the relationships between large scale variations in shear velocity density and compressional velocity in the earth s mantle a large data set of surface wave phase anomalies body wave travel times normal mode splitting functions and long period waveforms is used to investigate the scaling between shear velocity density and compressional velocity in the earth s mantle we introduce a methodology that allows construction of joint models with various levels of scaling complexity d ln d lnvs d lnvs d lnvp in order to detect seismological signatures of chemical heterogeneity we demonstrate that the data sets considered cannot be fit concurrently with a uniform or a positive and uniform throughout the mantle the variance reductions to p wave travel times and vp sensitive modes are up to 40 higher with our preferred model of anisotropic shear and compressional velocity than the recent anisotropic shear velocity model s362ani m which was constructed assuming a uniform throughout the mantle several features reported in earlier tomographic studies persist after the inclusion of new and larger data sets anticorrelation between bulk sound and shear velocities in the lowermost mantle as well as an increase in with depth in the lower mantle are largely independent of the regularization scheme when correlations between density and shear velocity variations are imposed in the lowermost mantle variance reductions of several spheroidal and toroidal modes deteriorate by as much as 40 recent measurements of the splitting of 0s2 in particular are largely incompatible with perfectly correlated shear velocity and density heterogeneity throughout the mantle a way to significantly improve the fits to various data sets is by allowing independent density perturbations in the lowermost mantle our preferred joint model consists of denser than average anomalies 1 peak to peak at the base of the mantle roughly coincident with the low velocity superplumes the relative variation of shear velocity density and compressional velocity in our study disfavors a purely thermal contribution to heterogeneity in the lowermost mantle with implications for the long term stability and evolution of superplumes

influence of rotation on the metal rain in a hadean magma ocean 1 today it is widely accepted that during its early evolution the earth experienced a magma ocean that covered most of its surface the separation of metal from silicate was much facilitated in the environment of such a magma ocean the differentiation mechanism is known as the metal rain scenario our study will focus on the settling dynamics of these metal droplets because of the low viscosity of molten silicate and a higher rotation period of the earth at that time the rotation has a potentially strong influence on the dynamics of the magma ocean we use numerical 3d fluid simulations to analyze the combined effects of strong rotation and convection on the settling of the iron droplets we show that the influence of rotation on the settling depends on the latitude at the poles the influence of rotation is only marginal at the equator three different scenarios can be distinguished first at low rotation rates the particles form a dense layer at the bottom second for strong rotation the particles stay mostly suspended and layers form in the temperature field third at higher rotation rates the particles form a ribbon like structure in the middle of the box the influence of rotation on the iron droplets may lead to a scenario where part of the iron is kept in the mantle instead of transported to the core this would have a strong influence on the later states of the differentiation process and the amount of siderophile elements in the mantle

crystals stirred up 2 numerical insights into the formation of the earliest crust on the moon 1 this is the second paper in a two part series examining the fluid dynamics of crystal settling and flotation in the lunar magma ocean in the first paper we develop a direct numerical method for resolving the hydrodynamic interactions between crystals and their feedback on the flow field in magmatic liquid in this paper we use this computational technique to test the leading model for the formation of the earliest crust on the moon the anorthositic lithology of the lunar crust is thought to have been formed by the flotation of buoyant plagioclase crystals at a time when the lunar mantle was still wholly or largely molten this model is appealing from an observational point of view but its fluid dynamical validity is not obvious because 1 plagioclase probably started crystallizing very late i e when the magma ocean was already 80 solidified and 2 a significant portion of the shallow lunar crust consists of almost pure plagioclase 90 vol requiring very efficient plagioclase segregation the goal of this study is to better understand the fluid dynamical conditions that hinder or facilitate crystal settling or flotation our approach complements earlier studies by explicitly linking the petrological and fluid dynamical evolution and by focusing on the effect of increasing crystal fraction we find that crystal settling was probably possible throughout the entire solidification history of the lunar magma ocean as long as crystal sizes were sufficiently large r 1 mm and crystal fraction sufficiently low 13

connectivity of molten fe alloy in peridotite based on in situ electrical conductivity measurements implications for core formation in terrestrial planets abstract the connectivity of molten fe s in peridotite has been experimentally investigated by means of in situ electrical conductivity measurements at high temperatures and 1 gpa starting materials were powdered mixtures of peridotite klb 1 with various amounts 0 3 6 13 19 24 vol of the 1 gpa eutectic composition in the fe fes binary system at temperatures above the eutectic point in the fe fes system 980 c and below the solidus of klb1 1200 c molten fe s in a solid silicate matrix interconnects when the volume fraction is over 5 conductivity temperature paths indicate that in the presence of partial silicate melting the connectivity of molten fe s in a peridotite matrix is inhibited based on observations of retrieved samples the percolation threshold of fe s melts in the presence of low to moderate degrees of silicate melt is estimated at 13 2 vol these results indicate that if the volume fraction of fe alloy in a planetesimal was initially greater than 5 and if early heating by decay of radionuclides raised the temperature of the interior above the fe alloy melting point initial metal segregation was controlled by permeable flow of molten iron alloy in a solid silicate matrix these conditions were likely met by many terrestrial objects in the early solar nebula efficient removal of residual fe alloy 5 vol from silicate requires high degree melting of silicate so that metal can segregate as droplets giant impacts during the final stage of accretion of large planetary objects could supply the energy required for high degrees of melting alternatively if initial metal segregation were delayed until a planetary object grew to large size 1000 km in diameter release of gravitational potential energy due to metal segregation could contribute enough heat to form a magma ocean

hyperconcentrated flows on a forested alluvial fan of eastern canada geomorphic characteristics return period and triggering scenarios the assessment of the dominant flow type on alluvial fans usually refers to two categories debris flow fans i e sediment gravity flows and fluvial fans i e fluid gravity flows here we report the results of combined morphometric stratigraphic and sedimentological approaches which suggest that hyperconcentrated flows a transitional process rheologically distinct from debris flows and floods and sometimes referred to as debris floods mud floods or transitional debris flows are the dominant fan building process in eastern canada these flows produce transitional facies between those of debris flows which consist of a cohesive matrix supported diamicton and those of river flows which display more distinct stratification the size of the blocks in the channels and the abrasion scars at the base of several trees attest to the high transport capacity of these flows the fan channels are routed according to various obstacles comprised primarily of woody debris that impede sediment transit however these conditions of sediment storage are combined with readily available sediment due to the friable nature of the local lithology tree ring analysis allowed the reconstruction of eight hydrogeomorphic events which are characterized by a return period of 9 25 years for the period 1934 2008 although most of the analyzed events occurred after 1970 historical weather data analysis indicates that they were related to rare hydrometeorological events at regional and local scales this evidence led to the elaboration of weather scenarios likely responsible for triggering flows on the fan according to these scenarios two distinct hydrologic regimes emerge the torrential rainfall regime and the nival regime related to snowmelt processes hydrogeomorphic processes occurring in a cold temperate climate and particularly on small forested alluvial fans of north eastern north america should receive more attention from land managers given the hazard they represent as well as because of their sensitivity to various meteorological parameters copyright 2014 john wiley sons ltd

numerical models of martian mantle evolution induced by magmatism and solid state convection beneath stagnant lithosphere 1 numerical models of magmatism in a convecting mantle are presented to understand martian mantle evolution the viscosity is strongly temperature dependent and the lithosphere is stagnant magmatism is modeled as a permeable flow of basaltic magma generated by decompression melting when the initial mantle temperature is sufficiently high a magma ocean develops to generate a thick basaltic crust and create a compositionally layered mantle the upper layer of the mantle consists of compositionally buoyant residue of the basaltic crust while the lower layer consists of compositionally denser materials that are not as depleted in the basaltic component hot plumes grow from the lower layer making it thinner with time by erosion the hot plumes also induce magmatism which extracts heat producing elements hpes from the mantle the hpe extraction regulates plume magmatism activity and controls the duration of plume magmatism plume magmatism also keeps the mantle temperature below the solidus by efficiently extracting heat as soon as the mantle temperature exceeds the solidus the martian mantle is likely to have evolved as a relaxation from a compositionally layered state formed by the magma ocean and plume magmatism has probably played a crucial role in the relaxation process

thermodynamics of silicate liquids in the deep earth article i nfo we discuss the geophysical implications of recent first principles molecular dynamics simulations of mgsio3 liquid in particular the findings that the gruneisen parameter increases by a factor of three on two fold compression and the predicted melting curve the predicted melting temperature of mgsio3 perovskite at 136 gpa is 5400 600 k which if lowered by freezing point depression by 1300 k yields a mantle solidus temperature of 4100 k identical to recent estimates of the temperature at the base of the mantle we argue on this basis that partial melting at the base of the mantle is plausible while mgsio3 perovskite is denser than the isochemical liquid reasonable values of iron partitioning and bulk iron contents leads to the conclusion that a melt at the base of the multi component mantle would be denser than its surroundings and therefore buoyantly stable we predict the bulk sound velocity of this melt to be 10 9 km s 1 less than that of ultra low velocity zones and consistent with the explanation of these regions as being due to partial melting the increase on compression of the gruneisen parameter in the liquid state yields isentropes that are much hotter than previously thought a potential temperature of only 2450 k is sufficient to melt the entire mantle and a magma ocean will begin crystallization at mid mantle depths rather than at the base of the mantle

