the historical and palaeoflood record of katherine river northern australia evaluating the likelihood of extreme discharge events in the context of the 1998 flood the discharge regimes of the large rivers of northern australia are characterized by the occurrence of extreme flood events with far reaching environmental and societal impacts in january 1998 the largest flood ever recorded on the katherine river northern australia resulted in widespread inundation and resultant damage to the town of katherine the occurrence of the flood emphasized the unreliability of the then available flood probability estimates and prompted a palaeoflood approach to estimate the recurrence interval of the event the location of katherine is ideal for such a study as the town is located immediately downstream from katherine gorge which provides the necessary bedrock confined channel required for such an approach in addition previous work in katherine gorge had demonstrated that the gorge sections hold suitable deposits for palaeoflood stage reconstruction the results of the present study show that at least two flow events with discharges similar to the 1998 flood have occurred within the last 600 years and that high magnitude floods are a general feature of the discharge record of the katherine river over the last c 2000 years furthermore because the study was undertaken within a few months of the occurrence of the 1998 flood it provided the opportunity to evaluate the previously obtained flood discharge estimates and draw attention to the general uncertainties associated with palaeoflood studies our results emphasize that palaeoflood stage estimates based on slackwater deposits need to be treated as conservative estimates only more specifically with respect to the 1998 event our study demonstrates that the controls of flood peak were more complex than simply flood routing through the gorge sections it is clear that the areas downstream from katherine gorge made an important contribution to the flood peak of the 1998 event copyright 2005 john wiley sons ltd

intersector element partitioning in tourmaline a potentially powerful single crystal thermometer hourglass sector zoning and related polar overgrowths are common features of metamorphic tourmaline developing as a result of variations in element preference on the different growth surfaces for sector zoned crystals three domains are present for each growth zone c c and a with compositional differences most distinct for ca and ti and among c and c sectors intersector differences vary commonly showing decreasing fractionation from core to rim attributed to increasing metamorphic grade here we show that intersector element partitioning is temperature dependent and derive empirical geothermometers based on c c and c a partitioning of ca and ti these thermometers are applicable over a range of temperatures and bulk rock compositions intersector partitioning is not affected by re equilibration and records and preserves complete t histories of individual tourmaline grains from prograde to peak and on to retrograde growth information on element mobility is preserved by tourmaline composition because intersector partitioning is independent of element concentration these factors make intersector partitioning an ideal tool to elucidate the thermal history of tourmaline grains and thus their host environment and tourmaline s refractory nature preserves these signatures even into the sedimentary record

the origin and mode of emplacement of lujavrites in the ilimaussaq alkaline complex south greenland abstract lujavrites are rare meso to melanocratic agpaitic nepheline syenites that are characterized by elevated contents of elements such as li be zr ree nb th and u they are the most evolved members of the three large composite agpaitic complexes lovozero kola peninsula russia pilansberg south africa and ilimaussaq south greenland and are inferred to stem from the same deep fractionating magma sources that fed the earlier members of the complexes the composition of the melts that evolved into lujavrites is however not well known the agpaitic part of the ilimaussaq complex is divided into a roof series a floor series of cumulates and an intermediate series of lujavrites sandwiched between the two in the traditional view the lujavrites formed from residual melts left between the downward crystallizing roof series and the floor cumulates new field observations and geochemical data suggest that the floor cumulates and the main mass of lujavrites constituted a separate intrusive phase which was emplaced into the already consolidated roof series rocks largely by piecemeal stoping studies of the contact facies of the floor cumulates indicate that the initial magma of the floor cumulate lujavrite sequence was peralkaline nepheline syenitic with enhanced contents of zr hf hree y nb ta f ba and sr subsequent crystallization in a closed system resulted in the formation of the floor cumulates and lujavrites chemical analyses of dykes within and outside the complex represent stages in the magmatic evolution of the agpaitic rocks

