inconsistent magnetic polarities between greigite and pyrrhotite magnetite bearing marine sediments from the tsailiao chi section southwestern taiwan abstract to establish a magnetobiostratigraphy for a 620 m thick middle to late pleistocene mudstone sequence in the lower gutingkeng formation of the tsailiao chi tlc section in southwestern taiwan we conducted paleomagnetic and mineral magnetic measurements together with sediment granulometry and calcareous nannofossil identification paleomagnetic samples from 65 sites revealed two types of thermal demagnetization 25 400 c behavior 1 single component stable characteristic remanence in magnetite and pyrrhotite dominated samples type s and 2 abrupt changes in polarity when samples with significant greigite concentrations were heated above 320 340 c type c the characteristic polarities derived from type s samples and from magnetite dominated type c samples obtained above 340 c are consistent with those determined from nannofossil biostratigraphy this implies that the nrm carried by magnetite and pyrrhotite is reliable the essentially antiparallel remanence components in type c samples below 340 c are attributed to greigite the almost antiparallel direction could have resulted from delayed formation of greigite but in this case the different direction of this component must have resulted from variable remanence lock in times alternatively the opposite polarities may result from self reversal which warrants further investigation pyrrhotite and greigite may have both formed authigenically but there is no clear explanation for the observed differences in direction

authigenic greigite in mud from the continental shelf of the yellow sea off the southwest korean peninsula abstract this is the first reported occurrence of greigite in korea which was found in semi consolidated near surface mud on the continental shelf of the southeastern yellow sea the seafloor 70 m of water in the sampling site is composed of alternating massive sand and homogeneous mud which are presumably part of the holocene transgressive deposits greigite grains 0 1 2 mm in size are disseminated or form a single lamina in the mud the mineral is strongly magnetic and black with metallic luster some grains have a reddish brown tarnish caused by oxidation in reflected light greigite occurs as yellowish white to pale creamy tint and isotropic globular aggregates the mineral greigite has a chemical composition of fe 54 4 s 42 4 as 0 14 si 2 3 wt and the empirical formula on the basis of s 4 is fe2 95s4 cell dimensions cubic are measured as a 9 8635 ra v 959 6 a 3 and d 4 094 g cm3 it probably formed in a reducing micro environment around decaying organic matter

rock properties of the upper crust in central apennines italy derived from high resolution 3 d tomography 1 high resolution 3 d p and s wave velocity models of a central sector of the apennines central italy are computed by inverting first arrival times from an aftershock sequence september december 1997 following the mw 5 7 and mw 6 0 umbria marche earthquakes that occurred on september 26 1997 the high quality of the data set especially for the s wave allows us to compute 3 d variations in vp vp vs and vp vs the anomalies can be interpreted as lateral changes in rock type and fracturing which control fluid diffusion and variation in pore pressure this is in agreement with a poro elastic view that can be inferred from the spatio temporal evolution of the seismic sequence

diagenetic magnetic enhancement of sapropels from the eastern mediterranean sea diagenetic dissolution of magnetic minerals has been widely observed in organic rich sediments from many environments organic rich sediments from the eastern mediterranean sea sapropels recovered during leg 160 of the ocean drilling program reveal a surprising catalogue of magnetic properties sapropels from all sites studied across the eastern mediterranean sea are strongly magnetic and the magnetization is directly proportional to the organic carbon content the magnetization of the sapropels is dominated by a low coercivity probably single domain magnetic mineral with an inverse magnetic fabric that exhibits a clear decay in magnetic properties when exposed to air during heating the magnetic particles irreversibly break down between 360 and 400 c the contrast between the magnetic properties of sapropels and surrounding sediments is marked with remanence intensities of sapropels often being more than three orders of magnitude higher than those of underlying sediments the contrast between the magnetic properties of sapropels and the surrounding sediments is apparently controlled by non steady state diagenesis sulphate reducing conditions dominated during sapropel deposition while overlying sediments were deposited under oxic conditions the mineral responsible for the magnetic properties of sapropels is most likely to have formed under sulphate reducing conditions that existed during times of sapropel formation attempts to identify this mineral have been unsuccessful but several lines of evidence point toward an unknown ferrimagnetic iron sulphide phase the influence of diagenesis on the magnetic properties of cyclically deposited eastern mediterranean sedimentary sequences suggests that magnetic parameters may be a useful proxy for diagenesis in these sediments

