identification and diagenesis of a phylloid alga archaeolithophyllum from the pennsylvanian providence limestone western kentucky abstract phylloid algae in the pennsylvanian providence limestone desmoinesian in western kentucky are typical in appearance thin arcuate leaflike forms with a calcite mosaic interior cathodoluminescence and backscattered electron imaging reveal well preserved skeletal structure and their identity as archaeolithophyllum sp johnson 1956 and a missouriensum johnson 1956 thin skeletal walls are composed of nonluminescent neomorphic calcite polygonal hypothallial and perithallial cells in the skeletons are filled by luminescent calcite cement chemical staining also distinguishes cell morphology when ferroan calcite cement is present in skeletal pores in contrast to the nonferroan calcite forming skeletal walls hypothallial cells in archaeolithophyllum are 25 m 50 m and are commonly arranged in arcuate layers skeletal walls 5 m thick are composed of calcite and lack distinctive relict features although some are microporous and contain fine disseminated pyrite some thalli contain large irregularly shaped hypothallial cells 50 100 m partitioned by skeletal walls these are interpreted as poorly calcified thallus fragments neomorphic calcite of the skeletons contains high concentrations of sr average 3702 ppm range 339 10 549 ppm strongly suggesting that the original archaeolithophyllum skeleton was aragonitic archaeolithophyllum shares morphological structural and compositional characteristics with holocene peyssonnelid algae this evidence substantiates earlier hypotheses that archaeolithophyllum may be an ancestral peyssonnelid alga calcite cements filling skeletal cells include a bright yellow cl phase and two subsequent phases of dull red and dull yellow luminescence mg mn and fe are enriched in these calcites reflecting reducing diagenetic fluids particularly enriched in fe cementation of skeletons by ferroan calcite during early diagenesis appears to have protected skeletons from dissolution and promoted slow rates of neomorphism conditions of a nearly closed system are constrained by the high retention of sr in the skeletal calcite

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

calcification of encrusting aragonitic algae peyssonneliaceae implications for the origin of late paleozoic reefs and cements abstract encrusting aragonitic calcareous algae of the family peyssonneliaceae are the largest group of calcified red algae outside the well known mg calcite corallinaceae they are distributed worldwide are most heavily calcified in temperate and tropical waters and grow as prone but arched sheets on soft mud substrates on hard rock surfaces as extensive bridge like networks between corals in reefs and as concentric layers in nodules calcification is entirely aragonitic species specific and both intracellular and extracellular below the thallus as a hypobasal layer the hypobasal layer develops outside the tissue as an encrustation of small aragonite botryoids attached to the lower surface between rhyzoids and on living plants it may exceed the thickness of the thallus calcification ranges from nonexistent in some cold water forms to thallus calcification only to both thallus and hypobasal calcification to species in which the thallus is noncalcified but there is a hypobasal layer of aragonite botryoids although the confirmed fossil range of this family extends only to the early cretaceous striking similarities between these aragonitic forms and some late paleozoic phylloid algae suggest that they may be closely related their ability to grow on soft mud substrates and form structures composed of irregular arched sheets with extensive pore space as well as their brittle nature so susceptible to fragmentation are all characteristics of mound forming fossil phylloid algae the hypobasal layer of botryoidal aragonite developed while the plant is still growing could easily act as a nucleation site for further epitaxial submarine precipitation thus explaining the common association of paleozoic phylloid algae and extensive fossil reef cements that resemble botryoidal aragonite the presence of hypobasal botryoidal aragonite on plants with a noncalcified thallus raises the possibility that some fossil reef cements may be related to now vanished algae

the composition and evolution of the continental crust rare earth element evidence from sedimentary rocks the composition of the present day upper crust inferred from the uniformity of sedimentary rock r e e rare earth element patterns is close to that of granodiorite a revised andesite model is used to obtain total crustal composition the lower crust is the composition remaining assuming that the upper crust one third of the total is derived from intracrustal partial melting the upper crustal r e e pattern has pronounced eu depletion eu eu 0 64 the lower crustal pattern has eu enrichment eu eu 1 17 and the total crust has no eu anomaly relative to chondritic abundances the eu depletion in the upper crust is attributed to retention of eu in plagioclase in the lower crust because plagioclase is not stable below 40 km 10 kbar the anomaly is intracrustal in origin the archaean upper crust has a different r e e pattern to that of the present day upper crust being lower in total r e e and la yb ratios and lacking an eu anomaly these data are used to infer the archaean upper crustal composition which resembles that of the present day total crust except that ni and cr contents are higher the archaean crustal composition can be modelled by a mixture of tholeiites and tonalite trondhjemites the latter have steep light r e e enriched heavy r e e depleted patterns consistent with equilibration with garnet and hence probable mantle derivation there is little reason to suppose that the archaean lower crust was different in composition from the upper crust except locally where partial melting episodes occurred the r e e evidence is consistent with isotopic and geological evidence for a low continental growth rate in the early archaean a massive increase to about 70 of the total crust between about 3000 and 2500 ma b p and a slow increase until the present day the change from archaean to post archaean r e e patterns in the upper crust is not isochronous but is reflected in the sedimentary rock r e e patterns at differing times in different continents on the basis of a model composition for the mantle 36 of the potassium 30 of uranium 15 of lanthanum and 3 of ytterbium are concentrated in the present continental crust this enrichment is related to ionic size and valency differences from common mantle cations e g mg fe pre 3 9 ga b p crusts were obliterated by meteorite bombardment no geochemical evidence exists for primordial anorthositic sialic or mafic crusts

