high grade magnetite mineralization at 1 86 ga in neoarchean banded iron formations gongchangling china in situ u pb geochronology of metamorphic hydrothermal zircon and monazite

low frequency variation in the seasonal intensity of coastal weather systems and sediment movement on the beachface of a sandy beach abstract variation in the seasonal intensity of weather systems generating onshore winds incident on port kembla n s w have been examined for the period 1965 to 1983 the onshore wind events were identified from anemograph records in turn they were related to synoptic weather records an intensity index 1 for each weather system was estimated as a function of the barometric pressure gradient between port kembla and the system centre the events were grouped by seasons and the intensity of the upper tercile i 1 3 value for each season utilised to represent the record for that season values of the seasonal i 1 3 intensities were spectrally analysed by fast fourier transform techniques the results identified quasi periodic variations of onshore wind activity with recurrence intervals corresponding to those in the frequency band shared by the southern oscillation so as well as the stratospheric quasi biennial oscillation qbo and the tropospheric quasi biennial oscillation bo the dominant quasi periodic components identified from a time series filtered to remove high frequency fluctuations include 3 years 27 months and 21 6 months the triennial and biennial components combine to account for approximately 32 of variance in the time series describing seasonal i 1 3 anomalies in onshore wind activity the filtered time series correlated with the southern oscillation index soi with r 0 49 p i 1 3 anomalies with the period of both the qbo and the m1 index of the tropospheric biennial oscillation were also noted in the latter instance direct comparison of the m1 phase shift was not possible because the i 1 3 data is contaminated with a strong soi type signal peak i 1 3 intensities are in phase to 1 month with the monthly mean sea level peaks at fort denison sydney n s w over corresponding periods more accurate resolution is not possible because of the specification of the weather system intensities as seasonal values in turn the sea level fluctuations lead movement of sediment on warilla beach n s w by a month over the 9 years for which observations are available from 1976 to 1985 peak weather system intensities for port kembla are co incidental with low volumes of sediment stored above msl on warilla beach conversely periods of low onshore wind activity are associated with increases in the volume of sediment stored on the beach

composition and origin of intermediate solid solutions in the system thorite xenotime zircon coffinite abstract a comprehensive survey of the accessory mineral assemblages in variscan granites of the german erzgebirge and pan african granites from jordan revealed the occurrence of intermediate solid solutions of the tetragonal thorite xenotime zircon coffinite mineral group with partially novel compositions these solid solutions preferentially formed in evolved and metasomatically altered p poor leucogranites of either i or a type affinity thorite from the erzgebirge contained up to 18 8 wt y2o3 16 1 wt zro2 and 23 3 wt uo2 xenotime and zircon have incorporated th in abundances up to 36 3 wt and 41 8 wt tho2 respectively extended compositional gradation with only minor gaps is confined to hydrated members of this mineral group and is observed to exist between thorite and xenotime thorite and coffinite and y hree bearing thorite and zircon complex hydrous solid solutions containing elevated abundances of three or more of the endmembers are subordinate previously reported intermediate solid solutions between anhydrous zircon and xenotime and anhydrous zircon and thorite are not observed and are in conflict with experimental work demonstrating very limited miscibility between anhydrous species of endmember composition the majority of hydrous intermediate solid solutions in the th y zr u system are likely thermodynamically unstable instead they are probably metastable responses to unusual physico chemical conditions involving various parameters and conditions the relative importance of which is incompletely known leaching and dissolution of preexisting accessory phases during interaction with f bearing hydrous fluids enriched in th y hree zr and or u and common deposition of the various elements at disequilibrium supersaturation seems to play a key role but other processes may be of similar importance experimental work involving hydrous conditions and complex systems composed of more than two endmembers are needed to shed light into the stability relations of the chemically uncommon compositions treated in this study

residence of ree y th and u in granites and crustal protoliths implications for the chemistry of crustal melts a systematic study with laser ablation icp ms scanning electron microscopy and electron microprobe revealed that 70 95 wt of ree except eu y th and u in granite rocks and crustal protoliths reside within reeythu rich accessories whose nature composition and associations change with the rock aluminosity the accessory assemblage of peraluminous granites migmatites and high grade rocks is composed of monazite xenotime in low ca varieties apatite zircon thorthosilicate uraninite and betafite pyrochlore metaluminous granites have allanite sphene apatite zircon monazite and thorthosilicaie peralkaline granites have aeschinite fergusonite samarskite bastnaesite fluocerite allanite sphene zircon monazite xenotime and th orthosilicate granulite grade garnets are enriched in nd and sm by no less than one order of magnitude with respect to amphibolite grade garnets granulitegrade feldspars are also enriched in lree with respect to amphibolite grade feldspars accessories cause non henrian behaviour of ree y th and u during melt solid partitioning because elevated fractions of monazite xenotime and zircon in common migmatites are included within major minerals their behaviour during anatexis is controlled by that of their host settling curves calculated for a convecting magma show that accessories are too small to settle appreciably being separated from the melt as inclusions within larger minerals biotite has the greatest tendency to include accessories thereby indirectly controlling the geochemistry of ree y th and u we conclude that ree y th and u are unsuitable for petrogenetical modelling of granitoids through equilibrium based trace element fractionation equations

