mass transfer and problems of secondary porosity creation in deeply buried hydrocarbon reservoirs abstract secondary porosity created by the post depositional leaching of detrital grains and cements can be of great economic importance the term secondary porosity is only descriptive and does not give any information on whether the porosity of the rock has been enhanced in reality there are two end member volumetric outcomes to the leaching process firstly the mineral can be completely dissolved and its components transported out of the system in such an instance the porosity of the rock will be enhanced secondly it is possible that a mineral will decompose and by product minerals will be precipitated which will occupy approximately the same volume as the original mineral the latter case is more likely where the pore waters are close to equilibrium with the majority of the minerals of the rock this will occur at elevated temperatures and or where the pore waters have been in contact with the rock for a long time these conditions are commonly met during intermediate to deep burial many metastable minerals such as high temperature feldspars probably decompose in this way a consequence of the decomposition of such metastable minerals is that primary porosity will be swapped for secondary and that older and more deeply buried rocks will contain a higher proportion of secondary porosity the mass transport equation may be used to examine the physico chemical environment where enhanced porosities most likely occur during leaching by using a simple non equilibrium mass transport model based on the silica system it is possible to demonstrate the relative importance of flow rate reaction rates specific surfaces and temperature in controlling the areal extent of leaching wide leaching zones are related to high flow rates which in turn promote a high throughput of undersaturated fluid and dispersion leaching over a wide area is also favoured by low reaction rates which will occur at low temperatures although it is true to say that less of a given silicate mineral can be dissolved by an undersaturated pore water at low temperature than at high temperature it is probable that pore fluids from deeply buried sediments are more likely to be close to equilibrium with a given mineral than for instance meteoric water thus the most likely environment for the production of widespread enhanced porosity is in the shallow subsurface the lower flow rates and higher temperatures that are encountered during deep burial diagenesis will result in far narrower more intense leaching zones as a result providing sufficient reactive mineral is present any undersaturated pore water will approach equilibrium in a short distance in order to transport undersaturated pore waters appreciable distances in the deep subsurface it is necessary to minimize their interaction with the host rock this could occur if the pore fluid were to move through a fracture system where it would interact with a far smaller surface area of reactive mineral than if it moved through the pore network

interpretation of ph and eh trends in a fluvial sand aquifer system ground waters and aquifer materials from a shallow fluvial sand aquifer system 1 km long flow path were sampled and analyzed to determine the hydrogeochemical processes affecting ph and eh measured pt electrode potential the aquifer system is a fine grained sand k 10 3 cm s composed principally of quartz and plagioclase 70 of all grains with minor biotite partially altered to vermicuiite and trace amounts of calcite acid neutralization capacity measurements and x ray diffractograms suggest that acid precipitation recharging the aquifer undergoes a two step neutralization process the first step involves reactions with the surfaces of mineral grains mainly with plagioclase and biotite and the second step involves an irreversible neutralization involving biotite alteration to vermiculite and carbonate mineral dissolution during migration through deep confined parts of the aquifer ground waters attain equilibrium with calcite a thermodynamically based redox model of a closed oxidant system satisfactorily accounts for the sequential reduction of dissolved oxygen ferric oxides and sulfate in the aquifer by the oxidation of dissolved organic carbon and for oxygen only ferrous iron because of the problems of using pt electrodes in ground waters it is recommended that eh measurements be supplemented with dissolved oxygen and sulfide measurements

elasticity of mgsio3 in the ilmenite phase abstract the single crystal elastic moduli of the ilmenite phase of mgsio 3 have been determined from brillouin spectroscopy they are c 11 472 c 12 168 c 33 382 c 13 70 c 44 106 c 14 27 c 66 152 and c 25 24 in gpa these elastic properties are consistent with a structural mechanical model where the silicon octahedra are very stiff under compression and shear this latter property yields an unexpectedly high shear modulus for the magnesium silicate ilmenite as compared with analogue compounds the further transformation to perovskite will probably be associated with a significant increase in elastic properties since the strong silicon polyhedra form a structural network in this phase the transformation of spinel and stishovite to ilmenite is associated with a slight density increase and a slight decrease in acoustic velocities this transformation will probably not produce a seismic discontinuity even if it does occur in the earth s mantle

texture based image segmentation applied to the quanti cation of superficial sand in salmonid river gravels the presence of fine sediment in river gravels is widely recognized as being detrimental to salmonid habitat quality in order to facilitate quantification of sand presence at larger scales this paper presents an application of image processing allowing for rapid and accurate assessments of superficial sand presence in dry exposed fluvial gravels images for the process are acquired with a 35 mm slr film camera and then scanned with a desktop scanner texture based segmentation is then applied to differentiate between sand and clast areas results show that the method is accurate and therefore it offers an alternative to bulk sampling in cases where rapid assessments of sand presence are required copyright 2005 john wiley sons ltd

raman spectroscopy of perovskite and post perovskite phases of mggeo3 to 123 gpa abstract raman spectra of the perovskite pv and post perovskite ppv phases of mggeo 3 were measured in the laser heated diamond cell up to 123 gpa between 14 and 51 gpa we observed a total of seven pv modes the frequencies and relative intensities of which are similar to mgsio 3 pv with systematically lower frequencies we also observe a total of ten ppv modes which are much more intense than pv modes indicating strong polarizability of the bonds in ppv the observed raman mode frequency range of ppv extends to much higher frequencies than pv which can be related to the edge sharing of the geo 6 octahedra in ppv which would make ge o bonds stronger the spectroscopic gruneisen parameters of pv and ppv are constrained to be 1 56 0 10 and 1 15 0 06 respectively at the ppv transition we also estimated that the thermal expansion parameter decreases by 25 10 across the ppv transition if a similar change occurs in mgsio 3 the low thermal expansivity would dynamically stabilize the ppv layer at the lowermost mantle using our raman measurements and a kieffer type model the clapeyron slope of the ppv transition is constrained to be 20 10 mpa k the strong positive slope is consistent with the prediction for mgsio 3 and is related to a positive shift of phonon density of states at high frequency region resulting from the formation of the edge sharing among the geo 6 or sio 6 octahedra in ppv

