crustal heat production and mantle heat flow in central and eastern europe abstract the conversion of seismic velocity p into radiogenic heat production a enables the distribution of crustal heat sources to be estimated this technique was used to assess the mantle moho heat flow for 49 seismic velocity depth profiles located along five continental traverses in central and eastern europe the effect of pressure and temperature on p was taken into account as was the age dependence of a the uppermost part of the crust is dominated by microcracks that may have allowed a certain redistribution of radioactive elements by deep groundwater migration furthermore owing to the highly variable value of the pressure derivative of v p in the uppermost crust the use of a a p relationship is problematic within this depth range this radioactivity enriched zone the thickness of which can be determined from the parameters of the heat flow heat production relationship was therefore treated separately according to the model adopted for the upper crust the moho heat flow ranges from 14 to 26 mw m 2 in the stable continental areas such as the shields or ancient platforms younger terrains are characterized by elevated moho heat flows of 20 to 40 mw m 2 and the moho heat flow may eventually attain values over 50 mw m 2 in regions characterized by very high surface heat flow such as the pannonian basin for example the present data were compared with crustal models proposed by other authors moho heat flow estimates based on a simple exponential distribution of heat sources valid for the whole crust might be too high if applied to stable continental crust our data confirm a considerable variability in the mantle heat flow corresponding to the large scale tectonothermal evolution with a generally lower moho heat flow typical of consolidated stable continental crust the discrepancy in relation to the above estimates can be accounted for by a heat generation hump beneath an upper zone of exponential decline

intersector element partitioning in tourmaline a potentially powerful single crystal thermometer hourglass sector zoning and related polar overgrowths are common features of metamorphic tourmaline developing as a result of variations in element preference on the different growth surfaces for sector zoned crystals three domains are present for each growth zone c c and a with compositional differences most distinct for ca and ti and among c and c sectors intersector differences vary commonly showing decreasing fractionation from core to rim attributed to increasing metamorphic grade here we show that intersector element partitioning is temperature dependent and derive empirical geothermometers based on c c and c a partitioning of ca and ti these thermometers are applicable over a range of temperatures and bulk rock compositions intersector partitioning is not affected by re equilibration and records and preserves complete t histories of individual tourmaline grains from prograde to peak and on to retrograde growth information on element mobility is preserved by tourmaline composition because intersector partitioning is independent of element concentration these factors make intersector partitioning an ideal tool to elucidate the thermal history of tourmaline grains and thus their host environment and tourmaline s refractory nature preserves these signatures even into the sedimentary record

the variation of heat generation density and seismic velocity with rock type in the continental lithosphere abstract the petrophysical properties radioactive heat generation compressional wave velocity and density are related to rock type in crystalline rocks the cation fraction in the rock forming minerals is applied to determine the relationships quantitatively heat generation exhibits considerable variation with rock type as well as with the geologic age of the rocks therefore the relation between heat generation and rock type has been split into a relation for phanerozoic rocks and another for precambrian rocks which exhibit significantly lower heat generation only 1 3 of that of phanerozoic rocks the interrelations between the petrophysical properties are applied to fennoscandia precambrian terrane and southern bavaria northern alpine foreland phanerozoic rocks to estimate the heat generation by radioactivity in the crust and the heat flow density from the upper mantle

evaluation of proposed early holocene advances of alpine glaciers in the north cascade range washington state usa constraints provided by palaeoenvironmental reconstructions many palaeoenvironmental reconstructions from across western north america indicate that the early to mid holocene was warmer and drier than present the wide distribution of these records suggests that relatively mild and arid conditions were regionally ubiquitous during the early holocene in contrast two recently proposed advances of alpine glaciers in the cascade range of washington state corresponding to equilibrium line altitude depressions of 350 to 450 m are placed in the early holocene the juxtaposition of the proposed major expansion of early holocene alpine glaciers with the constraint provided by a number of palaeoenvironmental reconstructions from directly adjacent areas results in palaeoclimatic gradients that are untenable the apparent diachronous behaviour of adjacent palaeoenvironmental records may be an artifact of dating errors

seismic basement in poland the area of contact between precambrian and phanerozoic europe in poland has complicated structure of sedimentary cover and basement the thinnest sedimentary cover in the mazury belarus anteclize is only 0 3 1 km thick increases to 7 8 km along the east european craton margin and 9 12 km in the trans european suture zone tesz the variscan domain is characterized by a 1 to 2 km thick sedimentary cover while the carpathians are characterized by very thick sediments up to c 20 km the map of the basement depth is created by combining data from geological boreholes with a set of regional seismic refraction profiles these maps do not provide data about the basement depth in the central part of the tesz and in the carpathians therefore the data set is supplemented by 32 models from deep seismic sounding profiles and a map of a high resistivity low conductivity layer from magnetotelluric soundings identified as a basement all of these data provide knowledge about the basement depth and of p wave seismic velocities of the crystalline and consolidated type of basement for the whole area of poland finally the differentiation of the basement depth and velocity is discussed with respect to geophysical fields and the tectonic division of the area

8000 year old wood from the athabasca glacier alberta several wood fragments of pinus sp dated at 8230 80 and 8000 90 years bp and abies sp were recovered from the snout of the athabasca glacier this wood derived from an unknown source up valley indicates that the glacier was less extensive than at present during the hypsithermal and that an area up valley of the present snout was tree covered ca 8000 8300 years bp

gravitational orogenic collapse vs plate boundary stresses a numerical modelling approach to the permo carboniferous evolution of central europe a two dimensional thermo mechanical finite element model is used to study the permo carboniferous evolution of central europe along a lithosphere scale transect from the variscan internides to the undeformed foreland the study concentrates on a quantitative evaluation of the processes controlling late orogenic extension and destruction of the variscides particularly the gravitational instability of thickened crust modelling results suggest that gravitational forces along cannot reproduce the observed timing and amount of permo carboniferous crustal thinning tensile plate boundary forces are required in addition to gravitation to restore a crustal thickness of approximately 30 km in the variscan internides stresses as little as 10 mpa result in up to 28 extension and a good fit between observed data and model predictions it is concluded that the stephanian to rotliegend evolution in the vicinity of the modelled traverse resulted not from gravitational forces inherited from variscan crustal thickening but was related to a change in orientation of the plate boundary stresses at the end of the westphalian

an 18 000 year palynological record from the southern alberta segment of the classical wisconsinan ice free corridor radiocarbon dates of 18 300 380 years bp gsc 2668 and 18 400 1090 years bp gsc 2670 on moss fragments from the clay near the base of a core from chalmers bog alberta indicate that the classical wisconsinan ice free corridor was in existence in the foothills of southern alberta by this time palynological studies show sparse herbaceous tundra like vegetation probably prevailed at this time in the area surrounding the small lake formed in the abandoned glacial spillway later shrubs became more prominent to form a shrub tundra environment sometime before 8220 years bp gsc 2851 trees began to invade the area and the pinus contorta dominated coniferous forest extant in the area today began to form bog and fen vegetation invaded the shallow lake basin about this time as well to form the bog that occupies the basin to the present day

lithospheric structure of the bohemian massif and adjacent variscan belt in central europe based on profile s01 from the sudetes 2003 experiment 1 the sudetes 2003 seismic experiment investigated the lithospheric structure of the eastern part of the variscan belt of central europe the key profile of this experiment s01 was 630 km long and extended southwestward from the margin of the east european craton across the trans european suture zone tesz and sudetes and across the bohemian massif that contains the active eger ohre rift which is an element of the european cenozoic rift system good quality first arrivals and later phases of refracted reflected p and s waves were interpreted using 2 d ray tracing techniques the derived seismic model shows large variations in the internal structure of the crust while the depth to the moho varies in the relatively narrow depth interval of 28 35 km except for the polish basin on the northeast end of the profile the sedimentary cover is thin the crystalline upper and middle crust with velocities of 5 9 6 4 km s 1 is about 20 km thick and the 7 10 km thick lower crust can be divided into three regions based on p wave velocities a low velocity region 6 5 6 6 km s 1 beneath eger rift and sudetes that is bounded on the southwest and northeast by regions of significantly higher velocity 6 8 7 1 km s 1 beneath the saxothuringian and moldanubian in the southwest and fore sudetic monocline and polish basin in the northeast high velocity bodies vp 6 5 km s 1 were delineated in the upper crust of the eger rift region the seismic structure along the s01 profile images a variscan orogenic wedge resting on the down warped margin of the plate margin containing the tesz this situation implies the northerly directed subduction of the rheic ocean that existed between the southern margin of the old red continent and the armorican terranes presently accreted into the variscan belt closure of this ocean produced the rheic suture between low velocity crust of the variscan orogenic wedge and higher velocity crust of the tesz

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

boron isotope variations in tourmaline from hydrothermal ore deposits a review of controlling factors and insights for mineralizing systems abstract tourmaline group minerals are typically the predominant host of boron in hydrothermal mineral deposits boron is a fluid mobile element whose isotopic composition reflects many factors that are relevant to understanding mineralizing processes including fluid source s fluid rock interaction and formational temperature a new compilation of 2622 published 11b values for tourmaline from diverse types of hydrothermal ore deposits is presented here with the focus 2215 analyses on seven main types porphyry cu mo au deposits granite related sn w deposits iocg deposits orogenic au deposits stratabound vms and sedex deposits and sediment hosted u deposits the total range of 11b values for the seven types is 26 8 to 35 0 four granite sn w orogenic au stratabound vms and sedex have median 11b values close to the continental crustal average of about 10 the median values for iocg and porphyry cu mo au deposits are higher 3 9 and 2 1 respectively whereas sediment hosted u deposits have distinctly high 11b median 25 3 importantly a considerable range of 11b values exists for tourmaline within each deposit type the smallest 17 8 for granite sn w deposits and the largest 48 0 for iocg deposits the boron isotope variations in tourmaline from different deposits are suggested reflect three levels of controlling factors and how these factors operated is illustrated with selected number of case studies the primary factor is the composition of the boron source secondary effects relate to fluid tourmaline fractionation equilibrium or rayleigh there are commonly also tertiary factors that depend on evolution of the specific deposit these include fluid mixing changing water rock ratio and or depositional temperature influences of other boron bearing minerals and where relevant post ore metamorphism separating the effects of these factors is rarely possible from boron isotopes alone however the growth of multi isotope studies of tourmaline and coexisting phases such as mica as well as developments in modelling experimentation of boron isotopes and element partitioning suggest that this limitation will be overcome

