illite neoformation in plagioclase during weathering evidence from semi arid northeast brazil illite minerals in soils and weathered rocks are usually interpreted as secondary clays derived from the transformation of primary rock forming minerals with similar properties e g muscovite or as direct products of hydrothermal alteration after feldspar i e sericite with the help of detailed investigations involving x ray diffraction scanning electron microscopy and x ray element mapping this study testifies to the neoformation of illite inside plagioclase feldspar crystals after their partial dissolution in the weathering zone of luvisols in semi arid northeast brazil our results thus reveal that meteoric weathering can produce illite not only from mica i e by a transformation process but also within non alkali feldspar by a neoformation process at least under the semi arid conditions that have long prevailed in the study area given that illite in weathering mantles has recurrently been attributed often by default to hydrothermal processes results shown here provide new focus to an alternative pathway of illite formation primarily controlled by climate

impact of atmospheric deposition biogeochemical cycling and water mineral interaction on ree fractionation in acidic surface soils and soil water the strengbach case leaf litter contains not only important quantities of elements derived from decomposition of organic matter but also atmospheric compounds this is illustrated by sr and nd isotope data from soils of the strengbach catchment which show that soil litter contains more than 50 of atmospheric sr and nd downward migrating soil water becomes strongly acidic during flow through litter and humus layers ph 3 8 4 at 5 10 cm depth causing not only intense mobilization of elements in the underlying acid brown and podzolic soils at depths between 10 and 50 cm but also the downward transfer of some litter derived compounds the sr and nd isotope data allow to quantify that soil water from 10 to 70 cm depth contains 45 to 65 of litter derived nd and sr sequential leaching experiments have been performed on soil samples in order to recover adsorbed trace elements or those fixed in acid soluble mineral phases such as fe mn oxyhydroxides and phosphate minerals the isotope data of these leachates of the uppermost soil horizons point similarly to the presence of important quantities of litter derived sr and nd in the uppermost 30 cm of the soils with the exception of the litter layer the soil profiles are substantially depleted in ca and p down to 50 cm depth which can be related to low apatite and plagioclase contents these minerals have probably been preferentially weathered and ca and p have been removed by percolating soil water and plant uptake leaching of primary granite derived apatite controls rare earth element ree fractionation only below 50 cm depth rhabdophane ree po4 has been observed as secondary replacement mineral of apatite this replacement is reflected by ca p ratios that are low at the surface and which increase regularly with depth implying that some of the apatite derived p has been integrated into newly formed rhabdophane and some of the p and ca have been exported either by soil solutions or plant uptake during downward transport litter derived elements are adsorbed on soil particles and or coprecipitate with authigenic minerals such as fe mn oxyhydroxide or rhabdophane alternatively litter derived elements may remain in solution or like ca be absorbed by vegetation the soil solutions from the uppermost 30 cm of the soil profiles and the corresponding soil leachates show very similar ree distribution patterns and are compared to the waters of the strengbach stream which drains the forested catchment strongly enriched in light rare earth elements lree however soil solutions from 60 to 70 cm depth are compared to litter strongly lree depleted and show stream water like ree distribution patterns it is suggested that this evolution of the ree in the soil solutions is due to the following processes taking place above 50 cm depth 1 precipitation of lree rich phosphate minerals like rhabdophane 2 diminution of the formation of organic dissolved or colloidal phases in association with fe mn and al oxyhydroxides and 3 preferential lree uptake by vegetation below 50 cm the ree distribution patterns are further modified by dissolution precipitation reactions and adsorption the combination of all these fractionation processes finally leads to the ree patterns of the strengbach stream at the catchment outlet

strong climate coupling of terrestrial and marine environments in the miocene of northwest europe a palynological and organic geochemical record from a shallow marine paleoenvironmental setting in se netherlands documents the coupled marine and terrestrial climate evolution from the late burdigalian 17 ma through the early zanclean 4 5 ma proxy climate records show several coeval variations in both relative sea surface deduced from percent cool dinocysts and terrestrial subtropical vs cool temperate pollen temperature indices the terrestrial climatic trend is confirmed by a quantitative reconstruction of annual mean air temperature based on the distribution of fossil branched glycerol dialkyl glycerol tetraethers showing a cooling from 27 c to 14 c between 17 and 5 ma punctuated by short term variations decreases in sea surface temperature broadly correlate to inferred third order sea level variations and correspond to isotope glacial events mi 3 through mi 7 an additional strong sst decrease occurs around 8 4 ma coincident with a strong reduction and regional disappearance of subtropical pollen types this cooling phase seems associated with lowered sea levels but it has not yet been described from the deep sea 18o record 2009 elsevier b v

influence of phosphate on mobility and adsorption of rees during weathering of granites in thailand abstract the permo jurassic north thai nt granites and the late cretaceous to paleogene western province wp granites in thailand are contrasting in terms of tectonic settings and chemical compositions the nt granites which are dominated by s type features are characterized by lower sio2 contents and higher p2o5 contents than the wp granites in this study in order to compare the mobility and adsorption of rare earth elements rees during weathering of the two granite suites geochemical analyses were conducted on the granite and weathered granites the weathered wp granites show wider ranges of rees y rey contents percentages of ion exchangeable rey and ce anomalies than the weathered nt granites these results indicate that rees were less mobile during weathering of the nt granites than those of the wp granites the low mobility of rees can be explained by the occurrences of residual monazite and secondary ree phosphates which immobilize rees during weathering therefore in the weathered nt granites rees are mostly contained in the phosphate minerals in contrast the weathered wp granites are dominated by ion exchangeable rees adsorbed rees which are likely to exist on the surface of clays previous studies and our study results suggest that the ion exchangeable rees in the weathered granites were probably sourced from weatherable allanite titanite apatite and or ree fluorocarbonate and rarely from monazite and zircon which are resistant to weathering the weathered granites of low phosphate contents potentially show high percentages of ion exchangeable rey although they can be influenced by the degree of hydrothermal alteration or weathering of granites

geological geochemical and mineralogical characteristics of the mandan and deh now bauxite deposits zagros fold belt iran the mandan and deh now bauxite deposits are located 40 km northeast of the dehdasht city in the zagros simply fold belt these deposits occur in eroded major nw se trending anticlines and occupy karst cavities near or at the boundary between the sarvak and ilam formations local uplifts at the end of the cenomanian and the mid turonian caused erosion and karstification of the sarvak formation these unconformities in the upper cretaceous favoured the formation and enrichment of bauxite deposits in the zagros fold belt the bauxite sequence in the mandan deposit consists of white gray black pisolitic red and yellow bauxites this sequence was repeated in the deh now area but without gray and black bauxites the present mineralogical studies of the sarvak formation and the mandan and deh now bauxite deposits indicate oxidizing to reducing conditions during the upper cretaceous in the zagros fold belt which had a significant effect on the compositions of the bauxites at least two phases of bauxitization can be distinguished in the study area i an oxidizing phase represented by boehmite diaspore hematite and kaolinite and ii a reducing phase represented by pyrite and chlorite geochemical data show that trace elements like zr hf nb ta th and u were enriched during bauxitization the bauxite deposits and carbonate rocks show similar ree patterns namely they are enriched in rees although the lrees are more enriched than the hrees mass change calculations demonstrate that mg mn ca k and p2o5 were leached out of the weathered system whereas al fe and si become concentrated in the residual system this study indicates that the mandan and deh now deposits are karst type bauxites formed by karstification and weathering of the sarvak formation

mobility and fractionation of rees during deep weathering of geochemically contrasting granites in a tropical setting malaysia in this study we describe the mobility and fractionation of rees in two deep up to 30 m tropical weathering profiles developed on two granites from the kuala lumpur pluton malaysia sampled at cheras and rawang on the basis of na2o and k2o both are s type granites but rawang has higher cao mgo and feo than cheras and lower sio2 with respect to al saturation rawang is i type and cheras is s type we compared the two profiles in terms of total rees magnitude and changes in ce and eu anomalies ree mobility and lree hree fractionation rawang profiles have higher ree contents display lower mobility for most except the heaviest rees and show higher lree hree fractionation than those from cheras these differences can be linked to differences in primary mineralogy and degree of weathering the latter controlling the type and volume of secondary minerals specifically bowl shaped parent rock normalised patterns in the cheras saprolites appear to be a result of apatite dissolution moreover moderate weathering evident in lower mineralogical indices of alteration mia at cheras has conserved parent rock ree patterns and fractionation factors in the saprolites by contrast more intense weathering observed in rawang profiles has produced abundant kaolinite group minerals that have preferentially retained lree which consequently display high lree hree fractionation this study provides important insights into the factors controlling ree mobility during tropical weathering and its potential as an indicator of weathering intensity

central european vegetation response to abrupt climate change at 8 2 ka oxygen isotope records show a major climatic reversal at 8 2 ka in greenland and europe annually laminated sediments from two lakes in switzerland and germany were sampled contiguously to assess the response of european vegetation to climate change ca 8 2 ka with time resolution and precision comparable to those of the greenland ice cores the pollen assemblages show pronounced and immediate responses 0 20 yr of terrestrial vegetation to the climatic change at 8 2 ka a sudden collapse of corylus avellana hazel was accompanied by the rapid expansion of pinus pine betula birch and tilia linden and by the invasion of fagus silvatica beech and abies alba fir vegetational changes suggest that climatic cooling reduced drought stress allowing more drought sensitive and taller growing species to out compete corylus avellana by forming denser forest canopies climate cooling at 8 2 ka and the immediate reorganization of terrestrial ecosystems has gone unrecognized by previous pollen studies on the basis of our data we conclude that the early holocene high abundance of c avellana in europe was climatically caused and we question the conventional opinion that postglacial expansions of f silvatica and a alba were controlled by low migration rates rather than by climate the close connection between climatic change and vegetational response at a subcontinental scale implies that forecasted global warming may trigger rapid collapses expansions and invasions of tree species

late glacial climatic changes in eastern france lake lautrey from pollen lake levels and chironomids high temporal resolution analyses of pollen chironomid and lake level records from lake lautrey provide multi proxy quantitative estimates of climatic change during the late glacial period in eastern france past temperature and moisture parameters were estimated using modern analogues and plant functional types transfer function methods for three pollen records obtained from different localities within the paleolake basin the comparison of these methods shows that they provide generally similar climate signals with the exception of the bolling comparison of pollen and chironomid based temperature of the warmest month reconstructions generally agree except during the bolling major abrupt changes associated with the oldest dryas bolling allerod younger dryas and the younger dryas preboreal transitions were quantified as well as other minor fluctuations related to the cold events e g preboreal oscillation the temperature of the warmest month increased by not vert similar5 c at the start of bolling and by 1 5 3 c at the onset of the holocene while it fell by ca 3 to 4 c at the beginning of younger dryas the comparative analysis of the results based on the three lautrey cores have highlighted significant differences in the climate reconstructions related to the location of each core underlining the caution that is needed when studying single cores not taken from deepest part of lake basins

biomarker reconstruction of the early eocene paleotopography and paleoclimate of the northern sierra nevada we reconstruct ancient temperature and elevation gradients across the early eocene 52 49 ma northern sierra nevada california united states using organic molecular proxies that record atmospheric and ground level effects of topography paleoelevation was determined by reconstructing the change in the hydrogen isotopic composition of precipitation d precip and mean annual temperature t gdgt glycerol dialkyl glycerol tetraethers from the isotopic composition of fossil angiosperm leaf n alkanes and the distribution of microbially produced soil tetraethers preserved in leaf bearing sediments organic molecular data produce equivalent range scale d n alkane and channel t gdgt paleoelevation estimates that show the northern sierra nevada was a warm 6 8 c warmer than modern high elevation 2 km and moderate to low relief landscape at the eocene climatic optimum modern northern sierra nevada topography likely refl ects post paleocene reduction of mean surface elevation and late cenozoic increases in relief