geochemistry and origins of carbonate fluorapatite in seamount fe mn crusts from the pacific ocean abstract seamount phosphates are increasingly regarded as potential resources for rare earth elements ree and plus yttrium rey carbonate fluorapatite cfa formed within seamount ferromanganese fe mn crusts is the most common seamount phosphate mineral however reports on the mineralogy and geochemistry of cfa are few and thus its origin and acquisition of trace elements are not well understood in this study we analyzed the major and trace elements of cfa in fe mn crusts collected from western and central pacific seamounts to investigate the genesis of trace elements in the cfa this is the first study to use in situ analytical techniques such as electron microprobe analyzer epma and laser ablation inductively coupled plasma mass spectrometry la icp ms to analyze seamount cfa we found that the cfa hosts abundant minor and trace elements and propose that ionic substitutions are responsible for the high contents of so3 sio2 rey sr na fe and mn in the cfa veins found in the fe mn crusts i e sio32 and so42 substitute for po42 while ree3 y3 na fe2 and mn2 substitute for ca2 ree3 substitutions for ca2 in the cfa are charge compensated by na substitution for ca2 fourier transform infrared spectroscopy ftir analysis shows that co32 mainly substitutes for po42 in the cfa crystal structure and there is a minor substitution of po42 by co3f3 ocean water is the major source of the p and rey which when precipitated as seamount cfa is characterized by high ree 345 to 6016 ppm and heavy ree hree enrichments monazite grains dispersed in the seamount cfa contribute trace amount of rey these results shed light on the composition and element mobility of seamount cfa with economic potential which also provides valuable insights into global ocean chemical cycling e g ree

the mineralogical diversity of alkaline igneous rocks critical factors for the transition from miaskitic to agpaitic phase assemblages geochemically the large family of alkaline plutonic rocks both qtz undersaturated and oversaturated compositions can be subdivided into metaluminous na 2 o k 2 o al 2 o 3 types in this paper we discuss two important aspects of the mineralogical evolution of such rocks with respect to their fe mg phases a major mineralogical transition observed is the precipitation of arfvedsonite or aegirine instead of fayalite or magnetite ilmenite the relative stability of these phases is controlled by oxygen fugacity and na activity in the crystallizing melts if na activity in the melt is high enough arfvedsonite aegirine form a common assemblage in peralkaline rocks under both reduced and oxidized conditions major mineralogical differences within this rock group exist with respect to their high field strength element hfse rich minerals most syenitic rocks known as miaskites contain zircon titanite or ilmenite as hfse rich minerals whereas in agpaites complex na k ca ti zr silicates incorporate the hfse similarly only a small group of peralkaline granites are found to lack zircon titanite or ilmenite but instead contain na k ca ti zr silicates here we present a detailed phase petrological analysis of the chemical parameters na 2 o cao k 2 o that influence the transition from miaskitic to agpaitic rocks based on the occurrence of ti and zr minerals several transitional mineral assemblages are identified and two major evolution trends for agpaites are distinguished a high ca trend which is exemplified by the alkaline rocks of the kola province russia and a ca depletion trend which is displayed by the alkaline rocks of the gardar province south greenland both trends show significant na enrichment during magmatic evolution high ca agpaites evolve from nephelinitic parental melts that did not crystallize large amounts of plagioclase in contrast agpaites showing ca depletion originate by extensive fractionation of plagioclase from basaltic parental melts in some peralkaline granites evolutionary trends are observed that culminate in agpaite like hfse mineral associations in the most evolved rocks

comment on apatite a new redox proxy for silicic magmas geochimica et cosmochimica acta 132 2014 101 119

volatiles in a peralkaline system abiogenic hydrocarbons and f cl br systematics in the naujaite of the ilimaussaq intrusion south greenland agpaitic rocks comprise most of the exposed part of the 1 16 ga old 8 17 km large and about 1700 m thick ilimaussaq intrusion in south greenland within these more than 600 m thick sequence of sodalite rich naujaites mainly sodalite arfvedsonite alkali feldspar nepheline eudialyte aenigmatite are interpreted as a sodalite flotation cumulate sodalites show two to three different zones in cathodoluminescence cl and at least two zones in thin sections the cl zones can be related to chemical differences detectable by electron microprobe whereas relations with optical zonations are less obvious compositional trends in sodalite reflect trends in the evolution of volatile contents in the melt the sodalite at ilimaussaq is almost free of ca and closely corresponds to the pure na cl sodalite endmember with about 7 wt of cl s contents reach up to 0 9 wt cl br ratios range from 500 to 1700 raman spectroscopy shows that s is present as so4 2 in sodalite although sphalerite zns is a stable phase in naujaites peralkalinity and fo2 conditions allow s2 and so4 2 to be present contemporaneously the whole naujaite sequence is divided into two parts an upper part with low homogeneous s contents and cl br ratios in the sodalite cores and a lower part with strongly variable and higher s contents and with cl br ratios which are decreasing downwards the details of the s content and the cl br ratio evolution show that sodalite strongly influences the halogen contents of the melt by scavenging cl and br the naujaites were formed from a highly reduced halogen rich magma in equilibrium with magmatic methane at about 800 c which upon ascent cooling and fractionation exsolved an aqueous fluid phase both fluids were trapped in separate inclusions indicating their immiscibility micrometer sized aegirine crystals and primary hydrocarbon bearing inclusions are abundant in the crystal cores the inclusions were trapped at pressures up to 4 kbar although the emplacement pressure of the intrusion is about 1 kbar this indicates growth of the sodalite during melt ascent and a very effective mechanism of trace element scavenging during sodalite growth sodalite rims are devoid of aegirine or primary hydrocarbon inclusions and probably reflect the emplacement stage

