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Sample records for mantle heat flow

  1. Penetrative convective flows induced by internal heating and mantle compressibility

    NASA Technical Reports Server (NTRS)

    Machetel, Philippe; Yuen, David A.

    1989-01-01

    Penetrative convective flows induced in a spherical shell by combined effects of internal heating and mantle compressibility are investigated using mathematical and numerical formulations for compressible spherical shell convection. Isothermal stress-free boundary conditions applied at the top and the bottom of the shell are solved using a time-dependent finite difference code in a temperature, vorticity, stream function formulation for Rayleigh numbers ranging from the critical Rc up to 2000 Rc. Results indicate that compressibility, together with internal heating, could be a mechanism capable of generating spontaneously layered convection and local melting in the mantle and that non-Boussinesq effects must be considered in interpretations of geophysical phenomena.

  2. Influence of magmatism on mantle cooling, surface heat flow and Urey ratio

    NASA Astrophysics Data System (ADS)

    Nakagawa, T.; Tackley, P.

    2012-04-01

    Two-dimensional thermo-chemical mantle convection simulations are used to investigate the influence of melting-inducted differentiation on the thermal evolution of Earth's mantle, focussing on matching the present-day surface heat flow and the 'Urey ratio'. The influence of heat production rate, initial mantle temperature and partitioning of heat-producing elements into basaltic crust are studied. High initial mantle temperatures cause major differences in early mantle thermo-chemical structures but by the present day surface heat flux and internal structures are indistinguishable from cases with a low initial temperature. Assuming three different values of mantle heat production that vary by more than a factor of two results in small differences in present-day heat flow, as does assuming different partitioning ratios of heat-producing elements into crust. As a consequence of the model present-day surface heat flow varying only slightly with parameters, the Urey ratio is highly dependent on the amount of heat production, and due to the large uncertainty, the Urey ratio is considered to be a much poorer constraint on thermal evolution than the heat flow. The range of present-day Urey ratio observed in simulations here is about 0.3 to 0.5, which is consistent with observational and geochemical constraints [Jaupart et al., 2007]. Magmatic heat transport contributes about 10% to Earth's present-day heat loss but a much higher fraction at earlier times — often more than convective heat loss — so neglecting this causes an overestimation of the Urey ratio. Magmatic heat transport also plays an important role in mantle cooling. Considering these points, it is important to include magmatic effects when attempting to understand the thermal evolution of the Earth. In addition, we will show some preliminary results on thermal evolution of Earth's mantle and core including additional compositional anomalies at the base of mantle known as the BAsal Melange 'BAM' [Tackley

  3. Deep mantle heat flow and thermal evolution of the Earth's core based on thermo-chemical mantle convection

    NASA Astrophysics Data System (ADS)

    Nakagawa, T.; Tackley, P.; Buffett, B.

    2004-12-01

    A coupled core-mantle evolution model that combines the global heat balance in the core with a fully-dynamical thermo-chemical mantle convection [Nakagawa and Tackley, 2004 published in EPSL] is used to investigate the deep mantle heat flow that is required to sustain the magnetic field generated by the geodynamo process. Effects of a radioactive heat source due to potassium in the core are also included in the global heat balance in the Earth??s core. Two important parameters are checked in this study; (1) density variation between depleted hartzbergite and basaltic material (0 to 3 percent) and (2) concentration of radioactive potassium in the core alloy (0ppm to 400ppm). The parameter set that most closely satisfies the criteria of size of the inner core (1220km at present time) is around 2 percent of density difference in a convecting mantle and 200ppm of radioactive heat source in the core. The concentration of potassium in the core is consistent with the geochemical approach [Murthy et al., 2003] but smaller than other successful thermal evolution models [Labrosse, 2003; Nimmo et al., 2004]. Heat flow through the core-mantle boundary and the contribution of radioactive heat sources in the core are consistent with theoretical estimates [e.g. Buffett, 2002] and geochemical constraints [Gessmann and Wood, 2002]. The power available to the geodynamo, based on the predicted heat flow through the core-mantle boundary, is approximately four times greater than the value predicted by numerical models of the geodynamo [Christensen and Kutzner, 2004] but closer to theoretical estimates [e.g. Buffett, 2002].

  4. Influence of magmatism on mantle cooling, surface heat flow and Urey ratio

    NASA Astrophysics Data System (ADS)

    Nakagawa, Takashi; Tackley, Paul J.

    2012-05-01

    Two-dimensional thermo-chemical mantle convection simulations are used to investigate the influence of melting-inducted differentiation on the thermal evolution of Earth's mantle, focussing in particular on matching the present-day surface heat flow and the 'Urey ratio'. The influence of internal heating rate, initial mantle temperature and partitioning of heat-producing elements into basaltic crust are studied. High initial mantle temperatures, which are expected following Earth's accretion, cause major differences in early mantle thermo-chemical structures, but by the present-day surface heat flux and internal structures are indistinguishable from cases with a low initial temperature. Assuming three different values of mantle heat production that vary by more than a factor of two results in small differences in present-day heat flow, as does assuming different partitioning ratios of heat-producing elements into crust. Indeed, all of the cases presented here, regardless of exact parameters, have approximately Earth's present-day heat flow, with substantial fractions coming from the core and from mantle cooling. As a consequence of the model present-day surface heat flow varying only slightly with parameters, the Urey ratio (the ratio of total heat production to the total surface heat flow) is highly dependent on the amount of internal heat production, and due to the large uncertainty in this, the Urey ratio is considered to be a much poorer constraint on thermal evolution than the heat flow. The range of present-day Urey ratio observed in simulations here is about 0.3 to 0.5, which is consistent with observational and geochemical constraints (Jaupart et al., 2007). Magmatic heat transport contributes an upper bound of 9% to Earth's present-day heat loss but a much higher fraction at earlier times—often more than convective heat loss—so neglecting this causes an overestimation of the Urey ratio. Magmatic heat transport also plays an important role in mantle

  5. Birch's Crustal Heat Production-Heat Flow Law: Key to Quantifying Mantle Heat Flow as a function of time

    NASA Astrophysics Data System (ADS)

    Blackwell, D. D.; Thakur, M.

    2007-12-01

    parameters of Birch's Law equation represent the starting place for discussions of lithospheric thermal regime and evolution. The stability of the values of intercept Qo for areas with thermal ages of Paleozoic and older prove that the lithosphere heat flow does not vary significantly with age as is demonstrated in the companion paper. The minimum mantle heat flow for preMesozoic thermal terrains is 20 - 25 mWm-2. This value is consistent with the lack of indication from xenolith data that lithosphere thickness changes with age and with theoretical models of mantle convection.

  6. Upper mantle velocity-temperature conversion and composition determined from seismic refraction and heat flow

    NASA Astrophysics Data System (ADS)

    Perry, H. K. C.; Jaupart, C.; Mareschal, J.-C.; Shapiro, N. M.

    2006-07-01

    We compile upper mantle Pn velocities from seismic refraction/wide-angle reflection surveys in the southern Superior Province of the Canadian Shield and compare them with temperatures at the Moho deduced from heat flow data. Calculated Moho temperatures and Pn velocities correlate well, showing that in this area, Pn depends primarily on temperature. The obtained values of ∂V(Pn)/∂T depend weakly on the assumed value of Moho heat flow and are on the order of -6.0 × 10-4 ± 10% km s-1 K-1, within the range of temperature derivatives obtained in laboratory studies of ultramafic rocks. Comparison between observed Pn velocities and predicted values for several mineralogical models at Moho temperatures allows constraints on both the Moho heat flow and the shallow mantle composition. For all Moho heat flows, undepleted (clinopyroxene-rich) mantle compositions do not allow a good fit to the data. For depleted mantle compositions, temperatures consistent with the observed Pn velocities correspond to values of Moho heat flow larger than 12 mW m-2. For our preferred Moho heat flow of 15 mW m-2, the best fit mantle composition is slightly less depleted than models for average Archean subcontinental lithospheric mantle. This may be due to rejuvenation by melt-related metasomatism during the Keweenawan rifting event. The similarity in Pn - T conversion factors estimated from this empirical large-scale geophysical study and those from laboratory data provides confidence in the absolute temperature values deduced from heat flow measurements and seismic studies.

  7. Modulation of mantle plumes and heat flow at the core mantle boundary by plate-scale flow: results from laboratory experiments

    NASA Astrophysics Data System (ADS)

    Gonnermann, Helge M.; Jellinek, A. Mark; Richards, Mark A.; Manga, Michael

    2004-09-01

    We report results from analog laboratory experiments, in which a large-scale flow is imposed upon natural convection from a hot boundary layer at the base of a large tank of corn syrup. The experiments show that the subdivision of the convective flow into four regions provides a reasonable conceptual framework for interpreting the effects of large-scale flow on plumes. Region I includes the area of the hot thermal boundary layer (TBL) that is thinned by the large-scale flow, thereby suppressing plumes. Region II encompasses the critically unstable boundary layer where plumes form. Region III is the area above the boundary layer that is devoid of plumes. Region IV comprises the area of hot upwelling and plume conduits. Quantitative analysis of our experiments results in a scaling law for heat flux from the hot boundary and for the spatial extent of plume suppression. When applied to the Earth's core-mantle boundary (CMB), our results suggest that large-scale mantle flow, due to sinking lithospheric plates, can locally thin the TBL and suppress plume formation over large fractions of the CMB. Approximately 30% of heat flow from the core may be due to increased heat flux from plate-scale flow. Furthermore, CMB heat flux is non-uniformly distributed along the CMB, with large areas where heat flux is increased on average by a factor of 2. As a consequence, the convective flow pattern in the outer core may be affected by CMB heat-flux heterogeneity and sensitive to changes in plate-scale mantle flow. Because of plume suppression and 'focusing' of hot mantle from the CMB into zones of upwelling flow, plume conduits (hotspots) are expected to be spatially associated with lower-mantle regions of low seismic velocities, inferred as hot upwelling mantle flow.

  8. Mantle heat flow and thermal structure of the northern block of Southern Granulite Terrain, India

    NASA Astrophysics Data System (ADS)

    Manglik, Ajay

    2006-07-01

    Continental shield regions are normally characterized by low-to-moderate mantle heat flow. Archaean Dharwar craton of the Indian continental shield also follows the similar global pattern. However, some recent studies have inferred significantly higher mantle heat flow for the Proterozoic northern block of Southern Granulite Terrain (SGT) in the immediate vicinity of the Dharwar craton by assuming that the radiogenic elements depleted exposed granulites constitute the 45-km-thick crust. In this study, we use four-layered model of the crustal structure revealed by integrated geophysical studies along a geo-transect in this region to estimate the mantle heat flow. The results indicate that: (i) the mantle heat flow of the northern block of SGT is 17 ± 2 mW/m 2, supporting the global pattern, and (ii) the lateral variability of 10-12 mW/m 2 in the surface heat flow within the block is of crustal origin. In terms of temperature, the Moho beneath the eastern Salem-Namakkal region appears to be at 80-100 °C higher temperature than that beneath the western Avinashi region.

  9. Abnormal high surface heat flow caused by the Emeishan mantle plume

    NASA Astrophysics Data System (ADS)

    Jiang, Qiang; Qiu, Nansheng; Zhu, Chuanqing

    2016-04-01

    It is commonly believed that increase of heat flow caused by a mantle plume is small and transient. Seafloor heat flow data near the Hawaiian hotspot and the Iceland are comparable to that for oceanic lithosphere elsewhere. Numerical modeling of the thermal effect of the Parana large igneous province shows that the added heat flow at the surface caused by the magmatic underplating is less than 5mW/m2. However, the thermal effect of Emeishan mantle plume (EMP) may cause the surface hear-flow abnormally high. The Middle-Late Emeishan mantle plume is located in the western Yangtze Craton. The Sichuan basin, to the northeast of the EMP, is a superimposed basin composed of Paleozoic marine carbonate rocks and Mesozoic-Cenozoic terrestrial clastic rocks. The vitrinite reflectance (Ro) data as a paleogeothermal indicator records an apparent change of thermal regime of the Sichuan basin. The Ro profiles from boreholes and outcrops which are close to the center of the basalt province exhibit a 'dog-leg' style at the unconformity between the Middle and Upper Permian, and they show significantly higher gradients in the lower subsection (pre-Middle Permian) than the Upper subsection (Upper Permian to Mesozoic). Thermal history inversion based on these Ro data shows that the lower subsection experienced a heat flow peak much higher than that of the upper subsection. The abnormal heat flow in the Sichuan basin is consistent with the EMP in temporal and spatial distribution. The high-temperature magmas from deep mantle brought heat to the base of the lithosphere, and then large amount of heat was conducted upwards, resulting in the abnormal high surface heat flow.

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

    USGS Publications Warehouse

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

    1997-01-01

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

  11. Plume's buoyancy and heat fluxes from the deep mantle estimated by an instantaneous mantle flow simulation based on the S40RTS global seismic tomography model

    NASA Astrophysics Data System (ADS)

    Yoshida, Masaki

    2012-11-01

    It is still an open question as to how much heat is transported from the deep mantle to the upper mantle by mantle upwelling plumes, which would impose a strong constraint on models of the thermal evolution of the earth. Here I perform numerical computations of instantaneous mantle flow based on a recent highly resolved global seismic tomography model (S40RTS), apply new simple fluid dynamics theories to the plume's radius and velocity, considering a Poiseuille flow assumption and a power-law relationship between the boundary layer thickness and Rayleigh number, and estimate the plume's buoyancy and heat fluxes from the deep lower mantle under varying plume viscosity. The results show that for some major mantle upwelling plumes with localized strong ascent velocity under the South Pacific and Africa, the buoyancy fluxes of each plume beneath the ringwoodite to perovskite + magnesiowüstite ("660-km") phase decomposition boundary are comparable to those inferred from observed hotspot swell volumes on the earth, i.e., on the order of 1 Mg s-1, when the plume viscosity is 1019-1020 Pa s. This result, together with previous numerical simulations of mantle convection and the gentle Clausius-Clapeyron slope for the 660-km phase decomposition derived from recent high-pressure measurements under dehydrated/hydrated conditions in the mantle transition zone, implies that mantle upwelling plumes in the lower mantle penetrate the 660-km phase decomposition boundary without significant loss in thermal buoyancy because of the weak thermal barrier at the 660-km boundary. The total plume heat flux under the South Pacific is estimated to be about 1 TW beneath the 660-km boundary, which is significantly smaller than the core-mantle boundary heat flux. Previously published scaling laws for the plume's radius and velocity based on a plume spacing theory, which explains well plume dynamics in three-dimensional time-dependent mantle convection, suggest that these plume fluxes depend

  12. Surface heat flow and the mantle contribution on the margins of Australia

    NASA Astrophysics Data System (ADS)

    Goutorbe, Bruno; Lucazeau, Francis; Bonneville, Alain

    2008-05-01

    We present thermal data from 473 oil exploration wells in Australia and New Zealand. Approximately 2300 bottom-hole temperatures are corrected to form a homogeneous set along with 86 temperatures from reservoir tests. Thermal conductivity profiles are estimated from a set of geophysical well logs using a recently developed neural network approach. Retaining wells in which temperature and thermal conductivity data overlap over an interval greater than 1000 m, we estimate 10 heat flow values in the Taranaki basin of New Zealand and 270 values in the northwestern, western, and southern margins and in the intracontinental Canning basin of Australia. The values are in the range 30-80 mW m-2. As a result of several differences in the data and methods, our heat flow values are 10-20 mW m-2 lower compared to previously published estimates for the same wells in New Zealand. For Australia, our values are consistent with previously measured values and trends in the continental and marine regions. On the northwestern and southeastern margins, we interpret the variations as reflecting changes in the nature of the underlying basement. Consistent with onshore data, it is inferred that the Archean crust is depleted in radiogenic elements compared to Proterozoic regions and that recent volcanism affects the eastern Paleozoic area. After removing from surface heat flow the sediment contributions, including a permanent radiogenic heat component and a transient sedimentation effect, a simple crustal model suggests that mantle heat flow on the continental margin bordering the Pilbara craton is higher than below the craton itself. Moreover, heat flow corrected for the sediment contributions is markedly lower in the Petrel intracontinental basin than in the adjacent margin, although the crust is thinner below this latter region. As both are underlaid by the same basement, this observation may indicate that the mantle contribution is also higher below that margin. Such a higher mantle

  13. Time variability in Cenozoic reconstructions of mantle heat flow: Plate tectonic cycles and implications for Earth's thermal evolution

    PubMed Central

    Loyd, S. J.; Becker, T. W.; Conrad, C. P.; Lithgow-Bertelloni, C.; Corsetti, F. A.

    2007-01-01

    The thermal evolution of Earth is governed by the rate of secular cooling and the amount of radiogenic heating. If mantle heat sources are known, surface heat flow at different times may be used to deduce the efficiency of convective cooling and ultimately the temporal character of plate tectonics. We estimate global heat flow from 65 Ma to the present using seafloor age reconstructions and a modified half-space cooling model, and we find that heat flow has decreased by ∼0.15% every million years during the Cenozoic. By examining geometric trends in plate reconstructions since 120 Ma, we show that the reduction in heat flow is due to a decrease in the area of ridge-proximal oceanic crust. Even accounting for uncertainties in plate reconstructions, the rate of heat flow decrease is an order of magnitude faster than estimates based on smooth, parameterized cooling models. This implies that heat flow experiences short-term fluctuations associated with plate tectonic cyclicity. Continental separation does not appear to directly control convective wavelengths, but rather indirectly affects how oceanic plate systems adjust to accommodate global heat transport. Given that today's heat flow may be unusually low, secular cooling rates estimated from present-day values will tend to underestimate the average cooling rate. Thus, a mechanism that causes less efficient tectonic heat transport at higher temperatures may be required to prevent an unreasonably hot mantle in the recent past. PMID:17720806

  14. Time variability in Cenozoic reconstructions of mantle heat flow: plate tectonic cycles and implications for Earth's thermal evolution.

    PubMed

    Loyd, S J; Becker, T W; Conrad, C P; Lithgow-Bertelloni, C; Corsetti, F A

    2007-09-04

    The thermal evolution of Earth is governed by the rate of secular cooling and the amount of radiogenic heating. If mantle heat sources are known, surface heat flow at different times may be used to deduce the efficiency of convective cooling and ultimately the temporal character of plate tectonics. We estimate global heat flow from 65 Ma to the present using seafloor age reconstructions and a modified half-space cooling model, and we find that heat flow has decreased by approximately 0.15% every million years during the Cenozoic. By examining geometric trends in plate reconstructions since 120 Ma, we show that the reduction in heat flow is due to a decrease in the area of ridge-proximal oceanic crust. Even accounting for uncertainties in plate reconstructions, the rate of heat flow decrease is an order of magnitude faster than estimates based on smooth, parameterized cooling models. This implies that heat flow experiences short-term fluctuations associated with plate tectonic cyclicity. Continental separation does not appear to directly control convective wavelengths, but rather indirectly affects how oceanic plate systems adjust to accommodate global heat transport. Given that today's heat flow may be unusually low, secular cooling rates estimated from present-day values will tend to underestimate the average cooling rate. Thus, a mechanism that causes less efficient tectonic heat transport at higher temperatures may be required to prevent an unreasonably hot mantle in the recent past.

  15. A two Layer Convecting Mantle With Exchange : A Unified Model Based on Geochemical, Seismic and Heat Flow Observations

    NASA Astrophysics Data System (ADS)

    Allègre, C. J.; Jaupart, C.; Nolet, G.

    2007-12-01

    The question of layered versus whole mantle convection has been pending since early models of mantle convection (Oxburgh and Turcotte, 1967; McKenzie and Richter, 1978). In a first phase, layered mantle models appeared to be the winners, because they explained most of geochemical observations. They of course also explained the seismic focal solutions (compressive/ non compressive) in subducting plate and the heat flow constraints (Richter, 1980). Later on, the discovery that slabs could penetrate the lower mantle was considered as proof of whole mantle convection. Most numerical experiments were then developed in this context, overlooking many geochemical observations such as rare gas isotopes or radioactive elements. In this presentation, we will examine the different data one by one. a) geochemical constraints include the budget equations for Sr, Nd, Hf, isotopes, the budget equation for He, Ne, Ar, the budget for heat producing elements U, Th, K (including Th/U and K/U ratios). (Allègre and al., 1979, 1982; De Paolo and Wasserburg, 1977; O'Nions and al.,1977). b) Constrains linking geochemical observations and geodynamics. How the so-called depleted mantle is generated ? Continuities and affinities between MORB and OIB, including the Dupal and Non Dupal provinces: The non-pristine source for OIB based on Pb isotope data. The marble cake structure for upper mantle. Continental crust recycling via sediments and delamination processes. In thise respect, we emphasize the difference in statistical variance of isotope or trace element ratios in the different/types of basalts reflecting the difference in stirring intensity in their sources. We also use information from extinct radioactivities 142Nd and 129Xe. In each case, we estimate the errors for measurements and models. c) The seismic evidence of slab penetration into the lower mantle are from Creager and Jordan(1984) to Van der Hilst et al.(1991), Sparkman and al.(1993), with the counter example of non

  16. Increased mantle heat flow with on-going rifting of the West Antarctic rift system inferred from characterisation of plagioclase peridotite in the shallow Antarctic mantle

    NASA Astrophysics Data System (ADS)

    Martin, A. P.; Cooper, A. F.; Price, R. C.

    2014-03-01

    The lithospheric, and shallow asthenospheric, mantle in Southern Victoria Land are known to record anomalously high heat flow but the cause remains imperfectly understood. To address this issue plagioclase peridotite xenoliths have been collected from Cenozoic alkalic igneous rocks at three localities along a 150 km transect across the western shoulder of the West Antarctic rift system in Southern Victoria Land, Antarctica. There is a geochemical, thermal and chronological progression across this section of the rift shoulder from relatively hot, young and thick lithosphere in the west to cooler, older and thinner lithosphere in the east. Overprinting this progression are relatively more recent mantle refertilising events. Melt depletion and refertilisation was relatively limited in the lithospheric mantle to the west but has been more extensive in the east. Thermometry obtained from orthopyroxene in these plagioclase peridotites indicates that those samples most recently affected by refertilising melts have attained the highest temperatures, above those predicted from idealised dynamic rift or Northern Victoria Land geotherms and higher than those prevailing in the equivalent East Antarctic mantle. Anomalously high heat flow can thus be attributed to entrapment of syn-rift melts in the lithosphere, probably since regional magmatism commenced at least 24 Myr ago. The chemistry and mineralogy of shallow plagioclase peridotite mantle can be explained by up to 8% melt extraction and a series of refertilisation events. These include: (a) up to 8% refertilisation by a N-MORB melt; (b) metasomatism involving up to 1% addition of a subduction-related component; and (c) addition of ~ 1.5% average calcio-carbonatite. A high MgO group of clinopyroxenes can be modelled by the addition of up to 1% alkalic melt. Melt extraction and refertilisation mainly occurred in the spinel stability field prior to decompression and uplift. In this region mantle plagioclase originates by a

  17. New Insights Into the Heat Sources of Mantle Plumes, or: Where Does all the Heat Come From, Heat Producing Elements, Advective or Conductive Heat Flow?

    NASA Astrophysics Data System (ADS)

    Rushmer, T.; Beier, C.; Turner, S.

    2007-12-01

    Melting anomalies in the Earth's upper mantle have often been attributed to the presence of mantle plumes that may originate in the lower mantle, possibly from the core-mantle boundary. Globally, mantle plumes exhibit a large range in buoyancy flux that which is proportional to their temperature and volume. Plumes with higher buoyancy fluxes should have higher temperatures and experience higher degrees of partial melting. Excess heat in mantle plumes could reflect either a) an enrichment of the heat producing elements (HPE: U, Th, K) in their mantle source leading to an increase of heat production by radioactive decay or b) advective or conductive heat transport across the core-mantle boundary. The advective transport of heat may result in a physical contribution of material from the core to the lower mantle. If core material is incorporated into the lower mantle, mantle plumes with a higher buoyancy flux should have higher core tracers, e.g. increased 186Os and Fe concentrations. Geophysical and dynamic modelling indicate that at least Afar, Easter, Hawaii, Louisville and Samoa may all originate at the core-mantle boundary. These plumes encompass the whole range of known buoyancy fluxes from 1.2 Mgs -1(Afar) to 6.5 Mgs -1 (Hawaii) providing evidence that the buoyancy flux is largely independent of other geophysical parameters. In an effort to explore whether the heat producing elements are the cause of excess heat we looked for correlations between fractionation corrected concentrations of the HPE and buoyancy flux. Our results suggest that there is no correlation between HPE concentrations and buoyancy flux (with and without an additional correction for variable degrees of partial melting). As anticipated, K, Th and U are positively correlated with each other (e.g. Hawaii, Iceland and Galapagos have significantly lower concentrations than e.g. Tristan da Cunha, the Canary Islands and the Azores). We also find no correlation between currently available Fe

  18. Heat flow increase following the rise of mantle isotherms and crustal thinning

    NASA Technical Reports Server (NTRS)

    Mareschal, J. C.; Bergantz, G.

    1985-01-01

    Heat flow measurements in the western United States define a zone of high heat flow which coincides with the Basin and Range Province where extension has taken place recently. In this region, the average reduced heat flow is approx 30 mW sq. meters higher than in stable continental provinces; locally (e.g., Battle Mountain High), the heat flow anomaly can be more than 100 mW/sq meters above average. Estimates of the amount of extension range between 30% and 100% for the past 30 Ma. In the Colorado Plateau, which has been uplifted without major tectonic deformation, the heat flow is only slightly above average. Analytical calculations show that an abrupt change in heat flow at the base of the lithosphere 30 Ma ago would not affect the surface significantly. Uplift would proceed at a slow rate. A thermal perturbation at the base of a 40 km thick crust, however, would reach the surface faster and, after 30 Ma, the increase in surface heat flow would be about 75% of the amplitude of the heat flow anomaly. The number of volcanic rocks in the Basin and Range suggests that magma intrusions may provide an effective heat transfer mechanism. It can be show that if the source of the intrusions is at the base of the lithosphere, the response time will be much longer than 30 Ma, and most ot the heat transferred from the asthenosphere will be absorbed in the lithosphere.

  19. Heat sources for mantle plumes

    NASA Astrophysics Data System (ADS)

    Beier, C.; Rushmer, T.; Turner, S. P.

    2008-06-01

    Melting anomalies in the Earth's upper mantle have often been attributed to the presence of mantle plumes that may originate in the lower mantle, possibly from the core-mantle boundary. Globally, mantle plumes exhibit a large range in buoyancy flux that is proportional to their temperature and volume. Plumes with higher buoyancy fluxes should have higher temperatures and experience higher degrees of partial melting. This excess heat in mantle plumes could reflect either (1) an enrichment of the heat-producing elements (HPE: U, Th, K) in their mantle source leading to an increase of heat production by radioactive decay, (2) material transport from core to mantle (either advective or diffusive), or (3) conductive heat transport across the core-mantle boundary. The advective/diffusive transport of heat may result in a physical contribution of material from the core to the lower mantle. If core material is incorporated into the lower mantle, mantle plumes with a higher buoyancy flux should have higher core tracers, e.g., increased 186Os, 187Os, and Fe concentrations. Geophysical and dynamic modeling indicate that at least Afar, Easter, Hawaii, Louisville, and Samoa may all originate at the core-mantle boundary. These plumes encompass the whole range of known buoyancy fluxes from 0.9 Mg s-1 (Afar) to 8.7 Mg s-1 (Hawaii), providing evidence that the buoyancy flux is largely independent of other geophysical parameters. In an effort to explore whether the heat-producing elements are the cause of excess heat we looked for correlations between fractionation-corrected concentrations of the HPE and buoyancy flux. Our results suggest that there is no correlation between HPE concentrations and buoyancy flux (with and without an additional correction for variable degrees of partial melting). As anticipated, K, Th, and U are positively correlated with each other (e.g., Hawaii, Iceland, and Galapagos have significantly lower concentrations than, e.g., Tristan da Cunha, the Canary

  20. 2-D numerical simulations of groundwater flow, heat transfer and 4He transport — implications for the He terrestrial budget and the mantle helium heat imbalance

    NASA Astrophysics Data System (ADS)

    Castro, Maria Clara; Patriarche, Delphine; Goblet, Patrick

    2005-09-01

    Because helium and heat production results from a common source, a continental 4He crustal flux of 4.65 * 10 - 14 mol m - 2 s - 1 has been estimated based on heat flow considerations. In addition, because the observed mantle He / heat flux ratio at the proximity of mid-ocean ridges (6.6 * 10 - 14 mol J - 1 ) is significantly lower than the radiogenic production ratio (1.5 * 10 - 12 mol J - 1 ), the presence of a terrestrial helium-heat imbalance was suggested. The latter could be explained by the presence of a layered mantle in which removal of He is impeded from the lower mantle [R.K. O'Nions, E.R. Oxburgh, Heat and helium in the Earth, Nature 306 (1983) 429-431; E.R. Oxburgh, R.K. O'Nions, Helium loss, tectonics, and the terrestrial heat budget, Science 237 (1987) 1583-1588]. van Keken et al. [P.E. van Keken, C.J. Ballentine, D. Porcelli, A dynamical investigation of the heat and helium imbalance, Earth Planet, Sci. Lett. 188 (2001) 421-434] have recently claimed that the helium-heat imbalance remains a robust observation. Such conclusions, however, were reached under the assumption that a steady-state regime was in place for both tracers and that their transport properties are similar at least in the upper portion of the crust. Here, through 2-D simulations of groundwater flow, heat transfer and 4He transport carried out simultaneously in the Carrizo aquifer and surrounding formations in southwest Texas, we assess the legitimacy of earlier assumptions. Specifically, we show that the driving transport mechanisms for He and heat are of a fundamentally different nature for a high range of permeabilities ( k ≤ 10 - 16 m 2) found in metamorphic and volcanic rocks at all depths in the crust. The assumption that transport properties for these two tracers are similar in the crust is thus unsound. We also show that total 4He / heat flux ratios lower than radiogenic production ratios do not reflect a He deficit in the crust or mantle original reservoir. Instead, they

  1. Location of eastern Mediterranean hot springs induced by mantle heat flow due to slab roll-back and tearing

    NASA Astrophysics Data System (ADS)

    Roche, V. M.; Sternai, P.; Guillou-Frottier, L.; Jolivet, L.; Gerya, T.

    2016-12-01

    The Aegean-Anatolian retreating subduction and collision zones have been investigated through 3D numerical geodynamic models involving slab rollback/tearing/breakoff constrained by, for instance, seismic tomography or anisotropy and geochemical proxies. Here we integrate these investigations by using geothermal anomaly measurements from western Turkey. Such data provides insights into the thermal state of the Aegean-Anatolian region at depth and reflects the development of a widespread active geothermal province that is unlikely to be related only to the Quaternary volcanism because this has a too limited extent in space and time. Firstly, we look for possible connections with larger-scale mantle dynamics and use 3D high-resolution petrological and thermo-mechanical numerical models to quantify the potential contribution of the Aegean-Anatolian subduction dynamics to such measured thermal anomalies. Secondly, the subduction-induced thermal signature at the base of the continental crust is then inserted as the imposed basal thermal condition of 2D models dedicated to the understanding of fluid flow in the shallow crust. These models couple heat transfer and fluid flow equations with appropriate fluid and rock physical properties. Results from the 3D numerical models suggest an efficient control of subduction-related asthenospheric return flow on the regional distribution of thermal anomalies. Results from the 2D numerical models also highlight that low angle normal faults (detachments) in the back-arc region can control the bulk of the heat transport and fluid circulation patterns. Such detachments can drain hot crustal and/or mantellic fluids down to several kilometers depths, thus allowing for or fostering deep fluid circulation.

  2. Mantle flow reversals in cylindrical Earth models

    NASA Astrophysics Data System (ADS)

    Ghias, Sanaz R.; Jarvis, Gary T.

    2007-12-01

    We employ a two-dimensional model of mantle convection in a cylindrical shell to study the influence of curvature on the phenomenon of spontaneous flow reversal, which has been found previously only in plane layer models in Cartesian geometry. Our model includes rigidly moving plates, with weak zones at each end, and uniformly distributed internal heat sources. Surface plates in this model are passive in that their lateral velocities reflect the overall buoyancy in the underlying mantle and, at each time step, match the average surface velocity that would occur in the absence of plates. Our principal finding is that flow reversals, similar to those in plane layers, are also found in our cylindrical shell models, thereby attesting to the robustness of this feature. We conduct systematic investigations of the impact on the flow reversal behavior of varying degree of curvature, plate thickness, internal heating rate and aspect ratio of the convection cells. Flow reversals are driven by a build-up of internally heated material adjacent to a major mantle downwelling. When thermal instabilities develop in the upper boundary layer they develop into intermediate sinking plumes which disrupt the build-up of hot material near sinking plumes. Accordingly, parameter values which tend to stabilize the upper thermal boundary layer (low degree of curvature, high plate thickness, small aspect ratio and intermediate internal heating rate) favor regular flow reversals.

  3. A Numerical Study of Energy Balances and Flow Planforms in Earth's Mantle with Radioactive Heating, the 660 km-depth Phase Boundary and Continents

    NASA Astrophysics Data System (ADS)

    Sinha, Gunjan

    wavelength of convective flows and mixed surface boundary conditions strongly increase the horizontal wavelength of convection. My study shows that for mixed cases the effects of the surface boundary conditions dominate the effects of the phase boundary. I show that the calculations with complete continental coverage have the most significantly decoupled lower and upper mantle flows and substantial thermal and mechanical layering. Unlike the free-slip case where the surface heat flux decreases substantially with increasing magnitude of the Clapeyron slope, surface heat flux is shown to be almost independent of the Clapeyron slope for mixed boundary condition cases. Although very different when not layered, models with free and mixed surfaces have very similar planforms with very large aspect ratio flows when run with large magnitudes of the Clapeyron slope. I also calculate the critical boundary layer Rayleigh number as a measure of the thermal resistance of the surface boundary layer. My results show that the thermal resistance in the oceanic and the continental regions of the mixed cases are similar to fully free and no-slip cases, respectively. I find that, even for purely basally heated models, the mantle becomes significantly subadiabatic in the presence of partial continental coverage. This is due to the significant horizontal advection of heat that occurs with very large aspect ratio convection cells.

  4. Exploring Geothermal Energy Potential in Ireland through 3-D Geophysical-Petrological Modelling of Surface Heat-Flow and Crustal and Upper-Mantle Structure

    NASA Astrophysics Data System (ADS)

    Fullea, J.; Muller, M. R.; Jones, A. G.

    2012-04-01

    Little is known of Ireland's deep, low-enthalpy geothermal resources and the potential for space heating and/or electricity generation based on geothermal energy to displace Ireland's significant reliance on carbon-based fuels. IRETHERM (www.iretherm.ie) is a four-and-a-half year, all-island, academic-government-industry collaborative project, initiated in 2011, with the overarching objective of developing a strategic and holistic understanding of Ireland's geothermal energy potential through integrated modelling of new and existing geophysical and geological data. One of the challenges in searching for deep geothermal resources in the relatively unexplored setting of Ireland lies in identifying those areas most likely to support significantly elevated temperatures at depth. Available borehole data, although sparse and clustered around areas of mineral and hydrocarbon interest, suggest a marked regional increase in surface heat-flow across Ireland, from ~40 mW/m2 in the south to >80 mW/m2 in the north. The origins of both the observed regional heat-flow trend and local temperature anomalies have not been investigated and are not currently understood. Although variations in the structure of the crust and lithosphere have been revealed by a number of active-source seismic and teleseismic experiments, their effects on surface heat-flow have not been modelled. Bulk 3-D variation in crustal heat-production across Ireland, which may contribute significantly to the observed regional and local temperature variations, has also not been determined. We investigate the origins of Ireland's regional heat-flow trend and regional and local temperature variations using the software package LitMod. This software combines petrological and geophysical modelling of the lithosphere and sub-lithospheric upper mantle within an internally consistent thermodynamic-geophysical framework, where all relevant properties are functions of temperature, pressure and chemical composition. The major

  5. Convectively Driven Heat Flux Heterogeneity in Europa's Mantle

    NASA Astrophysics Data System (ADS)

    Travis, Bryan; Schubert, G.; Palguta, J.

    2006-09-01

    Features on the surface of Europa may reflect non-uniform heating in an underlying ocean due to variations in heat flux at the mantle surface. Pore water convection can generate a spatially heterogeneous heat flux in a fractured, permeable mantle, as illustrated in 2-D computer simulations of the thermal evolution of Europa. The model uses three layers - core, silicate mantle, and H2O (liquid and frozen). Processes active in the model include radiogenic heating, tidal dissipative heating (TDH), thermal diffusion, latent heat of melting and pore water convection. Starting from a cold Europa, radiogenic heating and TDH produce a temperature profile ranging from a peak near 1150 oC in the deep interior to 15 oC at the mantle surface, overlain by an 80 km deep ocean layer at 3 oC, capped by an ice shell approximately 20 km thick. This structure provides initial conditions for our pore water convection simulation. Mantle permeability is based on Earth values. An initial, very strong flow gives way to a weaker quasi-steady pattern of convection in the mantle's porosity. Plumes rise from the mantle at a roughly 10o spacing, through the ocean layer up to the base of the ice. These are typically 50 - 100 km wide at the base of the ice. Plume heat flux is 10-12 W/m2 during the initial transient, but later drops to about 0.5 - 1.5 W/m2. Heating at the base of the ice shell is spatially heterogeneous, but only strong enough to produce significant melt-through during the initial transient. However, strong spatial heterogeneity of basal heating of the ice shell could significantly influence convection in the ice phase. This work was supported by a grant from the Institute of Geophysics and Planetary Physics at Los Alamos National Laboratory and by the NASA Planetary Geology and Geophysics Program.

  6. On the role of the porous shell of the solid core of the earth in the anomalous heat and mass flow to the mantle

    SciTech Connect

    Pikin, S. A.

    2013-03-15

    The model of the pressure-induced first-order phase transition of a metal melt to the metallicglass state considers a thermodynamically nonequilibrium porous near-surface shell of the solid core of the Earth, which contacts cyclonic vortices in the liquid core. Anomalous flows of heat and light-material mass to the mantle from the solid core at these contact points are calculated. These anomalous flows are shown to be comparable with the observed ones under the assumption of a rapid increase in the melt viscosity at pressures of 1-10 Mbar, which is characteristic of a solid core. In this case, the porous layer permeability may be very low.

  7. Sharp Thermal Transition in the Forearc Mantle Wedge as a Consequence of Nonlinear Mantle Wedge Flow

    NASA Astrophysics Data System (ADS)

    Wada, I.; Wang, K.; Jiangheng, H.

    2009-12-01

    . The change is even more abrupt if the dislocation-creep rheology is applied to both the mantle wedge and interface. The abrupt onset of interface coupling and the bimodal flow behaviour leads to a sharp thermal transition between the cold stagnant and hot flowing parts of the forearc mantle wedge, explaining the observed attenuation structure of the forearc mantle wedge. The onset of interface coupling at 70-80 km depth can explain the location of the sharp attenuation increase and also the observed surface heat flow pattern and petrologically and geochemically constrained mantle temperatures beneath the arc in most subduction zones. In Mariana, where attenuation in the wedge nose is relatively high, the effect of the cold wedge nose on attenuation is likely to be offset by a high degree of serpentinization as evidenced by wide-spread serpentine mud volcanism (Wada and Wang, 2009, G-cubed, in press).

  8. Horizontal mantle flow controls subduction dynamics.

    PubMed

    Ficini, E; Dal Zilio, L; Doglioni, C; Gerya, T V

    2017-08-08

    It is generally accepted that subduction is driven by downgoing-plate negative buoyancy. Yet plate age -the main control on buoyancy- exhibits little correlation with most of the present-day subduction velocities and slab dips. "West"-directed subduction zones are on average steeper (~65°) than "East"-directed (~27°). Also, a "westerly"-directed net rotation of the lithosphere relative to the mantle has been detected in the hotspot reference frame. Thus, the existence of an "easterly"-directed horizontal mantle wind could explain this subduction asymmetry, favouring steepening or lifting of slab dip angles. Here we test this hypothesis using high-resolution two-dimensional numerical thermomechanical models of oceanic plate subduction interacting with a mantle flow. Results show that when subduction polarity is opposite to that of the mantle flow, the descending slab dips subvertically and the hinge retreats, thus leading to the development of a back-arc basin. In contrast, concordance between mantle flow and subduction polarity results in shallow dipping subduction, hinge advance and pronounced topography of the overriding plate, regardless of their age-dependent negative buoyancy. Our results are consistent with seismicity data and tomographic images of subduction zones. Thus, our models may explain why subduction asymmetry is a common feature of convergent margins on Earth.

  9. Superplumes from the core-mantle boundary to the lithosphere: implications for heat flux.

    PubMed

    Romanowicz, Barbara; Gung, Yuancheng

    2002-04-19

    Three-dimensional modeling of upper-mantle anelastic structure reveals that thermal upwellings associated with the two superplumes, imaged by seismic elastic tomography at the base of the mantle, persist through the upper-mantle transition zone and are deflected horizontally beneath the lithosphere. This explains the unique transverse shear wave isotropy in the central Pacific. We infer that the two superplumes may play a major and stable role in supplying heat and horizontal flow to the low-viscosity asthenospheric channel, lubricating plate motions and feeding hot spots. We suggest that more heat may be carried through the core-mantle boundary than is accounted for by hot spot fluxes alone.

  10. Petrologically-constrained thermo-chemical modelling of cratonic upper mantle consistent with elevation, geoid, surface heat flow, seismic surface waves and MT data

    NASA Astrophysics Data System (ADS)

    Jones, A. G.; Afonso, J. C.

    2015-12-01

    The Earth comprises a single physio-chemical system that we interrogate from its surface and/or from space making observations related to various physical and chemical parameters. A change in one of those parameters affects many of the others; for example a change in velocity is almost always indicative of a concomitant change in density, which results in changes to elevation, gravity and geoid observations. Similarly, a change in oxide chemistry affects almost all physical parameters to a greater or lesser extent. We have now developed sophisticated tools to model/invert data in our individual disciplines to such an extent that we are obtaining high resolution, robust models from our datasets. However, in the vast majority of cases the different datasets are modelled/inverted independently of each other, and often even without considering other data in a qualitative sense. The LitMod framework of Afonso and colleagues presents integrated inversion of geoscientific data to yield thermo-chemical models that are petrologically consistent and constrained. Input data can comprise any combination of elevation, geoid, surface heat flow, seismic surface wave (Rayleigh and Love) data and receiver function data, and MT data. The basis of LitMod is characterization of the upper mantle in terms of five oxides in the CFMAS system and a thermal structure that is conductive to the LAB and convective along the adiabat below the LAB to the 410 km discontinuity. Candidate solutions are chosen from prior distributions of the oxides. For the crust, candidate solutions are chosen from distributions of crustal layering, velocity and density parameters. Those candidate solutions that fit the data within prescribed error limits are kept, and are used to establish broad posterior distributions from which new candidate solutions are chosen. Examples will be shown of application of this approach fitting data from the Kaapvaal Craton in South Africa and the Rae Craton in northern Canada. I

  11. Upper-Mantle Flow Driven Dynamic Topography in Eastern Anatolia

    NASA Astrophysics Data System (ADS)

    Sengul Uluocak, Ebru; Pysklywec, Russell; Eken, Tuna; Hakan Gogus, Oguz

    2016-04-01

    Eastern Anatolia is characterized by 2 km plateau uplift -in the last 10 Myrs-, high surface heat flow distribution, shallow Curie-point depth, anomalous gravity field. Seismological observations indicate relatively high Pn and Sn attenuation and significant low seismic velocity anomalies in the region. Moreover, the surface geology is associated predominantly with volcanic rocks in which melt production through mantle upwelling (following lithospheric delamination) has been suggested. It has been long known that the topographic loading in the region cannot be supported by crustal thickness (~45 km) based on the principle of Airy isostasy. Recent global geodynamic studies carried out for evaluating the post-collisional processes imply that there is an explicit dynamic uplift in Eastern Anatolia and its adjacent regions. In this study we investigate the instantaneous dynamic topography driven by 3-D upper-mantle flow in Eastern Anatolia. For this purpose we conducted numerous thermo-mechanical models using a 2-D Arbitrary Lagrangian Eulerian (ALE) finite element method. The available P-wave tomography data extracted along 10 profiles were used to obtain depth-dependent density anomalies in the region. We present resulting dynamic topography maps and estimated 3D mantle flow velocity vectors along these 2-D cross sections for each profile. The residual topography based on crustal thickness and observed topography was calculated and compared with other independent datasets concerning geological deformation and dynamic topography predictions. The results indicate an upper mantle driven dynamic uplift correlated with the under-compensated characteristic in Eastern Anatolia. We discuss our results combined with 3D mantle flow by considering seismic anisotropy studies in the region. Initial results indicate that high dynamic uplift and the localized low Pn velocities in concurrence with Pn anisotropy structures show nearly spatial coherence in Eastern Anatolia.

  12. Mantle flow drives the subsidence of oceanic plates.

    PubMed

    Adam, Claudia; Vidal, Valérie

    2010-04-02

    The subsidence of the sea floor is generally considered a consequence of its passive cooling and densifying since its formation at the ridge and is therefore regarded as a function of lithospheric age only. However, the lithosphere is defined as the thermal boundary layer of mantle convection, which should thus determine its structure. We examined the evolution of the lithosphere structure and depth along trajectories representative of the underlying mantle flow. We show that along these flow lines, the sea-floor depth varies as the square root of the distance from the ridge (as given by the boundary-layer equation) along the entire plate, without any flattening. Contrary to previous models, no additional heat supply is required at the base of the lithosphere.

  13. Seismic evidence for a tilted mantle plume and north-south mantle flow beneath Iceland

    USGS Publications Warehouse

    Shen, Y.; Solomon, S.C.; Bjarnason, I. Th; Nolet, G.; Morgan, W.J.; Allen, R.M.; Vogfjord, K.; Jakobsdottir, S.; Stefansson, R.; Julian, B.R.; Foulger, G.R.

    2002-01-01

    Shear waves converted from compressional waves at mantle discontinuities near 410- and 660-km depth recorded by two broadband seismic experiments in Iceland reveal that the center of an area of anomalously thin mantle transition zone lies at least 100 km south of the upper-mantle low-velocity anomaly imaged tomographically beneath the hotspot. This offset is evidence for a tilted plume conduit in the upper mantle, the result of either northward flow of the Icelandic asthenosphere or southward flow of the upper part of the lower mantle in a no-net-rotation reference frame. ?? 2002 Elsevier Science B.V. All rights reserved.

  14. Map of Io's volcanic heat flow

    NASA Astrophysics Data System (ADS)

    Davies, Ashley Gerard; Veeder, Glenn J.; Matson, Dennis L.; Johnson, Torrence V.

    2015-12-01

    We present a map of Io's volcanic heat flow. Io's high heat flow is a result of intense tidal heating, which generates widespread volcanic activity. The surface expression of ongoing volcanic activity constrains the location and magnitude of tidal dissipation within Io. Tidal heating models place heating either at relatively shallow (aesthenosphere) levels, or deep in the mantle. It was thought that actual tidal heating could be approximated using a combination of these end-member models. Io's volcanic heat flow has now been mapped in sufficient detail to compare with the models. Our maps show that the distribution of heat flow is not matched by current models of deep nor shallow tidal heating, nor by any combination of these two models. We find relatively low heat flow at sub-jovian (0°W) and anti-jovian (180°W) longitudes, at odds with the pure aesthenospheric heating model. Furthermore, there are large swaths of Io's surface where there is poor correlation between the number of hot spots in an area and the power emitted. We have previously accounted for ≈54% of Io's observed heat flow. We now show that Io's anomalously warm poles, possibly the result of heat flow from deep-mantle heating, would yield the ;missing; energy (48 TW) if the polar surfaces are at temperatures of ∼90 K to ∼95 K and cover latitudes above ∼43° to ∼48° respectively. This possibility implies a ratio of deep to shallow heating of about 1:1. However, explaining regional variations in surface volcanic activity requires more detailed modeling of the location and magnitude of the internal tidal dissipation and the consequences of mantle convection and advection within Io. Future model predictions can be compared to our heat flow map.

  15. Role of mantle flow in Nubia-Somalia plate divergence

    NASA Astrophysics Data System (ADS)

    Stamps, D. S.; Iaffaldano, G.; Calais, E.

    2015-01-01

    Present-day continental extension along the East African Rift System (EARS) has often been attributed to diverging sublithospheric mantle flow associated with the African Superplume. This implies a degree of viscous coupling between mantle and lithosphere that remains poorly constrained. Recent advances in estimating present-day opening rates along the EARS from geodesy offer an opportunity to address this issue with geodynamic modeling of the mantle-lithosphere system. Here we use numerical models of the global mantle-plates coupled system to test the role of present-day mantle flow in Nubia-Somalia plate divergence across the EARS. The scenario yielding the best fit to geodetic observations is one where torques associated with gradients of gravitational potential energy stored in the African highlands are resisted by weak continental faults and mantle basal drag. These results suggest that shear tractions from diverging mantle flow play a minor role in present-day Nubia-Somalia divergence.

  16. Numerical Modeling of Deep Mantle Flow: Thermochemical Convection and Entrainment

    NASA Astrophysics Data System (ADS)

    Mulyukova, Elvira; Steinberger, Bernhard; Dabrowski, Marcin; Sobolev, Stephan

    2013-04-01

    One of the most robust results from tomographic studies is the existence of two antipodally located Large Low Shear Velocity Provinces (LLSVPs) at the base of the mantle, which appear to be chemically denser than the ambient mantle. Results from reconstruction studies (Torsvik et al., 2006) infer that the LLSVPs are stable, long-lived, and are sampled by deep mantle plumes that rise predominantly from their margins. The origin of the dense material is debated, but generally falls within three categories: (i) a primitive layer that formed during magma ocean crystallization, (ii) accumulation of a dense eclogitic component from the recycled oceanic crust, and (iii) outer core material leaking into the lower mantle. A dense layer underlying a less dense ambient mantle is gravitationally stable. However, the flow due to thermal density variations, i.e. hot rising plumes and cold downwelling slabs, may deform the layer into piles with higher topography. Further deformation may lead to entrainment of the dense layer, its mixing with the ambient material, and even complete homogenisation with the rest of the mantle. The amount of the anomalous LLSVP-material that gets entrained into the rising plumes poses a constraint on the survival time of the LLSVPs, as well as on the plume buoyancy, on the lithospheric uplift associated with plume interaction and geochemical signature of the erupted lavas observed at the Earth's surface. Recent estimates for the plume responsible for the formation of the Siberian Flood Basalts give about 15% of entrained dense recycled oceanic crust, which made the hot mantle plume almost neutrally buoyant (Sobolev et al., 2011). In this numerical study we investigate the mechanics of entrainment of a dense basal layer by convective mantle flow. We observe that the types of flow that promote entrainment of the dense layer are (i) upwelling of the dense layer when it gets heated enough to overcome its stabilizing chemical density anomaly, (ii

  17. Role of subduction obliquity in controlling mantle wedge flow and subduction zone processes

    NASA Astrophysics Data System (ADS)

    Wada, I.; He, J.; Jilek, E.

    2016-12-01

    In this study, we investigate the role of subduction obliquity and its along-arc variation in controlling the 3-D mantle wedge flow pattern and subduction zone processes, using 3-D coupled kinematic-dynamic models that are developed for regions with oblique subduction, including southern Cascadia, Northeast Japan, Hikurangi, and the Izu-Bonin-Mariana arc. In subduction zones, the motion of the subducting slab drives the overlying mantle to flow away from the mantle wedge corner. The dynamic pressure gradient induced by the mantle outflow then drives the mantle in the back-arc region to flow in towards the wedge corner, resulting in mantle wedge flow. 3-D subduction models with realistic slab geometries indicate that the obliquity of the subduction direction relative to the local strike of the subducting slab is a critical factor that contributes to along-arc dynamic pressure gradients in the mantle wedge, inducing a 3-D mantle wedge flow pattern. In general, oblique subduction causes the streamlines of mantle inflow and outflow to be approximately symmetric about the axis normal to the strike of the slab, and the angle between the two streamlines increases with subduction obliquity. In regions with large subduction obliquity, such as southern Hikurangi and northern Mariana, the angle can locally become so large that mantle flow appears nearly arc-parallel. Along-arc variation in the slab geometry adds further complexity to the 3-D mantle wedge flow pattern via changes in the strike of the slab and thus subduction obliquity. Mantle wedge flow patterns affect a number of important processes in subduction zones, such as the transport of heat and volatiles, development of crystal and shape preferred orientations, mantle wedge hydration, and slab dehydration. We test the modeled-predicted mantle wedge flow patterns for the aforementioned subduction zones against available geophysical observations, including seismic velocity and attenuation structures, mantle wedge

  18. Planetary Cores Flows Driven by Mantle Libration

    NASA Astrophysics Data System (ADS)

    Noir, J.; Aurnou, J.; Wicht, J.

    2007-12-01

    We investigate, via a set of laboratory and numerical experiments, the flow induced inside a spherical fluid cavity by torsional oscillation of the outer shell. Our goal is to produce models of libration-driven flows within planetary cores and subsurface oceans. Such models will improve our understanding of a number of planetary bodies including Mercury, Europa, Io, Callisto, Ganymede and the Earth's Moon. Here we focus on the case of a spherical shell with either a small inner core or no inner core; moderate planetary rotation rate (Ekman number E = 10- 4); and libration frequency equal to the planetary rotation frequency ("synchronous libration"). We vary only the non-dimensional amplitude of libration α, defined as α=Δ φ (2 π flib) / Ømega, where Δ φ is the total angular displacement, flib is the libration frequency and Ømega is the background angular rotation rate. Different core flow regimes are observed as α is increased. For a small amplitude of libration (α \\ll 1)), the oscillatory motion of the outer boundary drives laminar flows that are well described as inertial modes and waves. For α ~ 0.5, azimuthal roll instabilities periodically develop and decay along the outer shell boundary during each libration cycle. These instabilities tend to develop when the outer shell is decelerating and decay when it is accelerating. By further increasing α, the flow pattern transitions from axisymmetric rolls (m=0) to wavy rolls (m ≠ 0), and then to turbulent flow. Extrapolating our present results to Mercury suggests that mantle libration can drive large-scale instabilities in its liquid metal core. The authors wish to the thank NASA's PG&G and PME Programs for reasearch funding under grant #NNG0697G.

  19. Thermal Evolution of Diapirs with Complex Mantle Wedge Flow

    NASA Astrophysics Data System (ADS)

    Sylvia, R. T.; Kincaid, C.

    2016-12-01

    Subduction of oceanic lithosphere drives heat and mass exchange between Earth's interior and surface. One proposed transport mechanism for thermally and chemically distinct material through the wedge is the diapir model. The dominant driver of flow in the upper mantle is a mode of forced convection responding to motion of a tabular slab. A set of 4D laboratory experiments was conducted exploring the relationship between buoyancy flux and subduction parameters and subsequent effects on diapir transport. Variable subduction styles tested include downdip and rollback motion, slab gaps, slab steepening and backarc extension. The mantle is modeled using viscous glucose syrup with an Arrhenius type temperature dependent viscosity. Diapirs representing homogeneous mechanically mixed melange layer are introduced as buoyant fluid injected at multiple point sources situated along the surface of the sinking slab. Laboratory data is collected using high definition time-lapse photography and quantified using image velocimetry techniques. Here we present results from numerical simulation of the thermal evolution of spherical mantle wedge diapirs using 2D axisymmetric advection-diffusion model with internal diapir flow described by an analytic potential flow solution. A suite of wedge temperature profiles are used as thermal forcing on diapirs traversing the wedge along experimentally observed 4D ascent pathways. Scaling arguments suggest that for systems with Péclet number on the order of 15 advective heat transport is expected to dominate over diffusive heat transport, but the range of observed P-T-t paths and vigorous internal flow complicate this assumption. Interactions between modes of free (diapiric) and forced (wedge) convection lead to complex spatio-temporal variability in slab-to-arc connectivity patterns. Rollback induced toroidal flow, along trench changes in dip, convergence rate and backarc extension all produce a significant ( 500 km) trench-parallel transport

  20. Pitfalls in modeling mantle convection with internal heat production

    NASA Astrophysics Data System (ADS)

    Korenaga, Jun

    2017-05-01

    The mantle of the Earth, and probably of other terrestrial planets as well, is heated from below and within. The heating mode of mantle convection is thus mixed heating, and it is also time dependent because the amount of heat-producing isotopes in the mantle is steadily decreasing by radioactive decay and because the basal heat flux originating in the cooling of the core can vary with time. This mode of transient mixed heating presents its own challenges to the study of mantle convection, but such difficulties are not always appreciated in the recent literature. The purpose of this tutorial is to clarify the issue of heating mode by explaining relevant concepts in a coherent manner, including the internal heating ratio, the Urey ratio, secular cooling, and the connection between the thermal budget of the Earth and the geochemical models of the Earth. The importance of such basic concepts will be explained with some illustrative examples in the context of the thermal evolution of the Earth, and a summary of common pitfalls will be provided, with a possible strategy for how to avoid them.

  1. Heat flow in the Kenya rift zone

    NASA Astrophysics Data System (ADS)

    Wheildon, J.; Morgan, Paul; Williamson, K. H.; Evans, T. R.; Swanberg, C. A.

    1994-09-01

    An understanding of the processes of continental rifting is fundamental to understanding the evolution of the continents. Considerable evidence exists to suggest that continental rift zones are associated with high heat flow and elevated lithospheric geotherms, but direct heat-flow measurements from young rifts do not clearly define surface heat-flow anomalies associated with deep-seated thermal processes in these rifts. The first detailed compilation of heat-flow data from the Neogene Kenya rift is presented here. Heat-flow data are presented from traditional heat-flow determinations in water drill-holes, from bottom-hole-temperature measurements in oil wells, and from heat-flow estimates from groundwater silica data. These data define generally low heat flow on the flanks of the Kenya rift, with high, but variable heat flow on the rift floor. There is a spatial association among high heat-flow values, Quaternary volcanism and faulting, and hydrothermal manifestations on the rift floor. We interpret these results to suggest that any deep-seated thermal anomaly associated with the Kenya rift has not yet been conducted to the surface. The high heat-flow values are interpreted to result from heat advected into the axial rift zone with local redistribution of this heat by hydrothermal convection. Normal to moderately high heat flow was measured in eastern Kenya between the rift zone and the coast. The regional heat flow in eastern Kenya is interpreted to be normal, with local shallow modification by groundwater flow eastward from the Kenya dome. These interpretations support a model of relatively young evolution of the asthenospheric anomaly beneath the Kenya rift zone, with the age of heating of the mantle at the Mono no older than about 10 Ma.

  2. Mantle convection with continental drift and heat source around the mantle transition zone

    NASA Astrophysics Data System (ADS)

    Ichikawa, H.; Kameyama, M.; Kawai, K.

    2012-12-01

    Geological studies have suggested that significant amount of granitic crustal materials have been lost from the surface by the delamination (~1.1 km^3/yr) [1], continental collision (~0.4-0.7 km^3/yr) [1, 2], and subduction at ocean-margin (~2.5-3 km^3/yr) [1, 2]. At ocean-margin subduction zones, most of the granitic materials subducted from the surface are expected to be conveyed through subduction channels by viscous drag to 270km depth [Ichikawa el al., in revision]. If so, then the subducted crustal materials might be expected to be trapped in the mid-mantle owing to the density difference from peridotitic materials induced by the phase transition from coesite to stishovite at 270km depth. In other words, strong heat source materials are most likely to be accumulated around the mantle transition zone, at least, near the plate subduction zones. In this study, we conducted two-dimensional numerical experiments of mantle convection with continental drift and a heat source placed around the mantle transition zone, in order to study the effect of the subducted granitic materials drifting around the mantle transition zone. The simulations deal with a time-dependent convection of fluid under the extended Boussinesq approximation in a model of a two-dimensional rectangular box of 2900km height and 11600km width, where a continent and heat source is imposed. We found that the addition of the heat source considerably reduces the time scale of continental drift. In the absence of the heat source, the resulting time scale is too long compared with that of the so-called supercontinent cycle, where the breakup is induced from a plume generated by an insulating effect of the continent. The heat source also causes massive mechanical mixing especially on the upper mantle. The result suggests that the heat source drifting around mantle transition zone can be a possible candidate inducing the supercontinent cycle in an appropriate time scale. [1] Clift, P. D., P. Vannucchi, and

  3. Geoneutrino perspective on Earth's heat budget and mantle structure

    NASA Astrophysics Data System (ADS)

    Sramek, O.; McDonough, W. F.; Kite, E. S.; Lekic, V.; Dye, S.; Zhong, S.

    2012-12-01

    Neutrino geophysics is an emerging interdisciplinary field with the potential to map the abundances and distribution of radiogenic heat sources in the continental crust and deep Earth. To date, data from two different experiments quantify the amount of Th and U in the Earth, and begin to put constraints on radiogenic power in the Earth available for driving mantle convection and plate tectonics. New improved detectors are under construction or in planning stages. Critical testing of compositional models of the Earth requires integrating geoneutrino and geological observations. Such tests will lead to significant constraints on the absolute and relative abundances of Th and U in the continents. High radioactivity in continental crust puts limits on land-based observatories' capacity to resolve mantle models with current detection methods. However, the quantification of deep-seated radioactivity is crucial for understanding the composition and dynamics of the Earth, including its thermal evolution, the style and planform of mantle convection, and the energetics of the core. Estimates of mantle radiogenic heat production vary significantly between some models. Th and U budget of Earth's compositional models based on enstatite chondrite chemistry, as well as models that employ an early loss of crustal material by a collisional erosion mechanism are consistent with a uniform mantle composition. Typically, these models end up with negligible amount of radiogenic power in the mantle after accounting for that in the crust. On the other hand, models constrained by composition of available Earth rock samples and C1 chondritic ratios of refractory lithophile elements require a mantle reservoir enriched in heat producing elements relative to the source of mid-oceanic ridge basalts. Such a reservoir is likely to show strong variation in thickness in the convecting mantle; it is usually identified with the seismically seen low shear wave velocity provinces (LLSVPs) in the deep

  4. On retrodictions of global mantle flow with assimilated surface velocities

    NASA Astrophysics Data System (ADS)

    Colli, Lorenzo; Bunge, Hans-Peter; Schuberth, Bernhard S. A.

    2015-10-01

    Modeling past states of Earth's mantle and relating them to geologic observations such as continental-scale uplift and subsidence is an effective method for testing mantle convection models. However, mantle convection is chaotic and two identical mantle models initialized with slightly different temperature fields diverge exponentially in time until they become uncorrelated, thus limiting retrodictions (i.e., reconstructions of past states of Earth's mantle obtained using present information) to the recent past. We show with 3-D spherical mantle convection models that retrodictions of mantle flow can be extended significantly if knowledge of the surface velocity field is available. Assimilating surface velocities produces in some cases negative Lyapunov times (i.e., e-folding times), implying that even a severely perturbed initial condition may evolve toward the reference state. A history of the surface velocity field for Earth can be obtained from past plate motion reconstructions for time periods of a mantle overturn, suggesting that mantle flow can be reconstructed over comparable times.

  5. On retrodictions of global mantle flow with assimilated surface velocities

    NASA Astrophysics Data System (ADS)

    Colli, Lorenzo; Bunge, Hans-Peter; Schuberth, Bernhard S. A.

    2016-04-01

    Modeling past states of Earth's mantle and relating them to geologic observations such as continental-scale uplift and subsidence is an effective method for testing mantle convection models. However, mantle convection is chaotic and two identical mantle models initialized with slightly different temperature fields diverge exponentially in time until they become uncorrelated, thus limiting retrodictions (i.e., reconstructions of past states of Earth's mantle obtained using present information) to the recent past. We show with 3-D spherical mantle convection models that retrodictions of mantle flow can be extended significantly if knowledge of the surface velocity field is available. Assimilating surface velocities produces in some cases negative Lyapunov times (i.e., e-folding times), implying that even a severely perturbed initial condition may evolve toward the reference state. A history of the surface velocity field for Earth can be obtained from past plate motion reconstructions for time periods of a mantle overturn, suggesting that mantle flow can be reconstructed over comparable times.

  6. The mantle flow field beneath western North America.

    PubMed

    Silver, P G; Holt, W E

    2002-02-08

    Although motions at the surface of tectonic plates are well determined, the accompanying horizontal mantle flow is not. We have combined observations of surface deformation and upper mantle seismic anisotropy to estimate this flow field for western North America. We find that the mantle velocity is 5.5 +/- 1.5 centimeters per year due east in a hot spot reference frame, nearly opposite to the direction of North American plate motion (west-southwest). The flow is only weakly coupled to the motion of the surface plate, producing a small drag force. This flow field is probably due to heterogeneity in mantle density associated with the former Farallon oceanic plate beneath North America.

  7. Internally heated mantle convection and the thermal and degassing history of the earth

    NASA Technical Reports Server (NTRS)

    Williams, David R.; Pan, Vivian

    1992-01-01

    An internally heated model of parameterized whole mantle convection with viscosity dependent on temperature and volatile content is examined. The model is run for 4l6 Gyr, and temperature, heat flow, degassing and regassing rates, stress, and viscosity are calculated. A nominal case is established which shows good agreement with accepted mantle values. The effects of changing various parameters are also tested. All cases show rapid cooling early in the planet's history and strong self-regulation of viscosity due to the temperature and volatile-content dependence. The effects of weakly stress-dependent viscosity are examined within the bounds of this model and are found to be small. Mantle water is typically outgassed rapidly to reach an equilibrium concentration on a time scale of less than 200 Myr for almost all models, the main exception being for models which start out with temperatures well below the melting temperature.

  8. Internally heated mantle convection and the thermal and degassing history of the earth

    NASA Technical Reports Server (NTRS)

    Williams, David R.; Pan, Vivian

    1992-01-01

    An internally heated model of parameterized whole mantle convection with viscosity dependent on temperature and volatile content is examined. The model is run for 4l6 Gyr, and temperature, heat flow, degassing and regassing rates, stress, and viscosity are calculated. A nominal case is established which shows good agreement with accepted mantle values. The effects of changing various parameters are also tested. All cases show rapid cooling early in the planet's history and strong self-regulation of viscosity due to the temperature and volatile-content dependence. The effects of weakly stress-dependent viscosity are examined within the bounds of this model and are found to be small. Mantle water is typically outgassed rapidly to reach an equilibrium concentration on a time scale of less than 200 Myr for almost all models, the main exception being for models which start out with temperatures well below the melting temperature.

  9. Planetary heat flow measurements.

    PubMed

    Hagermann, Axel

    2005-12-15

    The year 2005 marks the 35th anniversary of the Apollo 13 mission, probably the most successful failure in the history of manned spaceflight. Naturally, Apollo 13's scientific payload is far less known than the spectacular accident and subsequent rescue of its crew. Among other instruments, it carried the first instrument designed to measure the flux of heat on a planetary body other than Earth. The year 2005 also should have marked the launch of the Japanese LUNAR-A mission, and ESA's Rosetta mission is slowly approaching comet Churyumov-Gerasimenko. Both missions carry penetrators to study the heat flow from their target bodies. What is so interesting about planetary heat flow? What can we learn from it and how do we measure it?Not only the Sun, but all planets in the Solar System are essentially heat engines. Various heat sources or heat reservoirs drive intrinsic and surface processes, causing 'dead balls of rock, ice or gas' to evolve dynamically over time, driving convection that powers tectonic processes and spawns magnetic fields. The heat flow constrains models of the thermal evolution of a planet and also its composition because it provides an upper limit for the bulk abundance of radioactive elements. On Earth, the global variation of heat flow also reflects the tectonic activity: heat flow increases towards the young ocean ridges, whereas it is rather low on the old continental shields. It is not surprising that surface heat flow measurements, or even estimates, where performed, contributed greatly to our understanding of what happens inside the planets. In this article, I will review the results and the methods used in past heat flow measurements and speculate on the targets and design of future experiments.

  10. Tomography-based mantle flow beneath Mongolia-Baikal area

    NASA Astrophysics Data System (ADS)

    Zhu, Tao

    2014-12-01

    Recent progress in seismic tomography of Asia allows us to explore and understand more clearly the mantle flow below the Mongolia-Baikal area. We present a tomography-based model of mantle convection that provides a good match to the residual topography. The model provides predictions on the present-day mantle flow and flow-induced asthenospheric deformation which give us new insights on the mantle dynamics in the Mongolia-Baikal area. The predicted mantle flow takes on a very similar pattern at the depths shallower or deeper than 400 km and almost opposite flow directions between the upper (shallower than 400 km) and lower (deeper than 400 km) parts. The flow pattern could be divided into the 'simple' eastern region and the 'complex' western region in the Mongolia. The upwelling originating from about 350 km depth beneath Baikal rift zone is an important possible drive force to the rifting. The seismic anisotropy cannot be simply related with asthenospheric flow and flow-induced deformation in the entire Mongolia-Baikal area, but they could be considered as an important contributor to the seismic anisotropy in the eastern region of Mongolia and around and in Sayan-Baikal orogenic belt.

