long period lunar tides at the south pole vertical gravity data from 6 3 years of observations at the geographic south pole have been analyzed to determine the gravimetric factor and phase angle of the long period tides annual and semiannual tides are obscured by the combination of signals arising from instrumental drift and the large annual component of barometric pressure changes at pole gravimetric factors for the three major long period tides are m 1 1589 0 0017 mm 1 1406 0 0085 and mtm 1 1692 0 0068 the only statistically significant phase shift is for the fortnightly component 0 0151 0 0032 days a phase lead our data analysis for the gravitational factor for m at the south pole indicates that the calculation of the influence of the long period ocean tides on the earth tides at the south pole should be reconsidered

geochemical and mineralogical control of different genetic types of deep sea nodules from the pacific ocean deep sea nodules from the northeast pacific nodule belt and the southeast pacific sonne basin being formed in areas bordering the equatorial zone of high biological productivity accumulate by two basically different growth processes a early diagenetic growth by supply from pore water and b hydrogenetic growth by supply from near bottom sea water these growth processes lead to different genetic types of nodules early diagenetic type a hydrogenetic type b and mixed type ab a further type ac very rich in mn is being formed by increasing influence of early diagenesis these types can clearly be distinguished by their shapes surface textures mineral constituents of oxide fraction internal microstructures and geochemistry a genetical classification is being proposed on the basis of statistically computed interelement relationships todorokite very poor in fe is the main mn phase in the early diagenetic substance mno2 intimately intergrown with feooh xh2o is the main phase in the hydrogenetic substance consequently an important difference can be pointed out the metal supply for the growth of the early diagenetic nodules is based on an ionic solution of me2 e g mn2 ni2 cu2 zn2 whereas the supply for the hydrogenetic nodules is caused by transport of colloidal particles mobilization of mn2 and fractionation from fe is controlled by the amount of decomposing organic matter in the peneliquid layer of the sediments the main factor controlling the intensity of early diagenesis is the biological productivity in surface waters the crucial point of reversal at a mn fe ratio of about 5 obtained by hyperbolical regression of the analyses of nodules from the southeast pacific represents best concentrations in ni and cu mn fe quotients greater than 5 cause a decrease of ni and cu content nodules from the northeast pacific nodule belt generally contain higher concentrations in cu than nodules from the southeast pacific this can be explained by an additional supply of cu transported below ccd by siliceous plankton

separation of iron from manganese and growth of manganese nodules as a consequence of diagenetic ageing of radiolarians abstract 111 samples of diagenetically aged radiolarians sampled in the central pacific manganese nodules belt were investigated chemically and microscopically authigenic clays of the smectite group are precipitated in the cavities of radiolarian tests metal oxides are precipitated on the surfaces of radiolarian tests during these processes a separation of iron from manganese takes place about 96 of the iron is bound to smectites and all of the manganese is bound to the oxide coatings of the radiolarians with further diagenesis radiolarian tests are dissolved together with their oxide coatings this dissolution of the oxide coatings provides material for the growth of manganese nodules material which is depleted in fe and enriched in mn cu and zn the smectite aggregates that fill the cavities of radiolarian tests contain iron bound to their crystal lattice whereas radiolarian tests are dissolved during the diagenesis these smectite aggregates do not dissolve and thus become enriched in older samples

metal diagenesis in oxic marine sediments the metal nutrient relationships observed for nickel and cadmium in the deep ocean are continued at the interface between seawater and oxidizing pore water this continuum results in pore water concentrations of these metals which are only slightly greater than near bottom seawater levels manganese concentrations in these oxidizing pore waters are also extremely low less than three times bottom water in contrast release in the boundary layer produces a maximum of dissolved copper which is 10 40 times ambient seawater assuming these pore waters are at steady state flux estimates based on these measurements suggest that the manganese in todorokite rich nodules of the central equatorial pacific was not supplied by upward diffusion through pore waters below the interface most nodular nickel is precipitated with manganese while nodular copper is supplied by diffusion

influence of sedimentation on enrichment of manganese and growth of ferromanganese micronodules bengal fan india abstract based upon down core variations in o mn ratio in sediment and in micronodules mn content organic carbon and abundance of micronodules in two box cores from high and low sedimentation regions of the bay of bengal 0 20 and 0 40 cm levels were identified as mn oxidation zone in the western and the eastern regions of the bay despite similarity in bottom water o 2 and organic carbon contents of the region a higher abundance of micronodules down to the deeper levels was observed in the area of low sedimentation but in the upper surfaces increased enrichment of mn was observed in core 1 located in the area of higher sediment accumulation rapid recycling of mn faster burial transfer to mn reduction zone mn dissolution and its upward diffusion re precipitation increasing upward flux of mn ii and associated higher consumption of o 2 limits the width of mn oxidation zone and appears to be responsible for enhanced enrichment of mn in the area of high sedimentation the results of the present study also suggest that though the availability of mn controls the formation of micronodules their resident time in mn oxic zone regulates their growth and influences their morphology

estimating growth rates of ferromanganese nodules from chemical compositions implications for nodule formation processes abstract using available information on the accretion rates and the bulk chemical compositions of oceanic ferromanganese nodules it can be shown that the accumulation rate of manganese is proportional to the square of the accumulation rate of iron this relationship has been used to derive an equation that predicts nodule growth rates from their chemical compositions the equation accurately predicts growth rates up to about 50 mm 10 6 yr but yields incorrect rates for faster growing concretions from this relationship nodules underneath water of high primary productivity grow most rapidly and accumulate transition metals most rapidly however nodules from regions of highest primary productivity do not have the highest concentrations of nickel and copper reduction of manganese within the sediment column and remobilization of a fraction to the surface sediments adds manganese to nodules without substantially augmenting the supply of other transition elements the addition of remobilized manganese to the nodule dilutes the concentrations of nickel copper and iron even though their rates of accumulation are also high

observation and analysis of the tidal gravity variations at asuka station located on the antarctic ice sheet tidal gravity observations were made at asuka station 71 5 s 24 1 e antarctica the lacoste romberg model g 805 gravity meter was altered to integrate an electrostatic feedback amplifier and was installed in a snow pit records for tidal analysis were obtained from june 26 to november 13 1987 at a sampling interval of 30 min from the estimated tidal amplitudes corrections for the oceanic effects were made using schwiderski s cotidal maps the ocean tide corrected factors which define the response of the deformable earth to lunar solar tidal forces were found to be 1 169 0 008 o1 1 127 0 017 p1 1 135 0 006 k1 1 261 0 033 m2 and 1 302 0 039 s2 the diurnal factors agree with those obtained from statistically derived formulas by melchior and de becker however the semidiurnal factors m2 and s2 are 10 larger than the theoretical values predicted by wahr this is much larger than the typical 1 2 discrepancy between the statistical model and theory similar tidal gravity observations made at syowa station 69 0 s 39 6 yielded consistent results with those monitored at asuka station the observed m2 factors have a tendency to increase from the equator toward the southern high latitudes the increasing effect of inaccurate ocean load tidal corrections may be due to schwiderski s cotidal chart tidal analysis resulted in a gravity admittance of 0 24 0 04 gal mbar for the air pressure change at asuka station the smaller magnitude compared with the typical value of 0 35 gal mbar for a normal crust may be explained by the loading deformation of the ice sheet under the air mass covering an extent of 30 km over the site

