inferences on the mesozoic evolution of the north aegean from the isotopic record of the chalkidiki block the chalkidiki block is a major domain in the north aegean that contrary to other domains in the region largely escaped thermal perturbations during tertiary extension as a result the chalkidiki block is an ideal candidate to glean information related to the timing of mesozoic thermal events using appropriate geochronological techniques we have undertaken a laser ablation inductively coupled plasma mass spectrometry la icp ms study u th pb on monazites and u pb on zircons coupled with 40ar 39ar dating on nine samples from various structural levels within the thrust system of the chalkidiki block the eastern and structurally lower part of the system revealed a complete isotopic reset of carboniferous early triassic monazites coeval with partial monazite destruction ree mobilisation and formation of apatite allanite epidote coronas at 132 ma a reaction that is commonly observed in amphibolite facies rocks these coronas formed after crystallisation of garnet i e at t 580 c and in all probability either close to the peak temperature conditions 620 c on a prograde path or during retrogression between the peak temperature and the low temperature boundary of the amphibolite facies cooling of these rocks and arrival at mid crustal levels occurred at 95 100 ma by contrast the western and structurally uppermost part of the system went through the same event by 120 125 ma further structural considerations with respect to medium temperature geochronology data imply that syn metamorphic thrusting must have ceased by early late cretaceous we emphasize that with the sole exception of the chalkidiki block no pre 45 ma medium temperature geochronology data are preserved in other north aegean domains a feature that is clearly related to the extension induced thermal perturbation of the region during the tertiary

u pb monazite ages in amphibolite to granulite facies orthogneiss reflect hydrous mineral breakdown reactions sveconorwegian province of sw norway in the rogaland vest agder terrain of the sveconorwegian province of sw norway two main sveconorwegian metamorphic phases are reported a phase of regional metamorphism linked to orogenic thickening m1 and a phase of low pressure thermal metamorphism associated with the intrusion of the 931 2 ma anorthosite charnockite rogaland igneous complex m2 phase m1 reached granulite facies to the west of the terrane and m2 culminated locally at 800 850 c with the formation of dry osumilite bearing mineral associations monazite and titanite u pb geochronology was conducted on 17 amphibolite to granulite facies orthogneiss samples mainly from a suite of 1050 2 8 ma calc alkaline augen gneisses the feda suite in these rocks prograde negatively discordant monazite crystallized during breakdown of allanite and titanite in upper amphibolite facies at 1012 1006 ma in the feda suite and other charnockitic gneisses concordant to slightly discordant monazite at 1024 997 ma probably reflects breakdown of biotite during granulite facies m1 metamorphism a spread of monazite ages down to 970 ma in biotite hornblende samples possibly corresponds to the waning stage of this first event in the feda suite a well defined monazite growth episode at 930 925 ma in the amphibolite facies domain corresponds to major clinopyroxene formation at the expense of hornblende during m2 growth or resetting of monazite was extremely limited during this phase in the granulite facies domain up to the direct vicinity of the anorthosite complex the m2 event was shortly followed by cooling through ca 610 c as indicated by tightly grouped u pb ages of accessory titanite and titanite relict inclusions at 918 2 ma over the entire region a last generation of u poor monazite formed during regional cooling below 610 c in hornblende rich samples at 912 904 ma this study suggests 1 that monazite formed during the prograde path of high grade metamorphism may be preserved 2 that monazite ages reflect primary or secondary growth of monazite linked to metamorphic reactions involving redistribution of rees and th and or fluid mobilisation 3 that the u pb system in monazite is not affected by thermal events up to 800 850 c provided that conditions were dry during metamorphism

replacement of primary monazite by apatite allanite epidote coronas in an amphibolite facies granite gneiss from the eastern alps accessory monazite crystals in granites are commonly unstable during amphibolite facies regional metamorphism and typically become mantled by newly formed apatite allanite epidote coronas this distinct textural feature of altered monazite and its growth mechanism were studied in detail using backscattered electron imaging in a sample of metagranite from the tauern window in the eastern alps it appears that the outer rims of the former monazites were replaced directly by an apatite ring with tiny thorite intergrowths in connection with ca supply through metamorphic fluid around the apatite zone a proximal allanite ring and a distal epidote ring developed this concentric corona structure with the monazite core regularly preserved in the center shows that the reaction kinetics were diffusion controlled and relatively slow quantitative electron microprobe analyses suggest that the elements released from monazite breakdown p ree y th u were diluted and redistributed in the newly formed apatite allanite and epidote overgrowth rings and were unable to leave the corona this supports the common hypothesis that these trace elements are highly immobile during metamorphism furthermore microprobe data suggest that the preserved monazite cores lost little possibly none of their radiogenic lead during metamorphism thus metastable monazite grains from orthogneisses appear to be very useful for constraining u th pb protolith ages on the basis of these findings and a review of literature data it seems that monazite stability in amphibolite facies metamorphic rocks depends strongly on lithologic composition while breaking down in granitoids monazite may grow during prograde metamorphism in other rocks such as metapelites

an enigmatic kilometer scale concentration of small mytilids late miocene guadalquivir basin s spain abstract upper miocene heterozoan carbonates crop out extensively in a ne sw trending belt 42 km long and 1 5 8 km wide along the so called el alcor topographic high from carmona to dos hermanas seville s spain these carbonates formed at the southern active margin of the guadalquivir basin the foreland basin of the betic cordillera they change to marls basinward ne and to sands landward se and sw therefore carbonate production was constrained to a limited area in an otherwise siliciclastic shelf the carbonates up to 40 m thick overlie a gradually coarsening upward succession of marls followed by silts and sandstones the carbonate sequence can be divided into three subunits corresponding from bottom to top to lowstand transgressive and highstand system tract deposits the lower subunit exhibiting extensive trough cross bedding is interpreted as a shallow water bar deposit the intermediate subunit onlaps underlying sediments and was deposited in deeper low turbulence conditions the upper subunit deposits accumulated in a well oxygenated outer platform based on benthic foraminiferal assemblages the presence of hummocky and swaley cross stratification in these latter deposits suggests that they were affected by storms pervasive fluid escape structures are also observed throughout the carbonates the three subunits consist of bioclastic packstones to rudstones made up of abundant fragments of small mytilids isotopic data from serpulid polychaete ditrupa tubes show 13c depleted values up to 16 1 whereas 18o yields normal marine values additional isotopic data on shells of scallops oysters and small mussels as well as bulk sediment show diagenetic alterations based on actualistic examples of massive concentrations of mussels the nearly monospecific composition of the el alcor deposits together with negative 13c values of ditrupa tubes indicates that cold seeps presumably promoted carbonate formation however the absence of typical features of cold seep deposits such as authigenic carbonates mediated by anaerobic bacterial activity and the typical chemosynthetic shelly organisms makes the large carbonate body of el alcor an unusual cold seep deposit

