WorldWideScience

Sample records for earth crust

  1. Lime-Crusted Rammed Earth: Materials Study

    OpenAIRE

    Mileto, Camilla; Vegas López-Manzanares, Fernando; Alejandre, Francisco Javier; Martín, Juan Jesús; Garcia Soriano, Lidia

    2013-01-01

    This study analyses the durability of rammed-earth wall construction techniques. The analysis focuses on three medieval masonry types from the Castle of Villavieja (Castellón, Spain) using two variations of lime-reinforced rammed earth in its walls: lime-crusted rammed earth and brick-reinforced rammed earth. Materials analysis reveals the good properties of the materials used in the outer wall facing despite its age. It also clearly shows how deterioration depends more on the construction t...

  2. Relamination of mafic subducting crust throughout Earth's history

    Science.gov (United States)

    Maunder, Ben; van Hunen, Jeroen; Magni, Valentina; Bouilhol, Pierre

    2016-09-01

    Earth has likely cooled by several hundred degrees over its history, which has probably affected subduction dynamics and associated magmatism. Today, the process of compositional buoyancy driven upwelling, and subsequent underplating, of subducted materials (commonly referred to as ;relamination;) is thought to play a role in the formation of continental crust. Given that Archean continental crust formation is best explained by the involvement of mafic material, we investigate the feasibility of mafic crust relamination under a wide range of conditions applicable to modern and early Earth subduction zones, to assess if such a process might have been viable in an early Earth setting. Our numerical parametric study illustrates that the hotter, thicker-crust conditions of the early Earth favour the upward relamination of mafic subducting crust. The amount of relaminating subducting crust is observed to vary significantly, with subduction convergence rate having the strongest control on the volume of relaminated material. Indeed, removal of the entire mafic crust from the subducting slab is possible for slow subduction (∼2 cm/yr) under Archean conditions. We also observe great variability in the depth at which this separation occurs (80-120 km), with events corresponding to shallower detachment being more voluminous, and that relaminating material has to remain metastably buoyant until this separation depth, which is supported by geological, geophysical and geodynamical observations. Furthermore, this relamination behaviour is commonly episodic with a typical repeat time of approximately 10 Myrs, similar to timescales of episodicity observed in the Archean rock record. We demonstrate that this relamination process can result in the heating of considerable quantities of mafic material (to temperatures in excess of 900 °C), which is then emplaced below the over-riding lithosphere. As such, our results have implications for Archean subduction zone magmatism, for

  3. Energy conservation in the earth's crust and climate change.

    Science.gov (United States)

    Mu, Yao; Mu, Xinzhi

    2013-02-01

    Among various matters which make up the earth's crust, the thermal conductivity of coal, oil, and oil-gas, which are formed over a long period of geological time, is extremely low. This is significant to prevent transferring the internal heat of the earth to the thermal insulation of the surface, cooling the surface of the earth, stimulating biological evolution, and maintaining natural ecological balance as well. Fossil energy is thermal insulating layer in the earth's crust. Just like the function of the thermal isolation of subcutaneous fatty tissue under the dermis of human skin, it keeps the internal heat within the organism so it won't be transferred to the skin's surface and be lost maintaining body temperature at low temperatures. Coal, oil, oil-gas, and fat belong to the same hydrocarbons, and the functions of their thermal insulation are exactly the same. That is to say, coal, oil, and oil-gas are just like the earth's "subcutaneous fatty tissue" and objectively formed the insulation protection on earth's surface. This paper argues that the human large-scale extraction of fossil energy leads to damage of the earth's crust heat-resistant sealing, increasing terrestrial heat flow, or the heat flow as it is called, transferring the internal heat of the earth to Earth's surface excessively, and causing geotemperature and sea temperature to rise, thus giving rise to global warming. The reason for climate warming is not due to the expansion of greenhouse gases but to the wide exploitation of fossil energy, which destroyed the heat insulation of the earth's crust, making more heat from the interior of the earth be released to the atmosphere. Based on the energy conservation principle, the measurement of the increase of the average global temperature that was caused by the increase of terrestrial heat flow since the Industrial Revolution is consistent with practical data. This paper illustrates "pathogenesis" of climate change using medical knowledge. The

  4. Gold in meteorites and in the earth's crust

    Science.gov (United States)

    Jones, Robert Sprague

    1968-01-01

    The reported gold contents of meteorites range from 0.0003 to 8.74 parts per million. Gold is siderophilic, and the greatest amounts in meteorites are in the iron phases. Estimates ,of the gold content of the earth's crust are in the range of 0.001 to 0.006 parts per million.

  5. Evolution of the earth's crust: Evidence from comparative planetology

    Science.gov (United States)

    Lowman, P. D., Jr.

    1973-01-01

    Geochemical data and orbital photography from Apollo, Mariner, and Venera missions were combined with terrestrial geologic evidence to study the problem of why the earth has two contrasting types of crust (oceanic and continental). The following outline of terrestrial crustal evolution is proposed. A global crust of intermediate to acidic composition, high in aluminum, was formed by igneous processes early in the earth's history; portions survive in some shield areas as granitic and anorthositic gneisses. This crust was fractured by major impacts and tectonic processes, followed by basaltic eruptions analogous to the lunar maria and the smooth plains of the north hemisphere of Mars. Seafloor spreading and subduction ensued, during which portions of the early continental crust and sediments derived therefrom were thrust under the remaining continental crust. The process is exemplified today in regions such as the Andes/Peru-Chile trench system. Underplating may have been roughly concentric, and the higher radioactive element content of the underplated sialic material could thus eventually cause concentric zones of regional metamorphism and magmatism.

  6. Continental crust formation on early Earth controlled by intrusive magmatism

    Science.gov (United States)

    Rozel, A. B.; Golabek, G. J.; Jain, C.; Tackley, P. J.; Gerya, T.

    2017-05-01

    The global geodynamic regime of early Earth, which operated before the onset of plate tectonics, remains contentious. As geological and geochemical data suggest hotter Archean mantle temperature and more intense juvenile magmatism than in the present-day Earth, two crust-mantle interaction modes differing in melt eruption efficiency have been proposed: the Io-like heat-pipe tectonics regime dominated by volcanism and the “Plutonic squishy lid” tectonics regime governed by intrusive magmatism, which is thought to apply to the dynamics of Venus. Both tectonics regimes are capable of producing primordial tonalite-trondhjemite-granodiorite (TTG) continental crust but lithospheric geotherms and crust production rates as well as proportions of various TTG compositions differ greatly, which implies that the heat-pipe and Plutonic squishy lid hypotheses can be tested using natural data. Here we investigate the creation of primordial TTG-like continental crust using self-consistent numerical models of global thermochemical convection associated with magmatic processes. We show that the volcanism-dominated heat-pipe tectonics model results in cold crustal geotherms and is not able to produce Earth-like primordial continental crust. In contrast, the Plutonic squishy lid tectonics regime dominated by intrusive magmatism results in hotter crustal geotherms and is capable of reproducing the observed proportions of various TTG rocks. Using a systematic parameter study, we show that the typical modern eruption efficiency of less than 40 per cent leads to the production of the expected amounts of the three main primordial crustal compositions previously reported from field data (low-, medium- and high-pressure TTG). Our study thus suggests that the pre-plate-tectonics Archean Earth operated globally in the Plutonic squishy lid regime rather than in an Io-like heat-pipe regime.

  7. Continental crust formation on early Earth controlled by intrusive magmatism.

    Science.gov (United States)

    Rozel, A B; Golabek, G J; Jain, C; Tackley, P J; Gerya, T

    2017-05-18

    The global geodynamic regime of early Earth, which operated before the onset of plate tectonics, remains contentious. As geological and geochemical data suggest hotter Archean mantle temperature and more intense juvenile magmatism than in the present-day Earth, two crust-mantle interaction modes differing in melt eruption efficiency have been proposed: the Io-like heat-pipe tectonics regime dominated by volcanism and the "Plutonic squishy lid" tectonics regime governed by intrusive magmatism, which is thought to apply to the dynamics of Venus. Both tectonics regimes are capable of producing primordial tonalite-trondhjemite-granodiorite (TTG) continental crust but lithospheric geotherms and crust production rates as well as proportions of various TTG compositions differ greatly, which implies that the heat-pipe and Plutonic squishy lid hypotheses can be tested using natural data. Here we investigate the creation of primordial TTG-like continental crust using self-consistent numerical models of global thermochemical convection associated with magmatic processes. We show that the volcanism-dominated heat-pipe tectonics model results in cold crustal geotherms and is not able to produce Earth-like primordial continental crust. In contrast, the Plutonic squishy lid tectonics regime dominated by intrusive magmatism results in hotter crustal geotherms and is capable of reproducing the observed proportions of various TTG rocks. Using a systematic parameter study, we show that the typical modern eruption efficiency of less than 40 per cent leads to the production of the expected amounts of the three main primordial crustal compositions previously reported from field data (low-, medium- and high-pressure TTG). Our study thus suggests that the pre-plate-tectonics Archean Earth operated globally in the Plutonic squishy lid regime rather than in an Io-like heat-pipe regime.

  8. Synthetic petroleum stability under thermobaric conditions of the Earth crust

    Science.gov (United States)

    Serovaiskii, Aleksandr; Kolesnikov, Anton; Kutcherov, Vladimir

    2016-04-01

    Nowadays there are several dozens of large crude oil deposits at the depth more than 10 km (Kutcherov and Krayushkin, 2010). The existence of such deep oil fields at the depth exceeding conventional "oil window" could be explained by the migration of the deep fluid from the asthenosphere. This fluid migrates up to the surface and forms oil and gas deposits in different kind of rocks in the on various depths of the Earth's crust. Crude oil consists of a great numbers of different hydrocarbons. Its precise molecular composition is impossible to investigate nowadays. Instead of the natural hydrocarbons mixture synthetic petroleum with simpler composition was used in the experiments. The synthetic petroleum stability was investigated at the Earth crust thermobaric conditions corresponding to the depth down to 50 km. The experiments were carried out in Diamond Anvil Cells (DAC) with the internal resistive heating. Raman spectroscopy was used to analyse the petroleum composition. The analysis of the sample was made in situ during the experiment. Ruby and Sm:YAG Raman shifts were the controllers of the temperature and pressure inside the sample (Trots et al., 2012; Mao et al., 1986). Three series of the experiments were carried out at 320°C and 0.7GPa, 420°C and 1.2GPa, 450°C and 1.4GPa. After the experiment the Raman spectra of the sample was compared to the reference spectra of the petroleum before the experiment. The comparison showed no changes in the sample's composition after the experiment. Obtained data may explain the existence of deep oil fields located deeper than the "oil window". It can broaden the knowledge about the existing range of depths for the crude oil and natural gas deposits in the Earth crust. The evidence of the petroleum existence in the Earth low crust may support the existence of unconventional, deep abyssal hydrocarbons source.

  9. Morphodynamical geodiversity of the Earth's crust, relief, and landscapes

    Science.gov (United States)

    Lastochkin, Alexander; Zhirov, Andrey; Boltramovich, Sergei

    2014-05-01

    Morphodynamical geodiversity of the Earth's crust is determined by tectonic flows, which create various folded, faulted and injective dislocations. Folded dislocations (plicatives) correspond in plan to the eight types of conic cross-sections and in profile - to variation of the amplitudes. Faulted dislocations (disjunctives) are reflected in the angles of fault planes and the amplitudes of displacements. Injective dislocations vary in size and amplitudes of their vertical penetrations inside sedimentary layers and on the Earth's surface. In turn, surface and above-the-surface material and energy flows, or geoflows, create geotops - elementary landscapes that are tied up to corresponding elementary surfaces. Geotops are responsible for the morphodynamical geodiversity of relief and landscapes. Within the three-dimensional space of the geotop each geoflow can be divided into currents and links. The first of which are transverse to the front of the geoflow, the second - the longitudinal. Geotops and geoflows, mainly descending and lateral, influence each other according to their specifics: lithological, biological, hydrological, thermobaric features, etc. This interaction determines the geodiversity as a whole. By their altitude, gradient and dip azimuth, geotops can be classified as initial (upper), transit (slope) and terminal (lower) - with respect to descending geoflows. By their functional role, geotops can also be divided into: 1) flat-topped and flat-bottomed geotops that are out of the descending geoflows; 2) upper disintegrating geotops (apices, ridges); 3) translators (geotops of faces and feet); 4) vertical barriers (cliffs); 5) intermediate accumulators (terraces); 6) lower accumulators (basins) and conductors (valleys). Geotops and their elementary surfaces influence also the geometry of geoflows, performing the function of disintegrators (centrifugal and bilateral ones), concentrators (centripetal and bilateral ones) or just conductors (straight ones

  10. No evidence for Hadean continental crust within Earth's oldest evolved rock unit

    Science.gov (United States)

    Reimink, J. R.; Davies, J. H. F. L.; Chacko, T.; Stern, R. A.; Heaman, L. M.; Sarkar, C.; Schaltegger, U.; Creaser, R. A.; Pearson, D. G.

    2016-10-01

    Due to the acute scarcity of very ancient rocks, the composition of Earth's embryonic crust during the Hadean eon (>4.0 billion years ago) is a critical unknown in our search to understand how the earliest continents evolved. Whether the Hadean Earth was dominated by mafic-composition crust, similar to today's oceanic crust, or included significant amounts of continental crust remains an unsolved question that carries major implications for the earliest atmosphere, the origin of life, and the geochemical evolution of the crust-mantle system. Here we present new U-Pb and Hf isotope data on zircons from the only precisely dated Hadean rock unit on Earth--a 4,019.6 +/- 1.8 Myr tonalitic gneiss unit in the Acasta Gneiss Complex, Canada. Combined zircon and whole-rock geochemical data from this ancient unit shows no indication of derivation from, or interaction with, older Hadean continental crust. Instead, the data provide the first direct evidence that the oldest known evolved crust on Earth was generated from an older ultramafic or mafic reservoir that probably surfaced the early Earth.

  11. Abyssal Sequestration of Nuclear Waste in Earth's Crust

    Science.gov (United States)

    Germanovich, L. N.; Garagash, D.; Murdoch, L. C.; Robinowitz, M.

    2013-12-01

    This work outlines a new method for disposing of hazardous (e.g., nuclear) waste. The technique is called Abyssal Sequestration, and it involves placing the waste at extreme depths in Earth's crust where it could achieve the geologically-long period of isolation. Abyssal Sequestration involves storing the waste in hydraulic fractures driven by gravity, a process we term gravity fracturing. In short, we suggest creating a dense fluid (slurry) containing waste, introducing the fluid into a fracture, and extending the fracture downward until it becomes long enough to propagate independently. The fracture will continue to propagate downward to great depth, permanently isolating the waste. Storing solid wastes by mixing them with fluids and injecting them into hydraulic fractures is a well-known technology. The essence of our idea differs from conventional hydraulic fracturing techniques only slightly in that it uses fracturing fluid heavier than the surrounding rock. This difference is fundamental, however, because it allows hydraulic fractures to propagate downward and carry wastes by gravity instead of or in addition to being injected by pumping. An example of similar gravity-driven fractures with positive buoyancy is given by magmatic dikes that may serve as an analog of Abyssal Sequestration occurring in nature. Mechanics of fracture propagation in conditions of positive (diking) and negative (heavy waste slurry) buoyancy is similar and considered in this work for both cases. Analog experiments in gelatin show that fracture breadth (horizontal dimension) remains nearly stationary when fracturing process in the fracture 'head' (where breadth is 'created') is dominated by solid toughness, as opposed to the viscous fluid dissipation dominant in the fracture tail. We model propagation of the resulting 'buoyant' or 'sinking' finger-like fracture of stationary breadth with slowly varying opening along the crack length. The elastic response of the crack to fluid loading

  12. Thermochemical structure of the Earth's mantle and continental crust

    DEFF Research Database (Denmark)

    Guerri, Mattia

    task. In this thesis, I adopt a multidisciplinary approach geared towards the unification of geochemical and geophysical constraints within a framework provided by theoretical and experimental mineral and rock physics. In the first part, I focus on the Continental crust, assessing the relations between...... elastic properties and chemical composition taking into account the thermal and pressure effects. I found that even small amounts of H2O have an extremely high impact on the elastic properties of crustal rock. In addition, I show the potential that modifications in the stable mineralogical assemblage have...

  13. The contribution of amphibole from deep arc crust to the silicate Earth's Nb budget

    Science.gov (United States)

    Tiepolo, Massimo; Vannucci, Riccardo

    2014-11-01

    The continental crust (CC) and the depleted mantle (DM) are generally assumed to be complementary reservoirs within the Earth. However, the mixture between CC and upper mantle does not generate the Nb/Ta and Nb/La ratios of chondrites. A reservoir with superchondritic ratios for Nb/Ta and Nb/La is thus required in the Earth's system. The occurrence of a hidden amphibole reservoir in the lower arc crust has been recently proposed. This, coupled with the capability of calcic amphibole to give rise to a superchondritic Nb/Ta and Nb/La reservoir, led us to determine to what extent amphibole-rich ultramafic rocks can account for the Nb (and Nb/Ta, Nb/La as well) imbalance on Earth. We have considered lower crust mafic and ultramafic amphibole-rich intrusive rocks from collisional settings worldwide. Because CC is considered to have primarily formed in collisional setting these rocks are important for its genetic model. We modeled Nb, Ta and La contents of the hidden Nb reservoir by mass balance calculations between continental crust, depleted mantle and primitive mantle. Modeling shows that amphibole-rich mafic lower crust can solve the so-called Nb paradox if large volumes of materials are supposed to be returned into the mantle during the Earth's history. A possible mechanism is recycling, particularly in Precambrian times, of eclogites that underwent pre-eclogitic melting in the amphibolite facies field and then recrystallized under eclogite-facies conditions.

  14. Thermochemical structure of the Earth's mantle and continental crust

    DEFF Research Database (Denmark)

    Guerri, Mattia

    A detailed knowledge of the Earth's thermal structure and chemical composition is fundamental in order to understand the processes driving the planet ormation and evolution. The inaccessibility of most of the Earth's interior makes the determination of its thermo-chemical conditions a challenging...... in determining crustal seismic discontinuities. In the second chapter, I deal about the possibility to disentangle the dynamic and isostatic contribution in shaping the Earth's surface topography. Dynamic topography is directly linked to mantle convection driven by mantle thermo-chemical anomalies, and can...... argue therefore that our understandings of the lithosphere density structure, needed to determine the isostatic topography, and of the mantle density and viscosity, required to compute the dynamic topography, are still too limited to allow a robust determination of mantle convection effects on the Earth...

  15. A metasomatic mechanism for the formation of Earth's earliest evolved crust

    Science.gov (United States)

    Baker, Don R.; Sofonio, Kassandra

    2017-04-01

    Following giant impacts the early Hadean Earth was shrouded in a steam atmosphere for durations on the order of 1 Ma. In order to investigate the potential of this atmosphere to fractionate major elements between various silicate reservoirs and influence a planet's geochemical evolution, we performed experiments simulating the interaction of a post-giant-impact steam atmosphere with a bulk silicate Earth (BSE) composition. Our experiments indicate that the composition of the solute in a water-rich atmosphere at 10 MPa and ∼727 °C is remarkably similar to that of Earth's modern continental crust and would constitute up to 10% of the solution mass. This solute composition is similar to solute compositions previously measured at higher pressures, but distinct from those of near-solidus peridotite melts. Mass balance calculations based upon the hypothesis that Earth's initial water concentration was similar to that in CI carbonaceous chondrites, and that degassing and metasomatism produced the BSE, indicate that metasomatism could produce from 10 to 300% of the mass of the modern crust. If instead the amount of metasomatism is estimated by the difference between the water concentration in the BSE and in the depleted upper mantle, then a mass of up to approximately 4% of the current crust could be produced by metasomatism. Using results of earlier research we find that the solute is expected to have a smaller Sm/Nd ratio than the residual BSE, and if the solute was formed early in Earth's history its Nd isotopic signatures would be highly enriched. Although we cannot be certain that the metasomatic process created a significant fraction of Earth's crust in the early Hadean, our research indicates that it has the potential to form crustal nuclei and possibly was responsible for the production of incompatible-element enriched reservoirs in the early Earth, as seen in the isotopic signatures of Archean rocks.

  16. Emergence of blueschists on Earth linked to secular changes in oceanic crust composition

    Science.gov (United States)

    Palin, Richard M.; White, Richard W.

    2016-01-01

    The oldest blueschists--metamorphic rocks formed during subduction--are of Neoproterozoic age, and 0.7-0.8 billion years old. Yet, subduction of oceanic crust to mantle depths is thought to have occurred since the Hadean, over 4 billion years ago. Blueschists typically form under cold geothermal gradients of less than 400 °C GPa-1, so their absence in the ancient rock record is typically attributed to hotter pre-Neoproterozoic mantle prohibiting such low-temperature metamorphism; however, modern analogues of Archaean subduction suggest that blueschist-facies metamorphic conditions are attainable at the slab surface. Here we show that the absence of blueschists in the ancient geological record can be attributed to the changing composition of oceanic crust throughout Earth history, which is a consequence of secular cooling of the mantle since the Archaean. Oceanic crust formed on the hot, early Earth would have been rich in magnesium oxide (MgO). We use phase equilibria calculations to show that blueschists do not form in high-MgO rocks under subduction-related geothermal gradients. Instead, the subduction of MgO-rich oceanic crust would have created greenschist-like rocks--metamorphic rocks formed today at low temperatures and pressures. These ancient metamorphic products can hold about 20% more water than younger metamorphosed oceanic crust, implying that the global hydrologic cycle was more efficient in the deep geological past than today.

  17. Differentiation of crusts and cores of the terrestrial planets - Lessons for the early earth

    Science.gov (United States)

    Solomon, S. C.

    1980-01-01

    The extent and mechanisms of global differentiation and the early thermal and tectonic histories of the terrestrial planets are surveyed in order to provide constraints on the first billion years of earth history. Indirect and direct seismic evidence for crusts on the moon, Mars and Venus is presented, and it is pointed out that substantial portions of these crusts have been in place since the cessation of heavy bombardment of the inner solar system four billion years ago. Evidence for sizable cores on Mars and Mercury and a small core on the moon is also discussed, and the heat involved in core formation is pointed out. Examination of the volcanic and tectonic histories of planets lacking plate tectonics indicates that core formation was not closely linked to crust formation on the moon or Mars, with chemical differentiation restricted to shallow regions, and was much more extensive on Mercury. Extension of these considerations to the earth results in a model of a hot and vigorously convecting mantle with an easily deformable crust immediately following core formation, and the gradual development of a lithosphere and plates.

  18. Role of minerals properties on leaching process of weathered crust elution-deposited rare earth ore

    Institute of Scientific and Technical Information of China (English)

    肖燕飞; 刘向生; 冯宗玉; 黄小卫; 黄莉; 陈迎迎; 吴文远

    2015-01-01

    Granite belonged to intrusive rock and volcanic was extrusive rock. There may be many differences in their degree of weathering and mineral chemical composition. The present study investigated the minerals properties and the leaching mechanism of the granitic weathered crust elution-deposited rare earth ore from Longnan Rare Earth Mine area (LN ores) and volcanic weathered crust elution-deposited rare earth ore from Liutang Rare Earth Mine area (LT ores). The X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) were used to characterize the phase of rare earth ores. The particle size distributions and main composition of the ore were also presented in this paper. The leaching mechanisms of two kinds of rare earth ores were analyzed with different kinetics models and could be described by the shrinking-core model. They were all inner diffusion-controlled leaching processes. The leaching equation of the kinetics of the LN ores could be expressed as:4 LN LN 1.096 10 2/3 0.377 8.314 0 2 3=0.1061 (1 ) Tr e tη η×−−− − −, leaching equation of kinetics of LT ores was 3 LT LT 4.640 10 2/3 0.411 8.314 0 32 3=8.33 101 (1 ) Tr e tη η×−− −×− − −. The rare earth leaching rate of LT ores was always lower in the same condition, and it would need more time and more (NH4)2SO4 consump-tion to achieve the same rare earth leaching efficiency, which would lead to more serious ammonia-nitrogen pollution. Therefore, magnesium salt was proposed as the leaching agent to eliminate ammonia-nitrogen pollution and further studies would be taken in the future.

  19. Beyond the crust : journey closer to the centre of the Earth

    Energy Technology Data Exchange (ETDEWEB)

    Smith, M.

    2005-09-01

    Scientists of the Integrated Ocean Drilling Program (IODP) are targeting the thinnest layers of the Earth's crust under the ocean floor. The crust below the Earth's ocean is only about 6 to 10 km thick, compared to an average 35 km under the continents. The primary objective of the IODP is to learn about the evolution of oceanic crust formed at slow-spreading oceanic ridges and to gain a better understanding of the oceanic core complexes. However, a by-product of the research may be improved oil and gas exploration and production. Although the drilling program does not have a link with the petroleum industry, representatives from the oil and gas sector have provided guidance in technology development for the past decade. The role of the oil and gas industry may intensify in the near future because of its expertise in coring operations. IODP has avoided potential hydrocarbon intersections, but has been involved in developing their technology for gas hydrate research. IODP researchers have completed the third deepest well ever drilled into the basement from a vessel which drilled 1,415 metres below the seafloor. The gabbroic rocks recovered from the drilling program have compositions that represent some of the most primitive lower crust ever sampled. Sections of the rocks are very fresh, with less than 1 to 2 per cent alteration. Scientists have come to within 3,000 metres to the Mohorovicic Discontinuity, the boundary between the crust and the mantle.The Chikyu 57,500 ton, half-billion dollar deep-sea drilling vessel is expected to undergo experimental voyages in late 2005 and is expected to begin deep-sea drilling in 2007. This research vessel is the first to adopt the riser drilling system typically used by the oil industry. The first task of the vessel, which can drill 7,000 metres below the sea floor, will be to study plate tectonics off the coast of Japan. Scientists hope that it will eventually break-through into the mantle to provide information

  20. Correlation analysis on partition of rare earth in ion-exchangeable phase from weathered crust ores

    Institute of Scientific and Technical Information of China (English)

    CHI Ru-an; DAI Zu-xu; XU Zhi-gao; WU Yuan-xin; WANG Cun-wen

    2006-01-01

    The rare earth(RE) in weathered crust ores mainly exists as ion-exchangeable phase, approximately 80%. The correlation analysis on partition of 376 samples in ion-exchangeable phase from weathered crust ores was conducted. The results show that partition both among heavy RE elements and light RE elements with high partition appears positive correlation, but partition sums between the heavy RE elements and the light RE elements appear close negative correlation obviously. Clear negative correlations exist between the light RE elements (except Ce) and yttrium(Y). Matrix of correlation analysis on this partition can be divided into three zones. The correlated coefficient variation from negative to positive in zones B and C occurs at Gd, so does that in zones B and A (except Ce, Eu, and Sm), suggesting that RE elements can be divided into two groups with Gd as border. This phenomenon is called Gadolinium-broken effect.

  1. New Aspects of Structure of Earth Crust (Based on Data of Super Deep Wells Kola and Saatly)

    Science.gov (United States)

    Galant, Yuri

    2013-04-01

    In order to ensure the sustainability of Planet Earth the latest information regarding the structure of the Earth is necessary. It common accepted that Earth Crust consists of 2 layers: granite and basalt. Unique depth 12 600 meter have been reached by unique drills Kola located on the Arhenian Baltic plate. But haven't passed/reached border of Conrad that expected to be on the 4 000 meters. In additions corroborate this fact Saatly super deep well haven't come out from basalt in spite of unique depth 8 600 meter in Kura rift Alpine geosynclinals belts. These facts from conversely different tectonic regions let to build new model structure of Earth Crust. Based on the seismic interpretations and the geological data analysis obtained from super deep drills Kola (12 600meters) and Saatly (8 280 meters), the comprehensive 1 layer geologic -geotectonic-geochemical model interruption-blocks structure of the Earth Crust has been created. Such model is leading to following reasoning. Geologic aspect: 1) Earth Crust on lateral. consists of separated blocks/domain of Granite and separated blocks/domain Basalt, lies directly on mantle.Tectonical aspects: 2) There is no subduction, 3) There is thrust 4) Earth Crust has separated into granite and basalts domains/blocks. Geochemical aspect: 5) Distribution of acid components in Earth Crust n prevailing on base components. 6) Power intensity degassation the depth increasing on old structure. Paleo- aspect: 7) Forming Earth crust began from forming the granites. Societal aspect: 8) Let us to build a new model of forming and development of atmosphere, hydrosphere and mineral fields.

  2. Earth's crust model of the South-Okhotsk Basin by wide-angle OBS data

    Science.gov (United States)

    Kashubin, Sergey N.; Petrov, Oleg V.; Rybalka, Alexander V.; Milshtein, Evgenia D.; Shokalsky, Sergey P.; Verba, Mark L.; Petrov, Evgeniy O.

    2017-07-01

    -waves velocity models of the sedimentary strata and the upper consolidated crust. Velocity values in the upper consolidated crust beneath the South-Okhotsk Basin (Vp = 5.50-5.80 km/s, Vp/Vs = 1.74-1.76) allow interpretation of this 2.5-3.5-km-thick layer to be consistent with a felsic (granodioritic) crust. These results suggest that the Earth's crust in this region can be considered continental in nature, rather than previously accepted oceanic crust. Even though, the crust is thinned and stretched at this location.

  3. Accelerated hydration of the Earth's deep crust induced by stress perturbations.

    Science.gov (United States)

    Jamtveit, B; Austrheim, H; Malthe-Sørenssen, A

    2000-11-01

    The metamorphic cycle associated with the formation of mountain belts produces a lower crust containing little or no free fluid. The introduction of external fluids to dry and impermeable volumes of the Earth's crust is thus a prerequisite for the retrogressive metamorphism later observed in such regimes. Such metamorphism can cause significant changes in the crust's physical properties, including its density, rheology and elastic properties. On a large scale, the introduction of fluids requires the presence of high-permeability channels, such as faults or fractures, which are the result of external tectonic stresses. But extensive interaction between externally derived fluids and the fractured rock requires efficient mass transport away from the initial fractures into the rock itself, and this transport often occurs over distances much longer than expected from grain-boundary diffusion. Here we present both field observations and a simple network model that demonstrate how the transport of fluids into initially dry rock can be accelerated by perturbations in the local stress field caused by reactions with fluids. We also show that the morphology of reaction fronts separating 'dry' from 'wet' rocks depends on the anisotropy of the external stress field.

  4. Local Doppler Effect, Index of Refraction through the Earth Crust, PDF and the CNGS Neutrino Anomaly?

    Directory of Open Access Journals (Sweden)

    Assis A. V. D. B.

    2012-04-01

    Full Text Available In this brief paper, we show the neutrino velocity discrepancy obtained in the OPERA experiment may be due to the local Doppler effect between a local clock attached to a given detector at Gran Sasso, say C G , and the respective instantaneous clock crossing C G , say C C , being this latter at rest in the instantaneous inertial frame having got the velocity of rotation of CERN about Earth’s axis in relation to the fixed stars. With this effect, the index of refraction of the Earth crust may accomplish a refractive effect by which the neutrino velocity through the Earth crust turns out to be small in relation to the speed of light in the empty space, leading to an encrusted discrepancy that may have contamined the data obtained from the block of detectors at Gran Sasso, leading to a time interval excess that did not provide an exact match between the shift of the protons PDF (probability distribution function by TOF c and the detection data at Gran Sasso via the maximum likelihood matching.

  5. Modeling of Dynamic Deformation of The Earth Crust: A Tool For Evaluation of Future Earthquakes Parameters

    Science.gov (United States)

    Ovcharenko, A.; Sokolov, V.; Loh, C.-H.; Wen, K.-L.

    The method for evaluation of seismic and geodynamic hazard, which is based on the models of dynamic deformation of the Earth' crust, is proposed. The 4D-model of deformation (x, y, z, t - geographic coordinates, depth, time) is constructed on the basis the geophysical data: Global Positioning System (GPS) network, Persistent Sea Water Level (PSWL) monitoring and seismic catalogues. It is possible to utilize also other indirect geophysical data that reflect the dynamic process of the Earth' crust deformation. The process of deformation is considered in the form of interaction of slow-propagating waves of deformation, the moving velocities of which vary from 0.05 per year up to 300 km per year, and the effective widths of which are about sev- eral tens of kilometers. The main goal of the modeling is to determine characteristics of these waves (fronts) of dynamic deformation on the basis of observed data. The possible seismic events (earthquakes), on the one hand, could be revealed by analysis of distribution of deformation inside the Earth' crust. The recent 1999 Chi-Chi, Tai- wan, earthquake (M=7.6) is used as an example. On the other hand, it is proposed to consider seismic events as the peculiar points of the field of dynamic deformation - the moments of interaction of four and more fronts of deformation. The 5D-model (ge- ographic coordinates, depth, time, magnitude), which describes the seismic process statistically, is used for evaluation of the earthquakes magnitude. The 4D/5D-models are applied jointly for compilation of theoretical seismic catalogue for the nearest tens and hundreds years (future and past) that, in turn, is used for purposes of seismic zona- tion and hazard assessment. The process and results of the modeling are described for the case of Taiwan region. When comparing the real and modeled seismic catalogues, it has been shown that the standard errors of determination of the earthquake param- eters do not exceed 5-10 km by coordinates, 0

  6. Seismic measurements to reveal short-term variations in the elastic properties of the Earth crust

    Science.gov (United States)

    Piccinini, Davide; Zaccarelli, Lucia; Pastori, Marina; Margheriti, Lucia; Pio Lucente, Francesco; De Gori, Pasquale; Faenza, Licia; Soldati, Gaia

    2013-04-01

    Since the late the late '60s-early '70s era seismologists started developed theories that included variations of the elastic property of the Earth crust and the state of stress and its evolution crust prior to the occurrence of a large earthquake. Among the others the theory of the dilatancy (Scholz et al., 1973): when a rock is subject to stress, the rock grains are shifted generating micro-cracks, thus the rock itself increases its volume. Inside the fractured rock, fluid saturation and pore pressure play an important role in earthquake nucleation, by modulating the effective stress. Thus measuring the variations of wave speed and of anisotropic parameter in time can be highly informative on how the stress leading to a major fault failure builds up. In 80s and 90s such kind of research on earthquake precursor slowed down and the priority was given to seismic hazard and ground motions studies, which are very important since these are the basis for the building codes in many countries. Today we have dense and sophisticated seismic networks to measure wave-fields characteristics: we archive continuous waveform data recorded at three components broad-band seismometers, we almost routinely obtain high resolution earthquake locations. Therefore we are ready to start to systematically look at seismic-wave propagation properties to possibly reveal short-term variations in the elastic properties of the Earth crust. One seismological quantity which, since the '70s, is recognized to be diagnostic of the level of fracturation and/or of the pore pressure in the rock, hence of its state of stress, is the ratio between the compressional (P-wave) and the shear (S-wave) seismic velocities, the Vp/Vs (Nur, 1972; Kisslinger and Engdahl, 1973). Variations of this ratio have been recently observed and measured during the preparatory phase of a major earthquake (Lucente et al. 2010). In active fault areas and volcanoes, tectonic stress variation influences fracture field orientation

  7. A new type of rare earth elements deposit in weathering crust of Permian basalt in western Guizhou, NW China

    Institute of Scientific and Technical Information of China (English)

    YANG Ruidong; WANG Wei; ZHANG Xiaodong; LIU Ling; WEI Huairui; BAO Miao; WANG Jingxin

    2008-01-01

    A new type of rare earth elements (REEs) deposit was discovered from the gaolinite mudstone in the weathering crust of Permian basalt, Bijie region, western Guizhou, China. It contained ∑-RE2O3 0.065%-1.086%. This type of REEs deposit was widely distributed with steady horizon and thickness of 3-4 m. The ore-bearing weathering crust (kaolinite) of the three discovered REEs deposits belonged to the third episode of the Emeishan basalt eruption. The new type of REEs deposit was suggested that basalt (tuff) weathering could lead to the en- richment of the rare earth elements. Therefore, it is of important economic significance to explore REEs deposits in the weathering crust of basalt (tufts) in Yunnan, Guizhou, and Sichuan Provinces.

  8. Emergence of silicic continents as the lower crust peels off on a hot plate-tectonic Earth

    Science.gov (United States)

    Chowdhury, Priyadarshi; Gerya, Taras; Chakraborty, Sumit

    2017-09-01

    The rock record and geochemical evidence indicate that continental recycling has been occurring since the early history of the Earth. The stabilization of felsic continents in place of Earth's early mafic crust about 3.0 to 2.0 billion years ago, perhaps due to the initiation of plate tectonics, implies widespread destruction of mafic crust during this time interval. However, the physical mechanisms of such intense recycling on a hotter, (late) Archaean and presumably plate-tectonic Earth remain largely unknown. Here we use thermomechanical modelling to show that extensive recycling via lower crustal peeling-off (delamination but not eclogitic dripping) during continent-continent convergence was near ubiquitous during the late Archaean to early Proterozoic. We propose that such destruction of the early mafic crust, together with felsic magmatism, may have caused both the emergence of silicic continents and their subsequent isostatic rise, possibly above the sea level. Such changes in the continental character have been proposed to influence the Great Oxidation Event and, therefore, peeling-off plate tectonics could be the geodynamic trigger for this event. A transition to the slab break-off controlled syn-orogenic recycling occurred as the Earth aged and cooled, leading to reduced recycling and enhanced preservation of the continental crust of present-day composition.

  9. The Impact of Guiding Materials on Students' Conceptual Understanding: The Case of "What Is the Earth's Crust Composed of?

    Science.gov (United States)

    Çoruhlu, Tülay Senel; Er Nas, Sibel

    2017-01-01

    The aim of this research is to determine the effect of the use of guidance material based on the 5E model on students' conceptual understanding of a topic entitled "What is the earth's crust composed of?" The sample consists of 40 students from the 5th grade (experimental group 20, control group 20). A concept test, a drawing test, and…

  10. Interconnection of tectonic stresses in the Earth's crust and dynamics of the groundwater basin functioning

    Science.gov (United States)

    Koneshov, Vycheslav; Trifonova, Tatiana; Trifonov, Dmitriy; Arakelian, Sergey

    2016-04-01

    1. Possible influence of tectonic stresses on the occurrence of catastrophic floods by the mechanism of modification of the 3D-cracknet of the rock formations and the transit of the groundwater in this natural transport system in the conditions of functioning of the river catchment basin is discussed. Several floods (not freshets) took place in 2013-2014, which probably could be associated with corresponding seismic processes in the Earth's crust, are considered. 2. A river basin formation in the mountain slope can be considered as a self-organizing staged process of its evolution passing through several non-equilibrium but steady-state conditions. The controlling parameter is the process of the crack spreading out. Crack development up the slope but downward substance transit, stipulates a feedback within the unified 3D-river basin system. 3. We have briefly described and rendered the mechanism of the influence of seismic activity on the occurrence of concrete floods with the use of combined maps of groundwater resources and the boundaries of lithospheric plates on the territory and the revealed regularities in seismic waves propagation and interaction with groundwater. 4. In the practical aspect a proposed hypothesis can be useful during the definition of potentially dangerous areas for catastrophic water events taking into account the interference of the state of the underground hydrosphere and the tectonic structure of the rheological section of bowels of the earth on the concrete territories under some adjustable (seismic) conditions.

  11. Influence of Earth crust composition on continental collision style in Precambrian conditions: Results of supercomputer modelling

    Science.gov (United States)

    Zavyalov, Sergey; Zakharov, Vladimir

    2016-04-01

    A number of issues concerning Precambrian geodynamics still remain unsolved because of uncertainity of many physical (thermal regime, lithosphere thickness, crust thickness, etc.) and chemical (mantle composition, crust composition) parameters, which differed considerably comparing to the present day values. In this work, we show results of numerical supercomputations based on petrological and thermomechanical 2D model, which simulates the process of collision between two continental plates, each 80-160 km thick, with various convergence rates ranging from 5 to 15 cm/year. In the model, the upper mantle temperature is 150-200 ⁰C higher than the modern value, while the continental crust radiogenic heat production is higher than the present value by the factor of 1.5. These settings correspond to Archean conditions. The present study investigates the dependence of collision style on various continental crust parameters, especially on crust composition. The 3 following archetypal settings of continental crust composition are examined: 1) completely felsic continental crust; 2) basic lower crust and felsic upper crust; 3) basic upper crust and felsic lower crust (hereinafter referred to as inverted crust). Modeling results show that collision with completely felsic crust is unlikely. In the case of basic lower crust, a continental subduction and subsequent continental rocks exhumation can take place. Therefore, formation of ultra-high pressure metamorphic rocks is possible. Continental subduction also occurs in the case of inverted continental crust. However, in the latter case, the exhumation of felsic rocks is blocked by upper basic layer and their subsequent interaction depends on their volume ratio. Thus, if the total inverted crust thickness is about 15 km and the thicknesses of the two layers are equal, felsic rocks cannot be exhumed. If the total thickness is 30 to 40 km and that of the felsic layer is 20 to 25 km, it breaks through the basic layer leading to

  12. Global variations in azimuthal anisotropy of the Earth's upper mantle and crust

    Science.gov (United States)

    Schaeffer, A. J.; Lebedev, S.

    2013-12-01

    Deformation within the Earth's crust and mantle often results in crystallographic preferred orientations that produce measurable seismic anisotropy. Shear wave splitting measurements have the benefit of excellent lateral resolution and are an unambiguous indicator of the presence of seismic anisotropy; however, they suffer from poor depth resolution (integrated measurement from CMB to surface), in addition to being geographically limited (measurements only made at seismometer locations). The analysis of surface wave propagation also provides insight into the azimuthal variations in wave-speed, but with significantly better depth resolution. Thanks to the rapid increase in the number of seismic stations around the world, increasingly accurate, high-resolution 3D models of azimuthal anisotropy can be calculated using surface-wave tomography. We present our new global, azimuthally anisotropic model of the upper mantle and the crust. Compared to its recent predecessor, SL2013sv (Schaeffer and Lebedev, 2013), it is constrained by an even larger waveform fit dataset (>900,000 versus 712,000 vertical-component seismograms, respectively) and was computed using a more precise regularization of anisotropy, tuned to honour the amplitude and orientation of the anisotropic terms uniformly, including near the poles. Automated, multimode waveform inversion was used to extract structural information from surface and S wave forms, yielding resolving power from the crust down to the transition zone. Our unprecedentedly large waveform dataset, with complementary high-resolution regional arrays (including USArray) and global network sub-sets within it, produces improved resolution of global azimuthal anisotropy patterns. The model also reveals smaller scale patterns of 3D anisotropy variations related to regional lithospheric deformation and mantle flow, in particular in densely sampled regions. In oceanic regions, we examine the strength of azimuthal anisotropy, as a function of

  13. Temperature-dependent thermal diffusivity of the Earth's crust and implications for magmatism.

    Science.gov (United States)

    Whittington, Alan G; Hofmeister, Anne M; Nabelek, Peter I

    2009-03-19

    The thermal evolution of planetary crust and lithosphere is largely governed by the rate of heat transfer by conduction. The governing physical properties are thermal diffusivity (kappa) and conductivity (k = kapparhoC(P)), where rho denotes density and C(P) denotes specific heat capacity at constant pressure. Although for crustal rocks both kappa and k decrease above ambient temperature, most thermal models of the Earth's lithosphere assume constant values for kappa ( approximately 1 mm(2) s(-1)) and/or k ( approximately 3 to 5 W m(-1) K(-1)) owing to the large experimental uncertainties associated with conventional contact methods at high temperatures. Recent advances in laser-flash analysis permit accurate (+/-2 per cent) measurements on minerals and rocks to geologically relevant temperatures. Here we provide data from laser-flash analysis for three different crustal rock types, showing that kappa strongly decreases from 1.5-2.5 mm(2) s(-1) at ambient conditions, approaching 0.5 mm(2) s(-1) at mid-crustal temperatures. The latter value is approximately half that commonly assumed, and hot middle to lower crust is therefore a much more effective thermal insulator than previously thought. Above the quartz alpha-beta phase transition, crustal kappa is nearly independent of temperature, and similar to that of mantle materials. Calculated values of k indicate that its negative dependence on temperature is smaller than that of kappa, owing to the increase of C(P) with increasing temperature, but k also diminishes by 50 per cent from the surface to the quartz alpha-beta transition. We present models of lithospheric thermal evolution during continental collision and demonstrate that the temperature dependence of kappa and C(P) leads to positive feedback between strain heating in shear zones and more efficient thermal insulation, removing the requirement for unusually high radiogenic heat production to achieve crustal melting temperatures. Positive feedback between

  14. The South India Precambrian crust and shallow lithospheric mantle: Initial results from the India Deep Earth Imaging Experiment (INDEX)

    Indian Academy of Sciences (India)

    S S Rai; Kajaljyoti Borah; Ritima Das; Sandeep Gupta; Shalivahan Srivastava; K S Prakasam; K Sivaram; Sudesh Kumar; Rishikesh Meena

    2013-12-01

    We present here the most comprehensive study of the thickness and composition (/ ratio) of the South India Precambrian crust and the nature of shallower mantle inferred from analysis of teleseismic receiver functions from 70 broad-band seismic stations operated as a part of the India Deep Earth Imaging Experiment (INDEX). South India could be broadly divided into regions with thin crust (32–38 km) and thick crust (38–54 km). Thin crust domains include the East Dharwar Craton (EDC), Cuddapah basin and Madurai/Kerala Khondalite Block. The thicker crust domain includes the Western Dharwar Craton (WDC) and northern part of Southern Granulite Terrain. The WDC shows progressive increase in thickness from 38 km in north to 46–54 km in south, compared to an almost flat Moho beneath the EDC. Compositionally, most of the crustal domains are felsic to intermediate (/ ∼ 1.69–1.75) except the mid Archean block in the southern WDC where it is mafic (/ < 1.81). Considering erosion depth in the WDC, we argue for Himalaya like ∼70 km thick crust beneath it during the Archean. Variation in crustal thickness does not have a first-order influence on regional topography in South India and suggests significant role for the crustal composition. We also present evidence of mid-lithospheric low velocity at ∼85–100 km beneath South India.

  15. How Does Boiling in the Earth's Crust Influence Metal Speciation and Transport?

    Science.gov (United States)

    Kam, K.; Lemke, K.

    2014-12-01

    The presence of large quantities of precious metals, such as gold and copper, near the Earth's surface (upper crust) is commonly attributed to transport in aqueous solution and precipitation upon variations in temperature and pressure. As a consequence, gold exploration is closely linked to solution chemistry, i.e. hydrothermal processes involving aqueous fluids with densities of around unity. However, as crustal fluids buoyantly ascend, boiling produces a coexisting low-density aqueous liquid with fundamentally different physical and chemical properties, and a, most importantly, a high affinity for coinage metals (Heinrich et al., Econ Geol., 1992, 87, 1566). From recent experimental studies of Au (Hurtig and Williams-Jones, 2014, Geochim. Cosmochim. Acta,, 127, 304), we know that metal speciation in this low-density phase differs fundamentally from that observed in bulk solution, clearly, with important implications for Au, and metal speciation in general, transport and ore concentrations processes (these processes would also be operable in industrial geothermal plants given the quite special solvent properties of steam). In brief, this study focuses on the speciation of select metal halides in bulk solution as well as in water vapor, and is driven by our need to understand the solvent properties of around 2.0x109 cubic kilometers of free water (or 2,500 times as much water as stored in all lakes and rivers) present in the Earth's crust. The scope of this study has particular applications in the geothermal and oil industries, as both deal with high temperature low-density aqueous fluids. Understanding how metal halide species behave upon boiling can also provide insight into how metals, such as copper and silver, coat turbine equipment and steam piping in geothermal plants, ultimately rendering these components inoperable. This study will also provide preliminary results from mass spectrometric experiments of transition metal halides, and will be augmented with

  16. Making Earth's earliest continental crust - an analogue from voluminous Neogene silicic volcanism in NE-Iceland

    Science.gov (United States)

    Berg, Sylvia E.; Troll, Valentin R.; Burchardt, Steffi; Riishuus, Morten S.; Deegan, Frances M.; Harris, Chris; Whitehouse, Martin J.; Gústafsson, Ludvik E.

    2014-05-01

    Borgarfjörður Eystri in NE-Iceland represents the second-most voluminous exposure of silicic eruptive rocks in Iceland and is a superb example of bimodal volcanism (Bunsen-Daly gap), which represents a long-standing controversy that touches on the problem of crustal growth in early Earth. The silicic rocks in NE-Iceland approach 25 % of the exposed rock mass in the region (Gústafsson et al., 1989), thus they significantly exceed the usual ≤ 12 % in Iceland as a whole (e.g. Walker, 1966; Jonasson, 2007). The origin, significance, and duration of the voluminous (> 300 km3) and dominantly explosive silicic activity in Borgarfjörður Eystri is not yet constrained (c.f. Gústafsson, 1992), leaving us unclear as to what causes silicic volcanism in otherwise basaltic provinces. Here we report SIMS zircon U-Pb ages and δ18O values from the region, which record the commencement of silicic igneous activity with rhyolite lavas at 13.5 to 12.8 Ma, closely followed by large caldera-forming ignimbrite eruptions from the Breiðavik and Dyrfjöll central volcanoes (12.4 Ma). Silicic activity ended abruptly with dacite lava at 12.1 Ma, defining a ≤ 1 Myr long window of silicic volcanism. Magma δ18O values estimated from zircon range from 3.1 to 5.5 (± 0.3; n = 170) and indicate up to 45 % assimilation of a low-δ18O component (e.g. typically δ18O = 0 ‰, Bindeman et al., 2012). A Neogene rift relocation (Martin et al., 2011) or the birth of an off-rift zone to the east of the mature rift associated with a thermal/chemical pulse in the Iceland plume (Óskarsson & Riishuus, 2013), likely brought mantle-derived magma into contact with fertile hydrothermally-altered basaltic crust. The resulting interaction triggered large-scale crustal melting and generated mixed-origin silicic melts. Such rapid formation of silicic magmas from sustained basaltic volcanism may serve as an analogue for generating continental crust in a subduction-free early Earth (e.g. ≥ 3 Ga, Kamber et

  17. Time Passes - Argon Isotopes as Tracers of Fluids in the Earth's Crust

    Science.gov (United States)

    Kelley, Simon P.

    2016-04-01

    Recent experimental measurements of noble gas solubility in silicate minerals (e.g. Jackson et al. 2013, 2015) means that we can begin to explore the use of noble gas partition between minerals and fluids to understand their residence and transport in the Earth's crust. One starting point for this exploration is the distribution of noble gases and halogens in crustal fluids which was reviewed by Kendrick and Burnard (2013). In particular, K&B (2013) noted that time is a key parameter in understanding noble gas tracers in crustal processes; yielding information such as the residence time of water in a reservoir based on 4He acquired from aquifer rocks, and the 40Ar/39Ar age of fluid inclusions based on trapped fluid and minerals in quartz. Argon isotope variations in natural systems have been measured during studies of 40Ar/39Ar ages to quantify the rates and timescales of crustal processes. There are also studies of fluids in similar rocks, notably in fluid inclusions, providing the opportunity to quantify the variations in the crust. Partition of argon between mineral phases under conditions of varying fluid availability can be compared in systems where 40Ar/39Ar measurements indicate the preservation of non-radiogenic argon (both excess and atmospheric) in the minerals. Rather than a simple picture of radiogenic argon contents increasing with crustal age, and gradual depletion of atmospheric argon in deeper fluids, what emerges is a sometimes dynamic and sometimes static system in different zones of the crust. While it can be shown that the hydrous fluid in sandstone reservoirs contained excess argon, analyses of authigenic minerals rarely exhibit 40Ar/39Ar ages in excess of the growth age. In this scenario, the incompatible nature of argon means that the fluid acts as an effective infinite reservoir and radiogenic argon dominates the potassium rich authigenic minerals. The controls on noble gas distribution are also well illustrated by deep crustal rocks such as

  18. Geoacoustic method for continuous monitoring of stressed-strained state of Earth's crust

    Science.gov (United States)

    Verbitskiy, T. Z.

    1984-05-01

    Ceramic piezoelectric transducers with characteristic frequencies 10-15 KHz are used as sources and detectors of longitudinal waves in a geoacoustic measuring system. The source is excited by an alternating voltage of 150-300 V with a frequency of 1-10 KHz. The electric signals from the detectors are amplified and filtered for discriminating the frequency harmonics. The phase shift of the received signal of the fundamental frequency and the amplitude of oscillations of the fundamental and multiple frequencies are determined. The measured wave parameters are registered on punched tape, facilitating computer input. Measuring system stability is monitored. The supply voltage, as well as atmospheric pressure, humidity and temperature are continuously monitored. Measurements made in the Carpathian Geodynamic Polygon Carpathian reveal a substantial influence of tidal deformations of the Earth. It can be postulated that short anomalies are caused by the discharge of stresses in the investigated rock complex. More prolonged anomalies are caused by deformations of the crust accompanying preparation for tectonic earthquakes.

  19. Geochemistry of Rare Earth Elements (REE) in the Weathered Crusts from the Granitic Rocks in Sulawesi Island, Indonesia

    Institute of Scientific and Technical Information of China (English)

    Adi Maulana; Kotaro Yonezu; Koichiro Watanabe

    2014-01-01

    We report for the first time the geochemistry of rare earth elements (REE) in the weath-ered crusts of I-type and calc-alkaline to high-K (shoshonitic) granitic rocks at Mamasa and Palu re-gion, Sulawesi Island, Indonesia. The weathered crusts can be divided into horizon A (lateritic profile) and B (weathered horizon). Quartz, albite, kaolinite, halloysite and montmorrilonite prevail in the weathered crust. Both weathered profiles show that the total REE increased from the parent rocks to the horizon B but significantly decrease toward the upper part (horizon A). LREE are enriched toward the upper part of the profile as shown by La/YbN value. However, HREE concentrations are high in horizon B1 in Palu profile. The total REE content of the weathered crust are relatively elevated com-pared to the parent rocks, particularly in the lower part of horizon B in Mamasa profile and in horizon B2 in Palu profile. This suggests that REE-bearing accessory minerals may be resistant against weath-ering and may remain as residual phase in the weathered crusts. The normalized isocon diagram shows that the mass balance of major and REE components between each horizon in Mamasa and Palu weathering profile are different. The positive Ce anomaly in the horizon A of Mamasa profile indicated that Ce is rapidly precipitated during weathering and retain at the upper soil horizon.

  20. Simulation of seismic waves at the Earth crust (brittle-ductile transition) based on the Burgers model

    OpenAIRE

    Carcione, J.M.; Poletto, F.; B. Farina; A. Craglietto

    2014-01-01

    The Earth crust presents two dissimilar rheological behaviours depending on the in-situ stress-temperature conditions. The upper, cooler, part is brittle while deeper zones are ductile. Seismic waves may reveal the presence of the transition but a proper characterization is required. We first obtain a stress–strain relation including the effects of shear seismic attenuation and ductility due to shear deformations and plastic flow. The anelastic behaviour i...

  1. Simulation of seismic waves at the earth's crust (brittle–ductile transition) based on the Burgers model

    OpenAIRE

    Carcione, J.M.; Poletto, F.; B. Farina; A. Craglietto

    2014-01-01

    The earth's crust presents two dissimilar rheological behaviors depending on the in situ stress-temperature conditions. The upper, cooler part is brittle, while deeper zones are ductile. Seismic waves may reveal the presence of the transition but a proper characterization is required. We first obtain a stress–strain relation, including the effects of shear seismic attenuation and ductility due to shear deformations and plastic flow. The anelastic behavior is based on the Bur...

  2. Magma redox and structural controls on iron isotope variations in Earth's mantle and crust

    Science.gov (United States)

    Dauphas, N.; Roskosz, M.; Alp, E. E.; Neuville, D. R.; Hu, M. Y.; Sio, C. K.; Tissot, F. L. H.; Zhao, J.; Tissandier, L.; Médard, E.; Cordier, C.

    2014-07-01

    The heavy iron isotopic composition of Earth's crust relative to chondrites has been explained by vaporization during the Moon-forming impact, equilibrium partitioning between metal and silicate at core-mantle-boundary conditions, or partial melting and magma differentiation. The latter view is supported by the observed difference in the iron isotopic compositions of MORBS and peridotites. However, the precise controls on iron isotope variations in igneous rocks remain unknown. Here, we show that equilibrium iron isotope fractionation is mainly controlled by redox (Fe3+/Fetot ratio) and structural (e.g., polymerization) conditions in magmas. We measured, for the first time, the mean force constants of iron bonds in silicate glasses by synchrotron Nuclear Resonant Inelastic X-ray Scattering (NRIXS, also known as Nuclear Resonance Vibrational Spectroscopy - NRVS, or Nuclear Inelastic Scattering - NIS). The same samples were studied by conventional Mössbauer and X-ray Absorption Near Edge Structure (XANES) spectroscopy. The NRIXS results reveal a +0.2 to +0.4‰ equilibrium fractionation on 56Fe/54Fe ratio between Fe2+ and Fe3+ end-members in basalt, andesite, and dacite glasses at magmatic temperatures. These first measurements can already explain ∼1/3 of the iron isotopic shift measured in MORBs relative to their source. Further work will be required to investigate how pressure, temperature, and structural differences between melts and glasses affect equilibrium fractionation factors. In addition, large fractionation is also found between rhyolitic glass and commonly occurring oxide and silicate minerals. This fractionation reflects mainly changes in the coordination environment of Fe2+ in rhyolites relative to less silicic magmas and mantle minerals, as also seen by XANES. We provide a new calibration of XANES features vs. Fe3+/Fetot ratio determinations by Mössbauer to estimate Fe3+/Fetot ratio in situ in glasses of basaltic, andesitic, dacitic, and rhyolitic

  3. Geochemistry of rare earth elements in cobalt-rich crusts from the Mid-Pacific M seamount

    Institute of Scientific and Technical Information of China (English)

    CUI Yingchun; LIU Jihua; REN Xiangwen; SHI Xuefa

    2009-01-01

    Rare earth elements (REEs) and major elements of 25 cobalt-rich crusts obtained from different depths of Mid-Pacific M seamount were analyzed using inductively coupled plasma-atomic emission spectrometer and gravimetric method. The results showed that they were hydrogenous crusts with average ∑REE content of 2084.69 μg/g and the light REE (LREE)/heavy REE (HREE) ratio of 4.84. The shale-normalized REE patterns showed positive Ce anomalies. The total content of strictly trivalent REEs increased with water depth. The Ce content and LREE/HREE ratios in Fe-Mn crusts above 2000 m were lower than those below 2000 m. The change in REE with water depth could be explained by two processes: adsorptive scavenging by setting matters and behaviors of REE in seawater. However, the Ce abundance took no obvious correlation with water depth reflects the constant Ce flux. The Ce in crusts existed mainly as Ce(IV), implying that the oxidative-enriching process was controlled by kinetic factors.

  4. Comparison of the partitioning behaviours of yttrium, rare earth elements, and titanium between hydrogenetic marine ferromanganese crusts and seawater

    Science.gov (United States)

    Bau, M.; Koschinsky, A.; Dulski, P.; Hein, J.R.

    1996-01-01

    In order to evaluate details of the partitioning behaviours of Y, rare earth elements (REEs), and Ti between inorganic metal oxide surfaces and seawater, we studied the distribution of these elements in hydrogenetic marine ferromanganese (Fe-Mn) crusts from the Central Pacific Ocean. Nonphosphatized Fe-Mn crusts display shale-normalized rare earths and yttrium (REYSN) patterns (Y inserted between Dy and Ho) that are depleted in light REEs (LREEs) and which show negative anomalies for YSN, and positive anomalies for LaSN, EuSN, GdSN, and in most cases, CeSN. They show considerably smaller Y/ Ho ratios than seawater or common igneous and clastic rocks, indicating that Y and Ho are fractionated in the marine environment. Compared to P-poor crusts, REYSN patterns of phosphatized Fe-Mn crusts are similar, but yield pronounced positive YSN anomalies, stronger positive LaSN anomalies, and enrichment of the HREEs relative to the MREEs. The data suggest modification of REY during phosphatization and indicate that studies requiring primary REY distributions or isotopic ratios should be restricted to nonphosphatized (layers of) Fe-Mn crusts. Apparent bulk coefficients, KMD, describing trace metal partitioning between nonphosphatized hydrogenetic Fe-Mn crusts and seawater, are similar for Pr to Eu and decrease for Eu to Yb. Exceptionally high values of KCeD, which are similar to those of Ti, result from oxidative scavenging of Ce and support previous suggestions that Ce(IV) is a hydroxide-dominated element in seawater. Yttrium and Gd show lower KD values than their respective neighbours in the REY series. Results of modelling the exchange equilibrium between REY dissolved in seawater and REY sorbed on hydrous Fe-Mn oxides corroborate previous studies that suggested the surface complexation of REY can be approximated by their first hydroxide binding constant. Negative "anomalies" occur for stabilities of bulk surface complexes of Gd, La, and particularly Y. The differences in

  5. Structure and thickness of the Earth's crust in the northeastern part of the Indian Ocean

    Science.gov (United States)

    Schreider, A. A.; Mazo, E. L.; Kulikova, M. P.; Gilod, D. A.

    2008-10-01

    A digital database on the seismostratigraphy of the oceanic crust of the northeastern part of the Indian Ocean is compiled. In the first layer of the crust, the interval seismic wave velocities are 3.02 ± 0.16 km/s; in the second layer, they equal to 5.31 ± 0.27 km/s; and, in the third layer, the values are 6.46 ± 0.30 km/s. The bottom of the third seismic layer is represented by mantle rocks with an average velocity of 8.10 ± 0.16 km/s. Schemes of the distribution of the thicknesses of the second and third layers of the oceanic crust, of the total thickness of the crust, of the surface of the basement, and of the Mohorovicic discontinuity for the area considered are presented. The schemes compiled allow one to update and complement the ideas about the configuration of the major tectonic structures of the area.

  6. Geodynamics and Stress State of the Earth's Crust in the Greater and Lesser Caucasus (Azerbaijan) collision region

    Science.gov (United States)

    Babayev, Gulam; Akhmedova, Elnare; Babayev, Elvin

    2017-04-01

    The current study researches the present-day stress state of the Earth's crust within the territory of Azerbaijan by using the database of the international research project "World Stress Map" (WSM). The present stress state was also assessed by exploring the effects of the contemporary topographic properties of Caucasus in three-dimensional frame. Aiming to explore the relative roles of regional tectonic conditions in the definition of stress state of Greater and Lesser Caucasus, stress distribution model was developed by the earthquake data (1998-2016) and by the standard techniques of stress field calculation. The results show that the stress orientations are influenced also by the combination of topography and crust thickness distribution even at very large depth. Stress data and earthquake focal mechanisms indicate that the stress state of the Earth's crust of the Greater and Lesser Caucasus is characterized by the compression predominantly oriented across the regional strike. The model results suggest that the Lesser Caucasus and Kur depression are rotating coherently, with little or no internal deformation in a counter-clockwise rotation located near the north-eastern corner of the Black Sea. Orientation of stress axes well consistent with earthquake focal mechanisms revealed that within Upper and Lower Crusts, earthquakes are predominantly thrust-faulting with a number of normal-faulting and some strike-slip faulting. The map of the focal mechanisms and stress distribution suggests that the research area is characterized by the thrust of horizontal compression trending north-north-east in the western part of the southern Caucasus. In the western part of Azerbaijan, the compression takes place between the Main Caucasus Fault and the Kur depression, which strikes south along the northern margin of the mountain range. In addition, a clear transition from the left-lateral strike slip to the predominantly right-lateral strike slip is observed in the southern of

  7. Study on Microbes and Their Effects on Rare Earth Extraction in Weathering Crust of Granite

    Institute of Scientific and Technical Information of China (English)

    陈炳辉; 毋福海; 刘琥琥

    2001-01-01

    Microbes were cultured from the samples at various depths in a weathering profile of RE-bearing granite in Gonghe RE mine, Guangdong Province. The cultured microbes, existing at a depth of 0.2~12 m and being more plentiful within 3 m in the profile,include bacteria (Bacillus,Enterobacter, Escherichia, Alkaligenes, Neisseria, Staphylococcus and anaerobic bacteria such as Clostridium), fungi (Aspergillus niger, Aspergillus flavus, Penicillium, Mucor and Saccharomycete) and actinomyces. Experiments were made under room temperature by using solutions of the cultured microbes and their metabolites, compared with distilled water and the culture solution without microbes, to leach RE from the sample of the weathering crust. The results are shown by the experiments: (1) The mixed microbes cultured from the profile and their metabolites increase the quantity of RE leached from the sample and reduce the pH of the solutions. (2) The ability to leach RE from the sample varies with various microbes, decreasing in a sequence of fungi (Mucor, saccharomycete, Aspegillus and Penicillium), zymotic bacilli (Enterobacter, Escherichia etc.), Staphylococcus, zymotic Bacillus, actinomyces and Alkaligenes. (3) The RE leached with bacteria is mainly related to the pH value of the solutions influenced by the metabolites of the bacteria; whereas that leached with fungi is mainly related to the adsorption and imbibition of RE by the fungi and the complexing of RE with their metabolites. (4) Compared with that leached with ammonium sulfate, the fractionation of the RE leached with microbes is characterized by higher δCe, lower δEu and lower ratios of NLa/Sm and NGd/Yb. The result of the fractionation of RE accords with the distribution of RE in the various layers of a profile of weathering crust of granite in South China. The experimental results indicate that microbes and their metabolites should play a positive role in the mobilization, migration and fractionation of RE in the

  8. Resistivity and heterogeneity of Earth crust in an active tectonic region, Southern Tuscany (Italy

    Directory of Open Access Journals (Sweden)

    A. Manzella

    2004-06-01

    Full Text Available Southern Tuscany, belonging to the inner zone of the Northern Apennines, Italy, is an ideal laboratory for observing the physical features of the lithosphere and their evolution in tectonically active regions. Here the crust is very thin, with a thickness of less than 25 km, and heat flow is very high, hence only very shallow depths of exploration are needed to investigate many of the middle-deep crustal features that are common to many other parts of the world. The magnetotelluric (MT surveys performed in this region have provided information on the resistivity structure, which is related to the extent and distribution of free fluids and to the partial melts in the crust. The picture emerging from these MT surveys is that of a resistivity structure that is only partly related to the heat flow regime of the area. A very low resistivity was found below the vapour-dominated geothermal system of Larderello and below areas that have no clear connection to any geothermal system, whereas this reduction of resistivity is less conspicuous below the water-dominated geothermal system of Mt. Amiata.

  9. The Ghost in the Machine: Fracking in the Earth's Complex Brittle Crust

    Science.gov (United States)

    Malin, P. E.

    2015-12-01

    This paper discusses in the impact of complex rock properties on practical applications like fracking and its associated seismic emissions. A variety of borehole measurements show that the complex physical properties of the upper crust cannot be characterized by averages on any scale. Instead they appear to follow 3 empirical rule: a power law distribution in physical scales, a lognormal distribution in populations, and a direct relation between changes in porosity and log(permeability). These rules can be directly related to the presence of fluid rich and seismically active fractures - from mineral grains to fault segments. (These are the "ghosts" referred to in the title.) In other physical systems, such behaviors arise on the boundaries of phase changes, and are studied as "critical state physics". In analogy to the 4 phases of water, crustal rocks progress upward from a un-fractured, ductile lower crust to nearly cohesionless surface alluvium. The crust in between is in an unstable transition. It is in this layer methods such as hydrofracking operate - be they in Oil and Gas, geothermal, or mining. As a result, nothing is predictable in these systems. Crustal models have conventionally been constructed assuming that in situ permeability and related properties are normally distributed. This approach is consistent with the use of short scale-length cores and logs to estimate properties. However, reservoir-scale flow data show that they are better fit to lognormal distributions. Such "long tail" distributions are observed for well productivity, ore vein grades, and induced seismic signals. Outcrop and well-log data show that many rock properties also show a power-law-type variation in scale lengths. In terms of Fourier power spectra, if peaks per km is k, then their power is proportional to 1/k. The source of this variation is related to pore-space connectivity, beginning with grain-fractures. We then show that a passive seismic method, Tomographic Fracture

  10. Exploring the Earth's crust: history and results of controlled-source seismology

    Science.gov (United States)

    Prodehl, Claus; Mooney, Walter D.

    2012-01-01

    This volume contains a comprehensive, worldwide history of seismological studies of the Earth’s crust using controlled sources from 1850 to 2005. Essentially all major seismic projects on land and the most important oceanic projects are covered. The time period 1850 to 1939 is presented as a general synthesis, and from 1940 onward the history and results are presented in separate chapters for each decade, with the material organized by geographical region. Each chapter highlights the major advances achieved during that decade in terms of data acquisition, processing technology, and interpretation methods. For all major seismic projects, the authors provide specific details on field observations, interpreted crustal cross sections, and key references. They conclude with global and continental-scale maps of all field measurements and interpreted Moho contours. An accompanying DVD contains important out-of-print publications and an extensive collection of controlled-source data, location maps, and crustal cross sections.

  11. Is lithostatic loading important for the slip behavior and evolution of normal faults in the Earth's crust?

    Energy Technology Data Exchange (ETDEWEB)

    Kattenhorn, Simon A. [Department of Geological and Environmental Sciences, Stanford University, Stanford, California (United States); Pollard, David D. [Department of Geological and Environmental Sciences, Stanford University, Stanford, California (United States)

    1999-12-10

    Normal faults growing in the Earth's crust are subject to the effects of an increasing frictional resistance to slip caused by the increasing lithostatic load with depth. We use three-dimensional (3-D) boundary element method numerical models to evaluate these effects on planar normal faults with variable elliptical tip line shapes in an elastic solid. As a result of increasing friction with depth, normal fault slip maxima for a single slip event are skewed away from the fault center toward the upper fault tip. There is a correspondingly greater propagation tendency at the upper tip. However, the tall faults that would result from such a propagation tendency are generally not observed in nature. We show how mechanical interaction between laterally stepping fault segments significantly competes with the lithostatic loading effect in the evolution of a normal fault system, promoting lateral propagation and possibly segment linkage. Resultant composite faults are wider than they are tall, resembling both 3-D seismic data interpretations and previously documented characteristics of normal fault systems. However, this effect may be greatly complemented by the influence of a heterogeneous stratigraphy, which can control fault nucleation depth and inhibit fault propagation across the mechanical layering. Our models demonstrate that although lithostatic loading may be an important control on fault evolution in relatively homogeneous rocks, the contribution of lithologic influences and mechanical interaction between closely spaced, laterally stepping faults may predominate in determining the slip behavior and propagation tendency of normal faults in the Earth's crust. (c) 1999 American Geophysical Union.

  12. Can anisotropic conductivity in the lower ionosphere and in the Earth's crust be studied by Schumann resonance transients?

    Science.gov (United States)

    Ludván, Brigitta; Bór, József; Steinbach, Péter; Novák, Attila; Sátori, Gabriella

    2015-04-01

    Schumann resonance transients (SRTs) are extremely low frequency (ELF, 3-3000 Hz) wave packets of high amplitude electromagnetic (EM) waves produced by intense lightning discharges worldwide. Near the lower end of the ELF band, frequencies are close to the lowest spherical eigenfrequencies of the closed EM waveguide formed by the surface of the Earth and the lower ionosphere. Therefore, these waves suffer little attenuation during their propagation and can be detected globally at any point on Earth. SRTs detected both in the vertical electric and in the horizontal magnetic components of the atmospheric EM field at the Széchenyi István Geophysical Observatory (NCK, 16.7 E, 47.6 N) on 1st and 2nd August, 2012 have been analyzed. Azimuths of their parent lightning discharges were calculated from the horizontal components of the corresponding Poynting vector. Parent lightning strokes of the considered SRTs (342 and 245 events on the first and on the second day, respectively) have been identified in the records of the World Wide Lightning Location Network (WWLLN) using the detection times of the events in the two datasets. It was found that the azimuths of the sources at NCK station deduced from ELF records systematically differ from source azimuths calculated using WWLLN provided lightning locations. The difference between the corresponding azimuth values from the two methods shows the same pattern on both examined days when it is plotted as function of the WWLLN data based source azimuth. The symmetry of this pattern agrees well with the symmetry of the conductivity variations of the Earth's crust determined by independent magnetotelluric methods at NCK station. The differences have similar diurnal variation, too, on the two days with the largest difference occurring near midnight, local time. Our results agree well with findings of Füllekrug and Sukhorukov (GRL, 1999) and support the idea that the azimuthal dependence of source azimuth differences can be related

  13. Widespread mixing and burial of Earth's Hadean crust by asteroid impacts.

    Science.gov (United States)

    Marchi, S; Bottke, W F; Elkins-Tanton, L T; Bierhaus, M; Wuennemann, K; Morbidelli, A; Kring, D A

    2014-07-31

    The history of the Hadean Earth (∼4.0-4.5 billion years ago) is poorly understood because few known rocks are older than ∼3.8 billion years old. The main constraints from this era come from ancient submillimetre zircon grains. Some of these zircons date back to ∼4.4 billion years ago when the Moon, and presumably the Earth, was being pummelled by an enormous flux of extraterrestrial bodies. The magnitude and exact timing of these early terrestrial impacts, and their effects on crustal growth and evolution, are unknown. Here we provide a new bombardment model of the Hadean Earth that has been calibrated using existing lunar and terrestrial data. We find that the surface of the Hadean Earth was widely reprocessed by impacts through mixing and burial by impact-generated melt. This model may explain the age distribution of Hadean zircons and the absence of early terrestrial rocks. Existing oceans would have repeatedly boiled away into steam atmospheres as a result of large collisions as late as about 4 billion years ago.

