petrogenesis of the elephant moraine a79001 meteorite multiple magma pulses on the shergottite parent body abstract the eeta 79001 achondrite consists of two distinct igneous lithologies joined along a planar non brecciated contact both are basaltic rocks composed primarily of pigeonite augite and maskelynite but one contains zoned megacrysts of olivine orthopyroxene and chromite that represent disaggregated xenoliths of harzburzite both lithologies probably formed from successive volcanic flows or multiple injections of magma into a small shallow chamber many similarities between the two virtually synchronous magmas suggest that they are related possible mechanisms to explain their differences involve varying degrees of assimilation fractionation from similar parental magmas or partial melting of a similar source peridotite of these assimilation of the observed megacryst assemblage seems most plausible however some isotopic contamination may be required in any of these petrogenetic models the meteorite has suffered extensive shock metamorphism and localized melting during a large impact event that probably excavated and liberated it from its parent body both basaltic lithologies and the inferred ultramafic protolith of the megacryst assemblage are petrologically similar to other members of the shergottite group and all may have been derived from a volcanic plutonic complex on a planetary body

ultrahigh pressure macro diamonds from copeton new south wales australia based on raman spectroscopy of inclusions abstract mining of cenozoic alluvial deposits at copeton and bingara eastern australia has produced two million macrodiamonds 0 25 ct median size raman spectroscopy is used to identify included minerals within uncut copeton diamonds with sealed chamber remnant pressures of 31 7 to 35 6 kbar for coesite 13 6 and 22 7 kbar for clinopyroxene and 7 6 kbar for grossular garnet assuming elastic behaviour these values generate inclusion entrapment pt loci which intersect restricting diamond formation conditions from 250 c 43 kbar to 800 c 52 kbar larger than error 100 c and 4 kbar this range shows a systematic variation in inclusion composition with diamond zoning and n properties published research shows 1 copeton and bingara diamonds are unique and 2 modern alluvium in the bingara district carries mantle formed garnet captured by post tectonic alkali basalt from an extensive diamondiferous ultrahigh pressure uhp terrane that stalled at depth because it is dominated by mafic eclogite the combined raman and geological results indicate two sets of subduction uhp diamond formation conditions protolith are required firstly cooler oceanic slab and secondly including higher temperature continental crust the copeton and bingara stones are uhp macrodiamonds and carboniferous 40 ar 39 ar age dates on clinopyroxene inclusions should be interpreted as ages of crystallisation representing the termination of subduction the characteristic features of ruptured inclusions and etched percussion marks on copeton and bingara diamond indicate volcanic delivery to the earth s surface alluvial deposits elsewhere in eastern australia may carry similar diamond along with diamond of different origin

constraints on mantle anelasticity from geodetic observations and implications for the j2 anomaly summary we use geodetic observations of the earth to constrain anelasticity in the earth s mantle at periods between 12 hr and 18 6 yr the observations include satellite laser ranging slr measurements of 12 hr and 18 6 yr tides in the j 2 component of the gravity field spacebased observations of tidal variations in the earth s rotation rate and optical and space based measurements of the chandler wobble period and damping these geophysical signals are mostly sensitive to the lower mantle the results suggest the dissipative process could consist of a single absorption band that extends across seismic periods out at least as far as 20 yr the results also require values of the anelastic parameter q that are smaller than those required by seismic observations we interpret this as evidence that q in the lower mantle is frequency dependent the frequency dependence suggested by the geodetic observations is reasonably consistent with laboratory measurements though those measurements have only been done on rocks at upper mantle conditions after fitting and removing the 18 6 yr tide from the slr j 2 results we find that the 1998 2002 anomaly present in the original j 2 observations is no longer a singular anomaly in the j 2 residuals but becomes one of a series of maxima in a quasi decadal oscillation

improved estimates of the dynamical state of the north pacific ocean from a 4 dimensional variational data assimilation 1 a 4 dimensional variational data assimilation system has been used to better define the mean seasonal state of the north pacific the synthesis of available observational records and a sophisticated general circulation model produces a dynamically consistent time varying dataset which exhibits realistic features of the global ocean circulation and requires no artificial sources or sinks for the temperature and salinity fields the dataset enables us to clarify the water mass formation and movement processes a sensitivity experiment using our system reveals that the origin of the north pacific intermediate water can be traced back to the okhotsk and bering seas in the subarctic region and to the subtropical kuroshio region further south consistent with recent observational findings this result illustrates that the ocean state derived from our data assimilation has greater information and forecast potential than that obtained from earlier methods

pacific bidecadal climate variability regulated by tidal mixing around the kuril islands 1 18 6 year period variability has been detected in various aspects of the climate especially in and around the pacific ocean although it is believed to be caused by 18 6 year period tidal cycle no study has directly shown how the tidal cycle regulates such variability using a state of the art climate model we show that the 18 6 year cycle in strong tidal mixing localized around the kuril islands induces 18 6 year periodicity in el nino southern oscillation like pacific climate variability influence of the tidal mixing propagates along the pacific western rim as coastally trapped waves temperature anomaly is generated in the subsurface western equatorial pacific which propagates along the equatorial thermocline and eventually excites 18 6 year periodicity in the equatorial sea surface temperature

raman spectroscopy for mineral identification and quantification for in situ planetary surface analysis a point count method quantification of mineral proportions in rocks and soils by raman spectroscopy on a planetary surface is best done by taking many narrow beam spectra from different locations on the rock or soil with each spectrum yielding peaks from only one or two minerals the proportion of each mineral in the rock or soil can then be determined from the fraction of the spectra that contain its peaks in analogy with the standard petrographic technique of point counting the method can also be used for nondestructive laboratory characterization of rock samples although raman peaks for different minerals seldom overlap each other it is impractical to obtain proportions of constituent minerals by raman spectroscopy through analysis of peak intensities in a spectrum obtained by broad beam sensing of a representative area of the target material that is because the raman signal strength produced by a mineral in a rock or soil is not related in a simple way through the raman scattering cross section of that mineral to its proportion in the rock and the signal to noise ratio of a raman spectrum is poor when a sample is stimulated by a low power laser beam of broad diameter results obtained by the raman point count method are demonstrated for a lunar thin section 14161 7062 and a rock fragment 15273 7039 major minerals plagioclase and pyroxene minor minerals cristobalite and k feldspar and accessory minerals whitlockite apatite and baddeleyite were easily identified identification of the rock types kreep basalt or melt rock from the 100 location spectra was straightforward

strong vertical mixing in the urup strait 1 microstructure measurements were conducted in one of the kuril straits in the summer of 2007 over the course of 1 day of repeated observations across the pacific side of the steep sill of the urup strait extremely strong mixing was observed during periods of pacific ward down sill flows and during the transition from pacific ward to okhotsk ward up sill flows with a turbulent energy dissipation rate of 10 6 to 10 5 w kg 1 and vertical diffusivity of 10 1 to 5 10 1 m2 s 1 during the period of strong mixing we observed homogeneous layers with a thickness of 300 600 m and potential density of 26 6 26 7 occupying the entire water column in one case high values of within this layer indicate the injection of diapycnal flows from the upper and lower layers possibly contributing to southward intrusion of intermediate water into the subtropical gyre

a doubling of the post perovskite phase boundary and structure of the earth s lowermost mantle a new model of the deep earth allows geophysicists to measure variations in earth s temperature near the boundary between the rocky mantle and core using a recently discovered phase change in the lowest part of the earth s mantle where atoms rearrange themselves in crystals under extreme pressure and temperature the model also explains odd features of this part of the mantle such as patchy regions that reflect seismic waves generated by large earthquakes and inferences of dense partial melting combined with observations the results imply very large variations in temperature providing further evidence for circulation of material throughout the earth s mantle the thermal structure of the earth s lowermost mantle the d layer spanning depths of 2 600 2 900 kilometres1 is key to understanding the dynamical state and history of our planet earth s temperature profile the geotherm is mostly constrained by phase transitions such as freezing at the inner core boundary or changes in crystal structure within the solid mantle that are detected as discontinuities in seismic wave speed and for which the pressure and temperature conditions can be constrained by experiment and theory a recently discovered phase transition at pressures of the d layer2 3 4 is ideally situated to reveal the thermal structure of the lowermost mantle where no phase transitions were previously known to exist here we show that a pair of seismic discontinuities observed in some regions of d can be explained by the same phase transition as the result of a double crossing of the phase boundary by the geotherm at two different depths this simple model can also explain why a seismic discontinuity is not observed in some other regions and provides new constraints for the magnitude of temperature variations within d

