phosphatised limestones and associated sediments from the western continental shelf of india abstract the phosphatised limestones and associated sediments of the outer continental shelf of the west coast of india between goa and ratnagiri at depths of between 70 and 120 m have been studied the highest p 2 o 5 content 9 ranging from 2 to 9 depending on location occur in the algal nodules polished and thin sections show that the algal nodules grew with the occasional microbial mat these mats apparently formed by trapping and binding of sediment particles which were subsequently phosphatised phosphate also occurs as pellets and rounded structures high magnesium calcite and carbonate fluorapatite are the major minerals aragonite low magnesium calcite and quartz are also present in some samples microprobe geochemistry of the phosphatised material of the algal nodules reveals the presence of land derived siliciclastic detritus and the possibility of more than one source for ca and p phosphate also occurred as cavity fillings in coral and bryozoan limestones but not in oolitic limestones regardless of their occurrence at the same depths and in the vicinity of the other limestones the associated sediments are mostly sandy and show smaller concentrations of p 2 o 5 average 0 3 and organic carbon average 0 93 as compared to the regions of upwelling where phosphorites are forming the correlation exhibited between the p 2 o 5 and the organic carbon is negative the environmental conditions for the formation of phosphatised limestones and possible sources of phosphate are discussed sheath organic matter associated with filaments appears to be the major source for phosphorus the phosphatisation is a microbial process which takes place at shallow depths the impact of present day upwelling is insignificant in the phosphatisation of the limestones

conditions of formation and diagenetic evolution of upper proterozoic phosphate nodules from southern sweden evidence from petrology mineral chemistry and isotopes abstract dark gray to black cryptocrystalline francolite occurs as nodules 2 8 cm in diameter which are embedded in organic matter rich mudstones of the visingso group upper proterozoic southern sweden the 13cpdb values 18 4 to 0 98 of structural co2 complemented by studies of the petrographic character and strontium isotopic composition of francolite indicate precipitation in the suboxic and sulfate reduction zones francolite is intergrown with berthierine that has formed in the suboxic fe reduction zone calcite enriched in mn and to a lesser extent fe occurs as fracture and void fillings and as replacement of francolite mn and mg rich calcian siderites have precipitated as pseudomorphs after bacteria in the zone of microbial methanogenesis the carbon 13 c pdb 0 75 to 7 04 and oxygen 18 o pdb 14 21 to 10 58 isotopes of calcite suggest derivation of carbonate ions from microbial methanogenesis and from thermal decarboxylation of organic matter at temperatures of 60 to 80 c some of the void and fracture filling calcites 13 c 20 8 to 18 63 18 o 5 46 to 5 21 have however precipitated at lower temperatures 25 30 c in the sulfate reduction zone

palaeoenvironmental reconstruction of a condensed hardground type depositional sequence at the cretaceous tertiary contact in the parnassus ghiona zone central greece abstract phosphatic hardgrounds at the k t boundary in the parnassus ghiona zone reflect a major stratigraphic break the hardgrounds developed on top of the uppermost maastrichtian beds which represent a condensed pelagic carbonate sequence of seamount type synsedimentary lithification and hardground formation took place on shallow periodically emerged seafloors phosphate cementation includes fillings of intra and inter particle porosity and occludes passive framework open spaces as well as rim cement fabrics developed through mineralization by non phototropic microbial communities within the hardground superstructure a highly condensed phosphate sediment was precipitated post dating the hardground formation phosphate cementation was developed under well oxygenated conditions involved in a low productivity phosphogenic system phosphate ions were released into pore waters through bacterial decomposition of organic matter glauconite developed due to prolonged contact of lithified chalk with seawater the irregular bored impermeable and phosphate cemented pavements are covered by stratiform and columnar laminated phosphatic stromatolitic crusts trapping early paleocene pelagic sediments deposited during the subsequent danian transgression the source of phosphorus was external either marine or continental phosphatization occurred during the bacterial degradation of the organic sheaths pyrite crystals within the stromatolitic laminae suggest a sulphidic environment beneath the mat forming communities successive phases of intraformational reworking resulted in mature hardground development lags from eroded subjacent hardgrounds were accumulated in neighbouring submarine depressions marly material rich in quartz has been concentrated along discontinuities on former topographic heights both the phosphatic hardground and stromatolites have been assimilated by a cryptocrystalline phosphatic material rich in clay iron oxides and quartz considered to originate from subaerial weathering phoscretization

depositional sequences of the duwi sibâiya and phosphate formations egypt phosphogenesis and glauconitization in a late cretaceous epeiric sea

diagenetic evolution of the upper devonian phosphorites alborz mountain range northern iran abstract the upper devonian mixed siliciclastic carbonate stratigraphic succession of the geirud formation in the alborz mountain range north of iran hosts numerous phosphorites and phosphatic rocks these phosphorites which represent one of the most globally important deposits in the devonian have gained little attention regarding their genesis and diagenetic evolution this study focuses mainly on the post depositional changes that occurred during shallow to deep burial diagenetic evolution and subaerial weathering of the geirud phosphorites the phosphorites consist of phosphatic massive mudclasts detritus rich lithoclasts bioclasts and bones formed by several stages of phosphogenesis and erosion reworking winnowing and condensation associated with famennian sea level changes the phosphatic clasts consist of early diagenetic poorly crystalline carbonate fluorapatite cfa and pyrite cementing detrital quartz illite muscovite rutile and zircon phosphatic clasts are intensely compacted with sutured grain contacts along which dissolution and reprecipitation of chemically refined well crystalline cfa with a bright blue cathodoluminescence and illite occurred during deep burial diagenesis similarly quartz shows deformation planar features overgrowth cement was developed as a result of pressure dissolution in phosphatic sandstones followed by precipitation of ferroan dolomite ankerite and chlorite in secondary porosity subaerial weathering led to oxidation of pyrite and generation of acidic ph condition under which ca and p from phosphates fe and s from pyrite fe ca mg and mn from ferroan carbonates and al and si from aluminosilicates were released to form goethite psilomelane calcite gypsum and crandallite the paas normalized rare earth elements rees show bell shaped patterns with middle rees enrichment positive eu anomaly and a weak negative ce anomaly this implies recrystallization of cfa in phosphorites and phosphatic rocks during deep burial diagenesis deviating from the modern seawater like ree patterns in this regard deep burial diagenesis affecting the upper devonian geirud phosphorites is possibly a common process in the proterozoic paleozoic phosphorites in northern iran and elsewhere in the world

microbial processes in the negev phosphorites southern israel microscopic and sem observations indicate that cyanobacterial activity was important during the formation of the campanian negev phosphorites one aspect of such activity is the development of phosphorites through the binding of phosphate particles these sediments often demonstrate a conspicuous smooth cryptalgal lamination the algal binder was fossilized as intertwined phosphatic sheaths that coat and seal off the phosphate grains different types of sheaths representing the remnants of an algal community were found thick apatite overgrowth commonly deforms the microbial fossils converting them into barely recognizable forms fabrication of phosphate particles is another aspect of the microbial activity phosphate algal coated grains are a common constituent of the negev phosphorites the algal coating consists of stacked phosphatic tubes and colonies of coccoid unicells with an apatite infilling fragmented phosphatic sheath bundles form another type of phosphate particle produced by algae obliteration of algal structures is common resulting in undifferentiated groundmasses of cryptocrystalline apatite the extremely close connection between microbial structures and phosphatization processes suggests cyanobacterial participation in phosphorus enrichment