the impact of redox conditions on the rare earth element signature of redoximorphic features in a soil sequence developed from limestone abstract redox processes which are widespread in soils need to be quantified for an improved comprehension of the dynamics of fe and mn oxides and their associated trace elements the classical methodology used to study these redox processes generally relies on the quantification of all mineral species in the various pedological features that can be related to different redox stages however this approach usually encounters the difficulty of precisely quantifying the different forms of poorly crystallised fe and mn oxides in this study we use the signature of rare earth elements rees to visualise and eventually quantify the importance of redox processes in soils our approach relies on that developed by laveuf et al 2008 and the idea that the relative contribution to the mobilisation of rees that is made by the primary minerals reactive to redox conditions depends on the following factors i their initial proportion in the different pedological features that can be related to various redox processes ii their relative mobilisation during the redox process in question and iii their initial ree signatures the catena studied is characterised by two stages of redox conditions the first is related to the formation and subsequent dissolution of fe mn concretions and the second is related to the bleaching of the soil matrix due to morphological degradation in this soil the main minerals reactive to redox conditions are mn oxides ferrihydrite goethite and fluor apatite the results indicate that the primary redox conditions can be characterised by a positive ce anomaly on the ree pattern which has been attributed to a preferential immobilisation of this element due to its association with mn oxides the results also indicate that the secondary redox conditions can be characterised by depletion in medium rees mrees in the ree pattern which has been attributed to a preferential release of these elements during the dissolution of fluor apatite and to a lesser extent of ferrihydrite these results emphasise the potential of ree signatures of the visualisation of the various redox processes that have been active in a soil additionally ree signatures are a proxy of the frequency and intensity of the redox conditions

behaviour of rare earth elements and yttrium in ferromanganese concretions gibbsite spots and the surrounding terra rossa over dolomite during chemical weathering abstract the behaviour of rare earth elements rees and yttrium y during chemical weathering processes has been investigated on a 4 05 m thick terra rossa profile over dolomite on the yunnan guizhou plateau china in this profile ferromanganese concretions and gibbsite spots coexist in the terra rossa solum analyses of rees y zr f s and toc as well as mineralogical studies were conducted on a suite of ferromanganese concretions gibbsite spots terra rossas dolomites and insoluble residues from the underlying dolomite these analyses helped us to understand the mobilization redistribution and fractionation of rees and y during chemical weathering the rees and y are mobilized and redistributed during the terra rossa formation rees except for ce are removed from the upper and middle profiles transferred downwards and then precipitated in the base profile resulting in remarkable enrichment in the terra rossa near the weathering front the significant increase of ph near the weathering front was responsible for ree excluding ce and y enrichment in the base profile y is quite mobile during extreme chemical weathering and most of it was carried away from the profile because of very efficient oxidative fractionation of ce a significant positive ce anomaly in terra rossa was found in the middle of the profile whereas the terra rossa near the weathering front exhibited notably negative ce anomalies moreover the presence of cerianite and its content in the ferromanganese concretions can explain the markedly positive ce anomaly and the variation of ce ce values with depth in profile these ce anomalies are characteristic of the geochemical environment especially the redox condition studies of ree distribution in the ferromanganese concretions gibbsite spots and surrounding terra rossa revealed that significant ree fractionation occurred rees and y were preferentially concentrated in the ferromanganese concretions rather than in the gibbsite spots the water rock interaction resulted in m type tetrad effects in some of the ferromanganese concretions gibbsite spots and terra rossa samples in addition the tetrad effect in terrestrial weathering processes likely played an important role in the fractionation of rees and y such as y ho sm nd and the eu anomaly change

rare earth elements ree and yttrium in stream waters stream sediments and fe mn oxyhydroxides fractionation speciation and controls over ree y patterns in the surface environment we have collected 500 stream waters and associated bed load sediments over an 400 km 2 region of eastern canada and analyzed these samples for fe mn and the rare earth elements ree y in addition to analyzing the stream sediments by total digestion multi acid dissolution with metaborate fusion we also leached the sediments with 0 25 m hydroxylamine hydrochloride in 0 05 m hcl to determine the ree y associated with amorphous fe and mn oxyhydroxide phases we are thus able to partition the ree into dissolved 0 45 lm labile hydroxylamine and detrital sediment fractions to investigate ree fractionation and in particular with respect to the development of ce and eu anomalies in oxygenated surface environments surface waters are typically lree depleted la sm nasc ranges from 0 16 to 5 84 average 0 604 n 410 where the ree are normalized to the north america shale composite have strongly negative ce anomalies ce ce nasc ranges from 0 02 to 1 25 average 0 277 n 354 and commonly have positive eu anomalies eu eu nasc ranges from 0 295 to 1 77 average 0 764 n 84 in contrast the total sediment have flatter ree y patterns relative to nasc la sm nasc ranges from 0 352 to 1 12 average 0 778 n 451 and are slightly middle ree enriched gd yb nasc ranges from 0 55 to 3 75 average 1 42 most total sediments have negative ce and eu anomalies ce ce nasc ranges from 0 097 to 2 12 average 0 799 and eu eu nasc ranges from 0 39 to 1 43 average 0 802 the partial extraction sediments are commonly less lree depleted than the total sediments la sm nasc ranges from 0 24 to 3 31 average 0 901 n 4537 more mree enriched gd yb nasc ranges from 0 765 to 6 28 average 1 97 and ce and eu anomalies negative and positive are more pronounced the partial extraction recovered on average 20 of the fe in the total sediment 80 of the mn and 21 29 of the rees ce 19 and y 32 comparison between rees in water partial extraction and total sediment analyses indicates that rees y in the stream sediments have two primary sources the host lithologies i e mechanical dispersion and hydromorphically transported the labile fraction furthermore eu appears to be more mobile than the other ree whereas ce is preferentially removed from solution and accumulates in the stream sediments in a less labile form than the other rees y despite poor statistical correlations between the rees y and mn in either the total sediment or partial extractions based on apparent distribution coefficients and the ph of the stream waters we suggest that either sediment organic matter and or possibly d mno2 feooh are likely the predominant sinks for ce and to a lesser extent the other ree in the stream sediments