the donoso copper rich tourmaline bearing breccia pipe in central chile petrologic fluid inclusion and stable isotope evidence for an origin from magmatic fluids the copper rich tourmaline bearing donoso breccia pipe is one among more than 15 different mineralized breccias in the giant 50 million metric tonnes of copper miocene and pliocene rio blanco los bronces copper deposit in the high andes of central chile this breccia pipe bracketed in age between 5 2 and 4 9 ma has dimensions of 500 by 700 m at the current surface 3 670 m above sea level its roots have yet to be encountered and it is 300 m in diameter at the depth of the deepest drill holes the donoso breccia is for the most part monolithic containing clasts of the equigranular quartz monzonite pluton which hosts the pipe it is matrix supported with between 5 and 25 of the total rock volume consisting of breccia matrix minerals which include tourmaline quartz chalcopyrite pyrite specularite and lesser amounts of bornite and anhydrite an open pit mine centered on this breccia pipe has a current production of 50 000 tonnes of ore per day at an average grade of 1 2 copper and copper grade in the breccia matrix is significantly higher measured 18o for tourmaline and quartz from the matrix of the donoso breccia at different levels of the pipe range from 6 9 to 12 0 and measured d in tourmaline ranges from 73 to 95 temperatures of crystallization of these minerals as determined by the highest homogenization temperatures of highly saline fluid inclusions range from 400 to 690 c when corrected for these temperatures the stable isotope data indicate that fluids from which these breccia matrix minerals precipitated were magmatic with 18o between 5 6 to 9 1 and d between 51 to 80 these isotopic data preclude participation of a significant amount of meteoric water in the formation of the donoso breccia they support a model in which brecciation is caused by expansion of magmatic fluids exsolved from a cooling pluton and breccia matrix minerals including copper sulfides precipitated from the same magmatic fluids responsible for brecciation sericitic alteration of clasts in the breccia was also caused by these magmatic fluids different types of fluid inclusions imply that several different magmatic fluids were involved in formation of the donoso breccia these include high temperature highly saline non boiling fluids trapped in inclusions that homogenize by halite dissolution which probably exsolved from a magma cooling under relatively high 1 kbar lithostatic pressure conditions consistent with geologic constraints other high temperature highly saline fluids are trapped in inclusions that homogenize by vapor bubble disappearance and are spatially associated with vapor rich inclusions suggesting either phase separation boiling or simultaneous separation of immiscible brine and vapor from a magma cooling at lower hydrostatic pressure conditions both types of high temperature highly saline fluids circulated intermittently as pressure fluctuated between lithostatic and hydrostatic conditions because of episodes of sealing and rebrecciation

reconstructing millennial scale regional paleoclimates of boreal canada during the holocene abstract regional paleoclimate reconstructions for northern canada quantify holocene climate variability on orbital and millennial time scales and provide a context to better understand the current global warming the reconstructions are based on available pollen diagrams from the boreal and low arctic zones of canada and use the modern analog technique mat four regional reconstructions document the space time evolution of the climate during the holocene highest summer and winter temperatures anomalies are found in central canada during the early holocene eastern canada was relatively cool in the early holocene whereas central canada was warmest at that time labrador was relatively dry in the early to mid holocene during which time western canada was relatively moist millennial scale temperature variations especially the medieval warm period and little ice age are seen across the continent with some suggestion of time transgressive changes from west to east at the millennial scale precipitatio

syn convergent exhumation and lateral extrusion in continental collision zones insights from three dimensional numerical models abstract three dimensional thermomechanical finite element models are used to simulate the evolution of collisional orogens of finite axial extent special focus is on the spatial and temporal variations of stress and strain in the resulting orogen leading to lateral extrusion and syn convergent exhumation besides the collision zone the model incorporates an area which is not constrained by a convergent boundary condition and thus allows orogenic material to flow out laterally altogether 17 different model scenarios were tested starting from a model with standard material parameters and boundary conditions several variations concerning crustal temperature rheology convergence rates crust mantle coupling as well as the geodynamic setting of the evolving orogen are examined modelling results indicate that orogen parallel extension is intimately related to continental collision and occurs even during the early stages of convergence unless a rigid block adjoins and prevents lateral extrusion it typically reaches 20 40 of the amount of convergence the models show substantial spatial and temporal variations of stress and strain in the collision zone and its surrounding in particular the near surface stress field in the orogen s interior completely reorganises during convergence at later convergence stages the uppermost crust is subject to normal faulting while contemporaneously at deeper crustal levels compressive stress fields prevail the spatial relation of these different stress regimes in the orogenic crust strongly favours syn convergent exhumation by tectonic denudation finally a semiquantitative comparison between the modelling results and three modern collision zones in the alpine himalayan belt addresses the distribution of different tectonic styles the respective amounts of lateral extrusion as well as seismological observations

from the variscan to the alpine orogeny crustal structure of the bohemian massif and the western carpathians in the light of the sudetes 2003 seismic data summary the variscan orogeny is the major middle to late palaeozoic tectonometamorphic event in central europe and the bohemian massif is the largest exposure of rocks deformed during this orogeny the bohemian massif consists of the saxothuringian barrandian and moldanubian units adjacent to this massif in the southeast the western carpathians form an arc shaped mountain range related to the alpine orogeny during the cretaceous to tertiary the complex crustal scale geological structure of the variscan bohemian massif and the western carpathians and especially their contact were analysed in this study employing the data of the sudetes 2003 international seismic refraction experiment the analysed seismic data were acquired along the 740 km long nw se oriented s04 profile that crossed the bohemian massif and the western carpathians before terminating in the pannonian basin the data were interpreted by 2 d trial and error forward modelling of p waves and additional constraints on crustal structure were provided by gravity modelling the complex velocity structure derived in our analysis included low velocities of 5 85 km s 1 at the contact of the saxothuringian and barrandian units that reflect the presence of low density granites there are distinct lateral variations in deep crustal structure in the transition between the bohemian massif and the western carpathians the abrupt change of the crustal thickness in this transition zone may be associated with the pieniny klippen belt a deep seated boundary between the colliding palaeozoic lithospheric plate to the north and the alcapa microplate to the south in the upper crust of this transition low velocities of 4 km s 1 extend to 6 km and represent the sedimentary fill of the carpathian flysch and foredeep that thins towards the foreland this basin is also expressed as a pronounced gravity low the moho in the carpathians reaches a depth of 32 33 km in contrast in the pannonian basin the moho rises to a depth of 25 km which corresponds to the pannonian gravity high

synthesis of tourmaline solid solutions in the system na 2 o mgo al 2 o 3 sio 2 b 2 o 3 h 2 o hcl and the distribution of na between tourmaline and fluid at 300 to 700 c and 200 mpa tourmaline has been synthesized hydrothermally at 200 mpa between 300 and 700 c from oxide mixtures with mg al ratios for the end members dravite namg3al6 si6o18 bo3 3 oh 3 oh and mg foitite mg2al al6 si6o18 bo3 3 oh 3 oh six different na concentrations were investigated to determine the distribution of na between tourmaline and fluid in the sio2 saturated system na2o mgo al2o3 sio2 b2o3 h2o hcl synthetic tourmaline ranges from x site vacant tourmaline mg foitite to nearly ideal dravite with na 0 95 apfu there are small but significant amounts of proton deficiency and negligible tetrahedral al chemical variation is primarily caused by the substitutions al mg 1na 1 and minor almg 1h 1 varying amounts of na and determine the mg al ratios besides tourmaline and quartz additional mg al phases are chlorite and at 700 c cordierite albite is also present at high na concentrations in the bulk composition the c dimension of the tourmaline crystals increases with na in tourmaline the amount of na in the x site depends strongly on the bulk concentration of na in the system as well as on the temperature these factors in turn control the phase assemblage and the composition of the fluid phase for the assemblage tourmaline quartz chlorite cordierite fluid a linear relationship exists between na concentration in the fluid quenched after the run and tourmaline with temperature t c 25 c nafluid natur 558 878 14 692 r2 0 96

crustal temperatures along the central segment of the european geotraverse abstract by including the data on crustal structure the temperature distribution was calculated for a sizeable part of the central segment of the european geotraverse a two dimensional steady state equation of heat conduction in an inhomogeneous medium was solved by means of the finite difference method and several slightly different approaches are compared and discussed the data compiled on the surface heat flow together with the data from the vertical distribution of thermal conductivity and from the heat production along the egt served to test the computation techniques and assess the resultant temperature field it is shown that quite flat isotherms could be expected along the central segment with values of 800 900 c which are typical at 40 km deep

postglacial vegetational history of tonquin pass british columbia a pollen and macrofossil study of peat sediments in tonquin pass british columbia provides the oldest dated record of vegetational and climatic changes in the middle canadian rockies paleoecological interpretation of these events dated by tephrochronology and radiocarbon dating is facilitated by comparisons with other regional pollen profiles late wisconsin ice receded from tonquin pass prior to 10 000 years bp by 9700 years bp a pinus contorta forest with an understory dominated by ferns had colonized the area the climate of this period was cool and moist following this interval was a brief episode 9000 8040 years bp of haploxylon pine dominance during which the climate became colder a long warm period beginning by 8040 years bp was characterized by desiccation of local meadows and fens and invasions of these areas by trees principally picea dated fossil picea and abies logs from alpine bogs within jasper national park document that timberlines had advanced beyond present limits by 8770 years b

trace elements in tourmalines from massive sulfides deposits and tourmalinites geochemical controls and exploration applications trace element contents of tourmalines from massive sulfide deposits and tourmalinites have been determined in situ by proton microprobe 390 analyses were acquired from 32 polished thin sections concentrations of trace elements in the tourmalines vary widely from 40 to 3 770 ppm mn 4 to 1 800 ppm ni 2 to 1 430 ppm cu 9 to 4 160 ppm zn 3 to 305 ppm ga 6 to 1 345 ppm sr 10 to 745 ppm sn 49 to 510 ppm ba and 3 to 4 115 ppm pb individual grains and growth zones are relatively homogeneous suggesting that these trace elements are contained within the crystal structure of the tourmaline and are not present in inclusions the highest base metal contents are in ore related tourmaline samples from kidd creek ontario broken hill australia and sazare japan tourmaline data from these and many other massive sulfide deposits cluster by sample and display broadly linear trends on zn vs fe plots suggesting chemical control by temperature and hydrothermal and or metamorphic fluid mineral equilibria significant ni occurs only in samples from the kidd creek cu zn pb ag deposit which is associated with a large footwall ultramafic body an overall antithetic relationship between zn and ni probably reflects fluid source controls mn is correlated with fe in tourmalines from barren associations and possibly in some tourmalines associated with sulfide vein deposits sn increases systematically with fe content irrespective of association the highest values are found in schorls from granites other trace elements are generally uncorrelated with major element concentrations e g sr ca base metal proportions in the tourmalines show systematic patterns on ternary cu pb zn diagrams that correlate well with the major commodity metals in the associated massive sulfide deposits for example data for tourmalines from cu zn deposits e g ming mine newfoundland fall mainly on the cu zn join whereas those from pb zn deposits e g broken hill australia plot on the pb zn join no data fall on the cu pb join consistent with the lack of this metal association in massive sulfide deposits the systematic relationship between base metal proportions in the tourmalines and the metallogeny of the host massive sulfide deposits indicates that the analyzed tourmalines retain a strong chemical signature of their original hydrothermal formation in spite of variable metamorphic recrystallization such trace element patterns in massive sulfide tourmalines may be useful in mineral exploration specifically for the evaluation of tourmaline concentrations in rocks soils and stream sediments

chemical composition of biotite from the casino porphyry cu au mo mineralization yukon canada evaluation of magmatic and hydrothermal fluid chemistry abstract the chemical composition of biotite has been determined for the dawson range batholith and the casino porphyry style cu au mo occurrence yukon territory canada biotite from the propylitic phyllic and potassic alteration zones of the casino occurrence possesses higher x mg al 2 o 3 sio 2 f and cl and lower tio 2 bao and mno concentrations than biotite outside these alteration zones this phenomenon is similar to that recorded for biotite of other porphyry cu deposits however the absolute concentrations of the oxides and halogens vary significantly among deposits calculated log f h 2 o f hf f h 2 o f hcl f hcl f hf ratios determined from biotite microprobe data indicate that hydrothermal fluids associated with potassic alteration at casino were similar to those associated with phyllic alteration in contrast fluids responsible for propylitic alteration had higher log f h 2 o f hf and less negative log f hf f hcl values the log f h 2 o f hcl and f hf f hcl ratios established for casino are similar to those for other porphyry cu deposits however log f h 2 o f hf values vary greatly among porphyry deposits this variation in log f h 2 o f hf values may be related to the source of the magmas and or magmatic processes assimilation fractional crystallization associated with melt on its ascent through the crust prior to the exsolution of magmatic fluids that are responsible for porphyry mineralization the biotite compositions from the dawson range batholith are either not consistent with the fe f and mg cl avoidance principles or record changes in the f cl ratio of the fluid during crystallization of the granitic body