geochemistry of the peat bog at etang de la gruere jura mountains switzerland and its record of atmospheric pb and lithogenic trace metals sc ti y zr and ree since 12 370 14 c yr bp a 650 cm core from a swiss bog represents 12 370 14c years of peat accumulation and provides the first complete record of atmospheric pb deposition for the entire holocene excess non atmospheric sr in the peat was calculated by normalizing sr sc to crustal abundance this was used to differentiate between the ombrogenic section of the bog in which inorganic solids are supplied exclusively by atmospheric deposition and the minerogenic zone where mineral water interactions contribute metals to the peat while sediment dissolution contributes significantly to the sr inventory of the minerogenic section of the peat profile there is no measurable effect of this process on the pb burden isotopic analyses 204pb 206pb 207pb 208pb show that effectively all of the pb in the peat profile was supplied exclusively from the atmosphere to separate natural and anthropogenic pb sc was selected over ti y zr hf and ree as a conservative reference element which is supplied by soil dust aerosols derived from rock weathering enrichment factors ef were calculated using the pb sc ratio in the peat samples normalized to the natural background pb sc which is found in peats dating from 8030 to 5320 14c yr bp the results show that anthropogenic source have dominated the supply of atmospheric pb to the peat core continuously since 3000 14c yr bp the aerosols supplied to the bog can be divided into 3 classes a pre anthropogenic older than 3000 14c yr bp with pb ef 1 194 b pre industrial dating from 3000 240 14c yr bp with pb ef 2 but 20 and 206pb 207pb 1 179 elevated soil dust fluxes are observed at 5320 8230 and 10 590 14c yr bp the latter corresponds to the younger dryas aluminum zr hf and ree sc ratios also are elevated at the same depths suggesting differences in particle size wind strength or source regions pre anthropogenic aerosols deposited since 8230 14c yr bp reveal pb sc which is significantly higher and 206pb 207pb which is less radiogenic than during the early holocene while the trend toward increasing pb sc could be due to chemical weathering and soil development this could not explain the shift in pb isotopic composition the changes which took place at 8230 14c bp therefore may be related to a large scale climatic reorganization which at present is poorly understood

nano mineralogy and geochemistry of high grade diasporic karst type bauxite from parnassos ghiona mines greece abstract in the present work a combination of various techniques is utilized for the study of nano mineralogy and geochemistry of high grade karst type bauxite al rich and fe depleted samples al2o3 ca 80 wt from the parnassos ghiona mines located in greece initial characterization using pxrd and electron microscopy in microscale and mesoscale sem eds including stem mode proved the presence of fe cr ti containing diaspore anatase and minor rutile the study by means of 57fe mossbauer spectroscopy in correlation with magnetic susceptibility measurements and complemented with synchrotron based spectroscopies at the microscale sr micro xrf and micro xanes exafs indicated that fe3 in contrast to 6 cr3 is not exclusively a component of the diaspore structure while cr3 substitutes al3 in octahedral sites of diaspore 6 cr3 6 al3 the electron microscopy in nanoscale tem eds eels revealed that fe exists in the form of peculiar fe3 bearing nanominerals most likely maghemite type phases between 25 and 45 nm in size in addition to the fe3 ions substituting al3 in the diaspore structure moreover it was proven that tio2 polymorph mineral nanoparticles particularly rounded anatase mesocrystals and nanocrystals and individual needle shaped rutiles are dispersed into the diaspore matrix thus diaspore in the studied bauxite concerns in fact a distinct fe3 cr3 alooh low t authigenic phase demonstrated for the first time in literature on the other hand the observed tio2 mineral nanoparticles formed together with diaspore during diagenesis and fe nanominerals formed during epigenesis were hitherto unknown not only for the allochthonous karst type bauxite deposits of greece but also for the overall bauxite deposits worldwide

terrestrial deposition processes of quaternary gibbsite nodules in the yongjiang basin southeastern margin of tibet and implication for the genesis of ancient karst bauxite abstract the terrestrial deposition process for karst bauxite is difficult to constrain due to its allochthonous origin multiple controls and the difficulty in geodynamic reconstruction this ambiguity has been clarified from investigation of the provenance and geologic geographic conditions for the formation of quaternary gibbsite nodules in the yongjiang basin this karst basin located at the southeastern propagation front of the tibet plateau was affected by the se asia monsoon climate developed since the late oligocene and a later quaternary glaciation a thick blanket of quaternary laterite is located on paleozoic carbonate bedrock and covers an area about 1000 km2 along the east flowing river systems in the basin the laterite profiles are well layered with a layer of iron rich gibbsite nodules overlying on a basal clay zone and irregularly covered by a thin clayey topsoil gibbsite nodules from most localities yield detrital zircons with age peaks at ca 1000 ma 450 ma and 250 ma corresponding to those of the mesozoic clastic and magmatic rocks exposed on the western and southern surrounding highlands nevertheless those from the pingtianshan area produce an exclusive spike at ca 100 ma consistent with the emplacement age of nearby granites apatite fission track modeling for the mesozoic clastic rocks and darongshan granites shows a rapid cooling since the early miocene and that for the pingtianshan cretaceous granite reveals fast exhumation since the late miocene these data indicate differential erosion reshaped the topography and consequently a low relief karst basin was developed allowing a diverse material supply from the surrounding and local highlands via sheet flow and east flowing rivers under a monsoon influenced subtropical climate aluminum and iron oxides hydroxides were accumulated as nodules or concretions which were cemented by and coated with fe oxides due to variations in redox potential and alternating consolidation and swelling while silica was leached at greater depth groundwater solutions preferentially removed and brought upward fe under a reducing environment during the wet seasons while an underlying clay layer occurred due to the reduced solubility of silica later this bauxitization process was probably hindered by the quaternary glaciation which could have promoted the formation of the top clay layer this terrestrial deposition process of quaternary gibbsite nodules serves as one analogue for ancient karst bauxite in which the following submergence would improve the quality via further precipitation of alumina hydroxide and leaching of extra fe

rare earth elements in sedimentary phosphate deposits solution to the global ree crisis abstract the critical role of rare earth elements rees particularly heavy rees hrees in high tech industries has created a surge in demand that is quickly outstripping known global supply and has triggered a worldwide scramble to discover new sources the chemical analysis of 23 sedimentary phosphate deposits phosphorites in the united states demonstrates that they are significantly enriched in rees leaching experiments using dilute h2so4 and hcl extracted nearly 100 of their total ree content and show that the extraction of rees from phosphorites is not subject to the many technological and environmental challenges that vex the exploitation of many identified ree deposits our data suggest that phosphate rock currently mined in the united states has the potential to produce a significant proportion of the world s ree demand as a byproduct importantly the size and concentration of hrees in some unmined phosphorites dwarf the world s richest ree deposits secular variation in phosphate ree contents identifies geologic time periods favorable for the formation of currently unrecognized high ree phosphates the extraordinary endowment combined with the ease of ree extraction indicates that such phosphorites might be considered as a primary source of rees with the potential to resolve the global ree particularly for hree supply shortage

impact of dia and catagenesis on sulphur and oxygen sequestration of biomarkers as revealed by artificial maturation of an immature sedimentary rock hydrous pyrolysis of an immature ro 0 25 sulphur rich marl from the gessoso solfifera formation messinian in the vena del gesso basin was carried out at 160 c t 330 c for 72 h to study the effect of progressive diagenesis and early catagenesis on the abundance and distribution of sulphur containing and sulphur and oxygen linked carbon skeletons in low molecular weight and high molecular weight fractions e g kerogen to this end compounds in the saturated hydrocarbon fraction monoaromatic hydrocarbon fraction polyaromatic hydrocarbon fraction alkylsulphide fraction and ketone fraction were quantified as well as compounds released after desulphurisation of the polar fraction and hilialh4 treatment of the desulphurised polar fraction sulphur bound phytane and 20r 5 14 17 h and 20r 5 14 17 h c27 c29 steranes in the polar fraction become less abundant with increasing maturation temperature whereas the amount of their corresponding hydrocarbons increases in the saturated hydrocarbon fraction carbon skeletons that are bound in the kerogen by multiple bonds e g c38n alkane and isorenieratane are first released into the polar fraction and then as free hydrocarbons these changes occur at relatively low levels of thermal maturity ro 0 6 as evidenced by the immature values of biomarker maturity parameters such as the c35 hopane ratio and the 22s 22s 22r 17 21 h c35 hopane ratio sulphur and oxygen bound moieties present in the polar fraction are not stable with increasing thermal maturation however alkylthiophenes ketones 1 2 di n alkylbenzenes and free n alkanes seem to be stable thermal degradation products of these sulphur and oxygen bound moieties thus apart from free n alkanes which are abundantly present in more mature sedimentary rocks and crude oils alkylthiophenes 1 2 di n alkylbenzenes and ketones can also be expected to occur the positions of the thiophene moiety and the carbonyl group coincide with the original positions of the functional groups of their precursors thus important information about palaeobiochemicals is retained throughout the sequestration degradation process

model data comparison for the 8 2 ka bp event confirmation of a forcing mechanism by catastrophic drainage of laurentide lakes abstract to improve our understanding of the mechanism behind the 8 2 ka bp cooling event we compare proxy evidence with climate model simulations in which the thermohaline ocean circulation is perturbed by a freshwater pulse into the labrador sea both the proxy data and model results show a cooling that is mainly concentrated in the north atlantic region ranging from more than 5 c cooling in the nordic seas to about 0 5 1 c over europe and less than 0 5 c over the subtropical north atlantic data and model also indicate a weakening of the summer monsoon and generally a drier circum north atlantic over the south atlantic ocean the model simulates a slight warming mostly less than 0 5 c which falls within the uncertainty of proxy data and thus could not be confirmed to examine in detail the structure of the 8 2 ka bp event we also compare the modeled climatological evolution at two locations with high quality records revealing a generally consistent picture the good model data agreement confirms the hypothesis that the 8 2 ka bp event was forced by a freshwater induced weakening of the thermohaline circulation other forcings are unlikely since they would result in an alternative geographical distribution and expression of the climate response

environmental controls on branched tetraether lipid distributions in tropical east african lake sediments abstract quantifying past continental temperature changes is an important aspect of paleoclimate research as it allows us to constrain the amplitude of natural variability test predictive climate models and provide a proper context for changes that may arise in response to anthropogenically induced climate change the recently developed biomarker based methylation index of branched tetraethers cyclization ratio of branched tetraethers mbt cbt proxy shows potential as a new method for continental temperature reconstruction but thus far it has only been applied successfully in ocean margin sediments to assess whether this proxy is also applicable to the sedimentary record in tropical lacustrine systems we investigated the distribution of branched glycerol dialkyl glycerol tetraethers gdgts in recently deposited sediments from 46 lakes in tropical east africa these lakes span a substantial range in surface elevation 770 4500 m above sea level and thus also a wide gradient of mean annual temperature we find that saline lakes excepted branched gdgts are universally abundant in the lakes investigated and can be used to predict mean annual air temperature maat with a high degree of accuracy however the existing global mbt cbt calibration for maat based on soils predicts inaccurate temperatures when applied to our african lake dataset this observation together with the fact that surface water ph and to lesser extent lake depth appear to influence the distribution of branched gdgts among sites leads us to conclude that in situ production of branched gdgts in lakes is likely the robust relationship between branched gdgt distribution and the temperature and ph of african freshwater lakes makes these compounds suitable for paleoenvironmental reconstruction however we urge caution in using branched gdgts in lake sediments to infer past temperatures unless their exact origin can be determined

