primary platinum mineralization in the nizhny tagil and kachkanar ultramafic complexes urals russia a genetic model for pge concentration in chromite rich zones the nizhny tagil uralian alaskan type ultramafic complex is composed of a dunite core with a rim of wehrlite and pyroxenite the dunite unit which has a uniform mineral composition olivine fo 89 8 92 1 avg 0 25 wt cao represents an accumulation of olivine and minor chromite from a mafic magma in an open system magma chamber after solidification of the dunite differentiation began with the formation of the wehrlite olivine fo 77 9 88 8 and pyroxenite corresponding to the closure of the magmatic system two main types of chromitite occurrence are observed in the dunite body small 100 5 cm scattered schlieren of chromite crystals within the ultramafic unit and much larger up to 100 5 m concentrations the chromite composition in both types is similar and uniform cr cr al fe 3 66 02 mg mg fe 2 49 05 and cr cr al fe 3 69 14 mg mg fe 2 49 81 respectively the larger concentrations of chromite include brecciated and net textured ore or massive veins that reflect the dynamic accumulation of chromite crystals in cavities along magma conduits inside the dunite body these cavities are analogous to small magma chambers within the consolidated part of the dunite body and similar to podiform chromitites in ophiolites were created by continuous feeding of magma to the system the platinum group element pge content of the chromite free facies of the dunite is relatively low pt being the only significant pge typically between 0 3 35 ppb but as much as 98 ppb in one sample in contrast both types of chromite occurrence are enriched in pge two pge mineralizing episodes are distinguished an ir ru rh os rich pt pd poor episode in which the platinum group minerals pgm are mainly ir alloys and a pt pd rich episode in which the pgm are mainly pt alloys i e pt 2 fe ni cu ptfeni 2 and tetraferroplatinum and tulameenite like compositions along with rare hollingworthite and an unidentified rhnias mineral the primary pgm have been affected locally by a serpentinization related low temperature alteration that is characterized by addition of copper with alteration to complex pt fe ni cu alloys of varied stoichiometry including tulameenite and platinian copper placer concentrations derived from the nizhny tagil complex have a slightly different assemblage of pgm with abundant isoferroplatinum the presence of gold commonly aggregating the pgm and unusual au sn and au pb alloys the kachkanar complex situated 120 km north of the nizhny tagil complex has essentially the same characteristics apart from a slightly different composition of the ultramafic cumulates suggesting that they were derived from a magma of different composition the pgm distribution also differs in that it contains more abundant isoferroplatinum than other pgm the high pt concentrations are the result of the affinity of platinum minerals for chromite and the mode of chromite deposit formation in the cavities in which chromite crystallized pgm tended to be incorporated in chromite or remained attached to chromite crystals to explain the very high concentrations of chromite associated pgm we define a cr factor which is the ratio of the mass of silicate magma to the mass of chromite in contact with the ascending magma where the cr is high i e a relatively low proportion of chromite in contact with a large amount of magma crystallizing the pt minerals the efficiency of the mechanical collection of pt minerals is at a maximum and the pt concentration i e amount of pt minerals will be high possible variations due to the collection of pge by a sulfide liquid have not been established a model is proposed whereby the observed chromite and associated pt mineralization can result from the normal magmatic evolution of the complex provided that a structural hydrodynamic trap is available to concentrate the chromite

global upper mantle structure from finite frequency surface wave tomography 1 we report global shear wave velocity structure and radial anisotropy in the upper mantle obtained using finite frequency surface wave tomography based upon complete three dimensional born sensitivity kernels because wavefront healing effects are properly taken into account finite frequency surface wave tomography improves the resolution of small scale mantle heterogeneities especially for deep anomalies that are constrained by the longest period surface waves in our finite frequency model ffsw1 the globally averaged radial anisotropy shows a transition from positive sh sv to negative anisotropy sv sh at about 220 km consistent with a change in the dominant mantle circulation pattern from predominantly horizontal flow at shallow depths to vertical flow at greater depths the radial anisotropy beneath cratons and the old pacific plate agrees well with previous studies however our model exhibits a strong negative radial anisotropy at depths greater than 120 km beneath mid ocean ridges a feature that is not present in previous upper mantle models more interestingly the depth extent of the ridge anomalies is distinctly different beneath fast and slow spreading centers anomalies beneath fast spreading centers are stronger but the strength decreases rapidly below 250 km in contrast beneath slow spreading centers such as the northern mid atlantic ridge and the red sea anomalies extend down at least to the top of the transition zone the different depth extent of the ridge anomalies suggests that the primary driving force of slow spreading seafloor may be different from that of fast spreading seafloor and that active upwelling beneath slow spreading ridges may play a major role in the opening of the seafloor

recent sediment accumulation and origin of shelf mud deposits in the yellow and east china seas abstract modern last 100 yr accumulation rates of shelf mud deposits in the yellow and east china seas were investigated using the distribution of excess 210pb 210pbex in sediment core samples compilation and merger of new and previously published data helped clarify sediment accumulation in these seas the estimated accumulation rates together with data of suspended sediment concentrations provided findings on the sediment budget origin and transport pathway of the mud deposits the overall accumulation distribution in the yellow and east china sea shelf revealed a general cross shelf decreasing trend along the sediment dispersal system away from the rivers except for the south sea ssm and southeastern yellow sea seysm mud patches found along the korean coast notably 210pbex activity profiles within the ssm and the seysm yielded a relatively high accumulation rate of 2 5 mm yr implying a sedimentation rate of 4 15 107 tons per year in this coastal zone such an annual accumulation rate is about one order of magnitude greater than the total sediment discharge 6 20 106 tons yr from korean rivers suggesting an additional offshore source the distribution pattern of the well defined suspended plume clearly showed the possible transport and exchange of fine grained sediments between the ecs shelf and the coastal area of korea especially during winter such a high accumulation in korean coastal areas is attributable to the sediments supplied from the mud deposit of the ecs i e swcim with origins in chinese rivers therefore the korean coastal area may be an important sink for some of chinese river sediments being transported from the south by the yellow sea warm current

crystallographic preferred orientation of olivine in the earth s deep upper mantle abstract simple shear deformation experiments of olivine were conducted at pressures of 11 1 12 7 gpa and temperatures of 1670 1770 k c type olivine fabric developed by the 1 0 0 0 0 1 slip system and similar fabrics were dominantly developed in a wide range of water content coh 49 19 242 ppm h si in olivine because the seismic fast a axes are perpendicular to the shear plane only for c type fabric a positive negative transition of vsh vsv difference in velocity between horizontally and vertically polarized shear waves inevitably occurs when c type fabric is developed by a pressure induced fabric transition the positive negative transition of vsh vsv at 200 km depth reported in global one dimensional models is known to be well explained by the horizontal flow of olivine with a low water content

alpe arami a peridotite massif from depths of more than 300 kilometers the abundance of fetio 3 and chromite precipitates in olivine of the alpe arami peridotite massif switzerland requires a much higher solubility for highly charged cations than is found in mantle xenoliths from depths of 250 kilometers three previously unknown crystal structures of fetio 3 were identified that indicate that the originally exsolved phase was the high pressure perovskite polymorph of ilmenite implying a minimum depth of origin of 300 kilometers these observations coupled with the unique lattice preferred orientation of olivine further suggest that the original composition of olivine may reflect that of a precursor phase perhaps wadsleyite that is stable only at depths greater than 400 kilometers

cross shelf transport of terrestrial al enhanced by the transition of northeasterly to southwesterly monsoon wind over the east china sea aluminum al is one of the key parameters of geotraces in spring 2011 we examined the distribution of dissolved al in the east china sea ecs to assess the potential passage of coastal water across the shelf to the western pacific measurement of dissolved al in coastal shelf and shelf break waters indicated decreasing concentrations with distance from the coast however the northward increase of dissolved al in the upper 100 m along the shelf break transect corresponding to the northward flow of kuroshio water along the okinawa trough from the north of taiwan to the tokara strait indicates contributions of terrestrial material the presence of an al plume indicated cross shelf transport at the subsurface at a potential density of 23 3 24 0 kg m3 this plume originates from the near bottom layer along the coast off zhejiang and fujian provinces and first moves southeastward to the north of taiwan and then northeastward to shelf break with export at 29 n 127 e we calculated the cross shelf fluxes of water and dissolved al based on simulation results of the 3 d massachusetts institute of technology general circulation model mitgcm the calculated cross shelf fluxes of al at the subsurface layer indicate that the ecs is highly efficient in pumping al rich coastal waters northward to the japan sea east sea and or eastward into the western pacific we also identified an important role of the monsoon with a change from northeasterly wind to southwesterly wind in spring on the cross shelf transport of al by use of numerical tracer experiments

high temperature elasticity of iron bearing olivines the first high temperature data on the nine adiabatic elastic moduli for iron bearing olivine are reported these measurements are on two single crystal specimens of natural olivine at ambient pressure and from room temperature to a maximum of 1500 k the two specimens contain 8 and 9 modal percent fayalite which required the oxygen fugacity be controlled at high temperature to preserve their chemical stability the rectangular parallelepiped resonance apparatus was adapted to buffer the specimens from the atmosphere with a mixture of co and co2 gas a small increase 1 2 gpa in the adiabatic bulk modulus of each specimen over that of end member forsterite was found the data are high quality to extreme temperatures with good agreement found when comparing the temperature derivatives of the elastic moduli of the two specimens neither specimen exhibits measurable nonlinear temperature dependence in the computed isotropic bulk and shear moduli which is in contrast to published forsterite data the temperature derivatives of the isotropic bulk modulus ks are 1 69 1 80 10 2 gpa k 1 for the two olivine specimens and the shear modulus g derivatives are 1 38 1 36 10 2 gpa k 1 these derivatives are only slightly larger in magnitude than ks t p 1 56 10 2 and g t p 1 30 10 2 gpa k 1 found previously for iron bearing olivine over a very small temperature range there are also no significant differences between the temperature derivatives found here and the average derivatives of end member forsterite from data retrieved over a slightly larger temperature range several dimensionless parameters have been calculated from these results and are discussed in view of systematics which bear on high pressure phases in earth s transition zone one result from these systematics related to the seismic velocities in the earth and especially the shear wave velocities is that an olivine content of less than 50 is implied at the 400 km discontinuity if earth s upper mantle is isochemical furthermore the substitution of almost 10 iron for magnesium at the forsterite end of the olivine solid solution series has little effect on the dimensionless parameters or on the temperature derivatives of the elastic moduli at high temperature