a phase altimetric simulator studying the sensitivity of earth reflected gnss signals to ocean topography this paper presents a simulation study on global navigation satellite system gnss reflections focusing on a phase altimetric method for ocean topography retrieval it examines carrier phase residuals of earth reflected gnss signals in preparation for the gnss reflectometry radio occultation and scatterometry experiment aboard the international space station geros iss the residuals sensitivity to ocean topography maximum of 2 m amplitude variation of global sea level is shown a trigonometric approach to determine the specular reflection point is proposed reflection events are simulated assuming different low earth orbit receivers and gnss type transmitters suitable events for phase altimetry are assumed between 5 and 30 elevation lasting between 10 and 15 min with ground tracks length of 3000 km typical along track footprints 1 s integration time have a length of about 5 km within the assumed elevation range the coherent footprint ellipse has a major axis between 1 and 6 km a master slave sampling is proposed to approximate large scale delay and doppler variations of the reflected signal slave channel relative to the direct signal master channel slave residuals of an example event are simulated to retrieve a small scale phase delay for ocean topography inversion the signal to noise ratio restricts the quality of the topography results height precision on sub decimeter level for 30 db snr is degraded up to a meter level for 20 db snr ionosphere free linear combination allows keeping the precision level troposphere refraction degrades precision particularly at the low elevation limit precision improves toward higher elevations the tolerance to ocean roughness decreases in the same way

early diagenesis of inner shelf phosphorite and iron silicate minerals lower cretaceous of the orpheus graben southeastern canada implications for the origin of chlorite rims wells in the orpheus graben encountered the most proximal part of the deltaic lower cretaceous rocks of the scotian basin more distal sandstones are important gas reservoir rocks with good reservoir quality where fe rich chlorite chamosite rims on framework grains have inhibited quartz cementation cutting samples from the orpheus graben show the presence of fe rich sheet silicates berthierine or chamosite and early diagenetic phosphorite these minerals were analyzed by electron microprobe and their textures were mapped with backscattered electron images studies in the north sea have shown a relationship between high phosphorus and the presence of good chlorite rims in reservoir rocks the mineralization of pore water phosphorus instead of its return to seawater is favored by fe rich sediments and sorption on iron oxides during shallow sea floor diagenesis the fe ti and p contents are uncommonly high in scotian basin shales compared with global average shale compositions the uncommon occurrence of inner shelf phosphorite in this study is interpreted to be a consequence of the same high fe content of the sediment that also favors the formation of fe rich sheet silicates in rapidly deposited deltaic sandstones of the offshore reservoirs the dominance of type 3 kerogen led to sulfate depletion occurring at depths of tens of meters and a corresponding great thickness for overlying eh oxidation potential controlled diagenetic zones the thick fe reduction zone allowed the formation of early diagenetic berthierine which on burial formed the chamosite rims that resulted in the improved reservoir quality in sandstones the distribution of phosphorus minerals may be an indicator of conditions suitable for berthierine formation

oxygen isotope variations in phosphate of biogenic apatites ii phosphorite rocks abstract phosphorites from sedimentary sequences ranging in age from archaean to recent were analysed for 18 o in both the po 4 18 o p and co 3 18 o c in the apatite lattice the oxygen isotope record is considerably better preserved in phosphates than in either carbonates or cherts the use of the longinelli and nuti 8 temperature equation yields temperatures for recent phosphorites that are in good agreement with those measured in the field the 18 o p values of ancient phosphorites decrease with increasing age these changes with time are not likely to be due to post depositional exchange changes in 18 o values of seawater and variations of temperature with time can account for the 18 o p time trend but the latter explanation is preferred in ancient phosphorites 18 o c in structurally bound carbonate in apatite is not a reliable geochemical indicator

orbitally paced phosphogenesis in mediterranean shallow marine carbonates during the middle miocene monterey event during the oligo miocene major phases of phosphogenesis occurred in the earth s oceans however most phosphate deposits represent condensed or allochthonous hemipelagic deposits formed by complex physical and chemical enrichment processes limiting their applicability for the study regarding the temporal pacing of miocene phosphogenesis the oligo miocene decontra section located on the maiella platform central apennines italy is a widely continuous carbonate succession deposited in a mostly middle to outer neritic setting of particular interest are the well winnowed grain to packstones of the middle miocene bryozoan limestone where occurrences of authigenic phosphate grains coincide with the prominent carbon isotope excursion of the monterey event this unique setting allows the analysis of orbital forcing on phosphogenesis within a bio chemo and cyclostratigraphically constrained age model la icp ms analyses revealed a significant enrichment of uranium in the studied authigenic phosphates compared to the surrounding carbonates allowing natural gamma radiation gr to be used as a qualitative proxy for autochthonous phosphate content time series analyses indicate a strong 405 kyr eccentricity forcing of gr in the bryozoan limestone these results link maxima in the gr record and thus phosphate content to orbitally paced increases in the burial of organic carbon particularly during the carbon isotope maxima of the monterey event thus phosphogenesis during the middle miocene in the mediterranean was controlled by the 405 kyr eccentricity and its influence on large scale paleoproductivity patterns rare earth element data were used as a tool to reconstruct the formation conditions of the investigated phosphates indicating generally oxic formation conditions which are consistent with microbially mediated phosphogenesis

carbon and phosphorus burial associated with modern phosphorite formation phosphorite formation plays a significant but poorly constrained role in the marine c and p cycles this report concerns a site of modern phosphorite formation on the upper continental slope off southern baja california mexico sta 6 380 m water depth 23 41 n 111 05 w at this site a series of six narrow 1 3 cm partially indurated phosphorite layers have formed authigenically during the last 15 000 years within a surficial section of slowly but steadily accumulating 3 8 10 3 cm year 1 organic rich mud a poorly oxygenated benthic environment has prevailed at the study site since approximately 8100 year b p probably helping to produce and preserve the pristine phosphorite layers the mean p burial flux 1 1 mol cm 2 year 1 recorded by these deposits agrees closely with the downward diffusive p flux 1 3 mol cm 2 year 1 attributed to active francolite growth such a coincidence implies that the phosphorite layers could have formed entirely under present conditions however a much larger upward diffusive p flux 4 2 mol cm 2 year 1 directed out of the sediment limits the efficiency of ongoing phosphorite formation and the most recently deposited sediment does not contain enough labile p to maintain the overall p regeneration rate indefinitely attendant burial fluxes of inorganic and especially organic c 7 7 and 6 6 mol cm 2 year 1 respectively do not accord with a depositional model of coastal upwelling suggesting that an alternative mechanism possibly fe redox cycling controls porewater p concentrations and hence phosphorite formation a comparison with previously published p burial fluxes for a wide variety of other modern marine settings reveals that phosphorite formation in general does not disproportionately affect the global p burial flux from these data we tentatively estimate a minimum global p burial flux of approximately 70 109 mol year 1 with almost 80 occurring on continental margins