behaviors of rees during pedogenetic processes in the karst areas of southwest china abstract to understand the behavior of rare earth elements rees during pedogenetic processes in karst area sw china we investigated the leaching characteristics in order to better understand the mobility and fractionation of rees in two soil profiles developed on dolomite the two soil profiles namely qingzhen qz and pingba pb were sampled from guizhou province hydrochloric acid leaching method was used and the soil samples from the profiles were compared ree contents decreased from the bottom of the profiles 1360 39 ppm of qz and 2236 61 ppm of pb to the topsoil 247 32 ppm of qz and 168 ppm of pb from the soil samples to leachates la yb n n means chondrite normalized values increased from 3 8 92 to 2 36 25 02 in qz and 6 34 9 06 to 5 28 14 83 in pb and gd yb n increased from 1 01 1 80 to 1 40 2 71 in qz and 1 16 2 03 to 2 07 3 29 in pb these results indicate that the degree of ree fractionation increases with continuous weathering obvious differences in lree hree and ree th ratios between the soil samples and leachates indicated strong weathering and pedogenesis under a simulated acid leaching environment negative and positive cerium ce anomalies were observed in the lower and upper parts respectively of the profiles ce anomalies in the soil samples and leachates may be due to the sensitivity of ce to redox conditions given that the decrease of y ho ratio and the negative correlation with soil ph incipient pedogenetic processes likely play an important role in y ho fractionation on the basis of the characteristics of ree behavior the studied profiles have the characteristics of in situ weathering

ree and other trace elements in a granitic weathering profile from serre southern italy abstract ree v cr ni rb sr y zr and nb behaviour in a granitic weathering profile in southern italy is studied in the saprolites of the considered profile depletion of v cr ni rb sr zr and nb is observed this is quite remarkable for sr and cr whereas ree and y are enriched in the more altered portion of the profile and especially in its m fraction such enrichment is associated with the lree hree fractionation and the positive ce anomaly the former results from an increased solubility of hree in a non acid environment as well as from the removal of the hree rich phases from the residual component the latter is related to the redox chemistry of ce which as ceo 2 is less soluble than the other ree no analogy is observed between the behaviour of ce and fe mn and cr saprolites also exhibit a negative eu anomaly which is mostly inherited from the parental material finally the influence of accessory minerals in the ree distribution of weathering products and in sediments calls for a careful evaluation of preferential settling phenomena of heavy minerals during transportation and deposition processes this is especially true in the parent material sediment relationships

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

mobility of rare earth elements during weathering of till in northern sweden abstract continuous volume controlled sampling from the surface down to a depth of 130 cm was conducted at two stations on weathered till typic haplocryods all the samples were analysed for major and trace elements including the rare earth elements ree eight thousand seven hundred years of weathering since the glacial ice left the area has resulted in a strong depletion of ree in the e horizon this loss decreases as atomic number increases so that 80 85 of the la and 54 60 of the yb have been lost europium has been lost to a greater degree than have the neighbouring elements possible explanations for the release of ree are weathering of common silicates such as hornblende and epidote and plagioclase in the case of eu weathering of apatite weathering of rare but ree rich minerals such as allanite and monazite and release of ree adsorbed on clay minerals further studies on various size fractions and minerals are needed to quantify the importance of the various possible mechanisms of ree release the release of ree continues within and below the bs1 horizon but the results from one station show that light ree can be enriched in the bs1 horizon this secondary enrichment could be caused by adsorption on secondary oxy hydroxides on clay minerals or on organic material however the net result of the weathering is that all ree have been released to the groundwater

seafloor precipitated carbonate fans in the neoproterozoic rainstorm member johnnie formation death valley region usa cm sized carbonate seafloor fans occur in the neoproterozoic rainstorm member of the johnnie formation death valley usa the fans formed in a mixed carbonate clastic succession near storm wave base at the base of parasequences on a storm dominated ramp petrographic observations indicate that the fans were originally precipitated as aragonite and later inverted to calcite during diagenesis although not directly dated the rainstorm member preserves a large magnitude negative carbon isotopic anomaly down to 11 pdb tentatively correlated to the largest known carbon isotope excursion found in many stratigraphic successions around the world between 585 ma and 550 ma thus the age distribution of seafloor aragonite fans in neoproterozoic strata appears more widespread than previously thought occurring in strata significantly younger than the last widespread neoproterozoic glaciation rainstorm member carbonate fans and oolitic units representing time correlative shallower environments record similar carbon isotope ratios during the negative carbon isotopic anomaly the carbon isotopic homogeneity displayed between fans and other carbonate sediments implies that waters across the shelf were well mixed rather than stratified during the late neoproterozoic isotopic anomaly in addition the similarity of carbon isotope ratios shared among fans along a stratigraphic horizon on a m to cm scales suggests that the local source of alkalinity required for fan growth was derived from a well mixed reservoir likely seawater rather than local diagenetic fluids increased alkalinity and the presence of inhibitors to carbonate nucleation perhaps fe2 under anoxic conditions likely fostered precipitation of aragonite crystal fans on the seafloor