stratigraphic evidence for a high marine shore line during the late weichselian deglaciation on the kullen peninsula southern sweden mineral magnetic properties and the carbon content of a sediment sequence in lake kullatorpssjon on the kullen peninsula in northwest scania southern sweden were investigated diatom and ostracod analyses were undertaken for palaeoecological reconstruction and a chronology was constructed from accelerator mass spectrometry ams radiocarbon dating of terrestrial plant remains and mosses five stratigraphical units were identified units 1 5 from oldest to youngest the two lowermost units consist of clay the lowest clay unit 1 is strikingly black 2 m thick and has magnetic properties dominated by high concentrations of authigenic greigite fe3s4 in contrast the overlying clay unit 2 is grey 1 18 m thick and has magnetic properties dominated by low concentrations of detrital magnetite fe3o4 a major palaeoecological change is reflected in the diatom flora and ostracod fauna at the transition from unit 1 to unit 2 the sediment stratigraphy geochemical mineral magnetic and palaeoecological analyses also point to a significant change in depositional environment at this transition which is proposed to represent the isolation of lake kullatorpssjon from the kattegat sea earlier investigations have determined the marine limit to ca 65 m a s l on the kullen peninsula the separate independent lines of evidence presented here however suggest that the late weichselian marine limit developed at 85 90 m a s l at the deglaciation ca 17 200 cal yr bp ca 14 500 yr bp this limit is ca 25 m higher than assumed previously lake kullatorpssjon formed ca 1000 cal yr later when the basin became isolated from the kattegat sea copyright c 1999 john wiley sons ltd less

nucleosynthetic w isotope anomalies and the hf w chronometry of ca al rich inclusions abstract ca al rich inclusions cai are the oldest dated objects formed in the solar system and are pivotal reference points in early solar system chronology knowledge of their initial 182hf 180hf and 182w 184w is essential not only for obtaining precise hf w ages relative to the start of the solar system but also to assess the distribution of short lived radionuclides in the early solar nebula however the interpretation of hf w data for cai is complicated by nucleosynthetic w isotope variations to explore their extent and nature and to better quantify the initial hf and w isotope compositions of the solar system we obtained hf w data for several fine and coarse grained cai from three cv3 chondrites the fine grained cai exhibit large and variable anomalies in e183w e i w equals 0 01 deviation from terrestrial values extending to much larger anomalies than previously observed in cai and reflecting variable abundances of s and r process w isotopes conversely the coarse grained mostly type b inclusions show only small if any nucleosynthetic w isotope anomalies the investigated cai define a precise correlation between initial e182w and e183w providing a direct empirical means to correct the e182w of any cai for nucleosynthetic isotope anomalies using their measured e183w after correction for nucleosynthetic w isotope variations the cai data define an initial 182hf 180hf of 1 018 0 043 10 4 and an initial e182w of 3 49 0 07 the hf w formation intervals of the angrites d orbigny and sahara 99555 relative to this cai initial is 4 8 0 6 ma in good agreement with al mg ages of these two angrites this renders a grossly heterogeneous distribution of 26al in the inner solar system unlikely at least in the region were cai and angrites formed

sulfur contents of the parental metallic cores of magmatic iron meteorites abstract magmatic iron meteorites are thought to be samples of the central metallic cores of asteroid sized parent bodies sulfur is believed to have been an important constituent of these parental cores but due to the low solubility of s in solid metal initial s contents for the magmatic groups cannot be determined through direct measurements of the iron meteorites however experimental solid metal liquid metal partition coefficients show a strong dependence on the s content of the metallic liquid thus by using the experimental partition coefficients to model the fractional crystallization trends within magmatic iron meteorite groups the s contents of the parental cores can be indirectly estimated modeling the au ga ge and ir fractionations in four of the largest magmatic iron meteorite groups leads to best estimates for the s contents of the parental cores of 12 1 5 wt for the iiiab group 17 1 5 wt for the iiab group and 1 1 wt for the ivb group the iva elemental fractionations are not adequately fit by a simple fractional crystallization model with a unique initial s content these s content estimates are much higher than those recently inferred from crystallization models involving trapped melt the discrepancy is due largely to the different partition coefficients that are used by the two models when only partition coefficients that are consistent with the experimental data are used the trapped melt model and the low s contents it advocates cannot match the ge and ir fractionations that are observed in iiiab iron meteorites

