic-ultramafic intrusions, shoshonitic and ultrapotassic volcanics, adakitic magmatics, glaucophane-bearing gabbros, metamorphic and ultramafic massifes. This study focuses on the petrology, geotectonic setting and evidence for subduction polarity of the Upper Cretaceous shoshonitic and ultrapotassic volcanics exposed in the most southerly part of the eastern Pontide magmatic arc. Geological, geochemical and isotopic data indicate that there were two distinct cycles of high-K volcanic activity in the southern part of the eastern Pontide magmatic arc during the Late Cretaceous. The first cycle (Early Campanian), represented by shoshonitic trachyandesites and associated pyroclastics, containing high K2O (2.74-4.81 wt %) and Na2O (3.60-5.51 wt %), overlies the Middle-Cretaceous ophiolitic-olistostromal melange formed during the rifting stage of a back-arc basin (Neotethys). The second cycle of high-K volcanism is characterized by potassic or ultrapotassic analcime-bearing volcanics, erupted in a lagoonal environment during the Maastrichtian. Progressive shallowing of the basin indicates that Upper Cretaceous high-K volcanism developed during the final stage of pull-apart basin development in the southern zone of the eastern Pontides. These volcanic rocks, intercalated with continental detritus, are characterized by high Na2O (3.22-7.16 wt %) concentrated in secondary analcime crystals. Their K2O contents also range between 0.83 and 6.05 (wt %). Volcanic rocks belonging to both cycles have remarkable similarity in their trace and rare earth element concentrations and display variable enrichment in large ion lithophile elements (LILE), high field strength elements (HFSE), light rare earth elements (LREE) and heavy rare earth elements (HREE) with respect to primitive mantle and chondrite. Negative Nb, Ta, Zr, Hf and Ti anomalies are typical of subduction-related arc magmas. In addition, Nd-Sr and Pb isotope ratios of the investigated volcanics support that they are products of a similar mantle source. Undoubtedly, the existence of the subduction-related high-K volcanics in the southern part of the eastern Pontide magmatic arc is very important for interpretation of subduction polarity. Southward subduction of the Paleotethys oceanic crust during Mesozoic can be separated into two main stages. The first stage of southward subduction ended with slab break-off of the old and dense part of the Paleotethys oceanic crust during the Mid-Cretaceous. This process caused upwelling of the asthenospheric mantle and opening of the back-arc basins in the eastern Pontides. Middle Cretaceous olistostromal ophiolitic mélange formed on the transitional crust or on true oceanic crust restricted by deep spreading troughs of the pull-apart basins. Deformation of the deep-spreading troughs, in which the mélange formed, was initially extensional (drifting stage) but became increasingly compressional (infilling stage) as the strike-slip cycle was completed. Southward migration of the Upper Cretaceous volcanism in the eastern Pontides (arranged TH-CA in the north, CA-A in the south and shoshonitic-ultrapotassic in the far south) implies that the remaining undepleted part of Paleotethys oceanic crust continued to subduct southward. In addition, intense volcanic activity and emplacement of granite, gabbro and diorite intrusions in the northern part of the arc caused break-up of the Malm-Lower Cretaceous carbonate platform during the Upper Cretaceous.

  18. 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-Miocene dynamics and which are overprinted or crosscut by the modern orogen (Dumont et al., 2011). Theses examples show that, in different structural and geodynamic settings, detailed analysis of basin floor morphology, (re)sediments transport directions, syndepositional deformations and provenance of exotic blocks can provide useful information about the regional kinematics, which can be integrated with other datasets, i.e. tectonic, metamorphic, thermochronologic, etc. Dumont T., Schwartz S., Guillot S., Simon-Labric T., Tricart P. & Jourdan S. (2011), Structural and sedimentary records of the Oligocene revolution in the Western Alpine arc. Jour. Geodyn., in press. Ferry S. & Flandrin J. (1979), Mégabrèches de resédimentation, lacunes mécaniques et pseudo-« hard-grounds » sur la marge vocontienne au Barrémien et à l'Aptien inférieur (SE France). Géologie Alpine, 55, p. 75-92. Michard A., Dumont T., Andreani L. & Loget N. (2010), Structural and sedimentary records of the Oligocene revolution in the Western Alpine arc. Bull. Soc. Géol. Fr., 181, p. 565-581.

  19. 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

    The recent and active deformation that affects the crest zone of the Umbria-Marche belt (Northern Apennines, Italy) displays a remarkable extensional character, outlined by development of normal fault sets that overprint pre-existing folds and thrusts of Late Miocene-Early Pliocene age. The main extensional fault systems often bound intermontane depressions hosting recent, mainly continental, i.e. fluvial or lacustrine deposits, separating the latter from Triassic-Miocene, mainly carbonatic and siliciclastic marine rocks that belong to the Romagna-Umbria-Marche stratigraphic succession. Stratigraphic data indicate that the extensional strain responsible for the development of normal fault-bounded continental basins in the outer zones of the Northern Apennines was active until Middle Pleistocene time. Since Middle Pleistocene time onwards a major geodynamic change has affected the Central Mediterranean region, with local reorganization of the kinematics in the Adria domain and adjacent Apennine belt. A wide literature illustrates that the overall deformation field of the Central Mediterranean area is presently governed by the relative movements between the Eurasia and Africa plates. The complex interaction of the Africa-Adria and the Anatolian-Aegean-Balkan domains has led the Adria microplate to migrate NW-ward and to collide against Eurasia along the Eastern Southern Alps. As a consequence Adria is presently moving with a general left-lateral displacement with respect to the Apennine mountain belt. The sinistral component of active deformations is also supported by analysis of earthquake focal mechanisms. A comparison between geophysical and geological evidence outlines an apparent discrepancy: most recognized recent and active faults display a remarkable extensional character, as shown by the geometry of continental basin-bounding structutes, whereas geodetic and seismologic evidence indicates the persistency of an active strike-slip, left-lateral dominated 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.

  20. 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 ?Hf (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 ?Hf (t) = 3.8-8.2, with TDM2 of 741-1024 Ma, suggesting the major involvement of juvenile crustal components. The various ?Hf values of the Carboniferous Baolidao and Triassic Halatu granitoids indicates a hybrid magma source of juvenile material with old crustal component, and the ?Hf (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.

  1. The lithosphere architecture and geodynamic of the Middle and Lower Yangtze metallogenic belt in eastern China: constraints from integrated geophysical data

    NASA Astrophysics Data System (ADS)

    Lü, Qingtian; Shi, Danian; Jiang, Guoming; Dong, Shuwen

    2014-05-01

    The lithosphere structure and deep processes are keys to understanding mineral system and ore-forming processes. Lithosphere-scale process could create big footprints or signatures which can be observed by geophysics methods. SinoProbe has conducted an integrated deep exploration across middle and lower reaches of Yangtze Metallogenic Belt (YMB) in Eastern China, these included broadband seismic, reflection seismic, wide-angle reflection and magnetotellurics survey. Seismic reflection profiles and MT survey were also performed in Luzong, Tongling and Ningwu ore districts to construct 3D geological model. The resulting geophysical data provides new information which help to better understanding the lithosphere structure, geodynamic, deformation and heat and mass transportation that lead to the formation of the Metallogenic Belt. The major results are: (1) Lower velocity body at the top of upper mantle and a SE dipping high velocity body were imaged by teleseismic tomography beneath YMB; (2) Shear wave splitting results show NE parallel fast-wave polarization direction which parallel with tectonic lineament; (3) The reflection seismic data support the crustal-detachment model, the lower and upper crust was detached during contraction deformation near Tanlu fault and Ningwu volcanic basin; (4) Broadband and reflection seismic confirm the shallow Moho beneath YMB; (5) Strong correlation of lower crust reflectivity with magmatism; (6) The lower crust below Luzong Volcanics shows obvious reflective anisotropy both at the crust-mantle transition and the brittle-ductile transition in the crust. All these features suggest that introcontinental subduction, lithosphere delamination, mantle sources magmatic underplating, and MASH process are responsible for the formation of this Mesozoic metallogenic belt. Acknowledgment: We acknowledge the financial support of SinoProbe by the Ministry of Finance and Ministry of Land and Resources, P. R. China, under Grant sinoprobe-03, and financial support by National Natural Science Foundation of China under Grant 40930418

  2. Seismic and gravity constraints on the nature of the basement in the Africa-Eurasia plate boundary: New insights for the geodynamic evolution of the SW Iberian margin

    NASA Astrophysics Data System (ADS)

    Martínez-Loriente, Sara; Sallarès, Valentí; Gràcia, Eulàlia; Bartolome, Rafael; Dañobeitia, Juan José; Zitellini, Nevio

    2014-01-01

    We present a new classification of geological domains at the Africa-Eurasia plate boundary off SW Iberia, together with a regional geodynamic reconstruction spanning from the Mesozoic extension to the Neogene-to-present-day convergence. It is based on seismic velocity and density models along a new transect running from the Horseshoe to the Seine abyssal plains, which is combined with previously available geophysical models from the region. The basement velocity structure at the Seine Abyssal Plain indicates the presence of a highly heterogeneous, thin oceanic crust with local high-velocity anomalies possibly representing zones related to the presence of ultramafic rocks. The integration of this model with previous ones reveals the presence of three oceanic domains offshore SW Iberia: (1) the Seine Abyssal Plain domain, generated during the first stages of slow seafloor spreading in the NE Central Atlantic (Early Jurassic); (2) the Gulf of Cadiz domain, made of oceanic crust generated in the Alpine-Tethys spreading system between Iberia and Africa, which was coeval with the formation of the Seine Abyssal Plain domain and lasted up to the North Atlantic continental breakup (Late Jurassic); and (3) the Gorringe Bank domain, made of exhumed mantle rocks, which formed during the first stages of North Atlantic opening. Our models suggest that the Seine Abyssal Plain and Gulf of Cadiz domains are separated by the Lineament South strike-slip fault, whereas the Gulf of Cadiz and Gorringe Bank domains appear to be limited by a deep thrust fault located at the center of the Horseshoe Abyssal Plain.

  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. The Alps 1: A working geodynamic model for burial and exhumation of (ultra)high-pressure rocks in Alpine-type orogens

    NASA Astrophysics Data System (ADS)

    Butler, Jared P.; Beaumont, Christopher; Jamieson, Rebecca A.

    2013-09-01

    Eocene (ultra)high-pressure ((U)HP) rocks exposed in the Western Alps are generally interpreted to result from subduction of European continental crust beneath Adria and its subsequent exhumation. However, the roles of extension (either from plate divergence or internal to the orogen) and erosion during exhumation remain controversial. Here we use 2D numerical geodynamic models to explain the formation and exhumation of (U)HP rocks in an Alpine-type orogen and interpret the results in the conceptual Prowedge-Uplifted Plug-Retrowedge-Conduit (PURC) framework. (U)HP metamorphism of oceanic and microcontinent crust in the models results from burial and accretion to a subduction channel/conduit formed beneath an advancing retrocontinent. Rapid exhumation from (U)HP conditions is achieved by the buoyancy-driven transport of a composite plume of stacked (U)HP oceanic and microcontinent crust from the subduction conduit to the overlying orogenic prowedge, accommodated by coeval thrusting and normal-sense shearing. Subsequent 'trans-crustal' exhumation is achieved by a combination of doming/internal extension and later retrotransport of the (U)HP plume through the uplifted plug, during underthrusting of the thick continental margin crust, coupled with increased erosion. Our proposed mechanism implies that exhumation-related normal-sense shearing in the Western Alps, per se, was driven from below by the buoyancy of the ascending plume, and that extension owing to plate divergence is not required to explain (U)HP rock exhumation. The efficiency of the exhumation mechanism depends strongly on the buoyancy and strength of the (U)HP plume, suggesting that in order to exhume rapidly, it must achieve a critical size. By implication, the multiple small Eocene (U)HP complexes within the Internal Crystalline Massifs may have been exhumed as part of a single composite body comprising diverse units aggregated from different levels of the subduction conduit during burial or ascent, rather than as individual small bodies exhumed in separate pulses.

  5. 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 recent back-arc basins. The difference in geological and isotope ages between the bimodal basalt-rhyolite volcanism with A-type granite plutonism (72 Ma) and the final synkinematic S-type granite plutonism (48 Ma) can be taken as a lifetime of the presumed BARB system of the Dinaridic Tethys. Remnants of this presumed subduction zone can be traced for 300 km along the surrounding northernmost Dinarides.

  6. New insights in the geodynamics of the Lipari-Vulcano area (Aeolian Archipelago, southern Italy) from geological, geodetic and seismological data

    NASA Astrophysics Data System (ADS)

    Barreca, G.; Bruno, V.; Cultrera, F.; Mattia, M.; Monaco, C.; Scarfì, L.

    2014-12-01

    Geological, geodetic and seismological data have been analyzed in order to frame the Lipari-Vulcano complex (Aeolian archipelago, southern Italy) into the geodynamic context of the southeastern Tyrrhenian Sea. It is located at the northern end of a major NNW-SSE trending right-lateral strike-slip fault system named "Aeolian-Tindari-Letojanni" which has been interpreted as a lithospheric discontinuity extending from the Aeolian Islands to the Ionian coast of Sicily and separating two different tectonic domains: a contractional one to the west and an extensional one to the north-east. Structural field data consist of structural measurements performed on well-exposed fault planes and fractures. The mesostructures are mostly represented by NW-SE striking normal faults with a dextral-oblique component of motion. Minor structures are represented by N-S oriented joints and tension gashes widespread over the whole analyzed area and particularly along fumarolized sectors. The analyzed seismological dataset (from 1994 to 2013) is based on earthquakes with magnitude ranging between 1.0 and 4.8. The hypocenter distribution depicts two major alignments corresponding to the NNW-SSE trending Aeolian-Tindari-Letojanni fault system and to the WNW-ESE oriented Sisifo-Alicudi fault system. GPS data analysis displays ?3.0 mm/yr of active shortening between the two islands, with a maximum shortening rate of about 1.0 × 10-13 s-1, between La Fossa Caldera and south of Vulcanello. This region is bounded to the north by an area where the maximum values of shear strain rates, of about 0.7 × 10-13 s-1 are observed. This major change occurs in the area south of Vulcanello that is also characterized by a transition in the way of the vertical axis rotation. Moreover, both the islands show a clear subsidence process, as suggested by negative vertical velocities of all GPS stations which exhibit a decrease from about -15 to -7 mm/yr from north to south. New data suggest that the current kinematics of the Lipari-Vulcano complex can be framed in the tectonic context of the eastward migrating Sisifo-Alicudi fault system. This is dominated by transpressive tectonics in which contractional and minor extensional structures can coexist with strike-slip motion.

  7. The Geodynamic Setting of Tertiary-Quaternary Intra-plate Magmatism in Europe: Is There a Link With the Iceland Plume System?

    NASA Astrophysics Data System (ADS)

    Wilson, M.

    2002-12-01

    Despite recent improvements in our understanding of the nature of mantle convection we still have few constraints on the geometry of the thermal (and chemical anomalies) widely referred to as mantle plumes. Several different scale lengths of convective instability are probable, with hot upwellings originating from thermal boundary layers in the Earth's mantle such as the 660 km discontinuity or the core-mantle boundary. Paleocene-Recent volcanism within western and central Europe, which is spatially and temporally linked to the development of a major intra-continental rift system and to domal uplift of Variscan basement massifs, has been attributed to the diapiric upwelling of small-scale, finger-like, convective instabilities from the base of the upper mantle. Evidence for this model comes from the French Massif Central and the Eifel province of northern Germany where both local and global seismic tomographic studies indicate the existence of localised zones of mantle upwelling from the base of the upper mantle, 100-300 km across and 100-200 degrees Centigrade hotter than ambient mantle. Global seismic tomographic studies also suggest the existence of a zone of low seismic velocities at depths of 900 to 1400 km in the lower mantle, extending from Iceland to the Eifel volcanic province of northern Germany, the Massif Central of France, the Hoggar massif in northern Africa and the Canary Islands. This raises the intriguing possibility that the diapiric upper mantle upwellings inferred to have triggered the Tertiary-Quaternary volcanic activity within Europe may be linked dynamically to the upwelling of the Iceland mantle plume. The spectrum of primitive mafic magma compositions within the European volcanic province ranges from melilite nephelinites and melilitites, through basanites and alkali basalts to subalkaline tholeiites; these are considered to be the products of variable degrees of partial melting of a relatively homogeneous HIMU-like reservoir within the upper mantle, the European Asthenospheric Reservoir or EAR. Variations in the trace element and Sr-Nd-Pb isotopic characteristics of magmas are consistent with mixing of partial melts from both lithospheric and asthenospheric mantle sources. A component geochemically similar to the EAR also exists within the Icelandic plume system; this is preferentially sampled by relatively rare, small degree, partial melts (nephelinites and alkali basalts). Thus both geophysical and geochemical data can be used to support a geodynamic link between the Paleocene-Recent activity of the Icelandic mantle plume system and the magmatism much further to the south in western and central Europe.

  8. 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 processes of continental drift, seems to be associated more to major changes in the Southern Ocean such as the evolution of the Scotia Arc and the deepening of the Drake Passage. Accordingly, these results support a genetic continuity between Antarctica and South America, probably along the Scotia Ridge, until the middle Miocene and a late ACC intensification at the Mio-Pliocene boundary.

  9. La Mamora, charnière entre la Meseta et le Rif: son importance dans l'évolution géodynamique postpaléozoïque du Maroc \\/ The Mamora Plain, a hinge between the Meseta and the Rif. Its importance in the post-Paleozoic geodynamic evolution of Morocco

    Microsoft Academic Search

    Lahcen Zouhri; Christian Lamouroux; Christophe Buret

    2001-01-01

    The Mamora area (Morocco) is located in the northern part of the Meseta and the southern part of Rharb. The recent formations (Mesozoic to Quaternary) lie unconformably on a Paleozoic basement. This study based on hydrogeological, sedimentological, drilling data and seismic reflection profiles interpretation, proposes new interpretations of geodynamical evolution of this area particularly in terms of tectonic patterns. The

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Structural and geodynamic study in central Tunisia using field and geophysical data: new structural interpretation of the N-S axis and associated Atlassic structures

    NASA Astrophysics Data System (ADS)

    Dhahri, Ferid; Tanfous, Dorra; Gabtni, Hakim; Boukadi, Noureddine

    2015-02-01

    A structural and geodynamic evolution of central Tunisia is constructed from field studies and geophysical data within the Tunisian Atlassic domain. Bouguer gravity and horizontal gradient magnitude (HGM) maps indicate that computed anomalies are related to subsurface structures and are in accordance with the general structural trends of central Tunisia. Near Cherichira fault, the strike is ENE-WSW, whereas it is N-S along the N-S axis, a major discontinuity between the Pelagian shelf to the east and Central Atlas Mountains to the west. E-W-oriented HGM profiles on the north side of the Cherichira fault show moderate HGM variations, which correspond to the NE-SW fault system of the Ousselet-Bou Dabbous. This trend is also expressed by the second-order vertical derivative map of this area. However, on the south side of the fault, a dominant peak is indicated rather than the anomalies characteristic of the north side of the fault. This anomaly is associated with the N-S axis discontinuity. Seismic reflection data are also used to elucidate the structural configuration and style north and south of the Cherichira fault. The seismic lines demonstrate that faulting and associate halokinesis in Ousselet-Bou Dabbous area are not comparable to the paleogeographic fault system of the N-S axis southward. To the south of Cherichira fault, the seismic lines show massive Triassic evaporates piercing along the major paleogeographic faults associated with thickness variations of Mesozoic and Cenozoic stratigraphic units and a reverse slip of western structural elements. It seems that the N-S axis corresponds to a steeply dipping major zone of weakness in the Tunisian Atlassic Mountains and indicates evidence of several stages of activity, including the rise of Triassic evaporates rise up which outcrop at several localities such as Rheouis and Mezzouna. The loading and upward rise of Triassic evaporites along this weak zone are a key factor in the thinning of the Mesozoic-Cenozoic sedimentary cover along this paleogeographic discontinuity. These new data indicate the northeast extrapolation of fold and grabens of the Central Atlas of Tunisia to the northeast of Kairouan, whereas the northern extent of the N-S axis is limited to south of the Cherichira fault. The Cherichira fault is NE-SW oriented and parallels the Ballouta-Zaghouan fault system, which reflects the regional strike of the Tellian orogeny and the associated nappes to the north. The geometry and kinematics of these Tellian features are linked to the tectonic evolution of the northern African margin, including Mesozoic extension separating the African and European plates to the inversion of these structures since the Late Cretaceous. The N-S axis is correlated in its direction and tectonic framework to the strike-slip fault system of the African craton, which is present to the south in the Algerian Saharan domain of Hoggar.

  15. Geodynamic implications of Collo-Bougaroun Miocene magmatic complex (Eastern Algerian margin): a review of U-Pb, K-Ar chronology and geochemistry

    NASA Astrophysics Data System (ADS)

    Fatiha, Abbassene; Aziouz, Ouabadi; Gilles, Chazot; Hervé, Bellon; René, Maury; Olivier, Bruguier

    2014-05-01

    The ''Petite-Kabylie' comprises all eastern Algerian coastal magmatic chain outcropping from Jijel to the west, up to the plain of Annaba, to the east. At the western part of this area, the Kabylie of Collo stretches between 6° and 7° E and 36° 30 'and 37° 06' N towards Skikda. The Bougaroun magmatic complex form a large elliptical batholith oriented ENE-WSW over 20 km that intrudes serpentinized peridotites and kinzigites of the Bougaroun basement to the east. This granitic pluton gives time constraints as it induces deformation and contact metamorphism of the Oligo-Miocene Kabyle sedimentary cover which are well observed at ''Collo-Oued Zhour' basin in the south. The Collo-Bougaroun volcano-plutonic complex, of ca. 300 km2, comprises (1) granular rocks, mainly cordierite bearing peraluminous granites (Bougaroun pluton to the north, the BeniToufout to the south and the Filfila to the east), (2) gabbros that occur at the northern and southern parts of Cap Bougaroun pluton where they are associated with ultramafic (3) microgranular rocks, mainly microgranites, that outcrop at the eastern part of the Bougaroun pluton, in Collo basin and El Milia, microdiorites in Bouserdoum and some doleritic or microgabbroic metric veins at Cap Bougaroun and (4) of lava in the Kef Cheraïa rhyolitic complex. Rocks from Collo-Bougaroun sites belong either to low-K, medium-K or high-K calc-alkaline series. The geochemistry of basic rocks (gabbros and dolerites) places strong constraints on their origin. Their LREE-depleted patterns, enrichment in LILE and slight depletion in HFSE are discussed in the very particular geodynamic context of the northern Algerian margin. Indeed, such depleted magmas could hardly have been emplaced over the African basement without experiencing any contamination imprint. Whole rock K/Ar ages were performed on 150-300 ?m grains from a set of representative magmatic rocks from Collo-Bougaroun region. The mafic rocks ages show a probable rejuvenation from (21.25 ± 6.01 (large error linked to the K2O wt% of 0.04) to 16.45 ± 0.52 Ma). This feature is attributed to a late K-gain during hydrothermal processes. This interpretation is supported by the occurrence of low temperature minerals (Adularia) in microgabbros and fine grained gabbros (microprobe analyses). The granite ages scatter between 20.85 ± 0.51 and 17.88 ± 0.5 Ma. The latter is consistent with 206U-238Pb age of 16.96±0.09 Ma obtained from 28 laser ablation spots analyses performed on zircon grains. Microgranites usually outcropping in Langhian ''post-nappes' basins, yield ages ranging from 14.17 ± 0.35 to 13.59 ± 0.33 Ma.

  16. Mantle sources and magma genesis in the Albanide-Hellenide ophiolites: Implications for the Triassic-Jurassic geodynamic evolution of the Eastern Tethyan branch

    NASA Astrophysics Data System (ADS)

    Saccani, Emilio; Beccaluva, Luigi; Photiades, Adonis; Zeda, Ottavia

    2010-05-01

    The Albanide-Hellenide ophiolites and related ophiolitic mélanges include eight different types of volcanic and subvolcanic rocks. They are: 1) Triassic alkaline rocks generated in within-plate settings (WPB); 2) Triassic high-Ti mid-ocean ridge basalts showing enriched compositions (E-MORB); 3) Triassic-Jurassic high-Ti mid-ocean ridge basalts showing normal compositions (N-MORB); 4) Jurassic basalts with geochemical features intermediate between MORB and island arc tholeiites; hereafter defined as medium-Ti basalts (MTB); 5) Jurassic low-Ti, island arc tholeiitic (IAT) rocks; 6) Jurassic very low-Ti (boninitic) rocks; 7) Jurassic backarc basin basalts and basaltic andesites (BABB); 8) Triassic and Jurassic calc-alkaline (CAB). It can be assumed that these different rock-types have formed from distinct mantle sources that are associated in turn to distinct tectonic settings within an oceanic environment (and surrounding areas), and that they record the fundamental stages of ocean basin development: continental break-up, sea-floor spreading, subduction initiation, and supra-subduction zone (SSZ) lithospheric accretion. The main aim of this work is therefore to identify the possible petrogenetic mechanisms (associated to mantle evolution) for the distinct lava groups and their related tectonic settings of formation, in order to propose a reconstruction of the geodynamic evolution of the Mesozoic Tethys in the Dinaride sector. The results of this study are mainly based on REE modelling of mantle sources, primary melt generation, and mantle residua and can be synthesised as follows: 1) From the Late Paleozoic - Early Triassic, extensional tectonics affecting the Gondwana trigged the rifting of the continental lithosphere. The associated magmatic activity included: (a) the formation of calc-alkaline rocks from a sub-continental mantle modified by geochemical components inherited from Hercynian subduction below Gondwana; (b) the eruption of alkaline basalts deriving from an OIB-type mantle source associated, in turn, with plume-type components. 2) During Mid-Late Triassic, the uprising of primitive asthenosphere led to the generation of the Tethyan oceanic lithosphere. This stage is associated with the formation of: (a) N-MORB magmatism derived from ~10-20% partial melting of primitive asthenosphere; (b) the persistence of alkaline WPBs; (c) generation of E-MORBs due to ~12% partial melting of primitive asthenosphere influenced by the OIB-type component. Residual MORB mantle is represented by depleted lherzolites. 3) During the Early Jurassic, the oceanic spreading involved only primitive asthenospheric mantle sources and their partial melt derivatives (N-MORBs). 4) From the Early-Mid Jurassic, the tectonic regime was dominated by intra-oceanic convergence associated with the development of MTB and IAT magmatisms, which derived respectively from ~10% and 10-20% partial melting of the MORB residual mantle with variable addition of subduction components. Afterwards, the progressive slab roll-back led to mantle diapirism toward the forearc and incipient arc spreading associated either with 10-20% partial melting of previously depleted mantle sources (harzburgites) or with ~30% partial melting of the MORB residual mantle (depleted lherzolites), both enriched in LREE by subduction-derived fluids. These partial-melting events produced the boninitic magmas in both forearc and inner arc and left depleted extremely depleted harzburgites and dunites as the residual mantle. 5) During the Late Jurassic, a magmatic arc developed onto the Eurasia continental realm, leading to the formation of CAB rocks by ~15-20% partial melting of depleted peridotite mantle significantly enriched in Th and LREE by subduction-derived fluids. Soon after, extension in the backarc region (most likely favoured by strike-slip tectonics) led to the uprising of primitive asthenosphere, which was enriched in Th and LREE by the nearby subduction. 10-20% partial melting of this source produced the BABBs, which crop out (with CAB intercalations) in the Guevgueli Com

  17. 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 ?Nd(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 ?Nd(t) values (- 2.7 to - 3.2) are typical of adakitic magmas generated by partial melting of a subducted slab. These magmas were then hybridized in the mantle wedge with peridotite melt. The quartz diorite-tonalite-granodiorite stock and granodiorite batholith could be considered as arc-related granitoid intrusions, which were emplaced during the northward subduction of Paleo-Tethys Ocean crust beneath the Turan micro-continent. The monzogranite is strongly peraluminous (Al2O3/(CaO + Na2O + K2O) Mol. = 1.07-1.17), alkali-rich with normative corundum ranging between 1.19% and 2.37%, has high initial 87Sr/86Sr ratios (0.707457-0.709710) and low initial 143Nd/144Nd ratios (0.512042-0.512111) and ?Nd(t) values (- 5.3 to - 6.6) that substantiate with geochemical attributes of S-type granites formed by dehydration-melting of heterogeneous metasedimentary assemblages in thickened lower continental crust. The monzogranite was emplaced as a consequence of high-temperature metamorphism during the final integration of Turan and Iran plates. The ages found in the Mashhad granites show that the subduction of Paleo-Tethys under the Turan plate that led to the generation of arc-related Mashhad granites in late-Triassic, finally ceased due to the collision of Iran and Turan micro-plates in early Jurassic.

  18. Quaternary, catastrophic rock avalanches in the Central Apennines (Italy): Relationships with inherited tectonic features, gravity-driven deformations and the geodynamic frame

    NASA Astrophysics Data System (ADS)

    Bianchi Fasani, G.; Di Luzio, E.; Esposito, C.; Evans, S. G.; Scarascia Mugnozza, G.

    2014-04-01

    Five cases of Quaternary rock avalanches detached from carbonate mountain ridges in the Central Apennines are presented. Due to the large amount of rock masses involved, the width of accumulation and detachment areas and the damming in the host environment, the analysed rock avalanches can be considered as catastrophic rock slope failures, sporadic events in a mountain region characterized by low elevation but where mountain ridges can have a relative elevation of up to 1 km above the lowermost valley floors. The geological setting of tectonic structures that originated during the Apennine orogenesis influenced rock avalanche characteristics, determining the location and shape of detachment areas, the kind of rock mass involved, and the failure mechanisms. Two main types have been identified: i) forelimb rock-slide avalanches (FRSA) such as the Lettopalena and Mt. Arezzo rock avalanche which involved Cenozoic, heterogeneous sequences of carbonate ramp deposits detached from box-shaped source areas according to a rock sliding mechanism; and ii) backlimb slide-wedge rock avalanches (BSWRA) such as the Campo di Giove, Scanno and Celano rock avalanches that detached from sub-circular source areas carved on fault-bounded ridges and involving Meso-Cenozoic carbonate rocks with a combined sliding and rock wedge failure mechanism. The Campo di Giove, Lettopalena and Scanno rock avalanches originated from mountain ridges bounded by inactive fault zones and undergoing deep-seated gravitational slope deformations (DSGSDs) at the mountain scale. These three rock slope failures are considered as isolated events of long-lasting deformative processes featuring creep deformation. Gravity-driven deformations firstly generated as a response to stacking processes and synchronous normal faulting during the Neogene-Early Pleistocene Apennine tectonics. In particular, the Caramanico Fault System (CFS) and the Genzana Fault (GF), bordering the carbonate ridges from which the Campo di Giove and Scanno rock avalanches originated respectively, are here considered as backlimb collapse structures accommodating the passive uplift and deformation of positive tectonic structures. Gravity-driven deformations persisted during the post-Early Pleistocene dome-like uplift of the whole Apennine region. The regional uplift created the first-order (200 km) topographic wave-length of the belt, i.e. a periodic loading which has been balanced by the deflection of the Apennine crust and lithosphere. On the contrary, shorter topographic wave-lengths inherited from former thrusting and synchronous normal faulting determined local isostatic imbalances bearing a large potential for the mature development of DSGSDs on mountain ridges, favoured also by lateral unloading due to linear erosion and increase of topographic stress. Thus, a cause-effect relationship is hypothesized between the geodynamic evolution of the belt and mountain-sized gravity-driven deformations including large rock slope failures.

  19. Petrogenesis and U-Pb zircon chronology of felsic tuffs interbedded with turbidites (Eastern Pontides Orogenic Belt, NE Turkey): Implications for Mesozoic geodynamic evolution of the eastern Mediterranean region and accumulation rates of turbidite sequences

    NASA Astrophysics Data System (ADS)

    Eyuboglu, Yener

    2015-01-01

    The Meso-Cenozoic geodynamic evolution of the Eastern Pontides Orogenic Belt, which is one of the key areas of the Alpine-Himalayan system, is still controversial due to lack of systematic geological, geophysical, geochemical and chronological data. The prevailing interpretation is that this belt represents the southern margin of Eurasia during the Mesozoic and its geodynamic evolution is related to northward subduction of oceanic lithosphere. This paper reports the first detailed geological, geochemical and chronological data from felsic tuffs interbedded with late Cretaceous turbidites in the Southern Zone of the Eastern Pontides Orogenic Belt. Individual tuff layers are thin, mostly < 2 m in thickness, implying that these are dominantly air-fall tuffs. Petrographic data indicate that the felsic tuffs, which exhibit various degrees of alteration, can be classified as crystal-rich and crystal-poor tuffs. The crystal-poor tuffs consist mainly of 45-65% devitrified glass shards and 10-20% broken quartz crystals, whereas the crystal-rich tuffs consist of > 50% crystals. The zircon U-Pb data show three statistically distinct ages at 84, 81 and 77 Ma, with uncertainties of about 1 Ma, suggesting that tuff-forming late Cretaceous magmatism started about 84 Ma ago and was episodically active over a minimum of 7 Ma. The age data also indicate that the average accumulation rate of the turbiditic sequence that hosts the felsic tuffs remained constant between 36 and 40 cm/10 ky. Their enrichment in LIL and LRE elements relative to HFS and HRE elements, and also strongly negative Nb, Ta and Ti anomalies, are consistent with those of magmas generated by subduction-related processes. The tuffs have relatively low initial ratios of 143Nd/144Nd (0.512296-0.512484; ?Nd: - 2.1 and - 7.2) and 87Sr/86Sr (0.704896-0.706159). Their initial Pb isotopic compositions range from 18.604 to 18.646 for 206Pb/204Pb, from 15.644 to 15.654 for 207Pb/206Pb and from 38.712 to 38.763 for 208Pb/204Pb. The distribution of Sr-Nd isotopic compositions in the late Cretaceous igneous rocks from different locations of the Eastern Pontides Orogenic Belt is consistent with two-component mixing between depleted mantle and crust. However, the Pb isotopic data are not compatible with two-component mixing and require at least a third component. Considering all of the new data and also previous data such as southward migration and increasing potassium content of the late Cretaceous arc volcanism, the northward migration of Cenozoic igneous activity, northward drift of the belt since the late Cretaceous and the existence of south-dipping reverse fault systems in the whole region, the Meso-Cenozoic geodynamic evolution of the Eastern Pontides Orogenic Belt can be best explained by southward subduction of Tethys oceanic lithosphere, rather than northward subduction.

