the direction of fluid flow during contact metamorphism of siliceous carbonate rocks new data for the monzoni and predazzo aureoles northern italy and a global review periclase formed in siliceous dolomitic marbles during contact metamorphism in the monzoni and predazzo aureoles the dolomites northern italy by infiltration of the carbonate rocks by chemically reactive h2o rich fluids at 500 bar and 565 710 c the spatial distribution of periclase and oxygen isotope compositions is consistent with reactive fluid flow that was primarily vertical and upward in both aureoles with time integrated flux 5 000 and 300 mol fluid cm2 rock in the monzoni and predazzo aureoles respectively the new results for monzoni and predazzo are considered along with published studies of 13 other aureoles to draw general conclusions about the direction amount and controls on the geometry of reactive fluid flow during contact metamorphism of siliceous carbonate rocks flow in 12 aureoles was primarily vertically upward with and without a horizontal component directed away from the pluton fluid flow in two of the other three was primarily horizontal directed from the pluton into the aureole the direction of flow in the remaining aureole is uncertain earlier suggestions that fluid flow is often horizontal directed toward the pluton are likely explained by an erroneous assumption that widespread coexisting mineral reactants and products represent arrested prograde decarbonation reactions with the exception of three samples from one aureole time integrated fluid flux was in the range 102 104 mol cm2 both the amount and direction of fluid flow are consistent with hydrodynamic models of contact metamorphism the orientation of bedding and lithologic contacts appears to be the principal control over whether fluid flow was either primarily vertical or horizontal other pre metamorphic structures including dikes faults fold hinges and fracture zones served to channel fluid flow as well

searching for eustasy in deglacial sea level histories abstract perturbations to the earth s gravity field and solid surface associated with glacial isostatic adjustment gia cause the total observable sea level change to depart from the eustatic curve which is defined as a spatially uniform height shift of the ocean surface to accommodate any mass gained lost from grounded ice in this study we apply a state of the art model of gia induced sea level change to quantify the magnitude and spatial form of this departure at the global scale for a range of model parameters with an aim to identify regions that are well suited to obtain accurate and precise estimates of eustatic sea level and therefore past grounded ice volume in general our results indicate that eustatic sea level is not a directly measurable quantity and so must be estimated by subtracting a model derived estimate of non eustatic contributions from observations in this regard we use our results to isolate regions where this procedure can be applied with optimal accuracy and precision that is where 1 the gia predictions are relatively insensitive to plausible ranges in input parameters and 2 where the non eustatic contribution is small i e the predicted sea level closely approximates the eustatic value we present maps that can be employed by the field community to identify areas where sea level reconstructions would be well suited to arrive at robust estimates of eustatic sea level note that sea level changes associated with tectonic motion and changes in ocean water temperature salinity which also lead to departures from eustasy are not considered in this analysis

identifying the causes of sea level change global mean sea level change has increased from a few centimetres per century over recent millennia to a few tens of centimetres per century in recent decades a review of the latest work shows that global mean sea level rise is unlikely to exceed one metre over the twenty first century but regional departures from this global mean could reach several decimetres

carbonate hosted talc deposits in the contact aureole of an igneous intrusion hwanggangri mineralized zone south korea geochemistry phase relationships and stable isotope studies many talc deposits occur in the hwanggangri mineralized zone hmz in dolomitic marbles of the cambro ordovician samtaesan formation within 1 km of the contact with the cretaceous muamsa granite talc commonly forms fine grained fibrous aggregates or pseudomorphs after tremolite abundant tremolite is included as impurities in the talc ore talc generally was derived from tremolite in calc silicate rock within the dolomitic marble calc silicate rock consisting mainly of tremolite and diopside was generated from silicic metasomatism during the prograde stage which promoted decarbonation reactions until dolomite was exhausted locally hydrothermal alteration of calc silicate rock to talc is marked by the addition of mg and si and the leaching of ca cr co and ni were relatively immobile during the retrograde stage contact metamorphism related to the granite intrusion generated the successive appearance of tremolite diopside and forsterite or wollastonite bearing assemblages in the marble depending on the bulk rock composition the xco2 content of the metamorphic fluids rose initially above xco2 0 6 and decreased steadily toward a water rich composition with increasing temperature above 600 c in the calcitic marble while buffered reaction of the dolomitic marble occurred at higher xco2 conditions above 600 c talc mineralization developed under metastable conditions with infiltration of large amounts of igneous fluids along a fault shattered zone during the retrograde stage and is characterized by the loss of ca2 with the addition of mg2 oxygen and carbon isotopic variations of carbonate and calc silicate minerals are in agreement with theoretical relationships determined for decarbonation products of contact metamorphism talc formation temperatures obtained from oxygen isotope fractionation t xco2 relationships and activity diagrams range from 380 to 400 c