genesis of karst bauxite bearing sequences in baofeng henan china and the distribution of critical metals abstract bauxite bearing sequences are not only the main economic sources of aluminum but also of many critical metals the distribution of critical metals was determined from six bauxite profiles in baofeng and an evolution model was proposed for the formation of bauxite bearing sequences following a terrestrial deposition of the lower pisolitic bauxite horizon and the underlying clayey layer transportation and redeposition of bauxitic materials during submergence led to the formation of the upper bauxite horizon presenting finely clastic and oolitic textures as well as the intercalated clayey layers both bauxite ores and clay samples contain highly elevated contents of li b sc v ga zr nb w and total rees li contents are extremely low in high grade bauxite ores 10 92 44 77 ppm compared to highly elevated values in low grade bauxite ores 35 81 1601 ppm and clay samples 38 54 1965 ppm enlightening a new potential resource for li the bauxite bearing sequences resting on karstified carbonate the distribution pattern of ga is similar to that of li and the correlation analysis indicates that ga is primarily associated with silicates i e clay minerals the vertical distribution of li b v cr and ga shares the same pattern similar to that of k2o and sio2 being highly enriched in clayey layers relative to bauxite horizons both sc and total rees are also highly enriched in baofeng bauxite profiles highlighting a potential sc and rees resource

experimental studies of ree fractionation during water mineral interactions ree release rates during apatite dissolution from ph 2 8 to 9 2 rare earth elements ree release rates were measured during the open system dissolution of natural apatite at 25 c 2 8 ph 9 2 and at ionic strengths ranging from 0 001 to 0 02 mol kg all inlet solutions were ca ree and p free in agreement with previous studies apatite dissolution rates determined from outlet solution ca concentrations decrease monotonically with increasing ph outlet solution molar ree ca ratios differ from that of the dissolving apatite during the experiments this behaviour is interpreted to stem from dissolution or precipitation of minor quantities of rhabdophane ree po4 nh2o this interpretation is supported by solute speciation calculations which indicate that ree are retained in the solid phase when the outlet fluids are supersaturated with respect to nd rhabdophane ksp 10 24 5 0 5 but preferentially released when the outlet fluids are undersaturated with respect to nd rhabdophane the relative concentrations of the ree in the outlet solutions suggest that the secondary rhabdophane is slightly enriched in light ree ce to eu the results of this study suggest that rhabdophane dissolution and precipitation during apatite fluid interaction plays a major role in controlling surface and ground water ree signatures

mobilization and redistribution of rees and thorium in a syenitic lateritic profile a mass balance study abstract ree th geochemistry and mineralogy have been studied in a lateritic profile derived from a syenite at akongo in sw cameroon ree and th mass balance calculations for the host rock minerals show that at least 70 of the lree s and 50 of the hrees are contained in allanite apatite titanite and epidote and at least 50 of the th is controlled by the same accessory minerals which represent about 2 wt of the unaltered syenite these accessory phases are destroyed during the first stages of weathering causing most of the rees and th to be rapidly released into the soil comparison of the variation in the zr ti and th content as a function of the apparent density of the different zones of the saprolite shows that th is the least mobile element the presence of secondary thorianite tho2 the etched surface on zircon grains and the presence of ti in secondary cerianite support this geochemical interpretation the concentration of thorium was therefore chosen as invariant relative to the concentration of the other elements especially the rees in mass balance calculations most of the rees are leached in the iron rich upper horizons loose nodular horizon iron crust and top of mottled clay horizon where the groundwater table moves saprolite and bottom of the mottled clay horizon the rees are fractionated and redistributed there is a juxtaposition of leached and accumulation zones with precipitation of lree aluminous hydrated phosphates this study supports the existence of two different cycles for the redistribution of elements in the soil 1 1 as dissolved ions in the saprolite horizon and 2 2 as individual particles in the upper part of the profile

δ13c values and radiocarbon dates of microbial biomarkers as tracers for carbon recycling in peat deposits this paper describes the first application of compound specific stable carbon isotope and radiocarbon isotope analyses to the investigation of microbial processes in peat deposits

climatic and hydrologic controls on upper paleozoic bauxite deposits in south china abstract the late paleozoic era was an interval of major tectonic and climatic changes including formation of the supercontinent pangea and the 60 myr long late paleozoic ice age lpia although bauxite formation declined globally from the carboniferous to the permian in conjunction with global cooling it was an interval of widespread bauxite formation in china in south china 1 the jiujialu formation bauxite deposits in central and northern guizhou zunyi area are of early middle visean age 2 the dazhuyaun formation bauxite deposits in northern guizhou wuchuan zheng an daozheng area to southern chongqing nanchuan area and southeastern guizhou fuquan kaili area are of late pennsylvanian early permian age and 3 the heshan formation bauxite deposits in western guangxi to yunnan are of middle late permian age in north china the benxi formation bauxite deposits are of late mississippian middle pennsylvanian age the contrasting trends in bauxite metallogenesis between china and the rest of the world imply different climatic patterns in the eastern tethys high annual humidity with seasonal dryness and pangea aridification this hypothesis is further supported by differences in the chemical index of alteration or cia 80 in the eastern tethys vs 50 in western pangea and in paleotemperatures mean annual temperature or mat 20 c in the eastern tethys vs 4 c in western pangea determined from permo carboniferous siliciclastic deposits permo carboniferous bauxite deposits in south china formed in coastal plain and coastal karstic depression environments in which the position of the groundwater table was related to sea level changes during the late paleozoic high frequency eustatic fluctuations caused by waxing and waning of gondwana icesheets controlled sedimentation in these coastal depositional systems leading to cyclic accumulation of coal and bauxite deposits and cycles of vadose and phreatic type bauxite formation the results of the present study show that during interglacial stages lateritization resulted from high pco2 high sea level and groundwater table elevations low precipitation and limited vegetation cover whereas during glacial stages bauxitization of these ferralitic weathering products was promoted by low pco2 low sea level and groundwater table elevations high precipitation and more extensive vegetation cover thus a unique combination of geographic climatic and eustatic factors accounted for widespread formation of bauxite in south china during the lpia

fluxes and distribution of tetraether lipids in an equatorial african lake constraints on the application of the tex86 palaeothermometer and bit index in lacustrine settings abstract the distribution of isoprenoid and branched glycerol dialkyl glycerol tetraether gdgt lipids was studied in material from various sources in and around lake challa a crater lake on the southeastern slope of mt kilimanjaro tanzania to examine the provenance of gdgts in lake sediments and their potential application as palaeoenvironmental and palaeoclimatic proxies the study material included samples collected at monthly intervals in a sediment trap over one complete annual cycle particles suspended in the stratified water column profundal surface sediments and soils surrounding the lake the sediment trap time series revealed that crenarchaeol and related isoprenoid gdgts were predominantly produced in january and february following the locally prominent short rain season november december the tex 86 inferred temperature derived from sedimenting particles corresponded well with lake surface water temperature at this time of largest crenarchaeol flux molecular ecological analysis showed that group 1 1a and 1 1b crenarchaeota are the most likely source organisms of these gdgts gdgt 0 in the lake sediments does not only originate from lake surface dwelling crenarchaeota but seems predominantly derived from archaea residing in the deeper anoxic part of the water column the main flux of branched gdgts to the sediment was during the short rain season and is most probably derived from eroded catchment soils in surface run off however a contribution from in situ production of branched gdgts in the lake sediment or water or in groundwater cannot be fully excluded we conclude that palaeoclimatic reconstruction based on branched gdgt distributions in lake sediments should only be performed when the origin of those branched gdgts is well constrained

coupled thermal and hydrological evolution of tropical africa over the last deglaciation we analyzed the distribution of branched tetraether membrane lipids derived from soil bacteria in a marine sediment record that was recovered close to the congo river outflow and the results enabled us to reconstruct large scale continental temperature changes in tropical africa that span the past 25 000 years tropical african temperatures gradually increased from 21 to 25 c over the last deglaciation which is a larger warming than estimated for the tropical atlantic ocean a direct comparison with sea surface temperature estimates from the same core revealed that the land sea temperature difference was through the thermal pressure gradient an important control on central african precipitation patterns

genesis of the dogankuzu and mortas bauxite deposits taurides turkey separation of al fe and mn and implications for passive margin metallogeny the taurides region of turkey is host to a number of important bauxite al rich laterite and mn deposits the most important bauxite deposits dog ankuzu and mortas are karst related unconformity type deposits in upper cretaceous limestone the bottom contact of the bauxite ore is undulatory and bauxite fills depressions and sinkholes in the footwall limestone whereas its top surface is concordant with the hanging wall limestone the thickness of the bauxite varies from 1 to 40 m and consists of bohmite hematite pyrite marcasite anatase diaspore gypsum kaolinite and smectite the strata bound sulfide and sulfate bearing low grade lower part of the bauxite ore bed contains pyrite pseudomorphs after hematite and is deep red in outcrop owing to supergene oxidation the lower part of the bauxite body contains local intercalations of calcareous conglomerate that formed in fault controlled depressions and sinkholes bauxite ore is overlain by fine grained fe sulfidebearing and calcareous claystone and argillaceous limestone which are in turn overlain by massive compact limestone of santonian age that 50 m thick limestone is in turn overlain by well bedded bioclastic limestone of campanian or maastrichtian age rich with rudist fossils fracture fillings in the bauxite orebody are up to 1 m thick and consist of bluish gray green pyrite and marcasite 20 with bohmite diaspore and anatase these sulfide veins crosscut and offset the strata bound sulfide zones sulfur for the sulfides was derived from the bacterial reduction of seawater sulfate and fe was derived from alteration of oxides in the bauxite iron sulfides do not occur within either the immediately underlying or overlying limestone the platform limestone and shale that host the bauxite deposits formed at a passive margin of the tethys ocean extensive vegetation developed on land as the result of a humid climate thereby creating thick and acidic soils and enhancing the transport of large amounts of organic matter to the ocean alteration of the organic matter provided co2 that contributed to formation of a relatively 12 c rich marine footwall limestone relative sea level fall resulted from strike slip faulting associated with closure of the ocean and local uplift of the passive margin that uplift resulted in karstification and bauxite formation in topographic lows as repre

critical metals distribution in tethyan karst bauxite the cretaceous italian ores abstract bauxite is a residual rock consisting mainly of a mixture of aluminium hydroxides whose industrial significance is primarily due to its profitably exploitable alumina contents in the last decades bauxite mainly karst bauxite has been also considered as possible resource of a great number of economically interesting elements including some critical metals such as rare earth elements sc co ni and nb in this study we present results of univariate and multivariate r mode factor analysis statistics performed on a large data set including chemical composition of the principal cretaceous karst bauxites from central and southern italy with the twofold aim to evaluate the inter elemental relationship among major oxides and critical metals and describe factors affecting their distribution univariate statistics reveal that some critical metals co ni and lree have a significant number of outliers the co ni relationship associated to the outliers dataset suggests that co is likely hosted in ni rich phases whereas ce accumulation in authigenic minerals carbonate fluoride and phosphate is at the origin of lree outliers multivariate r mode statistics applied to the outliers devoid database instead demonstrate that in absence of specific mineralization events the distribution of most critical metals is controlled by al fe and ti oxi hydroxides and to a lesser extent by detrital phases among the critical metals cr and y are the exceptions their geochemical behaviour seems to be influenced primarily by their own chemical features that are responsible for the mobility of cr during bauxitization and for the decoupling of y from the rees