physical state of the very early earth abstract the earliest surface environment of the earth is reconstructed in accordance with the planetary formation theory formation of an atmosphere is an inevitable consequence of earth s formation the atmosphere near the close of accretion is composed of 200 300 bars of h2 and h2o and several tens of bars of co and co2 either by the blanketing effect of the proto atmosphere or heating by large planetesimal impacts a magma ocean is formed during accretion we can distinguish three stages for the thermal evolution of the magma ocean and proto crust stage 0 is characterized by a super liquidus or completely molten regime near the surface at this stage the surface of the earth is covered by a super liquidus magma ocean no chemical differentiation is expected during this stage once the energy flux released by planet formation decreases to the 200 w m2 level the super liquidus magma ocean then disappears within a time interval of 1 m y this is the transition from stage 0 to 1 stage 1 is characterized by a partially molten magma ocean in the magma ocean consisting of 20 30 partial melt heat transport is controlled by melt solid separation a type of compositional convection rather than thermal convection chemical differentiation of the mantle mainly occurs in this stage once the energy flux drops to the 160 w m2 level more than 90 of water vapor in the proto atmosphere condense to form the proto oceans several tens of bars of co and co2 remain in the atmosphere just after formation of the oceans water oceans are occasionally evaporated by large impacts after each such event recondensation of the ocean takes several hundred years although the surface is covered by a chilled proto crust it is short lived because of extensive volcanic resurfacing activity as well as meteorite impacts resurfacing this stage ends when the energy flux drops to 0 1 1 w m2 level the duration time of stage 1 is estimated to be several hundred million years the best estimate is about 400 m y stage 2 is characterized by solid state convection this stage continues to the present day one of the most important change on the proto earth is the transition from stage 1 to 2 which occurs several hundred million years after the earth formation long lived crust is formed only after this transition

near far side asymmetry in the tidally heated moon abstract using viscoelastic mass spring model simulations to track heat distribution inside a tidally perturbed body we measure the near far side asymmetry of heating in the crust of a spin synchronous moon in eccentric orbit about the earth with the young moon within 8 earth radii of the earth we find that tidal heating per unit area in a lunar crustal shell is asymmetric due to the octupole order moment in the earth s tidal field and is 10 to 20 higher on its near side than on its far side tidal heating reduces the crustal basal heat flux and the rate of magma ocean crystallization assuming that the local crustal growth rate depends on the local basal heat flux and the distribution of tidal heating in latitude and longitude a heat conductivity model illustrates that a moderately asymmetric and growing lunar crust could maintain its near far side thickness asymmetry but only while the moon is near the earth

plate tectonics on the terrestrial planets abstract plate tectonics is largely controlled by the buoyancy distribution in oceanic lithosphere which correlates well with the lithospheric age buoyancy also depends on compositional layering resulting from pressure release partial melting under mid ocean ridges and this process is sensitive to pressure and temperature conditions which vary strongly between the terrestrial planets and also during the secular cooling histories of the planets in our modelling experiments we have applied a range of values for the gravitational acceleration representing different terrestrial planets potential temperatures representing different times in the history of the planets and surface temperatures in order to investigate under which conditions plate tectonics is a viable mechanism for the cooling of the terrestrial planets in our models we include the effects of mantle temperature on the composition and density of melt products and the thickness of the lithosphere our results show that the onset time of negative buoyancy for oceanic lithosphere is reasonable less than a few hundred million years for potential temperatures below 1500 c for the earth and 1450 c for venus in the reduced gravity field of mars a much thicker stratification is produced and our model indicates that plate tectonics could only operate on reasonable time scales at a potential mantle temperature below about 1300 1400 c

modeling of cbm production co2 injection and tracer movement at a field co2 sequestration site sequestration of carbon dioxide in unmineable coal seams is a potential technology mainly because of the potential for simultaneous enhanced coalbed methane production ecbm several pilot tests have been performed around the globe leading to mixed results numerous modeling efforts have been carried out successfully to model methane production and carbon dioxide co sub 2 injection sensitivity analyses and history matching along with several optimization tools were used to estimate reservoir properties and to investigate reservoir performance geological and geophysical techniques have also been used to characterize field sequestration sites and to inspect reservoir heterogeneity the fate and movement of injected co sub 2 can be determined by using several monitoring techniques monitoring of perfluorocarbon pfc tracers is one of these monitoring technologies as a part of this monitoring technique a small fraction of a traceable fluid is added to the injection wellhead along with the co sub 2 stream at different times to monitor the timing and location of the breakthrough in nearby monitoring wells or offset production wells a reservoir modeling study was performed to simulate a pilot sequestration site located in the san juan coal basin of northern new mexico several unknown reservoir properties at the field site were estimatedmore by modeling the coal seam as a dual porosity formation and by history matching the methane production and co sub 2 injection in addition to reservoir modeling of methane production and co sub 2 injection tracer injection was modeled tracers serve as a surrogate for determining potential leakage of co sub 2 the tracer was modeled as a non reactive gas and was injected into the reservoir as a mixture along with co sub 2 geologic and geometric details of the field site numerical modeling details of methane production co sub 2 injection and tracer injection are presented in this paper moreover the numerical predictions of the tracer arrival times were compared with the measured field data results show that tracer modeling is useful in investigating movement of injected co sub 2 into the coal seam at the field site also such new modeling techniques can be utilized to determine potential leakage pathways and to investigate reservoir anisotropy and heterogeneity less

metal silicate fractionation in the growing earth energy source for the terrestrial magma ocean based on the homogeneous accretion model of planets thermal evolution of the growing earth has been studied after the surface of the growing earth starts melting owing to the blanketing effect of the primordial atmosphere gravitational differentiation between metallic and silicate materials takes place in its upper region the differentiation would give rise to a large amount of gravitational energy release as well as layered structure inside the proto earth a part of released energy would be transported outward by convection considering the effects of gravitational fractionation and convection we have pursued numerically the evolution of the growing earth our results show that gravitational differentiation can supply energy large enough to keep the whole silicate layer in the molten state and that half of the released energy is conveyed outward by convective heat transport in the growing stage the temperature distribution in the silicate layer always lies between liquidus and solidus temperatures except in an uppermost thin zone the thermal structure obtained favors a notion of the primordial magma ocean and of chemical differentiation of mantle the structure of the growing earth which is composed of the central protocore the metallic layer and the silicate layer magma ocean would become gravitationally unstable and overturn to form a metallic core energy released by this overturn would not affect the structure of the upper magma ocean too much but undifferentiated primordial materials which come from the protocore would add to mantle materials through the overturn and this would help explain the isotopic mantle heterogeneity presently observed

thermodynamic properties of mg2sio4 liquid at ultra high pressures from shock measurements to 200 gpa on forsterite and wadsleyite polycrystalline samples of mg 2sio 4 forsterite and wadsleyite were synthesized and then dynamically loaded to pressures of 39 200 gpa differences in initial density and internal energy between these two phases lead to distinct hugoniots each characterized by multiple phase regimes transformation to the high pressure phase assemblage mgo mgsio 3 perovksite is complete by 100 gpa for forsterite starting material but incomplete for wadsleyite the datum for wadsleyite shocked to 136 gpa however is consistent with the assemblage mgo mgsio 3 post perovksite marked increases in density along the hugoniots of both phases between 130 and 150 gpa are inconsistent with any known solid solid phase transformation in the mg 2sio 4 system but can be explained by melting density increases upon melting are consistent with a similar density increase observed in the mgsio 3 system this implies that melts with compositions over the entire mg si range likely for the mantle would be negatively or neutrally buoyant at conditions close to the core mantle boundary supporting the partial melt hypothesis to explain the occurrence of ultra low velocity zones at the base of the mantle from the energetic difference between the high pressure segments of the two hugoniots we estimate a gruneisen parameter of 2 6 0 35 for mg 2sio 4 liquid between 150 and 200 gpa comparison to low pressure data and fitting of the absolute pressures along the melt hugoniots both require that for the melt increases with increasing density similar behavior was recently predicted in mgsio 3 liquid via molecular dynamics simulations this result changes estimates of the temperature profile and hence the dynamics of a deep terrestrial magma ocean

early magnetic field and magmatic activity on mars from magma ocean cumulate overturn abstract significant and perhaps complete melting of the young terrestrial planets is expected from their heat of accretion and core formation the process of subsequent magma ocean fractional solidification creates a cumulate mantle unstable to gravitational overturn overturn should be fast 1 to 10 ma and result in increasing mantle density with depth this stable stratification inhibits later thermal convection preserving geochemical heterogeneities overturn places cold cumulates against the core mantle boundary which creates sufficient heat flux to drive a core dynamo producing a brief strong magnetic field during overturn hot cumulates rise from depth and melt adiabatically creating an early crust to record this field and leaving behind mantle reservoirs with isotopic fractionations dating from the early evolution of the planet

rheology of the upper mantle a synthesis rheological properties of the upper mantle of the earth play an important role in the dynamics of the lithosphere and asthenosphere however such fundamental issues as the dominant mechanisms of flow have not been well resolved a synthesis of laboratory studies and geophysical and geological observations shows that transitions between diffusion and dislocation creep likely occur in the earth s upper mantle the hot and shallow upper mantle flows by dislocation creep whereas cold and shallow or deep upper mantle may flow by diffusion creep when the stress increases grain size is reduced and the upper mantle near the transition between these two regimes is weakened consequently deformation is localized and the upper mantle is decoupled mechanically near these depths