  14. A survey of lunar rock types and comparison of the crusts of earth and moon

    Science.gov (United States)

    Wood, J. A.

    1977-01-01

    The principal known types of lunar rocks are briefly reviewed, and their chemical relationships discussed. In the suite of low-KREEP highland rocks, Fe/(Fe + Mg) in the normative mafic minerals increases and the albite content of normative plagio-clase decreases as the total amount of normative plagioclase increases, the opposite of the trend predicted by the Bowen reaction principle. The distribution of compositions of rocks from terrestrial layered mafic intrusives is substantially different: here the analyses fall in several discrete clusters (anorthositic rocks, norites, granophyres and ferrogabbros, ultramafics), and the chemical trends noted above are not reproduced. It is suggested that the observed trends in lunar highland rocks could be produced by crystal fractionation in a deep global surface magma system if (1) plagiociase tended to float, upon crystallization, and (2) the magma was kept agitated and well mixed (probably by thermal convection) until crystallization was far advanced and relatively little residual liquid was left. After the crustal system solidified, but before extensive cooling had developed a thick, strong lithosphere, mantle convection was able to draw portions of the lunar anorthositic crust down into the mantle.

  15. Heatflow in Young Oceanic Crust. Is Earth's Heat Flux 44 TW or 31 TW?

    Science.gov (United States)

    Gosnold, W. D.

    2008-05-01

    We address the question of heat flow in young oceanic crust using a 2-D finite difference heat flow model of sea floor spreading. The model parameters include thermal conductivity variation with temperature, a fixed T-z profile at the ridge that follows the mantle liquidus, constant spreading rate, and constant heat flow into the base of the lithosphere. The output of the model is a 2-D temperature-depth grid that provides a comparison with various analytical models of oceanic heat flow. We tested the reliability of the computations using different half-spreading rates and different node spacings and verified that the models yield equivalent results at equivalent times and depths. To address the question of global heat flux with respect to heat flow at oceanic spreading centers, we summed heat flux on the oceanic ridge system assuming a length of 65000 km and a half-spreading rate of 2.5 cm/y. Our results show that the GDH1, HSC, and PSM models overestimate heat flow close to the ridge, but the differences are less than 5 percent beyond 2 ma. Our model converges with GDH1 at a young age of 4.32 my and actually shows slightly lower heat flow than HSC and PSM models for ages greater than 5 ma. Total heat flux for GDH1 between 80ky and 2.32 my is 6.24 TW and our model yields 5.56 TW. Assuming agreement with heat flux over the rest of the globe, our model is only 0.68 TW different from 44TW. However, our result for heat flux in a 2 km wide section over the global ridge crest is 0.161 TW while the analytical models predict infinite heat flow.

  16. Freshly brewed continental crust

    Science.gov (United States)

    Gazel, E.; Hayes, J. L.; Caddick, M. J.; Madrigal, P.

    2015-12-01

    Earth's crust is the life-sustaining interface between our planet's deep interior and surface. Basaltic crusts similar to Earth's oceanic crust characterize terrestrial planets in the solar system while the continental masses, areas of buoyant, thick silicic crust, are a unique characteristic of Earth. Therefore, understanding the processes responsible for the formation of continents is fundamental to reconstructing the evolution of our planet. We use geochemical and geophysical data to reconstruct the evolution of the Central American Land Bridge (Costa Rica and Panama) over the last 70 Ma. We also include new preliminary data from a key turning point (~12-6 Ma) from the evolution from an oceanic arc depleted in incompatible elements to a juvenile continental mass in order to evaluate current models of continental crust formation. We also discovered that seismic P-waves (body waves) travel through the crust at velocities closer to the ones observed in continental crust worldwide. Based on global statistical analyses of all magmas produced today in oceanic arcs compared to the global average composition of continental crust we developed a continental index. Our goal was to quantitatively correlate geochemical composition with the average P-wave velocity of arc crust. We suggest that although the formation and evolution of continents may involve many processes, melting enriched oceanic crust within a subduction zone, a process probably more common in the Achaean where most continental landmasses formed, can produce the starting material necessary for juvenile continental crust formation.

  17. The Gassmann-Burgers Model to Simulate Seismic Waves at the Earth Crust And Mantle

    Science.gov (United States)

    Carcione, José M.; Poletto, Flavio; Farina, Biancamaria; Craglietto, Aronne

    2016-12-01

    The upper part of the crust shows generally brittle behaviour while deeper zones, including the mantle, may present ductile behaviour, depending on the pressure-temperature conditions; moreover, some parts are melted. Seismic waves can be used to detect these conditions on the basis of reflection and transmission events. Basically, from the elastic-plastic point of view the seismic properties (seismic velocity and density) depend on effective pressure and temperature. Confining and pore pressures have opposite effects on these properties, such that very small effective pressures (the presence of overpressured fluids) may substantially decrease the P- and S-wave velocities, mainly the latter, by opening of cracks and weakening of grain contacts. Similarly, high temperatures induce the same effect by partial melting. To model these effects, we consider a poro-viscoelastic model based on Gassmann equations and Burgers mechanical model to represent the properties of the rock frame and describe ductility in which deformation takes place by shear plastic flow. The Burgers elements allow us to model the effects of seismic attenuation, velocity dispersion and steady-state creep flow, respectively. The stiffness components of the brittle and ductile media depend on stress and temperature through the shear viscosity, which is obtained by the Arrhenius equation and the octahedral stress criterion. Effective pressure effects are taken into account in the dry-rock moduli using exponential functions whose parameters are obtained by fitting experimental data as a function of confining pressure. Since fluid effects are important, the density and bulk modulus of the saturating fluids (water and steam) are modeled using the equations provided by the NIST website, including supercritical behaviour. The theory allows us to obtain the phase velocity and quality factor as a function of depth and geological pressure and temperature as well as time frequency. We then obtain the PS and SH

  18. The Gassmann-Burgers Model to Simulate Seismic Waves at the Earth Crust And Mantle

    Science.gov (United States)

    Carcione, José M.; Poletto, Flavio; Farina, Biancamaria; Craglietto, Aronne

    2017-03-01

    The upper part of the crust shows generally brittle behaviour while deeper zones, including the mantle, may present ductile behaviour, depending on the pressure-temperature conditions; moreover, some parts are melted. Seismic waves can be used to detect these conditions on the basis of reflection and transmission events. Basically, from the elastic-plastic point of view the seismic properties (seismic velocity and density) depend on effective pressure and temperature. Confining and pore pressures have opposite effects on these properties, such that very small effective pressures (the presence of overpressured fluids) may substantially decrease the P- and S-wave velocities, mainly the latter, by opening of cracks and weakening of grain contacts. Similarly, high temperatures induce the same effect by partial melting. To model these effects, we consider a poro-viscoelastic model based on Gassmann equations and Burgers mechanical model to represent the properties of the rock frame and describe ductility in which deformation takes place by shear plastic flow. The Burgers elements allow us to model the effects of seismic attenuation, velocity dispersion and steady-state creep flow, respectively. The stiffness components of the brittle and ductile media depend on stress and temperature through the shear viscosity, which is obtained by the Arrhenius equation and the octahedral stress criterion. Effective pressure effects are taken into account in the dry-rock moduli using exponential functions whose parameters are obtained by fitting experimental data as a function of confining pressure. Since fluid effects are important, the density and bulk modulus of the saturating fluids (water and steam) are modeled using the equations provided by the NIST website, including supercritical behaviour. The theory allows us to obtain the phase velocity and quality factor as a function of depth and geological pressure and temperature as well as time frequency. We then obtain the PS and SH

  19. Early history of Earth's crust-mantle system inferred from hafnium isotopes in chondrites

    DEFF Research Database (Denmark)

    Bizzarro, Martin; Haack, Henning; Rosing, M.;

    2003-01-01

    depleted mantle reservoir. Here we report Lu-Hf isotope measurements of different Solar System objects including chondrites and basaltic eucrites. The chondrites define a Lu-Hf isochron with an initial Hf/Hf ratio of 0.279628 ± 0.000047, corresponding to ¿176 = 1.983 ± 0.033 x 10yr using an age of 4.56 Gyr...... for the chondrite-forming event. This ¿176 value indicates that Earth's oldest minerals were derived from melts of a mantle source with a time-integrated history of depletion rather than enrichment. The depletion event must have occurred no later than 320 Myr after planetary accretion, consistent with timing...

  20. Simulation of seismic waves at the Earth crust (brittle-ductile transition based on the Burgers model

    Directory of Open Access Journals (Sweden)

    J. M. Carcione

    2014-06-01

    Full Text Available The Earth crust presents two dissimilar rheological behaviours depending on the in-situ stress-temperature conditions. The upper, cooler, part is brittle while deeper zones are ductile. Seismic waves may reveal the presence of the transition but a proper characterization is required. We first obtain a stress–strain relation including the effects of shear seismic attenuation and ductility due to shear deformations and plastic flow. The anelastic behaviour is based on the Burgers mechanical model to describe the effects of seismic attenuation and steady-state creep flow. The shear Lamé constant of the brittle and ductile media depends on the in-situ stress and temperature through the shear viscosity, which is obtained by the Arrhenius equation and the octahedral stress criterion. The P- and S-wave velocities decrease as depth and temperature increase due to the geothermal gradient, an effect which is more pronounced for shear waves. We then obtain the P-S and SH equations of motion recast in the velocity-stress formulation, including memory variables to avoid the computation of time convolutions. The equations correspond to isotropic anelastic and inhomogeneous media and are solved by a direct grid method based on the Runge–Kutta time stepping technique and the Fourier pseudospectral method. The algorithm is tested with success against known analytical solutions for different shear viscosities. A realistic example illustrates the computation of surface and reverse-VSP synthetic seismograms in the presence of an abrupt brittle-ductile transition.

  1. Geochemistry of U and Th and its Influence on the Origin and Evolution of the Crust of Earth and the Biological Evolution

    CERN Document Server

    Bao, Xuezhao

    1998-01-01

    We have investigated the migration behaviors of uranium (U) and thorium (Th) in the Earth and other terrestrial planets. Theoretical models of U and Th migration have been proposed. These models suggest that the unique features of the Earth are closely connected with its unique U and Th migration models and distribution patterns. In the Earth, U and Th can combine with oxidative volatile components and water, migrate up to the asthenosphere position to form an enrichment zone (EZ) of U and Th first, and then migrate up further to the crusts through magmatism and metamorphism. We emphasize that the formation of an EZ of U, Th and other heat-producing elements is a prerequisite for the formation of a plate tectonic system. The heat-producing elements, currently mainly U and Th, in the EZ are also the energy sources that drive the formation and evolution of the crust of Earth and create special granitic continental crusts. In other terrestrial planets, including Mercury, Venus, and Mars, an EZ can not be formed ...

  2. Velocity characteristics of the earth crust in the Issyk-Kul'sk depresion as recorded from explosion and earthquake data

    Energy Technology Data Exchange (ETDEWEB)

    Moldobekov, K.; Sadybakasov, I.

    1979-01-01

    Results are given for studies of wave field change in the aforementioned region on the basis of earthquakes and explosions. Station anomalies are studied as well on the basis of experimental and theoretical studies. A velocity model of earth crust region is constructed from experimental hodographs, whose probability was found to be +-0.5 divided by +-1.0 second between the observed and computed gap time of total seismic waves. 5 references, 4 figures.

  3. Deep observation and sampling of the earth's continental crust (DOSECC): Continental scientific drilling workshop

    Energy Technology Data Exchange (ETDEWEB)

    1985-01-01

    Research summaries are presented of ongoing or proposed deep drilling programs to explore hydrothermal systems, buried astroblemes, continental crust, magma systems, mountain belt tectonics, subduction zones, and volcanoes. Separate abstracts have been prepared for individual papers. (ACR)

  4. Process optimization of rare earth and aluminum leaching from weathered crust elution-deposited rare earth ore with compound ammonium salts

    Institute of Scientific and Technical Information of China (English)

    何正艳; 张臻悦; 余军霞; 徐志高; 池汝安

    2016-01-01

    In order to intensify the leaching process of rare earth (RE) and reduce the impurities in the leachate, ammonium chloride (NH4Cl) and ammonium nitrate (NH4NO3) were mixed as a compound leaching agent to treat the weathered crust elution-deposited RE ore. Effects of molar ratio of NH4Cl and NH4NO3, ammonium (NH4+) concentration, leaching agent pH and flow rate on the leaching process of RE were studied and evaluated by the chromatographic plate theory. Leaching process of the main impurity alu-minium (Al) was also discussed in detail. Results showed that a higher initial ammonium concentration in a certain range could en-hance the mass transfer process of RE and Al by providing a driving force to overcome the resistance of diffusion. pH almost had no effects on the mass transfer efficiency of RE and Al in the range of 4 to 8. The relationship between the flow rate and height equiva-lent to a theoretical plate (HETP) could fit well with the Van Deemter equation, and the flow rate at the lowest HETP was determined. The optimum conditions of column leaching for RE and Al were 1:1 (molar ratio) of NH4Cl and NH4NO3, 0.2 mol/L of ammonium concentration, pH 4–8 of leaching agent and 0.5 mL/min of flow rate. Under this condition, the mass transfer efficiency of RE was improved, but no change was observed for Al compared with the most widely used ammonium sulfate. Moreover, the significant dif-ference value (around 20 mL) of retention volume at the peak concentration between RE and Al provided a possibility for their sepa-ration. It suggested the potential application of the novel compound leaching agent (NH4Cl/NH4NO3). It was found that the relative concentration of RE in the leachate could be easily obtained by monitoring the pH of leachate.

  5. Recent structures and tectonic regimes of the stress-strain state of the Earth's crust in the northeastern sector of the Russian Arctic region

    Science.gov (United States)

    Imaeva, L. P.; Imaev, V. S.; Mel'nikova, V. I.; Koz'min, B. M.

    2016-11-01

    A comprehensive investigation aimed at determining seismotectonic types of destruction and the stress-strain state of the Earth's crust in the main seismogenerating structures of the Arctic-Asian seismic belt is conducted for the territory of the northeastern sector of the Russian Arctic region. Based on the degree of activity of geodynamical processes, the regional principles for ranking neotectonic structures are elaborated, and neotectonic zoning is carried out based on the substantiated differentiation of the corresponding classes. Within the limits of the Laptev Sea, Kharaulakh, and Lena-Anabar segments, we analyzed I the structural-tectonic position of the most recent structures, II the deep structure parameters, III the parameters of the active fault system, and IV the parameters of the tectonic stress field, as revealed from tectonophysical analysis of Late Cenozoic fault and fold deformations. Based on the seismological data, the mean seismotectonic deformation tensors are calculated to determine, in combination with geological and geophysical data, the orientations of the principal stress axes and to reveal the structural-tectonic regularity for tectonic regimes of the stress-strain state of the Earth's crust in the Arctic sector of the boundary between the Eurasian and North American lithospheric plates.

  6. LITHO1.0 - An Updated Crust and Lithospheric Model of the Earth Developed Using Multiple Data Constraints

    Science.gov (United States)

    Pasyanos, M. E.; Masters, G.; Laske, G.; Ma, Z.

    2012-12-01

    Models such as CRUST2.0 (Bassin et al., 2000) have proven very useful to many seismic studies on regional, continental, and global scales. We have developed an updated, higher resolution model called LITHO1.0 that extends deeper to include the lithospheric lid, and includes mantle anisotropy, potentially making it more useful for a wider variety of applications. The model is evolving away from the crustal types strongly used in CRUST5.1 (Mooney et al., 1998) to a more data-driven model. This is accomplished by performing a targeted grid search with multiple data inputs. We seek to find the most plausible model which is able to fit multiple constraints, including updated sediment and crustal thickness models, upper mantle velocities derived from travel times, and surface wave dispersion. The latter comes from a new, very large, global surface wave dataset built using a new, efficient measurement technique that employs cluster analysis (Ma et al., 2012), and includes the group and phase velocities of both Love and Rayleigh waves. We will discuss datasets and methodology, highlight significant features of the model, and provide detailed information on the availability of the model in various formats.

  7. Electromagnetic sounding of the Earth's crust in the vicinities of the SG-6 and SG-7 superdeep boreholes in the fields of natural and powerful controlled sources

    Science.gov (United States)

    Zhamaletdinov, A. A.; Petrishchev, M. S.; Shevtsov, A. N.; Kolobov, V. V.; Selivanov, V. N.; Esipko, O. A.; Kopytenko, E. A.; Grigorjev, V. F.

    2012-07-01

    The results of electromagnetic sounding of the Earth's crust in the vicinities of the SG-6 and SG-7 superdeep boreholes (Yamal-Nenets Autonomous Okrug) are presented. The studies were conducted in the fields of natural sources (AMT-MTS) and in the field of the Zevs ULF antenna located at a distance of more than 2000 km from the receiver points. In the vicinity of the SG-7 superdeep borehole, where the small industrial noise was observed, the results of inverse problem solution are completely consistent with the electric logging data. The conducting layers have been identified at the depths of 150 m and 1.1 km. The roof of rocks having small electrical conductivity and belonging to the Permian-Triassic trappean complex has been found at the depth of about 7 km. The response of the Zevs signal (the frequency range of 44-182 Hz) has indicated the properties of the upper part of the geoelectrical section better than audiomagnetotelluric sounding for both boreholes. Based on the sounding in the vicinity of the SG-6 superdeep borehole, with the data of the Novosobirsk observatory taken into account, the distribution of resistivity down to about 800 km depth has been obtained. This distribution can serve as additional information in calculation of the temperature and rheological regime of the lithosphere and the upper mantle in the region of Western Siberia.

  8. Searching for cavities of various densities in the Earth's crust with a low-energy electron-antineutrino beta-beam

    CERN Document Server

    Argüelles, C A; Gago, A M

    2012-01-01

    We propose searching for deep underground cavities of different densities in the Earth's crust using a long-baseline electron-antineutrino disappearance experiment, realised through a low-energy beta-beam with highly enhanced luminosity. We focus on four real-world cases: water-filled cavities, iron-banded formations, heavier mineral deposits, and regions of abnormal charge accumulation that, supposedly, appear prior to the occurrence of an intense earthquake. The sensitivity to identify cavities attains confidence levels higher than 3$\\sigma$ and 5$\\sigma$ for exposures times of 3 months and 1.5 years, respectively, and cavity densities below 1 g cm$^{-3}$ or above 5 g cm$^{-3}$, with widths greater than 200 km. We reconstruct the cavity density, width, and position, assuming one of them known while keeping the other two free, in each of the aforementioned cases. Finally, we introduce an observable to quantify the presence of a cavity by changing the orientation of the electron-antineutrino beam.

  9. Raising the continental crust

    Science.gov (United States)

    Campbell, Ian H.; Davies, D. Rhodri

    2017-02-01

    The changes that occur at the boundary between the Archean and Proterozoic eons are arguably the most fundamental to affect the evolution of Earth's continental crust. The principal component of Archean continental crust is Granite-Greenstone Terranes (GGTs), with granites always dominant. The greenstones consist of a lower sequence of submarine komatiites and basalts, which erupted onto a pre-existing Tonalite-Trondhjemite-Granodiorite (TTG) crust. These basaltic rocks pass upwards initially into evolved volcanic rocks, such as andesites and dacites and, subsequently, into reworked felsic pyroclastic material and immature sediments. This transition coincides with widespread emplacement of granitoids, which stabilised (cratonised) the continental crust. Proterozoic supra-crustal rocks, on the other hand, are dominated by extensive flat-lying platform sequences of mature sediments, which were deposited on stable cratonic basements, with basaltic rocks appreciably less abundant. The siliceous TTGs cannot be produced by direct melting of the mantle, with most hypotheses for their origin requiring them to be underlain by a complimentary dense amphibole-garnet-pyroxenite root, which we suggest acted as ballast to the early continents. Ubiquitous continental pillow basalts in Archean lower greenstone sequences require the early continental crust to have been sub-marine, whereas the appearance of abundant clastic sediments, at higher stratigraphic levels, shows that it had emerged above sea level by the time of sedimentation. We hypothesise that the production of komatiites and associated basalts, the rise of the continental crust, widespread melting of the continental crust, the onset of sedimentation and subsequent cratonisation form a continuum that is the direct result of removal of the continent's dense amphibole-garnet-pyroxenite roots, triggered at a regional scale by the arrival of a mantle plume at the base of the lithosphere. Our idealised calculations suggest

  10. SALSA3D - A Global 3D P-Velocity Model of the Earth's Crust and Mantle for Improved Event Location

    Science.gov (United States)

    Ballard, S.; Begnaud, M. L.; Young, C. J.; Hipp, J. R.; Chang, M.; Encarnacao, A. V.; Rowe, C. A.; Phillips, W. S.; Steck, L.

    2010-12-01

    To test the hypothesis that high quality 3D Earth models will produce seismic event locations which are more accurate and more precise, we are developing a global 3D P wave velocity model of the Earth’s crust and mantle using seismic tomography. In this paper, we present the most recent version of our model, SALSA3D version 1.5, and demonstrate its ability to reduce mislocations for a large set of realizations derived from a carefully chosen set of globally-distributed ground truth events. Our model is derived from the latest version of the Ground Truth (GT) catalog of P and Pn travel time picks assembled by Los Alamos National Laboratory. To prevent over-weighting due to ray path redundancy and to reduce the computational burden, we cluster rays to produce representative rays. Reduction in the total number of ray paths is ~50%. The model is represented using the triangular tessellation system described by Ballard et al. (2009), which incorporates variable resolution in both the geographic and radial dimensions.. For our starting model, we use a simplified two layer crustal model derived from the Crust 2.0 model over a uniform AK135 mantle. Sufficient damping is used to reduce velocity adjustments so that ray path changes between iterations are small. We obtain proper model smoothness by using progressive grid refinement, refining the grid only around areas with significant velocity changes from the starting model. At each grid refinement level except the last one we limit the number of iterations to prevent convergence thereby preserving aspects of broad features resolved at coarser resolutions. Our approach produces a smooth, multi-resolution model with node density appropriate to both ray coverage and the velocity gradients required by the data. This scheme is computationally expensive, so we use a distributed computing framework based on the Java Parallel Processing Framework, providing us with ~400 processors. Resolution of our model is assessed using a

  11. The Earth's early evolution.

    Science.gov (United States)

    Bowring, S A; Housh, T

    1995-09-15

    The Archean crust contains direct geochemical information of the Earth's early planetary differentiation. A major outstanding question in the Earth sciences is whether the volume of continental crust today represents nearly all that formed over Earth's history or whether its rates of creation and destruction have been approximately balanced since the Archean. Analysis of neodymium isotopic data from the oldest remnants of Archean crust suggests that crustal recycling is important and that preserved continental crust comprises fragments of crust that escaped recycling. Furthermore, the data suggest that the isotopic evolution of Earth's mantle reflects progressive eradication of primordial heterogeneities related to early differentiation.

  12. Rare-earth-element minerals in martian breccia meteorites NWA 7034 and 7533: Implications for fluid-rock interaction in the martian crust

    Science.gov (United States)

    Liu, Yang; Ma, Chi; Beckett, John R.; Chen, Yang; Guan, Yunbin

    2016-10-01

    Paired martian breccia meteorites, Northwest Africa (NWA) 7034 and 7533, are the first martian rocks found to contain rare-earth-element (REE) phosphates and silicates. The most common occurrence is as clusters of anhedral monazite-(Ce) inclusions in apatite. Occasionally, zoned, irregular merrillite inclusions are also present in apatite. Monazite-bearing apatite is sometimes associated with alkali-feldspar and Fe-oxide. Apatite near merrillite and monazite generally contains more F and OH (F-rich region) than the main chlorapatite host and forms irregular boundaries with the main host. Locally, the composition of F-rich regions can reach pure fluorapatite. The chlorapatite hosts are similar in composition to isolated apatite without monazite inclusions, and to euhedral apatite in lithic clasts. The U-Th-total Pb ages of monazite in three apatite are 1.0 ± 0.4Ga (2σ), 1.1 ± 0.5Ga (2σ), and 2.8 ± 0.7Ga (2σ), confirming a martian origin. The texture and composition of monazite inclusions are mostly consistent with their formation by the dissolution of apatite and/or merrillite by fluid at elevated temperatures (>100 °C). In NWA 7034, we observed a monazite-chevkinite-perrierite-bearing benmoreite or trachyandesite clast. Anhedral monazite and chevkinite-perrierite grains occur in a matrix of sub-micrometer REE-phases and silicates inside the clast. Monazite-(Ce) and -(Nd) and chevkinite-perrierite-(Ce) and -(Nd) display unusual La and Ce depletion relative to Sm and Nd. In addition, one xenotime-(Y)-bearing pyrite-ilmenite-zircon clast with small amounts of feldspar and augite occurs in NWA 7034. One xenotime crystal was observed at the edge of an altered zircon grain, and a cluster of xenotime crystals resides in a mixture of alteration materials. Pyrite, ilmenite, and zircon in this clast are all highly altered, zircon being the most likely source of Y and HREE now present in xenotime. The association of xenotime with zircon, low U and Th contents, and the

  13. Estimation of a stress field in the earth`s crust using drilling-induced tensile fractures observed at well WD-1 in the Kakkonda geothermal field; Kakkonda WD-1 sei de kansokusareta drilling induced tensile fracture ni yoru chikaku oryokuba no suitei

    Energy Technology Data Exchange (ETDEWEB)

    Okabe, T. [GERD Geothermal Energy Research and Development Co. Ltd., Tokyo (Japan); Hayashi, K. [Tohoku Univ., Sendai (Japan). Inst. of Fluid Science; Kato, O.; Doi, N.; Miyazaki, S. [Japan Metals and Chemicals Co. Ltd., Tokyo (Japan); Uchida, T. [New Energy and Industrial Technology Development Organization, Tokyo, (Japan)

    1997-05-27

    This paper describes estimation of a stress field in the earth`s crust in the Kakkonda geothermal field. Formation micro imager (FMI) logging known as a crack detecting logging was performed in the well WD-1. This FMI logging has made observation possible on cracks along well axis thought to indicate size and direction of the crust stress, and drilling-induced tensile fractures (DTF). It was verified that these DTFs are generated initially in an azimuth determined by in-situ stress (an angle up to the DTF as measured counterclockwise with due north as a starting point, expressed in {theta}) in the well`s circumferential direction. It was also confirmed that a large number of cracks incline at a certain angle to the well axis (an angle made by the well axis and the DTF, expressed in {gamma}). The DTF is a crack initially generated on well walls as a result of such tensile stresses as mud pressure and thermal stress acting on the well walls during well excavation, caused by the in-situ stress field. Measurement was made on the {theta} and {gamma} from the FMI logging result, and estimation was given on a three-dimensional stress field. Elucidating the three-dimensional crust stress field in a geothermal reservoir is important in making clear the formation mechanism thereof and the growth of water-permeable cracks. This method can be regarded as an effective method. 9 refs., 8 figs., 1 tab.

  14. Rare-Earth Minerals in Martian Meteorite NWA 7034/7533: Evidence for Fluid-Rock Interaction in the Martian Crust

    OpenAIRE

    Liu, Yang; Ma, Chi; Chen, Yang; Beckett, John; Guan, Yunbin

    2015-01-01

    Monazite, chevkinite-perrierite and xenotime are common rare-earth minerals in terrestrial rocks and important repositories for the rare-earth-elements (REE). Liu and Ma [1-2] reported finding monazite, chevkinite-perrierite and xenotime in NWA 7034/7533, the ‘Black Beauty’ meteorite. Here, we provide a more detailed textural and compositional analysis of these minerals; our results suggest an origin via fluid-rock interaction.

  15. Structure of the earth's crust in the northern Apennines and neighbouring areas with particular regard to geothermal anomaly in Tuscany. Die Krustenstruktur des Nordapennins und angrenzender Gebiete mit besonderer Beruecksichtigung der geothermischen Anomalie der Toskana

    Energy Technology Data Exchange (ETDEWEB)

    Wigger, P.J.

    1984-01-01

    This study describes the constitution and structure of the earth's crust for the area extending from the western and northwestern boundary of the Adriatic plate to the foredeeps north and east of the Apennines, as well as to the European plate at the Western Alps and the Ligurian Sea region. The basis for analysis and interpretation is all the deep seismic sounding data available from this area. As well as my own results, I have also made use of already published results to describe the crustal structure of the adjacent regions. The results are summarized in a contour map of the Mohorovicic discontinuity as well as in crustal sections. The crustal structure of the area under study is very heterogeneous and the deduced velocity-depth functions vary greatly. Main characteristics include lateral changes in the crustal structure. A differentiation and classification of the resulting crustal types has been undertaken. 69 figures.

  16. Similar quartz crystallographic textures in rocks of continental earth's crust (by neutron diffraction data): II. Quartz textures in monophase rocks

    Energy Technology Data Exchange (ETDEWEB)

    Nikitin, A. N., E-mail: nikitin@nf.jinr.ru; Ivankina, T. I. [Joint Institute for Nuclear Research (Russian Federation); Ullemeyer, K. [Universitaet Kiel, Institut fuer Geowissenschaften (Germany); Vasin, R. N. [Joint Institute for Nuclear Research (Russian Federation)

    2008-09-15

    The types of quartz textures found in a large collection of multiphase rocks from different regions of the earth are analyzed. Crystallographic textures of granulite, amphibolite, slate, and gneiss samples are measured, classified, and compared with the similar textures of monomineral rocks.

  17. Earth

    CERN Document Server

    Carter, Jason

    2017-01-01

    This curriculum-based, easy-to-follow book teaches young readers about Earth as one of the eight planets in our solar system in astronomical terms. With accessible text, it provides the fundamental information any student needs to begin their studies in astronomy, such as how Earth spins and revolves around the Sun, why it's uniquely suitable for life, its physical features, atmosphere, biosphere, moon, its past, future, and more. To enhance the learning experience, many of the images come directly from NASA. This straightforward title offers the fundamental information any student needs to sp

  18. Applications of seismic pattern recognition and gravity inversion techniques to obtain enhanced subsurface images of the Earth's crust under the Central Metasedimentary Belt, Grenville Province, Ontario

    Science.gov (United States)

    Roy, Baishali; Mereu, R. F.

    2000-12-01

    Project Lithoprobe's Abitibi-Grenville transect seismic reflection lines 32 and 33 traverse the exposed Central Metasedimentary Belt (CMB) located in the Grenville province of the Precambrian Shield of Canada in southern Ontario. These seismic lines image a zone with a protracted deformational history spanning more than 300Myr. Detailed examination of the commercially processed stacked sections reveals a number of significant deficiencies in some important areas. The image quality in these zones of reduced coherency needs to be enhanced to examine specific features and their relation to the surface geology. Examination of near-vertical seismic data from Lines 32 and 33 revealed that the signal-to-noise ratio was not improved by stacking, due to misalignment of signals even after static, normal moveout corrections and residual static corrections. The presumed reason is that reflected seismic energy following long ray paths in heterogeneous media suffers from relative advances and delays in its propagation, and hence arrives at slightly different times at the receivers, tending to be poorly aligned relative to its theoretical traveltime curves. A pattern recognition (PR) method for signal enhancement followed by energy stacking in moving time windows was used in this study to improve the images in spite of misalignments. Reprocessing has refined the geometry of the reflection profiles. The objective of this paper is to use enhanced images of the seismic reflection data obtained by using a PR approach together with gravity data, using 2.5-D forward and 3-D inversion routines, to give an improved model of subsurface structure in the vicinity of lines 32 and 33. Line 32 is dominated by southeast-dipping reflectors soling into the lower crust. The listric geometry of the strong reflection packages of the CMB boundary thrust zone is interpreted to represent a crustal-scale ramp-flat geometry that accommodated northwest-directed tectonic transport of the CMB. This

  19. Scales of Heterogeneities in the Continental Crust and Upper Mantle

    OpenAIRE

    M. Tittgemeyer; F. Wenzel; Trond Ryberg; Fuchs, K

    1999-01-01

    A seismological characterization of crust and upper mantle can refer to large-scale averages of seismic velocities or to fluctuations of elastic parameters. Large is understood here relative to the wavelength used to probe the earth. In this paper we try to characterize crust and upper mantle by the fluctuations in media properties rather than by their average velocities. As such it becomes evident that different scales of heterogeneities prevail in different layers of crust mantle. Although ...

  20. Growth of the lower continental crust

    Science.gov (United States)

    Rudnick, Roberta L.

    1988-01-01

    One of the largest uncertainties in crustal composition and growth models is the nature of the lower continental crust. Specifically, by what processes is it formed and modified, and when is it formed, particularly in reference to the upper crust? The main reason for this lack of information is the scarcity of lower crustal rock samples. These are restricted to two types: rocks which outcrop in granulite facies terrains and granulite facies xenoliths which are transported to the earth's surface by young volcanics. The important conclusions arising from the xenolith studies are: the majority of mafic lower crustal xenoliths formed through cumulate process, resitic xenoliths are rare; and formation and metamorphism of the deep crust is intimately linked to igneous activity and/or orogeny which are manifest in one form or another at the earth's surface. Therefore, estimates of crustal growth based on surface exposures is representative, although the proportion of remobilized pre-existing crust may be significantly greater at the surface than in the deep crust.

  1. Early formation of evolved asteroidal crust.

    Science.gov (United States)

    Day, James M D; Ash, Richard D; Liu, Yang; Bellucci, Jeremy J; Rumble, Douglas; McDonough, William F; Walker, Richard J; Taylor, Lawrence A

    2009-01-08

    Mechanisms for the formation of crust on planetary bodies remain poorly understood. It is generally accepted that Earth's andesitic continental crust is the product of plate tectonics, whereas the Moon acquired its feldspar-rich crust by way of plagioclase flotation in a magma ocean. Basaltic meteorites provide evidence that, like the terrestrial planets, some asteroids generated crust and underwent large-scale differentiation processes. Until now, however, no evolved felsic asteroidal crust has been sampled or observed. Here we report age and compositional data for the newly discovered, paired and differentiated meteorites Graves Nunatak (GRA) 06128 and GRA 06129. These meteorites are feldspar-rich, with andesite bulk compositions. Their age of 4.52 +/- 0.06 Gyr demonstrates formation early in Solar System history. The isotopic and elemental compositions, degree of metamorphic re-equilibration and sulphide-rich nature of the meteorites are most consistent with an origin as partial melts from a volatile-rich, oxidized asteroid. GRA 06128 and 06129 are the result of a newly recognized style of evolved crust formation, bearing witness to incomplete differentiation of their parent asteroid and to previously unrecognized diversity of early-formed materials in the Solar System.

  2. Icelandic-type crust

    Science.gov (United States)

    Foulger, G.R.; Du, Z.; Julian, B.R.

    2003-01-01

    Numerous seismic studies, in particular using receiver functions and explosion seismology, have provided a detailed picture of the structure and thickness of the crust beneath the Iceland transverse ridge. We review the results and propose a structural model that is consistent with all the observations. The upper crust is typically 7 ?? 1 km thick, heterogeneous and has high velocity gradients. The lower crust is typically 15-30 ?? 5 km thick and begins where the velocity gradient decreases radically. This generally occurs at the V p ??? 6.5 km s-1 level. A low-velocity zone ??? 10 000 km2 in area and up to ??? 15 km thick occupies the lower crust beneath central Iceland, and may represent a submerged, trapped oceanic microplate. The crust-mantle boundary is a transition zone ???5 ?? 3 km thick throughout which V p increases progressively from ???7.2 to ???8.0 km s-1. It may be gradational or a zone of alternating high- and low-velocity layers. There is no seismic evidence for melt or exceptionally high temperatures in or near this zone. Isostasy indicates that the density contrast between the lower crust and the mantle is only ???90 kg m-3 compared with ???300 kg m-3 for normal oceanic crust, indicating compositional anomalies that are as yet not understood. The seismological crust is ???30 km thick beneath the Greenland-Iceland and Iceland-Faeroe ridges, and eastern Iceland, ???20 km beneath western Iceland, and ???40 km thick beneath central Iceland. This pattern is not what is predicted for an eastward-migrating plume. Low attenuation and normal V p/V s ratios in the lower crust beneath central and southwestern Iceland, and normal uppermost mantle velocities in general, suggest that the crust and uppermost mantle are subsolidus and cooler than at equivalent depths beneath the East Pacific Rise. Seismic data from Iceland have historically been interpreted both in terms of thin-hot and thick-cold crust models, both of which have been cited as supporting the plume

  3. Finite-difference migration of the field of refracted waves in studies of the deep structure of the Earth's crust and the upper mantle based on the DSS (on the example of the DOBRE profile)

    Science.gov (United States)

    Pilipenko, V. N.; Verpakhovskaya, A. O.; Starostenko, V. I.; Pavlenkova, N. I.

    2010-11-01

    The main results of deep seismic sounding (DSS) are usually presented in the form of high-velocity models of the medium. Some model examples and the international DOBRE profile have shown that the informativeness of the data obtained can be significantly enhanced by the construction of wave images of the Earth’s crust, based on the migration of refracted and wide-angle reflected waves. The Donets Basin Refraction/Reflection Experiment ( DOBRE) profile crosses the Dnieper-Donets paleorift zone in the Donbas region. Along the profile, refracted waves from the basement and the upper mantle and the reflections from the crust basement (the M boundary) are reliably traced. This wave migration has been used to construct a wave image of the structure of the Earth’s crust. As a result, a clear seismic image of the basement surface, whose depth changes along the profile from 0 to 20 km, was obtained. In near-slope parts of the basin, several major faults were identified that had not been identified previously during standard kinematic data processing. It is shown that the crust-upper mantle transition zone is a clearly reflective horizon only within the crystalline massifs; under a depression, it is represented by a lens-shaped highly-heterogeneous area. As shown in the model examples, the images obtained using such a migration accurately reflect the structural features of the medium, in spite of its complicated structure.

  4. Continental crust composition constrained by measurements of crustal Poisson's ratio

    Science.gov (United States)

    Zandt, George; Ammon, Charles J.

    1995-03-01

    DECIPHERING the geological evolution of the Earth's continental crust requires knowledge of its bulk composition and global variability. The main uncertainties are associated with the composition of the lower crust. Seismic measurements probe the elastic properties of the crust at depth, from which composition can be inferred. Of particular note is Poisson's ratio,Σ ; this elastic parameter can be determined uniquely from the ratio of P- to S-wave seismic velocity, and provides a better diagnostic of crustal composition than either P- or S-wave velocity alone1. Previous attempts to measure Σ have been limited by difficulties in obtaining coincident P- and S-wave data sampling the entire crust2. Here we report 76 new estimates of crustal Σ spanning all of the continents except Antarctica. We find that, on average, Σ increases with the age of the crust. Our results strongly support the presence of a mafic lower crust beneath cratons, and suggest either a uniformitarian craton formation process involving delamination of the lower crust during continental collisions, followed by magmatic underplating, or a model in which crust formation processes have changed since the Precambrian era.

  5. Formation of lower continental crust by relamination of buoyant arc lavas and plutons

    Science.gov (United States)

    Kelemen, Peter B.; Behn, Mark D.

    2016-03-01

    The formation of the Earth's continents is enigmatic. Volcanic arc magmas generated above subduction zones have geochemical compositions that are similar to continental crust, implying that arc magmatic processes played a central role in generating continental crust. Yet the deep crust within volcanic arcs has a very different composition from crust at similar depths beneath the continents. It is therefore unclear how arc crust is transformed into continental crust. The densest parts of arc lower crust may delaminate and become recycled into the underlying mantle. Here we show, however, that even after delamination, arc lower crust still has significantly different trace element contents from continental lower crust. We suggest that it is not delamination that determines the composition of continental crust, but relamination. In our conceptual model, buoyant magmatic rocks generated at arcs are subducted. Then, upon heating at depth, they ascend and are relaminated at the base of the overlying crust. A review of the average compositions of buoyant magmatic rocks -- lavas and plutons -- sampled from the Aleutians, Izu-Bonin-Marianas, Kohistan and Talkeetna arcs reveals that they fall within the range of estimated major and trace elements in lower continental crust. Relamination may thus provide an efficient process for generating lower continental crust.

  6. Laboratory experiments duplicate conditions in the Earth’s crust

    Science.gov (United States)

    Peselnick, L.; Dieterich, J.H.; Stewart, R.M.

    1974-01-01

    An experimental device that simulates conditions in the Earth's crust at depths of up to 30 kilometers has been constructed by geophysicists working at the U.S Geological Survey laboratories in Menlo Park, California. A high pressure "bomb" is being used to experimentally measure the velocity of seismic waves in different types of rock at various confining pressures and temperatures. The principal purpose of these measurements is to determine the elastic and non-elastic properties of rocks and minerals under conditions of high-pressure such as exist deep in the Earth's crust

  7. Personal Inquiry in the Earth Sciences.

    Science.gov (United States)

    Kaufman, W. Paul

    Designed as a basic workbook using the inquiry process or as a supplementary text in the classroom, this 129 page booklet is divided into five units: Moving in on the Earth From Space, The Earth's Great Bodies of Water, Composition of the Solid Earth, The Earth's Crust is Constantly Changing, and Studying the Earth's History. The exercises are…

  8. Geoelectromagnetic investigation of the earth’s crust and mantle

    CERN Document Server

    Rokityansky, Igor I

    1982-01-01

    Electrical conductivity is a parameter which characterizes composition and physical state of the Earth's interior. Studies of the state equations of solids at high temperature and pressure indicate that there is a close relation be­ tween the electrical conductivity of rocks and temperature. Therefore, measurements of deep conductivity can provide knowledge of the present state and temperature of the Earth's crust and upper mantle matter. Infor­ mation about the temperature of the Earth's interior in the remote past is derived from heat flow data. Experimental investigation of water-containing rocks has revealed a pronounced increase of electrical conductivity in the temperature range D from 500 to 700 DC which may be attributed to the beginning of fractional melting. Hence, anomalies of electrical conductivity may be helpful in identitying zones of melting and dehydration. The studies of these zones are perspective in the scientific research of the mobile areas of the Earth's crust and upper mantle where t...

  9. The continental record and the generation of continental crust

    OpenAIRE

    Cawood, Peter Anthony; Hawkesworth, Chris; Dhuime, Bruno Philippe Marcel

    2013-01-01

    Continental crust is the archive of Earth history. The spatial and temporal distribution of Earth's record of rock units and events is heterogeneous; for example, ages of igneous crystallization, metamorphism, continental margins, mineralization, and seawater and atmospheric proxies are distributed about a series of peaks and troughs. This distribution reflects the different preservation potential of rocks generated in different tectonic settings, rather than fundamental pulses of activity, a...

  10. Oceanic crust recycling and the formation of lower mantle heterogeneity

    Science.gov (United States)

    van Keken, Peter E.; Ritsema, Jeroen; Haugland, Sam; Goes, Saskia; Kaneshima, Satoshi

    2016-04-01

    The Earth's lower mantle is heterogeneous at multiple scales as demonstrated for example by the degree-2 distribution of LLSVPs seen in global tomography and widespread distribution of small scale heterogeneity as seen in seismic scattering. The origin of this heterogeneity is generally attributed to leftovers from Earth's formation, the recycling of oceanic crust, or a combination thereof. Here we will explore the consequences of long-term oceanic crust extraction and recycling by plate tectonics. We use geodynamical models of mantle convection that simulate plates in an energetically consistent manner. The recycling of oceanic crust over the age of the Earth produces persistent lower mantle heterogeneity while the upper mantle tends to be significantly more homogeneous. We quantitatively compare the predicted heterogeneity to that of the present day Earth by tomographic filtering of the geodynamical models and comparison with S40RTS. We also predict the scattering characteristics from S-P conversions and compare these to global scattering observations. The geophysical comparison shows that lower mantle heterogeneity is likely dominated by long-term oceanic crust recycling. The models also demonstrate reasonable agreement with the geochemically observed spread between HIMU-EM1-DMM in ocean island basalts as well as the long-term gradual depletion of the upper mantle as observed in Lu-Hf systematics.

  11. Physics of Neutron Star Crusts

    Directory of Open Access Journals (Sweden)

    Chamel Nicolas

    2008-12-01

    Full Text Available The physics of neutron star crusts is vast, involving many different research fields, from nuclear and condensed matter physics to general relativity. This review summarizes the progress, which has been achieved over the last few years, in modeling neutron star crusts, both at the microscopic and macroscopic levels. The confrontation of these theoretical models with observations is also briefly discussed.

  12. Effect of Phosphatization on Element Concentration of Cobalt-Rich Ferromanganese Crusts

    Institute of Scientific and Technical Information of China (English)

    PAN Jiahua; E. H. De CARLO; YANG Yi; LIU Shuqin; YOU Guoqin

    2005-01-01

    A detailed study on a small scale of the effect of phosphatization on the chemistry of marine cobalt-rich ferromanganese crusts supplies useful information for the evaluation and comprehensive utilization of crust mineral resources. Sub-samples from top to bottom of a 10-cm thick sample from the NW Pacific Magellan seamount were taken at 5 mm intervals. The concentration profiles of ore-forming and rare earth elements show that obvious differences exist between young unphosphatized crusts and old phosphatized crusts. In the old crusts Fe, Mn, Si, Al, Zn, Mg, Co, Ni and Cu elements are depleted and Ca, P, Sr, Ba and Pb elements are enriched. The order of depletion is Co > Ni > Mg > Al > Mn >Si> Cu > Zn > Fe, while the order of enrichment is P > Ca > Ba > Pb > Sr. The phosphate mineral controls the concentration variation of the ore-forming elements in crusts and causes loss of the main ore-forming elements such as Co and Ni. The phosphatization also affects the abundance of REEs in the crusts. REEs are more abundant and the content of Ce in old crusts is higher than that in young crusts, however, the pattern of REEs and their fractionation characteristics in new and old crusts are not fundamentally changed. A Y-positive anomaly in old crusts has no relationship to the phosphatization.

  13. Structure and composition of the continental crust in East China

    Institute of Scientific and Technical Information of China (English)

    高山; 骆庭川; 张本仁; 张宏飞; 韩吟文; 赵志丹; KERN; Hartmut

    1999-01-01

    Crustal structures of nine broad tectonic units in China, except the Tarim craton, are derived from 18 seismic refraction profiles including 12 geoscience transects. Abundances of 63 major, trace and rare earth elements in the upper crust in East China are estimated. The estimates are based on sampling of 11 451 individual rock samples over an area of 950 000 km~2, from which 905 large composite samples are prepared and analyzed by 13 methods. The middle, lower and total crust compositions of East China are also estimated from studies of exposed crustal cross sections and granulite xenoliths and by correlation of seismic data with lithologies. All the tectonic units except the Tarim craton and the Qinling orogen show a four-layered crustal structure, consisting of the upper, middle, upper lower, and lowermost crusts. P-wave velocities of the bulk lower crust and total crust are 6.8—7.0 and 6.4—6.5 km/s, respectively. They are slower by 0.2—0.4 km/s than the global averages. The bulk lower crust is su

  14. Dynamics of Pre-3 Ga Crust-Mantle Evolution

    Science.gov (United States)

    Patchett, P. J.; Chase, C. G.; Vervoort, J. D.

    2004-05-01

    During 3.0 to 2.7 Ga, the Earth's crust underwent a non-uniformitarian change from a pre-3.0 Ga environment where long-term preservation of cratons was rare and difficult, to post-2.7 Ga conditions where cratons were established and new continental crust generation took place largely at craton margins. Many models view the Earth's surface during pre-3 Ga time as broadly equivalent to the post 2.7 Ga regime. Any such uniformitarian or gradual evolution cannot explain the conundrum that only a tiny amount of pre-3 Ga crust is preserved today coupled with the fact that very little pre-3 Ga crust was incorporated into the large amount of new craton that came into existence during 3.0-2.7 Ga. If large volumes of pre-3 Ga continental crust existed, it disappeared either just prior to 3 Ga, or during 3.0-2.7 Ga. To explain sudden appearance of surviving but dominantly juvenile continental crust in a model where continents were large prior to 3 Ga, it would be necessary either that pre-3 Ga continent was recycled into the mantle at sites systematically different from those where new 3.0-2.7 Ga crust was made, or that widespread continent destruction preceded the 3.0-2.7 Ga crustal genesis. From expected mantle overturn in response to the heat budget, it is likely that most pre-3 Ga crust was both more mafic and shorter-lived than after 3 Ga. Although Nd and Hf ratios for pre-3 Ga rocks are uncertain due to polymetamorphism, it appears that depleted upper mantle was widespread by 2.7 Ga, even pre-3 Ga. Depletion may have been largely achieved by formation, subduction and storage of mafic crust for periods of 200-500 m.y. The rapid change to large surviving continents during 3.0-2.7 Ga was due to declining mantle overturn, and particularly to development of the ability to maintain subduction in one zone of the earth's surface for the time needed to allow evolution to felsic igneous rock compositions. In as much as storage of subducted slabs is probably occurring today, and

  15. Creep behavior of microbiotic crust

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The creep behavior of microbiotic crust at room temperature was revealed by the creep bending tests of cantilever beam under constant-load conditions.The variation in the deflection with time can be depicted well by a standard creep curve.Creep rupture is a fundamental failure mechanism of microbiotic crust due to creep.A simple theory was then applied to describe this new me-chanical behavior.The existence of creep phenomenon brings into question the validity of widely used methods for measuring the strength of microbiotic crust.

  16. High precision computation and numerical value characteristics of gravity emendation values arising from mass of the Earth's crust at the distance over 169 km from the observation point%169 km以远地壳质量的重力校正值高精度计算及其数值特征

    Institute of Scientific and Technical Information of China (English)

    安玉林; 郭良辉; 张明华

    2015-01-01

    In the previous textbooks of gravitational prospecting, the computation of gravity emendation values arising from mass of the Earth's crust at the distance over 2 km from the observation point is confined only to an area of circular ring 2.0~166.7 km in breadth and the computation expressions coming into existence in the orthogonal coordinate system are adopted. China Geological Survey has generalized in recent years the computation program of gravity emendation value that adopts the computation expressions both in the or⁃thogonal coordinate system and in the spherical coordinate system;nevertheless, the computation of gravity emendation values remains confined to an area of circular ring 2.0~166.7 km in breadth and fails to take into account the gravitation arising from mass of the Earth's crust at the distance over 166.7 km from the observation point. 10 years ago, the authors deduced alone gravity expression of the hexahedron with a spherical crust form and other expressions re⁃lated to the computation of gravity emendation values. After this, adopting these expressions, the authors conducted researches on high precision computation and numerical value characteristics of gravity emendation values arising from mass of the Earth's crust in pure spherical coordinate system, with the following computation achievements obtained: ① high precision computation result of "Gravity Emendation Value arising from Mass of the Earth's Crust at Distance Over 169 km From Observation Point" ( GEVMECDO 169 km FOP ) at the square grid 40 km in breadth on whole Earth's land and ocean surface; ② high precision computation achievements of GEVMECDO 169 km FOP at longitude and latitude grid of China's continent;③ high precision computation achievements of GEVM⁃ECDO 169km FOP at the square grid 0.556km in breadth in local 3°×2° area along the large curved portion of the Yarlung Zang Zang⁃bo River. Based on analyzing numerical values distribution characteristics of

  17. Crust Formation in Aluminum Cells

    Science.gov (United States)

    Oedegard, R.; Roenning, S.; Rolseth, S.; Thonstad, J.

    1985-11-01

    This paper examines the catalytic effects offlourides on the ϒ→α-Al2O3 phase transformation by heat treating commercial alumina samples with 2wt% additions of different flouride compounds. The various additives were ranked according to their effect on transformation temperature. Experiments were conducted to explain the high temperature coherence of crusts. The findings indicate that an alumina network is formed during ϒ→α phase transformation, which reinforces the crust on top of the cryolite bath.

  18. Lead isotopic evolution of Archean continental crust, Northern Tanzania

    Science.gov (United States)

    Bellucci, J. J.; McDonough, W. F.; Rudnick, R. L.; Walker, R. J.

    2010-12-01

    The continental crust is stratified in composition; the upper crust is generally enriched in highly incompatible trace elements relative to the lower crust [1]. The Western Granulite section of the Mozambique Belt of Northern Tanzania yields Archean Nd model ages and has zircons with U-Pb ages of ~2.6 Ga [2,3], but was strongly re-worked during the Pan-African Orogeny, ca. 560 Ma [2,3,4]. Here we use time-integrated Pb isotopic modeling for lower and middle crustal xenoliths, as well as upper crustal granulites to determine the timing of, and degree of intra-crustal differentiation. The Pb isotopic compositions of most feldspars in the lower crustal samples, measured via LA-MC-ICPMS, fall on the trend defined by the Tanzanian Craton [5] and therefore, were most likely extracted from the mantle at a similar time, ca. 2.7 Ga. However, some xenoliths fall off this trend and show enrichment in 207Pb/204Pb, which we interpret as reflecting derivation from more heterogeneous mantle than that sampled in the Tanzanian Craton. In contrast to lower crustal xenoliths from the Tanzanian Craton [5], we see no single feldspar Pb-Pb isochrons, which indicates complete re-homogenization of the Pb isotopic composition of the feldspars in the lower crust of the Mozambique Belt during the Pan-African Orogeny, and heating to > 600°C [5]. Using time integrated Pb modeling, the upper crust of the Western Granulites is enriched in U by ˜ 2.5 relative to that of the lower crust, which must have taken place around the time of mantle extraction (ca. 2.7 Ga). In addition, these calculations are consistent with a Th/U ratio of ˜ 4 for the bulk lower crust and ˜ 3 for the bulk upper crust. The common Pb isotopic composition of a single middle crustal xenolith implies a Th/U of 20, but is unlikely to be generally representative of the middle crust. [1] Rudnick, R. L. and Gao, S. (2003). In the Crust, vol. 3, Treatise on Geochemistry:1-64. [2] Mansur, A. (2008) Masters Thesis, University of

  19. Cobalt- and platinum-rich ferromanganese crusts and associated substrate rocks from the Marshall Islands

    Science.gov (United States)

    Hein, J.R.; Schwab, W.C.; Davis, A.

    1988-01-01

    Ferromanganese crusts cover most hard substrates on seafloor edifices in the central Pacific basin. Crust samples and their associated substrates from seven volcanic edifices of Cretaceous age along the Ratak chain of the Marshall Islands are discussed. The two most abundant substrate lithologies recovered were limestone, dominantly fore-reef slope deposits, and volcanic breccia composed primarily of differentiated alkalic basalt and hawaiite clasts in a phosphatized carbonate matrix. The degree of mass wasting on the slopes of these seamounts is inversely correlated with the thickness of crusts. Crusts are generally thin on limestone substrate. Away from areas of active mass-wasting processes, and large atolls, crusts may be as thick as 10 cm maximum. The dominant crystalline phase in the Marshall Islands crusts is ??-MnO2 (vernadite). High concentrations of cobalt, platinum and rhodium strongly suggest that the Marshall Islands crusts are a viable source for these important metals. Many metals and the rare earth elements vary significantly on a fine scale through most crusts, thus reflecting the abundances of different host mineral phases in the crusts and changes in seawater composition with time. High concentrations of cobalt, nickel, titanium, zinc, lead, cerium and platinum result from a combination of their substitution in the iron and manganese phases and their oxidation potential. ?? 1988.

  20. The Significance of Crust Structure and Continental Dynamics Inferred from Receiver Functions in West Yunnan

    Institute of Scientific and Technical Information of China (English)

    HE Chuansong; ZHU Lupei; WANG Qingcai

    2009-01-01

    In our study we collected the teleseismic record of 31 broadband stations and 9 PASSCAL stations in West Yunnan, as well as extracted more than a million receiver functions. Using the waveform model and stacking techniques, we calculated the earth crust thicknesses and V_p/V_s ratios below the stations and obtained 35 valid data points. At the same time, we evenly stacked the receiver functions at the same station and superimposed the two profiles' cross sections of the main tectonic units. The results show a clear difference between the crust thicknesses of different tectonic units. Because of the magma underplatting and delimanition of the lower crust in the role of deep process, the West Yunnan's crust can be divided two kinds-mafic-uitramafic and feidspathic crusts. The research also shows that the mafic-ultramafic crust corresponds to a good background of mineralization. The delamination of the lower crust is one of the leading causes for moderate to strong earthquake prone in central Yunnan. The thinner crust and high velocity ratio as well as the muitimodal structure of P_s in the Tengchong volcanic area confirms existence of a deep process of the strong magma underplating. Due to the basic crust structure and nature, it is believed that the Honghe fault is a main suture of the Gondwana and Eurasia continents.

  1. Palaeomagnetism and the continental crust

    Energy Technology Data Exchange (ETDEWEB)

    Piper, J.D.A.

    1987-01-01

    This book is an introduction to palaeomagnetism offering treatment of theory and practice. It analyzes the palaeomagnetic record over the whole of geological time, from the Archaean to the Cenozoic, and goes on to examine the impact of past geometries and movements of the continental crust at each geological stage. Topics covered include theory of rock and mineral magnetism, field and laboratory methods, growth and consolidation of the continental crust in Archaean and Proterozoic times, Palaeozoic palaeomagnetism and the formation of Pangaea, the geomagnetic fields, continental movements, configurations and mantle convection.

  2. 3D models of slow motions in the Earth's crust and upper mantle in the source zones of seismically active regions and their comparison with highly accurate observational data: I. Main relationships

    Science.gov (United States)

    Molodenskii, S. M.; Molodenskii, M. S.; Begitova, T. A.

    2016-09-01

    Constructing detailed models for postseismic and coseismic deformations of the Earth's surface has become particularly important because of the recently established possibility to continuously monitor the tectonic stresses in the source zones based on the data on the time variations in the tidal tilt amplitudes. Below, a new method is suggested for solving the inverse problem about the coseismic and postseismic deformations in the real non-ideally elastic, radially and horizontally heterogeneous, self-gravitating Earth with a hydrostatic distribution of the initial stresses from the satellite data on the ground surface displacements. The solution of this problem is based on decomposing the parameters determining the geometry of the fault surface and the distribution of the dislocation vector on this surface and elastic modules in the source in the orthogonal bases. The suggested approach includes four steps: 1. Calculating (by the perturbation method) the variations in Green's function for the radial and tangential ground surface displacements with small 3D variations in the mechanical parameters and geometry of the source area (i.e., calculating the functional derivatives of the three components of Green's function on the surface from the distributions of the elastic moduli and creep function within the volume of the source area and Burgers' vector on the surface of the dislocations); 2. Successive orthogonalization of the functional derivatives; 3. Passing from the decompositions of the residuals between the observed and modeled surface displacements in the system of nonorthogonalized functional derivatives to their decomposition in the system of orthogonalized derivatives; finding the corrections to the distributions of the sought parameters from the coefficients of their decompositions in the orthogonalized basis; and 4. Analyzing the ambiguity of the inverse problem solution by constructing the orthogonal complement to the obtained basis. The described

  3. Neutrino oscillations in the presence of the crust magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Syska, J., E-mail: jacek.syska@us.edu.p [Department of Field Theory and Particle Physics, Institute of Physics, University of Silesia, Katowice (Poland)

    2011-02-21

    It is noted that the crustal magnetic spectrum exhibits the signal from the partly correlated domain dipoles on the space-scale up to approximately 500 km. This suggests the nonzero correlation among the dynamical variables of the ferromagnetic magnetization phenomenon on the small domain scale inside the earth's crust also. Therefore the influence of the mean of the zero component of the polarization on the CP matter-induced violation indexes is discussed.

  4. Scales and effects of fluid flow in the upper crust.

    Science.gov (United States)

    Cathles, L M

    1990-04-20

    Two of the most important agents of geological change, solar energy and internal heat from the mantle, meet and battle for dominance in propelling aqueous and related fluids in the earth's upper crust. Which prevails and how they interact are subjects of active research. Recent work has demonstrated that both agents can propel fluids over nearly continental-scale distances in a fashion that influences a host of important geological processes and leaves a record in chemical alteration, mineral deposits, and hydrocarbon resources.

  5. Generation of new continental crust by sublithospheric silicic-magma relamination in arcs: A test of Taylor's andesite model

    NARCIS (Netherlands)

    Castro, Antonio; Vogt, Katharina; Gerya, Taras

    2013-01-01

    The paradox of the Earth's continental crust is that although this reservoir is generally regarded as having differentiated from the mantle, it has an andesitic bulk composition that contrasts with the intrinsic basaltic composition of mantle-derived melts. Classical models for new crust generation

  6. Statistics of Magnetar Crusts Magnetoemission

    Science.gov (United States)

    Kondratyev, V. N.; Korovina, Yu. V.

    2016-05-01

    Soft repeating gamma-ray (SGR) bursts are considered as magnetoemission of crusts of magnetars (ultranamagnetized neutron stars). It is shown that all the SGR burst observations can be described and systematized within randomly jumping interacting moments model including quantum fluctuations and internuclear magnetic interaction in an inhomogeneous crusty nuclear matter.

  7. Statistics of Magnetar Crusts Magnetoemission

    Directory of Open Access Journals (Sweden)

    Kondratyev V. N.

    2016-01-01

    Full Text Available Soft repeating gamma-ray (SGR bursts are considered as magnetoemission of crusts of magnetars (ultranamagnetized neutron stars. It is shown that all the SGR burst observations can be described and systematized within randomly jumping interacting moments model including quantum fluctuations and internuclear magnetic interaction in an inhomogeneous crusty nuclear matter.

  8. The Current Situation and Trends of the Technology for Impurity Removal of Weathering Crust Ion - absorbed Type Rare Earth Ores%风化壳淋积型稀土矿提取除杂技术现状及进展

    Institute of Scientific and Technical Information of China (English)

    邱廷省; 伍红强; 方夕辉; 李晓波

    2012-01-01

    On the basis of reviewing extensive literatures, the paper described the current situation of the technology for impurity removal of weathering crust ion - absorbed type rare earth ores,analyzed the main features of the technology,and proposed some problems existed in the process. Finally,the main future research directions were indicated on the theory research of the impurity removal technology, the development of new effective suppression agents for impurities, the optimization of process,the use of a combined flowsheet of mining,beneficiution and smelting,and so on.%在查阅大量文献资料的基础上,阐述了风化壳淋积型稀土矿除杂技术的研究现状,分析了目前风化壳淋积型稀土矿各种除杂技术的主要特点;提出了目前除杂技术中存在的一些问题;在风化壳淋积型稀土矿提取除杂技术的理论研究、开发新型的高效抑杂剂、优化工艺流程和运用采选冶联合流程等方面提出了今后的主要研究方向.

  9. Archean upper crust transition from mafic to felsic marks the onset of plate tectonics.

    Science.gov (United States)

    Tang, Ming; Chen, Kang; Rudnick, Roberta L

    2016-01-22

    The Archean Eon witnessed the production of early continental crust, the emergence of life, and fundamental changes to the atmosphere. The nature of the first continental crust, which was the interface between the surface and deep Earth, has been obscured by the weathering, erosion, and tectonism that followed its formation. We used Ni/Co and Cr/Zn ratios in Archean terrigenous sedimentary rocks and Archean igneous/metaigneous rocks to track the bulk MgO composition of the Archean upper continental crust. This crust evolved from a highly mafic bulk composition before 3.0 billion years ago to a felsic bulk composition by 2.5 billion years ago. This compositional change was attended by a fivefold increase in the mass of the upper continental crust due to addition of granitic rocks, suggesting the onset of global plate tectonics at ~3.0 billion years ago. Copyright © 2016, American Association for the Advancement of Science.

  10. Advances in the Study of Geochemistry and Paleo-oceanography of the Co-rich Crust

    Institute of Scientific and Technical Information of China (English)

    Cai Yihua; Huang Yipu

    2002-01-01

    The current advances in the study of geochemistry and paleo-oceanography of the Co-rich crust are reviewed in this paper. We summarize the study of geochemistry of the Co-rich crust, discuss the diffusion of elements in the Co-rich crust and the exchange with ambient seawater. Besides, we discuss the effect of phosphatization and substrate rocks on the composition of the Co-rich crust. We also introduce the application of stable isotopes (including the stable isotopes of Pb, Nd, and Hf), radioactive isotopes (including the radioactive isotopes of Be, U and Th), and elements (including the major elements, minor elements and rare earth elements) to the study of paleo-oceanography of the Co-rich crust.

  11. Study of Vertical Movements of the European Crust Using Tide Gauge and Gnss Observations

    Directory of Open Access Journals (Sweden)

    Tretyak Kornyliy

    2015-02-01

    Full Text Available This research is devoted to the study of vertical movements of the European crust on the basis of two independent methods, namely tide gauge and GNSS observations results. The description and classification of factors affecting sea level change has been made. The precision with which the movement of the earth's crust according to the results of tide gauge observations can be explored has been calculated . A methodology to identify the duration of tide gauge observations required for studies of vertical movements of the earth 's crust has been presented. Approximation of tide gauge time series with the help of Fourier series has been implemented, the need for long-term observations in certain areas has been explained. The diagram of the velocities of the vertical movements of the European crust on the basis of the tide gauge data and GNSS observations has been built and the anomalous areas where the observations do not coincide have been identified.

  12. Formation of hybrid arc andesites beneath thick continental crust

    Science.gov (United States)

    Straub, Susanne M.; Gomez-Tuena, Arturo; Stuart, Finlay M.; Zellmer, Georg F.; Espinasa-Perena, Ramon; Cai, Yue; Iizuka, Yoshiyuki

    2011-03-01

    Andesite magmatism at convergent margins is essential for the differentiation of silicate Earth, but no consensus exists as to andesite petrogenesis. Models proposing origin of primary andesite melts from mantle and/or slab materials remain in deadlock with the seemingly irrefutable petrographic and chemical evidence for andesite formation through mixing of basaltic mantle melts with silicic components from the overlying crust. Here we use 3He/4He ratios of high-Ni olivines to demonstrate the mantle origin of basaltic to andesitic arc magmas in the central Mexican Volcanic Belt (MVB) that is constructed on ~ 50 km thick continental crust. We propose that the central MVB arc magmas are hybrids of high-Mg# > 70 basaltic and dacitic initial mantle melts which were produced by melting of a peridotite subarc mantle interspersed with silica-deficient and silica-excess pyroxenite veins. These veins formed by infiltration of reactive silicic components from the subducting slab. Partial melts from pyroxenites, and minor component melts from peridotite, mix in variable proportions to produce high-Mg# basaltic, andesitic and dacitic magmas. Moderate fractional crystallization and recharge melt mixing in the overlying crust produces then the lower-Mg# magmas erupted. Our model accounts for the contrast between the arc-typical SiO2 variability at a given Mg# and the strong correlation between major element oxides SiO2, MgO and FeO which is not reproduced by mantle-crust mixing models. Our data further indicate that viscous high-silica mantle magmas may preferentially be emplaced as intrusive silicic plutonic rocks in the crust rather than erupt. Ultimately, our results imply a stronger turnover of slab and mantle materials in subduction zones with a negligible, or lesser dilution, by materials from the overlying crust.

  13. Granitic Perspectives on the Generation and Secular Evolution of the Continental Crust

    Science.gov (United States)

    Kemp, A. I. S.; Hawkesworth, C. J.

    2003-12-01

    Every geologist is acquainted with the principle of "uniformitarianism," which holds that present-day processes are the key to those that operated in the past. But the extent this applies to the processes driving the growth and differentiation of the Earth's continental crust remains a matter of debate. Unlike its dense oceanic counterpart, which is recycled back into the mantle by subduction within 200 Ma (see Chapter 3.13), the continental crust comprises buoyant quartzofeldspathic materials and is difficult to destroy by subduction. The continental crust is, therefore, the principal record of how conditions on the Earth have changed, and how processes of crust generation have evolved through geological time. It preserves evidence of secular variation in crustal compositions, and thus the way in which the crust has formed throughout Earth's history. Exploring the nature and origin of these variations is the focus of this chapter.Continental rocks are highly differentiated, and so the crust is enriched in incompatible components compared to the primeval chondritic composition (see Chapter 3.01). Of these, water is perhaps the most relevant, both for the origin and evolution of life, and also for many models of crust generation and differentiation. Similarly, the mass of continental crust is just 0.57% of the silicate Earth, and yet it contains ˜35% of the potassium (using the crustal composition estimates in Table 1). Continental rocks comprise the buoyant shell that was once thought to float on a basaltic substratum, inferred from the wide distribution of chemically similar continental flood basalts (von Cotta, 1858). The links with the adjacent oceans were perhaps unclear, "the greatest mountains confront the widest oceans" ( Dana, 1873). Yet, it has long been argued that the rock that has the most similar composition to the average continental crust, andesite, may be generated by fractional crystallization of basalt ( Daly (1914) and Bowen (1928); but see the

  14. What Hf isotopes in zircon tell us about crust-mantle evolution

    Science.gov (United States)

    Iizuka, Tsuyoshi; Yamaguchi, Takao; Itano, Keita; Hibiya, Yuki; Suzuki, Kazue

    2017-03-01

    The 176Lu-176Hf radioactive decay system has been widely used to study planetary crust-mantle differentiation. Of considerable utility in this regard is zircon, a resistant mineral that can be precisely dated by the U-Pb chronometer and record its initial Hf isotope composition due to having low Lu/Hf. Here we review zircon U-Pb age and Hf isotopic data mainly obtained over the last two decades and discuss their contributions to our current understanding of crust-mantle evolution, with emphasis on the Lu-Hf isotope composition of the bulk silicate Earth (BSE), early differentiation of the silicate Earth, and the evolution of the continental crust over geologic history. Meteorite zircon encapsulates the most primitive Hf isotope composition of our solar system, which was used to identify chondritic meteorites best representative of the BSE (176Hf/177Hf = 0.282793 ± 0.000011; 176Lu/177Hf = 0.0338 ± 0.0001). Hadean-Eoarchean detrital zircons yield highly unradiogenic Hf isotope compositions relative to the BSE, providing evidence for the development of a geochemically enriched silicate reservoir as early as 4.5 Ga. By combining the Hf and O isotope systematics, we propose that the early enriched silicate reservoir has resided at depth within the Earth rather than near the surface and may represent a fractionated residuum of a magma ocean underlying the proto-crust, like urKREEP beneath the anorthositic crust on the Moon. Detrital zircons from world major rivers potentially provide the most robust Hf isotope record of the preserved granitoid crust on a continental scale, whereas mafic rocks with various emplacement ages offer an opportunity to trace the Hf isotope evolution of juvenile continental crust (from εHf[4.5 Ga] = 0 to εHf[present] = + 13). The river zircon data as compared to the juvenile crust composition highlight that the supercontinent cycle has controlled the evolution of the continental crust by regulating the rates of crustal generation and intra

  15. Low-Reflectance Material in Mercury's Crust

    Science.gov (United States)

    Denevi, B. W.; Robinson, M. S.; Murchie, S. L.; Blewett, D. T.; Holsclaw, G. M.; McClintock, W. E.; McCoy, T. J.; McNutt, R. L.; Solomon, S. C.