crustal tilting derived from holocene sea level observations along the east coast of hokkaido in japan and upper mantle rheology late holocene sea level observations at sites along the east coast of hokkaido in japan indicate a gradual decrease of the altitude of relative sea level eastward toward the tip of nemuro peninsula these observations in seismically active areas can be explained by glaciohydroisostatic adjustment due to the last deglaciation for an earth model with a thin lithosphere of 30 40 km thickness and with no low viscosity layer or with a 25 km lithosphere overlying a low viscosity layer less than 50 km although more data as a function of time are needed to distinguish these models thus the vertical crustal displacement associated with the subduction of the pacific plate seems to has not been cumulated on a time scale of 103 104 years

mantle dynamics postglacial rebound and the radial viscosity profile abstract we infer the radial viscosity structure of the earth s mantle from observations of long wavelength geoid glacially induced sea level changes and changes in the earth s rotation and gravitational field we employ a combination of forward and formal inverse modeling of long term mantle circulation driven by large scale density differences deduced from seismic tomography based on the resulting unscaled mantle viscosity profiles we model the time dependent glacial isostatic adjustment of the earth related to past and present changes in the ice ocean mass imbalance and we deduce scaled mantle viscosity profiles which simultaneously fit the long wavelength geoid constraint and glacially induced changes of the earth s shape three mantle viscosity profiles are fitting the observational data equally well all profiles are characterized by a two order of magnitude variation of viscosity within the earth s mantle variations of viscosity in the upper mantle are less than one order of magnitude in the lower mantle the viscosity differs significantly with depth for all models average viscosities in the upper and lower mantle are around 2 5 1020 and 1 3 1022 pa s respectively

evidence for smoothly falling sea level relative to north queensland australia during the past 6 000 yr post glacial sea level curves are expected to differ between different parts of the world as a result of global isostatic changes1 or perhaps other forms of geoidal changes2 i report here results from the inner part of the northern great barrier reef which seem to show a pattern of smoothly falling sea level during the past 6 000 yr the results are consistent with stratigraphical results from prograded mangrove coasts on the nearby north queensland mainland the region is remote from the tectonically active margin of the south west pacific ocean and the results contribute to the global data set relevant to isostatic changes being assembled by the international sea level project igcp project no 61 they also provide a baseline relevant to holocene coral reef growth in the inner great barrier reef

late pleistocene and holocene sea level change along the australian coast abstract tectonically the australian continent is relatively stable and as such it provides a good platform for studying late pleistocene and holocene sea level change the observations indicate that present sea level was reached at about 6000 years ago and that since then level has remained constant to within a few metres considerable spatial variability in the amplitude of the emergence and in the time at which sea levels first reached their present values have been observed spatial variability has also been observed in the sea level during the last glacial maximum and during the late phase of the holocene transgression much of this variaiblity is the result of the earth s adjustment to the glacial melting in the late pleistocene early holocene time and the concomitant distribution of this meltwater into the oceans conclusions that are drawn from matching observations with this glacio hydro isostatic model include the following 1 the mantle viscosity increases with depth the average upper mantle viscosity is about 2 3 10 20 pa s and the average lower mantle defined as below 670 km depth viscosity is about 10 22 pa s the average lithospheric thickness for the coastal and offshore region is about 70 80 km lateral variations in these mantle parameters are indicated 2 the addition of melwater into the oceans did not cease 6000 years ago but continued at a reduced rate up to more recent times adding an amount of water equivalent to a 3 m sea level rise in this interval 3 the amplitude of the holocene emergence is a function inter alia of coastal geometry and significant variations occur over distances of a few hundred kilometres and more holocene highstands of 1 2 m are generally well developed at the continental margins but are less well developed or do not developed at all at offshore islands and reefs 4 variations in the time of maximum emergence also occur being earlier at upstream tidal river sites than at coastal sites at offshore reefs or islands the sea level curve lags the coastal curves by 1000 years or more 5 considerable spatial variability occurs in the sea levels at the time of the last glacial maximum with variations of up to 30 m occurring across the continental shelves 6 there is generally no need to invoke tectonic movements to explain the sea level data along the australian coast but possible exceptions occur for the perth region and for tasmania