morphochemistry of patterns produced by mixing of rhyolitic and basaltic melts abstract in this work we present the results of time series experiments performed by mixing basaltic and rhyolitic melts at high temperature using a device recently developed to trigger chaotic dynamics in a mixing system the morphology of mixing patterns is quantified at different times by measuring their fractal dimension and a linear relationship is derived between mixing time and morphological complexity the complexity of mixing patterns is also compared to the degree of homogenization of chemical elements during mixing and empirical relationships are established between the fractal dimension and the temporal variation of concentration variance of elements new concepts and tools to study the magma mixing process unfold from the experimental results presented in this work the first one is that the mixing patterns are fractals and they can be quantified by measuring their fractal dimension this represents a further step in the quantification of the magma mixing process the second outcome is that the relationship between the fractal dimension of the mixing patterns and mixing time is linear this has important volcanological implications as the analyses of the morphology of mixing patterns in volcanic rocks can be complemented by experiments to build a new chronometer to estimate the mixing to eruption time a further result from this work is the relationship between the fractal dimension of mixing patterns and concentration variance of chemical elements this represents the first morphochemical study in igneous petrology bringing with it the potential to infer the relative mobility of chemical elements during the time progression of mixing by analyzing the morphology of mixing patterns in the rocks

modeling of ecbm recovery from amasra coalbed in zonguldak basin turkey abstract zonguldak coal basin is the only productive hard coal basin of turkey the eastern part of the basin is called as bartin amasra district which has deeper coal seams the depth and difficulty of mining these coal seams make this district an important candidate for coalbed methane cbm recovery however there is not enough reservoir data for modeling purposes in this study the lithologic information collected for coal mining industry was used to determine the correlations and the continuity of the coal seams the lithologic information was examined and the depths of the coal seams and the locations of the exploration boreholes were used to perform a reliable correlation using a new method as a result of the correlation study 63 continuous coal layers were found a statistical reserve estimation of each coal layer for methane was made by using monte carlo simulation method the initial methane in place found in the coal layers both in free and adsorbed states were estimated using probabilistic simulations resulted in possible reserve p10 of 2 07 billion m 3 probable reserve p50 of 1 35 billion m 3 and proven reserves p90 of 0 86 billion m 3 among the determined continuous coal layers coal layer 26 was selected for a preliminary investigation of the applicability of enhanced coalbed methane ecbm recovery and co 2 storage the scarcity of coal seam reservoir data required a sensitivity study for the effects of reservoir parameters on operational performance indicators the effects of adsorption coal density permeability cleat porosity and permeability anisotropy parameters were examined using the computer modeling group s cmg gem module

structural and tidal models of titan and inferences on cryovolcanism titan saturn s largest satellite is subject to solid body tides exerted by saturn on the timescale of its orbital period the tide induced internal redistribution of mass results in tidal stress variations which could play a major role for titan s geologic surface record we construct models of titan s interior that are consistent with the satellite s mean density polar moment of inertia factor obliquity and tidal potential love number k2 as derived from cassini observations of titan s low degree gravity field and rotational state in the presence of a global liquid reservoir the tidal gravity field is found to be consistent with a subsurface water ammonia ocean more than 180 km thick and overlain by an outer ice shell of less than 110 km thickness the model calculations suggest comparatively low ocean ammonia contents of less than 5 wt and ocean temperatures in excess of 255 k i e higher than previously thought thereby substantially increasing titan s potential for habitable locations the calculated diurnal tidal stresses at titan s surface amount to 20 kpa almost comparable to those expected at enceladus and europa tidal shear stresses are concentrated in the polar areas while tensile stresses predominate in the near equatorial midlatitude areas of the sub and anti saturnian hemispheres the characteristic pattern of maximum diurnal tidal stresses is largely compliant with the distribution of active regions such as cryovolcanic candidate areas the latter could be important for titan s habitability since those may provide possible pathways for liquid water ammonia outbursts on the surface and the release of methane in the satellite s atmosphere

dynamics of metal silicate separation in a terrestrial magma ocean in a terrestrial magma ocean the metal silicate separation involved small metal droplets our goal is to better understand the dynamics of the metal droplet scenario the mechanism of sedimentation in a vigorously convecting and strongly rotating magma ocean may differ significantly from settling droplets in a still fluid in order to systematically study the parameter dependence on the style of motion we utilize two dimensional and three dimensional numerical convection models combined with a tracer based sedimentation method we investigate the characteristic flow patterns resulting from the competing effects of convection and droplet settling and find three styles of motion a temperature dominated style where most droplets remain suspended a droplet dominated style where the droplets separate from the fluid and a style of repetitive motion we find that the droplet dominated style is relevant to the magma ocean in this scenario the droplets settle and form a dense bottom layer one of the key findings of this work is that the formation of the dense bottom layer and therefore the separation of metal droplets from the liquid silicate occurs on a characteristic timescale which is identical with the stokes settling time finally we study the chemical interaction of settling metal droplets and liquid silicate and discuss how accurately a simple parameterized model can describe the chemical equilibration in the metal rain scenario of a terrestrial magma ocean we find agreement between the parameterized model and our two dimensional model our simulations which include thermal convection into the metal rain model confirm the fundamental observation that metal droplets are not permanently suspended in the convecting silicate melt but that they sink and rapidly form a dense layer at the base of the magma ocean

earth and mars early thermal profiles abstract the extent of formation heating for the earth and mars has been evaluated assuming that the terrestrial planets accumulated from planetesimals the main result is that even if a long accumulation time is assumed 100 ma it is possible to obtain a planetary structure with a large melted shell taking into account the role played by massive projectiles which upon reaching depths of several kilometres are able to deposit heat significantly below the planetary surface internal temperatures sufficient for the downward migration of the liquid iron alloy have been obtained

carboniferous coals of the zonguldak basin northwest turkey implications for coalbed methane potential we investigated the carboniferous coals in the zonguldak basin northwest turkey using a multidisciplinary approach including petrographical and geochemical analyses gas adsorption and gas content measurements artificial maturation experiments on selected coals and one dimensional 1 d modeling of the basin evolution and hydrocarbon generation the main emphasis was set on the definition of coalbed methane cbm generation capability and adsorption capacity of the coals considering these properties of coals and the amount and composition of gas within the coal seams we carried out a comprehensive evaluation of the cbm potential of the basin three areas in the basin namely armutcuk zonguldak and amasra were investigated separately for their cbm potential from the standpoint of petroleum oil and or gas generation the coals in the armutcuk and amasra areas are located within the oil generation window the coals of the zonguldak area are located within the oil and gas generation window computer aided basin modeling using a basin specific kinetic data set of hydrocarbon generation from coals suggests that significant quantities of gas have been generated only in the zonguldak area modeling results also indicate that major gas generation from the base of the westphalian a kozlu formation in the zonguldak area occurred between 80 and 42 ma during the late cretaceous early eocene prior to basin inversion that started at 42 ma and continues at present the predicted amount of generated coalbed gas from coal seams in the gas generation zone is several times higher than the adsorption capacity of the respective seams a certain amount of this gas controlled by the adsorption capacity is stored within the coal seams where it is generated gas generated in excess of storage capacity obviously would have been expelled from the coal part of the expelled gas is accumulated in coal seams located above the gas generation zone however the coal seams within and above the gas generation zone are undersaturated with respect to their adsorption capacity the undersaturation is probably caused by remigration of gas that is desorbed because of pressure decrease during basin inversion of more than 2500 m 8203 ft over the last 42 m y the rest of the gas generated within the coal seams and expelled first because of the overflow of adsorption capacity and then because of the desorption during basin inversion has either migrated to source conventional gas reservoirs or has been lost to the surface during basin inversion because the basin has not been explored for conventional gas reservoirs a conclusive mass balance cannot yet be performed despite basin inversion and remigration of gas some coal seams still contain gas amounts of up to 10 cm 3 g of coal indicating a cbm potential

onset of solid state mantle convection and mixing during magma ocean solidification energy sources involved in the early stages of planetary formation can cause partial or even complete melting of the mantle of terrestrial bodies leading to the formation of magma oceans upon planetary cooling solidification is expected to take place from the bottom upwards because of the steeper slope of the liquid adiabat with respect to the liquidus elkins tanton 2012 solomatov 2015 fractional solidification in particular can lead to the formation of a compositional layering that can play a fundamental role for the subsequent long term dynamics and evolution of the interior tosi et al 2013 plesa et al 2014 in order to assess to what extent primordial compositional heterogeneities generated upon magma ocean solidification can be preserved we investigate the cooling and solidification of a whole mantle magma ocean along with the conditions that allow solid state convection to start mixing the mantle before solidification has completed to this end we run 2 d numerical simulations in cylindrical geometry using the finite volume code gaia huttig et al 2013 we treat the liquid magma ocean in a parametrized fashion while we self consistently solve the conservation equations of thermochemical convection in the growing solid mantle accounting for pressure temperature and melt dependent rheology we consider two end member cases fractional crystallization where melt is instantaneously extracted into the overlying liquid leaving beneath a differentiated mantle and batch crystallization where melt remains in contact with the silicate matrix throughout solidification causing no differentiation by testing the effects of different cooling rates and rayleigh numbers we show that for a lifetime of the liquid magma ocean between 1 and 10 myr lebrun et al 2013 the onset of solid state convection prior to complete mantle crystallization is possible and that part or even all of the compositional heterogeneities generated upon fractionation can be erased by efficient mantle stirring figure 1 we discuss the consequences of our findings in relation to the early and long term evolution of compositional heterogeneities generated via fractional crystallization of magma oceans in terrestrial bodies with emphasis on mars thermochemical history

coupled thermal orbital evolution of the early moon abstract coupled thermal orbital histories of early lunar evolution are considered in a simple model we consider a plagioclase lid overlying a magma ocean overlying a solid mantle tidal dissipation occurs in the plagioclase lid and heat transport is by conduction and melt migration we find that large orbital eccentricities can be obtained in this model we discuss possible consequences of this phase of large eccentricities for the shape of the moon and geochronology of lunar samples we find that the orbit can pass through the shape solution of garrick bethell et al garrick bethell i wisdom j zuber m 2006 science 313 652 but we argue that the shape cannot be maintained against elastic deformation as the orbit continues to evolve