b type olivine fabric in the mantle wedge insights from high resolution non newtonian subduction zone models several hypotheses have been proposed to explain trench parallel shear wave splitting in the mantle wedge of subduction zones these include 3 d flow effects parallel melt filled cracks and b type olivine fabric we predict the distribution of btype and other fabrics with high resolution thermal and stress models of subduction zones a composite viscous rheology is used that incorporates wet diffusion creep wet dislocation creep and a stress limiting approximated peierls creep law rheological parameters for dislocation and diffusion creep are based on deformation experiments the effects of variable viscous coupling between the slab and mantle are explored using kinematic boundary conditions that change along the top of the slab two end member models are observed which depend on the depth of partial viscous coupling between the slab and mantle 1 deep partial coupling which gives rise to cold high stress conditions in the forearc mantle and high temperature low stress conditions in the arc and back arc mantle 2 full viscous coupling at the base of a 40 km conducting lid which is characterized by high temperature and low stress the case with deep partial coupling which produces a better match with attenuation tomography and heat flow shows a large region with suitable conditions for b type fabric in the forearc mantle and a rapid transition toward the back arc to conditions that are more suitable for a c or e type fabrics full viscous coupling gives rise to high temperature low stress conditions unsuitable for b type fabric our modeling predicts that the best candidates for regions with b type fabric are the forearc mantle and a cold 10 15 km layer above the slab d 2005 elsevier b v all rights reserved

sediment transport in the yellow sea and east china sea abstract eight survey cruises in different seasons have been conducted in the yellow sea ys and east china sea ecs during the period from 2000 to 2008 suspended sediment concentration ssc and hydrological data were collected during each cruise data analysis showed that total suspended sediment mass was approximately 0 18 109 tons in the surveyed area during spring and autumn seasons highly turbid waters were found in the shallow waters between the subei coast the changjiang estuary and the zhejiang coast with seasonal variations the investigation provided convincing evidence that suspended sediments were transported from the subei coast and the southern entrance of the yellow sea trough to the central ys muddy patches were found at the sea bed when tidal currents were too weak to erode the bottom sediments and water column stratification and eddies provided favorable conditions for trapping the fine grained suspended sediments the investigation indicated that the different front may have different effect on sediment transport during different seasons the front between the yellow sea cold water and the coastal water in the subei coast appeared to trap the high ssc sediments on the shallow water side of the front during summer the front along the zhejiang coast seemed to prevent suspended sediments from transport across the front due to circulation in the front zone and upwelling along the zhejiang coast during winter sediments were likely transported across the front to the central continental shelf of the ecs with the help of the downwelling and lateral ekman transport driven by monsoon winds

deformation fabrics of the cima di gagnone peridotite massif central alps switzerland evidence of deformation at low temperatures in the presence of water we report a new observation of the olivine b type lattice preferred orientation lpo from the garnet peridotite at cima di gagnone switzerland the olivine b type fabric forms at low temperatures and or high stress in the presence of water and is of particular interest because it may be used to explain the trench parallel shear wave splitting that is often observed at subduction zones in conjunction with the olivine b type fabric we have found strong orthopyroxene lpo that is identical to those formed under water free conditions this suggests that water may not have a significant effect on orthopyroxene fabric from the olivine microstruc ture we determine that a stress of 22 8 mpa was applied during the deformation event that formed the olivine lpo using an olivine flow law and assuming geological strain rates we determine the temperature of deformation to be 800 175c this does not preclude an ultra deep origin for the ultramafic rocks at cima di gagnone but indicates that much of the deformation recorded in the microstructure occurred at modest temperatures

platinum group minerals in tasmania platinum group minerals in tasmania occur mostly in placer deposits and are composed mainly of iridosmine and rutheniridosmine platinum rich alloys are rare silicate inclusions in the metals include olivine fo sub 94 89 enstatite and nonstoichiometric pyroxene rich in ca mg and al the silicate compositions confirm a genetic association between the platinum group minerals and ultramafic rocks already suspected from their distributions

seasonal exchanges of the kuroshio and shelf waters and their impacts on the shelf currents of the east china sea previous in situ observations and modeling studies have indicated that through mass and momentum exchanges across the shelf edge the kuroshio can significantly influence the shelf currents of the east china sea ecs here instead of localized observations this study uses 25yr of drifter data supported by satellite and other data to identify seasonal cross shelf exchanges along the entire shelf edge the authors show that kuroshiomeandersonshorefromfalltowinterandoffshorefromspringtosummer withthelargestamplitude northeast of taiwan the influence is limited to the shelf edge when the kuroshio meanders offshore in spring and summer by contrast strong onshelf intrusions and cross shelf exchanges occur when the kuroshio meanders onshore in fall and winter drifters intrude onshelf northeast of taiwan and spread as far north as 308n against the strong northeasterly wind the forcing on the shelf is identified as a northward downsloping of the sea level that is steepest north of taiwan at 258 288n but which is 3 times weaker farther north the vorticity budget computed from a numerical model indicates that intrusion during fall andwinter is primarily a result of balancebetweenonshelfadvectionofambientpotentialvorticityandvorticityproductionbythealong isobath pressure gradient acting on the changing mass of water column across the continental slope

ore mineralogy of pgm placers in siberia and the russian far east abstract platinum group minerals pgm placers of siberia and the russian far east are subdivided into three associations on the basis of mineralogical and geochemical features the first is a ruthenium iridium osmium ophiolitic association from zolotaya suyenga and balyksa river placers a type restricted to ultramafic rocks of the ophiolitic belts os ir ru alloys are dominant over pt fe nuggets two magmatic parageneses of source rocks are typical in a type association early osmium iridium and isoferroplatinum ruthenium which forms after the os ir ru system is saturated with ru in early paragenesis the distribution coefficient of ru between osmium and iridium kdruhex cube is 1 35 1 97 with the composition plots of os ir ru alloys on an os ru ir pt diagram forming a ruthenium trend the second association is ruthenium iridium osmium b type the source of which has not been located although b type materials are found along the ko tayenza rivers in this assemblage os ir ru alloys are dominant over other platinum group element pge minerals and their compositions vary from os to ir on the os ru ir pt diagram with no ruthenium trend os ir ru alloys are characterized by gradual and contrast zoning in composition from osmium in the centre to ruthenium or iridium in the rim the kdruhex cube is less than 1 with an average 0 4 isoferroplatinum occurs as discrete grains and inclusions in these os ir ru alloys a third association is that of isoferroplatinum and is restricted to the alaskan type inagli gal moenan philippa massifs and occurs in the kuznetsk alatau along the kaura kaurchak rivers placers pt fe solid solution mostly pt3fe is dominant in these placers two parageneses are typical in source rocks an early isoferroplatinum osmium parageneses and later isoferroplatinum iridium parageneses the second one is the result of exsolution structure development from primary pt ir ru os solid solutions which formed as the ore forming system saturated with ir plots of osmium composition form an osmium trend on the os ru ir pt diagram in the all associations products of alteration and replacement of primary magmatic minerals caused by late magmatic s and as enriched residual fluids or by late serpentinization are observed the main secondary minerals comprise pge sulphoarsenides and laurite in the os it ru alloys and cooperite and sperrylite in the pt fe alloys

spatial and temporal distributions of clay minerals in mud deposits on the inner shelf of the east china sea implications for paleoenvironmental changes in the holocene abstract we present a paleoclimatic reconstruction for the holocene by clay mineral analyses of sediments from core mz02 retrieved from the mud area of the inner continental shelf of the east china sea ecs the clay minerals mainly consist of illite 66 79 and chlorite 12 19 with minor kaolinite 7 13 and smectite 0 6 provenance analysis suggests that the illite dominated clay minerals were derived mainly from the detrital outputs of the changjiang minjiang and small rivers from taiwan island our study indicates that the sea level rise since the last glacial the strength of the taiwan warm current twc and chinese coastal current ccc have controlled the dispersal and deposition of clay minerals on the ecs that in turn determined the clay mineral compositions in the core sediments during 13 000 9500 bp due to the lower sea level and shorter distance between these three estuaries and core mz02 fine sediments on the inner shelf of the ecs were primarily supplied by mixed provenances from the changjiang taiwanese and minjiang rivers during the early holocene 9500 6200 bp stronger sediment reworking and erosion at the shelf edge was responsible for the increased lateral transport of fine sediments in the ecs which lead to a dominance of the sediment source from the changjiang while the taiwanese and minjiang rivers only provided minor components of detrital sediment to the shelf increased strength of twc might have played an important role in the sediment dispersal and deposition on the inner shelf of the ecs during 6200 2400 bp with a dominance of more than 60 sediments transported from taiwanese rivers furthermore our study implies that the asian monsoon and the weakening of twc were linked to the abrupt increase of changjiang and minjiang derived terrigenous detritus materials since 2400 bp

flux and fate of yangtze river sediment delivered to the east china sea numerous cores and dating show the yangtze river has accumulated about 1 16 x 10 12 t sediment in its delta plain and proximal subaqueous delta during holocene high resolution seismic profiling and coring in the southern east china sea during 2003 and 2004 cruises has revealed an elongated similar to 800 km distal subaqueous mud wedge extending from the yangtze river mouth southward off the zhejiang and fujian coasts into the taiwan strait overlying what appears to be a transgressive sand layer this distal clinoform thins offshore from similar to 40 in thickness between the 20 and 30 m water depth to 1 2 in between 60 and 90 m water depth corresponding to an across shelf distance of less than 100 km total volume of this distal mud wedge is about 4 5 x 10 11 m 3 equivalent to similar to 5 4 x 10 11 t of sediment most of the sediment in this mud wedge comes from the yangtze river with some input presumably coming from local smaller rivers thus the total yangtze derived sediments accumulated in its deltaic system and east china sea inner shelf have amounted to about 1 7 x 10 12 t preliminary analyses suggest this longshore and across shelf transported clinoform mainly formed in the past 7000 yrs after postglacial sea level reached its mid holocene highstand and after re intensification of the chinese longshore current system sedimentation accumulation apparently increased around 2000 yrs bp reflecting the evolution of the yangtze estuary and increased land erosion due to human activities such as fanning and deforestation the southward flowing china coastal current the northward flowing taiwan warm current and the kuroshio current appear to have played critical roles in transporting and trapping most of yangtze derived materials in the inner shelf and hence preventing the sediment escape into the deep ocean c 2006 elsevier b v all rights reserved