land use and geologic controls on the major elemental and isotopic δ15n and 87sr 86sr geochemistry of the connecticut river watershed usa abstract we studied the relationship between land use geology and water chemistry in the connecticut river watershed of northeastern usa by combining geographic information systems gis with nitrogen and strontium isotopic analyses and major cation and anion geochemistry river water was sampled at 35 sites in the summer and fall of 1998 and the spring of 1999 in an attempt to distinguish spatial and temporal changes in geochemical signatures related to land use and bedrock geology we coupled 87sr 86sr values and major element concentrations from river water to quantify the relationship between bedrock geology and riverine geochemistry the results in our study show that strontium isotopes of tributary waters reflect their catchment bedrock lithology our results also suggest that major cations in the connecticut river water are dominated by carbonate weathering despite the limited presence of calcareous metasedimentary rocks 10 of watershed bedrock in addition the relative contribution of carbonate to silicate weathering increases downriver as a result of input from tributaries draining paleozoic carbonate bearing rocks in contrast nitrate concentrations and nitrogen isotopic ratios of nitrate in water were highly variable nitrate concentrations were highest for tributaries draining developed and agricultural sites suggesting anthropogenic inputs however it was difficult to determine the source of nitrate because of the wide scatter in the nitrogen isotopic data which for the most part did not correlate with land use the only systematic trends in nitrogen isotopic values are found in waters collected in the summer however these data show that 15n values of nitrate from agricultural sites were lower than 15n values of nitrate from forested sites a result that is inconsistent with previous studies our study suggests that strontium isotopes provide a better biomarker for tracking atlantic salmon salmo salar than nitrogen isotopes because unlike 15n 14n ratios 87sr 86sr ratios are both predictable and seasonally constant in water

decouverte de microstructures de nodules polymetalliques dans les mineralisations manganesiferes metamorphiques de falotta et de parsettens grisons suisse les mineralisations manganesiferes de falotta et de parsettens grisons suisse se manifestent dans les radiolarites du jurassique superieur et elles sont deposees sur les ophiolites du domaine pennique ce minerai presente des microstructures botryoidales caracteristiques des nodules polymetalliques les phases mineralogiques des nodules sous l effet du metamorphisme alpin se transforment de facon progressive en braunite faiblement cristallisee avec un important exces en sio2 a la peripherie des structures botryoidales par contre vers la partie centrale de ces structures la braunite est souvent largement cristallisee sa teneur en sio2 est normale de fines veinules constituees de termes intermediaires de la serie isostructurale de la cryptomelanehollandite recoupent la mineralisation de braunite et indiquent la deuxieme etape dans l evolution du minerai oxyde de falotta et parsettens la troisieme etape est representee par la presence de la todorokite et de la birnessite due a l oxydation des veinules posterieures de rhodonite ces deux oxydes n ont aucun rapport direct avec la mineralisation primaire l existence de structures sedimentaires et volcaniques non deformees dans les ecailles superieures de la nappe de platta permet d expliquer la conservation de microstructures primaires de nodules polymetalliques dans le minerai de braunite la variation de la teneur en sr2 observee lorsque l on va de falotta vers parsettens dans les termes intermediaires de la serie isostructurale de la cryptomelane hollandite ainsi que la destabilisation de la braunite au voisinage des veinules seraient liees a la difference du degre de deformation entre ces deux zones il est important de remarquer que les parametres geochimiques fe mn ou mn co cu ni couramment utilises dans les travaux sur les nodules polymetalliques sont inadequats meme dans les structures les mieux preservees

morphological and interlayer geochemical studies on manganese nodules from the southwestern carlsberg ridge abstract mixed facies of manganese nodules from the southwestern carlsberg ridge have been analysed for mn fe ni cu co and zn we present 71 analyses including the averages for outer layer inner layer and near core material morphological studies show seven types of nodules of which medium size spheroidal ellipsoidal and intergrown nodules are most abundant only spheroidal and ellipsoidal nodules with rough surfaces show higher concentrations of mn fe cu ni co and zn towards the outer layer whereas the smooth surface nodules other than the spheroidal type show higher concentrations of these elements towards the core region the other nodule types show a decreasing content of these elements in all the layers analysed copper and ni are present in low concentrations and are associated with zn and mn the mineralogy indicates diagenetic processes involving metal remobilisation and the chemistry suggests the precipitation of metals mostly from seawater variations in the source of supply of the elements are responsible for the observed variations in the chemical composition of the nodules

long period lunar earth tides at the geographic south pole and recent models of ocean tides for many years the ocean tide models of schwiderski 1980 were the standards used by the earth tide community to interpret deviations of observed earth tides from predictions on the basis of earth models constructed by seismologists recently the topex poseidon altimeter mission provided new and improved information on pelagic ocean tides which led several research groups to generate new models of the major oceanic tides this in turn renewed our own interest in the observations of long period lunar tides at the geographic south pole that were reported many years ago with an attempt to interpret the deviation from predictions using the schwiderski models we used four different models of the fortnightly mf and monthly mm ocean tides to calculate their attraction and loading effects at the south pole and compared the results with the observed gravity tides in our earlier interpretation we did not realize that for long period ocean tides the so called greenwich phase does not refer to the phase of these tides at the latitude of greenwich but to the phase at the equator this resulted in a mistake in the relative phases of earth tide and ocean effect at the south pole for mf we now find that all models predict the phase lead of the observed versus theoretical tides within the formal uncertainties however the amplitude is still underpredicted by 1 5 2 per cent this could be due to several reasons instrument calibration errors in the body and or ocean tide models relaxation of the earth s elastic properties and the huge ice sheet of antarctica these possibilities are discussed for the mm tide the observed amplitude is well predicted within error however the uncertainties in the measurements are rather large

the relationship between the nitrate concentration and hydrology of a small chalk spring israel discharge from a spring draining a small perched cretaceous chalk aquifer in the upper galilee israel was monitored over a period of two years the water has elevated nitrate concentrations with 15n 14n and chemical data suggesting that it is a mixture of low nitrate and high nitrate end members the latter derived from the sewage of a centuries old village served by septic tanks hydrograph data allowed distinction between fissure flow during the period of winter rainfall and matrix drainage during the dry summer months these different flow types however did not have markedly different nitrate concentrations a 50 fold increase in spring discharge due to fissure flow compared with matrix drainage was reflected in only a 35 decrease in nitrate concentrations the relatively high nitrate concentrations in the fissure waters suggests that they have had close contact with and are possibly displaced from the matrix this should help to accelerate the decline in the spring s nitrate concentrations following the recent completion of the village s central sewage drainage system