rare earth elements in apatite as a monitor of magmatic and metasomatic processes the ilimaussaq complex south greenland abstract textural and compositional variations of apatite from the plutonic ilimaussaq complex in south greenland and its surrounding country rocks track magmatic and metasomatic processes detailed back scattered electron bse imaging reveals various types of apatite textures including i growth zonation concentric oscillatory as well as sector zonation formed during magmatic differentiation ii resorption and overgrowth textures due to fluid melt induced metasomatic overprint of precursor apatite and iii replacement textures indicating the destabilization of apatite in favor of monazite in the least evolved rocks of the ilimaussaq complex apatite incorporates rare earth elements and y rey mainly via the coupled substitution ca 2 p 5 rey 3 si 4 in the more evolved peralkaline rocks and in metasomatically overprinted rocks however the coupled substitution 2 ca 2 rey 3 na becomes increasingly relevant and apatite incorporates successively more lree compared to hree as shown by increasing la gd n and gd yb n ratios similarly at the contact between the ilimaussaq rocks and the granitic country rocks the metasomatic effect of the emplacement of the ilimaussaq melts is preserved in partly resorbed precursor apatite which is overgrown by rey enriched apatite with higher la gd n and gd yb n ratios compared to apatite from granites more distant from the contact this study shows that apatite textures and compositions are suitable to track both primary magmatic and later fluid present metasomatic processes the incorporation of rey in apatite is not only dependent on the amount of rey present but also depends largely on na activity in the apatite precipitating melts and fluids

arrested kinetic li isotope fractionation at the margin of the ilimaussaq complex south greenland evidence for open system processes during final cooling of peralkaline igneous rocks li contents li and isotopic composition 7 li of mafic minerals mainly amphibole and clinopyroxene from the alkaline to peralkaline ilimaussaq plutonic complex south greenland track the behavior of li and its isotopes during magmatic differentiation and final cooling of an alkaline igneous system li in amphibole increase from b10 ppm in caamphiboles of the least differentiated unit to n3000 ppm in na amphiboles of the highly evolved units in contrast li in clinopyroxene are comparatively low b85 ppm and do not vary systematically with differentiation the distribution of li between amphibole and pyroxene is controlled by the major element composition of the minerals ca rich and na rich respectively and changes in oxygen fugacity due to li incorporation via coupled substitution with ferric iron during magmatic differentiation 7 li values of all minerals span a wide range from 17 to 8 with the different intrusive units of the complex having distinct li isotopic systematics amphiboles which dominate the li budget of whole rocks from the inner part of the complex have constant 7 li of 1 8 2 2 2 n 15 this value reflects a homogeneous melt reservoir and is consistent with their mantle derivation in agreement with published o and nd isotopic data clinopyroxenes of these samples are consistently lighter with 7 liamph cpx as large as 8 and are thus not in li isotope equilibrium these low values probably reflect late stage diffusion of li into clinopyroxene during final cooling of the rocks thus enriching the clinopyroxene in 6 li at the margin of the complex 7 li in the syenites increases systematically from 2 to high values of 14 this coupled with the observed li isotope systematics of the granitic country rocks reflects post magmatic open system processes occurring during final cooling of the intrusion although the shape and magnitude of the li isotope and elemental profiles through syenite and country rock are suggestive of diffusion driven isotope fractionation they cannot be modeled by one dimensional diffusive transport and point to circulation of a fluid having a high 7 li value possibly seawater along the chilled contact in all this study

apatite in the dike gabbro transition zone of mid ocean ridge evidence for brine assimilation by axial melt lens we present textures and halogen and trace element compositions of apatites in intrusive rocks from the dike gabbro transition zone of a fast spreading mid ocean ridge which was formed at the east pacific rise and recently drilled by iodp hole 1256d these data are used to discuss the properties of parental magmas and seawater derived hydrothermal fluids at the roof of the axial melt lens during the formation of oceanic crust in general zoning of apatites from three different lithologies tonalites diorites and gabbros is common and shows a consistent evolution trend with depletion in cl and rees from core to rim the cores are usually homogenous in composition and interpreted as magmatic origin whereas zones with lower cl and rees are disseminated with heterogeneous concentrations indicating exchanges with hydrothermal fluids the apatite cores in tonalites are rich in both f and cl with x ap f proportion of fluorapatite end member up to 0 5 and x ap cl proportion of chlorapatite end member up to 0 4 in contrast the apatite cores in gabbros have high x ap cl up to 0 85 and very low x ap f s in some parts of the apatite crystals mainly rim can be explained by removal of these components via hydrothermal fluids based on available f cl oh exchange coefficients for apatite melt the very high cl oh and cl f ratios and high cl contents calculated for tonalitic melts cannot be reconciled with a formation of these felsic melts by partial melting of amphibole bearing metabasalts but indicate that an assimilation of high cl brines must have occurred similarly the low f chlorapatites in gabbros also imply an assimilation of high cl brines the source of high cl fluids in the axial magmatic system may result from seawater derived fluids which may form immiscible vapor and brine at high temperatures as a result of hydrothermal boiling