recovery of marine primary producers after the cretaceous tertiary mass extinction paleocene calcareous red algae from the iberian peninsula abstract calcareous red algae corallines solenoporaceans and peyssonneliaceans are major contributors to paleocene platform deposits in the pyrenean basin n spain and prebetic zone betic cordillera se spain the earliest danian middle thanetian time interval in the pyrenean basin is represented by four depositional sequences the ma da earliest danian da 1 early danian da 2 late danian and th 1 selandian mid thanetian sequences from bottom to top this precise chronostratigraphic framework allows an accurate assessment of the recovery of these calcareous algal groups after the cretaceous tertiary k t mass extinction calcareous algae are recorded shortly after the k t boundary 0 2 0 3 ma after the k t although the richness of identifiable species remains low during the danian 9 species in the earliest danian 9 species in the early danian and 11 species in the late danian in addition no change in taxonomic composition is observed in this interval since approximately the same algal species occur in all three danian sequences the same low species richness 11 species and species composition is observed in the danian algal assemblages of the betic cordillera however this low level of diversification changes radically in the selandian mid thanetian interval when 29 species are recorded together with the increase in species richness the taxonomic composition also changes since 19 species of corallines are recorded for the first time in the th 1 sequence therefore it can be deduced that species diversity recovery due to a significant radiation of corallines was delayed 6 ma after the end cretaceous event the recovery of corallines during the paleocene shows a characteristic depth dependent pattern throughout the danian middle thanetian interval representatives of the family hapalidiaceae subfamily melobesioideae and plants of the family sporolithaceae largely dominate the algal assemblages in the deep water outer platform settings as they do in present day seas members of these two groups are also the most abundant coralline algae in the paleocene reef and back reef paleoenvironments indicating that the shallowest and best illuminated areas were occupied by algal groups that in modern tropical seas mainly occur in relatively deep habitats this suggests that all platform habitats were re occupied after the end cretaceous event by the groups that selectively survived the extinction only after a time interval of about 6 ma did the habitat distribution of coralline groups change to its modern patterns the subfamilies most abundant in present day shallow tropical waters that is mastophoroideae and lithophylloideae for the first time account for more than 1 of the algal assemblages in the thanetian and even then they remain very minor components these shallow water coralline groups were affected more intensively by the k t extinction event accounting for the delay in their recovery in their preferred shallow water habitats shallow water lithophylloids and geniculate corallines have not been found in danian sequences

reservoir characterization of the pennsylvanian caddo limestone in stephens county texas a case study of komia dominated algal mounds abstract the caddo limestone forms economic carbonate reservoirs in stephens county northern texas this study demonstrates that in the caddo limestone of the eliasville and breckenridge fields porosity and permeability are best developed in phylloid algal wackestones and packstones as well as komia wackestones and packstones prevalent within the uppermost interval i e cycle a of the formation in the study area the main reservoirs formed in the upper and middle intervals of the caddo algal mounds because of meteoric dissolution related to subaerial exposure which created a large volume of secondary pores and early cementation that prevented mechanical compaction a great portion of the secondary pores remain open providing the principal pore spaces of the reservoir interval vugs including moldic voids are abundant and dissolution enhanced intragranular pores are very common within widespread komia intercrystalline pores are prevalent in dolomitized and neomorphised lithofacies where micrite was converted to microsparitic and sparitic calcite micropores are abundant in the matrix and within grains especially komia fragments the lower or basal interval of cycle a is commonly much less porous owing to the substantial loss of primary pores by physical compaction and lack or rare presence of secondary pores laterally wells in the areas with thicker cycle a interpreted as algal mounds have higher porosity and thicker net reservoir than those in intermound areas this work provides a case study of carbonate reservoirs in which komia wackestones and packstones are the major reservoir rocks

constitutive mass balance relations between chemical composition volume density porosity and strain in metasomatic hydrochemical systems results on weathering and pedogenesis relations characterizing the chemical physical and mechanical changes resulting from metasomatic hydrochemical processes are developed using mass balance models which formally link chemical composition to bulk density mineral density volumetric properties porosity and amount of deformation strain rigorous analysis of aqueous solute transport effects is then made possible in a variety of porous media flow environments including chemical weathering pedogenesis soil formation diagenesis ore deposition and enrichment and metamorphism application of these linear constitutive relations to chemical weathering profiles shows that immobile and locally mobile chemical elements with masses conserved on the scale of soil profiles can be accurately identified from analysis of appropriate data arrays and then used as natural geochemical tracers to infer the nature and extent of hydrochemical weathering processes and volume changes during pedogenesis assumptions commonly made in the past about the supposed immobility of certain elements e g ti and zr become unnecessary quantitative differentiation between the effects of residual and supergene fractionation is then easily made these methods are applied to ni rich laterites developed by weathering of ultramafic rocks showing that during ordinary residual enrichment ni is concentrated by as much as 4 protolith peridotite concentrations this occurs simply by silicate mineral dissolution and removal of chemical elements other than ni e g mg with a corresponding reduction in saprolite density and increase in bulk porosity without significant deformation in contrast laterites with mineable concentrations of ni which are similarly undeformed such as the nickel mountain mine in riddle oregon have experienced in addition to residual enrichment strong supergene enrichment by fractionation of ore elements between a leached zone from which ni is extracted and a complementary enriched zone positioned farther along the direction of ground water flow soil forming processes in podzol chronosequences developed on sandy beach terraces of the mendocino coast of california involved soil column collapse of 60 percent by dissolution of silicate minerals in the albic horizon of al and fe leaching and 70 percent dilation expansion in the overlying organic rich layer by root growth the amount of erosion based upon paleosurface reconstructions using the excess mass of fe al pb ga and cu in the zone of supergene enrichment spodic horizon below the ground water table indicates that subsurface erosion by dissolutional collapse is three times that of surficial erosion finally using published chemical data for ti zr and cr on major bauxite deposits in australia where erosion rates are thought to be low we infer that there may have been major amounts of dissolutional collapse to explain the upwards increase of detrital zircon and rutile in weathering profiles