allanite and other ree rich epidote group minerals epidote group minerals rich in rare earth elements ree in particular allanite are common accessory phases in igneous metamorphic metasomatic and sedimentary rocks small amounts of ree are present in most epidote group minerals but in allanite and the related minerals dissakisite ferriallanite dollaseite khristovite and androsite the ree are essential structural constituents an important characteristic of ree rich epidote group minerals is that their octahedrally coordinated m sites contain major amounts of divalent cations this paper summarizes literature data for these minerals and discusses their chemistry occurrence phase relations and petrologic and geologic significance the chapter emphasizes allanite because it is the most common and best studied of the ree rich epidote group minerals epidote group minerals contain isolated silicon tetrahedra and corner sharing groups of two tetrahedra and are thus assigned to the disilicate or sorosilicate structural family for a detailed description of the structure see franz and liebscher 2004 the epidote group structural formula is a2m3 sio4 si2o7 o f oh or in a simplified form a2m3si3o11 o f oh in which a ca sr pb2 mn2 th ree3 and u and m al fe3 fe2 mn3 mn2 mg cr3 and v3 deer et al 1986 there are two structurally different a sites a 1 and a 2 with different coordination numbers and there are three different m sites m 1 m 2 and m 3 which are all octahedrally coordinated ueda 1955 dollase 1971 in epidote group minerals trivalent ree are accommodated in the a sites which in endmember epidote both contain ca the incorporation of ree3 is commonly charge balanced by a divalent cation fe2 mn2 mg substituted for a trivalent one in the m sites table 1

detrital and newly formed metamorphic monazite in amphibolite facies metapelites from the motajica massif bosnia abstract the motajica massif in bosnia situated in the sava zone between the tisza unit and the dinarides hosts a late cretaceous flysch series which is partly preserved in an anchimetamorphic state partly affected by amphibolite facies overprint samples from both parts contain abundant accessory monazite which was investigated by means of the electron microprobe with reference to age and composition in the amphibolite facies samples new metamorphic monazite has formed chemical th u pb monazite ages indicate that the regional metamorphic event happened in the late cretaceous or the early palaeogene in addition inherited detrital monazite of permian age has been identified based on various observations it is argued that the detrital monazite was not the direct precursor to the metamorphic monazite the latter may rather have grown from other more reactive ree carrier minerals either detrital ones e g detrital allanite or such that formed during diagenesis and low grade metamorphism a later greenschist facies event that occurred in connection with a ca 27 ma old granodiorite intrusion led in some samples to the formation of late fluorapatite allanite coronas around both detrital and newly formed monazites the anchimetamorphic samples contain exclusively detrital monazite these are partly of permian as well as jurassic to early cretaceous age based on their compositional and textural features the jurassic to early cretaceous monazite relics are considered to be mainly derived from metamorphic rocks the permian monazite displays high yttrium content up to ca 3 5 wt y 2 o 3 indicating a high formation temperature 650 c and therefore probably a magmatic origin apart from almost ubiquitous permian high y monazite the motajica flysch also contains large permian xenotime with magmatic zoning patterns fluorapatite with parasitic monazite inclusions formerly ree rich fluorapatite and zircon with a type granite morphology this accessory mineral spectrum implies that among others rift related ree rich permian a type granites or rhyolites should be considered as a source for the sava zone flysch

characterising the u th pb systematics of allanite by id and la icpms implications for geochronology abstract allanite has the potential to be a useful chronometer of crustal evolution forming in response to a wide spectrum of metamorphic and magmatic conditions and incorporating weight percent concentrations of lree th and u despite its growing use in in situ u th pb geochronology allanite reference materials lack sufficient u th pb isotopic characterisation and little is known concerning the response of u th pb systematics of allanite to hydrothermal alteration and self irradiation this contribution presents the results of a combined id tims and la icpms u th pb study on a suite of five allanite crystals spanning 2 6 ga and including three commonly used allanite reference materials the siss bona and tara allanites siss and bona allanites preserve an inherited ca 1 ga pb component consistent with the presence of xenocrystic allanite cores or the presence of zircon micro inclusions tara allanite yields concordant u pb ages 407 430 ma but is affected by th u fractionation likely caused by hydrothermal alteration additionally the tendency for th to become mobilised post crystallisation is further evidenced by two precambrian allanite megacrysts le40010 ca 2 8 ga and le2808 ca 1 1 ga that both exhibit discordant th pb analyses linked to the formation of thorite micro inclusions along hydration pathways self irradiation dose versus discordance relationships show that a percolation threshold is present in allanite at cumulative dose values close to 3 10 17 decay g 1 an order of magnitude smaller than zircon collectively the presence of common pb and excess 206 pb its susceptibility to incur th u fractionation and hydrothermal pb loss complicates the use of allanite as a geochronometer these factors explain dispersion of 4 in the isotopic compositions of siss and tara allanites measured by la icpms providing a fundamental limit on the accuracy of the allanite chronometer using these reference materials

