rare earth elements in the sediments of the north atlantic ocean amazon delta and east china sea reinterpretation of terrigenous input patterns to the oceans

balancing rare earth element distributions in the northwestern mediterranean sea abstract elemental concentrations of rare earth elements ree and isotopic compositions of neodymium end have been measured in three water column profiles in the north western mediterranean sea clear enrichments of ree are observed when comparing to adjacent atlantic waters suggesting ree inputs along the circulation in this area for the first time relative proportions of external sources including submarine groundwater discharges sgd have been quantified for the studied area atmospheric deposition is estimated to be the most important external source for all the ree with an average contribution of 44 followed by diffusion from porewaters which provide a 30 dissolved riverine fluxes account for 11 sgd for 10 and dissolution of remobilized surface sediments the remaining 6 mass balances accounting for seawater transport and identified external sources have been delineated for the three main water masses modified atlantic waters levantine intermediate waters and western mediterranean deep waters they show that the balances of ree in this area are dominated by seawater mass mixing superimposed on this hydrography ree vertical profiles are affected by external sources and biogeochemical cycling dissolved ree are correctly balanced in deep waters whereas substantial missing fluxes are identified in the surface and intermediate water masses additional net lree outputs and hree inputs are required in the surface waters while net output fluxes for all the ree are missing at intermediate waters the most likely process suggested here is an active reversible scavenging consistent with a stronger adsorption of lree compared to hree in the particular case of the redox sensitive cerium the most plausible mechanism to explain the net output missing fluxes is ce 3 removal by particle scavenging via oxidation to insoluble ce 4 estimated ce oxidation rates of 0 33 d 1 in surface waters agree well with previously published values exchange fluxes derived from the isotopic nd mass balance indicate higher nd scavenging in surface compared to intermediate waters

comment on the paper w and m type tetrad effects in ree patterns for water rock systems in the tono uranium deposit central japan takahashi et al 2002 have determined the rare earth element ree concentrations of weathered granite and related groundwater samples from the tono area central japan the chondrite normalized ree distribution patterns of rock and water samples were found to exhibit the lanthanide tetrad effect the ree distribution patterns of the weathered granite were typified by a convex m shaped tetrad effect whereas the groundwater samples showed lanthanide distribution patterns with a concave w shaped tetrad effect based on this observation it was suggested that the m shaped tetrad effect of the granite primarily represents a residual ree pattern resulting from the extraction of a mirroring w shaped tetrad effect by the groundwater this interpretation was further substantiated by the observation that sedimentary rocks in the tono area show ree distribution patterns with a w shaped tetrad effect implying that fixation of groundwater ree onto the sedimentary rocks was significant takahashi et al 2002 suggested that the size of the tetrad effect in the ree distribution patterns of

origin of convex tetrads in rare earth element patterns of hydrothermally altered siliceous igneous rocks from the zinnwald sn w deposit germany the chondrite normalized rare earth element ree patterns of whole rock samples from evolved granitic systems hosting rare metal deposits sometimes show a split into four consecutive curved segments referred to as tetrads in the present contribution a rigorous statistical method is proposed that can be used to test whether geological significance should be attributed to tetrads that are only of limited size the method involves a detailed evaluation of element and sample specific random and systematic errors that are constrained on the basis of independent repeated preparations and analyses of sample and reference materials application of the proposed method to samples from the granite hosted zinnwald sn w deposit germany revealed that at least two tetrads in normalized whole rock ree patterns have to be analytically significant to rule out that fractional crystallization led to the unusual behavior of the rees based on the analysis of altered albite granite and greisen samples from the endocontact of the zinnwald granite massif it is demonstrated that the lanthanide tetrad effect is responsible for the formation of the convex tetrads geological and petrological evidence suggests that the tetrads in the samples developed prior to greisenization and related cassiterite precipitation in contrast to the endocontact samples the rhyolitic wall rocks are typified by normalized ree patterns having tetrads that are variable in size and frequently close to the limit of analytical significance the sizes of the tetrads apparently correlate with the intensity of albitization but show no relation to subsequent alteration processes including greisenization and low temperature argillization this observation proves that curved segments in normalized whole rock ree patterns can be introduced during hydrothermal fluid rock interaction

rare earth patterns with positive cerium anomaly in alkaline waters from lake van turkey abstract the distribution of rare earth elements has been studied for aerobic alkaline ph 9 6 carbonate rich waters from lake van turkey shale normalized ree ree sn patterns display an almost linear increase from the light to the heavy rees and strong positive ce sn anomalies there exist neither positive nor negative gd sn anomalies the ree sn patterns are consistent with domination of ree speciation in solution by poly carbonato complexes generating enrichment of the heavy rees that is even more pronounced than that seen in seawater this is the first report of positive ce sn anomalies observed in ree sn patterns of aerobic natural waters these anomalies apparently result from stabilization of penta carbonato ce iv complexes in solution leading to enhanced abundances of ce in comparison with its trivalent ree neighbours thus in remarkable contrast to seawater positive ce sn anomalies may be general features of alkaline carbonate rich and aerobic lake waters

geochemical behavior under tropical weathering of the barama mazaruni greenstone belt at omai gold mine guiana shield abstract mineralogical petrographical and geochemical studies of the weathering profile have been carried out at omai au mine guyana the area is underlain by felsic to mafic volcanic and sedimentary rocks of the barama mazaruni supergroup part of the paleoproterozoic greenstone belts of the guiana shield tropical rainy climate has favoured extensive lateritization processes and formation of a deeply weathered regolith the top of the weathering profile consists of lateritic gravel or is masked by the pleistocene continental deltaic berbice formation mineralogical composition of regolith consists mainly of kaolinite goethite and quartz and subordinately sericite feldspar hematite pyrite smectite heavy minerals and uncommon mineral phases nacrite ephesite corrensite guyanaite a specific feature of the weathering profile at omai is the preservation of fresh hydrothermal pyrite in the saprolith horizon chemical changes during the weathering processes depend on various physicochemical and structural parameters consequently the depth should not be the principal criterion for comparison purposes of the geochemical behavior within the weathering profile but rather an index that measures the degree of supergene alteration that has affected each analyzed sample independently of the depth of sampling thus the mineralogical index of alteration mia can provide more accurate information about the behavior of major and trace elements in regolith as opposed to unweathered bedrock it can also aid in establishing a quantitative relationship between intensity of weathering and mobility leaching or accumulation of each element in each analyzed sample at omai some major and trace elements that are commonly considered as immobile ex tio2 zr etc during weathering could become mobile in several rock types and cannot be used to calculate the mass and volume balance in addition due to higher immobile element ratios the weathered felsic volcanic rocks plotted in identification diagrams are shifted towards more mafic rock types and a negative adjustment of 20 units is necessary for correct classification in contrast these elements could aid in defining the material source in sedimentary rocks affected by weathering generally the rare earth element ree patterns of the bedrock are preserved in the saprolith horizon this can represent a potentially useful tool for geochemical exploration in tropical terrains strong negative ce and tb anomalies are displayed by weathered pillowed andesites which are explained by the influence of the water rock ratio

element behaviour during interaction of magma and fluid a case study of chamuhan granite and implications on the genesis of w mo mineralisation abstract the chamuhan granite is located in the eastern part of the central asian orogen where it crops out as an elongated ne trending composite monzogranite the pluton consists of two phases with a fine grained monzogranite g2 at depth in sharp contact with a medium grained monzogranite g1 above the medium grained monzogranite can be subdivided into g1a and g1b based on the degree of metasomatism affecting it with the g1b being more altered tungsten molybdenum mineralisation is hosted by quartz fluorite veins or forms disseminated sulfides in g1a indicating a genetic association between the monzogranite and ore magmatic zircons from g1a yield a weighted mean age of 144 2 ma and hydrothermal zircons from g1a yield a weighted mean age of 143 1 ma indicating that the hydrothermal zircons are very close in age to the medium grained monzogranite monazite grains yield u pb isotope ages of 138 3 ma for g1a 137 1 ma for g1b and 139 2 ma for the fine grained monzogranite g2 phase these dates are the same within analytical error and are coeval with the molybdenite re os weighted mean age of 140 2 ma indicating that the monazite and molybdenite were deposited during hydrothermal alteration the chamuhan granite is geochemically a metaluminous to slightly peraluminous high k calc alkaline granite and is especially characterised by its ree tetrad pattern and a huge eu depletion that are accompanied by a non charge and radius controlled charac trace element behaviour this and the o isotopic data from the granite phases are indicative of a highly differentiated magma that interacted strongly with a co existing fluid emanating from the magma during the late stage of its crystallisation the interaction between the magma and related hydrothermal fluid resulted in the enrichment of w mo nb ta th u hf rb y all the studied granitic rocks have homogeneous initial isotope values with positive end t values of 0 1 3 and tdm2 dates between 924 and 691 ma this is consistent with granites derived from a pre existing juvenile crust derived from a depleted mantle during the neoproterozoic the molybdenite in the chamuhan w mo deposit has a narrow 34svcdt range of 0 1 1 6 characteristic of a magmatic origin and the pb isotopic compositions with 206pb 204pb ratios between 18 298 and 18 882 207pb 204pb ratios between 15 494 and 15 538 and 208pb 204pb ratios between 38 046 and 38 206 are similar to the calculated initial pb isotopic ratios of the chamuhan granite we thus suggest that there is an intimate relationship between the chamuhan granite and mineralisation and that the mineralising process is related to a post collisional extensional event following the formation of an over thickened continental crust and during closure of the mongol okhotsk and paleo pacific oceanic plates

