226 ra excess ba growth rates and u th ra ba systematic of baltic mn fe crusts abstract we analyzed 238u 234u 232th 230th and 226ra by thermal ionization mass spectrometry tims and ba by inductively coupled plasma optical emission spectrometry icp oes on eight mn fe crusts from the mecklenburg bay sw baltic and on one from the bothnian bay n baltic to test the 226raex ba ratio as potential geochronometer 226raex ba ratios decrease as a function of depth within the concretions in all analyzed profiles calculated diffusion coefficients are relatively low 9 10 7 cm2 yr for ra and 5 10 7 cm2 yr for ba and suggest that diffusion is negligible for the ra and ba record in addition 226raex ba ages are consistent and independent from the growth rate and growth direction within a crust thus the decline in 226raex ba ratio is most likely due to radioactive decay of 226raex although the influence of varying oxic conditions has still to be evaluated 226raex ba growth rates range from 0 021 to 0 0017 mm yr and tend to be lower than those calculated and based on stratigraphic methods 1 to 0 013 mm yr 226raex ba ages of concretions from shallow water environment 20 m depth mecklenburg bay sw baltic cover a time interval from 990 140 yr to 4310 310 yr bp corresponding to the stabilization of the sea level close to the present position about 5500 to 4500 yr ago one sample from greater depth 70 m bothnian bay n baltic showed a higher 226raex ba age of 6460 520 yr bp

rare earth abundance patterns in ferromanganese concretions from the gulf of bothnia and the barents sea abstract ferromanganese concretions from the svalbard shelf in the barents sea show slightly convex shale normalized ree patterns with no eu anomalies concretions from the gulf of bothnia northern part of the baltic sea exhibit an enrichment of light ree and negative eu anomalies this difference is interpreted as a consequence of different conveyor mechanisms of the ree to the sediment it is suggested that dissolving biogenic debris contributes to the convex pattern obtained in the barents sea whereas an inorganic suspended fraction with scavenged ree is the main carrier in the gulf of bothnia during oxic diagenesis in the sediment the scavenged ree are set free into the porewater and contribute to the distribution pattern in concretions found in the gulf of bothnia small mn rich spheroidal concretions are enriched two to five times in ree compared to average shale whereas mn poor flat concretions are low in ree specific surface area of the concretion and the depth of burial in the oxidized surface sediment are two factors that strongly affect the enrichment of the ree weak ce anomalies are present in the analysed concretions and a redox level dependence is seen

phosphorites co rich mn nodules and fe mn crusts from galicia bank ne atlantic reflections of cenozoic tectonics and paleoceanography a wide variety of marine mineral deposits were recovered from 750 to 1400 m water depths on galicia bank iberian margin mineral deposits include 1 carbonate fluorapatite phosphorite slabs and nodules that replaced limestone and preserved original protolith fabric 2 ferromanganese vernadite crusts with high mn and fe mn fe 1 contents and thick stratabound layers consisting mainly of mn up to 27 mno and fe 15 fe2o3 which impregnated and replaced the phosphorite 3 co rich mn nodules are composed of romanechite and todorokite laminae mn rich layers up to 58 mno contain up to 1 8 co 4 goethite nodules with fe up to 67 fe2o3 have low mn and trace metals we interpret this mineralization paragenesis to be related to major changes in oceanographic and tectonic regimes three phosphatization generations formed hardgrounds dated by 87sr 86sr isotopes as late oligocene early miocene and latest early miocene during the latest early miocene the hardground was fractured and breached due to regional intraplate tectonism which was coeval with a widespread regional erosional unconformity the stratabound layers and co rich manganese nodules were derived from low temperature geothermally driven hydrothermal fluids with fluid conduits along reactivated faults during middle and late miocene the introduction of vigorous deep water flow from the arctic generated growth of hydrogenetic ferromanganese crusts finally growth of diagenetic fe rich nodules late pliocene was promoted by the introduction of hypersaline mediterranean outflow water into the atlantic ocean

petrogenesis of the middle devonian gushan diorite pluton on the northern margin of the north china block and its tectonic implications the gushan diorite pluton located at the northern margin of the north china block was emplaced during middle devonian times shrimp u pb zircon age of 390 5 ma rocks from the pluton are characterized by low sio 2 and high alkali contents and they show monzodiorite compositions in a total alkali v silica tas plot they exhibit light ree enrichment no to slightly positive eu anomalies strong depletion in rb th u nb ta p zr hf and ti enrichment in ba k and sr low contents of y and yb and high sr y ratios they have a relatively narrow range of isotopic compositions with initial 87 sr 86 sr ratios of 0 7050 e nd t values of 9 5 to 7 5 and zircon e hf t values from 11 8 to 5 8 these features are remarkably similar to another middle devonian intrusion the shuiquangou syenitic complex at the northern margin of the north china block these similarities suggest that the two intrusions probably have a common origin they were considered to be derived from a type i enriched mantle ultimately with some involvement of ancient lower crustal components and were likely emplaced in a back arc extension environment related to southward subduction of the palaeo asian oceanic plate or during the cessation of the subduction aluminium in hornblende barometry studies of the middle devonian gushan pluton yielded emplacement depths of about 18 km combined with previous geobarometry results on the carboniferous plutons within the inner mongolia palaeo uplift on the northern margin of the north china block it is inferred that the uplift and exhumation of the plutons within the inner mongolia palaeo uplift during middle devonian to late carboniferous times were not as distinct as those during late carboniferous to early jurassic times and the strong uplift and exhumation of the inner mongolia palaeo uplift were achieved during late carboniferous to early jurassic times

cycling of iron manganese silica phosphorus calcium and potassium in two stratified basins of shagawa lake minnesota geochemical studies of fe mn si p ca and k were made in two basins of shagawa lake minnesota during summers 1977 1979 within the metalimnion upward and laterally diffusing fe ii oxidizes and co precipitates a large fraction of soluble p nevertheless the soluble fep ratio decreases while progressing upward through the oxidation zone the mean paniculate fesi ratio is 3 0 0 5 in the thermocline but because of the stoichiometric excess of dissolved si over fe and preferential associations between fe and p the oxidation of fe has a negligible effect on the dissolved sio2 profiles the lake sediments are net sources of ca k and p during summer stratification these elements are transported upward through the thermocline and exported from the lake despite the very active sediment release of dissolved sio2 and upward transport through the thermocline the lake acts as a net sink for biogenic opal in summer the prominent soluble mn maxima in the thermocline of the east basin result from antecedent sediment release mn2 and vertical transport primarily in the west basin followed by dispersion and oxidation in the epilimnion and finally downward settling and dissolution within the east basin thermocline rhodochrosite solubility does not influence mn2 profile development very large percentage increases in epilimnetic fe mn si and p occur simultaneously during episodes of wind activated entrainment of metalimnion water these increases are in stoichiometric agreement with the entrained water mass provided account is also taken of the preformed slurries overlying the metalimnetic shelf sediments in mid summer the bathylimnetic soluble fep ratio remains low since the cultural inputs of p were terminated in early 1973 this geochemical stability is explained by the large reserves of potentially mobile p in the upper post cultural sediments phosphorus release from these sediments and transport phenomena account for the persistent eutrophic condition of the lake during mid late summer despite the 80 reduction in external p loading

electrical resistivity structure of the upper mantle beneath northeastern china implications for rheology and the mechanism of craton destruction abstract the north china craton ncc and central asian orogen belt caob in northeastern china experienced a range of tectonic events during the phanerozoic dominated by lithospheric thinning of the eastern ncc in the late mesozoic and cenozoic in order to better understand the tectonic evolution of the ncc and the caob new broadband and long period magnetotelluric data were collected along a north west to south east trending profile that extended from the caob across the yanshan belt the tanlu fault zone to the liaodong peninsula a two dimensional 2 d resistivity model was derived from inversion of the transverse electric mode transverse magnetic mode and vertical magnetic field data in the crust of the caob the resistivity model shows a northwest dipping low resistivity zone beneath the solonker suture that is identified as the suture zone formed by the collision between the siberian and north china cratons the upper mantle of the caob is characterized by moderate resistivity values 300 1000 m that are best explained by the presence of hydrogen dissolved in olivine the water concentration of the caob mantle is comparable to values reported for the asthenosphere and cratons that have been significantly hydrated the ncc upper mantle is generally lower in resistivity than the caob upper mantle and a zone of lower resistivity is observed in the upper mantle at the southeast end of the profile beneath the ncc superimposed on this southeast decrease in upper mantle resistivity three low resistivity zones were imaged 1 below the xilamulun fault 2 close to the north south gravity lineament and 3 between the northern yanshan belt and tanlu fault zone the low resistivities can be explained as regions of partial melts or fluids perhaps caused by asthenospheric upwelling together with seismic imaging results and geochemical data the resistivity model shows that the modification of the lithosphere associated with craton destruction has occurred in a spatially non uniform manner in the region of the ncc investigated in this study