crustal inheritance and a top down control on arc magmatism at mount st helens in a subduction zone the volcanic arc marks the location where magma generated via flux melting in the mantle wedge migrates through the crust and erupts while the location of deep magma broadly defines the arc position here we argue that crustal structures identified in geophysical data from the washington cascades magmatic arc are equally important in controlling magma ascent and defining the spatial distribution and compositional variability of erupted material as imaged by a three dimensional resistivity model a broad lower crustal mush zone containing 3 10 interconnected melt underlies this segment of the arc interpreted to episodically feed upper crustal magmatic systems and drive eruptions mount st helens is fed by melt channelled around a mid tertiary batholith also imaged in the resistivity model and supported by potential field data regionally volcanism and seismicity are almost exclusive of the batholith while at mount st helens along its margin the ascent of viscous felsic melt is enabled by deep seated metasedimentary rocks both the anomalous forearc location and composition of st helens magmas are products of this zone of localized extension along the batholith margin this work is a compelling example of inherited structural control on local stress state and magmatism crustal structures are as important as deep mantle melting in controlling magma ascent and the composition and distribution of erupted material according to 3d resistivity modelling geophysical data and the distribution of quaternary volcanism

boron isotopes in tourmaline as a tracer of metasomatic processes in the bamble sector of southern norway the bamble sector of southern norway comprises metagabbros and metasediments that were metasomatically altered to various extents during a late stage of the sveconorwegian orogeny 1 06 ga the infiltration of highly saline brines along veins led to penetrative scapolitization and albitization on a regional scale and the local deposition of fe ti oxides typical secondary mineral assemblages include either scapolite apatite amphibole phlogopite tourmaline or albite epidote calcite chlorite white mica indicating that the fluids introduced large amounts of na cl mg ca k p and b to the system metasomatic tourmalines associated with different alteration stages as identified by variations in major element composition and initial 87sr 86sr were analyzed for b isotopic compositions to constrain possible sources and the evolution of the hydrothermal fluid s measured 11b values range from 5 to 27 relative to srm 951 suggesting marine evaporites interlayered with various amounts of continental detritus and pelagic clay as a possible b source reservoir the influence of a seawater derived component is clearly indicated by the heavy b isotope signature of tourmaline related to al mg rich metapelites in contrast negative 11b values can be explained by the influence of pneumatolytic fluids associated with granitic pegmatites on a regional scale i e several km 11b values in tourmaline vary widely whereas variations within a single outcrop tens of m are typically small and can be ascribed to different generations of tourmaline related to several fluid pulses

comparative radiocarbon dating of terrestrial plant macrofossils and aquatic moss from the ice free corridor of western canada in order to assess the reliability of aquatic moss for radiocarbon dating sup 14 c analyses were performed on a stratigraphic series of terrestrial plant macrofossils and samples of drepanocladus crassicostatus from a small hard water lake ph 8 2 in the ice free corridor of alberta all sup 14 c dating was done by using accelerator mass spectrometry mazama ash provided an independent chronological control the aquatic bryophyte samples consistently produced sup 14 c ages significantly older than the terrestrial macrofossils the relation between the radiocarbon dates from the macrofossils and the moss was not linear and age differences ranged from approximately 1400 to 6400 yr the sup 14 c content of d crassicostatus growing in the lake at present was less than 85 modern despite the apparent inability to take up sup 14 c deficient carbon by the direct incorporation of bicarbonate the bryophytes clearly do not provide reliable material sup 14 c dating the sup 14 c deficiency of aquatic mosses may be explained by the generation of sup 14 c deficient co sub 2 through isotopic exchange the formation of co sub 2 from bicarbonate by chemical processes and metabolic co sub 2 production these results demonstrate the potential unreliability of sup 14 c dates from aquatic mosses and raise serious concernsmore about the deglaciation dates from the ice free corridor that were obtained from aquatic drepanocladus less

discriminating hydrothermal fluid sources using tourmaline boron isotopes example from bailingshan fe deposit in the eastern tianshan nw china abstract tourmaline is an important b bearing mineral in many types of hydrothermal deposits and its chemical and boron isotopic signatures shed light on the nature and evolution of the metallogenic processes two generations of hydrothermal tourmaline in potassic altered rocks tourmaline i and subsequent veinlets tourmaline ii have been identified at the volcanic hosted bailingshan fe deposit in the chinese eastern tianshan nw china both tourmaline i and ii have low ca contents and x site occupancy and belong to the alkali group tourmaline i grains plot in the schorl field or between the dravite and schorl fields whereas tourmaline ii grains are largely mg rich dravitic mineral textural and geochemical features suggest that the compositions of tourmaline i and ii were mainly controlled by the host rock and hydrothermal fluid compositions respectively in situ b isotope analyses of tourmaline i yielded 11b values of 1 7 to 4 1 whereas tourmaline ii yielded slightly higher values of 3 5 to 6 6 calculated b isotope compositions 11bh2o of the hydrothermal fluids in equilibrium with tourmaline i are 3 3 to 5 7 at 550 c suggesting a mixed magmatic fluid major and basinal brine minor origin meanwhile tourmaline ii forming fluids yielded 11bh2o values of 6 2 to 9 3 at 400 c based on geological constraints and modal calculations we suggest that the observed b isotope variations from tourmaline i to ii are mainly controlled by rayleigh fractionation process and indicate that they may have crystallized from similar fluids the presence of basinal brine incursion into the k rich hydrothermal fluids and geological constraints lead us to suggest that the bailingshan deposit was likely formed in a paleozoic aqishan yamansu arc related basin in the eastern tianshan

origin of the high temperature olserum djupedal ree phosphate mineralisation se sweden a unique contact metamorphic hydrothermal system abstract the swedish part of the fennoscandian shield hosts a variety of rare earth element ree deposits including magmatic to magmatic hydrothermal types this paper focuses on the origin of the olserum djupedal ree phosphate mineralisation located in the sparsely studied vastervik region se sweden here mineralisation occurs in three main areas olserum djupedal and bersummen primary hydrothermal ree mineralisation formed at high temperatures about 600 c leading to precipitation of monazite ce xenotime y fluorapatite and minor y ree u fe nb ta oxides in veins and vein zones dominated by biotite amphibole magnetite and quartz the veins are hosted primarily by metasedimentary rocks present close to or within the contact aureole of a local 1 8 ga ferroan alkali feldspar granite pluton but also occur within in the chemically most primitive granite in the outermost part of that pluton in the djupedal area ree mineralised metasedimentary bodies are extensively migmatised with migmatisation post dating the main stage of mineralisation in the olserum and bersummen areas the ree bearing veins are cross cut by abundant pegmatitic to granitic dykes the field relationships demonstrate a protracted magmatic evolution of the granitic pluton and a clear spatial and temporal relationship of the ree mineralisation to the granite the major and trace element chemistry of ore associated biotite and magnetite support genetic links between all mineralised areas biotite mineral chemistry data further demonstrate a distinct chemical trend from metasediment hosted ore associated biotite distal to the major contact of the granite to the biotite in the granite hosted veins this trend is characterised by a systematic decrease in mg and na and a coupled increase in fe and ti with proximity to the granite hosted veins the halogen compositions of ore associated biotite indicate elevated contents of hcl and hf in the primary ree mineralising fluid calculated log fhf fhcl values in the olserum area suggest a constant ratio of about 1 at temperatures of 650 550 c during the evolution of the primary hydrothermal system in the djupedal and bersummen areas the fluid locally equilibrated at lower log fhf fhcl values down to 2 high na contents in ore associated biotite and amphibole and the abundance of primary ore associated biotite indicate a k and na rich character of the primary ree mineralising fluid and suggest initial high temperature k na metasomatism with subsequent cooling of the system the fluid evolved locally to more ca rich compositions as indicated by the presence of the ca rich minerals allanite ce and uvitic tourmaline and by the significant calcic alteration of monazite ce the later ca rich stages were probably coeval with low to medium high temperature 200 500 c na ca metasomatism variably affecting the granite and the wall rocks producing distinct white quartz plagioclase rocks all observations and data lead us to discard the prevailing model that the ree mineralisation in the olserum djupedal district represents assimilated and remobilised former heavy mineral rich beds instead we propose that the primary ree mineralisation formed by granite derived fluids enriched in ree and p that were expelled early during the evolution of a local granitic pluton the ree mineralisation developed primarily in the contact aureole of this granite and represents the product of a high temperature contact metamorphic hydrothermal mineralising system the ree mineralisation probably formed synchronously with k na and subsequent na ca metasomatism affecting the granite and the wall rocks the later na ca metasomatic stage is probably related to a regional na ca metasomatic and associated u ree mineralising system operating concurrently with granitic magmatism at c 1 8 ga in the vastervik region this highlights the potential for discovering hitherto unknown ree deposits and for the reappraisal of already known deposits in this part of the fennoscandian shield

determinants of fire activity during the last 3500 yr at a wildland urban interface alberta canada abstract long term records of wildfires and their controlling factors are important sources of information for informing land management practices here dendrochronology and lake sediment analyses are used to develop a 3500 yr fire and vegetation history for a montane forest in jasper national park alberta canada the tree ring record ad 1771 2012 indicates that this region historically experienced a mixed severity fire regime and that effective fire suppression excluded widespread fire events from the study area during the 20th century a sediment core collected from little trefoil lake located near the jasper townsite is analyzed for subfossil pollen and macroscopic charcoal 150 m when comparing the tree ring record to the 3500 yr record of sediment derived fire events only high severity fires are represented in the charcoal record comparisons between the charcoal record and historical climate and pollen data indicate that climate and vegetation composition have been important controls on the fire regime for most of the last 3500 yr although fire frequency is presently within the historical range of variability the fire return interval of the last 150 yr is longer than expected given modern climate and vegetation conditions indicating that humans have become the main control on fire activity around little trefoil lake