modeling the role of sodic alteration in the genesis of iron oxide copper gold deposits eastern mount isa block australia liberation of iron and potassium by widespread postmetamorphic albitization of country rocks was one of the likely contributing processes in the formation of both barren and mineralized magnetite chalcopyrite biotite gold hematite clinopyroxene actinolite apatite ironstones in the cloncurry district of the proterozoic mount isa block whole rock geochemical data indicate nearly immobile al ga ti zr during transformation of a variety of least altered rocks toward albitite the data indicate that the addition of na from a brine to the rock accompanied the loss of fe k ba rb ca sr co v mn pb and zn from those altered rocks and enrichment in the brine but that cu was not systematically stripped from a variety of wall rocks during albitization conversely the formation of metasomatic ironstones the immediate hosts to some cu au ores involves addition of most of the same elements that were lost during albitization the correlation between intensity of alteration its distribution and timing e g in breccias cored by ca 1530 1500 ma granitoids and convergence of all rock types toward magmatic stable isotope values provides strong evidence for a substantial component of igneous derived fluid simulations of the albitization process were carried out isothermally at 550 c and 350 mpa and polythermally from these conditions down to 400 c and 200 mpa using the gibbs minimization method with hch software and the unitherm database both simple fluid rock mixing models and more complicated reactor style algorithms used a range of input fluids from fluids equilibrated fluid with two feldspar granite through to na k ratios consistent with fluid inclusion results and geochemical data for initially unaltered wall rocks the apparent paradox of widespread albitization resulting from fluid released by two feldspar granites can be explained by relatively small shifts away from the k feldspar albite equilibrium curve and even isothermal model fluids derived from two feldspar granites produce albitites in calc silicate rocks outboard of granite proximal k feldspar clinopyroxene skarns matching field patterns those models with fluid na k ratios similar to those of fluid inclusions produced the most realistic alteration assemblages dominated by albite for both isothermal conditions and decreasing temperature which approximate those observed in the field pixe and microthermometric data on fluid inclusions from quartz in two feldspar quartz monzonite and pegmatite at the top of the mount angelay pluton indicate bulk na k molar ratios in the fluid of between 10 and 20 considerably higher than our thermodynamically calculated values for fluid in equilibrium with two feldspar granite of around 3 at 550 c 350 mpa such shifts may have been attained by admixture of magmatic hydrothermal fluid with small amounts of nacl brines trapped along grain boundaries in scapolite bearing calc silicate wall rocks by fluid immiscibility due to high initial co2 contents in the felsic intrusions by contributions from mafic magmas or from dissolution of salt rich layers into the intrusions prior to crystallization and fluid release with increasing amounts of fluid rock interaction in the models the fluids were enriched in k fe and ca approaching compositions observed in fluid inclusions in the ore deposits these fluids reacted with pelitic rocks which are common ore hosts would produce magnetite clinopyroxene biotite actinolite alteration at high temperature similar to the proximal alteration around ore deposits we infer that precipitation of sulfides in the cu au deposits was the result of mixing of cu bearing brine of ultimately magmatic origin but modified extensively via albitization with sulfur bearing fluids or reaction of the brine with sulfur bearing rocks when cu was absent from the initial magmatic fluid barren ironstones may have been the result

the use of jadammina macrescens brady and balticammina pseudomacrescens bronnimann lutze and whittaker protozoa foraminiferida as sea level indicators in studies of foraminiferal distributions in saltmarshes in new england and atlantic canada balticammina pseudomacrescens and jadammina macrescens have formerly been grouped as trochammina macrescens this study recognises them as distinct species and shows that they have significantly different distributions on the surface of saltmarshes in maine here relative abundances of j macrescens correlate with tidal elevation r2 0 55 p 0 00 whereas those of b pseudomacrescens do not r2 0 03 p 0 34 therefore j macrescens is a better sea level indicator in maine marshes than b pseudomacrescens in menunketesuck river marsh connecticut a clear vertical zonation of saltmarsh foraminifera is absent which hinders interpretation of fossil data this study shows that in maine separating b pseudomacrescens and j macrescens in counts of fossil data facilitates the detection of transgressional and regressional events in the biostratigraphical record and hence the reconstruction of local sea level histories regional variability between northern and southern new england saltmarshes necessitates the establishment of local reference sets of modern analogue data to aid palaeoecological interpretations

foraminiferal biofacies eco succession and holocene sealevels port pirie south australia abstract at port pirie on the eastern coast of northern spencer gulf south australia 10 cores taken along a 3 km transect recovered a succession of holocene marine sediments facies representing shallow subtidal posidonia seagrass and intertidal sandflat mangrove and back storm ridge coastal lagoon environments are recognized on the basis of lithological characteristics and their preserved foraminifera an assemblage dominated by nubecularia lucifuga peneroplis planatus and discorbis dimidiatus signifies sediments of shallow subtidal posidonia seagrass meadows subtle changes in the numerical distribution of these species upcore are used to infer the change from subtidal to intertidal sandflat facies elphidium crispum and elphidium macelliforme become more numerous across this transition the mangrove facies is characterized by trochammina inflata this species is present significantly in only one seaward core where modern mangrove woodland continues to grow today and no equivalent biofacies are recognized in other cores the lagoonal sediments preserve a rich assemblage of species of euryhaline foraminifera together with those of the mangrove woodland they exhibit an ecological succession which can be related to decreasing intervals of tidal inundation and increasing salinity helenina anderseni with subordinate ammonia beccarii and elphidium cf articulatum are the pioneer species in the euryhaline setting giving way to trichohyalus tropicus and miliolinella schauinslandi late stages of hypersaline sedimentation are characterized by triloculina inflata triloculina oblonga in the mangroves h anderseni a beccarii and elphidium cf articulatum are replaced by trochammina inflata as the dominant species in turn as further sediment aggradation leads to ever shorter intervals of tidal inundation at the landward side of the mangrove woodland trochammina inflata is overtaken by ammobaculites barwonensis quantitative foraminiferal biofacies analysis confirms and refines the sedimentological interpretation of intertidal sediment facies from macro observations of the core materials it provides independent estimates of the elevation of key facies boundaries in cores and confirmation of a general relative fall in sealevel in northern spencer gulf over the past 7000 yr

the ca 1740 1710 ma leichhardt event inversion of a continental rift and revision of the tectonic evolution of the north australian craton abstract interpretation and modelling of high resolution regional geophysical data of the central leichhardt river fault trough in the mount isa inlier are used to determine the timing of a major basin inversion event following the development of the ca 1780 1740 ma leichhardt superbasin inversion of the leichhardt superbasin formed the regional north south trending leichhardt anticline during east west shortening the limbs of the anticline are overprinted by several east west trending wedge shaped non magnetic sub basins filled with ca 1710 ma calvert and isa superbasin successions these relationships suggest inversion of the leichhardt superbasin occurred between ca 1740 and 1710 ma the event is also known to have affected the northern and eastern north australian craton the scale of the inversion suggests it was a significant event that we have defined as the leichhardt event this event requires a major tectonic driver to the east of the north australian craton possibly the accretion of a micro continental ribbon to the east of the mount isa inlier the results of this study have implication for paleogeographic reconstruction of the australian continent during the formation of nuna because eastern north australian craton faced an ocean at ca 1740 1720 ma the results also challenge the significance and intensity of crustal shortening associated with the ca 1600 1500 ma isan orogeny throughout the western mount isa inlier

interannual fluctuations of the tropical pacific wind field and the southern oscillation abstract linear regression analysis of tropical pacific winds versus a southern oscillation index soi show departures from the seasonal mean wind associated with the phase of soi when the soi is low the largest departures are westerlies on the equator and in the subtropics west of the dateline the intertropical convergence zone itcz and the south pacific convergence zone spcz shift equatorward departures from mean wind are strongest from september through february and weakest from march to may the usual pattern of cyclonic wind stress curl in the tropics and anticyclonic wind stress curl in the subtropics intensifies when the soi is low effects of these changes on ocean circulation are discussed and compared to changes in ocean circulation data