geometry and grain size characteristics of the basal surface of a braided river deposit description of the three dimensional geometry and grain size patterns of fluvial deposits and their relationship to the morphodynamics of the river has been an elusive objective in sedimentology hindered by limited exposure and the time scale of fluvial dynamics in small scale physical models the time scales are short enough to map river morphology and sedimentology during significant and continuous morphological development of the river and its deposits especially for braided rivers using close range digital photogrammetry the dynamics of the river morphology and resulting deposit geometry and sedimentology were captured using digital elevation model differencing techniques combined with automated grain size mapping from image texture analysis using these novel methods we show the temporal development and characteristics of braided river deposit geometry and for the first time map the characteristics and development of the basal surface of braided river deposits in relation to river morphodynamics and formative processes the basal surface has considerable relief wide variation in grain size similar to that of the river as a whole develops progressively over time by switching of channels producing adjacent patches and ribbons of basal incision of different ages and is only partially related to bed scour associated with laterally migrating channel confluences

peridotitic minerals of the nidar ophiolite in the nw himalaya sourced from the depth of the mantle transition zone and above the nidar ophiolite complex noc consists of a c 10 km thick ophiolite suite in the nw himalaya india the c 7 km thick lower ultramafic part of the ophiolite body terminates against the tso morari crystallines which represent the leading edge of the indian continental margin mineral inclusions from the peridotites in the lower ultramafic part of the noc were studied including c 2 c clinoenstatite disordered coesite and high pressure mg 2 sio 4 probably mg 2 sio 4 these minerals found in two lherzolite bodies from the ophiolite s mantle section were characterized by laser raman spectroscopy and electron micro probe analysis textural evidence supporting decompression from an ultra high pressure condition was also observed such as cr spinel exsolution needles in olivine crystals the systematic mineral phase transitions of coesite quartz high pressure clinoenstatite orthoenstatite and mg 2 sio 4 cr spinel exsolution needles in olivine suggest that the mantle section of the nidar ophiolite evolved from the deep mantle beneath a palaeo spreading centre the phase stabilities of these high pressure minerals require derivation from the depth of the mantle transition zone 410 660 km a transport mechanism for these minerals is suggested via dunite channels along a mantle adiabat in the focused convective flow below the spreading centre this mechanism brought these deep mantle phases into the ultramafic part of the noc these observations suggest that some part of the mantle section of the noc in the nw himalaya originated in a mid ocean ridge setting

heterogeneity patterns of quaternary glaciofluvial gravel bodies sw germany application to hydrogeology abstract the architecture of sedimentary bodies determines the heterogeneity of many aquifers thus for environmental risk assessment and quantification of clean up efficiencies determination of the spatial distribution of hydraulic properties is required in this study outcrop analogues of glaciofluvial gravel bed deposits are used for a process based analysis of sedimentary heterogeneities which in turn are transformed into hydraulic parameters three scales of heterogeneities are distinguished a the lithofacies scale is formed by unique transport and depositional processes that form the fundamental building blocks hydrofacies types b the depositional element scale shows distinct geometrical characteristics internal structure and bounding surfaces and determines the local distribution of lithofacies and hence the correlation structure of permeabilities c the architectural scale of gravel bodies is formed by the stacking of depositional elements which is controlled by the dynamics of aggrading paleofluvial systems comparison of numerous gravel pits in sw germany revealed three major architectural patterns of glaciofluvial gravel bodies that can be distinguished statistically by the preservation of depositional elements as well as the frequency of lithofacies types the facies analysis results in three conceptual facies models of proglacial river systems which are regionally classified as main intermediate and minor discharge types based on calculated and laboratory measured hydraulic properties of the various lithofacies types detailed outcrop wall maps were digitized into polygons of defined hydrofacies types by using the gis system arc info the two dimensional fields of hydraulic properties were then transferred into a numerical model of groundwater flow modeling results clearly illustrate that the three heterogeneity patterns of gravel bodies also have distinguishable hydraulic response characteristics

using two and three dimensional georadar methods to characterize glaciofluvial architecture abstract the threat of pollution in the shallow subsurface has led to an increasing need to understand how complex heterogeneities in gravel aquifers influence groundwater transport to characterize these heterogeneities we have conducted extensive two dimensional 2 d and three dimensional 3 d ground penetrating radar gpr or georadar surveys in two quarries within the rhine valley of northeastern switzerland the quarries comprised gravel and sand deposited in a proglacial braided river system that followed the maximum wurm stage glaciation after the surveys the terrace walls beneath the two study sites were photographed as they were being excavated by combining information extracted from the 2 and 3 d georadar images with the outcrop photographs it was possible to correlate georadar facies with the various glaciofluvial architectural elements the dominant elements were scour pools formed at or near the confluences of two stream channels and horizontally bedded and massive gravel sheets deposited during moderate to high water flow conditions and exposed during low flow conditions architectural elements were generally elongated parallel to the mean flow directions of the ancient river system variations in the strike of their long axes reflected lateral and vertical changes in the local flow direction time slices showed structural trends not evident on 2 d georadar images and photographs data interpretation was quicker more complete and less ambiguous when georadar facies analyses were based on a combination of georadar vertical profiles and time slices than when based on georadar vertical profiles alone

constraints on the development of secondary porosity in the subsurface re evaluation of processes abstract secondary porosity formed by the dissolution of grains and cements is of great economic importance in both clastic and carbonate reservoirs a review of the commonly proposed mechanisms for the production of secondary porosity indicates that meteoric water penetration and mixing corrosion may be able to create significant volumes of secondary porosity in the shallow subsurface leaching by acidic fluids generated by solution of co 2 or monocarboxylic acids both derived during the thermal maturation of organic matter or by acidic fluids created by clay mineral reactions in shales are the most commonly proposed mechanisms by which secondary porosity is said to form in the deep subsurface however these mechanisms suffer from great difficulties in producing significant volumes of secondary porosity once mass balance and fluid migration problems are taken into account it is highly likely that the correct mechanism for the creation of economically significant amounts of secondary porosity in the deep subsurface is yet to be found

a quantitative three dimensional depositional model of gravelly braided rivers a quantitative three dimensional depositional model of gravelly braided rivers has been developed based largely on the deposits of the sagavanirktok river in northern alaska these deposits were described using cores wireline logs trenches and ground penetrating radar profiles the origin of the deposits was inferred from observations of 1 channel and bar formation and migration and channel filling interpreted from aerial photographs 2 water flow during floods and 3 the topography and texture of the river bed at low flow stage this depositional model quantitatively represents the geometry of the different scales of strataset the spatial relationships among them and their sediment texture distribution porosity and permeability in the model are related to sediment texture the geometry of a particular type and scale of strataset is related to the geometry and migration of the bedform type e g ripples dunes bedload sheets bars associated with deposition of the strataset in particular the length to thickness ratio of stratasets is similar to the wavelength to height ratio of associated bedforms furthermore the wavelength and height of bedforms such as dunes and bars are related to channel depth and width therefore the thickness of a particular scale of strataset i e medium scale cross sets and large scale sets of inclined strata will vary with river dimensions these relationships between the dimensions of stratasets bedforms and channels mean that this depositional model can be applied to other gravelly fluvial deposits the depositional model can be used to interpret the origin of ancient gravelly fluvial deposits and to aid in the characterization of gravelly fluvial aquifers and hydrocarbon reservoirs