rock magnetic signatures in diagenetically altered sediments from the niger deep sea fan 1 diagenesis has extensively affected the magnetic mineral inventory of organic rich late quaternary sediments in the niger deep sea fan changes in concentration grain size and coercivity document modifications of the primary magnetic mineral assemblages at two horizons the first front the modern iron redox boundary is characterized by a drastic decline in magnetic mineral content coarsening of the grain size spectrum and reduction in coercivity beneath a second front the transition from the suboxic to the sulfidic anoxic domain a further but less pronounced decrease in concentration and bulk grain size occurs finer grains and higher coercive magnetic constituents substantially increase in the anoxic environment low and high temperature experiments were performed on bulk sediments and on extracts which have also been examined by x ray diffraction thermomagnetic analyses proved ferrimagnetic titanomagnetites of terrigenous provenance as the principal primary magnetic mineral components their broad range of titanium contents reflects the volcanogenic traits of the niger river drainage areas diagenetic alteration is not only a grain size selective process but also critically depends on titanomagnetite composition low titanium compounds are less resistant to diagenetic dissolution intermediate titanium content titanomagnetite thus persists as the predominant magnetic mineral fraction in the sulfidic anoxic sediments at the fe redox boundary precipitation of authigenic possibly bacterial magnetite is documented the presence of hydrogen sulfide in the pore water suggests a formation of secondary magnetic iron sulfides in the anoxic domain grain size specific data argue for a gradual development of a superparamagnetic and single domain iron sulfide phase in this milieu most likely greigite

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

182w and 187re 187os systematics of iron meteorites chronology for melting differentiation and crystallization in asteroids w isotopic compositions measured by n tims in five iron meteorite groups are used in conjunction with 187re 187os isotopic data to constrain the timing of metal segregation and crystallization respectively in the iron meteorite parent bodies fractionation of the parent isotope 182hf half life 9 2 ma from the daughter 182w likely occurred during segregation of metal from silicate in the iron meteorite parent bodies if w isotopic equilibrium was achieved between silicate and metal during metal segregation then the w isotopic compositions in the irons should record the timing of this event samples were taken from the five largest iron meteorite groups including the four magmatic groups iiab iiiab iva and ivb and the nonmagmatic iab iiicd group together these groups comprise approximately 90 by weight of iron meteorites classified so far with the exception of the iva group the groups have well defined 187re 187os isochron ages which are interpreted as the time of crystallization of the metal of their parent bodies within each magmatic group samples that crystallized both early and late in the sequence of each core were analyzed to evaluate possible evolution of the w isotopic composition during crystallization all the samples examined display very similar w values within a narrow range of compositions between 5 1 and 3 1 witzation began less than a few percent of additional metal was segregated to the cores moreover the average w values for the five groups have no resolvable difference ranging from 4 08 0 69 iva to 3 30 0 15 iab iiicd these data indicate that all of the iron meteorite parent bodies underwent metal segregation within 5 ma of each other apparently independent of their composition size and time of crystallization of the metal in all groups except the iiiab group there is a resolvable time interval between the timing of metal segregation as constrained by the w isotopic data and the initiation of core crystallization as given by the re os isotopic systematics