zircon trace element characteristics and ages in granulite xenoliths a key to understanding the age and origin of the lower crust arkhangelsk kimberlite province russia garnet granulite and pyroxenite xenoliths from the grib kimberlite pipe arkhangelsk nw russia represent the lower crust beneath russian platform in close vicinity to the cratonic region of the north eastern baltic fennoscandian shield many of the xenoliths have experienced strong interaction with the kimberlite host but in others some primary granulite facies minerals are preserved calculated bulk compositions for the granulites suggest that their protoliths were basic to intermediate igneous rocks pyroxenites were ultrabasic to basic cumulates a few samples are probably metasedimentary in origin zircons are abundant in the xenoliths they exhibit complex zoning in cathodoluminescence with relic cores and various metamorphic rims cores include oscillatory zircon crystallized in magmatic protoliths and metamorphic and magmatic sector zoned zircons recrystallization of older zircons led to the formation of bright homogeneous rims in some samples homogeneous shells are surrounded by darker convoluted overgrowths that were formed by subsolidus growth when a change in mineral association occurred the source of zr was a phase consumed during a reaction which produced garnet late generation zircons in all xenoliths show concordant u pb ages of 1 81 1 84 ga 1 826 11 ma interpreted as the age of last granulite facies metamorphism this event completely resets most zircon cores an earlier metamorphic event at 1 96 1 94 ga is recorded by some rare cores and a few magmatic oscillatory zircons have retained a neoarchaean age of 2 719 14 ma the assemblage of metaigneous and metasedimentary rocks was probably formed before the event at 1 96 ga inherited magmatic zircons indicate the existence of continental crust by the time of intrusion of magmatic protoliths in the late archaean the u pb zircon ages correspond to major events recorded in upper crustal rocks of the region collisional metamorphism and magmatism 2 7 ga ago and reworking of archaean rocks at around 1 95 1 75 ga however formation of the granulitic paragenesis in lower crustal rocks occurred significantly later than the last granulite facies event seen in the upper crust and correlates instead with retrograde metamorphism and small volume magmatism in the upper crust

metamorphic formation of sr apatite and sr bearing monazite in a high pressure rock from the bohemian massif accessory 10 300 m grains of sr apatites with sro contents up to 33 wt were found in a high pressure 26 3 kbar 830 30 c garnet rich rock from the bohemian massif czech republic furthermore this rock contains unusual sr bearing accessory monazite sro up to 2 wt it is argued that the sr apatite and the sr bearing monazite formed as a result of plagioclase breakdown during hp metamorphism during a subsequent phase of near isothermal decompression and partial retrogression of the hp paragenesis at 8 2 kbar and 800 900 c many apatites have lost their sr through diffusion to newly formed plagioclase some of which accommodated sro contents of ca 7 wt at apatite plagioclase contacts a distribution coefficient c p l s r c a p s r of ca 4 was measured implying that in plagioclase bearing rocks i e most crustal rocks sr apatites have little chance to form in the investigated rock only apatites enclosed and shielded in unretrogressed garnet were able to preserve high sr despite strong compositional differences from grain to grain individual apatites are homogenous with respect to contents of sr as well as ree and y showing that at ca 800 c rapid diffusion must have taken place in contrast to the apatites monazite grains inside and outside of garnet were both equally sr bearing lacking any signs of a secondary diffusion related sr depletion even in the most marginal zones this observation in conjunction with an occasionally preserved growth zoning illustrates the status of monazite as a slow diffusion mineral therefore sr bearing monazite potentially may be an important long term indicator of a hp history of rock units or terranes

experimental evidence bearing on the stability of monazite during crustal anaatexis a major host for lree and the heat producing elements th and u in peraluminous granites is monazite and the stability of monazite will affect the redistribution of these elements within the crust during anatexis the compositional stability of monazite in granitic melts ranging from peraluminous to metaluminous compostions has been investigated under water saturated conditions between 850 1000 c at 8 kb monazite solubility concentration of lree s in saturated melts increases with the values of m 1 3 2ca na k alxsi in the melt and is constant for m 1 3 the temperature dependence of monazite saturation has been determined by rapp and watson 1986 for a melt of m 1 3 and model should be applicable to all peraluminous magmas application of the monazite solubility model to crustal anatexis indicates that for fusion temperatures at or below 800 c anatexis producing peraluminous magmas may lead to an enrichment of monazite in the restitic lower crust depending upon the initial lree concentration in the source at temperatures approaching 850 c enrichment of monazite in the lower crust by anatexis is unlikely due to the high monazite saturation concentrations

apatite monazite and xenotime in metamorphic rocks this chapter focuses on phosphates that are significant in metamorphic rocks a quick survey of phosphate mineral descriptions at a commercial mineral web site revealed over 500 phosphate mineral names remarkably only three are common in metamorphic rocks apatite monazite and xenotime and this chapter is restricted to discussion of these minerals apatite monazite and to a lesser extent xenotime have enjoyed intensive study during the previous half century following world war ii considerable study was made of minerals that contain fissionable materials and the sometimes large concentrations of u and th in monazite culminated in a number of seminal papers on the occurrence of that mineral e g overstreet 1967 during the 1970s and early 1980s the study of apatite and monazite turned towards their role as a sink for rees and other trace elements in rocks e g watson 1980 watson and capobianco 1981 throughout this period monazite and to some extent xenotime enjoyed attention as a geochronometer e g parrish 1990 and through today this attention has continued to grow accessory minerals such as monazite xenotime and apatite have come to the forefront of research in metamorphic petrology in recent years for two reasons first it has recently been recognized that trace elements in metamorphic rocks and especially trace element zoning in garnet and other major phases contain considerable detailed information about the reaction history a rock has experienced coupled with the fact that diffusion of many trace elements in metamorphic minerals is in general considerably slower than diffusion of major elements in those same minerals the possibility has recently emerged of recovering details of metamorphic petrogenesis that were previously unattainable inasmuch as accessory minerals play a dominant role in the mass budget of many trace elements attention has naturally turned to their paragenesis it has also recently been discovered that

multiple stages of hydrothermal ree remobilization recorded in fluorapatite in the paleoproterozoic yinachang fe cu ree deposit southwest china abstract the yinachang deposit in the kangdian region southwest china contains large amounts of fe cu and ree and formed at 1700 ma in this deposit there are three stages of alteration and mineralization including pre ore na fe alteration fe ree mineralization and cu ree mineralization in the fe ree mineralization stage ree rich fluorapatite with total ree concentrations ranging from 10 700 to 34 000 ppm formed together with magnetite in the following cu ree mineralization stage large amounts of ree especially lree were leached out of the ree rich fluorapatite due to the interaction between fluorapatite and cl f co2 and ca rich but ree unsaturated fluids the leaching of ree was associated with the removal of si na th u pb and ba and modification of the oxygen isotope signature in the fluorapatite during a 840 ma tectonothermal event ree rich fluorapatite underwent the second interaction with oxidized f co2 and possibly cl rich but na and ca deficient fluids due to fluid fluorapatite interaction ree were removed from the fluorapatite but were immediately reincorporated into new phases within the fluorapatite thus the altered fluorapatite contains abundant ree mineral inclusions including bastnasite ce monazite ce and minor xenotime y a very small portion of the lree were transported out of the fluorapatite and formed bastnasite ce and monazite ce grains in the vicinity of the altered fluorapatite in addition to the metasomatism of fluorapatite allanite and primary synchysite ce from the cu ree mineralization stage were also altered with variable replacement of allanite by an assemblage of synchysite ce chlorite bastnasite ce and primary synchysite ce by bastnasite ce these styles of alteration were possibly synchronous with the second alteration phase of the fluorapatite this study demonstrates that ree can be mobilized during multiple stages of hydrothermal activities and highlights the significant controls fluid compositions have on ree transportation and deposition in hydrothermal system