rare earth elements in apatite uptake from h2o bearing phosphate fluoride melts and the role of volatile components the partitioning of rare earth elements rees between fluorapatite fap and h sub 2 o bearing phosphate fluoride melts has been studied at about 700 and 800 degrees c and 0 10 0 15 gpa ree uptake patterns i e plots of d ree fap melt are convex upwards and peak near nd for single ree substituted fap at minor 0 03 0 25 wt ree sub 2 o sub 3 abundances and binary lree hree substituted fap and hexa ree substituted fap at minor to major 0 25 7 8 wt ree sub 2 o sub 3 abundances partition coefficients for minor abundances of ree and depolymerized phosphate melts are about 5 8 and 1 for la nd and lu respectively and broadly comparable to those for early fluorapatite in the fractionation of melts of basaltic composition the ca2 site exerts marked control on the selectivity of apatite for ree because it preferentially incorporates lree and its effective size varies with substitution of the a site volatile anion component f cl oh using simple crystal chemical arguments melt or fluid normalized ree patterns are predicted to peak near nd for fluorapatite and be more lree enriched for chlorapatite these predictions are consistent with data from natural rocks and laboratory experiments the wide variation in d ree apatite melt in nature from 1 for whitlockite bearing lunar rocks to about 100 for evolved alkalic rocks ismore attributed largely to the influence of the volatile components 49 refs 8 figs 3 tabs less

accessory mineral chemistry as a monitor of petrogenetic and metallogenetic processes a comparative study of zircon and apatite from wushan cu and zhuxiling w mo mineralization related granitoids abstract in this study we explore the chemistry of accessory apatite and zircon as tools to monitor the petrogenetic and metallogenetic processes involved in the formation of the wushan cu and zhuxiling w mo mineralization related granodiorite porphyry the wushan granitoids are metaluminous with a cnk of 0 88 1 01 and the zhuxiling intrusions are weakly peraluminous with higher a cnk values 1 02 1 12 the wushan granitoids have end t values of 4 6 to 4 7 which combined with the relatively elevated mg values 57 62 and adakitic features high sr y ratios of 51 60 indicate that they were derived from melting of a thickened lower crust of the yangtze block with addition of small amounts of mantle components compared to the wushan granitoids the zhuxiling granitoids have relatively high 87sr 86sr i 0 70945 0 70951 and low end t values 5 9 to 6 3 and zircon ehf t values 3 8 to 9 0 suggesting their derivation dominantly from partial melting of the neoproterozoic crust the apatites from the zhuxiling samples are characterized by relatively high mno and feo variable y and low ce which is consistent with the weakly peraluminous feature of whole rock chemistry these apatites show notable depletion of th and lree with a lower la sm n ratio 0 74 1 44 and la yb n ratio 6 2 17 9 relative to those of the host rock 3 04 3 61 and 19 1 23 4 respectively suggesting early crystallization of some lree and th enriched minerals such as allanite monazite before apatite crystallization the steep trend of ce sm versus yb gd ratios shown by zircons from the zhuxiling granitoids suggests that the crystallization of zircon is affected by the crystallization of titanite and apatite thus the crystallization sequence of accessory minerals in the zhuxiling intrusion is allanite apatite titanite and zircon the apatites from the wushan granitoids however show strongly lree enriched ree patterns with weak negative eu anomalies which indicate minor feldspar fractionation and mildly magmatic differentiation the flat trend of ce sm versus yb gd ratios shown by zircon from the wushan pluton indicates that its ree composition is affected by hornblende saturation zircon grains from the metaluminous wushan granitoids exhibit remarkably higher ce4 ce3 ratios and weaker eu eu anomalies than those of the peraluminous zhuxiling samples and the apatites from the wushan samples show higher eu eu 0 55 0 62 and lower ce ce 0 91 1 04 and mno 0 05 0 09 compared to those of the zhuxiling pluton with eu eu 0 41 0 50 ce ce 1 06 1 11 and mno 0 15 0 18 respectively the apatite and zircon chemistry suggest that the cu bearing granitoid formed at an oxygen fugacity higher than the w bearing granitoid which agrees with the fact that the wushan granitoids show whole rock fe3 fe2 ratios higher than the zhuxiling granitoids in addition apatites from the wushan intrusion show enrichment of cl and higher f cl ratios compared to those of the zhuxiling samples suggesting that a water rich parental magma with relatively high cl content is favourable for copper mineralization this case study shows that apatite and zircon chemistry could reflect the geochemical characteristics of their host rock and magma evolution moreover they provide insights into the oxidation state halogen fugacity and magma differentiation of the magmatic system which are key factors for mineralization our data suggest that magma associated with cu mineralization is relatively oxidizing chlorine enriched and less fractionated compared to w bearing magma

