age and cooling history of the manaslu granite implications for himalayan tectonics abstract the manaslu granite is one of the high himalayan leucogranites which are believed to be derived by partial melting of quartzofeldspathic gneissess of the high himalayan crystallines hhc and emplaced at the contact between the hhc and the tethyan sedimentary series we have analyzed a suite of muscovite 15 biotite 3 and alkali feldspar 10 by the 40 ar 39 ar method to help constrain the age and cooling history of the granite 40 ar 39 ar ages ranges are 18 4 to 13 3 ma 17 0 to 14 7 and 16 4 to 3 4 for muscovite biotite and k feldspar respectively based on the muscovite analyses and a re interpretation of a previously published u pb monazite age we conclude that the crystallization age of the manaslu granite is everywhere 20 ma the postcrystallization cooling history given by the micas and the feldspars suggests the presently exposed parts of the pluton were emplaced at depths of 8 to 15 km these data place a minimum age of movement on the mct in this area of 20 ma we estimate the time of magma segregation and transport to be no more than 5 ma

origin of rhythmic layering in the calamity peak satellite pluton of the harney peak granite south dakota the role of boron abstract the calamity peak satellite granite pluton on the flanks of the harney peak granite south dakota displays prominent mineral and textural layering the latter defined by alternating fine grained and pegmatitic granite superimposed on the fine grained granite layers is a fine scale 0 1 5 cm rhythmic layering defined by modal differences in tourmaline microcline albite and muscovite there is very little variation in the major element mineral compositions in the whole complex analyses by prompt gamma neutron activation gave a b2o3 content of 0 07 in the light layers albite quartz and muscovite and 0 65 in the dark layers tourmaline microcline quartz and albite these contents are essentially proportional to tourmaline abundance in each layer the textural and mineralogic layering is the result of the interplay of tourmaline crystallization and shifts in phase equilibria due to changes in b concentration in the melt initial cotectic crystallization of albite quartz and muscovite increased the activity of fe and mg in the adjacent melt to levels sufficient for tourmaline to form tourmaline crystallization depleted b and decreased the solubility of h2o in the melt causing exsolution of h2o from the melt and further removal of b due to high fluid melt partition coefficient this process also resulted in the precipitation of k feldspar partly at the expense of muscovite and partly due to a slight increase in the solidus temperature once the crystallization front moved to an fe and mg poor region of the melt tourmaline precipitation ceased and the equilibrium shifted back toward quartz muscovite and albite the pegmatitic layers some of which cut across previously formed rhythmic layers and commonly have tourmaline along their borders appear to have crystallized from melt enriched in the exsolved fluid phase

chemical characteristics of migmatites accessory phase distribution and evidence for fast melt segregation rates equilibration between melt and solid is inhibited by rapid melt extraction and by restricted equilibration armouring slow dissolution when segregation occurs by channelised migration along high porosity pathways melt migration is more rapid than trace element diffusion rates in silicates and faster than accessory phase dissolution rates evidence for channelised flow and deformation enhanced melt segregation into boudin necks fractures and micro shears at low melt fractions is present in the moine kirtomy migmatitie suite kms in sutherland scotland melt migration distances are on a metre to tens of metres scale concordant leucosomes in stromatic migmatities in the kms have low zr contents low lree light rare earth element and h heavy ree contents and positive eu anomalies ree patterns of this type can be produced by removal of leucosome before complete equilibration with source due to the inhibited dissolution of lree and hree bearing accessory phases in water undersaturated melts melting in the kms however occurred at or near the wet granite solidus leaving biotite as a residual phase detailed back scattered electron imaging shows that ree bearing accessory phases remained as residual phases and were concentrated in the melanosome and at the melanosome leucosome boundary irregularly shaped patches of diatexite contain a small proportion of excess zr consistent with entrainment of melanosome schlieren enriched in zircon these data indicate that deformation enhanced melt extraction led to the rapid migration of small melt fractions from the melting site on a time scale less than that required to saturate the melt in zr leucosomes were thus prevented from equilibrating with accessory phases before extraction

trace element modelling of pelite derived granites the presence or absence of a vapour phase during incongruent melt reactions of muscovite and biotite together with the composition of the protolith determines the trace element characteristics of the resulting melt provided that equilibrium melting occurs for those phases that host the tracc elements of interest for granitic melts rb sr and ba provide critical constraints on the conditions that prevailed during melting whereas ree are primarily controlled by accessory phase behaviour mass balance constraints for eutectic granites that are formed by the incongruent melting of muscovite in pelites indicate that melting in the presence of a vapour phase will result in a large melt fraction and deplete the restite in feldspar hence the melt will be characterized by low rb sr and high sr ba ratios in contrast vapour absent melting will result in a smaller melt fraction and an increase in the restitic feldspar consequently high rb sr and low sr ba ratios are predicted vapour absent melting will also enhance the negative eu anomaly in the melt granites that result from the incongruent melting of biotite in the source will be characterized by higher rb concentrations than those that result from the incongruent melting of muscovite the himalayan leucogranites provide an example of unfractionated crustally derived eutectic melts that are enriched in rb but depleted in sr and ba relative to their metasedimentary protoliths these compositions may be generated by the incongruent melting of muscovite as a low melt fraction f 0 1 from a pelitic source under vapour absent conditions

climate and abrupt vegetation change in northern europe since the last deglaciation a long standing question in palaeoecology has been to determine the importance of climate driving vegetation change since the last deglaciation here we investigate the local to regional dynamics of vegetation change during the lateglacial and the holocene in northern europe we extracted sites from the european pollen database and used the squared chord distance scd dissimilarity metric to identify time periods of high pollen assemblage turnover representing periods of abrupt vegetation change in addition a set of generalized additive mixed models were applied to investigate the underlying dynamics of two periods of higher rates of turnover the younger dryas early holocene transition yd eh 11 6 9 0 kyr and early middle holocene emh 9 0 6 0 kyr results revealed a high frequency of turnover events between 12 75 11 5 10 75 11 10 25 10 7 75 7 25 3 25 3 0 and 1 75 25 kyr furthermore there was a strong linear relationship between pollen assemblage turnover and large directional temperature

water in albitic glasses infrared spectroscopy has been calibrated to provide a precise and accurate method for determining the concentrations of molecular water and hydroxyl groups in hydrous albitic glasses at total water contents less than 4 wt most of the water is dissolved as hydroxyl groups at higher total water contents molecular water becomes the dominant species for total water contents above 4 wt the amount of water dissolved as hydroxyl groups is nearly constant at about 2 wt and additional water is incorporated as molecular water these trends in the concentrations of the h bearing species are similar to those observed in other silicate glasses using infrared and nmr spectroscopies the ratio of molecular water to hydroxyl groups at a given total water content is independent of the pressure and only weakly dependent on the temperature of equilibration molecular water and hydroxyl group concentrations in glasses provide constraints on the dissolution mechanisms of water in silicate liquids several mixing models involving homogeneous equilibria of the form h 2o o 2 2oh among melt species in albitic melts have been developed these models can account for the measured species concentrations if the effects of non ideal behavior or mixing of polymerized units are included or by allowing for several different anhydrous species we used two thermodynamic models of hydrous albitic melts to calculate phase equilibria the first assumes that henry s law holds for molecular water in albitic liquids i e that the activity of molecular water in the melt is proportional to its mole fraction as determined by infrared spectroscopy the second describes the speciation and thermodynamics of hydrous albitic melts using the formalism of a strictly regular solution these models can account reasonably well for the position of the vapor saturated solidus of high albite and the pressure and temperature dependence of the solubility of water in albitic melts to the extent that these models are successful our approach provides a direct link between measured species concentrations in hydrous albitic glasses and the macroscopic thermodynamic properties of the naalsi 3o 8 h 2o system

integrated varve and pollen based temperature reconstruction from finland evidence for holocene seasonal temperature patterns at high latitudes a detailed understanding of decadal to millennial scale climate changes requires seasonal scale summer winter reconstructions of past precipitation and temperature fluctuations comparing seasonally resolved varve records with pollen based sum of growing degree days gdd reconstructions from lake nautajarvi we examined the intra annual nature of climate variability in central southern finland during the holocene the organic varve record and the gdd reconstruction show roughly comparable trends supporting the interpretation that both proxies predominantly reflect summer temperatures in the study area the records suggest low but rising early holocene 9500 to 8500 cal yr bp summer temperatures the holocene thermal maximum htm in the gdd record dates to about 7500 to 4500 cal yr bp but the organic varve record along with reconstructed changes in vegetation composition notably a peak of tilia pollen percentages indicate that during the htm there was a trend towards a more continental climate with maximum mid summer temperatures reached at 6500 to 4500 cal yr bp both records reflect the start of the post htm cooling at about 4500 cal yr bp simultaneously with an increase of the amount of catchment erosion and mineral matter influx into the lake suggesting gradually colder and or longer winters with high net accumulation of snow the organic varve record and the gdd record start to diverge at 2000 cal yr bp possibly owing to the human influence on catchment processes the reconstructed mid holocene summer temperature peak deviates from the regional climate model outputs which suggest highest summer temperatures during the early holocene

the selection of sites for paleovegetational studies the judicious selection of sites for paleovegetational and paleoclimatic studies permits paleoecologists to answer specific research questions that go beyond primary descriptions of past vegetation we present a model that describes the relationship between basin size and pollen source area and predicts the proportions of local extralocal and regional pollen sampled by lake basins of different size the distinctive sampling properties of lakes peats and small hollows can be exploited to provide details of pattern in paleovegetation so long as attention is given to the limitations and problems of these types of sites combinations of site types in a single study most fully exploit the information contained in sediments

dissolution of corundum and andalusite in h2o saturated haplogranitic melts at 800 c and 200 mpa constraints on diffusivities and the generation of peraluminous melts of h2o in the aluminum alkali eigenvector could not be obtained the mechanisms and kinetics of equilibration between peraluminous from our results we propose that some h2o may provide charge minerals and granitic melt were investigated experimentally by balance for excess aluminum multicomponent diffusion models the dissolution of corundum and andalusite into h2o saturated yield eigenvalues for the corresponding aluminum alkali eigenvector metaluminous haplogranitic melt at 800 c and 200 mpa mineral of 0 3 10 to 1 9 10 cm s calculated effective and haplogranitic glass rods were juxtaposed inside platinum binary diffusion coefficients for al2o3 are higher 1 0 10 to capsules and then subjected to experimental conditions for times 3 6 10 cm s these diffusion coefficients are used to ranging from 12 to 2900 h upon melting the mineral melt calculate equilibration times between peraluminous minerals and interface retreats with the square root of time the composition of granitic melts in a model system in which two grains of corundum the melt at the interface changes with time but its asi aluminum or andalusite 1 cm apart are connected via a narrow melt column saturation index molar al2o3 cao na2o k2o at the conditions of the experiments diffusive equilibrium through remains constant at 1 20 after 480 h this value is close to initially metaluminous h2o saturated melt would be attained within the asi of an h2o saturated haplogranitic melt in equilibrium with 10 10 years at h2o activity well below saturation of the corundum or andalusite which may indicate that the composition of melt lower diffusivity of all components may increase the time to the melt at the interface follows the liquidus of these minerals in equilibration to 10 10 years approaching possible time frames the system sodium and potassium diffuse rapidly uphill across the for the generation and extraction of crustal melts entire length of the charge towards the interface resulting in a rapid and uniform increase in asi throughout the entire melt column this uphill diffusion of alkalis is due to coupling with excess aluminum entering the melt at the interface and involves long range