post peak fluid mediated modification of granulite facies zircon and monazite in the trivandrum block southern india the quarry at kottavattom in the trivandrum block of southern india contains spectacular examples of fluid assisted alteration of high grade metamorphic rocks garnet biotite gneiss has undergone a change in mineral assemblage to form submetre scale orthopyroxene bearing patches later retrogressed to form an amphibole bearing lithology these patches often referred to as arrested or incipient charnockite crosscut the original metamorphic foliation and are typically attributed to passage of a low ah2o fluid through the rock whilst this conversion is recognised as a late stage process little detailed chronological work exists to link it temporally to metamorphism in the region zircon and monazite analysed from kottavattom not only record metamorphism in the trivandrum block but also show internal lobate textures crosscutting the original zoning consistent with fluid aided coupled dissolution reprecipitation during formation of the orthopyroxene bearing patches high grade metamorphism at the quarry occurred between the formation of metamorphic monazite at 585 ma and the growth of metamorphic zircon at 523 ma the fluid assisted alteration of the garnet biotite gneiss is poorly recorded by altered zircon with only minimal resetting of the u pb system whereas monazite has in some cases undergone complete u pb resetting and records an age for fluid infiltration at 495 ma the fluid event therefore places the formation of the altered patches at least 25 myr after the zircon crystallisation in the garnet biotite gneiss the most likely fluid composition causing the modification and u pb resetting of zircon and monazite is locally derived hypersaline brine

ecologie des pseudobiohermes des terres noires jurassiques lies a paleo sources sous marines le site oxfordien de beauvoisin drome bassin du sud est france abstract pseudobioherms are fossiliferous calcareous bodies well exposed within jurassic calcareous shales of se france their genesis is unknown oxfordian psedobioherms of the outcrop of beauvoisin are studied here several kinds of results show that they are probably built at vent of submarine springs in a bathyal environment among their related fauna bivalves are thriving they show some remarkable analogies morphology growth distribution with some typical bivalves of recent springs hydrothermal vents or cold seeps like calyptogena isotopic composition of their shell exhibits a highly positive 13c and emphasizes this resemblance this suggests a chemosynthetic food supply through a bacterial symbiosis the whole fauna microfauna and macrofauna was inventoried within pseudobioherms and their close and far environment a comparative paleoecological study has been carried out to evaluate the faunal anomaly shown by a selected pseudobioherm two contemporaneous sections one close to this pseudobioherm and one other in a distant area without pseudobioherms have been studied in detail all taphonomic disturbances which are able to alter data have been carefully studied the paleobiocoenose suggests a slightly higher environmental stability because of an additional food supply within an environment usually less favorable it also suggests some permanency of spring activity the impact of the supposed springs on the benthic fauna is localized and slightly preserved through fossil fauna it mainly expresses itself in bivalves and organisms able to eat them crustacean cephalopods considering these various observations and after a critical comparison with characteristics and geological setting of recent submarine springs a model is suggested to understand the highly original paleo ecosystem of pseudobioherms

three metamorphic monazite generations in a high pressure rock from the bohemian massif and the potentially important role of apatite in stimulating polyphase monazite growth along a pt loop abstract based on microstructural and compositional criteria three generations of monazite can be identified in a peraluminous garnet rich high pressure metamorphic rock from the bohemian massif the first monazite generation m1 formed probably on the prograde part of the clockwise pt loop a second m2 during the high pressure stage 26 3 kbar and 830 30 c and a third generation m3 during subsequent near isothermal decompression of the rock to 8 2 kbar the high pressure m2 monazites are volumetrically dominant and form 100 300 m grains they are characterised by an unusual sr brabantite component sro up to 2 wt and grew together with accessory sr rich fluorapatites sro up to 33 wt the sr contents of both minerals are indicative of high pressure conditions and result from the breakdown of plagioclase and the release of sr that occurred during this process m3 monazites occur exclusively as small grains 10 100 m within and at the rims of apatite microstructures show that they grew at the expense of the apatite extracting lrees from the latter under retrograde conditions these parasite monazites in apatite are characterised by very low th contents which is consistent with having been derived primarily from an apatite source m1 monazites are represented by resorbed irregular shaped cores which are occasionally preserved within the sr brabantite rich high pressure monazites m2 these m1 cores are generally sr poor indicating that they should have formed prior to the high pressure stage in the presence of plagioclase the dissolution of m1 monazite and the reprecipitation of a th u enriched m2 monazite during the high pressure stage implies that lrees were taken up by the high pressure sr rich fluorapatite to some extent and not completely processed for the formation of the m2 monazite this would also explain the widespread retrograde growth of m3 monazite within the apatite the ability of apatite to act as an interim host for lrees at peak pt conditions could be one of the reasons why monazite growth during regional metamorphism is often periodic

dating shear zones with plastically deformed titanite new insights into the orogenic evolution of the sudbury impact structure ontario canada abstract the sudbury structure is a mineralized impact crater that hosts different families of ore controlling shear zones with poorly known orogenic affinities discriminating whether these deformation events relate to the 1 85 ga crater modification stage or later regional tectonism that collapsed the impact structure is important both for crustal and mineral exploration studies we have combined underground mapping with isotopic and microstructural analysis of titanite and host minerals in a benchmark ore controlling mylonitic shear zone of the mining camp the six shaft shear zone from the creighton mine three growth stages of chemically and microstructurally characterised titanite grains were identified related with the pre syn and late deformation stages in situ u pb age dating of the syndeformational grains demonstrates that a shearing event took place at 1645 54 ma during the mazatzalian labradorian orogeny 1 7 1 6 ga this event led to the plastic deformation and local scale remobilization of primary ni cu pge sulphides in creighton mine sudbury south range the adopted novel petrochronological approach can reveal the age significance of syn deformational processes and holds promise for the untangling of complex syn orogenic processes in precambrian terranes globally