manganese cycles and the origin of manganese nodules oneida lake new york u s a abstract oneida lake is a large shallow lake in central new york that is characterized by high algal productivity and concentrated deposits of freshwater manganese nodules budgets for mn in the lake and its tributaries show a net loss of 23 metric tons of manganese within the lake per year with 95 deposited in manganese nodules and the rest incorporated in the sediments erosion of nodules in the shallow well oxygenated central part of the lake produces fragments of nodules as well as mn coated sand grains that are transported to adjacent deeper more reducing parts of the lake where they sink into the anoxic sediments and mno2 is reduced to mn2 this produces a high concentration of mn2 in the pore waters of these sediments and mn2 diffuses back into the water column growth of manganese nodules in oneida lake is characterized by periods of rapid accretion 1 mm 100 yr alternating with periods of no growth or erosion rapid growth of nodules may be aided by the stripping of mn from the water column by algae and bacteria in addition the high algal productivity of oneida lake produces a high ph high oxygen environment during the summer months that is maintained throughout the water column in the central part of the lake by almost continuous wind mixing thus the cycle of mn within the lake involves an interaction of the weather the biota the sediments the nodules and mn dissolved in the lake and interstitial waters

strontium dissolved and particulate loads in fresh and brackish waters the baltic sea and mississippi delta a study was conducted of the isotopic composition and concentration of sr and of major elements in dissolved and suspended loads of fresh and brackish waters the purpose was to establish the contributions of different parent rocks and minerals to sr during weathering and transport and to identify the role of fe mn oxyhydroxides in the redistribution of sr in the water column during the sedimentary cycle studies were conducted on a profile across an oxic anoxic boundary in the baltic and on rivers covering behavior over an annual cycle in general the 87sr 86sr ratios differ between particulate and dissolved loads with more radiogenic sr in the particulate loads these differences are attributed to differential weathering of minerals where high rb sr minerals dominate the particulate load and low rb sr the dissolved load there is broad correlation of 87 sr 86 sr with k al in the suspended load the differences in 87 sr 86 sr between suspended and dissolved load are highly variable and are related to the fe or mn concentration on the particulates in samples with high fe al the difference becomes small a good correlation was found between sr al and fe al or mn al in the particulates both in brackish and fresh waters sr is removed from solution both in rivers and in the baltic sea whenever there is formation of fe mn oxyhydroxide particulates this precipitation greatly diminishes the difference in isotopic composition of the dissolved and suspended loads as the particles containing fe mn oxyhydroxides settle they dissolve in anoxic zones and release sr this provides a mechanism for sr redistribution in the water column sr is thus only quasi conservative in environments where fe mn oxyhydroxides form or dissolve from consideration of the isotopic differences in sr between dissolved and suspended loads it follows that the net sr input depends upon weathering characteristics of the contributing mineral phases changes in weathering mechanisms due to climate change may cause sr isotopic shifts in the marine environment

end permian to mid triassic termination of the accretionary processes of the southern altaids implications for the geodynamic evolution phanerozoic continental growth and metallogeny of central asia the altaids is one of the largest accretionary orogenic collages in the world with the highest rate of phanerozoic continental growth and significant metallogenic importance it is widely accepted that subduction related orogenesis of the altaids started in the late precambrian and gradually migrated southward present coordinates however it is uncertain when and how the building of the altaids was finally completed based on structural geology geochemical geochronological and paleomagnetic data this paper presents late paleozoic to early mesozoic accretionary tectonics of two key areas north xinjiang in the west and inner mongolia in the east together with neighboring mongolia the late paleozoic tectonics of north xinjiang and adjacent areas were characterized by continuous southward accretion along the wide southern active margin of siberia and its final amalgamation with the passive margin of tarim which may have lasted to the end permian to early mid triassic in contrast in inner mongolia and adjacent areas two wide accretionary wedges developed along the southern active margin of siberia and the northern active margin of the north china craton which may have lasted to the mid triassic the final products of the long lived accretionary processes in the southern altaids include late paleozoic to permian arcs late paleozoic to mid triassic accretionary wedges composed of radiolarian cherts pillow lavas and ophiolitic fragments and high pressure ultrahigh pressure metamorphic rocks permian alaskan type zoned mafic ultramafic complexes intruded along some major faults of the tien shan we define a new tarim suture zone immediately north of the tarim craton that is probably now buried below the tien shan as a result of northward subduction of the tarim block in the cenozoic the docking of the tarim and north china cratons against the southern active margin of siberia in the end permian to mid triassic resulted in the final closure of the paleoasian ocean and terminated the accretionary orogenesis of the southern altaids in this part of central asia this complex geodynamic evolution led to formation of giant metal deposits in central asia and to substantial continental growth

crustal structure of mainland china from deep seismic sounding data abstract since 1958 about ninety seismic refraction wide angle reflection profiles with a cumulative length of more than sixty thousand kilometers have been completed in mainland china we summarize the results in the form of 1 a new contour map of crustal thickness 2 fourteen representative crustal seismic velocity depth columns for various tectonic units and 3 a pn velocity map we found a north south trending belt with a strong lateral gradient in crustal thickness in central china this belt divides china into an eastern region with a crustal thickness of 30 45 km and a western region with a thickness of 45 75 km the crust in these two regions has experienced different evolutionary processes and currently lies within distinct tectonic stress fields our compilation finds that there is a high velocity 7 1 7 4 km s layer in the lower crust of the stable tarim basin and ordos plateau however in young orogenic belts including parts of eastern china the tianshan and the tibetan plateau this layer is often absent one exception is southern tibet where the presence of a high velocity layer is related to the northward injection of the cold indian plate this high velocity layer is absent in northern tibet in orogenic belts there usually is a low velocity layer lvl in the crust but in stable regions this layer seldom exists the pn velocities in eastern china generally range from 7 9 to 8 1 km s and tend to be isotropic pn velocities in western china are more variable ranging from 7 7 to 8 2 km s and may display azimuthal anisotropy

crustal structure of the northern margin of the north china craton and adjacent region from sinoprobe02 north china seismic war r experiment abstract the sinoprobe02 north china seismic experiment consisted of three seismic recording efforts along a 450 km long profile the profile extended from northwest of beijing across the northern margin of the north china craton ncc and across the southeastern portion of the central asian orogenic belt caob to the solonker suture zone we processed analyzed and modeled the data collected during a wide angle reflection and refraction effort the recording of seismic waves from 8 explosions was conducted in 4 deployments of 300 texan recorders with station spacings of 1 1 5 km the p wave field provided good quality data for most of the profile arrivals of refracted and reflected waves from sediments and basement pg intracrustal phases pcp plp and the moho pmp pn were typically observed travel time modeling was done layer by layer using the top to bottom approach and was constrained by a coincident deep reflection seismic profile the initial velocity model was altered by trial and error and the forward model was updated by damped least squares inversion in our modeling calculated travel times fit observed arrivals for all 1439 traces with an average rms error of 0 113 s the final 2 d p wave velocity model contains many features of tectonic significance 1 the velocity structure varies significantly from the ncc to the caob 2 thicker crust appears beneath the yinshan yanshan belt and was probably generated by compression in the early jurassic and modified during the craton s destabilization and extension the flat and relatively shallow moho in the caob may be attributed to the extension 3 strong velocity variations beneath the bainaimiao arc and ondor sum subduction accretion complex indicate that multiple pulses of magmatism occurred during the complex tectonic evolution of this area

geochemistry of ferromanganese nodules from domes site a northern equatorial pacific multiple diagenetic metal sources in the deep sea abstract the major and minor element composition of ferromanganese nodules from domes site a has been determined by x ray fluorescence methods three phases appear to control the bulk compositions mn and fe oxyhydroxides and aluminosilicates relatively wide compositional variations are evident throughout the area nodules with high mn fe ratios high cu mg mo ni and zn concentrations and high todorokite mno 2 ratios have granular surface textures and are confined to an east west trending depression with thin quaternary sediment cover nodules with low mn fe ratios high concentrations of as ca ce co la p sr ti v y and zr and low todorokite mno 2 ratios have smooth surfaces and are confined to shallower areas with relatively thick quaternary sediment to the north and south of the depression all nodules in the area have compositions which are influenced by diagenesis but those with the most marked diagenetic signature high mn fe and cu ni ratios low ce la ratios and more todorokite are found in areas of very slow or non existent sedimentation many of these nodules are actually in contact with outcropping tertiary sediment this paradox may be resolved by postulating by analogy with some shallow water occurrences that the nodules accrete from bottom waters which have enhanced particulate and dissolved metal contents derived from diagenetic reaction in areas remote from the site of nodule formation the metals are supplied in a bottom flow probably antarctic bottom water which also erodes or prevents modern sedimentation in the depression nodules on the flanks of the depression are not evidently affected by this flow and derive at least pan of their constituent metals from diagenetic reaction in the underlying quaternary sediment apparently abyssal diagenetic nodules can have an immediate and a remote diagenetic metal source metal fluxes derived from pore water dissolved metal gradients may not be relevant to particular accreting nodules if a significant fraction of their metals is derived from outside the area in which they form