petrology and major element geochemistry of peru margin phosphorites and associated diagenetic minerals authigenesis in modern organic rich sediments abstract new petrographic and major element geochemical data from modern peru margin upper slope outer shelf phosphorites are presented which provide insight into their origin and paragenetic relationship with other authigenic minerals glauconite pyrite and dolomite occurring in organic rich sediments glauconites are precipitated relatively early following the partial reduction of ferric iron and following this process phosphate pyrite and then dolomite precipitation take place at progressively deeper levels in the sediment in association with microbial reduction of sulfate as in many ancient economic phosphorite deposits the phosphatic facies here consist of nodules crusts coatings and strata composed of phosphatic pelletal grains ooids structureless grains intraclasts clumps and biogenic grains in association with organic rich biosiliceous sediments all are considered to have formed within a few centimeters or within a few tens of centimeters below the sediment water interface important factors that influence which morphology will tend to develop include the amount of available pore space the presence of suitable nucleation sites the amount and size of siliciclastic detritus incorporated as inclusions and the relative solution chemistries of the precipitating solutions bacterial mediation may play an important but as yet unspecified role in the precipitation process textural data and factor analysis of chemical data suggest that structureless pellets are relatively inclusion free na f mg co3 substituted pore water precipitates whereas ooids are inclusion rich pore water precipitates poor in lattice substituted components variations in nodular cement birefringence and crystallinity are suggested to have been produced by similar lattice substitutions that directly reflect pore water carbonate ion concentrations and thus relative degrees of organic matter degradation phosphate and dolomite are intimately mixed yet mineralogically distinct phases in phosphatized dolomicrites depth stratified threshold carbonate ion concentrations may control the lower limit at which phosphatic minerals may precipitate below depths of a few centimeters excessive carbonate ion concentrations and diminished reactive iron and sulfate concentrations favor the development of dolomite while precluding further development of phosphatic minerals and pyrite periodic sediment reorganization bioturbation current winnowing and erosion mass wasting etc plays an important role in both concentrating pelletal grains and maintaining nodules and crusts at critical depth levels in the sediment as well as mixing ordered mineral parageneses into complicated sequences

bacterial origin of east australian continental margin phosphorites many models of the origin of marine phosphorites require a sediment rich in organic matter which by decomposition releases phosphorus for the precipitation of carbonate fluorapatite1 7 this concept is useful in explaining contemporary phosphorite in areas of very high productivity off the coasts of peru chile and south west africa8 10 where there are high organic matter fluxes to the sea floor4 7 11 it does not explain the origin of marine phosphorite deposits which formed in regions of limited oceanic upwelling and productivity12 14 the east australian continental margin an area of phosphogenesis throughout the late pleistocene and holocene13 14 is a modern analogue of an east coast phosphogenic province15 17 with low productivity over the upper slope region where the most recent phosphorites have been found18 evidence is reported here for the carbonate fluorapatite in the east australian phosphorites being located within bacterial cellular structures and a model proposed for the origin of these deposits through the slow bacterial assimilation of phosphorus from seawater in an area of restricted sedimentation

hawaiian basalt and icelandic rhyolite indicators of differentiation and partial melting in spite of the voluminous basaltic volcanism on the island of hawaii rhyolite is not produced iceland on the other hand exhibits common rhyolitic volcanism amounting to some 10 12 of its surface rocks this contrast is investigated using the fundamental igneous processes exhibited by sheet like hawaiian lava lakes and shonkin sag laccolith in montana highly differentiated residual melts normally reside within inwardly advancing solidification fronts and are generally inaccessible to eruptive processes only when a large initial phenocryst population is present from which a thick basal cumulate can rapidly form is it possible to supply highly differentiated melt into the active i e eruptable portion of the magma chamber although there is protracted control of differentiation at hawaii by settling of olivine further differentiation occurs within the solidification fronts only by repeated transport and holding is it possible to differentiate beyond the critical composition of the leading edge of the solidification front 7 mgo and 51 5 sio2 crystal size distributions csds for hawaii and shonkin sag are used to demonstrate the inferred physical and chemical processes of solidification including the kinetics of crystallization

phosphate regeneration from sediments of the peru continental margin by dissolution of fish debris generally oxidative regeneration of phosphate from anoxic sediments is by microbially mediated sulfate reduction processes stoichiometric modelling of such reactions takes into consideration varying proportions of decomposable organically bound p to account for the ratios among nutrients in depth concentration profiles of near surface sediments new results of interstitial water composition from sediments underlying the water masses influenced by coastal upwelling of the eastern boundary current system off peru indicate that dissolution of phosphatic fish debris represents a mechanism for remineralization of phosphate comparable to or larger in magnitude than that by oxidative regeneration of organically bound p dissolved interstitial phosphate from fish debris is revealed by an excess amount of phosphate over that predicted from a simple stoichiometric oxidative regeneration model and by anomalously high dissolved interstitial fluoride concentrations phosphate flux estimates based on diffusion from the sediment suggest that this mechanism may generate up to 10 of the nutrient pool in the waters of the peru undercurrent partitioning of p among the two sources reveals further that fish debris phosphate is about four times more important than organically bound p in nutrient generation from sediments of the peru continental margin not only does this mechanism of regeneration affect the nutrient cycling but may also control widespread phosphorite formation in this area

distribution texture and composition of modern phosphate pellets in peru shelf muds abstract textural analysis including estimates of concentrations of authigenic phosphate pellets were made for eight sediment cores from the peru continental margin phosphatic pellets separated from these modern organic rich sediments are black spherical ovoidal in shape and in thin section often display a concentric structure around a nucleus consisting of inorganic mineral grains some pellets have a gray white exterior coating which appears to be secondary diagenetic calcite phosphatic pellets account for upwards of 80 of the sediment mass in some cores pellets concentrate in specific size classes generally between 125 and 500 m in diameter and occur within a poorly sorted sediment

genesis of apatite in the phosphatized limestones of the western continental shelf of india phosphatized corals algal nodules encrustations and pelletal limestones occur at depths between 60 and 100 m on the western continental shelf of india microstructural studies of limestones by sem indicate that phosphate occurs as a brown infillings in boring septal cavities of corals b trapped material between algal laminations and c cement in pelletal limestones phosphate is in the form of ovoids rods and dumb bell shaped apatite microparticles or their coalesced aggregate forms or microbial filaments these apatite microparticles resemble fossilized bacteria and are often adhered to clays sem coupled with eds shows that the phosphate is associated with siliciclastic material it appears that abundant terrigenous flux was transported to the shelf at about 8300 yr b p resulted in the demise of corals and favoured the growth of crustose coralline algae for short duration this flux also filled the pores cavities of corals and coralline algae subsequently microbial organisms colonized the sediments and empty as well as sediment filled pores of the limestones and favoured rapid precipitation of apatite locally by utilizing organic phosphate and phosphate adsorbed on to clays phosphatization of the limestones is thus a short event in the early holocene influenced by microbial processess