geology of the mount st helens area record of discontinuous volcanic and plutonic activity in the cascade arc of southern washington the quaternary edifice of mount st helens volcano was built upon a deeply eroded terrane of gently folded and altered volcanic and plutonic rocks that represent the core of the tertiary cascade magmatic arc these rocks constitute an east dipping homoclinal sequence several kilometers thick of subaerially erupted mafic to silicic flows and volcaniclastic strata k ar ages from this section range from about 28 to 23 ma late oligocene and earliest miocene which corresponds to an apparent lull in cascade volcanism to the north of mount rainier volcanism was essentially continuous during this period of time and neither a well defined base nor top of the section is exposed within the mapped area basalt and basaltic andesite dominate the lower part of the mid tertiary section whereas andesitic and dacitic rocks comprise most of the upper part this section was intruded by numerous mafic to silicic dikes sills and irregular plutonic bodies most no more than a few million years younger than their host rocks and subjected to pervasive burial metamorphism and widespread hydrothermal alteration large areas of hornfelsed rock surrounding even relatively small intrusions indicate that the proportion of plutonic rock becomes significantly greater at shallow depth beneath the existing erosion surface a large granitic pluton intruded the mid tertiary section north of spirit lake at about 21 ma the earl porphyry copper deposit occurs within the pluton but appears too young 17 ma to be genetically related to it in contrast to the rather continuous and voluminous oligocene to early miocene activity volcanism since then in the mount st helens area has been localized and volumetrically minor products of three younger eruptive periods have been recognized a sequence of 15 m y old pyroxene andesite flows resting unconformably on mid tertiary strata south of mount st helens widespread shallow dikes and sills of pyroxene andesite between 10 and 8 m y old and compositionally diverse rocks erupted during the past 3 m y the quaternary lavas are more potassic than the tertiary lavas and typically contain phenocrysts of hornblende and biotite which are absent from the older rocks a number of tertiary structures define a broad nne trending zone that may reflect a deep seated lithospheric flaw that has controlled the locus of cascade magmatism in southern washington for the past 25 m y mount st helens lies within this zone at the intersection of the nnw striking st helens seismic zone shz and an ene trending alignment of pleistocene silicic plug domes no surface breakage has been detected along the shz which is apparently very young the linear zone of silicic vents is probably controlled by a fault that has been interpreted from seismic records to occur directly beneath the volcano this zone parallels the directions of regional maximum horizontal compressive stress and north america juan de fuca plate convergence mount st helens is an example of a low volume tectonically controlled magmatic system in an early stage of development

trace element systematics of tourmaline in pegmatitic and hydrothermal systems from the variscan schwarzwald germany the importance of major element composition sector zoning and fluid or melt composition article an extensive data set on the compositional variation of tourmaline from granitic pegmatites from migmatitic gneisses and from various types of hydrothermal veins from the schwarzwald germany is provided the investigated tourmalines are members of the alkali and x vacant groups representing mostly dravite schorl solid solutions with some analyses belonging to the foitite mg foitite series oxygen isotope data on quartz tourmaline pairs indicate formation temperatures between 550 and 350 c for most of the quartz tourmaline veins most of the tourmalines show strong sector zonation fractionating certain major e g na mg minor e g ti ca and trace elements e g sr pb ree among the different crystallographic sectors of the crystals we conclude that comparison of tourmaline compositions for petrogenetic interpretations must be based on the concentrations in the neutral a sector in order to eliminate the effects of intra crystalline fractionation most trace element contents vary over several orders of magnitude with median concentrations generally be tween 0 1 and 10 g g the highest concentrations are found for zn v sr sc sn and li median concentrations of several tens to hundreds of g g whereas very low median concentrations b0 1 g g were found for u th bi tl and cs the concentration of several trace elements e g sr ree co correlates with the major element composition of the tourmaline which implies potential crystal chemical effects on their incorporation conse quently the general assumption that tourmaline is a passive monitor for the chemical compositions of the melts or fluids from which it crystallizes has to be questioned nevertheless our study demonstrates that the trace element composition of tourmaline allows to distinguish between geochemically distinct fluid sources and the trace element composition of tourmaline may therefore be used to unravel the chemical complexity of granite related hydrothermal systems

melt biotite 11b 10b isotopic fractionation and the boron local environment in the structure of volcanic glasses abstract this paper is focused on the role of boron coordination in determining the 11b 10b isotopic fractionation between melt glass and biotite at magmatic temperatures for this purpose three evolved volcanic rocks from roccastrada mt amiata and mt cimini belonging to the neogene quaternary magmatism of central italy were studied in these samples the measured boron biotite glass partition coefficient ranges between 0 004 and 0 011 indicating that boron behaves as an incompatible element during biotite crystallization the 11b magic angle spinning nuclear magnetic resonance nmr spectra reveal the presence of trigonal bo3 2 units tetrahedral bo4 2 sites and three coordinated bo2 2o species containing one nonbridging oxygen the relative contributions of these different boron sites were estimated by spectral deconvolution and it was observed that the fraction of trigonally coordinated boron decreases with increasing k2o concentration in the glass the 11b 10b isotopic fractionation between biotite and melt glass was observed to be large even at magmatic temperatures and was found to be 1 0066 roccastrada sample 1 00535 mt amiata sample and 1 00279 mt cimini sample fractionation is mostly related to the relative amount of trigonal and tetrahedral boron sites in the glass network rather than to other processes including the speciation of hydrous species in the glass structure the measured values are significantly higher than the calculated ones obtained using the reduced partition function ratios rpfrs for b oh 3 and b oh 4 as reported by kakihana et al 1977 and the abundance of trigonal and tetrahedral boron obtained by 11b nmr spectra furthermore a nonlinear relationship is observed between the percentage of bo4 in the glass structure and the measured 1000ln suggesting that the approximation of monomeric b oh 3 and b oh 4 species contributions through ideal mixing in calculating the rpfrs in polyanions oi et al 1989 probably does not apply to silicate glasses the large b isotopic fractionation measured between glass and biotite and its dependence on the boron coordination in the glass are a limitation to the use of 11b in the mineral to characterize magmas nonetheless the high incompatible behavior of boron in the most common magmatic minerals rules out that fractional crystallization significantly modified the b isotopic composition of the melt

the boron isotopic composition of tourmaline as a guide to fluid processes in the southwestern england orefield an ion microprobe study the boron isotopic composition 11b and chemistry of tourmalines from a series of sites in the western southwest england orefield has been determined using ion microprobe and electron microprobe techniques respectively the range of 11b values determined is relatively wide 0 6 to 12 7 and falls at the lighter end of the range for typical continental crust within this range granite tourmalines show a depletion in 11b from coarse grained early magmatic examples to fine grained late magmatic tourmaline we attribute this to fractionation of boron isotopes between aqueous and melt species during the exsolution of an aqueous fluid phase from the magma the aqueous phase formed by degassing of the magma is considered to have crystallised to form the tourmalinites and quartz topaztourmaline rocks common throughout the area decreases in the 11b values occur within certain zones of individual tourmaline crystals from these rocks this is ascribed to loss of 11b in the vapour phase during boiling caused by decompression of the aqueous fluid on fracturing the calculated boron isotope composition of fluids in equilibrium with tourmalines from the cligga head greisen bordered vein system agrees closely with that calculated for the tourmalinite fluid and suggests a constant granite derived source of boron during the early hydrothermal evolution of the stock the lack of isotopic zoning within the tourmalines from the cligga head hydrothermal veins suggests that phase separation did not occur or was very limited during hydrothermal circulation in the vein system

in situ elemental and boron isotopic variations of tourmaline from the sanfang granite south china insights into magmatic hydrothermal evolution abstract tourmaline often occurs in boron rich granites and its genesis is still in dispute either formed from residual boron rich silicate melt or from magmatic hydrothermal fluids with or without external fluid involvement here we present a systematic investigation of in situ major trace elemental and boron isotopic variations of tourmaline from the sanfang granite in guangxi province of south china which demonstrate both the magmatic and hydrothermal origin for the formation of the tourmalines the tourmaline occurs mainly in quartz tourmaline nodules and tourmaline pegmatitic segregations within the sanfang granite four types of tourmaline are identified 1 isolated and disseminated tourmaline tur d type distributed in granite 2 euhedral and subhedral tourmaline in quartz tourmaline nodules tur n type 3 the earlier stage tourmaline tur pe type in pegmatitic segregations and 4 the later stage tourmaline tur pl type which replaced the tur pe type tourmaline in pegmatitic segregations all the tourmalines belong to the alkali group representing dravite schorl solid solution series with the former three types being schorl and the tur pl type being dravite petrography chemical discrimination diagrams and al occupations in the y site suggest that the tur d tur n and tur pe type tourmalines are of magmatic origin and the tur pl type tourmalines are of hydrothermal fluid origin elemental and boron isotopic composition variations of tourmalines reflect the compositional and environmental evolution from late boron rich magma to exsolved hydrothermal fluids chemical variations from the tur d to the tur n tourmalines are controlled by magma differentiation the increase of mg mg fe and ca ca na ratios from the tur n to the tur pe tourmalines suggests the contamination of surrounding strata e g the sibao group hydrothermal tourmalines have higher mg mg fe and lower na na ca ratios than the magmatic tourmalines there is clear correlation at least in some trace elements e g sr pb with major elements for all tourmalines indicating the potential crystal chemical effects on their incorporation other trace element incorporation in tourmaline is largely controlled by melt and fluid composition hydrothermal tourmalines have high and stable v co and ni contents indicating relatively constant partition coefficient between hydrothermal tourmalines and the fluid hydrothermal tourmalines exhibit lower total ree contents but more pronounced positive eu anomalies than the magmatic tourmalines the 11b values of all tourmalines from the sanfang granite vary from 14 4 to 9 3 which indicate the boron in the sanfang granite was mainly derived from partial melting of the metasedimentary source rocks boron isotopic variations of tourmaline are controlled by fractionation between melt fluid and rayleigh fractionation

holocene glacier fluctuations in the canadian cordillera alberta and british columbia abstract although the record of holocene glacier fluctuations in british columbia and alberta is still very fragmentary much recent progress has been made in their study dating of end moraines has been supplemented by studies of lateral moraine stratigraphy and dating of glacially overridden organic matter upstream of end moraines dates from sites close to contemporary glaciers indicate that ice had retreated to about its present limits before 10 ka bp prior to deposition of mazama tephra a minor pre hypsithermal readvance the crowfoot advance left deposits in the rockies and the interior of british columbia the earliest known neoglacial advances occurred 5 6 ka bp in the coast mountains and shortly after 4 ka bp in the rockies an advance culminating ca 4 3 ka bp has been reported from bugaboo glacier while evidence of another advance culminating in the period ca 2 5 1 8 ka bp the tiedemann advance is reported from more than one site following a recession the little ice age expansion the cavell advance began shortly after 900 bp this advance culminated in most cases in the 18th or 19th centuries the crowfoot tiedemann and little ice age advances were apparently of roughly the same magnitude the latter was most extensive in most cases but at several sites crowfoot moraines lie slightly farther downvalley than little ice age moraines during the present century ice fronts have generally retreated particularly rapidly in the period 1920 1950 a d although rates of retreat have decreased in the last three decades and some glaciers have readvanced slightly