crustal structures revealed from a deep seismic reflection profile across the solonker suture zone of the central asian orogenic belt northern china an integrated interpretation abstract the solonker suture zone is one of the most important tectonic boundaries in the southeastern part of the central asian orogenic belt caob an 630 km long reflection seismic profile across this suture was recently completed by the chinese sinoprobe project the processed seismic data show clear crustal structures and provide new constraints on the tectonic and crustal evolution models the moho is delineated as a relatively flat boundary between a strongly reflective lower crust and a transparent mantle at a depth of 40 45 km 14 5 s two way travel time which is in agreement with the refraction data recorded along the same profile in a broad view the profile images an orogen that appears bivergent with and approximately centered on the solonker suture zone the southern portion of this profile is dominated by a crustal scale cratonward propagating fold and thrust system that formed during the late permian and triassic through collision and subsequent convergence in a post collisional stage the major thrust faults are truncated by mesozoic granitoid plutons in the upper crust and by the moho at the base of the crust this geometry suggests that the moho was formed after the thrusting event the northern portion of the profile although partially obliterated by post collisional magmatic bodies shows major south dipping folding and thrusting bands of layered reflectors immediately overlying the moho are interpreted as basaltic sills derived from the mantle episodic mafic underplating may have occurred in this region giving rise to post collisional magmatic events and renewal of the moho a few mantle reflectors are also visible the overall geometry of these mantle reflectors supports the tectonic models that the southern orogen manchurides experienced south directed subduction and the northern orogen altaids underwent north directed subduction prior to collision along the solonker suture zone

hematite spherules at meridiani results from mi mini tes and pancam 1 we report on observations of hematite bearing spherules at meridiani planum made using the microscopic imager mi mini thermal emission spectrometer mini tes and panoramic camera pancam instruments on the mars exploration rover opportunity spherules were observed on soil surfaces and in outcrop rocks both on undisturbed surfaces and in abraded surfaces ground using the rock abrasion tool rat spherule size and shape change little along the 850 m eastward traverse from eagle crater to endurance crater but spherules decrease and then slightly increase in size along the 6 km traverse from endurance south to victoria crater local populations range from submillimeters to several millimeters in diameter an additional small diameter 100 m size population is possible an increase in irregular shapes is found near victoria crater this combined with the size decrease south of endurance suggests either a changing depositional environment or variation in the duration and timing of diagenetic events the dominant smaller size population observed early in the mission in aeolian areas and ripple crests is observed as the primary size population in abraded outcrop farther south this suggests that successively younger beds are exposed at the surface along the southward traverse stratigraphically higher units removed by erosion could be recorded by the present surface lag deposit coordinated systematic observations are used to determine optical and infrared hematite indices of the surface soils in pancam and mini tes in spite of the systematic variation seen in mi both pancam and mini tes indices are highly variable based on the local surface and neither show systematic trends south of endurance the lack of a 390 cm 1 feature in mini tes spectra suggests concentric or radial interior structure within the spherules at scales too fine for mi to observe mini tes does not detect any silicate component in the spherules a bound water component in soils or in exchange with the atmosphere is observed these spherules have been previously interpreted as concretions formed within what were once water saturated diagenetically altered dirty evaporate sandstone sediments our observations support this interpretation however no single terrestrial analog provides a model that can account for all attributes of the spherules on mars

massive mn carbonate formation in the landsort deep baltic sea hydrographic conditions temporal succession and mn budget calculations abstract the sediments of the landsort deep and gotland basin in the central baltic sea are strongly enriched in mn carbonate however conceptual models attempting to explain the intense mn carbonate precipitation in both basins are in part conflicting in the gotland basin model deposited mn oxides are converted to mn carbonate after the oxygenation of euxinic bottom waters enriched in dissolved mn by major baltic inflows huckriede and meischner 1996 by contrast according to the landsort deep model mn carbonate precipitation occurs independent of oxygenation events below a euxinic water column lepland and stevens 1998 lenz et al 2015 in this study we investigated mn solid phase signatures in recent sub recent well dated sediments from the landsort deep and compared them to long term observations to identify the hydrographic conditions favoring mn carbonate formation the comparisons of water column o2 and sulfide time series with sedimentary mn carbonate enrichments identified long lasting bottom water oxygenation as an important environmental factor in the enhancement of mn carbonate precipitation up to 32 wt mn in the landsort deep thus by preventing the escape of dissolved mn from still reducing sediments into the open water column these conditions allow the accumulation of large amounts of mn oxide particles at the sediment water interface with their subsequent conversion to mn carbonate the euxinic conditions that have prevailed almost continuously in the landsort deep since roughly ad 2000 do not favor mn enrichment maximum 0 9 wt mn highlighting the importance of the recurring oxygenation of bottom water most likely via medium intensity inflows the mn abundances in seven sediment cores from water depths of 190 437 m together with mn balance calculations indicated that the mn inventory in the water column in response to porewater mn reflux and detrital mn input is sufficient for mn carbonate enrichment only in the deepest part of the basin

palaeozoic accretionary and convergent tectonics of the southern altaids implications for the growth of central asia the southern altaids present a unidirectional section from mongolia to china through an accretionary orogen that youngs progressively from neoproterozoic in the north to permian in the south the orogen formed by forearc accretion of island arcs accretionary wedges ophiolites and precambrian microcontinents this regularity was upset by early growth within the ocean of arcs that later collided at the accreting continental margin by imbrication of old ophiolites with young arcs and by himalayan style thrust nappe tectonics when an arc collided into a microcontinent lateral growth of the southern altaids represents a massive addition of juvenile material to the palaeozoic crust

the lithospheric structure of the solonker suture zone and adjacent areas crustal anisotropy revealed by a high resolution magnetotelluric study

the enigmatic yinshan fold and thrust belt of northern china new views on its intraplate contractional styles the east to east northeast trending yinshan belt lies within north china extending westward at least 1100 km from china s eastern coast to inner mongolia this intraplate jurassic cretaceous belt underwent contractional and normal faulting folding and contemporaneous terrestrial sedimentation and magmatism current views on its contractional deformational style favor relatively limited thick skinned faulting of archean basement and cover units these views are challenged however by recent discoveries in the eastern part of the belt of south directed ductile nappe formation and large displacement 40 45 km thin skinned northward thrust faulting both involving archean and younger rock units collision of the siberian and north china plates upon closure of a jurassic and early cretaceous mongolo okhotsk ocean more than 800 1100 km to the north may have been responsible for yinshan north south contraction some patterns of contraction e g jurassic cretaceous ductile nappe formation appear to have been influenced by a superposed magmatic regime related to westward subduction of a pacific basin plate beneath the north china plate

crustal structure across the yanshan belt at the northern margin of the north china craton abstract we applied an integrated receiver function imaging technique to the teleseismic data from 54 ncisp iii broadband seismic stations to study the fine scale crustal structure beneath the eastern yanshan belt ysb and adjacent areas at the northern margin of the north china craton ncc the robustness and reliability of the resultant crustal image were noticeably improved by achieving imaging consistency between common conversion point stacking and waveform inversion of the receiver functions our imaging result revealed substantial lateral heterogeneities in the crust of the study region as displayed by the undulating intra crustal interfaces highly varying upper middle and lower crust thicknesses and interlayers of low and high velocities the crustal structure of the ysb is characterized by significant structural variations together with a sharp moho a thin to normal crust and a lower crust with lower velocity and normal thickness it differs markedly from the bohai bay basin and the taihang mountains within the interior of the ncc the distinct features and structural complexity of the ysb might be attributed to the complex tectonic history of the region especially the multiple phases of contraction and possible occurrence of crustal delamination which is in large contrast to other subregions of the ncc where tectonic extension likely dominated the crustal deformation since the late mesozoic

the ratio of tellurium and selenium in geological material as a possible paleo redox proxy abstract only few data for both tellurium and selenium in different geological materials including international reference materials have been available so far in this study the te se ratio has been investigated in more detail to provide a better understanding of the correlation of these two elements in the geological environment nine international reference materials irms and 79 different geological samples spanning a wide range of formation times and conditions from the paleoproterozoic to present were analyzed with quadrupole dynamic reaction cell drc icp ms these samples include basalts shales river and beach sediments loess dolomites a recent cold water coral precambrian manganese and iron formations and cenozoic marine ferromanganese nodules and crusts a wide range of concentrations between 0 01 and 1 5 g g for se and 0 01 and 90 g g for te was measured and the most interesting feature was found to be the te se ratio in the different geological matrices while most rock and sediment samples fall within the range of te se ratios typical of the average earth s crust a significant enrichment of te over se is evident for modern marine mn fe oxide precipitates with the most pronounced te enrichment found for hydrogenetic ferromanganese crusts which form under fully oxidizing conditions the apparent positive trend of the degree of te se fractionation with the redox potential of the formation environment suggests that the te se ratio may represent a potential paleo proxy for redox environments

land uplift effects on the phosphorus cycle of the baltic sea the isostatic land uplift after the latest glaciation period in northern europe means that the descending wave base in the eutrophicated baltic sea continuously exposes new bottom areas to increasing wind and wave induced erosion erosion adds considerable amounts of phosphorus p and clay particles to the water column this study has used a dynamic mass balance model to investigate how land uplift affects the whole p cycle in the five major subbasins of the baltic sea the model uses a unitary set of variables and constants for all subbasins with the exception of measurable basin specific driving variables differences in p concentrations between the subbasins could be quite accurately quantified only when the land uplift gradient was used as a driving variable the clarifying effect from clay particles was found to be a major reason why those subbasins with the most intensive land uplift rates were also the ones with the lowest p concentrations without using the land uplift gradient as a model input concentration differences could not be quantitatively explained in a meaningful way furthermore simulations showed that clay particle erosion from land uplift has a substantial impact on all major internal p fluxes of the baltic sea at the turn of the millennium one of the subbasins the bothnian bay was oligotrophic whilst the other four major subbasins were mesotrophic without the clarifying effect from the clay particles added to the water column during erosion of the rising seafloor all five major subbasins of the baltic sea would probably be substantially more eutrophic