shisha pangma leucogranite south tibetan himalaya field relations geochemistry age origin and emplacement the shisha pangma pluton forming most of the xixabangma 8027 m massif in south tibet is one of the 20 larger leucogranite intrusives that mark the highest structural levels of the himalayan metamorphic core the pluton occurs immediately below the shisha pangma detachment a strand of the south tibetan detachment std system a low angle 30 north dipping normal fault placing paleozoic black slates atop sillimanite grade pelites and calc silicate rocks k feldspar augen gneisses containing fibrolite and sillimanite paragneisses along the footwall show strong internal s c fabrics indicative of down to the north extension the shisha pangma leucogranite is a heterogeneous polyphase intrusion with an earlier foliated biotite rich phase and a later tourmaline muscovite rich phase typically containing the assemblage kfs pl qtz ms tur gt bt sil ap the highly peraluminous granites have high 87sr 86sr ratios 0 738 0 750 typical of pelite derived anatectites nd depleted mantle model

holocene dynamics of the southern boreal forest in sweden holocene vegetation dynamics in the ecotone between the boreo nemoral and boreal forest were reconstructed from sediment cores of two small lakes using pollen and macrofossil analyses competition

petrogenetic relationships between pegmatite and granite based on geochemistry of muscovite in pegmatite wall zones black hills south dakota usa abstract the compositions of large samples of granitic pegmatite wall zones have been determined for a suite of ten pegmatites of diverse geochemical character and degree of compositional evolution in the keystone area of the black hills whole rock compositions are strongly peraluminous and they deviate substantially from the granite minimum composition in quartz albite orthoclase normalized components showing considerably more scatter than harney peak granite whole rocks wall zone minerals are commonly coarsely segregated leading to large modal variability among whole rocks these features make whole rock samples of wall zones unsuitable for the determination of initial pegmatite bulk compositions trace and minor element compositions of muscovite separates from the wall zones were thus determined to eliminate the effects of modal variability on trace element concentrations so that geochemical differences between pegmatites could be modeled estimates of initial pegmatite melt trace element concentrations range from 800 4000 ppm rb 100 1000 ppm cs 200 2000 ppm li and 1 50 ppm ba trace element concentrations of muscovite from a given pegmatite generally cluster together although several show considerable intra pegmatite scatter and there are large overlaps among different pegmatites the geochemical characteristics of samples from the etta pegmatite indicate mixing with and assimilation of country rocks exceptionally low rb cs ratios of muscovite from the etta pegmatite are similar to those of muscovite from k feldspar rich assemblages of other pegmatites where the rb concentration of melt may have been buffered by crystallizing assemblages that had bulk rb distribution coefficients close to 1 the large degree of scatter of geochemical parameters among these pegmatites precludes derivation of the entire suite by either single stage crystallization or partial melting processes nor can the pegmatites be satisfactorily related by any fractionation trajectory from a single starting composition fractional crystallization is difficult to model due to an apparent geochemical decoupling that exists among several of these elements in different pegmatites e g rb from cs or li from rb cs and nonsystematic variation of ba concentrations however the magnitude of observed rare element enrichments could be achieved by 75 90 fractional crystallization of melts that crystallized harney peak granite in nearby exposures the inter pegmatite scatter and apparent geochemical decoupling that characterize the suite indicate an origin by partial melting of a heterogeneous source rock or rock sequence followed by an intermediate episode of fractional crystallization prior to final emplacement of the pegmatite melts additional compositional variations among samples from the wall zones of individual pegmatites were caused by processes during or after emplacement including local interaction with host metamorphic rocks and fractionation during internal evolution of the pegmatites as they crystallized

the partitioning behavior of silver in a vapor brine rhyolite melt assemblage abstract the partitioning of silver in a sulfur free rhyolite melt vapor brine assemblage has been quantified at 800 c pressures of 100 and 140 mpa and f o 2 nno nickel nickel oxide silver solubility 2 in rhyolite increases 5 fold from 105 21 to 675 98 g g as pressure increases from 100 to 140 mpa nernst type partition coefficients d ag i j 2 describing the mass transfer of silver at 100 mpa between vapor and melt brine and melt and vapor and brine are 32 30 1151 238 and 0 026 0 004 respectively at 140 mpa values for d ag i j 2 for vapor and melt brine and melt and vapor and brine are 32 10 413 172 and 0 06 0 03 respectively apparent equilibrium constant values 2 describing the exchange of silver and sodium between vapor and melt k ag na v m at 100 and 140 mpa are 105 68 and 14 6 the average values 2 for silver and sodium exchange between brine and melt k ag na b m at 100 and 140 mpa are 313 288 and 65 12 these data indicate that the mass transfer of silver from rhyolite melt to an exsolved volatile phase s is enhanced at 100 mpa relative to 140 mpa suggesting that decompression increases the silver ore generative potential of an evolving silicate magma model calculations using the new data suggest that the evolution of low density aqueous fluid i e vapor may be responsible for the the silver tonnage of many porphyry type and perhaps epithermal type ore deposits for example halter et al halter w e pettke t and heinrich c a 2002 the origin of cu au ratios in porphyry type ore deposits science 296 1842 1844 used detailed silicate and sulfide melt inclusion and vapor and brine fluid inclusions analyses to estimate a melt volume on the order of 15 km3 to satisfy the copper budget at the bajo de la alumbrera copper gold silver ore deposit using their melt volume estimate with the data presented here model calculations for a 15 km3 felsic melt saturated with pyrrhotite and magnetite suggest that a low salinity magmatic vapor may scavenge on the order of 7 1012 g of silver from the melt this quantity of silver exceeds the discovered 2 109 g of ag at alumbrera calculated tonnages for numerous other deposits yield similar results the excess silver in the vapor remaining after porphyry formation is then available to precipitate at lower ptconditions in the stratigraphically higher epithermal environment these data suggest that silver and perhaps other ore metals in the porphyry epithermal continuum may be derived solely from the time integrated flux of dominantly low salinity vapor exsolved from a series of sequential magma batches

from sediment to granite timescales of anatexis in the upper crust abstract granite formation is the culmination of a sequence of events initiated by prograde heating of the protolith and followed by formation of a grain boundary melt melt segregation into a vein network ascent of the melt through the network and finally crystallisation of the melt experimental constraints on the formation of a crustal melt from the incongruent melting of muscovite combined with geochemical studies of anatexis in the high himalaya allow the timescales required for each of these processes to be assessed discordant temperatures determined from monazite and zircon thermometry for himalayan anatectic granites indicate that at least for some intrusives the melt was undersaturated in lree implying that melts have probably been extracted in less than 10 ka experimental studies suggest that some himalayan melts are also undersaturated in zr implying segregation may have occurred within 100 years such short timescales confirm that deformation driven mechanisms are important in extracting these melts from their source the transport distances of himalayan granitic melts of 10 km may be achieved by the ascent of magma through dykes in about 1 day at such rates even the largest granite could theoretically be emplaced in 10 years crystallisation of himalayan melts involves much longer periods if emplaced as thin sheets 100 m wide a timescale of 500 years is required compared with 30 ka for single stage intrusion of the larger laccoliths for composite sheet complexes magma crystallisation rather than melt ascent comprises the rate determining step on the emplacement of the intrusion the overall timescales of melt segregation and emplacement for many orogenic granites are therefore less than 10 ka and possibly less than 1 ka in contrast the timescale required for prograde heating of the protolith is 1 ma since the melt production rate is determined by heat flow into the protolith and not by reaction kinetics for any geologically significant period we conclude that heat flow determined by both the mechanism of heating and the thermal diffusivities of crustal rocks provides the overall rate determining step of crustal anatexis

badrinath gangotri plutons garhwal india petrological and geochemical evidence for fractionation processes in a high himalayan leucogranite the gangotri leucogranite is the western end of the badrinath granite one of the largest bodies of the high himalayan leucogranite belt hhl it is a typical fine grained tourmaline muscovite biotite leucogranite the petrography shows a lack of restitic phases the inferred crystallization sequence is characterized by the early appearance of plagioclase quartz and biotite and by the late crystallization of the k feldspar this suggests that in spite of being of near minimum melt composition the granite probably had long crystallization or melting interval in agreement with previous experimental studies tourmaline and muscovite have a mainly magmatic origin even though the major element composition is homogeneous there are several geochemical trends when cao decreases there is an increase in na2o rb sn u b f and a decrease in k2o fe2o3 tio2 sr ba zr ree th which are best explained by a fractionation process with early crystallizing phases experimental solubility models for zircon and monazite in felsic melt support a magmatic origin for these two accessory phases as well rb sr isotope data show this granite to have like other hhl heterogeneous isotopic values for sr initial 87sr 86sr ratios calculated at 20 ma range between 0 765 and 0 785 therefore no mixing i e no convection occurred between the different batches of magma in contrast 18o data show little variation 13 04 0 25 implying a source with homogeneous 18o values differences in timing between fluid infiltration and the onset of melting related to differences in temperature of the source could explain why source homogenization occurred for the gangotri and not for the manaslu granite the use of experimental results for solubility and the position of the accessory minerals during melting predict a low viscosity for the melt during its extraction this in turn explains the lack of restitic phases major and accessory in the granite as well as some field features lensoid shape pronounced magmatic layering based on the petrographic and isotopic studies it is suggested that the mechanism of ascent was not diapiric but rather that the melt ascended along several fractures and the level of emplacement was partialy controlled by the density contrast between the melt and host rocks

boron in granitic magmas stability of tourmaline in equilibrium with biotite and cordierite experiments at 750 c 200 mpa h2o a h2o 1 and fo2 ni nio established that the equilibrium among tourmaline biotite cordierite and melt spinel aluminosilicate or corundum occurs with 2 wt b2o3 in strongly peraluminous melt with an aluminosity measured by the parameter asi of 1 2 the experiments demonstrate the relationship of tourmaline stability to the activity product of the tourmaline components boron and aluminum which are inversely related to one another tourmaline is unstable in metaluminous to mildly peraluminous melts asi 2 wt b2o3 in their bulk magmas

assessing bulk assimilation in cordierite bearing granitoids from the central system batholith spain experimental geochemical and geochronological constraints

lateglacial and early holocene environmental dynamics in northern lithuania a multi proxy record from ginkūnai lake abstract to reconstruct the lateglacial and early holocene palaeoenvironmental dynamics in the northern part of lithuania the sediment record from gink nai lake was studied applying a multi proxy approach involving pollen diatom and plant macrofossil surveys as well as 18 o 13 c 14 c and loss on ignition loi measurements together with geochemical investigations the obtained data suggest the deglaciation of the area started at approximately 16 000 16 500 cal bp followed by the formation of a tree less tundra the obtained palaeobotanical records indicate the scarcity of the vegetation cover and the flourishing of the non arboreal taxa in the local flora suggesting a severe climatic regime after 13 700 cal bp the pinus betula predominating forest progressively expanded although this process was partly reversed during the recurrence of a cold interval recorded from 13 000 to 13 100 cal bp since 12 600 cal bp rapid aridification of the climatic regime reflected in the isotope record was accompanied by the formation of cold adapted vegetation including picea stands which acted as an intensive supply of allochthonous material into the basin thereby decreasing the water level the identified period of physical disturbance lasted until approximately 11 800 cal bp significant changes of the palaeoenvironmental regime subsequently occurred in the area and were manifested in most of the obtained proxies i e changes in the sediment type transformations of the vegetation cover and fluctuations of the sedimentation regime isotope records along with the geochemical data indicate a major climatic turn in terms of the temperature and moisture after 11 500 cal bp the rising productivity of the basin was coincident with the stabilisation of the soil layer and the formation of dense vegetation cover enriched by corylus ca 9800 cal bp and ulmus ca 10 300 cal bp during the early holocene after 10 800 cal bp the investigated part of the basin changed to a peat bog