experiments on turbulent metal silicate mixing in a magma ocean we compare the results of laboratory fluid dynamics experiments with theoretical models of turbulent entrainment in two phase buoyant plumes and thermals to estimate the amount of mixing between the iron core of a planetesimal or planetary embryo and the molten silicates in a magma pool formed by its impact with a growing planet during accretion we demonstrate experimentally that turbulent plumes in immiscible fluids fragment into droplets and that the envelope of the droplet distribution is indistinguishable from the envelope of a turbulent plume in a single phase fluid under the same dynamical conditions implying that turbulent entrainment concepts are applicable to immiscible fluids mixing a series of experiments are made on the time evolution of a two phase turbulent thermal representing a planetesimal core falling under its own negative buoyancy in a spherical fluid representing an impact produced magma pool two stages of mixing are observed in these experiments the first corresponding to turbulent entrainment during free fall of the thermal the second corresponding to entrainment in turbulent gravity currents that form after the thermal reaches the base of the magma pool we demonstrate that the amount of mixing between metals and silicate liquids in a magma pool depends on the rouse number of the metal fragments and increases rapidly with the radius of the proto planet we derive a similarity model for metal silicate mixing in a spherical magma pool assuming a constant entrainment coefficient for the turbulent liquid metal phase this model supports our experimental finding that a small metal core of an impactor will become diluted i e mix within a deep magma pool but a large impacting core will not fully dilute before reaching the base of the magma pool

a record of reversed polarity carried by the iron sulphide greigite in british early pleistocene sediments abstract palaeomagnetic measurements were made on samples extracted from a short sequence of early pleistocene estuarine clays now exposed in a sea cliff near sheringham on the north norfolk coast uk on the basis of earlier palynological work these clays had been ascribed a pastonian late tiglian age the clays show marked changes in colour from reddish brown at the top of the unit to blue grey in the middle and grey brown at the base the palaeomagnetic data vary in close association with these colour changes the top and basal brown clays show scattered normal directions of low intensity while the middle blue clays show strongly clustered reversed directions of much higher intensities some samples taken from the boundary between the middle blue and upper red clays show upon demagnetisation a normal overprint on a stable reversed polarity using high gradient magnetic extraction magnetic concentrates have been obtained from the strongly magnetic middle blue clays the presence of iron sulphide minerals in these concentrates was identified using energy dispersive x ray analysis during scanning electron microscopy more specifically x ray diffraction identifies greigite as the only detectable ferrimagnetic mineral in the magnetic concentrates rock magnetic measurements show clear qualitative differences in the magnetic mineralogies of the three clay subunits but absolute identification of the magnetic mineralogy of the weakly magnetic upper and basal brown clays has not yet been possible we interpret the sequence as a primary reversed polarity record this record is carried by the iron sulphide greigite as a chemical remanence acquired during syn depositional reduction of iron via the decomposition of organic material in these anoxic tidal clays subsequently the upper and basal subunits of the clay have been oxidised by permeation of groundwater from the adjacent coarse grained sediments most of the griegite in the oxidised margins of the clay has been altered as a result to a new less efficient magnetic recording material which thus carries a later scattered low intensity normal overprint

geodesy constraints on the interior structure and composition of mars abstract knowledge of the interior structure of mars is of fundamental importance to the understanding of its past and present state as well as its future evolution the most prominent interior structure properties are the state of the core solid or liquid its radius and its composition in terms of light elements the thickness of the mantle its composition the presence of a lower mantle and the density of the crust in the absence of seismic sounding only geodesy data allow reliably constraining the deep interior of mars those data are the mass moment of inertia and tides they are related to mars composition to its internal mass distribution and to its deformational response to principally the tidal forcing of the sun here we use the most recent estimates of the moment of inertia and tidal love number k2 in order to infer knowledge about the interior structure of the mars we have built precise models of the interior structure of mars that are parameterized by the crust density and thickness the volume fractions of upper mantle mineral phases the bulk mantle iron concentration and the size and the sulfur concentration of the core from the bulk mantle iron concentration and from the volume fractions of the upper mantle mineral phases the depth dependent mineralogy is deduced by using experimentally determined phase diagrams the thermoelastic properties at each depth inside the mantle are calculated by using equations of state since it is difficult to determine the temperature inside the mantle of mars we here use two end member temperature profiles that have been deduced from studies dedicated to the thermal evolution of mars we calculate the pressure and temperature dependent thermoelastic properties of the core constituents by using equations state and recent data about reference thermoelastic properties of liquid iron liquid iron sulfur and solid iron to determine the size of a possible inner core we use recent data on the melting temperature of iron sulfur within our model assumptions the geodesy data imply that mars has no solid inner core and that the liquid core contains a large fraction of sulfur the absence of a solid inner is in agreement with the absence of a global magnetic field we estimate the radius of the core to be 1794 65 km and its core sulfur concentration to be 16 2 wt we also show that it is possible for mars to have a thin layer of perovskite at the bottom of the mantle if it has a hot mantle temperature moreover a chondritic fe si ratio is shown to be consistent with the geodesy data although significantly different value are also possible our results demonstrate that geodesy data alone even if a mantle temperature is assumed can almost not constrain the mineralogy of the mantle and the crust in order to obtain stronger constraints on the mantle mineralogy bulk properties like a fixed fe si ratio have to be assumed