  20. Early Cambrian Post-collisional volcanosedimentary Rey Bouba greenstone belt in northern Cameroun: LA-MC-ICP-MS U-Pb geochronology and implications for the geodynamic evolution of the Central African Fold Belt (CAFB).

    NASA Astrophysics Data System (ADS)

    Bouyo, Merlain

    2014-05-01

    The Rey Bouba Greenstone Belt (RBGB) is a greenschist volcanosedimentary basin representing the youngest accretion event that characterized the geodynamic evolution of the CAFB of Northern Cameroon. LA-MC-ICP-MS U-Pb detrital zircon data indicate that both older PP to MP and younger NP to Early Cambrian sources from ca 2000 to ca 540 Ma, with main provenance being zircon grains from Cryogenian igneous rocks (between ca 850 and ca 650 Ma) were involved in the formation of the RBGB basin. Considering the age of metamorphism inferred from high pressure granulites at ca 600 Ma within the CAFB of northern Cameroon as the most direct evidence for the timing of continental collision, we conclude that the deformation associated with migmatites and post-collisional granites which fed the Rey Bouba basin mostly with NP zircon lasts until post 540 Ma, in correlation with the final amalgamation of the Gondwana Supercontinent during Latest Neoproterozoic-Earliest Cambrian. Therefore, the RBGB may represent the youngest post-collisional metavolcanosedimentary basin within the CAFB.

  1. 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

    Petrological and geochronological data of high pressure (HP) rocks from Cuba and Dominican Republic indicate continuous subduction in the northern edge of the Caribbean since ca. 120 Ma. However, expected correlation of the associated subduction zone towards the west in Guatemala is uncertain, for similar HP rocks in this region have metamorphic ages as old as 150 Ma. In this contribution we present new geochemical and U-Pb/Lu-Hf ages of HP rocks from the Escambray terrane and the central Cuba serpentinite mélange that allow geodynamic correlations between the Greater Antilles and Guatemala during the early and late Cretaceous. The Escambray composite terrane constitutes a metamorphic accretionary complex containing oceanic and platform-derived metasedimentary and metaigneous rocks that were tectonically assembled in the Caribbean subduction environment during the latest Cretaceous. The complex crops out as two domes, named Trinidad to the west and Sancti Spiritus to the east, forming a tectonic window below the arc-related Mabujina amphibolite complex and the allochthonous Cretaceous volcanic arc terrane. The latter overrides the central Cuba mélange, which contains low-pressure ophiolitic blocks and HP blocks of eclogite, garnet amphibolite and blueschist facies rocks within a serpentinitic matrix. This serpentinite mélange and similar melange bodies within the Escambray complex have been interpreted as fragments of the Caribbean subduction channel. The studied HP samples are of basaltic composition, poor in K2O (<0.34 wt %) and Rb (< 3.05 ppm), relatively rich in Ta (0.07-0.77 ppm) and Hf (0.74-4.17 ppm), and rich in Nb (0.68- 13.53 ppm). Most samples show a REE chondrite-normalised patterns characterized by a subtle LREE depletion, except a few samples which are characterized by slight enrichment in LREE. Based on their distinctive trace-element contents, most of the basaltic protholiths of the samples are identified as E- to N-MORB signature. Some samples 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.

  2. Projection for Space Geodynamics, 1988-1998

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Premises defining the technical and operational environment of the next decade are listed. Observational programs required to satisfy scientific objectives in the study of geopotential fields, global dynamics, tectonics, and regional tectonics/crustal hazards are defined. Capabilities and applications of the Geopotential Research Mission to be launched in the early 1990's are explored and the benefits of more detailed measurements of the Moon and planets are indicated. Earthquake prediction in the western part of the U.S. is discussed. The use of decimeter, centimeter, and millimeter systems for very long baseline interferometry, satellite laser ranging, and lunar ranging techniques are discussed. Geographic regions of particular interest are identified.

  3. 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.

  4. Precise leveling, space geodesy and geodynamics

    NASA Technical Reports Server (NTRS)

    Reilinger, R.

    1981-01-01

    The implications of currently available leveling data on understanding the crustal dynamics of the continental United States are investigated. Neotectonic deformation, near surface movements, systematic errors in releveling measurements, and the implications of this information for earthquake prediction are described. Vertical crustal movements in the vicinity of the 1931 Valentine, Texas, earthquake which may represent coseismic deformation are investigated. The detection of vertical fault displacements by precise leveling in western Kentucky is reported. An empirical basis for defining releveling anomalies and its implications for crustal deformation in southern California is presented. Releveling measurements in the eastern United States and their meaning in the context of possible crustal deformation, including uplift of the Appalachian Mountains, eastward tilting of the Atlantic Coastal Plain, and apparent movements associated with a number of structural features along the east coast, are reported.

  5. 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.

  6. CONSTRAINTS ON SUBDUCTION GEODYNAMICS FROM SEISMIC ANISOTROPY

    E-print Network

    made over the past several decades in delineating the structure of subducting slabs, but several key include those related to mantle wedge viscosity and rheology, slab hydration and dehydration, mechanical

  7. 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.

  8. Geodynamics: How plumes help to break plates

    NASA Astrophysics Data System (ADS)

    Buiter, Susanne

    2014-09-01

    Computer models show how hot material that rises from Earth's interior is affected by plate tectonics, producing unexpected irregularities in Earth's topography and assisting in the break-up of continental plates. See Letter p.85

  9. Aral Sea Basin Evolution: Geodynamic Aspect

    Microsoft Academic Search

    Bakhtiar Nurtaev

    \\u000a The Aral Sea lies in the Aral-Sarykamysh depression, which is bordered by the low plains of Central Asia. The climate is continental\\u000a and extremely dry, and surface runoff is virtually zero. Since direct precipitation over the lake comprises only 10% of the\\u000a water budget, lake-level fluctuations are largely determined by changes in inflow from the Amu Darya and Syr Darya

  10. 12.520 Geodynamics, Fall 2004

    E-print Network

    Hager, Bradford H.

    This course deals with mechanics of deformation of the crust and mantle, with emphasis on the importance of different rheological descriptions: brittle, elastic, linear and nonlinear fluids, and viscoelastic.

  11. Metamorphic chemical geodynamics of subduction zones

    Microsoft Academic Search

    Gray E. Bebout

    2007-01-01

    Study of metamorphic suites directly representing the deep subduction of altered oceanic crust and sediments can help elucidate the geochemical evolution of the forearc-to-subarc slab mantle interface, the nature of slab-derived fluids added to arc lava source regions, and the chemical changes in subducting rocks potentially contributing to the geochemical heterogeneity of the deeper mantle. The stage is set for

  12. On the geodynamic setting of kimberlite genesis

    NASA Technical Reports Server (NTRS)

    England, P.; Houseman, G.

    1984-01-01

    The emplacement of kimberlites in the North American and African continents since the early Palaeozoic appears to have occurred during periods of relatively slow motion of these continents. The distribution of kimberlites in time may reflect the global pattern of convection, which forces individual plates to move faster or slower at different times. Two-dimensional numerical experiments on a convecting layer with a moving upper boundary show two different regimes: in the first, when the upper boundary velocity is high, heat is transferred by the large-scale circulation and in the second, when the upper boundary velocity is lower, heat is predominantly transferred by thermal plumes rising from the lower boundary layer. For a reasonable mantle solidus, this second regime can give rise to partial melting beneath the moving plate, far from the plate boundaries. The transition between these modes takes place over a small range of plate velocities; for a Rayleigh number of 1,000,000 it occurs around 20 mm/yr. It is suggested that the generation of kimberlite magmas may result from thermal plumes incident on the base of a slowly moving plate.

  13. Geodynamic Information in Peridotite CLAUDE HERZBERG*

    E-print Network

    in kimberlite. Some of these differences reflect variable temperature and pressure conditions of melt extraction's mantle occur as xenoliths in kimberlite and alkali basalt, tectonic crustal emplacements (i.e. Alpine

  14. International lithosphere program - Exploiting the geodynamics revolution

    NASA Technical Reports Server (NTRS)

    Flinn, E. A.

    1984-01-01

    After presenting a development history of the application of spacecraft technology in the field of earth dynamics, which encompasses the measurement of the motion and the large scale deformation of the tectonic plates as well as the monitoring of earth's gravity and magnetic fields, attention is given to the International Lithosphere Program (ILP). ILP studies the dynamics and evolution of the lithosphere, with a view to earth resources identification and geological hazard reduction. Among the major problems being addressed is the mechanism by which magmas are generated, extruded, and intruded, at convergent and divergent plate boundaries and within plates. By contrast to current understanding of rifting, almost nothing is known about how the process of subduction begins. The methods used to measure tectonic plate phenomena are: laser ranging to both the moon and man-made satellites, and VLBI.

  15. Applied Geodynamics Laboratory Salt Tectonics Sandbox Animations

    NSDL National Science Digital Library

    Giovanni Guglielmo

    This collection of salt tectonics sandbox animation movies done by Giovanni Guglielmo, and available at UT Austin website, can be used to illustrate concepts and processes in a structural geology course. To access the animations, click on the 'animations' link in the menu on the left side of the web page. The animations are excellent for illustrating that the path from undeformed strata to final cross section is highly dynamic and can include a world of unrealized intermediate geometries. For example, the animations 'Rising and falling diapirs' can be used to introduce the concepts, and 'Raft Tectonics - Kwanza Basin' to illustrate the possibilities.

  16. Magmatism and Geodynamics of Eastern Turkey

    NASA Astrophysics Data System (ADS)

    Keskin, Mehmet; Oyan, Vural; Sharkov, Evgenii V.; Chugaev, Andrey V.; Genç, ?. Can; Ünal, Esin; Aysal, Nam?k; Duru, Olgun; Kavak, Orhan

    2013-04-01

    Eastern Turkey has been an active collision zone for the last 15 My between the Arabian Plate and Eurasian continent. The collision initiated after the closure of the southern branch of the Neotethys Ocean by northward subduction beneath E Anatolia at ~15 Ma. The collision-related volcanism started immediately after the closure of the ocean (again at around 15 Ma) in the north of the present day Lake Van with the eruption of mostly intermediate to acid lavas displaying distinct subduction characteristics. Both continental collision and the magmatism are still active, because the Arabian plate still converges to Anatolia with a velocity of ~2.5 cm/y. The overriding Anatolian block experienced a major uplift event around 10 Ma. The region once resided below the sea level merged as a widespread plateau ~2 km above the sea level as part of a regional dome structure with ~1000 km diameter, extending from Central Anatolia in the West to Azerbaijan in the East. The first alkaline lavas derived from a relatively more enriched source erupted to the surface in the N of Lake Van coeval with the initiation of the uplift at around 10 Ma. The underthrusting Arabian platform, on the other hand, was deformed as a result of both crustal-scale east-west folds adjacent to the major thrust zone and extensional deformations perpendicular to the suture zone. Alkaline within-plate lavas with no subduction component erupted through these extension zones. This intraplate volcanism focused on the Karacada? volcanic complex that covers an area of ~10,000 km2. Early Stage volcanism of Karacada? was dominated by magmas derived from a shallower metasomatized (litospheric) mantle source, while magmas of the later stages were derived from deeper (asthenospheric) sources. The Karacada? volcanic area of SE Anatolia was sourced by a garnet bearing, deep asthenospheric mantle which is similar to that of Afar in terms of its Pb isotopic ratios. This brings into question whether the mantle material from the Afar plume reached beneath Eastern Anatolian by a mantle convection cell. We argue that both the uplift and the widespread volcanism across the region share a common reason: a major "slab-steepening and breakoff event beneath the large Eastern Anatolian Accretionary Complex". We argue that the older intermediate calc-alkaline volcanic products displaying a distinct subduction signature were possibly derived from the mantle wedge that opened out due to the steepening of the slab after the continental collision. Being unsupported by the subduction, the slab started to be steepened beneath the region, possibly resulting in widening, invasion and upwelling of the mantle wedge beneath E Anatolian accretionary complex. This possibly created a sucking effect on the asthenosphere, creating a mantle flow from the Pontides in the north to the south. The inferred asthenospheric flow perhaps pulled a portion of the asthenosphere that once had resided beneath the Pontide arc. Therefore, the subduction component was inherited from the previous Pontide arc magmatism. The widespread decompressional melting generated voluminous magmas with the aforementioned inherited subduction signature in a period from 15 to 10 Ma. The slab broke off beneath the region, creating a slab window at around 10 Ma. This caused the enriched asthenospheric mantle with no subduction component beneath the Arabian continent to flow to the north through a slab-window. As a result, the subduction-modified E Anatolian and the enriched Arabian asthenospheric mantles started to mix into each other. We interpret the eruption of the first alkaline lavas in the region at around 10 Ma (e.g. tephrites and alkaline basalts in the N of Lake Van) as the indication of the formation of the slab-window beneath the region due to tearing of the slab. The volcanism in the collision zone continued till the historical times. The region includes some of the largest volcanic centers (e.g. Ararat, Nemrut, Tendürek and Süphan volcanoes) and plateaus (e.g. The Erzurum-Kars Plateau) around the Mediterranean

  17. 12.520 Geodynamics, Fall 2005

    E-print Network

    Hager, Bradford H.

    This course deals with mechanics of deformation of the crust and mantle, with emphasis on the importance of different rheological descriptions: brittle, elastic, linear and nonlinear fluids, and viscoelastic.

  18. Geodynamic control on melt production in the central Azores : new insights from major and trace elements, Sr, Nd, Pb, Hf isotopic data and K/Ar ages on the islands of Terceira, Sao Jorge and Faial

    NASA Astrophysics Data System (ADS)

    Hildenbrand, A.; Weis, D. A.; Madureira, P.; Marques, F. O.

    2012-12-01

    A combined geochronological and geochemical study has been carried out on the volcanic islands of Terceira, São Jorge, and Faial (central Azores) to examine the relationships between mantle dynamics, melt production and regional deformation close to the triple junction between the American, the Eurasian and the Nubian lithospheric plates. The lavas analyzed span the last 1.3 Myr, and have been erupted during two main periods prior to 800 ka and after 750 ka, respectively. They range in composition from alkaline basalts/basanites to trachytes, and overall exhibit a strong enrichment in highly incompatible elements. The whole range of isotopic compositions here reported (87Sr/86Sr: 0.703508-0.703913; 143Nd/144Nd: 0.512882-0.513010; 206Pb/204Pb: 19.0840- 20.0932; 207Pb/204Pb: 15.5388-15.6409; 208Pb/204Pb: 38.7416-39.3921; 176Hf/177Hf: 0.282956-0.283111) suggests the involvement of three components: (1) a weakly radiogenic component reflecting the source of regional MORBs, (2) a main HIMU-type component represented in the three islands, and (3) an additional component in Faial recent lavas, which appears similar to the EM type end-member previously recognized on other Azores eruptive complexes. The geographical distribution of the enriched components and the synchronous construction of various islands at the regional scale rules out a single narrow active plume. They suggest in turn the presence of dispersed residual enriched mantle blobs, interpreted as remnants from a large heterogeneous plume probably responsible for edification of the Azores plateau several Myr ago. The lavas erupted in São Jorge and Faial prior to 800 ka have similar and homogeneous isotopic ratios, which partly overlap the compositional field of MORBs from the adjacent portion of the Mid-Atlantic Ridge (MAR). Their genesis can be explained by the regional development of N150 transtensive tectonic structures, which promoted significant decompression melting of the upper mantle, with correlative dilute expression of the enriched components. In contrast, the youngest lavas (< 750 ka) erupted along the N110 main structural direction on the three islands are significantly enriched in LILE and LREE, and generally have variable but more radiogenic isotopic compositions. Such characteristics suggest low-degree partial melting and greater incorporation of fertile residual mantle anomalies during passive tectonic reactivation of pre-existing transform faults promoted by recent ridge-push at the MAR. We propose that sub-aerial volcanism over the last 1.3 Myr in the central Azores recorded a sudden change in the conditions of melt generation which most probably reveals a major reconfiguration of regional deformation accompanying the recent geodynamic reorganization of the Eurasia-Nubia plate boundary.

  19. NASA geodynamics program investigations summaries: A supplement to the NASA geodynamics program overview

    NASA Technical Reports Server (NTRS)

    1982-01-01

    The development of a time series of global atmospheric motion and mass fields through April 1984 to compare with changes in length of day and polar motion was investigated. Earth rotation was studied and the following topics are discussed: (1) computation of atmospheric angular momentum through April 1984; (2) comparisons of psi sub values with variations in length of day obtained by several groups utilizing B.I.H., lunar laser ranging, VLBI, or Lageos measurements; (3) computation of atmospheric excitation of polar motion using daily fields of atmospheric winds and pressures for a short test period. Daily calculations may be extended over a longer period to examine the forcing of the annual and Chandler wobbles, in addition to higher frequency nutations.

  20. Utilization of range-difference observations in geodynamics

    NASA Technical Reports Server (NTRS)

    1982-01-01

    The utilization of simultaneous laser range differences (SRD) for the determination of Earth orientation and baseline variations is summarized. Results from the Aug. 1980 Lageos data collected during the short MERIT campaign, and simulations for a possible station arrangement for the main campaign are reported.

  1. The significance of Antarctica for studies of global geodynamics

    USGS Publications Warehouse

    Sutherland, R.

    2007-01-01

    Antarctica has geometric significance for global plate kinematic studies, because it links seafloor spreading systems of the African hemisphere (Indian and Atlantic Oceans) with those of the Pacific. Inferences of plate motions back to 44 Ma, around the onset of rapid spreading south of Australia and formation of a new boundary through New Zealand, are consistent with Antarctic rifting and formation of the Adare Basin during 44-26 Ma (i.e., no additional plate motions are required in the South Pacific). The time period 52-44 Ma represents a profound global and South Pacific tectonic change, and significant details remain unresolved. For 74 Ma a significant nonclosure of the South Pacific plate-motion circuit is identified if Antarctic motion is not included. Alternate inferences of motion through Antarctica during the interval 74-44 Ma imply significantly different subduction volumes and directions around the Pacific, and imply different relative motions between hotspots

  2. Mars north polar deposits: stratigraphy, age, and geodynamical response

    USGS Publications Warehouse

    Phillips, R.J.; Zuber, M.T.; Smrekar, S.E.; Mellon, M.T.; Head, J.W.; Tanaka, K.L.; Putzig, N.E.; Milkovich, S.M.; Campbell, B.A.; Plaut, J.J.; Safaeinili, A.; Seu, R.; Biccari, D.; Carter, L.M.; Picardi, G.; Orosei, R.; Surdas, Mohit P.; Heggy, E.; Zurek, R.W.; Egan, A.F.; Giacomoni, E.; Russo, F.; Cutigni, M.; Pettinelli, E.; Holt, J.W.; Leuschen, C.J.; Marinangeli, L.

    2008-01-01

    The Shallow Radar (SHARAD) on the Mars Reconnaissance Orbiter has imaged the internal stratigraphy of the north polar layered deposits of Mars. Radar reflections within the deposits reveal a laterally continuous deposition of layers, which typically consist of four packets of finely spaced reflectors separated by homogeneous interpacket regions of nearly pure ice. The packet/interpacket structure can be explained by approximately million-year periodicities in Mars' obliquity or orbital eccentricity. The observed ???100-meter maximum deflection of the underlying substrate in response to the ice load implies that the present-day thickness of an equilibrium elastic lithosphere is greater than 300 kilometers. Alternatively, the response to the load may be in a transient state controlled by mantle viscosity. Both scenarios probably require that Mars has a subchondritic abundance of heat-producing elements.

  3. Seismicity of oceanic and continental rifts—a geodynamic approach

    Microsoft Academic Search

    P. O. Sobolev; D. V. Rundquist

    1999-01-01

    Two major kinds of divergent structures—oceanic and intracontinental rifts—were compared in principal seismic and tectonic characteristics. First, the role of main components of the mid-oceanic ridges (MOR) was estimated for the whole Earth. We considered two levels of the MOR segmentation. The first-order structures are the segments of MOR between triple junctions and the second-order structures are a transform faults

  4. Techniques for the analysis of geodynamic effects using laser data

    NASA Technical Reports Server (NTRS)

    Dunn, P. J.; Smith, D. E.; Kolenkiewicz, R.

    1973-01-01

    New orbit computation techniques have been developed to realize the full precision of laser ranging measurements from a single tracking station used to accurately determine the orbital inclination of a satellite. In order to evaluate earth and ocean tidal effects on the satellite and polar motion effects on the station latitude, improved computational techniques are described for perturbations significantly influencing the satellite's inclination, such as solar radiation pressure and geopotential resonance. By using the time independent value of maximum latitude reached by the satellite as the experimental variable, orbit tracking errors caused by imprecise modelling of the gravity field and atmospheric drag have been largely overcome and made possible long term analysis of osculating elements. With these techniques, quarter day spans of laser data have been employed to monitor the inclination of the satellite to the order 0.01 arcseconds precision over a period of seventeen months.

  5. Geodynamics applications of continuum physics to geological problems

    Microsoft Academic Search

    D. L. Turcotte; G. Schubert

    1982-01-01

    This textbook deals with the fundamental physical processes necessary for an understanding of plate tectonics and a variety of geologic phenomena. The first chapter reviews plate tectonics; its main purpose is to provide physics, chemistry, and engineering students with the geologic background necessary to understand the applications throughout the rest of the book. It goes on to discuss in following

  6. Emplacement of volcanic vents and geodynamics of Central Anatolia, Turkey

    Microsoft Academic Search

    D. Dhont; J. Chorowicz; T. Yurur; J.-L. Froger; O. Kose; N. Gundogdu

    1998-01-01

    Observations on Synthetic Aperture Radar (SAR) scenes of the European Remote Sensing (ERS) satellite and Digital Elevation Models (DEMs), complemented by field structural analysis permit a new understanding of relationships between tectonics and volcanism since the late Miocene (10 Ma) in Central Anatolia. Volcanic edifices form elongate stratovolcanoes, linear clusters and volcanic ridges. They indicate emplacement on tension fractures and

  7. GS of CAS Geodesy & Geodynamics Beijing June 20041 SEISMIC CYCLE

    E-print Network

    Vigny, Christophe

    June 20048 Difficulty of earthquake prediction Even though a given fault can have a characteristic Earthquake repeating itself over a characteristic time, earthquake prediction is difficult because : 1. Those and rupture on a fault. Example on a Strike-slip fault and a Subduction fault · Size of an earthquake · Time

  8. Prelaunch optical characterization of the Laser Geodynamic Satellite (LAGEOS 2)

    NASA Technical Reports Server (NTRS)

    Minott, Peter O.; Zagwodzki, Thomas W.; Varghese, Thomas; Seldon, Michael

    1993-01-01

    The optical range correction (the distance between the apparent retroreflective skin of the satellite and the center of mass) of the LAGEOS 2 was determined using computer analysis of theoretical and experimentally measured far field diffraction patterns, and with short pulse lasers using both streak camera-based range receivers and more conventional PMT-based range receivers. The three measurement techniques yielded range correction values from 248 to 253 millimeters dependent on laser wavelength, pulsewidth, and polarization, location of the receiver in the far field diffraction pattern and detection technique (peak, half maximum, centroid, or constant fraction). The Lidar cross section of LAGEOS 2 was measured at 4 to 10 million square meters, comparable to the LAGEOS 1.

  9. A proposed test area for the spaceborne geodynamic ranging system

    NASA Technical Reports Server (NTRS)

    Lowman, P. D., Jr.

    1978-01-01

    Precise geodetic measurements are proposed in which an orbiting laser obtains intersite distance between retroreflectors 25 to 100 km apart on the ground. The recommended area is a rectangle 200 by 400 km in southern California and adjacent Nevada, trending northeast. It includes the entire width of the San Andreas fault zone, the Garlock fault, the thrust faults of the Transverse Ranges, and the active strike-slip faults of the Mojave Desert.

  10. Geodynamics applications of continuum physics to geological problems

    SciTech Connect

    Turcotte, D.L.; Schubert, G.

    1982-01-01

    This textbook deals with the fundamental physical processes necessary for an understanding of plate tectonics and a variety of geologic phenomena. The first chapter reviews plate tectonics; its main purpose is to provide physics, chemistry, and engineering students with the geologic background necessary to understand the applications throughout the rest of the book. It goes on to discuss in following chapters: stress and strain relationships in the earths crust; basic principles of linear elasticity and the lithosphere; heat conduction in the earths crust; principles of gravity measurements; problems involving mantle convection and post glacial rebound; rock mechanics and rheology; principles of fluid flow in porous media; and, fault displacement measurements.

  11. Geodynamical basis for crustal deformation under the Tibetan Plateau

    NASA Technical Reports Server (NTRS)

    Liu, H.-S.

    1985-01-01

    Plate tectonics and satellite-derived gravity data are used to examine crustal deformation under the Tibetan Plateau. A spherical harmonic analysis is given for the global plate boundary system, and the crustal stresses in Tibet are calculated from satellite gravity data. A superimposed stress system is constructed. The stress patterns reveal that the cold downwelling mantle convection flow beneath southern Tibet pulls the Indian plate down but applies a bending moment on the end of the plate to uplift and support the mass of the Himalayas.

  12. Geodynamics of the Western Pacific-Indonesian region. Vol. II

    SciTech Connect

    Hilde, T.W.C.; Uyeda, S.

    1983-01-01

    This book contains papers which are grouped into general studies and regional studies. The first section examines the dynamic processes as well as the systematic geological and geophysical relationships found in the region as a whole. The second section focuses on specific areas and features of the Western Pacific.

  13. The 1755 ``Meknes'' earthquake (Morocco): field data and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Moratti, G.; Piccardi, L.; Vannucci, G.; Belardinelli, M. E.; Dahmani, M.; Bendkik, A.; Chenakeb, M.

    2003-09-01

    The source of the famous 1 November, 1755 "Lisbon" earthquake has been constrained to be an up to 200 km long structure in the offshore west of Cabo de S. Vincente. The magnitude of this earthquake was estimated in the range of 8.5-9.4. The stress regime argued for this shock would have been characterised by an around NNW-SSE-oriented compression. Less well studied is the successive "Meknes" earthquake, which occurred a few days later in Morocco (27 November), and was erroneously confused by the European contemporary reports with a strong aftershock, occurred on 18 November, of the main seismic sequence of the 1 November earthquake. The Meknes earthquake had destructive effects in the region of Meknes and Fes and along the E-W trending Rides Prérifaines, the main frontal thrust of the Rif. Historical data indicate a macroseismic field closed around the towns of Meknes and Fes. Our structural-geological fieldwork and remote sensing analysis in the epicentral area of the Meknes earthquake, along the local major recent faults, indicate that the E-W-oriented thrusts of the Rides Prérifaines are active. Through a re-examination of historical sources compared with field work and air photo interpretation, we could individuate the traces of coseismic surface faulting of the 1755 Meknes earthquake in two areas of the Rides Prérifaines, both part of the local thrust front: the Jebel Zerhoun area and the Jebel Zalagh area. Tectonic data on the Quaternary stress fields derived from our fieldwork and from literature, consistently with the revised focal mechanisms in the region, indicate active shortening oriented NNW-SSE to N-S in northern Morocco. The data collected seem therefore to indicate the thrusts of the Rides Prérifaines, located within the macroseismic area of the Meknes earthquake, as the most probable seismic source of that event. As such, the activation of the thrusts of the Rides Prérifaines would be consistent with this stress regime, which in turn would be similar to the stress field maintained as responsible for the 1 November, 1755 Lisbon earthquake. We also attempted an estimate of the change due to the Lisbon earthquake of the Coulomb Failure Function (CFF) on the Meknes structure, as identified in this paper, in order to evaluate if the Meknes earthquake could have been induced by the 1 November, 1755 Lisbon earthquake, or a local distinct earthquake. Our modelling suggests that the latter hypothesis is the more likely one.

  14. Geodynamics of the Taiwan arc-arc collision

    Microsoft Academic Search

    Jean-Claude Sibuet; Shu-Kun Hsu

    1997-01-01

    Hsu and Sibuet (1995), on the basis of an overview of the satellite-derived marine gravity anomalies, postulated that the Ryukyu subduction zone extended before the formation of Taiwan a few hundreds kilometres south of its present-day termination, and that Taiwan resulted from an arc-arc collision rather than from an arc-continent collision.An analysis of the structure and timing of rifting in

  15. 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.

  16. The Gurupi Belt, northern Brazil: Lithostratigraphy, geochronology, and geodynamic evolution

    Microsoft Academic Search

    Evandro L. Klein; Candido A. V. Moura; Robert S. Krymsky; William L. Griffin

    2005-01-01

    The Gurupi Belt is located in northern Brazil on the southern margin of the São Luís Craton, which is dominated by juvenile calc-alkaline rocks formed in intra-oceanic island arcs between 2240 and 2150Ma. The Gurupi Belt consists of: (i) small lenses of an Archean metatonalite of 2594Ma; (ii) calc-alkaline\\/TTG tonalites and gneisses of 2147–2168Ma and juvenile Nd isotope signature, formed

  17. (C.Bina, 9/2011) From thermodynamics to geodynamics

    E-print Network

    Cerveny, Vlastislav

    #12;(C.Bina, 9/2011) (fromB.Hacker) podrobnjsímetamorfnífacie(stupnmetamorfózy) #12;(C.Bina, 9 reactions. (faciesboundariesfromB.Hacker) Precise boundaries involve several reactions and depend upon bulk (over a temperature interval of more than 50°). (faciesboundariesfromB.Hacker) Precise boundaries

  18. Wilson study cycles: Research relative to ocean geodynamic cycles

    NASA Technical Reports Server (NTRS)

    Kidd, W. S. F.

    1985-01-01

    The effects of conversion of Atlantic (rifted) margins to convergent plate boundaries; oceanic plateaus at subduction zones; continental collision and tectonic escape; southern Africa rifts; and global hot spot distribution on long term development of the continental lithosphere were studied.

  19. The Coming Role of GPU in Computational Geodynamics (Invited)

    NASA Astrophysics Data System (ADS)

    Yuen, D. A.; Knepley, M. G.; Erlebacher, G.; Wright, G. B.

    2009-12-01

    With the proliferation of GPU ( graphics accelerator board) the computing landscape has changed enormously in the last 3 years. The new additional capabilities of the GPU , such as larger shared memories and load-store operations , allow it to be considered as a viable stand-alone computational and visualization engine. Today the massive threading and computing capability of GPU can deliver at least an order of magnitude performance over the multi-core CPU architecture. The cost of a GPU system is also considerably cheaper than a CPU cluster by more than an order of magnitude.The introduction of CUDA and ancillary software aids, such as Jackets, have allowed the rapid translation of many venerable codes into software usable on GPU. We will discuss our experience acquired over the past year in attacking five different computational problems in the geosciences, using the GPU. They include (1.) 3-D seismic wave propagation with the spectral-element method (2.)2-D shallow water equation as applied to tsunami wave propagation, using finite-differences (3.) 3-D mantle convection with constant viscosity using a 4th order compact finite-difference operator (4.) non-linear heat-diffusion equation in 2-D using a collocation method based on radial basis functions over an elliptical area . Grid points are divided so as to lie on a centroidal Voronoi mesh . Derivatives are calculated at each grid point using a point-dependent stencil computed from the nearest neighbors .(5.) Stokes flow with variable viscosity by means of a pre-conditioner calculated on the GPU based on the vortex method using Green’s functions, along with the radial basis functions and the fast multi-pole method. The Krylov method is used on the CPU for the final iterative step .We will discuss the relative speed-ups of the GPU over the CPU in each of these cases. We will point out the need to go to more computationally intensive mode with multiple GPUs, which calls for key CPUs to control the message passing between the different computational domains by means of MPI. In our CPU-GPU system a separate GPU, the Nvidia GTX 295 , is also devoted for visualizing the ongoing computed results. According to some circles, the future roadmap of GPU seems to be at least one and a half order of magnitude brighter than the CPU in the next 6 years.