temporal variations in dissolved and suspended iron and manganese in the kalix river northern sweden abstract particulate and dissolved fe and mn were measured once a week from may to september 1982 in the kalix river north sweden during winter baseflow the dissolved fe concentration was 450 g l 1 early snow melt discharge increased the concentration slightly but during springflood maximum the concentration decreased to a minimum value of 60 g l 1 in mid july particulate matter in the kalix river is dominated by fe which ranges between 14 and 38 of the ashed suspended load 70 80 of the total fe load being retained by 0 45 m filters approximately 10 of particulate fe can be accounted for by a detrital phase the particulate fe al ratio showed a mean value of 6 5 which is more than ten times the ratio in mean world river particulate fe showed a peak during early snowmelt and decreased during maximum discharge similar to dissolved fe dissolved mn concentrations ranged from 1 1 to 53 4 m l 1 with a mean value of 11 2 12 4 g l 1 whereas particulate mn ranged from 3 1 ti 18 2 g l 1 with a mean concentration of 10 6 4 9 g l 1 during may and june most mn was transported in the dissolved phase whereas in july and august the particulate fraction dominated there was a drastic increase in non detrital particulate mn with a concomitant decrease in the dissolved fraction in early july with peak values in mid july and early august the decrease in dissolved mn and increase of particulate mn is probably the consequence of two processes namely addition of non detrital particulate mn to the river possibly from lakes and transformation of dissolved mn to a particulate phase within the river a combination of increased ph temperature and particulate mn triggered the precipitation of dissolved mn although the significance of each factor can not be evaluated from this study

geochemistry of manganese in the kalix river northern sweden dissolved and suspended mn in the kalix river northern sweden were measured weekly over a period of eighteen months during the same period four lakes in the kalix catchment were sampled at their outlets and in vertical profiles within the lakes together with a stream draining a series of mires with shallow lakes snow melting in mid may increased the dissolved mn concentration in the river tenfold compared with a concentration of 5 g l 1 during the winter discharge january to april we suggest that the increase was caused by mn rich mire water mixing with melting snow and being transported to the river large concentrations of dissolved mn built up in the hypolimnion of the lakes studied during the icecovered period break up of the ice and spring overturn in june increased the dissolved mn concentration tenfold in lake discharge and a concomitant peak in the dissolved mn concentration was observed in the river lake derived mn was the dominant source for mn in the river during this time suspended mn in the river was hosted mainly in detrital particles during flood in may in mid june non detrital suspended mn started to accumulate and reached a maximum in late july and early august the mnal ratio was 25 times higher during this period than during flood in may suggesting the precipitation of an mn oxyhydroxide phase the precipitation of the non detrital mn rich phase was correlated in time with increased temperature increased ph and increased concentration of suspended biogenic particles the precipitation of dissolved mn was biologically mediated sedimentation and mineralisation of the non detrital mn phase in river and lake sediments resulted in a steady increase of the dissolved mn concentration in the river water during autumn

sedimentological geochemical and microfaunal responses to environmental changes around the cenomanian turonian boundary in the outer carpathian basin a record from the subsilesian nappe poland abstract sedimentological micropalaeontological and geochemical data from the upper cenomanian lower turonian zasan section outer carpathians subsilesian nappe poland provide new insights into the sedimentary environment and its changes in a basin at the northern margin of the western tethys a global oceanic event oae2 has been identified on the basis of lithology and radiolarian stratigraphic data this event is marked by a series of organic rich toc up to 5 non calcareous shales practically devoid of benthic microfossils indicative of bottom water anoxia the marine type of organic matter and the occurrence of radiolarian rich layers with abundant small opportunistic forms suggest that coastal upwelling was probably the main driving force for the accumulation of organic matter during the latest cenomanian the early diagenetic ferromanganese nodules followed by a 30 cm thick series of manganese rich non calcareous variegated shales and bentonites directly overlie the black facies of oae2 the fe mn nodules formed in two stages reflecting changes in bottom water dynamics across the c t boundary during the first stage the fe mn carbonate nodules were precipitated in presence of anoxic pore and or bottom water that could be episodically oxygenated later an increase in deep water circulation led to strong oxygenation of the bottom and pore water causing diagenetic modification of the nodule carbonate into ferromanganese oxides and hydroxides the manganiferous sediments recorded in the zasan section represent an isochronous horizon within the outer carpathian basin probably concurrent with manganese enrichments in many other epicontinental seas and deep water basins coinciding with the end of the carbon isotope excursion close to the base of the turonian the manganese event may have been related to increased deep water circulation associated with the maximum flooding of the late cenomanian early turonian transgression the mn event may have also been enhanced as a result of remobilization of mn 2 dissolved in anoxic bottom and pore waters in the organic rich sediments directly underlying the manganese sediments the lower turonian succession records increasing but not completed oxygenation of bottom water the oxygenation was interrupted by periods of anoxia marked by a few intervals of dark laminated black shales strongly enriched in organic matter toc up to 10 their marine origin and the occurrence of radiolarian rich layers demonstrate enhanced primary productivity and a low clastic supply during the sea level high stand frequency of radiolarian rich layers increases up section reflecting an increase in upwelling circulation at the northern margin of the carpathian basin during the early turonian

fast growing shallow water ferro manganese nodules from the western baltic sea origin and modes of trace element incorporation abstract ferro manganese nodules of the western baltic sea reveal enhanced heavy metal concentrations since the end of the 19th century and are therefore potentially useful for retrospective monitoring of the heavy metal pollution history however only zn shows a significant rise even though cu is also introduced to the western baltic sea by natural and anthropogenic sources this study focused on geochemical considerations to evaluate the mechanism responsible for the predominance of zn in ferro manganese nodules compared to cu the particulate and dissolved metal fractions in the water column in the fluffy layer an approximately 2 cm thick sediment layer situated at the sediment water interface and in the pore water adjacent to ferro manganese nodules were studied the analysis of the dissolved fraction and speciation studies were carried out using cathodic stripping voltammetry csv the particulate fraction and the pore water were analyzed via graphite furnace atomic absorption spectroscopy gf aas and inductively coupled plasma optical emission spectroscopy icp oes the fluffy layer provides high quantities of mn fe zn and cu to the dissolved fraction of the bottom water during the stratification period hence the signal manifested in the ferro manganese nodules consists of newly emitted elements on top of the amount collected in the fluffy layer over many years and remobilized throughout the stratification trace elements with the tendency to form weak inorganic complexes in the water column like zn are more likely to be incorporated in ferro manganese nodules and therewith document the anthropogenic metal input while elements which tend to form strong organic complexes such as cu are scavenged by particulate organic matter in the water column and the fluffy layer

architecture and mineral deposit settings of the altaid orogenic collage a revised model abstract the altaids are an orogenic collage of neoproterozoic paleozoic rocks located in the center of eurasia this collage consists of only three oroclinally bent neoproterozoic early paleozoic magmatic arcs kipchak tuva mongol and mugodzhar rudny altai separated by sutures of their former backarc basins which were stitched by new generations of overlapping magmatic arcs in addition the altaids host accreted fragments of the neoproterozoic to early paleozoic oceanic island chains and neoproterozoic to cenozoic plume related magmatic rocks superimposed on the accreted fragments all these assemblages host important many world class late proterozoic to early mesozoic gold copper molybdenum lead zinc nickel and other deposits of various types in the late proterozoic during breakup of the supercontinent rodinia the kipchak and tuva mongol magmatic arcs were rifted off eastern europe siberia and laurentia to produce oceanic backarc basins in the late ordovician the siberian craton began its clockwise rotation with respect to eastern europe and this coincides with the beginning of formation of the mugodzhar rudny altai arc behind the kipchak arc these earlier arcs produced mostly cu pb zn vms deposits although some important intrusion related orogenic au deposits formed during arc arc collision events in the middle cambrian and late ordovician the clockwise rotation of siberia continued through the paleozoic until the early permian producing several episodes of oroclinal bending strike slip duplication and reorganization of the magmatic arcs to produce the overlapping kazakh mongol and zharma saur valerianov beltau kurama arcs that welded the extinct kipchak and tuva mongol arcs this resulted in amalgamation of the western portion of the altaid orogenic collage in the late paleozoic its eastern portion amalgamated only in the early mesozoic and was overlapped by the transbaikal magmatic arc which developed in response to subduction of the oceanic crust of the paleo pacific ocean several world class cu mo porphyry cu pb zn vms and intrusion related au mineral camps which formed in the altaids at this stage coincided with the episodes of plate reorganization and oroclinal bending of magmatic arcs major pb zn and cu sedimentary rock hosted deposits of kazakhstan and central asia formed in backarc rifts which developed on the earlier amalgamated fragments major orogenic gold deposits are intrusion related deposits often occurring within black shale bearing sutured backarc basins with oceanic crust after amalgamation of the western altaids this part of the collage and adjacent cratons were affected by the siberian superplume which ascended at the permian triassic transition this plume related magmatism produced various deposits such as famous ni cu pge deposits of norilsk in the northwest of the siberian craton in the early mesozoic the eastern altaids were oroclinally bent together with the overlapping transbaikal magmatic arc in response to the northward migration and anti clockwise rotation of the north china craton the following collision of the eastern portion of the altaid collage with the siberian craton formed the mongol okhotsk suture zone which still links the accretionary wedges of central mongolia and circum pacific belts in the late mesozoic a system of continent scale conjugate northwest trending and northeast trending strike slip faults developed in response to the southward propagation of the siberian craton with subsequent post mineral offset of some metallogenic belts for as much as 70 400 km possibly in response to spreading in the canadian basin india asia collision rejuvenated some of these faults and generated a system of impact rifts

