modeling of multilayer cohesive bank erosion with a coupled bank stability and mobile bed model streambank erosion can be an important form of channel change in unstable alluvial environments it should be accounted for in geomorphic studies river restoration dam removal and channel maintenance projects recently one dimensional and two dimensional flows and mobile bed numerical models have become useful tools for predicting morphological responses to stream modifications most however either ignore bank failure mechanisms or implement only simple ad hoc methods in this study a coupled model is developed that incorporates a process based bank stability model within a recently developed two dimensional mobile bed model to predict bank retreat a coupling procedure that emphasizes solution robustness as well as ease of use is developed and described the coupled model is then verified and validated by applying it to multilayer cohesive bank retreat at a bend of goodwin creek mississippi comparisons are made between the predicted and measured data as well as results of a previous modeling study on one hand the study demonstrates that the use of two dimensional mobile bed models leads to promising improvements over that of one dimensional models it therefore encourages the use of multidimensional models in bank erosion predictions on the other hand the study also identifies future research needs in order to improve numerical modeling of complex streams the developed model is shown to be robust and easy to apply it may be used as a practical tool to predict bank erosion caused by fluvial and geotechnical processes

last interglacial climates of south eastern australia plant and beetle based reconstructions from yarra creek king island tasmania this paper explores the palaeoclimatic significance of a fossil plant and insect record from yarra creek on king island between tasmania and the australian mainland the record dates based upon a thermoluminescence chronology and other evidence to marine isotope stage 5 mis 5 the exact timing is impossible to ascertain given the resolution of the thermoluminescence results and the presence of an unconformity in the dated section the presence of a cool temperate rainforest flora outside its modern range and other independent evidence suggest the sequence may represent the last interglacial mis 5e rather than a later mis 5 substage using coexistence methods that compare modern climatic ranges of the taxa in the assemblage we reconstruct independent beetle and plant based annual and seasonal temperate and precipitation parameters the results imply the assemblage was deposited under a wetter summer climate and suggest conditions of enhanced temperature seasonality it is probable that enhanced temperature seasonality is a methodological artefact reflecting the rarity of extremely equable climates like king island in modern climate space this would indicate a limitation of most methods of palaeoclimatic reconstruction that rely on modern datasets it is only possible to reconstruct past climates as being within the range of values in that currently exist in modern climate space

late quaternary climates of the australian arid zone a review abstract aridity in australia has generally been associated with glacial intervals of the last few glacial cycles the causes and nature of aridity varied from north to south over the continent in northern and central australia reduced monsoon rain in global cold stages caused lakes and rivers to dry vegetation to become more sparse sand dunes to become active and dust advection to increase while the monsoon is correlated with warmer global temperatures and high sea levels overall the exact timing of the greatest development of the monsoon in stage 5 remains uncertain in southeastern australia the proxy records give a less clear picture while vegetation seems to have been more sparse in cold stages and sand dune activity and dust flux consequently greater records of runoff in rivers and lakes have mixed or opposite behaviour to northern or central australia the nature of aridity in southeastern australia is not analogous to conditions anywhere on the continent today greatly reduced temperatures over the central and southern interior greater influence of snow and periglaciation on runoff high groundwater tables lower rainfall and reduced atmospheric carbon dioxide levels may all have contributed to and interacted to produce the reconstructed picture of a cold sparsely vegetated arid landscape with large rivers and perennial lakes the largest changes in circulation patterns over the glacial cycle probably occurred in the location and or intensity of summer tropical convergence in northern australia over southern australia changes to the temperature and humidity of the westerly circulation have been more significant than the small fluctuations in latitude of the sub tropical high pressure ridge

magmatic hydrothermal processes recorded by muscovite andcolumbite group minerals from the bailongshan rare element pegmatites in the west kunlun karakorum orogenic belt nw china abstract the mineralization of rare element pegmatites is attributed to complex magmatic hydrothermal processes such as magma fractionation fluid exsolution and fluid melt metasomatism however it is still unclear how these processes affect the evolution of pegmatites and the fractionation of rare elements here we use the textures and major and trace element compositions of muscovite and columbite group minerals cgm from the newly discovered bailongshan li cs ta lct type pegmatites in the west kunlun karakorum orogenic belt nw china to decipher the magmatic hydrothermal processes related to enrichment of rare elements four major regional zones are recognized in the bailongshan area quartz albite tourmaline qat zone quartz muscovite qm zone quartz albite spodumene qas zone and quartz spodumene qs zone the qat and qm zones are barren whereas the qas and qs zones host six major li rb ore segments i to vi along the nww see strike from the qm zone through the qas to the qs zone the k rb ratios of muscovite decrease gradually from 26 0 to 7 8 and cgm has mn s increasing from 0 28 to 0 56 consistent with the trend of progressive evolution of the pegmatites the ta profiles across individual cgm grains reveal a three stage growth process i e from a nb rich cgm magmatic stage to a ta rich cgm magmatic stage to a nb rich cgm hydrothermal stage high resolution elemental mapping of primary muscovite from the qas and qs zones shows that melt metasomatism induced local enrichment of f li cs and ta and the precipitation of secondary lepidolite along the rims or cleavages of primary muscovite in addition late stage f poor fluid metasomatism caused the release of fe mn b rb and cs from primary muscovite and induced complex zoning patterns and crystallization of hydroxylapatite in cleavage planes of primary muscovite secondary muscovite has higher li be b rb and cs and lower nb than primary muscovite indicating that these elements may have been partially dissolved and remobilized from primary spodumene muscovite and cgm into late stage hydrothermal fluids from which the secondary muscovite and nb rich cgm crystallized therefore the complex zoning patterns and compositional variations of both muscovite and cgm from the bailongshan pegmatites record a progressive magmatic hydrothermal process related to the rare metal mineralization

modeling the evolution of incised streams ii streambank erosion incision and ensuing widening of alluvial stream channels is widespread in the midsouth and midwestern united states and represents an important form of channel adjustment streambanks have been found to contribute as much as 80 of the total suspended load the location timing and magnitude of streambank erosion are difficult to predict results from field studies to characterize the resistance of fine grained materials to hydraulic and geotechnical erosion the impact of pore water pressures on failure dimensions and shearing resistance and the role of riparian vegetation on matric suction streambank permeability and shearing resistance are used to enhance the channel evolution model concepts conservational channel evolution and pollutant transport system this paper discusses the conceptualization of the above mentioned physical processes and demonstrates the ability of the derived model to simulate streambank failure processes the model is tested against observed streambank erosion of a bendway on goodwin creek miss between march 1996 and march 2001 where it accurately predicts the rate of retreat of the outside bank of the bendway the observed change in average channel width within the central section of the bendway is 2 96 m over the simulation period whereas a retreat of 3 18 m 7 4 larger is simulated the observed top bank retreat within the central section of the bendway is 3 54 m over the simulation period whereas a retreat of 3 01 m 15 smaller is simulated doi 10 1061 asce0733 94292008134 7905 ce database subject headings bank erosion limit equilibrium mathematical models sensitivity analysis numerical analysis

evidence for aqueous liquid liquid immiscibility in highly evolved tin bearing granites mount pleasant new brunswick canada abstract three distinct types of fluid inclusions i e liquid vapor lv liquid vapor solid lvs and v only co exist within a single primary fluid inclusion assemblage in fluorite crystals that formed prior to and in close association with cassiterite mineralization in an assemblage comprising fluorite arsenopyrite topaz cassiterite in the sn w mo deposit of the north zone mount pleasant new brunswick the mineral assemblage occurs in vugs with late quartz and chlorite filling the remainder of the open space solid bearing inclusions contain up to eight optically different solids which are estimated to occupy up to approximately 70 vol of the fluid inclusions in a given fluid inclusion assemblage each type of fluid inclusion shows consistent l v or l v s phase ratios the results of microthermometric analyses show that lv inclusions have low salinities that vary from 0 to 10 wt nacl eq and homogenization temperatures that vary from 91 to 250 c within a given assemblage the ranges of salinity and homogenization temperatures of lv inclusions are even less in contrast co existing lvs inclusions are highly saline with salinities ranging from 36 to 40 wt nacl eq and have much higher homogenization temperatures that vary from 425 c to 600 c the upper limit of the microthermometric stage the salinity and homogenization temperature ranges of lvs inclusions show a limited range for a given assemblage the solids in lvs inclusions are interpreted as daughter phases due to consistent phase ratios in lvs fluid inclusions and because during heating experiments all solid phases melted prior to liquid vapor homogenization the consistency of phase ratios and the results of microthermometric analysis among lv or among lvs inclusions show that these inclusions were not formed through necking down of larger inclusions in addition the absence of sweat halos and re entrants rules out water loss as a possible mechanism for producing these coexisting fluid inclusions fluid inclusions of highly contrasting salinities and homogenization temperatures are therefore interpreted to be the result of trapping from two immiscible aqueous liquids it is unknown whether the two liquids exsolved from one single aqueous fluid or have different origins but consideration of the nature of inclusion assemblages in samples from other parts of the system suggest the latter topaz and cassiterite within the same mineral assemblage as well as late quartz contain lv fluid inclusion assemblages with microthermometric behaviors that are similar to the lv type inclusions in coexisting fluorite hosted lv and lvs inclusions suggesting that cassiterite deposited from the low salinity and temperature fluid

the behavior of trace elements during the chemical evolution of the h 2 o b and f rich granite pegmatite hydrothermal system at ehrenfriedersdorf germany a sxrf study of melt and fluid inclusions detailed melt and fluid inclusion studies in quartz hosts from the variscan ehrenfriedersdorf complex revealed that ongoing fractional crystallization of the highly evolved h2o b and f rich granite magma produced a pegmatite melt which started to separate into two immiscible phases at about 720 c 100 mpa with cooling and further chemical evolution the immiscibilty field expanded two conjugate melts a peraluminous one and a peralkaline one coexisted down to temperatures of about 490 c additionally high salinity brine exsolved throughout the pegmatitic stage along with low density vapor towards lower temperatures a hydrothermal system gradually developed boiling processes occurred between 450 and 400 c increasing the salinities of hydrothermal fluids at this stage below the late hydrothermal stage is dominated by low salinity fluids using a combination of synchrotron radiation induced x ray fluorescence analysis and raman spectroscopy the concentration of trace elements mn fe zn as sb rb cs sr zr nb ta ag sn ta w rare earth elements ree and cu was determined in 52 melt and 8 fluid inclusions that are representative of distinct stages from 720 c down to 380 c homogenization temperatures and water contents of both melt and fluid inclusions are used to estimate trapping temperatures thus revealing the evolutionary stage during the process trace elements are partitioned in different proportions between the two pegmatite melts high salinity brines and exsolving vapors concentrations are strongly shifted by co ncomitant crystallization and precipitation of ore forming minerals for example pegmatite melts at the initial stage 700 c have about 1 600 ppm of sn concentrations in both melts decrease towards lower temperatures due to the crystallization of cassiterite between 650 and 550 c tin is preferentially fractionated into the peralkaline melt by a factor of 2 3 while the last pegmatite melts are low in sn 64 ppm at 500 c early hydrothermal fluids become again enriched with about 800 ppm of sn at the boiling stage a sudden drop in late hydrothermal fluids 23 ppm of sn at 370 c results from precipitation of another cassiterite generation between 400 and 370 c zinc concentrations in peraluminous melts are low some tens of parts per million and are not correlated with temperature in coexisting peralkaline melts and high t brines they are higher by a factor of 2 3 zinc continuously increases in hydrothermal fluids 3 000 ppm at 400 c where the precipitation of sphalerite starts the main removal of zn from the fluid system occurs at lower temperatures similarly melt and fluid inclusion concentrations of many other trace elements directly reflect the crystallization and precipitation history of minerals at distinctive temperatures or temperature windows