anisotropic shear wave velocity structure of the earth s mantle a global model 1 we combine a new large data set of surface wave phase anomalies long period waveforms and body wave travel times to construct a three dimensional model of the anisotropic shear wave velocity in the earth s mantle our modeling approach is improved and more comprehensive compared to our earlier studies and involves the development and implementation of a new spherically symmetric reference model simultaneous inversion for velocity and anisotropy as well as discontinuity topographies and implementation of nonlinear crustal corrections for waveforms a comparison of our new three dimensional model s362ani with two other models derived from comparable data sets but using different techniques reveals persistent features 1 strong 200 km thick high velocity anomalies beneath cratons likely representing the continental lithosphere underlain by weaker fast anomalies extending below 250 km which may represent continental roots 2 weak velocity heterogeneity between 250 and 400 km depths 3 fast anomalies extending horizontally up to 2000 3000 km in the mantle transition zone beneath subduction zones 4 lack of strong long wavelength heterogeneity below 650 km suggesting inhibiting character of the upper mantle lower mantle boundary and 5 slow velocity superplumes beneath the pacific and africa the shear wave radial anisotropy is strongest at 120 km depth in particular beneath the central pacific lateral anisotropic variations appreciably improve the fit to data that are predominantly sensitive to the uppermost and lowermost mantle but not to the waveforms that control the transition zone and midmantle depths tradeoffs between lateral variations in velocity and anisotropy are negligible in the uppermost mantle but noticeable at the bottom of the mantle

numerical study of the ocean circulation on the east china sea shelf and a kuroshio bottom branch northeast of taiwan in summer using the regional ocean model system the ocean circulation on the east china sea ecs shelf was examined by a fine resolution model which was nested in a coarse resolution pacific ocean model the high resolution simulation shows an accurate volume transport of 2 70 sv sv 10 6 m 3 s 1 through the tsushima strait which is more consistent with the previous 5 5 year observation value 2 64 sv than former model results for the taiwan strait it also shows a close volume transport 1 03 sv to a recent estimate 1 20 sv at the same time the model results reproduced almost all of the known circulation structure on the ecs shelf in addition the hindcast of 2009 shows a kuroshio bottom branch current to the northeast of taiwan kbbcnt the kbbcnt is confirmed by the observational bottom high salinity water from 15 august to 2 september 2009 whose distribution is also reproduced by the model results tracer and particle experiments were carried out to elucidate the formation of the high salinity water and the pathway of the kbbcnt in light of the field observation and numerical experiments a new pathway of the kbbcnt is proposed bifurcated from the subsurface water of kuroshio northeast of taiwan it upwells northwestward gradually from 300 to 60 m then turns to northeast in the region around 27 5 degrees n 122 degrees e and finally reaches 31 degrees n off the mouth of the changjiang river along similar to 60 m isobaths forming the bottom saline water off the coast of zhejiang province china

flow behavior and microstructures of hydrous olivine aggregates at upper mantle pressures and temperatures deformation experiments on olivine aggregates were performed under hydrous conditions using a deformation dia apparatus combined with synchrotron in situ x ray observations at pressures of 1 5 9 8 gpa temperatures of 1223 1800 k and strain rates ranging from 0 8 10 5 to 7 5 10 5 s 1 the pressure and strain rate dependencies of the plasticity of hydrous olivine may be described by an activation volume of 17 6 cm3 mol 1 and a stress exponent of 3 2 0 6 at temperatures of 1323 1423 k a comparison between previous data sets and our results at a normalized temperature and a strain rate showed that the creep strength of hydrous olivine deformed at 1323 1423 k is much weaker than that for the dislocation creep of water saturated olivine and is similar to that for diffusional creep and dislocation accommodated grain boundary sliding while dislocation microstructures showing the 001 slip or the 001 100 slip system were developed at temperatures of 1633 1800 k a much stronger pressure effect on creep strength was observed for olivine with an activation volume of 27 7 cm3 mol 1 assuming a stress exponent of 3 5 water fugacity exponent of 1 2 and activation energy of 520 kj mol 1 i e power law dislocation creep of hydrous olivine because of the weak pressure dependence of the rheology of hydrous olivine at lower temperatures water weakening of olivine could be effective in the deeper and colder part of earth s upper mantle

re os isotopic constraints on the source of platinum group minerals pgms from the vestřev pyrope rich garnet placer deposit bohemian massif abstract mineralogical studies of the heavy fraction from a holocene pyrope rich garnet placer deposit at vest ev krkonose piedmont basin bohemian massif have identified the presence of very rare grains of platinum group minerals pgm pt fe alloy grains are accompanied by os ir ru minerals native osmium iridium and ruthenium with inclusions of pt fe alloy and hongshiite ptcu this mineral assemblage is typical for several mantle settings including ophiolites the chemistry of the os ir ru minerals shows an enrichment of the pgm in ru which is typical of ophiolites the grain morphology of pgm and pyrope rich garnet mostly rounded with numerous euhedral subhedral grains does not exclude a common source in situ laser ablation mc icp ms was used to measure the re os isotopic compositions of single os rich grains which show heterogeneous subchondritic os isotopic compositions 187 os 188 os 0 12082 0 12505 0 00003 this precludes their low temperature origin and indicates derivation of platinum group elements pges essentially from mantle derived rocks without a significant contribution of crustal os the mantle model age t ma and re depletion model age t rd model ages range from 0 4 to 1 0 ga and most likely reflect a long history of melt depletion that affected the mantle sources of pgm

a three dimensional radially anisotropic model of shear velocity in the whole mantle summary we present a 3 d radially anisotropic s velocity model of the whole mantle saw642an obtained using a large three component surface and body waveform data set and an iterative inversion for structure and source parameters based on non linear asymptotic coupling theory nact the model is parametrized in level 4 spherical splines which have a spacing of 8 the model shows a link between mantle flow and anisotropy in a variety of depth ranges in the uppermost mantle we confirm observations of regions with vsh vsv starting at 80 km under oceanic regions and 200 km under stable continental lithosphere suggesting horizontal flow beneath the lithosphere we also observe a vsv vsh signature at 150 300 km depth beneath major ridge systems with amplitude correlated with spreading rate for fast spreading segments in the transition zone 400 700 km depth regions of subducted slab material are associated with vsv vsh while the ridge signal decreases whilethemid mantlehasloweramplitudeanisotropy vsv in the lowermost 300 km which appears to be a robust conclusion despite an error in our previous paper which has been corrected here the 3 d deviations from this signature are associated with the large scale low velocity superplumes underthecentralpacificandafrica suggestingthatvsh vsv isgeneratedinthepredominant horizontal flow of a mechanical boundary layer with a change in signature related to transition to upwelling at the superplumes

switching from seismic faulting to silent slips in harzburgite induced by h2o fluid at upper mantle pressures slow slip events frequently occur but regular earthquakes are much less active on the h2o fluid rich subduction interface at depths of 40 km the characteristic duration for silent earthquakes which are categorized as the great slow slip events is more than five orders of magnitude longer than that for regular earthquakes such phenomena are often attributed to the slippage of the softer part of the subduction interface but the impact of h2o fluid on aseismic slip is still unsolved here we conduct deformation experiments on water saturated harzburgite at pressures of 1 2 to 3 0 gpa and temperatures of 770 to 1250 k corresponding to the conditions of the lower part of the overriding plate just above the subduction interface we observe deformation of the harzburgite followed by silent faulting at a significantly low stress level down to 0 3 gpa under fluid bearing conditions even though many acoustic emissions are generated at the onset of faulting in fluid free harzburgite we find that the observed silent faulting is caused by the detachment of asperity contacts by high pore pressures and lubrication of the fault plane by a hydration reaction we therefore propose that h2o fluid may prevent the occurrence of regular intraslab earthquakes but trigger silent earthquakes

an olivine fabric database an overview of upper mantle fabrics and seismic anisotropy we present a unique database of 110 olivine petrofabrics and their calculated seismic properties the samples come from a variety of the upper mantle geodynamic environments ophiolites subduction zones and kimberlites with a wide range of micro structures a phenomenological relationship is established between p and s wave seismic anisotropy and the degree of crystal alignment fabric strength seismic anisotropy increases rapidly at low fabric strength before reaching a near saturation level of 15 to 20 for p waves and 10 to 15 for s waves despite a large variation in the symmetry of fabric patterns the average seismic properties of the different fabric micro structural and geodynamic settings have similar anisotropies in both magnitude and symmetry hence it would seem possible to determine some measure of fabric strength from seismic anisotropy if the dimensions of the anisotropic region are known but not geodynamic environment or details of the petrofabric pattern a simple pattern of seismic anisotropy characterises the average sample of the database which has the following features the polarisation plane of the fastest s wave is parallel or sub parallel to the foliation plane the maximum shear wave splitting is parallel to the y structural direction in foliation plane and normal to the lineation the maximum of the p wave velocity is parallel to the high concentration of 100 axes which is sub parallel to the lineation the 100 orientation distribution has the greatest influence on the p wave seismic anisotropy the 100 and 001 orientation distributions have the greatest influence on the symmetry of s wave anisotropy although the magnitude of anisotropy is influenced by the distribution of all three principal axes although the database only contains olivine petrofabrics this statistical study clearly shows that seismic anisotropy can be used to deduce the orientation of the structural frame in the upper mantle 1998 elsevier science b v all rights reserved

natural examples of olivine lattice preferred orientation patterns with a flow normal a axis maximum tectonic plate motion is thought to cause solid state plastic flow within the underlying upper mantle and accordingly lead to the development of a lattice preferred orientation of the constituent olivine crystals the mechanical anisotropy that results from such preferred orientation typically produces a direction of maximum seismic wave velocity parallel to the plate motion direction this has been explained by the existence of an olivine preferred orientation with an a axis maximum parallel to the induced mantle flow direction in subduction zones however the olivine a axes have been inferred to be arranged roughly perpendicular to plate motion which has usually been ascribed to localized complex mantle flow patterns recent experimental work suggests an alternative explanation under conditions of high water activity a b type olivine preferred orientation may form with the a axis maximum perpendicular to the flow direction natural examples of such b type preferred orientation are however almost entirely unknown here we document widespread b type olivine preferred orientation patterns from a subduction type metamorphic belt in southwest japan and show that these patterns developed in the presence of water our discovery implies that mantle flow above subduction zones may be much simpler than has generally been thought