age and provenance constraints on seismically determined crustal layers beneath the paleozoic southern central asian orogen inner mongolia china abstract we present 110 ages and 51 in situ 18o values for zircon xenocrysts from a post 99 ma intraplate basaltic rock suite hosted in a subduction accretion complex of the southern central asian orogenic belt in order to constrain a seismic profile across the paleozoic southern orogen of inner mongolia and the northern margin of the north china craton two zircon populations are recognized namely a phanerozoic group of 70 zircons comprising granitoid derived ca 431 99 ma n 31 peak at 256 ma meta granitoid derived ca 449 113 ma n 24 peak at 251 ma and gabbro derived 436 242 ma n 15 peaks at 264 and 244 ma grains each textural type is characterized by a distinct zircon oxygen isotope composition and is thus endowed with a genetic connotation the precambrian population 2605 741 ma n 40 exhibits a prominent age peak at 2520 ma granulite facies metamorphism and four small peaks at ca 1900 1600 and 800 ma our new data together with literature zircon ages significantly constrain models of three seismically determined deep crustal layers beneath the fossil subduction zone forearc along the active northern margin of the north china craton namely 1 an upper arc crust of early to mid paleozoic age intruded by a major permian triassic composite granitoid gabbroic pluton 8 20 km depth 2 a middle crust predominantly consisting of mid meso to neoproterozoic felsic and mafic gneisses and 3 a lower crust composed predominantly of late archean granulite facies rocks we conclude that the paleozoic orogenic crust is limited to the upper crustal level and the middle to lower crust has a north china craton affinity furthermore integrating our data with surface geological petrological and geochronological constraints we present a new conceptual model of orogenic uplift lithospheric delamination and crustal underthrusting for this key ocean continent convergent margin

recycling of manganese from anoxic sediments in stagnant basins by seawater inflow a study of surface sediments from the gotland basin baltic sea abstract the occurrence of mn carbonates in sapropelic sediments has been proposed to indicate that the host sediment originally accumulated under oxygenated bottomwaters in the central baltic sea ca rich rhodochrosite layers in sapropelic sediments have been related to inflows of oxic seawater from the north sea into the brackish predominantly anoxic deeps of the central baltic this study attempts to verify the model of authigenic mn carbonate formation by comparing oceanographic records directly with the composition of surficial sediments of the gotland basin surface sediments of the gotland deep sampled in 1997 displayed significant ca rich rhodochrosite enrichments at 6 5 11 and 15 cm sediment depth which reflect periods of intense seawater inflows in 1969 76 1948 56 and 1931 39 respectively however the latest major seawater inflow detected in 1993 was not reflected in the surface sediment the topmost 6 cm of the sediment was totally depleted in mn and 210pb data implied a disturbed top layer down to 5 cm calculations of saturation indices indicate that the porewaters were undersaturated with respect to mn and ca carbonate phases in the uppermost 8 cm in 1997 at greater depths the porewaters were close to equilibrium with respect to calcite and rhodochrosite the ca rhodochrosite layers corresponded well to a sediment core sampled at the same location in 1994 but that core displayed a further enrichment of ca rich rhodochrosite close to the sediment surface which can be related to a major inflow of north sea water in 1993 the significant decrease of about 2 3 mol m2 mn in the uppermost 6 cm of a disturbed sediment surface from 1994 to 1997 corresponds to an enrichment of about 20 mol l of dissolved mn within the 90 m thick anoxic water column in 1997 we conclude that several inflows of dense seawater into the gotland deep monitored between 1994 and 1997 led to a resuspension of the unstable fluffy surface sediment layer authigenic ca rich rhodochrosite which had formed immediately after the major inflow of oxic seawater in 1993 was therefore redissolved in undersaturated bottomwaters and mn was recycled from surficial sediments into the water column this in turn means that in contrast to the established model of ca rhodochrosite formation as a result of seawater inflow the occurrence of mixed mn depleted layers does not prove that seawater inflow has not occurred during the deposition of these sediments

fe and mn enrichment in middle ordovician hematitic argillites preceding black shale and flysch deposition the shoal arm formation north central newfoundland the middle ordovician shoal arm formation in the central volcanic belt of north central newfoundland consists of hematitic argillites overlain by grey cherts then black shales directly underneath a late ordovician early silurian flysch sequence using principal component analysis geochemically definable components within related lithologie groups are 1 biogenic 2 mixed detrital 3 hydrothermal and 4 mn ca carbonate close sampling of the whole 350 m thick sequence provides reconstruction of variations among the sediment components through time at the base of the hematitic section a sharp increase in the hydrothermal component enrichment in mn fe ni pb and zn decreases stratigraphically upward and disappears in the upper red shoal arm formation the mn ca carbonate component also decreases upward but persists into the grey cherts indicating an additional source of mn the clastic component is largely mixed mafic pelagic clay like detritus with a strong pulse of zr nb and y rich

pathways of organic carbon oxidation in three continental margin sediments we have combined several different methodologies to quantify rates of organic carbon mineralization by the various electron acceptors in sediments from the coast of denmark and norway rates of nh4 and sigma co2 liberation sediment incubations were used with o2 penetration depths to conclude that o2 respiration accounted for only between 3 6 17 4 of the total organic carbon oxidation dentrification was limited to a narrow zone just below the depth of o2 penetration and was not a major carbon oxidation pathway the processes of fe reduction mn reduction and sulfate reduction dominated organic carbon mineralization but their relative significance varied depending on the sediment where high concentrations of mn oxide were found 3 4 wt mn only mn reduction occurred with lower mn oxide concentrations more typical of coastal sediments fe reduction and sulfate reduction were most important and of a similar magnitude overall most of the measured o2 flux into the sediment was used to oxidized reduced inorganic species and not organic carbon we suspect that the importance of o2 respiration in many coastal sediments has been overestimated whereas metal oxide reduction both fe and mn reduction has probably been well underestimated

geochemistry and origin of ferromanganese concretions in the gulf of bothnia abstract ferromanganese concretions cover large areas of the gulf of bothnia they are flat to well rounded the rounded ones being richer in oxyhydroxides of iron and manganese rounded and ellipsoidal nodules particularly those in the northern gulf of bothnia are richest in mn ni ba and cu which probably coexist in a mn oxyhydroxide phase flat nodules are enriched in fe p rare earths and as probably associated with an fe oxy hydroxide component aluminum v cr and ti occur in still another phase the sediments of the gulf generally consist of a 10 50 mm thick layer of oxidized surface sediment enriched in mn ba p and ni lying on top of reduced sediments which are diagenetically depleted in these elements the remobilized elements have redeposited in the nodules but this process cannot explain the origin of all the nodular material some released mn ba and ni furthermore enter into suspended phases which eventually leave the baltic sea the economic value of the nodules in the gulf of bothnia is probably limited at present

effects of ocean chemistry sea level and climate on the formation of primary sedimentary manganese ore deposits the mineralogy geochemistry and in some cases the mode of origin of many phanerozoic sedimentary manganese orebodies are fairly well known but the effects of the important variables represented by changing ocean chemistry sea level and climate on ore formation are only recently being considered the high degree of mobility of manganese particularly through redox processes insures that it can change phase during weathering transport deposition and diagenesis during chemical weathering manganese is solubilized in acid reducing conditions and carried in surface and subsurface waters to the coastal zone where many of the exploitable deposits can form in slightly reducing carbonate ores to oxidizing conditions oxide ores rainfall controls ground water acidity through fostering vegetation growth major deposits at groote eylandt australia and the extensive deposits of the paratethys seaway in eastern europe and the soviet union accumulated as a result of large scale delivery of dissolved mn to restricted black shale basins during marine transgressions the deposits show compositional zoning and display evidence of having been deposited in shallow marine environments following accumulation of a dilute ore solution in the basin interiors manganese was precipitated when the environments of the basin became oxidized apparently during the early stages of marine regressions during the phanerozoic the concentrations of dissolved oxygen and carbon in the oceans varied significantly in response to large changes in the burial rate of organic carbon when the rate was high there was a drawdown of atmospheric co 2 which led to global reverse greenhouse cooling later upon oxidation of sea floor organic matter co 2 was released and greenhouse warming eventuated manganese is now known to have precipitated rapidly as crusts in the oceans late in the glacial and early in the interglacial stages of the quaternary probably as a result of extensive sea floor oxidation accompanying the release of co 2 this same set of processes operating over geologic time may have played a significant role first in generating large reservoirs of dissolved manganese in intracratonic basins and in the oceans and second by providing the metal for the formation of ore deposits when conditions changed