    2008-12-01

    Mercury's reflectance and spectral slope are broadly similar to that of the lunar nearside. However, a host of Earth-based measurements and spacecraft data indicate that the composition and physical makeup of their surfaces may exhibit significant differences. Apollo samples and orbital remote sensing show that the lunar nearside surface is generally high in FeO (6 to 20 wt %) while the farside surface abundance is somewhat lower (3 to 10 wt %). Earth-based remote sensing of Mercury indicates that its surface contains less than 6 wt % FeO and perhaps even lower than 3 wt %. The reflectance of the Moon, and most likely Mercury, is controlled to first order by variations in iron and titanium abundances. If Mercury's ferrous iron content is much lower than that of the lunar nearside, then why is its reflectance comparable (0.019 vs. 0.021 at phase angle 65°, respectively)? Two-color vidicon observations by Mariner 10 revealed patchy low-reflectance, relatively blue units within Mercury's crust. Hapke and coworkers first speculated that opaque minerals (most likely ilmenite) could explain the color and reflectance of this low-reflectance component. Multispectral image data obtained by MESSENGER during its January 2008 flyby of Mercury covered new terrain and provided higher resolution, better signal-to-noise ratio, and extended wavelength coverage above that obtained by Mariner 10. The new data confirmed the existence of the low-reflectance material (LRM) and its relatively blue color and provide much better geologic context to interpret the origin of this material. MESSENGER multispectral data show the LRM to be widespread across the surface and to occur at depth within the crust. Three key observations show the vertical distribution of LRM. First the rims and floors of 100-km-scale craters within the Caloris basin are composed of LRM, streamers of LRM occur in ejecta traceable back to outcrops in crater floors (e.g. Mozart), and large continuous sections of ejecta

  16. Whole-Earth Decompression Dynamics

    CERN Document Server

    Herndon, J M

    2005-01-01

    The principles of Whole-Earth Decompression Dynamics are disclosed leading to a new way to interpret whole-Earth dynamics. Whole-Earth Decompression Dynamics incorporates elements of and unifies the two seemingly divergent dominant theories of continential displacement, plate tectonics theory and Earth expansion theory. Whole-Earth decompression is the consequence of Earth formation from within a Jupiter-like protoplanet with subsequent loss of gases and ices and concomitant rebounding. The initial whole-Earth decompression is expected to result in a global system of major primary decompression cracks appearing in the rigid crust which persist as the basalt feeders for the global, mid-oceanic ridge system. As the Earth subsequently decompresses, the area of the Earth's surface increases by the formation of secondary decompression cracks, often located near the continental margins, presently identified as oceanic trenches. These secondary decompression cracks are subsequently in-filled with basalt, extruded fr...

  17. Permanent components of the crust, geoid and ocean depth tides

    Science.gov (United States)

    Sun, Wenke; Sjöberg, Lars E.

    2001-04-01

    The tidal deformation caused by the luni-solar potential includes not only a periodic part, but also a time-independent part, called the permanent tide. How to deal with the tidal correction in gravimetric observations, especially the treatment of the permanent tide, has been discussed for a long time, since some practical and physical problems exist anyhow. A resolution adopted by IAG (1983) was that the permanent tidal attraction of the Moon and the Sun should be eliminated, but the permanent tidal deformation of the Earth be maintained. This is called zero gravity, and the geoid associated with it is the zero geoid. As to the crust deformation, Poutanen et al. (Poutanen, M., Vermeer, M., Mäkinen, J., 1996. The permanent tide in GPS positioning. Journal of Geodesy 70, 499-504.) suggested that co-ordinates should be reduced to the zero crust, i.e. the crust that includes the effect of the permanent tide. This research shows that horizontal components of the permanent earth tides, which are not considered in recent studies, are also important in GPS positioning and geoid determination. Since the tide-generating potential can be expanded into harmonics and divided into two parts (geodetic coefficients and the group of harmonic waves), the permanent earth tides can be easily obtained by multiplying the amplitude of the zero-frequency wavelength by the corresponding geoid geodetic coefficient. Formulas for both elastic and fluid cases are presented. Numerical results for the elastic case show that he vertical permanent crust (zero crust), geoid and ocean depth tides reach -12.0, -5.8 and 6.1 cm at the poles, and 5.9, 2.9 and -3.0 cm at the equator, respectively. The horizontal permanent crust, geoid and ocean depth tide components reach as much as 2.5, 8.7 and 6.3 cm, respectively. According to the solution of IAG (1983), the permanent vertical components are kept in GPS positioning and geoid computation. Thus, it is natural to include the horizontal components

  18. Hornblendite delineates zones of mass transfer through the lower crust

    Science.gov (United States)

    Daczko, Nathan R.; Piazolo, Sandra; Meek, Uvana; Stuart, Catherine A.; Elliott, Victoria

    2016-08-01

    Geochemical signatures throughout the layered Earth require significant mass transfer through the lower crust, yet geological pathways are under-recognized. Elongate bodies of basic to ultrabasic rocks are ubiquitous in exposures of the lower crust. Ultrabasic hornblendite bodies hosted within granulite facies gabbroic gneiss of the Pembroke Valley, Fiordland, New Zealand, are typical occurrences usually reported as igneous cumulate hornblendite. Their igneous features contrast with the metamorphic character of their host gabbroic gneiss. Both rock types have a common parent; field relationships are consistent with modification of host gabbroic gneiss into hornblendite. This precludes any interpretation involving cumulate processes in forming the hornblendite; these bodies are imposter cumulates. Instead, replacement of the host gabbroic gneiss formed hornblendite as a result of channeled high melt flux through the lower crust. High melt/rock ratios and disequilibrium between the migrating magma (granodiorite) and its host gabbroic gneiss induced dissolution (grain-scale magmatic assimilation) of gneiss and crystallization of mainly hornblende from the migrating magma. The extent of this reaction-replacement mechanism indicates that such hornblendite bodies delineate significant melt conduits. Accordingly, many of the ubiquitous basic to ultrabasic elongate bodies of the lower crust likely map the ‘missing’ mass transfer zones.

  19. Water in granulites: implications for the nature and evolution of the lower continental crust

    Institute of Scientific and Technical Information of China (English)

    YANG Xiaozhi; XIA Qunke; Etienne DELOULE; FAN Qicheng; HAO Yantao

    2007-01-01

    The lower continental crust is one of the most important sphere-layers in the deep earth, and is the direct place where the crust-mantle interactions occur. Granulites are the dominated rocks in the lower crust, and have critical implications for the knowledge of the composition, nature and evolution of the deep crust; fluids are important mediums influencing many geochemical, geophysical and geodynamical characteristics of the lower crust, and may also play a fundamental role in the petrogenesis of granulites and the formation of the lower crusts. In this paper, we review recent advances involved with the deep continental crust, granulites and fluids, and some longstanding debates. Combined with the Fourier-transform infrared spectroscopy (FTIR) analysis performed on the mineral assemblages (cpx, opx, plag and grt) in lower crustal granulite xenoliths and terrains (exposed section) from east China, it is suggested that structural water, dominated by OH, in these nominally anhydrous phases may constitute the most important water reservoir in the deep crust. This structual water may help to understand many lower crustal geological processes and phenomena (e. G. Seismic activities and electrical conductive anomalies), and influences from these water must be taken into consideration.

  20. Continental crust generated in oceanic arcs

    Science.gov (United States)

    Gazel, Esteban; Hayes, Jorden L.; Hoernle, Kaj; Kelemen, Peter; Everson, Erik; Holbrook, W. Steven; Hauff, Folkmar; van den Bogaard, Paul; Vance, Eric A.; Chu, Shuyu; Calvert, Andrew J.; Carr, Michael J.; Yogodzinski, Gene M.

    2015-04-01

    Thin oceanic crust is formed by decompression melting of the upper mantle at mid-ocean ridges, but the origin of the thick and buoyant continental crust is enigmatic. Juvenile continental crust may form from magmas erupted above intra-oceanic subduction zones, where oceanic lithosphere subducts beneath other oceanic lithosphere. However, it is unclear why the subduction of dominantly basaltic oceanic crust would result in the formation of andesitic continental crust at the surface. Here we use geochemical and geophysical data to reconstruct the evolution of the Central American land bridge, which formed above an intra-oceanic subduction system over the past 70 Myr. We find that the geochemical signature of erupted lavas evolved from basaltic to andesitic about 10 Myr ago--coincident with the onset of subduction of more oceanic crust that originally formed above the Galápagos mantle plume. We also find that seismic P-waves travel through the crust at velocities intermediate between those typically observed for oceanic and continental crust. We develop a continentality index to quantitatively correlate geochemical composition with the average P-wave velocity of arc crust globally. We conclude that although the formation and evolution of continents may involve many processes, melting enriched oceanic crust within a subduction zone--a process probably more common in the Archaean--can produce juvenile continental crust.

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

    Science.gov (United States)

    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

  2. Compositional variation and genesis of ferromanganese crusts of the Afanasiy-Nikitin Seamount, Equatorial Indian Ocean

    Indian Academy of Sciences (India)

    R P Rajani; V K Banakar; G Parthiban; A V Mudholkar; A R Chodankar

    2005-02-01

    Eight ferromanganese crusts (Fe-Mn crusts) with igneous and sedimentary substrates collected at different water depths from the Afanasiy-Nikitin Seamount are studied for their bulk major, minor and rare earth element composition. The Mn/Fe ratios > 1.5 indicate the hydrogenetic accretion of the Fe-Mn hydroxides. These Fe-Mn crusts are enriched in Co (up to 0.9%, average ∼0.5%) and Ce. The Ce-content is the highest reported so far (up to 3763 ppm, average ∼2250 ppm) for global ocean seamount Fe-Mn crusts. In spite of general similarity in the range of major, minor, and strictly trivalent rare earth element composition, the dissimilarity between the present Fe-Mn crusts and the Pacific seamount Fe-Mn crusts in Co and Ce associations with major mineral phases indicates inter-oceanic heterogeneity and region-specific conditions responsible for their enrichment. The decrease in Ce-anomaly (from ∼8 to ∼1.5) with increasing water depth (from ∼1.7km to ∼3.2 km) might suggest that the modern intermediate depth low oxygen layer was shifted and sustained at a deeper depth for a long period in the past.

  3. Controls on ferromanganese crust composition and reconnaissance resource potential, Ninetyeast Ridge, Indian Ocean

    Science.gov (United States)

    Hein, James R.; Conrad, Tracey; Mizell, Kira; Banakar, Virupaxa K.; Frey, Frederick A.; Sager, William W.

    2016-04-01

    derived predominantly from weathering of local volcanic outcrops. Fe-Mn crusts from a dredge haul at 3412 m water depth, 2°S latitude, are pervasively phosphatized along with the substrate rocks (site D7). Phosphatization took place through replacement of carbonate, preferential replacement of Fe oxyhydroxide relative to Mn oxide in the crusts, preferential replacement of silica-rich phases relative to Al-rich phases in the crusts, and precipitation of carbonate fluorapatite in pore space. The preferentially replaced silica may have been Si adsorbed on the Fe oxyhydroxide. The enrichment of Ni, Zn, and Cu in the phosphatized crust reflects preferential adsorption into the tunnel structure of todorokite. The rare earth element plus yttrium (REY) patterns indicate a lower oxidation potential during phosphatization of the NER crusts compared to Pacific phosphatized crusts. NER phosphatization occurred in a deeper-water environment than typical for phosphatization of Pacific crusts, occurred post-middle Miocene, a younger age than phosphatization the Pacific crusts, and had in part a different set of chemical changes produced by the phosphatization than did the Pacific crusts. The southern third of NER has Fe-Mn crusts with the highest Co (0.91%), Ni (0.43%), ΣREY (0.33%), Cu (0.22%), Te (146 ppm), Pt (1.5 ppm), Ru (52 ppb), and Rh (99 ppb) contents. These are among the highest Pt, Ru, and Rh concentrations measured in marine Fe-Mn deposits. Because of these high metal concentrations, exploration is warranted for the southern sector of the NER, especially at shallower-water sites where the platinum group elements (PGE) and Co are likely to be even more enriched.

  4. Crustal radiogenic heat production and the selective survival of ancient continental crust

    Science.gov (United States)

    Morgan, P.

    1985-01-01

    It is pointed out that the oldest terrestrial rocks have so far revealed no evidence of the impact phase of earth evolution. This observation suggests that processes other than impact were dominant at the time of stabilization of these units. However, a use of the oldest terrestrial rocks as a sample of the early terrestrial crust makes it necessary to consider the possibility that these rocks may represent a biased sample. In the present study, the global continental heat flow data set is used to provide further evidence that potassium, uranium, and thorium abundances are, on the average, low in surviving Archean crust relative to younger continental crust. An investigation is conducted of the implications of relatively low crustal radiogenic heat production to the stabilization of early continental crust, and possible Archean crustal stabilization models are discussed.

  5. Density constraints on the formation of the continental Moho and crust

    Science.gov (United States)

    Herzberg, C. T.; Carr, M. J.; Fyfe, W. S.

    1983-01-01

    As part of a general review of recent high-resolution seismological data, constraints are established for the distribution of mass in the continental crust and upper mantle of the earth. It is shown that the densities of mantle magmas such as MORB-like tholeiites, oicrites, and komatites at 10 kilobars are greater than densities in the continental crust. In order to explain the deviation, a mechanism is proposed for the control of mass transfer during igneous and metamorphic processes throughout geological time. Within the context of a description of the mechanism, the continental crust is characterized as a density filter through which only highly evolved magmas with H2O may pass. It is shown that the removal of less evolved magmas can lead to an over accretion (penetration) or an under accretion (underplating) of magmas in the continental Moho. Some implications of the proposed mechanism for current theoretical models of crust formation are discussed in detail.

  6. Pulsar glitches: The crust is not enough

    CERN Document Server

    Andersson, N; Ho, W C G; Espinoza, C M

    2012-01-01

    Pulsar glitches are traditionally viewed as a manifestation of vortex dynamics associated with a neutron superfluid reservoir confined to the inner crust of the star. In this Letter we show that the non-dissipative entrainment coupling between the neutron superfluid and the nuclear lattice leads to a less mobile crust superfluid, effectively reducing the moment of inertia associated with the angular momentum reservoir. Combining the latest observational data for prolific glitching pulsars with theoretical results for the crust entrainment we find that the required superfluid reservoir exceeds that available in the crust. This challenges our understanding of the glitch phenomenon, and we discuss possible resolutions to the problem.

  7. Behavior of leaching and precipitation of weathering crust ion-absorbed type by magnetic field

    Institute of Scientific and Technical Information of China (English)

    QIU Tingsheng; FANG Xihui; CUI Lifeng; FANG Yanxi

    2008-01-01

    With weathering crust Ion-Absorbed Type Rare Earth (IATRE) ores in southern Jiangxi as an example, rare earth percolation leaching and leaching solution precipitation process research were carried out under conditions of magnetic field. The effect on the rare earth leaching process such as magnetic field strength, magnetization time, magnetization manner, and other factors were discussed. The effect on the mother rare earth liquor sedimentation rate, purity, and crystallization behavior such as magnetic field strength, magnetization time, and magnetization manner were investigated. Leaching and precipitation mechanism of magnetization on IATRE were analyzed. The results showed that the magnetic treatment can improve leaching rate of weathering crust IATRE and the sedimentation rate, and reduce consumption of reagents.

  8. Origin of the earth's ocean basins

    Science.gov (United States)

    Frey, H.

    1977-01-01

    The earth's original ocean basins are proposed to be mare-type basins produced 4 billion y.a. by the flux of asteroid-sized objects responsible for the lunar mare basins. Scaling upward from the observed number of lunar basins for the greater capture cross-section and impact velocity of the earth indicates that at least 50% of an original global crust would have been converted to basin topography. These basins were flooded by basaltic liquids in times short compared to the isostatic adjustment time for the basin. The modern crustal dichotomy (60% oceanic, 40% continental crust) was established early in the history of the earth, making possible the later onset of plate tectonic processes. These later processes have subsequently reworked, in several cycles, principally the oceanic parts of the earth's crust, changing the configuration of the continents in the process. Ocean basins (and oceans themselves) may be rare occurrences on planets in other star systems.

  9. Formation of Fe-Mn crusts within a continental margin environment

    Science.gov (United States)

    Conrad, Tracey A.; Hein, James R.; Paytan, Adina; Clague, David A.

    2017-01-01

    Prime Crust Zone and other open-ocean basins. However, concentrations of total rare earth elements and yttrium average only slightly lower contents and in the future may be a strategic resource for the U.S.

  10. Granulites: Melts and fluids in the deep crust

    Science.gov (United States)

    Valley, John W.

    1988-01-01

    Known examples of granulite facies metamorphism span at least 3.5 by. of Earth history. Mineralogic geobarometry indicates that such metamorphism has occurred in the deep crust, typically at 20 to 30 km (6 to 9 kbar). Geothermometry indicates that peak T = 700 to 900 C and therefore that T was elevated by at least 200 C over an anorgenic geotherm of 15 to 20 C/km. Commonly invoked sources of heat include rising magmas, radioactive decay insulated by continent/continent collision, mantle volatiles, or crustal thinning. Present day crustal thicknesses are normal beneath exposed granulite terranes and the common absence of evidence for post-metamorphic underplating suggests synmetamorphic thicknesses of 60 to 80 km. Thus granulites form in tectonically active regions of thickened crust and elevated geotherm. Xenolith suites suggest that granulite facies mineralogy persists in the deepest crust after tectonism in spite of declining temperature to greenschist/amphibolite facies conditions. The relative proportions of granulite terranes that are formed by Adirondack-type metamorphism dominantly magmatic/fluid-absent), India-type metamorphism (CO2 saturated), or some combination of 1 and 2 remains an important tectonic question.

  11. Fluid Release and the Deformation of Subducting Crust

    Science.gov (United States)

    Maunder, Benjamin; van Hunen, Jeroen; Magni, Valentina; Bouilhol, Pierre

    2014-05-01

    It is known that slab dehydration is crucial in subduction dynamics and for the formation of arc-magmatism. Previous studies of this process have constrained this intake and subsequent release of fluids into the mantle wedge by considering the stability hydrous phases within the slab. Other, more dynamical effects of this hydration state and partial melting have also been suggested, such as the possibility of "cold plumes", crustal delamination, and subduction channel return flow. These processes have been inferred to play a role in the generation of continental crust over time through accumulation and melting beneath the overriding plate. Water content and melt fraction have a strong control on the rheology of the system. Therefore we investigate the effect of these parameters on the dynamics of a subducting slab, with the aim to establish the physical bounds on the delamination process. To do this we use a coupled geodynamical-petrological model that tracks dehydration and melting reactions in order to factor in the rheological effect of metamorphism and magmatism on slab and mantle wedge dynamics. We focus primarily on the strength of the subducting crust and the possibility of delamination. We then extend this investigation by considering whether early earth crust formation could have been the result of such a processes by looking at a hypothetical Archean setting.

  12. Primary carbonatite melt from deeply subducted oceanic crust

    Energy Technology Data Exchange (ETDEWEB)

    Walter, M.J.; Bulanova, G.P.; Armstrong, L.S.; Keshav, S.; Blundy, J.D.; Gudfinnesson, G.; Lord, O.T.; Lennie, A.R.; Clark, S.M.; Smith, C.B.; Gobbo, L.

    2008-07-01

    Partial melting in the Earth's mantle plays an important part in generating the geochemical and isotopic diversity observed in volcanic rocks at the surface. Identifying the composition of these primary melts in the mantle is crucial for establishing links between mantle geochemical 'reservoirs' and fundamental geodynamic processes. Mineral inclusions in natural diamonds have provided a unique window into such deep mantle processes. Here they provide exper8imental and geochemical evidence that silicate mineral inclusions in diamonds from Juina, Brazil, crystallized from primary and evolved carbonatite melts in the mantle transition zone and deep upper mantle. The incompatible trace element abundances calculated for a melt coexisting with a calcium-titanium-silicate perovskite inclusion indicate deep melting of carbonated oceanic crust, probably at transition-zone depths. Further to perovskite, calcic-majorite garnet inclusions record crystallization in the deep upper mantle from an evolved melt that closely resembles estimates of primitive carbonatite on the basis of volcanic rocks. Small-degree melts of subducted crust can be viewed as agents of chemical mass-transfer in the upper mantle and transition zone, leaving a chemical imprint of ocean crust that can possibly endure for billions of years.

  13. The ESA earth observation polar platform programme

    Science.gov (United States)

    Rast, M.; Readings, C. J.

    1991-08-01

    The overall scenario of ESA earth observation polar platform program is reviewed with particular attention given to instruments currently being considered for flight on the first European polar platforms. The major objectives of the mission include monitoring the earth's environment on various scales; management and monitoring of the earth's resources; improvement of the service provided to the worldwide operational meteorological community, investigation of the structure and dynamics of the earth's crust and interior. The program encompasses four main elements: an ERS-1 follow-on mission (ERS-2), a solid earth gravity mission (Aristoteles), a Meteosat Second Generation, and a series of polar orbit earth observation missions.

  14. A plate tectonics oddity: Caterpillar-walk exhumation of subducted continental crust

    NARCIS (Netherlands)

    Tirel, C.; Brun, J.-P.; Burov, E.; Wortel, M.J.R.; Lebedev, S.

    2013-01-01

    Since plate tectonics began on Earth, grandiose "subduction factories" have continually shaped the continents, accreting continental blocks and new crust at the convergent plate boundaries. An enigmatic product of subduction factories is the high-pressure to ultrahigh-pressure (HP-UHP) metamorphic

  15. A plate tectonics oddity: Caterpillar-walk exhumation of subducted continental crust

    NARCIS (Netherlands)

    Tirel, C.; Brun, J.-P.; Burov, E.; Wortel, M.J.R.; Lebedev, S.

    2013-01-01

    Since plate tectonics began on Earth, grandiose "subduction factories" have continually shaped the continents, accreting continental blocks and new crust at the convergent plate boundaries. An enigmatic product of subduction factories is the high-pressure to ultrahigh-pressure (HP-UHP) metamorphic c

  16. A plate tectonics oddity: Caterpillar-walk exhumation of subducted continental crust

    NARCIS (Netherlands)

    Tirel, C.; Brun, J.-P.; Burov, E.; Wortel, M.J.R.; Lebedev, S.

    2013-01-01

    Since plate tectonics began on Earth, grandiose "subduction factories" have continually shaped the continents, accreting continental blocks and new crust at the convergent plate boundaries. An enigmatic product of subduction factories is the high-pressure to ultrahigh-pressure (HP-UHP) metamorphic c

  17. Molecular mobility in crispy bread crust

    NARCIS (Netherlands)

    Nieuwenhuijzen, van N.H.

    2008-01-01

    The aim of the PhD study on molecular mobility was to analyse the molecular grounds for the deterioration of crispy/crunchy characteristics of cellular solid foods. A fresh baguette for example has a crispy crust and a moist and soft interior. Moisture migrates from crumb to crust. Already at a wate

  18. Eocene deep crust at Ama Drime, Tibet

    DEFF Research Database (Denmark)

    Kellett, Dawn; Cottle, John; Smit, Matthijs Arjen

    2014-01-01

    burial and exhumation of a cold subducted slab. The rocks instead resulted from crustal thickening during the early stages of continental collision, and resided in the lower-middle crust for >20 m.y. before they were exhumed and reheated. These new data provide solid evidence for the Indian crust having...

  19. Water Uptake Mechanism in Crispy Bread Crust

    NARCIS (Netherlands)

    Nieuwenhuijzen, van N.H.; Meinders, M.B.J.; Tromp, R.H.; Hamer, R.J.; Vliet, van T.

    2008-01-01

    Crispness is an important quality characteristic of dry solid food products such as crispy rolls. Its retention is directly related to the kinetics of water uptake by the crust. In this study, a method for the evaluation of the water sorption kinetics in bread crust is proposed. Two different sorpti

  20. Microbial community on oceanic ferro-manganese crusts from Takuyo-Daigo Seamount and Ryusei Seamount

    Science.gov (United States)

    Nitahara, S.; Kato, S.; Yamagishi, A.

    2012-12-01

    Background and Purpose Iron and manganese oxide deposits are often found on deep seafloor. Rocks covered with these oxides are called ferro-manganese crusts (Mn crusts), and are ubiquitously distributed on deep seafloor (Rona 2003). Because Mn crusts contain rare metals such as Co, Pt and rare earth element, it can be resources in the future. Mn crusts and microbes on Mn crusts may contribute to material, especially carbon and nitrogen circulation between hydrosphere and lithosphere. Mechanism of Mn crust formation is not completely understood. Wang et al. propose a model that microorganisms associate with initial Mn mineral deposition (Wang et al., 2011). There is a possibility that microbes may contribute to formation of Mn crust relying on their ability to oxidize Fe and Mn. However, there is limited information about diversity, spatial distribution and abundance of microbes on Mn crust surface. Our purpose is to clarify microbial community composition, spatial distribution, diversity and abundance of microbes on Mn crusts collected from Takuyo-Daigo seamount and Ryusei seamount. Method We collected Mn crusts, sediments and ambient seawater from Takuyo-Daigo seamount at the depth of 1200 m, 1419 m, 2209 m and 2991 m during NT09-02 cruise in Feb 2009 and Ryusei seamount at the depth of 1194 m, 2079 m during KY11-02 in Feb 2011 with remotely operated vehicle Hyper-Dolphin (JAMSTEC). Genomic DNA was extracted from each sample using Fast DNA kit for soil (Qbiogene). Partial 16S rRNA gene and amoA gene were amplified by PCR with prokaryote-universal primer set (Uni516F-Uni1407R) and bacterial and archaeal amoA specific primer sets. PCR products were cloned. The nucleotide sequences of randomly selected clones were determined. We performed phylogenetic and statistical analysis to determine microbial community compositions, and estimated diversity indices. We also estimated the copy numbers of 16S rRNA and amoA genes of Bacteria and Archaea by quantitative PCR. Results

  1. Secular geodynamic changes at the base of the crust recorded by anorthosites

    Science.gov (United States)

    Bybee, G. M.; Parman, S. W.

    2016-12-01

    Proterozoic anorthosites (PA) were formed by fractionation of large basaltic magma bodies as they impinged on the continental crust. Despite their complex magmatic origins, the composition of plagioclases in PA are notably constant, most lying between An 40 and 60. PA first appear in the geological record at 2.7 Ga and disappear at 0.6 Ga. The constancy of mineral composition and texture over 2 Ga is remarkable. But what caused PA to begin to form at 2.7 Ga? And what ended their formation at 0.6 Ga? PA are produced by a distinct set of conditions: 1) voluminous batholiths of high-Al basaltic magma (±104 km3for the largest batholiths), 2) highly effective separation of plagioclase from melt and mafic crystals, 3) crystallization at lower crustal conditions (>30km depth) and 4) fairly anhydrous conditions. The lack of PA prior to 2.7 Ga and after 0.6 Ga implies these conditions did not exist on the Earth at those times, suggesting fundamental secular change. Observations of both the Earth's interior (zircon age distributions, age of cratonic mantle) and atmosphere/hydrosphere (S-MIF in sediments, d13C in organic carbon) suggest 2.7 Ga was a unique period in Earth's history. The appearance of PA at this time implies that whatever was driving these effects involved not just the Earth's surface (e.g. area of exposed continent, continental geometry) as has been postulated, but also secular changes in conditions at the base of the crust. One possibility is that the continental crust thickened or stiffened dramatically at this time, producing conditions necessary for PA production (i.e. high pressure at the crust/mantle boundary) not present in pre-2.7 Ga crust. Longer-lived subduction events could also promote extensive basaltic magma ponding at the base of the crust. At 0.6 Ga, the crust may have become too thick or stiff to allow passage of large, viscous mushes. Thus PA could record the thermo-tectonic evolution of the continental crust. Alternatively, the high

  2. On mega-undations: A new model for the earth's evolution

    NARCIS (Netherlands)

    Bemmelen, R.W. van

    Two fundamentally different views on the origin of the sialic crust of the earth are possible. According to one view the sialic crust has been produced from the inside by progressive physico-chemical differentiation of the earth's material into concentric spheres. Such an endogenic origin of the

  3. On mega-undations: A new model for the earth's evolution

    NARCIS (Netherlands)

    Bemmelen, R.W. van

    1966-01-01

    Two fundamentally different views on the origin of the sialic crust of the earth are possible. According to one view the sialic crust has been produced from the inside by progressive physico-chemical differentiation of the earth's material into concentric spheres. Such an endogenic origin of the cru

  4. Large-scale subduction of continental crust implied by India-Asia mass-balance calculation

    Science.gov (United States)

    Ingalls, Miquela; Rowley, David B.; Currie, Brian; Colman, Albert S.

    2016-11-01

    Continental crust is buoyant compared with its oceanic counterpart and resists subduction into the mantle. When two continents collide, the mass balance for the continental crust is therefore assumed to be maintained. Here we use estimates of pre-collisional crustal thickness and convergence history derived from plate kinematic models to calculate the crustal mass balance in the India-Asia collisional system. Using the current best estimates for the timing of the diachronous onset of collision between India and Eurasia, we find that about 50% of the pre-collisional continental crustal mass cannot be accounted for in the crustal reservoir preserved at Earth's surface today--represented by the mass preserved in the thickened crust that makes up the Himalaya, Tibet and much of adjacent Asia, as well as southeast Asian tectonic escape and exported eroded sediments. This implies large-scale subduction of continental crust during the collision, with a mass equivalent to about 15% of the total oceanic crustal subduction flux since 56 million years ago. We suggest that similar contamination of the mantle by direct input of radiogenic continental crustal materials during past continent-continent collisions is reflected in some ocean crust and ocean island basalt geochemistry. The subduction of continental crust may therefore contribute significantly to the evolution of mantle geochemistry.

  5. Heat transport within the Earth

    CERN Document Server

    Herndon, J Marvin

    2011-01-01

    Numerous attempts have been made to interpret Earth's dynamic processes based upon heat transport concepts derived from ordinary experience. But, ordinary experience can be misleading, especially when underlain by false assumptions. Geodynamic considerations traditionally have embraced three modes of heat transport: conduction, convection, and radiation. Recently, I introduced a fourth, "mantle decompression thermal tsunami" that, I submit, is responsible for emplacing heat at the base of the Earth's crust. Here, I review thermal transport within the Earth and speculate that there might be a fifth mode: "heat channeling", involving heat transport from the core to "hot-spots" such as those that power the Hawaiian Islands and Iceland.

  6. The earth's shape and gravity

    CERN Document Server

    Garland, G D; Wilson, J T

    2013-01-01

    The Earth's Shape and Gravity focuses on the progress of the use of geophysical methods in investigating the interior of the earth and its shape. The publication first offers information on gravity, geophysics, geodesy, and geology and gravity measurements. Discussions focus on gravity measurements and reductions, potential and equipotential surfaces, absolute and relative measurements, and gravity networks. The text then elaborates on the shape of the sea-level surface and reduction of gravity observations. The text takes a look at gravity anomalies and structures in the earth's crust; interp

  7. Sulfur Earth

    Science.gov (United States)

    de Jong, B. H.

    2007-12-01

    Variations in surface tension affect the buoyancy of objects floating in a liquid. Thus an object floating in water will sink deeper in the presence of dishwater fluid. This is a very minor but measurable effect. It causes for instance ducks to drown in aqueous solutions with added surfactant. The surface tension of liquid iron is very strongly affected by the presence of sulfur which acts as a surfactant in this system varying between 1.9 and 0.4 N/m at 10 mass percent Sulfur (Lee & Morita (2002), This last value is inferred to be the maximum value for Sulfur inferred to be present in the liquid outer core. Venting of Sulfur from the liquid core manifests itself on the Earth surface by the 105 to 106 ton of sulfur vented into the atmosphere annually (Wedepohl, 1984). Inspection of surface Sulfur emission indicates that venting is non-homogeneously distributed over the Earth's surface. The implication of such large variation in surface tension in the liquid outer core are that at locally low Sulfur concentration, the liquid outer core does not wet the predominantly MgSiO3 matrix with which it is in contact. However at a local high in Sulfur, the liquid outer core wets this matrix which in the fluid state has a surface tension of 0.4 N/m (Bansal & Doremus, 1986), couples with it, and causes it to sink. This differential and diapiric movement is transmitted through the essentially brittle mantle (1024 Pa.s, Lambeck & Johnson, 1998; the maximum value for ice being about 1030 Pa.s at 0 K, in all likely hood representing an upper bound of viscosity for all materials) and manifests itself on the surface by the roughly 20 km differentiation, about 0.1 % of the total mantle thickness, between topographical heights and lows with concomitant lateral movement in the crust and upper mantle resulting in thin skin tectonics. The brittle nature of the medium though which this movement is transmitted suggests that the extremes in topography of the D" layer are similar in range to

  8. Making continental crust: The sanukitoid connection

    Institute of Scientific and Technical Information of China (English)

    Yoshiyuki TATSUMI

    2008-01-01

    The average continental crust possesses intermediate compositions that typify arc magmatism and as a result it is believed to have been created at ancient convergent plate boundaries. One possible mechanism for intermediate continental crust formation is the direct production of andesitic melts in the upper mantle. Sanukitoids, which characterize the Setouchi volcanic belt, SW Japan, include unusually high-Mg andesites (HMA). They were generated by slab melting and subsequent melt-mantle interactions under unusual tectonic settings such as where warm lithosphere subducts into hot upper mantle. Such conditions would have existed in the Archean. Hydrous HMA magmas are likely to have solidified within the crust to form HMA plutons, which were then remelted to produce differentiated sanukitoids. At present, generation and differentiation of HMA magmas may be taking place in the Izu-Bonin-Mariana arc-trench system (IBM), because (1) HMA magmatism characterizes the initial stages of the iBM evolution and (2) the IBM middle crust exhibits Vp identical to that of the bulk continental crust. Vp estimates for plutonic rocks with HMA compositions support this. However tonalitic composition for middle-crust-forming rocks cannot be ruled out, suggesting an alternative possibility that the continental crust has been created by differentiation of mantle-derived basaltic magmas.

  9. Microphytic crusts: 'topsoil' of the desert

    Science.gov (United States)

    Belnap, Jayne

    1990-01-01

    Deserts throughout the world are the home of microphytic, or cryptogamic, crusts. These crusts are dominated by cyanobacteria, previously called blue-green algae, and also include lichens, mosses, green algae, microfungi and bacteria. They are critical components of desert ecosystems, significantly modifying the surfaces on which they occur. In the cold deserts of the Colorado Plateau (including parts of Utah, Arizona, Colorado, and New Mexico), these crusts are extraordinarily well-developed, and may represent 70-80% of the living ground cover.

  10. Eocene deep crust at Ama Drime, Tibet

    DEFF Research Database (Denmark)

    Kellett, Dawn; Cottle, John; Smit, Matthijs Arjen

    2014-01-01

    for burial of the lower Indian crust beneath Tibet reported from the central-eastern Himalaya. Granulite-facies overprinting followed at ca. 15–13 Ma, as indicated by U-Pb zircon ages. Unlike ultrahigh-pressure eclogites of the northwest Himalaya, the Ama Drime eclogites are not characteristic of rapid...... burial and exhumation of a cold subducted slab. The rocks instead resulted from crustal thickening during the early stages of continental collision, and resided in the lower-middle crust for >20 m.y. before they were exhumed and reheated. These new data provide solid evidence for the Indian crust having...

  11. Crust rheology, slab detachment and topography

    Science.gov (United States)

    Duretz, T.; Gerya, T. V.

    2012-04-01

    The collision between continents following the closure of an ocean can lead to the subduction of continental crust. The introduction of buoyant crust within subduction zones triggers the development of extensional stresses in slabs which eventually result in their detachment. The dynamic consequences of slab detachment affects the development of topography, the exhumation of high-pressure rocks and the geodynamic evolution of collision zones. We employ two-dimensional thermo-mechanical modelling in order to study the importance of crustal rheology on the evolution of spontaneous subduction-collision systems and the occurrence of slab detachment. The modelling results indicate that varying the rheological structure of the crust can results in a broad range of collisional evolutions involving slab detachment, delamination (associated to slab rollback), or the combination of both mechanisms. By enhancing mechanical coupling at the Moho, a strong crust leads to the deep subduction of the crust (180 km). These collisions are subjected to slab detachment and subsequent coherent exhumation of the crust accommodated by eduction (inversion of subduction sense) and thrusting. In these conditions, slab detachment promotes the development of a high (> 4.5 km) and narrow (delamination of the lithosphere, preventing slab detachment to occur. Further shortening leads to buckling and thickening of the crust resulting in the development of topographic bulging on the lower plate. Collisions involving rheologically layered crust are characterised by a decoupling level at mid-crustal depths. These initial condition favours the delamination of the upper crust as well as the deep subduction of the lower crust. These collisions are thus successively affected by delamination and slab detachment and both processes contribute to the exhumation of the subducted crust. A wide (> 200 km) topographic plateau develops as the results of the buoyant extrusion of the upper crust onto the foreland

  12. Biogenic crust dynamics on sand dunes

    CERN Document Server

    Kinast, Shai; Yizhaq, Hezi; Ashkenazy, Yosef

    2012-01-01

    Sand dunes are often covered by vegetation and biogenic crusts. Despite their significant role in dune stabilization, biogenic crusts have rarely been considered in studies of dune dynamics. Using a simple model, we study the existence and stability ranges of different dune-cover states along gradients of rainfall and wind power. Two ranges of alternative stable states are identified: fixed crusted dunes and fixed vegetated dunes at low wind power, and fixed vegetated dunes and active dunes at high wind power. These results suggest a cross-over between two different forms of desertification.

  13. Temperature distribution in magnetized neutron star crusts

    CERN Document Server

    Geppert, U; Page, D

    2004-01-01

    We investigate the influence of different magnetic field configurations on the temperature distribution in neutron star crusts. We consider axisymmetric dipolar fields which are either restricted to the stellar crust, ``crustal fields'', or allowed to penetrate the core, ``core fields''. By integrating the two-dimensional heat transport equation in the crust, taking into account the classical (Larmor) anisotropy of the heat conductivity, we obtain the crustal temperature distribution, assuming an isothermal core. Including quantum magnetic field effects in the envelope as a boundary condition, we deduce the corresponding surface temperature distributions. We find that core fields result in practically isothermal crusts unless the surface field strength is well above $10^{15}$ G while for crustal fields with surface strength above a few times $10^{12}$ G significant deviations from isothermality occur at core temperatures inferior or equal to $10^8$ K. At the stellar surface, the cold equatorial region produce...

  14. On the differences in continental rifting at the Earth, Mars and Venus

    Science.gov (United States)

    Nikishin, A. M.; Milanovsky, E. E.

    1985-01-01

    During the process of continental rifting on Earth, the lower ductile crust stretches, forming a neck, while the upper brittle crust is broken in blocks by faults, and the blocks sink down the thinned lower crust; if the stretching continues, the neck may break and a newly originated oceanic crust is formed at this place. The rift system structure depends on the depth of the boundary surface between the brittle crust and the ductile crust, the litospheric thickness, the tension value, etc.. The rigid brittle rifting when narrow necks form in the lower crust is characteristic of the contemporary Earth; on Mars the brittle rifting with large subsidence was characteristic of the Tharsis upland formation epoch. The ductile rifting is typical of the Venus. The differences in rheologic features of the lithospheres of different planets causes the variation in types of rifting.

  15. Neutron Star Crust and Molecular Dynamics Simulation

    CERN Document Server

    Horowitz, C J; Schneider, A; Berry, D K

    2011-01-01

    In this book chapter we review plasma crystals in the laboratory, in the interior of white dwarf stars, and in the crust of neutron stars. We describe a molecular dynamics formalism and show results for many neutron star crust properties including phase separation upon freezing, diffusion, breaking strain, shear viscosity and dynamics response of nuclear pasta. We end with a summary and discuss open questions and challenges for the future.

  16. How development and disturbance of biological soil crust do affect runoff and erosion in drylands?

    Energy Technology Data Exchange (ETDEWEB)

    Chamizo, S.; Canton, Y.; Afana, A.; Lazaro, R.; Domingo, F.; Sole-Benet, A.

    2009-07-01

    Deserts and semiarid ecosystems (shrub lands and grasslands) are the largest terrestrial biome, covering more than 40% of the Earth's terrestrial surface and Biological Soil Crusts (BSCs) are the predominant surface type in most of those ecosystems covering up to 70% of its surface. BSCs have been demonstrated to be very vulnerable to disturbance due to human activities and their loss has been implicated as a factor leading to accelerate soil erosion and other forms of land degradation. Incorporation of the response of different type of soil crusts and the effects of the their disturbance is likely to improve the prediction of runoff and water erosion models in arid and semi-arid catchments. The aim of this work is to analyse the influence of crust disturbance on infiltration and erosion. Extreme rainfall simulations at micro plots scale were performed in two semiarid ecosystems with different lithology and conditions of occurrence of BSCs: El Cautivo and Amoladeras. (Author) 10 refs.

  17. A new extreme environment for aerobic anoxygenic phototrophs: biological soil crusts.

    Science.gov (United States)

    Csotonyi, Julius T; Swiderski, Jolantha; Stackebrandt, Erko; Yurkov, Vladimir

    2010-01-01

    Biological soil crusts improve the health of arid or semiarid soils by enhancing water content, nutrient relations and mechanical stability, facilitated largely by phototrophic microorganisms. Until recently, only oxygenic phototrophs were known from soil crusts. A recent study has demonstrated the presence of aerobic representatives of Earth's second major photosynthetic clade, the evolutionarily basal anoxygenic phototrophs. Three Canadian soil crust communities yielded pink and orange aerobic anoxygenic phototrophic strains possessing the light-harvesting pigment bacteriochlorophyll a. At relative abundances of 0.1-5.9% of the cultivable bacterial community, they were comparable in density to aerobic phototrophs in other documented habitats. 16S rDNA sequence analysis revealed the isolates to be related to Methylobacterium, Belnapia, Muricoccus and Sphingomonas. This result adds a new type of harsh habitat, dry soil environments, to the environments known to support aerobic anoxygenic phototrophs.

  18. Niobium-tantalum Fractionation During Slab Subduction:Implications for the Formation of Continental Crust

    Institute of Scientific and Technical Information of China (English)

    Yilin Xiao; Weidong Sun; Jochen Hoefs; Klaus Simon; Zeming Zhang; Shuguang Li; Albrecht W. Hofmann

    2007-01-01

    @@ Compared with the oceanic crust, knowledge about the formation of the continental crust (CC) is relatively poor. Although melting of subducted slabs in the early history of the Earth has been considered as the major way that shaped the chemical characteristics of the CC by most geologists, as the CC shares many characteristics with modern adakites, some geologists argued that Archean TTG was formed in the same way as modern arcs rather than slab melting, whereas others proposed that melting at the bottom of the thickened oceanic crust was more important. Recently,the debate is mainly focused on the unique subchondritic Nb/Ta value of the CC, and particularly, how Nb and Ta fractionated from each other and consequently how, in detail, the CC was built.

  19. Biomineralisation of the ferromanganese crusts in the Western Pacific Ocean

    Science.gov (United States)

    Jiang, Xiao-Dong; Sun, Xiao-Ming; Guan, Yao; Gong, Jun-Li; Lu, Yang; Lu, Rong-Fei; Wang, Chi

    2017-04-01

    Ferromanganese (Fe-Mn) crusts are deep-sea sedimentary polymetallic minerals that are explored for their economic potential, particularly for Mn, Cu, Co, Ni and rare earth elements (REEs). The precipitation mechanism of the metallic elements in crusts has remained controversial between chemical oxidation (abiotic origin) and microbial enzymatic processes (biomineralization). In this study, the microbial mineralization in ferromanganese crusts from the Western Pacific Ocean was explored. Scanning electron microscope (SEM) and transmission electron microscope (TEM) analyses showed abundant micron-scale spherical aggregates of Mn-oxide filaments (20-80 nm), which are closely associated with filamentous cells within the biofilm (biofilm mineralization) exist within the stromatolitic structure. The high-throughput sequencing of 16S rRNA and phylogenetic analysis suggests that biofilms are dominated by three Mn-oxidizing bacterial species from the families Bacillus, Arthrobacter and Pseudomonas. In addition, Mn concentration in the biofilms is approximately 108 times that of the associated seawater (2.3 ppb Mn). Iron (16.2 wt%), Cu (0.11 wt%), Co (0.719 wt%) and Ni (0.459 wt%) were found in the biofilms via X-ray Fluorescence Spectrometer (XRF) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). We suggest that biomineralization provides a new perspective for understanding Fe-Mn crustal-related mineral deposits, and the ultra-high microbial trace element enrichment ability is noteworthy. Utilization of microbial activities in accumulating precious metals from seawater may offer a viable alternative for the world's metal production in the future.

  20. Tectonic escape in the evolution of the continental crust

    Science.gov (United States)

    Burke, K.; Sengor, C.

    1986-01-01

    The continental crust originated by processes similar to those operating today and continents consist of material most of which originated long ago in arc-systems that have later been modified, especially at Andean margins and in continental collisions where crustal thickening is common. Collision-related strike-slip motion is a general process in continental evolution. Because buoyant continental (or arc) material generally moves during collision toward a nearby oceanic margin where less buoyant lithosphere crops out, the process of major strike-slip dominated motion toward a 'free-face' is called 'tectonic escape'. Tectonic escape is and has been an element in continental evolution throughout recorded earth-history. It promotes: (1) rifting and the formation of rift-basins with thinning of thickened crust; (2) pervasive strike-slip faulting late in orogenic history which breaks up mountain belts across strike and may juxtapose unrelated sectors in cross-section; (3) localized compressional mountains and related foreland-trough basins.

  1. Geological cycles and a two-stage history of the Continental Crust (Robert Wilhelm Bunsen Medal Lecture)

    Science.gov (United States)

    Hawkesworth, Chris J.; Cawood, Peter A.; Dhuime, Bruno

    2014-05-01

    The continental crust is the archive of Earth history, and the apparently cyclical nature of geological evolution is a feature of the geological record. The advent of radiometric ages has highlighted that the spatial and temporal distribution of the Earth's record of rock units and events is heterogeneous with distinctive peaks and troughs in the distribution of ages of igneous crystallization, metamorphism, continental margins and mineralization. It is argued that the temporal distribution largely reflects the different preservation potential of rocks generated in different tectonic settings, rather than fundamental pulses of activity, and the peaks of ages are linked to the timing of supercontinent assembly. In contrast there are other signals, such as the Sr isotope ratios of seawater, mantle temperatures, and redox conditions on the Earth, where the records are regarded as primary because they are not sensitive to the numbers of samples of different ages that have been analysed. Models based on the U-Pb, Hf and O isotope ratios of detrital zircons suggest that at least ~60-70% of the present volume of the continental crust had been generated by 3 Ga. The sedimentary record is biased by preferential sampling of relatively young material in their source terrains. The implication is that there were greater volumes of continental crust in the Archaean than might be inferred from the compositions of detrital zircons and sediments. The growth of continental crust was a continuous rather than an episodic process, but the rates of continental growth were significantly higher before 3 Ga than subsequently. The time-integrated Rb/Sr ratios, and the average SiO2 contents, indicate that new continental crust was largely mafic over the first 1.5 Ga of Earth's evolution, and that significant volumes of pre-3 Ga crust may have been associated with intraplate magmatism. Since ~3 Ga there has been an increase in Rb/Sr, SiO2, and the inferred thickness of new crust, consistent

  2. Paleoenvironmental implications of high-density records in Co-rich seamount crusts from the Pacific Ocean

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Co-rich seamount crusts have been shown to possess great potential for providing information on paleoceanographic and paleoclimatic changes. High resolution data are essential to decipher and correctly understand such high-density records. With the development of modern microprobe techniques, detailed sampling of crusts can be performed and it is possible to retrieve detailed information about envi- ronmental changes recorded in the seamount crusts. We report here geochemical results of more than 40 elements (including all rare earth elements) of four Co-rich seamount crust samples, which were collected from seamounts in the central and western Pacific Ocean. These data were obtained with two micro-probe techniques: Electron Probe Micro Analyzer and Laser Ablation Inductively Coupled Plasma Mass Spectrometry. The chronological framework of the seamount crust samples was determined using the cos- mogenic 10Be and the Co-chronometer. Records of elemental composition, P, and Al/(Fe + Mn) and Y/Ho ratios across the sections of the four samples are used to identify paleoceanographic and paleoclimatic events over the past ~30 Ma. These data show that: (1) Al/(Fe + Mn) in the western Pacific seamount crust is a useful proxy for the assessment of changes of source materials related to the variability of the Asian monsoon; (2) P and Y/Ho can be used as proxies to infer biogenic episodes. Finally we discuss the methodology related to dating and micro-probe analysis used in crust study.

  3. Paleoenvironmental implications of high-density records in Co-rich seamount crusts from the Pacific Ocean

    Institute of Scientific and Technical Information of China (English)

    WANG XiaoHong; ZHOU LiPing; WANG YiMin; ZHANG XueHua; LIU XiaoMing; FAN XingTao; LIU KeXin; ZHOU JianXiong

    2008-01-01

    Co-rich seamount crusts have been shown to possess great potential for providing information on paleoceanographic and paleoclimatic changes. High resolution data are essential to decipher and correctly understand such high-density records. With the development of modern micro-probe techniques, detailed sampling of crusts can be performed and it is possible to retrieve detailed information about environmental changes recorded in the seamount crusts. We report here geochemical results of more than 40elements (including all rare earth elements) of four Co-rich seamount crust samples, which were collected from seamounts in the central and western Pacific Ocean. These data were obtained with two micro-probe techniques: Electron Probe Micro Analyzer and Laser Ablation Inductively Coupled Plasma Mass Spectrometry. The chronological framework of the seamount crust samples was determined using the cosmogenic 10Be and the Co-chronometer. Records of elemental composition, P, and Al/(Fe + Mn) and Y/Ho ratios across the sections of the four samples are used to identify paleoceanographic and paleoclimatic events over the past -30 Ma. These data show that: (1) AI/(Fe + Mn) in the western Pacific seamount crust is a useful proxy for the assessment of changes of source materials related to the variability of the Asian monsoon; (2) P and Y/Ho can be used as proxies to infer biogenic episodes. Finally we discuss the methodology related to dating and micro-probe analysis used in crust study.

  4. The Continental Crust: A Geophysical Approach

    Science.gov (United States)

    Christensen, Nikolas I.

    Nearly 80 years ago, Yugoslavian seismologist Andrija Mohorovicic recognized, while studying a Balkan earthquake, that velocities of seismic waves increase abruptly at a few tens of kilometers depth , giving rise to the seismological definition of the crust. Since that discovery, many studies concerned with the nature of both the continental and oceanic crusts have appeared in the geophysical literature.Recently, interest in the continental crust has cascaded. This is largely because of an infusion of new data obtained from major reflection programs such as the Consortium for Continental Reflection Profiling (COCORP) and British Institutions Reflection Profiling Syndicate (BIRPS) and increased resolution of refraction studies. In addition, deep continental drilling programs are n ow in fashion. The Continental Crust: A Geophysical Approach is a summary of present knowledge of the continental crust. Meissner has succeeded in writing a book suited to many different readers, from the interested undergraduate to the professional. The book is well documented , with pertinent figures and a complete and up-to-date reference list.

  5. Biological soil crusts: Diminutive communities of potential global importance

    Science.gov (United States)

    Ferrenberg, Scott; Tucker, Colin; Reed, Sasha C.

    2017-01-01

    Biological soil crusts (biocrusts) are widespread, diverse communities of cyanobacteria, fungi, lichens, and mosses living on soil surfaces, primarily in drylands. Biocrusts can locally govern primary production, soil fertility, hydrology, and surface energy balance, with considerable variation in these functions across alternate community states. Further, these communities have been implicated in Earth system functioning via potential influences on global biogeochemistry and climate. Biocrusts are easily destroyed by disturbances and appear to be exceptionally vulnerable to warming temperatures and altered precipitation inputs, signaling possible losses of dryland functions with global change. Despite these concerns, we lack sufficient spatiotemporal data on biocrust function, cover, and community structure to confidently assess their ecological roles across the extensive dryland biome. Here, we present the case for cross-scale research and restoration efforts coupled with remote-sensing and modeling approaches that improve our collective understanding of biocrust responses to global change and the ecological roles of these diminutive communities at global scales.

  6. Partitioning properties of rare earth ores in China

    Institute of Scientific and Technical Information of China (English)

    CHI Ru'an; LI Zhongjun; PENG Cui; ZHU Guocai; XU Shengming

    2005-01-01

    The properties of rare earth partitioning in Chinese industrial rare earth ores were analyzed. Rare earth ores can be divided into the single-mineral type ore with bastnaesite, the multi-mineral type ore with bastnaesite and monazite, and the weathering crust type. Both the Bayan Obo rare earth ore and the Zhushan rare earth ore are a kind of mixed ore, consisting of bastnaesite and monazite. Their rare earth partitionings are strongly enriched in light rare earths, where CeO2 is 50% and the light rare earth partitioning is totally over 95%. The Mianning rare earth ore as well as the Weishan rare earth is a kind of rare earth ore only having bastnaesite. Their rare earth partitionings are also strongly enriched in light rare earths,in which CeO2 is 47% and the light rare earth partitioning is totally over 94%. For the weathering crust type rare earth ore,there are the Longnan rare earth ore, the Xunwu rare earth ore, and the middle yttrium and rich europium ore. In the Longnan rare earth ore, which is strongly enriched in heavy rare earths, Y2O3 is 64.83%, and the heavy and light rare earth partitionings are 89.40% and 10.53%, respectively. In the Xunwu rare earth ore, which is strongly enriched in light rare earths, CeO2 is 47.16%, and the light rare earth partitioning is totally 93.25%. Y and Eu are enriched in the middle yttrium and rich europium ore. Its middle rare earth partitioning is totally over 10%, and Eu2O3 and Y2O3 are over 0.5% and 20%,respectively, which are mainly industrial resources of the middle and the heavy rare earths.

  7. Crust formation in drying colloidal suspensions

    KAUST Repository

    Style, R. W.

    2010-06-30

    During the drying of colloidal suspensions, the desiccation process causes the suspension near the air interface to consolidate into a connected porous matrix or crust. Fluid transport in the porous medium is governed by Darcy\\'s law and the equations of poroelasticity, while the equations of colloid physics govern processes in the suspension. We derive new equations describing this process, including unique boundary conditions coupling the two regions, yielding a moving-boundary model of the concentration and stress profiles during drying. A solution is found for the steady-state growth of a nedimensional crust during constant evaporation rate from the surface. The solution is used to demonstrate the importance of the system boundary conditions on stress profiles and diffusivity in a drying crust. © 2011 The Royal Society.

  8. The Early Evolution of Mars' Crust

    Science.gov (United States)

    Samuel, H.; Baratoux, D.; Kurita, K.

    2014-12-01

    The Mars crustal density and thickness have been recently re-evaluated using petrological constraints from remote sensing, in-situ data, and SNC meteorites. This work indicates that the present-day Martian crust is denser and thicker than previously proposed if essentially basaltic in composition. As a consequence, the average crustal thickness would be commensurable with the depth of the basalt/eclogite transition, re-opening the question of crustal recycling on Early Mars and more generally throughout all its history. We have therefore investigated the conditions under which a thick ancient crust with an eclogitic root could survive through the history of Mars using numerical modelling. Delamination may occur if the combination of poorly constrained physical parameters induces the presence of gravitationally unstable layers and favors a rheological decoupling. To study the conditions and the time scales for the occurrence of crustal delamination on Mars, we investigated the influence of critical parameters for a plausible range of values corresponding to the Martian mantle. For each case we follow the dynamic evolution over geological times of a three-layer system (i.e., crust-mantle with a distinction between low pressure, buoyant basaltic crust and higher pressure, denser eclogitic material). We systematically varied four governing parameters within plausible ranges: (1) the basalt-eclogite transition depth, (2) the density difference between the mantle and the basaltic crust, (3) the density difference between the eclogitic crust and the lithosphere & mantle, (4) the viscous rheology. These experiments allow determining the average Martian crustal thickness at early and late evolutionary stages.

  9. Hafnium isotope stratigraphy of ferromanganese crusts

    Science.gov (United States)

    Lee, D.-C.; Halliday, A.N.; Hein, J.R.; Burton, K.W.; Christensen, J.N.; Gunther, D.

    1999-01-01

    A Cenozoic record of hafnium isotopic compositions of central Pacific deep water has been obtained from two ferromanganese crusts. The crusts are separated by more than 3000 kilometers but display similar secular variations. Significant fluctuations in hafnium isotopic composition occurred in the Eocene and Oligocene, possibly related to direct advection from the Indian and Atlantic oceans. Hafnium isotopic compositions have remained approximately uniform for the past 20 million years, probably reflecting increased isolation of the central Pacific. The mechanisms responsible for the increase in 87Sr/86Sr in seawater through the Cenozoic apparently had no effect on central Pacific deep-water hafnium.

  10. Osmium isotope and highly siderophile element systematics of the lunar crust

    Science.gov (United States)

    Day, James M. D.; Walker, Richard J.; James, Odette B.; Puchtel, Igor S.

    2010-01-01

    Coupled 187Os/ 188Os and highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, and Re) abundance data are reported for pristine lunar crustal rocks 60025, 62255, 65315 (ferroan anorthosites, FAN) and 76535, 78235, 77215 and a norite clast in 15455 (magnesian-suite rocks, MGS). Osmium isotopes permit more refined discrimination than previously possible of samples that have been contaminated by meteoritic additions and the new results show that some rocks, previously identified as pristine, contain meteorite-derived HSE. Low HSE abundances in FAN and MGS rocks are consistent with derivation from a strongly HSE-depleted lunar mantle. At the time of formation, the lunar floatation crust, represented by FAN, had 1.4 ± 0.3 pg g - 1 Os, 1.5 ± 0.6 pg g - 1 Ir, 6.8 ± 2.7 pg g - 1 Ru, 16 ± 15 pg g - 1 Pt, 33 ± 30 pg g - 1 Pd and 0.29 ± 0.10 pg g - 1 Re (˜ 0.00002 × CI) and Re/Os ratios that were modestly elevated ( 187Re/ 188Os = 0.6 to 1.7) relative to CI chondrites. MGS samples are, on average, characterised by more elevated HSE abundances (˜ 0.00007 × CI) compared with FAN. This either reflects contrasting mantle-source HSE characteristics of FAN and MGS rocks, or different mantle-crust HSE fractionation behaviour during production of these lithologies. Previous studies of lunar impact-melt rocks have identified possible elevated Ru and Pd in lunar crustal target rocks. The new results provide no supporting evidence for such enrichments. If maximum estimates for HSE in the lunar mantle are compared with FAN and MGS averages, crust-mantle concentration ratios ( D-values) must be ≤ 0.3. Such D-values are broadly similar to those estimated for partitioning between the terrestrial crust and upper mantle, with the notable exception of Re. Given the presumably completely different mode of origin for the primary lunar floatation crust and tertiary terrestrial continental crust, the potential similarities in crust-mantle HSE partitioning for the Earth and Moon are

  11. Osmium isotope and highly siderophile element systematics of the lunar crust

    Science.gov (United States)

    Day, J.M.D.; Walker, R.J.; James, O.B.; Puchtel, I.S.

    2010-01-01

    Coupled 187Os/188Os and highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, and Re) abundance data are reported for pristine lunar crustal rocks 60025, 62255, 65315 (ferroan anorthosites, FAN) and 76535, 78235, 77215 and a norite clast in 15455 (magnesian-suite rocks, MGS). Osmium isotopes permit more refined discrimination than previously possible of samples that have been contaminated by meteoritic additions and the new results show that some rocks, previously identified as pristine, contain meteorite-derived HSE. Low HSE abundances in FAN and MGS rocks are consistent with derivation from a strongly HSE-depleted lunar mantle. At the time of formation, the lunar floatation crust, represented by FAN, had 1.4 ?? 0.3 pg g- 1 Os, 1.5 ?? 0.6 pg g- 1 Ir, 6.8 ?? 2.7 pg g- 1 Ru, 16 ?? 15 pg g- 1 Pt, 33 ?? 30 pg g- 1 Pd and 0.29 ?? 0.10 pg g- 1 Re (??? 0.00002 ?? CI) and Re/Os ratios that were modestly elevated (187Re/188Os = 0.6 to 1.7) relative to CI chondrites. MGS samples are, on average, characterised by more elevated HSE abundances (??? 0.00007 ?? CI) compared with FAN. This either reflects contrasting mantle-source HSE characteristics of FAN and MGS rocks, or different mantle-crust HSE fractionation behaviour during production of these lithologies. Previous studies of lunar impact-melt rocks have identified possible elevated Ru and Pd in lunar crustal target rocks. The new results provide no supporting evidence for such enrichments. If maximum estimates for HSE in the lunar mantle are compared with FAN and MGS averages, crust-mantle concentration ratios (D-values) must be ??? 0.3. Such D-values are broadly similar to those estimated for partitioning between the terrestrial crust and upper mantle, with the notable exception of Re. Given the presumably completely different mode of origin for the primary lunar floatation crust and tertiary terrestrial continental crust, the potential similarities in crust-mantle HSE partitioning for the Earth and Moon are somewhat

  12. Palaeoceanographic conditions during the formation of ferromanganese crust from the Afanasiy Nikitin seamount, north central Indian Ocean: geochemical evidence

    Digital Repository Service at National Institute of Oceanography (India)

    Banakar, V.K.; Pattan, J.N.; Mudholkar, A.V.

    coherent behaviour of trivalent rare earth elements (3 + REE) is not observed in the crust. La, Yb and Lu show a positive association with the CFA phase elements (CA and P) and Pr, Nd and Sm with the Mn-oxide phase elements (Mn, Co and Ni). this leads...

  13. Pulsar Glitches: The Crust may be Enough

    CERN Document Server

    Piekarewicz, J; Horowitz, C J

    2014-01-01

    Pulsar glitches-the sudden spin-up in the rotational frequency of a neutron star-suggest the existence of an angular-momentum reservoir confined to the inner crust of the neutron star. Large and regular glitches observed in the Vela pulsar have originally constrained the fraction of the stellar moment of inertia that must reside in the solid crust to about 1.4%. However, crustal entrainment-which until very recently has been ignored-suggests that in order to account for the Vela glitches, the fraction of the moment of inertia residing in the crust must increase to about 7%. This indicates that the required angular momentum reservoir may exceed that which is available in the crust. We explore the possibility that uncertainties in the equation of state provide enough flexibility for the construction of models that predict a large crustal thickness and consequently a large crustal moment of inertia. Given that analytic results suggest that the crustal moment of inertia is sensitive to the transition pressure at ...

  14. Dew formation and activity of biological crusts

    NARCIS (Netherlands)

    Veste, M.; Heusinkveld, B.G.; Berkowicz, S.M.; Breckle, S.W.; Littmann, T.; Jacobs, A.F.G.

    2008-01-01

    Biological soil crusts are prominent in many drylands and can be found in diverse parts of the globe including the Atacama desert, Chile, the Namib desert, Namibia, the Succulent-Karoo desert, South Africa, and the Negev desert, Israel. Because precipitation can be negligible in deserts ¿ the

  15. Norwegian crusted scabies: an unusual case presentation.

    Science.gov (United States)

    Maghrabi, Michael M; Lum, Shireen; Joba, Ameha T; Meier, Molly J; Holmbeck, Ryan J; Kennedy, Kate

    2014-01-01

    Scabies is a contagious condition that is transmitted through direct contact with an infected person and has been frequently associated with institutional and healthcare-facility outbreaks. The subtype Norwegian crusted scabies can masquerade as other dermatologic diseases owing to the heavy plaque formation. Successful treatment has been documented in published reports, including oral ivermectin and topical permethrin. Few case studies documenting the treatment of Norwegian crusted scabies have reported the use of surgical debridement as an aid to topical and/or oral treatment when severe plaque formation has been noted. A nursing home patient was admitted to the hospital for severe plaque formation of both feet. A superficial biopsy was negative for both fungus and scabies because of the severity of the plaque formation on both feet. The patient underwent a surgical, diagnostic biopsy of both feet, leading to the diagnosis of Norwegian crusted scabies. A second surgical debridement was then performed to remove the extensive plaque formation and aid the oral ivermectin and topical permethrin treatment. The patient subsequently made a full recovery and was discharged back to the nursing home. At 2 and 6 months after treatment, the patient remained free of scabies infestation, and the surgical wound had healed uneventfully. The present case presentation has demonstrated that surgical debridement can be complementary to the standard topical and oral medications in the treatment of those with Norwegian crusted scabies infestation.

  16. Geophysics of an Oceanic Ice Shell on Snowball Earth

    Science.gov (United States)

    Gaidos, E. J.

    2000-01-01

    Kirschvink proposed Precambrian low-latitude glaciation could result in an albedo-driven catastrophic runaway to a "Snowball Earth" state in which pack ice up to 1 km thick covered the world ocean. The geophysical state of an ice crust on a Snowball Earth is examined.

  17. Global rare earth resources and scenarios of future rare earth industry

    Institute of Scientific and Technical Information of China (English)

    CHEN Zhanheng

    2011-01-01

    It is known to all that China is abundant in rare earth resources. But rare earth deposits are really not that rare in the earth crust. In the five continents, i.e. Asia, Europe, Australia, North and South America, and Africa, there are about thirty four countries found to have rare earth deposits; Brazil might surpass China and rank the first in rare earth deposits. At present, investment in rare earth production was surged,there have been about 200 projects, and the total production for 25 of them would be more than 170 thousand tons after 2015, a multi-supply system on rare earths is being established worldwide. Cautions on the investment of rare earth production are involved.

  18. Petrological and two-phase flow modelling of deep arc crust: insights on continental crust formation

    Science.gov (United States)

    Riel, Nicolas; Bouilhol, Pierre; van Hunen, Jeroen; Cornet, Julien

    2017-04-01

    The genesis of felsic crust is generally attributed to two main processes: the differentiation of primary magmas by crystallization within the crust or uppermost mantle and the partial melting of older crustal rocks. The Mixing/Assimilation/Hybridization of these magmas in the deep crust (MASH zone) and their subsequent segregation constitutes the principal process by which continents have become differentiated into a more mafic, residual lower crust and a more felsic and hydrated upper crust. Although this model describes qualitatively how continental crust forms, little is known on the physical and chemical mechanisms occurring at the root of volcanic arcs. To assess the dynamics of partial melting, melt injection and hybridization in the deep crust, a new 2-D two-phase flow code using finite volume method has been developed. The formulation takes into account: (i) melt flow through porosity waves/channels, (ii) heat transfer, assuming local thermal equilibrium between solid and liquid, (iii) thermodynamic modelling of stable phases and (iv) injection of mantle-derived melt at the Moho. Our parametric study shows that pressure, heat influx and melt:rock ratio are the main parameters controlling the volume and composition of differentiated magma. Overall the composition of segregated products scatters in two groups: felsic (80-68% SiO2) and intermediate (60-52% SiO2), with an average andesitic composition. The bimodal distribution is controlled by amphibole which buffer the composition of segregated products to high SiO2-content when stable. As the amphibole-out melting reaction is crossed segregated products become intermediate. When compared to available geological evidence, the liquid line of descent of mantle-derived magma do not fit the Mg# versus silica trends of exposed volcanic arcs. Instead our modelling results show that reactive flow of those same magma through a mafic crust is able to reproduce such trends.

  19. Microbiotic crusts on soil, rock and plants: neglected major players in the global cycles of carbon and nitrogen?

    Directory of Open Access Journals (Sweden)

    W. Elbert

    2009-07-01

    Full Text Available Microbiotic crusts consisting of bacteria, fungi, algae, lichens, and bryophytes colonize most terrestrial surfaces, and they are able to fix carbon and nitrogen from the atmosphere. Here we show that microbiotic crusts are likely to play major roles in the global biogeochemical cycles of carbon and nitrogen, and we suggest that they should be further characterized and taken into account in studies and models of the Earth system and climate.

    For the global annual net uptake of carbon by microbiotic crusts we present a first estimate of ~3.6 Pg a−1. This uptake corresponds to ~6% of the estimated global net carbon uptake by terrestrial vegetation (net primary production, NPP: ~60 Pg a−1, and it is of the same magnitude as the global annual carbon turnover due to biomass burning. The estimated rate of nitrogen fixation by microbiotic crusts (~45 Tg a−1 amounts to ~40% of the global estimate of biological nitrogen fixation (107 Tg a−1. With regard to Earth system dynamics and global change, the large contribution of microbiotic crusts to nitrogen fixation is likely to be important also for the sequestration of CO2 by terrestrial plants (CO2 fertilization, because the latter is constrained by the availability of fixed nitrogen.

  20. Microbiotic crusts on soil, rock and plants: neglected major players in the global cycles of carbon and nitrogen?

    Science.gov (United States)

    Elbert, W.; Weber, B.; Büdel, B.; Andreae, M. O.; Pöschl, U.

    2009-07-01

    Microbiotic crusts consisting of bacteria, fungi, algae, lichens, and bryophytes colonize most terrestrial surfaces, and they are able to fix carbon and nitrogen from the atmosphere. Here we show that microbiotic crusts are likely to play major roles in the global biogeochemical cycles of carbon and nitrogen, and we suggest that they should be further characterized and taken into account in studies and models of the Earth system and climate. For the global annual net uptake of carbon by microbiotic crusts we present a first estimate of ~3.6 Pg a-1. This uptake corresponds to ~6% of the estimated global net carbon uptake by terrestrial vegetation (net primary production, NPP: ~60 Pg a-1), and it is of the same magnitude as the global annual carbon turnover due to biomass burning. The estimated rate of nitrogen fixation by microbiotic crusts (~45 Tg a-1) amounts to ~40% of the global estimate of biological nitrogen fixation (107 Tg a-1). With regard to Earth system dynamics and global change, the large contribution of microbiotic crusts to nitrogen fixation is likely to be important also for the sequestration of CO2 by terrestrial plants (CO2 fertilization), because the latter is constrained by the availability of fixed nitrogen.

  1. Intensive Ammonia and Methane Oxidation in Organic Liquid Manure Crusts

    DEFF Research Database (Denmark)

    Nielsen, Daniel Aagren; Nielsen, Lars Peter; Schramm, Andreas;

    of the crusts. PCR targeting the unique methane and ammonia monooxygenases were applied together with FISH to detect the presence of the two bacterial groups. Potential activity was assessed by short term slurry incubations of crust samples while monitoring NO2- production or CH4 consumption. Crusts were...... also CH4 emission mitigation, an organic surface crust can be effective if populations of MOB and AOB are allowed to build up....

  2. Microbial community structure in three deep-sea carbonate crusts

    NARCIS (Netherlands)

    Heijs, S. K.; Aloisi, G.; Bouloubassi, I.; Pancost, R. D.; Pierre, C.; Damste, J. S. Sinninghe; Gottschal, J. C.; van Elsas, J. D.; Forney, L. J.

    2006-01-01

    Carbonate crusts in marine environments can act as sinks for carbon dioxide. Therefore, understanding carbonate crust formation could be important for understanding global warming. In the present study, the microbial communities of three carbonate crust samples from deep-sea mud volcanoes in the eas

  3. Permeability of crust is key to crispness retention

    NARCIS (Netherlands)

    Hirte, A.; Hamer, R.J.; Meinders, M.B.J.; Primo-Martin, C.

    2010-01-01

    Bread loses crispness rapidly after baking because water originating from the wet crumb accumulates in the dry crust. This water accumulation might be increased by the dense and low permeable character of the bread crust. Our objective was to investigate the influence of permeability of the crust on

  4. Permeability of crust is key to crispness retention

    NARCIS (Netherlands)

    Hirte, A.; Hamer, R.J.; Meinders, M.B.J.; Primo-Martin, C.

    2010-01-01

    Bread loses crispness rapidly after baking because water originating from the wet crumb accumulates in the dry crust. This water accumulation might be increased by the dense and low permeable character of the bread crust. Our objective was to investigate the influence of permeability of the crust on

  5. Inversion of gravity and topography data for the crust thickness of China and its adjacent region

    Institute of Scientific and Technical Information of China (English)

    HUANG Jian-ping; FU Rong-shan; XU Ping; HUANG Jian-hua; ZHENG Yong

    2006-01-01

    The data of Bouguer gravity and topography are inverted to obtain the crust thickness of China. In order to reduce the effect of regional non-isostasy we corrected the reference Moho depth in the inversion with regional topography relief, and performed multiple iterations to make the result more reliable. The obtained crust thickness of China is plotted on a map in cells of 1°×1°. Then we analyzed the correlation between the Bouguer gravity anomaly and fluctuation of the Moho depth. A good linear correlation is found, with a correlation coefficient of -0.993.Different correlation coefficients, 0.96 and 0.91, are found for the data in land and ocean region, respectively. The correlation result also shows that the boundary between land and ocean is generally along the bathymetric line of -800 m. In order to examine the influence of the Earth's curvature on the calculated result, we tried two inversion models: the inversion for the whole region and the inversion for 4 sub-regions. The difference in the crust thickness deduced from the two models is less than 5 km. Possible explanation for the difference is discussed. After comparing our result with that of other studies, we suggest that with our method the Bouguer gravity and the topography data can be independently inverted to obtain the crust thickness of China and its adjacency.