effect of temperature on the b to c type olivine fabric transition and implication for flow pattern in subduction zones abstract the effect of temperature on the b to c type fabric transition in olivine was investigated by large strain shear deformation experiments a new series of deformation experiments was conducted at 1273 1373 k 2 0 gpa and strain rates ranging from 3 8 10 4 to 3 2 10 5 s 1 under water saturated conditions and combined with previous results at 1473 k the influence of temperature on deformation fabrics was investigated two types of olivine fabrics were identified one in which the olivine 0 0 1 axis is subparallel to the shear direction and the 0 1 0 plane is parallel to the shear plane b type and another one in which the 0 0 1 axis is parallel to the shear direction and the 1 0 0 plane is parallel to the shear plane c type the b type olivine fabric occurs at higher stress than the c type but the stress magnitude at which the b to c type fabric transition occurs decreases significantly with decreasing temperature the temperature dependence of the transition stress is parameterized using a range of exponential flow law that is constrained by the experimental study when the experimental results are extrapolated to lower temperatures the fabric transition between b and c type is predicted to occur at 1 mpa and 1000 k this prediction is consistent with the olivine fabrics in naturally deformed peridotites found in plate convergent regions the present study indicates that when some amounts of water 200 ppm h si are present the b type fabric will dominate in low temperature regions of the upper mantle whereas the c type or e type fabric will dominate at high temperatures the complex seismic anisotropy in subduction zones can be explained by changes in the dominant type of olivine fabrics caused by spatial variations in physical and chemical variables such as temperature and water content rather than by complexities in mantle wedge flow pattern

grain growth kinetics in wadsleyite effects of chemical environment abstract grain growth kinetics in wadsleyite was investigated using a multianvil high pressure apparatus fine grained wadsleyite aggregates were synthesized by isostatic hot pressing and were subsequently annealed under high pressure and temperature in a controlled chemical environment wadsleyite samples show normal grain growth characterized by a log normal grain size distribution following the relation l n l 0 n k t where n is a constant l the grain size at time t l0 the grain size at time t 0 and k is a rate constant that depends on temperature t and chemical environments f o 2 oxygen fugacity in pa coh water content in h 106si as k a d f o 2 r d exp h d r t a w f o 2 r w c oh q exp h w r t with a d 10 4 9 6 1 8 0 7 4 m n s 1 p a r d rd 0 12 0 11 0 20 0 14 h d 410 230 500 270 kj mol a w 10 18 2 1 4 24 0 1 7 m n s 1 p a r w rw 0 14 0 05 0 22 0 06 q 1 7 0 3 2 2 0 3 and h w 120 60 160 70 kj mol with assumed value of n 2 3 values in parentheses denote parameters for n 3 both water and oxygen fugacities significantly enhance grain growth kinetics the large value of the parameter describing the water fugacity dependence q 1 5 2 5 cannot be explained solely by a simple model in which grain growth is controlled by diffusion of atoms defects across the grain boundaries the interaction of grain boundaries with charged defects or the density of hydrated ledges may be important factors that control the grain growth kinetics of wadsleyite when compared at similar thermo chemical conditions grain growth of wadsleyite is found to be more sluggish than grain growth of olivine the present results show that a small wadsleyite grain size 100 000 h 106si is present a small grain size

change of olivine a axis alignment induced by water origin of seismic anisotropy in subduction zones abstract the effects of water on the crystallographic preferred orientation cpo of olivine aggregates were investigated through simple shear deformation experiments under asthenospheric upper mantle conditions pressure 2 1 5 2 gpa temperature 1490 1830 k using a deformation dia apparatus formation of the a type olivine fabric developed by the 010 100 slip system was observed under water depleted conditions coh 1000 ppm h si in comparison with fabrics of anhydrous olivine 111 ppm h si those of olivine having higher water contents 625 ppm h si in olivine showed stronger anisotropic properties e g p wave anisotropy s wave polarization anisotropy and the ratio of horizontally and vertically polarized shear waves the water induced olivine cpo transition from a type to b type like fabric accompanies a change in the alignment of the seismic fast a axes resulting in flow parallel and flow perpendicular shear wave splitting under water depleted and water rich conditions respectively the rotation of the fast direction of shear wave splitting across an arc which is observed in many subduction zones is well explained by the likely bimodal water distribution along the mantle wedge i e water rich in fore arc and water depleted in back arc regions and the developments of two different types of olivine fabrics i e b type like fabric in fore arc and a type fabric in back arc regions

strong seismic anisotropy in the deep upper mantle beneath the cascadia backarc constraints from probabilistic finite frequency sks splitting intensity tomography abstract the volcanically active high lava plains hlp region is a striking tectonomagmatic feature of eastern oregon in the backarc of the cascadia subduction zone it features young

platinum mineralization of the svetly bor and nizhny tagil intrusions ural platinum belt abstract this paper presents the results of a detailed mineralogical and micro analytical study of two ural alaskan type intrusions in the ural platinum belt 1 the dunite hosted mineralization of the svetly bor intrusion and 2 the chromitite mineralization of the nizhny tagil intrusion two generations of platinum minerals are typical of both intrusions magmatic pt fe ni alloys and post magmatic pt fe ni cu alloys a trend from ferroan platinum to isoferroplatinum pt fe pt 3 fe is shown for magmatic alloys of the svetly bor intrusion magmatic alloys of the nizhny tagil intrusion are represented by ferroan platinum with ni only varying in fe the magmatic pt fe alloys of both intrusions were depleted in fe during the evolution of ore forming systems and crystallized during the entire magmatic process generally as fine cubic crystals and anhedral grains hosted by dunite at the magmatic stage during and after the crystallization of dunite platinum dunite type of the svetly bor intrusion the evolution of mineral paragenesis was accompanied by a temperature drop as well as increases in f o 2 and f s 2 most of the platinum was concentrated in the residual melts together with chromium and crystallized in the final stage of the magmatic process platinum chromite ore of the nizhny tagil intrusion post magmatic pt fe cu ni alloys formed during the serpentinization of dunite evolved according to a general compositional trend from tetraferroplatinum and ferronickelplatinum to tulameenite and later to pt cu alloy and pt oxide ptfe pt fe cu ni cu 3 pt pt o platinum rich mineralization of both intrusions was formed in the late magmatic stage from a melt rich in volatiles regardless of their location in dunite or chromitites most probably the rock structure fracture systems was the determining factor in the migration of pge rich residual melts and ore accumulation

holocene sedimentary evolution and hypoxia development in the subaqueous yangtze changjiang delta china abstract this study investigates holocene sedimentary evolution and hypoxia development using borehole cores cjk06 and cjk09 in combination with other published core data based on lithology and microfossil benthic foraminifera characteristics seven types of sedimentary facies were identified from the base upward river tidal flat tide influenced river transgressive lag estuary inner shelf and prodelta isochronous correlation among the cores was established relying on accelerator mass spectrometry 14c dates facies succession indicates that a weak progradation occurred in coastal environments 12 10 ka bp due to the younger dryas induced deceleration of sea level rise rapid deposition locally occurred in the southern marginal area of tide dominated estuary environments 10 8 ka bp likely due to the junction of the yangtze and qiantangjiang river currents and marine current induced fluid mudflows prevailed in the shallow marine environments 8 1 ka bp with the cooling climates of 5 1 ka bp furthermore prodelta and shallow marine environments co occurred with an uneven progradation of the delta within the last 1 ka while deposition occurred just inside the more southern delta influenced area the occurrence of euryhaline benthic foraminifera suggests that an enhanced freshwater discharge of the mid holocene 8 5 ka bp was followed by a sharp decline in the late holocene 5 1 ka bp with climate change the occurrence of cold water benthic foraminifera indicates a severe cold water condition during the mid holocene due to the intrusion of upwelling currents triggered by the propelling force of warm currents and summer monsoon winds in addition the occurrence of low oxygen foraminiferal assemblages reveals that hypoxia has developed since 10 ka bp in stages consistent with the sedimentary evolution localized hypoxia formation coincident with the southern depocenter during the early holocene 10 8 ka bp severe hypoxia with enhanced freshwater discharge and upwelling current intrusion during the mid holocene and weakened hypoxia of the late holocene mainly due to the sharp decline in freshwater discharge within 1 ka bp freshwater discharge from the approaching river mouth and increased nutrient inputs from enhanced human activities on land have contributed to the prevalence of hypoxia especially in the southern deltaic area overall it was revealed that the freshwater discharge modulated with climate variations and delta progradation plays a primary role in controlling the sedimentary evolution and hypoxia development during the mid late holocene

evidence of high water content in the deep upper mantle inferred from deformation microstructures deep upper mantle rocks from the norwegian caledonides show evidence for large strain deformation in both olivine and garnet under varying water contents using microstructural observations including lattice preferred orientation of olivine and subgrain boundaries of majoritic garnet we infer the following deformation history at depths exceeding 150 km large strain deformation occurred at low stress 10 mpa and modest temperature 1300 k involving high water content 1000 h 10 6 si in olivine this was followed by low strain deformation at lower water content 200 1000 h 10 6 si and modest stress 40 mpa in the shallower parts these observations show that the deep upper mantle in this region had a considerably higher water content than the upper mantle near mid ocean ridges

olivine 100 normal to foliation lattice preferred orientation in prograde garnet peridotite formed at high h2o activity cima di gagnone central alps automated electron backscattered diffraction ebsd was applied using a scanning electron microscope to obtain lattice preferred orientation lpo data for olivine in garnet peridotites of the central alps as a reference frame the lpos of enstatite were also investigated in the garnet peridotite at cima di gagnone cdg a weak foliation carrying a distinct lineation is present the lineation is characterized by elongated enstatite olivine and poikiloblastic garnet olivine shows a very unusual lpo with 100 normal to foliation and 001 parallel to lineation achsenverteilungsanalyse ava maps demonstrate that 001 of olivine grains corresponds quite well to their maximum length axes which are preferentially parallel to the lineation numerous planar hydrous defects within 001 planes of olivine are marked by palisades of ilmenite rods and show a preferred orientation normal to lineation calculated p wave velocities for cdg are fastest 8 32 km s 1 normal to foliation with a relatively low anisotropy 2 9 compared to mantle peridotites with the usual 010 100 lpo where the fastest vp direction is towards the lineation the relationship between flow geometry and seismic anisotropy is significantly different at cdg several mechanisms for the formation of the lpo type at cdg are considered with glide possible on 100 001 of olivine on the basis of field data as well as petrographic and petrologic evidence it has been demonstrated that the cdg garnet peridotite formed by prograde metamorphism from a hydrous protolith at pressures and temperatures of about 3 0 gpa and 750 c respectively the cdg lpo is interpreted to have formed during hydrous subduction zone metamorphism the same interpretation may hold for the previously investigated olivine lpo at alpe arami which is similar to that at the nearby cdg the observed anomalous lpo is no proof for ultradeep 3 0 gpa conditions