challenges of anticipating the 2011 tohoku earthquake and tsunami using coastal geology 1 can the magnitude of a giant earthquake be estimated from paleoseismological data alone attempts to estimate the size of the jogan earthquake of ad 869 whose tsunami affected much of the same coast as the 2011 tohoku tsunami offers an excellent opportunity to address this question which is fundamental to assessing earthquake and tsunami hazards at subduction zones between 2004 and 2010 examining stratigraphy at 399 locations beneath paddy fields along 180 km of coast mainly south of sendai we learned that a tsunami deposit associated with the ad 869 jogan earthquake had run inland at least 1 5 km across multiple coastal lowlands and that one of the lowlands had subsided during the jogan earthquake and an earlier earthquake as well radiocarbon ages just below above sand deposits left by the pre jogan tsunamis suggested recurrence intervals in the range of 500 to 800 years modeling inundation and subsidence we estimated size of the jogan earthquake as moment magnitude 8 4 or larger and a fault rupture area 200 km long we did not consider a longer rupture like the one in 2011 because coastal landform and absence of a volcanic ash layer make any jogan layer difficult to identify along the sanriku coast still sendai tsunami geology might have reduced casualties by improving evacuation maps and informing public awareness campaigns

bacterial tetraether membrane lipids in peat and coal testing the mbt cbt temperature proxy for climate reconstruction abstract peatlands are widespread and important natural archives of environmental change here we explore the potential of the recently introduced mbt cbt proxy methylation index and cyclisation ratio of branched tetraethers to estimate past annual mean air temperature mat based on the distribution of bacterially derived branched glycerol dialkyl glycerol tetraether gdgt membrane lipids in peat and coal to this end branched gdgts in an ombrotrophic peat bog from switzerland and three coal deposits of increasing maturity were analysed for the surface of the bog reconstructed annual mat is higher than both measured annual mat and measured in situ pore water temperature changes in the cbt ratio considered a proxy for ph with depth in the bog do not match with present day in situ pore water ph but coincide with a peat stratigraphic boundary this indicates that gdgts down the bog profile are predominantly fossil and not derived from extant biomass the mbt cbt derived annual mat record also shows a large drop at this stratigraphic boundary which likely relates to past change in trophic status of the bog branched gdgts are abundant in an immature lignite vitrinite reflectance r o 0 25 but occur in low amount in a slightly more mature coal r o 0 32 annual mat could be reconstructed for the lignite alone and is higher than other proxy based estimates from approximately the same time and location our results indicate potential for the application of the mbt cbt proxy in peat and immature coals but improved constraints on the effects of different types of peat on branched gdgt distributions as well as improved calibration of mat estimates are needed before the method can be confidently applied

warm arctic continents during the palaeocene eocene thermal maximum the palaeocene eocene thermal maximum petm 55 5 ma is a geologically relatively brief episode of extreme warmth both deep and surface ocean temperatures increased by up to 5 c in equatorial waters and up to 8 c in mid and high latitude waters from the continents the annual mean air temperature response during the petm is still largely unknown mainly due to a lack of quantitative temperature proxies and sufficient suitable continuous high resolution records recently a new proxy for continental temperature reconstructions has been proposed based on the distribution of membrane lipids of bacteria in present day soils j w h weijers s schouten j c van den donker e c hopmans j s sinninghe damste 2007 environmental controls on bacterial tetraether membrane lipid distribution in soils geochimica et cosmochimica acta 71 703 713 and shown to reconstruct annual mean air temperature in this study we applied this new proxy in an attempt to reconstruct the air temperature in high latitude continental areas during the petm by analysis of a marine sedimentary sequence obtained from the lomonosov ridge in the central arctic ocean integrated ocean drilling program expedition 302 site 004 hole a the results indicate a warming of 8 c above background values of 17 c this warming is coincident with a similar rise in sea surface temperatures documented earlier our results thus further confirm the warm conditions in the arctic and point to a strongly reduced latitudinal temperature gradient during the petm 2007 elsevier b v all rights reserved

surface temperature in nw europe during the younger dryas agcm simulation compared with temperature reconstructions during the younger dryas yd the climate in nw europe returned to near glacial conditions to improve our understanding of climate variability during this cold interval we compare an agcm simulation of this climate performed with the echam model with temperature reconstructions for nw europe based on geological and paleoecological records maps for the mean winter summer and annual temperature are presented the simulated winters are consistent with reconstructions in the northern part of the study area a strong deviation is noted in ireland and england where the simulation is too warm by at least 10 c it appears that the n atlantic was cooler than prescribed in the yd simulation including a southward expansion of the sea ice margin the comparison for the summer shows a too warm continental europe in the simulation supposedly these anomalously warm conditions are caused by the agcm s response to the prescribed increased summer insolation the region of maximum summer cooling is similar in both the simulation and reconstruction i e s sweden we suggest that this is due to the local cooling effect of the scandinavian ice sheet compared to the present climate a considerable increase of the annual temperature range is inferred especially for regions close to the atlantic ocean

major changes in glacial and holocene terrestrial temperatures and sources of organic carbon recorded in the amazon fan by tetraether lipids the amazon basin is a major component of the global carbon and hydrological cycles a significant natural source of methane and home to remarkable biodiversity and endemism reconstructing past climate changes in the amazon basin is important for a better understanding of the effect of such changes on these critical functions of the basin using a novel biomarker proxy based on the membrane lipids of soil bacteria with a new regional calibration we present a reconstruction of changes in mean annual air temperatures for the amazon catchment during the last 37 kyr b p biomarkers were extracted from ocean drilling program sediment core odp942 recovered from the amazon fan the amazon fan is a major depository for terrestrial sediments with the advantage that the terrestrial material captured reflects a regional integration of the whole river catchment the reconstructed tropical amazonian temperatures were similar to 5 degrees c cooler at the last glacial maximum similar to 21 degrees c compared to modern values similar to 26 degrees c this is in agreement with previous estimates of tropical continental temperatures in the tropical amazon basin and tropical africa during the last glacial maximum moreover we also illustrate how the soil bacterial membrane lipid record reveals major changes in basin dynamics and sediment provenance during the glacial holocene transition impacting the biomarker reconstructions from similar to 11 kyr onward

genesis of ree minerals in the karstic bauxite in western guangxi china and its constraints on the deposit formation conditions abstract karstic bauxites in western guangxi china comprise two subtypes permian bauxite and quaternary bauxite the quaternary bauxite originated from the breaking up rolling and accumulating of permian bauxite in karstic depressions in quaternary various types of rare earth element ree minerals were discovered during the formation of the permian and quaternary bauxites from the xinxu longhe and tianyang bauxite deposits in this study five types of ree minerals including bastnasite parisite cerianite rhabdophane and churchite were identified bastnasite and parisite are the most abundant and they are widely developed in the permian ore and also present in the quaternary ore obvious variations in bastnasite and parisite ree compositions were observed which is ascribed to distinctions in the source materials in the primary weathering profile from different areas the mode of occurrence of bastnasite and parisite suggests they were mainly precipitated under alkaline and reducing conditions during the permian bauxite forming stage and underwent intensive corrosion in the quaternary churchite was formed during the permian weathering stage under acidic condition both cerianite and rhabdophane occur in fractures within the permian bauxite ore indicating that both formed during the quaternary weathering stage it is considered that the rhabdophane enriched in ce have formed locally in the process of that the ce3 released from bastnasite rapidly entered the rhabdophane lattice before being oxidized to ce4 cerianite was mainly found in association with mn al hydroxides suggesting that the released ce3 was oxidized into ce4 and precipitated cerianite in fractures within the permian bauxite ore mass balance equations reveal a depletion in nearly all rees during the transformation from the permian to the quaternary bauxite ore mainly caused by the dissolution of bastnasite and parisite the genesis of the ree minerals together with the occurrence of other minerals indicates that intensively acidic and oxidizing conditions developed before the formation of the permian bauxite ore towards the end of the permian the conditions became reducing and alkaline favorable for the large scale bauxitization the quaternary bauxite forming stage was characterized by variable ph and eh conditions with acidic ph 4 6 and oxidizing eh 2 conditions at the surface of the exposed permian bauxite ore

cerium anomalies in lateritic profiles the ree geochemistry and mineralogy have been studied in four lateritic profiles one derived from a syenite akongo sw cameroon the others being developed on a gneissic basement and located along a soil toposequence goyoum e cameroon there is a fractionation between lree and hree in the lateritic samples during weathering the weathered residual products being enriched in lree from la to eu and depleted in hree from gd to lu sampled waters are enriched in hree in relation to the syenite host rock a positive ce anomaly has been found systematically at the top of the saprolite beneath a zone of iron oxide accumulation in the laterite up to 2000 ppm ce may be present in the akongo profile cerianite ceo2 is present as very fine coatings in non ferruginous clayey domains primary ree bearing accessory minerals are weathered at the bottom of the profile specifically allanite and apatite are transformed into florencite and rhabdophane but these phases have no ce anomaly all the data are interpreted as the result of the following processes 1 1 ree leaching in a reducing environment 2 2 oxidation of ce3 to ce4 in an oxidizing environment 3 3 deposition of cerium as cerianite whereas the other ree remain in solution

rare earth element mineralogy and geochemistry in a laterite profile from madagascar abstract in this study rare earth element ree distribution has been investigated in a weathering profile from central madagascar combination of bulk rock geochemical data elements and isotopes with mineral characterization reveals a remarkable evolution of the ree abundances and ree minerals in the vertical weathering profile in the fresh tonalite bedrock ree y concentrations are typical of granitoids 299 363 ppm and the main ree minerals are allanite and chevkinite in the c horizon saprolite primary ree minerals disappear and rees are transported via fluid to precipitate rhabdophane group minerals in cracks and pores the presence of sulfate ligands produced by sulfide oxidation may be responsible for the ree speciation as suggested by the composition of the secondary ree minerals rhabdophane group minerals contain up to 9 wt so 3 and 7 wt cao indicating a mixture between rhabdophane sensu stricto ree po 4 h 2 o and tristamite ca u fe iii po 4 so 4 2h 2 o due to intense ca leaching rhabdophane disappears and al phosphates alunite jarosite group are found in the soil cerianite ce iv o 2 also precipitates in the b horizon of the soil mass transfer calculations based on immobile ti indicate significant ree leaching in a horizon with preferential leaching of the heavy ree rees accumulate partly in the b horizon the uniform nd isotope compositions and the constant proportion of immobile elements do not reveal external input in the b horizon total ree y reach 2194 ppm with high ce concentrations 1638 ppm 9 ce bedrock compared to other ree 3 4 ree bedrock tetravalent ce state is dominant in the b horizon and requires oxidizing conditions that likely account for the accumulation of redox sensitive elements in b horizon e g mn fe co under oxidizing conditions cerianite precipitation causes a ce fractionation from other trivalent ree in comparison to the ion adsorption clay of southern china preferential heavy ree enrichment was not observed in the weathering profile another remarkable peculiarity of the studied profile is the occurrence of gd 2 so 6 grains the discovery of this new mineral demonstrates that a natural process exists that that can fractionate ree to such an extent to produce a pure gadolinium end member mineral an understanding of such a mechanisms is crucial for the ree geochemistry of low temperature alteration processes as well as for the formation of ree ore deposits or industrial processing