on the origin of late holocene sea level highstands within equatorial ocean basins abstract late holocene sea level highstands of amplitude 3 m are endemic to equatorial ocean basins these highstands imply an ongoing and moderate sub mm yr sea level fall in the far field of the late pleistocene ice cover that has long been linked to the process of glacial isostatic adjustment gia clark et al 1978 mitrovica and peltier 1991 coined the term equatorial ocean syphoning to describe the gia induced sea level fall and they provided the first physical explanation for the process they argued that water migrated away from far field equatorial ocean basins in order to fill space vacated by collapsing forebulges at the periphery of previously glaciated regions we provide a complete physical explanation for the origin of equatorial ocean syphoning and the associated development of sea level highstands using numerical solutions of the equation that governs meltwater redistribution on spherical viscoelastic earth models in particular we separate the total predicted sea level change into contributions associated with ice and meltwater loading effects and by doing so isolate a second mechanism that contributes significantly to the ocean syphoning process ocean loading at continental margins induces a levering of continents and a subsidence of offshore regions that has also long been recognized within the gia literature walcott 1972 we show that the influx of water into the volume created by this subsidence produces a sea level fall at locations distant from these margins indeed over the major ocean basins that is comparable in amplitude to the syphoning mechanism isolated by mitrovica and peltier 1991

holocene sea level change and hydro isostasy along the west coast of kyushu japan abstract mid to late holocene sea level variations have been obtained at sites along the west coast of kyushu japan sea level observations for this relatively stable area are very important for evaluating the crustal tilting associated with the hydro isostatic adjustment due to the last deglaciation and for examining the cause of underwater jomon sites submerged archeological sites during the jomon period of mid holocene typically observed in this region for these purposes we conducted systematic boring samplings at sites from goto island to tamana along the latitude of about 33 n then we performed diatom assemblage and pyrite sulfur analyses of these sediment samples and 14 c datings for intertidal shells in order to get the sea level variations for these sites observations at tsumizu faced to oomura bay with tidal range of 0 9 m show a sea level high stand of 1 m at about 5500 yr b p years before present followed by smoothly falling to the present level evidences for sea level oscillation of greater than 50 cm have not been found here relative sea levels at about 5000 yr b p are however 2 m at goto island 125 km west of tsumizu and 2 m at tamana 50 km east of tsumizu thus observations at sites along the traverse from goto island to tamana are indicative of crustal tilting of about 3 4 m for the distance of 175 km which seems to be consistent with the prediction caused by the hydro isostatic adjustment

high temperature contact metamorphism of calc silicate xenoliths in the kiglapait intrusion labrador calc silicate xenoliths occur as part of a xenolith and autolith swarm in the lower zone of the kiglapait intrusion labrador all xenoliths are lighter colored than the local troctolite host rock and are surrounded by a 1 2 cm thick reaction zone of clinopyroxenite the typical mineral assemblage in calc silicate xenoliths is diopside forsterite monticellite spinel and one also contains akermanite reaction zones are dominated by diopside and spinel all clinopyroxene compositions are fassaitic with high concentrations of al 2 o 3 4 12 wt tio 2 1 4 wt and calculated fe 2 o 3 fe 3 fe 2 in addition clinopyroxene grains locally display extreme zoning in si al ti and x mg akermanite contains up to 1 5 wt na 2 o textures in the xenoliths are complex with most containing highly irregular intergrowths of diopside forsterite and monticellite akermanite and forsterite are separated locally by a coarse symplectic intergrowth of diopside and monticellite which resulted from a retrograde reaction the dominant assemblage probably represents the production of monticellite from calcite clinopyroxene forsterite until calcite was consumed these reactions require metamorphic temperatures of 900 c and pressures 0 4 kbar such that the xenoliths were probably derived from the roof of the magma chamber whole rock compositions reflect either substantial chemical exchange with the kiglapait magma or a very impure dolomitic protolith the clinopyroxenite reaction zones were produced primarily by assimilation of carbonate by the kiglapait magma in combination with the effects of magma undercooling near the xenoliths

water load definition in the glacio hydro isostatic sea level equation abstract models of glacio hydro isostatic rebound and the concomitant sea level change have been progressively improved over the past three decades recently the procedures used by the group at the australian national university anu for the hydro isostatic component of the theory have been questioned quat sci rev 21 2002 409 although the details of the anu group s procedures have not been published because they are mainly computational in nature rather than representing significant conceptual advances because of this criticism we set out here in detail the procedures that have been used for the treatment of the migration of shorelines as sea levels rise and fall the effect of retreat and advancing grounded ice on shelves and shallow seas and the transitions from grounded to floating ice and vice versa we conclude that there is no basis for the criticism that these formulations and their implementation provide a high resolution and complete description of both sea level change and of the estimates of volumes of ice exchanged with the oceans the results from this formulation are confirmed by the entirely independent analyses of milne et al quat sci rev 21 2002 361 and mitrovica and milne geophys j int 2002 submitted for publication who conclude that our formulation is significantly more accurate than the procedure advocated by peltier science 265 1994 195 rev geophys 36 1998a 603 geophys res lett 25 1998b 3955