reconstructing random topography from preserved stratification one of the fundamental problems of interpreting the sedimentary record is reconstructing the original heights of palaeotopographical features such as bedforms or river channels this requires an understanding of the relationship between topography and set thickness but at present an exact theory exists only for periodic topography of uniform height the applicability of this simple theory is severely limited by the random variability characteristic of many sedimentary systems in this paper we develop an exact theory for the probability density function pdf of sets generated from topography of random height we focus on the limiting case of zero net deposition in order to provide a lower bound for the set thickness and derive an analytical set thickness pdf that is determined by one parameter of the pdf for topographical height this parameter measures the breadth of the tail of the topographical pdf the mean set thickness is 0 8225 for bedforms and 1 645 for river channels if the topographical height is gamma distributed the preservation ratio defined as mean thickness of preserved sets mean topographical height is 0 8225 r2 for bedforms and 1 645 r2 for river channels where r is the coefficient of variation standard deviation mean of the generating topography in a comparison with data from laboratory current ripples our analytical predictions compare well with observations of both mean set thickness and thickness distribution the preservation ratio for the ripples is about 0 5 whilst measured dune heights give a preservation ratio of about 0 12 depth data from two modern braided streams yield preservation ratios ranging from 0 4 to 0 75 as more data on the distributions of topographical height in modern environments become available calculations such as these should help provide reliable error bounds for quantitative topographical reconstruction

the role of solid solid phase transitions in mantle convection abstract with changing pressure and temperature conditions downwelling and upwelling crustal and mantle rocks experience several solid solid phase transitions that affect the mineral physical properties owing to structural changes in the crystal lattice and to the absorption or release of latent heat variations in density together with phase boundary deflections related to the non null reaction slope generate important buoyancy forces that add to those induced by thermal perturbations these buoyancy forces are proportional to the density contrast between reactant and product phases their volume fraction the slope and the sharpness of the reaction and affect the style of mantle convection depending on the system composition in a homogeneous pyrolitic mantle there is little tendency for layered convection with slabs that may stagnate in the transition zone because of the positive buoyancy caused by post spinel and post ilmenite reactions and hot plumes that are accelerated by phase transformations in the 600 800 km depth range by adding chemical and mineralogical heterogeneities as on earth phase transitions introduce bulk rock and volatiles filtering effects that generate a compositional gradient throughout the entire mantle with levels that are enriched or depleted in one or more of these components phase transitions often lead to mechanical softening or hardening that can be related to a different intrinsic mechanical behaviour and volatile solubility of the product phases the heating or cooling associated with latent heat and the transient grain size reduction in downwelling cold material strong variations in viscosity would enhance layered mantle convection causing slab stagnation and plume ponding at low temperatures and relatively dry conditions reactions are delayed due to the sluggish kinetics so that non equilibrium phase aggregates can persist metastably beyond the equilibrium phase boundary survival of low density metastable olivine ringwoodite pyroxene and pyrope garnet in the transition zone and uppermost lower mantle produces positive buoyancy forces that decrease the subduction velocity and may lead to slab stagnation in the transition zone the presence of deep metastable portions is still debated and should not be associated a priori with a completely dry slab as field observations suggest that heterogeneously hydrated oceanic plates could contain metastable dry portions surrounded by transformed wet rocks

constraints upon water advection in sediments of the mariana trough thermal gradient measurements consolidation tests and pore water compositions from the mariana trough imply that water is moving through the sediments in areas with less than about 100 m of sediment cover the maximum advection rates implied by the thermal measurements and consolidation tests may be as high as 10 5 cm s 1 but are most commonly in the range of 1 to 5 10 6 cm s 1 theoretical calculations of the effect of the highest advection rates upon carbonate dissolution indicate that dissolution may be impeded or enhanced depending upon the direction of flow by a factor of 2 to 5 times the rate for diffusion alone the average percentage of carbonate is consistently higher in two cores from the area with no advection or upward advection than the average percentage of carbonate in three cores from the area with downward advection this increase in average amount of carbonate in cores with upward moving water or no movement cannot be attributed solely to differences in water depth or in amount of terrigenous dilution if the sediment column acts as a passive boundary layer then the water velocities necessary to affect chemical gradients of silica are in the range 10 9 to 10 10 cm s l however if dissolution of silica occurs within the sediment column then the advection velocities needed to affect chemical gradients are at least 3 10 8 cm s l and may be as high as 3 10 6 cm s l this order of magnitude increase in advection velocities when chemical reactions occur within the sediments is probably applicable to other cations in addition to silica if so then the advection velocities needed to affect heat flow 10 8 cm s 1 and pore water chemical gradients are much nearer in magnitude than previously assumed

close range digital photogrammetric analysis of experimental drainage basin evolution brasington james smart r m a 2003 close range digital photogrammetric analysis of experimental drainage basin evolution earth surface processes and landforms 28 3 pp 231 247 rae2008 special issue the generation of high quality topographic data for hydrology and geomorphology

morpho sedimentary characteristics of proximal gravel braided river deposits in a froude scaled physical model a froude scaled physical model of a proximal gravel bed braided river was used to connect the river morphological characteristics and sedimentary processes and forms to deposit geometry high resolution continuous three dimensional topographic data was acquired from sequential photogrammetric digital elevation models paired with grain size surface maps derived from image analysis of textural properties of the surface from these data the full three dimensional development of the braided river deposit and grain size sorting patterns was compiled over an experimental time period of 40 hours during which the model river reworked a large portion of the braided channel the minimum surface of the deposit is developed progressively over time by erosion migration and avulsion of channels and by local scour at channel confluences the maximum surface of the deposit is formed by amalgamation of braid bar surfaces and has less overall relief than the minimum surface confluence scour constitutes about 5 of the area of the minimum surface migration of individual confluences is limited to distances of the order of the width and length of the confluence so that confluences do not form laterally extensive deposits and basal surfaces maximum and minimum surfaces have very similar grain size distributions and there is no extensive basal coarse layer deposit maximum thickness is strongly associated with large channel confluences which occur as deeper areas along the main channel belt and make up a large proportion of the thickest portions of the deposit this article is protected by copyright all rights reserved