uranium and rare earth elements in co2 rich waters from vals les bains france abstract waters from springs at vals les bains result from the mixing of a co2 rich highly mineralized water with dilute shallow subsurface water total content of dissolved species vary from 5 mmol 1 to 100 mmol 1 for many elements mixing of these waters is non linear non conservative and further water rock reactions take place the ph is controlled by co2 outgassing redox conditions are controlled by both the iron hydroxide siderite buffer and the introduction of oxygen with shallow subsurface waters among the major elements concentrations of ca mg mn fe are related to mixing co2 outgassing and carbonate precipitation uranium shows a complex behaviour controlled by carbonate complexing redox conditions mixing of waters and leaching from the rocks the 234 u 238 u activity ratio is near secular equilibrium in the more dilute waters dissolved rare earth element ree patterns are almost flat with a slight negative eu anomaly in the concentrated waters heavy rare earth elements gd yb hree are strongly enriched relative to light rare earth elements ce eu lree we relate the enrichment in hree to water chemistry and to complexing with carbonate species

the assessment of ree patterns and 143nd 144nd ratios in fish remains abstract the ree content and isotopic composition of sr and nd have been determined in fish teeth ranging in age from the trias to the present and from various localities mostly around the atlantic these measurements have been carried out on selachian and teleost remains from the same locality in togo and show no appreciable difference which suggests with the help of a mass balance calculation of the ce anomaly that diagenetic effects are not responsible for the ree enrichment of biogenic phosphates one group of fossil teeth has about 3 times the ree abundances of shale and a shale normalized pattern with a minimum at sm it is thought to reflect deposition in the open sea environment a second group has ree concentration about 10 times higher than the first group with either a regular light ree enrichment or more frequently a maximum in the middle ree both being probably indicative of deposition in estuarine or near shore conditions the shape of the ree spectra and the size of the ce anomaly can be used semi quantitatively to determine the depth of deposition the results presented here on late cretaceous eocene fish teeth samples from morocco reflect an increasing influx of deep waters with a lowla yb ratio and strong negative ce anomaly which agrees well with the evolution of sediment chemistry and microfauna associations in contrast nd is typical of the water mass in which the fish debris decayed examples of nearly isolated basins identified with nd isotopes include the south atlantic prior to the lutetian nd 13 5 the miocene persian gulf nd 3 1 and bolivia during the late cretaceous nd 12 8 togo and guinea bissau results suggest that in the south atlantic the meridional oceanic circulation had not started before 45 ma ago combination of ree and nd data suggests that the assignment of jurassic cretaceous samples measured so far to open sea water masses is still ambiguous

the behavior of rare earth elements in seawater precise determination of variations in the north pacific water column abstract we present new highly precise and accurate data for ten rare earth elements rees in two water column profiles and in bottom waters from three additional localities in the north pacific our results presented here and in an earlier publication indicate that the water column in the western north pacific is stratified with respect to the isotopic composition of nd as well as nd la sm nd and er la both the nd isotopic and the ree data show that ree transport is strongly influenced by horizontal advection even in the sluggish circulation of the pacific in general rees increase in concentration with depth at mid latitude they reach a maximum concentration at about 3000 m and then decrease to the bottom at high latitude heavy rees reach a maximum concentration near 3000 m whereas light rees continue to increase in concentration with depth the deep water maximum and bottom water depletion is interpreted as an advective feature resulting from the flow of a lower concentration of rees in antarctic bottom water under a higher concentration of rees in the north pacific concentrations of rees do not show a linear relationship with those of si indicating that the ree cycle is not directly coupled to that of the si cycle ree element ratios i e nd la correlate with hydrographie properties which suggests that major features of the ree patterns may be conserved during lateral transport comparison of our ree data to those in previously published reports on pacific seawater shows that the identification of ree distributions affected by advection is only made possible by the high precision analysis we developed for this study the ce concentration we observe is relatively constant over 200 4500 m depth at both sites where we have complete profiles this unique constancy of ce is in contrast to the contiguous rees la and nd which show substantial concentration variations with depth

rare earth elements in river waters we measured rare earth element ree concentrations in river waters to characterize the suspended and dissolved river flux of the ree to the oceans the ree pattern of river suspended materials is sensitive to drainage basin geology a positive correlation is observed between la yb ratios and nd model ages for the rivers studied major rivers have light ree enriched patterns relative to the north american shale composite nasc with la yb n 1 6 2 7 river water dissolved material 0 2 m is heavy ree enriched relative to suspended material and the most pronounced negative ce anomalies occur in rivers of high ph light ree concentrations vary by approximately 3 orders of magnitude and are inversely related to ph and major cation concentrations from these data we estimate that typical major river runoff has heavy ree depleted suspended material with la yb n 1 9 we conclude that the terrigenous input to the oceans from major rivers is heavy ree depleted relative to shales from the available data average river water dissolved material appears to be heavy ree enriched with la yb n 0 4 estuarine removal processes lower the dissolved ree river flux by approximately 60 and result in a flux that is more heavy ree enriched with la yb n 0 2 calculated oceanic residence times with respect to river input range from 2300 to 21 000 years are shortest for ce and greatest for the heavy ree and la such long residence times may suggest the presence of additional sources of ree in seawater

experimental geochemical mineralogical and o isotope constraints on the late magmatic history of the fichtelgebirge granites germany mineralogical experimental geochemical and stable isotope data give evidence for an aqueous late stage fluid which develops increasingly from the less to the more highly evolved granites of the fichtelgebirge g1 g4 in less evolved granites particularly g1 only minor chloritization and sericitization minor hydration and corrosion of zircons low leachable fractions of sr and zr the nearly chondritic ratios of zr hf and y ho and rare earth element ree patterns lacking the tetrad effect provide evidence of a less differentiated granitic melt system poor in complexing agents and water with insignificant late magmatic fluid rock interaction the subsequent low temperature alteration which is suggested by oxygen isotope composition of quartz and biotite did not affect the whole rock chemical composition in the highly evolved granites particularly g4 albitization sericitization and fluoritization ubiquitous hydration and corrosion of zircons high leachable fractions of sr and zr zr hf and y ho ratios very different from the chondritic ratios and ree patterns showing a marked tetrad effect point to the presence of a highly specialized fluid system rich in water and complexing agents such as fluorine leading to a marked magmatic hydrothermal alteration the oxygen isotopes also indicate alteration by high temperature fluids which were likely exsolved during the final stage of crystallization

the luanchuan mo w pb zn ag magmatic hydrothermal system in the east qinling metallogenic belt china constrains on metallogenesis from c h o s pb isotope compositions and rb sr isochron ages abstract the luanchuan mo w pb zn ag polymetallic ore district is located in the east qinling metallogenic belt on the southern margin of the north china craton two ore fields nannihu and yuku are recognized in the district and three types of deposits are identified from the two ore fields as follows 1 the 6 proximal porphyry skarn type mo w deposits occurring at the inner contact zone of the granite porphyries 2 the 3 middle skarn hydrothermal type zn deposits and 3 the 8 distal hydrothermal type pb zn ag deposits at the periphery of the porphyry we present c h o isotope compositions of hydrothermal quartz and calcite s pb isotope compositions of sulfide minerals and sphalerite rb sr isochron ages from the 17 deposits the geochemical and geochronological data from the two ore fields all show systematic temporal and spatial variation and primarily lead to the following inferences 1 the temperatures and salinities of the ore forming fluids decreased during mineralization the ore forming fluids gradually evolved from magmatic water to mixed magmatic meteoric water 2 the metallogenic components were primarily derived from igneous rocks with increasing proportions of the materials from the ore bearing rocks 3 the mineralization ages of these deposits are close 147 136 ma which correspond to the emplacement of the granite intrusions 4 the three types of deposits and the ore related late mesozoic intrusives constitute a unified magmatic hydrothermal mineralization system finally we also suggest exploration strategies for the luanchuan ore district