a model for monazite melt equilibrium and application to the generation of granitic magmas abstract in order to model the behaviour of zr hf ti p u th y and the rare earth elements ree in the continental crust the parameters which control the equilibria between accessory minerals and granitic melts must be determined this paper proposes equations for the equilibrium between monazite and ca poor felsic melts in a first step all the light ree are considered as a single component and an equation describing monazite solubility is deduced from the available experimental data in a second step the fractionation of ree by monazite is investigated on the basis of a natural example of coexisting monazite and obsidian from macusani peru the solubility of monazite can be used as a thermometer based on the total ree content of natural magmatic rocks application of ree thermometry to various peraluminous rock series suggests that it is a reliable tool for determining temperatures of magmatic processes the equation governing ree fractionation by monazite is used to discuss genetic relationships between a melt and a presumed parental rock using the composition of the monazite in the parental rocks and the ree pattern of the daughter rock this method has been applied successfully to high himalayan manaslu and tibetan slab granites it is suggested that detailed petrographical work on monazite including electron microprobe analyses and sem imaging of its internal structures combined with the model presented here can be a useful tool for deciphering the genesis and the differentiation of peraluminous granitic magmas in the continental crust

reinterpretation of middle cambrian stratigraphy of the rifted western laurentian margin burgess shale formation and contiguous units sauk ii megasequence rocky mountains canada abstract until recently research on the renowned fossil animals of the burgess shale has advanced to a greater degree than an understanding of the rocks in which they are found studies addressing lithostratigraphy and hydrothermal petrography of the so called inner carbonate belt and adjacent chancellor group however have begun to re evaluate long standing hypotheses on the middle cambrian of western canada tectonic activity along the kicking horse rim buried remnants of neoproterozoic rifting during the cambrian period had more influence on local sedimentation than previously thought notably large scale collapse of the cathedral carbonate platform margin at 509 ma bp is evidence of reactivated basement faults these failures produced listric megatruncation surfaces having near vertical escarpments 150 m in height where they terminate against the platform the majority of what have been interpreted as shed olistoliths from the cathedral platform margin is herein shown instead to be carbonate mud mounds these grew in situ along the face of the cathedral escarpment and are associated with fossiliferous intervals in overlying basinal mudstones at three distinct stratigraphic horizons two within the burgess shale during the delamaran and marjuman stages the mounds nucleated where deep seated normal faults intersected the seafloor building primarily during periods of relative sea level transgression mound growth is associated with syndepositional exhalative activity inferred from stratigraphic relations sedimentology and geochemistry the new name monarch formation is proposed for the initial post collapse beds and mounds deposited against the cathedral escarpment early glossopleura zone the variably defined term takakkaw tongue is thereby confined to pre collapse slope deposits coeval to and correlative with the cathedral formation

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

abyssal erosion and scarp retreat deep tow observations of the blake escarpment and blake spur abstract deep tow surveys conducted at two sites at the base of the blake spur and blake escarpment serve to delineate the contact between mesozoic platform carbonates of the blake plateau and adjacent abyssal strata the continental margin in the surveyed areas consists of steep limestone cliffs and headlands with over 2 km of relief this extreme topography distorts the hydrographic structure of the water column and intensifies abyssal current flow in the surveyed areas significant lateral scarp retreat is indicated by the presence of broad nearly horizontal benches of mesozoic limestone presently exposed at the base of the blake spur and escarpment in 4 5 5 km water depth and by angular apparently truncated limestone ledges that crop out on the cliff face at the blake spur the contact between mesozoic platformal limestones and basinal tertiary strata does not occur directly at the foot of the cliff but is exposed on the abyssal plain within a 50 m deep erosional moat here strong 2 knots south flowing bottom currents occur within 100 m of the sea floor the coincidence of this vigorous current flowing within the moat near the base of the escarpment and the eroded character of the sea floor suggests that currents are an important mechanism in sculpting this abyssal headland and contributing to lateral scarp retreat similar erosional processes are indicated along the blake escarpment near 29 03 n where the relatively straight cliff face is interrupted by occasional steep walled box canyons on the headland between the canyons the mesozoic outcrop projects into the blake bahama basin for several kilometers as a broad arcuate gently sloping bench these outcropping benches of mesozoic strata at the base of the escarpment are analogous to larger scale buried benches observed in the subsurface that were formed by pre miocene erosion neogene and quaternary scarp retreat is suggested by the location of the contact between mesozoic rocks and younger strata seaward of the steeper cliff face and is probably the result of current induced erosion focused erosion may be facilitated by the presence of a thin 50 m filament of corrosive antarctic bottom water aabw that flows vigorously along the base of the cliff at both sites the recessed position of the canyons shelters them from the main flow of this abyssal current but the steepness and morphology of the canyon walls suggest that additional unidentified erosional processes are focused at the canyon heads

earthquake damage orientation to infer seismic parameters in archaeological sites and historical earthquakes abstract studies to provide information concerning seismic parameters and seismic sources of historical and archaeological seismic events are used to better evaluate the seismic hazard of a region this is of especial interest when no surface rupture is recorded or the seismogenic fault cannot be identified the orientation pattern of the earthquake damage ed e g fallen columns dropped key stones that affected architectonic elements of cities after earthquakes has been traditionally used in historical and archaeoseismological studies to infer seismic parameters however in the literature depending on the authors the parameters that can be obtained are contradictory it has been proposed the epicenter location the orientation of the p waves the orientation of the compressional strain and the fault kinematics and authors even question these relations with the earthquake damage the earthquakes of lorca in 2011 christchurch in 2011 and emilia romagna in 2012 present an opportunity to measure systematically a large number and wide variety of earthquake damage in historical buildings the same structures that are used in historical and archaeological studies the damage pattern orientation has been compared with modern instrumental data which is not possible in historical and archaeoseismological studies from measurements and quantification of the orientation patterns in the studied earthquakes it is observed that there is a systematic pattern of the earthquake damage orientation edo in the proximity of the seismic source fault trace