  6. A new environment for aerobic anoxygenic phototrophic bacteria: biological soil crusts.

    Science.gov (United States)

    Csotonyi, Julius T; Swiderski, Jolantha; Stackebrandt, Erko; Yurkov, Vladimir

    2010-10-01

    Phototrophic microorganisms are critical to the carbon cycling and productivity of biological soil crusts, which enhance water content, nutrient relations and mechanical stability of arid soils. Only oxygen-producing phototrophs, including cyanobacteria and algae, are known from soil crusts, but Earth's second major branch of photosynthetic organisms, the evolutionarily earlier anoxygenic phototrophs, is unreported. We announce the discovery of aerobic anoxygenic phototrophs in three Canadian soil crust communities. We found in a culture-based study that they comprised 0.1-5.9% of the cultivable bacterial community in moss-, lichen- and cyanobacteria-dominated crust from sand dunes and sandy soils. Comparable in density to aerobic phototrophs in other habitats, the bacteriochlorophyll a-possessing pink and orange isolates were related to species of Methylobacterium (99.0-99.5%), Belnapia (97.4-98.8%), Muricoccus (94.4%) and Sphingomonas (96.6-98.5%), based on 16S rRNA gene sequences. Our results demonstrate that proteobacterial anoxygenic phototrophs may be found in dry soil environments, implying desiccation resistance as yet unreported for this group. By utilizing sunlight for part of their energy needs, aerobic phototrophs can accelerate organic carbon cycling in nutrient-poor arid soils. Their effects will be especially important as global climate change enhances soil erosion and consequent nutrient loss.

  7. Excavation and Melting of the Hadean Continental Crust by Late Heavy Bombardment

    CERN Document Server

    Shibaike, Yuhito; Ida, Shigeru

    2015-01-01

    No Hadean rocks have ever been found on Earth's surface except for zircons---evidence of continental crust, suggesting that Hadean continental crust existed but later disappeared. One hypothesis for the disappearance of the continental crust is excavation/melting by the Late Heavy Bombardment (LHB), a concentration of impacts in the last phase of the Hadean eon. In this paper, we calculate the effects of LHB on Hadean continental crust in order to investigate this hypothesis. Approximating the size-frequency distribution of the impacts by a power-law scaling with an exponent {\\alpha} as a parameter, we have derived semi-analytical expressions for the effects of LHB impacts. We calculated the total excavation/melting volume and area affected by the LHB from two constraints of LHB on the moon, the size of the largest basin during LHB, and the density of craters larger than 20 km. We also investigated the effects of the value of {\\alpha}. Our results show that LHB does not excavate/melt all of Hadean continental...

  8. Density Sorting During the Evolution of Continental Crust

    Science.gov (United States)

    Kelemen, P. B.; Behn, M. D.; Hacker, B. R.

    2015-12-01

    We consider two settings - in addition to "delamination" of arc lower crust - in which dense, mafic eclogites founder into the convecting mantle while buoyant, felsic lithologies accumulate at the base of evolving continental crust. Arc processes play a central role in generating continental crust, but it remains uncertain how basaltic arc crust is transformed to andesitic continental crust. Dense, SiO2-poor products of fractionation may founder from the base of arc crust by "delamination", but lower arc crust after delamination has significantly different trace elements compared to lower continental crust (LCC). In an alternative model, buoyant magmatic rocks generated at arcs are first subducted, mainly via subduction erosion. Upon heating, these buoyant lithologies ascend through the mantle wedge or along a subduction channel, and are "relaminated" at
the base of overlying crust (e.g., Hacker et al EPSL 11, AREPS 15). Average buoyant lavas and plutons
for the Aleutians, Izu-Bonin-Marianas, Kohistan and Talkeetna arcs fall within the range of estimated LCC major and trace elements. Relamination is more efficient in generating continental crust than delamination. Himalayan cross-sections show Indian crust thrust beneath Tibetan crust, with no intervening mantle. There is a horizontal Moho at ca 80 km depth, extending from thickened Indian crust, across the region where Tibetan crust overlies Indian crust, into thickened Tibetan crust. About half the subducted Indian crust is present, whereas the other half is missing. Data (Vp/Vs; Miocene lavas formed by interaction of continental crust with mantle; xenolith thermometry) indicate 1000°C or more from ca 50 km depth to the Moho since the Miocene. We build on earlier studies (LePichon et al Tectonics 92, T'phys 97; Schulte-Pelkum et al Nature 05; Monsalve et al JGR 08) to advance the hypothesis that rapid growth of garnet occurs at 70-80 km and 1000°C within subducting Indian crust. Dense eclogites founder

  9. Can Seismology Detect Ductile Deformation in the Deep Continental Crust?

    Science.gov (United States)

    Lloyd, G. E.; Halliday, J. M.; Butler, R. W.; Casey, M.; Kendall, J.

    2005-12-01

    Various models exist to explain deformation in deep continental crust, broadly divisible into localized simple shear and distributed pure shear. Although seismic imaging is perhaps the most effective way to determine deformation at depth, the veracity of any interpretation depends critically upon knowledge of the seismic properties of the rocks. As a region of active crustal thickening and exhumation, the Nanga Parbat Massif (NPM), Pakistan Himalaya, offers insight into how localized thrust faults at the Earth's surface couple with distributed strain at depth. Gneissic, mylonitic and cataclastic rocks at the surface were sampled as proxies for lithologies and fabrics currently accommodating deformation at depth. The LPO of individual minerals were measured using SEM/EBSD, from which elastic constants, 3D seismic velocities and anisotropies were predicted. Micas contribute most to the bulk anisotropy; only when mica content is low and/or LPO is weak do other minerals contribute significantly. The anisotropy varies with deformation style: background gneiss samples have highest AVs anisotropy (9.5 percent) compared with highly strained gneiss samples (5.1-6.3 percent) and cataclasite (0.4 percent). This suggests that some shear zones are characterized by low anisotropy. Sample elastic constants were used to construct models, based on current ideas of NPM tectonics, through which P-, S- and converted waves were ray traced. Foliation orientation and intensity have dramatic impacts on seismic waves: rocks with 9.5 percent AVs and vertically aligned foliation persistent through 40km of crust induce ~1.5s AVs compared to horizontal alignment that induces only 0.2s AVs. Mode conversions and transverse component energy are also diagnostic of foliation intensity and orientation. The models indicate that it is possible to discriminate between different deformation processes active at depth using seismic measurements and we conclude that the dominant process in the NPM is

  10. Crusted Scabies in the Burned Patient

    DEFF Research Database (Denmark)

    Berg, Jais Oliver; Alsbjørn, Bjarne

    2011-01-01

    The objectives of this study were 1) to describe a case of crusted scabies (CS) in a burned patient, which was primarily undiagnosed and led to a nosocomial outbreak in the burn unit; 2) to analyze and discuss the difficulties in diagnosing and treating this subset of patients with burn injury......; and 3) to design a treatment strategy for future patients. Case analysis and literature review were performed. The index patient had undiagnosed crusted scabies (sive Scabies norvegica) with the ensuing mite hyperinfestation when admitted to the department with minor acute dermal burns. Conservative...... healing and autograft healing were impaired because of the condition. Successful treatment of the burns was only accomplished secondarily to scabicide treatment. An outbreak of scabies among staff members indirectly led to diagnosis. CS is ubiquitous, and diagnosis may be difficult. This is the first...

  11. Towards a metallurgy of neutron star crusts

    CERN Document Server

    Kobyakov, D

    2013-01-01

    In the standard picture of the crust of a neutron star, matter there is simple: a body-centered-cubic (bcc) lattice of nuclei immersed in an essentially uniform electron gas. We show that at densities above that for neutron drip ($\\sim4\\times10^11$) g cm$^{-3}$ or roughly one thousandth of nuclear matter density, the interstitial neutrons give rise to an attractive interaction between nuclei that renders the lattice unstable. We argue that the likely equilibrium structure is similar to that in displacive ferroelectric materials such as BaTiO$_3$. As a consequence, properties of matter in the inner crust are expected to be much richer than previously appreciated and we mention consequences for observable neutron star properties.

  12. Towards a metallurgy of neutron star crusts.

    Science.gov (United States)

    Kobyakov, D; Pethick, C J

    2014-03-21

    In the standard picture of the crust of a neutron star, matter there is simple: a body-centered-cubic lattice of nuclei immersed in an essentially uniform electron gas. We show that, at densities above that for neutron drip (∼ 4 × 1 0(11)  g cm(-3) or roughly one-thousandth of nuclear matter density), the interstitial neutrons give rise to an attractive interaction between nuclei that renders the lattice unstable. We argue that the likely equilibrium structure is similar to that in displacive ferroelectric materials such as BaTiO3. As a consequence, the properties of matter in the inner crust are expected to be much richer than previously appreciated, and we mention possible consequences for observable neutron star properties.

  13. Seismic structure of ultra-slow spreading crust formed at the Mid-Cayman Spreading Centre, Caribbean Sea

    Science.gov (United States)

    Grevemeyer, I.; Merz, M.; Dannowski, A.; Papenberg, C. A.; Hayman, N. W.; Van Avendonk, H. J.; Peirce, C.

    2015-12-01

    About 57% of the Earth's surface is covered by oceanic crust and new ocean floor is continuously created along the ~60.000 km long mid-ocean ridge (MOR) system. About 25% of the MOR spread at an ultra-slow spreading rate of spreading rates the melt supply to the ridge is thought to dramatically decrease and crustal thickness decreases to a thickness of spreading rates. A formation of crust from a magma chamber would suggest the creation of a well stratified crust, with an extrusive upper crust (layer 2) and a lower gabbroic crust (lower 3) and a well-defined crust-mantle boundary and hence a seismic Moho. In contrast, decompressional melting without formation of a magma chamber would support a crustal structure where seismic velocities change gradually from values typical of crustal rocks to mantle rocks. Here, we report initial results from a survey from the ultra-slow spreading Cayman Spreading Centre in the Caribbean Sea, sampling mature crust along a flowline from both conjugated ridge flanks. The seismic refraction and wide-angle survey was conducted using ocean-bottom-seismometers from Germany, the UK, and Texas and a 5500 cubic-inch airgun-array source towed by the German research vessel METEOR in April 2015. Typical crustal velocities support a thin crust of 3 to 5 km thickness. However, a well-defined Moho boundary was not observed. Thus, velocities change gradually from crustal-type velocities (<7.2 km/s) to values of 7.6-7.8 km/s, supporting mantle rocks. We suggest that reduced mantle velocities indicate gabbroic intrusions within the mantle rather than indicating serpentinization.

  14. Excited nuclei in neutron star crusts

    CERN Document Server

    Takibayev, Nurgali; Nasirova, Diana

    2012-01-01

    The paper considers the chains of successive electron capture reactions by nuclei of the iron group which take place in the crystal structures of neutron star envelopes. It is shown that as a result of such reactions the daughter nuclei in excited states accumulate within certain layers of neutron star crusts. The phonon model of interactions is proposed between the excited nuclei in the crystalline structure, as well as formation of highly excited nuclear states which emit neutrons and higher energy photons.

  15. Topological characterization of neutron star crusts

    CERN Document Server

    Dorso, C O; López, J A

    2012-01-01

    Neutron star crusts are studied using a classical molecular dynamics model developed for heavy ion reactions. After the model is shown to produce a plethora of the so-called "pasta" shapes, a series of techniques borrowed from nuclear physics, condensed matter physics and topology are used to craft a method that can be used to characterize the shape of the pasta structures in an unequivocal way.

  16. Cyclic growth in Atlantic region continental crust

    Science.gov (United States)

    Goodwin, A. M.

    1986-01-01

    Atlantic region continental crust evolved in successive stages under the influence of regular, approximately 400 Ma-long tectonic cycles. Data point to a variety of operative tectonic processes ranging from widespread ocean floor consumption (Wilson cycle) to entirely ensialic (Ampferer-style subduction or simple crustal attenuation-compression). Different processes may have operated concurrently in some or different belts. Resolving this remains the major challenge.

  17. Expanding earth

    Energy Technology Data Exchange (ETDEWEB)

    Carey, S.W.

    1976-01-01

    Arguments in favor of an expanding earth are presented. The author believes that the theory of plate tectonics is a classic error in the history of geology. The case for the expanding earth is organized in the following way: introductory review - face of the earth, development of expanding earth concept, necessity for expansion, the subduction myth, and definitions; some principles - scale of tectonic phenomena, non-uniformitarianism, tectonic profile, paleomagnetism, asymmetry of the earth, rotation of the earth, and modes of crustal extension; regional studies - western North America, Central America, South-East Asia, and the rift oceans; tests and cause of expansion. 824 references, 197 figures, 11 tables. (RWR)

  18. Regional study of the Archean to Proterozoic crust at the Sudbury Neutrino Observatory (SNO+), Ontario: Predicting the geoneutrino flux

    CERN Document Server

    Huang, Yu; Mantovani, Fabio; Shirey, Steven B; Rudnick, Roberta L; McDonough, William F

    2014-01-01

    The SNO+ detector, a new kiloton scale liquid scintillator detector capable of recording geoneutrino events, will define the strength of the Earth radiogenic heat. A detailed 3-D model of the regional crust, centered at SNO+ and based on compiled geological, geophysical and geochemical information, was used to characterize the physical and chemical attributes of crust and assign uncertainties to its structure. Monte Carlo simulations were used to predict the U and Th abundances and uncertainties in crustal lithologies and to model the regional crustal geoneutrino signal originating from the at SNO+.

  19. FAST TRACK PAPER: Older crust underlies Iceland

    Science.gov (United States)

    Foulger, G. R.

    2006-05-01

    The oldest rocks outcropping in northwest Iceland are ~16 Myr old and in east Iceland ~13 Myr. The full plate spreading rate in this region during the Cenozoic has been ~2 cm a-1, and thus these rocks are expected to be separated by ~290 km. They are, however, ~500 km apart. The conclusion is inescapable that an expanse of older crust ~210 km wide underlies Iceland, submerged beneath younger lavas. This conclusion is independent of any considerations regarding spreading ridge migrations, jumps, the simultaneous existence of multiple active ridges, three-dimensionality, or subsidence of the lava pile. Such complexities bear on the distribution and age of the older crust, but not on its existence or its width. If it is entirely oceanic its maximum age is most likely 26-37 Ma. It is at least 150 km in north-south extent, but may taper and extend beneath south Iceland. Part of it might be continental-a southerly extension of the Jan Mayen microcontinent. This older crust contributes significantly to crustal thickness beneath Iceland and the ~40 km local thickness measured seismically is thus probably an overestimate of present-day steady-state crustal production at Iceland.

  20. Pyrolysis of waste plastic crusts of televisions.

    Science.gov (United States)

    Liu, Xinmin; Wang, Zhen; Xu, Dongyan; Guo, Qingjie

    2012-09-01

    The disposal of waste plastic crusts of televisions is an issue that is gaining increasing interest around the world. In this investigation, the pyrolysis and catalytic cracking of the waste television crusts mainly composed of acrylonitrile--butadiene-styrene copolymer was studied. Thermogravimetric analysis was used for initial characterization of the pyrolysis of the waste plastic, but most of the investigations were carried out using a 600 mL tubing reactor. Effects of temperature, reaction time and catalyst on the pyrolysis of the waste television crusts were investigated. The results showed that the oil yield increased with increasing temperature or with prolongation of reaction time. With increasing temperature, the generating percentage of gasoline and diesel oil increased, but the heavy oil yield decreased. Zinc oxide, iron oxide and fluid catalytic cracking catalyst (FCC catalyst) were employed to perform a series of experiments. It was demonstrated that the liquid product was markedly improved and the reaction temperature decreased 100 degrees C when FCC was used. The composition ofpyrolysis oils was analysed using gas chromatography-mass spectrometry, and they contained 36.49% styrene, 19.72% benzenebutanenitrile, 12.1% alpha-methylstyrene and 9.69% dimethylbenzene.

  1. Potential mechanisms of pore-fluid movement from continental lithospheric mantle into upper continental crust

    Institute of Scientific and Technical Information of China (English)

    ZHAO Chong-bin; PENG Sheng-lin; LIU Liang-ming; B.E.HOBBS; A.ORD

    2008-01-01

    Through integrating the state of the art scientific knowledge in different research fields, some potential mechanisms of large-scale movements of underground pore-fluids such as H2O and CO2 in the continental lithosphere were presented and discussed. The results show that the generation and propagation of porosity waves are important mechanisms to transport mass and heat fluxes from the continental lithospheric mantle into the lower continental crust; the generation and propagation of porosity waves, pore-fluid flow focusing through lower and middle crustal faults, aclvection of pore-fluids through the lower and middle crust, and whole-crustconvection in some particular cases are important mechanisms to transport mass and heat fluxes from the lower into the upper continental crust; heat and mass transport through convective pore-fluid flow is the most effective mechanism of ore body formation and mineralization in hydrothermal systems; due to heat and mass exchange at the interface between the earth surface, hydrosphere and atmosphere, it is very important to consider the hydro-geological effect of the deep earth pore-fluids such as H2O and CO2 on the global warming and climate change in future investigations.

  2. The Active Solid Earth

    Science.gov (United States)

    Ebinger, Cynthia

    2016-04-01

    Dynamic processes in Earth's crust, mantle and core shape Earth's surface and magnetic field over time scales of seconds to millennia, and even longer time scales as recorded in the ca. 4 Ga rock record. Our focus is the earthquake-volcano deformation cycles that occur over human time scales, and their comparison with time-averaged deformation studies, with emphasis on mantle plume provinces where magma and volatile release and vertical tectonics are readily detectable. Active deformation processes at continental and oceanic rift and back arc zones provide critical constraints on mantle dynamics, the role of fluids (volatiles, magma, water), and plate rheology. For example, recent studies of the East African rift zone, which formed above one of Earth's largest mantle upwellings reveal that magma production and volatile release rates are comparable to those of magmatic arcs, the archetypal zones of continental crustal creation. Finite-length faults achieve some plate deformation, but magma intrusion in the form of dikes accommodates extension in continental, back-arc, and oceanic rifts, and intrusion as sills causes permanent uplift that modulates the local time-space scales of earthquakes and volcanoes. Volatile release from magma intrusion may reduce fault friction and permeability, facilitating aseismic slip and creating magma pathways. We explore the implications of active deformation studies to models of the time-averaged structure of plume and extensional provinces in continental and oceanic plate settings.

  3. Telluric currents have no significant effect on the Earth's core seismicity

    Science.gov (United States)

    Chernogor, L. F.

    2017-01-01

    We show that telluric currents have no effect on the formation of macrofaults in the Earth's crust or on implementation of the intensification regime. This is mainly associated with the weakness of telluric currents and induction of the geomagnetic field.

  4. New index of ferromanganese crusts reflecting oceanic environmental oxidation

    Institute of Scientific and Technical Information of China (English)

    WU GuangHai; ZHOU HuaiYang; ZHANG HaiSheng; LING HongFei; MA WeiLin; ZHAO HongQiao; CHEN JianLin; LIU JieHong

    2007-01-01

    Ferromanganese crusts (hereinafter crusts)form in aerobic environment and the environmental oxidation degree is recorded by the redox sensitive element Co in the crusts.The ages of the layers from the surface to bottom of the crusts are determined,and main element contents at high resolution along the depth sections of three crusts from the Pacific Ocean are analyzed by an electron microprobe.Thus the variations of Co/(Fe+Mn)and Co/(Ni+Cu)with age/depth of the crust layers are obtained.By comparing the ratios of co/(Fe+Mn)and Co/(Ni+Cu)with theδ18O curves of the Pacific benthic foraminifera,we find that these two ratios can reflect the variation of the environmental oxidation state under which the crust layers deposit.The evolution of the oxidation degree reflected by the two indexes resembles the evolution of temperature since the Oligocene reflected by theδ18O curves of the Pacific benthic foraminifera.This suggests that the crust-forming environment after the Oligocene is controlled mainly by the oxygen-rich bottom water originated from the Antarctic bottom water (AABW).However it is not the case prior to the Oligocene.Furthermore it suggests that the environmental oxidation degree controls the formation of the crusts and the Co contents in the crusts.This explains why the Co contents in the crusts increase with time up to now.

  5. New index of ferromanganese crusts reflecting oceanic environmental oxidation

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Ferromanganese crusts (hereinafter crusts) form in aerobic environment and the environmental oxida-tion degree is recorded by the redox sensitive element Co in the crusts. The ages of the layers from the surface to bottom of the crusts are determined, and main element contents at high resolution along the depth sections of three crusts from the Pacific Ocean are analyzed by an electron microprobe. Thus the variations of Co/(Fe+Mn) and Co/(Ni+Cu) with age/depth of the crust layers are obtained. By comparing the ratios of Co/(Fe+Mn) and Co/(Ni+Cu) with the δ 18O curves of the Pacific benthic foraminifera, we find that these two ratios can reflect the variation of the environmental oxidation state under which the crust layers deposit. The evolution of the oxidation degree reflected by the two indexes resembles the evo-lution of temperature since the Oligocene reflected by the δ 18O curves of the Pacific benthic foraminif-era. This suggests that the crust-forming environment after the Oligocene is controlled mainly by the oxygen-rich bottom water originated from the Antarctic bottom water (AABW). However it is not the case prior to the Oligocene. Furthermore it suggests that the environmental oxidation degree controls the formation of the crusts and the Co contents in the crusts. This explains why the Co contents in the crusts increase with time up to now.

  6. No significant production of continental crust prior to 3.8 Ga

    Science.gov (United States)

    Vervoort, J. D.; Kemp, T.; Fisher, C. M.

    2012-12-01

    In his final paper before his death in 1991 (The Persistent Myth of Crustal Growth), Dick Armstrong argued that continental crustal recycling has kept pace with crustal growth and that the volume of continental crust has been in an approximate steady state (no net growth) for at least the past 4 Ga. Although this has been a minority viewpoint (most scientists favor some manner of progressive crustal growth) Armstrong's no-growth model has had some vehement supporters over the years. Since this paper was published, most of the discussion in the literature has focused on the isotopic record—particularly that of the oldest preserved igneous rocks. Recently, attention has shifted to detrital zircons and, in particular, the Hf isotopic record in the oldest known zircons. Two main features from these data have been used to argue for widespread crust in the early Earth: 1) heterogeneous Hf isotopic compositions of the oldest zircons; and 2) Hf model ages in Archean detrital zircons that are much older than their crystallization ages. The dataset on which these observations have been based, however, is not robust. Many data are compromised by complexities in age and isotopic composition. Hf zircon model ages are even more problematic as they are loaded with assumptions and based on a depleted mantle evolution reference that is not well known, is most likely wrong prior to 3.8 Ga, and has uncertain relevance for understanding crustal growth. In order to provide a less ambiguous isotopic record, a better approach is needed: the integration of age (U-Pb zircon) and isotopic information (Hf-Nd whole rock, Hf-O in zircons) from the oldest, but also least complicated and altered, magmatic samples. Several lines of evidence suggest that formation of continental crust did not begin in earnest until ca. 3.8-3.5 Ga: 1) lack of older crust or inherited pre-4 Ga zircon cores in the geological record in shield areas; 2) conspicuous lack of pre-4 Ga zircons in nearly all Archean

  7. Titanium isotopic evidence for felsic crust and plate tectonics 3.5 billion years ago.

    Science.gov (United States)

    Greber, Nicolas D; Dauphas, Nicolas; Bekker, Andrey; Ptáček, Matouš P; Bindeman, Ilya N; Hofmann, Axel

    2017-09-22

    Earth exhibits a dichotomy in elevation and chemical composition between the continents and ocean floor. Reconstructing when this dichotomy arose is important for understanding when plate tectonics started and how the supply of nutrients to the oceans changed through time. We measured the titanium isotopic composition of shales to constrain the chemical composition of the continental crust exposed to weathering and found that shales of all ages have a uniform isotopic composition. This can only be explained if the emerged crust was predominantly felsic (silica-rich) since 3.5 billion years ago, requiring an early initiation of plate tectonics. We also observed a change in the abundance of biologically important nutrients phosphorus and nickel across the Archean-Proterozoic boundary, which might have helped trigger the rise in atmospheric oxygen. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  8. Decoupled Rb-Sr and Sm-Nd isotopic evolution of the continental crust

    Science.gov (United States)

    Goldstein, S. L.

    1988-01-01

    Evidence was presented that the Rb-Sr and Sm-Nd isotopic systems are decoupled in crust-mantle evolution. Rare earth element (including Sm and Nd) residue principally in silicates, and are resistant to mobilization by weathering and metamorphism. In contrast, Rb and Sr are easily fractionated by crustal processes and residue in carbonates as well as in silicates. As a result, continental Sr, but not Nd, can be recycled into the mantle by exchange of seawater with basalt at spreading ridges and by subduction of carbonates associated with ridge processes. These effects result in mean Rb-Sr ages of the continental crust and of the upper mantle that are too young. Crustal growth curves based largely on Rb-Sr data, such that of Hurley and Rand, are therefore incorrect.

  9. The effect of thicker oceanic crust in the Archaean on the growth of continental crust through time

    Science.gov (United States)

    Wilks, M. E.

    1988-01-01

    Present crustal evolution models fail to account for the generation of the large volume of continental crust in the required time intervals. All Archaean plate tectonic models, whether invoking faster spreading rates, similar to today's spreading rates, or longer ridge lengths, essentially propose that continental crust has grown by island arc accretion due to the subduction of oceanic crust. The petrological differences that characterize the Archaean from later terrains result from the subduction of hotter oceanic crust into a hotter mantle. If the oceanic crust was appreciably thicker in the Archaean, as geothermal models would indicate, this thicker crust is surely going to have an effect on tectonic processes. A more valid approach is to compare the possible styles of convergence of thick oceanic crust with modern convergence zones. The best modern analog occurs where thick continental crust is colliding with thick continental crust. Oceanic crustal collision on the scale of the present-day Himalayan continental collision zone may have been a frequent occurrence in the Archaean, resulting in extensive partial melting of the hydrous underthrust oceanic crust to produce voluminous tonalite melts, leaving a depleted stabilized basic residuum. Present-day island arc accretion may not have been the dominant mechanism for the growth of the early Archaean crust.

  10. Tectonic erosion, subduction accretion and arc collision as controls on the growth of the continental crust

    Science.gov (United States)

    Clift, P.; Vannucchi, P.; Draut, A.

    2003-04-01

    Subduction plate boundaries, at which tectonic erosion removes material from the overriding plate, account for 57% of the total length of the global subduction system and are favored where convergence rates exceed 7 cm/yr and where the sedimentary cover is less than 1 km. Accretion conversely preferentially occurs in regions of slow convergence (1 km. The slope gradients and taper angle of accretionary plate margins correlates with plate convergence rates, while erosive margin slopes appear to be independent of this. Rates of trench retreat do not appear to correlate with any simple characteristic of the plate interaction, but are largely a function of the history of seamount or ridge collisions. Mass balances of the global subduction system indicate that the entire volume of the continental crust can be recycled through the subduction system every 2.6 Ga. Even in accretionary margins a median of only 32% of the incoming sedimentary mass is accreted over time scales of 10 my or greater, resulting in long-term net loss of continental crust along continental active margins. Average magmatic productivity in the active margins must exceed 75 km3/my if the volume of the continental crust is to reach the slow growth rate indicated by isotopic and continental freeboard arguments. Geological arguments indicate that magmatic accretion rates must be faster in oceanic arcs (87-95 km3/my) and less in the continental arcs (65-83 km3/my). Mass balance arguments in oceanic arcs require that their crustal thicknesses must be Continental growth is principally achieved through the collision of oceanic island arcs to continental margins. Although oceanic arcs are chemically distinct from continental crust, the collision process involves the loss of mafic and ultramafic lower crust and the emplacement of voluminous, high silica, light rare earth element enriched melts, transforming the net composition into something more continental in character.

  11. Crust and upper mantle electrical conductivity beneath the Yellowstone Hotspot Track

    Science.gov (United States)

    Kelbert, A.; Egbert, G. D.

    2012-12-01

    We have used high-quality electromagnetic data obtained through the EarthScope USArray project to obtain detailed three-dimensional images of electrical resistivity / conductivity in the crust and upper mantle beneath the Snake River Plain/Yellowstone (SRP/Y) volcanic province (Idaho and Wyoming, United States). The lowest resistivities in the area can only plausibly be explained by partial melt and/or fluids, providing valuable new information about the distribution of these phases deep within the Earth beneath the volcanic system. Unexpectedly, in light of the mantle plume models often used to explain Yellowstone volcanism, the electromagnetic data imply that there is no interconnected melt in the lower crust and uppermost mantle directly beneath the modern Yellowstone caldera. Instead, low resistivities consistent with 1-3% melt in the uppermost mantle (depths of 40-80 km) extend at least 200 km southwest of Yellowstone. Shallower areas of reduced resistivity extend upward into the mid-crust around the edges of the seemingly impermeable Snake River Plain province, including beneath Yellowstone. We suggest that the elevated temperatures beneath the active volcanic center have resulted in greater permeability, allowing magma to ascend to shallower depths and pool in the crust. Little melt is entering the system from below at present, perhaps due to intermittency of supply. We describe these results in the context of larger scale electrical resistivity and seismic tomography models of the western US and employ joint interpretation to formulate hypotheses that would explain this unexpected melt distribution beneath the SRP/Y. Our 3-D model is available at http://www.iris.edu/dms/products/emc/models/SRPY-MT.htm

  12. Radiogenic heat production in the continental crust

    Science.gov (United States)

    Jaupart, Claude; Mareschal, Jean-Claude; Iarotsky, Lidia

    2016-10-01

    The thermal structure and evolution of continents depend strongly on the amount and distribution of radioactive heat sources in the crust. Determining the contribution of crustal rocks beneath a superficial layer is a major challenge because heat production depends weakly on major element composition and physical properties such as seismic wavespeed and density. Enriched granitic intrusives that lie at the current erosion level have a large impact on the surface heat flux but little influence on temperatures in the deep crust. Many lower crustal rocks that are poor in heat producing elements are restites from ancient orogenic events, implying that enrichment of the upper crust was achieved at the expense of deeper crustal levels. For the same total heat production, concentrating heat sources in an upper layer acts to reduce temperatures in the lower crust, thereby allowing stabilization of the crust. The present-day structure of the crust is a consequence of orogeny and should not be adopted for thermal models of the orogenic event itself. This review summarizes information extracted from large data sets on heat flow and heat production and provides estimates of crustal stratification and heat production in several geological provinces. Analysis of global and regional data sets reveals the absence of a positive correlation between surface heat flow and crustal thickness, showing that the average crustal heat production is not constant. Differences of heat flow between geological provinces are due in large part to changes of crustal structure and bulk composition. Collating values of the bulk crustal heat production in a few age intervals reveals a clear trend of decrease with increasing age. This trend can be accounted for by radioactive decay, indicating that thermal conditions at the time of crustal stabilization have not changed significantly. For the average crustal thickness of 40 km, Moho temperatures are near solidus values at the time of stabilization

  13. Studying the viscosity of lower crust of Qinghai-Tibet Plateau according to post-seismic deformation

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The viscosity of lower crust of Qinghai-Tibet Plateau on earth should be determined. It has become a predominant problem in quantitative research on geodynamics. Its order of magnitude will have a great influence on the results of quantitative modeling. To obtain the viscosity of lower crust of Qinghai-Tibet Plateau, this parameter was calculated by three methods. The first is based on the estimation on the temperature state of Qinghai-Tibet Plateau in the deep part, and the viscosity of lower crust of northern Plateau was recomputed with strain rate derived from rheology law and GPS observation. Effective viscosity of middle crust in Kunlun region is between 1020 and 1022 Pa·s, and that of lower crust is be- tween 1019 and 1021 Pa·s; the second is based on three kinds of rheological models used to fit the post-seismic deformation recorded by cross-over fault GPS sites set after Ms8.1 Kunlun earthquake in 2001. The viscosity of lower crust obtained by this method is of 1017 Pa·s order of magnitude. However, higher viscosity is required to fit the data of south fault better, and the lower one is required to fit the data of north fault better. The viscosity of lower crust, which was obtained by fitting the cross-over fault post-seismic deformation after Ms7.6 Luhuo earthquake in 1973, is of 1019 Pa·s order of magnitude. Non-linear relationship between effective viscosity and strain rate is ignored in the former research of effective viscosity. This research shows the difference of effective viscosity obtained from laboratory experiment, and shorter and longer time post-seismic deformation after large earthquakes can be explained in phase.

  14. Geoneutrinos and the Earth inner parts structure

    CERN Document Server

    Sinev, V V

    2010-01-01

    The connection between geoneutrino registration and the Earth theory test is discussed. We compare standard theory of lithosphere plates and hypothesis of hydride Earth. Last hypothesis adds additional neutrino source $-$ planet core in which the initial Earth composition is conserved. Large volume scintillation detector is supposed to install at Baksan neutrino observatory INR RAS at Caucasus. The detector will register all possible neutrino fluxes, but mainly geo-neutrinos. So kind a detector (or detector net) placed in a number of sites on the Earth surface can measure all radioactivity from $^{238}$U and $^{232}$Th, because their neutrino energy exceeds the inverse beta-decay reaction threshold. By this way it will it possible to understand if there are any more neutrino sources in the Earth other than the crust and mantle.

  15. Longitudinal photosynthetic gradient in crust lichens' thalli.

    Science.gov (United States)

    Wu, Li; Zhang, Gaoke; Lan, Shubin; Zhang, Delu; Hu, Chunxiang

    2014-05-01

    In order to evaluate the self-shading protection for inner photobionts, the photosynthetic activities of three crust lichens were detected using Microscope-Imaging-PAM. The false color images showed that longitudinal photosynthetic gradient was found in both the green algal lichen Placidium sp. and the cyanolichen Peltula sp. In longitudinal direction, all the four chlorophyll fluorescence parameters Fv/Fm, Yield, qP, and rETR gradually decreased with depth in the thalli of both of these two lichens. In Placidium sp., qN values decreased with depth, whereas an opposite trend was found in Peltula sp. However, no such photosynthetic heterogeneity was found in the thalli of Collema sp. in longitudinal direction. Microscope observation showed that photobiont cells are compactly arranged in Placidium sp. and Peltula sp. while loosely distributed in Collema sp. It was considered that the longitudinal photosynthetic heterogeneity was ascribed to the result of gradual decrease of incidence caused by the compact arrangement of photobiont cells in the thalli. The results indicate a good protection from the self-shading for the inner photobionts against high radiation in crust lichens.

  16. Mesoscopic pinning forces in neutron star crusts

    CERN Document Server

    Seveso, Stefano; Grill, Fabrizio; Haskell, Brynmor

    2014-01-01

    The crust of a neutron star is thought to be comprised of a lattice of nuclei immersed in a sea of free electrons and neutrons. As the neutrons are superfluid their angular momentum is carried by an array of quantized vortices. These vortices can pin to the nuclear lattice and prevent the neutron superfluid from spinning down, allowing it to store angular momentum which can then be released catastrophically, giving rise to a pulsar glitch. A crucial ingredient for this model is the maximum pinning force that the lattice can exert on the vortices, as this allows us to estimate the angular momentum that can be exchanged during a glitch. In this paper we perform, for the first time, a detailed and quantitative calculation of the pinning force \\emph{per unit length} acting on a vortex immersed in the crust and resulting from the mesoscopic vortex-lattice interaction. We consider realistic vortex tensions, allow for displacement of the nuclei and average over all possible orientation of the crystal with respect to...

  17. Shear modulus of neutron star crust

    CERN Document Server

    Baiko, D A

    2011-01-01

    Shear modulus of solid neutron star crust is calculated by thermodynamic perturbation theory taking into account ion motion. At given density the crust is modelled as a body-centered cubic Coulomb crystal of fully ionized atomic nuclei of one type with the uniform charge-compensating electron background. Classic and quantum regimes of ion motion are considered. The calculations in the classic temperature range agree well with previous Monte Carlo simulations. At these temperatures the shear modulus is given by the sum of a positive contribution due to the static lattice and a negative $\\propto T$ contribution due to the ion motion. The quantum calculations are performed for the first time. The main result is that at low temperatures the contribution to the shear modulus due to the ion motion saturates at a constant value, associated with zero-point ion vibrations. Such behavior is qualitatively similar to the zero-point ion motion contribution to the crystal energy. The quantum effects may be important for li...

  18. Crusted Demodicosis in an Immunocompetent Pediatric Patient

    Directory of Open Access Journals (Sweden)

    Guillermo Antonio Guerrero-González

    2014-01-01

    Full Text Available Demodicosis refers to the infestation by Demodex spp., a saprophytic mite of the pilosebaceous unit. Demodex proliferation can result in a number of cutaneous disorders including pustular folliculitis, pityriasis folliculorum, papulopustular, and granulomatous rosacea, among others. We report the case of a 7-year-old female presenting with pruritic grayish crusted lesions over her nose and cheeks, along with facial erythema, papules, and pustules. The father referred chronic use of topical steroids. A potassium hydroxide mount of a pustule scraping revealed several D. folliculorum mites. Oral ivermectin (200 μg/kg, single dose plus topical permethrin 5% lotion applied for 3 consecutive nights were administered. Oral ivermectin was repeated every week and oral erythromycin plus topical metronidazole cream was added. The facial lesions greatly improved within the following 3 months. While infestation of the pilosebaceous unit by Demodex folliculorum mites is common, only few individuals present symptoms. Demodicosis can present as pruritic papules, pustules, plaques, and granulomatous facial lesions. To our knowledge, this is the first reported case of facial crusted demodicosis in an immunocompetent child. The development of symptoms in this patient could be secondary to local immunosuppression caused by the chronic use of topical steroids.

  19. Early Differentiation of the Crust-Mantle System: a Hf Isotope Perspective

    Science.gov (United States)

    Scherer, E.; Munker, C.; Mezger, K.

    2001-12-01

    The Lu decay constant recently determined by Scherer et al. 2001 (i.e., 1.865 x 10-11 yr-1) agrees with the results of the two latest physical counting experiments (1.86 x 10-11 yr-1; Dalmasso et al 1992, Nir-El and Lavi 1998), but is ca. 4 percent lower than the decay constants that have been used throughout the Hf isotope literature (e.g., 1.94 x 10-11, Tatsumoto et al., 1981; 1.93 x 10-11 Sguigna et al, 1982). In addition to making Lu-Hf ages older by ca. 4 percent, the revised decay constant also shifts the calculated initial epsilon Hf values of early Archean and Hadean rocks and zircons that are used to constrain crust-mantle differentiation in the early Earth. The initial epsilon Hf values for low-Lu/Hf samples such as zircons and evolved felsic rocks shift downward by 2-4 epsilon units, primarily due to the shift in the position of the CHUR evolution curve rather than that of the samples themselves. Mafic rocks, such as komatiites have higher Lu/Hf ratios that are closer to that of CHUR and therefore their initial epsilon Hf values do not shift as much (up to 1.3 epsilon units lower or 0.4 epsilon units higher). Using the old decay constant, some early Archean rocks (e.g., Amitsoq gneisses; Vervoort et al., 1996, Vervoort and Blichert-Toft, 1999) seemed to have very high initial epsilon Hf values (up to +6), implying that the upper mantle was moderately depleted in the early Archean and that a substantial volume of crust was produced in the Hadean. However, when recalculated with the new decay constant, the data suggest that the mantle was only slightly depleted, requiring less early crust extraction, and allowing a later date for the onset of significant crust production. In contrast, the extremely low recalculated epsilon Hf values of Earth's oldest zircons (Amelin et al., 1999, Amelin et al., 2000) indicate that Earth's first crust formed at or before 4.3 Ga, and that this crust remained intact long enough (>200 million years) to evolve to such low

  20. Does subduction zone magmatism produce average continental crust

    Science.gov (United States)

    Ellam, R. M.; Hawkesworth, C. J.

    1988-01-01

    The question of whether present day subduction zone magmatism produces material of average continental crust composition, which perhaps most would agree is andesitic, is addressed. It was argued that modern andesitic to dacitic rocks in Andean-type settings are produced by plagioclase fractionation of mantle derived basalts, leaving a complementary residue with low Rb/Sr and a positive Eu anomaly. This residue must be removed, for example by delamination, if the average crust produced in these settings is andesitic. The author argued against this, pointing out the absence of evidence for such a signature in the mantle. Either the average crust is not andesitic, a conclusion the author was not entirely comfortable with, or other crust forming processes must be sought. One possibility is that during the Archean, direct slab melting of basaltic or eclogitic oceanic crust produced felsic melts, which together with about 65 percent mafic material, yielded an average crust of andesitic composition.

  1. A Crust-based Method of Reconstructing Human Bone

    Institute of Scientific and Technical Information of China (English)

    MA Shu-chao; LIU Yi

    2014-01-01

    We present a crust-based procedure for modeling human being’s bone, which is based on voronoi diagram and its dual, Delaunay triangulation. In three-dimensional space, the crust algorithm can generate a 3D-model using a set of sample points. The purposes of this paper is to extract precise contour from CT series, then refer to these contours as sample points, and then apply the crust algorithm to these sample points to get three dimensional mesh.

  2. Cementing mechanism of algal crusts from desert area

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    34-, 17-, 4-, 1.5-year old natural algal crusts were collected from Shapotou Scientific Station of the Chinese Academy of Sciences, 40-day old field and greenhouse artificial algal crusts were in situ developed in the same sandy soil and the same place (37°27′N, 104°57′E). Their different cohesions both against wind force and pressure were measured respectively by a sandy wind-tunnel experiment and a penetrometer. On the basis of these algal crusts, the cementing mechanism was revealed from many subjects and different levels. The results showed that in the indoor artificial crusts with the weakest cohesion bunchy algal filaments were distributed in the surface of the crusts, produced few extracellular polymers (EPS), the binding capacity of the crusts just accomplished by mechanical bundle of algal filaments. For field crusts, most filaments grew toward the deeper layers of algal crusts, secreted much more EPS, and when organic matter content was more than 2.4 times of chlorophyll a, overmuch organic matter (primarily is EPS) began to gather onto the surface of the crusts and formed an organic layer in the relatively lower micro-area, and this made the crust cohesion increase 2.5 times. When the organic layer adsorbed and intercepted amounts of dusts, soil particles and sand grains scattered down from wind, it changed gradually into an inorganic layer in which inorganic matter dominated, and this made the crusts cohesion further enhanced 2-6 times. For crust-building species Microcoleus vaginatus, 88.5% of EPS were the acidic components, 78% were the acidic proteglycan of 380 kD. The uronic acid content accounted for 8% of proteglycan, and their free carboxyls were important sites of binding with metal cations from surrounding matrix.

  3. Treatment of crusted scabies with albendazole: A case report.

    Science.gov (United States)

    Douri, Thaer; Shawaf, A Z

    2009-10-15

    Crusted scabies is a severe variant of scabies caused by the ectoparasite Sarcoptes scabiei. It is characterized by high mite burden, extensive hyperkeratotic scaling, crusted lesions, variable pruritus, generalized lymphadenopathy, erythroderma, and eosinophilia, in some cases. There is an increased incidence of crusted scabies, particularly among patients with HIV infection. We describe a 22-year-old Syrian immunocompetent female who had hyperkeratotic psoriasiform plaques and hyperkeratosis without itching. She was treated with oral albendazole and topical crotamiton with salicylic acid 5 percent.

  4. Earth's surface heat flux

    Directory of Open Access Journals (Sweden)

    J. H. Davies

    2009-11-01

    Full Text Available We present a revised estimate of Earth's surface heat flux that is based upon a heat flow data-set with 38 347 measurements, which is 55% more than used in previous estimates. Our methodology, like others, accounts for hydrothermal circulation in young oceanic crust by utilising a half-space cooling approximation. For the rest of Earth's surface, we estimate the average heat flow for different geologic domains as defined by global digital geology maps; and then produce the global estimate by multiplying it by the total global area of that geologic domain. The averaging is done on a polygon set which results from an intersection of a 1 degree equal area grid with the original geology polygons; this minimises the adverse influence of clustering. These operations and estimates are derived accurately using methodologies from Geographical Information Science. We consider the virtually un-sampled Antarctica separately and also make a small correction for hot-spots in young oceanic lithosphere. A range of analyses is presented. These, combined with statistical estimates of the error, provide a measure of robustness. Our final preferred estimate is 47±2 TW, which is greater than previous estimates.

  5. Crust formation and its effect on the molten pool coolability

    Energy Technology Data Exchange (ETDEWEB)

    Park, R.J.; Lee, S.J.; Sim, S.K. [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1995-09-01

    Experimental and analytical studies of the crust formation and its effect on the molten pool coolability have been performed to examine the crust formation process as a function of boundary temperatures as well as to investigate heat transfer characteristics between molten pool and overlying water in order to evaluate coolability of the molten pool. The experimental test results have shown that the surface temperature of the bottom plate is a dominant parameter in the crust formation process of the molten pool. It is also found that the crust thickness of the case with direct coolant injection into the molten pool is greater than that of the case with a heat exchanger. Increasing mass flow rate of direct coolant injection to the molten pool does not affect the temperature of molten pool after the crust has been formed in the molten pool because the crust behaves as a thermal barrier. The Nusselt number between the molten pool and the coolant of the case with no crust formation is greater than that of the case with crust formation. The results of FLOW-3D analyses have shown that the temperature distribution contributes to the crust formation process due to Rayleigh-Benard natural convection flow.

  6. Quantifying glassy and crystalline basalt partitioning in the oceanic crust

    Science.gov (United States)

    Moore, Rachael; Ménez, Bénédicte

    2016-04-01

    The upper layers of the oceanic crust are predominately basaltic rock, some of which hosts microbial life. Current studies of microbial life within the ocean crust mainly focus on the sedimentary rock fraction, or those organisms found within glassy basalts while the potential habitability of crystalline basalts are poorly explored. Recently, there has been recognition that microbial life develops within fractures and grain boundaries of crystalline basalts, therefore estimations of total biomass within the oceanic crust may be largely under evaluated. A deeper understanding of the bulk composition and fractionation of rocks within the oceanic crust is required before more accurate estimations of biomass can be made. To augment our understanding of glassy and crystalline basalts within the oceanic crust we created two end-member models describing basalt fractionation: a pillow basalt with massive, or sheet, flows crust and a pillow basalt with sheeted dike crust. Using known measurements of massive flow thickness, dike thickness, chilled margin thickness, pillow lava size, and pillow lava glass thickness, we have calculated the percentage of glassy versus crystalline basalts within the oceanic crust for each model. These models aid our understanding of textural fractionation within the oceanic crust, and can be applied with bioenergetics models to better constrain deep biomass estimates.

  7. Nitrogen fixation in biological soil crusts from southeast Utah, USA

    Science.gov (United States)

    Belnap, J.

    2002-01-01

    Biological soil crusts can be the dominant source of N for arid land ecosystems. We measured potential N fixation rates biweekly for 2 years, using three types of soil crusts: (1) crusts whose directly counted cells were >98% Microcoleus vaginatus (light crusts); (2) crusts dominated by M. vaginatus, but with 20% or more of the directly counted cells represented by Nostoc commune and Scytonema myochrous (dark crusts); and (3) the soil lichen Collema sp. At all observation times, Collema had higher nitrogenase activity (NA) than dark crusts, which had higher NA than light crusts, indicating that species composition is critical when estimating N inputs. In addition, all three types of crusts generally responded in a similar fashion to climate conditions. Without precipitation within a week of collection, no NA was recorded, regardless of other conditions being favorable. Low (26??C) temperatures precluded NA, even if soils were moist. If rain or snow melt had occurred 3 or less days before collection, NA levels were highly correlated with daily average temperatures of the previous 3 days (r2=0.93 for Collema crusts; r2=0.86 for dark crusts and r2=0.83 for light crusts) for temperatures between 1??C and 26??C. If a precipitation event followed a long dry period, NA levels were lower than if collection followed a time when soils were wet for extended periods (e.g., winter). Using a combination of data from a recording weather datalogger, time-domain reflectometry, manual dry-down curves, and N fixation rates at different temperatures, annual N input from the different crust types was estimated. Annual N input from dark crusts found at relatively undisturbed sites was estimated at 9 kg ha-1 year-1. With 20% cover of the N-fixing soil lichen Collema, inputs are estimated at 13 kg ha-1 year-1. N input from light crusts, generally indicating soil surface disturbance, was estimated at 1.4 kg ha-1 year-1. The rates in light crusts are expected to be highly variable, as

  8. Generation of continental crust in intra-oceanic arcs

    Science.gov (United States)

    Gazel, E.; Hayes, J. L.; Kelemen, P. B.; Everson, E. D.; Holbrook, W. S.; Vance, E.

    2014-12-01

    The origin of continental crust is still an unsolved mystery in the evolution of our planet. Although the best candidates to produce juvenile continental crust are intra-oceanic arcs these systems are dominated by basaltic lavas, and when silicic magmas are produced, the incompatible-element compositions are generally too depleted to be a good match for continental crust estimates. Others, such as the W. Aleutians, are dominated by andesitic melts with trace element compositions similar to average continental crust. In order to evaluate which intra-oceanic arcs produced modern continental crust, we developed a geochemical continental index (CI) through a statistical analysis that compared all available data from modern intra-oceanic arcs with global estimates of continental crust. Our results suggest that magmas from Costa Rica (100 have the least continent-like geochemical signatures. In these arcs the subducting plate is old (>100 Ma), not overprinted by enriched intraplate volcanism and the geochemistry may be dominated by slab-derived, aqueous fluids. We also found a strong correlation between the CI and average crustal P-wave velocity, validating the geochemical index with the available seismic data for intra-oceanic arcs. In conclusion, the production of young continental crust with compositions similar to Archean continental crust is an unusual process, limited to locations where there are especially voluminous partial melts of oceanic crust.

  9. Biological Soil Crusts: Webs of Life in the Desert

    Science.gov (United States)

    Belnap, Jayne

    2001-01-01

    Although the soil surface may look like dirt to you, it is full of living organisms that are a vital part of desert ecosystems. This veneer of life is called a biological soil crust. These crusts are found throughout the world, from hot deserts to polar regions. Crusts generally cover all soil spaces not occupied by green plants. In many areas, they comprise over 70% of the living ground cover and are key in reducing erosion, increasing water retention, and increasing soil fertility. In most dry regions, these crusts are dominated by cyanobacteria (previously called blue-green algae), which are one of the oldest known life forms. Communities of soil crusts also include lichens, mosses, microfungi, bacteria, and green algae. These living organisms and their by-products create a continuous crust on the soil surface. The general color, surface appearance, and amount of coverage of these crusts vary depending on climate and disturbance patterns. Immature crusts are generally flat and the color of the soil, which makes them difficult to distinguish from bare ground. Mature crusts, in contrast, are usually bumpy and dark-colored due to the presence of lichens, mosses, and high densities of cyanobacteria and other organisms.

  10. Earth\\'s Mass Variability

    CERN Document Server

    Mawad, Ramy

    2014-01-01

    The perturbation of the Earth caused by variability of mass of Earth as additional reason with gravity of celestial bodies and shape of the Earth. The Earth eating and collecting matters from space and loss or eject matters to space through its flying in the space around the Sun. The source of the rising in the global sea level is not closed in global warming and icebergs, but the outer space is the additional important source for this rising. The Earth eats waters from space in unknown mechanism. The mass of the Earth become greater in November i.e. before transit apoapsis two months, and become latter in February i.e. after transit apoapsis to two months.

  11. Crustal redistribution, crust-mantle recycling and Phanerozoic evolution of the continental crust

    Science.gov (United States)

    Clift, Peter D.; Vannucchi, Paola; Morgan, Jason Phipps

    2009-12-01

    We here attempt a global scale mass balance of the continental crust during the Phanerozoic and especially the Cenozoic (65 Ma). Continental crust is mostly recycled back into the mantle as a result of the subduction of sediment in trenches (1.65 km 3/a), by the subduction of eroded forearc basement (1.3 km 3/a) and by the delamination of lower crustal material from orogenic plateaus (ca. 1.1 km 3/a). Subduction of rifted crust in continent-continent collision zones (0.4 km 3/a), and dissolved materials fixed into the oceanic crust (ca. 0.4 km 3/a) are less important crustal sinks. At these rates the entire continental crust could be reworked in around 1.8 Ga. Nd isotope data indicate that ca. 80% of the subducted continental crust is not recycled by melting at shallow levels back into arcs, but is subducted to depth into the upper mantle. Continent-continent collision zones do not generally form new crust, but rather cause crustal loss by subduction and as a result of their physical erosion, which exports crust from the orogen to ocean basins where it may be subducted. Regional sedimentation rates suggest that most orogens have their topography eliminated within 100-200 million years. We estimate that during the Cenozoic the global rivers exported an average of 1.8 km 3/a to the oceans, approximately balancing the subducted loss. Accretion of sediment to active continental margins is a small contribution to crustal construction (ca. 0.3 km 3/a). Similarly, continental large igneous provinces (flood basalts) represent construction of only around 0.12 km 3/a, even after accounting for their intrusive roots. If oceanic plateaus are accreted to continental margins then they would average construction rates of 1.1 km 3/a, meaning that to keep constant crustal volumes, arc magmatism would have to maintain production of around 3.8 km 3/a (or 94 km 3/Ma/km of trench). This slightly exceeds the rates derived from sparse seismic experiments in oceanic arc systems. Although

  12. Zinc Isotopic Signatures of the Upper Continental Crust

    Science.gov (United States)

    Xia, Y.; Zhang, X.; Zhang, H.; Huang, F.

    2016-12-01

    To examine the Zn isotope systematics within the Upper Continental Crust (UCC), and isotope fractionation during chemical weathering in large spatial and temporal scales, we analyzed Zn isotopic compositions of loess, glacial diamictites, river sediments, and igneous rocks (samples in total 77). The Zn isotopic compositions (δ66Zn relative to JMC-Lyon) of loess display a limited variation (0.17‰ to 0.29‰), which is negatively correlated with Zn content and proxies for chemical weathering (e.g. CIA values), reflect the impact of chemical weathering. Glacial diamictites have more variable δ66Zn (0.09‰ to 0.48‰), but the average δ66Zn (0.29±0.03‰, 2SD) is similar to loess. δ66Zn of glacial diamictites correlate roughly negatively with CIA values, but have no correlation with Zn content, implying source heterogeneity and effect from chemical weathering. δ66Zn of A-type (0.39‰ to 0.45‰) and S-type (0.28‰ to 0.35‰) granites are both homogeneous, but the latter have systematically lighter δ66Zn. This may reflect no Zn isotopic fractionation during magmatic processes and involvement of isotopically light meta-sedimentary into the sources of S-type granites. Furthermore, δ66Zn in riverine sediments display a small variation from 0.23‰ to 0.37‰, while δ66Zn of the the shales vary from 0.14‰ to 0.53‰, which could result from a combination of processes, such as biological cycling and chemical weathering. Overall, our data suggest that incipient chemical weathering can fractionate Zn isotopes significantly, meanwhile, during this process, heavy Zn are released preferentially. The UCC is estimated to have an average δ66Zn of 0.30 ±0.03‰ (2SD) with data collected in this study, which is similar to the estimated value of Bulk Silicate Earth (0.28±0.05‰)[1] and mean dissolved riverine flux (0.33‰)[2], but distinctly lighter than the bulk composition of dissolved Zn in the ocean (0.51‰)[2]. [1] Chen et al., Zinc isotope fractionation

  13. Biological soil crusts in a xeric Florida shrubland: composition, abundance, and spatial heterogeneity of crusts with different disturbance histories.

    Science.gov (United States)

    Hawkes, C V; Flechtner, V R

    2002-01-01

    Biological soil crusts consisting of algae, cyanobacteria, lichens, fungi, bacteria, and mosses are common in habitats where water and nutrients are limited and vascular plant cover is discontinuous. Crusts alter soil factors including water availability, nutrient content, and erosion susceptibility, and thus are likely to both directly and indirectly affect plants. To establish this link, we must first understand the crust landscape. We described the composition, abundance, and distribution of microalgae in crusts from a periodically burned, xeric Florida shrubland, with the goal of understanding the underlying variability they create for vascular plants, as well as the scale of that variability. This is the first comprehensive study of crusts in the southeastern United States, where the climate is mesic but sandy soils create xeric conditions. We found that crusts were both temporally and spatially heterogeneous in depth and species composition. For example, cyanobacteria and algae increased in abundance 10-15 years after fire and away from dominant shrubs. Chlorophyll a levels recovered rapidly from small-scale disturbance relative to intact crusts, but these disturbances added to crust patchiness. Plants less than 1 m apart can experience different crust environments that may alter plant fitness, plant interactions, and plant community composition.

  14. Moho vs crust-mantle boundary: Evolution of an idea

    Science.gov (United States)

    O'Reilly, Suzanne Y.; Griffin, W. L.

    2013-12-01

    The concept that the Mohorovicic Discontinuity (Moho) does not necessarily coincide with the base of the continental crust as defined by rock-type compositions was introduced in the early 1980s. This had an important impact on understanding the nature of the crust-mantle boundary using information from seismology and from deep-seated samples brought to the surface as xenoliths in magmas, or as tectonic terranes. The use of empirically-constrained P-T estimates to plot the locus of temperature vs depth for xenoliths defined a variety of geotherms depending on tectonic environment. The xenolith geotherms provided a framework for constructing lithological sections through the deep lithosphere, and revealed that the crust-mantle boundary in off-craton regions commonly is transitional over a depth range of about 5-20 km. Early seismic-reflection data showed common layering near the Moho, correlating with the petrological observation of multiple episodes of basaltic intrusion around the crust-mantle boundary. Developments in seismology, petrophysics and experimental petrology have refined interpretation of lithospheric domains. The expansion of in situ geochronology (especially zircon U-Pb ages and Hf-isotopes; Os isotopes of mantle sulfides) has defined tectonic events that affected whole crust-mantle sections, and revealed that the crust-mantle boundary can change in depth through time. However, the nature of the crust-mantle boundary in cratonic regions remains enigmatic, mainly due to lack of key xenoliths or exposed sections. The observation that the Moho may lie significantly deeper than the crust-mantle boundary has important implications for modeling the volume of the crust. Mapping the crust using seismic techniques alone, without consideration of the petrological problems, may lead to an overestimation of crustal thickness by 15-30%. This will propagate to large uncertainties in the calculation of elemental mass balances relevant to crust-formation processes

  15. Early Earth(s) Across Time and Space

    Science.gov (United States)

    Mojzsis, S.

    2014-04-01

    The geochemical and cosmochemical record of our solar system is the baseline for exploring the question: "when could life appear on a world similar to our own?" Data arising from direct analysis of the oldest terrestrial rocks and minerals from the first 500 Myr of Earth history - termed the Hadean Eon - inform us about the timing for the establishment of a habitable silicate world. Liquid water is the key medium for life. The origin of water, and its interaction with the crust as revealed in the geologic record, guides our exploration for a cosmochemically Earth-like planets. From the time of primary planetary accretion to the start of the continuous rock record on Earth at ca. 3850 million years ago, our planet experienced a waning bolide flux that partially or entirely wiped out surface rocks, vaporized oceans, and created transient serpentinizing atmospheres. Arguably, "Early Earths" across the galaxy may start off as ice planets due to feeble insolation from their young stars, occasionally punctuated by steam atmospheres generated by cataclysmic impacts. Alternatively, early global environments conducive to life spanned from a benign surface zone to deep into crustal rocks and sediments. In some scenarios, nascent biospheres benefit from the exogenous delivery of essential bio-elements via leftovers of accretion, and the subsequent establishment of planetary-scale hydrothermal systems. If what is now known about the early dynamical regime of the Earth serves as any measure of the potential habitability of worlds across space and time, several key boundary conditions emerge. These are: (i) availability and long-term stability of liquid water; (ii) presence of energy resources; (iii) accessibility of organic raw materials; (iv) adequate inventory of radioisotopes to drive internal heating; (v) gross compositional parameters such as mantle/core mass ratio, and (vi) P-T conditions at or near the surface suitable for sustaining biological activity. Life could

  16. Ca isotope fingerprints of early crust-mantle evolution

    Science.gov (United States)

    Kreissig, K.; Elliott, T.

    2005-01-01

    The utility of 40Ca/ 44Ca as a tracer of pre-existing crustal contributions in early Archaean cratons has been explored to identify traces of Hadean crust and to assess the style of continental growth. The relatively short half-life of 40K (˜1.3 Gy) means that its decay to 40Ca occurs dominantly during early Earth History. If Archaean crust had a significant component derived from a more ancient protolith, as anticipated by "steady state" crustal evolution models, this should be clearly reflected in radiogenic 40Ca/ 44Ca ratios (or positive initial ɛ Ca) in different Archaean cratons. A high precision thermal ionisation technique has been used to analyse the 40Ca/ 44Ca ratios of plagioclase separates and associated whole rocks in ˜3.6 Ga (early Archaean) samples from Zimbabwe and West Greenland. Three out of four tonalite, trondhjemite, granodiorite (TTG) suite samples from Zimbabwe display initial 40Ca/ 44Ca ratios indistinguishable from our measured modern MORB value (i.e., ɛ Ca(3.6) ˜ 0). Greenland samples, however, are very diverse ranging from ɛ Ca(3.7) = 0.1 in mafic pillow lavas and felsic sheets from the Isua supracrustal belt, up to very radiogenic signatures (ɛ Ca(3.7) = 2.9) in both mafic rocks of the Akilia association and felsic TTG from the coastal Amîtsoq gneisses. At face value, these results imply the Zimbabwe crust is juvenile whereas most Greenland samples include an earlier crustal component. Yet the west Greenland craton, as with many Archaean localities, has experienced a complex geological history and the interpretation of age-corrected initial isotope values requires great care. Both felsic and mafic samples from Greenland display ɛ Ca(3.7) so radiogenic that they are not readily explained by crustal growth scenarios. The presence of such radiogenic 40Ca/ 44Ca found in low K/Ca plagioclases requires Ca isotope exchange between plagioclase and whole rock during later metamorphic event(s). In addition the unexpectedly radiogenic Ca

  17. Li Isotopic Composition and Concentration of the Upper Continental Crust: New Insights from Desert Loess

    Science.gov (United States)

    Sauzeat, L.; Rudnick, R. L.; Chauvel, C.

    2014-12-01

    The isotopic composition of lithium (δ7Li) is recognized to be an excellent proxy of near-surface fluid-rock reactions during weathering. Using Li as a tracer of these processes however requires constraints on the average Li composition of terrestrial reservoirs, in particular that of the upper continental crust. To date, only one value for the average δ7Li value of the upper continental crust, derived from periglacial loess, shales, and granites is available in the literature (7δLi = 0 ± 4 (2σ), Teng et al., 2004). Several values exist for the average [Li] of the upper crust, but they differ by more than 30%. We measured the Li isotopic composition of about 30 desert and periglacial loess (unweathered windblown sediments) from several parts of the world (Europe, Argentina, China and Tajikistan). We demonstrate that desert loess, which is more homogeneous and representative of larger portions of the Earth's surface, provides a better proxy for the average composition of the upper continental crust compared to periglacial loess. The Li isotopic compositions and concentrations of desert loess are controlled by eolian sorting, which can be quantified as a binary isotopic mixing between a weathered fine-grained end-member and an unweathered coarse-grained end-member. Using correlations between Li isotopic compositions, Li concentrations and trace element concentrations in desert loess, we estimate new average values for the upper continental crust: 1 ± 2 (2σ); [Li] = 35.3 ± 4.6 (2σ) ppm. This δ7Li value is slightly higher than that previously published in Teng et al. (2004), but overlaps within uncertainty, whereas the [Li] is identical to that of Teng et al. (2004: 35 ± 11, 2σ); both new estimates have lower uncertainty. Our new estimate of [Li], along with that of Teng et al. (2004), are higher than all previous estimates for the upper continental crust, raising the question as to whether the average concentrations of other mobile alkali metals such as

  18. Modeling the evolution of the lower crust with laboratory derived rheological laws under an intraplate strike slip fault

    Science.gov (United States)

    Zhang, X.; Sagiya, T.

    2015-12-01

    The earth's crust can be divided into the brittle upper crust and the ductile lower crust based on the deformation mechanism. Observations shows heterogeneities in the lower crust are associated with fault zones. One of the candidate mechanisms of strain concentration is shear heating in the lower crust, which is considered by theoretical studies for interplate faults [e.g. Thatcher & England 1998, Takeuchi & Fialko 2012]. On the other hand, almost no studies has been done for intraplate faults, which are generally much immature than interplate faults and characterized by their finite lengths and slow displacement rates. To understand the structural characteristics in the lower crust and its temporal evolution in a geological time scale, we conduct a 2-D numerical experiment on the intraplate strike slip fault. The lower crust is modeled as a 20km thick viscous layer overlain by rigid upper crust that has a steady relative motion across a vertical strike slip fault. Strain rate in the lower crust is assumed to be a sum of dislocation creep and diffusion creep components, each of which flows the experimental flow laws. The geothermal gradient is assumed to be 25K/km. We have tested different total velocity on the model. For intraplate fault, the total velocity is less than 1mm/yr, and for comparison, we use 30mm/yr for interplate faults. Results show that at a low slip rate condition, dislocation creep dominates in the shear zone near the intraplate fault's deeper extension while diffusion creep dominates outside the shear zone. This result is different from the case of interplate faults, where dislocation creep dominates the whole region. Because of the power law effect of dislocation creep, the effective viscosity in the shear zone under intraplate faults is much higher than that under the interplate fault, therefore, shear zone under intraplate faults will have a much higher viscosity and lower shear stress than the intraplate fault. Viscosity contract between

  19. Symmetry energy effects in the neutron star crust properties

    CERN Document Server

    Porebska, J

    2009-01-01

    Different shapes of the nuclear symmetry energy leads to a different crust-core transition point in the neutron star. The basic properties of a crust, like thickness, mass and moment of inertia were investigated for various forms of the symmetry energy.

  20. Structure of the Crust and the Lithosperic Mantle in Siberia

    DEFF Research Database (Denmark)

    Cherepanova, Yulia

    the development of a new regional crustal model, SibCrust, that is a digital crustal model for both the Siberian Craton and the West Siberian Basin. The SibCrust model, constrained by digitizing of all available seismic profiles and crustal velocity models across the Siberia, also includes a critical quality...

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

    Science.gov (United States)

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

    2016-04-01

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

  2. Growth response of a deep-water ferromanganese crust to evolution of the Neogene Indian Ocean

    Science.gov (United States)

    Banakar, V.K.; Hein, J.R.

    2000-01-01

    A deep-water ferromanganese crust from a Central Indian Ocean seamount dated previously by 10Be and 230Th(excess) was studied for compositional and textural variations that occurred throughout its growth history. The 10Be/9Be dated interval (upper 32 mm) yields an uniform growth rate of 2.8 ?? 0.1 mm/Ma [Frank, M., O'Nions, R.K., 1998. Sources of Pb for Indian Ocean ferromanganese crusts: a record of Himalayan erosion. Earth Planet. Sci. Lett., 158, pp. 121-130.] which gives an extrapolated age of ~ 26 Ma for the base of the crust at 72 mm and is comparable to the maximum age derived from the Co-model based growth rate estimates. This study shows that Fe-Mn oxyhydroxide precipitation did not occur from the time of emplacement of the seamount during the Eocene (~ 53 Ma) until the late Oligocene (~ 26 Ma). This paucity probably was the result of a nearly overlapping palaeo-CCD and palaeo-depth of crust formation, increased early Eocene productivity, instability and reworking of the surface rocks on the flanks of the seamount, and lack of oxic deep-water in the nascent Indian Ocean. Crust accretion began (older zone) with the formation of isolated cusps of Fe-Mn oxide during a time of high detritus influx, probably due to the early-Miocene intense erosion associated with maximum exhumation of the Himalayas (op. cit.). This cuspate textured zone extends from 72 mm to 42 mm representing the early-Miocene period. Intense polar cooling and increased mixing of deep and intermediate waters at the close of the Oligocene might have led to the increased oxygenation of the bottom-water in the basin. A considerable expansion in the vertical distance between the seafloor depth and the CCD during the early Miocene in addition to the influx of oxygenated bottom-water likely initiated Fe-Mn crust formation. Pillar structure characterises the younger zone, which extends from 40 mm to the surface of the crust, i.e., ~ 15 Ma to Present. This zone is characterised by > 25% higher

  3. Has 7% of Continental Crust been Lost since Pangea Broke Up?

    Science.gov (United States)

    Scholl, D. W.; Stern, R. J.

    2012-12-01

    km3/Myr/km) previously estimated for Cenozoic ocean-margin SZs. During the past 50 Myr, at Tethyan SZs from Gibraltar to western Australia, we estimate an average rate of lower plate continental crust recycling at ~900 km3/Myr/km. NEGATIVE CRUSTAL GROWTH AND IMPLICATIONS After the breakup of Pangea, the volume of continental crust recycled into the mantle is estimated to be ~500 x 10^6 km3 greater than that created (~400 x 10^6 km3). The net loss is ~7% of Earth's continental crust existing volume (7 x 10^9 km3), an estimate that does not include delamination losses. A large part of SZ losses (~40%) occurred during the past 50 Myr as a consequence of closing the Tethys, a process still underway. It seems likely that a long supercontinent cycle of breakup and dispersal of fragments favors positive crustal growth effected by elevated rates of magmatism at new SZs, whereas a shorter cycle involving rapid reassembly favors negative crustal growth effected by elevated rates of losses at crustal collision zones. Fragmentation of Pangea and the partial reassembly of its parts within 150 Myrs may be representative of a short, crustal destructive supercontinent cycle.

  4. Komatiites: From Earth's Geological Settings to Planetary and Astrobiological Contexts

    OpenAIRE

    Nna-Mvondo, Delphine; Martinez-Frias, Jesus

    2005-01-01

    Komatiites are fascinating volcanic rocks. They are among the most ancient lavas of the Earth following the 3.8 Ga pillow basalts at Isua and they represent some of the oldest ultramafic magmatic rocks preserved in the Earth's crust at 3.5 Ga. This fact, linked to their particular features (high magnesium content, high melting temperatures, low dynamic viscosities, etc.), has attracted the community of geoscientists since their discovery in the early sixties, who have tried to determine their...

  5. Continental Crust Growth as a Result of Continental Collision: Ocean Crust Melting and Melt Preservation

    Science.gov (United States)

    Niu, Y.; Zhao, Z.; Zhou, S.; Zhu, D.; Dong, G.; Mo, X.; Xie, G.; Dong, X.

    2010-12-01

    The significance of the continental crust (CC) on which we live is self-evident. However, our knowledge remains limited on its origin, its way and rate of growth, and how it has acquired the “andesitic” composition from mantle derived magmas. Compared to rocks formed from mantle derived magmas in all tectonic settings, volcanic arc rocks associated with oceanic lithosphere subduction share some common features with the CC; both are relatively depleted in “fluid-insoluble” elements (e.g., Nb, Ta and Ti), but enriched in “fluid-soluble” elements (e.g., U, K and Pb). These chemical characteristics are referred to as the “arc-like signature”, and point to a genetic link between subduction-zone magmatism and CC formation, thus leading to the “island-arc” model widely accepted for the origin of the CC over the past 40 years. However, it has been recognized also that this “island-arc” model has several difficulties. These include (1) bulk arc crust (AC) is basaltic, whereas the bulk CC is andesitic [1]; (2) AC has a variably large Sr excess whereas the CC is Sr deficient [2]; and (3) AC production is mass-balanced by subduction-erosion and sediment recycling, thus contributing no new mass to CC growth, at least in the Phanerozoic [3,4]. Our data on magmatic rocks (both volcanic and intrusive) formed during the India-Asia continental collision (~65 - ~45Ma) [5] show a remarkable compositional similarity to the bulk CC with the typical “arc-like signature” [6]. Also, these syncollisional felsic rocks exhibit strong mantle isotopic signatures, implying that they were recently derived from a mantle source. The petrology and geochemistry of these syncollisional felsic rocks is most consistent with an origin via partial melting of upper oceanic crust (i.e., last fragments of underthrusting oceanic crust) under amphibolite facies conditions, adding net mantle-derived materials to form juvenile CC mass. This leads to the logical and testable hypothesis

  6. Earth materials and earth dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, K; Shankland, T. [and others

    2000-11-01

    In the project ''Earth Materials and Earth Dynamics'' we linked fundamental and exploratory, experimental, theoretical, and computational research programs to shed light on the current and past states of the dynamic Earth. Our objective was to combine different geological, geochemical, geophysical, and materials science analyses with numerical techniques to illuminate active processes in the Earth. These processes include fluid-rock interactions that form and modify the lithosphere, non-linear wave attenuations in rocks that drive plate tectonics and perturb the earth's surface, dynamic recrystallization of olivine that deforms the upper mantle, development of texture in high-pressure olivine polymorphs that create anisotropic velocity regions in the convecting upper mantle and transition zone, and the intense chemical reactions between the mantle and core. We measured physical properties such as texture and nonlinear elasticity, equation of states at simultaneous pressures and temperatures, magnetic spins and bonding, chemical permeability, and thermal-chemical feedback to better characterize earth materials. We artificially generated seismic waves, numerically modeled fluid flow and transport in rock systems and modified polycrystal plasticity theory to interpret measured physical properties and integrate them into our understanding of the Earth. This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL).