the early geodynamic evolution of mars type planets abstract it is not clear whether mars once possessed active tectonics yet the question is critical for understanding the thermal evolution of mars and the origin and longevity of its early dynamo to address these issues we have coupled mantle flow simulations together with parameterized core evolution models to simulate the early evolution of mars like planets and constrain the influence of early mobile lid tectonics on core evolution we have explored a wide parameter suite encapsulating a range of uncertainties in initial conditions rheological parameters and surface strength we present successful models that experience early mobile lid behaviour with a later transition into a stagnant lid mode which reproduce core dynamo histories similar to the magnetic history of early mars

multi branched horizontal wells for coalbed methane production field performance and well structure analysis abstract horizontal wells such as multi lateral and multi branched horizontal wells mbhws have been effectively used in the development of coalbed methane cbm fields especially for coal beds with very low permeability and low compressive strength in which the performance of conventional fracture stimulated vertical wells is ineffective in this study the performance of mbhws in the liulin block of the ordos basin in central north china is analyzed and compared to that of hydraulically fractured vertical wells the field pilot data show that the gas production rate of most fractured vertical wells decreased rapidly after a short period of time far below expectation while the performance of mbhws is satisfactory and relatively stable during 3 years of production a numerical simulation model was established based on the coal reservoir characteristics the productivities of different well types are predicted and compared to the field data the poor performance of the fractured vertical wells is thought to be caused by the early closure of the fractures and proppant embedded in the coal matrix or by a poor proppant delivery inside the fractures the high and stable productivity of the mbhws is attributed to their large drainage volume and to the stability of the wellbores simulation results show that the parameters of a mbhw such as the branch angle length and spacing can be optimized to maximize its productivity though the drilling cost of a mbhw is relatively high in comparison to vertical wells its high and stable productivity can compensate for the drilling cost therefore mbhws are thought to be more appropriate than vertical wells for the successful exploitation of the cbm resource potential in the liulin block and surrounding area

nonfractional crystallization of a terrestrial magma ocean it has been suggested that evolution of a terrestrial magma ocean does not unavoidably follow a fractional crystallization scenario convection is able to preclude differentiation until a sharp viscosity increase occurs near some critical crystal fraction however this kind of crystallization and its physical and chemical consequences have not been previously studied we consider an end member called here nonfractional crystallization we begin with a simple equilibrium thermodynamical model of partial melts which is based on an ideal three component phase diagram it allows a self consistent calculation of physical and chemical parameters in the melting range at all interesting pressures in particular adiabats of the convecting magma ocean are calculated the sharp increase in the viscosity is supposed to occur near the maximum packing crystal fraction however almost independently of this value convection occurs even in the highly viscous quasi solid part of the magma ocean and it is strong enough to prevent differentiation in deep regions a kind of compositional convection occurs due to the layered differentiation although it is weaker than the thermal convection only a surface region undergoes an essential differentiation via melt expulsion by compaction the thickness of this layer depends on the rheology of partial melts critical crystal fraction and crystal sizes but in any case the basal pressure hardly can exceed 5 10 gpa because of lower pressures in the moon the thickness of the differentiating layer is large and thus the entire lunar magma ocean could undergo a strong differentiation remelting due to the energy released by differentiation is crucial only for much deeper layers possibly deeper than about 1000 km for the earth for the remaining shallow layer p 5 10 gpa the predicted increase of the melt fraction is less than 40 at the surface and decreases to zero at the bottom of the differentiating layer thus the nonfractional crystallization is suggested to be a likely alternative to the fractional crystallization the crucial and still poorly understood factors are suspension in convective layers rheology of partial melts crystal size and surface conditions the most pronounced chemical consequence of the nonfractional crystallization is an almost completely preserved undifferentiated lower mantle and possibly a significant undifferentiated part of the upper mantle at all depths in the beginning of differentiation not only the first liquidus solid phase but also subsequent phases have been partially crystallized so when the differentiation begins it involves mixtures of phases it is important for the remaining layer where differentiation is unavoidable this layer does not have as strong differentiation of minor elements as in the case of fractional crystallization but it will still involve differentiation of major elements future geochemical calculations of this multiphase differentiation considering both major and minor elements could help to constrain the differentiation further

coupled flow and anisotropy in the ultralow velocity zones abstract seismic observations reveal a patchwork of thin and dense structures named ultralow velocity zones ulvzs atop the earth s core mantle boundary the high width to height ratio of the ulvzs their spatial correlation with the edges of large low shear velocity provinces llsvps and their preservation as distinct structures in the convecting mantle remain an enigmatic problem in this article we carry out a series of numerical simulations using fast multipole boundary elements method fmbem to address these questions and study the internal deformation within the ulvzs our results demonstrate that coupled flow between dense low viscosity ulvz patches and the llsvp accumulates the ulvz into stable piles along llsvp corners while coalescence and gravitational drainage leads to thin and wide ulvzs away from the corners deformation of the matrix is localized within the weaker ulvz and the llsvp edges while the strain in the interior of the llsvp remains uniform and low explaining the observed localized anisotropy near llsvp edges

accretion timescale and impact history of mars deduced from the isotopic systematics of martian meteorites abstract high precision sm nd isotopic analyses have been completed on a suite of 11 martian basaltic meteorites in order to better constrain the age of silicate differentiation on mars associated with the formation of their mantle sources these data are used to evaluate the merits and disadvantages of various mathematical approaches that have been employed in previous work on this topic ages determined from the sm nd isotopic systematics of individual samples are strongly dependent on the assumed nd isotopic composition of the bulk planet this assumption is problematic given differences observed between the nd isotopic composition of earth and chondritic meteorites and the fact that these materials are both commonly used to represent bulk planetary nd isotopic compositions ages determined from the slope of 146sm 142nd whole rock isochrons are not dependent on the assumed 142nd 144nd ratio of the planet but require the sample suite to be derived from complementary contemporaneously formed reservoirs in this work we present a mathematical expression that defines the age of formation of the source regions of such a suite of samples that is based solely on the slope of a 143nd 142nd whole rock isochron and is also independent of any a priori assumptions regarding the bulk isotopic composition of the planet this expression is also applicable to mineral isochrons and has been used to successfully calculate 143nd 142nd model crystallization ages of early refractory solids as well as lunar samples this permits ages to be obtained using only nd isotopic measurements without the need for 147sm 144nd isotope dilution determinations when used in conjunction with high precision nd isotopic measurements completed on martian meteorites this expression yields an age of formation of the martian basaltic meteorite source regions of 4504 6 ma because the sm nd model ages for the formation of martian source regions are commonly interpreted to record the age at which large scale mantle reservoirs formed during planetary differentiation associated with magma ocean solidification the age determined here implies that magma ocean solidification occurred several tens of millions of years after the beginning of the solar system recent thermal models however suggest that mars sized bodies cool rapidly in less than 5 ma after accretion ceases even in the presence of a thick atmosphere assuming these models are correct an extended period of accretion is necessary to provide a mechanism to keep portions of the martian mantle partially molten until 4504 ma late accretional heating of mars could either be associated with protracted accretion occurring at a quasi steady state or alternatively be associated with a late giant impact if this scenario is correct then accretion of mars sized bodies takes up to 60 ma and is likely to be contemporaneous with the core formation and possibly the onset of silicate differentiation this further challenges the concept that isotopic equilibrium is attained during primordial evolution of planets and may help to account for geochemical evidence implying addition of material into planetary interiors after core formation was completed

timescale of overturn in a magma ocean cumulate abstract the formation and differentiation of planetary bodies are thought to involve magma oceans stages we study the case of a planetary mantle crystallizing upwards from a global magma ocean in this scenario it is often considered that the magma ocean crystallizes more rapidly than the time required for convection to develop in the solid cumulate this assumption is appealing since the temperature and composition profiles resulting from the crystallization of the magma ocean can be used as an initial condition for convection in the solid part we test here this assumption with a linear stability analysis of the density profile in the solid cumulate as crystallization proceeds the interface between the magma ocean and the solid is a phase change interface convecting matter arriving near the interface can therefore cross this boundary via melting or freezing we use a semi permeable condition at the boundary between the magma ocean and the solid to account for that phenomenon the timescale with which convection develops in the solid is found to be several orders of magnitude smaller than the time needed to crystallize the magma ocean as soon as a few hundreds kilometers of cumulate are formed on a mars to earth size planet the phase change boundary condition is found to decrease this timescale by several orders of magnitude for a moon size object the possibility of melting and freezing at the top of the cumulate allows the overturn to happen before complete crystallization the convective patterns are also affected by melting and freezing at the boundary the linearly most unstable mode is a degree 1 translation mode instead of the approximately aspect ratio one convection rolls found with classical non penetrative boundary conditions the first overturn of the crystallizing cumulate on mars and the moon could therefore be at the origin of their observed degree 1 features