  11. Mantle flow influence on the evolution of subduction systems.

    NASA Astrophysics Data System (ADS)

    Chertova, Maria; Spakman, Wim; Steinberger, Bernhard

    2016-04-01

    Evolution of the subducting slab has been widely investigated in the past two decades be means of numerical and laboratory modeling, including analysis of the factors controlling its behavior. However, until present, relatively little attention has been paid to the influence of the mantle flow. While for large subduction zones, due to the high slab buoyancy force, this effect might be small, mantle flow might be a primary factor controlling the evolution of a regional subduction zone. Here we investigate the impact of prescribed mantle flow on the evolution of both generic and real-Earth subduction models by means of 3D thermo-mechanical numerical modeling. The generic setup consists of a laterally symmetric subduction model using a 3000×2000×1000 km modeling domain with a lateral slab width varying from 500 to 1500 km. Non-linear rheology is implemented including diffusion, dislocation creep and a viscosity-limiter. To satisfy mass conservation, while implementing mantle inflow on some side boundaries, we keep other sides open (Chertova et al. 2012). To test the mantle flow influence on the dynamics of real-Earth subduction zone we adopt the numerical model from Chertova et al. (2014) for the evolution of the western Mediterranean subduction since 35 Ma. First, this model was tested with the arbitrary mantle flow prescribed on one of the four side boundaries or for the combination of two boundaries. In the last set of experiments, for side boundary conditions we use time-dependent estimates of actual mantle flow in the region based on Steinberger (2015) given for every 1 My. We demonstrate that for the western-Mediterranean subduction, the surrounding mantle flow is of second-order compared to slab buoyancy in controlling the dynamics of the subducting slab. Introducing mantle flow on the side boundaries might, however, improve the fit between the modeled and real slab imaged by tomography, although this may also trade-off with varying rheological parameters of

  12. Heat flow in Oklahoma

    NASA Astrophysics Data System (ADS)

    Cranganu, Constantin

    Twenty new heat flow values are incorporated, along with 40 previously published data, into a heat flow map of Oklahoma. The new heat flow data were estimated using previous temperature measurements in boreholes made by American Petroleum Institute researchers and 1,498 thermal conductivity measurements on drill cuttings. The mean of 20 average thermal gradients is 30.50sp°C/km. In general, thermal gradients increase from SW (14.11sp°C/km) to NE (42.24sp°C/km). The range of 1,498 in situ thermal conductivity measurements (after corrections for anisotropy, in situ temperature, and porosity) is 0.90-6.1 W/m-K; the average is 1.68 W/m-K. Estimated near-surface heat flow (±20%) at 20 new sites in Oklahoma varies between 22 ± 4 mW/msp2 and 86 ± 17 mW/msp2; the average is 50 mW/msp2. Twenty-seven new heat-generation estimates, along with 22 previously published data, are used to create a heat generation map of Oklahoma. The range of heat production estimates is 1.1-3.5 muW/msp3, with an average of 2.5 muW/msp3. The heat flow regime in Oklahoma is primarily conductive in nature, except for a zone in northeast. Transient effects due to sedimentary processes and metamorphic/igneous activity, as well as past climatic changes, do not significantly influence the thermal state of the Oklahoma crust. Heat flow near the margins of the Arkoma and Anadarko Basins may be depressed or elevated by 5-13 mW/msp2 by refraction of heat from sedimentary rocks of relatively low thermal conductivity (1-2 W/m-K) into crystalline basement rocks of relatively high thermal conductivity (˜3-4 W/m-K). The heat generation-heat flow relationship shows a modest correlation. The relatively high heat flow (˜70-80 mW/msp2) in part of northeastern Oklahoma suggests that the thermal regime there may be perturbed by regional groundwater flow originating in the fractured outcrops of the Arbuckle-Simpson aquifer in the Arbuckle Mountains.

  13. Seismic anisotropy and mantle flow below subducting slabs

    NASA Astrophysics Data System (ADS)

    Walpole, Jack; Wookey, James; Kendall, J.-Michael; Masters, T.-Guy

    2017-05-01

    Subduction is integral to mantle convection and plate tectonics, yet the role of the subslab mantle in this process is poorly understood. Some propose that decoupling from the slab permits widespread trench parallel flow in the subslab mantle, although the geodynamical feasibility of this has been questioned. Here, we use the source-side shear wave splitting technique to probe anisotropy beneath subducting slabs, enabling us to test petrofabric models and constrain the geometry of mantle fow. Our global dataset contains 6369 high quality measurements - spanning ∼ 40 , 000 km of subduction zone trenches - over the complete range of available source depths (4 to 687 km) - and a large range of angles in the slab reference frame. We find that anisotropy in the subslab mantle is well characterised by tilted transverse isotropy with a slow-symmetry-axis pointing normal to the plane of the slab. This appears incompatible with purely trench-parallel flow models. On the other hand it is compatible with the idea that the asthenosphere is tilted and entrained during subduction. Trench parallel measurements are most commonly associated with shallow events (source depth < 50 km) - suggesting a separate region of anisotropy in the lithospheric slab. This may correspond to the shape preferred orientation of cracks, fractures, and faults opened by slab bending. Meanwhile the deepest events probe the upper lower mantle where splitting is found to be consistent with deformed bridgmanite.

  14. Has Northern Hemisphere Heat Flow Been Underestimated?

    NASA Astrophysics Data System (ADS)

    Gosnold, W. D.; Majorowicz, J.; Safanda, J.; Szewczyk, J.

    2005-05-01

    We present three lines of evidence to suggest the hypothesis that heat flow in the northern hemisphere may have been underestimated by 15 to 60 percent in shallow wells due to a large post-glacial warming signal. First, temperature vs. depth (T-z) measurements in parts of Europe and North America show a systematic increase in heat flow with depth. This phenomenon is best recognized in analyses of deep (greater than 2km) boreholes in non-tectonic regions with normal to low background heat flow. In Europe, the increase in heat flow with depth has been observed by analysis of more than 1500 deep boreholes located throughout the Fennoscandian Shield, East European Platform, Danish Basin, Germany, Czech Republic, and Poland. There are significantly fewer deep boreholes in North America, but the increase in heat flow with depth appears in a suite of 759 sites in the IHFC Global Heat Flow Database for the region east of the Rocky Mountains and north of latitude 40 N. Second, surface heat flow values in southern hemisphere shields average approximately 50 mWm-2, but surface heat flow values in northern hemisphere shields average 33 mWm-2. Unless crustal radioactivity or mantle heat flow or both factors are greater in southern hemisphere continents, there is no reason for the northern and southern shield areas having similar ages to have different heat flow values. Third, two recently published surface heat flow maps show anomalously low heat flow in the Canadian Shield in a pattern that is coincident with the Wisconsinan ice sheet. The coincidence of low heat flow and ice accumulation has no geophysical basis, thus the coincidence may suggest the existence of a transient signal caused by a warming event. Recent studies of heat flow in North America indicate that in several sites, the ice base temperature was close to the pressure melting point. We hypothesize that there may have been cold ice-free periods during the Pleistocene that would account for the apparent colder

  15. Resolving the Mantle Heat Transfer Discrepancy by Reassessing Buoyancy Flux Estimates of Upwelling Plumes

    NASA Astrophysics Data System (ADS)

    Hoggard, Mark; Parnell-Turner, Ross; White, Nicky

    2017-04-01

    The size and relative importance of mantle plumes is a controversial topic within the geodynamics community. Numerical experiments of mantle convection suggest a wide range of possible behaviours, from minor plumelets through to large scale, whole-mantle upwellings. In terms of observations, recent seismic tomographic models have identified many large, broad plume-like features within the lower mantle. In contrast, existing estimates of buoyancy flux calculated from plume swells have suggested that these upwellings transfer a relatively minor amount of material and heat into the uppermost mantle. Here, we revisit these calculations of buoyancy flux using a global map of plume swells based upon new observations of dynamic topography. Usually, plume flux is calculated from the cross-sectional area of a swell multiplied by either plate velocity or spreading rate. A key assumption is that plume head material flows laterally at or below the velocity of the overriding plate. Published results are dominated by contributions from the Pacific Ocean and suggest that a total of ˜ 2 TW of heat is carried by plumes into the uppermost mantle. An alternative approach exploits swell volume scaled by a characteristic decay time, which removes the reliance on plate velocities. The main assumption of this method is that plumes are in quasi-steady state. In this study, we have applied this volumetric approach in a new global analysis. Our results indicate that the Icelandic plume has a buoyancy flux of ˜ 27 ± 4 Mg s-1 and the Hawaiian plume is ˜ 2.9 ± 0.6 Mg s-1. These revised values are consistent with independent geophysical constraints from the North Atlantic Ocean and Hawaii. All magmatic and amagmatic swells have been included, suggesting that the total heat flux carried to the base of the plates is ˜ 10 ± 2 TW. This revised value is a five-fold increase compared with previous estimates and provides an improved match to published predictions of basal heat flux across the

  16. Enceladus' Enigmatic Heat Flow

    NASA Astrophysics Data System (ADS)

    Howett, C.; Spencer, J. R.; Spencer, D.; Verbiscer, A.; Hurford, T.; Segura, M.

    2013-12-01

    Accurate knowledge of Enceladus' heat flow is important because it provides a vital constraint on Enceladus' tidal dissipation mechanisms, orbital evolution, and the physical processes that generate the plumes. In 2011 we published an estimate of the current heat flow from Enceladus' active south polar terrain: 15.8 +/- 3.1 GW (Howett et al., 2011). This value was calculated by first estimating by modeling, and then removing, the passive component from 17 to 1000 micron observations made of the entire south polar terrain by Cassini's Composite Infrared Spectrometer (CIRS). The heat flow was then directly calculated from the residual, assumed endogenic, component. The derived heat flow of 15.8 GW was surprisingly high, about 10 times greater than that predicted by steady-state tidal heating (Meyer and Wisdom, 2007). CIRS has also returned high spatial resolution observations of Enceladus' active south polar terrain. Two separate observations are used: 9 to 16 micron observations taken over nearly the complete south polar terrain and a single 17 to 1000 micron scan over Damascus, Baghdad and Cairo. The shorter wavelength observations are only sensitive to high temperature emission (>70 K), and so longer wavelength observations are required (despite their limited spatial coverage) to estimate the low temperature emission from the stripes. Analysis of these higher resolution observations tells a different story of Enceladus' endogenic heat flow: the preliminary estimate of the heat flow from the active tiger stripes using these observations is 4.2 GW. An additional 0.5 GW must be added to this number to account for the latent heat release by the plumes (Ingersoll and Pankine 2009), giving a total preliminary estimate of 4.9 GW. The discrepancy in these two numbers is significant and we are currently investigating the cause. One possible reason is that there is significantly higher endogenic emission from the regions between the tiger stripes than we currently estimate

  17. Convective heat flow probe

    DOEpatents

    Dunn, James C.; Hardee, Harry C.; Striker, Richard P.

    1985-01-01

    A convective heat flow probe device is provided which measures heat flow and fluid flow magnitude in the formation surrounding a borehole. The probe comprises an elongate housing adapted to be lowered down into the borehole; a plurality of heaters extending along the probe for heating the formation surrounding the borehole; a plurality of temperature sensors arranged around the periphery of the probe for measuring the temperature of the surrounding formation after heating thereof by the heater elements. The temperature sensors and heater elements are mounted in a plurality of separate heater pads which are supported by the housing and which are adapted to be radially expanded into firm engagement with the walls of the borehole. The heat supplied by the heater elements and the temperatures measured by the temperature sensors are monitored and used in providing the desired measurements. The outer peripheral surfaces of the heater pads are configured as segments of a cylinder and form a full cylinder when taken together. A plurality of temperature sensors are located on each pad so as to extend along the length and across the width thereof, with a heating element being located in each pad beneath the temperature sensors. An expansion mechanism driven by a clamping motor provides expansion and retraction of the heater pads and expandable packer-type seals are provided along the probe above and below the heater pads.

  18. Convective heat flow probe

    DOEpatents

    Dunn, J.C.; Hardee, H.C.; Striker, R.P.

    1984-01-09

    A convective heat flow probe device is provided which measures heat flow and fluid flow magnitude in the formation surrounding a borehole. The probe comprises an elongate housing adapted to be lowered down into the borehole; a plurality of heaters extending along the probe for heating the formation surrounding the borehole; a plurality of temperature sensors arranged around the periphery of the probe for measuring the temperature of the surrounding formation after heating thereof by the heater elements. The temperature sensors and heater elements are mounted in a plurality of separate heater pads which are supported by the housing and which are adapted to be radially expanded into firm engagement with the walls of the borehole. The heat supplied by the heater elements and the temperatures measured by the temperature sensors are monitored and used in providing the desired measurements. The outer peripheral surfaces of the heater pads are configured as segments of a cylinder and form a full cylinder when taken together. A plurality of temperature sensors are located on each pad so as to extend along the length and across the width thereof, with a heating element being located in each pad beneath the temperature sensors. An expansion mechanism driven by a clamping motor provides expansion and retraction of the heater pads and expandable packet-type seals are provided along the probe above and below the heater pads.

  19. Heat Flow Measurement

    NASA Technical Reports Server (NTRS)

    1993-01-01

    Heat gauges are used to measure heat flow in industrial activities. They must periodically be certified by instruments designed to provide a heat flux measurement standard. CSTAR, a NASA CCDS, and REMTECH have developed a portable heat flux checker/calibrator. The Q-CHEC can be carried to the heat gauge for certification, reducing out of service time for the gauge and eliminating the need for a replacement gauge during certification. It can provide an "end-to-end" check of the instrumentation measurement system or be used as a standalone calibrator. Because Q-CHEC offers on-site capability to detect and eliminate measurement errors, measurements do not have to be repeated, and money is saved.

  20. Radial flow heat exchanger

    DOEpatents

    Valenzuela, Javier

    2001-01-01

    A radial flow heat exchanger (20) having a plurality of first passages (24) for transporting a first fluid (25) and a plurality of second passages (26) for transporting a second fluid (27). The first and second passages are arranged in stacked, alternating relationship, are separated from one another by relatively thin plates (30) and (32), and surround a central axis (22). The thickness of the first and second passages are selected so that the first and second fluids, respectively, are transported with laminar flow through the passages. To enhance thermal energy transfer between first and second passages, the latter are arranged so each first passage is in thermal communication with an associated second passage along substantially its entire length, and vice versa with respect to the second passages. The heat exchangers may be stacked to achieve a modular heat exchange assembly (300). Certain heat exchangers in the assembly may be designed slightly differently than other heat exchangers to address changes in fluid properties during transport through the heat exchanger, so as to enhance overall thermal effectiveness of the assembly.

  1. Lunar heat flow: Regional prospective of the Apollo landing sites

    NASA Astrophysics Data System (ADS)

    Siegler, M. A.; Smrekar, S. E.

    2014-01-01

    reexamine the Apollo Heat Flow Experiment in light of new orbital data. Using three-dimensional thermal conduction models, we examine effects of crustal thickness, density, and radiogenic abundance on measured heat flow values at the Apollo 15 and 17 sites. These models show the importance of regional context on heat flux measurements. We find that measured heat flux can be greatly altered by deep subsurface radiogenic content and crustal density. However, total crustal thickness and the presence of a near-surface radiogenic-rich ejecta provide less leverage, representing only minor (<1.5 mW m-2) perturbations on surface heat flux. Using models of the crust implied by Gravity Recovery and Interior Laboratory results, we found that a roughly 9-13 mW m-2 mantle heat flux best approximate the observed heat flux. This equates to a total mantle heat production of 2.8-4.1 × 1011 W. These heat flow values could imply that the lunar interior is slightly less radiogenic than the Earth's mantle, perhaps implying that a considerable fraction of terrestrial mantle material was incorporated at the time of formation. These results may also imply that heat flux at the crust-mantle boundary beneath the Procellarum potassium, rare earth element, and phosphorus (KREEP) Terrane (PKT) is anomalously elevated compared to the rest of the Moon. These results also suggest that a limited KREEP-rich layer exists beneath the PKT crust. If a subcrustal KREEP-rich layer extends below the Apollo 17 landing site, required mantle heat flux can drop to roughly 7 mW m-2, underlining the need for future heat flux measurements outside of the radiogenic-rich PKT region.

  2. Heat flow in Oklahoma

    SciTech Connect

    Cranganu, C.; Deming, D.

    1996-12-31

    Oklahoma is one area in which terrestrial heat flow data are sparse. The thermal state of the southern mid-continent, however, is a key to understanding several important geologic problems. These include thermal anomalies associated with Paleozoic fluid migrations and the formation of Mississippi Valley-type lead-zinc deposits, the thermal evolution of the Arkoma and Anadarko sedimentary basins, and the history of hydrocarbon generation and overpressuring in the Anadarko Basin. In the late 1920s, the American Petroleum Institute made a set of equilibrium temperature logs in idle oil wells. These temperature data are generally regarded as being high quality, accurate estimates of rock temperature and they cover the entire central part of Oklahoma. Average thermal gradients in the API survey range from 14 to 43 {sup 0}C/km (average 31.2 {sup 0}C/km) over depth intervals that extend from the surface to a an average depth of 961 m. Geothermal gradients decrease from NNE to SSW. The observed change in thermal gradients could be due to a number of factors. The change in thermal gradients could simply reflect changes in lithology and thermal conductivity. Alternatively, the variation in thermal gradients could be indicative of a change in heat flow related perhaps to variations in the concentration of radioactive heat-producing elements in the crust or heat transport by one or more regional groundwater flow systems. We are proceeding to reduce ambiguity in interpretation by estimating heat flow from thermal conductivity measurements on drill cuttings and heat production from available gamma-ray logs which penetrate basement rocks.

  3. Heat flow in Oklahoma

    SciTech Connect

    Cranganu, C.; Deming, D. )

    1996-01-01

    Oklahoma is one area in which terrestrial heat flow data are sparse. The thermal state of the southern mid-continent, however, is a key to understanding several important geologic problems. These include thermal anomalies associated with Paleozoic fluid migrations and the formation of Mississippi Valley-type lead-zinc deposits, the thermal evolution of the Arkoma and Anadarko sedimentary basins, and the history of hydrocarbon generation and overpressuring in the Anadarko Basin. In the late 1920s, the American Petroleum Institute made a set of equilibrium temperature logs in idle oil wells. These temperature data are generally regarded as being high quality, accurate estimates of rock temperature and they cover the entire central part of Oklahoma. Average thermal gradients in the API survey range from 14 to 43 [sup 0]C/km (average 31.2 [sup 0]C/km) over depth intervals that extend from the surface to a an average depth of 961 m. Geothermal gradients decrease from NNE to SSW. The observed change in thermal gradients could be due to a number of factors. The change in thermal gradients could simply reflect changes in lithology and thermal conductivity. Alternatively, the variation in thermal gradients could be indicative of a change in heat flow related perhaps to variations in the concentration of radioactive heat-producing elements in the crust or heat transport by one or more regional groundwater flow systems. We are proceeding to reduce ambiguity in interpretation by estimating heat flow from thermal conductivity measurements on drill cuttings and heat production from available gamma-ray logs which penetrate basement rocks.

  4. Lattice thermal conductivity of lower mantle minerals and heat flux from Earth’s core

    PubMed Central

    Manthilake, Geeth M.; de Koker, Nico; Frost, Dan J.; McCammon, Catherine A.

    2011-01-01

    The amount of heat flowing from Earth’s core critically determines the thermo-chemical evolution of both the core and the lower mantle. Consisting primarily of a polycrystalline aggregate of silicate perovskite and ferropericlase, the thermal boundary layer at the very base of Earth’s lower mantle regulates the heat flow from the core, so that the thermal conductivity (k) of these mineral phases controls the amount of heat entering the lowermost mantle. Here we report measurements of the lattice thermal conductivity of pure, Al-, and Fe-bearing MgSiO3 perovskite at 26 GPa up to 1,073 K, and of ferropericlase containing 0, 5, and 20% Fe, at 8 and 14 GPa up to 1,273 K. We find the incorporation of these elements in silicate perovskite and ferropericlase to result in a ∼50% decrease of lattice thermal conductivity relative to the end member compositions. A model of thermal conductivity constrained from our results indicates that a peridotitic mantle would have k = 9.1 ± 1.2 W/m K at the top of the thermal boundary layer and k = 8.4 ± 1.2 W/m K at its base. These values translate into a heat flux of 11.0 ± 1.4 terawatts (TW) from Earth’s core, a range of values consistent with a variety of geophysical estimates. PMID:22021444

  5. Heat flow of the Norwegian continental shelf

    NASA Astrophysics Data System (ADS)

    Pascal, Christophe

    2015-04-01

    Terrestrial heat flow influences a large collection of geological processes. Its determination is a requirement to assess the economic potential of deep sedimentary basins. Published heat flow calculations from e.g. major oil provinces are however seldom. Robust heat flow determinations in drillholes require logging of undisturbed temperatures and intensive sampling of core material for petrophysical measurements. Temperature logging in exploration drillholes is traditionally conducted during drill breaks or shortly after drilling, resulting in temperatures severely disturbed by mud circulation and coring is restricted to selected intervals. Alternatively, test temperatures, information from electric logs and lithological descriptions of drill cuttings can be used to overcome these limitations. The present contribution introduces new heat flow determinations based on 63 exploration drillholes from the Norwegian North Sea, the Mid Norway Margin and the Barents Shelf. Our analyses are based on released DST temperatures, precise lithological descriptions of drill cuttings, previously measured rock matrix thermal conductivities and established porosity laws. Our results suggest median heat flow values of 64 mW/m2, 65 mW/m2 and 72 mW/m2 for the North Sea, the Mid Norway Margin (mainly the Trøndelag Platform) and the SW Barents Shelf respectively. The Barents Shelf shows significantly high heat flow, suggesting lateral transfer of heat from the mantle of the adjacent young ocean. In detail, heat flow increases by ~ 10 mW/m2 from the southern Norwegian North Sea towards the Mid Norway Margin. This result appears to be in very good agreement with seismic tomographic studies suggesting northward thinning of the underlying mantle lithosphere. Our results together with published marine heat flow data from the Mid Norway Margin suggest a gradual decrease in heat flow levels from both the North Sea and the Trøndelag Platform towards the centres of the deep Møre and V

  6. Heat flow in structures

    SciTech Connect

    Burrer, G.J.

    1980-01-01

    Heat is transferred through a wall structure by the mechanisms of conduction, convection, and radiation. These mechanisms are introduced and developed in terms of their thermal resistances. Temperature difference is identified as the cause of heat flow through the structure which is impeded by the thermal resistances of the structures. Calculations are made of the thermal resistances at several points in a specific test wall section. The performance predicted from these calculations is compared to thermographic measurements made on the wall under laboratory controlled conditions. These comparisons are used to draw conclusions as to the usefulness and limitations of thermographic practices.

  7. Flow of mantle fluids through the ductile lower crust: Heliumisotope trends

    SciTech Connect

    Kennedy, B. Mack; van Soest, Matthijs C.

    2007-10-07

    Heat and mass are injected into the shallow crust when mantle fluids are able to flow through the ductile lower crust. Minimum 3He/4He ratios in surface fluids from the northern Basin and Range province, western North America increase systematically from low, crustal values in the east to high, mantle values in the west, a regional trend that correlates with the rates of active crustal deformation. The highest ratios occur where the extension and shear strain rates are greatest. The correspondence of helium isotope ratios and active trans-tensional deformation indicates a deformation enhanced permeability and that mantle fluids can penetrate the ductile lithosphere in regions even where there is no significant magmatism. Superimposed on the regional trend are local, high-{sup 3}He/{sup 4}He anomalies signifying hidden magmatic activity and/or deep fluid production with locally enhanced permeability, identifying zones with high resource potential, particularly for geothermal energy development.

  8. Mantle Flow Pattern and Dynamic Topography beneath the Eastern US

    NASA Astrophysics Data System (ADS)

    Liu, S.; King, S. D.; Adam, C. M.; Long, M. D.; Benoit, M. H.; Kirby, E.

    2015-12-01

    The complex tectonic history of the eastern US over the past billion years includes episodes of subduction and rifting associated with two complete cycles of supercontinent assembly and breakup. Both the previous global tomography models (S40RTS, SAVANI, TX2011, GyPSuM, SMEAN) and the analysis of the shear-wave splitting from the broadband seismic stations find a distinct coast-to-inland differentiation pattern in the lithosphere and upper mantle. The Mid-Atlantic Geophysical Integrative Collaboration (MAGIC) includes a dense linear seismic array from the Atlantic coast of Virginia to the western boarder of Ohio, crossing several different tectonic zones. To derive the regional mantle flow pattern along with its surface expression such as dynamic topography and aid the interpretation of the seismic observations, we are building a new geodynamic model based on ASPECT (Advanced Solver for Problems in Earth CovecTion) that uses buoyancy derived from seismic tomography along with realistic lithosphere and sub-lithosphere structure. At present, we use S40RTS and SAVANI tomography models together with the temperature-dependent viscosity to compute the mantle flow and dynamic topography. Beneath the eastern US, the upper mantle flow in our model is primarily parallel to the trend of the Appalachian belt, which is broadly consistent with the direction of the local shear-wave splitting. The dynamic topography results exhibit a coast-to-inland magnitude differentiation along the MAGIC seismic deployment. The numerical tests also show that both the magnitude and pattern of the dynamic topography are quite sensitive to the density perturbation and rigidity of the lithosphere/sub-lithosphere. Our future work involves using other tomography and viscosity models to obtain the mantle flow pattern as well as the resulting dynamic topography and geoid.

  9. Heat flow and heat generation in greenstone belts

    NASA Technical Reports Server (NTRS)

    Drury, M. J.

    1986-01-01

    Heat flow has been measured in Precambrian shields in both greenstone belts and crystalline terrains. Values are generally low, reflecting the great age and tectonic stability of the shields; they range typically between 30 and 50 mW/sq m, although extreme values of 18 and 79 mW/sq m have been reported. For large areas of the Earth's surface that are assumed to have been subjected to a common thermotectonic event, plots of heat flow against heat generation appear to be linear, although there may be considerable scatter in the data. The relationship is expressed as: Q = Q sub o + D A sub o in which Q is the observed heat flow, A sub o is the measured heat generation at the surface, Q sub o is the reduced heat flow from the lower crust and mantle, and D, which has the dimension of length, represents a scale depth for the distribution of radiogenic elements. Most authors have not used data from greenstone belts in attempting to define the relationship within shields, considering them unrepresentative and preferring to use data from relatively homogeneous crystalline rocks. A discussion follows.

  10. New Map of Io's Volcanic Heat Flow

    NASA Astrophysics Data System (ADS)

    Davies, A. G.; Veeder, G. J.; Matson, D.; Johnson, T. V.

    2014-12-01

    We have created a global map of Io's volcanic heat flow from 245 thermal sources indicative of ongoing or recent volcanic activity, and 8 additional outbursts [1,2]. We incorporate data from both spacecraft and ground-based instruments that have observed Io primarily at infrared wavelengths. This map provides a snapshot of Io's volcanic activity and distribution during the Galileo epoch. Io's volcanic activity, in terms of thermal emission from individual eruptive centres, spans nearly six orders of magnitude, from Surt in 2001 (78 TW) [3] to a faint hot spot in patera P197 (0.2 GW) [1]. We account for ≈54% of Io's yearly volcanic heat flow, which emanates from ≈2% of Io's surface [1]. Averaged heat flow from the non-active surface is 1 ± 0.2 W m2. This quantification of volcanic heat flow map provides constraints for modelling the magnitude and location of the internal heating of Io by tidal dissipation. The observed heat flow distribution is the result of interior heating and volcanic advection, the delivery of magma to the surface regardless of its depth of origin. As noted previously [1, 2] the distribution of heat flow is not uniform, which is not unexpected. The volcanic heat flow does not match the expected distributions from end-member models for both the deep-seated (mantle) heating model (which predicts enhanced polar heating) and the shallow (aesthenospheric) heating model, which predicts enhanced thermal emission at sub-jovian and anti-jovian longitudes. Intriguingly, heat flow curves using a bin size of 30 degrees show a longitudinal offset from the shallow heating model prediction of some tens of degrees [2], suggesting a more complex mixture of deep and shallow heating. Future work includes refinement of thermal emission by including temporal variability of thermal emission at individual volcanoes, and comparing the heat flow map with the Io Geological Map [4] and global topography [5]. We thank the NASA OPR Program for support. Part of this

  11. Experimental investigation of flow-induced fabrics in rocks at upper-mantle pressures. Application to understanding mantle dynamics and seismic anisotropy

    SciTech Connect

    Durham, William B.

    2016-05-02

    The goal of this collaborative research effort between W.B. Durham at the Massachusetts Institute of Technology (MIT) and D.L. Kohlstedt and S. Mei at the University of Minnesota (UMN) was to exploit a newly developed technology for high-pressure, high-temperature deformation experimentation, namely, the deformation DIA (D-DIA), to determine the deformation behavior of a number of important upper mantle rock types including olivine, garnet, enstatite, and periclase. Experiments were carried out under both hydrous and anhydrous conditions and at both lithospheric and asthenospheric stress and temperature conditions. The result was a group of flow laws for Earth’s upper mantle that quantitatively describe the viscosity of mantle rocks from shallow depths (the lithosphere) to great depths (the asthenosphere). These flow laws are fundamental for modeling the geodynamic behavior and heat transport from depth to Earth’s surface.-

  12. Experimental investigation of flow-induced fabrics in rocks at upper-mantle pressures: Application to understanding mantle dynamics and seismic anisotropy

    SciTech Connect

    Kohlstedt, David L.

    2016-04-26

    The goal of this collaborative research effort between W.B. Durham at the Massachusetts Institute of Technology (MIT) and D.L. Kohlstedt and S. Mei at the University of Minnesota (UMN) was to exploit a newly developed technology for high-pressure, high-temperature deformation experimentation, namely, the deformation DIA (D-DIA) to determine the deformation behavior of a number of important upper mantle rock types including olivine, garnet, enstatite, and periclase. Experiments were carried out under both hydrous and anhydrous conditions and at both lithospheric and asthenospheric stress and temperature conditions. The result was a group of flow laws for Earth’s upper mantle that quantitatively describe the viscosity of mantle rocks from shallow depths (the lithosphere) to great depths (the asthenosphere). These flow laws are fundamental for modeling the geodynamic behavior and heat transport from depth to Earth’s surface.

  13. Mantle flow field in the southern Ryukyu subduction system

    NASA Astrophysics Data System (ADS)

    Lin, S.; Kuo, B.

    2012-12-01

    The Okinawa trough in the Ryukyu subduction system is the only active back arc basin formed within a continental lithosphere. Recent shear-wave splitting measurements show variable fast directions along the trough suggesting complex three-dimensional flow field in the mantle wedge. In this study we use numerical subduction models to explore the effects of plate thickness variations caused by non-uniform lithospheric stretching on the dynamics in the southern Ryukyu subduction system. We calculate orientations of infinite strain axes as a proxy for olivine lattice preferred orientations and orientations of seismic anisotropy. Our models demonstrate that flow patterns may vary significantly with depth near the plate edge as a result of the along-arc variations in lithospheric thickness. The model results show that the toroidal circulation around the lateral slab edge predominates at greater depths. The thick neighboring lithosphere acts as an effective barrier of the lateral mass exchanges in the shallow portion of the mantle wedge. The wedge material is drawn in horizontally toward the plate edge from the central region of the subduction zone induced by pressure gradients, opposite to the inwards lateral flow at greater depths. Model predictions for the lattice preferred orientations of olivine aggregates agree reasonably well with the observed shear-wave splitting patterns. The results suggest that the depth-varying flow field near the subduction zone edge and the westward flow components in the shallow portion of the mantle wedge may contribute to complex patterns of seismic anisotropy and arc isotopic systematics.

  14. Effects of a core/mantle chemical boundary layer with variable internal heat production on the thermal evolution of the core

    NASA Astrophysics Data System (ADS)

    Lassiter, J. C.

    2006-12-01

    Estimates of conductive heat flow across the core/mantle boundary suggest high heat flow values of 7-14 TW for a core/mantle temperature drop of 1000-1800 K. This level of heat flow predicts an inner core age of less than 1-2 Ga. However, some models of core/mantle thermal evolution predict late onset of inner core crystallization may require implausibly high core temperatures in the Archaean [1]. Sequestration of heat producing elements at the base of the mantle may reduce core/mantle heat flow and increase the age of the inner core [1]. In addition, Boyet and Carlson [2] reported ^{142}Nd excesses in terrestrial samples relative to chondrites, and proposed that an enriched reservoir produced by early differentiation may be "hidden" at the base of the mantle, and that this reservoir could contain up to 43% of the Earth's heat producing elements. The runaway core thermal evolution predicted by Buffett [1] for models with a relatively young inner core results from two assumptions. First, Buffett assumes that core/mantle heat flow has decreased ~3x since the onset of inner core crystallization, because the power required to drive the geodynamo today is much lower than prior to inner core crystallization. Second, Buffett treats the core/mantle boundary as a thermal boundary with strongly temperature-dependant viscosity, so that relatively small increases in core temperature result in a large decrease in boundary layer thickness and increase in core/mantle heat flow. If the core/mantle boundary is a chemical rather than purely thermal boundary the boundary layer thickness need not be time- or temperature-dependant. As a result, core/mantle heat flow is roughly linearly proportional to core-mantle ΔT, rather than exponential. Provided that modern core/mantle heat flow is greater than the heat flow required to drive the geodynamo in the absence of inner core crystallization, no significant secular evolution in core/mantle heat flow is required. Given these assumptions

  15. Geodynamics of the Yellowstone hotspot and mantle plume: Seismic and GPS imaging, kinematics, and mantle flow

    NASA Astrophysics Data System (ADS)

    Smith, Robert B.; Jordan, Michael; Steinberger, Bernhard; Puskas, Christine M.; Farrell, Jamie; Waite, Gregory P.; Husen, Stephan; Chang, Wu-Lung; O'Connell, Richard

    2009-11-01

    Integration of geophysical and geological data show that the Yellowstone hotspot resulted from a mantle plume interacting with the overriding North America plate, a process that has highly modified continental lithosphere by magmatic and tectonic processes and produced the 16-17 Ma, 700-km-long Yellowstone-Snake River Plain (YSRP) silicic volcanic system. Accessibility of the YSRP allowed large-scale geophysical projects to seismically image the hotspot and evaluate its kinematic properties using geodetic measurements. Seismic tomography reveals a crustal magma reservoir of 8% to 15% melt, 6 km to 16 km deep, beneath the Yellowstone caldera. An upper-mantle low-P-wave-velocity body extends vertically from 80 km to 250 km beneath Yellowstone, but the anomalous body tilts 60 °WNW and extends to 660 km depth into the mantle transition zone. We interpret this conduit-shaped low-velocity body as a plume of up to - 3.5% Vp and - 5.5% Vs perturbation that corresponds to a 1-2% partial melt. Models of whole mantle convection reveal eastward upper-mantle flow beneath Yellowstone at relatively high rates of 5 cm/yr that deflects the ascending plume into its west-tilted geometry. A geodynamic model of the Yellowstone plume constrained by Vp and Vs velocities and attenuation parameters suggests low excess temperatures of up to 120 K, corresponding to a maximum 2.5% melt, and a small buoyancy flux of 0.25 Mg/s, i.e., properties of a cool, weak plume. The buoyancy flux is many times smaller than for oceanic plumes, nonetheless, plume buoyancy has produced a ~ 400-km-wide, ~ 500-m-high topographic swell centered on the Yellowstone Plateau. Contemporary deformation derived from GPS measurements reveals SW extension of 2-3 mm/yr across the Yellowstone Plateau, one-fourth of the total Basin-Range opening rate, which we consider to be part of Basin-Range intraplate extension. Locally, decadal episodes of subsidence and uplift, averaging ~ 2 cm/yr, characterize the 80-year

  16. Upper mantle flow and lithospheric dynamics beneath the Eurasian region

    NASA Astrophysics Data System (ADS)

    Zhang, G.; Jiang, G.; Jia, Z.; Gao, R.; Fu, R.

    2010-12-01

    Evidence from seismic tomography, geothermal and short wavelength geoid anomalies reveals the existence of small-scale convective systems in the upper mantle, with scales ranging from 500 km to 700 km. It is reasonable to suggest that these small-scale convective systems probably control the regional tectonic structure and the dynamical processes of the lithosphere. Here we have calculated the patterns of small-scale convection in the upper mantle for the Eurasian region (20°E~170°E,15°N~75°N), using the anomaly of isostatic gravity. The results show that the regional lithospheric tectonics is strongly correlated with the upper mantle flow in the Eurasian region. Two intensive convective belts against the weak background convection can be recognized from convection patterns in this region: Alpine-Himalayan collision belt and West Pacific island arc-underthrust belt. Alpine-Himalayan belt is caused by the collision between the northern plate (Eurasian plate) and the southern plates (African plate and Indian plate). West Pacific island arc-underthrust belt is caused by the subduction of the Pacific plate beneath the Eurasian plate. Both of them are also seismotectonic belts. The collision and the subduction are two important geological events occurred since Mesozoic era and Cenozoic era in the Eurasian region. Therefore, the mantle flows may be one of the main driving forces of two events. In addition, most plate boundaries in this region can be recognized and the characteristics of upper mantle convection are different completely between the Eurasian plate and the plates around it (African plate, Arabian plate, Indian plate, Philippine Sea plate and Pacific plate). Main structures and geodynamic characteristics of the Eurasian can also be explained by our model results. The Tibet plateau is located in the intensive convective belt. Around the belt, the upwelling materials push the lithosphere to lift unitarily and form the plateau. Towards the north of the Tibet

  17. The Evolution of the Earth's Mantle Structure and Surface and Core-mantle Boundary Heat Flux since the Paleozoic

    NASA Astrophysics Data System (ADS)

    Zhang, N.; Zhong, S.

    2010-12-01

    The cause for and time evolution of the seismically observed African and Pacific slow anomalies (i.e., superplumes) are still unclear with two competing proposals. First, the African and Pacific superplumes have remained largely unchanged for at least the last 300 Ma and possibly much longer. Second, the African superplume is formed sometime after the formation of Pangea (i.e., at 330 Ma ago) and the mantle in the African hemisphere is predominated by cold downwelling structures before and during the assembly of Pangea, while the Pacific superplume has been stable for the Pangea supercontinent cycle (i.e., globally a degree-1 structure before the Pangea formation). Here, we construct a plate motion history back to 450 Ma and use it as time-dependent surface boundary conditions in 3-dimensional spherical models of thermochemical mantle convection to study the evolution of mantle structure as well as the surface and core-mantle boundary heat flux. Our results for the mantle structures suggest that while the mantle in the African hemisphere before the assembly of Pangea is predominated by the cold downwelling structure resulting from plate convergence between Gondwana and Laurussia, it is unlikely that the bulk of the African superplume structure can be formed before ~240 Ma (i.e., ~100 Ma after the assembly of Pangea). The evolution of mantle structure has implications for heat flux at the surface and core-mantle boundary (CMB). Our results show that while the plate motion controls the surface heat flux, the major cold downwellings control the core-mantle boundary heat flux. A notable feature in surface heat flux from our models is that the surface heat flux peaks at ~100 Ma ago but decreases for the last 100 Ma due to the breakup of Pangea and its subsequent plate evolution. The CMB heat flux in the equatorial regions shows two minima during period 320-250 Ma and period 120-84 Ma. The first minimum clearly results from the disappearance of a major cold downwelling

  18. Visualization of Flow Behavior in Earth Mantle Convection.

    PubMed

    Schroder, S; Peterson, J A; Obermaier, H; Kellogg, L H; Joy, K I; Hagen, H

    2012-12-01

    A fundamental characteristic of fluid flow is that it causes mixing: introduce a dye into a flow, and it will disperse. Mixing can be used as a method to visualize and characterize flow. Because mixing is a process that occurs over time, it is a 4D problem that presents a challenge for computation, visualization, and analysis. Motivated by a mixing problem in geophysics, we introduce a combination of methods to analyze, transform, and finally visualize mixing in simulations of convection in a self-gravitating 3D spherical shell representing convection in the Earth's mantle. Geophysicists use tools such as the finite element model CitcomS to simulate convection, and introduce massless, passive tracers to model mixing. The output of geophysical flow simulation is hard to analyze for domain experts because of overall data size and complexity. In addition, information overload and occlusion are problems when visualizing a whole-earth model. To address the large size of the data, we rearrange the simulation data using intelligent indexing for fast file access and efficient caching. To address information overload and interpret mixing, we compute tracer concentration statistics, which are used to characterize mixing in mantle convection models. Our visualization uses a specially tailored version of Direct Volume Rendering. The most important adjustment is the use of constant opacity. Because of this special area of application, i. e. the rendering of a spherical shell, many computations for volume rendering can be optimized. These optimizations are essential to a smooth animation of the time-dependent simulation data. Our results show how our system can be used to quickly assess the simulation output and test hypotheses regarding Earth's mantle convection. The integrated processing pipeline helps geoscientists to focus on their main task of analyzing mantle homogenization.

  19. Effects from equation of state and rheology in dissipative heating in compressible mantle convection

    NASA Technical Reports Server (NTRS)

    Yuen, David A.; Quareni, Francesca; Hong, H.-J.

    1987-01-01

    The effects of compressibility on mantle convection are considered, incorporating the effects of equations of state and rheology in the dissipative heating term of the energy equation. The ways in which compression may raise the interior mantle temperature are explicitly demonstrated, and it is shown how this effect can be used to constrain some of the intrinsic parameters associated with the equation of state in the mantle. It is concluded that the coupling between variable viscosity and equation of state in dissipative heating is potentially an important mechanism in mantle convection. These findings emphasize that rheology, equation of state, and radiogenic heating are all linked to each other by nonlinear thermomechanical couplings.

  20. Effects from equation of state and rheology in dissipative heating in compressible mantle convection

    NASA Technical Reports Server (NTRS)

    Yuen, David A.; Quareni, Francesca; Hong, H.-J.

    1987-01-01

    The effects of compressibility on mantle convection are considered, incorporating the effects of equations of state and rheology in the dissipative heating term of the energy equation. The ways in which compression may raise the interior mantle temperature are explicitly demonstrated, and it is shown how this effect can be used to constrain some of the intrinsic parameters associated with the equation of state in the mantle. It is concluded that the coupling between variable viscosity and equation of state in dissipative heating is potentially an important mechanism in mantle convection. These findings emphasize that rheology, equation of state, and radiogenic heating are all linked to each other by nonlinear thermomechanical couplings.

  1. Energetics and heat budget of the earth's mantle convection constrained by plume and slab dynamics

    NASA Astrophysics Data System (ADS)

    Leng, Wei

    Understanding the heat budget and energetics of the Earth's mantle convection is important for constraining the thermal evolution history and chemical composition of the Earth's core and mantle. Mantle plumes and subducted slabs are two most important agents for energy transfer in the Earth's mantle convection. With numerical modeling and theoretical analysis, here we show that surface observations of plumes and slabs can be used to constrain the internal heating ratio of the mantle, the core-mantle boundary (CMB) heat flux and the viscous dissipation in the plate bending zones. We also show that including more realistic physics may significantly affect the surface manifestation of the conventional mantle plume model. Our main conclusions are summarized as below. First, mantle plumes account for 80%-90% of the CMB heat flux. Due to the steeper adiabatic gradient of plumes compared with ambient mantle, plume heat flux and plume excess temperature decrease approximately by a factor of two during plumes' ascent. In order to reproduce surface plume-related observations, ˜70% internal heating ratio of the Earth's mantle, i.e. ˜11 TW of CMB heat flux, is required. Second, the total viscous dissipation and the total adiabatic heating balance out each other at any instant in time for compressible mantle convection. The viscous dissipation in the plate bending zones only account for <10% of the total viscous dissipation in the Earth's mantle, thus plays a minor role in Earth's thermal evolution history. Third, instead of causing surface uplift as suggested by convectional plume models, a plume head temporarily ponding below the 660-km phase boundary may cause significant surface subsidence over an extended time period before it reaches surface and generates flood basalt eruptions. Therefore, the observed surface subsidence history in many flood basalt provinces may be used as diagnostics for identifying plume-induced flood basalt events.

  2. Heat Flow of the Norwegian Continental Shelf

    NASA Astrophysics Data System (ADS)

    Pascal, C.

    2015-12-01

    Terrestrial heat flow determination is of prime interest for oil industry because it impacts directly maturation histories and economic potential of oil fields. Published systematic heat flow determinations from major oil provinces are however seldom. Robust heat flow determinations in drillholes require logging of undisturbed temperatures and intensive sampling of core material for petrophysical measurements. Temperature logging in exploration drillholes is traditionally conducted during drill breaks or shortly after drilling, resulting in temperatures severely disturbed by mud circulation and coring is restricted to selected intervals. Alternatively, test temperatures, information from electric logs and lithological descriptions of drill cuttings can be used to overcome these limitations. The present contribution introduces new heat flow determinations based on 63 exploration drillholes from the Norwegian North Sea, the Mid Norway Margin and the Barents Shelf. Our analyses are based on released DST temperatures, precise lithological descriptions of drill cuttings, previously measured rock matrix thermal conductivities and established porosity laws. For the sake of comparison, we carefully review previous heat flow studies carried out both onshore and offshore Norway. Our results suggest median heat flow values of 64 mW/m2, 65 mW/m2 and 72 mW/m2 for the North Sea, the Mid Norway Margin (mainly the Trøndelag Platform) and the SW Barents Shelf respectively. In detail, heat flow increases by ~ 10 mW/m2 from the southern Norwegian North Sea towards the Mid Norway Margin. This result appears to be in very good agreement with seismic tomographic studies suggesting northward thinning of the underlying mantle lithosphere. Our results together with published marine heat flow data from the Mid Norway Margin suggest a gradual decrease in heat flow levels from both the North Sea and the Trøndelag Platform towards the centres of the deep Møre and Vøring basins. This latter

  3. Heat Pipe Blocks Return Flow

    NASA Technical Reports Server (NTRS)

    Eninger, J. E.

    1982-01-01

    Metal-foil reed valve in conventional slab-wick heat pipe limits heat flow to one direction only. With sink warmer than source, reed is forced closed and fluid returns to source side through annular transfer wick. When this occurs, wick slab on sink side of valve dries out and heat pipe ceases to conduct heat.

  4. Subduction, back-arc spreading and global mantle flow

    NASA Technical Reports Server (NTRS)

    Hager, B. H.; Oconnell, R. J.; Raefsky, A.

    1983-01-01

    It is pointed out that the subducted lithosphere associated with Benioff zones provides the only direct evidence about the flow in the earth's interior associated with plate motions. It is the primary objective of the present investigation to study the relation between the orientation of subducting lithosphere and the flow patterns (both local and global) near subduction zones. Most of the calculations conducted are based on simple flow models for radially symmetric, Newtonian viscous spheres. The investigation is concerned with the possibility that a simple model of global mantle flow could account for some features of subduction zones. It is found that such a model can account for the orientation of the seismic zones, and, in addition, also for features related to back-arc spreading and perhaps the maximum earthquake size.

  5. Magnetic heat pump flow director

    NASA Technical Reports Server (NTRS)

    Howard, Frank S. (Inventor)

    1995-01-01

    A fluid flow director is disclosed. The director comprises a handle body and combed-teeth extending from one side of the body. The body can be formed of a clear plastic such as acrylic. The director can be used with heat exchangers such as a magnetic heat pump and can minimize the undesired mixing of fluid flows. The types of heat exchangers can encompass both heat pumps and refrigerators. The director can adjust the fluid flow of liquid or gas along desired flow directions. A method of applying the flow director within a magnetic heat pump application is also disclosed where the comb-teeth portions of the director are inserted into the fluid flow paths of the heat pump.

  6. The present-day heat flow structure of Mars

    NASA Astrophysics Data System (ADS)

    Parro, L. M.; Jiménez-Díaz, A.; Mansilla, F.; Ruiz, J.

    2016-12-01

    Until the arrival of in-situ measurements, the study of the current heat flow of Mars goes through indirect methods, mainly based on the relation between the thermal state of lithosphere and their mechanical strength, or on theoretical models of internal evolution. Here, we present a first-order global model for the present-day surface heat flow for Mars, based on the current radiogenic heat production of the crust and mantle, scaling heat flow variations arising from crustal thickness and topography crustal thickness variations, and on the heat flow derived from the effective elastic thickness of the lithosphere beneath the North Polar Region. Our preferred model find heat flows varying between 14 and 23 mW m-2, with an average value of 18.6 mW m-2. Similar results are obtained if we use heat flow based on the lithosphere strength of the South Polar Region. Moreover, expressing our results in terms of the Urey ratio (the ratio between total internal heat production and heat loss), we have values close to 0.8, which indicates a moderate contribution of secular cooling to the heat flow of Mars (consistent with low heat flow values deduced from lithosphere strength), unless that heat-producing elements abundances for Mars are subchondritics.

  7. Present-day heat flow model of Mars

    PubMed Central

    Parro, Laura M.; Jiménez-Díaz, Alberto; Mansilla, Federico; Ruiz, Javier

    2017-01-01

    Until the acquisition of in-situ measurements, the study of the present-day heat flow of Mars must rely on indirect methods, mainly based on the relation between the thermal state of the lithosphere and its mechanical strength, or on theoretical models of internal evolution. Here, we present a first-order global model for the present-day surface heat flow for Mars, based on the radiogenic heat production of the crust and mantle, on scaling of heat flow variations arising from crustal thickness and topography variations, and on the heat flow derived from the effective elastic thickness of the lithosphere beneath the North Polar Region. Our preferred model finds heat flows varying between 14 and 25 mW m−2, with an average value of 19 mW m−2. Similar results (although about ten percent higher) are obtained if we use heat flow based on the lithospheric strength of the South Polar Region. Moreover, expressing our results in terms of the Urey ratio (the ratio between total internal heat production and total heat loss through the surface), we estimate values close to 0.7–0.75, which indicates a moderate contribution of secular cooling to the heat flow of Mars (consistent with the low heat flow values deduced from lithosphere strength), unless heat-producing elements abundances for Mars are subchondritic. PMID:28367996

  8. Present-day heat flow model of Mars.

    PubMed

    Parro, Laura M; Jiménez-Díaz, Alberto; Mansilla, Federico; Ruiz, Javier

    2017-04-03

    Until the acquisition of in-situ measurements, the study of the present-day heat flow of Mars must rely on indirect methods, mainly based on the relation between the thermal state of the lithosphere and its mechanical strength, or on theoretical models of internal evolution. Here, we present a first-order global model for the present-day surface heat flow for Mars, based on the radiogenic heat production of the crust and mantle, on scaling of heat flow variations arising from crustal thickness and topography variations, and on the heat flow derived from the effective elastic thickness of the lithosphere beneath the North Polar Region. Our preferred model finds heat flows varying between 14 and 25 mW m(-2), with an average value of 19 mW m(-2). Similar results (although about ten percent higher) are obtained if we use heat flow based on the lithospheric strength of the South Polar Region. Moreover, expressing our results in terms of the Urey ratio (the ratio between total internal heat production and total heat loss through the surface), we estimate values close to 0.7-0.75, which indicates a moderate contribution of secular cooling to the heat flow of Mars (consistent with the low heat flow values deduced from lithosphere strength), unless heat-producing elements abundances for Mars are subchondritic.

  9. Present-day heat flow model of Mars

    NASA Astrophysics Data System (ADS)

    Parro, Laura M.; Jiménez-Díaz, Alberto; Mansilla, Federico; Ruiz, Javier

    2017-04-01

    Until the acquisition of in-situ measurements, the study of the present-day heat flow of Mars must rely on indirect methods, mainly based on the relation between the thermal state of the lithosphere and its mechanical strength, or on theoretical models of internal evolution. Here, we present a first-order global model for the present-day surface heat flow for Mars, based on the radiogenic heat production of the crust and mantle, on scaling of heat flow variations arising from crustal thickness and topography variations, and on the heat flow derived from the effective elastic thickness of the lithosphere beneath the North Polar Region. Our preferred model finds heat flows varying between 14 and 25 mW m-2, with an average value of 19 mW m-2. Similar results (although about ten percent higher) are obtained if we use heat flow based on the lithospheric strength of the South Polar Region. Moreover, expressing our results in terms of the Urey ratio (the ratio between total internal heat production and total heat loss through the surface), we estimate values close to 0.7-0.75, which indicates a moderate contribution of secular cooling to the heat flow of Mars (consistent with the low heat flow values deduced from lithosphere strength), unless heat-producing elements abundances for Mars are subchondritic.

  10. Heat exchanger with oscillating flow

    NASA Technical Reports Server (NTRS)

    Scotti, Stephen J. (Inventor); Blosser, Max L. (Inventor); Camarda, Charles J. (Inventor)

    1993-01-01

    Various heat exchange apparatuses are described in which an oscillating flow of primary coolant is used to dissipate an incident heat flux. The oscillating flow may be imparted by a reciprocating piston, a double action twin reciprocating piston, fluidic oscillators or electromagnetic pumps. The oscillating fluid flows through at least one conduit in either an open loop or a closed loop. A secondary flow of coolant may be used to flow over the outer walls of at least one conduit to remove heat transferred from the primary coolant to the walls of the conduit.

  11. Heat exchanger with oscillating flow

    NASA Technical Reports Server (NTRS)

    Scotti, Stephen J. (Inventor); Blosser, Max L. (Inventor); Camarda, Charles J. (Inventor)

    1992-01-01

    Various heat exchange apparatuses are described in which an oscillating flow of primary coolant is used to dissipate an incident heat flux. The oscillating flow may be imparted by a reciprocating piston, a double action twin reciprocating piston, fluidic oscillators, or electromagnetic pumps. The oscillating fluid flows through at least one conduit in either an open loop or a closed loop. A secondary flow of coolant may be used to flow over the outer walls of at least one conduit to remove heat transferred from the primary coolant to the walls of the conduit.

  12. Heat flow evolution of the Earth from paleomantle temperatures: Evidence for increasing heat loss since ∼2.5 Ga

    NASA Astrophysics Data System (ADS)

    Ruiz, Javier

    2017-08-01

    Earth currently loses two to five times as much heat through its surface as it is internally produced by radioactivity. This proportion cannot be extrapolated into the past, because it would imply high interior temperatures and catastrophic melting of the planet in ancient times. The heat loss evolution of the Earth cannot therefore be described by a constant heat flow decreasing. This is consistent with previous work finding that the mantle heated up until ∼2.5-3.0 Ga and then progressively cooled down. The present work derives a first-order heat loss evolution of the Earth by comparing the evolution of the total heat content of the silicate Earth (as described by mantle potential temperatures deduced from the melting conditions of ancient non-arc basalts) with the total radioactive heat production. The results show that the heat flow was declining, and the mantle heating-up, until ∼2.5 Ga, but that after this time the heat flow has been slowly (but constantly) increasing, and the mantle cooling-down, until the present-day. The change in heat loss trend is roughly coeval with other major geological, geochemical and environmental changes, and could indicate the starting of the modern-style of plate tectonics. This work provides therefore the first quantitative evidence of change in terrestrial heat loss regime, and suggests that substantial variations in the internal heat budget occurred during Earth's history.

  13. Mapping mantle flow with observations of seismic anisotropy: Progress and prospects

    NASA Astrophysics Data System (ADS)

    Long, M. D.

    2016-12-01

    Observations of seismic anisotropy, or the directional dependence of seismic wavespeeds, provide some of the most direct constraints available on patterns of flow and deformation in the Earth's mantle. This is because of the causative link between deformation and anisotropy: when a mantle rock is subjected to deformation due to mantle convection or tectonic processes such as orogenesis, it develops a preferred orientation that manifests itself as seismic anisotropy. The measurement and interpretation of anisotropy, therefore, has the potential to constrain a host of fundamental processes in the Earth's interior. These include the present-day pattern of mantle convection, the evolution and deformation of continents, subduction dynamics and the cycling of water in subduction systems, the behavior of subducted slabs in the mid-mantle, and the pattern of flow at the base of the mantle and its relationship with large-scale structures such as Large Low Shear Velocity Provinces (LLSVP). In this talk I will highlight examples of exciting recent discoveries related to mantle anisotropy, which are leading to new perspectives on mantle dynamics. These include new constraints on anisotropy in the mid-mantle (transition zone and uppermost lower mantle), which is often assumed to be isotropic; measurements of mid-mantle anisotropy may shed light on the question of how slabs interact with the phase transitions and likely viscosity increase in the mid-mantle. New constraints on anisotropy in the continental upper mantle beneath North America illuminate the relationships between structural features such as the mid-lithospheric discontinuity (MLD) and the ancient Appalachian orogeny and lithospheric deformation processes. In the lowermost mantle, new observational strategies are leading to datasets that can constrain the geometry of anisotropy more tightly; in combination with insights from forward modeling based on insights from mineral physics, recent observations of lowermost

  14. Magnetic Heat Pump Containing Flow Diverters

    NASA Technical Reports Server (NTRS)

    Howard, Frank S.

    1995-01-01

    Proposed magnetic heat pump contains flow diverters for suppression of undesired flows. If left unchecked, undesired flows mix substantial amounts of partially heated and partially cooled portions of working fluid, effectively causing leakage of heat from heated side to cooled side. By reducing leakage of heat, flow diverters increase energy efficiency of magnetic heat pump, potentially offering efficiency greater than compressor-driven refrigerator.

  15. Heat Transport in the Hadean Mantle: From Heat Pipes to Plates

    NASA Astrophysics Data System (ADS)

    Kankanamge, Duminda G. J.

    Plate tectonics is a unique feature of Earth and it plays a dominant role in transporting Earth's internally generated heat. It also governs the nature, shape and the motion of the surface of Earth. The initiation of plate tectonics on Earth has been difficult to establish observationally, and modeling of the plate breaking process has not consistently accounted for the nature of the pre-plate tectonic Earth. Prior to the onset of plate tectonics, the Earth was dominated by volcanic heat transport, called the heat-pipe mode of planetary cooling. Numerical simulations of heat transport were performed in the pre-plate tectonic Earth to understand the transition to plate tectonic behavior and to analyze the boundary layer dynamics which lead to that transition. These simulations of Earth's mantle include heat transport by melting and melt segregation (volcanism), Newtonian temperature-dependent viscosity, and internal heating. The results show that when heat pipes are active, the lithosphere thickens and lithospheric isotherms are kept flat by the solidus. Both of these effects act to suppress plate tectonics. As volcanism wanes, conduction begins to control lithospheric thickness, and large slopes arise at the base of the lithosphere. This produces large lithospheric stress and focuses it on the thinner regions of the lithosphere resulting in plate breaking events. Thus, it is evident that before transition to the plate tectonics, Earth has probably transferred its internal energy through heat pipes. Depending on their mass and internal energy, other planetary bodies transition directly from heat pipes to the stagnant lid or they will eventually transition to plate tectonics after a long period of heat-pipe volcanism. Also, a parameterization was developed using melting and convective parameters to include the effect of melting on planetary heat transport. The heat flux due to melting, the internal temperature of the mantle, the temperature of the lid base, the lid

  16. Global Transition Zone Anisotropy and Consequences for Mantle Flow and Earth's Deep Water Cycle

    NASA Astrophysics Data System (ADS)

    Beghein, C.; Yuan, K.

    2011-12-01

    The transition zone has long been at the center of the debate between multi- and single-layered convection models that directly relate to heat transport and chemical mixing throughout the mantle. It has also been suggested that the transition zone is a reservoir that collects water transported by subduction of the lithosphere into the mantle. Since water lowers mantle minerals density and viscosity, thereby modifying their rheology and melting behavior, it likely affects global mantle dynamics and the history of plate tectonics. Constraining mantle flow is therefore important for our understanding of Earth's thermochemical evolution and deep water cycle. Because it can result from deformation by dislocation creep during convection, seismic anisotropy can help us model mantle flow. It is relatively well constrained in the uppermost mantle, but its presence in the transition zone is still debated. Its detection below 250 km depth has been challenging to date because of the poor vertical resolution of commonly used datasets. In this study, we used global Love wave overtone phase velocity maps, which are sensitive to structure down to much larger depths than fundamental modes alone, and have greater depth resolution than shear wave-splitting data. This enabled us to obtain a first 3-D model of azimuthal anisotropy for the upper 800km of the mantle. We inverted the 2Ψ terms of anisotropic phase velocity maps [Visser, et al., 2008] for the first five Love wave overtones between 35s and 174s period. The resulting model shows that the average anisotropy amplitude for vertically polarized shear waves displays two main stable peaks: one in the uppermost mantle and, most remarkably, one in the lower transition zone. F-tests showed that the presence of 2Ψ anisotropy in the transition zone is required to improve the third, fourth, and fifth overtones fit. Because of parameter trade-offs, however, we cannot exclude that the anisotropy is located in the upper transition zone as

  17. Martian surface heat production and crustal heat flow from Mars Odyssey Gamma-Ray spectrometry

    NASA Astrophysics Data System (ADS)

    Hahn, B. C.; McLennan, S. M.; Klein, E. C.

    2011-07-01

    Martian thermal state and evolution depend principally on the radiogenic heat-producing element (HPE) distributions in the planet's crust and mantle. The Gamma-Ray Spectrometer (GRS) on the 2001 Mars Odyssey spacecraft has mapped the surface abundances of HPEs across Mars. From these data, we produce the first models of global and regional surface heat production and crustal heat flow. As previous studies have suggested that the crust is a repository for approximately 50% of the radiogenic elements on Mars, these models provide important, directly measurable constraints on Martian heat generation. Our calculations show considerable geographic and temporal variations in crustal heat flow, and demonstrate the existence of anomalous heat flow provinces. We calculate a present day average surface heat production of 4.9 ± 0.3 × 10-11 W · kg-1. We also calculate the average crustal component of heat flow of 6.4 ± 0.4 mW · m-2. The crustal component of radiogenically produced heat flow ranges from <1 mW · m-2 in the Hellas Basin and Utopia Planitia regions to ˜13 mW · m-2 in the Sirenum Fossae region. These heat production and crustal heat flow values from geochemical measurements support previous heat flow estimates produced by different methodologies.

  18. Joule heating in electrokinetic flow.

    PubMed

    Xuan, Xiangchun

    2008-01-01

    Electrokinetic flow is an efficient means to manipulate liquids and samples in lab-on-a-chip devices. It has a number of significant advantages over conventional pressure-driven flow. However, there exists inevitable Joule heating in electrokinetic flow, which is known to cause temperature variations in liquids and draw disturbances to electric, flow and concentration fields via temperature-dependent material properties. Therefore, both the throughput and the resolution of analytic studies performed in microfluidic devices are affected. This article reviews the recent progress on the topic of Joule heating and its effect in electrokinetic flow, particularly the theoretical and experimental accomplishments from the aspects of fluid mechanics and heat/mass transfer. The primary focus is placed on the temperature-induced flow variations and the accompanying phenomena at the whole channel or chip level.

  19. Heat transport in the Hadean mantle: From heat pipes to plates

    NASA Astrophysics Data System (ADS)

    Kankanamge, Duminda G. J.; Moore, William B.

    2016-04-01

    Plate tectonics is a unique feature of Earth, and it plays a dominant role in transporting Earth's internally generated heat. It also governs the nature, shape, and the motion of the surface of Earth. The initiation of plate tectonics on Earth has been difficult to establish observationally, and modeling of the plate breaking process has not consistently accounted for the nature of the preplate tectonic Earth. We have performed numerical simulations of heat transport in the preplate tectonic Earth to understand the transition to plate tectonic behavior. This period of time is dominated by volcanic heat transport called the heat pipe mode of planetary cooling. These simulations of Earth's mantle include heat transport by melting and melt segregation (volcanism), Newtonian temperature-dependent viscosity, and internal heating. We show that when heat pipes are active, the lithosphere thickens and lithospheric isotherms are kept flat by the solidus. Both of these effects act to suppress plate tectonics. As volcanism wanes, conduction begins to control lithospheric thickness, and large slopes arise at the base of the lithosphere. This produces large lithospheric stress and focuses it on the thinner regions of the lithosphere resulting in plate breaking events.

  20. The role of heat source for spatio-temporal variations of mantle plumes

    NASA Astrophysics Data System (ADS)

    Kumagai, I.; Yamagishi, Y.; Davaille, A.

    2014-12-01

    Hot mantle plumes ascending from the core-mantle boundary experience a filtering effect by the endothermic phase change at the 660-km discontinuity. Fluid dynamics predicts that some hot mantle plumes stagnate at the phase boundary and locally heat the bottom of the upper mantle. This generates the secondary plumes in the upper mantle originating hotspots volcanic activities on the Earth's surface. Recently, seismic tomographic images around the upper-lower mantle boundary showed that the horizontal scale of the low velocity regions, which corresponds to that of the thermally buoyant heat sources, is the order of 100-1000 km. Although most of the fluid dynamic theories on the thermal plumes have been developed using an assumption that the heat source effect is negligible, the behaviors of the starting plumes in the upper mantle should depend on the size of heat source, which is generated by the hotter plume from the CMB. In order to understand the effects of heater size on the starting plume generation, we have experimentally investigated the behaviors of thermally buoyant plumes using a localized heat source (circular plate heater). The combination of quantitative visualization techniques of temperature (Thermochromic Liquid Crystals) and velocity (Particle Image Velocimetry) fields reveals the transient nature of the plume evolution: a variety of the spatio-tempotal distribution of plumes. Simple scaling laws for their ascent velocity and spacing of the plumes are experimentally determined. We also estimate the onset time of the secondary plumes in the upper mantle which depends on the local characteristics of the thermal boundary layer developing at the upper-lower mantle boundary.

  1. Mapping mantle flow during retreating subduction: Laboratory models analyzed by feature tracking

    NASA Astrophysics Data System (ADS)

    Funiciello, F.; Moroni, M.; Piromallo, C.; Faccenna, C.; Cenedese, A.; Bui, H. A.

    2006-03-01

    Three-dimensional dynamically consistent laboratory models are carried out to model the large-scale mantle circulation induced by subduction of a laterally migrating slab. A laboratory analogue of a slab-upper mantle system is set up with two linearly viscous layers of silicone putty and glucose syrup in a tank. The circulation pattern is continuously monitored and quantitatively estimated using a feature tracking image analysis technique. The effects of plate width and mantle viscosity/density on mantle circulation are systematically considered. The experiments show that rollback subduction generates a complex three-dimensional time-dependent mantle circulation pattern characterized by the presence of two distinct components: the poloidal and the toroidal circulation. The poloidal component is the answer to the viscous coupling between the slab motion and the mantle, while the toroidal one is produced by lateral slab migration. Spatial and temporal features of mantle circulation are carefully analyzed. These models show that (1) poloidal and toroidal mantle circulation are both active since the beginning of the subduction process, (2) mantle circulation is intermittent, (3) plate width affects the velocity and the dimension of subduction induced mantle circulation area, and (4) mantle flow in subduction zones cannot be correctly described by models assuming a two-dimensional steady state process. We show that the intermittent toroidal component of mantle circulation, missed in those models, plays a crucial role in modifying the geometry and the efficiency of the poloidal component.

  2. Mantle flow pressure and the angle of subduction - Non-Newtonian corner flows

    NASA Technical Reports Server (NTRS)

    Tovish, A.; Schubert, G.; Luyendyk, B. P.

    1978-01-01

    Corner flows of Newtonian and non-Newtonian fluids are used to model the flow in a subduction zone which is viscously driven by the motions of the converging plates and the descending slab. The pressures induced by the flow tend to lift the slab up beneath the overriding plate thereby offsetting the tendency of gravity to align the slab with the vertical. The low angles of subduction observed in Peru and Central Chile may be the result of strong dynamic pressures forcing the slab up against the overriding plate. Viscous coupling between the overriding plate and the downgoing slab is essential if the nonvertical dips of slabs are a consequence of the balance between gravitational and pressure torques. For a Newtonian mantle, shear stresses and pressures on the top of the slab are comparable. If the mantle is non-Newtonian, however, the pressures greatly exceed the shear stresses, for most acute dip angles. Thus frictional forces on the top and bottom surfaces of slabs are less important in resisting slab descent into a non-Newtonian mantle than they are in resisting penetration into a Newtonian mantle.

  3. Mantle flow pressure and the angle of subduction - Non-Newtonian corner flows

    NASA Technical Reports Server (NTRS)

    Tovish, A.; Schubert, G.; Luyendyk, B. P.

    1978-01-01

    Corner flows of Newtonian and non-Newtonian fluids are used to model the flow in a subduction zone which is viscously driven by the motions of the converging plates and the descending slab. The pressures induced by the flow tend to lift the slab up beneath the overriding plate thereby offsetting the tendency of gravity to align the slab with the vertical. The low angles of subduction observed in Peru and Central Chile may be the result of strong dynamic pressures forcing the slab up against the overriding plate. Viscous coupling between the overriding plate and the downgoing slab is essential if the nonvertical dips of slabs are a consequence of the balance between gravitational and pressure torques. For a Newtonian mantle, shear stresses and pressures on the top of the slab are comparable. If the mantle is non-Newtonian, however, the pressures greatly exceed the shear stresses, for most acute dip angles. Thus frictional forces on the top and bottom surfaces of slabs are less important in resisting slab descent into a non-Newtonian mantle than they are in resisting penetration into a Newtonian mantle.

  4. Seismic Anisotropy and Mantle Flow Beneath Northeastern Africa and Arabia

    NASA Astrophysics Data System (ADS)

    Elsheikh, A.; Gao, S. S.; Liu, K. H.; Abdelsalam, M. G.

    2011-12-01

    The Afar Depression in NE Africa hosts the Earth's only RRR triple junction exposed on land, and is an ideal place to study processes involved in the transition from continental rifting to seafloor spreading. In order to image the crust and upper mantle structure under Afar with an unprecedented spatial resolution, eighteen broadband seismic stations were deployed between Dec. 2009 and May 2011 along an approximately 250 km long profile across the Tendaho Graben in central Afar as part of the Afar Lithosphere Imaging Experiment (ALIE). Here we present results from teleseismic shear-wave (XKS) splitting analysis using data from ALIE and all the available broadband seismic data archived at the IRIS Data Center. Several previous studies of shear wave splitting in the region suggested that the observed anisotropy could be attributed to preexisting Precambrian fabrics, while others argue that vertical magmatic dikes or rift parallel mantle flow are responsible for the observed anisotropy. All of those studies utilized limited quality and quantity of XKS measurements which resulted in the inconsistency of conclusions. This work presents about 200 XKS splitting measurements obtained using data from ALIE and over 400 measurements from other stations in Afar, the Main Ethiopian Rift (MER), Ethiopian Plateau, and the Arabian plate. A robust process to reliably assess and objectively rank XKS splitting parameters was used to produce the results. Manual screening was applied to the results of the automatic calculations to ensure that no high quality events were ignored and no low quality results were selected. This study found that the ~450 measurements in the Ethiopian Plateau and in the MER have insignificant azimuthal variations with MER dominated by a rift parallel fast direction suggestive of a single layer of anisotropy. In contrast, measurements in the Afar Depression show a systematic azimuthal dependence of splitting parameters with a 90-degree periodicity, which

  5. Constraints on Crustal Heat Production from Heat Flow Data

    NASA Astrophysics Data System (ADS)

    Jaupart, C.; Mareschal, J.-C.