assessment of southern oscillation sea level pressure indices abstract monthly sea level pressure anomalies at easter island rapa tahiti and darwin for the period 1951 79 are analysed to reveal their temporal characteristics and the coherence and time lead lag relationships among them for interannual scale oscillations the pressure variations at rapa and easter island lead those at tahiti and those of opposite phase at darwin by 2 8 months where the large lead times are associated with lower frequency oscillations of the four stations rapa has the smallest percentage of its variance in the range of periods containing the southern oscillation darwin has the largest spatial smoothing by combining stations enhances the percentage of variance in the longer periods combining tahiti and darwin gives a substantial increase combining rapa and easter island much less normalization of the time series through division by the monthly standard deviations is also treated the combination of tahiti and darwin is recommended as a southern oscillation index for diagno

uranium deposits of the mount isa region and their relationship to deformation metamorphism and copper deposition the mount isa region contains over 20 uranium deposits few of which contain economic concentrations of uranium they are thought to be significant in the exploration for new copper deposits based on the model that the uranium deposits are located in the pathways of oxidized hydrothermal fluids that formed the postmetamorphic mount isa copper orebodies there are two uranium deposit types both hosted in volcanosedimentary rocks we suggest that they represent one mineralization event but different metamorphic histories examples in the eastern low grade metamorphic zone are dominated by a brannerite anatase apatite assemblage and are low in uranium the examples in the western high grade metamorphic zone are characterized by uraninite and titanite with higher uranium concentrations the chemical association of u ti and ca is consistent for all deposits however phosphate is only important at low metamorphic grade the most likely mechanism of formation in the lower metamorphic grade anderson s lode example is the complete replacement of chlorite in the sedimentary host rock matrix by the mineralizing assemblage in this model chlorite acted as a reductant allowing the deposition of uranium from an oxidized fluid this mechanism of uranium deposition is similar to that proposed for unconformity type uranium deposits we conclude that these uranium deposits are metamorphosed equivalents of proterozoic unconformity type uranium deposits found elsewhere in northern australia at anderson s lode brannerite and apatite were concentrated in veinlets by pressure dissolution after the deposition of the original assemblage these pressure dissolution seams are cut by premetamorphic quartz chlorite veins examples at higher metamorphic grade have textures that suggest uranium deposition was pre to synmetamorphic at the latest this precludes any genetic or temporal connection between the uranium deposits and the postmetamorphic mount isa copper deposit

correlation between foraminifera and sedimentary environments in recent estuaries of southwestern spain applications to holocene reconstructions a multivariate analysis of the foraminifera collected in three estuaries of southwestern spain guadiana piedras tinto odiel permits recognition of three main assemblages with spatial distribution depending on sedimentary environments grain size classes and salinity variations assemblage 1 trochammina inflata jadammina macrescens is typical of salt marsh deposits with high salinity variations and percentages of important silt assemblage 2 ammonia beccarii ammonia tepida astrononion stelligerum elphidium williamsoni includes the most abundant estuarine species with increasing densities from the channel margin to the subtidal channel assemblage 3 quinqueloculina seminulum elphidium crispum is mainly found in the sandy sediments of the subtidal channels located near the mouth with normal marine conditions these results and the sedimentological interpretation of seven drill cores collected in the domingo rubio channel tinto river allow reconstruction of the palaeogeographic changes of this small estuary in the last ca 6500 14 c years bp seven phases were distinguished with an evolution from an open marine bay to

the mobility of zirconium and other immobile elements during hydrothermal alteration abstract development of zircon and other zr phases in hydrothermal deposits indicates that zr can be highly mobile in these systems mobility is most common in but not restricted to f rich hydrothermal systems related to alkalic f rich igneous suites these suites can range from peralkaline through metaluminous to peraluminous a few examples are neither alkalic nor f rich three locations in the trans pecos magmatic province texas u s a demonstrate this hydrothermal zr mobility all three igneous systems are alkalic and f rich but vary in alkali al ratios peralkaline rhyolites and trachytes in the christmas mountains contain as much as 2100 ppm zr mostly in aegirine or arfvedsonite zircon is rare or absent fluorspar replacement deposits in limestone at contacts with the rhyolites contain as much as 38 000 ppm zr occurring as small disseminated zircons the deposits also are enriched in a variety of incompatible elements including be rare earth elements ree y nb mo hf pb th and u the sierra blanca intrusions a series of mildly peraluminous f rich rhyolite laccoliths contain as much as 1000 ppm zr mostly as zircon hydrothermal zircon occurs as overgrowths on magmatic grains as veinlets connected to overgrowths and in fluorspar replacement bodies in adjacent limestone the highest zr concentrations in fluorspar are 200 ppm metaluminous quartz monzonite from the infiernito caldera contains 400 600 ppm zr mostly as zircon euhedral zircon in quartz fluorite veins in the quartz monzonite indicates mobility of zr zirconium concentrations in the veins are unknown but the paucity of zircon suggests little zr enrichment relative to the host zircon and more rarely zirconolite occur in skarn in the ertsberg district of irian jaya indonesia unlike in texas related igneous rocks are metaluminous and the hydrothermal system was f poor worldwide hydrothermal zircon other zr phases and ti and al bearing phases occur in skarn epithermal precious metal veins volcanogenic massive sulfide deposits and mylonites we propose that differences in zr mineralogy of igneous source rocks is an important factor in determining the availability of zr to hydrothermal fluids although zr concentrations in the sierra blanca and christmas mountains rhyolites are similar zr enrichment in fluorspar was much greater in the christmas mountains we suggest that hydrothermal solutions could easily break down aegirine and arfvedsonite to release zr but that zircon was only moderately attacked therefore far more zr was available for transport and subsequent deposition in the christmas mountains than at sierra blanca availability of other trace elements probably is also governed by their mineral host although zr mobility is most common in f rich hydrothermal systems related to alkalic and f rich igneous systems mobility at ertsberg may have been promoted by sulfate complexing