constraints on short term mantle rheology from the j observation and the dispersion of the 18 6 y tidal love number abstract the nature of short term mantle rheology for timescales between the seismic frequency band and a few hundred years remains relatively unknown we have made use of two pieces of information which have emerged as a consequence of the recent acquisition of data from the lageos satellite to place some contraints on the rheological parameters of short term mantle rheology the first is the secular variation of the gravitational harmonic j the second is the amount of dispersion of the tidal love number for the 18 6 y tide which has been inferred to be 20 two types of rheology have been considered the first is a frequency dependent q rheology an analytical expression for the transformed shear modulus has been developed from the truncated retardation spectrum explicitly for this purpose the second anelastic rheology we have used is a standard linear solid where the parameters of importance are the relaxation strength and the short term viscosity 2 rheological parameters of the frequency dependent q model previously proposed by lambeck and nakiboglu to explain the dispersion of the tidal love number for a 18 6 y period are found to produce too much dispersion for the chandler wobble and to yield seismic q s between o 103 and o 104 for fundamental toroidal modes which are not compatible with the data we have used instead a three layer model consisting of an elastic lithosphere a mantle with a standard linear solid rheology whose debye peak lies beyond the long time cutoff of the retardation spectrum and an inviscid core for relaxation strength of around 1 and short term viscosity 2 j would result from earthquake excitation a sharp decrease of the tidal dispersion takes place for 2 5 1020 p and 1 0 for smaller values of relaxation strength 0 15 the maximum tidal dispersion is only 9 and decreases gradually as 2 is increased beyond 5 1020 p we have found that the maximum dispersion caused by the maxwell rheology is small around 5 even for asthenospheric viscosities of o 1018p these results suggest that the datum of 18 6 y tidal dispersion can be utilized eventually to place constraints on potential candidates of short term mantle rheology

the viscosity structure of the d layer of the earth s mantle inferred from the analysis of chandler wobble and tidal deformation abstract the viscosity structure of the d layer of the earth s mantle is inferred from the decay time of the chandler wobble and semi diurnal to 18 6 years tidal deformations combined with model viscosity depth profiles corresponding to a range of temperature depth models we use two typical temperature profiles of the d layer by considering its dynamic state i bottom thermal boundary layer of the mantle convection tbl model and ii vigorously small scale convecting layer con model three possible models are derived from the comparison between the numerical and observationally inferred decay times of chandler wobble and tidal deformation the first and second models are those with a viscosity of 10 16 pa s at the core mantle boundary the temperature gradient for the first one tbl model with a thickness of the d layer l of 200 km is nearly constant within the d layer the second one tbl and con models with l 300 km requires that the temperature gradient of the lower part 100 km thickness is larger than that of the upper part the temperature increases within the d layer for these two models are larger than 1500 k the third model has a constant low viscosity layer 100 km thickness and viscosity smaller than 10 17 pa s at the bottom of the d layer in tbl l 200 and 300 km and con l 300 km models the temperature increases would be 1000 1600 k depending on the viscosity at the top of the d layer 10 21 10 22 pa s the heat flows from the core to the mantle for these three models are estimated to be larger than 5 tw the third model may be preferable after comprehensively taking account of the fitness of the decay time of the chandler wobble and the tidal deformations for each model

glacial isostatic adjustment i the forward problem summary the isostatic adjustment of a radially stratified visco elastic spheroid is treated using space time green functions for the associated surface mass load boundary value problem these impulse response functions are convolved with a heaviside function to give the time dependent deformation of the planet which would be produced by a unit point mass brought up from infinity at t 0 and allowed to remain on the surface the resulting heaviside green functions can be employed to simulate all of the important signatures of glacial isostatic adjustment given a space time dependent surface mass load consisting of ice sheet ablation histories and a model of the simultaneous filling of the ocean basins these source terms are simply convolved with the heaviside green function appropriate to a specific response signature a realistic model of the spatial distribution of the main late pleistocene ice loads and of their temporal disintegration is constructed the response of two visco elastic earth models is computed and compared to a global set of relaxation data relative sea level curves on the basis of this initial comparison of theory and observation the possibility that the lower mantle has a viscosity which is significantly in excess of the viscosity of the upper mantle is excluded in addition clear evidence of the presence of the lithosphere has been found in relaxation data from sites which were near the edge of the laurentide ice sheet such data should therefore prove useful as a basis for analysis of lateral variations in lithosphere thickness further extensions of the calculation are suggested

pleistocene deglaciation and the earth s rotation implications for mantle viscosity summary recent results from the analysis of postglacial rebound data suggest that the viscosity of the earth s mantle increases through the transition region models which fit both relative sea level and free air gravity data have viscosities which increase from a value near 1022 poise in the upper mantle beneath the lithosphere to a value of about 1023 poise in the lower mantle in this paper we analyse the effect of deglaciation upon the earth s rotation and thereby show that the observed secular trend polar wander evident in the ils ipms pole path and measurements of the non tidal acceleration of the length of day are both consistent with the viscosity profile deduced from postglacial rebound the two analyses are therefore mutually reinforcing

geochemistry petrology and cooling history of 14161 7373 a plutonic lunar sample with textural evidence of granitic fraction separation by silicate liquid immiscibility we report new findings related to sample 14161 7373 the first analyzed lunar intrusive rock to show textural evidence for the formation of granitic material by silicate liquid immiscibility sli and geochemical evidence for separation of that material at least on a small scale from mafic residua ion microprobe analyses of rare earth element ree concentrations in silicates record the compositional evolution of this late stage assemblage for a sample whose bulk assemblage that of whitlockite monzogabbro has ree concentrations at 5 6 kreep levels the silicates have only moderately high ree concentrations the calculated ree concentrations of melt in equilibrium with pigeonite after re integration of pigeonite host and augite lamellae is approximately 2 high k kreep the high bulk ree concentrations of the assemblage are the result of a high proportion of whitlockite probably an excess i e the assemblage is a whitlockite cumulate variations in silicate ree concentrations reflect the co crystallization of whitlockite which we interpret to have begun crystallizing prior to the onset of late stage immiscibility of the felsic melt fraction calculated cooling rates based on a quantitative model of pyroxene exsolution reveal a two stage thermal history which involved initial crystallization at a minimum depth of 700 800 m during which the primary augite and pigeonite grains unmixed to form the observed host lamella pairs unusual compositional profiles close to the host lamella interface are consistent with a second stage of mild reheating followed by rapid cooling at a depth of 30 m most likely in an ejecta blanket the shallow depth of origin indicated for 14161 7373 is consistent with other studies of evolved lunar intrusive rocks supporting the interpretation that lunar qmd and granite as found among the apollo samples are late stage differentiates of high level intrusions and are not related to differentiation of deep crustal kreep reservoirs

raman spectroscopy as a method for mineral identification on lunar robotic exploration missions fiber bundle that carried the laser beam and returned the scattered radiation could be placed against surfaces at any desired angle by a deployment mechanism otherwise the instrument would need no moving parts a modem micro raman spectrometer with its beam broadened to expand the spot to 50 gm diameter and set for low resolution 7 cm in the 100 1400 cm region relative to 514 5 nm excitation was used to simulate the spectra anticipated from a rover instrument we present spectra for lunar mineral grains 1 mm soil fines breccia fragments and glasses from frequencies of olivine peaks we derived sufficiently precise forsteritc contents to correlate the analyzed grains to known rock types and we obtained appropriate forsteritc contents from weak signals above background in soil fines and breccias peak positions of pyroxenes were sufficiently well determined to distinguish among orthorhombic monoclinic and triclinic pyroxenoid structures additional information can be obtained from pyroxene spectra but requires further laboratory calibration plagioclase provided sharp peaks in soil fines and most breccias even when the glass content was high

some mineral physics constraints on the rheology and geothermal structure of earth s lower mantle we explore the implications of recent mineral physics measurements of diffusion coefficients and melting temperatures of lower mantle materials on the rheological and geothermal structure of earth s lower mantle we show that mgsio3 perovskite is significantly stronger than mgo periclase and therefore the rheology of the lower mantle depends strongly on the geometry of a weaker phase periclase we calculate viscosities of the lower mantle for two cases 1 where periclase occurs as isolated grains and 2 where periclase occurs as continuous films using mineral physics data and models of two phase rheology we find that the effective viscosity for the former is about 10 1000 times higher than the latter we therefore suggest that the rheology of the lower mantle is structure and hence strain dependent leading to weakening at large strains due to the formation of continuous films of periclase overall depth variation of viscosity depends not only on the pressure dependence of creep but also on the geothermal gradient both mgsio3 perovskite and periclase have relatively small activation energies e g r t m with g 10 14 where r is the gas constant and t m is melting temperature and therefore the depth variation of viscosity is rather small even for a nearly adiabatic temperature gradient however the geothermal gradients consistent with the geodynamical inference of nearly depth independent viscosity are sensitive to the pressure dependence of viscosity which is only poorly understood a superadiabatic gradient of up to 0 6 k km is also consistent with mineral physics and geodynamical observations

characterization and comparison of structural and compositional features of planetary quadrilateral pyroxenes by raman spectroscopy this study reports the use of raman spectral features to characterize the structural and compositional characteristics of different types of pyroxene from rocks as might be carried out using a portable field spectrometer or by planetary on surface exploration samples studied include lunar rocks martian meteorites and terrestrial rocks the major structural types of quadrilateral pyroxene can be identified using their raman spectral pattern and peak positions values of mg mg fe ca of pyroxene in the mg fe ca quadrilateral can be determined within an accuracy of 0 1 the precision for ca mg fe ca values derived from raman data is about the same except that corrections must be made for very low ca and very high ca samples pyroxenes from basalts can be distinguished from those in plutonic equivalents from the distribution of their mg mg mg fe and wo values and this can be readily done using point counting raman measurements on unprepared rock samples the correlation of raman peak positions and spectral pattern provides criteria to distinguish pyroxenes with high proportions of non quadrilateral components from mg fe ca quadrilateral pyroxenes