quantitative reconstruction of holocene sediment source variations in the yellow and northern east china seas and their forcings abstract sediment provenance in the yellow sea and northern east china seas yecss has long been a subject of interest but its quantification is still inconclusive here we present an improved al mg regression analysis by refining its methodological approach to strengthen quantification of sediment source to sink transports in the yecss with focus on its forcing mechanisms during the holocene our quantitative source estimates clearly depict a considerable supply of the chinese river cr sediments 50 to the southwestern korean coastal region and the korean river kr sediments 30 40 to the central yellow sea mud deposit which accounts for a good balance between the sediment supply and budget of the shelf deposit of particular note is an abrupt decline in the cr contributions around 124 e which indicates that the cr sediments do not directly reach the eastern part of the yellow sea blocked by a strong physical boundary further the observed variations in proportions between huanghe changjiang and korean river derived sediments over the last 15 kyr notably an abrupt increase of cr contribution since 7 ka followed by a sudden drop at 3 4 ka exhibit a good correspondence with other mineralogical proxy records these temporal provenance changes witnessed robust palaeoenvironmental signals which fit to major climatic and oceanographic events linked with sea level intensity of the kuroshio current inflow and the east asian monsoon this study improves understanding of what pathways and sinks exist within the yecs basin and how rates of sediment supply from adjacent rivers have changed over time

experimental deformation of olivine single crystals at mantle pressures and temperatures abstract deformation experiments were carried out in a deformation dia high pressure apparatus d dia on oriented san carlos olivine single crystals at pressure p ranging from 3 5 to 8 5 gpa temperature t from 1373 to 1673 k and in poor water condition oxygen fugacity fo2 was maintained within the olivine stability field and contact with enstatite powder ensured an orthopyroxene activity aopx 1 two compression directions were tested promoting either 1 0 0 slip alone or 0 0 1 slip alone in 0 1 0 crystallographic plane here called respectively a slip and c slip constant applied stress and specimen strain rates e were monitored in situ using time resolved x ray synchrotron diffraction and radiography respectively transmission electron microscopy tem investigation of run products revealed that dislocation creep was responsible for sample deformation comparison of the obtained high p deformation data with the data obtained at room p by bai et al bai q mackwell s l kohlstedt d l 1991 high temperature creep of olivine single crystals 1 mechanical results for buffered samples journal of geophysical research 96 2441 2463 on identical materials deformed at comparable t fo2 aopx conditions allowed quantifying the p effect on a slip and c slip rheological laws a slip transition with increasing pressure from dominant a slip to dominant c slip is documented a slip appears sensitive to pressure which translates into the high activation volume v a 12 4 c m 3 mol in the corresponding rheological law while pressure has little effect on c slip with v c 3 4 c m 3 mol these results may explain the discrepancy between olivine low p and high p deformation data which has been debated in the literature for more than a decade

sedimentary responses to the cross shelf transport of terrigenous material on the east china sea continental shelf sedimentary responses to the cross shelf transport on the east china sea continental shelf are ascertained based on analyses of the sediment grain size and detrital mineral components of surficial sediments sedimentological data show that fine grained sediments can be transported across the continental shelf and have formed a tongue shaped zone with an axis located near 29 degrees n that extends from the coast to 124 degrees 40 e or beyond the sediments in this tongue shaped zone are rich in very fine silt and day as are the dominant sediment fractions discharged by the modern yangtze river indicating a modem terrigenous source sediment with grain sizes 7 9 phi is the main fraction that is transported across the continental shelf in contrast to the regions in the same longitude in the tongue shaped zone the relatively low heavy mineral content high schistose mineral content and high dolomite content and the mixture of fresh and weathered minerals show that modern yangtze river sediment has been widely transported to this region meanwhile the simultaneous existence of the fine grained tongue and a coarse grained area immediately south of the base of the tongue coincident with the nearshore kuroshio branch current intrusion area indicate that the kuroshio intrusion plays an important role in triggering the cross shelf flows c 2019 elsevier b v all rights reserved

colloform high purity platinum from the placer deposit of koura river gornaya shoriya russia abstract a microinclusion of colloform high purity platinum in a grain of platinum group minerals pgm from the alluvial gold bearing placer deposit in the south of western siberia russia was detected and characterized for the first time it is different in composition texture and conditions of formation from high purity platinum of other regions described in the literature the main characteristics of investigated high purity platinum are colloform layered texture admixture of fe 0 37 0 78 wt and paragenesis of cu rich isoferroplatinum hongshiite and rhodarsenide the pgm grain with high purity platinum is multiphase and heterogeneous in texture it is a product of intensive metasomatic transformation of cu rich isoferroplatinum pt 3 fe 0 6 cu 0 4 the transformation was carried out in two stages 1 copper stage including three substages cu rich isoferroplatinum copper platinum and hongshiite and 2 arsenic rhodarsenide the formation of high purity platinum was separated in time from the formation of isoferroplatinum and was carried out by precipitation from postmagmatic solutions

sedimentary signals of the upwelling along the zhejiang coast china abstract the muddy deposits of the zhe min coastal area have attracted much recent research interest however the sedimentary processes that dominate along the zhejiang coast remain controversial determining sedimentation rates is important for understanding sedimentary processes and depositional patterns in the present study 23 vibrocores were collected from the muddy area along the zhejiang coast to analyse their sediment accumulation rates over the past 100 years using 210pb geochronology three types of typical excess 210pb profiles were identified in the sediment vibrocores the spatial distribution of the sedimentation rates derived from the 23 vibrocores as well as previously published data demonstrated that the middle part of the study area around 29 n experienced relatively high sedimentation rates and that the rate of deposition gradually decreased landwards and seawards the location of high sedimentation rates is approximately consistent with that of the holocene maximum thickness deposition finest surface sediments and high concentration of chlorophyll resulting from the existence of upwelling along the zhejiang coast besides the fluvial inputs

in situ observation of crystallographic preferred orientation of deforming olivine at high pressure and high temperature abstract simple shear deformation experiments on polycrystalline olivine and olivine single crystal were conducted at pressures of 1 3 3 8 gpa and temperatures of 1223 1573 k to understand the achievement of steady state fabric strength and the process of dynamic recrystallization development of crystallographic preferred orientation cpo of olivine was evaluated from two dimensional x ray diffraction patterns and shear strain was measured from x ray radiographs the steady state fabric strength of the a type fabric was achieved within total shear strain of 2 at strains higher than 1 an increase in concentration of the 0 1 0 axes mainly contributes to an increase in fabric strength at strains higher than 2 the magnitude of v sh v sv i e ratio of horizontally and vertically polarized shear wave velocities scarcely increased in most of the runs the v sh v sv of peridotite 70 vol olivine 30 vol minor phases having the steady state a type olivine fabric coincides with that of recent global one dimensional models under the assumption of horizontal flow suggesting that the seismic anisotropy observed in the shallow upper mantle is mostly explained by the development of a type olivine fabric experimental results on the deformation of single crystal olivine showed that the cpo of olivine is influenced by the initial orientation of the starting single crystal because strain is concentrated in the recrystallized areas and the relic of the starting single crystal remains in the upper mantle the old cpo of olivine developed in the past may affect the olivine cpo developed in the present

probability of radial anisotropy in the deep mantle article i nfo it is well established that the earth s uppermost mantle is anisotropic but observations of anisotropy in the deeper mantle have been more ambiguous radial anisotropy the discrepancy between love and rayleigh waves was included in the top 220 km of prem but there is no consensus whether anisotropy is present below that depth fundamental mode surface waves for commonly used periods up to 200 s are sensitive to structure in the first few hundred kilometers and therefore do not provide information on anisotropy below higher mode surface waves however have sensitivities that extend to and below the transition zone and should thus give insight about anisotropy at greater depths but they are very difficult to measure we previously developed a new technique to measure higher mode surface wave phase velocities with consistent uncertainties these data are used here to construct probability density functions of a radially anisotropic earth model down to approximately 1500 km in the uppermost mantle we obtain a high probability of faster horizontally polarized shear wave speed likely to be related to plate motion in the asthenosphere and transition zone however we find a high probability of faster vertically polarized shear wave speed to a depth of 1500 km in the lower mantle we see no significant shear wave anisotropy this is consistent with results from laboratory measurements which show that lower mantle minerals are anisotropic but lpo is unlikely to develop in the pressure temperature conditions present in the mid mantle 2008 elsevier b v all rights reserved

precipitation and dissolution of chromite by hydrothermal solutions in the oman ophiolite new behavior of cr and chromite chromite is a typical refractory igneous mineral precipitated from mafic magmas at relatively high temperatures chromites commonly occur in sedimentary metamorphic and metasomatic rocks where they are interpreted as relics of an igneous phase and serve as the source of cr for low temperature cr bearing minerals we present evidence for the nucleation of chromite within hydrothermal solutions we have found minute euhedal chromite grains enclosed by uvarovite ca cr garnet in a diopsidite metasomatically replacing the layered gabbro of the oman ophiolite the uvarovite shows oscillatory concentric zoning in terms of cr no cr cr al and the chromite is embedded only in the high cr no zones of the uvarovite another diopsidite replacing peridotite in the underlying upper mantle section contains xenocrystic chromite which is partly dissolved this suggests that a hydrothermal solution collected cr by partial to total dissolution of chromite within the upper mantle and precipitated chromite along with high cr no uvarovite within the lower crust upsection the metasomatic agent involved was a co2 so2 and cl bearing hydrothermal solution containing appreciable silicate components that could carry cr possibly as a complex the hydrothermal chromite is similar in chemistry to that commonly found in igneous rocks e g cr no 0 8 mg mg fe2 0 1 0 2 tio2 0 3 wt and fe3 cr al fe3 up to 0 3 but its cr no is clearly different from that of mantle chromite 0 6 0 7 in peridotites and chromitites from the oman ophiolite the results from this study suggest that a hydrothermal origin is possible for chromites in ultramafic rocks that have experienced fluid activity assuming that there is sufficient chromite at the fluid source