critical assessment of jet erosion test methodologies for cohesive soil and sediment abstract the submerged jet erosion test jet is a commonly used technique to assess the erodibility of cohesive soil employing a linear excess shear stress equation and impinging jet theory simple numerical methods have been developed to analyze data collected using a jet to determine the critical shear stress and erodibility coefficient of soil these include the blaisdell iterative and scour depth methods and all have been organized into easy to use spreadsheet routines the analytical framework of the jet and its associated methods however are based on many assumptions that may not be satisfied in field and laboratory settings the main objective of this study is to critically assess this analytical framework and these methodologies part of this assessment is to include the effect of flow confinement on the jet the possible relationship between the derived erodibility coefficient and critical shear stress a practical tool in soil erosion assessment is examined and a review of the deficiencies in the jet methodology also is presented using a large database of jet results from the united states and data from literature it is shown that each method can generate an acceptable curve fit through the scour depth measurements as a function of time the analysis shows however that the scour depth and iterative methods may result in physically unrealistic values for the erosion parameters the effect of flow confinement of the impinging jet increases the derived critical shear stress and decreases the erodibility coefficient by a factor of 2 4 relative to unconfined flow assumption for a given critical shear stress the length of time over which scour depth data are collected also affects the calculation of erosion parameters in general there is a lack of consensus relating the derived soil erodibility coefficient to the derived critical shear stress although empirical relationships are statistically significant the calculated erodibility coefficient for a given critical shear stress has an uncertainty of several orders of magnitude this study shows that jet results should be used with caution and the magnitude of the uncertainty in the derived erodibility parameters should be carefully considered

exsolution of magmatic volatile phases from cl enriched mineralizing granitic magmas and implications for ore metal transport abstract to understand cl dissolution in aluminosilicate liquids and the exsolution of cl rich magmatic volatile phases experiments were conducted to determine the solubility of nacl kcl and h2o in felsic liquids at 0 5 and 2 kbar the cl content of h2o poor nacl saturated and kcl saturated silicate liquids is low i e 1 3 wt to very low i e 0 2 wt and varies with changes in pressure and composition the cl concentration increases with the f concentration and the molar al na ca mg si ratio of the liquid and decreases with increasing activity of h2o in the system exsolution of a volatile phase depends on the partial pressures of all dissolved volatiles and low cl solubilities in nacl saturated and kcl saturated silicate liquids imply that exsolution of a cl bearing volatile phase will occur early in cl bearing granitic magmas i e prior to extensive melt crystallization and or at comparatively low water fugacities the solubility behavior of h2o and cl is very similar to that of co2 and h2o in felsic liquids small quantities of co2 are known to facilitate volatile phase exsolution holloway 1976 and in a similar manner volatile phases may exsolve early in cl enriched granite magmas whereas 5 to 6 wt dissolved h2o is necessary for volatile phase exsolution from a co2 free and cl free haplogranite liquid at 2 kbar and 800 c a cl rich brine will exsolve if the liquid contains only 1 wt h2o and 0 26 wt cl at the same conditions these new solubility data are interpreted in light of h2o f and cl concentrations in felsic liquids determined from silicate melt inclusions to constrain the exsolution of cl bearing magmatic volatile phases from mineralizing granitic magmas felsic magmas genetically associated with cu porphyry and mo porphyry mineralization contain sufficient h2o and cl to become saturated with respect to a hypersaline brine without strong pressure reduction boiling of the volatile phase i e exsolution of immiscible vapor and brine or strong volatile enrichment resulting from extensive crystal fractionation experiments were also conducted to investigate the solubility of mo in highly saline volatile phases coexisting with granitic liquids at 2 and 0 5 kbar the apparent partition coefficient for mo in the volatile phase s relative to silicate liquid d mo is defined as the computed concentration of mo in a volatile phase or phases the measured concentration of mo in granite glass d mo ranges from 8 to 80 as the nacl and kcl content of the volatile phase s increases from 15 to 90 wt because mo does not complex with cl in aqueous fluids it appears that mo solubility may be a strong function of the activity of na and k in alkali chloride rich volatile phases

liquid immiscibility in the caf2 granite system and trace element partitioning between the immiscible liquids abstract the recent discoveries of ca fluoride melt in magmatic systems especially in peralkaline granites with rare earth element enrichment has raised questions about the presence and nature of liquid immiscibility in caf2 granite systems as well as the partitioning behavior of trace elements between such immiscible liquids we have experimentally explored the immiscibility in this system using natural granite fluorite starting materials at fast and slow cooling rates temperatures from 500 c to 1200 c and 1 atmosphere pressure our experiments confirm the presence of a miscibility gap in the caf2 granite system over a wide range of temperatures the two immiscible liquids are a mafic fluorosilicate melt fm with high cao and f and a felsic oxysilicate melt sm with high sio2 and alkalis immiscibility is encountered when the bulk f content exceeds approximately 4 4 wt at 1200 c and then rapidly decreases to only 0 75 wt at low temperature below 900 c this indicates that calcic magmas are able to evolve to the liquid immiscibility domain by the residual enrichment of fluorine resulting from fractional crystallization and that liquid immiscibility should be common the peritectic reaction fm sm fluorite removes the fluorosilicate liquid around 600 c and could explain the absence of fluorosilicate observations in natural granites the compositions of the liquids in fast cooling experiments show a significantly larger miscibility gap which is characterized by compared to slow cooling runs similar sm compositions but higher ca and f content in fm this difference is caused by suppression of fluorite nucleation and is interpreted as a metastable extension of the high temperature liquid immiscibility immiscibility results in strong fractionation of trace elements which is primarily governed by melt structure and the ionic potential z r of the elements the behavior of trace elements can be categorized into three groups 1 network formers si al ga pb b partition into the oxysilicate melt 2 the partitioning of the alkalis and alkali earths is strongly dependent on the ionic potential with the partitioning coefficients d fm sm in the order dcs

magmatic immiscibility and fluid phase evolution in the mount genis granite southeastern sardinia italy the mount genis granite is one of the post tectonic intrusives emplaced late in the magmatic history of the hercynian batholith in sardinia devitrified silicate melt inclusions are present in some magmatic rock forming and miarolitic quartz these magmatic remnants show initial melting at 680 720 c high temperature observations 700 800 c revealed the presence in some of the inclusions of mixed hydrosaline melt l1 and silicate melt l2 with extremely variable l1l2 ratios electron microprobe analyses indicate l1 to be k na dominated chlorides inclusions of mixed silicate and hydrosaline melts are interpreted to have been formed by heterogeneous trapping of two immiscible fluid phases silicate hydrosaline after second boiling most likely during the final crystallization stage magma derived brines 63 eq wt nacl circulated at subsolidus conditions from 600 c and were retained in the miarolitic cavities down to about 400 c fluid unmixing occurred locally in the miarolitic cavities from 550 to 412 c at temperatures of 400 to 100 c the microgranite was invaded by diluted waters 4 5 eq wt nacl a possible model for fluid evolution begins with a hydrosaline melt exsolving from the magma at the late magmatic stage the absence of boiling within the volatile hydrosaline system shows that brines can occur by direct magmatic immiscibility the comprehensive hydrothermal evolution suggests a nearly isobaric cooling path with local boiling episodes in the miaroles probably in coincidence with invasion of external waters

liquid immiscibility and its role at the magmatic hydrothermal transition a summary of experimental studies several types of fluid immiscibility may affect the evolution of volatile rich magmatic systems at the magmatic hydrothermal transition the topology of silicate salt h2o systems implies that three fluid immiscibility silicate melt hydrosaline melt vapour should be stable in a broad range of compositions and p t conditions the most important factor controlling the immiscibility appears to be the coulombic properties electric charges z and ionic radii r of the main network modifying cations and the capacity for immiscibility appears to decrease in the following sequence mg ca sr ba li na k liquid immiscibility is enhanced in peralkaline compositions and in the presence of nonsilicate anions such as f cl co32 and bo33 in volatile rich magmatic systems the h2o is likely to react with the chloride fluoride borate and carbonate species and the chemical effects of high temperature hydrolysis may be greatly enhanced by phase separation in systems with multiple immiscible fluid phases natural granitic magmas can thus exsolve a range of chemically and physically diverse hydrosaline liquids and the role of these fluid phases is likely to be especially significant in pegmatites and li f rare metal granites

the coexistence approach a method for quantitative reconstructions of tertiary terrestrial palaeoclimate data using plant fossils abstract the coexistence approach is introduced as a method for quantitative terrestrial palaeoclimate reconstructions in the tertiary it is based on the assumption that tertiary plant taxa have similar climatic requirements to their nearest living relatives the aim of the coexistence approach is to find for a given fossil flora and a given climate parameter the climatic interval in which all nearest living relatives of the fossil flora can coexist for this purpose we have developed a data base climbot containing for over 800 tertiary plant taxa the nearest living relatives and their climatic requirements and an algorithm for analysis climst for all types of fossil floras the coexistence approach thus allows the rapid quantitative reconstruction of 10 different climate parameters including the mean annual temperature temperature of the warmest month temperature of the coldest month mean annual precipitation maximum monthly precipitation minimum monthly precipitation precipitation of the warmest month relative humidity potential evaporation as well as the ratio of mean annual precipitation over potential evaporation the reliability and resolution of the coexistence approach are tested with various techniques and proved to be reasonably good for instance the resolution with respect to the mean annual temperature can be up to 1 c applications to various modern and fossil floras are illustrated and the advantages and disadvantages of the coexistence approach are discussed

modeling the evolution of incised streams i model formulation and validation of flow and streambed evolution components a robust computational model for simulating the long term evolution of incised and restored or rehabilitated stream corridors is presented the physically based model simulates the three main processes that shape incised streams hydraulics sediment transport and streambed and bank adjustments a generalized implicit preissmann scheme is used for the spatial and temporal discretization of the flow governing equations to accommodate large time steps and cross sections spaced at irregular intervals the solution method introduces several enhancements that increase its robustness specifically to simulate flashy flows transport of cohesive or cohesionless graded bed material is based on a total load concept and suspended and bed load transport modes are accounted for through nonequilibrium effects the model simulates channel width adjustment by hydraulic erosion and gravitational mass failure of heterogeneous bank material the present paper focuses mainly on the treatment of streamflow hydraulics and evolution of graded streambeds and reports simulations of published experiments on degrading and aggrading channels with graded bed material description and validation of the model s stream bank erosion component and the application of the model to incised stream systems are presented elsewhere

formation of extremely f rich hydrous melt fractions and hydrothermal fluids during differentiation of highly evolved tin granite magmas a melt fluid inclusion study quartz crystals from topaz zinnwaldite albite granites from zinnwald erzgebirge germany contain in addition to primary and secondary fluid inclusions fis abundant crystalline silicate melt inclusions mis with diameters up to 200 m these mis represent various stages of evolution of a highly evolved melt system that finally gave rise to granite related sn w mineralization the combination of special experimental techniques with confocal laser raman microprobe spectroscopy and empa permits precise measurement of elevated contents of h2o f and b in re homogenized mis the contents of h2o and f were observed to increase from 3 to 30 and 1 9 to 6 4 wt respectively during magma differentiation however there is a second mi group very rich in h2o with values up to 55 wt h2o and an f concentration of approximately 3 wt ongoing enrichment of volatiles h2o f b and cl and of cs and rb can be explained in terms of magma differentiation triggered by fractional crystallization and thus is suggested to reflect elemental abundances in natural magmas and not boundary layer melts partitioning between melt and cogenetic fluids has further modified the magmatic concentrations of some elements particularly sn the coexistence of two types of mis with primary fis indicates fluid saturation early in the history of magma crystallization connected with a continuous sequestration of sn f and b the results of this study provide additional evidence for the extraordinary importance of the interplay of h2o f and b in the enrichment of sn during magma differentiation by decreasing the viscosity of and increasing the diffusivity in the melts as well as by the formation of various stable fluoride complexes in the melt and coexisting fluid