remobilization of transition metals in surficial pelagic sediments from the eastern pacific abstract the top thirty centimeters of sediment at two sites in the eastern equatorial pacific contain evidence of post depositional remobilization of mn fe co ni cu and zn remobilization takes place as mn and fe oxyhydroxides are released to the pore water during the microbially mediated decomposition of organic matter precipitation of the dissolved metals in near surface more oxic strata controls the solid phase distribution of mn fe and zn the solid phase redistribution of co and ni requires only suitable material for readsorption comparison of pore water fluxes with solid phase metal distributions in the solid sediment indicates no loss of dissolved metal to the overlying water column at the present time loss of mn during the quaternary is indicated by the composition of the sediments however leaching experiments suggest that portions of the mobile mn fe co ni and cu are fixed by incorporation in authigenic smectite in the surficial sediments

observations of load tides at the south pole abstract the use of tidal observations to study the nearly diurnal free wobble mode of the earth is possible if oceanic effects in the tidal record are accurately removed we have analyzed vertical gravity data from the south pole to determine the amplitude and phase of the small daily and semidaily tides observed at the pole since these signals at the pole are most probably caused by oceanic tides our observations provide an excellent target for the oceanic models a comparison with the best models of the oceans now available indicates the need for improvement in measuring and modeling the southern oceans

geochemical processes controlling the relationship between co mn and fe in early diagenetic deep sea nodules abstract early diagenetic manganese nodules from the northeast pacific nodule belt and from the southeast pacific peru basin show primary growth features of dendritic microtextures consisting of alternating laminae of crystalline 10 amanganate a1 substance and amorphous material which is composed of an intimate mixture of ferric hydroxide silicate and mno 2 a2 substance the formation of rhythmic sequences of a1 and a2 microlayers is explained by physico chemical changes in the peneliquid sediment layer and in the microenvironment of the accreting nodule surface a upward diffusion of mn 2 in the interstitial water as a result of decay of organic matter and mn mobilization b oxidation of mn 2 and formation of 10 amanganate in the upper part of the peneliquid sediment layer leading to ph depression in the microenvironment of the nodule surface which decreases the mobility of silicate resulting in formation of a2 layers c restoration of ph and renewed precipitation of 10 amanganate based on data of 171 bulk analyses and on electron microprobe investigations interelement relationships between co mn and fe are pointed out fe and co show a significant positive correlation r 0 84 while mn and co are poorly negatively correlated r 0 21 assuming linear regression the enrichment of co within the amorphous a2 phase is attributed to specific surface adsorption and subsequent oxidation of co 2 to co 3 in the strong electric field of si 4 robust complexes of co iii and feh 2 sio 4 prevent most of the co from being available for the 10 amanganate precipitation concerning the relation between mn and fe and co respectively the highest correlation coefficients are obtained using an inverse logarithmic regression under early diagenetic conditions the concentration and precipitation of mn 2 in the interstitial water depends on the redox gradient which is controlled by the amount of decomposing organic matter the nernst equation describes the relationship as a reciprocal logarithmic function however the quantities of colloidal ferric hydroxide and of dissolved silicate are not affected by variations of the redox potential these different characteristics in the precipitation of mn and the fe and si rich colloidal phase may cause the significantly negative logarithmic correlation of mn versus fe and co respectively

mineralogy and composition of concentric layers within a manganese nodule from the north pacific ocean abstract the minor element composition of concentric layers within a single ferromanganese nodule from the eastern north pacific exhibits strong correlations with fe and mn contents but appears to be independent of pronounced mineralogic variations on the basis of these correlations the elemental composition of individual layers apparently is controlled by the relative contribution of two sources seawater and interstitial water of associated sediment in contrast the mineralogy of the nodule consisting of birnessite in the outer few layers and todorokite in the inner layers is considered to be a function of nodule diagenesis

composition and growth history of surficial and buried manganese nodules in the penrhyn basin southwestern pacific abstract a comparative study of occurrence and composition of hydrogenetic manganese nodules and their relation to sediment lithology were carried out on material from the penrhyn basin in the southwestern pacific the regional distribution of the nodules and compositional variations within nodules are closely correlated to the sedimentary history of the basin radiochemical and fossil data indicate that the nodules started to grow after the initiation of sea floor spreading in cretaceous time or later initially co poor nodules grew on pelagic clay sediments as a result of continuous uplifting although some of them were left behind within the sediment old generation through paleogene time more abundant co rich nodules followed during or after a hiatus through to the present and formed the large manganese nodule provinces these young generation encrusted old small nodules stiff pelagic clay sediments hydrothermal manganese deposits and fossils aabw played an important role in the formation of the young generation of nodules it is inferred that the aabw flows through the aitutaki passage into the penrhyn basin and runs along the western margin of the basin scattered thick young sediments in places in the survey area have prevented the growth of nodules

the formation of todorokite and birnessite in sea water pumped from under ground abstract manganese oxides precipitated from aerated well sea water at the marine science museum tokai university have been analyzed chemically and mineralogically the o mn ratios are lower in todorokite than in birnessite but these minerals have similar contents of minor transition metals which can be taken up additionally from sea water after the precipitation of mn oxides on the basis of these results the genesis of mn minerals is discussed in relation to marine mn nodules

fluxes of metals to a manganese nodule radiochemical chemical structural and mineralogical studies fluxes of metals to the top and bottom surfaces of a manganese nodule were determined by combining radiochemical 230th 231pa 232th 238u 234u and detailed chemical data the top of the nodule had been growing in its collected orientation at 4 7 mm myr 1 for at least 0 5 myr and accreting mn at 200 g cm 2 kyr 1 the bottom of the nodule had been growing in its collected orientation at about 12 mm myr 1 for at least 0 3 myr and accreting mn at about 700 g cm 2 yr 1 although the top of the nodule was enriched in iron relative to the bottom the nodule had been accreting fe 50 faster on the bottom 232th was also accumulating more rapidly in the bottom despite a 20 fold enrichment of230th on the top the distribution of alpha emitting nuclides calculated from detailed radiochemical measurements matched closely the pattern revealed by 109 day exposures of alpha sensitive film to the nodule however the shape and slope of the total alpha profile with depth into the nodule was affected strongly by226ra and222rn migrations making the alpha track technique alone an inadequate method of measuring nodule growth rates diffusion of radium in the nodule may have been affected by diagenetic reactions which produce barite phillipsite and todorokite within 1 mm of the nodule surface however our sampling interval was too broad to document the effect we have not been able to resolve the importance of nodule diagenesis on the gross chemistry of the nodule