numerical study on the pattern and origins of kuroshio branches in the bottom water of southern east china sea in summer pattern and origins of kuroshio branches in the bottom water of southern east china sea ecs were carefully examined by numerical simulations based on the regional ocean modeling system roms together with observations model results show that in the bottom water of ecs the intrusion pattern of kuroshio is mainly composed of an offshore kuroshio branch current okbc which bifurcated from the kuroshio northeast of taiwan flows nearly along the isobath of similar to 100 m and a nearshore kuroshio branch current nkbc which originated from the kuroshio northeast of taiwan upwells northwestward gradually from similar to 250 m to similar to 60 m then turns to northeast around 27 5 degrees n 122 e thereafter flows northeastward along the isobath of similar to 60 m and finally reaches at 30 5 degrees n where it turns to east furthermore we found that the nkbc mostly originated in the kuroshio subsurface water 120 250 m east of taiwan whereas the okbc mainly stemmed from the kuroshio water 60 120 m east of taiwan this pattern and origins of okbc and nkbc well addressed the observational phenomena that off the coast of zhejiang province china there were colder less saline and more phosphate rich bottom water near the isobath of similar to 60 m rather than near the isobath of similar to 100 m in august 2009 finally it is proposed that on southern ecs continental shelf kuroshio exhibits its intrusion branches by an anticyclonical stair structure bottom stair nkbc middle stair okbc and top stair kuroshio surface branch kbc

origin and emplacement of tertiary ultramafic complexes in northwest colombia evidence from geochemistry and kar smnd and rbsr isotopes abstract si undersaturated high mg basalts with early fractionated ultramafic cumulates viravira complex and a zoned ultramafic alaskan type intrusion condoto complex are located in the upper condoto river within the western cordillera of colombia these complexes are related in space and time and originated from a common parental magma the isotopic characteristics of the complexes are similar and plot close together near the mantle array in the nd vs sr diagram it is argued that the compositions of the viravira basalts and of geochemically comparable hornblende plagioclase dykes in the zoned complex are close to the parental melt from which both complexes derived this melt probably had a mafic tholeiitic composition and was supplied from two sources high grade partial melting 20 of moderately depleted mantle above a subduction zone major part and modification by a metasomatic lile and slightly lree enriched fluid which could have originated by dewatering of the subducting slab k ar dates of hornblende of the condoto complex indicate an emplacement age of about 20 ma this represents the youngest age on the earth of a zoned ultramafic intrusion textural features demonstrate that the zonal arrangement with a dunitic core was the result of a series of crystal mush intrusions of deeper seated unconsolidated cumulate fractionations the occurrence of these and further ultramafic complexes along a major n s strike slip fault substantiates an exceptional tectonic activity on the northwestern edge of the south american continent during the tertiary horizontal plate movements along the deeply penetrating fault system favoured a release of pressure and the formation of si undersaturated mg rich melts in the mantle high heat flow and the possibility of vertical migration allowed the intrusion of mantle derived melts into shallow levels of the upper crust in the condoto region these conditions were particularly provided by the intersection of the n s fault system with wnw ese trending transverse and oblique faults

viscoplastic self consistent and equilibrium based modeling of olivine lattice preferred orientations implications for the upper mantle seismic anisotropy anisotropy of upper mantle physical properties results from lattice preferred orientation lpo of upper mantle minerals in particular olivine we use an anisotropic viscoplastic self consistent vpsc and an equilibrium based model to simulate the development of olivine lpo and hence of seismic anisotropy during deformation comparison of model predictions with olivine lpo of naturally and experimentally deformed peridotites shows that the best fit is obtained for vpsc models with relaxed strain compatibility slight differences between modeled and measured lpo may be ascribed to activation of dynamic recrystallization during experimental and natural deformation in simple shear for instance experimental results suggest that dynamic re crystallization results in further reorientation of the lpo leading to parallelism between the main 010 100 slip system and the macroscopic shear thus modeled simple shear lpos are slightly misoriented relative to lpos measured in natural and experimentally sheared peridotites this misorientation is higher for equilibrium based models yet seismic properties calculated using lpo simulated using either anisotropic vpsc or equilibrium based models are similar to those of naturally deformed peridotites errors in the prediction of the polarization direction of the fast s wave and of the fast propagation direction for p waves are usually 15 moreover overestimation of lpo intensities in equilibrium based and vpsc simulations at high strains does not affect seismic anisotropy estimates because these latter are weakly dependent on the lpo intensity once a distinct lpo pattern has been developed thus both methods yield good predictions of development of upper mantle seismic anisotropy in response to plastic flow two notes of caution have nevertheless to be observed in using these results 1 the dilution effect of other upper mantle mineral phases in particular enstatite has to be taken into account in quantitative predictions of upper mantle seismic anisotropy and 2 lpo patterns from a few naturally deformed peridotites cannot be reproduced in simulations these abnormal lpos represent a small percent of the measured natural lpos but the present sampling may not be representative of their abundance in the earth s upper mantle

silicate inclusions in isoferroplatinum constraints on the origin of platinum mineralization in podiform chromitites abstract the origin of large platinum group mineral pgm nuggets inside chromitite schlieren in some ural alaskan type ultramafic complexes has been assigned to orthomagmatic processes a promising phenomenon which may provide new insights into the processes responsible for pge mineralization formation or at least place constraints on existing models are the multiphase inclusions hosted in pgm which have been previously found in platinum nuggets from alluvial deposits for the first time this study examines multiphase inclusions hosted in isoferroplatinum nuggets from lode chromitite schlieren in almost unaltered dunite from the matysken ural alaskan type complex koryak highlands far east russia these multiphase inclusions are comprised of diopside hydrous silicates apatite plagioclase k feldspar silica and other minerals that are distinctly different from the host dunite mineralogy taken together with similar mineral assemblages in cr spinel hosted inclusions these inclusions cannot be crystallization products of a mafic ultramafic melt but instead require an alternative explanation we critically evaluate different genetic models and conclude that a range of fluid assisted metamorphic processes should be involved in producing massive pgm within chromitite schlieren in dunites

deep structure and seismic anisotropy beneath the east pacific rise seismic velocities in the upper mantle beneath mid ocean ridges are known to exhibit anisotropy especially at depths shallower than 200 km in this study we present evidence for deeper anisotropy beneath fast spreading ridges based on simultaneous inversion of body wave travel times waveforms and surface wave phase velocities the dverticalt bsv shear wave speed is systematically faster by more than 2 than the dhorizontalt bsh one at depths of 200 300 km beneath the east pacific rise a result that is consistent with vertical alignment of the fast crystallographic axis of olivine this anomaly is especially coherent beneath the northern east pacific rise where the observations also support the presence of a modest mantle reflector near 260 km depth the anisotropy may be associated with deep vertical flow or finite strain and the presence of this reflector could signal a rheological transition near the bottom of the asthenosphere reflecting changes in flow direction development of partial melt or the persistence of a deep pre existing strain regime d 2005 elsevier b v all rights reserved

new type of olivine fabric from deformation experiments at modest water content and low stress a new type of olivine fabric was found by high strain simple shear deformation experiments in the presence of trace amounts of water at 0 5 2 2 gpa and 1470 1570 k in this fabric called e type fabric the olivine 100 axis is subparallel to the shear direction and the 001 plane is parallel to the shear plane this geometry suggests that the 100 001 slip system makes the dominant contribution to total strain this fabric is dominant at a modest water content 200 coh 1000 h 10 6 si at low stresses and high temperatures some mylonites from peridotite massifs show this type of olivine fabric which suggests the presence of water during the shear localization the seismic anisotropy caused by this fabric is qualitatively similar to that by dry fabric a type but the magnitudes of anisotropy are different between the two types for horizontal flow the amplitude of vsh vsv anisotropy is weaker but the amplitude of shear wave splitting is stronger for the e type fabric than for the a type dry fabric seismic anisotropy in the oceanic upper mantle may be due to the olivine e type fabric

pleistocene volcanic rocks from the fly highlands province of western papua new guinea a note on new sr and nd isotopic data and their petrogenetic implications abstract rb sr and sm nd isotopic and trace element abundance values have been determined for 15 mafic and intermediate rocks from six pleistocene volcanic centres of the fly highlands province 87sr 86sr and n d values range from 0 70362 to 0 70540 and 1 9 to 5 9 respectively these new data can be accounted for by contamination of mantle derived magmas by the continental crust through which the magmas have risen they do not however preclude derivation of some of the sr and nd from subducted crust nor are they inconsistent with sr and nd enrichments having taken place by means of mantle metasomatic events nevertheless there is no benioff zone beneath the fly highlands province although there is geological evidence for cretaceous subduction a preferred interpretation is that uncontaminated mantle derived magmas are related to the pliocene crustal uplift that caused the development of the highlands and which formed in response to a mid tertiary continent island arc collision

mantle dynamics beneath the east pacific rise at 17 s insights from the mantle electromagnetic and tomography melt experiment 1 the electromagnetic data from the mantle electromagnetic and tomography melt experiment are inverted for a two dimensional transversely anisotropic conductivity structure that incorporates a correction for three dimensional topographic effects on the magnetotelluric responses the model space allows for different conductivity values in the along strike cross strike and vertical directions along with imposed constraints of model smoothness and closeness among the three directions anisotropic models provide a slightly better fit to the data for a given level of model smoothness and are more consistent with other geophysical and laboratory data the preferred anisotropic model displays a resistive uppermost 60 km thick mantle independent of plate age except in the vicinity of the ridge crest in most inversions a vertically aligned sheet like conductor at the ridge crest is especially prominent in the vertical conductivity its presence suggests that the melt is more highly concentrated and connected in the vertical direction immediately beneath the rise axis the melt zone is at least 100 km wide and is asymmetric having a greater extent to the west off axis and to the east of the ridge the mantle is more conductive in the direction of plate spreading at depths greater than 60 km the flat resistive conductive boundary at 60 km agrees well with the inferred depth of the dry solidus of peridotite and the deeper conductive region is consistent with the preferred orientation of olivine inferred from seismic observations this suggests that the uppermost 60 km represents the region of mantle that has undergone melting at the ridge and has been depleted of water dissolved hydrogen by contrast the underlying mantle has retained a significant amount of water