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

the cretaceous megabreccias of the gargano promontory apulia southern italy their stratigraphic and genetic meaning in the evolutionary framework of the apulia carbonate platform huge megabreccias occur at the eastern margin of the cretaceous apulia carbonate platform gargano promontory southern italy their stratigraphic and genetic meaning are controversial in the debated geological evolution of the apulia platform new stratigraphic analyses have revealed that three distinct megabreccia levels occur within the coarse debrites that were previously interpreted to be the result of repeated collapses of a scalloped platform margin during the late albian cenomanian each level has peculiar chronostratigraphic distribution geometry composition and genetic features they are the posta manganaro megabreccias late early aptian to late albian pp monte s angelo megabreccias early middle cenomanian and belvedere di ruggiano megabreccias middle turonian these deposits overlie regional tectonically enhanced unconformities of late early aptian late albian and late cenomanian age these megabreccias which were formed respectively during drowning prograding and exposure events of the apulia platform reflect important turning points in its cretaceous geodynamic evolution

miocene shallow marine cold seep carbonate in fold and thrust western foothills sw taiwan a mound shaped authigenic carbonate buildup 50 m wide and 5 m high occurred in the middle part of the late miocene shallow marine succession the hunghuatzu formation exposed along the nantzuhsien river sw taiwan the carbonate concretions are classified into four types based on morphology which appeared to develop in upward sequence with vague boundaries 1 flat pipe shaped nodules highly dolomitic small pipes or nodules subparallel to the host strata 2 bulb shaped nodules discrete or combined small mesoclots with subspherical to irregular shapes 3 mushroom shaped concretions large mushroom like or irregular shaped blocks with chimney or vent structures and 4 carbonated layers with sedimentary structures these concretions are mainly composed of dolomite micrites quartz feldspar muscovite and clay minerals ubiquitously interweaved with blackish brown colored low magnesium calcite lmc veins low delta c 13 vpdb values 51 8 parts per thousand to 29 8 parts per thousand of all types of the carbonates reveal that the carbonates were mainly derived from anaerobic oxidation of hydrocarbons many samples are also o 18 depleted delta o 18 vpdb 11 5 parts per thousand to 1 00 parts per thousand due to the mixture with isotopically light lmc veins likely precipitated from meteoric waters there are numerous chemosymbiotic bivalve fossils genus monitilora diameter 3 4 cm in growth position just above the carbonate buildup according to the geological and isotopic signatures the hunghuatzu carbonates are related to a cold seep pseudobioherm which formed in a very shallow marine environment like tidal flat in a passive margin setting exposures of the hunghuatzu pseudobioherm may provide clues for tracking and comparing the evolution history of gas reservoir systems and hints of active tectonics of the sw taiwan region c 2012 elsevier ltd all rights reserved

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

seepage induced erosion of submarine carbonate escarpments a numerical simulation abstract a three dimensional numerical model has been constructed to examine the seepage induced erosional process of the florida carbonate escarpment the erosion takes place either by the mechanical failure associated with the seepage force or the corrosion due to the fluid chemistry the numerical model assumes homogeneous darcian fluid flow and uses the strongly implicit finite different scheme the erosion is reflected in the model as removal of the finite difference cells whose pore pressure gradient exceeds a prescribed critical value for failure seafloor is the surface boundary of zero excess pore pressure the fluid is assumed to enter from the landward side of the formation the model results show that the topographic variation of the surface boundary causes refraction of the fluid flow field and that the flow focuses at the base of the escarpment the seepage induced erosion takes place bottom up steepens the lower escarpment slope and hence further intensifies the flow at the base because of this positive feed back mechanism between the hydrogeological regime and the geomorphogy the escarpment wall keeps retreating landward this mechanism can also be responsible for the formation and growth of the theater headed submarine canyons on the florida escarpment spacing and shape of these canyons are strongly influenced by the geometrical and hydrological parameters of the carbonate escarpment

monazite allanite phase relations in metapelites abstract calculations of the transition from allanite to monazite bearing assemblages in typical pelitic bulk compositions have been made using thermodynamic data estimated from oxide sums and inferred from natural parageneses calculations in the cfashpce and mnnckfmashpce systems place the allanite to monazite transition in the middle amphibolite facies 525 600 c for a bulk composition similar to shaw s average pelite the temperature of the transition is pressure dependent and strongly dependent on the bulk rock cao content consistent with inferences from natural parageneses the transition is also a function of the bulk al 2 o 3 content although the calculated result is opposite to that inferred from natural samples comparison with published results in the la mg system suggest that the nature of the ree phosphate does not greatly influence the conditions of the transition

continental margin brine seeps their geological consequences local dissolution observed at the base of the florida escarpment appears to result from acid generated by sea floor oxidation of dissolved sulfide species carried in brines that seep from the base of the escarpment the extent of seep corrosion depends upon the amount of sulfide that has exited the platform and the efficiency with which the acid attacks the limestones of the escarpment calculations suggest that brine seepage influences the shape of these escarpments by undercutting and steepening the carbonate continental margin edges other processes competing for the dissolved sulfides are bacterial chemosynthesis and sulfide mineralization which produces organic carbon and sulfide mineral rich deposits along the unconformity that separates the buried escarpment from onlapping abyssal sediments