numerical study on the impact of the 18 6 year period nodal tidal cycle on water masses in the subarctic north pacific 1 a series of numerical experiments is performed to test the hypothesis that temporal variations in localized strong tidal mixing related to the 18 6 year period nodal tidal cycle induce water mass variations it is suggested that enhanced mixing around the bering sea as that around the okhotsk sea have an impact on water masses broadly in the north pacific including the bering sea and the okhotsk sea oscillatory tidal mixing with a 18 6 year period reproduces water mass variations in salinity and isopycnal potential temperature around the subarctic north pacific that are qualitatively consistent with observed variations when the amplitude of oscillatory vertical diffusivity is 15 of the long term mean and even when the amplitude is as small as 3 cm2 s as obtained for a long term mean of 20 cm2 s the amplitude of the salinity variation near regions of strong mixing is smaller than but on the same order of magnitude as that observed the induced salinity anomaly spreads broadly over a distance of several hundreds of kilometers by mean currents with a short lag time of less than 3 years and is suggested to influence the model winter mixed layer over broad regions these results support the hypothesis stated above and suggest that it is necessary to clarify spatial and temporal variations in tidal mixing to reproduce both the mean states of and temporal variations in water masses of the subarctic north pacific

apatite glaucony association in the ediacaran doushantuo formation south china and implications for marine redox conditions abstract major phosphogenic events took place in the late paleoproterozoic and the ediacaran both of which followed an episode of atmospheric oxygenation these apparent coincidences have led to suggestions that the precambrian phosphorus cycle was partly regulated by oceanic redox conditions although direct evidence is lacking in this paper we report the discovery of glaucony in drill cores from the phosphorite rich ediacaran doushantuo formation at weng an south china which provides new insights into redox conditions and geochemical cycles during the deposition and early diagenesis of the lower doushantuo formation the presence of flaser and lenticular bedding in the sandstones suggests deposition in a tidally influenced shallow water environment apatite is present as millimeter scale flasers in sandstones but more commonly as intraclastic grains glaucony typically occurs as interstitial aggregates cementing and replacing detrital minerals and phosphatic grains with an upsection decrease in abundance the doushantuo glauconies have consistently high k2o 7 6 9 6 wt in particular phosphorite hosted glaucony has generally higher total iron tfe2o3 than sandstone hosted glaucony consistent with al3 fe3 substitution in the octahedral site as supported by raman peaks slightly shifted towards lower wavenumbers for higher fe content a decrease in detrital input probably resulted in limited al availability during early diagenesis which in turn led to the waning of glaucony upsection the phosphate grains do not show any negative ce anomalies consistent with precipitation of authigenic apatite in suboxic environments with insignificant preferential remobilisation of ce during deposition and early diagenesis ree y features show variable diagenetic ree enrichment in phosphorites but identical concave down patterns the wide occurrence of glaucony cement further documents the presence of a generally suboxic early diagenetic environment on the seafloor which was in active exchange with bottom seawater slight fluctuations of redox states in the porewater and bottom water would have promoted the cycling of fe enrichment of phosphate and ree and extensive glaucony authigenesis therefore the glaucony bearing phosphorites in the doushantuo formation are a direct result of fe redox driven diagenesis apatite glaucony association likely forms in suboxic environments and is considered as a useful mineralogical proxy for paleoredox conditions on the precambrian ocean floors

fine and microstructure observations in the urup strait kuril islands during august 2006 1 for the first time we performed continuous observations of turbulent mixing upon the sill of the urup strait kuril islands for a period of 1 day during august of 2006 time series of velocity profiles water properties and isopycnal depths show variability with a period of about 1 day however the water mass variability is not explained by simple water exchange between the sea of okhotsk and the north pacific empirical orthogonal function eof analysis of isopycnal coordinates extracted variability presumed to represent tidal flows as major eofs in profiles of the residual flow after subtracting the mean flow and major eofs we detected phase propagations consistent with internal gravity waves with an approximate period of 9 1 11 4 h the turbulent energy dissipation rate and vertical diffusivity k ranged from 1 10 9 to 3 10 8 w kg 1 and from 3 10 5 to 2 10 3 m2s 1 respectively occurrences of high dissipation rates generally corresponded to either strong shear or weak stratification a significant contribution of shear s to the dissipation rate was indicated with a relationship of s1 4 s1 8 probably related to propagating internal waves a strong mixing event was observed within the water column with extremely weak stratification and a richardson number below the critical value of 0 25 when the flow direction changed from up sill to down sill

genesis of compositional characteristics of stillwater an i and an ii thick anorthosite units a single 10 m 10 m outcrop of stillwater anorthosite unit an ii was mapped for pyroxene mode on a decimeter scale and samples from each range of pyroxene proportion were analyzed for major and trace elements distinct one to several square meter regions of different pyroxene mode were observed samples from regions with 10 pyroxene showed strong elemental correlations and anticorrelations with mgo concentrations that can be interpreted in terms of the following scheme for development of the stillwater anorthosites aggregates containing 50 to 80 cumulus plagioclase average 67 formed stable frameworks in a crystal mush of complexly zoned plagioclase the interstices among the plagioclase grains in these frameworks filled in part with pyroxene and plagioclase that were produced in equilibrium with the bulk melt and in part with pyroxene and plagioclase derived by crystallization of trapped intercumulus liquid the proportions of these three types of materials were mutually constrained in a manner that gave rise to lines instead of fields on two element variation diagrams samples richest in cumulus plagioclase are also richest in intercumulus plagioclase and pyroxene regions of the outcrop with 10 original pyroxene underwent substantial alteration by hydrous fluids that produced variations in fe2o3 tio2 loi and most incompatible trace elements

high pressure minerals in mafic microgranular enclaves evidences for co mingling between lamprophyric and syenitic magmas at mantle conditions mafic microgranular enclaves composed of diopside and rare magnesium biotite phenocrysts in a groundmass of diopside biotite apatite fe ti oxides and alkali feldspar are associated with neoproterozoic piquiri potassic syenite in southern brazil co genetic mica and clinopyroxene cumulates present inclusions of pyrope rich garnet in diopside phenocrysts textural evidence as well as the chemical and mineralogical composition suggest that enclaves crystallized from a lamprophyric magma and co mingled with the host syenitic magma the contrasting temperature between both magmas and the consequent chilling was important for the preservation of some early crystallized minerals in the mafic magma diopside groundmass grains contain micro inclusions of k rich augite and phlogopite and some clinopyroxene phenocrysts and elongate groundmass crystals have potassium rich cores the pyrope rich garnet have high mg number 67 68 with appreciable amounts of na2o and k2o comparable to pyrope synthesized at 5 gpa the extremely high k2o contents of k rich augite micro inclusions suggest non equilibrium with the parental magma whereas the other k rich clinopyroxenes are similar to k clinopyroxenes produced at 5 6 gpa k clinopyroxene and garnet in mafic microgranular enclaves suggest that lamprophyric magma started its crystallization at upper mantle conditions and chilled clinopyroxenes with measurable amounts of k2o are taken as evidence that co mingling began still at mantle pressures

low viscosity of the bottom of the earth s mantle inferred from the analysis of chandler wobble and tidal deformation abstract viscosity of the d layer of the earth s mantle the lowermost layer in the earth s mantle controls a number of geodynamic processes but a robust estimate of its viscosity has been hampered by the lack of relevant observations a commonly used analysis of geophysical signals in terms of heterogeneity in seismic wave velocities suffers from major uncertainties in the velocity to density conversion factor and the glacial rebound observations have little sensitivity to the d layer viscosity we show that the decay of chandler wobble and semi diurnal to 18 6 years tidal deformation combined with the constraints from the postglacial isostatic adjustment observations suggest that the effective viscosity in the bottom 300 km layer is 1019 1020 pa s and also the effective viscosity of the bottom part of the d layer 100 km thickness is less than 1018 pa s such a viscosity structure of the d layer would be a natural consequence of a steep temperature gradient in the d layer and will facilitate small scale convection and melt segregation in the d layer

development of the mars microbeam raman spectrometer mmrs 1 raman spectroscopy is a powerful tool for mineral characterization and for detection of water and organic and inorganic forms of carbon the mars microbeam raman spectrometer mmrs is designed for close up analysis of rocks and soils in planetary surface exploration the mmrs consists of a probe in a flight unit to be deployed by a robotic arm and a spectrograph laser source and electronics in a flight unit to reside on a rover or lander the raman probe has a scanning optical bench that enables a 1 cm linear traverse across a target rock or soil both on target materials as encountered and on fresh surfaces of rocks exposed by abrasion or coring from these spectra one can identify major minor and trace minerals obtain their approximate relative proportions and determine chemical features e g mg fe ratio and rock textural features e g mineral clusters amygdular fill and veins one can also detect and identify organic species graphitic carbon and water bearing phases extensive performance tests have been done on a brassboard model of the mmrs using a variety of geological materials minerals rocks martian meteorites etc these tests show that a raman spectrometer can be built that is suitably miniaturized sufficiently robust and low enough in power usage to serve as an on surface planetary instrument yet the spectrometer can retain high detection sensitivity and yield near laboratory quality spectra over a broad wavelength range these features are essential to provide definitive mineralogy in a planetary exploration