regional metamorphism of the vassalboro formation south central maine usa a case study of the role of fluid in metamorphic petrogenesis progressively metamorphosed carbonate rocks of the vassalboro formation serve a natural laboratory for the investigation of fluid rock interactions during metamorphism an integrated study of their whole rock chemistry mineralogy mineral chemistry and mineral abundances has led to the following results a prograde mineral reactions involved hydrolysis as well as dehydration and decarbonation the hydrolysis reactions have resulted in an almost quantitative extraction of k and na from high grade metacarbonates b prograde mineral reactions buffered the x co 2 of coexisting metamorphic fluid during almost all of the rocks metamorphic history c the carbonate rocks were infiltrated by large volumes of h 2 o rich fluid while the buffering reactions progressed during the metamorphic event some high grade metacarbonates were infiltrated by at least 3 rock volumes of fluid combined buffering and infiltration appears to be a general metamorphic phenomenon in carbonate bearing rocks to depths of 30 km in the crust d there is an excellent positive correlation between the heat budget of individual metacarbonate rock samples and calculated fluid rock ratios convective heat transfer by metamorphic fluids is therefore likely to be an important item in the heat budget of metamorphic terrains consideration of these results leads to a model of regional metamorphism which involves infiltration of rock by large volumes of acid h 2 o rich fluid large scale acid infiltration metasomatism in this model the infiltrating fluid exerts enormous control over the mineralogical evolution of the carbonate rocks during the metamorphic event it drives mineral reactions it changes whole rock chemistry and it supplies heat

on eustatic sea level history last glacial maximum to holocene abstract this paper addresses the question of the magnitude and time dependence of the globally averaged eustatic rise of sea level that occurred subsequent to the time of last glacial maximum lgm at approximately 21 000 calendar years before present through the analysis of relative sea level rsl histories predicted by a realistic mass conserving and gravitationally self consistent theory of postglacial sea level change it is demonstrated that there are preferred oceanic locations at which this eustatic function is well approximated by local sea level history one such location is the island of barbados in the caribbean sea a site from which a coral based record exists that extends from mid holocene to lgm because of the sea level ambiguity that is inherent to coral based records however it is important that the global ice equivalent eustatic sea level curve inferred on the basis of the barbados data be tested against observations at other locations from which similarly extensive records are also available but which are derived on the basis of sea level indicators which are not subject to the ambiguities inherent to corals it is shown that when the eustatic function employed in the global theoretical model is tuned so as to enable the model to fit the barbados observations where the maximum relative sea level rsl depression is assumed to be near 120 m then the theory misfits the record from the sunda shelf in the indonesian archipelago as well as the record from j bonaparte gulf in northern australia both of these recently published records appear to constrain the lgm low stand of rsl to a value above 120 m the implications of these results for interpretation of the long coral derived records from the huon peninsula of papua new guinea and the island of tahiti are also discussed

glacial rebound and relative sea level variations a new appraisal summary late pleistocene and holocene changes in sea level at technically stable shorelines contain information on the melting history of the ice sheets and on the response of the earth to changes in surface loads on time scales of 104yr some separation of parameters defining the ice loads and the earth s response can be achieved by examining sea level change at different sites around the world and at different epochs this paper examines the mathematical requirements for obtaining satisfactory solutions for the sea level equation rather than emphasizing results for the earth s response to the surface loads an examination of the equation expressing the sea level variation on a viscoelastic earth indicates that careful consideration needs to be given to both the definition of the ice load and the geometry of the redistributed water load if geophysically significant earth response parameters are to be deduced from observations of relative sea level the spectrum of the 5 x 5 area mean description of the ice load widely used in glacial rebound studies contains significant power at high degrees n 30 and can result in substantial spatial variations in sea level unless a thick lithosphere is introduced in the earth s response function a smoothed 1 1 description of the ice model avoids these high degree oscillations in relative sea level and produces satisfactory sea level results without requiring a thick lithosphere at far field sites the holocene sea levels are sensitive to the earth s response to the meltwater loading in the vicinity of the site and a high degree spatial resolution of coastline geometry is required to model the mantle flow driven by the differential loading about the site at some sites convergence of the solution to the sea level equation is not obtained even when the solution is expanded to degree 180 convergent solutions at lower degrees can be achieved by introducing earth models with a moderately thick lithosphere if high resolution ice and meltwater load models are not used then the tendency will be to overestimate the effective elastic thickness of the lithosphere estimates of mantle viscosity are also of questionable value if these high resolution models are not used a preliminary examination of sea levels at sites in both the near and far field places an upper limit of about 50 80 km on the effective lithospheric thickness these sea level observations are also consistent with an upper mantle viscosity of about 1021 pas with a lower mantle viscosity in the range of 1021 1023pa s