petrology of the hegenshan ophiolite and its implication for the tectonic evolution of northern china abstract petrographic observations and mineralogical and geochemical analyses have revealed that the hegenshan ophiolite is of mid ocean ridge origin and has been subjected to dynamothermal metamorphism at medium p t conditions the metamorphism is characterized by a prograde change in paragenesis from the greenschist to epidote amphibolite facies with peak temperature conditions of 570 640 c at pressures of 4 10 kbar the amphiboles formed by this metamorphism show k ar ages of 110 130 ma the metamorphic conditions and k ar ages suggest that the hegenshan ophiolite is located at the suture between the siberian and north china continental blocks where the continental collision in this area took place in middle mesozoic time given the temporal and spatial distribution of the igneous activity around the da hinggan ling mountains it is suggested that the extensive yanshanian magmatism in this region resulted predominantly from a southward subduction of an oceanic plate prior to collision alternatively it may possibly have resulted from the collision itself at the final stage

genesis of the eastern paratethys manganese ore giants impact of events at the eocene oligocene boundary abstract the giant mn ore deposits of the paratethys are located on the slopes and or margins of deep basins the eocene ocean and associated basins were strongly influenced by large scale submarine hydrothermal activity which supplied prodigious amounts of ca co2 sio2 mn and other components to the oceans this caused a substantial shift in seawater composition and resulted in the deposition of carbonates as well huge amounts of mn the giant mn ore deposits of the eastern paratethys were formed as a consequence of the early oligocene global transgression in shelf environments of marginal and epicontinental seas frequently with anoxic regime of the bottom water

the lithosphere of north china craton from surface wave tomography abstract fundamental mode rayleigh wave group velocity dispersion data were used in a tomographic study to reconstruct the crust and upper mantle shear velocity structure in east asia this article expounds the features of lithosphere structure in different sub regions of north china and discusses their implications for the tectonic evolution and present tectonics of north china craton ncc the study revealed that strong earthquakes took place in the low velocity zones and along the boundaries between high and low velocities in the middle and lower crust the active nw trending zhangjiakou bohai seismic belt corresponds to a prominent low velocity zone in the crust and upper mantle lid in addition to the well known structural difference between western and eastern ncc we are able to resolve clearly the lithospheric features of sub regions in eastern ncc the southern north china basin and north yellow sea are characterized by a high velocity crust and upper mantle lid down to 70 80 km depth while the northern north china basin has a low velocity crust and the velocity below moho to about 130 km is rather uniform and low there is also a general trend of velocity decrease in the upper mantle from west to east the velocity images bear the imprints of subduction and collision that took place in the periphery of ncc since mesozoic and shed some light on the mechanism of mesozoic lithospheric thinning of eastern ncc

nd isotope signature of holocene baltic mn fe precipitates as monitor of climate change during the little ice age neodymium nd isotope profiles were analyzed on two baltic mn fe precipitates 99 2 and tl1 from shallow water 20 m of the mecklenburg bay the age range of these mn fe precipitates determined by 226raex ba dating reaches from recent growth back to 4300 and 1000 yr bp respectively over this time range the nd isotope composition varies from end 0 13 1 to 17 5 in the selected baltic precipitates indicating substantial changes in the nd isotope composition of the baltic sea the lowest end values were recorded during the time interval of the little ice age lia ad 1350 to 1850 these minimum values indicate either an increase of the input of less radiogenic nd from scandinavian archean proterozoic sources end about 22 to the baltic sea or a decrease of the input of more radiogenic nd from continental european sources end about 12 and or north sea water end about 10 variations of both erosive continental input and north sea inflow may indicate a direct response of the nd isotope signal in the baltic sea to climate changes during the lia and be related to cyclic shifts in the atmospheric circulation triggered by the north atlantic oscillation nao another aspect that possibly influenced the input of trace elements and nd isotopes into the baltic sea is the population development in the circum baltic area during the lia the lowest end values also correspond to the medieval demographic crises that led to a significant decrease of agricultural activity and farmland the reduction of soil erosion and enhanced regrowth of natural vegetation may have changed the amount and proportions of dissolved and suspended particulate matter transported into the baltic sea by rivers which in turn may have resulted in a change of the nd isotope composition of baltic sea water

experimental study of dense pyroclastic density currents using sustained gas fluidized granular flows we present the results of laboratory experiments on the behaviour of sustained dense granular flows in a horizontal flume in which high gas pore pressure was maintained throughout the flow duration by continuous injection of gas through the flume base the flows were fed by a sustained 0 5 30 s supply of fine 75 15 m particles from a hopper the falling particles impacted an impingement surface at concentrations of 3 to 45 where they densified rapidly to generate horizontally moving dense granular flows when the gas supplied through the flume base was below the minimum fluidization velocity of the particles i e aerated flow conditions three flow phases were identified i an initial dilute spray of particles travelling at 1 2 m s 1 followed by ii a dense granular flow travelling at 0 5 1 m s 1 then by iii sustained aggradation of the deposit by a prolonged succession of thin flow pulses the maximum runout of the phase 2 flow was linearly dependent on the initial mass flux and the frontal velocity had a square root dependence on mass flux the frontal propagation speed during phase 3 had a linear relationship with mass flux the total mass of particles released had no significant control on either flow velocity or runout in any of the phases high frequency flow unsteadiness during phase 3 generated deposit architectures with progradational and retrogradational packages and multiple internal erosive contacts when the gas supplied through the flume base was equal to the minimum fluidization velocity of the particles i e fluidized flow conditions the flows remained within phase 2 for their entire runout no deposit formed and the particles ran off the end of the flume sustained granular flows differ significantly from instantaneous flows generated by lock exchange mechanisms in that the sustained flows generate by prolonged progressive aggradation deposits that are much thicker than the flowing layer of particles at any given moment the experiments offer a first attempt to investigate the physics of the sustained pyroclastic flows that generate thick voluminous ignimbrites

the sources and transport of sr and nd isotopes in the baltic sea we have determined the concentration and isotopic composition of sr and nd in waters from the baltic sea the baltic sea is an intracontinental stratified brackish water estuarine like system and the rivers emptying into it drain a suite of terranes ranging from proterozoic archean in the north to phanerozoic in the south the sampled brackish waters range in salinity from seawater sw at 35 289 to a minimum of 2 460 at the surface in the innermost part of the gulf of bothnia the sr concentrations show generally conservative behavior indicating a simple two component mixing however small deviations 3 70 from a perfect mixing line reveal that the imprints from rivers with different sr concentrations are preserved in the blending strontium concentrations from a depth profile across the redoxcline in the baltic proper indicate that vertical particle transport alters the sr concentration in the water our estimated concentration of sr in the average freshwater input to the baltic is 0 03 ppm which is only about 0 4 of the sw concentration the sr isotopic data range from e sr sw 0 in seawater to e sr bw sw 7 8 in the least saline baltic water bw sample in the gulf of bothnia the isotopic composition of sr versus 1 sr in the baltic sea follows an almost perfect mixing line which shows that seawater sr is mixed with much more radiogenic components calculated end member values of e sr sw for each sample show that the riverine input into the gulf of bothnia has e sr sw 120 200 and 10 50 e units in the baltic proper these values are in general agreement with direct measurements of river waters in each region however the calculated values in the gulf of bothnia are lower than the measured river water input in this region which indicates the presence of less radiogenic sr presumably originating from the river waters draining the southern part of the basin which are partially transported northward and mixed with sr from the gulf of bothnia rivers the nd concentration in the baltic sea is not conservative varying between 5 and 45 ppt with the highest concentrations in the bottom waters due to vertical particulate transport a plot of e nd o in baltic water yields a good correlation with the calculated freshwater end member e sr sw the data show that it is possible to unravel the different freshwater sources into the baltic and to identify the zones of particulate removal of both non conservative species such as the ree and of quasi conservative species such as sr the use of isotopic tracers in this estuarine environment may provide a much better insight into mixing and element transport it should also be possible to trace lateral movements of freshwater inputs