zircon solubility in alkaline aqueous fluids at upper crustal conditions field evidence and thermodynamic data at ambient conditions suggest that complexing of zr with hydroxyl ions at high ph enhances the solubility of zircon we tested this hypothesis by measuring the solubilities of the assemblages zircon zrsio 4 baddeleyite z b and zircon quartz z q in neutral to alkaline fluids at 0 2 gpa and 450 750 c in neutral to alkaline fluids 0 0 1 1m naoh zircon dissolved incongruently in quartz undersaturated fluids to form baddeleyite at 450 c various na zr silicates precipitated from fluids saturated and undersaturated in quartz we observed no significant dependence of solubility on temperature the measured solubilities of zircon in pure h 2o at 600 and 750 c are only slightly higher than the procedural blank of 3 3 10 7 m zr however the measured solubility of zircon increases with increasing aqueous silica suggesting that zirconium complexes with silica in the fluid at 600 c linear regression of experimental results yielded ln zr 0 25 2 9 ln si where terms in parentheses represent molal concentrations zircon solubility also seems to increase with increasing hydroxyl concentration in the fluid enhanced solubility in silica rich alkaline fluids may cause dissolution reprecipitation of zircon and resetting of its isotopic clocks suggesting that some zircon u pb ages may correspond to fluid events

low frequency changes of sediment volume on the beachface at warilla beach new south wales 1975 1985 abstract characteristic patterns of shore parallel and shore normal movements of sediment on a sandy beach are described in this study the sediment movements are apparent as low frequency variations in the volume of sediment stored above mean low water spring tide mlwst level on warilla beach n s w they were determined by an empirical orthogonal function eof analysis of beach profile records the profiles were surveyed from eighteen stations along a 2 km long beach at least monthly generally fortnightly for over 10 years from july 1975 until august 1985 results from the eof analysis confirm and substantially extend an earlier study of warilla beach when the first 5 years of the beach survey record was examined the importance of low frequency beachface change identified in the earlier shorter study was confirmed from the extended data set zones of maximum variability linked with rip current activity are consistent in both studies and similar patterns of alongshore sediment movement in the swash zone were determined from both analyses the principal differences between the two sets of results highlight beachface responses to processes operating in different time scales amplitude spectra from time series describing the characteristic modes of sediment movement along and across the beachface have periodicities of 2 0 1 7 and 1 0 years beach changes with periods close to 3 years are apparent in the record but cannot be resolved by standard spectral analysis techniques each period is associated with a characteristic pattern of beach change the triennial and 1 7 year cycles with alongshore sediment transport and the biennial cycle with onshore offshore sediment exchange eigenvectors from the eof analysis identify the characteristic patterns of beach change from survey data specified to highlight the shore parallel sediment movement along 0 5 m deep horizontal segments of beach and shore normal sediment movement along the beach profiles in the analysis of shore parallel variation in beach profile configuration the fundamental eigenvectors explain between 70 and 80 of beachface variance in each instance and different patterns of sediment movement were identified for each horizontal slice on the upper part of the beachface all eigenvectors identified a zone of low variability along the shoreline skirting a rockwall below berm crest in the swash and intertidal zones of the beach and away from the rockwall the northern half of the beach was highly variable second mode eigenvectors cellular flux modes explain a further 5 to 14 of the variance and describe sediment exchanges between discrete zones in each horizontal segment of the beachface zones of greatest variability occurred landward of places where rip currents frequently develop conversely zones of low variability are coincident with areas of beachface in the lee of places where inshore bars frequently form analysis of sediment movement along each profile is consistent with the beach changes described the fundamental eigenvectors account for 91 to 99 of the variance on each profile they describe an onshore offshore movement of sediment through the intertidal zone of the beach

high radiogenic heat producing granites and metamorphism an example from the western mount isa inlier australia the origins of metamorphism 600 c and 3 4 kbar in the western mount isa inlier australia remain controversial for a number of reasons 1 no synmetamorphic intrusive bodies can be recognized 2 high temperatures appear to be sustained for periods 100 m y and 3 metamorphism follows an extended phase of thermal subsidence we show that the burial of granite batholiths enriched in radiogenic elements beneath the thick insulating sedimentary succession of the mount isa group deposited in response to repeated rift sag cycles was capable of generating steep upper crustal thermal gradients immediately prior to the isan orogeny these gradients are appropriate to peak metamorphic conditions such that the ensuing isan orogeny required no significant additional heat input this result is significant in that it may provide a mechanism for understanding the origins of high temperature metamorphism in other terranes where the involvement of transient heating is not obvious

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

influence of el nino southern oscillation enso events on the evolution of central california s shoreline significant sea cliff erosion and storm damage occurred along the central coast of california during the 1982 1983 and 1997 1998 el nino winters this generated interest among scientists and land use planners in how historic el nino southern oscillation enso winters have affected the coastal climate of central california a relative enso intensity index based on oceanographic and meteorologic data defines the timing and magnitude of enso events over the past century the index suggests that five higher intensity relative values 4 6 and 17 lower intensity relative values 1 3 enso events took place between 1910 and 1995 the enso intensity index correlates with fluctuations in the time series of cyclone activity precipitation detrended sea level wave height sea surface temperature and sea level barometric pressure wave height sea level and precipitation which are the primary external forcing parameters in sea cliff erosion increase nonlinearly with increasing relative enso event intensity the number of storms that caused coastal erosion or storm damage and the historic occurrence of largescale sea cliff erosion along the central coast also increase nonlinearly with increasing relative event intensity these correlations and the frequency distribution of relative enso event intensities indicate that moderate to high intensity enso events cause the most sea cliff erosion and shoreline recession over the course of a century

the holocene transgression into the estuarine central basin of the odiel river mouth cadig gulf sw spain lithology and faunal assemblages abstract six estuarine facies were distinguished recording the holocene history of sea level rise relating according to the start and development of the holocene transgression which flooded the coast of huelva facies 2 gravels facies 3 grey clayey silts facies 5 well sorted sands facies 4 silty sands facies 5 black clayey silts and facies 6 red muds this group overlies neogene sediments facies 1 three faunal assemblages open bay ob central estuary ce and wave domination wd including remains of macrofauna foraminifers and ostracods plus depositional features are identified in a sedimentological log constructed from a borehole with a continuous core sunk in the central basin of the odiel river estuary huela coast sw spain the ob assemblage requires shallow and protected zones controlled by low energy tidal currents the ce assemblage is located within an intertidal zone where reworked marine forms of foraminifers ostracods and scattered macrofauna co exist with small estuarine foraminifers and ostracods the wd assemblage comprises tests of marine macrofauna with fractured shells plus large marine foraminifers and estuarine ostracods during the first stage of continuous sea level rise 8720 260 bp to 5390 155 bp estuarine accretion high energy tidal currents and wave action took place successively allowing the development of the ob ce and wd assemblages the second stage 5390 155 bp to present with a stabilized sea level comprised a vertical decrease of energy with tidal currents favouring deposition in shallow tidal channels and marsh zones leading to less energetic ce assemblages within the estuarine central basin high sediment supply resulted in deposition during this stage which shows a regressive nature