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

the behaviour of rees in thailand s mae klong estuary suggestions from the y ho ratios and lanthanide tetrad effects abstract the concentrations of rare earth elements and yttrium rey were measured in dissolved phase in suspended particulate matter spm and in sediments in seven sampling stations in the mae klong estuarine system inner thailand gulf in order to study their behaviour and distribution pattern the analysed samples generally show high rare earth element ree content in the dissolved phase with high medium rare earth elements mrees and y enrichments in the shale normalized pattern versus paas these chemical features are interpreted in terms of direct influences of weathering processes of ree rich minerals e g phosphates which abundantly out crop in the mae klong watershed these large mree enrichments also suggest that dissolved sulphate complexes play an important role in the dissolved ree fate close to the marine coastal system the shale normalized rees and y ho ratios additionally indicate a direct rey co precipitation with fe oxyhydroxides along the river path and consequent adsorption as coating onto feooh surfaces the rey behaviour in spm appears strongly influenced by al fe and mn content suggesting that the formation of an authigenic fe mn oxyhydroxides and aluminosilicate particulate leads to rey adsorption and or co precipitation the observed variations in the y ho ratios suggest that different y ho fractionation processes take place in the studied estuarine system strong similarities among chondrite normalized ree patterns in both sediments and granitic rocks out cropping in the surrounding regions suggest a generic relationship between the two groups of materials

raised channel systems as indicators of palaeohydrologic change a case study from oman abstract the aim of this paper is to determine the extent to which raised channel systems may be used as indicators of long term paleohydrologic change and hence of broader paleoenvironmental changes in arid areas during the cenozoic the paper reviews the paleohydrologic significance of former drainage systems in arid areas and demonstrates the application of paleohydrologic methods to the analysis of the long term evolution of a complex series of exhumed multistorey raised channel systems in interior oman the paper discusses the range of possible autocyclic and allocyclic controls on changes in channel behaviour through time as a means of establishing the paleoenvironmental significance of observed changes in paleochannel pattern morphology sedimentology and stability the paper identifies some of the major allocyclic controls including climatic changes and particularly the seasonality magnitude frequency and distribution of rainfall events during the cenozoic together with the degree of continentality and hence the strength and persistence of arid wind systems base level changes due to eustatic fluctuations and or tectonic activity may also act to control long term patterns of aggradation followed by large scale landscaping lowering however long term fan ageing associated with progressive aggradation and steepening of paleochannel systems may also eventually lead to fanhead trenching independent of any external controls in addition progressive expansion of the drainage network and resulting river capture can lead to marked increases in water and sediment supplies to the fluvial system the paper also emphasizes the difficulties involved both in differentiating the wide range of possible controls on paleohydrologic response and also in developing an accurate and precise chronology for desert paleodrainage systems and in their correlation with non fluvial sedimentological sequences the raised channel systems of interior oman consist of heavily desert varnished chert and or ophiolite rich gravels dating from some time during the plio pleistocene period the paleochannels from sinuous gravel ridges rising the observed changes have resulted from a complex combination of both internally and externally generated environmental changes during the cenozoic progressive extension of the drainage network on to the ophiolite massif of the mountain source area resulted in river capture and a concomitant increase both in paleodischarges and in supplies of ophiolitic sediments to the paleodrainage system the early sinuous channels may have developed under a humid to sub humid climate in which perennial or seasonal flows allowed the distinct meander paleochannels to form ephemeral flows characterized by flash flood regimes were probably associated with the later distributary systems which may reflect semi arid to arid climatic conditions the large scale deflation of the interfluve sediments which resulted in the eventual exhumation of the cemented gravel capped multistorey paleochannel sequence is also likely to have occurred during periods of marked continentality probably during periods of low sea level associated with the quaternary glaciations

assessing the impact of black shale processes on ree and the u pb isotope system in the southern appalachian basin abstract upper devonian java and huron shales from the southern appalachian basin exhibit evidence of ree redistribution and resetting of the u pb isotopic system at the time of deposition ca 365 ma this alteration to the primary detrital signature of these shales is indicative of black shale diagenetic depositional processes that in effect obscure paleoenvironmental and provenance information that may be recorded the most direct evidence of these black shale processes is the rotated nature of the whole rock ree patterns from this sequence of presumably source related shales the neo formation of ree bearing diagenetic phases such as apatite and possibly carbonate has led to an unusually large range in the whole rock 147 sm 144 nd and the ce ce for this sequence of shales changes to these whole rock ratios will effectively alter the nd model age and create a ce ce that records evidence of diagenetic processes rather than information about the paleooceanographic conditions of the basin simultaneously the sequestration of u at the time of deposition and subsequent fixation in diagenetic phases such as apatite has effectively reset the 238 u 206 pb isotopic system at 340 50 ma overprinting the pb isotopic signature of the source area the trace element and isotopic signatures recorded by the java and huron formation shales from the study area reveal a syn postdepositional history dominated by what can be referred to as black shale processes the diagenetic conditions that develop at and below the sediment water interface during the deposition of organic rich shale are unique and consequently leave behind a unique geochemical fingerprint that can potentially overprint paleoenvironmental and provenance information

ree geochemistry of fine grained sediments from major rivers around the yellow sea abstract to investigate the distribution pattern and controlling factors of rare earth elements rees in riverine sediments river mouth sediments were collected at five geographically different rivers around the yellow sea two 1 m hcl leached and residual fractions and five step sequential extraction schemes the sedex method were applied to size separated sediments