quantitative palaeotemperature records inferred from fossil pollen and chironomid assemblages from lake gilltjarnen northern central sweden palaeotemperature reconstructions based on radiocarbon dated fossil pollen and chironomid stratigraphies obtained from lake gilltjarnen provide evidence of climate changes during the last 11 000 years in the boreal zone of northern central sweden the records show consistent trends during the early and mid holocene indicating low temperatures at 11 000 10 000 cal yr bp followed by a rising trend and a period of maximum values from about 7000 to 4000 cal yr bp at 3000 cal yr bp the chironomid inferred temperature values rise abruptly deviating from the late holocene cooling trend indicated by the pollen based reconstruction and most of the other palaeotemperature records from central scandinavia probably as a result of local limnological changes in lake gilltjarnen and its catchment comparison of the present results with a lake level reconstruction from lake ljustjarnen ca 100 km southwest of lake gilltjarnen shows that the low early holocene temperatures were associated with high lake levels at 10 500 8500 cal yr bp whereas low lake levels and dry conditions prevailed during the period of high temperatures at between 7500 and 5000 cal yr bp probably due to high summer evapotranspiration and lower precipitation copyright 2006 john wiley sons ltd

chronological framework for the lateglacial pollen and macrofossil sequence in the pirin mountains bulgaria lake besbog and lake kremensko 5 the sediments of numerous cirque lakes in the pirin mountains have yielded several generalized pollen diagrams but low stratigraphic and temporal resolution has hampered detailed reconstruction of the vegetational history especially for the lateglacial new pollen and macrofossil analyses of high stratigraphic resolution combined with well controlled timedepth curves for lake besbog and lake kremensko 5 now permit the firm identification of the lateglacial interstadial interval bollingallerod dated at 13 8 12 6 ka cal bp at besbog and 14 1 12 8 ka cal bp at kremensko 5 and correlated with the greenland interstadial gi 1 14 5 12 6 ka cal bp macrofossil analyses indicate that during the bolling allerod period betula and juniperus occurred around the lakes at 2124 2250 m a s l following the younger dryas a betula woodland covered the mountains between 1900 and 2250 m in the early holocene because of higher summer insolation at this time the temperate deciduous forest reached up to 1900 m or 800 m above their present limit producing a regional pollen rain that dominated pollen deposition in the cirque lakes after about 7000 cal yr bp conifer forests replaced the birch woodland at middle and high elevations

exploring holocene continentality changes in fennoscandia using present and past tree distributions with global warming the distribution of warmth through the year is likely to change in the future and comparable changes may have occurred over the course of the holocene its effect on vegetation composition and species distribution can be compared to that of a continental versus an oceanic climate the distribution of five major tree species along a continentality gradient was studied in fennoscandia based on distribution maps and on their proportions of pollen in surface sediment samples both analyses indicate that the five arboreal species show similar patterns of response to a continentality index in the order ulmus glabra corylus avellana quercus robur tilia cordata and picea abies from the most oceanic to most continental continentality growing degree days above 5 degrees c and january temperature were reconstructed quantitatively from four pollen diagrams using transfer functions based on a combined fennoscandian pollen surface sample data set quantitative reconstructions indicate that the climate in fennoscandia has become increasingly more continental over the last 7000 years and this is largely an effect of winter cooling early holocene vegetation composition has poor analogues to the present vegetation in fennoscandia which hampers quantitative reconstructions qualitative reconstructions suggest that the early holocene in fennoscandia was the most oceanic period but probably with a high variability in temperature c 2008 elsevier ltd all rights reserved

calamity peak layered granite pegmatite complex black hills south dakota part i structure and emplacement the calamity peak pluton is a satellitic granite pegmatite intrusion located 2 km southwest of the main harney peak granite dome in the black hills south dakota many aspects of the structural development of the calamity peak pluton 1 km 2 mimic those of the larger harney peak dome 100 km 2 thus the model described here for the calamity peak pluton provides a general basis for evaluating the evolution of proterozoic granite pegmatite intrusives of the harney peak granite system the overall structure of the intrusive rocks at calamity peak is that of a dome as shown by the general geometry of the pluton contacts and by a domical pattern of internal textural layering textural layering is defined by alternating bands of pegmatite and fine grained granite 0 1 2 0 m thick fine grained layers are in turn banded on a scale of 2 20 mm owing to modal variations of tourmaline quartz and feldspars textural differentiation of at least some of these layers resulted from segregation of initially homogeneous magmas into pegmatitic upper and aplitic lower components during crystallization relationships between the pluton and regionally dipping schistose country rocks however do not support a simple domal structure schistosity conforms to the contact only along the southern margin of the pluton the side facing with the regional dip country rock schistosity is at a high angle to the contact at the apparent floor of the pluton which is exposed in the core of the dome and along the northern margin the side that opposes the regional dip in order to explain the structural observations it is inferred that the initial intrusive body at calamity peak consisted of a flat lying discordant sheet intruded into steeply dipping quartz mica schist country rock however an arcuate sheet concave downward cannot be ruled out new magma pulses possibly several thousands were successively emplaced along the hanging wall contact of earlier pulses as indicated by the upward truncation of early layers creating a composite layered pluton intrusions of individual magma pulses were localized in three major composite sheets which form structurally and chemically discrete portions of the pluton growth of the pluton proceeded by forcible distension and plastic deformation of overlying country rocks schistosity was molded into a conformable attitude in portions of the hanging wall and pre intrusive country rock lineations were deflected around the pluton the layered granite pegmatite series is crosscut by four successive stages of fracture filling bodies the orientations and compositions of these bodies record the late stages in the structural and fluid evolution of the plutonic system

phase equilibria and compositions of fe mg al minerals and melts in water saturated peraluminous granitic systems phase assemblages and phase compositions were studied experimentally in water saturated biotite bearing peraluminous granitic melts as a function of alumina excess and temperature the runs were performed at 2 and 5 kbars under nno buffer biotite was stable only in composition containing 5 of normative corundum it coexisted with cordierite and hercynite at 2 kbars and with hercynite at 5 kbars in composition containing 10 of normative corundum biotite was not observed abundant cordierite and hercynite were the only fe mg al minerals these relationships show that at constant pressure the amount of cordierite increases with increasing excess of alumina simultaneously the stability of biotite decreases due to preferential partitioning of mg into cordierite and fe into biotite besides the distribution of fe mg and al among the coexisting solid phases solubility of these elements in the melts is given below 900 c melts are poor in iron and magnesium and correspond in terms of these elements to leucogranites it is suggested that the leucogranitic magmas such as parental magmas of european hercynian and himalayan leucogranites must have been formed through highly efficient separation of partial melt from restite in which ferromagnesian components are concentrated peraluminous granites rich in ferromagnesian minerals originate supposedly from restite bearing magmas

origin and evolution of a peraluminous silicic ignimbrite suite the violet town volcanics the violet town volcanics are a 373 ma old comagmatic s type volcanic sequence mainly comprising crystal rich intracaldera ignimbrites rock types vary from rhyolites to rhyodacites all containing magmatic cordierite and garnet phenocrysts variation in the suite is primarily due to fractionation of early crystallized quartz plagioclase and biotite plus minor accessory phases in a high level magma chamber prior to eruption early magmatic crystallization occurred at around 4 kb and 850 c with melt water contents between 2 8 and 4 wt this high temperature markedly water undersaturated restite poor granitic magma was generated by partial melting reactions involving biotite breakdown in a dominantly quartzofeldspathic source terrain leaving a granulite facies residue

an insight into the breakup of gondwana identifying events through low temperature thermochronology from the basement rocks of madagascar 1 fission track analysis was applied to the precambrian suites of madagascar in order to identify the lower temperature cooling histories and their relationships to the phanerozoic events that affected the island apatite ages range from 431 to 68 ma and zircon ages range from 452 to 238 ma thermochronologically the island can be divided into a southern central and northern region each with a subdivision on an east west basis the southern region is sharply separated from the central region by strongly contrasting apparent apatite ages over the northwest southeast striking ranotsara shear zone rsz the change in apparent ages over the rsz is indicative of later reactivation along younger brittle faults the central region has the oldest ages of the island and has a diffuse contact to the third region northward along the entire western margin of the precambrian basement initial paleozoic exhumation was followed by heating burial by sediments during jurassic and cretaceous times a decrease in ages along the eastern margin from 119 to 68 ma coincides with the predicted positions of the marion hot spot after effects of erosion are considered on the other hand these ages may represent progressive opening of the margin in a southward direction together with associated denudation of the rift shoulder the eastern part of the central region has remained very stable since at least devonian times undergoing only long term very slow exhumation at rates of 1 5 m myr

stability of andalusite and sillimanite and the al_ 2 sio_ 5 triple point constraints from the ballachulish aureole scotland andalusite and and sillimanite sil occur in well defined zones in the ballachulish aureole in most of the aureole s sillimanite bearing rocks sillimanite grain diameters range from 2 m to 10 m the boundary between prograde andalusite and prograde sillimanite is constrained to a zone of max 30 m width upgrade of the muscovite quartz andalusite k feldspar h 2 o reaction isograd this boundary is interpreted to correspond to the and sil equilibrium the common occurrence of andalusite well upgrade of the first occurrence of sillimanite is ascribed to sluggish kinetics of the polymorphic inversion the p t position of the and sil equilibrium in the aureole is estimated as 645 20 c and 3 0 0 4 kbar based on a combination of 1 location of the ms qtz and kfs h 2 o reaction corrected for non end member fluid and mineral compositions and 2 independent pressure estimates obtained from equilibria in metapelites marbles calcsilcates and granitoids all in exce