mean sea level and beach width variation at scarborough western australia abstract a sixteen year record of beach width change at six profile stations on scarborough beach in the perth metropolitan area of western australia was analysed by eliot and colleagues their results described long term beach progradation measured over the sixteen years and identified cyclic beach changes with periods of 0 5 1 0 3 5 and 7 0 yrs and a long term secular progradational trend in this paper the beach width measurements from scarborough are compared with twelve years of mean sea level record from fremantle western australia approximately 18 km south of scarborough beach the annual cycles of each respond in an inverse manner such that a 1 cm rise in mean sea level corresponds with a 1 m decrease in the beach width the sea level rise leads the beach width retreat by approximately one fifth of a cycle a long period oscillation of 3 5 yrs in the mean sea level shows a similar 100 1 ratio for beach gradation with a lead of approximately one tenth of a cycle however the secular trend in beach width change was not evident in the mean sea level record indicating that the progradation is tied to other processes such as a northerly sediment drift related to prevailing sw swell and associated current activity

proterozoic low pressure high temperature metamorphism and an anticlockwise p t t path for the hazeldene area mount isa inlier queensland australia in the hazeldene area situated in the mount isa inlier queensland the metamorphic grade changes from chlorite zone through biotite and cordierite zones to sillimanite k feldspar zone microstructural studies of rocks near the sillimanite isograd demonstrate that cordierite grew early during the development of a steep foliation s2 was replaced by biotite andalusite and sillimanite at the metamorphic peak late in s2 and in turn by kyanite chlorite adjacent to localized small post d2 shear zones although the anticlockwise p t t path is well defined the precise p t conditions are uncertain because of problems with experimental and thermodynamic data the best estimate for the metamorphic peak for rocks close to the sillimanite isograd is around 600 c at 4 kbar the metamorphism has been dated at 1544 ma and was synchronous with a major crustal shortening event because proposed extensional events occurred more than 60 ma earlier their contribution to the peak metamorphic thermal perturbation would have been insignificant the syn metamorphic mica creek pegmatites the abundance of high heat producing elements in the nearby pre d2 sybella granite and advective heat by fluids which caused considerable metasomatism in the hazeldene area may have each contributed to the thermal budget however the metamorphic thermal gradient may be 80 c km 1 or higher strongly suggesting a local magmatic control as none are known in the area such syn metamorphic plutons would have to lie beneath the exposed high grade rocks

depositional history of estuarine infill during the last postglacial transgression gulf of cadiz southern spain abstract the late pleistocene and holocene evolution of the estuaries in the gulf of cadiz is interpreted for the first time using drill cores logs trenches and 38 new radiocarbon data and the results compared with the shelf the odiel tinto and guadalete rivers deposited conglomerates during a highstand that did not reach the present sea level dated at ca 25 30 ka isotopic stage is 3 corresponding to a relatively humid period in the area rivers incised these coarse grained deposits during the last main lowstand at ca 18 ka when sea level dropped to 120 m and the coastline lay 14 km seawards from the present the erosional surface is a sequence boundary and the flooding surface of the postglacial eustatic rise overlain by the valley fill deposits of the transgressive and highstand phases of the last fourth and fifth order depositional sequences recognised in the shelf the first marine influence in the estuaries during the transgression occurs at 25 30 m at ca 10 000 years bp according to fossil assemblages the transgressed basins changed from brackish to more open marine as the sea rose until ca 6500 years bp when it reached the maximum flooding and the sandy estuarine barriers ceased to retrograde toward the muddy central basins then the rate of eustatic rise decreased drastically and the estuarine filling followed a two fold pattern governed by the progressive change from vertical accretion to lateral centripetal progradation at ca 4000 years bp the fluvial input surpassed the already negligible rate of rise causing partial emergence of tidal flats and spit barriers in the largely filled estuarine basins prevalence of coastal progradation upon vertical accretion at ca 2400 years bp caused accelerated expansion of tidal flats and rapid growth of the sandy barriers further changes since the 16th century reflect widespread anthropic impacts

the proterozoic albitite hosted valhalla uranium deposit queensland australia a description of the alteration assemblage associated with uranium mineralisation in diamond drill hole v39 the valhalla uranium deposit located 40 km north of mount isa queensland australia is an albitite hosted mesoproterozoic u deposit similar to albitite hosted uranium deposits in the ukraine sweden brazil and guyana uranium mineralisation is hosted by a thick package of interbedded fine grained sandstones arkoses and gritty siltstones that are bound by metabasalts belonging to the ca 1 780 ma eastern creek volcanics in the western succession of the mount isa basin alteration associated with u mineralisation can be divided into an early main and late stage the early stage is dominated by laminated and intensely altered rock comprising albite reibeckite calcite titano magnetite brannerite the main stage of mineralisation is dominated by brecciated and intensely altered rocks that comprise laminated and intensely altered rock cemented by brannerite apatite uranoan zircon uraninite anatase albite reibeckite calcite and hematite the late stage of mineralisation comprises uraninite red hematite dolomite calcite chlorite quartz and pb fe cu sulfides brannerite has u pb and pb pb ages that indicate formation between 1 555 and 1 510 ma with significant pb loss evident at ca 1 200 ma coincident with the assemblage of rodinia the oldest ages of the brannerite overlap with 40ar 39ar ages of 1 533 9 ma and 1 551 7 ma from early and main stage reibeckite and are interpreted to represent the timing of formation of the deposit these ages coincide with the timing of peak metamorphism in the mount isa area during the isan orogeny lithogeochemical assessment of whole rock data that includes mineralised and unmineralised samples from the greater mount isa district reveals that mineralisation involved the removal of k ba and si and the addition of na ca u v zr p sr f and y u th ratios indicate that the ore forming fluid was oxidised whereas the crystal chemistry of apatite and reibeckite within the ore zone suggests that f and text po 3 4 were important ore transporting complexes 18o values of co existing calcite and reibeckite indicate that mineralisation occurred between 340 and 380 c and involved a fluid having 18ofluid values between 6 5 and 8 6 reibeckite d values reveal that the ore fluid had a dfluid value between 98 and 54 the mineral assemblages associated with early and main stages of alteration plus 18ofluid and dfluid values and timing of the u mineralisation are all very similar to those associated with na ca alteration in the eastern succession of the mount isa basin where a magmatic fluid is favoured for this style of alteration however isotopic data from valhalla is also consistent with that from the nearby mount isa cu deposit where a basinal brine is proposed for the transport of metals to the deposit based on the evidence to hand the source fluids could have been derived from either or both the metasediments that underlie the eastern creek volcanics or magmatism that is manifest in the mount isa area as small pegmatite dykes that intruded during the isan orogeny