    2003-12-01

    The continental crust is an important repository of highly incompatible elements such as uranium and thorium. Exactly how much it contains is a key issue for the thermal regime of continents and for understanding how the Earth's mantle has evolved through geological time due to crust extraction. Recent estimates of the average uranium, thorium, and potassium concentrations in the continental crust vary by almost a factor of 2 (Wedepohl, 1995;Rudnick and Fountain, 1995; Taylor and McLennan, 1995; see also Chapter 3.01). These estimates are based on different assumptions regarding crustal structure and rely on different types of crustal samples, ranging from xenoliths to shales. They require an extrapolation in scale from tiny specimens to the whole crust of a geological province. Uranium and thorium tend to be located in accessory minerals and on grain boundaries, which are not related simply to bulk chemical composition. Thus, their concentrations vary on the scale of a petrological thin section, a hand sample, an outcrop, and a whole massif. In a geological province, abundant rocks such as gneisses and metasedimentary rocks are usually under-studied because of their complex origin and metamorphic history. A final difficulty is to evaluate the composition of intermediate and lower crustal levels, which are as heterogeneous as the shallow ones (e.g., Fountain and Salisbury, 1981; Clowes et al., 1992).Independent estimates of the amount of uranium and thorium in the continental crust can be obtained from heat flow data. The energy produced by the decay of these radioactive elements accounts for a large fraction of the heat flow at the surface of continents (Birch, 1954; Wasserburg et al., 1964; Clark and Ringwood, 1964; Sclater et al., 1980; Taylor and McLennan, 1995). This may be the only case where geophysical data bear directly on geochemical budgets. Since the mid-1970s, there has been much progress in our understanding of continental heat flow. The relationship

  6. Mantle upwelling and trench-parallel mantle flow in the northern Cascade arc indicated by basalt geochemistry

    NASA Astrophysics Data System (ADS)

    Mullen, E.; Weis, D.

    2013-12-01

    Cascadia offers a unique perspective on arc magma genesis as an end-member ';hot' subduction zone in which relatively little water may be available to promote mantle melting. The youngest and hottest subducting crust (~5 Myr at the trench) occurs in the Garibaldi Volcanic Belt, at the northern edge of the subducting Juan de Fuca plate [1]. Geochemical data from GVB primitive basalts provide insights on mantle melting where a slab edge coincides with high slab temperatures. In subduction zones worldwide, including the Cascades, basalts are typically calc-alkaline and produced from a depleted mantle wedge modified by slab input. However, basalts from volcanic centers overlying the northern slab edge (Salal Glacier and Bridge River Cones) are alkalic [2] and lack a trace element subduction signature [3]. The mantle source of the alkalic basalts is significantly more enriched in incompatible elements than the slab-modified depleted mantle wedge that produces calc-alkaline basalts in the southern GVB (Mt. Baker and Glacier Peak) [3]. The alkalic basalts are also generated at temperatures and pressures of up to 175°C and 1.5 GPa higher than those of the calc-alkaline basalts [3], consistent with decompression melting of fertile, hot mantle ascending through a gap in the Nootka fault, the boundary between the subducting Juan de Fuca plate and the nearly stagnant Explorer microplate. Mantle upwelling may be related to toroidal mantle flow around the slab edge, which has been identified in southern Cascadia [4]. In the GVB, the upwelling fertile mantle is not confined to the immediate area around the slab edge but has spread southward along the arc axis, its extent gradually diminishing as the slab-modified depleted mantle wedge becomes dominant. Between Salal Glacier/Bridge River and Glacier Peak ~350 km to the south, there are increases in isotopic ratios (ɛHf = 8.3 to13.0, ɛNd = 7.3 to 8.5, and 208Pb*/206*Pb* = 0.914 to 0.928) and trace element indicators of slab

  7. Reconciling surface plate motions with rapid three-dimensional mantle flow around a slab edge.

    PubMed

    Jadamec, Margarete A; Billen, Magali I

    2010-05-20

    The direction of tectonic plate motion at the Earth's surface and the flow field of the mantle inferred from seismic anisotropy are well correlated globally, suggesting large-scale coupling between the mantle and the surface plates. The fit is typically poor at subduction zones, however, where regional observations of seismic anisotropy suggest that the direction of mantle flow is not parallel to and may be several times faster than plate motions. Here we present three-dimensional numerical models of buoyancy-driven deformation with realistic slab geometry for the Alaska subduction-transform system and use them to determine the origin of this regional decoupling of flow. We find that near a subduction zone edge, mantle flow velocities can have magnitudes of more than ten times the surface plate motions, whereas surface plate velocities are consistent with plate motions and the complex mantle flow field is consistent with observations from seismic anisotropy. The seismic anisotropy observations constrain the shape of the eastern slab edge and require non-Newtonian mantle rheology. The incorporation of the non-Newtonian viscosity results in mantle viscosities of 10(17) to 10(18) Pa s in regions of high strain rate (10(-12) s(-1)), and this low viscosity enables the mantle flow field to decouple partially from the motion of the surface plates. These results imply local rapid transport of geochemical signatures through subduction zones and that the internal deformation of slabs decreases the slab-pull force available to drive subducting plates.

  8. Heat budgets of crustal and mantle rocks revealed by exchange thermometers involving cations with differing diffusivities

    NASA Astrophysics Data System (ADS)

    Kostopoulos, Dimitrios; Moulas, Evangelos

    2017-04-01

    The development of two new thermometers based on exchange of cations, between orthopyroxene (opx) and clinopyroxene (cpx), with differing diffusivities, and employing a novel thermodynamic approach, has allowed us to decipher the thermal history and tectonic setting of crustal and mantle rocks containing these minerals. Calculated temperatures reflect the temperatures at which the diopside (i.e. CaMg; hereafter TDi) and Cr-Tschermak's (i.e. CrAl; hereafter TCrTs) exchange between opx and cpx were effectively blocked. Granulites and subcontinental lithospheric mantle peridotites invariably show TCrTs>TDi, suggesting slow cooling with CaMg exchange blocking at lower T compared to CrAl exchange as a result of faster vs. slower diffusion rates respectively. Volcanic rocks show TCrTs=TDi, indicating "freezing" of the above exchange reactions immediately upon eruption. Cumulate rocks show either TCrTs≈TDi or TCrTsMantle peridotites from ophiolites and oceanic back-arcs as well as most abyssal peridotites show TCrTsheat flow 33mW/m2). This is consistent with a lithosphere thickness of about 250km requiring, in turn, the removal of 150km from the lithospheric keel beneath eastern China since the Proterozoic.

  9. Mantle flow through a tear in the Nazca slab inferred from shear wave splitting

    NASA Astrophysics Data System (ADS)

    Lynner, Colton; Anderson, Megan L.; Portner, Daniel E.; Beck, Susan L.; Gilbert, Hersh

    2017-07-01

    A tear in the subducting Nazca slab is located between the end of the Pampean flat slab and normally subducting oceanic lithosphere. Tomographic studies suggest mantle material flows through this opening. The best way to probe this hypothesis is through observations of seismic anisotropy, such as shear wave splitting. We examine patterns of shear wave splitting using data from two seismic deployments in Argentina that lay updip of the slab tear. We observe a simple pattern of plate-motion-parallel fast splitting directions, indicative of plate-motion-parallel mantle flow, beneath the majority of the stations. Our observed splitting contrasts previous observations to the north and south of the flat slab region. Since plate-motion-parallel splitting occurs only coincidentally with the slab tear, we propose mantle material flows through the opening resulting in Nazca plate-motion-parallel flow in both the subslab mantle and mantle wedge.

  10. Stress and heat flow

    SciTech Connect

    Lachenbrunch, A.H.; McGarr, A.

    1990-01-01

    As the Pacific plate slides northward past the North American plate along the San Andreas fault, the frictional stress that resists plate motion there is overcome to cause earthquakes. However, the frictional heating predicted for the process has never been detected. Thus, in spite of its importance to an understanding of both plate motion and earthquakes, the size of this frictional stress is still uncertain, even in order of magnitude.

  11. Insights on slab-driven mantle flow from advances in three-dimensional modelling

    NASA Astrophysics Data System (ADS)

    Jadamec, Margarete A.

    2016-10-01

    The wealth of seismic observations collected over the past 20 years has raised intriguing questions about the three-dimensional (3D) nature of the mantle flow field close to subduction zones and provided a valuable constraint for how the plate geometry may influence mantle flow proximal to the slab. In geodynamics, there has been a new direction of subduction zone modelling that has explored the 3D nature of slab-driven mantle flow, motivated in part by the observations from shear wave splitting, but also by the observed variations in slab geometries worldwide. Advances in high-performance computing are now allowing for an unprecedented level of detail to be incorporated into numerical models of subduction. This paper summarizes recent advances from 3D geodynamic models that reveal the complex nature of slab-driven mantle flow, including trench parallel flow, toroidal flow around slab edges, mantle upwelling at lateral slab edges, and small scale convection within the mantle wedge. This implies slab-driven mantle deformation zones occur in the asthenosphere proximal to the slab, wherein the mantle may commonly flow in a different direction and rate than the surface plates, implying laterally variable plate-mantle coupling. The 3D slab-driven mantle flow can explain, in part, the lateral transport of geochemical signatures in subduction zones. In addition, high-resolution geographically referenced models can inform the interpretation of slab structure, where seismic data are lacking. The incorporation of complex plate boundaries into high-resolution, 3D numerical models opens the door to a new avenue of research in model construction, data assimilation, and modelling workflows, and gives 3D immersive visualization a new role in scientific discovery.

  12. Seismic imaging of structural heterogeneity in Earth's mantle: evidence for large-scale mantle flow.

    PubMed

    Ritsema, J; Van Heijst, H J

    2000-01-01

    Systematic analyses of earthquake-generated seismic waves have resulted in models of three-dimensional elastic wavespeed structure in Earth's mantle. This paper describes the development and the dominant characteristics of one of the most recently developed models. This model is based on seismic wave travel times and wave shapes from over 100,000 ground motion recordings of earthquakes that occurred between 1980 and 1998. It shows signatures of plate tectonic processes to a depth of about 1,200 km in the mantle, and it demonstrates the presence of large-scale structure throughout the lower 2,000 km of the mantle. Seismological analyses make it increasingly more convincing that geologic processes shaping Earth's surface are intimately linked to physical processes in the deep mantle.

  13. Lunar heat-flow experiment

    NASA Technical Reports Server (NTRS)

    Langseth, M. G.

    1977-01-01

    The principal components of the experiment were probes, each with twelve thermometers of exceptional accuracy and stability, that recorded temperature variations at the surface and in the regolith down to 2.5 m. The Apollo 15 experiment and the Apollo 17 probes recorded lunar surface and subsurface temperatures. These data provided a unique and valuable history of the interaction of solar energy with lunar surface and the effects of heat flowing from the deep interior out through the surface of the moon. The interpretation of these data resulted in a clearer definition of the thermal and mechanical properties of the upper two meters of lunar regolith, direct measurements of the gradient in mean temperature due to heat flow from the interior and a determination of the heat flow at the Apollo 15 and Apollo 17 sites.

  14. Microwave heating device for internal heating convection experiments, applied to Earth's mantle dynamics.

    PubMed

    Surducan, E; Surducan, V; Limare, A; Neamtu, C; Di Giuseppe, E

    2014-12-01

    We report the design, construction, and performances of a microwave (MW) heating device for laboratory experiments with non-contact, homogeneous internal heating. The device generates MW radiation at 2.47 GHz from a commercial magnetron supplied by a pulsed current inverter using proprietary, feedback based command and control hardware and software. Specially designed MW launchers direct the MW radiation into the sample through a MW homogenizer, devised to even the MW power distribution into the sample's volume. An adjustable MW circuit adapts the MW generator to the load (i.e., the sample) placed in the experiment chamber. Dedicated heatsinks maintain the MW circuits at constant temperature throughout the experiment. Openings for laser scanning for image acquisition with a CCD camera and for the cooling circuits are protected by special MW filters. The performances of the device are analyzed in terms of heating uniformity, long term output power stability, and load matching. The device is used for small scale experiments simulating Earth's mantle convection. The 30 × 30 × 5 cm(3) convection tank is filled with a water‑based viscous fluid. A uniform and constant temperature is maintained at the upper boundary by an aluminum heat exchanger and adiabatic conditions apply at the tank base. We characterize the geometry of the convective regime as well as its bulk thermal evolution by measuring the velocity field by Particle Image Velocimetry and the temperature field by using Thermochromic Liquid Crystals.

  15. Microwave heating device for internal heating convection experiments, applied to Earth's mantle dynamics

    SciTech Connect

    Surducan, E.; Surducan, V.; Neamtu, C.; Limare, A.; Di Giuseppe, E.

    2014-12-15

    We report the design, construction, and performances of a microwave (MW) heating device for laboratory experiments with non-contact, homogeneous internal heating. The device generates MW radiation at 2.47 GHz from a commercial magnetron supplied by a pulsed current inverter using proprietary, feedback based command and control hardware and software. Specially designed MW launchers direct the MW radiation into the sample through a MW homogenizer, devised to even the MW power distribution into the sample's volume. An adjustable MW circuit adapts the MW generator to the load (i.e., the sample) placed in the experiment chamber. Dedicated heatsinks maintain the MW circuits at constant temperature throughout the experiment. Openings for laser scanning for image acquisition with a CCD camera and for the cooling circuits are protected by special MW filters. The performances of the device are analyzed in terms of heating uniformity, long term output power stability, and load matching. The device is used for small scale experiments simulating Earth's mantle convection. The 30 × 30 × 5 cm{sup 3} convection tank is filled with a water‑based viscous fluid. A uniform and constant temperature is maintained at the upper boundary by an aluminum heat exchanger and adiabatic conditions apply at the tank base. We characterize the geometry of the convective regime as well as its bulk thermal evolution by measuring the velocity field by Particle Image Velocimetry and the temperature field by using Thermochromic Liquid Crystals.

  16. Microwave heating device for internal heating convection experiments, applied to Earth's mantle dynamics

    NASA Astrophysics Data System (ADS)

    Surducan, E.; Surducan, V.; Limare, A.; Neamtu, C.; Di Giuseppe, E.

    2014-12-01

    We report the design, construction, and performances of a microwave (MW) heating device for laboratory experiments with non-contact, homogeneous internal heating. The device generates MW radiation at 2.47 GHz from a commercial magnetron supplied by a pulsed current inverter using proprietary, feedback based command and control hardware and software. Specially designed MW launchers direct the MW radiation into the sample through a MW homogenizer, devised to even the MW power distribution into the sample's volume. An adjustable MW circuit adapts the MW generator to the load (i.e., the sample) placed in the experiment chamber. Dedicated heatsinks maintain the MW circuits at constant temperature throughout the experiment. Openings for laser scanning for image acquisition with a CCD camera and for the cooling circuits are protected by special MW filters. The performances of the device are analyzed in terms of heating uniformity, long term output power stability, and load matching. The device is used for small scale experiments simulating Earth's mantle convection. The 30 × 30 × 5 cm3 convection tank is filled with a water-based viscous fluid. A uniform and constant temperature is maintained at the upper boundary by an aluminum heat exchanger and adiabatic conditions apply at the tank base. We characterize the geometry of the convective regime as well as its bulk thermal evolution by measuring the velocity field by Particle Image Velocimetry and the temperature field by using Thermochromic Liquid Crystals.

  17. Interactions of 3D mantle flow and continental lithosphere near passive margins

    NASA Astrophysics Data System (ADS)

    Farrington, R. J.; Stegman, D. R.; Moresi, L. N.; Sandiford, M.; May, D. A.

    2010-03-01

    We investigate the time evolution of 3D numerical models of convection in the upper mantle which incorporate both plate motions and thick continental lithosphere. The resultant flow in the upper mantle is driven by a combination of bottom heated convection and applied shear velocity boundary conditions that represents plate motion. Both the plate velocity and continental lithosphere topography are varied in a way to assess the general influence of 3D geometry as well as a more specific tectonic analogue of the Australian plate. Transient thermal events offshore of the trailing passive margin are observed and include plume migration, boundary layer instability growth at the passive margin and variations in surface heat flux. The geometry and plate velocity both play a significant role in controlling the magnitude and duration of these transient features. In particular, there are large differences between the different models in the oceanic region downstream of the trailing edge of the continent. At near-stationary plate speeds, cold linear downwelling sheets propagate away from the 3D edge of the continent, with regions offshore of the continents central axis localising hot cylindrical upwelling plumes. At very fast plate speeds, the shear flow is dominated by the plate motions. This causes regions neighbouring the trailing edge of the continent to produce broad, hot upwellings and the cold linear sheets to migrate around the continent. At moderate (2 cm/yr) plate speeds, oceanic lithosphere neighbouring the passive margin along the trailing edge of the continent is buffered by cold, downwelling instabilities sinking along the edges of the continental lithosphere. Such neighbouring regions are subjected to larger heat flux than for regions distant to the passive margin, yet also record smaller and less variable vertical surface velocities. These dynamics have implications for volcanism and surface topography, for which 3D aspects play a significant role.

  18. Subduction-controlled mantle flow and seismic anisotropy in South America

    NASA Astrophysics Data System (ADS)

    Hu, Jiashun; Faccenda, Manuele; Liu, Lijun

    2017-07-01

    Seismic anisotropy records both the past and present deformation inside the solid Earth. In the mantle, seismic anisotropy is mainly attributed to the lattice preferred orientation (LPO) of mineral fabrics, caused by the shear deformation due to mantle flow. However, contributions from different tectonic processes remain debated, and a single geodynamic model that simultaneously explains the observed mantle structures and various seismic anisotropy measurements is still lacking. Here, we present a model for the Cenozoic subduction history in South America using a geodynamic simulation constrained by both past plate reconstructions and present mantle seismic structures. With a recently developed software package DRexS, we further predict azimuthal seismic anisotropy at different depths and generate synthetic shear wave splitting (SWS) measurements using the resulting mantle flow. Our results provide a good match to both depth-dependent surface wave anisotropy and various land-based SWS records. We find that the dominant control on seismic anisotropy in South America comes from subduction-induced mantle flow, where anisotropy below the subducting Nazca Plate aligns with plate-motion-induced Couette flow and that below the overriding South American Plate follows slab-induced Poiseuille flow. This large-scale mantle flow can be diverted by secondary slabs, such as that below the Antilles subduction zone. In contrast, the contribution to SWS from fossil continental anisotropy and from the effects due to mantle flow modulation by lithosphere thickness variation are minor. Upper-mantle fast seismic anomalies beneath the southern Atlantic margin should have close-to-neutral buoyancy in order to satisfy the observed seismic anisotropy.

  19. The dynamics of plate tectonics and mantle flow: from local to global scales.

    PubMed

    Stadler, Georg; Gurnis, Michael; Burstedde, Carsten; Wilcox, Lucas C; Alisic, Laura; Ghattas, Omar

    2010-08-27

    Plate tectonics is regulated by driving and resisting forces concentrated at plate boundaries, but observationally constrained high-resolution models of global mantle flow remain a computational challenge. We capitalized on advances in adaptive mesh refinement algorithms on parallel computers to simulate global mantle flow by incorporating plate motions, with individual plate margins resolved down to a scale of 1 kilometer. Back-arc extension and slab rollback are emergent consequences of slab descent in the upper mantle. Cold thermal anomalies within the lower mantle couple into oceanic plates through narrow high-viscosity slabs, altering the velocity of oceanic plates. Viscous dissipation within the bending lithosphere at trenches amounts to approximately 5 to 20% of the total dissipation through the entire lithosphere and mantle.

  20. Preliminary heat flow and radioactivity studies in Wyoming

    SciTech Connect

    Decker, E.R.; Baker, K.R.; Bucher, G.J.; Heasler, H.P.

    1980-01-10

    Twelve new heat flow values in Wyoming are in the range 0.6--2.1 ..mu..cal/cm/sup 2/ s (25--88 mW/m/sup 2/). Radioactive heat productions at eight localities range from approx.0 to approx.1.3 ..mu mu..cal/cm/sup 3/ s (approx.0--5.4 ..mu..W/m/sup 3/). These data are consistent with the following interpretations: (1) The Laramie Mountains--eastern Wyoming Basin area is a zone of normal heat flow (0.6--1.6 ..mu..cal/cm/sup 2/ s (25--67 mW/m/sup 2/) that is characterized by low flux (approx.0.6 ..mu..cal/cm/sup 2/ s (approx.25 mW/m/sup 2/) from the lower crust and upper mantle. (2) The eastern boundary of the Yellowstone caldera heat flow high (> or =2.5 ..mu..cal/cm/sup 2/ s (> or =105 mW/m/sup 2/)) is narrow. (3) The heat flow is high (1.9--2.1 ..mu..cal/cm/sup 2/ s (79--88 mW/m/sup 2/)) in parts of the Black Hills in northeastern Wyoming and western South Dakota. From the data presented, a major heat flow transition occurs between the Medicine Bow and Laramie mountains in Wyoming (0.6--1.3 ..mu..cal/cm/sup 2/ s (25Pxn54 mW/m/sup 2/)) and the Rocky Mountains in northern Colorado (2.2--3.0 ..mu..cal/cm/sup 2/ s (92--125 mW/m/sup 2/)). The high flux in this part of the Southern Rockies may mean that the zone of high heat flow associated with the Rio Grande rift extends to the Colorado-Wyoming Border. The normal heat flow in the Laramie Mountains--eastern Wyoming Basin area implies submelting temperatures in the upper mantle. In contrast, the very hgih flux in northern Colorado may be related to high-temperature, nonradiogenic heat sources in the lower crust and upper mantle because the width of the transition to normal flux in the Laramie Mountains in southern Wyoming is narrow (< or =70 km).

  1. Pure climb creep mechanism drives flow in Earth's lower mantle.

    PubMed

    Boioli, Francesca; Carrez, Philippe; Cordier, Patrick; Devincre, Benoit; Gouriet, Karine; Hirel, Pierre; Kraych, Antoine; Ritterbex, Sebastian

    2017-03-01

    At high pressure prevailing in the lower mantle, lattice friction opposed to dislocation glide becomes very high, as reported in recent experimental and theoretical studies. We examine the consequences of this high resistance to plastic shear exhibited by ringwoodite and bridgmanite on creep mechanisms under mantle conditions. To evaluate the consequences of this effect, we model dislocation creep by dislocation dynamics. The calculation yields to an original dominant creep behavior for lower mantle silicates where strain is produced by dislocation climb, which is very different from what can be activated under high stresses under laboratory conditions. This mechanism, named pure climb creep, is grain-size-insensitive and produces no crystal preferred orientation. In comparison to the previous considered diffusion creep mechanism, it is also a more efficient strain-producing mechanism for grain sizes larger than ca. 0.1 mm. The specificities of pure climb creep well match the seismic anisotropy observed of Earth's lower mantle.

  2. Polar Heat Flow on Io

    NASA Technical Reports Server (NTRS)

    Veeder, G. J.; Matson, D. L.; Johnson, T. V.; Davies, A. G.; Blaney, D. L.

    2003-01-01

    Recently, Galileo spacecraft data have revealed Io's polar regions to be much warmer than previously expected. This unexpected development came from Photo-Polarimeter Radiometer (PPR) data which show that the minimum night temperatures are in the range of 90-95 K virtually everywhere on Io. The minimum night temperatures show no dependence upon latitude and, when away from the sunset terminator, they show no dependence upon time of night. This is indeed bizarre behavior for surface units which generally had been assumed to be passive with respect to Io's pervasive volcanism. Night temperatures of 90-95 K at high, polar latitudes are particularly hard to explain. Even assuming infinite thermal inertia, at these latitudes there is insufficient sunlight to support these warm night temperatures. Thus, through the process of elimination of other possibilities, we come to the conclusion that these surfaces are volcanically heated. Taking previously passive units and turning them into new sources of heat flow is a radical departure from previous thermophysical model paradigms. However, the geological interpretation is straight forward. We are simply seeing the effect of old, cool lava flows which cover most of the surface of Io but yet have some heat to radiate. Under these new constraints, we have taken on the challenge of formulating a physical model which quantitatively reproduces all of the observations of Io's thermal emission. In the following we introduce a new parametric model which suffices to identify a previously unrecognized polar component of Io's heat flow.

  3. Simultaneous solution for core magnetic field and fluid flow beneath an electrically conducting mantle

    NASA Technical Reports Server (NTRS)

    Voorhies, Coerte V.; Nishihama, Masahiro

    1993-01-01

    The effects of laterally homogeneous mantle electrical conductivity were included in steady, frozen-flux core surface flow estimation along with refinements in method and weighting. The refined method allows simultaneous solution for both the initial radial geomagnetic field component at the core-mantle boundary (CMB) and the sub-adjacent fluid motion; it also features Gauss' method for solving the non-linear inverse problem associated with steady motional induction. The tradeoff between spatial complexity of the derived flows and misfit to the weighted Definitive Geomagnetic Reference Field models (DGRF's) is studied for various mantle conductivity profiles. For simple flow and a fixed initial geomagnetic condition, a fairly high deep-mantle conductivity performs better than either insulating or weakly conducting profiles; however, a thin, very high conductivity layer at the base of the mantle performs almost as well. Simultaneous solution for both initial geomagnetic field and flow reduces the misfit per degree of freedom even more than does changing the mantle conductivity profile. Moreover, when both core field and flow are estimated, the performance of the solutions and the derived flows become insensitive to the conductivity profile.

  4. Simultaneous solution for core magnetic field and fluid flow beneath an electrically conducting mantle

    NASA Technical Reports Server (NTRS)

    Voorhies, Goerte V.; Nishihama, Masahiro

    1994-01-01

    The effects of laterally homogeneous mantle electrical conductivity have been included in steady, frozen-flux core surface flow estimation along with refinements in method and weighting. The refined method allows simultaneous solution for both the initial radial geomagnetic field component at the core-mantle boundary and the subadjacent fluid motion; it also features Gauss' method for solving the nonlinear inverse problem associated with steady motional induction. The trade-off between spatial complexity of the derived flows and misfit to the weighted Definitive Geomagnetic Reference Field models is studied for various mantle conductivity profiles. For simple flow and a fixed initial geomagnetic condition a fairly high deep-mantle conductivity performs better than either insulating or weakly conducting profiles; however, a thin, very high conductivity layer at the base of the mantle performs almost as well. Simultaneous solution for both initial geomagnetic field and fluid flow reduces the misfit per degree of freedom even more than does changing the mantle conductivity profile. Moreover, when both core field and flow are estimated, the performance of the solutions and the derived flows become insensitive to the conductivity profile.

  5. The Cascadia Paradox: Mantle flow and slab fragmentation in the Cascadia subduction system

    NASA Astrophysics Data System (ADS)

    Long, Maureen D.

    2016-12-01

    The pattern of mantle flow in subduction systems and the processes that control the mantle flow field represent fundamental but still poorly understood aspects of subduction dynamics. The Cascadia subduction zone is a compelling system in which to understand the controls on mantle flow, especially given the dense geophysical observations recently provided by EarthScope, GeoPRISMS, the Cascadia Initiative, and related efforts. Observations of seismic anisotropy, which provide relatively direct constraints on mantle flow, are particularly intriguing in Cascadia because they seem to yield contradictory views of the mantle flow field in different parts of the system. Specifically, observations of seismic anisotropy on the overriding plate, notably in the central portion of the backarc, apparently require a significant component of three-dimensional, toroidal flow around the slab edge. In contrast, new observations from offshore stations are compellingly explained with a simple two-dimensional entrained flow model. Recent evidence from seismic tomography for the likely fragmentation of the Cascadia slab at depth provides a further puzzle: how does a fragmented slab provide a driving force for either two-dimensional entrained flow or three-dimensional toroidal flow due to slab rollback? Resolution of this apparent paradox will require new imaging strategies as well as the integration of constraints from seismology, geodynamics, and geochemistry.

  6. Heat Loss of the Earth and Energy Budget of the Mantle

    NASA Astrophysics Data System (ADS)

    Mareschal, J.; Jaupart, C.

    2009-05-01

    Determination of the rate of Earth's energy loss is based a very large number of heat flux measurements in a variety of geological settings. Difficulties in integrating the flux over the Earth surface stem from two facts. One is that heat flux varies on a wide range of spatial scales and, in continents, is not a function of a single variable such as geological age, for example. The other difficulty is that the data exhibit large scatter. Advances in the interpretation of oceanic heat flux data are due to a thorough understanding of hydrothermal circulation through oceanic crust and sediments. In continents, the total heat loss has been constrained by sampling of old cratons is now adequate and systematic studies of heat flux and heat production have provided robust constraints on the crustal contribution to the surface heat flux. Heat loss through the ocean floor cannot be determined from the raw data because they are affected by hydrothermal circulation and irregularities in sediment cover. Predictions of the "half-space" model for the conductive cooling of oceanic lithosphere are consistent with heat flux measurements in selected "noise-free" environments as well as with the bathymetry of the sea floor. They are also consistent with values of the mantle temperature beneath oceanic ridges derived from petrology. This cooling model is also consistent with numerical calculations of mantle convection with plates. Using an accurate determination of the area extent of oceanic sea floor including marginal basins and accounting for enhanced heat flux over hot spots, we estimated the rate of heat loss through the oceans to be 32±2 TW (1012 Watts). This result is valid only for the present-day age distribution of sea floor and heat loss may have been different in the past when the distribution of sea floor ages was different from the present. For continents, bias due to the very uneven sampling of the surface heat flux is removed by area- weighting the average. The

  7. Fast asthenosphere motion in high-resolution global mantle flow models

    NASA Astrophysics Data System (ADS)

    Weismüller, Jens; Gmeiner, Björn; Ghelichkhan, Siavash; Huber, Markus; John, Lorenz; Wohlmuth, Barbara; Rüde, Ulrich; Bunge, Hans-Peter

    2015-09-01

    A variety of geologic observations point to fast upper mantle flow that may exceed plate tectonic velocities by an order of magnitude. At the same time there is mounting evidence from seismology for flow-like structures in the upper 100-200 km of the mantle. Here we present a set of geodynamic simulations to link these observations. In a synthetic setting, we include asthenospheric channels of varying thickness, with an extreme case of 100 km, and a significant viscosity contrast of up to 4 orders of magnitude relative to the deeper mantle. Using our new global high-resolution code TERRA-NEO, we obtain an increase in velocity by a factor of 10 between a 1000 km thick and the very thin channel, translating into velocities of ˜ 20 cm/a within the narrow asthenosphere. We further present and verify a simple Poiseuille flow model, predicting that the upper mantle velocity scales with the inverse of the asthenosphere thickness.

  8. Stability of laser heated flows

    NASA Technical Reports Server (NTRS)

    Wu, P. K. S.; Pirri, A. N.

    1976-01-01

    A local stability analysis is utilized to determine the stability of disturbances generated at each point along a nozzle of variable area ratio for a one-dimensional flow heated by laser radiation entering from the upstream direction. The governing equations for the quasi-one-dimensional flow without viscous dissipation, diffusion, and thermal conduction but including radiative heat transfer are given. The governing equations are combined to yield a relationship which governs the Mach number variation through the nozzle. The complete steady-state solution can be calculated from knowledge of the Mach number profile, the inlet conditions, and the laser power. The local stability analysis permits obtaining contour (or contours) of neutral stability. Solutions have been obtained for various nozzle configurations, but only one set of example calculations is presented. The results obtained indicate that the analysis serves as an important indicator as to where potential absorption wave phenomena may be initiated.

  9. Heat flow map of the western Mediterranean basins

    SciTech Connect

    Foucher, J.P.; Burrus, J.; Vedova, B.D.

    1988-08-01

    More than 400 terrestrial heat flow determinations have been carried our in the western Mediterranean basins. These include results of detailed surveys in the Ligurian Sea and in the Gulf of Lions and Tyrrhenian basins, as well as sparse measurements in the Gulf of Valencia and the Algerian basin. Most of the measurements are surficial, obtained from the temperatures sensed by outrigged thermistors mounted on weight-driven probes penetrating the sediment to 3 to 10 m. Thermal conductivity was measured either on cores or in situ. The authors present a heat flow map of the western Mediterranean basins based on the available geothermal results. Mean regional heat flow values range from 55 to 105 mW m/sup /minus/2/ in the Lugiran and Gulf of Lions basin and from 50 to 200 m mW m/sup /minus/2/ in the Tyrrhenian Sea. In the latter basin, high heat flow characterizes areas of recent intensive thinning of the continental crust and associated incipient oceanic crust formation. In the former basins, heat flow tends to increase from the Provencal coast of France to the Corsican and Sardinian margins, which may reflect on increasing heat contribution from the mantle.

  10. Mantle flow and dynamic topography associated with slab window opening

    NASA Astrophysics Data System (ADS)

    Guillaume, Benjamin; Moroni, Monica; Funiciello, Francesca; Martinod, Joseph; Faccenna, Claudio

    2010-05-01

    A slab window is defined as an 'hole' in the subducting lithosphere. In the classical view, slab windows develop where a spreading ridge intersects a subduction zone. The main consequences of this phenomenon are the modifications of the physical, chemical and thermal conditions in the backarc mantle that in turn affect the tectonic and magmatic evolution of the overriding plate. In this work, we perform dynamically self-consistent mantle-scale laboratory models, to evaluate how the opening of a window in the subducting panel influences the geometry and the kinematics of the slab, the mantle circulation pattern and, finally, the overriding plate dynamic topography. The adopted setup consists in a two-layer linearly viscous system simulating the roll-back of a fixed subducting plate (simulated using silicone putty) into the upper mantle (simulated using glucose syrup). Our experimental setting is also characterized by a constant-width rectangular window located at the center of a laterally confined slab, modeling the case of the interaction of a trench-parallel spreading ridge with a wide subduction zone. We find that the geometry and the kinematics of the slab are only minorly affected by the opening of a slab window. On the contrary, slab induced mantle circulation, quantified using Feature Tracking image analysis technique, is strongly modified and produces a peculiar non-isostatic topographic signal on the overriding plate. Assuming that our modeling results can be representative of the natural behavior of subduction zones, we compare them to the Patagonian subduction zone finding that anomalous backarc volcanism that developed since middle Miocene could result from the lateral flowage of subslab mantle, and that part of the Patagonian uplift could be dynamically supported.

  11. Mantle flow and dynamic topography associated with slab window opening: Insights from laboratory models

    NASA Astrophysics Data System (ADS)

    Guillaume, Benjamin; Moroni, Monica; Funiciello, Francesca; Martinod, Joseph; Faccenna, Claudio

    2010-12-01

    We present dynamically self-consistent mantle-scale laboratory models that have been conducted to improve our understanding of the influence of slab window opening on subduction dynamics, mantle flow and associated dynamic topography over geological time scales. The adopted setup consists of a two-layer linearly viscous system simulating the subduction of a fixed plate of silicone (lithosphere) under negative buoyancy in a viscous layer of glucose syrup (mantle). Our experimental setting is also characterized by a constant-width rectangular window located at the center of a laterally confined slab, modeling the case of the interaction of a trench-parallel spreading ridge with a wide subduction zone. We found that the opening of a slab window does not produce consistent changes of the geometry and the kinematics of the slab. On the contrary, slab-induced mantle circulation, quantified both in the vertical and horizontal sections using the Feature Tracking image analysis technique, is strongly modified. In particular, rollback subduction and the opening of the slab window generate a complex mantle circulation pattern characterized by the presence of poloidal and toroidal components, with the importance of each evolving according to kinematic stages. Mantle coming from the oceanic domain floods through the slab window, indenting the supra-slab mantle zone and producing its deformation without any mixing between mantle portions. The opening of the slab window and the upwelling of sub-slab mantle produce a regional-scale non-isostatic topographic uplift of the overriding plate that would correspond to values ranging between ca. 1 and 5 km in nature. Assuming that our modeling results can be representative of the natural behavior of subduction zones, we compared them to the tectonics and volcanism of the Patagonian subduction zone. We found that the anomalous backarc volcanism that has been developing since the middle Miocene could result from the lateral flow of sub

  12. Seismic anisotropy and mantle flow beneath western Venezuela

    NASA Astrophysics Data System (ADS)

    Masy, J.; Niu, F.; Levander, A.

    2009-12-01

    We measured shear wave splitting from SKS and SKKS data recorded by the national seismic network of Venezuela and a linear broadband PASSCAL/Rice seismic array across the Merida Andes. The linear array was installed as a second phase of the passive seismic component of the BOLIVAR project (Broadband Onshore-offshore Lithospheric Investigation of Venezuela and the Antilles arc Region) to better understand the complicated regional tectonics in western Venezuela. Polarization direction (φ) of the faster S wave and delay time (δt) between the fast and slow wavelets from 20 stations were obtained using a stacking method proposed by Wolfe and Silver (1998). For each station, SKS or SKKS waveform data from 2 to 36 earthquakes, mostly from the Tonga subduction zone, were selected for splitting analysis. We assumed that shear wave splitting observed at each station is caused by upper mantle seismic anisotropy beneath the station. The best splitting parameters (φ,δt) were estimated when the summed eigenvalue ratio ∑(SNRi[λ2i(φ,δt)/λ1i(φ,δt)]) of the covariance matrix of the corrected particle motion reaches its minimum. We used signal-to-noise ratio (SNR) calculated from a noise time window before SKS as the weight of the summation. The fast polarization directions can be divided into 3 zones, all in agreement with local GPS data: The first zone is the stations north of the dextral strike-slip Oca fault, an extinct part of the San Sebastian-El Pilar plate boundary zone. These stations show the largest split times (1.6-2.0s), oriented in a roughly EW direction, and are similar to splitting observations made further to the east along the strike slip plate boundary. Zone two is the Maracaibo block, bounded on the southeast by the right lateral Bocono fault, where split orientations are at N45°E, suggesting that the observed seismic anisotropy is likely caused by lithospheric deformation parallel to the Bocono. Zone three is east of the Bocono fault inside the

  13. High Resolution Modelling of Mantle Convective Flow Below the North American Plate.

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

    Recent progress in joint seismic-geodynamic tomographic imaging of both thermal and compositional anomalies in Earth's mantle allows us to carry out new high-resolution calculations of the present-day mantle convective flow at all depths, from the lithosphere down to the core-mantle boundary. We are therefore able to delineate the detailed connections between fundamental geological and geophysical surface processes and the underlying mantle convection. We employ these convection calculations to consider North American continental dynamics, with a special focus on the detailed relationship between flow in upper mantle, especially in the asthenosphere, and the impact on present-day dynamic topography as well as its rate-of- change. The surface dynamics that we obtain show a clear and detailed connection to the mantle flow driven by the descent of the ancient Kula-Farallon plate system and a buoyant, actively ascending hot upwelling under the western US. Of particular importance is the relationship of the deep-seated upwelling under the Colorado Plateau as a driving force for current rifting in the Rio Grande River valley. This rifting and its temporal evolution bears a strong resemblance to the convection-induced rifting our convection model also predicts under the East African Rift system. The close similarity between these two rifts, in terms of asthenospheric flow dynamics, will be discussed.

  14. Convective vigour and heat flow in chemically differentiated systems

    NASA Astrophysics Data System (ADS)

    van Thienen, P.

    2007-05-01

    Parametric models of planets used to study their thermal evolution are generally based on scaling laws for purely thermal convection. However, planetary mantles may be chemically highly differentiated due to partial melting, which may form thick layers of depleted and dehydrated melting residue (e.g. continental roots). This results in inhomogeneity of density, which affects the driving force of convection, and viscosity (through the water content), which directly influences the dynamics of the system. This work investigates the applicability of scaling laws developed for purely thermally convecting systems to chemically differentiated systems representative of planetary mantles. The effects of depletion related buoyancy and melting related dehydration, and particularly the stratified convection patterns which may result from these, are considered. Two different strategies are applied to this end. First, a large number of numerical thermochemical convection experiments are performed, of which the dynamics and heat flow characteristics are studied. Secondly, theoretical approximations are developed from existing scaling laws to describe the heat flow of chemically stratified systems with separately convecting layers. These are tested using numerical simulations. The results show that the presence of a chemical stratification in the mantle may significantly alter heat flow patterns relative to a purely thermally convecting system by either influencing the thickness of the thermal boundary layer or dividing the convecting part of the system in vertically separate cells. This is consistent with recent petrological findings. Although the chemical stratification may be inherently instable against remixing, the present results suggest that the timescales of remixing may be much larger than those of thermal equilibration. Therefore, it is important to consider chemical stratification in thermal evolution models. For present-day Earth conditions and realistic rheological

  15. A review of the heat flow data of NE Morocco

    NASA Astrophysics Data System (ADS)

    Chiozzi, Paolo; Barkaoui, Alae-Eddine; Rimi, Abdelkrim; Verdoya, Massimo; Zarhloule, Yassine

    2016-04-01

    The Atlas chain is characterised by a SW-NE trending volcanic belt roughly extending from the Atlantic to the Mediterranean Sea and showing activity that spans in age mainly from Middle Miocene to Quaternary (14.6-0.3 Ma). The geochemical features of volcanism are mostly intraplate and alkaline with the exception of the northeastern termination of the belt where calc-alkaline series crop out. Lithospheric thermal and density models so far proposed, constrained by heat flow, gravity anomalies, geoid, and topography data, show that the Atlas chain is not supported isostatically by a thickened crust and a thin, hot and low-density lithosphere explains the high topography. One of the possible explanations for lithospheric mantle thinning, possibly in relation with the observed alkaline volcanism, is thermal erosion produced by either small-scale convection or activation of a small mantle plume, forming part of a hot and deep mantle reservoir system extending from the Canary Islands. This paper focuses on the several geothermal data available in the northeastern sector of the volcanic belt. The occurrence of an extensive, often artesian, carbonatic reservoir hosting moderately hot groundwater might boost the temperature gradient in the overlying impermeable cover, and consequently mask the deep thermal regime. We therefore revised the available dataset and investigated the contribution of advection. Temperature data available from water and oil wells were reprocessed and analysed in combination with thermal conductivity measurements on a wide set of lithotypes. Data were filtered according to rigid selection criteria, and, in the deeper boreholes, the heat flow was inferred by taking into account the porosity variation with depth and the temperature effect on the matrix and pore-filling fluid conductivity. Moreover, the possible effect of advection was evaluated with simple analytical models which envisage the carbonatic layers as confined aquifers heated by the

  16. Mantle flow geometry from ridge to trench beneath the Gorda-Juan de Fuca plate system

    NASA Astrophysics Data System (ADS)

    Martin-Short, Robert; Allen, Richard M.; Bastow, Ian D.; Totten, Eoghan; Richards, Mark A.

    2015-12-01

    Tectonic plates are underlain by a low-viscosity mantle layer, the asthenosphere. Asthenospheric flow may be induced by the overriding plate or by deeper mantle convection. Shear strain due to this flow can be inferred using the directional dependence of seismic wave speeds--seismic anisotropy. However, isolation of asthenospheric signals is challenging; most seismometers are located on continents, whose complex structure influences the seismic waves en route to the surface. The Cascadia Initiative, an offshore seismometer deployment in the US Pacific Northwest, offers the opportunity to analyse seismic data recorded on simpler oceanic lithosphere. Here we use measurements of seismic anisotropy across the Juan de Fuca and Gorda plates to reconstruct patterns of asthenospheric mantle shear flow from the Juan de Fuca mid-ocean ridge to the Cascadia subduction zone trench. We find that the direction of fastest seismic wave motion rotates with increasing distance from the mid-ocean ridge to become aligned with the direction of motion of the Juan de Fuca Plate, implying that this plate influences mantle flow. In contrast, asthenospheric mantle flow beneath the Gorda Plate does not align with Gorda Plate motion and instead aligns with the neighbouring Pacific Plate motion. These results show that asthenospheric flow beneath the small, slow-moving Gorda Plate is controlled largely by advection due to the much larger, faster-moving Pacific Plate.

  17. Numerical Simulation Analysis of Deformation Effect of The Upper Mantle Flow to Ordos and Its Surroundings

    NASA Astrophysics Data System (ADS)

    Yun, S.; Ping, L. C.; Qi, D.

    2014-12-01

    Ordos block is a typical representative of cratonic lithosphere in North China. It is stable in the block ,but around the block there are a series of faulted basins and folded mountains, the new tectonic movement around the block is intense. Some scholars propose that the upper mantle flow is an important factor to the extension activity of the fault zone around the block. But it has never been discussed in detail that how the upper mantle flow affects the movement and deformation around Ordos block? A 3D viscoelastic modeling is realized for studying the deformation effect of the upper mantle flow to Ordos and its surroundings, based on the comprehensive geological and geophysical data ,such as 3d rheological structure, the active blocks of China, thermal structure, shear wave splitting, et al. The modeling results indicate that in the vertical direction, compared with the local uplift and depression caused by the compression among the plates, the uplifting of Ordos block as a whole is mainly effected by mantle upwelling. In general the upper mantle surrounding of Ordos block is upwelling, Linfen basin goes up more faster. In the horizontal direction, The general flow direction of upper mantle in the study area is NE, basically the same as Qingzang block movement direction. But there is a bifurcation flow along the southwestern margin of Liupanshan. Generally speaking, the regional deformation is drive mainly by the movement of Qingzang block and adjacent blocks pushing into each other,the deformation effect of the upper mantle flow to Ordos and its surroundings is a superposition and partial adjustment.

  18. Evidence for trench-parallel mantle flow in the northern Cascade Arc from basalt geochemistry

    NASA Astrophysics Data System (ADS)

    Mullen, Emily K.; Weis, Dominique

    2015-03-01

    Geochemical data for basalts from the Garibaldi Volcanic Belt (northern segment of the Cascade Arc) define arc-parallel gradients in trace elements and isotope ratios that extend at least 150 km into the arc from the northern margin of the subducting Juan de Fuca plate. Southerly increases in Zr/Nb, Ba/Nb, Th/La, Pb/Ce, 208Pb/204Pb and 176Hf/177Hf indicate greater mantle depletion and higher slab-derived contributions with distance from the slab edge. Temperatures and pressures of mantle melt segregation also decrease to the south. The gradients are most plausibly explained as a consequence of slab rollback-induced toroidal flow at the northern slab edge (Nootka fault zone), whereby enriched (OIB-type) NE Pacific asthenospheric mantle from beneath the slab is drawn into the mantle wedge in a trench-parallel southerly flow pattern. Melts of the enriched asthenosphere are progressively diluted to the south by melts of the slab-modified, depleted mantle wedge. Arc-parallel changes in slab thermal conditions cannot account for these gradients. Trench parallel geochemical gradients in the northern Cascade Arc are consistent with shear wave splitting data, numerical modeling, and experimental studies showing that trench-parallel mantle flow may be a common phenomenon near slab edges and slab gaps.

  19. Utilizing thermal isostasy to estimate sub-lithospheric heat flow and anomalous crustal radioactivity

    NASA Astrophysics Data System (ADS)

    Hasterok, D.; Gard, M.

    2016-09-01

    While surface heat flow relates to the heat loss through the lithosphere, it can be difficult to quantify and separate the heat produced internally through radiogenic decay from the heat transferred across the base of the lithosphere by mantle convection. In this study, we apply a thermo-isostatic analysis to Australia and estimate the sub-lithospheric and radiogenic heat flow components by employing a simple 1-D conservation of energy model. We estimate an anomalous radiogenic heat production across much of eastern Australia generally accounting for >50 mW m-2, while western Australia appears to have high crustal compositionally corrected elevation, possibly related to chemical buoyancy of the mantle lithosphere. A moderately high sub-lithospheric heat flow (∼40 mW m-2) along the eastern and southeastern coast, including Tasmania, is coincident with locations of Cenozoic volcanism and supports an edge-driven convection hypothesis. However, the pattern of sub-lithospheric heat flow along the margin does not support the existence of hotspot tracks. Thermo-isostatic models such as these improve our ability to identify and quantify crustal from mantle sources of heat loss and add valuable constraints on tectonic and geodynamic models of the continental lithosphere's physical state and evolution.

  20. The mantle convection model with non-Newtonian rheology and phase transitions: The flow structure and stress fields

    NASA Astrophysics Data System (ADS)

    Bobrova, A. M.; Baranov, A. A.

    2016-01-01

    The mantle convection model with phase transitions, non-Newtonian viscosity, and internal heat sources is calculated for two-dimensional (2D) Cartesian geometry. The temperature dependence of viscosity is described by the Arrhenius law with a viscosity step of 50 at the boundary between the upper and lower mantle. The viscosity in the model ranges within 4.5 orders of magnitude. The use of the non-Newtonian rheology enabled us to model the processes of softening in the zone of bending and subduction of the oceanic plates. The yield stress in the model is assumed to be 50 MPa. Based on the obtained model, the structure of the mantle flows and the spatial fields of the stresses σ xz and σ xx in the Earth's mantle are studied. The model demonstrates a stepwise migration of the subduction zones and reveals the sharp changes in the stress fields depending on the stage of the slab detachment. In contrast to the previous model (Bobrov and Baranov, 2014), the self-consistent appearance of the rigid moving lithospheric plates on the surface is observed. Here, the intense flows in the upper mantle cause the drift and bending of the top segments of the slabs and the displacement of the plumes. It is established that when the upwelling plume intersects the boundary between the lower and upper mantle, it assumes a characteristic two-level structure: in the upper mantle, the ascending jet of the mantle material gets thinner, whereas its velocity increases. This effect is caused by the jump in the viscosity at the boundary and is enhanced by the effect of the endothermic phase boundary which impedes the penetration of the plume material from the lower mantle to the upper mantle. The values and distribution of the shear stresses σ xz and superlithostatic horizontal stresses σ xx are calculated. In the model area of the subducting slabs the stresses are 60-80 MPa, which is by about an order of magnitude higher than in the other mantle regions. The character of the stress fields

  1. Laboratory convection experiments with internal, noncontact, microwave generated heating, applied to Earth's mantle dynamics

    NASA Astrophysics Data System (ADS)

    Limare, Angela; Surducan, Emanoil; di Giuseppe, Erika; Surducan, Vasile; Neamtu, Camelia; Vilella, Kenny; Fourel, Loic; Farnetani, Cinzia; Kaminski, Edouard; Jaupart, Claude

    2014-05-01

    The thermal evolution of terrestrial planets is controlled by secular cooling and internal heating due to the decay of radiogenic isotopes, two processes which are equivalent from the standpoint of convection dynamics. Few studies have been devoted to the intrinsic characteristics of this form of convection, which are dominated by instabilities of a single boundary layer and which involve a non-isentropic interior thermal structure. Laboratory studies of such convection have been plagued by considerable technical difficulties and have been mostly restricted to aqueous solutions with moderate values of the Prandtl number, contrary to planetary mantles. Here, we describe a new laboratory setup to generate internal heating in controlled conditions based on microwave (MW) absorption. The advantages of our technique include, but are not limited to: (1) a volumetric heat source that can be localized or distributed in space, (2) selectively heating part of the volume with time varying intensity and space distribution. Our tank prototype had horizontal dimensions of 30 cm × 30 cm and 5 cm height. A uniform and constant temperature was maintained at the upper boundary by an aluminium heat exchanger and adiabatic conditions were imposed at the tank base. Experimental fluids were hydroxyethylcellulose - water mixtures whose viscosities were varied within a wide range depending on concentration. Experimental Prandtl numbers were set at values larger than 100. Thermochromic Liquid Crystals (TLC) were used to visualize the temperature field, and the velocity field was determined using Particle Image Velocimetry (PIV). The Rayleigh-Roberts number was varied from 105 to 107. We also conducted numerical simulations in 3D cartesian geometry using Stag-3D (Tackley 1993) to reproduce the experimental conditions, including the tank aspect ratio and the temperature dependence of physical properties. We observed that convection is driven by cold descending plumes generated at the upper

  2. Mantle Convection in a Microwave Oven: New Perspectives for the Internally Heated Convection

    NASA Astrophysics Data System (ADS)

    Limare, A.; Fourel, L.; Surducan, E.; Neamtu, C.; Surducan, V.; Vilella, K.; Farnetani, C. G.; Kaminski, E. C.; Jaupart, C. P.

    2015-12-01

    The thermal evolution of silicate planets is primarily controlled by the balance between internal heating - due to radioactive decay - and heat transport by mantle convection. In the Earth, the problem is particularly complex due to the heterogeneous distribution of heat sources in the mantle and the non-linear coupling between this distribution and convective mixing. To investigate the behaviour of such systems, we have developed a new technology based on microwave absorption to study internally-heated convection in the laboratory. This prototype offers the ability to reach the high Rayleigh-Roberts and Prandtl numbers that are relevant for planetary convection. Our experimental results obtained for a uniform distribution of heat sources were compared to numerical calculations reproducing exactly experimental conditions (3D Cartesian geometry and temperature-dependent physical properties), thereby providing the first cross validation of experimental and numerical studies of convection in internally-heated systems. We find that the thermal boundary layer thickness and interior temperature scale with RaH-1/4, where RaH is the Rayleigh-Roberts number, as theoretically predicted by scaling arguments on the dissipation of kinetic energy. Our microwave-based method offers new perspectives for the study of internally-heated convection in heterogeneous systems which have been out of experimental reach until now. We are able to selectively heat specific regions in the convecting layer, through the careful control of the absorption properties of different miscible fluids. This is analogous to convection in the presence of chemical reservoirs with different concentration of long-lived radioactive isotopes. We shall show results for two different cases: the stability of continental lithosphere over a convective fluid and the evolution of a hidden enriched reservoir in the lowermost mantle.

  3. The Role of Deep Mantle Flow in Shaping the Hawaiian-Emperor Bend

    NASA Astrophysics Data System (ADS)

    Hassan, R.; Müller, D.; Gurnis, M.; Williams, S.; Flament, N. E.

    2016-12-01

    Age-progressive volcanic hotspot tracks are typical surface expressions of plate tectonic movement on top of narrow plumes of hot material within Earth's mantle. Seismic imaging reveals that these plumes can be of deep origin, potentially rooted on thermochemical structures in the lower mantle. Although palaeomagnetic and radiometric age data suggest that mantle flow can advect plume conduits laterally, the flow dynamics underlying the formation of the sharp bend occurring only in the Hawaiian-Emperor hotspot track in the Pacific Ocean remains enigmatic. The north Pacific features long-lasting subduction systems, unlike those in the south Pacific. We present palaeogeographically-constrained numerical models of thermochemical convection demonstrating that flow in the deep lower mantle under the north Pacific was anomalously vigorous between 100 Ma and 50 Ma. These models show a sharp bend in the Hawaiian-Emperor hotspot track arising from the interplay of plume tilt and the lateral advection of plume sources. We show that the different trajectories of the Hawaiian and Louisville hotspot tracks arise from asymmetric deformation of thermochemical structures under the Pacific between 100 Ma and 50 Ma. This asymmetric deformation waned just before the Hawaiian-Emperor bend developed, owing to flow in the deepest lower mantle associated with slab descent in the north and south Pacific.

  4. A rapid burst in hotspot motion through the interaction of tectonics and deep mantle flow.

    PubMed

    Hassan, Rakib; Müller, R Dietmar; Gurnis, Michael; Williams, Simon E; Flament, Nicolas

    2016-05-12

    Volcanic hotspot tracks featuring linear progressions in the age of volcanism are typical surface expressions of plate tectonic movement on top of narrow plumes of hot material within Earth's mantle. Seismic imaging reveals that these plumes can be of deep origin--probably rooted on thermochemical structures in the lower mantle. Although palaeomagnetic and radiometric age data suggest that mantle flow can advect plume conduits laterally, the flow dynamics underlying the formation of the sharp bend occurring only in the Hawaiian-Emperor hotspot track in the Pacific Ocean remains enigmatic. Here we present palaeogeographically constrained numerical models of thermochemical convection and demonstrate that flow in the deep lower mantle under the north Pacific was anomalously vigorous between 100 million years ago and 50 million years ago as a consequence of long-lasting subduction systems, unlike those in the south Pacific. These models show a sharp bend in the Hawaiian-Emperor hotspot track arising from the interplay of plume tilt and the lateral advection of plume sources. The different trajectories of the Hawaiian and Louisville hotspot tracks arise from asymmetric deformation of thermochemical structures under the Pacific between 100 million years ago and 50 million years ago. This asymmetric deformation waned just before the Hawaiian-Emperor bend developed, owing to flow in the deepest lower mantle associated with slab descent in the north and south Pacific.

  5. A rapid burst in hotspot motion through the interaction of tectonics and deep mantle flow

    NASA Astrophysics Data System (ADS)

    Hassan, Rakib; Müller, R. Dietmar; Gurnis, Michael; Williams, Simon E.; Flament, Nicolas

    2016-05-01

    Volcanic hotspot tracks featuring linear progressions in the age of volcanism are typical surface expressions of plate tectonic movement on top of narrow plumes of hot material within Earth’s mantle. Seismic imaging reveals that these plumes can be of deep origin—probably rooted on thermochemical structures in the lower mantle. Although palaeomagnetic and radiometric age data suggest that mantle flow can advect plume conduits laterally, the flow dynamics underlying the formation of the sharp bend occurring only in the Hawaiian-Emperor hotspot track in the Pacific Ocean remains enigmatic. Here we present palaeogeographically constrained numerical models of thermochemical convection and demonstrate that flow in the deep lower mantle under the north Pacific was anomalously vigorous between 100 million years ago and 50 million years ago as a consequence of long-lasting subduction systems, unlike those in the south Pacific. These models show a sharp bend in the Hawaiian-Emperor hotspot track arising from the interplay of plume tilt and the lateral advection of plume sources. The different trajectories of the Hawaiian and Louisville hotspot tracks arise from asymmetric deformation of thermochemical structures under the Pacific between 100 million years ago and 50 million years ago. This asymmetric deformation waned just before the Hawaiian-Emperor bend developed, owing to flow in the deepest lower mantle associated with slab descent in the north and south Pacific.

  6. On the Origin of Localized Fast Mantle Flow Velocity in Numerical Models of Subduction

    NASA Astrophysics Data System (ADS)

    Billen, M. I.; Jadamec, M.

    2011-12-01

    Recent regional (Jadamec and Billen, 2010) and global (Stadler et al., 2010; Alisic et al., 2010) models of subduction zones using non-linear rheology include results with localized regions of fast mantle velocities with magnitudes up to 90 cm/yr or roughly 20 times the speed of the subducting plate at the surface. These surprising results challenge the commonly held assumption that observed plate velocities are a good indication of mantle flow rates, and therefore the modeling has come under intense scrutiny to insure that these results are not an artifact of the model implementation. The previous models used realistic 3D geometries based on constraints from seismology (e.g., seismicity, tomography) and plate age to define slab temperature and viscosity, making it somewhat difficult to clearly demonstrate the physical cause of the localized fast flow velocities. Here we investigate the origin of fast mantle flow near subduction zones using 3D models with a simple planar slab geometry. Two suites of models are presented with either a slab that is free to sink into the mantle or a slab that is attached to a lithospheric layer. The rheology in the models is either Newtonian with a prescribed low viscosity mantle wedge region or non-Newtonian, in which low viscosity regions form in response to the instantaneous flow. The results show that there are two aspects of the models that lead to localized fast velocities. First, reduction in the mantle viscosity surrounding the sinking slab leads to faster overall flow rates induced by the sinking slab. Second, geometric affects limit the volume of the mantle surrounding the slab that can participate in the slab-induced return flow, and therefore a balance of stresses requires faster local flow rates within this smaller volume of material. Specifically, a strong dipping slab that is attached to the subducting lithosphere concentrates flow on the mantle-wedge side of the slab and in a narrow vertical portion of the

  7. Subducted slabs and the geoid: Constraints on mantle rheology and flow

    NASA Technical Reports Server (NTRS)

    Hager, B. H.

    1983-01-01

    The total geoid anomaly which is the result of a given density contrast in a convecting viscous earth is affected by the mass anomalies associated with the flow induced deformation of the upper surface and internal compositional boundaries, as well as by the density contrast itself is discussed. If the internal density contrasts can be estimated, the depth and variation of viscosity with depth of the convecting system can be constrained. The observed long wavelength geoid is highly correlated with that predicted by a density model for seismically active subducted slabs. The amplitude of the correlation is explained if the density contrasts associated with subduction extend into the lower mantle or if subducted slabs exceeding 350 km in thickness are piled up over horizontal distances of thousands of km at the base of the upper mantle. Mantle wide convection in a mantle that has a viscosity increasing with depth provides the explanation of the long-wavelength geoid anomalies over subduction zones.

  8. Inferences on flow at the base of Earth's mantle based on seismic anisotropy.

    PubMed

    Panning, Mark; Romanowicz, Barbara

    2004-01-16

    We applied global waveform tomography to model radial anisotropy in the whole mantle. We found that in the last few hundred kilometers near the core-mantle boundary, horizontally polarized S-wave velocities (VSH) are, on average, faster (by approximately 1%) than vertically polarized S-wave velocities (VSV), suggesting a large-scale predominance of horizontal shear. This confirms that the D" region at the base of the mantle is also a mechanical boundary layer for mantle convection. A notable exception to this average signature can be found at the base of the two broad low-velocity regions under the Pacific Ocean and under Africa, often referred to as "superplumes," where the anisotropic pattern indicates the onset of vertical flow.

  9. Axial flow heat exchanger devices and methods for heat transfer using axial flow devices

    DOEpatents

    Koplow, Jeffrey P.

    2016-02-16

    Systems and methods described herein are directed to rotary heat exchangers configured to transfer heat to a heat transfer medium flowing in substantially axial direction within the heat exchangers. Exemplary heat exchangers include a heat conducting structure which is configured to be in thermal contact with a thermal load or a thermal sink, and a heat transfer structure rotatably coupled to the heat conducting structure to form a gap region between the heat conducting structure and the heat transfer structure, the heat transfer structure being configured to rotate during operation of the device. In example devices heat may be transferred across the gap region from a heated axial flow of the heat transfer medium to a cool stationary heat conducting structure, or from a heated stationary conducting structure to a cool axial flow of the heat transfer medium.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  11. Descent of the ancient Farallon slab drives localized mantle flow below the New Madrid seismic zone

    NASA Astrophysics Data System (ADS)

    Forte, A. M.; Mitrovica, J. X.; Moucha, R.; Simmons, N. A.; Grand, S. P.

    2007-02-01

    The great earthquake sequence that occurred in the central Mississippi River Valley during the winter of 1811-1812 is unprecedented in the historical record of seismicity within stable continental plate interiors. We show, using viscous flow models based on high resolution seismic tomography, that the descent of the ancient Farallon slab into the deep mantle beneath central North America induces a highly localized flow directly below the New Madrid seismic zone (NMSZ). This localization arises because of structural variability in the Farallon slab and the low-viscosity of the sub-lithospheric upper mantle, and it represents a heretofore unrecognized and possibly significant driving mechanism for the enigmatic intraplate seismicity.

  12. Microwave-based laboratory experiments for internally-heated mantle convection

    NASA Astrophysics Data System (ADS)

    Limare, A.; Surducan, E.; Surducan, V.; Neamtu, C.; di Giuseppe, E.; Vilella, K.; Farnetani, C. G.; Kaminski, E.; Jaupart, C.

    2013-11-01

    The thermal evolution of terrestrial planets is mainly controlled by the amount of radioactive heat sources in their mantle, and by the geometry and efficiency of solid state thermo-chemical convection within. So far, these systems have been studied using numerical methods only and cross validation by laboratory analogous experiments has not been conducted yet. To fill this gap we perform the first laboratory experiments of mantle convection driven by microwave-generated internal heating. We use a 30×30×5 cm3 experimental tank filled with 0.5 % Natrosol in water mixture (viscosity 0.6 Pa.s at 20°C). The fluid is heated from within by a microwave device that delivers a uniform volumetric heating from 10 to 70 kW/m3; the upper boundary of the fluid is kept at constant temperature, whereas the lower boundary is adiabatic. The velocity field is determined with particle image velocimetry and the temperature field is measured using thermochromic liquid crystals which enable us to charaterize the geometry of the convective regime as well as its bulk thermal evolution. Numerical simulations, conducted using Stag-3D in 3D cartesian geometry, reproduce the experimental setup (i.e., boundary conditions, box aspect ratio, temperature dependence of physical parameters, internal heating rate). The successful comparison between the experimental and numerical results validates our approach of modelling internal heating using microwaves.

  13. Microwave-based laboratory experiments for internally-heated mantle convection

    SciTech Connect

    Limare, A.; Di Giuseppe, E.; Vilella, K.; Farnetani, C. G.; Kaminski, E.; Jaupart, C.; Surducan, E.; Surducan, V.; Neamtu, C.

    2013-11-13

    The thermal evolution of terrestrial planets is mainly controlled by the amount of radioactive heat sources in their mantle, and by the geometry and efficiency of solid state thermo-chemical convection within. So far, these systems have been studied using numerical methods only and cross validation by laboratory analogous experiments has not been conducted yet. To fill this gap we perform the first laboratory experiments of mantle convection driven by microwave-generated internal heating. We use a 30×30×5 cm{sup 3} experimental tank filled with 0.5 % Natrosol in water mixture (viscosity 0.6 Pa.s at 20°C). The fluid is heated from within by a microwave device that delivers a uniform volumetric heating from 10 to 70 kW/m{sup 3}; the upper boundary of the fluid is kept at constant temperature, whereas the lower boundary is adiabatic. The velocity field is determined with particle image velocimetry and the temperature field is measured using thermochromic liquid crystals which enable us to charaterize the geometry of the convective regime as well as its bulk thermal evolution. Numerical simulations, conducted using Stag-3D in 3D cartesian geometry, reproduce the experimental setup (i.e., boundary conditions, box aspect ratio, temperature dependence of physical parameters, internal heating rate). The successful comparison between the experimental and numerical results validates our approach of modelling internal heating using microwaves.

  14. Fast asthenosphere motion in high-resolution global mantle flow models

    NASA Astrophysics Data System (ADS)

    Weismüller, Jens; Gmeiner, Björn; Bunge, Hans-Peter

    2016-04-01

    A variety of geologic observations point to fast upper mantle flow that may exceed plate tectonic velocities by an order of magnitude. At the same time there is mounting evidence from seismology for flow like structures in the upper 100-200 km of the mantle. Here we present a set of geodynamic simulations to link these observations. We model asthenospheric channels of varying thickness, in a range from a wide 1000 km channel to an extremely thin channel of 100 km, and viscosity contrasts between one and four orders of magnitude relative to the lower mantle. Using our new global high resolution mantle convection prototype Terra-Neo, we obtain an increase in velocity by a factor of ten between the thick and the very thin channel, translating into velocities of about 20 cm/a within the narrow asthenosphere. We further present and verify a simple Poiseuille flow model, which predicts that the upper mantle velocity scales with the inverse of the asthenosphere thickness.

  15. P-wave anisotropy, mantle wedge flow and olivine fabrics beneath Japan

    NASA Astrophysics Data System (ADS)

    Liu, Xin; Zhao, Dapeng

    2017-09-01

    We present a new 3-D anisotropic P-wave velocity (Vp) model for the crust and upper mantle of the Japan subduction zone obtained by inverting a large number of high-quality P-wave traveltime data of local earthquakes and teleseismic events. By assuming orthorhombic anisotropy with a vertical symmetry axis existing in the modeling space, isotropic Vp tomography and 3-D Vp azimuthal and radial anisotropies are determined simultaneously. According to a simple flow field and the obtained Vp anisotropic tomography, we estimate the distribution of olivine fabrics in the mantle wedge. Our results show that the forearc mantle wedge above the subducting Pacific slab beneath NE Japan exhibits an azimuthal anisotropy with trench-parallel fast velocity directions (FVDs) and Vhf > Vv > Vhs (here Vv is Vp in the vertical direction, Vhf and Vhs are P-wave velocities in the fast and slow directions in the horizontal plane), where B-type olivine fabric with vertical trench-parallel flow may dominate. Such an anisotropic feature is not obvious in the forearc mantle wedge above the Philippine Sea (PHS) slab under SW Japan, probably due to higher temperatures and more fluids there associated with the young and warm PHS slab subduction. Trench-normal FVDs and Vhf > Vv > Vhs are generally revealed in the mantle wedge beneath the arc and backarc in Japan, where E-type olivine fabric with FVD-parallel horizontal flow may dominate. Beneath western Honshu, however, the mantle wedge exhibits an anisotropy of Vv > Vhf > Vhs and so C-type olivine fabric may dominate, suggesting that the water content is the highest there, because both the PHS and Pacific slabs exist there and their dehydration reactions release abundant fluids to the overlying mantle wedge.

  16. Effect of Mantle Rheology on Viscous Heating induced during Ice Sheet Cycles

    NASA Astrophysics Data System (ADS)

    Huang, Pingping; Wu, Patrick; van der Wal, Wouter

    2017-04-01

    Hanyk et al. (2005) studied the viscous shear heating in the mantle induced by the surface loading and unloading of a parabolic-shaped Laurentide-size ice sheet. They found that for linear rheology, viscous heating is mainly concentrated below the ice sheet. The depth extent of the heating in the mantle is determined by the viscosity distribution. Also, the magnitude of viscous heating is significantly affected by the rate of ice thickness change. However, only one ice sheet has been considered in their work and the interactions between ice sheets and ocean loading have been neglected. Furthermore, only linear rheology has been considered, although they suggested that non-Newtonian rheology may have a stronger effect. Here we follow Hanyk et al. (2005) and computed the viscous dissipation for viscoelastic models using the finite element methodology of Wu (2004) and van der Wal et al. (2010). However, the global ICE6G model (Peltier et al. 2015) with realistic oceans is used here to provide the surface loading. In addition, viscous heating in non-linear rheology, composite rheology, in addition to linear rheology with uniform or VM5a profile are computed and compared. Our results for linear rheology mainly confirm the findings of Hanyk et al. (2005). For both non-linear and composite rheologies, viscous heating is also mainly distributed near and under the ice sheets, but, more concentrated; depending on the horizontal dimension of the ice sheet, it can extend into the lower mantle, but for some of the time, not as deep as that for linear rheology. For composite rheology, the viscous heating is dominated by the effect of non-linear relation between the stress and the strain. The ice history controls the time when the local maximum in viscous heating appears. However, the magnitude of the viscous heating is affected by mantle rheology as well as the ice loading. Due to viscosity stratification, the shape of the region with high viscous heating in model VM5a is a

  17. Heat transport in the high-pressure ice mantle of large icy moons

    NASA Astrophysics Data System (ADS)

    Choblet, G.; Tobie, G.; Sotin, C.; Kalousová, K.; Grasset, O.