diagenetic quartzarenite and destruction of secondary porosity an example from the middle jurassic brent sandstone of northwest europe significant amounts of feldspar have been dissolved from middle jurassic sandstone oil reservoirs in the north sea northwest europe during burial diagenesis sandstones of the middle jurassic brent group become increasingly quartzose with increasing burial depth at statfjord field 2500 m depth sandstones are arkose to subarkose at hutton field 3050 m depth they are subarkose to quartzarenite and at lyell field 3500 m depth sandstones are typically quartzarenite in spite of extensive feldspar dissolution the abundance of secondary porosity due to feldspar dissolution is similar for all fields averaging 2 9 of the total rock volume thus far more feldspar has been dissolved than is recorded as secondary porosity the limit on preservation of secondary porosity may be largely the effect of the mechanical strength of the rock an excessive number of large secondary pores lowers the rock strength below the point at which the rock can withstand overburden stress thus causing collapse of some of the secondary pores

quaternary phosphorites from the continental margin off chennai southeast india analogs of ancient phosphate stromatolites abstract pleistocene phosphorites occur on the continental margin off chennai abundantly in the depth range of 186 293 m they are associated with outer shelf glauconites and carbonate skeletals including large shells of molluscs and rhodoliths these are primary phosphate deposits and are similar to phosphate stratiform stromatolites this is the first report of phosphate stratiform stromatolites during the quaternary and modern times and they provide a quaternary analog for ancient phosphorites thin sections of phosphorites exhibit laminated phosphatized microbial mats consisting of mechanically deposited clastic particles or of phosphatic molds clay particles are scattered throughout the matrix sem studies reveal that the laminated phosphate matrix is made of thin sheets of tightly packed apatite globules densely packed intertwined microfilaments or filament molds phosphate with obscured laminae is composed of phosphate tubules cell like structures resembling coccoid cyanobacteria or their botryoidal aggregates are common carbonate fluorapatite and low magnesium and high magnesium calcites are the major mineral phases the structural co2 content of apatite ranges from 4 to 5 5 quartz feldspar and goethite are accessory minerals the microbial mats were formed on the outer shelf most probably during conditions of low sea level in the quaternary and microbial processes played a major role in direct phosphatization of these mats the primary phosphorus source seems to have been the continental supply and degradation of organic matter associated with benthic microbial communities the phosphate stratiform stromatolites thus formed were subsequently reworked into a shelf margin depression and resulted in the occurrence of condensed phosphorites

the changing vision of marine minerals abstract non fuel marine minerals are reviewed from the perspective of resources and their value as active analogs that can advance understanding of types of ancient ore deposits that formed in marine settings the theory of plate tectonics is the largest influence in expanding our vision of marine minerals and in developing our understanding of geologic controls of mineralization in space and time prior to the advent of plate tectonics we viewed the ocean basins as passive sinks that served as containers for particulate and dissolved material eroded from land this view adequately explained marine placer deposits heavy minerals and gems aggregates sand and gravel and precipitates phosphorites and manganese nodules although numerous sites of placer mineral deposits are known on continental shelves worldwide current activity pertains to diamond mining off southwestern africa tin mining off southeastern asia and intermittent gold mining off northwestern north america which are all surpassed economically by worldwide recovery of marine sand and gravel in turn dwarfed by offshore oil and gas with the advent of plate tectonics plate boundaries in ocean basins are recognized as active sources of mineralization in the form of hydrothermal massive sulfide deposits and proximal lower temperature deposits hosted in oceanic crust mafic at ocean ridges and felsic at volcanic island arcs and of magmatic ni cu sulfide chromite and pge deposits inferred to be present in the oceanic upper mantle lower crust based on their occurrence in ophiolites some 300 sites of hydrothermal active and relict mineralization most of them minor are known at this early stage of seafloor exploration on ocean ridges in fore arc volcanoes at back arc spreading axes and in arc rifts deposits formed at spreading axes and transported off axis by spreading are present in oceanic lithosphere but are virtually unknown the tag trans atlantic geotraverse hydrothermal field in the axial valley of the mid atlantic ridge latitude 26 n is considered to exemplify a major volcanogenic massive sulfide vms deposit forming at a spreading axis the most prospective of these occurrences lie within the 200 nautical mile 370 km wide exclusive economic zone eez of the nations of the volcanic island arcs of the western pacific where metal content of massive sulfides ag au ba cu pb sb zn exceeds that at ocean ridges plate tectonics early provided a framework for mineralization on the scale of global plate boundaries and is providing guidance to gradually converge on sites of mineralization through regional scales of plate reorganization with the potential to elucidate the occurrence of individual deposits e g eocene carlin type gold deposits investigation of the spectrum of marine minerals as active analogs of types of ancient mineral deposits is contributing to this convergence consideration of questions posed by brian skinner 1997 of what we do and do not know about ancient hydrothermal mineral deposits demonstrates the ongoing advances in understanding driven by investigation of marine minerals

uranium series isotopic studies of marine phosphorites and associated sediments from the east australian continental margin the uranium series disequilibria of phosphorites sediments and coexisting solitary corals from the outer continental shelf and upper slope off eastern australia have been determined in an attempt to relate the genesis of phosphorites in this area to an absolute time scale the234u 238u 230th 234u and231pa 235u activity ratios in the phosphorites are internally consistent and indicate that the apatite component of the phosphorites has remained a closed system with respect to u th and pa except for very minor losses of234u these losses do not affect the230th 234u derived ages and comprise only 1 2 of the total234u activity significantly less than the losses observed in phosphorite nodules from off peru chile a morphological subdivision of the phosphorites into either non ferruginous or ferruginous is supported by the isotopic data earthy friable non ferruginous phosphatic nodules range in age from 2 5 to 250 kyr holocene ages were obtained from five different locations in water depths ranging from 365 to 450 m in contrast the uranium series isotopes in well indurated ferruginous nodules occurring in the same general area but in shallower 350 m water are in radioactive equilibrium indicating that their ages exceed 800 kyr solitary corals caryophyllia planilamellata dennant 1906 are associated with non ferruginous nodules on the upper slope and commonly contain internal phosphatic molds several corals and their internal molds from one location were dated by uranium series methods the coral ages ranged from 17 to 20 kyr and were typically 10 15 kyr older than their respective phosphatic internal molds these results are consistent with the sedimentological observations and provide independent evidence that geologically meaningful ages can be obtained from marine phosphorites phosphate deposition off eastern australia appears to have been largely continuous throughout the late quaternary rather than being restricted to times of high sea level as reported for phosphorites off peru chile

paleoceanographic model of neogene phosphorite deposition u s atlantic continental margin the neogene stratigraphic section of the southeastern u s continental shelf coastal plain system is characterized by i a series of major regional phosphogenic episodes ii a strong spatial relationship between the structural or topographic framework and phosphate deposition and iii distinct cyclical and regional patterns of deposition of the terrigenous carbonate and phosphate lithofacies the complex depositional patterns are explained by a paleoceanographic model based upon the interaction of glacial eustatic sea level fluctuations associated changes in climate and the dynamics of the gulf stream in response to the bathymetric configurations of the continental margin during the past 20 million years