  20. 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 scaled to the Earth's mantle through a combination of a Peclet number and a plume buoyancy number. A range of spreading rates, ridge migration rates, and plume excess temperatures representative of the Earth are considered.

  1. BORIS J.P. KAUS Geophysics and Geodynamics

    E-print Network

    Kaus, Boris

    D numerical models. Journal of Geophysical Research Peer-reviewed: - JOHNSON T.E., BROWN M., KAUS B lithospheric-scale local- ization: does it result in subduction? Earth and Planetary Science Letters. Vol. 359-360

  2. Prelaunch testing of the laser geodynamic satellite (LAGEOS)

    NASA Technical Reports Server (NTRS)

    Fitzmaurice, M. W.; Minott, P. O.; Abshire, J. B.; Rowe, H. E.

    1977-01-01

    The LAGEOS was extensively tested optically prior to launch. The measurement techniques used are described and resulting data is presented. Principal emphasis was placed on pulse spreading characteristics, range correction for center of mass tracking, and pulse distortion due to coherent effects. A mode-locked freqeuncy doubled Nd:YAG laser with a pulse width of about 60 ps was used as the ranging transmitter and a crossfield photo-multiplier was used in the receiver. High speed sampling electronics were employed to increase receiver bandwidth. LAGEOS reflected pulses typically had a width of 250 ps with a variability in the range correction of less than 2 mm rms. Pulse distortion due to coherent effects was inferred from average waveforms and appears to introduce less than + or - 50 ps jitter in the location of the pulse peak. Analytic results on this effect based on computer simulations are also presented. Theoretical and experimental data on the lidar cross section were developed in order to predict the strength of lidar echoes from the satellite. Cross section was measured using a large aperture laser collimating system to illuminate the LAGEOS. Reflected radiation far-field patterns were measured using the collimator in an autocollimating mode. Data were collected with an optical data digitzer and displayed as a three-dimensional plot of intensity versus the two far-field coordinates. Measurements were made at several wavelengths, for several types of polarizations, and as a function of satellite orientation.

  3. Temporal variation of geodynamical properties due to tidal friction

    Microsoft Academic Search

    P. Varga

    2006-01-01

    Fossils and tidal deposits as well as the possibility to compute values of the lunar tidal torque for different geological epochs allow us to model the variations in time of the Earth's figure, assuming that the latter remains, on a global scale, close to a hydrostatic equilibrium figure. On this basis, one can infer the variations of the Earth's most

  4. Erosion, Himalayan Geodynamics, and the Geomorphology of Metamorphism

    Microsoft Academic Search

    Peter K. Zeitler; Anne S. Meltzer; Peter O. Koons; David Craw; Bernard Hallet; C. Page Chamberlain; William S. F. Kidd; Stephen K. Park; Leonardo Seeber; Michael Bishop; John Shroder

    2001-01-01

    Is erosion important to the structural and petrological evolution of mountain belts? The nature of active metamorphic massifs co-located with deep gorges in the syntaxes at each end of the Himalayan range, together with the magnitude of erosional fluxes that occur in these regions, leads us to concur with suggestions that erosion plays an integral role in collisional dynamics. At

  5. Complex seismic anisotropy beneath western Tibet and its geodynamic implications

    NASA Astrophysics Data System (ADS)

    Wu, Jing; Zhang, Zhongjie; Kong, Fansheng; Yang, Bin B.; Yu, Youqiang; Liu, Kelly H.; Gao, Stephen S.

    2015-03-01

    Shear wave splitting parameters obtained along a linear array of 23 stations deployed in western Tibet during a two-year period from 2011 to 2013 demonstrate strong and systematic azimuthal variations with a 90-degree periodicity, suggesting the existence of double-layer anisotropy with a horizontal axis of symmetry. The predominant fast orientations are mostly E-W for events from the east and southeast, and NE-SW or N-S for events from the northwestern quadrant. Under the assumption of a two-layer anisotropic structure, we grid-search for the two pairs of parameters that characterize the complex anisotropy. The resulting fast orientation for the lower layer is mostly N-S, which is consistent with the direction of mantle flow caused by the subduction of the Indian continent beneath Tibet. For the upper layer, the fast orientation is NE-SW, which is significantly different from the strike of dominant surface structures, and can be explained by lower crustal flow in western Tibet. This interpretation is supported by the NE-SW orientation and significant strength (with splitting times as large as 1.3 s) of crustal anisotropy revealed using the sinusoidal moveout of the P-to-S converted phases from the Moho. To our knowledge, this is the first time when upper layer anisotropy revealed from SWS analysis is reliably constrained in the crust using independently determined crustal anisotropy measured by the P-to-S converted phase from the Moho. The observations provide additional evidence for the existence of a subducted Indian slab that is undeformed and is decoupled from the significantly shortened crust, extending to the northern margin of the Qiangtang block.

  6. 35. DIORITIC BASEMENT, SITE 493: PETROLOGY, GEOCHEMISTRY, AND GEODYNAMICS1

    Microsoft Academic Search

    H. Bellon; R. C. Maury; J. F. Stephan

    At Site 493, DSDP Leg 66, dioritic basement was reached below lower Miocene (NN1 Zone, 22-24 Ma) terrigenous sediments. Petrographical, mineralogical (including microprobe analyses), and chemical features of the dioritic rocks reveal their magmatic affinity with the calc-alkaline series. Furthermore, their radiometric age (35.3 m.y.) links the basement to the Sierra Madre Occidental in Mexico and to mid-Tertiary volcanic arcs

  7. 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.

  8. Geodynamics of the zone of continental continuation of Mid-Arctic earthquakes belt (Laptev Sea)

    Microsoft Academic Search

    G. P Avetisov

    1999-01-01

    On the basis of a generalization of all available data on the distribution of earthquake epicenters and their focal mechanisms, the opinion is expressed that there is no thorough splitting of Laptev Sea lithosphere associated with the divergent boundary between the Eurasia and North American plates. There are two fragments of this boundary which are laterally separated by hundreds of

  9. Regional Lineament Net of Uzbekistan: RemoteSensing&GIS, mineral deposits and geodynamic structures

    NASA Astrophysics Data System (ADS)

    Sidorova, I. P.

    2005-12-01

    This paper deals with the application of complex study of Remote Sensing images and deep Lithospheric structures to the knowledge of spatial interrelations between regional lineaments and mineral deposits in Uzbekistan. Deciphering of structural units of Uzbekistan territory using space ASTER images allows us to reveal regional, deep-rooted lineament, extending in latitudinal direction over Uzbekistan territory and neighboring countries. Thus lineament could penetrate the Earth up to deep Lithosphere layers, inheriting a position of old fault-lineament systems which origin related to Paleocene tectonic processes. The most extended latitudinal lineament is the Transregional lineament of Central Asia located within 42-44N zone. It stretches for more than 2000km from Sultan-Uvais mountains (Karakalpakstan), through Kyzylkums and Nurata mountains (Uzbekistan), Turkestan-Alay and Atbashi- Inylchek mountains (Kyrgyzstan), to Chinese border with possible extension along the Chinese Tien- Shan. The main objective is to associate the surface indicators as geological, geophysical and tectonic base of data using RS & GIS with the purpose to identify the occurrence special geoobjects of economic interest. Additionally, it will be possible to evaluate geospatial distributions of these altered zones related to morphological structures using Digital Elevation Modelling (DEM) products of ASTER images. RS&GIS methods were used to determine the interrelations of the volcanic and granitic rocks distribution-mineralization-alteration with the faults-lineaments, circular structures. The alteration zones, the tectonic lines and the circular structures related to the cones and calderas determined these methods and checked by group truth studies may be target areas to explore for some new ore deposits. As a result, our investigations envelops more then 10 mineral deposits of such kind bearing Au, Ag, Pt, U, Zn, Cu, Ni, rare earth elements and diamonds. In conclusion, it is necessary to note that such structures are well-known in the American, Australian continents. They are recognized as deep structures and served as channels for the heat (endogenous) energy, magmas and fluids to come out of the core and mantle of the Earth. It gives us an opportunity to concentrate there our efforts for prospecting of such kind mineral deposits.

  10. Fluids from the Deeply Continental Subduction Zone and the Metamorphic Chemical Geodynamics

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Wang, J.; Shen, K.

    2009-05-01

    The complex vein associations hosted in southern Sulu ultrahigh-pressure (UHP) eclogites contain quartz À omphacite (or jadeite) À kyanite À allanite À zoisite À rutile À garnet. These minerals have chemical compositions similar to those of host eclogites. Inclusions of polycrystalline quartz pseudomorphs after coesite were identified in vein allanite and garnet, and coesite inclusions were found in vein zircon. These facts suggest that the veins together with host eclogites have been subjected to synchronous UHP metamorphism. The vein minerals contain relatively high concentrations of rare earth elements (REE), high field strength elements (HFSE) and transition metal elements (TME). A kyanite-quartz vein has a whole-rock composition similar to adjacent UHP metamorphic granitic gneisses. Abundant primary multi-solid fluid inclusions trapped within UHP vein minerals contain complex daughter minerals of muscovite, calcite, anhydrite, magnetite, pyrite, apatite, celestite and liquid and gas phase of H2O with solids up to 30 to 70% of the inclusion volume. Presence of daughter mineral anhydrite and magnetite indicates the high oxygen fugacity in subduction released fluids, and provides a feasible interpretation to the high oxygen fugacity in convergent margins. These characteristics imply that the UHP vein minerals were crystallized from supercritical silicate-rich aqueous fluids that were in equilibrium with peak-UHP minerals, and that the fluids in deeply subducted continental crust may contain very high concentrations of silicate as well as HREE, HFSE and TME. Such fluids might have resulted in major fractionation between Nb and Ta, i.e. the UHP fluids have subchondritic Nb/Ta values, whereas the host eclogites after extraction of the fluids have suprachondritic Nb/Ta values. Therefore, voluminous residual eclogites with high Nb/Ta ratios may be the complementary suprachondritic reservoir capable of balancing the subchondritic depleted mantle and continental crust reservoirs.

  11. 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.

  12. Late paleozoic base and precious metal deposits, East Tianshan, Xinjiang, China: Characteristics and geodynamic setting

    USGS Publications Warehouse

    Mao, J.; Goldfarb, R.J.; Wang, Y.; Hart, C.J.; Wang, Z.; Yang, J.

    2005-01-01

    The East Tianshan is a remote Gobi area located in eastern Xinjiang, northwestern China. In the past several years, a number of gold, porphyry copper, and Fe(-Cu) and Cu-Ag-Pb-Zn skarn deposits have been discovered there and are attracting exploration interest. The East Tianshan is located between the Junggar block to the north and early Paleozoic terranes of the Middle Tianshan to the south. It is part of a Hercynian orogen with three distinct E-W-trending tectonic belts: the Devonian-Early Carboniferous Tousuquan-Dananhu island arc on the north and the Carboniferous Aqishan - Yamansu rift basin to the south, which are separated by rocks of the Kanggurtag shear zone. The porphyry deposits, dated at 322 Ma, are related to the late evolutionary stages of a subduction-related oceanic or continental margin arc. In contrast, the skarn, gold, and magmatic Ni-Cu deposits are associated with post-collisional tectonics at ca. 290-270 Ma. These Late Carboniferous - Early Permian deposits are associated with large-scale emplacement and eruption of magmas possibly caused by lithosphere delamination and rifting within the East Tianshan.

  13. 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 both modeled and observed stress fields, suggesting that elevated fluid pressure may be required to trigger fault rupture. ?? 2006 Geological Society of America.

  14. The Midcontinent rift in the Lake Superior region with emphasis on its geodynamic evolution

    USGS Publications Warehouse

    Cannon, W.F.

    1992-01-01

    The Midcontinent rift is a Middle Proterozoic continental rift which records about 15 m.y. of extension, subsidence, and voluminous volcanism in the period 1109-1094 Ma in the central part of North America. During that time the crust was nearly totally separated and as much as 25 km of subaerial basalts accumulated in a deep central depression. Following extension and volcanism, a longer period of subsidence resulted in development of a post-rift sedimentary basin in which as much a 8 km of fluvial and lacustrine clastic rocks were deposited. Partial inversion of the central depression occurred about 30-50 m.y. after extension to produce the current configuration of a central horst, composed mostly of thick volcanic accumulations, between shallower flanking basins. ?? 1992.

  15. Geodynamics of collision and collapse at the AfricaArabiaEurasia subduction zone an introduction

    E-print Network

    Utrecht, Universiteit

    ; (2) continental drift, sea-floor spreading and formation of ocean basins; (3) subduction initiation and drifting in the Western Mediterranean (Dercourt et al. 1986), and with initiation of the Tyrrhenian oceanic subduction stage closes the oceanic basin, even- tually resulting in the arrival of a continental

  16. 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).

  17. The characteristics, origins, and geodynamic settings of supergiant gold metallogenic provinces

    Microsoft Academic Search

    Robert Kerrich; Richard Goldfarb; David Groves; Steven Garwin; Yiefei Jia

    2000-01-01

    There are six distinct classes of gold deposits, each represented by metallogenic provinces, having 100's to >1000 tonne gold\\u000a production. The deposit classes are: (1) orogenic gold; (2) Carlin and Carlin-like gold deposits; (3) epithermal gold-silver\\u000a deposits; (4) copper-gold porphyry deposits; (5) iron-oxide copper-gold deposits; and (6) gold-rich volcanic hosted massive\\u000a sulfide (VMS) to sedimentary exhalative (SEDEX) deposits. This classification

  18. Geodynamic models of the Weddell Sea embayment in view of new geophysical data

    Microsoft Academic Search

    Wilfried Jokat; Notker Fechner; Michael Studinger

    New high quality seismic reflection and refraction data were collected along the Filch- ner-Ronne Ice Shelf during the austral summer 1994\\/95. Seismic refraction data pro- vide the first detailed P-wave velocity information at the transition of the Antarctic Peninsula to the Filchner-Ronne Basin. The velocity data document the change from a normal to a strongly stretched continental crust in this

  19. Constraints on Hadean geodynamics from mineral inclusions in > 4 Ga zircons

    NASA Astrophysics Data System (ADS)

    Hopkins, Michelle D.; Harrison, T. Mark; Manning, Craig E.

    2010-10-01

    The inclusion mineralogy of 1450 zircons over 4 billion years in age from the Jack Hills, Western Australia, was characterized for composition and phase assemblage. Results confirm that the inclusion population of these largely igneous zircons is dominated by muscovite and quartz (~ 75%). If the inclusions are original to the igneous zircons, this observation alone restricts the host melts to formation at pressure-temperature ( P- T) conditions of ~ 650-800 °C and > 4 kbar. Several lines of evidence support the view that most of the analyzed mineral inclusions are primary, including their lack of association with cracks, magmatic crystal forms, and lack of exchange with fuchsitic (Cr-rich) micas in the host conglomerate. The application of Ti-in-zircon thermometry, and phengite, Ti-in-quartz, and Al-in-hornblende barometry to these inclusion assemblages yields estimates of magmatic P-T conditions from 5 to > 12 kbar and 700 ± 40 °C. These data indicate zircon formation along geotherms of ? 60 °C/km and imply conductive near-surface heat flow of < 40 to 85 mW/m 2— a range that is substantially lower than most estimates of global Hadean heat flow. Of the possible environments capable of generating melting under such locally low heat flow early in Earth history, underthrusting, possibly in a manner similar to modern convergent margins, appears most consistent with numerous other geochemical constraints derived from investigation of Hadean zircons.

  20. Early Eocene Arc–Continent Collision in Kamchatka, Russia: Structural Evolution and Geodynamic Model

    Microsoft Academic Search

    E. Konstantinovskaya

    \\u000a The major event in the Cenozoic evolution of the Kamchatka orogen was the Early Eocene collision of the Ozernoy-Valagina (Olutorsky)\\u000a arc terrane with the continental margin of Asia. The arc–continent collision developed progressively from southwest to northeast\\u000a from the Early Eocene in South Kamchatka to the early Mid Eocene in the Olutorsky region. The nature of the continental margin\\u000a of

  1. Geodynamical model of development the gold ore deposit Muruntau in Central Kyzylkums /Western Uzbekistan/

    NASA Astrophysics Data System (ADS)

    Sidorova, I. P.

    2004-12-01

    Recent advances in geology and sciences dealing with planets resulted in ever-growing information on the internal structure and composition of upper and lower mantle and its role in the development of mineral deposits. Thus, the analysis of geologic-geophysical velocity sections on DSS-MOVZ profiles, that cross Central Kyzylkum, has revealed a number of features, which are characteristic of the upper mantle rocks, related to morphology of bodies, their physical properties, consisting mainly in their contrasting values for contiquous blocks, and general increased velocity and density of the rocks they contain. Petrologic-geophysical analysis of the same profiles proved the previous conclusions, and besides it allowed us to create the geodinamical model of development of a complicated continental lithosphere within Central Kyzylkum Ore Magmatic Concenter (CKOMC). CKOMC is a part of Western Uzbekistan's territory, that has maximum concentration of gold ore deposits of different scale, including the gigantic one- Muruntau. There are two main factors, that condition the area of the concenter: 1.Obduction of crust of the ocean to continental one during the Upper Paleozoic collision of Kyrgiz-Kazakh and Karakum-Tadjik microcontinents; 2.Geochemical gold specialization of Turkestan paleo-ocean's lithosphere. As a result of obduction of doubled, and sometimes even trebled crust of the ocean to continental, the front of rock granitization shifted to the sphere of ocean sediments development, and granite-gneiss layer of the continental crust went down to granulite zone. The latter factor provoked mass penetration of fluids from the former granite-gneiss and sedimentary-metamorphic layers, which due to their uprush to the surface, formed fluid-hydrothermal system , enriched with gold, in the new upper crust. This, in its turn, conditioned the formation of numerous gold ore deposits of different facies and formations observed in Central Kyzylkums. Abrupt increase in the crust's thickness has broken the balance of the crust and mantle, melts of which also rushed upwards along the rift zones and faults, replacing the ancient and the newly formed granite-gneiss layer. Such a mechanism of the continental lithosphere formation explains the formation of blocks of crust, conditioned by the abrupt change of rocks having different density (1), and the presence single parts «waveguides» in lower parts of the upper crust, which are considered to be relics of the primary granite-gneiss layer enriched with fluids. Only the wedge of crust of the ocean thrusted over the continental crust could cause formation of rock blocks of unusual shape and content, but of the same metallogenic gold ore trend. The studied profiles allowed us to determine one more magmatogene structure of mantle formation. It has funnel shape, with its basement directed to the surface. Complex ring plutons and tectonic ring-shaped disturbances these can be seen during the analysis of space images. The narrowed part of the structure goes down to the lower mantle, and can form a shape of «sand-glass», the surface of which served as a «conductor» of mantle plumes to the upper crust. Evidence of this are bodies of alkaline mafites and ultramafites in the upper crust of Central Kyzylkums, and presence of non-coherent elements containing gold (such as platinum and rare earth elements) at gold ore deposits.

  2. 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 grateful to Prof. Kopytenko, Yu. A. and participants of the scientific seminars and conferences in IZMIRAN and Space Research Institute, Russian Acad. Sci., for discussions and researchers of the IZMIRAN observatory for data about the K index dynamics.

  3. Permian age of the Burpala alkaline pluton, Northern Transbaikalia: Geodynamic implications

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    This paper presents the U-Pb zircon age of pulaskite of the main phase (294 ± 1 Ma) and the rare metal syenite (283 ± 8 Ma) of the Burpala alkaline pluton. The geochronological data show that it was formed in the Early Permian. By age, it is comparable with the Synnyr pluton of the Synnyr rift zone, alkaline granitic rocks and bimodal volcanic associations of the Uda-Vitim rift zone, and carbonatites of the Saizhen rift zone of the Central Asian foldbelt. These intraplate igneous complexes were formed almost simultaneously with crustal granitic rocks of the Angara-Vitim batholite. All of this gives ground to suppose that the origination of their parental melts is a result of the influence of the mantle hot spot or mantle plume on the lithosphere that led to extensive crustal anatexis.

  4. Petrogenesis and geodynamic implications of the Gejiu igneous complex in the western Cathaysia block, South China

    NASA Astrophysics Data System (ADS)

    Cheng, Yanbo; Mao, Jingwen; Spandler, Carl

    2013-08-01

    The Gejiu tin district in western Cathaysia block comprises a series of igneous rocks including equigranular and porphyritic granites, gabbro and nepheline syenite. Systematic SHRIMP or LA-ICP-MS zircon U-Pb analyses of 15 representative samples from various phases of the Gejiu complex yielded Late Cretaceous ages of 78-85 Ma. Based on their mineralogical, geochemical and Sr-Nd-Hf isotope characteristics, these rocks are categorized into three groups: felsic rocks, alkaline rocks and mafic rocks. The felsic rock group includes the equigranular and porphyritic granites. Geochemical characteristics include high SiO2 contents, enrichment in Rb, Th, U, Nb, Ta, Nd and Hf and depletion in Ba, K, Sr, P, Eu and Ti compared to primitive mantle. REE patterns feature slight LREE enrichment with pronounced negative Eu anomalies. Geochemical data and Sr-, Nd- and Hf-isotopic compositions indicate that the felsic rocks were probably generated by partial melting of crustal source rocks with a minor input from mantle materials. The mafic rocks (gabbro and mafic microgranular enclaves) have distinct geochemical and isotopic features consistent with derivation from an enriched mantle source, with variable degrees of mixing with crustal-derived magmas. Strontium-, Nd- and Hf-isotopic compositions of the alkaline rocks are similar with those of the mafic rocks, suggesting that they have a similar source. Nevertheless, petrological and geochemical characteristics of these rocks indicate that they experienced extensive crystal fractionation and limited crustal contamination. Based on the emplacement of the gabbro-mafic microgranular enclaves-syenite-granites in the Gejiu district, together with contemporaneous geological events in other parts of the western Cathaysia block, we suggest that a widespread extension-related magmatic episode affected the entire region in the late Cretaceous, possibly as a result of lithospheric thinning, basaltic underplating and associated crustal melting.

  5. Geodynamics of late Paleozoic magmatism in the Tien Shan and its framework

    NASA Astrophysics Data System (ADS)

    Biske, Yu. S.; Konopelko, D. L.; Seltmann, R.

    2013-07-01

    The Devonian-Permian history of magmatic activity in the Tien Shan and its framework has been considered using new isotopic datings. It has been shown that the intensity of magmatism and composition of igneous rocks are controlled by interaction of the local thermal upper mantle state (plumes) and dynamics of the lithosphere on a broader regional scale (plate motion). The Kazakhstan paleocontinent, which partly included the present-day Tien Shan and Kyzylkum, was formed in the Late Ordovician-Early Silurian as a result of amalgamation of ancient continental masses and island arcs. In the Early Devonian, heating of the mantle resulted in the within-plate basaltic volcanism in the southern framework of the Kazakhstan paleocontinent (Turkestan paleoocean) and development of suprasubduction magmatism over an extensive area at its margin. In the Middle-Late Devonian, the margins of the Turkestan paleoocean were passive; the area of within-plate oceanic magmatism shifted eastward, and the active margin was retained at the junction with the Balkhash-Junggar paleoocean. A new period of active magmatism was induced by an overall shortening of the region under the settings of plate convergence. The process started in the Early Carboniferous at the Junggar-Balkhash margin of the Kazakhstan paleocontinent and the southern (Paleotethian) margin of the Karakum-Tajik paleocontinent. In the Late Carboniferous, magmatism developed along the northern boundary of the Turkestan paleoocean, which was closing between them. The disappearance of deepwater oceanic basins by the end of the Carboniferous was accompanied by collisional granitic magmatism, which inherited the paleolocations of subduction zones. Postcollision magmatism fell in the Early Permian with a peak at 280 Ma ago. In contrast to Late Carboniferous granitic rocks, the localization of Early Permian granitoids is more independent of collision sutures. The magmatism of this time comprises: (1) continuation of the suprasubduction process (I-granites, etc.) with transition to the bimodal type in the Tien Shan segment of the Kazakhstan paleocontinent that formed; (2) superposition of A-granites on the outer Hercynides and foredeep at the margin of the Tarim paleocontinent (Kokshaal-Halyktau) and emplacement of various granitoids (I, S, and A types, up to alkali syenite) in the linear Kyzylkum-Alay Orogen; and (3) within-plate basalts and alkaline intrusions in the Tarim paleocontinent. Synchronism of the maximum manifestation and atypical combination of igneous rock associations with spreading of magmatism over the foreland can be readily explained by the effect of the Tarim plume on the lithosphere. Having reached maximum intensity by the Early Permian, this plume could have imparted a more distinct thermal expression to collision. The localization of granitoids in the upper crust was controlled by postcollision regional strike-slip faults and antiforms at the last stage of Paleozoic convergence.

  6. Geodynamic evolution of the Baguio Mineral District: Unlocking the Cenozoic record from clastic rocks

    NASA Astrophysics Data System (ADS)

    Dimalanta, Carla B.; Yumul, Graciano P.; Imai, Akira

    2013-03-01

    Geochemical studies done on the Baguio Mineral District had dominantly looked at the igneous rocks. A major gap is the scarcity of studies dealing with the sedimentary rock geochemistry for this district which this paper intends to address. The petrographic data and major and trace element compositions of the siltstones-sandstones from the lower member of the Late Oligocene to Early Miocene Zigzag Formation show that they are generally quartz-rich and have high K2O, Th and La/Sc contents. The chondrite-normalized REE pattern exhibits a negative Eu anomaly, enrichment in LREEs and flat HREEs similar to typical post-Archean shales. Taken together, the data indicate derivation of the lower member of the Zigzag Formation from intermediate to acid igneous rock sources generated in an active margin setting. A likely candidate source is the Cordon Syenite Complex/Palali Formation in the Northern Sierra Madre - Caraballo Mountains. Derivation from mafic source rocks in an oceanic island arc setting is inferred for samples of the Middle to Late Miocene Klondyke, Late Miocene to Early Pliocene Amlang and Late Pliocene Cataguintingan Formations. These samples are characterized by low K2O, Th and La/Sc but high Cr/Th values. Unroofing of the Pugo Metavolcanics and the younger plutons in the Central Cordillera provided the materials which eventually produced the Klondyke and Amlang Formations. Continuous uplift and shallowing of the basin resulted in the deposition of the Cataguintingan Formation. The petrography, geochemistry and geological features of the sedimentary rocks clearly define the change in sediment provenance from quartz-rich during the Oligocene to quartz-deficit in the Miocene. This offers additional constraints in understanding the geological evolution of the mineral district.

  7. Quantitative analysis of the extensional tectonics of Tharsis bulge, Mars - Geodynamic implications

    NASA Astrophysics Data System (ADS)

    Thomas, P. G.; Allemand, P.

    1993-07-01

    The amount of horizontal strain on the Martian Tharsis bulge is quantified in order to provide further information on the tectonic evolution of this province. About 10 percent of the Tharsis surface bulge exhibits elliptical impact craters, which are the largest strain markers in the solar system. It is shown that these strain ellipses indicate more strain than could be due to the bulge building alone. The existence of such intensely deformed areas, the direction of the extensive strain, the localization of these areas on the bulge crest or on the top of topographic slopes, and the evidence of nonthinned crust under these areas may all be explained by gravitational slidings of the bulge surface over the topographic slope. This sliding would be possible because of the presence of a decollement level two kilometers below the surface, and because of the prefracturation which have made the detachment possible.

  8. Rock Breakage Energy and Large-Scale Low-Friction Geodynamic Phenomena

    NASA Astrophysics Data System (ADS)

    Davies, T. R.; McSaveney, M. J.

    2010-12-01

    We show that the anomalously low frictional resistance to the motion of large rock ava-lanches, gigantic blockslides and large faults can be explained quantitatively by including the energetics of rock breakage in a simulation model. Griffith (1920) defined fracture energy as the amount of energy needed to create unit area of new rock surface by breaking rocks into smaller fragments, and assumed that fracture energy was entirely consumed in the fracture process, manifesting as unavailable “surface energy”. This concept is widely accepted and used in rock breakage analysis and in earthquake and landslide energy budgets. While the first use is sensi-ble, the latter two are not. Breakage of an intact rock clast by applied force first involves elastic deformation of the whole clast, and elastic strain energy accumulates in the clast interior. At failure, this strain en-ergy is a maximum and (by definition) equal to the fracture energy. During failure, the strain energy suddenly reduces to zero as through-going cracks release the applied forces, and frag-ments recover their unstressed shapes. The strain energy released is equal to the work done in stressing the clast to breakage, again equalling the fracture energy. Evidently some of the re-leased strain energy is initially present in the kinetic energy of fragment shape recovery. If Griffith’s assumption, that all the fracture energy used to break the rock becomes “surface energy”, were true, no mechanical energy would be available to provide rock fragments with kinetic energy, and rock fragments smaller than a few microns cannot be broken in two. How-ever, experiments show that fragment KE is at least 50% of the stored elastic strain energy in breakage of rock, and up to 85% with Pyrex; evidently the “surface energy” is substantially less than the fracture energy. In the energetics of earthquakes and large landslides this is fundamen-tally important, because the mechanical energy recycled by breaking grains to their environment is significant in the dynamics of the process - particularly when the grains involved are very small, as are many in large landslides and faults. Rock bursts in deep mines generate fragment velocities of many tens of metres per second, showing that large mechanical forces are exerted on the environment by grain breakage. We show that the average pressure exerted on its surroundings by a breaking clast is of the order of one-third of its average failure strength, which for unconfined intact crustal rock is in the order of 108 Pa - this is clearly significant in the dynamics of geophysical phenomena. Under high geostatic stresses, such as at the base of a large rock avalanche or in a fault at seismic depth, the failure strength is substantially higher and local dynamic pressures resulting from grain frag-mentation can be in the GPa range. We demonstrate, using a specific case study, that consideration of the dynamic pressures ex-erted by breaking rocks provides a simple and quantitative explanation for the anomalously low frictional resistance to the motion of a large debris avalanche. Griffith, A.A. (1920), The phenomena of rupture and flowing solids. Philosophical transactions of the Royal Society of London. A221: 163-198

  9. The Fanos granite: structure, emplacement and geodynamic significance (Eastern Axios/Vardar Zone, Northern Greece)

    NASA Astrophysics Data System (ADS)

    Michail, Maria; Kilias, Adamantios; Koroneos, Antonios; Ntaflos, Theodoros; Pipera, Kyriaki

    2014-05-01

    The Fanos granite occurs in the Peonia Subzone of the Eastern Axios-Vardar Zone in Northern Greece. It is a Late Jurassic (158±1 Ma), N-S trending granite, intruding the Mesozoic back-arc Geuvgeuli ophiolitic complex (Peonia Subzone). It is composed of three main rock types namely aplitic granite, granite and microgranite evolved by fractional crystallization. At the eastern contact of the Fanos granite with the host ophiolitic rocks the initial intrusion character of the granitic bodies is well preserved. On the other hand, the western contact is overprinted by a few meters thick, westward-vergent semiductile thrust zone, probably of Late Jurassic-Early Cretaceous age. For the better understanding of the geotectonic evolution of the broader area, the Fanos granite is compared with the Mid-Late Jurassic Kastaneri volcano-sedimentary formation allocated on the eastern part of the Paikon Massif, on which the Guevgeuli ophiolites were obducted. In our study we address three major topics: a) the origin of the Fanos granite, b) the geochemical correlation between Fanos granite and Kastaneri formation and c) the relationship of the granite with the remnants of an oceanic island-arc or an active continental margin geotectonic setting situated in the Neotethys (=Axios/Vardar ocean). The collected rock samples are granites, aplitic granites, microgranites, rhyolites, quartz diorites, migmatites and amphibolites. These samples were analysed by X-ray fluorence for major and trace elements. The granite shows peraluminous characteristics, high-K calc-alkaline affinities and I-type features. The Sr initial isotopic ratios of the granite range between 0.70519 and 0.70559, while the Nd initial isotopic ratios range between 0.51236 and 0.51239, reflecting EM-I (Enriched Mantle-I) component. The trace element patterns along with the isotopic composition of the rocks indicate absence of continental crustal material contamination. Moreover, the geochemical data imply a common origin between the Fanos granite and the Kastaneri formation. Taking into account our structural and geochemical data along with the existing isotopic and geotectonic data of the broader Axios/Vardar Zone, we suggest that the studied granitic rocks were formed during an intraoceanic-subduction within the Neotethys ocean, approximately at the same time with the amphibolite sole formation, rather than during the evolution of an active continental margin. In the Late Jurassic, a general westward ophiolite obduction on the Pelagonian continental margin, resulted to the thrusting of the Fanos granite together with the obducted ophiolites.