    2017-03-01

    While the existence of a buried ocean sandwiched between surface ice and high-pressure (HP) polymorphs of ice emerges as the most plausible structure for the hundreds-of-kilometers thick hydrospheres within large icy moons of the Solar System (Ganymede, Callisto, Titan), little is known about the thermal structure of the deep HP ice mantle and its dynamics, possibly involving melt production and extraction. This has major implications for the thermal history of these objects as well as on the habitability of their ocean as the HP ice mantle is presumed to limit chemical transport from the rock component to the ocean. Here, we describe 3D spherical simulations of subsolidus thermal convection tailored to the specific structure of the HP ice mantle of large icy moons. Melt production is monitored and melt transport is simplified by assuming instantaneous extraction to the ocean above. The two controlling parameters for these models are the rheology of ice VI and the heat flux from the rock core. Reasonable end-members are considered for both parameters as disagreement remains on the former (especially the pressure effect on viscosity) and as the latter is expected to vary significantly during the moon's history. We show that the heat power produced by radioactive decay within the rock core is mainly transported through the HP ice mantle by melt extraction to the ocean, with most of the melt produced directly above the rock/water interface. While the average temperature in the bulk of the HP ice mantle is always relatively cool when compared to the value at the interface with the rock core (∼ 5 K above the value at the surface of the HP ice mantle), maximum temperatures at all depths are close to the melting point, often leading to the interconnection of a melt path via hot convective plume conduits throughout the HP ice mantle. Overall, we predict long periods of time during these moons' history where water generated in contact with the rock core is transported to

  18. Heat transport in the high-pressure ice mantle of large icy moons

    NASA Astrophysics Data System (ADS)

    Choblet, Gael; Tobie, Gabriel; Sotin, Christophe; Kalousova, Klara; Grasset, Olivier

    2017-04-01

    While the existence of a buried ocean sandwiched between surface ice and high-pressure (HP) polymorphs of ice emerges as the most plausible structure for the hundreds-of-kilometers thick hydrospheres within large icy moons of the Solar System (Ganymede, Callisto, Titan), little is known about the thermal structure of the deep HP ice mantle and its dynamics, possibly involving melt production and extraction. This has major implications for the thermal history of these objects as well as on the habitability of their ocean as the HP ice mantle is presumed to limit chemical transport from the rock component to the ocean. Here, we describe 3D spherical simulations of subsolidus thermal convection tailored to the specific structure of the HP ice mantle of large icy moons. Melt production is monitored and melt transport is simplified by assuming instantaneous extraction to the ocean above. The two controlling parameters for these models are the rheology of ice VI and the heat flux from the rock core. Reasonable end-members are considered for both parameters as disagreement remains on the former (especially the pressure effect on viscosity) and as the latter is expected to vary significantly during the moon's history. We show that the heat power produced by radioactive decay within the rock core is mainly transported through the HP ice mantle by melt extraction to the ocean, with most of the melt produced directly above the rock/water interface. While the average temperature in the bulk of the HP ice mantle is always relatively cool when compared to the value at the interface with the rock core (˜ 5 K above the value at the surface of the HP ice mantle), maximum temperatures at all depths are close to the melting point, often leading to the interconnection of a melt path via hot convective plume conduits throughout the HP ice mantle. Overall, we predict long periods of time during these moons' history where water generated in contact with the rock core is transported to

  19. Louisville seamount subduction and its implication on mantle flow beneath the central Tonga-Kermadec arc.

    PubMed

    Timm, Christian; Bassett, Daniel; Graham, Ian J; Leybourne, Matthew I; de Ronde, Cornel E J; Woodhead, Jon; Layton-Matthews, Daniel; Watts, Anthony B

    2013-01-01

    Subduction of intraplate seamounts beneath a geochemically depleted mantle wedge provides a seldom opportunity to trace element recycling and mantle flow in subduction zones. Here we present trace element and Sr, Nd and Pb isotopic compositions of lavas from the central Tonga-Kermadec arc, west of the contemporary Louisville-Tonga trench intersection, to provide new insights into the effects of Louisville seamount subduction. Elevated (206)Pb/(204)Pb, (208)Pb/(204)Pb, (86)Sr/(87)Sr in lavas from the central Tonga-Kermadec arc front are consistent with localized input of subducted alkaline Louisville material (lavas and volcaniclastics) into sub-arc partial melts. Furthermore, absolute Pacific Plate motion models indicate an anticlockwise rotation in the subducted Louisville seamount chain that, combined with estimates of the timing of fluid release from the subducting slab, suggests primarily trench-normal mantle flow beneath the central Tonga-Kermadec arc system.

  20. Louisville seamount subduction and its implication on mantle flow beneath the central Tonga-Kermadec arc

    NASA Astrophysics Data System (ADS)

    Timm, Christian; Bassett, Daniel; Graham, Ian J.; Leybourne, Matthew I.; de Ronde, Cornel E. J.; Woodhead, Jon; Layton-Matthews, Daniel; Watts, Anthony B.

    2013-04-01

    Subduction of intraplate seamounts beneath a geochemically depleted mantle wedge provides a seldom opportunity to trace element recycling and mantle flow in subduction zones. Here we present trace element and Sr, Nd and Pb isotopic compositions of lavas from the central Tonga-Kermadec arc, west of the contemporary Louisville-Tonga trench intersection, to provide new insights into the effects of Louisville seamount subduction. Elevated 206Pb/204Pb, 208Pb/204Pb, 86Sr/87Sr in lavas from the central Tonga-Kermadec arc front are consistent with localized input of subducted alkaline Louisville material (lavas and volcaniclastics) into sub-arc partial melts. Furthermore, absolute Pacific Plate motion models indicate an anticlockwise rotation in the subducted Louisville seamount chain that, combined with estimates of the timing of fluid release from the subducting slab, suggests primarily trench-normal mantle flow beneath the central Tonga-Kermadec arc system.

  1. A global view of shear wave splitting and mantle flow in subduction systems

    NASA Astrophysics Data System (ADS)

    Long, Maureen; Silver, Paul; Hanna, Jenny; Wirth, Erin; Kincaid, Chris; Montesi, Laurent

    2010-05-01

    The character of the mantle flow field in subduction zone regions remains poorly understood, despite its importance for our understanding of subduction dynamics. Observations of seismic anisotropy, which manifests itself in shear wave splitting, can shed light on the geometry of mantle flow in subduction zones, but placing constraints on anisotropy in various parts of the subduction system (including the overriding plate, the mantle wedge, the subducting slab, and the sub-slab mantle) remains challenging from an observational point of view. In order to identify dynamic processes that make first-order contributions to the pattern of mantle flow in subduction zones, we analyze a global compilation of shear wave splitting measurements for a variety of ray paths, including SK(K)S and teleseismic S phases as well as local S and source-side splitting from slab earthquakes. Key challenges associated with assembling such a compilation include correctly assessing and accounting for any dependence of local S splitting parameters on frequency and correctly characterizing any contribution to SKS splitting measurements from anisotropy within the subducting slab that is unrelated to active mantle flow. We present local case studies from the Japan and Izu-Bonin-Marianas subduction zones that explore frequency-dependent splitting due to heterogeneous anisotropy in the mantle wedge and that use a variety of raypath combinations to isolate the contribution from anisotropy within the slab. Keeping these results in mind, we have compiled shear wave splitting measurements from subduction zones globally from the literature and from our own work to produce estimates of average shear wave splitting parameters - and their spatial variation - for the mantle wedge and the sub-wedge region for individual subduction segments. These estimates are then compared to other parameters that describe subduction. The sub-wedge splitting signal is relatively simple and is dominated by trench

  2. Seismic evidence for rotating mantle flow around subducting slab edge associated with oceanic microplate capture

    NASA Astrophysics Data System (ADS)

    Mosher, Stephen G.; Audet, Pascal; L'Heureux, Ivan

    2014-07-01

    Tectonic plate reorganization at a subduction zone edge is a fundamental process that controls oceanic plate fragmentation and capture. However, the various factors responsible for these processes remain elusive. We characterize seismic anisotropy of the upper mantle in the Explorer region at the northern limit of the Cascadia subduction zone from teleseismic shear wave splitting measurements. Our results show that the mantle flow field beneath the Explorer slab is rotating anticlockwise from the convergence-parallel motion between the Juan de Fuca and the North America plates, re-aligning itself with the transcurrent motion between the Pacific and North America plates. We propose that oceanic microplate fragmentation is driven by slab stretching, thus reorganizing the mantle flow around the slab edge and further contributing to slab weakening and increase in buoyancy, eventually leading to cessation of subduction and microplate capture.

  3. Thermochemical flows couple the Earth's inner core growth to mantle heterogeneity.

    PubMed

    Aubert, Julien; Amit, Hagay; Hulot, Gauthier; Olson, Peter

    2008-08-07

    Seismic waves sampling the top 100 km of the Earth's inner core reveal that the eastern hemisphere (40 degrees E-180 degrees E) is seismically faster, more isotropic and more attenuating than the western hemisphere. The origin of this hemispherical dichotomy is a challenging problem for our understanding of the Earth as a system of dynamically coupled layers. Previously, laboratory experiments have established that thermal control from the lower mantle can drastically affect fluid flow in the outer core, which in turn can induce textural heterogeneity on the inner core solidification front. The resulting texture should be consistent with other expected manifestations of thermal mantle control on the geodynamo, specifically magnetic flux concentrations in the time-average palaeomagnetic field over the past 5 Myr, and preferred eddy locations in flows imaged below the core-mantle boundary by the analysis of historical geomagnetic secular variation. Here we show that a single model of thermochemical convection and dynamo action can account for all these effects by producing a large-scale, long-term outer core flow that couples the heterogeneity of the inner core with that of the lower mantle. The main feature of this thermochemical 'wind' is a cyclonic circulation below Asia, which concentrates magnetic field on the core-mantle boundary at the observed location and locally agrees with core flow images. This wind also causes anomalously high rates of light element release in the eastern hemisphere of the inner core boundary, suggesting that lateral seismic anomalies at the top of the inner core result from mantle-induced variations in its freezing rate.

  4. Seismic Anisotropy and Mantle Flow Driven by the Cocos Slab Under Southern Mexico

    NASA Astrophysics Data System (ADS)

    Bernal-López, Leslie A.; Garibaldi, Berenice R.; León Soto, Gerardo; Valenzuela, Raúl W.; Escudero, Christian R.

    2016-10-01

    Shear wave splitting measurements were made using SKS and SKKS waves recorded by the Meso-American Subduction Experiment, which was deployed in southern Mexico starting at the coast of the Pacific Ocean and running north toward the Gulf of Mexico. In this segment of the Middle America Trench the oceanic Cocos plate subducts under the continental North American plate. The active volcanic arc is located at the southern end of the Trans-Mexican Volcanic Belt. Unlike most subduction zones, however, the volcanic arc is not subparallel to the trench. In the fore-arc, between the trench and the Trans-Mexican Volcanic Belt, the Cocos slab subducts subhorizontally. Beneath the volcanic belt, however, the slab dives steeply into the mantle. A marked difference in the orientation of the fast polarization directions is observed between the fore-arc and the back-arc. In the fore-arc the fast axes determined using SKS phases are oriented NE-SW, in the same direction as the relative motion between the Cocos and North American plates, and are approximately perpendicular to the trench. Physical conditions in the subslab mantle are consistent with the existence of A-type olivine and consequently entrained mantle flow is inferred. Strong coupling between the slab and the surrounding mantle is observed. In the back-arc SKS fast polarization directions are oriented N-S and are perpendicular to the strike of the slab. Given the high temperatures in the mantle wedge tip, the development of A-type, or similar, olivine fabric throughout the mantle wedge is expected. The orientation of the fast axes is consistent with corner flow in the mantle wedge.

  5. A High Core Heat Flow Solution to Earth's Thermal and Magnetic Paradoxes

    NASA Astrophysics Data System (ADS)

    Driscoll, P. E.

    2014-12-01

    Recent discoveries relating to the thermal and magnetic history of the Earth have revealed that a clement surface and a dynamo generated magnetic field have persisted over almost all of Earth history. However, the preferred mantle radioactivity and heat loss efficiency predict wide spread mantle melting, or "thermal catastrophe", only 2-3 Ga. Similarly, paleomagnetic observations that indicate a geodynamo as old as 3.4 Gyr are at odds with the "new core paradox", which claims insufficient energy to drive the ancient geodynamo prior to inner core nucleation ~ 1 Ga in light of recent revisions to the thermal conductivity of the core. We demonstrate that to avoid both the mantle and core paradoxes restricts the present core heat flow to 13 - 17 TW, radiogenic core heat production to 1.5 - 2.0 TW, and inner core age to 0.4 - 0.5 Ga. This solution accommodates the geochemically preferred mantle radiogenic heat production of 13 TW, while maintaining a mostly solid mantle and core generated magnetic field over the geological history of the planet. Inner core nucleation should be accompanied by a boost in magnetic energy in the core and latent heat released at the inner-core boundary, which may be imprinted in the surface paleomagnetic and hot-spot record at that time.

  6. Western US intermountain seismicity caused by changes in upper mantle flow.

    PubMed

    Becker, Thorsten W; Lowry, Anthony R; Faccenna, Claudio; Schmandt, Brandon; Borsa, Adrian; Yu, Chunquan

    2015-08-27

    Understanding the causes of intraplate earthquakes is challenging, as it requires extending plate tectonic theory to the dynamics of continental deformation. Seismicity in the western United States away from the plate boundary is clustered along a meandering, north-south trending 'intermountain' belt. This zone coincides with a transition from thin, actively deforming to thicker, less tectonically active crust and lithosphere. Although such structural gradients have been invoked to explain seismicity localization, the underlying cause of seismicity remains unclear. Here we show results from improved mantle flow models that reveal a relationship between seismicity and the rate change of 'dynamic topography' (that is, vertical normal stress from mantle flow). The associated predictive skill is greater than that of any of the other forcings we examined. We suggest that active mantle flow is a major contributor to seismogenic intraplate deformation, while gravitational potential energy variations have a minor role. Seismicity localization should occur where convective changes in vertical normal stress are modulated by lithospheric strength heterogeneities. Our results on deformation processes appear consistent with findings from other mobile belts, and imply that mantle flow plays a significant and quantifiable part in shaping topography, tectonics, and seismic hazard within intraplate settings.

  7. Effects of change in slab geometry on the mantle flow and slab fabric in Southern Peru

    NASA Astrophysics Data System (ADS)

    Knezevic Antonijevic, Sanja; Wagner, Lara S.; Beck, Susan L.; Long, Maureen D.; Zandt, George; Tavera, Hernando

    2016-10-01

    The effects of complex slab geometries on the surrounding mantle flow field are still poorly understood. Here we combine shear wave velocity structure with Rayleigh wave phase anisotropy to examine these effects in southern Peru, where the slab changes its geometry from steep to flat. To the south, where the slab subducts steeply, we find trench-parallel anisotropy beneath the active volcanic arc that we attribute to the mantle wedge and/or upper portions of the subducting plate. Farther north, beneath the easternmost corner of the flat slab, we observe a pronounced low-velocity anomaly. This anomaly is caused either by the presence of volatiles and/or flux melting that could result from southward directed, volatile-rich subslab mantle flow or by increased temperature and/or decompression melting due to small-scale vertical flow. We also find evidence for mantle flow through the tear north of the subducting Nazca Ridge. Finally, we observe anisotropy patterns associated with the fast velocity anomalies that reveal along strike variations in the slab's internal deformation. The change in slab geometry from steep to flat contorts the subducting plate south of the Nazca Ridge causing an alteration of the slab petrofabric. In contrast, the torn slab to the north still preserves the primary (fossilized) petrofabric first established shortly after plate formation.

  8. Magnetic resonance imaging analysis of water flow in the mantle cavity of live Mytilus galloprovincialis.

    PubMed

    Seo, Eriko; Ohishi, Kazue; Maruyama, Tadashi; Imaizumi-Ohashi, Yoshie; Murakami, Masataka; Seo, Yoshiteru

    2014-07-01

    Water flow inside the shell of Mytilus galloprovincialis was measured by phase-contrast magnetic resonance imaging (MRI). In seawater without algal cells at 23 °C, water approached the mussel from the posterior-ventral side, and entered through the inhalant aperture at a velocity of 40-20 mm s(-1). The flow rate in the lower mantle cavity decreased to 10-20 mm s(-1), the water flowed in the anterior-dorsal direction and approached the demibranches at a velocity of 5-10 mm s(-1). After passing through the lamellae to the upper mantle cavity, the water stretched the interlamellar cavity, turned to the posterior-dorsal direction and accumulated in the epibranchial cavity. The water flows came together at the ventral side of the posterior adductor muscle. The velocity increased more to than 50 mm s(-1) in the exhalant siphon, and exhaled out in the posterior-dorsal direction. The anterior-posterior direction of the flow was imaged every 1.92 s by the inflow effect of T1-weighted MRI. The flow seemed to be constant, and no cyclic motion of the mantles or the gills was detected. Spontaneous closure of the shells caused a quick drop of the flow in the mantle cavity. In the opening process of the shells, water flow in the interlamellar cavities increased before the opening, followed by an increase of flows in the exhalant siphon and inhalant aperture with minimum delay, reaching a plateau within 1 min of the shells opening. This provides direct evidence that the lateral cilia drive water in the mussel M. galloprovincialis. © 2014. Published by The Company of Biologists Ltd.

  9. Giant impacts, heterogeneous mantle heating and a past hemispheric dynamo on Mars

    NASA Astrophysics Data System (ADS)

    Monteux, J.; Amit, H.; Choblet, G.; Langlais, B.; Tobie, G.

    2015-10-01

    The martian surface exhibits a strong dichotomy in elevation, crustal thickness and magnetization between the southern and northern hemispheres. A giant impact has been proposed as an explanation for the for-mation of the Northern Lowlands on Mars. Such an impact probably led to strong and deep mantle heat-ing which may have had implications on the magnetic evolution of the planet. We model the effects of such an impact on the martian magnetic field by imposing an impact induced thermal heterogeneity, and the sub-sequent heat flux heterogeneity, on the martian core- mantle boundary(CMB). The CMB heat flux lateral variations as well as the reduction in the mean CMB heat flux are determined by the size and geographic location of the impactor. A polar impactor leads to a north-south hemispheric magnetic dichotomy that is stronger than an east-west dichotomy created by an equatorial impactor. The amplitude of the hemispheric magnetic dichotomy is mostly controlled by the horizontal Rayleigh number Rah which represents the vigor of the convection driven by the lateral variations of the CMB heat flux. We show that, for a given Rah, an impact induced CMB heat flux heterogeneity is more efficient than a synthetic degree-1 CMB heat flux heterogeneity in generating strong hemispheric magnetic dichotomies. Large Rah values are needed to get a dichotomy as strong as the observed one, favoring a reversing paleo-dynamo for Mars. Our results imply that an impactor radius of˜1000 km could have recorded the magnetic dichotomy observed in the mar- tian crustal field only if very rapid post-impact magma cooling took place.

  10. Heat flow in eastern Egypt - The thermal signature of a continental breakup

    NASA Technical Reports Server (NTRS)

    Morgan, P.; Boulos, F. K.; Hennin, S. F.; El-Sherif, A. A.; El-Sayed, A. A.

    1985-01-01

    Data on the heat flow in eastern Egypt were collected to provide information related to the mode and the mechanism of the Red Sea opening. The data indicate a general increase in heat flow towards the Red Sea (75-100 mW/sq m in a zone within 40 km of the coast compared with 35-55 mW/sq m inland). Moderately high heat flow (about 70 mW/sq m) was found for the Gulf of Suez. Heat production data indicate that the coastal thermal anomaly is not primarily related to crustal radiogenic heat production. Possible causes of the anomaly (one of which could be a high mantle heat flow causing a lithospheric thinning centered beneath the Red Sea) are discussed.

  11. Giant impacts, heterogeneous mantle heating and a past hemispheric dynamo on Mars

    NASA Astrophysics Data System (ADS)

    Monteux, Julien; Amit, Hagay; Choblet, Gael; Langlais, Benoît; Tobie, Gabriel

    2015-04-01

    The martian surface exhibits a strong dichotomy in elevation, crustal thickness and magnetization between the southern and northern hemispheres. A giant impact has been proposed as an explanation for the formation of the Northern Lowlands on Mars. Such an impact probably led to strong and deep mantle heating which may have had implications on the magnetic evolution of the planet. We model the effects of such an impact on the martian magnetic field by imposing an impact induced thermal heterogeneity, and the subsequent heat flux heterogeneity, on the martian core-mantle boundary (CMB). The CMB heat flux lateral variations as well as the reduction in the mean CMB heat flux are determined by the size and geographic location of the impactor. A polar impactor leads to a north-south hemispheric magnetic dichotomy that is stronger than an east-west dichotomy created by an equatorial impactor. The amplitude of the hemispheric magnetic dichotomy is mostly controlled by the horizontal Rayleigh number Rah which represents the vigor of the convection driven by the lateral variations of the CMB heat flux. We show that, for a given Rah, an impact induced CMB heat flux heterogeneity is more efficient than a synthetic degree-1 CMB heat flux heterogeneity in generating strong hemispheric magnetic dichotomies. Large Rah values are needed to get a dichotomy as strong as the observed one, favoring a reversing paleo-dynamo for Mars. Our results imply that an impactor radius of ~ 1000 km could have recorded the magnetic dichotomy observed in the martian crustal field only if very rapid post-impact magma cooling took place.

  12. Heat flow and convection demonstration (Apollo 14)

    NASA Technical Reports Server (NTRS)

    Bannister, T. C.

    1973-01-01

    Apollo 14 Astronaut Stuart A. Roosa conducted a group of experiments during the lunar flyback on February 7, 1971, to obtain information on heat flow and convection in gases and liquids in an environment of less than 0.000001 g. Flow observations and thermal data have shown that: (1) as expected, there are convective motions caused by surface tension gradients in a plane liquid layer with a free upper surface; (2) heat flow in enclosed liquids and gases occurs mainly by diffusive heat conduction; and (3) some convective processes, whose characteristics are not fully known, add to the heat transfer. The raw data are presented, and the analysis approach is given.

  13. Comparisons between seismic Earth structures and mantle flow models based on radial correlation functions

    SciTech Connect

    Jordan, T.H.; Puster, P. ); Glatzmaier, G.A. ); Tackley, P.J. )

    1993-09-10

    Three-dimensional numerical simulations were conducted of mantle convection in which flow through the transition zone is impeded by either a strong chemical change or an endothermic phase change. The temperature fields obtained from these models display a well defined minimum in the vertical correlation length at or near the radius where the barrier is imposed, even when the fields were filtered to low angular and radial resolutions. However, evidence for such a feature is lacking in the shear-velocity models derived by seismic tomography. This comparison suggests that any stratification induced by phase or chemical changes across the mid-mantle transition zone has a relatively small effect on the large-scale circulation of mantle material.

  14. Comparisons between seismic Earth structures and mantle flow models based on radial correlation functions.

    PubMed

    Jordan, T H; Puster, P; Glatzmaier, G A; Tackley, P J

    1993-09-10

    Three-dimensional numerical simulations were conducted of mantle convection in which flow through the transition zone is impeded by either a strong chemical change or an endothermic phase change. The temperature fields obtained from these models display a well-defined minimum in the vertical correlation length at or near the radius where the barrier is imposed, even when the fields were filtered to low angular and radial resolutions. However, evidence for such a feature is lacking in the shear-velocity models derived by seismic tomography. This comparison suggests that any stratification induced by phase or chemical changes across the mid-mantle transition zone has a relatively small effect on the large-scale circulation of mantle material.

  15. Thermographic heat transfer measurements in separated flows

    NASA Astrophysics Data System (ADS)

    Scherer, V.; Wittig, S.; Bittlinger, G.; Pfeiffer, A.

    1993-12-01

    A measurement technique to determine the surface heat transfer distribution in complex turbulent flows is described. For this purpose, a constant wall heat flux test surface has been designed. To measure the surface temperature of the test plate, an infrared camera was used. The instrumentation allows the determination of the heat transfer with high accuracy and detailed spatial resolution. In examining combustor-type separated flow, the capabilities of the technique are demonstrated and its accuracy is verified by appropriate conventional techniques.

  16. Dynamics and Upper Mantle Structure Beneath the Northwestern Andes: Subduction Segments, Moho Depth, and Possible Relationships to Mantle Flow

    NASA Astrophysics Data System (ADS)

    Monsalve, G.; Yarce, J.; Becker, T. W.; Porritt, R. W.; Cardona, A.; Poveda, E.; Posada, G. A.

    2014-12-01

    The northwestern South American plate shows a complex tectonic setting whose causes and relationship to mantle structure are still debated. We combine different techniques to elucidate some of the links between slabs and surface deformation in Colombia. Crustal structure beneath the Northern Andes was inferred from receiver functions where we find thicknesses of nearly 60 km beneath the plateau of the Eastern Cordillera and underneath the southern volcanic area of the Central Cordillera. We infer that such crustal thickening resulted from shortening, magmatic addition, and accretion-subduction. Analyses of relative teleseismic travel time delays and estimates of residual surface topography based on our new crustal model suggest that there are at least two subduction segments underneath the area. The Caribbean slab lies at a low angle beneath northernmost Colombia and steepens beneath the Eastern Cordillera. Such steepening is indicated by negative travel time relative residuals in the area of the Bucaramanga Nest, implying a cold anomaly in the upper mantle, and by positive residual topography just off the east of this area, perhaps generated by slab-associated return flow. Results for the western Andes and the Pacific coastal plains are consistent with "normal" subduction of the Nazca plate: travel time relative residuals there are predominantly positive, and the residual topography shows an W-E gradient, going from positive at the Pacific coastline to negative at the Magdalena Valley, which separates the eastern cordillera from the rest of the Colombian Andean system. Azimuthal analysis of relative travel time residuals further suggests the presence of seismically slow materials beneath the central part of the Eastern Cordillera. Azimuthal anisotropy from SKS splitting in that region indicates that seismically fast orientations do not follow plate convergence, different from what we find for the western Colombian Andes and the Caribbean and Pacific coastal plains

  17. Seismic evidence for flow in the hydrated mantle wedge of the Ryukyu subduction zone

    PubMed Central

    Nagaya, Takayoshi; Walker, Andrew M.; Wookey, James; Wallis, Simon R.; Ishii, Kazuhiko; Kendall, J. -Michael

    2016-01-01

    It is widely accepted that water-rich serpentinite domains are commonly present in the mantle above shallow subducting slabs and play key roles in controlling the geochemical cycling and physical properties of subduction zones. Thermal and petrological models show the dominant serpentine mineral is antigorite. However, there is no good consensus on the amount, distribution and alignment of this mineral. Seismic velocities are commonly used to identify antigorite-rich domains, but antigorite is highly-anisotropic and depending on the seismic ray path, its properties can be very difficult to distinguish from non-hydrated olivine-rich mantle. Here, we utilize this anisotropy and show how an analysis of seismic anisotropy that incorporates measured ray path geometries in the Ryukyu arc can constrain the distribution, orientation and amount of antigorite. We find more than 54% of the wedge must consist of antigorite and the alignment must change from vertically aligned to parallel to the slab. This orientation change suggests convective flow in the hydrated forearc mantle. Shear wave splitting analysis in other subduction zones indicates large-scale serpentinization and forearc mantle convection are likely to be more widespread than generally recognized. The view that the forearc mantle of cold subduction zones is dry needs to be reassessed. PMID:27436676

  18. Mantle flow and melt migration beneath oceanic ridges: Models derived from observations in ophiolites

    NASA Astrophysics Data System (ADS)

    Ceuleneer, Georges; Rabinowicz, Michel

    The tectonic and volcanic features of the Earth are largely conditioned by processes taking place in the upper mantle. However our present knowledge of the mantle is essentially derived from indirect evidence. As pointed out by Oliver [1991], the promising technologies of very deep drilling and of high resolution geophysical imagery which should improve our views of the Earth's interior are still to be invented. In the meantime, to progress in the study of geological stuffs, widespread and of easy access at the Earth surface, and in their interpretation in terms of mantle processes, is not a vain task. For example, the Earth's magmatic budget is largely dominated by oceanic ridge and hotspot volcanism [e.g. Crisp, 1984]. The basaltic melts erupted there are likely produced by pressure-release induced partial melting of a peridotitic source. Consequently, their composition and distribution are expected to be sensitive to the thermal and flow structure of the mantle. Potentially, basalts constitute a widespread and abundant pool of information about mantle convection, and one of the goals pursued by petrological studies is to decipher this message [e.g. Klein and Langmuir, 1987; McKenzie and Bickle, 1988; Watson and McKenzie, 1991; Albarede, 1992, Langmuir et al., this volume; Grove et al., this volume].

  19. Seismic evidence for flow in the hydrated mantle wedge of the Ryukyu subduction zone

    NASA Astrophysics Data System (ADS)

    Nagaya, Takayoshi; Walker, Andrew M.; Wookey, James; Wallis, Simon R.; Ishii, Kazuhiko; Kendall, J.-Michael

    2016-07-01

    It is widely accepted that water-rich serpentinite domains are commonly present in the mantle above shallow subducting slabs and play key roles in controlling the geochemical cycling and physical properties of subduction zones. Thermal and petrological models show the dominant serpentine mineral is antigorite. However, there is no good consensus on the amount, distribution and alignment of this mineral. Seismic velocities are commonly used to identify antigorite-rich domains, but antigorite is highly-anisotropic and depending on the seismic ray path, its properties can be very difficult to distinguish from non-hydrated olivine-rich mantle. Here, we utilize this anisotropy and show how an analysis of seismic anisotropy that incorporates measured ray path geometries in the Ryukyu arc can constrain the distribution, orientation and amount of antigorite. We find more than 54% of the wedge must consist of antigorite and the alignment must change from vertically aligned to parallel to the slab. This orientation change suggests convective flow in the hydrated forearc mantle. Shear wave splitting analysis in other subduction zones indicates large-scale serpentinization and forearc mantle convection are likely to be more widespread than generally recognized. The view that the forearc mantle of cold subduction zones is dry needs to be reassessed.

  20. Seismic evidence for flow in the hydrated mantle wedge of the Ryukyu subduction zone.

    PubMed

    Nagaya, Takayoshi; Walker, Andrew M; Wookey, James; Wallis, Simon R; Ishii, Kazuhiko; Kendall, J-Michael

    2016-07-20

    It is widely accepted that water-rich serpentinite domains are commonly present in the mantle above shallow subducting slabs and play key roles in controlling the geochemical cycling and physical properties of subduction zones. Thermal and petrological models show the dominant serpentine mineral is antigorite. However, there is no good consensus on the amount, distribution and alignment of this mineral. Seismic velocities are commonly used to identify antigorite-rich domains, but antigorite is highly-anisotropic and depending on the seismic ray path, its properties can be very difficult to distinguish from non-hydrated olivine-rich mantle. Here, we utilize this anisotropy and show how an analysis of seismic anisotropy that incorporates measured ray path geometries in the Ryukyu arc can constrain the distribution, orientation and amount of antigorite. We find more than 54% of the wedge must consist of antigorite and the alignment must change from vertically aligned to parallel to the slab. This orientation change suggests convective flow in the hydrated forearc mantle. Shear wave splitting analysis in other subduction zones indicates large-scale serpentinization and forearc mantle convection are likely to be more widespread than generally recognized. The view that the forearc mantle of cold subduction zones is dry needs to be reassessed.

  1. Post-Eocene Subduction Dynamics and Mantle Flow beneath Western U.S.

    NASA Astrophysics Data System (ADS)

    Liu, L.; Zhou, Q.; Leonard, T.

    2015-12-01

    Both surface geology and mantle seismic images suggest a complex late Cenozoic history of mantle dynamics over western U.S. We try to understand this history by simulating the Farallon subduction since 40 Ma. Forward subduction models assimilating time dependent seafloor ages, plate kinematics and evolving plate boundaries suggest that the present-day 3D distribution of fast seismic anomalies below western U.S. mostly represent late Cenozoic slabs, which experienced multiple phases of segmentation during subduction because of their young age and small mechanical strength (Liu & Stegman, 2011). A major slab segmentation event occurred around mid-Miocene, with the resulting slab tear and induced asthenosphere upwelling correlating with the Steens-Columbia River flood basalts (SCRB) eruption both in space and in time (Liu & Stegman, 2012). This suggests that a mantle plume is not required for the formation of the SCRB. Segmentation of the Farallon slab generates rapid toroidal flows around the newly formed slab edges beneath the Cascadia arc. These mantle flows may affect both the pattern and composition of arc volcanism through transportation of oceanic asthenosphere material into the mantle wedge. Based on the forward model, we further test the influence of slow seismic anomalies on mantle dynamics. On the one hand, we explicitly input a deep hot anomaly to represent the putative Yellowstone plume. On the other hand, we develop a hybrid scheme that combines the adjoint inverse method with the high-resolution forward simulation approach, so that the present-day mantle seismic structure is entirely consistent with the convection model. Our preliminary results suggest that a hot plume could actively rise up only when it is several hundreds of kilometers away from the slabs, as is the case prior to 20 Ma. Subsequently, the plume is dominated by the surrounding slabs, resulting in an overall downwelling mantle flow. This suggests that a plume might have contributed to

  2. Fluid flow and heat transfer in polygonal micro heat pipes

    NASA Astrophysics Data System (ADS)

    Rao, Sai; Wong, Harris

    2015-11-01

    Micro heat pipes have been used to cool microelectronic devices, but their heat transfer coefficients are low compared with those of conventional heat pipes. We model heat and mass transfer in triangular, square, hexagonal, and rectangular micro heat pipes under small imposed temperature differences. A micro heat pipe is a closed microchannel filled with a wetting liquid and a long vapor bubble. When a temperature difference is applied across a micro heat pipe, the equilibrium vapor pressure at the hot end is higher than that at the cold end, and the difference drives a vapor flow. As the vapor moves, the vapor pressure at the hot end drops below the saturation pressure. This pressure drop induces continuous evaporation from the interface. Two dimensionless numbers emerge from the momentum and energy equations: the heat-pipe number H, and the evaporation exponent S. When H >> 1 and S >> 1, vapor-flow heat transfer dominates and a thermal boundary layer appears at the hot end, the thickness of which scales as L/S, where L is the half-length of the pipe. A similar boundary layer exists at the cold end. Outside the boundary layers, the temperature is uniform. We also find a dimensionless optimal pipe length Sm =Sm(H) for maximum evaporative heat transfer. Thus, our model suggests that micro heat pipes should be designed with H >> 1 and S =Sm. We calculate H and S for four published micro-heat-pipe experiments, and find encouraging support for our design criterion.

  3. Instantaneous mantle flow induced by subduction of a freely sinking slab

    NASA Astrophysics Data System (ADS)

    Piromallo, C.; Becker, T. W.; Funiciello, F.; Faccenna, C.

    2007-05-01

    We conduct three-dimensional (3-D) subduction experiments by a finite element approach to study flow around slabs which are prescribed based on a transient subduction stage from a laboratory model. Instantaneous velocity fields are examined for a slab that sinks freely into the mantle, focusing on the toroidal vs. poloidal components as a function of boundary conditions (BCs), plate width, and viscosity contrast between slab and mantle. Results show that the toroidal flow is important for the circulation geometries in the vertical plane. In particular, the material resumed at surface in the back-arc wedge by the return flow cell below the slab tip is minimal with respect to 2-D models, in agreement with laboratory models. Furthermore, we find that circulation is characterized by an upward flow component close to slab sides that could be important for local tectonic structures at slab edges. We show that BCs affect the magnitude and pattern of velocities. In particular, in proximity of the slab the flow field is similar for no- and free-slip BCs, while strong variations exist elsewhere. Moreover, the characteristic spatial length-scale is given by the box height. By modeling different viscosity contrasts between slab and mantle (η'), we find that significant return flow around edges can only be obtained for stiff slabs and that the strength of the toroidal/poloidal Ratio increases with η', nearly independent of slab width. For η' ≥ 103, the toroidal is ~60-70% of the poloidal component, while we estimate about 40-50% for lower viscosity contrasts. In our models, the toroidal term peaks for slab/mantle viscosity ratios η'max~ 102. This trend is found not only for transient but also for steady-state, rollback subduction. Estimates for effective viscosity contrasts in nature are comparable to, or somewhat higher than ηmax.

  4. Heat Transfer Correlations for compressible flow in Micro Heat Exchangers

    NASA Astrophysics Data System (ADS)

    Coppola, M. A.; Croce, G.

    2016-09-01

    The paper discusses the definition of dimensionless parameters useful to define a local correlation for convective heat transfer in compressible, micro scale gaseous flows. A combination of static and stagnation temperatures is chosen, as it allows to weight the temperature change related to the heat transfer and that induced by conversion of internal energy into kinetic one. The correlation offers a purely convective local Nusselt number, i.e. correlating the heat flow rate with the local flow parameters and wall surface temperature. The correlation is validated through a series of numerical computations in both counter-current and co-current micro heat exchanger configurations. The numerical computations take into account rarefaction and conjugate heat transfer effects.

  5. Heat flow and energetics of the San Andreas Fault Zone

    NASA Astrophysics Data System (ADS)

    Lachenbruch, Arthur H.; Sass, J. H.

    1980-11-01

    200 bars. The development of the broad Coast Range heat flow anomaly southward from Cape Mendocino suggests that heat flow increases by a factor of 2 within 4 m.y. after the passage of the Mendocino Triple Junction. This passage leaves the San Andreas transform fault zone in its wake; the depth of the anomalous sources cannot be much greater than the depth of the seismogenic layer. Some of the anomalous heat may be supplied by conduction from the warmer mantle that must occur south of the Mendocino transform (where there is no subducting slab), and some might be supplied by shear heating in the fault zone. With no contribution from shear heating, extreme mantle upwelling would be required, and asthenosphere conditions should exist today at depths of only ˜20 km in the northernmost Coast Ranges. If there is an appreciable contribution from shear heating, the heat flow constraint implies that the seismogenic layer is partially decoupled at its base and that the basal traction is in the sense that resists right lateral motion on the fault(s). As a result of these basal tractions, the average shearing stress in the seismogenic layer would increase with distance from the main fault, and the seismogenic layer would offer substantial resistance to plate motion even though resistance on the main fault might be negligible. These speculative models have testable consequences.

  6. Map of Io Volcanic Heat Flow

    NASA Image and Video Library

    2015-09-15

    This frame from an animation shows Jupiter volcanic moon Io as seen by NASA Voyager and Galileo spacecraft (at left) and the pattern of heat flow from 242 active volcanoes (at right). The red and yellow areas are places where local heat flow is greatest -- the result of magma erupting from Io's molten interior onto the surface. The map is the result of analyzing decades of observations from spacecraft and ground-based telescopes. It shows Io's usual volcanic thermal emission, excluding the occasional massive but transient "outburst" eruption; in other words, this is what Io looks like most of the time. This heat flow map will be used to test models of interior heating. The map shows that areas of enhanced volcanic heat flow are not necessarily correlated with the number of volcanoes in a particular region and are poorly correlated with expected patterns of heat flow from current models of tidal heating -- something that is yet to be explained. This research is published in association with a 2015 paper in the journal Icarus by A. Davies et al., titled "Map of Io's Volcanic Heat Flow," (http://dx.doi.org/10.1016/j.icarus.2015.08.003.) http://photojournal.jpl.nasa.gov/catalog/PIA19655

  7. A New Model for Heat Flow in Extensional Basins: Estimating Radiogenic Heat Production

    SciTech Connect

    Waples, Douglas W.

    2002-06-15

    Radiogenic heat production (RHP) represents a significant fraction of surface heat flow, both on cratons and in sedimentary basins. RHP within continental crust-especially the upper crust-is high. RHP at any depth within the crust can be estimated as a function of crustal age. Mantle RHP, in contrast, is always low, contributing at most 1 to 2 mW/m{sup 2} to total heat flow. Radiogenic heat from any noncrystalline basement that may be present also contributes to total heat flow. RHP from metamorphic rocks is similar to or slightly lower than that from their precursor sedimentary rocks. When extension of the lithosphere occurs-as for example during rifting-the radiogenic contribution of each layer of the lithosphere and noncrystalline basement diminishes in direct proportion to the degree of extension of that layer. Lithospheric RHP today is somewhat less than in the distant past, as a result of radioactive decay. In modeling, RHP can be varied through time by considering the half lives of uranium, thorium, and potassium, and the proportional contribution of each of those elements to total RHP from basement. RHP from sedimentary rocks ranges from low for most evaporites to high for some shales, especially those rich in organic matter. The contribution to total heat flow of radiogenic heat from sediments depends strongly on total sediment thickness, and thus differs through time as subsidence and basin filling occur. RHP can be high for thick clastic sections. RHP in sediments can be calculated using ordinary or spectral gamma-ray logs, or it can be estimated from the lithology.

  8. Predicting SKS-splitting from 35 Myr of subduction and mantle flow evolution in the western Mediterranean

    NASA Astrophysics Data System (ADS)

    Chertova, Maria; Spakman, Wim; Faccenda, Manuele

    2017-04-01

    We investigate the development of mantle anisotropy associated with the evolution of the Rif-Gibraltar-Betic (RGB) slab of the western Mediterranean and predict SKS-splitting directions for comparison with the recent observations compiled in Diaz and Gallart (2014). Our numerical model of slab evolution starts at 35 Ma and builds on our on recent work (Chertova et al., 2014) with the extension of imposing mantle flow velocities on the side boundaries of the model (Chertova et al., 2017). For the calculation of the evolution of finite strain deformation from the mantle flow field and for prediction of SKS-splitting directions we use the modified D-Rex program of Faccenda (2014). We test the predicted splitting observations against present-day shear wave splitting observations for subduction models with open boundary conditions (Chertova, 2014) and for models with various prescribed mantle flow conditions on the model side boundaries. The latter are predicted time-dependent (1 Myr time steps) velocity boundary conditions computed from back-advection of a temperature and density model of the present-day mantle scaled from a global seismic tomography model (Steinberger et al., 2015). These boundary conditions where used recently to demonstrate the relative insensitivity of RGB slab position and overall slab morphology for external mantle flow (Chertova et al., 2017). Using open boundaries only we obtain a poor to moderate fit between predicted and observed splitting directions after 35 Myr of slab and mantle flow evolution. In contrast, a good fit is obtained when imposing the computed mantle flow velocities on the western, southern, and northern boundaries during 35 Myr of model evolution. This successful model combines local slab-driven mantle flow with remotely forced mantle flow. We are in the process to repeat these calculations for shorter periods of mantle flow evolution to determine how much of past mantle flow is implicitly recorded in present-day observation

  9. Io: Heat flow from dark volcanic fields

    NASA Astrophysics Data System (ADS)

    Veeder, Glenn J.; Davies, Ashley Gerard; Matson, Dennis L.; Johnson, Torrence V.

    2009-11-01

    Dark flow fields on the jovian satellite Io are evidence of current or recent volcanic activity. We have examined the darkest volcanic fields and quantified their thermal emission in order to assess their contribution to Io's total heat flow. Loki Patera, the largest single source of heat flow on Io, is a convenient point of reference. We find that dark volcanic fields are more common in the hemisphere opposite Loki Patera and this large scale concentration is manifested as a maximum in the longitudinal distribution (near ˜200 °W), consistent with USGS global geologic mapping results. In spite of their relatively cool temperatures, dark volcanic fields contribute almost as much to Io's heat flow as Loki Patera itself because of their larger areal extent. As a group, dark volcanic fields provide an asymmetric component of ˜5% of Io's global heat flow or ˜5 × 10 12 W.

  10. Pneumatic Proboscis Heat-Flow Probe

    NASA Technical Reports Server (NTRS)

    Zacny, Kris; Hedlund, Magnus; Mumm, Eric; Shasho, Jeffrey; Chu, Philip; Kumar, Nishant

    2013-01-01

    Heat flow is a fundamental property of a planet, and provides significant constraints on the abundance of radiogenic isotopes, the thermal evolution and differentiation history, and the mechanical properties of the lithosphere. Heat-flow measurements are also essential in achieving at least four of the goals set out by the National Research Council for future lunar exploration. The heat-flow probe therefore directly addresses the goal of the Lunar Geophysical Network, which is to understand the interior structure and composition of the Moon. A key challenge for heat flow measurement is to install thermal sensors to the depths approximately equal to 3 m that are not influenced by the diurnal, annual, and longer-term fluctuations of the surface thermal environment. In addition, once deployed, the heat flow probe should cause little disturbance to the thermal regime of the surrounding regolith. A heat-flow probe system was developed that has two novel features: (1) it utilizes a pneumatic (gas) approach, excavates a hole by lofting the lunar soil out of the hole, and (2) deploys the heat flow probe, which utilizes a coiled up tape as a thermal probe to reach greater than 3-meter depth. The system is a game-changer for small lunar landers as it exhibits extremely low mass, volume, and simple deployment. The pneumatic system takes advantage of the helium gas used for pressurizing liquid propellant of the lander. Normally, helium is vented once the lander is on the surface, but it can be utilized for powering pneumatic systems. Should sufficient helium not be available, a simple gas delivery system may be taken specifically for the heat flow probe. Either way, the pneumatic heat flow probe system would be much lighter than other systems that entirely rely on the electrical power of the lander.

  11. Lower Mantle Superplume Growth Stimulates Geomagnetic Reversals

    NASA Astrophysics Data System (ADS)

    Olson, P.; Amit, H.

    2014-12-01

    Seismic images of the lower mantle heterogeneity consistently show two large-scale, low shear wave velocity provinces beneath Africa and the Pacific that are variously interpreted as superplumes, plume clusters, or piles of dense mantle material associated with the D" boundary layer. Hotspot reconstructions and mantle general circulation models indicate these structures have persisted for 100 Ma or longer. Here we demonstrate that time variations in the height of these structures perturbs the thickness of the D" thermal boundary layer and the heat flow across the core-mantle boundary, thereby altering the rate at which geomagnetic polarity reversals occur in the core. First we show that superplume growth increases the average heat flow on the core-mantle boundary as well as its lateral heterogeneity. We then use numerical dynamos to demonstrate that this increased core-mantle boundary heat flow stimulates magnetic polarity reversals, and conversely, that reduced core-mantle boundary heat flow associated with superplume collapse tends to inhibit polarity reversals. Our results suggest that the long, stable polarity geomagnetic superchrons such as occurred in the Cretaceous, Permian, and earlier in the geologic record may have begun and ended, respectively, by collapse and growth of one or more lower mantle superplumes.

  12. Anomalous heat flow belt along the continental margin of Brazil

    NASA Astrophysics Data System (ADS)

    Hamza, Valiya M.; Vieira, Fabio P.; Silva, Raquel T. A.

    2017-06-01

    A comprehensive analysis of thermal gradient and heat flow data was carried out for sedimentary basins situated in the continental margin of Brazil (CMB). The results point to the existence of a narrow belt within CMB, where temperature gradients are higher than 30 °C/km and the heat flow is in excess of 70 mW/m2. This anomalous geothermal belt is confined between zones of relatively low to normal heat flow in the adjacent continental and oceanic regions. The width of the belt is somewhat variable, but most of it falls within the range of 100-300 km. The spatial extent is relatively large in the southern (in the basins of Pelotas, Santos and Campos) and northern (in the basins of Potiguar and Ceará) parts, when compared with those in the central parts (in the basins of South Bahia, Sergipe and Alagoas). The characteristics of heat flow anomalies appear to be compatible with those produced by thermal sources at depths in the lower crust. Hence, magma emplacement at the transition zone between lower crust and upper mantle is considered the likely mechanism producing such anomalies. Seismicity within the belt is relatively weak, with focal depths less than 10 km for most of the events. Such observations imply that "tectonic bonding" between continental and oceanic segments, at the transition zone of CMB, is relatively weak. Hence, it is proposed that passive margins like CMB be considered as constituting a type of plate boundary that is aseismic at sub-crustal levels, but allows for escape of significant amounts of earth's internal heat at shallow depths.

  13. Magnetic fabrics reveal Upper Mantle Flow fabrics in the Troodos Ophiolite Complex, Cyprus

    NASA Astrophysics Data System (ADS)

    Borradaile, Graham J.; Lagroix, France

    2001-08-01

    The foliations and lineations recognized in outcrops of the Troodos mantle-sequence provide relatively few and imprecise observations of the mineral fabric. Thus, their kinematic interpretation, and any inferences about the metamorphic flow patterns are tenuous. However, every outcrop yields the anisotropy of magnetic susceptibility (AMS) from which we may infer the combined orientation-distribution response of silicates (pyroxene, serpentine) and magnetite. Furthermore, in many outcrops, the anisotropy of anhysteretic remanence (AARM) isolates the contribution of magnetite to the orientation-distribution. AMS and AARM each provide a magnitude ellipsoid whose principal directions define the orientation-distribution of several hundred minerals in each sample, and thus their flow fabric. Within the Troodos mantle-sequence, high-temperature, semi-cataclastic silicate flow directions were uniform through volumes of ˜1 km 3 but differ between adjacent subareas. This reflects the scale of the heterogeneity of solid-state flow. However, averaged over the entire area of ˜100 km 2, the global orientation-distribution of silicate alignments were consistent, indicating early, silicate flow up to the west, away from a spreading axis that lay east of the Troodos range. On the same regional scale, later magnetite alignments indicate flow up to the north-west. The non-horizontal and non-coaxial flow stages suggest that the mantle sequence was affected by diapiric rise in the solid-state, radiating from centres which may originally have been magma chambers. The one responsible for the recorded flow patterns may have been approximately 30 km in diameter and located SE of Mount Troodos.

  14. Flow and heat transfer enhancement in tube heat exchangers

    NASA Astrophysics Data System (ADS)

    Sayed Ahmed, Sayed Ahmed E.; Mesalhy, Osama M.; Abdelatief, Mohamed A.

    2015-11-01

    The performance of heat exchangers can be improved to perform a certain heat-transfer duty by heat transfer enhancement techniques. Enhancement techniques can be divided into two categories: passive and active. Active methods require external power, such as electric or acoustic field, mechanical devices, or surface vibration, whereas passive methods do not require external power but make use of a special surface geometry or fluid additive which cause heat transfer enhancement. The majority of commercially interesting enhancement techniques are passive ones. This paper presents a review of published works on the characteristics of heat transfer and flow in finned tube heat exchangers of the existing patterns. The review considers plain, louvered, slit, wavy, annular, longitudinal, and serrated fins. This review can be indicated by the status of the research in this area which is important. The comparison of finned tubes heat exchangers shows that those with slit, plain, and wavy finned tubes have the highest values of area goodness factor while the heat exchanger with annular fin shows the lowest. A better heat transfer coefficient ha is found for a heat exchanger with louvered finned and thus should be regarded as the most efficient one, at fixed pumping power per heat transfer area. This study points out that although numerous studies have been conducted on the characteristics of flow and heat transfer in round, elliptical, and flat tubes, studies on some types of streamlined-tubes shapes are limited, especially on wing-shaped tubes (Sayed Ahmed et al. in Heat Mass Transf 50: 1091-1102, 2014; in Heat Mass Transf 51: 1001-1016, 2015). It is recommended that further detailed studies via numerical simulations and/or experimental investigations should be carried out, in the future, to put further insight to these fin designs.

  15. Plastic Flow of Pyrope at Mantle Pressure and Temperature

    SciTech Connect

    Li,L.; Long, H.; Weidner, D.; Raterron, P.

    2006-01-01

    Despite the abundance of garnet in deforming regions of the Earth, such as subduction zones, its rheological properties are not well defined by laboratory measurements. Here we report measurements of steady-state plastic properties of pyrope in its stability field (temperature up to 1573 K, pressure up to 6.8 GPa, strain rate {approx}10-5 s-1) using a Deformation-DIA apparatus (D-DIA) coupled with synchrotron radiation. Synthetic pyrope (Py100) and natural pyrope (Py70Alm16Gr14) are both studied in a dry environment. Transmission electron microscopy (TEM) investigation of the run products indicates that dislocation glide, assisted by climb within grains and dynamic recrystallization for grain-boundary strain accommodation, is the dominant deformation process in pyrope. Both synthetic-and natural-pyropes' stress and strain-rate data, as measured in situ by X-ray diffraction and imaging, are best fitted with the single flow law:

  16. Pluto's Polygonal Terrain Places Lower Limit on Planetary Heat Flow

    NASA Astrophysics Data System (ADS)

    Trowbridge, A.; Steckloff, J. K.; Melosh, H., IV; Freed, A. M.

    2015-12-01

    During its recent flyby of Pluto, New Horizons imaged an icy plains region (Sputnik Planum) whose surface is divided into polygonal blocks, ca. 20-30 km across, bordered by what appear to be shallow troughs. The lack of craters within these plains suggests they are relatively young, implying that the underlying material is recently active. The scale of these features argues against an origin by cooling and contraction. Here we investigate the alternative scenario that they are the surface manifestation of shallow convection in a thick layer of nitrogen ice. Typical Rayleigh-Bernard convective cells are approximately three times wider than the depth of the convecting layer, implying a layer depth of ca. 7-10 km. Our convection hypothesis requires that the Rayleigh number exceed a minimum of about 1000 in the nitrogen ice layer. We coupled a parameterized convection model with a temperature dependent rheology of nitrogen ice (Yamashita, 2008), finding a Rayleigh number 1500 to 7500 times critical for a plausible range of heat flows for Pluto's interior. The computed range of heat flow (3.5-5.2 mW/m2) is consistent with the radiogenic heat generated by a carbonaceous chondrite (CC) core implied by Pluto's bulk density. The minimum heat flow at the critical Rayleigh number is 0.13 mW/m2. Our model implies a core temperature of 44 K in the interior of the convecting layer. This is very close to the exothermic β-α phase transition in nitrogen ice at 35.6 K (for pure N2 ice; dissolved CO can increase this, depending on its concentration), suggesting that the warm cores of the rising convective cells may be β phase, whereas the cooler sinking limbs may be α phase. This transition may thus be observable due to the large difference in their spectral signature. Further applying our model to Pluto's putative water ice mantle, the heat flow from CC is consistent with convection in Pluto's mantle and the activity observed on its surface.

  17. Io: Heat Flow from Dark Volcanic Fields

    NASA Astrophysics Data System (ADS)

    Veeder, G. J.; Matson, D. L.; Davies, A. G.; Johnson, T. V.

    2008-03-01

    We focus on the heat flow contribution from dark volcanic fields on Io. These are concentrated in the anti-Loki hemisphere. We use the areas and estimated effective temperatures of dark flucti to derive their total power.

  18. Heat flow from the West African shield

    SciTech Connect

    Brigaud, F.; Lucazeau, F.; Ly, S.; Sauvage, J.F.

    1985-09-01

    The heat flow over Precambrian shields is generally lower than over other continental provinces. Previous observations at 9 sites of the West African shield have shown that heat flow ranges from 20 mW m/sup -2/ in Niger to 38-42 mW m/sup -2/ in Liberia, Ghana and Nigeria. Since some of these values are lower than expected for Precambrian shields, it is important to find out whether or not they are representative of the entire shield before trying to derive its thermal structure. In this paper, we present new heat flow determinations from seven sites of the West African shield. These indicate that the surface heat flow is comparable with that of other Precambrian shields in the world.

  19. Experiments on flow focusing in soluble porous media, with applications to melt extraction from the mantle

    SciTech Connect

    Kelemen, P.B.; Whitehead, J.A.; Aharonov, E.; Jordahl, K.A.

    1995-01-01

    We demonstrate finite strucutres formed as a consequence of the `reactive infiltration instability` in a series of laboratory and numerical experiments with growth of solution channels parallel to the fluid flow direction. Our experiments demonstrate channel growth in the presence of an initial solution front and without an initial solution front where there is a gradient in the solubility of the solid matrix. In the gradient case, diffuse flow is unstable everywhere, channels can form and grow at any point, and channels may extend over the length scale of the gradient. As a consequence of the gradient results, we suggest that the reactive infiltration instability is important in the Earth`s mantle, where partial melts in the mantle ascend adiabatically. This hypothesis represents an important alternative to mid-oceanic ridge basalts (MORB) extraction in fractures, since fractures may not form in weak, viscously deforming asthenospheric mantle. We also briefly consider the effects of crystallization, rather than dissolution reactions, on the morphology of porous flow via a second set of experiments where fluid becomes supersaturated in a solid phase. This process may produce a series of walled conduits, as in our experiments. Development of a low-porosity cap overlying high porosity conduits may create hydrostatic overpressure sufficient to cause fracture and magma transport to the surface in dikes.

  20. The Yellowstone Hotspot and Related Plume: Volcano-Tectonics, Tomography, Kinematics, Dynamics and Mantle Flow

    NASA Astrophysics Data System (ADS)

    Jordan, M.; Smith, R. B.; Puskas, C.; Farrell, J.; Waite, G.

    2005-12-01

    Earth's violent forces have produced the renowned scenery and the world's largest display of geysers at Yellowstone National Park. The energy responsible for these features is related to the Yellowstone hotspot, a coupled crust-mantle magmatic system that has had a profound influence on a much larger area of the western US: the Yellowstone-Snake River Plain-Newberry volcanic field (YSRPN). The volcanic system has produced a 16 Ma track of NE-trending, time progressive, silicic-basaltic volcanism from the Snake River Plain (SNR) to Yellowstone with a mirror image of NW-trending magmatism across the high lava plains to the Newberry caldera, OR. The origin of this magmatic-tectono system has been variously ascribed to plume-plate interaction, lithosphere extension, return mantle flow, decompression melting, etc. We interpret and integrate results from modeling of data from a prototype EarthScope experiment in 1999-2002. These include crust-mantle tomography, geoid and gravity modeling, kinematics from GPS, and geodynamic models. We present a comprehensive model for the mechanism behind YSRPN that is in accordance with our observations and models, e.g. from GPS and seismology. Geodetic data show high rates of deformation at the Yellowstone Plateau, with periods of pronounced uplift and subsidence as well as significant EW extension. Seismic tomography reveals a pronounced mid-crustal P- and S-wave low velocity body of > 8% melt extending from ~6 km to 15 km beneath the caldera. This system is fed by an upper-mantle low velocity plume-like body of up to 1.5% melt in the upper 200 km. The body further extends down to the the base of the transition zone at 650 km depth, notably tilting WNW. At this depth, we estimate the excess temperature between 85 K and 120 K, depending on the water content. Using the inclined plume-geometry and the 650-km source depth we extrapolate the mantle source southwestward as a plume-head in oceanic-type lithosphere beneath the Columbia

  1. Subducted slabs and the geoid - Constraints on mantle rheology and flow

    NASA Technical Reports Server (NTRS)

    Hager, B. H.

    1984-01-01

    The total geoid anomaly which is the result of a given density contrast in a convecting viscous earth is affected by the mass anomalies associated with the flow induced deformation of the upper surface and internal compositional boundaries, as well as by the density contrast itself is discussed. If the internal density contrasts can be estimated, the depth and variation of viscosity with depth of the convecting system can be constrained. The observed long wavelength geoid is highly correlated with that predicted by a density model for seismically active subducted slabs. The amplitude of the correlation is explained if the density contrasts associated with subduction extend into the lower mantle or if subducted slabs exceeding 350 km in thickness are piled up over horizontal distances of thousands of km at the base of the upper mantle. Mantle wide convection in a mantle that has a viscosity increasing with depth provides the explanation of the long-wavelength geoid anomalies over subduction zones. Previously announced in STAR as N83-22874

  2. Subducted slabs and the geoid - Constraints on mantle rheology and flow

    NASA Technical Reports Server (NTRS)

    Hager, B. H.

    1984-01-01

    The total geoid anomaly which is the result of a given density contrast in a convecting viscous earth is affected by the mass anomalies associated with the flow induced deformation of the upper surface and internal compositional boundaries, as well as by the density contrast itself is discussed. If the internal density contrasts can be estimated, the depth and variation of viscosity with depth of the convecting system can be constrained. The observed long wavelength geoid is highly correlated with that predicted by a density model for seismically active subducted slabs. The amplitude of the correlation is explained if the density contrasts associated with subduction extend into the lower mantle or if subducted slabs exceeding 350 km in thickness are piled up over horizontal distances of thousands of km at the base of the upper mantle. Mantle wide convection in a mantle that has a viscosity increasing with depth provides the explanation of the long-wavelength geoid anomalies over subduction zones. Previously announced in STAR as N83-22874

  3. Heat Flow Partitioning Between Continents and Oceans - from 2D to 3D

    NASA Astrophysics Data System (ADS)

    Moresi, L. N.; Cooper, C. M.; Lenardic, A.

    2010-12-01

    Scalings derived from thermal network theory explain how the presence of continents can influence the Earth’s overall heat loss. Intuitively, it may seem that increasing the proportion of a planet’s surface area covered by continents would decrease the efficiency of heat transfer given that continents do not participate in convective overturn. However, this ignores the potential feedback between the insulating effect of continents and the temperature-dependent viscosity of the mantle (Lenardic et al, 2005, Cooper et al, 2007). When this feedback is considered, a clear regime exists in which the partial stagnation and insulation of the surface by buoyant continental crust can lead to an increase in heat flow compared to the uninsulated case. The numerical results used to verify the scalings have mostly been conducted in two dimensions in order to cover a very wide range of Rayleigh number, fraction of continental coverage, and continental thickness. However as more recent results show that the configuration of the crust also plays a role in determining the heat flow partitioning and global heat flow (See Lenardic et al, “Continents, Super-Continents, Mantle Thermal Mixing, and Mantle Thermal Isolation” in this session), we have begun to repeat this exhaustive and exhausting 2D study in 3D. Cooper, C.M., A. Lenardic, and L.-N. Moresi "Effects of continental insulation and the partioning of heat producing elements on the Earth's heat loss." Geophys. Res. Lett., 33 ,10.1029, 2006. Lenardic, A., L.-N. Moresi, A.M. Jellinek, and M. Manga "Continental insulation, mantle cooling, and the surface area of oceans and continents." Earth Planet. Sci. Lett., 234 ,317-333, 2005.

  4. Conjugate Heat Transfer Study in Hypersonic Flows

    NASA Astrophysics Data System (ADS)

    Sahoo, Niranjan; Kulkarni, Vinayak; Peetala, Ravi Kumar

    2017-05-01

    Coupled and decoupled conjugate heat transfer (CHT) studies are carried out to imitate experimental studies for heat transfer measurement in hypersonic flow regime. The finite volume based solvers are used for analyzing the heat interaction between fluid and solid domains. Temperature and surface heat flux signals are predicted by both coupled and decoupled CHT analysis techniques for hypersonic Mach numbers. These two methodologies are also used to study the effect of different wall materials on surface parameters. Effectiveness of these CHT solvers has been verified for the inverse problem of wall heat flux recovery using various techniques reported in the literature. Both coupled and decoupled CHT techniques are seen to be equally useful for prediction of local temperature and heat flux signals prior to the experiments in hypersonic flows.

  5. A regional test of global models for flow, rheology, and seismic anisotropy at the base of the mantle

    NASA Astrophysics Data System (ADS)

    Ford, Heather A.; Long, Maureen D.

    2015-08-01

    The study of flow patterns and seismic anisotropy in the lowermost mantle is fraught with uncertainties, given the limitations in our understanding of the physical properties of the lowermost mantle and the relationships between deformation and anisotropy. Here we use a set of SKS, SKKS, and ScS splitting measurements that sample the eastern edge of the African Large Low Shear Velocity Province to test predictions of seismic anisotropy derived from previously published 3D global mantle flow models and anisotropy modeling (Walker et al., 2011). The observations can be fit by a model that invokes flow directed to the southwest with a component of downwelling in our study region, and slip that occurs along the (0 1 0) plane of post-perovskite. Most importantly, we demonstrate the ability of a regional shear wave splitting data set to test the robustness of models for flow and deformation in the lowermost mantle.

  6. Io: Heat flow from dark paterae

    NASA Astrophysics Data System (ADS)

    Veeder, Glenn J.; Davies, Ashley Gerard; Williams, David A.; Matson, Dennis L.; Johnson, Torrence V.; Radebaugh, Jani

    2011-03-01

    Dark paterae on the jovian satellite Io are evidence of recent volcanic activity. Some paterae appear to be entirely filled with dark volcanic material, while others have only partially darkened floors. Dark paterae have area and heat flow longitudinal distributions that are bimodal as well as anti-correlated with the longitudinal distribution of mountains on Io at a global scale. As part of our study of Io’s total heat flow, we have examined the darkest paterae and quantified their thermal emission in order to assess their contribution. This is the first time that the areas of the dark material in these paterae have been measured with such precision and correlated with their thermal emission. Dark paterae yield a significantly larger contribution to Io’s heat flow than dark volcanic fields. Dark paterae (including Loki Patera) yield at least ∼4 × 1013 W or ∼40% of Io’s total heat flow. In comparison, dark flow fields yield ∼1013 W or ∼10% of Io’s total heat flow. Of the total heat loss from dark paterae, Loki Patera alone yields ∼1013 W or ∼10% of Io’s total thermal emission.

  7. The Upper Mantle Flow Field around South-Africa as Reflected by Isotopic Provinciality

    NASA Astrophysics Data System (ADS)

    Meyzen, C.; Blichert-Toft, J.; Ludden, J.; Humler, E.; Mevel, C.; Albarede, F.

    2006-12-01

    Isotopic studies of MORB have established the existence of broad isotopic provinces within the underlying asthenosphere, such as in the Indian Ocean (DUPAL). How these features relate to mantle circulation is, however, still unknown. The steepness of the transition between such isotopic provinces will define the geometry of the velocity field in the upper mantle. In this respect, the transition between the Indian and South Atlantic provinces, two domains that are isotopically contrasted, should be readily identifiable over this long ridge segment. Here, we present Hf isotope data for 60 samples dredged along the SWIR between 35° and 69°E. The new Hf isotope data show that the Indian asthenosphere does not spill directly into the South Atlantic upper mantle: the general decreasing southward gradient observed for ^{176}Hf/^{177}Hf down the mid- Atlantic Ridge, and also for Sr isotopes and model Th/U ratios (derived from Pb isotopes), is overprinted by material with radiogenic Sr, unradiogenic Hf and high Th/U. The Indian domain grades into the South Atlantic around Bouvet, while the South Atlantic collides with the Atlantic province around Tristan. We interpret these features to represent fronts between three adjacent isotopic provinces similar to what has been suggested for the Australian-Antarctic Discordance. The common DUPAL signature of MORB and OIB from the Indian province and the geochemistry of Gulf of Aden MORB and the Afar plume suggest that the source of this distinctive mantle component is deep and lies to the north of the province. This is also what the three-dimensional flow field computed by Behn et al. (2004) from shear-wave splitting shows with a major lower mantle upwelling radiating at the base of the asthenosphere under the Afar plume. Lower mantle gushing out from this source flows southward unimpeded along the Indian ridges, whereas it only reaches the South Atlantic ridge after first having been deflected under the deep roots of the South

  8. Heat Flow Investigations in Western Anatolia

    NASA Astrophysics Data System (ADS)

    Sari, C.; Salk, M.

    2003-04-01

    The purposes of geothermic researches are to find out the temperature distribution in the lithosphere-astenosphere system, the structure of possible heat cells, and especially the deep lateral and vertical changes within the crust by making heat flow measurements. Some local investigations showed that Turkey was placed in a high-heat-flow region in Europe. Unfortunately, a detailed heat-flow map could not be prepared for our country due to the absence of systematical temperature logs and especially the lack of knowledge on the heat conductivity coefficients and lithology of log samples taken from the deep wells drilled for oil exploration purposes. To determine the shallow and deep subsurface temperature conditions more accurately in the Western Anatolia, it is essential to have a new and detailed Heat Flow Data Base and based on that it is necessary to investigate the lateral changes of vertical geothermal gradient in the lithosphere. The investigations for these purposes were done by Istanbul University, Istanbul Technical University, and Dokuz Eylul University under a consortium sponsored by TUBITAK and MTA. It is quite important to make measurements for heat conductivity coefficients of some rock units and to investigate its changes due to some physical effects to determine and interpret the heat-flow accurately. For this purpose, measurements were made for the heat conductivity coefficients of some well samples and surface rock samples in a research program started at Western Anatolia. Furthermore, quite few geothermal gradient measurements were made in Western Anatolia. Quite number of the wells, where the investigations were done, were drilled to supply drinking water to some local small towns. The effects of ground water and heat circulation could be seen quite often in these shallow-deep wells. In these geothermal investigations, proper temperature data were observed only in a few wells in surrounding mountains near by Gokova, Mugla. The circulation of

  9. Mantle viscosity - A comparison of models from postglacial rebound and from the geoid, plate driving forces, and advected heat flux

    NASA Technical Reports Server (NTRS)

    Hager, Bradford H.

    1991-01-01

    Models of the radial variation of effective viscosity inferred from the earth's response to surface loads associated with Pleistocene deglaciation are compared to structures inferred from models of geodynamic phenomena associated with convection: the geoid, plate-driving forces, and advected heat flux. While observations of the earth's response to surface loads do not have sufficient resolution to justify more than two viscous layers, adequately matching the observed long-wavelength geoid anomalies associated with density contrasts in the lower mantle (inferred from seismic tomography) and in the upper mantle (inferred from a model of subducted slabs) requires more structure. It is possible to explain the geoid, observed plate velocities, the advected heat flux in the lower mantle, and relative sea-level variations in oceanic regions, all with a mantle with a high-viscosity/elastic lid, an asthenospheric channel of 2 x 10 exp 19 Pa s from 100 to 400-km depth, a 6 x 10 exp 20 Pa s transition zone, and a lower mantle of 6 x 10 exp 21 Pa s. The uplift history of Australia, Fennoscandia, and Laurentia can be explained with an asthenospheric viscosity less than a factor of 10 higher. Lateral variations in lower mantle viscosity are not required. Transient creep appears to be unimportant for the recent response-to-surface loads from Pleistocene deglaciation.

  10. Mantle Flow, Dynamic Topography and Rift-Flank Uplift of Arabia

    NASA Astrophysics Data System (ADS)

    Daradich, A. L.; Mitrovica, J. X.; Pysklywec, R. N.; Willett, S. D.