eocene to pleistocene phosphogenesis off western south africa abstract uranium series dating of phosphorites from the continental margin of south africa shows that phosphogenesis has occurred during at least four periods around 63 83 and 250 800 ka and between 800 ka and the middle eocene petrographic study shows that five distinct apatite microfabrics can be recognised in our samples and confirms that several episodes of phosphatisation have occurred isotopic data for carbon and sulphur show that the phosphogenesis took place in oxic or post oxic sediments and so was probably unrelated to enhanced coastal upwelling the chemical composition of the francolite that formed between 91 and 62 ka differs from that in older samples these differences possibly record variations in the composition of sea water during the late tertiary

amino acid biogeochemistry and dating of offshore peru chile phosphorites abstract amino acid biogeochemical results for a suite of indurated sea floor phosphate nodules from the peru chile margin confirm the youthful nature of these deposits as previously indicated by uranium series disequilibrium dating isoleucine epimerization is significant in the hydrolyzed acid soluble fraction of the nodules with a range in the d alloisoleucine l isoleucine ratio from 0 06 to 0 32 amino acid compositional patterns are uniform for all nodules and are similar to unlithified surface sediments from the region suggesting that the nodules and sediments constitute a single genetic series

the phosphorus cycle phosphogenesis and marine phosphate rich deposits abstract phosphorus in the form of phosphate is an essential nutrient and energy carrier on many different levels of life and a key element in mediating between living and lifeless parts of the biosphere one of the most important aspects of the phosphorus cycle is its vital role in governing productivity thereby interacting with the exogenic part of the carbon cycle which in turn is important in regulating earth s climate phosphorus is a prime element to be traced in earth s history because it allows for the reconstruction of long term feedback mechanisms between climate environment and ecology and of global change as such marine sedimentary phosphate deposits are particularly suited to study aspects of the phosphorus cycle because in the case of ubiquity their origin may result from a general acceleration of the global phosphorus cycle sources of sedimentary phosphate are microbial breakdown of buried organic matter and redox driven phosphate desorption from iron and manganese oxyhydroxides dissolved sea water phosphate represents an additional source which may become important in the formation of phosphatic hardgrounds the main locus of phosphogenesis is near the sediment water interface but phosphogenesis also occurs at greater sediment depths current induced winnowing and transport processes along the sea floor concentrate phosphate precipitates into deposits which exhibit internal stratification patterns typical for the prevailing hydraulic energy regime in a sequence stratigraphic context phosphate deposits preferentially occur along marine or maximum flooding surfaces consequent sedimentary reworking may result in the transfer of phosphates to highstand or lowstand deposits bio chemical weathering on continents represents the most significant source of bioavailable phosphorus this implies that long term changes in marine phosphorus levels and with these changes in marine ecology productivity rates and ratios of exported carbonate carbon and organic carbon are a response to changes in continental weathering rates a compilation of marine sedimentary phosphorus burial rates for the last 160 myr suggests that natural variations have occurred that span one order of magnitude for the late jurassic cretaceous and most of the paleogene the phosphorus cycle appears to have been accelerated in times of climate warming which was most likely due to the spreading of zones of humid climate and more intense continental weathering in the neogene the phosphorus cycle appears to have responded to changes in glacially induced weathering this suggests that uniform interpretations with respect to the emplacement of major phosphorite deposits should be treated with caution integrated analyses of the sedimentary and biogeochemical context of phosphorite occurrences may help to identify paleoenvironmental conditions as well as to improve our understanding of periods of enhanced phosphate accumulation periods which were usually characterized by steep gradients in the development of climate and environment with regard to the complexity of feedback mechanisms between the phosphorus cycle and the biosphere the present day input rates of phosphate into the world s oceans should be of great concern they are more than doubled by anthropogenic means and affect ecological systems on a rapidly increasing scale

biomineralization of iron phosphates in the water column of lake pavin massif central france the availabilities of iron and phosphorus have considerably impacted biological productivity in past and present natural aquatic environments and therefore have been key regulators of climate changes over geological time scales microbial organisms are known to play important roles in reactions that drive fe and p cycling at redox interfaces in earth s surface environments here we study the depth variations of fe and p speciation in lake pavin massif central france a deep bottom depth 92 m and permanently stratified lake with anoxic and ferruginous conditions in the water column below 60 m depth we particularly focus on the potential roles of microbes on fe and p transformations and traces left by these processes in the sedimenting particular matter bulk chemical analyses powder x ray diffraction and x ray absorption spectroscopy xas at the fe k edge were performed to characterize the mineralogy and fe oxidation state of solid particles at different depths in the water column and in sediments deposited at the bottom of the lake fe is mainly hosted by fe iii oxyhydr oxides and phyllosilicates in the shallower oxygenated water column of the lake 25 m the amount of fe in suspended matter increases with depth and an additional amorphous fe ii fe iii phosphate phase is detected close to the chemocline at 56 m depth while vivianite an fe ii phosphate with a formula of fe ii 3 po4 2 8 h2o becomes dominant in the deeper anoxic water 67 m and 86 m depths fe oxyhydr oxides are preserved down to these depths in the water column suggesting that fe reduction has little impact on the particulate fe budget over the monimolimnion these fe oxyhydr oxides undergo reductive dissolution at the surface of the sediments where vivianite is the main fe bearing phase these results are confirmed by imaging at the micrometer and nano scales using scanning electron microscopy sem transmission electron microscopy tem and synchrotron based scanning transmission x ray microscopy stxm as well as high spatial and energy resolution xanes spectra at the fe l2 3 edges and the c k edge moreover polyphosphate accumulating microorganisms were observed by microscopy and chemical imaging at all depths except in the deeper part of the lake 86 m and some fe was associated with these polyphosphate inclusions below 56 m finally the fe phosphates encrust microbial bodies suggesting that microbial activities might be involved in the formation of these phases based on comparisons with laboratory experiments we propose that fe oxidation in contrast to fe reduction may play a role in the precipitation of fe phosphates in the water column of lake pavin polyphosphate accumulating microorganisms could also be involved in fe phosphate formation in the lake for instance by increasing dissolved phosphate concentrations in the monimolimnion

the eddy experiment accurate gnss r ocean altimetry from low altitude aircraft 1 during the eddy experiment two synchronous gps receivers were flown at 1 km altitude to collect l1 signals and their reflections from the sea surface for assessment of altimetric precision and accuracy wind speed u10 was around 10 m s and swh up to 2 m a geophysical parametric waveform model was used for retracking and estimation of the lapse between the direct and reflected signals with a 1 second precision of 3 m the lapse was used to estimate the ssh along the track using a differential model the rms error of the 20 km averaged gnss r absolute altimetric solution with respect to jason 1 ssh and a gps buoy measurement was of 10 cm with a 2 cm mean difference multipath and retracking parameter sensitivity due to the low altitude are suspected to have degraded accuracy this result provides an important milestone on the road to a gnss r mesoscale altimetry space mission