altered granitic rocks nusab el balgum area southwestern desert egypt mineralogical and geochemical aspects of rees abstract gabel nusab el balgum is located in the northern part of bir safsaf area southwestern desert egypt about 600 km southwest of aswan city and covers an area of about 40 km 2 a few workers have investigated the nusab el balgum area from the mineralogical and geochemical point of view the area consists mainly of devonian sandstone permo triassic volcanic rocks altered granitic rocks and post granitic dykes the altered granitic rocks silicified and kaolinized have undergone several hydrothermal alteration processes and were subjected to different types of alteration hematitization carbonatization kaolinization sericitization and silicification and are characterized by extreme enrichment in rare metals such as zr nb y and rees bastnaesite parisite fergusonite columbite hydrothermal zircon monazite and xenotime are common in the silicified and kaolinized granites the silicified granite commonly contains more rare metals than the kaolinized granite the rees in nusab el balgum granites were introduced by hydrothermal fluids during alteration and occur in carbonate minerals such as bastnaesite lree co 3 f and parisite ca lree 2 co 3 3 f 2 the ree chondrite normalized patterns of altered granites show an m type tetrad effect and indicate higher lrees negative ce anomaly due to alteration by hydrothermal fluids and negative eu anomaly

tetrad effect in rare earth element distribution patterns a method of quantification with application to rock and mineral samples from granite related rare metal deposits abstract in some geological environments the tetrad effect can be observed as a split of rare earth element ree patterns into four rounded segments a new method is proposed to quantify the sizes of the individual segments and for the first time the significance of observed tetrad effects is evaluated by taking analytical errors into account the outlined method was applied to lanthanide patterns of whole rock and fluorite samples collected from granite related rare metal deposits the ree patterns of the granite and greisen samples investigated exhibit significant tetrad effects that may not be accounted for by analytical uncertainties it is shown that the study of whole rock samples is insufficient to determine whether this effect is developed during fractional crystallization or is due to other processes such as fluid rock interaction a concave tetrad effect mirroring the pattern of the whole rock samples was not observed in the ree patterns of related vein fluorite samples therefore it is unlikely that the convex tetrad effect in the samples from the magmatic environment can be explained by removal of a respective complementary ree pattern by a coexisting hydrothermal fluid as previously suggested it is proposed that the tetrad effect formed within the magma fluid system before emplacement in the subvolcanic environment where phase separation caused a split of this system into fluid and magma subsystems alternatively the tetrad effect may also be inherited from an external fluid influencing the system during or after the emplacement of the magma on the basis of the fluorite data it is shown that the behavior of eu in the fluids is not related to the tetrad effect consequently different physico chemical factors control the occurrence of both phenomena y was found to be strongly enriched in samples precipitating from hydrothermal fluids that experienced prolonged interaction with the wall rocks whereas the tetrad effect in the fluids vanished with time and increasing distance from the ore bearing granite thus these different geochemical parameters can be used to reconstruct different aspects of the fluid evolution within this type of deposit

inter and intra crystal ree variations in apatite from the bob ingersoll pegmatite black hills south dakota abstract concentrations of rare earth elements ree have been measured on a suite of apatite crystals from an internally zoned granitic pegmatite enriched in li b be f nb ta sn and u with a cameca ims 3f ion microprobe using energy filtering an apatite specimen from the tin mountain pegmatite analyzed previously by isotope dilution was used as a standard the chondrite normalized pattern determined with the ion microprobe closely matches the pattern determined by isotope dilution with maxima at sm and dy and minima at nd and er apatite samples from the bob ingersoll pegmatite show a large range of ree patterns and concentrations in one case apatite crystals within millimeters show differences in ree concentrations and pattern shapes including a switch from positive to negative eu anomalies samples from several mineral assemblages show patchy individual crystal zoning with respect to the ree that is not mirrored by major element zoning this indicates disequilibrium conditions on a small scale consistent with rapid growth from a melt fluid system that was either of locally heterogeneous melt structure or in which the melt structure fluctuated rapidly as volatile rich minerals such as tourmaline crystallized these effects may be coupled with non ideal partitioning of ree in a heterogeneous mixture of melt aqueous fluid and crystals ree concentrations in apatite samples from the different pegmatite zones indicate a large variation in outer zones 10 500x chondrite high concentrations 100 1000x chondrite near the pegmatite core and very low concentration in the core 2 20x chondrite patterns are flat to slightly inclined ce yb 1 to 5 and most samples have positive eu anomalies the magnitude of positive eu anomalies decreases with inward position in the pegmatite possibly indicating a progressive increase in o 2 and a sharp increase may be indicated by systematic ce depletion in apatite from the pegmatite core ree specific volatile complexes may contribute to variations including unusual kinks observed in ree patterns of apatite from mineral assemblages in upper parts of the pegmatite

anomalies in rare earth distributions in seawater gd and tb we have measured profiles of the rare earth elements ree in atlantic and pacific ocean waters the data normalized versus shales exhibit a pronounced anomaly in gd relative to its neighbors eu and tb in the ree series such that the gd concentrations are high by 30 50 closer inspection reveals that the anomaly is made up of both elevated gd and depressed tb concentrations likely associated with solution chemistry shifts in the transition from an exactly half filled 4f electron shell anomalies in gd and tb solution complexation are also indicated by the turner whitfield dickson speciation model the overall trend of heavy ree iii enrichment in seawater and the gdtb anomaly described here tend to support scavenging as an important removal mechanism for the ree from seawater

rare earth element and nd isotopic variations in regionally extensive dolomites from the burlington keokuk formation mississippian implications for ree mobility during carbonate diagenesis abstract marine carbonates of the burlington keokuk fm miss of the midcontinent region have been subject to two major episodes of regionally extensive 100 000 km2 dolomitization previous studies of the cathodoluminescent petrography sr c and o isotopic compositions and sr fe mn and ca concentrations of burlington keokuk dolostones outline a diagenetic history in which lime mud was pervasively dolomitized by a seawater dominated fluid at many localities this early dolomite generation dolomite i was recrystallized by nonmarine diagenetic fluids at shallow burial depths to produce dolomite ii dolomites i and ii have similar rare earth element ree patterns and abundances and a narrow range of initial 143nd 144nd isotope ratios of 0 511906 0 000025 1 this consistency in the nd isotope ratios and ree patterns along with the presence of anomalously low abundances of cerium in the dolomites cherts glauconite pellets fish apatite and crinoids suggests that 1 seawater derived ree dominated the system and 2 the extensive water rock interaction that produced profound textural and compositional changes during the formation of dolomite ii did not significantly alter the ree patterns or nd isotopic signatures of the dolomites the results of quantitative modeling of isotopic and trace lement exchange during water rock interaction in carbonate systems indicate that extremely large water rock ratios are required to alter the ree signatures of diagenetic carbonates such large water rock ratios can reflect either 1 large extents of fluid flow during carbonate recrystallization or 2 minimal interaction between diagenetic fluids and host rocks during carbonate cement crystallization late vug filling calcite and dolomite have low sm nd and high ce nd n ratios relative to the dolostones such distinct ree signatures probably reflect limited interaction between late diagenetic fluids and burlington keokuk host rocks penecontemporaneous clastic sediments have similar initial 143nd 144nd isotope ratios 0 511857 0 511877 and lower sm nd ratios compared to the dolomites suggesting 1 a common crustal source of ree for the clastics and carbonates and 2 ree fractionation during the formation of carbonate apatite glauconite and other authigenic phases in the marine environment

icp ms a powerful tool for high precision trace element analysis in earth sciences evidence from analysis of selected u s g s reference samples abstract inductively coupled plasma mass spectrometry icp ms is a powerful analytical technique with considerable application to geochemistry in this paper we demonstrate the power of icp ms as a tool in petrogenetic studies data for 28 elements in seven u s g s basalt and andesite reference samples agv 1 bcr 1 bhvo 1 bir 1 dnc 1 w 1 and w 2 are presented accuracy and precision standard deviation for 26 of these elements is either excellent a detailed description of the icp ms technique we have developed is given a simple hf hno 3 dissolution in screwtop teflon bombs was used for sample preparation icp ms instrumental sensitivity was measured by external solutions with surrogate calibration for 4 elements matrix correction was made by use of standard addition naturally occurring internal standards rb y ce and pb were used to correct for instrumental drift between sample and spiked sample measurements we report data for the elements li cs rb sr ba zr hf nb ta y sc u th pb and all 14 of the ree in addition the procedure acquired data for be mo w tl and bi many elements in this array are crucial for the evaluation of petrogenetic models and source tracing herein lies the real power of icp ms one technique one dissolution small sample size good limits of detection good to excellent accuracy and good precision for many geochemically important elements