petrology of the coyaguayma ignimbrite northern puna of argentina origin and evolution of a peraluminous high sio2 rhyolite magma abstract the coyaguayma ignimbrite is a strongly peraluminous sp sillimanite garnet bearing silicic rhyolite which erupted in the northern puna segment of the central andean plateau in the upper miocene 11 ma a period that was characterized by the eruption of voluminous 100s to 1000s km3 dacitic ignimbrites of high k calc alkaline affinity in this region the sp magmatic rocks are both rare and small but their importance is potentially much greater as rocks of this type are usually interpreted as products of crustal melting and therefore useful for addressing mantle addition vs crustal recycling in the central andes the phenocryst assemblage of the coyaguayma ignimbrite comprises plagioclase an26 18 quartz ba rich and ba poor sanidine minor al rich ferromagnesian minerals alt and alvi rich biotite almandine spessartine garnet and sillimanite as well as accessory zircon and monazite textural relations suggest that the accessory and ferromagnesian phases crystallized before quartz and feldspars mineral equilibria suggest that crystallization of the rhyolite magma began at 5 kbar and 800 c and continued almost isobarically to 720 c causing the residual liquid to increase h2o contents from 4 5 to 7 5 before eruption most major features e g high sio2 a cnk 1 3 low cao mgo tio2 and feo and trace element patterns low ba sr th lree and eu eu high rb u y and nb along with the thermobarometric constraints on magmatic p t and water contents are consistent with an origin by mica dehydration melting of metapelitic sources e g typical biotite muscovite gneisses from the outcropping s puna basement however the relatively low initial 87sr 86sr 0 7125 and high 143nd 144nd 0 512200 ratios invalidate a pure crustal origin instead we propose contamination of calc alkaline dacitic magmas similar to typical puna ignimbrites by metapelite at mid crustal settings 18 km depth geochemical modeling that satisfies the chemical and isotopic data suggests mixing of 70 dacite and 30 of metapelite partial melts followed by extensive 70 fractionation of plagioclase k feldspar quartz and biotite with minor magnetite and apatite from the hybrid magma sillimanite in the coyaguayma rhyolite is interpreted as a restite mineral or a product of incongruent melting of the metapelite which was preserved intact in the hybrid melt due to local equilibrium this petrogenetic model explains most characteristics of crystal poor sp rhyolites from the puna plateau e g tocomar ramadas rhyolites and it may be more generally applicable to occurrences of sp magmas in andean type continental arcs dominated by calc alkaline magmatism

mueilha rare metals granite eastern desert of egypt an example of a magmatic hydrothermal system in the arabian nubian shield abstract the mueilha granite pluton is one of the rare metals bearing peraluminous granitic plutons in the arabian nubian shield it represents the apical part of a highly evolved magma chamber emplaced at a shallow level subsequent to the post pan african orogeny the pluton can be seen as a highly leucocratic medium grained albite oligoclase framework infilled with quartz k feldspar and muscovite that are variably overgrown by k feldspar muscovite quartz and topaz megacrysts the increasing number and size of the k feldspar megacrysts at the expense of the whitened albite oligoclase framework imparts variably red color to the mueilha granite contacts between the milky white and red granites are usually gradational but may be locally sharp or may form narrow transition zones resulting from abrupt variations in texture and lithology textural relations indicate an initial stage of hydrothermal albitization of magmatic plagioclase and crystallization of topaz megacrysts resulting from infiltration of na rich fluorine bearing fluids a subsequent stage of metasomatic enrichment is characterized by extensive growth of large k feldspar quartz and muscovite megacrysts at the expense of the albite oligoclase crystals as a result of infiltration of k si rich hydrous fluids post magmatic infiltration of hydrous fluids along the fault planes is shown by the intense replacement of alkali feldspar megacrysts by quartz development of myrmekitic intergrowth pockets along the k feldspar megacrysts and sealing of the micro fractures by cryptocrystalline mixtures of clay minerals iron oxides sericite and chlorite compositionally the red granitic rocks have higher sio 2 fe 2 o 3total k 2 o na 2 o ree y th u zr and zn and lower al 2 o 3 ga ta nb and mo compared to the milky white granites lile and sn do not show clear variation trends throughout the mueilha granite pluton suggesting their immobility during hydrothermal alteration microthermometric measurements indicate that the interactions with the hydrothermal fluids started at a minimum temperature 400 c most likely during the late stage crystallization of the mueilha granite and continued after their complete solidification i e subsolidus conditions at a temperature as low as 120 c the high fertility of mueilha granite is most plausibly the result of partial melting within the undepleted juvenile crust of the arabian nubian shield that has formed during the pan african orogeny

tourmaline occurrences within the penamacor monsanto granitic pluton and host rocks central portugal genetic implications of crystal chemical and isotopic features tourmalinization associated with peraluminous granitic intrusions in metapelitic host rocks has been widely recorded in the iberian peninsula given the importance of tourmaline as a tracer of granite magma evolution and potential indicator of sn w mineralizations in the penamacor monsanto granite pluton central eastern portugal central iberian zone tourmaline occurs 1 as accessory phase in two mica granitic rocks muscovite granites and aplites 2 in quartz mica tourmaline rocks tourmalinites in several exocontact locations and 3 as a rare detrital phase in contact zone hornfels and metapelitic host rocks electron microprobe and stable isotope 18o d 11b data provide clear distinctions between tourmaline populations from these different settings a schorl oxyschorl tourmalines from granitic rocks have variable foititic component x 17 57 and mg mg fe ratios 0 19 0 50 in two mica granitic rocks and 0 05 0 19 in the more differentiated muscovite granite and aplites granitic tourmalines have constant 18o values 12 1 0 1 with wider ranging d 78 2 4 7 and 11b 10 7 to 9 0 values b vein breccia oxyschorl mg mg fe 0 31 0 44 results from late b and fe enriched magma derived fluids and is characterized by 18o 12 4 d 29 5 and 11b 9 3 while replacement tourmalines have more dravitic compositions mg mg fe 0 26 0 64 close to that of detrital tourmaline in the surrounding metapelitic rocks and yield relatively constant 18o values 13 1 13 3 though wider ranging d 58 5 to 36 5 and 11b 10 2 to 8 8 values and c detrital tourmaline in contact rocks and regional host metasediments is mainly dravite mg mg fe 0 35 0 78 and oxydravite mg mg fe 0 51 0 58 respectively boron contents of the granitic rocks are low 650 ppm compared to the minimum b contents normally required for tourmaline saturation in granitic melts implying loss of b and other volatiles to the surrounding host rocks during the late magmatic stages this process was responsible for tourmalinization at the exocontact of the penamacor monsanto pluton either as direct tourmaline precipitation in cavities and fractures crossing the pluton margin vein breccia tourmalinites or as replacement of mafic minerals chlorite or biotite in the host rocks replacement tourmalinites along the exocontact of the granite thermometry based on 18o equilibrium fractionation between tourmaline and fluid indicates that a late b enriched magmatic aqueous fluid av 18o 12 1 at 600 c precipitated the vein breccia tourmaline 18o 12 4 at 500 550 c and later interacted with the cooler surrounding host rocks to produce tourmaline at lower temperatures 400 450 c and an average 18o 13 2 closer to the values for the host rock although b metasomatism associated with some granitic plutons in the iberian peninsula seems to be relatively confined in space extending integrated studies such as this to a larger number of granitic plutons may afford us a better understanding of variscan magmatism and related mineralizations

calculated relationships between activity of alumina and phase assemblages of silica saturated igneous rocks petrogenetic implications of magmatic cordierite garnet and aluminosilicate abstract many peraluminous igneous rocks are characterized by the presence of al rich minerals such as cordierite garnet and aluminosilicate polymorphs clearly one of the important thermodynamic intensive variables controlling the stability of these minerals relative to al poor phases such as ortho and clinopyroxene must be the activity of al 2 o 3 a al 2 o 3 in the melt calculated phase relationships of anhydrous mineral assemblages in equilibrium with quartz saturated liquids show that at crustal pressures less than about 10 kbar garnet cordierite and aluminosilicate are only likely to crystallize from melts in which a al 2 o 3 is up to one order of magnitude higher than that required for orthopyroxene clinopyroxene crystallization in spite of this peraluminous granitoid liquids saturated with orthopyroxene garnet or orthopyroxene cordierite do not ordinarily contain significantly larger amounts of excess al al in excess of that required to form feldspars than peraluminous liquids saturated with orthopyroxene clinopyroxene these observations indicate that there must be profound compositional controls on the activity coefficient of al in silicic melts and the strongest of such controls appears to be the total alkali content of the melt the activity coefficient of al in silicic melts varies directly with total alkali oxide content so that alkali poor melts can become markedly peraluminous without ever becoming saturated in aluminous phases whereas alkali rich melts of similar normative corundum content can crystallize garnet cordierite or even aluminosilicate because activity of alumina in a silicic melt is not a simple function of excess al content classification schemes for silicic igneous rocks based on model mineralogical assemblages which reflect the value of the thermodynamic effective concentration of al during crystallization convey more petrologic information than those based on chemical parameters such as normative corundum content or alumina saturation index

manaslu leucogranite a collision signature of the himalaya a model for its genesis and emplacement the manaslu pluton is one of 10 leucogranites that formed in the overthrusted higher himalaya after the indo eurasian collision field and analytical data indicate that the underlying migmatites of the tibetan slab may be where the leucogranitic melts were generated the himalayan crustal thrusting of a hot slab over a rather cold volcano sedimentary pile le fort 1975a provides the necessary release of fluids these fluids cross the main central thrust mct induce the partial anatexis of the overheated tibetan slab and produce a leucogranitic magma the emplacement of the magma at first is located along the main disharmonic plane above the mct between the infrastructure and the superstructure there it generates a convective hydrothermal system extending very far laterally according to the stratification of permeabilities progressive emplacement of the granite proceeds as the convected fluids including the fluids released by the saturated magma dissolve the mainly calcareous host rocks of tibetan sedimentaries a frozen image of this caving out progression is given by the extensive network of granitic dikes outside the pluton the two quite independant fluid cycles of the generation and of the emplacement were triggered or guided by the tectonics due to collision this two fold model dominated by fluid activity may be of importance for other leucogranites and granites

genetic significance of multiple enclave types in a peraluminous ignimbrite suite lachlan fold belt australia the violet town volcanics lachlan fold belt australia are an s type ignimbrite suite containing microgranitoid enclaves basaltic andesite enclaves and enclaves of high silica rhyolite the microgranitoid enclaves are similar to those in peraluminous granites they typically have lower initial sr sr and higher e i than the host and represent globules of a mafic mantle derived magma ivhich was hybridized by mixing and diffusional exchange with the host magma the basaltic andesite enclaves were incorporated into the ignimbrite as xenoliths but their parental magma may have been similar to that of the microgranitoid enclaves they are isotopically less depleted than other mantle derived rocks from the lachlan fold belt reflecting contamination by crustal material or derivation from less depleted mantle sources the high silica rhyolite enclaves previously interpreted to be related to the ignimbrite by crystal fractionation have ejw values up to 3 units higher than their host and cannot be related to their host by crystal fractionation or assimilation fractional crystallization afc processes the coexistence of s type magmas and mantle derived magmas suggests that the latter may have played a role in the palaeozoic magmatism of the lachlan fold belt acting as a heat source for melting and perhaps also contributing chemical components to the crustally derived magmas

reconstruction of late glacial and early holocene near surface temperature anomalies in europe and their statistical interpretation abstract this paper presents the results of a variational analysis study based on the recently developed method by gebhardt et al to reconstruct paleo temperature fields on the typical scale of climate model output providing the necessary basis for quantitative comparison of reconstructions and model results additionally an extension of the approach takes into account the full statistics of the analysis error of the variational analysis to study the inherent uncertainties of the proxy data representing the imperfect paleo climate information and their impact on the field reconstruction the method is applied to reconstruct realizations of monthly mean temperature anomaly fields in europe for january and july in europe as averages for several time slices in the late glacial and holocene single realizations can differ substantially from the field of expectation values in terms of spatial patterns due to the inherent correlation of the spatial uncertainties of the paleo proxy data additionally the fields of expectation values generally are much smoother than the realizations this indicates that it is misleading to only consider expectation values further the ensembles of realization are used to calculate robust error measures for area mean values which is valuable for the quantitative comparison of the results of different time slices