mineralogical and isotopic zonation in the sur sur tourmaline breccia rio blanco los bronces cu mo deposit chile implications for ore genesis the sur sur tourmaline breccia is located in the southeast part of the rio blanco los bronces porphyry copper molybdenum deposit central chile the breccia hosts approximately one quarter of the total resource of 57 mt of fine copper at rio blanco the breccia is hosted within and contains altered clasts of granodiorite from the 12 to 8 ma san francisco batholith which intruded a sequence of miocene volcanic and volcaniclastic rocks a series of weakly mineralized to barren felsic porphyries cut the breccia and indicate a minimum age of approximately 6 ma for mineralization at sur sur the sur sur breccia dike is at least 3 km long 0 2 km wide and has a vertical extent of at least 1 km the breccia has been cemented by early biotite and anhydrite at depth and by tourmaline and specularite at higher altitudes these early formed cements have been overgrown and in some cases replaced by chalcopyrite magnetite pyrite and quartz mineralogical zonation in the breccia includes a transition from biotite cement and related biotite alteration upward to tourmaline cement and quartz sericite tourmaline alteration at approximately 3 000 m elevation iron oxide minerals are also zoned with a transition upward from a magnetite dominated zone below 3 330 m to a specularite dominated zone above 3 600 m pyrite is the dominant sulfide at altitudes above 4 000 m secondary liquid rich vapor rich and hypersaline fluid inclusions are preserved in quartz and tourmaline cement measured homogenization temperatures are mostly between 300 degrees and 450 degrees c and salinities range from 0 to 69 wt percent nacl equiv sulfur isotope compositions of sulfide cement range from 4 1 to 2 7 per mil the lowest delta 34s sulfide values are in samples from between 3 700 and 4 000 m elevation where they correspond to the highest copper grades in the tourmaline breccia this high grade zone also contains abundant specularite locally replaced by magnetite modeling of sulfate sulfide equilibrium indicate that approximately 150 degrees c of cooling over a vertical interval of 100 m would be required to account for the zonation of sulfide isotope compositions at sur sur making conductive cooling an unlikely ore forming mechanism measured 206pb 204pb values of lead in anhydrite cement in the sur sur tourmaline breccia and the rio blanco magmatic breccia range from 17 558 to 18 479 207pb 204pb values range from 15 534 to 15 623 and 208pb 204pb values range from 37 341 to 38 412 the lead in anhydrite is considerably less radiogenic than that indicated by values obtained previously for lead in sulfide ores and igneous host rocks at rio blanco los bronces the source of lead in anhydrite must have been from rocks external to the main magmatichydrothermal system probably the precordilleran basement a magmatic hydrothermal explosion from a deep seated crystallizing intrusion triggered breccia formation at sur sur hydrostatic pressures catastrophically exceeded lithostatic load plus the tensile strength of the confining granodiorite leading to widespread brecciation and subsequent invasion by large volumes of magmatic gas and hypersaline brine the low density gas phase carrying h2o so2 hcl and b2o3 separated physically from the dense copper bearing brine and flushed through the breccia column first where it condensed into ground waters of uncertain derivation anhydrite specularite and tourmaline were deposited from this lowsalinity acidic oxidized hybrid solution subsequent upwelling of magmatic hydrothermal brine resulted in sulfide deposition high grade copper deposition is interpreted to have occurred in response to mixing of the oxidized acidic water with the copper bearing magmatic hydrothermal brine

sensitivity and response time of natural systems to climatic change in the late quaternary abstract although the leading theory for the cause of climatic change the milankovitch perturbations in insolation indicates variable rates of change at different latitudes any discussion of the sensitivity and response time of different natural systems is most practical when the climatic change is considered to be relatively abrupt and global rather than gradual and regional the oxygen isotope record in glacial ice should have the swiftest response time but the stratigraphic record in ice sheets at particular localities may be obscured or confused if the glacier flow is irregular the oxygen isotope stratigraphy of ocean sediment cores is a sensitive reflection primarily of contemporaneous ice volume and to a lesser extent ocean temperature ocean temperature however is recorded more specifically by microfossils in ocean sediments and may reflect global insolation directly except that in the north atlantic the influence of glacial meltwater and various feedbacks may override the insolation factor the differential lags in the response of isotopes and faunas to insolational change are apparent in the ocean sediment stratigraphy ice sheets themselves at their terminus may respond to climatic change only slowly if a change in snow accumulation is the factor because of the time involved in building a thickness sufficient for flow to great distances but if wastage near the margin is the factor then the response may be more rapid some glaciers however may advance rapidly without regard to climatic change as in the case of surging or they may retreat just as rapidly if they terminate in deep water through iceberg formation world sea level is depressed with glacial growth and thus reflects the volume of ice sheets but isostatic changes in the crust complicate the sea level response not only locally beneath the ice load but elsewhere as well the pluvial lakes of the american southwest correlated in their high levels with intervals of glaciation show a direct response to climatic patterns resulting from the expansion of the north american ice sheets and thus may lag with respect to the primary climatic change that causes ice sheet growth north african lakes on the other hand respond to the intensity of monsoonal circulation which is controlled directly by insolational shifts the response of plants and insects to deglaciation can be immediate in the case of pioneers on newly exposed terrain although the deglaciation itself may lag behind climatic change succession can follow rapidly but then more slowly as other plants immigrate from great distances it is heare where the more realistic assumption of continuing climatic change may be necessary to explain the dynamics of long range vegetational change following the last deglaciation the distribution and abundance of vertebrate populations reflect primarily their food resources and the disharmonious faunas of the last glacial period in north america with components that no longer have overlapping ranges perhaps may be explained by vegetational associations that likewise may have no modern analogues the cause may be a different climatic seasonality wastage of the ice sheet itself lagging behind the climatic change may have changed the seasonal climatic patterns sufficiently to bring about the precipitous extinction of many vertebrate species

holocene paleohydrology of central alberta testing the general circulation model climate simulations paleoecological investigations of 28 lakes and bogs provide the basis for a holocene paleohydrological record for central alberta shallow basins empty during the early holocene began flooding shortly after 8000 years ago most filled from 6500 to 4500 years ago and none filled later than 3000 years ago pollen of a hypersaline indicator genus ruppia was found in cores of lakes where the plant does not presently grow indicating lower lake levels evaporation stress and increased salinity from 8000 to 3000 years ago moore lake 54 30 n 100 30 w may have dropped 15 m from 9200 to 5900 years ago and lofty lake 54 44 n 112 29 w largely dried up between 8700 and 6300 years ago lower water levels are suggested for several lakes by shifts in fossil diatom populations from planktonic to benthic particularly epipelic species including pioneering taxa these shallow warm lakes were highly productive and sedimentary pigment levels reached maximum values between about 9000 and 4000 years ago the pale

late quaternary landscape history and archaeology in the ice free corridor some recent results from alberta abstract multidisciplinary research programs conducted within the alberta portion of the ice free corridor since 1986 as part of the archaeological survey s first albertans project have used studies of palaeogeography and palaeoenvironments to formulate archaeological search strategies this approach has resulted in the discovery of two new important sites saskatoon mountain ghqt 4 and the james pass meadow complex ekpu 3 to 9 that are yielding information on terminal late wisconsinan early holocene human occupation of the corridor both sites are dated by ams or conventional radiocarbon dates to the millennium 10 000 9 000 bp in the fifteen years since the 1978 amqua conference on the corridor other researchers have identified four additional significant paleo indian sites in this region so far none confirm human occupation of the ice free corridor region before about 11 000 bp

detrital metamorphic and metasomatic tourmaline in high pressure metasediments from syros greece intra grain boron isotope patterns determined by secondary ion mass spectrometry the boron isotopic composition of zoned tourmaline in two metasediments from the island of syros determined by secondary ion mass spectrometry sims reflects the sedimentary and metamorphic record of the rocks tourmaline from a silicate bearing marble contains small 20 m detrital cores with highly variable 11b values 10 7 to 3 6 pointing to a heterogeneous protolith derived from multiple sources the sedimentary b isotopic record survived the entire metamorphic cycle with peak temperatures of 500 c prograde to peak metamorphic rims are homogeneous and similar among all analysed grains 11b 0 9 the varying 11b values of detrital cores in the siliceous marble demonstrate that in situ b isotope analysis of tourmaline by sims is a potentially powerful tool for provenance studies not only in sediments but also in metasediments a meta tuffitic blueschist bears abundant tourmaline with dravitic cores of detrital or authigenic origin 11b 3 3 and prograde to peak metamorphic overgrowth zones 1 6 fe rich rims formed during influx of b bearing fluids under retrograde conditions show strongly increasing 11b values up to 7 7 towards the margins of the grains the 11b values of metamorphic tourmaline from syros formed in mixed terrigenous marine sediments reflect the b signal blended from these two different sources and was probably not altered by dehydration during subduction

evidence for a neoglacial advance of the boundary glacier banff national park alberta direct evidence for an early neoglacial advance in the canadian rocky mountains is presented radiocarbon dates from buried peat and tree remains at boundary glacier suggest limiting dates for this advance of between 3800 and 4200 years bp these data from boundary glacier are consistent with previously published dates for the onset of the neoglacial and an early neoglacial advance

late quaternary paleoenvironments of the morley flats and kananaskis valley of southwestern alberta a 3 1 m section of limnic sediment and peat from a bog on the morley flats and a 2 8 m section of limnic sediment from wedge lake in the kananaskis valley have yielded the first comprehensive late quaternary biostratigraphic record from south western alberta both sections were analyzed for subfossil pollen molluscs and several sedimentary indices two distinct pollen zones were recognised the basal zone characterized by high relative abundancy of artemisia salix juniperus suggests that the morley flats were dominated by a sparse vegetation composed of aggressive pioneer species following deglaciation until prior to approximately 10 000 bp similarly the mollusc fauna from this zone is dominated by northern ranging species the second zone is typified by a predominance of pinus and picea this reflects the expansion of coniferous forest into the region both the relative abundance of southern ranging mollusc species and the total carbonate concentration in the sediment increase in this zone the veg

titanium aluminum and interlayer cation substitutions in biotite from high grade gneisses west greenland detailed electron microprobe study pelitic to mafic metamorphic rocks from two localities higher ti k k na and possible k na similar al iv and lower al vi in granulite vs amphibolite grade samples modified journal abstract

on the occurrence and boron isotopic composition of tourmaline in ultra high pressure metamorphic rocks abstract the extensive p t stability and the high chemical variability of tourmaline tur together with its common occurrence in metasediments proves its high potential for petrological and isotope geochemical studies on fluid rock interaction in subduction and collision related rocks this paper reviews the occurrence major element chemistry and boron isotopic composition of tur in high and ultrahigh pressure metamorphic uhpm rocks in addition it presents a new discovery of coesite bearing tur schorl from the erzgebirge germany as well as tur dravite related to the retrograde history of coesite and diamond bearing rocks from the erzgebirge and the kokchetav massif kazakhstan the scarce data on worldwide occurrences of u hpm tur reveal a high occupation of the crystallographic x site dominated by na and the possible presence of excess b with little further distinctiveness in its major element composition when compared with tur from medium grade rocks high k 2 o contents in tur are probably not related to uhp growth or equilibration the b isotopic composition of u hpm tur ranges in 11 b from 16 to 1 with many samples in or below the range of continental crust in contrast tur formed during retrograde fluid influx typically shows high 11 b values up to 28 suggesting heavy b fluids infiltrating the exhuming u hpm units coesite inclusions in tur characterized by raman spectroscopy are regarded as the best indicator for its uhp stability supplementary material analytical methods tourmaline compositions and boron isotope values are available at http www geolsoc org uk sup18354

holocene palaeoenvironmental record preserved in a paraglacial alluvial fan sunwapta pass jasper national park alberta canada abstract the soil stratigraphy of a 1 5 m section in the distal portion of a paraglacial alluvial fan in sunwapta pass jasper national park has been examined as part of a long term investigation into holocene palaeoenvironments of the area the section is complex and its characteristics are a result of both episodic sediment inputs and pedogenesis a series of sediments comprising debris flows and aeolian material including three discrete tephra layers mazama st helens yn bridge river underlie the present day soil multiple criteria including stratigraphy radiocarbon dates glass shard morphology and electron microprobe analysis of glass and titanomagnetite composition confirmed the identity of the tephras most fan development occurred before deposition of mazama tephra pedogenesis has been active on the fan throughout the holocene soils have formed between phases of sediment deposition during periods of greater relative site stability soil horizonation is best developed where tephric material has influenced soil chemistry and clay mineralogy leading to the formation of brunisols the sequence of events inferred from the icefield fan s stratigraphy accord well with the holocene palaeoenvironmental history inferred from other sites in the canadian rockies