geochemical characteristics of phosphorite and carbonate nodules from the miocene funakawa formation western margin of the yokote basin northeast japan abstract phosphorite nodules were discovered in diatomite and diatomaceous mudstones of the late miocene funakawa formation in dewa height on the western margin of the yokote basin northeast japan they occur as small nodules cemented burrows and small trace fossils in diatom rich sediment that was deposited just above the contact between underlying siliceous shales the underlying shales are essentially devoid of fossils and the overlying bioturbated diatomaceous mudstones are fossil rich the underlying shale is rich in manganese mn calcite nodules and the overlying mudstone is rich in magnesian mg calcite nodules some phosphorite nodules exhibit a zonal structure caused by two phases of mg calcite cementation with or without mn calcite within the pore space of the nodule the phosphorus p content of these nodules exceeded 25 wt in p2o5 the principle phosphate mineral composing the nodules is fluor f carbonate apatite crystals which are a few m in length and cocoon shaped their aggregate includes a small amount of silica aluminum and water si al and h2o respectively the rare earth element ree composition of the phosphorite nodules is characterized by a positive europium eu anomaly and no cerium ce anomaly the biomarker distribution of the phosphorite nodules is characterized by low cpi low carbon number n alkane and high hopenes type hopane and isoprenoid ketone phosphorite nodules originate from the phosphate contained in diatoms the mineralization occurs in the bacterial sulphate reduction zone and bacteria appear to have played an important role in the concentration of p and precipitation of apatite

miocene phosphorites from the murray ridge northwestern arabian sea abstract phosphorites from the murray ridge nw arabian sea comprise nodules bioclasts and bone fragments the nodules are made up of a homogeneous light colored phosphate nucleus consisting of rivulariacean filamentous cyanobacteria and a thin dark grey colored phosphate cortex showing abundant microbial filaments and microborings the bioclasts comprise of 14 14 5 ma old planktonic foraminifers accepted as the time of deposition spherical to ovoid shaped apatite microparticles resembling fossil bacteria are distinct components in the bioclasts bone fragments exhibit apatite fillings the nodules and bone fragments consist entirely of carbonate fluorapatite cfa with low al k and th concentrations suggesting absence of continental detritus shale normalized ree patterns of the samples support a seawater derived composition the highly uniform initial nd values of 4 8 to 5 1 are interpreted as the seawater value at the onset of phosphatization 14 ma ago in contrast 87sr 86sr ratios show a large range of 0 709055 to 0 709124 corresponding to unusually young stratigraphic ages of 1 to 3 ma the data are interpreted as evidence for post depositional sr exchange of the recrystallizing phosphorites with fluids isotopically not much different from modern seawater it is concluded that the phosphorites formed under oxic shallow water conditions where microbial populations assimilated phosphorus primarily from seawater and mediated precipitation of cfa during early diagenesis at the sediment water interface on different substrates

first spaceborne observation of sea surface height using gps reflectometry an analysis of spaceborne global positioning system reflectometry gps r data from the techdemosat 1 tds 1 satellite is carried out to image the ocean sea surface height ssh an ssh estimation algorithm is applied to gps r delay waveforms over two regions in the south atlantic and the north pacific estimates made from tds 1 overpasses during a 6 month period are aggregated to produce ssh maps of the two regions the maps generally agree with the global dtu10 mean sea surface height the gps r instrument is designed to make bistatic measurements of radar cross section for ocean wind observations and its altimetric performance is not optimized the differences observed between measured and dtu10 ssh can be attributed to limitations with the gps r instrument and the lack of precision orbit determination by the tds 1 platform these results represent the first observations of ssh by a spaceborne gps r instrument

nannostructure and genesis of phosphorites from odp leg 112 the peru margin abstract a sem based petrographic study of miocene to quaternary phosphorites recovered during odp leg 112 shows that they contain a variety of apatitic nannostructures in porous types apatite appears as ovoid dumbbell like botryoid micron sized and inframicron apatite particles and flakes these structures are probably due to microbially mediated apatite precipitation in compact varieties diagenesis reduced the porosity obscuring the original apatite microparticles macroscopic aspects of phosphorites colour brightness hardness density are essentially linked to the porosity of apatitic structures but independent of the apatite particles and structures generally they reflect diagenetic stages in evolution the variety and distribution of the apatite particles and structures suggest that phosphorites mainly formed in three different ways phosphatization of 1 fish excrements forming copronodules 2 diatom muds producing nodules and 3 faecal pellets resulting in rounded grains these phosphorite particles formed in low energy conditions many of them were subsequently reworked

significance of secondary porosity in interpreting sandstone composition secondary porosity resulting from dissolution of unstable framework grains such as feldspar and rock fragments including chert is common in sandstones extensive dissolution of framework grains may result in misinterpreting the original composition of a sandstone and hence in misinterpreting its provenance to avoid these problems secondary porosity caused by grain dissolution must be recognized sandstone composition may be properly evaluated by including the dissolved portion of a framework grain as a grain rather than as porosity while point counting this should be useful in interpreting original composition of sandstones and in paleogeographic reconstruction of prospect areas

improved gnss r ocean surface altimetry with cygnss in the seas of indonesia ocean surface altimetry with gnss reflectometry gnss r has the potential to improve the observation and retrieval of mesoscale ocean current flows by increasing the spatial density of ocean surface observations the leading challenges in current gnss r altimetry investigations include precise delay retracking correction of ionospheric effects and spacecraft receiver positioning here we present improved methods to account for these challenges a reflection model based approach is presented for delay retracking that uses simulated delay doppler maps ddms to retrieve the specular delay from measured ddms global ionosphere maps are used to estimate the group delay effect along the direct and reflection paths precise orbit determination techniques are used to improve estimates of the receiving spacecraft position and reduce systematic intersatellite biases we analyze altimetric height retrievals from two cases strongly coherent or diffuse reflections we study the residual systematic error signals with a focus on understanding the errors identified above the strong coherent observations have narrow symmetric delay waveforms and provide higher than average signal to noise ratio the ddms of diffuse observations originate from relatively rough ocean surfaces and have the characteristic horse shoe shape only measurements from the ocean and seas surrounding indonesia are considered as this area provides a significant number of strongly coherent reflections more than 50 000 single point observations and week long averaged results are presented to quantify the noise and systematic characteristics of the retrieved surface heights

global mapping functions for the atmosphere delay at radio wavelengths i have developed expressions for calculating the ratios mapping functions of the line of sight hydrostatic and wet atmospheric path delays to their corresponding zenith delays at radio wavelengths for elevation angles down to 3 the coefficients of the continued fraction representation of the hydrostatic mapping function depend on the latitude and height above sea level of the observing site and on the day of the year the dependence of the wet mapping function is only on the site latitude by comparing with mapping functions calculated from radiosonde profiles for sites at latitudes between 43 s and 75 n the hydrostatic mapping function is seen to be more accurate than and of comparable precision to mapping functions currently in use which are parameterized in terms of local surface meteorology when the new mapping functions are used in the analysis of geodetic very long baseline interferometry vlbi data the estimated lengths of baselines up to 10 400 km long change by less than 5 mm as the minimum elevation of included data is reduced from 12 to 3 the independence of the new mapping functions from surface meteorology while having comparable accuracy and precision to those that require such input makes them particularly valuable for those situations where surface meteorology data are not available