active width of gravel bed braided rivers previous analyses have identified the active width of braided rivers the bed area over which bed load flux and short term morphological change occurs as an important element of braiding dynamics and predictions of bed load flux here we compare theoretical predictions of active width in gravel bed braided rivers with observations from sunwapta river and from a generic physical model of gravel braided rivers to provide general observations of the variation in active width and to develop an understanding of the causes of variation bed topography was surveyed daily along a 150 m reach of the pro glacial sunwapta river for a total of four weeks during summer when flow was above threshold for morphological activity in the laboratory detailed digital elevation models dems were derived from photogrammetric survey at regular intervals during a constant discharge run from the field and flume observations there is considerable local and circumstantial variation in active width but also a general trend in average active width with increasing discharge there is also a clear relationship of active width with active braiding index number of active branches in the braided channel network and with dimensionless stream power which appears to be consistent across the range of data from field and physical models thus there is a link between active width and the river morphology and dynamics and the possibility of a general relationship for estimating active width from channel pattern properties or reach scale stream power values from which approximate bedload flux calculations may be made the analysis also raises questions about differences between hydraulically based numerical model computations of instantaneous active width and observation of time integrated morphological active width understanding these differences can give insight into the nature of bedload transport in braided rivers and the relationship to morphological processes of braiding copyright 2011 john wiley sons ltd

estimates of mantle relevant clapeyron slopes in the mgsio3 system from high pressure spectroscopic data the phase diagram for mgsio was estimated using the entropy enthalpy thermal expansivity and volumes of all the phases entropy at the various p t conditions in the phase diagram was estimated using statistical thermodynamics and spectroscopic data at ambient and high pressures for each of the phases nearly complete 1 atm polarized raman spectra of end member mgsio 3 orthoenstatite and new high pressure raman data on orthoenstatite pbca to 24 5 gpa and majorite to 33 6 gpa are presented both of these minerals exhibit profound changes in their spectra as pressure is increased and the pressure dependence of the raman modes changes substantially at 5 gpa for orthoenstatite and 26 gpa for majorite these like mgsio 3 perovskite appear to change symmetry even at room temperature the slopes for the following transitions are reported clinoenstatite c2 c to majorite 12 bar k majorite to ilmenite 46 bar k ilmenite to perovskite 46 bar k majorite to perovskite 26 bar k a volume change of 0 6 cm mol for the orthopyroxene to high pressure clinopyroxene transition was estimated using the previously measured phase boundary and the present entropy data clapeyron slopes are overestimated by 20 to 100 if the pressure dependence of delta s across the transitions at various p t conditions is not included in the thermodynamic calculations

porosity preservation in the upper smackover jurassic carbonate grainstone walker creek field arkansas response of paleophreatic lenses to burial processes reply a section of the arco bodcaw no 1 core from the upper smackover jurassic of southern arkansas was studied in detail in an effort to understand the control of porosity petrographic isotopic atomic absorption and cathodoluminescence data on whole rocks and components were generated on 24 samples from a 115 foot length of core the core is composed almost entirely of accretionary and cryptocrystalline grains and cement porosity is unrelated to grain type size or sorting on a sample to sample basis the porous intervals are interpreted to have been stablized to calcite under fresh water phreatic conditions the porous intervals approach fresh water values of 5 0 per thousand delta 18 o 1 5 mol percent mg and 300 ppm sr and are further characterized by luminescent oolites and relatively slight solution compaction effects the nonporous intervals represent relict vadose and subphreatic environments which stabilized after burial the nonporous intervals approach burial values of 2 8 per thousand delta 18 o 2 5 mol percent mg and 600 ppm sr and are further characterized by nonluminescent grains and intense solution compaction data indicate that oolites were initially composed of a metastable mineralogy cryptocrystalline grains were composed of a more stable mineralogy and algal grains were composed of a mixture of mineralogies oolites in the vadose and subphreatic environments were not fully stabilized under fresh water conditions but vadose grains carried with them a light delta 13 c soil gas signal after burial these grains were fully stabilized under post fresh water burial conditions observed porosity distribution is readily explained in terms of solution compaction and cementation grains with metastable mineralogy in relict vadose and subphreatic intervals were heavily solution compacted at relatively shallow depths before being converted to stable calcite intense solution compaction destroyed pore space in these intervals dolomite cementation seems linked with the compaction process the stablized mineralogy of the phreatic lens together with associated meteoric cements resisted solution compaction and thereby preserved pore space

grain size sorting within river bars in relation to downstream fining along a wandering channel the textural variability of river bed gravels at bar scales is poorly understood as are the relations between variability at this scale and at reach and river scales surface and subsurface grain size distributions were therefore examined at reach bar and bedform scales along lower fraser river british columbia canada grain size variations within compound bars are conditioned by longitudinal position elevation and morphological setting surface and subsurface sediments tend to decrease in median size from bar head to bar tail by 33 and 17 respectively sediment size is constrained at some upper limit that is inversely related to bar surface elevation and which is consistent with competence considerations the surface sediments on unit bars are finer and better sorted than the bed materials in bar top channels and along the main bar edges secondary unit bars tend to have a lower sand content than other features a consequence of sediment resorting individual unit bars and gravel sheets exhibit streamwise grain size fining and lee side sand deposition over time significant amounts of cut and fill do not ipso facto cause changes in surface grain sizes yet sediment characteristics can change without any significant morphological adjustment taking place at the reach scale there is a clear downstream fining trend but local variability is consistently high due to within bar variations the surface median grain size range on individual bars is on average 25 of that along the entire 50 km reach but is 68 on one bar while the overall fining trend yields a downstream change in surface median size of 0 76 mm km 1 the average value for head to tail size reduction on individual bars is 6 3 mm km 1 an order of magnitude difference that highlights the effectiveness of bar scale sorting processes in gravel bed rivers possibilities for modelling bar scale variability and the interaction of the different controls that are identified are discussed

formation of braided river floodplains waimakariri river new zealand floodplains along the braided gravel bed waimakariri river are discontinuous although generally extensive landforms composed predominantly of gravel bars capped with vertically accreted fines in order of importance three mechanisms lead to floodplain formation river bed abandonment by lateral migration of the braid train initiates the formation of the largest floodpiains which usually occur downstream of tributary fans and valley bedrock spurs in the headwater reaches localized river bed aggradation during high magnitude events leads to floodplain formation by producing a surface resistant to erosion by lesser events due to either the coarse nature of the deposit or by its elevation over the river bed or both the least important mechanism initiating floodplain development is localized river or channel incision a six stage model is proposed for the sequential development of floodplains on the waimakariri river from i active river bed ii stabilizing bar iii incipient floodplain iv established floodplain v mature floodplain and to vi terrace two mechanisms lateral migration by the braid train and reactivation of abandoned channels within floodplains operating separately or in combination are responsible for floodplain reworking and their relatively young age 250 years clearly braided rivers can construct substantial areas of well developed floodplain