magmatic hydrothermal fluids and volatile metals in the spirit lake pluton and margaret cu mo porphyry system sw washington usa the halogen bearing minerals tourmaline amphibole and biotite formed during magmatic hydrothermal processes associated with the late stage cooling of the spirit lake granitoid pluton mt st helens wa and with the younger sulphide mineralised rocks of the margaret cu mo porphyry deposit located entirely within the pluton major and trace element discrimination suggests that one tourmaline population crystallised from fractionated late stage melt pockets in granodiorite monzogranitic dykes of the pluton these coarse euhedral oscillatory and complexly sector zoned uvite tourmalines span a limited range in mg mg fe mg space 0 4 0 7 apfu and show the highest ti ca f nb and ta contents and low x site vacancies 0 6 apfu lower ca and f contents and the highest li as and hree contents 80 ppm li 1200 ppm as this population appears to record direct rapid crystallisation from magmatic meteoric fluid s bearing the signature of the breakdown of primary feldspars and pyroxenes with fluid exsolution from fractionated melt patches likely triggered by the formation of the previous generation of tourmaline mineralised porphyry deposit tourmaline compositions from the stockwork span a much larger range in mg space 0 05 0 9 apfu and are almost entirely ca free x sites of these schorl tourmalines are dominated by na or vacancies and the y sites are strongly fe enriched the highest mn and zn concentrations 4000 and 1000 ppm respectively potentially reflect the composition of mineralising fluids during ore deposition a number of boron isotopic analyses yield predominantly heavy boron but 11b values range from 5 2 to 6 2 and average 1 4 whilst most plutonic tourmalines conform to reported a and c sector element partitioning models those from the mineralised porphyry show large and variable sector fractionation differences suggesting that external controls may also be important wider evidence for late stage pervasive metasomatism by halogen bearing exsolved fluid s is provided by the high mg 70 secondary amphiboles and biotites from within the spirit lake pluton where the amphiboles are clear replacement products of primary pyroxenes fluid halogen fugacity ratios calculated from the biotite compositions overlap with other global mineralised porphyry systems despite not being immediately associated with sulphide ores the evidence suggests complex fluid processes and the coincidental development of the mineralised porphyry system within the pluton heat fluids and metals were therefore likely supplied by a later phase of magmatism unrelated to the consolidation of the main spirit lake granitoid these new constraints on magmatic hydrothermal fluid signatures have wider applicability to potentially tracing proximal barren and mineralised processes and for distinguishing between formation mechanisms for primary and secondary halogen bearing minerals

hourglass sector zoning in metamorphic tourmaline and resultant major and trace element fractionation a new type of sector zoning with an hourglass shape has been identified in metamorphic tourmalines that formed under a wide variety of physical and chemical conditions the two sectors in the c direction are not equivalent due to asymmetry in the crystal structure of tourmaline along the c axis the c sector is characterized by low concentrations of ti ca mg and na although al is high and has a pale commonly blue or pale green color conversely the c sector is low in mg and al and high in ca fe and ti the latter two causing the dark brown color of this sector the a sector has intermediate characteristics and probably approximates a sector free tourmaline thin sectioning of these sector zoned tourmalines perpendicular to the c axis can produce three types of apparent radial zoning patterns blue green cores dark brown cores or no distinct cores these apparent cores will further vary in relative diameter depending on the sectioning level furthermore core boundaries can be straight or ragged depending on whether the relative growth speeds for the different faces was constant or variable these textures have been used to argue for a prograde or detrital origin of tourmaline cores however sector zoning is a more appealing explanation for most of these textures and can further explain the textural resemblance among metamorphic tourmalines from highly variable bulk rock composition metamorphic history and mineral paragenesis the sector zoning that is described here develops by preferential uptake of elements on the r growth plane resulting from a combined effect of differences in surface charge and morphology of this plane in the c and c directions this leads to the preferential incorporation of more positively charged elements in the c direction and a preference for a vacant x site in the c direction because the compositional differences among the sectors are pronounced in both major and trace elements and in the same order of magnitude as growth zoning variability the presence of sector zoning must be established and taken into account when making inferences from tourmaline chemistry

reconstruction of holocene changes in alpine vegetation and climate in the maligne range jasper national park alberta abstract pollen macrofossil logs and needles and oxygen isotope data from tree rings are presented for three alpine bog sites in the maligne range of the canadian rockies organic sedimentation at the watchtower site began prior to ca 9500 14 c yr b p and by 8770 yr b p timberlines were at least 100 m above present levels the two pollen records are dominated by pinus and subsequent changes in timberlines are inferred from pollen ratio data abies pinus and from macrofossils the recovered records indicate two periods of high hypsithermal timberlines ca 8800 7500 and 7200 5200 yr b p separated by a short interval ca 7300 7400 yr b p when timberline approached modern levels after ca 4500 yr b p timberlines have been similar to or lower than present reaching minimum values in the last 500 yr 18 o determinations from the cellulose of samples of 5 or 10 annual rings cut from contemporary picea englemannii at timberline show strong correlations with mean annual temperatures at jasper isotopic determinations from hypsithermal age logs recovered from sites above present timberline indicate mean annual temperatures were at least 0 5 c warmer ca 8060 and 8770 yr b p than at present at the watchtower site data from logs at the maligne pass site suggest that temperatures were about 1 2 and 1 6 c warmer ca 6000 and 5300 yr b p estimates of temperature from the pollen ratio data are more conservative and suggest maximum differences of ca 1 0 c in july temperatures over the last 8000 yr

a mid holocene vegetational and climatic record from the subalpine zone of the maligne valley jasper national park alberta canada abstract pollen macrofossils and isotopic data 13 c 18 o from gastropod shells are used to reconstruct holocene vegetational and climatic changes for a lower subalpine forest site elevation 1690 m in the maligne valley jasper national park alberta subalpine forest has characterized the site since the inception of the sedimentary record in this small pond ca 8500 yr b p in contrast to the vertical timberline fluctuations recorded at nearby sites above present tree line vegetational changes at the site appear to have been mainly horizontal i e forest cover and tree density expanded or contracted laterally in response to climatic warming or cooling at maligne lake forest cover was probably at its maximum extent about 7500 yr b p when pseudotsuga and other montane elements had migrated to this elevation but did not displace the existing vegetation the modern mosaic of discontinuous subalpine forest and extensive dwarf birch dominated damp meadows and fens emerged only during the last 1300 years a warmer neoglacial episode dated ca 2600 3400 yr b p is indicated by increases in the temperature limited gastropod lymnaea palustris and by progressive enrichment in the 18 o and 13 c contents of their shells summer temperatures during this period which has been tentatively identified elsewhere in the canadian rockies may have risen by as much as 1 8 c

preferential soft tissue preservation in the hot creek carbonate spring deposit british columbia canada abstract the relict holocene hot creek carbonate spring deposit in southeast british columbia is characterized by excellent preservation of soft tissue organisms e g cyanobacteria but poor preservation of organisms with hard tissue e g wood diatoms the deposit is formed mainly of calcified cyanobacteria with fewer mineralized macrophytes plants bryophytes mosses wood and diatoms cyanobacteria grew as solitary filaments lyngbya and as radiating hemispherical colonies rivularia both were preserved by encrustation and encapsulation while alive and as casts after filament death and decay sheath impregnation was rare to absent filament encrustation whereby calcite crystals nucleated on and grew away from the sheath exterior produced moulds that replicated external filament morphology but hastened filament decay filament encapsulation whereby calcite nucleated in the vicinity of and grew towards the encapsulated filament promoted sheath preservation even after trichome decay subsequent calcite precipitation inside the hollow sheath generated sheath casts the inability of mineralizing spring water to penetrate durable cell walls meant that bryophytes macrophytes and most wood was preserved by encrustation some wood resisted complete decay for several thousand years and its lignified cell walls allowed rare permineralizations diatoms were not preserved in the relict deposit because the frustules were dissolved by the basic spring water amorphous calcium carbonate produced by photosynthetic co 2 removal may have acted as nucleation sites for physicochemically precipitated calcite thus metabolic activities of floral organisms probably initiated biotic mineralization but continuous inorganic calcite precipitation on and in flora ensured that soft tissues were preserved

using discriminant function analysis to identify holocene tephras based on magnetite composition a case study from the sunwapta pass area jasper national park the magnetite composition from three sets of samples of mazama st helens set y and bridge river tephras from jasper and banff national parks are used to test whether discriminant function analysis can unambiguously distinguish these tephras the multivariate method is found to be very sensitive to the change in reference samples st helens set y tephra is clearly distinguished however discrimination between mazama and bridge river tephras is less distinct a set of unknown tephras from the sunwapta pass area was used to test the classification schemes unknown tephras are assigned to different tephra types depending on which reference tephra set is used in the discriminant function analysis

partitioning of fluorine and chlorine between biotite and granitic melt experimental calibration at 200 mpa h 2 o experiments from 640 to 680 c 200 mpa h2o at fo2 nno employing a natural f rich vitrophyric rhyolite from spor mountain utah assessed the effect of variable mg 100mg mg mn fe on the partitioning of fluorine and chlorine between biotite bt and melt over this temperature interval bt fluorite quartz is the sole liquidus phase partition coefficients for fluorine between biotite and glass dfbt melt show a strong dependence on the mg of bt dfbt melt varies from 1 5 to 7 2 over the range of mg from 21 to 76 a strong linear correlation between dfbt melt and mg has a slope of 9 4 and extrapolates through the origin i e dfbt melt 0 at mg 0 an annite siderophyllite solid solution in these experiments dclbt melt values 1 to 6 in the same experiments vary inversely with mg the al content of biotite does not vary with the aluminum saturation index asi molar al2o3 alkali and alkaline earth oxides of melt but two exchange mechanisms involving al appear to operate in these micas 1 alvi aliv siiv mgiv and mgiv 2aliv 2siiv iv the effects of other components such as li or other intensive parameters including fo2 have yet to be evaluated systematically at comparable mg of bt however the spor mountain rhyolite yields higher dfbt melt values than an li rich strongly peraluminous melt previously investigated the results indicate that the mg of bt exerts the principal control on halogen partitioning with asi and t as second order variables the experimental partition coefficients compare well with other experimental results but not with most volcanic rocks magmatic bt from most rhyolites records higher dfbt melt due to reequilibration with degassed h2o depleted magma and perhaps with f2o 1 exchange that may accompany oxidation fe3 o fe2 oh 1 this behavior is evident in magmatic biotite from a zoned peraluminous rhyolite complex near morococala bolivia bt is sharply zoned with f rich rims but bt core melt inclusion pairs fall on our experimental curve for dfbt melt these experimental data can be used in part to assess the preservation of magmatic volatile contents in plutonic or volcanic silicic rocks for plutonic rocks the actual f content of melt not a relative activity ratio involving hf species can be reasonably estimated if the mica has not undergone subsolidus reequilibration this information is potentially useful for some shallow level ca poor magmas that are thought to be rich in f e g a and s type granites but do not conserve f well as rocks

pollen stratigraphy of eaglenest lake northeastern alberta pollen analysis of a 7 65 m sediment core from eaglenest lake 57 46 n 112 06 w provides evidence of the postglacial development of vegetation in the mixedwood section of the boreal forest from the time of deglaciation approximately 12 000 11 500 years bp to 11 000 bp the area was colonized by mainly nonarboreal flora dominated by artemisia and gramineae populus the only tree taxon present grew in sheltered areas while salix and cyperaceae were common on poorly drained sites open parkland prevailed under a dry windy climate summer temperatures were rising rapidly from glacial minima in response to increased solar insolation by 11 000 bp picea initially p glauca and betula mainly tree betula migrated to the area forest prevailed but the canopy was likely more open than at present by 9000 bp peak warm and dry conditions had passed although conditions warmer and drier than at present persisted alnus migrated to the area 8450 bp pinus reached the birch mountains about 7500 bp no maj