iron and titanium solution properties in peraluminous and peralkaline rhyolitic liquids the saturation surface of pseudobrookite fe2tio5 was determined for melts in the system sio2 al2o3 k2o feo fe2o3 tio2 at 1400 c and 1 atm the variation in concentrations of fe2o3 tio2 and fe2tio5 in liquids can be used to infer relative changes in activity coefficients of these components with changing k2o k2o al2o3 of the melts saturation concentrations of these components are low and relatively constant in the peraluminous melts and increase with increasing k2o k2o al2o3 in peralkaline liquids the activity coefficients of fe2o3 and tio2 and fe2tio5 therefore are higher in peraluminous liquids than in peralkaline liquids in this system in addition the iron redox ratio was measured as a function of k2o k2o al2o3 for liquids just below the saturation surface f text o text 2 was fixed so all variations in redox ratio are entirely due to changes in melt composition the redox ratio from unsaturated liquids was applied to saturated liquids where redox analysis of the glass is impossible the homogeneous equilibrium experiments indicate that the activity coefficient of fe2o3 relative to that of feo is significantly greater in peraluminous melts than peralkaline melts both the heterogeneous and homogeneous equilibria suggest that in peralkaline liquids k in excess of that required to charge balance tetrahedral al 3 is used to stabilize both fe 3 and ti 4 calculations show that ferric iron and titanium compete equally effectively for charge balancing potassium but neither can outcompete aluminum the observed changes in solution properties of fe2o3 and tio2 in the synthetic melts are used to explain variations in fe ti oxide stabilities in natural peraluminous and peralkaline rhyolites and granites since the activity coefficients of both ferric iron and titanium are significantly higher in peraluminous liquids than in peralkaline liquids fe ti oxides should occur earlier in the crystallization sequence in peraluminous rhyolites than in peralkaline rhyolites in addition iron will be reduced in peraluminous granites and rhyolites relative to peralkaline ones under comparable p t and f text o text 2 finally observed crystallization patterns for minerals containing highly charged cations other than ferric iron and titanium are evaluated in the context of this and other experimental studies

water fluxed melting of the continental crust a review abstract water fluxed melting also known as fluid or water present melting is a fundamental process in the differentiation of continents but its importance has been underestimated in the past 20 years during which research efforts focused mostly on dehydration melting reactions involving hydrate phases in the absence of a separate aqueous phase the presence of a free aqueous phase in anatectic terranes influences all major physical and chemical aspects of the melting process from melt volumes viscosity and ability to segregate from rock pores to melt chemical and isotopic composition a review of the literature shows that melting due to the fluxing of aqueous fluids is a widespread process that can take place in diverse tectonic environments active tectono magmatic processes create conditions for the release of aqueous fluids and deformation driven transient high permeability channels capable of fluxing high temperature regions of the crust where they trigger voluminous melting water fluxed melting can be either congruent in regions at the water saturated solidus or incongruent at suprasolidus p t conditions incongruent melting reactions can give rise to peritectic hornblende or to nominally anhydrous minerals such as garnet sillimanite or orthopyroxene in this case the presence of an aqueous phase is indicated by a mismatch between the large melt fraction generated and the much smaller fractions predicted in its absence the relatively small volumes of aqueous fluids compared to that of rocks imply that melting reactions are generally rock buffered fluids tend to move upwards and down temperature however there are cases in which pressure gradients drive fluids up temperature potentially fluxing suprasolidus terranes crustal regions at conditions equivalent to the water saturated solidus represent a natural impediment to the up temperature migration of aqueous fluids because they are consumed in melting reactions in this case continued migration into supra solidus terranes take place through the migration of water rich melts thus melts become the transport agent of water into supra solidus terranes and responsible for water fluxed melting other processes such as the relatively rapid fluid migration through fractures also allow regional aqueous fluids to by pass the water saturated solidus fluid trap and trigger melting above solidus conditions when aqueous fluids or hydrous melts flux rocks at supra solidus conditions they equilibrate with the surroundings through further melting decreasing water activity and giving rise to undersaturated melts it is in these conditions that hornblende or anhydrous peritectic phases are stabilized unlike dehydration melting the melt fraction generated in this case is not limited by the water contained in hydrous minerals but by the volume of water added to the system unlike melting at the water saturated solidus these melts are capable of rising without freezing and do give rise to upper crustal granitic bodies

solubility of excess alumina in hydrous granitic melts in equilibrium with peraluminous minerals at 700 800 c and 200 mpa and applications of the aluminum saturation index we have studied the controls on the alumi num saturation index asi molec al2o3 cao na2o k2o and the concentration of normative corundum of granitic liquids saturated in alumina by equilibrating peraluminous minerals with initially meta luminous haplogranitic minimum composition liquids at 700 800 c and 200 mpa at and below h2o saturation the asi and normative corundum increase with increasing h2o concentration in the melt 0 04 to 0 10 moles excess al2o3 per mole of h2o temperature and with addition of the non haplogranitic components fe mg and b the asi parameter and concentration of normative corundum cannot be used to monitor aal2o3 between different mineral assemblages and melt because other components that affect the solubility of alumina including h2o fe mg and b do not appear in their formulations asi and normative corundum however provide petrogenetic information about magmas gener ated by partial melting of strongly peraluminous proto liths by virtue of their regular and predictable variation with melt composition e g h2o concentration and temperature for the application of these data to natural rocks it is necessary to choose as an analogue system the asi solubility or normative corundum solubility relations of the most chemically complex peraluminous mineral present in the rock comparison of asi values of anatectic leucosomes and allochthonous leucogranites with experimentally predicted values suggests low h2o concentrations in melt during crustal partial melting rapid melt segregation before equilibration with restitic peraluminous phases is also suggested in some cases

a spatio temporal reconstruction of holocene temperature change in southern scandinavia holocene mean july tjul and mean january tjan temperatures were reconstructed at lake trehorningen in southwest sweden using pollen climate calibration functions and converted into anomalies re

geochemical constraints on the bimodal origin of high himalayan leucogranites major and trace element and rb sr isotope systematics of the manaslu leucogranite central nepal have been examined to constrain the role of mineral fractionation and fluids in peraluminous granite petrogenesis biotite and tourmaline are for the most part mutually exclusive with a predominance of two mica leucogranites over tourmaline leucogranites the 87sr86sr initial isotopic ratios sri indicate that leucogranitic melts were derived from two different sources the two mica leucogranites having a metagreywacke origin with sri 0 752 nd 15 such a bimodal nature of the source zone does not directly influence the magmatic evolution except that probably the higher initial boron content in the metapelitic rocks may increase the na2ok2o ratio in contrast the amount of water present during melting principally controls in part anatectic processes and element behaviour water saturated conditions probably occured during melting of metagreywackeous rocks and favoured crystallization of two mica leucogranites whereas water absent conditions prevailed during melting of metapelitic layers and favoured biotite plagioclase and monazite fractionation in the source zone and tourmaline crystallization in the leucogranite

a 11 000 yr palaeotemperature reconstruction from the southern boreal zone in finland abstract the ecotone between the boreo nemoral hemiboreal and the southern boreal vegetation zones constitutes the northern distributional limit of a number of thermophilous tree species in northern europe and is to a large extent controlled by climatic conditions we present a quantitative annual mean temperature reconstruction from a high resolution pollen stratigraphy in southern boreal finland using a pollen climate calibration model with a cross validated prediction error of 0 9 c our model reconstructs low but steadily rising annual mean temperature from 10 700 to 9000 cal yr bp at 8000 4500 cal yr bp reconstructed annual mean temperature reaches a period of highest values holocene thermal maximum with particularly high temperatures 2 0 1 5 c higher than at present at 8000 5800 cal yr bp from 4500 cal yr bp to the present day reconstructed annual mean temperature gradually decreases by ca 1 5 c comparison of present results with palaeotemperature records from the greenland ice cores notably with the northgrip 18 o record shows marked similarities suggesting parallel large scale holocene temperature trends between the north atlantic and north european regions the verification of the occurrence timing and nature of the short term temperature fluctuations during the holocene in the southern boreal zone in europe requires replicate high resolution climate reconstructions from the region

accessory phase controls on the geochemistry of crustal melts and restites produced during water undersaturated partial melting the profound geochemical conseqences of accessory phase behaviour during partial melting of highgrade metapelites are demonstrated with reference to two geochemically distinct crustal melts produced by biotite dehydration melting reactions under granulite facies kbar 860 cc conditions these two leucogneiss suites from the brattstrand bluffs coastline eastern antarctica have similar field relations transport distances 10 100 s of metres and major element chemistry type 1 leucogneisses have low zr th and lree positive eu anomalies and zr zr and lreet lreet values less than 1 0 i e less than required to saturate the melt mass balance constraints suggest that these melts have been extracted before equilibration with host melanosomes the dry peraluminous nature of vapour undersaturated melts inhibits monazite and zircon solubility and results in concentration of these phases in the residue melts are consequently depleted in lree and hree melanosomes show complementary enrichment in lree while hree patterns are dominated by residual garnet type 2 leucogneisses in contrast have strongly enriched zr th and lree abundances negative eu anomalies and zr zr and lreet lreet 1 resulting from accessory phase entrainment vapour absent partial melting under moderate 6 8 kbar pressure granulite facies conditions of a pelitic source containing monazite is likely to give disequilibrium melts depleted in lree and hree as monazite and garnet are concentrated in the residue if temperatures are high enough 850 870 c to permit relatively large degrees of partial melting then the feldspar component of the source will be removed almost completely giving melts with large positive eu anomalies melts formed under vapour present conditions are unlikely to show such extreme lree and hree depletion or positive eu anomalies even at high degrees of partial melting disequilibrium melting coupled with source entrainment could fortuitously produce ree and trace element signatures similar to those typical of s type granites and usually ascribed to equilibrium melting conditions