stratigraphic interpretation of rare earth element signatures in pleistocene mammal bones a case study from kharabai site east siberia a significant portion of the quaternary mammal remains is not found in situ which limits their biostratigraphic potential and the possibility of studying evolutionary changes to determine stratigraphic position of such finds we used the geochemical interpretations of rare earth element relative concentrations and fractionations ree signatures in the faunal remains and surrounding sediments ree signatures vary between different profile deposits due to differences in deposit sources conditions and ree fractionation during deposition and diagenesis redeposited faunal remains can retain evidence of unique ree signatures of surrounding deposits which allows assigning such bones to their proper depositional units this method is tested here on the material from the kharabai site viluy river central yakutia 63 77 n 121 10 e we determined that the ree signatures from the faunal remains collected at the base of the exposure showed a statistically significant correspondence to certain stratigraphic layers indicating the original deposition location of these remains importantly the biochronological age of the mammals determined using their evolutionary position was consistent with the stratigraphic position of the layers with which they were associated using the ree signatures this research suggests that the lower layers of the kharabai site date to early middle pleistocene while the upper ones date to late pleistocene

steep rock lake sedimentology and geochemistry of an archean carbonate platform abstract the 2800 ma mosher carbonate formation at steep rock lake in south central canada is one of earth s oldest limestone deposits it is both thick up to 500 m and relatively well preserved and was one of the first precambrian successions to be noted for evidence of early life it continues to provide information on the antiquity of such processes as photosynthesis the carbonate contains a variety of fabrics and facies from apparently fine grained bedded limestones with domal and columnar stromatolites atikokania radial fans and sheet cracks to closely packed metric scale hybrid domes of originally aragonite seafloor crust interlayered with fenestral fabric here we review previous work provide new observations concerning these sediments and their geochemistry and discuss the inception overall development and ultimate demise of the steep rock platform we divide the mosher carbonate into the lower hogarth member and upper elbow point member these units constitute a shallow water carbonate platform succession the hogarth member overlies eroded 3000 ma tonalite and is at least 120 m thick thin horizons of domal pseudocolumnar columnar and fenestral stratiform stromatolites and occasional layers of atikokania radial crystal fans occur within relatively fine grained thin bedded limestone with iron carbonate horizons in the upper part meter scale domes occur locally with sheet cracks and stromatactis the irregular laminae that build the small domal and columnar stromatolites are interpreted to be lithified mats and biofilms presumably cyanobacteria dominated fine grained well bedded facies of the lower hogarth member and its varied association of small stromatolites is interpreted to have accumulated in a relatively protected inner platform environment numerous very thin horizons of iron carbonate in the lower and upper parts of the hogarth member suggest temporally limited influence of iron rich offshore waters vertical trends in fe mn ba sr ce and 13 c probably reflect progressive restriction of circulation with at least one abrupt but short lived change back to more open seawater conditions the upper hogarth member with large banded domes and fenestral crusts and stromatolites is interpreted as back margin facies the overlying elbow point member is at least 70 m thick and appears to be entirely composed of innumerable juxtaposed elongate smooth and thickly layered domes lacking intervening sediment each dome is typically several meters across and composed of centimetric alternations of cuspate fenestral fabric possibly microbial and crystal fan fabric that is probably abiotic seafloor aragonite precipitate adjacent cuspate fenestral and crystal fan fabric show significant differences in concentration of 13 c sr ba fe and mn this giant dome facies is interpreted as a platform margin deposit in which alternating calcite aragonite mineralogies within each dome reflect a laterally fluctuating offshore redox boundary negative ce anomalies positive gd anomalies and reduced positive eu anomalies relative to laterally correlative deep water iron formation occur in the majority of crystal fan samples and in some cuspate fenestral fabric samples ca carbonate precipitation at the margin of an anoxic iron rich sea would have been promoted by oxygenic removal of iron from seawater otherwise fe carbonate would have been favored over ca carbonate precipitation the mosher carbonate formation is interpreted as an early marine oxygen oasis a shallow platform that favored cyanobacterial productivity was sufficiently isolated from open marine circulation for the seawater to become relatively oxygenated and where carbonate sediment aggradation was a positive feedback that sustained these shallow water conditions limestone accumulation terminated as transgressive suboxic and anoxic seawater deposited first manganese oxide rich and then manganese oxide poor iron formation sediments

rare earth elements in pore waters of marine sediments abstract the rare earth elements rees were measured in pore waters of the upper 25 cm of sediment from one site off peru and three sites on the california margin the pore water ree concentrations are higher than sea water and show systematic down core variations in both concentration and normalized pattern from these analyses and from comparison to other chemical species measured dissolved fe mn ba oxygen nitrate phosphate it is suggested that pore water rees can be grouped into three categories those that are from an fe source those that are from a poc source and cerium oxide rees from the fe source appear where anoxia is reached they have a distinctive middle ree mree enriched pattern the concentrations in this source are so elevated that they dominate ree trends in the fe oxide reduction zone the net result of flux from the poc source is relative enrichment of heavy rees hrees over light rees lrees reflecting remineralizing poc and complexation with doc a common linear ree pattern seen in both oxic and anoxic sediments is associated with this poc source as well as a hree enriched pattern that is seen in surficial sediments at the peru site overall the pore water results indicate that mn oxides are not an important carrier of rees in the oceans a ree biogeochemical model is presented which attempts to reconcile ree behavior in the water and sediment columns of the oceans the model proposes that poc fe oxide and ce oxide sources can explain the ree concentration profiles and relative abundance patterns in environments ranging from oxic sea water to anoxic pore water the model is also consistent with our observation that the ce anomaly of pore water does not exceed unity under any redox condition

rare earth distributions with a positive ce anomaly in the western north atlantic ocean from the vertical distributions of the rare earth elements ree in the sargasso sea we now report the first profiles of pr tb ho tm and lu in seawater together with profiles for la ce sm eu and yb the first observations of positive ce anomalies in seawater are ascribed to reducing inshore sediments as a source for ce ref 1 all vertical profiles are consistent with adsorption of trivalent rare earths by settling particles possibly siliceous or calcareous followed by their release at or near the sea floor on dissolution of the carriers the very different ce profile demonstrates the additional effects of oxidation reduction reactions

the lanthanide tetrad effect and its correlation with k rb eu eu sr eu y ho and zr hf of evolving peraluminous granite suites lanthanide tetrad effects are often observed in ree patterns of more highly evolved variscan peraluminous granites of mid eastern germany central erzgebirge western erzgebirge fichtelgebirge and northern oberpfalz the degree of the tetrad effect te1 3 is estimated and plotted vs k rb sr eu eu eu y ho and zr hf the diagrams reveal that the tetrad effect develops parallel to granite evolution and significant tetrad effects are strictly confined to highly differentiated samples mineral fractionation as a cause for the tetrad effect is not supported by a calculated rayleigh fractionation which also could not explain the fractionation trends of sr eu and eu eu the strong decrease of eu concentrations in highly evolved rocks suggests that eu fractionates between the residual melt and a coexisting aqueous high temperature fluid mineral fractionation as a reason for the tetrad effect is even more unlikely as ree patterns of accessory minerals display similar tetrad effects as the respective host rocks the accessory minerals inherit the ree signature of the melt and do not contribute to the bulk rock tetrad effect via mineral fractionation these results point in summary to significant changes of element fractionation behavior in highly evolved granitic melts ionic radius and charge which commonly control the element distribution between mineral and melt are no longer the exclusive control the tetrad effect and the highly fractionated trace element ratios of y ho and zr hf indicate a trace element behavior that is similar to that in aqueous systems in which chemical complexation is of significant influence this distinct trace element behavior and the common features of magmatic hydrothermal alteration suggest the increasing importance of an aqueous like fluid system during the final stages of granite crystallization the positive correlation of te1 3 with bulk rock fluorine contents hints at the importance of ree fluorine complexation in generating the tetrad effect as the evolution of a ree pattern with tetrad effect m type implies the removal of a respective mirroring ree pattern w type the tetrad effect identifies open system conditions during granite crystallization