processes and forms of an unstable alluvial system with resistant cohesive streambeds as a response to channelization projects undertaken near the turn of the 20th century and in the late 1960s upstream reaches and tributaries of the yalobusha river mississippi usa have been rejuvenated by upstream migrating knickpoints sediment and woody vegetation delivered to the channels by mass failure of streambanks has been transported downstream to form a large sediment debris plug where the downstream end of the channelized reach joins an unmodified sinuous reach classification within a model of channel evolution and analysis of thalweg elevations and channel slopes indicates that downstream reaches have equilibrated but that upstream reaches are actively degrading the beds of degrading reaches are characterized by firm cohesive clays of two formations of palaeocene age the erodibility of these clay beds was determined with a jet test device and related to critical shear stresses and erosion rates repeated surveys indicated that knickpoint migration rates in these clays varied from 0 7 to 12 m a 1 and that these rates and migration processes are highly dependent upon the bed substrate resistant clay beds of the porters creek clay formation have restricted advancement of knickpoints in certain reaches and have caused a shift in channel adjustment processes towards bank failures and channel widening channel bank material accounts for at least 85 per cent of the material derived from the channel boundaries of the yalobusha river system strategies to reduce downstream flooding problems while preventing upstream erosion and land loss are being contemplated by action agencies one such proposal involves removal of the sediment debris plug bank stability analyses that account for pore water and confining pressures have been conducted for a range of hydrologic conditions to aid in predicting future channel response if the sediment debris plug is removed to improve downstream drainage care should be taken to provide sufficient time for drainage of groundwater from the channel banks so as not to induce accelerated bank failures published in 2002 john wiley sons ltd

immiscibility and continuous felsic melt fluid evolution within the rio blanco porphyry system chile evidence from inclusions in magmatic quartz the 5 2 to 3 9 ma late porphyries at rio blanco are spatially associated with hydrothermal tourmaline cemented breccias and a significant cu mo deposit magmatic inclusions in quartz from these rocks are used to better understand late stage magmatic processes particularly those involving melt melt and melt fluid immiscibility inclusions are represented by glass of common rhyolitic composition hereafter type 1 crystallized volatile rich felsic melt type 2 h2o and salt rich fluids and microphenocrysts coexistence of types 1 and 2 material within the same growth plane and within a single inclusion suggests that crystallizing rhyolitic magma separated into two silicate melts volatile poor and volatile rich the volatile rich silicate melt had a prolonged evolution extending below the solidus of volatile poor silicate melt with a progressive reduction of the silicate volatile ratio and ultimately to highly saline fluids the latter may have been the source of hydrothermal fluids that had the potential to transport metals the occurrence of immiscibility in the rio blanco rhyolites may be in some ways comparable to that in volatile rich pegmatites and strongly suggests that this process may be common in other se normal felsic magmas and important in the origin of mineralized porphyries

magmatic hydrothermal evolution of highly fractionated granites evidence from the kuiqi miarolite in fujian province se china abstract the kuiqi miarolite a highly evolved alkaline granite pluton is situated in fujian province southeastern china quartz crystals from the kuiqi miarolite contain abundant inclusions which have preserved a complete record of the magmatic hydrothermal evolution five inclusion type were identified i e the melt m type melt fluid ml type daughter mineral bearing s type vapor rich v type and aqueous l type inclusions integrated petrographic microthermometric and laser raman spectroscopy studies demonstrate that the whole magmatic hydrothermal evolution at kuiqi comprises three stages i e the magmatic magmatic hydrothermal and hydrothermal stages the m type inclusions minimal trapping temperatures ca 710 800 c represent the melts entrapped at the magmatic stage of crystallization while the occurrence of euhedral prismatic arfvedsonites in these melt inclusions indicates that the granitic magma was probably volatile rich at the magmatic hydrothermal stage both the ml type inclusions t h ca 500 710 c and coexisting m and v type inclusions reflect the presence of late magmatic fluid circulation and melt volatile immiscibility exhibiting a transition toward the hydrothermal stage at the hydrothermal stage the pressure and temperature 700 485 c drop may have led to oversaturation of the primary saline fluids resulting in the phase separation a highly saline and a volatile rich fluid occurred accompanied by the widespread vapor brine immiscibility the l type inclusions in the miarolitic quartz display bimodal salinity distribution the t h and salinity of the inclusions at the bottom l 1 miarolitic quartz are ca 303 427 c and ca 6 6 17 9 wt nacl equiv respectively while that of the inclusions at the top l 2 are ca 165 232 c and ca 0 2 5 7 wt nacl equiv respectively this indicates a drop of fluid temperature and salinity during the miarolitic cavity formation moreover the low homogenization temperatures and salinities of the l type inclusions suggest an influx of meteoric water during the late hydrothermal evolution stage

stable isotope b h o and mineral chemistry constraints on the magmatic to hydrothermal evolution of the varutrask rare element pegmatite northern sweden abstract the internal evolution of the varutrask rare element pegmatite skellefte district northern sweden has been investigated using stable isotope b h o geochemistry of tourmaline and coexisting micas feldspar and quartz varutrask is a classic and typical example of highly fractionated lct type pegmatites with a pronounced concentric zoning pattern composed of well developed border wall and intermediate zones and a quartz core the pegmatite displays considerable rare element enrichment culminating in the formation of albite lepidolite and pollucite units in the innermost zones major and trace element variations in tourmaline from the main pegmatite zones correlate well with the internal zoning pattern mineral compositions record an abrupt change in fractionation trends between the barren outer and intermediate zones and the inner late stage assemblages that carry rare element mineralization this change is also shown by the b isotope variations of tourmaline early and mid stage tourmalines record a systematic increase in 11 b from 14 6 to 6 2 which can be explained by closed system melt mineral isotope fractionation whereby crystallization of large amounts of muscovite preferentially removes 10 b from the residual melt in contrast tourmaline from late stage assemblages in the inner zones and cross cutting veinlets shows a reversal in the b isotope trend with a decrease in 11 b from 8 to 14 1 this reversal cannot be explained by mineral melt isotope fractionation but requires fluid melt partitioning and partial fluid loss hydrogen isotope variations in mica support this model the systematic increase in d from 75 in the outer zones muscovite to 63 and 53 in the inner zones li micas cannot be explained by closed system variations in temperature or melt mica fractionation but it is consistent with late fluid exsolution oxygen isotope compositions of tourmaline 18 o from 9 7 to 11 6 quartz 13 3 to 14 and mica 10 3 to 11 3 show good agreement with equilibrium partitioning and yield temperatures in the range 450 c to 600 c combining this with the stability fields of li aluminosilicates petalite and spodumene indicates crystallization pressures of 2 3 kbar taken together the stable isotope and mineral chemistry data demonstrate that rare element enrichment in the innermost fractionated assemblages in the varutrask pegmatite was associated with the transition from purely magmatic crystallization to conditions where a separate aqueous fluid phase became important

melt and fluid inclusions in hydrothermal veins the magmatic to hydrothermal evolution of the elatsite porphyry cu au deposit bulgaria the magmatic to hydrothermal transition in the late cretaceous elatsite porphyry cu au mo platinum group element deposit has been studied in a suite of samples with clear timing relations between porphyry dikes magmatic hydrothermal veins silicate melt inclusions in quartz veins fluid inclusion generations and ore minerals ore mineralization occurs late at temperatures 200 to 300 c below those of the early multistage interplay between magmatic and hydrothermal processes at near magmatic temperature pressure conditions crosscutting relations and petrography indicate that shortly after the intrusion of the earliest monzodioritic dikes fluids precipitated a first generation of granular quartz veins accompanied by potassic alteration the second vein generation with crystalline quartz textures and k feldspar alteration halos formed at the same time as the second granodioritic pulse of porphyry intrusions cathodoluminescence imaging of quartz growth textures reveals that the earliest fluid inclusions in the crystalline quartz veins are of intermediate density and 8 wt nacl equiv salinity probably trapped at near lithostatic pressures of 1 200 to 1 300 bars at near magmatic temperatures 730 c and implies a depth of 4 to 5 km depressurization led to phase separation indicated by a first generation of coexisting brine and vapor inclusions trapped at temperatures of 640 c and suprahydrostatic pressures of 920 bars a second quartz generation in crystalline quartz veins precipitated during progressive depressurization and hosts assemblages of coexisting brine vapor and silicate melt inclusions trapped at temperatures in excess of 600 c and suprahydrostatic pressures of 630 to 880 bars some open spaced quartz veins were filled with aplite during this stage field relations and geochemical evidence suggest that the aplites as well as the silicate melt inclusions in hydrothermal quartz veins represent volumetrically minor residual melts that evolved directly from granodiorite porphyries at the level of deposit formation and do not represent aliquots of metal supplying magma at depth fluid inclusions coexisting with the silicate melt inclusions are metal rich but these fluids predate sulfide precipitation and are therefore not the dominant fluids responsible for the cu au mineralization at elatsite melt fluid metal separation processes recorded in these co trapped silicate melt and fluid inclusions in vein quartz are small scale local phenomena and do not appear to be suited for understanding and quantifying metal segregation in the deeper source microthermometry data of fluid inclusions trapped during the later stages of the formation of the second quartz generation show further depressurization to 260 to 325 bars and cooling to 460 c representing a hot hydrostatic regime bornite chalcopyrite and magnetite seem to be slightly later precipitated at temperatures 460 c in separate veins or opened spaces of preexisting veins dissolution textures of the second quartz generation indicate a subsequent local redissolution of vein quartz most likely as a result of passing through a window of retrograde quartz solubility upon further cooling below 460 c the next economically most important chalcopyrite pyrite stage is largely devoid of quartz precipitation and is mostly expressed as paint veins due to the lack of fluid inclusions the temperature pressure conditions of formation of these veins could not be constrained the waning phase of hydrothermal activity is represented by a quartz carbonate zeolite stage formed at low temperature 145 c as indicated by microthermometry of fluid inclusions trapped in quartz from this stage laser ablation inductively coupled plasma mass spectrometry analyses of fluid inclusions show very high cu contents in early intermediate density fluid inclusions and in the first vapor inclusion generation followed by a drastic decrease in the second generation of vapor inclusions the decrease correlates with the appearance of anhydrite inclusions in the second quartz generation and may indicate that a lack of sulfur in these later vapor inclusions led to cu partitioning into the brine alternatively it is also possible that unlike early vapor inclusions the later vapor inclusions were not susceptible to postentrapment copper enrichment in accordance with recent experiments a progressive cu enrichment in the brine phase correlates well with depressurization prior to mineralization mass balance considerations based on analyzed fluid components and fluid phase relations indicate that brine was volumetrically minor and therefore likely stagnant but this may have prepared ore precipitation by accumulating cu stripped from ascending vapor

revisiting complete miscibility between silicate melts and hydrous fluids and the extreme enrichment of some elements in the supercritical state consequences for the formation of pegmatites and ore deposits abstract using water and major and trace element data obtained from melt inclusions primarily in pegmatite quartz we have shown in this and previous papers that melt melt fluid immiscibility is widespread and an important process during the generation of granitic pegmatites furthermore we have shown that the formation of pegmatites actually begins in the supercritical melt fluid stage in this study we extend previous work and in particular explore the behavior of 10 different elements be f p s cl as rb sn cs and ta in the supercritical range from preliminary studies we suggest that other elements such as b na k zn nb and sb will behave similarly near the solvus crest of a generalized pseudo binary melt water system this provides important evidence that pegmatite forming processes have already begun at high temperatures in the range of 850 750 c and that may require a re think on the partitioning behavior of metals in late stage residual melts exsolved from granitic magmas the existence of this parental supercritical silicate melt fluid although derived from granitic magmas imposes significant constraints of its own so drawing conclusions about pegmatite forming processes from data gained from slightly modified granite compositions becomes highly problematic we propose that the extremely high concentration of some elements over a small but well defined water concentration range symmetrically distributed around the critical point of the pseudo binary solvus must be derived from the unusual properties of the near critical or supercritical phases these unusual properties include extremely low density viscosity and surface tension and high diffusivity reactivity and mobility these are exactly the qualities that make such supercritical fluids an excellent medium for the formations of pegmatites by reactions with the existing matrix melt crystal mush and for the extreme enrichment of some ore forming elements highly soluble in alkali and water rich supercritical fluids a very important point in mineral crystallization is the non uniform local enrichment of rare and economically significant elements at specific locations in pegmatites granites and other rocks given the properties of the supercritical phase identified from melt inclusions the process of ostwald ripening can operate very effectively the driving force for ostwald ripening arises because the concentration of solute in the vicinity of small crystals or clusters is greater than and in the vicinity of larger crystals or clusters less than the average supersaturation the solute in the supercritical fluid therefore flows from the small crystals to the larger crystals and permits the growth of very large crystals at the expense of smaller ones this is favored by the extraordinary properties of supercritical fluids given the low surface tension the supercritical fluid can move also through grain boundaries and small channels or dislocation pipes aiding incompatible element transport additionally their consequences for the formation of some important granite related ore deposits are briefly outlined