isotopic and structural responses of granite to successive deformation and metamorphism within the sybella granite west of mount isa in northern australia differential response of u pb and rb sr isotopic systems to deformation metamorphism enables ages of emplacement and three discrete deformation metamorphic events to be determined based on zircon u pb systems two of the plutons were emplaced at 1671 pm 8 ma and 1668 pm 26 21 ma and the third at 1610 pm 10 ma a separate microgranite body gives aberrantly old u pb ages of up to 1780 ma due to partial inheritance of older zircon the three discrete deformation metamorphic events d 1 d 2 and d 3 occurred at 1610 pm 13 ma 1544 pm 12 ma and 1510 pm 13 ma respectively based on whole rock rb sr isotopic systems the youngest body was emplaced syntectonically and has possible significance to the origin of the mount isa ag pb zn orebodies homogenization of rb and sr isotopes via extensive syntectonic fluid migration associated with deformation partitioning and resultant solution transfer appears to have been

late quaternary palaeoecology palynology and palaeolimnology of a tropical lowland swamp rawa danau west java indonesia abstract sedimentological limnological and palynological analyses of a sediment core from a lowland site in west java indonesia provide a detailed palaeoenvironmental record for the late glacial and the holocene the record suggests open vegetation under inferred drier climatic conditions for the late glacial however there is no unequivocal evidence for cooler conditions at this time the onset of the holocene coincides with a change to more humid climatic conditions with the development of a fern rich closed forest vegetation type dramatic changes in diatom community composition provide a striking record of habitat change associated with lake shallowing but this process appears to be a result of basin in filling rather than variations in precipitation evaporation balance associated with climatic fluctuations evidence for human impact on the vegetation development is restricted to the last few hundred years

hydrothermal alteration of magmatic zircon related to nacl rich brines diffusion reaction and dissolution reprecipitation processes magmatic zircon from altered gabbros adjacent to the 1 07 ga lala fe cu deposit sw china was modified by nacl rich brines related to the fe cu mineralization the modified zircon grains are composed mostly of both inclusion free and porous domains and some grains also have overgrowth rims the inclusion free domains commonly overgrown by the porous domains are roughly homogeneous under bse imaging but display oscillatory or sector zoning under cl imaging in contrast the porous domains are distinctly mosaic like under cl imaging and contain abundant pores and mineral inclusions such as thorite xenotime ree rich phases actinolite albite biotite and calcite the inclusion free domains have concentrations of non formula elements for example al ca and fe much higher than the magmatic zircon and are thus interpreted to be products of interaction between magmatic zircon possibly metamictized and the fluids via a diffusion reaction process however these resultant domains have retained the th and u contents ree patterns u pb ages and hf isotopes of the precursor magmatic zircon on the other hand the porous domains have stoichiometric end member compositions that is lowered th u ree y and p and given that they are porous and inclusion rich we proposed that they have formed from the precursor element rich inclusion free domains or magmatic zircon via a fluid induced dissolution reprecipitation process it is notable that the porous domains retained the 177hf 176hf ratios of the precursors but possess modified and meaningless u pb ages instead a meaningful u pb age 1006 62 ma similar to the timing of the lala deposit is well recorded by the overgrowth rims with distinctly high lrees la 50 700 ppm and elevated hf isotopic ratios our new results reveal that in the presence of the nacl rich brines the nature of the precursor magmatic zircon that is high element budgets and or metamictization plays a key role on hydrothermal alteration of zircon

the solubility of fluorite in h2o and h2o nacl at high pressure and temperature abstract the solubility of fluorite in h2o and h2o nacl has been measured at 600 1000 c 0 5 2 0 gpa in a piston cylinder apparatus fluorite dissolves congruently at all conditions investigated the data indicate that the concentration of fluorite dissolved in h2o is low at 600 c and 0 5 gpa 0 0014 mol kg h2o but increases strongly with temperature t and pressure p to 0 247 mol kg h2o at 1000 c 2 gpa the data were fit with the equation log mcaf2 6 587 2 774p1 2 2 266 10 3 4 699 10 4p t where mcaf2 is molality of caf2 t is in kelvin and p is in gpa fluorite solubility was also measured in h2o nacl fluids at 800 c and 1 0 gpa results indicate a strong increase in dissolved fluorite concentration with increasing nacl content from 0 028 mol kg h2o at xnacl 0 to 1 673 mol kg h2o at xnacl 0 486 where xnacl is the mole fraction of nacl in the fluid the data were fit to mcaf2 0 01035 1 141xnacl 4 694xnacl2 the results indicate that f mobility will be further enhanced by saline brines in high p t igneous and metamorphic environments high f solubility in h2o and h2o nacl in the deep crust and upper mantle can promote mobilization of high field strength elements rare earth elements u and th through transport as f bearing complexes

amount of subsidence during a late holocene earthquake evidence from fossil tidal marsh foraminifera at vancouver island west coast of canada abstract fossil foraminifera in intertidal deposits beneath a marsh near tofino on west central vancouver island british columbia provide a basis for estimating the amount of subsidence during a large earthquake less than 400 years ago we compared the fossil foraminiferal assemblages with present day assemblages along a surveyed transect across the marsh and we estimated paleo elevation by means of both subjective and quantitative methods the comparisons suggest that the site subsided at least 0 2 m and perhaps more than 1 m during the earthquake most of the subsidence was tectonic for the deposits rest on a pleistocene substrate unlikely to have compacted much when shaken soon after the earthquake the land began to rebound tectonically most of the 0 2 1 m of recorded subsidence was recovered during deposition of the first 6 cm of sediment above the buried marsh surface probably within a few decades after the earthquake because of the speed at which the land rebounded some recovery may have occurred before the first post earthquake sediments were deposited if so the actual amount of subsidence is larger than the foraminiferal data indicate