    2002-12-01

    The Red Sea is flanked by highlands. To the east, the Arabian platform is broadly tilted along an axis that runs parallel to the sea, and the long tail of high topography has been described as a classic example of `rift-flank uplift' [Wernicke, 1985]. A suite of thermal and mechanical effects have been invoked to derive generic mechanisms for flank uplift and these have been applied, with varying levels of success, to the Arabian case. We propose that dynamic topography supported by large scale mantle flow beneath the Africa-Arabia system contributes significantly to the observed pattern of Arabian rift-flank uplift. Seismic tomographic images indicate the existence of large scale (anomalously slow) heterogeneity originating from the deep mantle under southern Africa and, apparently, connecting to more shallow structure beneath the East African Rift system and the Arabian plate. We predict Arabian topography driven by viscous stresses associated with this buoyant megastructure. We first convert velocity anomalies given by the seismic S-wave model S20RTS [Ritsema et al., 1999] to density anomalies using standard scaling profiles, and then input these into a 2-D mantle convection model. Normal stresses derived from the flow models are then used to compute associated profiles of surface (`dynamic') topography. These profiles reconcile the observed topography of the Arabian platform and they provide an explanation for the distinct geometry of rift-flank uplift across the two sides of the Red Sea. Our calculations do not preclude a contribution to topography from previously described thermal and/or mechanical effects; however, they indicate that future analyses of rift-flank uplift should consider the potential contribution from large scale mantle flow.

  11. Rheologic effects of crystal preferred orientation in upper mantle flow near plate boundaries

    NASA Astrophysics Data System (ADS)

    Blackman, Donna; Castelnau, Olivier; Dawson, Paul; Boyce, Donald

    2016-04-01

    Observations of anisotropy provide insight into upper mantle processes. Flow-induced mineral alignment provides a link between mantle deformation patterns and seismic anisotropy. Our study focuses on the rheologic effects of crystal preferred orientation (CPO), which develops during mantle flow, in order to assess whether corresponding anisotropic viscosity could significantly impact the pattern of flow. We employ a coupled nonlinear numerical method to link CPO and the flow model via a local viscosity tensor field that quantifies the stress/strain-rate response of a textured mineral aggregate. For a given flow field, the CPO is computed along streamlines using a self-consistent texture model and is then used to update the viscosity tensor field. The new viscosity tensor field defines the local properties for the next flow computation. This iteration produces a coupled nonlinear model for which seismic signatures can be predicted. Results thus far confirm that CPO can impact flow pattern by altering rheology in directionally-dependent ways, particularly in regions of high flow gradient. Multiple iterations run for an initial, linear stress/strain-rate case (power law exponent n=1) converge to a flow field and CPO distribution that are modestly different from the reference, scalar viscosity case. Upwelling rates directly below the spreading axis are slightly reduced and flow is focused somewhat toward the axis. Predicted seismic anisotropy differences are modest. P-wave anisotropy is a few percent greater in the flow 'corner', near the spreading axis, below the lithosphere and extending 40-100 km off axis. Predicted S-wave splitting differences would be below seafloor measurement limits. Calculations with non-linear stress/strain-rate relation, which is more realistic for olivine, indicate that effects are stronger than for the linear case. For n=2-3, the distribution and strength of CPO for the first iteration are greater than for n=1, although the fast seismic

  12. Heat flow in eastern Egypt - The thermal signature of a continental breakup

    NASA Technical Reports Server (NTRS)

    Morgan, P.; Boulos, F. K.; Hennin, S. F.; El-Sherif, A. A.; El-Sayed, A. A.

    1985-01-01

    It is noted that the Red Sea is a modern example of continental fragmentation and incipient ocean formation. A consistent pattern of high heat flow in the Red Sea margins and coastal zone, including Precambrian terrane up to at least 30 km from the Red Sea, has emerged from the existing data. It is noted that this pattern has important implications for the mode and mechanism of Red Sea opening. High heat flow in the Red Sea shelf requires either a high extension of the crust in this zone (probably with major basic magmatic activity) or young oceanic crust beneath this zone. High heat flow in the coastal thermal anomaly zone may be caused by lateral conduction from the offshore lithosphere and/or from high mantle heat flow. It is suggested that new oceanic crust and highly extended continental crust would be essentially indistinguishable with the available data in the Red Sea margins, and are for many purposes essentially identical.

  13. Heat flow in eastern Egypt - The thermal signature of a continental breakup

    NASA Technical Reports Server (NTRS)

    Morgan, P.; Boulos, F. K.; Hennin, S. F.; El-Sherif, A. A.; El-Sayed, A. A.

    1985-01-01

    It is noted that the Red Sea is a modern example of continental fragmentation and incipient ocean formation. A consistent pattern of high heat flow in the Red Sea margins and coastal zone, including Precambrian terrane up to at least 30 km from the Red Sea, has emerged from the existing data. It is noted that this pattern has important implications for the mode and mechanism of Red Sea opening. High heat flow in the Red Sea shelf requires either a high extension of the crust in this zone (probably with major basic magmatic activity) or young oceanic crust beneath this zone. High heat flow in the coastal thermal anomaly zone may be caused by lateral conduction from the offshore lithosphere and/or from high mantle heat flow. It is suggested that new oceanic crust and highly extended continental crust would be essentially indistinguishable with the available data in the Red Sea margins, and are for many purposes essentially identical.

  14. Porous Flow and Diffusion of Water in the Mantle Wedge: Melting and Hydration Patterns

    NASA Astrophysics Data System (ADS)

    Conder, J. A.

    2005-12-01

    It is widely accepted that melting at volcanic arcs is primarily triggered by fluxing the mantle wedge from the dehydrating subducting slab. However, there is less concensus regarding how water moves into and within the mantle wedge. There are at least four possible mechanisms for water migration in the wedge: buoyant porous flow, diffusion through mineral crystals, advection of hydrated minerals, and compositionally buoyant diapers. The latter two mechanisms require at least one of the first two to occur to get water from the slab into the wedge before they can function. Using geodynamic models of mantle flow in a simplified subduction setting, we explore the implications of diffusion and porous flow of water in the wedge, particularly as they would affect the time for recycling water through the subduction factory and the predicted pattern of basalt hydration across the arc. The slab is assumed to dehydrate in a continuous fashion as the solubility of water in subducted oceanic crust decreases with temperature and pressure and the water then enters the wedge via one of the two transport mechanisms. Diffusion is controlled by temperature and by which minerals are present. Although olivine dominates the mantle mineral fraction, pyroxenes may control the diffusion of water in the wedge as the diffusivity of pyroxene is one or more orders of magnitude greater than olivine. Even assuming the faster diffusion rate of orthopyroxene in the models, diffusion can only be an important transport mechanism when subduction rates are slower than ~3 cm/yr. Flux melting occurs in the wedge above where the slab is ~100-160 km deep with the maximum above where the slab is ~120 km deep. Models including porous flow can result in melting at higher subduction rates provided the permeability of the mantle is greater than 10-17 m2. The true magnitude of the permeability likely varies with the corresponding porosity created by the free phase. With porous flow, melting occurs 20-30 km

  15. Mantle Flow Across the Baikal Rift Constrained With Integrated Seismic Measurements

    NASA Astrophysics Data System (ADS)

    Lebedev, S.; Meier, T.; van der Hilst, R. D.

    2005-12-01

    The Baikal Rift is located at the boundary of the stable Siberian Craton and deforming central Mongolia. The origin of the late Cenozoic rifting and volcanism are debated, as is the mantle flow beneath the rift zone. Here we combine new evidence from azimuthally-anisotropic upper-mantle tomography and from a radially-anisotropic inversion of interstation surface-wave dispersion curves with previously published shear-wave-splitting measurements of azimuthal anisotropy across the rift (Gao et al. 1994). While our tomographic model maps isotropic and anisotropic shear-velocity heterogeneity globally, the inversion of interstation phase-velocity measurements produces a single, radially-anisotropic, shear-velocity profile that averages from the rift to 500 km SE of it. The precision and the broad band (8-340 s) of the Rayleigh and Love wave curves ensures high accuracy of the profile. Tomography and shear-wave splitting both give a NW-SE fast direction (perpendicular to the rift) in the vicinity of the rift, changing towards W-E a few hundred kilometers from it. Previously, this has been interpreted as evidence for mantle flow similar to that beneath mid-ocean ridges, with deeper vertical flow directly beneath the rift also proposed. Our radially anisotropic profile, however, shows that while strong anisotropy with SH waves faster than SV waves is present in the thin lithosphere and upper asthenosphere beneath and SE of the rift, no anisotropy is required below 110 km. The tomographic model shows thick cratonic lithosphere north of the rift. These observations suggest that instead of a flow diverging from the rift axis in NW and SE directions, the most likely pattern is the asthenospheric flow in SE direction from beneath the Siberian lithosphere and across the rift. Possible driving forces of the flow are large-scale lithospheric deformation in East Asia and the draining of asthenosphere at W-Pacific subduction zones; a plume beneath the Siberian craton also cannot be

  16. Fluid Flow, Reactions and Exhumation of Mantle Peridotite Along a Serpentinite Fault Zone.

    NASA Astrophysics Data System (ADS)

    Tulley, C. J.; Smith, S. A. F.; Scott, J.; Tarling, M. S.; le Roux, P. J.

    2016-12-01

    The last phase of exhumation of a > 1000 km long belt of Permian mantle (Dun Mountain Ophiolite Belt) in New Zealand was achieved by movements along the Livingstone Fault. At Mt Raddle and Mt Richards in the Olivine Range, near-pristine mantle harzburgite shows a complete transition through to the serpentinite melange of the Livingstone Fault, which juxtaposes the ultramafics against quartzofeldspathic crust. A talc-tremolite-diopside reaction zone developed at the serpentinite-crustal contact, with diopside overgrowing tremolite. We suspect that the initial formation of frictionally weak talc helped to localise deformation within the reaction zone. The hydration of peridotite is intimately linked to fluid flow along the Livingstone Fault, since water-bearing phases increase with proximity to the fault melange. The transformation of harzburgite to serpentinite is marked by serpentinisation of clinopyroxene and olivine, development of chromite from Cr spinel (Cr# increases from 45 to 97) and overgrowths of secondary olivine ( Fo82-85) around orthopyroxene. As the melange is approached, magnetite forms at the expense of Fe-bearing mantle minerals. The replacement of primary spinel released Al and Mg, which now forms nano-scale intergrowths of chlorite and lizardite. The scaly serpentinite melange is up to 80 m wide at Mt Raddle and contains pods of massive serpentinite, some with remnant peridotite texture. At Mt Richards, 2 km along strike, the melange narrows and fresh peridotite is exposed within 20 m of the quartzofeldspathic rocks. This change in fault zone structure implies that fluid ingress into the ultramafics was highly variable during the exhumation process. The Livingstone Fault may provide insights in to the decoupling of crust and mantle above a subduction zone. The infiltration of fluid along the fault interface acted as a lubricant, driving hydration reactions and enabling adjacent fresh mantle peridotite to be brought towards the Earth's surface.

  17. The Role Of Mantle Flow At The North Fiji Basin: Clues From Anomalous Surface Topography

    NASA Astrophysics Data System (ADS)

    Zhang, N.; Pysklywec, R.

    2005-12-01

    The North Fiji Basin (NFB) is a complex back-arc system situated between the opposite-facing underlying Tonga and New Hebrides subduction zones. A unique configuration of ridges, which includes a triple-juction shape of three ridges and a high intersecting angle between the Hazel Holme ridge and the New Hebrides trench, distinguishes the NFB with other back-arc basins (e.g. Japan Sea Basin, Bransfield Basin) which are characterized by approximately parallel trench and back-arc ridges. Lagabrielle et al. (1997) proposed that a buoyant hot upwelling upper mantle beneath the back-arc basin might partially account for the unique configuration of the NFB. Another notable feature of the NFB is its topography. The back-arc region is anomalously high and our calculations of residual topography reveal that it reaches up to 2000 m above what should be isostatically supported. To account for the anomalous topography, our study aims to test whether a hot buoyant upwelling is required beneath the NFB to support the high elevation. The mantle thermal structure beneath the NFB is inferred from the global seismic tomographic model S20RTS, where seismic velocity anomalies are converted to density/temperature anomalies. This thermal structure is input into a 3D mantle convection code, CitcomS, and the flow-induced surface topography is calculated. The predicted dynamic topography is compared with the observed residual topography. The primary focus is to determine what size and magnitude of the buoyant mantle structure can support the anomalous topography. Specifically, we conduct a series of experiments where we eliminate the slow velocity anomalies interpreted as hot regions at different depths in the mantle. This considers an alternative interpretation of the slow seismic anomalies, for example that they may represent chemical heterogeneity in the shallow upper mantle. The experiments suggest that the anomalous topography in the NFB requires the support of hot upper mantle

  18. Late Cretaceous to Paleogene plate motion, mantle flow and polar wander constrained by paleomagnetic data

    NASA Astrophysics Data System (ADS)

    Tarduno, J. A.; Bono, R.

    2011-12-01

    A wide range of investigations including plate circuit analyses, comparisons of the age progression of coeval hotspots on the Pacific plate and geodynamic modeling are consistent with paleomagnetic results that indicate motion of hotspots in Earth's mantle during Late Cretaceous to Paleogene times, with important changes in the rate of motion near 50 Ma. In the Pacific, the change has been hypothesized to reflect plume dynamics and hotspot-ridge capture; in the Cretaceous the two long-lived Pacific hotspots with well-defined age progressive tracks (Hawaii and Louisville) were near ridges that subsequently waned. In the case of the Hawaiian hotspot, the ridge in question appears to have become extinct close to the time of the bend in the hotspot track. Testing whether a deeper component of Pacific mantle flow also changed near 50 Ma requires a higher resolution investigation of reference frames for absolute plate motion. Here we use select paleomagnetic data prior to and after 50 Ma to test prior inferences about absolute plate motion changes and polar wander, and use these analyses to parse components of mantle flow.

  19. The effect of vacuum mixing and pre-heating the femoral component on the mechanical properties of the cement mantle.

    PubMed

    Baleani, M; Bialoblocka-Juszczyk, E; Engels, G E; Viceconti, M

    2010-03-01

    We investigated the effect of pre-heating a femoral component on the porosity and strength of bone cement, with or without vacuum mixing used for total hip replacement. Cement mantles were moulded in a manner simulating clinical practice for cemented hip replacement. During polymerisation, the temperature was monitored. Specimens of cement extracted from the mantles underwent bending or fatigue tests, and were examined for porosity. Pre-heating the stem alone significantly increased the mean temperature values measured within the mantle (+14.2 degrees C) (p < 0.001) and reduced the mean curing time (-1.5 min) (p < 0.001). The addition of vacuum mixing modulated the mean rise in the temperature of polymerisation to 11 degrees C and reduced the mean duration of the process by one minute and 50 seconds (p = 0.01 and p < 0.001, respectively). In all cases, the maximum temperature values measured in the mould simulating the femur were < 50 degrees C. The mixing technique and pre-heating the stem slightly increased the static mechanical strength of bone cement. However, the fatigue life of the cement was improved by both vacuum mixing and pre-heating the stem, but was most marked (+ 280 degrees C) when these methods were combined. Pre-heating the stem appears to be an effective way of improving the quality of the cement mantle, which might enhance the long-term performance of bone cement, especially when combined with vacuum mixing.

  20. Heat-flow anomaly and residual topography in the Mascarene hotspot swell (Indian Ocean)

    NASA Astrophysics Data System (ADS)

    Chiozzi, P.; Verdoya, M.

    2017-03-01

    We review the sea-bottom heat-flow determinations and present a new heat-flow observation on the Mauritius island, which is part of the long-lived Reunion hotspot track. The marine heat flow is on average 66 ± 11 mW m-2 and is consistent with the on-land value of 61 ± 18 mW m-2 found in Mauritius. Since these values do not significantly deviate from the reference cooling-plate model, lithosphere erosion does not seem a likely mechanism for the swell formation. The lack of significant reheating due to a mantle plume impacting the lithosphere base is confirmed by thermal modelling. Moreover, the coherency between on-land and marine data is argument against advective redistribution of heat near the axis of the swell. We also analyse the large-scale features of the ocean lithosphere, which are not simply a function of the plate cooling and can reflect variations in mantle dynamic topography. The predicted topography variation along the swell shows amplitude and wavelength comparable to other hotspots. Both the topographic swell magnitude and the wavelength increase northwards with the increase of the age of volcanism. The estimated flux of material from the mantle follows the same trend, being larger in the northern part of the swell. The result that residual topography and the buoyancy flux are smaller at the active volcano of Reunion could be evidence that the activity of the plume has decreased with time.

  1. How Point Defects and Dislocations Drive Flow in the Deep Mantle

    NASA Astrophysics Data System (ADS)

    Cordier, P.; Boioli, F.; Carrez, P.; Gouriet, K.; Hirel, P.; Kraych, A.; Ritterbex, S.

    2015-12-01

    Large scale flows which are responsible for the dynamics of planetary interiors rely ultimately on the motion of lattice defects: point defects, dislocations, grain boundaries. A description of the defects at the atomic scale is necessary to describe how their mobility depend on pressure, temperature, stress. A key stage in multiscale numerical modeling is the description of the collective behavior of defects which depends not only on their mobilities, but also on their interactions. Creep mechanisms usually involve interaction between different kind of defects. In diffusion creep, grain boundaries are sources and sinks for point defects. In dislocation creep dislocations not only glide, but also climb by emitting absorbing point defects. In this presentation we describe new results on the interaction between point defects and dislocations in mantle minerals and how dislocation mobilities are affected resulting in novel deformation mechanisms in the lower mantle.

  2. Subslab seismic anisotropy and mantle flow in the western Pacific subduction zones

    NASA Astrophysics Data System (ADS)

    Peng, C. C.; Kuo, B. Y.; Chen, C. W.

    2014-12-01

    We present source-side anisotropy for a few subduction zones in an attempt to map the mantle flow beneath the slab. Shear-wave splitting parameters of S were measured at stations towards the back of the subduction with the receiver-side anisotropy removed. We examined the observed fast directions against tilting/rotation of olivine fabric relative to the geometry of the subduction. We found that at the SW edge of the Ryukyu subduction zone the olivine fabric in the subslab mantle must rotate clockwise by 25 degrees from the slab subduction trajectory to explain the observed pattern of shear-wave splitting. This rotation echoes the deformation model of the slab when it is impinging against the Eurasian lithosphere. In the Vanuatu (New Hebrides) subduction zone, the olivine fabric may rotate dramatically to accommodate the rapid retreat of the trench and flipping of subduction polarity in the past a few Mys.

  3. Influence of mantle flow on the drainage of eastern Australia since the Jurassic Period

    NASA Astrophysics Data System (ADS)

    Salles, T.; Flament, N.; Müller, D.

    2017-01-01

    Recent studies of the past eastern Australian landscape from present-day longitudinal river profiles and from mantle flow models suggest that the interaction of plate motion with mantle convection accounts for the two phases of large-scale uplift of the region since 120 Ma. We coupled the dynamic topography predicted from one of these mantle flow models to a surface process model to study the evolution of the eastern Australian landscape since the Jurassic Period. We varied the rainfall regime, erodibility, sea level variations, dynamic topography magnitude, and elastic thickness across a series of experiments. The approach accounts for erosion and sedimentation and simulates catchment dynamics. Despite the relative simplicity of our model, the results provide insights on the fundamental links between dynamic topography and continental-scale drainage evolution. Based on temporal and spatial changes in longitudinal river profiles as well as erosion and deposition maps, we show that the motion of the Australian plate over the convecting mantle has resulted in significant reorganization of the eastern Australian drainage. The model predicts that the Murray river drained eastward between 150 and ˜120 Ma, and switched to westward draining due to the tilting of the Australian plate from ˜120 Ma. First order comparisons of eight modeled river profiles and of the catchment shape of modeled Murray-Darling Basin are in agreement with present-day observations. The predicted denudation of the eastern highlands is compatible with thermochronology data and sedimentation rates along the southern Australian margin are consistent with cumulative sediment thickness.

  4. Aerodynamic heating in hypersonic flows

    NASA Technical Reports Server (NTRS)

    Reddy, C. Subba

    1993-01-01

    Aerodynamic heating in hypersonic space vehicles is an important factor to be considered in their design. Therefore the designers of such vehicles need reliable heat transfer data in this respect for a successful design. Such data is usually produced by testing the models of hypersonic surfaces in wind tunnels. Most of the hypersonic test facilities at present are conventional blow-down tunnels whose run times are of the order of several seconds. The surface temperatures on such models are obtained using standard techniques such as thin-film resistance gages, thin-skin transient calorimeter gages and coaxial thermocouple or video acquisition systems such as phosphor thermography and infrared thermography. The data are usually reduced assuming that the model behaves like a semi-infinite solid (SIS) with constant properties and that heat transfer is by one-dimensional conduction only. This simplifying assumption may be valid in cases where models are thick, run-times short, and thermal diffusivities small. In many instances, however, when these conditions are not met, the assumption may lead to significant errors in the heat transfer results. The purpose of the present paper is to investigate this aspect. Specifically, the objectives are as follows: (1) to determine the limiting conditions under which a model can be considered a semi-infinite body; (2) to estimate the extent of errors involved in the reduction of the data if the models violate the assumption; and (3) to come up with correlation factors which when multiplied by the results obtained under the SIS assumption will provide the results under the actual conditions.

  5. Joule heating effects on electroosmotic entry flow.

    PubMed

    Prabhakaran, Rama Aravind; Zhou, Yilong; Patel, Saurin; Kale, Akshay; Song, Yongxin; Hu, Guoqing; Xuan, Xiangchun

    2017-03-01

    Electroosmotic flow is the transport method of choice in microfluidic devices over traditional pressure-driven flow. To date, however, studies on electroosmotic flow have been almost entirely limited to inside microchannels. This work presents the first experimental study of Joule heating effects on electroosmotic fluid entry from the inlet reservoir (i.e., the well that supplies fluids and samples) to the microchannel in a polymer-based microfluidic chip. Electrothermal fluid circulations are observed at the reservoir-microchannel junction, which grow in size and strength with the increasing alternating current to direct current voltage ratio. Moreover, a 2D depth-averaged numerical model is developed to understand the effects of Joule heating on fluid temperature and flow fields in electrokinetic microfluidic chips. This model overcomes the problems encountered in previous unrealistic 2D and costly 3D models, and is able to predict the observed electroosmotic entry flow patterns with a good agreement.

  6. Non-equilibrium effects of core-cooling and time-dependent internal heating on mantle flush events

    NASA Astrophysics Data System (ADS)

    Yuen, D. A.; Balachandar, S.; Steinbach, V. C.; Honda, S.; Reuteler, D. M.; Smedsmo, J. J.; Lauer, G. S.

    We have examined the non-equilibrium effects of core-cooling and time-dependent internal-heating on the thermal evolution of the Earth's mantle and on mantle flush events caused by the two major phase transitions. Both two- and three-dimensional models have been employed. The mantle viscosity responds to the secular cooling through changes in the averaged temperature field. A viscosity which decreases algebraically with the average temperature has been considered. The time-dependent internal-heating is prescribed to decrease exponentially with a single decay time. We have studied the thermal histories with initial Rayleigh numbers between 2 x 107 and 108 . Flush events, driven by the non-equilibrium forcings, are much more dramatic than those produced by the equilibrium boundary conditions and constant internal heating. Multiple flush events are found under non-equilibrium conditions in which there is very little internal heating or very fast decay rates of internal-heating. Otherwise, the flush events take place in a relatively continuous fashion. Prior to massive flush events small-scale percolative structures appear in the 3D temperature fields. Time-dependent signatures, such as the surface heat flux, also exhibits high frequency oscillatory patterns prior to massive flush events. These two observations suggest that the flush event may be a self-organized critical phenomenon. The Nusselt number as a function of the time-varying Ra does not follow the Nusselt vs. Rayleigh number power-law relationship based on equilibrium (constant temperature) boundary conditions. Instead Nu(t) may vary non-monotonically with time because of the mantle flush events. Convective processes in the mantle operate quite differently under non-equilibrium conditions from its behaviour under the usual equilibrium situations.

  7. Permian Basin maturation: proof for pervasive magmatic heat flow in the Netherlands

    NASA Astrophysics Data System (ADS)

    Bonte, Damien; van Wees, Jan Diederik; Fattah, Rader Abdul; Nelskamp, Suzanne; Cloetingh, Sierd

    2014-05-01

    The area of the Permian Basin is marked by significant Stephanian-Permian magmatism that is related to the Variscanorogenic collapse, resulting in pervasive mantle upwelling. Large extrusive evidence is visible in the North German Basin and in the Central North Sea. Theoretical models for tectonic heat flow and maturity evolution show that mantle upwelling, underplating, and intrusions are likely to have a significant effect on maturity-depth trends. Tectonic modelling of selected wells shows that tectonic subsidence and exhumation can be reconciled with a significant heat flow pulse at the Stephanian-Permian, and this could well explain the widespread elevated depth gradient of maturity in Carboniferous rocks. The quantitative assessment of heat flow, which is based on a kinematic model of the process of orogenic collapse, shows that the mantle upwelling and underplating at the base of the crust proposed by earlier studies in fact provides insufficient heat flow to explain strongly elevated maturity-depth trends. However, the Southern part of the Texel IJsselmeer High shows unusually high maturation values that cannot be explained by the simple effect of burial alone. This area of high maturation is also associated with evidence of intrusive magmatic rocks. By modelling five wells in the Texel IJsselmeer High, we conclude that the burial of the sediments and a shallow intrusion in the upper crust provide an elevated heat flow mechanism that has a regional impact, consistent with observed high maturity-depth trends. In each well, the model that best matches the elevated maturity data of the Carboniferous demonstrates the impact of a large intrusion emplacement in the upper crust at the time of the collapse of the Variscan orogen. The impact of this magmatic intrusion at such a shallow depth is extremely likely to have brought the maturity to the gas window during the heat pulse, and, based on the tectonic subsidence record, the model allows us to position this

  8. Flow losses in Stirling engine heat exchangers

    NASA Astrophysics Data System (ADS)

    Jones, J. D.

    1988-01-01

    In the present attempt to formulate closed-form expressions for the rapid and accurate calculation of crank-driven Stirling-cycle machines' pressure variation, flow velocities, and flow friction losses, compression and expansion spaces are assumed to be isothermal, with sinusoidally varying volumes. From the closed-form expressions deduced for the amplitude and phase of these variations, formulas are derived for friction losses in the three heat exchangers, taking into account the mass flow rate variation over the cycle and the variation in mass flow amplitude between the two ends of the regenerator.

  9. The role of the heating mode of the mantle in intermittent reorganization of the plate velocity field

    NASA Astrophysics Data System (ADS)

    Lowman, Julian P.; King, Scott D.; Gable, Carl W.

    2003-02-01

    The geological record indicates that stages of relatively steady plate motion have been punctuated by comparatively brief periods in which plate velocities have reorganized. The distribution of buoyancy sources in the mantle has generally been regarded as evolving too slowly to explain these rapid transitions in plate velocity. We investigate the feedback between mantle convection and plate velocity using 2-D and 3-D mantle convection models that incorporate mobile dynamic plates. We focus on the influence of internal heating in the mantle and consider the effect of mantle viscosity stratification and different plate geometries on the plate velocity time dependence. As either the Rayleigh number or the internal heating rate is increased to magnitudes approaching mantle values, the record of the plate motion from our calculations becomes characterized by intermittent changes in direction. This behaviour is a result of the influence of plates on heat loss from the inherently unsteady, internally heated convecting system. Plate motion instills a pattern of organization on the underlying convection that reflects the plate geometry and results in the formation of sheet-like downwelling structures at convergent plate boundaries in both 2-D and 3-D calculations (in contrast, upwellings in 3-D models are not sheet-like). The role of the sheet-like downwellings is critical in the observed episodic reorganization of the plate velocities. Warm material below the plates is entrained by plate motion into regions enveloping the downwelling sheets. During periods of fairly steady plate motion, buoyancy associated with the build-up of heat around the downwelling sheets leads to the creation of an unstable convection pattern. This build-up of heat is dramatic in calculations with mantle-like internal heating rates and resists continued long-term plate motion towards mature downwellings. When there are limitations on the degree of freedom of the direction of plate movement, such as

  10. How Irreversible Heat Transport Processes Drive Earth's Interdependent Thermal, Structural, and Chemical Evolution Providing a Strongly Heterogeneous, Layered Mantle

    NASA Astrophysics Data System (ADS)

    Hofmeister, A.; Criss, R. E.

    2013-12-01

    Because magmatism conveys radioactive isotopes plus latent heat rapidly upwards while advecting heat, this process links and controls the thermal and chemical evolution of Earth. We present evidence that the lower mantle-upper mantle boundary is a profound chemical discontinuity, leading to observed heterogeneities in the outermost layers that can be directly sampled, and construct an alternative view of Earth's internal workings. Earth's beginning involved cooling via explosive outgassing of substantial ice (mainly CO) buried with dust during accretion. High carbon content is expected from Solar abundances and ice in comets. Reaction of CO with metal provided a carbide-rich core while converting MgSiO3 to olivine via oxidizing reactions. Because thermodynamic law (and buoyancy of hot particles) indicates that primordial heat from gravitational segregation is neither large nor carried downwards, whereas differentiation forced radioactive elements upwards, formation of the core and lower mantle greatly cooled the Earth. Reference conductive geotherms, calculated using accurate and new thermal diffusivity data, require that heat-producing elements are sequestered above 670 km which limits convection to the upper mantle. These irreversible beginnings limit secular cooling to radioactive wind-down, permiting deduction of Earth's inventory of heat-producing elements from today's heat flux. Coupling our estimate for heat producing elements with meteoritic data indicates that Earth's oxide content has been underestimated. Density sorting segregated a Si-rich, peridotitic upper mantle from a refractory, oxide lower mantle with high Ca, Al and Ti contents, consistent with diamond inclusion mineralogy. Early and rapid differentiation means that internal temperatures have long been buffered by freezing of the inner core, allowing survival of crust as old as ca.4 Ga. Magmatism remains important. Melt escaping though stress-induced fractures in the rigid lithosphere imparts a

  11. Method for identifying anomalous terrestrial heat flows

    DOEpatents

    Del Grande, Nancy Kerr

    1977-01-25

    A method for locating and mapping the magnitude and extent of terrestrial heat-flow anomalies from 5 to 50 times average with a tenfold improved sensitivity over orthodox applications of aerial temperature-sensing surveys as used for geothermal reconnaissance. The method remotely senses surface temperature anomalies such as occur from geothermal resources or oxidizing ore bodies by: measuring the spectral, spatial, statistical, thermal, and temporal features characterizing infrared radiation emitted by natural terrestrial surfaces; deriving from these measurements the true surface temperature with uncertainties as small as 0.05 to 0.5 K; removing effects related to natural temperature variations of topographic, hydrologic, or meteoric origin, the surface composition, detector noise, and atmospheric conditions; factoring out the ambient normal-surface temperature for non-thermally enhanced areas surveyed under otherwise identical environmental conditions; distinguishing significant residual temperature enhancements characteristic of anomalous heat flows and mapping the extent and magnitude of anomalous heat flows where they occur.

  12. Short wavelength and high amplitude (~ 1 km) surface uplift in the western Colorado Plateau driven by recent and ongoing mantle flow

    NASA Astrophysics Data System (ADS)

    Crow, R.; Karlstrom, K. E.

    2011-12-01

    upper mantle are driving differential uplift of the lithosphere along the western flank of the Colorado Plateau. The differential uplift across the faults and the length scale of the high mantle velocity gradient area indicate that the zone of uplift has an amplitude of ca. 1000 m and a wavelength of ca. 200 m. High amplitude and short wavelength dynamic topography reflect mantle flow forcings, suggested by the extremely sharp mantle velocity gradients, filtered through a thinned lithosphere with high heat flow and thin effective elastic thickness that suggest upper mantle melt-filled shear zone conduits. This new geologic evidence for recent and ongoing surface uplift offers an important constraint for geodynamic models which are beginning to elucidate the mantle processes that are producing dynamic topography on the western edge of the Colorado Plateau.

  13. MOTION UNDER THE OCEAN: Determining mantle flow of the Northeast Caribbean with seismic anisotropy

    NASA Astrophysics Data System (ADS)

    Mintz, H. E.; Pulliam, J.

    2011-12-01

    Active plate boundaries in the Northeast Caribbean have formed a complex tectonic environment which includes transform and subduction zones. The Caribbean-North America plate boundary is one such active margin, where subduction transitions from arc- to oblique-type off the northeast coast of Puerto Rico. Several lines of evidence support the notion of a slab tear within the subducting North American plate at this transition zone, including the counter-clockwise rotation of the Puerto Rico microplate over the past 10 Ma and clusters of small seismic events. Understanding mantle flow in this region will not only help determine the nature of tectonic activity controlling these margins, but will also aid our understanding of anomalies, such as slab tears. Mantle flow and crustal deformation are believed to be the main controls of anisotropy in the lithosphere and asthenosphere. When a shear-wave passes through an anisotropic medium, it is split into a fast and slow component, with the fast shear-wave polarized along the fast direction of that medium. Shear-wave splitting is a tool used to determine the strength and direction of such anisotropy. Previous studies in the Caribbean have generally shown fast shear-wave polarization directions parallel to trenches and/or plate boundaries, indicating mantle flow around the plate (Growdon et al. 2009; Masy et al. 2011; Piñero-Feliciangeli and Kendall 2008). We have focused a detailed investigation of seismic anisotropy from 31 stations across six networks in the Northeast Caribbean to better constrain mantle flow in this region. Shear-wave splitting measurements of teleseismic core phases (e.g., SKS and SKKS) were completed using SplitLab, a Matlab° based environment created by Wüstefeld et al. (2008). This program enables the user to compare the quality of results from three splitting methods: rotation correlation (Bowman and Ando, 1987), minimum energy (Silver and Chan, 1991) and eigenvalue (Silver and Chan, 1991). Noisy

  14. Large fluctuations of shallow seas in low-lying Southeast Asia driven by mantle flow

    NASA Astrophysics Data System (ADS)

    Zahirovic, Sabin; Flament, Nicolas; Dietmar Müller, R.; Seton, Maria; Gurnis, Michael

    2016-09-01

    The Sundaland continental promontory, as the core of Southeast Asia, is one of the lowest lying continental regions, with half of the continental area presently inundated by a shallow sea. The role of mantle convection in driving long-wavelength topography and vertical motion of the lithosphere in this region has often been ignored when interpreting regional stratigraphy, including a widespread Late Cretaceous-Eocene unconformity, despite a consensus that Southeast Asia is presently situated over a large-amplitude dynamic topography low resulting from long-term post-Pangea subduction. We use forward numerical models to link mantle flow with surface tectonics and compare predicted trends of dynamic topography with eustasy and regional paleogeography to determine the influence of mantle convection on regional basin histories. A Late Cretaceous collision of Gondwana-derived terranes with Sundaland choked the active margin, leading to slab breakoff and a ˜10-15 Myr-long subduction hiatus. A subduction hiatus likely resulted in several hundred meters of dynamic uplift and emergence of Sundaland between ˜80 and 60 Ma and may explain the absence of a Late Cretaceous-Eocene sedimentary record. Renewed subduction from ˜60 Ma reinitiated dynamic subsidence of Sundaland, leading to submergence from ˜40 Ma despite falling long-term global sea levels. Our results highlight a complete "down-up-down" dynamic topography cycle experienced by Sundaland, with transient dynamic topography manifesting as a major regional unconformity in sedimentary basins.

  15. Multiple subduction imprints in the mantle below Italy detected in a single lava flow

    NASA Astrophysics Data System (ADS)

    Nikogosian, Igor; Ersoy, Özlem; Whitehouse, Martin; Mason, Paul R. D.; de Hoog, Jan C. M.; Wortel, Rinus; van Bergen, Manfred J.

    2016-09-01

    Post-collisional magmatism reflects the regional subduction history prior to collision but the link between the two is complex and often poorly understood. The collision of continents along a convergent plate boundary commonly marks the onset of a variety of transitional geodynamic processes. Typical responses include delamination of subducting lithosphere, crustal thickening in the overriding plate, slab detachment and asthenospheric upwelling, or the complete termination of convergence. A prominent example is the Western-Central Mediterranean, where the ongoing slow convergence of Africa and Europe (Eurasia) has been accommodated by a variety of spreading and subduction systems that dispersed remnants of subducted lithosphere into the mantle, creating a compositionally wide spectrum of magmatism. Using lead isotope compositions of a set of melt inclusions in magmatic olivine crystals we detect exceptional heterogeneity in the mantle domain below Central Italy, which we attribute to the presence of continental material, introduced initially by Alpine and subsequently by Apennine subduction. We show that superimposed subduction imprints of a mantle source can be tapped during a melting episode millions of years later, and are recorded in a single lava flow.

  16. Dynamic topography, gravity and the role of lateral viscosity variations from inversion of global mantle flow

    NASA Astrophysics Data System (ADS)

    Yang, Ting; Gurnis, Michael

    2016-11-01

    Lateral viscosity variations (LVVs) in the mantle influence geodynamic processes and their surface expressions. With the observed long-wavelength geoid, free-air anomaly, gravity gradient in three directions and discrete, high-accuracy residual topography, we invert for depth- and temperature-dependent and tectonically regionalized mantle viscosity with a mantle flow model. The inversions suggest that long-wavelength gravitational and topographic signals are mainly controlled by the radial viscosity profile; the pre-Cambrian lithosphere viscosity is slightly (˜ one order of magnitude) higher than that of oceanic and Phanerozoic lithosphere; plate margins are substantially weaker than plate interiors; and viscosity has only a weak apparent, dependence on temperature, suggesting either a balancing between factors or a smoothing of actual higher amplitude, but short wavelength, LVVs. The predicted large-scale lithospheric stress regime (compression or extension) is consistent with the world stress map (thrust or normal faulting). Both recent compiled high-accuracy residual topography and the predicted dynamic topography yield ˜1 km amplitude long-wavelength dynamic topography, inconsistent with recent studies suggesting amplitudes of ˜100 to ˜500 m. Such studies use a constant, positive admittance (transfer function between topography and gravity), in contrast to the evidence which shows that the earth has a spatially and wavelength-dependent admittance, with large, negative admittances between ˜4000 and ˜104 km wavelengths.

  17. Colorado Heat Flow Data from IHFC

    SciTech Connect

    Zehner, Richard E.

    2012-02-01

    Citation Information: Originator: Earth Science &Observation Center (ESOC), CIRES, University of Colorado at Boulder Originator: The International Heat Flow Commission (IHFC) Publication Date: 2012 Title: Colorado IHFC Data Edition: First Publication Information: Publication Place: Earth Science & Observation Center, Cooperative Institute for Research in Environmental Science (CIRES), University of Colorado, Boulder Publisher: Earth Science &Observation Center (ESOC), CIRES, University of Colorado at Boulder Description: Abstract: This layer contains the heat flow sites and data of the State of Colorado compiled from the International Heat Flow Commission (IHFC) of the International Association of Seismology and Physics of the Earth's Interior (IASPEI) global heat flow database (www.heatflow.und.edu/index2.html). The data include different items: Item number, descriptive code, name of site, latitude and longitude, elevation, depth interval, number of temperature data, temperature gradient, number of conductivity measurement, average conductivity, number of heat generation measurements, average heat production, heat flow, number of individual sites, references, and date of publication. Spatial Domain: Extent: Top: 4522121.800672 m Left: 165356.134075 m Right: 621836.776246 m Bottom: 4097833.419676 m Contact Information: Contact Organization: Earth Science &Observation Center (ESOC), CIRES, University of Colorado at Boulder Contact Person: Khalid Hussein Address: CIRES, Ekeley Building Earth Science & Observation Center (ESOC) 216 UCB City: Boulder State: CO Postal Code: 80309-0216 Country: USA Contact Telephone: 303-492-6782 Spatial Reference Information: Coordinate System: Universal Transverse Mercator (UTM) WGS’1984 Zone 13N False Easting: 500000.00000000 False Northing: 0.00000000 Central Meridian: -105.00000000 Scale Factor: 0.99960000 Latitude Of Origin: 0.00000000 Linear Unit: Meter Datum: World Geodetic System 1984 (WGS ’1984) Prime Meridian: Greenwich

  18. Stirling Engine With Radial Flow Heat Exchangers

    NASA Technical Reports Server (NTRS)

    Vitale, N.; Yarr, George

    1993-01-01

    Conflict between thermodynamical and structural requirements resolved. In Stirling engine of new cylindrical configuration, regenerator and acceptor and rejector heat exchangers channel flow of working gas in radial direction. Isotherms in regenerator ideally concentric cylinders, and gradient of temperature across regenerator radial rather than axial. Acceptor and rejector heat exchangers located radially inward and outward of regenerator, respectively. Enables substantial increase in power of engine without corresponding increase in diameter of pressure vessel.

  19. Magma genesis and mantle flow at a subducting slab edge: the South Sandwich arc-basin system

    NASA Astrophysics Data System (ADS)

    Leat, P. T.; Pearce, J. A.; Barker, P. F.; Millar, I. L.; Barry, T. L.; Larter, R. D.

    2004-10-01

    The intra-oceanic South Sandwich subduction system is distinctive in having a narrow slab with slab edges at its northern and southern ends. We present new geochemical data to investigate magma genesis beneath the parts of the arc and back-arc segments that lie close to the two slab edges: Kemp and Nelson seamounts at the southern edge of the South Sandwich arc, and segments E1 and E2 in the south, plus segments E9 and E10 in the north, of the East Scotia Sea. In the arc, Kemp and Nelson seamounts exhibit enhanced subduction fluxes compared to the remainder of the arc. The southernmost (Nelson) has the isotope (low Nd and high Sr isotope ratios) and elemental (ultra-high Th and Ba and high Hf/Nd ratios) characteristics of a sediment melt, or supercritical aqueous fluid, component. The more northerly (Kemp) has the same characteristics as the remainder of the arc (high Nd and slightly raised Sr isotope ratios, high Nd/Hf ratios, high Ba/Th ratios), indicative of a fluid component derived mainly from subducted crust, but has a greater mass fraction of that component than the rest of the arc. In the back-arc basin, the slab-edge segments are generally fed by more fertile mantle (E-MORB in all but E1) than the segments in the centre of the basin (N-MORB). At the edges, segments furthest from the trench (E2, E9) have small subduction components while those nearer to the trench (E1, E10) have larger subduction components and slightly more depleted mantle. We argue that several processes were important at the slab edges: roll-back of the slab, forcing sideways flow of relatively enriched mantle into the mantle wedge; convergence of the arc with the back-arc spreading centre, imparting a greater subduction component into the back-arc lavas; and anomalous heating of the subducting slab, increasing subduction fluxes and the contribution of sediment melts to the subduction component.

  20. Complicated 3D mantle flow beneath Northeast China from shear wave splitting and its implication for the Cenozoic intraplate volcanism

    NASA Astrophysics Data System (ADS)

    Li, Shilin; Guo, Zhen; Chen, Y. John

    2017-07-01

    We obtained shear wave splitting measurements from XKS (SKS and SKKS) phases recorded by the NECESSArray project consisting of 127 seismic stations in Northeast China (NEC). The most salient feature of the anisotropy in NE China is the alignment of subduction-parallel fast direction, which can be explained by the background upper mantle flow in the big mantle wedge (BMW). However, the geographical variations of fast direction and delay time, which closely follow the geometry of subducting Pacific slab, suggests that the slab morphology controls the geometry of 3-D mantle flow in the BMW. The most significant finding of this study is the complex anisotropic pattern with most nulls observed in the Changbaishan mountain region (CBM) and southern Songliao basin. At the southern Songliao basin, the small delay times as well as null measurements of shear wave splitting are coincident with the high velocity in the upper mantle down to 300 km from previous studies. The observed anisotropy likely arises from the combination of BMW convection and more localized upper mantle convection, that is, a plume-like mantle upwelling from the mantle transition zone beneath the Changbaishan region triggers the down-welling beneath the southern Songliao basin.

  1. Heat transfer mechanisms in microgravity flow boiling.

    PubMed

    Ohta, Haruhiko

    2002-10-01

    The objective of this paper is to clarify the mechanisms of heat transfer and dryout phenomena in flow boiling under microgravity conditions. Liquid-vapor behavior in annular flow, encountered in the moderate quality region, has extreme significance for practical application in space. To clarify the gravity effect on the heat transfer observed for an upward flow in a tube, the research described here started from the measurement of pressure drop for binary gas-liquid mixture under various gravity conditions. The shear stress acting on the surface of the annular liquid film was correlated by an empirical method. Gravity effects on the heat transfer due to two-phase forced convection were investigated by the analysis of velocity and temperature profiles in the film. The results reproduce well the trends of heat transfer coefficients varying with the gravity level, quality, and mass velocity. Dryout phenomena in the moderate quality region were observed in detail by the introduction of a transparent heated tube. At heat fluxes just lower and higher than CHF value, a transition of the heat transfer coefficient was calculated from oscillating wall temperature, where a series of opposing heat transfer trends--the enhancement due to the quenching of dried areas or evaporation from thin liquid films and the deterioration due to the extension of dry patches--were observed between the passage of disturbance waves. The CHF condition that resulted from the insufficient decrease of wall temperature in the period of enhanced heat transfer was overcome by a temperature increase in the deterioration period. No clear effect of gravity on the mechanisms of dryout was observed within the range of experiments.

  2. Gravity crustal models and heat flow measurements for the Eurasia Basin, Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Urlaub, Morelia; Schmidt-Aursch, Mechita C.; Jokat, Wilfried; Kaul, Norbert

    2009-12-01

    The Gakkel Ridge in the Arctic Ocean with its adjacent Nansen and Amundsen Basins is a key region for the study of mantle melting and crustal generation at ultraslow spreading rates. We use free-air gravity anomalies in combination with seismic reflection and wide-angle data to compute 2-D crustal models for the Nansen and Amundsen Basins in the Arctic Ocean. Despite the permanent pack-ice cover two geophysical transects cross both entire basins. This means that the complete basin geometry of the world’s slowest spreading system can be analysed in detail for the first time. Applying standard densities for the sediments and oceanic crystalline crust, the gravity models reveal an unexpected heterogeneous mantle with densities of 3.30 × 103, 3.20 × 103 and 3.10 × 103 kg/m3 near the Gakkel Ridge. We interpret that the upper mantle heterogeneity mainly results from serpentinisation and thermal effects. The thickness of the oceanic crust is highly variable throughout both transects. Crustal thickness of less than 1 km dominates in the oldest parts of both basins, increasing to a maximum value of 6 km near the Gakkel Ridge. Along-axis heat flow is highly variable and heat flow amplitudes resemble those observed at fast or intermediate spreading ridges. Unexpectedly, high heat flow along the Amundsen transect exceeds predicted values from global cooling curves by more than 100%.

  3. Numerical studies of mantle evolution in planets of various sizes

    NASA Astrophysics Data System (ADS)

    Ogawa, M.; Kameyama, M.; Yanagisawa, T.

    2016-12-01

    The size of a planet exerts control over its tectonic and volcanic activities. Our linear stability analysis of thermal convection of a variable viscosity fluid in a basally heated spherical shell suggests that the mantle of the present Moon that appears to be tectonically dead is indeed convectively stable, while that the mantles of Mars and larger planets that are more tectonically active are unstable. Our two-dimensional numerical models of magmatism in a convecting mantle show that the style of magmatism also depends on the size of planet. In the Moon, mantle upwelling flow causes mild magmatism that continues for several hundred million years. In larger planets, however, magmatism that is caused by a mantle upwelling flow boosts the flow itself. This positive feedback (the magmatism-mantle upwelling, or MMU, feedback) makes magmatism vigorous and episodic. In Venus and the Earth, the solid-solid phase transitions at the top of the lower mantle are also important for magmatism in the early mantle that is abundant in heat producing elements (HPEs); the phase transitions cause episodic upwelling flow, or burst, of hot lower mantle materials into the upper mantle to trigger vigorous magmatism. In spite of the compositional differentiation of the mantle by this magmatism, the mantle remains rather homogeneous because of a strong convective stirring caused by the MMU feedback. When we further reproduced tectonic plates in this model of magmatism and mantle convection by assuming a stress-history dependent rheology for the lithosphere, we obtained a two-stage evolution model of the Earth. On the early stage, bursts frequently occur to make plate motion chaotic and to keep the mantle rather homogeneous. As HPEs decay, however, the mantle evolves into the later stage where bursts subside, tectonic plates move more steadily, and subducted basaltic crusts accumulate on the core-mantle boundary to form a large thermo-chemical pile.

  4. Three-dimensional Numerical Models of Mantle Flow Through the Cocos-Nazca Slab Gap

    NASA Astrophysics Data System (ADS)

    Jadamec, M.; Fischer, K. M.

    2013-05-01

    Global slab geometry models suggest a 350 km to 1000 km spacing between the southern extent of the Cocos slab and the northern extent of the Nazca slab (Gudmundsson and Sambridge, 1998; Syracuse and Abers, 2006; Hayes et al., 2012). The apparent gap between the east-dipping Cocos and Nazca slabs at depth correlates to several tectonic features on the Pacific side of Central and northern South America that may limit subduction, namely the (a) Panama Fault zone, (b) incoming young lithosphere associated with the Cocos-Nazca spreading center, and (c) the Cocos, Coiba, Malpelo, and Carnegie ridges associated with the Galapogos hotspot and Cocos-Nazca spreading center (Protti et al., 1994; Johnston and Thorkelson, 1997; Gutscher et al., 1999; Abratis and Worner, 2001; Sdrolias and Muller, 2006; Mann et al., 2007; Gazel et al., 2011). In addition, on the Caribbean side of Central and northern South America, seismic data suggest that part of the Caribbean plate is subducting and dipping in a direction opposite to the Cocos and Nazca slabs (van der Hilst and Mann, 1994; Camacho et al., 2010). We construct high-resolution three-dimensional numerical models of the Cocos-Nazca subduction system to test the effects of a slab gap and variable overriding plate thickness on surface plate motion and mantle flow. The 3D tectonic configuration is generated with SlabGenerator (Jadamec and Billen, 2010, 2012) and the mantle convection code CitcomCU is used to solve for the viscous flow (Moresi and Solomatov, 1995; Zhong, 2006). The negative thermal buoyancy of the slabs drive the flow. No driving velocities are applied to the plates or any of the slabs in the model. The detailed geometries of the Cocos and Nazca slabs are constructed from seismicity and seismic tomography (Protti et al., 1994; Colombo et al., 1997; Gudmundsson and Sambridge, 1998; Rogers et al., 2002; Husen et al., 2003; Syracuse and Abers, 2006; Syracuse et al., 2008; Dzierma et al., 2011). Seismic tomography

  5. The feasibility of inverting for flow in the lowermost mantle (Invited)

    NASA Astrophysics Data System (ADS)

    Nowacki, A.; Walpole, J.; Wookey, J. M.; Walker, A.; Forte, A. M.; Masters, G.; Kendall, J. M.

    2013-12-01

    At the core-mantle boundary (CMB), the largest change in physical properties occurs within the Earth. Furthermore, up to a few hundred kilometres above the CMB--the region known as D″--the largest lateral variations in seismic wave speed are observed outside the upper mantle. Observations of shear wave splitting in D″ shows that these variations are dependent not only on position, but also wave propagation direction and polarisation; that is, strong seismic anisotropy is a pervasive feature of D″, just as in the upper mantle (UM). Similarly to the UM, it is frequently argued that alignment of anisotropic minerals due to flow is the cause of this. Were this the case, this anisotropy could be used to retrieve the recent strain history of the lowermost mantle. Recent modelling of mineral alignment in D″ [1,2] has shown that quite simple models of mantle flow do not produce simple anisotropy, hence one must make use of the most information about the type and orientation of anisotropy possible. Global inversion for radial anisotropy permits complete coverage of the CMB but so far has relied on core-diffracted waves (Sdiff) which are challenging to accurately interpret [3]. The assumption of radial anisotropy may also be too restrictive [4]. Shear wave splitting studies do not impose any assumed type of anisotropy but have been traditionally limited in their geographical scope. We present the results of a consistent analysis of core-reflected shear waves (ScS) for shear wave splitting, producing near-global coverage [5] of D″. Over 12,000 individual measurements are made, from ~470 events. Along well-studied paths such as beneath the Caribbean, our results agree excellently with previous work. Elsewhere, a full range of fast orientations are observed, indicating that simple SV-SH comparisons may not accurately reflect the elasticity present. We compare these results to candidate models of D″ anisotropy assuming a simple flow model derived from geophysical

  6. Helium isotopes, tectonics and heat flow in the Northern Caucasus

    NASA Astrophysics Data System (ADS)

    Polyak, B. G.; Tolstikhin, I. N.; Kamensky, I. L.; Yakovlev, L. E.; Cheshko, A. L.; Marty, B.

    2000-06-01

    109 new measurements of 3He/ 4He ≡ R in subsurface fluids of the Northern Caucasus coupled with the data obtained previously allow regional regularities in the distribution of helium isotopic composition to be examined. Cis-Caucasian foredeeps show the lowest radiogenic R-values. The average Rav-value is slightly higher in gases of the Scythian plate beyond the Stavropol arch. Within the arch, elevated R = (1.6-4.5) × 10 -7 indicates an input of mantle-derived helium. This input is even more evident to the south of Starvropol arch, in the Caucasian Mineral Water area, where the ≈8 Ma old laccolithes occur and R-values approach (5-11) × 10 -7. The highest R-values, up to (0.7-0.9) × 10 -5, are observed further to the south, in the central segment of the Greater Caucasus, where recent volcanism is manifested. Enhanced R-values do not correlate with the crustal thickness but reflect degassing of magmatic reservoirs including those yet unknown. According to the recent Sr-Nd-O data, the young volcanic rocks are of mantle affinity but they are contaminated by a crustal component. The average Rav-values in fluids and 87Sr/ 86Sr ratios in host magmatic rocks show an inverse correlation suggesting mixing of crustal and mantle materials. R-values vary inversely with apatite fission-track ages of crystalline basement rocks. The ages increase westward of the Elbrus volcano, most likely recording the thermal degradation of the Greater Caucasus since the pre-Cainozoic magmatic activity. A direct correlation between Rav-values and background conductive heat flow densities implies that discharge of the mantle melts into the crust is the common cause of the geochemical, geochronological and geothermal regularities observed. Elevated R-values are generally observed in CO 2-bearing fluids, low values are typical of CH 4 gases, a few N 2-rich gases display highly variable R. Relationships between the major gas constituents and noble gas isotopes are discussed. Fractionation

  7. Numberical Solution to Transient Heat Flow Problems

    ERIC Educational Resources Information Center

    Kobiske, Ronald A.; Hock, Jeffrey L.

    1973-01-01

    Discusses the reduction of the one- and three-dimensional diffusion equation to the difference equation and its stability, convergence, and heat-flow applications under different boundary conditions. Indicates the usefulness of this presentation for beginning students of physics and engineering as well as college teachers. (CC)

  8. Effects of subduction and slab gaps on mantle flow beneath the Lesser Antilles based on observations of seismic anisotropy

    NASA Astrophysics Data System (ADS)

    Schlaphorst, David; Kendall, J.-Michael; Baptie, Brian; Latchman, Joan L.; Bouin, Marie-Paule

    2016-04-01

    Subduction is a key process in the formation of continental crust. However, the interaction of the mantle with the subducting slab is not fully understood and varies between subduction zones. The flow geometry and stress patterns influence seismic anisotropy; since anisotropic layers lead to variations in the speed of seismic waves as a function of the direction of wave propagation, mantle flow can be constrained by investigating the structure of these anisotropic layers. In this study we investigate seismic anisotropy in the eastern Greater and the Lesser Antilles along a subduction environment, including the crust and the upper mantle as regions of interest. We use a combination of teleseismic and local events recorded at three-component broadband seismic stations on every major island in the area to observe and distinguish between anisotropy in the crust, the mantle wedge and the sub-slab mantle. Local event delay times (0.21±0.12s) do not increase with depth, indicating a crustal origin and an isotropic mantle wedge. Teleseismic delay times are larger (1.34±0.47s), indicating sub-slab anisotropy. The results suggest trench-parallel mantle flow, with the exception of trench-perpendicular alignment in narrow regions east of Puerto Rico and south of Martinique, suggesting mantle flow through gaps in the slab. This agrees with the continuous northward mantle flow that is caused by the subducting slab proposed by previous studies of that region. We were able to identify a pattern previously unseen by other studies; on St. Lucia a trench-perpendicular trend also indicated by the stations around can be observed. This pattern can be explained by a mantle flow through a gap induced by the subduction of the boundary zone between the North and South American plates. This feature has been proposed for that area using tomographic modelling (van Benthem et al., 2013). It is based on previous results by Wadge & Shepherd (1984), who observed a vertical gap in the Wadati

  9. Constraints on Fault Permeability from Helium and Heat Flow in the Los Angeles Basin

    NASA Astrophysics Data System (ADS)

    Garven, G.; Boles, J. R.

    2016-12-01

    Faults have profound controls on fluid flow in the Earth's crust. Faults affect the diagenesis of sediments, the migration of brines and petroleum, and the dynamics of hydrothermal mineralization. In southern California, the migration of petroleum and noble gases can be used to constrain fault permeability at both the formation and crustal scale. In the Los Angeles Basin, mantle-derived helium is a significant component of casing gas from deep production wells along the Newport-Inglewood Fault zone (NIFZ). Helium isotope ratios are as high as 5.3 Ra, indicating up to 66% mantle contribution along parts of this strike-slip fault zone (Boles et al., 2015). The 3He inversely correlates with CO2, a potential magmatic-derived carrier gas, and the d13C of the CO2 in the 3He rich samples is between 0 and -10 per mil, suggesting a mantle influence. The strong mantle-helium signal along the NIFZ is surprising, considering that the fault is currently in a transpressional state of stress (rather than extensional), has no history of recent magma emplacement, and lacks high geothermal gradients. Structurally it has been modeled as being truncated by a "potentially seismically active" décollement beneath the LA basin. But the geochemical data demonstrate that the NIFZ is a deep-seated fault connected with the mantle. Assuming that the helium migration is linked to the bulk fluid transport in the crust, we have used 1-D reactive mass transport theory to calculate a maximum inter-seismic Darcy flow rate of 2.2 cm yr-1 and intrinsic permeability of 160 microdarcys (1.6 x 10 -16 m2), vertically averaged across the crust. Based on thermal Peclet numbers and numerical models for the basin, we show that fault-focused fluid flow is too slow to elevate heat flow around the NIFZ. Although heat flow data are sparse, there generally doesn't appear to be any clear pattern of anomalous heat flow with the large strike-slip faults of southern California, suggesting that neither bulk fluid flow

  10. Heterogeneities in the thickness of the elastic lithosphere of Mars: Constraints on heat flow and internal dynamics

    SciTech Connect

    Solomon, S.C. ); Head, J.W. )

    1990-07-10

    Derived values of the thickness of the effective elastic lithosphere on Mars are converted to estimates of lithospheric thermal gradients and surface heat flow by finding the thickness of the elastic-plastic plate having the same bending moment and curvature, subject to assumed strain rates and temperature-dependent flow laws for crustal and mantle material. Local thermal gradients and heat flow values so estimated were 10-14 K km{sup {minus}1} and 25-35 mW m{sup {minus}2}, respectively, at the time of formation of flexurally induced graben surrounding the Tharsis Montes and Alba Patera, while gradients and heat flow values of less than 5-6 K km{sup {minus}1} and 17-24 mW m{sup {minus}2}, respectively, characterized the lithosphere beneath the Isidis mascon and Olympus Mons at the time of emplacement of these loads. On the basis of the mean global thickness of the elastic lithosphere inferred to support the Tharsis rise and estimates of mantle heat production obtained from SNC meteorites, it is suggested that the present average global heat flux on Mars is in the range 15-25 mW m{sup {minus}2}. Approximately 3-5% of this heat flux during the Amazonian epoch has been contributed by excess conducted heat in the central regions of major volcanic provinces. Most likely, this excess heat flux has been delivered to the base of the lithosphere by mantle plumes. The fractional mantle heat transport contributed by plumes during the last 2 b.y. on Mars is therefore similar to that at present on Earth.

  11. The impact of slab dip variations, gaps and rollback on mantle wedge flow: insights from fluids experiments

    NASA Astrophysics Data System (ADS)

    MacDougall, Julia G.; Kincaid, Chris; Szwaja, Sara; Fischer, Karen M.

    2014-05-01

    Observed seismic anisotropy and geochemical anomalies indicate the presence of 3-D flow around and above subducting slabs. To investigate how slab geometry and velocity affect mantle flow, we conducted a set of experiments using a subduction apparatus in a fluid-filled tank. Our models comprise two independently adjustable, continuous belts to represent discrete sections of subducting slabs that kinematically drive flow in the surrounding glucose syrup that represents the upper mantle. We analyse how slab dip (ranging from 30° to 80°), slab dip difference between slab segments (ranging from 20° to 50°), rates of subduction (4-8 cm yr-1) and slab/trench rollback (0-3 cm yr-1) affect mantle flow. Whiskers were used to approximate mineral alignment induced by the flow, as well as to predict directions of seismic anisotropy. We find that dip variations between slab segments generate 3-D flow in the mantle wedge, where the path lines of trenchward moving mantle material above the slab are deflected towards the slab segment with the shallower dip. The degree of path line deflection increases as the difference in slab dip between the segments increases, and, for a fixed dip difference, as slab dip decreases. In cases of slab rollback and large slab dip differences, we observe intrusion of subslab material through the gap and into the wedge. Flow through the gap remains largely horizontal before eventual downward entrainment. Whisker alignment in the wedge flow is largely trench-normal, except near the lateral edges of the slab where toroidal flow dominates. In addition, whisker azimuths located above the slab gap deviate most strongly from trench-normal orientations when slab rollback does not occur. Such flow field complexities are likely sufficient to affect deep melt production and shallow melt delivery. However, none of the experiments produced flow fields that explain the trench-parallel shear wave splitting fast directions observed over broad arc and backarc

  12. Boundary-layer mantle flow under the Dead Sea transform fault inferred from seismic anisotropy.

    PubMed

    Rümpker, Georg; Ryberg, Trond; Bock, Günter

    2003-10-02

    Lithospheric-scale transform faults play an important role in the dynamics of global plate motion. Near-surface deformation fields for such faults are relatively well documented by satellite geodesy, strain measurements and earthquake source studies, and deeper crustal structure has been imaged by seismic profiling. Relatively little is known, however, about deformation taking place in the subcrustal lithosphere--that is, the width and depth of the region associated with the deformation, the transition between deformed and undeformed lithosphere and the interaction between lithospheric and asthenospheric mantle flow at the plate boundary. Here we present evidence for a narrow, approximately 20-km-wide, subcrustal anisotropic zone of fault-parallel mineral alignment beneath the Dead Sea transform, obtained from an inversion of shear-wave splitting observations along a dense receiver profile. The geometry of this zone and the contrast between distinct anisotropic domains suggest subhorizontal mantle flow within a vertical boundary layer that extends through the entire lithosphere and accommodates the transform motion between the African and Arabian plates within this relatively narrow zone.

  13. Quantitative assessments of mantle flow models against seismic observations: Influence of uncertainties in mineralogical parameters

    NASA Astrophysics Data System (ADS)

    Schuberth, Bernhard S. A.

    2017-04-01

    One of the major challenges in studies of Earth's deep mantle is to bridge the gap between geophysical hypotheses and observations. The biggest dataset available to investigate the nature of mantle flow are recordings of seismic waveforms. On the other hand, numerical models of mantle convection can be simulated on a routine basis nowadays for earth-like parameters, and modern thermodynamic mineralogical models allow us to translate the predicted temperature field to seismic structures. The great benefit of the mineralogical models is that they provide the full non-linear relation between temperature and seismic velocities and thus ensure a consistent conversion in terms of magnitudes. This opens the possibility for quantitative assessments of the theoretical predictions. The often-adopted comparison between geodynamic and seismic models is unsuitable in this respect owing to the effects of damping, limited resolving power and non-uniqueness inherent to tomographic inversions. The most relevant issue, however, is related to wavefield effects that reduce the magnitude of seismic signals (e.g., traveltimes of waves), a phenomenon called wavefront healing. Over the past couple of years, we have developed an approach that takes the next step towards a quantitative assessment of geodynamic models and that enables us to test the underlying geophysical hypotheses directly against seismic observations. It is based solely on forward modelling and warrants a physically correct treatment of the seismic wave equation without theoretical approximations. Fully synthetic 3-D seismic wavefields are computed using a spectral element method for 3-D seismic structures derived from mantle flow models. This way, synthetic seismograms are generated independent of any seismic observations. Furthermore, through the wavefield simulations, it is possible to relate the magnitude of lateral temperature variations in the dynamic flow simulations directly to body-wave traveltime residuals. The

  14. Anisotropy and Mantle Flow in the Eastern Sierras Pampeanas from Shear Wave Splitting

    NASA Astrophysics Data System (ADS)

    Wood, F. D.; Anderson, M. L.; Gilbert, H. J.; Alvarado, P. M.; Martino, R.

    2009-12-01

    The South American subduction zone has extreme examples of active flat-slab subduction and is believed to be an analog for subduction that occurred during the Cretaceous-Eocene age ("Laramide") mountain building events in the Western U.S. This region is therefore ideal for gaining a better understanding of shallow slab subduction and its influences on deformation of the surrounding mantle and overriding crust. Shear wave splitting analysis is used to test a model for the direction of mantle flow beneath the Eastern Sierras Pampeanas (ESP) in the Sierras de Córdoba region of Argentina to better understand the dynamics of flat-slab subduction. This study may also contribute to our understanding of the role the slab plays in deforming the overriding crust. The results of Anderson et al. (2004) indicate that the seismic fast directions underlying Chile and western Argentina are oriented N-S, or trench parallel. To the east, under the Sierras Pampeanas and coincident with a segment of flat subduction, the seismic fast direction is E-W, or trench perpendicular. Anderson et al. formulated several hypotheses to explain this apparent heterogeneity in the anisotropy. One explanation is that the retrograde motion of the subducting slab, caused by the westward movement of the overriding slab, prohibits E-W mantle flow, thus causing an overall N-S flow direction and the observed N-S oriented fast directions. The E-W oriented fast directions would then result from anisotropy due to mantle material being drawn into the area vacated by the slab as it is flattened. If this is the case, E-W fast directions should only be measured at stations directly above the flat slab. As alternative interpretations, the detected heterogeneous anisotropy may be due to strong lithospheric anisotropy or differences in the hydration state in the mantle. In the case of hydration state, E-W fast directions would be expected in the backarc south of the flat slab segment, where normal subduction occurs

  15. The first deep heat flow determination in crystalline basement rocks beneath the Western Canadian Sedimentary Basin

    NASA Astrophysics Data System (ADS)

    Majorowicz, Jacek; Chan, Judith; Crowell, James; Gosnold, Will; Heaman, Larry M.; Kück, Jochem; Nieuwenhuis, Greg; Schmitt, Douglas R.; Unsworth, Martyn; Walsh, Nathaniel; Weides, Simon

    2014-05-01

    relationship determined for other provinces of the Canadian Shield. However, this relationship could not be established for Q estimates from industrial temperatures data for the study area that includes the Taltson Magmatic Zone and neighbouring Buffalo High and Buffalo Utikuma domains to the west. It appears that the spatial wavelength of heat generation change is much smaller than that of heat flow. Thermal modelling of heat flow and heat generation data from the Hunt Well, using mantle heat flow contributions of 15 ± 5 mW m-2 results in lithosphere-asthenosphere boundary depth estimates of near 200 km. This mantle heat flow value is consistent with the range for the stable continental areas, 15 (±3) mW m-2.

  16. Thermochemical evolution of the core constrained by mantle global circulation

    NASA Astrophysics Data System (ADS)

    Olson, P.; Zhong, S.; Rudolph, M. L.; Deguen, R.

    2013-12-01

    Reconstructions of the Phanerozoic history of the mantle using global circulation models (mantle GCMs) that include past plate motions are used to constrain the thermochemical evolution of the core. Mantle GCMs predict that the present-day global mean heat flow at the core-mantle boundary lies in the range 80-90 mW/m^2, with low spherical harmonic degree spatial variations of 100 mW/m^2 . Based on the recently-determined high conductivity of core compounds, we infer that the present-day outer core is thermally unstable beneath 30-40% of the core-mantle boundary, including beneath the high seismic velocity regions in the lower mantle, and thermally stable elsewhere, including beneath the large low seismic velocity provinces in the lower mantle. During times of faster plate speeds and elevated core heat flow, such as in the Cretaceous, the thermally unstable portions beneath the core-mantle boundary expanded to around 60%, according to our mantle GCMs. We calculate the growth the inner core using a standard thermochemical evolution model of the core. Mantle GCM heat flow statistics predict that the inner core nucleated between 650 and 950 Ma, the older age corresponding to radioactive heating from an assumed 300 ppm of potassium in the core. In terms of energetics, we find that core-mantle boundary heat flows of 80-90 mW/m^2 are adequate for convection-driven dynamo action during inner core growth, but higher heat flow or additional energy sources may be needed to sustain the geodynamo prior to inner core nucleation

  17. Coupled Afterslip and Mantle Flow Following the 1992 Landers and the 1999 Hector Mine, CA Earthquakes

    NASA Astrophysics Data System (ADS)

    Barbot, S. D.; Fialko, Y.