using isotope fractionation of nitrate nitrogen and nitrate oxygen for evaluation of microbial denitrification in a sandy aquifer the nitrate input into the groundwater from forest and agricultural land in the fuhrberger feld catchment area is virtually completely degraded by microbial denitrification in the aquifer five multilevel groundwater sampling wells show characteristic depth functions of nitrate proving the denitrification process a series of 10 samples of arable land groundwater was taken from different depths at these multilevel wells and isotope ratios of 15n14n and 18o16o in the nitrate were measured the sampling was based on the two dimensional vertical plane groundwater flownet and on the knowledge of the landuse upgradient of the multilevel wells high nitrate concentrations are associated with low 15n and low 18o values and vice versa the 15n 18o ratio indicates a linear increase with a slope of 1 2 1 the microbial dentrification accords with a rayleigh process with calculated enrichment factors of e 15 9 for 15n and e 8 0 for 18o three samples taken from groundwater recharged under coniferous forest show deviating characteristics low nitrate concentrations with low 15n values 1 4 but very high 18o values 40 50 using the previously quantified enrichment factors for 15n and 18o an attempt was made to ascertain the significance of denitrification in specific depth sections at two other multilevel wells 7 samples in two cases quantitative assessments on the degree of nitrate concentration decrease owing to denitrification were possible however in other cases the specific nitrate isotope fractionation was masked by the variability of nitrate concentration and of nitrate isotope ratios in the corresponding groundwater recharge preventing definite interpretations

petrogenesis of ferromanganese nodules from east of the chagos archipelago central indian basin indian ocean abstract deep sea ferromanganese nodules occur over a large area and on many different sediment types of the central indian basin indian ocean selected samples were studied to determine their chemical and mineralogical compositions and microstructural features repeated laminations of variable thickness alternately dominated by todorokite and vernadite are characteristic of these nodules these laminae show on electron microprobe line scans corresponding interlaminar partitioning of mn cu ni and fe co the bulk chemical compositions of these nodules plot in both the hydrogenetic and early diagenetic fields on the fe mn ni cu co 10 ternary diagram the binary diagram depicting the covariation of mn ni cu against fe co shows two distinct parallel regression lines one delineated by nodules from terrigenous siliceous ooze and siliceous ooze terrigenous sediments and the other by nodules from red clay siliceous ooze red clay and calcareous ooze red clay an increasing diagenetic influence in the nodules with the nature of the host sediment types was observed in the sequence terrigenous siliceous ooze and red clay siliceous calcareous ooze red clay a negative correlation between mn fe ratio and co and a positive correlation between mn fe ratio and ni cu was established the nodules show dendritic laminated and globular microstructures formed by primary growth of fe mn oxide laminae depositional hiatuses in the primary microstructures indicate that the growth of these nodules was episodic the oxide laminations show extremely complex growth patterns scattered biogenic remains and mineral grains acted as accessory seeds for growth of oxide layers in addition to the main nuclei none of the primary microstructures can be uniquely linked to a particular growth process or growth rate radial cracks cutting across primary microstructures are often filled by todorokite of a later generation post depositional modifications of the nodules were largely controlled by accreted biogenic remains as indicated by their progressive dissolution with increasing depth from nodule surfaces their pseudomorphic replacement by todorokite and the later growth of phillipsite and todorokite in the microfossil molds the growth patterns of the in filled oxides are often controlled entirely by the cavity walls and are discordant with the primary growth fabric primary todorokite was recrystallized to coarser grains of different chemical composition later generation veins of todorokite cut across and chaotically disrupted primary laminae

a comparative analysis of compositional variations in and between marine ferromanganese nodules and crusts in the south pacific and their environmental controls abstract regional variation of mn fe co ni and cu in ferromanganese oxides nodules and crusts in the central south pacific is related to primary productivity oxygen minimum layer and calcium carbonate compensation depth the largely latitudinal influence of these environmental parameters on nodule and crust composition reflects their predominantly latitudinal variation primary productivity is the principal regional environmental control influencing diagenetic enrichment of these elements in nodules through its effect mediated by the ccd on supply and concentration of labile organic matter vs carbonate remains to the sediments it influences hydrogenetic enrichment of these elements in nodules and crusts through its effect mediated by the oxygen minimum layer mainly in the case of crusts on their export from surface waters the elements varying susceptibility to being scavenged or organically bound influences the contrasting composition of diagenetic vs hydrogenetic ferromanganese oxides which is further influenced by depth hydrogenesis is the fundamental process governing nodule and crust formation superimposed on which is diagenesis under specific circumstances both are subject to intermittent interruption diminution and augmentation by changes in environmental parameters application of regionally operative environmental controls locally explains local compositional variations and helps refine exploration criteria for economically viable nodules and crusts

ferromanganese nodules from manop sites h s and r control of mineralogical and chemical composition by multiple accretionary processes abstract the chemical composition of ferromanganese nodules from the three nodule bearing manop sites in the pacific can be accounted for in a qualitative way by variable contributions of distinct accretionary processes these accretionary modes are 1 1 hydrogenous i e direct precipitation or accumulation of colloidal metal oxides in seawater 2 2 oxic diagenesis which refers to a variety of ferromanganese accretion processes occurring in oxic sediments and 3 3 suboxic diagenesis which results from reduction of mn 4 by oxidation of organic matter in the sediments geochemical evidence suggests processes 1 and 2 occur at all three manop nodule bearing sites and process 3 occurs only at the hemipelagic site h which underlies the relatively productive waters of the eastern tropical pacific a normative model quantitatively accounts for the variability observed in nearly all elements zn and na however are not well explained by the three end member model and we suggest that an additional accretionary process results in greater variability in the abundances of these elements variable contributions from the three accretionary processes result in distinct top bottom compositional differences at the three sites nodule tops from h are enriched in ni cu and zn instead of the more typical enrichments of these elements in nodule bottoms in addition elemental correlations typical of most pelagic nodules are reversed at site h the three accretionary processes result in distinct mineralogies hydrogenous precipitation produces mno2 oxic diagenesis however produces cu ni rich todorokite and suboxic diagenesis results in an unstable todorokite which transforms to a 7 a phase birnessite upon dehydration the presence of cu and ni as charge balancing cations influence the stability of the todorokite structure in the bottoms of h nodules which accrete dominantly by suboxic diagenesis na and possibly mn 2 provide much of the charge balance for the todorokite structure limited growth rate data for h nodules suggest suboxic accretion is the fastest of the three processes with rates at least 200 mm 106 yr oxic accretion is probably 10 times slower and hydrogenous 100 times slower since these rates predict more suboxic component in bulk nodules than is calculated by the normative analysis we propose that suboxic accretion is a non steady state process variations in surface water productivity cause pulses of particulate flux to the sea floor which result in transient mn reduction in the surface sediments and reprecipitation on nodule surfaces