the generation and crystallization conditions of the proterozoic harney peak leucogranite black hills south dakota usa petrologic and geochemical constraints the mineralogy petrology and geochemistry of the proterozoic harney peak granite black hills south dakota were examined in view of experimentally determined phase equilibria applicable to granitic systems in order to place constraints on the progenesis of peraluminous leucogranites and commonly associated rare element pegmatites the granite was emplaced at 3 4 kbar as multiple sills and dikes into quartz mica schists at the culmination of a regional high temperature low pressure metamorphic event principally along the periphery of the main pluton and in satellite intrusions the sills segregated into granite pegmatite couplets the major minerals include quartz k feldspar sodic plagioclase and muscovite biotite mg no molar mgo mgo feo 0 32 0 38 is the predominant ferromagnesian mineral in the granite s core whereas at the periphery of the main pluton and in the satellite intrusions tourmaline mg no 0 18 0 48 is the dominant ferromagnesian phase almandine spessartine garnet is also found in the outer intrusions there is virtually a complete overlap in the wide concentration ranges of sio2 cao mgo feo sr zr w of the biotite and tourmaline bearing granite suites with no discernable differentiation trends on harker diagrams precluding the derivation of one suite from the other by differentiation following emplacement this is consistent with the oxygen isotope compositions which are 11 5 0 6 for the biotite granites and 13 2 0 8 for the tourmaline granites suggesting derivation from different sources the concentrations of tio2 and possibly ba are higher and of mno and b are lower in the biotite granites the normative orthoclase albite ratio is extremely variable ranging from 0 26 to 1 65 in the biotite granites to 0 01 1 75 in the tourmaline granites very few sample compositions fall near the high pressure watersaturated haplogranite minima eutectic trend indicating that the granites for the most part are not minimum melts generated under conditions with a text h text 2 text o 1 instead most biotite granites are more potassic than the water saturated minima and eutectics and in analogy with experimentally produced granitic melts they are best explained by melting at 6 kbar a text h text 2 text o 1 and temperatures 800 c such high temperatures are also indicated by oxygen isotope equilibration among the constituent minerals nabelek et al 1992 several of the tourmaline granite samples contain virtually no k feldspar and have oxygen isotope equilibration temperatures 716 775 c therefore they must represent high temperature accumulations of liquidus minerals crystallized under equilibrium conditions from melts more sodic than the water saturated haplogranite minima or during fractionation of intruded melts into granite pegmatite couplets accompanied by volatile aided differentiation of the alkali elements the indicated high temperatures a text h text 2 text o 1 the relatively high tio2 and ba concentrations and the relatively low partial 18 text o values of the biotite granites suggest that they were generated by high extent biotite dehydration melting of an immature archean metasedimentary source the ascent of the hot melts may have triggered low extent muscovite dehydration melting of schists higher in the crust producing the high b low ti melts comprising the periphery of the main pluton and the satellite intrusions alternatively the different granite types may be the result of melting of a vertical section of the crust in response to the ascent of a thermal pulse with the low partial 18 text o biotite granites generated at a deeper hotter region and the high partial 18 text o tourmaline granites at a higher cooler region of the crust the low ti and high b concentrations in the high partial 18 text o melts resulted in the crystallization of tourmaline rather than biotite which promoted the observed differentiation of the melts into the granitic and pegmatitic layers found along the periphery of the main pluton and the satellite intrusions

vegetation pattern and sedimentation changes in the context of the lateglacial climatic events case study of staroje lake eastern belarus abstract a lake sediment core collected from the staroje lake southeastern belarus reveals significant changes of the terrestrial and limnic environmental during the lateglacial and early holocene in the periglacial zone of the late weichselian glaciation the combination of lithological loss on ignition palaeobotanical pollen non pollen palynomorphs diatoms and isotopic 18o 13c 14c proxy parameters was applied for the reconstruction of the vegetation pattern and sedimentation regime the lateglacial pre interstadial gs 2 vegetation was dominated by mineral soil pioneers with scattered occurrence of pinus and betula an interstadial gi 1 dominated by pinus forest with increasing representation of open ground species since approximately 13 500 cal bp and lateglacial stadial gs 1 with recurring opening of the vegetation pattern with scattered tree patches including those of picea presence of pinus stomata confirms the local origin of this plant since the pre interstadial starting from the holocene birch later accompanied by other deciduous species ulmus alnus quercus corylus took over in the local vegetation structure isotopic records 18o 13c obtained on bulk carbonates as well as diatom data exhibit several shifts reflecting variations both in terrestrial and limnic environment distinct negative excursion of 18o curve recorded during the first half of the gi 1 event suggests intensive groundwater discharge accompanied by active transportation of detrital carbon in to the basin limited basin productivity is also indicated by lithological and diatom records since approximately 13 700 cal bp sedimentation regime in the lake stabilised and productivity of the basin started to increase in positive correlation with loi data a considerable decrease in 18o values punctuated by a rapid jump in the middle of the interval was recorded during the gs 1 stadial and could be associated with the deterioration of the environmental regime and degradation of the soil layer increasing erosion activity alongside the rising input of detrital carbonates into the basin the water table was low as indicated by diatom data recovery of the environmental regime preceded the gs 1 holocene boundary as is seen in lithostratigraphical and isotopic data during the early holocene stable isotopes show several episodes with altered levels suggesting instability of the environmental regime most probably related with the global climatic alterations

an evaluation of synthetic fluid inclusions for the purpose of trapping equilibrated coexisting immiscible fluid phases at magmatic conditions we report data that allow us to evaluate the method of trapping immiscible saline aqueous fluids i e vapor and brine in the nacl kcl hcl fecl2 auhcl2 h2o system as synthetic fluid inclusions in pre fractured quartz cores in order to quantify the concentrations of au fe k and na among coexisting three phase immiscible fluids i e haplogranite melt brine and vapor at magmatic conditions coexisting vapor and brine were trapped experimentally at 800 c and 100 110 mpa as synthetic fluid inclusions in both quartz microfractures and quenched silicate melt i e glass and also sampled indirectly using the recovered quenched aqueous fluid quartz hosted and glass hosted brine inclusions were analyzed by laser ablation inductively coupled plasma mass spectrometry la icpms and instrumental neutron activation analysis inaa respectively quenched aqueous fluid from each experiment containing a quartz core was recovered and analyzed by atomic absorption spectrophotometry aas the composition of aqueous fluids trapped as quartz hosted inclusions glass hosted inclusions and those recovered after quench yield consistent and precise data at the 2 uncertainty level for the elements of interest the overlapping au fe k and na concentrations in aqueous fluids trapped and analyzed via three entirely different instrumental techniques i e la icpms inaa and aas suggest strongly that quartz microfractures heal on a slow enough time scale to permit entrapment of fully equilibrated aqueous fluids at our experimental ptx conditions the data evince clearly that the chemical composition of fluids in quartz microfractures at the time of self healing represents equilibrium conditions hence synthetic fluid inclusions in experiments with low thermal gradients across the charge provide a reasonable estimate of fluid composition at least at the experimental conditions examined in this study

new geochronological constraints on the thermal and exhumation history of the lesser and higher himalayan crystalline units in the kullu kinnaur area of himachal pradesh india new geochronological petrological and structural data from the beas sutlej area of himachal pradesh india are used to reconstruct the tectonothermal and exhumation history of this part of the himalayan orogen sm nd garnet ages at 40 5 1 3 ma obtained on a pegmatoid from the inverse metamorphic high himalayan crystalline hhc in the malana parbati area probably mark local melting during initial decompression ongoing exhumation in ductilely deformed leuco gneiss is constrained by sm nd garnet ages at 29 1 ma and white mica rb sr ages around 24 20 ma while bt rb sr ages indicate a drop of regional metamorphic temperatures below 300 c between 15 and 12 ma the deep sutlej gorge exposes medium grade paragneisses and proterozoic orthogneisses of the lesser himalayan crystalline lhc overthrust by the hhc along the main central thrust mct mica cooling ages in the hhc are in the range of 14 11 ma above the extruded wedge of the hhc the leo pargil leucogranite and associated dykes intrude the haimanta unit hu below the weakly metamorphic palaeo mesozoic sediments of the tethyan himalayas th the leo pargil leucogranite yielded a mean sm nd garnet age of 19 1 ma and rb sr muscovite and biotite cooling ages between 16 4 and 11 6 ma marked young extrusion of lhc units resulted in differentiated exhumation cooling of more frontal parts of the orogen very young ductile deformation of lhc gneisses near wangtu is constrained by late kinematic pegmatite intrusions crosscutting the main mylonitic foliation sm nd garnet and rb sr muscovite ages of these pegmatites range between 7 9 0 9 and 5 5 0 1 ma published apatite ft ages down to 0 6 ma also document accelerated diachronous sub recent exhumation of different parts of the orogen together with geochronological data from the literature the new results demonstrate that the hhc and the hu were deformed by shortening and crustal thickening during the eohimalayan phase late eocene oligocene followed by a strong thermal overprint and intrusions of granitoids during the neohimalayan phase early to middle miocene the lhc experienced amphibolite facies metamorphic conditions in the late miocene prior to extrusion between the hhc and the very low grade lesser himalayan sediments in conjunction with climate changes young tectonic activity in this central part of the himalayan orogen may have strongly influenced fluvial incision and erosion and therefore contributed to the accelerated uplift as indicated by extensive accumulation of late miocene to early pleistocene fluviatile lacustrine sediments in the zanda basin the transhimalayan headwaters of the sutlej in western tibet

archean rocks of the black hills south dakota reworked basement from the southern extension of the trans hudson orogen the little elk and the bear mountain terranes on the margin of the precambrian core of the black hills provide the only known exposures of archean rocks between the archean wyoming and superior provinces the little elk terrane consists of a supracrustal sequence dominated by biotite feldspar gneiss meta arkose or metatuff that is intruded by the slightly metaluminous to peraluminous calc alkaline little elk granite which has a u pb intercept age of 2 549 11 m y a biotite plagioclase schist metagraywacke dominates the bear mountain terrane and is intruded subparallel to foliation by the peraluminous granite at bear mountain an isochron calculated from six severely discordant u pb zircon analyses yields an age of 2 393 230 m y the archean terranes participated in the trans hudson orogenic event suggested by a published rb sr age for the little elk granite 1 850 m y 1 87 1 97 gaigneous activity in the black hills and the similarity in orientation of the proterozoic deformational fabric with geophysical anomalies interpreted to be associated with the trans hudson orogen the metamorphic conditions estimated for the archean rocks may be the result of a thermal event that produced the proterozoic harney peak granite and thermal high northeast of lead south dakota the unexposed precambrian basement is probably dominated by granites similar to the little elk granite and supracrustal rocks consisting of continental margin deposits based on the ree contents of the archean schists and on the heavy mineral assemblages in the uraniferous nature of and the metasedimentary clasts in the lower proterozoic box elder creek formation the ages and the relatively long lived crustal sources for these archean granites and the similarity of the inferred basement characteristics to those of rocks in the wyoming province suggest that the black hills archean rocks may be the easternmost exposures of this province the probable trans hudsonian reworking of the black hills proterozoic rocks and their similarity to those in northern saskatchewan imply that the black hills occupies a tectonic position comparable to that of rocks described from the cree lake zone of saskatchewan

reconstructing palaeoclimatic variables from fossil pollen using boosted regression trees comparison and synthesis with other quantitative reconstruction methods abstract we test and analyse a new calibration method boosted regression trees brts in palaeoclimatic reconstructions based on fossil pollen assemblages we apply brts to multiple holocene and lateglacial pollen sequences from northern europe and compare their performance with two commonly used calibration methods weighted averaging regression wa and the modern analogue technique mat using these calibration methods and fossil pollen data we present synthetic reconstructions of holocene summer temperature winter temperature and water balance changes in northern europe highly consistent trends are found for summer temperature with a distinct holocene thermal maximum at ca 8000 4000 cal a bp with a mean t jja anomaly of ca 0 7 c at 6 ka compared to 0 5 ka we were unable to reconstruct reliably winter temperature or water balance due to the confounding effects of summer temperature and the great between reconstruction variability we find brts to be a promising tool for quantitative reconstructions from palaeoenvironmental proxy data brts show good performance in cross validations compared with wa and mat can model a variety of taxon response types find relevant predictors and incorporate interactions between predictors and show some robustness with non analogue fossil assemblages