mgsio3 phase boundaries measured in the laser heated diamond cell abstract new data on phase equilibria in the mgsio3 system relevant to the stability of mg si perovskite perovskite are obtained in the laser heated diamond cell using improved techniques for accurate pressure measurement and novel heating techniques eliminating temperature gradients the data of the mgsio3 ilmenite akimotoite perovskite phase boundary measured in the range of 19 25 5 gpa and 1800 2350 k are consistent with the pressure and temperature conditions generally assumed at 660 km depth and agree within the experimental uncertainties with earlier multi anvil quench experiments the triple point wadsleyite stishovite akimotoite perovskite is at 21 gpa and 2300 k the slope of the akimotoite perovskite boundary is not well constrained by reversal experiments alone due to large hysteresis but results using glass starting materials yield a value of 0 004 0 002 gpa k the slopes of the phase transitions to mg si perovskite in both olivine and pyroxene systems are less negative than those required to cause layering in mantle convection at the pressure of the 660 km seismic discontinuity 23 8 gpa the phase boundary between akimotoite and perovskite yields a slightly lower temperature than that of the ringwoodite to perovskite periclase transition in the mg2sio4 system 1900 100 k garnet majorite is not observed above 21 gpa

measurements in a braided river chute and lobe 2 sorting of bed load during entrainment transport and deposition grain size distributions of bed material bed load and bar head deposition were sampled during the evolution of a chute and lobe in the braided gravel bed sunwapta river alberta although bed shear stress and total bed load transport rate varied substantially within the reach and from day to day ferguson et al this issue the median diameter d50 of bed load was remarkably constant the bed initially fined from chute to bar head but became more uniform sediment deposited on the bar head also had a near constant d50 similar to that of the bed load truncated at the same lower size limit both load and deposition were finer on average than the bed suggesting overall selective transport despite little sign of local sorting in contrast to median diameters maximum sizes dmax of sediment in motion and deposited on the bar head varied substantially and showed a weak but significant dependence on shear stress inferring selective entrainment from this evidence alone would be dubious because dmax was also found to increase systematically with the mass of sediment sampled however two different methods of analysis of fractional transport rates throughout the size range also showed size selective entrainment and transport in the marginal transport conditions of this study size sorting appears to occur but only weakly and mainly in the coarser fractions

compaction and movement of interstitial water in bottom sediments of the saguenay fjord quebec canada abstract eight sediment cores were collected along the length of the saguenay fjord and baie des ha ha quebec canada profiles of the sediment water contents were determined for each core porosities were fitted to an exponential relation with core depth the relation was modified to account for variations in granulometry and in organic carbon contents of the sediments porosities were observed to be more sensitive to variations in organic content than to variations in granulometry and grain sorting appeared more important than grain size grain size distribution of the sediments is in agreement with a sedimentation model where most of the suspended load enters the fjord from the saguenay river and is deposited downstream with the surface current the coarse particles are mainly found close to the head of the fjord whereas the fine particles are carried farther downstream surface porosities were observed to be proportional to the sedimentation fluxes obtained from the literature whereas the compaction showed an inverse relationship the fractional decreases in porosity due to compaction along the fjord indicate some horizontal flow of the interstitial water at both ends of the sampled part of the fjord an average vertical interstitial pore water flow of 0 4 cm yr 1 with respect to the surface horizon is estimated from the data this is small compared with the diffusion of the major constituents of sea water through the sediment

burial diagenesis and porosity evolution upper jurassic smackover arkansas and louisiana the jurassic upper smackover ooid lime grainstone of the central gulf coast has been a major hydrocarbon exploration target for nearly half a century study of the geologic and sedimentologic framework petrography two phase fluid inclusions and trace element and stable isotope chemistry indicates the following diagenetic history the upper smackover is a blanket ooid grainstone ranging in thickness from 300 to 400 ft 91 to 122 m and covering at least 4 000 sq mi 10 400 sq km in the northern part of the arkansas shelf a regional meteoric water system was established in the grainstone shortly after deposition and prior to significant burial this meteoric water system gave way to conditions which were increasingly more marine toward the south near the louisiana arkansas state line the fresh to marine hydrologic gradient is responsible for the strong precompaction regional diagenetic overprint that eventually controlled available diagenetic pathways for the unit during burial three diagenetic zones are present 1 a northern zone dominated by oomoldic porosity and preburial spar cementation 2 a sou hern zone characterized by compaction effects late subsurface cement primary porosity preservation and late secondary subsurface porosity generation and 3 a transitional zone having characteristics common to both the northern and southern zones during the shallow burial phase compaction became increasingly more important to the south in zones dominated by marine connate fluid whereas rock integrity and a secondary oomoldic porosity system had already been established in the northern zone as burial increased brine originating in the underlying louann salt reached the shelf grainstone and began to displace the original connate fluid the brine triggered the inversion to calcite of remaining grains and cement composed of unstable mineralogy when the louann brine had displaced the original connate fluid caso4 replacement as gypsum and anhydrite was common across all three diagenetic zones also precompaction fine cement associated with oomoldic porosity was recrystallized and reequilibrated with the concentrate brine localized replacement dolomitization may well have developed throughout the burial history of the sequence but was most commonly postcompactional postcompaction poikilitic calcite cement and baroque dolomite were precipitated from the louann brine under conditions of elevated temperature and pressure as subsidence continued organic material from the basinward equivalents of the upper smackover lime grainstone arrived on the shelf and catalyzed so4 reduction resulting in pyrite and galena replacement in the southern and transitional zones as hydrocarbon maturation continued in the fine grained equivalents of the upper smackover h2s and co2 by products of these processes began to increase in the brine of the southern and transitional zones ultimately causing regional dissolution of existing carbonate and significantly enhancing preserved porosity porosity in the northern zone was established early and preserved through moderate burial although porosity is well developed permeability has been largely destroyed by recrystallization dolomitization is a prerequisite for economic reservoir development in the northern zone porosity in the southern zone is solution enhanced preserved primary intergranular porosity compaction is the most important porosity destruction process compaction in the absence of an early diagenetic overprint is affected primarily by grain type and secondarily by size and sorting pellets and oncolites compact easily yet destroy porosity during burial ooids and rhodolites resist compaction during burial therefore are related to porosity preservation grain type distribution as well as size and sorting are controlled by depositional environment processes with the most favorable areas for porosity development concentrations of ooids and rhodolites associated with early salt related structural movement porosity distribution in the southern zone therefore can be outli ed with the aid of geophysical end page 597 techniques porosity in the transitional zone is early secondary or preserved primary intergranular or a combination porosity in this zone therefore is highly unpredictable and a strong potential exists for diagenetic traps unrelated to structure or original depositional environment documentation of significant deep subsurface secondary porosity possibly associated with hydrocarbon maturation opens the potential for hydrocarbon exploration in deeply buried carbonate dominated basins this would include carbonate rocks heretofore thought to be well below the depth of carbonate porosity maintenance because of lithostatic load