on the occurrence of ferromanganese micronodules from the sediments of the bengal fan a high terrigenous sediment input region studies of 13 samples 10 surface sediments and 3 cores from across the middle fan region of the bay of bengal reveal the presence of micronodules area 0 22 million km2 over the entire bay these micronodules have two dominant morphological forms botryoidal in the eastern bay and spheroidal in the central and the western regions of the bay the abundance of the micronodules was found to be higher in the eastern region of the bay in the cores the micronodules were generally found to decrease in abundance down core the core from the eastern region had micronodules down to deeper levels than the western side todorokite is the manganese mineral present in the micronodules associated mineral phases are quartz feldspar and phillipsite these micronodules have high mn 19 20 32 13 rather low fe 1 20 1 83 ni 0 10 1 14 zn 0 10 0 30 and co 0 01 0 04 and their mnfe ratio ranges from 10 55 to 25 42 the contents of mn ni cu and zn and the mnfe ratio decrease down core based upon the variations in the abundance morphology mnfe ratio of the micronodules and the elemental distributions and the omn ratio in the sediments remobilization of mn from deeper levels and its precipitation at the upper surfaces of the sediment column in an oxic environment is suggested the results of the present study also suggest that a high rate of sedimentation is not a limiting factor for the formation of micronodules although it might affect their growth

geochemical composition and inferred accretion rates of sediments and managanese nodules from a submarine hill in the madeira abyssal plain eastern north atlantic abstract the porewater and sediment composition of two boxcores and of a small gravity core taken on a manganese nodule covered hill and in the madeira abyssal plain proper respectively are compared the pore water study of the two boxcores indicates that oxic conditions prevail in both cores in addition it indicates that no detectable fluxes of mn or fe occur from the porewater to the ocean bottom water variations in the geochemical composition of the sediments can be explained by fluctuations in the amount of carbonate which acts as a diluting agent a clear carbonate minimum is observed at 20 22 cm depth in the two cores this minimum is likely to be associated with the last glacial period 10 20 kyr b p this association is supported by the sediment accumulation rate of 15 mm kyr as found by extrapolation from the rate for pelagic sediments in the madeira abyssal plain the bulk composition of the manganese nodules recovered from the submarine hill is chemically almost identical to the average composition of atlantic nodules the trace metal and rare earth elements composition indicate a hydrogenous origin for the manganese nodules of this study on the basis of the chemical composition and that of nodules relative to that of the adjacent sediments an average nodule accretian rate of 2 8 3 3 mm myr has been calculated although the analyses of the entire ferromanganese nodules that have been studied seem to indicate a homogenous composition internal structures of the nodules reveal great inhomogeneity both visually and chemically these fluctuations may be related to variations in the fluxes of mn and fe which in turn could be climate related

mineralogy of the groote eylandt manganese oxides a review abstract the mineralogy and genesis of the tetravalent manganese oxides present in the groote eylandt ore are discussed on the basis of recent mineralogical concepts their mechanisms of formation on groote eylandt are described in terms of primary sedimentation formation of vernadite romanechite pyrolusite todorokite diagenesis formation of pyrolusite supergene processes formation of cryptomelane and lithiophorite and pedogenic processes formation of chalcophanite and birnessite these geochemical processes have resulted in the formation of deposits of metallurgical ore of a cryptomelane pyrolusite mineralogy and a battery active ore of vernadite todorokite pyrolusite mineralogy

δ13c and δ15n in the ornithogenic sediments from the antarctic maritime as palaeoecological proxies during the past 2000 yr abstract in this paper we have examined carbon and nitrogen isotopic compositions in two ornithogenic sediment profiles from the ardley island and barton peninsula of antarctica for palaeoecological changes during the past 2000 yr the 13 c values of the two sediment profiles range from 22 26 to 19 15 pdb in core g and from 24 01 to 19 87 in profile a showing that the predominant carbon source in the sediments plausibly comes from terrestrial and aquatic plants in antarctic such as mosses lichens and algae in lakes as these 13 c values are also close to those in the fresh lake sediments that are not influenced by penguin guano one may not use the 13 c values as evidence for the influence of guano on the sediments the 15 n values of the two profiles range from 4 75 to 18 34 air and from 5 17 to 10 38 for core g and core a respectively the 15 n variations have positive correlations with the trends of the bio element contents in the sediments as the levels of these bio elements in ornithogenic sediments had been used to reconstruct the changes of historical penguin population and tundra vegetation abundance and diversity we then suggest that the 15 n records can be utilized to study palaeoecological processes of penguin our results show that penguin population and activity has generally decreased over the past 2000 yr from 1300 to 900 yr bp and from 1790 to 1860 ad penguin population and activity experienced two strong decreases it will be interesting to understand the cause of these decreases

atypical ferromanganese nodules from pelagic areas of the central indian basin equatorial indian ocean abstract two box core samples one each from red clay and siliceous ooze sediment provinces from the central indian basin indian ocean were studied both cores contained ferromanganese nodules at their tops the red clay sediment also hosts buried nodules at a depth of 82 cm chemical characterization of the sediments indicates that early diagenetic remobilization of transitional metals is pronounced in the siliceous ooze sediment while in the red clay no such effect is discernible this is further corroborated by the abundance and dissolution patterns of microorganisms and ferromanganese micronodules occurring in the two sediment columns bulk chemical analyses indicate that all the nodules are of the hydrogenetic b type vernadite and todorokite are the major minerals both of which constitute laminated nondirectional colloform and cuspate microstructures petrographic studies yield evidence of recrystallization of todorokite and partial transformation of vernadite to todorokite the former process being more advanced in buried nodules microprobe analyses revealed that primary todorokite has a lower mn fe ratio and higher ni content than recrystallized todorokite in the same sample the mineralogical reconstitution in the nodules is attributed to postdepositional intranodule diagenesis the present study does not reveal the correlation between mineralogy and microstructure in the nodules which has been suggested for the nodules from the pacific neither can any mineral or microstructure be considered specific for any particular genetic model the studied nodules are therefore atypical the mineralogical and chemical reordering in these ferromanganese nodules raises the question of the viability of radiometric methods in determining growth rates of such nodules

geochemistry of ferromanganese nodules from the central indian basin abstract the major and minor elements and mineralogical composition of a suite of abyssal ferromanganese nodules from the southwestern and south central portion of the central indian basin suggest two accretionary processes for the formation of these nodules a hydrogenous precipitation of colloidal metal oxides from seawater and b oxic diagenesis which involves reactions in oxidised sediments samples from the south central part of the basin have high mn fe ratios with todorokite as principal mn phase these nodules also contain relatively high concentration of elements associated with manganese nodules from the southwestern part have less todorokite low mn fe ratios and higher concentrations of minor elements associated with iron there is a significant correlation between mn and cu ni ba and zn contents while ti p pb co sr y and zr concentrations are related with total fe contents an estimation of the growth rates from the chemical composition indicates that the nodules from the central region have relatively higher values 17 0 37 4 mm ma 1 than nodules from the western part 4 2 14 7 mm ma 1