rapid early holocene deglaciation of the laurentide ice sheet the demise of the laurentide ice sheet during the early holocene epoch is the most recent and best constrained disappearance of a large ice sheet in the northern hemisphere and thus allows an assessment of rates of ice sheet decay as well as attendant contributions to sea level rise here we use terrestrial and marine records of the deglaciation to identify two periods of rapid melting during the final demise of the laurentide ice sheet when melting ice contributed about 1 3 and 0 7cm of sea level rise per year respectively our simulations with a fully coupled ocean atmosphere model suggest that increased ablation due to enhanced early holocene boreal summer insolation was the predominant cause of laurentide ice sheet retreat although the surface radiative forcing in boreal summer during the early holocene is twice as large as the greenhouse gas forcing expected by the year 2100 the associated increase in summer surface air temperatures is very similar we conclude that our geologic evidence for a rapid retreat of the laurentide ice sheet may therefore describe a prehistoric precedent for mass balance changes of the greenland ice sheet over the coming century

formation and destruction of periclase by fluid flow in two contact aureoles periclase formed in steeply dipping marbles from the beinn an dubhaich aureole scotland and the silver star aureole montana by the reaction dolomite periclase calcite co2 equilibrium between rock and fluids with x co 2 1 requires that reaction was infiltration driven brucite pseudomorphs after periclase occur in the beinn an dubhaich aureole either as bed by bed replacement of dolomite or in a lens along the contact between dolomite and a pre metamorphic dike transport theory predicts that infiltration drove both periclase reaction and 18o depletion fronts which moved at significantly different velocities along the flow path the distributions of brucite and 18o depleted rocks are identical in surface exposures thus indicating upward flow time integrated flux q was 500 mol cm2 and the fluid source was magmatic because periclase and its hydrated equivalent brucite are unaltered to dolomite by retrograde reactions the exposure of brucite marbles accurately images the flow paths of peak metamorphic fluids in the silver star aureole brucite pseudomorphs after periclase exclusively occur in tabular bodies that are beds with elevated mg ca the spatial pattern of 18o depletion requires upward vertical fluid flow estimated prograde q 103 104 mol cm2 and the fluid source was magmatic low mg ca 18o depleted brucite free rocks pose a dilemma because the periclase reaction front should have traveled 18 times further through them than the isotope alteration front the dilemma is resolved by reaction textures that indicate periclase and brucite were destroyed in low mg ca rocks by infiltration driven retrograde carbonation reactions values of retrograde q were 103 104 mol cm2 brucite after periclase was preserved only in high mg ca layers where periclase developed in greater abundance the geometry of brucite marbles at silver star thus reflects the location of high mg ca beds rather than the geometry of fluid flow retrograde reactions must be considered before the mineralogical record of prograde fluid flow can correctly be interpreted in both aureoles fluid flow mineral reaction and isotope depletion were structurally controlled by bedding and lithologic contacts

sea level changes since the last glacial maximum an appraisal of the ipcc fourth assessment report the ipcc fourth assessment report ar4 stated that global sea level rose by about 120 m between the last glacial maximum lgm and 3 2 ka and did not rise again until the late 19th century a review of relevant literature demonstrates that the rise may have been larger by 10 15 m that the timing of stabilisation is poorly constrained within the last 7 ka bp and that the onset of modern rates of sea level rise is not synchronous and uniform across the globe the lgm lowstand as defined in the ar4 is based on the classic barbados sea level history but the sea level curve from this island may not be an accurate eustatic approximation if glacial isostatic adjustment gia processes were significant as suggested by various authors the barbados sea level curve revealed the existence of meltwater pulse mwp 1a at around 14 000 cal a bp questions about the source and causal mechanism of mwp 1a are still being explored by field scientists and gia modellers these problems have direct relevance for contemporary measurements of ice mass changes because space geodetic measurements rely on information provided by gia models to separate land motion from ice mass changes global patterns of holocene sea level change are controlled by regional sea level variability not only through isostatic and tectonic processes but also through steric effects longer wavelength gravitational changes produced by changing ice ocean mass flux and hemispheric scale perturbations in the earth s rotation eustasy is therefore merely a concept not a measurable quantity constraining the late holocene ice melt contribution to global sea level rise and determining regional sea level rise patterns in the 18th and 19th centuries are important future tasks for sea level scientists these will establish the baseline contributions to 20th and 21st century sea level rise and will help to determine the causes of modern rates of sea level rise constraining historical sea level accelerations and short term ice mass flux will aid models of ice sheet dynamics and help to reduce current uncertainties in future sea level predictions the ar4 shows that regional sea level variability is clearly present in sea level change patterns for the past 50 a and an important challenge for the next ipcc assessment is to incorporate this variability into regional future sea level rise scenarios copyright 2009 john wiley sons ltd