coupled substitutions involving rees and na and si in apatites in alkaline rocks from the ilimaussaq intrusion south greenland and the petrological implications ansrnlcr apatites from the ilimaussaq augite syenite the sodalite foyaite and a qtartz bearing peralkaline pegmatite have been analyzed using an electron microprobe for the major elements plus na si and selected rare earth elements rees in all three rock types the maximum reeto3 content in the apatite exceeds 16 0 wt0 0 apatite from the augite syenite and primary apatite from the sodalite foyaite are characterizedby a low na content that varies independently of the ree content the composition of these apatites approaches 25 molo o of the end member carreq sio4 3 oh f cl lessingite in response to the substitution ree3 sia ca2 ps ree and na enriched apatites from the quartzbearing peralkaline pegmatite are almost si free and rees and na are positively correlated the composition of these apatites approaches 25 molo o of the hypothetical endmember na5ree5 po4 6 oh f ci 2 in response to the substitution na ree3 2ca2 the compositional trend of late crystalllzing apatite from the sodalite foyaite reflects almost equal contributions of the two substitutions the relationship between these substitutions in a given apatite and its associated mineral assemblage indicates that the na component is only present in considerable amounts when apatite crystallizes in a strongly peralkaline environment

apatite liquid partition coefficients for the rare earth elements and strontium abstract sixteen sets of apatite liquid partition coefficients dap liq for the rare earth elements ree la sm dy lu and six values for sr were experimentally determined in natural systems ranging from basanite to granite the apatite melt glass assemblages were obtained from starting glasses artificially enriched in ree sr and fluorapatite components these were run under dry and hydrous conditions of 7 5 20 kbar and 950 1120 c in a solid media piston cylinder apparatus an sem equipped electron microprobe was used for subsequent measurement of ree and sr concentrations in coexisting apatites and quenched glasses the resulting partition coefficient patterns resemble previously determined apatite phenocryst groundmass concentration ratios in the following respects 1 the rare earth patterns are uniformly concave downward i e the middle ree are more compatible in apatite than the light and heavy ree 2 dreeap liq is much higher for silicic melts than for basic ones and 3 strontium and therefore eu2 is less concentrated by apatite than are the trivalent ree the effects of both temperature and melt composition on dreeap liq are systematic and pronounced at 950 c for example a change in melt sio2 content from 50 to 68 wt causes the average ree partition coefficient to increase from 7 to 30 a 130 c increase in temperature on the other hand results in a two fold decrease in dreeap liq partitioning of sr is insenstitive to changes in melt composition and temperature and neither the sr nor the ree partition coefficients appear to be affected by variations in pressure or h2o content of the melt the experimentally determined partition coefficients can be used not only in trace element modelling but also to distinguish apatite phenocrysts from xenocrysts in rocks reported apatite megacryst host basalt ree concentration ratios 12 for example are considerably higher than the equilibrium partition coefficients which suggest that in this particular case the apatite is actually xenocrystic a reversal experiment incorporated in our study yielded diffusion profiles of ree in apatite from which we extracted a ree ca interdiffusion coefficient of 2 4 10 14 cm2 s at 1120 c extrapolated downward to crustal temperatures this low value suggests that complete ree equilibrium between felsic partial melts and residual apatite is rarely established