space time dynamics of depositional systems experimental evidence and theoretical modeling of heavy tailed statistics 1 in depositional systems channels migrate from one location to another causing erosion and deposition at any given point in the domain the durations of depositional and erosional events as well as their magnitudes control the structure of the stratigraphic record in this study we use high resolution temporal surface elevation data from a controlled experiment to quantify the probability distributions of the processes that govern the evolution of depositional deltaic systems heavy tailed statistics of erosional and depositional events are documented indicating that a small but significant chance exists for the occurrence of extreme events we show that the periods of inactivity when neither deposition nor erosion occurs follow a truncated pareto distribution whose truncation scale is set by the mean characteristic avulsion time scale in the system further we show that the heavy tails in the magnitudes of the erosional and depositional events are not preserved in the stratigraphic record resulting instead in an exponential distribution for the bed sediment thickness it is also shown that the temporal evolution of surface elevation exhibits self similarity with a nonlinear spectrum of scaling exponents multifractality quantifying the complex dynamics of the system finally we show how the results of this study can lead to improved diffusional models for surface evolution using the tools of fractional calculus

small scale cyclicity in alpine proglacial fluvial sedimentation abstract this paper compares contemporary sedimentation in an alpine proglacial braided river with deposits from inactive areas of the braidplain this approach allows confidence in determining the key characteristics of alpine proglacial braided river deposits the diagnostic features are 1 repeated coarse fine couplets in fine grained sediment

structures and textures in triassic braided stream conglomerates bunter pebble beds in the sherwood sandstone group north staffordshire england in the northern parts of the needwood and stafford eccleshall basins england the pebble beds of the sherwood sandstone group contain thick successions of texturally mature fluvial pebble cobble conglomerates which are organized into either horizontal or cross stratified sets the horizontally lying sets generally coarser grained and more poorly sorted than the cross bedded sets are usually disorganized and either matrix or clast supported although thin lenses of well sorted occasionally openwork units interpreted as falling stage phenomena are often present the cross stratified conglomerates have foresets exhibiting remarkable textural organization with a coarse bimodal sometimes matrix supported part grading upwards or being abruptly overlain by a finer well sorted occasionally openwork part and finally capped by sandstone these rhythmic textural changes are attributed partly to an avalanche process at high stage and partly to falling stage conditions the most common types of vertical association are thick successions of horizontally bedded conglomerates up to 20 m and sequences of an upwards coarsening nature 2 12 m in which cross stratified sets are overlain by flat lying sets the environment of deposition of the gravels is interpreted as one in which water depths at high stage were greater than depths in most modern braided stream plains proglacial or alluvial fan but shallower than depths associated with the pleistocene catastrophic floods from which texturally mature giant gravel bars have been recorded recent braided streams with relatively confined channels and considerable bar channel relief are better analogues in particular medial or mid channel bars with a two tier structure subaqueous and partly emergent portions may explain the upward coarsening sequences in which horizontally lying conglomerates overlie cross stratified conglomerates the thicker sequences of horizontally stratified conglomerates represent proximal longitudinal bar deposits sheets of pebbly sandstone and argillaceous sandstone lying between the conglomerates and commonly occurring towards the top of the succession largely represent deposition from sandwaves and dunes finer interbedded argillaceous sandstones siltstones and mudstones are interpreted as overbank and waning flood deposits basin forming tectonism of increasing intensity probably caused the initial coarsening upwards of the lower part of the succession whilst more stable tectonic conditions and decreasing relief on the margins of the basins and in the areas of provenance in the midlands and the hercynides account for the upwards fining of the upper part of the succession

assessment of morphological changes induced by flow and flood pulses in a gravel bed braided river the tagliamento river italy large gravel bed braided rivers show a highly dynamic evolution where even moderate flow pulses can produce significant morphological adjustment an estimation of network variations is needed by river authorities as well as by ecologists for better managing river ecosystems however few field investigations have been performed to measure the effect of unsteady discharges in braided rivers in this paper we report on the morphological changes induced by six different floods in a 1 km long reach of the tagliamento river italy topographic surveys were performed after each significant flood and an automatic digital camera continuously monitored the planimetric configuration repeated measurements of cross section profiles allowed the quantification of the transported sediments volume and in particular provided a basis to estimate the percentage of the floodplain subject to morphological evolution data analysis showed a good relationship between peak flow level active width and mean bed level changes similarly lateral channel shifting is likely to increase for larger floods monitoring of a range of discharges up to bankfull conditions revealed a fundamental difference between flow pulses events on the average occurring one or more times per year and flood pulses with a return period larger than two years the morphological evolution in the former case is mainly limited to a few active branches and is locally driven by bank erosion at the bend apex on the other hand larger floods induce a complete reworking of the network configuration where bifurcations and confluences play a crucial role single morphological units like branches nodes bars are no longer recognizable after this type of event braided rivers are therefore characterized by the occurrence of two different spatial and temporal scales that force the ecosystem dynamics

