relationship between organic matter and mercury in recent lake sediment the physical geochemical aspects abstract this study addresses the physical geochemical aspects of the relationship between hg and organic matter in recent sediment from eutrophic lakes in central alberta canada the types of organic matter in the sediment are classified based on their degree of thermal degradation and their petrographical characteristics this study uniquely applies the methods conventionally used in petroleum geosciences rock eval analyses and organic petrology to investigate the relationship between various types of organic matter and the concentration of hg in sediment the results show that the total organic carbon toc in sediment represents the sum of various organic compounds which may play a completely different role in the distribution and accumulation of hg strong correlations between toc and the concentration of hg in the studied sediment arise mainly from the thermally labile portion of organic matter released during pyrolysis under 300 c these compounds primarily consist of easily degradable algal derived lipids and various pigments which are petrographically described as soluble organic matter som the preserved som in sediment is commonly entrapped within the cell walls of phytoplankton and also appear as surface coating on sediment particles the strong affinity between hg and som is due not only to its chemical reactivity but also to the physical characteristic of these labile compounds the som may provide a substrate with enormous surface area by concentrating on the finer sediment size fractions and potentially acting as a concentrator for hg and other organic associated elements lastly the quantity of the som has been calculated as an elemental concentrator portion of the toc which plays the most important role in the distribution of hg in sediment

geochemistry and mineralogical residences of trace elements in oil shales from julia creek queensland australia abstract abundances and mineralogical residences have been determined for a comprehensive range of trace elements in julia creek oil shale many trace elements are well above normal abundances in shales of these elements v and mo are potentially useful by products whereas as se mo cd tl and u are of possible environmental or occupational health concern samples from a stratigraphic reference bore core through the toolebuc formation near julia creek in queensland were chemically analysed using the multi element techniques of neutron activation analysis and spark source mass spectrometry inter element correlation techniques selective leaching procedures and electron microprobe analyses were used to establish geochemical associations and specific mineralogical residences for a full range of elements the results provide a definitive chemical and mineralogical characterization of the oil shale and identify the major mineralogical residences of the important trace elements v occurs mainly in a mixed layer mica montmorillonite clay mineral and to a lesser extent in kerogen whereas most trace elements of environmental concern are resident in the sulphide minerals pyrite and sphalerite u is concentrated in the fluorapatite of fish debris a sound basis is established for understanding the inorganic chemistry involved in oil shale processing and waste disposal

upb la mc icp ms dating of rutile new reference materials and applications to sedimentary provenance in response to the general lack of sufficiently abundant and high quality rutile usingle bondpb reference materials for in situ geochronology we have characterised two new potential rutile 1 8 ga reference materials sugluk 4 and pca s207 from granulite facies belts of the canadian shield namely the northern cape smith belt of quebec and the snowbird tectonic zone sasatchewan characterisation includes id tims and la icp ms usingle bondpb dating imaging and trace element analysis we compare these materials with existing rutiles used already r19 and r10 luvizotto et al 2009 and zack et al 2011 and show that the measured usingle bondpb compositions i e including any common pb of our rutiles are considerably more homogeneous this makes possible a usingle bondpb normalisation procedure not reliant upon a common pb correction that results in a significant decrease in the uncertainty contribution from the common pb correction and better reproducibility of reference materials and unknowns for provenance analysis and other applications the reproducibility is 2 4 2rsd for 206pb 238u and 207pb 206pb only slightly greater than long term data for zircon reference materials we show in a rutile provenance study from young orogens bhutan himalaya and canadian cordillera that the sensitivity of our analytical set up allows dating of 90 of rutiles in a sediment using a 50 m laser ablation spotsize within samples containing rutile as young as 10 20 ma and obviates the requirement for u concentration pre screening thus reducing or eliminating rutile selection bias unsuccessful analyses are due to poor quality rutiles with predominant common pb 207pb signal below detection or u content below 1 2 ppm we have used the 207pb method using the tera wasserburg diagram to correct for substantial common pb in very young and or very low u rutiles rather than developing an on line correction since rutile ages reflect mainly the time of cooling rutile is a sensitive recorder of metamorphic thermochronological information and therefore is an excellent complement to detrital zircon u207pb data the contrast between zircon and rutile signatures in himalayan samples with rutile as young as 10 ma is shown to be very dramatic most zircons from the same sample are 480 ma with only a few grains or metamorphic rims reflecting miocene metamorphism as such rutile provides complementary information about the thermal events within the source regions of the grains rutile usingle bondpb dating is an underexploited provenance method with wide applicability to sedimentary provenance studies

reply to comment by wang et al on paleoproterozoic arc continent collision in the north china craton evidence from the zanhuang complex by li et al 2016 precambrian research 286 281 305