provenance information recorded by mineral inclusions in detrital garnet abstract garnet single grain analysis is an often used and well established tool in sedimentary provenance studies especially when metamorphic source rocks are involved so far however solely the geochemical composition of detrital garnets is considered to draw conclusions concerning probable source rocks the gained information is often limited by i geochemical overlap of garnets derived from different lithology and metamorphic grade ii similar probabilities of belonging to more than one source rock type and iii the limitations of discriminating different protolith compositions here we present the first attempt of using mineral inclusions in detrital garnet as a provenance tool we analyzed the inclusions of 300 fine to medium sand sized detrital garnets from two proximal modern sand samples taken in the hp uhp western gneiss region of sw norway all mineral inclusions 2 m were identified by raman spectroscopy showing that i most garnets from hp uhp metamorphic source rocks contain mineral inclusions 2 m ii raman spectroscopy is a very powerful tool to characterize the inclusion types and iii less stable mineral phases like kyanite omphacite diopside enstatite coesite amphibole group and epidote group minerals occur as inclusions in garnet these minerals which are important for provenance studies can thus be preserved in the sedimentary record as long as garnet is stable the combination of inclusion types in garnet and geochemical garnet classification shows that i inclusions well reflect the geological characteristics of the sampled catchments implying that they are useful indicators for hp uhp provenance and ii inclusions in garnet can be used to support and enhance the provenance information obtained by garnet geochemistry

polar wander of the earth associated with the quaternary glacial cycle on a convecting mantle summary observed true polar wander tpw at the present day with the speed of 1 myr 1 towards hudson bay has been generally examined based on the glacial isostatic adjustment gia for the quaternary glacial cycle the observation is however affected by the present day melting events of polar ice sheets and mountain glaciers and convective processes in the mantle in this study i examine tpw due to gia and convective processes by developing the liouville equation including these two processes referred to as generalized liouville equation here the generalized liouville equation makes it possible to evaluate the effects of convective related non forcing inertia elements i11 i22 i33 and i12 and forcing elements i13 and i23 on the polar wander for the quaternary ice age phase and clearly indicates that the excess flattening of the earth inferred from the non hydrostatic geoid stabilizes the polar motion as discussed by mitrovica et al 2005 also numerical experiments for examining the effects of time dependent convective processes on tpw indicate that reasonable convection scenarios with a time dependence in the inertia tensor of 1031 kg m2 myr 1 ricard et al 1993 insignificantly contribute to the observed present day tpw moreover the predicted tpw with magnitude of convective related forcing rates di13 dt and di23 dt larger than 5 1031 kg m2 myr 1 is significantly different from the observation these results may provide a framework for separating the contributions of gia and convection to the observed present day polar wander

remote impacts of the 18 6 year period modulation of localized tidal mixing in the north pacific 1 the impact of the 18 6 year period modulation of the localized strong tidal mixing on the annual mean sea surface temperature sst in the open north pacific ocean is analyzed in a numerical experiment using an ocean general circulation model oscillatory sst anomalies induced in this model move eastward along the boundary between the subarctic and the subtropical gyres from the western boundary to the central pacific in about 10 years with a speed slower than that of the surface currents anomalous currents in the upper 300 m play an important role in inducing sst anomalies these anomalous currents are coupled to subsurface density anomalies and could be related to eastward moving low mode second or higher baroclinic long rossby waves these results suggest that the 18 6 year modulation of localized strong tidal mixing can influence large scale sst and or heat flux and thus climate as a result of remote impacts associated with changes in the mid depth density structure induced locally where mixing is strong that move horizontally into the open ocean

spatial distributions of secondary minerals in the martian meteorite mil 03346 168 determined by raman spectroscopic imaging miller range mil 03346 is a nakhlite meteorite that has been extensively studied due to its unique complex secondary mineral phases and their potential implications for the hydrologic history of mars we conducted a set of raman spectroscopic and raman imaging studies of mil 03346 168 focusing on the secondary mineral phases and their spatial distributions with a goal to better understand the possible processes by which they were generated on mars this study revealed three types of calcium sulfates a solid solution of k na jarosite and two groups of hydrated species with low crystallinity hslc in the veins and or mesostasis areas of the meteorite the most abundant ca sulfate is bassanite that suggests two possible paths for its direct precipitation from a ca s h2o brine either having low water activity or with incomplete development producing bassanite with gypsum microcrystals on mars the second most abundant ca sulfate is soluble caso4 which raises a new question on the origins of this phase in the martian meteorite since caso4 readily hydrates in the laboratory but is apparently stable in atacama desert the close spatial relationship of k na jarosite solid solutions with rasvumite kfe2s3 magnetite hslc and fine grained low crystallinity alkali feldspar in mesostasis suggests a potential in situ formation of mesostasis jarosite from these fe k na s o h2o species

estimates of tidal energy dissipation and diapycnal diffusivity in the kuril straits using topex poseidon altimeter data the kuril straits separating the okhotsk sea from the north pacific ocean are representative regions of strong tidal mixing in the world s oceans in the present study we first carry out numerical simulation of the barotropic tidal elevation field in the okhotsk sea using a horizontally two dimensional primitive equation model it is found that to reproduce realistic tidal elevations in the okhotsk sea the energy lost by the incoming barotropic tides to internal waves within the kuril straits should be taken into account the numerical experiments show that the model predicted tidal elevations in the okhotsk sea best fit the topex poseidon altimeter data when we take into account the baroclinic energy conversion in the kuril straits 16 gw for the k 1 tidal constituent and 37 gw for the major four tidal constituents k 1 o 1 m 2 s 2 for this baroclinic energy conversion diapycnal diffusivity averaged over the whole area of the kuril straits is estimated to be 8 x 10 4 m 2 s 1 this value is about 1 order of magnitude less than assumed for the kuril straits in previous ocean general circulation models we offer this study as a warning against using diapycnal diffusivity just as a tuning parameter to reproduce large scale phenomena

constraints on q at long periods from earth s rotation in this work we assess constant q and frequency dependent q models of mantle anelasticity our assessment uses the degree 2 love numbers we had inferred previously from a comparison of observed and predicted changes in the length of day at monthly fortnightly and nine day lunar tidal periods the comparison accounted for variable contributions to the tidal signals by dynamic oceans and allowed for axial core mantle coupling that was either complete or absent the love number derived from an earlier analysis of the period of the chandler wobble is also employed we find that the similarity of the degree 2 love number inferred at a nine day period to that at seismic frequencies combined with the significant amount of relaxation at the chandler period together imply that q models operating within the seismic band cannot extend all the way to long tidal periods our analysis of q also allows us to refine estimates of the love number at fortnightly and monthly periods

the pressures and temperatures of meteorite impact evidence from micro raman mapping of mineral phases in the strongly shocked taiban ordinary chondrite taiban is a heavily shocked l6 chondrite showing opaque melt veins raman spectroscopy was used to characterize the high pressure silicate assemblages in a thin section crossed by a shock created 4 mm wide melt vein raman spectra using different excitation wavelengths allowed identification of mineral phases such as olivine wadsleyite ringwoodite high ca clinopyroxene majorite pyrope jadeite maskelynite and lingunite olivine is fe depleted in contact with the ringwoodite which suggests chemical fractionation during a solid state olivine ringwoodite transformation raman imaging revealed a close correlation between the blue ringwoodite color and the peak observed at 877 cm 1 this signal shows strong near resonance raman enhancement when measured with near ir excitation lines 785 and 830 nm close to the optical absorption bands of the ringwoodite we propose that the blue color of the ringwoodite is due to a small amount of iron in fourfold coordination inside the spinel structure and that yields the observed spectral features in differently colored ringwoodite under the formation conditions of the studied silicate pocket all enstatite transformed to a majorite pyrope solid solution whereas the high ca clinopyroxene likely remained unchanged maskelynite grains in the margins of the pocket often contain lingunite or are totally transformed to jadeite based on static high pressure results the mineral assemblages in the pocket suggest peak pressure in the 17 20 gpa range with maximum temperature t max in the range 1850 1900 k as the formation conditions for this taiban chondrite during shock

a new inference of mantle viscosity based upon joint inversion of convection and glacial isostatic adjustment data we present new profiles of mantle viscosity derived on the basis of non linear occam style joint inversions of an extensive set of data associated with mantle convection and glacial isostatic adjustment gia the convection related observables include satellite derived free air gravity harmonics the geodetically inferred excess ellipticity of the cmb and tectonic plate motions the gia constraints involve two classes of observables previously shown to be relatively insensitive to errors in the late pleistocene ice history the so called fennoscandian relaxation spectrum frs and a set of site specific decay times determined from the postglacial sea level history in hudson bay and sweden the inverted viscosity profiles show a significant three orders of magnitude increase from the upper mantle mean value of f4 10 20 pa s to a high viscosity 10 23 pa s peak at