the chemical composition of ree y th u rich accessory minerals in peraluminous granites of the erzgebirge fichtelgebirge region germany part i the monazite ce brabantite solid solution series peraluminous granites of the erzgebirge fichtelgebirge germany are hosts of various members of the monazite group of minerals that display an unprecedented compositional diversity the eibenstock s type granite constitutes the third reported occurrence worldwide of brabantite and the first occurrence of this mineral in a granite many new occurrences of cheralite ce as well as a monazite group mineral intermediate between monazite ce and huttonite for which the term huttonitic monazite is proposed were discovered even common monazite ce may show extreme ranges of actinide and lanthanide element concentrations the granites that host brabantite and cheralite ce are highly differentiated strongly peraluminous low temperature residual melts of s type affinity which are rich in fluorine and other volatile constituents but depleted in thorium and the light rare earth elements such highly evolved volatile rich compositions resemble rare element pegmatites and appear favorable for the precipitation of cheralite ce and brabantite but not of monazite with large amounts of huttonitic substitution instead these minerals occur preferentially in f poor biotite and f rich li mica granites of a type affinity irrespective of the level of uranium in silicate melts which may exceed that of thorium the substitution of uranium in monazite remains limited the compositional data reported here are consistent with complete miscibility in the monazite ce brabantite solid solution series under magmatic conditions these granites contain monazites that span almost the entire compositional range reported for monazite group minerals worldwide and therefore granites appear to be ideal rocks in which to study the crystal chemistry of this mineral group in general

dissolved rare earth elements distribution in the solomon sea abstract trace elements and isotopes teis were measured as part of the geotraces pandora cruise july august 2012 r v l atalante among them rare earth elements rees as pertinent tracers of land ocean inputs and water mass transformations this work discusses results of 19 dissolved ree dree profiles measured using a trispike method in the coral sea and inside and at the exits of the solomon sea a semi enclosed sea with complex topography and straits overall drees except the insoluble ce show nutrient like profiles i e depleted at the surface and enriched at depth illustrative nd concentrations range from 5 pmol kg at the surface to 25 pmol kg at 5000 m depth however local dree enrichments are observed mostly in the straits indispensable solomon and vitiaz straits and along the island coasts a box model allows calculating and discussing the fate of the drees in the different water layers flowing through the solomon sea finally subtle variations revealed by la ce eu anomalies and the normalized light versus heavy ree ratio expressed as ndn ybn allows the identification of specific mechanisms affecting the distribution of the different drees the positive eu anomaly observed in the surface layers reflects the basaltic origin of external inputs consistent with the intensive weathering and or volcanic activity affecting the surrounding islands these data also confirm that the distributions of heavy drees like yb are better correlated to the dsi concentrations than that of the other rees this article is part of a special issue entitled cycles of trace elements and isotopes in the ocean geotraces and beyond edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

the ree and end of 40 70 ma old fish debris from the west african platform ree concentrations and nd isotopic compositions have been determined in late cretaceous early cenozoic fish debris from west african and israeli platform sediments and show a strong regional control independent of time except for those from the northern morocco it is suggested that although diagenetic fluids do not contribute ree s directly to the phosphatic debris they may significantly change the ce anomaly and the end t value of the epicontinental seas which in turn control the ree in marine phosphates it is shown that over the investigated period the north moroccan shelf seawater was progressively flushed by deep north atlantic water

redistribution of fissiogenic and non fissiogenic ree th and u in and around natural fission reactors at oklo and bangombe gabon abstract elemental abundances and isotopic compositions of rare earth elements ree th and u of twenty eight samples from four kinds of natural fission reactors at the oklo and bangombe uranium ores were determined by mass spectrometry fissiogenic and non fissiogenic ree components of each sample were calculated from the isotopic compositions the geochemical distribution of both fissiogenic and non fissiogenic ree differs among the four reactors each reactor shows the following features possibly associated with the local geochemical conditions 1 reactor 9 at the shallow depth of the oklo deposit contains higher amounts of non fissiogenic ree than the other reactors the distribution of non fissiogenic ree does not reflect the primordial ree abundance patterns and might have been disturbed in and around the reactor due to supergene alteration our results suggest that significant amounts of fissiogenic lighter ree lree such as la ce and pr were mobile in the reactor 2 reactors 10 and 13 located deep underground have much lower contents of non fissiogenic ree than reactor 9 all fissiogenic ree show high retention in the reactors non fissiogenic ree of reactor 10 inform of the primordial ore formation without any geochemical disturbance little redistribution of both fissiogenic and non fissiogenic ree in the reactor 10 was observed and 3 the bangombe reactor located at shallow depth has apparently well preserved fissiogenic ree non fissiogenic ree in the bangombe reactor might have been disturbed possibly by hydrothermal processes the distribution behavior of fissiogenic ree is considered to be related with physico chemical reactor conditions such as nuclear reaction temperature and chemical compositions of each reactor but clear relationship between nuclear parameters and the ree distribution could not be obtained in this study

tologoi key section a unique archive for pliocene pleistocene paleoenvironment dynamics of transbaikalia bikal rift zone abstract the multi layered key section of tologoi is situated on the selenga river left bank 15 km southwest of ulan ude city 51o45 n 107o29 e in the western transbaikal region it holds a long record of quaternary sedimentation since early late pliocene through holocene with the only minor gap in the beginning of early pleistocene comprehensive studies have been carried out on the lithology geochemistry fauna succession and paleoenvironment reconstructions this paper summarizes the data acquired on the geology and stratigraphy of the tologoi section the authors investigated the composition structure and formation conditions of the section as well as the intensity of weathering rock geochemistry grain size and biostratigraphy

a jurassic garnet bearing granitic pluton from ne china showing tetrad ree patterns abstract ne china is characterized by the massive distribution of phanerozoic granitoids most of them are of i and a type granites whereas s type granites are rarely documented the present work deals with the dongqing pluton a small granitic body emplaced in the southern zhangguangcai range the pluton comprises a two mica garnet granite and a garnet bearing muscovite granite the latter occurs as veins in the former the pluton shows a gradational contact with the surrounding host granites rb sr and sm nd isotope analyses on whole rocks and minerals reveal that the two types of granites were emplaced synchronously at about 160 ma the pluton was emplaced coeval with the surrounding i type granitic pluton and had a rapid cooling history it is characterized by an initial sr isotopic ratio of 0 706 slightly negative end t values 0 5 to 1 9 and young depleted mantle model ages 970 1090 ma this suggests that the parent magma originated from partial melting of relatively juvenile crust which is largely compatible with the general scenario for much of the phanerozoic granitoids emplaced in the central asian orogenic belt geochemically the granites of the dongqing pluton are peraluminous with a shand index molar ratio a cnk of 1 0 1 1 for the two mica granites and 1 2 1 3 for the garnet bearing granites all the garnet bearing granites and some of the two mica granites show tetrad ree patterns tetrad group whereas most two mica granites show normal granitic ree patterns normal group the normal group granites exhibit depletion in nb ta p and ti in spidergrams and generally weak positive eu anomalies in ree patterns by contrast the tetrad group granites manifest depletion in ba nb ta sr p and ti and significant negative eu anomalies the trace element data constrain the parental magmas to having undergone extensive magmatic differentiation during their late stage magmatic evolution intense interaction of residual melts with aqueous hydrothermal fluids resulted in the non charac charge and radius controlled trace element behavior and the tetrad effect in ree distribution patterns this in turn leads to the invalidation of the commonly used tectonic discrimination criteria derived from trace element abundances of normal granites in view of this and previous studies we conclude that there were probably no s type granites produced in ne china during the phanerozoic consequently weathered sedimentary material did not play an important role in the genesis of the strongly peraluminous granites in the zhangguangcai range

vestige of an early cambrian incipient oceanic crust incorporated in the variscan orogen letovice complex bohemian massif abstract the letovice complex composed of metamorphosed enriched mid ocean ridge basalts with trondhjemitic sheets as well as gabbroic and ultrabasic bodies is exposed within an important variscan suture separating the moldanubian domain to the west from the brunovistulicum to the east in the eastern part of the bohemian massif czech republic a polyphase tectonic evolution of the study area was connected with underthrusting and subsequent exhumation of the former oceanic realm which resulted in three deformation phases d 1 d 3 new u pb laser ablation inductively coupled plasma mass spectrometry dating of magmatic zircons from amphibolite and trondhjemite yielded statistically identical concordia ages of 530 6 ma and 529 7 ma 2 respectively these are interpreted as dating intrusions of the early cambrian protoliths of the studied rocks based on this age as well as whole rock geochemical and nd isotopic data the letovice complex is interpreted as a vestige of an incipient oceanic basin developing on attenuated crust the most likely geotectonic setting was a post cadomian extensional regime at the northern margin of gondwana that marked the onset of its break up supplementary material photomicrographs of microstructures sample locations descriptions of analytical techniques and selected electron microprobe analyses of the main rock forming minerals are available at http www geolsoc org uk sup18424