heterogeneous melt and hypersaline liquid inclusions in shallow porphyry type mineralization as markers of the magmatic hydrothermal transition cerro de pasco district peru recently identified occurrences of porphyry style mineralization evidence the link of the world s second largest known epithermal base metal cerro de pasco deposit peru to a porphyry system emplaced at depth they consist of i quartz monzonite dykes and ii the south western part of the large diatreme dome complex adjacent to the main ore bodies of cerro de pasco and iii stockwork of banded quartz magnetite chalcopyrite pyrite porphyry type veinlets crosscutting trachyte porphyritic intrusion cropping out at surface in the central part of the diatreme dome complex the latter porphyry type mineralization observed at the same erosion level as the main epithermal base metal carbonate replacement ore bodies is the subject of this work geological constraints indicate a shallow emplacement level depth 1 km p 270 bar implying rather unusual low pressure and high temperature environment for the formation of porphyry style mineralization the banded porphyry type veinlets record a multiphase history of formation with two successive high temperature n600 c stages followed by a lower temperature b350 c stage more than 90 of the quartz in veinlets precipitates during the first two high temperature stages stage 1 is characterized by the entrapment in hydrothermal quartz of inclusions containing variable proportions of both silicate melt and metal rich hypersaline n90 wt nacl eq liquid hereafter referred to as heterogeneous silicate melt inclusions hsmis the latter are rarely described in porphyry type mineralization we suggest that during stage 1 the inclusions result from heterogeneous entrapment of an evolved hydrous rhyolitic melt mixed with a hypersaline fluid phase at low pressure 270 bar and high temperature n600 c the stage 2 is marked by the entrapment of metaland sulfur rich hypersaline liquid inclusions with salinity around 70 wt nacl eq originated from the adiabatic ascent of magmatic hypersaline fluids transferred fromdeeper parts of the system the lower temperature stage 3 is characterized by an important temperature drop from n600 c to b350 c as revealed bymicrothermometry of aqueous two phase liquid vapor l v inclusions quartz textures revealed by sem cl imaging allowascribing the sulfide precipitation to the low temperaturemineralization stage 3 in situ sims 18o 16o isotope analyses of quartz across the veinlets are indicative of a magmatic signature of the fluids during the first two stages while quartz from stage 3 has oxygen isotopic compositions suggestive of minor contribution of meteoric waters to a predominantly magmatic aqueous fluid 10 vol of meteoric input which probably triggered cu fe sulfide precipitation in the stockwork high metal and sulfur contents of hsmis and hypersaline liquid inclusions determined by la icp ms are interpreted to represent the fluid composition prior to the main sulfide precipitation event the similar pb zn ratio of the bulk ore extracted from the epithermal ore bodies at cerro de pasco and the hsmis and hypersaline liquid inclusions suggest a common source of the fluids associated with the different mineralization styles at cerro de pasco

primary aqueous fluids in rhyolitic magmas melt inclusion evidence for pre and post trapping exsolution abstract this study examines melt inclusions containing bubbles of aqueous fluid l v and l v occurring in rhyolites from the okataina volcanic centre new zealand and the rio blanco cu mo deposit chile we demonstrate that these aqueous fluids coexisted with silicate melts magmas and represent either post trapping exsolution in the case of okataina or co trapping of phases already coexisting in the magma in the case of rio blanco microthermometry proves that some of the bubbles are a single phase aqueous liquid and all are shown by pixe analysis to be metal rich saline solutions as such these aqueous fluids provide the closest approximation to direct testing of the proposition that cooling magmas exsolve metal rich aqueous fluid in the case of pre trapping exsolution at rio blanco we show that some inclusions record and preserve magmatic emulsions melt aqueous fluid that are the first stage in the evolution of hydrothermal fluids we demonstrate that heating experiments on volatile rich melt inclusions can produce in situ exsolution of hypersaline metal rich aqueous fluid bubbles potentially permitting magma chamber processes to be experimentally modelled

major episodes of quaternary activity in the lower neales river northwest of lake eyre central australia abstract the lake eyre basin australia s largest internal drainage system represents a key site in unravelling the complexities of terrestrial climate change the basin covering one sixth of the australian continent spans a number of climatic zones including the tropical monsoon system to the north and the mid latitude westerly circulation to the south this study describes four major episodes of quaternary fluvial lacustrine and aeolian activity in the neales river a western catchment of lake eyre the first phase is represented by coarse grained fluvial aggradation which dates to at least 170 ka the depocentre of lake eyre is believed to have been located further to the east during this phase the second episode is a phase of high lake level lacustrine deposition which occurred before 103 ka the deltaic margin of the lake at this time was approximately 20 km west of the present playa the third phase was characterised by significant base level lowering and channel incision after 50 ka but before 31 ka lake level lowering induced fluvial incision of up to 9 m scouring several metres into the basal silicified miocene sediments some time after 50 ka the final phase was a period of aeolian and ephemeral fluvial deposition which peaked between 20 ka and 18 ka coincident with the last glacial maximum these episodes are compared with chronostratigraphic data from the monsoon dominated catchments of the cooper and diamantina rivers the nature and record of fluvial and lacustrine deposition are correlated throughout the basin during the penultimate and last interglacial cycles the late quaternary record is more ambiguous and further studies are required to elucidate the precise nature of climate change in the basin over the last 30 ka

pleistocene coastal stratigraphy sea level highstands and neotectonism of the southern australian passive continental margin a review located in a tectonically stable intraplate setting and in the far field of former ice sheets the southern australian passive continental margin represents a globally important region for quantifying sea level during pleistocene highstands the stratigraphical record of the southern australian margin is dominated by geographically extensive coastal barrier estuarine and peritidal landforms of bioclastic temperate carbonate affinity a function of regional aridity siliciclastic successions dominate the eastern australian coastline despite the generally high level of tectonic stability regional contrasts are evident in the elevation of pleistocene shoreline deposits that largely relate to pre quaternary geotectonic setting the most complete record of pleistocene highstand deposits occurs in the murray basin coorong coastal plain region and indicates that interglacial sea level highstands for at least the past 11 interglacials did not deviate by more than 6 m from present sea level the pleistocene marginal marine record of southern australia is dominantly represented by coastal successions deposited during marine oxygen isotope stages 5e and 7 equating with relative sea level maxima of 2 6 m and greater than 1 m above present sea level apsl respectively intertidal facies of late pleistocene interstadial successions rarely occur above present sea level the most reliable record of glacio eustatic ice equivalent sea level is registered on coastlines developed on stable precambrian cratons such as the gawler craton eyre peninsula where a consistent elevation of 2 m apsl is registered for over 500 km for the last interglacial shoreline 125 ka copyright 2002 john wiley sons ltd

a simplified 2d model for meander migration with physically based bank evolution abstract the rate of migration calculated by numerical models of river meandering is commonly based on a method that relates the rate of migration to near bank excess velocity multiplied by a dimensionless coefficient notwithstanding its simplicity since the early 1980s this method has provided important insight into the long term evolution of meander planforms through theoretical exercises its use in practice has not been as successful because the complexity of the physical processes responsible for bank retreat the heterogeneity in floodplain soils and the presence of vegetation make the calibration of the dimensionless coefficient rather challenging this paper presents a new approach that calculates rates of meander migration using physically based streambank erosion formulations the university of illinois rvr meander model which simulates meandering river flow and bed morphodynamics is integrated with algorithms for streambank erosion of the us department of agriculture channel evolution computer model concepts the performance of the proposed approach is compared to that of the more simple classic method through the application to several test cases for idealized and natural planform geometry the advantages and limitations of the approach are discussed focusing on simulated planform pattern the impact of soil spatial heterogeneity the relative importance of the different processes controlling bank erosion hydraulic erosion cantilever and planar failure the requirements for obtaining stable migration patterns centerline filtering and interpolation of bank physical properties and the capability of predicting the planform evolution of natural rivers over engineering time scales i e 50 to 100 years the applications show that the improved physically based method of bank retreat is required to capture the complex long term migration patterns of natural channels which cannot be merely predicted from hydrodynamics only

metal fractionation between magmatic brine and vapor determined by microanalysis of fluid inclusions the major and trace element compositions of individual fluid inclusions from a range of magmatic hydrothermal ore deposits were analyzed by laser ablation inductively coupled plasma mass spectrometry to explore the behavior of ore forming components during fluid phase separation boiling in high temperature saline fluid systems data from 13 samples showing unambiguous evidence for coeval trapping of a liquid brine and a coexisting vapor phase identify two groups of elements with drastically different geochemical behavior na k fe mn zn rb cs ag sn pb and tl preferentially partition into the brine probably as cl complexes whereas cu as au probably as hs complexes and b selectively partition into the vapor fluid phase separation is probably a major previously underestimated process in the chemical differentiation that contributes to the extreme range of selective element enrichments in magmatic hydrothermal systems from deep plutons through porphyry style and greisen deposits to epithermal mineralization and volcanic fumaroles

late quaternary vegetation and climate change in southeastern australia palynological evidence from marine core e55 6 abstract palynological analysis of core e55 6 obtained from off shore western victoria provides a record of vegetation and climate change in the southeastern south australian and western victorian region spanning much of the last 125 000 yr an accompanying oxygen isotope record provides a chronology for the sequence the pollen record suggests that maximum effective precipitation occurred during the height of the last interglacial oxygen isotope substage 5e with wet sclerophyll forest and rainforest widespread in the region effective precipitation appears to have decreased during substage 5d promoting the expansion of dry sclerophyll communities then increased slightly during substage 5c with the limited re occurrence of wetter forest types climatic conditions gradually became drier from substage 5b with the replacement of eucalypt dominated forest by more open heath and mallee type communities in the arid glacial conditions of isotopic stage 4 a brief phase of increased effective precipitation occurred during the interstadial stage 3 with limited expansion of eucalyptus followed by a steady decline in effective precipitation and the expansion of open heath and grass communities pollen is very sparse in the top section of the core making environmental interpretation difficult nevertheless it appears that grass and heath communities dominated the region during stage 2 there is no clear record of the holocene due to the presence of mudflow sediments in the top of the core the pollen evidence also suggests that continental shelf exposed as sea levels fell was colonised by a mosaic of coastal vegetation including myrtaceae dominated scrub eucalypt and casuarina woodland asteraceae and chenopodiaceae dominated heath and grassland the charcoal record expressed as a ratio to pollen concentration gives evidence of increased burning during the height of the last interglacial period most likely in response to increased fuel loads with the expansion of eucalypt dominated forest this record also indicates a second phase of increased burning commencing in stage 2 which gives possible evidence for increased anthropogenic activity in the region

a 100 000 year record of annual and seasonal rainfall and temperature for northwestern australia based on a pollen record obtained offshore pollen recovered from core tops of deep sea cores from offshore northwestern western australia were used to build climatic transfer functions applied to sediment samples from major rivers bordering the ocean in the same region and a deep sea core offshore northwest cape results show for the last 100 000 years with a gap in the record spanning the 64 000 to 46 000 years interval that from about 100 000 to 82 000 yr bp climatic conditions represented by rainfall temperature and number of humid months were significantly higher than today s values for the entire record the coldest period occurred about 43 000 to 39 000 yr bp but it was wetter than today whereas the last glacial maximum saw a significant reduction in summer rainfall interpreted as a result of the absence of monsoonal activity in the region the holocene can be divided into two distinct phases one peaking around 6000 cal yr bp with highest rainfall and summer temperatures the second one commencing at 5000 cal yr bp and showing a progressive decrease in summer rainfall in contrast to an increase in winter rainfall paralleled by a progressive decrease in temperatures copyright 2006 john wiley sons ltd