geochemistry of zircon and apatite from the mo ore forming granites in the dabie mo belt east china implications for petrogenesis and mineralization abstract the dabie molybdenum mo belt in east china is an important mo belt in both china and the world all of the mo deposits in the dabie area are porphyry skarn type the ore related granite samples from the qian echong tangjiaping and doupo mo deposits in the mo belt have been collected for zircon and apatite trace elements analysis additionally the doupo ore related granite has also been chosen for zircon u pb dating la icp ms zircon u pb dating of the ore related granite in the doupo mo deposit yields a crystallization age of 127 1 ma which is consistent with the molybdenite re os age of the deposit the chondrite normalized patterns of all zircons are characterized by positive ce anomalies with variable negative eu anomalies the ore related granites in the qian echong and tangjiaping mo deposits show relatively high magmatic oxygen fugacity fmq 1 5 whereas the doupo ore related granite has a relatively low magmatic oxygen fugacity fmq 0 3 which might have caused it to have relatively small mo reserve compared to the qian echong and tangjiaping deposits all of the apatites from the three mo deposits are characterized by lree enriched and hree depleted chondrite normalized patterns with various degrees of eu depletion and ce enrichment not only redox condition but also other factors could have influenced the eu eu or and ce ce of apatite in this study and the anomalies of eu and ce of apatites from the ore related granites in this study could not be used to evaluate the magma redox states the geochemical characteristics of apatite indicate that the ore forming magmas of the mo deposits in this study are oxidized and metaluminous i or a type magmas during the early cretaceous regional extension and asthenospheric upwelling in the dabie orogen partial melting of the crustal rocks generated oxidized mo bearing magma relatively oxidized condition prevents mo from incorporating into sulfides or silicates in the magma and finally leads to mo precipitation from the ore forming fluids which released from the magma

experimental determination of stability relations between monazite fluorapatite allanite and ree epidote as a function of pressure temperature and fluid composition the experimental alteration of monazite to allanite ree epidote fluorapatite and or fluorapatite britholite was investigated at 450 to 610 mpa and 450 to 500 c experiments involved monazite albite k feldspar muscovite biotite sio 2 caf 2 and variety of fluids including h 2 o kcl h 2 o nacl h 2 o cacl 2 h 2 o na 2 si 2 o 5 h 2 o 1 m hcl 2 m naoh 2 m koh 1 m ca oh 2 2 m ca oh 2 and caco 3 h 2 o the reaction products or lack thereof clearly show that the stability relations between monazite fluorapatite and allanite or ree epidote are more dependent on the fluid composition and the ratio of silicate minerals than on the p t conditions a high ca content in the fluid promotes monazite dissolution and the formation of fluorapatite and allanite or ree epidote lowering the ca content and raising the na content in the fluid decreases the solubility of monazite but promotes the formation of allanite replacing na with k in the same fluid causes fluorapatite with a britholite component to form from the monazite however allanite and ree epidote are not formed monazite is stable in the presence of nacl brines in kcl brine monazite shows a very limited reaction to fluorapatite when the fluid is na 2 si 2 o 5 h 2 o strong dissolution of monazite occurs resulting in the mobilization of rees and actinides to form fluorapatite britholite and turkestanite these experimental results are consistent with natural observations of the partial to total replacement of monazite by fluorapatite ree epidote and allanite in fluid aided reactions involving the anorthite component in plagioclase at mid to high grade metamorphic conditions in contrast an alkali bearing environment with excess na prevents the growth of allanite and eventually promotes the precipitation of secondary monazite the results from this study provide implications for geochronology and for deducing fluid compositions in metamorphic rocks

whole rock phosphate and silicate compositional trends across an amphibolite to granulite facies transition tamil nadu india chemical trends from north amphibolite facies to south granulite facies along a 95 km traverse in tamil nadu southern india include whole rock depletion of rb cs th and u enrichment in ti and f and depletion in fe and mn in biotite and amphibole increases in al and decreases in mn in orthopyroxene enrichment of fluorapatite in f k feldspar blebs are widespread along quartz plagioclase grain boundaries and could indicate either partial melting or metasomatism in the northernmost portion of the traverse the principal rare earth element ree bearing minerals are allanite and titanite south of a clinopyroxene isograd monazite grains independent of fluorapatite are the major ree and th bearing phase further south independent monazite is rare but th free monazite inclusions are common in fluorapatite during prograde metamorphism independent monazite was replaced by ree rich fluorapatite in which the monazite inclusions later formed the loss of independent monazite was accompanied by a loss of whole rock th and possibly a small depletion in light ree most mineralogical features along the traverse can be accounted for by progressive dehydration and oxidation reactions trace element depletion is best explained by the action of an externally derived low h2o activity brine migrating from a source at greater depth possibly preceded or accompanied by partial melting

deciphering magmatic and metasomatic processes recorded by fluid inclusions and apatite within the cu ni pge sulfide mineralized bathtub intrusion of the duluth complex ne minnesota usa