w and m type tetrad effects in ree patterns for water rock systems in the tono uranium deposit central japan abstract abundances of rare earth elements plus y ree were determined for granitic rocks tertiary sedimentary rocks and related groundwater in the tono area central japan tetrad effects concave curves in ree patterns were found for these rocks and groundwater samples conjugate m and w types of tetrad effects were simultaneously observed in these specimens which constitute the water rock system the granitic rocks show the m type tetrad effects while the groundwater and the sedimentary rocks exhibit the w type tetrad effects non chondritic y ho ratios were found especially in the groundwater y ho ratios showed larger values than the chondritic value for the samples showing w type tetrad effects and vice versa these results suggest that 1 preference of the groundwater for a w type tetrad effect and larger y ho ratio than chondrite produces an m type tetrad effects and lower y ho ratios in the granitic rocks during weathering processes 2 the w type tetrad effect and larger y ho ratio for the sedimentary rocks is brought about by the fixation of groundwater ree onto the sedimentary rocks the variation of the tetrad effect and y ho ratio was confirmed by laboratory experiments on the leaching of ree from the granitic rocks the w type tetrad effect and large y ho ratio in the u mineralization zone in the sedimentary rocks were also found by sims analysis which is consistent with the w type tetrad effect and larger y ho ratio in the whole rock abundances of the sedimentary rocks disequilibrium of the u series 234 u 238 u analyzed by sims in the u mineralization zone suggests that the u bearing minerals were formed through precipitation from groundwater as it became reducing these results suggest that the ree in the sedimentary rocks were transported by the groundwater from the granitic rocks in the tono area based on this study it is implied that the degree of the tetrad effects and the variation of y ho ratio can be valuable tools to investigate the migration of ree during water rock interactions in natural systems

rare earth element geochemistry of sulphide weathering in the sao domingos mine area iberian pyrite belt a proxy for fluid rock interaction and ancient mining pollution gossan disseminated orebody waste other mining wastes minesoils and acid mine drainage amd in the abandoned sao domingos mine area iberian pyrite belt ipb have been analyzed for rare earth elements ree the main aim is to understand ree mobility during sulphide weathering so that the lanthanide series can be used both as a record of the water rock interaction and as a tool for identifying impacts of amd on natural ecosystems north american shale composite nasc normalized ree patterns corresponding to the disseminated orebody waste are relatively flat emree 0 01 0 12 however nasc normalized ree distributions in amd from sulphide oxidation tend to be enriched in middle ree mree compared to light ree lree and heavy ree hree as a consequence gossan resulting from supergene alteration of massive sulphide presents an evident nasc normalized mree depleted signature thus the overall water sulphide interaction defines complementary convex emree 0 72 0 25 and concave emree 0 31 0 12 nasc normalized patterns in draining waters and oxidation products respectively solutions extracted from minesoils have also nasc normalized patterns with mree enriched signature emree 0 62 0 22 similar to amd the emree parameter is proposed to measure the curvature in the mree segment and its size is quantified as the normalized maximum vertical difference between the polynomial curve fitting of the mree region and its theoretical y axis position in the absence of enrichment or depletion emree 0 for mree enriched signatures 0 for mree depleted signatures and 0 for horizontal patterns the sao domingos stream although it has been highly affected by amd flows into the guadiana river that has an estuarine system where pollution is considerably attenuated due to the mixing according to the metal geoaccumulation indexes currently used in the literature however sediments of this estuary were also analyzed and reflect mree enriched signatures emree 0 25 0 03 which demonstrate that this apparently non polluted estuarine system is being certainly affected by historical mining activities from the ipb the emree index is more sensitive to recognize curved mree signatures than other normalized ratios such as la gd nasc validating the use of ree patterns as a proxy for environmental pollution by amd

rare earth elements in sinters from the geothermal waters hot springs on the tibetan plateau china abstract the mineralogical and geochemical composition of sinters from the geothermal areas on the tibetan plateau was determined they occur as siliceous salty and calcareous sinters but biogenic siliceous sinters were also found the analyses indicate that there are no distinct inter element relationships between individual rare earth elements rees and other elements formed from the same geothermal water the mineralogical and chemical composition of the sinters is influenced by their genesis and formation conditions the ree distributions depend on the origin of the sinters fe mn phases in sinters tend to scavenge more rees from geothermal water neither the ree fractionation nor the ce anomaly seems to be associated with fe mn phases in the sinters the fourth tetrads of some sinters display weak w type concave effects in contrast the third tetrads present large effects in some sinters due to positive gd anomalies the origin of the positive eu anomalies in some sinters seems to be caused by preferential dissolution of feldspars during water rock interaction the complexing ligands in geothermal water may contribute significantly to the fractionation of rees in sinters the dominant co 3 2 and hco 3 complexing in geothermal water favors enrichment of heavy rees in calcareous sinters

kimuraite cay 2 co 3 4 6h 2 o a new mineral from fissures in an alkali olivine basalt from saga prefecture japan and new data on lokkaite

interleaving intrusions produced by internal waves a laboratory experiment a statically stable stratified water column that also contains horizontal property contrasts either of passive tracer alone or of two dynamically active solutes is generated and continuously maintained for a long period by releasing two turbulent buoyant plumes of equal buoyancy fluxes into opposite ends of a long channel of water the bottom outflows from the plumes also continuously excite internal gravity waves that produce a series of counter flowing quasi horizontal shear layers which are quasi stationary relative to the box but whose phase propagates downward through the upward moving water column we report that the flow further involves an oscillation associated with the internal waves that gives rise to a sequence of interleaving intrusions across the horizontal gradient region the wave driven intrusions are advected upward with the filling box circulation and have the appearance of a spatially growing instability the intrusions are examined in cases having no horizontal property differences other than a passive tracer in further experiments where one plume is salt solution and the other is sugar solution there is vigorous double diffusive convection on the interleaving intrusions including salt fingering and diffusive density interfaces but this convection has only a weak influence on the intrusion thicknesses and velocities we conclude that under all conditions attained in these experiments the interleaving is driven by internal waves and not by the property gradients and we infer that the wave generated intrusions enhance double diffusive buoyancy fluxes

the lanthanide tetrad effect in apatite from the altay no 3 pegmatite xingjiang china an intrinsic feature of the pegmatite magma abstract apatite and associated minerals such as spessartite tourmaline beryl and alkali feldspar from the altay no 3 granite pegmatite in xinjiang china have highly variable concentrations of rare earth elements rees and possess chondrite normalized ree patterns that show a clear convex tetrad effect the y ho and sr eu ratios of the apatite samples are extremely fractionated relative to the corresponding chondritic values based on the la lu sr eu and y ho ratios of these minerals the crystallization zones of the pegmatite can be divided into two groups that are interpreted to reflect two main stages of magma evolution namely a magmatic and a magmatic hydrothermal transition stage the degree of the lanthanide tetrad effect in ree patterns of the apatite expressed by the quantification factor te 1 3 ranges from 1 3 to 1 9 the size of the tetrads correlates with y ho eu eu and sr eu ratios in addition to the mineral samples from the pegmatite the ree patterns of the altered wall rocks also show a convex tetrad effect a mass balance calculation was carried out to constrain the ree partitioning between the aqueous fluid crystalline phases and the residual melt it was found that the ree patterns of these three phases are dominated by the concentration of the rees in the initial pegmatite forming melt accordingly it is proposed that the ree tetrad effect and the fractionation of the chemically coherent isovalent element pairs in the studied mineral separates represent intrinsic features of the granitic pegmatite forming melt it appears unlikely that these geochemical characteristics developed as a result of melt mineral fluid interactions taking place during magma crystallization after its intrusion interaction of an external fluid with pegmatite magma before emplacement or with parent materials of the highly evolved granitic rocks before melting would be favorable for producing the ree tetrad effect in highly evolved granitic rocks

monazite and xenotime solubility in granitic melts and the origin of the lanthanide tetrad effect the solubility of synthetic pure rare earth phosphates with monazite or xenotime structure lapo4 to lupo4 in hydrous haplogranitic melts was measured at 2 kbar and 800 1 100 c experiments were run for up to 2 months to attain equilibrium monazite and xenotime solubility decreases with increasing phosphorus concentration in the melt published equations for monazite solubility in felsic melts which do not explicitly include phosphorus concentration in the melt should therefore be treated with caution the effect of phosphorus can be quantitatively modeled if one assumes that monazite partially dissolves as ionic and molecular species in the melt ree3 and reepo4 equilibrium constants for the dissolution reactions as well as quantitative data on speciation were derived from the solubility data monazite and xenotime solubility strongly increases with the peralkalinity of the melt this effect is mostly due to an increase in the solubility of the ionic species which are probably stabilized by non bridging oxygen atoms in the melt in peraluminous melts the solubility of monazite and xenotime is nearly constant fluorine has no major effect on monazite and xenotime solubility in fact the solubility appears to slightly decrease with increasing fluorine content the solubility of rare earth phosphates is not a simple continuous function of atomic number or ionic radius rather the solubility shows a tetrad like pattern with several local maxima of solubility at individual rare earth elements the solubilities of neighboring rare earth elements sometimes differ by more than a factor of two these effects are far outside any analytical error the tetrad pattern is particularly clearly seen in some of the peralkaline melts and in the fluorine rich metaluminous melts some features however such as a solubility maximum at ytterbium are seen in virtually all melts the lanthanide tetrad effect in some highly evolved granites may therefore be a result of monazite and xenotime fractionation the solubility of monazite and xenotime in silicate melt probably shows the tetrad effect because of the very unusual coordination of the rare earth elements in these phosphate minerals which is different from the coordination of the melt and therefore causes different crystal field interactions with the partially filled f orbitals of the rare earths the tetrad effect in granites cannot be used as an indicator of fluid rock or fluid melt interaction since it can be experimentally reproduced in the absence of any fluids