paleoproterozoic arc continent collision in the north china craton evidence from the zanhuang complex abstract the trans north china orogen tnco marks the major ca 300 km wide paleoproterozoic collisional suture between the eastern and western blocks of the north china craton ncc which also incorporates several microblocks or complexes here we investigate the zanhuang complex along the eastern margin of tnco we present petrological geochemical zircon u pb and lu hf data on a suite of quartz mica schist metavolcanics and diorite from the central zanhuang domain czd as well as granitoids and amphibolite that constitute the basement rocks of the western zanhuang domian wzd and eastern zanhuang domain ezd our study represents a cross section across two continental margins and covers the paleo ocean tract in between the metavolcanics show calc alkaline to tholeiitic affinity and negative correlations of la sm n vs p nd ti ti ce ce and positive with nb nb the granitoids fall within the vag field the iab and morb features of the volcanic suite are consistent with magma derivation in arc to back arc environment from an enrichment source the magmatic suite also displays lree enrichment positive rb k la pb nd anomalies and negative ta nb ce ti anomalies la cipms u pb geochronology of detrital zircon grains shows two age populations in the quartz mica schist with 207pb 206pb mean ages of 2499 14 ma and 2252 22 2216 39 ma and the timing of deposition is estimated as ca 2 3 2 2 ga zircons from the granodioritic gneiss yield 207pb 206pb mean age of 2508 14 ma representing neoarchean continental basement the metavolcanics and two diorite samples yield ages of 2302 30 ma 2089 63 ma marking the timing of an active arc the metamorphic zircons from these rocks show an age of 1882 15 ma the zircon lu hf data yield both positive and negative ehf t values suggesting depleted mantle source mixed with crustal components their crustal residence ages t dm c range from 3875 to 2224 ma and depleted model ages t dm range from 3415 to 2092 ma suggesting mixed juvenile and reworked crustal components and possible vestiges of mesoarchean basement we propose that the zanhuang complex is one of the paleoproterozoic arcs within the tnco which was accreted to the neoarchean continent along the eastern block of the ncc during the suturing along the tnco the tectonics associated with crustal growth and recycling in the tnco and the arc continent collision broadly coincided with the building of the columbia supercontinent

metal organic associations in sediments i comparison of unpolluted recent and ancient sediments and sediments affected by anthropogenic pollution abstract the concentrations of 19 trace elements were determined by plasma emission spectrometry in organic fractions organic solvent extractables soluble humics protokerogen and kerogen concentrates separated from various recent and ancient sediments mangrove sediments algal mats oil shales phosphorites as well as sediments polluted by industrial metal emissions rhine river port pirie smelter effluent often the organic constituents were found to be enriched in trace elements especially b v mn co ni cu zn as mo ag cd sb hg and pb up to more than three orders of magnitude compared to the bulk sediments indicating the importancesof organic substances with respect to transport and fixation of trace elements within sediments the formation of metal organic associations was found to reflect the environment of deposition marine to terrestrial as well as diagenetic transformations recent to ancient against an unpolluted natural background increasing metal pollution led to increasing metal potake by organic substances especially for b cr fe co cu zn as cd and pb

the building of an archean microcontinent evidence from the north china craton abstract continents on the early earth are considered to have been built through the accretion of microterranes oceanic arcs and plateaus the north china craton ncc envisaged in recent models as a collage of several microblocks which were amalgamated along multiple zones of ocean closure during the late neoarchean provide a typical case to investigate the origin and amalgamation of microcontinents through convergent margin processes here we report a suite of magmatic rocks developed at the periphery of one of these microblocks the jiaoliao block that forms part of the composite eastern block of the ncc we integrate our new data with those from various parts of this microblock to elucidate the mechanism of continent building in the archean we present petrological geochemical and zircon u pb geochronological and lu hf isotopic data from the magmatic suite that belongs to the yishui complex geochemically the felsic units of the suite straddle from monzonite through granodiorite to granite with dominantly metaluminous affinity magnesian composition and arc related features the metagranites ttg gneisses and charnockites are characterized by negative nb ta anomalies and positive k and pb anomalies the diorites and gabbros display negative anomalies of th u nb ta and zr hf and positive anomalies at ba pb and sm with negative eu anomalies and minor positive ce anomalies attesting to arc related features in the tectonic discrimination diagrams the rocks plot in the volcanic arc field indicating arc related origin in subduction setting zircon grains from all the rocks display core rim texture with the cores showing magmatic crystallization and the narrow structureless rims corresponding to metamorphic overgrowth the magmatic zircons from the metagranites show upper intercept ages or 207 pb 206 pb weighted mean ages of 2505 29 ma and 2569 20 ma to 2513 27 ma those from the ttg gneisses show 2535 17 ma to 2546 39 ma from charnockites display 2543 20 ma 2555 15 ma and diorite and gabbro show 2587 15 ma and 2516 13 ma respectively the zircon rim ages of 2472 23 ma 2457 35 ma 2545 30 ma and 2511 35 ma suggest the timing of metamorphism ca 2 55 2 45 ga magmatic zircons with slightly older ages of ca 2 73 ga 2 64 ga also occur suggesting multiple magmatic pulses the lu hf isotopic data show positive ehf t values ranging from 0 2 to 5 7 for metagranites with hf model ages of 2602 2815 ma t dm and 2658 3002 ma t dm c whereas for ttg gneisses the positive ehf t values are up to 6 5 and display dominant mesoarchean hf model ages with limited early neoarchean hf model ages charnockite samples show positive ehf t values 2 3 5 7 and display the hf model ages ranging from 2601 ma to 2772 ma t dm and 2658 ma to 2904 ma t dm c diorite and gabbro also show positive ehf t 2 3 6 9 and yield hf model ages of 2625 2788 ma t dm and 2647 ma to 2903 ma t dm c the hf isotopic data indicate that the magmas were derived from neoarchean mesoarchean juvenile sources integrating our data with those from the entire jiaoliao microblock reveals vestiges of hadean crust involved in building the eoarchean nucleus of this microblock vigorous convergent margin processes ranging from mesoarchean to late neoarchean with multiple pules of arc magmatism associated with subduction tectonics led to further growth of continental crust culminating in paired high temperature and high pressure metamorphism during late neoarchean early paleoproterozoic transition