the deep earth may not be cooling down abstract the earth is a thermal engine generating the fundamental processes of geomagnetic field plate tectonics and volcanism large amounts of heat are permanently lost at the surface yielding the classic view of the deep earth continuously cooling down contrary to this conventional depiction we propose that the temperature profile in the deep earth has remained almost constant for the last 4 3 billion years the core mantle boundary cmb has reached a temperature of 4400 k in probably less than 1 million years after the moon forming impact regardless the initial core temperature this temperature corresponds to an abrupt increase in mantle viscosity atop the cmb when 60 of partial crystallization was achieved accompanied with a major decrease in heat flow at the cmb then the deep earth underwent a very slow cooling until it reached 4100 k today this temperature at or just below the mantle solidus is suggested by seismological evidence of ultra low velocity zones in the d layer such a steady thermal state of the cmb temperature excludes thermal buoyancy from being the predominant mechanism to power the geodynamo over geological time an alternative mechanism to sustain the geodynamo is mechanical forcing by tidal distortion and planetary precession motions in the outer core are generated by the conversion of gravitational and rotational energies of the earth moon sun system mechanical forcing remains efficient to drive the geodynamo even for a sub adiabatic temperature gradient in the outer core our thermal model of the deep earth is compatible with an average cmb heat flow of 3 0 to 4 7 tw furthermore the regime of core instabilities and or secular changes in the astronomical forces could have supplied the lowermost mantle with a heat source of variable intensity through geological time episodic release of large amounts of heat could have remelted the lowermost mantle thereby inducing the dramatic volcanic events that occurred during the earth s history in this scenario because the moon is a necessary ingredient to sustain the magnetic field the habitability on earth appears to require the existence of a large satellite

particle velocity and concentration profiles in bedload experiments on a steep slope depth profiles of particle streamwise velocity concentration and bedload sediment transport rate were measured in a turbulent and supercritical water flow one size 6 mm diameter spherical glass beads were transported at equilibrium in a two dimensional 10 steep channel with a mobile bed flows were filmed from the side by a high speed camera particle tracking algorithms made it possible to determine the position velocity and trajectory of a very large number of particles approximately half of the sediment transport rate was composed by rolling grains and the other half by saltation this revealed a complex structure with several concentration and flux peaks due to rolling and one peak due to saltation with an increase of the sediment transport rate the depth structure remained the same at the water granular interface with peak value increases but with no shift in elevations the saltation region expanded towards higher elevations with an increase of the particle velocity commensurate to the water velocity the proportion of the sediment transport rate in saltation did not vary significantly the particle streamwise velocity profiles exhibited three segments an exponential decay in the bed a linear increase where rolling and saltation co existed and above this a logarithmic like shape due to saltating particles these results are comparable to profiles measured and modelled in dry granular free surface flows and in more intense bedload such as sheet flows copyright 2014 john wiley sons ltd

early evolution of the earth accretion atmosphere formation and thermal history atmospheric and thermal evolution of the earth growing by planetesimal impacts was modeled by taking into account the blanketing effect of an impact induced h2o atmosphere and the temperature dependence of h2o degassing when the water content of planetesimals is larger than 0 1 by weight and the accretion time of the earth is less than 5 107 years the surface of the accreting earth melts and thus a magma ocean forms and covers the surface the formation of a magma ocean will result in the initiation of core mantle separation and mantle differentiation during accretion once a magma ocean is formed the surface temperature the degree of melting in the magma ocean and the mass of the h2o atmosphere are nearly constant as the protoplanet grows further the final mass of the h2o atmosphere is about 1021 kg a value which is insensitive to variations in the model parameter values such as the accretion time and the water content of planetesimals that the final mass of the h2o atmosphere is close to the mass of the present oceans suggests an impact origin for the earth s hydrosphere on the other hand most of the h2o retained in planetesimals will be deposited in the solid earth free water within the proto earth may affect differentiation of the proto mantle in particular the mantle feo abundance and the incorporation of a light element in the outer core

crustal evolution and the temporality of anorthosites abstract types of rock such as komatiite which formed entirely or dominantly during restricted time periods in solar system history are important indicators of how planetary bodies evolved in deep time in this paper we characterize three different types of temporally restricted anorthosites and discuss their significance to the broad scale evolution of planetary processes primordial anorthosites which constitute the bulk of the lunar crust were sampled during apollo and luna missions and have subsequently been identified in our meteorite collections they are characterized by very calcic plagioclase an93 98 and all have magmatic crystallization ages 4 3 ga suggesting that the earliest planetary crust forming processes on the moon and possibly elsewhere involved substantial if not total melting the magma ocean hypothesis which has endured for nearly 50 years argues that the lunar anorthositic rocks represent global flotation cumulates of plagioclase which crystallized after extensive precipitation and sinking of olivine and pyroxene another possibility revitalized by critical filtering of age data involves serial magmatism whereby the lunar crust was constructed by younger smaller episodic magmatic events on earth two distinct types of temporally restricted anorthosites offer opportunities to understand the evolution of terrestrial geodynamics tectonics and magmatic processes archean megacrystic anorthosites formed only between 3 73 and 2 49 ga as small bodies

the effects of kinetic sorting on sediment mobility on steep slopes in poorly mobile static armour sorting is usually considered the result of hiding exposure effects we called this effect static sorting in opposition to very efficient grain to grain mechanisms produced by a mobile mixture called kinetic sorting we hypothesized that kinetic sorting can be an important contributor to the morphodynamics of mountain streams and attempted to demonstrate this with new flume experiments two long runs were produced with natural poorly sorted sediments and with transport stages of the coarse fraction defined by the ratio between the shear stress and the critical shear stress for transport smaller and higher than 1 respectively both runs produced an efficient transfer downstream of the injected material but with a major difference the first run no kinetic sorting produced permanent armour figuring clusters akin to what has already been observed in similar experiments the second run with kinetic sorting also produced bed armouring but this armour was periodically totally destroyed leading to substantial bed erosion this phenomenon was explained by kinetic sorting the effects of which are to produce an efficient downward migration of fine materials and bed surface armouring the consequence is that fine materials are hidden to the flow during aggradation allowing the slope to attain values much steeper than would have been expected at equilibrium for the mixture however whereas the surface armouring tends to stabilize the bed construction of a layer of fine sediments at the subsurface also contributes to making it very unstable these two contradictory effects explain the complex bed behaviours and the existence of very large bedload and slope fluctuations copyright 2014 john wiley sons ltd

a low viscosity lunar magma ocean forms a stratified anorthitic flotation crust with mafic poor and rich units much of the lunar crust is monomineralic comprising 98 plagioclase the prevailing model argues the crust accumulated as plagioclase floated to the surface of a solidifying lunar magma ocean lmo whether 98 pure anorthosites can form in a flotation scenario is debated an important determinant of the efficiency of plagioclase fractionation is the viscosity of the lmo liquid which was unconstrained here we present results from new experiments conducted on a late lmo relevant ferrobasaltic melt the liquid has an exceptionally low viscosity of 0 22 0 19 0 11 to 1 45 0 82 0 46 pa s at experimental conditions 1 300 1 600 c 0 1 4 4 gpa and can be modeled by an arrhenius relation extrapolating to lmo relevant temperatures our analysis suggests a low viscosity lmo would form a stratified flotation crust with the oldest units containing a mafic component and with very pure younger units old impure crust may have been buried by lower crustal diapirs of pure anorthosite in a serial magmatism scenario

martian mantle mineralogy investigated by the 176lu 176hf and 147sm 143nd systematics of shergottites abstract chemical heterogeneities in the martian mantle are believed to result from the crystallization of a magma ocean in the first 100 million years of its history shergottite meteorites from mars are thought to retain a compositional record of such early differentiation and the resulting mineralogy at different depths the coupled 176 lu 176 hf and 147 sm 143 nd isotope systematics in 9 shergottites are used here to investigate these issues three compositional groups in the shergottites display distinct isotope systematics one group commonly termed as depleted is characterized by positive 176 hf i from 46 2 to 50 4 and 143 nd i from 36 2 to 39 1 another termed as enriched has negative 176 hf i 16 5 to 13 2 and 143 nd i 7 0 to 6 5 the third group is intermediate between the depleted and enriched groups with positive 176 hf i 30 0 to 33 4 and 143 nd i 16 9 together they describe mixing curves between 176 hf 177 hf 143 nd 144 nd lu hf and sm nd implying that they sample two distinct sources in the martian mantle all shergottites are characterized by sm nd source sample but lu hf source lu hf sample this decoupling can be explained by two successive partial melting episodes in the depleted shergottite source and localized in the martian upper mantle the genesis of shergottites can be modeled using non modal equilibrium partial melting in a source initially composed of 60 olivine 21 clinopyroxene 9 orthopyroxene and 10 garnet with degrees of partial melting of 8 8 and 3 9 respectively for the two successive events the enriched end member of the shergottite mixing curve is best modeled by late stage quenched residual melt resulting from the crystallization of a magma ocean the depleted shergottite source may be modeled as a mixture of cumulates and residual melt as convection in the martian magma ocean is expected to reduce the incompatible trace element heterogeneity in the final solidified layers consequently equilibrium crystallization is preferred to model the crystallization of the martian magma ocean the models that best explain the shergottite data are those where the magma ocean is at a depth of at least 1350 km in mars

bedload transport measurements at the erlenbach stream with geophones and automated basket samplers in the erlenbach stream a pre alpine steep channel in switzerland sediment transport has been monitored for more than 25 years near the confluence with the main valley river stream flow is monitored and sediment is collected in a retention basin with a capacity of about 2000 m3 the basin is surveyed at regular intervals and after large flood events in addition sediment transport has been continuously monitored with piezoelectric bedload impact and geophone sensors since 1986 in 2008 2009 the measuring system in the erlenbach stream was enhanced by installing an automatic system to obtain bedload samples movable metal baskets are mounted on a rail at the downstream wall of the large check dam above the retention basin and they can be moved automatically into the flow to take bedload transport samples the wire mesh of the baskets has a spacing of 10 mm to sample all sediment particles coarser than this size which is about the limiting grain size detected by the geophones the upgraded measuring system permits to obtain bedload samples over short sampling periods and to measure the grain size distribution of the transported material and its variation over time and with discharge the analysis of calibration relationships for the geophone measuring system confirms findings from very similar measurements which were performed until 1999 with piezoelectric bedload impact sensors there is a linear relationship between impulse counts and bedload mass passing over the sensors findings from flume experiments are used to discuss the most important factors which affect the calibration of the geophone signal the bedload transport rates as measured by the moving baskets are among the highest measured in natural streams with values of the order of several kilograms per meter per second copyright 2012 john wiley sons ltd