geochronological and petrogeochemical constraints on the skarn deposits in tongshanling ore district southern hunan province implications for jurassic cu and w metallogenic events in south china abstract southern hunan province south china is located in the central part of the qin hang metallogenic belt and is characterized by abundant cu pb zn and w sn polymetallic ore deposits the cu pb zn deposits are associated with jurassic granodiorite porphyries whereas the w sn deposits occur within jurassic granite porphyries here we present geochronologic and geochemical data for the tongshanling cu mo pb zn deposit and the weijia w deposit in the district of tongshanling southern hunan zircon u pb dating and molybdenite re os geochronology indicate that the emplacement of the tongshanling granodiorite porphyry and the associated cu mineralization occurred at 162 160 ma slightly earlier than the formation of the xianglinpu granite porphyry and associated w mineralization at 159 158 ma the tongshanling granodiorite is high k calc alkaline weakly peraluminous and weakly fractionated with zircon e hf t values of 15 1 to 5 6 in contrast the xianglinpu granite is alkaline peraluminous and highly fractionated with e hf t values of 9 5 to 0 9 our data indicate that the tongshanling granodiorite is relatively oxidized and was formed by the partial melting of paleoproterozoic crustal material with inputs of mafic magma which was derived from a subduction modified lithospheric mantle in contrast the xianglinpu granite porphyry is relatively reduced and was formed by direct interaction between the crust and asthenospheric mantle the difference in magma generation and tectonics is considered to have resulted in the different types of mineralization associated with these two intrusive bodies

a possible linkage between highly fractionated granitoids and associated w mineralization in the mesozoic yaogangxian granitic intrusion nanling region south china abstract the yaogangxian ygx w deposit in the central nanling w province south china is one of the largest w deposits worldwide both vein type wolframite and skarn type scheelite orebodies were exposed in ygx these scheelite and wolframite mineralization are spatially associated with the ygx granitic intrusion the exposed intrusion contains two main intrusive phases lower zone coarse grained two mica granite and upper zone fine grained muscovite granite an integrated study of whole rock geochemistry la icp ms zircon u pb geochronology and zircon hf isotopic geochemistry of the ygx granitic intrusion was undertaken to constrain its magmatic source and petrogenesis cassiterite la icp ms u pb dating was also undertaken to constrain the connection between the intrusion and hydrothermal w mineralization zircon u pb dating yielded weighted mean ages of 161 3 and 157 2 ma for the two mica and muscovite granites respectively cassiterite crystals from wolframite quartz veins display growth zonation under cathodoluminescence and have a weighted mean zircon u pb age of 158 2 ma the formation of the muscovite granite and related w mineralization in the ygx deposit was thus initiated during the early yanshanian the ygx granites display typical metaluminous to strongly peraluminous characteristics with high sio2 73 5 79 1 wt and k2o 3 0 5 0 wt contents they are enriched in heavy rare earth elements rees comparative to light rees notably they exhibited strong negative eu anomalies and are depleted in sr ba p and ti in addition muscovite granites in ygx are more significantly enriched in heavy rees relative to light rees than two mica granites indicating that the former experienced higher degree fractionation than the latter zircon grains of the ygx granitoids have strongly negative ehf t 15 to 10 3 with two stage hf model ages of 2 15 1 86 ga indicating a magma source of reworked ancient crustal material without obvious involvement of juvenile materials the results of petrology and geochemistry indicate that the ygx granitic intrusion is a highly fractionated s type granite emplaced during widespread 160 150 ma granitic magmatism in the nanling region further evolution to late stage for multiphase ygx granitic intrusion is needed to enrich ore forming elements after magmatic emplacement it is suggested that the extensional environment of continental lithosphere caused by the northwest subduction of the paleo pacific plate may play an key role in the genesis of ygx s type granite w rich proterozoic basement rocks and fractional crystallization may provide material for the formation of the granite related tungsten mineralization

a geochemical study of loess and desert sand in northern china implications for continental crust weathering and composition abstract chemical compositional variations of desert sands and loess loess like deposits river deposits and saline lacustrine deposits collected mostly from the southern margin of the taklimakan desert china provide strong constraints on the chemical weathering processes of continental crust and also on the provenance compositions of these quaternary deposits constant but lower concentrations of al relative to the average upper continental crust ucc in these quaternary deposits could be attributed to chemical weathering of al rich minerals such as feldspar and mica and removal of clay minerals by wind and water large variations of mobile na ca mg and sr compared to relatively immobile al k and ba resulted from the chemical weathering of plagioclase and carbonate minerals salinization and carbonation of the arid lands most trace elements are not significantly fractionated their variations in absolute concentration are caused by the dilution of quartz evaporates and carbonate minerals variations in sn concentrations probably depend on relative contents of some heavy minerals high sr ba low th u k cs ratios of the saline lake deposits suggest differences in aqueous chemistry of these elements the occurrence of the m type tetrad effect a ree pattern with four convex curves of ree compositions found mainly in the river deposits is considered the result of water particle interaction during chemical weathering of crustal materials y ho ratios of these samples are significantly higher than those of chondrite and the ucc this suggests different chemical behavior of these two elements and possibly the enrichment of carbonate materials the low lree hree feature of the saline lake deposits can be interpreted as due to the different aqueous chemical behavior of the ree s however it can also be reasonably considered as the result of inheritance from their provenance since lree and lree hree variations may be related to the geological setting of the source according to some elements that are not significantly fractionated the average provenance composition of these quaternary deposits are probably characterized by enrichments of ni cr and v over fe higher la th lower la sc and th sc and lower ta w and nb w ratios compared with the ucc composition

geochronology geochemistry and sr nd isotopes of the granitic rocks associated with tungsten deposits in beishan district nw china central asian orogenic belt petrogenesis metallogenic and tectonic implications abstract the beishan orogenic belt is an important tectonic unit and a suitable target to investigate and understand the paleozoic tectonic framework of the central asian orogenic belt paleozoic granitic rocks are widely distributed in the area and closely related to the tungsten deposits at hongjianbingshan guoqing yingzuihongshan and yushan to understand the petrogenesis of the intrusions we performed sims zircon u pb o and whole rock major trace element contents and sr nd isotopic analyses two major suites of granitic intrusions associated with tungsten mineralization have been recognized during 424 314 ma and 286 244 ma the former suite shows variable sr nd and o compositions average 87sr 86sr i 0 7149 or 0 7034 end t 6 3 or 7 6 t2dm 1 68 or 0 41 ga 18o 9 3 or 5 9 indicating an ancient crust or a juvenile lower crust origin whereas the latter suite shows a type affinity and the sr nd and o compositions average 87sr 86sr i 0 7125 end t 4 5 t2dm 1 42 ga 18o 6 9 suggest the precambrian metasedimentary strata may have exerted a significant role in the magma source the proposed magma sources combined with the geochemical differences between these two suites of intrusions indicating the silurian carboniferous mineralization such as hongjianbingshan guoqing and yingzuihongshan are closely associated with subduction accretion and generation of gongpoquan arc accretionary system while the permian mineralization including yushan deposit are attributed to continuing accretion and subsequent post collision these tungsten related granitic rocks are enriched in lree and depleted in hree and ba sr nb p eu and ti suggesting they may have experienced advanced fractional crystallization furthermore a spectacular tetrad effect in their ree distribution patterns has been discovered showing the granites are highly evolved rocks with strong hydrothermal interaction the prolonged fractional crystallization and magmatic hydrothermal interactions have contributed to the formation of the silurian permian tungsten mineralization