lithification of peritidal carbonates by continental brines at fisherman bay south australia to form a megapolygon spelean limestone association abstract groundwater springs in the supratidal zone at fisherman bay south australia are the sites of aragonite precipitation and cementation of holocene marine carbonates lithification which commenced less than 3000 years bp and is still active has formed a cavernous limestone containing megapolygons tepees and speleothems including pisoliths floe aragonite and aragonitic pool deposits the emerging waters are from a continental source and have evolved from low alkalinity waters of pleistocene sand and clay coastal plain aquifers which have passed through an underlying tertiary marine carbonate aquifer the resulting waters have high pco2 total carbonate ca and sulphate concentrations they are close to saturation with respect to aragonite and their mmg2 mca2 ratios approach or exceed the critical aragonite precipitation value aragonite is precipitated from these waters when they approach the surface and evolve co2 features which taken together may diagnose ancient examples of this process include 1 primary aragonitic cements with high msr2 mca2 values 2 nonmarine 34s values in associated gypsum 3 two superimposed networks of surface polygons one delineated by extensional boundaries the other by tepees 4 high water vadose zone isopachous grain cements 5 interconnected speleothem lined cavities and 6 the presence of evaporites only in surface sediments possible ancient examples of peritidal carbonate lithification by saline spring waters rising from confined aquifers are recognized in descriptions of carbonates from west texas lombardy and the atlas mountains the areal extent of each of these deposits suggests that the process may be a geologically important feature and its products may be diagnostic of semi arid or arid zone paralic sedimentation

compositional similarities of non solvent extractable fatty acids from recent marine sediments deposited in differing environments abstract five recent sediment samples from a variety of north american continental shelves were analyzed for fatty acids fas in the solvent extractable solex lipids as well as four types of non solvent extractable nonex lipids the nonex lipids were operationally defined by the succession of extraction procedure required to recover them the complete procedure included i very mild acid treatment ii hf digestion and iii saponification of the sediment residue following exhaustive solvent extraction the distribution pattern and various compositional parameters of solex fas in the five sediments were divided into three different groups indicating the difference of biological sources and also diagenetic factors and processes among the three groups of samples nevertheless the compositions of the corresponding nonex fas after acid treatment were surprisingly very similar this was also true for the remaining nonex fa groups in the five sediment samples the findings implied that most of the nonex fas reported here are derived directly from living organisms it is also concluded that a large part of nonex fas are much more resistant to biodegradation than we have thought so that they can form the large percentage of total lipids with increasing depth of water and sediments

estimating the fluvial sediment input to the coastal sediment budget a case study of ghana knowledge of fluvial sediment supply to the coastal sediment budget is important for the assessment of the impacts on coastal stability such knowledge is valuable for designing coastal engineering schemes and the development of shoreline management planning policies it also facilitates understanding of the connection between rivers in the hinterland and adjoining coastal systems ghana s coast has many fluvial sediment sources and this paper provides the first quantitative assessments of their contributions to the coastal sediment budget the methods use largely existing data and attempt to cover all of ghana s significant coastal rivers initially work was hindered by insufficient direct measured data however the problem was overcome by the application of a regression approach which provides an estimated sediment yield for non gauged rivers based on data from gauged rivers with similar characteristics the regression approach was effective because a regional coherence in behaviour was determined between those rivers where direct measured data were available the results of the assessment revealed that ghana s coast is dissected by many south draining rivers stream and lagoons these rivers streams and lagoons supply significant amounts of sediment to coastal lowlands and therefore contribute importantly to beaches anthropogenic impoundment of fluvial sediment especially the akosombo dam on the volta river has reduced the total fluvial sediment input to the coast from about 71 106 m3 a before 1964 pre akosombo dam to about 7 106 m3 a at present post akosombo dam this sharp reduction threatened the stability of the east coast and prompted an expensive 83 million defence scheme to be implemented to protect 8 4 km long coastline at keta sections of ghana s coast are closely connected to the hinterland through the fluvial sediment input from local rivers therefore development in the hinterland that alters the fluvial sediment input from those local rivers could have significant effects on the coast there is the need therefore to ensure that catchment management plans and coastal management plans are integrated or interconnected

spatial distribution of 1950 1800 ma metamorphic events in the north china craton implications for tectonic subdivision of the craton abstract great progress has been made in the last twenty years in understanding the unification of the north china craton according to a prevailing model it developed by amalgamation of four sub blocks by three spatially and temporally separate orogenic belts the first at 1950 ma formed the western block the second at 1900 ma created the eastern block and the third at 1850 ma unified the eastern and western blocks however new data show that the 1950 ma orogen was affected by granulite facies reequilibration at 1800 ma and parts of the 1850 ma orogen have evidence of metamorphism at 1950 1900 ma new zircon u pb ages enable the paleoproterozoic metamorphic events to be statistically sub divided into four at 1955 ma m 1 1920 ma m 2 1885 ma m 3 and 1850 ma m 4 the m 1 2 events always appear together mainly in two belt areas including the helanshan qianlishan northern ordos yinshan liangcheng huai an lushan jiaobei and liaodong regions whereas the m 3 4 events are distributed over larger areas and were superimposed on the m 1 2 activities this age distribution is inconsistent with previous models of three separate orogens it should also be noted that the igneous rocks contemporary with the regional ultra high temperature high pressure granulite facies metamorphisms m 1 2 were previously described as arc related series i e the gabbro norites i s type granites and trimodal volcanics based on the spatial distribution of the paleoproterozoic metamorphic events m 1 4 and of the coeval igneous rocks we speculate that the assembly of the ncc was created by one orogen which formed between the eastern and western cratons in two tectonic stages two marginal arcs the korean and xuwujia developed against both eastern sides of the two sub cratons and were both accreted and deformed at 1965 1900 ma m 1 2 subsequently the amalgamation of the two sub cratons resulted in metamorphism on the western side of the eastern craton and in metamorphism that was superimposed on both accreted arcs at 1900 1790 ma m 3 4