  7. Crust-mantle transitional zone of Tianshan orogenic beltand Junggar Basin and its geodynamic implication

    Institute of Scientific and Technical Information of China (English)

    ZHAO; Junmeng

    2001-01-01

    [1]Zeng Rongsheng, Kan Rongju, He Chuanda, Refraction from the basement and wide angle reflection in Chaidamu basin,Chinese Journal of Geophysics, 1961, 10: 54-66.[2]Davydova, N. I., Possibilities of the DSS Technique in Studying Properties of the Deep Seated Interface in Seismic Properties of Mohorovicic Discontinuity, Springfield, Va: National Technical Information Service, US Dept. of Commerce,1975.4-22.[3]Wang Chunyong. Wu Qingju, Tang Jingjian et al., Discussion on tectonic feature of the crust mantle transitional zone in Jizhong depression, in Seismology in Progress(in Chinese) (ed. Lu Zaoxun), Beijing: Seismological Press, 1995, 172-179.[4]Zhao Junmeng. Meng Buzai, Li Aimin et al., Tectonic characteristics of the Moho discontinuity in southem Liaoning Province, in Seismology in Progress(in Chinese) (ed. Lu Zaoxun), Beijing: Seismological Press, 1995, 223-229.[5]Ma Zongjin, Zhao Junmeng, Contrast research on Tianshan orogenic belt and Yinshan-Yanshan orogenic belt, Earth Science Frontiers(in Chinese), 1999, (3): 95-102.[6]Zhao Junmeng, Tang Ji, Zhang Haijiang et al., Wavelet transform and its application in data processing and interpretation of seismic reflection/refraction profile, Chinese Joumal of Geophysics, 2000, 43(5): 666-676.[7]Zhao Junmeng, Zhang Xiankang, Zhao Guoze et al., Structure of crust mantle transitional zone in different tectonic environments, Earth Science Frontiers(in Chinese), 1999, (3): 165-172.[8]Liu Guodong, Continental crust and dynamics, in A Collection of Papers for Discussing Modem Day Dynamic Problems (in Chinese). Beijing: Seismological Press, 1994, 131-153.[9]Zhao Junmeng, Lu Zaoxun, Deep structure of the Liaohe riff and the lateral migration of the rifting, Seismology and Geology(in Chinese), 20(3): 225-233.

  8. Development of Soil Crusts Under Simulated Rainfall and Crust Formation on a Loess Soil as Influenced by Polyacrylamide

    Institute of Scientific and Technical Information of China (English)

    HU Xia; LIU Lian-You; LI Shun-Jiang; CAI Qiang-Guo; L(U) Yan-Li; GUO Jin-Rui

    2012-01-01

    This study evaluated the morphological characteristics and dynamic variation in characteristics of soil crust and identified the relationships between soil crust and splash erosion under simulated rainfall.The effect of polyacrylamide (PAM) on soil aggregate stabilization and crust formation was also investigated.A laboratory rainfall simulation experiment was carried out using soil sample slices.The slices were examined under a polarized light microscopy and a scanning electron microscope (SEM).The results revealed that the soil crusts were thin and were characterized by a greater density,higher shear strength,finer porosity,and lower saturated hydraulic conductivity than the underlying soil.Two types of crusts,i.e.,structural and depositional crusts,were observed.Soil texture was determined to be the most important soil variable influencing surface crust formation; depositional crust formation was primarily related to the skeleton characteristics of the soil and happened when the soil contained a high level of medium and large aggregates.The crust formation processes observed were as follows:1) The fine particles on the soil surface became spattered,leached,and then rough in response to raindrop impact and 2) the fine particles were washed into the subsoil pores while a compact dense layer concurrently formed at soil surface due to the continual compaction by the raindrops.Therefore,the factors that influenced structural crust formation were a large amount of fine particles in the soil surface,continual impact of raindrops,dispersion of aggregates into fine particles,and the formation of a compact dense layer concurrently at the soil surface.It was concluded that the most important factor in the formation of soil crusts was raindrop impact.When polyacrylamide (PAM) was applied,it restored the soil structure and greatly increased soil aggregate stabilization.This effectively prevented crust formation.However,this function of PAM was not continuously effective and

  9. Revised Thickness of the Lunar Crust from GRAIL Data: Implications for Lunar Bulk Composition

    Science.gov (United States)

    Taylor, G. Jeffrey; Wieczorek, Mark A.; Neumann, Gregory A.; Nimmo, Francis; Kiefer, Walter S.; Melosh, H. Jay; Phillips, Roger J.; Solomon, Sean C.; Andrews-Hanna, Jeffrey C.; Asmar, Sami W.; Konopliv, Alexander S.; Lemoine, Frank G.; Smith, David E.; Watkins, Michael W.; Williams, James G.; Zuber, Maria T.

    2013-01-01

    High-resolution gravity data from GRAIL have yielded new estimates of the bulk density and thickness of the lunar crust. The bulk density of the highlands crust is 2550 kg m-3. From a comparison with crustal composition measured remotely, this density implies a mean porosity of 12%. With this bulk density and constraints from the Apollo seismic experiment, the average global crustal thickness is found to lie between 34 and 43 km, a value 10 to 20 km less than several previous estimates. Crustal thickness is a central parameter in estimating bulk lunar composition. Estimates of the concentrations of refractory elements in the Moon from heat flow, remote sensing and sample data, and geophysical data fall into two categories: those with refractory element abundances enriched by 50% or more relative to Earth, and those with abundances the same as Earth. Settling this issue has implications for processes operating during lunar formation. The crustal thickness resulting from analysis of GRAIL data is less than several previous estimates. We show here that a refractory-enriched Moon is not required

  10. Digital Crust: Information architecture for heterogeneous data integration

    Science.gov (United States)

    Richard, S. M.; Zaslavsky, I.; Fan, Y.; Bristol, S.; Peters, S. E.

    2015-12-01

    The Digital Crust EarthCube Building block is addressing the issue of multiple, heterogeneous but related datasets characteristic of field and sample based research using a 'loose-schema' approach, with linked entity and attribute definitions in an information model (ontology) registry (IMR). Various data entities (RDA 'data types') are defined by mapping entity and attribute definitions to definitions in the IMR. Inclusion (loading) of new data at the simplest level can bring in entities that are not registered, but these will not be 'integratable' with other data until someone does the schema matching into the IMR. New datasets can be designed using registered entity and attributes that will from the beginning be integrated into the system (similar to the approach used by the National Information Exchange Model). The fundamental abstract components in this system are 1) a data repository that allows storage of key-value structured data objects; and 2) a registry that documents information models-- the base data types, attributes and entities -- and mappings from the registered types in the datastore to the registered items. This constitutes the data repository subsystem. Data access is enabled by caching views of aggregated data from the datastore (aggregated based on the semantics of the registered items in the IMR) and creating indexes based on the registered items in the IMR. Contributing data to this system will be greatly facilitated by using existing, documented information models. It can accept datasets that are not 'standardized' as well, but the consequence is that those data will not be integratable with other existing data until the work is done to document the entities and attributes in the data and to map those into existing registered types.

  11. Paleomagnetism of late Archaean flood basalt terrains : implications for early Earth geodynamics and geomagnetism

    NARCIS (Netherlands)

    Strik, G.H.M.A.

    2004-01-01

    Palaeomagnetic studies are e.g. important for demonstrating and quantifying horizontal movement and rotation of pieces of the Earth's crust. The constant movement and recycling of plates, in other words plate tectonics, is an important mechanism for the Earth to lose its heat. It is generally

  12. Palaeomagnetism of late Archaean flood basalt terrains : implications for early Earth geodynamics and geomagnetism

    NARCIS (Netherlands)

    Strik, Gerardus Henricus Martina Anna

    2004-01-01

    Palaeomagnetic studies are e.g. important for demonstrating and quantifying horizontal movement and rotation of pieces of the Earth's crust. The constant movement and recycling of plates, in other words plate tectonics, is an important mechanism for the Earth to lose its heat. It is generally

  13. Palaeomagnetism of late Archaean flood basalt terrains : implications for early Earth geodynamics and geomagnetism

    NARCIS (Netherlands)

    Strik, Gerardus Henricus Martina Anna

    2004-01-01

    Palaeomagnetic studies are e.g. important for demonstrating and quantifying horizontal movement and rotation of pieces of the Earth's crust. The constant movement and recycling of plates, in other words plate tectonics, is an important mechanism for the Earth to lose its heat. It is generally accept

  14. Paleomagnetism of late Archaean flood basalt terrains : implications for early Earth geodynamics and geomagnetism

    NARCIS (Netherlands)

    Strik, G.H.M.A.

    2004-01-01

    Palaeomagnetic studies are e.g. important for demonstrating and quantifying horizontal movement and rotation of pieces of the Earth's crust. The constant movement and recycling of plates, in other words plate tectonics, is an important mechanism for the Earth to lose its heat. It is generally accept

  15. Palaeomagnetism of late Archaean flood basalt terrains : implications for early Earth geodynamics and geomagnetism

    NARCIS (Netherlands)

    Strik, Gerardus Henricus Martina Anna

    2004-01-01

    Palaeomagnetic studies are e.g. important for demonstrating and quantifying horizontal movement and rotation of pieces of the Earth's crust. The constant movement and recycling of plates, in other words plate tectonics, is an important mechanism for the Earth to lose its heat. It is generally accept

  16. Paleomagnetism of late Archaean flood basalt terrains : implications for early Earth geodynamics and geomagnetism

    NARCIS (Netherlands)

    Strik, G.H.M.A.

    2004-01-01

    Palaeomagnetic studies are e.g. important for demonstrating and quantifying horizontal movement and rotation of pieces of the Earth's crust. The constant movement and recycling of plates, in other words plate tectonics, is an important mechanism for the Earth to lose its heat. It is generally accept

  17. Issues of oxygen excess in the crust and upper mantle lithosphere

    Science.gov (United States)

    Balashov, Y. A.; Martynov, E. V.

    2012-04-01

    Application of a new geochemical buffer, 'CeB' - Ce+4/Ce+3 for zircons, is promising for oxygen fugacity (FO2) estimation in crust and mantle. Absence of Ce+4 and Eu+2-enriched zircons are typical of the lower lithosphere. Reducing setting dominate in mantle rocks. Subduction adds oxidized substance for lithosphere into deeper mantle (Balashov ea, 2011-2012). The zircons in upper lithosphere are oxidized. Peridotites minerals show increased H2O and OH- preserves to 150-160 km at ΔFMQ -1.4 - -0.1 (Babushkina et al, 2009) comparable with CeB 2.2 - 3.9. Increasing oceanic mass in the geological time controls water efflux and oxidation of upper the lithosphere. Oxygen source in crust and upper mantle is the most important, yet outstanding issues in geochemistry of Earth's upper shells. Oxygen excess in atmosphere correlating with long-term emergence and evolution of Earth's biosphere is an approach reflected in the schemes of cycle- and phase-wise biosphere evolution (Dobretsov et al, 2006; Sorokhtin et al, 2010). The both schemes demonstrate ideas for oxygen evolution of atmosphere, but are not confirmed by geochronology. Applying these outlines an actual picture FO2 evolution. Precambrian granitoids, detrital zircons and upper mantle lithosphere have similar CeB. The initial data include Australian Hadean and Archaean detrital zircons (Peck et al, 2001), CeB: 27.1 -1.96, and Eu+2/Eu+3: 0.015-0.12 (Balashov, Skublov, 2011). Greenland tonalities (3813 Ma) and granodiorite (3638 Ma) (Whitehouse, Kamber, 2002) CeB: 34 - 0.5. In oldest crust rocks dominated zircons with generation under high and heterogeneous FO2. Zircons in younger mantle-crustal rocks of S. American subduction zones (Ballard et al, 2002; Hoskin et al, 2000, etc.) show the same. Upper mantle lithosphere and crust represent continuously interacted with oxygen. If Progressively oxygen increase from Hadean to modern state (Dobretsov ea, 2006; Sorokhtin ea, 2010), contradicts with actual Archaean data. We

  18. Soil crusts to warm the planet

    Science.gov (United States)

    Garcia-Pichel, Ferran; Couradeau, Estelle; Karaoz, Ulas; da Rocha Ulisses, Nunes; Lim Hsiao, Chiem; Northen, Trent; Brodie, Eoin

    2016-04-01

    Soil surface temperature, an important driver of terrestrial biogeochemical processes, depends strongly on soil albedo, which can be significantly modified by factors such as plant cover. In sparsely vegetated lands, the soil surface can also be colonized by photosynthetic microbes that build biocrust communities. We used concurrent physical, biochemical and microbiological analyses to show that mature biocrusts can increase surface soil temperature by as much as 10 °C through the accumulation of large quantities of a secondary metabolite, the microbial sunscreen scytonemin, produced by a group of late-successional cyanobacteria. Scytonemin accumulation decreases soil albedo significantly. Such localized warming had apparent and immediate consequences for the crust soil microbiome, inducing the replacement of thermosensitive bacterial species with more thermotolerant forms. These results reveal that not only vegetation but also microorganisms are a factor in modifying terrestrial albedo, potentially impacting biosphere feedbacks on past and future climate, and call for a direct assessment of such effects at larger scales. Based on estimates of the global biomass of cyanobacteria in soil biocrusts, one can easily calculate that there must currently exist about 15 million metric tons of scytonemin at work, warming soil surfaces worldwide

  19. A new crystalline phase in magnetar crusts

    CERN Document Server

    Bedaque, Paulo F; Ng, Nathan; Sen, Srimoyee

    2013-01-01

    We show that ions at the low densities and high magnetic fields relevant to the outer crust of magnetars form a novel crystalline phase where ions are strongly coupled along the magnetic field and loosely coupled in the transverse direction. The underlying cause is the anisotropic screening of the Coulomb force by electrons in the presence of a strongly quantizing magnetic field which leads to Friedel oscillations in the ion-ion potential. In particular, the Friedel oscillations are much longer-ranged in the direction of the magnetic field than is the case in the absence of magnetic fields, a factor that has been neglected in previous studies. These "Friedel crystals" have very anisotropic elastic moduli, with potentially interesting implications for the Quasi-periodic Oscillations seen in the X-ray flux of magnetars during their giant flares. We find the minimum energy configuration of ions taking into account these anisotropic effects and find that, depending on the density, temperature and magnetic field s...

  20. Temporal Evolution of the Upper Continental Crust: Implications for the Mode of Crustal Growth and the Evolution of the Hydrosphere

    Science.gov (United States)

    Rudnick, R. L.; Gaschnig, R. M.; Li, S.; Tang, M.; Qiu, L.; Valley, J. W.; Zurkowski, C.; McDonough, W. F.

    2014-12-01

    The upper continental crust (UCC), the interface between the atmosphere and solid Earth, is the site of weathering that produces sedimentary rocks, influences ocean chemistry through runoff of soluble elements, and affects climate through CO2 draw-down. The UCC also contains more than 50% of the crust's highly incompatible element budget (including K, Th, and U). Therefore, understanding its composition and evolution provides insight into how continents have formed, evolved, and interacted with the hydrosphere. New major and trace element compositions of >100 glacial diamictites and >100 Archean shales, plus δ7Li and δ18O for a subset of these samples, combined with data from the literature, show that the average composition of the UCC has changed through time, reflecting both the rise of atmospheric oxygen and its attendant effects on weathering, as well as the mode of crust formation and differentiation. Some changes that occur as a step function near the Archean/Proterozoic boundary (increased Th/U, decreased Mo/Pr, V/Lu) reflect the rise of oxygen at the great oxidation event (GOE) and its influence on chemical weathering signatures in the UCC. Other changes are more gradual with time (e.g., higher Th/Sc and δ18O, lower Ni/Co, La/Nb, Eu/Eu* and transition metal abundances) and reflect an UCC that has transitioned from a more mafic to a more felsic bulk composition, and which experienced increased interaction with the hydrosphere with time. The gradual nature of these compositional changes likely reflects the waning heat production of the Earth, rather than an abrupt change in tectonics or style of crust formation. These more gradual changes in crust composition, which contrast with the abrupt changes associated with the GOE, suggest that a fundamental change in the nature of crust differentiation is unlikely to be responsible for the rise of atmospheric oxygen (cf. Keller and Schoene, 2012). Indeed, it appears that the opposite may be true: that the rise of

  1. Isotopic mass independent signature of black crusts: a proxy for atmospheric aerosols formation in the Paris area (France).

    Science.gov (United States)

    Genot, Isabelle; Martin, Erwan; Yang, David Au; De Rafelis, Marc; Cartigny, Pierre; Wing, Boswell; Le Gendre, Erwann; Bekki, Slimane

    2016-04-01

    In view of the negative forcing of the sulfate aerosols on climate, a more accurate understanding of the formation of these particles is crucial. Indeed, despite the knowledge of their effects, uncertainties remain regarding the formation of sulfate aerosols, particularly the oxidation processes of S-bearing gases. Since the discovery of oxygen and sulfur mass independent fractionation (O- and S-MIF) processes on Earth, the sulfate isotopic composition became essential to investigate the atmospheric composition evolution and its consequences on the climate and the biosphere. Large amount of S-bearing compounds (SO2 mainly) is released into the atmosphere by anthropogenic and natural sources. Their oxidation in the atmosphere generates sulfate aerosols, H2SO4, which precipitate on the earth surface mainly as acid rain. One consequence of this precipitation is the formation of black crust on buildings made of carbonate stones. Indeed the chemical alteration of CaCO3 by H2SO4 leads to gypsum (CaSO4·2H2O) concretions on building walls. Associated to other particles, gypsum forms black-crusts. Therefore, black crusts acts as 'sulfate aerosol traps', meaning that their isotopic composition reveals the composition and thus the source and formation processes of sulfate aerosols in the atmosphere in a specific region. In this study we collected 37 black crusts on a 300km NW-SE profile centered on Paris (France). In our samples, sulfate represent 40wt.% and other particles 60wt.% of the black crusts. After sulfate extraction from each samples we measured their O- and S-isotopes composition. Variations of about 10‰ in δ18O and δ34S are observed and both O-MIF (Δ17O from 0 to 1.4‰) and S-MIF (Δ33S from 0 to -0.3‰) compositions have been measured. In regards to these compositions we can discuss the source and formation (oxidation pathways) of the sulfate aerosols in troposphere above the Paris region that covers urban, rural and coastal environments. Furthermore

  2. What governs the enrichment of Pb in the continental crust? An answer from the Mexican Volcanic Belt

    Science.gov (United States)

    Goldstein, S. L.; Lagatta, A.; Langmuir, C. H.; Straub, S. M.; Martin-Del-Pozzo, A.

    2009-12-01

    One of Al Hofmann’s many important contributions to our understanding of geochemical cycling in the Earth is the observation that Pb behaves like the light rare earth elements Ce and Nd during melting to form oceanic basalts, but is enriched in the continental crust compared to the LREE by nearly an order of magnitude (Hofmann et al. 1986). This is unusual behavior, and has been called one of the Pb paradoxes, since in most cases, the ratios of elements are effectively the same in the continental crust and oceanic basalts if they show similar mantle melting behavior. One of several mechanisms suggested to mediate this special enrichment is hydrothermal circulation at ocean ridges, which preferentially transports Pb compared to the REE from the interior of the ocean crust to the surface. We confirm the importance of hydrothermal processes at the East Pacific to mediate Pb enrichment at the Trans-Mexican Volcanic Belt (TMVB, through comparison of Pb isotope and Ce/Pb ratios of TMVB lavas with sediments from DSDP Site 487 near the Middle America trench. The lavas of the Trans-Mexican Volcanic Belt include “high Nb” alkali basalts (HNAB), whose trace element patterns lack subduction signatures. The HNAB basalts and hydrothermally affected sediments from DSDP 487, form end-members that bound calcalkaline lavas from volcanoes Colima, Toluca, Popocatépetl, and Malinche in Ce/Pb versus Pb isotope space. The HNAB represent the high Ce/Pb and high Pb-isotope end-member. The hydrothermal sediments have Pb isotopes like Pacific MORB but Ce/Pb ratios typical of the arcs and the continental crust, and an order of magnitude lower than MORB. No analyzed calcalkaline lavas are have compositions outside of the bounds formed by the HNAB and the hydrothermal sediments. The Ce/Pb and Pb isotope ratios show that the calcalkaline lava compositions are inconsistent with contributions from HNAB and EPR MORB, rather the contributions are from HNAB upper mantle and subducted

  3. The stability of the crust of the dwarf planet Ceres

    Science.gov (United States)

    Formisano, M.; Federico, C.; De Angelis, S.; De Sanctis, M. C.; Magni, G.

    2016-11-01

    In this article, we study the possibility that Ceres has, or had in the past, a crust heavier than a pure or muddy ice mantle, in principle gravitationally unstable. Such a structure is not unusual in the Solar system: Callisto is an example. In this work, we test how the composition (i.e. the volumetric quantity of ice) and the size of the crust can affect its survival during thermo-physical evolution after differentiation. We have considered two different configurations: the first characterized by a dehydrated silicate core and a mantle made of pure ice, the second with a hydrated silicate core and a muddy mantle (ice with silicate impurities). In both cases, the crust is composed of a mixture of ice and silicates. These structures are constrained by a recent measurement of the mean density by Park et al. The Rayleigh-Taylor instability, which operates in such an unstable structure, could reverse all or part of the crust. The whole unstable crust (or part of it) can interact chemically with the underlying mantle and what is currently observed could be a partially/totally new crust. Our results suggest that, in the case of a pure ice mantle, the primordial crust has not survived until today, with a stability timespan always less than 3 Gyr. Conversely, in the case of a muddy mantle, with some `favourable' conditions (low volumetric ice percentage in the crust and small crustal thickness), the primordial crust could be characterized by a stability timespan compatible with the lifetime of the Solar system.

  4. Ancient and Medieval Earth in Armenia

    Science.gov (United States)

    Farmanyan, S. V.

    2015-07-01

    Humankind has always sought to recognize the nature of various sky related phenomena and tried to give them explanations. The purpose of this study is to identify ancient Armenians' pantheistic and cosmological perceptions, world view, notions and beliefs related to the Earth. The paper focuses on the structure of the Earth and many other phenomena of nature that have always been on a major influence on ancient Armenians thinking. In this paper we have compared the term Earth in 31 languages. By discussing and comparing Universe structure in various regional traditions, myths, folk songs and phraseological units we very often came across to "Seven Heavens" (Seven heavens is a part of religious cosmology found in many major religions such as Islam, Judaism, Hinduism and Christianity (namely Catholicism) and "Seven Earths". Armenians in their turn divided Earth and Heavens into seven layers. And in science too, both the Earth and the Heavens have 7 layers. The Seven Heavens refer to the layers of our atmosphere. The Seven Earths refer to the layers of the Earth (from core to crust), as well as seven continents. We conclude that the perception of celestial objects varies from culture to culture and preastronomy had a significant impact on humankind, particularly on cultural diversities.

  5. Crust and upper-mantle seismic anisotropy variations from the coast to inland in central and Southern Mexico

    Science.gov (United States)

    Castellanos, Jorge; Pérez-Campos, Xyoli; Valenzuela, Raúl; Husker, Allen; Ferrari, Luca

    2017-07-01

    Subduction zones are among the most dynamic tectonic environments on Earth. Deformation mechanisms of various scales produce networks of oriented structures and faulting systems that result in a highly anisotropic medium for seismic wave propagation. In this study, we combine shear wave splitting inferred from receiver functions and the results from a previous SKS-wave study to quantify and constrain the vertically averaged shear wave splitting at different depths along the 100-station MesoAmerican Subduction Experiment array. This produces a transect that runs perpendicular to the trench across the flat slab portion of the subduction zone below central and southern Mexico. Strong anisotropy in the continental crust is found below the Trans-Mexican Volcanic Belt (TMVB) and above the source region of slow-slip events. We interpret this as the result of fluid/melt ascent. The upper oceanic crust and the overlying low-velocity zone exhibit highly complex anisotropy, while the oceanic lower crust is relatively homogeneous. Regions of strong oceanic crust anisotropy correlate with previously found low Vp/Vs regions, indicating that the relatively high Vs is an anisotropic effect. Upper-mantle anisotropy in the southern part of the array is in trench-perpendicular direction, consistent with the alignment of type-A olivine and with entrained subslab flow. The fast polarization direction of mantle anisotropy changes to N-S in the north, likely reflecting mantle wedge corner flow perpendicular to the TMVB.

  6. Collective Modes in the Superfluid Inner Crust of Neutron Stars

    CERN Document Server

    Urban, Michael

    2015-01-01

    The neutron-star inner crust is assumed to be superfluid at relevant temperatures. The contribution of neutron quasiparticles to thermodynamic and transport properties of the crust is therefore strongly suppressed by the pairing gap. Nevertheless, the neutron gas still has low-energy excitations, namely long-wavelength collective modes. We summarize different approaches to describe the collective modes in the crystalline phases of the inner crust and present an improved model for the description of the collective modes in the pasta phases within superfluid hydrodynamics.

  7. Researchers Reveal Ecological Roles of Biological Soil Crusts in Desert

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    @@ Biological soil crust is a complex organic integrity of cyanobacteria, green algae, lichens and mosses, fungi, and other bacteria. This is a common and widespread phenomenon in desert areas all over the world. Biologically,this kind of soil crust differs a lot from physical ones in terms of physical and chemical properties, and become important biological factors in vegetation succession. Despite its unassuming appearance, the crust plays a significant role in the desert ecosystem, involving the process of soil formation, stability and fertility,the prevention of soil erosion by water or wind, the increased possibility of vascular plants colonization, and the stabilization of sand dunes.

  8. Hawaiian submarine manganese-iron oxide crusts - A dating tool?

    Science.gov (United States)

    Moore, J.G.; Clague, D.A.

    2004-01-01

    Black manganese-iron oxide crusts form on most exposed rock on the ocean floor. Such crusts are well developed on the steep lava slopes of the Hawaiian Ridge and have been sampled during dredging and submersible dives. The crusts also occur on fragments detached from bedrock by mass wasting, on submerged coral reefs, and on poorly lithified sedimentary rocks. The thickness of the crusts was measured on samples collected since 1965 on the Hawaiian Ridge from 140 dive or dredge localities. Fifty-nine (42%) of the sites were collected in 2001 by remotely operated vehicles (ROVs). The thinner crusts on many samples apparently result from post-depositional breakage, landsliding, and intermittent burial of outcrops by sediment. The maximum crust thickness was selected from each dredge or dive site to best represent crusts on the original rock surface at that site. The measurements show an irregular progressive thickening of the crusts toward the northwest-i.e., progressive thickening toward the older volcanic features with increasing distance from the Hawaiian hotspot. Comparison of the maximum crust thickness with radiometric ages of related subaerial features supports previous studies that indicate a crust-growth rate of about 2.5 mm/m.y. The thickness information not only allows a comparison of the relative exposure ages of two or more features offshore from different volcanoes, but also provides specific age estimates of volcanic and landslide deposits. The data indicate that some of the landslide blocks within the south Kona landslide are the oldest exposed rock on Mauna Loa, Kilauea, or Loihi volcanoes. Crusts on the floors of submarine canyons off Kohala and East Molokai volcanoes indicate that these canyons are no longer serving as channelways for downslope, sediment-laden currents. Mahukona volcano was approximately synchronous with Hilo Ridge, both being younger than Hana Ridge. The Nuuanu landslide is considerably older than the Wailau landslide. The Waianae

  9. Snowball Earth

    OpenAIRE

    2016-01-01

    In the ongoing quest to better understand where life may exist elsewhere in the Universe, important lessons may be gained from our own planet. In particular, much can be learned from planetary glaciation events that Earth suffered ∼600 million years ago, so-called `Snowball Earth' episodes. I begin with an overview of how the climate works. This helps to explain how the ice-albedo feedback effect can destabilise a planet's climate. The process relies on lower temperatures causing more ice to ...

  10. Digital Earth - A sustainable Earth

    Science.gov (United States)

    Mahavir

    2014-02-01

    All life, particularly human, cannot be sustainable, unless complimented with shelter, poverty reduction, provision of basic infrastructure and services, equal opportunities and social justice. Yet, in the context of cities, it is believed that they can accommodate more and more people, endlessly, regardless to their carrying capacity and increasing ecological footprint. The 'inclusion', for bringing more and more people in the purview of development is often limited to social and economic inclusion rather than spatial and ecological inclusion. Economic investment decisions are also not always supported with spatial planning decisions. Most planning for a sustainable Earth, be at a level of rural settlement, city, region, national or Global, fail on the capacity and capability fronts. In India, for example, out of some 8,000 towns and cities, Master Plans exist for only about 1,800. A chapter on sustainability or environment is neither statutorily compulsory nor a norm for these Master Plans. Geospatial technologies including Remote Sensing, GIS, Indian National Spatial Data Infrastructure (NSDI), Indian National Urban Information Systems (NUIS), Indian Environmental Information System (ENVIS), and Indian National GIS (NGIS), etc. have potential to map, analyse, visualize and take sustainable developmental decisions based on participatory social, economic and social inclusion. Sustainable Earth, at all scales, is a logical and natural outcome of a digitally mapped, conceived and planned Earth. Digital Earth, in fact, itself offers a platform to dovetail the ecological, social and economic considerations in transforming it into a sustainable Earth.

  11. Continental crust formation: Numerical modelling of chemical evolution and geological implications

    Science.gov (United States)

    Walzer, U.; Hendel, R.

    2017-05-01

    Oceanic plateaus develop by decompression melting of mantle plumes and have contributed to the growth of the continental crust throughout Earth's evolution. Occasional large-scale partial melting events of parts of the asthenosphere during the Archean produced large domains of precursor crustal material. The fractionation of arc-related crust during the Proterozoic and Phanerozoic contributed to the growth of continental crust. However, it remains unclear whether the continents or their precursors formed during episodic events or whether the gaps in zircon age records are a function of varying preservation potential. This study demonstrates that the formation of the continental crust was intrinsically tied to the thermoconvective evolution of the Earth's mantle. Our numerical solutions for the full set of physical balance equations of convection in a spherical shell mantle, combined with simplified equations of chemical continent-mantle differentiation, demonstrate that the actual rate of continental growth is not uniform through time. The kinetic energy of solid-state mantle creep (Ekin) slowly decreases with superposed episodic but not periodic maxima. In addition, laterally averaged surface heat flow (qob) behaves similarly but shows peaks that lag by 15-30 Ma compared with the Ekin peaks. Peak values of continental growth are delayed by 75-100 Ma relative to the qob maxima. The calculated present-day qob and total continental mass values agree well with observed values. Each episode of continental growth is separated from the next by an interval of quiescence that is not the result of variations in mantle creep velocity but instead reflects the fact that the peridotite solidus is not only a function of pressure but also of local water abundance. A period of differentiation results in a reduction in regional water concentrations, thereby increasing the temperature of the peridotite solidus and the regional viscosity of the mantle. By plausibly varying the

  12. Nuclear superfluidity and cooling time of neutron-star crust

    Energy Technology Data Exchange (ETDEWEB)

    Monrozeau, C.; Margueron, J. [Institut de Physique Nucleaire, Universite Paris Sud, F-91406 Orsay CEDEX (France); Sandulescu, N. [Institut de Physique Nucleaire, Universite Paris Sud, F-91406 Orsay CEDEX (France); Institute of Physics and Nuclear Engineering, RO-76900 Bucharest (Romania)

    2007-03-15

    We analyse the effect of neutron superfluidity on the cooling time of inner crust matter in neutron stars, in the case of a rapid cooling of the core. The specific heat of the inner crust, which determines the thermal response of the crust, is calculated in the framework of HFB approach at finite temperature. The calculations are performed with two paring forces chosen to simulate the pairing properties of uniform neutron matter corresponding respectively to Gogny-BCS approximation and to many-body techniques including polarisation effects. Using a simple model for the heat transport across the inner crust, it is shown that the two pairing forces give very different values for the cooling time. (authors)

  13. Formation and development of salt crusts on soil surfaces

    KAUST Repository

    Dai, Sheng

    2015-12-14

    The salt concentration gradually increases at the soil free surface when the evaporation rate exceeds the diffusive counter transport. Eventually, salt precipitates and crystals form a porous sodium chloride crust with a porosity of 0.43 ± 0.14. After detaching from soils, the salt crust still experiences water condensation and salt deliquescence at the bottom, brine transport across the crust driven by the humidity gradient, and continued air-side precipitation. This transport mechanism allows salt crust migration away from the soil surface at a rate of 5 μm/h forming salt domes above soil surfaces. The surface characteristics of mineral substrates and the evaporation rate affect the morphology and the crystal size of precipitated salt. In particular, substrate hydrophobicity and low evaporation rate suppress salt spreading.

  14. A chemical and petrological model of the lunar crust

    Science.gov (United States)

    Spudis, Paul D.; Davis, Philip A.

    1987-01-01

    Information is given on the composition and structure of the lunar crust. A lunar model is illustrated, indicating that it has essentially two layers, anorthositic mixed rocks overlaying a generally noritic crystalline basement. Implications relative to lunar evolution are discussed.

  15. Strange Stars: Can Their Crust Reach the Neutron Drip Density?

    Institute of Scientific and Technical Information of China (English)

    Hai Fu; Yong-Feng Huang

    2003-01-01

    The electrostatic potential of electrons near the surface of static strange stars at zero temperature is studied within the frame of the MIT bag model. We find that for QCD parameters within rather wide ranges, if the nuclear crust on the strange star is at a density leading to neutron drip, then the electrostatic potential will be insufficient to establish an outwardly directed electric field, which is crucial for the survival of such a crust. If a minimum gap width of 200 fm is brought in as a more stringent constraint, then our calculations will completely rule out the possibility of such crusts. Therefore, our results argue against the existence of neutron-drip crusts in nature.

  16. Breaking strain of neutron star crust and gravitational waves.

    Science.gov (United States)

    Horowitz, C J; Kadau, Kai

    2009-05-15

    Mountains on rapidly rotating neutron stars efficiently radiate gravitational waves. The maximum possible size of these mountains depends on the breaking strain of the neutron star crust. With multimillion ion molecular dynamics simulations of Coulomb solids representing the crust, we show that the breaking strain of pure single crystals is very large and that impurities, defects, and grain boundaries only modestly reduce the breaking strain to around 0.1. Because of the collective behavior of the ions during failure found in our simulations, the neutron star crust is likely very strong and can support mountains large enough so that their gravitational wave radiation could limit the spin periods of some stars and might be detectable in large-scale interferometers. Furthermore, our microscopic modeling of neutron star crust material can help analyze mechanisms relevant in magnetar giant flares and microflares.

  17. [Crusted scabies induced by topical corticosteroids: A case report].

    Science.gov (United States)

    Bilan, P; Colin-Gorski, A-M; Chapelon, E; Sigal, M-L; Mahé, E

    2015-12-01

    The frequency of scabies is increasing in France. Crusted (or Norwegian) scabies is a very contagious form of scabies because of the huge number of mites in the skin. It is observed in patients suffering from immunodepression, motor or sensory deficiency, or mental retardation. The clinical presentation, except for the classic manifestation of scabies, is characterized by crusted lesions. Treatment is not easy and requires hospitalization. Topical corticosteroids are frequently used for children's dermatological diseases. Their long-term and inappropriate application in an infested scabies child can induce crusted scabies. We report on a case of an 8-year-old boy who developed crusted scabies induced by topical corticosteroid application. We discuss the therapeutic aspects of this severe form of scabies.

  18. Intensive Ammonia and Methane Oxidation in Organic Liquid Manure Crusts

    DEFF Research Database (Denmark)

    Nielsen, Daniel Aagren; Nielsen, Lars Peter; Schramm, Andreas

    of the crusts. PCR targeting the unique methane and ammonia monooxygenases were applied together with FISH to detect the presence of the two bacterial groups. Potential activity was assessed by short term slurry incubations of crust samples while monitoring NO2- production or CH4 consumption. Crusts were......Intensive agricultural practice leads to periodic accumulation of enormous amounts of liquid manure (slurry) from animal husbandry, and large quantities of environmentally hazardous ammonia and methane are emitted from the manure storages. Floating surface crusts have been suggested to harbour...... methane oxidizing bacteria (MOB) and are known to accumulate nitrite and nitrate, indicating the presence of ammonia oxidizers (AOB). We have surveyed six manure tanks with organic covers to investigate the prevalence of MOB and AOB and to link the potential activity with physical and chemical aspects...

  19. Russian Federation Snow Depth and Ice Crust Surveys

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Russian Federation Snow Depth and Ice Crust Surveys, dataset DSI-9808, contains routine snow surveys that run throughout the cold season every 10 days (every five...

  20. Impacts of the Nuclear Symmetry Energy on Neutron Star Crusts

    CERN Document Server

    Bao, Shishao

    2015-01-01

    Using the relativistic mean-field theory, we adopt two different methods, namely, the coexisting phase method and the self-consistent Thomas-Fermi approximation, to study the impacts of the nuclear symmetry energy on properties of neutron star crusts within a wide range of densities. It is found that the nuclear symmetry energy and its density slope play an important role in determining the pasta phases and the crust-core transition.

  1. Chemical composition of upper crust in eastern China

    Institute of Scientific and Technical Information of China (English)

    鄢明才; 迟清华; 顾铁新; 王春书

    1997-01-01

    In an area of 3. 3 ×106 km" within eastern China, 28 253 rock samples were collected systematically and combined into 2 718 composite samples which were analyzed by 15 reliable methods using national preliminary certified reference materials (CRMs) for data quality monitoring. The average chemical compositions of the exposed crust, the sedimentary cover and the exposed basement as well as the upper crust for 76 chemical elements in eastern China are given.

  2. Early Earth tectonics: A high-resolution 3D numerical modelling approach

    Science.gov (United States)

    Fischer, R.; Gerya, T.

    2014-12-01

    Early Earth had a higher amount of remaining radiogenic elements as well as a higher amount of leftover primordial heat. Both contributed to the increased temperature in the Earth's interior and it is mainly this increased mantle potential temperature ΔTp that controls the dynamics of the crust and upper mantle and the style of Early Earth tectonics. For a minor increase in temperature ΔTp buckling, delamination and Rayleigh-Taylor style dripping of the plate is observed in addition. For higher temperatures ΔTp > 250 K no subduction can be observed anymore and tectonics is dominated by delamination and Rayleigh-Taylor instabilities. We conduct 3D petrological-thermomechanical numerical modelling experiments of the crust and upper mantle under Early Earth conditions and a plume tectonics model setup. For varying crustal structures and an increased mantle potential temperature ΔTp, a thermal anomaly in the bottom temperature boundary introduces a plume. The model is able to self-sufficiently form depleted mantle lithosphere after repeated melt removal. New crust can be produced in the form of volcanics or plutonics. To simulate differentiation the newly formed crust can have a range in composition from basaltic over dacitic to granitic depending on its source rock. Models show large amounts of subcrustal decompression melting and consequently large amounts of new formed crust which in turn influences the dynamics. Mantle and crust are convecting separately. Dome-shaped plutons of mafic or felsic composition can be observed in the crust. Between these domes elongated belts of upper crust, volcanics and sediments are formed. These structures look similar to, for example, the Kaapvaal craton in South Africa where the elongated shape of the Barberton Greenstone Belt is surrounded by multiple plutons.

  3. Diversity of burial rates in convergent settings decreased as Earth aged.

    Science.gov (United States)

    Nicoli, Gautier; Moyen, Jean-François; Stevens, Gary

    2016-05-24

    The evolution and the growth of the continental crust is inextricably linked to the evolution of Earth's geodynamic processes. The detrital zircon record within the continental crust, as well as the isotopic composition of this crust, indicates that the amount of juvenile felsic material decreased with time and that in geologically recent times, the generation of new crust is balanced by recycling of the crust back into the mantle within subduction zones. However it cannot always have been so; yet the nature of the crust and the processes of crustal reworking in the Precambrian Earth are not well constrained. Here we use both detrital zircon ages and metamorphic pressure-temperature-time (P-T-t) information from metasedimentary units deposited in proposed convergent settings from Archaean, Proterozoic and Phanerozoic terrains to characterize the evolution of minimum estimates of burial rate (km.Ma(-1)) as a function of the age of the rocks. The demonstrated decrease in burial rate correlates positively with a progressive decrease in the production of juvenile felsic crust in the Archaean and Proterozoic. Burial rates are also more diverse in the Archaean than in modern times. We interpret these features to reflect a progressive decrease in the diversity of tectonic processes from Archaean to present, coupled with the emergence of the uniquely Phanerozoic modern-style collision.

  4. Estimates of geodynamic state and structure of the local crust on the base of microseismic noise analysis

    Science.gov (United States)

    Loktev, D.; Spivak, A.

    2013-05-01

    A method for obtaining estimates of geodynamic state of the local crust and rock masses on the base of microseismic noise analysis is discussed. Microseismic noise is considered as a superposition of background microvibrations and a discrete component in the form of weak microseismic pulses generated by relaxational processes in the medium [1]. Currently active tectonic faults can be identified as zones with clustered sources of microseismic pulses and more intense amplitude variations of background microvibrations in tidal waves and baric variations in the atmosphere [2,3]. The presence of underground nonheterogeneities (i.e. contrasts in mechanic properties) and their scales are obtained from analysis of spectral characteristics of microseismic noise [4]. In the epicentral zone of an underground inhomogeneity we evidence characteristic quasi-chromatic pulses, stronger spectral density of local noise at high frequencies (more than 10 Hz) as well as maximum of spatial distribution of horizontal to vertical component spectral noise ratio (Nakamura parameter). The size of structural elements (blocks) of the Earth's crust is estimated by peak frequencies of momochromatic components of the spectrum on the base of the elaborated analytical model [1]. Parameters of weak pulses generated by relaxation (such as max velocity of oscillations, dominating (observed) period, etc.) yield estimates of differential movements of structural blocks in the medium as well as max stresses in the latter [5,6]. Examples are given to illustrate application of the proposed method to locating and mapping fault zones and underground nonheterogeneities in the Earth's crust, as well as to estimating scales of active structural blocks and their mobility potential when assessing places for nuclear atomic plants and underground nuclear waste storages. The method has also been successfully used for ranging hillsides of South Alps in terms of their liability to landslides. [1]. A.A. Spivak, S

  5. Geochemistry of the high-Mg andesites at Zhangwu, western Liaoning: Implication for delamination of newly formed lower crust

    Institute of Scientific and Technical Information of China (English)

    HUANG; Hua; GAO; Shan; HU; ZhaoChu; LIU; XiaoMing; YUAN; HongLing

    2007-01-01

    Ten volcanic samples at Zhangwu, western Liaoning Province, North China were selected for a systematic geochemical, mineralogical and geochronological study, which provides an opportunity to explore the interaction between the continental crust and mantle beneath the north margin of the North China craton. Except one basalt sample (SiO2= 50.23%), the other nine samples are andesitic with SiO2 contents ranging from 53% to 59%. They have relatively high MgO (3.4%-6.1%, Mg#=50-64) and Ni and Cr contents (Ni 27×10-6-197×10-6, Cr 51×10-6-478×10-6). Other geochemical characteristics of Zhangwu high-Mg andesites (HMAs) include strong fractionation of light rare earth elements (LREE) from heavy rare earth elements (HREE), and Sr from Y, with La/Yb greater than 15, and high Sr/Y (34-115). Zircons of andesite YX270 yield three age groups with no Precambrian age, which precludes origin of the Zhangwu HMAs from the partial melting of the Precambrian crust. The oldest age group peaking at 253 Ma is interpreted to represent the collision of the Siberia block and the North China block, resulting in formation of the Central Asian orogenic belt by closure of the Mongol-Okhotsk Ocean. The intermediate age group corresponds to the basalt underplating which caused the widespread coeval granitoids in the North China craton with a peak 206Pb/238U age of 172 Ma. The youngest age group gives a 206Pb/238U age of 126±2 Ma, which is interpreted as the eruption age of the Zhangwu HMAs. The high 87Sr/86Sri(126 Ma)>0.706 and low -Nd(t)= -6.36--13.99 of the Zhangwu HMAs are distinct from slab melts. The common presence of reversely zoned clinopyroxene phenocrysts in the Zhangwu HMAs argues against the origin of the Zhangwu HMAs either from melting of the water saturated mantle or melting of the lower crust. In light of the evidence mentioned above, the envisaged scenario for the formation of the Zhangwu HMAs is related to the basaltic underplating at the base of the crust, which led to

  6. Effects of crust and cracks on simulated catchment discharge and soil loss

    NARCIS (Netherlands)

    Stolte, J.; Ritsema, C.J.; Roo, de A.P.J.

    1997-01-01

    Sealing, crusting and cracking of crusts of the soil surface has been observed in many parts of the world in areas with sandy, silty and loamy soils. Sealing and crust formation occurs under the influence of rain storm and drying weather. With prolonged drying, surface crusts might crack, leading to

  7. Effect of water activity on fracture and acoustic characteristics of a crust model

    NARCIS (Netherlands)

    Primo-Martín, C.; Sözer, N.; Hamer, R.J.; Vliet, T. van

    2009-01-01

    A crust model is described that is suited to study crispness of bread crusts as a function of steady state water activity. The study of crispness of this type of products as a function of water activity is complicated since the way a bread crust fractures does not depend on the crust only but also o

  8. Effect of water activity on fracture and acoustic characteristics of a crust model

    NARCIS (Netherlands)

    Primo-Martín, C.; Sözer, N.; Hamer, R.J.; Vliet, T. van

    2009-01-01

    A crust model is described that is suited to study crispness of bread crusts as a function of steady state water activity. The study of crispness of this type of products as a function of water activity is complicated since the way a bread crust fractures does not depend on the crust only but also

  9. Origin and age of the earliest Martian crust from meteorite NWA 7533.

    Science.gov (United States)

    Humayun, M; Nemchin, A; Zanda, B; Hewins, R H; Grange, M; Kennedy, A; Lorand, J-P; Göpel, C; Fieni, C; Pont, S; Deldicque, D

    2013-11-28

    The ancient cratered terrain of the southern highlands of Mars is thought to hold clues to the planet's early differentiation, but until now no meteoritic regolith breccias have been recovered from Mars. Here we show that the meteorite Northwest Africa (NWA) 7533 (paired with meteorite NWA 7034) is a polymict breccia consisting of a fine-grained interclast matrix containing clasts of igneous-textured rocks and fine-grained clast-laden impact melt rocks. High abundances of meteoritic siderophiles (for example nickel and iridium) found throughout the rock reach a level in the fine-grained portions equivalent to 5 per cent CI chondritic input, which is comparable to the highest levels found in lunar breccias. Furthermore, analyses of three leucocratic monzonite clasts show a correlation between nickel, iridium and magnesium consistent with differentiation from impact melts. Compositionally, all the fine-grained material is alkalic basalt, chemically identical (except for sulphur, chlorine and zinc) to soils from Gusev crater. Thus, we propose that NWA 7533 is a Martian regolith breccia. It contains zircons for which we measured an age of 4,428 ± 25 million years, which were later disturbed 1,712 ± 85 million years ago. This evidence for early crustal differentiation implies that the Martian crust, and its volatile inventory, formed in about the first 100 million years of Martian history, coeval with earliest crust formation on the Moon and the Earth. In addition, incompatible element abundances in clast-laden impact melt rocks and interclast matrix provide a geochemical estimate of the average thickness of the Martian crust (50 kilometres) comparable to that estimated geophysically.

  10. Pre-earthquake signals – Part II: Flow of battery currents in the crust

    Directory of Open Access Journals (Sweden)

    F. T. Freund

    2007-09-01

    Full Text Available When rocks are subjected to stress, dormant electronic charge carriers are activated. They turn the stressed rock volume into a battery, from where currents can flow out. The charge carriers are electrons and defect electrons, also known as positive holes or pholes for short. The boundary between stressed and unstressed rock acts as a potential barrier that lets pholes pass but blocks electrons. One can distinguish two situations in the Earth's crust: (i only pholes spread out of a stressed rock volume into the surrounding unstressed rocks. This is expected to lead to a positive surface charge over a wide area around the future epicenter, to perturbations in the ionosphere, to stimulated infrared emission from the ground, to ionization of the near-ground air, to cloud formation and to other phenomena that have been reported to precede major earthquakes. (ii both pholes and electrons flow out of the stressed rock volume along different paths, sideward into the relatively cool upper layers of the crust and downward into the hot lower crust. This situation, which is likely to be realized late in the earthquake preparation process, is necessary for the battery circuit to close and for transient electric currents to flow. If burst-like, these currents should lead to the emission of low frequency electromagnetic radiation. Understanding how electronic charge carriers are stress-activated in rocks, how they spread or flow probably holds the key to deciphering a wide range of pre-earthquake signals. It opens the door to a global earthquake early warning system, provided resources are pooled through a concerted and constructive community effort, including seismologists, with international participation.

  11. Early evolution of the continental crust, the oxygenated atmosphere and oceans, and the heterogeneous mantle

    Science.gov (United States)

    Ohmoto, H.

    2011-12-01

    The current paradigm for the evolution of early Earth is that, only since ~2.5 Ga ago, the Earth began to: (a) form a large granitic continental crust; (b) form an oxygenated atmosphere; (c) operate oxidative weathering of rocks on land; (d) form Fe-poor, but S-, U- and Mo-rich, oceans; (e) operate large-scale transfers of elements between oceans and oceanic crust at MORs; (f) subduct the altered oceanic crust; (g) create the mantle heterogeneity, especially in the concentrations and isotopic compositions of Fe(III), Fe(II), U, Pb, alkali elements, C, S, REEs, and many other elements; (h) create chemical and isotopic variations among OIB-, OPB-, and MORB magmas, and between I- and S-type granitoid magmas; and (i) create variations in the chemical and isotopic compositions of volcanic gas. Submarine hydrothermal fluids have typically developed from seawater-rock interactions during deep (>2 km) circulation of seawater through underlying hot volcanic rocks. When the heated hydrothermal fluids ascend toward the seafloor, they mix with local bottom seawater to precipitate a variety of minerals on and beneath the seafloor. Thus, the mineralogy and geochemistry of submarine hydrothermal deposits and associated volcanic rocks can be used to decipher the chemistry of the contemporaneous seawater, which in turn indicate the chemistry of the atmosphere and the compositions and size of the continental crust. The results of mineralogical and geochemical investigations by our and other research groups on submarine hydrothermal deposits (VMS and BIF) and hydrothermally-altered submarine volcanic rocks in Australia, South Africa, and Canada, ~3.5-2.5 Ga in ages, suggest that the above processes (a)-(i) had began by ~3.5 Ga ago. Supportive evidence includes, but not restricted to, the similarities between Archean submarine rocks and modern ones in: (1) the abundance of ferric oxides; (2) the Fe(III)/Fe(I) ratios; (3) the abundance of barite; (4) the increased Li contents; (5) the

  12. The nature of orogenic crust in the central Andes

    Science.gov (United States)

    Beck, Susan L.; Zandt, George

    2002-10-01

    The central Andes (16°-22°S) are part of an active continental margin mountain belt and the result of shortening of the weak western edge of South America between the strong lithospheres of the subducting Nazca plate and the underthrusting Brazilian shield. We have combined receiver function and surface wave dispersion results from the BANJO-SEDA project with other geophysical studies to characterize the nature of the continental crust and mantle lithospheric structure. The major results are as follows: (1) The crust supporting the high elevations is thick and has a felsic to intermediate bulk composition. (2) The relatively strong Brazilian lithosphere is underthrusting as far west (65.5°W) as the high elevations of the western part of the Eastern Cordillera (EC) but does not underthrust the entire Altiplano. (3) The subcrustal lithosphere is delaminating piecemeal under the Altiplano-EC boundary but is not completely removed beneath the central Altiplano. The Altiplano crust is characterized by a brittle upper crust decoupled from a very weak lower crust that is dominated by ductile deformation, leading to lower crustal flow and flat topography. In contrast, in the high-relief, inland-sloping regions of the EC and sub-Andean zone, the upper crust is still strongly coupled across the basal thrust of the fold-thrust belt to the underthrusting Brazilian Shield lithosphere. Subcrustal shortening between the Altiplano and Brazilian lithosphere appears to be accommodated by delamination near the Altiplano-EC boundary. Our study suggests that orogenic reworking may be an important part of the "felsification" of continental crust.

  13. Lithospheric cooling as a basin forming mechanism within accretionary crust.

    Science.gov (United States)

    Holt, P. J.; Allen, M.; van Hunen, J.; Björnseth, H. M.

    2009-04-01

    Widely accepted basin forming mechanisms are limited to flexure of the lithosphere, lithospheric stretching, lithospheric cooling following rifting and, possibly, dynamic topography. In this work forward models have been used to investigate lithospheric growth due to cooling beneath accretionary crust, as a new basin forming mechanism. Accretionary crust is formed from collision of island arcs, accretionary complexes and fragments of reworked older crust at subduction zones, and therefore has thin lithosphere due to melting and increased convection. This is modeled using a 1D infinite half space cooling model similar to lithospheric cooling models for the oceans. The crustal composition and structure used in the models has been varied around average values of accretionary crust to represent the heterogeneity of accretionary crust. The initial mantle lithosphere thickness used in the model was 20 km. The model then allows the lithosphere to thicken as it cools and calculates the subsidence isostatically. The model produces sediment loaded basins of 2-7 km for the various crustal structures over 250 Myrs. Water-loaded tectonic subsidence curves from the forward models were compared to tectonic subsidence curves produced from backstripping wells from the Kufrah and Ghadames basins, located on the accretionary crust of North Africa. A good match between the subsidence curves for the forward model and backstripping is produced when the best estimates for the crustal structure, composition and the present day thickness of the lithosphere for North Africa are used as inputs for the forward model. This shows that lithospheric cooling provides a good method for producing large basins with prolonged subsidence in accretionary crust without the need for initial extension.

  14. Contrasting effects of microbiotic crusts on runoff in desert surfaces

    Science.gov (United States)

    Kidron, Giora J.; Monger, H. Curtis; Vonshak, Ahuva; Conrod, William

    2012-02-01

    Microbiotic crusts (MCs) play an important role in surface hydrology by altering runoff yield. In order to study the crust's role on water redistribution, rainfall and runoff were measured during 1998-2000 at three sites within the northern Chihuahuan Desert, New Mexico, USA: the Sevilleta National Wildlife Refuge (SEV), the White Sands National Monument (WS), and the Jornada Experimental Range (JER). Whereas quartz and gypsum sand characterize the SEV and WS sites, respectively, both of which have high infiltration rates, silty alluvial deposits characterize the JER site. Runoff was measured in four pairs of 1.8-6.4 m 2 plots having MCs, one of which was scalped in each pair. No runoff was generated at WS, whether on the crusted or the scalped plots. Runoff was however generated at SEV and JER, being higher on the crusted plots at SEV and lower on the JER plots. The results were explained by the combined effect of (a) parent material and (b) the crust properties, such as species composition, microrelief (surface roughness) and exopolysaccharide (EPS) content (reflected in the ratio of carbohydrates to chlorophyll). Whereas the effective rainfall, the fines and the EPS content were found to explain runoff initiation, the effective rainfall and the crust microrelief were found to explain the amount of runoff at SEV and JER where runoff generation took place. The findings attest to the fundamental role of the parent material and the crust's species composition and properties on runoff and hence to the complex interactions and the variable effects that MCs have on dryland hydrology.

  15. Living in Salt: The formation and development of extremophile habitats and biosignatures within salt crusts of the hyperarid Atacama Desert

    Science.gov (United States)

    Finstad, K. M.; Amundson, R.

    2013-12-01

    It has become increasing apparent that salt-rich deposits are present on the Martian surface and that aqueous alteration has occurred sometime during the planet's past. In the hyperarid Atacama Desert in Chile, an important Earth-based analogue to Mars, microbial life has been discovered inhabiting halite (NaCl) surface crust deposits. Is it possible that similar salt deposits on Mars once harbored microbial life? If so, what adaptations were likely necessary for survival in such an environment and what biosignatures are expected to remain? Although this fascinating ecosystem in the Atacama Desert has been recognized, neither the physical processes of halite crust formation, nor the microorganisms residing within the salts have been extensively studied. To better understand the formation and geochemical dynamics of this unique habitat, we chose two sites within the Atacama Desert which exhibit both active crust formation as well as the presence of microbial communities: one site is on a dry Holocene age lake bed, while the other is of Pleistocene age. At each site soil profiles were excavated and total geochemical analyses were performed. Field observations clearly showed that the soils exhibited transitions of carbonate to sulfate to chloride salt deposition with decreasing depth, and that the thickness and mass of halite in the surficial crust was related to the age of the soil. Isotope profiles of carbon, nitrogen, and sulfur from these soils were also analyzed. Once exposed to the atmosphere, the halite crusts reside in a dynamic state of dissolution and erosion by wind and fog, and reformation due to fog and dew. In the crust nodules, microbial communities were sampled, in centimeter increments from the surface, for carbon, nitrogen, and sulfur isotope/concentration profiles. Our analyses help elucidate the physical and geochemical processes linked to the formation and evolution of these dynamic salt crusts, and the imprint of microbial life within them. A

  16. Andean Adakites: Products of Slab Melting, Magma Evolution in Thickened Crust and Crustal Recycling by Forearc Subduction Erosion

    Science.gov (United States)

    Kay, S. M.; Kay, R. W.; Goss, A.

    2009-12-01

    Adakites in the southern and central Andes show a residual garnet signature that can variously be related to local slab melting associated with subduction of hot oceanic crust at the Chile Triple Junction, widespread interaction of mafic magmas in regions of thickened crust, and episodic melting of crust removed by forearc subduction erosion, particularly at times of frontal arc migration. Among the most convincing slab-melt adakites on Earth are the late Miocene Cerro Pampa type dacitic adakites east of the Chile Triple Junction whose low 87Sr/86Sr ratios (0.7028-0.7033) and high Sr contents (up to 2300 ppm) are difficult to explain by any other mechanism. Elsewhere the appearance of transient extreme adakitic signatures at times of frontal arc migration can be explained by forearc subduction erosion and the evolution of magmas at deep crustal levels in a contractional regime provided the crust is thick. Transient steep adakitic-like REE patterns at times of arc migration fit with forearc crust being transported down the subduction channel, entering the tip of the asthenospheric wedge and being incorporated into the arc mantle source. Evidence for a genetic link for transient adakite signatures, arc migration and forearc subduction erosion comes from changing isotopic ratios in mafic magmas erupted before and after arc migration on the edges of the Chilean flat-slab near 27°S and 34°S (Kay et al 2005) where the arc front has migrated up to 50 km eastward in the last 8 Ma. The chemistry of these mafic magmas cannot be explained by enriched mantle or incorporation of subducted sediments or in situ crust. Sharp increases in 87Sr/86Sr ratios and transient steep REE patterns in Andean arc rocks erupted in the final stages of Cretaceous to early Tertiary magmatic cycles at 21°S to 26°S (see Haschke et al. 2002) can also be attributed to forearc subduction erosion. Forearc subduction erosion provides a better explanation for the formation of Aleutian and Central

  17. Real-time capability of GEONET system and its application to crust monitoring

    Science.gov (United States)

    Yamagiwa, Atsushi; Hatanaka, Yuki; Yutsudo, Toru; Miyahara, Basara

    2006-03-01

    The GPS Earth Observation Network system (GEONET) has been playing an important role in monitoring the crustal deformation of Japan. Since its start of operation, the requirements for accuracy and timeliness have become higher and higher. On the other hand, recent broadband communication infrastructure has had capability to realize real-time crust monitoring and to aid the development of a location-based service. In early 2003, the Geographical Survey Institute (GSI) upgraded the GEONET system to meet new requirements. The number of stations became 1200 in total by March, 2003. The antennas were unified to the choke ring antennas of Dorne Margolin T-type and the receivers were replaced with new ones that are capable of real-time observation and data transfer. The new system uses IP-connection through IP-VPN (Internet Protocol Virtual Private Network) for data transfer, which is provided by communication companies. The Data Processing System, which manages the observation data and analyses in GEONET, has 7 units. GEONET carries out three kinds of routine analyses and an analysis of RTK-type for emergencies. The new system has shown its capability for real-time crust monitoring, for example, the precise and rapid detection of coseismic (and post-seismic) motion caused by 2003 Tokachi-Oki earthquake.

  18. 200-kg large explosive detonation facing 50-km thick crust beneath west Qinling, northeastern Tibetan plateau

    Institute of Scientific and Technical Information of China (English)

    Qiusheng Li; Rui Gao; Haiyan Wang; Jisheng Zhang; Zhanwu Lu; Pengwu Li; Ye Guan; Rizheng He

    2009-01-01

    It is difficult to acquire deep seismic reflection profiles on land using the standard oil-industry acquisition pa-rameters. This is especially true over much of Tibetan plateau not only because of severe topography and rapid variation of both velocity and thickness of near-surface layer, but also strong attenuation of seismic wave through the thickest crust of the Earth. Large explosive sources had been successfully detonated in US, but its application in Tibetan plateau rarely has an example of good quality. Presented herein is the data of a 200-kg single shot we recorded in west Qinling, northeastern Ti-betan plateau. The shot gather data with phenomenal signal-to-noise ratios illustrate the energy of the ProP phase. Although the observations are only limited to the northeastern Tibetan plateau and thus cannot comprise an exhaustive study, they nev-ertheless suggest that large explosions may be a useful exploration tool in Tibetan Plateau where standard seismic sources and profiling methods fail to produce adequate data of low crust.

  19. Assessing life's effects on the interior dynamics of planet Earth using non-equilibrium thermodynamics

    Directory of Open Access Journals (Sweden)

    J. G. Dyke

    2010-09-01

    Full Text Available Vernadsky described life as the geologic force, while Lovelock noted the role of life in driving the Earth's atmospheric composition to a unique state of thermodynamic disequilibrium. Here, we use these notions in conjunction with thermodynamics to quantify biotic activity as a driving force for geologic processes. Specifically, we explore the hypothesis that biologically-mediated processes operating on the surface of the Earth, such as the biotic enhancement of weathering of continental crust, affect interior processes such as mantle convection and have therefore shaped the evolution of the whole Earth system beyond its surface and atmosphere. We set up three simple models of mantle convection, oceanic crust recycling and continental crust recycling. We describe these models in terms of non-equilibrium thermodynamics in which the generation and dissipation of gradients is central to driving their dynamics and that such dynamics can be affected by their boundary conditions. We use these models to quantify the maximum power that is involved in these processes. The assumption that these processes, given a set of boundary conditions, operate at maximum levels of generation and dissipation of free energy lead to reasonable predictions of core temperature, seafloor spreading rates, and continental crust thickness. With a set of sensitivity simulations we then show how these models interact through the boundary conditions at the mantle-crust and oceanic-continental crust interfaces. These simulations hence support our hypothesis that the depletion of continental crust at the land surface can affect rates of oceanic crust recycling and mantle convection deep within the Earth's interior. We situate this hypothesis within a broader assessment of surface-interior interactions by setting up a work budget of the Earth's interior to compare the maximum power estimates that drive interior processes to the power that is associated with biotic activity

  20. Two-Dimensional Porosity of Crusted Silty Soils: Indicators of Soil Quality in Semiarid Rangelands?

    OpenAIRE

    2011-01-01

    Little is known about the morphological characteristics of pores in soil crusts. The objective was to characterize the 2D-porosity (amount, shape, size and area of pores) of soil crusts to ascertain their potential as indicators of soil quality for natural crusted soils. 2D-porosity was described in thin sections and measured by image analysis of polished resin-impregnated soil blocks. Physical soil crust and incipient biological soil crusts appear to be the lowest-quality soil...

  1. Carbon from Crust to Core: A history of deep carbon science

    Science.gov (United States)

    Mitton, Simon

    2017-04-01

    As an academic historian of science, I am writing a history of the discovery of the interior workings of our dynamic planet. I am preparing a book, titled Carbon from Crust to Core: A Chronicle of Deep Carbon Science, in which I will present the first history of deep carbon science. I will identify and document key discoveries, the impact of new knowledge, and the roles of deep carbon scientists and their institutions from the 1400s to the present. This innovative book will set down the engaging human story of many remarkable scientists from whom we have learned about Earth's interior, and particularly the fascinating story of carbon in Earth. I will describe a great journey of discovery that has led to a better understanding of the physical, chemical, and biological behaviour of carbon in the vast majority of Earth's interior. My poster has a list of remarkable Deep Carbon Explorers, from Georgius Agricola (1494-1555) to Claude ZoBell (1904-1989). Come along to my poster and add to my compilation: choose pioneers from history, or nominate your colleagues, or even add a selfie! As a biographer, I am keen to add researchers who may have been overlooked in the standard histories of geology and geophysics. And I am always on the lookout for standout stories and personal recollections. I am equipped to do oral history interviews. What's your story? Cambridge University Press will publish the book in 2019.

  2. Linking biological soil crust diversity to ecological functions

    Science.gov (United States)

    Glaser, Karin; Borchhardt, Nadine; Schulz, Karoline; Mikhailyuk, Tatiana; Baumann, Karen; Leinweber, Peter; Ulf, Karsten

    2016-04-01

    Biological soil crusts (BSCs) are an association of different microorganisms and soil particles in the top millimeters of the soil. They are formed by algae, cyanobacteria, microfungi, bacteria, bryophytes and lichens in various compositions. Our aim was to determine and compare the biodiversity of all occurring organisms in biogeographically different habitats, ranging from polar (both Arctic and Antarctic), subpolar (Scandinavia), temperate (Germany) to dry regions (Chile). The combination of microscopy and molecular techniques (next-generation sequencing) revealed highly diverse crust communities, whose composition clustered by region and correlates with habitat characteristics such as water content. The BSC biodiversity was then linked to the ecological function of the crusts. The functional role of the BSCs in the biogeochemical cycles of carbon, nitrogen and phosphorous is evaluated using an array of state of the art soil chemistry methods including Py-FIMS (pyrolysis field ionization mass spectrometry) and XANES (x-ray absorbance near edge structure). Total P as well as P fractions were quantified in all BSCs, adjacent soil underneath and comparable nearby soil of BSC-free areas revealing a remarkable accumulation of total phosphorous and a distinct pattern of P fractions in the crust. Further, we observed an indication of a different P-speciation composition in the crust compared with BSC-free soil. The data allow answering the question whether BSCs act as sink or source for these compounds, and how biodiversity controls the biogeochemical function of BSCs.

  3. Measurement of129I in ferromanganese crust with AMS

    Institute of Scientific and Technical Information of China (English)

    JI Lihong; LIU Guangshan; CHEN Zhigang; HUANG Yipu; XING Na; JIANG Shan; HE Ming

    2015-01-01

    In the present study, the analytical method for129iodine (129I) in ferromanganese crusts is developed and 129iodine/127iodine (129I/127I) ratio in ferromanganese crusts is measured by the accelerator mass spectrometry (AMS). The developed method is applied to analyze129I/127I ratio in two ferromanganese crusts MP5D44 and CXD08-1 collected from the Mid-Pacific Ocean. The results show that129I/127I ratio in MP5D44 and CXD08-1 crusts varies from 7×10–14 to 1.27×10–12, with the lowest value falling on the detection limit level of AMS reported by previous literatures. For the depth distribution of129I/127I, it is found that both MP5D44 and CXD08-1 crusts have two growth generations, and the129I/127I profiles in two generations all displayed an approximate exponential decay. According to the129I/127I ratio, the generate age of bottom layer of MP5D44 and CXD08-1 was estimated to be 54.77 and 69.69 Ma, respectively.

  4. Microenvironments and microscale productivity of cyanobacterial desert crusts

    Science.gov (United States)

    Garcia-Pichel, F.; Belnap, Jayne

    1996-01-01

    We used microsensors to characterize physicochemical microenvironments and photosynthesis occurring immediately after water saturation in two desert soil crusts from southeastern Utah, which were formed by the cyanobacteria Microcoleus vaginatus Gomont, Nostoc spp., and Scytonema sp. The light fields within the crusts presented steep vertical gradients in magnitude and spectral composition. Near-surface light-trapping zones were formed due to the scattering nature of the sand particles, but strong light attenuation resulted in euphotic zones only ca. 1 mm deep, which were progressively enriched in longer wavelengths with depth. Rates of gross photosynthesis (3.4a??9.4 mmol O2A?ma??2A?ha??1) and dark respiration (0.81a??3.1 mmol Oa??2A?ma??2A?ha??1) occurring within 1 to several mm from the surface were high enough to drive the formation of marked oxygen microenvironments that ranged from oxygen supersaturation to anoxia. The photosynthetic activity also resulted in localized pH values in excess of 10, 2a??3 units above the soil pH. Differences in metabolic parameters and community structure between two types of crusts were consistent with a successional pattern, which could be partially explained on the basis of the microenvironments. We discuss the significance of high metabolic rates and the formation of microenvironments for the ecology of desert crusts, as well as the advantages and limitations of microsensor-based methods for crust investigation.

  5. Trends and opportunities for the radioactive waste disposal in the Earth crust

    Directory of Open Access Journals (Sweden)

    Zsold Szentirmai

    2007-01-01

    Full Text Available This paper deals with the problems of designing and realization of permanent disposal sites for nuclear wastes. It points out the possibilities of the development of new and modern technologies of drilling, mining, or driving of underground works.The paper is primarily aimed at the cuttingof the period of storage building, the reaching of larger depths, the reduction of territory of storage area as well as the increase of its safety.

  6. Abiogenic formation of alkanes in the Earth's crust as a minor source for global hydrocarbon reservoirs

    Science.gov (United States)

    Sherwood Lollar, B.; Westgate, T. D.; Ward, J. A.; Slater, G. F.; Lacrampe-Couloume, G.

    2002-04-01

    Natural hydrocarbons are largely formed by the thermal decomposition of organic matter (thermogenesis) or by microbial processes (bacteriogenesis). But the discovery of methane at an East Pacific Rise hydrothermal vent and in other crustal fluids supports the occurrence of an abiogenic source of hydrocarbons. These abiogenic hydrocarbons are generally formed by the reduction of carbon dioxide, a process which is thought to occur during magma cooling and-more commonly-in hydrothermal systems during water-rock interactions, for example involving Fischer-Tropsch reactions and the serpentinization of ultramafic rocks. Suggestions that abiogenic hydrocarbons make a significant contribution to economic hydrocarbon reservoirs have been difficult to resolve, in part owing to uncertainty in the carbon isotopic signatures for abiogenic versus thermogenic hydrocarbons. Here, using carbon and hydrogen isotope analyses of abiogenic methane and higher hydrocarbons in crystalline rocks of the Canadian shield, we show a clear distinction between abiogenic and thermogenic hydrocarbons. The progressive isotopic trends for the series of C1-C4 alkanes indicate that hydrocarbon formation occurs by way of polymerization of methane precursors. Given that these trends are not observed in the isotopic signatures of economic gas reservoirs, we can now rule out the presence of a globally significant abiogenic source of hydrocarbons.

  7. Yttrium and rare earth element contents in seamount cobalt crusts in the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Balaram, V.; Banakar, V.K.; Subramanyam, K.S.V.; Roy, P.; Satyanarayan, M.; RamMohan, M.; Sawant, S.S.

    . and Holzhtter, H. G., Metannogen: annotation of biological reaction networks. Bioinformatics, 2011, 27, 2763–2764. 19. Félix, L. and Valiente, G., Validation of metabolic pathway data- bases based on chemical substructure search. Biomol. Eng., 2007, 24, 327.... Andrews, D. H. and Kokes, R. J., Fundamental Chemistry, Wiley, New York, 1963. 23. Das, S. C., A mathematical method of balancing a chemical equa- tion. Int. J. Math. Educ. Sci. Technol., 1986, 17, 191–200. 24. Sen, S. K., Agarwal, H. and Sen, S...