asymmetric electrical structure in the mantle beneath the east pacific rise at 17 s the magnetotelluric component of the mantle electromagnetic and tomography melt experiment measured the electrical resistivity structure of the mantle beneath the fast spreading southern east pacific rise epr the data reveal an asymmetric resistivity structure with lower resistivity to the west of the ridge the uppermost 100 kilometers of mantle immediately to the east of the ridge is consistent with a dry olivine resistivity structure indicating a mantle depleted of melt and volatiles mantle resistivities to the west of the ridge are consistent with a low melt fraction about 1 to 2 percent interconnected melt distributed over a broad region and extending to depths of about 150 kilometers the asymmetry in resistivity structure may be the result of asymmetric spreading rates and a westward migration of the ridge axis and suggests distinct styles of melt formation and delivery in the mantle beneath the two plates

global mantle flow and the development of seismic anisotropy differences between the oceanic and continental upper mantle 1 viscous shear in the asthenosphere accommodates relative motion between earth s surface plates and underlying mantle generating lattice preferred orientation lpo in olivine aggregates and a seismically anisotropic fabric because this fabric develops with the evolving mantle flow field observations of seismic anisotropy can constrain asthenospheric flow patterns if the contribution of fossil lithospheric anisotropy is small we use global viscous mantle flow models to characterize the relationship between asthenospheric deformation and lpo and compare the predicted pattern of anisotropy to a global compilation of observed shear wave splitting measurements for asthenosphere 500 km from plate boundaries simple shear rotates the lpo toward the infinite strain axis isa the lpo after infinite deformation faster than the isa changes along flow lines thus we expect the isa to approximate lpo throughout most of the asthenosphere greatly simplifying lpo predictions because strain integration along flow lines is unnecessary approximating lpo with the isa and assuming a type fabric olivine a axis parallel to isa we find that mantle flow driven by both plate motions and mantle density heterogeneity successfully predicts oceanic anisotropy average misfit 13 continental anisotropy is less well fit average misfit 41 but lateral variations in lithospheric thickness improve the fit in some continental areas this suggests that asthenospheric anisotropy contributes to shear wave splitting for both continents and oceans but is overlain by a stronger layer of lithospheric anisotropy for continents the contribution of the oceanic lithosphere is likely smaller because it is thinner younger and less deformed than its continental counterpart

petrofabrics and seismic properties of garnet peridotite from the uhp sulu terrane china implications for olivine deformation mechanism in a cold and dry subducting continental slab abstract lattice preferred orientations lpo of olivine diopside enstatite and garnet from the zhimafang garnet peridotite body in the sulu ultrahigh pressure uhp metamorphic terrane china were measured using the electron backscatter diffraction ebsd technique the peridotite was captured from a mantle wedge immediately adjacent the subducted yangtze slab and then experienced the uhp metamorphism at 750 950 c and 4 7 gpa the olivine lpo is characterized by the 001 axis close to the stretching lineation and the 100 plane subparallel to the foliation indicating the prevailing of 100 001 slip enstatite lpo displays the dominance of 100 001 slip diopside developed complex lpo patterns that are difficult to explain using a single slip system of 100 001 garnet is almost randomly oriented due to its low volume fractions cubic symmetry and the presence of numerous slip systems calculated seismic properties of the peridotite yield a maximum p wave velocity normal to the foliation and a minimum along the foliation with anisotropy up to 8 in strongly sheared samples the s wave velocity pattern is complex but the fast polarization plane generally normal to the foliation the inferred shear sense from the olivine lpo is top to se in contrary to exhumation induced top to nw thrusting recorded in the quartz lpo implying that the olivine lpo formed at early uhp metamorphic conditions the olivine crystals have relatively low water contents 141 475 h 106 si indicating a fluid deficient environment for the lpo formation the present study suggests that a combination of low temperature and uhp plays a much more important role than the water content to promote the activation of 100 001 slip in olivine

variation of turbidity and particle transport in the bottom layer of the east china sea abstract field surveys of the bottom turbid layer were undertaken from the changjiang estuary to the mid continental slope area in the east china sea to study the bottom turbid layer formation process and ascertain the role of material transport a dramatic development of bottom turbid layers in the continental shelf area of the east china sea was observed from summer to fall this seasonal variation is relatively consistent with seasonal changes in the discharge of suspended particles ss from the changjiang the ss forming the bottom turbid layer in the east china sea are often fine grained particles transported from the continental coastal area which undergo continuous settling and resuspension during transport through the convectively mixed seawater season the average current velocities at the bottom b 10 m layer at the edge of the continental shelf were approximately 5 2 cm s in an east northeast direction but 2 9 cm s almost true north during the stratified season with the 200 m depth contour as the benchmark the bottom current at the continental shelf edge flowed from inside the continental shelf outward during the mixing season and from outside the continental shelf inward during the stratified seawater season the average horizontal flux of the ss is 60 mg m 2 s during the mixing season and 24 mg m 2 s during the stratified season with almost the same direction as that of the bottom current the direction of the ss horizontal flux in the bottom layers is dominated by the bottom current which is driven by the strong south north monsoon in the east china sea

northeastern pacific mantle conductivity profile from long period magnetotelluric sounding using hawaii to california submarine cable data we present results of a long period magnetotelluric mt investigation of the electrical structure beneath the eastern north pacific the electric field data consist of 2 years of continuously recorded voltages across an unpowered 4000 km long submarine telephone cable haw 1 extending from point arena california to oahu hawaii the electric field measurements are coherent to some degree with magnetic field measurements from honolulu observatory at periods of 0 1 to 45 days this coherence is enhanced at long periods over that observed with point electric field sensors due to horizontal averaging of the motional electric fields of spatial scale smaller than the cable length significantly diminishing their effect robust controlled leverage mt response estimates and their jacknife confidence limits are computed for the haw 1 to honolulu data an equivalent scalar mt response obtained from honolulu magnetic variations data is used to correct the haw 1 mt response for static shift and to extend the mt response estimate to periods of 100 days the composite response function satisfies necessary and sufficient conditions for consistency with a one dimensional conductivity structure and is most sensitive to structure between 150 and 1000 km inversion of the mt response reveals a conductive zone 0 05 0 1 s m between 150 and 400 km depth and a positive gradient below 500 km these observations are consistent with previous mt studies in the north pacific this upper mantle conductivity is too high to be explained by solid state conduction in dry olivine using reasonable mantle geotherms calculations based on measurements of hydrogen solubility and diffusivity in olivine indicate that h dissolved in olivine possibly combined with a lattice preferred orientation consistent with measured seismic anisotropy provide sufficient conductivity enhancement to explain the inversion results the high conductivity may also be explained by the presence of gravitationally stable partial melt comparison of the haw 1 results with long period mt studies conducted on land reveals differences in upper mantle conductivity between different tectonic regimes in particular the upper mantle beneath the pacific ocean is considerably more conductive than that beneath the canadian shield and similar in conductivity to that beneath the basin and range

environmental evolution of the east china sea inner shelf and its constraints on pyrite sulfur contents and isotopes since the last deglaciation abstract to better understand the depositional constraints on the sulfate reduction process we present a set of sulfur isotope data for hand picked pyrites 34spyr from the coarse fraction 63 250 m of bulk sediments coupled with the contents of carbonate total organic carbon toc and nitrogen tn as well as 13c values of the toc from sediments of core ec2005 on the inner shelf of the east china sea ecs since 16 4 ka our results show that core sediments were deposited in a terrestrial environment before 13 1 ka stage i when pyrite rarely occurred during stages ii 13 1 12 3 ka and iii 12 3 12 1 ka seawater began to influence the core location forming a tidal flat environment where abundant pyrites are well preserved then the inner shelf of the ecs was fully flooded and two intervals with high stage iv 12 1 6 0 ka stage vi 5 2 1 5 ka and low sedimentation rate stage v 6 0 5 2 stage vii 1 5 ka present are identified respectively when compared with previous 34s values of chromium reducible sulfur 34scrs derived from the bulk sediments 34spyr values are usually higher indicating the macroscopic pyrites form in the later stages of sedimentary diagenesis when ongoing sulfate reduction has distilled porewater sulfate to a high degree considering the wide occurrence of biogenic shallow gas dominated by ch4 in these sediments sulfate driven anaerobic oxidation of methane so4 aom and organoclastic sulfate reduction osr are expected to be two competitive pathways for sulfate reduction we propose that the changes in sedimentation rate controls the pace of migration of the sulfate methane transition zone smtz when sedimentation rate is low the smtz may be fixed in a certain depth e g sediments deposited in stage iii and v where h2s is produced by so4 aom in contrast when sedimentation rate is very high 1 cm yr the smtz would be deep and h2s is mostly produced by osr further our results imply that sulfur diagenesis in recent since 1 5 ka ecs mud sediments might be influenced by physical reworking e g typhoon and or biological activity bioturbation resulting in partial reoxidation of pyrite crystals in fluid mud our findings therefore demonstrate that pyrite sulfur isotope compositions bulk 34scrs hand picked 34spyr are sensitive to local environmental evolution and the combined use of these two indicators can provide new insights into pathway of sulfate reduction in unsteady environments

chemical composition and origin of platinum group minerals from placers of the aunik river buryatia russia abstract platinum group minerals pgms are occasionally encountered in gold placers around the world most research related to the gold placer deposits focuses on the origin migration and concentration of gold the primary commercial mineral in the placers both origin and fate of pgm are rarely studied the present study of pgm grains reveals complex relationships between the mineral phases within the grains conforms to the published results on immiscibility within certain pgm solid solutions presents evidence of alteration of pgms and shows the presence of unusual secondary minerals within the grains the studied pgm grains are os ir ru alloys and can be divided into two types based on their chemical composition the first type is solid solutions enriched in os and ru bearing inclusions of silicates such as olivine pyroxene and amphibole the second type is enriched in ir and pt with inclusions of sulfides tellurides and selenides such as cuproiridsite iridisite malanite cooperite laurite erlichmanite and tolovkite these two types of pgm have been described in other regions and the first type was attributed to ophiolitic origin of the mineralization the authors confirm this theory and find that the pgm of the aunik river placers likely originated from ophiolites of the shamanskaya spreading zone with a possible contribution from ultrabasic rocks of ural alaskan type the secondary mineralization of the pgm especially prominent in the peripheral parts of many studied samples is most likely the result of post magmatic metasomatic alteration interestingly an unnamed new mineral phase ir os se2 was detected in a hydrothermally altered grain