live and dead benthic foraminiferal faunas from whittard canyon ne atlantic focus on taphonomic processes and paleo environmental applications abstract dead benthic foraminiferal assemblages were studied in the 150 m fraction of 4 5 cm deep sediment levels at 18 stations in the whittard canyon area in june 2007 this sediment layer is composed of fairly recent sediment in both canyon branches the population dynamics such as seasonal response to phytodetritus deposition certainly contribute to differences between live and dead faunas for instance bulimina marginata which is usually considered as an opportunistic species is over represented in the dead assemblage the fragility of the tests of some species can explain their total absence in the thanatocoenoses this concerns many organic cemented arenaceous tests miliolid tests sensitive to dissolution and perforate taxa with thin tests furthermore transport e g sediment gravity flows active in both canyon branches leads to an increasing relative contribution of allochthonous individuals originating from outer shelf and upper canyon sites towards the deeper canyon stations consequently the dead faunas do no reflect local environmental conditions the high abundance of transported dead foraminifera in both canyon branches leads to important biases in the foraminiferal assemblage composition but may also significantly bias the interpretation of 13 c 18 o trace elements and 14 c concentration in foraminiferal shells it may therefore strongly complicate the reconstruction of environmental parameters such as bottom water temperature or exported paleoproductivity and radiocarbon dating of the foraminiferal assemblages therefore in both canyon axes the use of dead foraminiferal faunas to reconstruct paleoenvironmental in situ conditions is precluded however the study of dead assemblages in the canyon branches in particular the quantity of allochthonous foraminifera can give important clues about the downslope sedimentary dynamics on both open slopes despite taphonomic test destruction and biological processes population dynamics the distribution and the composition of the live fauna resemble those of the dead assemblage in these areas dead foraminiferal faunas include much less material derived from downslope transport consequently on the open slope dead assemblages appear to better reflect local conditions therefore the ecological information obtained from fossil open slope samples can be more reliably used to reconstruct paleoenvironmental conditions

pyrite pyrrhotite stability in a metamorphic aureole implications for orogenic gold genesis it is generally thought that orogenic gold deposit formation is associated in many cases with metamorphic fluids these fluids are mainly liberated by chlorite breakdown in the upper greenschist facies and there is some debate as to whether the pyrite to pyrrhotite desulfidation reaction precedes or coincides with this fluid release since pyrite is an important metal host in metamorphic rocks its breakdown to pyrrhotite may allow complexation of au with liberated sulfur thus the question of the temperature pressure conditions required for pyrite desulfidation is important because it determines which tectonic processes and which parts of the crust are relevant to gold deposit genesis here we investigate metal redistribution during pyrite breakdown using laser ablation inductively coupled plasma mass spectrometry and bulk rock analysis on greenschist to amphibolite facies rocks of the ballachulish metamorphic aureole scotland results suggest that the pyrite to pyrrhotite transition field spans a broader temperature range than indicated by recent modeling and that pyrite breaks down simultaneously with chlorite gold as bi sb mn and w were likely removed from the rock in chlorite derived fluid nickel co ga ge mo tl v and cr are retained in the rock by uptake in pyrrhotite copper is retained by growth of chalcopyrite as temperature increases whereas pb and zn are retained by progressive uptake in nonsulfide minerals these elements are not depleted during amphibolite facies metamorphism the tendency of s to react with silicate hosted fe and be retained in the rock implies that fe poor pyritic sedimentary rocks may produce more s and metal rich fluids in source regions

fluid immiscibility in metamorphic rocks evidence of fluid immiscibility in metamorphic rocks comes in the best of all worlds from fluid inclusion observations in fact fluid immiscibility should be anticipated over the full range of metamorphic conditions provided that appropriate bulk fluid compositions are present in a review paper entitled metamorphic fluids the evidence from fluid inclusions crawford and hollister 1986 summarized the role of fluid immiscibility in metamorphism was only recognized after serious study of fluid inclusions in metamorphic rocks was underway in the late 1970s and has yet to attract the attention of more than a handful of petrologists studying metamorphic rocks since then tremendous progress has been made a huge amount of fluid inclusion studies have convincingly shown that immiscible fluids can be present in rocks of all bulk compositions and at all p t conditions thermodynamic databases of minerals solid solutions and fluid mixtures along with the development of gibbs free energy minimization programs now allow for detailed prediction of the evolution of phase assemblages and mineral compositions in p t space significant progress has also been made in understanding reaction kinetics diffusional and convective mass transport and the interpretation of fluid rock interaction during metamorphism given the vast fluid inclusion evidence of immiscibility it would appear however that phase petrology and mass transport in any specific rock where fluids are involved are not correctly interpreted if possible or proven immiscibility is not considered relatively few studies directly link mineral reactions with immiscible fluids therefore this review aims at working out the effects of fluid immiscibility on the progress of metamorphic reactions and fluid transport over a wide range of conditions questions arise directly from the fluid inclusion record in metamorphic rocks this chapter however is organized the other way round at first it summarizes phase relations of fluid systems pertinent to

global and regional factors controlling changes of coastlines in southern iberia spain during the holocene the interaction between global glacio eustatic sea level rise and regional factors oceanographic and tectonic has controlled the evolution of coastline during the holocene in southem iberia at ca 10 000 14c years bp a deceleration of relative sea level rise took place both in the atlantic and mediterranean littorals with a maximum transgression at 6450 14c years bp in subsiding areas present tidal flats estuaries illustrate a clear marine influence recorded both in sediments and the fauna while in uplifting areas prograding spit bar systems developed two phases of major progradation are distinguished in these systems the first one between 6450 and 3000 14c years bp with a sedimentary gap at ca 4000 14c years bp and the second one from 2750 14c years bp up to present with an intervening gap between 1200 and 1050 14c years bp these progradation phases develop during stillstands followed by relative sea level fall while the sedimentary gaps represent relative high sea level in the mediterranean areas with a higher uplift rate marine terraces almost coeval to those gaps occur the most pronounced modifications in littoral dynamics occurred at between 3000 and 2750 14c years bp represented by changes in the direction of longshore drift and prevailing winds and in the predominance of progradation over aggradation processes at ca 1000 14c years bp the estuaries record a greater fluvial than marine influence and at 500 years ago an extraordinary increase in coastal progradation took place in all littoral zones the european medieval warm period is characterized at least during its initial phase by low pressure climate conditions while during the little ice age anticyclonic conditions gave rise to a strong coastal progradation

direct evidence for the source of uranium in the baiyanghe deposit from accessory mineral alteration in the yangzhuang granite porphyry xinjiang province northwest china

release of uranium from highly radiogenic zircon through metamictization the source of orogenic uranium ores although circumstantial evidence from ore deposit mineralogy and geochemistry can imply potential sources for fluids and metals rarely is direct evidence for metal leaching from source rocks seen in the vicinity of deposits here we investigate the source of metals for a series of fault zone and shear zone hosted uranium occurrences in the mount isa inlier australia as well as containing uranium these deposits are enriched in zr and rare earth elements rees requiring that unusual fluids were responsible for addition of these typically immobile elements during the isan orogeny highly saline metamorphic fluids infiltrated the sheared margin of a highly evolved granite intrusion which contains elevated u th f zr and rees synchrotron x ray fluorescence spectroscopy and high resolution electron microprobe mineral mapping show that this radioactive element rich characteristic caused zircon crystals to become highly metamict allowing the elements therein to become mobile thus when orogenic fluids pervasively infiltrated along shear zones 100 m y after granite intrusion their unusually saline character allowed enhanced dissolution of regional carbonates and fluorite from the granite providing the ligands needed for transport of uranium and the normally immobile elements from the metamict zircons