the early caledonian finnmarkian event reassessed in finnmark 40ar 39ar cleavage age data from nw varangerhalvoya n norway abstract the relative significance of early finnmarkian and late scandian caledonian deformation in n norway is uncertain early studies suggested pervasive finnmarkian deformation whilst later results indicated a restricted finnmarkian domain the present work suggests it was more widespread than accepted and that inter finnmarkian scandian deformation occurred 40 ar 39 ar dating of 2 6 and 6 11 m pelitic fractions from the lower to mid greenschist facies tanahorn nappe five samples base middle allochthon and the epizone lokvikfjellet and barents sea groups three samples north varanger region in the north scandinavian caledonides show slightly discordant spectra most spectra from the tanahorn nappe preserve possible evidence of an early caledonian event in the high temperature steps with recoil excess ar effects in the low temperature steps no pre caledonian relict component has been recorded the results indicate finnmarkian deformation continued to 460 ma with scandian reactivation at 425 415 ma from the north varanger region a strongly crenulated sample yielded plateau ages 444 442 ma means of combined young steps from weakly to uncrenulated samples gave 470 450 ma suggesting penetrative strike slip deformation occurred in the late finnmarkian to inter finnmarkian scandian period no scandian ages were recorded in the north varanger region reassessment of published data from the laksefjord nappe and gaissa thrust belt suggests they were affected by finnmarkian deformation

apatite in the ilimaussaq alkaline complex occurrence zonation and compositional variation abstract apatite from the augite syenite and the roof sequence of layered nepheline syenites pulaskite foyaite sodalite foyaite and naujaite of the ilimaussaq alkaline complex has been analysed by electron microprobe for ca p na si selected rare earth elements ree f and cl in the augite syenite chilled facies and middle zone euhedral apatite crystals are relatively abundant as inclusions in other liquidus phases the ree content is ca 1 wt ree 2 o 3 the same level is found in interstitial apatite in the coarse grained innermost facies ree enriched intercumulus apatite overgrowths are common and can have up to ca 18 wt ree 2 o 3 apatite is a common phase in the pulaskite and foyaite whereas it is rare in the sodalite foyaite and naujaite based on compositional variation and zoning it is possible to distinguish four generations of apatite in the layered roof sequence 1 primary apatite belonging to the high temperature mineral assemblage this apatite occurs in the pulaskite foyaite and sodalite foyaite as oscillatory zoned crystals whereas only remnants are found in the naujaite the ree enrichment is dominated by the ca 2 p 5 ree 3 si 4 substitution and maximum ree 2 o 3 exceeds 20 wt 2 irregularly zoned apatite occurs as rim zones on the primary apatite in the foyaite and as the dominant type of apatite in the sodalite foyaite and naujaite most irregularly zoned grains are altered primary apatite during the dissolution and recrystallisation process the composition gradually changed towards a lower ree content 3 overgrowths of homogeneous apatite on the irregularly zoned apatite in the naujaite 4 na and ree rich apatites occur in the foyaite sodalite foyaite and naujaite either as overgrowths on earlier generations of apatite or as individual crystals calculated chondrite normalised patterns show that the later generations of apatite are relatively enriched in lree and depleted in hree the most pronounced evolution is found in na and ree rich apatite apatite melt partition coefficients for la ce nd sm dy y and yb are calculated for the augite syenite and nepheline syenites of the roof sequence the coefficients show the characteristic convex shape with a maximum around nd and sm using the calculated partition coefficients and the chemical composition of the na and ree rich apatite the ree content of a late aqpaitic melt in the roof sequence is estimated the shape of the chondrite normalised pattern is similar to that of a late arfvedsonite lujavrite dyke and steeper than the patterns of the primary magma

apatite in igneous systems apatite is a minor but ubiquitous mineral in most igneous rocks although the modal proportion of apatite in common rocks is generally low it can reach high concentrations in enclaves cumulates and other rocks of low abundance i e rocks that constitute a small volume of the crust and mantle e g nelsonites the presence of apatite in most rocks is due not only to its low solubility in naturally occurring melts and aqueous solutions but also to the limited ability of common rock forming minerals to accept the amount of phosphorus that occurs in most rocks into their structure in this paper we will discuss some aspects of the occurrence texture composition physical chemistry and petrogenetic significance of apatite in felsic rocks i e andesite to rhyolite and their plutonic analogs in mafic i e basalts and related rocks and plutonic analogs and ultramafic rocks of the earth s crust and mantle fluorapatite is by far the most common member of apatite family found in igneous rocks however most natural fluorapatite contains some chlorine and hydroxyl as well and these constituents can attain high concentrations in some cases the other halogens bromine and iodine also occur in apatite but their concentrations are much lower than chlorine and fluorine many cations commonly substitute for calcium and phosphorus in apatite however they rarely reach concentrations that warrant the definition of a separate mineral species apatite can be described by the general formula a5 xo4 3z following sommerauer and katz lehnert 1985 the a site accommodates large cations e g ca2 sr2 pb2 ba2 mg2 mn2 fe2 ree3 eu2 cd2 na pan and fleet ch 2 in this volume and comprises two sites that exhibit vii fold