the complex hydrothermal history of granitic rocks multiple feldspar replacement reactions under subsolidus conditions recurring subsolidus re equilibration of granitic feldspars induced by fluid infiltration events provides a record of fluid rock interactions that affect large volumes of the earth s continental crust this has a direct bearing on the interpretation of the present day granitic rock mineralogy and geochemistry we examine palaeoproterozoic grey and red stained granitoids from the simpevarp and laxemar areas in se sweden particularly focusing on consecutive feldspar replacement reactions to provide an in depth understanding of subsolidus re equilibration of granitic rocks with hydrothermal fluids the apparently most unaltered grey granitoids contain highly porous oligoclase grains that enclose crystallographically continuous microcline relicts this texture suggests that the oligoclase is already secondary and may be a replacement product of original microcline oligoclase is progressively replaced by albite an9 along polysynthetic twinning and intragranular fractures the features of this replacement are characteristic of a dissolution reprecipitation mechanism finegrained mica sericite is closely associated with the albite porosity within micron sized pores observable with scanning electron microscopy as well as in nanopores imaged with transmission electron microscopy the reddening phenomenon in the vicinity of fractures is contemporaneously related to the k feldspathization of sericite which is restricted to the altered oligoclase submicron size hematite precipitation within orthoclase pores at the replacement front results in the red coloration the complex associations between the fluid feldspar reactions indicate that the replacement reactions may be due to sequential fluid infiltration events and that the granitoids have undergone extensive subsolidus re equilibration changing the original magmatic mineralogy therefore the effects of large scale re equilibrations of granitic rocks through hydrothermal convection systems should be more closely considered

chemical and boron isotope variations in tourmalines from an s type granite and its source rocks the erongo granite and tourmalinites in the damara belt namibia tourmaline is widespread in metapelites and pegmatites from the neoproterozoic damara belt which form the basement and potential source rocks of the cretaceous erongo granite this study traces the b isotope variations in tourmalines from the basement from the erongo granite and from its hydrothermal stage tourmalines from the basement are alkali deficient schorl dravites with b isotope ratios typical for continental crust 11b average 8 4 1 4 n 11 one sample at 13 n 2 virtually all tourmaline in the erongo granite occurs in distinctive tourmaline quartz orbicules this main stage tourmaline is alkali deficient schorl 20 30 x site vacancy fe fe mg 0 8 1 with uniform b isotope compositions 11b 8 7 1 5 n 49 that are indistinguishable from the basement average suggesting that boron was derived from anatexis of the local basement rocks with no significant shift in isotopic composition secondary hydrothermal tourmaline in the granite has a bimodal b isotope distribution with one peak at about 9 like the main stage tourmaline and a second at 2 we propose that the tourmaline rich orbicules formed late in the crystallization history from an immiscible na b fe rich hydrous melt the massive precipitation of orbicular tourmaline nearly exhausted the melt in boron and the shift of 11b to 2 in secondary tourmaline can be explained by rayleigh fractionation after about 90 b depletion in the residual fluid

isotopic and elemental partitioning of boron between hydrous fluid and silicate melt the fractionation of b and its isotopes between aqueous fluid and silicate melt has been studied from 550 to 1100 c and 100 500 mpa fluid melt partition coefficients are 1 for rhyolite melt this shows that b is not always strongly extracted from melts into hydrous fluids boron isotopic fractionation is large compared with the carbon and oxygen stable isotopic systems especially at high t and is most simply explained by differences in coordination trigonal vs tetrahedral among coexisting phases combined with earlier measurements on illite water 300 350 c b isotopic fractionation defines a temperature dependent trend from 300 to 1100 c because of the large magnitude and apparent low sensitivity to bulk composition b isotopic fractionation can be readily applied to studies of diagenesis hydrothermal alteration of planetary bodies subduction zone processing and arc magma generation and magma chamber evolution

partitioning of f between h2o and co2 fluids and topaz rhyolite melt implications for mineralizing magmatic hydrothermal fluids in f rich granitic systems fluid melt distribution coefficients for f have been determined in experiments conducted with peraluminous topaz rhyolite melts and fluids consisting of h2o and h2o co2 at pressures of 0 5 to 5 kbar temperatures of 775 1000 c and concentrations of f in the melt ranging from 0 5 to 6 9 wt the major element f and cl concentrations of the starting material and run product glasses were determined by electron microprobe and the concentration of f in the fluid was calculated by mass balance the h2o concentrations of some run product glasses were determined by ion microprobe sims the solubility of melt in the fluid phase increases with increasing f in the system the solubility of h2o in the melt is independent of the f concentration of the system with up to 6 3 wt f in the melt no evidence of immiscible silica and fluoriderich liquids was detected in the hydrous but water undersaturated starting material glasses 8 5 wt f in melt or in the water saturated run product glasses f concentrates in topaz rhyolite melts relative to coexisting fluids at most conditions studied however df wt f in fluid wt f in melt increases strongly with increasing f in the system maximum values of df in this study are significantly larger than those previously reported in the literature linear extrapolation of the data suggests that df is greater than one for water saturated peraluminous granitic melts containing 8 wt f at 800 c and 2 kbar df increases as temperature and as h2o h2o co2 of the fluid increase for topaz rhyolite melts containing 1 wt f and with h2o rich fluids df is independent of changes in pressure from 2 to 5 kbar at 800 c for melts containing 1 wt f and in equilibrium with co2 bearing fluids the concentrations of f in fluid increases with increasing pressure f and lithophile element enriched granites may evolve to compositions containing extreme concentrations of f during the final stages of crystallization if f in the melt exceeds 8 wt df is greater than one and the associated magmatic hydrothermal fluid contains 4 molal f such f enriched fluids may be important in the mass transport of ore constituents i e f mo w sn li be rb cs u th nb ta and b from the magma

the role of discontinuous magma inputs in felsic magma and ore generation for a long time granites have been considered as passive bodies ascending under intrinsic negative density and viscosity contrasts with their host rocks chemical variations within a granitic body resulted from in situ differentiation and crystal fractionation since the mid 1980s this global view has been significantly modified by i shifting melting from water saturated conditions to fluid absent reactions ii increasing the role played by the mantle during granite generation iii reassessing the rheology of partially molten rocks iv demonstrating stepwise segregation and ascent of magmas by analogue and numerical models v combining structural geophysical and geochemical studies to reveal the internal structures in granitic plutons it results that a granitic body is built up by a discontinuous accumulation of successive magma intrusions the discontinuous nature of magma emplacement has also significant consequences for its ability to generate ore the processes that lead to ore deposits are examined with a brief review of the magmatic and fluid phases that concentrate ore forming elements examples are taken from crustal derived granites and porphyry type deposits those are considered as the two end members of magmatic and hydrothermal ore deposits the source characteristics of the magma the emplacement mechanisms and magma mixing processes are the frame that controls the potential to carry base metals with the magma the distribution of elements is controlled by diffusion partition between minerals and melt solubility and redox conditions variations of those parameters are examined by considering their activation energy which controls the exponential dependence with temperature a characteristic length depending on the activation energy temperature variation and time is estimated for a characteristic time lag of 30 ka the intrusion of a magma into a magma chamber of similar composition hence temperature has few effects on diffusion partition coefficient and redox conditions because of a too low temperature contrast the intrusion of a mafic magma into a felsic one induces a variation of 300 c in both magmas the characteristic length of diffusion may vary by up to two orders of magnitude whereas the variation of partition coefficients is only one order of magnitude the redox conditions are about 2 5 log unit in the mafic magma but they can vary by 7 log units in the felsic magma hence a strong decrease in d values is observed in porphyry type deposits the effect is a removal of the elements with higher activation energy w sn zr from the mafic to the felsic magma deformation during the late stages of emplacement also controls ore formation

primary magmatic biotite in granitoid intrusions associated with late mesozoic jinchanggouliang erdaogou lode gold deposits north china craton linkage to gold mineralization abstract the late mesozoic jinchanggouliang and erdaogou lode gold deposits in the central segment of the northern north china craton are mainly hosted in late archaean metamorphic rocks of the jianping formation and jurassic volcanic sedimentary rocks these deposits are spatially and temporally associated with a series of i type granitoid intrusions i e the 128 136 ma duimiangou granodiorite complex with a massive margin and a porphyritic center at jinchanggouliang the 161 4 1 1 ma loushang quartz diorite intrusion and numerous syenite porphyry dykes 160 9 1 0 ma at erdaogou and the 227 217 ma xitaizi monzogranite batholith compositions of primary magmatic biotite in these granitoid intrusions have been used to investigate the nature of granitoid magmas and the evolution of magmatic processes and to identify possible linkages between gold mineralization and granitoid magmatism all primary magmatic biotite grains are mg rich in composition xmg mg mg fe 0 41 0 69 the cl contents of biotite 0 09 0 42 wt in the loushang quartz diorite and the duimiangou massive granodiorite correlate negatively with xmg and are consistent with the mg cl avoidance rule the cl contents of biotite 0 01 0 14 wt in the duimiangou porphyritic granodiorite syenite porphyry and xitaizi monzogranite on the other hand remain relatively constant and may be affected by multiple variables such as cl rich fluids and subtle changes in temperature halogen fugacity of the parental magma calculated from biotite shows that the duimiangou granodiorite complex at jinchanggouliang and syenite porphyry dykes at erdaogou have the log fhf fhcl ranges of 0 71 to 0 27 and 2 16 to 1 08 respectively and have similar log fh2o fhcl values from 3 53 to 4 23 oxygen fugacities logfo2 calculated from biotite equilibria for the duimiangou granodiorite complex and syenite porphyry dykes are 13 7 to 7 2 straddling on the nickel nickel oxide and hematite magnetite buffers the xitaizi monzogranite and the loushang quartz diorite have lower log fo2 values from 14 9 to 12 4 between the nickel nickel oxide and hematite magnetite buffers the duimiangou granodiorite complex and syenite porphyry dykes with high oxygen fugacities are similar to oxidized magmas associated with porphyry cu mo au deposits these results suggest that multiple episodes of i type granitoid magmas in the study area were rich in cl and high in oxygen fugacity especially those associated with the duimiangou granodiorite complex and syenite porphyry dykes the i type melts represented by the duimiangou granodiorite complex and syenite porphyry dykes as well as their related cl rich oxidizing fluids were likely efficient in dissolving transporting and precipitating gold for the formation of the jinchanggouliang and erdaogou lode gold deposits

late quaternary vegetation history of wilcox pass jasper national park alberta five pollen zones are recognized in a radiocarbon and tephra dated core from an alpine site at an elevation of ca 2355 masl in wilcox pass jasper national park and record late quaternary vegetation history the two lower zones underlie material dated at 9600 305 yr b p gx 8785 and record early postglacial vegetation the basal zone wp1 containing an artemisia dominated assemblage represents tundra vegetation after deglaciation in zone wp2 arboreal pollen mainly diploxylon pine becomes dominant and represents a lodgepole pine forest the pollen assemblage of zone wp3 which initially contains large amounts of haploxylon pine as well as picea and abies pollen shows a transition from a forest with large amounts of whitebarkpine to vegetation resembling present day subalpine forest during this phase temperatures were probably warmer than present zone wp4 beginning after the influx of mazama tephra 6800 yr b p to the site records an expansion of the subalpine forest to higher elevations with a warmer climate in zone wp5 beginning about 2800 yr b p values of the main arboreal components fluctuate indicating cooler temperatures and less favourable environmental conditions probably associated with neoglacial ice advances the environmental trends observed from this record accord with those from other vegetation records in the canadian rockies