  10. Metamorphic diamonds in a garnet megacryst from the Edough Massif (northeastern Algeria). Recognition and geodynamic consequences

    NASA Astrophysics Data System (ADS)

    Caby, Renaud; Bruguier, Olivier; Fernandez, Laure; Hammor, Dalila; Bosch, Delphine; Mechati, Mehdi; Laouar, Rabah; Ouabadi, Aziouz; Abdallah, Nachida; Douchet, Chantal

    2014-12-01

    We report for the first time the discovery of diamond inclusions (5-30 ?m in size), identified by Raman spectroscopy and the characteristic sharp band at 1332 cm- 1 for crystalline diamond, in a garnet megacryst (? 5 cm) from the Edough Massif (NE Algeria). The garnet is adjacent to actinolite and ultramafic boudins and slices of marbles that are inserted within a major mylonite-ultramylonite band. This tectonic contact sharply delineates the Kef Lakhal oceanic unit from the granite-gneiss core below. The host garnet is almandine-dominant and is rich in exsolution of acicular rutile needles. Major and trace elements show a gradual but significant zonation from core to rim, and a sharp increase in grossular component in the rim. Trace element analyses of prismatic rutile inclusions up to 300 ?m in size indicate that the host metamorphic rock was a mafic protolith of MORB affinity. The Zr-in-rutile thermometry indicates a temperature range of 724-778 °C that we relate to rutile growth, either during prograde metamorphism or under peak UHP metamorphic conditions of ? 3.6 GPa that were reached during subduction of the UHP-rock precursors. We suggest that the mafic protolith originates from the subducted retreating Calabrian branch of the Tethyan slab, that broke or tore, and which fragments were dragged upward and thrust onto the North African margin along with the Kef Lakhal unit, shortly followed by formation of the Edough dome and opening of the Algerian basin.

  11. GS of CAS Geodesy & Geodynamics Beijing June 20041 Fundamentals of GPS

    E-print Network

    Vigny, Christophe

    and is used to make ionosphere Total Electron Containt (TEC) maps of the ionosphere) #12;GS of CAS ­ Geodesy) 4. reference frames : how do we map ? with what precision ? What influence on results ? #12;GS

  12. Geodynamic Model of the New Zealand-Antarctica Conjugate Margin Since the Late Cretaceous

    Microsoft Academic Search

    S. Spasojevic; R. Sutherland; M. Gurnis

    2008-01-01

    Present-day plate boundaries in the Southwest Pacific were created through continental rifting since Late Cretaceous. Spreading on the Pacific-Antarctic Ridge and the southeast Indian Ridge started around 95-90 Ma and continues to the present. The New Zealand and Antarctica conjugate margins are characterized by a number of anomalous observations. The Antarctica margin and adjacent sea floor is approximately 1 km

  13. Real episodic growth of continental crust or artifact of preservation? A 3-D geodynamic model

    NASA Astrophysics Data System (ADS)