iron oxyhydroxide and sulphide mineralization in hydrocarbon seep related carbonate submarine chimneys gulf of cadiz sw iberian peninsula this paper aims to investigate the iron mineralization hosted in the submarine hydrocarbon seep related carbonate chimneys from the gulf of cadiz continental slope sw iberia chimneys are made of a general fine groundmass of major fe rich dolomite ankerite and calcite small grains of quartz and phyllosilicates and some foraminifer tests and ostracod shells primary porosity is frequently generated inside foraminifer chambers and ostracod shells and is filled with closely packed microcrystals of iron oxyhydroxide and sulphide minerals forming framboids some extremely peculiar multiframboidal textures are also detected corresponding to microcrystal groups spherical framboids and euhedral crystals without framboidal texture the mineralogy observed is mainly goethite pyrite pseudomorphs traces of tiny grains of pyrite were also observed cubic octahedral and pyritohedral are the habits observed in both minerals chemical analyses of framboids and euhedral crystals display high often erratic amounts of as co ni and mo in oxyhydroxides and mo pb v and co in sulphides versus almost always negligible concentrations of cu and zn a textural geochemical and mineralogical evolution is proposed to explain the coexistence of different morphologies in the multiframboidal texture a growth and aggregation of microcrystals as typical framboidal type mineralogical associations b development of euhedral habits c coalescence and homogenization of the microcrystal into large size euhedral to anhedral crystals and d formation of euhedral crystals or polycrystalline masses with complete loss of framboidal texture along this process an increase of the concentration of fe s mn and ti linked to a decrease in mg si al as p ca and v was observed the study of the iron mineralization in the gulf of cadiz is a first and can give clues to understand the complex geobiological interactions in this and other similar extreme hydrocarbon bearing submarine ecosystems

mineralogical and geochemical features of karst bauxites from poci western henan china implications for parental affinity and bauxitization abstract the poci bauxite deposits in western henan china are hosted in the lower member of upper carboniferous benxi formation unconformably overlying upon the paleokarst surface of the ordovician majiagou formation the orebodies comprise a high grade bauxite horizon characterized by the association of diaspore illite anatase and a basal iron rich horizon diaspore goethite hematite illite anatase sandwiched between the overlying clayey layer illite diaspore goethite anatase and the underlying clayey layer illite diaspore microcline goethite geochemical investigations reveal that rb cs ba cu zn are depleted while b ga bi v sc zr hf nb ta w u and th are enriched in bauxite horizons b is highly enriched in bauxite ores and clays contents 176 1061 ppm and positively associated with sio2 indicating b is mainly hosted in clay components e g dominantly illite which are considered a mixture of authigenic minerals transformed from kaolinites during diagenesis and unaltered detrital minerals mass change calculations reveal that hf zr nb ta u th sc cr and ga are stable relative to tio2 during the bauxitization process indicating these elements are mainly associated with anatase and diaspore the bauxite horizons and the underlying clays are more enriched in total ree contents rees and display more intense lree hree fractionation than the overlying clays provenance analysis shows that parental materials of poci bauxites were mainly derived from felsic dominated igneous rocks along the southern margins of the north china craton with minor contribution from siliciclastic sedimentary rocks and argillaceous components of underlying carbonates a conceptual model is proposed for the formation and evolution of poci bauxites uplift caused by the north qinling orogenesis along the southwestern margin of ncc led to the formation of karstic topography allowing aluminum rich source materials to be transported to the low karst plain and transformed into incipient bauxites under hot and humid tropical conditions when the platform was submerged fe2 ions were released from fe al oxides hydroxides under the reducing conditions associated with bacteria activity in an organic rich environment and redeposited as pyrites and siderites generating a high grade bauxite horizon and an iron rich bauxite horizon this marine modification resulted in further aluminum enrichment of bauxite ores

geochemical and mineralogical characteristics of ion adsorption type ree mineralization in phuket thailand geochemical and mineralogical studies were conducted on the 12 m thick weathering profile of the kata beach granite in phuket thailand in order to reveal the transport and adsorption of rare earth elements ree related to the ion adsorption type mineralization the parent rock is ilmenite series biotite granite with transitional characteristics from i type to s type abundant in ree 592 ppm ree are contained dominantly in fluorocarbonate as well as in allanite titanite apatite and zircon the chondrite normalized ree pattern of the parent granite indicates enrichment of lree relative to hree and no significant ce anomaly the upper part of the weathering profile from the surface to 4 5 m depth is mostly characterized by positive ce anomaly showing lower ree contents ranging from 174 to 548 ppm and lower percentages of adsorbed ree from 34 to 68 compared with the parent granite in contrast the lower part of the profile from 4 5 to 12 m depth is characterized by negative ce anomaly showing higher ree contents ranging from 578 to 1 084 ppm and higher percentages from 53 to 85 the negative ce anomaly and enrichment of ree in the lower part of the profile suggest that acidic soil water in an oxidizing condition in the upper part mostly immobilized ce4 as ceo2 and transported ree3 downward to the lower part of the profile the transported ree3 were adsorbed onto weathering products or distributed to secondary minerals such as rhabdophane the immobilization of ree results from the increase of ph due to the contact with higher ph groundwater since the majority of ree in the weathered granite are present in the ion adsorption fraction with negative ce anomaly the percentages of adsorbed ree are positively correlated with the whole rock negative ce anomaly the result of this study suggests that the ion adsorption type ree mineralization is identified by the occurrence of easily soluble ree fluorocarbonate and whole rock negative ce anomaly of weathered granite although fractionation of ree in weathered granite is controlled by the occurrence of ree bearing minerals and adsorption by weathering products the ion adsorption fraction tends to be enriched in lree relative to weathered granite

genesis of the guangou karstic bauxite deposit in western henan china abstract the guangou bauxite deposit in western henan china is located in the north china block and to the north of the north qinling orogenic belt the orebody is hosted within the lower member of the carboniferous benxi formation which overlies unconformably upon the ordovician majiagou formation in the lower member of the benxi formation the bauxite orebody with a diaspore illite anatase mineral assemblage is sandwiched between underlying ferric clay illite hematite goethite and overlying top clay kaolinite quartz goethite according to field observations and geochemical evidence including trace and rare earth element ree compositions especially zr hf ratios the ferric clays were weathered from the underlying argillaceous limestones in the majiagou formation during this weathering process trace elements s zn ni cr v sc f ba and be are depleted li rb and b are enriched and zr hf bi ta ga nb and th are relatively immobile rees exhibit evident differentiation with enrichment of la ce pr and nd and depletion of gd tb dy ho er tm yb and lu the bauxite formed in weak reducing slightly basic water conditions according to the geneses of coexisting diaspore and anatase and it was altered during the epigenetic and second exposure periods forming kaolinite and goethite respectively interelemental relationship analyses of the ores suggest that the elemental behaviors of trace elements and rees in the bauxitization process are mainly controlled by the mineral compositions in bauxite ore and chemical properties of the elements for instance zircon rutile and anatase contain zr hf nb ta w and u based on geochemical evidence together with age data and chemical compositions of the detrital minerals both distant igneous rocks in the plate margin and paleozoic carbonates and precambrian rocks inside north china block provide the miscellaneous material for the bauxite ore and the top clay

metallogenic and tectonic implications of detrital zircon u pb hf isotopes and detrital rutile geochemistry of late carboniferous karstic bauxite on the southern margin of the north china craton abstract late carboniferous bauxite is widely developed on the north china craton ncc and is referred to as the g layer bauxite the bauxite ores of the southern ncc are closely related to the tectonic evolution of the ncc and its neighboring north qinling belt nqb to the south in this study based on the geological and mineralogical observations we used the u pb and hf isotopes of detrital zircons and chemical compositions of detrital rutiles from the gunziying and shibanhe bauxite deposits along the southern margin of the ncc to study the metallogenic process of bauxite ores and their tectonic implications one and two bauxite ore layers were observed in the gunziying and shibanhe bauixte deposits respectively the bauxite ore is dominated by diaspore illite anatase kaolinite pyrite zircon and rutile analyses of detrital zircons revealed that the largest group 432 515 ma at a peak age of 450 ma is spread throughout the late carboniferous bauxite deposits with ehf t values of 5 7 21 4 similar to the zircons from the nqb similarly the detrital zircons with peak ages of 950 ma and age clusters at 1 1 ga 1 3 ga and 1 8 ga as well as those ranging in age from 635 to 797 ma also exhibited ehf t values similar to the zircons from the nqb in addition the results suggested that 62 73 and 75 88 2 of detrital rutiles showed metapelitic protoliths and amphibolite eclogite facies temperatures respectively while 23 27 and 10 11 8 exhibited metamafic protoliths and granulite facies temperatures respectively based on the results above we propose that the provenance of the bauxite ores on the southern margin of the ncc is primarily from the nqb the dominant contributors were the neoproterozoic kuanping group and the meso neoproterozoic qinling group the archean proterozoic metamorphic rocks in the paleo uplifts of the ncc were also likely involved in the bauxite formation a probable outline of the bauxite formation process on the southern ncc former weathered residuals and subsequent deposition is proposed and a reasonable interpretation that the nqb was accreted to the ncc in the late carboniferous and formed a northward lying slope basin within the ncc is supported

application of bacterial glycerol dialkyl glycerol tetraethers gdgts to develop modern and past temperature estimates from new zealand lakes abstract branched isoalkyl glycerol dialkyl glycerol tetraethers gdgts of bacterial origin have been found in high abundance in both modern and glacial sediments of new zealand south island freshwater lakes covering a wide range of altitude 101 2000 m like isoprenoid gdgts of archaeal origin they provide excellent potential for temperature assessment for this study their distribution patterns mbt methylation ratio and cbt cyclisation ratio of branched gdgts have been successfully used to develop an initial temperature calibration for the study area and to provide preliminary palaeo environmental interpretations mbt data from modern lake sediments correlate well with measured annual air temperature r2 0 74 enabling a regional calibration for reconstructing palaeotemperatures for fossil samples mbt derived palaeotemperatures for alpine lake calibrated against mean annual temperature were determined for the last glacial during an early cold phase between 29 000 and 26 000 years bp and for later less cold phases between 23 000 and 18 000 years bp compared with the modern temperature regime the mbt data indicate a decrease of ca 5 6 and 2 8 c respectively during this time modern and past mbt derived temperatures correlate with chironomid based temperature reconstructions in the area archaeal gdgts commonly used for the tex86 index are abundant in fossil sediments alpine lake but scarce in modern sediments hindering a new local calibration for this palaeotemperature proxy

ree fractionation during granite weathering and removal by waters and suspended loads sr and nd isotopic evidence very few studies deal with ree rare earth element mobility within the system soil soil solution streamwater in this article we try to characterize the fractionation and the migration of the ree in a granite derived soil system located in a small catchment of the vosges mountains icp ms and tims measurements were performed on both solid samples fresh granite soil and suspended load of the stream and waters soil solutions springwater and streamwater to determine their respective ree concentrations and sr and nd isotopic compositions the paas normalized ree pattern of the bedrock is characterized by a strong depletion in hree heavy ree and a negative eu anomaly 0 46 similarly the granite normalized ree distribution patterns of the soil samples show hree depletions that become more important with decreasing depth the correlative behavior between p2o5 th and ree with depth indicates that besides apatite other phosphate minerals such as monazite are the most important phases controlling the th and ree budget in the soil profile on the other hand at greater depth zircon seems to be another important mineral phase controlling especially the hree enrichment as shown by the positive relationship between zr content and the yb ho ratio different grain size fractions show similar ree distribution patterns and are only weakly fractionated compared with bulk soil sample however the finest fraction 0 20 m is more enriched in sr and ree suggesting a stronger concentration of ree carrying minerals in this fraction the suspended and dissolved load of the stream show as a whole an enrichment in hree if compared with the granite or with the different soil samples however compared with the uppermost soil samples the suspended load is significantly more enriched in hree its ree distribution pattern is more similar to that of the finest fraction of the deeper soil sample and to the fresh granite thus most probably the ree of the suspended load originated from a source with ree characteristics found in the deep soil horizons this source might have been situated in the uppermost soil profile which is actually ree depleted the weathering process can be compared with a leaching experiment where the waters correspond to the leachate and the soil to the residual phase of the granite the sr isotope data indicate that the suspended load originates from the finest soil fraction the sr and nd isotopic data of the suspended load suggest that it contains up to 3 sr and nd from apatite and up to 97 from feldspar most of the sr and nd in the waters originate from apatite leaching or dissolution