first principles computation of mantle materials in crystalline and amorphous phases abstract first principles methods based on density functional theory are used extensively in the investigation of the behavior and properties of mantle materials over broad ranges of pressure temperature and composition that are relevant a review of computational results reported during the last couple of decades shows that essentially all properties including structure phase transition equation of state thermodynamics elasticity alloying conductivity defects interfaces diffusivity viscosity and melting have been calculated from first principles using mgo the second most abundant oxide of earth s mantle as a primary example and considering many other mantle materials in their crystalline and amorphous phases we have found that most properties are strongly pressure dependent sometimes varying non monotonically and anomalously with the effects of temperature being systematically suppressed with compression the overall agreement with the available experimental data is excellent it is remarkable that the early calculated results such as shear wave velocities of two key phases mgo and mgsio 3 perovskite were subsequently reproduced by experimentation covering almost the entire mantle pressure regime as covered in some detail the defect formation and migration enthalpies of key mantle materials increase with pressure the predicted trend is that partial mgo schottky defects are energetically most favorable in mg silicates but their formation enthalpies are high so the diffusion in the mantle is likely to be in the extrinsic regime preliminary results on mgo and forsterite hint that the grain boundaries can accommodate point defects including impurities and enhance diffusion rates at all pressures the structures are highly distorted in the close vicinity of the defects and at the interface with excess space recent simulations of mgo sio 2 binary and other silicate melts have found that the melt self diffusion and viscosity vary by several orders of magnitudes with pressure temperature and composition the predicted high compressibility and complex dynamical behavior can be associated with structural changes involving non bridging oxygen oxygen tri clusters si o pentahedra etc occurring on compression we envision future prospect for massively parallel distributed computing of unprecedented magnitude and scope in the study of relevant materials for earth super earth and other planets a renewed computational theme perhaps should be the first principles simulations of large systems with long runs that are necessary to explore realistic natural compositions polycrystalline phases multi component melts crystal melt interfaces trace element partitioning etc

thermal and chemical evolution of the terrestrial magma ocean abstract the earth is likely to have experienced a magma ocean stage during accretion thermal and chemical evolution of magma ocean is investigated based on a one dimensional two phase flow heat and mass transfer model differentiation at lower mantle pressure depends on the type of magma ocean and surrounding atmosphere if the magma ocean is formed by the blanketing effect of a solar type proto atmosphere extensive differentiation proceeds at lower mantle pressure if the magma ocean is formed by the blanketing effect of an impact induced steam atmosphere no differentiation at lower mantle pressure is likely if a very deep magma ocean is formed by a giant impact whether differentiation proceeds at lower mantle pressure or not depends on grain size viscosity of melt and or properties of a transient atmosphere on the contrary chemical differentiation likely proceeds at upper mantle pressure irrespective of magma ocean type a shallow magma ocean can remain for 100 200 my without any heating processes

the fate of water within earth and super earths and implications for plate tectonics the earth is likely to have acquired most of its water during accretion internal heat of planetesimals by short lived radioisotopes would have caused some water loss but impacts into planetesimals were insufficiently energetic to produce further drying water is thought to be critical for the development of plate tectonics because it lowers viscosities in the asthenosphere enabling subduction the following issue persists if water is necessary for plate tectonics but subduction itself hydrates the upper mantle how is the upper mantle initially hydrated the giant impacts of late accretion created magma lakes and oceans which degassed during solidification to produce a heavy atmosphere however some water would have remained in the mantle trapped within crystallographic defects in nominally anhydrous minerals in this paper we present models demonstrating that processes associated with magma ocean solidification and overturn may segregate sufficient quantities of water within the upper mantle to induce partial melting and produce a damp asthenosphere thereby facilitating plate tectonics and in turn the habitability of earth like extrasolar planets this article is part of the themed issue the origin history and role of water in the evolution of the inner solar system

impact induced dehydration of serpentine and the evolution of planetary atmospheres shock recovery experiments in the 25 to 45 gpa range on antigorite serpentine determine the amount of shock induced loss of structural water as a function of shock pressure infrared absorption spectra of shock recovered samples demonstrate systematic changes in the amount of structural water and molecular surface adsorbed water these yield qualitative estimates of shock induced water loss and demonstrate that a portion of the shock released structural water is readsorbed on interfacial grain surfaces determination of the post shock water content of the shocked samples relates shock induced water loss and shock pressure based on the present results and theoretical predictions we conclude that shock pressures of from 20 to 60 gpa induce incipient to complete water loss respectively this result agrees closely with theoretical estimates for total dehydration the dehydration interval and the activation energies for dehydration in shocked samples decrease systematically with increasing shock pressure as experienced by the sample we believe the present experiments are applicable to describing dehydration processes of serpentine like minerals in the accretional environment of the terrestrial planets we conclude that complete loss of structural water in serpentine could have occurred from accretional impacts of 3 km sec when earth and venus have grown to about 50 of their final size accreting planetesimals impacting mars never reached velocities sufficient for complete dehydration of serpentine our results support a model in which an impact generated atmosphere hydrosphere forms while the earth is accreting

magma oceans in the inner solar system theory and observations point to the occurrence of magma ponds or oceans in the early evolution of terrestrial planets and in many early accreting planetesimals the apparent ubiquity of melting during giant accretionary impacts suggests that silicate and metallic material may be processed through multiple magma oceans before reaching solidity in a planet the processes of magma ocean formation and solidification therefore strongly influence the earliest compositional differentiation and volatile content of the terrestrial planets and they form the starting point for cooling to clement habitable conditions and for the onset of thermally driven mantle convection and plate tectonics this review focuses on evidence for magma oceans on planetesimals and planets and on research concerning the processes of compositional differentiation in the silicate magma ocean distribution and degassing of volatiles and cooling

bedload transport measurements with impact plate geophones comparison of sensor calibration in different gravel bed streams indirect bedload transport measurements have been made with the swiss plate geophone system in five gravel bed mountain streams these geophone sensors record the motion of bedload particles transported over a steel plate mounted flush with the channel bed to calibrate the geophone system direct bedload transport measurements were undertaken simultaneously at the erlenbach in switzerland a moving basket sampler was used at the fischbach and ruetz streams in austria a helley smith type bedload sampler provided the calibration measurements a bunte type bedload trap was used at the rofenache stream in austria at the nahal eshtemoa in israel reid type slot bedload samplers were used to characterize the response of the geophone signal to bedload particles impacting on the plate geophone summary values were calculated from the raw signal and stored at one second intervals the number of impulses i e the number of peaks above a pre defined threshold value of the geophone output signal correlated well with field measured gravel transport loads and was found to be a robust parameter the relations of impulses to gravel transport loads were generally near linear but the steepness of the calibration relations differed from site to site by comparing the calibration measurements from the different field sites and utilizing insights gained during preliminary flume experiments it has been possible to identify the main factors that are responsible for site specific differences in the calibration coefficient the analysis of these calibration measurements indicates that the geophone signal also contains some information about the grain size distribution of bedload copyright 2013 john wiley sons ltd

chaotic flow patterns from a deep plutonic environment a case study on natural magma mixing this work focuses on the mixing between basalt and granite in a deep plutonic environment the description of mixing patterns and measurements of fractal dimensions and the evaluation of geochemical data from a cambro ordovician granitic pluton are summarized and discussed different morphologic domains within the pluton reveal concentric fragmented and or folded layers of granite in a gabbro granite mixed matrix this stands in contrast to two predominantly regular gabbroic regions these regular regions are separated by tightly stretched filament areas in which mixing is enhanced sharp and gradational contacts between granitic and gabbroic domains depict the interplay among frozen flows mingling and convection enhanced diffusion processes mixing measurements of fractal dimensions at different scales and analysis of normalized concentration variance for major elements point towards magma mixing the compositional variability and flow patterns of the studied pluton have been greatly controlled by a natural chaotic mixing process between a granitic and a basaltic end member during the mixing process coeval fractional crystallization no doubt contributed to increasing the complexity of the system however since flow and therefore mixing stops with temperature decrease flow patterns must have retained the predominant morphology and composition of the moment at which both contrasting magmas came together and froze flow patterns have been preserved with further temperature decrease fractional crystallization took over and hybrid rocks were generated from the fractionation of magmas previously mixed in different proportions

the tethered moon abstract we address the thermal history of the earth after the moon forming impact taking tidal heating and thermal blanketing by the atmosphere into account the atmosphere sets an upper bound of 100 w m2 on how quickly the earth can cool the liquid magma ocean cools over 2 10 myr with longer times corresponding to high angular momentum events tidal heating is focused mostly in mantle materials that are just beginning to freeze the atmosphere s control over cooling sets up a negative feedback between viscosity dependent tidal heating and temperature dependent viscosity of the magma ocean while the feedback holds evolution of the moon s orbit is limited by the modest radiative cooling rate of earth s atmosphere orbital evolution is orders of magnitude slower than in conventional constant q models which promotes capture by resonances the evection resonance is encountered early when the earth is molten capture by the evection resonance appears certain but unlikely to generate much eccentricity because it is encountered early when the earth is molten and q q tidal dissipation in the earth becomes more efficient q q later when the moon is between 20 r and 40 r if lunar eccentricity grew great this was when it did so perhaps setting the table for some other process to leave its mark on the inclination of the moon