shock metamorphic features in amphiboles from the xiuyan crater of china amphibole bearing gneiss fragments are common in the impact breccias of the xiuyan crater china three kinds of amphibole bearing gneiss fragments with different shock metamorphic levels have been identified shock metamorphic features of amphiboles in these gneisses were investigated in situ by optical microscope electron microprobe raman spectroscopy and x ray diffraction amphiboles in the weakly shocked gneiss shock pressure less than 10 gpa basically remain intact amphiboles in the moderately shocked gneiss shock pressure range between 35 and 45 gpa show strong deformation reduced optical interference color and partial loss of oh in the strongly shocked gneiss shock pressure above 50 gpa amphiboles are completely melted and dendritic pyroxenes crystallize from the melt the formation of dendritic pyroxenes shows nearly complete loss of water in the amphibole melt at shock induced high temperature above 1 500 c the occurrence of both diopside and pigeonite dendrites crystallized in the same amphibole melt shows inhomogenous melt composition and rapid cooling of the melt

application of laser raman micro analyses to earth and planetary materials abstract raman spectroscopy contributed greatly in the past 30 years or so for the advances of our understanding of earth and planetary materials and their associated geological processes after a brief introduction of the history and basic theory of raman spectroscopy the advantages and disadvantages of this spectroscopic analysis method were listed and examples were given when appropriate for its applications to the analyses of earth materials which include minerals and organic materials silicate glasses and melts aqueous solutions and gases and h2o gas systems previous works were discussed and cited this was followed by a review on applications of raman spectroscopic studies of minerals and fluids to petrogenesis and crustal evolution in which several p t diagrams were given to show metamorphic evolution of ultra high pressure units as well as a schematic cross section of the earth s outer shells showing recycling of crustal materials in different tectonic regimes for its applications to the analyses of planetary materials which include lunar samples martian meteorites and other extraterrestrial materials a brief history on the starting and development of raman spectroscopy technique was given we then discussed raman point counting and quantitative chemical analysis methods developed for obtaining quantitative information on mineral proportions and mineral chemistry in planetary surface explorations respectively finally new developments and future works which include quantitative analyses raman mapping portable raman systems and raman effects resonance raman spectroscopy cars sers and their associated applications were discussed

estimating compositions of natural ringwoodite in the heavily shocked grove mountains 052049 meteorite from raman spectra a combined raman spectroscopy and electron probe microanalysis study of the heavily shocked grove mountains grv 052049 meteorite revealed the largest chemical fractionation of natural ringwoodite and composition dependent variation of the intensities and or wavenumbers of raman bands with fa content atomic ratio of fe fe mg of ringwoodite varying from 27 8 to 81 6 mol the peak position of the single band around 290 cm 1 sb1 which relates to the sio4 translation mode shifts from 296 0 to 284 6 cm 1 and one of the doublets around 790 cm 1 db1 which relates to the symmetric stretching of sio4 shifts from 796 3 to 782 7 cm 1 in addition the relative intensities of sb1 and the other band of the doublet around 840 cm 1 db2 which relates to asymmetric stretching of sio4 increases with fa content based on the paired raman epma data single peak and two peak calibrations were established which can be used to derive fa contents of ringwoodite from the raman spectra the accuracy of raman derived fa content of ringwoodite is better than 5 mol the correlation of sb1 intensity with the fa content of ringwoodite suggests that the vibration of sb1 is enhanced with the substitution of mg2 by fe2 the correlation between raman spectra and the chemical composition of ringwoodite have potential applications in on line measurement of high pressure experiments and in situ mineralogical determination in future planetary explorations

the 18 6 year period moon tidal cycle in pacific decadal oscillation reconstructed from tree rings in western north america 1 time series of pacific decadal oscillation pdo reconstructed from tree rings in western north america is found to have a statistically significant periodicity of 18 6 year period lunar nodal tidal cycle negative positive pdo tends to occur in the period of strong weak diurnal tide in the 3rd and 5th 10th 11th and 13rd year after the maximum diurnal tide mean pdo takes significant negative positive value suggesting that the aleutian low is weak strong western central north pacific in 30 50 n is warm cool and equator eastern rim of the pacific is cool warm this contributes to climate predictability with a time table from the astronomical tidal cycle

total meltwater volume since the last glacial maximum and viscosity structure of earth s mantle inferred from relative sea level changes at barbados and bonaparte gulf and gia induced j2

pyroxene as a recorder of cumulate formational processes in asteroids moon mars earth reading the record with the ion microprobe igneous cumulate rocks provide an important record of planetary magmatism but there are pitfalls in their interpretation cumulus minerals may react with the trapped melt and other cumulus phases during sub solidus reactions thus losing a direct record of their igneous history one of the best approaches for estimating the melt compositions parental to the cumulates is to analyze the cores of cumulus phases for elements with slow diffusion rates e g ree in pyroxene because these most reliably retain a record of the mineralmelt partitioning we have conducted sims studies of pyroxenes from a variety of planetary cumulates including lunar norites martian orthopyroxenites asteroidal orthopyroxenites diogenites asteroidal pyroxene plagioclase cumulates cumulate eucrites and terrestrial orthopyroxenites and norites stillwater complex montana we emphasized the ree la ce nd sm eu dy er yb along with sr y and zr in these investigations our studies yielded the several conclusions i lunar mg suite norites crystallized from highly evolved kreepy melts that were emplaced into the lunar anorthositic crust one viable model suggests remobilization of kreep lithologies that formed late in the crystallization of the lunar magma ocean 2 orthopyroxenites from asteroid 4 vesta diogenites likely formed as cumulates from melts derived from depleted mantle which had previously experienced eucritic basalt removal the calculated parental melts show a limited range of major element compositions but an exceedingly large range of trace element variation that is difficult to explain by any simple crystallization or melting models 3 the diogenites of 4 vesta are cumulates from melts derived from many depleted mantle reservoirs that either formed numerous orthopyroxene plutons later mixed by impact brecciation or commingled by magma mixing to form a limited number of differentiated plutons we base this conclusion on a comparative investigation of a well studied terrestrial orthopyroxenite sequence bronzitite zone of the stillwater complex an important lesson to be learned from these studies in comparative planetology is that if simple petrogenetic models do not work for well studied terrestrial occurrences there is little reason to believe that they will work for planetary environments where we have little geologic control on sampling

dynamics and structure of a stirred partially molten ultralow velocity zone abstract the seismic properties of thin 5 40 km thickness patches exhibiting low seismic velocities termed ultralow velocity zones or ulvz just above the core mantle boundary cmb might be explained by the presence of partially molten rock where a liquid phase occupies interstices within a skeletal network of solid grains however a key problem with this explanation is that in the absence of improbably strong surface tension effects partial melt is expected to drain by percolation over geological time scales to form a dense melt rich layer at the cmb with physical properties that are inconsistent with seismic and other geophysical constraints here we consider whether stirring within ulvz driven by viscous coupling to convective motions in the overlying mantle can inhibit the production of such stratification and maintain a partially molten region with a structure and constitution comparable to what is inferred seismically we use two dimensional numerical simulations of the response of a melt solid mixture to stirring imposed from above and scaling analysis to identify conditions leading to melt separation retention and drainage over a broad range of parameters we find that melt migration at plausible ulvz conditions is governed predominantly by dynamic pressure gradients arising from the viscous deformation related to mantle stirring rather than by the buoyancy effects driving melt percolation in particular dense melt that would otherwise drain downward and accumulate at the cmb is expected to remain in suspension as a result of the stirring driven within ulvz in addition our model predicts that partially molten ulvz patches will be characterized by a positive gradient in seismic shear velocity i e increasing with depth consistent with seismic inferences and may persist in this state over geological time scales

high resolution 3 d s velocity structure in the d region at the western margin of the pacific llsvp evidence for small scale plumes and paleoslabs abstract although previous tomographic studies found a large low s velocity province llsvp in the lowermost mantle beneath the pacific due to a lack of resolution it remains unclear whether the llsvp consists of clusters of small scale low velocity anomalies or large scale anomalies we recently deployed a seismic array in thailand which provides a dataset with wide azimuthal coverage at the western pacific llsvp we analyze the new dataset using waveform inversion and find high velocity anomalies extending vertically to a height of 400 km above the core mantle boundary cmb beneath the philippine sea and small scale low velocity patches with a diameter of 300 km at the cmb beneath new guinea the locations of the high velocity anomalies are consistent with the past izanagi plate subduction boundary and the low velocity anomalies can be interpreted as a small scale plume cluster hence we conclude that vertical flow upwelling plumes and downwelling of slabs is dominant in the lowermost mantle beneath the western pacific region

dynamical ocean response controlling the eastward movement of a heat content anomaly caused by the 18 6 year modulation of localized tidally induced mixing