predicting strontium isotope variation and fish location with bedrock geology understanding the effects of geologic heterogeneity recent advances in using naturally occurring isotopes to reconstruct movement patterns have revolutionized the study of migration and spatial patterns across taxa isoscape approaches utilize isotopic variation in the underlying geology to quantify migration pathways spatial patterns in the geology can be used to predict isotopic variation such as 87sr 86sr however previous attempts to create predictive models have had mixed results our primary objective was to investigate the relationship between bedrock lithology and 87sr 86sr ratio as a tool to extend the spatial resolution of animal migration studies secondly we investigated the ability to use geologic prediction as an a priori tool for determining chemically distinct watersheds we first developed a regression model to relate known stream water 87sr 86sr to rock information from geologic maps then used model outputs to classify adult fall chinook salmon to their juvenile rearing location from 87sr 86sr signatures recorded in their otoliths ear bones we discuss the effect of scale and geologic heterogeneity on our ability to determine 87sr 86sr ratios within the study area our results indicate that the relationship between 87sr 86sr values and bedrock lithology can be used to accurately determine the rearing location of fish using otolith 87sr 86sr signatures the scale at which geology can be used as a predictor of 87sr 86sr values is constrained by geologic heterogeneity and inherent variability in 87sr 86sr ratios within major rock categories further our results indicate that geological data alone can be used to quantitatively investigate which watersheds are likely to be distinguishable using this method within a basin geologic prediction also has the potential to improve the scale and resolution of isotopic studies and the development of isoscapes by applying measures of spatial heterogeneity we will be better able to quantitatively place limits on the accuracy of geologic predictions of 87sr 86sr ratios

geochemistry of ferromanganese micronodules and associated mn and trace metals diagenesis at high terrigenous depositional site of middle fan region bay of bengal abstract the influence of sedimentation on the morphology growth and geochemistry of the micronodules and on mn enrichment in the sediments of the bay of bengal has been evaluated mn accumulation is 307 219 mg cm2 kyr 1 in cores having 20 17 cm kyr 1 sedimentation rate but drops to 34 17 7 mg cm2 kyr 1 in cores with 3 4 cm kyr 1 sedimentation rates however mn enrichment zone becomes thinner with increased sedimentation the abundance of the micronodules increases and they have been observed down to the deeper levels with higher contents of mn ni cu and zn from the areas of the lower sedimentation the results of the present study reveal that though the higher sedimentation may be conducive for higher mn accumulation in the upper surfaces of the sediments the growth abundance and enrichment of mn ni cu and zn in the micronodules are mostly regulated by their residence time within mn oxidation zone the influence of residence time on the morphology and the internal structures of the micronodules are also evaluated

10be dating of large manganese nodules from world oceans the results of 10be and 9be measurements in several sections of ten large manganese nodules are presented along with u and th isotope data on five of them the 10be and 10be 9be methods yield growth rates covering a period of 5 10 ma which are in excellent agreement with each other in three cases these rates are also in very good agreement with those derived from the 230th methods whereas in the other two the 230th based rates are faster by over a factor of two based on the discrepancy between the inventory of 10be as well as 230th in nodules and the overhead seawater column it is calculated that the former scavenge their be and th isotopes from 2 900 m of the overhead water column the deduced 9be concentrations of ocean water based on its 10be contents and the 10be 9be ratios of nodule surfaces are found to be in good agreement with the direct 9be measurements of seawater implying that 9be in nodules like10be is mostly authigenic

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

local variability of manganese nodule facies on small abyssal hills of the central pacific basin abstract local variability of manganese nodule facies and associated sediments were studied around abyssal hills 60 60 km 2 located in the equatorial zone of the central pacific basin small scale variations in nodule occurrence mineralogy chemistry and internal structure are discussed in relation to seismic records and sediment lithology the slow sedimentation rate from the late tertiary to the quaternary appear to have promoted formation of nodules around the abyssal hills although the plio pleistocene hiatus at depths below sediment surface suggests no clear evidence of increased growth of nodules during the period in the area of rapid and continuous sedimentation away from the hill areas nodules are rare probably because of insufficient lifting force for nodules mineralogical and chemical studies reveal that the two principal nodule morphologies smooth and rough surfaces result from preferential deposition of hydrogenous or diagenetic manganese minerals in relation to early diagenesis of surface siliceous sediments regional variability of nodule surface morphology and composition suggests a very local change in sedimentary conditions in space and internal mineral variation suggests changes in sedimentary conditions with time the geological factors controlling the small scale variability of nodule facies seem to be similar to those controlling regional scale variations

long period tidal factors at antarctica syowa station determined from 10 years of superconducting gravimeter data 1 we determined long period gravimetric tidal parameters from 10 years of superconducting gravimeter observations at syowa station in antarctica the obtained amplitude and phase lead for the mm wave were 6 106 0 030 gal gal 10 8 m s 2 0 32 0 28 respectively and those for the mf wave were 11 657 0 018 gal 0 78 0 09 respectively we also determined the parameters of other tidal constituents with periods of 6 to 32 days mqm msqm mtm mstm msf msm and their frequency dependence was estimated by means of a weighted least squares method the observed values corrected by the four ocean tide models of schwiderski nao 99l fes99 and tpxo6 0 were compared with the theoretical values calculated from the elastic and inelastic solid earth tide models by dehant et al even though the values of the ocean tide corrections have relatively large discrepancies between the four models and it is still difficult to discuss the degree of inelasticity of the earth for this frequency band we can say that the observations favor the inelastic earth model rather than the elastic model

element supply to surface manganese nodules along the aitutaki jarvis transect south pacific supply of metals to manganese nodules in the south equatorial pacific is heavily dependent on variations in biological productivity in the northern part of the aitutaki jarvis transect under high biological productivity in the surface waters there is a high flux of mn ni cu and zn to the nodules diagenetically cycled through the interstitial waters of the uppermost sediments together in the nodules with the formation of 10a manganite to the south of the high productivity zone these elements decrease in the nodules at the expense of fe co and pb of hydrogenetic provenance and mno2 is more abundant however nodule compositions also reflect the position of the deposits relative to the carbonate compensation depth ccd which deepens northwards throughout the region with mn ni cu and zn being enriched in 10a manganite bearing nodules from near the ccd under high productivity waters and fe co and pb being more abundant in x ray amorphous or mno2 bearing nodules away from the ccd and or in the south of the transect under low productivity waters