  8. LITHO1.0: An Updated Crust and Lithosphere Model of the Earth

    Science.gov (United States)

    2010-09-01

    A. M., S. Bloch, and M. Landisman (1969). A technique for the analysis of transient seismic signals. Bull. Seism . Soc. Am. 59: 427^44. Durek, J. and...G. Ekstrom (1996). A radial model of anelasticity consistent with long-period surface-wave attenuation, Bull. Seism . Soc. Am. 86: 144 158. Goes, S...Peculiarities of surface wave propagation across central Eurasia, Bull. Seism . Soc. Am. 82: 2464 2493. Levshin, A. L., M. H. Ritzwoller, and J. Resovsky

  9. Global redox cycle of biospheric carbon: Interaction of photosynthesis and earth crust processes.

    Science.gov (United States)

    Ivlev, Alexander A

    2015-11-01

    A model of the natural global redox cycle of biospheric carbon is introduced. According to this model, carbon transfer between biosphere and geospheres is accompanied by a conversion of the oxidative forms, presented by CO2, bicarbonate and carbonate ions, into the reduced forms, produced in photosynthesis. The mechanism of carbon transfer is associated with two phases of movement of lithospheric plates. In the short-term orogenic phase, CO2 from the subduction (plates' collisions) zones fills the "atmosphere-hydrosphere" system, resulting in climate warming. In the long-term quiet (geosynclynal) phase, weathering and photosynthesis become dominant depleting the oxidative forms of carbon. The above asymmetric periodicity exerts an impact on climate, biodiversity, distribution of organic matter in sedimentary deposits, etc. Along with photosynthesis expansion, the redox carbon cycle undergoes its development until it reaches the ecological compensation point, at which CO2 is depleted to the level critical to support the growth and reproduction of plants. This occurred in the Permo-Carboniferous time and in the Neogene. Shorter-term perturbations of the global carbon cycle in the form of glacial-interglacial oscillations appear near the ecological compensation point.

  10. Eastern Indian 3800-million-year-old crust and early mantle differentiation

    Science.gov (United States)

    Basu, A.R.; Ray, S.L.; Saha, A.K.; Sarkar, S.N.

    1981-01-01

    Samarium-neodymium data for nine granitic and tonalite gneisses occurring as remnants within the Singhbhum granite batholith in eastern India define an isochron of age 3775 ?? 89 ?? 106 years with an initial 143Nd/144Nd ratio of 0.50798 ?? 0.00007. This age contrasts with the rubidium-strontium age of 3200 ?? 106 years for the same suite of rocks. On the basis of the new samarium-neodynium data, field data, and petrologic data, a scheme of evolution is proposed for the Archean crust in eastern India. The isotopic data provide evidence that parts of the earth's mantle were already differentiated with respect to the chondritic samarium-neodymium ratio 3800 ?? 106 years ago.

  11. Volcanic-plutonic parity and the differentiation of the continental crust.

    Science.gov (United States)

    Keller, C Brenhin; Schoene, Blair; Barboni, Melanie; Samperton, Kyle M; Husson, Jon M

    2015-07-16

    The continental crust is central to the biological and geological history of Earth. However, crustal heterogeneity has prevented a thorough geochemical comparison of its primary igneous building blocks-volcanic and plutonic rocks-and the processes by which they differentiate to felsic compositions. Our analysis of a comprehensive global data set of volcanic and plutonic whole-rock geochemistry shows that differentiation trends from primitive basaltic to felsic compositions for volcanic versus plutonic samples are generally indistinguishable in subduction-zone settings, but are divergent in continental rifts. Offsets in major- and trace-element differentiation patterns in rift settings suggest higher water content in plutonic magmas and reduced eruptibility of hydrous silicate magmas relative to dry rift volcanics. In both tectonic settings, our results indicate that fractional crystallization, rather than crustal melting, is predominantly responsible for the production of intermediate and felsic magmas, emphasizing the role of mafic cumulates as a residue of crustal differentiation.

  12. Anisotropic crystal structure of magnetized neutron star crust

    Science.gov (United States)

    Baiko, D. A.; Kozhberov, A. A.

    2017-09-01

    Although crystallized neutron star crust is responsible for many fascinating observational phenomena, its actual microscopic structure in tremendous gravitational and magnetic fields is not understood. Here we show that in a non-uniform magnetic field, three-dimensional ionic Coulomb crystals comprising the crust may stretch or shrink while their electrostatic pressure becomes anisotropic. The pressure depends non-linearly on the magnitude of the stretch, so that a continuous magnetic field evolution may result in an abrupt crystal elongation or contraction. This may provide a trigger for magnetar activity. A phonon mode instability is revealed, which sets the limits of magnetic field variation beyond which the crystal is destroyed. These limits sometimes correspond to surprisingly large deformations. It is not known what happens to crust matter subject to a pressure anisotropy exceeding these limits. We hypothesize that the ion system then possesses a long-range order only in one or two dimensions, that is becomes a liquid crystal.

  13. Vortex pinning and dynamics in the neutron star crust

    CERN Document Server

    Wlazłowski, Gabriel; Magierski, Piotr; Bulgac, Aurel; Forbes, Michael McNeil

    2016-01-01

    The nature of the interaction between superfluid vortices and the neutron star crust, conjectured by Anderson and Itoh in 1975 to be at the heart vortex creep and the cause of glitches, has been a longstanding question in astrophysics. Previous estimates of the vortex-"nucleus" interaction have been error-prone, being either phenomenological or derived from tiny differences of large energies of stationary configurations. Using a qualitatively new approach, we follow the dynamics as superfluid vortices move in response to the presence of "nuclei" (nuclear defects in the crust). The resulting motion is perpendicular to the force, similar to the motion of a spinning top when pushed. We show that nuclei repel vortices in the neutron star crust, leading thus to interstitial vortex pinning, and characterize the force as a function of the vortex-nucleus separation.

  14. Magnetic field evolution in magnetar crusts through three dimensional simulations

    CERN Document Server

    Gourgouliatos, Konstantinos N; Hollerbach, Rainer

    2016-01-01

    Current models of magnetars require extremely strong magnetic fields to explain their observed quiescent and bursting emission, implying that the field strength within the star's outer crust is orders of magnitude larger than the dipole component inferred from spin-down measurements. This presents a serious challenge to theories of magnetic field generation in a proto-neutron star. Here, we present detailed modelling of the evolution of the magnetic field in the crust of a neutron star through 3-D simulations. We find that, in the plausible scenario of equipartition of energy between global-scale poloidal and toroidal magnetic components, magnetic instabilities transfer energy to non-axisymmetric, kilometre-sized magnetic features, in which the local field strength can greatly exceed that of the global-scale field. These intense small-scale magnetic features can induce high energy bursts through local crust yielding, and the localised enhancement of Ohmic heating can power the star's persistent emission. Thus...

  15. Neutrino-pair bremsstrahlung in a neutron star crust

    CERN Document Server

    Ofengeim, D D; Yakovlev, D G

    2014-01-01

    Based on the formalism by Kaminker et al. (Astron. Astrophys. 343 (1999) 1009) we derive an analytic approximation for neutrino-pair bremsstrahlung emissivity due to scattering of electrons by atomic nuclei in the neutron star crust of any realistic composition. The emissivity is expressed through generalized Coulomb logarithm which we fit by introducing an effective potential of electron-nucleus scattering. In addition, we study the conditions at which the neutrino bremsstrahlung in the crust is affected by strong magnetic fields. The results can be applied for modelling of many phenomena in neutron stars, such as thermal relaxation in young isolated neutron stars and in accreting neutron stars with overheated crust in soft X-ray transients.

  16. Sulfur and metal fertilization of the lower continental crust

    Science.gov (United States)

    Locmelis, Marek; Fiorentini, Marco L.; Rushmer, Tracy; Arevalo, Ricardo; Adam, John; Denyszyn, Steven W.

    2016-02-01

    Mantle-derived melts and metasomatic fluids are considered to be important in the transport and distribution of trace elements in the subcontinental lithospheric mantle. However, the mechanisms that facilitate sulfur and metal transfer from the upper mantle into the lower continental crust are poorly constrained. This study addresses this knowledge gap by examining a series of sulfide- and hydrous mineral-rich alkaline mafic-ultramafic pipes that intruded the lower continental crust of the Ivrea-Verbano Zone in the Italian Western Alps. The pipes are relatively small (tectonic architecture of any given terrain, metals and volatiles stored in the lower continental crust may become available as sources for subsequent ore-forming processes, thus enhancing the prospectivity of continental block margins for a wide range of mineral systems.

  17. Light dark matter scattering in outer neutron star crusts

    CERN Document Server

    Cermeño, Marina; Silk, Joseph

    2016-01-01

    We calculate for the first time the phonon excitation rate in the outer crust of a neutron star due to scattering from light dark matter (LDM) particles gravitationally boosted into the star. We consider dark matter particles in the sub-GeV mass range scattering off a periodic array of nuclei through an effective scalar-vector interaction with nucleons. We find that LDM effects cause a modification of the net number of phonons in the lattice as compared to the standard thermal result. In addition, we estimate the contribution of LDM to the ion-ion thermal conductivity in the outer crust and find that it can be significantly enhanced at large densities. Our results imply that for magnetized neutron stars the LDM-enhanced global conductivity in the outer crust will tend to reduce the anisotropic heat conduction between perpendicular and parallel directions to the magnetic field.

  18. Rapid rotational crust-core relaxation in magnetars

    CERN Document Server

    Sedrakian, Armen

    2016-01-01

    If a magnetar interior $B$-field exceeds $10^{15}$ G it will unpair the proton superconductor in the star's core by inducing diamagnetic currents which destroy the Cooper pair coherence. Then, the $P$-wave neutron superfluid in these non-superconducting regions will couple to the stellar plasma by scattering of protons off the quasiparticles confined in the cores of neutron vortices via the strong (nuclear) force. The dynamical time-scales associated with this interaction span from several minutes at the crust-core interface to a few seconds in the deep core. We show that (a) the rapid crust-core coupling is incompatible with oscillation models of magnetars which decouple completely the core superfluid from the crust and (b) magnetar precession is damped by the coupling of normal fluids to the superfluid core and, if observed, needs to be forced or continuously excited by seismic activity.

  19. Light dark matter scattering in outer neutron star crusts

    Science.gov (United States)

    Cermeño, Marina; Pérez-García, M. Ángeles; Silk, Joseph

    2016-09-01

    We calculate for the first time the phonon excitation rate in the outer crust of a neutron star due to scattering from light dark matter (LDM) particles gravitationally boosted into the star. We consider dark matter particles in the sub-GeV mass range scattering off a periodic array of nuclei through an effective scalar-vector interaction with nucleons. We find that LDM effects cause a modification of the net number of phonons in the lattice as compared to the standard thermal result. In addition, we estimate the contribution of LDM to the ion-ion thermal conductivity in the outer crust and find that it can be significantly enhanced at large densities. Our results imply that for magnetized neutron stars the LDM-enhanced global conductivity in the outer crust will tend to reduce the anisotropic heat conduction between perpendicular and parallel directions to the magnetic field.

  20. Vortex Pinning and Dynamics in the Neutron Star Crust.

    Science.gov (United States)

    Wlazłowski, Gabriel; Sekizawa, Kazuyuki; Magierski, Piotr; Bulgac, Aurel; Forbes, Michael McNeil

    2016-12-02

    The nature of the interaction between superfluid vortices and the neutron star crust, conjectured by Anderson and Itoh in 1975 to be at the heart vortex creep and the cause of glitches, has been a long-standing question in astrophysics. Using a qualitatively new approach, we follow the dynamics as superfluid vortices move in response to the presence of "nuclei" (nuclear defects in the crust). The resulting motion is perpendicular to the force, similar to the motion of a spinning top when pushed. We show that nuclei repel vortices in the neutron star crust, and characterize the force per unit length of the vortex line as a function of the vortex element to the nucleus separation.

  1. Implication of Flow in the Lower Crust on Strain Localization

    Science.gov (United States)

    Le Pourhiet, Laetitia

    2016-04-01

    A major difference between oceanic and continental crust is the capacity of the lower crust to flow. This has been the moto of the research group centered around Genia Burov over the last 15 years and I will try to summarize the results of number of numerical models run in different geodynamic setting to tackle the question of the rheology of the lithosphere and crust at the scale of plate tectonics. I will insist on how apriori very complex numerical models have helped the community to build our intuition on geodynamics processes and change the way of thinking the interactions between mantle process and crustal processes which are the core of plate tectonic and beyond. I will finally discuss what have we learn about the rheology of the lithosphere so far and how we intend to pursues evgeni's fundamental contribution to the field.

  2. Global Carbon Cycle of the Precambrian Earth

    DEFF Research Database (Denmark)

    Wiewióra, Justyna

    The carbon isotopic composition of distinct Archaean geological records provides information about the global carbon cycle and emergence of life on early Earth. We utilized carbon isotopic records of Greenlandic carbonatites, diamonds, graphites, marbles, metacarbonates and ultramafic rocks...... to investigate carbon fluxes between Precambrian Earth’s mantle and crust and to trace the evolution of life in the Eoarchaean oceans. The world’s desire for diamonds gives us a unique opportunity to obtain insight into the nature of metasomatic fluids affecting the subcratonic lithospheric mantle (SCLM) beneath...

  3. Mission to Very Early Earth

    Energy Technology Data Exchange (ETDEWEB)

    Hutcheon, I D; Weber, P K; Fallon, S J; Smith, J B; Aleon, J; Ryerson, F J; Harrison, T M; Cavosie, A J; Valley, J W

    2007-03-13

    The Hadean Earth is often viewed as an inhospitable and, perhaps, unlikely setting for the rise of primordial life. However, carbonaceous materials supplied by accreting meteorites and sources of chemical energy similar to those fueling life around modern deep-sea volcanic vents would have been present in abundance. More questionable are two other essential ingredients for life - liquid water and clement temperatures. Did the Hadean Earth possess a hydrosphere and temperate climate compatible with the initiation of biologic activity? If so, the popular model of an excessively hot planetary surface characterized by a basaltic crust, devoid of continental material is invalid. Similarly, establishment of an Hadean hydrosphere prior to the cessation of heavy asteroid bombardment may mean that primitive life could have evolved and then been extinguished, only to rise again. The most effective means of determining the environmental conditions on this young planet is through geochemical analysis of samples retrieved from the Early Earth. While rocks older than 4 billion years (4 Ga) have not been found, individual zircon grains, the detritus of rocks long since eroded away, have been identified with ages as old as 4.4 Ga - only {approx}160 million years younger than the Earth itself. If we can use the geochemical information contained in these unique samples to infer the nature of their source rocks and the processes that formed them, we can place constraints on the conditions prevailing at the Earth's surface shortly after formation. This project utilizes a combined analytical and experimental approach to gather the necessary geochemical data to determine the parameters required to relate the zircons to their parent materials. Mission to Early Earth involves dating, isotopic and chemical analyses of mineral and melt inclusions within zircons and of the zircons themselves. The major experimental activity at LLNL focused on the partitioning of trace elements between

  4. Reduced and unstratified crust in CV chondrite parent body.

    Science.gov (United States)

    Ganino, Clément; Libourel, Guy

    2017-08-15

    Early Solar System planetesimal thermal models predict the heating of the chondritic protolith and the preservation of a chondritic crust on differentiated parent bodies. Petrological and geochemical analyses of chondrites have suggested that secondary alteration phases formed at low temperatures (hydrothermal fluid. Putative 'onion shell' structures are not anymore a requirement for the CV parent body crust.Meteorites may unlock the history of the early solar system. Here, the authors find, through Ca-Fe-rich secondary phases, that the distinction between reduced and oxidized CV chondrites is invalid; therefore, CV3 chondrites are asteroid fragments that percolated heterogeneously via porous flow of hydrothermal fluid.

  5. Earth survey applications division: Research leading to the effective use of space technology in applications relating to the Earth's surface and interior

    Science.gov (United States)

    Carpenter, L. (Editor)

    1980-01-01

    Accomplishments and future plans are described for the following areas: (1) geology - geobotanical indicators and geopotential data; (2) modeling magnetic fields; (3) modeling the structure, composition, and evolution of the Earth's crust; (4) global and regional motions of the Earth's crust and earthquake occurrence; (5) modeling geopotential from satellite tracking data; (6) modeling the Earth's gravity field; (7) global Earth dynamics; (8) sea surface topography, ocean dynamics; and geophysical interpretation; (9) land cover and land use; (10) physical and remote sensing attributes important in detecting, measuring, and monitoring agricultural crops; (11) prelaunch studies using LANDSAT D; (12) the multispectral linear array; (13) the aircraft linear array pushbroom radiometer; and (14) the spaceborne laser ranging system.

  6. Experimental study on the P wave velocity in rocks from lower crust and crust-mantle transitional zone beneath the Hannuoba

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Cenozoic basalt-borne mafic granulite-facies plagioclase pyroxenite and eclogite-facies garnet pyroxenite xenoliths from the Hannuoba, as well as nearby Archean terrain granulites, are selected for the experimental study on the P wave velocity at high temperature and high pressure in order to reveal the present-day compositional features for the lower crust and crust-mantle transitional zone. Results show that mafic xenoliths have high Vp (7.0~8.0 km/s), in contrast, the Archean terrain granulites have low Vp (<7.0 km/s). High Vp mafic xenoliths can represent the present-day compositional features for the lower crust and crust-mantle transitional zone beneath the Hannuoba. This provides new evidence for the crust vertical growth and the formation of the crust-mantle transitional zone resulting from the magma underplating. Low Vp Archean granulite still remains the characteristics of the early lower crust.

  7. Nature and Composition of Planetary Surficial Deposits and Their Relationship to Planetary Crusts

    Science.gov (United States)

    McLennan, S. M.

    2010-12-01

    Planetary soils constitute micron to meter sized debris blankets covering all or parts of the surfaces of many planetary bodies. Recent results from the Martian surface, by the MER rovers and Phoenix lander, the Huygens probe at Titan and perhaps even the NEAR mission to asteroid 433 Eros suggest a continuum between classic planetary soils, such as those on the Moon, and conventional sediments, such as those on Earth. Controls on this variation are governed by complex interactions related to (1) impact and volcanic history, (2) presence and nature of atmospheres (and thus climate), (3) occurrence, composition and physical state of near-surface volatiles (e.g., water, methane), and (4) presence and nature of crustal tectonics, crustal evolution, and so forth. The Moon represents one extreme where surficial deposits result almost exclusively from impact processes. Absence of water and air restrict further reworking or transport on a significant scale after initial deposition. Disruption and mixing of lunar soils takes place but is related to impact gardening operating on relatively local scales and largely in a vertical sense; alteration is restricted to space weathering. The effect is that lunar soils are compositionally variable and match the composition of the crust in the vicinity of where they form. Thus lunar soils in the highlands are fundamentally different in composition than those on maria. Earth provides the other extreme where the highly dynamic geochemical and geophysical nature of the surface precludes preservation of classic planetary soils, although analogs may exist in ejecta blankets and eolian loess. Instead, a complex suite of sedimentary deposits form in response to chemical and physical weathering, erosion, transport and deposition by a variety of mechanisms involving water, wind, ice and biology. Although there is substantial sedimentary lithological differentiation (e.g., shales, sands, carbonates, evaporites), greatly influenced by the

  8. Nature of the crust under Afar: new igneous, not thinned continental

    Science.gov (United States)

    Mohr, Paul

    1989-10-01

    Thinned continental crust is considered absent from beneath Afar, except for isolated remnants such as comprise the Danakil Block. The Ethiopian Plateau sialic crust thins abruptly across the plateau-Afar margin to abut new igneous crust under Afar, generated during the early development of the Red Sea basin. Analyses of stretching and sea-floor spreading amounts elsewhere in the Red Sea and Gulf of Aden basins are employed to support this concept. The dual layering of the Afar crust, and the similarity of P-wave velocities in these layers to velocities in sialic crust, lead to the proposal that new continental crust can be generated at magmatic rift zones.

  9. The Rock Record Has It About Right—No Significant Continental Crust Formation Prior to 3.8 Ga

    Science.gov (United States)

    Vervoort, J. D.; Kemp, A. I.; Fisher, C.; Bauer, A.; Bowring, S. A.

    2015-12-01

    Although limited in its exposed extent and by its quality of preservation, the geologic record through the first two billion years of Earth's history provides surprisingly tight constraints on the growth and evolution of continental crust. The magmatic zircon record for this period is dominated by Neoarchean U-Pb ages, with greatly diminishing abundance of older rocks and no known zircon bearing rocks much older than 4.0 Ga. A similar pattern exists for the ages of detrital zircons but with important addition of zircons as old as 4.4 Ga, mostly from the Jack Hills metaconglomerate. It has been suggested that this represents an artefact of preservation rather than the actual production rate of older crust, with the implication that large volumes of older crust have been destroyed by various recycling processes. This undoubtedly has happened to some extent, but there is considerable uncertainty as to how much has been destroyed and the nature of the early-formed crust. Here is where the long-lived radiogenic isotopic record, particularly Lu-Hf, can provide important information on the sources of the zircons by integrating age and tracer isotopic information in not only the same sample or zircon but even in the same domain of zircon. Using the most robust data from zircon and whole rock samples, excluding those with unconstrained ages and mixed-domain analyses, the most radiogenic Hf isotope compositions are characterized by ~ chondritic Hf isotopic compositions from 4.4 to ~ 3.8 Ga and a nearly linear evolution trend from epsilon Hf of 0 at 3.8 Ga to ~ epsilon Hf of +16 at present. There remains no evidence from the Hf isotope record for widespread mantle depletion prior to 3.8 Ga. Excluding the Jack Hills zircons, there is a conspicuous lack of pre 3.9 Ga zircons in even the oldest sediments1. This indicates that crust prior to 3.8 Ga was likely small in volume and/or effectively recycled back into the mantle on short time scales and did not result in significant

  10. 世界海洋结核结壳稀土成因初探%Concentration of REY in world polymetallic nodules and cobalt-rich crusts

    Institute of Scientific and Technical Information of China (English)

    吴西顺; 黄文斌; 任颖芝; 王淑玲

    2016-01-01

    大洋海底蕴藏着丰富的稀土矿产资源,包括深海富稀土软泥和多金属锰结核和富钴结壳.本文则关注了多金属锰结核和富钴结壳中的稀土元素的富集机制.作者首先统计了全世界范围内各重要海域的结核与结壳的稀土元素和钇(REY)的含量,发现重稀土和钇(H EY)在结核结壳中的比重普遍大于15%,而结核与结壳的稀土含量则普遍高于深海洋泥,其中结壳的稀土含量普遍高于结核.针对这类重要的稀土矿藏,作者以库克群岛为例,初步研究了稀土富集机制.分析认为,稀土元素与铁和磷酸盐的含量具有强相关性,且铁锰结核或结壳中的稀土很可能是主要通过胶状羟基氧化铁吸附而缓慢富集起来的.%There are abundant mineral rare earth resources on the ocean floor such as abyssal rare earth mud ,polymetallic nodules and cobalt-rich crusts .This paper focuses on the concentration mechanism of rare earth elements(REE) in polymetallic nodules and cobalt-rich crusts .The authors firstly sum up the content of REE and yttrium(∑REY) in polymetallic nodules and cobalt-rich crusts all over the world ,finding that the proportions of their heavy REE and yttrium(HEY) are completely higher than 15% .In addition ,∑REY in polymetallic nodules and cobalt-rich crusts is generally higher that in abyssal REE-rich muds ,and ∑REY in crusts is generally higher than that in nodules .Taking Cook Islands as an example ,we study the concentration mechanism of ∑REY in such significant rare earth resources .Analysis shows that there are strong correlations between ∑REY with Fe and P .Also ,it is most likely that ∑REY in polymetallic nodules and cobalt-rich crusts is slowly concentrated by means of the adsorption of iron oxyhydroxide colloid .

  11. Rainfall intensity effects on crusting and mode of seedling ...

    African Journals Online (AJOL)

    2014-09-03

    Sep 3, 2014 ... However, soils with extensive cracking are likely to have higher EMP and lower MED ... impact and rapid wetting (Liu et al., 2011). Moreover, higher ... formation of crusts at the soil–atmosphere interface adversely affects crop ...

  12. The off-crust origin of granite batholiths

    Institute of Scientific and Technical Information of China (English)

    Antonio Castro

    2014-01-01

    Granitod batholiths of I-type features (mostly granodiorites and tonalites), and particularly those forming the large plutonic associations of active continental margins and intracontinental collisional belts, represent the most outstanding magmatic episodes occurred in the continental crust. The origin of magmas, however, remains controversial. The application of principles from phase equilibria is crucial to understand the problem of granitoid magma generation. An adequate comparison between rock com-positions and experimental liquids has been addressed by using a projected compositional space in the plane F(Fe þ Mg)eAnorthiteeOrthoclase. Many calc-alkaline granitoid trends can be considered cotectic liquids. Assimilation of country rocks and other not-cotectic processes are identified in the projected diagram. The identification of cotectic patterns in batholith implies high temperatures of magma segregation and fractionation (or partial melting) from an intermediate (andesitic) source. The com-parison of batholiths with lower crust granulites, in terms of major-element geochemistry, yields that both represent liquids and solid residues respectively from a common andesitic system. This is compatible with magmas being formed by melting, and eventual reaction with the peridotite mantle, of subducted mélanges that are finally relaminated as magmas to the lower crust. Thus, the off-crust generation of granitoids batholiths constitutes a new paradigm in which important geological implica-tions can be satisfactorily explained. Geochemical features of Cordilleran-type batholiths are totally compatible with this new conception.

  13. Fracture behaviour of bread crust: Effect of bread cooling conditions

    NARCIS (Netherlands)

    Primo-Martín, C.; Beukelaer, H. de; Hamer, R.J.; Vliet, T. van

    2008-01-01

    The effect of air and vacuum cooling on the fracture behaviour and accompanying sound emission, moisture content and crispness of bread crust were investigated. Vacuum cooling resulted in rapid evaporative cooling of products that contained high moisture content. Fracture experiments showed a clear

  14. Crusted scabies in a chid with systemic lupus erythematosus

    Directory of Open Access Journals (Sweden)

    Nurimar C.F. Wanke

    1992-03-01

    Full Text Available A child with systemic lupus erythematosus who has been treated with prednisone for three years, developed crusted scabies. Scrapings from lesions revealed Sarcoptes scabiei adult mites mad eggs. The patient died with septicemia and renal failure soon after starting topical 20% sulfur. A marked improvement was observed in the cutaneous lesions.

  15. Fracture behaviour of bread crust: Effect of bread cooling conditions

    NARCIS (Netherlands)

    Primo Martin, C.; Beukelaer, de H.J.; Hamer, R.J.; Vliet, van T.

    2008-01-01

    The effect of air and vacuum cooling on the fracture behaviour and accompanying sound emission, moisture content and crispness of bread crust were investigated. Vacuum cooling resulted in rapid evaporative cooling of products that contained high moisture content. Fracture experiments showed a clear

  16. Water Sorption and Transport in Dry, Crispy Bread Crust

    NARCIS (Netherlands)

    Meinders, M.B.J.; Nieuwenhuijzen, N.H. van; Tromp, R.H.; Hamer, R.J.; Vliet, T. van

    2010-01-01

    Water - sorption and dynamic properties of bread crust have been studied in gravimetric sorption experiments. Water uptake and loss were measured while relative humidity (RH) was stepwise increased or decreased (isotherm experiment) or varied between two adjusted values (oscillatory experiment). Exp

  17. Water sorption and transport in dry crispy bread crust

    NARCIS (Netherlands)

    Meinders, M.B.J.; Nieuwenhuijzen, van N.H.; Tromp, R.H.; Hamer, R.J.; Vliet, van T.

    2010-01-01

    Water sorption and dynamical properties of bread crust have been studied using gravimetric sorption experiments. Water uptake and loss were followed while relative humidity (RH) was stepwise in- or decreased (isotherm experiment) or varied between two adjusted values (oscillatory experiment). Experi

  18. Magnetization of the oceanic crust: TRM or CRM?

    Science.gov (United States)

    Raymond, C. A.; Labrecque, J. L.

    1987-01-01

    A model was proposed in which chemical remanent magnetization (CRM) acquired within the first 20 Ma of crustal evolution may account for 80% of the bulk natural remanent magnetization (NRM) of older basalts. The CRM of the crust is acquired as the original thermoremanent magnetization (TRM) is lost through low temperature alteration. The CRM intensity and direction are controlled by the post-emplacement polarity history. This model explains several independent observations concerning the magnetization of the oceanic crust. The model accounts for amplitude and skewness discrepancies observed in both the intermediate wavelength satellite field and the short wavelength sea surface magnetic anomaly pattern. It also explains the decay of magnetization away from the spreading axis, and the enhanced magnetization of the Cretaceous Quiet Zones while predicting other systematic variations with age in the bulk magnetization of the oceanic crust. The model also explains discrepancies in the anomaly skewness parameter observed for anomalies of Cretaceous age. Further studies indicate varying rates of TRM decay in very young crust which depicts the advance of low temperature alteration through the magnetized layer.

  19. Pristine Igneous Rocks and the Genesis of Early Planetary Crusts

    Science.gov (United States)

    Warren, Paul H.; Lindstrom, David (Technical Monitor)

    2002-01-01

    Our studies are highly interdisciplinary, but are focused on the processes and products of early planetary and asteroidal differentiation, especially the genesis of the ancient lunar crust. The compositional diversity that we explore is the residue of process diversity, which has strong relevance for comparative planetology.

  20. The off-crust origin of granite batholiths

    Directory of Open Access Journals (Sweden)

    Antonio Castro

    2014-01-01

    Full Text Available Granitod batholiths of I-type features (mostly granodiorites and tonalites, and particularly those forming the large plutonic associations of active continental margins and intracontinental collisional belts, represent the most outstanding magmatic episodes occurred in the continental crust. The origin of magmas, however, remains controversial. The application of principles from phase equilibria is crucial to understand the problem of granitoid magma generation. An adequate comparison between rock compositions and experimental liquids has been addressed by using a projected compositional space in the plane F(Fe + Mg–Anorthite–Orthoclase. Many calc-alkaline granitoid trends can be considered cotectic liquids. Assimilation of country rocks and other not-cotectic processes are identified in the projected diagram. The identification of cotectic patterns in batholith implies high temperatures of magma segregation and fractionation (or partial melting from an intermediate (andesitic source. The comparison of batholiths with lower crust granulites, in terms of major-element geochemistry, yields that both represent liquids and solid residues respectively from a common andesitic system. This is compatible with magmas being formed by melting, and eventual reaction with the peridotite mantle, of subducted mélanges that are finally relaminated as magmas to the lower crust. Thus, the off-crust generation of granitoids batholiths constitutes a new paradigm in which important geological implications can be satisfactorily explained. Geochemical features of Cordilleran-type batholiths are totally compatible with this new conception.

  1. Fracture behaviour of bread crust: Effect of ingredient modification

    NARCIS (Netherlands)

    Primo-Martin, C.; Beukelaer, de H.J.; Hamer, R.J.; Vliet, van T.

    2008-01-01

    The influence of the formulation on the crispness of bread crust was studied. Crispness is a relevant sensory attribute that depends on several factors particularly the plasticizer content (water), the mechanical properties of the solid matrix and the morphological architecture of the bread. Enzymes

  2. Evolution of Fractal Parameters through Development Stage of Soil Crust

    Science.gov (United States)

    Ospina, Abelardo; Florentino, Adriana; Tarquis, Ana Maria

    2016-04-01

    Soil surface characteristics are subjected to changes driven by several interactions between water, air, biotic and abiotic components. One of the examples of such interactions is provided through biological soil crusts (BSC) in arid and semi-arid environments. BSC are communities composed of cyanobacteria, fungi, mosses, lichens, algae and liverworts covering the soil surface and play an important role in ecosystem functioning. The characteristics and formation of these BSC influence the soil hydrological balance, control the mass of eroded sediment, increase stability of soil surface, and influence plant productivity through the modification of nitrogen and carbon cycle. The site of this work is located at Quibor and Ojo de Agua (Lara state, Venezuela). The Quibor Depression in Venezuela is a major agricultural area being at semi-arid conditions and limited drainage favor the natural process of salinization. Additionally, the extension and intensification of agriculture has led to over-exploitation of groundwater in the past 30 years (Méndoza et al., 2013). The soil microbial crust develops initially on physical crusts which are mainly generated since wetting and drying, being a recurrent feature in the Quíbor arid zone. The microbiotic crust is organic, composed of macro organisms (bryophytes and lichens) and microorganisms (cyanobacteria, fungi algae, etc.); growing on the ground, forming a thickness no greater than 3 mm. For further details see Toledo and Florentino (2009). This study focus on characterize the development stage of the BSC based on image analysis. To this end, grayscale images of different types of biological soil crust at different stages where taken, each image corresponding to an area of 12.96 cm2 with a resolution of 1024x1024 pixels (Ospina et al., 2015). For each image lacunarity and fractal dimension through the differential box counting method were calculated. These were made with the software ImageJ/Fraclac (Karperien, 2013

  3. Earth Sciences Division annual report 1990

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1991-06-01

    This Annual Report presents summaries of selected representative research activities grouped according to the principal disciplines of the Earth Sciences Division: Reservoir Engineering and Hydrogeology, Geology and Geochemistry, and Geophysics and Geomechanics. Much of the Division`s research deals with the physical and chemical properties and processes in the earth`s crust, from the partially saturated, low-temperature near-surface environment to the high-temperature environments characteristic of regions where magmatic-hydrothermal processes are active. Strengths in laboratory and field instrumentation, numerical modeling, and in situ measurement allow study of the transport of mass and heat through geologic media -- studies that now include the appropriate chemical reactions and the hydraulic-mechanical complexities of fractured rock systems. Of particular note are three major Division efforts addressing problems in the discovery and recovery of petroleum, the application of isotope geochemistry to the study of geodynamic processes and earth history, and the development of borehole methods for high-resolution imaging of the subsurface using seismic and electromagnetic waves. In 1989 a major DOE-wide effort was launched in the areas of Environmental Restoration and Waste Management. Many of the methods previously developed for and applied to deeper regions of the earth will in the coming years be turned toward process definition and characterization of the very shallow subsurface, where man-induced contaminants now intrude and where remedial action is required.

  4. Diversity of burial rates in convergent settings decreased as Earth aged

    Science.gov (United States)

    Nicoli, Gautier; Moyen, Jean-François; Stevens, Gary

    2016-05-01

    The evolution and the growth of the continental crust is inextricably linked to the evolution of Earth’s geodynamic processes. The detrital zircon record within the continental crust, as well as the isotopic composition of this crust, indicates that the amount of juvenile felsic material decreased with time and that in geologically recent times, the generation of new crust is balanced by recycling of the crust back into the mantle within subduction zones. However it cannot always have been so; yet the nature of the crust and the processes of crustal reworking in the Precambrian Earth are not well constrained. Here we use both detrital zircon ages and metamorphic pressure-temperature-time (P-T-t) information from metasedimentary units deposited in proposed convergent settings from Archaean, Proterozoic and Phanerozoic terrains to characterize the evolution of minimum estimates of burial rate (km.Ma-1) as a function of the age of the rocks. The demonstrated decrease in burial rate correlates positively with a progressive decrease in the production of juvenile felsic crust in the Archaean and Proterozoic. Burial rates are also more diverse in the Archaean than in modern times. We interpret these features to reflect a progressive decrease in the diversity of tectonic processes from Archaean to present, coupled with the emergence of the uniquely Phanerozoic modern-style collision.

  5. Shallow Moho with aseismic upper crust and deep Moho with seismic lower crust beneath the Japanese Islands obtained by seismic tomography using data from dense seismic network

    Science.gov (United States)

    Matsubara, Makoto; Obara, Kazushige

    2015-04-01

    . The Moho discontinuity deepens over 35 km in the collision zone like as Kanto Mountains, the volcanic underplating zone as the Tohoku backbone range, and non-tension region like as Chugoku Mountains. These regions associated with deep Moho are characterized by the crustal seismicity within the depth range from 20 to 30 km. The iso-depth contour of 35 km beneath the southwestern Japan is consistent with that derived from the receiver function method (Shiomi et al. 2006). There are nonvolcanic tremors and short-time slow slip events (SSE) beneath the southwestern Japan (eg. Obara, 2002). Matsubara et al. (2009) consider that the tremors and SSEs occur along the contact zone of Moho discontinuity beneath the Eurasian plate and the subducting Philippine Sea plate beneath southwestern Japan. Our Moho model is consistent with this since they exist along the southern edge of the Moho discontinuity of the continental Eurasian plate. Reference: Hirata, N., Sakai, S., Nakagawa, S., Ishikawa, M., Sato, H., Kasahara, K., Kimura, H. and Honda, R. (2012) A new tomographic image on the Philippine Sea Slab beneath Tokyo - Implication to seismic hazard in the Tokyo metropolitan region, EOS, Transactions, AGU, T11C-06. Kita, S., T. Okada, A. Hasegawa, J. Nakajima, and T. Matsuzawa (2010) Anomalous deepening of a seismic belt in the upper-plane of the double seismic zone in the Pacific slab beneath the Hokkaido corner: Possible evidence for thermal shielding caused by subducted forearc crust materials, Earth Planet. Science Lett., 290, 415-426. Matsubara, M. and K. Obara (2011) The 2011 Off the Pacific Coast of Tohoku earthquake related to a strong velocity gradient with the Pacific plate, Earth Planets Space, 63, 663-667. Matsubara, M., K. Obara, and K. Kasahara (2009) High-Vp/Vs zone accompanying non-volcanic tremors and slow-slip events beneath southwestern Japan, Tectonophysics, 472, 6-17, doi:10.1016/j.tecto.2008.06.013. Obara, K. (2002) Nonvolcanic deep tremor associated with

  6. Helium isotopes in ferromanganese crusts from the central Pacific Ocean

    Science.gov (United States)

    Basu, S.; Stuart, F.M.; Klemm, V.; Korschinek, G.; Knie, K.; Hein, J.R.

    2006-01-01

    Helium isotopes have been measured in samples of two ferromanganese crusts (VA13/2 and CD29-2) from the central Pacific Ocean. With the exception of the deepest part of crust CD29-2 the data can be explained by a mixture of implanted solar- and galactic cosmic ray-produced (GCR) He, in extraterrestrial grains, and radiogenic He in wind-borne continental dust grains. 4He concentrations are invariant and require retention of less than 12% of the in situ He produced since crust formation. Loss has occurred by recoil and diffusion. High 4He in CD29-2 samples older than 42 Ma are correlated with phosphatization and can be explained by retention of up to 12% of the in situ-produced 4He. 3He/4He of VA13/2 samples varies from 18.5 to 1852 Ra due almost entirely to variation in the extraterrestrial He contribution. The highest 3He/4He is comparable to the highest values measured in interplanetary dust particles (IDPs) and micrometeorites (MMs). Helium concentrations are orders of magnitude lower than in oceanic sediments reflecting the low trapping efficiency for in-falling terrestrial and extraterrestrial grains of Fe-Mn crusts. The extraterrestrial 3He concentration of the crusts rules out whole, undegassed 4–40 μm diameter IDPs as the host. Instead it requires that the extraterrestrial He inventory is carried by numerous particles with significantly lower He concentrations, and occasional high concentration GCR-He-bearing particles.

  7. Primitive layered gabbros from fast-spreading lower oceanic crust.

    Science.gov (United States)

    Gillis, Kathryn M; Snow, Jonathan E; Klaus, Adam; Abe, Natsue; Adrião, Alden B; Akizawa, Norikatsu; Ceuleneer, Georges; Cheadle, Michael J; Faak, Kathrin; Falloon, Trevor J; Friedman, Sarah A; Godard, Marguerite; Guerin, Gilles; Harigane, Yumiko; Horst, Andrew J; Hoshide, Takashi; Ildefonse, Benoit; Jean, Marlon M; John, Barbara E; Koepke, Juergen; Machi, Sumiaki; Maeda, Jinichiro; Marks, Naomi E; McCaig, Andrew M; Meyer, Romain; Morris, Antony; Nozaka, Toshio; Python, Marie; Saha, Abhishek; Wintsch, Robert P

    2014-01-09

    Three-quarters of the oceanic crust formed at fast-spreading ridges is composed of plutonic rocks whose mineral assemblages, textures and compositions record the history of melt transport and crystallization between the mantle and the sea floor. Despite the importance of these rocks, sampling them in situ is extremely challenging owing to the overlying dykes and lavas. This means that models for understanding the formation of the lower crust are based largely on geophysical studies and ancient analogues (ophiolites) that did not form at typical mid-ocean ridges. Here we describe cored intervals of primitive, modally layered gabbroic rocks from the lower plutonic crust formed at a fast-spreading ridge, sampled by the Integrated Ocean Drilling Program at the Hess Deep rift. Centimetre-scale, modally layered rocks, some of which have a strong layering-parallel foliation, confirm a long-held belief that such rocks are a key constituent of the lower oceanic crust formed at fast-spreading ridges. Geochemical analysis of these primitive lower plutonic rocks--in combination with previous geochemical data for shallow-level plutonic rocks, sheeted dykes and lavas--provides the most completely constrained estimate of the bulk composition of fast-spreading oceanic crust so far. Simple crystallization models using this bulk crustal composition as the parental melt accurately predict the bulk composition of both the lavas and the plutonic rocks. However, the recovered plutonic rocks show early crystallization of orthopyroxene, which is not predicted by current models of melt extraction from the mantle and mid-ocean-ridge basalt differentiation. The simplest explanation of this observation is that compositionally diverse melts are extracted from the mantle and partly crystallize before mixing to produce the more homogeneous magmas that erupt.

  8. [Diversity of nitrogen-fixing microorganisms in biological soil crusts of copper mine wastelands].

    Science.gov (United States)

    Zhan, Jing; Yang, Gui-De; Sun, Qing-Ye

    2014-06-01

    Biological soil crusts play an important role in increasing the accumulation of organic matter and nitrogen in re-vegetated mining wastelands. The diversity of nitrogen-fixing microorganisms in three types of biological soil crusts (algal crust, moss crust and algal-moss crust) from two wastelands of copper mine tailings were investigated by polymerase chain reaction-denaturing gradient gel electrophoresis, based on the nifH gene of diazotrophs, to investigate: The diversity of nifH gene in the crusts of mine wastelands, and whether and how the nifH gene diversity in the crusts could be affected by the development of plant communities. The algal crust on the barren area displayed the highest nifH gene diversity, followed by the algal-moss crusts within vascular plant communities, and the moss crust displayed the lowest nifH gene diversity. The diversity of diazotrophs in algal-moss crust within vascular plant communities decreased with the increase of height and cover of vascular plant communities. No significant relationship was found between wasteland properties (pH, water content, contents of organic matter, nitrogen and phosphorus and heavy metal concentration) and nifH gene diversity in the crusts. Sequencing and phylogenetic analysis indicated that most nitrogen-fixing taxa in the crusts of mine wastelands belonged to Cyanobacteria, especially nonheterocystous filamentous Cyanobacteria.

  9. [Effects of soil crusts on surface hydrology in the semiarid Loess hilly area].

    Science.gov (United States)

    Wei, Wei; Wen, Zhi; Chen, Li-Ding; Chen, Jin; Wu, Dong-Ping

    2012-11-01

    Soil crusts are distributed extensively in the Chinese Loess Plateau and play key roles in surface hydrological processes. In this study, a typical loess hilly region in Anjiagou catchment, Dingxi city, Gansu province was selected as the study region, and soil crusts in the catchment were investigated. Then, the hydrological effect of soil crusts was studied by using multi-sampling and hydrological monitoring experiments. Several key results were shown as follows. Firstly, compared with bared soil without crust cover, soil crusts can greatly reduce the bulk density, improve the porosity of soil, and raise the holding capacity of soil moisture which ranges from 1.4 to 1.9 times of that of bared soil. Secondly, the role of soil crust on rainfall interception was very significant. Moss crust was found to be strongest on rainfall interception, followed by synantectic crusts and lichen crusts. Bared soil without covering crusts was poorest in resisting rainfall splash. Thirdly, hydrological simulation experiments indicate that soil crusts play a certain positive role in promoting the water infiltration capacity, and the mean infiltration rate of the crusted soil was 2 times higher than that of the no-crust covered soils. While the accumulated infiltrated water amounts was also far higher than that of the bared soil.

  10. The sensitivity of surface mass loading displacement response to perturbations in the elastic structure of the crust and mantle

    Science.gov (United States)

    Martens, Hilary R.; Rivera, Luis; Simons, Mark; Ito, Takeo

    2016-05-01

    Surface mass loads generate a rich spectrum of deformation responses in the solid Earth that might be exploited to probe the material properties of the crust and mantle. Here we present a detailed examination of load-induced surface displacements and their sensitivities to systematic perturbations in elastic Earth structure. We compute Love numbers and displacement load Green's functions (LGFs) by integrating the equations of motion for spheroidal deformation of a radially heterogeneous and self-gravitating Earth. Sensitivity kernels are derived for individual Love numbers numerically using finite differences and quasi-analytically using calculus of variations. We then generate sensitivity kernels for displacement LGFs by systematically perturbing the preliminary reference Earth model. We find that displacement LGFs are most sensitive to elastic structural perturbations within 500 km depth from the surface and for short source-receiver distances. For separate perturbations to the shear modulus, bulk modulus, and density within the crust and mantle, the sensitivity kernels exhibit unique patterns, consistent with the possibility to constrain the parameters independently given a spatially distributed set of sufficiently accurate loading response observations. The sensitivity to density structure, however, is generally weak in comparison to elastic structure. We also examine the sensitivity of surface displacements caused by M2 ocean tidal loading (OTL) to systematic perturbations in the elastic moduli and density. Since OTL-induced surface displacements are load and site dependent, we focus on high-resolution profiles across Iceland as a case study. The sensitivity kernels constitute a key element in the formulation of the inverse problem with application to geodetic tomography.

  11. Comparison of element abundance between the exposed crust of the continent of China and the global averaged upper continental crust: Constraints on crustal evolution and some speculations

    Institute of Scientific and Technical Information of China (English)

    WANG Yang

    2007-01-01

    Based on the results of a study of regional element abundance in eastern China and the 1:200 000 geochemical surveys in northern Xinjiang, the element geochemical characteristics of the exposed crust in 23 tectonic units of the continent of China are summarized.Compared with the global average abundance of the upper continental crust, the exposed crust of the continent of China is compositionally more evolved than the upper crust of the island arc, but less evolved than the mature Precambrian Canadian shield. The exposed crust of the North China and Yangtze platforms has a lower SiO2 content, but markedly higher CaO and MgO contents due to the presence of widespread carbonate strata, which suggests that we should not neglect the contribution of carbonate rocks in the study of the exposed crust and the element abundance of the upper crust, in comparison with two recently published average compositional models of the global upper continental crust,the exposed crust of the continent of China is depleted in Au,Hg, Mo, Sn, and W, which suggests that their abundance in the present global models is overestimated. The exposed crust of the North China plat form and the Qinling-Dabieshan fold belt to its south has lower μ(238U/204pb) values(8), but other regions of the continent of China exhibit much higher μ values, which implies that the low μ feature of the North China platform and its adjacent regions does not have global significance. Considering the apparent lateral variation in composition of the exposed crust for the tectonic units of the continent of China, there is no adequate reason to take the average upper crust compositional model of the North China platform and its adjacent regions as a reliable composition representative for Chinese and global upper continental crust composition.

  12. Earth System Oxygenation: Toward an Integrated Theory of Earth Evolution

    Science.gov (United States)

    Anbar, A. D.

    2015-12-01

    The cause of the progressive oxygenation of Earth's biosphere remains poorly understood. The problem is bounded by the interplay of three irreversible, secular changes: the escape of H to space, which makes the planet more oxidized; the evolution of photoautotrophy - which converts solar energy into redox disequilbrium - and related metabolisms; and the cooling of the planet, which affects the exchange of material between Earth's reduced interior and relatively oxidized surface through a variety of processes. The first of these changes is quantitatively considered elsewhere, and is connected to the other two because H escape depends on atmospheric H2 and CH4 contents. The second of these changes is an area of vigorous research, particularly over the past decade. Important work included efforts to constrain the timing of key evolutionary events using organic geochemical and genomic records, and to understand the timing and tempo of environmental oxidation, particularly preceding the "Great Oxidation Event" (GOE) at ~2.4 Ga. As the community sorts through various debates, evidence is accumulating that the pre-GOE period was a dynamic era of transient "whiffs" of oxidation, most likely due to small amounts of biogenic O2 that appeared as early as ~3.0 Ga. The implication is that O2 sinks generally overwhelmed substantial O2 sources through the first half of Earth history, and that a decrease in sink strength and/or increase in source strength could have resulted in increasing instability of trace pO2 in the runup to the GOE. The most likely sinks are coupled to reductants in Earth's interior, which leads us to the third major change—secular cooling of the planet. It is almost certain that this cooling led to changes in mantle dynamics, rates of plate motion, and melting behaviors, which in turn affected volcanism, crust composition, hydrothermal and metamorphic alteration, ocean nutrient budgets, and recycling at subduction zones. These factors have all been

  13. Satellite measurements of the earth's crustal magnetic field

    Science.gov (United States)

    Schnetzler, C. C.

    1989-01-01

    The literature associated with the Magsat mission has evaluated the capabilities and limitations of satellite measurements of the earth's crustal magnetic field, and demonstrated that there exists a 300-3000 km magnetic field, related to major features in the earth's crust, which is primarily caused by induction. Due to its scale and sensitivity, satellite data have been useful in the development of models for such large crustal features as subduction zones, submarine platforms, continental accretion boundaries, and rifts. Attention is presently given to the lack of agreement between laboratory and satellite estimates of lower crustal magnetization.

  14. Percutaneous quadriceps tendon pie-crusting release of extension contracture of the knee

    National Research Council Canada - National Science Library

    Liu, H X; Wen, H; Hu, Y Z; Yu, H C; Pan, X Y

    2014-01-01

    ...: percutaneous quadriceps tendon pie-crusting release. Percutaneous pie-crusting release was performed using an 18-gauge needle to puncture the stiff fibrous band of the distal and lateral quadriceps tendon under maximum knee flexion...

  15. Experimental constraints on phase relations in subducted continental crust

    Science.gov (United States)

    Hermann, Jörg

    2002-01-01

    Synthesis piston cylinder experiments were carried out in the range 2.0-4.5 GPa and 680-1,050 °C to investigate phase relations in subducted continental crust. A model composition (KCMASH) has been used because all major ultrahigh-pressure (UHP) minerals of the whole range of rock types typical for continental crust can be reproduced within this system. The combination of experimental results with phase petrologic constraints permits construction of a UHP petrogenetic grid. The phase relations demonstrate that the most important UHP paragenesis consists of coesite, kyanite, phengite, clinopyroxene, and garnet in subducted continental crust. Below 700 °C talc is stable instead of garnet. As most of these minerals are also stable at much lower pressure and temperature conditions it is thus not easy to recognize UHP metamorphism in subducted crust. A general feature, however, is the absence of feldspars at H2O-saturated conditions. Plagioclase is never stable at UHP conditions, but K-feldspar can occur in H2O-undersaturated rocks. Mineral compositions in the experiments are fully buffered by coexisting phases. The Si content of phengite and biotite increase with increasing pressure. At 4.0 GPa, 780 °C, biotite contains 3.28 Si per formula unit, which is most probably caused by solid solution of biotite with talc. Above 800 °C, the CaAl2SiO6 component in clinopyroxene buffered with kyanite, coesite and a Mg-phase increases with increasing temperature, providing a tool to distinguish between 'cold' and 'hot' eclogites. Up to 10% Ca-eskolaite (Ca0.5[]0.5AlSi2O6) in clinopyroxene has been found at the highest temperature and pressure investigated (>900 °C, 4.5 GPa). Garnet buffered with coesite, kyanite and clinopyroxene displays an increase of grossular component with increasing pressure for a given temperature. Although the investigated system represents a simplification with respect to natural rocks, it helps to constrain general features of subducted continental

  16. Seismic lamination and anisotropy of the Lower Continental Crust

    Science.gov (United States)

    Meissner, Rolf; Rabbel, Wolfgang; Kern, Hartmut

    2006-04-01

    Seismic lamination in the lower crust associated with marked anisotropy has been observed at various locations. Three of these locations were investigated by specially designed experiments in the near vertical and in the wide-angle range, that is the Urach and the Black Forrest area, both belonging to the Moldanubian, a collapsed Variscan terrane in southern Germany, and in the Donbas Basin, a rift inside the East European (Ukrainian) craton. In these three cases, a firm relationship between lower crust seismic lamination and anisotropy is found. There are more cases of lower-crustal lamination and anisotropy, e.g. from the Basin and Range province (western US) and from central Tibet, not revealed by seismic wide-angle measurements, but by teleseismic receiver function studies with a P-S conversion at the Moho. Other cases of lamination and anisotropy are from exhumed lower crustal rocks in Calabria (southern Italy), and Val Sesia and Val Strona (Ivrea area, Northern Italy). We demonstrate that rocks in the lower continental crust, apart from differing in composition, differ from the upper mantle both in terms of seismic lamination (observed in the near-vertical range) and in the type of anisotropy. Compared to upper mantle rocks exhibiting mainly orthorhombic symmetry, the symmetry of the rocks constituting the lower crust is either axial or orthorhombic and basically a result of preferred crystallographic orientation of major minerals (biotite, muscovite, hornblende). We argue that the generation of seismic lamination and anisotropy in the lower crust is a consequence of the same tectonic process, that is, ductile deformation in a warm and low-viscosity lower crust. This process takes place preferably in areas of extension. Heterogeneous rock units are formed that are generally felsic in composition, but that contain intercalations of mafic intrusions. The latter have acted as heat sources and provide the necessary seismic impedance contrasts. The observed

  17. Rare Earth Market Review

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ Oversupply of rare earths led to the significant price drop of rare earth mineral products and separated products in Chinese domestic market. To stabilize the price, prevent waste of resources, further improve regulation capability on domestic rare earth market and rare earth price and maintain sustaining and healthy development of rare earth industry, partial rare earth producers in Baotou and Jiangxi province projected to cease the production for one month.

  18. A New Device for Studying Deep-Frying Behavior of Batters and Resulting Crust Properties

    NARCIS (Netherlands)

    Visser, J.E.; Beukelaer, de H.J.; Hamer, R.J.; Vliet, van T.

    2008-01-01

    The formation and properties of a crust during and after deep frying are difficult to study. Batter pickup (the amount of batter adhering to a product) and core properties affect crust formation and properties of the crust in such way that it is difficult to compare batters of different viscosity or

  19. Composition and origin of ferromanganese crusts from equatorial western Pacific seamounts

    Science.gov (United States)

    Wang, Guozhi; Jansa, Luba; Chu, Fengyou; Zou, Can; Sun, Guosheng

    2015-04-01

    In the equatorial western Pacific, iron-manganese oxyhydroxide crusts (Fe-Mn crusts) and nodules form on basaltic seamounts and on the top of drowned carbonate platform guyots that have been swept free of pelagic sediments. To date, the Fe-Mn crusts have been considered to be almost exclusively of abiotic origin. However, it has recently been suggested that these crusts may be a result of biomineralization. Although the Fe-Mn crust textures in the equatorial western Pacific are similar to those constructed by bacteria and algae, and biomarkers also document the existence of bacteria and algae dispersed within the Fe-Mn crusts, the precipitation, accumulation and distribution of elements, such as Fe, Mn, Ni and Co in Fe-Mn crusts are not controlled by microbial activity. Bacteria and algae are only physically incorporated into the crusts when dead plankton settle on the ocean floor and are trapped on the crust surface. Geochemical evidence suggests a hydrogenous origin of Fe-Mn crusts in the equatorial western Pacific, thus verifying a process for Fe-Mn crusts that involves the precipitation of colloidal phases from seawater followed by extensive scavenging of dissolved trace metals into the mineral phase during crust formation.

  20. A New Device for Studying Deep-Frying Behavior of Batters and Resulting Crust Properties

    NARCIS (Netherlands)

    Visser, J.E.; Beukelaer, de H.J.; Hamer, R.J.; Vliet, van T.

    2008-01-01

    The formation and properties of a crust during and after deep frying are difficult to study. Batter pickup (the amount of batter adhering to a product) and core properties affect crust formation and properties of the crust in such way that it is difficult to compare batters of different viscosity or

  1. Tillage and farmyard manure efects on crusting and compacting soils at Katumani, Semi-arid Kenya

    NARCIS (Netherlands)

    Biamah, E.K.; Sterk, G.; Stroosnijder, L.

    2008-01-01

    In semi-arid Kenya, the most dominatn soil types are of limited agricultural productivity due to crusting and compaction. The occurence of soil crusting and compaction is attributed to seasonal rainfall characteristics, physical soil properties and bad tillage practices. Soil crusting and compaction

  2. A Fungal-Prokaryotic Consortium at the Basalt-Zeolite Interface in Subseafloor Igneous Crust.

    Science.gov (United States)

    Ivarsson, Magnus; Bengtson, Stefan; Skogby, Henrik; Lazor, Peter; Broman, Curt; Belivanova, Veneta; Marone, Federica

    2015-01-01

    We have after half a century of coordinated scientific drilling gained insight into Earth´s largest microbial habitat, the subseafloor igneous crust, but still lack substantial understanding regarding its abundance, diversity and ecology. Here we describe a fossilized microbial consortium of prokaryotes and fungi at the basalt-zeolite interface of fractured subseafloor basalts from a depth of 240 m below seafloor (mbsf). The microbial consortium and its relationship with the surrounding physical environment are revealed by synchrotron-based X-ray tomographic microscopy (SRXTM), environmental scanning electron microscopy (ESEM), and Raman spectroscopy. The base of the consortium is represented by microstromatolites-remains of bacterial communities that oxidized reduced iron directly from the basalt. The microstromatolites and the surrounding basalt were overlaid by fungal cells and hyphae. The consortium was overgrown by hydrothermally formed zeolites but remained alive and active during this event. After its formation, fungal hyphae bored in the zeolite, producing millimetre-long tunnels through the mineral substrate. The dissolution could either serve to extract metals like Ca, Na and K essential for fungal growth and metabolism, or be a response to environmental stress owing to the mineral overgrowth. Our results show how microbial life may be maintained in a nutrient-poor and extreme environment by close ecological interplay and reveal an effective strategy for nutrient extraction from minerals. The prokaryotic portion of the consortium served as a carbon source for the eukaryotic portion. Such an approach may be a prerequisite for prokaryotic-eukaryotic colonisation of, and persistence in, subseafloor igneous crust.

  3. First investigation of the microbiology of the deepest layer of ocean crust.

    Directory of Open Access Journals (Sweden)

    Olivia U Mason

    Full Text Available The gabbroic layer comprises the majority of ocean crust. Opportunities to sample this expansive crustal environment are rare because of the technological demands of deep ocean drilling; thus, gabbroic microbial communities have not yet been studied. During the Integrated Ocean Drilling Program Expeditions 304 and 305, igneous rock samples were collected from 0.45-1391.01 meters below seafloor at Hole 1309D, located on the Atlantis Massif (30 °N, 42 °W. Microbial diversity in the rocks was analyzed by denaturing gradient gel electrophoresis and sequencing (Expedition 304, and terminal restriction fragment length polymorphism, cloning and sequencing, and functional gene microarray analysis (Expedition 305. The gabbroic microbial community was relatively depauperate, consisting of a low diversity of proteobacterial lineages closely related to Bacteria from hydrocarbon-dominated environments and to known hydrocarbon degraders, and there was little evidence of Archaea. Functional gene diversity in the gabbroic samples was analyzed with a microarray for metabolic genes ("GeoChip", producing further evidence of genomic potential for hydrocarbon degradation--genes for aerobic methane and toluene oxidation. Genes coding for anaerobic respirations, such as nitrate reduction, sulfate reduction, and metal reduction, as well as genes for carbon fixation, nitrogen fixation, and ammonium-oxidation, were also present. Our results suggest that the gabbroic layer hosts a microbial community that can degrade hydrocarbons and fix carbon and nitrogen, and has the potential to employ a diversity of non-oxygen electron acceptors. This rare glimpse of the gabbroic ecosystem provides further support for the recent finding of hydrocarbons in deep ocean gabbro from Hole 1309D. It has been hypothesized that these hydrocarbons might originate abiotically from serpentinization reactions that are occurring deep in the Earth's crust, raising the possibility that the lithic

  4. Tectonic controls on hydrothermal mineralisation in hot continental crust: Thermal modelling and spatial analysis

    Science.gov (United States)

    Gessner, K.; Porwal, A.

    2009-04-01

    Hydrothermal ore deposits provide a record of excess energy flux and mass transfer in the Earth's lithosphere. The heterogeneous distribution of ore deposits in space and time provides a challenge to uniformitarian geodynamic and tectonic concepts, but unusual thermal and structural events often coincide with high mineral endowment. In the Australian Proterozoic continental backarcs and intracratonic rifts host large resources of base metals, gold, and uranium. We present thermal models and spatial analyses of mineral occurrences within the Mount Isa Inlier, an inverted Mesoproterozoic rift in northwest Queensland, Australia, to demonstrate how thermal structure, tectonic style and crustal scale fluid flow are related. In the Mount Isa Inlier, radiogenic heat production contributes significantly to present day surface heat flow, and Mesoproterozoic geotherms of 40°C km-1 in the upper crust can be inferred from lithosphere-scale conductive models. The combination of thick continental crust and high temperatures implies that localization of deformation was limited to a thin upper crustal layer. During rifting mid-crustal rocks intruded by syn-extensional granites were exhumed as metamorphic core complexes in strike-parallel linear basement belts. The resulting horizontal strength contrast between sedimentary basins and shallow basement domains became a focus for deformation during subsequent crustal shortening. Our spatial analysis of mineral occurrences demonstrates that epigenetic copper mineralization at Mount Isa correlates positively with steep fault zones bounding linear basement domains, and granites within these domains. Mineralization potential is greatly increased, because high permeability along steep fault zones enables hydrothermal fluid flow between magmatic, metamorphic and sedimentary reservoirs. We argue that the deformation behavior of hot continental lithosphere generates a favorable environment for hydrothermal mineralization by linking shallow

  5. Middle and upper crust shear-wave velocity structure of the Chinese mainland

    Institute of Scientific and Technical Information of China (English)

    FENG Mei; AN Mei-jian

    2007-01-01

    In order to give a more reliable shallow crust model for the Chinese mainland, the present study collected many short-period surface wave data which are better sensitive to shallow earth structures. Different from traditional two-step surface wave tomography, we developed a new linearized surface wave dispersion inversion method to directly get a 3D S-wave velocity model in the second step instead of inverting for 1D S-velocity profile cell by cell. We convert all the regionalized dispersions into linear constraints for a 3D S-velocity model. Checkerboard tests show that this method can give reasonable results. The distribution of the middle- and upper-crust shear-wave velocity of the Chinese mainland in our model is strongly heterogeneous and related to different geotectonic terrains. Low-velocity anomalies delineated very well most of the major sedimentary basins of China. And the variation of velocities at different depths gives an indication of basement depth of the basins. The western Tethyan tectonic domain (on the west of the 95°E longitude) is characterized by low velocity, while the eastern Tethyan domain does not show obvious low velocity. Since petroleum resources often distribute in sedimentary basins where low-velocity anomaly appears, the low velocity anomalies in the western Tethyan domain may indicate a better petroleum prospect than in its eastern counterpart. Besides, low velocity anomaly in the western Tethyan domain and around the Xing'an orogenic belt may be partly caused by high crustal temperature. The weak low-velocity belt along ~105°E longitude corresponds to the N-S strong seismic belt of central China.

  6. A Fungal-Prokaryotic Consortium at the Basalt-Zeolite Interface in Subseafloor Igneous Crust.

    Directory of Open Access Journals (Sweden)

    Magnus Ivarsson

    Full Text Available We have after half a century of coordinated scientific drilling gained insight into Earth´s largest microbial habitat, the subseafloor igneous crust, but still lack substantial understanding regarding its abundance, diversity and ecology. Here we describe a fossilized microbial consortium of prokaryotes and fungi at the basalt-zeolite interface of fractured subseafloor basalts from a depth of 240 m below seafloor (mbsf. The microbial consortium and its relationship with the surrounding physical environment are revealed by synchrotron-based X-ray tomographic microscopy (SRXTM, environmental scanning electron microscopy (ESEM, and Raman spectroscopy. The base of the consortium is represented by microstromatolites-remains of bacterial communities that oxidized reduced iron directly from the basalt. The microstromatolites and the surrounding basalt were overlaid by fungal cells and hyphae. The consortium was overgrown by hydrothermally formed zeolites but remained alive and active during this event. After its formation, fungal hyphae bored in the zeolite, producing millimetre-long tunnels through the mineral substrate. The dissolution could either serve to extract metals like Ca, Na and K essential for fungal growth and metabolism, or be a response to environmental stress owing to the mineral overgrowth. Our results show how microbial life may be maintained in a nutrient-poor and extreme environment by close ecological interplay and reveal an effective strategy for nutrient extraction from minerals. The prokaryotic portion of the consortium served as a carbon source for the eukaryotic portion. Such an approach may be a prerequisite for prokaryotic-eukaryotic colonisation of, and persistence in, subseafloor igneous crust.

  7. Electromagnetic fields generated by constrained rotation of structural blocks in the Earth’s crust

    Science.gov (United States)

    Losseva, T. V.; Kuzmicheva, M. Y.; Spivak, A. A.

    2009-12-01

    Specific features of low frequency electromagnetic impulses in the subsurface Earth’s crust with a low moisture content are defined by the tectonic activity of the region and its structure as well as the stressed-strained state. Electromagnetic effects related to seismic and deformation processes in rocks are very diverse and their physical nature is different. The electric polarization of rocks deserves special attention, since this mechanism is implied in an explosive loading of rocks or relaxation processes in any hierarchic block geophysical medium [1]. The amplitudes of electromagnetic pulses generated by electric currents in a relaxing block-structured stress-strained medium have been obtained by 3D numerical modeling. The source of currents is formed by electric polarization of solids filled inter-block gaps on the active face of a block which, in turn, rotates constrainedly under relaxation. The electric current impulse is defined by the shape of the seismic impulse of the block under relaxation. The block is embedded in the crust. The full system of Maxwell equations in a conductive medium has been solved. The numerical method used has been developed to describe properly the geometry of strain as well as impressed current and conductivity profiles at every time. The figure below presents the maximal amplitudes of electric fields Emax for different active block sizes L (curves 1, 2, 3) versus the relative distances from the source epicenter x/L. Here circles denote the experimental data obtained for the Kurai tectonic structure [1]. We see that the results of numerical simulations are in good agreement with the results of measurements. This proves the validity of our model for the estimation of electric effects in the low moisture rock medium. References: [1] S.P. Soloviev and A.A. Spivak, Doklady Earth Sciences, 2007, Vol. 417A, No. 9, pp. 1449-1453.

  8. Giant pulsar glitches and the inertia of neutron star crusts

    Science.gov (United States)

    Delsate, T.; Chamel, N.; Gürlebeck, N.; Fantina, A. F.; Pearson, J. M.; Ducoin, C.

    2016-07-01

    Giant pulsar frequency glitches as detected in the emblematic Vela pulsar have long been thought to be the manifestation of a neutron superfluid permeating the inner crust of a neutron star. However, this superfluid has been recently found to be entrained by the crust, and as a consequence it does not carry enough angular momentum to explain giant glitches. The extent to which pulsar-timing observations can be reconciled with the standard vortex-mediated glitch theory is studied considering the current uncertainties on dense-matter properties. To this end, the crustal moment of inertia of glitching pulsars is calculated employing a series of different unified dense-matter equations of state.

  9. Symmetry energy, unstable nuclei, and neutron star crusts

    CERN Document Server

    Iida, Kei

    2013-01-01

    Phenomenological approach to inhomogeneous nuclear matter is useful to describe fundamental properties of atomic nuclei and neutron star crusts in terms of the equation of state of uniform nuclear matter. We review a series of researches that we have developed by following this approach. We start with more than 200 equations of state that are consistent with empirical masses and charge radii of stable nuclei and then apply them to describe matter radii and masses of unstable nuclei, proton elastic scattering and total reaction cross sections off unstable nuclei, and nuclei in neutron star crusts including nuclear pasta. We finally discuss the possibility of constraining the density dependence of the symmetry energy from experiments on unstable nuclei and even observations of quasi-periodic oscillations in giant flares of soft gamma-ray repeaters.

  10. Symmetry energy, unstable nuclei and neutron star crusts

    Energy Technology Data Exchange (ETDEWEB)

    Iida, Kei [Kochi University, Department of Natural Science, Kochi (Japan); RIKEN Nishina Center, Saitama (Japan); Oyamatsu, Kazuhiro [RIKEN Nishina Center, Saitama (Japan); Aichi Shukutoku University, Department of Human Informatics, Aichi (Japan)

    2014-02-15

    The phenomenological approach to inhomogeneous nuclear matter is useful to describe fundamental properties of atomic nuclei and neutron star crusts in terms of the equation of state of uniform nuclear matter. We review a series of researches that we have developed by following this approach. We start with more than 200 equations of state that are consistent with empirical masses and charge radii of stable nuclei and then apply them to describe matter radii and masses of unstable nuclei, proton elastic scattering and total reaction cross sections off unstable nuclei, and nuclei in neutron star crusts including nuclear pasta. We finally discuss the possibility of constraining the density dependence of the symmetry energy from experiments on unstable nuclei and even observations of quasi-periodic oscillations in giant flares of soft gamma-ray repeaters. (orig.)

  11. Spin diffusive modes and thermal transport in neutron star crusts

    CERN Document Server

    Sedrakian, Armen

    2015-01-01

    In this contribution we first review a method for obtaining the collective modes of pair-correlated neutron matter as found in a neutron star inner crust. We discuss two classes of modes corresponding to density and spin perturbations with energy spectra $\\omega = \\omega_0 + \\alpha q^2$, where $\\omega_0 = 2\\Delta$ is the threshold frequency and $\\Delta$ is the gap in the neutron fluid spectrum. For characteristic values of Landau parameters in neutron star crusts the exitonic density modes have $\\alpha 0$ and they exist above $\\omega_0$ which implies that these modes are damped. As an application of these findings we compute the thermal conductivity due to spin diffusive modes and show that it scales as $T^{1/2} \\exp(-2\\omega_0/T)$ in the case where their two-by-two scattering cross-section is weakly dependent on temperature.

  12. Crusted (Norwegian) scabies following systemic and topical corticosteroid therapy.

    Science.gov (United States)

    Binić, Ivana; Janković, Aleksandar; Jovanović, Dragan; Ljubenović, Milanka

    2010-01-01

    It is a case study of a 62-yr-old female with crusted (Norwegian) scabies, which appeared during her treatment with systemic and topical corticosteroid therapy, under the diagnosis of erythroderma. In the same time, the patient had been suffered from hypothyoidism, and her skin changes were misdiagnosed, because it was thought that they are associated with her endocrine disorder. Suddenly, beside the erythema, her skin became hyperkeratotic, with widespread scaling over the trunk and limbs, and crusted lesions appeared on her scalp and ears. The microscopic examination of the skin scales with potassium hydroxide demonstrated numerous scabies mites and eggs. Repeated topical treatments with lindan, benzoyl benzoat and 10% precipitated sulphur ointment led to the complete resolution of her skin condition.

  13. The outer crust of non-accreting cold neutron stars

    CERN Document Server

    Ruster, S B; Schaffner-Bielich, J; Ruster, Stefan B.; Hempel, Matthias; Schaffner-Bielich, Jurgen

    2006-01-01

    The properties of the outer crust of non-accreting cold neutron stars are studied by using modern nuclear data and theoretical mass tables updating in particular the classic work of Baym, Pethick and Sutherland. Experimental data from the atomic mass table from Audi, Wapstra, and Thibault of 2003 is used and a thorough comparison of many modern theoretical nuclear models, relativistic and non-relativistic ones, is performed for the first time. In addition, the influences of pairing and deformation are investigated. State-of-the-art theoretical nuclear mass tables are compared in order to check their differences concerning the neutron dripline, magic neutron numbers, the equation of state, and the sequence of neutron-rich nuclei up to the dripline in the outer crust of non-accreting cold neutron stars.

  14. Obstacle performance of cobalt-enriching crust wheeled mining vehicle

    Institute of Scientific and Technical Information of China (English)

    HUANG Zhong-hua; LIU Shao-jun; XIE Ya

    2006-01-01

    A cobalt-enriching crust mining vehicle with four independent driven wheels was proposed. The influence of center-of-gravity position of mining vehicle on obstacle performance was studied. The results show that the mining vehicle has optimal obstacle performance with center-of-gravity position in the middle of suspension. A virtual prototype based on ADAMS software was built and its obstacle performance was simulated. Simulation results show that the mining vehicle with four independent driven wheels has excellent obstacle performance, the maximum climbing capacity is no less than 30°, the maximal ditch width and shoulder height are no less than wheel radius ofmining vehicle. Thus wheeled mining vehicle is feasible for cobalt-enriching crust commercial mining.