incongruent dissolution of ree and sr rich apatite in peraluminous granitic liquids differential apatite monazite and xenotime solubilities during anatexis the relative solubilities of monazite mnz xenotime xno and apatite ap ree and sr rich and ree and sr poor have been studied in peraluminous granitic liquids in month long experiments at 750 c and 200 mpa ph20 in contrast with the high solubility of the apatite 0 7 wtojop205 in strongly peraluminous liquids monazite and xenotime have much lower solubilities 0 05 wt jop205 in mildly to strongly peraluminous compositions p205 in the liquid is 0 03 0 04 wt joat xenotime saturation and 0 02 0 05 wt jo at monazite saturation in keeping with the low p in the glasses re203 contents are below emp detection thresholds 50 08 wt jo for all conditions of experiments saturation of liquid at equilibrium and local saturation around apatite apatite dissolves incongruently crystallizing ree rich monazite on its surface 1 4 m iong grains resulting in similar low ree contents in liquids monazite precipitation occurs along the margins of dissolving apatite crystals even though the bulk liquid is not monazite saturated the abundance of monazite microcrystals increases with the ree content of the apatite and the degree of apatite dissolution the reaction relationship ap liqi mnz liq2 stemming from differences in relative solubilities greater than an order of magnitude between apatite and monazite results in the dissolution of much smaller amounts of ree into peraluminous liquids than expected by simple evaluation of apatite ree contents the amount of ree contributed from apatite directly to peraluminous granitic liquid is related to the amount of apatite dissolved by simple mass balance only if the total ree content of the apatite is sufficiently low that monazite saturation in liquid 50 100 ppm re203 at 750 c is avoided during dissolution of sr rich apatite the sr partitions into the liquid and at 750 c and 200 mpa ph20 the diffusion coefficient of sr in liquid is 2 x 10 10 cm2js r2 0 659 the reaction relationships described above may have application to some textural features observed in natural igneous rocks for example clusters of monazite microcrystals might be indicators of dissolved apatite monazite morphology can be used to distinguish the source of its ree and the general petrological process rock anatexis or magma crystallization under which the monazite formed in addition monazite microcrystals could serve as nucleation sites for other minerals which might explain their common inclusion in biotite and amphibole within granitoids

petrochronology based on ree minerals monazite allanite xenotime apatite ree minerals monazite xenotime and allanite are ree1 minerals sensu stricto because lanthanides la lu and yttrium are critical constituents in them apatite does not require ree but because it contains substantial ree in many rocks it is included in this review all four minerals also host unusually high radionuclide concentrations notably th and u forming the basis of their utility as geochronometers this quartet of accessory minerals is playing an increasingly important role in petrochronology because they provide ways to link robust spot ages to petrogenetic p t conditions so can lend petrogenetic context to chronology based on other minerals part i of this review assembles the basic requisites prior to integrative petrochronologic analysis individual characteristics of the four ree minerals are addressed first i e their crystal chemistry and stability relations thermobarometers and trace element geochemistry used for tracing petrogenesis are discussed next and finally their chronology is summarized part ii presents case studies to highlight the specific strengths of ree minerals used to resolve the dynamics of a broad range of processes from diagenetic to magmatic conditions finally a brief section at the end outlines a few of the current challenges and promising perspectives for future work to introduce the four ree minerals in style let us recall the origins of their names the three phosphates have well respected greek grandparents and allanite has solid scottish roots yet of all four of them show idiosyncracies in etymology or type material apatite had long puzzled naturalists as it shows great chemical and physical variability and can resemble other minerals once properly identified abraham gottlieb werner named it apatite his reasoning referred to the greek root and giving the precise latin translation decipio taken literally both mean i deceive or i mislead which sounds like an apt confession from this mineral for having fooled

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

chemical and isotopic evidence of gas influenced flow at a transform plate boundary monterey bay california chemical and isotopic compositions of pore fluids document upward flow through communities of vesicomyid clams in monterey bay california within the clam communities the sulfate reduction zone is only 10 cm thick and ca and mg concentrations decrease to values as low as 2 2 mm and 34 5 mm respectively at depths less than 30 cm below the sediment water interface less than 5 m outside the communities the base of the sulfate reduction zone is deeper than the greatest penetration of the cores 30 cm and ca and mg exhibit only minor changes from seawater values the sediment exhibits no significant variation in grain size mineralogy organic carbon nitrogen or carbonate content throughout the region the composition of pore fluid within clam communities results from upward flow of altered fluid rather than different diagenetic reactions within and outside the communities isotopically light dissolved inorganic carbon dic with 13c values ranging from 3 2 to 54 1 could reflect carbon sources from either oxidized thermogenic methane and or a mixture of oxidized microbial methane and solid organic carbon the c1 c2 c3 ratios ranging from 34 to 1142 and the hydrogen and carbon isotopic compositions of methane d values of 109 to 156 13c values of 30 6 to 86 6 suggest that methane is primarily microbial but that a minor component could be thermally generated any thermogenic methane would have migrated from great depths possibly 2 km the presence of methane is likely to contribute to fluid flow by reducing the density of the fluids past fluid migration and venting are reflected by widespread carbonate mineralization at the sediment water interface this mineralization and the geographic distribution and proportions of microbial and thermogenic methane suggest that vent sites migrate when permeability is reduced during carbonate cementation these results demonstrate that along with convergent and divergent plate boundaries transform plate boundaries are characterized by fluid flow and that the flow may be widespread occurring at sites away from fault zones

platform margin collapses and sequence stratigraphic organization of carbonate slopes cretaceous eocene gargano promontory southern italy we describe the sequence stratigraphic organization and the associated sedimentological characteristics of cretaceous to eocene slope and base of slope carbonate successions the study area is located in the gargano promontory which belongs to the stable foreland of southern italy the succession consists of three superimposed depositional sequences separated by major unconformities the upper two sequences are clear examples of sequence stratigraphic organization in fact they both start with huge megabreccia wedges lst followed upward by thin pelagic units tst and a thick package of calciturbidites and debrites that alternate with pelagic mudstone hst the cretaceous highstand systems tract is clearly arranged in a number of coarsening upward cycles while the eocene one which also comprises a toplap shallow water unit is not the gargano stratigraphic palimpsest and the entire margin of the apulia platform show remarkable similarities with present day carbonate platform margins and slopes where irregular convex bankward embayments suggest large scale failures it is clear that classic sequence stratigraphic organization can result from simple platform dismantling having no or little time relation with global sea level fluctuations in fact as the margin failure lst interrupts the carbonate production a period of starvation tst along the entire slope and base of slope follows necessarily finally when the margin once again becomes active and productive sediment exportation starts again and the system begins to prograde hst