mineralogy and crystal chemistry of mn fe co ni and cu in a deep sea pacific polymetallic nodule minor element concentrations in marine ferromanganese nodules are primarily controlled by the mineralogy which itself depends on redox conditions at the sediment water interface results are presented for the first in depth x ray microstructural and microspectroscopic investigation of a mixed hydrogenetic diagenetic nodule which is representative of ferromanganese deposits on abyssal plains the measurements were conducted by micro x ray diffraction and x ray absorption spectroscopy both xanes and exafs on hydrogeneous and diagenetic regions of the nodule the hydrogenetic diagenetic interface was imaged by x ray microfluorescence after which regions of interest were chosen to represent mineralogical and chemical transformations that occurred at the early stage of suboxic diagenesis in the hydrogenetic nodule oxic environment mn is speciated as fe vernadite a nanocomposite material composed of intergrown feroxyhite feooh and monodispersed phyllomanganate layers having no interlayer mn vernadite in the diagenetic nodule suboxic environment mn is speciated dominantly as mg rich 10 a vernadite which consists of a random intergrowth of vernadite and its transformation product todorokite the authigenic 10 a vernadite precipitated from the components of vernadite in fe vernadite that were dissolved in suboxic microenvironments of the sediment direct evidence supporting a redox driven dissolution reaction is provided by the valence composition of mn as measured by micro xanes which is 0 69mn4 0 24mn3 0 07mn2 average 3 62 0 04 v u for fe vernadite and 0 61mn4 0 23mn3 0 16mn2 average 3 28 0 04 v u for 10 a vernadite ni and cu derived mainly from dissolved vernadite and oxidized organic matter replace structural mn3 4 in both the mno2 layer and todorokite domains of 10 a vernadite pure todorokite in highly diagenetic regions of the nodule has an average formula of mg2 0 167 mn4 0 783 mn3 0 099co3 0 002ni2 0 076cu2 0 040 o2 n h2o with an atomic ratio of cu ni co mn 0 13 which is slightly lower than 0 167 1 6 the maximum metal uptake capacity reported for marine nodules by analogy with synthetic todorokites we infer that mg2 which has a hydrated diameter close to that of the 3 3 tunnel size of todorokite and mn3 and cu2 which prefer jahn teller distorted octahedra play a crucial role in templating the topotactic transformation of 10 a vernadite to todorokite and stabilizing todorokite in suboxic marine sediments

the response of the earth to tidal body forces described by second and third degree spherical harmonics as derived from a 12 year series of measurements with the superconducting gravimeter gwr t3 in brussels abstract a 12 year tidal gravity registration performed in brussels with a gwr superconducting gravimeter allows us to separate six tidal components derived from the third degree lunar potential from those derived from the classical second degree luni solar potential 39 components with which they differ in frequency by the lunar perigee period 8 847 year four ter diurnal waves are also separated such a separation appears necessary as the results show a non negligible residue on the third degree frequency wave m 1 lunar day period owing to an amplification of the corresponding oceanic component in the north atlantic ocean the other third degree components also differ slightly from the theoretical model amplitudes a correct determination of the free core nutation resonance acting on the 1 diurnal solar wave is discussed in relation to atmospheric pressure gravitational effects and climatological disturbances the zonal fortnightly tide mf is also deduced with precision but its comparison with the theoretical model raises a problem

sr isotopic composition of hydroxyapatite from recent and fossil salmon the record of lifetime migration and diagenesis by comparing the sr isotopic composition of migratory fossil salmon which lived in the ocean but died in continental regions to the well established marine sr isotopic record the age of the continental deposit could be determined with high accuracy this approach to marine continental correlation and dating requires 1 that marine resident salmon bear a marine s7sr 86sr value in their bones or teeth and 2 that the original s7sr 86sr value of fossils is not overprinted by diagenesis the vertebrae of modern hatchery reared salmon exhibit sr isotopic variations indicative of freshwater to marine migration during bone growth modern marine s7sr s6sr values were preserved in growth layers formed later in life marine phase growth layers in the bones and teeth of the late miocene migratory salmon oncorhynchus rastrosus were subjected to stepwise selective leaching to separate biogenic hydroxyapatite from diagenetic calcium carbonate and recrystallized hydroxyapatite although the procedure yielded leachates with sr ca and ca p values characteristic of apatite the leachates had 87sr s6sr values consistently less radiogenic than values for late miocene seawater 0 7087 the fossils were substantially contaminated by sr from the hosting clastic sediments specimens in continental deposits differed in 87sr 86sr value from host sediments by 0 0002 to 0 0200 supporting the conclusion that these salmon were migrants from marine waters however because the original sr isotopic composition of fossil bones and teeth cannot be determined with confidence archaeological paleobiological and stratigraphic applications of this technique may be limited

long period tides observed with a superconducting gravimeter at syowa station antarctica and their implication to global ocean tide modeling abstract the long period tides mf and mm waves were analyzed with the 2 years data obtained with a superconducting gravimeter sg installed at syowa station 69 0 s 39 6 e antarctica the observed amplitudes phase lags and amplitude factors factors were 11 642 0 035 gal 0 12 0 17 and 1 1218 0 0034 for the mf wave and 6 143 0 058 gal 0 33 0 54 and 1 1205 0 0106 for the mm wave respectively 1 gal 10 8 m s 2 the ocean tide effects effects of the attraction and loading due to the ocean mass at the observation site were estimated using the five global ocean tide models equilibrium ocean tide model schwiderski model schwiderski e w 1980 on charting global ocean tides rev geophys space phys 18 243 268 dickman model dickman s r 1989 a complete spherical harmonic approach to luni solar tides geophys j int 99 457 468 csr model eanes r j 1995 private communication and desai and wahr model desai s h wahr j m 1995 empirical ocean tide models estimated from topex poseidon altimetry j geophys res 100 25205 25228 the averages of the five estimates are 0 433 gal and 0 244 gal in amplitude and 192 9 and 179 5 in phase for the mf and mm waves respectively the five estimates differ by a maximum of 0 104 gal in amplitude and 18 8 in phase for the mf wave and by 0 033 gal and 6 4 for the mm wave the estimated mm phases are nearly 180 for the five models and the variation of their values among the models is relatively small compared with that of the mf phases these indicate that the mm wave is much closer to an equilibrium tide than the mf wave due to the variation of the ocean tide corrections the corrected factors were scattered within the ranges of 1 158 to 1 169 for the mf wave and of 1 163 to 1 169 for the mm wave however it is noted that the mean factors of the five ocean models i e 1 162 0 023 for the mf wave and 1 165 0 014 for the mm wave prefer slightly larger value rather than those estimated from the theory of the elastic tide

seasonality of bedrock weathering chemistry and co2 consumption in a small watershed the white river vermont abstract the draw down of co2 from the atmosphere during mineral weathering plays a major role in the global budget of this greenhouse gas silicate minerals remove twice the co2 of carbonate minerals per mole of calcium in runoff during weathering bedrock weathering chemistry was investigated in the white river watershed of northeastern usa to investigate whether there are seasonal differences in carbonate and silicate weathering chemistry geographic information systems analyses of bedrock geology were combined with major element concentrations in river waters to gain an understanding of the consistency of mineral weathering during three seasons the percent of carbonate mineralogy comprising the bedrock in tributaries of the white river varied from less than 5 to 45 by area a mass balance calculation using major element concentrations in waters was applied to estimate the seasonal relationships between bedrock geology and bicarbonate flux in all tributaries and the main stem of the white river the highest calculated percent of bicarbonate from carbonate mineral weathering was measured in the late fall the results suggest that carbonate and silicate bedrock weathering processes are seasonally controlled thus single season sampling could not accurately represent an entire year s geochemical budget in the white river water samples obtained solely during the summer would consistently underestimate the total yearly source of bicarbonate from carbonate bedrock weathering the same sample set would also provide data that would lead to an underestimation of the yearly atmospheric co2 draw down by bedrock weathering in the watershed for example at four of the seven locations studied there was an almost two fold difference between summer and spring calculated atmospheric co2 consumption rates