geochemical and isotopic disequilibrium in crustal melting an insight from the anatectic granitoids from toledo spain in the hercynian anatectic complex of toledo act the anatectic granitoids include leucogranitic leucosomes leucogranitic massifs and restite rich granites they show a broad range of initial sr and nd isotope ratios from 0 711 to 0 720 and 0 51164 to 0 51203 respectively which clearly indicate the absence of isotopic homogenization in the melts broadly the ranges reflect the isotopic variation of the metapelitic protoliths if crustal melting occurs under water undersaturated conditions as is the case of the act the generated melts do not isotopically and chemically equilibrate with the granulitic residuum the preservation of heterogeneities could arise through a number of processes 1 duration of the process in which the presence of melts with disequilibrium features and the high solid content of several of the granites in the act point to a very short lived magmatic system 2 limited diffusion in which poorly segregated and volatile undersaturated granitoids have a very restricted opportunity for isotopic and chemical homogenization and 3 magma dynamics in which the low melting rates the high restite and low water contents and the silica rich composition of these granites together with the small volume and high viscosity values of the melts seriously restrict the physical processes leading to homogenization

garnet tourmaline and muscovite bearing leucogranites gneisses and migmatites of the higher himalayas from zanskar kulu lahoul and kashmir

magma mixing and the production of compositional variation within granite suites evidence from the granites of southeastern australia granite suites are groups of plutons possessing characteristic features that are a result of their derivation from source material of a specific composition variation within suites has been ascribed to a variety of processes magma mixing or mingling is a popular hypothesis generally proposed in terms of blending between a crustal melt and mafic material from the mantle that caused that melting when the compositions of pain of suites from the bega batholith of southeastern australia are compared any differences seen at either end of the range in composition are also seen at the other limit so that both the most mafic and mostfelsic rocks show similar relative abundances of particular elements similar relationships are seen for other granites in the region these observations are not consistent with largescale magma mixing or mingling and although those processes may operate on a small scale they cannot have been responsible for the major compositional variations likewise assimilation of country rocks had no significant role in producing variation in the granites of southeastern australia the production of variation by differential separation of melt from residual solid source material or restite must be favoured for many of the granite suites of this region

aluminum partitioning between zircon and haplogranitic melts the influence of temperature and melt composition abstract we present measurements of al concentrations in zircon xalzrc in ppm grown from one peralkaline one metaluminous and two peraluminous melts in the na2o k2o cao al2o3 sio2 system with 10 wt h2o twenty experiments were conducted at 1 gpa from 1100 to 1400 c and we infer two main conclusions first xalzrc is strongly dependent on melt aluminum saturation index asi molar ratio of al2o3 cao na2o k2o and m molar ratio of k na 2ca si al that is as melt asi values increase from 0 50 to 1 38 or m values decrease from 3 25 to 1 17 xalzrc increase correspondingly second for similar melt compositions xalzrc is positively related to temperature our data confirm that the melt parameter asi or m are appropriate compositional proxies that describe al concentration in zircon our preferred model which relates melt asi composition asimelt and temperature t in k to al in zircon xalzrc in ppm is given by log x al zrc in ppm 0 98 0 07 asi melt 4334 459 t k 4 09 0 31 this model lays the groundwork to define natural zircon parent melt composition s including changes in melt composition during zircon crystallization we extrapolate our experimental results to previously measured xalzrc data from rocks of known parentage when using whole rock as a proxy for the melt composition al concentrations in peraluminous zircon are in broad agreement with the empirical model however the model predicts lower asi values when applied to metaluminous natural zircons the model presented here is derived from high temperature and high h2o content experiments 1100 1400 c h2o 10 wt and a compositionally limited suite of melt compositions and will therefore require further development for more accurate extrapolation to lower temperatures these results demonstrate feasibility of this approach to reveal zircon parent melt composition

holocene changes in atmospheric circulation recorded in the oxygen isotope stratigraphy of lacustrine carbonates from northern sweden the oxygen isotope composition of local precipitation delta 18 o p is reconstructed from carbonate lake sediment components in a sediment core covering the last 10000 calendar years from lake tibetanus a small hydrologically open groundwater fed take in the abisko area northern sweden comparison of the delta 18 o p history with a pollen based palaeotemperature record from the same core clearly reveals pronounced deviations from the normally expected temporal delta 18 o p temperature relation so called dansgaard relation that may be a function of changing oceanicity the transition from relatively moist maritime conditions in the early holocene to a much drier climate after 6500 cal bp is reflected by major changes in forest extent and composition as recorded by pollen and plant macrofossil data at the time of maximum influence of westerly air mass circulation high zonal index c 9500 cal bp brought about by high summer insolation and enhanced meridional pressure gradients delta 18 o p at lake tibetanus was about 2 higher than would be predicted by the modem isotope temperature relation the occurrence of long term changes in delta 18 o p temperature relations which are more sensitive measures of palaeoclimate than either delta 18 o p or temperature alone needs to be taken into account when extracting palaeoclimatic information from continental oxygen isotope records less

primary crustal melt compositions insights into the controls mechanisms and timing of generation from kinetics experiments and melt inclusions abstract we explore the controls mechanisms and timing of generation of primary melts and their compositions and show that the novel studies of melt inclusions in migmatites can provide important insights into the processes of crustal anatexis of a particular rock partial melting in the source region of granites is dependent on five main processes i supply of heat ii mineral melt interface reactions associated with the detachment and supply of mineral components to the melt iii diffusion in the melt iv diffusion in minerals and v recrystallization of minerals as the kinetics of these several processes vary over several orders of magnitude it is essential to evaluate in nature which of these processes control the rate of melting the composition of melts and the extent to which residue melt chemical equilibrium is attained under different circumstances to shed light on these issues we combine data from experimental and melt inclusion studies first data from an extensive experimental program on the kinetics of melting of crustal protoliths and diffusion in granite melt are used to set up the necessary framework that describes how primary melt compositions are established during crustal anatexis then we use this reference frame and compare compositional trends from experiments with the composition of melt inclusions analyzed in particular migmatites we show that for the case of el hoyazo anatectic enclaves in lavas the composition of glassy melt inclusions provides important information on the nature and mechanisms of anatexis during the prograde suprasolidus history of these rocks including melting temperatures and reactions and extent of melt interconnection melt homogenization and melt residue equilibrium compositional trends in several of the rehomogenized melt inclusions in garnet from migmatites granulites in anatectic terranes are consistent with diffusion in melt controlled melting though trace element compositions of melt inclusions and coexisting minerals are necessary to provide further clues on the nature of anatexis in these particular rocks

maximum and minimum water contents of granitic melts generated in the crust a reevaluation and implications abstract recent results of studies aimed to determine the water solubilities and the liquidus temperatures in synthetic and natural granitic systems are used to constrain the minimum water contents of granitic melts generated in the crust as a function of pressure temperature melt composition and water activity it is concluded that melts generated in the crust at high temperature and low water activities such as a type granites contain higher water contents than previously assumed up to 20 at 800 900 c and 3 7 kbar as a consequence the melt fraction produced at a given amount of available water can be up to 20 lower the minimum water content of melts generated by partial melting of crustal protoliths especially quartzofeldspathic rocks can be predicted adequately from the liquidus curves in granitic systems this water content can be higher if the melt composition departs from a minimum or eutectic quartzofeldspathic composition melts generated from quartzofeldspathic rocks at low temperature 750 c and below are necessarily water rich 5 wt h 2 o and have approximately the same viscosity or even slightly lower viscosities than melts generated at higher temperatures viscosities in the range 10 4 3 10 5 4 pa s recent experimental data also show that the value of the positive d p d t slope of the liquidus curves for fixed water contents above 800 c is lower than predicted by previous models thus adiabatic decompression produces a higher amount of melt than previously assumed at high temperature the formation of melt by adiabatic decompression can be up to 50 higher than assumed

the solubility of h_ 2 o in melts in the system sio_ 2 al_ 2 o_ 3 na_ 2 o k_ 2 o at 1 to 2 kbars the solubilities of water in six melts in the system k 2 o na 2 o al 2 o 3 sio 2 were determined at 970 1630 bars and 800 c melts were synthesized hydrothermally in pt capsules in cold seal vessels and then quenched isobarically the solubilities were determined by micromanometric measurement of h 2 o evolved during vacuum fusion of vesicle free glass wafers and are reproducible to 2 8 2 s d of the concentration the solubilities at 970 bars for the granitic and phonolitic minimum melts are 2 88 pm 0 10 wt and 5 01 pm 0 14 wt respectively both peralkaline and peraluminous granitic melts have higher h 2 o solubilities than the 1 kbar p h 2 o minimum melt and indicate the existence of minima in solubilities at molar na k al 1 along joins of constant sio 2 two melts at constant sio 2 and na k al ratio but varying in na na k 0 57 0 69 molar have the same solubility 2 88 pm 0 10 2 74 pm 0 10 wt the compositional depend

early holocene dune field development in dalarna central sweden a geomorphological and geophysical case study bonasheden sweden s largest continuous dune field situated in the county of dalarna central sweden has been investigated using lidar light detection and ranging remote sensing ground penetrating radar as well as by field observations and luminescence dating the use of lidar in conjunction with geographic information system gis software proved to be efficient in mapping the inactive dune field and classifying the dune morphology especially when slope raster images were used the dunes have formed mostly by winds from the northwest nw and are of a transverse type still other dune types such as parabolic dunes and transverse dunes with a deviating orientation are present also there seems to be different generations of dunes suggesting a complex palaeowind environment with a change from predominantly north westerly winds to more westerly winds luminescence dating finally allows us to have an absolute chronology of the development of the bonasheden dune field revealing formation of the dune field closely following the de glaciation of this part of sweden c 10 5ka the well preserved transverse shape of the majority of the dunes suggests rapid stabilization by vegetation although sand drift still seems to have been active on a noticeable scale for at least 1500years and also occasionally and patchy as coversand deposition during the late holocene a simple model is proposed for the dune field development of bonasheden based on our findings this model is a useful addition since the majority of present day dune field models focus on the formation of parabolic dunes or large unvegetated dune fields our results suggest that most models cannot adequately simulate the formation of such small dune fields as that of bonasheden with apparently rapidly fixated transverse dunes in a previously glaciated now vegetated area less

holocene history of landscape development in the catchment of lake skogstjern southeastern norway based on a high resolution multi proxy record a high resolution multi proxy record from sediments of a small sized lake situated in telemark southeastern norway was used to reconstruct the local landscape development of the past c 10 500 years our data demonstrate that changes in vegetation composition and structure in the first two thirds of the holocene are principally attributable to climatic changes and high erosion rates as deduced from geochemical and physical loss on ignition proxy analyses the highest signals of erosional inputs to the lake c 8030 5760 cal bp can be correlated with the first part of the holocene thermal maximum nevertheless evidence from pollen non pollen palynomorphs and microscopic charcoal analyses indicates the presence of nutrient rich and disturbed environments already during the middle mesolithic c 10 050 9400 cal bp it also shows traces of animal husbandry c 5580 cal bp and small scale cereal cultivation c 5520 cal bp in the early neolithic in subsequent periods human impact remains at a