energy time and channel evolution in catastrophically disturbed fluvial systems abstract two diverse fluvial systems show that with time channels adjust such that the rate of energy dissipation is minimized one fluvial system characterized by high relief and coarse grained sediment was subjected to an explosive volcanic eruption the other system characterized by low relief and fine grained sediment was subjected to dredging and straightening study of the expenditure of kinetic and potential energy components of total mechanical energy provide an energy based rationale of the interdependency between processes and forms during channel evolution spatial and temporal trends of aggradation and degradation are similar although relative amounts of aggradation in the high energy system are greatly enhanced by the deposition of large amounts of eroded bank material from upstream reaches degradation accompanied by widening is the most efficient means of energy dissipation because all components of total mechanical energy decrease with time widening dominates energy dissipation in the coarse grained system to offset increases in hydraulic depth caused by incision in the low energy fine grained system channel adjustment and energy dissipation are dominated by vertical processes because of low relative values of kinetic energy and because eroded bank sediment is transported out of the drainage basin and does not aid in downstream aggradation energy dissipation or channel recovery specific energy is shown to decrease nonlinearly with time during channel evolution and provides a measure of reductions in available energy at the channel bed data from two sites show convergence towards a minimum specific energy with time time dependent reductions in specific energy at a point act in concert with minimization of the rate of energy dissipation over a reach during channel evolution as the fluvial systems adjust to a new equilibrium

fluid inclusion evidence for magmatic silicate saline co2 immiscibility and geochemistry of alkaline xenoliths from ventotene island italy abstract fluid and melt inclusions and geochemical features of alkali syenite mafic and ultramafic cumulate xenoliths in the last ignimbritic event volcanism up to 300 ky b p at the island of ventotene in the pontine archipelago gaeta gulf were investigated to establish the genesis and evolution of the fluids trapped in the inclusions ranges in lead isotopic compositions of the xenoliths as a group are narrow 206pb 204pb 18 778 18 864 207pb 204pb 15 641 15 701 208pb 204pb 38 858 39 090 the values overlap among the groups implying that the xenoliths are closely related the xenoliths straddle the best fit line describing the regional nw se variation of values for uranogenic pb in volcanic rocks from the roman alkaline province the similarity between the xenoliths and volcanic rocks permits the interpretation that the xenoliths are representative of the source region of the volcanic rocks residues after partial melting of the source region or fractional crystallization of the volcanic rocks or even that the xenoliths represent assimilants obtained during the evolution of the magmas that produced the volcanic rocks xenoliths belonging to the ultramafic mafic cumulate group contain only silicate melt inclusions vapor bubble droplets of an opaque phase and rarely some co2 trapped in silicate melt inclusions xenoliths in the alkali syenite group have three types of fluid inclusions 1 single phase vapor and silicate melt inclusions 2 two phase silicate melt salt silicate melt co2 v aqueous l v and silicate melt vapor inclusions and 3 three phase and multiphase inclusions co2 l co2 v h2o silicate melt saline melt h2o birefringent or opaque trapped minerals h2o salt silicate glass birefringent trapped minerals during heating experiments melting of salt occurs at temperatures from 565 to 815 c depending on the water content of the inclusions homogenization of the vapor bubble occurs from 850 1160 c and complete melting of the silicate glass at about 950 c the highly variable proportions of the individual phases in the silicate melt salt h2o inclusions and the coexistence of silicate melt co2 inclusions indicates immiscibility during the crystallization of the magma primary and secondary co2 inclusions in the alkali syenite suite indicate lower densities from 0 10 to 0 22 g cm3 than those resulting from primary co2 inclusions in the gabbroic suite from 0 34 to 0 42 g cm3 the p t trajectory of the probable fluid evolution path shows that the crystallization of gabbro occurred between 1 and 1 4 kbars whereas alkali syenite crystallized between 200 and 400 bars the secondary h2o inclusions in alkali syenite were trapped in the later stages of the hydrothermal process and at much lower temperatures 130 290 c but at pressures relatively close to those of alkali syenite crystallization the almost isobaric conditions during the final stage of the fluid evolution path are explained by the very shallow emplacement of the alkali syenite intrusive body

a high resolution record of vegetation and climate through the last glacial cycle from caledonia fen southeastern highlands of australia a blocked tributary has provided a rare site of long term sediment accumulation in montane southeastern australia this site has yielded a continuous detailed pollen record through the last ca 140 000 years and revealed marked vegetation and environmental changes at orbital to sub millennial scales radiocarbon and optically stimulated luminescence osl or optical ages provide some chronological control for the last ca 70 000 years most of the sediment is inorganic but with well preserved pollen that accumulated under unproductive and probably largely ice covered lake conditions the lake was surrounded by low growing plants with an alpine character exceptions include three discrete periods of high organic sedimentation in the basin and forest development in the surrounding catchment the two major periods of forest expansion are related to the last interglacial and the holocene with the third shorter period considered to represent an interstadial in the early part of marine isotope stage mis 3 the latter part of the last glacial period is characterised by abrupt sub millennial amelioration events that may relate to documented global oscillations emanating from the north atlantic there are systematic changes through the record that can be partly attributed to basin infilling but the progressive reduction and regional extinction of some plant taxa is attributed to a long term trend towards climatic drying copyright 2007 john wiley sons ltd

late pleistocene vegetation and climate history of lake selina western tasmania analysis of pollen nrm intensity of sediments and dating of a 397 cm core from lake selina in western tasmania provides a detailed record of vegetation and climate changes for the last interglacial last glacial cycle the vegetation record shows that cool temperate rainforest was present during isotope substage 5e and during the holocene wet montane forest and subalpine shrublands dominated the early last glacial interstades subalpine alpine heathlands and herbfield the stadials stages 4 2 mainly had grassland herbland and heath vegetation there is close correlation between phases of maximum magnetic intensity in the sediments with pollen zones indicating presence of herbaceous vegetation this suggests erosion of the catchment was greater in the absence of forest or woodland climate may have been slightly cooler than present during substage 5e but the evidence is not definitive climate was colder at all times during the last glacial stage until after ca 14 kyr bp maximum temperature depression from present during stage 2 was 3 5 c at lake selina but probably as much as 6 5 c in the west coast range holocene climate was cool and wet comparison of the lake selina record with others in western tasmania and victoria indicate that variations in vegetation during the last interglacial last glacial cycle were primarily responses to temperature changes in western tasmania and to precipitation changes particularly summer drought in western victoria

stratigraphy sedimentology chronology and palaeohydrology of quaternary lacustrine deposits at madigan gulf lake eyre south australia abstract madigan gulf is a large bay at the southern end of lake eyre north a major ephemerally flooded playa in arid central australia at the southwestern margin of a vast 1 300 000 km2 internal drainage basin the stratigraphy and chronology of the quaternary sequence in the gulf is described from 8 cores and a cliff exposure at the gulf margin a number of depositional environments are recognised and their distinctive sedimentary components are described facies recognised include deep and shallow water lacustrine environments dominated by surface water processes and dry or ephemerally flooded playa environments dominated by groundwater controlled processes sedimentary components include terrigenous clastics from river inflow and shoreline erosion carbonates of detrital inorganic or biological origin and gypsum and halite evaporites carbonates and gypsum evaporites precipitated within the basin are frequently reworked as clastic components the establishment of a preliminary chronology for the sequence by the application of thermoluminescence uranium thorium disequilibrium amino acid racemization and radiocarbon dating techniques has allowed a reconstruction of the last 130 ka of lake eyre palaeohydrology the wettest phase occurred during the last interglacial early in oxygen isotope stage 5 when an enlarged lake eyre was up to 25 m deep subsequently there has been a number of dry periods separating successively less effective wet phases culminating in the deposition of a substantial halite salt crust around the time of the glacial maximum the dry interludes are characterised by deflation of salts and sediment from the basin a process controlled by lowering of the watertable the record from madigan gulf demonstrates the dramatic and repetitive impact of lake deflation on the quaternary record of lake eyre in the early holocene a minor but mostly perennial lacustrine event was terminated at about 3 4 ka when the modern ephemeral playa regime was established the major catchment of lake eyre is located in the monsoon watered areas of northern australia as demonstrated by large floodings of the modern ephemeral regime major lacustrine episodes must indicate enhanced monsoon precipitation in northern australia in the holocene the lake has not risen to levels achieved during the early stage 5 lacustral phase indicating a marked reduction in the effectiveness of the monsoon in the present interglacial by comparison with its predecessor

multiple fluids involved in granite related w sn deposits from the world class jiangxi province china abstract this paper aims at providing new insights into w sn ore forming processes within one of the largest granitic provinces in the world nanling range south china which was emplaced during the jurassic cretaceous period the origin composition and pressure temperature conditions of fluids involved in the w sn ore forming processes have been investigated by microthermometry raman spectroscopy la icpms hydrogen isotope analyses of fluid inclusions and oxygen isotope analyses of minerals from the maoping and piaotang w sn deposits for each deposit pre quartz syn wolframite and cassiterite and post ore quartz topaz and fluorite minerals were studied in both deposits the vast majority of fluid inclusions are aqueous with salinities between 0 0 and 12 6 wt equiv nacl and homogenization temperatures between 136 and 349 c a minor proportion 5 of inclusions observed in the ore stage quartz from maoping have aquo carbonic compositions for both deposits four compositional groups are defined early quartz fluid inclusions are characterized by salinities between 0 4 and 9 0 wt equiv nacl trapping temperatures between 150 and 350 c and pressures between 20 and 150 mpa la icpms analyses of these fluid inclusions reveal a wide range of na k and li concentrations as well as relatively low metal contents w at piaotang fluid inclusions in wolframite as well as in post ore quartz and fluorite have salinities of 5 6 to 12 6 wt eq nacl trapping temperatures between 150 and 400 c and pressures of 20 to 150 mpa la icpms analyses of these fluid inclusions reveal similar compositions to early quartz fluid inclusions values of 18o in wolframite and quartz crystals range from 0 8 to 5 2 vsmow while the d values of fluid inclusions range from 66 to 62 vsmow collectively the data suggest the involvement of four aqueous fluid end members mixed episodically in the mineralization process a a low salinity low temperature metal poor low 18o low d fluid derived from meteoric water b a high salinity high temperature metal poor high 18o low d fluid derived from a differentiated peraluminous granitic magma c a high salinity high temperature metal rich lower d magmatic fluid derived from a more differentiated peraluminous granitic magma and d a high salinity high temperature metal rich high 18o low d magmatic fluid this study shows that multiple fluids with distinct magmatic and meteoric origins were involved in the formation of these w sn deposits and that the dilution of metal bearing magmatic fluids by meteoric fluids was probably the main driver for ore deposition the common fluid history of the two deposits studied as well as similarities with other deposits in the jiangxi province points toward common ore forming processes at the regional scale

water solubility and chlorine partitioning in cl rich granitic systems effects of melt composition at 2 kbar and 800 c abstract experiments have been conducted in the system na2o k2o al2o3 sio2 h2o cl2o 1 at 2 kbar and 800 c to determine the effects of melt composition on the solubility of water in haplogranite melt and on the distribution of cl between aqueous fluid and haplogranite melt the melts studied include peraluminous subaluminous and peralkaline haplogranites and quartz albite and quartz orthoclase compositions the solubility of water at 2 kbar and 800 c in water saturated haplogranite melts varies strongly as a function of melt composition water solubility in melt decreases in the order strongly peralkaline haplogranite quartz albite composition moderately peralkaline haplogranite peraluminous haplogranite subaluminous haplogranite quartz orthoclase composition d cl wt cl in fluid wt cl in melt is a strong function of system composition d cl increases as the concentration of cl in the system increases a comparison of the distribution of cl between haplogranite melts of subaluminous peraluminous and peralkaline compositions and aqueous fluids shows that with similar concentrations of cl in the system d cl is largest for subaluminous melts a nk 1 having relatively high k2o concentrations as the a nk of melt increases or decreases from 1 or as the n nk of the melt increases both d cl and the concentration of cl in the fluid decrease the experimental data imply that complexes involving cl and na in hydrous subaluminous granite melts are dominant furthermore the data imply that in hydrous peraluminous granite melts cl complexes with network modifying a13 and in hydrous peralkaline granite melts cl complexes with network modifying na k on a molar basis cl apparently complexes with network modifying a13 in peraluminous melts as strongly as it does with na and k in peralkaline melts experimental studies of cl partitioning in granitic systems suggest that the strongest enrichment of magmatic hydrothermal fluids in cl and ore metals complexed with cl will most likely occur in fluids exsolved from subaluminous granite magmas that are relatively enriched in k2o sio2 and cl and relatively depleted in f co2 and na2o