onset of long term cooling of greenland near the eocene oligocene boundary as revealed by branched tetraether lipids the eocene oligocene e o boundary interval is considered to be one of the major transitions in earth s climate witnessing the fi rst major expansion of the east antarctic ice sheet however the extent of the associated climatic cooling especially for high northern latitude continental landmasses is poorly constrained in this study we reconstruct the fi rst mean annual air temperature maat for the greenland landmass during the late eocene and early oligocene by applying a new proxy based on the distribution of branched tetraether lipids derived from soil bacteria preserved in a marine sediment core from the greenland basin the temperature estimates are compared with a composite continental temperature record based on bioclimatic analysis of pollen assemblages both proxies reveal comparable late eocene maats of 13 15 c and a gradual long term cooling of 3 5 c starting near the e o boundary these data are in agreement with other maat reconstructions from northern midlatitude continents and suggest a general cooling of the northern hemisphere during the e o transition

episodic mineralization of hydrothermal illite in the soultz sous forets granite upper rhine graben france episodic and localized illite mineralization is documented in the hydrothermally altered soultz sous forets granite upper rhine graben france separated grain size fractions of altered granite and argillite vein samples contain mixtures of 2m1 and 1m trans vacant illite varieties the platy pseudohexagonal 2m1 illite phases dominate the vein fillings whereas the 1m illite occurs largely as a fibrous pore filling variety which is particularly abundant in the granite matrix multiple phases of fluid injections into the granite body have resulted in different illite assemblages each sample containing a mixture of polytype generations formed during different crystal growth events on the basis of mineralogical and k ar isotopic constraints the ages of these vein mineralizing events are determined by plotting the k ar values of the various grain size fractions against polytype abundance and the fitted volume weighted crystallite thickness distributions the results suggest a permian age for the formation of the studied argillite veins characterized by successive injections of hydrothermal fluids secondary episodes of illite crystallization occurred during jurassic and cretaceous or even younger times in both the veins and the granite matrix there are indications that the polytype structure and composition of illite were strongly influenced by variations in fluid chemistry and the degree of fluid rock interaction as the granite was progressively sealed during post variscan episodic hydrothermal activity

distributions of branched gdgts in a tropical lake system implications for lacustrine application of the mbt cbt paleoproxy branched glycerol dialkyl glycerol tetraether gdgt lipids are abundant and ubiquitous in lake sediments potentially allowing for a paleolimnological application of the so called mbt cbt proxy methylation index of branched tetraethers cyclization ratio of branched tetraethers to investigate the origin and characteristics of these compounds in lacustrine environments we examined the distributions of gdgts in soils river sediments and lake sediments from lake towuti on the island of sulawesi indonesia we found significant differences in the degree of methylation and cyclization expressed by way of the mbt and cbt indices between the soil samples and the aquatic samples suggesting that there may be in situ production of gdgts in the aquatic environment based on these findings we urge caution in the application of the mbt cbt paleoproxy to lake sediments and encourage more rigorous study of these compounds in freshwater environments

mean july temperatures during the younger dryas in northwestern and central europe as inferred from climate indicator plant species abstract we estimated minimum mean july temperatures in northwestern and central europe during the younger dryas 10 950 10 15014c yr b p from distributions of climate indicator plant species which were reconstructed from 140 pollen and plant macrofossil diagrams paleobotanical records mainly from the central and eastern part of the study area show that the coldest conditions occurred early in the younger dryas before 10 55014c yr b p for this phase mean july temperatures at sea level of around 10 c are suggested for the northern part of the british isles and for ice free scandinavia we estimated a mean july temperature of 12 c for central england the netherlands and northern germany the 13 c mean july isotherm largely based on the modern distribution oftypha latifolia was most probably located in southern england belgium central germany and poland the reappearance of thermophilous elements in the records after 10 55014c yr b p suggests a summer warming at least temporarily of 1 to 2 c in the study area the reconstructed temperatures are comparable with temperature estimates based on beetle data however they appear rather high when compared with estimates based on glaciological evidence

mineralogical and geochemical evolution of the bidgol bauxite deposit zagros mountain belt iran implications for ore genesis rare earth elements fractionation and parental affinity the present study focuses on the late cretaceous bidgol bauxite deposit in the zagros simply fold belt sw iran the orebody is located in the eroded major nw se trending koh e hosseyn anticline and hosted as discontinuous stratified layers and lenses within the upper member of the cenomanian turonian sarvak formation detailed mineralogical analysis reveals that diaspore hematite goethite anatase clinochlore chamosite and calcite are the major mineral components accompanied by minor amounts of detrital and ree bearing minerals such as rutile zircon and parisite the ore texture suggest that the bauxite material has an authigenic origin but in some parts it has been transported short distances from a primary in situ environment and redeposited in karstic depressions the spheroidal pisolites of the bidgol bauxite formed under conditions of low water activity favouring the formation of large diaspore cores and a single dry to wet climatic fluctuation the mass change calculations relative to the immobile element ti show that elements such as si fe mg k na and sr are leached out of the weathered system al ni zr ga cr and ba are concentrated in the residual system and hf ta co rb cs be and u are relatively immobile during the bauxitisation processes the nb th y v sc sn and ree are relatively immobile in the initial stage of bauxitisation processes in the bauxite ores but were slightly mobile at the later stage of bauxitisation geochemical data reveal progressive enrichment of the ree and intense lree hree fractionation toward the lower parts of the bauxite profile cerium behaves differently from the other rees especially lree and show positive anomalies in the upper horizons that gradually become negative in the deeper parts of the profile the distribution and fractionation of trace elements and rees during the bauxitisation process in the bidgol deposit are mainly controlled by the presence of ree bearing minerals fluctuations in soil solution ph ree ionization potential and the presence of bicarbonates or organic matter geochemical analyses confirm a protolith contribution from the bedrock argillaceous limestone and suggest that the source material for the bidgol bauxite was provided from a siliciclastic material derived from a continental margin the mid turonian uplift led to the formation of karstic topography rubbly breccia and a layer of ferruginous argillaceous debris that was affected by lateritic weathering under humid tropical climate subsequently mobile elements are removed from the profiles while al fe and ti are enriched resulting in the formation of the pristine bauxite materials when the platform subsided into the water again the pristine bauxitic materials were partly converted to bauxite during the exposure of bauxite orebodies on the limbs and crests of anticlines and subsequent eroding and accumulation in the karstic depressions during folding and faulting in oligocene miocene important factors such as intensity of the weathering drainage and floating flow may have improved the qualities of the bauxite ores

oxygen isotope and paleobotanical estimates of temperature and δ18o latitude gradients over north america during the early eocene empirical estimates of climate parameters such as mean annual temperature mat are essential to describe both ancient climate and to ground truth climate model simulations of past climates in terrestrial settings no single proxy record is able to provide detailed temporal yet geographically widespread information and it thus becomes essential that paleoclimatic information obtained from different proxies be comparable as an example of how to compare estimates and to illustrate what can be learned by doing so we measured oxygen isotope ratios of phosphate in the tooth enamel of fossil mammals and the body scales of freshwater fish in order to estimate the mean annual temperature mat in which they lived the samples were collected from paleogene rocks of the bighorn green river and powder river basins of wyoming earliest eocene samples provide mat estimates that are similar to mat estimates for the same times and areas obtained from leaf margin analysis furthermore isotopic data from the paleocene eocene thermal maximum petm which has not yet yielded fossil floras indicate a significantly higher mat of 26 c we also used temperature estimates obtained by both methods to investigate paleoelevation and to reconstruct geographic patterns of mat over north america for the early eocene larger laramide basins have higher temperatures and lower inferred elevations compared to associated volcanic highlands where cooler temperatures are consistent with substantial elevations in turn latitudinal gradients in temperature indicate that warming centered on polar regions played an important role during the eocene hothouse lastly we show that the reconstructed eocene relation between oxygen isotope ratios of precipitation and mat is significantly different from the modern relation between these two variables because the relation has changed over time the modern correlation should not be used to estimate paleo mat from measurements of oxygen isotope ratios in fossil material

ce anomalies in the textural components of upper cretaceous karst bauxites from the apulian carbonate platform southern italy the chemical and mineralogical composition of upper cretaceous apulian karst bauxites southern italy and their textural components i e ooids and matrix has been studied the bulk samples are composed of boehmite hematite anatase and kaolinite the samples collected along a vertical profile show a downward enrichment for the elements rb sr ba ni and cr a similar distribution is observed in deposits bauxitized in situ at the expense of matrix like material collected in the karst zone the ooids consist mainly of hematite with minor boehmite and anatase whereas in the matrix boehmite prevails on hematite kaolinite and anatase in the void fillings in the matrix there is a ca fluorocarbonate having a ce ce of 5 8 the ooids with the exception of ce are enriched in ree and show a higher la yb ch ratio relative to the matrix the matrix exhibits a large positive ce anomaly whereas the ooids have negative ce anomaly the ce fractionation between the textural components can be explained assuming 1 ce oxidation and cerianite precipitation in the uppermost part of the deposits 2 scavenging of ree from ce depleted percolating solutions by the iron oxide inducing both ree enrichment and ce negative anomalies in ooids 3 remobilization of cerium as fluoride complex as a consequence of more acidic conditions in the uppermost part of the deposit and precipitation of ce3 as fluorocarbonate mineral toward the carbonate bedrock barrier at alkaline ph alternatively the cerium remobilization possibly as a carbonate fluoride complex could be due to an eh decrease favoured by a rise of the groundwater level

rare earth element contents of jurassic fish and reptile teeth and their potential relation to seawater composition anglo paris basin france and england the rare earth element ree chemistry of jurassic shelf seawater from western europe anglo paris basin was investigated by analyzing the fish and reptile teeth deposited in shallow to deeper water 200 m environments ree patterns in apatites are controlled by the host sediments vertebrate teeth sampled from the siliciclastic sediments calcareous sandstones and shales show flat shale normalized ree patterns that reflect the dominant influence of the continental source from which the ree were derived carbonate deposits protected from the clastic sources contain fish and reptile teeth whose ree patterns reflect more accurately the ree composition of the overlying water column the ree patterns are similar through the bajocian to the oxfordian and are characterized by a depletion in heavy rare earth element dy ybn 1 8 5 0 compared to modern seawater compositions dy ybn 0 8 0 9 the fractionations among hree in the jurassic seawater are more efficient than in modern oceans and increases with depth instead of decreasing these hree removal processes operated as early as the paleozoic and disappeared during the late cretaceous the fractionation of hree relative to lree is correlated with the increasing depth of the basin as indicated by two independent criteria that are the sedimentary structures and the oxygen isotope composition of coexisting brachiopods the dy ybn ratio of the marine biogenic phosphates can be used as a proxy of paleo water depths at the scale of a water mass ce anomalies ce in biogenic apatite bearing limestones are variable and systematically negative relative to modern surface seawater and bathonian values mean ce 0 63 0 10 weak ce anomalies during the callovian mean ce 0 21 0 09 suggest the onset of more reducing conditions this redox change coincided with an increase of seawater temperatures as suggested by the oxygen isotope compositions measured on the same teeth we speculated that the callovian low ce could result from a decrease in the po2 due to the warming of seawater