boron isotope and light element sector zoning in tourmaline implications for the formation of b isotopic signatures hourglass sector zoning in metamorphic tourmaline is known to effectively fractionate the major and trace elements between different sectors producing three distinct compositions at the growth surface here we show that the light elements li be h and b as well as the 11 b signature are also affected by sector zoning the sector enrichment in elements is controlled by a dual process of initial preference due to growth surface charge and morphology followed by consecutive charge balance controlled enrichment the light elements especially b and h appear to act as charge balance cations in this mechanism with a preferred b 3 for si 4 and o 2 for oh substitution in the c sector a lighter 11 b signature d c c 1 8f0 6x accompanies this increase in b iv in the c sector in line with the lighter signatures for b iv compared to b iii in minerals however it exceeds this theoretical fractionation by a factor of 10 although we have not identified a definite process that is responsible for this fractionation it may be related to local variations in host medium along the growth surface resulting from preferred uptake of elements these observations show that 11 b signatures in tourmaline are not an independent measure of its host environment but also a function of mineral composition and the 3 dimensional zoning variations herein 2007 elsevier b v all rights reserved

revised 14c age for st helens y tephra at tonquin pass british columbia the age of a mount st helens set y tephra at tonquin pass british columbia previously assumed to be 4300 years bp is revised to ca 3400 years bp based on bracketing 14c dates of 3140 70 beta 13558 and 3680 80 years bp beta 13559 the implications of this revision for tephrostratigraphy of this area are discussed

the little ice age in the canadian rockies abstract this paper reviews the evidence and history of glacier fluctuations during the little ice age lia in the canadian rockies episodes of synchronous glacier advance occurred in the 12th 13th early 18th and throughout the 19th centuries regional ice cover was probably greatest in the mid 19th century although in places the early 18th century advance was more extensive glaciers have lost over 25 of their area in the 20th century selective preservation of the glacier record furnishes an incomplete chronology of events through the 14th 17th centuries in contrast varve sequences provide continuous annually resolved records of sediments for at least the last millennium in some highly glacierized catchments such records have been used to infer glacier fluctuations evaluation of recent proxy climate reconstructions derived from tree rings provides independent evidence of climate fluctuations over the last millennium most regional glacier advances follow periods of reduced summer temperatures reconstructed from tree rings particularly ca 1190 1250 1280 1340 1690s and the 1800s reconstructed periods of higher precipitation at banff alberta since 1500 are 1515 1550 1585 1610 1660 1680 and the 1880s glacier advances in the early 1700s the late 1800s and in places the 1950 1970s reflect both increased precipitation and reduced summer temperatures negative glacier mass balances from 1976 to 1995 were caused by decreased winter balances the glacier fluctuation record does not contain a simple climate signal it is a complex response to several interacting factors that operate at different timescales evaluation of climate proxies over the last millennium indicates continuous variability at several superimposed timescales dominated by decade century patterns only the 19th century shows a long interval of sustained cold summers this suggests that simplistic concepts of climate over this period should be abandoned and replaced with more realistic records based on continuous proxy data series the use of the term lia should be restricted to describing a period of extended glacier cover rather than being used to define a period with specific climate conditions

late stage oxide growth associated with hydrothermal alteration of the western granite isle of rum nw scotland 1 the paleogene western granite isle of rum nw scotland represents a westward tilted shallow level felsic intrusion associated with the early growth stages of the classic early paleogene rum igneous centre rock magnetic data reveal an east to west variability in magnetic properties across the intrusion that is also reflected in petrographic and geochemical observations it is argued that the subtle intraplutonic variations in oxide grain size and composition observed in the western granite might be a common feature of shallow epizonal igneous intrusions as these mineralogical differences are not easily detectable without detailed rock magnetic study this research underscores the need for comprehensive rock magnetic studies when interpreting the postemplacement history of shallow level plutons paleomagnetic data indicate that the eastern part of the intrusion represents the shallower part of the exposed intrusion as further evidenced by roof pendants of lewisian gneiss and abundant drusy miarolitic cavities indicative of shallow emplacement in contrast the western part represents a deeper 900 m part of the intrusion as evidenced by the lack of roof pendants and existence of only minor drusy cavities rock magnetic data indicate that the dominant magnetic phase is low ti titanomagnetite with some titanomaghemite magnetic grain sizes range from pseudosingle domain in the west and multidomain in the east with a slight increase in ti content of the titanomagnetite phases in the east as revealed by curie point estimates we interpret these data to indicate that late stage subsolidus hydrothermal deuteric fluids associated with emplacement of the stage 2 rum layered suite produced secondary growth of fe ti oxide mineral phases along silicate grain boundaries in the eastern part of the intrusion the secondary oxide growth resulted in a slightly coarser magnetic grain size fraction and an increase in ti content of the titanomagnetite grains the deeper structural levels of the western part of the intrusion and its distance from the contact of the rum layered suite inhibited secondary oxide growth and thus this part of the intrusion preserves a primary magmatic oxide phase of a smaller magnetic grain size and near pure magnetite chemistry

time dependent thermal state of the lithosphere in the foreland of the eastern carpathians bend insights from new geothermal measurements and modelling results summary the time dependent heat budget thermal evolution and rheology of the lithosphere in the last 13myr along a 120 km long profile in the foreland of the eastern carpathians bend is presented the study area a complex tectonic environment in the vicinity of the wellknown intermediate depth seismogenic vrancea zone includes the deepest sedimentary basin in romania 18 km with a recent rapid evolution in the last 13myr 8 km of sediments detailed high resolution temperature logs in the depth ranges from 0 700 m to 0 2400 m in eight thermally stabilized boreholes together with logging and geological information on structure lithology and time evolution of the sedimentary pile have been used to model the thermal evolution by means of a 2 d finite element model which includes sedimentation history sediment compaction lateral and vertical variation of thermal properties of sediments and consolidated crust modelling results have been compared to measured temperatures corrected for palaeoclimate effects in a trial and error iterative approach sedimentation palaeoclimate undercompaction and heat refraction effects on one hand and the heat generated in the upper crust on the other combine to explain the observed subsurface temperature field and in particular the pronounced curvature of the vertical temperature profiles the neogene quaternary sedimentation resulted in a rather uniform deficit of the surface heat flux of about 12 mw m 2 in the study area in spite of the marked lateral variation of the sedimentary pile thickness the palaeoclimate effect is responsible for a surface heat flux depression of 7 8 mw m 2 uniform along the study profile unlike older sedimentary basins in the study area transient sedimentation thermal effects add to palaeoclimate effects in establishing the temperature field in the depth range of geothermal measurements the lateral variation of the palaeoclimatically corrected surface heat flux from the centre of the focsani depression 40 mw m 2 to its margin and the foreland platform 70 mw m 2 is mainly the result of the lateral variation of the heat produced in the upper crust where thickness varies from 7 to 21 km respectively a heat production of 2 3 wm 3 for the southeastern end of the profile and of 2 15 wm 3 for the rest of it has been modelled as a result of the sedimentation process temperature variations as large as 70 100 c occurred in the pre neogene sediments and the crystalline crust immediately under the sedimentary pile with consequences on the metamorphic state and rheological behaviour of the foreland

late quaternary environmental change in the lake o hara region yoho national park british columbia abstract palaeoenvironmental reconstructions for the upper cataract brook valley are derived from radiocarbon and tephra dated cores recovered from subalpine lake o hara and alpine opabin lake located near the continental divide in the central canadian rocky mountains late quaternary vegetational and climatic changes are based on pollen and macrofossil data and are supplemented by preliminary diatom data the postglacial colonizing vegetation prior to ca 10 100 yr b p at lake o hara and before ca 8530 yr b p at opabin lake was a shrub herb community dominated by artemisia gramineae and alnus pioneering forests at both sites were composed of pinus cf albicaulis flexilis and abies with lesser abundances of picea and pinus cf contorta timberline remained above the elevation of opabin lake at least 90 m above modern timberline elevation during the period ca 8500 yr b p to ca 3000 yr b p in response to warmer climatic conditions associated with restricted glacial activity forest compositions resembling the modern subalpine picea abies forest had developed by the end of this period the period ca 3000 yr b p to present was marked by deteriorating climatic conditions associated with renewed glacial activity in the opabin cirque and declining timberlines to below the elevation of opabin lake glacigenic sediments in the opabin record from the post bridge river ca 2350 yr b p interval are associated with reduced diatom production and a change in dominant diatom taxa to those characteristic of turbid water conditions and unstable catchment areas

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

abiotic versus biotic controls on the development of the fairmont hot springs carbonate deposit british columbia canada the relict fairmont hot springs deposit formed largely of carbonates covers an area of 0ae 5k m 2 and is up to 16 m thick the triangle shaped discharge apron which broadens down valley is divided into a proximal part with beds dipping at 10 and a distal part with beds dipping at 10 to 15 the deposit is formed of the 1 basal macrophyte 2 lower carbonate 3 middle clastic 4 upper carbonate and 5 upper clastic sequences two charcoal samples embedded in the lower carbonate sequence yielded dates of 8690 90 and 8270 70 cal yr bp indicating that much of the deposit formed post glacially during the early to mid holocene deposit aggradation ceased in the mid to late holocene when the fairmont creek valley was incised the lower and upper carbonate sequences which are the thickest sequences are composed of nearly equal parts of travertine abiotic and tufa biotic with feather dendrite travertine radiating dendrite travertine and stromatolite tufa dominating competition between calcite precipitation rates and biotic growth rates controlled the distribution of tufa and travertine across the discharge apron calcite and biotic growth rates were controlled largely by flow velocity across the apron which in turn was controlled by topography and regular fluctuations in spring water discharge volume during times of high spring discharge slow sheet flow over the proximal part of the apron promoted stromatolite growth whereas fast turbulent flow on the distal part of the apron induced rapid feather dendrite formation during times of low spring discharge quiescent shallow evaporative pools conducive to radiating dendrite formation formed on the proximal part of the apron whereas slow flow on the distal part promoted stromatolite growth facies with high calcite supersaturation experienced rapid abiotic dendrite growth that precluded most biotic growth

did the variscides collapse or were they torn apart a quantitative evaluation of the driving forces for postconvergent extension in central europe extension following immediately after the end of convergence caused rapid destruction of the european variscan orogen and resulted in the formation of numerous sedimentary basins and widespread magmatism possible driving forces for this phase of extension i e gravitational collapse of the thickened crust or reorientation of the far field stress regime are assessed quantitatively using a two dimensional thermomechanical finite element modeling approach the initial model setup approximates the geometry and physical properties of a lithosphere scale half profile through the variscan orogen and its foreland various numerical simulations and parameter studies suggest that the gravitational instability of the variscan orogen alone was not sufficient to explain the observed amount and timing of crustal extension tensile plate boundary stresses of the order of 10 mpa superposed on the gravitational forces are required to overcome the finite strength of the crust and restore a uniform crustal thickness in the variscan realm modeling results are constrained by comparison with existing data sets from the central european variscides for example crustal structure seismic reflectivity as well as temporal and spatial distribution of magmatic activity

late pleistocene northward dispersing bison antiquus from the bighill creek formation gallelli gravel pit alberta canada and the fate of bison occidentalis late pleistocene bison skeletal remains from the gallelli gravel pit in the bighill creek formation at calgary alberta document at least two individuals including the largest postglacial bison r