fluid inclusions from the jinchang cu au deposit heilongjiang province ne china genetic style and magmatic hydrothermal evolution abstract the jinchang cu au deposit is located in the easternmost part of the central asian orogenic belt caob the mineralization here is associated with cretaceous porphyritic intrusions of ca 120 110 ma and is mainly hosted within intensely altered mesozoic granites breccia pipes ringed and radial faults the gold ores are disseminated in the wall rock and also occur as massive auriferous quartz sulfide veins in fractures and breccias fluid inclusion data from breccias chalcopyrite quartz vein and pyrite quartz vein display homogenization temperatures in the range of 200 to 550 c and the fluids show variable salinity in the range of 0 58 wt nacl equiv the halite absent fluid inclusions shows a slight increase in salinity with a sharp decrease in temperature we interpret that the high salinity brine and low salinity vapor or aqueous rich fluids from ores represent fluid unmixing from magma the fluid inclusion data from jinchang demonstrate that the main mineralization took place at temperatures from 480 c to 200 c and evolved from high to low salinities geology and fluid inclusion data suggest that the jinchang deposit is an oxidized intrusion related cu au deposit the voluminous hydrothermal magnetite formed during high temperature potassic alteration of wall rocks in this ore deposit can be used as a potential prospecting tool

immiscibility of magmatic fluids and their relation to mo and cu mineralization at the bangpu porphyry deposit tibet china abstract the coexistence of aqueous fluid inclusions and silicate melt inclusions in quartz phenocrysts from porphyrites at the bangpu porphyry mo cu deposit tibet china were examined to characterize the immiscibility processes during the magmatic to hydrothermal transition the physical and chemical environment during crystallization of the magmas has been reconstructed on the basis of microthermometric experiments and trace element microanalysis compositions of melt and brine fluid phases are determined using synchrotron radiation x ray fluorescence analysis sem eds and laser raman spectroscopy analyses brine fluids were directly exsolved by a crystallizing melt and the simultaneous entrapment of volatile rich brine fluid and volatile poor immiscible phases silicate melt occurred at 670 700 c and 1 6 1 95 kbar when the magma had h2o contents between 5 and 6 wt and crystal contents of 60 80 a later low density fluid with a higher mo concentration exsolved after about 80 90 crystallization had occurred this fluid contained significant concentrations of cl na k ca fe cu zn rb and small amounts of mn br and pb immiscibility of magmatic fluids can lead to different metal partitioning behaviors between residual melt and volatile phases which generate variable metal ratios copper was partitioned preferentially into the brine phase in contrast to the behavior observed in other porphyry cu deposits ore deposition by a dense brine could explain the partially deep cu mineralization condensation of brine from a later low density parental fluid could be an efficient mechanism to concentrate shallow cu mineralization and broadly distributed mo mineralization the source of the mo mineralizing fluids probably was a particularly large magma chamber that crystallized and fractionated at depth greater than upper continental crust level

a chronology for the long pollen record from lake wangoom western victoria australia as derived from uranium thorium disequilibrium dating the chronology of a long pollen record from lake wangoom one of the few long palaeoenvironmental records from southeastern australia is discussed in light of the acquisition of new uranium thorium disequilibrium utd dates of crucial importance has been the estimation of ages for two major pre holocene phases of forest expansion recorded in the sequence with implications for the timing of periods of high effective precipitation in the region the new utd ages indicate that the oldest forest phase falls within the penultimate interglacial whereas the later phase corresponds with the last interglacial this is older than indicated by previously reported utd and radiocarbon dates but confirms a chronology based on direct correlation with the pollen record from marine core e55 6 the new chronology of the lake wangoom sequence provides evidence that phases of sustained forest development in southeast australia relate to interglacial periods in comparison interstadial periods appear to be characterised by only minor arboreal development marked differences in the pattern of vegetation development evident in each of the interglacials are thought to reflect varying climatic and anthropogenic influences copyright 2002 john wiley sons ltd

exsolution of immiscible vapor and liquid phases from a crystallizing silicate melt implications for chlorine and metal transport abstract the compositional variation of a cl bearing aqueous fluid exsolving from a crystallizing silicate melt is evaluated for the system haplogranitic melt na k c1 h 2 o with attention to the effect of vaporliquid immiscibility on the aqueous fluid above critical pressures for the aqueous fluid p 1 5 kb at 800 c where the fluid is single phase the cl concentration in the aqueous fluid c cl aq gradually decreases with crystallization of a silicate melt under rayleigh fractionation as demonstrated by previous studies however the variation of ca is quite different below critical pressures where vapor liquid immiscibility occurs in particular at low pressures p cl h 2 o ratio in a melt is small and ca will increase with crystallization a high cl h 2 o ratio at low pressure results in liquid exsolution and decreasing ca with crystallization eventually both vapor and liquid phases will exsolve simultaneously regardless of the initial exsolving phase during this simultaneous exsolution the composition of the exsolving vapor and liquid phases the mass ratio of these phases and the cl concentration of the silicate melt will all remain constant comparison of the model and published experimental data indicates that the simultaneous exsolution of vapor and liquid may occur from a normal rhyolite crystallized at pressures below the critical pressure for the aqueous fluid therefore simultaneous exsolution of the immiscible aqueous phases is likely to be a common phenomenon in magmatic hydrothermal systems at conditions for the vapor liquid immiscibility model calculations at 0 6 and 1 2 kb indicate that major amounts of cl in the system will be distributed to the liquid phase particularly at the lower pressure this suggests that the majority of chloridecomplexed metals exsolving from a magma may be transported in the liquid phase under shallow crustal conditions

trace element compositions and br cl ratios of fluid inclusions in the tsushima granite japan significance for formation of granite derived fluids abstract fluid inclusions in quartz samples from a miarolitic cavity two quartz veins and a hydrothermal ore vein in the tsushima granite japan were analyzed by particle induced x ray emission to examine the chemistry and process of formation of hydrothermal fluids in an island arc granite most of the inclusions were polyphase or vapor and there were smaller numbers of two phase aqueous inclusions the inclusions contained cl k ca ti mn fe cu zn ge br rb sr ba and pb for each inclusion there was a strong positive correlation between cl content and contents of other elements identified concentration ranges for most elements other than rb and ge in polyphase inclusions from the miarolitic cavity were comparable to those from cavities in alkaline granites those from the ore vein were comparable to large scale continental hydrothermal ore deposits the lower rb and higher ge contents in the polyphase inclusions of the tsushima granite may be characteristic of hydrothermal fluids from calc alkaline granites in an island arc setting br cl ratios by weight for the vapor and two phase inclusions were 0 0013 0 0030 and differed among the three geological settings br cl ratios of polyphase inclusions increased with increasing cl content in single crystal and polycrystalline quartz and high values of more than 0 0100 were found the high br cl ratios and the differences among the geological settings sampled may be due to pressure dependences of partitioning of cl and br between fluid and magma during fluid segregation and between liquid and vapor during boiling using a simple model based on these dependences we calculated br cl ratios greater than 0 01 in brine generated at pressures

stability analysis of semicohesive streambanks with concepts coupling field and laboratory investigations to quantify the onset of fluvial erosion and mass failure abstractthe overarching goal of this study is to perform a comprehensive bank stability analysis that is phenomenologically sound by considering both mass failure and fluvial erosion the nature of this study is twofold first field and experimental analyses are conducted to generate data for channel cross section properties soil index properties and mechanical and erosional strengths at two sites in a representative midsize midwestern stream in southeastern iowa that is subjected to frequent flash floods and characterized by active fluvial erosion and cantilever failure second the channel surveys and data obtained from the field and laboratory analyses are used as input parameters for an established one dimensional channel evolution model namely the conservational channel evolution and pollutant transport system concepts version 2 0 langendoen and alonso 2008 to estimate the factor of safety for mass failure fsm and fluvial erosion fsf and simulate the bank retreat as a result of eithe

refining the eustatic sea level curve since the last glacial maximum using far and intermediate field sites the eustatic component of relative sea level change provides a measure of the amount of ice transferred between the continents and oceans during glacial cycles this has been quantified for the period since the last glacial maximum by correcting observed sea level change for the glacio hydro isostatic contributions using realistic ice distribution and earth models during the last glacial maximum lgm the eustatic sea level was 125 5 m lower than the present day equivalent to a land based ice volume of 4 6 4 9 107 km3 evidence for a non uniform rise in eustatic sea level from the lgm to the end of the deglaciation is examined the initial rate of rise from ca 21 to 17 ka was relatively slow with an average rate of ca 6 m ka 1 followed by an average rate of ca 10 m ka 1 for the next 10 ka significant departures from these average rates may have occurred at the time of the younger dryas and possibly also around 14 ka most of the decay of the large ice sheets was completed by 7 ka but 3 5 m of water has been added to the oceans since that time

late quaternary climate change in the awatere valley south island new zealand using a sine model with a maximum likelihood envelope on fossil beetle data we present a new climatic reconstruction method appropriate for biological proxies where modern distributions are poorly defined and data sets are small the technique uses a sine function in conjunction with maximum likelihood estimates of best high and best low values for the distribution of each species to demonstrate the model we present temperature reconstructions for the last glacial maximum lgm and holocene from beetle fossil assemblages from the awatere valley new zealand the temperature estimates are determined by the mutual overlap of the climate range for all the species in the assemblage the overlap is then compared with modern physio chemical conditions for our example we estimate the lgm summer february mean temperature was about 3 5 4degreesc cooler and july winter mean daily minimum temperature was about 4 5degreesc cooler than present day temperatures the maximum likelihood estimates broaden the reconstructed temperature ranges to 2 5 5degreesc cooler for february temperatures and 3 5 6 0degreesc cooler for mean minimum daily temperature of the coldest month july these estimates are consistent with lgm temperature estimates of 4 7degreesc from other climate proxy indicators estimates of holocene temperatures are very similar to modern estimates are compared with results from the established mutual climatic range mcr technique and the results are compatible mcr is less robust than the sine model approach for these data because it requires the pre determination of the critical physiochemical controls and assumes gaussian distributions in climate space the sine model is conceptually superior to traditional bioclim modelling with which it shares many features because bioclim also assumes gaussian distributions and the sine model allows attribute testing of the data sets which are not possible with bioclim c 2004 elsevier ltd all rights reserved

modeling the evolution of incised streams iii model application incision and the ensuing widening of alluvial stream channels represent important forms of channel adjustment two accom panying papers have presented a robust computational model for simulating the long term evolution of incised and restored or rehabili tated stream corridors this work reports on applications of the model to two incised streams in northern mississippi james creek and the yalobusha river to assess 1 its capability to simulate the temporal progression of incised streams through the different stages of channel evolution and 2 model performance when available input data regarding channel geometry and physical properties of channel boundary materials are limited in the case of james creek model results show that temporal changes in channel geometry are satisfactorily simulated the mean absolute deviation mad between observed and simulated changes in thalweg elevations is 0 16 m for the yalobusha river and 0 57 m for james creek which is approximately 8 1 and 23 of the average degradation of the respective streams the mad between observed and simulated changes in channel top width is 5 7 of the channel top width along the yalobusha river and 31 of the channel top width along james creek the larger discrepancies for james creek are mainly due to unknown initial channel geometry along its upper part the model applications also emphasize the importance of accurate characterization of channel boundary materials and geometry