on the cooling of a deep terrestrial magma ocean several episodes of complete melting have probably occurred during the first stages of the earth s evolution we have developed a numerical model to monitor the thermal and melt fraction evolutions of a cooling and crystallizing magma ocean from an initially fully molten mantle for this purpose we numerically solve the heat equation in 1d spherical geometry accounting for turbulent heat transfer and integrating recent and strong experimental constraints from mineral physics we have explored different initial magma ocean viscosities compositions thermal boundary layer thicknesses and initial core temperatures we show that the cooling of a thick terrestrial magma ocean is a fast process with the entire mantle becoming significantly more viscous within 20 kyr due to the slope difference between the adiabats and the melting curves the solidification of the molten mantle occurs from the bottom up in the meantime a crust forms due to the high surface radiative heat flow the last drop of fully molten silicate is restricted to the upper mantle among the studied parameters the magma ocean lifetime is primarily governed by its viscosity depending on the thermal boundary layer thickness at the core mantle boundary the thermal coupling between the core and magma ocean can either insulate the core during the magma ocean solidification and favor a hot core or drain the heat out of the core simultaneously with the cooling of the magma ocean reasonable thickness for the thermal boundary layer however suggests rapid core cooling until the core mantle boundary temperature results in a sluggish lowermost mantle once the crystallization of the lowermost mantle becomes significant the efficiency of the core heat loss decreases since a hotter liquidus favors crystallization at hotter temperatures a hotter deep mantle liquidus favors heat retention within the core in the context of an initially fully molten mantle it is difficult to envision the formation of a basal magma ocean or to prevent a major heat depletion of the core as a consequence an earth s geodynamo sustained only by core cooling during 4 gyr seems unlikely and other sources of motion need to be invoked

a top down origin for martian mantle plumes the two main volcanic centers on mars tharsis and elysium are often interpreted in terms of mantle plume hotspots even though there are several problems with the plume hypothesis for mars we present results of 2d cylindrical shell numerical mantle convection experiments in which we try to ascertain whether flushing of the hot lower mantle could provide a mechanism for the generation of a small number of plume like features i e localized upwelling of hot material in this scenario the formation of hot upwellings is driven from the top by cold downwellings rather than from a hot thermal boundary layer at the cmb first we construct a range of mars interior structure models consistent with observations in order to demonstrate that the presence of a thin lower mantle in the martian interior is a viable scenario then we use a series of numerical convection experiments to investigate the effects of solid state phase transitions different stratified and temperature dependent viscosity models and the presence of a thick southern hemisphere crust on the operation of such a mechanism our results show that it is possible to generate hot strong localized upwellings from top down dynamics if the lithosphere is thin or actively involved in the convective pattern the presence of a thick immobile insulating southern hemisphere crust reduces the number of upwellings and the perovskite phase transition causes a focusing of the upwellings further experiments demonstrate that an initial 500 myr phase of mobile lid is sufficient to start this process create an upwelling which is stable for billions of years

suspension in convective layers and style of differentiation of a terrestrial magma ocean recent physical theories for the formation of the earth suggest that about 4 5 b y ago the mantle of the earth was partially or completely molten fractional crystallization of this hypothetical magma ocean would result in a strong chemical stratification of the earth s mantle such a scenario is controversial from the geochemical point of view however it has been noted that the simple scenario of fractional crystallization could be avoidable in a convective magma ocean if crystals remain suspended in this paper the problem of suspension is developed with the help of an energetic approach convection must do some work against gravitational settling we distinguish three regimes of convective suspensions absolute or complete sedimentation occurs when the energy dissipation due to the settling exceeds the heat loss from the convective layer this is possible only in large scale systems like magma oceans and implies that cooling can proceed only together with sedimentation crystallization and a decrease in the liquidus temperature at a constant pressure a regime of partial differentiation occurs when the energy dissipation due to the settling is less than the total heat loss but larger than the power which can be spent by convection on the crystal reentrainment process the differentiation is not complete and a competition between the rate of cooling the rate of sedimentation and the rate of turbulent diffusion determines the degree of differentiation the third regime is an absolute suspension which could be sustained for an indefinitely long time in this case sedimentation starts only when the crystal fraction reaches the maximum packing value when the viscosity of the magma rapidly increases the power which can be spent by convection on reentrainment is equal to e gd cp of the total energy supply to the convective layer where e 15 gpa or 10 3 10 1 cm during crystallization of shallow layers the first regime fractional crystallization is unavoidable the estimates depend on various poorly constrained parameters and processes such as heat flux viscosity thermodynamical disequilibrium and highly variable viscosity convection for absolute suspension the crystal size must be at least e times less or 10 3 10 1 cm and 10 4 10 2 cm respectively if e 0 01 the partial differentiation occurs in a narrow one decade range between these two regimes the radius of about 1 cm must be considered as an absolute upper bound above which fractional differentiation is guaranteed these estimates for the critical crystal size are orders of magnitude lower than suggested previously and thus the problem of crystal sizes becomes a central one for magma oceans a necessary condition for reentrainment is the existence of local mechanisms the absence of such mechanisms to reentrain the particles from the bottom would mean that an absolute suspension is impossible even if the energetics allows it turbulence is considered as a possible important factor a simple model of convection predicts a strong turbulence provided the viscosity is less than 10 9 10 10 p rotation reduces this critical viscosity to 10 5 10 8 p but this is still sufficiently large and is reached only near the maximum packing crystal fraction power law or bingham rheology of partial melts can exclude any turbulence already at 20 30 of crystal fraction we also show that the energetic criterion for the absolute suspension with e 1 coincides with the condition that the particle concentration gradient suppresses the turbulence

shock induced volatile loss from a carbonaceous chondrite implications for planetary accretion solid recovery impact induced volatile loss experiments on the murchison c2m meteorite indicate that for an impact of a given velocity h 2o and total volatiles are driven from the sample in the same proportion as present initially we infer that the volatiles other than h 2o driven from the meteorite also have the same bulk composition as those of the starting material thus the early bulk composition of an impact induced atmosphere of a planet growing by accretion from material like murchison would be the same as the volatile composition of the incident planetesimals incipient devolatilization of murchison occurs at an initial shock pressure of about 11 gpa and complete devolatilization occurs at a pressure of about 30 gpa if an earth sized planet were formed from the infall of planetesimals of murchison composition incipient and complete devolatilization of accreting planetesimals would occur when the planet reached approximately 12 and 27 respectively of its final radius thus impact induced devolatilization of accreting planetesimals and of the hydrated surface would profoundly affect the distribution of volatiles within the accreting planet for example for a cold homogeneous accretion of a planet prior to metallic core formation and internal differentiation the growing planet would have a very small core with the same volatile content as the incident material a volatile depleted mantle and an extremely volatile rich surface

phase relations and melt compositions in cmas pyrolite h2o system up to 25 gpa abstract phase relations and melt compositions in the cao mgo al 2 o 3 sio 2 pyrolite under hydrous 2 of h 2 o and anhydrous conditions have been determined at 10 25 gpa and temperatures from 1400 to 2400 c at the pressure of 16 and 25 gpa the apparent solidus temperatures for the hydrous system are about 200 and 100 c lower than the solidus temperatures for the dry system respectively the apparent solidus temperature changes drastically from 1600 c at 13 5 gpa to about 1850 c at 16 gpa majorite is a liquidus phase in the hydrous pyrolite from 10 to 25 gpa the liquidus phases in the dry pyrolite are olivine at 10 14 gpa majorite at 14 20 gpa and periclase at pressures above 20 gpa we observed expansion of the stability field of anhydrous phase b and its complex relations with the other phases in the cmas pyrolite system we suppose it is formed not only by incongruent melting of wadsleyite but also by the subsolidus reaction of wadsleyite and majorite in the dry condition compositions of partial melts formed by low degree of melting 10 20 have al 2 o 3 depleted and cao rich compositions up to 22 gpa and enriched in al 2 o 3 5 7 wt and cao at 25 gpa at 10 gpa dry and hydrous melts formed by low degree of melting have high sio 2 48 51 wt and relatively high al 2 o 3 3 5 5 2 wt their compositions are generally consistent with those of aluminum depleted komatiite at 13 22 gpa dry and hydrous melts have low sio 2 44 49 wt and al 2 o 3 1 7 3 0 wt and high cao contents 9 15 wt an essential depression of the apparent solidus temperature in the hydrous deep upper mantle compared to that in the transition zone provides the dehydration melting of the hydrous plume the present results support a model of komatiite genesis by dehydration melting of rising wet plumes at the base of the upper mantle

transport properties of mg2sio4 liquid at high pressure physical state of a magma ocean abstract we use a flexible potential model to perform large scale molecular dynamics simulations on self diffusivity and viscosity of mg 2 sio 4 melt up to pressures of 32 gpa and over a temperature range of 2600 to 3200 k we find that self diffusivity decreases and viscosity increases uniformly with pressure the latter from values of 10 2 pa s at 0 gpa to 10 1 pa s at 32 gpa 2600 k both transport properties can be readily fit with a closed arrhenius expression over the whole pressure and temperature range considered independent estimates of self diffusivities and viscosity allow us to examine their relation through the stokes einstein and the eyring equations while at low pressures the sio 4 tetrahedron seems to be the viscous flow unit bare ion diffusion becomes more dominant at high pressure combining previous simulation results on thermodynamic properties with the current viscosity simulations we compute a magma ocean adiabat and the associated viscosity profile we find that viscosity in the magma ocean is 2 10 2 pa s near the surface and that it increases by less than 0 5 log unit up to 35 gpa combining scenarios for magma ocean dimensions in the young earth with thermodynamic properties and viscosity of mg 2 sio 4 melt we compute a magma ocean rayleigh number ra in the range of 10 28 and 10 29 putting the magma ocean in the dynamic regime of hard turbulence using scaling relations for the nusselt number nu at very high ra we estimate the heat flux of the magma ocean to be in the range of 10 18 to 10 19 w