early holocene history of the baltic sea as reflected in coastal sediments in blekinge southeastern sweden integrated palaeoecological studies of two fiord sediment sequences in the province of blekinge se sweden covering the time span 11 000 5000 cal bp reveal the timing and the environment for the ancylus lake littorina sea transition 9800 8500 cal bp the first ingression of saline water into the baltic sea through the danish straits occurred earlier than formerly assumed new evidence particularly mineral magnetic and palaeobotanical analyses demonstrate that on the general trend of the eustatically caused littorina transgression several minor fluctuations of the water level can be identified between 8500 and 5000 cal years bp a distinct regression phase around 8 100 cal bp is correlated with the greenland ice core cold event dated to 8200 ice core years bp this is described as a regional climatic catastrophe for the baltic sea region the coastal stratigraphy is compared with the offshore stratigraphy earlier studied a tentative shore displacement curve for early and middle holocene is presented

viscosity measurements of subliquidus magmas alkali olivine basalt from the higashi matsuura district southwest japan abstract we carried out viscosity measurements and sampling of a crystal suspension derived from alkali olivine basalt from the matsuura district sw japan at subliquidus temperatures from 1230 c to 1140 c under 1 atm with nno oxygen buffered conditions viscosity increased from 31 to 1235 pa s with a decrease in temperature from 1230 to 1140 c on cooling olivine first appeared at 1210 c followed by plagioclase at 1170 c the crystal content of the sample attained 31 vol at 1140 c plagioclase 22 olivine 9 non newtonian behaviors including thixotropy and shear thinning were pronounced in the presence of tabular plagioclase crystals the cause of such behavior is discussed in relation to shear induced changes in melt crystal textures relative viscosities r s m where s and m are the viscosities of the suspension and the melt respectively were obtained by calculating melt viscosities from the melt composition and temperature at 1 atm using the equation proposed by giordano and dingwell giordano d dingwell d b 2003 non arrhenian multicomponent melt viscosity a model earth and planetary science letters 208 337 349 the obtained relative viscosities are generally consistent with the einstein roscoe relation which represents r for suspensions that contain equant and equigranular crystals even though the crystal suspension analyzed in the present experiments contained tabular plagioclase and granular olivine of various grain sizes this consistency is attributed to the fact that the effect of crystal shape was counterbalanced by the effect of the dispersion of crystal size the applicability of the einstein roscoe equation with respect to crystal shape is discussed on the basis of the present experimental results our experiments and those of sato sato h 2005 viscosity measurement of subliquidus magmas 1707 basalt of fuji volcano journal of mineralogical and petrological sciences 100 133 142 show that the relationship between relative viscosity and crystal fraction is consistent with the einstein roscoe relationship for axial ratios that are smaller than the critical value of 4 6 5 but discrepancies occur for higher ratios

greigite from carbonate concretions of the ediacaran doushantuo formation in south china and its environmental implications abstract greigite fe 3 s 4 is a ferrimagnetic iron sulfide that commonly forms as a precursor of pyrite in anoxic environments where the supply of reactive fe outpaces that of sulfide h 2 s and hs because of its metastability and sensitivity to redox changes during burial greigite has been rarely documented in rocks older than the cretaceous here we report well preserved greigite in carbonate concretions of the upper doushantuo formation ca 551 ma in the yangtze gorge area south china greigite in the carbonate concretions coexists with anhedral and framboidal pyrite and is distributed in clay rich carbonates with card house microtextures and dolomitic spherical structures indicative of early diagenetic formation during shallow burial preservation of greigite in carbonate concretions of the upper doushantuo formation implies that these concretions maintained a closed micro system since their formation and that they provide information about the ancient depositional and early diagenetic environments