direct evolution of brine from a crystallizing silicic melt at the questa new mexico molybdenum deposit molybdenum mineralization in the southwest orebody at the questa deposit is associated with crystallization of aplite porphyry explosive brecciation and exsolution of magmatic hydrothermal fluids quartz k feldspar fluorophlogopite and molybdenite precipitated from exsolving aqueous fluids and cemented aplite porphyry and andesite wall rock clasts forming a magmatic hydrothermal breccia ore fluid inclusions in quartz in the breccia matrix trapped aqueous fluids that transported and precipitated molybdenum two fluid inclusion populations associated with molybdenite mineralization were identified the largest population commonly contains liquid vapor halite sylvite and one or more opaque daughter crystals these inclusions homogenize between 200 degrees and 500 degrees c and have a prominent mode at 360 degrees to 400 degrees c salinities vary from 31 to 57 wt percent nacl equiv low first ice melting temperatures suggest that additional fluid components possibly calcium or magnesium chlorides may be present approximately 80 percent of these inclusions homogenize by halite dissolution phase equilibria constraints require that these inclusions trapped fluids in the vapor absent field the remaining saline inclusions homogenize to liquid at temperatures above halite dissolution temperatures significantly the saline fluid did not coexist with a low density aqueous fluid a second population of inclusions contains fluids with salinities of 2 7 to 25 0 wt percent nacl equiv and homogenizes by vapor bubble disappearance vapor bubble expansion or critical behavior textural relationships and phase behavior during microthermometry indicate that these inclusions constitute a single population which formed as pressure and temperature fluctuated at near critical conditions pressure changes related to brecciation followed by crystallization and system resealing produced the observed fluids saline fluids were trapped as the system sealed following a major brecciation event these high salinity fluids were produced as the melt under pressure that increased from hydrostatic to lithostatic partitioned increasing amounts of chlorine into the exsolving aqueous fluid renewed fracturing and abrupt pressure decrease to hydrostatic conditions reduced the mass of chlorine partitioning to the exsolving fluid lower salinity fluids exsolved at near critical conditions and were trapped by inclusions that homogenize to liquid to vapor or by critical behavior the lack of cogenetic liquid and vapor rich fluid inclusions and phase equilibria constraints indicate that high salinity fluids or 57 wt nacl equiv were generated directly by the crystallizing magma and were not a product of aqueous fluid immiscibility

evidence for a copper bearing fluid in magma erupted at the valley of ten thousand smokes alaska several lines of evidence point to the existence of a pre eruptive fluid phase in the magmas erupted in 1912 at the valley of ten thousand smokes alaska the discovery of rare cu rich bubbles in some melt inclusions is best explained by the random entrapment of a low density fluid phase within growing phenocrysts the h2o s and cl concentrations of the high silica rhyolite are also consistent with fluid saturation in the rhyolite water contents as determined by infrared spectroscopy on doubly polished melt inclusions cluster between 3 5 and 4 5 wt h2o without any apparent differences between magmas vented explosively and effusively these concentrations would be sufficient for h2o saturation at a pressure of 100 mpa though the presence of other volatiles such as co2 and so2 could allow saturation with respect to a fluid phase at higher pressures the s cu and cl contents of the phenocryst assemblages as determined by xrf analyses are too low to account for the decrease in the concentrations of s and cu in the melt and only modest increase in cl with differentiation therefore the behavior of these volatile elements was controlled either by eryptic fractionation if phenocryst phasese or more likely by partitioning into a coexisting fluid phase the presence of this low density phase apparently provided metals such as cu with a volatile phase into which they could partition the concentration of cu in this fluid reached tens to hundreds of times that of the coexisting silicate melt and may have been as rich as 0 05 wt cu the distribution of cu in the magma was also controlled by sulfides such as intermediate solid solution and pyrrhotite which cyrstallized directly from the silicate melt

magmatic precursors of hydrothermal fluids at the rio blanco cu mo deposit chile links to silicate magmas and metal transport in most porphryr systems the obscuring effects of hydrothermal processes and subsequent alteration along with limited exposure of source rocks preclude a detailed understanding of how and where metals and volatiles were derived however in this study we examine melt inclusions which have escaped alteration and that sampled all of the phases coexisting in the magma in late and postmineral rhyolitic units from the rio blanco cu mo deposit chile these inclusions demonstrate the existence of a volatile rich melt the exsolution from it of an aqueous volatile rich phase initially as melt vapor bubble emulsions and the disruption of these emulsions into melt and primary magmatic fluids trapping of these emulsions may explain the occurrence of melt inclusions containing widely varying proportions of melt and aqueous fluid found at rio blanco we demonstrate the sequestering of metals into the exsolved volatile phases and the derivation from these of possible ore forming hydrothermal fluids with particular reference to the implications for metal transport melt inclusions show differences between adjacent comagmatic intrusions that may be directly related to the extent of mineralization of the respective bodies in one of the rio blanco postmineral rhyolite bodies melt inclusions show exsolution of the volatile rich phase but only minor evidence of trapping of a metal rich vapor in contrast inclusions from an adjacent late mineral rhyolite body show similar volatile phase exsolution but also provide evidence of ponding of metal rich hydrothermal fluids during the final stages of cooling

volatile exsolution at the dinkidi cu au porphyry deposit philippines a melt inclusion record of the initial ore forming process immiscible phases derived from degassing silicate magmas are considered to be precursors of metal bearing hydrothermal fluids in porphyry deposits the development of melt inclusion techniques provides a window into this critical period of porphyry formation when the cooling decompression and crystallization of silicate melts result in the formation of immiscible phases the record of magmatic to hydrothermal evolution is presented using inclusions in clinopyroxene phenocrysts from the syenitic balut dike one of the host rock lithologies for mineralization at the dinkidi cu au porphyry deposit philippines primary inclusions include silicate glass multiphase aggregates comprising salts silicates sulfates carbonates sulfides and oxides and highly saline aqueous fluids various analyses including in situ laser ablation inductively coupled plasma mass spectrometry of the multiphase inclusions determined elevated concentrations of cl s as tl k na and a number of metals including those that form ore grade deposits e g cu and those that do not e g mo pb zn and w at the dinkidi porphyry deposit silicate melt and multiphase salt rich inclusions in clinopyroxene are interpreted as having originally formed as immiscible phases at magmatic temperatures

comparative uranium thorium and thermoluminescence dating of weathered quaternary alluvium in the tropics of northern australia abstract thermoluminescence tl age determinations of alluvial sediments in the tropics are evaluated by comparison with u th age determinations of pedogenic accumulations in the alluvium of the lower gilbert river a large fan delta in the wet dry tropics of northern queensland australia this study extends u th dating by applying it not only to calcretes but also to fe mn oxyhydroxide oxide accumulations while a direct correlation cannot be made between u th dates from secondary minerals and tl dates from the host sediments both sets of data show broad consistency in addition to providing a minima for acceptable tl ages u th dates are useful for determining the chronology of pedogenesis diagenesis they show that calcretes and ferricretes have formed under similar climatic conditions in the wet dry tropics of northern australia during the late pleistocene beneath about 5 12 m the gilbert fan delta consists of an extensive sand body older than 85 000 yr and probably about 120 000 yr in age representative of a period of major fluvial activity not repeated since this time above are muds and fine sandy muds that extend uninterrupted to the present surface except in the downstream fan where they are bisected by a thin unit of medium sand that tl dates at 40 000 50 000 yr b p a system of sandy distributary channels over the fan surface represents an early holocene fluvial phase probably more active than at present

vegetative impacts on hydraulics and sediment processes across the fluvial system summary vegetation creates a complicated system of feedbacks and linkages across the fluvial system that is realized through river planform shape interactions occur among flow hydraulics sediment deposition and erosion and plant morphology density and biomechanics interest in the interactions and feedback loops between vegetation and the fluvial system has grown extensively in the past few years this interest is partially driven by the popularity of stream restoration activities worldwide that include re vegetation of stream banks and formation of an ecosystem that is intended to encourage the growth of aquatic macrophytes we present a review of the research into the interactions and dependencies between vegetation and the fluvial system to identify hydraulic and sediment dynamics that are consistent around vegetation located in the channel on channel banks and over the floodplain we illustrate process commonalities operating across spatial locations within the fluvial system and highlight some of the current research opportunities and challenges to encourage research collaborations between those working in areas of the fluvial system traditionally viewed as disparate

magmatic hydrothermal transition of mo w mineralized granite pegmatite greisen system recorded by trace elements in quartz krupka district eastern krusne hory erzgebirge abstract magmatic hydrothermal transition of highly evolved granitic melts enriched in volatile and incompatible elements can involve disequilibrium intermediate products between aluminosilicate melt and hydrothermal fluid hydrosilicate liquids with high ore forming potential we investigate evolution from li f rich granites through pegmatites greisens and quartz veins in a composite stock at knottel in the krupka district eastern krusne hory erzgebirge mountain range by monitoring trace element variations in quartz interelemental correlations reveal si4 li al3 and likely si4 h al3 to be the most important substitution mechanisms variations in ti vs li be and al define distinct evolutionary trends i magmatic high li ti or al ti trend granites aplites k feldspar pegmatite ii transitional medium li ti trend quartz megacrysts and pegmatite lenses in granite quartz protolithionite pegmatite iii hydrothermal low li ti or al ti trend stockwork of coarse grained hydrothermal quartzites and quartz veins quartz replacement in greisens the medium li ti trend represents hydrosilicate liquid an h2o and sio2 rich medium with low density and effective viscosity that was probably formed during disequilibrium crystallization in front of rapidly propagating solidification front thermal evolution of the magmatic hydrothermal system was monitored by ti in quartz thermometry calculated rutile activity of the granites is very low 0 3 0 05 but it increases up to 1 that is saturation towards pegmatites and hydrothermal veins magmatic crystallization granites and aplites is constrained to 700 580 c pegmatite and bulk greisenization stage occurred at 600 500 c followed by a late hydrothermal stage associated with the formation of distal quartz veins at 500 390 c the granite pegmatite systems at knottel and in erzgebirge in general reach extremely high al li rb and ge and low ti concentrations in quartz in comparison with igneous rocks worldwide the knottel stock belongs to p poor a type granites in the erzgebirge and is linked with them by similar evolutionary trends in quartz trace elements furthermore the knottel system exhibits be enrichment in quartz probably related to high contents of f and this appears to be typical feature of mo w mineralized systems in general the hydrothermal phase with mo w mineralization at knottel is closely related to the magmatic phase of parental granite body which seems to be an important condition for mo w mineralization formation

first direct evidence for natural occurrence of colloidal silica in chalcedony hosted vacuoles and implications for ore forming processes different forms of abundant silica e g quartz and chalcedony are closely associated with many types of ore deposits in igneous metamorphic and sedimentary environments occurrence of quartz and metal bearing minerals together strongly indicates that silica is an important component in hydrothermal fluids transporting and concentrating economic metals to the ore grade however chemical and physical characteristics of such ore forming media remain debated understanding of the environment in which chalcedony forms is largely hampered by the lack of chalcedony hosted fluid inclusions our study reports for the first time fortuitously preserved large sized up to 150 m fluid inclusions in chalcedony from the gonchak deposit of optical calcite in the early triassic basalts belonging to the siberian large igneous province the application of microthermometric methods scanning electron microscopy with cathodoluminescence and laser raman spectroscopy to the fluid inclusions and their host chalcedony recognized the formation of chalcedony from a colloidal suspension the fluid inclusions represent a gel like saline aqueous fluid that is residual after precipitation of spherulitic chalcedony aggregates with numerous h2o bearing and h2o poor layers we propose that the colloidal nature of fluids forming chalcedony lends strong support to the natural existence of experimentally predicted silicothermal fluids such fluids can be instrumental in mobilizing and transporting large quantities of both silica and nano and micro particles of ore minerals followed by efficient separation of the latter from coagulating silica gel into ore rich zones and bodies