the lunar magma ocean reconciling the solidification process with lunar petrology and geochronology abstract the moon is thought to have originated with a magma ocean that produced a plagioclase flotation crust as solidification proceeded ages of anorthositic crust range over at least 200 million years the model for solidification presented here integrates chemical and physical constraints of lunar magma ocean solidification to determine 1 the final thickness of flotation crust generated by a fractionally solidifying magma ocean 2 the timescale of crystallization before plagioclase is a stable phase 3 the timescale of solidification after the formation of the plagioclase flotation crust and 4 the post overturn lunar mantle composition and structure we find that magma oceans of as much as 1000 km depth are consistent with creating an anorthositic crust 40 to 50 km in thickness solidification of the magma ocean prior to formation of the flotation crust may occur on the order of 1000 years and complete solidification would require additional ten to tens of millions of years reconciling these short model timescales with radiometric dates of crustal samples requires either a very late forming moon combined with finding older crustal ages to be incorrect or calling on tidal heating of the crust by the early earth to prolong solidification gravitationally driven overturn of cumulates during tidal heating provides a mechanism for creating the compositions and ages of the lunar mg suite of crustal rocks further we find that upon crystallization the moon likely began with an azimuthally heterogeneous gravitationally stable mantle after magma ocean cumulate overturn this result may help explain the experimentally determined origin of picritic glasses at similar depths but from different source materials

a re evaluation of metal diapir breakup and equilibration in terrestrial magma oceans abstract due to mechanisms such as impact heating early atmospheric thermal blanketing and radioactive heating the presence of at least one global magma ocean stage in the early histories of terrestrial planets seems unavoidable in such a context a key question to constrain the early thermo chemical evolution of the earth is how much iron diapirs provided by differentiated impactors emulsified during their sinking towards the bottom of an early magma ocean in the past years several workers have focused on this question using however various approaches and making different assumptions while most studies favor rapid breakup and equilibration of iron bodies during their sinking through the magma ocean recent work suggests that iron bodies of size comparable or greater than a few tens of kilometers may preserve most of their initial volume as they reach the bottom of a magma ocean therefore leading to metal silicate disequilibrium to clarify the discrepancies and the differences among studies i have conducted a series of numerical simulations and theoretical calculations to derive the conditions and the timing for the breakup of metal diapirs of any size sinking through a silicate magma ocean with a large range of plausible viscosity values the obtained breakup criterion is used to derive stable diapir sizes and their ability to equilibrate with the surrounding silicates i show that for plausible magma ocean viscosities diapirs with initial radii smaller than the thickness of a magma ocean rapidly break up into stable diapir sizes smaller than 0 2 m at which metal silicate equilibration is rapidly achieved

the equation of state of a molten komatiite 2 application to komatiite petrogenesis and the hadean mantle new experimental data for the equation of state of a komatiitic liquid were used to model adiabatic melting in a peridotitic mantle if komatiites are formed by 30 partial melting of a peridotitic mantle then komatiites generated by adiabatic melting come from source regions that began their unmelted ascent in the lower transition zone 500 670 km or the lower mantle 670 km the great depth of incipient melting implied by this model suggests that komatiitic liquids may form in a pressure regime where they are denser than their coexisting crystals possibly the bulk mantle although komatiitic magmas are thought to separate from residual crystals in the mantle at a temperature 200 c greater than modem mid ocean ridge basalts morbs their ultimate sources are predicted to be diapirs that if adiabatically decompressed from initially solid mantle were more than 700 c hotter than the sources of morbs and were derived from great depth we also studied the evolution of an initially molten mantle i e a magma ocean our model considers the thermal structure of the magma ocean density constraints on crystal segregation and approximate phase relationships for a nominally chondritic mantle crystallization will begin at the core mantle boundary perovskite buoyancy at 70 gpa may lead to a compositionally stratified lower mantle with iron enriched magnesiowustite content increasing with depth large convective velocities in the magma ocean would prohibit crystal liquid fractionation by settling or flotation until quiescent boundary layers form such boundary layers could form when the crystal content of the magma reaches a critical value near 44 vol and in the late stages of crystallization around unmelted blocks of foundered protocrust matrix compaction and diapirism could also lead to fractionation effects the upper mantle could be depleted or enriched in perovskite components relative to the bulk mantle olivine neutral buoyancy may lead to the formation of a dunite septum in the upper mantle partitioning the ocean into upper and lower reservoirs but this septum must be permeable

natural fracture cleat and strong adsorption impact on low oil and condensate retention in the carboniferous shales and coals of the western black sea basin of turkey total organic carbon toc values of the carboniferous shales and coals of the western black sea basin of turkey range from 0 72 to 71 52 wt with an average of 32 3 wt and generation potential chance from 0 33 to 184 64 with an average of 82 47 mg hc g rock hydrogen index hi values of the shales and coals range from 24 to 384 mg hc g toc the hi versus pyrolysis temperature at the maximum rate of kerogen conversion plot indicates that the organic matter is type ii iii the calculated vitrinite reflectance equivalent values of the shales and coals range from 0 63 to 1 32 thus the shales and coals of the carboniferous formations are represented by immature effective oil and condensate generation windows the shales and coals of the alacaagzi formation contain high quartz and lower clay oil saturation index osi values of the shales and coals have been calculated as being 0 7 and 12 mg hc g toc indicating possible lack of producible oil and condensate the osi values are lower than those of other coal bearing and marine shales of the world first strong adsorption capacity may be a cause of the lower oil and condensate retention second faults natural fractures and cleats related fluid flows may be important factors in these lower osi ratios the extensional collisional and inverse tectonic stages and diagenetic processes of coalification formed multiple interconnected faults natural opening mode fractures and cleats in the shales and coals thus 15 coalbed methane exploration wells failed to produce any economical coalbed methane

bedload hysteresis in a glacier fed mountain river sediment transport during flood events often reveals hysteretic patterns because flow discharge can peak before counterclockwise hysteresis or after clockwise hysteresis the peak of bedload hysteresis in sediment transport has been used in the literature to infer the degree of sediment availability counterclockwise and clockwise hysteresis have been in fact interpreted as limited and unlimited sediment supply conditions respectively hysteresis has been mainly explored for the case of suspended sediment transport but it was rarely reported for bedload transport in mountain streams this work focuses on the temporal variability of bedload transport in an alpine catchment saldur basin 18 6 km2 italian alps where bedload transport was monitored by means of an acoustic pipe sensor which detects the acoustic vibrations induced by particles hitting a 0 5m long steel pipe runoff dynamics are dominated by snowmelt in late spring early summer mostly by glacier melt in late summer early autumn and by a combination of the snow and glacier melt in mid summer the results indicate that hysteretic patterns during daily discharge fluctuations are predominantly clockwise during the snowmelt period likely due to the ready availability of unpacked sediments within the channel or through bank erosion in the lower part of the basin on the contrary counterclockwise hysteresis tend to be more frequent during late glacier melting period possibly due to the time lag needed for sediment provided by the glacial and peri glacial area to be transported to the monitoring section however intense rainfall events occurring during the glacier melt period generated predominantly clockwise hysteresis thus indicating the activation of different sediment sources these results indicate that runoff generation processes play a crucial role on sediment supply and temporal availability in mountain streams

the space and time complexity of chaotic mixing of silicate melts implications for igneous petrology abstract we present new experimental results on the study of the space and time modulation of compositional fields during chaotic mixing between mafic and felsic silicate melts the experimental strategy was planned using numerical simulations performed using the experimental geometry these mixing experiments were performed using a recently developed experimental apparatus which is capable of mixing high viscosity silicate melts at high temperatures and under precisely controlled conditions of fluid dynamics and strain the compositional variability produced by the mixing process was investigated both along linear analytical transects and on high resolution 2d x ray maps covering the mixing patterns our results indicate that chaotic flow fields represent very powerful dynamics to blend silicate melts even under laminar fluid dynamic conditions reynolds number ca 10 7 and for dissimilar melts with high viscosity ratios on the order of 103 the repetition of stretching and folding processes between the two melts induced a strong increase of contact interfaces thus favoring efficient chemical exchanges as a result the initial mafic composition is no longer detectable in the mixing system after ca 2 h i e the duration of the experiment a further important result is the observation of highly non linear patterns in inter elemental plots produced by the onset of diffusive fractionation processes this is contrary to common thinking that magma mixing should always produce linear trends between pairs of chemical elements a new measure the concentration variance is proposed to quantify chemical element mobility during the mixing process this measure is statistically robust and can be quantitatively used to measure chemical element mobility independently of the geometry in which the compositional variation i e transects areas etc is embedded or the local strain history of the mingling our results highlight concentration variance as a robust probe of the as yet poorly understood processes involved in the common petrological process of magma mixing

early martian mantle overturn inferred from isotopic composition of nakhlite meteorites following the crystallization of a magma ocean the martian mantle probably underwent an overturning event but its initiation timing and geochemical consequences are poorly constrained isotopic data for martian meteorites and numerical simulations provide strong evidence for early overturning in the martian mantle