geochemistry mineralogy and geochemical mass balance on major elements in two peat bog profiles jura mountains switzerland abstract the mineralogical and chemical composition of peats from two sphagnum bogs in the franches montagnes region jura mountains switzerland were compared the peats in the top 102 cm at etang de la gruere egr represent 2110 years of peat formation compared with 1730 years for the first 84 cm at tourbiere de genevez tge scandium was used as a conservative tracer to distinguish between the primary sources of major elements to the bogs atmospheric deposition of soil derived aerosols egr and tge physical incorporation of elements along with mineral matter from the underlying sediments tge and adsorption or complexation by the peat following diffusion from groundwater tge these results support previous findings which showed that the egr core 102 cm is exclusively ombrogenic compared with tge where the peats below approx 30 cm become predominantly minerogenic the modern rates of sc accumulation past 100 years are similar in the two cores 39 g m 2 a 1 at egr versus 52 g m 2 a 1 at tge however comparison with deeper sections of the egr core reveals that the present day rates of atmospheric sc deposition are nearly 3 times greater than the long term average rate reflecting the higher concentrations of soil derived atmospheric aerosols today the rates of sc accumulation in the tge core are slightly higher than at egr this reflects the incorporation of mineral matter from the underlying sediments in the deeper minerogenic peats at tge the long term rates of fe and ca accumulation are 5 and 7 times higher respectively than in the egr core these fluxes greatly exceed the difference in sc flux and cannot be explained by the differences in amount of mineral matter in the peats these enrichments require an independent explanation and are most likely the result of adsorption and or complexation of cationic ca and fe species diffusing from deeper layers in the profile the mineralogical composition of the ash is mainly quartz 60 90 with feldspar 5 15 and muscovite 5 15 although various other minerals 5 10 are commonly present biogenic si represents another important fraction of ash and is abundant 30 70 at discrete depths the vertical profiles showed no significant changes in mineralogy with depth assuming a constant composition of source materials the lack of progressive mineralogical change suggests that the fine grained silicates supplied by soil dust have not been measurably weathered during the past two millennia a number of peaks in fe sc are found in both cores above peaks in ash content and density these appear to correspond with temporal fluctuations in wet dry conditions accumulation of fe oxides during dry periods and leaching during wetter conditions

the effect of maturity and depositional redox conditions on archaeal tetraether lipid palaeothermometry recently we proposed a new organic sea surface temperature proxy tex86 based on the distribution of archaeal tetraether lipids here we have examined the effect of oxic degradation and maturity on this new temperature proxy our results show that oxic degradation does not appear to affect the tex86 values within the analytical error hydrous pyrolysis experiments suggest that thermal maturity does have an effect on tex86 sediments with relatively high amounts of 22s hopanes 22s 22s 22r ratios 0 1 or 17 21 h hopanes ratios 0 5 may have tex86 values which are biased towards lower values and thus lower sea surface temperatures

metallogeny of the large scale carboniferous karstic bauxite in the sanmenxia area southern part of the north china craton china abstract above two billion tons of bauxite were formed during the exposure of the north china craton ncc in 445 300 ma mineralogical geochemical and isotopic analyses of karstic bauxite deposits in the sanmenxia area situated within southern ncc were conducted to explore the genetic processes of carboniferous bauxite the bauxite contains three layers a lower fe bearing claystone layer a middle bauxite ore layer and an upper claystone layer fe bearing claystone is dominated by illite and hematite in the uplift and illite siderite and pyrite in the depression bauxite ore is composed of diaspore illite pyrite and anatase and the upper claystone consists of illite diaspore and anatase distinct pyrite 34s values 11 7 15 2 and 11 5 to 1 0 illite 87sr 86sr i 0 711917 0 713588 and 0 708000 0 711057 and end t 12 2 to 11 4 and 11 8 to 9 7 values and the immobile elemental ratios were obtained between the lower fe bearing claystone and upper bauxite ore and claystone together with chemistry of detrital rutile it is denoted the fe bearing claystone was formed from the underlying limestone whereas the bauxite ore and claystone were derived from both igneous rocks along craton margin and regional precambrian metamorphic rocks the visible microorganisms and wide development of framboidal pyrite with negative 34s within the bauxite ore provide evidences of microbial activity during bauxite formation bio leaching process after the deposition of allochthonous source materials caused the downward migration of ions al3 fe2 ti4 ree3 etc these ions encountered an alkaline and reducing condition in the karstic depression forming diaspore pyrite and anatase and ree enrichment at the bottom of bauxite ore this large input of raw materials warm and humid climate and microorganisms led to large scale bauxite formation in the ncc during late carboniferous

revised phosphate water fractionation equation reassessing paleotemperatures derived from biogenic apatite oxygen isotopes of biogenic apatite have been widely used to reassess anomalous temperatures inferred from oxygen isotope ratios of ancient biogenic calcite more prone to diagenetic alteration however recent studies have highlighted that oxygen isotope ratios of biogenic apatite differ dependent on used analytical techniques this questions the applicability of the phosphate water fractionation equations established over 25 years ago using earlier analytical techniques to more recently acquired data in this work we present a new phosphate water oxygen isotope fractionation equation based on oxygen isotopes determined on fish raised in aquariums at controlled temperature and with monitored water oxygen isotope composition the new equation reveals a similar slope but an offset of about 2 to the earlier published equations this work has major implications for paleoclimatic reconstructions using oxygen isotopes of biogenic apatite since calculated temperatures have been underestimated by about 4 to 8 c depending on applied techniques and standardization of the analyses

petrographic characteristics of the wyodak anderson coal bed paleocene powder river basin wyoming u s a abstract six lithofacies of the thick 30 m wyodak anderson subbituminous coal bed of the fort union formation paleocene powder river basin wyoming can be delimited using megascopic and petrographic data previous lithofacies analysis of the rock types associated with the wyodak anderson bed suggested that raised peat accumulated in restricted parts of an inland flood plain the peat bodies were separated by deposits of contemporaneous possibly anastomosed channels in this study megascopic descriptions from four mine highwalls of the wyodak anderson coal bed were found to be similar to facies defined by microscopic data from core and highwall samples the data indicate that the upper and lower parts of the coal bed are rich in preserved wood remains for instance humotelinite whereas the middle part of the bed contains comparatively larger amounts of material that resulted from degradation and comminution of the peat e g eugelinite the facies are interpreted to be the result of different chemical and biological environments at the time of peat formation

branched glycerol dialkyl glycerol tetraethers in lake sediments can they be used as temperature and ph proxies a series of surface sediments from 82 lakes of variable water depth and size was analyzed for glycerol dialkyl glycerol tetraethers gdgts in order to investigate the potential of the mbt cbt methylation ratio cyclization ratio of branched tetraethers as a continental palaeothermometer in lacustrine environments branched gdgts dominated in most sediments as indicated by the high branched vs isoprenoid tetraether bit values we observed that cbt and mbt varied substantially mean annual air temperature maat reconstructed and ph values were calculated using the cbt and mbt values and the calibration from the global soil data set the mbt cbt inferred temperatures were considerably lower than measured values nevertheless there was a significant correlation between maat reconstructed and maat observed on site although there was still considerable scatter r2 0 47 lacustrine sediments integrate organic remains of organisms in a lake and its drainage basin thereby offering a unique opportunity for calibrating mbt and cbt as small scale variability is averaged out since the source of the branched gdgts in the lake sediments is ambiguous it is not clear whether only temperature and ph in the catchment area are the driving factors therefore even in lake sediments with high concentrations of branched gdgts the straightforward application of mbt cbt as palaeoproxies may be difficult given the uncertainties regarding their source and origin

contribution to the geochemistry of the rare earth elements in the karst bauxite deposits of yugoslavia and greece abstract distribution of the rare earth elements ree including la lu y along vertical profiles is presented for four well studied karst bauxite deposits from yugoslavia and greece for one deposit from jamaica la and y contents are given all deposits a downward enrichment of the ree culminating at the base where authigenic ree minerals have been formed this ree pattern is characteristic for karst bauxites formed in situ through the bauxitization of argillaceous material collected in karstic depressions in this way the highest enrichment of the ree in the sedimentary cycle has been achieved both light ree lree and heavy ree hree were mobile during the bauxitization process and were concentrated at the alkaline barrier of the carbonate footwall in four out of five studied deposits the ratios lre hree and la y in bauxites decrease downwards showing an enrichment of the hree relative to lree a further fractionation of the ree took place in the formation of authigenic ree minerals which exhibit a very high enrichment of lree relative to hree in spite of this these minerals and bauxites in four studied deposits have a general similarity of the ree distribution patterns which indicate a close genetic relationship

origin and geochemical evolution from ferrallitized clays to karst bauxite an example from the lower cretaceous of ne spain abstract four outcrops of lower cretaceous barremian karst bauxites located in teruel ne spain were analysed the deposits show a heterogeneous chaotic lithostructure consisting of pisolitic bauxite blocks embedded in lateritic red clays filling karst cavities the research has focused on the geochemical study of major minor and trace elements including some critical to industry of both the bauxites and clays the objective was to investigate the bauxite precursor material and to characterize the system s geochemical evolution geochemical analyses were carried out by inductively coupled plasma optical emission and mass spectroscopy an absolute weathering index has been calculated to estimate element mobility assuming ti as an immobile element and the upper continental crust ucc as parent material further selected samples were observed by field emission scanning electron microscopy the data indicate that both the bauxites and red clays originated by intense chemical weathering from more mafic argillaceous sediments than the ucc ongoing weathering caused the bauxitization of the upper parts of the original profile preventing the lower parts from being bauxitized thus producing the ferrallitized clays underlying the pisolitic bauxites subsequent karst reactivation gave rise to the current lithostructure ferrallitization is related to fe sc and v enrichment on the other hand although bauxites are relatively enriched in some elements compared to clays the more intense chemical weathering associated with bauxitization led to chemical homogenization and widespread element depletion during the bauxitization al ti zr cr and probably hf and the critical element nb behaved as more immobile elements in the system bauxitization also enhanced homogenization and depletion of the ree which is more pronounced for the lree hree trends seem to be partly related to the concentration of ti oxides in the bauxites whereas p bearing phases more frequent in the clays control the lree subsequent to bauxitization partial kaolinization of the bauxite took place related to the circulation of acid solutions that also caused the karst reactivation these late processes caused some al depletion in the bauxites and enhanced fe loss together with v and to a lesser extent ge

comparison of instrumental and gdgt based estimates of sea surface and air temperatures from the skagerrak sea surface temperatures ssts and annual mean air temperatures mats are estimated for the last 200 years from glycerol dialkyl glycerol tetraethers gdgts proxies in a marine sediment core from the skagerrak off southern norway the reconstructed values compare well with annual ssts and summer air temperatures obtained from composite regional instrumental records the results provide further confidence in the application of proxies based on gdgts to estimate past temperatures

a review on the potentiality of rare earth elements to trace pedogenetic processes abstract this review aims at considering the use of rees to trace pedogenetic processes in order to quantify the respective contribution of the successive processes on pedogenesis we first consider the origins and contents of rees in soils to assess their natural occurrence and tackle the common data treatment used to interpret their concentrations we review subsequently the impact of the different pedogenetic processes on the fate of rees in soils from their release into a soil solution by primary mineral heavy minerals phosphates silicates and carbonates dissolution during weathering to their fixation on or into main ree bearing secondary minerals clay minerals fe mn oxides and carbonates then their mobilization by plant recycling and organic matter and finally the impact of argilluviation and redox processes on their fractionation we conclude that rees much more than other trace elements can interestingly trace the considered processes that are encountered in a large diversity of non polluted soils arising from diverse parent materials weathering generally fractionates rees and accounts for a significant part of the variation in the initial ree stock of the soils plant recycling induces a weak mobilization of rees and their accumulation in topsoil argilluviation can be traced using the mree enrichment and the eu anomaly of the clay minerals redox processes can be traced by the ce anomaly caused by the precipitation of cerium on mn oxides to use rees as tracers of pedogenetic processes we recommend to i precisely characterize the ree bearing minerals ii adapt the choice of reference s for normalization and iii perform mass balance calculations