    Walzer, Uwe; Hendel, Roland

    2013-05-01

    Abstract We investigate whether the observed zircon age distribution of continental crust (CC) is produced by real crustal growth episodes or is only an artifact of preservation. In connection with the second alternative of this question, other authors proposed that there was little episodicity in the production of new CC and that modeling corroborates this opinion. We conclude that a combination of the two answers might be possible. In matters of modeling, however, we ascertain that a dynamic modeling of the convection-differentiation system of the mantle reveals the high probability of magmatic episodes. We solve the full set of balance equations in a 3-D spherical-shell mantle. The heat-producing elements are redistributed by chemical differentiation. A realistic solidus model of mantle peridotite is essential for an applicable model. The solidus depends not only on depth but also on the volatile concentration. Furthermore, we introduced realistic profiles of Grüneisen parameter, viscosity, adiabatic temperature, thermal expansivity, and specific heat. Our model automatically produces lithospheric plates and growing continents. Regarding number, size, form, distribution, and surface velocity of the continents, no constraints have been prescribed. Regions of the input parameter space (Ra,?y,k,f3) that are favorable with respect to geophysical quantities show simultaneously not only episodicity of CC growth but also a reproduction of the observed zircon-age maxima referring to the instants of time. We also obtain Archean events for ages greater than 3000 Ma that are not or scarcely visible in the observed zircon ages. Sinusoidal parts of the evolution curve of qob, Ur, and Ekin are superposed with a monotonous decrease. The volumetrically averaged mantle temperature, Tmean, however, decreases smoothly and slowly, nearly without pronounced variations. Therefore, we can dismiss catastrophic mechanisms that simultaneously incorporate the whole mantle.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=EPRINT&redirectUrl=http://www.earthbyte.org/people/dietmar/Pdf/Muller_fromzero-to-infinity-Geodynamics2003.pdf"><span id="translatedtitle">Chapter 8: Understanding How the Earth Works: A <span class="hlt">Geodynamic</span> Revolution Based on Linux Computing INTRODUCTION</span></a></p> <p><a target="_blank" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p>Müller, Dietmar</p> <p></p> <p>INTRODUCTION Planet Earth is an extremely complex system, partly because of the existence of plate tectonics. Plate tectonics is an expression of slow convection of the Earth's mantle over geological timesEarthlosesitsinternalheat(seeglossarypagexx).Onageologicaltimescale(i.e.millions of years), plate tectonics exerts major controls on global sea-level changes and geochemical cycles. We</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=PUBMED&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/22422979"><span id="translatedtitle">A change in the <span class="hlt">geodynamics</span> of continental growth 3 billion years ago.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dhuime, Bruno; Hawkesworth, Chris J; Cawood, Peter A; Storey, Craig D</p> <p>2012-03-16</p> <p>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</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-STC&redirectUrl=http://www.osti.gov/scitech/biblio/21313740"><span id="translatedtitle"><span class="hlt">GEODYNAMICS</span> AND RATE OF VOLCANISM ON MASSIVE EARTH-LIKE PLANETS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kite, E. S.; Manga, M. [Department of Earth and Planetary Science, University of California at Berkeley, Berkeley, CA 94720 (United States); Gaidos, E. [Department of Geology and Geophysics, University of Hawaii at Manoa, Honolulu, HI 96822 (United States)], E-mail: kite@berkeley.edu</p> <p>2009-08-01</p> <p>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.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-STC&redirectUrl=http://www.osti.gov/scitech/biblio/6747855"><span id="translatedtitle">Plate Tectonics: <span class="hlt">Geodynamic</span> models of evolution of oil and gas bearing basins of Kazakhstan</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zholtayev, G. (Kazakhpolitecnic Institute, Almaty (Kazakhstan))</p> <p>1994-07-01</p> <p>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.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=EPRINT&redirectUrl=http://rses.anu.edu.au/~nick/papers/tecto2010b.pdf"><span id="translatedtitle">Convergent plate margin dynamics: New perspectives from structural geology, geophysics and <span class="hlt">geodynamic</span> modelling</span></a></p> <p><a target="_blank" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p>Rawlinson, Nick</p> <p></p> <p>: Convergent plate margin Subduction Collision Orogenesis Slab Plate tectonics Convergent plate margins occur when two adjoining tectonic plates come together to form either a subduction zone, where at least one and discussions since the advent of plate tectonic theory. This paper provides a historical background</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/1996IJEaS..85..705M"><span id="translatedtitle">A traverse through the western Kunlun (Xinjiang, China): tentative <span class="hlt">geodynamic</span> implications for the Paleozoic and Mesozoic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mattern, Frank; Schneider, Werner; Li, Yongan; Li, Xiangdong</p> <p></p> <p>The northern part of the western Kunlun (southern margin of the Tarim basin) represents a Sinian rifted margin. To the south of this margin, the Sinian to Paleozoic Proto-Tethys Ocean formed. South-directed subduction of this ocean, beneath the continental southern Kunlun block during the Paleozoic, resulted in the collision between the northern and southern Kunlun blocks during the Devonian. The northern part of the Paleo-Tethys Ocean, located to the south of the southern Kunlun, was subducted to the north beneath the southern Kunlun during the Late Paleozoic to Early Mesozoic. This caused the formation of a subduction-accretion complex, including a sizeable accretionary wedge to the south of the southern Kunlun. A microcontinent (or oceanic plateau?), which we refer to as "Uygur terrane," collided with the subduction complex during the Late Triassic. Both elements together represent the Kara-Kunlun. Final closure of the Paleo-Tethys Ocean took place during the Early Jurassic when the next southerly located continental block collided with the Kara-Kunlun area. From at least the Late Paleozoic to the Early Jurassic, the Tarim basin must be considered a back-arc region. The Kengxiwar lineament, which "connects" the Karakorum fault in the west and the Ruoqiang-Xingxingxia/Altyn-Tagh fault zone in the east, shows signs of a polyphase strike-slip fault along which dextral and sinistral shearing occurred.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/1996GeoRu..85..705M"><span id="translatedtitle">A traverse through the western Kunlun (Xinjiang, China): tentative <span class="hlt">geodynamic</span> implications for the Paleozoic and Mesozoic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mattern, F.; Schneider, W.; Li, Y.; Li, X.</p> <p>1996-12-01</p> <p>The northern part of the western Kunlun (southern margin of the Tarim basin) represents a Sinian rifted margin. To the south of this margin, the Sinian to Paleozoic Proto-Tethys Ocean formed. South-directed subduction of this ocean, beneath the continental southern Kunlun block during the Paleozoic, resulted in the collision between the northern and southern Kunlun blocks during the Devonian. The northern part of the Paleo-Tethys Ocean, located to the south of the southern Kunlun, was subducted to the north beneath the southern Kunlun during the Late Paleozoic to Early Mesozoic. This caused the formation of a subduction-accretion complex, including a sizeable accretionary wedge to the south of the southern Kunlun. A microcontinent (or oceanic plateau?), which we refer to as “Uygur terrane,” collided with the subduction complex during the Late Triassic. Both elements together represent the Kara-Kunlun. Final closure of the Paleo-Tethys Ocean took place during the Early Jurassic when the next southerly located continental block collided with the Kara-Kunlun area. From at least the Late Paleozoic to the Early Jurassic, the Tarim basin must be considered a back-arc region. The Kengxiwar lineament, which “connects” the Karakorum fault in the west and the Ruogiang-Xingxingxia/Altyn-Tagh fault zone in the east, shows signs of a polyphase strike-slip fault along which dextral and sinistral shearing occurred.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2011AGUFM.T11B2324M"><span id="translatedtitle">Along-Strike Variations in Crustal Seismicity in the Central Andes and <span class="hlt">Geodynamic</span> Implications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Metcalf, K.; Pearson, D. M.; Kapp, P. A.; McGroder, M.; Kendall, J. J.</p> <p>2011-12-01</p> <p>For the central Andes, we compiled relocated crustal earthquakes (magnitude ? 4.5) from the EHB Bulletin and Nipress et al. [2007] and focal mechanisms from the Global CMT catalog and published literature [Alvarado et al., 2005]. These data were plotted in map, cross section, and 3D views in the context of local tomography [Koulakov et al., 2006] and lithospheric boundaries [Tassara et al., in prep]. The results imply major along-strike variations in the mechanisms of crustal deformation. At the latitude of the Altiplano, there is scarce forearc seismicity. The thin-skinned Bolivian retroarc thrust belt shows no seismic events (magnitude ? 4.5), suggesting that it is deforming aseismically or locked. In contrast, at the latitude of the Puna to the south (20-25°S), crustal seismicity is more prevalent in both the forearc and retroarc. Within this region, active deformation in the Coastal Cordillera near Antofagasta is occurring along steeply east-dipping normal faults at 15-41 km depth; this is the only part of the central Andean forearc that displays prominent extension. Outboard of this, thrust events at ~15 km depth in the forearc wedge display gently dipping nodal planes, and may be signatures of underplating crust that was tectonically eroded at the trench. Underplating is a likely process by which this region of the forearc has undergone ~1 km of surface uplift during the Neogene. Seismicity with thrust or reverse and oblique focal mechanisms in the retroarc wedge is localized beneath the frontal part of the thick-skinned Eastern Cordilleran thrust belt and the Santa Barbara ranges. Seismicity along discrete, east- and west-dipping planes occurs to near Moho depths (~50 km). While retroarc crustal seismicity continues to the south toward the Juan Fernandez flat slab, there is a concentration of seismic events in the retroarc at the latitude (22-23°S) where there is prominent normal faulting in the forearc. We interpret the compiled data to suggest that at the latitude of the Puna, orogenic wedge tapers of both the forearc and retroarc wedges may be supercritical as a result of late Miocene to Recent lithosphere removal from beneath the hinterland.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASA-TRS&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19850023289&hterms=rodley&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Drodley"><span id="translatedtitle">Investigation of dynamic noise affecting <span class="hlt">geodynamics</span> information in a tethered subsatellite</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gullahorn, G. E.</p> <p>1985-01-01</p> <p>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.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2010EGUGA..12.8862L"><span id="translatedtitle"><span class="hlt">Geodynamical</span> evolution of the Southern Carpathians: inferences from computational models of lithospheric gravitational instability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lorinczi, Piroska; Houseman, Gregory</p> <p>2010-05-01</p> <p>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 variable density and viscosity and we assume that deformation is initially localized in the Carpathian region because its crust and/or mantle layers are weakened by some prior tectonic or magmatic process.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/1990Tectp.184..405M"><span id="translatedtitle"><span class="hlt">Geodynamic</span> models for the Azores triple junction: A contribution from tectonics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Madeira, José; Ribeiro, António</p> <p>1990-12-01</p> <p>The American, Eurasian and African lithospheric plates meet at the Azores triple junction. The nature of the northern and southern branches of the junction is well known and uncontroversial, the American plate is separated from Eurasia and Africa by the Mid-Atlantic Ridge (MAR). The western group of islands of the Azores archipelago (Flores and Corvo) lies on the American plate, just west of the rift, and their tectonic features agree with that location. The nature of the third branch of the junction, to the east of the MAR, is however still controversial. Some authors believe that a ridge-ridge-ridge junction occurs in the Azores area and adopt the structure known as the "Terceira Ridge" (working as a simple rift boundary) as the third branch. Another model proposes a triangular microplate in the Azores region bounded by the Mid-Atlantic Rift to the west, the East Azores Fault Zone to the south and a fault crossing S. Miguel and the Terceira islands to the northeast; in this model the fault zones are pure dextral strike-slip boundaries. Both models would create space problems at Gloria Fault, a well-known pure dextral strike-slip structure. In the first model transtension would be necessary at Gloria Fault to accommodate plate motion, while the second would require a transpressive regime on that structure. Neotectonic and seismotectonic data in the Azores indicate a transtensile regime in the central and eastern island groups in present and recent times. This is compatible with a "leaky transform" structure acting as the third branch of the junction in the Azores area, a model which has already been presented by several authors in the past. Stress trajectories deduced from neotectonic studies in some of the islands suggest that the main plate boundary passes between the islands of S. Jorge and Pico south of S. Miguel and joins Gloria Fault east of Santa Maria. This model and boundary location is also compatible with seismotectonic and magnetic data.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASA-TRS&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19840016855&hterms=noise+cancellation+devices&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dnoise%2Bcancellation%2Bdevices"><span id="translatedtitle">Investigation of dynamic noise affecting <span class="hlt">geodynamics</span> information in a tethered subsatellite</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gullahorn, G. E.</p> <p>1984-01-01</p> <p>The effects of a tethered satellite system's internal dynamics on the subsatellite were calculated including both overall motions (libration and attitude oscillations) and internal tether oscillations. The SKYHOOK tether simulation program was modified to operate with atmospheric density variations and to output quantities of interest. Techniques and software for analyzing the results were developed including noise spectral analysis. A program was begun for computing a stable configuration of a tether system subject to air drag. These configurations will be of use as initial conditions for SKYHOOK and, through linearized analysis, directly for stability and dynamical studies. A case study in which the subsatellite traverses an atmospheric density enhancement confirmed some theoretical calculations, and pointed out some aspects of the interaction with the tether system dynamics.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2014EGUGA..1610097S"><span id="translatedtitle">Archean plate tectonics <span class="hlt">geodynamics</span>: example from the Belomorian province, Fennoscandian Shield</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Slabunov, Alexander</p> <p>2014-05-01</p> <p>A fragment of the Archean collisional Belomorian orogen has been identified as the Belomorian province (BP) of the Fennoscandian Shield (Slabunov, 2008; Holtta et al., 2014). The province consists dominantly of Archean rocks, Early Paleoproterozoic rocks being less abundant. Rock of BP exhumed from middle crustal depths in Paleoproterozoic time (1.94-1.8 Ga). Seismic (CDP) profiling data (Sharov et al., 2010) show that the internal structure of BP reflects nappe tectonics: in Archean time, a collage of numerous slides was formed, and in Paleoproterozoic time the BP was thrusted on the Karelian craton and, in turn, was thrusted by rocks of the Kola province. The BP consists dominantly of Meso- and Neoarchean rock association (Slabunov et al. 2006). Neoarchean granitoids predominate, but eclogite-bearing metam?lange (Volodichev et al., 2004; Mints et al., 2010; Shchipansky et al., 2012), island-arc volcanics, front-arc basin sediments, ophiolite-type oceanic plateau-type rocks, collisional S-granites, kyanite-facies metamorphic rocks, molassa-type rocks, subalkaline granitoids and leucogabbro have been revealed among supracrustal rock associations. Rocks of the Belomorian province were subjected to multiple metamorphism in Archean and Paleoproterozoic time at moderately high to high pressures and were considerably deformed. High-grade supracrustal complexes make up not more than 20 % of the BP, but as they probably host ore and are crucial for the understanding of the formation and evolution of the structure, they are given close attention. Five generations of greenstone complexes of different ages: 2.88-2.82 Ga, 2.8-2.78 Ga, ca. 2.75 Ga , ca. 2.72 Ga and not later than 2.66 Ga, and two paragneiss complex in which sediments were formed 2.89-2.82 and 2.78 Ga ago, are distinguished. The main stages of crustal evolution in the BP: ca 2.88-2.82 Ga - the first subduction-accretion event marked by the following complexes: island-arc volcanics of the Keret GB; metagraywacke (front-arc basin sediments) of the Chupa paragneiss belt; Salma eclogites; 2.81?2.78 Ga - the second subduction-accretion event marked by the following complexes: island-arc volcanics, supra-subduction ophiolite (Iringora), graywackes, granulites (Notozero) and 4) eclogites (Kuru-Vaara); 2.75 Ga - the third subduction event marked by island-arc volcanics (Chelozero); 2.73-2.72 Ga - the fourth subduction-accretion event marked by : island-arc volcanics (Mil'kevich et al., 2007), granulites and Gridino eclogites; ca 2.7-2.66 Ga - collisional event marked by: collisional S-granites, kyanite-facies metamorphic rocks, molassa-type rocks, subalkaline granitoids and leucogabbro. The crustal evolution of the BP in the period 2.88-2.66 Ga is similar to the evolution of Phanerozoic collision orogens. This is a contribution to RFBR Project 13-05-91162.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/1992JAfES..14..351R"><span id="translatedtitle"><span class="hlt">Geodynamic</span> of the Gulf of Suez-Red Sea rifting and origin of within plate magmatism</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ragab, A. I.; El-Kaliouby, B. A.</p> <p>1992-04-01</p> <p>This study is an attempt to follow up the overall picture of the geologic processes of the "Wilson Cycle" in the Gulf of Suez Red Sea region. A plate-tectonic model is suggested covering the Pan-African collisional tectonics, post-Pan-African magmatism in space and time, and rifting stages in the Red Sea region. Field relations, petrography, and petrochemistry of the Tertiary basalt sheets of Abu Zenima area, Sinai, have been studied and correlated with some petrochemical data of Phanerozoic magmatic activities in the Red Sea region. The sequence of events of the tectonics and magmatic activities in the Gulf of Suez-Red Sea rift system may belong to six stages post Pan-African orogeny: (1) Paleozoic-Cretaceous continental bimodal alkaline magmatism resulting from the sinking of detached subducted oceanic plates, in the late stages of the Pan-African collisional tectonics. Consequently causing convection currents around them and partial melting of a deep undepleted mantle source; (2) Paleogene crustal doming and stretching as a result of asthenosphere upwelling activated by a long period of (? 300 m.y.) within plate alkaline magmatism; (3) Late Oligocene fissure-eruption of transitional (T-type MORBs) plateau basalts, dykes and sills on a regional scale. The transitional character of this basaltic activity is attributed to the soaking of the asthenosphere, during its slow upwelling, in the rising alkaline magmatism; (4) Early Miocene narrow long continental rifting in the Gulf of Suez-Red Sea region, probably due to a thermal contraction process resulting from the eruption of the Tertiary transitional, fissure-eruption basalts in large volumes from the upwelled asthenosphere; (5) Initiation of crustal separation of the very early stage of seafloor spreading, which is most probably characterized by mafic igneous rocks underplating of the crustal faulted blocks by dyke injection and related plutonic rocks; (6) Pliocene oceanic rifting and seafloor spreading generating N-type MORBs in the central parts of the Red Sea axial trough. In this stage, subsidence of the Red Sea passive marging could be due to a second stage of thermal contraction resulting from the extrusion and crystallization of asthenosphere material to construct the new oceanic crust.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2012AGUFM.T32D..02D"><span id="translatedtitle">The Contribution of the Topo-Iberia Project to the Knowledge of the Western Mediterranean <span class="hlt">Geodynamics</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Diaz Cusi, J.</p> <p>2012-12-01</p> <p>The large scale research program Topo-Iberia aims to unravel the complex structure and mantle processes in the area of interaction between the African and European continental plates in the western Mediterranean. The project, funded by the Spanish Ministry of Science and Education, started in 2007 and will be active till Fall 2013. Topo-Iberia has gathered expertise of different fields of the Earth Sciences. One of the key assets of the project involves the deploying of a technological observatory platform, IberArray, with unprecedented resolution and coverage. This platform is currently building up a comprehensive, multidisciplinary data set, stored by the SIGEOF database, which includes seismological, GPS and magnetotelluric data. Using also other analytical methodologies included in the Topo-Iberia program (potential fields, quantitative analysis of the topography, dating methods) the final scope of the project is to study the relationship between superficial and deep-rooted processes. Topo-Iberia has also benefited from the interaction with other projects investigating the same area, as the American program PICASSO, the French Pyrope or the Portuguese WILAS. This interaction includes sharing the available data to better assess the key geological questions. This contribution will present the current state of the most significant scientific results which are arising from the data acquired using the Iberarray platform. -. SKS splitting analysis has provided a spectacular image of the anisotropic pattern over the area, including a clear rotation of the fast velocity direction along the Gibraltar Arc. -. Receiver functions have revealed the crustal thickness variations beneath the Rif and southern Iberia, including a crustal root beneath the Rif not clearly documented previously. The 410-km and 660-km upper mantle discontinuities have been investigated using novel cross-correlation/stacking techniques. -. Surface wave tomography using both earthquakes and ambient 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.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-STC&redirectUrl=http://www.osti.gov/scitech/servlets/purl/80379"><span id="translatedtitle">Interface deformation in low reynolds number multiphase flows: Applications to selected problems in <span class="hlt">geodynamics</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gable, C.; Travis, B.J. [Los Alamos National Lab., NM (United States); O`Connell, R.J.; Stone, H.A. [Harvard Univ., Cambridge, MA (United States)</p> <p>1995-06-01</p> <p>Flow in the mantle of terrestrial planets produces stresses and topography on the planet`s surface which may allow us to infer the dynamics and evolution of the planet`s -interior. This project is directed towards understanding the relationship between dynamical processes related to buoyancy-driven flow and the observable expression (e.g. earthquakes, surface topography) of the flow. Problems considered include the ascent of mantle plumes and their interaction with compositional discontinuities, the deformation of subducted slabs, and effects of lateral viscosity variations on post-glacial rebound. We find that plumes rising from the lower mantle into a lower-viscosity upper mantle become extended vertically. As the plume spreads beneath the planet`s surface, the dynamic topography changes from a bell-shape to a plateau shape. The topography and surface stresses associated . with surface features called arachnoids, novae and coronae on Venus are consistent with the surface expression of a rising and spreading buoyant volume of fluid. Short wavelength viscosity variations, or sharp variations of lithosphere thickness, have a large effect on surface stresses. This study also considers the interaction and deformation of buoyancy-driven drops and bubbles in low Reynolds number multiphase systems. Applications include bubbles in magmas, the coalescence of liquid iron drops during core formation, and a wide range of industrial applications. Our methodology involves a combination of numerical boundary integral calculations, experiments and analytical work. For example, we find that for deformable drops the effects of deformation result in the vertical alignment of initially horizontally offset drops, thus enhancing the rate of coalescence.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-MAS&redirectUrl=http://academic.research.microsoft.com/Publication/41055487"><span id="translatedtitle">A review of the geology and <span class="hlt">geodynamic</span> evolution of the Palaeoproterozoic Earaheedy Basin, Western Australia</span></a></p> <p><a target="_blank" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p>Franco Pirajno; Roger M. Hocking; Steven M. Reddy; Amanda J. Jones</p> <p>2009-01-01</p> <p>The Palaeoproterozoic Earaheedy Basin is one of a series of basins that extend for about 700 km east–west and are part of the Capricorn Orogen, situated between the Archaean Pilbara and Yilgarn Cratons. The Earaheedy Basin contains sedimentary rocks that were deposited on the northern passive continental margin of the Yilgarn Craton, probably as a result of continental breakup at 1.8 Ga.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASA-TRS&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=20040171158&hterms=south+america+australia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dsouth%2Bamerica%2Baustralia"><span id="translatedtitle">Deep Structure of the Earth and Concentration of Metals in the Lithosphere: A <span class="hlt">Geodynamic</span> Approach</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Taylor, Patrick T.; Kutina, J.; Pei, R.</p> <p>2004-01-01</p> <p>A discussion of and introduction to satellite-altitude geopotential fields studies and their interpretation with emphasis on results from metalliferous regions will be given. The magnetic and gravimetric measurements from satellite altitudes show heterogeneity in deeper parts of the lithosphere. These patterns of magnetic anomalies do not only reveal the largest iron ore deposits such as Kiruna, Sweden and Kursk, Russia, but also linear features indicating structural discontinuities. Changes of magnetic amplitude of these patterns are caused by intersecting transverse fractures localizing magmatism and concentration of metals. The role of trans-regional mantle-rooted structural discontinuities in the concentration of metals will be discussed and a new type of mineral prognosis map will be presented. Deep-rooted structural discontinuities, defined by combination of geological and geophysical criteria, with spacing of several hundred kilometers, reveal a quite uniform pattern in the deeper parts of the lithosphere. As these structures provide favorable pathways for the ascent of heat, magmas and ore-forming fluids, their recognition is of crucial importance and can be used in the compilation of a new type of mineral prognosis map. Examples are shown from the United States, Canada, China, Burma, South America, Europe and Australia. The European example includes a pattern of east west trending structural discontinuities or belts and their junction with the NW-trending Tornqvist-Teisseyre Line. The Upper Silesian-Cracovian Zn-Pb district occurs along one of the latitudinal belts. Leslaw Teper of the University of Silesia has been invited to show the fractures in crystalline basement beneath the sediments hosting the Zn-Pb ores.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2010EGUGA..12.2103R"><span id="translatedtitle">A link between geochemistry and <span class="hlt">geodynamics</span>: carbonatites and kimberlites, Polar Siberia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rass, Irene</p> <p>2010-05-01</p> <p>Geophysical evidence indicates that the Moho surface beneath the northern Siberian Platform composes crests (or ranges) up to 14 km high above deeper areas and 50-80 to 150 km wide (Chernyshov and Bokaya, 1983). These ranges at the Moho likely mark ancient rift zones with a thinner crust. More than 70% kimberlites in structures surrounding the Anabar Shield occur along these Moho crests (Kravchenko et al., 1997; Rosen and Kostyuchenko, 1998). Carbonate-rich rocks that compose pipes, along with kimberlites, in kimberlite fields, were recognized as an individual type of carbonatite rocks: kimberlitic carbonatites (Lapin and Marshintsev, 1984). They abound in kimberlite fields of both Paleozoic and Mesozoic age southeast and east of the Anabar Shield. The liquidus temperatures of related kimberlites, determined based on their major-component chemistries, are 1429-1441?C and 1349-1518?C, respectively (Perchuk and Vaganov, 1980). Compared to classic carbonatites in ring complexes, kimberlitic carbonatites are characterized by the lowest relative concentrations of P and Sr, slightly lower REE, and high contents of Cr, Ti, and Zr (Rass, 1998). Mesozoic kimberlitic carbonatites exhibit a dependence of their geochemistry, position relative to the axial zones of the Moho crests, and the temperatures of the associated kimberlites, from the Kuoika to the Lower Kuonamka field: from <42 km and 1518 ?C to ~50 km and 1395 ?C (Rass et al., 2000). Away from the maximum heights of the Moho crests, which mark ancient rifts in the northern part of the Siberian Platform and with a decrease in the liquidus temperatures of the associated kimberlites, the relative P and Nb concentrations in these rocks increase, and those of REE, Cr, and, to a lesser extent, Ni and Co decrease. The depths of the Moho surface beneath carbonatites in Mesozoic ring structures of the Odikhincha, Guli, Magan, and Yraas complexes in the Maymecha-Kotui alkaline-ultrabasic-carbonatite province west of the Anabar Shield and in Maldzhangarka complex south of the Shield are 36, <42, 42-46, and 50 km, respectively. Their geochemical characteristics show analogous zoning relative to the axial zones of the Moho crests. The geochemical features of kimberlitic carbonatites are controlled, first of all, by the partition coefficients of trace elements between the silicate and carbonate components of the deep-sitting magmas. Their experimentally determined parameters are still scarce (Green, 1994) and obviously insufficient for any conclusions about the physicochemical conditions of the exsolution and/or melting of the parental magmas, so that any empirical dependences the identified in them provide information on the lateral heterogeneity of the mantle material in the northern Siberian Platform. References Chernyshov N.V. and Bokaya L.I., in: Structural Elements of the Earth's Crust and Their Evolution. Nauka, Novosibirsk, 1983: 144-150 (in Russ.) Green T.H. Chemical Geology, 1994, vol.117: 1-36 Kravchenko S.M., Schakhotko L.I., Rass I.T. Global Tectonics and Metallogeny, 1997, vol.6, No.2: 137-140 Lapin A.V., Marshintsev V.K. Geology of Ore Deposits, 1984, No.3: 28-42 Perchuk L.L., Vaganov V.I. Contrib.Mineral.Petrol., 1980, vol.72: 219-228 Rass I.T. Geochem. Int., 1998, vol.36, No.2: 107-116 Rass I.T., Ilupin I.P., Marchenko T.M., Schakhotko L.I., in: The 2nd Russ. Conf. Transactions, Syctyvkar, 2000, vol.4: 307-308 (in Russ.) Rosen O.M., Kostyuchenko S.L., in: Khain V.Ye. (Ed.) Explanatory notes for the tectonic map..., Moskow, 1998: 10-42</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2013AGUFMEP33B0889U"><span id="translatedtitle">Reconstructing the formation and in-filling of Lake Manuherikia, Otago: Linking <span class="hlt">geodynamics</span> and surface processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Upton, P.; Duclaux, G.; Craw, D.; Salles, T. B.; Walcott, R.</p> <p>2013-12-01</p> <p>The Miocene geography of Central Otago, New Zealand was dominated by a long-lived region of subsidence culminating in an orogen-scale large lake complex that existed for at least 10 Ma. Subsidence was terminated by uplift of orogen-perpendicular ranges with orogen-parallel subsidiary ranges infilling of the lake and coincident major drainage reorientation. We used a combination of a 3D numerical model with geophysical and geological observations to show that the subsidence is a predictable consequence of the lithospheric structure and tectonic history of the region. A weak lower crust beneath Otago, bounded along strike by two stronger regions, subjected to dextral strike-slip tectonics produces characteristic topography including uplift to the north and subsidence to the south. Second-order features such as pre-existing faults influenced local topography and regional drainage reorientation. We then model the Pliocene in-filling of Lake Manuherikia using a surface dynamics code in which we constrain uplift rates, precipitation, underlying structure (pre-existing faults) and track Plio-Pleistocene sediments. As the Central Otago ranges shed coarse sediment into the lake eventually drowning it, the dominant river system shifted from draining southwest to draining to the east. Fault zones, cored by weak gouge zones, facilitated erosion through the uplifting ranges and allowed the Clutha River to incise a path from the Main Divide to the south-eastern Otago coast. To unravel the complex topographic evolution of the region since the early Miocene, it is essential to constrain our surface process models with information about the underlying lithosphere. In this situation, the rheology of the lower crust is important for the first order topographic development while the pre-existing structure controls second order features such as river incision and local topography.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2014JAfES..99..353H"><span id="translatedtitle">Paleomagnetic dating of continental geological formations: Strong diachronism evidenced in the Saharan platform and <span class="hlt">geodynamical</span> implications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Henry, B.; Derder, M. E. M.; Amenna, M.; Maouche, S.; Bayou, B.; Ouabadi, A.; Bouabdallah, H.; Beddiaf, M.; Ayache, M.; Bestandji, R.</p> <p>2014-11-01</p> <p>The paleomagnetism is a powerful tool to date formations that have age not constrained by paleontological, stratigraphical or radiochronological data. It was applied, on the western border of the Murzuq basin in Algeria (Saharan platform), to the Zarzaïtine formation, attributed to a Middle-Upper Triassic-Lower Jurassic age. Comparison of the obtained paleomagnetic pole with previous poles from the same geological formation outcropping in another basin and from other Carboniferous to Lower Mesozoic African formations yielded a clearly older age (Late Permian) than expected. That evidences a strong diachronism (at least 40 My) of the deposition of this formation on the Saharan platform. The post-Hercynian structural evolution was therefore different according to the parts of this platform, with significant differential vertical tectonic movements. The latter were at the origin of erosion, hiatus or sediments deposition according to areas.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2013EGUGA..1511638N"><span id="translatedtitle">Linking seismology, mineralogy and <span class="hlt">geodynamics</span> with seismic anisotropy in the lowermost mantle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nowacki, Andy; Walker, Andrew; Wookey, James; Walpole, Jack; Masters, Guy; Kendall, J.-Michael</p> <p>2013-04-01</p> <p>The core-mantle boundary (CMB) is the site of the largest change in properties in the Earth, where the liquid outer core and solid mantle meet. Forming the lower boundary layer in the convecting mantle, D? (the lowermost mantle) may hold the key to understanding dynamics both above and below. One property of the region which holds much potential to advance this understanding is its seismic anisotropy, which may be caused by factors such as the alignment of anisotropic mineral grains in response to mantle flow. Anisotropy is widely observed in D?, yet not in the overlying mantle more than a few hundred kilometres above the CMB, as evidenced by numerous tomographic and waveform studies. Shear wave splitting is an unambiguous indicator of the presence of anisotropy and measurements thereof need not make any simplification regarding the kind of anisotropy. Such measurements therefore allow us to test the widest range of candidate processes which might cause D" anisotropy. Ultimately, if one cause such as mineral alignment is more likely than others, we can then use seismic anisotropy to directly infer flow in the lowermost mantle. In order to test candidate processes for D? anisotropy, we construct a series of elastic models of the lowermost mantle. Each is based on a different assumption regarding the cause of lowermost mantle anisotropy, concentrating thus far on the development of lattice-preferred orientation in dislocation creep in lower mantle mineral phases such as perovskite, post-perovskite and (Mg,Fe)O (and mixtures thereof). In order to do this, for these phases we require mineral physical data regarding the single-crystal elasticity and deformation mechanisms. Whilst there exists some uncertainty in these parameters, we can nevertheless test what effect these have on our final models. We then use a steady-state mantle flow field retrieved from seismic, geodetic and mineral physical observables, and calculate the texturing along pathlines in the lowermost mantle, eventually producing a three-dimensional model of completely general elasticity. Observations of seismic anisotropy in ScS waves are then re-created for our candidate models and direct comparison can be made with the data. A complicating factor is that the ray-theoretical assumption may not accurately capture the sensitivity of the waves to varying D? elastic structure, and thus we use a spectral-element approach to calculate synthetic seismograms at the same frequency as the observations (~0.2 Hz). The calculations involve thousands of processors and terabytes of memory, but are necessary for retrieving the wavefield in a fully anisotropic medium. We compare a new set of global observations of shear wave splitting in ScS, corrected for upper mantle anisotropy, and can potentially rule in or out different causative mechanisms for anisotropy in the lowermost mantle. More constraints can be incorporated in the future as our method allows the measurement of any seismic phase and any causative mechanism.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2009AGUFM.V12B..06C"><span id="translatedtitle">The non-chondritic composition of the Earth and its consequences for chemical <span class="hlt">geodynamics</span> (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Caro, G.; Bourdon, B.</p> <p>2009-12-01</p> <p>Super-chondritic 142Nd signatures are ubiquitous in terrestrial and lunar samples, and indicate that the Earth may have accreted from material with Sm/Nd ratio higher than chondritic [1]. This early Sm/Nd fractionation must predate both core formation and the giant impact [2], and could therefore result from the loss of crustal material by collisional erosion during the early stages of planetary accretion [3]. These observations contradict the long-held view that chondrites represent a reference composition for the 147Sm-143Nd system. Using coupled 146Sm-142Nd and 147Sm-143Nd systematics in planetary samples, we have proposed a new set of values for the 147Sm/144Nd and 143Nd/144Nd ratios of the bulk silicate Earth [1]. Here, we revise the Bulk Silicate Earth estimates for the 176Lu-176Hf system using coupled Nd-Hf systematics in terrestrial rocks and show that these estimates are consistent with lunar Hf-Nd data. The implications of a non-chondritic silicate Earth with respect to the geochemical evolution of the mantle-crust system are then examined. We show that the positive ?143Nd and ?176Hf values ubiquitous in the Archean mantle can be accounted for by the non-chondritic Sm/Nd and Lu/Hf composition of the primitive mantle rather than early crustal formation, which solves the paradox that early Archean domains only have a limited extension in the present-day continents. Re-examination of Sm-Nd mass balance for the mantle-crust system shows that currently ongoing crustal extraction processes can readily explain the isotopic and trace elements systematics in oceanic basalts, without the need to call upon hidden crustal or mantle reservoirs. References: [1] Caro, G., Bourdon, B., Halliday, A. N., and Quitté, G., 2008. Super-chondritic Sm/Nd ratios in Mars, the Earth and the Moon. Nature 452, 336-339. [2] Bourdon, B., Touboul, M., Caro, G., and Kleine, T., 2008. Early differentiation of the Earth and the Moon. Phil. Trans. Roy. Soc. 366, 4105-4128. [3] O'Neill, H. S. C. and Palme, H., 2008. Collisional erosion and the non-chondritic composition of the terrestrial planets. Phil. Trans. Roy. Soc. 366, 4205-4238.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2013CEJG....5..523A"><span id="translatedtitle">Geochemistry and <span class="hlt">geodynamics</span> of the Mawat mafic complex in the Zagros Suture zone, northeast Iraq</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Azizi, Hossein; Hadi, Ayten; Asahara, Yoshihiro; Mohammad, Youssef Osman</p> <p>2013-12-01</p> <p>The Iraqi Zagros Orogenic Belt includes two separate ophiolite belts, which extend along a northwest-southeast trend near the Iranian border. The outer belt shows ophiolite sequences and originated in the oceanic ridge or supra-subduction zone. The inner belt includes the Mawat complex, which is parallel to the outer belt and is separated by the Biston Avoraman block. The Mawat complex with zoning structures includes sedimentary rocks with mafic interbedded lava and tuff, and thick mafic and ultramafic rocks. This complex does not show a typical ophiolite sequences such as those in Penjween and Bulfat. The Mawat complex shows evidence of dynamic deformation during the Late Cretaceous. Geochemical data suggest that basic rocks have high MgO and are significantly depleted in LREE relative to HREE. In addition they show positive ? Nd values (+5 to+8) and low 87Sr/86Sr ratios. The occurrence of some OIB type rocks, high Mg basaltic rocks and some intermediate compositions between these two indicate the evolution of the Mawat complex from primary and depleted source mantle. The absence of a typical ophiolite sequence and the presence of good compatibility of the source magma with magma extracted from the mantle plume suggests that a mantle plume from the D? layer is more consistent as the source of this complex than the oceanic ridge or supra-subduction zone settings. Based on our proposed model the Mawat basin represents an extensional basin formed during the Late Paleozoic to younger along the Arabian passive margin oriented parallel to the Neo-Tethys oceanic ridge or spreading center. The Mawat extensional basin formed without creation of new oceanic basement. During the extension, huge volumes of mafic lava were intruded into this basin. This basin was squeezed between the Arabian Plate and Biston Avoraman block during the Late Cretaceous.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2014EGUGA..1616763O"><span id="translatedtitle">Pronounced zonation of seismic anisotropy in the Western Hellenic subduction zone and its <span class="hlt">geodynamic</span> significance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Olive, Jean-Arthur; Pearce, Frederick; Rondenay, Stéphane; Behn, Mark</p> <p>2014-05-01</p> <p>Many subduction zones exhibit significant retrograde motion of their arc and trench. The observation of fast shear-wave velocities parallel to the trench in such settings has been inferred to represent trench-parallel mantle flow beneath a retreating slab. Here, we investigate this process by measuring seismic anisotropy in the shallow Aegean mantle. We carry out shear-wave splitting analysis on a dense array of seismometers across the Western Hellenic Subduction Zone, and find a pronounced zonation of anisotropy at the scale of the subduction zone. Fast SKS splitting directions subparallel to the trench-retreat direction dominate the region nearest to the trench. Fast splitting directions abruptly transition to trench-parallel above the corner of the mantle wedge, and rotate back to trench-normal over the back-arc. We argue that the trench-normal anisotropy near the trench is explained by entrainment of an asthenospheric layer beneath the shallow-dipping portion of the slab. Toward the volcanic arc this signature is overprinted by trench-parallel anisotropy in the mantle wedge, likely caused by a layer of strained serpentine immediately above the slab. Arcward steepening of the slab and horizontal divergence of mantle flow due to rollback may generate an additional component of sub-slab trench-parallel anisotropy in this region. Poloidal flow above the retreating slab is likely the dominant source of back-arc trench-normal anisotropy. We hypothesize that trench-normal anisotropy associated with significant entrainment of the asthenospheric mantle near the trench may be widespread, but only observable at shallow-dipping subduction zones where stations nearest the trench do not overlie the mantle wedge.