fine scale study of major and trace elements in the fe mn nodules from the south china sea and their metallogenic constraints abstract many marine fe mn polymetallic nodules may contain high concentrations of mn cu ni zn co and rare earth elements plus yttrium rey to determine the occurrence and enrichment processes of these metals in the fe mn nodules we conducted high resolution mineralogical and geochemical studies on the fe mn nodules collected from the south china sea in situ epma and la icp ms analyses and elemental imaging were performed on individual microlayers of the nodules to reveal the major and trace element distributions the whole rock mineralogical and chemical compositions of the fe mn nodules indicate a hydrogenetic origin the mn mineral phases are mainly composed of nanocrystalline vernadite with interlayered 10 a and 7 a phyllomanganates such as todorokite birnessite and buserite fe ti oxides hydroxides are intergrown and essentially x ray amorphous feroxyhyte and goethite we recognize two main types of microlayers type a layer suboxic diagenetic precipitates containing a high mn fe ratio and high concentrations of cu ni zn ba li and mg and type b layer oxic hydrogenetic accretions with low fractionation of mn and fe and high contents of co rey ti sr and pb furthermore elemental mapping indicates that the enrichments of co and rey are mainly associated with fe mineral phases rather than mn ones which are enriched in mg cu ni zn li and ba two mineralization processes and metal distributions in the individual microlayers are identified in the fe or mn mineral phases the occurrence of 10 a and 7 a phyllomanganates in type a layers are commonly enriched in trace metals such as ni cu zn li ba and mg whereas the metals for the type b layers include co ti pb sr rey which may be carried by the intergrowing fe ti oxyhydroxides and vernadite thus hydrogenesis and diagenesis facilitate the enrichment of fe co ti sr pb rey and mn ni zn cu li ba mg respectively during the mineralization of the south china sea nodules

15n enrichment in agricultural catchments field patterns and applications to tracking atlantic salmon salmo salar abstract nitrogen isotopes were used to study the source of nitrate and its uptake into the food web of a northeastern river in vermont usa in six tributaries of the white river vermont nitrate concentrations were elevated in streams flowing through areas with agricultural land use as compared to streams flowing through pristine forested areas we observed a strong positive correlation between 15n values of stream water nitrate and percent of agricultural land use within a given catchment agricultural sites had relatively high 15n values of nitrate 7 3 compared to forested sites 2 0 these relatively high 15n values coupled with relatively high concentrations of nitrate in agricultural streams suggest the introduction of 15 n enriched nitrate draining from agricultural areas additionally elevated 15n values of algae aquatic insects and atlantic salmon salmo salar in agricultural sites compared to lower 15n values of their counterparts in forested sites suggest the uptake of nitrate from agricultural sources by stream organisms we observe a similar positive correlation between the 15n of atlantic salmon and the percent of agricultural land in a catchment the nitrogen isotope values of both atlantic salmon and water nitrate reflect land use thus nitrogen isotope ratios in salmon especially when coupled with strontium isotope ratios which reflect catchment geology create unique isotopic identities for atlantic salmon stocking streams and thereby provide a means of determining the natal origin of juvenile salmon

geochemical variations of ferromanganese nodules and crusts from different provinces of the pacific ocean and their genetic control abstract the chemical composition of nodule samples from the northeast pacific nodule belt and from the northern part of the nazca plate in the southeast pacific have been investigated ni and cu contents increase with increasing mn fe ratio up to a value of 5 in samples from both provinces the nodules from the southeast pacific show a decrease in ni and cu contents when the mn fe ratio increases above a value of 5 nodules with a mn fe ratio of 5 have the highest concentrations of ni and cu a similar relationship cannot clearly be observed in nodules from the northeast pacific where the mn fe ratio does not exceed values of 7 4 the observed decrease in the ni and cu contents at mn fe ratios greater than 5 is a consequence of an enhanced supply of mn2 ions within the pore water environment of the upper centimeters to decimeters of the sediment column this leads to the incorporation of mn2 ions instead of ni2 and cu2 ions in the intermediate layers of the todorokite lattice increased amounts of organic matter in the sediment deposits below the equatorial zone of high biological productivity result in a decrease in the redox potential within the uppermost part of the sediment column which promotes the mobilization of mn nodules grow faster under these conditions and are enriched in mn and depleted in ni and cu the co contents of the nodules from the southeast pacific decrease in general with rising mn fe ratio considering three phase diagrams the geochemical discrimination of different genetic types of nodules is possible plotting only co vs mn and fe in a three phase diagram it can be elucidated that ferromanganese deposits richest in co only occur at mn fe ratios between 1 and 2 however the individual co values show a great range of variation in the case of early diagenetic nodules the samples from the southeast pacific show on the average lower concentrations of co than the nodules from the northeast pacific

geochemistry of sediments from the romanche fracture zone equatorial atlantic abstract a suite of sediment samples from the romanche fracture zone in the equatorial atlantic has been subjected to bulk and partition chemical and mineralogical analyses together with radiometric dating in order to study the main controls on composition and origin the interelement relationships in the sediments revealed by geostatistical analysis indicate that 1 ca sr and p 2 al fe ti v zn li be and k 3 mn co ni and cu and 4 mg cr and ni are associated partition chemical data suggest that these element associations represent respectively biogenic terrigenous igneous and hydrogenic phases of the sediment surface and downcore sediment data indicate that the distribution of the biogenic component of the sediment is influenced by water depth the distribution of the igneous component is largely controlled by a contribution from ultramafic sources and shows the influence of subsea erosion on the surface sediments the distribution of the hydrogenic component is influenced by contribution from the water column sediment accumulation rate data indicate that these sediments have accumulated fairly rapidly bottom topography and turbidity current activity are probably the main factors controlling their accumulation metal accumulation rate data indicate that there is no significant hydrothermal contribution to the deposits as has been suggested by other workers

a global marine fixed nitrogen isotopic budget implications for holocene nitrogen cycling 1 a nitrogen stable isotopic model was constructed in order to constrain the holocene marine fixed nitrogen budget the primary sources and sinks considered were riverine and atmospheric sources nitrogen fixation sedimentary and water column denitrification and sediment burial the source budget was found to be insensitive to changes in nitrogen fixation rates and thus could not be used to constrain this term however the isotopic value of fixed nitrogen losses was very sensitive to the amount of sedimentary denitrification if the isotopic value of marine fixed nitrogen has not changed during the holocene as supported by sedimentary records then in order to balance the isotopic value of sinks and sources approximately 280 tg n yr 1 of sedimentary denitrification is required if such a high rate of denitrification has been sustained throughout the holocene it implies that present day estimates of marine nitrogen fixation are grossly underestimated it also implies that the marine nitrogen budget has a residence time of less than 2000 years