  15. Explaining the thick crust in Paraná basin, Brazil, with satellite GOCE gravity observations

    Science.gov (United States)

    Mariani, Patrizia; Braitenberg, Carla; Ussami, Naomi

    2013-08-01

    Seismologic observations in the last decades have shown that the crustal thickness in Paraná basin locally is over 40 km thick, which is a greater value than expected by the simple isostatic model considering the topographic load. The goal of this work is to explain this apparent discrepancy by modeling the internal crustal density anomalies through the gravity field. We use the latest Earth Gravity Model derived from the observations of the GOCE satellite mission, to retrieve the gravity anomaly and correct it for topographic effects, thus obtaining the Bouguer field. We then model the gravity effect of known stratigraphic units and of the seismological crustal thickness. The large Paraná basin comprises over 3500 m of Paleozoic sedimentary sequence with density between 2400 and 2600 kg/m3. During the Early Cretaceous the same basin was affected by a large amount of igneous activity with a volume of over 0.1 Mkm3. The flood basalt volcanism is known as the Serra Geral Formation, and has a maximum thickness of 1500 m. The stratigraphic units of the basin are topped by post-volcanic deposits of the Bauru Group, of about 300 m thickness, located in the northern part of the basin. The density and thickness of the sedimentary sequence are constrained by sonic logs of drill-holes and exploration seismic. We use the crustal thickness estimated from the newest seismological results for South America to calculate its gravity effect. Further we model the isostatic crustal thickness variation, allowing the comparison between a seismological Moho, an isostatic Moho, and a gravity-based Moho. We find that there is a clear positive Bouguer residual anomaly located in the northern and southern part of the Paraná basin, indicating the presence of a hidden mass, not considered up to now. We propose a model that explains this mass as magmatic rock, probably gabbro in lower crust, with density contrast of 200 kg/m3 and thickness of more than 10 km, thus demonstrating that the

  16. Ultra-deep Subduction of Continental Crust: Evidence from Natural Rocks and Experimental Investigations

    Science.gov (United States)

    Dobrzhinetskaya, L.; Green, H. W.

    2005-12-01

    Much of what we know about the deep subduction of continental crust is gained from study of the mineralogy of ultrahigh-pressure metamorphic (UHPM) rocks incorporated within continent-continent collision belts. UHPM rocks of metasedimentary origin were only recently recognized due to discovery of coesite, diamond, titanite inferred to have contained six-fold coordinated Si before exsolution of coesite, and TiO2 with alpha-PbO2 structure. Modern seismic tomography provides remarkable images that suggest lithospheric plates are subducted to the core-mantle boundary and may remain there stagnated during long geological times; the presence of continental material within such plates cannot be excluded. The mineral phase transformations possible within deeply subducted continental crust have been the subject of intensive laboratory experimentation during the last decade. Though many new UHP minerals were synthesized at P~ 6 to >20 GPa (e.g., wadeite, topaz-OH, phase Egg, K- and Na-hollandite) in the KNASH, KASH and ASH chemical systems, none except topaz-OH has yet been identified in UHPM rocks. The microstructural evidence of former majoritic garnet decompression is proven only for garnet peridotite, whereas no evidence of such structures has been reported yet from diamondiferous felsic rocks. It is not clear if this is because the UHPM minerals of felsic rocks are easily lost during retrograde metamorphism, or if this is because garnets crystallized in the felsic systems do not contain a large majoritic component at high pressures. There is no clear indication of what portion of subducted continental crust is returned back to Earth's surface, and what fraction may have become more dense than mantle rocks and sunk down to the mantle transition zone and even deeper. Is there any connection between mantle plumes and deeply subducted continental rocks? The UHPM discipline would also benefit from new experiments designed to reproduce decompression structures of UHP minerals

  17. Seismic anisotropy in the lower crust: The link between rock composition, microstructure, texture and seismic properties.

    Science.gov (United States)

    Czaplinska, Daria; Piazolo, Sandra; Almqvist, Bjarne

    2015-04-01

    Seismic anisotropy observed in Earth's interior is caused by the presence of aligned anisotropic minerals (crystallographic and shape preferred orientation; CPO and SPO respectively), and fluid and/or melt inclusions related to deformation. Therefore, the variations in seismic anisotropy carry valuable information about the structure of the mantle and crust. For example, anisotropy observed in the upper mantle is mainly attributed to the CPO of olivine, and provides strong evidence for the flow within the upper mantle. Seismic anisotropy in the crust is still poorly constrained, mostly due to the much larger heterogeneity of the crustal rocks in comparison with the more homogenous mantle. Anisotropy in the crust will be affected by the variations in rock composition, microstructure, texture (presence or lack of CPO), brittle structures (e.g. fracture systems) and chemical composition of the minerals. However, once the relationships between those variables and seismic properties of the crustal rocks are established, seismic anisotropy can be used to derive characteristics of rocks otherwise out of reach. Our study focuses on two sets of samples of middle to lower crustal rocks collected in Fiordland (New Zealand) and in Sweden. Samples from Fiordland represent a root of a thick (ca. 80 km) magmatic arc and comprise igneous rocks, which crystallized at high P and T conditions and were subsequently metamorphosed and deformed. Samples from Sweden are derived from a metasedimentary nappe in the Caledonian orogenic belt, which is mostly composed of gneisses, amphibolites and calc-silicates that have experienced different amounts of strain. We use large area EBSD mapping to measure the CPO of the constituent phases and record the geometric relationships of the rock microstructure. Data is then used to calculate the elastic properties of the rock from single-crystal stiffnesses. Here, we utilize the EBSD GUI software (Cook et al., 2013), which offers varied homogenization

  18. Water in the Earth's Interior: Distribution and Origin

    Science.gov (United States)

    Peslier, Anne H.; Schönbächler, Maria; Busemann, Henner; Karato, Shun-Ichiro

    2017-08-01

    The concentration and distribution of water in the Earth has influenced its evolution throughout its history. Even at the trace levels contained in the planet's deep interior (mantle and core), water affects Earth's thermal, deformational, melting, electrical and seismic properties, that control differentiation, plate tectonics and volcanism. These in turn influenced the development of Earth's atmosphere, oceans, and life. In addition to the ubiquitous presence of water in the hydrosphere, most of Earth's "water" actually occurs as trace amounts of hydrogen incorporated in the rock-forming silicate minerals that constitute the planet's crust and mantle, and may also be stored in the metallic core. The heterogeneous distribution of water in the Earth is the result of early planetary differentiation into crust, mantle and core, followed by remixing of lithosphere into the mantle after plate-tectonics started. The Earth's total water content is estimated at 18_{-15}^{+81} times the equivalent mass of the oceans (or a concentration of 3900_{-3300}^{+32700} ppm weight H2O). Uncertainties in this estimate arise primarily from the less-well-known concentrations for the lower mantle and core, since samples for water analyses are only available from the crust, the upper mantle and very rarely from the mantle transition zone (410-670 km depth). For the lower mantle (670-2900 km) and core (2900-4500 km), the estimates rely on laboratory experiments and indirect geophysical techniques (electrical conductivity and seismology). The Earth's accretion likely started relatively dry because it mainly acquired material from the inner part of the proto-planetary disk, where temperatures were too high for the formation and accretion of water ice. Combined evidence from several radionuclide systems (Pd-Ag, Mn-Cr, Rb-Sr, U-Pb) suggests that water was not incorporated in the Earth in significant quantities until the planet had grown to ˜60-90% of its current size, while core formation

  19. Continental crust under the southern Porcupine Seabight west of Ireland

    Science.gov (United States)

    Makris, J.; Egloff, R.; Jacob, A. W. B.; Mohr, P.; Murphy, T.; Ryan, P.

    1988-08-01

    Two new seismic refraction/wide-angle reflection profiles demonstrate that the crust beneath the southern Porcupine Seabight, out to water depths in excess of 4000 m, is of continental type. They also reveal the rifted margin of the Porcupine basin on its eastern side. Crustal thickness under the Seabight, inclusive of sediments which are up to 6 km thick, decreases from 23 km in the east to about 10 km at a sharp continent-ocean transition in the west.

  20. The complex isostatic equilibration of Australia's deep crust.

    Science.gov (United States)

    Aitken, Alan; Gross, Lutz; Altinay, Cihan

    2016-04-01

    A recent study, using a new finite-element based gravity inversion method has modelled in high-resolution the density and pressure fields for the Australian continent. Here we analyse the pressure results to consider how Australia's lower-crust and Moho contribute to the isostatic equilibration of topography and crustal masses. We find that the situation is more complex than the commonly applied model of isostatic compensation through crustal thickness variations. Key differences include low pressure-variability at ca. 30-35 km, suggesting that the thickness of the felsic-intermediate crust equilibrates most of the upper-crustal loads; increasing pressure-variability between 30-50 km, suggesting that positively buoyant deep-crustal roots generate disequilibrium. These large roots have previously been inferred to represent mafic underplates. Pressure-variability in the uppermost lithospheric mantle reduces to a minimum at ~125 km depth, suggesting that these loads are compensated by dense mantle at ~100 km depth, rather than by crustal loads or topography. This raises the notion that Australia's lithosphere is isostatically compensated at two levels: Crustal compensation involving topography and the felsic to intermediate crust; and deep-lithosphere compensation involving the mafic lower crust and lithospheric mantle. Rather than its traditional role of compensating for crustal masses, the Moho in this case appears to be a source of isostatic disequilibrium, acting in a separate cell with lithospheric mantle density sources. These results imply that, for cratonised continents like Australia, the notion of crustal isostasy is a poor descriptor of the system.

  1. Analysis of the black crust on Saint Michael's Church

    Science.gov (United States)

    Popister, I.; Zeman, A.

    2012-04-01

    The goal of the present study is to characterize the black crust on the main stone used at Saint Michael's Church in Cluj-Napoca, Romania. The gases in the atmosphere, along with natural and artificial pollutants can cause damage the integrity of the stone when it comes in contact with the stone's chemistry. In order to explain the mechanism of stone decay due to black crust it is necessary to know what "weathering" means, so it must be seen as a complex process that consists of: type of material, the environment in which the material is located, and the amount of time required for the process to take place. Each material has particular properties, due to its composition and genesis. When it comes in contact with the acidity of the "acid rain" (caused by sulphur, nitrogen oxides and carbon dioxide), the rain penetrates into the pore structure, corroding it and "allowing" the atmospheric particles to penetrate the stone. St. Michael's Church is one of the oldest Gothic architectural monuments in Cluj, Romania, being built predominantly from Cenozoic (Upper Eocene) limestone, locally known as the Cluj Limestone. The main quarry was in Baciu, near Cluj. The samples that were collected from the Saint Michael's Church were characterized by means of: optical microscope, Scattering Electronic Microscope, thin sections, EDS The samples that were collected from the Saint Michael's Church went through a series of tests: optical microscope, Scattering Electronic Microscope, thin sections, EDX, and cross-section. The optical microscope analysis of the thin sections revealed that the black crust layer is approximately 0.01mm, and in the sample there are perfectly shaped ooides, which is characteristic to this type of limestone. The SEM analysis shows a resedimentation layer on the surface of the black crust, which occurred probably due to the effect of acid rain. Further information regarding the results of the test will be presented on the poster.

  2. Crusted (Norwegian) Scabies Following Systemic and Topical Corticosteroid Therapy

    OpenAIRE

    Binić, Ivana; Janković, Aleksandar; Jovanović, Dragan; Ljubenović, Milanka

    2009-01-01

    It is a case study of a 62-yr-old female with crusted (Norwegian) scabies, which appeared during her treatment with systemic and topical corticosteroid therapy, under the diagnosis of erythroderma. In the same time, the patient had been suffered from hypothyoidism, and her skin changes were misdiagnosed, because it was thought that they are associated with her endocrine disorder. Suddenly, beside the erythema, her skin became hyperkeratotic, with widespread scaling over the trunk and limbs, a...

  3. The Seismic Structure of the Crust of Madagascar

    Science.gov (United States)

    Wysession, M. E.; Andriampenomanana Ny Ony, F. S. T.; Tsiriandrimanana, R.; Pratt, M. J.; Aleqabi, G. I.; Wiens, D. A.; Nyblade, A.; Shore, P.; Rambolamanana, G.; Tilmann, F. J.

    2015-12-01

    The structure of Madagascar's crust is determined using both body wave receiver functions as well as an analysis of surface waves using ambient-noise and two-plane-wave earthquake surface waves analyses. The primary data used are from the 2011-2013 MACOMO (Madagascar, the Comoros, and Mozambique) broadband seismic array from the PASSCAL program of IRIS (Incorporated Research Institutions for Seismology), funded by the NSF. Additional data came from the RHUM-RUM project (led by G. Barruol and K. Sigloch), the Madagascar Seismic Profile (led by F. Tilmann), and the GSN. The crustal structure of Madagascar, which had previously only been inferred from a gravity survey assuming isostasy, shows a strong correlation with its tectonic history. Crustal thicknesses are greatest, reaching 45 km, along the spine of Madagascar's mountains, which run north-south across the island. Crustal thicknesses thin to the east and west, which are both regions of tectonic separation, however, with very different results. Extensive crustal thinning occurred along the western coasts of Madagascar when the island rifted away from mainland Africa beginning 160 Ma ago. The crust is as thin as 20 km here, but the thickness of basin sediments is as great as 9 km, with the crystalline basement continental crust thinning to 12 km at its thinnest. Along the east coast, the crustal thickness is within the 33-38 km range, but it is thickest in the two places where mesoarchaean crust was rifted off from the Indian subcontinent when it broke away from Madagascar. Surface wave studies show that velocities beneath Madagascar are generally slow, when compared to global models such as AK135. This appears to be due to the occurrence of Cenozoic intraplate volcanism in three regions of Madagascar (north, central, and southwest), each of which has strong underlying seismic low-velocity anomalies in the lithospheric mantle and asthenosphere.

  4. Biological soil crusts as an integral component of desert environments

    Science.gov (United States)

    Belnap, Jayne; Weber, Bettina

    2013-01-01

    The biology and ecology of biological soil crusts, a soil surface community of mosses, lichens, cyanobacteria, green algae, fungi, and bacteria, have only recently been a topic of research. Most efforts began in the western U.S. (Cameron, Harper, Rushforth, and St. Clair), Australia (Rogers), and Israel (Friedmann, Evenari, and Lange) in the late 1960s and 1970s (e.g., Friedmann et al. 1967; Evenari 1985reviewed in Harper and Marble 1988). However, these groups worked independently of each other and, in fact, were often not aware of each other’s work. In addition, biological soil crust communities were seen as more a novelty than a critical component of dryland ecosystems. Since then, researchers have investigated many different aspects of these communities and have shown that although small to microscopic, biological soil crusts are critical in many ecological processes of deserts. They often cover most of desert soil surfaces and substantially mediate inputs and outputs from desert soils (Belnap et al. 2003). They can be a large source of biodiversity for deserts, as they can contain more species than the surrounding vascular plant community (Rosentreter 1986). These communities are important in reducing soil erosion and increasing soil fertility through the capture of dust and the fixation of atmospheric nitrogen and carbon into forms available to other life forms (Elbert et al. 2012). Because of their many effects on soil characteristics, such as external and internal morphological characteristics, aggregate stability, soil moisture, and permeability, they also affect seed germination and establishment and local hydrological cycles. Covering up to 70% of the surface area in many arid and semi-arid regions around the world (Belnap and Lange 2003), biological soil crusts are a key component within desert environments.

  5. Q-tubes, Q-rings and Q-crusts

    CERN Document Server

    Sakai, Nobuyuki; Nakao, Ken-ichi

    2010-01-01

    We re-analyse scalar field theories which allow Q-ball solutions. We find new types of non-topological solitons: tube-shaped in SO(2) models, ring-shaped in SO(3) models, and crust-shaped in SO(3)\\times U(1) models. Although their field configurations are analogous to cosmic global strings or global monopoles, their gravitational mass are finite without gauge fields.

  6. Sr-Nd-Pb isotopic compositions of the lower crust beneath northern Tarim: insights from igneous rocks in the Kuluketage area, NW China

    Science.gov (United States)

    Zhang, Yan; Wei, Xun; Xu, Yi-Gang; Long, Xiao-Ping; Shi, Xue-Fa; Zhao, Jian-Xin; Feng, Yue-Xing

    2016-09-01

    The composition of lower crust of the Tarim Craton in NW China is essential to understand the petrogenesis of the ~290-275 Ma Tarim basalts and associated intermediate-felsic rocks. However, it remains poorly constrained because extremely sparse granulite terrains or granulite xenoliths have been found in the Tarim Craton. New trace element and Sr-Nd-Pb isotopic data are reported for the Neoarchean and Neoproterozoic igneous rocks widely distributed in the northern margin of the Tarim Craton. The Neoarchean granitic gneisses show fractionated REE (rare earth element) patterns [(La/Yb) N = 12-58, YbN = 10.6-36] with pronounced negative Nb-Ta and Ti anomalies. These features, together with negative ɛNdi (-0.7 to -3.2) suggest that they were derived from melting of mafic lower crust. The Neoproterozoic biotite granodiorites are strongly depleted in HREE with (La/Yb) N up to 55. They are characterized by high Sr (671-789 ppm) but very low Y (7.10-8.06 ppm) and Yb contents (0.47-0.58 ppm), showing typical features of adakitic rocks. The samples with different SiO2 contents display identical 87Sr/86Sri (0.7101-0.7103), ɛNdi (-14.1 to -15.7) and Pb isotopes (208Pb/204Pbi = 36.94-37.07). These features together with arc-like trace element patterns suggest that they were derived from melting of thickened lower crust. In comparison, the Neoproterozoic hornblende-biotite granodiorites have similar trace element compositions except for weaker depletion in HREE and have lower 87Sr/86Sri (0.7078) and initial Pb isotopes, and higher ɛNdi (-12.3 to -12.7). This suggests that they were formed by melting of old lower continental crust at a shallower depth than the biotite granodiorites. These rocks were derived from the lower crust, thus providing valuable information on the nature of the lower crust beneath northern Tarim. Combined with published data, the 87Sr/86Sri, ɛNdi, 206Pb/204Pbi and ɛHfi of the northern Tarim lower crust ranges from 0.7055 to 0.7103, from -12 to -17

  7. Pinned vortex hopping in a neutron star crust

    CERN Document Server

    Haskell, Brynmor

    2015-01-01

    The motion of superfluid vortices in a neutron star crust is at the heart of most theories of pulsar glitches. Pinning of vortices to ions can decouple the superfluid from the crust and create a reservoir of angular momentum. Sudden large scale unpinning can lead to an observable glitch. In this paper we investigate the scattering of a free vortex off a pinning potential and calculate its mean free path, in order to assess whether unpinned vortices can skip multiple pinning sites and come close enough to their neighbours to trigger avalanches, or whether they simply hop from one pinning site to another giving rise to a more gradual creep. We find that there is a significant range of parameter space in which avalanches can be triggered, thus supporting the hypothesis that they may lie at the origin of pulsar glitches. For realistic values of the pinning force and superfluid drag parameters we find that avalanches are more likely in the higher density regions of the crust where pinning is stronger. Physical dif...

  8. Reflection attributes of paragneiss in the upper crust

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The integrated study of the geological and seismic reflection data from the drilling area of CCSD has discovered that the density and the P-wave velocity of orthogneiss are almost the same as that of the paragneiss in the area; but the orthogneiss and the paragneiss hold different reflection attributes. The strong seismic reflector packes coinciding spatially with the paragneiss suites have implied that the paragneiss buried in the metamorphic crust itself can cause bone-like seismic reflector sets. The P-wave velocity of paragneiss shows little apparent difference with that of the orthogneiss; but its transverse wave velocity is lower, with the Vp/Vs ratios being high. The paragneiss has partially inherited the layering structures and textures of the protolithe of sedimentary rocks, hence shows strong heterogeneity and anisotropy, that is why the paragneiss are able to produce the bone-like reflectors in the upper crust. The low transverse wave velocity of paragneiss often means weak shear resistance, which will further cause cracks or fractures in the rock, consequentially increase its porosity and permeability during tectonic movements, and form the paragneiss reservoirs of low-permeability zones for gases uplifted from the deeper crust. Because the paragneiss in the crustal metamorphic basement can cause the seismic reflectors, seismic reflection sections are able to provide information about the paragneiss under certain prerequisites.

  9. Radiogenic heat production, thermal regime and evolution of continental crust

    Science.gov (United States)

    Mareschal, Jean-Claude; Jaupart, Claude

    2013-12-01

    Heat flow and heat production data complement seismic information and provide strong constraints on crustal composition, thickness and evolution. They have helped understand the nature of the Mohorovicic discontinuity and the variations in seismic velocities below the Moho. Notably, heat flow studies have delineated the vertical distribution of heat producing elements throughout the crust and in the upper most mantle lithosphere. Analysis of global data sets on heat flow and crustal thickness demonstrate that there is no correlation between these two variables. This is due to the large spatial variations in crustal composition and heat production that exist within a single geological province. For a given crustal thickness, the Moho temperature varies within a wide range (≈ 300 K) depending on surface heat flux and crustal heat production. Thus one cannot use generic models based on a “type” crustal column to calculate crustal geotherms. In stable regions, lower crustal temperatures depend on the amount and vertical distribution of heat producing elements in the crust. These temperatures determine the conditions of crustal stability and impose a limit on the maximum thickness of a stabilized crust.

  10. Attenuation of S wave in the crust of Ordos massif

    Institute of Scientific and Technical Information of China (English)

    LIU Hong-gui; CHUO Yong-qing; CHEN Shu-qing; JIN Chun-hua

    2005-01-01

    We presented attenuation characteristics of S waves in the crust of Ordos massif. Using 487 pieces of digital oscillograms of 19 seismic events recorded by 32 seismologic stations located on Ordos massif and its surroundings, we have calculated the parameter of three-segment geometric attenuation and give the relation of inelastic attenuation Q value with frequency in the crust of Ordos massif, site responses of 32 stations, and source parameters of 19 events by the genetic algorithm. The results indicate that Q value (at 1 Hz) of S-wave in the crust of Ordos massif is much larger than that in the geologically active tectonic region. The site responses of the 32 stations in the high-frequency section do not show clear amplification effect except one or two stations, while in the low-frequency section, there is difference among the stations. The logarithmic value of seismic moment and the magnitude ML of 19 seismic events has a very good linear relationship.

  11. Investigation of Biological Soil Crusts Metabolic Webs Using Exometabolomic Analysis

    Science.gov (United States)

    Northen, T.; Karaoz, U.; Jenkins, S.; Lau, R.; Bowen, B.; Cadillo-Quiroz, H.; Garcia-Pichel, F.; Brodie, E.; Richard, B.

    2014-12-01

    Desert biological soil crusts are simple cyanobacteria-dominated surface soil microbial communities found in areas with infrequent wetting, often extreme temperatures, low coverage of vascular plants and constitute the world's largest biofilm. They exist for extended periods in a desiccated dormant state, yet rapidly re-boot metabolism within minutes of wetting. These soil microbial communities are highly dependent on filamentous cyanobacteria such as Microcoleus vaginatusto stabilize the soil and to act as primary producers for the community through the release carbon sources to feed a diversity of heterotrophs. Exometabolomic analysis was performed using liquid chromatography coupled to tandem mass spectrometry on biological soil crust pore water and spent media of key soil bacterial isolates. Comparison of spent vs. fresh media was used to determine uptake or release of metabolites by specific microbes. To link pore water experiments with isolate studies, metabolite extracts of authentic soil were used as supplements for isolate exometabolomic profiling. Our soil metabolomics methods detected hundreds of metabolites from soils including may novel compounds. Only a small set of which being targeted by all isolates. Beyond these few metabolites, the individual bacteria examined showed specialization towards specific metabolites. Surprisingly, many of the most abundant oligosaccharides and other metabolites were ignored by these isolates. The observed specialization of biological soil crust bacteria may play a significant role in determining community structure.

  12. Potentially exploitable supercritical geothermal resources in the ductile crust

    Science.gov (United States)

    Watanabe, Noriaki; Numakura, Tatsuya; Sakaguchi, Kiyotoshi; Saishu, Hanae; Okamoto, Atsushi; Ingebritsen, Steven E.; Tsuchiya, Noriyoshi

    2017-01-01

    The hypothesis that the brittle–ductile transition (BDT) drastically reduces permeability implies that potentially exploitable geothermal resources (permeability >10−16 m2) consisting of supercritical water could occur only in rocks with unusually high transition temperatures such as basalt. However, tensile fracturing is possible even in ductile rocks, and some permeability–depth relations proposed for the continental crust show no drastic permeability reduction at the BDT. Here we present experimental results suggesting that the BDT is not the first-order control on rock permeability, and that potentially exploitable resources may occur in rocks with much lower BDT temperatures, such as the granitic rocks that comprise the bulk of the continental crust. We find that permeability behaviour for fractured granite samples at 350–500 °C under effective confining stress is characterized by a transition from a weakly stress-dependent and reversible behaviour to a strongly stress-dependent and irreversible behaviour at a specific, temperature-dependent effective confining stress level. This transition is induced by onset of plastic normal deformation of the fracture surface (elastic–plastic transition) and, importantly, causes no ‘jump’ in the permeability. Empirical equations for this permeability behaviour suggest that potentially exploitable resources exceeding 450 °C may form at depths of 2–6 km even in the nominally ductile crust.

  13. Potentially exploitable supercritical geothermal resources in the ductile crust

    Science.gov (United States)

    Watanabe, Noriaki; Numakura, Tatsuya; Sakaguchi, Kiyotoshi; Saishu, Hanae; Okamoto, Atsushi; Ingebritsen, Steven E.; Tsuchiya, Noriyoshi

    2017-01-01

    The hypothesis that the brittle-ductile transition (BDT) drastically reduces permeability implies that potentially exploitable geothermal resources (permeability >10-16 m2) consisting of supercritical water could occur only in rocks with unusually high transition temperatures such as basalt. However, tensile fracturing is possible even in ductile rocks, and some permeability-depth relations proposed for the continental crust show no drastic permeability reduction at the BDT. Here we present experimental results suggesting that the BDT is not the first-order control on rock permeability, and that potentially exploitable resources may occur in rocks with much lower BDT temperatures, such as the granitic rocks that comprise the bulk of the continental crust. We find that permeability behaviour for fractured granite samples at 350-500 °C under effective confining stress is characterized by a transition from a weakly stress-dependent and reversible behaviour to a strongly stress-dependent and irreversible behaviour at a specific, temperature-dependent effective confining stress level. This transition is induced by onset of plastic normal deformation of the fracture surface (elastic-plastic transition) and, importantly, causes no `jump' in the permeability. Empirical equations for this permeability behaviour suggest that potentially exploitable resources exceeding 450 °C may form at depths of 2-6 km even in the nominally ductile crust.

  14. Formation and evolution of Precambrian continental crust in South China

    Institute of Scientific and Technical Information of China (English)

    ZHENG YongFei; ZHANG ShaoBing

    2007-01-01

    The occurrence of zircons with U-Pb ages of ~3.8 Ga and Hf model ages of ~4.0 Ga in South China suggests the existence of the Hadean crustal remnants in South China. Furthermore, a detrital zircon with a U-Pb age as old as 4.1 Ga has been found in Tibet. This is the oldest zircon so far reported in China. These results imply that continental crust was more widespread than previously thought in the late Hadean, but its majority was efficiently reworked into Archean continental crust. On the basis of available zircon U-Pb age and Hf isotope data, it appears that the growth of continental crust in South China started since the early Archean, but a stable cratonic block through reworking did not occur until the Paleoproterozoic. Thus the operation of some form of plate tectonics may occur in China continents since Eoarchean. The initial destruction of the South China craton was caused by intensive magmatic activity in association with the assembly and breakup of the supercontinent Rodinia during the Neoproterozoic. However, most of the Archean and Paleoproterozoic crustal materials in South China do not occur as surface rocks, but exist as sporadic crustal remnants. Nevertheless, the occurrence of Neoproterozoic magmatism is still a signature to distinguish South China from North China.

  15. Mechanical Properties of non-accreting Neutron Star Crusts

    CERN Document Server

    Hoffman, Kelsey

    2012-01-01

    The mechanical properties of a neutron star crust, such as breaking strain and shear modulus, have implications for the detection of gravitational waves from a neutron star as well as bursts from Soft Gamma-ray Repeaters (SGRs). These properties are calculated here for three different crustal compositions for a non-accreting neutron star that results from three different cooling histories, as well as for a pure iron crust. A simple shear is simulated using molecular dynamics to the crustal compositions by deforming the simulation box. The breaking strain and shear modulus are found to be similar in the four cases, with a breaking strain of ~0.1 and a shear modulus of ~10^{30} dyne cm^{-2} at a density of \\rho = 10^{14} g cm^{-3} for simulations with an initially perfect BCC lattice. With these crustal properties and the observed properties of {PSR J2124-3358} the predicted strain amplitude of gravitational waves for a maximally deformed crust is found to be greater than the observational upper limits from LIG...

  16. Biological soil crusts in Chile along the precipitation gradient

    Science.gov (United States)

    Samolov, Elena; Glaser, Karin; Baumann, Karen; Leinweber, Peter; Jung, Patrick; Büdel, Burkhard; Mikhailyuk, Tatiana; Karsten, Ulf

    2017-04-01

    Biological soil crusts in Chile along a precipitation gradient Elena Samolov* (1), Karin Glaser (1), Karen Baumann (2), Peter Leinweber (2), Patrick Jung (3), Burkhard Büdel (3), Tatiana Mikhailyuk (4) and Ulf Karsten (1) (1) Institute of Biological Sciences - Applied Ecology and Phycology, University of Rostock, Rostock, Germany, (2) Faculty of Agricultural and Environmental Sciences - Soil Sciences, University of Rostock, Rostock, Germany (3) University of Kaiserslautern, Kaiserslautern, Germany (4) M.H. Kholodny Institute of Botany, National Academy of Science of Ukraine, Kyiv, Ukraine * elena.samolov@uni-rostock.de Biological soil crusts (BSCs) are an association of different microorganisms and soil particles in the top millimeters of the soil. They are formed by algae, cyanobacteria, microfungi, bacteria, bryophytes and lichens in various compositions; together with their by-products they create a micro-ecosystem that performs important ecological functions, e.g. primary production, nitrogen fixation, mineralization and stabilization of soils. These top-soil assemblages are almost unstudied in South America (Büdel et al. 2016). Therefore, our aim is to investigate for the first time biodiversity of the key photosynthetic organisms, green algae and cyanobacteria following a precipitation gradient along the west coast of Chile. We are applying polyphasic approach - a combination of microscopy, culture dependent (16S and 18S rRNA, ITS) and culture independent molecular techniques (NGS). First results, based on culturing and light microscopy, showed high diversity of eukaryotic algae in biocrusts from humid regions, followed by semi-arid regions. Lichen dominated biocrusts from arid regions were characterized by a high diversity of green algae, while cyanobacteria were scarcely present. The functional role of the BSCs in the biogeochemical cycle of phosphorous (P) was evaluated using state of the art analytical methods including 31P-NMR (nuclear magnetic

  17. Rare earth element enrichment using membrane based solvent extraction

    Science.gov (United States)

    Makertiharta, I. G. B. N.; Dharmawijaya, P. T.; Zunita, M.; Wenten, I. G.

    2017-01-01

    The chemical, catalytic, electrical, magnetic, and optical properties of rare earth elements are required in broad applications. Rare earth elements have similar physical and chemical properties thus it is difficult to separate one from each other. Rare earth element is relatively abundant in earth's crust but rarely occur in high concentrated deposits. Traditionally, ion-exchange and solvent extraction techniques have been developed to separate and purify single rare earth solutions or compounds. Recently, membrane starts to gain attention for rare earth separation by combining membrane and proven technologies such as solvent extraction. Membrane-based process offers selective, reliable, energy efficient and easy to scale up separation. During membrane-based separation process, one phase passes through membrane pores while the other phase is rejected. There is no direct mixing of two phases thus the solvent loss is very low. Membrane can also lower solvent physical properties requirement (viscosity, density) and backmixing, eliminate flooding phenomenon and provide large interfacial area for mass transfer. This paper will summarize research efforts in developing membrane technology for rare earth element separation. Special attention will be given to solvent extraction related process as the commonly used method for rare earth element separation. Furthermore, membrane configuration and its potentials will also be discussed.

  18. Earth from Above

    Science.gov (United States)

    Stahley, Tom

    2006-01-01

    Google Earth is a free online software that provides a virtual view of Earth. Using Google Earth, students can view Earth by hovering over features and locations they preselect or by serendipitously exploring locations that catch their fascination. Going beyond hovering, they can swoop forward and even tilt images to make more detailed…

  19. Magma underplating and Hannuoba present crust-mantle transitional zone composition: Xenolith petrological and geochemical evidence

    Institute of Scientific and Technical Information of China (English)

    FAN Qicheng; ZHANG Hongfu; SUI Jianli; ZHAI Mingguo; SUN Qian; LI Ni

    2005-01-01

    On the basis of mineral assemblage, mineralogy, petrology, and major, trace elemental and isotopic geochemistry of the underplated granulite- and eclogite-facies accumulate, peridotite and pyroxenite xenoliths entrained in Hannuoba Cenozoic basalts, this work constrained the petrological constituents for the crust-mantle transitional zone, which is supported by the results of high-temperature and pressure velocity experiments on rocks and geophysics deep survey. Present lower part of lower crust is mainly composed of granulite-facies mafic accumulates (dominantly plagioclase websterite) and crust-mantle transitional zone dominantly composed of eclogite-facies pyroxenites with or without garnet and spinel lherzolites; Archaean terrain granulite is only nominally early lower crust. Magma underplating in the crust-mantle boundary led to the crustal vertical accretion and the formation of the crust-mantle transitional zone, which is a significant mechanism for the chemical adjustment of the crust-mantle boundary since the Phanerozoic.

  20. Equation of state and thickness of the inner crust of neutron stars

    CERN Document Server

    Grill, Fabrizio; Providência, Constança; Vidaña, Isaac; Avancini, Sidney S

    2014-01-01

    The cell structure of $\\beta$-stable clusters in the inner crust of cold and warm neutron stars is studied within the Thomas-Fermi approach using relativistic mean field nuclear models. The relative size of the inner crust and the pasta phase of neutron stars is calculated, and the effect of the symmetry energy slope parameter, $L$, on the profile of the neutron star crust is discussed. It is shown that while the size of the total crust is mainly determined by the incompressibility modulus, the relative size of the inner crust depends on $L$. It is found that the inner crust represents a larger fraction of the total crust for smaller values of $L$. Finally, it is shown that at finite temperature the pasta phase in $\\beta$-equilibrium matter essentially melts above $5-6$ MeV, and that the onset density of the rodlike and slablike structures does not depend on the temperature.

  1. Rare Earth Resolution

    Institute of Scientific and Technical Information of China (English)

    Mei Xinyu

    2012-01-01

    BEFORE the early 1970s, China had no rare earth exports, and the world rare earth market was dominated by the United States, Europe and Japan. In the 1970s, China began to enter the world rare earth market and its share has picked up sharply in the following decades. Today, having the monopoly over global rare earth production, China must improve the benefits from rare earth production, not only from producing individual rare earth products, but also from mastering the intensive processing of rare earth products.

  2. Seismic structure of the European crust and upper mantle based on adjoint tomography

    Science.gov (United States)

    Zhu, Hejun

    We use adjoint tomography to estimate three-dimensional variations in seismic parameters within the crust and upper mantle beneath Europe and the North Atlantic Ocean. Spectral-element and adjoint methods are used to numerically calculate synthetic seismograms and sensitivity kernels in three-dimensional Earth models. Combined with gradient- based optimization algorithms, e.g., preconditioned conjugate-gradient and L-BFGS methods, we iteratively update seismic models of Earth's interior. A three-stage inversion strategy is designed to estimate variations in elastic wavespeeds, anelastic attenuation and radial & azimuthal anisotropy. In stage one, frequency-dependent phase differences between observed and simulated seismograms are used to determine a new radially anisotropic wavespeed model for the European crust and upper mantle, namely EU30. Long-wavelength structures in EU30 compare favorably with previous body- and surface-wave tomographic models. Some hitherto unidentified features naturally emerge from the smooth starting model. In stage two, frequency-dependent amplitude differences combined with remaining phase anomalies are used to simultaneously constrain elastic and anelastic structures. A new anelastic model, named EU50, is constructed in this stage. We observe several notable features, such as enhanced attenuation within the mantle transition zone beneath the North Atlantic Ocean. In the first two stages, long-period surface waves and short-period body waves in three-component seismograms are combined to simultaneously constrain shallow and deep structures. In stage three, frequency-dependent phase and amplitude anomalies of three-component surface waves are used to construct a radially and azimuthally anisotropic model EU60. We find that the direction of the fast axis is closely tied to the tectonic evolution in this region, such as extension along the North Atlantic Ridge, trench retreat in the Mediterranean, and counterclockwise rotation of the

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

    Science.gov (United States)

    Pavlenkova, N.

    2009-04-01

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

  4. Cyanobacterial crust induction using two non-previously tested cyanobacterial inoculants: crusting capability and role of EPSs

    Science.gov (United States)

    Mugnai, Gianmarco; Rossi, Federico; De Philippis, Roberto

    2017-04-01

    The use of cyanobacteria as soil improvers and bio-conditioners (a technique often referred to as algalization) has been studied for decades. Several studies proved that cyanobacteria are feasible eco-friendly candidates to trigger soil fertilization and enrichment from agricultural to arid and hyper-arid systems. This approach can be successful to achieve stabilization and rehabilitation of degraded environments. Much of the effectiveness of algalization is due to the productivity and the characteristics of extracellular polysaccharides (EPSs) which, among their features, embed soil particles and promote the development of a first stable organo-mineral layer (cyanobacterial crusts). In natural settings, cyanobacterial crust induction represents a first step of a succession that may lead to the formation of mature biological soil crusts (Lan et al., 2014). The aim of this research was to investigate the crusting capabilities, and the characteristics of excreted EPSs by two newly tested non-heterocystous cyanobacterial inoculants, in microcosm experiments carried out using oligothrophic sand collected from sand dunes in Negev Desert, Israel. The cyanobacteria tested were Schizothrix AMPL1601, originally isolated from biocrusts collected in Hobq Desert, Inner Mongolia (China) and Leptolyngbia ohadii, originally isolated from biocrusts collected in Negev Desert, Israel. Inoculated microcosms were maintained at 30 °C in a growth chamber under continuous illumination and minimal water availability. Under such stressing conditions, and for a three-months incubation time, the growth and the colonization of the strains in the microcosms were monitored. At the same time, EPSs production and their chemical and macromolecular characteristics were determined by applying a methodology optimized for the purpose. Notably, EPSs were analyzed in two operationally-defined fractions, one more dispersed in the crust matrix (loosely bound EPSs, LB-EPSs) and one more condensed and

  5. The Role of KREEP in the Production of Mg-Suite Magmas and Its Influence on the Extent of Mg-Suite Magmatism in the Lunar Crust

    Science.gov (United States)

    Elardo, S. M.; Shearer, C. K.; McCubbin, F. M.

    2017-01-01

    The lunar magnesian-suite, or Mg-suite, is a series of ancient plutonic rocks from the lunar crust. They have received a considerable amount of attention from lunar scientists since their discovery for three primary reasons: 1) their ages and geochemistry indicate they represent pristine magmatic samples that crystallized very soon after the formation of the Moon; 2) their ages often overlap with ages of the ferroan anorthosite (FAN) crust; and 3) planetary-scale processes are needed in formation models to account for their unique geochemical features. Taken as a whole, the Mg-suite samples, as magmatic cumulate rocks, approximate a fractional crystallization sequence in the low-pressure forsterite-anorthite-silica system, and thus these samples are generally thought to be derived from layered mafic intrusions which crystallized very slowly from magmas that intruded the anorthositic crust. However, no direct linkages have been established between different Mg-suite samples based either on field relationships or geochemistry.The model for the origin of the Mg-suite, which best fits the limited available data, is one where Mg-suite magmas form from melting of a hybrid cumulate package consisting of deep mantle dunite, crustal anorthosite, and KREEP (potassium-rare earth elements-phosphorus) at the base of the crust under the Procellarum KREEP Terrane (PKT). In this model, these three LMO (Lunar Magma Ocean) cumulate components are brought into close proximity by the cumulate overturn process. Deep mantle dunitic cumulates with an Mg number of approximately 90 rise to the base of the anorthositic crust due to their buoyancy relative to colder, more dense Fe- and Ti-rich cumulates. This hybridized source rock melts to form Mg-suite magmas, saturated in Mg-rich olivine and anorthitic plagioclase, that have a substantial KREEP component.

  6. Martian methane and link with clathrates in the crust of Mars

    Science.gov (United States)

    Gloesener, Elodie; Karatekin, Ozgur; Dehant, Veronique

    2013-04-01

    The recent detection of methane in the Martian atmosphere (Krasnopolsky et al., 2004; Formisano et al., 2004; Geminale et al., 2008; Mumma et al., 2009; Fonti and Marzo, 2010) generated a large interest among the scientific community in particular because the source of this gas is still unknown and because it is a potential biomarker. Methane, observed at a level of 10 parts per billion and per volume, has a non-uniform distribution involving a photochemical lifetime of 200 days (Lefevre and Forget, 2009), smaller than the 300 years calculated by photochemical models. In addition, there is a correlation between the mixing ratio of water vapor and methane (Geminale et al., 2008). In order to explain this phenomenon, the existence of metastable clathrates decomposing in the atmosphere and releasing CH4 has been suggested (Chassefière, 2009). Clathrates are chemical compounds formed by the inclusion of gas molecules in the cavities of a water molecules network and are stable at high pressure and low temperature. In addition to the biological origin, often invoked to explain most of the methane on Earth, the Martian methane may also have been produced by hydrogeochemical or volcanic processes or may be the last traces of an amount brought by a meteoritic impact a few hundred or thousands years (Atreya et al., 2007). Methane could also come from the exposure to ultraviolet of meteorites falling continuously on the surface of Mars (Keppler et al., 2012). Although the process is very likely to occur on Mars, it does not produce all the expected amount of methane currently measured. Moreover, conditions in the Martian crust are favorable to the stability of methane clathrates. So CH4 emissions observed may also be due to the dissociation of the clathrates due to a change in temperature, pressure or composition. Current conditions of Mars do not allow them to be stable on the surface but they can remain stable in the crust if they were formed below a certain depth

  7. Spectroscopic surrogates of soil organic matter resilience in crusted semiarid Mediterranean ecosystems

    Science.gov (United States)

    Miralles Mellado, Isabel; Almendros, Gonzalo; Ortega, Raúl; Cantón, Yolanda; Poveda, Francisco; van Wesemael, Bas

    2016-04-01

    Arid and semiarid ecosystems represent nearly a third of the Earth's total land surface. In these ecosystems, there is a critical balance between C sequestration and biodegradation that could easily be altered due to human disturbance or global change. These ecosystems are widely characterized by the presence of biological soil crusts (BSCs) which play the most important role in the C-cycle in arid and semiarid areas. Consequently, soil organic matter (SOM) characteristics of crusted soil could readily reflect important information on the resilience of SOM in response to any global temperature increase or to inappropriate soil management practices. In this research, representative BSCs and underlying soils were studied in two different semiarid ecosystems in Southern Spain, i.e., Amoladeras (located in Cabo de Gata Natural Park), and El Cautivo (located in Tabernas desert). Chemical fractionation and characterization of the SOM in BSCs and underlying soils were carried out in order to assess not only the total amount of organic C sequestered but mainly the quality of humic-type organic fractions. After isolating the major organic fractions (particulate fraction, humic acid-like (HA), alkali-extracted fulvic acid (FA) and H3PO4-FAs), the macromolecular, HA fraction was purified and studied by derivative visible spectroscopy and resolution-enhanced infrared (IR) spectroscopy. Our results show differences in the structural characteristics of the HA-type substances, interpreted as progressive stages of diagenetic transformation of biomacromolecules. Amoladeras showed higher SOM content, and higher values of HA and HA/FA ratio than El Cautivo, with lower SOM content in BSCs and underlying soils. The latter site accumulates SOM consisting mainly of comparatively less recalcitrant organic fractions with small molecular sizes (H3PO4-FAs and FAs). Moreover HAs in samples from Amoladeras showed higher condensation and aromaticity (higher E4, lower E4/E6 ratio), pointing to

  8. Reconstruction of food webs in biological soil crusts using metabolomics.

    Science.gov (United States)

    Baran, Richard; Brodie, Eoin L.; Mayberry-Lewis, Jazmine; Nunes Da Rocha, Ulisses; Bowen, Benjamin P.; Karaoz, Ulas; Cadillo-Quiroz, Hinsby; Garcia-Pichel, Ferran; Northen, Trent R.

    2015-04-01

    Biological soil crusts (BSCs) are communities of organisms inhabiting the upper layer of soil in arid environments. BSCs persist in a dessicated dormant state for extended periods of time and experience pulsed periods of activity facilitated by infrequent rainfall. Microcoleus vaginatus, a non-diazotrophic filamentous cyanobacterium, is the key primary producer in BSCs in the Colorado Plateau and is an early pioneer in colonizing arid environments. Over decades, BSCs proceed through developmental stages with increasing complexity of constituent microorganisms and macroscopic properties. Metabolic interactions among BSC microorganisms probably play a key role in determining the community dynamics and cycling of carbon and nitrogen. However, these metabolic interactions have not been studied systematically. Towards this goal, exometabolomic analysis was performed using liquid chromatography coupled to tandem mass spectrometry on biological soil crust pore water and spent media of key soil bacterial isolates. Comparison of spent vs. fresh media was used to determine uptake or release of metabolites by specific microbes. To link pore water experiments with isolate studies, metabolite extracts of authentic soil were used as supplements for isolate exometabolomic profiling. Our soil metabolomics methods detected hundreds of metabolites from soils including many novel compounds. Overall, Microcoleus vaginatus was found to release and utilize a broad range of metabolites. Many of these metabolites were also taken up by heterotrophs but there were surprisingly few metabolites uptaken by all isolates. This points to a competition for a small set of central metabolites and specialization of individual heterotrophs towards a diverse pool of available organic nutrients. Overall, these data suggest that understanding the substrate specialization of biological soil crust bacteria can help link community structure to nutrient cycling.

  9. Continental crust anisotropy measurements from tectonic tremor in Cascadia

    Science.gov (United States)

    Huesca-Pérez, Eduardo; Ortega, Roberto; Valenzuela, Raúl W.

    2017-05-01

    We present new observations of crustal anisotropy in the southern Cascadia fore arc from tectonic tremor. The abundance of tremor activity in Oregon and northern California during slow-slip events offers an enormous amount of information with which to measure and analyze anisotropy in the upper brittle continental crust. To accomplish this, we performed analyses of wave polarization and shear wave splitting of tectonic tremor signals by using three component broadband seismic stations. The splitting times range between 0.11 and 0.32 s and are consistent with typical values observed in the continental crust. Fast polarization azimuths are, in general, margin parallel and trend N-S, which parallels the azimuths of the maximum compressive stresses observed in this region. This pattern is likely to be controlled by the stress field. Comparatively, the anisotropic structure of fast directions observed in the northern section of the Cascadia margin is oblique with respect to the southern section of Cascadia, which, in general, trends E-W and is mainly controlled by active faulting and geological structures. Source distribution analysis using a bivariate normal distribution that expresses the distribution of tremors in a preferred direction shows that in northern California and Oregon, the population of tremors tends to distribute parallel to fast polarization azimuths and maximum compressive stresses, suggesting that both tremor propagation and anisotropy are influenced by the stress field. Results show that the anisotropy reflects an active tectonic process that involves the northward movement of the Oregon Block, which is rotating as a rigid body. In northern Cascadia, previous results of anisotropy show that the crust is undergoing a shortening process due to velocity differences between the Oregon Block and the North America plate, which is moving more slowly with respect to the Oregon Block, making it clash against Vancouver Island.

  10. Microbial exopolysaccharides as determinants of geomorphological, hydrological and optical properties of soil crusts from the Precambrian till today

    Science.gov (United States)

    Garcia-Pichel, F.

    2012-04-01

    The presence of microbial extracellular polysaccharides (EPS) in the soil solution and/or in association with particular microbial types can impart novel properties to biological soil crust (BSC), and hence to soil surfaces. For the most part these properties are of a geobiological relevance that exceeds what one could surmise from its relatively low specific mass content. I will review some examples that range from the mundane to the unexpected. EPS associated with filamentous cyanobacteria can effectively and in the long term stabilize the soil surface against erosive forces, even after the microbes are long gone. Electrostatic interactions between EPS and blowing dust may help retain dust particles, enriching the soil with new nutrient sources. In a telltale sign of BSC presence, EPS is the agent that allows sandy soils to fold and curl-up, to form pee-tee's and elephant-skin surfaces, and to crack into polygons like clays would. EPS in large quantities in flat crusts can retain fluids (both liquid and gaseous) resulting in the alteration of hydrological flow and in the formation of internal vesicular horizons, gas bubbles, pock-marked surfaces and other characteristic structures. Yet, in some settings, EPS plays an architectural role in creating a "spongy" texture that increases hydraulic conductivity. This architectural role can indirectly result in significant increases of a crust's albedo. While the diversity of consequences of EPS presence is far from understood, evidence for its sustained role through Earth's history can be found in the form of sedimentary bio-signatures as far back as the Proterozoic.

  11. Relating the Seismic Character of the Crust and Upper Mantle to Late-Cenozoic Extension in Southwestern N.A.

    Science.gov (United States)

    Thurner, S.; Frassetto, A.; Porter, R.; Zandt, G.

    2008-12-01

    A recent tectonic reconstruction (McQuarrie and Wernicke, 2005) places detailed constraints on the magnitude and scope of late-Cenozoic extension throughout Southwestern North America. This project seeks to better understand the distribution of extension throughout the crust and upper mantle and elucidate the transition from the highly extended Basin and Range to the relatively unextended Colorado Plateau. To this end, we present teleseismic receiver functions generated from 31 broadband seismometers associated with EarthScope's BigFoot Array, TriNet, and PASSCAL stations deployed across Southern California and Arizona. We employ the common-conversion-point stacking method to analyze variations in lithospheric structure. Additionally, in regions with clear converted wave reverberations we analyze the trade-off between crustal thickness and bulk Vp/Vs to improve our view of how crustal thickness and Vp/Vs relate to different tectonic environments and degree of extension. Our preliminary estimates indicate crustal thicknesses of ~25-30 km in eastern California increasing to ~40- 45 km within the southern Colorado Plateau. The transition between thin to thick crust appears to occur over as little as 20 km. Crustal Vp/Vs varies considerably, with Vp/Vs greater than 1.8 near the Transverse Ranges and Colorado Plateau, and less than 1.8 in the southern Basin and Range. We also view a change in the nature of the Moho approaching the Colorado Plateau. Initial calculations indicate the amplitude of the converted wave from the Moho is twice as strong beneath the Mojave and Southern Basin and Range than the Colorado Plateau. Additionally, we observe laminated crust in the western Mojave Desert approaching the Transverse Ranges.

  12. Hadean Earth and primordial continents: The cradle of prebiotic life

    Directory of Open Access Journals (Sweden)

    M. Santosh

    2017-03-01

    Full Text Available The Hadean history of Earth is shrouded in mystery and it is considered that the planet was born dry with no water or atmosphere. The Earth-Moon system had many features in common during the birth stage. Solidification of the dry magma ocean at 4.53 Ga generated primordial continents with komatiite. We speculate that the upper crust was composed of fractionated gabbros and the middle felsic crust by anorthosite at ca. 21 km depth boundary, underlain by meta-anorthosite (grossular + kyanite + quartz down to 50–60 km in depth. The thickness of the mafic KREEP basalt in the lower crust, separating it from the underlying upper mantle is not well-constrained and might have been up to ca. 100–200 km depending on the degree of fractionation and gravitational stability versus surrounding mantle density. The primordial continents must have been composed of the final residue of dry magma ocean and enriched in several critical elements including Ca, Mg, Fe, Mn, P, K, and Cl which were exposed on the surface of the dry Earth. Around 190 million years after the solidification of the magma ocean, “ABEL bombardment” delivered volatiles including H2O, CO2, N2 as well as silicate components through the addition of icy asteroids. This event continued for 200 Myr with subordinate bombardments until 3.9 Ga, preparing the Earth for the prebiotic chemical evolution and as the cradle of first life. Due to vigorous convection arising from high mantle potential temperatures, the primordial continents disintegrated and were dragged down to the deep mantle, marking the onset of Hadean plate tectonics.

  13. The neutron star inner crust and symmetry energy

    CERN Document Server

    Grill, Fabrizio; Providência, Constança

    2012-01-01

    The cell structure of clusters in the inner crust of a cold \\beta-equilibrium neutron star is studied within a Thomas Fermi approach and compared with other approaches which include shell effects. Relativistic nuclear models are considered. We conclude that the symmetry energy slope L may have quite dramatic effects on the cell structure if it is very large or small. Rod-like and slab-like pasta clusters have been obtained in all models except one with a large slope L.

  14. Stability of Hall equilibria in neutron star crusts

    OpenAIRE

    Marchant P.; Reisenegger A.; Valdivia J.A.; Hoyos J.H.

    2014-01-01

    In the solid crusts of neutron stars, the advection of the magnetic field by the current-carrying electrons, an effect known as Hall drift, should play a very important role as the ions remain essentially fixed (as long as the solid does not break). Although Hall drift preserves the magnetic field energy, it has been argued that it may drive a turbulent cascade to scales at which Ohmic dissipation becomes effective, allowing a much faster decay in objects with very strong fields. On the other...

  15. Excess hafnium-176 in meteorites and the early Earth zircon record

    DEFF Research Database (Denmark)

    Bizzarro, Martin; Connelly, J.N.; Thrane, K.

    2012-01-01

    suggesting early extraction of a continental crust (>4.5 Gyr) but fail to identify a prevalent complementary depleted mantle reservoir, suggesting that crust formation processes in the early Earth were fundamentally distinct from today. However, this conclusion assumes that the Hf-isotope composition of bulk...... chondrite meteorites can be used to estimate the composition of Earth prior to its differentiation into major silicate reservoirs, namely the bulk silicate Earth (BSE). We report a Lu- Hf internal mineral isochron age of 4869 34 Myr for the pristine SAH99555 angrite meteorite. This age is ~300 Myr older...... than the age of the Solar System, confirming the existence of an energetic process yielding excess Hf in affected early formed Solar System objects through the production of the Lu isomer (t ~3.9 hours). Thus, chondrite meteorites contain excess Hf and their present-day composition cannot be used...

  16. Thermal neutrons' flux near the Earth's surface as an evidence of the crustal stress

    Science.gov (United States)

    Sigaeva, Ekaterina; Nechayev, Oleg; Volodichev, Nikolay; Antonova, Valentina; Kryukov, Sergey; Chubenko, Alexander; Shchepetov, Alexander

    There are some ideas about the Earth’s global seismic activity appearance due to tidal forces. At the same time, the correlations between the big series of the earthquakes and the New and Full Moons and between the New and Full Moons and the increasings of the thermal neutrons’ flux from the Earth’s crust were observed. It is as though there are internal links between these three natural phenomena and the physical reasons for their appearance are the same. The paper presents the results of the ground-based thermal neutrons observations during different time periods characterized with phenomena in the near-Earth space (for instance, the New and Full Moon). Basing on the up-to-date conception of the tidal waves influence on the Earth's crust the authors confirm the role of the Moon in the production of the neutron flux near the Earth's surface.

  17. Predicting the Isotopic Composition of Subduction-Filtered Subducted Oceanic Crust and Sediment

    Science.gov (United States)

    White, W. M.

    2010-12-01

    The chemical and isotopic character of mantle plumes, which produce oceanic island volcanoes, are widely thought to reflect the presence of recycled oceanic crust and sediment. Isotopic systematics suggest the “cycle time” for this process is 1 Ga or longer, but it should be possible to use a simple mass balance approach to discern how the presently operating subduction zone filter affects the ratios of radioactive parent to radiogenic daughter isotopes. Simple uniformitarian assumptions can then be used to predict the present isotopic composition of anciently subducted lithosphere. Our underlying assumption in deciphering the subduction zone filter is that the flux of an element into the deep mantle is simply equal to the flux of element into the subduction zone less the flux of that element into subduction zone magmas. The former is readily calculated from published data. The latter can be calculated by estimating parental magma compositions, arc accretion rates, and the assumption that arc magma compositions differ from MORB only because of material derived from subducting crust and sediment. Using this approach for 8 intra-oceanic subduction zones, we find 73% of Th and Pb, 79% of U, 80% of Rb and Sr, 93% of Nd and 98% of Sm survive the subduction zone filter. The subduction zone filter systematically increases Sm/Nd ratios in all subduction zones, but the effect is small, with a weighted mean increase of 1.5%. The effect of subduction is to decrease the Sm/Nd of the mantle, but only slightly. The effect of subduction is to increase the Rb/Sr of the mantle, but the subduction zone filter does not have a systematic effect on Rb/Sr ratios: it significantly increases in Rb/Sr in 3 subduction zones and significantly decreases it in one; the weighted mean shows no significant change. The effect of the subduction zone filter on U/Pb is also not systematic. U/Pb ratios in the mantle fluxes are bimodal, with values equal to or lower than the bulk Earth value in 4

  18. The Lifeworld Earth and a Modelled Earth

    Science.gov (United States)

    Juuti, Kalle

    2014-01-01

    The goal of this paper is to study the question of whether a phenomenological view of the Earth could be empirically endorsed. The phenomenological way of thinking considers the Earth as a material entity, but not as an object as viewed in science. In the learning science tradition, tracking the process of the conceptual change of the shape of the…

  19. The Lifeworld Earth and a Modelled Earth

    Science.gov (United States)

    Juuti, Kalle

    2014-01-01

    The goal of this paper is to study the question of whether a phenomenological view of the Earth could be empirically endorsed. The phenomenological way of thinking considers the Earth as a material entity, but not as an object as viewed in science. In the learning science tradition, tracking the process of the conceptual change of the shape of the…

  20. The effect of recycled oceanic crust in the thermal evolution of the Galapagos Plume

    Science.gov (United States)

    Gazel, E.; Herzberg, C. T.; Vidito, C. A.

    2011-12-01

    Current models suggest that the massive basaltic production responsible for the emplacement of Large Igneous Provinces (LIPS) during the Permian-Paleocene may represent the initial phases (plume heads) of some of the mantle plumes that feed the current ocean island basalts (OIB). In many cases, magmatism associated with the initiation of mantle plumes was so voluminous that produced global environmental impacts. The origin of these intra-plate magmatism is still debated but recent petrological, geochemical and geophysical studies of some of these localities like Samoa, Hawaii, Galapagos, provide evidence that melting is related to a true mantle plume, representing a geochemically heterogeneous, hot-buoyant domain that originates from a boundary layer beneath the upper mantle. Thus, plume-related magmas produced in OIB and LIPS and their connecting plume tracks are windows into the Earth's mantle, providing evidence on mantle temperature, size and composition of heterogeneities, and the deep earth geochemical cycles. Our preliminary petrological modeling suggests that mantle plumes for LIPS with Permian-Paleocene ages were generally hotter and melted more extensively than plumes of more modern oceanic islands. Although a lot of work has been done on LIPS and OIB, no complete record of the evolution of a mantle plume is available to this point, mostly due to the inaccessibility of the submerged sections of almost all plume tracks. Galapagos-related lavas provide a complete record of the evolution of a mantle plume since the plume's initial stages in the Cretaceous. In the case of the Galapagos, our work suggests a decrease from TP(max) of1650 C in the Cretaceous to 1500 C in the present day. Our recent work on the Galapagos Islands and the preliminary work on older Galapagos-related terranes suggest that this secular cooling is directly related with increasing amounts of recycled crust in the plume.

  1. Early degassing of lunar urKREEP by crust-breaching impact(s)

    Science.gov (United States)

    Barnes, Jessica J.; Tartèse, Romain; Anand, Mahesh; McCubbin, Francis M.; Neal, Clive R.; Franchi, Ian A.

    2016-08-01

    Current models for the Moon's formation have yet to fully account for the thermal evolution of the Moon in the presence of H2O and other volatiles. Of particular importance is chlorine, since most lunar samples are characterised by unique heavy δ37Cl values, significantly deviating from those of other planetary materials, including Earth, for which δ37Cl values cluster around ∼0‰. In order to unravel the cause(s) of the Moon's unique chlorine isotope signature, we performed a comprehensive study of high-precision in situ Cl isotope measurements of apatite from a suite of Apollo samples with a range of geochemical characteristics and petrologic types. The Cl-isotopic compositions measured in lunar apatite in the studied samples display a wide range of δ37Cl values (reaching a maximum value of +36‰), which are positively correlated with the amount of potassium (K), Rare Earth Element (REE) and phosphorous (P) (KREEP) component in each sample. Using these new data, integrated with existing H-isotope data obtained for the same samples, we are able to place these findings in the context of the canonical lunar magma ocean (LMO) model. The results are consistent with the urKREEP reservoir being characterised by a δ37Cl ∼+30‰. Such a heavy Cl isotope signature requires metal-chloride degassing from a Cl-enriched urKREEP LMO residue, a process likely to have been triggered by at least one large crust-breaching impact event that facilitated the transport and exposure of urKREEP liquid to the lunar surface.

  2. A unique basaltic micrometeorite expands the inventory of solar system planetary crusts

    Science.gov (United States)

    Gounelle, Matthieu; Chaussidon, Marc; Morbidelli, Alessandro; Barrat, Jean-Alix; Engrand, Cécile; Zolensky, Michael E.; McKeegan, Kevin D.

    2009-01-01

    Micrometeorites with diameter ≈100–200 μm dominate the flux of extraterrestrial matter on Earth. The vast majority of micrometeorites are chemically, mineralogically, and isotopically related to carbonaceous chondrites, which amount to only 2.5% of meteorite falls. Here, we report the discovery of the first basaltic micrometeorite (MM40). This micrometeorite is unlike any other basalt known in the solar system as revealed by isotopic data, mineral chemistry, and trace element abundances. The discovery of a new basaltic asteroidal surface expands the solar system inventory of planetary crusts and underlines the importance of micrometeorites for sampling the asteroids' surfaces in a way complementary to meteorites, mainly because they do not suffer dynamical biases as meteorites do. The parent asteroid of MM40 has undergone extensive metamorphism, which ended no earlier than 7.9 Myr after solar system formation. Numerical simulations of dust transport dynamics suggest that MM40 might originate from one of the recently discovered basaltic asteroids that are not members of the Vesta family. The ability to retrieve such a wealth of information from this tiny (a few micrograms) sample is auspicious some years before the launch of a Mars sample return mission. PMID:19366660

  3. The crust and lithosphere thicknesses of Greenland revisited: what do recent gravity data tell us?

    Science.gov (United States)

    Steffen, Rebekka; Lund, Björn

    2016-04-01

    Crustal and lithospheric thicknesses are nowadays extensively studied and several datasets exist for most parts of the Earth; however, for some regions only a few estimations are available. For high resolution models of glacial isostatic adjustment (GIA), the thickness of the crust and lithosphere beneath the glaciated regions are very important as they affect the calculation of past and future sea level changes. Greenland, with its decreasing ice sheet and rapidly retreating outlet glaciers, is one such region where the GIA estimation is important but where the ice sheet itself prevents extensive studies of the crustal and lithospheric thicknesses. Most of the thickness estimates have so far been obtained from seismological studies, which depend on the density of the station networks. We will present newly obtained crustal and lithospheric thickness maps, which are estimated from gravity data using the Parker-Oldenburg inversion algorithm. The gravity dataset will be presented together with all the necessary corrections which have to be applied before the inversion procedure. The obtained thickness maps will be compared to former results of seismological and gravimetric studies and differences will be discussed, also from a geodynamic point of view.

  4. Nanometer properties of oceanic polymetallic nodules and cobalt-rich crusts

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    An ammonia leaching process was utilized to extract Co, Ni and Cu from oceanic polymetallic nodules, whereas an acid leaching process was utilized to extract Co, Ni, Cu, Zn and Mn from cobalt-rich crusts. Both processes produced nanometer materials--ammonia leaching residue and acid leaching residue. A systematic study was conducted on the phase, composition and physicochemistry properties of these residues. The result shows that both residues contain a large amount of nanometer minerals. Ammonia leaching residue mainly consists of rhodochrosite, with the average grain diameter of 17.9 nm; whereas the acid leaching residue mainly consists of well-developed bassanite, with the average grain deameter of 9.5 nm. The bassanite also has a microporous structure, the volume of the pore space is 1.23×10?2 mL/g. Both the ammonia and acid leaching residues have a large specific surface area, and they display a strong adsorption capacity to saturate sodium chloride vapour, N2 and SO2. Both residues have high contents of rare earth elements, and most of these elements exist in the state of ionic adsorption. The content of ∑FeO is high. The P2O5 enrichment is observable in acid leaching residues. The unique composition and nanometer solid properties of the leaching residues displayed their potential value and promised a bright future for their application in the field of environmental protection and materials.

  5. Compositional evolution of the upper continental crust through time, as constrained by ancient glacial diamictites

    Science.gov (United States)

    Gaschnig, Richard M.; Rudnick, Roberta L.; McDonough, William F.; Kaufman, Alan J.; Valley, John W.; Hu, Zhaochu; Gao, Shan; Beck, Michelle L.

    2016-08-01

    The composition of the fine-grained matrix of glacial diamictites from the Mesoarchean, Paleoproterozoic, Neoproterozoic, and Paleozoic, collected from four modern continents, reflects the secular evolution of the average composition of the upper continental crust (UCC). The effects of localized provenance are present in some cases, but distinctive geochemical signatures exist in diamictites of the same age from different localities, suggesting that these are global signatures. Archean UCC, dominated by greenstone basalts and to a lesser extent komatiites, was more mafic, based on major elements and transition metal trace elements. Temporal changes in oxygen isotope ratios, rare earth elements, and high field strength elements indicate that the UCC became more differentiated and that tonalite-trondhjemite-granodiorite suites became less important with time, findings consistent with previous studies. We also document the concentrations of siderophile and chalcophile elements (Ga, Ge, Cd, In, Sn, Sb, W, Tl, Bi) and lithophile Be in the UCC through time, and use the data for the younger diamictites to construct a new estimate of average UCC along with associated uncertainties.

  6. A unique basaltic micrometeorite expands the inventory of solar system planetary crusts.

    Science.gov (United States)

    Gounelle, Matthieu; Chaussidon, Marc; Morbidelli, Alessandro; Barrat, Jean-Alix; Engrand, Cécile; Zolensky, Michael E; McKeegan, Kevin D

    2009-04-28

    Micrometeorites with diameter approximately 100-200 microm dominate the flux of extraterrestrial matter on Earth. The vast majority of micrometeorites are chemically, mineralogically, and isotopically related to carbonaceous chondrites, which amount to only 2.5% of meteorite falls. Here, we report the discovery of the first basaltic micrometeorite (MM40). This micrometeorite is unlike any other basalt known in the solar system as revealed by isotopic data, mineral chemistry, and trace element abundances. The discovery of a new basaltic asteroidal surface expands the solar system inventory of planetary crusts and underlines the importance of micrometeorites for sampling the asteroids' surfaces in a way complementary to meteorites, mainly because they do not suffer dynamical biases as meteorites do. The parent asteroid of MM40 has undergone extensive metamorphism, which ended no earlier than 7.9 Myr after solar system formation. Numerical simulations of dust transport dynamics suggest that MM40 might originate from one of the recently discovered basaltic asteroids that are not members of the Vesta family. The ability to retrieve such a wealth of information from this tiny (a few micrograms) sample is auspicious some years before the launch of a Mars sample return mission.

  7. Crust and upper mantle structure beneath the Pacific Northwest from joint inversions of ambient noise and earthquake data

    Science.gov (United States)

    Wagner, Lara S.; Fouch, Matthew J.; James, David E.; Hanson-Hedgecock, Sara

    2012-12-01

    We perform a joint inversion of phase velocities from both earthquake and ambient noise induced Rayleigh waves to determine shear wave velocity structure in the crust and upper mantle beneath the Pacific Northwest. We focus particularly on the areas affected by mid-Miocene to present volcanic activity. The joint inversion, combined with the high density seismic network of the High Lava Plains seismic experiment and data from the EarthScope Transportable Array, provides outstanding resolution for this area. In Oregon, we find that the pattern of low velocities in the crust and uppermost mantle varies between the High Lava Plains physiographic province and the adjacent northwestern Basin and Range. These patterns may be due to the presence of the Brothers Fault Zone which separates the clockwise rotating northwest Basin and Range from the relatively undeformed areas further north. Further to the east, the Owyhee Plateau, Snake River Plain (SRP) and northeastern Basin and Range are characterized by high crustal velocities, though the depth extent of these fast wave speeds varies by province. Of particular interest is the mid-crustal high velocity sill, previously only identified within the SRP. We show this anomaly extends significantly further south into Utah and Nevada. We suggest that one possible explanation is lateral crustal extrusion due to the emplacement of the high density mafic mid-crustal sill structures within the SRP.

  8. Activity and phylogenetic diversity of sulfate-reducing microorganisms in low-temperature subsurface fluids within the upper oceanic crust

    Directory of Open Access Journals (Sweden)

    Alberto eRobador

    2015-01-01

    Full Text Available The basaltic ocean crust is the largest aquifer system on Earth, yet the rates of biological activity in this environment are unknown. Low-temperature (<100 °C fluid samples were investigated from two borehole observatories in the Juan de Fuca Ridge flank, representing a range of upper oceanic basement thermal and geochemical properties. Microbial sulfate reduction rates were measured in laboratory incubations with 35S-sulfate over a range of temperatures, with microbial activity limited by the availability of organic electron donors. Thermodynamic calculations indicate energetic constraints for metabolism in the higher temperature, more altered and isolated fluids, which together with relatively higher cell-specific sulfate reduction rates reveal increased maintenance requirements, consistent with novel species-level dsrAB phylotypes of thermophilic sulfate-reducing microorganisms. Our estimates suggest that microbially-mediated sulfate reduction may account for the removal of organic matter in fluids within the upper oceanic crust and underscore the potential quantitative impact of microbial processes in deep subsurface marine crustal fluids on marine and global biogeochemical carbon cycling.

  9. Determination of the age of the earth from Kamland measurement of geo-neutrinos

    OpenAIRE

    Mohanty, Subhendra

    2003-01-01

    The low energy component of the antineutrino spectrum observed in the recent Kamland experiment has significant contribution from the radioactive decay of $^{238}U$ and $^{232}Th$ in the crust and mantle of the earth. By taking the ratio of the antineutrino events obeserved in two different energy ranges we can determine the present value $[Th/U]$ independent of the U,Th distribution in the earth. Comparing with the r-process initial value of $[Th/U]_0$ we determine the age of the earth as a ...

  10. Formation of Fast-Spread Ocean Crust : Crystallographic Preferred Orientations From a Reference Lower Crust Section in the Oman Ophiolite

    Science.gov (United States)

    Ildefonse, B.; Mueller, T.; Mock, D.; Koepke, J.

    2016-12-01

    About 20 years ago, two competing models were proposed for the formation of the lower, gabbroic crust at fast-spreading ridges. The lower crust is either formed by downward flow of mushy material from the shallow axial melt lens (gabbro glacier), or by sill intrusions (sheeted sills). To further test these end-member models, we characterized the vertical distribution of Crystallographic Preferred Orientations (CPO) in Wadi Gideah gabbro section (Sumail ophiolite, Sultanate Oman), using the Electron Backscattered Diffraction (EBSD) technique. CPO were measured on 67 gabbro samples, documenting a 5 km thick section, with an average interval of 80 m between samples. EBSD data sets were processed using MTEX, a free Matlab toolbox. Average misorientation in grains (angle between each pixel orientation and mean orientation of the grain) is very low ( 0.25°). This is consistent with magmatic flow in these rocks, and the paucity of crystal-plastic overprint. The strength (J index) of plagioclase CPO increases down-section, with a more pronounced variability in the layered gabbros. For clinopyroxene, the difference between upper (foliated) and lower (layered) gabbros is stronger, with low J in upper gabbros, and higher and more variable J in lower gabbros. In upper gabbros the symmetry of plagioclase and clinopyroxene CPO progressively evolves downward to progressively more oblate. Continuing down-section, the trend reverses, with progressively more prolate CPO in lower gabbros. The crystallographic fabric variability in the lower crust section calls for distinct formation mechanisms in the upper and lower gabbros. It is consistent with a hybrid model for crustal formation (Boudier et al., 1996, doi:10.1016/0012-821X(96)00167-7). The genesis of the upper foliated gabbro can be at least partly explained by the gabbro glacier model, while the continuous emplacement of sheeted sills at various depths is a more plausible model for the lower layered gabbro section.