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-MAS&redirectUrl=http://academic.research.microsoft.com/Publication/41996533"><span id="translatedtitle">Fine details of the Wadati-Benioff zone under Indonesia and its <span class="hlt">geodynamic</span> implications</span></a></p> <p><a target="_blank" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p>Hans-Joachim Schöffel; Shamita Das</p> <p>1999-01-01</p> <p>Using about 5200 handpicked P, S, pP, sP, PcP, and ScP phases from digitally recorded seismograms, together with International Seismological Center reported phases, we obtain improved hypocentral locations for ~1790 earthquakes, ~983 of them having 90% confidence limits 50 km, in the period 1962 to September 1996, along the Indonesian subduction zone. We use an improved joint hypocenter determination method</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-MAS&redirectUrl=http://redalyc.uaemex.mx/redalyc/pdf/568/56846102.pdf"><span id="translatedtitle"><span class="hlt">Geodynamics</span> of the Wadati-Benioff zone earthquakes: The 2004 Sumatra earthquake and other great earthquakes</span></a></p> <p><a target="_blank" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p>Giancarlo Scalera</p> <p>2007-01-01</p> <p>The displacement of the Earth's instantaneous rotation pole - observed at ASI of Matera, Italy - the seismic data (USGS) in the two days following the main shock, the high frequency P-wave radiation, the geomorphologic data, and the satellite data of uplift\\/subsidence of the coasts (IGG) converge toward a new interpretation of the Great Sumatran earthquake (TU=26 December 2004 -</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2014EGUGA..16.5728F"><span id="translatedtitle">Building topography in Cyprus and south Turkey: geological constraints and <span class="hlt">geodynamic</span> models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fernández-Blanco, David; Bertotti, Giovanni; Cassola, Teodoro; Willett, Sean</p> <p>2014-05-01</p> <p>We present a regional synthesis of the geometries and Neogene vertical motions and horizontal deformations of the central sector of the Cyprus arc-trench system, which are used to constrain 2D thermo-mechanical numerical models. We used depth-converted seismic reflection lines, basin analysis techniques and fieldwork observations, combined with available literature. From the Cyprus arc trench to the Central Anatolia Plateau, three independent vertical motion domains are identified: the Cyprus structural high; the Cilicia Basin and the Tauride Range. Early Miocene regional subsidence that still continues in the Cilicia Basin was disrupted by surface uplift in the north and south domains during Late Miocene or younger times. Coevally, N-S shortening developed regional contractional structures along the margin. The large-wavelength Miocene monocline fold that formed in S Turkey reveals relative vertical displacement rates of 0.5 mm/y and horizontal shortening values of <1%, along our studied sections. Shortening led to S-dipping thrusts in the center of the Cilicia Basin, and further developed the S-verging Kyrenia thrust system in N Cyprus. The observed deformation patterns and associated vertical motions suggest that the Anatolian upper-plate topography, including the uplifted south Turkey, results from wedge deformation in relation to the Cyprus arc. We use numerical finite element models to test this hypothesis. Models show that the mechanical growth of both the Anatolian accretionary complex and its forearc basin system caused sedimentary thickening and overburden, which led to the development of a sedimentary blanket that started to control the thermal distribution in the margin; relative temperatures decreased within the blanket and increased underneath it. This resulted in thermally weakened viscous deformation of the lower crust, which eventually forced the surface uplift of the landward side of the forearc basin and created a forearc-high, the modern Taurides. We also analyzed the influence of factors such as viscous properties of the crust and sedimentary accumulation rates. These parameters have a strong impact in the overall evolution of the margin as well as in when and whether surface uplift in the forearc-high occurs. Higher values in the viscous parameters drive older, more pronounced uplift, than lower viscosity values. Decreasing values change the shape and time-evolution of uplift, from older rounded-shaped uplift to mid-aged box-shaped uplift to absence of uplift. Large accumulation rates develop thicker basins that stabilize the margin and shift deformation towards their margins. This also induces surface uplift to take place at younger times and can lead to avoid its happening, i.e, if sediment accumulation rates are large, the subduction system needs longer times to develop the forearc-high. We conclude that the Cyprian subduction system drives mechanical accretion in Cyprus and deep-seated deformation in S Turkey, which in turn control vertical tectonic motions and topography development in the margin.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2012Tecto..31.6003S"><span id="translatedtitle">The Binalud Mountains: A key piece for the <span class="hlt">geodynamic</span> puzzle of NE Iran</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shabanian, Esmaeil; Bellier, Olivier; Siame, Lionel; Abbassi, Mohammad R.; BourlèS, Didier; Braucher, RéGis; Farbod, Yassaman</p> <p>2012-12-01</p> <p>We applied a combined approach of morphotectonic analyzes of SPOT-5 satellite images and field surveys complemented by in situ-produced10Be exposure dating to determine the kinematics and rate of active faulting in the Binalud Mountains bounded by the Neyshabur Fault System to the southwest and the Mashhad Fault Zone to the northeast. Three regional episodes of alluvial surface abandonment were dated at ˜4.8 ka (Q1), ˜105 ka (Q3), and ˜255 ka (S3). Along the Neyshabur Fault System, cumulative offsets recorded by Q3fan surfaces yield slip rates of 2.4 ± 0.5 and 2.8 ± 0.6 mm/yr for right-lateral and reverse components of active faulting (corresponding to an oblique slip rate of 3.6 ± 1.0 mm/yr), respectively. Reconstructing the cumulative right-lateral offset recorded by S3surfaces, a maximum slip rate of 1.3 ± 0.1 mm/yr is suggested for the Mashhad Fault Zone. These imply an overall rate of 3.7 ± 0.6 mm/yr for the range-parallel displacement and an uplift rate of ˜2.8 mm/yr due to the range-normal shortening (1.6-2.2 mm/yr) during late Quaternary. The Binalud Mountains are deformed as a soft-linked restraining relay zone, taking up the motion between central Iran and Eurasia at a rate of 4.0 ± 1.3 mm/yr; this translates central Iran in the ˜N340°E direction. Our data favor localized faulting, instead of distributed deformation, at the northeastern boundary of the Arabia-Eurasia collision zone.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2014EGUGA..16.1965C"><span id="translatedtitle">Reprocessing of the CEGRN network and its impact on the <span class="hlt">geodynamics</span> of Central Europe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Caporali, Alessandro</p> <p>2014-05-01</p> <p>The IAG Working Group on "Integration of Dense Velocity Fields in the ITRF", the EUREF Working Group on Deformation Models and the project EPOS encourage initiatives aiming at estimating velocities of GNSS sites in a rigorous manner, both for reference frame applications and 3D tectonic deformation problems. Thirteen measurement campaigns between 1994 and 2013 with epoch and permanent GNSS stations make the CEGRN network one of the most regularly and accurately surveyed networks for scientific applications in Europe. We have reprocessed the CEGRN GNSS (GPS+GLONASS) data with the Bernese Software 5.2 using consistent IGb08 orbits and antenna models and aligned the resulting network to ETRF2000 Reference Frame using the position and velocities of Class A stations of the EUREF Permanent Network (EPN). The intent is to bring down to regional, i.e. Central European scale the same standard of accuracy as the EPN long-term solution. This paper presents first results of the CEGRN densification of the EPN: we review the input data, the processing strategies and the results, in terms of positions, velocities and Helmert parameters. Possible further combination, in a rigorous geodetic sense, with multiyear regional solutions, for example in Greece and Italy, processed with similar standards have an important potential to quantify the deformation field, for example in the Balkans. Preliminary results on possible locking depths and areas of higher probability of failure are reviewed.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-MAS&redirectUrl=http://academic.research.microsoft.com/Publication/54104954"><span id="translatedtitle"><span class="hlt">Geodynamical</span> and Geochemical Features of Oil Generation in Sedimentary Basin of Volga-Ural Region</span></a></p> <p><a target="_blank" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p>I. Plotnikova</p> <p>2009-01-01</p> <p>Oil and gas prospects of Paleozoic sedimentary rocks of Volga-Ural Anticline (VUA) various researchers evaluate in different ways. More than 150 oil fields in Paleozoic formations were discovered in the eastern half of Republic of Tatarstan of the East European Platform. There were not found any significant fields in the western areas of investigation region. According to many investigators, the</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2006JGRB..111.3101S"><span id="translatedtitle">New Late Cretaceous and Paleogene paleomagnetic results from south China and their <span class="hlt">geodynamic</span> implications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sun, Zhiming; Yang, Zhenyu; Yang, Tienshui; Pei, Junling; Yu, Qinfan</p> <p>2006-03-01</p> <p>To better understand the tectonic evolution of South China Block (SCB) in response to the India-Asia collision, we present new paleomagnetic results from Late Cretaceous and Paleogene red bed formations of the Hengyang basin of Hunan province, in the interior part of the SCB. Stepwise thermal demagnetization of the rocks isolated a high-temperature component. The tilt-corrected mean direction from the Late Cretaceous rocks is D = 15.6°, I = 29.9° with a95 = 5.7°, N = 26 sites, corresponding to a paleopole at 71.9°N, 236.3°E with A95 = 4.7°, which passes reversal tests. The tilt-corrected mean direction (D = 358.9°, I = 35.4° with a95 = 5.0°, N = 22 sites) from the Paleogene rock, which passes the reversal test, gives a pole at 82.6°N, 300.6°E with A95 = 4.4°. The low-field anisotropy of magnetic susceptibility results suggest that the red beds have not experienced significant strain due to compaction or tectonic stress, while the anisotropy of isothermal remanence results suggest that postdepositional compaction in these red beds produced no more than 3°-4° of inclination shallowing. These paleomagnetic and rock magnetic tests imply that the remanence is primary. On the basis of paleomagnetic results obtained from coeval basalts in Mongolia and Siberia, we suggest that no significant latitudinal motion has taken place between the SCB and Siberia since the Late Cretaceous. The significant latitudinal discrepancy between the SCB and European block could be due to nonrigid behavior of the Eurasian plate since the Late Cretaceous. A 16.7 ± 5.0° clockwise rotation of the SCB during the Late Cretaceous to the Paleogene could be related to the collision of India and Asia in the west and the subduction of the circum-Pacific plate to eastern Asia in the east.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2013EGUGA..1513722D"><span id="translatedtitle">Fluid mixing and ore deposition during the <span class="hlt">geodynamic</span> evolution of the Sierra Almagrera (Betics, Spain)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dyja, Vanessa; Tarantola, Alexandre; Hibsch, Christian; Boiron, Marie-Christine; Cathelineau, Michel</p> <p>2013-04-01</p> <p>Marine and continental intramountaineous basins developed during the Neogene orographic evolution of the Betico-rifan orogenic wedge, as well as the related uplifted ranges within the Sierra Almagrera Metamorphic Core Complexes (MCC). The NNE-SSW striking trans-Alboran transcurrent fault system crosscuts the MCC post-dating the extensional exhumation stages recorded in the metamorphic fabric. Iron ores (± Pb, Cu, Zn) are encountered either as stratabound ore deposits in the Neogene basins or as vein networks crosscutting the metamorphic fabric of graphitic phyllites from the Sierra Almagrera. These Late Miocene ore deposits are related to the activity of the N-S striking Palomares fault segment of the Trans-Alboran fault system. Three sets of quartz veins (V?, V?? and V?) and one set of mineralized vein (V?, siderite, barite) are distinguished. The V? and V?? respectively are totally or partially transposed into the foliation. The V? and V? veins are discordant to the foliation. The problem addressed in this study concerns the nature of the fluids involved in the metal deposits and their relationships with the main reservoir fluids, e.g. the deep metamorphic fluids, the basinal fluids, and eventually the recharge meteoric fluids. This study focuses thus on the evolution of the fluids at different stages of ductile-brittle exhumation of the metamorphic ranges (Sierras) and their role during the exhumation and later on in relation with the hydrothermalism and metal deposition at a regional scale. Paleofluids were studied as inclusions in quartz, siderite and barite from veins by microthermometry and Raman spectroscopy, and a stable isotope study is in progress. Earliest fluids recorded in (V??) quartz veins are H2O- NaCl + CaCl2 (17 wt. %) - (traces of CO2, CH4, N2) metamorphic brines trapped at the ductile brittle transition at a minimum trapping temperatures (Th) of 340 °C. Older metamorphic fluids in (V?) veins were lost during the complete recrystallization of the original quartz grains during transposition. The second fluid type is characterized by very low salinity inclusions (1.2 wt.% NaCl) found in veins discordant to the foliation (V?), and precedes brines (23 wt. % NaCl + CaCl2 with Th of 320 °C) trapped in transgranular fluid inclusion planes (FIP). The NW-SE to N-S directions of these FIP appears coherent with shortening directions related to Tortonian and Messinian basin development (Montenat, 1990). The halogen signatures of the latest brines confirm that they derive from primary brines issued from sea water evaporation. Fluid inclusions in barites and siderites from (V?) veins display a Br/Cl ratio more typical of secondary brines and a rather large range of salinities, this indicating distinct fluid movements and the dissolution of evaporates by dilute fluids may be of meteoric origin. Fluids in siderites show the lowest trapping temperature conditions around 190 °C. The existence of a sea water component in fluids was previously mentioned by Morales Ruano et al. (1995) indicate a ?34S of 22,1-23.9 ‰ for barite from Sierra Almagrera. In conclusion, during the Neogene multistage evolution of the Almagrera MCC, fluids of different origins e.g. basinal, meteoric and metamorphic fluids have circulated within the crust, and locally interacted with evaporites. The resulting brines formed Fe-(Ba, Pb, Cu) ores in discontinuities affecting both the metamorphic and sedimentary rocks. Morales Ruano, S., Both, R., and Fenoll Hach-Ali, P., 1995, Fluid evolution and mineral deposition in the Aguilas - Sierra Almagrera base metal ores, southeastern Spain.: Mineral Deposits, p. 365-368. Montenat, C., 1990, Les Bassins néogènes du domaine bétique oriental (Espagne), Documents et Travaux IGAL n°12-13, 392 p.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=PUBMED&redirectUrl=http://www.ncbi.nlm.nih.gov/pubmed/15236485"><span id="translatedtitle">Petrology, geochemistry and <span class="hlt">geodynamics</span> of basic granulite from the Altay area, North Xinjiang, China.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, Zi-Long; Chen, Han-Lin; Yang, Shu-Feng; Dong, Chuan-Wan; Xiao, Wen-Jiao</p> <p>2004-08-01</p> <p>The basic granulite of the Altay orogenic belt occurs as tectonic lens in the Devonian medium- to lower-grade metamorphic beds through fault contact. The Altay granulite (AG) is an amphibole plagioclase two-pyroxene granulite and is mainly composed of two pyroxenes, plagioclase, amphibole and biotite. Its melano-minerals are rich in Mg/(Mg+Fe2+), and its amphibole and biotite are rich in TiO2. The AG is rich in Mg/(Mg+Fe2+), Al2O3 and depletion of U, Th and Rb contents. The AG has moderate SigmaREE and LREE-enriched with weak positive Eu anomaly. The AG shows island-arc pattern with negative Nb, P and Ti anomalies, reflecting that formation of the AG may be associated with subduction. Geochemical and mineral composition data reflect that the protolith of the AG is calc-alkaline basalt and formed by granulite facies metamorphism having peak P-T conditions of 750 degrees C-780 degrees C and 0.6-0.7 Gpa. The AG formation underwent two stages was suggested. In the early stage of oceanic crustal subduction, calc-alkaline basalt with island-arc environment underwent granulite facies metamorphism to form the AG in deep crust, and in the late stage, the AG was thrust into the upper crust. PMID:15236485</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2010Geote..44..388B"><span id="translatedtitle">Tien Shan, Pamir, and Tibet: History and <span class="hlt">geodynamics</span> of phanerozoic oceanic basins</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burtman, V. S.</p> <p>2010-09-01</p> <p>Geological and biogeographical data on the paleooceanic basins of the Tien Shan and High Asia are summarized. The oceanic crustal rocks in the Tien Shan, Pamir, and Tibet belong to the Tethian and Turkestan-Paleoasian systems of paleooceanic basins. The tectonic evolution of these systems in the Phanerozoic was not coeval and unidirectional. The sialic blocks of the future Tien Shan, Pamir, and Tibet were incorporated into the Eurasian continent during several stages. In the Late Ordovician and Silurian several microcontinents were preliminarily combined into the Kazakh-Kyrgyz continent as a composite aggregation. The territories of the Tien Shan and Tarim became a part of Eurasia after the closure of the Turkestan, Ural, and Paleotethian oceans in the Late Carboniferous and Early Permian. The territories of the Pamir, Karakorum, Kunlun, and most of Tibet attached to the Eurasian continent in the Triassic. The Lhasa and Kohistan blocks were incorporated into Eurasia in the Cretaceous, whereas Hindustan was docked to Eurasia in the Paleogene.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2013Tectp.590..151B"><span id="translatedtitle">Fluid seepage variability across the external Northern Apennines (Italy): Structural controls with seismotectonic and <span class="hlt">geodynamic</span> implications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bonini, Marco</p> <p>2013-04-01</p> <p>The relations between fluid seeps and tectonic structures have been targeted in some key areas of the axial sector, and partly at the edge of the exposed Northern Apennines (Pede-Apennine margin). In the axial zone, fluid seepage is dominated by methane venting, which may occur in the form of dry seeps or associated with mineral springs. Surface venting is linked to the presence of foreland-dipping normal faults, or related to reservoirs localised at inactive anticlines. The Pede-Apennine margin is instead dominated by thrusting and mud volcanism. The two different categories of fluid seepage appear strongly coupled to the dissimilar stress fields (compressional or extensional) operating in these sectors. Pressure data inferred from deep wells delineate an overall fluid pressure increase from the axial zone toward the Pede-Apennine margin, possibly as a result of the growth of tectonic compaction in this direction. The increase of fluid pressure at the Pede-Apennine margin is thus interpreted as the primary control on the transition from dry vents to mud volcanism. The intimate association between seepage modes and distinct tectonic structures involves relevant consequences on fluid-fault interactions and seismotectonics, and also shows connections with processes dictating the internal deformation of evolving fold-and-thrust belts.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2011PhDT.......463K"><span id="translatedtitle">I. Climate change on ancient Mars. II. Exoplanet <span class="hlt">geodynamics</span> and climate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kite, Edwin Stephen</p> <p></p> <p>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. Seasonal snowmelt on Early Mars is possible under unusual orbital conditions provided that the snow is dust-contaminated. The predicted distribution of snowmelt can explain the distribution of sedimentary rocks on Mars, but only if Mars had a thin atmosphere when the sedimentary rocks formed. This framework is the first to link upcoming observations by the Mars Science Laboratory Curiosity rover at the lower Gale Crater mound to past global climate on Mars. The model makes predictions about the lower Gale Crater mound that can be tested using Curiosity rover data. Earth is the only example of long term climate stability that is available for study, so long term climate stability is difficult to understand. Extrasolar planets may ameliorate this problem of uniqueness. It is clear that rates of volcanic activity and of surface weathering are important in regulating long term climate. In the second part of this thesis, I model the rate of volcanism on massive Earth-like planets, and the surface weathering rate on planets in 1:1 spin:orbit resonance. "Super-Earths" in the range 1-10 Earth masses have been detected by radial velocity and transit methods. Using an idealized mantle thermal evolution model to drive mantle-melting models, I show that the rate of volcanism on massive Earth like planets is a weak function of planet mass. Planet mass can, however, affect tectonics by changing the mode of mantle convection. Earth's climate stability depends on a negative feedback involving the temperature-dependent rate of weathering and mean surface temperature. I use an idealized model to show that for intermediate surface pressures and for low-opacity atmospheres, nonlinearities in the surface energy balance can reverse the sign of this dependence on tidally-locked planets. This leads to climate instability. I conclude by discussing future observations and research aimed at understanding long-term climate stability.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2014GeoRL..41.8029L"><span id="translatedtitle">Constraining Cretaceous subduction polarity in eastern Pacific from seismic tomography and <span class="hlt">geodynamic</span> modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Lijun</p> <p>2014-11-01</p> <p>Interpretation of recent mantle seismic images below the America ignited a debate on the Cretaceous subduction polarity in the eastern Pacific Ocean. The traditional view is that the massive vertical slab wall under eastern North America resulted from an eastward Farallon subduction. An alternative interpretation attributes this prominent seismic structure to a westward subduction of the North American Plate against a stationary intraoceanic trench. Here I design quantitative subduction models to test these two scenarios, using their implied plate kinematics as velocity boundary conditions. Modeling results suggest that the westward subduction scenario could not produce enough slab volume as seismic images reveal, as is due to the overall slow subduction rate (~2.5 cm/yr). The results favor the continuous eastward Farallon subduction scenario, which, with an average convergence rate of >10 cm/yr prior to the Eocene, can properly generate both the volume and the geometry of the imaged lower mantle slab pile. The eastward subduction model is also consistent with most Cretaceous geological records along the west coast of North America.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-MAS&redirectUrl=http://www.crust.irk.ru/gt/files/2/119.pdf"><span id="translatedtitle">NEW TYPE OF ELASTIC ROTATIONAL WAVES IN GEO-MEDIUM AND VORTEX <span class="hlt">GEODYNAMICS</span></span></a></p> <p><a target="_blank" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p>V. Vikulin</p> <p>2010-01-01</p> <p>Natural-science concepts of rotational movements and the 'lumpy' structure of medium are reviewed with a focus on key aspects. Through using torsional traps for hunting and «implementing» mechanical torque for ignition, Homo sapiens developed to man. Vortex movements «impregnated» in spiral structures of shells and torsional move- ments of toothy whales and fish were intuitively perceived by man as major</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2009EGUGA..1110386D"><span id="translatedtitle">Lower Oligocene Alpine <span class="hlt">geodynamic</span> change: tectonic and sedimentary evidences in the western arc</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dumont, T.; Rolland, Y.; Simon-Labric, T.</p> <p>2009-04-01</p> <p>The formation of the western Alpine arc started during the earliest Oligocene, after a drastic kinematic change in the collisional regime. (A) Previously, south-southeast dipping subduction of the European lithosphere (including Briançonnais) underneath Adria resulted in an underfilled flexural basin propagating towards the north-northwest on the European foreland, which had already been moderately deformed due to the Iberian microplate motion. This propagation appears consistent with the Africa-Europe relative motion (Rosenbaum et al., 2002). During this early stage of collision, some oceanic units were obducted over the southern part of European continent (Corsica, Briançonnais). (B) From the early Oligocene on, the western Alps kinematics were dominated by lateral (westward) escape of the Internal Alps indenter, whose displacement with anticlockwise rotation progressively formed the arc. The structures of this mature stage of collision crosscut the buildup issued from (A), and its kinematics were probably more driven by local lithospheric forces of the Mediterranean domain (Jolivet et al., 1999) than by Africa-Europe convergence. The western and southern parts of the western Alpine arc display many evidences for this major syn-collisional change: - Structural interferences are found at various scales. For example, the circular-shape Pelvoux massif resulted in part from crossed shortening stages (SE-NW and E-W; Dumont et al., 2008). It is located in the footwall of two nappes stacks having propagated northwestwards and west- to southwestwards, respectively. The latter crosscuts the former south of Briançon city. - Tectonic transport directions are strongly variable both in the external and in the internal zones, but they consistently display anticlockwise rotation through time. The most important changes are found in the southern part of the western Alps, giving birth to a radial distribution propagating into the external zone. - Instead of beeing gradual, the propagation of syn-orogenic basins changed abruptly in earliest Oligocene times. In the southern Subalpine domain, previously SE-NW gradients (sedimentary transport, onlaps, thickness changes) shifted to westwards or southwestwards ones. This major syn-collisional change must have occurred in a short time interval bracketed between thrusting of the earliest, gravity-driven nappes over the Paleogene flexural basin, whose youngest sediments are dated as lowermost Oligocene, and eastwards underthrusting of the Pelvoux basement in the footwall of the Internal Alps indenter, having yielded Ar39/Ar40 ages of 31,2 ± 0,3 Ma to 33,7 ± 0,2 Ma (Simon-Labric et al. et al., in press). This 32 to 34 Ma old event can be traced all over the Alpine chain through its kinematic, structural, metamorphic and magmatic consequences. It played a key role in the generation of the modern, arcuate shape of the Western Alps. References: Dumont T., Champagnac J.D., Crouzet C. & Rochat P. (2008). Multistage shortening in the Dauphiné zone (French Alps): the record of Alpine collision and implications for pre-Alpine restoration. Swiss J. Geosci., 101, suppl. 1, p. 89-110. Jolivet L., Frizon De Lamothte D., Mascle A. & Séranne M. (1999). The Mediterranean Basins : Tertiary extension within the Alpine orogen - an introduction. In: Durand B., Jolivet L., Horwath F. & Séranne M. (eds.), Geological Soc. Spec. Publication, 156, p. 1-34. Simon-Labric T., Rolland Y., Dumont T., Heymes T., Authemayou C., Corsini M. & Fornari M. (in press). Ar39/Ar40 dating of Penninic Front tectonic displacement (W. Alps) during the Lower Oligocene (31-34 Ma). Terra Nova, in press. Rosenbaum G. & Lister G.S (2005). The Western Alps from the Jurassic to Oligocene: spatio-temporal constraints and evolutionary reconstructions. Earth-Sc. Rev., 69, p. 281-306.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-MAS&redirectUrl=http://www.agu.org/journals/jb/v101/iB02/95JB02401/95JB02401.pdf"><span id="translatedtitle">The continental collision zone, South Island, New Zealand: Comparison of <span class="hlt">geodynamical</span> models and observations</span></a></p> <p><a target="_blank" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p>Christopher Beaumont; Peter J. J. Kamp; Juliet Hamilton; Philippe Fullsack</p> <p>1996-01-01</p> <p>The South Island zone of oblique continent-continent convergence occurs along a 400 km-long section of the modern Australia-Pacific plate boundary zone, across which about 50 km of shortening has been accommodated since about 10 Ma. The orogen comprises a central mountain range (Southern Alps) flanked on both sides by what are interpreted to be foreland basins. Two essential features that</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-STC&redirectUrl=http://www.osti.gov/scitech/biblio/6827722"><span id="translatedtitle"><span class="hlt">Geodynamically</span> unusual settings of sedimentary rock and ore formation due to tectonic-decompression effects</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Goryainov, P.M.</p> <p>1984-05-01</p> <p>The traditional views of terrigenous rocks as products of classical sedimentary cycle, ''mobilization-transport-deposition,'' are not universal. Detrital rocks are sometimes formed due to flaking and fracturation of rocks of rising blocks. The process is produced by tectonic-decompression mechanisms - the origination of a gradient of excessive stress and its discharge. It is incorrect to classify rocks created by this phenomenon with weathering crusts. The origins of certain terrigenous rocks, as well as products of low-temperature chemical processing, are connected with deep-volume decompression (brecciation, stockwork formation, formation of pipes and columns of igneous rocks, and chamber pegmatite and karst formation). The ore concentrations associated with such entities and appearing as stratiform deposits are most likely not exogenous, but they complete the endogenous history of the block concerned. The means and methods tested on typical endogenous deposits may therefore prove valuable in predicting certain varieties of stratiform deposits.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/1997GeoJI.131....1T"><span id="translatedtitle">The geoid constraint in global <span class="hlt">geodynamics</span>: viscosity structure, mantle heterogeneity models and boundary conditions.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thoraval, C.; Richards, M. A.</p> <p>1997-10-01</p> <p>The authors address several of the most straightforward problems inherent in geoid modelling, namely the issues of viscosity structure resolution, uncertainties in appropriate boundary conditions, and differences among mantle heterogeneity models. A robust feature of all models is a lower-mantle viscosity at least a factor of 30 greater than that of the upper mantle, but there is little resolution with regard to finer details such as lithospheric or uppermost mantle ("low-viscosity zone") viscosity. Ironically, free-slip boundary conditions result in the best fits to the geoid in all cases, but all boundary conditions exhibit predictable trade-offs with the uppermost-mantle viscosity. Models with a single viscosity layer representing the lower mantle yield similar dynamic topography estimates of the order of 700-1000 m in amplitude, regardless of the finer details of upper-mantle viscosity structure, boundary conditions or input heterogeneity models. Comparing mantle heterogeneity models based on two independent seismological determinations (Harvard and Berkeley models) and on the history of subduction, the authors find that these models are virtually indistinguishable regarding inferences of mantle viscosity structure and amplitude of dynamic topography, and in terms of the effects of different boundary conditions. Uncertainties concerning which type of boundary condition is appropriate are much more important than which mantle heterogeneity model is chosen. Given other uncertainties in modelling the geoid, particularly the strong effects due to lateral viscosity variations for intermediate (<10,000 km) wavelengths, the authors conclude that the class of dynamic geoid models explored so far cannot reliably elucidate the details of upper-mantle viscosity structure.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=EPRINT&redirectUrl=http://hal.archives-ouvertes.fr/docs/00/50/91/14/PDF/Choulet-JasianEarthScience-2010.pdf"><span id="translatedtitle">Late Paleozoic paleogeographic reconstruction of Western Central Asia based upon paleomagnetic data and its <span class="hlt">geodynamic</span> implications</span></a></p> <p><a target="_blank" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p>Paris-Sud XI, Université de</p> <p></p> <p>that they were rigidly welded since that time, and (3) anticlockwise rotations of Tarim, Yili and South Junggar with respect to the welded Siberia-Kazakhstan-West Junggar block. Such rotations may have been accommodated to the Pacific Ocean between the main continents of Baltica, Siberia, Tarim and North China (Figs. 1a and 1b</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-MAS&redirectUrl=http://www.agu.org/journals/je/je0808/2007JE002980/2007JE002980.pdf"><span id="translatedtitle">Strike-slip faults on Mars: Observations and implications for global tectonics and <span class="hlt">geodynamics</span></span></a></p> <p><a target="_blank" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p>Jeffrey C. Andrews-Hanna; Maria T. Zuber; Steven A. Hauck II</p> <p>2008-01-01</p> <p>The tectonic evolution of Mars has been driven primarily by the interaction of Tharsis-induced loading stresses with a uniform contractional stress field, leading to global assemblages of graben and wrinkle ridges. Until recently, strike-slip faults have appeared to be largely absent from the tectonic record. We here present evidence for a new set of Noachian to Early Hesperian strike-slip faults</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2012EGUGA..14.4314P"><span id="translatedtitle">Petrogenesis and <span class="hlt">geodynamic</span> significance of silicic volcanism in the western Trans-Mexican Volcanic Belt</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Petrone, C. M.; Ferrari, L.; Orozco, M. A.; Lopez Martinez, M.</p> <p>2012-04-01</p> <p>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 produced pulses of mafic magma that were partly trapped in the crust yielding crustal melting. Extensional faulting since the Pliocene favours the eruption of silicic magma as effusive dome and lava flows. Rifting at the boundaries of the Jalisco block is seen as a rollback induced reactivation of crustal structures but is unlike to evolve into a Jalisco microplate.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=USGSPUBS&redirectUrl=http://pubs.er.usgs.gov/publication/pp1765B"><span id="translatedtitle">Appendix B: Description of Map Units for Northeast Asia Summary <span class="hlt">Geodynamics</span> Map</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Parfenov, Leonid M.; Badarch, Gombosuren; Berzin, Nikolai A.; Hwang, Duk-Hwan; Khanchuk, Alexander I.; Kuzmin, Mikhail I.; Nokleberg, Warren J.; Obolenskiy, Alexander A.; Ogasawara, Masatsugu; Prokopiev, Andrei V.; Rodionov, Sergey M.; Smelov, Alexander P.; Yan, Hongquan</p> <p>2009-01-01</p> <p>The major purposes of this chapter are to provide (1) an overview of the regional geology, tectonics, and metallogenesis of Northeast Asia for readers who are unfamiliar with the region, (2) a general scientific introduction to the succeeding chapters of this volume, and (3) an overview of the methodology of metallogenic and tectonic analysis used in this study. We also describe how a high-quality metallogenic and tectonic analysis, including construction of an associated metallogenic-tectonic model will greatly benefit other mineral resource studies, including synthesis of mineral-deposit models; improve prediction of undiscovered mineral deposit as part of a quantitative mineral-resource-assessment studies; assist land-use and mineral-exploration planning; improve interpretations of the origins of host rocks, mineral deposits, and metallogenic belts, and suggest new research. Research on the metallogenesis and tectonics of such major regions as Northeast Asia (eastern Russia, Mongolia, northern China, South Korea, and Japan) and the Circum-North Pacific (the Russian Far East, Alaska, and the Canadian Cordillera) requires a complex methodology including (1) definitions of key terms, (2) compilation of a regional geologic base map that can be interpreted according to modern tectonic concepts and definitions, (3) compilation of a mineral-deposit database that enables a determination of mineral-deposit models and clarification of the relations of deposits to host rocks and tectonic origins, (4) synthesis of a series of mineral-deposit models that characterize the known mineral deposits and inferred undiscovered deposits in the region, (5) compilation of a series of metallogenic-belt belts constructed on the regional geologic base map, and (6) construction of a unified metallogenic and tectonic model. The summary of regional geology and metallogenesis presented here is based on publications of the major international collaborative studies of the metallogenesis and tectonics of Northeast Asia that have been led by the U.S. Geological Survey (USGS). These studies have produced two broad types of publications (1) a series of regional geologic, mineral-deposit, and metallogenic-belt maps, with companion descriptions of the region, and (2) a suite of metallogenic and tectonic analyses of the same region. The study area consists of eastern Russia (most of eastern Siberia and the Russian Far East), Mongolia, northern China, South Korea, Japan, and adjacent offshore areas. The major cooperative agencies are the Russian Academy of Sciences; the Academy of Sciences of the Sakha Republic (Yakutia); VNIIOkeangeologia and Ministry of Natural Resources of the Russian Federation; the Mongolian Academy of Sciences; the Mongolian University of Science and Technology; the Mongolian National University; Jilin University, Changchun, People?s Republic of China, the China Geological Survey; the Korea Institute of Geosciences and Mineral Resources; the Geological Survey of Japan/AIST; the University of Texas, Arlington, and the U.S. Geological Survey (USGS). This study builds on and extends the data and interpretations from a previous project on the Major Mineral Deposits, Metallogenesis, and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera conducted by the USGS, the Russian Academy of Sciences, the Alaska Division of Geological and Geophysical Surveys, and the Geological Survey of Canada. The major products of this project were summarized by Naumova and others (2006) and are described in appendix A.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2007AGUFM.V13A1142Z"><span id="translatedtitle">Polymetamorphic complexes in the eastern parts of the Balkan Peninsula: 600 Ma of <span class="hlt">geodynamic</span> evolution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zagorchev, I.</p> <p>2007-12-01</p> <p>Polymetamorphic amphibolite-facies complexes are exposed in the eastern and central parts of the Balkan Peninsula in different Alpine tectonic zones and under different Cadomian to Alpine collisional and exhumation histories and regimes. All complexes consist mostly of biotite and two-mica gneisses and schists, and amphibolites. Strong Cadomian overprint led to intimate mixing (tectonometamorphic amalgamation) of crustal and mantle (and/or oceanic crust)-derived (serpentinized ultramafics, eclogites) products. The pre-Cadomian complex in Central Sredna-gora Mountains evolved through Cadomian collision with c. 617 Ma granites, Hercynian 340 to 250 Ma granitoids, Late Permian exhumation, and Triassic-Jurassic sedimentation followed by Mid-Cretaceous exhumation. P-T conditions never reached amphibolite facies in post-Cadomian times except for some shear zones. The pre-Cadomian amphibolite-facies complex in Sakar Mt. was intruded by c. 500 Ma old granites, deeply eroded in late Permian time, and covered with depositional contact by Triassic terrestrial and marine sediments. Both basement and Triassic cover suffered folding and amphibolite-facies metamorphism (c. 150 Ma BP) followed by exhumation. Included in the Srednogorie Late Cretaceous volcanic arc as crystalline cores, these complexes have been affected by latest Cretaceous exhumation. Amphibolite-facies polymetamorphic cores (Ograzhdenian complex) within the Serbo-Macedonian massif and other units in SW Bulgaria and the adjacent countries were subjected to intense Cadomian (560 - 520 Ma BP) synmetamorphic collision and granite activity. Some units suffered Cadomian collision under greenschist-facies with a Neoproterozoic to Cambrian diabase-phyllitoid complex or have been exhumed and directly covered by Cambrian (followed by Cambrian limestones) or Tremadocian marine sandstones. After Palaeozoic exhumation, their structure was sealed by Permian, Triassic and Jurassic terrestrial and marine sediments, and after intense Mid-Cretaceous folding and thrusting, exhumed again in Palaeogene times. In the Rhodope region, the Mesoproterozoic? to Neoproterozoic supracrustal Rhodopian complex is built up of kyanite-, garnet- and staurolite-bearing biotite and two-mica gneisses and schists, amphibolites, marbles, calcareous schists, quartzo-feldspathic gneisses (derived of possible arkosic or rhyolitic protoliths), and orthoamphibolite, metaperidotite and eclogite rootless bodies. Migmatites and anatexites crop out in the cores of Rhodopian domes. Mid-Cretaceous thrusting in greenschist-facies conditions is documented at the peripheries of the Rhodope massif, and probably contributed to considerable (up to 70 km; now about 50 km) crustal thickening in the interior. The cores underwent very late (Early to Late Palaeogene) exhumation. Eclogitic rootless bodies that witness HP to UHP metamorphic events crop out in all complexes mentioned. Eclogite formation is referred to different mechanisms (burial through subduction of oceanic crust; amalgamation of mantle and crustal slivers in depth; metamorphism of deep norite to troctolite intrusions; local increase of pressure and temperature along minor shear zones) and times (Cadomian, Hercynian, Cimmerian and/or Alpine).</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-MAS&redirectUrl=http://academic.research.microsoft.com/Publication/54247832"><span id="translatedtitle">Origin of Siberian Large Igneous Province : link between petrology and <span class="hlt">geodynamics</span></span></a></p> <p><a target="_blank" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p>A. V. Sobolev</p> <p>2010-01-01</p> <p>The composition of parental melts and their mantle sources were recently reconstructed for different types of Siberian Flood basalts [1] and meimechites [2] based on the compositions of olivine phenocrysts and their melt inclusions. It was shown that mantle source of early flood basalts (Gudchikhinskaya suite) was composed entirely from olivine-free pyroxenite, produced by reaction of recycled oceanic crust and</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2010EGUGA..12.5495S"><span id="translatedtitle">Origin of Siberian Large Igneous Province : link between petrology and <span class="hlt">geodynamics</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sobolev, A. V.</p> <p>2010-05-01</p> <p>The composition of parental melts and their mantle sources were recently reconstructed for different types of Siberian Flood basalts [1] and meimechites [2] based on the compositions of olivine phenocrysts and their melt inclusions. It was shown that mantle source of early flood basalts (Gudchikhinskaya suite) was composed entirely from olivine-free pyroxenite, produced by reaction of recycled oceanic crust and peridotite. The composition of these lavas suggests that they were likely produced at depths of more than 130 km. However, in a very short time (150 m or 5% of lava column) afterwards the source composition of lavas (Tuklonskaya suite) has drastically changed incorporating up to 60% of peridotite. In addition, source of lavas has moved upwards to the depths of less than 70 km, where the major volume of Siberian traps have been produced. These observations suggest very fast, even catastrophic removal of at least 60 km of lithosphere, which led to massive melt production. Based on experimental and modeling results it was suggested that a Permian-Triassic plume, with potential temperature of up to 1650°C transported a large amount of recycled ancient oceanic crust (up to 15-20%) as SiO2-oversaturated carbonated eclogite. Low-degree partial melting of eclogite at depths of 250-300 km produced carbonate-silicate melt that metasomatized the lithospheric roots of the Siberian shield. Further rise of the plume under relatively attenuated lithosphere (eg. 130-140 km in Norilsk area) led to progressive melting of eclogite and formation of reaction pyroxenite, which then melted at depths of 130-180 km. Consequently, a large volume of melt(Gudchikhinskaya suite) penetrated into the lithosphere and caused its Relay-Taylor instability and destruction. Delaminated lithosphere that included fragments of locally metasomatized depleted harzburgite subsided into the plume and was heated to the temperatures of the plume interior with subsequent generation of meimechite magma. Meimechites showed up at the surface only under thicker part of the lithosphere aside from major melting zone above because otherwise they were mixed up in more voluminous flood basalts. I further show that meimechites, uncontaminated Siberian flood basalts and kimberlites all likely share the same source of strongly incompatible elements, the carbonated recycled oceanic crust carried up by hot mantle plume. References: 1. Sobolev, A.V., Krivolutskaya N.A., and Kuzmin, D.V. (2009). Petrology of the parental melts and mantle sources of Siberian trap magmatism. Petrology, 17 (3), 253-286. 2. Sobolev, A.V., Sobolev, S.V., Kuzmin, D.V. , Malitch, K.N., and Petrunin, A.G. (2009). Siberian meimechites: origin and relation to flood basalts and kimberlites. Russian Geology and Geophysics, 50, 1-33.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2013IzPSE..49..402B"><span id="translatedtitle">On the question of the interrelation between variations in crustal electrical conductivity and <span class="hlt">geodynamical</span> processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bataleva, E. A.; Batalev, V. Yu.; Rybin, A. K.