radar architecture and evolution of channel bars in wandering gravel bed rivers fraser and squamish rivers british columbia canada abstract the alluvial architecture and evolution of two kilometer scale compound bars in the wandering gravel bed fraser and squamish rivers british columbia canada are described integrating ground penetrating radar bathymetry and aerial photographs enables the internal architecture to be linked to the evolution of the gravelly barforms over the previous 50 years these linkages reveal the sedimentary mechanisms that formed the various architectural packages within compound bars and unit bars growth of compound bars is controlled by the accretion of unit bars onto discrete segments along their gravelly edges the attachment of unit bars deflects the thalweg to impinge on and erode specific portions of bars and channel banks bar growth leads to the stabilization of bars vegetation colonization of bar interiors and island formation it is the formation of islands along with channel avulsions that maintains channel division in wandering rivers seven styles of gravelly deposition are imaged in the alluvial architecture vertical accretion deposits formed from the deposition of gravelly bedload sheets are the most common strata a moderate abundance of slipface deposits preserves high relief bar margins lateral accretion dominates point bar deposits downstream accretion deposits govern some phases of down bar growth partial and complete channel fill and chute fill deposits are eroded into underlying sediments as are scour and fill deposits upstream accretion deposits are uncommon a depositional model of gravelly channel bars in the two rivers is presented and reveals that the architecture is made up of depositional styles similar to those observed in braiding river successions although the sedimentary packages are preserved in different proportions differences in braiding river and wandering river sedimentology largely reflect the relatively frequent migration of channels and bars in braiding rivers which preserve high proportions of channel fill and chute fill and confluence scour and fill deposits conversely the moderately stable island and channel network in wandering rivers limits channel shifting and consequently preserves a low number of channel fills moderate proportions of slipface strata and coherent patterns of sand deposition along bar tops provide evidence of comparatively uniform flow patterns in independent channel segments divided by islands these patterns of bar sedimentation and channel shifting preserved in the alluvial architecture appear to be signature characteristics of wandering rivers the occurrence of similar architecture in both the fraser and squamish rivers suggests that the model likely applies to most wandering gravel bed rivers

pressure induced pbca p21 c phase transition of natural orthoenstatite compositional effect and its geophysical implications raman spectroscopy has been employed to investigate possible compositional effects on the high pressure phase transition of mg rich orthoenstatite to a newly discovered p 21 c phase three natural orthoenstatite oen samples were used in this study near end member mg orthoenstatite zabargad island egypt al free fe bearing orthoenstatite morogoro tanzania and al rich fe ca bearing orthoenstatite kilbourne hole new mexico experiments were carried out at room temperature for all samples the high pressure phase transition is characterized by a splitting of the 660 680 cm 1 doublet in the raman spectrum into a triplet with a corresponding change of peak intensities these spectral changes are caused by the lowered symmetry of the high pressure phase as indicated by structural refinement from single crystal x ray diffraction results the high pressure phase of all samples appears to have space group p 21 c no evidence for a c 2 c phase was observed our results indicate that upon compression the presence of 10 mol fe decreases the onset pressure of formation of the high pressure p 21 c phase by about 1 gpa results for the kilbourne hole oen show that upon compression a combined enrichment of al and ca contents increases the onset pressure of formation of high pressure clinoesntatite hpcen2 by over 3 gpa relative to tanzania oen upon decompression all samples revert to single crystals of the orthoenstatite starting phase our measurements suggest that orthoenstatite is the prevalent phase of mg rich pyroxene throughout the uppermost mantle whereas the newly discovered p 21 c phase might be present near the bottom of uppermost mantle slightly shallower than the top of the transition zone

raman spectroscopy of fe ti cr oxides case study martian meteorite eeta79001 raman spectral features of chromite ulvospinel magnetite ilmenite hematite and some of their solid solutions are presented although most fe ti cr oxides produce relatively weak raman signals compared to oxyanionic minerals sufficient information can be extracted from their spectra to identify the end member mineral phases as well as some information about compositional variations in solid solutions correlations between raman spectral features and mineral chemistry are used to interpret the raman data of fe ti cr oxides found during raman point count measurements on rock chips of martian meteorite eeta79001 as an analog to mars on surface planetary investigations in general ulvospinel magnetite and chromite end members are readily distinguished by their raman spectral patterns as are ilmenite and hematite in the low signal to noise s n spectra generally obtained from the raman point count procedure the position and shape of the strongest peak of fe ti cr oxides in the region 660 680 cm 1 a1g mode is the most useful for discriminating fe3 ti cr al substitutions in the magnetite ulvospinel ulvospinel chromite and chromite spinel series but minor peaks in the range 300 600 cm 1 also assist in discrimination these spectral features are useful for investigating the variability among fe ti cr al oxide solid solutions in natural samples in eeta79001 a martian basaltic meteorite most of the oxide grains as measured with the electron microprobe are ulvospinel chromian ulvospinel and chromite but ilmenite titanian chromite and titanomagnetite are also observed the fe ti cr oxides identified by raman point count include end member ilmenite low al chromite spinel solid solutions ulvospinel magnetite solid solutions and more complex chromite spinel ulvospinel magnetite solid solutions the latter exhibit a wide range of main peak positions and broadened peak widths that may reflect structural disorder as well one raman spectrum suggests end member magnetite and one spectrum from a different rock chip appears to be that of non terrestrial hematite reflecting local oxidizing alteration which has not been observed previously in this meteorite these results show that analyses done in an automated mode on the surface of an unprepared martian rock sample can provide useful constraints on the fe ti cr oxide mineralogy present and on compositional variations within those minerals including an indication of oxygen fugacity

pore velocity estimation uncertainties geostatistical data analysis techniques were used to stochastically model the spatial variability of groundwater pore velocity in a potential waste repository site kriging algorithms were applied to hanford reservation data to estimate hydraulic conductivities hydraulic head gradients and pore velocities a first order taylor series expansion for pore velocity was used to statistically combine hydraulic conductivity hydraulic head gradient and effective porosity surfaces and uncertainties to characterize the pore velocity uncertainty use of these techniques permits the estimation of pore velocity uncertainties when pore velocity measurements do not exist large pore velocity estimation uncertainties were found to be located in the region where the hydraulic head gradient relative uncertainty was maximal

the role of discharge variability in determining alluvial stratigraphy we illustrate the potential for using physics based modeling to link alluvial stratigraphy to large river morphology and dynamics model simulations validated using ground penetrating radar data from the rio parana argentina demonstrate a strong relationship between bar scale set thickness and channel depth which applies across a wide range of river patterns and bar types we show that hydrologic regime indexed by discharge variability and flood duration exerts a first order influence on morphodynamics and hence bar set thickness and that planform morphology alone may be a misleading variable for interpreting deposits indeed our results illustrate that rivers evolving under contrasting hydrologic regimes may have very similar morphology yet be characterized by marked differences in stratigraphy this realization represents an important limitation on the application of established theory that links river topography to alluvial deposits and highlights the need to obtain field evidence of discharge variability when developing paleoenvironmental reconstructions model simulations demonstrate the potential for deriving such evidence using metrics of paleocurrent variance