iron mineralization of peritidal carbonate sediments by continental groundwaters fisherman bay south australia abstract high concentrations of goethite limonite and iron sulphides and lesser concentrations of hematite and ferromanganese oxides are forming in holocene carbonate sediments in the peritidal zone of fisherman bay a hypersaline marine embayment on the semi arid northeast shore of spencer gulf south australia the iron and manganese are precipitating from seawards flowing saline groundwaters as they emerge from red bed aquifer systems of the coastal plain iron concentrations in these groundwaters are as high as 67 ppm and they produce fe2o3 concentrations of 30 to 70 w w in a lens shaped deposit of ferric oxyhydroxides located near the interface of the marine carbonates and underlying red bed sediments the fe in the lens occurs as a limonite and goethite cement binding detrital quartz grains together with a minor proportion of haematitic concretions the mineralogy and textures of the fisherman bay iron lens are similar in some respects to those of the oxide facies of some minette ironstones sandy clayey oolitic shallow inland sea iron formations and it is forming at a rate comparable to those of the more rapidly formed deposits however the iron enriched sediments are of limited extent geochemically they are more akin to the volcanically associated lahn dill ironstones and in general marine hosted ironstones lack red bed associations

use of composite fingerprints to determine the provenance of the contemporary suspended sediment load transported by rivers sediment fingerprinting appears to offer a valuable alternative to direct monitoring for elucidating the provenance of suspended sediment and the relative importance of spatial zones or subcatchments comprising larger 500 km 2 drainage basins against this background a quantitative composite fingerprinting technique incorporating both statistically verified multicomponent signatures and a multivariate sediment mixing model has been employed to determine the spatial origin of contemporary suspended sediment transported from the upper and middle reaches of the river exe 601km 2 and river severn 4325 km 2 basins uk spatial origin is addressed in terms of the relative contribution from three distinct geological subareas constituting each study basin the consistency of the composite fingerprinting approach is examined using the estimates for mean and seasonal variations in source area contributions and also a comparison between the results obtained for individual flood events and alternative lines of evidence provided by flood travel times and the spatial distribution of precipitation it is argued that fingerprinting estimates for sediment provenance are consistent with existing information on suspended sediment yields from different subcatchments within the study basins although in the severn the role of storage and remobilization in producing signature averaging may complicate comparison of the fingerprinting data with typical floodwater routing times validation represents the greatest problem for the cost benefit of fingerprinting and scope still exists for further refinement of the procedures involved 1998 john wiley sons ltd

heavy metal enrichments bacterial sulphate reduction and iron sulphide formation in shallow water carbonate sediments offshore from a smelting complex at port pirie south australia abstract the interactions of fe and above normal concentrations of pb zn and cd with the products of bacterial sulphate reduction have been investigated using vibrocores from shallow subtidal seagrass colonized carbonate environments near to and remote from a pb zn smelting complex on the shore of spencer gulf south australia sediments remote from the smelter are coarse grained rich in seagrass low in pb zn and cd and contain only traces of sulphide near the smelter an additional 10 15 cm thick layer of relatively fine grained pb zn and cd rich carbonate is present at the surface and inhibits exchange of the sediment pore waters with the overlying oxic seawater as a result bacterial sulphate reduction has become strongly established and concomitant diagenetic reactions have produced dissolved sulphide iron monosulphides and trace quantities of pyrite sulphur isotope data indicate that the present stage of sulphate reduction in which the amount of sulphide in the deeper coarse grained sediments is equivalent to the amount of sulphate removed from the pore waters may have been preceded by a period in which the first formed sulphide was reoxidized within the sediments the high ratio of iron monosulphides to pyrite results from a rapid rate of deposition of the surface layer and in the deeper sediments limitations on the oxygen supply pore waters associated with the metal rich surface layer contain high concentrations of zn 392 g 1 1 and low concentrations of pb and cd but this has not resulted in significant spatial separation of these metals in the sediment column in the surface sediments pb and zn are probably not present as sulphides although in the deeper sediments zn concentrations are at a minimum in a zone of high dissolved sulphide concentration