radiation damage in zircon and monazite monazite and zircon respond differently to ion irradiation and to thermal and irradiation enhanced annealing monazite cannot be amorphized by 800 kev kr ions at temperatures greater than 175 c whereas zircon can be amorphized at temperatures up to 740 c the damage process i e elastic interactions leading to amorphization in radioactive minerals metamictization is basically the same as for the ion beam irradiated samples with the exception of the dose rate which is much lower in the case of natural samples the crystalline to metamict transition in natural samples with different degrees of damage from almost fully crystalline to completely metamict is compared to the sequence of microstructures observed for ion beam irradiated monazite and zircon the damage accumulation process representing the competing effects of radiation induced structural disorder and subsequent annealing mechanisms irradiation enhanced and thermal occurs at much higher temperatures for zircon than for monazite the amorphization dose expressed as displacements per atom is considerably higher in the natural samples and the atomic scale process leading to metamictization appears to develop differently ion beam induced amorphization data were used to calculate the decay event dose required for amorphization in terms of a critical radionuclide concentration i e the concentration above which a sample of a given age will become metamict at a specific temperature this equation was applied to estimate the reliability of u pb ages to provide a qualitative estimate of the thermal history of high u natural zircons and to predict whether actinide bearing zircon or monazite nuclear waste forms will become amorphous metamict over long timescales

the distribution of contemporary intertidal foraminifera at cowpen marsh tees estuary uk implications for studies of holocene sea level changes abstract foraminiferal assemblages were collected at 2 weekly intervals over a period of 12 months from the intertidal zone of cowpen marsh statistical analyses indicate that the foraminiferal distributions for this site are controlled predominantly by altitude furthermore the contemporary foraminiferal assemblages from cowpen marsh broadly reflect vertical floral zones based on vascular plants cluster analysis separates foraminiferal assemblages into four zones two high and middle marsh zones consisting of differing abundances of jadammina macrescens and trochammina inflata a low marsh zone dominated by jadammina macrescens and miliammina fusca and a mudflat zone dominated by calcareous foraminiferal species notably elphidium williamsoni haynesina germanica and quinqueloculina spp the altitudinal ranges of the faunal zones are employed to identify the vertical relationship of the local environment in which the assemblage accumulated to a reference tide level

recent coastal evolution of the donana national park sw spain abstract since the last holocene sea level rise about 6900 bp a series of depositional littoral landforms has been generated at the outlet of the guadalquivir river with progradation along the predominant longshore drift towards the east the first coastal progradation occurred between 6900 and 4500 bp the donana and perhaps la algaida spits both associated with the oldest and highest marshland in the donana national park are assumed to have been developed at an early stage originally the guadalquivir estuary was wider and deeper than now and its environment was mainly marine the oldest littoral formations have been dated as ca 4735 bp they show erosional events and indicate the breaking up of earlier spit barriers to form inlets the marine environment became increasingly dominant with heavy erosion of cliffs and a retreating coastline this period was followed by another sedimentary cycle 4200 2600 bp that surrounded the earlier eroded barriers the size of the estuary decreased due to the increasing marsh deposits and a fluvial environment was born about 2600 years ago progradation gave way to a new period of intense erosion the resulting morphology of littoral strands and erosional surfaces permitted the return to a marine environment the shoreline again retreated from 2300 bp coastal progradation has prevailed with an erosional interruption at 1000 bp the present day outlet of the guadalquivir is an estuarine delta of inactive marshland the donana national park the dominant environment is fluvial

fluorine and chlorine behaviour during progressive dehydration melting consequences for granite geochemistry and metallogeny dehydration melting of biotite is the main control on crustal differentiation in the mid to lower continental crust because this reaction produces the most voluminous and most mobile granitic melts biotite breaks down over a broad temperature interval so the partitioning behaviour of elements between biotite and melt is likely to vary it has been hypothesized that fluorine may stabilize biotite to higher melting temperatures because biotite is typically f rich in ultra high temperature uht metamorphic rocks if true f would be an important influence on crustal differentiation because not only would it broaden the temperature range of melting but also elevated f concentration decreases melt viscosity furthermore ligand partitioning between biotite and melt may be an important influence on the metallogeny of magmas this study used electron microprobe analysis of biotite in rocks from the ballachulish and rogaland metamorphic aureoles to investigate the concentration of f and cl in biotite heated to 600 1 000 c results show a broad increase in biotite f content up to 5 04 f with temperature until 850 920 c beyond which f content decreases 2 5 f chlorine concentrations in biotite are consistently lower 1 cl and show a progressive decrease after the onset of partial melting it was found that mg content and the processes that control mg distribution are most strongly correlated with f and cl concentration in biotite calculations based on these results indicate that f enriched biotite could be a significant source of f for continental crust derived melts generation of a hot f rich melt at uht conditions could be important for transporting lower crustal metals to the upper crust

newly discovered uranium mineralization at 2 0 ma in the menggongjie granite hosted uranium deposit south china abstract the southeastern part of the nanling metallogenic province south china contains numerous economically important granite hosted hydrothermal vein type uranium deposits the miao ershan mes uranium ore field is one of the most important uranium sources in china hosts the largest chanziping carbonaceous siliceous pelitic rock type uranium deposit and several representative granite hosted uranium deposits the geology and geochemistry of these deposits have been extensively studied however accurate and precise ages for the uranium mineralization are scarce because uranium minerals in these deposits are usually fine grained and may have formed in several stages thus hindering the understanding of the uranium metallogenesis of this province the menggongjie mgj uranium deposit is one of the largest granite hosted uranium deposits in the mes ore field uranium mineralization in this deposit occurs at the central part of the mes granitic complex accompanied with silicification fluorination k metasomatism and hematitization the ore minerals are dominated by uraninite occurring in quartz or fluorite veinlets along fractures in altered granite in situ sims u pb dating on the uraninite yields the u pb isotopic age of 1 9 0 7 ma which is comparable to the chemical u th pbtol uraninite age of 2 3 0 1 ma such ages agree well with the eruption ages of the extension related quaternary volcanics 2 1 1 2 ma in south china suggesting that the uranium mineralization have formed at an extensional setting possibly related to the quaternary volcanic activities therefore our robust new dating results of the mgj uranium deposit make it the youngest granite hosted uranium deposit reported so far in south china and the mineralization event represents a newly identified mineralization epoch