  11. Magnetic Fields Induced in the Solid Earth and Oceans

    DEFF Research Database (Denmark)

    Kuvshinov, Alexei; Olsen, Nils

    Electromagnetic induction in the Earth's interior is an important contributor to the near-Earth magnetic field. Oceans play a special role in the induction, due to their relatively high conductance of large lateral variability. Electric currents that generate secondary magnetic fields are induced...... in the oceans by two different sources: by time varying external magnetic fields, and by motion of the conducting ocean water through the Earth's main magnetic field. Significant progress in the accurate and detailed prediction of magnetic fields induced by these sources has been achieved during the last years......, utilizing realistic 3-D conductivity models of the oceans, crust and mantle. In addition to these improvements in the prediction of 3-D induction effects, much attention has been paid to identifying magnetic signals of oceanic origin in observatory and satellite data. During the talk we will present...

  12. A New Basis of Geoscience: Whole-Earth Decompression Dynamics

    CERN Document Server

    Herndon, J Marvin

    2013-01-01

    Neither plate tectonics nor Earth expansion theory is sufficient to provide a basis for understanding geoscience. Each theory is incomplete and possesses problematic elements, but both have served as stepping stones to a more fundamental and inclusive geoscience theory that I call Whole-Earth Decompression Dynamics (WEDD). WEDD begins with and is the consequence of our planet's early formation as a Jupiter-like gas giant and permits deduction of:(1) Earth's internal composition, structure, and highly-reduced oxidation state; (2) Core formation without whole-planet melting; (3) Powerful new internal energy sources - proto-planetary energy of compression and georeactor nuclear fission energy; (4) Georeactor geomagnetic field generation; (5) Mechanism for heat emplacement at the base of the crust resulting in the crustal geothermal gradient; (6) Decompression driven geodynamics that accounts for the myriad of observations attributed to plate tectonics without requiring physically-impossible mantle convection, an...

  13. The earth as a planet - Paradigms and paradoxes

    Science.gov (United States)

    Anderson, D. L.

    1984-01-01

    The independent growth of the various branches of the earth sciences in the past two decades has led to a divergence of geophysical, geochemical, geological, and planetological models for the composition and evolution of a terrestrial planet. Evidence for differentiation and volcanism on small planets and a magma ocean on the moon contrasts with hypotheses for a mostly primitive, still undifferentiated, and homogeneous terrestrial mantle. In comparison with the moon, the earth has an extraordinarily thin crust. The geoid, which should reflect convection in the mantle, is apparently unrelated to the current distribution of continents and oceanic ridges. If the earth is deformable, the whole mantle should wander relative to the axis of rotation, but the implications of this are seldom discussed. The proposal of a mantle rich in olivine violates expectations based on evidence from extraterrestrial sources. These and other paradoxes force a reexamination of some long-held assumptions.

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

    Science.gov (United States)

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

    2016-04-01

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

  15. Ultramafic Terranes and Associated Springs as Analogs for Mars and Early Earth

    Science.gov (United States)

    Blake, David; Schulte, Mitch; Cullings, Ken; DeVincezi, D. (Technical Monitor)

    2002-01-01

    Putative extinct or extant Martian organisms, like their terrestrial counterparts, must adopt metabolic strategies based on the environments in which they live. In order for organisms to derive metabolic energy from the natural environment (Martian or terrestrial), a state of thermodynamic disequilibrium must exist. The most widespread environment of chemical disequilibrium on present-day Earth results from the interaction of mafic rocks of the ocean crust with liquid water. Such environments were even more pervasive and important on the Archean Earth due to increased geothermal heat flow and the absence of widespread continental crust formation. The composition of the lower crust and upper mantle of the Earth is essentially the-same as that of Mars, and the early histories of these two planets are similar. It follows that a knowledge of the mineralogy, water-rock chemistry and microbial ecology of Earth's oceanic crust could be of great value in devising a search strategy for evidence of past or present life on Mars. In some tectonic regimes, cross-sections of lower oceanic crust and upper mantle are exposed on land as so-called "ophiolite suites." Such is the case in the state of California (USA) as a result of its location adjacent to active plate margins. These mafic and ultramafic rocks contain numerous springs that offer an easily accessible field laboratory for studying water/rock interactions and the microbial communities that are supported by the resulting geochemical energy. A preliminary screen of Archaean biodiversity was conducted in a cold spring located in a presently serpentinizing ultramafic terrane. PCR and phylogenetic analysis of partial 16s rRNA, sequences were performed on water and sediment samples. Archaea of recent phylogenetic origin were detected with sequences nearly identical to those of organisms living in ultra-high pH lakes of Africa.

  16. Outer crust of a cold non-accreting magnetar

    CERN Document Server

    Basilico, D; Roca-Maza, X; Colò, G

    2015-01-01

    The outer crust structure and composition of a cold, non-accreting magnetar is studied. We model the outer crust to be made of fully equilibrated matter where ionized nuclei form a Coulomb crystal embedded in an electron gas. The main effects of the strong magnetic field are those of quantizing the electron motion in Landau levels and of modifying the nuclear single particle levels producing, on average, an increased binding of nucleons in nuclei present in the Coulomb lattice. The effect of an homogeneous and constant magnetic field on nuclear masses has been predicted by using a covariant density functional, in which induced currents and axial deformation due to the presence of a magnetic field that breaks time-reversal symmetry have been included self-consistently in the nucleon and meson equations of motion. Although not yet observed, for $B\\gtrsim 10^{16}$G both effects contribute to produce different compositions and to enlarge the range of pressures typically present in common neutron stars. Specifical...

  17. Magnetar activity mediated by plastic deformations of neutron star crust

    CERN Document Server

    Lyutikov, Maxim

    2014-01-01

    We advance a "Solar flare" model of magnetar activity, whereas a slow evolution of the magnetic field in the upper crust, driven by electron MHD (EMHD) flows, twists the external magnetic flux tubes, producing persistent emission, bursts and flares. At the same time the neutron star crust plastically relieves the imposed magnetic field stress, limiting the strain $ \\epsilon_t $ to values well below the critical strain $ \\epsilon_{crit}$ of a brittle fracture, $ \\epsilon_t \\sim 10^{-2}\\epsilon_{crit} $. Magnetar-like behavior, occurring near the magnetic equator, takes place in all neutron stars, but to a different extent. The persistent luminosity is proportional to cubic power of the magnetic field (at a given age), and hence is hardly observable in most rotationally powered neutron stars. Giant flares can occur only if the magnetic field exceeds some threshold value, while smaller bursts and flares may take place in relatively small magnetic fields. Bursts and flares are magnetospheric reconnection events t...

  18. Biological soil crusts as soil stabilizers: Chapter 16

    Science.gov (United States)

    Belnap, Jayne; Buedel, Burkhard; Weber, Bettina; Buedel, Burkhard; Belnap, Jayne

    2016-01-01

    Soil erosion is of particular concern in dryland regions, as the sparse cover of vascular plants results in large interspaces unprotected from the erosive forces of wind and water. Thus, most of these soil surfaces are stabilized by physical or biological soil crusts. However, as drylands are extensively used by humans and their animals, these crusts are often disturbed, compromising their stabilizing abilities. As a result, approximately 17.5% of the global terrestrial lands are currently being degraded by wind and water erosion. All components of biocrusts stabilize soils, including green algae, cyanobacteria, fungi, lichens, and bryophytes, and as the biomass of these organisms increases, so does soil stability. In addition, as lichens and bryophytes live atop the soil surface, they provide added protection from raindrop impact that cyanobacteria and fungi, living within the soil, cannot. Much research is still needed to determine the relative ability of individual species and suites of species to stabilize soils. We also need a better understanding of why some individuals or combination of species are better than others, especially as these organisms become more frequently used in restoration efforts.

  19. A Seafloor Microbial Biome Hosted within Incipient Ferromanganese Crusts

    Energy Technology Data Exchange (ETDEWEB)

    Templeton, Alexis S.; Knowles, A. S.; Eldridge, D. L.; Arey, Bruce W.; Dohnalkova, Alice; Webb, Samuel M.; Bailey, B. E.; Tebo, Bradley M.; Staudigel, Hubert

    2009-11-15

    Unsedimented volcanic rocks exposed on the seafloor at ridge systems and Seamounts host complex, abundant and diverse microbial communities that are relatively cosmopolitan in distribution (Lysnes, Thorseth et al. 2004; Mason, Stingl et al. 2007; Santelli, Orcutt et al. 2008). The most commonly held hypothesis is that the energy released by the hydration, dissolution and oxidative alteration of volcanic glasses in seawater drives the formation of an ocean crust biosphere (Thorseth, Furnes et al. 1992; Fisk, Giovannoni et al. 1998; Furnes and Staudigel 1999). The combined thermodynamically favorable weathering reactions could theoretically support anywhere from 105 to 109 cells/gram of rock depending upon the metabolisms utilized and cellular growth rates and turnover (Bach and Edwards 2003; Santelli, Orcutt et al. 2008). Yet microbially-mediated basalt alteration and energy conservation has not been directly demonstrated on the seafloor. By using synchrotron-based x-ray microprobe mapping, x-ray absorption spectroscopy and high-resolution scanning and transmission electron microscopy observations of young volcanic glasses recovered from the outer flanks of Loihi Seamount, we intended to identify the initial rates and mechanisms of microbial basalt colonization and bioalteration. Instead, here we show that microbial biofilms are intimately associated with ferromanganese crusts precipitating onto basalt surfaces from cold seawater. Thus we hypothesize that microbial communities colonizing seafloor rocks are established and sustained by external inputs of potential energy sources, such as dissolved and particulate Fe(II), Mn(II) and organic matter, rather than rock dissolution.

  20. Applicability of salt reduction strategies in pizza crust.

    Science.gov (United States)

    Mueller, Eva; Koehler, Peter; Scherf, Katharina Anne

    2016-02-01

    In an effort to reduce population-wide sodium intake from processed foods, due to major health concerns, several different strategies for sodium reduction in pizza crust without any topping were evaluated by sensory analyses. It was possible to reduce sodium by 10% in one single step or to replace 30% of NaCl by KCl without a noticeable loss of salty taste. The late addition of coarse-grained NaCl (crystal size: 0.4-1.4 mm) to pizza dough led to an enhancement of saltiness through taste contrast and an accelerated sodium delivery measured in the mouth and in a model mastication simulator. Likewise, the application of an aqueous salt solution to one side of the pizza crust led to an enhancement of saltiness perception through faster sodium availability, leading to a greater contrast in sodium concentration. Each of these two strategies allowed a sodium reduction of up to 25% while maintaining taste quality. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Material Properties of Marine Hydrogenous Ferromanganese Crust and Its Performance in Desulfurization

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Marine hydrogenous ferromanganese crust, an important metal resource in the future, has significant potential in various applications as a type of natural nano-structured material. By employing scanning electronic microscopy, nitrogen adsorption-desorption isotherm measurement, Xray fluorescence spectrometer and X-ray diffraction methods, the micro-structure, surface properties and chemical composition of several plate-like ferromanganese crusts sampled from the northwestern Pacific were investigated comprehensively. Although obvious differences were observed from different layers, the crust is a typical porous material with high specific surface area, unique pore structure and abundant transition elements. Furthermore, the performance of natural crust in desulfurization process was preliminarily tested in laboratory experiments. The sulfur capacities of the crust are 13.1%and 18.1% at room temperature and 350 ℃, respectively. The crust can be used not only as a metal resource, but also as an environmental material.

  2. Prilimary result of temperature distribution and associated thermal stress in crust in Tianshui, China

    Institute of Scientific and Technical Information of China (English)

    LIU Yao-wei; GAO An-tai; SHI Jin; SU He-jun

    2007-01-01

    The heat flow in crust and the thermal stress generated by the flow play a very important role in earthquake occurrence. Different crustal structure has different effect on heat distribution and associated thermal stress. In all of typical seismogenic crustal structure models, including the bulge of Moho surface, the deep-large fault in the mid-lower crust, low-velocity and high-conductive layer in the middle crust, and the typical crustal structure in mid-upper crust, the thermal stress produced by deep heat disturbance may move up to the mid-upper crust. This leads to upper brittle part of crust break and hence, strong earthquakes. This result is constructive in enhancing our understanding of the role of deep heat flow in curst in development of earthquake and its generation, as well as the generation mechanism of the shallow flowing fluid.

  3. EarthKAM

    Data.gov (United States)

    National Aeronautics and Space Administration — Sponsored by NASA, EarthKAM (Earth Knowledge Acquired by Middle School Students) is an educational outreach program allowing middle school students to take pictures...

  4. Earth on the Move.

    Science.gov (United States)

    Naturescope, 1987

    1987-01-01

    Provides background information on the layers of the earth, the relationship between changes on the surface of the earth and its insides, and plate tectonics. Teaching activities are included, with some containing reproducible worksheets and handouts to accompany them. (TW)

  5. NASA Earth Exchange (NEX)

    Data.gov (United States)

    National Aeronautics and Space Administration — The NASA Earth Exchange (NEX) represents a new platform for the Earth science community that provides a mechanism for scientific collaboration and knowledge sharing....

  6. Global Carbon Cycle of the Precambrian Earth

    DEFF Research Database (Denmark)

    Wiewióra, Justyna

    to investigate carbon fluxes between Precambrian Earth’s mantle and crust and to trace the evolution of life in the Eoarchaean oceans. The world’s desire for diamonds gives us a unique opportunity to obtain insight into the nature of metasomatic fluids affecting the subcratonic lithospheric mantle (SCLM) beneath...... derived from surface water. Partitioning of carbon between 13C-rich oxidized and 13C-poor reduced species indicates that life in the early ocean had to be well evolved before 3.8 Ga. Therefore, the Isua ultramafic rocks may be considered as an indirect biomarker for ancient life.......The carbon isotopic composition of distinct Archaean geological records provides information about the global carbon cycle and emergence of life on early Earth. We utilized carbon isotopic records of Greenlandic carbonatites, diamonds, graphites, marbles, metacarbonates and ultramafic rocks...

  7. Evolution of the depleted mantle and growth of the continental crust: improving on the imperfect detrital zircon record

    Science.gov (United States)

    Vervoort, J. D.; Kemp, A. I. S.; Patchett, P. J.

    2012-04-01

    One of the basic tenets of terrestrial geochemistry is that the continental crust has been extracted from the mantle leaving the latter depleted in incompatible elements. Nd and Hf isotopes have long shown that this process has been an essential feature of the Earth throughout its history. There is wide agreement on the general nature of this process, but the details of the isotopic record—and their implications for the depletion of the mantle and the extraction of continental crust—remain debated. Recently, much attention has been given to detrital zircons in both modern and ancient sediments. An advantage of this approach is the integration of the crystallization history of the zircon from the U-Pb chronometer with its Hf isotopic composition, which can provide important information on whether the zircons have been derived from juvenile or reworked crust. One essential requirement in this approach, however, is to unambiguously determine the crystallization ages of the zircons. We suggest that this represents an important—but generally ignored—source of uncertainty in the Hf isotopic record from detrital zircons. The quality filter most often used to assess the integrity of zircon U-Pb systematics is concordance; if a zircon is concordant, it is assumed that the U-Pb age is accurate. A concordance filter is less effective in old zircons, however, because ancient Pb loss, viewed today, parallels concordia. Without the benefit from the geological context of the host rock to the zircons, it is impossible to unambiguously determine it true crystallization age. Ancient Pb loss in zircons produces an apparent age less than the true magmatic age. The initial Hf isotopic composition of these zircons, as a result, will be calculated at the wrong age and will be anomalously low (by ~2.2 epsilon Hf units per 0.1 Ga). Hf model ages, calculated from these parameters, will be artificially old and spurious. The combination of unradiogenic Hf and Hf model ages > U-Pb ages

  8. Crusted Scabies: Presenting as erythroderma in a human immunodeficiency virus-seropositive patient

    Directory of Open Access Journals (Sweden)

    Shruti Kulkarni

    2016-01-01

    Full Text Available Crusted scabies is a rare manifestation of scabies characterized by uncontrolled proliferation of mites in the skin. It is common in patients with sensory neuropathy, mentally retarded persons and in patients who are immunosuppressed. Further, crusted scabies can rarely present as erythroderma (<0.5% cases necessitating a high index of suspicion for its diagnosis. Because of its rare occurrence, we are reporting a case of crusted scabies presenting as erythroderma, in a human immunodeficiency virus seropositive patient.

  9. Oxygen Distribution and Potential Ammonia Oxidation in Floating, Liquid Manure Crusts

    DEFF Research Database (Denmark)

    Nielsen, Daniel Aagren; Nielsen, Lars Peter; Schramm, Andreas;

    2010-01-01

    Floating, organic crusts on liquid manure, stored as a result of animal production, reduce emission of ammonia (NH3) and other volatile compounds during storage. The occurrence of NO2- and NO3- in the crusts indicate the presence of actively metabolizing NH3 oxidizing bacteria (AOB) which may...... microorganisms, including AOB. The microbial activity may thus contribute to a considerable reduction of ammonia emissions from slurry tanks with well-developed crusts....

  10. Evaporative sodium salt crust development and its wind tunnel derived transport dynamics under variable climatic conditions

    Science.gov (United States)

    Nield, Joanna M.; McKenna Neuman, Cheryl; O'Brien, Patrick; Bryant, Robert G.; Wiggs, Giles F. S.

    2016-12-01

    Playas (or ephemeral lakes) can be significant sources of dust, but they are typically covered by salt crusts of variable mineralogy and these introduce uncertainty into dust emission predictions. Despite the importance of crust mineralogy to emission potential, little is known about (i) the effect of short-term changes in temperature and relative humidity on the erodibility of these crusts, and (ii) the influence of crust degradation and mineralogy on wind speed threshold for dust emission. Our understanding of systems where emission is not driven by impacts from saltators is particularly poor. This paper describes a wind tunnel study in which dust emission in the absence of saltating particles was measured for a suite of climatic conditions and salt crust types commonly found on Sua Pan, Botswana. The crusts were found to be non-emissive under climate conditions characteristic of dawn and early morning, as compared to hot and dry daytime conditions when the wind speed threshold for dust emission appears to be highly variable, depending upon salt crust physicochemistry. Significantly, sodium sulphate rich crusts were found to be more emissive than crusts formed from sodium chloride, while degraded versions of both crusts had a lower emission threshold than fresh, continuous crusts. The results from this study are in agreement with in-situ field measurements and confirm that dust emission from salt crusted surfaces can occur without saltation, although the vertical fluxes are orders of magnitude lower (∼10 μg/m/s) than for aeolian systems where entrainment is driven by particle impact.

  11. Impact of Crust Matter on Properties of Neutron Star with Supersoft Symmetry Energy

    Institute of Scientific and Technical Information of China (English)

    HUANG Qi-Zhi; WEN De-Hua

    2011-01-01

    By employing three typical equations of states (EOSs) of the crust matter, the effect of the crust on the structure and properties are investigated, where the core matter is described by the MDIxl model and the non-Newtonian gravity (described by the Yukawa contribution) is considered.It is shown that the EOSs of the crust matter have a notable effect on the mass-radius relation and the moment of inertia.

  12. Impact of neutron star crust on gravizational waves from the axial w-modes

    Institute of Scientific and Technical Information of China (English)

    Wen De-Hua; Fu Hong-Yang; Chen Wei

    2011-01-01

    The imprints of the neutron star crust on the gravitational waves emitted from the axial w-modes are investigated by adopting two typical equations of state (EOSs) of the crust matter and two representative EOSs of the core matter. It is shown that there is a significant effect of the crust EOSs on the gravitational waves from the axial w-mode oscillation for a stiff core EOS.

  13. Evidence for mechanical coupling and strong Indian lower crust beneath southern Tibet

    OpenAIRE

    Copley, Alex; Avouac, Jean-Philippe; Wernicke, Brian P.

    2011-01-01

    How surface deformation within mountain ranges relates to tectonic processes at depth is not well understood. The upper crust of the Tibetan Plateau is generally thought to be poorly coupled to the underthrusting Indian crust because of an intervening low-viscosity channel. Here, however, we show that the contrast in tectonic regime between primarily strike-slip faulting in northern Tibet and dominantly normal faulting in southern Tibet requires mechanical coupling between the upper crust of ...

  14. Deep structure of the central Lesser Antilles Island Arc : relevance for the formation of continental crust

    OpenAIRE

    H. Kopp; Weinzierl, W.; Becel, A.; Charvis, Philippe; Evain, M.; Flueh, E. R.; Gailler, A.; Galve, A.; Hirn, A.; Kandilarov, A.; D. Klaeschen; M. Laigle; Papenberg, C.; L. Planert; Roux, E.

    2011-01-01

    Oceanic island arcs are sites of high magma production and contribute to the formation of continental crust. Geophysical studies may provide information on the configuration and composition of island arc crust, however, to date only few seismic profiles exist across active island arcs, limiting our knowledge on the deep structure and processes related to the production of arc crust. We acquired active-source wide-angle seismic data crossing the central Lesser Antilles island arc north of Domi...

  15. Oxygen Distribution and Potential Ammonia Oxidation in Floating, Liquid Manure Crusts

    DEFF Research Database (Denmark)

    Nielsen, Daniel Aagren; Nielsen, Lars Peter; Schramm, Andreas

    2010-01-01

    Floating, organic crusts on liquid manure, stored as a result of animal production, reduce emission of ammonia (NH3) and other volatile compounds during storage. The occurrence of NO2- and NO3- in the crusts indicate the presence of actively metabolizing NH3 oxidizing bacteria (AOB) which may...... microorganisms, including AOB. The microbial activity may thus contribute to a considerable reduction of ammonia emissions from slurry tanks with well-developed crusts....

  16. Fractal characteristics of resource quantity of cobalt crusts and seamount topography, the West Pacific

    Institute of Scientific and Technical Information of China (English)

    ZHANG Weiyan; ZHANG Fuyuan; YANG Kehong; HU Guangdao; YANG Shengxiong; CHENG Yongshou; ZHAO Guojun

    2007-01-01

    This paper presents the fractal distribution of topography of seamounts from the West Pacific and the resource quantity of cobalt crust therein. The cobalt resource quantity has three to four variable fractal dimensions, corre- sponding to the distinct slopes and water depths of the sea- mount. The multiple fractal property of resource quantity may have resulted from various factors, such as types and components of cobalt crusts and ages of oceanic crusts host- ing the seamounts. Individual seamounts display complex topography and quantity of cobalt crust, both in the same and different regions.

  17. Ecological and environmental explanation of microbiotic crusts on sand dune scales in the Gurbantonggut Desert, Xinjiang

    Institute of Scientific and Technical Information of China (English)

    CHEN Yaning; LI Weihong; ZHOU Zhibing; LIU Jiazhen

    2005-01-01

    Results obtained from the field investigation and the analysis in laboratory show that many species of microbiotic crusts of lichens, mosses and algae develop extensively in the Gurbantonggut Desert, Xinjiang. The formation, species and distribution are closely related to the environmental conditions at the different positions of sand dunes. The animalcule crusts develop mainly on the mobile or semi-mobile sand surface of dune tops, the alga crusts develop mainly at the upper to middle parts of dune slopes, the lichen crusts develop at middle and lower parts of dune slopes, and the moss crusts are mainly distributed at the lower part of dune slopes and the interdune lowlands. The species, thickness and developing degree of microbiotic crusts increase from the upper part to the middle and lower parts of dune slopes and the interdune lowlands, and an obvious contrast between the microbiotic crusts and the different species of plant communities forms. The development and differentiation of microbiotic crusts at the different positions of dunes are the ecological appearance and the natural selection of synthetic adaptability of the different microbiotic crust species to the local environmental conditions, and are closely related to the ecological conditions, such as the physiochemical properties of soils and stability of topsoil texture.

  18. Influence of the symmetry energy on nuclear pasta in neutron star crusts

    CERN Document Server

    Bao, S S

    2014-01-01

    We investigate the effects of the symmetry energy on nuclear pasta phases and the crust-core transition in neutron stars. We employ the relativistic mean-field approach and the coexisting phases method to study the properties of pasta phases presented in the inner crust of neutron stars. It is found that the slope of the nuclear symmetry energy at saturation density plays an important role in the crust-core transition and pasta phase properties. The correlation between the symmetry energy slope and the crust-core transition density obtained in this study is consistent with those obtained by other methods.

  19. Methanotrophs, methanogens, and microbial community structure in livestock slurry surface crusts

    DEFF Research Database (Denmark)

    Duan, Yun-Feng (Kevin); Abu Al-Soud, Waleed; Brejnrod, Asker Daniel

    2014-01-01

    , dominated the MOB community, whereas Methanocorpusculum was the predominant methanogen. Higher numbers of OTUs representing Type I than Type II MOB were found in all crusts. Potential CH4 oxidation rates were determined by incubations of crusts with CH4, and CH4 oxidization was observed in cattle......, but not in swine slurry crusts. Conclusions: Slurry surface crusts harbor a diverse microbial community. Type I MOB are more diverse and abundant than Type II MOB in this environment. The distinct CH4 oxidation rates could be related to microbial compositions. Significance and Impact of Study: This study...

  20. Note to Energy Source of Tsunami Earthquake on the Planet Earth

    Science.gov (United States)

    Nakamura, S.

    2012-04-01

    Note to Energy Source of Tsunami Earthquake on the Planet Earth Shigehisa Nakamura Kyoto University, Japan This note concerns to an energyy source of tsunami earthquake. In the case of the earthquake on 11 March 2011, a satellite monitoring by the Geographic Survey Institute informed some spcific pattern of the earth surface displacements just around tothe epicenter of the interested earthquake. The monitoring pattern shows that the pattern of the earth surface displacements must be understood well when the earth surface as a part of the spherical earth crusts with a physical property of a visco-plastic material rather than with a solid plate consisted by rigid material made by the products of the magma in the planet earth. This means that the pattern was appared in a short time of only several minutes, say, two or three munutes after the seismic shock was happened. The pattern of the displacement shows as if it was for a pattern of a visco-plastic fluid flowing to the pit hole force for the at the epicenter out of a conduit of the magma in order to return to the mother magma flow under the spherical crust of the planet earth. This pattern is raising us to find an updateddd model after an advanced reserarch as soon as possible in order to realize what should be a reasonable energy source to see the tsunami earthquake.

  1. New Tracers of Gas Migration in the Continental Crust

    Energy Technology Data Exchange (ETDEWEB)

    Kurz, Mark D. [Woods Hole Oceanographic Inst., MA (United States)

    2015-11-01

    Noble gases are exceptional tracers in continental settings due to the remarkable isotopic variability between the mantle, crust, and atmosphere, and because they are inert. Due to systematic variability in physical properties, such as diffusion, solubility, and production rates, the combination of helium, neon, and argon provides unique but under-utilized indices of gas migration. Existing noble gas data sets are dominated by measurements of gas and fluid phases from gas wells, ground waters and hot springs. There are very few noble gas measurements from the solid continental crust itself, which means that this important reservoir is poorly characterized. The central goal of this project was to enhance understanding of gas distribution and migration in the continental crust using new measurements of noble gases in whole rocks and minerals from existing continental drill cores, with an emphasis on helium, neon, argon. We carried out whole-rock and mineral-separate noble gas measurements on Precambrian basement samples from the Texas Panhandle. The Texas Panhandle gas field is the southern limb of the giant Hugoton-Panhandle oil and gas field; it has high helium contents (up to ~ 2 %) and 3He/4He of 0.21 (± 0.03) Ra. Because the total amount of helium in the Panhandle gas field is relatively well known, crustal isotopic data and mass balance calculations can be used to constrain the ultimate source rocks, and hence the helium migration paths. The new 3He/4He data range from 0.03 to 0.11 Ra (total), all of which are lower than the gas field values. There is internal isotopic heterogeneity in helium, neon, and argon, within all the samples; crushing extractions yield less radiogenic values than melting, demonstrating that fluid inclusions preserve less radiogenic gases. The new data suggest that the Precambrian basement has lost significant amounts of helium, and shows the importance of measuring helium with neon and argon. The 4He/40Ar values are particularly useful

  2. Composition and origin of Archean lower crust, Northern Tanzania

    Science.gov (United States)

    Mansur, A. T.; Manya, S.; Rudnick, R.

    2008-12-01

    Granulite-facies xenoliths from tuff cones erupted on the margin of the Tanzanian craton and within the adjacent Mozambique belt in northern Tanzania offer an opportunity to assess the role of lower crustal processes in the tectonic evolution of these two terranes. Both terranes are Archean, but record very different histories, starting in the Proterozoic and continuing today. Whereas the craton experienced little metamorphism or igneous activity following its stabilization around 2.8 Ga, Archean rocks of the Mozambique belt in the study area experienced at least one episode of high-grade metamorphism during the East African orogeny (ca. 640 Ma). Today, the East African rift exists at the contact between the Mozambique belt and the craton, implying a fundamental lithospheric weakness at this boundary. Granulite xenoliths come from Labait, on the craton margin, and Lashaine and Naibor Soito in the metamorphic belt. Most xenoliths are mafic and all are igneous in origin. Cratonic xenoliths (pl- opx±cpx±gt±hbl) are primarily anhydrous two-pyroxene granulites that likely originated as crystallized high-Ni, Archean basaltic melts. Xenoliths from the Mozambique belt are dominated by mafic granulites (pl-cpx-gt±opx) at Lashaine and banded, mafic to intermediate granulites at Naibor Soito. Positive Sr and Eu anomalies imply that the Lashaine granulites originated as plagioclase cumulates. The wide range in SiO2 (47-65 wt%) and correlation of Ni-MgO in the Naibor Soito xenoliths suggests they may have originated as igneous rocks that subsequently underwent partial melting to form the mafic (pl- opx±cpx±gt±hbl±bt) and felsic bands (pl-qtz-opx±kfs). U-Pb zircon ages for xenoliths from both terranes are Archean, as are most TDM ages, though younger TDM ages are seen in some Lashaine samples that were contaminated by rift magma. High pressures (up to 2.7GPa) are recorded by the Mozambique belt xenoliths, suggesting equilibration in thickened crust during the East

  3. Capturing Near Earth Objects

    OpenAIRE

    Baoyin, Hexi; CHEN Yang; Li, Junfeng

    2011-01-01

    Recently, Near Earth Objects (NEOs) have been attracting great attention, and thousands of NEOs have been found to date. This paper examines the NEOs' orbital dynamics using the framework of an accurate solar system model and a Sun-Earth-NEO three-body system when the NEOs are close to Earth to search for NEOs with low-energy orbits. It is possible for such an NEO to be temporarily captured by Earth; its orbit would thereby be changed and it would become an Earth-orbiting object after a small...

  4. Investigation of the earth's crustal structure using earthquake and deep seismic sounding data obtained for the Carpathians

    Science.gov (United States)

    Kondorskaya, N. V.; Slavina, L. B.; Pivovarova, N. B.; Sollogub, V. B.; Chekunov, A. V.; Sagalova, E. A.; Shchukin, Y. K.

    1981-11-01

    The joint analysis performed for the Carpathian region from seismological data (three-dimensional fields of velocities, areas of concentration of earthquake foci in the Vrancea focal zone) and interpretation of DSS data and those of other geophysical fields have permitted to obtain new evidence for the earth's crust and mantle structure in this region.

  5. Tectonics, Climate and Earth's highest peaks

    Science.gov (United States)

    Robl, Jörg; Prasicek, Günther; Hergarten, Stefan

    2016-04-01

    Prominent peaks characterized by high relief and steep slopes are among the most spectacular morphological features on Earth. In collisional orogens they result from the interplay of tectonically driven crustal thickening and climatically induced destruction of overthickened crust by erosional surface processes. The glacial buzz-saw hypothesis proposes a superior status of climate in limiting mountain relief and peak altitude due to glacial erosion. It implies that peak altitude declines with duration of glacial occupation, i.e., towards high latitudes. This is in strong contrast with high peaks existing in high latitude mountain ranges (e.g. Mt. St. Elias range) and the idea of peak uplift due to isostatic compensation of spatially variable erosional unloading an over-thickened orogenic crust. In this study we investigate landscape dissection, crustal thickness and vertical strain rates in tectonically active mountain ranges to evaluate the influence of erosion on (latitudinal) variations in peak altitude. We analyze the spatial distribution of serval thousand prominent peaks on Earth extracted from the global ETOPO1 digital elevation model with a novel numerical tool. We compare this dataset to crustal thickness, thickening rate (vertical strain rate) and mean elevation. We use the ratios of mean elevation to peak elevation (landscape dissection) and peak elevation to crustal thickness (long-term impact of erosion on crustal thickness) as indicators for the influence of erosional surface processes on peak uplift and the vertical strain rate as a proxy for the mechanical state of the orogen. Our analysis reveals that crustal thickness and peak elevation correlate well in orogens that have reached a mechanically limited state (vertical strain rate near zero) where plate convergence is already balanced by lateral extrusion and gravitational collapse and plateaus are formed. On the Tibetan Plateau crustal thickness serves to predict peak elevation up to an altitude

  6. Modeling Continental Growth and Mantle Hydration in Earth's Evolution and the Impact of Life

    Science.gov (United States)

    Höning, Dennis; Spohn, Tilman

    2016-04-01

    The evolution of planets with plate tectonics is significantly affected by several intertwined feedback cycles. On Earth, interactions between atmosphere, hydrosphere, biosphere, crust, and interior determine its present day state. We here focus on the feedback cycles including the evolutions of mantle water budget and continental crust, and investigate possible effects of the Earth's biosphere. The first feedback loop includes cycling of water into the mantle at subduction zones and outgassing at volcanic chains and mid-ocean ridges. Water is known to reduce the viscosity of mantle rock, and therefore the speed of mantle convection and plate subduction will increase with the water concentration, eventually enhancing the rates of mantle water regassing and outgassing. A second feedback loop includes the production and erosion of continental crust. Continents are formed above subduction zones, whose total length is determined by the total size of the continents. Furthermore, the total surface area of continental crust determines the amount of eroded sediments per unit time. Subducted sediments affect processes in subduction zones, eventually enhancing the production rate of new continental crust. Both feedback loops affect each other: As a wet mantle increases the speed of subduction, continental production also speeds up. On the other hand, the total length of subduction zones and the rate at which sediments are subducted (both being functions of continental coverage) affect the rate of mantle water regassing. We here present a model that includes both cycles and show how the system develops stable and unstable fixed points in a plane defined by mantle water concentration and surface of continents. We couple these feedback cycles to a parameterized thermal evolution model that reproduces present day observations. We show how Earth has been affected by these feedback cycles during its evolution, and argue that Earth's present day state regarding its mantle water

  7. Magnetic field decay with Hall drift in neutron star crusts

    CERN Document Server

    Kojima, Yasufumi

    2012-01-01

    The dynamics of magnetic field decay with Hall drift is investigated. Assuming that axisymmetric magnetic fields are located in a spherical crust with uniform conductivity and electron number density, long-term evolution is calculated up to Ohmic dissipation. The nonlinear coupling between poloidal and toroidal components is explored in terms of their energies and helicity. Nonlinear oscillation by the drift in strongly magnetized regimes is clear only around the equipartition between two components. Significant energy is transferred to the poloidal component when the toroidal component initially dominates. However, the reverse is not true. Once the toroidal field is less dominant, it quickly decouples due to a larger damping rate. The polar field at the surface is highly distorted from the initial dipole during the Hall drift timescale, but returns to the initial dipole in a longer dissipation timescale, since it is the least damped one.

  8. Dating low-temperature alteration of the upper oceanic crust

    Science.gov (United States)

    Coogan, L. A.; Hinton, R. W.; Gillis, K. M.; Dosso, S. E.

    2011-12-01

    Off-axis hydrothermal systems lead to extensive chemical exchange between the oceans and upper oceanic crust but it is unclear when this exchange occurs. We address this using a new dating approach and via the re-evaluation of existing data that contain age information. We have developed a method to directly date adularia, a common alkali-rich phase in old oceanic crust, using the 40K to 40Ca radiogenic decay system. In situ analysis, using the Cameca 1270 ion microprobe at the University of Edinburgh, allows small, replacive, secondary mineral grains to be analyzed. In comparison to previous radiogenic dating of low-temperature secondary minerals, using Rb-Sr and K-Ar approaches on mineral separates, this approach has the advantages that: (i) analysis is not limited to large, void filling, grains; (ii) the initial isotopic ratio is well constrained; (iii) contamination and phase heterogeneity are minimized; and (iv) the daughter isotope is relatively immobile. However, the requirement to analyse doubly charged ions, to reduce molecular interferences and suppress the presence of 40K on 40Ca, leads to low count rates [1]; e.g. single spot ages have uncertainties of 10's of millions of years. Combining all analyses for a given sample gives best fitting instantaneous precipitation "ages" of 102 and 70 Myr for DSDP Holes 417A and 543A (versus crustal ages of 120 and 80 Myr). The scatter in the data are consistent with adularia precipitation over >30 Myr. The timing of carbonate precipitation in the upper oceanic crust can be constrained from comparison of their 87Sr/86Sr to the seawater Sr-isotope curve if the proportion of basaltic Sr in the fluid can be constrained. Modeling such data from 12 drill cores shows that they are best fit by a model in which >90% of carbonate precipitation occurs over ≤20 Myr after crustal formation [2]. Evaluation of published Rb-Sr "isochron" data [3,4] shows that these data can be explained in different ways. The "isochron

  9. Superfluid hydrodynamics in the inner crust of neutron stars

    CERN Document Server

    Martin, Noël

    2016-01-01

    The inner crust of neutron stars is supposed to be inhomogeneous and composed of dense structures (clusters) that are immersed in a dilute gas of unbound neutrons. Here we consider spherical clusters forming a BCC crystal and cylindrical rods arranged in a hexagonal lattice. We study the relative motion of these dense structures and the neutron gas using superfluid hydrodynamics. Within this approach, which relies on the assumption that Cooper pairs are small compared to the crystalline structures, we find that the entrainment of neutrons by the clusters is very weak since neutrons of the gas can flow through the clusters. Consequently, we obtain a low effective mass of the clusters and a superfluid density that is even higher than the density of unbound neutrons. Consequences for the constraints from glitch observations are discussed.

  10. Superfluid hydrodynamics in the inner crust of neutron stars

    Science.gov (United States)

    Martin, Noël; Urban, Michael

    2016-12-01

    The inner crust of neutron stars is supposed to be inhomogeneous and composed of dense structures (clusters) that are immersed in a dilute gas of unbound neutrons. Here we consider spherical clusters forming a body-centered cubic (BCC) crystal and cylindrical rods arranged in a hexagonal lattice. We study the relative motion of these dense structures and the neutron gas using superfluid hydrodynamics. Within this approach, which relies on the assumption that Cooper pairs are small compared to the crystalline structures, we find that the entrainment of neutrons by the clusters is very weak since neutrons of the gas can flow through the clusters. Consequently, we obtain a low effective mass of the clusters and a superfluid density that is even higher than the density of unbound neutrons. Consequences for the constraints from glitch observations are discussed.

  11. Brane-world dark stars with solid crust

    CERN Document Server

    Ovalle, Jorge; Casadio, Roberto

    2014-01-01

    The minimal geometric deformation approach is employed to show the existence of brane-world stellar distributions with vacuum Schwarzschild exterior, thus without energy leaking from the exterior of the brane-world star into the extra dimension. The interior satisfies all elementary criteria of physical acceptability for a stellar solution, namely, it is regular at the origin, the pressure and density are positive and decrease monotonically with increasing radius, finally all energy conditions are fulfilled. A very thin solid crust with negative radial pressure separates the interior from the exterior, having a thickness $\\Delta $ inversely proportional to both the brane tension $\\sigma $ and the radius $R$ of the star, i.e. $\\Delta ^{-1}\\sim R\\,\\sigma $. This brane-world star with Schwarzschild exterior would appear dark to a distant observer and be fully compatible with the stringent constraints imposed on stellar parameters by observations of gravitational lensing, orbital evolutions or properties of accre...

  12. Hydromechanical Modeling of Fluid Flow in the Lower Crust

    Science.gov (United States)

    Connolly, J.

    2011-12-01

    The lower crust lies within an ambiguous rheological regime between the brittle upper crust and ductile sub-lithospheric mantle. This ambiguity has allowed two schools of thought to develop concerning the nature of fluid flow in the lower crust. The classical school holds that lower crustal rocks are inviscid and that any fluid generated by metamorphic devolatilization is squeezed out of rocks as rapidly as it is produced. According to this school, permeability is a dynamic property and fluid flow is upward. In contrast, the modern school uses concepts from upper crustal hydrology that presume implicitly, if not explicitly, that rocks are rigid or, at most, brittle. For the modern school, the details of crustal permeability determine fluid flow and as these details are poorly known almost anything is possible. Reality, to the extent that it is reflected by inference from field studies, offers some support to both schools. In particular, evidence of significant lateral and channelized fluid flow are consistent with flow in rigid media, while evidence for short (104 - 105 y) grain-scale fluid-rock interaction during much longer metamorphic events, suggests that reaction-generated grain-scale permeability is sealed rapidly by compaction; a phenomenon that is also essential to prevent extensive retrograde metamorphism. These observations provide a compelling argument for recognizing in conceptual models of lower crustal fluid flow that rocks are neither inviscid nor rigid, but compact by viscous mechanisms on a finite time-scale. This presentation will review the principle consequences of, and obstacles to, incorporating compaction in such models. The role of viscous compaction in the lower crust is extraordinarily uncertain, but ignoring this uncertainty in models of lower crustal fluid flow does not make the models any more certain. Models inevitably invoke an initial steady state hydraulic regime. This initial steady state is critical to model outcomes because it

  13. Physical processes in the growth of the continental crust

    Science.gov (United States)

    Schubert, G.

    1988-01-01

    Major mechanisms of crustal addition are volcanism and plutonism at plate boundaries and within plate interiors. One approach to deciding if island arc magmatism dominated ancient crustal growth is to assess the rate at which the process has operated in the recent past. The localized addition rates were found to be comparable to present day global rates. One physical observable that was used to constrain models of crustal growth is sea level. A simple physical model was developed to explore the consequences of constant freeboard (the height of the continents above sea level). Global geoid and sea floor topography data were used to identify and study oceanic plateaus and swells that have either continental crustal roots or anomalously thick ocean crusts.

  14. A ~400 ka supra-Milankovitch cycle in the Na, Mg, Pb, Ni, and Co records of a ferromanganese crust from the Vityaz fracture zone, central Indian ridge

    Directory of Open Access Journals (Sweden)

    R. Banerjee

    2010-07-01

    Full Text Available A ~400 ka (kilo years supra-Milankovitch cycle, recorded in the sodium, magnesium, lead, nickel and cobalt contents of a 32 mm thick ferromanganese crust from Vityaz fracture zone, central Indian ridge is reported here. To arrive at the geological ages, we used both 230Thexeccs and Co-chronometric datings. The correlation coefficient between the 230Thexeccs based dates and Co-chronometric dates for the top 0–8 mm is very high (r=0.9734, at 99.9% significance. The cobalt chronometric age for the bottom most oxide layer of this crust is computed as 3.5 Ma. Red-fit and multi-taper spectral analyses of time series data revealed the existence of the significant ~400 ka cycle, representing the changes in the hydrogeochemical conditions in the ocean due to the Earth's orbital eccentricity related summer insolation at the equator. This is the first report of such cycle from a hydrogenous ferromanganese crust from equatorial Indian ocean.

  15. Thermal history of the Earth and its petrological expression

    Science.gov (United States)

    Herzberg, Claude; Condie, Kent; Korenaga, Jun

    2010-03-01

    Non-arc basalts of Archean and Proterozoic age have model primary magmas that exhibit mantle potential temperatures TP that increase from 1350 °C at the present to a maximum of ˜ 1500-1600 °C at 2.5-3.0 Ga. The overall trend of these temperatures converges smoothly to that of the present-day MORB source, supporting the interpretation that the non-arc basalts formed by the melting of hot ambient mantle, not mantle plumes, and that they can constrain the thermal history of the Earth. These petrological results are very similar to those predicted by thermal models characterized by a low Urey ratio and more sluggish mantle convection in the past. We infer that the mantle was warming in deep Archean-Hadean time because internal heating exceeded surface heat loss, and it has been cooling from 2.5 to 3.0 Ga to the present. Non-arc Precambrian basalts are likely to be similar to those that formed oceanic crust and erupted on continents. It is estimated that ˜ 25-35 km of oceanic crust formed in the ancient Earth by about 30% melting of hot ambient mantle. In contrast, komatiite parental magmas reveal TP that are higher than those of non-arc basalts, consistent with the hot plume model. However, the associated excess magmatism was minor and oceanic plateaus, if they existed, would have had subtle bathymetric variations, unlike those of Phanerozoic oceanic plateaus. Primary magmas of Precambrian ambient mantle had 18-24% MgO, and they left behind residues of harzburgite that are now found as xenoliths of cratonic mantle. We infer that primary basaltic partial melts having 10-13% MgO are a feature of Phanerozoic magmatism, not of the early Earth, which may be why modern-day analogs of oceanic crust have not been reported in Archean greenstone belts.

  16. Geochemical characteristics and metal element enrichment in crusts from seamounts of the Western Pacific

    Institute of Scientific and Technical Information of China (English)

    Xiaoyu ZHANG; Kechao ZHU; Yong DU; Fuyuan ZHANG; Weiyan ZHANG; Xiangwen REN; Binbin JIANG

    2016-01-01

    Elemental geochemistry is an essential part of understanding mineralization mechanisms.In this paper,a data set of 544 cobalt crust samples from seamounts of the Western Pacific are used to study the enrichment characteristics of metal elements.REE normalization is utilized to reveal the origin of the crusts;effects of water depth on Co enrichment and impacts ofphosphatization on mineral quality are discussed to obtain the evolution of these marine mineral deposits,which gives support to further resource assessment.Conclusions are reached as follows:1) Elemental abundances,inter-element relationships,and shale-normalized REE patterns for phosphatepoor crusts from different locations reflect hydrogenetic origin of the crusts.EFs (enrichment coefficients) of REE exhibit exponential increase from surface sediments to phosphorite to polymetallic nodules to crusts,suggesting that the improved degree of hydrogeneous origin induces the enrichment of REE.2) The crusts in the Westem Pacific,formed through hotspot produced guyots trails,have relatively lower REE than those in the Mid-Pacific.The latter could be attributed to the peculiar submarine topography of seamounts formed by intraplate volcanism.3) The non-phosphatized younger crust layers have 40% higher Co than the phosphatized older layers.This indicates the modification of the elemental composition in these crusts by phosphatization.A general depletion of hydroxide-dominated elements such as Co,Ni,and Mn and enrichment of P,Ca,Ba,and Sr is evident in phosphatized crusts,whereas non-phosphatized younger generation crusts are rich in terrigenous aluminosilicate detrital matter.4) Co increases above the carbonate compensation depth (CCD) from less than 0.53% to over 0.65% in seamount regions with water depth of less than 2,500 m,suggesting the significance of the dissolution of carbonate in the sea water column to the growth and composition of crusts.

  17. Copper-nickel-rich, amalgamated ferromanganese crust-nodule deposits from Shatsky Rise, NW Pacific

    Science.gov (United States)

    Hein, J.R.; Conrad, T.A.; Frank, M.; Christl, M.; Sager, W.W.

    2012-01-01

    A unique set of ferromanganese crusts and nodules collected from Shatsky Rise (SR), NW Pacific, were analyzed for mineralogical and chemical compositions, and dated using Be isotopes and cobalt chronometry. The composition of these midlatitude, deep-water deposits is markedly different from northwest-equatorial Pacific (PCZ) crusts, where most studies have been conducted. Crusts and nodules on SR formed in close proximity and some nodule deposits were cemented and overgrown by crusts, forming amalgamated deposits. The deep-water SR crusts are high in Cu, Li, and Th and low in Co, Te, and Tl concentrations compared to PCZ crusts. Thorium concentrations (ppm) are especially striking with a high of 152 (mean 56), compared to PCZ crusts (mean 11). The deep-water SR crusts show a diagenetic chemical signal, but not a diagenetic mineralogy, which together constrain the redox conditions to early oxic diagenesis. Diagenetic input to crusts is rare, but unequivocal in these deep-water crusts. Copper, Ni, and Li are strongly enriched in SR deep-water deposits, but only in layers older than about 3.4 Ma. Diagenetic reactions in the sediment and dissolution of biogenic calcite in the water column are the likely sources of these metals. The highest concentrations of Li are in crust layers that formed near the calcite compensation depth. The onset of Ni, Cu, and Li enrichment in the middle Miocene and cessation at about 3.4 Ma were accompanied by changes in the deep-water environment, especially composition and flow rates of water masses, and location of the carbonate compensation depth.

  18. Spatial and temporal distribution of cyanobacterial soil crusts in the Kalahari: Implications for soil surface properties

    Science.gov (United States)

    Thomas, A. D.; Dougill, A. J.

    2007-03-01

    Localised patterns of erosion and deposition in vegetated semi-arid rangelands have been shown to influence ecological change and biogeochemical cycles. In the flat, vegetated Kalahari rangelands of Southern Africa the factors regulating erodibility of the fine sand soils and the erosivity of wind regimes require further investigation. This paper reports on the spatial and temporal patterns of cyanobacterial soil crust cover from ten sites at five sampling locations in the semi-arid Kalahari and discusses the likely impact on factors regulating surface erodibility and erosivity. Cyanobacterial soil crust cover on Kalahari Sand varied between 11% and 95% of the ground surface and was higher than previously reported. Cover was inversely related to grazing with the lowest crust cover found close to boreholes and the highest in the Game Reserve and Wildlife Management Zone. In grazed areas, crusts form under the protective canopies of the thorny shrub Acacia mellifera. Fenced plot data showed that crusts recover quickly from disturbance, with a near complete surface crust cover forming within 15 months of disturbance. Crust development is restricted by burial by wind blown sediment and by raindrop impact. Crusts had significantly greater organic matter and total nitrogen compared to unconsolidated surfaces. Crusts also significantly increased the compressive strength of the surface (and thus decreased erodibility) and changed the surface roughness. Establishing exactly how these changes affect aeolian erosion requires further process-based studies. The proportion of shear velocity acting on the surface in this complex mixed bush-grass-crust environment will be the key to understanding how crusts affect erodibility.

  19. Crust and subduction zone structure of Southwestern Mexico

    Science.gov (United States)

    Suhardja, Sandy Kurniawan; Grand, Stephen P.; Wilson, David; Guzman-Speziale, Marco; Gomez-Gonzalez, Juan Martin; Dominguez-Reyes, Tonatiuh; Ni, James

    2015-02-01

    Southwestern Mexico is a region of complex active tectonics with subduction of the young Rivera and Cocos plates to the south and widespread magmatism and rifting in the continental interior. Here we use receiver function analysis on data recorded by a 50 station temporary deployment of seismometers known as the MARS (MApping the Rivera Subduction zone) array to investigate crustal structure as well as the nature of the subduction interface near the coast. The array was deployed in the Mexican states of Jalisco, Colima, and Michoacan. Crustal thickness varies from 20 km near the coast to 42 km in the continental interior. The Rivera plate has steeper dip than the Cocos plate and is also deeper along the coast than previous estimates have shown. Inland, there is not a correlation between the thickness of the crust and topography indicating that the high topography in northern Jalisco and Michoacan is likely supported by buoyant mantle. High crustal Vp/Vs ratios (greater than 1.82) are found beneath the trenchward edge of magmatism including below the Central Jalisco Volcanic Lineament and the Michoacan-Guanajuato Volcanic Field implying a new arc is forming closer to the trench than the Trans Mexican Volcanic Belt. Elsewhere in the region, crustal Vp/Vs ratios are normal. The subducting Rivera and Cocos plates are marked by a dipping shear wave low-velocity layer. We estimate the thickness of the low-velocity layer to be 3 to 4 km with an unusually high Vp/Vs ratio of 2.0 to 2.1 and a drop in S velocity of 25%. We postulate that the low-velocity zone is the upper oceanic crust with high pore pressures. The low-velocity zone ends from 45 to 50 km depth and likely marks the basalt to eclogite transition.

  20. Evidence for oceanic crust in the Herodotus Basin

    Science.gov (United States)

    Granot, Roi

    2016-04-01

    Some of the fundamental tectonic problems of the Eastern Mediterranean remain unresolved due to the extremely thick sedimentary cover (10 to 15 km) and the lack of accurate magnetic anomaly data. I have collected 7,000 km of marine magnetic profiles (2012-2014) across the Herodotus and Levant Basins, Eastern Mediterranean, to study the nature and age of the underlying igneous crust. The towed magnetometer array consisted of two Overhauser sensors recording the total magnetic anomaly field in a longitudinal gradiometer mode, and a fully oriented vector magnetometer. The total field data from the Herodotus Basin reveal a newly detected short sequence of long-wavelength NE-SW lineated anomalies that straddle the entire basin suggesting a deep two-dimensional magnetic source layer. The three components of the magnetic vector data indicate that an abrupt transition from a 2D to 3D magnetic structure occurs east of the Herodotus Basin, along where a prominent NE-SW gravity feature is found. Altogether, these new findings confirm that the Herodotus Basin preserves remnants of oceanic crust that formed along the Neotethyan mid-ocean ridge system. The continuous northward and counterclockwise motion of the African Plate during the Paleozoic and Mesozoic allow predicting the evolution of remanent magnetization directions, which in-turn dictate that shape of the anomalies. The shape of the Herodotus anomalies best fit Late Carboniferous to Early Permian (300±20 Myr old) magnetization directions. Finally, I will discuss the implications of these results on the tectonic architecture of the region as well as on various geodynamic processes.

  1. Felsic Magmatism through Intracrustal Melting of Previously Formed Volcanic-Arc Crust: Implications for Differentiation and Secular Evolution of the Continental Crust

    Science.gov (United States)

    G R, R. K.; C, S.

    2015-12-01

    The fundamental challenge in understanding the origin and evolution of the continental crust is to recognize how primary mantle source, and oceanic crust, which are essentially mafic to ultramafic in composition, could differentiate into a more or less felsic compositions. It is possible to understand growth and differentiation of the continental crust by constraining the interplay of magmatism, deformation, and high-grade metamorphism in the lower crust. Here, we apply this knowledge on the lower crustal granitoids of southern India and speculate on the variations in geochemistry as a consequence of differentiation and secular evolution of the continental crust.The major groups of granitoids of southern India are classified as metatonalites, comparable to typical Archaean TTGs with pronounced calc-alkaline affinity, and metagranites which are magmatic fractionation produced by reworking of early crust. Metatonalites are sodic-trondhjemites with slightly magnesian, moderate LREE (average LaN = 103) and low HREE (average YbN = 2) characerestics, where as metagranites are calc-alkaline ferroan types with enriched LREE (average LaN = 427) and HREE (average YbN = 23). Petrogenetic characteristics of granitoids illustrate continuous evolution of a primary crust into diverse magmatic units by multiple stages of intracrustal differentiation processes attributed to following tectonic scenarios: (1) formation of tonalitic magma by low- to moderate-degree partial melting of hydrated basaltic crust at pressures high enough to stabilize garnet-amphibole residue and (2) genesis of granite in a continental arc-accretion setting by an episode of crustal remelting of the tonalitic crust, within plagioclase stability field. The first-stage formed in a flat-subduction setting of an volcanic-arc, leading to the formation of tonalites. The heat budget required is ascribed to the upwelling of the mantle and/or basaltic underplating. Progressive decline in mantle potential temperature

  2. Depth profiles of 230Th excess, transition metals and mineralogy of ferromanganese crusts of the Central Indian Ocean basin and implications for palaeoceanographic influence on crust genesis

    Digital Repository Service at National Institute of Oceanography (India)

    Banakar, V.K.; Borole, D.V.

    . The interpolated age of these crusts is between 10 and I3 Ma which is comparable to the period of increased carbonate dissolution due to enhanced activity of AABW (Antarctic Bottom Water) currents during the middle Miocene. Probably the middle Miocene... which are controlled by both hydrogenetic and diagenetic processes (Halbach et al., 198 1). The metal composi- tion of the crusts are dependent on water depth, latitude and age (Halbach and Puteanus, 1984b). Hence the geochemical variation...

  3. Crustal decoupling and mantle dynamics on Venus: implications for Earth-like planets

    Science.gov (United States)

    Ghail, Richard

    2013-04-01

    Venus is physically similar to Earth but with a hot dense atmosphere and no oceans; four-fifths of its surface is apparently volcanic in origin and likely basaltic in composition. Erosion and sedimentary processes are largely absent, preserving a near-random distribution of impact craters that led to the hypothesis of episodic global resurfacing, which proposes that the entire lithosphere was recycled in a short period (~50 Ma) about 750 Ma ago, and is currently in a stagnant-lid state, in which the crust and lithosphere are strongly coupled to a sluggishly convecting mantle. This hypothesis is at odds with the complex and diverse range of geological features on Venus that imply a continuum of activity, at a level at least similar to Earth's continental interiors, with little evidence for a sudden change in past rates of activity. An alternative hypothesis is presented here based on geological interpretation, topographic and gravitational data, and geomechanical inferences. The elevated surface temperature results in a weak lower crust, similar to certain terrestrial continental crust strength profiles, that is effectively decoupled from the mantle. The subcrustal lithosphere is therefore able to behave in a plate-like way, with boundary conditions defined by the base of the crust. Hypsographic data are used to infer the average plate thickness (100 ± 6 km), subcrustal plate creation rate (3·8 to 4·6 km² a-¹) and mean half-spreading rate (29 to 35 mm a-¹). The observed 55,000 to 65,000 km long network of rift systems observed on Venus are predicted to correspond to subcrustal spreading ridges; fits to their topography demonstrate that they are consistent with the model but with a range of subcrustal spreading rates from 11 to 97 mm a-¹. Geoid lows correspond well with predicted sites of subcrustal subduction. Since stress transmission is restricted by the weak lower crust, the surface is tectonically modified at only a modest rate, similar to terrestrial

  4. Annual review of earth and planetary sciences. Volume 17

    Energy Technology Data Exchange (ETDEWEB)

    Wetherill, G.W.; Albee, A.L.; Stehli, F.G.

    1989-01-01

    Recent advances in earth and planetary science are examined in reviews by leading experts. The subjects discussed include geochemistry and the dynamics of the Yellowstone hydrothermal system, Alpine and Himalayan blueschists, pressure solution during diagenesis, achondrites and igneous processes on asteroids, Sr isotopes in seawater, sediment magnetization and the evolution of magnetite biomineralization, active deformation of the continents, the nature of deep-focus earthquakes, and the use of Raman spectroscopy in mineralogy and geochemistry. Consideration is given to the mechanics of faulting, the crustal structure of western Europe, gases in diamonds, metamorphic fluids in the deep crust, faunal dynamics of pleistocene mammals, magma chambers, and the nature of the Mohorovicic discontinuity.

  5. Geochemical and Sr-Nd-Pb isotopic evidence for ancient lower continental crust beneath the Xi Ujimqin area of NE China

    Science.gov (United States)

    Gao, Xiaofeng; Guo, Feng; Xiao, Peixi; Kang, Lei; Xi, Rengang

    2016-05-01

    The Central Asian Orogenic Belt (CAOB) is the largest Phanerozoic accretionary orogen on Earth. The role that Precambrian continental microblocks played in its formation, however, remains a highly controversial topic. New zircon U-Pb age data and whole-rock geochemical and Sr-Nd-Pb isotopic studies on Permian (253-251 Ma) andesites from the Xi Ujimqin area provide the first evidence for the existence of a continental lower mafic crust in the eastern segment of the CAOB. These Permian lavas generally have chemical compositions similar to experimental melts of garnet pyroxenites. Based on Sr-Nd-Pb isotopic compositional differences, they can be further subdivided into two groups. Group 1 has moderately radiogenic Sr (87Sr/86Sr(i) = 0.7060-0.7062) and nonradiogenic Nd (εNd(t) = - 9.0-8.3) and Pb (e.g., 206Pb/204Pb = 17.18-17.23) isotopic compositions similar to the ancient lower mafic crust beneath the North China Craton (NCC). Compared with Group 1, Group 2 has less radiogenic Sr (87Sr/86Sr(i) = 0.7051-0.7055), and more radiogenic Nd (εNd(t) = - 0.2-+1.4) and Pb (e.g., 206Pb/204Pb = 18.04-18.20) isotopic compositions as observed in the Phanerozoic granitoids and felsic lavas of the CAOB. The combined geochemical and isotopic data indicate that Group 1 was derived from ancient lower mafic crust of the NCC affinity, with a residual assemblage of pyroxene + plagioclase + amphibole. The source for Group 2 was a mixture of ancient lower mafic crust and a juvenile crustal component, and melting left a residue of orthopyroxene + clinopyroxene + plagioclase + garnet + amphibole. Generation of these two types of late Permian andesites favors a model whereby breakoff of a subducted slab and subsequent lithospheric extension triggered extensive asthenospheric upwelling and melting of the continental mafic lower crust of the eastern CAOB. The discovery of ancient lower continental crust of the NCC affinity in the CAOB implies that the NCC experienced continental breakup during

  6. Rheology of the lower crust beneath the northern part of North China: Inferences from lower crustal xenoliths from Hannuoba basalts, Hebei Province, China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Lower crustal xenoliths brought up rapidly by basaltic magma onto the earth surface may provide di-rect information on the lower crust. The main purpose of this research is to gain an insight into the rheology of the lower crust through the detailed study of lower crustal xenoliths collected from the Hannuoba basalt, North China. The lower crustal xenoliths in this area consist mainly of two pyroxene granulite, garnet granulite, and light-colored granulite, with a few exception of felsic granulite. The equilibration temperature and pressure of these xenoliths are estimated by using geothermometers and geobarometers suitable for lower crustal xenoliths. The obtained results show that the equilibration temperature of these xenoliths is within the range of 785―900℃, and the equilibrium pressure is within the range of 0.8―1.2 GPa, corresponding to a depth range of 28―42 km. These results have been used to modify the previously constructed lower crust-upper mantle geotherm for the studied area. The dif-ferential stress during the deformation process of the lower crustal xenoliths is estimated by using recrystallized grain-size paleo-piezometer to be in the range of 14―20 MPa. Comparing the available steady state flow laws for lower crustal rocks, it is confirmed that the flow law proposed by Wilks et al. in 1990 is applicable to the lower crustal xenoliths studied in this paper. The strain rate of the lower crust estimated by using this flow law is within the range of 10-13―10-11 s-1, higher than the strain rate of the upper mantle estimated previously for the studied area (10-17―10-13 s-1); the equivalent viscosity is estimated to be within the range of 1017―1019Pa·s, lower than that of the upper mantle (1019―1021 Pa·s). The constructed rheological profiles of the lower crust indicate that the differential stress shows no significant linear relation with depth, while the strain rate increases with depth and equivalent vis-cosity decrease with depth

  7. Chlorophytes of biological soil crusts in Gurbantunggut Desert, Xinjiang Autonomous Region, China

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In this paper, chlorophytes collected from 253 biological soil crust samples in Gurbantunggut Desert in Xinjiang Autonomous Region, China were studied by field investigation and microscopical observation in lab. The flora composition, ecological distribution of chlorophytes in the desert and dynamic changes of species composition of chlorophytes in different developing stages of biological soil crusts are preliminarily analyzed. Results showed that there were 26 species belonging to 14 genera and 10 families, in which unicellular chlorophytes were dominant. There existed some differences in distribution of varied sand dune positions. The taxa of chlorophytes in leeward of sand dunes are most abundant, but the taxa in windward, interdune and the top of sand dunes reduced gradually. Chlorophytes were mainly distributed within the crust and the taxa of chlorophytes decrease obviously under the crust. In the devel-oping stages of the biological soil crust, species diversity of chlorophytes changed a little, but species composition pre-sented some differences. Chlorococcum humicola, Chlorella vulgaris, Chlamydomonas ovalis and Chlamydomonas sp. nearly existed in all developing stages of biological crusts. In several former stages of the biological soil crust there were spherical chlorophytes and filamentous ones. When moss crust formed, filamentous chlorophytes disappeared, such as Microspora and Ulothrix.

  8. The growth of the continental crust: Constraints from radiogenic isotope geochemistry

    Science.gov (United States)

    Taylor, Paul N.

    1988-01-01

    Most models for evolution of continental crust are expressed in the form of a diagram illustrating the cumulative crustal mass (normalized relative to the present crustal mass) as a function of time. Thus, geochronological data inevitably play a major role in either constructing or testing crustal growth models. For all models, determining the start-time for effective crustal accretion is of vital importance. To this end, the continuing search for, and reliable characterization of, the most ancient crustal rock-units remains a worthy enterprise. Another important role for geochronology and radiogenic isotope geochemistry is to assess the status of major geological events as period either of new crust generation or of reworking of earlier formed continental crust. For age characterization of major geological provinces, using the critieria outined, the mass (or volume) of crust surviving to the present day should be determinable as a function of crust formation age. More recent developments, however, appear to set severe limitations on recycling of crust, at least by the process of sediment subduction. In modeling crustal growth without recycling, valuable constaints on growth rate variations through time can be provided if variations in the average age of the continental crust can be monitored through geological history. The question of the average age of the exposed continental crust was addressed by determining Sm-Nd crustal residence model ages (T-CR) for fine-grained sediment loads of many of the world's major rivers.

  9. The role of the gluten network in the crispness of bread crust

    NARCIS (Netherlands)

    Primo-Martín, C.; Pijpekamp, A.v.d.; Vliet, T.v.; Jongh, H.H.J.d.; Plijter, J.J.; Hamer, R.J.

    2006-01-01

    Crispness features of baked products strongly determine consumer acceptability. For many baked products, such as bread, the outer crust gives the crispy sensation. Confocal scanning laser microscopy of the structure of bread crust revealed a continuous protein phase and a discontinuous

  10. Water content or water activity: What rules crispy behavior in bread crust?

    NARCIS (Netherlands)

    Nieuwenhuijzen, N.H. van; Primo-Martín, C.; Meinders, M.B.J.; Tromp, R.H.; Hamer, R.J.; Vliet, T. van

    2008-01-01

    A dry crust loses its crispness when water migrates into the crust. It is not clear if it is the amount of water absorbed or the water activity (a w) that leads to a loss of crispness. The hysteresis effect observed when recording a water sorption isotherm allowed us to study the effects of aw and m

  11. Water content or water activity: What rules crispy behavior in bread crust?

    NARCIS (Netherlands)

    Nieuwenhuijzen, N.H. van; Primo-Martín, C.; Meinders, M.B.J.; Tromp, R.H.; Hamer, R.J.; Vliet, T. van

    2008-01-01

    A dry crust loses its crispness when water migrates into the crust. It is not clear if it is the amount of water absorbed or the water activity (a w) that leads to a loss of crispness. The hysteresis effect observed when recording a water sorption isotherm allowed us to study the effects of aw and m

  12. Heterogeneity of Parent Rocks and Its Constraints on Geochemical Criteria in Weathering Crusts of Carbonate Rocks

    Institute of Scientific and Technical Information of China (English)

    WANG Shijie; FENG Zhigang

    2004-01-01

    Owing to the low contents of their acid-insoluble components, carbonate rocks tend to decrease sharply in volume in association with the formation of weathering crust. The formation of a 1 m-thick weathering crust would usually consume more than ten meters to several tens of meters of thickness of parent rocks. The knowledge of how to identify the homogeneity of parent rocks is essential to understand the formation mechanism of weathering crust in karst regions,especially that of thick-layered red weathering crust. In this work the grain-size analyses have demonstrated that the three profiles studied are the residual weathering crust of carbonate rocks and further showed that there objectively exists the heterogeneity of parent rocks in the three studied weathering crusts. The heterogeneity of parent rocks can also be reflected in geochemical parameters of major elements, just as the characteristics of frequency plot of grain-size distribution.Conservative trace element ratios Zr/Hf and Nb/Ta are proven to be unsuitable for tracing the heterogeneity of parent rocks of weathering crust, but its geochemical mechanism is unclear. The authors strongly suggest in this paper that the identification of the homogeneity of parent rocks of weathering crust in karst regions is of prime necessity.

  13. Crust morphology and crispness development during deep-fat frying of potato

    NARCIS (Netherlands)

    Koerten, van K.N.; Schutyser, M.A.I.; Somsen, D.; Boom, R.M.

    2015-01-01

    Crust formation is an important factor in determining the crispness of French fries. This study aimed at unravelling detailed structural and textural properties of the crust in relation to crispness during frying as a function of the process temperature and time. X-ray tomography showed a larger ove

  14. Physical characterization, spectral response and remotely sensed mapping of Mediterranean soil surface crusts

    NARCIS (Netherlands)

    Jong, S.M. de; Addink, E.A.; Duijsing, D.; Beek, L.P.H. van

    2011-01-01

    Soil surface crusting and sealing are frequent but unfavorable processes in Mediterranean areas. Soil crust and seals form on bare soil subject to high-intensity rainfall, resulting in a hard, impenetrable layer that impedes infiltration and hampers the germination and establishment of plants. The a

  15. The role of the gluten network in the crispness of bread crust

    NARCIS (Netherlands)

    Primo-Martín, C.; Pijpekamp, A.v.d.; Vliet, T.v.; Jongh, H.H.J.d.; Plijter, J.J.; Hamer, R.J.

    2006-01-01

    Crispness features of baked products strongly determine consumer acceptability. For many baked products, such as bread, the outer crust gives the crispy sensation. Confocal scanning laser microscopy of the structure of bread crust revealed a continuous protein phase and a discontinuous non-gelatiniz

  16. Water Content or Water Activity: What Rules Crispy Behavior in Bread Crust?

    NARCIS (Netherlands)

    Nieuwenhuijzen, van N.H.; Primo-Martin, C.; Meinders, M.B.J.; Tromp, R.H.; Hamer, R.J.; Vliet, van T.

    2008-01-01

    A dry crust loses its crispness when water migrates into the crust. It is not clear if it is the amount of water absorbed or the water activity (aw) that leads to a loss of crispness. The hysteresis effect observed when recording a water sorption isotherm allowed us to study the effects of aw and mo

  17. Lateral spreading in the Svecofennian mid-crust revealed by seismic attribute analysis

    DEFF Research Database (Denmark)

    Torvela, Taija; Moreau, Julien; Butler, Robert

    In orogenic belts, crustal thickening precedes rheological weakening of the middle and lower orogenic crust leading to lateral spreading and, ultimately, to collapse of an orogen. Recent studies have implied similar development in the middle crust during the Palaeoproterozoic composite Svecofenni...

  18. Controls on ferromanganese crust composition and reconnaissance resource potential, Ninetyeast Ridge, Indian Ocean

    Science.gov (United States)

    Hein, James; Conrad, Tracey A.; Mizell, Kira; Banakar, Virupaxa K.; Frey, Frederick A.; Sager, William W.

    2016-01-01

    A reconnaissance survey of Fe-Mn crusts from the 5000 km long (~31°S to 10°N) Ninetyeast Ridge (NER) in the Indian Ocean shows their widespread occurrence along the ridge as well as with water depth on the ridge flanks. The crusts are hydrogenetic based in growth rates and discrimination plots. Twenty samples from 12 crusts from 9 locations along the ridge were analyzed for chemical and mineralogical compositions, growth rates, and statistical relationships (Q-mode factor analysis, correlation coefficients) were calculated. The crusts collected are relatively thin (maximum 40 mm), and those analyzed varied from 4 mm to 32 mm. However, crusts as thick as 80 mm can be expected to occur based on the age of rocks that comprise the NER and the growth rates calculated here. Growth rates of the crusts increase to the north along the NER and with water depth. The increase to the north resulted from an increased supply of Mn from the oxygen minimum zone (OMZ) to depths below the OMZ combined with an increased supply of Fe at depth from the dissolution of biogenic carbonate and from deep-sourced hydrothermal Fe. These increased supplies of Fe increased growth rates of the deeper-water crusts along the entire NER. Because of the huge terrigenous (rivers, eolian, pyroclastic) and hydrothermal (three spreading centers) inputs to the Indian Ocean, and the history of primary productivity, Fe-Mn crust compositions vary from those analyzed from open-ocean locations in the Pacific.

  19. Greenhouse gas microbiology in wet and dry straw crust covering pig slurry

    DEFF Research Database (Denmark)

    Hansen, Rikke Ruth; Nielsen, Daniel Aagren; Schramm, Andreas

    2009-01-01

    microbiology had an effect on the emission of the potent greenhouse gases CH4 and nitrous oxide (N2O) when crust moisture was manipulated ("Dry", "Moderate", and "Wet"). The dry crust had the deepest oxygen penetration (45 mm as compared to 20 mm in the Wet treatment) as measured with microsensors, the highest...

  20. Comparison of internal features and microchemistry of ferromanganese crusts from the Central Indian Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Iyer, S.D.

    are enriched in Ni and Cu. Microstructural and elemental variations, from the ferromanganese crust outer surface to the basalt substrate, probably reflect changes in the accretion or in the source of metals. The major source of the crust metals in seawater...