variability of cross shelf penetrating fronts in the east china sea images of 8 day mean chlorophyll a concentrations of the moderate resolution imaging spectroradiometer modis onboard of aqua satellite from 2002 to 2007 and of the sea viewing wide field of view sensor seawifs satellite from 1998 to 2007 are used to study the variability of the cross shelf penetrating fronts cpfs in the east china sea the analysis suggests that the generation of the cpfs has strong seasonal to interannual variations with more cpfs in summer and winter than in spring and fall each cpf lasts for a few days to a month the majority of the fronts are triangle shaped with their broad bases nearby the coast and their sharp heads penetrating into the middle shelf there are over 40 cpfs with penetrating distances exceeding 100 km over the east china sea during the past 10 years of the satellite era with the maximum ones reaching the kuroshio at the edge of the continental shelf of all the low cloud scenes of the satellite images more than 25 contain at least one cpf the high frequency occurrence of the cpfs suggests that the cpfs play an important role in cross shelf transport of heat effluent and land derived materials in the east china sea

development of a type olivine fabric in water rich deep upper mantle abstract water controls the activity of slip systems in olivine resulting in various types of olivine crystallographic preferred orientation i e fabric in mantle rocks the a type olivine fabric is the most commonly observed olivine fabric in natural peridotites development of a type olivine fabric developed by the 010 100 slip system is known to be limited to the water poor conditions of the shallow upper mantle 2130 ppm h si in olivine while b type fabric by the 010 001 slip system was observed under moderately wet conditions 750 2130 ppm h si developments of c type by the 100 001 slip system fabric was limited to water poor conditions v sh v sv the ratio of horizontally and vertically polarized shear waves with depth in the global one dimensional models is well explained by the olivine fabrics developed in the horizontal flow of a water poor mantle only a type olivine fabric can explain the vertical mantle flow which associates the seismic anisotropy of v sh v sv 200 km depth a strong anomaly of v sh v sv

high pressure and temperature fabric transitions in olivine and variations in upper mantle seismic anisotropy the effects of pressure on crystallographic preferred orientation cpo of olivine aggregates were investigated through simple shear deformation experiments at pressures between 2 1 and 7 6 gpa and temperatures of 1493 1673 k under dry conditions using a deformation dia apparatus and the variations in seismic anisotropy were evaluated under the earth s upper mantle conditions we found that the monotonic decrease in seismic anisotropy with depth is caused by the pressure dependency of the seismic properties of a type developed by the 010 100 100 slip system olivine fabric while the rapid decrease is caused by the fabric transition from a type to b c type by the hk0 001 001 slip systems at 7 6 gpa and 1673 k moreover an alternative transition from a type fabric to b type like fabric by the 010 001 001 slip system occurs at 7 6 gpa and lower temperature these two temperature dependent fabric transitions occurring at 7 6 gpa result in low seismic anisotropy with vsh vsv the ratio of horizontally and vertically polarized shear waves 1 at low temperatures i e old continental mantle conditions and vsh vsv 1 at high temperatures i e oceanic mantle conditions at greater depths consistent with seismological observations thus the variations of cpo with pressure and temperature in olivine under dry conditions can explain the seismic anisotropy signatures observed in the upper mantle without invoking other mechanisms

thermodynamics of water solubility and partitioning when it was realized that nominally anhydrous minerals could be a major storage site of water in the mantle smyth 1987 bell and rossman 1992 it also became rather obvious that many mantle samples probably have lost most of their water during ascent e g ingrin and skogby 2000 while analyses of natural samples therefore in many circumstances only provide a lower limit of the actual water content in the mantle measurements of water solubility give an upper limit of the amount of water that might be stored in a mineral experimental measurements of water solubility have therefore naturally evolved in the last decades as a major tool for understanding the water storage capacity of the mantle closely related to studies of water solubility are studies of water partitioning among minerals if the water solubility in two minerals is known under given conditions the partition coefficient is just the ratio of the water solubilities under the same conditions provided that the composition of the fluid coexisting with the two minerals is the same since the pioneering work of bai and kohlstedt 1992 and of kohlstedt et al 1996 the water solubility in all major upper mantle minerals has been studied as well as the partitioning of water between the minerals of the lower mantle and the transition zone solubility studies by themselves do not directly give the water content in the mantle they constrain the storage capacity of the mantle i e the maximum amount of water that may be stored if the mantle were water saturated however as most of the mantle is very likely water undersaturated the actual water content is probably far below the storage capacity estimates of the actual abundance and distribution of water in the mantle may be obtained by combining solubility and partitioning data with direct

global radially anisotropic mantle structure from multiple datasets a review current challenges and outlook abstract since the 1960s seismologists have mapped anisotropy in the uppermost mantle the mantle transition zone and the d region when combined with constraints from mineral physics and geodynamics anisotropy provides critical information on the geometry of mantle flow here we review the theory early work recent tomographic models and experimental constraints on radial anisotropy we discuss current challenges in resolving radial anisotropy seismically in particular we show that it is highly beneficial to use multiple datasets in inversions for anisotropy notably short period group velocity data with strong sensitivity to the crust we present a new whole mantle model of radial anisotropy based on surface wave and body wave travel time data along with incorporated moho perturbations our whole mantle model shares common features with previous global models and is consistent with results from several high resolution regional studies

cross shelf penetrating fronts off the southeast coast of china observed by modis 1 images of chlorophyll a concentration of the moderate resolution imaging spectroradiometer modis onboard of terra satellite show significant cross shelf penetrating fronts off the southeast coast of china in october 2000 and july 2002 analyses indicate that the significant offshore excursion of the october 2000 front is produced by a cross shelf jet that coincides with passages of atmospheric cold fronts which generate downwelling favorable winds the frontal activities during july 2002 are associated with strong southwesterly winds in favor of upwelling and are likely produced by instabilities of the coastal currents multiple fronts within the tongue of the changjiang yangtze river diluted water are observed in the summer of 2002 the significant cross shelf jet the instability waves and the multiple tongues of the changjiang diluted water are reported for the first time

effect of iron content on the creep behavior of olivine 1 anhydrous conditions high temperature high pressure triaxial compressive creep experiments were carried out on polycrystalline samples of olivine fexmg1 x 2sio4 with x fe fe mg 1 0 0 75 0 5 and 0 3 to investigate the influence of fe content on rheological properties of olivine under anhydrous conditions samples with grain sizes of 50 m were deformed at differential stresses of 50 to 300 mpa primarily in the dislocation accommodated grain boundary sliding creep regime for temperatures between 1273 and 1473 k with a confining pressure of 300 mpa our results combined with published results on aggregates of fa10 demonstrate that samples of fa30 fa50 fa75 and fa100 creep 15 75 365 and 1480 times faster than samples of fa10 respectively under the same conditions our experimental results can be described by the flow law e e gbs0 ngbs bd 2xfapexp qgbso xfart with e gbs0 6 2 5 2 105s 1 ngbs 3 9 p 1 5 0 1 qgbs0 440 10 kj mol and 45 4 kj mol based on measured dependence of strain rate on iron concentration we conclude that at the same thermodynamic conditions the martian mantle which is more rich in fe than earth s mantle will be a factor of 10 less viscous than earth s mantle

kuroshio subsurface water feeds the wintertime taiwan warm current on the inner east china sea shelf the taiwan warm current twc has an overwhelming influence on the heat salt and nutrients balance on one of the broadest shelf in the world the east china sea shelf in winter the twc flows in an unusual upwind direction and reaches the changjiang yangtze river estuary but its origin and pathway are intensely debated here combined evidences from current measurement hydrographic and stable isotopic data all suggest that the wintertime twc intrusion off the changjiang estuary mainly originates from the kuroshio subsurface water northeast of taiwan rather than from the taiwan strait warm water the kuroshio branched water northeast of taiwan can intrude into the inner shelf near the zhe min coast via bottom layer manifesting by a pronounced boundary at 50 m isobath around 28 n and thereby feeds the twc intrusion into the changjiang estuary the intrusion complicates the hydrological process in the estuary and shelf sea and its impact on marine environment deserves more research attentions

crustal evolution of island arc ultramafic magma galmoenan pyroxenite dunite plutonic complex koryak highland far east russia alaskan type platinum bearing plutons and potassium enriched mafic to ultramafic volcanic rocks are temporally and spatially associated within the late cretaceous paleocene achalvayam valaginskii intra oceanic palaeo arc system allochthonousy present in the kogak highland and kamchatka peninsula far east russia the compositions of the parental magmas to the alaskan type complexes are estimated using the galmoenan platonic complex as an example this complex composed of dunites pyroxenites and minor gabbros is the largest 20 km3 in the system and the best studied owing to associated platinum placer deposits the compositions of the principal mineral phases in the galmoenan intrusive rocks olivine fo 79 92 clinopyroxene 1 3 5 wt al2o3 0 1 0 5 wt tio2 and cr spinel 5 15 wt al2o3 and 0 3 0 7 wt tio2 are typical of liquidus assemblages in primitive island arc magmas in intra oceanic settings and closely resemble the mineral compositions in the achaivayam valaginskii ultramafic volcanic rocks the temporal and spatial association of intrusive and extrusive units and the similarity of their mineral compositions suggest that both suites were formed from similar parental magmas ne composition of the parental magma for the galmoenan platonic rocks is estimated using previously reported data for the achaivayam valaginskii ultramafic volcanic rocks and phenocryst hosted melt inclusions quantitative simulation of crystallization of the parental magma in the galmoenan magma chamber shows that the compositions of the cumulate units are best modelled by fractional cryallization with periodic magma replenishment the model calculations reproduce well the observed mineral assemblages and the trace element abundances in clinopyroxene based upon the estimated composition of the parental magmas and their mantle source we consider that fluxing of a highly refractory mantle wedge similar to the source of boninites by chlorine rich aqueous fluids is primarily responsible for both high degrees of partial melting and the geochemical characteristics of the magmas including their enrichment in platinum group elements