lree redistribution among fluorapatite monazite and allanite at high pressures and temperatures the ree enrichment process in fluorapatite and the ree redistribution among fluorapatite monazite and allanite were studied in a series of three sets of experimental runs at p t conditions of 0 5 to 4 gpa and 650 to 900 c the first two sets of experimental runs utilized fluorapatite as a p source synthetic monazite or allanite as the ree sources albite quartz and naf h2o or nacl h2o the third set of runs was carried out with powdered ca3 po4 2 allanite quartz al2o3 and a naf h2o solution in all runs ree bearing fluorapatite with up to 28 wt ree2o3 formed at the expense of monazite or allanite either as narrow zones at the margin of synthetic fluorapatite in runs 1 and 2 or as discrete grains in run 3 the ree enrichment of fluorapatite in melt bearing runs is explained in terms of the high solubility of monazite in the presence of alkali rich melts together with the high partitioning values for rees among fluorapatite and alkali rich melts the formation of ree enriched fluorapatite in melt absent runs implies that the solubility of monazite and the ree uptake of fluorapatite are similarly high in both alkali rich melts and fluids and depends foremost on the activity of alkalis in fluids or melts the results from this study show the importance of fluorapatite as a ree carrier in rocks whose petrogenesis involved alkali bearing fluids melts in metamorphic rocks alkali enriched fluids or melts will likely form under higher grade conditions explaining the preferential occurrence of reeenriched fluorapatite in granulite and eclogite facies rocks

solubility of cepo4 monazite and ypo4 xenotime in h2o and h2o nacl at 800 c and 1 gpa implications for ree and y transport during high grade metamorphism abstract monazite and xenotime are important accessory minerals in metasediments because they host ree and are useful for geochronology and geothermometry it is therefore essential to understand their behavior during metasomatic processes that attend metamorphism and subduction in order to constrain the solubility of monazite and ypo 4 xenotime at high pressure and temperature we carried out weight loss experiments on synthetic single crystals of cepo 4 monazite and ypo 4 xenotime using hydrothermal piston cylinder methods at 800 c and 1 gpa in h 2 o and h 2 o nacl fluids results indicate that cepo 4 and ypo 4 dissolved congruently and that their solubilities in pure h 2 o are very low 0 04 0 04 and 0 25 millimolal respectively the solubility of cepo 4 rises to an increasing extent with added nacl to 7 94 0 07 millimolal at 50 mol nacl in contrast the solubility of ypo 4 rises to a decreasing degree with increasing nacl to 4 36 0 08 millimolal at 50 mol nacl best fit equations for the solubilities of the two phases are m cepo 4 3 56 10 5 5 82 10 3 x nacl 1 97 10 2 x 2 nacl and m ypo 4 2 48 10 4 1 26 10 2 x nacl 8 89 10 3 x 2 nacl the solubility of ypo 4 is greater than that of cepo 4 at nacl mole fractions x nacl of 0 00 0 27 the solubility enhancement behavior implies that ce dissolves as anhydrous chloride complexes whereas y forms mixed cl oh solutes the results provide a simple mechanism for redistributing ree and y in deep crustal and upper mantle environments the h 2 o ce ratio inferred for subduction zone melts and silicate rich fluids can also be produced by a cepo 4 saturated fluid with x nacl 0 1 in addition neutral ph h 2 o nacl fluids can transport substantial ree and y obviating the need to invoke highly acid solutions in environments where they are unlikely

cretaceous cold seep communities and methane derived carbonates in the canadian arctic lower cretaceous cold seep fossil assemblages have been found in the canadian arctic archipelago serpulid worm tubes and bivalves are most abundant in these communities in contrast fossils are scarce in the surrounding strata the fossils are contained in an isotopically light delta 13 c 25 to 50 per mil carbonate rock groundmass that is interpreted to have formed from bacterial oxidation of methane the rocks were deposited at intermediate depth 400 meters in a cold marine environment nearby normal faults may have provided a conduit for seeping methane and hydrogen sulfide needed to fuel chemosynthetic bacteria and in turn the higher life forms

scales and effects of fluid flow in the upper crust two of the most important agents of geological change solar energy and internal heat from the mantle meet and battle for dominance in propelling aqueous and related fluids in the earth s upper crust which prevails and how they interact are subjects of active research recent work has demonstrated that both agents can propel fluids over nearly continental scale distances in a fashion that influences a host of important geological processes and leaves a record in chemical alteration mineral deposits and hydrocarbon resources

experimental determination of the solubility of ce monazite in sio2 al2o3 k2o na2o melts at 800 c 2 kbar under h2o saturated conditions the solubility of cerium monazite cepo4 in sio2 al2o3 k2o na2o melts was determined at 800 c 2 kbar under water saturated conditions dissolution experiments using synthetic ce monazite crystals and crystallization experiments using ce and po4 bearing glasses yield results in good agreement microprobe analyses of glasses using a sensitive method detection limit to 130 ppm show that the solubility of monazite is dependent on the melt composition and is especially low for peraluminous compositions application of these data to various geologic occurrences is in good agreement with petrographic and geochemical observations and shows that monazite fractionation is probably a very common phenomenon in two mica granites this provides a good explanation for the light ree and th depletion commonly observed in such rocks

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

seawater circulation through the flank of the florida platform evidence and implications dense biological communities at the base of the florida escarpment depend on energy provided by reduced compounds for bacterial chemosynthetic production sharp gradients in the concentrations of ch4 h2s nh4 so42 cl na mg2 sr2 i and seabed 226ra2 exist in the sediments underlying these communities the compositions of this fluid departs from that of normal seawater indicating the importance of microbial and diagenetic reactions within the escarpment before it is advected to the seafloor the 87sr 86sr ratios in the seep fluids range from 0 70920 seawater to 0 70773 which requires addition of light mesozoic strontium 18o values 0 3 to 0 1 smow and d values 2 6 smov of these waters are similar to normal seawater values and do not indicate that either meteoric processes or gas hydrates are involved in the genesis of the seeping fluid concentrations of cl ca2 and na suggest that the fluids which arrive at the seafloor are a mixture of mostly seawater with 4 7 formation brine from within the florida bahama platform mesozoic brines within the florida platform occupy levels above the scarp base a density driven flow system in implied which involves mesozoic platform brines that are greatly diluted by seawater entrained through the flanks of the platform the observed depletion of sulfate in the seeping fluids requires that sulfate reduction must occur in the platform within the zone where the recharging seawater and platform brines mix in order to produce the high concentrations of biogenic methane observed methanogenesis is inferred to be occuring within the platform in a zone where sulfate reduction has gone to completion the zone where the mixing of brine and seawater occurs should be cooled by the flushing seawater and heavily corroded by under saturation occurring as a result of the mixing the platform interior mixing is non conservative because of the addition of light mesozoic sr2 and the relative depletion in mg2 with espect to cl ca2 and na2 concentrations the inferred uptake of mg2 and concurrent depletion of so42 on the flanks of this margin