mineralogical and geochemical studies of boron rich bauxite ore deposits in the songqi region sw henan china the songqi region sw henan is an important bauxite province in china the bauxite ore deposits occur unconformably on the top of middle ordovician argillaceous carbonates the bauxite ores from the songqi region are characterized by unusually high boron contents in this paper we report the mineralogical and chemical compositions of selected bauxite ores from the region these new data together with existing geochemical data of soils in the region are used to evaluate the origin of boron enrichment in the bauxite ores the compositional characteristics of tourmaline in the bauxite ores suggests that this mineral was likely derived from a meta sedimentary protolith mass balance calculation reveals that tourmaline only accounts for a small portion of boron in the bauxite ores the majority of boron in the ores must occur in other forms possibly by ion absorption on the surfaces of diaspore and clay minerals in the songqi region the precambrian meta sedimentary rocks are known to contain abundant tourmalines whereas the cambrian ordovician argillaceous carbonates and the upper proterozoic shales are all enriched in boron in free ion state we suggest that these rocks provided tourmaline and boron ion to the bauxite deposits in the region most known bauxite deposits in the songqi region occur at the margins of boron rich soil domains suggesting that boron in soils is a potential exploration indicator for unknown bauxite deposits in this region

molecular and isotopic stratigraphy in an ombrotrophic mire for paleoclimate reconstruction a 40 cm deep sphagnum dominated peat monolith from bolton fell moss in northern england was systematically investigated by lipid molecular stratigraphy and compound specific 13c and d analysis using gas chromatography gc gc mass spectrometry gc ms gc combustion isotope ratio ms gc c irms and gc thermal conversion irms gc tc irms techniques 210pb dating showed the monolith accumulated during the last ca 220 yr a period encompassing the second part of little ice age while the distributions of lipids including n alkan 1 ols n alkan 2 ones wax esters sterols n alkanoic acids alkandioic acids and hydroxy acids display relatively minor changes with depth the cooler climate event was recorded in the concentrations of n alkanes and organic carbon cpi values of n alkanes and n alkanoic acids and the ratio of 5 n alkylresorcinols sterols superimposed on the fossil fuel effect the relatively cooler climate event was also recorded by 13c values of individual hydrocarbons especially the c23n alkane a major compound in certain sphagnum spp the d values of the c29 and c33n alkanes correlated mainly with plant composition and were relatively insensitive to climatic change in contrast the c23n alkane displayed variation that correlated strongly with recorded temperature for the period represented by the monolith agreeing with previously reported deuterium records in tree ring cellulose spanning the same period in scotland germany and the usa with more negative values occurring during the second part of little ice age these biomarker characteristics including the compound specific 13c and d records provide a new set of proxies of climatic change potentially independent of preserved macrofossils which will be of value in deeper sections of the bog where the documentary records of climate are unavailable and humification is well advanced

quantitative reconstruction of younger dryas to mid holocene paleoclimates at le locle swiss jura using pollen and lake level data abstract pollen and lake level data from le locle in the swiss jura were used to quantitatively reconstruct climatic parameters for the younger dryas event and the first half of the holocene period the younger dryas cold event at le locle was characterized by i a general trend toward a slight increase in summer temperature and a decrease in annual precipitation and ii a marked drying phase at ca 11 900 cal yr b p that occurred between two wetter ones further phases of major deficit in moisture occured at ca 11 500 cal yr b p younger dryas holocene transition 10 800 cal yr b p 8700 cal yr b p and 6500 cal yr b p climatic parameters reconstructed here suggest that phases of higher lake level developing at ca 12 500 12 000 11 750 11 600 11 200 10 900 synchronous with the preboreal oscillation 10 400 8900 8400 8300 possibly related to the 8200 yr event and 7800 7000 cal yr b p coincided with an increase in annual precipitation a decrease in summer temperature and a shorter growing season conversely periods of low lake level corresponded to a decrease in annual precipitation an increase in summer temperature and a longer growing season this general pattern could have resulted from alternate southward northward displacements of the atlantic westerly jet

late paleocene early eocene climate changes in southwestern wyoming paleobotanical analysis the warmest global temperatures of the cenozoic era occurred in early eocene time following a warming trend that started in late paleocene time the greater green river basin of southwestern wyoming is one of the best areas in the rocky mountains for paleobotanical investigation of the paleocene eocene climatic transition intensive sampling has resulted in the recovery of an estimated 189 species of plant macrofossils from the tiffanian clarkforkian wasatchian and bridgerian land mammal ages the leaf morphologies and taxonomic affinities of these fossils were used in combination with other indicators to evaluate paleocene eocene climates following cool humid conditions in the tiffanian the clarkforkian was humid and subtropical and several plant families with modern tropical affinities appeared however as in the tiffanian clarkforkian floras had low diversity and were dominated by a single species in the birch family mean annual temperature mat rose from an estimated 12 c in the tiffanian to 19 c in the clarkforkian while mean annual precipitation map for the tiffanian and clarkforkian is estimated to have been 130 150 cm little fossil plant material is preserved from the latest clarkforkian or the earliest wasatchian which is thought to have contained an interval of cooling and drying followed by renewed warming by the middle wasatchian the time of the cenozoic thermal maximum the inferred mat was about 21 c and the map was near 140 cm a second influx of plant families with tropical affinities appeared in the area and diversity increased significantly but most plant families known from the clarkforkian persisted species turnover from the clarkforkian to the wasatchian was greater than 80 a second turnover of more than 80 of species but not families from the wasatchian to the early bridgerian accompanied drying and increased seasonality of precipitation the early bridgerian mat is inferred to have been near 20 c and the map to have been about 80 cm except for the tiffanian and possibly portions of the early wasatchian paleoclimates during the study interval were predominantly frost free although the moderating influence of the green river lake system has been suggested as a possible explanation for mild eocene winters in wyoming this study shows that virtually frostfree climates existed in the area prior to and independent of significant lake development

palaeoclimate records in compound specific δd values of a lipid biomarker in ombrotrophic peat compound specific d values recorded by means of gas chromatography thermal conversion isotope ratio mass spectrometry gc tc irms of the biomarker n alkane n tricosane n c23 representative of the dominant sphagnum species in a 40 cm peat profile from bolton fell moss cumbria uk correlate with vegetation changes in the past 200 years age depth model based on 210pb dating the bog vegetation is sensitive to climate change correlating with the global scale cooler period of the later 19th and early 20th centuries the correlation with meteorological records suggests compound specific d values of lipid biomarkers have potential for use as a new climate proxy

significantly warmer arctic surface temperatures during the pliocene indicated by multiple independent proxies temperatures in the arctic have increased by an astounding 1 c in response to anthropogenic forcing over the past 20 years and are expected to rise further in the coming decades the pliocene 2 6 5 3 ma is of particular interest as an analog for future warming because global temperatures were signifi cantly warmer than today for a sustained period of time with continental confi gurations similar to present here we estimate mean annual temperature mat based upon three independent proxies from an early pliocene peat deposit in the canadian high arctic our proxies including oxygen isotopes and annual ring widths mat 0 5 1 9 c coexistence of paleovegetation mat 0 4 4 1 c and bacterial tetraether composition in paleosols mat 0 6 5 0 c yield estimates that are statistically indistinguishable the consensus among these proxies suggests that arctic temperatures were 19 c warmer during the pliocene than at present while atmospheric co 2 concentrations were 390 ppmv these elevated arctic pliocene temperatures result in a greatly reduced and asymmetrical latitudinal temperature gradient that is probably the result of increased poleward heat transport and decreased albedo these results indicate that arctic temperatures may be exceedingly sensitive to anthropogenic co 2 emissions

geochemical and mineralogical features of karst bauxite deposits from the alborz zone northern iran implications for conditions of formation behavior of trace and rare earth elements and parental affinity abstract the present study focuses on three outcrops of upper permian to lower jurassic karst bauxite deposits in the alborz zone north of iran the deposits occur as sharp semi continuous lenses within the upper permian ruteh formation gheshlagh and the upper triassic elika formation siahrudbar and separdeh carbonate rocks textural characteristics such as pelitomorphic matrix local ooidic pisoidic fluidal and clastic textures indicate authigenic allothigenic origins mineralogically kaolinite boehmite goethite and hematite in the gheshlagh diaspore hematite and kaolinite in the siahrudbar and kaolinite hematite goethite diaspore siderite and chamosite in the separdeh deposits are the main phases the distribution patterns of major elements normalized to the upper continental crust ucc depict enrichments of al fe and ti in all three deposits the three deposits are variably enriched in transition trace elements cr ni co v u th and high field strength elements ga hf zr nb y relative to ucc the studied bauxites have average concentrations of rare earth elements ree la lu between 305 97 and 373 69 ppm geochemical data reveal progressive enrichment of ree and an intense lree hree n fractionation toward the lower parts of the profile in the separdeh deposit due to the alkaline conditions of the carbonate bedrock and irregular distribution patterns at the gheshlagh and siahrudbar deposits due to water level and ph fluctuations the positive ce anomalies at separdeh and siahrudbar suggest oxidizing conditions in the upper parts of the profiles at gheshlagh the negative to nil ce anomalies reflect low intensity of oxidation based on previous geochemical analysis data the upper permian basalts in the gheshlagh and the upper triassic basalts in the separdeh and siahrudbar areas were the most likely source materials the local uplift of the permian upper triassic series led to the formation of karstic topography filled with materials derived from weathering of the basaltic rocks under humid tropical paleoclimate the initial weathering converted the source rocks to kaolinitic soils characterized by the enrichment of al fe and ti then they were transferred to the karstic depressions and sinkholes and underwent in situ leaching and desilicification bringing about a relatively higher ore grade the overall field and petrographic evidence demonstrate that these deposits were formed in shallow and swampy environments in the eastern part of the alborz zone at siahrudbar and gheshlagh better drainage conditions have enhanced the quality of ores

provenance of late carboniferous bauxite deposits in the north china craton new constraints on marginal arc construction and accretion processes abstract the north china craton ncc is bounded by two paleozoic accretionary arc terranes the north qinling terrane to the south and the bainaimiao terrane to the north the timing of arc accretion to the ncc and the architecture of the bainaimiao arc remain unclear during the building and accretion of the arcs along its margins the ncc experienced a long sedimentary hiatus since the ordovician which ended with the deposition of bauxite bearing sediments in the late carboniferous in this paper we report the u pb and hf isotopes of detrital zircons from the late carboniferous bauxite layer and use these data to constrain the tectonic evolution of the margin of the ncc the detrital zircons yield a minimum u pb age of ca 310 ma and a prominent age peak at ca 450 ma zircon crystals with ages of ca 330 ma and ca 1900 ma are more common in the bauxite samples from the northern part of the ncc than in those from the central part the ehf t values of the ca 450 ma detrital zircon crystals of the bauxite samples from the ncc are similar to those of the contemporaneous detrital zircon crystals from the north qinling arc terrane to the south but different from those of the contemporaneous detrital zircon crystals from the bainaimiao arc terrane to the north the ca 450 ma detrital zircon crystals in the ca 310 ma bauxite deposits are therefore interpreted to have been derived from the north qinling arc terrane the source of the ca 330 ma detrital zircon crystals of the bauxite deposits is interpreted to be the northern margin of the ncc where intermediate felsic plutons formed at ca 330 ma are common the results from this study support the interpretation that the paleozoic continental arc terranes and their concomitant back arc basins were developed along the margins of the ncc before ca 450 ma and the arc complexes were subsequently accreted to the craton in the late carboniferous this was then followed by the formation of a walled continental basin within the ncc