recent salt marsh development and natural regeneration of reclaimed areas in the plentzia estuary n spain the distribution of benthic foraminifera a range of elements and 137cs and 210pb were studied in surface sediments and 0 5 m cores from the plentzia estuarine marshes northern spain to determine the recent development of these previously reclaimed coastal areas these marshes receive abundant calcium carbonate from regional rocks and this allows calcareous foraminifera to colonize all marsh subenvironments good preservation of the original foraminiferal assemblages in the buried sediments is also favoured by high regional background carbonate benthic foraminifera are shown to be sensitive to both elevation above mean sea level exposure and salinity results from the chemical analyses indicate moderate anthropogenic pollution in the estuary and maximum input seems to have occurred in the 1960s recent marsh foraminiferal assemblages are good analogues for the palaeoenvironmental interpretation of historical and holocene cores and the combined micropalaeontological geochemical approach is demonstrated to be successful for the identification of short term anthropogenic impacts on this coastal region

tracer properties of eroded sediment and source material this paper examines the conservativeness of tracers through the sediment generation process this is done by comparing a selection of tracer properties of sediment eroded from large plots by simulated rainfall with the corresponding properties of the source materials within the plots sediment was generated using three simulated rainfall events for each of five selected erosion source types in the tarago catchment victoria australia as there were particle size and organic content differences between the source material and the generated sediment the measured tracer properties of the source material were corrected for these differences the possible role of analytical errors in this investigation was also addressed the geochemical property concentration of fe2o3 was not conservative for any of the process sources investigated concentration of al2o3 was not conservative for three of the four process sources investigated and the sum of molecular proportions of cao na2o k2o and al2o3 was not conservative for two of the four process sources investigated mineral magnetic properties irm850 and were also found to be not conservative although this may be the result of the complex relationship between particle size and mineral magnetic properties not being adequately accommodated in this analysis the radionuclide tracers 137cs and 210pbex were found to be conservative through the sediment generation process copyright 2002 john wiley sons ltd

determining the sources of suspended sediment in a forested catchment in southeastern australia 1 knowledge is scarce regarding the relative contributions from harvested areas and unsealed roads to sediments in forested catchments we investigate the source composition of suspended sediment using sediment tracers and an improved multivariate mixing model sediment samples were collected during six rainfall events geochemical and radiometric tracer properties were corrected for particle size and organic content as well as conservativeness during erosion and sediment delivery the mixing model incorporates variability of the tracer properties using a monte carlo simulation technique mean sediment contribution from the undisturbed forest was 50 70 harvested areas gravel surfaced roads and ungravelled roads contributed 5 15 6 14 and 12 25 respectively the unsealed roads contribute 20 to 60 times more sediment than the undisturbed forest and about 10 times more sediment than the harvested areas on a per unit area basis harvested areas contribute 1 to 5 times greater sediment than the undisturbed forest these results support other studies that identify unsealed roads as important sediment sources in forested catchments

geochemistry and mineralogical residences of trace elements in oil shales from the condor deposit queensland australia abstract stratigraphically selected samples from several bore cores were chemically analysed for trace elements using neutron activation analysis and x ray fluorescence spectrometry inter element correlation techniques selective leaching procedures x ray diffraction and electron microprobe analyses were used to establish geochemical associations and specific mineralogical residences for a comprehensive range of elements abundances and mineralogical residences have been determined for a comprehensive range of trace elements in condor oil shale trace element abundances are generally similar to or less than those reported for an average shale the exceptions are pyritic s inorganic n and mn which are often above normal abundances and together with as are of possible environmental concern during processing the results provide a definitive chemical and mineralogical characterization of the oil shale and identify the major mineralogical residences of the important trace elements s as ni and co occur mainly in the mineral pyrite while mn is resident in siderite and magnesian siderite s ni and co also occur to a lesser extent in the kerogen inorganic n occurs in the ammonium feldspar buddingtonite which formed by diagenetic replacement of k feldspar a sound basis is established for studies of mineral reactions during retorting spent shale combustion and waste disposal

sources and preservation of organic matter in the cretaceous toolebuc formation eastern australia abstract the organic matter rich toolebuc formation of eastern australia was deposited in a lower cretaceous epicontinental sea parameters from biological marker studies indicate that the organic matter is immature to marginally mature for hydrocarbon generation the occurrence of abundant coccoliths and the distribution of alkane biomarkers suggest that the organic matter type ii is largely of planktonic origin and only in the southeastern part of the depositional area can a terrestrial influence be discerned variations in kerogen composition can be attributed to the extent of the oxidation of the source materials and the degree of incorporation of sulphur the atomic h c ratios c 1 1 are remarkably constant for most of the toolebuc formation atomic o c ratios vary from 0 1 and 0 4 and can be related both to depth and paleogeographic position kerogen sulphur contents range up to 7 and the highest values occur in the most carbonate rich sediments total sulphur inorganic organic to carbon ratios in the sediments vary from 1 to