possible explanation linking 18 6 year period nodal tidal cycle with bi decadal variations of ocean and climate in the north pacific 1 bi decadal climate variation is dominant over the north pacific on inter decadal timescale however the mechanism has not been fully understood we here find that the bi decadal variations in the north pacific climate and intermediate waters possibly relate to the 18 6 year period modulation of diurnal tide in the period of strong diurnal tide tide induced diapycnal mixing makes surface salinity and density higher and the upper layer shallower along the kuril islands and the east coast of japan simple model results suggest that the coastal depth adjustment by baroclinic kelvin waves enhances the thermohaline circulation the upper layer poleward western boundary current and associated heat transport by about 0 05pw this could also explain the warmer sst in the kuroshio oyashio extension regions where positive feedback with aleutian low might amplify the bidecadal variations the 18 6 year tidal cycle hence could play a role as a basic forcing for the bi decadal ocean and climate variations

numerical study of k1 internal tides in the kuril straits 1 tide induced strong diapycnal mixing in the kuril straits is thought to be one of the essential processes controlling water mass formation in the north pacific in order to make a definite quantification of diapycnal diffusivity in the kuril straits we drive a three dimensional numerical model and examine the generation propagation and dissipation features of internal waves which play an essential role in transferring energy from the predominant k1 barotropic tide to diapycnal mixing processes it is shown that most of the internal wave energy subtracted from the k1 barotropic tide is dissipated within the kuril straits such that the local dissipation efficiency becomes 0 8 1 0 about three times the value previously employed this is because the k1 tidal frequency is subinertial in this area so that significant amount of k1 tidal energy is fed into coastal trapped waves ctws which stay around each island without propagating away from the straits ctws induce strong velocity shear near the ocean bottom causing bottom confined intense mixing with a vertical decay scale 200 m less than half the value previously employed although there remains some uncertainties resulting from the employed parameterizations of viscosity and diffusivity the average diapycnal diffusivity in the kuril straits becomes 25 10 4 m2 s 1 about three times the value previously estimated although it is still an order of magnitude less than assumed for the kuril straits in the existing ocean general circulation models

cosmochemical and spectroscopic properties of northwest africa 7325 a consortium study this work is part of a project to build an infrared database in order to link ir data of planetary materials and therefore possible mercury material with remote sensing observations of mercury which will probably be obtained by the mertis instrument on the forthcoming bepicolombo mission the unique achondrite northwest africa nwa 7325 which has previously been suggested to represent the first sample from mercury was investigated by optical and electron microscopy and infrared and raman spectroscopy in addition the oxygen strontium xenon and argon isotopes were measured and the abundance of selected trace elements determined the meteorite is a cumulate rock with subchondritic abundances of hfse and ree and elevated sr contents which underwent a second heating and partial remelting process oxygen isotope measurements show that nwa 7325 plots in the ureilite field close to the alm a trachyandesitic fragment found in the unique almahata sitta meteorite breccia on the other hand mineralogical investigations of the pyroxenes in nwa 7325 provide evidence for similarities to the lodranites and acapulcoites furthermore the rock is weakly shocked and argon isotope data record ancient 4 5 ga plateau ages that have not been reset the sample records a cosmogenic exposure age of 19 ma systematics of rb sr indicate an extreme early volatile depletion of the precursor material similar to many other achondrite groups however despite its compositional similarities to other meteorite groups our results suggest that this meteorite is unique and unrelated to any other known achondrite group an origin for nwa 7325 as a sample from the planet mercury is not supported by the results of our investigation in particular the evidence from infrared spectroscopy indicates that a direct relationship between nwa 7325 and the planet mercury can be ruled out no acceptable spectral match between laboratory analyses and remote sensing observations from mercury has been obtained however we demonstrate that infrared spectroscopy is a rapid and nondestructive method to characterize mineral phases and thus an excellent tool for planetary surface characterization in space missions

the period and q of the chandler wobble summary we have extended our calculation of the theoretical period of the chandler wobble to account for the non hydrostatic portion of the earth s equatorial bulge and the effect of the fluid core upon the lengthening of the period due to the pole tide we find the theoretical period of a realistic perfectly elastic earth with an equilibrium pole tide to be 426 7 sidereal days which is 8 5 day shorter than the observed period of 435 2 day using rayleigh s principle for a rotating earth we exploit this discrepancy together with the observed chandler q to place constraints on the frequency dependence of mantle anelasticity if q in the mantle varies with frequency u as u between 30 s and 14 months and if q in the lower mantle is of order 225 at 30 s we find that 0 04 5 a 5 0 1 1 if instead q in the lower mantle is of order 350 near 200 s we find that 0 11 5 a 0 19 in all cases these limits arise from exceeding the 68 per cent confidence limits of 2 6 day in the observed period since slight departures from an equilibrium pole tide affect the q much more strongly than the period we believe these limits to be robust

extracting olivine fo fa compositions from raman spectral peak positions the dominant feature of the olivine raman spectrum is a doublet that occurs in the spectral region of 815 825 cm 1 db1 and 838 857 cm 1 db2 these features arise from coupled symmetric and asymmetric stretching vibrational modes of the constituent sio4 tetrahedra the frequencies of both peaks show monotonic shifts following cation substitution between forsterite and fayalite we present a calibration for extracting olivine fo contents fo mg mg fe molar ratio fo0 100 from the peak positions of this doublet permitting estimates of chemical composition from raman spectra acquired in the laboratory or field as well as providing information on crystal structure distinction of polymorphs eight samples spanning the compositional range from forsterite to fayalite were used to develop the calibration equations for the db1 and db2 peaks individually and together the data indicate that the db1 peak is more reliable for calculating the compositions of fe rich olivine but that the db2 peak is better for magnesian compositions the two peak calibration overcomes the limitations of the single peak calibrations and is capable of calculating olivine compositions to within 10 fo units

subducted slabs and the geoid constraints on mantle rheology and flow geoid anomalies are primarily the result of the density contrasts driving mantle convection and plate motion the total geoid anomaly resulting from a given density contrast in a convecting earth is affected by the mass anomalies associated with the flow induced deformation of the upper surface and internal compositional boundaries as well as by the density contrast itself these boundary deformations and hence the total gravity field depend on the radial distribution of effective viscosity if the internal density contrasts can be estimated as is the case for subducted slabs useful constraints can be placed on the depth and on the variation of viscosity with depth of the convecting system the degree 4 9 components of the observed long wavelength geoid are highly correlated with those predicted by a density model for seismically active subducted slabs the positive sign of the correlation requires that the effective viscosity increases with depth by a factor of 30 or more the amplitude of the correlation cannot be explained by the density contrasts associated with just the seismically active parts of subducted slabs however the amplitude can be explained if the density contrasts associated with subduction extend into the lower mantle or if old lithosphere is piled up at the base of the upper mantle beneath subduction zones to a thickness in excess of 350 km over horizontal distances of thousands of kilometers mantlewide convection in a mantle that has a viscosity increasing with depth provides a simple explanation of the long wavelength geoid anomalies over subduction zones

deep intense vertical mixing in the bussol strait 1 to reveal the intensity of deep mixing in the bussol strait we performed the direct observations of turbulence for the first time vigorous vertical mixing with a turbulent energy dissipation rate e above 10 6 w kg and diapycnal diffusivity k above 103 cm2 s were observed at depths of 600 1300 m potential densities of 27 0 27 5 at the western gap of the bussol strait possibly affecting water mass transformation and thermohaline circulation the strong vertical mixing with a diurnal period occurred when the diurnal tidal current flowed toward the okhotsk sea corresponding to a period of enhanced shear consisting of the mean flow with a two layered structure and the large amplitude diurnal tidal current with a vertical structure explained by a low vertical mode topographically trapped wave the empirical relationship ofe 10 1 46 1 91 s2 16 0 72 is obtained between e and the shear sreconstructed from the 50 m scale mean diurnal and semi diurnal tidal currents

late pleistocene and holocene sea level change in the australian region and mantle rheology summary spatial and temporal variations in sea level are produced by the melting of the late pleistocene ice and by the earth s response to the redistribution in surface loads by examining different parts of the sea level curves of the past 20 000 yr from geographically widely distributed regions it becomes possible to constrain models of the melting history of the ice sheets and of the earth s rheology observations from sites away from the former arctic ice sheets such as the australian and south pacific region are particularly important for constraining the total meltwater volumes added into the oceans in the past 20 000 yr and the rates at which this occurred these observations indicate that the antarctic ice sheets provided a significant contribution to the sea level rise at a rate that was approximately synchronous with the melting of the laurentide ice sheet except for the interval 9000 6000 yr ago when it may have lagged behind minor melting of the antarctic ice sheet appears to have continued throughout the late holocene differential observations of the late holocene sea level change recorded at sites in the same region are particularly useful for estimating parameters describing the earth s non elastic response to surface loading the effective parameters used here are a lithospheric thickness an upper mantle viscosity and a lower mantle viscosity describing the response below 670 km depth with the observations used here it is not possible to separate the lithospheric thickness h from the upper mantle viscosity and the viscosity results are based on the assumption that 50 h 100 km neither do these observations provide a resolution of the depth dependence of viscosity in the upper mantle and the resulting estimates are effective parameters only differential sea levels along continental margins and along the shores of large gulfs and bays constrain the effective upper mantle viscosity to be about 1 2 1020 pa s 1 while differential values from islands of different sizes are suggestive of a somewhat lower value the lower mantle taken to be below 670 km depth viscosity is about two orders of magnitude greater than this the estimated ice and rheological models explain many of the holocene sea level observations throughout the australian and southern pacific region the tilting of continental margins as exemplified by observations of variable amplitudes of the holocene high stands and the variable times at which sea levels first reached their present level along the north queensland coast and great barrier reef is well represented by these models differential holocene sea levels observed along the narrow spencers gulf of south australia are also well explained by the models and in neither case is it necessary to invoke tectonic motions predicted late holocene sea levels at small to medium sized islands are characterized by small amplitude high stands that reached their maximum values about 4000 2000 yr ago consistent with observations from the society cook and tuamotu islands