paleoreef maps evaluation of a comprehensive database on phanerozoic reefs to get a better understanding of controls on reef development through time we created a comprehensive database on phanerozoic reefs the database currently comprises 2470 reefs and contains information about geographic position paleoposition age reef type dimensions environmental setting paleontological and petrographical features and reservoir quality of each buildup reef data were analyzed in two qualitatively different ways the first type of analysis was by visualization of paleogeographic reef distribution maps five examples late devonian early permian late triassic late jurassic middle miocene are presented to show the potential of paleoreef maps for paleogeographic and paleoclimatological reconstructions the second type of analysis was a numerical processing of coded reef characteristics to realize major trends in reef evolution and properties of reef carbonates the analysis of paleolatitudinal reef distributions through time shows pronounced asymmetries in some time slices probably related to climatic asymmetries rather than controlled by plate tectonic evolution alone the dominance of particular reef builders through time suggests that there are seven cycles of phanerozoic reef development first curves for the phanerozoic distribution of bioerosion in reefs bathymetric setting and debris potential of reefs are presented the observed pattern in the temporal and spatial distribution of reefs with reservoir quality may assist in hydrocarbon exploration statistical tests on the dependencies of reefal reservoir quality suggest that large size high debris potential low paleolatitude high amount of marine aragonite cement and a platform shelf edge setting favor reservoir quality reefal reservoirs are significantly enhanced in times of high evaporite sedimentation elevated burial of organic carbon low oceanic crust production low atmospheric co2 content and cool paleoclimate as well as when they are present in aragonite oceans

the estuarine geochemistry of rare earth elements and indium in the chao phraya river thailand abstract a new filtration method using a 0 04 m hollow fiber filter was applied to the river estuarine and coastal waters in the chao phraya estuary for geochemical investigation the filtered waters were analyzed for all the lanthanides y and in by using inductively coupled plasma mass spectrometry icpms the dissolved concentrations of rare earth elements rees are significantly lower than those reported previously for other rivers presumably because of effective removal of river colloids by the ultra filtration the variation of dissolved rees in the estuary is dependent on the season the light rees vary considerably in the low salinity s 3 show almost conservative trends being consistent with some of the previous works europium is strongly enriched in the river and estuarine waters compared to the south china sea waters thus the ree source of the chao phraya river must be fractionated and modified in entering to the south china sea dissolved in and ce in the high salinity s 20 25 zone of the estuary are lower than those of the offshore waters and therefore the dissolved flux of the chao phraya river cannot account for the higher concentrations of dissolved in and ce in the surface waters of the south china sea the negative ce anomaly is progressively developed with increasing salinity being consistent with continued oxidation of ce iii to ce iv in the estuary fractionation of the light to heavy rees seems to take place whereas the y ho fractionation is unclear in the estuarine mixing zone

differentiated hydrothermal and meteoric alterations of the lueshe carbonatite complex democratic republic of congo identified by a ree study combined with a sequential acid leaching experiment the behavior of rare earth elements ree during hydrothermal alteration and progressive weathering has been studied by acid leaching experiments on minerals and whole rock samples of the lueshe carbonatite complex ne of democratic republic of congo the fresh and hydrothermally altered samples were successively leached with acetic acid hac 1 n and hydrochloric acid hcl 1 n an additional leaching step with nitric acid hno3 1 n was applied on meteoric weathered material after this sequential extraction procedure the residues were dissolved in a fluorhydric nitric solution hf hno3 the lueshe carbonatite complex contains a suite of ree carriers identified as ca bearing minerals including carbonates apatite and pyrochlore as primary minerals that are accompanied by hydrothermal ancylite ce parisite ce synchysite ce and monazite ce the hydrothermal alteration induces an enrichment in the light ree but the authigenic minerals except monazite do not in fact play an important part in the pre lateritic ree stock because of their low amounts during the early stage of weathering the residual minerals retain the bulk of the ree the distribution being only slightly modified during intense weathering the leaching experiments indicate that the ree are redistributed among secondary ree phosphate minerals and bonded to fe hydroxides in the lateritic profile

rare earth elements in suspended particulate material of north atlantic surface waters on a transect between the northwest and northeast atlantic ocean 30 n 60 w to 60 n 2 w june july 1996 suspended particulate material spm in 24 near surface water samples 4 to 22 m3 with spm concentrations between 32 and 447 mg m 3 has been collected using a large volume centrifuge system the samples have been analyzed for y the rare earth elements rees and major inorganic and biogenic carrier phases such as al clay fe mn poc opal and caco3 the concentration pattern of particulate rees roughly follows the spm distribution average values pmol l 1 are for y 2 36 la 0 84 ce 0 82 pr 0 17 nd 0 67 sm 0 14 eu 0 030 gd 0 15 tb 0 024 dy 0 16 ho 0 036 er 0 12 tm 0 018 yb 0 13 and lu 0 022 extensive variability in negative ce anomalies have been observed along our transect with the strongest anomalies in areas of high poc abundances significant fractionation between lrees and hrees has been found for all major particulate phases these data are characterized by 1 strong relationships p 0 001 exist between concentrations of nonlithogenic excess hrees tb lu and poc values indicating that complexation with organic ligands promotes temporary hree enrichment on solid surfaces 2 the behavior of particulate fe and mn fractions is decoupled while fe and al clay phases exhibit preferential uptake of lrees la gd with crust like signatures particulate excess mn is strongly coupled to the poc phase r2 0 82 and to excess hrees we therefore suggest that the enrichment of rees in mn particles occurs via the formation of biogenic material probably mediated by bacteria and is not caused by adsorption onto mn oxihydroxides another result is that y in all studied relationships with the major inorganic and biogenic phases is very similar to ho implying their chemistries in surface ocean particulates are dominated by similar valency and ionic radii the y ho ratios average of 69 7 mol mol 1 have been very constant along our transect and lie in between the ratios for seawater 100 and continental crust 50