dynamics of 30 large channel bars in the lower mississippi river in response to river engineering from 1985 to 2015 abstract channel bars are a major depositional feature in alluvial rivers and their morphodynamics has been investigated intensively in the past several decades however relatively less is known about how channel bars in alluvial rivers respond to river engineering and regulations in this study we assessed 30 yr morphologic changes of 30 large emerged bars located in a 223 km reach of the highly regulated lower mississippi river from vicksburg mississippi to the mississippi atchafalaya river diversion landsat imagery and river stage data between 1985 and 2015 were utilized to characterize bar morphologic features and quantify decadal changes based on bar surface areas estimated with the satellite images at different river stages a rating curve was developed for each of the 30 bars to determine their volumes results from this study show that the highly regulated river reach favored the growth of mid channel and attached bars while more than half of the point bars showed degradation currently the mid channel and attached bars accounted for 38 and 34 of the total volume of the 30 bars the average volume of a single mid channel bar is over two times that of an attached bar and over four times that of a point bar overall in the past three decades the total volume of the studied 30 bars increased by 110 118 000 m 3 41 total dike length in a dike field was found mostly contributing to the bar volume increase currently the emerged volume of the 30 bars was estimated approximately 378 183 000 m 3 the total bar volume is equivalent to 530 million metric tons of coarse sand based on an average measured bulk density of 1 4 t m 3 for the bar sediment the findings show that these bars are large sediment reservoirs

boron metasomatism of the alta stock contact aureole utah evidence from borates mineral chemistry and geochemistry geochemical study of the alta stock and adjacent contact aureole rocks provides information concerning the source composition and physical chemical conditions of infiltrating fluids special emphasis was given to boron b as a tracer of fluid rock interactions due to the occurrence of borate minerals ludwigite kotoite and szaibelyite in skarn deposits around the stock in addition thin section alpha track mapping implies significant b enrichments in fluid altered minerals within the stock stockwork veins and related selvages igneous sills near the stock contact skarns and in marbles up to 500 m from the stock forsterite clinohumite lizardite and malachite contain between 50 and 1200 ppm b diopside calcite clintonite phlogopite brucite hedenbergite tremolite and other minerals host b to a lesser extent aureole b enrichments correlate well with major and other trace element enrichments and support existing models of element transport in magmatic fluids with lateral down temperature flow large variations in mineral b concentrations reflect changes in b concentrations of these fluids through time mass balance calculations indicate that magmatic fluids emanating from the alta pluton could supply most b in the alta aureole it is estimated that the emplaced magma had an initial b concentration between 7 10 ppm indicated exhalative losses of b from the pluton are on the order of 50 we estimate that the exsolved fluids had a time integrated b concentration of 160 40 ppm although much higher concentrations may have attended local borate mineralization

ice 3g a new global model of late pleistocene deglaciation based upon geophysical predictions of post glacial relative sea level change a new high resolution global model of late pleistocene deglaciation is inferred on the basis of geophysical predictions of postglacial relative sea level variations in which the ice ocean solid earth interaction is treated in a gravitationally self consistent fashion for the purpose of these analyses the radial viscoelastic structure of the planet is assumed known on the basis of previously published sensitivity tests on solutions of the forward problem only radiocarbon controlled relative sea level histories from sites that were actually ice covered with one or two additions are employed to constrain the model leaving relative sea level rsl data from sites that were not ice covered to be employed to confirm its consistency results for these confirmatory analyses are reported elsewhere here the new deglaciation model referred to as ice 3g is compared to previous models derived by several independent means and tested against a number of additional observations other than sea level histories including geologically controlled retreat isochrones oxygen isotope data from deep sea sedimentary cores and coral terrace elevations the latter two observations strongly constrain the net sea level rise that has occurred since the onset of deglaciation and therefore the mass of ice that melted during the last glacial interglacial transition