redox dependent changes in manganese speciation in baltic sea sediments from the holocene thermal maximum an exafs xanes and la icp ms study manganese mn enrichments in sediments of the deep basins of the baltic sea are believed to consist of ca mn carbonates that form from mn oxides following periodic inflows of oxygen rich north sea waters however a range of mn bearing mineral phases that besides mn carbonates e g ca rhodochrosite can include mn sulfides are known to be present in marine sediments with formation mechanisms that are sensitive to redox conditions in this study we use high resolution synchrotron exafs and xanes combined with la icp ms and micro xrf to investigate the nature of the mn enrichments in sediments from the holocene thermal maximum approx 8000 4000 cal yr bp at a site in the northern gotland basin analyses were performed on epoxy embedded sediment sequences we specifically address the role of changes in redox conditions in bottom waters as inferred from sediment molybdenum mo contents for mn sequestration we find that an up core increase in mo indicating a transition into more anoxic and sulfidic euxinic bottom water conditions is accompanied by a decline in total sediment mn contents while mn carbonates dominate the mn mineral fraction in the low mo interval in the more sulfidic high mo interval mn is associated with framboidal pyrite mn fe ratios in the sulfidic interval vary between the investigated sequences but reach values of up to 7 7 mol this exceeds ratios previously reported for sedimentary pyrite and exafs spectra indicate that sulfide bound mn is predominately tetrahedrally coordinated when mn fe ratios are high this suggests that mn is incorporated in other fe s phases such as mackinawite besides pyrite there is also evidence for the presence of a low concentration of mn associated with detrital aluminosilicates throughout the investigated intervals our results suggest that increased bottom water euxinia inhibited the formation of mn carbonate at this site during the holocene thermal maximum possibly due to a more rapid reduction of mn oxides in more sulfidic bottom waters c 2014 elsevier b v all rights reserved less

development of anoxia during the holocene fresh brackish water transition in the baltic sea one of the most pronounced environmental changes during the holocene baltic sea history was the transition from the freshwater ancylus lake to the brackish water litorina sea the establishment of

archean blocks and their boundaries in the north china craton lithological geochemical structural and p t path constraints and tectonic evolution an examination of lithological geochemical geochronological structural and metamorphic p t path data suggests that the basement of the north china craton can be divided into eastern and western blocks separated by major crustal boundaries that roughly correspond with the limits of a 300 km wide zone called the trans north china orogen the eastern block consists predominantly of late archean domiform tonalitic trondhjemitic granodioritic ttg batholiths surrounded by anastomosing networks and linear belts of open to tight synforms of minor volcanic and sedimentary rocks metamorphosed from greenschist to granulite facies at 2 5 ga with anticlockwise p t paths some early to middle archean rocks are locally present in the eastern block but their tectonic history is unclear due to reworking by the 2 5 ga tectonothermal event the western block has a late archean assemblage structural style and metamorphic history similar to that of the eastern block but it differs in the absence of early to middle archean assemblages and in being overlain by and interleaved with paleoproterozoic khondalites which were affected by a 1 8 ga metamorphic event involving clockwise p t paths a mantle plume model is proposed for the formation and evolution of late archean basement rocks in the eastern and western blocks based on a combination of extensive exposure of ttg gneisses affinities of mafic rocks to continental tholeiitic basalts presence of voluminous komatiitic rocks dominant diaprism related domiform structures anticlockwise p t paths and a short time span from the primary emplacement of ttg and ultramafic to mafic rocks until the onset of regional metamorphism between the two blocks is the trans north china orogen which is bounded by two major fault systems and is composed of late archean to paleoproterozoic ttg gneisses and granitoids interleaved with abundant sedimentary and volcanic rocks that are geochemically interpreted as having developed in magmatic arc and intra arc basin environments these rocks underwent multiple phases of compressional deformation and peak high pressure metamorphism followed by rapid exhumation during the late paleoproterozoic at 1 8 ga as a result of collision between the eastern and western blocks resulting in the amalgamation of the north china craton

formation and solid solution behavior of ca rhodochrosites in marine muds of the baltic deeps authigenic ca rhodochrosites are found in organic rich sediments in the deep anoxic basins of the baltic sea rhodochrosite formation is apparently the result of organic matter degradation the rhodochrosite contains 10 to 40 mol caco3 and 2 to 5 mol mgco3 as determined by microprobe the composition of the carbonates at a given depth varies by about 5 mol mnco3 sem revealed the rhodochrosite to be present as globular aggregates consisting of microcrystallites dissolution features such as cavities within the aggregates are frequently observed and indicate that extensive recrystallization takes place pore waters are greatly supersaturated with respect to both rhodochrosite and calcite rhodochrosite is only found in sediments where pore waters show the highest degree of supersaturation due to ion exchange ca2 diffuses from the underlying freshwater clays this results in increasing aca2 amn2 ratios in the pore waters from the sediment surface downward in response to this the maximum caco3mnco3 ratio also increases with depth the composition of rhodochrosite which forms under these conditions may be determined by both the porewater aca2 amn2 and precipitation kinetics however if their composition is controlled solely by the aca2 amn2 in solution their behavior can be described by a regular solid solution model

carboniferous granitic plutons from the northern margin of the north china block implications for a late palaeozoic active continental margin we report four late palaeozoic zircon sensitive high resolution ion microprobe shrimp u pb ages for granitic plutons from the inner mongolia palaeo uplift on the northern margin of the north china block these cast a new light on the poorly understood tectonic history of the northern margin of the north china block and the central asian orogenic belt during the late palaeozoic the plutons have for a long time been considered to belong to the early precambrian basement of the north china block our new shrimp u pb zircon dating of four plutons at longhua daguangding boluonuo and hushiha has yielded intrusive ages of 311 2 ma 324 6 ma 302 4 ma and 310 5 ma respectively geochemical data suggest that these granitoids have a calc alkaline subduction related i type signature indicating the existence of an andean style continental arc along the northern margin of the north china block during the late palaeozoic our results also indicate that the palaeo asian ocean still existed during latest carboniferous earliest permian time and that the final collision between the southern mongolia composite terranes and the north china block occurred later than c 290 ma we suggest that the northern margin of the north china block was an active continental margin and the inner mongolia palaeo uplift is a deeply exhumed mid crustal root of a late palaeozoic andean style continental arc

isotopic compositions of ce nd and sr in ferromanganese nodules from the pacific and atlantic oceans the baltic and barents seas and the gulf of bothnia abstract ferromanganese nodules from the pacific and atlantic oceans the barents and baltic seas and the gulf of bothnia were analyzed for the isotopic compositions of ce nd and sr and the abundances of ree ba and sr ree patterns of barents baltic and bothnian samples show no ce anomaly or even a negative one in contrast to the positive anomaly observed for the pacific and atlantic samples moreover the baltic and bothnian samples have distinctly low end values average end values of the four regions are as follows pacific 5 barents 10 atlantic 11 and baltic inclusive of gulf of bothnia 19 the characteristic low end values of the baltic samples are indicative of the influence of precambrian rocks from the baltic shield of particular interest is the feature of the ce isotopic composition that ece values of the samples from the pacific are negative and those from the other three regions positive this novel finding might suggest a difference in sources of ce between the pacific and other regions these results demonstrate that ce isotopic ratios can be a useful tracer in marine geochemistry in combination with isotopic compositions of nd and sr

the distribution of rare earth and other elements and the mineralogy of the iron oxyhydroxide phase in marine ferromanganese concretions from within slupsk furrow in the southern baltic abstract rare earth element concentrations in ferromanganese concretions sampled from slupsk furrow in the polish exclusive economic zone are similar to those of concretions from the gulf of bothnia the lack of positive ce anomalies in the concretions from slupsk furrow indicates that they are formed under less oxidizing conditions than spheroidal concretions from the gulf of bothnia mossbauer studies indicate that poorly crystalline lepidocrosite is the principal iron oxyhydroxide mineral present in these concretions

hydrocarbon derived ferromanganese nodules in carbonate mud mounds from the gulf of cadiz mud breccia sediments and clasts as nucleation sites abstract more than 500 fe mn nodules were sampled during the anastasya 01 cruise tasyo project along the continental margin of the gulf of cadiz eastern central atlantic at the confluence of the mediterranean sea with the atlantic ocean where extensive nodule fields were discovered based on wide previous studies that included swath bathymetry multi channel and very high resolution seismic reflection gravimetry magnetism and underwater photography surveys nodules were collected at water depths ranging from 850 to 1000 m associated with hydrocarbon derived ankerite and dolomite chimneys and crusts thirty six selected samples among the various morphological types were used for the laboratory analysis of physical properties morphology colour surface texture sphericity weight and size mineralogy xrd optical and electronic microscopy and geochemistry xrf aas icp ms epma gc ms s c and o isotopes nodules show a wide range of sizes densities weights and morphologies nodules are formed of multiple millimetre thick layers of fe and mn oxyhydroxides surrounding the nucleus composed of early middle miocene plastic marl the textures developed by the fe and mn oxyhydroxides layers are massive laminated detrital and mottled to dendritic goethite lepidocrocite mn oxides 7 a manganates and 10 a manganates quartz and phyllosilicates are the main components accessory minerals are calcite dolomite siderite rhodochrosite kutnohorite pyrite chalcopyrite potassium feldspar zircon rutile ilmenite and chlorite fe mn carbonates from the siderite rhodochrosite continuous series are forming part of the marl nuclei framboidal filamentous and globular textures are observed in fe mn oxides and pyrite suggesting biogenic origin nodules show a high mean abundance of fe 38 6 moderate mn 6 0 and low contents of trace metals and rees compared to the average content of deep seabed polymetallic nodules from other oceanic areas the mn fe ratio ranges from 0 07 to 0 25 the studied nodules hold in their oxide layers hydrocarbons n alkanes derived from marine bacterial activity aromatic hydrocarbons in the form of phenanthrene are also present which is characteristic of mature petroleum the structure mineralogy and chemical composition in the studied nodules are similar to those of diagenetic hydrogenetic continental margin nodules rather than deep sea nodules we suggest that the formation of this type of nodule occurred through a combined diagenetic hydrogenetic growth process involving fluid venting from deep seated hydrocarbon reservoirs bio mineralization processes and bottom current erosion