mg fractionation in crustose coralline algae geochemical biological and sedimentological implications of secular variation in the mg ca ratio of seawater the mg ca ratio of seawater has varied significantly throughout the phanerozoic eon primarily as a function of the rate of ocean crust production specimens of the crustose coralline alga neogoniolithon sp were grown in artificial seawaters encompassing the range of mg ca ratios shown to have existed throughout the phanerozoic significantly the coralline algae s skeletal mg ca ratio varied in lockstep with the mg ca ratio of the artificial seawater specimens grown in seawater treatments formulated with identical mg ca ratios but differing absolute concentrations of mg and ca exhibited no significant differences in skeletal mg ca ratios thereby emphasizing the importance of the ambient mg ca ratio and not the absolute concentration of mg in determining the mg ca ratio of coralline algal calcite specimens grown in seawater of the lowest molar mg ca ratio mmg ca 1 0 actually changed their skeletal mineralogy from high mg skeletal mmg ca 0 04 to low mg calcite skeletal mmg ca 0 04 suggesting that ancient calcitic red algae which exhibit morphologies and modes of calcification comparable to neogoniolithon sp would have produced low mg calcite from the middle cambrian to middle mississippian and during the middle to late cretaceous when oceanic mmg ca approached unity by influencing the original mg content of carbonate facies in which these algae have been ubiquitous this condition has significant implications for the geochemistry and diagenesis of algal limestones throughout most of the phanerozoic the crustose coralline algae s precipitation of high mg calcite from seawater that favors the abiotic precipitation of aragonite indicates that these algae dictate the precipitation of the calcitic polymorph of caco3 however the algae s nearly abiotic pattern of mg fractionation in their skeletal calcite suggests that their biomineralogical control is limited to polymorph specification and is generally ineffectual in the regulation of skeletal mg incorporation therefore the mg ca ratio of well preserved fossils of crustose coralline algae when corrected for the effect of seawater temperature may be an archive of oceanic mg ca throughout the phanerozoic magnesium fractionation algorithms that model algal skeletal mg ca as a function of seawater mg ca and temperature are presented herein the results of this study support the empirical fossil evidence that secular variation of oceanic mg ca has caused the mineralogy and skeletal chemistry of many calcifying marine organisms to change significantly over geologic time

trace element mobility during spheroidal weathering of basalts and andesites in hawaii and guatemala abstract trace element mobility has been studied in spheroidally weathered corestone shell complexes developed on late tertiary and quaternary volcanic rocks the parent materials are basalts and andesites related to 1 a subduction zone tecuamburro and moyuta volcanoes guatemala and 2 a hot spot hawaiian islands of oahu maui and hawai i the initial major element compositions are largely preserved in the corestones each corestone sample shows major element abundances characteristic of the different magmatic processes through which the lavas were generated however the changes in trace element compositions due to weathering show similar patterns in the corestone shell complexes independent of the tectonic setting and age element mobility within the different corestone shell complex was determined using an isovolumetric reference frame in this method bulk density is chosen as an independent measure of the extent of weathering based on volumetric concentrations the notion of element immobility cannot be applied to all the corestone shell complexes elements commonly assumed to be immobile e g zr ti and al vary in volumetric concentration for some corestone shell complex despite petrographic evidence of only minor weathering two corestones oahu and tecuamburro have become enriched in ree 3 relative to other lava flows from the same volcanoes and display negative ce anomalies the exfoliated shells from these complexes tend to have lower concentrations of ree 3 and have positive ce anomalies the fractionation of ce from the other rare earth elements ree is inferred to be a manifestation of changes in the valence state of ce from trivalent to tetravalent under oxidizing conditions in settings where the development of corestone shell complex is advanced an acidic solution can mobilize trivalent ree leach them out of more extensively weathered materials and transport them to less acidic portions of the regolith undergoing incipient weathering the precipitation of the ree 3 in the rinds and centers of the corestones are likely due to increases of the ph of the weathering solution systematic weathering induced ree behavior enrichment of most ree with lesser ce enrichment resulting in a negative ce anomaly can be discerned even in corestone samples that exhibit major element abundances and petrographic features otherwise similar to unweathered basalts and andesites

rare earth elements as reactive tracers of biogeochemical weathering in forested rhyolitic terrain article rareearthelements rees were evaluatedaspotentialtracers of biogeochemicalweathering atpedon hillslope and catchment scales in the jemez river basin critical zone observatory jrb czo valles caldera national pre serve nm usa we investigated time series of ree patterns in precipitation soil pore water groundwater and stream water and related these data to ree composition of soil rock and atmospheric dust ree signatures in stream waters are dynamic reflecting processes that occur along hydrologic flowpaths during transport to the stream including organic matter complexation primary and secondary mineral weathering water soil bedrock interaction and atmospheric deposition strong compositional similarities for the ree between soil waters and stream waters during the initial snowmelt are consistent with shallow subsurface flows to streams most bio

rare earth element mobility during conversion of nepheline syenite into lateritic bauxite at passa quatro minais gerais brazil abstract in a lateritic bauxite formed by weathering of nepheline syenite at passa quatro minas gerais state brazil bauxites on the hill tops directly develop from the syenite bed rock while downslope a kaolinitic layer occurs between bauxite and synetie a petrological investigation was performed on undisturbed weathered rock samples collected from a representative upslope pit the undisturbed weathered rocks were chemically analysed for major trace elements including ree and zr mass balance calculations were applied and the behaviour of the ree in the passa quatro weathering system was established compared to ree reference chondrite and to ree reference parent rock in the lateritic bauxite the results suggest that the first stages of weathering induce a volumetric change of 50 i e collapse with respect to the parent rock and remove ree with a slightly larger loss of the lree except ce compared to the hree in the upper layers where bauxite is more mature a net mass gain in ree is observed relative to the underlying layers this gain takes place during the reduction of the upper layer during the downward progression of the weathering front very significant ree losses occurs during the bauxitization processes throughout the upslope profile in addition the downslope kaolinitic system is demonstrated to be depleted in ree in the same proportions as the upslope bauxite we proposed that the ree exported in solution from the whole weathering mantle have enriched neighbouring watershed sediments