assembling north china craton within the columbia supercontinent the role of double sided subduction abstract an evaluation of recent s wave receiver functions s wave velocities and two versions of p wave tomographic images along various transects in the north china craton provides some clues on the subduction collision history of the different crustal blocks and their final amalgamation within the paleoproterozoic columbia supercontinent interpretation of a n s seismic section of the craton suggests thick slab debris sinking to various depths in the mantle the w e seismic corridors show the preservation of a thick 200 km lithospheric root tectosphere beneath the ordos block and its variable and extensive erosion towards the yanliao block eastern block this zone is characterized by layers with marked velocity contrast and suggests repeated stacking of the remnants of underplated and accreted paleoproterozoic oceanic lithosphere the present day lithosphere asthenosphere boundary beneath this region probably marks the erosional plane along which decratonization occurred through subduction erosion from the east and thermal and material erosion by upwelling asthenosphere from below resulting in the partial destruction of the tectosphere and its thinning towards the east within the asthenosphere below the yanliao block younger and thinner slabs predominate in the absence of any prominent thick high velocity layers these younger slabs define a westward polarity and constitute a mega scale duplex formed by underplating through phanerozoic subduction process particularly the pacific plate subduction from the east the lithologic associations within the inner mongolia suture zone dividing the yinshan block to the north and ordos block to the south correspond to an accreted ocean plate stratigraphic sequence with the tonalite trondhjemite granodiorite ttg gneisses charnockites and calc alkaline granites representing a continental arc built up through subduction from the north the seismic transects bring out a contrasting polarity in the subduction regime with an oblique east to southward subduction of the yinshan block and a westward subduction of the yanliao block here i propose a double sided subduction history for the ncc similar to the ongoing subduction process in the western pacific such double sided subduction is considered to promote rapid amalgamation of continental fragments within supercontinents and the subduction polarities and mantle dynamics of ncc are therefore considered to be critical in evaluating the final assembly of the paleoproterozoic supercontinent columbia

comments on paleoproterozoic arc continent collision in the north china craton evidence from the zanhuang complex by li et al 2016 precambrian research 286 281 305

shrimp u pb zircon geochronology of palaeoproterozoic metasedimentary rocks in the north china craton evidence for a major late palaeoproterozoic tectonothermal event abstract although metasedimentary successions are widely distributed across the north china craton those of palaeoproterozoic age are restricted to three orogenic belts namely the trans north china orogen the khondalite belt and the jiao liao ji belt prior to this work some of those successions were considered to be archaean in age the palaeoproterozoic metasedimentary rocks contain detrital igneous zircon grains with ages ranging from 3 0 to 2 1 ga with the majority recording an age between 2 3 and 2 0 ga this latter group define a series of magmatic events that occurred between formation of the archaean basement and deposition of the metasedimentary rock protoliths the metasedimentary rocks occur as two associations older volcano sedimentary units that formed between 2 37 and 2 0 ma and younger sedimentary units that formed mainly between 2 0 and 1 88 ga all these rock associations were then subjected to metamorphism during the late palaeoproterozoic 1 88 and 1 85 ga tectonothermal event named the luliang movement in early chinese literature which was a continent continent collision that led to the amalgamation of the north china craton

2090 2070 ma a type granitoids in zanhuang complex further evidence on a paleoproterozoic rift related tectonic regime in the trans north china orogen abstract the xuting pluton located at the north section of the zanhuang complex contains potassic and sodic granite in both of which shallow level emplacement is shown by graphic texture feldspar and quartz intergrowth two potassic granite and one sodic granite samples yielded zircon 207 pb 206 pb ages of 2066 17 ma 2092 14 ma and 2071 14 ma respectively suggesting that the xuting pluton emplaced between 2070 ma and 2090 ma which is coeval with the paleoproterozoic gantaohe group dominated by mafic volcanic and sedimentary rocks the potassic granite is enriched in sio 2 total feo rees except eu zr nb ga and y and depleted in mgo cao al 2 o 3 sr v cr and ni with high tfeo mgo ratios consistent with the features of a type granite except for the high mgo and low k 2 o contents the sodic granite also presents most of the features of a type granites the zircon saturation temperatures from the potassic and sodic granites range from 855 to 998 c and 853 to 933 c respectively indicating that they are from the high temperature magma the potassic granites have the e hf t ranging from 5 9 to 1 33 and hf model ages of 2 5 2 8 ga which are identical with the ages of neoarchean ttg gneisses in the zanhuang complex we propose that the potassic granite in the xuting pluton derived from the partial melting of neoarchean ttg gneisses the sodic granites also present negative e hf t values from 4 81 to 0 76 and hf model ages of 2 5 2 8 ga suggesting that they come from the partial melting of the neoarchean crust however with relative enrichment in mgo and total feo and lower k 2 o and rb the sodic granite was derived from a mafic source in the lower crust the likely heat source was high heatflow associated with mantle upwelling the a type xuting pluton and mafic volcanic rocks in the gantaohe group constitute a bimodal lithologic association from a paleoproterozoic continental rift environment 2 2 2 0 ga magmas are widely distributed along the trans north china orogen tnco and also present a bimodal character we propose that 2 2 2 0 ga bimodal magmas throughout the tnco were likely formed in a paleoproterozoic rifting setting considering the widespread 2 2 2 0 ga magmatic rocks in the north china craton ncc we infer that the magmatism likely occurs in tensional environment after the initial amalgamation of the ncc in the late archean