hydrochemical evolution of the east midlands triassic sandstone aquifer england a detailed hydrogeochemical interpretation has been made of the red bed sherwood sandstone triassic aquifer of the east midlands of england on which a radiocarbon model has been used to establish a chronology of groundwaters along the flow line groundwater evolution is dominated by carbonate and sulphate mineral solution and precipitation and by redox reactions cation exchange reactions are negligible and the hydrogeochemistry has evolved in the absence of residual saline water three distinct zones are recognised 1 i recent groundwater mainly 100 y oxidising dominated by congruent dissolution of dolomite and by inputs from atmospheric and anthropogenic sources 2 ii groundwater age 103 104 y predominantly reducing dominated by incongruent dissolution of dolomite 3 iii groundwater age 104 y reducing conditions approach to isotopic and chemical equilibrium in the carbonate system dominance of gypsum dissolution the minor and trace element variation can be interpreted in relation to the principal geochemical reactions and recharge history na cl f and b are controlled by atmospheric inputs sr2 and mn2 trends can be explained by carbonate and sulphate mineral dissolution ba2 is derived from carbonates but controlled by barite equilibrium fe so42 no3 and u are strongly influenced by redox reactions the concentrations of transition metals and other elements remain very low only li and k are considered to represent additions by reaction of silicate minerals the extent of direct anthropogenic influence is probably limited to enhanced so4 no32 and possibly cu zn and pb in zone i

magnitude and frequency in proglacial rivers a geomorphological and sedimentological perspective abstract proglacial fluvial sedimentary systems receive water from a variety of sources and have variable discharges with a range of magnitudes and frequencies little attention has been paid to how these various magnitude and frequency regimes interact to produce a distinctive sedimentary record in modern and ancient proglacial environments this paper reviews the concept of magnitude and frequency in relation to proglacial fluvial systems from a geomorphic and sedimentary perspective rather than a hydrological or statistical perspective the nature of the meltwater inputs can be characterised as low magnitude high frequency primarily controlled by ablation inputs from the source glacier or high magnitude low frequency primarily controlled by exceptional inputs the most important high magnitude low frequency inputs are catastrophic outburst floods often referred to by the term jokulhlaup icelandic for glacier burst glacier surges are an additional form of cyclical variation impacting the proglacial environment which briefly alter the volumes and patterns of meltwater input the sedimentary consequences of low magnitude high frequency discharges are related to frequent variations in stage the greater directional variability that sediment will record and the increased significance of channel confluence sedimentation in contrast the most significant characteristics of high magnitude low frequency flooding include the presence of large flood bars and mid channel jokulhlaup bars hyperconcentrated flows large gravel dunes and the formation of ice block kettle hole structures and rip up clasts glacier surges result in a redistribution of low magnitude high frequency processes and products across the glacier margin and small floods may occur at the surge termination criteria for distinguishing magnitude and frequency regimes in the proglacial environment are identified based on these major characteristics studies of quaternary proglacial fluvial sediments are used to determine how the interaction of the various magnitude and frequency regimes might produce a distinctive sedimentary record consideration of sandur architecture and stratigraphy shows that the main controls on the sedimentary record of proglacial regions are the discharge magnitude and frequency regime sediment supply the pattern of glacier advance or retreat and proglacial topography a model of sandur development is suggested which shows how discharge magnitude and frequency in combination with sandur incision and aggradation controlled by glacier advance and retreat can control sandur stratigraphy

planform dynamics of braided streams the high dynamism and complexity of braided networks poses a series of open questions significant for river restoration and management the present work is aimed at the characterization of the morphology of braided streams in order to assess whether the system reaches a steady state under constant flow conditions and in that case to determine how it can be described and on which parameters it depends a series of 14 experimental runs were performed in a laboratory physical model with uniform sand varying the discharge and the longitudinal slope planimetric and altimetric configurations were monitored in order to assess the occurrence of a steady state a set of parameters was considered such as the braid plain width and the number and typology of branches and nodes results point out that a relationship exists between braiding morphology and two dimensionless parameters related to total water discharge and stream power we found that network complexity increases at higher values of water discharge and a larger portion of branches exhibits morphological activity results are then compared to the outputs of a simple one dimensional model that allows to easily predict the average network complexity once the bed topography is known model computations permit also the investigation of the effect of water discharge variations and to compare different width definitions the at a station variability of planimetric parameters shows a peculiar behaviour both regarding number of branches and wetted width in particular the analysis of the relationship between width and discharge highlighted relevant differences in comparison to single thread channel copyright 2009 john wiley sons ltd

petrological layering induced by an endothermic phase transition in the earth s mantle 1 we investigate the effect of an endothermic phase transition on the average petrology of the mantle as function of depth we study chemical differentiation using a numerical model in which the oceanic lithosphere comprised of a crustal layer overlying depleted harzburgite is injected at the ridges three families of tracers are used each one with its own buoyancy to distinguish oceanic crust harzburgite and peridotite the depth of the phase transition and the clapeyron slope are assumed to be the same whatever the petrological component of the mantle velocities are imposed at the surface to mimic plate tectonics the viscosity is depth and temperature dependent the negative clapeyron slope tends to induce a segregation of the heavy material below the phase transition and of the light material above the phase transition with a compositional jump across the transition zone

thermodynamic properties and phase relations in mantle minerals investigated by first principles quasiharmonic theory this research has been motivated by geophysics and materials physics the objective of this research has been to advance materials theory and computations for high pressure and high temperature applications to the point that it can make a difference in our understanding of the earth understanding of the mineralogy composition and thermal structure of the earth evolves by close interaction of three fields seismology geodynamics and mineral physics earth s structure is imaged by seismology which obtains body wave velocities and density throughout the earth s interior fig 1 interpretation of this data relies on knowledge of aggregate properties of earth forming materials either measured in laboratory or calculated in many cases by both however the conditions of the earth s interior especially at the core may be challenging for important experiments and materials computations have emerged to contribute decisively to this field earth s evolution is simulated by geodynamics but these simulations need as input information about rheological and thermodynamic properties of minerals including phase transformation properties such as clapeyron slopes our research has concentrated on the phases of the earth s mantle particularly the deep mantle whose conditions are more challenging for experiments the mantle accounts for 83 of the earth s volume in this article we will review the essential first principles approach used to investigate solids at high temperatures and pressures summarize their performance for mantle minerals fig 2 and point to critical results that have stirred us in the current research path the success is remarkable but some limitations point the way to future developments in this field figure 1 a velocities and density profiles kennett et al 1995 b earth s cross section and c composition and mineralogy of earth s layers figure 2 phases proportions versus depth and or pressure ol mg fe 2sio4 olivine also known as phase mg fe