the response of the north pacific ocean to decadal variability in atmospheric forcing wind versus buoyancy forcing abstract both wind and buoyancy forcing result in variability in the north pacific ocean thermocline a vertical modal analysis of the density deviations in a 30 yr run of an ocean general circulation model of the north pacific forced by atmospheric variability is used to identify the spatial and temporal patterns of the different baroclinic modes the different dynamic vertical modes show distinct propagation characteristics with the first baroclinic mode exhibiting consistent westward propagation at all latitudes the higher baroclinic modes show westward phase propagation at low latitudes but propagate eastward at higher latitudes the propagation characteristics of each mode can be understood by the inclusion of the zonal mean flow in the vertical structure equation evaluation of the ekman pumping and diapycnal fluxes in the quasigeostrophic potential vorticity equation for each dynamic vertical mode distinguishes their effects on the thermocline variability wind variability dominantly forces the f

bidecadal variability in the bering sea and the relation with 18 6 year period nodal tidal cycle 1 bidecadal variations are investigated in the bering sea especially in the southeastern basin adjacent to the aleutian passes where vertical mixing may be strong because of the diurnal tide those variations found in this region are synchronized with the 18 6 year period nodal tidal cycle and the temporal patterns are similar to ones around the northwestern subarctic pacific near the kuril straits reported by a previous study salinity and density in the upper layer are high in the periods when the diurnal tide is strong in the intermediate layer layer thickness is large and isopycnal potential temperature and apparent oxygen utilization are low in the same periods it is shown that these variations are consistent with the patterns expected from the nodal modulation of vertical mixing and a simple two dimensional model assuming a balance between anomalous vertical mixing and advection of anomaly by the mean current succeeds to some extent in explaining the variations of the upper layer salinity and isopycnal temperature and apparent oxygen utilization in the intermediate layer

bidecadal variability in the intermediate waters of the northwestern subarctic pacific and the okhotsk sea in relation to 18 6 year period nodal tidal cycle 1 on the basis of historical oceanographic data we investigated the long term variations of the intermediate waters in the four regions in the northwestern subarctic pacific oyashio okhotsk sea mode water upstream oyashio and east kamchatka current we found bidecadal oscillations in these water properties that are synchronized with the 18 6 year period nodal cycle in periods when the diurnal tide is strong the following characteristics are found apparent oxygen utilization and phosphate are low in oyashio and okhotsk sea mode water the thickness of the intermediate layers is large and thus potential vorticity is correspondingly low in oyashio okhotsk sea mode water and upstream oyashio around the mesothermal temperature maximum water isopycnal potential temperature are low in the areas on the pacific side and high in the intermediate layer of okhotsk sea mode water the mixing ratio of okhotsk sea mode water in the upstream oyashio water is high these bidecadal oscillations can be explained by changes in the vertical mixing around the kuril straits induced by the diurnal tide whose amplitude is modulated with the 18 6 year nodal cycle higher sea surface salinity water around the kuril straits caused by stronger tidal mixing is possibly transported northward along the cyclonic okhotsk sea gyre and possibly enhances the formation of the dense shelf water this makes apparent oxygen utilization phosphate and potential vorticity lower in okhotsk sea mode water and oyashio

shock conditions recorded in nwa 8159 martian augite basalt with implications for the impact cratering history on mars nwa 8159 is an augite rich martian basalt formed by cooling of a relatively evolved ca rich ti poor and lree depleted lava under relatively oxidizing conditions during the early amazonian in addition to its distinct igneous petrogenesis and high fo 2 nwa 8159 is also set apart from most martian shergottites with respect to the low degree of shock metamorphism required to preserve crystalline igneous plagioclase an 50 65 in this study mineral transformations within and adjacent to shock veins in nwa 8159 were investigated using scanning electron microscopy raman spectroscopy and transmission electron microscopy to better constrain the unusal shock history of this meteorite the transformation of olivine to ahrensite fe ringwoodite along shock vein margins and tissintite and coesiteformed from igneous mineral labradorite and silica grains entrained as clasts within shock veins has been documented in this study we report on a previously unidentified mineral assemblage of ca na majoritic garnet sodic clinopyroxene and stishovite crystallized from shock melt this mineral assemblage indicates a crystallization pressure of approximately 16 gpa which is within the range of previous shock pressure estimates for this meteorite 15 23 gpa the presence of a majoritic garnet bearing assemblage throughout veins up to 0 6 mm wide indicates that the sample remained at high pressure throughout the melt vein quench based on thermal models the sample must have remained at high pressure for 100 ms this shock duration is an order of magnitude longer than those experienced by more highly shocked shergottites such as tissint or zagami 30 gpa 10 20 ms and would seem to imply a relatively large impact event recent numerical models demonstrate that a range of shock pressures and durations are realized by rocks within the ejected spall zone of a hypervelocity impact the shock conditions experienced by nwa 8159 therefore do not require an impact event distinct from other shergottites rather our findings suggest that this meteorite originated from near the martian surface at the edge of the impact site the shock history of nwa 8159 provides a picture of mars consistent with that derived from remote observation that of a random cratering process that samples a geologically long lived and complex planet

isopycnal mixing in ocean circulation models abstract a subgrid scale form for mesoscale eddy mixing on isopycnal surfaces is proposed for use in non eddy resolving ocean circulation models the mixing is applied in isopycnal coordinates to isopycnal layer thickness or inverse density gradient as well as to passive scalars temperature and salinity the transformation of these mixing forms to physical coordinates is also presented

raman spectroscopic characterization of a martian snc meteorite zagami to demonstrate the ability of raman spectroscopy to determine the mineralogical character of a rock that originated on mars we analyzed a small slab of normal zagami by point analyses and multipoint scans using laboratory spectrometers spectra of clinopyroxenes were dominant their compositions were estimated from a calibration of raman peak positions with mg mg fe based on lunar pyroxenes of known composition and these agree with compositions obtained by electron microprobe a few spectra of orthopyroxene were observed the broad spectrum of maskelynite was observed but not that of plagioclase feldspar spectra of minor phosphates magnetite and pyrrhotite were obtained as were spectra of an organic contaminant and of hematite both apparently introduced during sample handling prior to raman analysis the modal analysis based on the multipoint scans agrees well with published values if the spectra had been obtained on the surface of mars by raman spectroscopic analysis as a stand alone method and no other information about the sample was available and by ignoring the spurious hematite and organic material we could rule out sedimentary and plutonic rock types and conclude that the sample was a pyroxene phyric basalt

high pressure polymorphs of magnesian orthopyroxene from a shock vein in the yamato 000047 lherzolitic shergottite abstract we found a simple thin shock vein less than or equal to about 60 m in width and 1 8 mm in length in the poikilitic area in the yamato y 000047 lherzolitic shergottite the shock vein occurs only in magnesian ca poor clinopyroxene which may have transformed from orthopyroxene during the pressure increase at the shock event the shock vein consists of mg0 8 fe0 2 sio3 pyroxene polymorphs such as columnar akimotoite two kinds of pyroxene glasses dendritic akimotoite and framboidal pyroxene glass in the order from the periphery to the center the compositions and textures suggest that columnar akimotoite in the periphery of the shock vein crystallized from solid state phase transition of clinopyoroxene during the cooling of the vein and the remains in the shock vein solidified from shock produced melt the glass includes two kinds of massive glass in the vein and framboidal glass in the vein center the framboidal glass is the most magnesian and may have been vitrified from perovskite crystallized from high pressure melt produced at high temperature 3000 c and high pressure 23 40 gpa dendritic akimotoites in the vein center metastably crystallized from residual shock melt the formation sequences of the constituent phases in the shock vein happen in the following order columnar akimotoites rim glass center glass framboidal glass and dendritic akimotoites the increase of the raman intensity of 660 670 cm 1 in the order of rim glass center glass and framboidal glass suggests that the formation of the pyroxene chain proceeds faster in the vein center than in the vein rim due to its slower cooling the finding of the shock vein consisting merely of high pressure polymorphs of pyroxene akimotoite and framboidal glass vitrified perovskite is the first reported among all martian meteorites