5 cm precision aircraft ocean altimetry using gps reflections 1 we present the first two aircraft global positioning system gps reflection altimetry measurements the most precise gps ocean altimetry measurement and demonstrate the altimetric precision and spatial resolution necessary to map mesoscale eddies our first experiment demonstrated a 14 cm precision single satellite ocean altimetry measurement while our more recent experiment demonstrates 5 cm altimetric precision with 5 km spatial resolution the new results show significant improvement over our previous effort due to improved modeling greater aircraft altitudes and velocities improved receiver positioning and better experimental control plans to further reduce speckle and refine models to obtain 5 cm altimetric accuracy are presented

rare earth elements in hamersley bif minerals abstract minerals from the hamersley banded iron formation western australia were analyzed for y and rare earth elements yrees by laser ablation icp ms to investigate diagenetic pathways from precursor phases to bif minerals one group of apatites carries the seawater ree signature giving evidence that p and rees thoroughly scavenged from the water column by si ferrihydrite particles were released upon microbial fe 3 reductive dissolution of si ferrihydrite in pore water and finally sequestered mainly in authigenic apatite the absence of fractionation between apatite and seawater suggests that ree were first incorporated into an amorphous calcium phosphate as fully hydrated cations i e as outer sphere complexes the iron oxides and carbonates carry only a small fraction of the whole rock ree budget their ree patterns are distinctly enriched in yb and show some m type tetrad effect consistent with experimental k d ree between solid and saline solution with low carbonate ion concentrations it is deduced that hematite formed at an incipient stage of fe 2 catalyzed dissolution of si ferrihydrite via a dissolution reprecipitation pathway the ree pattern of greenalite found as sub micron particles in quartz in a chert siderite sample is consistent with its authigenic origin by precipitation in pore water after dissolution of a small amount of si ferrihydrite magnetite carries very low yrees ppb level has an homogeneous pattern distinctly enriched in the mid rees compared to hematite and includes a late population depleted in light rees ba and as magnetite forming aggregates and massive laminae is tentatively interpreted as reflecting some fluid aided hematite magnetite re equilibration or transformation at low grade metamorphic temperatures

geochemistry of iron rich sediments on the outer continental shelf off northern new south wales abstract iron rich sediments on the outer continental shelf off northern new south wales have formed as a result of authigenesis mainly within skeletal chambers these sediments are significantly enriched in fe and marginally enriched in p as and mn when compared to other shelf sediments from the same region mineralogical data and microprobe analyses of the authigenic phases indicate that berthierine chamosite rather than glauconite was the primary mineral but this has subsequently broken down to poorly crystalline phases that are intermediate between berthierine and goethite during this breakdown the foraminiferal infillings and pellets have become enriched in fe and both p and as have been incorporated by anionic adsorption the geochemical data for the sediments and associated phosphatic nodules suggest that the source of phosphorus for the nodules may be the surrounding iron rich sediments the phosphatic nodules are relatively enriched in fe and as and low in p2o5 compared to modern phosphorites associated with upwelling regions it is postulated that reduction of the iron rich sediments produces significant quantities of inorganic phosphate within the interstitial waters that are ultimately precipitated as carbonate fluorapatite this could explain the formation of modern an ancient phosphorites in east coast situations that are not related to upwelling

pleistocene phosphorites off the west coast of south africa we report here relatively modern phosphogenesis on the continental margin off south africa where palaeontologically old limestone middle eocene middle miocene has been phosphatized in late pleistocene times 62 76 kyr in an area of only moderate and seasonal present day upwelling1 2 previously modern phosphogenesis had been reported as occurring only off namibia3 15 peru chile16 21 and very recently east australia22 23 this report and those describing the late quaternary east australia phosphorite22 23 suggest that contrary to established opinion strongly enhanced upwelling may not be necessary for phosphorite formation and that oceanic phos phogenic models need not be based exclusively on localized oceanographie regimes such as exist off peru and namibia

the application of reflected gps signals to ocean remote sensing abstract the l band broadcast signal from the global positioning system gps reflected off of the sea surface is under study for use as a ocean coastal and wetlands remote sensing tool the reflected signal from a given gps satellite is cross correlated with the pseudorandom noise code uniquely identifying that satellite the shape of this cross correlation ordinarily a very sharp triangle when tracking a direct line of sight signal becomes wider and smoother as the mean square slope of the reflecting surface increases it is proposed that the surface wind speed can be determined by matching the recorded shape of this cross correlation to that predicted by theoretical models as a function of wind speed and direction the significance of these effects increases with altitude of the receiver experimental data have been collected using a specially modified gps receiver on aircraft and on a balloon at altitudes of up to 25 km these data compare favorably with predictions of analytical models and demonstrate the dependence of the waveform shape on surface wind speed and receiver altitude the advantages that this measurement technique has over conventional scatterometers is the small size low cost and simplicity of the receiver hardware no requirement for a transmitter and the ability to simultaneously collect data from usually 10 or more points from a low earth orbiting satellite this number could be larger if the russian global navigation satellite system satellites are also considered as additional sources of radiation furthermore the bistatic scattering geometry is complementary to the backscatter used by conventional scatterometers

microbial controls on phosphate and lanthanide distributions during granite weathering and soil formation abstract both microbial and geochemical factors control the form distribution and abundance of lanthanides during weathering and soil formation in a profile in the bemboka granodiorite from southern new south wales australia during the initial stages of weathering hydrous ce bearing lanthanide and lanthanide aluminum phosphates including rhabdophane and florencite crystallize on etched apatite surfaces throughout the profile however their fate depends greatly on their location within the profile in rocks weathered 5 6 m below the soil zone the lower profile secondary lanthanide phosphates persist long after all apatite has been dissolved however in rocks weathered within 2 m of the soil zone the upper profile secondary phosphates are dissolved and lanthanides other than ce are removed bacteria and fungal hyphae are localized on secondary phosphate surfaces suggesting that rhabdophane and florencite are solubilized in the upper profile due to organic complexation of dissolved lanthanides and or uptake of phosphate by cells in the soils defined by loss of granitic texture secondary phosphates are replaced by ce oxides lanthanides other than ce removed in solution from the upper profile precipitate as ce poor phosphates in the lower profile when the solubility product is exceeded due to high dissolved phosphate concentrations in proximity to apatite thus the upper profile is the source of lanthanides added to the lower profile in both the lower and upper weathered granite the degree to which weight based ce abundances increase with increasing weathering is consistent with ce immobility on the centimeter scale we attribute the very high weight based ce abundances up to 12 concentrations in fresh rock to extensive leaching and compaction during transformation of weathered rock to soil