fluid induced nucleation of y ree phosphate minerals within apatite nature and experiment part i chlorapatite this study investigates chlorapatite ideally ca10 po4 6cl2 from two spatially separated locations in the odegardens verk apatite mine bamble sector se norway which was partially metasomatized under amphibolite facies conditions relative to the original chlorapatite metasomatized areas in sample dl136 are enriched in oh and f depleted in na si and y ree and contain numerous inclusions 1 15 m of monazite and xenotime in contrast metasomatized areas in sample tn174 are enriched in f and si depleted in na show y ree abundances similar to the original chlorapatite and host only a few monazite and xenotime grains in order to define the role of fluids in the formation of y ree phosphate minerals associated with apatite a series of experiments covering wide ranges of temperature 900 300 c and pressure 1000 500 mpa for a series of fluid compositions pure h2o a 50 50 molar mix of h2o and caf2 and co2 with 1 2 wt h2o were conducted on unaltered chlorapatite from the odegardens verk in the h2o experiments features due to metasomatic alteration depletion in na si and y ree as well as numerous monazite and xenotime inclusions as observed in the natural sample dl136 were fully reproduced monazite and xenotime grains were also observed growing on the surface of the apatite in dissolution embayments in metasomatized areas in the 50 50 caf2 h2o experiments metasomatized regions are strongly enriched in f and si depleted in na show unchanged y ree abundances and contain only a very few small monazite and xenotime grains similar to what was observed in sample tn174 natural and experimental observation imply the presence of two coupled substitutions na y ree 3 2 ca2 and si4 y ree 3 p5 ca2 in the case of dl136 and h2o fluid experiments na and si4 went into solution whereas the released y ree contributed to the growth of monazite and xenotime within the metasomatized apatite structure for sample tn174 and the 50 50 caf2 h2o fluid experiments na in apatite became depleted but si was enriched thereby stabilizing the y ree in the now recrystallized fluor hydroxylapatite structure which retarded the growth of monazite or xenotime inclusions the basic conclusion of this study is that nucleation of monazite and xenotime in the metasomatized chlorapatite is principally a function of the composition of the infiltrating fluid and to a much lesser extent temperature and pressure

metallogeny of the zoujiashan uranium deposit in the mesozoic xiangshan volcanic intrusive complex southeast china insights from chemical compositions of hydrothermal apatite and metal elements of individual fluid inclusions abstract the zoujiashan u deposit in the mesozoic xiangshan volcanic intrusive complex is one of the largest volcanic related type u deposits in china chemical composition of hydrothermal apatite and metal contents in individual fluid inclusions of quartz and fluorite are investigated in order to understand the precipitation mechanism of u and to further constrain the origin of u and ore forming fluids of the zoujiashan deposit illitization hematitization and u mineralization successively occurred within rhyolite and porphyritic lava three types of hydrothermal apatite are identified apatite type 1 ap1 and apatite type 2 ap2 are both euhedral subhedral crystals found in hematitization zone while only ap2 shows evident irregular chemical zoning along its rims apatite type 3 ap3 occurs as anhedral aggregates closely associated with u minerals in u ore veins implying synchronous precipitation of ap3 and u ores comparable chemical compositions of ap1 and cores of ap2 including similar high cl content indicate both of them were precipitated from a cl rich fluid that induced hematitization the elevated f contents of ap3 and rims of ap2 implies that a f rich fluid was involved and altered ap2 during the main stage of u deposition ap1 and cores of ap2 have lower mn contents than ap3 and rims of ap2 indicating an oxidized character for the cl rich fluid and a reducing character for the f rich fluid metal contents of fluid inclusions in fluorite and quartz occurring in u ores suggest that two end members of fluids including a u rich and a u poor were involved in the main stage of u mineralization mixing between these two fluids led to the deposition of u and th minerals through oxidation reduction reactions and destabilization of th f complexes respectively the u rich fluid is depleted in th and sr compared with the u poor fluid based on comparison of chemical compositions of apatite and fluid inclusions we suggest that the cl rich fluid precipitating ap1 and ap2 corresponds to the u rich end member fluid while the f rich fluid precipitating ap3 represents a mixture between the two end members the high u 12 7 58 5 ppm in the u rich end member fluid is in agreement with a relatively high oxygen fugacity and a surface derived origin the u poor end member fluid has lower rb cs than the u rich end member and the unaltered host rocks indicating the u poor fluid was derived from a mantle wedge that experienced addition of cs by fluids generated from the devolatilization of the subducted paleo pacific slab