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

fenitization at the alno carbonatite complex sweden distribution mineralogy and genesis re mapping of the alno complex has radically reduced the area identified as fenite in comparison with the classic work of eckermann 1948 a marginal fenite zone generally 500 600 m wide is present around the complex and the petrography and mineralogy of six selected key areas have been investigated in detail fenitization of the country rock migmatitic gneiss led to replacement of quartz feldspars biotite and chlorite by alkali pyroxene and amphibole new generations of feldspars calcite titanite fluorite and apatite in some areas however a distinctive narrow band of fenitization referred to as contact fenite adjacent to large sovite dykes contains mineral assemblages that include phlogopite nepheline melanite and wollastonite amphiboles in the fenites are richterite katophorite arfvedsonite and eckermannite there is a very wide variation in the composition of pyroxenes which vary between diopside aergirine augite and aergirine although trends from aergirine to aegirine augite and aegirine augite to diopside have been defined which are similar to those of other fenite localities distinctive trends for the eastern part of the aureole have been identified that converge on aegirine and approximate trends in some series of alkaline igneous rocks analyses of mica garnet wollastonite and feldspar are also presented and discussed the mineralogical data are used to estimate the conditions of temperature oxidation state and activity of co2 h2o and silica pertaining during the fenitization process the fluids with which the fenites equilibrated were apparently different in composition in different parts of the aureole and varied with time implying more than one magmatic source the various evolutionary trends identified in the pyroxenes and amphiboles in particular are explained in terms of two main fluid types which emanated from ijolitic and carbonatitic magma sources

far field test of the ice 4g model of global isostatic response to deglaciation using empirical and theoretical holocene sea level reconstructions for the fiji islands southwestern pacific holocene paleosea level data for fiji represented by 77 dates and emergence magnitudes are presented screened and adjusted most data are from coral microatolls potentially the most precise paleosea level indicators in this region holocene sea level changes are reconstructed for five areas within fiji known to have had different late quaternary tectonic histories resulting analysis suggests that postglacial sea level in fiji reached its present level more than 6900 14c yr b p it also suggests either that a single maximum 5650 3200 14c yr b p perhaps 2 19 m but more likely 1 35 1 50 m occurred or that two maxima occurred 6100 4550 14c yr b p 0 75 1 85 m and 3590 2800 14c yr b p 0 90 2 46 m broad agreement exists between these empirical sea level reconstructions and those derived theoretically using the ice 4g model predicted maximum 4000 14c yr b p 2 1 m this suggests that both methods of reconstructing holocene sea level changes are valid as are the assumptions underpinning the ice 4g model the most important of these that eustatic sea level had effectively stopped rising by late middle holocene time 5000 4000 yr b p is confirmed by observations from fiji

ijolite versus carbonatite as sources of fenitization ijolite carbonatite complexes are ubiquitously surrounded of an aureole of metasomatically altered rocks the process of alteration is termed fenitization and is generally caused by peralkaline fluids emanating from cooling alkaline i e ijolite and carbonatite magmas ijolites and carbonatites normally occur together and attempts to determine the source of the fenitizing fluids may therefore lead to controversial if not erroneous conclusions mineralogical and chemical data of fenites from oldoinyo lengai tanzania fen norway and alno sweden are reviewed in the present paper in order to reveal the main factors controlling the fenitization around ijolite and carbonatite despite the overall alkaline nature of the process variables such as xco2 of the fluid activity gradients of sio2 al2o3 and cao feo mgo ratio fo2 and temperature gradients may differ producing distinctive patterns of fenitization around the two magmatic sources the ijolitic type fluid has low xco2 high activities of alkalies sio2 and al2o3 and low activity of cao the fo2 evolves along the hm mt buffer conditions and the temperature falls gradually with distance from the magmatic source the carbonatitic type fluid has high xco2 high activities of alkalies and cao and low activities of sio2 and al2o3 temperatures and fo2 are initially high but decrease sharply with distance from the source moreover the co2 rich fluid may complex and transport the ree