    2009-12-01

    We investigate the postseismic deformation following the 1992 Landers and the 1999 Hector Mine earthquakes (Mojave desert, eastern California) using all available geodetic data including GPS and InSAR time series between 1992-2009. We test the possible mechanisms of postseismic relaxation using physically-based time-dependent models of deformation driven by coseismic stress changes. Considered mechanisms include power-law viscoelastic flow in the lower crust and upper mantle, afterslip governed by a rate-dependent friction, and poroelastic rebound. For the post-Landers transient, we compare the model predictions to the campaign GPS data referenced to some chosen station within the network. We find that both afterslip and viscoelastic relaxation models can explain the data equally well. Identification of a "preferred" mechanism depends on a choice of a reference GPS station. For the post-Hector Mine transient, we isolate the postseismic signal in the GPS time series by assuming a complete relaxation 8-10 years after the rupture. Such an assumption is supported by the fact that sites that predate the earthquake returned to preseismic velocities after several years following the event, so that the velocity contribution from the late postseismic signal (after eight years) is small compared to the secular velocities. We find that models of stress-driven afterslip (assuming a velocity-neutral depth of 15 km) can explain the amplitude of surface displacements in the near field (within 50 km from the rupture). Afterslip models indicate a characteristic relaxation timescale of ~1-2 years. However, the orientation of the postseismic velocity vectors warrants the occurrence of both afterslip and viscoelastic flow in the upper mantle. The data do not require a stress-dependent viscosity, and can be explained equally well by power-law and linear Maxwell viscoelastic models. We quantify a tradeoff between the assumed thickness of the elastic layer and the viscosity of the

  18. Seismic Anisotropy near Hawaii - Evidence for plume-related mantle flow

    NASA Astrophysics Data System (ADS)

    Laske, Gabi; Marzen, Rachel

    2016-04-01

    During the Hawaiian PLUME (Plume-Lithosphere Undersea Melt Experiment) deployment, we collected continuous seismic data at ten land stations and nearly 70 ocean bottom sites from 2005 through mid-2007. Both the usage broad-band seismometers as well as the central location of Hawaii with good azimuthal seismicity coverage has allowed us to conduct a comprehensive analysis of surface wave azimuthal anisotropy at periods between 20 and 100 s. We use a sub-array approach to successively fit propagating spherical wave fronts in order to obtain frequency-dependent estimates at a large number of points. We use the standard Smith-and-Dahlen parameterization to express azimuthal variations. A systematic comparison between results obtained for different truncation levels in the trigonometric expansion allows us to assess stability of the results and assign error bars. At short periods, the fast direction aligns coherently with the fossil spreading direction across the entire PLUME network. This result supports the idea that flow-aligned asthenospheric material is "frozen" to the bottom of the cooling plate as it thickens. However, at longer periods, that sense the asthenosphere below the fast direction rotates incoherently, indicating that flow in the asthenosphere is significantly perturbed from the direction of current plate motion. A published shear-wave splitting study (Collins et al., 2012) found no evidence for such an anomalous mantle flow and therefore seems inconsistent with our results. We present initial surface-wave inversion results that suggest that plume-related mantle flow does not reach into the upper lithosphere. We also present forward-modeling results attempting to reconcile both surface-wave and shear-wave splitting observations. Collins, J.A., Wolfe, C.J. and Laske, G., 2012. Shear wave splitting at the Hawaiian hots pot from the PLUME land and ocean bottom seismometer deployments, Geochem. Geophys. Geosys., 13, doi:10.1029/2011gc003881.

  19. Turbulent Heat Transfer in Ribbed Pipe Flow

    NASA Astrophysics Data System (ADS)

    Kang, Changwoo; Yang, Kyung-Soo

    2012-11-01

    From the view point of heat transfer control, surface roughness is one of the popular ways adopted for enhancing heat transfer in turbulent pipe flow. Such a surface roughness is often modeled with a rib. In the current investigation, Large Eddy Simulation has been performed for turbulent flow in a pipe with periodically-mounted ribs at Reτ=700, Pr=0.71, and p / k =2, 4, and 8. Here, p and k represent the pitch and rib height, respectively. The rib height is fixed as one tenth of the pipe radius. The profiles of mean velocity components, mean temperature, root-mean-squares (rms) of temperature fluctuation are presented at the selected streamwise locations. In comparison with the smooth-pipe case at the same Re and Pr, the effects of the ribs are clearly identified, leading to overall enhancement of turbulent heat transfer in terms of Nu. The budget of temperature variance is presented in the form of contours. The results of an Octant analysis are also given to elucidate the dominant events. Our LES results shed light on a complete understanding of the heat-transfer mechanisms in turbulent ribbed-pipe flow which has numerous applications in engineering. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. 2012013019).

  20. Shear wave splitting, mantle flow, and young tectonomagmatism in the High Lava Plains of Oregon

    NASA Astrophysics Data System (ADS)

    Long, M. D.; Klaus, A.; Fouch, M. J.; James, D. E.; Wagner, L. S.

    2008-12-01

    The High Lava Plains (HLP) of southeastern and central Oregon represents a young (< 15 Ma), bimodal volcanic province that exhibits an age progression in rhyolitic volcanism towards the northwest, along with widespread basaltic volcanic activity. The age progression in the rhyolites is oblique to plate motion and approximately mirrors that of the presumed Yellowstone hotspot track, as inferred from Snake River Plain volcanism. Several models have been proposed to explain volcanic activity in the HLP; these variously invoke interactions between the tail of the inferred Yellowstone plume and asthenospheric corner flow, the rollback and steepening of the Cascadia slab, and/or significant lithospheric extension, perhaps associated with the Basin and Range province to the south. A temporary array of broadband seismometers (the High Lava Plains experiment, jointly operated by the Carnegie Institution of Washington and Arizona State University) was deployed in the region beginning in 2006. As of fall 2008 118 sites have been occupied as part of the HLP seismic experiment (with 104 currently operating), in addition to the broadband stations operated here as part of the USArray Transportable Array (TA). Here we present a data set of shear wave splitting measurements for SKS phases recorded at ~ 150 stations during the period 2006-2008. SKS splitting is used to characterize upper mantle anisotropy and when properly interpreted can place constraints on the geometry of upper mantle flow associated with tectonic processes. Stations in the HLP exhibit significant shear wave splitting, with average split times between ~ 0.8 seconds and ~ 3.0 seconds and average fast directions near N80°E. Although the backazimuthal coverage for SKS is not ideal, there is little evidence for backazimuthal variations in splitting parameters that might suggest complex anisotropic structure. The average split time in the HLP is ~ 1.8 sec, well above the global average of ~ 1 sec for continental

  1. Triaxial thermopile array geo-heat-flow sensor

    DOEpatents

    Carrigan, C.R.; Hardee, H.C.; Reynolds, G.D.; Steinfort, T.D.

    1990-01-01

    A triaxial thermopile array geothermal heat flow sensor is designed to measure heat flow in three dimensions in a reconstituted or unperturbed subsurface regime. Heat flow can be measured in conductive or permeable convective media. The sensor may be encased in protective pvc tubing and includes a plurality of thermistors and an array of heat flow transducers produce voltage proportional to heat flux along the subsurface regime and permit direct measurement of heat flow in the subsurface regime. The presence of the thermistor array permits a comparison to be made between the heat flow estimates obtained from the transducers and heat flow calculated using temperature differences and Fourier's Law. The device is extremely sensitive with an accuracy of less than 0.1 Heat Flow Units (HFU) and may be used for long term readings. 6 figs.

  2. Triaxial thermopile array geo-heat-flow sensor

    DOEpatents

    Carrigan, Charles R.; Hardee, Harry C.; Reynolds, Gerald D.; Steinfort, Terry D.

    1992-01-01

    A triaxial thermopile array geothermal heat flow sensor is designed to measure heat flow in three dimensions in a reconstituted or unperturbed subsurface regime. Heat flow can be measured in conductive or permeable convective media. The sensor may be encased in protective pvc tubing and includes a plurality of thermistors and an array of heat flow transducers arranged in a vertical string. The transducers produce voltage proportional to heat flux along the subsurface regime and permit direct measurement of heat flow in the subsurface regime. The presence of the thermistor array permits a comparison to be made between the heat flow estimates obtained from the transducers and heat flow calculated using temperature differences and Fourier's Law. The device is extremely sensitive with an accuracy of less than 0.1 Heat Flow Units (HFU) and may be used for long term readings.

  3. Reconstructing mantle flow and long-wavelength dynamic topography since the Jurassic Period (GD Division Outstanding ECS Award Lecture)

    NASA Astrophysics Data System (ADS)

    Flament, Nicolas

    2017-04-01

    Global tectonic reconstructions can be used as boundary conditions of forward mantle convection models to simulate past mantle flow and long-wavelength dynamic topography. The predictions of such models can be compared to seismic tomography, to estimates of residual topography and to geological indicators of past vertical motions. Here we present models that reproduce the present-day structure of the lower mantle, including two large structures that resemble the Pacific and African Large Low Shear Velocity Provinces (LLSVPs, ˜15,000 km in diameter) and a smaller structure that resembles the recently discovered Perm Anomaly (˜1,000 km in diameter). The match between predicted and seismically inferred lower mantle structure is quantified across a series of mantle flow and tomography models. In the models, the Perm-like anomaly forms in isolation within a closed and long-lived subduction network (East Asia, Northern Tethys and Mongol-Okhotsk) ˜22,000 km in circumference before migrating ˜1,500 km westward at an average rate of 1 cm yr-1 since 150 million years ago. These results indicate a greater mobility of deep mantle structures than previously recognized, and illustrate that the predictive power of mantle flow models has significantly increased over the last thirty years. We suggest that the mobile Perm Anomaly could be linked to the ˜258 Ma Emeishan volcanics, in contrast to the previously proposed ˜251 Ma Siberian Traps. We also compare the present-day dynamic topography predicted by forward mantle flow models to residual topography models, and show that radial and lateral viscosity variations significantly influence the distribution of power of predicted dynamic topography as a function of spherical harmonic degree. We finally show how past vertical motions preserved in the geological record and the present-day position of slabs in the mantle inferred from seismic tomography may be used to constrain tectonic reconstructions and mantle rheology, including

  4. Terrestrial heat flow distribution in Japan area based on the temperature logging in the borehole of NIED Hi-net

    NASA Astrophysics Data System (ADS)

    Matsumoto, T.

    2007-12-01

    , the slab-derived fluids, which cause fracturing within the crust, result in easier transfer of fluids, mixed with mantle helium, to the surface (Notsu et al., 2006). This movement of the slab-derived fluids also transports the heat of mantle wedge, which cause the terrestrial high heat flow anomaly.

  5. Core cooling by subsolidus mantle convection. [thermal evolution model of earth

    NASA Technical Reports Server (NTRS)

    Schubert, G.; Cassen, P.; Young, R. E.

    1979-01-01

    Although vigorous mantle convection early in the thermal history of the earth is shown to be capable of removing several times the latent heat content of the core, a thermal evolution model of the earth in which the core does not solidify can be constructed. The large amount of energy removed from the model earth's core by mantle convection is supplied by the internal energy of the core which is assumed to cool from an initial high temperature given by the silicate melting temperature at the core-mantle boundary. For the smaller terrestrial planets, the iron and silicate melting temperatures at the core-mantle boundaries are more comparable than for the earth; the models incorporate temperature-dependent mantle viscosity and radiogenic heat sources in the mantle. The earth models are constrained by the present surface heat flux and mantle viscosity and internal heat sources produce only about 55% of the earth model's present surface heat flow.

  6. Seismic Anisotropy and Mantle Flow from Ridge to Trench Below the Gorda-Juan de Fuca Plate System

    NASA Astrophysics Data System (ADS)

    Martin-Short, R.; Allen, R. M.; Bastow, I. D.; Richards, M. A.; Totten, E. J.

    2015-12-01

    Tectonic plates are underlain by a low viscosity layer of the mantle, the asthenosphere, which flows. Flow in the asthenosphere may be induced by motion of the overriding plate, or by deeper mantle convection. Measurement of seismic anisotropy, the directional dependence of seismic wave speed, is an important tool in understanding mantle structure and dynamics, and is often used to infer information about asthenospheric flow geometry. However, isolation of asthenospheric signals is challenging because most seismometers are located on the continents, whose complex structure influences seismic waves en-route to the surface. Thus the challenge is to record seismic data on oceanic lithosphere, which is much thinner and simpler. We present stacked shear wave splitting results from phases 1 to 3 of the Cascadia Initiative: An ambitious, large-scale deployment of offshore seismometers across the Gorda and Juan-de-Fuca plates. Fast splitting directions (FSD) can approximate mantle flow geometry, thus for the first time allowing an interpretation of flow beneath an ocean basin from ridge to trench. The Juan-de-Fuca plate appears able to influence mantle flow: FSD rotate towards the absolute plate motion direction (APM) with increasing distance from the ridge. In contrast, Gorda FSD align with the motion of the adjacent Pacific plate rather than Gorda APM. These observations suggest that drag caused by motion the Pacific plate controls asthenospheric flow beneath Gorda, and thus that the Gorda plate may be decoupled from the asthenosphere. We also construct a simple geodynamic model of this situation, which supports its plausibility. Our findings imply that tectonic plates must reach a minimum size and speed before they are able to exert influence on asthenospheric flow.

  7. Subsurface heat flow in an urban environment

    NASA Astrophysics Data System (ADS)

    Ferguson, Grant; Woodbury, Allan D.

    2004-02-01

    The subsurface temperature field beneath Winnipeg, Canada, is significantly different from that of the surrounding rural areas. Downward heat flow to depths as great as 130 m has been noted in some areas beneath the city and groundwater temperatures in a regional aquifer have risen by as much as 5°C in some areas. Numerical simulation of heat transport supports the conjecture that these temperature changes can be largely attributed to heat loss from buildings and the temperature at any given point is sensitive to the distance from and the age of any buildings. The effect is most noticable when buildings are closely spaced, which is typical of urban areas. Temperature measurements in areas more than a few hundred meters away from any heated structure were only a few tenths of a degree Celsius greater than those observed outside the city, suggesting that other reasons for increases in subsurface temperature, such as changes in surface cover or climate change, may be responsible for some of the some of the observed increase in temperatures. These sources of additional heat to the subsurface make it difficult to resolve information on past climates from temperatures measured in boreholes and monitoring wells. In some areas, the temperature increases may also have an impact on geothermal energy resources. This impact might be in the form of an increase in heat pump efficiency or in the case of the Winnipeg area, a decrease in the efficiency of direct use of groundwater for cooling.

  8. Creep of Bridgmanite Analog, Neighborite (NaMgF3), and Implications for Viscous Flow in the Lower Mantle

    NASA Astrophysics Data System (ADS)

    Kaercher, P. M.; Mecklenburgh, J.; Mariani, E.; Wheeler, J.

    2016-12-01

    The rheology of the lower mantle directly influences mantle viscosity and strength and therefore affects a number of geophysical processes including mantle mixing, formation of mantle plumes and hotspots, slab subduction and stagnation, and plate motion. Experimental flow laws of lower mantle minerals, which quantify rheology of the lower mantle, are needed to help resolve discrepancies in estimates of lower mantle viscosity, better constrain geophysical models, and answer a number of outstanding questions such as, why slabs descend to different depths, and why the lower mantle is mostly isotropic despite large strains predicted by convection models. However, we lack natural lower mantle samples from which to infer deformation history. Furthermore, deformation experiments at lower mantle pressures and temperatures are challenging, and strain rates and stress cannot always be precisely controlled or measured. As a valuable alternative we have synthesized and deformed neighborite (NaMgF3), a low pressure analog of bridgmanite (MgSiO3), the most abundant mineral in the lower mantle and the Earth. Neighborite was deformed at 200 MPa confining pressure and between 500-700°C in compression using a fluid-medium deformation apparatus, and in torsion using a Patterson rig. In these experiments strain rate and stress can be accurately controlled and measured, and flow laws reliably determined. In addition we have recovered samples and examined deformation microstructures in a scanning electron microscope using electron backscatter diffraction. Preliminary mechanical results show a switch from linear-viscous deformation at lower stress (<50 MPa) to power law creep accommodated by grain boundary sliding at higher stress (>50 MPa). We also see strain weakening. Microstructures of samples deformed at a range of stress steps show grain boundary migration recrystallization (likely from lower stress) and crystallographic preferred orientation with poles to (100) planes parallel to

  9. Mantle flow and oceanic crust formation during the opening of the Tyrrhenian back-arc basin

    NASA Astrophysics Data System (ADS)

    Magni, Valentina

    2017-04-01

    The formation of the Tyrrhenian back-arc basin occurred through short-lived episodes of fast spreading alternated with periods of slow rifting. I present results from three-dimensional numerical models of laterally varying subduction to explain the mechanism of back-arc basin opening and its episodic spreading behaviour. Moreover, I explore the consequences of this alternation between fast and slow episodes of extension on the production of new oceanic crust in the back-arc basin. Results show that the presence of continental plates (i.e. Africa and Adria) nearby the oceanic subduction of the Ionian slab produces localised deformation within the overriding plate and it is, thus, crucial for the opening of the back-arc basin. Moreover, the occurrence of collision results in the formation of two slab windows at the ocean-continent boundaries, which is in very good agreement with what is observed in the Central Mediterranean, nearby the Calabrian slab. During the evolution of the system the trench velocity shows pulses of fast trench retreat that last a few millions of years. This is associated with episodes of more intense melting of the asthenosphere rising at the back-arc basin. Finally, these three-dimensional models are used to track the mantle flow throughout the model evolution and the source of the mantle melting at the spreading centre.

  10. Rheology of two-phase composites: implications for flow properties of the lower mantle

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Nishiyama, N.; Hilairet, N.; Fiquet, G.; Tsuchiya, T.

    2011-12-01

    We examine flow properties and deformation-induced fabric evolution in two-phase composites using the deformation DIA (D-DIA) and the high-pressure x-ray tomography microscope (HPXTM) with monochromatic synchrotron radiation. Stress-strain curves were determined on an analog lower mantle material CaGeO3 perovskite (GePv) plus MgO. The sintered polycrystalline rock was synthesized from the disproportionation reaction of CaMgGeO4 (olivine) - GePv+MgO at 12 GPa and 1573 K for 4 h. The sample contains 28 vol% MgO, and is an excellent analog material for the lower mantle. Scanning electron microscopy showed that the average grain size was about 1 micron. The sample was deformed in the D-DIA at pressures from 4 to 12 GPa, temperatures 600 to 1200 K, and strain rates from 1x to 3x10-5 s-1. The maximum axial strain was 16 %. Elastic constants for GePv were calculated using first-principles with the generalized gradient corrections (GGC) technique. In order to examine effects of the second phase on flow properties, a pure GePv sample was deformed under identical conditions. Flow properties of MgO are available from our previous studies [1]. The relative stress levels in GePv and MgO in the composite sample are in general agreement with numerical simulations [2]. Another analog, a mixture of San Carlos olivine and Fe-S, was examined in the HPXTM. The strength contrast of two phases is similar to that of perovskite and ferropericlase. The initial texture was of the load-bearing framework (LBF) type, with isolated "weak" Fe-S grains sounded by "strong" silicate framework. During shear deformation, a strong shape preferred orientation began to develop in the sample at shear strains above 300%, forming an interconnected weak layer (IWL) texture. The development of deformation fabric was continuously monitored by tomographic imaging under high pressure to a maximum shear strain of 1300%. Applications of these results to dynamics of the lower mantle are discussed. [1] Uchida, T

  11. Critical heat flux in subcooled flow boiling

    NASA Astrophysics Data System (ADS)

    Hall, David Douglas

    The critical heat flux (CHF) phenomenon was investigated for water flow in tubes with particular emphasis on the development of methods for predicting CHF in the subcooled flow boiling regime. The Purdue University Boiling and Two-Phase Flow Laboratory (PU-BTPFL) CHF database for water flow in a uniformly heated tube was compiled from the world literature dating back to 1949 and represents the largest CHF database ever assembled with 32,544 data points from over 100 sources. The superiority of this database was proven via a detailed examination of previous databases. The PU-BTPFL CHF database is an invaluable tool for the development of CHF correlations and mechanistic models that are superior to existing ones developed with smaller, less comprehensive CHF databases. In response to the many inaccurate and inordinately complex correlations, two nondimensional, subcooled CHF correlations were formulated, containing only five adjustable constants and whose unique functional forms were determined without using a statistical analysis but rather using the parametric trends observed in less than 10% of the subcooled CHF data. The correlation based on inlet conditions (diameter, heated length, mass velocity, pressure, inlet quality) was by far the most accurate of all known subcooled CHF correlations, having mean absolute and root-mean-square (RMS) errors of 10.3% and 14.3%, respectively. The outlet (local) conditions correlation was the most accurate correlation based on local CHF conditions (diameter, mass velocity, pressure, outlet quality) and may be used with a nonuniform axial heat flux. Both correlations proved more accurate than a recent CHF look-up table commonly employed in nuclear reactor thermal hydraulic computer codes. An interfacial lift-off, subcooled CHF model was developed from a consideration of the instability of the vapor-liquid interface and the fraction of heat required for liquid-vapor conversion as opposed to that for bulk liquid heating. Severe

  12. Small-scale upper mantle flow during the initiation of craton destruction

    NASA Astrophysics Data System (ADS)

    Zhao, Liang; Wang, Kun; Xu, Xiaobing

    2017-04-01

    owing to the fossil anisotropy in the lithosphere during the N-S shortening in Jurassic. The other is located in the Solonker suture zone beneath where the Moho and lithosphere and asthenosphere boundary (LAB) have sharp variation in depth. It suggests that the subduction of Pacific plate apparently reactivates the upper mantle of the north edge of the NCC but has minor effects westwards. The inconsistency in FPDs may result from small-scale mantle flow in the upper mantle, which could be the dominant operating mode of the Pacific subduction during the initiation of cratonic destruction.

  13. Heat flow diagnostics for helicon plasmas

    SciTech Connect

    Berisford, Daniel F.; Bengtson, Roger D.; Raja, Laxminarayan L.; Cassady, Leonard D.; Chancery, William J.

    2008-10-15

    We present experimental studies of power balance in an argon helicon discharge. An infrared camera measures the heating of the dielectric tube containing a helicon discharge based on measurement of temperature profiles of the tube surface before and after a rf pulse. Using this diagnostic, we have measured surface heating trends at a variety of operating conditions on two helicon systems: the 10 kW VASIMR VX-50 experiment and the University of Texas at Austin 1 kW helicon experiment. Power losses downstream from the antenna are measured using thermocouples and probes. The heating of the dielectric tube increases with decreasing magnetic fields, higher gas flow rates, and higher molecular mass of the gas. These preliminary results suggest that cross-field particle diffusion contributes a significant proportion of the energy flux to the wall.

  14. Heat flow diagnostics for helicon plasmas.

    PubMed

    Berisford, Daniel F; Bengtson, Roger D; Raja, Laxminarayan L; Cassady, Leonard D; Chancery, William J

    2008-10-01

    We present experimental studies of power balance in an argon helicon discharge. An infrared camera measures the heating of the dielectric tube containing a helicon discharge based on measurement of temperature profiles of the tube surface before and after a rf pulse. Using this diagnostic, we have measured surface heating trends at a variety of operating conditions on two helicon systems: the 10 kW VASIMR VX-50 experiment and the University of Texas at Austin 1 kW helicon experiment. Power losses downstream from the antenna are measured using thermocouples and probes. The heating of the dielectric tube increases with decreasing magnetic fields, higher gas flow rates, and higher molecular mass of the gas. These preliminary results suggest that cross-field particle diffusion contributes a significant proportion of the energy flux to the wall.

  15. Heat flow diagnostics for helicon plasmasa)

    NASA Astrophysics Data System (ADS)

    Berisford, Daniel F.; Bengtson, Roger D.; Raja, Laxminarayan L.; Cassady, Leonard D.; Chancery, William J.

    2008-10-01

    We present experimental studies of power balance in an argon helicon discharge. An infrared camera measures the heating of the dielectric tube containing a helicon discharge based on measurement of temperature profiles of the tube surface before and after a rf pulse. Using this diagnostic, we have measured surface heating trends at a variety of operating conditions on two helicon systems: the 10kW VASIMR VX-50 experiment and the University of Texas at Austin 1kW helicon experiment. Power losses downstream from the antenna are measured using thermocouples and probes. The heating of the dielectric tube increases with decreasing magnetic fields, higher gas flow rates, and higher molecular mass of the gas. These preliminary results suggest that cross-field particle diffusion contributes a significant proportion of the energy flux to the wall.

  16. Heat flow and near-surface radioactivity in the Australian continental crust

    USGS Publications Warehouse

    Sass, J.H.; Jaeger, J.C.; Munroe, Robert J.

    1976-01-01

    Heat-flow data have been obtained at 44 sites in various parts of Australia. These include seven sites from the old (~ 2500 m.y.) Precambrian shield of Western Australia, seventeen from the younger (~ 600- 2000 m.y.) Precambrian rocks of South Australia, the Northern Territory, and Queensland, and twenty within the eastern Paleozoic and younger rocks. Thirty of the sites are located where no previous heat-flow data existed, and the remainder provide significant extensions or refinements of areas previously studied. Where the holes studied penetrated the crystalline basement rocks, or where the latter rocks were exposed within a few kilometers of the holes, the upper crustal radiogenic heat production has been estimated based on gamma-ray spectrometric determinations of U, Th, and K abundances. Three heat-flow provinces are recognized in Australia based on the linear relation (q = q* + DA0 ) between heat flow q and surface radioactivity A0. New data from the Western Australian shield support earlier studies showing that heat flow is low to normal with values ranging from 0.7 to 1.2 hfu and with the majority of values less than 1.0 hfu, and the parameters q* = 0.63 hfu and 0 = 4.5 km determined previously were confirmed. Heat flow in the Proterozoic shield of central Australia is quite variable, with values ranging between about l and 3 hfu. This variability is attributed mainly to variations in near-surface crustal radioactivity. The parameters of the heat-flow line are q* = 0.64 hfu and 0 = 11.1 km and moderately high temperatures are predicted for the lower crust and upper mantle. Previous suggestions of a band of l ow- to - normal heat flow near the coast in eastern Australia were confirmed in some areas, but the zone is interrupted in at least one region (the Sydney Basin), where heat flow is about 2.0 hfu over a large area. The reduced heat flow, q*, in the Paleozoic intrusive rocks of eastern Australia varies from about 0.8 to 2.0 hfu . This variability might

  17. Mantle flow beneath a continental strike-slip fault: Postseismic deformation after the 1999 Hector Mine earthquake

    USGS Publications Warehouse

    Pollitz, F.F.; Wicks, C.; Thatcher, W.

    2001-01-01

    Two recent large earthquakes in the Mojave Desert, California - the magnitude 7.3 1992 Landers and magnitude 7.1 1999 Hector Mine earthquakes - have each been fog[owed by elevated crustal strain rates over periods of months and years. Geodetic data collected after the Hector Mine earthquake exhibit a temporaLLy decaying horizOntaL velocity field and a quadrant uplift pattern opposite to that expected for LocaLized shear beneath the earthquake rupture. We interpret the origin of this accelerated crustal deformation to be vigorous flow in the upper mantle in response to the stress changes generated by the earthquake. Our results suggest that transient flow in the upper mantle is a fundamental component of the earthquake cycle and that the Lower crust is a coherent stress guide coupling the upper crust with the upper mantle.

  18. Volcanism on Mercury (dikes, lava flows, pyroclastics): Crust/mantle density contrasts, the evolution of compressive stress and the presence of mantle volatiles

    NASA Astrophysics Data System (ADS)

    Wilson, L.; Head, J. W., III

    2008-09-01

    Background. There is great uncertainty about the internal structure of Mercury and the composition of the mantle [e.g., 1, 2]. The high mean density of the body suggests that it may have lost parts of its crust and mantle in a giant impact at some stage after most of its initial accretion was sufficiently complete that at least partial separation of a core had occurred. It is the uncertainty about the timing of the giant impact, and hence the physico-chemical state of proto-Mercury at the time that it occurred, that leads to difficulties in predicting the interior structure and mantle composition. However, it seems reasonable to assume that the Mercury we see today has some combination of a relatively low-density crust and a relatively highdensity mantle; uncertainty remains about the presence and types of volatiles [2]. The second uncertainty is the nature of the surface plains units, specifically, are these lava flows and pyroclastics erupted from the interior, or impact-reworked earlier crust [3-5] (Figs. 1-2)? The detection of candidate pyroclastic deposits [4] has very important implications for mantle volatiles. Furthermore, whatever the surface composition, the presence of planet-wide systems of wrinkle ridges and thrust faults implies that a compressive crustal stress regime became dominant at some stage in the planet's history [3, 6]. If the plains units are indeed lava flows, then the fact that the products of the compressive regime deform many plains units suggests that the development of the compressive stresses may have played a vital role in determining when and if surface eruptions of mantle-derived magmas could occur. This would be analogous to the way in which the change with time from extensional to compressive global stresses in the lithosphere of the Moon influenced the viability of erupting magmas from deep mantle sources [7-9]. Analysis: To investigate the relationship between lithospheric stresses and magma eruption conditions [e.g., 9-11] we

  19. Mantle Flow Implications across Easter and Southern Africa from Shear Wave Splitting Measurements

    NASA Astrophysics Data System (ADS)

    Ramirez, C.; Nyblade, A.; Bagley, B. C.; Mulibo, G. D.; Tugume, F.; Wysession, M. E.; Wiens, D.; van der Meijde, M.

    2015-12-01

    In this study, we present new shear wave splitting results from broadband seismic stations in Botswana and Namibia, and combine them with previous results from stations in Kenya, Uganda, Tanzania, Malawi, Zambia, South Africa, Mozambique, Zimbabwe, and Angola to further examine the pattern of seismic anisotropy across southern Africa. The new results come from stations in northern Namibia and Botswana, which help to fill in large gaps in data coverage. Our preliminary results show that fast polarization directions overall trend in a NE orientation. The most noticeable measurements that deviate from this pattern are located around the Archean Tanzania Craton in eastern Africa. The general NE pattern of fast polarization directions is attributed to mantle flow linked to the African superplume. Smaller scale variations from this general direction can be explained by shape anisotropy in the lithosphere in magmatic regions in the East African rift system and to fossil anisotropy in the Precambrian lithosphere.

  20. Combined micro and macro geodynamic modelling of mantle flow: methods, potentialities and limits.

    NASA Astrophysics Data System (ADS)

    Faccenda, M.

    2015-12-01

    Over the last few years, geodynamic simulations aiming at reconstructing the Earth's internal dynamics have increasingly attempted to link processes occurring at the micro (i.e., strain-induced lattice preferred orientation (LPO) of crystal aggregates) and macro scale (2D/3D mantle convection). As a major outcome, such a combined approach results in the prediction of the modelled region's elastic properties that, in turn, can be used to perform seismological synthetic experiments. By comparison with observables, the geodynamic simulations can then be considered as a good numerical analogue of specific tectonic settings, constraining their deep structure and recent tectonic evolution. In this contribution, I will discuss the recent methodologies, potentialities and current limits of combined micro- and macro-flow simulations, with particular attention to convergent margins whose dynamics and deep structure is still the object of extensive studies.

  1. Laboratory Investigations of Lava Flow Heat Transfer

    NASA Astrophysics Data System (ADS)

    Fagents, S. A.; Rumpf, M. E.; Hamilton, C. W.

    2011-12-01

    To investigate the effectiveness with which lava can heat substrates of different types, we conducted a suite of experiments in which molten basalt was poured onto solid or particulate materials, and the downward propagation of the heat pulse was measured. The motivation for this work lies in seeking to understand how lava flows on the Moon would have heated the underlying regolith, and thus to determine the depths at which solar wind particles implanted in the regolith would have been protected from the heat of the overlying flow. Extraction and analysis of ancient solar wind samples would provide a wealth of information on the evolution and fate of the Sun. Our experimental device consists of a box constructed from 1"-thick calcium silicate sheeting with interior dimensions of 20 x 20 x 25 cm. The substrate material (a particulate lunar regolith simulant or solid basalt) occupies the lower 15 cm of the box, which is embedded with an array of 8 thermocouples. Up to 6 kg of crushed basalt collected from the 2010 Kilauea lava flows is heated to supraliquidus temperatures and poured directly onto the substrate. The evolution of the temperature profile within the lava flow and substrate is recorded as the basalt cools, and the surface temperature distribution is recorded using a Forward Looking Infrared Radiometer (FLIR) video camera. We have been using the experimental data sets to validate a numerical model of substrate heating. If the physics is appropriately formulated, the model will accurately predict both surface and internal temperature distribution as a function of time. A key issue has been incorporation of valid temperature-dependent thermophysical properties, because particulate materials are not well characterized at elevated temperatures. Regolith thermal conductivity in particular exerts a strong control over the depth of penetration of the thermal wave, so its accurate description is essential for a robust model. Comparison of experimental vs. modeled

  2. Geomechanical Fracturing with Flow and Heat

    SciTech Connect

    2009-01-01

    The GeoFracFH model is a particle-based discrete element model (DEM) that has been coupled with fluid flow and heat conduction/convection. In this model, the rock matrix material is represented by a network of DEM particles connected by mechanical bonds (elastic beams in this case, see Figure 1, gray particles connected by beams). During the simulation process, the mechanical bonds that have been stretched or bent beyond a critical strain (both tensile and shear failures are simulated) are broken and removed from the network in a progressive manner. Bonds can be removed from the network with rates or probabilities that depend on their stress or strain, or the properties of the discrete elements and bonds can be varied continuously to represent phenomena such as creep, strain hardening, and chemical degradation. The coupling of a DEM geomechanical model with models for Darcy flow and heat transport is also illustrated in Figure 1. Darcy flow and heat transport equations are solved on an underlying fixed finite difference grid with evolving porosity and permeability for each grid cell that depends on the local structure of the discrete element network (such as the DEM particle density). The fluid pressure gradient exerts forces on individual elements of the DEM network, which then deforms and fractures the rock matrix. The deformation/fracturing in turn changes the permeability which again changes the evolution of fluid pressure, coupling the two phenomena. The intimate coupling between fracturing, fluid flow, and thermal transport makes the GeoFracFH model, rather than conventional continuum mechanical models, necessary for coupled hydro-thermal-mechanical problems in the subsurface.

  3. Heat flow and bending-related faulting at subduction trenches: Case studies offshore of Nicaragua and Central Chile

    NASA Astrophysics Data System (ADS)

    Grevemeyer, Ingo; Kaul, Norbert; Diaz-Naveas, Juan L.; Villinger, Heinrich W.; Ranero, Cesar R.; Reichert, Christian

    2005-07-01

    Detailed heat flow surveys on the oceanic trench slope offshore Nicaragua and Central Chile indicate heat flow values lower than the expected conductive lithospheric heat loss and lower than the global mean for crust of that age. Both areas are characterised by pervasive normal faults exposing basement in a setting affected by bending-related faulting due to plate subduction. The low heat flow is interpreted to indicate increased hydrothermal circulation by the reactivation and new creation of faults prior to subduction. A previous global approach [1] [Stein C.A., Heat flow and flexure at subduction zones, Geophys. Res. Lett. 30 (2003) doi:10.1029/2003GL018478] failed to detect similar features in the global but sparse data set. Detailed inspection of the global data set suggests that the thickness of the sedimentary blanket on the incoming plate is an important factor controlling the local hydrogeological regime. Areas with a relatively thick sedimentary cover do not show any heat flow anomaly while areas where normal faulting exposes basement suffer from increased hydrothermal activity. Both geochemical data from arc volcanoes and seismological evidence from intra slab events suggest that the flux of water into the deep subduction zone is larger in areas characterised by reactivated hydrothermal circulation. It is reasonable to assume that the larger water flux is caused by serpentinization of the upper mantle, facilitated by bending-related faults cutting into the upper mantle.

  4. Lunar Heat Flow: A Global Prospective

    NASA Astrophysics Data System (ADS)

    Siegler, M. A.; Paige, D. A.; Williams, J.; Smrekar, S. E.

    2012-12-01

    Surface heat flow is a fundamental measurement for determining a body's interior composition, structure and evolution. Here we attempt to construct a global picture of heat flux from the Lunar interior including 3D thermal modeling and new measurements from Diviner Infrared Radiometer aboard the Lunar Reconnaissance Orbiter.___ Internal heat, due to radioactive decay, core crystallization, tidal dissipation and heat of formation, controls the occurrence of internal convection, crustal strength and thickness, volcanism, and surface tectonics. Near surface measurements, such as those of the Apollo Heat Flow Experiment [1], can therefore offer a deeper window into the Moon's origin and structure. However, the Apollo era measurements are believed to be biased by local subsurface density and radiogenic anomalies, and may not offer an easily interpretable measurement of global lunar heat flux ([2],[3]). Both the Apollo 15 and 17 landing sites lay at the edge of Mare/Highland density and crustal thickness boundaries and lay within a thorium-rich region of the Moon known as the Procellarum KREEP terrain [4]. Detailed models of the subsurface structure beneath these sites, including local crustal thickness, thermal/density properties, surface temperature and radiogenic nuclide concentration have not been feasible or fully informed in the past. Therefore, most authors simply examined a single effect or a conceptual model ([2],[3],[5]). With new computing tools (namely Comsol Multiphysics and Diviner Thermal models) and spacecraft measurement (namely gravity, topography, Gamma-ray spectra, and surface temperature) we seek to attempt to combine all available data.___ This data includes new measurements of several locations within impact craters near the lunar poles in which temperatures as low as 20 ± 2 K are observed [6], [7]. Watson [8] proposed such low temperature measurements could be used to infer internal heat flux. These low temperature values are of particular

  5. A coupled heat and water flow apparatus

    SciTech Connect

    Mohamed, A.M.O.; Caporouscio, F.; Yong, R.N. ); Cheung, C.H. ); Kjartanson, B.H. )

    1993-03-01

    Safe and permanent disposal of radioactive waste requires isolation of a number of diverse chemical elements form the environment. The Canadian Nuclear Fuel Waste Management Program is assessing the concept of disposing of waste in a vault excavated at a depth of 500 to 1000 m below the ground surface in plutonic rock of the Canadian Shield. The temperatures and hydraulic potential in the buffer and back fill material were investigated. To study the performance of a compacted buffer material under thermal and isothermal conditions, a coupled heat and water flow apparatus is designed and presented. In the preliminary design, a one-dimensional flow of heat and water was not achieved. however, control of temperature gradient, existence of one-dimensional flow, and uniformity of temperature and volumetric water content distributions at any cross section within the specimen are achieved in the modified design. Experimental results have shown that the temperature stabilizes very rapidly after a period of approximately 0. 107 days. The moisture moves away from the hot end along the longitudinal direction of the specimen due to imposed thermal gradient. The time required for moisture to stabilize is in order of days. 17 refs., 17 figs., 3 tabs.

  6. Investigating seismic anisotropy beneath the Reykjanes Ridge using models of mantle flow, crystallographic evolution, and surface wave propagation

    NASA Astrophysics Data System (ADS)

    Gallego, A.; Ito, G.; Dunn, R. A.

    2013-08-01

    Surface wave studies of the Reykjanes Ridge (RR) and the Iceland hotspot have imaged an unusual and enigmatic pattern of two zones of negative radial anisotropy on each side of the RR. We test previously posed and new hypotheses for the origin of this anisotropy, by considering lattice preferred orientation (LPO) of olivine A-type fabric in simple models with 1-D, layered structures, as well as in 2-D and 3-D geodynamic models with mantle flow and LPO evolution. Synthetic phase velocities of Love and Rayleigh waves traveling parallel to the ridge axis are produced and then inverted to mimic the previous seismic studies. Results of 1-D models show that strong negative radial anisotropy can be produced when olivine a axes are preferentially aligned not only vertically but also subhorizontally in the plane of wave propagation. Geodynamic models show that negative anisotropy on the sides of the RR can occur when plate spreading impels a corner flow, and in turn a subvertical alignment of olivine a axes, on the sides of the ridge axis. Mantle dehydration must be invoked to form a viscous upper layer that minimizes the disturbance of the corner flow by the Iceland mantle plume. While the results are promising, important discrepancies still exist between the observed seismic structure and the predictions of this model, as well as models of a variety of types of mantle flow associated with plume-ridge interaction. Thus, other factors that influence seismic anisotropy, but not considered in this study, such as power-law rheology, water, melt, or time-dependent mantle flow, are probably important beneath the Reykjanes Ridge.

  7. Revised lunar heat-flow values

    NASA Technical Reports Server (NTRS)

    Langseth, M. G.; Keihm, S. J.; Peters, K.

    1976-01-01

    The 3.5- and 2-year subsurface temperature histories at the Apollo 15 and 17 heat-flow sites have been analyzed, and the results yield significantly lower thermal conductivity determinations than the results of previous short-term experiments. The thermal conductivity determined by probes at a depth of about 150 cm and 250 cm lies in the range 0.9-1.3 times 10 to the -4th W/cm K. On the basis of measurements of variations of surface thorium abundance and inferred crustal thicknesses, the average global heat flux is estimated to be about 1.8 microwatts/sq cm. This requires a uranium concentration of 46 ppb.

  8. Hamiltonian thermostats fail to promote heat flow

    NASA Astrophysics Data System (ADS)

    Hoover, Wm. G.; Hoover, Carol G.

    2013-12-01

    Hamiltonian mechanics can be used to constrain temperature simultaneously with energy. We illustrate the interesting situations that develop when two different temperatures are imposed within a composite Hamiltonian system. The model systems we treat are ϕ4 chains, with quartic tethers and quadratic nearest-neighbor Hooke's-law interactions. This model is known to satisfy Fourier's law. Our prototypical problem sandwiches a Newtonian subsystem between hot and cold Hamiltonian reservoir regions. We have characterized four different Hamiltonian reservoir types. There is no tendency for any of these two-temperature Hamiltonian simulations to transfer heat from the hot to the cold degrees of freedom. Evidently steady heat flow simulations require energy sources and sinks, and are therefore incompatible with Hamiltonian mechanics.

  9. On Inverting the Heat Flow with Engineering Materials

    NASA Astrophysics Data System (ADS)

    Zhou, Li

    2016-02-01

    Transformation thermodynamics enriches our understanding of heat flow and makes it possible to manipulate the heat flow at will, like shielding, concentrating and inverting. The inverting of heat flow is the extreme one, which has not been studied specifically yet. In this study we firstly inverted the heat flow by transformation thermodynamics and provided the formula for the transformed thermal conductivity. Finite element simulations were conducted to realize the steady and non-steady inverting of heat flow, based on the eccentric-semi-ring structures with natural materials. To do the inverting of heat flow, a simple "L"-shape conductive structure was proposed and verified with an infrared camera. It is concluded that inverting heat flow can be done by both complex engineering materials and some simple structures.

  10. Anomalous subglacial heat flow in central Greenland induced by the Iceland plume.

    NASA Astrophysics Data System (ADS)

    Petrunin, Alexey G.; Rogozhina, Irina; Kaban, Mikhail K.; Vaughan, Alan P. M.; Steinberger, Bernhard; Johnson, Jesse; Koulakov, Ivan; Thomas, Maik

    2013-04-01

    3000 m of ice sheet thickness has ensured that central Greenland has kept it geothermal heat flow (GHF) distribution enigmatic. Some few direct ice temperature measurements from deep ice cores reveal a GHF of 50 to 60 mW/m² in the Summit region and this is noticeably above what would be expected for the underlying Early Proterozoic lithosphere. In addition, indirect estimates from zones of rapid basal melting suggest extreme anomalies 15 to 30 times continental background. Subglacial topography indicates caldera like topographic features in the zones hinting at possible volcanic activity in the past [1], and all of these observations combined hint at an anomalous lithospheric structure. Further supporting this comes from new high-resolution P-wave tomography, which shows a strong thermal anomaly in the lithosphere crossing Greenland from east to west [2]. Rock outcrops at the eastern and western end of this zone indicate significant former magmatic activity, older in the east and younger in the west. Additionally, plate modelling studies suggest that the Greenland plate passed over the mantle plume that is currently under Iceland from late Cretaceous to Neogene times, consistent with the evidence from age of magmatism. Evidence of rapid basal melt revealed by ice penetrating radar along the hypocentre of the putative plume track indicates that it continues to affect the Greenland continental geotherm today. We analyse plume-induced thermal disturbance of the present-day lithosphere and their effects on the central Greenland ice sheet by using a novel evolutionary model of the climate-ice-lithosphere-upper mantle system. Our results indicate that mantle plume-induced erosion of the lithosphere has occurred, explaining caldera-type volcanic structures, the GHF anomaly, and requiring dyke intrusion into the crust during the early Cenozoic. The residual thermo-mechanical effect of the mantle plume has raised deep-sourced heat flow by over 25 mW/m² since 60 Ma and

  11. Terrestrial heat flow and lithosphere structure

    NASA Astrophysics Data System (ADS)

    Lister, Clive

    The International Meeting on Terrestrial Heat Flow and Lithosphere Structure was held at the Castle of Bechyně, Czechoslovakia, during June 1-6, 1987. This meeting brought together 81 participants from 24 countries in a remarkable setting away from interruptions and distractions. The Castle of Bechyně is several hundred years old and is constructed in the Austrian imperial style. The compact, if somewhat primitive, accommodations for the conferees encouraged scientific exchanges and ensured a high level of attendance for the formal sessions.

  12. Controls on the Flow Regime and Thermal Structure of the Subduction Zone Mantle Wedge: A Systematic 2-D and 3-D Investigation

    NASA Astrophysics Data System (ADS)

    Le Voci, Giuseppe; Davies, Rhodri; Goes, Saskia; Kramer, Stephan; Wilson, Cian

    2014-05-01

    Arc volcanism at subduction zones is likely regulated by the mantle wedge's flow regime and thermal structure and, hence, numerous studies have attempted to quantify the principal controls on mantle wedge conditions. Here, we build on these previous studies by undertaking the first systematic 2-D and 3-D numerical investigation, across a wide parameter-space, into how hydration and thermal buoyancy influence the wedge's flow regime and associated thermal structure, above a kinematically driven subducting plate. We find that small-scale convection (SSC), resulting from Rayleigh-Taylor instabilities, or drips, off the base of the overriding lithosphere, is a typical occurrence, if: (i) viscosities are < 5×1018 Pa s; and (ii) hydrous weakening of wedge rheology extends at least 100-150 km from the trench. In 2-D models, instabilities generally take the form of 'drips'. Although along-strike averages of wedge velocities and temperature in 3-D structure are consistent with those in 2-D, fluctuations are larger in 3-D. Furthermore, in 3-D, two separate, but interacting, longitudinal Richter roll systems form (with their axes aligned perpendicular to the trench), the first below the arc region and the second below the back-arc region. These instabilities result in transient and spatial temperature fluctuations of 100-150K, which are sufficient to influence melting, the stability of hydrous minerals and the dehydration of crustal material. Furthermore, they are efficient at eroding the overriding lithosphere, particularly in 3-D and, thus, provide a means to explain observations of high heat flow and thin back-arc lithosphere at many subduction zones, if back-arc mantle is hydrated.

  13. Analysis of a Conductive Heat Flow Profile in the Ecuador Fracture Zone

    NASA Astrophysics Data System (ADS)

    Kolandaivelu, K. P.; Harris, R. N.; Alhamad, A.; Gregory, E. P. M.; Lowell, R. P.; Hobbs, R. W.

    2016-12-01

    We report 18 new conductive heat flow measurements that were collected from a sediment pond located in the Ecuador Fracture Zone (EFZ) in the Panama Basin. These data were collected as part of the major interdisciplinary collaboration entitled Oceanographic and Seismic Characterization of heat dissipation and alteration by hydrothermal fluids at an Axial Ridge (OSCAR), to better understand links between crustal evolution, hydrothermal heat loss and the impact of this heat loss and fluid mass discharge on deep ocean circulation. The data were collected along an East (E) - West (W) transect coincident with a multi-channel seismic reflection profile that extends from the Hole 504B to W of the sediment pond. The co-location of heat flow data with the reflection profile provides information on sediment thickness and underlying crustal structure that aids in the analysis of heat flow in the area. The ages on the younger side (W) and older side (E) of the EFZ at this location are 2Ma and 6Ma respectively, giving a mean predicted heat flow qpred = 284 mW/m2 based on half-space cooling with an uncertainty of +/- 76 mW/m2. Whereas the observed heat flow increases significantly from W-E across the sediment pond with the mean heat flow, qobs = 160 mW/m2. The effect of sedimentation has a negligible effect on the observed heat flow so the heat flow fraction, qobs/qpred, of 56% suggests the 44% deficit primarily results from redistribution of heat by lateral fluid flow in the basement. This analysis does not consider the possible effects of larger scale hydrothermal circulation or mantle related processes. The seismic data indicates that the sediment pond is bounded to the W by an outcrop that penetrates through the sediment layer and a normal fault on the E, providing pathways for fluid circulation between the crust and ocean. A simple aquifer flow model to explain observed deficit yields a fluid flux of approximately 300 ± 200 m2/year per unit of aquifer length perpendicular

  14. Thaw flow control for liquid heat transport systems

    DOEpatents

    Kirpich, Aaron S.

    1989-01-01

    In a liquid metal heat transport system including a source of thaw heat for use in a space reactor power system, the thaw flow throttle or control comprises a fluid passage having forward and reverse flow sections and a partition having a plurality of bleed holes therein to enable fluid flow between the forward and reverse sections. The flow throttle is positioned in the system relatively far from the source of thaw heat.

  15. Coupled flow, thermal and structural analysis of aerodynamically heated panels

    NASA Technical Reports Server (NTRS)

    Thornton, Earl A.; Dechaumphai, Pramote

    1986-01-01

    A finite element approach to coupling flow, thermal and structural analyses of aerodynamically heated panels is presented. The Navier-Stokes equations for laminar compressible flow are solved together with the energy equation and quasi-static structural equations of the panel. Interactions between the flow, panel heat transfer and deformations are studied for thin stainless steel panels aerodynamically heated by Mach 6.6 flow.

  16. New Insights Into the Dynamics of Wedge Areas from a 2d Numerical Study of the Effects of Shear Heating and Mantle Hydration on AN Ocean-Continent Subduction System

    NASA Astrophysics Data System (ADS)

    Regorda, A.; Roda, M.; Marotta, A. M.; Spalla, M. I.

    2015-12-01

    To obtain new insights regarding the mechanisms that favor the exhumation of buried crustal material during ocean-continent subduction, we have developed a 2D finite element model that investigates the effects of shear heating and mantle hydration on the dynamics of wedge areas. The development of the model consists of an initial phase of active oceanic subduction and a second phase, after collision, of pure gravitational evolution; in addition, it considers 3 different velocities of active subduction. Our results show that accounting for mantle hydration is essential to produce small-scale convective flows in a wedge area with the consequent recycling and exhumation of subducted material. In addition, the dynamics of hydrated areas are strictly correlated to the thermal state at the external boundaries of the mantle wedge, and the extension of hydrated areas is independent from the subduction velocities when mantle hydration and shear heating are simultaneously considered during the active subduction phase. During the pure gravitational phase, the hydrated portion of the wedge undergoes a progressive enlargement for models with a high subduction velocity during the previous active phase. Finally, a comparison between the predicted P/T ratios and the P-T conditions recorded by markers during subduction, which show metamorphic gradients that are traditionally considered to be distinctive examples of different phases of evolution in an ocean/continent subduction complex, supports the notion that contrasting P-T conditions can contemporaneously characterize different portions of the subduction system during successive phases of modeled subduction-collision.

  17. Mantle viscosity stratification and flow geometry - Implications for surface motions on earth and Venus

    NASA Technical Reports Server (NTRS)

    Kiefer, Walter S.

    1993-01-01

    For a fixed heat flow, the surface flow velocity of a convecting layer is not strongly sensitive to the variation of viscosity as a function of depth. Thus, the inferred absence of a low viscosity asthenosphere on Venus can not account for the limited surface motions there. The surface velocity is dependent on the convective geometry. Cartesian geometry convection can produce large surface velocities if the high viscosity surface layer is broken in places by weak zones. On the other hand, a high viscosity surface layer may inhibit the development of large surface velocities in axisymmetric convection.

  18. Variations in Moho and Curie depths and heat flow in Eastern and Southeastern Asia

    NASA Astrophysics Data System (ADS)

    Li, Chun-Feng; Wang, Jian

    2016-03-01

    The Eastern and Southeastern Asian regions witness the strongest land-ocean and lithosphere-asthenosphere interactions. The extreme diversity of geological features warrants a unified study for a better understanding of their geodynamic uniqueness and/or ubiquity from a regional perspective. In this paper we have explored a large coverage of potential field data and have detected high resolution Moho and Curie depths in the aforementioned regions. The oldest continental and oceanic domains, i.e. the North China craton and the Pacific and Indian Ocean have been found thermally perturbed by events probably linked to small-scale convection or serpentinization in the mantle and to numerous volcanic seamounts and ridges. The thermal perturbation has also been observed in proximity of the fossil ridge of the western Philippine Sea Basin, which shows anomalously small Curie depths. The western Pacific marginal seas have the lowest Moho temperature, with Curie depths generally larger than Moho depths. The contrary is true in most parts of easternmost Eurasian continent. Magmatic processes feeding the Permian Emeishan large igneous province could have also been genetically linked to deep mantle/crustal processes beneath the Sichuan Basin. The regionally elongated magnetic features and small Curie depths along the Triassic Yangtze-Indochina plate boundary suggest that the igneous province could be caused by tectonic processes along plate margins, rather than by a deep mantle plume. At the same time, we interpret the Caroline Ridge, the boundary between the Pacific and the Caroline Sea, as a structure having a continental origin, rather than as hotspot or arc volcanism. The surface heat flow is primarily modulated by a deep isotherm through thermal conduction. This concordance is emphasized along many subduction trenches, where zones of large Curie depths often correspond with low heat flow. Local or regional surface heat flow variations cannot be faithfully used in inferring

  19. Deep Mantle Dynamics under the North American Continent Drives Localised Flow and Stress Below the New Madrid Seismic Zone

    NASA Astrophysics Data System (ADS)

    Forte, A. M.; Mitrovica, J. X.; Moucha, R.; Simmons, N. A.; Grand, S. P.

    2007-12-01

    The origin of intraplate earthquakes represents one of the outstanding problems in modern geophysical research, and the major earthquake sequence that struck the central Mississippi River Valley in 1811-1812, the so-called New Madrid seismic sequence, has become a principal target of this research. As Johnston and Schweig (1996) have noted, the occurrence of such large magnitude earthquakes in "stable" North American crust, far from any plate boundaries, remains an enigma. To understand the possible origin of this enigmatic seismic activity we have developed a new high resolution model of mantle flow below North America. The model is constrained by simultaneously inverting global seismic and mantle-convection data sets and it includes an explicit treatment of the positive chemical buoyancy of the continental tectosphere. Moreover, it adopts a depth dependent mantle viscosity structure which reconciles both glacial isostatic adjustment (GIA) and convection data. The flow model successfully reproduces plate velocities and observations of surface gravity and topography, including the continent-scale quasi-linear depression (after corrections for GIA and crustal heterogeneity) extending from northern Alaska to Venezuela. The predictions also match lithospheric flow and stress fields inferred from local and regional measurements of seismic anisotropy and surface deformation. We demonstrate that these signals are largely driven by viscous flow coupled to density anomalies within the lower mantle associated with the descent of the ancient Kula-Farallon plate system. More importantly, the flow calculations elucidate how these large-scale heterogeneities give rise to flow and stress patterns below the New Madrid Seismic Zone which are favourably oriented with respect the local fault geometry in this portion of the Mississippi valley.

  20. The Anisotropic Structure of South China Sea: Using OBS Data to Constrain Mantle Flow

    NASA Astrophysics Data System (ADS)

    Li, L.; Xue, M.; Yang, T.; Liu, C.; Hua, Q.; Xia, S.; Huang, H.; Le, B. M.; Huo, D.; Pan, M.

    2015-12-01

    The dynamic mechanism of the formation of South China Sea (SCS) has been debated for decades. The anisotropic structure can provide useful insight into the complex evolution of SCS by indicating its mantle flow direction and strength. In this study, we employ shear wave splitting methods on two half-year seismic data collected from 10 and 6 passive source Ocean Bottom Seismometers (OBS) respectively. These OBSs were deployed along both sides of the extinct ridge in the central basin of SCS by Tongji University in 2012 and 2013 respectively, which were then successfully recovered in 2013 and 2015 respectively. Through processing and inspecting the global and regional earthquakes (with local events being processing) of the 2012 dataset, measurements are made for 2 global events and 24 regional events at 5 OBSs using the tangential energy minimization, the smallest eigenvalue minimization, as well as the correlation methods. We also implement cluster analysis on the splitting results obtained for different time windows as well as filtered at different frequency bands. For teleseismic core phases like SKS and PKS, we find the fast polarization direction beneath the central basin is approximately NE-SW, nearly parallel to the extinct ridge in the central basin of SCS. Whereas for regional events, the splitting analysis on S, PS and ScS phases shows much more complicated fast directions as the ray path varies for different phases. The fast directions observed can be divided into three groups: (1) for the events from the Eurasia plate, a gradual rotation of the fast polarization direction from NNE-SSW to NEE-SWW along the path from the inner Eurasia plate to the central SCS is observed, implying the mantle flow is controlled by the India-Eurasia collision; (2) for the events located at the junction of Pacific plate and Philippine plate, the dominant fast direction is NW-SE, almost perpendicular to Ryukyu Trench as well as sub-parallel to the absolute direction of

  1. Couette and Poiseuille flows in a low viscosity asthenosphere: Effects of internal heating rate, Rayleigh number, and plate representation

    NASA Astrophysics Data System (ADS)

    Shiels, C.; Butler, S. L.

    2015-09-01

    Mantle convection models with a low viscosity asthenosphere and high viscosity surface plates have been shown to produce very large aspect ratio convection cells like those inferred to exist in Earth's mantle and to exhibit two asthenospheric flow regimes. When the surface plate is highly mobile, the plate velocity exceeds the flow velocities in the asthenosphere and the plate drives a Couette-type flow in the asthenospheric channel. For sluggish plates, the flow velocities in the asthenosphere exceed the plate velocity and the asthenospheric flow is more Poiseuille-like. It has been shown that under certain circumstances, flows become increasingly Couette-like as the aspect ratio of the plate is increased in numerical simulations. These models also show an increase in the average surface heat flux with aspect ratio which is counterintuitive, as one would expect that large aspect ratio models would result in older and colder oceanic lithosphere. Previous investigations have used single internal heating rates and Rayleigh numbers and a plate formulation that did not preclude significant deformation within the plate. In this paper, we investigate the conditions necessary for Couette and Poiseuille asthenospheric flows and for surface heat flux to increase with plate aspect ratio by varying the internal heating rate, the Rayleigh number and the representation of surface plates in 2D mantle convection models Plates are represented as a high viscosity layer with (1) a free-slip top surface boundary condition and (2) a force-balance boundary condition that imposes a constant surface velocity within the plate. We find that for models with a free-slip surface boundary condition, the internal heating rate and Rayleigh number do not strongly affect the dominance of Couette or Poiseuille flows in the asthenosphere but the increase in surface heat flux with model aspect ratio in the Poiseuille asthenospheric flow regime increases with internal heating rate. For models using

  2. Advances and innovations in models of mantle convection

    NASA Astrophysics Data System (ADS)

    Kellogg, L. H.

    2002-12-01

    More than three decades ago, Turcotte and Oxburgh published their landmark paper showing how mantle convection drives motion of the continents, with the cold thermal boundary layers representing the surface plates. Since that time, models of mantle convection have made remarkable advancements and have been applied to the interiors of the terrestrial planets and moons, with many fundamental contributions by Don Turcotte and inspired by his work. Here, I will address some of the recent advances and innovations in mantle convection, with special emphasis on ideas emerging from the application of nonlinear dynamics and chemical geodynamics. Numerical models of convection, combined with observations from heat flow, cosmochemistry, and mantle geochemistry, provide constraints on models of the composition and structure of the mantle. Geochemical and heat flow observations appear to require long-lived heterogeneity in the mantle, while numerical models of convection generally exhibit rapid mixing, creating a distinctive ``marble-cake'' texture of recycled lithosphere. A variety of models have been suggested to reconcile these diverse inferences about mantle dynamics and structure from seemingly contradictory geochemical and geophysical observations. One straightforward explanation of combined geochemical and geophysical observations is a compositionally heterogeneous lowermost mantle. A difference between the composition of the MORB source and the composition of the deep mantle is also consistent with estimates of the properties of perovskite at high pressures and temperatures. Heterogeneity in the lower mantle may take the form of a hot abyssal layer of variable thickness starting at the mid-mantle or in the lowermost mantle, or may consist of "blobs" in the lower mantle. The hot abyssal layer model has an advantage over the blob model, because hot, neutrally buoyant blobs are unlikely to persist for the long times required by chemical geodynamics. Chemical geodynamics

  3. Heat flow and seismicity patterns in the vicinity of the eastern Snake River Plain, Idaho

    SciTech Connect

    Blackwell, D.D. Kelley, S.A.; Steele, J.L. . Dept. of Geological Sciences)

    1993-04-01

    New heat flow data and thermal modeling are used to calculate crustal temperatures in and adjacent to the eastern Snake River Plain (SRP). The estimated crustal temperature are then used to investigate the relationship between crustal strength and the observed parabolic pattern of seismicity around the SRP. Heat flow below the SRP aquifer in deep wells on the Idaho National Engineering Laboratory (INEL) site near the northern margin of the SRP is 107 [plus minus] 15 mWm[sup [minus]2]. Heat flow values from deep wells on both the northern and southern margins of the eastern SRP average 100 [plus minus] 15 mWm[sup [minus]2]. 2-D finite-difference thermal models were developed to fit seismic and heat flow data in the vicinity of the SRP. The models have a shallow silicic magma chamber that is as wide as the SRP. The silicic chamber is underlain by mafic heat sources in the middle to lower crust and in the upper mantle. The heat flow data are best fit by models with deep heat sources that are wider than the SRP. These results are consistent with the presence of young basaltic centers that have been observed outside the SRP. The temperature from the authors thermal models were used to calculate strength envelopes for the crust in the SRP/Basin and Range region. The weakest part of the crust is along the edge of the Basin and Range, where it is heated by the SRP; thus the boundary to the two provinces may be a zone of weak coupling. Their modeling indicates that it is difficult to explain the earthquake pattern in the vicinity of the SRP as a thermomechanical effect related to the passage of the Yellowstone hot spot.

  4. One dimensional lunar ash flow with and without heat transfer

    NASA Technical Reports Server (NTRS)

    Pai, S. I.; Hsieh, T.

    1971-01-01

    The characteristics of lunar ash flow are discussed in terms of the two phase flow theory of a mixture of a gas and small solid particles. A model is developed to present the fundamental equations and boundary conditions. Numerical solutions for special ash flow with and without heat transfer are presented. In the case of lunar ash flow with small initial velocity, the effect of the heat transfer makes the whole layer of ash flow more compacted together than the corresponding isothermal case.

  5. Seismic Anisotropy and SKS Splitting in the Sangihe Subduction Zone Predicted from 3-D Mantle Flow Models

    NASA Astrophysics Data System (ADS)

    Di Leo, J. F.; Li, Z.; Walker, A. M.; Wookey, J.; Kendall, J.; Ribe, N. M.; Tommasi, A.

    2012-12-01

    Observations of shear wave splitting are often interpreted as being due to strain-induced crystal alignment of olivine in the convecting upper mantle, and the polarization of the fast shear wave is frequently taken to directly indicate the direction of mantle flow. Caution must be exercised when making such inferences, as the relationship between olivine lattice-preferred orientation (LPO) and fast direction is dependent on many factors, including the entire deformation history. This is especially the case in regions where complex time-dependent mantle flow is expected, e.g., subduction zones. Observations of shear wave splitting at subduction zones are varied, ranging from trench-perpendicular to -parallel fast directions, or a combination of both. Rigorously interpreting this variety of observations requires modeling which properly accounts for LPO development in the near-slab mantle environment. To this end, we simulate olivine LPO evolution caused by defomation of polycrystalline aggregates as they deform and move along pathlines extracted from a 3-D mantle flow model at a subduction zone (Li & Ribe, 2012). The model is based on 3-D boundary-element numerical simulations of a dense fluid sheet (representing the slab) with a geometry approximating that of the Sangihe subduction zone in Indonesia, where trench-parallel fast directions have recently been measured and ascribed to trench-parallel sub-slab mantle flow (Di Leo et al., 2012). This subduction zone is unique in that it is part of the only double-sided subduction system on Earth. At the Sangihe trench, the Molucca Sea plate is subducting westwards beneath the Eurasian plate. However, this microplate is also subducting eastwards at the nearby Halmahera trench. To test whether the measured trench-parallel fast directions are due to sub-slab mantle flow, and whether this is only possible due to the double-sided geometry, we use two different flow models: one with single- and one with double-sided subduction

  6. Seismic b-Values, Bouguer Gravity and Heat Flow Data Beneath Eastern Anatolia, Turkey: Tectonic Implications

    NASA Astrophysics Data System (ADS)

    Maden, Nafiz; Öztürk, Serkan

    2015-07-01

    In this paper, we analyze the relationships between the seismic b-values, Bouguer gravity and heat flow data in the Eastern Anatolia region of Turkey. For this purpose, spatial distributions of b-value, Bouguer gravity and heat flow have been presented for different depths and locations. In distinction to previous studies which have used only two parameters (gravity and seismic b-value or heat flow and seismic b-value), we have combined seismic b-values, Bouguer gravity and heat flow data to determine the new results on the active tectonics of the Eastern Anatolia region. Our analysis shows that there are significant and robust correlations amidst the heat flow data, Bouguer gravity anomaly and seismic b-values. The crustal structure is thick in areas where the large negative gravity anomalies and low b-values are observed. On the contrary, the regions with positive gravity anomalies and high b-values are likely to be associated with magma chambers or crustal low-velocity zones. We also provide some evidence suggesting that high b-values and high heat flow values can be related to the magmatic activities beneath the volcanic chain in the Eastern Pontide orogenic belt. Consequently, we have reached some conclusions for the Eastern Anatolia region: (1) The Moho to surface is rather thick and earthquakes are relatively smaller beneath the volcanic chain where the high heat flow values are observed, (2) a southward subduction model could have existed for the development of the Pontides during the late Mesozoic-Cenozoic era, (3) hot and unstable mantle lid zones or a lithosphere deprived of mantle under the study region is much more plausible, (4) a southward movement of the subduction plate and a northward extension of the Black Sea increase the state of stress along the trench axis and decrease the b-value, and (5) these movements may load the stress energy to the fault zones, thereby causing the catastrophic earthquakes in the Eastern Anatolia region.

  7. Numerical Simulations of Texture Development and Associated Rheological Anisotropy in Regions of Complex Mantle Flow

    NASA Astrophysics Data System (ADS)

    Blackman, D. K.; Castelnau, O.; Becker, T. W.

    2008-12-01

    The aim of this study is to compare the predictions of different micromechanical approaches that have been employed recently to study mineral alignment during flow in the upper mantle. Computational capabilities are reaching a point where the potential rheological effects of such lattice-preferred orientation (LPO) can be considered as an integral part of determining the flow pattern and evolution. But, in order to have confidence in taking this next step, the detailed behavior of the different micromechanical models needs to be understood. An important consequence of LPO development is the subsequent anisotropy of the mechanical properties. Curiously, most published geophysical studies only address the elastic anisotropy, probably because of its link with the observed seismic anisotropy. The viscoplastic (or rheological) anisotropy has received much less attention, although it may have a notable influence on regional and global convective flow pattern, which in turn controls the LPO development. Micromechanical approaches aim at linking the rheological behaviour at the grain scale, associated with the activate deformation mechanisms (dislocation glide and climb, diffusion creep, "), with the overall rheology at the sample scale, including also other mechanisms such as recrystallization. This is achieved by an evaluation of the internal stress generated by the (strong) mechanical interaction between neighbour grains. All models proposed in the literature (kinematic model, finite strain model, tangent self-consistent model, lower bound model, ") make simplifying assumptions, since the mechanical problem is very complicated. One can distinguish between rather simple models that allow some freedom in deformation of individual grains, and more advanced techniques (and generally more accurate) that require a minimum number (=4) of independent slip systems (or directional deformation mechanisms) for the plastic strain to occur. In respect to this, unlike all other models

  8. Three-Dimensional Simulations of Mantle Convection in Io

    NASA Technical Reports Server (NTRS)

    Tackley, Paul J.; Schubert, Gerald; Glatzmaier, Gary A.; Schenk, Paul; Ratcliff, J. Todd; Matas, J.-P.

    2001-01-01

    Io has very high surface heat flow and an abundance of volcanic activity, which are thought to be driven by nonuniform tidal heating in its interior. This nonuniform heat is transported to the base of the lithosphere by very vigorous convection in Io's silicate mantle, the form of which is presumably responsible for the distribution of surface features such as volcanoes and mountains. We here present three-dimensional spherical calculations of mantle convection in Io, in order to ascertain the likely form of this convection and the resulting distribution of heat flow at the surface and core-mantle boundary. Different models of tidal dissipation are considered: the endmember scenarios (identified by M. N. Ross and G. Schubert) of dissipation in the entire mantle, or dissipation in a thin (approximately 100-km-thick) asthenosphere, as well as the 'preferred' distribution of M. N. Ross et al. comprising 1/3 mantle and 2/3 asthenosphere heating. The thermal structure of Io's mantle and asthenosphere is found to be strongly dependent on tidal heating mode, as well as whether the mantle-asthenosphere boundary is permeable or impermeable. Results indicate a large-scale flow pattern dominated by the distribution of tidal heating, with superimposed small-scale asthenospheric instabilities that become more pronounced with increasing Rayleigh number. These small-scale instabilities spread out the surface heat flux, resulting in smaller heat flux variations with increasing Rayleigh number. Scaled to Io's Rayleigh number of O(10(exp 12)) variations of order a few percent are expected. This small but significant variation in surface heat flux may be compatible with the observed distributions of volcanic centers and mountains, which appear fairly uniform at first sight but display a discernible distribution when suitably processed. The observed distribution of volcanic centers is similar to the asthenosphere heating distribution, implying that most of the tidal heating in Io

  9. Hotspot motion inferred from mantle flow models: implications on global plate reconstructions

    NASA Astrophysics Data System (ADS)

    Steinberger, B.; O'Connell, R. J.