phase relationships of s type granite with h2o to 35 kbar muscovite granite from harney peak south dakota muscovite granite 13 8 muscovite 4 8 normative corundum was reacted with varying percentages of h 2o in cold seal vessels at 2 kbar and in piston cylinder apparatus between 10 and 35 kbar the diagrams illustrating melting crystallization relationships are p t sections with both excess h 2o and with no h 2o added 0 66 h 2o in rock t x h 2o sections at 15 kbar and 25 kbar showing h 2o undersaturated conditions the h 2o undersaturated surface for the crystallization of quartz coesite small amounts of aluminosilicate minerals persist to higher temperatures glass compositions measured by electron microprobe from samples with 5 h 2o at 15 kbar confirm that liquids are syenitic through at least 100 c above the solidus as predicted from the effect of pressure on the residua system results are explained successfully by phase relationships involving muscovite quartz and orthoclase in k 2o al 2o 3 sio 2 h 2o with reactions depicted in a p total p e h 2o t model with special reference to the divariant surfaces in the region p e h 2o p total with reduced p e h 2o or a h 2o produced either by small amounts of h 2o and h 2o undersaturation or by co 2 h 2o mixtures subsolidus dehydration reaction temperatures decrease vapor present solidus temperatures increase and muscovite stability in presence of liquid increases in general muscovite biotite and amphibole can be precipitated from magmas containing only a few tenths per cent h 2o although the h 2o undersaturated liquids coexisting with crystals may contain 3 or more dissolved h 2o this particular granite cannot be a primary magma from mantle or subducted oceanic crust it is a possible product of partial fusion of pelitic rocks between about 20 km and 40 km depth given sufficient h2o and xenocrystal muscovite or sillimanite from the source rocks the phase relationships are consistent with the idea of s type granites but not sufficient to prove the origin of this rock additional tests require phase relationships of other associated granitic rocks and details of geochemistry geophysics and field relationships

holocene annual mean temperature changes in estonia and their relationship to solar insolation and atmospheric circulation patterns abstract we reconstructed annual mean temperature tann trends from three radiocarbon dated holocene pollen stratigraphies from lake sediments in estonia northern europe the reconstructions were carried out using a north european pollen climate calibration model based on weighted averaging partial least squares regression the cross validated prediction error of the model is 0 89 c and the coefficient of determination between observed modern tann values and those predicted by the model is 0 88 in the reconstruction the holocene thermal maximum htm is distinguishable at 8000 4500 cal yr b p with the expansion of thermophilous tree species and tann on average 2 5 c higher than at present the pollen stratigraphical data reflect progressively warmer and drier summers during the htm analogously with the modern decadal scale climatic variability in north europe we interpret this as an indication of increasing climatic continentality due to the intensification of anticyclonic circulation and meridional air flow post htm cooling started abruptly at around 4500 cal yr b p all three reconstructions show a transient ca 300 years cooling of 1 5 2 0 c at 8600 8000 cal yr b p we tentatively correlate this cold event with the north atlantic 8 2 ka event at 8400 8000 cal yr b p provided that the 8 2 ka event was caused by freshening of the north atlantic surface water our data provide evidence of the climatic and vegetational responsiveness of the boundary of the temperate and boreal zones to the weakening of the north atlantic thermohaline circulation and the zonal energy transport over europe no other cold events of comparable magnitude are indicated during the last 8000 years

platinum solubility and partitioning in a felsic melt vapor brine assemblage abstract the solubility and partitioning of pt in a s free vapor brine rhyolite melt pt metal assemblage has been quantified at 800 c f o 2 nno and pressures of 100 and 140 mpa vapor and brine were sampled at run conditions by trapping these phases as glass hosted fluid inclusions as the melt cooled through the glass transition temperature the vapor and brine were in equilibrium with the melt at the time of trapping and thus represent fluids which were sampled at the termination of each experimental run the microthermometrically determined salinities of vapor and brine are 2 and 63 wt nacl eq and 9 and 43 wt nacl eq at 100 and 140 mpa respectively platinum solubilities in vapor brine and glass i e quenched melt were quantified by using laser ablation inductively coupled plasma mass spectrometry la icp ms equilibrium is discussed with reference to the major and trace element concentrations of glass hosted fluid inclusions as well as the silicate melt over run times that varied from 110 to 377 h at 140 mpa and 159 to 564 h at 100 mpa platinum solubility values 1 in h2o saturated felsic melt are 0 28 0 13 g g and 0 38 0 06 g g at 140 and 100 mpa respectively platinum solubility values 1 x at 140 and 100 mpa respectively in aqueous vapor are 0 91 0 29 g g and 0 37 0 17 g g and in are brine 16 10 g g and 3 3 1 0 g g the measured solubility data were used to calculate nernst type partition coefficients for pt between vapor melt brine melt and vapor brine the partition coefficient values 1 x for vapor melt brine melt and vapor brine at 140 mpa are 2 9 1 0 67 27 and 0 13 0 05 and at 100 mpa are 1 0 0 2 6 8 2 4 and 0 15 0 05 the partitioning data were used to model the pt scavenging capacity of vapor and brine during the crystallization driven degassing i e second boiling of a felsic silicate melt over a depth range i e 3 6 km consistent with the evolution of magmatic hydrothermal ore deposits model calculations suggest that aqueous vapor and brine can scavenge sufficient quantities of pt and by analogy other platinum group elements pge to produce economically important pge rich magmatic hydrothermal ore deposits in earth s upper continental crust

aluminum in zircon as evidence for peraluminous and metaluminous melts from the hadean to present zircon structurally accommodates a range of trace impurities into its lattice a feature which is used extensively to investigate the evolution of silicate magmas one key compositional boundary of magmas is defined by whether the molar ratio of al2o3 cao na2o k2o is larger or smaller than unity here we report 800 al in zircon concentrations from 19 different rocks from the lachlan fold belt southeastern australia new england usa and arunachal leucogranites eastern himalaya with al2o3 cao na2o k2o whole rock values that range from 0 88 to 1 6 zircons from peraluminous rocks yield an average al concentration of 10 ppm which distinguishes them from crystals found in metaluminous rocks 1 3 ppm this difference is related to the materials involved in the melting assimilation and or magma differentiation processes for example magmas that assimilate al rich material such as metapelites are expected to produce melts with elevated alumina activities and thus zircons with high al concentrations these observations are applied to the archean and hadean jack hills detrital zircon record detrital archean zircons with ages from about 3 30 to 3 75 ga yield al in zircon concentrations consistent with origins in peraluminous rocks in 8 of the cases n 236 a single zircon from the pre 3 9 ga age group n 39 contains elevated al contents which suggests that metaluminous crustal rocks were more common than peraluminous rocks in the hadean weathered material assimilated into these hadean source melts was not dominated by al rich source material

the pace of holocene vegetation change testing for synchronous developments mid to high latitude forest ecosystems have undergone several major compositional changes during the holocene the temporal and spatial patterns of these vegetation changes hold potential information to their causes and triggers here we test the hypothesis that the timing of vegetation change was synchronous on a sub continental scale which implies a common trigger or a step like change in climate parameters pollen diagrams from selected european regions were statistically divided into assemblage zones and the temporal pattern of the zone boundaries analysed the results show that the temporal pattern of vegetation change was significantly different from random times of change cluster around 8 2 4 8 3 7 and 1 2 ka while times of higher than average stability were found around 2 1 and 5 1 ka compositional changes linked to the expansion of corylus avellana and alnus glutinosa centre around 10 6 and 9 5 ka respectively a climatic trigger initiating these changes may have occurred 0 5 to 1 ka earlier respectively the synchronous expansion of c avellana and a glutinosa exemplify that dispersal is not necessarily followed by population expansion the partly synchronous partly random expansion of a glutinosa in adjacent european regions exemplifies that sudden synchronous population expansions are not species specific traits but vary regionally

a model of pollen source area for an entire lake surface a model of pollen deposition on the surface of an entire basin is developed to estimate pollen source area and results are compared with those for a point at the center of a basin i c prentice 1985 quaternary research 23 76 86 1988 vegetation history pp 17 42 kluwer academic this model is more appropriate for approximating the source area of pollen in lake sediment since mixing in lake water and focusing of sediment redistribute pollen originally deposited over the entire surface in general the pollen source radius for the entire basin surface is 10 30 smaller than the source radius for a point at the center the difference in the source radius is more profound for heavier pollen types such as spruce and sugar maple than for lighter types such as oak and ragweed the average pollen input to the entire surface is more strongly influenced by nearby pollen sources than pollen deposition at the center the pollen record from a lake may therefore provide different spatial resolution than the record from a bog of similar radius

european lakes as palaeohydrological and palaeoclimatic indicators abstract lakes in temperate regions have fluctuated in size on annual to millenial time scales changes in water level or depth can be reconstructed by applying geomorphic sedimentological and biostratigraphic methods to transects of sediment cores this systematic field based approach has been used at a number of sites in europe it is illustrated by reconstructions of water level changes in lakes from southern sweden these lakes have shown broadly synchronous changes during the holocene such synchronous changes in water levels at several sites in a region reflect climatic changes inferences about the mechanism of the climatic change depend on identifying both synchronous changes within a region and differences in the direction magnitude and timing of lake level changes between regions continental compilations of lake level data are therefore necessary detailed studies are not available from enough sites but the interpretation of already existing stratigraphic and biostratigraphic data in terms of lake level changes has greatly increased the number of sites available for a continental scale synthesis in europe this eclectic literature based approach is illustrated with examples from southern europe lakes in the mediterranean region were high around the glacial maximum and again somtime during the first half of the holocene in the western mediterranean the peak of late glacial aridity occurred at 15 000 16 000 bp and the lakes were already high again by 12 000 bp in the east maximum late glacial aridity occurred between 13 000 and 11 000 bp and there was a gradual return to wetter climates during the early holocene such that 9000 bp was more arid than 6000 bp most lakes in the mediterranean region were high at 6000 bp the transition to arid conditions after 5000 bp occurred abruptly in the west and more gradually in the east the lakes of southern sweden indicate drier climates in the early holocene ca 9000 bp more effective moisture between 8000 and 6000 bp increased aridity between 5500 and 3500 bp and increased effective moisture again during the last 3000 years the history of lake level changes in southern sweden and the mediterranean region can be partially explained in terms of changes in the direct effects of insolation and in the strength and position of the westerlies and of the subtropical high pressure cell during the late quaternary

late magmatic immiscibility during batholith formation assessment of b isotopes and trace elements in tourmaline from the land s end granite sw england quartz tourmaline orbicules are unevenly distributed in the roof segment of the land s end granite sw england this study shows that the orbicules formed from an immiscible hydrous borosilicate melt produced during the late stages of crystallization and differentiates tourmaline formed by dominantly magmatic and dominantly hydrothermal processes trace elements and boron isotope fractionation can be tracked in tourmaline and create a timeline for crystallization tourmaline from the granite matrix has higher v cr and mg content and is isotopically heavier than the later crystallizing inner orbicule tourmaline overgrowths of blue tourmaline occurring together with quartz showing hydrothermal cathodoluminescence textures crystallized from an aqueous fluid during the very last crystallization and are significantly higher in sr and sn and isotopically heavier tourmaline associated with sn mineralization is also high in sr and sn but has boron isotopic compositions close to that of the magmatic tourmaline and is not formed by the same fluids responsible for the blue overgrowths the ore forming fluids precipitating tourmaline and cassiterite are likely derived from the same magma source as the granite but exsolved deeper in the magma chamber and at a later stage than orbicule formation tourmaline from massive quartz tourmaline rocks is concentrically zoned with major and trace element compositions indicating crystallization from a similar melt as for the orbicules but shows a more evolved signature