metamorphic degassing of carbonates in the contact aureole of the aguablanca cu ni pge deposit spain analysis of magmatic and sedimentary rocks of several large igneous provinces has demonstrated that the release of gas during plutonic metamorphic processes may be linked to global climate change and mass extinctions aguablanca one of the largest cu ni pge deposits in europe formed during the variscan orogeny when a mafic magma intruded limestones and shales creating a contact aureole composed of marble skarn and hornfels our petrological and geochemical investigation of the aureole provides evidence that a combination of the two processes led to the formation of the ore deposit the assimilation of terrigenous sediments supplied s to the magma while the assimilation of carbonates changed the oxygen fugacity and decreased the solubility of sulfur in the magma the metamorphic assemblages in the contact aureole are directly related to heterogeneity of the protolith and particularly to the original proportions of calcite and clay we modeled carbon dioxide degassing during contact metamorphism and showed that pure limestone is relatively unproductive because of its high reaction temperature the presence of clay however leads to the formation of calc silicates and significantly enhances co2 degassing our estimations suggest that degassing of the aguablanca contact aureole released about 74 8 mt of co2 a relatively low volume that we attribute to the composition of the host rock mainly a pure limestone a far larger volume of carbon dioxide was emitted by the contact metamorphism of dolostones in the contact aureole of panzhihua part of emeishan large igneous province sw china we propose that the level of emission of carbon dioxide depends strongly on the nature of the protolith and has to be considered when predicting environmental impact during the emplacement of large igneous provinces

on postglacial sea level summary an exact method is presented for calculating the changes in sea level that occur when ice and water masses are rearranged on the surface of elastic and viscoelastic non rotating earth models the method is used to calculate the instantaneous elastic and delayed vi scoelastic sea level changes following the partial melting of late quaternary ice sheets we find that there can be large errors in the usual assumption that changes in sea level are uniform over the ocean basins if a quantity of ice equivalent to a uniform 100 m rise in sea level melts from the laurentide and fennoscandian ice sheets then in the south pacific the instantaneous rise in sea level can be as large as 120m in the north atlantic the instantaneous rise is always less than 100 m there is a zone in the north atlantic with almost no sea level change and near greenland and norway the sea level falls rather than rises by over 100 m one thousand years after the melting a forebulge migrating towards the ice loads causes water to flow from the south pacific into the north pacific suggesting that raised beaches should occur in the south pacific the gravitational attraction of an ice mass upon a nearby ocean tends to hold sea level high in the vicinity of the ice this extra load near the ice may have a significant influence on postglacial isostatic adjustment

timing of the last glacial maximum from observed sea level minima during the last glacial maximum ice sheets covered large areas in northern latitudes and global temperatures were significantly lower than today but few direct estimates exist of the volume of the ice sheets or the timing and rates of change during their advance and retreat here we analyze four distinct sediment facies in the shallow tectonically stable bonaparte gulf australia each of which is characteristic of a distinct range in sea level to estimate the maximum volume of land based ice during the last glaciation and the timing of the initial melting phase we use faunal assemblages and preservation status of the sediments to distinguish open marine shallow marine marginal marine and brackish conditions and estimate the timing and the mass of the ice sheets using radiocarbon dating and glacio hydroisostatic modelling our results indicate that from at least 22 000 to 19 000 calendar years before present land based ice volume was at its maximum exceeding today s grounded ice sheets by 52 5 x 10 exp 6 cu km a rapid decrease in ice volume by about 10 percent within a few hundred years terminated the last glacial maximum at 19 000 250 years

fenitization at the fen complex southern norway abstract fenitization in three areas within the fenite aureole surrounding the fen complex is described in terms of petrography and mineral chemistry significant differences in fenite parageneses between the areas investigated suggest that fenitizing fluids emanating from different source rocks have been responsible for fenitization in the melteig area magnesio arfvedsonite quartz form the characteristic paragenesis the fenitizing fluids must have had low x co 2 high a sio 2 a na a k and a mg they have emanated from the nearby intrusions of melteigite and ijolite at holla riebeckite and ferro richterite are conspicuous the fenitizing fluids are characterized by high x co 2 low a sio 2 and high a na a ca and a fe their source rock would be the silico sovite of the area at ulefoss conditions similar to those at holla are pictured except for high a ca a k and a mg of the fenitizing fluids which most likely have emanated from the rather pure magnesian sovites piercing the fenites of the area

holocene sea level change and antarctic melting history derived from geological observations and geophysical modeling along the shimokita peninsula northern japan 1 a mid to late holocene sea level record based on combined geomorphological geological and micropaleontological observations was obtained from well developed wave cut benches subaerially exposed along the shimokita peninsula northern japan results indicate that the benches were formed during mid to late holocene sea level transgressions reaching a maximum highstand level of 2 m above present at about 4 000 years ago this timing corresponds to an abrupt order of magnitude decrease in sedimentation rate as recorded in a core recovered from proximal mutsu bay in addition glacio hydro isostatic adjustment due to crustal deformation in response to postglacial sea level rise was modeled and results are consistent with the reconstructed local 2 m highstand given that meltwater contributions from the major north american and european ice sheets had largely ceased by 7 000 years ago these independent lines of evidence taken together indicate that melting of the antarctic ice sheet ended by 4 000 years ago