    2003-04-01

    The Hawaiian hotspot track predicted from a plate circuit, assuming that the Hawaiian hotspot is fixed relative to African hotspots, does not fit the observed track: The divergence is steadily increasing back to 43 Ma, and the predicted track does not show a bend. Here we use a model of plumes distorted by global mantle flow to compute hotspot motion, and test whether this motion can explain the misfit. Computations consistently predict a south- to southeastward motion of the Hawaiian hotspot, and a motion of about 1000 km southward during the past 80 Ma is within the range of model results. Thus, we find that our model of hotspot motion can account for the divergence from 0 to 43 Ma, but can not account for the bend and the track prior to 43 Ma. For this, both a rather sharp change in hotspot motion at 43 Ma, and a westward component of hotspot motion prior to 43 Ma would be required, and neither is predicted in the model. However, a combination of modelled hotspot motion and a relatively modest motion between W and E Antarctica - about 15 degrees clockwise rotation of W vs. E Antarctica - would permit a fit to the Hawaiian track from 80 to 43 My. The required deformation could have been accomplished entirely within continental crust, with rates similar to e.g. present extension in the western U.S., and we will argue that it is not in conflict with, but actually supported by geologic evidence.

  10. The thermal state of the Arabian plate derived from heat flow measurements in Oman and Yemen

    NASA Astrophysics Data System (ADS)

    Rolandone, Frederique; Lucazeau, Francis; Leroy, Sylvie; Mareschal, Jean-Claude; Jorand, Rachel; Goutorbe, Bruno; Bouquerel, Hélène

    2013-04-01

    The dynamics of the Afar plume and the rifting of the Red Sea and the Gulf of Aden affect the present-day thermal regime of the Arabian plate. However, the Arabian plate is a Precambrian shield covered on its eastern part by a Phanerozoic platform and its thermal regime, before the plume and rifting activities, should be similar to that of other Precambrian shields with a thick and stable lithosphere. The first heat flow measurements in the shield, in Saudi Arabia, yielded low values (35-44 mW/m2), similar to the typical shields values. Recent heat flow measurements in Jordan indicate higher values (56-66 mW/m2). As part of the YOCMAL project (YOung Conjugate MArgins Laboratory), we have conducted heat flow measurements in southern and northern Oman to obtain 10 new heat flux values in the eastern Arabian plate. We also derived 20 heat flux values in Yemen and Oman by processing thermal data from oil exploration wells. The surface heat flux in these different locations is uniformly low (45 mW/m2). The heat production in samples from the Dhofar and Socotra Precambrian basement is also low (0.7 µW/m3). Differences in heat flow between the eastern (60 mW/m2) and the western (45 mW/m2) parts of Arabia reflect differences in crustal heat production as well as a higher mantle heat flux in the west. We have calculated a steady state geotherm for the Arabian platform that intersects the isentropic temperature profile at a depth of about 150 km, consistent with the seismic observations. Seismic tomography studies of the mantle beneath Arabia also show this east-west contrast. Seismic studies have shown that the lithosphere is rather thin, 100 km or less below the shield and 150 km below the platform. The lithospheric thickness for the Arabian plate is 150 km, and the progressive thinning near the Red Sea, caused by the thermal erosion of the plume material, is too recent to be detected at the surface. The Afar plume mostly affects the base of the Arabian lithosphere along

  11. Meteorological insights from planetary heat flow measurements

    NASA Astrophysics Data System (ADS)

    Lorenz, Ralph D.

    2015-04-01

    Planetary heat flow measurements are made with a series of high-precision temperature sensors deployed in a column of regolith to determine the geothermal gradient. Such sensors may, however, be susceptible to other influences, especially on worlds with atmospheres. First, pressure fluctuations at the surface may pump air in and out of pore space leading to observable, and otherwise unexpected, temperature fluctuations at depth. Such pumping is important in subsurface radon and methane transport on Earth: evidence of such pumping may inform understanding of methane or water vapor transport on Mars. Second, the subsurface profile contains a muted record of surface temperature history, and such measurements on other worlds may help constrain the extent to which Earth's Little Ice Age was directly solar-forced, versus volcanic-driven and/or amplified by climate feedbacks.

  12. Heat flow in the postquasistatic approximation

    SciTech Connect

    Rodriguez-Mueller, B.; Peralta, C.; Barreto, W.; Rosales, L.

    2010-08-15

    We apply the postquasistatic approximation to study the evolution of spherically symmetric fluid distributions undergoing dissipation in the form of radial heat flow. For a model that corresponds to an incompressible fluid departing from the static equilibrium, it is not possible to go far from the initial state after the emission of a small amount of energy. Initially collapsing distributions of matter are not permitted. Emission of energy can be considered as a mechanism to avoid the collapse. If the distribution collapses initially and emits one hundredth of the initial mass only the outermost layers evolve. For a model that corresponds to a highly compressed Fermi gas, only the outermost shell can evolve with a shorter hydrodynamic time scale.

  13. Seismological observations in Northwestern South America: Evidence for two subduction segments, contrasting crustal thicknesses and upper mantle flow

    NASA Astrophysics Data System (ADS)

    Yarce, Jefferson; Monsalve, Gaspar; Becker, Thorsten W.; Cardona, Agustín; Poveda, Esteban; Alvira, Daniel; Ordoñez-Carmona, Oswaldo

    2014-12-01

    The cause of tectonic deformation in northwestern South America and its link to upper mantle structure and flow are debated. We use a combination of broadband and short period travel time seismic data for P-waves to show that observations are consistent with the presence of two subduction segments in Colombia and contrasting values of crustal thickness. In Northern Colombia, at latitudes greater than 6°N, most of the seismic stations are associated with negative teleseismic travel time residuals, relative to a regional mean, suggesting that the upper mantle is seismically faster than predicted from global models. In particular, for the Caribbean coastal plains there are no signs of significant anomalies in the upper mantle, evidenced by the small magnitude of the travel time delays and subdued Pn speeds (~ 7.97 km/s). To the southeast of such plains there is an increase in magnitude of the negative travel time residuals, including the Northern Eastern Cordillera, the Perija Range and the Merida Andes. An analysis of non-isostatic residual topography, based on a model of crustal thickness in northwestern South America, is consistent with a slab-associated upper mantle flow beneath the region just east of the Bucaramanga Nest. We interpret these results to indicate the presence of a Caribbean slab, initially flat beneath the Caribbean coastal plains, and steepening sharply in the southeast, including the area of Bucaramanga. For most of the western Andean region and the Pacific coast, south of 6°N, teleseismic differential travel time residuals are predominantly positive, indicating that the upper mantle is in general seismically slower than the reference model. Beneath the Central Cordillera, just to the east of this area, the residuals become smaller and predominantly negative; residual non-isostatic topography is negative as well. These features are probably related to the effect of the Nazca subduction developing an asthenospheric wedge.

  14. Analysis of the transient compressible vapor flow in heat pipe

    NASA Technical Reports Server (NTRS)

    Jang, Jong Hoon; Faghri, Amir; Chang, Won Soon

    1989-01-01

    The transient compressible one-dimensional vapor flow dynamics in a heat pipe is modeled. The numerical results are obtained by using the implicit non-iterative Beam-Warming finite difference method. The model is tested for simulated heat pipe vapor flow and actual flow in cylindrical heat pipes. A good comparison of the present transient results for the simulated heat pipe vapor flow with the previous results of a two-dimensional numerical model is achieved and the steady state results are in agreement with the existing experimental data. The transient behavior of the vapor flow under subsonic, sonic, and supersonic speeds and high mass flow rates are successfully predicted. The one-dimensional model also describes the vapor flow dynamics in cylindrical heat pipes at high temperatures.

  15. Analysis of the transient compressible vapor flow in heat pipes

    NASA Technical Reports Server (NTRS)

    Jang, J. H.; Faghri, A.; Chang, W. S.

    1989-01-01

    The transient compressible one-dimensional vapor flow dynamics in a heat pipe is modeled. The numerical results are obtained by using the implicit non-iterative Beam-Warming finite difference method. The model is tested for simulated heat pipe vapor flow and actual vapor flow in cylindrical heat pipes. A good comparison of the present transient results for the simulated heat pipe vapor flow with the previous results of a two-dimensional numerical model is achieved and the steady state results are in agreement with the existing experimental data. The transient behavior of the vapor flow under subsonic, sonic, and supersonic speeds and high mass flow rates are successfully predicted. The one-dimensional model also describes the vapor flow dynamics in cylindrical heat pipes at high temperatures.

  16. Viscous Heating in Nanoscale Shear Driven Flows

    NASA Astrophysics Data System (ADS)

    Kim, Bohung; Beskok, Ali

    2009-11-01

    Three-dimensional Molecular Dynamics (MD) simulations of heat and momentum transport in liquid Argon filled shear-driven nano-channels are performed using 6-12 Lennard-Jones potential interactions. Work done by the viscous stresses heats the fluid, which is dissipated through the channel walls, maintained at isothermal conditions via a recently developed interactive thermal wall model. Momentum transport in shear driven nano-flow is investigated as a function of the surface wettability (ɛwf/ɛ), spatial variations in the fluid density, kinematic viscosity, shear- and energy dissipation rates are presented. Temperature profiles in the nano-channel are obtained as a function of the surface wettability, shear rate and the intermolecular stiffness of wall molecules. The energy dissipation rate is almost a constant for ɛwf/ɛ<0.6, which results in parabolic temperature profiles in the domain with temperature jumps due to the well known Kapitza resistance at the liquid/solid interfaces. Using the energy dissipation rates predicted by MD simulations and the continuum energy equation subjected to the temperature jump boundary conditions developed in [Kim et al., Journal of Chemical Physics, 129, 174701, 2008], we obtain analytical solutions for the temperature profiles, which agree well with the MD results.

  17. Minimal residual disease monitoring by 8-color flow cytometry in mantle cell lymphoma: an EU-MCL and LYSA study

    PubMed Central

    Cheminant, Morgane; Derrieux, Coralie; Touzart, Aurore; Schmit, Stéphanie; Grenier, Adrien; Trinquand, Amélie; Delfau-Larue, Marie-Hélène; Lhermitte, Ludovic; Thieblemont, Catherine; Ribrag, Vincent; Cheze, Stéphane; Sanhes, Laurence; Jardin, Fabrice; Lefrère, François; Delarue, Richard; Hoster, Eva; Dreyling, Martin; Asnafi, Vahid; Hermine, Olivier; Macintyre, Elizabeth

    2016-01-01

    Quantification of minimal residual disease may guide therapeutic strategies in mantle cell lymphoma. While multiparameter flow cytometry is used for diagnosis, the gold standard method for minimal residual disease analysis is real-time quantitative polymerase chain reaction (RQ-PCR). In this European Mantle Cell Lymphoma network (EU-MCL) pilot study, we compared flow cytometry with RQ-PCR for minimal residual disease detection. Of 113 patients with at least one minimal residual disease sample, RQ-PCR was applicable in 97 (86%). A total of 284 minimal residual disease samples from 61 patients were analyzed in parallel by flow cytometry and RQ-PCR. A single, 8-color, 10-antibody flow cytometry tube allowed specific minimal residual disease assessment in all patients, with a robust sensitivity of 0.01%. Using this cut-off level, the true-positive-rate of flow cytometry with respect to RQ-PCR was 80%, whereas the true-negative-rate was 92%. As expected, RQ-PCR frequently detected positivity below this 0.01% threshold, which is insufficiently sensitive for prognostic evaluation and would ideally be replaced with robust quantification down to a 0.001% (10-5) threshold. In 10 relapsing patients, the transition from negative to positive by RQ-PCR (median 22.5 months before relapse) nearly always preceded transition by flow cytometry (4.5 months), but transition to RQ-PCR positivity above 0.01% (5 months) was simultaneous. Pre-emptive rituximab treatment of 2 patients at minimal residual disease relapse allowed re-establishment of molecular and phenotypic complete remission. Flow cytometry minimal residual disease is a complementary approach to RQ-PCR and a promising tool in individual mantle cell lymphoma therapeutic management. PMID:26703963

  18. Minimal residual disease monitoring by 8-color flow cytometry in mantle cell lymphoma: an EU-MCL and LYSA study.

    PubMed

    Cheminant, Morgane; Derrieux, Coralie; Touzart, Aurore; Schmit, Stéphanie; Grenier, Adrien; Trinquand, Amélie; Delfau-Larue, Marie-Hélène; Lhermitte, Ludovic; Thieblemont, Catherine; Ribrag, Vincent; Cheze, Stéphane; Sanhes, Laurence; Jardin, Fabrice; Lefrère, François; Delarue, Richard; Hoster, Eva; Dreyling, Martin; Asnafi, Vahid; Hermine, Olivier; Macintyre, Elizabeth

    2016-03-01

    Quantification of minimal residual disease may guide therapeutic strategies in mantle cell lymphoma. While multiparameter flow cytometry is used for diagnosis, the gold standard method for minimal residual disease analysis is real-time quantitative polymerase chain reaction (RQ-PCR). In this European Mantle Cell Lymphoma network (EU-MCL) pilot study, we compared flow cytometry with RQ-PCR for minimal residual disease detection. Of 113 patients with at least one minimal residual disease sample, RQ-PCR was applicable in 97 (86%). A total of 284 minimal residual disease samples from 61 patients were analyzed in parallel by flow cytometry and RQ-PCR. A single, 8-color, 10-antibody flow cytometry tube allowed specific minimal residual disease assessment in all patients, with a robust sensitivity of 0.01%. Using this cut-off level, the true-positive-rate of flow cytometry with respect to RQ-PCR was 80%, whereas the true-negative-rate was 92%. As expected, RQ-PCR frequently detected positivity below this 0.01% threshold, which is insufficiently sensitive for prognostic evaluation and would ideally be replaced with robust quantification down to a 0.001% (10-5) threshold. In 10 relapsing patients, the transition from negative to positive by RQ-PCR (median 22.5 months before relapse) nearly always preceded transition by flow cytometry (4.5 months), but transition to RQ-PCR positivity above 0.01% (5 months) was simultaneous. Pre-emptive rituximab treatment of 2 patients at minimal residual disease relapse allowed re-establishment of molecular and phenotypic complete remission. Flow cytometry minimal residual disease is a complementary approach to RQ-PCR and a promising tool in individual mantle cell lymphoma therapeutic management. (clinicaltrials identifiers: 00209209 and 00209222).

  19. Geodynamo Models With a Thick Stable Layer and Heterogeneous CMB Heat Flow

    NASA Astrophysics Data System (ADS)

    Christensen, U. R.

    2015-12-01

    The upward revision of the thermal conductivity in the Earth's core makes it plausible that the mean heat flow at the core-mantle boundary (CMB) could be only afraction of what can be conducted down the core adiabat (perhaps one half). The upper part of the fluid core would be stably stratified to substantial depth. This is inconsistent with evidence for upwelling flow near the CMB from observations ofof magnetic flux expulsion. Heat flow at the CMB is likely very heterogeneous and would still be superadiabatic in some regions of the CMB. The dynamics of such a system is unclear. Gubbins et al. (Phys. Earth Planet. Int., in press, 2015)suggest that the locally unstable gradient would mix up the stable layer as a wholeand replace it by a weakly convecting one. We study dynamo models driven by a codensity flux from the inner core. On the outer boundary an inverse (on average) gradient is imposed, leading to stable stratification of the top 40% of the fluid shell. In addition to control cases with homogeneous CMB flux, we run models with two unstableregions centered on the equator. In the latter cases a predominantly horizontal circulation in a thin layer immediately below the outer boundary redistributes the heat that is conducted radially upward in the stable layer and transports ittowards the high heat-flow spots. Radial flow below these spots does not penetrate deeply into the stable layer, nor does the layer become mixed up to a significant degree. A dynamo operates in the convecting deep interior, however, its dipole moment is low in comparison to the Earth value. Heat flow heterogeneity at the CMB does not sem to solve the problems that exist for the geodynamo when the average heat flux is substantially subadiabatic.

  20. The Earth's Mantle.

    ERIC Educational Resources Information Center

    McKenzie, D. P.

    1983-01-01

    The nature and dynamics of the earth's mantle is discussed. Research indicates that the silicate mantle is heated by the decay of radioactive isotopes and that the heat energizes massive convention currents in the upper 700 kilometers of the ductile rock. These currents and their consequences are considered. (JN)

  1. The Earth's Mantle.

    ERIC Educational Resources Information Center

    McKenzie, D. P.

    1983-01-01

    The nature and dynamics of the earth's mantle is discussed. Research indicates that the silicate mantle is heated by the decay of radioactive isotopes and that the heat energizes massive convention currents in the upper 700 kilometers of the ductile rock. These currents and their consequences are considered. (JN)

  2. Seismic anisotropy beneath Cascadia and the Mendocino triple junction: Interaction of the subducting slab with mantle flow

    NASA Astrophysics Data System (ADS)

    Eakin, Caroline M.; Obrebski, Mathias; Allen, Richard M.; Boyarko, Devin C.; Brudzinski, Michael R.; Porritt, Robert

    2010-09-01

    Mantle flow associated with the Cascadia subduction zone and the Mendocino Triple Junction is poorly characterized due to a lack of shear wave splitting studies compared to other subduction zones. To fill this gap data was obtained from the Mendocino and FACES seismic networks that cover the region with dense station spacing. Over a period of 11-18 months, 50 suitable events were identified from which shear wave splitting parameters were calculated. Here we present stacked splitting results at 63 of the stations. The splitting pattern is uniform trench normal (N67°E) throughout Cascadia with an average delay time of 1.25 s. This is consistent with subduction and our preferred interpretation is entrained mantle flow beneath the slab. The observed pattern and interpretation have implications for mantle dynamics that are unique to Cascadia compared to other subduction zones worldwide. The uniform splitting pattern seen throughout Cascadia ends at the triple junction where the fast directions rotate almost 90°. Immediately south of the triple junction the fast direction rotates from NW-SE near the coast to NE-SW in northeastern California. This rotation beneath northern California is consistent with flow around the southern edge of the subducting Gorda slab.

  3. Seismic Anisotropy beneath Cascadia and the Mendocino Triple Junction: Interaction of the Subducting Slab with Mantle Flow

    NASA Astrophysics Data System (ADS)

    Eakin, C. M.; Obrebski, M. J.; Allen, R. M.; Boyarko, D. C.; Brudzinski, M. R.; Humphreys, E.; Levander, A.; O'Driscoll, L.; Porritt, R. W.; Zhai, Y.

    2009-12-01

    Mantle flow associated with the Cascadia subduction zone and the Mendocino Triple Junction is poorly characterized due to a lack of shear wave splitting studies compared to other subduction zones. To fill this gap data was obtained from the Mendocino and FACES seismic networks that cover the region with dense station spacing. Over a period of 11-18 months, 50 suitable events were identified from which shear wave splitting parameters were calculated. Here we present stacked splitting results at 63 of the stations. The splitting pattern is uniform trench normal (N67°E) throughout Cascadia with an average delay time of 1.25 seconds. This is consistent with subduction and our preferred interpretation is entrained mantle flow beneath the slab. The observed pattern and interpretation have implications for mantle dynamics that are unique to Cascadia compared to other subduction zones worldwide. The uniformity of the splitting directions along Cascadia ends at the triple junction where the fast directions rotate almost 90°. Immediately south of the triple junction the fast direction rotates from NW-SE near the coast to NE-SW in northeastern California. This rotation beneath northern California is consistent with flow around the southern edge of the subducting Gorda as predicted by numerical and laboratory models of slab rollback.

  4. Mantle dynamics following supercontinent formation

    NASA Astrophysics Data System (ADS)

    Heron, Philip J.

    This thesis presents mantle convection numerical simulations of supercontinent formation. Approximately 300 million years ago, through the large-scale subduction of oceanic sea floor, continental material amalgamated to form the supercontinent Pangea. For 100 million years after its formation, Pangea remained relatively stationary, and subduction of oceanic material featured on its margins. The present-day location of the continents is due to the rifting apart of Pangea, with supercontinent dispersal being characterized by increased volcanic activity linked to the generation of deep mantle plumes. The work presented here investigates the thermal evolution of mantle dynamics (e.g., mantle temperatures and sub-continental plumes) following the formation of a supercontinent. Specifically, continental insulation and continental margin subduction are analyzed. Continental material, as compared to oceanic material, inhibits heat flow from the mantle. Previous numerical simulations have shown that the formation of a stationary supercontinent would elevate sub-continental mantle temperatures due to the effect of continental insulation, leading to the break-up of the continent. By modelling a vigorously convecting mantle that features thermally and mechanically distinct continental and oceanic plates, this study shows the effect of continental insulation on the mantle to be minimal. However, the formation of a supercontinent results in sub-continental plume formation due to the re-positioning of subduction zones to the margins of the continent. Accordingly, it is demonstrated that continental insulation is not a significant factor in producing sub-supercontinent plumes but that subduction patterns control the location and timing of upwelling formation. A theme throughout the thesis is an inquiry into why geodynamic studies would produce different results. Mantle viscosity, Rayleigh number, continental size, continental insulation, and oceanic plate boundary evolution are

  5. A New Determination of Io's Heat Flow Using Diurnal Heat Balance Constraints

    NASA Technical Reports Server (NTRS)

    Spencer, J. R.; Rathbun, J. A.; McEwen, A. S.; Pearl, J. C.; Bastos, A.; Andrade, J.; Correia, M.; Barros, S.

    2002-01-01

    We use heat balance arguments to obtain a new estimate of Io's heat flow that does not depend on assumptions about the temperatures of its thermal anomalies. Our estimated heat flow is somewhat less than 2.2 +/- 0.9 W/sq m. Additional information is contained in the original extended abstract.

  6. A New Determination of Io's Heat Flow Using Diurnal Heat Balance Constraints

    NASA Technical Reports Server (NTRS)

    Spencer, J. R.; Rathbun, J. A.; McEwen, A. S.; Pearl, J. C.; Bastos, A.; Andrade, J.; Correia, M.; Barros, S.

    2002-01-01

    We use heat balance arguments to obtain a new estimate of Io's heat flow that does not depend on assumptions about the temperatures of its thermal anomalies. Our estimated heat flow is somewhat less than 2.2 +/- 0.9 W/sq m. Additional information is contained in the original extended abstract.

  7. Mantle devolatilization and rheology in the framework of planetary evolution

    NASA Technical Reports Server (NTRS)

    Franck, S.; Bounama, CH.

    1994-01-01

    We investigate the thermal history of an Earth-like planet with the help of a parameterized mantle convection model including the volatile exchange between mantle and surface reservoirs. The weakening of mantle silicates by dissolved volatiles is described by a functional relationship between creep rate and water fugacity. We use flow law parameters of diffusion creep in olivine under dry and wet conditions. The mantle degassing rate is considered as directly proportional to the seafloor spreading rate, which is also dependent on the mantle heat flow. To calculate the spreading rate, we assume that the heat flow under the mid-ocean ridges is double the average mantle heat flow. The rate of regassing also depends on the seafloor spreading rate as well as on other factors like the efficiency of volatile recycling through island arc volcanism. Both mechanisms (de- and regassing) are coupled self-consistently with the help of the parameterized convection model under implementation of a temperature and volatile-content-dependent mantle viscosity.

  8. Mantle devolatilization and rheology in the framework of planetary evolution

    NASA Technical Reports Server (NTRS)

    Franck, S.; Bounama, CH.

    1994-01-01

    We investigate the thermal history of an Earth-like planet with the help of a parameterized mantle convection model including the volatile exchange between mantle and surface reservoirs. The weakening of mantle silicates by dissolved volatiles is described by a functional relationship between creep rate and water fugacity. We use flow law parameters of diffusion creep in olivine under dry and wet conditions. The mantle degassing rate is considered as directly proportional to the seafloor spreading rate, which is also dependent on the mantle heat flow. To calculate the spreading rate, we assume that the heat flow under the mid-ocean ridges is double the average mantle heat flow. The rate of regassing also depends on the seafloor spreading rate as well as on other factors like the efficiency of volatile recycling through island arc volcanism. Both mechanisms (de- and regassing) are coupled self-consistently with the help of the parameterized convection model under implementation of a temperature and volatile-content-dependent mantle viscosity.

  9. Heat transfer research on supercritical water flow upward in tube

    SciTech Connect

    Li, H. B.; Yang, J.; Gu, H. Y.; Zhao, M.; Lu, D. H.; Zhang, J. M.; Wang, F.; Zhang, Y.

    2012-07-01

    The experimental research of heat transfer on supercritical water has been carried out on the supercritical water multipurpose test loop with a 7.6 mm upright tube. The experimental data of heat transfer is obtained. The experimental results of thermal-hydraulic parameters on flow and heat transfer of supercritical water show that: Heat transfer enhancement occurs when the fluid temperature reaches pseudo-critical point with low mass flow velocity, and peters out when the mass flow velocity increases. The heat transfer coefficient and Nusselt number decrease with the heat flux or system pressure increases, and increase with the increasing of mass flow velocity. The wall temperature increases when the mass flow velocity decreases or the system pressure increases. (authors)

  10. Working fluid flow visualization in gravity heat pipe

    NASA Astrophysics Data System (ADS)

    Nemec, Patrik; Malcho, Milan

    2016-03-01

    Heat pipe is device working with phase changes of working fluid inside hermetically closed pipe at specific pressure. The phase changes of working fluid from fluid to vapour and vice versa help heat pipe to transport high heat flux. The article deal about gravity heat pipe construction and processes casing inside during heat pipe operation. Experiment working fluid flow visualization is performed with two glass heat pipes with different inner diameter (13 mm and 22 mm) and filled with water. The working fluid flow visualization explains the phenomena as a working fluid boiling, nucleation of bubbles, and vapour condensation on the wall, vapour and condensate flow interaction, flow down condensate film thickness on the wall occurred during the heat pipe operation.

  11. The Earth's mantle in a microwave oven: thermal convection driven by a heterogeneous distribution of heat sources

    NASA Astrophysics Data System (ADS)

    Fourel, Loïc; Limare, Angela; Jaupart, Claude; Surducan, Emanoil; Farnetani, Cinzia G.; Kaminski, Edouard C.; Neamtu, Camelia; Surducan, Vasile

    2017-08-01

    Convective motions in silicate planets are largely driven by internal heat sources and secular cooling. The exact amount and distribution of heat sources in the Earth are poorly constrained and the latter is likely to change with time due to mixing and to the deformation of boundaries that separate different reservoirs. To improve our understanding of planetary-scale convection in these conditions, we have designed a new laboratory setup allowing a large range of heat source distributions. We illustrate the potential of our new technique with a study of an initially stratified fluid involving two layers with different physical properties and internal heat production rates. A modified microwave oven is used to generate a uniform radiation propagating through the fluids. Experimental fluids are solutions of hydroxyethyl cellulose and salt in water, such that salt increases both the density and the volumetric heating rate. We determine temperature and composition fields in 3D with non-invasive techniques. Two fluorescent dyes are used to determine temperature. A Nd:YAG planar laser beam excites fluorescence, and an optical system, involving a beam splitter and a set of colour filters, captures the fluorescence intensity distribution on two separate spectral bands. The ratio between the two intensities provides an instantaneous determination of temperature with an uncertainty of 5% (typically 1K). We quantify mixing processes by precisely tracking the interfaces separating the two fluids. These novel techniques allow new insights on the generation, morphology and evolution of large-scale heterogeneities in the Earth's lower mantle.

  12. Heat flow calorimeter. [measures output of Ni-Cd batteries

    NASA Technical Reports Server (NTRS)

    Fletcher, J. C.; Johnston, W. V. (Inventor)

    1974-01-01

    Heat flow calorimeter devices are used to measure heat liberated from or absorbed by an object. This device is capable of measuring the thermal output of sealed nickel-cadmium batteries or cells during charge-discharge cycles. An elongated metal heat conducting rod is coupled between the calorimeter vessel and a heat sink, thus providing the only heat exchange path from the calorimeter vessel itself.

  13. Temperature distribution in internally heated walls of heat exchangers composed of nonnuclear flow passages

    NASA Technical Reports Server (NTRS)

    Eckert, E R G; Low, George M

    1951-01-01

    In the walls of heat exchangers composed of noncircular passages, the temperature varies in the circumferential direction because of local variations of the heat-transfer coefficients. A prediction of the magnitude of this variation is necessary in order to determine the region of highest temperature and in order to determine the admissible operating temperatures. A method for the determination of these temperature distributions and of the heat-transfer characteristics of a special type of heat exchanger is developed. The heat exchanger is composed of polygonal flow passages and the passage walls are uniformly heated by internal heat sources. The coolant flow within the passages is assumed to be turbulent. The circumferential variation of the local heat-transfer coefficients is estimated from flow measurements made by Nikuradse, postulating similarity between velocity and temperature fields. Calculations of temperature distributions based on these heat-transfer coefficients are carried out and results for heat exchangers with triangular and rectangular passages are presented.

  14. Boiling heat transfer of refrigerant R-21 in upward flow in plate-fin heat exchanger

    NASA Astrophysics Data System (ADS)

    Kuznetsov, V. V.; Shamirzaev, A. S.

    2015-11-01

    The article presents the results of experimental investigation of boiling heat transfer of refrigerant R-21 in upward flow in a vertical plate-fin heat exchanger with transverse size of the channels that is smaller than the capillary constant. The heat transfer coefficients obtained in ranges of small mass velocities and low heat fluxes, which are typical of the industry, have been poorly studied yet. The characteristic patterns of the upward liquid-vapor flow in the heat exchanger channels and the regions of their existence are detected. The obtained data show a weak dependence of heat transfer coefficient on equilibrium vapor quality, mass flow rate, and heat flux density and do not correspond to calculations by the known heat transfer models. A possible reason for this behavior is a decisive influence of evaporation of thin liquid films on the heat transfer at low heat flux.

  15. Pure climb creep mechanism drives flow in Earth’s lower mantle

    PubMed Central

    Boioli, Francesca; Carrez, Philippe; Cordier, Patrick; Devincre, Benoit; Gouriet, Karine; Hirel, Pierre; Kraych, Antoine; Ritterbex, Sebastian

    2017-01-01

    At high pressure prevailing in the lower mantle, lattice friction opposed to dislocation glide becomes very high, as reported in recent experimental and theoretical studies. We examine the consequences of this high resistance to plastic shear exhibited by ringwoodite and bridgmanite on creep mechanisms under mantle conditions. To evaluate the consequences of this effect, we model dislocation creep by dislocation dynamics. The calculation yields to an original dominant creep behavior for lower mantle silicates where strain is produced by dislocation climb, which is very different from what can be activated under high stresses under laboratory conditions. This mechanism, named pure climb creep, is grain-size–insensitive and produces no crystal preferred orientation. In comparison to the previous considered diffusion creep mechanism, it is also a more efficient strain-producing mechanism for grain sizes larger than ca. 0.1 mm. The specificities of pure climb creep well match the seismic anisotropy observed of Earth’s lower mantle. PMID:28345037

  16. Pattern recognition constrains mantle properties, past and present

    NASA Astrophysics Data System (ADS)

    Atkins, S.; Rozel, A. B.; Valentine, A. P.; Tackley, P.; Trampert, J.

    2015-12-01

    Understanding and modelling mantle convection requires knowledge of many mantle properties, such as viscosity, chemical structure and thermal proerties such as radiogenic heating rate. However, many of these parameters are only poorly constrained. We demonstrate a new method for inverting present day Earth observations for mantle properties. We use neural networks to represent the posterior probability density functions of many different mantle properties given the present structure of the mantle. We construct these probability density functions by sampling a wide range of possible mantle properties and running forward simulations, using the convection code StagYY. Our approach is particularly powerful because of its flexibility. Our samples are selected in the prior space, rather than being targeted towards a particular observation, as would normally be the case for probabilistic inversion. This means that the same suite of simulations can be used for inversions using a wide range of geophysical observations without the need to resample. Our method is probabilistic and non-linear and is therefore compatible with non-linear convection, avoiding some of the limitations associated with other methods for inverting mantle flow. This allows us to consider the entire history of the mantle. We also need relatively few samples for our inversion, making our approach computationally tractable when considering long periods of mantle history. Using the present thermal and density structure of the mantle, we can constrain rheological and compositional parameters such as viscosity and yield stress. We can also use the present day mantle structure to make inferences about the initial conditions for convection 4.5 Gyr ago. We can constrain initial mantle conditions including the initial concentration of heat producing elements in the mantle and the initial thickness of primordial material at the CMB. Currently we use density and temperature structure for our inversions, but we can

  17. Multstage Melting and Mantle Flow in the Galapagos Plume-Ridge Province

    NASA Astrophysics Data System (ADS)

    Geist, D.

    2010-12-01

    residue from the upper melt zone (depleted in all incompatible elements) overlying residue from the lower melt zone (depleted in volatiles, including helium). The northern Galapagos volcanoes tap either ambient upper mantle or plume that has been depleted by both stages of melting, whereas the GSC is supplied by the deeper return flow, which has only been depleted of its volatile components.

  18. The silica heat flow interpretation technique: application to continental Australia

    NASA Astrophysics Data System (ADS)

    Pirlo, M. C.

    2002-06-01

    The silica heat flow interpretation technique [Swanberg, C.A. and Morgan, P., J. Geophys. Res. 117 (1979) 227-241; J. Geophys. Res. 85 (1980) 7206-7214] has been applied and tested in mainland Australia, using a database of approximately 41 000 Australian groundwater analyses. The silica geotemperature of the groundwaters was obtained by substituting the dissolved silica content of a groundwater into the quartz geothermometer equation of Truesdell [(1976) Proceedings of the Second United Nations Symposium on the Development and Use of Geothermal Resources. San Francisco, CA, USA, 20-29 May, 1975, Vol. 1]. The average silica geotemperature value for 1×1° (latitude×longitude) grid cells has been calculated and the results plotted against published traditional heat flow values for those grid cells [Cull, J.P. (1982) BMR J. Aust. Geol. Geophys. 7, 11-21], to form silica heat flow estimation models. Data exclusion criteria, based upon data quantity and statistical spread have been applied to both the groundwater data and the traditional heat flow data. This was done in order to exclude areas that were poorly categorized in terms of data quality and quantity. For the remaining data, a significant linear relationship between the groundwater geotemperature estimates and traditional heat flow measurements has been identified for four of the models with a t-test on the correlation coefficient. Estimates of regional heat flow were then made by applying the calibration models in areas with no traditional heat flow measurements but adequate groundwater data. A silica heat flow map has been constructed using one of the models and the differences between it and the traditional heat flow map evaluated. Good correlations exist between the silica heat flow map and the traditional heat flow map, except for the northwest Yilgarn, of WA, Australia, where silica heat flow data give significantly higher values than traditional data. The silica heat flow map identifies areas of high

  19. Planetary heat flow from shallow subsurface measurements: Mars

    NASA Astrophysics Data System (ADS)

    Cornwall, Marc; Hagermann, Axel

    2016-10-01

    Planetary heat flow probes measure heat flow (depth-resolved temperature and thermal conductivity) to provide insight into the internal state of a planet. The probes have been utilized extensively on Earth, twice on the Moon, and once on the Surface of comet 67P-CG. Mars is an important target for heat flow measurement as heat flow is a critical parameter in Martian thermal history models. Earlier studies indicate that Martian planetary heat flow can be accessed at 5 m below the surface in dry regolith monitored over at least one Martian year. A one Martian year monitoring period is necessary because, in the shallow subsurface, heat flow from the interior is superposed with time varying heat flow contributions, primarily due to insolation. Given that a heat flow probe may not achieve its target depth or monitoring period, this study investigates how the depth (2-5 m), duration (0-1 Martian year) and quality of measurements influence the accuracy of planetary heat flow. An inverse model is used to show that, in the preceding scenarios, the accuracy of planetary heat flow directly estimated from depth-dependent thermal conductivity with 10-20% precision errors, temperatures with 50-100 mK precision errors and modelling uncertainties up to 500 mK, can, on average, be improved by a factor of 27 with optimization to 13%. Accuracies increase with sensor penetration depth and regolith monitoring period. Heat flow optimized from instantaneous measurements or those with the shortest regolith monitoring periods have increased accuracy where the frequency and amplitude of the temperature variation are lowest. The inverse model is based on the Function Specification Inversion method. This study demonstrates that a solution subspace can be identified within a space of uncertainties modelled for the temperature measurements and planetary heat flow: the subspace is defined by a constant log-ratio of their respective standard deviations. Optimized heat flow estimates display

  20. Heat flow in the Great Plains of the United States

    NASA Astrophysics Data System (ADS)

    Gosnold, William D.

    1990-01-01

    Anomalous high heat flow previously reported for the Great Plains is inconsistent with the tectonic setting and requires reexamination. Forty-six new heat flow measurements, 12 revised heat flow values, and several hundred geothermal gradient measurements indicate extensive geothermal anomalies with heat flows ranging from 80 to 140 mW m-2 in the northern and central Great Plains. Heat flow in the Great Plains outside the geothermally anomalous regions ranges from 40 - 60 mW m-2. The heat flow anomalies result from the thermal effects of regional groundwater flow where it moves upward either within a dipping aquifer or by cross-formational flow through fractures. The gravitational driving force for the groundwater flow derives from the eastward sloping surface of the Great Plains, and the locations of the geothermal amonalies are determined by the structures of the aquifers and the crystalline basement rocks. The most widespread and largest-amplitude geothermal anomaly occurs in southern South Dakota and northern Nebraska. Another large anomaly occurs on the eastern flank of the Denver Basin, and small anomalies occur on structures such as the Billings and Nesson anticlines in the Williston Basin. Previous reports of high heat flow in the Great Plains generally are supported by the results of this study. However, the source of anomalous heat is shown to be nontectonic, and theoretical arguments for normal continental heat flow in the Great Plains are supported. Another difference from the results of previous heat flow studies is that the thermal conductivities of shales in the Mesozoic strata in the Great Plains are about 40% lower than the conductivities that commonly have been used for shales. This observation and recent studies which have suggested lower thermal conductivities for shales in the Great Plains are the reasons for revision of some previous heat flow calculations. A significant result of revising some of the previous heat flow values is that the high

  1. Numerical studies on convective stability and flow pattern in three-dimensional spherical mantle of terrestrial planets

    NASA Astrophysics Data System (ADS)

    Yanagisawa, Takatoshi; Kameyama, Masanori; Ogawa, Masaki

    2016-09-01

    We explore thermal convection of a fluid with a temperature-dependent viscosity in a basally heated 3-D spherical shell using linear stability analyses and numerical experiments, while considering the application of our results to terrestrial planets. The inner to outer radius ratio of the shell f assumed in the linear stability analyses is in the range of 0.11-0.88. The critical Rayleigh number Rc for the onset of thermal convection decreases by two orders of magnitude as f increases from 0.11 to 0.88, when the viscosity depends sensitively on the temperature, as is the case for real mantle materials. Numerical simulations carried out in the range of f = 0.11-0.55 show that a thermal boundary layer (TBL) develops both along the surface and bottom boundaries to induce cold and hot plumes, respectively, when f is 0.33 or larger. However, for smaller f values, a TBL develops only on the bottom boundary. Convection occurs in the stagnant-lid regime where the root mean square velocity on the surface boundary is less than 1 per cent of its maximum at depth, when the ratio of the viscosity at the surface boundary to that at the bottom boundary exceeds a threshold that depends on f. The threshold decreases from 106.5 at f = 0.11 to 104 at f = 0.55. If the viscosity at the base of the convecting mantle is 1020-1021 Pa s, the Rayleigh number exceeds Rc for Mars, Venus and the Earth, but does not for the Moon and Mercury; convection is unlikely to occur in the latter planets unless the mantle viscosity is much lower than 1020 Pa s and/or the mantle contains a strong internal heat source.

  2. The upper mantle transition region - Eclogite

    NASA Technical Reports Server (NTRS)

    Anderson, D. L.

    1979-01-01

    The upper mantle transition region is usually considered to be peridotite which undergoes a series of phase changes involving spinel and post-spinel assemblages. There are difficulties associated with attempts to explain the 220, 400 and 670 km discontinuities in terms of phase changes in a peridotitic mantle. Moreover, in a differentiated earth there should be large quantities of eclogite in the upper mantle. Eclogite is denser than Al2O3-poor mantle to depths of 670 km, but it stays in the garnet stability field to pressures in excess of those required to transform depleted mantle to denser phases such as ilmenite and perovskite. Eclogite, therefore, remains above 670 km. The seismic properties of the transition region are more consistent with eclogite than peridotite. Most of the mantle's inventory of incompatible trace elements may be in this layer, which is a potential source region for some basalt magmas. The radioactivity in this layer is the main source of mantle heat flow, 0.7 microcalorie/sq cm-sec, and drives upper mantle convection.

  3. The upper mantle transition region - Eclogite

    NASA Technical Reports Server (NTRS)

    Anderson, D. L.

    1979-01-01

    The upper mantle transition region is usually considered to be peridotite which undergoes a series of phase changes involving spinel and post-spinel assemblages. There are difficulties associated with attempts to explain the 220, 400 and 670 km discontinuities in terms of phase changes in a peridotitic mantle. Moreover, in a differentiated earth there should be large quantities of eclogite in the upper mantle. Eclogite is denser than Al2O3-poor mantle to depths of 670 km, but it stays in the garnet stability field to pressures in excess of those required to transform depleted mantle to denser phases such as ilmenite and perovskite. Eclogite, therefore, remains above 670 km. The seismic properties of the transition region are more consistent with eclogite than peridotite. Most of the mantle's inventory of incompatible trace elements may be in this layer, which is a potential source region for some basalt magmas. The radioactivity in this layer is the main source of mantle heat flow, 0.7 microcalorie/sq cm-sec, and drives upper mantle convection.

  4. 3D analytical investigation of melting at lower mantle conditions in the laser-heated diamond anvil cel

    NASA Astrophysics Data System (ADS)

    Nabiei, F.; Cantoni, M.; Badro, J.; Dorfman, S. M.; Gaal, R.; Piet, H.; Gillet, P.

    2015-12-01

    The diamond anvil cell is a unique tool to study materials under static pressures up to several hundreds of GPa. It is possible to generate temperatures as high as several thousand degrees in the diamond anvil cell by laser heating. This allows us to achieve deep mantle conditions in the laser-heated diamond anvil cell (LHDAC). The small heated volume is surrounded by thermally conductive diamond anvils results in high temperature gradients which affect phase transformation and chemical distribution in the LH-DAC. Analytical characterization of samples in three dimensions is essential to fully understand phase assemblages and equilibrium in LHDAC. In this study we used San Carlos olivine as a starting material as a simple proxy to deep mantle composition. Three samples were melted at ~3000 K and at ~45 GPa for three different durations ranging from 1 to 6 minutes; two other samples were melted at 30 GPa and 70 GPa. All samples were then sliced by focused ion beam (FIB). From each slice, an electron image and energy dispersive X-ray (EDX) map were acquired by scanning electron microscope (SEM) in the dual beam FIB instrument. These slices were collected on one half of the heated area in each sample, from which we obtained 3D elemental and phase distribution. The other half of the heated area was used to extract a 100 nm thick section for subsequent analysis by analytical transmission electron microscopy (TEM) to obtain diffraction patterns and high resolution EDX maps. 3D reconstruction of SEM EDX results shows at least four differentiated regions in the heated area for all samples. The exact Fe and Mg compositions mentioned below are an example of the sample melted at 45 GPa for 6 minutes. The bulk of the heated are is surrounded by ferropericlase (Mg0.92, Fe0.08)O shell (Fp). Inside this shell we find a thick region of (Mg,Fe)SiO3 perovskite-structured bridgmanite (Brg) coexisting with Fp. In the center lies a Fe-rich core which is surrounded by magnesiow

  5. Melting and reactive flow of a volatilized mantle beneath mid-ocean ridges: theory and numerical models

    NASA Astrophysics Data System (ADS)

    Keller, Tobias; Katz, Richard F.

    2015-04-01

    Laboratory experiments indicate that even small concentrations volatiles (H2O or CO2) in the upper mantle significantly affect the silicate melting behavior [HK96,DH06]. The presence of volatiles stabilizes volatile-rich melt at high pressure, thus vastly increasing the volume of the upper mantle expected to be partially molten [H10,DH10]. These small-degree melts have important consequences for chemical differentiation and could affect the dynamics of mantle flow. We have developed theory and numerical implementation to simulate thermo-chemically coupled magma/mantle dynamics in terms of a two-phase (rock+melt), three component (dunite+MORB+volatilized MORB) physical model. The fluid dynamics is based on McKenzie's equations [McK84], while the thermo-chemical formulation of the system is represented by a novel disequilibrium multi-component melting model based on thermo-dynamic theory [RBS11]. This physical model is implemented as a parallel, two-dimensional, finite-volume code that leverages tools from the PETSc toolkit. Application of this simulation code to a mid-ocean ridge system suggests that the methodology captures the leading-order features of both hydrated and carbonated mantle melting, including deep, low-degree, volatile-rich melt formation. Melt segregation leads to continuous dynamic thermo-chemical dis-equilibration, while phenomenological reaction rates are applied to continually move the system towards re-equilibration. The simulations will be used first to characterize volatile extraction from the MOR system assuming a chemically homogeneous mantle. Subsequently, simulations will be extended to investigate the consequences of heterogeneity in lithology [KW12] and volatile content. These studies will advance our understanding of the role of volatiles in the dynamic and chemical evolution of the upper mantle. Moreover, they will help to gauge the significance of the coupling between the deep carbon cycle and the ocean/atmosphere system. REFERENCES

  6. Helium in deep circulating groundwater in the Great Hungarian Plain: Flow dynamics and crustal and mantle helium fluxes

    NASA Astrophysics Data System (ADS)

    Stute, M.; Sonntag, C.; Deák, J.; Schlosser, P.

    1992-05-01

    Observed helium concentrations in deep circulating groundwater of the sedimentary basin of the Great Hungarian Plain (GHP), Hungary, cover a range of three orders of magnitude (≈4 ·10 -8 to 4 · 10 -5 ccSTP g-1). 3He /4He ratios and noble gas concentrations are used to separate helium components originating from the atmosphere, tritium decay, crustal production, and mantle degassing. The characteristic distribution of measured helium concentrations and isotope ratios can be reproduced qualitatively by a simple two-dimensional advection/diffusion model. Other simple models isolating parts of the regional flow domain (recharge, discharge, and horizontal flow) are discussed and applied to derive quantitative information on helium fluxes due to degassing of the Earth's crust /mantle and on the dynamics of groundwater flow. The estimated helium flux of 0.7-4.5 · 10 9 atoms 4He m -2 s -1 is lower than values derived from other deep groundwater circulation systems, probably because the relatively young upper few thousand meters of the sedimentary basin (Tertiary to Quaternary age) shield the flux from the deeper crust. The high mantle helium flux of up to 4.2 · 10 8 atoms 4He m -2 s -1 is probably related to the Miocene volcanism or to continuing intrusion accompanying extension. By fitting calculated helium depth profiles to measured data in the discharge area, vertical flow velocities of the order of 1.5 mm y -1 are estimated. Assuming that a flux of 0.7-4.5 · 10 9 atoms 4He m -2 s -1 is representative for the entire basin, the turnover time of the regional groundwater flow system is estimated to be about 10 6 y.

  7. A sharp cratonic lithosphere-asthenosphere boundary beneath the American Midwest and its relation to mantle flow

    NASA Astrophysics Data System (ADS)

    Foster, K.; Dueker, K.; Schmandt, B.; Yuan, H.

    2014-09-01

    Beneath the American Midwest, S-to-P (Sp) converted wave imaging and multi-mode surface wave tomography identify a north-trending transition in seismic structure at 150-250 km depth. To the east of this American Midwest transition (AMT), the lithosphere-asthenosphere boundary (LAB) is imaged as a 1-2% Sp/Sv amplitude arrival at 200-240 km depth, consistent with the depth of negative shear velocity and azimuthal anisotropy gradients imaged by surface wave tomography. To the west of the AMT, Sp conversions are much shallower at 150-190 km depth and are much weaker (<0.7%) or absent. Azimuthal anisotropy constrained by surface wave tomography also changes across the AMT, with stronger anisotropy to the east of the transition beneath the thicker lithospheric root. We suggest that the seismic changes across the AMT can be explained by considering the effects of asthenospheric flow beneath the leading edge of the thick lithospheric root. The mantle flow is dominantly driven by the drift of the North America plate. Locally higher flow velocities are expected where the asthenosphere is forced to flow beneath the thicker root. This mantle underflow could create a sharper seismic LAB east of the AMT via two effects. First, the local increase in flow velocities could steepen the thermal gradient at the base of the lithosphere, and hence the isotropic velocity contrast. Second, the increased strain rate along edge of the lithosphere could enhance the magnitude of azimuthal anisotropy. Our results suggest that seismically detectable LAB sharpness variations could be used to constrain geographic variations in coupling between plates and mantle convection. A secondary result is the image of a Mid-Lithospheric Discontinuity arrival at 80-110 km depth that is found primarily to the east of the AMT. This arrival is interpreted as produced by a layer of low-velocity metasomatic minerals that have accumulated since the >1.8 Ga creation of the lithosphere.

  8. Air-side flow and heat transfer in compact heat exchangers: A discussion of enhancement mechanisms

    SciTech Connect

    Jacobi, A.M.; Shah, R.K.

    1998-10-01

    The behavior of air flows in complex heat exchanger passages is reviewed with a focus on the heat transfer effects of boundary-layer development, turbulence, spanwise and streamwise vortices, and wake management. Each of these flow features is discussed for the plain, wavy, and interrupted passages found in contemporary compact heat exchanger designs. Results from the literature are used to help explain the role of these mechanisms in heat transfer enhancement strategies.

  9. Heat flow and convection demonstration experiments aboard Apollo 14.

    NASA Technical Reports Server (NTRS)

    Grodzka, P. G.; Bannister, T. C.

    1972-01-01

    A group of experiments was conducted by Apollo 14 astronaut Stuart A. Roosa during the lunar flyback on Feb. 7, 1971, to obtain information on heat flow and convection in gases and liquids in an environment of less than 0.000001 g gravity. Flow observations and thermal data have shown that: (1) there are, as expected, convective motions caused by surface tension gradients in a plane liquid layer with a free upper surface; (2) heat flow in enclosed liquids and gases occurs mainly by diffusive heat conduction; and (3) some convective processes, whose characteristics are not fully known, add to the heat transfer.

  10. Flow instability and flow reversal in heated annular multichannels with initial downward flow

    SciTech Connect

    Guerrero, H.N.; Hart, C.M.

    1992-01-01

    Experimental and theoretical results are presented regarding the stability of initial downward flow of single phase water in parallel annular channels of the Savannah River Site (SRS) fuel assembly. The test was performed on an electrically heated prototypic mockup of a Mark-22 fuel assembly. The test conditions consisted of mass fluxes, from 98--294 kg/m[sup 2]-sec, and inlet water temperatures of 25[degrees]C and 40[degrees]C. With increased power to the heaters, flow instability was detected, characterized by flow fluctuations and flow redistribution among subchannels of the outer flow channel. With increased power, a condition was observed indicating local subchannel flow reversals where certain subchannel fluid temperatures were high at the inlet and low at the exit. With additional power increased, a critical heat flux condition was observed indicating local subchannel flow reversals where certain subchannel fluid temperatures were high at the inlet and low at the exit. With additional power increases, a critical heat flux condition was reached in the outer channel.

  11. Flow instability and flow reversal in heated annular multichannels with initial downward flow

    SciTech Connect

    Guerrero, H.N.; Hart, C.M.

    1992-12-31

    Experimental and theoretical results are presented regarding the stability of initial downward flow of single phase water in parallel annular channels of the Savannah River Site (SRS) fuel assembly. The test was performed on an electrically heated prototypic mockup of a Mark-22 fuel assembly. The test conditions consisted of mass fluxes, from 98--294 kg/m{sup 2}-sec, and inlet water temperatures of 25{degrees}C and 40{degrees}C. With increased power to the heaters, flow instability was detected, characterized by flow fluctuations and flow redistribution among subchannels of the outer flow channel. With increased power, a condition was observed indicating local subchannel flow reversals where certain subchannel fluid temperatures were high at the inlet and low at the exit. With additional power increased, a critical heat flux condition was observed indicating local subchannel flow reversals where certain subchannel fluid temperatures were high at the inlet and low at the exit. With additional power increases, a critical heat flux condition was reached in the outer channel.

  12. Mantle-circulation models with sequential data assimilation: inferring present-day mantle structure from plate-motion histories.

    PubMed

    Bunge, Hans-Peter; Richards, M A; Baumgardner, J R

    2002-11-15

    Data assimilation is an approach to studying geodynamic models consistent simultaneously with observables and the governing equations of mantle flow. Such an approach is essential in mantle circulation models, where we seek to constrain an unknown initial condition some time in the past, and thus cannot hope to use first-principles convection calculations to infer the flow history of the mantle. One of the most important observables for mantle-flow history comes from models of Mesozoic and Cenozoic plate motion that provide constraints not only on the surface velocity of the mantle but also on the evolution of internal mantle-buoyancy forces due to subducted oceanic slabs. Here we present five mantle circulation models with an assimilated plate-motion history spanning the past 120 Myr, a time period for which reliable plate-motion reconstructions are available. All models agree well with upper- and mid-mantle heterogeneity imaged by seismic tomography. A simple standard model of whole-mantle convection, including a factor 40 viscosity increase from the upper to the lower mantle and predominantly internal heat generation, reveals downwellings related to Farallon and Tethys subduction. Adding 35% bottom heating from the core has the predictable effect of producing prominent high-temperature anomalies and a strong thermal boundary layer at the base of the mantle. Significantly delaying mantle flow through the transition zone either by modelling the dynamic effects of an endothermic phase reaction or by including a steep, factor 100, viscosity rise from the upper to the lower mantle results in substantial transition-zone heterogeneity, enhanced by the effects of trench migration implicit in the assimilated plate-motion history. An expected result is the failure to account for heterogeneity structure in the deepest mantle below 1500 km, which is influenced by Jurassic plate motions and thus cannot be modelled from sequential assimilation of plate motion histories

  13. A Prototype Flux-Plate Heat-Flow Sensor for Venus Surface Heat-Flow Determinations

    NASA Technical Reports Server (NTRS)

    Morgan, Paul; Reyes, Celso; Smrekar, Suzanne E.

    2005-01-01

    Venus is the most Earth-like planet in the Solar System in terms of size, and the densities of the two planets are almost identical when selfcompression of the two planets is taken into account. Venus is the closest planet to Earth, and the simplest interpretation of their similar densities is that their bulk compositions are almost identical. Models of the thermal evolution of Venus predict interior temperatures very similar to those indicated for the regions of Earth subject to solid-state convection, but even global analyses of the coarse Pioneer Venus elevation data suggest Venus does not lose heat by the same primary heat loss mechanism as Earth, i.e., seafloor spreading. The comparative paucity of impact craters on Venus has been interpreted as evidence for relatively recent resurfacing of the planet associated with widespread volcanic and tectonic activity. The difference in the gross tectonic styles of Venus and Earth, and the origins of some of the enigmatic volcano-tectonic features on Venus, such as the coronae, appear to be intrinsically related to Venus heat loss mechanism(s). An important parameter in understanding Venus geological evolution, therefore, is its present surface heat flow. Before the complications of survival in the hostile Venus surface environment were tackled, a prototype fluxplate heat-flow sensor was built and tested for use under synthetic stable terrestrial surface conditions. The design parameters for this prototype were that it should operate on a conforming (sand) surface, with a small, self-contained power and recording system, capable of operating without servicing for at least several days. The precision and accuracy of the system should be < 5 mW/sq m. Additional information is included in the original extended abstract.

  14. Continent-ocean chemical heterogeneity in the mantle based on seismic tomography.

    PubMed

    Forte, A M; Dziewonski, A M; O'connell, R J

    1995-04-21

    Seismic models of global-scale lateral heterogeneity in the mantle show systematic differences below continents and oceans that are too large to be purely thermal in origin. An inversion of the geoid, based on a seismic model that includes viscous flow in the mantle, indicates that the differences beneath continents and oceans can be accounted for by differences in composition in the upper mantle superposed on mantle-wide thermal heterogeneities. The net continent-ocean density differences, integrated over depth, are small and cause only a low flux of mass and heat across the asthenosphere and mantle transition zone.

  15. Inductive heating with magnetic materials inside flow reactors.

    PubMed

    Ceylan, Sascha; Coutable, Ludovic; Wegner, Jens; Kirschning, Andreas

    2011-02-07

    Superparamagnetic nanoparticles coated with silica gel or alternatively steel beads are new fixed-bed materials for flow reactors that efficiently heat reaction mixtures in an inductive field under flow conditions. The scope and limitations of these novel heating materials are investigated in comparison with conventional and microwave heating. The results suggest that inductive heating can be compared to microwave heating with respect to rate acceleration. It is also demonstrated that a very large diversity of different reactions can be performed under flow conditions by using inductively heated flow reactors. These include transfer hydrogenations, heterocyclic condensations, pericyclic reactions, organometallic reactions, multicomponent reactions, reductive cyclizations, homogeneous and heterogeneous transition-metal catalysis. Silica-coated iron oxide nanoparticles are stable under many chemical conditions and the silica shell could be utilized for further functionalization with Pd nanoparticles, rendering catalytically active heatable iron oxide particles. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Correlation Between Mobile Continents and Elevated Temperatures in the Subcontinental Mantle

    NASA Astrophysics Data System (ADS)

    Jain, C.; Rozel, A. B.; Tackley, P.

    2015-12-01

    Rolf et al. (EPSL, 2012) and Coltice et al. (Science, 2012) have previously shown that continents exert a first order influence on Earth's mantle flow by affecting convective wavelength and surface heat flow. With stationary continents, Heron and Lowman (JGR, 2014) highlighted the decreasing role of continental insulation on subcontinental temperatures with higher Rayleigh number (Ra). However, the question whether there exists a correlation between mobile continents and elevated temperatures in the subcontinental mantle or not remains to be answered. Continental motion is attributed to the viscous stresses imparted by the convecting mantle and the extent of this motion depends on the heat budget of the mantle. Core-mantle boundary (CMB) heat flux, internal heating from decay of radioactive elements, and mantle cooling contribute to this heat budget. Out of these sources, CMB heat flux is not well defined. However, the recent determination of core's high thermal conductivity requires a CMB heat flow of at least 12 TW (de Koker et al., PNAS 2012; Pozzo et al., Nature 2012; Gomi et al., PEPI 2013). Thus it is necessary to characterize the impact of basal heating on mantle dynamics with mobile continents and self-consistent plate tectonics. By systematically varying parameters such as CMB temperature, continental size, mantle heating modes, and Rayleigh number; we model Boussinesq, incompressible, thermo-chemical mantle convection with 2D spherical annulus geometry using StagYY (Tackley, PEPI 2008). We observe the aforementioned correlation irrespective of the variations in basal heating and continental size (except for very small continents). Moreover, we see episodicity between correlation-anticorrelation with increasing convective vigour. Furthermore, the effect of radioactivity in the continental crust on this correlation is investigated. At present, mobile continents in StagYY are simplified into a compositionally distinct field drifting at the top of the mantle

  17. Melt migration through Io's convecting mantle

    NASA Astrophysics Data System (ADS)

    Elder, C. M.; Showman, A. P.

    2013-12-01

    The extensive volcanism occurring on the surface of Io suggests that its interior must contain at least some partial melt. Unlike Earth, Io cannot lose its internal heat through convection alone [1]. Instead, melt moving through the solid mantle helps remove heat from Io's interior by carrying its latent heat towards the surface as it buoyantly ascends through the mantle. We investigate this process by considering melt migration in a column of rock rising through the mantle between downwelling plumes. Convective scaling laws provide the upwelling velocity and the temperature of the rising mantle. Properties of melt migration in this rising mantle are calculated using porous flow equations and an equation for the conservation of energy which includes latent heat consumption, heat advection and heat conduction [2]. This combination of convective scaling laws and porous flow laws allows us to self-consistently determine the radial melt fraction profile in Io's interior, the average melt fraction in Io's interior and the heat flux due to advection of melt. The average melt fraction can be compared to the melt fraction constraints calculated by [3] from Galileo magnetometer measurements. The surface heat flux calculations can be compared to the value of Io's observed surface heat flux which ranges with observation from 1.5-4 W m-2 [4]. [1] Moore W. B. (2003) J. Geophys. Res., 108, E8, 15-1. [2] Hewitt I. J. and Fowler A. C. (2008) Proc. R. Soc. A., 464, 2467-2491. [3] Khurana K. K. et al. (2011) Science, 332, 1186-1189. [4] Moore, W. B. et al. (2007) In: Io After Galileo, Springer-Praxis, 89-108.

  18. Heat transfer measurements of the 1983 kilauea lava flow.

    PubMed

    Hardee, H C

    1983-10-07

    Convective heat flow measurements of a basaltic lava flow were made during the 1983 eruption of Kilauea volcano in Hawaii. Eight field measurements of induced natural convection were made, giving heat flux values that ranged from 1.78 to 8.09 kilowatts per square meter at lava temperatures of 1088 and 1128 degrees Celsius, respectively. These field measurements of convective heat flux at subliquidus temperatures agree with previous laboratory measurements in furnace-melted samples of molten lava, and are useful for predicting heat transfer in magma bodies and for estimating heat extraction rates for magma energy.

  19. Heat-transfer measurements of the 1983 Kilauea lava flow

    SciTech Connect

    Hardee, H.C.

    1983-10-07

    Convective heat flow measurements of a basaltic lava flow were made during the 1983 eruption of Kilauea volcano in Hawaii. Eight field measurements of induced natural convection were made, giving heat flux values that ranged from 1.78 to 8.09 kilowatts per square meter at lava temperatures of 1088 and 1128 degrees Celsius, respectively. These field measurements of convective heat flux at subliquidus temperatures agree with previous laboratory measurements in furnace-melted samples of molten lava, and are useful for predicting heat transfer in magma bodies and for estimating heat extraction rates for magma energy.

  20. The vertical flow in the lowermost mantle beneath the Pacific from inversion of seismic waveforms for anisotropic structure

    NASA Astrophysics Data System (ADS)

    Kawai, Kenji; Geller, Robert J.

    2010-08-01

    It is impractical to directly constrain the elastic constants of a transversely isotropic (TI) medium using travel-time data. In contrast, as we show in this paper, the elastic constants can be determined straightforwardly by inversion of body-wave waveform data. We invert the horizontal components of observed seismic waveforms of S and ScS phases (as well as any other phases arriving in the time window) to determine the radial profile of TI shear wave velocity in the lowermost mantle beneath the Pacific. We find that the radial (SV) component is faster than the transverse (SH) component in the depth range from about 200-400 km above the core-mantle boundary (CMB). The major mineralogical components above the D″ discontinuity in this depth range are Mg-perovskite (pv) and ferropericlase (fp). The observed anisotropy can be interpreted as due to lattice preferred orientation (LPO) of either pv, fp, or both in the lowermost mantle induced by vertical flow due to thermal buoyancy, which might be related to the origin of the Hawaiian hotspot (although other possibilities such as a chemically distinct layer, LPO of post-perovskite (ppv), or LPO in counter-flow in and around a chemically dense pile cannot be excluded). We show that resolution of the velocity of SV shear waves very close to the CMB is inherently limited due to the boundary condition of zero tangential traction at the CMB; shear wave splitting studies thus cannot be used to investigate the anisotropy of the lowermost mantle.

  1. New Inferences of Earth's Mantle Viscosity Structure and Implications for Long-wavelength Structure in the Lower Mantle

    NASA Astrophysics Data System (ADS)

    Rudolph, M. L.; Lekic, V.; Lithgow-Bertelloni, C. R.

    2015-12-01

    predictions of evolving long-wavelength thermochemical structures as well as the core-mantle boundary heat flow.

  2. 3D crustal-scale heat-flow regimes at a developing active margin (Taranaki Basin, New Zealand)

    NASA Astrophysics Data System (ADS)

    Kroeger, K. F.; Funnell, R. H.; Nicol, A.; Fohrmann, M.; Bland, K. J.; King, P. R.

    2013-04-01

    The Taranaki Basin in the west of New Zealand's North Island has evolved from a rifted Mesozoic Gondwana margin to a basin straddling the Neogene convergent Australian-Pacific plate margin. However, given its proximity to the modern subduction front, Taranaki Basin is surprisingly cold when compared to other convergent margins. To investigate the effects of active margin evolution on the thermal regime of the Taranaki Basin we developed a 3D crustal-scale forward model using the petroleum industry-standard basin-modelling software Petromod™. The crustal structure inherited from Mesozoic Gondwana margin breakup and processes related to modern Hikurangi convergent margin initiation are identified to be the main controls on the thermal regime of the Taranaki Basin. Present-day surface heat flow across Taranaki on average is 59 mW/m2, but varies by as much as 30 mW/m2 due to the difference in crustal heat generation between mafic and felsic basement terranes alone. In addition, changes in mantle heat advection, tectonic subsidence, crustal thickening and basin inversion, together with related sedimentary processes result in variability of up to 10 mW/m2. Modelling suggests that increased heating of the upper crust due to additional mantle heat advection following the onset of subduction is an ongoing process and heating has only recently begun to reach the surface, explaining the relatively low surface heat flow. We propose that the depth of the subducted slab and related mantle convection processes control the thermal and structural regimes in the Taranaki Basin. The thermal effects of the subduction initiation process are modified and overprinted by the thickness, structure and composition of the lithosphere.

  3. Lithospheric stress and uppermantle dynamics in mainland China due to mantle flow based on combination of global- and regional-scale seismic tomography

    NASA Astrophysics Data System (ADS)

    Zhu, Tao

    2016-12-01

    In order to explore the importance of mantle flow to lithospheric stress field in mainland China, seismic tomography_based mantle flow models are used to predict the most compressive principal horizontal stress directions (MCPHSDs). Considered that regional-scale seismic tomography models have higher horizontal resolution to map the mantle structure, while global-scale models can present the information out of the imaging domains of regional-scale models although this information has relatively poor horizontal resolution, the combined global- and regional-scale seismic tomography_based mantle flow models (hereafter called combined models) are mainly used in this paper. After the comparison of the observed and our predicted MCPHSDs, it is suggested that (1) a combined model, compared with a only global-scale seismic tomography_based model, could improve greatly the predictions in some regions of mainland China such as Sichuan-Yunnan, South China and North China blocks; (2) the mantle flow model driven by both plate motions and mantle density heterogeneity (hereafter called plate-density-driven model), compared with the flow model driven only by mantle density heterogeneity (hereafter called density-driven model), has much better predictions in the eastern China; (3) the presence of density variations above 250 km could better dramatically the predictions in the eastern China; and (4) sublithospheric mantle flow causes the lithosphere under compression in mainland China, and plays an important role in forming the lithospheric stress in Alashan, Qaidam, western Tibetan and eastern Tarim blocks as well as the east of the eastern China.

  4. Exhaust bypass flow control for exhaust heat recovery

    DOEpatents

    Reynolds, Michael G.

    2015-09-22

    An exhaust system for an engine comprises an exhaust heat recovery apparatus configured to receive exhaust gas from the engine and comprises a first flow passage in fluid communication with the exhaust gas and a second flow passage in fluid communication with the exhaust gas. A heat exchanger/energy recovery unit is disposed in the second flow passage and has a working fluid circulating therethrough for exchange of heat from the exhaust gas to the working fluid. A control valve is disposed downstream of the first and the second flow passages in a low temperature region of the exhaust heat recovery apparatus to direct exhaust gas through the first flow passage or the second flow passage.

  5. Earth tides, global heat flow, and tectonics.

    PubMed

    Shaw, H R

    1970-05-29

    The power of a heat engine ignited by tidal energy can account for geologically reasonable rates of average magma production and sea floor spreading. These rates control similarity of heat flux over continents and oceans because of an inverse relationship between respective depth intervals for mass transfer and consequent distributions of radiogenic heat production.

  6. Cryogenic Heat Exchanger with Turbulent Flows

    ERIC Educational Resources Information Center

    Amrit, Jay; Douay, Christelle; Dubois, Francis; Defresne, Gerard

    2012-01-01

    An evaporator-type cryogenic heat exchanger is designed and built for introducing fluid-solid heat exchange phenomena to undergraduates in a practical and efficient way. The heat exchanger functions at liquid nitrogen temperature and enables cooling of N[subscript 2] and He gases from room temperatures. We present first the experimental results of…

  7. Cryogenic Heat Exchanger with Turbulent Flows

    ERIC Educational Resources Information Center

    Amrit, Jay; Douay, Christelle; Dubois, Francis; Defresne, Gerard

    2012-01-01

    An evaporator-type cryogenic heat exchanger is designed and built for introducing fluid-solid heat exchange phenomena to undergraduates in a practical and efficient way. The heat exchanger functions at liquid nitrogen temperature and enables cooling of N[subscript 2] and He gases from room temperatures. We present first the experimental results of…

  8. Earth tides, global heat flow, and tectonics

    USGS Publications Warehouse

    Shaw, H.R.

    1970-01-01

    The power of a heat engine ignited by tidal energy can account for geologically reasonable rates of average magma production and sea floor spreading. These rates control similarity of heat flux over continents and oceans because of an inverse relationship between respective depth intervals for mass transfer and consequent distributions of radiogenic heat production.

  9. Boiling inside tubes: Critical heat flux for upward flow in uniformly heated vertical tubes

    NASA Astrophysics Data System (ADS)

    1986-11-01

    ESDU 85041 recommended a procedure for estimating the heat flux at different locations along a heated tube through which a boiling liquid is flowing, assuming that the wall is wetted by the liquid. The purpose of this Data Item (ESDU 86032) is to enable the reader to check, in the case of flow up a uniformly heated vertical tube, that the heat flux does not exceed the critical value above which the liquid would not wet the wall. This point marks the onset of dryout accompanied by an increase in resistance to heat transfer and the possible onset of corrosion and overheating of the tube. The open literature contains many experimental values of the critical heat flux (CHF) in flow up electrically heated vertical tubes, mostly with water or R.12. These results have been used to check various procedures for predicting CHF with flow up vertical tubes. The recommended procedure is given in detail and illustrated in an example.