immiscibility between silicate magmas and aqueous fluids a melt inclusion pursuit into the magmatic hydrothermal transition in the omsukchan granite ne russia abstract exsolution unmixing of the volatile element rich phases from cooling and crystallising silicate magmas is critical for element transport from the earth s interior into the atmosphere hydrosphere crustal hydrothermal systems and the formation of orthomagmatic ore deposits unmixing is an inherently fugitive phenomenon and melt inclusions droplets of melt trapped by minerals provide robust evidence of this process in this study melt inclusions in phenocrystic and miarolitic quartz were studied to better understand immiscibility in the final stages of cooling of and volatile exsolution from granitic magmas using the tin bearing omsukchan granite ne russia as an example primary magmatic inclusions in quartz phenocrysts demonstrate the coexistence of silicate melt and magma derived cl rich fluids brine and vapour and emulsions of these during crystallisation of the granite magma microthermometric experiments in conjunction with pixe and other analytical techniques disclose extreme heterogeneity in the composition of the non silicate phases even in fluid globules within the same silicate melt inclusion we suggest that the observed variability is a consequence of strong chemical heterogeneity in the residual silicate melt brine vapour system on a local scale owing to crystallisation immiscibility and failure of individual phases to re equilibrate the possible evolution of non silicate volatile magmatic phases into more typical hydrothermal chloride solutions was examined using inclusions in quartz from associated miarolitic cavities

extreme chemical heterogeneity of granite derived hydrothermal fluids an example from inclusions in a single crystal of miarolitic quartz magma derived fluids are important in geologic processes e g metal sequestration and ore deposition but are intrinsically transient samples of magmatic fluids represented by fluid inclusions in a single zoned quartz crystal from a miarolitic cavity within a porphyritic leucogranite hosting the industrialnoe tin deposit northeastern russia were studied by using modern in situ analytical methods laser raman spectroscopy proton induced x ray emission the fluid inclusions are either dominated by vapor or by complex multiphase brines the inclusions within a given trapping plane have similar phase relationships however there are significant variations between inclusions in different healed fractures phase and chemical compositions of individual brine inclusions demonstrate significant compositional heterogeneity in terms of absolute element concentrations and ratios of high temperature magmatic fluids accumulated in the miarolitic cavity this finding suggests that fluids leaving a crystallizing magma may have variable initial compositions that are subsequently modified by reactions with the rocks while the fluid is in transit to a miarolitic cavity as well as by processes in the cavity such as mixing crystallization and boiling the inferred chemical diversity and fractionation of granite derived fluids at near magmatic conditions imply that fluids entering a cooler hydrothermal system are extremely complex and their metallogenic signature may differ from that of related ore deposits

lithium isotope fractionation during fluid exsolution implications for li mineralization of the bailongshan pegmatites in the west kunlun nw tibet abstract granitic pegmatites are considered significant host rocks for the rare metal deposits however the enrichment mechanisms for the rare metal elements e g li be nb and ta remain debated here we report the whole rock and mineral e g muscovite and spodumene major trace elements and li isotopic compositions of the bailongshan granitic pegmatites in the west kunlun nw tibet to address this issue the bailongshan pegmatites hosting a super large li rb polymetallic deposit are composed of li poor and li rich pegmatites the li poor pegmatites display high 7li values in the whole rock 2 30 4 94 and muscovite 2 22 7 55 in contrast the li rich pegmatites show low 7li values in the whole rock 1 89 to 0 35 muscovite 3 39 to 4 49 and spodumene 2 83 to 1 87 these results together with the variations of the elements suggest that the li poor and li rich pegmatites were produced by the melt fluid separation during the late stage of granitic magma evolution this means that the li poor pegmatites were formed in a h2o poor silicate rich melt system while the li rich pegmatites were generated in a h2o rich silicate poor melt supercritical fluid system the melt fluid separation can lead to significant li isotope fractionation with 7li enriched in the strongly bonded residual silicate melt and 6li preferring to weaker hydrated bonds in the fluid alternatively the li rich pegmatites enriched in 6li could have been induced by preferential accumulation of the faster diffusing 6li in the supercritical or near critical fluid the li rich pegmatites experienced extensive crystal fluid interaction in a relatively closed magmatic hydrothermal system which resulted in the leaching and reprecipitation of ore forming elements but produced restricted li isotope fractionation the exsolved supercritical fluid is more enriched in alkali fluxing components li rb cs p and f by the continuous interaction with the residual silicate melt therefore the supercritical fluid exsolution plays an important role in the li isotope fractionation and rare metal mineralization

fluid inclusion evidence for immiscibility in magmatic differentiation abstract after a brief review of recent work on melt inclusions in diamond and in normal magmatic environments the nature of the fluid inclusion evidence for various stages of magmatic immiscibility is summarized during magmatic differentiation by crystal fractionation from originally low volatile content silicate melts yielding normal plutonic rocks through hydrous silicate melts yielding pegmatites to late stage water rich fluids yielding quartz veins and ore deposits the composition of the residual liquid changes drastically in some geologic environments this change in composition of the residual liquid may be continuous with no phase change in the fluid part of the system under most natural conditions however it is far more likely to have one or more stages in the evolution during which globules of a separate new immiscible fluid phase exsolve the term immiscibility is used here in its more general sense to refer to the existence at equilibrium of two or more non crystalline polycomponent solutions fluids differing in properties and generally in composition i believe that the great bulk of the magmatic inclusions that are being studied today have come about through the intervention of one or more such stages of immiscible fluid separation i e magmatic differentiation by fluid immiscibility examples include silicate melt dense co2 fluid silicate melt sulfide melt silicate melt silicate melt silicate melt low density vapor i e vesiculation and as presented in more detail in this paper various stages of silicate melt hydrous saline melt aqueous fluid co2 fluid immiscibility generally only parts of these stages are recorded by the trapping of fluid inclusions and the interpretation of the inclusion record is commonly ambiguous and difficult particularly that stage between hydrous silicate melts and the hydrous saline melts and aqueous solutions responsible for many ore deposits the ambiguity results mainly from problems of inclusion origin and nonrepresentative trapping within any given individual inclusion thus the probability of trapping of only one vs various amounts of two immiscible fluids or of trapping solid phases along with the fluid present severe difficulties in addition there is the almost universal superposition of various stages of trapping of fluids within any given sample these problems can only be approached by very careful petrography and analysis of optimum material combined with field data and experimental p v t x studies of pertinent systems completely unequivocal statements of the course of evolution of the fluids in such natural systems may never be possible

first insights on the metallogenic signature of magmatic fluids exsolved from the active magma chamber of vesuvius ad 79 pompei eruption abstract fluid inclusions hosted in sanidine from xenoliths representing the crystallization front of the ad 79 magma chamber of vesuvius offer a rare opportunity to track the composition of magmatic fluids exsolving at the peripheral part of a growing k alkaline magma chamber disrupted by an explosive eruption this work demonstrates that the exsolving magmatic fluids have a complex composition taking in evidence the great capability of metal transport by means of these solutions inclusions are particularly enriched in zn mo w sb bi tl and pb metals display two different positive correlations 1 pb zn tl bi 2 mo w the different trends may reflect the different complexing agent for these elements probably chloride for pb zn tl bi and probably hydroxy for mo w the occurrence of a silicothermal component in these fluids may furthermore favor the metal transport of these solutions this is probably a major previously underestimated process in the enrichment of some metals in magmatic hydrothermal systems this hypothesis may challenge conventional ideas on fluid phase mass transport of components by means of magmatic hydrothermal fluids and should be taken into account in future works on these topics

the last glacial cycle from the humid tropics of northeastern australia comparison of a terrestrial and a marine record a detailed pollen record from the ocean drilling program site 820 core located on the upper part of the continental slope off the coast of northeast queensland was constructed to compare with the existing pollen record from lynch s crater on the adjacent atherton tableland and allow the production of a regional picture of vegetation and environmental change through the last glacial cycle some broad similarities in patterns of vegetation change are revealed despite the differences between sites and their pollen catchments which can be related largely to global climate and sea level changes the original estimated time scale of the lynch s crater record is largely confirmed from comparison with the more thoroughly dated odp record conversely the lynch s crater pollen record has assisted in dating problematic parts of the odp record in contrast to lynch s crater which reveals a sharp and sustained reduction in drier araucarian forest around 38 000 yrs bp considered to have been the result of burning by aboriginal people the odp record indicates most likely a stepwise reduction dating from 140 000 yrs bp or beyond the earliest reduction shows lack of a clear connection between araucaria decline and increased burning and suggests that people may not have been involved at this stage however a further decline in araucarian forest possibly around 45 000 yrs bp which has a more substantial environmental impact and is not related to a time of major climate change is likely at least partially the result of human burning the suggestion from the odp core oxygen isotope record of a regional sea surface temperature increase of around 4 degrees c between about 400 000 and 250 000 yrs bp may have had some influence on the overall decline in araucaria and its replacement by sclerophyll vegetation c 2000 elsevier science b v all rights reserved

fluid evolution and ore genesis of the dalingshang deposit dahutang w cu ore field northern jiangxi province south china the dalingshang w cu deposit is located in the north section of the dahutang ore field northern jiangxi province south china vein and breccia style tungsten copper mineralization is genetically associated with mesozoic s type granitic rocks infrared and conventional microthermometric studies of both gangue and ore minerals show that the homogenization temperatures for primary fluid inclusions in wolframite 340 c are similar to those in scheelite 330 c but about 40 c higher than those of apatite 300 c and generally 70 c higher than those in coexisting quartz 270 c laser raman analysis identifies ch4 and n2 without co2 in fluid inclusions in scheelite and coexisting quartz while fluid inclusions in quartz of the sulfide stage have variable co2 content the ore forming fluids overall are characterized by high to medium temperature low salinity ch4 n2 and or co2 bearing aqueous fluids chalcopyrite muscovite and sphalerite are the most abundant solids recognized in fluid inclusions from different ores the h o s pb isotope compositions favor a dominantly magmatic origin for ores and fluids while some depleted 34s values 14 4 to 0 9 of sulfides from the sulfide stage are most likely produced by an increase of oxygen fugacity possibly caused by inflow of oxidized meteoric waters the microthermometric data also indicate that a simple cooling process formed early scheelite and wolframite however increasing involvement of meteoric waters and fluid mixing may trigger a successive deposition of base metal sulfides fluid rock interaction was critical for scheelite mineralization as indicated by in situ la icp ms analysis of trace elements in scheelite

can economic porphyry copper mineralization be generated by a typical calc alkaline melt numerical simulation of chlorine and copper partitioning between a crystallizing melt and exsolving aqueous fluids indicates that typical calc alkaline magmas contain sufficient copper chlorine and water to produce economic porphyry copper mineralization neither an elevated copper content in the magma nor an additional large volume of magma are required to provide metals or volatiles the most important variables that determine the volume of melt necessary to produce sufficient copper are the degree of compatible behavior displayed by copper the ratio of initial water in the melt to the water saturation level and the initial chlorine water ratio of the melt the absolute values for initial water in the melt and water content at saturation are relatively unimportant in determining the required melt volume the bulk salinity of the exsolved fluid may vary from 2 0 wt nacl to saturation levels 84 wt nacl at 700 c indicating that boiling is not necessary to produce high salinity brines at appropriate p t xnacl conditions the magmatic aqueous fluid separates into a saline liquid which transports most of the copper and a low salinity vapor the salinities of the two immiscible phases are governed by the p t conditions while the bulk fluid salinity determines the mass fractions of liquid and vapor formed pressure quenching causes rapid crystallization of the aplitic groundmass in porphyritic rocks associated with copper mineralization and significantly reduces the amount of chlorine and copper partitioning to the aqueous fluid this results in abrupt and possibly large reductions in fluid salinity and causes copper to become concentrated in the melt as copper is transported from the melt by the earliest exsolving fluids in deep 2 0 kbar systems and by late exsolving fluids in shallow 0 5 kbar systems the relative timing of pressure quenching aplite formation and fluid transport of copper from the melt can vary significantly in systems produced under different confining pressures model results incorporating petrologic constraints determined for yerington nevada are in good agreement with observed mineralization