sedimentology geochemistry and origin of phosphatic chalks the upper cretaceous deposits of nw europe santonian lower campanian and lower maastrichtian phosphatic chalks in northern france southern england and belgium are europe s largest sedimentary phosphatc deposits the stratigraphy sediment ology petrography mineralogy and geochemistry of the lithofacies are reviewed and new data presented depositional and diagenetic models for phosphatic chalk deposits are developed using published experimental work and from observations of modern high and low productivity phosphogenic systems it is concluded that phosphatic chalks were deposited in well oxygenated current swept environments phosphatization required a delicate balance to be maintained between moderate organic carbon and carbonate sedimentation rates reduced bulk sediment accumulation rate and an enhanced rate of bioturbation precipitation of carbonate fluorapatite francolite accompanied the bacterially mediated decomposition of organic matter occurring within centimetres of the sediment seawater interface and taking place preferentially within microbial bodies and coatings in addition to the organically derived component pore water phosphate levels were enhanced by phosphate absorbed on ferric oxyhydroxides which was liberated during iron reduction mineralization was probably a dominantly post oxic process but occurred in a thick sediment mixed layer in which marine organic matter was undergoing intense mixed aerobic and anaerobic microbial degradation phosphogenesis occurred predominantly on the ne margins of the anglo paris basin where shallower sea floors and suitable palaeoceanographic conditions prevailed phosphogenic episodes were limited by sea level fluctuations which controlled the effectiveness of the erosional currents that formed and maintained the phosphatic basins and may have stimulated local productivity

stable isotopic characterisation of francolite formation stable isotopic data are presented for 112 samples of francolite from 18 separate phosphate deposits values of 13c and 34s in most offshore deposits suggest formation within oxic or suboxic environments either by carbonate replacement or direct precipitation of francolite from water of normal marine compositions the exceptions are concretionary francolite from namibia which has an isotopic composition in keeping with its formation within organic rich sediments and that from offshore morocco which has an isotopic signature of the anoxic suboxic interface onshore deposits from jordan mexico south africa and possibly the permian phosphoria formation in the western u s a are substantially depleted in18o they appear to be too altered for deductions to be made about their environments of formation in other onshore deposits which are unaltered or minimally altered the isotopic composition suggests that some formed within sulphate reducing sediments sedhura morocco whilst francolite from the georgina basin of australia formed at the oxic anoxic boundary where oxidation of biogenic h2s decreases the 34s of pore water in general pelletal samples show non oxic isotopic signatures whilst non pelletal samples show oxic isotopic signatures but samples from namibia peru ica plateau and the californian and moroccan margins are exceptions to this rule morphology may therefore be a misleading indicator of francolite genesis as no definitive relation exists between phosphorite type and isotopic signature

global ocean altimetry with gnss reflections from techdemosat 1 techdemosat 1 tds 1 is an experimental global navigation satellite system reflections gnss r satellite launched in 2014 the gnss r receiver onboard performs real time navigation and generates delay doppler correlation maps for earth reflected global positioning system gps l1 c a ranging signals this paper investigates the performance of the tds 1 data for ocean surface altimetry retrievals the analysis includes consideration of the transmitter and receiver orbits time tag corrections models for ionospheric and tropospheric delays zenith to nadir antenna baseline offsets ocean and solid earth tides and a comparison with mean sea surface topography an error budget is compiled to account for each error source and compared with the experimentally derived surface height retrievals by analyzing data sets covering global ocean surfaces over 60 latitude the current performance of spaceborne gnss r altimetry with the tds 1 data set is experimentally established in comparison with the mean sea surface topography the surface height residuals are found to be 6 4 m 1 sigma with a 1 s integration time a discussion of the factors limiting this performance is presented with implications for future gnss r altimetry missions designed for the observation of mesoscale ocean circulation

trace and rare earth element geochemistry of phosphate nodules from the lower cambrian black shale sequence in the mufu mountain of nanjing jiangsu province china abstract phosphate nodules are abundant in the lowermost section of the lower cambrian black shale sequence along a ne trend belt in the yangtze platform south china in this study we examined the neoproterozoic cambrian mufu mountain section near nanjing of jiangsu province and conducted a detailed trace and rare earth element ree study on the phosphate nodules we employed a step leaching acid dissolution protocol of 1 m hac and 1 m hcl respectively to separate carbonate from phosphate mineral contributions in the nodules both the hac leached and hcl leached fractions of the phosphate nodules show similar symmetrical variations in trace and ree concentrations and ratios the total rees and a number of redox sensitive trace metals such as v cr mo ni abundances show a systematic increase from the core to rim whereas the u and mn abundances decrease from the core to rim in most of the nodules similar trends are also observed for the rb sr u th co ni and v ni ratios but these trends in the hac leached fractions are less pronounced than the hcl leached fractions all of the hcl leached fractions for the nodule cores show seawater like shale normalized ree patterns but the rims of the nodules display slightly mree enriched and hree depleted patterns we suggest that the phosphate nodules may have formed in a basinal setting beneath a stratified water column during early cambrian and the compositional variations of rees and redox sensitive trace elements from the core to rim may record a changing redox condition and fluid mixing during different stages of nodule growth the cores of the nodules preserve more pronounced negative ce anomalies and progressively hree enriched patterns which may retain primary early cambrian seawater chemistry whereas the nodule rims record chemistry consistent with changed redox conditions and or influences from pore fluids such as generated from degradation of organic matter

the paris ocean altimeter in orbit demonstrator mesoscale ocean altimetry remains a challenge in satellite remote sensing conventional nadir looking radar altimeters can make observations only along the satellite ground track and many of them are needed to sample the sea surface at the required spatial and temporal resolutions the passive reflectometry and interferometry system paris using global navigation satellite systems gnss reflected signals was proposed as a means to perform ocean altimetry along several tracks simultaneously spread over a wide swath the bandwidth limitation of the gnss signals and the large ionospheric delay at l band are however issues which deserve careful attention in the design and performance of a paris ocean altimeter this paper describes such an instrument specially conceived to fully exploit the gnss signals for best altimetric performance and to provide multifrequency observations to correct for the ionospheric delay furthermore an in orbit demonstration mission that would prove the expected altimetric accuracy suited for mesoscale ocean science is proposed

phosphate stromatolites from condensed cephalopod limestones upper jurassic southern spain upper jurassic phosphate stromatolites of the almola sierra southern spain encrust macrofossils and hardgrounds and form oncoids included within pelagic condensed fossiliferous limestones their accretion was determined by bacterially mediated precipitation of phosphate by the trapping and binding of fine siliciclastics and pelagic biomicrite and by the encrustation of benthonic foraminifera phosphorous trace elements and rare earth elements were concentrated from degraded organic matter and seawater by stromatolite building communities which mediated the formation of phosphate rich and fe al si rich organic gels under oxic conditions favouring the precipitation of amorphous mineral precursors acp and fe al si oxyhydroxides the observed ce enrichment for some stromatolites is explained by oxidative scavenging of ce4 from seawater by fe mn oxyhydroxides the bacterially mediated gels were able to migrate and fill the voids of the stromatolite structure and later changed to carbonate fluorapatite haematite and poorly crystalline fe rich clays under postoxic conditions phosphatization of trapped carbonate particles also occurred the phosphate stromatolites formed on a sediment starved pelagic swell during periods of no carbonate sedimentation and hardground development stromatolite lamination provides evidence for rhythmic alternation between bacterially mediated phosphogenesis sedimentation and erosion suggesting episodic changes in the sedimentary environment although some of the parameters that controlled phosphate precipitation associated with the stromatolites local high organic productivity sediment starvation moderate depth of deposition and physicochemical conditions were similar to those found in modern and ancient phosphogenic settings the palaeogeographical framework and the intensity of sedimentary processes were different to those of the world s major phosphorite deposits