  10. Constraining the amount of radiogenic elements in the interior of Mars from the HP3 heat flow measurement

    NASA Astrophysics Data System (ADS)

    Grott, Matthias; Plesa, Ana-Catalina; Tosi, Nicola; Breuer, Doris

    2014-05-01

    The InSight mission (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) to be launched in 2016 will carry a seismometer (SEIS) and heat flow probe (HP3) to the martian surface, and address questions related to the size, physical state, and composition of the core and mantle, the thickness of the crust, and the thermal state of the interior. The heat flow measured at the surface depends on the amount of heat producing elements (HPE) present in the interior and offers a measurable quantity that can help to constrain the planetary heat budget. If the Urey ratio - the ratio between internal heat production and surface heat loss - is known, the heat production rate in the interior can be determined. We run thermal evolution models of increasing complexity and compared the obtained present-day Urey ratio for a set of different models/parameters. To this end, we used the 2D-3D mantle convection code Gaia [1], as well as 1D parameterized models [2]. We varied the initial amount of HPE [3, 4,5,6], used various viscosity formulations (temperature-, temperature- and depth-dependent viscosity, viscosity jump in the mid mantle), varied the size of the core, and considered models with and without phase transitions in the mantle. Additionally, we tested the effects of different partitioning of HPE between mantle and a fixed crust, different initial conditions (temperatures and boundary layer thicknesses) and reference viscosities. Our simulations show that, for a one-plate planet like Mars, the Urey ratio is mainly sensitive to the efficiency of mantle cooling, i.e. the mantle viscosity, and to the mean half-life of long-lived radiogenic isotopes. Given that models of the thermo-chemical evolution of Mars generally indicate reference viscosities below 1021 Pa s [3, 7], the martian Urey ratio is likely only a function of the Thorium concentration in the planetary interior. Surface radiogenic abundances determined from gamma-ray spectroscopy [8] are best

  11. Heat flow meter for the diagnostics of pipelines

    NASA Astrophysics Data System (ADS)

    Nussupbekov, Bekbolat R.; Karabekova, Dana Zh.; Khassenov, Ayanbergen K.; Zhirnova, Oxana; Zyska, Tomasz

    2016-09-01

    Thermal methods of nondestructive testing are widely used for the analysis of the thermal insulation of underground pipelines. In heat methadone nondestructive testing, the thermal energy is distributed in the test object. Temperature field of the object's surface is a source of information on the characteristics of heat transfer. This article describes the modifications we have developed some of the heat flux sensors. A common element of these devices is the battery thermoelectric sensor special design, acting as a thermoelectric converter heat flow.

  12. Effects of crystal preferred orientation on upper-mantle flow near plate boundaries: rheologic feedbacks and seismic anisotropy

    NASA Astrophysics Data System (ADS)

    Blackman, D. K.; Boyce, D. E.; Castelnau, O.; Dawson, P. R.; Laske, G.

    2017-09-01

    Insight into upper-mantle processes can be gained by linking flow-induced mineral alignment to regional deformation and seismic anisotropy patterns. Through a series of linked micro-macro scale numerical experiments, we explore the rheologic effects of crystal preferred orientation (CPO) and evaluate the magnitude of possible impacts on the pattern of flow and associated seismic signals for mantle that includes a cooling, thickening young oceanic lithosphere. The CPO and associated anisotropic rheology, computed by a micromechanical polycrystal model, are coupled with a large scale flow model (Eulerian Finite Element method) via a local viscosity tensor field, which quantifies the stress:strain rate response of a textured polycrystal. CPO is computed along streamlines throughout the model space and the corresponding viscosity tensor field at each element defines the local properties for the next iteration of the flow field. Stable flow and CPO distributions were obtained after several iterations for the two dislocation glide cases tested: linear and nonlinear stress:strain rate polycrystal behaviour. The textured olivine polycrystals are found to have anisotropic viscosity tensors in a significant portion of the model space. This directional dependence in strength impacts the pattern of upper-mantle flow. For background asthenosphere viscosity of ∼1020 Pa s and a rigid lithosphere, the modification of the corner flow pattern is not drastic but the change could have geologic implications. Feedback in the development of CPO occurs, particularly in the region immediately below the base of the lithosphere. Stronger fabric is predicted below the flanks of a spreading centre for fully coupled, power-law polycrystals than was determined using prior linear, intermediate coupling polycrystal models. The predicted SKS splitting is modestly different (∼0.5 s) between the intermediate and fully coupled cases for oceanic plates less than 20 Myr old. The magnitude of

  13. Flow and heat transfer in a curved channel

    NASA Technical Reports Server (NTRS)

    Brinich, P. F.; Graham, R. W.

    1977-01-01

    Flow and heat transfer in a curved channel of aspect ratio 6 and inner- to outer-wall radius ratio 0.96 were studied. Secondary currents and large longitudinal vortices were found. The heat-transfer rates of the outer and inner walls were independently controlled to maintain a constant wall temperature. Heating the inner wall increased the pressure drop along the channel length, whereas heating the outer wall had little effect. Outer-wall heat transfer was as much as 40 percent greater than the straight-channel correlation, and inner-wall heat transfer was 22 percent greater than the straight-channel correlation.

  14. Effects of flow maldistribution on the thermal performance of cross-flow micro heat exchangers

    NASA Astrophysics Data System (ADS)

    Nonino, C.; Savino, S.

    2016-09-01

    The combined effect of viscosity- and geometry-induced flow maldistribution on the thermal performance of cross-flow micro heat exchangers is investigated with reference to two microchannel cross-sectional geometries, three solid materials, three mass flow rates and three flow nonuniformity models. A FEM procedure, specifically developed for the analysis of the heat transfer between incompressible fluids in cross-flow micro heat exchangers, is used for the numerical simulations. The computed results indicate that flow maldistribution has limited effects on microchannel bulk temperatures, at least for the considered range of operating conditions.

  15. Observed quantization of anyonic heat flow

    NASA Astrophysics Data System (ADS)

    Banerjee, Mitali; Heiblum, Moty; Rosenblatt, Amir; Oreg, Yuval; Feldman, Dima E.; Stern, Ady; Umansky, Vladimir

    2017-04-01

    The quantum of thermal conductance of ballistic (collisionless) one-dimensional channels is a unique fundamental constant. Although the quantization of the electrical conductance of one-dimensional ballistic conductors has long been experimentally established, demonstrating the quantization of thermal conductance has been challenging as it necessitated an accurate measurement of very small temperature increase. It has been accomplished for weakly interacting systems of phonons, photons and electronic Fermi liquids; however, it should theoretically also hold in strongly interacting systems, such as those in which the fractional quantum Hall effect is observed. This effect describes the fractionalization of electrons into anyons and chargeless quasiparticles, which in some cases can be Majorana fermions. Because the bulk is incompressible in the fractional quantum Hall regime, it is not expected to contribute substantially to the thermal conductance, which is instead determined by chiral, one-dimensional edge modes. The thermal conductance thus reflects the topological properties of the fractional quantum Hall electronic system, to which measurements of the electrical conductance give no access. Here we report measurements of thermal conductance in particle-like (Laughlin-Jain series) states and the more complex (and less studied) hole-like states in a high-mobility two-dimensional electron gas in GaAs-AlGaAs heterostructures. Hole-like states, which have fractional Landau-level fillings of 1/2 to 1, support downstream charged modes as well as upstream neutral modes, and are expected to have a thermal conductance that is determined by the net chirality of all of their downstream and upstream edge modes. Our results establish the universality of the quantization of thermal conductance for fractionally charged and neutral modes. Measurements of anyonic heat flow provide access to information that is not easily accessible from measurements of conductance.

  16. Short-Term versus Steady-State Crustal Deformation: Are Some Anomalies Driven by Transient Coupling with Mantle Flow? (Invited)

    NASA Astrophysics Data System (ADS)

    Holt, W. E.; Fouch, M. J.; Flesch, L. M.; Klein, E. C.; West, J. D.

    2010-12-01

    500 km and perhaps more. Traction rates associated with the strain rate anomaly suggest inward-directed forcing, consistent with lithosphere coupling with mantle downwelling in the vicinity of the tomography anomaly. Whether this mantle flow is associated with an actual mantle drip [West et al., 2009] or with the sinking of a remnant section of the Juan de Fuca slab remains unresolved. Nevertheless, the contraction anomaly must constitute a transient feature, since the wider deformation field is purely extensional there. The loading mechanism of this elastic strain in the Great Basin region, as well as its release, may be related to the long-wavelength crustal velocity transients described by Wernicke et al. [2008] and Wernicke and Davis [2010].

  17. P/n/ velocity and cooling of the continental lithosphere. [upper mantle compression waves in North America

    NASA Technical Reports Server (NTRS)

    Black, P. R.; Braile, L. W.

    1982-01-01

    The average upper mantle compressional wave velocity and heat flow figures presently computed for continental physiographic provinces in North America exhibit an inverse relationship, and possess a statistically significant correlation coefficient. A correlation is also demonstrated between compressional wave velocity and material temperature by estimating crust-mantle boundary temperatures from heat flow values. The dependency of compressional wave velocity on temperature implies that the observed geographical distribution in upper mantle seismic velocity may be due to the temperature effect character of upper mantle compressional wave velocity variation.

  18. Heat transfer and flow characteristics on a gas turbine shroud.

    PubMed

    Obata, M; Kumada, M; Ijichi, N

    2001-05-01

    The work described in this paper is an experimental investigation of the heat transfer from the main flow to a turbine shroud surface, which may be applicable to ceramic gas turbines. Three kinds of turbine shrouds are considered with a flat surface, a taper surface and a spiral groove surface opposite to the blades in an axial flow turbine of actual turbo-charger. Heat transfer measurements were performed for the experimental conditions of a uniform heat flux or a uniform wall temperature. The effects of the inlet flow angle, rotational speed, and tip clearance on the heat transfer coefficient were clarified under on- and off-design flow conditions. The mean heat transfer coefficient was correlated to the blade Reynolds number and tip clearance, and compared with an experimental correlation and measurements of a flat surface. A comparison was also made for the measurement of static pressure distributions.

  19. Double Stage Heat Transformer Controlled by Flow Ratio

    NASA Astrophysics Data System (ADS)

    Silva-Sotelo, S.; Romero, R. J.; Rodríguez – Martínez, A.

    this paper shows the values of Flow ratio (FR) for control of an absorption double stage heat transformer. The main parameters for the heat pump system are defined as COP, FR and GTL. The control of the entire system is based in a new definition of FR. The heat balance of the Double Stage Heat Transformer (DSHT) is used for the control. The mass flow is calculated for a HPVEE program and a second program control the mass flow. The mass flow is controlled by gear pumps connected to LabView program. The results show an increment in the fraction of the recovery energy. An example of oil distillation is used for the calculation. The waste heat energy is added at the system at 70 °C. Water ™ - Carrol mixture is used in the DSHT. The recover energy is obtained in a second absorber at 128 °C with two scenarios.

  20. Numerical prediction of turbulent oscillating flow and associated heat transfer

    NASA Technical Reports Server (NTRS)

    Koehler, W. J.; Patankar, S. V.; Ibele, W. E.

    1991-01-01

    A crucial point for further development of engines is the optimization of its heat exchangers which operate under oscillatory flow conditions. It has been found that the most important thermodynamic uncertainties in the Stirling engine designs for space power are in the heat transfer between gas and metal in all engine components and in the pressure drop across the heat exchanger components. So far, performance codes cannot predict the power output of a Stirling engine reasonably enough if used for a wide variety of engines. Thus, there is a strong need for better performance codes. However, a performance code is not concerned with the details of the flow. This information must be provided externally. While analytical relationships exist for laminar oscillating flow, there has been hardly any information about transitional and turbulent oscillating flow, which could be introduced into the performance codes. In 1986, a survey by Seume and Simon revealed that most Stirling engine heat exchangers operate in the transitional and turbulent regime. Consequently, research has since focused on the unresolved issue of transitional and turbulent oscillating flow and heat transfer. Since 1988, the University of Minnesota oscillating flow facility has obtained experimental data about transitional and turbulent oscillating flow. However, since the experiments in this field are extremely difficult, lengthy, and expensive, it is advantageous to numerically simulate the flow and heat transfer accurately from first principles. Work done at the University of Minnesota on the development of such a numerical simulation is summarized.

  1. Flow in the western Mediterranean shallow mantle: Insights from xenoliths in Pliocene alkali basalts from SE Iberia (eastern Betics, Spain)

    NASA Astrophysics Data System (ADS)

    Hidas, Károly; Konc, Zoltán.; Garrido, Carlos J.; Tommasi, Andréa.; Vauchez, Alain; Padrón-Navarta, José Alberto; Marchesi, Claudio; Booth-Rea, Guillermo; Acosta-Vigil, Antonio; Szabó, Csaba; Varas-Reus, María. Isabel; Gervilla, Fernando

    2016-11-01

    Mantle xenoliths in Pliocene alkali basalts of the eastern Betics (SE Iberia, Spain) are spinel ± plagioclase lherzolite, with minor harzburgite and wehrlite, displaying porphyroclastic or equigranular textures. Equigranular peridotites have olivine crystal preferred orientation (CPO) patterns similar to those of porphyroclastic xenoliths but slightly more dispersed. Olivine CPO shows [100]-fiber patterns characterized by strong alignment of [100]-axes subparallel to the stretching lineation and a girdle distribution of [010]-axes normal to it. This pattern is consistent with simple shear or transtensional deformation accommodated by dislocation creep. One xenolith provides evidence for synkinematic reactive percolation of subduction-related Si-rich melts/fluids that resulted in oriented crystallization of orthopyroxene. Despite a seemingly undeformed microstructure, the CPO in orthopyroxenite veins in composite xenoliths is identical to those of pyroxenes in the host peridotite, suggesting late-kinematic crystallization. Based on these observations, we propose that the annealing producing the equigranular microstructures was triggered by melt percolation in the shallow subcontinental lithospheric mantle coeval to the late Neogene formation of veins in composite xenoliths. Calculated seismic properties are characterized by fast propagation of P waves and polarization of fast S waves parallel to olivine [100]-axis (stretching lineation). These data are compatible with present-day seismic anisotropy observations in SE Iberia if the foliations in the lithospheric mantle are steeply dipping and lineations are subhorizontal with ENE strike, implying dominantly horizontal mantle flow in the ENE-WSW direction within vertical planes, that is, subparallel to the paleo-Iberian margin. The measured anisotropy could thus reflect a lithospheric fabric due to strike-slip deformation in the late Miocene in the context of WSW tearing of the subducted south Iberian margin

  2. Electron temperature and heat flow in the nightside Venus ionosphere

    NASA Technical Reports Server (NTRS)

    Hoegy, W. R.; Brace, L. H.; Theis, R. F.; Mayr, H. G.

    1980-01-01

    A steady-state two-dimensional heat balance model is used to analyze the night side Venusian ionospheric electron temperatures given by the Pioneer Venus orbiter electron temperature probe. The energy calculation includes the solar EUV heating at the terminator, electron cooling to ions and neutrals, and heat conduction within the ionospheric plasma. An optimum magnetic field is derived by solving for the heat flux directions which force energy conservation while constrained by the observed temperatures within the range of 80-170 deg solar zenith angle and 160-170 km. The heat flux vectors indicate a magnetic field that connects the lower night side ionosphere to the day side ionosphere, and connects the upper ionosphere to the ionosheath. The lower ionosphere is heated through conduction of heat from the dayside, and the upper ionosphere is heated by the solar wind in the ionosheath with heat flowing downward and from the nightside to the day side.

  3. Flow in the uppermost mantle during back-arc spreading revealed by Ichinomegata peridotite xenoliths, NE Japan

    NASA Astrophysics Data System (ADS)

    Satsukawa, Takako; Michibayashi, Katsuyoshi

    2014-02-01

    Spinel peridotite xenoliths from the Ichinomegata Volcano (NE Japan) have distinct foliations defined by compositional layering between olivine-rich and pyroxene-rich layers as well as lineations defined by elongated spinel grains. Crystallographic preferred orientations (CPOs) of olivine are consistent with slip on (010)[100] and {0kl}[100]. The angles between the foliation and the olivine slip planes decrease with increasing values of the J-index (i.e. CPO strength). Such composite planar relationships within the peridotite xenoliths could result from shearing in the uppermost mantle, so that shear strains can be estimated by the angles between the foliation and the olivine slip plane in terms of simple shear strain (0.31-4.26). From these observations, we argue that a suite of the peridotite xenoliths recorded a rare snapshot of uppermost-mantle flow related to back-arc spreading during the opening of the Japan Sea. The peridotite xenoliths with higher J-indices (i.e. higher shear strain) tend to have slightly lower minimum temperatures, possibly defining a vertical strain gradient in the uppermost mantle section at the time of the volcano's eruption. The CPO data have been used to calculate the seismic properties of the xenoliths at PT conditions obtained from geothermobarometry, and are compared to field geophysical data from the literature. Our results are consistent with a roughly EW-oriented fastest P-wave propagation direction in the uppermost mantle beneath the northeast part of the Japan arc. Average samples are calculated based on three different structural reference frames; horizontal plane parallel to 1) foliation, 2) the plane containing the maximum concentration of olivine [100], and 3) P-wave maximum direction. S-wave anisotropy deduced from CPOs requires a reasonable thickness of the anisotropic layer (24.1-26.6 km), and the structural reference frame does not have significant effect on the estimation of thickness. Consequently, Ichinomegata

  4. Implications of Thermal Diffusity being Inversely Proportional to Temperature Times Thermal Expansivity on Lower Mantle Heat Transport

    NASA Astrophysics Data System (ADS)

    Hofmeister, A.

    2010-12-01

    Many measurements and models of heat transport in lower mantle candidate phases contain systematic errors: (1) conventional methods of insulators involve thermal losses that are pressure (P) and temperature (T) dependent due to physical contact with metal thermocouples, (2) measurements frequently contain unwanted ballistic radiative transfer which hugely increases with T, (3) spectroscopic measurements of dense samples in diamond anvil cells involve strong refraction by which has not been accounted for in analyzing transmission data, (4) the role of grain boundary scattering in impeding heat and light transfer has largely been overlooked, and (5) essentially harmonic physical properties have been used to predict anharmonic behavior. Improving our understanding of the physics of heat transport requires accurate data, especially as a function of temperature, where anharmonicity is the key factor. My laboratory provides thermal diffusivity (D) at T from laser flash analysis, which lacks the above experimental errors. Measuring a plethora of chemical compositions in diverse dense structures (most recently, perovskites, B1, B2, and glasses) as a function of temperature provides a firm basis for understanding microscopic behavior. Given accurate measurements for all quantities: (1) D is inversely proportional to [T x alpha(T)] from ~0 K to melting, where alpha is thermal expansivity, and (2) the damped harmonic oscillator model matches measured D(T), using only two parameters (average infrared dielectric peak width and compressional velocity), both acquired at temperature. These discoveries pertain to the anharmonic aspects of heat transport. I have previously discussed the easily understood quasi-harmonic pressure dependence of D. Universal behavior makes application to the Earth straightforward: due to the stiffness and slow motions of the plates and interior, and present-day, slow planetary cooling rates, Earth can be approximated as being in quasi

  5. Development of Stokes flow solver against a large contrast in viscosity: toward plate-mantle simulation with free surface

    NASA Astrophysics Data System (ADS)

    Furuichi, M.

    2009-12-01

    We are interested in solving a large-scale plate-mantle simulation enables capture of the large and complex deformation of a subducting plate. In our earlier study (Furuichi, et al 2008), we developed a numerical method toward plate-mantle simulation especially for the highly parallel vector supercomputer system (e.g. Earth Simulator). Our scheme is based on the finite volume method combines (i) the multigrid technique together with ACuTE smoother algorithm (Kameyama et al., 2005), and (ii) the low diffusive CIP-CSLR advection. The validity test of our simulation code by using a fluid rope coiling event (Furuichi, et al 2009) showed that our method enable us to reproduce large non-linear deformation problems of a rigid plate surrounded by soft material without serious quantitative errors. Then as a next step, I am trying to create a Stokes flow solver scalable against a large jump in a viscosity profile, for moving surface (geometrically free boundary) problems. It is for solving the Stokes flow motion under the same condition as real earth. In this presentation, I propose to apply BFBt preconditioner and AMG techniques for the problems of large viscosity contrast and moving free surface boundary condition respectively. I would like to show some numerical experiments for a self-gravitating motion of the layered Stokes flow.

  6. Application of heat flow models to SOI current mirrors

    NASA Astrophysics Data System (ADS)

    Yu, Feixia; Cheng, Ming-C.

    2004-11-01

    An analytical heat flow model for SOI circuits is presented. The model is able to account for heat exchanges among devices and heat loss from the silicon film and interconnects to the substrate through the buried oxide. The developed model can accurately and efficiently predict the temperature distribution in the interconnect/poly-lines and SOI devices. The model is applied to SOI current mirrors to study heat flow in different layout designs. The results from the developed model are verified with those from Raphael, a 3D numerical simulator that can provide the detailed 3D temperature distribution in interconnect/poly-lines.

  7. Hydrogeology of, and simulation of ground-water flow in a mantled carbonate-rock system, Cumberland Valley, Pennsylvania

    USGS Publications Warehouse

    Chichester, D.C.

    1996-01-01

    The U.S. Geological Survey conducted a study in a highly productive and complex regolith-mantled carbonate valley in the northeastern part of the Cumberland Valley, Pa., as part of its Appalachian Valleys and Piedmont Regional Aquifer-system Analysis program. The study was designed to quantify the hydrogeologic characteristics and understand the ground-water flow system of a highly productive and complex thickly mantled carbonate valley. The Cumberland Valley is characterized by complexly folded and faulted carbonate bedrock in the valley bottom, by shale and graywacke to the north, and by red-sedimentary and diabase rocks in the east-southeast. Near the southern valley hillslope, the carbonate rock is overlain by wedge-shaped deposit of regolith, up to 450 feet thick, that is composed of residual material, alluvium, and colluvium. Locally, saturated regolith is greater than 200 feet thick. Seepage-run data indicate that stream reaches, near valley walls, are losing water from the stream, through the regolith, to the ground-water system. Results of hydrograph-separation analyses indicate that base flow in stream basins dominated by regolith-mantled carbonate rock, carbonate rock, and carbonate rock and shale are 81.6, 93.0, and 67.7 percent of total streamflow, respectively. The relative high percentage for the regolith-mantled carbonate-rock basin indicates that the regolith stores precipitation and slowly, steadily releases this water to the carbonate-rock aquifer and to streams as base flow. Anomalies in water-table gradients and configuration are a result of topography and differences in the character and distribution of overburden material, permeability, rock type, and geologic structure. Most ground-water flow is local, and ground water discharges to nearby springs and streams. Regional flow is northeastward to the Susquehanna River. Average-annual water budgets were calculated for the period of record from two continuous streamflow-gaging stations. Average

  8. Two- phase flow patterns and heat transfer in parallel microchannels

    NASA Astrophysics Data System (ADS)

    Mosyak, A.; Segal, Z.; Pogrebnyak, E.; Hetsroni, G.

    2002-11-01

    Microchannel heat sinks with two-phase flow can satisfy the increasing heat removal requirements of modern micro electronic devices. One of the important aspects associated with two- phase flows in microchannels is to study the bubble behavior. However, in the literature most of the reports present data of only a single channel. This does not account for flow mixing and hydrodynamic instability that occurs in parallel microchannels, connected by common inlet and outlet collectors. In the present study, experiments were performed for air- water and steam- water flow in parallel triangular microchannels with a base of 200 300 µ m. The experimental study is based on systematic measurements of temperature and flow pattern by infrared radiometry and high-speed digital video imaging. In air-water flow, different flow patterns were observed simultaneously in the various microchannels at a fixed values of water and gas flow rates. In steam-water flow, instability in uniformly heated microchannels was observed. This work develops a practical modeling approach for two-phase microchannel heat sinks and considers discrepancy between flow patterns of air- water and steam- water flow in microchannels.

  9. Study of fluid flow in a channel with heated obstacle

    NASA Astrophysics Data System (ADS)

    Hossain, Md. Anowar; Kabir, K. M. Ariful; Sarker, M. M. A.

    2017-06-01

    The present paper deals with the numerical simulation of fluid flow with heated obstacle in a channel. A three dimensional finite element method for channel flow with heated obstacle is developed and a tool of computational fluid dynamics (CFD) is employed to assist the process. This study presents the detail effects with respect to the variations in the obstacle's height, width, spacing, and number. The studied results depict the trends due to variable obstacle thermal conductivity, fluid flow rate, pressure and heating method. The periodic behaviour of the velocity components and temperature distributions are also explicitly demonstrated.

  10. In-situ measurements of lunar heat flow

    NASA Technical Reports Server (NTRS)

    Langseth, M. G.; Keihm, S. J.

    1974-01-01

    During the Apollo program two successful heat flow measurements were made in situ on the lunar surface. At the Apollo 15 site a value of 0.0000031 watts/sqcm was measured and at the Apollo 17 site a value of 0.0000022 watts/sqcm was determined. Both measurements have uncertainty limits of + or - 20% and have been corrected for perturbing topographic effects. The apparent difference between the observations may correlate with observed variations in the surface abundance of thorium. Comparison with earlier determinations of heat flow, using the microwave emission spectrum from the moon, gives support to the high gradients and heat flows observed in situ.

  11. In-situ measurements of lunar heat flow

    NASA Technical Reports Server (NTRS)

    Langseth, M. B.; Keihm, S. J.

    1977-01-01

    During the Apollo program two successful heat flow measurements were made in situ on the lunar surface. At the Apollo 15 site a value of .0000031 W/sq cm was measured, and at the Apollo 17 site a value of .0000022 W/sq cm was determined. Both measurements have uncertainty limits of + or - 20 percent and have been corrected for perturbing topographic effects. The apparent difference between the observations may correlate with observed variations in the surface abundance of thorium. Comparison with earlier determinations of heat flow, using the microwave emission spectrum from the moon, gives support to the high gradients and heat flows observed in situ.

  12. Fundamental flow and heat transfer results relevant to oscillating flow regenerators

    NASA Astrophysics Data System (ADS)

    Hutchinson, R. A.; Ross, B. A.

    Preliminary reviews of literature on the subjects of oscillating flows, periodic flows, and porous media have brought to light interesting papers presenting a number of phenomena that may be of interest in heat engine regenerators. Some are also relevant to flows in other Stirling heat exchangers. These topics include heat transfer during compression, enhanced conduction in oscillating laminar flows, approaches to analysis of nonuniform porous media, and heat transfer enhancement mechanisms in porous media. Each topic is briefly described and discussed in this paper, and a summary of physical phenomena that may affect regenerator performance is presented.

  13. Analysis of heat transfers inside counterflow plate heat exchanger augmented by an auxiliary fluid flow.

    PubMed

    Khaled, A-R A

    2014-01-01

    Enhancement of heat transfers in counterflow plate heat exchanger due to presence of an intermediate auxiliary fluid flow is investigated. The intermediate auxiliary channel is supported by transverse conducting pins. The momentum and energy equations for the primary fluids are solved numerically and validated against a derived approximate analytical solution. A parametric study including the effect of the various plate heat exchanger, and auxiliary channel dimensionless parameters is conducted. Different enhancement performance indicators are computed. The various trends of parameters that can better enhance heat transfer rates above those for the conventional plate heat exchanger are identified. Large enhancement factors are obtained under fully developed flow conditions. The maximum enhancement factors can be increased by above 8.0- and 5.0-fold for the step and exponential distributions of the pins, respectively. Finally, counterflow plate heat exchangers with auxiliary fluid flows are recommended over the typical ones if these flows can be provided with the least cost.

  14. Analysis of Heat Transfers inside Counterflow Plate Heat Exchanger Augmented by an Auxiliary Fluid Flow

    PubMed Central

    Khaled, A.-R. A.

    2014-01-01

    Enhancement of heat transfers in counterflow plate heat exchanger due to presence of an intermediate auxiliary fluid flow is investigated. The intermediate auxiliary channel is supported by transverse conducting pins. The momentum and energy equations for the primary fluids are solved numerically and validated against a derived approximate analytical solution. A parametric study including the effect of the various plate heat exchanger, and auxiliary channel dimensionless parameters is conducted. Different enhancement performance indicators are computed. The various trends of parameters that can better enhance heat transfer rates above those for the conventional plate heat exchanger are identified. Large enhancement factors are obtained under fully developed flow conditions. The maximum enhancement factors can be increased by above 8.0- and 5.0-fold for the step and exponential distributions of the pins, respectively. Finally, counterflow plate heat exchangers with auxiliary fluid flows are recommended over the typical ones if these flows can be provided with the least cost. PMID:24719572

  15. Heat and mass transfer and hydrodynamics in swirling flows (review)

    NASA Astrophysics Data System (ADS)

    Leont'ev, A. I.; Kuzma-Kichta, Yu. A.; Popov, I. A.

    2017-02-01

    Research results of Russian and foreign scientists of heat and mass transfer in whirling flows, swirling effect, superficial vortex generators, thermodynamics and hydrodynamics at micro- and nanoscales, burning at swirl of the flow, and technologies and apparatuses with the use of whirling currents for industry and power generation were presented and discussed at the "Heat and Mass Transfer in Whirling Currents" 5th International Conference. The choice of rational forms of the equipment flow parts when using whirling and swirling flows to increase efficiency of the heat-power equipment and of flow regimes and burning on the basis of deep study of the flow and heat transfer local parameters was set as the main research prospect. In this regard, there is noticeable progress in research methods of whirling and swirling flows. The number of computational treatments of swirling flows' local parameters has been increased. Development and advancement of the up to date computing models and national productivity software are very important for this process. All experimental works are carried out with up to date research methods of the local thermoshydraulic parameters, which enable one to reveal physical mechanisms of processes: PIV and LIV visualization techniques, high-speed and infrared photography, high speed registration of parameters of high-speed processes, etc. There is a problem of improvement of researchers' professional skills in the field of fluid mechanics to set adequately mathematics and physics problems of aerohydrodynamics for whirling and swirling flows and numerical and pilot investigations. It has been pointed out that issues of improvement of the cooling system and thermal protection effectiveness of heat-power and heat-transfer equipment units are still actual. It can be solved successfully using whirling and swirling flows as simple low power consumption exposing on the flow method and heat transfer augmentation.

  16. Critical heat flux of subcooled flow boiling with water for high heat flux application

    NASA Astrophysics Data System (ADS)

    Inasaka, Fujio; Nariai, Hideki

    1993-11-01

    Subcooled flow boiling in water is thought to be advantageous in removing high heat load of more than 10 MW/m2. Characteristics of the critical heat flux (CHF), which determines the upper limit of heat removal, are very important for the design of cooling systems. In this paper, studies on subcooled flow boiling CHF, which have been conducted by the authors, are reported. Experiments were conducted using direct current heating of stainless steel tube. For uniform heating conditions, CHF increment in small diameter tubes (1 - 3 mm inside diameter) and the CHF characteristics in tubes with internal twisted tapes were investigated, and also the existing CHF correlations for ordinary tubes (more than 3 mm inside diameter) were evaluated. For peripherally non-uniform heating conditions using the tube, whose wall thickness was partly reduced, the CHF for swirl flow was higher than the CHF under uniform heating conditions with an increase of the non-uniformity factor.

  17. A Global Perspective on the Composition of the Continental Crust from the Distribution of Heat Producing Elements: Comparison Between Heat Flow Data and Seismological Crustal Models.

    NASA Astrophysics Data System (ADS)

    Iarotsky, L.; Mareschal, J. C.; Jaupart, C. P.

    2015-12-01

    The thermal evolution and the strength of continents critically depend on the amount and vertical distribution of heat producing elements in the crust. In turn, these two crustal characteristics provide constraints on the origin of the crust and its internal differentiation processes. Neither of them can be determined directly and they must be inferred from geochemical and geophysical data. One method relies on global crustal models such as CRUST1.0 which gives the structure of the continental crustal column on a 1o}x1{o grid. The crustal model is made up of sedimentary layers over basement consisting of upper, middle, and lower crust whose thicknesses and physical properties vary between provinces depending on age and tectonic type. One may then plug in the average values of heat production for these crustal layers from global geochemical studies. An alternative method consists of measuring the surface heat flow and subtracting the estimated Moho heat flux. Using the global crustal models, we have calculated the crustal heat production for the continents. We have also averaged and placed on the same worldwide grid all the land heat flow measurements. After removing the mantle heat flux and excluding the tectonically active regions, we have compared these two maps. On the global scale, the model based heat production map shows much less variability (σ = 7 mW m-2) than the map based on heat flow measurements (σ = 14 mW m^{-2}). Adjusting the heat production values to fit the heat flux measurements can cancel the difference between the means, but does not reduce the root mean square difference between the two sets. On a regional scale, abundant heat flow in southeastern Canada allow a very detailed comparison. Long wavelength trends of the heat flux data set are obliterated by the model. We attempted to change the crustal heat production values but found that it is impossible to obtain a good fit. Even when considering only the Archean Superior Province, using a

  18. Conjugate Compressible Fluid Flow and Heat Transfer in Ducts

    NASA Technical Reports Server (NTRS)

    Cross, M. F.

    2011-01-01

    A computational approach to modeling transient, compressible fluid flow with heat transfer in long, narrow ducts is presented. The primary application of the model is for analyzing fluid flow and heat transfer in solid propellant rocket motor nozzle joints during motor start-up, but the approach is relevant to a wide range of analyses involving rapid pressurization and filling of ducts. Fluid flow is modeled through solution of the spatially one-dimensional, transient Euler equations. Source terms are included in the governing equations to account for the effects of wall friction and heat transfer. The equation solver is fully-implicit, thus providing greater flexibility than an explicit solver. This approach allows for resolution of pressure wave effects on the flow as well as for fast calculation of the steady-state solution when a quasi-steady approach is sufficient. Solution of the one-dimensional Euler equations with source terms significantly reduces computational run times compared to general purpose computational fluid dynamics packages solving the Navier-Stokes equations with resolved boundary layers. In addition, conjugate heat transfer is more readily implemented using the approach described in this paper than with most general purpose computational fluid dynamics packages. The compressible flow code has been integrated with a transient heat transfer solver to analyze heat transfer between the fluid and surrounding structure. Conjugate fluid flow and heat transfer solutions are presented. The author is unaware of any previous work available in the open literature which uses the same approach described in this paper.

  19. The surface heat flow of the Arabian Shield in Jordan

    NASA Astrophysics Data System (ADS)

    Förster, A.; Förster, H.-J.; Masarweh, R.; Masri, A.; Tarawneh, K.; Desert Group

    2007-04-01

    Surface heat flow in southern Jordan (western part of the Arabian Plate) was determined in a dense cluster of five, up to 900-m-deep boreholes that have encountered sedimentary rocks of Paleozoic (Ordovician and Silurian) age. These rocks are underlain by an igneous and metamorphic basement, which has been studied for its radiogenic heat production, along the eastern margin of the Dead Sea Transform (DST) fault system. The heat flow, calculated from continuous temperature logs and laboratory-measured thermal conductivity of drillcores and surface samples, averages to 60.3 ± 3.4 mW m -2 and contrasts the common view of the late Proterozoic-consolidated Arabian Shield constituting a low heat-flow province of ⩽45 mW m -2. Although only characterizing an area of about 300 km 2, this average is unlikely representing a positive local anomaly caused by voluminous HHP granites/rhyolites at shallow depths. Instead, a heat flow of 60 mW m -2 is considered a robust estimate of the Phanerozoic conductive surface heat flow not only for Jordan, but for the Arabian Shield in areas unaffected by younger reactivation. The large variation in conductive heat flow (36-88 mW m -2) previously observed in Jordan, southern Syria, and Saudi Arabia is irreconcilable with their broad similarity in lithosphere structure and composition and rather reflects a combination of factors including low-quality temperature data and insufficient knowledge on thermal rock properties.

  20. Local heating, but not indirect whole body heating, increases human skeletal muscle blood flow

    PubMed Central

    Heinonen, Ilkka; Brothers, R. Matthew; Kemppainen, Jukka; Knuuti, Juhani; Kalliokoski, Kari K.

    2011-01-01

    For decades it was believed that direct and indirect heating (the latter of which elevates blood and core temperatures without directly heating the area being evaluated) increases skin but not skeletal muscle blood flow. Recent results, however, suggest that passive heating of the leg may increase muscle blood flow. Using the technique of positron-emission tomography, the present study tested the hypothesis that both direct and indirect heating increases muscle blood flow. Calf muscle and skin blood flows were evaluated from eight subjects during normothermic baseline, during local heating of the right calf [only the right calf was exposed to the heating source (water-perfused suit)], and during indirect whole body heat stress in which the left calf was not exposed to the heating source. Local heating increased intramuscular temperature of the right calf from 33.4 ± 1.0°C to 37.4 ± 0.8°C, without changing intestinal temperature. This stimulus increased muscle blood flow from 1.4 ± 0.5 to 2.3 ± 1.2 ml·100 g−1·min−1 (P < 0.05), whereas skin blood flow under the heating source increased from 0.7 ± 0.3 to 5.5 ± 1.5 ml·100 g−1·min−1 (P < 0.01). While whole body heat stress increased intestinal temperature by ∼1°C, muscle blood flow in the calf that was not directly exposed to the water-perfused suit (i.e., indirect heating) did not increase during the whole body heat stress (normothermia: 1.6 ± 0.5 ml·100 g−1·min−1; heat stress: 1.7 ± 0.3 ml·100 g−1·min−1; P = 0.87). Whole body heating, however, reflexively increased calf skin blood flow (to 4.0 ± 1.5 ml·100 g−1·min−1) in the area not exposed to the water-perfused suit. These data show that local, but not indirect, heating increases calf skeletal muscle blood flow in humans. These results have important implications toward the reconsideration of previously accepted blood flow distribution during whole body heat stress. PMID:21680875

  1. Constraints on hydrothermal heat flux through the oceanic lithosphere from global heat flow

    NASA Technical Reports Server (NTRS)

    Stein, Carol A.; Stein, Seth

    1994-01-01

    A significant discrepancy exists between the heat flow measured at the seafloor and the higher values predicted by thermal models of the cooling lithosphere. This discrepancy is generally interpreted as indicating that the upper oceanic crust is cooled significantly by hydrothermal circulation. The magnitude of this heat flow discrepancy is the primary datum used to estimate the volume of hydrothermal flow, and the variation in the discrepancy with lithospheric age is the primary constraint on how the hydrothermal flux is divided between near-ridge and off-ridge environments. The resulting estimates are important for investigation of both the thermal structure of the lithosphere and the chemistry of the oceans. We reevaluate the magnitude and age variation of the discrepancy using a global heat flow data set substantially larger than in earlier studies, and the GDHI (Global Depth and Heat Flow) model that better predicts the heat flow. We estimate that of the predicted global oceanic heat flux of 32 x 10(exp 12) W, 34% (11 x 10(exp 12) W) occurs by hydrothermal flow. Approximately 30% of the hydrothermal heat flux occurs in crust younger than 1 Ma, so the majority of this flux is off-ridge. These hydrothermal heat flux estimates are upper bounds, because heat flow measurements require sediment at the site and so are made preferentially at topographic lows, where heat flow may be depressed. Because the water temperature for the near-ridge flow exceeds that for the off-ridge flow, the near-ridge water flow will be even a smaller fraction of the total water flow. As a result, in estimating fluxes from geochemical data, use of the high water temperatures appropriate for the ridge axis may significantly overestimate the heat flux for an assumed water flux or underestimate the water flux for an assumed heat flux. Our data also permit improved estimates of the 'sealing' age, defined as the age where the observed heat flow approximately equals that predicted, suggesting

  2. Constraints on hydrothermal heat flux through the oceanic lithosphere from global heat flow

    NASA Technical Reports Server (NTRS)

    Stein, Carol A.; Stein, Seth

    1994-01-01

    A significant discrepancy exists between the heat flow measured at the seafloor and the higher values predicted by thermal models of the cooling lithosphere. This discrepancy is generally interpreted as indicating that the upper oceanic crust is cooled significantly by hydrothermal circulation. The magnitude of this heat flow discrepancy is the primary datum used to estimate the volume of hydrothermal flow, and the variation in the discrepancy with lithospheric age is the primary constraint on how the hydrothermal flux is divided between near-ridge and off-ridge environments. The resulting estimates are important for investigation of both the thermal structure of the lithosphere and the chemistry of the oceans. We reevaluate the magnitude and age variation of the discrepancy using a global heat flow data set substantially larger than in earlier studies, and the GDHI (Global Depth and Heat Flow) model that better predicts the heat flow. We estimate that of the predicted global oceanic heat flux of 32 x 10(exp 12) W, 34% (11 x 10(exp 12) W) occurs by hydrothermal flow. Approximately 30% of the hydrothermal heat flux occurs in crust younger than 1 Ma, so the majority of this flux is off-ridge. These hydrothermal heat flux estimates are upper bounds, because heat flow measurements require sediment at the site and so are made preferentially at topographic lows, where heat flow may be depressed. Because the water temperature for the near-ridge flow exceeds that for the off-ridge flow, the near-ridge water flow will be even a smaller fraction of the total water flow. As a result, in estimating fluxes from geochemical data, use of the high water temperatures appropriate for the ridge axis may significantly overestimate the heat flux for an assumed water flux or underestimate the water flux for an assumed heat flux. Our data also permit improved estimates of the 'sealing' age, defined as the age where the observed heat flow approximately equals that predicted, suggesting

  3. Different Behaviour of Heat Flow and Helium Anomalies Through the Geothermal Areas of Central Italy

    NASA Astrophysics Data System (ADS)

    Bellani, S.; Magro, G.

    2005-12-01

    The high enthalpy geothermal areas and more than 30% of the Italian spas are concentrated in central Italy (Tuscany and Latium regions). A wide part of this area is affected by a large heat-flow anomaly, with maxima corresponding to the geothermal fields of Larderello, Mt. Amiata and Latera. Mt.Amiata and Latera are located in areas of quaternary quiescent volcanism, while there are no outcrops of extrusive rocks in the Larderello geothermal field. Surface heat flow in a continental area has an average value of 50-60 mW/m2. The background regional value in these geothermal areas is 120-150 mW/m2, with peaks up to 1000 mW/m2 at Larderello, 600 mW/m2 at Mt. Amiata and 300 mW/m2 at Latera. Anomalous heat flow is very often related to the presence of 3He-enriched fluids. In central Italy the He isotopic ratio (3He/4He expressed as R/Ra), in gases from cold and thermal manifestations and in geothermal wells ranges from 0.2 to 3.2 R/Ra. In particular, Larderello fluids range between 0.5 and 3.2, while the interval for Mt. Amiata and Latera fluids spans from 0.2 to 0.6. The R/Ra and heat flow profiles through central Italy, NW-SE trending, show no straightforward correlation between the two parameters. A phased correlation exists between heat flow and R/Ra relative maxima at Larderello, while they are decoupled at Mt. Amiata and Latera geothermal fields. Different heat and He transport mechanisms through the crust are the most likely explanation: mantle 3He-enriched fluids move upwards mainly via fluid filled conduits, while heat diffuses faster than He throughout the entire bulk rock. At Larderello, the almost constant values of R/Ra in geothermal wells and paleo-fluids (fluid inclusions) indicate that the contribution of hot 3He-enriched fluids must have occurred through deeply rooted faults at least in the last 1 Ma. In the Mt. Amiata area the presence of several spas, marked by low R/Ra ratios down to crustal values, could indicate the addition of radiogenic 4He. Rock

  4. Enhanced two phase flow in heat transfer systems

    DOEpatents

    Tegrotenhuis, Ward E; Humble, Paul H; Lavender, Curt A; Caldwell, Dustin D

    2013-12-03

    A family of structures and designs for use in devices such as heat exchangers so as to allow for enhanced performance in heat exchangers smaller and lighter weight than other existing devices. These structures provide flow paths for liquid and vapor and are generally open. In some embodiments of the invention, these structures can also provide secondary heat transfer as well. In an evaporate heat exchanger, the inclusion of these structures and devices enhance the heat transfer coefficient of the evaporation phase change process with comparable or lower pressure drop.

  5. Frictional strength and heat flow of southern San Andreas Fault

    NASA Astrophysics Data System (ADS)

    Zhu, P. P.

    2016-01-01

    Frictional strength and heat flow of faults are two related subjects in geophysics and seismology. To date, the investigation on regional frictional strength and heat flow still stays at the stage of qualitative estimation. This paper is concentrated on the regional frictional strength and heat flow of the southern San Andreas Fault (SAF). Based on the in situ borehole measured stress data, using the method of 3D dynamic faulting analysis, we quantitatively determine the regional normal stress, shear stress, and friction coefficient at various seismogenic depths. These new data indicate that the southern SAF is a weak fault within the depth of 15 km. As depth increases, all the regional normal and shear stresses and friction coefficient increase. The former two increase faster than the latter. Regional shear stress increment per kilometer equals 5.75 ± 0.05 MPa/km for depth ≤15 km; regional normal stress increment per kilometer is equal to 25.3 ± 0.1 MPa/km for depth ≤15 km. As depth increases, regional friction coefficient increment per kilometer decreases rapidly from 0.08 to 0.01/km at depths less than ~3 km. As depth increases from ~3 to ~5 km, it is 0.01/km and then from ~5 to 15 km, and it is 0.002/km. Previously, frictional strength could be qualitatively determined by heat flow measurements. It is difficult to obtain the quantitative heat flow data for the SAF because the measured heat flow data exhibit large scatter. However, our quantitative results of frictional strength can be employed to investigate the heat flow in the southern SAF. We use a physical quantity P f to describe heat flow. It represents the dissipative friction heat power per unit area generated by the relative motion of two tectonic plates accommodated by off-fault deformation. P f is called "fault friction heat." On the basis of our determined frictional strength data, utilizing the method of 3D dynamic faulting analysis, we quantitatively determine the regional long-term fault

  6. Approximate convective heating equations for hypersonic flows

    NASA Technical Reports Server (NTRS)

    Zoby, E. V.; Moss, J. N.; Sutton, K.

    1979-01-01

    Laminar and turbulent heating-rate equations appropriate for engineering predictions of the convective heating rates about blunt reentry spacecraft at hypersonic conditions are developed. The approximate methods are applicable to both nonreacting and reacting gas mixtures for either constant or variable-entropy edge conditions. A procedure which accounts for variable-entropy effects and is not based on mass balancing is presented. Results of the approximate heating methods are in good agreement with existing experimental results as well as boundary-layer and viscous-shock-layer solutions.

  7. Water Recycling, Lower Mantle Slab Subduction, and Viscous Layering of the Deep Mantle

    NASA Astrophysics Data System (ADS)

    Williams, Q.; McNamara, A.; Garnero, E.

    2005-12-01

    which geochemically primordial material could be retained for extended periods, and produce a means for impeding heat flow through the deep mantle. The natural inference for water recycling is that hydration of the mantle has been driven by subduction, and that any leakage between an anhydrous viscous layer and the overlying mantle should produce a deepening of the viscous boundary with time. Thus, a continuous progression from pseudo-two-layer to one-layer mantle convection, hinging upon the degree to which water is present at depth, could be proceeding through time with water content exercising the ultimate control on mantle mixing. In short, water-depletion-induced viscous layering may be the simplest mechanism for inducing a time-dependent ``stealth`` layer within the deep mantle.

  8. Oregon Cascades Play Fairway Analysis: Faults and Heat Flow maps

    SciTech Connect

    Adam Brandt

    2015-11-15

    This submission includes a fault map of the Oregon Cascades and backarc, a probability map of heat flow, and a fault density probability layer. More extensive metadata can be found within each zip file.

  9. Constraints on rift thermal processes from heat flow and uplift

    NASA Technical Reports Server (NTRS)

    Morgan, P.

    1983-01-01

    The implications of heat flow data available from five major Cenozoic continental rift systems for the processes of continental rifting are discussed, and simple thermal models of lithospheric thinning which predict uplift are used to further constrain the thermal processes in the lithosphere during rifting. Compilations of the heat flow data are summarized and the salient results of these compilations are briefly discussed. The uplift predictions of the slow and rapid thinning models, in which thinning is assumed to occur at a respectively slower and faster rate than heat can be conducted into the lithosphere, are presented. Comparison of uplift rates with model results indicates that the lithosphere is in a state between the two models. While uplift is predicted to continue after thinning has ceased due to thermal relaxation of the lithosphere, the rapid thinning model is always predicted to apply to surface heat flow, and an anomaly in this flow is not predicted to develop until after thinning has stopped.

  10. Heat flow measurements on the southeast coast of Australia

    USGS Publications Warehouse

    Hyndman, R.D.; Jaeger, J.C.; Sass, J.H.

    1969-01-01

    Three boreholes have been drilled for the Australian National University near the southeast coast of New South Wales, Australia. The heat flows found are 1.1, 1.0, and 1.3 ??cal/cm2sec. The errors resulting from the proximity of the sea and a lake, surface temperature change, conductivity structure and water flow have been examined. The radioactive heat production in some of the intrusive rocks of the area have also been measured. The heat flows are much lower than the values of about 2.0 found elsewhere in south eastern Australia. The lower values appear to be part of a distinct heat flow province in eastern Australia. ?? 1969.

  11. Heat flow from eastern Panama and northwestern Colombia

    USGS Publications Warehouse

    Sass, J.H.; Munroe, R.J.; Moses, T.H.

    1974-01-01

    Heat flows were determined at 12 sites in four distinct areas between longitude 77?? and 80??W in eastern Panama and northwestern Colombia. Evidently, most of the region is underlain by mafic oceanic crust so that the crustal radiogenic component of heat flow is very small (??? 0.1 ??cal cm-2 sec-1). Low heat-flow values (??? 0.7 ??cal cm-2 sec-1) in northwestern Colombia may reflect thermal transients associated with shallow subduction. The normal values (??? 1) at about 78??W are consistent with the mean heat flow from the western Caribbean and the Gulf of Mexico. At 80??W, a fairly high value of 1.8 may define the easterly limit of thermal transients due to Cenozoic volcanic activity in Central America. ?? 1974.

  12. Flow-Dependent Vascular Heat Transfer during Microwave Thermal Ablation

    PubMed Central

    Chiang, Jason; Hynes, Kieran; Brace, Christopher L.

    2012-01-01

    Microwave tumor ablation is an attractive option for thermal ablation because of its inherent benefits over radiofrequency ablation (RFA) in the treatment of solid tumors such as hepatocellular carcinoma (HCC). Microwave energy heats tissue to higher temperatures and at a faster rate than RFA, creating larger, more homogenous ablation zones. In this study, we investigate microwave heating near large vasculature using coupled fluid-flow and thermal analysis. Low-flow conditions are predicted to be more likely to cause cytotoxic heating and, therefore, vessel thrombosis and endothelial damage of downstream tissues. Such conditions may be more prevalent in patient with severe cirrhosis or compromised blood flow. High-flow conditions create the more familiar heat-sink effect that can protect perivascular tissues from the intended thermal damage. These results may help guide placement and use of microwave ablation technologies in future studies. PMID:23367194

  13. Flow-dependent vascular heat transfer during microwave thermal ablation.

    PubMed

    Chiang, Jason; Hynes, Kieran; Brace, Christopher L

    2012-01-01

    Microwave tumor ablation is an attractive option for thermal ablation because of its inherent benefits over radiofrequency ablation (RFA) in the treatment of solid tumors such as hepatocellular carcinoma (HCC). Microwave energy heats tissue to higher temperatures and at a faster rate than RFA, creating larger, more homogenous ablation zones. In this study, we investigate microwave heating near large vasculature using coupled fluid-flow and thermal analysis. Low-flow conditions are predicted to be more likely to cause cytotoxic heating and, therefore, vessel thrombosis and endothelial damage of downstream tissues. Such conditions may be more prevalent in patient with severe cirrhosis or compromised blood flow. High-flow conditions create the more familiar heat-sink effect that can protect perivascular tissues from the intended thermal damage. These results may help guide placement and use of microwave ablation technologies in future studies.

  14. Modeling Io's Heat Flow: Constraints from Galileo PPR Data

    NASA Technical Reports Server (NTRS)

    Rathbun, J. A.; Spencer, J. R.; Tamppari, L. K.

    2000-01-01

    We attempt to improve on previous Io heat flow estimates by using higher resolution data from Galileo Photopolarimeter Radiometer (PPR) and improved thermophysical models of the surface, including finite thermal inertia, the pedestal effect, and disk-resolved radiance.

  15. A source-sink model of the generation of plate tectonics from non-Newtonian mantle flow

    SciTech Connect

    Bercovici, D.

    1995-02-01

    A model of mantle convection which generates plate tectonics requires strain rate- or stress-dependent rheology in order to produce strong platelike flows with weak margins as well as strike-slip deformation and plate spin (i.e., toroidal motion). Here, we employ a simple model of source-sink driven surface flow to determine the form of such a rheology that is appropriate for Earth`s present-day plate motions. In this model, lithospheric motion is treated as shallow layer flow driven by sources and sinks which correspond to spreading centers and subduction zones, respectively. Two plate motion models are used to derive the source sink field. As originally implied in the simpler Cartesian version of this model, the classical power law rheologies do not generate platelike flows as well as the hypothetical Whitehead-Gans stick-slip rheology (which incorporates a simple self-lubrication mechanism). None of the fluid rheologies examined, however, produce more than approximately 60% of the original maximum shear. For either plate model, the viscosity fields produced by the power law rheologies are diffuse, and the viscosity lows over strike-slip shear zones or pseudo-margins are not as small as over the prescribed convergent-divergent margins. In contrast, the stick-slip rheology generates very platelike viscosity fields, with sharp gradients at the plate boundaries, and margins with almost uniformly low viscosity. Power law rheologies with high viscosity contrasts, however, lead to almost equally favorable comparisons, though these also yield the least platelike viscosity fields. This implies that the magnitude of toroidal flow and platelike strength distributions are not necessarily related and thus may present independent constraints on the determination of a self-consistent plate-mantle rheology.

  16. A source-sink model of the generation of plate tectonics from non-Newtonian mantle flow

    NASA Technical Reports Server (NTRS)

    Bercovici, David

    1995-01-01

    A model of mantle convection which generates plate tectonics requires strain rate- or stress-dependent rheology in order to produce strong platelike flows with weak margins as well as strike-slip deformation and plate spin (i.e., toroidal motion). Here, we employ a simple model of source-sink driven surface flow to determine the form of such a rheology that is appropriate for Earth's present-day plate motions. In this model, lithospheric motion is treated as shallow layer flow driven by sources and sinks which correspond to spreading centers and subduction zones, respectively. Two plate motion models are used to derive the source sink field. As originally implied in the simpler Cartesian version of this model, the classical power law rheologies do not generate platelike flows as well as the hypothetical Whitehead-Gans stick-slip rheology (which incorporates a simple self-lubrication mechanism). None of the fluid rheologies examined, however, produce more than approximately 60% of the original maximum shear. For either plate model, the viscosity fields produced by the power law rheologies are diffuse, and the viscosity lows over strike-slip shear zones or pseudo-margins are not as small as over the prescribed convergent-divergent margins. In contrast, the stick-slip rheology generates very platelike viscosity fields, with sharp gradients at the plate boundaries, and margins with almost uniformly low viscosity. Power law rheologies with high viscosity contrasts, however, lead to almost equally favorable comparisons, though these also yield the least platelike viscosity fields. This implies that the magnitude of toroidal flow and platelike strength distributions are not necessarily related and thus may present independent constraints on the determination of a self-consistent plate-mantle rheology.

  17. Coupling of volatile transport and internal heat flow on Triton

    NASA Technical Reports Server (NTRS)

    Brown, Robert H.; Kirk, Randolph L.

    1994-01-01

    Recently Brown et al. (1991) showed that Triton's internal heat source could amount to 5-20% of the absorbed insolation on Triton, thus significantly affecting volatile transport and atmospheric pressure. Subsequently, Kirk and Brown (1991a) used simple analytical models of the effect of internal heat on the distribution of volatiles on Triton's surface, confirming the speculation of Brown et al. that Triton's internal heat flow could strongly couple to the surface volatile distribution. To further explore this idea, we present numerical models of the permanent distribution of nitrogen ice on Triton that include the effects of sunlight, the two-dimensional distribution of internal heat flow, the coupling of internal heat flow to the surface distribution of nitrogen ice, and the finite viscosity of nitrogen ice. From these models we conclude that: (1) The strong vertical thermal gradient induced in Triton's polar caps by internal heat-flow facilitates viscous spreading to lower latitudes, thus opposing the poleward transport of volatiles by sunlight, and, for plausible viscosities and nitrogen inventories, producing permanent caps of considerable latitudinal extent; (2) It is probable that there is a strong coupling between the surface distribution of nitrogen ice on Triton and internal heat flow; (3) Asymmetries in the spatial distribution of Triton's heat flow, possibly driven by large-scale, volcanic activity or convection in Triton's interior, can result in permanent polar caps of unequal latitudinal extent, including the case of only one permanent polar cap; (4) Melting at the base of a permanent polar cap on Triton caused by internal heat flow can significantly enhance viscous spreading, and, as an alternative to the solid-state greenhouse mechanism proposed by Brown et al. (1990), could provide the necessary energy, fluids, and/or gases to drive Triton's geyser-like plumes; (5) The atmospheric collapse predicted to occur on Triton in the next 20 years

  18. Coupling of volatile transport and internal heat flow on Triton

    NASA Technical Reports Server (NTRS)

    Brown, Robert H.; Kirk, Randolph L.

    1994-01-01

    Recently Brown et al. (1991) showed that Triton's internal heat source could amount to 5-20% of the absorbed insolation on Triton, thus significantly affecting volatile transport and atmospheric pressure. Subsequently, Kirk and Brown (1991a) used simple analytical models of the effect of internal heat on the distribution of volatiles on Triton's surface, confirming the speculation of Brown et al. that Triton's internal heat flow could strongly couple to the surface volatile distribution. To further explore this idea, we present numerical models of the permanent distribution of nitrogen ice on Triton that include the effects of sunlight, the two-dimensional distribution of internal heat flow, the coupling of internal heat flow to the surface distribution of nitrogen ice, and the finite viscosity of nitrogen ice. From these models we conclude that: (1) The strong vertical thermal gradient induced in Triton's polar caps by internal heat-flow facilitates viscous spreading to lower latitudes, thus opposing the poleward transport of volatiles by sunlight, and, for plausible viscosities and nitrogen inventories, producing permanent caps of considerable latitudinal extent; (2) It is probable that there is a strong coupling between the surface distribution of nitrogen ice on Triton and internal heat flow; (3) Asymmetries in the spatial distribution of Triton's heat flow, possibly driven by large-scale, volcanic activity or convection in Triton's interior, can result in permanent polar caps of unequal latitudinal extent, including the case of only one permanent polar cap; (4) Melting at the base of a permanent polar cap on Triton caused by internal heat flow can significantly enhance viscous spreading, and, as an alternative to the solid-state greenhouse mechanism proposed by Brown et al. (1990), could provide the necessary energy, fluids, and/or gases to drive Triton's geyser-like plumes; (5) The atmospheric collapse predicted to occur on Triton in the next 20 years

  19. ISS COLUMBUS laboratory experiment `GeoFlow I and II' -fluid physics research in microgravity environment to study convection phenomena inside deep Earth and mantle

    NASA Astrophysics Data System (ADS)

    Futterer, Birgit; Egbers, Christoph; Chossat, Pascal; Hollerbach, Rainer; Breuer, Doris; Feudel, Fred; Mutabazi, Innocent; Tuckerman, Laurette

    Overall driving mechanism of flow in inner Earth is convection in its gravitational buoyancy field. A lot of effort has been involved in theoretical prediction and numerical simulation of both the geodynamo, which is maintained by convection, and mantle convection, which is the main cause for plate tectonics. Especially resolution of convective patterns and heat transfer mechanisms has been in focus to reach the real, highly turbulent conditions inside Earth. To study specific phenomena experimentally different approaches has been observed, against the background of magneto-hydrodynamic but also on the pure hydrodynamic physics of fluids. With the experiment `GeoFlow' (Geophysical Flow Simulation) instability and transition of convection in spherical shells under the influence of central-symmetry buoyancy force field are traced for a wide range of rotation regimes within the limits between non-rotating and rapid rotating spheres. The special set-up of high voltage potential between inner and outer sphere and use of a dielectric fluid as working fluid induce an electro-hydrodynamic force, which is comparable to gravitational buoyancy force inside Earth. To reduce overall gravity in a laboratory this technique requires microgravity conditions. The `GeoFlow I' experiment was accomplished on International Space Station's module COLUM-BUS inside Fluid Science Laboratory FSL und supported by EADS Astrium, Friedrichshafen, User Support und Operations Centre E-USOC in Madrid, Microgravity Advanced Research and Support Centre MARS in Naples, as well as COLUMBUS Control Center COL-CC Munich. Running from August 2008 until January 2009 it delivered 100.000 images from FSL's optical diagnostics module; here more precisely the Wollaston shearing interferometry was used. Here we present the experimental alignment with numerical prediction for the non-rotating and rapid rotation case. The non-rotating case is characterized by a co-existence of several stationary supercritical

  20. Heat flow anomalies on the Western Mediterranean margins: first results from the WestMedFlux-2016 cruise

    NASA Astrophysics Data System (ADS)

    Poort, Jeffrey; Lucazeau, Francis; Le Gal, Virginie; Rabineau, Marina; Dal Cin, Michela; Bouzid, Abderrezak; Palomino, Desirée; Leroux, Estelle; Akhmanov, Grigory; Battani, Anne; Bachir, Roza Si; Khlystov, Oleg; Koptev, Aleksandre

    2017-04-01

    continent, both strongly reduced and elevated heat flow are observed and suggest other heat sink and sources. We will discuss on the different processes that might have affected the surface heat flow (e.g., bottom water currents, slope instabilities and focused fluid migrations) and try to link the large scale heat flow patterns with crustal nature, structuring of the margins and mantle dynamics.

  1. Heat flow vs. atmospheric greenhouse on early Mars

    NASA Technical Reports Server (NTRS)

    Fanale, F. P.; Postawko, S. E.

    1991-01-01

    Researchers derived a quantitative relationship between the effectiveness of an atmospheric greenhouse and internal heat flow in producing the morphological differences between earlier and later Martian terrains. The derivation is based on relationships previously derived by other researchers. The reasoning may be stated as follows: the CO2 mean residence time in the Martian atmosphere is almost certainly much shorter than the total time span over which early climate differences are thought to have been sustained. Therefore, recycling of previously degassed CO2 quickly becomes more important than the ongoing supply of juvenile CO2. If so, then the atmospheric CO2 pressure, and thereby the surface temperature, may be approximated mathematically as a function of the total degassed CO2 in the atmosphere plus buried material and the ratio of the atmospheric and regolith mean residence times. The latter ratio can also be expressed as a function of heat flow. Hence, it follows that the surface temperature may be expressed as a function of heat flow and the total amount of available CO2. However, the depth to the water table can simultaneously be expressed as a function of heat flow and the surface temperature (the boundary condition). Therefore, for any given values of total available CO2 and regolith conductivity, there exist coupled independent equations which relate heat flow, surface temperature, and the depth to the water table. This means we can now derive simultaneous values of surface temperature and the depth of the water table for any value of the heat flow. The derived relationship is used to evaluate the relative importance of the atmospheric greenhouse effect and the internal regolith thermal gradient in producing morphological changes for any value of the heat flow, and to assess the absolute importance of each of the values of the heat flow which are thought to be reasonable on independent geophysical grounds.

  2. Heat flow studies in Wyoming: 1979 to 1981

    SciTech Connect

    Heasler, H.P.; Decker, E.R.; Buelow, K.L.; Ruscetta, C.A.

    1982-05-01

    Heat flow values and updated maps of flux in Wyoming, northern Colorado, and southern Montana are presented. It is concluded that most of the heat flow values in the Wyoming Basin-Southern Rocky Mountains region in Southern Wyoming are low or normal, excluding the Saratoga Valley; that the regional flux in the Owl Creek Mountains area is above normal; and that the Meadow Creek Basin area is in a zone of high flux. (MJF)

  3. Study on the Heat-Flow Controllable Heat Exchanger-3rd report

    NASA Astrophysics Data System (ADS)

    Ishikawa, Osamu; Hamano, Masayoshi; Yanadori, Michio

    The heat-flow controllable heat exchanger for the purpose of heat recovery through the waste hot water at the bathroom and the washing room has been developed. The system is especially available at the house of cold area and the recovery heat is used to warm the suction air conducted from ventilation device. As the result of field test, it is clarified that the heat recovery rate by the system is very large. Also, the exchanger is possible to control the amount of recorery heat. Therefore, it is considered that the exchanger is applicable in the ventilation systems used the waste hot water.

  4. Transient flow in the mantle wedge in the last decade following great earthquakes in the Sumatran subduction zone

    NASA Astrophysics Data System (ADS)

    Qiu, Q.; Barbot, S.; Hill, E.; Moore, J. D. P.; Feng, L.; Ezer, T.

    2016-12-01

    Postseismic processes involve the response of Earth's lithosphere and asthenosphere to stress changes produced as a result of earthquake ruptures. Multiple postseismic mechanisms exist, including afterslip on the fault interface and viscoelastic flow of the asthenosphere. The effects of these processes on observations of post-earthquake surface deformation have traditionally been modeled independently - using inversion for afterslip, and forward models for viscous flow - resulting in tradeoffs and uncertainties in estimates for both the levels of afterslip and the viscoelastic rheology. Here, we present a newly developed technique that is capable of jointly inverting for fault afterslip and viscous strain in three-dimensional finite volumes located at asthenospheric depths, with no need for prior assumptions on the rheology or in situ conditions. We implement this approach for the Sumatra subduction zone to model postseismic deformation following the recent slew of great earthquakes over the last decade. The postseismic transients illuminate the rheology of the mantle wedge, ruling out linear Maxwellian viscosity. We show that the effective viscosity in the mantle wedge is significantly reduced by coseismic stress change and recovers to background levels after a period of one year. This behavior can be captured by a Burgers rheology, with estimated ηK 1017 Pa.s and ηM 1019 Pa.s and a rigidity of 70 GPa in the Kelvin body. This transient rheology contributes to significant deformation in the early stage of postseismic relaxation.

  5. Curie point depth and heat flow from spectral analysis of aeromagnetic data over the northern part of Western Desert, Egypt

    NASA Astrophysics Data System (ADS)

    Saada, Saada Ahmed

    2016-11-01

    The present work aims to estimate the Curie point depth and the surface heat flow for the northern part of the Western Desert using aeromagnetic data. Applying spectral analysis to aeromagnetic anomalies has provided equitable promising geological results, useful for further geothermal or petroleum exploration. The total intensity aeromagnetic map was first reduced to the north magnetic pole to correct the shape and position of different magnetic anomalies over their causative bodies. Secondly, the short wavelengths were removed to enhance the deeper long wavelengths related to the deep sources. Spectral analysis indicates that the area is underlined by an average Curie point depth of about 27 km. This implies an average thermal heat flow (53 mW/m2) lower than the average global heat flow. The investigated area was divided into eighteen blocks, where the average depths to centroid and top of the magnetic source were estimated for each block. The results of this work show a general depth increase of the magnetic boundaries from 24.5 km in the southern area to 33 km at the northern part. The calculated surface heat flow decreases from about 56 to 42 mW/m2 in the same direction. Consequently, this area is characterized by its low geothermal gradient and surface heat flow. This low geothermal gradient indicates that the upper mantle contributes to the magnetic features at the northern offshore parts. This work also recommends by deep drilling for petroleum exploration and production within the Egyptian Mediterranean Sea exploration strip.

  6. Horizontal extent of the urban heat dome flow.

    PubMed

    Fan, Yifan; Li, Yuguo; Bejan, Adrian; Wang, Yi; Yang, Xinyan

    2017-09-15

    Urban heat dome flow, which is also referred to as urban heat island circulation, is important for urban ventilation and pollutant transport between adjacent cities when the background wind is weak or absent. A "dome-shaped" profile can form at the upper boundary of the urban heat island circulation. The horizontal extent of the heat dome is an important parameter for estimating the size of the area it influences. This study reviews the existing data on the horizontal extent of the urban heat dome flow, as determined by using either field measurements or numerical simulations. A simple energy balance model is applied to obtain the maximum horizontal extent of a single heat dome over the urban area, which is found to be approximately 1.5 to 3.5 times the diameter of the city's urban area at night. A linearized model is also re-analysed to calculate the horizontal extent of the urban heat dome flow. This analysis supports the results from the energy balance model. During daytime, the horizontal extent of the urban heat dome flow is found to be about 2.0 to 3.3 times the urban area's diameter, as influenced by the convective turbulent plumes in the rural area.

  7. New computer program solves wide variety of heat flow problems

    NASA Technical Reports Server (NTRS)

    Almond, J. C.

    1966-01-01

    Boeing Engineering Thermal Analyzer /BETA/ computer program uses numerical methods to provide accurate heat transfer solutions to a wide variety of heat flow problems. The program solves steady-state and transient problems in almost any situation that can be represented by a resistance-capacitance network.

  8. Silica heat flow interpretation technique: assumptions and applications

    SciTech Connect

    Swanberg, C.A.; Morgan, P.

    1980-12-10

    We have previously established a linear relation between temperatures based on the silica content of groundwater and regional heat flow and used the relation to prepare a new heat flow map of the continental United States. We now examine the assumptions upon which the relation is based, the accuracy to which groundwater silica data can be used to estimate regional heat flow, and the limitation of the technique. By averaging silica geotemperatures and traditional heat flow values over 1/sup 0/ x 1/sup 0/ blocks, the linear regression is TSiO/sub 2/=mq+b, where m and b are constants determined to be 680 +- 67/sup 0/C m/sup 2/ W/sup -1/ and 12.4 +- 5.1 /sup 0/C. The physical significance of b is mean annual surface temperature, and the product of m times thermal conductivity reflects the minimum mean depth to which groundwaters may circulate. These values are not sufficiently different from our earlier values (m=670, b=13.2) to justify using the newer values. To illustrate the application of the linear regression in predicting regional heat flow, data sets are presented from upstate New York, south central New Mexico, and Egypt. In each case, the predicted heat flow is tectonically reasonable and consistent with whatever traditional data are available.

  9. Electroosmotic Entry Flow with Joule Heating Effects

    NASA Astrophysics Data System (ADS)

    Prabhakaran, Rama; Kale, Akshay; Xuan, Xiangchun

    Electrokinetic flow, which transports liquids by electroosmosis and samples by electrophoresis, is the transport method of choice in microfluidic chips over traditional pressure-driven flows. Studies on electrokinetic flows have so far been almost entirely limited to inside microchannels. Very litt