rare earth element tetrad effect and negative ce anomalies of the granite porphyries in southern qiangtang terrane central tibet new insights into the genesis of highly evolved granites abstract highly evolved granites are geochemically similar to the mature continental crust and are sometimes associated with w sn nb ta and rare metal mineralizations these rocks have important implications for tracing the compositional evolution of continental crust and magma metallogenesis they were commonly considered to have been produced by partial melting of crustal materials or by high degree fractional crystallization in this study we report on high sio2 granite porphyries in the xiabie co area of southern qiangtang terrane central tibet which provide new insights into the petrogenesis of the highly evolved granites zircon dating results indicate that they were generated in the late early cretaceous 107 1 ma they consist mainly of orthoclase albite and quartz with accessory minerals including zircon fluorite and fe ti oxides geochemically they have high sio2 but low mgo fe2o3t cao and p2o5 and are enriched in rb but depleted in ba sr eu and ti similar to highly evolved granitic rocks they are characterized by distinct rare earth element ree tetrad effects and negative ce anomalies they also have slightly higher end t values 0 99 to 0 36 than those of the adjacent early granites 2 05 to 3 01 and relatively high and variable zircon ehf t values ranging from 0 3 to 5 4 compared to typical highly evolved granites and petrological experiment data we suggest that the xiabie co granite porphyries represent highly evolved melts produced by fractional crystallization the interaction between fractionated melts and f rich aqueous fluids played an important role in the genesis of their ree tetrads effect involvement of meta sedimentary rocks that went through surficial chemical weathering into their source region is the predominant reason for the generation of negative ce anomalies this indicates that in addition to fractional crystallization the melt fluid interactions and partial melting of source materials also play important roles in the generation of highly evolved granites

highly differentiated magmas linked with polymetallic mineralization a case study from the cuihongshan granitic intrusions lesser xing an range ne china abstract the genetic link between granitoids and polymetallic skarn mineralization has remained equivocal the cuihongshan skarn porphyry w mo pb zn fe cu deposit in the eastern part of the central asian orogenic belt provides a unique example to address this issue the major rock types in the mine area are early paleozoic intrusions composed of biotite syenogranite and biotite porphyritic granite and early mesozoic intrusions represented by porphyritic quartz monzonite biotite monzogranite and porphyritic granite the diagnostic mineralogical and geochemical features indicate that the rocks belong to a2 type granites the early paleozoic suite shows zircon u pb ages of 501 ma and ehf t values of 4 4 to 2 7 and 2 4 to 7 6 respectively in combination with their coherent geochemical trends these rocks are inferred to be products of in situ differentiation although the mesozoic suite shows crystallization ages of 194 196 ma ehf t values are in the range of 2 5 to 7 5 for the porphyritic quartz monzonite the 1 8 to 4 5 values for the monzogranite and the 2 3 to 8 0 range for the porphyritic granite the porphyritic quartz monzonite displays distinct mineral assemblage and shows significant compositional gap with the other two lithofacies in contrast the monzogranite and porphyritic granite have similar geochemical features and are thus inferred to be co magmatic considering the high sio2 contents variable ehf t 4 4 to 8 0 and end t values 8 4 to 0 28 for the two suites we infer that both episodes of granitoid magmatism resulted from partial melting of crustal materials with a mixed source containing varying proportions of juvenile and precambrian crustal components the early mesozoic porphyritic granite shows a highly evolved f rich geochemical affinity and experienced magma fluid interaction cassiterite from the calcic skarn and the magnesian skarn that coexists with magnetite orebodies shows a mean u pb age of 195 4 1 9 ma and 191 2 7 5 ma respectively indicating that the mineralization is genetically related to the mesozoic granitic rocks we infer that halogen rich magmatic hydrothermal fluids were derived from the early mesozoic highly fractionated magma and the spatial association of the metallic elements with different geochemical behavior in the cuihongshan deposit is correlated to multiple stages of evolution of halogen rich magmatic hydrothermal fluids

formation mechanism of the lanthanide tetrad effect for a topaz and amazonite bearing leucogranite pluton in eastern xinjiang nw china abstract the baishitouquan bst pluton is a topaz and amazonite bearing leucogranite intrusion located in the middle tianshan orogen of xinjiang northwestern china this pluton exhibits five lithological zones gradational from the bottom upwards leucogranite zone a amazonite bearing granite zone b amazonite granite zone c topaz bearing amazonite granite zone d and topaz albite granite zone e contents of ree and other trace elements were analysed on major and accessory minerals including quartz plagioclase k feldspar white micas topaz fluorite garnet zircon and monazite separated from above five zones of the bst pluton chondrite normalized ree patterns of minerals from zone a to zone e display clear convex tetrad effect and the te1 3 quantification factor of tetrad effect values of these minerals increases from zone a to zone e except that a quartz sample from zone b and zircon from zone c exhibits w type tetrad effect therefore we conclude that ree tetrad features of the minerals such as quartz plagioclase zircon garnet and monazite are inherited directly from the melt and have not significantly affected by both fractional crystallization and surface weathering with progressing of magmatic differentiation total ree contents decrease eu anomaly becomes more negative whereas nb ta zr hf and y ho ratios decrease gradually from zone a to zone e with increasing te1 3 values therefore we suggest that f rich magmatic fluid melt interaction above its solidus may leave the residual silicate melt with the features of very low contents of all ree subchondritic y ho zr hf and nb ta values and with an m type tetrad pattern including minerals crystallizing from it such a pattern is manifested by both whole rock and separate minerals hydrothermal fluid rock interaction played only a minor role to the convex tetrad effect of the minerals and their host rocks

rare earth element geochemistry and the tetrad effect abstract the tetrad effect is found in the rare earth elements la lu and results from increased stability at quarter half three quarter and complete filling of the 4f electron shell suggestions that this effect is observed in ree patterns of seawater and other geological samples marine phases the mineral kimuraite late stage granitic rocks the mineral uraninite and siliciclastic sediments are not compelling in the cases of seawater and the carbonate mineral kimuraite a discontinuity at gd may be attributed to the tetrad effect but the complexity of the overall controls on these ree distributions leaves such an interpretation uncertain at best unusual ree patterns in leucogranites and pegmatites are best explained by fractionation of trace minerals notably apatite apparent tetrad anomalies in uraninite rees disappear when normalised to upper crustal i e shale abundances analytical difficulties probably explain apparent tetrad effects in some seawater limestone and siliciclastic ree patterns

geochemistry and hf nd isotope characteristics and forming processes of the yuntoujie granites associated with w mo deposit guangxi south china abstract the yuntoujie w mo deposit is so far the only indosinian granite related deposit with an element association of w mo in the nanling ore belt south china the granites in the yuntoujie ore field consist of the yuntoujie batholith and late stage granites the w mo mineralization is associated closely with the late stage granites here we report major and trace element sr nd isotope and zircon hf isotope compositions of the yuntoujie batholith and the late stage granites the yuntoujie batholith and the late stage granites have high sio 2 70 77 74 86 wt and alkaline k 2 o na 2 o 6 27 8 27 wt concentrations and are characterized as peraluminous a cnk 1 1 a nk 1 30 1 43 the yuntoujie batholith and late stage granites feature negative correlation between th y and rb no positive correlation between p 2 o 5 and sio 2 and high a cnk values 1 1 suggesting that they could be classified as s type granites the yuntoujie batholith and the late stage granites might be sourced from the partial melting of proterozoic crust without contribution from juvenile crust as evidenced from the low 143 nd 144 nd values of 0 511942 0 512477 the nd t values of 8 52 to 11 76 falling in the field of nd isotope evolution for the proterozoic crust and the zircon hf t values of 7 19 to 14 89 with the t dm2 ranging from 1713 ma to 2187 ma the major and trace element compositions of the yuntoujie batholith and late stage granites especially the low cao na 2 o and cao mgo feo t ratios and the high rb ba and rb sr ratios further indicate that their sources are predominantly argillaceous sedimentary the trace element characteristics such as the positive correlation between la yb and la and between ba and sr and negative correlation between ba and rb suggest that the late stage granites are the product of highly fractionated melts of the yuntoujie magma chamber moreover 1 the tetrad effect observed in the ree patterns for the late stage tourmaline muscovite monzogranite porphyry and 2 the abundant fluid inclusions in their quartz phenocrysts imply that the processes of the volatile phase exsolution and the fluid melt reaction had taken place in the evolved water saturated magma these geochemical features together with the fact that the yuntoujie magma chamber had survived for 10 myr suggest that the peraluminous magma experienced a prolonged period of crystallization differentiation which plays a key role in the formation of w mo mineralization associated with granites from the observations that the granites in the yuntoujie district were formed about 20 10 ma later than the peak age of the indosinian collisions and that they all fall in the post ceg area in the tectonomagmatic discrimination diagrams we proposed that the yuntoujie granites were formed in the post collisional environment