magnetostratigraphy of a greigite bearing core from the south yellow sea implications for remagnetization and sedimentation sediments from the continental shelf are sensitive to sea level climatic changes and local tectonic history in this study we carried out a high resolution magnetostratigraphic investigation on the longest core nhh01 125 64 m recovered from the south yellow sea sys an abnormal interval dominated by negative inclinations was discovered by applying alternating field demagnetization afd on samples from a greigite bearing layer 44 90 51 80 m in contrast the inclinations of most greigite bearing samples changed from negative to positive when heated to 360 c this strongly indicates that this inclination anomaly revealed by the afd alone is not a true negative subchron after neglecting the effects of greigite bearing layers the straightforward correlation of the interpreted magnetostratigraphy defines the matuyama brunhes boundary 781 ka and the jaramillo top 990 ka at 68 64 m and 101 54 m respectively the linearly extrapolated basal age of the core is 1 10 ma in addition several short lived inclination anomalies can be tentatively assigned to magnetic excursions which indicates that the sedimentation could be continuous even at the millennial time scale at depth intervals bracketing these fast geomagnetic events moreover the excellent correspondence between clay content variations of the core and the marine oxygen isotope record indicates the potential of clay content as a paleoclimatic proxy in the studied region in the past 1 ma in brief our study provides not only a robust age model in the sys but also a methodological guide for paleomagnetic studies in continental shelf region

sea level change and remagnetization of continental shelf sediments off new jersey odp leg 174a magnetite and greigite diagenesis summary palaeomagnetic and rock magnetic studies were performed on a seaward transect of continental shelf sediments from sites 1071 and 1072 of ocean drilling programme leg 174a on the new jersey margin the sediments recorded a polarity change from reversed to normal which was tentatively interpreted as the matuyama brunhes boundary the polarity boundary is closely correlated with the sequence boundary pp3 s which is considered to have formed as an erosional unconformity during regression and subsequent transgression related to global eustacy rock magnetic analyses indicate that the sediment contains comparable amounts of magnetite and greigite fe3s4 with possible trace amounts of haematite a marked change in rock magnetic properties is recorded at site 1072 with an increase in greigite concentration at the polarity boundary 62 4 metres below seafloor where the grain size does not change at site 1071 greigite is dominant from 2 m below pp3 s to 0 8 m above it these intervals are characterized by higher peak coercivities of remanence and subdued remanence in both the magnetite and greigite components palaeomagnetic analysis indicates that the intervals just below pp3 s have dual component magnetizations of reversed polarity and are considered to have been deposited during the matuyama chron c1r 1r and were possibly remagnetized during the brunhes chron through the formation of the pp3 s surface detrital magnetite and early diagenetic greigite might have carried the reversed polarity magnetization during the formation of pp3 s in the brunhes chron greigite might have formed at the oxidation front with ongoing downward formation due to oxidation of pyrite by percolating fresh water which might be a cause of the remagnetization our study indicates that careful rock magnetic investigation is necessary for magnetostratigraphic studies of continental shelf deposits in order to recognize remagnetizations induced by sea level changes

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

high iron glaucony from the continental shelf of the yellow sea off the southwestern korean peninsula abstract massive fractured and porous types of glauconies are found in subtidal sand and semi consolidated sand mud deposits from the continental shelf of the southeastern yellow sea thermal treatments on powdered glaucony increase the x ray intensity near 10 a suggesting the presence of some expandable layers ferric iron and mg 0 35 0 54 atoms progressively substitute for al from porous to massive glauconies a higher proportion of expandable layers is also observed with apparent increases from porous to massive type the clay preserved is ordered disordered massive to fractured type and interstratified illite smectite porous type containing 7 27 expandable layers glauconies from the yellow sea apparently form after deposition in reducing environments at the interface between dissolving clay minerals and degrading biogenic debris