</p> <p>2013-05-01</p> <p>The behavior of the variations in the crustal electrical conductivity in a wide range of periods is studied from the data of magnetotelluric soundings (MTS) during the Kambarata experiment (a strong industrial explosion to construct the blast-fill dam on the Naryn river), as well as at Aksu, a stationary geophysical monitoring point. The concept of the interrelation between the stress-strain state of the medium and the change in the apparent electrical resistivity, which is based on the idea of the redistribution of mineralized solutions between the crack networks, is confirmed experimentally. A procedure of azimuthal monitoring is developed, which allowed us not only to identify the anomalous changes in the module and phase of apparent resistivity but also to establish the directions of their maximum increases and decreases (the axes of compression and tension). For 34 points of deep MTS in the territory of Central Tien Shan, the depth intervals in the upper crust that are most sensitive to the changes in the stress-strain state of the medium are established. The variations in the electrical conductivity are compared with the solar-lunar tidal impacts. It is shown that by analyzing the recorded time series, it is possible to recognize the characteristic signs of the changes in the stress-strain state of the medium that are caused by seismic events.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=EPRINT&redirectUrl=http://arxiv.org/pdf/0809.2305v2"><span id="translatedtitle"><span class="hlt">Geodynamics</span> and Rate of Volcanism on Massive Earth-like Planets</span></a></p> <p><a target="_blank" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p>Edwin S. Kite; Michael Manga; Eric Gaidos</p> <p>2009-05-31</p> <p>We provide estimates of volcanism versus time for planets with Earth-like composition and masses from 0.25 to 25 times Earth, 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. Here 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 Tau Ceti system, and tidal forcing can be shown to be weak, this would be evidence for plate tectonics.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2014EGUGA..16..926A"><span id="translatedtitle"><span class="hlt">Geodynamic</span> modelling of non-volcanic rifted margins: sedimentation process and effects</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Andres-Martinez, Miguel; Perez-Gussinye, Marta; Phipps Morgan, Jason; Armitage, John; Monteiro da Silva, Rafael</p> <p>2014-05-01</p> <p>Non-volcanic rifted margins (NVRMs) are characterized by an anomalous lack of magmatism and a wide continental-ocean transition which has been interpreted as an expanse of exhumed and serpentinized mantle. NVRMs are represented all over the world as in Labrador Sea, Southeast Australia, Newfoundland, and West Iberian Margin (WIM), where a serpentinized peridotite ridge is found. Erosion and sedimentation are surficial processes that redistribute material along the margins, changing the forces along the margin and affecting its thermal structure. In order to study coupled mantle dynamics and sedimentation processes during rifting, we used a modified version of the dynamic 2D code MILAMIN (Dabrowski et al. 2008). Our modified version includes a free surface together with a free-surface stabilization algorithm to generate stable topographies, strain softening to simulate faulting, serpentinization, magmatism, erosion and sedimentation. Erosion and sedimentation algorithm is based on diffusion and transport equations in 1D. The code allow us to investigate how sedimentation process conditions the architecture of the margins during rifting and in which magnitude the width of the margins and the height of the rift shoulders are affected by surficial processes. Furthermore, we can study how sediments influence the temperature distribution and evolution and, ultimately, the rheology of the crust during rifting. We are also working on modelling sedimentation with high resolution meshes to try to reproduce break-up uncomformities and to study the thermal evolution of the sediments.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2014EGUGA..1613960T"><span id="translatedtitle">Lower Carboniferous carbonates rocks in Chukotka (North-East of Russia): paleogeographical reconstruction and <span class="hlt">geodynamic</span> events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tuchkova, Marianna; Sokolov, Sergey; Khudoley, Andrey; Pokrovsky, Boris; Vatrushkina, Elena</p> <p>2014-05-01</p> <p>Carbonates of Anyui-Chukotka fold belt are widespread in Devonian and Carboniferous age. Missisipian limestones of different tectonic structure were investigated. We examine limestones from i) South-Anyui Suture (Polarny Creek); ii) Alarmaut uplift, iii) Kibera Cape and iv) Wrangel island. Limestones of Polarny Creek contain fragments of fauna and they occur with basalt-chert rocks (Sizhykh et al., 1977; Sokolov et al., 2006). Carbonates of Alarmaut uplift have terrigenous materials (sandstones) and are associated with schists. Carboniferous rocks of Kibera Cape consist of sandstones, gravels and conglomerates in the lower part of Mississipian unit. In the upper part they replaced by limestones and dolostones. Lower Carboniferous formation of Wrangel Island is composed of clastic and carbonate rocks with evaporates (Kos'ko et al., 1993, 2003). The lower unit of the Lower Carboniferous formation is composed of conglomerate or gravelstone with fragments of locally derived Devonian rocks. All carbonate rocks contain lenses and interlayers of cherts. We used geochemical criteria and isotopic data for understanding the Paleogeographic position of different Carboniferous blocks. Sedimentation of carbonates of Wrangel Island and Kibera Cape was in shallow-marine shelf of carbonate platform with lagoon shoal. Carbonates of Alarmaut uplift accumulating in the shallow-marine environment, in active hydrodynamics conditions. Sedimentation of Polarny Creek (SAS) was not near from bioherm reef. We have demonstrated the different paleogeographic environments for Chukotka's carbonate platform. Sedimentological, geochemical and isotopic data indicate shallow sea-water of carbonate platform for limestones of Alarmaut uplift, Kibera Cape and Wrangel island. Limestones of Polarny Creek (South-Anyui Suture) may be a part of a carbonate sequence formed on a volcanic atoll. Paleozoic deposits of Wrangel Island are presented as fragment of Arctida-Crockerland basement (Shatsky, 1935; Eardly, 1948; Embry, 1993, 2011). In our opinion, Carboniferous carbonates rocks of Chukotka are the part of carbonate platform of Old continental block, that was existent in the north of Arctic. Lower Carboniferous limestones of South-Anyui Suture cannot be considered an element of the exhumed Paleozoic section of Anyui-Chukotka fold belt (Sokolov et al., 2006). Acknowledgments: This work is financially supported by RFBR Project nos. 11-05-00074, 11-05-00787, 14-05-00031 and Scientific School NSh - 2981.2014.5</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=EPRINT&redirectUrl=http://www.dst.uniroma1.it/dst1/sciterra/sezioni/doglioni/Publ_download/2012CarminatiEtAlMediterraneanTectonophysics.pdf"><span id="translatedtitle"><span class="hlt">Geodynamic</span> evolution of the central and western Mediterranean: Tectonics vs. igneous petrology constraints</span></a></p> <p><a target="_blank" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p>Doglioni, Carlo</p> <p></p> <p>and the Dinarides, respectively. The wide chemical composition of the igneous rocks emplaced during this tectonic the geochemical composition of igneous rocks to infer the coeval tectonic setting characteristics cannot be used, structures, igneous and metamorphic rocks having been described in detail. Also the crustal and the upper</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2013PhDT.......477S"><span id="translatedtitle">Contribution to defining a geodetic reference frame for Africa (AFREF): <span class="hlt">Geodynamics</span> implications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saria, Elifuraha E.</p> <p></p> <p>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 show a better fit with three sub-plates (Victoria, Rovuma and Lwandle) between the major plates Nubia and Somalia. We show that the earthquake slip vectors provide information that is consistent with the GPS velocities and significantly help reduce the uncertainties in plate angular velocity estimates. However, we find that 3.16 My average spreading rates along the Southwest Indian Ridge (SWIR) from MORVEL model are systematically faster than GPS-derived motions across that ridge, possibly reflecting the need to revise the MORVEL outward displacement correction. In the final step, we attempt to understand the hydrological loading in Africa, which may affect our geodetic estimates, particularly the uplift rates. In this work, we analyze 10 years (2002 - 2012) of continuous GPS measurements operating in Africa, and compare with the modeled hydrological loading deformation inferred from the Gravity Recovery and Climate Experiment (GRACE) at the same GPS location and for the same time period. We estimated hydrological loading deformation based on the Equivalent Water Height (EWH) derived from the 10-days interval reprocessed GRACE solution second release (RL02). We took in to account in both GPS and GRACE the systematic errors from atmospheric pressure and non-tidal ocean loading effects and model the Earth as perfect elastic and compute the deformation using appropriate Greens function. We analyze the strength of association between the observation (GPS) and the model (GRACE) in terms of annual amplitude and phase as well as the original data (time-series). We find a good correlation mainly in regions associated with strong seasonal hydrological variations. To improve the correlation between the two solutions, we subtract the GRACE-derived vertical displacement from GPS-observed time series and determine the variance reduction. Our solution shows average variance between the model and the observation reduced to ~40%. (Abstract shortened by UMI.)</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2009JGeo...48..279V"><span id="translatedtitle">Present day <span class="hlt">geodynamics</span> in Iceland monitored by a permanent network of continuous GPS stations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Völksen, Christof; Árnadóttir, Thóra; Geirsson, Halldór; Valsson, Guðmundur</p> <p>2009-12-01</p> <p>Iceland is located on the Mid-Atlantic Ridge and thereby offers a rare opportunity to study crustal movements at a divergent plate boundary. Iceland is not only characterized by the divergence of the Eurasian and North American Plates, as several active volcanoes are located on the island. Moderate size earthquakes occur in the transform zones, causing measurable crustal deformation. In 1999 the installation of a permanent network of continuous GPS stations (ISGPS) was initiated in order to observe deformation due to unrest in the Hengill volcanic system and at the Katla volcano. The ISGPS network has been enlarged over the years and consists today of more than 25 CGPS stations. Most of the stations are located along the plate boundary, where most of the active deformation takes place. Uplift due to post-glacial rebound due to the melting of the largest glacier in Europe, Vatnajökull, is also detected by the ISGPS network. This study presents results from analysis of 9 years of data from the ISGPS network, in the global reference frame PDR05, which has been evaluated by the Potsdam-Dresden-Reprocessing group with reprocessed GPS data only. We thus determine subsidence or land uplift in a global frame. The horizontal station velocities clearly show spreading across the plate boundary of about 20 mm/a. Stations in the vicinity of the glacier Vatnajökull indicate uplift in the range of 12 mm/a, while a station in the central part of Iceland shows uplift rates of about 25 mm/a. Tide gauge readings in Reykjavik and current subsidence rates observed with CGPS agree also quite well.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2000Tecto..19..300V"><span id="translatedtitle">An early Pliocene uplift of the central Apenninic foredeep and its <span class="hlt">geodynamic</span> significance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van der Meulen, M. J.; Buiter, S. J. H.; Meulenkamp, J. E.; Wortel, M. J. R.</p> <p>2000-04-01</p> <p>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.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2014EGUGA..16.1879G"><span id="translatedtitle">Density variability - fundamental basis of structure formation and tectonic-<span class="hlt">geodynamic</span> evolution of the Earth</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guliyev, Hatam; Guliyev, Ibrahim; Yetirmishli, Gurban</p> <p>2014-05-01</p> <p>It was shown that there are some common geomechanical basis of process of consolidation, deconsolidation, phase transitions, formation of zones of small shear stiffness (waveguides), realization of material and energetic mass flow in the internal structures of the Earth based on fundamental properties of basic systems of equations of nonlinear mechanics of the deformed bodies, data and results of Green, Ringwood, Liu's known experimental studies. Its instability for different geological media was shown studying the distribution of medium density depending on deformation changes. Distinguishing various forms of instability it was shown that there is general deformation mechanism of consolidation process of compressible medium according to which transfer to deconsolidation occurs at certain stages due to specific change of equilibrium states. Instability of deformation process contributes to emergence of geometric structures in composition of geological medium which are favorable to form deconsolidation zones and zones of small shear stiffness. Destruction by delamination at various depth of the Earth's interior can lead to formation of voids of various scale. Various forms of instability can be realized in the process of further evolution in the vicinity of these free surfaces, and voids can be filled by the loosened mass, i.e. deconsolidation process occurs under compression conditions. More hard bodies of local scale in the form of rod, strips, plates, cylindrical bodies, voids etc. can exist at different depth of mantle. These bodies can lose the stability under compression conditions. Therefore, part of their material and environment are loosened and deconsolidation process occurs again. The above described cases significantly depends on the realized form of deformation. Unevenness of deformation has a great value. Partial melting and magma formation can occur in these deconsolidated zones depending on mineral associations, petrochemical properties, thermobaric conditions and depth. This process becomes more feasible in case, when water appears as a result of dehydration in the considered zones. Some of these zones of deconsolidation can turn to focus of liquefied mass and give the beginning to mass flow on various directions in further evolution.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASA-TRS&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19750005833&hterms=satellite+based+positioning+TOA&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dsatellite%2Bbased%2Bpositioning%2BTOA"><span id="translatedtitle">Laser <span class="hlt">geodynamic</span> satellite/thermal/optical vibrational analyses and testing. Volume 2: Technical report, book 3</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1974-01-01</p> <p>The overall plan for accomplishing the various tests required to achieve the program objectives and tasks of the LAGEOS thermal/optical/vibration analysis and test program is described. The requirements for each test are identified for the purpose of program review for the design and fabrication of the required test article and test fixtures, for the allocation of test facilities, equipment and expendables, and for the generation of the detail test procedures by which the specified data will be obtained at specified test conditions. The current internal test program schedules, by which the various individual preparatory subtasks are to be accomplished to ensure that the individual test will be conducted within the time period required to meet program objectives are included.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2014JAESc..95..164L"><span id="translatedtitle">Petrology, geochemistry and geochronology of the magmatic suite from the Jianzha Complex, central China: Petrogenesis and <span class="hlt">geodynamic</span> implications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Xiaowei; Mo, Xuanxue; Bader, Thomas; Scheltens, Mark; Yu, Xuehui; Dong, Guochen; Huang, Xiongfei</p> <p>2014-12-01</p> <p>The intermediate-mafic-ultramafic rocks in the Jianzha Complex (JZC) at the northern margin of the West Qinling Orogenic Belt have been interpreted to be a part of an ophiolite suite. In this study, we present new geochronological, petrological, geochemical and Sr-Nd-Hf isotopic data and provide a different interpretation. The JZC is composed of dunite, wehrlite, olivine clinopyroxenite, olivine gabbro, gabbro, and pyroxene diorite. The suite shows characteristics of Alaskan-type complexes, including (1) the low CaO concentrations in olivine; (2) evidence of crystal accumulation; (3) high calcic composition of clinopyroxene; and (4) negative correlation between FeOtot and Cr2O3 of spinels. Hornblende and phlogopite are ubiquitous in the wehrlites, but minor orthopyroxene is also present. Hornblende and biotite are abundant late crystallized phases in the gabbros and diorites. The two pyroxene-bearing diorite samples from JZC yield zircon U-Pb ages of 245.7 ± 1.3 Ma and 241.8 ± 1.3 Ma. The mafic and ultramafic rocks display slightly enriched LREE patterns. The wehrlites display moderate to weak negative Eu anomalies (0.74-0.94), whereas the olivine gabbros and gabbros have pronounced positive Eu anomalies. Diorites show slight LREE enrichment, with (La/Yb)N ratios ranging from 4.42 to 7.79, and moderate to weak negative Eu anomalies (Eu/Eu? = 0.64-0.86). The mafic and ultramafic rocks from this suite are characterized by negative Nb-Ta-Zr anomalies as well as positive Pb anomalies. Diorites show pronounced negative Ba, Nb-Ta and Ti spikes, and typical Th-U, K and Pb peaks. Combined with petrographic observations and chemical variations, we suggest that the magmatism was dominantly controlled by fractional crystallization and crystal accumulation, with limited crustal contamination. The arc-affinity signature and weekly negative to moderately positive ?Nd(t) values (-2.3 to 1.2) suggest that these rocks may have been generated by partial melting of the juvenile 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.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2010Litho.117...20G"><span id="translatedtitle">Eocene potassic and ultrapotassic volcanism in south Tibet: New constraints on mantle source characteristics and <span class="hlt">geodynamic</span> processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gao, Yongfeng; Yang, Zhusen; Hou, Zengqian; Wei, Ruihua; Meng, Xiangjin; Tian, Shihong</p> <p>2010-06-01</p> <p>In the Yangbajing area, southern Tibet, several monogenic volcanoes were conformably superimposed on the Linzizong calc-alkaline volcanic successions. According to their petrologic and geochemical characteristics, these monogenic volcanoes are composed of three rock varieties: tephritic phonolitic plugs and shoshonitic and trachytic lavas. Their geochemical systematics reveals that low-pressure evolutionary processes in the large voluminous Linzizong calc-alkaline magmas were not responsible for the generation of these potassic-ultrapotassic rocks, but the significant change in petrologic and geochemical characteristics from the Linzizong calc-alkaline to potassic-ultrapotassic magma is likely accounted for the change of metasomatic agents in the southern Tibetan lithospheric mantle source during the Paleocene to Eocene. The tephritic phonolites containing both leucite and plagioclase show primary ultrapotassic character similar to that of Mediterranean plagioleucititic magmas. Radiogenic Sr increases with SiO 2 in the xenolith-bearing trachytes strongly suggesting significant crustal assimilation in the shoshonitic magmas. The Yangbajing ultrapotassic rocks have high K 2O and Al 2O 3, and show depletion of high field strength elements (HFSEs) with respect to large ion lithophile elements. In primitive mantle-normalized element diagrams, all samples are characterized by positive spikes at Th (U) and Pb with negative anomalies at Ba, Nb-Ta and Ti, reflecting the orogenic nature of the ultrapotassic rocks. They are characterized by highly radiogenic 87Sr/ 86Sr (i) ratios (0.7061-0.7063) and unradiogenic 143Nd/ 144Nd (i) (0.5125), and Pb isotopic compositions ( 206Pb/ 204Pb = 18.688-18.733, 207Pb/ 204Pb = 15.613-15.637, and 208Pb/ 204Pb = 38.861-38.930) similar to the global subducting sediment. Strong enrichment of incompatible trace elements and high Th fractionation from the other HFSEs (such as Nb and U) clearly indicate that the Th-enriched sedimentary component in a network veined mantle source was mainly introduced by sediment-derived melts. In addition, the ultrapotassic rocks have significant Ce (Ce/Ce* = 0.77-0.84) and Eu (Eu/Eu* = 0.72-0.75) anomalies, suggesting a subduction sediment input into the southern Tibetan lithospheric mantle source. In contrast, high U/Th (> 0.20) and Ba/Th (> 32) and low Th/La (< 0.3) in the shoshonites indicate that the Eocene potassic magma originated from partial melting of the surrounding peridotite mantle pervasively affected by slab-related fluid addition from the dehydration of either the subducting oceanic crust or the sediment. Thus, at least two different subduction-related metasomatic agents re-fertilized the upper mantle. According to the radiometric ages and spatial distribution, the Gangdese magmatic association shows a temporal succession from the Linzizong calc-alkaline to ultrapotassic magmas. This indicates a late arrival of recycled sediments within the Tibetan lithospheric mantle wedge. The most diagnostic signatures for the involvement of continent-derived materials are the super-chondritic Zr/Hf (45.5-49.2) and elevated Hf/Sm values (0.81-0.91) in the ultrapotassic rocks. Therefore, the occurrence of orogenic magmatism in the Gangdese belt likely represents the volcanic expression of the onset of the India-Asia collision, preceding the 10 Ma Neo-Tethyan slab break-off process at 42-40 Ma. The absence of residual garnet in the mantle source for the ultrapotassic volcanism seems to imply that the southern Tibetan lithosphere was not been remarkably thickened until the Eocene (˜ 50 Ma).</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2014Tectp.634....1S"><span id="translatedtitle">Post-rift <span class="hlt">geodynamics</span> of the Songliao Basin, NE China: Origin and significance of T11 (Coniacian) unconformity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Song, Ying; Ren, Jianye; Stepashko, Andrei A.; Li, Jianguo</p> <p>2014-11-01</p> <p>The T11 unconformity lies between the Qingshankou and Yaojia Formations in the post-rifting sequence of the Cretaceous Songliao Basin, NE China. It is intimately associated with petroleum reservoirs and considered to be a disconformity forming in the tectonic quiet stage. We present the interpretations from new seismic surveys and cored sections of the Cretaceous Continental Scientific Drilling borehole (CCSD-SK-1) in order to resolve the nature and origin of T11 unconformity. The T11 is often a low-angle unconformity with underlying Qingshankou Formation having been deformed and eroded prior to deposition of the Yaojia Formation. In the post-rift evolution of the basin it marks an abrupt change from a deep lake to shallow lake or subaerial environment, documented by reddening of the lacustrine mudstone, extinction of the ostracod assemblages and a great increase of coarse detrital inputs. The sharp change of depositional environment, the truncation of gentle folds and the cluster of volcanic and paleoearthquake activities, all happened simultaneously, immediately before the development of T11 unconformity, indicating a significant regional compressional uplift event in the basin. The timing of the T11 unconformity formation is within the interval 88-86.2 Ma. Correlations with coeval unconformities in other Cretaceous sedimentary basins in eastern Asia indicate that this compressional uplift coincided with an episode of global plate reorganization between the Eurasian and Paleo-Pacific plates that culminated at 88-87 Ma. During this short interval the northeast Asian margin, in eastern China, South Korea, Japan and Russian Far East experienced widespread violent volcanic and granite emplacement activity triggered by compression resulting from rapid and orthogonal slab subduction. The post-rift basin tectonic inversion occurred during T11 (Coniacian) time; thereafter the basin again evolved in an extension regime. Two subsidence phases in post-rift history took place as the direct consequence of Coniacian compression peak, which defined the distribution of oil sources and reservoirs.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2009AdG....22..181M"><span id="translatedtitle">A Terrestrial Reference Frame (TRF), coordinates and velocities for South American stations: contributions to Central Andes <span class="hlt">geodynamics</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mackern, M. V.; Mateo, M. L.; Robin, A. M.; Calori, A. V.</p> <p>2009-12-01</p> <p>Satellite positioning systems allow the fixing of the location of a point on the Earth's surface with very good precision and accuracy. To do this, however, it is necessary to determine the point coordinates taking account the reference system and the movements that affect them because of tectonic plate movements. These reference systems are materialized by a significant number of continuous measurement stations in South America. In SIRGAS (Sistema de Referencia Geocéntrico para las Américas), there are four Analysis Centers that process the data collected from satellites of the Global Navigation Satellite Systems (GNSS), with the primary purpose to maintain the international terrestrial reference frame through calculation of the coordinates and velocities of the continuous GNSS stations of the SIRGAS-CON Network. In this work, we demonstrate the quality of the solutions from CIMA, one of the SIRGAS official processing centers operating in Mendoza, Argentina, in comparison with other South American processing centers. The importance of precise calculations of coordinates and velocities in a global frame is also shown. Finally, we give estimations of velocities from stations located within deformation zones in the Central Andes.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2010DokES.432..839A"><span id="translatedtitle">Stanniferrous granites of Vietnam: Rb-Sr and Ar-Ar isotope age, composition, sources, and <span class="hlt">geodynamic</span> formation conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anh, Phan Luu; Vladimirov, A. G.; Kruk, N. N.; Polyakov, G. V.; Ponomarchuk, V. A.; Hoa, Tran Trong; Phuong, Ngo Thi; Kuibida, M. L.; Annikova, I. Yu.; Pavlova, G. G.; Kiseleva, V. Yu.</p> <p>2010-06-01</p> <p>Stanniferrous granite-leucogranite massifs in Vietnam to which the bedrock and placer commercial deposits of cassiterite are associated (Timtuc etc.) are of late Cretaceous age (˜85 Ma by Rb-Sr and Ar-Ar isotope dating). These massifs are presented by stocks and fracture intrusions (to 100 km2 in area) of simple homodromic structure: biotite granites ? two-mica and muscovite leucogranites ? topaz-containing aplites ? rare-metal pegmatites.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASA-TRS&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19750005832&hterms=TEMPRATURE+EFFECT&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DTEMPRATURE%2BEFFECT"><span id="translatedtitle">Laser <span class="hlt">geodynamic</span> satellite thermal/optical/ vibrational analyses and testing. Volume 2: Technical report, book 2. [retroreflector design</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1974-01-01</p> <p>A detailed analysis of a fused silica cube-corner retroreflector is presented. The effects of manufacturing errors and temperature variations, which may affect the performance of the cube-corner retroreflector are included. The process used in the cube-corner performance is illustrated. The effect of manufacturing error and the effects of manufacturing error combined with various temperature profiles were examined. The effects of a nonuniform wedge angle with manufacturing error and with a manufacturing/temperature profile combination were also analyzed.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2013EGUGA..15.9917R"><span id="translatedtitle">The Main Shear Zone in Sør Rondane: A key feature for reconstructing the <span class="hlt">geodynamic</span> evolution of East Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ruppel, Antonia; Läufer, Andreas; Lisker, Frank; Jacobs, Joachim; Elburg, Marlina; Damaske, Detlef; Lucka, Nicole</p> <p>2013-04-01</p> <p>Structural investigations were carried out along the Main Shear Zone (MSZ) of western Sør Rondane (22°-25°E, 71.5°-72.5°S) to gain new information about the position of the East-/West-Gondwana suture and the ancient plate tectonic configuration during Gondwana amalgamation. The WSW-ENE striking MSZ divides south-western Sør Rondane in a northern amphibolite-facies terrane and a southern tonalite-trondhjemite-granodiorite (TTG) terrane. The structure can be traced over a distance of ca. 100 km and reaches several hundred meters in width. It is characterized by a right-lateral sense of movement and marked by a transpressional and also transtensional regime. Ductilely deformed granitoids (ca. 560 Ma: SHRIMP U-Pb of zircon) and ductile - brittle structures, which evolved in a transitional ductile to brittle regime in an undeformed syenite (ca. 499-459 Ma, Ar-Ar mica), provide a late Proterozoic/ early Paleozoic time limit for the activity of the shear zone (Shiraishi et al., 2008; Shiraishi et al., 1997). Documentation of ductile and brittle deformation allows reconstructing up to eight deformation stages. Cross-cutting relationships of structural features mapped in the field complemented by published kinematic data reveal the following relative age succession: [i] Dn+1 - formation of the main foliation during peak metamorphism, [ii] Dn+2 - isoclinal, intrafolial folding of the main foliation, mostly foliation-parallel mylonitic shear zones (1-2 meter thick), [iii] Dn+3 - formation of tight to closed folds, [iv] Dn+4 - formation of relatively upright, large-scale open folds, [v] Dn+5 - granitoid intrusion (e.g. Vengen granite), [vi] Dn+6 - dextral shearing between amphibolite and TTG terranes, formation of the MSZ, [vii] Dn+7 - intrusion of late- to post-tectonic granitoids, first stage of brittle deformation (late shearing along MSZ), intrusion of post-kinematic mafic dykes, [viii] Dn+8 - second stage of brittle deformation including formation of conjugate fault systems. The latter point to a WNW-ESE respectively NW-SE oriented maximum paleostress direction and indicate the latest deformation event; they are possibly related to the break-up and fragmentation of Gondwana. Two contrasting models describe the configuration of East Gondwana during the Neoproterozoic and the final amalgamation of Gondwana. The first model proposes the existence of a Pan-African Orogen (East African/ Antarctic Orogen). The Main Shear Zone could represent the eastern extension of this orogen and may be related to a NE-directed lateral-escape tectonic model. Both published structural data from Sør Rondane and adjacent regions and the outcome of this study agree with this model and propose a suture of East- and West Gondwana located between Mühlig-Hofmann-Gebirge and Sør Rondane. The second model of an overlap of two orogens with different formation ages cannot be proved by structural data from the MSZ. Instead, tight test constraints of the second model may be provided by new magnetic anomaly maps based on a 2012/13 aerogeophysical survey. Shiraishi, K.; Dunkley, D.J.; Hokada, T.; Fanning, C.M.; Kagami, H.; and Hamamoto, T. (2008): Geochronological constraints on the Late Proterozoic to Cambrian crustal evolution of eastern Dronning Maud Land, East Antarctica: a synthesis of SHRIMP U-Pb age and Nd model age data. Geological Society, 308(1):21-67. Shiraishi, K.; Osanai, Y.; Ishizuka, H.; and Asami, M. (1997): Geological map of the Sør Rondane Mountains, Antarctica. Antarctica Geological Map Series, sheet 35, scale 1 : 25 0000. National Institute of PolarResearch, Tokyo.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2012SGeo...33..107W"><span id="translatedtitle">Making and Breaking of a Continent: Following the Scent of <span class="hlt">Geodynamic</span> Imprints on the African Continent Using Electromagnetics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weckmann, Ute</p> <p>2012-01-01</p> <p>The African continent inherits a long history of continental accretion and breakup. The stage of "making" a continent goes back to the Archean, when the first continental masses formed cratons which mostly remained stable ever since. Subsequent collision of weaker continental masses was followed by several extension and compression episodes that resulted in the formation of super-continents. After the assemblage of Gondwana, a period of predominantly "breaking" , i.e., the breakup of super-continents, took over. The modern-day African continent exhibits different types of margins; continental rifting occurs side by side with recent collision. Since the late 1960s, magnetotelluric (MT) experiments have played an important role in studies of the electrical conductivity structure of Africa. The early results significantly shaped the MT community's understanding of continental-scale conductivity belts and basic characteristics of cratons and mobile belts on both crustal and lithospheric mantle scales for some decades. Modern MT studies in Africa have generally supported earlier results with high resistivities observed on cratons and low resistivities observed across mobile belts. Advances in instrumentation, data processing and interpretation resulted in higher-resolution images of the lithosphere, which in consequence induce an improved understanding of tectonic processes and geological prerequisites for the occurrence of natural resources. The high electrical conductivity of mobile belts and their relation to reactivated fault and detachment zones were often interpreted to characterize mobile belts as tectonic weak zones, which can accommodate stress and constitute zones along which continents can break. Recent breaking of the African continent can be studied on land across the East African rift; however, the lack of amphibian MT experiments across today's margins does not allow for good resolution of remnants of continental breakup processes. Naturally, the regions and the focus of the MT studies in Africa are diverse, but they all contribute to the story of making and breaking a continent.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-MAS&redirectUrl=http://academic.research.microsoft.com/Publication/40732493"><span id="translatedtitle">The Early-Cambrian Boho volcano of the El Graara massif, Morocco: Petrology, <span class="hlt">geodynamic</span> setting and coeval sedimentation</span></a></p> <p><a target="_blank" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p>J. J. Álvaro; H. Ezzouhairi; E. Vennin; M. L. Ribeiro; S. Clausen; A. Charif; N. Ait Ayad; M. E. Moreira</p> <p>2006-01-01</p> <p>A major volcanic episode is recorded across the Neoproterozoic-Cambrian transition in the Moroccan Anti-Atlas. Several volcanic cones are still preserved in the El Graara massif, laterally correlatable with volcanic flows dated as Early Cambrian (U\\/Pb date of 534±10Ma). Volcanic ashes and flows are interbedded with the uppermost part of the Adoudou dolostones, whereas the best-preserved volcano (the Boho Jbel) is</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=EPRINT&redirectUrl=http://dspace.mit.edu/handle/1721.1/45774"><span id="translatedtitle">Surface uplift, fluvial incision, and <span class="hlt">geodynamics</span> of plateau evolution, from the western margin of the Central Andean plateau</span></a></p> <p><a target="_blank" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p>Schildgen, Taylor F. (Taylor Frances)</p> <p>2008-01-01</p> <p>The Colca-Majes and Cotahuasi-Ocona rivers in southwest Peru that cut through the western margin of the Andean plateau en route to the Pacific Ocean incised canyons over 3 km deep in response to late Cenozoic surface uplift. ...</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/1997JGR...10224669S"><span id="translatedtitle">Cenozoic <span class="hlt">geodynamics</span> of the Ross Sea region, Antarctica: Crustal extension, intraplate strike-slip faulting, and tectonic inheritance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Salvini, Francesco; Brancolini, Giuliano; Busetti, Martina; Storti, Fabrizio; Mazzarini, Francesco; Coren, Franco</p> <p>1997-11-01</p> <p>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.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2014CoMP..168.1078A"><span id="translatedtitle">Quaternary bimodal volcanism in the Ni?de Volcanic Complex (Cappadocia, central Anatolia, Turkey): age, petrogenesis and <span class="hlt">geodynamic</span> implications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aydin, Faruk; Schmitt, Axel K.; Siebel, Wolfgang; Sönmez, Mustafa; Ersoy, Yalç?n; Lermi, Abdurrahman; Dirik, Kadir; Duncan, Robert</p> <p>2014-11-01</p> <p>The late Neogene to Quaternary Cappadocian Volcanic Province (CVP) in central Anatolia is one of the most impressive volcanic fields of Turkey because of its extent and spectacular erosionally sculptured landscape. The late Neogene evolution of the CVP started with the eruption of extensive andesitic-dacitic lavas and ignimbrites with minor basaltic lavas. This stage was followed by Quaternary bimodal volcanism. Here, we present geochemical, isotopic (Sr-Nd-Pb and ?18O isotopes) and geochronological (U-Pb zircon and Ar-Ar amphibole and whole-rock ages) data for bimodal volcanic rocks of the Ni?de Volcanic Complex (NVC) in the western part of the CVP to determine mantle melting dynamics and magmatic processes within the overlying continental crust during the Quaternary. Geochronological data suggest that the bimodal volcanic activity in the study area occurred between ca. 1.1 and ca. 0.2 Ma (Pleistocene) and comprises (1) mafic lavas consisting of basalts, trachybasalts, basaltic andesites and scoria lapilli fallout deposits with mainly basaltic composition, (2) felsic lavas consisting of mostly rhyolites and pumice lapilli fall-out and surge deposits with dacitic to rhyolitic composition. The most mafic sample is basalt from a monogenetic cone, which is characterized by 87Sr/86Sr = 0.7038, 143Nd/144Nd = 0.5128, 206Pb/204Pb = 18.80, 207Pb/204Pb = 15.60 and 208Pb/204Pb = 38.68, suggesting a moderately depleted signature of the mantle source. Felsic volcanic rocks define a narrow range of 143Nd/144Nd isotope ratios (0.5126-0.5128) and are homogeneous in Pb isotope composition (206Pb/204Pb = 18.84-18.87, 207Pb/204Pb = 15.64-15.67 and 208Pb/204Pb = 38.93-38.99). 87Sr/86Sr isotopic compositions of mafic (0.7038-0.7053) and felsic (0.7040-0.7052) samples are similar, reflecting a common mantle source. The felsic rocks have relatively low zircon ?18O values (5.6 ± 0.6 ‰) overlapping mantle values (5.3 ± 0.3 %), consistent with an origin by fractional crystallization from a mafic melt with very minor continental crustal contamination. The geochronological and geochemical data suggest that mafic and felsic volcanic rocks of the NVC are genetically closely related to each other. Mafic rocks show a positive trend between 87Sr/86Sr and Th, suggesting simultaneous assimilation and fractional crystallization, whereas the felsic rocks are characterized by a flat or slightly negative variation. High 87Sr/86Sr gneisses are a potential crustal contaminant of the mafic magmas, but the comparatively low and invariant 87Sr/86Sr in the felsic volcanics suggests that these evolved dominantly by fractional crystallization. Mantle-derived basaltic melts, which experienced low degree of crustal assimilation, are proposed to be the parent melt of the felsic volcanics. Geochronological and geochemical results combined with regional geological and geophysical data suggest that bimodal volcanism of the NVC and the CVP, in general, developed in a post-collisional extensional tectonic regime that is caused by ascending asthenosphere, which played a key role during magma genesis.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2015Tecto..34..116C"><span id="translatedtitle">Tectonic magnetic lineation and oroclinal bending of the Alborz range: Implications on the Iran-Southern Caspian <span class="hlt">geodynamics</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cifelli, Francesca; Ballato, Paolo; Alimohammadian, Habib; Sabouri, Jafar; Mattei, Massimo</p> <p>2015-01-01</p> <p>In this study we use the anisotropy of magnetic susceptibility (AMS) and paleomagnetic data for deciphering the origin of magnetic lineation in weakly deformed sedimentary rocks and for evaluating oroclinal processes within the Arabia-Eurasia collision zone. In particular, we have analyzed the Miocene Upper Red Formation (URF) from the outer curved front of the southern Central Alborz Mountains of north Iran, to test for the first time with paleomagnetic data the origin (primary versus secondary) of this orogenic arc. AMS data document the existence of a magnetic lineation parallel to the orientation of the major tectonic structures, which vary along strike from WNW to ENE. These directions are highly oblique to the paleoflow directions and hence suggest that the magnetic lineation in the URF was produced by compressional deformation during layer-parallel shortening. In addition, our paleomagnetic data document clockwise and anticlockwise rotations along vertical axis for the western and eastern sectors of the Central Alborz Mountains, respectively. Combined, our results suggest that the orogen represents an orocline, which formed not earlier than circa 7.6 Ma most likely through bending processes caused by the relative motion between the rigid crustal blocks of the collision zone. Moreover, our study provides new insights into the Iran-Southern Caspian Basin kinematic evolution suggesting that the present-day SW motion of the South Caspian Basin with respect to Central Iran postdates oroclinal bending and hence cannot be as old as late Miocene to early Pliocene but a rather recent configuration (i.e., 3 to <1 Ma).</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2011MmSAI..82..377S"><span id="translatedtitle">Roots of modern <span class="hlt">geodynamical</span> views in Schiaparelli's thought. The volcano-seismic correlation events on the Andes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scalera, G.</p> <p></p> <p>The reflections of Schiaparelli in the branch of astronomy more extensively involved with the geophysics and geology was influential on the progress of Earth sciences, contributing to unprejudiced forms of reasoning about the evolution of our planet. Today some new factual evidence and interpretations of the phenomena linked to a volcano-seismic correlation and to a progressive shift of the Earth's rotation poles through geological time find their roots in the geoedynamical examples published in 1893 and 1891 by Schiaparelli. If a possible synchronicity of a volcano-seismic correlation - peculiar for the South American Pacific Margin - with features of the Markowitz oscillation of the secular Polar Motion will be confirmed by comparison of a longer series of Polar Motion data and volcano-seismic events (average return period of 40-50 years), we would reasonably be in the presence of a phenomenon that puts in communication the Earth's surface with its deeper interior (core-mantle boundary) and that should be directly linked to a slow asymmetrical expansion of the Earth.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2013AGUFM.T11F..02G"><span id="translatedtitle">Evolution of bimodal volcanism in Gona, Ethiopia: geochemical associations and <span class="hlt">geodynamic</span> implications for the East African Rift System</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghosh, N.; Basu, A. R.; Gregory, R. T.; Richards, I.; Quade, J.; Ebinger, C. J.</p> <p>2013-12-01</p> <p>The East African rift system in Ethiopia formed in the Earth's youngest flood basalt province, and provides a natural laboratory to study the geochemistry of bimodal volcanism and its implications for plume-derived magmatism, mantle-lithosphere interactions and evolution of continental rifts from plate extension to rupture. Our geochemical studies of the ~6 Ma to recent eruptive products from Gona within the Afar Rift Zone are understood in context of crustal and upper mantle seismic imaging studies that provide constraints on spatial variations. Geochemical (major element, trace element and isotope) analyses of basalts and rhyolitic tuff from Gona indicate a common magma source for these bimodal volcanics. Light rare earth elements (LREEs) are enriched with a strong negative Eu anomaly and a positive Ce anomaly in some of the silicic volcanic rocks. We observe strong depletions in Sr and higher concentrations of Zr, Hf, Th, Nb and Ta. We hypothesize that the silicic rocks may be residues from a plume-derived enriched magma source, following partial melting with fractional crystallization of plagioclase at shallow magma chambers. The absence of Nb-Ta anomaly shows no crustal assimilation by magmas. Sr isotopes, in conjunction with Nd and Pb isotopes and a strong Ce anomaly could reflect interaction of the parent magma with a deep saline aquifer or brine. Nd isotopic ratios (?Nd = 1.9 to 4.6) show similarity of the silicic tuffs and basalts in their isotopic compositions except for some ~6 Ma lavas showing MORB-like values (?Nd = 5 to 8.7) that suggest involvement of the asthenosphere with the plume source. Except for one basaltic tuff, the whole rock oxygen isotopic ratios of the Gona basalts range from +5.8‰ to +7.9‰, higher than the ? values for typical MORB, +5.7. The oxygen isotopes in whole rocks from the rhyolite tuffs vary from 14.6‰ to 20.9‰ while their Sr isotope ratios <0.706, indicative of post-depositional low T alteration of these silicic rocks by a fluid derived from seawater or some crustal fluid not enriched in radiogenic Sr. The bimodality of the volcanic rocks may be genetically related by fractional crystallization or by partial melting of a hydrothermally altered mafic crust from earlier magma generation in the rift, without continental crustal assimilation. The geochemical data, along with geophysical and geodetic studies, assist our understanding of the tectonics of continental break up and plume magmatism in the Afar depression and the East African Rift system.