environments and processes of manganese deposition concentration of manganese in solution and its deposition takes place by redox controlled processes in a variety of modern and ancient geologic and geochemical environments modern mn deposition occurs predominantly in deep sea areas rather than shallow water domains although deep sea sedimentary deposits dominate hydrothermal contribution of mn to the ocean system may be substantial mn deposition from hydrothermal solutions at or near sea floor spreading centers and less commonly in island arc areas is known in addition near and far field dispersion of mn from vent sites is also substantial such distributions are controlled by the flow rate and egress temperature of the solution and the residence time of mn in seawater thus even in sedimentary deposit domains at least partial derivation of mn from a hydrothermal source is possible sedimentary fe mn crusts on older volcanic substrates on seamounts form by hydrogenous deposition of metal concentrated from terrigenous sources in the mid water column oxygen minimum zones thus the presence or absence of volcanic rocks is not a clear indication of whether sedimentary mn deposits particularly in the ancient geologic record are the result of a totally terrigenous or a totally volcanogenic source abyssal fe mn nodules are considered to form from a basin water hydrogenous and or pore water early diagenetic supply of metals but in most cases the extent of supply from either of the sources is unknown the metal incorporation mechanisms of free moving nodules is little understood and it is possible that in most cases both sources contribute to the nodule composition therefore no nodule should be considered as totally hydrogenous or totally early diagenetic based only on its bulk composition the determined growth rate giving only an average value cannot by itself reveal the growth history of the nodules biological participation directly or indirectly controls mn deposition the stratified black sea demonstrates the concentration of mn in solution in an anoxic zone its advection toward the redox interface and its precipitation in an oxygenated condition similar stratified basins are contemplated for ancient mn deposition in shallow water basin margin areas geologic and geochemical signatures indicate that during sea level highstands stratified basins formed in which mn was concentrated in solution in the anoxic part corresponding transgression led to the impingement of the redox interface on the continental shelf and precipitation of mn oxides could take place across the interface during transgression regression cycles offshore in anoxic or dysaerobic conditions mn carbonate could form by early diagenetic reaction of mn super 2 with co 2 or hco 3 super produced by organic carbon oxidation critical mn deposits occurring in transgressive glaciogenic and black shale bearing ancient sequences support this paleoenvironmental model for mn deposition

iron and manganese layering in recent sediments in the gulf of bothnia abstract the oxidized surface layer of recent soft sediments in the gulf of bothnia northern part of the baltic sea has been investigated distinct stratification of fe and mn is observed with up to five different horizons in well developed profiles these layered top sediments although not previously noticed occur extensively in the gulf of bothnia there is a close association of mn and ni ba zn and cu whereas p ca and sr are associated with fe high dissolved fe and mn contents coupled with a strong redox gradient are recorded in the interstitial waters formation of these layers is linked to varying redox conditions fe and mn tend to be dissolved under reducing conditions to migrate upwards and to reprecipitate as oxyhydroxides along favourable redox horizons reaching oxidizing conditions fe precipitates prior to mn and is always found below the mnrich strata the character of the oxidized zone is quite different in the two sub basins of the gulf of bothnia mn rich horizons together with spherical mn rich nodules are frequently found in the bothnian bay while in the bothnian sea mostly fe rich layers are present together with abundant fe rich flat concretions this difference is interpreted as being due to a lower redox level in the bothnian sea

trace metal fluxes to ferromanganese nodules from the western baltic sea as a record for long term environmental changes trace element profiles in ferromanganese nodules from the western baltic sea were analyzed with laser ablation inductively coupled plasma mass spectroscopy la icp ms and synchrotron based micro x ray radiation techniques fluorescence msxrf and diffraction mxrd at high spatial resolution in growth direction of the trace elements studied zn cu cd ni co mo ba zn showed the most significant enrichment with values in the outermost surface layers of up to six fold higher than those found in older core parts the high resolution zn profiles provide the necessary temporal resolution for a dating method analogous to dendrochronology profiles in various samples collected during two decades were matched and the overlapping sections used for estimation of the accretion rates assuming a continuous accretion of these relatively fast growing nodules on average 20 mm a 1 over the last century the zn enrichment was thus assessed to have commenced around 1860 70 in nodules from the kiel bight and in 1880 90 from mecklenburg bight reflecting the enhanced heavy metal emissions with rising industrialization in europe apart from the obvious success with zn only as and co show significant but only 1 5 fold enrichments in the most recent growth layers of the nodules other anthropogenic trace metals like cu and cdmore are not at all enriched which together with the distinct early diagenetic fe mn banding weakens the potential of the nodules for retrospective monitoring less

geochemistry of wistarburgh glass ca 1739 1777 implications for batch recipes and distinction from other south jersey wares the wistarburgh factory was america s first successful glassworks since it operated largely prior to the american revolution little is known about its products and confusion surrounds the authenticity of some of the objects attributed to this factory however analysis of alkali lime glass sherds from the glassworks site shows that green wistarburgh bottle glass is much more calcic and is enriched in various trace elements notably the rare earth elements compared with later south jersey glass for which analytical data are available the compositional data indicate that wistarburgh s proprietors made use of a batch recipe containing approximately 68 wt local sand 24 dolomitic limestone and 3 each of soda ash and potash in addition to green bottle glass blue aquamarine and colourless potash lead glass and colourless potash glass were also recovered from the wistarburgh factory site suggesting that a range of specialized glasswares was produced by this factory resume l usine de wistarburgh a ete la premiere productrice de verre en amerique du nord les produits de cette usine qui fut surtout en production avant la revolution americaine ne sont cependant pas tres bien connus et des doutes persistent concernant la vraie provenance de plusieurs objets attribues au site de wistarburgh l analyses d eclats de verre de couleur verte trouves au site demontre cependant que ce verre est plus riche en calcium et en divers elements traces en terres rares particulierement que les autres types de verres de cette region les donnees de composition indiquent que le verre de wistarburgh a ete cree a partir d un melange de 68 de sable local 24 de calcaire dolomitique 3 d ecarbonate de sodium anhydre e t3 d e potasse en plus des eclats verts des morceaux de verre bleu et sans couleur riches en potasse et en plomb et de verre sans couleur riche en potasse ont ete retrouves au site de l usine de wistarburgh et suggerent que plusieurs types de verres specialises ont etes manufactures a cet endroit owen 697

early diagenesis of trace metals used as an indicator of past productivity changes in coastal sediments in sediments of kiel bight which differ significantly in their redox states and the rates of corg degradation depth profiles of both dissolved and solid phase fe mn cd cu ni and co were measured porewater fluxes of cd cu and ni were significantly higher at shallower more oxic stations as compared to highly reducing deeper subthermocline sediments while mn fluxes behaved the opposite way when normalized to fe for grain size correction the measured solid phase metal contents revealed that the high porewater flux has led to a near surface depletion of mn from more anoxic sediments and to a reduced rate of accumulation of anthropogenic cd in more oxic sediments this difference in early diagenetic behaviour suggests the use of these metals as a proxy for the redox state and the intensity of carbon recycling contrary to the recent sediment layers the normalized metal contents of preindustrially deposited sediment layers were similar for both metals at all stations thus at stations having highly anoxic sediments today the preindustrial benthic flux must have been lower for mn and higher for cd reflecting a shift from more oxic to more reducing conditions in subthermocline sediments during the last 100 years this change of the redox state in subthermocline sediments reflects an increase of primary production and of subsequent corg input to the sediment due to eutrophication which accompanied industrialization

progress in deep lithospheric exploration of the continental china a review of the sinoprobe abstract the sinoprobe deep exploration in china is a multidisciplinary earth science research program that aims at revealing the composition structure and evolution of the continental lithosphere in china the sinoprobe 2008 2012 has successfully conducted research and field experiments on determining the crustal and mantle structures using new deep seismic and magnetotelluric mt exploration this has allowed the accumulation of new exciting data that have significantly accelerated china s development on deep lithospheric exploration the new data also led to new understandings on the mesozoic and cenozoic geological evolution of the continental china the main results of the sinoprobe so far include 1 a collection of ca 6000 km long seismic reflection profile data 2 a nation wide geochemical baseline 3 a nation wide 4 4 mt array and regional 1 1 mt arrays in the north china and the qinghai tibet plateau 4 three dimensional 3 d exploration of ore districts in the eastern china 5 several continental scientific drilling holes 6 regional in situ stress monitoring networks 7 geodynamic modeling of the lithosphere underneath the continental china and 8 instrumentation development for deep exploration in china etc for the first time the sinoprobe has obtained deep seismic reflection evidence for the moho surface below the thick crust of the central qinghai tibet plateau it also reveals dipping fabrics in the lithospheric mantle beneath the northeastern china the preliminary results from mt array observation of the sinoprobe show an abnormal electric conductivity structure of the lithosphere beneath the ordos basin providing important evidence for the evolution mechanism of the north china craton ncc generally the sinoprobe has conducted successfully during its initial phase 2008 2012 which has settled a foundation for the next phase of the sinoprobe in the future