pleistocene deglaciation and the earth s rotation a new analysis summary this paper is concerned with an analysis of the effect of the pleistocene glacial cycle upon the earth s rotation we demonstrate that two important geophysical observables may be explained as aspects of the rotational response to surface mass loading by ice sheets these are the astronomically observed non tidal component of the acceleration of planetary rotation and the secular drift of the rotation pole relative to the surface geography which is evident in the ils pole path the former observation is shown to provide an unambiguous constraint upon the viscosity of the planetary mantle and requires a depth dependence of this parameter which is the same as that which has previously been inferred in studies of the relative sea level variations and free air gravity anomalies associated with post glacial rebound the observed secular drift of the pole cannot provide an independent estimate of the viscosity of the mantle because it depends jointly upon mantle viscosity and lithospheric thickness with the viscosity profile fixed by the rebound data the observed speed of polar wander suggests a continental lithospheric thickness which is in excess of that appropriate for old ocean basins but nevertheless in accord with independent constraints

joint modeling of lithosphere and mantle dynamics sensitivity to viscosities within the lithosphere asthenosphere transition zone and d layers abstract although mantle rheology is one of the most important properties of the earth how a radial mantle viscosity structure affects lithosphere dynamics is still poorly known particularly the role of the lithosphere asthenosphere transition zone and d layer viscosities using constraints from the geoid plate motions and strain rates within plate boundary zones we provide important new refinements to the radial viscosity profile within the key layers of the lithosphere asthenosphere transition zone and d layer we follow the approach of the joint modeling of lithosphere and mantle dynamics ghosh and holt 2012 ghosh et al 2013b 2019 wang et al 2015 to show how the viscosities within these key layers influence lithosphere dynamics we use the viscosity structure sh08 steinberger and holme 2008 as a starting model the density variations within the mantle are derived from the tomography models which based on prior modeling had provided a best fit to the surface observables wang et al 2015 our results show that narrow viscosity ranges of moderately strong lithosphere 2 6 5 6 1022 pa s and moderately weak transition zone 5 9 3 1020 pa s as well as slightly large ranges of moderately weak asthenosphere 5 34 1019 pa s and d layer 4 8 18 1020 pa s are necessary to match all the surface observables we also find that a very strong lithosphere 8 6 1022 pa s along with a weak asthenosphere

summertime evolution of decadal sea surface temperature anomalies in the midlatitude north pacific abstract to clarify the summertime evolution of decadal sea surface temperature sst anomalies and related physical processes in the midlatitudes of the north pacific numerical solutions of a three dimensional bulk mixed layer model are analyzed focusing on the contribution of the net shortwave radiative forcing at the sea surface a quantitative heat budget analysis for the ocean mixed layer relating to late 1980s decadal sst change reveals that the decadal sst anomalies decay from late spring to early summer over the entire midlatitudes of the north pacific this quasi seasonal decay of the decadal sst anomalies is controlled by an anomalous local thermal damping i e anomalous surface heat fluxes from midsummer to early autumn the anomalous net shortwave radiation flux associated with a meridional shift of the storm track acts to induce strong seasonal damping of the decadal sst anomaly in the northern kuroshio oyashio extension region in contrast in the north of the subtropical frontal region

crystallization experiments of intercumulus melts for nakhlites under qfm 2 at 1 bar crystallization of parent melts for nakhlites was experimentally studied under qfm 2 at one bar isothermal experiments suggest that melts having parent magma composition for nakhlites crystallize both augites and titanomagnetites at liquidus temperatures of 11441154 c compositions of the augites are identical to those of phenocrystic core augites en36 38fs22 25wo39 40 in nakhlites no olivines crystallize from the isothermal runs and solidus temperature is about 1000 c linear cooling experiments were carried out at various cooling rates 117 c h ranging from liquidus to solidus temperatures under similar pressure conditions to the isothermal runs augites titanomagnetites and fayalites crystallized in the cooling runs but magnesian olivines never crystallized there magnesian core augite in the cooling runs has the same composition as those of nakhlites rims of augite crystals from the cooling runs of 1 4 c h consist of two layers ferroan augite inner rim and hedenbergite outer rim which are very similar to those in the miller range mil 03346 nakhlite small amounts of pyroxferroite crystallized in mesostasis and augite rims from two cooling runs titanomagnetites from cooling runs never accompany ilmenite lamellae as seen in nakhlites suggesting that the subsolidus cooling rate of the cooling runs was much more rapid than those of nakhlite intercumulus melts the cooling experiments reproduce the crystallization processes of pyroxenes and the compositional change of residual melt for a rapidly cooled magma such as mil 03346

screening and classification of ordinary chondrites by raman spectroscopy classification of ordinary chondrite meteorites generally implies 1 determining the chemical group by the composition in endmembers of olivine and pyroxene and 2 identifying the petrologic group by microstructural features the composition of olivine and pyroxene is commonly obtained by microprobe analyses or oil immersion of mineral separates we propose raman spectroscopy as an alternative technique to determine the endmember content of olivine and pyroxene in ordinary chondrites by using the link between the wavelength shift of selected characteristic peaks in the spectra of olivine and pyroxene and the mg fe ratio in these phases the existing correlation curve has been recalculated from the raman spectrum of reference minerals of known composition and further refined for the range of chondritic compositions although the technique is not as accurate as the microprobe for determining the composition of olivine and pyroxene for most of the samples the chemical group can be easily determined by raman spectroscopy blind tests with ordinary chondrites of different provenance weathering and shock stages have confirmed the potential of the method therefore we suggest that a preliminary screening and the classification of most of the equilibrated ordinary chondrites can be carried out using an optical microscope equipped with a raman spectrometer

spectroscopic study of perchlorates and other oxygen chlorides in a martian environmental chamber abstract we report a study where the molecular spectral features of nine anhydrous and hydrous oxygen chlorides were analyzed both under mars atmospheric pressure and temperature conditions in a planetary environment and analysis chamber peach and for comparison under ambient laboratory conditions the goal is to understand the effect of mars environmental conditions mainly temperature t and co 2 pressure p on their spectral features as determined by both raman and nir spectroscopy these results will be used for in situ simultaneous identification of the cl o 4 and other intermediate oxygen chloride products generated during a dynamic electrostatic discharge esd experiment we have three major findings from the first phase of this study 1 the 1 raman peak position is the most sensitive parameter for identifying the cation speciation in perchlorates e g na mg ca the hydration state of magnesium perchlorate e g mg clo 4 2 x h 2 o x 0 2 4 6 and the degree of oxidation of sodium oxygen chlorides e g naclo y y 1 2 3 4 2 1 raman peak positions of most tested hydrous and anhydrous oxygen chlorides show no detectable changes within the tested t and p ranges relevant to the environmental conditions at mars surface and shallow subsurface but water raman peaks of the hydrated salts change following t decreases 3 under the p t conditions relevant to current surface and shallow subsurface at mars mid latitude regions both mg clo 4 2 6h 2 o and ca clo 4 2 2h 2 o are stable against dehydration while naclo 4 h 2 o dehydrates with a dehydration rate that is a function of t which was quantified by in situ nir spectroscopy these results are useful for the interpretations of the data from current orbital remote sensing vis nir spectra and from future landed missions raman spectra furthermore we have designed a set of systematic esd experiments to be conducted in peach for studying the pathways and the rates of oxygen chloride generation from chloride salts as a potential mechanism to form oxygen chlorides during martian dust storm the results of the current study will be used for in situ simultaneous identification of the cl o 4 and other intermediate oxygen chloride products generated during a dynamic esd experiment

amorphization in natural omphacite and its implications abstract high resolution transmission electron microscopic data have revealed the existence of nanoscale intragranular amorphous phase in omphacite of eclogite from the dabieshan uhp metamorphic belt eastern china the results of profiles in the omphacite across the amorphous phase and micro fractured regions indicate variations in compositions and oh band intensity respectively this implies that the occurrence of amorphization in the omphacite appears to be pressure induced and controlled by kinetics oh may diffuse outward and further react with the atom at m2 site during more distorted plastic deformation which occurs as the omphacite crystalline structure collapses to a denser amorphous phase the reported propensity to amorphization and the strong influence on the outcome of the initial structure and of the pressurization protocol indicate the presence of metastability and large kinetic barriers

origin of decadal scale eastward propagating heat content anomalies in the north pacific abstractupper ocean heat content ohc is at the heart of natural climate variability on interannual to decadal time scales providing climate memory and the source of decadal prediction skill in the midlatitude north pacific ocean ohc signals are often found to propagate eastward as opposed to the frequently observed westward propagation of sea surface height another variable that represents the ocean subsurface state this dichotomy is investigated using a 150 yr coupled gcm integration simulated ohc signals are distinguished in terms of two processes that can support eastward propagation higher baroclinic rossby wave rw modes that are associated with density perturbation and spiciness anomalies due to density compensated temperature and salinity anomalies the analysis herein suggests a unique role of the kuroshio oyashio extension koe region as an origin of the spiciness and higher mode rw signals wind forced westward propagating equivalent barotropic rws cause meridional shifts of the sub