yttrium the immobility mobility transition during basaltic weathering trace elements have been used as provenance indicators of igneous rocks for many years even though the conditions under which they remain immobile during subaerial weathering have not been thoroughly defined we have used a novel geochemical and quantitative mineralogical data set of variably weathered basaltic rocks from northeast ireland to investigate the immobility of various elements titanium and niobium seem to be the most immobile of all elements relative to these elements zirconium is predominantly depleted but is also locally enriched yttrium displays a marked depletion from the early stages of weathering during the growth of clay minerals yttrium zirconium and their ratios with other elements should thus be used with caution as provenance indicators unless the rocks show no detectable signs of weathering

rare earth element patterns in archean high grade metasediments and their tectonic significance abstract metasediments from two contrasting types of archean high grade terrains are interpreted as being derived from distinct tectonic settings the kapuskasing structural zone canada represents the deep roots of a typical greenstone belt whereas the limpopo province southern africa and western gneiss terrain australia mainly consist of shelf sediments deposited on a granitic basement and then buried to the depths required for granulite fades metamorphism upper amphibolite to granulite fades paragneisses from the kapuskasing structural zone have ree patterns similar to those of greenstone belt sediments except where partial melting has occurred forming restites with eu enrichment and melts with eu depletion except in this latter instance metamorphism has not affected the primary ree patterns ree patterns in archean upper amphibolite to granulite facies metasediments from the central limpopo province and western gneiss terrain show wide differences ranging from patterns which resemble those in post archean terrigenous sediments to typical archean sedimentary rock patterns the diversity in ree patterns for these shallow shelf metasediments is interpreted as resulting from derivation from local provenances samples with post archean patterns displaying eu depletion are interpreted as being derived from k rich granitic plutons which were portions of small stable early archean terrains precursors of the widespread late archean proterozoic episode of major cratonic development

how mineralogy and slope aspect affect ree release and fractionation during shale weathering in the susquehanna shale hills critical zone observatory abstract to understand the factors that control rare earth elements ree release and fractionation during shale weathering we investigate the ree contents in solid bedrock regolith stream sediments and natural waters stream and pore waters from a first order catchment developed entirely on gray shales in central pennsylvania usa up to 65 of the ree relative to parent bedrock is depleted from the weathering profiles in the acidic and organic rich soils due to chemical leaching in addition newly formed fine particles were also lost along with the down slope movement of soil waters weathering profiles on the south facing slope show less depletion of ree than those on the north facing slope 33 vs 45 on average we hypothesize that the different degrees of ree depletion on the two transects reflect a history of different chemical weathering rates and possible different surface erosion rates controlled by contrasting slope aspect induced microclimate conditions in addition weathering profiles natural waters and sequential extractions all show a preferential removal of middle ree up to 22 more relative to light ree and heavy ree during shale weathering due to preferential release of mree from rhabdophane furthermore the long term phosphate mineral dissolution rates e g rhabdophane were estimated at 10 15 to 10 14 mol m 2 s 1 under field conditions based on ree depletion profiles strong positive ce anomalies average ce ce n value 1 79 observed in the regolith stream sediments and regolith extractions point to the fractionation and preferential precipitation of ce as compared to other ree due to the generally oxidizing conditions during release transport and redistribution of ree in the surface and subsurface environments positive eu anomalies average eu eu n value 1 30 observed in the natural waters of the catchment are attributed to weathering of plagioclases in the shale bedrock this study highlights the use of ree as natural tracers for low temperature geochemical processes

redistribution and mobilization of titanium zirconium and thorium in an intensely weathered lateritic profile in western australia abstract the mobility of titanium zirconium and thorium elements commonly considered insoluble during supergene weathering is still not well understood especially in intensely weathered regolith thus an intensely weathered lateritic profile jg developed on meta granitoids in jarrahdale western australia was investigated the mobility of ti zr and th has been assessed at both mineral assemblage and profile scales and the mode of occurrence has been investigated through the combined use of geochemical data from bulk regolith particle size fractions and sequential extractions with in situ data determined by electron probe micro analyzer and synchrotron x ray powder diffraction neoformed poorly crystalline phases containing trace to minor amounts of zr ce and th unassociated with silicates or phosphates were identified on the walls of al fe rich pores in the ferruginous duricrust this implies that some mobilization and redistribution of zr and th occurs within a sample scale breakdown of primary thorite and rare earth element rich fluorocarbonates is thought to be the source for zr and th in the neoformed phases rather than zircon thus the mineral hosts of zr ti and th in the parent rock and their relative susceptibility to weathering are the fundamental controls on subsequent mobility during initial weathering trace amounts of th in secondary phases such as rhabdophane and florencite show translocation of th at the mineral scale while strong partitioning of th into gravel rather than matrix reflects redistribution of th at the profile scale the absence of primary sphene from the regolith and the presence of partially dissolved ilmenite and rutile grains in the ferruginous mottled zone suggest mobilization and translocation of ti at a mineral assemblage scale furthermore the fluctuation of ti zr in the ferruginous zone is in contrast to the consistency of zr hf throughout the profile in general within the range of parent meta granitoid this suggests that ti and zr fractionate from each other and partition between gravel and matrix during extreme weathering and advanced lateritization this study demonstrates that ti zr and th are mobile at a variety of scales an important consideration that is often overlooked when calculating element mass flux in intensely weathered regolith