formation waters from mississippian pennsylvanian reservoirs illinois basin usa chemical and isotopic constraints on evolution and migration we have analyzed a suite of seventy four formation water samples from mississippian and pennsylvanian carbonate and siliciclastic strata in the illinois basin for major minor and trace element concentrations and for strontium isotopic composition a subset of these samples was also analyzed for boron isotopic composition data are used to interpret origin of salinity and chemical and sr isotopic evolution of the brines and in comparison with a similar data set from an earlier study of basin formation waters from silurian devonian reservoirs systematics of cl br na show that present mississippian pennsylvanian brine salinity can be explained by a combination of subaerial seawater evaporation short of halite saturation and subsurface dissolution of halite from an evaporite zone in the middle mississippian st louis limestone along with extensive dilution by mixing with meteoric waters additional diagenetic modifications in the subsurface interpreted from cation br ratios include k depletion through interaction with clay minerals ca enrichment and mg depletion by dolomitization and sr enrichment through caco3 recrystallization and dolomitization ste genevieve limestone middle mississippian formation waters show 87sr86sr ratios in the range 0 70782 0 70900 whereas waters from the siliciclastic reservoirs are in the range 0 70900 0 71052 inverse correlations between 87sr86sr and b li and mg concentrations suggest that the brines acquired radiogenic 87sr through interaction with siliciclastic minerals completely unsystematic relations between 87sr86sr and 1 sr are observed sr concentrations in ste genevieve and aux vases middle mississippian waters appear to be buffered by equilibrium with respect to srso4 although there are many similarities in their origin and evolution these formation waters are distinguished from silurian devonian brines in the basin by elevated clbr and nabr ratios and by unsystematic sr isotope relationships thus waters from these two major segments of the illinois basin stratigraphic column form distinct geochemical regimes which are separated by the new albany shale group devonian mississippian regional aquitard geochemical evolution appears to have been influenced significantly by paleozoic and mesozoic hydrologic flow systems in the basin

paleoproterozoic arc magmatism in the north china craton no siderian global plate tectonic shutdown abstract arc magmatism in convergent plate margins has been a major contributor to continental growth following arc arc and arc continent collisions in the archean leading to the amalgamation of micro blocks the north china craton ncc witnessed major pulses of continental arc magmatism during the paleoproterozoic in this study we present geochemistry zircon u pb geochronology and lu hf isotope data from a suite of magmatic rocks sampled from the region of confluence of two major paleoproterozoic suture zones in the ncc the inner mongolia suture zone imsz and the trans north china orogen tnco our zircon u pb geochronological data indicate new zircon growth during multiple tectonothermal events as displayed in the 207pb 206pb weighted mean ages of 2410 41 ma for metagranite 2480 12 ma 2125 18 ma 1946 8 ma 1900 15 ma and 1879 12 ma from metagabbros 2446 11 ma from charnockite and 1904 6 ma and 1901 9 ma from metatuffs the 207pb 206pb upper intercept age of zircons in the khondalite shows 2102 76 ma which is identical to the age obtained from the magmatic zircons in one of the metagabbros the khondalites also carry a group of concordant metamorphic zircons with 207pb 206pb mean age of 1881 20 ma metamorphic zircons in the gabbros and charnockites also yield similar ages of 1890 14 ma and 1852 19 ma respectively the age data suggest prolonged arc magmatism in a convergent margin setting during ca 2 48 to 1 9 ga followed by metamorphism at ca 1 89 1 85 ga associated with the final collision lu hf analyses reveal that the dominant populations of zircons from all the rock types are characterized by positive ehf values 1 9 to 6 8 mean 1 8 the ehf and tdmc data suggest that the magmas were mostly derived from neoarchean and paleoproterozoic juvenile components the salient geochemical features of these rocks attest to magma generation from heterogeneous sources involving subduction derived arc components with minor input from continental crust the results presented in this study together with those from previous investigations in different domains of the imsz and tnco suggest major paleoproterozoic arc magmatic events in the ncc lasting for nearly 600 million years associated with the final assembly of the crustal blocks into a coherent craton construction of the final cratonic architecture of the ncc thus witnessed not only the arc continent amalgamations at 2 7 2 5 ga but also major crust building events in the paleoproterozoic through melts generated from juvenile and recycled components in continental magmatic arc systems along an active convergent margin followed by intense deformation and metamorphism during the final collision at 1 85 1 80 ga the prominent paleoproterozoic magmatic records in the ncc do not support the proposal of global plate tectonic shutdown in the siderian and confirm vigorous convergent margin magmatism and crust building processes throughout the paleoproterozoic

the uncertainties associated with sediment fingerprinting suspended and recently deposited fluvial sediment in the nene river basin the use of tracers within a sediment fingerprinting framework has become a commonly used technique for investigating the sources of fine sediment however uncertainties associated with tracer behaviour have been cited as major potential limitations to sediment fingerprinting methodologies this paper aims to determine the differences between fingerprinting results derived using different groups of tracer properties and to determine the role of organic matter content particle size and within source variability in tracer concentrations on the observed differences a mean difference of 24 1 between the predicted contributions of sediment originating from channel banks was found when using different tracer groups mean differences between tracer group predictions were lower at between 8 and 11 when fingerprinting contributions from urban street dusts organic matter content and or particle size showed little indication that they caused differences between tracer group predictions the within source variability in tracer concentrations and small contrasts between the tracer concentrations of different source groups were identified as probable causes of inherent uncertainty in the fingerprinting predictions we determined that the ratio of the percentage difference between median tracer concentrations in the source groups and the average within source tracer concentration coefficient of variation could indicate the likely uncertainty in model predictions prior to tracer use

trace metal speciation in julia creek oil shale the speciation of 16 trace elements in julia creek oil shale was estd based on the comparative evaluation of 3 different models referring to various chem digestion procedures demineralization steps were monitored by x ray diffraction and x ray fluorescence spectrometry and the results discussed together with those reported in literature although it is possible to det some enrichment of elements in the carbonate e g mn sr in the silicate e g ti v and in the sulfide fractions e g cu ga as enrichments in the kerogen phase can only be estd within a relatively broad range element distributions between different sedimentary phases seem to be very similar when comparing julia creek with other oil shales