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-MAS&redirectUrl=http://academic.research.microsoft.com/Publication/39661251"><span id="translatedtitle">The youngest basic oceanic magmatism in the Alps (Late Cretaceous ; Chiavenna unit, Central Alps): geochronological constraints and <span class="hlt">geodynamic</span> significance</span></a></p> <p><a target="_blank" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p>Anthi Liati; Dieter Gebauer; C. Mark Fanning</p> <p>2003-01-01</p> <p>Cathodoluminescence-controlled radiometric dating (U–Pb SHRIMP) was carried out on zircon domains from metabasic rocks of the Chiavenna unit, a major mafic\\/ultramafic-bearing unit in the Central Alps. Co-magmatic zircon domains from amphibolites near Chiavenna and Prata areas yielded weighted mean 206Pb\\/ 238U ages at 93.0±2.0 and 93.9±1.8 Ma, respectively, interpreted as the age of crystallization of the magmatic protoliths. These ages fit</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=EPRINT&redirectUrl=http://www.gps.caltech.edu/~dla/DLAScaling21Jan.pdf"><span id="translatedtitle">Submitted for publication in AGU Monograph Series Self-gravity, Self-consistency & Self-organization in <span class="hlt">Geodynamics</span> &</span></a></p> <p><a target="_blank" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p>Anderson, Don L.</p> <p></p> <p>of the subducting lithospheric plates are currently reaching the core- mantle boundary. Discontinuities in the deep-jack It is widely believed that the results of seismology and geochemistry for mantle structure are discordant, with the former favoring whole-mantle convection and the later favoring layered convection. However, a different</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=EPRINT&redirectUrl=http://www.math.colostate.edu/~liu/PUBS/ZhouLiuHarry_JCP_2012_MibmGeoDyn.pdf"><span id="translatedtitle">A matched interface and boundary method for solving multi-flow NavierStokes equations with applications to <span class="hlt">geodynamics</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p></p> <p></p> <p>­Stokes equations with discontinuous viscos- ity and density on non-staggered Cartesian grids. We have derived is the convection in Earth's mantle that occurs at depths ranging from about 100 km to 2900 km [7,21,33,40,61]. The rocks within Earth's mantle behave visco-plastically over geologic time scales (thousands to millions</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2008GeoOD..50..339L"><span id="translatedtitle">The Antei uranium deposit: A natural analogue of an SNF repository and an underground <span class="hlt">geodynamic</span> laboratory in granite</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Laverov, N. P.; Petrov, V. A.; Poluektov, V. V.; Nasimov, R. M.; Hammer, J.; Burmistrov, A. A.; Shchukin, S. I.</p> <p>2008-10-01</p> <p>The estimation of the long-term stability of crystalline rock massifs with respect to natural and technogenic loads in the course of long-term storage of spent nuclear fuel (SNF) is a special area of surveys at underground research laboratories (URLs). In parallel with these surveys, data on uranium deposits—natural analogues of repositories of SNF consisting of 95% UO2—are used for obtaining insight into the dynamics of radionuclide migration and validating barrier properties of host rocks. Examples of URLs located in granitic massifs of Sweden (Äspö), Canada (Whiteshell), Switzerland (Grimsel), Japan (Mizunami), and Finland (ONKALO), as well as the El Berrocal (Spain), Palmottu (Finland), Sanerliu (China), and Kamaishi (Japan) deposits, are considered in the paper. The objects listed above are distinct in tectonic settings, geology, control of ore mineralization, redox conditions of uranium migration, and character and intensity of filtration and transportation, which predetermine the direction and specific features of research conducted therein. A variant in which a URL and a natural analogue are combined in one object is especially promising for validation of safe long-term isolation of SNF. The Antei vein-stockwork uranium deposit in the southeastern Transbaikal region, localized in Paleozoic granite at a depth of 400 1000 m and opened by mine workings at six levels, is such an object. Its geological features, stress-strain state, and infrastructure of mine workings offer an opportunity to study the entire spectrum of processes proceeding in near-and far-field of an SNF repository. The structural geology, mineralogy and petrography, and petrophysical and tectonophysical features of the deposit at its three lower levels are considered. The sequence of metasomatic alteration of rocks and the dynamics of formation of ore-bearing faults that crosscut prototectonic elements, as well as relationships of physicomechanical properties of rocks as a function of 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.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-MAS&redirectUrl=http://academic.research.microsoft.com/Publication/44252224"><span id="translatedtitle"><span class="hlt">Geodynamic</span> significance of Late Triassic to Early Cretaceous volcanic sequences of Vizcaino Peninsula and Cedros Island, Baja California, Mexico</span></a></p> <p><a target="_blank" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p>C. Rangin; D. Girard; R. Maury</p> <p>1983-01-01</p> <p>The Mesozoic prebatholitic terranes of central Baja California include distinct volcanic sequences associated with sediments, ranging in age from Late Triassic to Early Cretaceous. These volcanic-sedimentary sequences are parts of a large ``nappe'' lying on top of blueschist-bearing melanges. The magmatic parentages of basic lavas from the allochthonous units have been determined from major- and trace-element analyses of total rocks</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2013PhDT.......194P"><span id="translatedtitle">Sequence stratigraphy, <span class="hlt">geodynamics</span>, and detrital geothermochronology of Cretaceous foreland basin deposits, western interior U.S.A</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Painter, Clayton S.</p> <p></p> <p>Three studies on Cordilleran foreland basin deposits in the western U.S.A. constitute this dissertation. These studies differ in scale, time and discipline. The first two studies include basin analysis, flexural modeling and detailed stratigraphic analysis of Upper Cretaceous depocenters and strata in the western U.S.A. The third study consists of detrital zircon U-Pb analysis (DZ U-Pb) and thermochronology, both zircon (U-Th)/He and apatite fission track (AFT), of Upper Jurassic to Upper Cretaceous foreland-basin conglomerates and sandstones. Five electronic supplementary files are a part of this dissertation and are available online; these include 3 raw data files (Appendix_A_raw_isopach_data.txt, Appendix_C_DZ_Data.xls, Appendix_C_U-Pb_apatite.xls), 1 oversized stratigraphic cross section (Appendix_B_figure_5.pdf), and 1 figure containing apatite U-Pb concordia plots (Appendix_C_Concordia.pdf). Appendix A is a combination of detailed isopach maps of the Upper Cretaceous Western Interior, flexural modeling and a comparison to dynamic subsidence models as applied to the region. Using these new isopach maps and modeling, I place the previously recognized but poorly constrained shift from flexural to non-flexural subsidence at 81 Ma. Appendix B is a detailed stratigraphic study of the Upper Cretaceous, (Campanian, ~76 Ma) Sego Sandstone Member of the Mesaverde Group in northwestern Colorado, an area where little research has been done on this formation. Appendix C is a geo-thermochronologic study to measure the lag time of Upper Jurassic to Upper Cretaceous conglomerates and sandstones in the Cordilleran foreland basin. The maximum depositional ages using DZ U-Pb match existing biostratigraphic age controls. AFT is an effective thermochronometer for Lower to Upper Cretaceous foreland stratigraphy and indicates that source material was exhumed from >4--5 km depth in the Cordilleran orogenic belt between 118 and 66 Ma, and zircon (U-Th)/He suggests that it was exhumed from <8--9 km depth. Apatite U-Pb analyses indicate that volcanic contamination is a significant issue, without which, one cannot exclude the possibility that the youngest detrital AFT population is contaminated with significant amounts of volcanogenic apatite and does not represent source exhumation. AFT lag times are <5 Myr with relatively steady-state to slightly increasing exhumation rates. Lag time measurements indicate exhumation rates of ~0.9->>1 km/Myr.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2004Tectp.393...87L"><span id="translatedtitle">The Early Triassic Indosinian orogeny in Vietnam (Truong Son Belt and Kontum Massif); implications for the <span class="hlt">geodynamic</span> evolution of Indochina</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lepvrier, C.; Maluski, H.; Van Tich, Vu; Leyreloup, A.; Truong Thi, Phan; Van Vuong, Nguyen</p> <p>2004-11-01</p> <p>New structural field data at various scale and 40Ar- 39Ar geochronological results, from the basement rocks in the Truong Son belt and Kontum Massif of Vietnam, confirm that ductile deformation and high-temperature metamorphism were caused by the Early Triassic event of the Indosinian Orogeny in the range of 250-240 Ma. A compilation of isotopic data obtained in other countries along the Sibumasu-Indochina boundary broadly indicates same interval of ages. This tectonothermal event is interpreted as the result of a synchronous oblique collision of Indochina with both Sibumasu and South China, inducing dextral and sinistral shearing along E-W to NW-SE and N-S fault zones, respectively. The collision along Song Ma follows the northwards subduction of Indochina beneath South China and the subsequent development of the Song Da zone which in turn was affected by the Late Triassic Indosinian phase of shortening. Within the Indochina plate, internal collisions occurred coevally in the Early Triassic, as along the Poko suture, at the western border of the Kontum Massif.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2009JAfES..53..122C"><span id="translatedtitle">Neoproterozoic and Hercynian metamorphic events in the Central Mauritanides: Implications for the <span class="hlt">geodynamic</span> evolution of West Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Caby, R.; Kienast, J. R.</p> <p>2009-02-01</p> <p>Field and petrostructural investigations in the Central Mauritanides provide new precisions on the polyorogenic character of the nappe edifice of this belt. The upper structural unit exposed in the Gaouâ area includes anatectic gneisses and high-grade metasediments affected by medium temperature, high-pressure metamorphism and cut by granitoids. They represent a basement unconformably overlain by a monometamorphic cover, the Gaouâ Group, of assumed lower Paleozoic age. Late Paleozoic regional metamorphism of metapelites from this cover is characterized by pyrophyllite-kyanite-chloritoid assemblages equilibrated at T around 420 °C and P = 1 GPa. In the lower structural unit exposed in the south around Boufkerine-Farkâkâ, metapelites of the Gadel Group display slightly retrogressed garnet-kyanite-staurolite-rutile assemblages that equilibrated at T around 600 °C and P ? 1.2 GPa before the intrusion of 639 Ma old plutons . The Gadel Group locally overlies in unconformity polycyclic gneisses. This continental assemblage represents an outboard terrane inserted between two monocyclic greenschist facies terranes: remnants of oceanic lithosphere in the east and arc-derived metasediments and metavolcanics cut by 670 Ma old calc-alkaline plutons in the west. All units have been involved in late Paleozoic nappes emplaced to the east above the West African craton and its late Neoproterozoic to Cambro-ordovician cover. Though an east-directed vergence is locally recorded in the Neoproterozoic units, most early E-W trending stretching and mineral lineations are synchronous with greenschist facies metamorphism developed during the Late Paleozoic and roughly coeval with the Applachian nappe system.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=EPRINT&redirectUrl=http://www.earthdynamics.org/steinberger/papers/jgeodyn05.pdf"><span id="translatedtitle">Journal of <span class="hlt">Geodynamics</span> 39 (2005) 493511 On the effect of a low viscosity asthenosphere on the temporal</span></a></p> <p><a target="_blank" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p>Steinberger, Bernhard</p> <p></p> <p>technology to measure changes in the Earth's gravity field gives new possibilities to detect layers of low Steinbergerb, Karen Niehuusc a SRON and Institute of Earth Science, University of Utrecht, The Netherlands b Institute for Frontier Research in Earth Evolution, Yokosuka, Japan c Institute of Meteorology</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=EPRINT&redirectUrl=http://hal.archives-ouvertes.fr/docs/00/66/33/67/PDF/DumontEtAl-JourGeod2011-HAL.pdf"><span id="translatedtitle">Paper in press in Journal of <span class="hlt">Geodynamics</span>, 2011; author's version Structural and Sedimentary records of the Oligocene revolution</span></a></p> <p><a target="_blank" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p>Paris-Sud XI, Université de</p> <p></p> <p>with deep lithospheric causes, i.e. partial detachment of the Tethyan slab and/or a change in motion and the incipient Ligurian rifting. insu-00663367,version1-26Jan2012 Author manuscript, published in "Journal</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2013AGUSM.T31A..02R"><span id="translatedtitle">Consequences of Chixculub Impact for the Tectonic and <span class="hlt">Geodynamic</span> Evolution of the Gulf of Mexico North Carribean Region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rangin, C.; Crespy, A.; Martinez-Reyes, J.</p> <p>2013-05-01</p> <p>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 complexes, but also the relatively recent motion along the Cayman Fault zone (Miocene instead of Eocene). These results are part of a cooperative research-industry programm conducted by CEREGE/EGERIE, Aix-en-Provence and GeoAzur, Nice, with Frontier Basin study group TOTAL S.A., Paris.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2015E%26PSL.417...28L"><span id="translatedtitle">Multiple sulfur isotope composition of oxidized Samoan melts and the implications of a sulfur isotope 'mantle array' in chemical <span class="hlt">geodynamics</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Labidi, J.; Cartigny, P.; Jackson, M. G.</p> <p>2015-05-01</p> <p>To better address how subducted protoliths drive the Earth's mantle sulfur isotope heterogeneity, we report new data for sulfur (S) and copper (Cu) abundances, S speciation and multiple S isotopic compositions (32S, 33S, 34S, 36S) in 15 fresh submarine basaltic glasses from the Samoan archipelago, which defines the enriched-mantle-2 (EM2) endmember. Bulk S abundances vary between 835 and 2279 ppm. About 17 ± 11% of sulfur is oxidized (S6+) but displays no consistent trend with bulk S abundance or any other geochemical tracer. The S isotope composition of both dissolved sulfide and sulfate yield homogeneous ?33S and ?36S values, within error of Canyon Diablo Troilite (CDT). In contrast, ?34S values are variable, ranging between +0.11 and +2.79‰?(±0.12‰?1?) for reduced sulfur, whereas oxidized sulfur values vary between +4.19 and +9.71‰?(±0.80‰, 1?). Importantly, ?34S of the reduced S pool correlates with the 87Sr/86Sr ratios of the glasses, in a manner similar to that previously reported for South-Atlantic MORB, extending the trend to ?34S values up to + 2.79 ± 0.04 ‰, the highest value reported for undegassed oceanic basalts. As for EM-1 basalts from the South Atlantic ridge, the linear ?34S-87Sr/86Sr trend requires the EM-2 endmember to be relatively S-rich, and only sediments can account for these isotopic characteristics. While many authors argue that both the EM-1 and EM-2 mantle components record subduction of various protoliths (e.g. upper or lower continental crust, lithospheric mantle versus intra-metasomatized mantle, or others), it is proposed here that they primarily reflect sediment recycling. Their distinct Pb isotope variation can be accounted for by varying the proportion of S-poor recycled oceanic crust in the source of mantle plumes.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASA-TRS&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19750005831&hterms=laser+lip&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dlaser%2Blip"><span id="translatedtitle">Laser <span class="hlt">geodynamic</span> satellite thermal/optical/ vibrational analyses and testing. Volume 2: Technical report, book 1. [retroreflector design</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1974-01-01</p> <p>The results of the LAGEOS thermal/optical/vibrational analysis and test program are reported. Through analyses and tests it is verified that the MSFC LAGEOS design provides a retroreflector thermal environment which maintains acceptable retroflector internal thermal gradients. The technical results of the study, organized by the major task areas are presented. The interrelationships of the major tasks are described and the major decisions are identified.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=EPRINT&redirectUrl=http://rainier.seis.sc.edu/camelia/Pubs/Mucuta_et_al_06.pdf"><span id="translatedtitle">Constraints from Moho geometry and crustal thickness on the <span class="hlt">geodynamic</span> origin of the Vrancea Seismogenic Zone (Romania)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p>Knapp, Camelia Cristina</p> <p></p> <p>narrow (30×70×200km3 ) near vertical zone atypical for a Wadati­Benioff plane, located in front Wadati­ Benioff planes that mark the subducting slab. Bird, in 1979, proposed delamination on a Wadati­Benioff plane. Delamination is thought to be caused by gravitational instability of over-thickene</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2014JAESc..96..178G"><span id="translatedtitle">Intra-platform tectono-sedimentary response to <span class="hlt">geodynamic</span> transition along the margin of the Tarim Basin, NW China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gao, Zhiqian; Fan, Tailiang</p> <p>2014-12-01</p> <p>The Tarim Basin has experienced three tectonic evolutionary phases from the Cambrian to Ordovician: (1) Regional extension from the late Neoproterozoic to Mid-Early Cambrian, (2) Relatively weak regional compression from the Late Cambrian to Mid-Early Ordovician, and (3) Regional compression during the Late Ordovician. Intra-platform tectonic and sedimentary characteristics indicate a clear linkage to the tectonic evolution of the basin margin during early Paleozoic time. During the Cambrian, small intra-platform rift-related depressions formed during an extensional setting. During the Mid-Early Ordovician, a transition from extension to compression caused formation of the Tazhong and Tabei paleo-uplifts and major unconformities T74 (base of the Late Ordovician). The evolving paleo-geomorphology led to differentiation of sedimentary facies, and numerous intra-platform shoals formed during deposition of the Early Ordovician Yingshan Formation. During the Late Ordovician, regional compression began, which changed the platform margin slopes into four slopes that surrounded the three isolated island uplifts of Tabei, Tazhong, and Tangnan in the Late Ordovician. Simultaneously, the basin margin dynamic conditions also changed the relative sea level and filling pattern of the basin. In the Early and Middle Cambrian, the Tarim Basin mainly developed a progradational ramp-type platform due to relative sea level fall. From the Late Cambrian to Early Ordovician the relative sea level began to rise, resulting in an aggradational-retrograding rimmed margins-type platform. In the Late Ordovician, along with a further rise in relative sea level, the basin mainly developed isolated platform.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASA-TRS&redirectUrl=http://ntrs.nasa.gov/search.jsp?R=19750015863&hterms=Cube&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DCube"><span id="translatedtitle">Laser <span class="hlt">geodynamic</span> satellite thermal/optical/vibrational analysis and testing, volume 2, book 2. [cubes and far fields</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1975-01-01</p> <p>The main tasks described involved an interferometric evaluation of several cubes, a prediction of their dihedral angles, a comparison of these predictions with independent measurements, a prediction and comparison of far field performance, recommendations as to revised dihedral angles and a subsequent analysis of cubes which were reworked to confirm the recommendations. A tolerance study and theoretical evaluation of several cubes was also performed to aid in understanding the results. The far field characteristics evaluated included polarization effects and treated both intensity distribution and encircled energy data. The energy in the 13.2 - 16.9 arc-sec annular region was tabulated as an indicator of performance sensitivity. The results are provided in viewgraph form, and show the average dihedral angle of an original set of test cubes to have been 1.8 arc-sec with an average far field annulus diameter of 18 arc-sec. Since the peak energy in the 13.2 - 16.9 arc-sec annulus was found to occur for a 1.35 arc-sec cube, and since cube tolerances were shown to increase the annulus diameter slightly, a nominal dihedral angle of 1.25 arc-sec was recommended.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-MAS&redirectUrl=http://academic.research.microsoft.com/Publication/40448538"><span id="translatedtitle"><span class="hlt">Geodynamics</span> of the western part of the Mongolia–Okhotsk collisional belt, Trans-Baikal region (Russia) and Mongolia</span></a></p> <p><a target="_blank" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p>Yu. A Zorin</p> <p>1999-01-01</p> <p>After the western edge of the Mongolian microcontinent joined the Siberian continent in the region of Central Mongolia in the earliest Permian, these two continental blocks remained turned at an angle of about 120° with respect to each other and separated (on greater extent of their present-day boundary) by an enormous gulf of the Paleopacific called the Mongolia–Okhotsk ocean. Closure</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2014SolE....5.1087H"><span id="translatedtitle">Using the level set method in <span class="hlt">geodynamical</span> modeling of multi-material flows and Earth's free surface</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hillebrand, B.; Thieulot, C.; Geenen, T.; van den Berg, A. P.; Spakman, W.</p> <p>2014-11-01</p> <p>The level set method allows for tracking material surfaces in 2-D and 3-D flow modeling and is well suited for applications of multi-material flow modeling. The level set method utilizes smooth level set functions to define material interfaces, which makes the method stable and free of oscillations that are typically observed in case step-like functions parameterize interfaces. By design the level set function is a signed distance function and gives for each point in the domain the exact distance to the interface as well as on which side it is located. In this paper we present four benchmarks which show the validity, accuracy and simplicity of using the level set method for multi-material flow modeling. The benchmarks are simplified setups of dynamical geophysical processes such as the Rayleigh-Taylor instability, post-glacial rebound, subduction and slab detachment. We also demonstrate the benefit of using the level set method for modeling a free surface with the sticky air approach. Our results show that the level set method allows for accurate material flow modeling and that the combination with the sticky air approach works well in mimicking Earth's free surface. Since the level set method tracks material interfaces instead of materials themselves, it has the advantage that the location of these interfaces is accurately known and that it represents a viable alternative to the more commonly used tracer method.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-MAS&redirectUrl=http://academic.research.microsoft.com/Publication/41166022"><span id="translatedtitle">Age of the source of the Jarrafa gravity and magnetic anomalies offshore Libya and its <span class="hlt">geodynamic</span> implications</span></a></p> <p><a target="_blank" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p>Giuma Reeh; Tahar Aïfa</p> <p>2008-01-01</p> <p>The interpretation of the Jarrafa magnetic and gravity highs, NW Libyan offshore, suggests that it may be caused by a body of high-density and high magnetization. Analysis of their power spectra indicates two groups of sources at: (1) 2.7km depth, probably related to the igneous rocks, some of which were penetrated in the JA-1 borehole, (2) 5km depth, corresponding to</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-MAS&redirectUrl=http://www.gm.univ-montp2.fr/spip/IMG/pdf/Reply_to_comment_3.pdf"><span id="translatedtitle">Latest-Cretaceous\\/Paleocene karsts with marine infillings from Languedoc (South of France); paleogeographic, hydrogeologic and <span class="hlt">geodynamic</span> implications</span></a></p> <p><a target="_blank" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p>Pierre-Jean Combes; Bernard Peybernès; Marie-José Fondecave-Wallez; Michel Séranne; Jean-Luc Lesage; Hubert Camus</p> <p>2007-01-01</p> <p>The Latest Cretaceous\\/Paleocene paleokarsts from Bas-Languedoc (South of France) are characterized by : 1) exokarstic paleosurfaces (sink holes, pinnacles, canyons) which are mostly superimposed onto the Late Jurassic limestones and partly filled up with breccias and sandy clays containing Paleocene planktonic foraminifera; 2) endokarstic cavities filled up by sandy pelites and laminated mudstones with similar micropaleontological assemblage. All these cavities</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2007JSAES..24...69R"><span id="translatedtitle">Genesis and <span class="hlt">geodynamic</span> significance of Mesoproterozoic and Early Cretaceous tholeiitic dyke swarms from the São Francisco craton (Brazil)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rosset, A.; De Min, A.; Marques, L. S.; Macambira, M. J. B.; Ernesto, M.; Renne, P. R.; Piccirillo, E. M.</p> <p>2007-06-01</p> <p>The eastern border of the São Francisco craton is characterized by widespread Mesoproterozoic (˜1.0 Ga) tholeiitic dykes and minor analogues of Early Cretaceous age (˜130 Ma). The Mesoproterozoic dykes (Salvador, Olivença, Espinhaço, Diamantina) show large elemental and Sr-Nd isotopic variations that suggest different parental melts related to a small-scale heterogeneous mantle of depleted residua and enriched components (Statistical Upper Mantle Assemblage, SUMA), responsible for plume- and crust-type signatures. The Mesoproterozoic intrusions, compatible with early stages of Rodinia breakup, may represent the initial breakup of the São Francisco-Congo junction. Early Cretaceous dykes (Espinhaço) reveal normal and reversed polarities, indicating two distinct intrusive periods. These intrusions have elemental and Sr-Nd isotopic compositions similar to those of the coeval (˜132 Ma) high-TiO 2 tholeiites from southern Paraná Basin (Urubicí-type, Brazil) and northern Etendeka (Khumib-type, Namibia). The genesis of these tholeiites requires lithospheric mantle components, as represented by K-alkaline (and carbonatitic) rocks from the Asuncion-Sapucai graben (Paraguay), that highlight the intriguing Pb-isotope relationships involving the Urubicí-Khumib tholeiites. The essential role of the Tristan plume is difficult to determine. The spatial distribution of such uncommon high-TiO 2 tholeiites reveals that similar lithospheric components may exist in different cratonic blocks and associated mobile belts.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-MAS&redirectUrl=http://academic.research.microsoft.com/Publication/46532144"><span id="translatedtitle"><span class="hlt">Geodynamic</span> evolution of the Pan-African orogenic belt: A new interpretation of the Hoggar shield (Algerian Sahara)</span></a></p> <p><a target="_blank" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p>J. M. L. Bertrand; R. Caby</p> <p>1978-01-01</p> <p>Zusammenfassung  Der panafrikanische Orogen-Gürtel des Hoggar-Gebirges in Südalgerien erstreckt sich über eine Breite von ca. 800 km und entspricht einer extrem eingeengten, aus komplexen geologischen Einheiten aufgebauten mobilen Zone. In seinem westlichen Teil zeugen bereits die untersten mächtigen metasedimentären Ablagerungen sowie die alkalischen und hyperalkalischen Intrusionen des mittleren Proterozoikums von der frühen Mobilität eines N-S streichenden ensialischen Bereiches. Vor ca. 800</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=EPRINT&redirectUrl=http://www.geologie.ens.fr/~vigny/articles/Walpersdorf_etal_Geodynamics_1999.pdf"><span id="translatedtitle">PERGAMON <span class="hlt">Geodynamics</span> 17 "0888# 114125 9153!2696:88:, ! see front matter 0888 Elsevier Science Ltd[ All rights reserved[</span></a></p> <p><a target="_blank" href="http://www.osti.gov/eprints/">E-print Network</a></p> <p>Vigny, Christophe</p> <p></p> <p>Abstract In November 0880\\ a network of about 29 GPS sites were measured in Djibouti "Somalian plate day data set include measurements from 0880 to 0884 on the large!scale baselines "Arta\\ Djibouti! Sana|a\\ YemenÐAddis Ababa\\ Ethiopia# and repeat measurements on more local baselines in Djibouti[ The station</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2014IJEaS.103.1533F"><span id="translatedtitle">Variscan orogeny in Corsica: new structural and geochronological insights, and its place in the Variscan <span class="hlt">geodynamic</span> framework</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Faure, Michel; Rossi, Philippe; Gaché, Julien; Melleton, Jérémie; Frei, Dirk; Li, Xianhua; Lin, Wei</p> <p>2014-09-01</p> <p>In Western Corsica, remnants of pre-batholitic lithological and metamorphic assemblages are preserved as km-scale septa enclosed within Lower Carboniferous to Early Permian plutons. Two groups of septa were recognized: (1) the Argentella and Agriates-Tenda fragments correspond to Neoproterozoic rocks deformed and metamorphosed during the Cadomian-Panafrican orogeny, and (2) the Zicavo, Porto-Vecchio, Solenzara-Fautea, Belgodère, Topiti, and Vignola fragments consist of Variscan metamorphic rocks. The lithological content and the main ductile deformation events for each septum are presented. In the Zicavo, Porto-Vecchio, and Topiti septa, a top-to-the-SW ductile shearing (D1 event) coeval with an amphibolite facies metamorphism is responsible for crustal thickening at ca 360 Ma. This main event was preceded by eclogite and granulite facies metamorphic events preserved as restites within migmatites dated at ca 345-330 Ma. A top-to-the-SE ductile shearing (D2 event) coeval with the crustal melting accommodated the exhumation of the D1 event. In contrast, the Belgodère segment is peculiar as it exhibits a top-to-the-E vergence, although retrogressed high-pressure rocks are also recognized. The pre-Permian fragments are arranged in four NW-SE-striking stripes that define a SW-NE zoning with (1) a Western domain in Topiti, Vignola, Zicavo, Porto-Vecchio, and Solenzara-Fautea; (2) a Neoproterozoic basement with its unconformable Early Paleozoic sedimentary cover in Argentella; (3) an Eastern metamorphic domain in Belgodère; (4) another Neoproterozoic basement with its Upper Paleozoic sedimentary cover in Agriates-Tenda. The Argentella basement is separated from the Western and Eastern domains by two sutures: S1 and S2. The Variscan Corsica represents the Eastern part of the Sardinia-Corsica-Maures segment. The comparison of this segment with other Variscan domains allows us to propose some possible correlations. We argue that the Western domain, Argentella, Belgodère, and Agriates-Tenda domains can be compared with the Southern Variscan belt exposed in French Massif Central-Southern Massif Armoricain, Armorica microblock, Léon block, respectively.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2013AGUFMDI11A2164S"><span id="translatedtitle">Seismic Anisotropy and Mantle Flow, Comparing Global <span class="hlt">Geodynamic</span> Models and Shear Wave Splitting Observations in Eastern Canada</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schow, B.; Darbyshire, F. A.; Forte, A. M.; Levin, V. L.</p> <p>2013-12-01</p> <p>Seismic anisotropy is often attributed to lattice preferred orientation of olivine in the upper mantle that originates from coherent deformation related to the past of present mantle flow. It is not yet clear whether anisotropy is dominated by contributions from the asthenosphere or if there is a significant contribution from the lithosphere. This anisotropy can be probed using analysis of the birefringence of shear waves from earthquakes at large distances. The data analyzed for this study were collected at four seismic stations of the Canadian National Seismic Network (A11, A21, A54, A64) on the shores of the St. Lawrence River in the Charlevoix region of Quebec. Two of these stations are situated on the southeast side of the Appalachian Front and two are situated on the northwest side. 13 years of teleseismic data were analyzed for shear wave splitting, using the cluster analysis method of Teanby et al (2004). We obtained about 70 new reliable results at each station. Mean splitting directions give a general east-west trend; however, individual measurements show systematic backazimuthal variation. Arrivals from the south show fast directions between 60 and 90 degrees, while arrivals from the north yield fast directions between 90 and 130 degrees with large scatter. This directional pattern appears to be common to all four stations analyzed. Tomography-based global models of the mantle convective flow predict flow directions and rate, as well as directions and magnitudes of maximum strain. In the upper mantle beneath the region we have probed, the flow models predict considerable variability of the flow and strain attributes with depth, prompting investigation of multiple layers of anisotropy. We investigate depth variation in the anisotropic properties of the upper mantle beneath Charlevoix area of Quebec using patterns of directional variation in measurements of anisotropy and forward modeling in simple layered structures. Observations of shear wave splitting at four stations plotted as a function of source polarization (equivalent to backazimuth). Red circles show splitting values with error bars. Blue squares show null measurements at corresponding backazimuth. Green line indicates average splitting direction obtained by stacking all data.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2014EGUGA..16.4850N"><span id="translatedtitle">Mesozoic and Cenozoic plate tectonics in the High Arctic: new 2D seismic data and <span class="hlt">geodynamic</span> models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nikishin, Anatoly; Kazmin, Yuriy; Glumov, Ivan; Petrov, Eugene; Poselov, Viktor; Burov, Evgueni; Gaina, Carmen</p> <p>2014-05-01</p> <p>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.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2004AGUFMGP41A0824B"><span id="translatedtitle">Comparative Analysis of Biogeographic, Sedimentologic and Paleomagnetic Data and the <span class="hlt">Geodynamics</span> of Terranes of Northeast Asia in Late Permian</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Biakov, A.; Kolosev, E.</p> <p>2004-12-01</p> <p>We present the first consistent model of the relative locations of the most important tectonic structures in Northeast of Asia for Late Paleozoic time. This model is based on comparative analysis of paleomagnetic, sedimentologic and biogeographic data. Results of research by the authors and critically reviewed data of the other researchers are used. The current paleomagnetic data for Permian rocks from the Northeast region still remain scanty and are practically non-existent for some tectonic structures such as the Okhotsk microcontinent. Nevertheless we believe that it can be shown that there was no major (thousands of kilometers) horizontal motion between the separate tectonic blocks of Yana-Kolyma fold-and-thrust area, at least starting Middle Paleozoic. In paleogeographic terms Northeast Asia in the Permian represented a system of marine basins of various types. Okhotsk microcontinent was outboard from the Siberian craton to the southeast (present day coordinates). A system of deepwater marginal type marine basins lay to the east of the Siberian craton. The Koni-Taigonos volcanic arc was along the south edge, and. its erosion products formed deepwater fore-arc basins. Significant differences between the Permian bivalve communities on the Omolon microcontinent and contemporary communities of Verkhoyansk indicate the existence of the deepwater Ayan-Yuryakh trough basin. The strata of the latter are characterized as thick (up to 7 km) flysch deposits plus thick diamictites. Paleobiogeographic studies show that major biogeographic units can be clearly distinguished in the Verkhoyansk-Okhotsk on one side and Kolyma-Omolon biochores on the other, which can be currently ranked as sub regions. Verkhoyansk-Okhotsk sub region includes Verkhoyansk epicontinental sea shelf and the Okhotsk microcontinent shelf. These can be further subdivided into a number of provinces. The Kolyma-Omolon sub region includes continental shelves of the Omolon, Omulevka, Prykolyma microcontinents and the Koni-Taigonos arc. The degree of diversity of these two biochores is so great that it requires separate development and indicates the existence of a major biogeographical barrier during the Permian. The distinctions between the Verkhoyansk-Okhotsk and Kolyma-Omolon sub regions are found througout the whole Permian and over other faunal groups such as brachiopods and ammonites as well as over the rest of bivalve taxons. Multiple use of biogeographic, sedimentologic and paleomagnetic materials including new original data on sedimentology and paleomagnetism allowed a model of the relative positions of the basic tectonic structures of Verkhoyansk-Kolyma fold-and-thrust area in the second half of the Permian. . These studies have been supported by the Russian Foundation for Basic Research, grant N 03-05-96012-Arctic and Far East Branch Russian Academy of Sciences, Grant N 04-3-A-08-014.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=SCIGOV-MAS&redirectUrl=http://academic.research.microsoft.com/Publication/3544584"><span id="translatedtitle">Paleomagnetic constraints on the <span class="hlt">geodynamic</span> history of the major blocks of China from the Permian to the present</span></a></p> <p><a target="_blank" href="http://academic.research.microsoft.com/">Microsoft Academic Search </a></p> <p>Randolph J. Enkin; Zhenyu Yang; Yan Chen; Vincent Courtillot</p> <p>1992-01-01</p> <p>All available paleomagnetic poles of Upper Permian to Tertiary age from the main blocks of China are critically reviewed with the aim of placing constraints on models of the formation and the subsequent deformation of the region. For first-order analysis, apparent polar wander paths are constructed for the major blocks. The compatibilities and contradictions between the geological and paleomagnetic records</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2014ISPAr.XL8...53K"><span id="translatedtitle"><span class="hlt">Geodynamics</span> of the Indian Lithospheric Plate relative to the neighbouring Plates as revealed by Space Geodetic Measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Krishna, S.; Mathew, J.; Majumdar, R.; Roy, P.; Vinod Kumar, K.</p> <p>2014-11-01</p> <p>The Indian Plate is highly dynamic in nature which in turn makes the Indo-Eurassian collision zone the foci of most of the historic large magnitude earthquakes. Processing of positional information from continuously observing reference stations is one of the space based geodetic techniques used globally and nationally to understand the crustal dynamics. The present study evaluates the dynamic nature of the Indian plate relative to its adjoining plates using the permanent GPS data (2011 to 2013) of 12 International GNSS Service (IGS), which are spread across the Indian, Eurassian, Australian, Somaliyan and African plates. The data processing was carried out using GAMIT/GLOBK software. The results indicate that the average velocity for the two IGS stations on the Indian Plate (Hyderabad and Bangalore) is 54.25 mm/year towards NE in the ITRF-2008 reference frame. The relative velocity of various stations with respect to the Indian plate has been estimated using the Bangalore station and has been found that the stations in the Eurasian plate (Lhasa, Urumqi, Bishkek and Kitab) are moving with velocity ranging from 25 to 33 mm/year in the SE direction resulting in compressional interaction with the Indian plate. This study reveals and confirms to the previous studies that the Indian- Eurassian-Australian Plates are moving at different relative velocities leading to compressional regimes at their margins leading to seismicity in these zones.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2012E%26PSL.357..405W"><span id="translatedtitle">Layer-parallel shortening across the Sevier fold-thrust belt and Laramide foreland of Wyoming: spatial and temporal evolution of a complex <span class="hlt">geodynamic</span> system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weil, Arlo Brandon; Yonkee, W. Adolph</p> <p>2012-12-01</p> <p>Varying patterns of layer-parallel shortening (LPS) and vertical-axis rotations from the thin-skin Sevier fold-thrust belt to the thick-skin Laramide foreland of Wyoming are quantified from integrated structural, anisotropy of magnetic susceptibility (AMS), and paleomagnetic analyses. Within the Sevier belt, widespread early LPS was accommodated by spaced cleavage, fracture sets, minor folds, and minor faults. LPS directions are subperpendicular to structural trends of systematically curved thrust sheets of the Wyoming salient, reflecting a combination of primary dispersion and secondary rotation during thrusting. Within the Laramide foreland, limited LPS was accommodated mostly by minor faults with conjugate wedge and strike-slip geometries. LPS directions in gentler fold limbs vary from perpendicular to acute with structural trends of variably oriented, anastomosing basement-cored arches. Steep forelimbs display more complex relations, including younger fault sets that developed during evolving stress states and localized vertical-axis rotations. Although internal strain is limited, weak AMS lineations defined by kinked and rotated phyllosilicates are widely developed and consistently oriented perpendicular to measured LPS directions. Palinspastically restored LPS directions, corrected for paleomagnetically determined vertical-axis rotations, vary on average from W-E in the Sevier belt to WSW-ENE in the Laramide foreland. In detail, LPS directions display deflections related to primary sedimentary wedge geometry and basement fabrics. LPS in the Sevier belt is interpreted to partly reflect stress transmitted from the hinterland through the growing orogenic wedge and topographic stress along the front of the wedge. LPS in the Laramide foreland is interpreted to partly reflect basal traction during flat-slab subduction beneath thick cratonic lithosphere, with spatial-temporal variations in stress trajectories related to basement heterogeneities and evolving fault systems. Evidence for significant late N-S Laramide shortening, as proposed by multi-stage shortening models, is not observed.</p> </li> <li> <p><a target="resultTitleLink" href="http://www.science.gov/scigov/desktop/en/ostiblue/service/link/track?type=RESULT&searchId=topic-pages&collectionCode=NASAADS&redirectUrl=http://adsabs.harvard.edu/abs/2009EGUGA..1111927A"><span id="translatedtitle">The evolution of bimodal volcanism in NW Anatolia (Turkey): Petrologic and <span class="hlt">geodynamic</span> implications for the origin of compositional gaps in calc-alkaline and shoshonitic lavas.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Altunkaynak, S.</p> <p>2009-04-01</p> <p>The Aegean province is a site of nearly continuous magmatism since the Early Eocene although the tectonic settings and melt sources of this widespread magmatism appear to have varied through time. NW Anatolia (Turkey) is part of the Aegean extensional province, which is one of the most seismically active and rapidly deforming domains of the Alpine-Himalayan mountain belt. The geological record of the Cenozoic magmatic events in the Aegean province is almost complete in western Anatolia, where both the modern landscape and the surface rocks are predominantly volcanic.Neogene young magmatism in NW Anatolia is associated commonly with NNE-SSW-trending lines of vents and/or fault systems that were also bounding local lacustrine depocenters. Magmatism evolved from all association of medium to high-K calc-alkaline, to shoshonitic to mildly alkaline and alkaline series. The early magmatic pulse in the region is represented by the Oligo-Miocene granitoid plutons and volcanic units . Volcanic rocks of this stage is characterized by medium to high-K calc-alkaline andesite, dacite to rhyolite that are overlain by ignimbrite flows, pumiceous air-fall and ash fall deposits that are intercalated with Lower to Middle Miocene lacustrine rocks and coal seams in NW Anatolia. Following this stage of volcanism, compositionally bimodal volcanism occurred by fissure eruptions and formed small cones in the wide area. The change from large-volume outpourings of intermediate magma to small-volume bimodal volcanism started in the the Early Miocene in the north and Middle Miocene in the south. Basic parental magmas of Early Miocene volcanism were produced from sources related to EM1-type mantle previously modified by subduction, whereas silicic rocks were probably produced through fractional crystallization implying the compositional gap between CA basalt and rhyolite has been generated by fractional crystallization. Assimilation of silicic crust has also occurred along with fractionation. Significant crustal component was recognized only in some slightly peraluminous granites and rhyolites with low contents of HFS elements in the south. The younger (Early-Middle Miocene) bimodal volcanism belongs to shoshonitic-mildly alkaline series is represented by transitional basalts, basaltic trachy-andesites and trachytes-phonolites-rhyolites. The ensuing Middle Miocene volcanism produced mildly alkaline lavas that are spatially associated with NNE-trending transtensional fault systems. The Early and Middle Miocene bimodal basic-acid volcanism presents a transitional chemical affinity from calc-alkaline collision related affinity to within plate alkaline series. Sr-Nd isotope data suggest that coexisting mafic and felsic magmas derived from lithospheric mantle source yielding depleted but LILE-enriched compositions, with subsequent contamination. The inferred crustal contamination appears to have been diminished by the Middle Miocene