geochemistry and mineralogy of the nw aegean sea surface sediments implications for river runoff and anthropogenic impact abstract surface sediments of the nw aegean sea were analyzed for clay mineral composition 94 samples organic c and carbonate content and major and minor elements 112 samples illite is the most abundant clay mineral followed by smectite chlorite and kaolinite clay minerals are preferentially deposited within the continental shelf and slope environment due to the prevailing cyclonic circulation and the formation of flocs in the rivers pro delta areas the spatial distribution of major lithogenic elements si al ti fe is substantially biased by the presence of relict sands located in the central eastern part of the thermaikos gulf continental shelf biogenic elements ca sr are noticeably pronounced on the northern flank of the north sporades islands organic c content and minor elements cu zn as and pb are enriched markedly over the thessaloniki bay and gulf suggesting substantial human impact deriving largely from untreated or partly treated domestic and industrial effluents the terrigenous component of the elements is preferentially contributed from the axios river zn and pb the aliakmon river cr co ni cu and as and to a lesser extent from the pinios river v co ni and cu a considerable part of the metals originates in ultra mafic and volcanic formations which are abundant in the rivers catchment basins carbonate content exhibits great variability with the highest values observed in biogenic sediments of the sporades basin in the latter area mn and fe oxides and hydroxides were found as coatings on calcite the coatings were enriched in cr co ni zn as mo and pb due to adsorption or ion exchange during early diagenesis the combined influence of the river systems the thessaloniki metropolis and the diverse sedimentological background generates great patchiness in the distribution of major and minor elements

origin distribution and accumulation of organic carbon in the skagerrak abstract organic carbon contents have been determined in grain size fractions of sediments from the skagerrak southern slope and basin c org concentrations were generally inversely related to grain size the 62 63 m fraction in surface sediments from deeper waters had higher contents attributable to agglutination of fine material by tube forming benthic organisms especially in the clay and fine silt fractions c org increased with increasing fraction content presumably as a result of higher grazing pressure on fine material in coarse sediments a comparison of high resolution age 210 pb porosity and grain size composition profiles indicates that deviations in the 210 pb curves are due both to bioturbation and sedimentation events porosity profiles also show high regional variability on a small scale when primary production c org vertical fluxes and accumulation rates are compared an excess of organic carbon stored in skagerrak sediments becomes apparent potential sources for this carbon such as river input dumping or sea floor erosion are examined

the geochemistry of au and pt in peat and algal mats a case study from sri lanka abstract the geochemistry of au and pt in the muthurajawela peat deposit the largest in sri lanka has been studied together with the au and pt contents of algal mats from the tidal flats of mannar nw of sri lanka both peat and algal mats are enriched in au and pt the source material presumably being a laterite known to contain large amounts of au and pt au appears to be enriched in the clay and fe and mn in the colloid phase whereas pt does not correlate with any particular element in the tidal flat environment of the algal mats au shows a greater tendency to migrate seawards whereas pt is enriched in the clastic rich landward side as well as in the seaward algal mats possibly being mobilized as the chloride complex

geophysical and geological tests of tectonic models of the north china craton abstract the geometry and timing of amalgamation of the north china craton have been controversial with three main models offering significantly different interpretations of regional structure geochronology and geological relationships one model suggests that the eastern and western blocks of the ncc formed separately in the archean and an active margin was developed on the eastern block between 2 5 and 1 85 ga when the two blocks collided above an east dipping subduction zone a second presumes the eastern block rifted from an unknown larger continent at circa 2 7 ga and experienced a collision with an arc perhaps attached to the western block above a west dipping subduction zone at 2 5 ga and the 1 85 ga metamorphism is related to a collision along the northern margin of the craton when the ncc joined the columbia supercontinent a third model suggests two collisions in the central orogenic belt at 2 1 and 1 88 ga but recognizes an early undated deformation event recent seismic results reveal details of the deep crustal and lithospheric structure that support both the second and third models showing that subduction beneath the central orogenic belt was west directed and that there is a second west dipping paleosubduction zone located to the east of the cob dipping beneath the western block ordos craton the boundaries identified through geophysics do not correlate with the boundaries of the trans north china orogen suggested in the first model and the subduction polarity is opposite that predicted by that model high pressure granulite facies metamorphism at 1 85 ga is not restricted to the tnco as suggested by the first model but is documented across the ncc as predicted by the second model suggesting a major continent continent collision along the north margin of the craton at 1 85 ga further it has recently been shown that in the southern tnco there is no record of metamorphism at circa 1 85 ga but only at 2 7 2 5 ga showing that the tnco as defined as a circa 1 85 ga orogen does not exist this is further confirmed by recent re os isotopic studies which show that the subcontinental lithospheric mantle beneath the southern cob is late archean in age and that a province in the northern ncc is circa 1 8 ga correlating with the proposed collision belt of the ncc with the columbia supercontinent across the entire ncc the cob is an archean convergent belt re worked in the paleoproterozoic and the paleoproterozoic tectonism is widespread across the ncc as predicted by the model whereby the previously amalgamated eastern and western blocks experienced a continental collision with columbia at circa 1 85 ga but uplift exhumation rates are slow necessitating a re evaluation of the tectonic models of the ncc